Effects of hydrogen sulfide in hyperhomocysteinemia-mediated skeletal muscle myopathy.

Although hyperhomocysteinemia (HHcy) occurs due to a deficiency in cystathionine-β-synthase (CBS), causing skeletal muscle myopathy, it is still unclear whether this effect is mediated through oxidative, endoplasmic reticulum (ER) stress, both or something else. Cystathionine γ-lyase (CSE) and CBS are the main H2S producing enzymes, which produce Hydrogen sulfide (H2S) from Hcy in the transsulfuration reaction. H2S is an anti-oxidant compound and patients with a CBS deficiency cannot produce enough H2S, thus rendering them vulnerable to excess Hcy-mediated damage. Both in-vitro (C2C12 cells) and in-vivo (CBS+/- mice) models were used to study HHcy-mediated muscle myopathy, and they were treated with sodium hydrogen sulfide (NaHS, an H2S donor) to mitigate the effect(s) of HHcy in skeletal muscle. To examine whether muscle myopathy is due to poor angiogenesis, we created a hind limb femoral artery ligation (FAL) in CBS+/- mouse model and treated them with GYY4137 (a long-acting H2S donor compound). Results showed that oxidative stress was reversed by NaHS (H2S donor) in Hcy-treated C2C12 cells. ER stress markers (GRP78, ATF6, and pIRE1α) were elevated both in-vivo and in-vitro, and NaHS mitigated these effects. JNK-phosphorylation was upregulated in C2C12 cells after Hcy treatment, but NaHS could not reduce this effect. Apoptosis was induced after Hcy treatment, and it was mitigated by the NaHS supplementation in C2C12 cells. HIF1-α, VEGF, PPAR-γ and p-eNOS expression levels were attenuated in skeletal muscle of CBS+/- mice after 21 days of FAL in comparison to WT mice and were improved via the GYY4137 (another H2S donor compound) treatment. Collateral vessel density and blood flow were significantly reduced in post-FAL CBS+/- mice compared to WT mice, and these effects were ameliorated by the GYY4137 treatment. Plasma nitrite levels were decreased in post-FAL CBS+/- mice compared to WT mice, and these were improved by GYY4137 supplementation. I also noticed FOXO1-mediated MuRF-1 upregulation, which further degrades MHC-I in CBS+/- mice compared to WT mice, and these effects were improved by NaHS intervention. Functional studies revealed that NaHS administration improved muscle fatigability in CBS+/- mice. This work provides evidence that H2S is beneficial in mitigating HHcy-mediated skeletal muscle injury incited by oxidative or ER stress responses and H2S might be employed as a potential therapeutic to alleviate the harmful metabolic effects of HHcy conditions

Remodeling of Retinal Architecture in Diabetic Retinopathy: Disruption of Ocular Physiology and Visual Functions by Inflammatory Gene Products and Pyroptosis

Diabetic patients suffer from a host of physiological abnormalities beyond just those of glucose metabolism. These abnormalities often lead to systemic inflammation via modulation of several inflammation-related genes, their respective gene products, homocysteine metabolism, and pyroptosis. The very nature of this homeostatic disruption re-sets the overall physiology of diabetics via upregulation of immune responses, enhanced retinal neovascularization, upregulation of epigenetic events, and disturbances in cells’ redox regulatory system. This altered pathophysiological milieu can lead to the development of diabetic retinopathy (DR), a debilitating vision-threatening eye condition with microvascular complications. DR is the most prevalent cause of irreversible blindness in the working-age adults throughout the world as it can lead to severe structural and functional remodeling of the retina, decreasing vision and thus diminishing the quality of life. In this manuscript, we attempt to summarize recent developments and new insights to explore the very nature of this intertwined crosstalk between components of the immune system and their metabolic orchestrations to elucidate the pathophysiology of DR. Understanding the multifaceted nature of the cellular and molecular factors that are involved in DR could reveal new targets for effective diagnostics, therapeutics, prognostics, preventive tools, and finally strategies to combat the development and progression of DR in susceptible subjects

Targeting Homocysteine and Hydrogen Sulfide Balance as Future Therapeutics in Cancer Treatment.

A high level of homocysteine (Hcy) is associated with oxidative/ER stress, apoptosis, and impairment of angiogenesis, whereas hydrogen sulfide (H2S) has been found to reverse this condition. Recent studies have shown that cancer cells need to produce a high level of endogenous H2S to maintain cell proliferation, growth, viability, and migration. However, any novel mechanism that targets this balance of Hcy and H2S production has yet to be discovered or exploited. Cells require homocysteine metabolism via the methionine cycle for nucleotide synthesis, methylation, and reductive metabolism, and this pathway supports the high proliferative rate of cancer cells. Although the methionine cycle favors cancer cells for their survival and growth, this metabolism produces a massive amount of toxic Hcy that somehow cancer cells handle very well. Recently, research showed specific pathways important for balancing the antioxidative defense through H2S production in cancer cells. This review discusses the relationship between Hcy metabolism and the antiapoptotic, antioxidative, anti-inflammatory, and angiogenic effects of H2S in different cancer types. It also summarizes the historical understanding of targeting antioxidative defense systems, angiogenesis, and other protective mechanisms of cancer cells and the role of H2S production in the genesis, progression, and metastasis of cancer. This review defines a nexus of diet and precision medicine in targeting the delicate antioxidative system of cancer and explores possible future therapeutics that could exploit the Hcy and H2S balance

HER3: Toward the Prognostic Significance, Therapeutic Potential, Current Challenges, and Future Therapeutics in Different Types of Cancer.

Human epidermal growth factor receptor 3 (HER3) is the only family member of the EGRF/HER family of receptor tyrosine kinases that lacks an active kinase domain (KD), which makes it an obligate binding partner with other receptors for its oncogenic role. When HER3 is activated in a ligand-dependent (NRG1/HRG) or independent manner, it can bind to other receptors (the most potent binding partner is HER2) to regulate many biological functions (growth, survival, nutrient sensing, metabolic regulation, etc.) through the PI3K-AKT-mTOR pathway. HER3 has been found to promote tumorigenesis, tumor growth, and drug resistance in different cancer types, especially breast and non-small cell lung cancer. Given its ubiquitous expression across different solid tumors and role in oncogenesis and drug resistance, there has been a long effort to target HER3. As HER3 cannot be targeted through its KD with small-molecule kinase inhibitors via the conventional method, pharmaceutical companies have used various other approaches, including blocking either the ligand-binding domain or extracellular domain for dimerization with other receptors. The development of treatment options with anti-HER3 monoclonal antibodies, bispecific antibodies, and different combination therapies showed limited clinical efficiency for various reasons. Recent reports showed that the extracellular domain of HER3 is not required for its binding with other receptors, which raises doubt about the efforts and applicability of the development of the HER3-antibodies for treatment. Whereas HER3-directed antibody-drug conjugates showed potentiality for treatment, these drugs are still under clinical trial. The currently understood model for dimerization-induced signaling remains incomplete due to the absence of the crystal structure of HER3 signaling complexes, and many lines of evidence suggest that HER family signaling involves more than the interaction of two members. This review article will significantly expand our knowledge of HER3 signaling and shed light on developing a new generation of drugs that have fewer side effects than the current treatment regimen for these patients

Targeting Homocysteine and Hydrogen Sulfide Balance as Future Therapeutics in Cancer Treatment

A high level of homocysteine (Hcy) is associated with oxidative/ER stress, apoptosis, and impairment of angiogenesis, whereas hydrogen sulfide (H2S) has been found to reverse this condition. Recent studies have shown that cancer cells need to produce a high level of endogenous H2S to maintain cell proliferation, growth, viability, and migration. However, any novel mechanism that targets this balance of Hcy and H2S production has yet to be discovered or exploited. Cells require homocysteine metabolism via the methionine cycle for nucleotide synthesis, methylation, and reductive metabolism, and this pathway supports the high proliferative rate of cancer cells. Although the methionine cycle favors cancer cells for their survival and growth, this metabolism produces a massive amount of toxic Hcy that somehow cancer cells handle very well. Recently, research showed specific pathways important for balancing the antioxidative defense through H2S production in cancer cells. This review discusses the relationship between Hcy metabolism and the antiapoptotic, antioxidative, anti-inflammatory, and angiogenic effects of H2S in different cancer types. It also summarizes the historical understanding of targeting antioxidative defense systems, angiogenesis, and other protective mechanisms of cancer cells and the role of H2S production in the genesis, progression, and metastasis of cancer. This review defines a nexus of diet and precision medicine in targeting the delicate antioxidative system of cancer and explores possible future therapeutics that could exploit the Hcy and H2S balance

How the Western Diet Thwarts the Epigenetic Efforts of Gut Microbes in Ulcerative Colitis and Its Association with Colorectal Cancer

Ulcerative colitis (UC) is an autoimmune disease in which the immune system attacks the colon, leading to ulcer development, loss of colon function, and bloody diarrhea. The human gut ecosystem consists of almost 2000 different species of bacteria, forming a bioreactor fueled by dietary micronutrients to produce bioreactive compounds, which are absorbed by our body and signal to distant organs. Studies have shown that the Western diet, with fewer short-chain fatty acids (SCFAs), can alter the gut microbiome composition and cause the host’s epigenetic reprogramming. Additionally, overproduction of H2S from the gut microbiome due to changes in diet patterns can further activate pro-inflammatory signaling pathways in UC. This review discusses how the Western diet affects the microbiome’s function and alters the host’s physiological homeostasis and susceptibility to UC. This article also covers the epidemiology, prognosis, pathophysiology, and current treatment strategies for UC, and how they are linked to colorectal cancer

Connecting homocysteine and obesity through pyroptosis, gut microbiome, epigenetics, peroxisome proliferator-activator receptor γ (PPARγ) and zinc finger protein 407 (Zfp407)

Abstract: Although homocysteine (Hcy), a part of the epigenome, contributes to cell death by pyroptosis and decreases PPARγ levels, the mechanisms are unclear. Hcy is found in high concentrations in the sera of obese individuals which can elicit an immune response as well by hypermethylating CpG islands of specific gene promoters, a marker of epigenetics. Hcy has also been established to chelate divalent metal ions like Cu+2 and Zn+2, but this role of Hcy has not been established in relationship with obesity. It has been known for a while that PPARγ dysregulation results in various metabolic disorders including glucose and lipid metabolism. Recently, zinc finger protein 407 (Zfp407) is reported to regulate PPARγ target gene expression without affecting PPARγ transcript and protein levels by synergistically working with PPARγ. However, the mechanism(s) of this synergy, as well as other factors contributing to or inhibiting this synergism have not been proven. This review suggests that Hcy contributes to pyroptosis, changes gut microbiome, alter PPARγ-dependent mechanism(s) via Zfp407 mediated upregulated adipogenesis and misbalanced fatty acid metabolism leading that can predispose to obesity and consequently the obesity-related metabolic disorders.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author