Soluble epoxide hydrolase and TRPC3 channels jointly contribute to homocysteine-induced cardiac hypertrophy: Interrelation and regulation by C/EBPβ

OBJECTIVES

Studies in certain cardiac hypertrophy models suggested the individual role of soluble epoxide hydrolase (sEH) and canonical transient receptor potential 3 (TRPC3) channels, however, whether they jointly mediate hypertrophic process remains unexplored. Hyperhomocysteinemia promotes cardiac hypertrophy while the involvement of sEH and TRPC3 channels remains unknown. This study aimed to explore the role of, and interrelation between sEH and TRPC3 channels in homocysteine-induced cardiac hypertrophy.

METHODS

Rats were fed methionine-enriched diet to induce hyperhomocysteinemia. H9c2 cells and neonatal rat cardiomyocytes were incubated with homocysteine. Cardiac hypertrophy was evaluated by echocardiography, histological examination, immunofluorescence imaging, and expressions of hypertrophic markers. Epoxyeicosatrienoic acids (EETs) were determined by ELISA. TRPC3 current was recorded by patch-clamp. Gene promotor activity was measured using dual-luciferase reporter assay.

RESULTS

Inhibition of sEH by 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) reduced ventricular mass, lowered the expression of hypertrophic markers, decreased interstitial collagen deposition, and improved cardiac function in hyperhomocysteinemic rats, associated with restoration of EETs levels in myocardium. TPPU or knockdown of sEH suppressed TRPC3 transcription and translation as well as TRPC3 current that were enhanced by homocysteine. Exogenous 11,12-EET inhibited homocysteine-induced TRPC3 expression and cellular hypertrophy. Silencing C/EBPβ attenuated, while overexpressing C/EBPβ promoted homocysteine-induced hypertrophy and expressions of sEH and TRPC3, resulting respectively from inhibition or activation of sEH and TRPC3 gene promoters.

CONCLUSIONS

sEH and TRPC3 channels jointly contribute to homocysteine-induced cardiac hypertrophy. Homocysteine transcriptionally activates sEH and TRPC3 genes through a common regulatory element C/EBPβ. sEH activation leads to an upregulation of TRPC3 channels via a 11,12-EET-dependent manner.

COVID-19 Mimics Pulmonary Dysfunction in Muscular Dystrophy as a Post-Acute Syndrome in Patients

Although progressive wasting and weakness of respiratory muscles are the prominent hallmarks of Duchenne muscular dystrophy (DMD) and long-COVID (also referred as the post-acute sequelae of COVID-19 syndrome); however, the underlying mechanism(s) leading to respiratory failure in both conditions remain unclear. We put together the latest relevant literature to further understand the plausible mechanism(s) behind diaphragm malfunctioning in COVID-19 and DMD conditions. Previously, we have shown the role of matrix metalloproteinase-9 (MMP9) in skeletal muscle fibrosis via a substantial increase in the levels of tumor necrosis factor-α (TNF-α) employing a DMD mouse model that was crossed-bred with MMP9-knockout (MMP9-KO or MMP9^-/-) strain. Interestingly, recent observations from clinical studies show a robust increase in neopterin (NPT) levels during COVID-19 which is often observed in patients having DMD. What seems to be common in both (DMD and COVID-19) is the involvement of neopterin (NPT). We know that NPT is generated by activated white blood cells (WBCs) especially the M1 macrophages in response to inducible nitric oxide synthase (iNOS), tetrahydrobiopterin (BH4), and tetrahydrofolate (FH4) pathways, i.e., folate one-carbon metabolism (FOCM) in conjunction with epigenetics underpinning as an immune surveillance protection. Studies from our laboratory, and others researching DMD and the genetically engineered humanized (hACE2) mice that were administered with the spike protein (SP) of SARS-CoV-2 revealed an increase in the levels of NPT, TNF-α, HDAC, IL-1β, CD147, and MMP9 in the lung tissue of the animals that were subsequently accompanied by fibrosis of the diaphragm depicting a decreased oscillation phenotype. Therefore, it is of interest to understand how regulatory processes such as epigenetics involvement affect DNMT, HDAC, MTHFS, and iNOS that help generate NPT in the long-COVID patients.

Low Dose of Folic Acid Can Ameliorate Hyperhomocysteinemia-Induced Cardiac Fibrosis and Diastolic Dysfunction in Spontaneously Hypertensive Rats

To evaluate whether lowering plasma homocysteine (Hcy) levels at different doses of folic acid (FA) could reduce cardiac fibrosis and diastolic dysfunction in spontaneously hypertensive rats (SHRs) with hyperhomocysteinemia (Hhcy) and investigate the possible mechanism of action.We randomly divided 32 male SHRs into control, Hhcy, Hhcy + low-dose FA (LFA), and Hhcy + high-dose FA (HFA) groups. Echocardiography and Masson staining of cardiac tissue were used to assess diastolic function and cardiac fibrosis. Blood pressure (BP) and Hcy levels were measured during the experiment. We also measured the indicators of oxidative stress (OS) and examined the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) genes and proteins using real-time polymerase chain reaction (PCR), immunohistochemistry, and western blotting to explore the possible mechanism of action.FA treatment reversed SHR cardiomyocyte interstitial and perivascular collagen deposition and diastolic dysfunction exacerbated by Hhcy. These effects were associated with promoting the translocation of Nrf2 from the cytoplasm to the nucleus, activating HO-1 expression and inhibiting OS. However, HFA did not show any additional benefit from LFA in reducing cardiac injury.Even at a low dose, FA can ameliorate Hhcy-induced cardiac fibrosis and diastolic dysfunction in SHRs by activating Nrf2/HO-1 pathway and inhibiting OS, independent of BP, providing evidence for the efficacy of LFA in the treatment of hypertension associated with Hhcy.

Hyperhomocysteinemia-induced Nrf2/HO-1 pathway suppression aggravates cardiac remodeling of hypertensive rats

ABJECTIVE

Interaction of hypertension and hyperhomocysteinemia (HHcy) leads to enhanced cardiac remodeling in hypertensive heart disease. However, the mechanism of collagen accumulation and cardiac remodeling remains unclear. In this study, we attempted to evaluate the relationship between hypertension and HHcy in the context of cardiac remodeling and to explore its mechanism of action.

METHODS

Wistar Kyoto (WKY) and spontaneous hypertension rats (SHR) were randomly divided into four groups, namely WKY group, WKY + HHcy group, SHR group and SHR + HHcy group. We measured blood pressure (BP), plasma homocysteine (Hcy), serum superoxide dismutase (SOD) and serum malondialdehyde (MDA). We also examined cardiac histopathology and gene and protein expression levels of Nrf2 and HO-1.

RESULTS

Compared with the WKY group, myocardial interstitial and perivascular collagen deposition in the WKY + HHcy group, the SHR group and the SHR + HHcy group increased successively, indicating that cardiac remodeling gradually increased, and HHcy aggravated cardiac remodeling was more serious in hypertensive rats. SOD decreased gradually in the four groups, while MDA was on the contrary. WKY + HHcy and SHR + HHcy groups both suppressed Nrf2 and HO-1 expression and inhibited the translocation of Nrf2 from cytoplasm to nucleus compared with their control groups, and the SHR + HHcy group had a stronger inhibitory effect.

CONCLUSION

HHcy enhanced cardiac remodeling in rats by enhancing oxidative stress, suppressing the Nrf2/HO-1 pathway and Nrf2 nuclear transport, and this inhibitory effect was stronger in the context of hypertension.

Homocysteine and Mitochondria in Cardiovascular and Cerebrovascular Systems

Elevated concentration of homocysteine (Hcy) in the blood plasma, hyperhomocysteinemia (HHcy), has been implicated in various disorders, including cardiovascular and neurodegenerative diseases. Accumulating evidence indicates that pathophysiology of these diseases is linked with mitochondrial dysfunction. In this review, we discuss the current knowledge concerning the effects of HHcy on mitochondrial homeostasis, including energy metabolism, mitochondrial apoptotic pathway, and mitochondrial dynamics. The recent studies suggest that the interaction between Hcy and mitochondria is complex, and reactive oxygen species (ROS) are possible mediators of Hcy effects. We focus on mechanisms contributing to HHcy-associated oxidative stress, such as sources of ROS generation and alterations in antioxidant defense resulting from altered gene expression and post-translational modifications of proteins. Moreover, we discuss some recent findings suggesting that HHcy may have beneficial effects on mitochondrial ROS homeostasis and antioxidant defense. A better understanding of complex mechanisms through which Hcy affects mitochondrial functions could contribute to the development of more specific therapeutic strategies targeted at HHcy-associated disorders.

Pathological Roles of Mitochondrial Oxidative Stress and Mitochondrial Dynamics in Cardiac Microvascular Ischemia/Reperfusion Injury

Mitochondria are key regulators of cell fate through controlling ATP generation and releasing pro-apoptotic factors. Cardiac ischemia/reperfusion (I/R) injury to the coronary microcirculation has manifestations ranging in severity from reversible edema to interstitial hemorrhage. A number of mechanisms have been proposed to explain the cardiac microvascular I/R injury including edema, impaired vasomotion, coronary microembolization, and capillary destruction. In contrast to their role in cell types with higher energy demands, mitochondria in endothelial cells primarily function in signaling cellular responses to environmental cues. It is clear that abnormal mitochondrial signatures, including mitochondrial oxidative stress, mitochondrial fission, mitochondrial fusion, and mitophagy, play a substantial role in endothelial cell function. While the pathogenic role of each of these mitochondrial alterations in the endothelial cells I/R injury remains complex, profiling of mitochondrial oxidative stress and mitochondrial dynamics in endothelial cell dysfunction may offer promising potential targets in the search for novel diagnostics and therapeutics in cardiac microvascular I/R injury. The objective of this review is to discuss the role of mitochondrial oxidative stress on cardiac microvascular endothelial cells dysfunction. Mitochondrial dynamics, including mitochondrial fission and fusion, are critically discussed to understand their roles in endothelial cell survival. Finally, mitophagy, as a degradative mechanism for damaged mitochondria, is summarized to figure out its contribution to the progression of microvascular I/R injury.

Homocysteine and homocysteine-related compounds: an overview of the roles in the pathology of the cardiovascular and nervous systems

Homocysteine, an amino acid containing a sulfhydryl group, is an intermediate product during metabolism of the amino acids methionine and cysteine. Hyperhomocysteinemia is used as a predictive risk factor for cardiovascular disorders, the stroke progression, screening for inborn errors of methionine metabolism, and as a supplementary test for vitamin B₁₂ deficiency. Two organic systems in which homocysteine has the most harmful effects are the cardiovascular and nervous system. The adverse effects of homocysteine are achieved by the action of several different mechanisms, such as overactivation of N-methyl-d-aspartate receptors, activation of Toll-like receptor 4, disturbance in Ca²⁺ handling, increased activity of nicotinamide adenine dinucleotide phosphate-oxidase and subsequent increase of production of reactive oxygen species, increased activity of nitric oxide synthase and nitric oxide synthase uncoupling and consequent impairment in nitric oxide and reactive oxygen species synthesis. Increased production of reactive species during hyperhomocysteinemia is related with increased expression of several proinflammatory cytokines, including IL-1β, IL-6, TNF-α, MCP-1, and intracellular adhesion molecule-1. All these mechanisms contribute to the emergence of diseases like atherosclerosis and related complications such as myocardial infarction, stroke, aortic aneurysm, as well as Alzheimer disease and epilepsy. This review provides evidence that supports the causal role for hyperhomocysteinemia in the development of cardiovascular disease and nervous system disorders.