The PhenX Toolkit: Measurement Protocols for Assessment of Social Determinants of Health

INTRODUCTION

Social determinants are structures and conditions in the biological, physical, built, and social environments that affect health, social and physical functioning, health risk, quality of life, and health outcomes. The adoption of recommended, standard measurement protocols for social determinants of health will advance the science of minority health and health disparities research and provide standard social determinants of health protocols for inclusion in all studies with human participants.

METHODS

A PhenX (consensus measures for Phenotypes and eXposures) Working Group of social determinants of health experts was convened from October 2018 to May 2020 and followed a well-established consensus process to identify and recommend social determinants of health measurement protocols. The PhenX Toolkit contains data collection protocols suitable for inclusion in a wide range of research studies. The recommended social determinants of health protocols were shared with the broader scientific community to invite review and feedback before being added to the Toolkit.

RESULTS

Nineteen social determinants of health protocols were released in the PhenX Toolkit (https://www.phenxtoolkit.org) in May 2020 to provide measures at the individual and structural levels for built and natural environments, structural racism, economic resources, employment status, occupational health and safety, education, environmental exposures, food environment, health and health care, and sociocultural community context.

CONCLUSIONS

Promoting the adoption of well-established social determinants of health protocols can enable consistent data collection and facilitate comparing and combining studies, with the potential to increase their scientific impact.

A Decade of Nutrition and Health Disparities Research at NIH, 2010-2019

INTRODUCTION

Nutrition health disparities include differences in incidence, prevalence, morbidity, and mortality of diet-related diseases and conditions. Often, race, ethnicity, and the social determinants of health are associated with dietary intake and related health disparities. This report describes the nutrition health disparities research supported by NIH over the past decade and offers future research opportunities relevant to NIH's mission as described in the Strategic Plan for NIH Nutrition Research.

METHODS

Data were extracted from an internal reporting system from FY2010 to FY2019 using the Research, Condition, and Disease Categorization spending categories for Nutrition and Health Disparities.

RESULTS

Over the past decade, NIH-supported nutrition and health disparities research increased, from 860 grants in 2010 to 937 grants in FY2019, whereas total nutrition and health disparities funding remained relatively stable. The top 5 Institutes/Centers that funded nutrition and health disparities research (on the basis of both grant numbers and dollars) were identified. Principal areas of focus included several chronic diseases (e.g., obesity, diabetes, cancer, heart disease) and research disciplines (e.g., clinical research and behavioral and social science). Focus areas related to special populations included pediatrics, minority health, aging, and women's health.

CONCLUSIONS

The gaps and trends identified in this analysis highlight the need for future nutrition and health disparities research, including a focus on American Indian and Asian populations and the growing topics of rural health, maternal health, and food insecurity. In alignment with the Strategic Plan for NIH Nutrition Research, health equity may be advanced through innovative research approaches to develop effective targeted interventions to address these disparities.

Substance use patterns in 9-10 year olds: Baseline findings from the adolescent brain cognitive development (ABCD) study

BACKGROUND

The Adolescent Brain Cognitive Development ™ Study (ABCD Study®) is an open-science, multi-site, prospective, longitudinal study following over 11,800 9- and 10-year-old youth into early adulthood. The ABCD Study aims to prospectively examine the impact of substance use (SU) on neurocognitive and health outcomes. Although SU initiation typically occurs during teen years, relatively little is known about patterns of SU in children younger than 12.

METHODS

This study aims to report the detailed ABCD Study® SU patterns at baseline (n = 11,875) in order to inform the greater scientific community about cohort's early SU. Along with a detailed description of SU, we ran mixed effects regression models to examine the association between early caffeine and alcohol sipping with demographic factors, externalizing symptoms and parental history of alcohol and substance use disorders (AUD/SUD).

PRIMARY RESULTS

At baseline, the majority of youth had used caffeine (67.6 %) and 22.5 % reported sipping alcohol (22.5 %). There was little to no reported use of other drug categories (0.2 % full alcohol drink, 0.7 % used nicotine, <0.1 % used any other drug of abuse). Analyses revealed that total caffeine use and early alcohol sipping were associated with demographic variables (p's<.05), externalizing symptoms (caffeine p = 0002; sipping p = .0003), and parental history of AUD (sipping p = .03).

CONCLUSIONS

ABCD Study participants aged 9-10 years old reported caffeine use and alcohol sipping experimentation, but very rare other SU. Variables linked with early childhood alcohol sipping and caffeine use should be examined as contributing factors in future longitudinal analyses examining escalating trajectories of SU in the ABCD Study cohort.

A Decade of Nutrition and Health Disparities Research at NIH, 2010–2019

Objectives

Nutrition health disparities include the differences in incidence, prevalence, morbidity, and mortality of diet-related diseases and conditions that disproportionally affect disadvantaged groups (e.g., race, ethnicity, socioeconomic status, disability, rural, immigration status). These disparities arise from the complex interaction of individual, interpersonal, community, and societal factors within the biological, behavioral, and environmental domains. The purpose of this study is to describe the scope of nutrition health disparities research supported by the National Institutes of Health (NIH) over the past decade to identify research gaps and opportunities relevant to NIH's mission.

Methods

Data were extracted from an internal reporting system from 2010 to 2019 using the Research, Condition, and Disease Categorization (RCDC) spending categories for “Nutrition” and “Health Disparities.”

Results

Over the past decade, the number of NIH supported nutrition and health disparities research studies have generally increased, with 860 grants funded in 2010 and 937 grants in 2019, while total nutrition and health disparities funding remained relatively stable. The top 5 Institutes/Centers that funded nutrition and health disparities research included the National Institute of Diabetes and Digestive and Kidney Diseases, National Heart Lung and Blood Institute, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Cancer Institute, and National Institute on Minority Health and Health Disparities.

Conclusions

Consistent with the mission of the top funding ICs, the top research areas were obesity, diabetes, digestive diseases, cancer, heart disease, clinical research, prevention, and behavioral and social sciences. Cross-cutting topics relevant to all NIH ICs included special populations areas such as pediatric and minority health followed by aging and women's health. Consistent with the Strategic Plan for NIH Nutrition Research, it is critical to advance health equity through the application of precision nutrition approaches that acknowledge the influence of biologic, behavioral, psychosocial, environmental, and social factors on nutrition health disparities, and to develop effective targeted interventions to address these disparities.

Funding Sources

None.

Rates of Incidental Findings in Brain Magnetic Resonance Imaging in Children

Importance

Incidental findings (IFs) are unexpected abnormalities discovered during imaging and can range from normal anatomic variants to findings requiring urgent medical intervention. In the case of brain magnetic resonance imaging (MRI), reliable data about the prevalence and significance of IFs in the general population are limited, making it difficult to anticipate, communicate, and manage these findings.

Objectives

To determine the overall prevalence of IFs in brain MRI in the nonclinical pediatric population as well as the rates of specific findings and findings for which clinical referral is recommended.

Design, Setting, and Participants

This cohort study was based on the April 2019 release of baseline data from 11 810 children aged 9 to 10 years who were enrolled and completed baseline neuroimaging in the Adolescent Brain Cognitive Development (ABCD) study, the largest US population-based longitudinal observational study of brain development and child health, between September 1, 2016, and November 15, 2018. Participants were enrolled at 21 sites across the US designed to mirror the demographic characteristics of the US population. Baseline structural MRIs were centrally reviewed for IFs by board-certified neuroradiologists and findings were described and categorized (category 1, no abnormal findings; 2, no referral recommended; 3; consider referral; and 4, consider immediate referral). Children were enrolled through a broad school-based recruitment process in which all children of eligible age at selected schools were invited to participate. Exclusion criteria were severe sensory, intellectual, medical, or neurologic disorders that would preclude or interfere with study participation. During the enrollment process, demographic data were monitored to ensure that the study met targets for sex, socioeconomic, ethnic, and racial diversity. Data were analyzed from March 15, 2018, to November 20, 2020.

Main Outcomes and Measures

Percentage of children with IFs in each category and prevalence of specific IFs.

Results

A total of 11 679 children (52.1% boys, mean [SD] age, 9.9 [0.62] years) had interpretable baseline structural MRI results. Of these, 2464 participants (21.1%) had IFs, including 2013 children (17.2%) assigned to category 2, 431 (3.7%) assigned to category 3, and 20 (0.2%) assigned to category 4. Overall rates of IFs did not differ significantly between singleton and twin gestations or between monozygotic and dizygotic twins, but heritability analysis showed heritability for the presence or absence of IFs (h2 = 0.260; 95% CI, 0.135-0.387).

Conclusions and Relevance

Incidental findings in brain MRI and findings with potential clinical significance are both common in the general pediatric population. By assessing IFs and concurrent developmental and health measures and following these findings over the longitudinal study course, the ABCD study has the potential to determine the significance of many common IFs.

Correspondence Between Perceived Pubertal Development and Hormone Levels in 9-10 Year-Olds From the Adolescent Brain Cognitive Development Study

Aim

To examine individual variability between perceived physical features and hormones of pubertal maturation in 9-10-year-old children as a function of sociodemographic characteristics.

Methods

Cross-sectional metrics of puberty were utilized from the baseline assessment of the Adolescent Brain Cognitive Development (ABCD) Study-a multi-site sample of 9-10 year-olds (n = 11,875)-and included perceived physical features via the pubertal development scale (PDS) and child salivary hormone levels (dehydroepiandrosterone and testosterone in all, and estradiol in females). Multi-level models examined the relationships among sociodemographic measures, physical features, and hormone levels. A group factor analysis (GFA) was implemented to extract latent variables of pubertal maturation that integrated both measures of perceived physical features and hormone levels.

Results

PDS summary scores indicated more males (70%) than females (31%) were prepubertal. Perceived physical features and hormone levels were significantly associated with child's weight status and income, such that more mature scores were observed among children that were overweight/obese or from households with low-income. Results from the GFA identified two latent factors that described individual differences in pubertal maturation among both females and males, with factor 1 driven by higher hormone levels, and factor 2 driven by perceived physical maturation. The correspondence between latent factor 1 scores (hormones) and latent factor 2 scores (perceived physical maturation) revealed synchronous and asynchronous relationships between hormones and concomitant physical features in this large young adolescent sample.

Conclusions

Sociodemographic measures were associated with both objective hormone and self-report physical measures of pubertal maturation in a large, diverse sample of 9-10 year-olds. The latent variables of pubertal maturation described a complex interplay between perceived physical changes and hormone levels that hallmark sexual maturation, which future studies can examine in relation to trajectories of brain maturation, risk/resilience to substance use, and other mental health outcomes.

NIMHD Transdisciplinary Collaborative Centers for Health Disparities Research Focused on Precision Medicine

The NIMHD Transdisciplinary Collaborative Centers for Health Disparities Research Focused on Precision Medicine (PM TCCs) comprise regional coalitions of research institutions and consortium partners focused on priority research topics in minority health and health disparities. In April 2016, NIMHD, in partnership with the National Human Genome Research Institute (NHGRI) and the National Cancer Institute (NCI), launched the PM TCC program to fund five centers across the United States to stimulate health disparities research with an emphasis on precision medicine to address one or more documented health disparities. The programs draw on expertise in genomics and other 'omics, physiology and medicine, population health disparities, behavioral and social sciences, and the science of translation, implementation and dissemination. The TCC program's overarching goal is to develop and disseminate effective interventions that can be implemented in real-world settings with the goal of promoting health equity and reducing health disparities. This special issue of Ethnicity & Disease is dedicated to cutting-edge research conducted by the five PM TCCs at the intersection between precision medicine and health disparities. Articles in this issue will enhance knowledge in a variety of research topics from perspectives on precision medicine among different health disparity populations to methods for reducing inequities in protocols, interventions, and health information and further efforts to promote inclusion of all populations, especially the most vulnerable.

From the Outside In: Biological Mechanisms Linking Social and Environmental Exposures to Chronic Disease and to Health Disparities

The ongoing epidemic of chronic diseases involves a spectrum of clinical entities now understood to represent late manifestations of progressive metabolic dysfunction initiated in early life. These diseases disproportionately affect disadvantaged populations, exacerbating health disparities that persist despite public health efforts. Excessive exposure to stressful psychosocial and environmental forces is 1 factor known to contribute to population-level disparities in at-risk settings. Yet increasing evidence reveals that even a single adverse environmental exposure-especially during very early developmental years-can become literally biologically embedded, inducing long-lasting disease-promoting pathways that amplify responses (e.g., cortisol, immune, inflammatory) to all future adverse stressors, thus enhancing their disease-promoting impacts. The same pathways may also interact with ancestrally linked genetic variants to modify chronic disease risk. We address how, in at-risk populations, environmentally activated disease-promoting pathways can contribute to a biologically based disease-susceptible phenotype; this is likely to be uniquely damaging in populations with multiple adverse exposures and is capable of cross-generational transmission. Intended to complement existing models, this biological perspective highlights key research opportunities and life-stage priorities with potential to enhance the reduction of health disparities.

APOL1 Long-term Kidney Transplantation Outcomes Network (APOLLO): Design and Rationale

INTRODUCTION

Much of the higher risk for end-stage kidney disease (ESKD) in African American individuals relates to ancestry-specific variation in the apolipoprotein L1 gene (APOL1). Relative to kidneys from European American deceased-donors, kidneys from African American deceased-donors have shorter allograft survival and African American living-kidney donors more often develop ESKD. The National Institutes of Health (NIH)-sponsored APOL1 Long-term Kidney Transplantation Outcomes Network (APOLLO) is prospectively assessing kidney allograft survival from donors with recent African ancestry based on donor and recipient APOL1 genotypes.

METHODS

APOLLO will evaluate outcomes from 2614 deceased kidney donor-recipient pairs, as well as additional living-kidney donor-recipient pairs and unpaired deceased-donor kidneys.

RESULTS

The United Network for Organ Sharing (UNOS), Association of Organ Procurement Organizations, American Society of Transplantation, American Society for Histocompatibility and Immunogenetics, and nearly all U.S. kidney transplant programs, organ procurement organizations (OPOs), and histocompatibility laboratories are participating in this observational study. APOLLO employs a central institutional review board (cIRB) and maintains voluntary partnerships with OPOs and histocompatibility laboratories. A Community Advisory Council composed of African American individuals with a personal or family history of kidney disease has advised the NIH Project Office and Steering Committee since inception. UNOS is providing data for outcome analyses.

CONCLUSION

This article describes unique aspects of the protocol, design, and performance of APOLLO. Results will guide use of APOL1 genotypic data to improve the assessment of quality in deceased-donor kidneys and could increase numbers of transplanted kidneys, reduce rates of discard, and improve the safety of living-kidney donation.

Endotoxin Removal from Whole Blood by a Novel Adsorption Resin: Efficiency and Hemocompatibility

The structural component of Gram- bacteria, endotoxin (ET), induces the release of endogenous mediators of sepsis. Attempts to remove these downstream molecules in vivo, have not improved survival. However, extracorporeal strategies such as continuous renal replacement therapy or therapeutic plasmapheresis have shown benefit. We are presenting an affinity-based extracorporeal technology for the removal of ET from whole blood. The small-scale device contains an adsorbent that removed 75% of ET present in whole blood. This affinity resin displayed good hemocompatibility regarding the coagulation pathway. Minimal platelet, neutrophil and complement activation were observed. There was also no evidence of consumption of coagulation factors or cell loss. In as much as ET participates in both the inflammatory and coagulation abnormalities in sepsis, this method represents an efficient and hemocompatible way to remove ET from whole blood, which, in an extracorporeal setting, may improve the outcome of sepsis.

Glycogen synthase kinase 3 inhibition slows mitochondrial adenine nucleotide transport and regulates voltage-dependent anion channel phosphorylation

Inhibition of glycogen synthase kinase (GSK)-3 reduces ischemia/reperfusion injury by mechanisms that involve the mitochondria. The goal of this study was to explore possible molecular targets and mechanistic basis of this cardioprotective effect. In perfused rat hearts, treatment with GSK inhibitors before ischemia significantly improved recovery of function. To assess the effect of GSK inhibitors on mitochondrial function under ischemic conditions, mitochondria were isolated from rat hearts perfused with GSK inhibitors and were treated with uncoupler or cyanide or were made anoxic. GSK inhibition slowed ATP consumption under these conditions, which could be attributable to inhibition of ATP entry into the mitochondria through the voltage-dependent anion channel (VDAC) and/or adenine nucleotide transporter (ANT) or to inhibition of the F(1)F(0)-ATPase. To determine the site of the inhibitory effect on ATP consumption, we measured the conversion of ADP to AMP by adenylate kinase located in the intermembrane space. This assay requires adenine nucleotide transport across the outer but not the inner mitochondrial membrane, and we found that GSK inhibitors slow AMP production similar to their effect on ATP consumption. This suggests that GSK inhibitors are acting on outer mitochondrial membrane transport. In sonicated mitochondria, GSK inhibition had no effect on ATP consumption or AMP production. In intact mitochondria, cyclosporin A had no effect, indicating that ATP consumption is not caused by opening of the mitochondrial permeability transition pore. Because GSK is a kinase, we assessed whether protein phosphorylation might be involved. Therefore, we performed Western blot and 1D/2D gel phosphorylation site analysis using phos-tag staining to indicate proteins that had decreased phosphorylation in hearts treated with GSK inhibitors. Liquid chromatographic-mass spectrometric analysis revealed 1 of these proteins to be VDAC2. Taken together, we found that GSK-mediated signaling modulates transport through the outer membrane of the mitochondria. Both proteomics and adenine nucleotide transport data suggest that GSK regulates VDAC and that VDAC may be an important regulatory site in ischemia/reperfusion injury.

Cortical spreading depression (CSD)-induced tolerance to transient focal cerebral ischemia in halothane anesthetized rats is affected by anesthetic level but not ATP-sensitive potassium channels

We investigated the participation of ATP-sensitive potassium (K(ATP)) channels, adenosine A1 receptors, and the effects of different levels of halothane anesthesia in the development of CSD-induced ischemic tolerance. To elicit CSD, 0.5 M KCl was applied for 2 h to the right hemisphere of halothane anesthetized male Wistar rats. The inhalation concentration of halothane during CSD was maintained at 0.5% (n = 8), 1.0% (n = 8), or 2.0% (n = 8). For control animals, saline was applied instead of KCl (n = 8). To inhibit K(ATP) channels or adenosine A1 receptors, glibenclamide (0.1 mg/kg icv; n = 8), 5-hydroxydeconaoate (5-HD; 100 mg/kg ip; n = 12), or 8-Cyclopentyl-1, 3-dipropylxanthine (DPCPX) (1.0 mg/kg ip; n = 8) was applied before preconditioning during 1.0% halothane anesthesia. Temporary occlusion (120 min) of the right middle cerebral artery was induced 4 days after preconditioning and the infarct volume was measured. Preconditioning elicited under 1.0% halothane reduced cortical infarct volume from 277 +/- 15 mm3 in the control group to 159 +/- 14 mm3 in the CSD group (mean +/- SEM, P < 0.05). In contrast, CSD induced during inhalation of 0.5% or 2.0% halothane did not confer ischemic tolerance. The reduction in infarct area with CSD during inhalation of 1% halothane was not changed in animals treated with glibenclamide or 5-HD or DPCPX. These results uncover a crucial role of halothane level but not of K(ATP) channels or adenosine A1 receptors in the preconditioning effects of CSD.

Targeting mitochondrial ATP-sensitive potassium channels--a novel approach to neuroprotection

Mitochondrial responses to ischemic stress play an important role in necrosis and apoptosis of brain cells. Recent studies using several different experimental preparations have shown that activation of ATP-sensitive potassium channels in mitochondria (mitoK(ATP) channels) is able to protect neurons and astroglia against injury and death. Thus, targeting of mitoK(ATP) channels appears to be a novel approach to neuroprotection. However, little is known about the mechanisms involved. The purpose of this review is to detail the current state of knowledge about this important, emerging area of investigation, and to provide suggestions for future studies.

Neuroprotection against hypoxia-ischemia in neonatal rat brain by novel superoxide dismutase mimetics

We investigated the effects of two new low molecular weight nonpeptidyl superoxide dismutase (SOD) mimetics (M40403/M40401; MetaPhore Pharmaceuticals) on infarct volume after hypoxia-ischemia injury (H/I) in immature rats. Animals received vehicle or different doses of M40403 or M40401 i.p. 2 h before exposure to 3 h of 8% hypoxia. The infarct volume of the hemisphere ipsilateral to carotid ligation 24 h later was 73.9+/-8.9% in vehicle animals (n=9), and decreased to 39.7+/-7.2% (P<0.05, n=10) in animals treated with 3 mg/kg M40403 and to 37.2+/-6.4% for animals receiving 3 mg/kg M40401 (P<0.05, n=8). These data indicate that the SOD mimetics M40403 and M40401 have protective effects against hypoxic-ischemic brain injury, and suggest the involvement of superoxide anion in neuronal cell injury during H/I.

Diazoxide pretreatment induces delayed preconditioning in astrocytes against oxygen glucose deprivation and hydrogen peroxide-induced toxicity

Recent studies suggest that activation of mitochondrial ATP-sensitive potassium channels (mK(ATP)) with diazoxide can protect neurons against ischemic stress. However, it is not yet known whether astrocytes, which are more resilient against ischemia, respond similarly to diazoxide. We exposed cultured astrocytes to oxygen-glucose deprivation (OGD) or hydrogen peroxide (H2O2) with or without pretreatment with the mK(ATP) opener diazoxide. Marked decreases in astrocyte viability were evident after 9 and 12 hr of OGD [76% +/- 3% (n = 50) and 60% +/- 1% (n = 50)] and 400 and 600 microM H2O2 [40% +/- 2% (n = 16) and 25% +/- 2% (n = 16)], respectively, compared with no treatment (100% +/- 1%). Diazoxide treatment (3 days of sequential application) dramatically reversed the negative effects of OGD and H2O2, resulting in complete blockade of astrocyte cell death. Effects of diazoxide were blocked by the mK(ATP) blocker 5-hydroxydecanoic acid (5-HD). Furthermore, incubation of astrocytes with diazoxide resulted in loss of mitochondrial membrane potential monitored by tetramethylrhodamineethylester fluorescence. Additionally, generation of reactive oxygen species was observed in response to diazoxide, assessed using the oxidation-sensitive dye hydroethidine, and this effect was abolished by antioxidants, catalase, and a superoxide dismutase mimetic, M40401. Finally, diazoxide increased the protein level of phosphorylated protein kinase C (PKC) revealed by immunoblot analysis. Our findings demonstrate that opening of mK(ATP) by diazoxide identifies a delayed preconditioning effect that is protective against two types of injury in astrocytes and that diazoxide may deliver protection via mitochondrial depolarization, free radical production, and PKC activation.

Opening of mitochondrial ATP-sensitive potassium channels is a trigger of 3-nitropropionic acid-induced tolerance to transient focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

The role of mitochondrial ATP-sensitive potassium channels (mitoK(ATP)) in ischemic tolerance has been well documented in heart, but little work has been done in brain. To investigate the involvement of mitoK(ATP) activation in chemical preconditioning in brain, we examined the effect of 5-hydroxydecanoate (5-HD), a selective mitoK(ATP) blocker, on neurotoxin 3-nitropropionic acid (3-NPA)-induced ischemic tolerance to transient focal cerebral ischemia in rats.

METHODS

Male Wistar rats were administrated 3-NPA (20 mg/kg IP; n=16) or vehicle (saline; n=16) 3 days before temporary occlusion (120 minutes) of the middle cerebral artery; 5-HD (40 mg/kg IP; n=16) was injected 20 minutes before 3-NPA administration. Infarct volumes were measured 4 days after reperfusion. To directly investigate whether chemical preconditioning activates mitoK(ATP), we tested the effect of prior incubation with 1 mmol/L 5-HD on 300 micromol/L 3-NPA-induced alterations of mitochondrial membrane potential (Delta(Psi)m) in cultured neurons and astrocytes using the fluorescent dye tetramethylrhodamine ethyl ester.

RESULTS

Treatment with 3-NPA exhibited a 16% reduction (P<0.05) and 23% reduction in infarct volume (P<0.01) for total brain and cortex, respectively. Pretreatment with 5-HD completely abolished the neuroprotective effect of chemical preconditioning. In cultured cells, 3-NPA resulted in mitochondrial depolarization. This change of Delta(Psi)m was completely blocked by 5-HD pretreatment.

CONCLUSIONS

These results strongly suggest that opening of mitoK(ATP) plays a key role as the trigger in the development of 3-NPA-induced ischemic tolerance in brain.

Protective effect of a new nonpeptidyl mimetic of SOD, M40401, against focal cerebral ischemia in the rat

We tested the neuroprotective effects of M40401, a new, low molecular weight (511.4 Da) maganese superoxide dismutase mimetic, against 90 min of middle cerebral artery occlusion (MCAO) in male Wistar rats. Animals received a single injection of vehicle (n=8), 1 mg/kg (n=6), or 3 mg/kg (n=7) 30 min before MCAO. Total lesion volume was reduced only in the group receiving 3 mg/kg M40401 (163.5+/-18.7 versus 43.4+/-7.0 mm(3), for vehicle and M40401, respectively; P<0.05), with almost complete reduction of lesion volume in the cortex but little protection in the basal ganglia. Neurological score was also improved in this group. The dose of 1 mg/kg M40401 had smaller and inconsistent effects on lesion parameters. Administration of a single dose of 3 mg/kg M40401 at 60 min of MCAO or at the end of MCAO (90 min) failed to significantly reduce lesion volume. A single dose of M40401 plus prolonged infusion into the post-MCAO period also failed to decrease lesion volume significantly. These data indicate that M40401 protects cerebral tissue from ischemic insult when administered before MCAO, probably by limiting damage mediated by detrimental actions of superoxide anion.

Transient focal ischemia increases endothelial nitric oxide synthase in cerebral blood vessels

BACKGROUND AND PURPOSE

Production of NO by endothelial NO synthase (eNOS) plays a protective role in cerebral ischemia. We studied the effects of transient focal ischemia on eNOS expression.

METHODS

Wistar rats (n=72) underwent reversible filament occlusion of the right middle cerebral artery for 75 minutes. After 6, 24, 72, or 168 hours of reperfusion, brains were removed and coronal sections cut for eNOS immunohistochemistry, eNOS-alkaline phosphatase costaining, and hematoxylin-eosin staining. Samples for eNOS immunoblots were taken from corresponding striatum and overlying parietal cortex bilaterally.

RESULTS

eNOS protein occurred in virtually all blood vessels and was consistently increased in microvessels in the ischemic striatum after 24 to 168 hours of reperfusion but not at 6 hours. eNOS upregulation in the parietal cortex was only present in animals with evidence of cortical infarcts documented on adjacent HE-stained sections. Costaining of endogenous alkaline phosphatase and eNOS demonstrated eNOS expression in all segments of cerebral microvessels. Quantitative analysis of eNOS immunostaining and immunoblots showed no attenuated increase in animals that were treated with indomethacin (5 mg/kg IP), NS398 (20 mg/kg IP), or L-arginine-methyl ester (10 mg/kg IP). In contrast to eNOS, levels of brain NOS did not increase after ischemia.

CONCLUSION

eNOS protein is upregulated in pre- and postcapillary microvessels and upregulation appears slower after transient compared with permanent ischemia. Cyclooxygenase and NOS products do not play a major role in postischemic eNOS induction.

MitoK(ATP) opener, diazoxide, reduces neuronal damage after middle cerebral artery occlusion in the rat

We investigated effects of diazoxide, a selective opener of mitochondrial ATP-sensitive K(+) (mitoK(ATP)) channels, against brain damage after middle cerebral artery occlusion (MCAO) in male Wistar rats. Diazoxide (0.4 or 2 mM in 30 microl saline) or saline (sham) was infused into the right lateral ventricle 15 min before MCAO. Neurological score was improved 24 h later in the animals treated with 2 mM diazoxide (13.8 +/- 0.7, n = 13) compared with sham treatment (9.5 +/- 0.2, n = 6, P < 0.01). The total percent infarct volume (MCAO vs. contralateral side) of sham treatment animals was 43.6 +/- 3.6% (n = 12). Treatment with 2 mM diazoxide reduced the infarct volume to 20.9 +/- 4.8% (n = 13, P < 0.05). Effects of diazoxide were prominent in the cerebral cortex. The protective effect of diazoxide was completely prevented by the pretreatment with 5-hydroxydecanoate (100 mM in 10 microl saline), a selective blocker of mitoK(ATP) channels (n = 6). These results indicate that selective opening of the mitoK(ATP) channel has neuroprotective effects against ischemia-reperfusion injury in the rat brain.

Activation of mitochondrial ATP-sensitive potassium channels prevents neuronal cell death after ischemia in neonatal rats

Activation of mitochondrial ATP-sensitive potassium channels (mK(ATP)) has been shown to protect against cell death following ischemia/reperfusion in the heart but not in brain. We examined whether mK(ATP) activation with diazoxide (DIZ) prevents neuronal cell death following hypoxia-ischemia (HI) in 7-day-old rat pups. Rat pups were subjected to HI (left carotid ligation; 8% O(2); 2.5 h), following administration of vehicle, 1.9 mg/kg DIZ, 3.8 mg/kg DIZ or DIZ plus 10 mg/kg 5-hydroxydecanoic acid (mK(ATP) antagonist). Total infarct volume was reduced from 99.8+/-2.7% in vehicle animals to 80.6+/-4.2% in 3.8 mg/kg DIZ treated animals (n=85, P<0.05). Western blotting showed K(ATP) subunits concentrated in mitochondria. Fluorescent studies indicated DIZ directly depolarized the mitochondria. In conclusion, selective opening of mK(ATP) prior to HI results in neuroprotection in immature rats.

Mitochondrial nitric oxide synthase is constitutively active and is functionally upregulated in hypoxia

Nitric oxide is a potent modulator of mitochondrial respiration, ATP synthesis, and K(ATP) channel activity. Recent studies show the presence of a potentionally new isoform of the nitric oxide synthase (NOS) enzyme in mitochondria, although doubts have emerged regarding the physiological relevance of mitochondrial NOS (mtNOS). The aim of the present study were to: (i) examine the existence and distribution of mtNOS in mouse tissues using three independent methods, (ii) characterize the cross-reaction of mtNOS with antibodies against the known isoforms of NOS, and (iii) investigate the effect of hypoxia on mtNOS activity. Nitric oxide synthase activity was measured in isolated brain and liver mitochondria using the arginine to citrulline conversion assay. Mitochondrial NOS activity in the brain was significantly higher than in the liver. The calmodulin inhibitor calmidazolium completely inhibited mtNOS activity. In animals previously subjected to hypoxia, mtNOS activity was significantly higher than in the normoxic controls. Antibodies against the endothelial (eNOS), but not the neuronal or inducible isoform of NOS, showed positive immunoblotting. Immunogold labeling of eNOS located the enzyme in the matrix and the inner membrane using electron microscopy. We conclude that mtNOS is a constitutively active eNOS-like isoform and is involved in altered mitochondrial regulation during hypoxia.

Isolation and characterization of intact mitochondria from neonatal rat brain

Poor outcome after neonatal brain injury may be associated with alterations in mitochondrial function. Thus, isolated mitochondria have been a useful tool in understanding the underlying mechanisms of mitochondrial dysfunction. However, isolation and characterization of mitochondria from neonatal rat brain are not fully described. Thus, the aim of this study was to develop a rapid method for the isolation and characterization of functional mitochondria from neonatal rat brain. Mitochondria were isolated from 7-day-old rat brain weighing approximately 500 mg using a discontinuous Percoll density gradient. Brains were homogenized in 12% Percoll/sucrose buffer and layered onto a 26% Percoll/40% Percoll gradient followed by centrifugation. Four methods were used for assessing mitochondrial integrity and function: (1) electron microscopy to assess the morphology of the mitochondria and to determine the relative purity of the preparation; (2) fluorescence of chloromethyl-X-rosamine (Mito Tracker Red) in mitochondria as an indicator of mitochondrial membrane potential (Delta psi(m)); (3) state 3 and 4 respiration; and (4) protein import into mitochondria using an in vitro-synthesized mitochondrial malate dehydrogenase (mMDH). These studies demonstrated that the morphology of mitochondria is maintained with intact outer membranes and well-developed cristae, and Delta psi(m) is preserved. Respiration measurements revealed tightly coupled mitochondria with a respiration control ratio (RCR) of 4.1+/-0.18 (n=6). Import of precursor mMDH into mitochondria increased in a time-dependent manner maximizing at 15 min. The results indicate that neonatal brain mitochondria isolated using this method are well coupled, morphologically intact and are capable of protein import across the outer and inner mitochondrial membranes.

Defining the impact of weakly estrogenic chemicals on the action of steroidal estrogens

We tested whether bisphenol A (BPA) or o,p'-DDT, when combined with 17beta-estradiol (E2), would contribute to the overall mixture effect using a yeast reporter gene assay, the yeast estrogen screen. Following comprehensive concentration-response analyses of the single agents, the pharmacologically well-founded models of concentration addition and independent action were used to predict entire concentration-response relationships for mixtures of the agents with a variety of fixed mixture ratios, assuming additivity. For molar mixture ratios proportional to the levels normally found in human tissues (i.e., below 1:5000, E2:BPA or o,p'-DDT), these predictions suggest that the effects of individual xenoestrogens are too weak to create an impact on the actions of steroidal hormones. However, at mixture ratios more in favor of the xenoestrogens, a significant contribution to the overall mixture effect was predicted. The predictions were tested experimentally. The observed combined effects of mixtures of E2 with either BPA or o,p'-DDT did not deviate from the additivity expectation. On combining E2 with either BPA or o,p'-DDT at approximately equieffective concentrations corresponding to molar mixture ratios between 1:20,000 and 1:100,000 (E2:BPA or o,p'-DDT), substantial modulations of the effects of E2 became discernible. The assumption that weak xenoestrogens are generally unable to create an impact upon the already strong effects of endogenous steroidal estrogens is not supported by our observations. Our studies indicate that the potential health implication of additive combination effects between xenoestrogens and steroidal estrogens deserve serious consideration.

Prediction and assessment of the effects of mixtures of four xenoestrogens

The assessment of mixture effects of estrogenic agents is regarded as an issue of high priority by many governmental agencies and expert decision-making bodies all over the world. However, the few mixture studies published so far have suffered from conceptual and experimental problems and are considered to be inconclusive. Here, we report the results of assessments of two-, three- and four-component mixtures of o,p'-DDT, genistein, 4-nonylphenol, and 4-n-octylphenol, all compounds with well-documented estrogenic activity. Extensive concentration-response analyses with the single agents were carried out using a recombinant yeast screen (yeast estrogen screen, YES). Based on the activity of the single agents in the YES assay we calculated predictions of entire concentration-response curves for mixtures of our chosen test agents assuming additive combination effects. For this purpose we employed the models of concentration addition and independent action, both well-established models for the calculation of mixture effects. Experimental concentration-response analyses revealed good agreement between predicted and observed mixture effects in all cases. Our results show that the combined effect of o,p'-DDT, genistein, 4-nonylphenol, and 4-n-octylphenol in the YES assay does not deviate from expected additivity. We consider both reference models as useful tools for the assessment of combination effects of multiple mixtures of xenoestrogens.