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Sharma A, Behl T, Sharma L, Shah OP, Yadav S, Sachdeva M, Rashid S, Bungau SG, Bustea C. Exploring the molecular pathways and therapeutic implications of angiogenesis in neuropathic pain. Biomed Pharmacother 2023; 162:114693. [PMID: 37062217 DOI: 10.1016/j.biopha.2023.114693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 03/26/2023] [Accepted: 04/10/2023] [Indexed: 04/18/2023] Open
Abstract
Recently, much attention has been paid to chronic neuro-inflammatory condition underlying neuropathic pain. It is generally linked with thermal hyperalgesia and tactile allodynia. It results due to injury or infection in the nervous system. The neuropathic pain spectrum covers a variety of pathophysiological states, mostly involved are ischemic injury viral infections associated neuropathies, chemotherapy-induced peripheral neuropathies, autoimmune disorders, traumatic origin, hereditary neuropathies, inflammatory disorders, and channelopathies. In CNS, angiogenesis is evident in inflammation of neurons and pain in bone cancer. The role of chemokines and cytokines is dualistic; their aggressive secretion produces detrimental effects, leading to neuropathic pain. However, whether the angiogenesis contributes and exists in neuropathic pain remains doubtful. In the present review, we elucidated summary of diverse mechanisms of neuropathic pain associated with angiogenesis. Moreover, an overview of multiple targets that have provided insights on the VEGF signaling, signaling through Tie-1 and Tie-2 receptor, erythropoietin pathway promoting axonal growth are also discussed. Because angiogenesis as a result of these signaling, results in inflammation, we focused on the mechanisms of neuropathic pain. These factors are mainly responsible for the activation of post-traumatic regeneration of the PNS and CNS. Furthermore, we also reviewed synthetic and herbal treatments targeting angiogenesis in neuropathic pain.
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Affiliation(s)
- Aditi Sharma
- School of Pharmaceutical Sciences, Shoolini University, Solan 173211, Himachal Pradesh, India
| | - Tapan Behl
- School of Health Sciences and Technology, University of Petroleum and Energy Studies, Bidholi, 248007 Dehradun, Uttarakhand, India.
| | - Lalit Sharma
- School of Pharmaceutical Sciences, Shoolini University, Solan 173211, Himachal Pradesh, India
| | - Om Prakash Shah
- School of Pharmaceutical Sciences, Shoolini University, Solan 173211, Himachal Pradesh, India
| | - Shivam Yadav
- Department of Pharmaceutical Sciences, School of Pharmaceutical Sciences, Chhatrapati Shahu ji Maharaj University, Kanpur 208024, Uttar Pradesh, India
| | - Monika Sachdeva
- Fatima College of Health Sciences, Al Ain 00000, United Arab Emirates
| | - Summya Rashid
- Department of Pharmacology & Toxicology, College of Pharmacy, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
| | - Simona Gabriela Bungau
- Department of Pharmacy, Faculty of Medicine and Pharmacy, University of Oradea, Oradea 410028, Romania; Doctoral School of Biomedical Sciences, University of Oradea, Oradea 410028, Romania.
| | - Cristiana Bustea
- Department of Preclinical Disciplines, Faculty of Medicine and Pharmacy, University of Oradea, Oradea 410073, Romania
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Lee J, Lee D, Suh GH, Choi J. Contrast-enhanced ultrasonography for evaluation of the blood perfusion of sciatic nerves in healthy dogs. Vet Radiol Ultrasound 2023; 64:322-329. [PMID: 36264587 DOI: 10.1111/vru.13180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Revised: 08/27/2022] [Accepted: 08/27/2022] [Indexed: 11/30/2022] Open
Abstract
Blood supply to the peripheral nerves is essential for fulfilling their structural and functional requirements. This prospective, experimental, exploratory study aimed to assess the feasibility of contrast-enhanced ultrasonography (CEUS) for evaluating blood perfusion of the sciatic nerve in normal dogs. Contrast-enhanced ultrasonography examinations were performed on the bilateral sciatic nerves after bolus injection of Sonazoid™ (0.015 mL/kg) in 12 healthy Beagles for 150 s. Then, qualitative assessment of the wash-in timing, degree and enhancement patterns, and quantitative measurement of the peak intensity and time to peak intensity were performed from the sciatic nerve. The results were compared to those obtained from the adductor muscle around the nerve and caudal gluteal artery. After contrast agent injection, the sciatic nerve was enhanced at approximately 13-14 s, immediately after wash-in of the caudal gluteal artery. The peak intensity of the sciatic nerve was significantly lower than that of the caudal gluteal artery and higher than that of the adductor muscle. The time to peak intensity was significantly slower than that of the caudal gluteal artery; but was not significantly different from that of the adductor muscle. There were no significant differences in the peak intensity and time to peak intensity between the left and right sciatic nerves. These results demonstrate the feasibility of CEUS to assess blood perfusion of the sciatic nerve in healthy dogs qualitatively and quantitatively. This result from healthy dogs could serve as a reference for further studies that evaluate the sciatic nerve under pathological conditions.
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Affiliation(s)
- Juryeong Lee
- Department of veterinary Medical Imaging, College of Veterinary Medicine, Chonnam National University, Gwangju, South Korea
| | - Dongjae Lee
- Department of Veterinary Medical Imaging, College of Veterinary medicine and Research Institute for Veterinary Science, Seoul National University, Seoul, South Korea
| | - Guk-Hyun Suh
- Department of veterinary Medical Imaging, College of Veterinary Medicine, Chonnam National University, Gwangju, South Korea
| | - Jihye Choi
- Department of Veterinary Medical Imaging, College of Veterinary medicine and Research Institute for Veterinary Science, Seoul National University, Seoul, South Korea
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Prospects for the Personalized Multimodal Therapy Approach to Pain Management via Action on NO and NOS. Molecules 2021; 26:molecules26092431. [PMID: 33921984 PMCID: PMC8122598 DOI: 10.3390/molecules26092431] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/17/2021] [Accepted: 04/19/2021] [Indexed: 12/15/2022] Open
Abstract
Chronic pain syndromes are an important medical problem generated by various molecular, genetic, and pathophysiologic mechanisms. Back pain, neuropathic pain, and posttraumatic pain are the most important pathological processes associated with chronic pain in adults. Standard approaches to the treatment of them do not solve the problem of pain chronicity. This is the reason for the search for new personalized strategies for the prevention and treatment of chronic pain. The nitric oxide (NO) system can play one of the key roles in the development of peripheral pain and its chronicity. The purpose of the study is to review publications devoted to changes in the NO system in patients with peripheral chronical pain syndromes. We have carried out a search for the articles published in e-Library, PubMed, Oxford Press, Clinical Case, Springer, Elsevier, and Google Scholar databases. The search was carried out using keywords and their combinations. The role of NO and NO synthases (NOS) isoforms in peripheral pain development and chronicity was demonstrated primarily from animal models to humans. The most studied is the neuronal NOS (nNOS). The role of inducible NOS (iNOS) and endothelial NOS (eNOS) is still under investigation. Associative genetic studies have shown that single nucleotide variants (SNVs) of NOS1, NOS2, and NOS3 genes encoding nNOS, iNOS, and eNOS may be associated with acute and chronic peripheral pain. Prospects for the use of NOS inhibitors to modulate the effect of drugs used to treat peripheral pain syndrome are discussed. Associative genetic studies of SNVs NOS1, NOS2, and NOS3 genes are important for understanding genetic predictors of peripheral pain chronicity and development of new personalized pharmacotherapy strategies.
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Involvement of oxidative stress in increased peripheral nerve firing during spontaneous dysesthesia in a mouse model of ischemia-reperfusion. Neurosci Lett 2016; 631:109-114. [DOI: 10.1016/j.neulet.2016.08.034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 08/18/2016] [Accepted: 08/18/2016] [Indexed: 12/21/2022]
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Sasaki A, Mizoguchi S, Kagaya K, Shiro M, Sakai A, Andoh T, Kino Y, Taniguchi H, Saito Y, Takahata H, Kuraishi Y. A Mouse Model of Peripheral Postischemic Dysesthesia: Involvement of Reperfusion-Induced Oxidative Stress and TRPA1 Channel. J Pharmacol Exp Ther 2014; 351:568-75. [DOI: 10.1124/jpet.114.217570] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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Olver TD, McDonald MW, Grisé KN, Dey A, Allen MD, Medeiros PJ, Lacefield JC, Jackson DN, Rice CL, Melling CWJ, Noble EG, Shoemaker JK. Exercise training enhances insulin-stimulated nerve arterial vasodilation in rats with insulin-treated experimental diabetes. Am J Physiol Regul Integr Comp Physiol 2014; 306:R941-50. [DOI: 10.1152/ajpregu.00508.2013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin stimulates nerve arterial vasodilation through a nitric oxide (NO) synthase (NOS) mechanism. Experimental diabetes reduces vasa nervorum NO reactivity. Studies investigating hyperglycemia and nerve arterial vasodilation typically omit insulin treatment and use sedentary rats resulting in severe hyperglycemia. We tested the hypotheses that 1) insulin-treated experimental diabetes and inactivity (DS rats) will attenuate insulin-mediated nerve arterial vasodilation, and 2) deficits in vasodilation in DS rats will be overcome by concurrent exercise training (DX rats; 75–85% V̇o2 max, 1 h/day, 5 days/wk, for 10 wk). The baseline index of vascular conductance values (VCi = nerve blood flow velocity/mean arterial blood pressure) were similar ( P ≥ 0.68), but peak VCi and the area under the curve (AUCi) for the VCi during a euglycemic hyperinsulinemic clamp (EHC; 10 mU·kg−1·min−1) were lower in DS rats versus control sedentary (CS) rats and DX rats ( P ≤ 0.01). Motor nerve conduction velocity (MNCV) was lower in DS rats versus CS rats and DX rats ( P ≤ 0.01). When compared with DS rats, DX rats expressed greater nerve endothelial NOS (eNOS) protein content ( P = 0.04). In a separate analysis, we examined the impact of diabetes in exercise-trained rats alone. When compared with exercise-trained control rats (CX), DX rats had a lower AUCi during the EHC, lower MNCV values, and lower sciatic nerve eNOS protein content ( P ≤ 0.03). Therefore, vasa nervorum and motor nerve function are impaired in DS rats. Such deficits in rats with diabetes can be overcome by concurrent exercise training. However, in exercise-trained rats (CX and DX groups), moderate hyperglycemia lowers vasa nervorum and nerve function.
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Affiliation(s)
- T. Dylan Olver
- Neurovascular Research Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Matthew W. McDonald
- Exercise Biochemistry Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Kenneth N. Grisé
- Exercise Biochemistry Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Adwitia Dey
- Exercise Biochemistry Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Matti D. Allen
- Neuromusclar Research Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Philip J. Medeiros
- A. C. Burton Laboratory for Vascular Research, Department of Medical Biophysics, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - James C. Lacefield
- Department of Electrical and Computer Engineering, Department of Medical Biophysics and Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
| | - Dwayne N. Jackson
- A. C. Burton Laboratory for Vascular Research, Department of Medical Biophysics, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Charles L. Rice
- Neuromusclar Research Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario, Canada; and
| | - C. W. James Melling
- Exercise Biochemistry Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Earl G. Noble
- Exercise Biochemistry Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - J. Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
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Jin HY, Cha YS, Baek HS, Park TS. Neuroprotective effects of Vitis vinifera extract on prediabetic mice induced by a high-fat diet. Korean J Intern Med 2013; 28:579-86. [PMID: 24009454 PMCID: PMC3759764 DOI: 10.3904/kjim.2013.28.5.579] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 06/29/2012] [Accepted: 07/18/2012] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND/AIMS Vitis vinifera grape seed extract (VVE) contains oligomeric proanthocyanidins that show antioxidant and free radical-scavenging activities. We evaluated VVE for its neuroprotective effect in prediabetic mice induce by a high-fat diet (HD). METHODS Mice were divided into four groups according to VVE dose: those fed a normal diet (ND; n = 10), HD (n = 10), HD with 100 mg/kg VVE (n = 10), and HD with 250 mg/kg VVE (n = 10). After 12 weeks, immunohistochemical analyses were carried out using a polyclonal antibody against antiprotein gene product 9.5 (protein-gene-product, 9.5), and intraepidermal innervation was subsequently quantified as nerve fiber abundance per unit length of epidermis (intraepidermal nerve fiber, IENF/mm). RESULTS Daily administration of VVE at doses of 100 or 250 mg/kg for 12 weeks protected HD mice from nerve fiber loss compared to untreated mice, as follows (IENF/mm): controls (40.95 ± 5.40), HD (28.70 ± 6.37), HD with 100 mg/kg (41.14 ± 1.12), and HD with 250 mg/kg (48.98 ± 7.01; p < 0.05, HD with VVE vs. HD). CONCLUSIONS This study provides scientific support for the therapeutic potential of VVE in peripheral neuropathy in an HD mouse model. Our results suggest that VVE could play a role in the management of peripheral neuropathy, similar to other antioxidants known to be beneficial for diabetic peripheral neuropathy.
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Affiliation(s)
- Heung Yong Jin
- Division of Endocrinology and Metabolism, Department of Internal Medicine and Research institute of Clinical Medicine, Chonbuk National University Medical School, Jeonju, Korea
- Biomedical Research Institute, Chonbuk National University Hospital, Jeonju, Korea
| | - Youn Soo Cha
- Department of Food Science and Human Nutrition and Research Institute of Human Ecology, Chonbuk National University, Jeonju, Korea
| | - Hong Sun Baek
- Division of Endocrinology and Metabolism, Department of Internal Medicine and Research institute of Clinical Medicine, Chonbuk National University Medical School, Jeonju, Korea
- Biomedical Research Institute, Chonbuk National University Hospital, Jeonju, Korea
| | - Tae Sun Park
- Division of Endocrinology and Metabolism, Department of Internal Medicine and Research institute of Clinical Medicine, Chonbuk National University Medical School, Jeonju, Korea
- Biomedical Research Institute, Chonbuk National University Hospital, Jeonju, Korea
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Van Dam PS, Cotter MA, Bravenboer B, Cameron NE. Pathogenesis of diabetic neuropathy: focus on neurovascular mechanisms. Eur J Pharmacol 2013; 719:180-186. [PMID: 23872412 DOI: 10.1016/j.ejphar.2013.07.017] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2013] [Accepted: 07/11/2013] [Indexed: 02/08/2023]
Abstract
Neuropathies of the peripheral and autonomic nervous systems affect up to half of all people with diabetes, and are major risk factors for foot ulceration and amputation. The aetiology is multifactorial: metabolic changes in diabetes may directly affect neural tissue, but importantly, neurodegenerative changes are precipitated by compromised nerve vascular supply. Experiments in animal models of diabetic neuropathy suggest that similar metabolic sequelae affect neurons and vasa nervorum endothelium. These include elevated polyol pathway activity, oxidative stress, the formation of advanced glycation and lipoxidation end products, and various pro-inflammatory changes such as elevated protein kinase C, nuclear factor κB and p38 mitogen activated protein kinase signalling. These mechanisms do not work in isolation but strongly interact in a mutually facilitatory fashion. Nitrosative stress and the induction of the enzyme poly (ADP-ribose) polymerase form one important link between physiological stressors such as reactive oxygen species and the pro-inflammatory mechanisms. Recently, evidence points to endoplasmic stress and the unfolded protein response as forming another crucial link. This review focuses on the aetiopathogenesis of neurovascular changes in diabetic neuropathy, elucidated in animal studies, and on putative therapeutic targets the majority of which have yet to be tested for efficacy in clinical trials.
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Affiliation(s)
- P Sytze Van Dam
- Onze Lieve Vrouwe Gasthuis, Department of internal Medicine, PO Box 95500, 1090HM Amsterdam, The Netherlands
| | - Mary A Cotter
- School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland UK
| | | | - Norman E Cameron
- School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland UK.
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Olver TD, Mattar L, Grisé KN, Twynstra J, Noble EG, Lacefield JC, Shoemaker JK. Glucose-stimulated insulin secretion causes an insulin-dependent nitric oxide-mediated vasodilation in the blood supply of the rat sciatic nerve. Am J Physiol Regul Integr Comp Physiol 2013; 305:R157-63. [PMID: 23616106 DOI: 10.1152/ajpregu.00095.2013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This study tested the hypothesis that acute hyperglycemia reduces sciatic nerve blood flow in Sprague-Dawley rats. Anesthetized rats underwent cannulation of their right jugular vein (for anesthetic/nutrient/drug infusion) and right carotid artery (for continuous blood pressure measurement via pressure transducer). The left sciatic nerve was exposed and nerve blood velocity (NBV) was assessed from an arterial segment lying superficially along the sciatic nerve (Doppler ultrasound, 40 MHz). NBV and mean arterial pressure (MAP) values were collected, and an index of nerve vascular conductance (NVC) was established (NBV/MAP) at baseline and at 5, 10, 20, and 30 min (and 80 min for insulin) following 1) low glucose infusion, 1 g/kg (50% solution); 2) high glucose infusion, 3 g/kg; 3) high glucose infusion in the absence of a functioning pancreas; 4) euglycemic hyperinsulinemic clamp-insulin infusion (10 mU·kg⁻¹·min⁻¹; 0.4 IU/ml); 5) high glucose infusion + NG-nitro-L-arginine methyl ester (L-NAME) infusion (30 mg/kg); and 6) L-NAME alone followed 20 min later by high glucose infusion. High glucose infusion increased NVC by ~120% relative to baseline (P < 0.001), and this dilation was attenuated in rats without a functioning pancreas (i.e., without insulin secretion) (P = 0.004) and following L-NAME infusion (P = 0.011). Therefore, the vasodilation in rat sciatic nerve during glucose infusion was dependent upon the insulin response and acted through a nitric oxide synthase pathway.
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Affiliation(s)
- T Dylan Olver
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
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Bhatwadekar AD, Yan Y, Qi X, Thinschmidt JS, Neu MB, Li Calzi S, Shaw LC, Dominiguez JM, Busik JV, Lee C, Boulton ME, Grant MB. Per2 mutation recapitulates the vascular phenotype of diabetes in the retina and bone marrow. Diabetes 2013; 62. [PMID: 23193187 PMCID: PMC3526035 DOI: 10.2337/db12-0172] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In this study, we assessed whether Per2 clock gene-mutant mice exhibit a vascular phenotype similar to diabetes. Per2 (B6.129-Per2(tm1Drw)/J) or wild-type control mice 4 and 12 months of age were used. To evaluate diabetes-like phenotype in Per2 mutant mice, retina was quantified for mRNA expression, and degree of diabetic retinopathy was evaluated. Bone marrow neuropathy was studied by staining femurs for tyrosine hydroxylase (TH) and neurofilament 200 (NF-200). The rate of proliferation and quantification of bone marrow progenitor cells (BMPCs) was performed, and a threefold decrease in proliferation and 50% reduction in nitric oxide levels were observed in Per2 mutant mice. TH-positive nerve processes and NF-200 staining were reduced in Per2 mutant mice. Both retinal protein and mRNA expression of endothelial nitric oxide synthase were decreased by twofold. Other endothelial function genes (VEGFR2, VEGFR1) were downregulated (1.5-2-fold) in Per2 mutant retinas, whereas there was an upregulation of profibrotic pathway mediated by transforming growth factor-β1. Our studies suggest that Per2 mutant mice recapitulate key aspects of diabetes without the metabolic abnormalities, including retinal vascular damage, neuronal loss in the bone marrow, and diminished BMPC function.
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Affiliation(s)
- Ashay D Bhatwadekar
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida, USA
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Cotter MA, Gibson TM, Nangle MR, Cameron NE. Effects of interleukin-6 treatment on neurovascular function, nerve perfusion and vascular endothelium in diabetic rats. Diabetes Obes Metab 2010; 12:689-99. [PMID: 20590746 DOI: 10.1111/j.1463-1326.2010.01221.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
AIM Interleukin-6 (IL-6), a member of the neuropoietic cytokine family, participates in neural development and has neurotrophic activity. Recent research has also indicated actions to improve vasa nervorum function in diabetes. Both these facets are potentially relevant for treatment of diabetic neuropathy. The aim of this study was to determine whether IL-6 treatment corrected changes in neurovascular function in streptozotocin-induced diabetic rats. METHODS After 1 month of diabetes, rats were given IL-6 for 1 month. The rats were subjected to sensory testing and measurements of nerve conduction velocities and nerve blood flow by hydrogen clearance microelectrode polarography. Further groups were used to study responses of the isolated gastric fundus and renal artery. Results were statistically analysed using ANOVA and post hoc tests. RESULTS Diabetic rats showed mechanical hyperalgesia, thermal hyperalgesia, and tactile allodynia. The former was unaffected by IL-6 treatment, whereas the latter two measures were corrected. Immunohistochemical staining of dorsal root ganglia for IL-6 did not reveal any changes with diabetes or treatment. The results showed that 22 and 17.4% slowing of sciatic motor and saphenous sensory nerve conduction velocities, respectively, with diabetes were improved by IL-6. Sciatic endoneurial perfusion was halved by diabetes and corrected by IL-6. A 40.6% diabetic deficit in maximal non-adrenergic, non-cholinergic relaxation of gastric fundus to nerve stimulation was unaffected by IL-6. Renal artery endothelium-dependent relaxation was halved by diabetes, the endothelium-derived hyperpolarizing factor (EDHF) component being severely attenuated. IL-6 did not affect nitric oxide-mediated vasorelaxation, but markedly improved EDHF responses. CONCLUSIONS IL-6 improved aspects of small and large nerve fibre and vascular endothelium dysfunction in diabetic rats. The functional benefits related to increased nerve blood flow via an EDHF mechanism, and IL-6 could have therapeutic potential in diabetic neuropathy and vasculopathy, which should be further evaluated.
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Affiliation(s)
- M A Cotter
- School of Medical Sciences, University of Aberdeen, Aberdeen, UK
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Brooks B, Delaney-Robinson C, Molyneaux L, Yue DK. Endothelial and neural regulation of skin microvascular blood flow in patients with diabetic peripheral neuropathy: effect of treatment with the isoform-specific protein kinase C beta inhibitor, ruboxistaurin. J Diabetes Complications 2008; 22:88-95. [PMID: 18280438 DOI: 10.1016/j.jdiacomp.2007.07.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 05/09/2007] [Accepted: 07/10/2007] [Indexed: 01/13/2023]
Abstract
PURPOSE This article aims to study the effects of ruboxistaurin (RBX) on skin microvascular blood flow (SkBF) and evaluate the relationship between endothelial and neural control of SkBF in patients with diabetic peripheral neuropathy (DPN). METHODS We studied 11 placebo- and 9 RBX (32 mg/day)-treated patients who participated in a 1-year, double-masked, randomized, Phase 3 study of RBX for treatment of DPN sensory symptoms. Patients had type 1 or type 2 diabetes, a detectable sural sensory nerve action potential, and Neuropathy Total Symptom Score-6 (NTSS-6) >6 points. SkBF was measured by laser Doppler velocimetry, combined with iontophoresis of acetylcholine and sodium nitroprusside, at baseline, 3 months, and 1 year. Sensory symptoms and electrophysiology were also evaluated during the study. The relationship between endothelial and neural control of SkBF at baseline was assessed using linear regression. RESULTS No significant differences (RBX vs. placebo) were demonstrable for post-iontophoresis SkBF [fold increase from basal state (1 year): endothelium-dependent, 3.6 vs. 8.6; endothelium-independent, 3.7 vs. 2.0; C fiber-mediated, 1.7 vs. 2.0; P>.05] or sensory symptoms [NTSS-6 total score (1 year): 7.7 vs. 6.0 points; P=.4]. There were also no significant between-group differences in nerve conduction parameters, except for placebo peroneal nerve conduction velocity, which demonstrated a statistically significant improvement of unknown clinical importance (Z=2.1; P=.034). At baseline, C fiber-mediated vasodilatation correlated well with endothelium-dependent vasodilation (r=.7, P<.01) but not with endothelium-independent vasodilatation (r=-.1, P=.7). CONCLUSIONS RBX demonstrated no effect on SkBF or sensory symptoms after 1 year in this cohort. The correlation between C fiber-mediated and endothelium-dependent SkBF at baseline suggests that improving endothelial function could affect the microcirculation not only locally but also via the neurovascular arcade.
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Affiliation(s)
- Belinda Brooks
- Diabetes Centre, Royal Prince Alfred Hospital, and Discipline of Medicine, The University of Sydney, Sydney, New South Wales, Australia.
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Bohlen HG. Microvascular Consequences of Obesity and Diabetes. Microcirculation 2008. [DOI: 10.1016/b978-0-12-374530-9.00021-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Inkster ME, Cotter MA, Cameron NE. Treatment with the xanthine oxidase inhibitor, allopurinol, improves nerve and vascular function in diabetic rats. Eur J Pharmacol 2007; 561:63-71. [PMID: 17291486 DOI: 10.1016/j.ejphar.2006.12.029] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Revised: 12/14/2006] [Accepted: 12/21/2006] [Indexed: 12/12/2022]
Abstract
Several putative sources of reactive oxygen species could potentially contribute to diabetic neuropathy and vasculopathy. The aim was to assess the involvement of elevated xanthine oxidase activity. After 6 weeks of streptozotocin-diabetes, groups of rats were given 2 weeks of high-dose allopurinol treatment (50 and 250 mg/kg) to gauge the effect of maximal blockade of xanthine oxidase. In the final experiments, rats were subjected to sensory testing and, under butabarbital anaesthesia, measurements were made on nerve conduction velocities and neural tissue blood flow estimated by hydrogen clearance microelectrode polarography. Further groups were used to study detailed responses of the isolated mesenteric vascular bed after 4 weeks of diabetes and allopurinol (150 mg/kg) treatment. Diabetes caused 20% and 14% reduction in motor and sensory conduction velocity, which were 78% and 81% corrected by allopurinol treatment respectively, both doses giving similar results. Diabetic rats showed tactile allodynia and thermal hyperalgesia, which were completely corrected by allopurinol, whereas mechanical hyperalgesia was only 45% ameliorated. Sciatic nerve and superior cervical ganglion blood flow was halved by diabetes and allopurinol corrected this by approximately 63%. Mesenteric endothelium-dependent vascular responses to acetylcholine, which depend upon nitric oxide and endothelium derived hyperpolarizing factor, were attenuated by diabetes. Allopurinol treatment gave approximately 50% protection for both components. Thus, xanthine oxidase is an important source of reactive oxygen species that contributes to neurovascular dysfunction in experimental diabetes. Inhibition of xanthine oxidase could be a potential therapeutic approach to diabetic neuropathy and vasculopathy.
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Affiliation(s)
- Melanie E Inkster
- School of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
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Costacou T, Chang Y, Ferrell RE, Orchard TJ. Identifying genetic susceptibilities to diabetes-related complications among individuals at low risk of complications: An application of tree-structured survival analysis. Am J Epidemiol 2006; 164:862-72. [PMID: 16928730 DOI: 10.1093/aje/kwj287] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The authors hypothesized that genetic predisposition to diabetes complications would be more evident among low-risk individuals and aimed to identify genes related to developing complications (confirmed distal symmetric polyneuropathy, overt nephropathy, or coronary artery disease) in low-risk groups. Participants in the Pittsburgh, Pennsylvania, Epidemiology of Diabetes Complications Study of childhood-onset type 1 diabetes, first seen in 1986-1988 (mean age, 28 years; diabetes duration, 19 years), were reexamined biennially for 10 years. For each complication, subgroups with the lowest disease risk were identified by using tree-structured survival analysis, and 15 candidate genes were compared between subjects with and without complications. In the group with the lowest incidence of confirmed distal symmetric polyneuropathy (n = 123), confirmed distal symmetric polyneuropathy risk increased fivefold for those with the eNOS GG genotype (p < 0.05). In the group with the lowest risk of overt nephropathy (n = 340), the ACE D polymorphism increased overt nephropathy risk twofold (p = 0.05), whereas a protective effect was observed for the LIPC CC genotype (p < 0.05). In the group with the lowest incidence of coronary artery disease (n = 331), the MTHFR CC genotype increased coronary artery disease risk threefold (p < 0.05). Tree-structured survival analysis may help identify genetic predispositions among individuals who, despite low risk, develop diabetes-related complications.
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Affiliation(s)
- Tina Costacou
- Department of Epidemiology, University of Pittsburgh, Pittsburgh, PA, USA
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Abstract
Peripheral neuropathy is a common problem encountered by neurologists and primary care physicians. While there are many causes for peripheral neuropathy, none can be identified in a large percentage of patients ("idiopathic neuropathy"). Despite its high prevalence, idiopathic neuropathy is poorly studied and understood. There is evolving evidence that impaired glucose tolerance (prediabetes) is associated with idiopathic neuropathy. Preliminary data from a multicenter study of diet and exercise in prediabetes (the Impaired Glucose Tolerance Neuropathy Study) suggests a diet and exercise counseling regimen based on the Diabetes Prevention Program results in improved metabolic measures and small fiber function. Prediabetes is part of the Metabolic Syndrome, which also includes hypertension, hyperlipidemia and obesity. Individual aspects of the Metabolic Syndrome influence risk and progression of diabetic neuropathy and may play a causative role in neuropathy both for those with prediabetes, and those with otherwise idiopathic neuropathy. Thus, a multifactorial treatment approach to individual components of Metabolic Syndrome may slow prediabetic neuropathy progression or result in improvement.
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Affiliation(s)
- A Gordon Smith
- Neurology and Pathology, University of Utah School of Medicine, 30 North 1900 East, SOM 3R152, Salt Lake City, UT 84132, USA.
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Cotter MA, Cameron NE. Effect of the NAD(P)H oxidase inhibitor, apocynin, on peripheral nerve perfusion and function in diabetic rats. Life Sci 2003; 73:1813-24. [PMID: 12888120 DOI: 10.1016/s0024-3205(03)00508-3] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Upregulation of vascular NAD(P)H oxidase has been considered an important source for elevated levels of reactive oxygen species that contribute to several cardiovascular disease states, including the vascular complications of diabetes mellitus. Previous studies have shown that treatment with antioxidants corrects impaired nerve function and blood flow in diabetic rats. The aim was to assess the degree of involvement of NAD(P)H oxidase in experimental diabetic neuropathy. To this end, after 6 weeks of untreated streptozotocin-diabetes, rats were treated for 2 weeks with the NAD(P)H oxidase, apocynin. Two high doses (15 and 100 mg/kg) were used to ensure that maximal effects were registered. Diabetes caused a 20% reduction in sciatic nerve motor conduction velocity, and a 14% deficit for sensory saphenous nerve. Apocynin treatment corrected these defects by 32% and 48%, respectively: there were no significant differences between the effects of the 2 doses. Sciatic nerve nutritive endoneurial perfusion was measured by hydrogen clearance microelectrode polarography. Blood flow and vascular conductance were 47% and 40% reduced by diabetes, respectively. Both doses of apocynin had similar effects, correcting the blood flow deficit by 31% and conductance by 47%. Thus, the data show that NAD(P)H oxidase contributes to the neurovascular deficits in diabetic rats. While only accounting for part of the elevated reactive oxygen species production in diabetes, this mechanism could provide a novel therapeutic candidate for further investigation in diabetic neuropathy and vasculopathy.
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Affiliation(s)
- M A Cotter
- Department of Biomedical Sciences, Institute of Medical Sciences, Aberdeen University, Foresterhill, AB25 2ZD Scotland, Aberdeen, UK
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Cotter MA, Ekberg K, Wahren J, Cameron NE. Effects of proinsulin C-peptide in experimental diabetic neuropathy: vascular actions and modulation by nitric oxide synthase inhibition. Diabetes 2003; 52:1812-7. [PMID: 12829651 DOI: 10.2337/diabetes.52.7.1812] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Proinsulin C-peptide treatment can partially prevent nerve dysfunction in type 1 diabetic rats and patients. This could be due to a direct action on nerve fibers or via vascular mechanisms as C-peptide stimulates the nitric oxide (NO) system and NO-mediated vasodilation could potentially account for any beneficial C-peptide effects. To assess this further, we examined neurovascular function in streptozotocin-induced diabetic rats. After 6 weeks of diabetes, rats were treated for 2 weeks with C-peptide to restore circulating levels to those of nondiabetic controls. Additional diabetic groups were given C-peptide with NO synthase inhibitor N(G)-nitro-L-arginine (L-NNA) co-treatment or scrambled C-peptide. Diabetes caused 20 and 16% reductions in sciatic motor and saphenous sensory nerve conduction velocity, which were 62 and 78% corrected, respectively, by C-peptide. L-NNA abolished C-peptide effects on nerve conduction. Sciatic blood flow and vascular conductance were 52 and 41%, respectively, reduced by diabetes (P < 0.001). C-peptide partially (57-66%) corrected these defects, an effect markedly attenuated by L-NNA co-treatment. Scrambled C-peptide was without effect on nerve conduction or perfusion. Thus, C-peptide replacement improves nerve function in experimental diabetes, and the data are compatible with the notion that this is mediated by a NO-sensitive vascular mechanism.
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Affiliation(s)
- Mary A Cotter
- Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Scotland, UK
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Cameron NE, Cotter MA. The effects of 5-hydroxytryptamine 5-HT2 receptor antagonists on nerve conduction velocity and endoneurial perfusion in diabetic rats. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2003; 367:607-14. [PMID: 12743678 DOI: 10.1007/s00210-003-0750-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2002] [Accepted: 03/21/2003] [Indexed: 10/25/2022]
Abstract
Reduced peripheral nerve perfusion participates in the aetiology of diabetic neuropathy. 5-Hydroxtryptamine causes vasa nervorum vasoconstriction and platelet aggregation, which are enhanced by diabetes. To assess whether these mechanisms could contribute to neuropathy, the effects of 5-hydroxytryptamine 5-HT2 receptor antagonist treatment were examined in streptozotocin-induced diabetic rats. One study determined the dose-response relationship for AT1015 (N-[2-[4-(5H-dibenzo[a,d]cyclohepten-5-ylidene)piperidino]ethyl]-1-formyl-4-piperidinecarboxamide monohydrochloride monohydrate). Two weeks AT1015 treatment after 6 weeks of diabetes dose-dependently corrected 19.7%, 54.1%, and 15.7% deficits in sciatic nerve motor conduction velocity and blood flow, and saphenous nerve sensory conduction: ED50 values were 0.52, 0.74 and 0.15 mg/kg(-1)/day(-1), respectively. In a second study, high-dose AT1015 (3 mg/kg(-1)/day(-1)) actions were compared with those of the 5HT2 receptor antagonists, ritanserin (10 mg/kg(-1)/day(-1)) and sarpogrelate (100 mg/kg(-1)/day(-1)), and the anti-platelet phosphodiesterase III inhibitor, cilostazol (100 mg/kg(-1)/day(-1)). Two weeks treatment with these drugs produced a marked correction (82.6-99.7%) of a 19.8% sciatic motor conduction deficit in diabetic rats. Similarly, 44.7% and 14.9% reductions in sciatic endoneurial blood flow and saphenous sensory conduction velocity were completely reversed. Thus, 5-HT2 receptor antagonists had marked beneficial effects in experimental diabetic neuropathy, and AT1015 appears suitable for further evaluation in clinical trials.
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Affiliation(s)
- Norman E Cameron
- Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, AB25 2ZD Aberdeen, Scotland, UK.
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Thomsen K, Rubin I, Lauritzen M. NO- and non-NO-, non-prostanoid-dependent vasodilatation in rat sciatic nerve during maturation and developing experimental diabetic neuropathy. J Physiol 2002; 543:977-93. [PMID: 12231652 PMCID: PMC2290537 DOI: 10.1113/jphysiol.2002.023564] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
This study examined NO- and non-NO-, non-prostanoid-dependent pathways of agonist-induced vasodilatation in streptozotocin (STZ)-induced diabetic rats and their age-matched controls at 1-2, 8-10 and 18-20 weeks after induction of diabetes. Using laser Doppler flowmetry, vasodilatory responses to acetylcholine (ACh; 0.1 mM) and morpholino-sydnonimine (SIN-1) were determined in the presence of Ringer solution, during inhibition of NO synthase (NOS) and cyclo-oxygenase (COX) with N(omega)-nitro-L-arginine (L-NNA; 1 mM) + indomethacin (10(-5) M), and during inhibition of K(+) channels, NOS and COX with tetraethylammonium (TEA; 10 mM) + L-NNA + indomethacin. Basal NOS activity and nerve conduction velocity were also determined. In age-matched controls, SIN-1-induced vasodilatation in the presence of TEA + L-NNA + indomethacin, basal NOS activity and the initial vasodilatory response to ACh during NOS and COX inhibition all decreased with maturation. In STZ-induced diabetics, SIN-1-induced vasodilatation in the presence of TEA + L-NNA + indomethacin was impaired immediately after induction of diabetes, but not at 18-20 weeks. NOS activity in STZ-induced diabetics displayed a transient 2-fold increase at 8-10 weeks, decreasing to age-matched control levels at 18-20 weeks. At 18-20 weeks of STZ-induced diabetes, ACh-induced vasodilatation during NOS and COX inhibition was prolonged due to increased K(+) channel activity and experimental diabetic sensory neuropathy (EDN) had developed. Thus, in sciatic nerve microcirculation of STZ-induced diabetic rats: (1) diabetic impairment of vasodilatation in response to exogenous NO was transient; (2) non-NO-, non-prostanoid-dependent vasodilatation and K(+) channel activity were augmented in STZ-induced diabetes; and (3) alterations in NO bioactivity were not related to the development of EDN.
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Affiliation(s)
- Kirsten Thomsen
- Department of Medical Physiology, University of Copenhagen and Department of Neurophysiology, Glostrup Hospital, Denmark.
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Cameron NE, Cotter MA. Effects of protein kinase Cbeta inhibition on neurovascular dysfunction in diabetic rats: interaction with oxidative stress and essential fatty acid dysmetabolism. Diabetes Metab Res Rev 2002; 18:315-23. [PMID: 12203947 DOI: 10.1002/dmrr.307] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Elevated protein kinase C (PKC) activity is thought to play a substantial role in the aetiology of diabetic microvascular complications, the PKCbeta isoform being identified as particularly important. Neuropathy has a vascular component; therefore, one aim was to assess whether the PKCbeta inhibitor, LY333531, could correct nerve conduction velocity (NCV) and perfusion deficits in diabetic rats. Neurovascular dysfunction also depends on oxidant stress and impaired omega-6 essential fatty acid metabolism; correctable by antioxidant and gamma-linolenic acid (GLA) treatments, respectively. A second aim was to assess whether there were interactions between these mechanisms and PKCbeta-mediated effects. METHODS Diabetes was induced by streptozotocin; duration was 8 weeks. NCV was monitored and blood flow was assessed by hydrogen clearance microelectrode polarography. RESULTS Diabetes caused 19.7% and 13.9% reductions in sciatic motor and saphenous sensory NCV, respectively. Two weeks of LY333531 treatment dose-dependently corrected these deficits. A dose of 10 mg kg(-1) day(-1) gave non-diabetic NCV values and also completely corrected a 50% diabetic reduction in sciatic endoneurial blood flow. Low-dose (0.25 mg kg(-1) day(-1)) LY333531 had modest effects ( approximately 20% correction) on NCV and sciatic perfusion. However, when combined with equi-effective doses of the antioxidants vitamin E or alpha-lipoic acid, or GLA, motor and sensory NCV and sciatic nerve perfusion were in the non-diabetic range. The joint effect was equivalent to that of the 10 mg kg(-1) day(-1) LY333531 dose, demonstrating synergism between PKCbeta, oxidative stress and essential fatty acid mechanisms. CONCLUSIONS LY333531, alone or combined with antioxidants or GLA, could form the basis for therapeutic intervention in neuropathy, which requires assessment in clinical trials.
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Affiliation(s)
- Norman E Cameron
- Department of Biomedical Sciences, University of Aberdeen, Scotland, UK.
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Keegan A, Cotter MA, Cameron NE. Corpus cavernosum dysfunction in diabetic rats: effects of combined alpha-lipoic acid and gamma-linolenic acid treatment. Diabetes Metab Res Rev 2001; 17:380-6. [PMID: 11747143 DOI: 10.1002/dmrr.215] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND The effects of streptozotocin-induced diabetes on nitric oxide (NO)-mediated relaxation of rat corpus cavernosum smooth muscle to neurogenic and endothelial stimulation was examined. The aim was to assess the effects of treatment with low doses of the antioxidant, alpha-lipoic acid, and the omega-6 essential fatty acid, gamma-linolenic acid, either separately or in combination. METHODS Treatment was preventive from diabetes induction or corrective over 4 weeks after 4 weeks of untreated diabetes. Corpus cavernosum responses were examined in vitro. RESULTS Neither diabetes nor treatment affected contractile responses to transmural electrical field stimulation of noradrenergic nerves. Stimulation of phenylephrine precontracted cavernosa in the presence of guanethidine and atropine caused relaxation via the nitrergic innervation. Maximum relaxation responses were 40% and 46% decreased after 4 and 8 weeks of diabetes, respectively. alpha-Lipoic acid, gamma-linolenic acid combination treatment fully prevented this deficit, and partially (52%) corrected the effect of 4 weeks of untreated diabetes. Neither alpha-lipoic acid nor gamma-linolenic components alone had significant effects, which suggests that there were synergistic interactions between the drugs. Both 4 and 8 weeks of untreated diabetes reduced maximum endothelium-dependent relaxation of phenylephrine precontracted cavernosa to acetylcholine by approximately 40%. While alpha-lipoic acid or gamma-linolenic acid were ineffective, joint treatment fully prevented and corrected this diabetic endothelial deficit. Neither diabetes nor treatment affected endothelium-independent relaxation to the NO donor, sodium nitroprusside. CONCLUSION The data show that alpha-lipoic acid and gamma-linolenic acid interact synergistically to improve NO-mediated neurogenic and endothelium-dependent relaxation of corpus cavernosum in experimental diabetes.
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Affiliation(s)
- A Keegan
- Department of Biomedical Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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Abstract
Impaired blood flow to peripheral nerve trunks makes a major contribution to the neuropathic complications of diabetes mellitus. Comparatively little attention has been paid to perfusion abnormalities for the cell bodies of origin of the autonomic and sensory nerves, although they are severely affected in diabetic neuropathy. The aim was to examine the time course of changes in superior cervical ganglion (SCG) perfusion in streptozotocin-induced diabetic rats. Ganglion blood flow, measured by hydrogen clearance microelectrode polarography, was approximately 70 ml min(-1) 100 g(-1). One week of diabetes caused a 46% perfusion deficit, which was maintained (54%) over 24 weeks. Thus, an early, profound, and long-lived reduction in ganglion perfusion may deleteriously affect neural cell body function and could contribute to autonomic neuropathy.
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Affiliation(s)
- N E Cameron
- Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK.
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Cotter MA, Mirrlees DJ, Cameron NE. Neurovascular interactions between aldose reductase and angiotensin-converting enzyme inhibition in diabetic rats. Eur J Pharmacol 2001; 417:223-30. [PMID: 11334854 DOI: 10.1016/s0014-2999(01)00909-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Increased polyol pathway flux has been linked to nerve complications in diabetic rats, which are attenuated by aldose reductase inhibitors, defective nitric oxide-mediated vasodilation being a particular target. Diabetes also elevates the endothelial angiotensin system, increasing vasa nervorum vasoconstriction. The aim was to assess whether promotion of vasodilation by treatment with the aldose reductase inhibitor, ZD5522 (3',5'-dimethyl-4'-nitromethylsulphonyl-2-(2-tolyl)acetanilide), coupled with reduced vasoconstriction using the angiotensin-converting enzyme inhibitor, lisinopril, interacted positively to improve neurovascular function. After 8 weeks of streptozotocin-induced diabetes, sciatic nerve blood flow and motor conduction velocity were 51% and 21% reduced, respectively. Two weeks of lisinopril treatment dose-dependently corrected the conduction deficit (ED(50) approximately 0.9 mg kg(-1)). Low-dose lisinopril (0.3 mg kg(-1)) or ZD5522 (0.25 mg kg(-1)) had modest corrective (10-20%) effects on nerve conduction and perfusion. However, when combined, blood flow and conduction velocity reached the nondiabetic range. The ZD5522 dose used gave a approximately 45% nerve sorbitol reduction but had no significant effect on fructose content; lisinopril co-treatment did not alter ZD5522 action on polyols. Thus, there was a marked neurovascular synergistic interaction between angiotensin-converting enzyme and aldose reductase inhibition in diabetic rats. This points to a potential therapeutic benefit, which requires evaluation in clinical trials.
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Affiliation(s)
- M A Cotter
- Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill Aberdeen, AB25 2ZD, Scotland, UK
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Ways DK, Sheetz MJ. The role of protein kinase C in the development of the complications of diabetes. VITAMINS AND HORMONES 2001; 60:149-93. [PMID: 11037624 DOI: 10.1016/s0083-6729(00)60019-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Diabetes mellitus produces a state of chronic hyperglycemia which in turn leads to the development of severe complications including retinopathy, nephropathy, neuropathy, and atherosclerosis. Many different mechanisms have been put forward to attempt to explain how glucose elevations can damage these various organ systems. Protein kinase C activation is one of the sequelae of hyperglycemia and is thought to play a role in the development of diabetic complications. There are multiple mechanisms for its activation in the diabetic state and multiple downstream effects attributable to that activation. The role of protein kinase C activation in the development of the above-mentioned complications of diabetes is discussed in this chapter. In addition, the potential use of isoform-specific inhibitors of protein kinase C for the treatment of diabetic complications is proposed.
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Affiliation(s)
- D K Ways
- Lilly Research Labs, Eli Lilly and Company Indianapolis, Indiana 46285, USA
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Hohman TC, Cotter MA, Cameron NE. ATP-sensitive K(+) channel effects on nerve function, Na(+), K(+) ATPase, and glutathione in diabetic rats. Eur J Pharmacol 2000; 397:335-41. [PMID: 10844132 DOI: 10.1016/s0014-2999(00)00227-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Some vasodilators correct nerve conduction velocity and endoneurial blood flow deficits in diabetic rats. It is not known whether vasa nervorum has ATP-sensitive K(+) (K(ATP)) channels that mediate vasodilation, or whether K(ATP) channels could modulate peripheral nerve function. Therefore, we examined the effects of 2 weeks treatment with the K(ATP) channel openers, celikalim and WAY135201 (R-4-[3, 4-dioxo-2-(1, 2, 2-trimethyl-propylamino)-cyclobut-1-1-enylamino]-3-methoxy-+ ++benzonitri le), on sciatic nerve blood flow, conduction velocity, Na(+)-K(+) ATPase activity and glutathione content after 6 weeks of untreated streptozotocin-diabetes in rats. Blood flow and motor conduction velocity, 47.6% and 20.3% reduced by diabetes, respectively, were completely restored by both celikalim and WAY135201 treatments. Diabetes diminished sciatic Na(+)-K(+) ATPase activity by 47.6% and this was 80-90% corrected by the K(ATP) channel openers. Sciatic nerve glutathione content, 30.3% reduced by diabetes, was unaffected by celikalim or WAY135201. Thus, K(ATP) channel openers had marked beneficial effects on nerve perfusion and function in experimental diabetic neuropathy, and may be suitable for further study in clinical trials.
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Affiliation(s)
- T C Hohman
- Wyeth-Ayerst Research, 09543-8000, Princeton, NJ, USA
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Keegan A, Jack AM, Cotter MA, Cameron NE. Effects of aldose reductase inhibition on responses of the corpus cavernosum and mesenteric vascular bed of diabetic rats. J Cardiovasc Pharmacol 2000; 35:606-13. [PMID: 10774792 DOI: 10.1097/00005344-200004000-00014] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We examined the effects of 2 months of streptozotocin-induced diabetes mellitus in rats on relaxation and contraction of corpus cavernosum and the mesenteric vascular bed in vitro. A further diabetic group was treated from diabetes induction with 10 mg/kg/day of the aldose reductase inhibitor, WAY121509. For corpus cavernosum, maximal acetylcholine-induced relaxation was 35.5% reduced (p < 0.001) by diabetes, and this deficit was completely prevented by WAY121509 treatment. Neither diabetes nor treatment affected contractile responses to field stimulation of noradrenergic nerves; however, nonadrenergic noncholinergic nerve relaxation responses were 32.9% decreased by diabetes and WAY 121509 attenuated this by 84% (p < 0.001). For the mesenteric vascular bed, diabetes depressed maximal endothelium-dependent vasodilation to acetylcholine by 25.2% (p < 0.001), and this was partially (50.6%; p < 0.01) prevented by WAY121509. Nitric oxide synthase blockade revealed endothelium-derived hyperpolarising factor-mediated vasodilation to acetylcholine that was 73.5% (p < 0.001) depressed by diabetes; WAY121509 provided partial (43.4%; p < 0.001) protection. Neither diabetes nor treatment affected endothelium-independent vasorelaxation to the nitric oxide donor, sodium nitroprusside, in corpus cavernosum or mesenteric vessels. Thus the data show protective effects of WAY121509 on nitric oxide-mediated cavernosal vasorelaxation responses and on mesenteric endothelium-derived hyperpolarising factor responses. Together these findings could account for the beneficial effects of aldose reductase inhibition on diabetic complications in experimental models.
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Affiliation(s)
- A Keegan
- Department of Biomedical Sciences, University of Aberdeen, Scotland
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Abstract
People with diabetes are prone to develop peripheral vascular and nerve abnormalities which, in extreme cases, can lead to limb amputations. Although numerous theories have been advanced for these complications, no firm explanation is yet available. Recently, evidence has appeared suggesting that these vascular and nerve abnormalities may involve transition metals; administration of chelators such as desferrioxamine has been shown to prevent or actually reverse slowed peripheral nerve conduction and neuronal blood flow, as well as impaired endothelium-dependent arterial relaxation. Here, we argue that (i) the heavily glycated proteins known to accumulate in people with diabetes gain an increased affinity for transition metals such as iron and copper, (ii) as a result, proteins such as elastin and collagen within the arterial wall-which are known to be particularly heavily glycosylated in diabetes-may accumulate bound metal, especially copper, (iii) the bound metal causes the catalytic destruction of endothelium derived relaxing factor (nitric oxide or a derivative thereof), thereby engendering a state of chronic vasoconstriction. The resulting impairment of blood flow to peripheral nerves restricts the delivery of oxygen and nutrients and, in extremis, nerve death eventuates. If this hypothesis is proved correct, there are important implications for the development of novel pharmaceuticals for the treatment of diabetic peripheral neuropathy.
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Affiliation(s)
- M Qian
- Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
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Abstract
Reactive oxygen species (ROS) are elevated by metabolic changes in diabetes, including autoxidation and increased advanced glycation. Endogenous protection by the glutathione redox cycle is also compromised by the competing NADPH requirement of elevated polyol pathway flux. Antioxidant treatment strategies prevent or reverse nerve conduction velocity (NCV) deficits in diabetic rats. These include lipophilic scavengers such as butylated hydroxytoluene, probucol and vitamin E, more hydrophilic agents like alpha-lipoic acid and acetyl cysteine, and transition metal chelators that inhibit autoxidation. In the long-term, elevated ROS cause cumulative damage to neurons and Schwann cells, however, they also have a deleterious effect on nerve blood flow in the short term. This causes endoneurial hypoxia, which is responsible for early NCV deficits. Antioxidant treatment corrects the blood flow deficit and promotes normal endoneurial oxygenation. ROS cause antioxidant-preventable vascular endothelium abnormalities, neutralizing nitric oxide mediated vasodilation and increasing reactivity to vasoconstrictors. Unsaturated fatty acids are a major target for ROS and essential fatty acid metabolism is impaired by diabetes. Gamma-linolenic acid stimulates vasodilator prostanoid production, and there are marked synergistic interactions between gamma-linolenic acid and antioxidants. This has encouraged the development of novel drugs such as ascorbyl-gamma-linolenic acid and gamma-linolenic acid-lipoic acid with enhanced therapeutic potential.
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Affiliation(s)
- N E Cameron
- Department of Biomedical Sciences, University of Aberdeen, Scotland, UK.
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Keegan A, Cotter MA, Cameron NE. Effects of chelator treatment on aorta and corpus cavernosum from diabetic rats. Free Radic Biol Med 1999; 27:536-43. [PMID: 10490273 DOI: 10.1016/s0891-5849(99)00125-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Transition-metal catalyzed reactions contribute to oxidative stress, which has been implicated in the pathogenesis of diabetic complications. The aim was to evaluate the effects of treatment with the transition metal chelator trientine on endothelium-dependent relaxation of aorta and corpus cavernosum from streptozotocin-induced diabetes of 8 weeks duration in rats. Effects on cavernosum autonomic innervation were also examined. Diabetes caused a 30.1 +/- 3.8% reduction in maximum aorta endothelium-dependent relaxation to acetylcholine (ACh), which was markedly attenuated (72.7 +/- 10.6%) by trientine treatment. Reversal treatment (4 weeks untreated diabetes, 4 weeks trientine) did not effect endothelium-dependent relaxation compared with aortas from rats with 4 weeks of diabetes, however, there was a 22.5 +/- 6.2% improvement compared with 8 weeks of diabetes. Eight weeks of diabetes caused a 41.5 +/- 6.6% reduction in corpus cavernosum endothelium-dependent maximum relaxation to ACh that was 70.1 +/- 16.9% prevented by trientine. Cavernosum nonadrenergic, noncholinergic (NANC) nerve stimulation caused frequency-dependent relaxation to a maximum of 40.9 +/- 2.4%, which was reduced by diabetes to 24.2 +/- 2.1%. Trientine partially prevented this deficit, maximum relaxation being 31.9 +/- 2.3%. Thus, metal chelator treatment has beneficial effects on aorta and cavernosum endothelium-dependent relaxation and on cavernosum NANC innervation.
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Affiliation(s)
- A Keegan
- Department of Biomedical Sciences, University of Aberdeen, Foresterhill, Scotland, United Kingdom
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Jack AM, Cameron NE, Cotter MA. Effects of the diacylglycerol complexing agent, cremophor, on nerve-conduction velocity and perfusion in diabetic rats. J Diabetes Complications 1999; 13:2-9. [PMID: 10232703 DOI: 10.1016/s1056-8727(98)00014-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The contribution of diacylglycerol (DAG) and protein kinase C (PKC) to diabetic complications has been the subject of debate. In vascular tissues, diabetes increases DAG content, which activates PKC and causes abnormal tissue perfusion. Reduced nerve blood flow has been implicated in the development of neuropathy. However, nerve DAG/PKC activity is not increased and may even be reduced by diabetes, which has also been implicated in neuropathy. The aim was to test whether 2 weeks of treatment with cremophor, an agent that complexes DAG and prevents PKC activation, could correct nerve-conduction velocity (NCV) deficits in rats with 6 weeks of untreated diabetes, as predicted on a vascular hypothesis, or whether this worsened the deficits, as predicted for a direct effect on nerve fibers. Diabetes caused 17.9 +/- 0.9% (+/- SEM) and 15.5 +/- 1.6% reductions in sciatic motor and saphenous sensory NCV, respectively, that were largely (79.6 +/- 6.3% and 57.8 +/- 11.5%) corrected by 100 mg x kg(-1) x day(-1) cremophor treatment. The effects of cremophor on motor and sensory NCV were completely attenuated by co-treatment with the nitric oxide synthase inhibitor, N(G)-nitro-l-arginine. In contrast, co-treatment with the cyclooxygenase inhibitor, flurbiprofen, had no effect on NCV. Sciatic nutritive and total endoneurial perfusion were 49.7 +/- 3.4% and 51.8 +/- 4.2% reduced by diabetes, respectively, and these deficits were 69.5 +/- 7.4% and 79.0 +/- 11.6% corrected by cremophor treatment. Thus the data suggest that an increased DAG/PKC vascular mechanism, perhaps linked to the nitric oxide system, contributes to the etiology of diabetic nerve dysfunction.
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Affiliation(s)
- A M Jack
- Department of Biomedical Sciences, University of Aberdeen, Marischal College, Scotland, United Kingdom
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Cotter MA, Cameron NE. Correction of neurovascular deficits in diabetic rats by beta2-adrenoceptor agonist and alpha1-adrenoceptor antagonist treatment: interactions with the nitric oxide system. Eur J Pharmacol 1998; 343:217-23. [PMID: 9570470 DOI: 10.1016/s0014-2999(97)01533-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The aims were to test whether 2 weeks treatment with the beta2-adrenoceptor agonist, salbutamol, or the alpha1-adrenoceptor antagonist, doxazosin, could correct nerve blood flow and conduction velocity deficits in 8 week streptozotocin-diabetic rats and to examine neurovascular mechanisms using co-treatment with the nitric oxide synthase inhibitor, NG-nitro-L-arginine. Sciatic motor conduction velocity, 20.3% reduced by diabetes, was corrected by 88.2 and 88.5% for salbutamol and doxazosin, respectively. A 47.6% diabetic deficit in sciatic nutritive endoneurial blood, was substantially reversed by salbutamol (117.0%) and doxazosin (61.0%) treatment. The effects of alpha1-adrenoceptor blockade and beta2-adrenoceptor stimulation on nerve blood flow and conduction velocity were almost completely (76.7-91.7%) attenuated by NG-nitro-L-arginine co-treatment. Thus, the data stress the importance of vasa nervorum alpha1 and beta2 adrenoceptors and the permissive role of nitric oxide in nerve blood flow control mechanisms. They also indicate that beta2-adrenoceptor agonists may be suitable for clinical trials of diabetic neuropathy.
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Affiliation(s)
- M A Cotter
- Department of Biomedical Sciences, Marischal College, University of Aberdeen, Scotland, UK
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