Deletion of Sigmar1 leads to increased arterial stiffness and altered mitochondrial respiration resulting in vascular dysfunction

Sigmar1 is a ubiquitously expressed, multifunctional protein known for its cardioprotective roles in cardiovascular diseases. While accumulating evidence indicate a critical role of Sigmar1 in cardiac biology, its physiological function in the vasculature remains unknown. In this study, we characterized the expression of Sigmar1 in the vascular wall and assessed its physiological function in the vascular system using global Sigmar1 knockout (Sigmar1-/-) mice. We determined the expression of Sigmar1 in the vascular tissue using immunostaining and biochemical experiments in both human and mouse blood vessels. Deletion of Sigmar1 globally in mice (Sigmar1-/-) led to blood vessel wall reorganizations characterized by nuclei disarray of vascular smooth muscle cells, altered organizations of elastic lamina, and higher collagen fibers deposition in and around the arteries compared to wildtype littermate controls (Wt). Vascular function was assessed in mice using non-invasive time-transit method of aortic stiffness measurement and flow-mediated dilation (FMD) of the left femoral artery. Sigmar1-/- mice showed a notable increase in arterial stiffness in the abdominal aorta and failed to increase the vessel diameter in response to reactive-hyperemia compared to Wt. This was consistent with reduced plasma and tissue nitric-oxide bioavailability (NOx) and decreased phosphorylation of endothelial nitric oxide synthase (eNOS) in the aorta of Sigmar1-/- mice. Ultrastructural analysis by transmission electron microscopy (TEM) of aorta sections showed accumulation of elongated shaped mitochondria in both vascular smooth muscle and endothelial cells of Sigmar1-/- mice. In accordance, decreased mitochondrial respirometry parameters were found in ex-vivo aortic rings from Sigmar1 deficient mice compared to Wt controls. These data indicate a potential role of Sigmar1 in maintaining vascular homeostasis.

Joint transformer architecture in brain 3D MRI classification: its application in Alzheimer's disease classification

Alzheimer's disease (AD), a neurodegenerative disease that mostly affects the elderly, slowly impairs memory, cognition, and daily tasks. AD has long been one of the most debilitating chronic neurological disorders, affecting mostly people over 65. In this study, we investigated the use of Vision Transformer (ViT) for Magnetic Resonance Image processing in the context of AD diagnosis. ViT was utilized to extract features from MRIs, map them to a feature sequence, perform sequence modeling to maintain interdependencies, and classify features using a time series transformer. The proposed model was evaluated using ADNI T1-weighted MRIs for binary and multiclass classification. Two data collections, Complete 1Yr 1.5T and Complete 3Yr 3T, from the ADNI database were used for training and testing. A random split approach was used, allocating 60% for training and 20% for testing and validation, resulting in sample sizes of (211, 70, 70) and (1378, 458, 458), respectively. The performance of our proposed model was compared to various deep learning models, including CNN with BiL-STM and ViT with Bi-LSTM. The suggested technique diagnoses AD with high accuracy (99.048% for binary and 99.014% for multiclass classification), precision, recall, and F-score. Our proposed method offers researchers an approach to more efficient early clinical diagnosis and interventions.

Neurogranin expression regulates mitochondrial function and redox balance in endothelial cells

Endothelial dysfunction and endothelial activation are common early events in vascular diseases and can arise from mitochondrial dysfunction. Neurogranin (Ng) is a 17kD protein well known to regulate intracellular Ca2+-calmodulin (CaM) complex signaling, and its dysfunction is significantly implicated in brain aging and neurodegenerative diseases. We found that Ng is also expressed in human aortic endothelial cells (HAECs), and depleting Ng promotes Ca2+-CaM complex-dependent endothelial activation and redox imbalances. Endothelial-specific Ng knockout (Cre-CDH5-Ngf/f) mice demonstrate a significant delay in the flow-mediated dilation (FMD) response. Therefore, it is critical to characterize how endothelial Ng expression regulates reactive oxygen species (ROS) generation and affects cardiovascular disease. Label-free quantification proteomics identified that mitochondrial dysfunction and the oxidative phosphorylation pathway are significantly changed in the aorta of Cre-CDH5-Ngf/f mice. We found that a significant amount of Ng is expressed in the mitochondrial fraction of HAECs using western blotting and colocalized with the mitochondrial marker, COX IV, using immunofluorescence staining. Seahorse assay demonstrated that a lack of Ng decreases mitochondrial respiration. Treatment with MitoEbselen significantly restores the oxygen consumption rate in Ng knockdown cells. With the RoGFP-Orp1 approach, we identified that Ng knockdown increases mitochondrial-specific hydrogen peroxide (H2O2) production, and MitoEbselen treatment significantly reduced mitochondrial ROS (mtROS) levels in Ng knockdown cells. These results suggest that Ng plays a significant role in mtROS production. We discovered that MitoEbselen treatment also rescues decreased eNOS expression and nitric oxide (NO) levels in Ng knockdown cells, which implicates the critical role of Ng in mtROS-NO balance in the endothelial cells.

Hypoxia increases persulfide and polysulfide formation by AMP kinase dependent cystathionine gamma lyase phosphorylation

Hydropersulfide and hydropolysulfide metabolites are increasingly important reactive sulfur species (RSS) regulating numerous cellular redox dependent functions. Intracellular production of these species is known to occur through RSS interactions or through translational mechanisms involving cysteinyl t-RNA synthetases. However, regulation of these species under cell stress conditions, such as hypoxia, that are known to modulate RSS remain poorly understood. Here we define an important mechanism of increased persulfide and polysulfide production involving cystathionine gamma lyase (CSE) phosphorylation at serine 346 and threonine 355 in a substrate specific manner, under acute hypoxic conditions. Hypoxic phosphorylation of CSE occurs in an AMP kinase dependent manner increasing enzyme activity involving unique inter- and intramolecular interactions within the tetramer. Importantly, both cellular hypoxia and tissue ischemia result in AMP Kinase dependent CSE phosphorylation that regulates blood flow in ischemic tissues. Our findings reveal hypoxia molecular signaling pathways regulating CSE dependent persulfide and polysulfide production impacting tissue and cellular response to stress.

Social-geographic disparities in suicidal ideations among methamphetamine users in the USA

IMPORTANCE

Methamphetamine use is a growing public health concern nationwide. Suicide is the second leading cause of death in 2019 for US citizens aged 10-14 years and 25-34 years and is also a significant public health concern. Understanding the intersection of methamphetamine use and suicidal ideation (SI) is necessary to develop public health and policy solutions that mitigate these ongoing severe public health issues.

OBJECTIVE

Our objective was to examine SI in methamphetamine users to allow us to determine prevalence and trends by age, sex, race, and geographical region.

DESIGN, SETTINGS, AND PARTICIPANTS

Using data collected between 2008 and 2019 from the National Inpatient Sample (NIS) database, we identified hospital admissions (HA) of patients ≥18 years of age with a primary or secondary diagnosis of SI who were also diagnosed as methamphetamine users. Those who used other substances with methamphetamine were excluded from the analysis.

MAIN OUTCOME AND MEASURES

To determine the trend and prevalence of hospital admissions due to SI and SI among methamphetamine users, we used trend weights to calculate the national estimates and performed design-based analysis to account for complex survey design and sampling weights on data collected between 2008 and 2019 in the US.

RESULTS

The prevalence ratio (PR) of hospitalizations with concurrent SI and methamphetamine use increased 16-fold from 2008 to 2019. The most significant increase occurred between 2015 and 2016; the PR doubled from 6.07 to 12.14. The PR of hospitalizations with concurrent SI and methamphetamine use was highest in patients aged 26-40 (49.08%) and 41-64 (28.49%). Patients aged 41-64 showed the most significant increase from 2008 to 2019 (15.8-fold). While non-Hispanic White patients comprised most of these hospitalizations (77.02%), non-Hispanic Black patients showed the highest proportional increase (39.1-fold). The Southern and Western regions in the US showed the highest PR for these hospitalizations (34.86% and 34.31%, respectively).

CONCLUSION AND RELEVANCE

Our findings indicate that SI in methamphetamine users has been increasing for some time and is likely to grow. In addition, our results suggest that these patients are demographically different. Both conditions are associated with a lesser likelihood of seeking and receiving care. Therefore, when addressing increased SI or methamphetamine use, learning more about patients who share both conditions is necessary to ensure proper care.

Adipocyte Glucocorticoid Receptor Inhibits Immune Regulatory Genes to Maintain Immune Cell Homeostasis in Adipose Tissue

Glucocorticoids acting via the glucocorticoid receptors (GR) are key regulators of metabolism and the stress response. However, uncontrolled or excessive GR signaling adversely affects adipose tissue, including endocrine, immune, and metabolic functions. Inflammation of the adipose tissue promotes systemic metabolic dysfunction; however, the molecular mechanisms underlying the role of adipocyte GR in regulating genes associated with adipose tissue inflammation are poorly understood. We performed in vivo studies using adipocyte-specific GR knockout mice in conjunction with in vitro studies to understand the contribution of adipocyte GR in regulating adipose tissue immune homeostasis. Our findings show that adipocyte-specific GR signaling regulates adipokines at both mRNA and plasma levels and immune regulatory (Coch, Pdcd1, Cemip, and Cxcr2) mRNA gene expression, which affects myeloid immune cell presence in white adipose tissue. We found that, in adipocytes, GR directly influences Cxcr2. This chemokine receptor promotes immune cell migration, indirectly affecting Pdcd1 and Cemip gene expression in nonadipocyte or stromal cells. Our findings suggest that GR adipocyte signaling suppresses inflammatory signals, maintaining immune homeostasis. We also found that GR signaling in adipose tissue in response to stress is sexually dimorphic. Understanding the molecular relationship between GR signaling and adipose tissue inflammation could help develop potential targets to improve local and systemic inflammation, insulin sensitivity, and metabolic health.

Exposure to Stress Alters Cardiac Gene Expression and Exacerbates Myocardial Ischemic Injury in the Female Murine Heart

Mental stress is a risk factor for myocardial infarction in women. The central hypothesis of this study is that restraint stress induces sex-specific changes in gene expression in the heart, which leads to an intensified response to ischemia/reperfusion injury due to the development of a pro-oxidative environment in female hearts. We challenged male and female C57BL/6 mice in a restraint stress model to mimic the effects of mental stress. Exposure to restraint stress led to sex differences in the expression of genes involved in cardiac hypertrophy, inflammation, and iron-dependent cell death (ferroptosis). Among those genes, we identified tumor protein p53 and cyclin-dependent kinase inhibitor 1A (p21), which have established controversial roles in ferroptosis. The exacerbated response to I/R injury in restraint-stressed females correlated with downregulation of p53 and nuclear factor erythroid 2-related factor 2 (Nrf2, a master regulator of the antioxidant response system-ARE). S-female hearts also showed increased superoxide levels, lipid peroxidation, and prostaglandin-endoperoxide synthase 2 (Ptgs2) expression (a hallmark of ferroptosis) compared with those of their male counterparts. Our study is the first to test the sex-specific impact of restraint stress on the heart in the setting of I/R and its outcome.

Elevated plasma sulfides are associated with cognitive dysfunction and brain atrophy in human Alzheimer's disease and related dementias

Emerging evidence indicates that vascular stress is an important contributor to the pathophysiology of Alzheimer's disease and related dementias (ADRD). Hydrogen sulfide (H2S) and its metabolites (acid-labile (e.g., iron-sulfur clusters) and bound (e.g., per-, poly-) sulfides) have been shown to modulate both vascular and neuronal homeostasis. We recently reported that elevated plasma sulfides were associated with cognitive dysfunction and measures of microvascular disease in ADRD. Here we extend our previous work to show associations between elevated sulfides and magnetic resonance-based metrics of brain atrophy and white matter integrity. Elevated bound sulfides were associated with decreased grey matter volume, while increased acid labile sulfides were associated with decreased white matter integrity and greater ventricular volume. These findings are consistent with alterations in sulfide metabolism in ADRD which may represent maladaptive responses to oxidative stress.

Highly socially vulnerable communities exhibit disproportionately increased viral loads as measured in community wastewater

Wastewater surveillance has proven to be a useful tool for evidence-based epidemiology in the fight against the SARS-CoV-2 virus. It is particularly useful at the population level where acquisition of individual test samples may be time or cost-prohibitive. Wastewater surveillance for SARS-CoV-2 has typically been performed at wastewater treatment plants; however, this study was designed to sample on a local level to monitor the spread of the virus among three communities with distinct social vulnerability indices in Shreveport, Louisiana, located in a socially vulnerable region of the United States. Twice-monthly grab samples were collected from September 30, 2020, to March 23, 2021, during the Beta wave of the pandemic. The goals of the study were to examine whether: 1) concentrations of SARS-CoV-2 RNA in wastewater varied with social vulnerability indices and, 2) the time lag of spikes differed during wastewater monitoring in the distinct communities. The size of the population contributing to each sample was assessed via the quantification of the pepper mild mottle virus (PMMoV), which was significantly higher in the less socially vulnerable community. We found that the communities with higher social vulnerability exhibited greater viral loads as assessed by wastewater when normalized with PMMoV (Kruskal-Wallis, p < 0.05). The timing of the spread of the virus through the three communities appeared to be similar. These results suggest that interconnected communities within a municipality experienced the spread of the SARS-CoV-2 virus at similar times, but areas of high social vulnerability experienced more intense wastewater viral loads.

Sigmar1 ablation leads to lung pathological changes associated with pulmonary fibrosis, inflammation, and altered surfactant proteins levels

Sigma1 receptor protein (Sigmar1) is a small, multifunctional molecular chaperone protein ubiquitously expressed in almost all body tissues. This protein has previously shown its cardioprotective roles in rodent models of cardiac hypertrophy, heart failure, and ischemia-reperfusion injury. Extensive literature also suggested its protective functions in several central nervous system disorders. Sigmar1's molecular functions in the pulmonary system remained unknown. Therefore, we aimed to determine the expression of Sigmar1 in the lungs. We also examined whether Sigmar1 ablation results in histological, ultrastructural, and biochemical changes associated with lung pathology over aging in mice. In the current study, we first confirmed the presence of Sigmar1 protein in human and mouse lungs using immunohistochemistry and immunostaining. We used the Sigmar1 global knockout mouse (Sigmar1-/-) to determine the pathophysiological role of Sigmar1 in lungs over aging. The histological staining of lung sections showed altered alveolar structures, higher immune cells infiltration, and upregulation of inflammatory markers (such as pNFκB) in Sigmar1-/- mice compared to wildtype (Wt) littermate control mice (Wt). This indicates higher pulmonary inflammation resulting from Sigmar1 deficiency in mice, which was associated with increased pulmonary fibrosis. The protein levels of some fibrotic markers, fibronectin, and pSMAD2 Ser 245/250/255 and Ser 465/467, were also elevated in mice lungs in the absence of Sigmar1 compared to Wt. The ultrastructural analysis of lungs in Wt mice showed numerous multilamellar bodies of different sizes with densely packed lipid lamellae and mitochondria with a dark matrix and dense cristae. In contrast, the Sigmar1-/- mice lung tissues showed altered multilamellar body structures in alveolar epithelial type-II pneumocytes with partial loss of lipid lamellae structures in the lamellar bodies. This was further associated with higher protein levels of all four surfactant proteins, SFTP-A, SFTP-B, SFTP-C, and SFTP-D, in the Sigmar1-/- mice lungs. This is the first study showing Sigmar1's expression pattern in human and mouse lungs and its association with lung pathophysiology. Our findings suggest that Sigmar1 deficiency leads to increased pulmonary inflammation, higher pulmonary fibrosis, alterations of the multilamellar body stuructures, and elevated levels of lung surfactant proteins.

Pathological Sequelae Associated with Skeletal Muscle Atrophy and Histopathology in G93A*SOD1 Mice

Amyotrophic lateral sclerosis (ALS) is a complex systemic disease that primarily involves motor neuron dysfunction and skeletal muscle atrophy. One commonly used mouse model to study ALS was generated by transgenic expression of a mutant form of human superoxide dismutase 1 (SOD1) gene harboring a single amino acid substitution of glycine to alanine at codon 93 (G93A*SOD1). Although mutant-SOD1 is ubiquitously expressed in G93A*SOD1 mice, a detailed analysis of the skeletal muscle expression pattern of the mutant protein and the resultant muscle pathology were never performed. Using different skeletal muscles isolated from G93A*SOD1 mice, we extensively characterized the pathological sequelae of histological, molecular, ultrastructural, and biochemical alterations. Muscle atrophy in G93A*SOD1 mice was associated with increased and differential expression of mutant-SOD1 across myofibers and increased MuRF1 protein level. In addition, high collagen deposition and myopathic changes sections accompanied the reduced muscle strength in the G93A*SOD1 mice. Furthermore, all the muscles in G93A*SOD1 mice showed altered protein levels associated with different signaling pathways, including inflammation, mitochondrial membrane transport, mitochondrial lipid uptake, and antioxidant enzymes. In addition, the mutant-SOD1 protein was found in the mitochondrial fraction in the muscles from G93A*SOD1 mice, which was accompanied by vacuolized and abnormal mitochondria, altered OXPHOS and PDH complex protein levels, and defects in mitochondrial respiration. Overall, we reported the pathological sequelae observed in the skeletal muscles of G93A*SOD1 mice resulting from the whole-body mutant-SOD1 protein expression.

Sulfide regulation of cardiovascular function in health and disease

Hydrogen sulfide (H2S) has emerged as a gaseous signalling molecule with crucial implications for cardiovascular health. H2S is involved in many biological functions, including interactions with nitric oxide, activation of molecular signalling cascades, post-translational modifications and redox regulation. Various preclinical and clinical studies have shown that H2S and its synthesizing enzymes - cystathionine γ-lyase, cystathionine β-synthase and 3-mercaptosulfotransferase - can protect against cardiovascular pathologies, including arrhythmias, atherosclerosis, heart failure, myocardial infarction and ischaemia-reperfusion injury. The bioavailability of H2S and its metabolites, such as hydropersulfides and polysulfides, is substantially reduced in cardiovascular disease and has been associated with single-nucleotide polymorphisms in H2S synthesis enzymes. In this Review, we highlight the role of H2S, its synthesizing enzymes and metabolites, their roles in the cardiovascular system, and their involvement in cardiovascular disease and associated pathologies. We also discuss the latest clinical findings from the field and outline areas for future study.

COVID-19 bacteremic co-infection is a major risk factor for mortality, ICU admission, and mechanical ventilation

BACKGROUND

Recent single-center reports have suggested that community-acquired bacteremic co-infection in the context of Coronavirus disease 2019 (COVID-19) may be an important driver of mortality; however, these reports have not been validated with a multicenter, demographically diverse, cohort study with data spanning the pandemic.

METHODS

In this multicenter, retrospective cohort study, inpatient encounters were assessed for COVID-19 with community-acquired bacteremic co-infection using 48-h post-admission blood cultures and grouped by: (1) confirmed co-infection [recovery of bacterial pathogen], (2) suspected co-infection [negative culture with ≥ 2 antimicrobials administered], and (3) no evidence of co-infection [no culture]. The primary outcomes were in-hospital mortality, ICU admission, and mechanical ventilation. COVID-19 bacterial co-infection risk factors and impact on primary outcomes were determined using multivariate logistic regressions and expressed as adjusted odds ratios with 95% confidence intervals (Cohort, OR 95% CI, Wald test p value).

RESULTS

The studied cohorts included 13,781 COVID-19 inpatient encounters from 2020 to 2022 in the University of Alabama at Birmingham (UAB, n = 4075) and Ochsner Louisiana State University Health-Shreveport (OLHS, n = 9706) cohorts with confirmed (2.5%), suspected (46%), or no community-acquired bacterial co-infection (51.5%) and a comparison cohort consisting of 99,170 inpatient encounters from 2010 to 2019 (UAB pre-COVID-19 pandemic cohort). Significantly increased likelihood of COVID-19 bacterial co-infection was observed in patients with elevated ≥ 15 neutrophil-to-lymphocyte ratio (UAB: 1.95 [1.21-3.07]; OLHS: 3.65 [2.66-5.05], p < 0.001 for both) within 48-h of hospital admission. Bacterial co-infection was found to confer the greatest increased risk for in-hospital mortality (UAB: 3.07 [2.42-5.46]; OLHS: 4.05 [2.29-6.97], p < 0.001 for both), ICU admission (UAB: 4.47 [2.87-7.09], OLHS: 2.65 [2.00-3.48], p < 0.001 for both), and mechanical ventilation (UAB: 3.84 [2.21-6.12]; OLHS: 2.75 [1.87-3.92], p < 0.001 for both) across both cohorts, as compared to other risk factors for severe disease. Observed mortality in COVID-19 bacterial co-infection (24%) dramatically exceeds the mortality rate associated with community-acquired bacteremia in pre-COVID-19 pandemic inpatients (5.9%) and was consistent across alpha, delta, and omicron SARS-CoV-2 variants.

CONCLUSIONS

Elevated neutrophil-to-lymphocyte ratio is a prognostic indicator of COVID-19 bacterial co-infection within 48-h of admission. Community-acquired bacterial co-infection, as defined by blood culture-positive results, confers greater increased risk of in-hospital mortality, ICU admission, and mechanical ventilation than previously described risk factors (advanced age, select comorbidities, male sex) for COVID-19 mortality, and is independent of SARS-CoV-2 variant.

Using the social vulnerability index to assess COVID-19 vaccine uptake in Louisiana

Using data from the Louisiana Department of Public Health, we explored the spatial relationships between the Social Vulnerability Index (SVI) and COVID-19-related vaccination and mortality rates. Publicly available COVID-19 vaccination and mortality data accrued from December 2020 to October 2021 was downloaded from the Louisiana Department of Health website and merged with the SVI data; geospatial analysis was then performed to identify the spatial association between the SVI and vaccine uptake and mortality rate. Bivariate Moran's I analysis revealed significant clustering of high SVI ranking with low COVID-19 vaccination rates (1.00, p < 0.001) and high smoothed mortality rates (0.61, p < 0.001). Regression revealed that for each 10% increase in SVI ranking, COVID-19 vaccination rates decreased by 3.02-fold (95% CI = 3.73-2.30), and mortality rates increased by a factor of 1.19 (95% CI = 0.99-1.43). SVI values are spatially linked and significantly associated with Louisiana's COVID-19-related vaccination and mortality rates. We also found that vaccination uptake was higher in whites than in blacks. These findings can help identify regions with low vaccination rates and high mortality, enabling the necessary steps to increase vaccination rates in disadvantaged neighborhoods.

Mitochondrial dysfunction and autophagy activation are associated with cardiomyopathy developed by extended methamphetamine self-administration in rats

The recent rise in illicit use of methamphetamine (METH), a highly addictive psychostimulant, is a huge health care burden due to its central and peripheral toxic effects. Mounting clinical studies have noted that METH use in humans is associated with the development of cardiomyopathy; however, preclinical studies and animal models to dissect detailed molecular mechanisms of METH-associated cardiomyopathy development are scarce. The present study utilized a unique very long-access binge and crash procedure of METH self-administration to characterize the sequelae of pathological alterations that occur with METH-associated cardiomyopathy. Rats were allowed to intravenously self-administer METH for 96 h continuous weekly sessions over 8 weeks. Cardiac function, histochemistry, ultrastructure, and biochemical experiments were performed 24 h after the cessation of drug administration. Voluntary METH self-administration induced pathological cardiac remodeling as indicated by cardiomyocyte hypertrophy, myocyte disarray, interstitial and perivascular fibrosis accompanied by compromised cardiac systolic function. Ultrastructural examination and native gel electrophoresis revealed altered mitochondrial morphology and reduced mitochondrial oxidative phosphorylation (OXPHOS) supercomplexes (SCs) stability and assembly in METH exposed hearts. Redox-sensitive assays revealed significantly attenuated mitochondrial respiratory complex activities with a compensatory increase in pyruvate dehydrogenase (PDH) activity reminiscent of metabolic remodeling. Increased autophagy flux and increased mitochondrial antioxidant protein level was observed in METH exposed heart. Treatment with mitoTEMPO reduced the autophagy level indicating the involvement of mitochondrial dysfunction in the adaptive activation of autophagy in METH exposed hearts. Altogether, we have reported a novel METH-associated cardiomyopathy model using voluntary drug seeking behavior. Our studies indicated that METH self-administration profoundly affects mitochondrial ultrastructure, OXPHOS SCs assembly and redox activity accompanied by increased PDH activity that may underlie observed cardiac dysfunction.

Methamphetamine causes cardiovascular dysfunction via cystathionine gamma lyase and hydrogen sulfide depletion

Methamphetamine (METH) is an addictive illicit drug used worldwide that causes significant damage to blood vessels resulting in cardiovascular dysfunction. Recent studies highlight increased prevalence of cardiovascular disease (CVD) and associated complications including hypertension, vasospasm, left ventricular hypertrophy, and coronary artery disease in younger populations due to METH use. Here we report that METH administration in a mouse model of 'binge and crash' decreases cardiovascular function via cystathionine gamma lyase (CSE), hydrogen sulfide (H2S), nitric oxide (NO) (CSE/H2S/NO) dependent pathway. METH significantly reduced H2S and NO bioavailability in plasma and skeletal muscle tissues co-incident with a significant reduction in flow-mediated vasodilation (FMD) and blood flow velocity revealing endothelial dysfunction. METH administration also reduced cardiac ejection fraction (EF) and fractional shortening (FS) associated with increased tissue and perivascular fibrosis. Importantly, METH treatment selectively decreased CSE expression and sulfide bioavailability along with reduced eNOS phosphorylation and NO levels. Exogenous sulfide therapy or endothelial CSE transgenic overexpression corrected cardiovascular and associated pathological responses due to METH implicating a central molecular regulatory pathway for tissue pathology. These findings reveal that therapeutic intervention targeting CSE/H2S bioavailability may be useful in attenuating METH mediated cardiovascular disease.

The ataxia-telangiectasia mutated gene product regulates the cellular acid-labile sulfide fraction

The ataxia-telangiectasia mutated (ATM) protein regulates cell cycle checkpoints, the cellular redox state, and double-stranded DNA break repair. ATM loss causes the disorder ataxia-telangiectasia (A-T), distinguished by ataxia, telangiectasias, dysregulated cellular redox and iron responses, and an increased cancer risk. We examined the sulfur pool in A-T cells, with and without an ATM expression vector. While free and bound sulfide levels were not changed with ATM expression, the acid-labile sulfide faction was significantly increased. ATM expression also increased cysteine desulfurase (NFS1), NFU1 iron-sulfur cluster scaffold homolog protein, and several mitochondrial complex I proteins' expression. Additionally, ATM expression suppressed cystathionine β-synthase and cystathionine γ-synthase protein expression, cystathionine γ-synthase enzymatic activity, and increased the reduced to oxidized glutathione ratio. This last observation is interesting, as dysregulated glutathione is implicated in A-T pathology. As ATM expression increases the expression of proteins central in initiating 2Fe-2S and 4Fe-4S cluster formation (NFS1 and NFU1, respectively), and the acid-labile sulfide faction is composed of sulfur incorporated into Fe-S clusters, our data indicates that ATM regulates aspects of Fe-S cluster biosynthesis, the transsulfuration pathway, and glutathione redox cycling. Thus, our data may explain some of the redox- and iron-related pathologies seen in A-T.

Neurogranin regulates calcium-dependent cardiac hypertrophy

Intracellular Ca²⁺-calmodulin (CaM) signaling plays an important role in Ca²⁺-CaM-dependent kinase (CaMKII) and calcineurin (CaN)-mediated cardiac biology. While neurogranin (Ng) is known as a major Ca²⁺-CaM modulator in the brain, its pathophysiological role in cardiac hypertrophy has never been studied before. In the present study, we report that Ng is expressed in the heart and depletion of Ng dysregulates Ca²⁺ homeostasis and promotes cardiac failure in mice. 10-month-old Ng null mice demonstrate significantly increased heart-to-body weight ratios compared to wild-type. Using histological approaches, we identified that depletion of Ng increases cardiac hypertrophy, fibrosis, and collagen deposition near perivascular areas in the heart tissue of Ng null mice. Ca²⁺ spark experiments revealed that cardiac myocytes isolated from Ng null mice have decreased spark frequency and width, while the duration of sparks is significantly increased. We also identified that a lack of Ng increases CaMKII_δ signaling and periostin protein expression in these mouse hearts. Overall, we are the first study to explore how Ng expression in the heart plays an important role in Ca²⁺ homeostasis in cardiac myocytes as well as the pathophysiology of cardiac hypertrophy and fibrosis.

Induction of glutathione biosynthesis by glycine-based treatment mitigates atherosclerosis

Lower circulating levels of glycine are consistently reported in association with cardiovascular disease (CVD), but the causative role and therapeutic potential of glycine in atherosclerosis, the underlying cause of most CVDs, remain to be established. Here, following the identification of reduced circulating glycine in patients with significant coronary artery disease (sCAD), we investigated a causative role of glycine in atherosclerosis by modulating glycine availability in atheroprone mice. We further evaluated the atheroprotective potential of DT-109, a recently identified glycine-based compound with dual lipid/glucose-lowering properties. Glycine deficiency enhanced, while glycine supplementation attenuated, atherosclerosis development in apolipoprotein E-deficient (Apoe^−/−) mice. DT-109 treatment showed the most significant atheroprotective effects and lowered atherosclerosis in the whole aortic tree and aortic sinus concomitant with reduced superoxide. In Apoe^−/− mice with established atherosclerosis, DT-109 treatment significantly reduced atherosclerosis and aortic superoxide independent of lipid-lowering effects. Targeted metabolomics and kinetics studies revealed that DT-109 induces glutathione formation in mononuclear cells. In bone marrow-derived macrophages (BMDMs), glycine and DT-109 attenuated superoxide formation induced by glycine deficiency. This was abolished in BMDMs from glutamate-cysteine ligase modifier subunit-deficient (Gclm^−/-) mice in which glutathione biosynthesis is impaired. Metabolic flux and carbon tracing experiments revealed that glycine deficiency inhibits glutathione formation in BMDMs while glycine-based treatment induces de novo glutathione biosynthesis. Through a combination of studies in patients with CAD, in vivo studies using atherosclerotic mice and in vitro studies using macrophages, we demonstrated a causative role of glycine in atherosclerosis and identified glycine-based treatment as an approach to mitigate atherosclerosis through antioxidant effects mediated by induction of glutathione biosynthesis.

The molecular role of Sigmar1 in regulating mitochondrial function through mitochondrial localization in cardiomyocytes

Sigmar1 is a widely expressed molecular chaperone protein in mammalian cell systems. Accumulating research demonstrated the cardioprotective roles of pharmacologic Sigmar1 activation by ligands in preclinical rodent models of cardiac injury. Extensive biochemical and immuno-electron microscopic research demonstrated Sigmar1's sub-cellular localization largely depends on cell and organ types. Despite comprehensive studies, Sigmar1's direct molecular role in cardiomyocytes remains elusive. In the present study, we determined Sigmar1's subcellular localization, transmembrane topology, and function using complementary microscopy, biochemical, and functional assays in cardiomyocytes. Quantum dots in transmission electron microscopy showed Sigmar1 labeled quantum dots on the mitochondrial membranes, lysosomes, and sarcoplasmic reticulum-mitochondrial interface. Subcellular fractionation of heart cell lysates confirmed Sigmar1's localization in purified mitochondria fraction and lysosome fraction. Immunocytochemistry confirmed Sigmar1 colocalization with mitochondrial proteins in isolated adult mouse cardiomyocytes. Sigmar1's mitochondrial localization was further confirmed by Sigmar1 colocalization with Mito-Tracker in isolated mouse heart mitochondria. A series of biochemical experiments, including alkaline extraction and proteinase K treatment of purified heart mitochondria, demonstrated Sigmar1 as an integral mitochondrial membrane protein. Sigmar1's structural requirement for mitochondrial localization was determined by expressing FLAG-tagged Sigmar1 fragments in cells. Full-length Sigmar1 and Sigmar1's C terminal-deletion fragments were able to localize to the mitochondrial membrane, whereas N-terminal deletion fragment was unable to incorporate into the mitochondria. Finally, functional assays using extracellular flux analyzer and high-resolution respirometry showed Sigmar1 siRNA knockdown significantly altered mitochondrial respiration in cardiomyocytes. Overall, we found that Sigmar1 localizes to mitochondrial membranes and is indispensable for maintaining mitochondrial respiratory homeostasis in cardiomyocytes.

Molecular Characterization of Skeletal Muscle Dysfunction in Sigma 1 Receptor (Sigmar1) Knockout Mice

Sigma 1 receptor (Sigmar1) is a widely expressed, multitasking molecular chaperone protein that plays functional roles in several cellular processes. Mutations in the Sigmar1 gene are associated with several distal neuropathies with strong manifestation in skeletal muscle dysfunction with phenotypes like muscle wasting and atrophy. However, the physiological function of Sigmar1 in skeletal muscle remains unknown. Herein, the physiological role of Sigmar1 in skeletal muscle structure and function in gastrocnemius, quadriceps, soleus, extensor digitorum longus, and tibialis anterior muscles was determined. Quantification of myofiber cross-sectional area showed altered myofiber size distribution and changes in myofiber type in the skeletal muscle of the Sigmar1-/- mice. Interestingly, ultrastructural analysis by transmission electron microscopy showed the presence of abnormal mitochondria, and immunostaining showed derangements in dystrophin localization in skeletal muscles from Sigmar1-/- mice. In addition, myopathy in Sigmar1-/- mice was associated with an increased number of central nuclei, increased collagen deposition, and fibrosis. Functional studies also showed reduced endurance and exercise capacity in the Sigmar1-/- mice without any changes in voluntary locomotion, markers for muscle denervation, and muscle atrophy. Overall, this study shows, for the first time, a potential physiological function of Sigmar1 in maintaining healthy skeletal muscle structure and function.

Stimulant Drugs of Abuse and Cardiac Arrhythmias

Nonmedical use of prescription and nonprescription drugs is a worldwide epidemic, rapidly growing in magnitude with deaths because of overdose and chronic use. A vast majority of these drugs are stimulants that have various effects on the cardiovascular system including the cardiac rhythm. Drugs, like cocaine and methamphetamine, have measured effects on the conduction system and through several direct and indirect pathways, utilizing multiple second messenger systems, change the structural and electrical substrate of the heart, thereby promoting cardiac dysrhythmias. Substituted amphetamines and cocaine affect the expression and activation kinetics of multiple ion channels and calcium signaling proteins resulting in EKG changes, and atrial and ventricular brady and tachyarrhythmias. Preexisting conditions cause substrate changes in the heart, which decrease the threshold for such drug-induced cardiac arrhythmias. The treatment of cardiac arrhythmias in patients who take drugs of abuse may be specialized and will require an understanding of the unique underlying mechanisms and necessitates a multidisciplinary approach. The use of primary or secondary prevention defibrillators in drug abusers with chronic systolic heart failure is both sensitive and controversial. This review provides a broad overview of cardiac arrhythmias associated with stimulant substance abuse and their management.

Bad Smells and Broken DNA: A Tale of Sulfur-Nucleic Acid Cooperation

Hydrogen sulfide (H2S) is a gasotransmitter that exerts numerous physiologic and pathophysiologic effects. Recently, a role for H2S in DNA repair has been identified, where H2S modulates cell cycle checkpoint responses, the DNA damage response (DDR), and mitochondrial and nuclear genomic stability. In addition, several DNA repair proteins modulate cellular H2S concentrations and cellular sulfur metabolism and, in turn, are regulated by cellular H2S concentrations. Many DDR proteins are now pharmacologically inhibited in targeted cancer therapies. As H2S and the enzymes that synthesize it are increased in many human malignancies, it is likely that H2S synthesis inhibition by these therapies is an underappreciated aspect of these cancer treatments. Moreover, both H2S and DDR protein activities in cancer and cardiovascular diseases are becoming increasingly apparent, implicating a DDR-H2S signaling axis in these pathophysiologic processes. Taken together, H2S and DNA repair likely play a central and presently poorly understood role in both normal cellular function and a wide array of human pathophysiologic processes. Here, we review the role of H2S in DNA repair.

Transient activation of notch signaling enhances endogenous stromal cell expansion and subsequent bone defect repair

BACKGROUND

Following traumatic bone loss or removal of bone tumors, the failure of bone allograft transplantation for large bone defect repair remains a significant problem in orthopedics. Therefore, new strategies that can efficiently enhance allograft healing and long-term incorporation are critically needed.

METHOD

In this study, we first injected Notch-activating Jagged1 peptide to mice and then isolated bone marrow tissues and cells for proliferation and differentiation assays. Femur bone allograft surgery was also performed in Jagged1 pre-treated mice, and bone defect healing process were monitored by histology, Micro-CT and biomechanical testing.

RESULT

Our results showed that Jagged1 therapeutic injection is sufficient to maximally activate Notch and promote bone marrow stromal cell proliferation in vivo, while no effects on bone structure were observed. More importantly, Jagged1 pre-treatment significantly promoted bone callus formation and increased bone mechanical strength during allograft healing in a femur bone defect mouse model.

CONCLUSION

This study reveals that Notch in vivo activation can be induced by injection of Jagged1 peptide for expansion of local native stromal cells that will significantly enhance bone callus formation.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

The clinical uses of this therapeutic strategy would be immediately applicable for chronic long bone defect repair. More importantly, this devised strategy for expansion of endogenous BMSCs can also be applied to enhance other tissue and organ repair.

Methods in sulfide and persulfide research

Sulfides and persulfides/polysulfides (R-Sn-R', n > 2; R-Sn-H, n > 1) are endogenously produced metabolites that are abundant in mammalian and human cells and tissues. The most typical persulfides that are widely distributed among different organisms include various reactive persulfides-low-molecular-weight thiol compounds such as cysteine hydropersulfide, glutathione hydropersulfide, and glutathione trisulfide as well as protein-bound thiols. These species are generally more redox-active than are other simple thiols and disulfides. Although hydrogen sulfide (H2S) has been suggested for years to be a small signaling molecule, it is intimately linked biochemically to persulfides and may actually be more relevant as a marker of functionally active persulfides. Reactive persulfides can act as powerful antioxidants and redox signaling species and are involved in energy metabolism. Recent evidence revealed that cysteinyl-tRNA synthetases (CARSs) act as the principal cysteine persulfide synthases in mammals and contribute significantly to endogenous persulfide/polysulfide production, in addition to being associated with a battery of enzymes including cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfurtransferase, which have been described as H2S-producing enzymes. The reactive sulfur metabolites including persulfides/polysulfides derived from CARS2, a mitochondrial isoform of CARS, also mediate not only mitochondrial biogenesis and bioenergetics but also anti-inflammatory and immunomodulatory functions. The physiological roles of persulfides, their biosynthetic pathways, and their pathophysiology in various diseases are not fully understood, however. Developing basic and high precision techniques and methods for the detection, characterization, and quantitation of sulfides and persulfides is therefore of great importance so as to thoroughly understand and clarify the exact functions and roles of these species in cells and in vivo.

Ethylmalonic Encephalopathy 1 Protein Is Increased in Colorectal Adenocarcinoma

BACKGROUND/AIM

Ethylmalonic encephalopathy 1 protein (ETHE1) plays an important role in sulfide catabolism and polysulfide formation. As sulfides and polysulfides have recently been identified as playing important roles in cancer, we hypothesized that ETHE1 expression would be increased in colon cancer.

MATERIALS AND METHODS

We used tissue microarray analysis to compare ETHE1 expression in benign colonic epithelium compared to colonic adenocarcinoma. In total, 26 benign colonic epithelial samples were compared to 122 cases of colonic adenocarcinomas.

RESULTS

Compared to benign colonic epithelium, ETHE1 expression was significantly increased (~two-fold) in colonic adenocarcinoma. Additionally, this expression increased with increasing colon cancer tumor grades.

CONCLUSION

ETHE1 expression is increased in colon cancer compared to benign colonic epithelium. These data, combined with previous studies, suggest that ETHE1 may contribute to colon carcinogenesis by promoting tumor cell bioenergetics and polysulfide formation.

Biology of COVID-19 and related viruses: Epidemiology, signs, symptoms, diagnosis, and treatment

Coronaviruses belong to the family Coronaviridae order Nidovirales and are known causes of respiratory and intestinal disease in various mammalian and avian species. Species of coronaviruses known to infect humans are referred to as human coronaviruses (HCoVs). While traditionally, HCoVs have been a significant cause of the common cold, more recently, emergent viruses, including severe acute respiratory syndrome coronavirus (SARS-CoV-2) has caused a global pandemic. Here, we discuss coronavirus disease (COVID-19) biology, pathology, epidemiology, signs and symptoms, diagnosis, treatment, and recent clinical trials involving promising treatments.

Cystathionine Gamma-Lyase Is Increased in Testicular Seminomas, Embryonal, and Yolk Sac Tumors

BACKGROUND

Testicular cancer constitutes 1.0% of male cancer and typically carries a good prognosis. As far as we are aware, the role for hydrogen sulfide in testicular cancer and the level of hydrogen sulfide-synthesizing enzyme have never been addressed. Here we examined cystathionine gamma-lyase (CSE) expression in several germ-cell testicular tumors.

MATERIALS AND METHODS

Tissue microarrays were employed to examine CSE expression in 32 benign testicular samples, 88 testicular seminomas, 34 embryonal carcinomas, 4 mature teratomas, and 16 yolk sac tumors, and CSE expression was compared to that seen in benign testicular tissue.

RESULTS

Compared to benign testicular tissue, CSE expression was increased in all three types of testicular neoplasm but not in mature teratomas. Highest CSE expression was identified in embryonal carcinomas, which often show a relatively aggressive clinical course.

CONCLUSION

For the first time, we show that CSE is increased in several common testicular germ-cell tumor types.

Suppression of mitochondrial respiration by hydrogen sulfide in hibernating 13-lined ground squirrels

Hibernating mammals may suppress their basal metabolic rate during torpor by up to 95% to reduce energy expenditure during winter, but the underlying mechanisms remain poorly understood. Here we show that hydrogen sulfide (H₂S), a ubiquitous signaling molecule, is a powerful inhibitor of respiration of liver mitochondria isolated from torpid 13-lined ground squirrels, but has a weak effect on mitochondria isolated during summer and hibernation arousals, where metabolic rate is normal. Consistent with these in vitro effects, we find strong seasonal variations of in vivo levels of H₂S in plasma and increases of H₂S levels in the liver of squirrels during torpor compared to levels during arousal and summer. The in vivo changes of liver H₂S levels correspond with low activity of the mitochondrial H₂S oxidizing enzyme sulfide:quinone oxidoreductase (SQR) during torpor. Taken together, these results suggest that during torpor, H₂S accumulates in the liver due to a low SQR activity and contributes to inhibition of mitochondrial respiration, while during arousals and summer these effects are reversed, H₂S is degraded by active SQR and mitochondrial respiration rates increase. This study provides novel insights into mechanisms underlying mammalian hibernation, pointing to SQR as a key enzyme involved in the control of mitochondrial function.

Sulfide catabolism ameliorates hypoxic brain injury

The mammalian brain is highly vulnerable to oxygen deprivation, yet the mechanism underlying the brain's sensitivity to hypoxia is incompletely understood. Hypoxia induces accumulation of hydrogen sulfide, a gas that inhibits mitochondrial respiration. Here, we show that, in mice, rats, and naturally hypoxia-tolerant ground squirrels, the sensitivity of the brain to hypoxia is inversely related to the levels of sulfide:quinone oxidoreductase (SQOR) and the capacity to catabolize sulfide. Silencing SQOR increased the sensitivity of the brain to hypoxia, whereas neuron-specific SQOR expression prevented hypoxia-induced sulfide accumulation, bioenergetic failure, and ischemic brain injury. Excluding SQOR from mitochondria increased sensitivity to hypoxia not only in the brain but also in heart and liver. Pharmacological scavenging of sulfide maintained mitochondrial respiration in hypoxic neurons and made mice resistant to hypoxia. These results illuminate the critical role of sulfide catabolism in energy homeostasis during hypoxia and identify a therapeutic target for ischemic brain injury.

Decreased availability of nitric oxide and hydrogen sulfide is a hallmark of COVID-19

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is involved in a global outbreak affecting millions of people who manifest a variety of symptoms. Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 is increasingly associated with cardiovascular complications requiring hospitalizations; however, the mechanisms underlying these complications remain unknown. Nitric oxide (NO) and hydrogen sulfide (H₂S) are gasotransmitters that regulate key cardiovascular functions.

METHODS

Blood samples were obtained from 68 COVID-19 patients and 33 controls and NO and H₂S metabolites were assessed. H₂S and NO levels were compared between cases and controls in the entire study population and subgroups based on race. The availability of gasotransmitters was examined based on severity and outcome of COVID-19 infection. The performance of H₂S and NO levels in predicting COVID-19 infection was also analyzed. Multivariable regression analysis was performed to identify the effects of traditional determinants of gasotransmitters on NO and H₂S levels in the patients with COVID-19 infection.

RESULTS

Significantly reduced NO and H₂S levels were observed in both Caucasian and African American COVID-19 patients compared to healthy controls. COVID-19 patients who died had significantly higher NO and H₂S levels compared to COVID-19 patients who survived. Receiver-operating characteristic analysis of NO and H₂S metabolites in the study population showed free sulfide levels to be highly predictive of COVID-19 infection based on reduced availability. Traditional determinants of gasotransmitters, namely age, race, sex, diabetes, and hypertension had no effect on NO and H₂S levels in COVID-19 patients.

CONCLUSION

These observations provide the first insight into the role of NO and H₂S in COVID-19 infection, where their low availability may be a result of reduced synthesis secondary to endotheliitis, or increased consumption from scavenging of reactive oxygen species.

Plasma hydrogen sulfide: A biomarker of Alzheimer's disease and related dementias

While heart disease remains a common cause of mortality, cerebrovascular disease also increases with age, and has been implicated in Alzheimer's disease and related dementias (ADRD). We have described hydrogen sulfide (H₂S), a signaling molecule important in vascular homeostasis, as a biomarker of cardiovascular disease. We hypothesize that plasma H₂S and its metabolites also relate to vascular and cognitive dysfunction in ADRD. We used analytical biochemical methods to measure plasma H₂S metabolites and MRI to evaluate indicators of microvascular disease in ADRD. Levels of total H₂S and specific metabolites were increased in ADRD versus controls. Cognition and microvascular disease indices were correlated with H₂S levels. Total plasma sulfide was the strongest indicator of ADRD, and partially drove the relationship between cognitive dysfunction and white matter lesion volume, an indicator of microvascular disease. Our findings show that H₂S is dysregulated in dementia, providing a potential biomarker for diagnosis and intervention.

Emergence in late 2020 of multiple lineages of SARS-CoV-2 Spike protein variants affecting amino acid position 677

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein (S) plays critical roles in host cell entry. Non-synonymous substitutions affecting S are not uncommon and have become fixed in a number of SARS-CoV-2 lineages. A subset of such mutations enable escape from neutralizing antibodies or are thought to enhance transmission through mechanisms such as increased affinity for the cell entry receptor, angiotensin-converting enzyme 2 (ACE2). Independent genomic surveillance programs based in New Mexico and Louisiana contemporaneously detected the rapid rise of numerous clade 20G (lineage B.1.2) infections carrying a Q677P substitution in S. The variant was first detected in the US on October 23, yet between 01 Dec 2020 and 19 Jan 2021 it rose to represent 27.8% and 11.3% of all SARS-CoV-2 genomes sequenced from Louisiana and New Mexico, respectively. Q677P cases have been detected predominantly in the south central and southwest United States; as of 03 Feb 2021, GISAID data show 499 viral sequences of this variant from the USA. Phylogenetic analyses revealed the independent evolution and spread of at least six distinct Q677H sub-lineages, with first collection dates ranging from mid-August to late November 2020. Four 677H clades from clade 20G (B.1.2), 20A (B.1.234), and 20B (B.1.1.220, and B.1.1.222) each contain roughly 100 or fewer sequenced cases, while a distinct pair of clade 20G clusters are represented by 754 and 298 cases, respectively. Although sampling bias and founder effects may have contributed to the rise of S:677 polymorphic variants, the proximity of this position to the polybasic cleavage site at the S1/S2 boundary are consistent with its potential functional relevance during cell entry, suggesting parallel evolution of a trait that may confer an advantage in spread or transmission. Taken together, our findings demonstrate simultaneous convergent evolution, thus providing an impetus to further evaluate S:677 polymorphisms for effects on proteolytic processing, cell tropism, and transmissibility.

Decreased bioavailability of hydrogen sulfide links vascular endothelium and atrial remodeling in atrial fibrillation

Oxidative stress drives the pathogenesis of atrial fibrillation (AF), the most common arrhythmia. In the cardiovascular system, cystathionine γ-lyase (CSE) serves as the primary enzyme producing hydrogen sulfide (H₂S), a mammalian gasotransmitter that reduces oxidative stress. Using a case control study design in patients with and without AF and a mouse model of CSE knockout (CSE-KO), we evaluated the role of H₂S in the etiology of AF. Patients with AF (n = 51) had significantly reduced plasma acid labile sulfide levels compared to patients without AF (n = 65). In addition, patients with persistent AF (n = 25) showed lower plasma free sulfide levels compared to patients with paroxysmal AF (n = 26). Consistent with an important role for H₂S in AF, CSE-KO mice had decreased atrial sulfide levels, increased atrial superoxide levels, and enhanced propensity for induced persistent AF compared to wild type (WT) mice. Rescuing H₂S signaling in CSE-KO mice by Diallyl trisulfide (DATS) supplementation or reconstitution with endothelial cell specific CSE over-expression significantly reduced atrial superoxide, increased sulfide levels, and lowered AF inducibility. Lastly, low H₂S levels in CSE KO mice was associated with atrial electrical remodeling including longer effective refractory periods, slower conduction velocity, increased myocyte calcium sparks, and increased myocyte action potential duration that were reversed by DATS supplementation or endothelial CSE overexpression. Our findings demonstrate an important role of CSE and H₂S bioavailability in regulating electrical remodeling and susceptibility to AF.

Dysfunctional Mitochondrial Dynamic and Oxidative Phosphorylation Precedes Cardiac Dysfunction in R120G-αB-Crystallin-Induced Desmin-Related Cardiomyopathy

Background The mutated α-B-Crystallin (CryABR120G) mouse model of desmin-related myopathy (DRM) shows an age-dependent onset of pathologic cardiac remodeling and progression of heart failure. CryABR120G expression in cardiomyocytes affects the mitochondrial spatial organization within the myofibrils, but the molecular perturbation within the mitochondria in the relation of the overall course of the proteotoxic disease remains unclear. Methods and Results CryABR120G mice show an accumulation of electron-dense aggregates and myofibrillar degeneration associated with the development of cardiac dysfunction. Though extensive studies demonstrated that these altered ultrastructural changes cause cardiac contractility impairment, the molecular mechanism of cardiomyocyte death remains elusive. Here, we explore early pathological processes within the mitochondria contributing to the contractile dysfunction and determine the pathogenic basis for the heart failure observed in the CryABR120G mice. In the present study, we report that the CryABR120G mice transgenic hearts undergo altered mitochondrial dynamics associated with increased level of dynamin-related protein 1 and decreased level of optic atrophy type 1 as well as mitofusin 1 over the disease process. In association with these changes, an altered level of the components of mitochondrial oxidative phosphorylation and pyruvate dehydrogenase complex regulatory proteins occurs before the manifestation of pathologic adverse remodeling in the CryABR120G hearts. Mitochondria isolated from CryABR120G transgenic hearts without visible pathology show decreased electron transport chain complex activities and mitochondrial respiration. Taken together, we demonstrated the involvement of mitochondria in the pathologic remodeling and progression of DRM-associated cellular dysfunction. Conclusions Mitochondrial dysfunction in the form of altered mitochondrial dynamics, oxidative phosphorylation and pyruvate dehydrogenase complex proteins level, abnormal electron transport chain complex activities, and mitochondrial respiration are evident on the CryABR120G hearts before the onset of detectable pathologies and development of cardiac contractile dysfunction.

Methamphetamine induces cardiomyopathy by Sigmar1 inhibition-dependent impairment of mitochondrial dynamics and function

Methamphetamine-associated cardiomyopathy is the leading cause of death linked with illicit drug use. Here we show that Sigmar1 is a therapeutic target for methamphetamine-associated cardiomyopathy and defined the molecular mechanisms using autopsy samples of human hearts, and a mouse model of "binge and crash" methamphetamine administration. Sigmar1 expression is significantly decreased in the hearts of human methamphetamine users and those of "binge and crash" methamphetamine-treated mice. The hearts of methamphetamine users also show signs of cardiomyopathy, including cellular injury, fibrosis, and enlargement of the heart. In addition, mice expose to "binge and crash" methamphetamine develop cardiac hypertrophy, fibrotic remodeling, and mitochondrial dysfunction leading to contractile dysfunction. Methamphetamine treatment inhibits Sigmar1, resulting in inactivation of the cAMP response element-binding protein (CREB), decreased expression of mitochondrial fission 1 protein (FIS1), and ultimately alteration of mitochondrial dynamics and function. Therefore, Sigmar1 is a viable therapeutic agent for protection against methamphetamine-associated cardiomyopathy.

Hydrogen sulfide and DNA repair

Recent evidence has revealed that exposing cells to exogenous H 2 S or inhibiting cellular H 2 S synthesis can modulate cell cycle checkpoints, DNA damage and repair, and the expression of proteins involved in the maintenance of genomic stability, all suggesting that H 2 S plays an important role in the DNA damage response (DDR). Here we review the role of H 2 S in the DRR and maintenance of genomic stability. Treatment of various cell types with pharmacologic H 2 S donors or cellular H 2 S synthesis inhibitors modulate the G 1 checkpoint, inhibition of DNA synthesis, and cause p21, and p53 induction. Moreover, in some cell models H 2 S exposure induces PARP-1 and g-H2AX foci formation, increases PCNA, CHK2, Ku70, Ku80, and DNA polymerase-d protein expression, and maintains mitochondrial genomic stability. Our group has also revealed that H 2 S bioavailability and the ATR kinase regulate each other with ATR inhibition lowering cellular H 2 S concentrations, whereas intracellular H 2 S concentrations regulate ATR kinase activity via ATR serine 435 phosphorylation. In summary, these findings have many implications for the DDR, for cancer chemotherapy, and fundamental biochemical metabolic pathways involving H 2 S.

•

Inhibition of the ATR kinase lowers intracellular H₂S concentrations.

•

Inhibition of H₂S synthesis activates the ATR kinase and increases its kinase activity.

•

Inhibition of H₂S synthesis combined with low-level oxidative stress increases genomic instability.

•

These findings may have applications the cancer chemotherapeutics.

Folic Acid Supplementation in Patients with Elevated Homocysteine Levels

Introduction

Folic acid is the most important dietary determinant of homocysteine (Hcy). Hcy serves as a critical intermediate in methylation reactions. It is created from methionine and either converted back to methionine or transformed into cysteine. This process is aided through several enzymes and three vitamins, folic acid, B12, and B6. Daily supplementation with 0.5–5.0 mg of folic acid typically lowers plasma Hcy levels by approximately 25%. Hyperhomocysteinemia is a known risk factor for coronary artery disease. In this regard, elevated levels of Hcy have been found in a majority of patients with vascular disease.

Methods

A literature review of folic acid supplementation for various disease states including cardiovascular disease was conducted. This article is based on previously conducted studies and does not contain any studies with human participants or animals performed by any of the authors.

Results

In this review, we discuss the biochemistry of folic acid, Hcy biosynthesis, Hcy and hydrogen sulfide bioavailability, pathogenesis of hyperhomocysteinemia and its role as a risk factor for disease, and treatment studies with folic acid supplementation in disease states.

Conclusion

Folic acid supplementation should be recommended to any patient who has an elevated Hcy level, and this level should be measured and treated at an early age, since folic acid is easily obtained and may likely reduce vascular disease and other deleterious pathologic processes in high-risk populations.

Pleiotropic effects of mdivi-1 in altering mitochondrial dynamics, respiration, and autophagy in cardiomyocytes

Mitochondria are highly dynamic organelles that constantly undergo fission and fusion events to adapt to changes in the cellular environment. Aberrant mitochondrial fission has been associated with several types of cardiovascular dysfunction; inhibition of pathologically aberrant mitochondrial fission has been shown to be cardioprotective. Pathological fission is mediated by the excessive activation of GTPase dynamin-related protein 1 (Drp1), making it an attractive therapeutic target in numerous cardiovascular diseases. Mitochondrial division inhibitor (mdivi-1) is widely used small molecule reported to inhibit Drp1-dependent fission, elongate mitochondria, and mitigate injury. The purpose of our study was to understand the pleiotropic effects of mdivi-1 on mitochondrial dynamics, mitochondrial respiration, electron transport activities, and macro-autophagy. In this study, we found that mdivi-1 treatment decreased Drp1 expression, proteolytically cleaved L-OPA1, and altered the expression of OXPHOS complex proteins, resulting in increased superoxide production. The altered expression of OXPHOS complex proteins may be directly associated with decreased Drp1 expression, as Drp1 siRNA knockdown in cardiomyocytes showed similar effects. Results from an autophagy flux assay showed that mdivi-1 induced impaired autophagy flux that could be restored by Atg7 overexpression, suggesting that mdivi-1 mediated inhibition of macro-autophagy in cardiomyocytes. Treatment with mdivi-1 resulted in increased expression of p62, which is required for Atg7 overexpression-induced rescue of mdivi-1-mediated impaired autophagy flux. In addition, mdivi-1-dependent proteolytic processing of L-OPA1 was associated with increased mitochondrial superoxide production and altered expression of mitochondrial serine/proteases. Overall, the novel pleiotropic effect of mdivi-1 in cardiomyocytes included proteolytically cleaved L-OPA1, altered expression of OXPHOS complex proteins, and increased superoxide production, which together resulted in defects in mitochondrial respiration and inhibition of macro-autophagy.

Hydrogen sulfide stimulates xanthine oxidoreductase conversion to nitrite reductase and formation of NO

Cardiovascular disease is the leading cause of death and disability worldwide with increased oxidative stress and reduced NO bioavailability serving as key risk factors. For decades, elevation in protein abundance and enzymatic activity of xanthine oxidoreductase (XOR) under hypoxic/inflammatory conditions has been associated with organ damage and vascular dysfunction. Recent reports have challenged this dogma by identifying a beneficial function for XOR, under similar hypoxic/acidic conditions, whereby XOR catalyzes the reduction of nitrite (NO2-) to nitric oxide (NO) through poorly defined mechanisms. We previously reported that hydrogen sulfide (H2S/sulfide) confers significant vascular benefit under these same conditions via NO2- mediated mechanisms independent of nitric oxide synthase (NOS). Here we report for the first time the convergence of H2S, XOR, and nitrite to form a concerted triad for NO generation. Specifically, hypoxic endothelial cells show a dose-dependent, sulfide and polysulfide (diallyl trisulfide (DATS)-induced, NOS-independent NO2- reduction to NO that is dependent upon the enzymatic activity of XOR. Interestingly, nitrite reduction to NO was found to be slower and more sustained with DATS compared to H2S. Capacity for sulfide/polysulfide to produce an XOR-dependent impact on NO generation translates to salutary actions in vivo as DATS administration in cystathionine-γ-lyase (CSE) knockout mice significantly improved hindlimb ischemia blood flow post ligation, while the XOR-specific inhibitor, febuxostat (Febx), abrogated this benefit. Moreover, flow-mediated vasodilation (FMD) in CSE knockout mice following administration of DATS resulted in greater than 4-fold enhancement in femoral artery dilation while co-treatment with Febx completely completely abrogated this effect. Together, these results identify XOR as a focal point of convergence between sulfide- and nitrite-mediated signaling, as well as affirm the critical need to reexamine current dogma regarding inhibition of XOR in the context of vascular dysfunction.

Notch Signaling in Osteogenesis, Osteoclastogenesis, and Angiogenesis

Skeletal tissue development and regeneration in mammals are intricate, multistep, and highly regulated processes. Various signaling pathways have been implicated in the regulation of these processes, including Notch. Notch signaling is a highly conserved, intercellular signaling pathway that regulates cell proliferation and differentiation, determines cell fate decision, and participates in cellular process in embryonic and adult tissue. Here, we review recent data showing the regulation of Notch signaling in osteogenesis, osteoclastogenesis, and angiogenesis. These processes are cell-context-dependent via direct or indirect mechanisms. Furthermore, Notch signaling may be highly beneficial for efficient coupling of osteogenesis and angiogenesis for tissue engineering and skeletal repair, which is critical to develop clinically therapeutic options.

Reactive Sulfur Species: A New Redox Player in Cardiovascular Pathophysiology

Hydrogen sulfide has emerged as an important gaseous signaling molecule and a regulator of critical biological processes. However, the physiological significance of hydrogen sulfide metabolites such as persulfides, polysulfides, and other reactive sulfur species (RSS) has only recently been appreciated. Emerging evidence suggests that these RSS molecules may have similar or divergent regulatory roles compared with hydrogen sulfide in various biological activities. However, the chemical nature of persulfides and polysulfides is complex and remains poorly understood within cardiovascular and other pathophysiological conditions. Recent reports suggest that RSS can be produced endogenously, with different forms having unique chemical properties and biological implications involving diverse cellular responses such as protein biosynthesis, cell-cell barrier functions, and mitochondrial bioenergetics. Enzymes of the transsulfuration pathway, CBS (cystathionine beta-synthase) and CSE (cystathionine gamma-lyase), may also produce RSS metabolites besides hydrogen sulfide. Moreover, CARSs (cysteinyl-tRNA synthetase) are also able to generate protein persulfides via cysteine persulfide (CysSSH) incorporation into nascently formed polypeptides suggesting a new biologically relevant amino acid. This brief review discusses the biochemical nature and potential roles of RSS, associated oxidative stress redox signaling, and future research opportunities in cardiovascular disease.

Neurogranin regulates eNOS function and endothelial activation

Endothelial nitric oxide (NO) is a critical mediator of vascular function and vascular remodeling. NO is produced by endothelial nitric oxide synthase (eNOS), which is activated by calcium (Ca²⁺)-dependent and Ca²⁺-independent pathways. Here, we report that neurogranin (Ng), which regulates Ca²⁺-calmodulin (CaM) signaling in the brain, is uniquely expressed in endothelial cells (EC) of human and mouse vasculature, and is also required for eNOS regulation. To test the role of Ng in eNOS activation, Ng knockdown in human aortic endothelial cells (HAEC) was performed using Ng SiRNA along with Ng knockout (Ng ^−/−) in mice. Depletion of Ng expression decreased eNOS activity in HAEC and NO production in mice. We show that Ng expression was decreased by short-term laminar flow and long-them oscillating flow shear stress, and that Ng siRNA with shear stress decreased eNOS expression as well as eNOS phosphorylation at S1177. We further reveled that lack of Ng expression decreases both AKT-dependent eNOS phosphorylation, NF-κB-mediated eNOS expression, and promotes endothelial activation. Our findings also indicate that Ng modulates Ca²⁺-dependent calcineurin (CaN) activity, which suppresses Ca²⁺-independent AKT-dependent eNOS signaling. Moreover, deletion of Ng in mice also reduced eNOS activity and caused endothelial dysfunction in flow-mediated dilation experiments. Our results demonstrate that Ng plays a crucial role in Ca²⁺-CaM-dependent eNOS regulation and contributes to vascular remodeling, which is important for the pathophysiology of cardiovascular disease.

•

Neurogranin is expressed in endothelial cell and is required for eNOS regulation.

•

Short-term laminar flow and long-them oscillating flow decrease Neurogranin expression in endothelial cells.

•

Neurogranin knockdown decreases both AKT-dependent eNOS phosphorylation and eNOS expression.

•

Deletion of Ng in mice reduces eNOS activity and caused endothelial dysfunction in flow-mediated dilation.

Macrophage Metabolism of Apoptotic Cell-Derived Arginine Promotes Continual Efferocytosis and Resolution of Injury

Continual efferocytic clearance of apoptotic cells (ACs) by macrophages prevents necrosis and promotes injury resolution. How continual efferocytosis is promoted is not clear. Here, we show that the process is optimized by linking the metabolism of engulfed cargo from initial efferocytic events to subsequent rounds. We found that continual efferocytosis is enhanced by the metabolism of AC-derived arginine and ornithine to putrescine by macrophage arginase 1 (Arg1) and ornithine decarboxylase (ODC). Putrescine augments HuR-mediated stabilization of the mRNA encoding the GTP-exchange factor Dbl, which activates actin-regulating Rac1 to facilitate subsequent rounds of AC internalization. Inhibition of any step along this pathway after first-AC uptake suppresses second-AC internalization, whereas putrescine addition rescues this defect. Mice lacking myeloid Arg1 or ODC have defects in efferocytosis in vivo and in atherosclerosis regression, while treatment with putrescine promotes atherosclerosis resolution. Thus, macrophage metabolism of AC-derived metabolites allows for optimal continual efferocytosis and resolution of injury.

Author Correction: The effect of endothelial nitric oxide synthase on the hemodynamics and wall mechanics in murine arteriovenous fistulas

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Methamphetamine Use and Cardiovascular Disease

While the opioid epidemic has garnered significant attention, the use of methamphetamines is growing worldwide independent of wealth or region. Following overdose and accidents, the leading cause of death in methamphetamine users is cardiovascular disease, because of significant effects of methamphetamine on vasoconstriction, pulmonary hypertension, atherosclerotic plaque formation, cardiac arrhythmias, and cardiomyopathy. In this review, we examine the current literature on methamphetamine-induced changes in cardiovascular health, discuss the potential mechanisms regulating these varied effects, and highlight our deficiencies in understanding how to treat methamphetamine-associated cardiovascular dysfunction.