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Bongiovanni G, Tonutti A, Stainer A, Nigro M, Kellogg DL, Nambiar A, Gramegna A, Mantero M, Voza A, Blasi F, Aliberti S, Amati F. Vasoactive drugs for the treatment of pulmonary hypertension associated with interstitial lung diseases: a systematic review. BMJ Open Respir Res 2024; 11:e002161. [PMID: 38479818 PMCID: PMC10941167 DOI: 10.1136/bmjresp-2023-002161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Accepted: 02/28/2024] [Indexed: 03/17/2024] Open
Abstract
OBJECTIVES Vasoactive drugs have exhibited clinical efficacy in addressing pulmonary arterial hypertension, manifesting a significant reduction in morbidity and mortality. Pulmonary hypertension may complicate advanced interstitial lung disease (PH-ILD) and is associated with high rates of disability, hospitalisation due to cardiac and respiratory illnesses, and mortality. Prior management hinged on treating the underlying lung disease and comorbidities. However, the INCREASE trial of inhaled treprostinil in PH-ILD has demonstrated that PH-ILD can be effectively treated with vasoactive drugs. METHODS This comprehensive systematic review examines the evidence for vasoactive drugs in the management of PH-ILD. RESULTS A total of 1442 pubblications were screened, 11 RCTs were considered for quantitative synthesis. Unfortunately, the salient studies are limited by population heterogeneity, short-term follow-up and the selection of outcomes with uncertain clinical significance. CONCLUSIONS This systematic review underscores the necessity of establishing a precision medicine-oriented strategy, directed at uncovering and addressing the intricate cellular and molecular mechanisms that underlie the pathophysiology of PH-ILD. PROSPERO REGISTRATION NUMBER CRD42023457482.
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Affiliation(s)
- Gabriele Bongiovanni
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072, Pieve Emanuele, Milan, Italy
| | - Antonio Tonutti
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072, Pieve Emanuele, Milan, Italy
| | - Anna Stainer
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072, Pieve Emanuele, Milan, Italy
- Respiratory Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089, Rozzano, Milan, Italy
| | - Mattia Nigro
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072, Pieve Emanuele, Milan, Italy
| | - Dean L Kellogg
- Division of Pulmonary and Critical Care, Department of Medicine, University of Texas Health San Antonio and the South Texas Veterans Health Care System, San Antonio, Texas, USA
| | - Anoop Nambiar
- Division of Pulmonary and Critical Care, Department of Medicine, University of Texas Health San Antonio and the South Texas Veterans Health Care System, San Antonio, Texas, USA
| | - Andrea Gramegna
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Università degli studi di Milano, Milan, Italy
- Respiratory Unit and Cystic Fibrosis Adult Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Marco Mantero
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Università degli studi di Milano, Milan, Italy
- Respiratory Unit and Cystic Fibrosis Adult Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Antonio Voza
- Emergency Medicine Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089, Rozzano, Milan, Italy
| | - Francesco Blasi
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Università degli studi di Milano, Milan, Italy
- Respiratory Unit and Cystic Fibrosis Adult Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Stefano Aliberti
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072, Pieve Emanuele, Milan, Italy
- Respiratory Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089, Rozzano, Milan, Italy
| | - Francesco Amati
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072, Pieve Emanuele, Milan, Italy
- Respiratory Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089, Rozzano, Milan, Italy
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Gonzales MM, Garbarino VR, Pollet E, Palavicini JP, Kellogg DL, Kraig E, Orr ME. Biological aging processes underlying cognitive decline and neurodegenerative disease. J Clin Invest 2022; 132:e158453. [PMID: 35575089 PMCID: PMC9106343 DOI: 10.1172/jci158453] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Alzheimer's disease and related dementias (ADRD) are among the top contributors to disability and mortality in later life. As with many chronic conditions, aging is the single most influential factor in the development of ADRD. Even among older adults who remain free of dementia throughout their lives, cognitive decline and neurodegenerative changes are appreciable with advancing age, suggesting shared pathophysiological mechanisms. In this Review, we provide an overview of changes in cognition, brain morphology, and neuropathological protein accumulation across the lifespan in humans, with complementary and mechanistic evidence from animal models. Next, we highlight selected aging processes that are differentially regulated in neurodegenerative disease, including aberrant autophagy, mitochondrial dysfunction, cellular senescence, epigenetic changes, cerebrovascular dysfunction, inflammation, and lipid dysregulation. We summarize research across clinical and translational studies to link biological aging processes to underlying ADRD pathogenesis. Targeting fundamental processes underlying biological aging may represent a yet relatively unexplored avenue to attenuate both age-related cognitive decline and ADRD. Collaboration across the fields of geroscience and neuroscience, coupled with the development of new translational animal models that more closely align with human disease processes, is necessary to advance novel therapeutic discovery in this realm.
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Affiliation(s)
- Mitzi M. Gonzales
- Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases
- Department of Neurology
| | | | - Erin Pollet
- Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases
| | - Juan P. Palavicini
- Barshop Institute for Longevity and Aging Studies, and
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - Dean L. Kellogg
- Barshop Institute for Longevity and Aging Studies, and
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
- Geriatric Research and Education Center, South Texas Veterans Health Care System, San Antonio, Texas, USA
| | - Ellen Kraig
- Barshop Institute for Longevity and Aging Studies, and
- Department of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - Miranda E. Orr
- Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
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Pandey A, Shah SJ, Butler J, Kellogg DL, Lewis GD, Forman DE, Mentz RJ, Borlaug BA, Simon MA, Chirinos JA, Fielding RA, Volpi E, Molina AJA, Haykowsky MJ, Sam F, Goodpaster BH, Bertoni AG, Justice JN, White JP, Ding J, Hummel SL, LeBrasseur NK, Taffet GE, Pipinos II, Kitzman D. Exercise Intolerance in Older Adults With Heart Failure With Preserved Ejection Fraction: JACC State-of-the-Art Review. J Am Coll Cardiol 2021; 78:1166-1187. [PMID: 34503685 PMCID: PMC8525886 DOI: 10.1016/j.jacc.2021.07.014] [Citation(s) in RCA: 72] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 07/09/2021] [Accepted: 07/13/2021] [Indexed: 12/16/2022]
Abstract
Exercise intolerance (EI) is the primary manifestation of chronic heart failure with preserved ejection fraction (HFpEF), the most common form of heart failure among older individuals. The recent recognition that HFpEF is likely a systemic, multiorgan disorder that shares characteristics with other common, difficult-to-treat, aging-related disorders suggests that novel insights may be gained from combining knowledge and concepts from aging and cardiovascular disease disciplines. This state-of-the-art review is based on the outcomes of a National Institute of Aging-sponsored working group meeting on aging and EI in HFpEF. We discuss aging-related and extracardiac contributors to EI in HFpEF and provide the rationale for a transdisciplinary, "gero-centric" approach to advance our understanding of EI in HFpEF and identify promising new therapeutic targets. We also provide a framework for prioritizing future research, including developing a uniform, comprehensive approach to phenotypic characterization of HFpEF, elucidating key geroscience targets for treatment, and conducting proof-of-concept trials to modify these targets.
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Affiliation(s)
- Ambarish Pandey
- University of Texas Southwestern Medical Center, Dallas, Texas, USA. https://twitter.com/ambarish4786
| | - Sanjiv J Shah
- Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Javed Butler
- University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Dean L Kellogg
- University of Texas Health Science Center and GRECC, South Texas Veterans Affairs Health System, San Antonio, Texas, USA
| | | | - Daniel E Forman
- University of Pittsburgh and VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania, USA
| | - Robert J Mentz
- Duke Clinical Research Center, Durham, North Carolina, USA
| | | | - Marc A Simon
- University of Pittsburgh and VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania, USA
| | | | | | - Elena Volpi
- University of Texas Medical Branch at Galveston, Galveston, Texas, USA
| | | | | | - Flora Sam
- Boston University School of Medicine, Boston, Massachusetts, USA
| | - Bret H Goodpaster
- Advent Health Translational Research Institute, Orlando, Florida, USA
| | - Alain G Bertoni
- Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Jamie N Justice
- Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | | | - Jingzhone Ding
- Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Scott L Hummel
- University of Michigan and the VA Ann Arbor Health System, Ann Arbor, Michigan, USA
| | | | | | | | - Dalane Kitzman
- Wake Forest School of Medicine, Winston-Salem, North Carolina, USA.
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Kellogg DL, Darling H, Crawford B, Garcia AJ, Camacho V. An Interdisciplinary Clinic for Former Prisoners of War. Fed Pract 2020; 37:182-185. [PMID: 32322150 PMCID: PMC7173639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
BACKGROUND The former prisoner of war (FPOW) population is mandated to "receive the highest quality care and benefit services" from the US Department of Veterans Affairs (VA). Each VA medical facility is required to have a special Care and Benefits Team to meet this policy goal. METHODS In South Texas, 40% of FPOWs had no VA primary care or clinic assignment. In consideration of the commitment of the VA to care for FPOWs, the unique POW-related medical and psychological issues, the geriatric age of many FPOWs, and the surprising number of FPOWs currently not receiving VA care, the South Texas Veterans Health Care System in San Antonio incorporated the concept of geriatric evaluation and management into its cognitive behavioral therapy team to create a specialized interdisciplinary FPOW Clinic. The main purpose of this project was to advise FPOWs of VA benefits and services as well as to facilitate the identification of overlooked conditions with a presumption of service connection, for example, exposure to Agent Orange. RESULTS As most FPOWs are aged > 65 years, the FPOW Clinic was designed as an interdisciplinary team similar to that proven successful in geriatric medicine. Overlooked FPOW presumptive conditions were identified for 34% of FPOWs. CONCLUSIONS FPOW veterans are rapidly dwindling in numbers and may live in rural areas. Consistent with the VA's desire to adopt novel technological approaches, we propose to modify our FPOW Clinic by adopting telehealth.
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Affiliation(s)
- Dean L Kellogg
- is a Staff Physician, and is the Administrative Officer for the Geriatric Research, Education, and Clinical Center (GRECC); and are Social Workers all at the South Texas Veterans Health Care System in San Antonio. Dean Kellogg is a Professor at the University of Texas Health Science Center
| | - Holly Darling
- is a Staff Physician, and is the Administrative Officer for the Geriatric Research, Education, and Clinical Center (GRECC); and are Social Workers all at the South Texas Veterans Health Care System in San Antonio. Dean Kellogg is a Professor at the University of Texas Health Science Center
| | - Bennetta Crawford
- is a Staff Physician, and is the Administrative Officer for the Geriatric Research, Education, and Clinical Center (GRECC); and are Social Workers all at the South Texas Veterans Health Care System in San Antonio. Dean Kellogg is a Professor at the University of Texas Health Science Center
| | - Andres J Garcia
- is a Staff Physician, and is the Administrative Officer for the Geriatric Research, Education, and Clinical Center (GRECC); and are Social Workers all at the South Texas Veterans Health Care System in San Antonio. Dean Kellogg is a Professor at the University of Texas Health Science Center
| | - Veronica Camacho
- is a Staff Physician, and is the Administrative Officer for the Geriatric Research, Education, and Clinical Center (GRECC); and are Social Workers all at the South Texas Veterans Health Care System in San Antonio. Dean Kellogg is a Professor at the University of Texas Health Science Center
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Kraig E, Linehan LA, Liang H, Romo TQ, Liu Q, Wu Y, Benavides AD, Curiel TJ, Javors MA, Musi N, Chiodo L, Koek W, Gelfond JAL, Kellogg DL. A randomized control trial to establish the feasibility and safety of rapamycin treatment in an older human cohort: Immunological, physical performance, and cognitive effects. Exp Gerontol 2018; 105:53-69. [PMID: 29408453 DOI: 10.1016/j.exger.2017.12.026] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 12/31/2017] [Indexed: 12/21/2022]
Abstract
Inhibition of the mechanistic target of rapamycin (mTOR) pathway by rapamycin (RAPA), an FDA-approved immunosuppressive drug used as a clinical therapy to prevent solid organ allograft rejection, enhances longevity in mice. Importantly, RAPA was efficacious even when initiated in relatively old animals, suggesting that mTOR inhibition could potentially slow the progression of aging-associated pathologies in older humans (Harrison et al., 2009; Miller et al., 2011). However, the safety and tolerability of RAPA in older human subjects have not yet been demonstrated. Towards this end, we undertook a placebo-controlled pilot study in 25 generally healthy older adults (aged 70-95 years); subjects were randomized to receive either 1 mg RAPA or placebo daily. Although three subjects withdrew, 11 RAPA and 14 controls completed at least 8 weeks of treatment and were included in the analysis. We monitored for changes that would indicate detrimental effects of RAPA treatment on metabolism, including both standard clinical laboratory assays (CBC, CMP, HbA1c) and oral glucose tolerance tests (OGTTs). We also monitored parameters typically associated with aging that could potentially be modified by RAPA; these included cognitive function which was assessed by three different tools: Executive Interview-25 (EXIT25); Saint Louis University Mental Status Exam (SLUMS); and Texas Assessment of Processing Speed (TAPS). In addition, physical performance was measured by handgrip strength and 40-foot timed walks. Lastly, changes in general parameters of healthy immune aging, including serum pro-inflammatory cytokine levels and blood cell subsets, were assessed. Five subjects reported potential adverse side effects; in the RAPA group, these were limited to facial rash (1 subject), stomatitis (1 subject) and gastrointestinal issues (2 subjects) whereas placebo treated subjects only reported stomatitis (1 subject). Although no other adverse events were reported, statistically significant decrements in several erythrocyte parameters including hemoglobin (HgB) and hematocrit (Hct) as well as in red blood cell count (RBC), red blood cell distribution width (RDW), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) were observed in the RAPA-treatment group. None of these changes manifested clinically significant effects during the short duration of this study. Similarly, no changes were noted in any other clinical laboratory, cognitive, physical performance, or self-perceived health status measure over the study period. Immune parameters were largely unchanged as well, possibly due to the advanced ages of the cohort (70-93 years; mean age 80.5). RAPA-associated increases in a myeloid cell subset and in TREGS were detected, but changes in most other PBMC cell subsets were not statistically significant. Importantly, the OGTTs revealed no RAPA-induced change in blood glucose concentration, insulin secretion, and insulin sensitivity. Thus, based on the results of our pilot study, it appears that short-term RAPA treatment can be used safely in older persons who are otherwise healthy; a trial with a larger sample size and longer treatment duration is warranted.
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Affiliation(s)
- Ellen Kraig
- Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center, San Antonio, USA; Department of Cell Systems and Anatomy, The University of Texas Health Science Center, San Antonio, USA.
| | - Leslie A Linehan
- Department of Cell Systems and Anatomy, The University of Texas Health Science Center, San Antonio, USA
| | - Hanyu Liang
- Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center, San Antonio, USA
| | - Terry Q Romo
- Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center, San Antonio, USA; GRECC, South Texas Veterans Health Care System, The University of Texas Health Science Center, San Antonio, USA
| | - Qianqian Liu
- Department of Epidemiology and Biostatistics, The University of Texas Health Science Center, San Antonio, USA
| | - Yubo Wu
- Department of Medicine, The University of Texas Health Science Center, San Antonio, USA
| | - Adriana D Benavides
- Department of Microbiology, Immunology, and Molecular Genetics, The University of Texas Health Science Center, San Antonio, USA
| | - Tyler J Curiel
- Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center, San Antonio, USA; Department of Medicine, The University of Texas Health Science Center, San Antonio, USA
| | - Martin A Javors
- Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center, San Antonio, USA; Department of Psychiatry, The University of Texas Health Science Center, San Antonio, USA
| | - Nicolas Musi
- Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center, San Antonio, USA; Department of Medicine, The University of Texas Health Science Center, San Antonio, USA; GRECC, South Texas Veterans Health Care System, The University of Texas Health Science Center, San Antonio, USA
| | - Laura Chiodo
- GRECC, South Texas Veterans Health Care System, The University of Texas Health Science Center, San Antonio, USA
| | - Wouter Koek
- Department of Cell Systems and Anatomy, The University of Texas Health Science Center, San Antonio, USA; Department of Psychiatry, The University of Texas Health Science Center, San Antonio, USA
| | - Jonathan A L Gelfond
- Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center, San Antonio, USA; Department of Epidemiology and Biostatistics, The University of Texas Health Science Center, San Antonio, USA
| | - Dean L Kellogg
- Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center, San Antonio, USA; Department of Medicine, The University of Texas Health Science Center, San Antonio, USA; GRECC, South Texas Veterans Health Care System, The University of Texas Health Science Center, San Antonio, USA
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Abstract
Cold exposure stimulates heat production and conservation to protect internal temperature. Heat conservation is brought about via reductions in skin blood flow. The focus, here, is an exploration of the mechanisms, particularly in humans, leading to that cutaneous vasoconstriction. Local skin cooling has several effects: (1) reduction of tonic nitric oxide formation by inhibiting nitric oxide synthase and element(s) downstream of the enzyme, which removes tonic vasodilator effects, yielding a relative vasoconstriction; (2) translocation of intracellular alpha-2c adrenoceptors to the vascular smooth-muscle cell membrane, enhancing adrenergic vasoconstriction; (3) increased norepinephrine release from vasoconstrictor nerves; and (4) cold-induced vasodilation, seen more clearly in anastomoses-rich glabrous skin. Cold-induced vasodilation occurs in nonglabrous skin when nitric oxide synthase or sympathetic function is blocked. Reflex responses to general body cooling complement these local effects. Sympathetic excitation leads to the increased release of norepinephrine and its cotransmitter neuropeptide Y, each of which contributes significantly to the vasoconstriction. The contributions of these two transmitters vary with aging, disease and, in women, reproductive hormone status. Interaction between local and reflex mechanisms is in part through effects on baseline and in part through removal of the inhibitory effects of nitric oxide on adrenergic vasoconstriction.
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Affiliation(s)
- John M Johnson
- Department of Physiology, University of Texas Health Center at San Antonio, San Antonio, TX, United States.
| | - Dean L Kellogg
- Department of Physiology, University of Texas Health Center at San Antonio, San Antonio, TX, United States; Department of Medicine, University of Texas Health Center at San Antonio, San Antonio, TX, United States
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Kellogg DL, McCammon KM, Hinchee-Rodriguez KS, Adamo ML, Roman LJ. Neuronal nitric oxide synthase mediates insulin- and oxidative stress-induced glucose uptake in skeletal muscle myotubes. Free Radic Biol Med 2017; 110:261-269. [PMID: 28666850 PMCID: PMC5554434 DOI: 10.1016/j.freeradbiomed.2017.06.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 06/13/2017] [Accepted: 06/26/2017] [Indexed: 10/19/2022]
Abstract
Previously published studies strongly suggested that insulin- and exercise-induced skeletal muscle glucose uptake require nitric oxide (NO) production. However, the signal transduction mechanisms by which insulin and contraction regulated NO production and subsequent glucose transport are not known. In the present study, we utilized the myotube cell lines treated with insulin or hydrogen peroxide, the latter to mimic contraction-induced oxidative stress, to characterize these mechanisms. We found that insulin stimulation of neuronal nitric oxide synthase (nNOS) phosphorylation, NO production, and GLUT4 translocation were all significantly reduced by inhibition of either nNOS or Akt2. Hydrogen peroxide (H2O2) induced phosphorylation of nNOS at the same residue as did insulin, and also stimulated NO production and GLUT4 translocation. nNOS inhibition prevented H2O2-induced GLUT4 translocation. AMP activated protein kinase (AMPK) inhibition prevented H2O2 activation and phosphorylation of nNOS, leading to reduced NO production and significantly attenuated GLUT4 translocation. We conclude that nNOS phosphorylation and subsequently increased NO production are required for both insulin- and H2O2-stimulated glucose transport. Although the two stimuli result in phosphorylation of the same residue on nNOS, they do so through distinct protein kinases. Thus, insulin and H2O2-activated signaling pathways converge on nNOS, which is a common mediator of glucose uptake in both pathways. However, the fact that different kinases are utilized provides a basis for the use of exercise to activate glucose transport in the face of insulin resistance.
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Affiliation(s)
- Dean L Kellogg
- Department of Biochemistry and Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229, United States
| | - Karen M McCammon
- Department of Biochemistry and Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229, United States
| | - Kathryn S Hinchee-Rodriguez
- Department of Biochemistry and Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229, United States
| | - Martin L Adamo
- Department of Biochemistry and Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229, United States
| | - Linda J Roman
- Department of Biochemistry and Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229, United States.
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Kar R, Kellogg DL, Roman LJ. Oxidative stress induces phosphorylation of neuronal NOS in cardiomyocytes through AMP-activated protein kinase (AMPK). Biochem Biophys Res Commun 2015; 459:393-7. [PMID: 25732085 DOI: 10.1016/j.bbrc.2015.02.113] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 02/19/2015] [Indexed: 02/05/2023]
Abstract
Neuronal nitric oxide synthase (nNOS) plays a critical role in regulating cardiomyocyte function. nNOS was reported to decrease superoxide production in the myocardium by inhibiting the function of xanthine oxidoreductase. However, the effect of oxidative stress on nNOS in cardiomyocytes has not been determined. We report here that brief exposure of HL-1 cardiomyocytes to hydrogen peroxide (H2O2) induces phosphorylation of nNOS at serine 1412. This increase in phosphorylation was concomitant with increased nitric oxide (NO) production. Prolonged exposure to the oxidant, however, resulted in decreased expression of the protein. H2O2 treatment for short periods also stimulated phosphorylation of AKT and AMPK. H2O2-induced phosphorylation of nNOS was reduced when AMPK activity was inhibited by compound C, suggesting that AMPK is a mediator of oxidative stress-induced phosphorylation of nNOS. However, inhibition of AKT activity by the pan AKT inhibitor, AKTi, had no effect on nNOS phosphorylation caused by H2O2. These data demonstrate the novel regulation of nNOS phosphorylation and expression by oxidative stress.
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Affiliation(s)
- Rekha Kar
- Department of Biochemistry, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229, USA.
| | - Dean L Kellogg
- Department of Biochemistry, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229, USA.
| | - Linda J Roman
- Department of Biochemistry, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229, USA.
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Hodges GJ, Kellogg DL, Johnson JM. Effect of skin temperature on cutaneous vasodilator response to the β-adrenergic agonist isoproterenol. J Appl Physiol (1985) 2015; 118:898-903. [PMID: 25701007 DOI: 10.1152/japplphysiol.01071.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 02/13/2015] [Indexed: 11/22/2022] Open
Abstract
The vascular response to local skin cooling is dependent in part on a cold-induced translocation of α2C-receptors and an increased α-adrenoreceptor function. To discover whether β-adrenergic function might contribute, we examined whether β-receptor sensitivity to the β-agonist isoproterenol was affected by local skin temperature. In seven healthy volunteers, skin blood flow was measured from the forearm by laser-Doppler flowmetry and blood pressure was measured by finger photoplethysmography. Data were expressed as cutaneous vascular conductance (CVC; laser-Doppler flux/mean arterial blood pressure). Pharmacological agents were administered via intradermal microdialysis. We prepared four skin sites: one site was maintained at a thermoneutral temperature of 34°C (32 ± 10%CVCmax) one site was heated to 39°C (38 ± 11%CVCmax); and two sites were cooled, one to 29°C (22 ± 7%CVCmax) and the other 24°C (16 ± 4%CVCmax). After 20 min at these temperatures to allow stabilization of skin blood flow, isoproterenol was perfused in concentrations of 10, 30, 100, and 300 μM. Each concentration was perfused for 15 min. Relative to the CVC responses to isoproterenol at the thermoneutral skin temperature (34°C) (+21 ± 10%max), low skin temperatures reduced (at 29°C) (+17 ± 6%max) or abolished (at 24°C) (+1 ± 5%max) the vasodilator response, and warm (39°C) skin temperatures enhanced the vasodilator response (+40 ± 9%max) to isoproterenol. These data indicate that β-adrenergic function was influenced by local skin temperature. This finding raises the possibility that a part of the vasoconstrictor response to direct skin cooling could include reduced background β-receptor mediated vasodilation.
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Affiliation(s)
- Gary J Hodges
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada; Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas; and
| | - Dean L Kellogg
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas; and Department of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - John M Johnson
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas; and
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10
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Abstract
In this review, we focus on significant developments in our understanding of the mechanisms that control the cutaneous vasculature in humans, with emphasis on the literature of the last half-century. To provide a background for subsequent sections, we review methods of measurement and techniques of importance in elucidating control mechanisms for studying skin blood flow. In addition, the anatomy of the skin relevant to its thermoregulatory function is outlined. The mechanisms by which sympathetic nerves mediate cutaneous active vasodilation during whole body heating and cutaneous vasoconstriction during whole body cooling are reviewed, including discussions of mechanisms involving cotransmission, NO, and other effectors. Current concepts for the mechanisms that effect local cutaneous vascular responses to local skin warming and cooling are examined, including the roles of temperature sensitive afferent neurons as well as NO and other mediators. Factors that can modulate control mechanisms of the cutaneous vasculature, such as gender, aging, and clinical conditions, are discussed, as are nonthermoregulatory reflex modifiers of thermoregulatory cutaneous vascular responses.
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Affiliation(s)
- John M Johnson
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas
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Zhao JL, Roman LJ, Wu Y, Johnson JM, Kellogg DL. Inhibition of the mammalian Target of Rapamycin (mTOR) does not alter nitric oxide or superoxide levels in human skin. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.lb699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Joan L Zhao
- PhysiologyUniv. of Texas Health Science Center at San AntonioSan AntonioTX
| | - Linda J Roman
- BiochemistryUniv. of Texas Health Science Center at San AntonioSan AntonioTX
| | - Yubo Wu
- PhysiologyUniv. of Texas Health Science Center at San AntonioSan AntonioTX
| | - John M Johnson
- PhysiologyUniv. of Texas Health Science Center at San AntonioSan AntonioTX
| | - Dean L Kellogg
- MedicineUniv. of Texas Health Science Center at San AntonioSan AntonioTX
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Panda SP, Polusani SR, Kellogg DL, Venkatakrishnan P, Roman MG, Demeler B, Masters BSS, Roman LJ. Intra- and inter-molecular effects of a conserved arginine residue of neuronal and inducible nitric oxide synthases on FMN and calmodulin binding. Arch Biochem Biophys 2013; 533:88-94. [PMID: 23507581 DOI: 10.1016/j.abb.2013.03.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 03/06/2013] [Accepted: 03/07/2013] [Indexed: 10/27/2022]
Abstract
Nitric oxide synthases (NOSs) synthesize nitric oxide (NO), a signaling molecule, from l-arginine, utilizing electrons from NADPH. NOSs are flavo-hemo proteins, with two flavin molecules (FAD and FMN) and one heme per monomer, which require the binding of calcium/calmodulin (Ca(2+)/CaM) to produce NO. It is therefore important to understand the molecular factors influencing CaM binding from a structure/function perspective. A crystal structure of the CaM-bound iNOS FMN-binding domain predicted a salt bridge between R536 of human iNOS and E47 of CaM. To characterize the interaction between the homologous Arg of rat nNOS (R753) and murine iNOS (R530) with CaM, the Arg was mutated to Ala and, in iNOS, to Glu. The mutation weakens the interaction between nNOS and CaM, decreasing affinity by ~3-fold. The rate of electron transfer from FMN is greatly attenuated; however, little effect on electron transfer from FAD is observed. The mutated proteins showed reduced FMN binding, from 20% to 60%, suggesting an influence of this residue on FMN incorporation. The weakened FMN binding may be due to conformational changes caused by the arginine mutation. Our data show that this Arg residue plays an important role in CaM binding and influences FMN binding.
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Affiliation(s)
- Satya Prakash Panda
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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Chaurasia CS, Müller M, Bashaw ED, Benfeldt E, Bolinder J, Bullock R, Bungay PM, DeLange ECM, Derendorf H, Elmquist WF, Hammarlund-Udenaes M, Joukhadar C, Kellogg DL, Lunte CE, Nordstrom CH, Rollema H, Sawchuk RJ, Cheung BWY, Shah VP, Stahle L, Ungerstedt U, Welty DF, Yeo H. AAPS-FDA Workshop White Paper: Microdialysis Principles, Application, and Regulatory Perspectives. J Clin Pharmacol 2013; 47:589-603. [PMID: 17442685 DOI: 10.1177/0091270006299091] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Chandra S Chaurasia
- Division of Bioequivalence, Office of Generic Drugs, Food and Drug Administration, Room 1360/HFD-650, 7520 Standish Place, Rockville, MD 20855, USA.
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Kellogg DL, Zhao JL, Wu Y, Johnson JM. Nitric oxide and receptors for VIP and PACAP in cutaneous active vasodilation during heat stress in humans. J Appl Physiol (1985) 2012; 113:1512-8. [PMID: 22961270 DOI: 10.1152/japplphysiol.00859.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
VPAC2 receptors sensitive to vasoactive intestinal polypeptide (VIP) and pituitary adenylyl cyclase activating polypeptide (PACAP), PAC1 receptors sensitive to PACAP, and nitric oxide (NO) generation by NO synthase (NOS) are all implicated in cutaneous active vasodilation (AVD) through incompletely defined mechanisms. We hypothesized that VPAC2/PAC1 receptor activation and NO are synergistic and interdependent in AVD and tested our hypothesis by examining the effects of VPAC2/PAC1 receptor blockade with and without NOS inhibition during heat stress. The VPAC2/PAC1 antagonist, pituitary adenylate cyclase activating peptide 6-38 (PACAP6-38) and the NOS inhibitor, N(G)-nitro-l-arginine methyl ester (l-NAME) were administered by intradermal microdialysis. PACAP6-38, l-NAME, a combination of PACAP6-38 and l-NAME, or Ringer's solution alone were perfused at four separate sites. Skin blood flow was monitored by laser-Doppler flowmetry at each site. Body temperature was controlled with water-perfused suits. Blood pressure was monitored by Finapres, and cutaneous vascular conductance (CVC) calculated (CVC = laser-Doppler flowmetry/mean arterial pressure). The protocol began with a 5- to 10-min baseline period without antagonist perfusion, followed by perfusion of PACAP6-38, l-NAME, or combined PACAP6-38 and l-NAME at the different sites in normothermia (45 min), followed by 3 min of whole body cooling. Whole body heating was then performed to induce heat stress and activate AVD. Finally, 58 mM sodium nitroprusside were perfused at all sites to effect maximal vasodilation for normalization of blood flow data. No significant differences in CVC (normalized to maximum) were found among Ringer's PACAP6-38, l-NAME, or combined antagonist sites during normothermia (P > 0.05 among sites) or cold stress (P > 0.05 among sites). CVC responses at all treated sites were attenuated during AVD (P < 0.05 vs. Ringer's). Attenuation was greater at l-NAME and combined PACAP6-38- and l-NAME-treated sites than at PACAP6-38 sites (P > 0.05). Because responses did not differ between l-NAME and combined treatment sites (P > 0.05), we conclude that VPAC2/PAC1 receptors require NO in series to effect AVD.
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Affiliation(s)
- Dean L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, Audie L. Murphy Memorial Veterans Hospital Division, San Antonio, TX 78229, USA.
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Kellogg DL, Zhao JL, Wu Y, Johnson JM. Antagonism of soluble guanylyl cyclase attenuates cutaneous vasodilation during whole body heat stress and local warming in humans. J Appl Physiol (1985) 2011; 110:1406-13. [PMID: 21292837 DOI: 10.1152/japplphysiol.00702.2010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that nitric oxide activation of soluble guanylyl cyclase (sGC) participates in cutaneous vasodilation during whole body heat stress and local skin warming. We examined the effects of the sGC inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), on reflex skin blood flow responses to whole body heat stress and on nonreflex responses to increased local skin temperature. Blood flow was monitored by laser-Doppler flowmetry, and blood pressure by Finapres to calculate cutaneous vascular conductance (CVC). Intradermal microdialysis was used to treat one site with 1 mM ODQ in 2% DMSO and Ringer, a second site with 2% DMSO in Ringer, and a third site received Ringer. In protocol 1, after a period of normothermia, whole body heat stress was induced. In protocol 2, local heating units warmed local skin temperature from 34 to 41°C to cause local vasodilation. In protocol 1, in normothermia, CVC did not differ among sites [ODQ, 15 ± 3% maximum CVC (CVC(max)); DMSO, 14 ± 3% CVC(max); Ringer, 17 ± 6% CVC(max); P > 0.05]. During heat stress, ODQ attenuated CVC increases (ODQ, 54 ± 4% CVC(max); DMSO, 64 ± 4% CVC(max); Ringer, 63 ± 4% CVC(max); P < 0.05, ODQ vs. DMSO or Ringer). In protocol 2, at 34°C local temperature, CVC did not differ among sites (ODQ, 17 ± 2% CVC(max); DMSO, 18 ± 4% CVC(max); Ringer, 18 ± 3% CVC(max); P > 0.05). ODQ attenuated CVC increases at 41°C local temperature (ODQ, 54 ± 5% CVC(max); DMSO, 86 ± 4% CVC(max); Ringer, 90 ± 2% CVC(max); P < 0.05 ODQ vs. DMSO or Ringer). sGC participates in neurogenic active vasodilation during heat stress and in the local response to direct skin warming.
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Affiliation(s)
- Dean L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, Audie L. Murphy Memorial Veterans Hospital Division, San Antonio, Texas, USA.
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Abstract
The level of skin blood flow is subject to both reflex thermoregulatory control and influences from the direct effects of warming and cooling the skin. The effects of local changes in temperature are capable of maximally vasoconstricting or vasodilating the skin. They are brought about by a combination of mechanisms involving endothelial, adrenergic, and sensory systems. Local warming initiates a transient vasodilation through an axon reflex, succeeded by a plateau phase due largely to nitric oxide. Both phases are supported by sympathetic transmitters. The plateau phase is followed by the die-away phenomenon, a slow reversal of the vasodilation that is dependent on intact sympathetic vasoconstrictor nerves. The vasoconstriction with local skin cooling is brought about, in part, by a postsynaptic upregulation of α(2c)-adrenoceptors and, in part, by inhibition of the nitric oxide system at at least two points. There is also an early vasodilator response to local cooling, dependent on the rate of cooling. The mechanism for that transient vasodilation is not known, but it is inhibited by intact sympathetic vasoconstrictor nerve function and by intact sensory nerve function.
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Affiliation(s)
- John M Johnson
- Dept. of Physiology, Univ. of Texas Health Science Center, 7703 Floyd Curl Dr., San Antonio TX 78231, USA.
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Abstract
The past 10-15 years has been a time of focus on the mechanisms of control in the human cutaneous circulation. Methodological developments have provided powerful means for resolving the important contributors to the reflex control of skin blood flow (thermoregulatory control) and also for the equally impressive effects of direct heating and cooling of the skin (thermal control). This review is devoted largely to that recent literature. We treat the sympathetic vasoconstrictor system and its transmitters and modulatory factors and the sympathetic active vasodilator system and its abundant mysteries, with focus on the putative transmitters and cotransmitters, the involvement of nitric oxide and the relationship to sweating and modulatory factors. We also deal with the current understanding of the mechanisms of vasoconstriction and vasodilation that accompany direct skin cooling and heating, noting that adrenergic function, afferent nerve function and the nitric oxide system are involved in the vascular responses to both thermal stimuli.
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Affiliation(s)
- John M Johnson
- Department of Physiology, University of Texas Health Science Center, San Antonio, TX 78229, USA.
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Kellogg DL, Zhao JL, Wu Y, Johnson JM. VIP/PACAP receptor mediation of cutaneous active vasodilation during heat stress in humans. J Appl Physiol (1985) 2010; 109:95-100. [PMID: 20395540 DOI: 10.1152/japplphysiol.01187.2009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vasoactive intestinal peptide (VIP) is implicated in cutaneous active vasodilation in humans. VIP and the closely related pituitary adenylate cyclase activating peptide (PACAP) act through several receptor types: VIP through VPAC1 and VPAC2 receptors and PACAP through VPAC1, VPAC2, and PAC1 receptors. We examined participation of VPAC2 and/or PAC1 receptors in cutaneous vasodilation during heat stress by testing the effects of their specific blockade with PACAP6-38. PACAP6-38 dissolved in Ringer's was administered by intradermal microdialysis at one forearm site while a control site received Ringer's solution. Skin blood flow was monitored by laser-Doppler flowmetry (LDF). Blood pressure was monitored noninvasively and cutaneous vascular conductance (CVC) calculated. A 5- to 10-min baseline period was followed by approximately 70 min of PACAP6-38 (100 microM) perfusion at one site in normothermia and a 3-min period of body cooling. Whole body heating was then performed to engage cutaneous active vasodilation and was maintained until CVC had plateaued at an elevated level at all sites for 5-10 min. Finally, 58 mM sodium nitroprusside was perfused through both microdialysis sites to effect maximal vasodilation. No CVC differences were found between control and PACAP6-38-treated sites during normothermia (19 +/- 3%max untreated vs. 20 +/- 3%max, PACAP6-38 treated; P > 0.05 between sites) or cold stress (11 +/- 2%max untreated vs. 10 +/- 2%max, PACAP6-38 treated, P > 0.05 between sites). PACAP6-38 attenuated the increase in CVC during whole body heating when compared with untreated sites (59 +/- 3%max untreated vs. 46 +/- 3%max, PACAP6-38 treated, P < 0.05). We conclude that VPAC2 and/or PAC1 receptor activation is involved in cutaneous active vasodilation in humans.
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Affiliation(s)
- Dean L Kellogg
- Division of Geriatrics and Gerontology, Department of Medicine, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229, USA.
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Zhao JL, Kellogg DL, Wu Y, Johnson JM. VPAC2 And/Or PAC1 Receptors Interact with NOS during Heat Stress in Humans. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.1039.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Dean L Kellogg
- Medicine
- Geriatric Research, Education and Clinical CenterAudie L. Murphy Memorial VA HospitalSan AntonioTX
| | | | - John M Johnson
- PhysiologyUniversity of TX Health Science Center at San AntonioSan AntonioTX
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Kellogg DL, Zhao JL, Wu Y, Johnson JM. cGMP is involved in Cutaneous Vasodilation in Local Skin Warming in Humans. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.1039.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Dean L Kellogg
- Medicine
- Geriatric Research, Education and Clinical CenterAudie L. Murphy Memorial VA HospitalSan AntonioTX
| | | | | | - John M Johnson
- PhysiologyUniversity of TX Health Science Center At San AntonioSan AntonioTX
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Kellogg DL, Masters BSS, Roman LJ. Mutational disruption of the nitric oxide synthase/calmodulin interaction causes increased formation of reactive oxygen species. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.463.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Dean L. Kellogg
- BiochemistryUniversity of Texas Health Science CenterSan AntonioTX
| | | | - Linda J. Roman
- BiochemistryUniversity of Texas Health Science CenterSan AntonioTX
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Kellogg DL, Zhao JL, Wu Y. Roles of nitric oxide synthase isoforms in cutaneous vasodilation induced by local warming of the skin and whole body heat stress in humans. J Appl Physiol (1985) 2009; 107:1438-44. [PMID: 19745188 DOI: 10.1152/japplphysiol.00690.2009] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nitric oxide (NO) participates in the cutaneous vasodilation caused by increased local skin temperature (Tloc) and whole body heat stress in humans. In forearm skin, endothelial NO synthase (eNOS) participates in vasodilation due to elevated Tloc and neuronal NO synthase (nNOS) participates in vasodilation due to heat stress. To explore the relative roles and interactions of these isoforms, we examined the effects of a relatively specific eNOS inhibitor, N(omega)-amino-l-arginine (LNAA), and a specific nNOS inhibitor, N(omega)-propyl-l-arginine (NPLA), both separately and in combination, on skin blood flow (SkBF) responses to increased Tloc and heat stress in two protocols. In each protocol, SkBF was monitored by laser-Doppler flowmetry (LDF) and mean arterial pressure (MAP) by Finapres. Cutaneous vascular conductance (CVC) was calculated (CVC = LDF/MAP). Intradermal microdialysis was used to treat one site with 5 mM LNAA, another with 5 mM NPLA, a third with combined 5 mM LNAA and 5 mM NPLA (Mix), and a fourth site with Ringer only. In protocol 1, Tloc was controlled with combined LDF/local heating units. Tloc was increased from 34 degrees C to 41.5 degrees C to cause local vasodilation. In protocol 2, after a period of normothermia, whole body heat stress was induced (water-perfused suits). At the end of each protocol, all sites were perfused with 58 mM nitroprusside to effect maximal vasodilation for data normalization. In protocol 1, at Tloc = 34 degrees C, CVC did not differ between sites (P > 0.05). LNAA and Mix attenuated CVC increases at Tloc = 41.5 degrees C to similar extents (P < 0.05, LNAA or Mix vs. untreated or NPLA). In protocol 2, in normothermia, CVC did not differ between sites (P > 0.05). During heat stress, NPLA and Mix attenuated CVC increases to similar extents, but no significant attenuation occurred with LNAA (P < 0.05, NPLA or Mix vs. untreated or LNAA). In forearm skin, eNOS mediates the vasodilator response to increased Tloc and nNOS mediates the vasodilator response to heat stress. The two isoforms do not appear to interact during either response.
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Affiliation(s)
- Dean L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, Audie L. Murphy Memorial Veterans Hospital Division, Texas, USA.
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Kellogg DL. Commentary on Viewpoint: The human cutaneous circulation as a model of generalized microvascular function. J Appl Physiol (1985) 2008; 105:377; author reply 389. [DOI: 10.1152/japplphysiol.90341.2008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Abstract
Nitric oxide (NO) participates in locally mediated vasodilation induced by increased local skin temperature (T(loc)) and in sympathetically mediated vasodilation during whole body heat stress. We hypothesized that endothelial NOS (eNOS) participates in the former, but not the latter, response. We tested this hypothesis by examining the effects of the eNOS antagonist N(G)-amino-l-arginine (l-NAA) on skin blood flow (SkBF) responses to increased T(loc) and whole body heat stress. Microdialysis probes were inserted into forearm skin for drug delivery. One microdialysis site was perfused with l-NAA in Ringer solution and a second site with Ringer solution alone. SkBF [laser-Doppler flowmetry (LDF)] and blood pressure [mean arterial pressure (MAP)] were monitored, and cutaneous vascular conductance (CVC) was calculated (CVC = LDF / MAP). In protocol 1, T(loc) was controlled with LDF/local heating units. T(loc) initially was held at 34 degrees C and then increased to 41.5 degrees C. In protocol 2, after a normothermic period, whole body heat stress was induced (water-perfused suits). At the end of both protocols, 58 mM sodium nitroprusside was perfused at both microdialysis sites to cause maximal vasodilation for data normalization. In protocol 1, CVC at 34 degrees C T(loc) did not differ between l-NAA-treated and untreated sites (P > 0.05). Local skin warming to 41.5 degrees C T(loc) increased CVC at both sites. This response was attenuated at l-NAA-treated sites (P < 0.05). In protocol 2, during normothermia, CVC did not differ between l-NAA-treated and untreated sites (P > 0.05). During heat stress, CVC rose to similar levels at l-NAA-treated and untreated sites (P > 0.05). We conclude that eNOS is predominantly responsible for NO generation in skin during responses to increased T(loc), but not during reflex responses to whole body heat stress.
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Affiliation(s)
- Dean L Kellogg
- Division of Geriatrics and Gerontology, Univ. of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
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Abstract
The physiological roles of constitutively expressed nitric oxide synthase (NOS) isoforms in humans, in vivo, are unknown. Cutaneous vasodilatation during both central nervous system-mediated, thermoregulatory reflex responses to whole-body heat stress and during peripheral axon reflex-mediated, local responses to skin warming in humans depend on nitric oxide (NO) generation by constitutively expressed NOS of uncertain isoform. We hypothesized that neuronal NOS (nNOS, NOS I) effects cutaneous vasodilatation during whole-body heat stress, but not during local skin warming. We examined the effects of the nNOS inhibitor 7-nitroindazole (7-NI) administered by intradermal microdialysis on vasodilatation induced by whole-body heat stress or local skin warming. Skin blood flow (SkBF) was monitored by laser-Doppler flowmetry (LDF). Blood pressure (MAP) was monitored and cutaneous vascular conductance calculated (CVC = LDF/MAP). In protocol 1, whole-body heat stress was induced with water-perfused suits. In protocol 2, local skin warming was induced through local warming units at LDF sites. At the end of each protocol, 56 mm sodium nitroprusside was perfused at microdialysis sites to raise SkBF to maximal levels for data normalization. 7-NI significantly attenuated CVC increases during whole-body heat stress (P < 0.05), but had no effect on CVC increases induced by local skin warming (P > 0.05). These diametrically opposite effects of 7-NI on two NO-dependent processes verify selective nNOS antagonism, thus proving that the nNOS isoform affects NO increases and hence vasodilatation during centrally mediated, reflex responses to whole-body heat stress, but not during locally mediated, axon reflex responses to local skin warming. We conclude that the constitutively expressed nNOS isoform has distinct physiological roles in cardiovascular control mechanisms in humans, in vivo.
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Affiliation(s)
- Dean L Kellogg
- Division of Geriatrics and Gerontology, Department of Medicine, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr, San Antonio, TX 78229, USA.
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Kellogg DL, Hodges GJ, Orozco CR, Phillips TM, Zhao JL, Johnson JM. Cholinergic mechanisms of cutaneous active vasodilation during heat stress in cystic fibrosis. J Appl Physiol (1985) 2007; 103:963-8. [PMID: 17600158 DOI: 10.1152/japplphysiol.00278.2007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To test the hypothesis that cutaneous active vasodilation in heat stress is mediated by a redundant cholinergic cotransmitter system, we examined the effects of atropine on skin blood flow (SkBF) increases during heat stress in persons with (CF) and without cystic fibrosis (non-CF). Vasoactive intestinal peptide (VIP) has been implicated as a mediator of cutaneous vasodilation in heat stress. VIP-containing cutaneous neurons are sparse in CF, yet SkBF increases during heat stress are normal. In CF, augmented ACh release or muscarinic receptor sensitivity could compensate for decreased VIP; if so, active vasodilation would be attenuated by atropine in CF relative to non-CF. Atropine was administered into skin by iontophoresis in seven CF and seven matched non-CF subjects. SkBF was monitored by laser-Doppler flowmetry (LDF) at atropine treated and untreated sites. Blood pressure [mean arterial pressure (MAP)] was monitored (Finapres), and cutaneous vascular conductance was calculated (CVC = LDF/MAP). The protocol began with a normothermic period followed by a 3-min cold stress and 30-45 min of heat stress. Finally, LDF sites were warmed to 42 degrees C to effect maximal vasodilation. CVC was normalized to its site-specific maximum. During heat stress, CVC increased in both CF and non-CF (P < 0.01). CVC increases were attenuated by atropine in both groups (P < 0.01); however, the responses did not differ between groups (P = 0.99). We conclude that in CF there is not greater dependence on redundant cholinergic mechanisms for cutaneous active vasodilation than in non-CF.
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Affiliation(s)
- D L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, Audie L. Murphy Memorial Veterans Hospital Division, San Antonio, TX 78229, USA.
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Chaurasia CS, Müller M, Bashaw ED, Benfeldt E, Bolinder J, Bullock R, Bungay PM, DeLange ECM, Derendorf H, Elmquist WF, Hammarlund-Udenaes M, Joukhadar C, Kellogg DL, Lunte CE, Nordstrom CH, Rollema H, Sawchuk RJ, Cheung BWY, Shah VP, Stahle L, Ungerstedt U, Welty DF, Yeo H. AAPS-FDA workshop white paper: microdialysis principles, application and regulatory perspectives. Pharm Res 2007; 24:1014-25. [PMID: 17458685 DOI: 10.1007/s11095-006-9206-z] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Accepted: 12/04/2006] [Indexed: 12/16/2022]
Abstract
Many decisions in drug development and medical practice are based on measuring blood concentrations of endogenous and exogenous molecules. Yet most biochemical and pharmacological events take place in the tissues. Also, most drugs with few notable exceptions exert their effects not within the bloodstream, but in defined target tissues into which drugs have to distribute from the central compartment. Assessing tissue drug chemistry has, thus, for long been viewed as a more rational way to provide clinically meaningful data rather than gaining information from blood samples. More specifically, it is often the extracellular (interstitial) tissue space that is most closely related to the site of action (biophase) of the drug. Currently microdialysis (microD) is the only tool available that explicitly provides data on the extracellular space. Although microD as a preclinical and clinical tool has been available for two decades, there is still uncertainty about the use of microD in drug research and development, both from a methodological and a regulatory point of view. In an attempt to reduce this uncertainty and to provide an overview of the principles and applications of microD in preclinical and clinical settings, an AAPS-FDA workshop took place in November 2005 in Nashville, TN, USA. Stakeholders from academia, industry and regulatory agencies presented their views on microD as a tool in drug research and development.
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Affiliation(s)
- Chandra S Chaurasia
- Division of Bioequivalence, Office of Generic Drugs, Food and Drug Administration, Rockville, MD, USA.
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Chaurasia CS, Müller M, Bashaw ED, Benfeldt E, Bolinder J, Bullock R, Bungay PM, DeLange ECM, Derendorf H, Elmquist WF, Hammarlund-Udenaes M, Joukhadar C, Kellogg DL, Lunte CE, Nordstrom CH, Rollema H, Sawchuk RJ, Cheung BWY, Shah VP, Stahle L, Ungerstedt U, Welty DF, Yeo H. AAPS-FDA workshop white paper: Microdialysis principles, application, and regulatory perspectives report from the Joint AAPS-FDA Workshop, November 4–5, 2005, Nashville, TN. AAPS J 2007. [DOI: 10.1208/aapsj0901006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
This review focuses on the neural and local mechanisms that have been demonstrated to effect cutaneous vasodilation and vasoconstriction in response to heat and cold stress in vivo in humans. First, our present understanding of the mechanisms by which sympathetic cholinergic nerves mediate cutaneous active vasodilation during reflex responses to whole body heating is discussed. These mechanisms include roles for cotransmission as well as nitric oxide (NO). Next, the mechanisms by which sympathetic noradrenergic nerves mediate cutaneous active vasoconstriction during whole body cooling are reviewed, including cotransmission by neuropeptide Y (NPY) acting through NPY Y1 receptors. Subsequently, current concepts for the mechanisms that effect local cutaneous vascular responses to direct skin warming are examined. These mechanisms include the roles of temperature-sensitive afferent neurons as well as NO in causing vasodilation during local heating of skin. This section is followed by a review of the mechanisms that cause local cutaneous vasoconstriction in response to direct cooling of the skin, including the dependence of these responses on intact sensory and sympathetic, noradrenergic innervation as well as roles for nonneural mechanisms. Finally, unresolved issues that warrant further research on mechanisms that control cutaneous vascular responses to heating and cooling are discussed.
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Affiliation(s)
- D L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, Audie L. Murphy Memorial Veterans Hospital Division, San Antonio, TX, USA.
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Royall DR, Gao JH, Kellogg DL. Insular Alzheimer's disease pathology as a cause of "age-related" autonomic dysfunction and mortality in the non-demented elderly. Med Hypotheses 2006; 67:747-58. [PMID: 16806725 DOI: 10.1016/j.mehy.2005.10.036] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Accepted: 10/28/2005] [Indexed: 10/24/2022]
Abstract
Only a few brain structures have been implicated in the autonomic control of blood pressure and heart rate. Among them are heteromodal association areas in the cortex, especially the insular cortex. Ischemic insular lesions have been associated with both cardiac arrhythmias and mortality. However, stroke may not be the only insular pathology with the potential to disrupt autonomic function. Alzheimer's disease (AD) is associated with both insular pathology and autonomic dysfunction. Alzheimer's dementia is merely the final stage of a pathological process that spans decades. Recent studies have demonstrated a hierarchichal sequence of AD pathology that includes the insular cortex. This may explain why AD has effects on BP and central autonomic cardio-regulatory functions. However, AD reaches the insular cortex at a "preclinical" stage in its development (i.e., before "dementia" can be diagnosed). Thus, AD pathology should also be considered as a possible explanation for autonomic morbidity and mortality in non-demented elderly persons. We hypothesize that autonomic dyscontrol, commonly seen in non-demented well elderly persons without significant cardiovascular disease (CVD), reflects subclinical stages of AD pathology affecting the insular cortex. If true, then preclinical AD pathology should be considered as a possible explanation for arrhythmia/fall related morbidity and mortality in non-demented elderly persons.
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Affiliation(s)
- Donald R Royall
- Department of Psychiatry, South Texas Veterans' Health System Audie L. Murphy Division GRECC and the University of Texas Health Science Center, 7703 Floyd Curl Dr., San Antonio, TX 78284-7792, United
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Abstract
Acetylcholine (ACh) can effect vasodilation by several mechanisms, including activation of endothelial nitric oxide (NO) synthase and prostaglandin (PG) production. In human skin, exogenous ACh increases both skin blood flow (SkBF) and bioavailable NO levels, but the relative increase is much greater in SkBF than NO. This led us to speculate ACh may dilate cutaneous blood vessels through PGs, as well as NO. To test this hypothesis, we performed a study in 11 healthy people. We measured SkBF by laser-Doppler flowmetry (LDF) at four skin sites instrumented for intradermal microdialysis. One site was treated with ketorolac (Keto), a nonselective cyclooxygenase antagonist. A second site was treated with NG-nitro-L-arginine methyl ester (L-NAME) to inhibit NO synthase. A third site was treated with a combination of Keto and L-NAME. The fourth site was an untreated control site. After the three treated sites received the different inhibiting agents, ACh was administered to all four sites by intradermal microdialysis. Finally, sodium nitroprusside (SNP) was administered to all four sites. Mean arterial pressure (MAP) was monitored by Finapres, and cutaneous vascular conductance (CVC) was calculated (CVC = LDF/MAP). For data analysis, CVC values for each site were normalized to their respective maxima as effected by SNP. The results showed that both Keto and L-NAME each attenuated the vasodilation induced by exogenous ACh (ACh control = 79 +/- 4% maximal CVC, Keto = 55 +/- 7% maximal CVC, L-NAME = 46 +/- 6% maximal CVC; P < 0.05, ACh vs. Keto or L-NAME). The combination of the two agents produced an even greater attenuation of ACh-induced vasodilation (31 +/- 5% maximal CVC; P < 0.05 vs. all other sites). We conclude that a portion of the vasodilation effected by exogenous ACh in skin is due to NO; however, a significant portion is also mediated by PGs.
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Affiliation(s)
- D L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
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Kashyap SR, Roman LJ, Lamont J, Masters BSS, Bajaj M, Suraamornkul S, Belfort R, Berria R, Kellogg DL, Liu Y, DeFronzo RA. Insulin resistance is associated with impaired nitric oxide synthase activity in skeletal muscle of type 2 diabetic subjects. J Clin Endocrinol Metab 2005; 90:1100-5. [PMID: 15562034 DOI: 10.1210/jc.2004-0745] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Type 2 diabetes is an insulin-resistant state characterized by hyperinsulinemia and accelerated atherosclerosis. In vitro and in vivo studies in rodents have suggested that nitric oxide generation plays an important role in glucose transport and insulin action. We determined nitric oxide synthase (NOS) activity in skeletal muscle of 10 type 2 diabetic (hemoglobin A(1C) = 6.8 +/- 0.1%) and 11 control subjects under basal conditions and during an 80 mU/m(2).min euglycemic insulin clamp performed with vastus lateralis muscle biopsies before and after 4 h of insulin. In diabetics, insulin-stimulated glucose disposal (Rd) was reduced by 50%, compared with controls (5.4 +/- 0.3 vs. 10.4 +/- 0.5 mg/kg.min, P < 0.01). Basal NOS activity was markedly reduced in the diabetic group (101 +/- 33 vs. 457 +/- 164 pmol/min.mg protein, P < 0.05). In response to insulin, NOS activity increased 2.5-fold in controls after 4 h (934 +/- 282 pmol/min.mg protein, P < 0.05 vs. basal), whereas insulin failed to stimulate NOS activity in diabetics (86 +/- 28 pmol/min.mg protein, P = NS from basal). Basal NOS protein content in muscle was similar in controls and diabetics and did not change following insulin. In controls, insulin-stimulated NOS activity correlated inversely with fasting plasma insulin concentration (r = -0.58, P = 0.05) and positively with Rd (r = 0.71, P = 0.03). In control and diabetic groups collectively, Rd correlated with insulin-stimulated NOS activity (r = 0.52, P = 0.02). We conclude that basal and insulin-stimulated muscle NOS activity is impaired in well-controlled type 2 diabetic subjects, and the defect in insulin-stimulated NOS activity correlates closely with the severity of insulin resistance. These results suggest that impaired NOS activity may play an important role in the insulin resistance in type 2 diabetic individuals.
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Affiliation(s)
- Sangeeta R Kashyap
- The University of Texas Health Science Center at San Antonio, Diabetes Division, Texas 78229, USA
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Abstract
This study examined whether nitric oxide (NO) is involved in the cutaneous response to reactive hyperemia (RH) in the human forearm. We enrolled seven healthy volunteers. NO concentrations were monitored using a NO selective amperometric electrode (ISO-NOP200, World Precision Instruments) inserted into the skin of the forearm. Laser-Doppler flowmetry (Moor Instruments) was used for monitoring skin blood flow (SkBF) at the same site. SkBF and NO levels were monitored and recorded continuously throughout the experiment. An intradermal microdialysis probe was inserted adjacent to the NO electrode for drug delivery. Data collection began 140 min after the NO electrodes and microdialysis probes were inserted. RH was achieved by the inflation of a blood pressure cuff to 25 mmHg above systolic pressure for 7 min after which the pressure in the cuff was abruptly released. Acetylcholine (ACh) was given by microdialysis probe at the end of RH study to verify the ability of the electrode system to detect changes in the NO concentration. SkBF and NO data before RH and immediately, 2, 5, 7, and 10 min after cuff deflation were used for analysis. SkBF increased immediately after release of the occlusion ( P < 0.0001) and remained elevated for 2 min. No significant NO changes occurred with the increases in LDF. ACh induced increases in both SkBF and NO ( P < 0.000 and P < 0.037, respectively). We conclude that RH increases SkBF by mechanisms that do not require a measurable increase in NO concentrations.
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Affiliation(s)
- J L Zhao
- Division of Geriatrics and Gerontology, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA
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Bennett LAT, Johnson JM, Stephens DP, Saad AR, Kellogg DL. Evidence for a role for vasoactive intestinal peptide in active vasodilatation in the cutaneous vasculature of humans. J Physiol 2003; 552:223-32. [PMID: 12847205 PMCID: PMC2343308 DOI: 10.1113/jphysiol.2003.042135] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Active vasodilatation (AVD) in human, non-glabrous skin depends on functional cholinergic fibres but not on acetylcholine (ACh). We tested whether AVD is a redundant system in which ACh and vasoactive intestinal polypeptide (VIP) are co-released from cholinergic nerves. (1) We administered VIP by intradermal microdialysis to four discrete areas of skin in the presence of different levels of the VIP receptor antagonist, VIP(10-28), also delivered by microdialysis. Skin blood flow (SkBF) was continuously monitored by laser Doppler flowmetry (LDF). Mean arterial pressure (MAP) was measured non-invasively and cutaneous vascular conductance (CVC) calculated as LDF/MAP. Subjects were supine and wore water-perfused suits to control whole-body skin temperature (Tsk) at 34 degrees C. Concentrations of 54 microM, 107 microM, or 214 microM VIP(10-28) were perfused via intradermal microdialysis at 2 microl min-1 for approximately 1 h. Then 7.5 microM VIP was added to the perfusate containing VIP(10-28) at the three concentrations or Ringer solution and perfusion was continued for 45-60 min. At the control site, this level of VIP caused approximately the vasodilatation typical of heat stress. All VIP(10-28)-treated sites displayed an attenuated dilatation in response to the VIP. The greatest attenuation was observed at the site that received 214 microM VIP(10-28) (P < 0.01). (2) We used 214 microM VIP(10-28) alone and with the iontophoretically administered muscarinic receptor antagonist atropine (400 microA cm-2, 45 s, 10 mM) in heated subjects to test the roles of VIP and ACh in AVD. Ringer solution and 214 microM VIP(10-28) were each perfused at two sites, one of which in each case was pretreated with atropine. After 1 h of VIP(10-28) treatment, individuals underwent 45-60 min of whole-body heating (Tsk to 38.5 degrees C). VIP(10-28), alone or in combination with atropine, attenuated the increase in CVC during heat stress, suggesting an important role for VIP in AVD.
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Affiliation(s)
- Lee Ann T Bennett
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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Abstract
To examine the role of nitric oxide (NO) in cutaneous active vasodilation, we measured the NO concentration from skin before and during whole body heat stress in nine healthy subjects. A forearm site was instrumented with a NO-selective, amperometric electrode and an adjacent intradermal microdialysis probe. Skin blood flow (SkBF) was monitored by laser-Doppler flowmetry (LDF). NO concentrations and LDF were measured in normothermia and heat stress. After heat stress, a solution of ACh was perfused through the microdialysis probe to pharmacologically generate NO and verify the electrode's function. During whole body warming, both SkBF and NO concentrations began to increase at the same internal temperature. Both SkBF and NO concentrations increased during heat stress (402 +/- 76% change from LDF baseline, P < 0.05; 22 +/- 5% change from NO baseline, P < 0.05). During a second baseline condition after heat stress, ACh perfusion led to increases in both SkBF and NO concentrations (496 +/- 119% change from LDF baseline, P < 0.05; 16 +/- 10% change from NO baseline, P < 0.05). We conclude that NO does increase in skin during heat stress in humans, attendant to active vasodilation. This result suggests that NO has a role beyond that of a permissive factor in the process; rather, NO may well be an effector of cutaneous vasodilation during heat stress.
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Affiliation(s)
- D L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, San Antonio, Texas 78229, USA.
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Abstract
To test the hypothesis that bradykinin effects cutaneous active vasodilation during hyperthermia, we examined whether the increase in skin blood flow (SkBF) during heat stress was affected by blockade of bradykinin B(2) receptors with the receptor antagonist HOE-140. Two adjacent sites on the forearm were instrumented with intradermal microdialysis probes for local delivery of drugs in eight healthy subjects. HOE-140 was dissolved in Ringer solution (40 microM) and perfused at one site, whereas the second site was perfused with Ringer alone. SkBF was monitored by laser-Doppler flowmetry (LDF) at both sites. Mean arterial pressure (MAP) was monitored from a finger, and cutaneous vascular conductance (CVC) was calculated (CVC = LDF/MAP). Water-perfused suits were used to control body temperature and evoke hyperthermia. After hyperthermia, both microdialysis sites were perfused with 28 mM nitroprusside to effect maximal vasodilation. During hyperthermia, CVC increased at HOE-140 (69 +/- 2% maximal CVC, P < 0.01) and untreated sites (65 +/- 2% maximal CVC, P < 0.01). These responses did not differ between sites (P > 0.05). Because the bradykinin B(2)-receptor antagonist HOE-140 did not alter SkBF responses to heat stress, we conclude that bradykinin does not mediate cutaneous active vasodilation.
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Affiliation(s)
- D L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA.
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Rao PK, Pérgola PE, Habiba NM, Liu Y, Kellogg DL. Double injection vs skin microdialysis technique in minimally invasive in vivo pharmacology. Br J Clin Pharmacol 2002; 54:333-4. [PMID: 12236855 PMCID: PMC1874415 DOI: 10.1046/j.1365-2125.2002.01655.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Kellogg DL, Liu Y, Pérgola PE. Selected contribution: Gender differences in the endothelin-B receptor contribution to basal cutaneous vascular tone in humans. J Appl Physiol (1985) 2001; 91:2407-11; discussion 2389-90. [PMID: 11641388 DOI: 10.1152/jappl.2001.91.5.2407] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To test whether the contribution of endothelin-B (ET-B) receptors to resting vascular tone differs between genders, we administered the ET-B receptor antagonist BQ-788 into the forearm skin of 11 male and 11 female subjects by intradermal microdialysis. Skin blood flow was measured using laser-Doppler flowmetry at the microdialysis site. The probe was perfused with Ringer solution alone, followed by BQ-788 (150 nM) and finally sodium nitroprusside (28 mM) to effect maximal cutaneous vasodilation. Cutaneous vascular conductance (CVC) was calculated (laser-Doppler flowmetry/mean arterial pressure) and normalized to maximal levels (%max). In male subjects, baseline CVC was (mean +/- SE) 19 +/- 3%max and increased to 26 +/- 5%max with BQ-788 (P < 0.05 vs. baseline). In female subjects, baseline CVC was 13 +/- 1%max and decreased to 10 +/- 1%max in response to BQ-788. CVC responses to BQ-788 differed with gender (P < 0.05); thus the contribution of ET-B receptors to resting cutaneous vascular tone differs between men and women. In men, ET-B receptors mediate tonic vasoconstriction, whereas, in women, ET-B receptors mediate tonic vasodilation.
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Affiliation(s)
- D L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, Audie L. Murphy Memorial Veterans Hospital Division, San Antonio, Texas 78229, USA.
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Stagni G, O'Donnell D, Liu YJ, Kellogg DL, Morgan T, Shepherd AM. Intradermal microdialysis: kinetics of iontophoretically delivered propranolol in forearm dermis. J Control Release 2000; 63:331-9. [PMID: 10601728 DOI: 10.1016/s0168-3659(99)00214-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Intradermal microdialysis permits us to measure the concentration in dermis of drugs applied to the skin. Microdialysis is especially efficient in sampling water-soluble molecules. Consequently, it appears particularly suitable to study current based delivery systems like iontophoresis that deliver ions or highly polar molecules. The purpose of this work was to evaluate the adequacy of a skin microdialysis technique to characterize and quantify the dermatopharmacokinetics of iontophoretically delivered propranolol in the dermis of healthy human volunteers. Linear microdialysis probes were inserted in the subject's forearm skin and an iontophoresis device was installed above them. Constant current was applied for two periods of 1 h each separated by a 1-h interval. Dialysate samples were collected every 6 min for 4.4 h and analyzed by HPLC. Probes were always placed in the dermis as measured by ultrasonography. Propranolol was detectable in the dialysate. It was possible to build detailed concentration vs. midtime profiles that mirrored the current applied. Elimination rate from the dermis had first-order kinetics and was similar in all subjects. Quantification of the absorption process, indexed by lag-time and area under the concentration curve showed a high inter- and intrasubject variability that did not correlate with probe depth.
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Affiliation(s)
- G Stagni
- Division of Clinical Pharmacology, Departments of Pharmacology and Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
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Abstract
Local warming of skin induces vasodilation by unknown mechanisms. To test whether nitric oxide (NO) is involved, we examined effects of NO synthase (NOS) inhibition with NG-nitro-L-arginine methyl ester (L-NAME) on vasodilation induced by local warming of skin in six subjects. Two adjacent sites on the forearm were instrumented with intradermal microdialysis probes for delivery of L-NAME and sodium nitroprusside. Skin blood flow was monitored by laser-Doppler flowmetry (LDF) at microdialysis sites. Local temperature (Tloc) of the skin at both sites was controlled with special LDF probe holders. Mean arterial pressure (MAP; Finapres) was measured and cutaneous vascular conductance calculated (CVC = LDF/MAP = mV/mmHg). Data collection began with a control period (Tloc at both sites = 34 degrees C). One site was then warmed to 41 degrees C while the second was maintained at 34 degrees C. Local warming increased CVC from 1.44 +/- 0.41 to 4.28 +/- 0.60 mV/mmHg (P < 0.05). Subsequent L-NAME administration reduced CVC to 2.28 +/- 0.47 mV/mmHg (P < 0.05 vs. heating), despite the continued elevation of Tloc. At a Tloc of 34 degrees C, L-NAME reduced CVC from 1.17 +/- 0.23 to 0.75 +/- 0.11 mV/mmHg (P < 0.05). Administration of sodium nitroprusside increased CVC to levels no different from those induced by local warming. Thus NOS inhibition attenuated, and sodium nitroprusside restored, the cutaneous vasodilation induced by elevation of Tloc; therefore, the mechanism of cutaneous vasodilation by local warming requires NOS generation of NO.
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Affiliation(s)
- D L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, University of Texas Health Science Center at San Antonio, 78284, USA.
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Abstract
When microdialysis (MD) is used to study dermal delivery by iontophoresis, the effects of current may alter MD recovery through an increase in temperature, a change of pH, hyperemia, and dermal hydration. The objective of this work is to assess whether these effects of current may cause a measurable change in the retrodialysis of a model compound (sodium fluorescein, Fl). Two linear MD-probes were inserted in the forearm dermis of healthy human volunteers and perfused with Ringer's solution containing Fl. Two identical iontophoresis chambers (IC, filled with NaCl in propylene glycol) were placed over the MD-probes. Each IC included a laser Doppler flowmetry probe to monitor skin blood flow. At one IC, current was applied for two periods of 30 min each, separated by 30 min of no current. No current was applied to the control site. Dialysate samples were collected every 5 min and analyzed for Fl by HPLC. Skin blood flow increased in response to iontophoresis, on average, 570% compared to the control site. However, there was no difference in the recovery of Fl between the current-active site versus the control site, and between the period with applied current versus the period with no current. In conclusion, iontophoretic current did not affect intradermal MD recovery.
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Affiliation(s)
- G Stagni
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, 78284-6205, USA.
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Abstract
Whether nitric oxide (NO) is involved in cutaneous active vasodilation during hyperthermia in humans is unclear. We tested for a role of NO in this process during heat stress (water-perfused suits) in seven healthy subjects. Two forearm sites were instrumented with intradermal microdialysis probes. One site was perfused with the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) dissolved in Ringer solution to abolish NO production. The other site was perfused with Ringer solution only. At those sites, skin blood flow (laser-Doppler flowmetry) and sweat rate were simultaneously and continuously monitored. Cutaneous vascular conductance, calculated from laser-Doppler flowmetry and mean arterial pressure, was normalized to maximal levels as achieved by perfusion with the NO donor nitroprusside through the microdialysis probes. Under normothermic conditions, L-NAME did not significantly reduce cutaneous vascular conductance. During hyperthermia, with skin temperature held at 38-38.5 degreesC, internal temperature rose from 36.66 +/- 0.10 to 37.34 +/- 0.06 degreesC (P < 0.01). Cutaneous vascular conductance at untreated sites increased from 12 +/- 2 to 44 +/- 5% of maximum, but only rose from 13 +/- 2 to 30 +/- 5% of maximum at L-NAME-treated sites (P < 0.05 between sites) during heat stress. L-NAME had no effect on sweat rate (P > 0.05). Thus cutaneous active vasodilation requires functional NO synthase to achieve full expression.
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Affiliation(s)
- D L Kellogg
- Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, Audie L. Murphy Division, San Antonio 78284, USA.
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Kellogg DL, Morris SR, Rodriguez SB, Liu Y, Grossmann M, Stagni G, Shepherd AM. Thermoregulatory reflexes and cutaneous active vasodilation during heat stress in hypertensive humans. J Appl Physiol (1985) 1998; 85:175-80. [PMID: 9655772 DOI: 10.1152/jappl.1998.85.1.175] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
During dynamic exercise in the heat, increases in skin blood flow are attenuated in hypertensive subjects when compared with normotensive subjects. We studied responses to passive heat stress (water-perfused suits) in eight hypertensive and eight normotensive subjects. Forearm blood flow was measured by venous-occlusion plethysmography, mean arterial pressure (MAP) was measured by Finapres, and forearm vascular conductance (FVC) was calculated. Bretylium tosylate (BT) iontophoresis was used to block active vasoconstriction in a small area of skin. Skin blood flow was indexed by laser-Doppler flowmetry at BT-treated and untreated sites, and cutaneous vascular conductance was calculated. In normothermia, FVC was lower in hypertensive than in normotensive subjects (P < 0.01). During heat stress, FVC rose to similar levels in both groups (P > 0.80); concurrent cutaneous vascular conductance increases were unaffected by BT treatment (P > 0.60). MAP was greater in hypertensive than in normotensive subjects during normothermia (P < 0.05, hypertensive vs. normotensive subjects). During hyperthermia, MAP fell in hypertensive subjects but showed no statistically significant change in normotensive subjects (P < 0.05, hypertensive vs. normotensive subjects). The internal temperature at which vasodilation began did not differ between groups (P > 0.80). FVC is reduced during normothermia in unmedicated hypertensive subjects; however, they respond to passive heat stress in a fashion no different from normotensive subjects.
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Affiliation(s)
- D L Kellogg
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284, USA.
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Abstract
We sought to identify whether reductions in cutaneous active vasodilation during simulated orthostasis could be assigned solely to cardiopulmonary or to carotid baroreflexes by unloading cardiopulmonary baroreceptors with low levels of lower body negative pressure (LBNP) or unloading carotid baroreceptors with external pressure applied over the carotid sinus area [carotid pressure (CP)]. Skin blood flow was measured at a site at which adrenergic function was blocked via bretylium tosylate iontophoresis and at an unblocked site. During LBNP of -5 and -10 mmHg in hyperthermia, neither heart rate (HR) nor cutaneous vascular conductance (CVC) at either site changed (P > 0.05 for both), whereas forearm vascular conductance (FVC) was reduced (-5 mmHg: from 21.6 +/- 4.8 to 19.8 +/- 4.1 FVC units, P = 0.05; -10 mmHg: from 22.3 +/- 4.0 to 19.3 +/- 3.7 FVC units, P = 0.002). LBNP of -30 mmHg in hyperthermia reduced CVC at both sites (untreated: from 51.9 +/- 5.7 to 43.2 +/- 5.1% maximum, P = 0.02; bretylium tosylate: from 60.9 +/- 5.4 to 53.2 +/- 4.4% maximum, P = 0.02), reduced FVC (from 23.2 +/- 3.6 to 18.1 +/- 3.3 FVC units; P = 0.002), and increased HR (from 83 +/- 4 to 101 +/- 3 beats/min; P = 0.003). Pulsatile CP (45 mmHg) did not affect FVC or CVC during normothermia or hyperthermia (P > 0.05). However, HR and mean arterial pressure were elevated during CP in both thermal conditions (both P < 0.05). These results suggest that neither selective low levels of cardiopulmonary baroreceptor unloading nor selective carotid baroreceptor unloading can account for the inhibition of cutaneous active vasodilator activity seen with simulated orthostasis.
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Affiliation(s)
- C G Crandall
- Department of Physiology, University of Texas Health Science Center at San Antonio 78284, USA
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Abstract
We examined the independent roles of whole body skin temperature (Tsk) and tissue temperature (local temperature, Tloc) in the control of skin blood flow (SBF) during cooling and the roles of the vasoconstrictor (VC) and active vasodilator (AVD) systems in mediating these effects. SBF was monitored by laser-Doppler flowmetry (LDF) at untreated sites and sites with local VC blockade by pretreatment with bretylium (BT). Seven subjects underwent four sessions of moderate bicycle exercise (20-30 min duration) at neutral Tsk and Tloc (34 degrees C), neutral Tsk and cool Tloc (27 degrees C), low Tsk (28 degrees C) and neutral Tloc, and low Tsk and Tloc. Cutaneous vascular conductance (CVC; LDF/mean arterial pressure) was expressed relative to the maximum. Cool Tsk increased the threshold level of internal temperature at which CVC began to rise equally at BT-treated and untreated sites (P < 0.05). The rate of increase in CVC relative to internal temperature was reduced by local cooling. BT pretreatment partially reversed this effect (P < 0.05). Thus a cool environment results in reflex inhibition of the onset of AVD activity by cool Tsk and a reduced rate of increase in CVC due, in part, to norepinephrine release stimulated by cool Tloc.
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Affiliation(s)
- P E Pérgola
- Department of Physiology, University of Texas Health Science Center at San Antonio 78284-7756, USA
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47
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Kellogg DL, Pérgola PE, Piest KL, Kosiba WA, Crandall CG, Grossmann M, Johnson JM. Cutaneous active vasodilation in humans is mediated by cholinergic nerve cotransmission. Circ Res 1995; 77:1222-8. [PMID: 7586235 DOI: 10.1161/01.res.77.6.1222] [Citation(s) in RCA: 270] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
During heat stress, increases in blood flow in nonglabrous skin in humans are mediated through active vasodilation by an unknown neurotransmitter mechanism. To investigate this mechanism, a three-part study was performed to determine the following: (1) Is muscarinic receptor activation necessary for active cutaneous vasodilation? We iontophoretically applied atropine to a small area of forearm skin. At that site and an untreated control site, we measured the vasomotor (laser-Doppler blood flow [LDF]) and sudomotor (relative humidity) responses to whole-body heat stress. Blood pressure was monitored. Cutaneous vascular conductance (CVC) was calculated (LDF divided by mean arterial pressure). Sweating was blocked at treated sites only. CVC rose at both sites (P < .05 at each site); thus, cutaneous active vasodilation is not effected through muscarinic receptors. (2) Are nonmuscarinic cholinergic receptors present on cutaneous arterioles? Acetylcholine (ACh) was iontophoretically applied to forearm skin at sites pretreated by atropine iontophoresis and at untreated sites. ACh increased CVC at untreated sites (P < .05) but not at atropinized sites. Thus, the only functional cholinergic receptors on cutaneous vessels are muscarinic. (3) Does cutaneous active vasodilation involve cholinergic nerve cotransmission? Botulinum toxin was injected intradermally in the forearm to block release of ACh and any coreleased neurotransmitters. Heat stress was performed as in part 1 of the study. At treated sites, CVC and relative humidity remained at baseline levels during heat stress (P > .05). Active vasodilator and sudomotor responses to heat stress were abolished by botulinum toxin. We conclude that cholinergic nerve activation mediates cutaneous active vasodilation through release of an unknown cotransmitter, not through ACh.
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Affiliation(s)
- D L Kellogg
- Department of Medicine, University of Texas Health Science Center at San Antonio 78284, USA
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48
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Abstract
To identify whether isometric handgrip exercise (IHG) affects cutaneous vasoconstrictor and/or active vasodilator activities, seven subjects (6 men and 1 woman) performed 30% maximal voluntary contraction of a forearm under normothermic (1 bout) and hyperthermic (2 bouts) conditions. Skin blood flow was indexed by laser-Doppler flowmetry at a contralateral forearm site at which adrenergic vasoconstrictor function was blocked by iontophoresis of bretylium tosylate (BT) and therefore only has active vasodilation as a mechanism for reflex control. Skin blood flow was also monitored at an adjacent untreated site. Cutaneous vascular conductance (CVC) was calculated from the flow signal and noninvasive blood pressure. CVC was normalized to the value obtained from maximal vasodilation at that site. Sweat rate (SR) was measured at the same locations. During normothermia, IHG did not affect CVC at the control or BT-treated sites, nor did IHG affect SR (P > 0.05). The second bout of IHG in hyperthermia evoked significant reductions in CVC at the untreated (69.4 +/- 3.4 to 58.9 +/- 2.5% of maximum, P < 0.05) and BT-treated sites (75.4 +/- 6.1 to 64.4 +/- 6.2% of maximum, P < 0.05), whereas SR significantly increased (0.62 +/- 0.16 to 0.70 +/- 0.17 mg.cm-2.min-1, P < 0.05). These findings uniquely show that, in hyperthermia, IHG reduces active vasodilator activity while at the same time sudomotor activity is increasing. This suggests independent control of these effectors.
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Affiliation(s)
- C G Crandall
- Department of Physiology, University of Texas Health Science Center, San Antonio 78284, USA
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49
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Grossmann M, Jamieson MJ, Kellogg DL, Kosiba WA, Pergola PE, Crandall CG, Shepherd AM. The effect of iontophoresis on the cutaneous vasculature: evidence for current-induced hyperemia. Microvasc Res 1995; 50:444-52. [PMID: 8583956 DOI: 10.1006/mvre.1995.1070] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Combining laser-Doppler blood flux measurements of the skin microcirculation with iontophoresis of vasoactive agents is a promising noninvasive tool for pharmacological studies. However, preliminary observations in our laboratories suggested significant current-associated vasodilation when an expected vasoconstrictor (NG-monomethyl-L-arginine acetate) was iontophoresed. The present study was designed to define nonspecific current-related versus specific pharmacological effects of iontophoretically administered ions on the cutaneous vasculature. Dose-response studies to a series of anions (nitrite, chloride, acetate, and bicarbonate) and cations (sodium, lithium, and acetylcholine) were carried out in six healthy volunteers (three male) by iontophoresis to the forearm skin on separate days. Laser-Doppler flux was measured at the same sites. All ions caused dose-dependent vasodilation. There was no difference in the response between chloride, bicarbonate, or acetate and nitrite, the nitric oxide donor. The acetylcholine dose response was shifted rightward after atropine pretreatment. Cutaneous vascular responses to iontophoresis comprise nonspecific, current-induced hyperemia and specific effects of the administered agent. Acetylcholine appears to cause muscarinic and current-induced dilatation. Nitrite may cause current-induced hyperemia alone. Current-induced hyperemia should be considered in interpreting the acute cutaneous vascular responses to iontophoretically administered agents in humans.
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Affiliation(s)
- M Grossmann
- Department of Pharmacology, University of Texas Health Science Center, San Antonio 78284-6205, USA
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50
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Abstract
OBJECTIVE The duration of direct current (DC) iontophoresis is limited to 10- to 15-minute periods because of electrochemical burns from hydrogen and hydroxide ions generated by the DC current. A new iontophoretic device, the Lectro Patch, uses a low-frequency alternating current (AC). AC current is theorized to generate H+ ions during one phase and OH- when the current reverses polarity, thus possibly neutralizing pH changes and avoiding burns. This study examined this possibility and evaluated drug delivery with AC iontophoresis, using hydroxocobalamin. DESIGN A known amount of hydroxocobalamin dissolved in 6mL of water was loaded in Lectro Patches, two of which were then taped on the forearms of 10 patient volunteers. One patch was activated to deliver drug by AC iontophoresis. The second patch was not activated and served as a control for delivery by diffusion. Trials were run for 2 and 4 hours, with both 1,000 micrograms/mL and 2,000 micrograms/mL concentrations. SETTING Study was conducted with inpatients in an extended care setting using volunteers. MAIN OUTCOME MEASURES Amounts of hydroxocobalamin remaining in the Lectro Patches after iontophoresis were assayed by spectrophotometry. Data were analyzed by ANOVA. RESULTS No burns occurred. Significantly greater losses occurred with 4 hours of iontophoresis than with 2 hours (p < 0.05). There was no significant effect of changing the concentration of hydroxocobalamin. CONCLUSIONS AC iontophoresis avoids electrochemical burns; charged drugs can be delivered by AC iontophoresis; and delivery of drug increases with duration of application.
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Affiliation(s)
- J P Howard
- Department of Medicine, University of Texas Health Science Center, San Antonio 78284-7756, USA
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