Hydrogen Sulfide Up-Regulates the Expression of ATP-Binding Cassette Transporter A1 via Promoting Nuclear Translocation of PPARα

LIFU-unlocked endogenous H2S generation for enhancing atherosclerosis-specific gas-enzymatic therapy

Atherosclerotic plaques, which are characterized by endothelial oxidative stress, lipid metabolism disorders and persistent inflammation, can induce serious cardiovascular diseases. However, the pharmacotherapies currently used to treat atherosclerosis (AS), such as lipid-lowering and antithrombotic drugs, can regulate only a single pathological feature of AS, and there is still a dearth of integrated platforms for the multifaceted regulation of AS progression. Herein, we developed a synergistic combination of endogenous H2S gas therapy with a multienzyme-like nanozyme (named LyP-1Lip@HS) for the treatment of AS. The high affinity of the LyP-1 peptide for macrophages and foam cells within plaques allows LyP-1Lip@HS to actively target atherosclerotic lesions. After cavitation was induced by low-intensity focused ultrasound (LIFU), the lipid membrane of LyP-1Lip@HS was disrupted, thereby "unlocking" the enzyme-like activity of hollow mesoporous Prussian blue (HMPB) and facilitating the release of the endogenous H2S donor S-allyl-L-cysteine (SAC). Notably, H2S endogenously generated by enzymatic catalysis plays multiple roles, upregulating the ATP-binding cassette transporter A1 in foam cells to increase lipid efflux and promote the conversion of M1 macrophages to M2 macrophages. Moreover, the high level of reactive oxygen species in the inflammatory microenvironment of the plaque was mitigated. Overall, LyP-1Lip@HS provides a specific and controlled treatment to prevent oxidative stress, inflammation and lipid metabolism disorders, making it a candidate for AS treatment.

Exploring gut microbial metabolites as key players in inhibition of cancer progression: Mechanisms and therapeutic implications

The gut microbiota plays a critical role in numerous biochemical processes essential for human health, such as metabolic regulation and immune system modulation. An increasing number of research suggests a strong association between the gut microbiota and carcinogenesis. The diverse metabolites produced by gut microbiota can modulate cellular gene expression, cell cycle dynamics, apoptosis, and immune system functions, thereby exerting a profound influence on cancer development and progression. A healthy gut microbiota promotes substance metabolism, stimulates immune responses, and thereby maintains the long-term homeostasis of the intestinal microenvironment. When the gut microbiota becomes imbalanced and disrupts the homeostasis of the intestinal microenvironment, the risk of various diseases increases. This review aims to elucidate the impact of gut microbial metabolites on cancer initiation and progression, focusing on short-chain fatty acids (SCFAs), polyamines (PAs), hydrogen sulfide (H2S), secondary bile acids (SBAs), and microbial tryptophan catabolites (MTCs). By detailing the roles and molecular mechanisms of these metabolites in cancer pathogenesis and therapy, this article sheds light on dual effects on the host at different concentrations of metabolites and offers new insights into cancer research.

Diosgenin attenuates nonalcoholic hepatic steatosis through the hepatic FXR-SHP-SREBP1C/PPARα/CD36 pathway

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide and has no approved treatment. The hepatic farnesoid X receptor (FXR) is one of the most promising therapeutic targets for NAFLD. Diosgenin (DG), a natural compound extracted from Chinese herbal medicine, is very effective in preventing metabolic diseases. Our research aims to determine the effects and molecular mechanisms of DG on NAFLD in vivo and in vitro. The effect of DG on hepatic steatosis was evaluated in Sprague‒Dawley (SD) rats induced by a high-fat diet (HFD) and in HepG2 cells exposed to free fatty acids (FFAs, sodium oleate:sodium palmitate = 2:1). DG treatment efficiently managed hepatic lipid deposition in vivo and in vitro. Mechanistically, DG upregulated the expression of FXR and small heterodimer partner (SHP) and downregulated the expression of genes involved in hepatic de novo lipogenesis (DNL), including sterol regulatory element-binding protein 1C (SREBP1C), acetyl-CoA carboxylase 1 (ACC1), and fatty acid synthase (FASN). Moreover, DG promoted the expression of peroxisome proliferator-activated receptor alpha (PPARα), which is related to fatty acid oxidation. In addition, DG inhibited the expression of the CD36 molecule (CD36) related to fatty acid uptake. However, hepatic FXR silencing weakened the regulatory effects of DG on these genes. Collectively, our data show that DG has a good effect on alleviating nonalcoholic hepatic steatosis via the hepatic FXR-SHP-SREBP1C/PPARα/CD36 pathway. DG promises to be a novel candidate FXR activator that can be utilized to treat NAFLD.

Valproic Acid-Induced Upregulation of Multidrug Efflux Transporter ABCG2/BCRP via PPARα-Dependent Mechanism in Human Brain Endothelial Cells

Despite the progress made in the development of new antiepileptic drugs (AEDs), poor response to them is a rising concern in epilepsy treatment. Of several hypotheses explaining AED treatment failure, the most promising theory is the overexpression of multidrug transporters belonging to ATP-binding cassette (ABC) transporter family at blood-brain barrier. Previous data show that AEDs themselves can induce these transporters, in turn affecting their own brain bioavailability. Presently, this induction and the underlying regulatory mechanism involved at human blood-brain barrier is not well elucidated. Herein, we sought to explore the effect of most prescribed first- and second-line AEDs on multidrug transporters in human cerebral microvascular endothelial cells, hCMEC/D3. Our work demonstrated that exposure of these cells to valproic acid (VPA) induced mRNA, protein, and functional activity of breast cancer resistance protein (BCRP/ABCG2). On examining the substrate interaction status of AEDs with BCRP, VPA, phenytoin, and lamotrigine were found to be potential BCRP substrates. Furthermore, we observed that siRNA-mediated knockdown of peroxisome proliferator-activated receptor alpha (PPARα) or use of PPARα antagonist, resulted in attenuation of VPA-induced BCRP expression and transporter activity. VPA was found to increase PPARα expression and trigger its translocation from cytoplasm to nucleus. Findings from chromatin immunoprecipitation and luciferase assays showed that VPA enhances the binding of PPARα to its response element in the ABCG2 promoter, resulting in elevated ABCG2 transcriptional activity. Taken together, these in vitro findings highlight PPARα as the potential molecular target to prevent VPA-mediated BCRP induction, which may have important implications in VPA pharmacoresistance. SIGNIFICANCE STATEMENT: Induction of multidrug transporters at blood-brain barrier can largely affect the bioavailability of the substrate antiepileptic drugs in the brains of patients with epilepsy, thus affecting their therapeutic efficacy. The present study reports a mechanistic pathway of breast cancer resistance protein (BCRP/ABCG2) upregulation by valproic acid in human brain endothelial cells via peroxisome proliferator-activated receptor alpha involvement, thereby providing a potential strategy to prevent valproic acid pharmacoresistance in epilepsy.

Gasotransmitters in the tumor microenvironment: Impacts on cancer chemotherapy (Review)

Nitric oxide, carbon monoxide and hydrogen sulfide are three endogenous gasotransmitters that serve a role in regulating normal and pathological cellular activities. They can stimulate or inhibit cancer cell proliferation and invasion, as well as interfere with cancer cell responses to drug treatments. Understanding the molecular pathways governing the interactions between these gases and the tumor microenvironment can be utilized for the identification of a novel technique to disrupt cancer cell interactions and may contribute to the conception of effective and safe cancer therapy strategies. The present review discusses the effects of these gases in modulating the action of chemotherapies, as well as prospective pharmacological and therapeutic interfering approaches. A deeper knowledge of the mechanisms that underpin the cellular and pharmacological effects, as well as interactions, of each of the three gases could pave the way for therapeutic treatments and translational research.

Role of hydrogen sulfide donors in cancer development and progression

In recent years, a vast number of potential cancer therapeutic targets have emerged. However, developing efficient and effective drugs for the targets is of major concern. Hydrogen sulfide (H2S), one of the three known gasotransmitters, is involved in the regulation of various cellular activities such as autophagy, apoptosis, migration, and proliferation. Low production of H2S has been identified in numerous cancer types. Treating cancer cells with H2S donors is the common experimental technique used to improve H2S levels; however, the outcome depends on the concentration/dose, time, cell type, and sometimes the drug used. Both natural and synthesized donors are available for this purpose, although their effects vary independently ranging from strong cancer suppressors to promoters. Nonetheless, numerous signaling pathways have been reported to be altered following the treatments with H2S donors which suggest their potential in cancer treatment. This review will analyze the potential of H2S donors in cancer therapy by summarizing key cellular processes and mechanisms involved.

Thrombin-Par1 signaling axis disrupts COP9 signalosome subunit 3-mediated ABCA1 stabilization in inducing foam cell formation and atherogenesis

ATP-binding cassette transporters A1 (ABCA1) and G1 (ABCG1) play a vital role in promoting cholesterol efflux. Although, the dysregulation of these transporters was attributed as one of the mechanisms of atherogenesis, what renders their dysfunction is not well explored. Previously, we have reported that thrombin without having any effect on ABCG1 levels depletes ABCA1 levels affecting cholesterol efflux. In this study, we explored the mechanisms underlying thrombin-induced depletion of ABCA1 levels both in macrophages and smooth muscle cells. Under normal physiological conditions, COP9 signalosome subunit 3 (CSN3) was found to exist in complex with ABCA1 and in the presence of proatherogenic stimulants such as thrombin, ABCA1 was phosphorylated and dissociated from CSN3, leading to its degradation. Forced expression of CSN3 inhibited thrombin-induced ABCA1 ubiquitination and degradation, restored cholesterol efflux and suppressed foam cell formation. In Western diet (WD)-fed ApoE^-/- mice, CSN3 was also disassociated from ABCA1 otherwise remained as a complex in Chow diet (CD)-fed ApoE^-/- mice. Interestingly, depletion of CSN3 levels in WD-fed ApoE^-/- mice significantly lowered ABCA1 levels, inhibited cholesterol efflux and intensified foam cell formation exacerbating the lipid laden atherosclerotic plaque formation. Mechanistic studies have revealed the involvement of Par1-Gα₁₂-Pyk2-Gab1-PKCθ signaling in triggering phosphorylation of ABCA1 and its disassociation from CSN3 curtailing cholesterol efflux and amplifying foam cell formation. In addition, although both CSN3 and ABCA1 were found to be colocalized in human non-lesion coronary arteries, their levels were decreased as well as dissociated from each other in advanced atherosclerotic lesions. Together, these observations reveal for the first time an anti-atherogenic role of CSN3 and hence, designing therapeutic drugs protecting its interactions with ABCA1 could be beneficial against atherosclerosis.

The impact of ATP-binding cassette transporters on metabolic diseases

Currently, many people worldwide suffer from metabolic diseases caused by heredity and external factors, such as diet. One of the symptoms of metabolic diseases is abnormal lipid metabolism. ATP binding cassette (ABC) transporters are one of the largest transport protein superfamilies that exist in nearly all living organisms and are mainly located on lipid-processing cells. ABC transporters have been confirmed to be closely related to the pathogenesis of diseases such as metabolic diseases, cancer and Alzheimer's disease based on their transport abilities. Notably, the capability to transport lipids makes ABC transporters critical in metabolic diseases. In addition, gene polymorphism in ABC transporters has been reported to be a risk factor for metabolic diseases, and it has been reported that relevant miRNAs have significant roles in regulating ABC transporters. In this review, we integrate recent studies to examine the roles of ABC transporters in metabolic diseases and aim to build a network with ABC transporters as the core, linking their transport abilities with metabolic and other diseases.

GYY4137 exhibits anti-atherosclerosis effect in apolipoprotein E (-/-) mice via PI3K/Akt and TLR4 signalling

Hydrogen sulphide (H2 S) had been suggested to be involved in the pathogenesis of atherosclerosis, but the underlying molecular mechanisms are poorly understood. In this study, we aimed to investigate the anti-atherosclerosis effect of morpholin-4-ium-methoxyphenyl-morpholino-phosphinodithioate (GYY4137) in RAW264.7 cell-derived foam cells formation and in the atherosclerotic plaque of ApoE-/- mice fed with a high-fat diet, and study the underlying mechanisms of phosphatidylinositol 3-kinase (PI3K), serine/ threonine kinase (Akt) and Toll-like receptor 4 (TLR4) signalling pathway. In the ApoE-/- mice fed with a high-fat diet, daily GYY4137 administration for 8 weeks effectively decreased carotid atherosclerotic plaque area and the volume of foam cells, regulated the lipid metabolism, down-regulated the pro-inflammatory cytokine levels and up-regulated the anti-inflammatory cytokines levels. Consistent with these findings, in the RAW264.7 cell-derived foam cells, GYY4137 ameliorated foam cell formation in vitro, and decreased the expression of pro-inflammatory cytokines. Furthermore, our studies showed that GYY4137 could activate the PI3K/Akt signalling pathway and consequently reduce the expression of TLR4 to be critical for foam cell formation, preventing atherosclerotic plaque formation and destabilization. LY294002, a PI3K inhibitor, could inhibit the phosphorylation of Akt and reduce the expression of TLR4, thus reduce the foam cell source and lipid volume in the unstable plaque tissue. Our results suggest that GYY4137 is an attractive novel therapeutic reagent for atherosclerosis diseases. This mechanism may be partially attributed to regulating the PI3K/Akt/TLR4 signalling pathway.

Hydrogen sulfide inhibits PCSK9 expression through the PI3K/Akt‑SREBP‑2 signaling pathway to influence lipid metabolism in HepG2 cells

Hydrogen sulfide (H₂S) is an endogenous gaseous signaling molecule that plays important roles in the cardiovascular system. In our previous studies, we demonstrated that H₂S regulates lipid metabolism. In the present study, we aimed to explore the mechanisms through which H₂ regulates lipid metabolism in HepG2 cells in vitro. Treatment of the HepG2 cells with H₂S inhibited the expression of proprotein convertase subtilisin/kexin type 9 (PCSK9) and increased the level of low-density lipoprotein receptor (LDLR) in a time- and dose-dependent manner. The knockdown of PCSK9 by siRNA effectively increased the levels of LDLR and 1,1′-dioctadecyl-3,3,3′,3′-tetramethyl-indocarbocyanine perchlorate-labeled LDL (DiI-LDL) uptake in the H₂S-treated HepG2 cells. Furthermore, the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)-sterol regulatory element binding proteins 2 (SREBP-2) signaling pathway was confirmed to be involved in H₂S-regulated PCSK9 expression. Notably, the HepG2 cells were incubated with 30% serum and DiI-LDL for 24 h, and the results revealed that H₂S increased lipid uptake, but caused no increase in lipid accumulation. On the whole, the findings of this study demonstrate that H₂S is involved in the regulation of lipid metabolism in HepG2 cells through the regulation of the expression of PCSK9 via the PI3K/Akt-SREBP-2 signaling pathway. To the very best of our knowledge, this study is the first to report that H₂S can regulate the expression of PCSK9.

Cystathionine γ-lyase deficiency aggravates obesity-related insulin resistance via FoxO1-dependent hepatic gluconeogenesis

Hepatic gluconeogenesis makes a significant contribution to the pathogenesis of obesity and its related insulin resistance. Cystathionine γ-lyase (CSE; also cystathionase), a principal hydrogen sulfide (H₂S)-synthesizing enzyme in the liver, is involved in glucose and lipid metabolism disorders. However, the roles and precise mechanisms of CSE/H₂S in obesity and its related insulin resistance remain obscure. Here we show that CSE knockout exacerbated high-fat diet-induced mouse obesity as well as its related insulin resistance. Further study elucidated that the inhibition of insulin and AMPK signaling pathways by CSE deficiency resulted in nuclear accumulation of Forkhead box protein O1 and subsequently promoted hepatic gluconeogenesis. These phenomena can be reversed by NaHS supplementation. However, in wild-type mice, NaHS treatment ameliorates high fat diet-induced obesity and metabolism disorders, indicating that maintaining an appropriate level of H₂S is critical for its mutual change of positive and negative effects of obesity-associated insulin resistance. Our study reveals a double-edged sword effect and a novel mechanism for CSE/H₂S in obesity associated with insulin resistance and provides evidence for CSE/H₂S as a promising therapeutic potential target for obesity-related insulin resistance.-Guo, W., Li, D., You, Y., Li, W., Hu, B., Zhang, S., Miao, L., Xian, M., Zhu, Y., Shen, X. Cystathionine γ-lyase deficiency aggravates obesity-related insulin resistance via FoxO1-dependent hepatic gluconeogenesis.

Hydrogen Sulfide (H2S)-Releasing Compounds: Therapeutic Potential in Cardiovascular Diseases

Cardiovascular disease is the main cause of death worldwide, but its pathogenesis is not yet clear. Hydrogen sulfide (H₂S) is considered to be the third most important endogenous gasotransmitter in the organism after carbon monoxide and nitric oxide. It can be synthesized in mammalian tissues and can freely cross the cell membrane and exert many biological effects in various systems including cardiovascular system. More and more recent studies have supported the protective effects of endogenous H₂S and exogenous H₂S-releasing compounds (such as NaHS, Na₂S, and GYY4137) in cardiovascular diseases, such as cardiac hypertrophy, heart failure, ischemia/reperfusion injury, and atherosclerosis. Here, we provided an up-to-date overview of the mechanistic actions of H₂S as well as the therapeutic potential of various classes of H₂S donors in treating cardiovascular diseases.

Hydrogen Sulfide Attenuates Atherosclerosis in a Partially Ligated Carotid Artery Mouse model via Regulating Angiotensin Converting Enzyme 2 Expression

Hydrogen sulfide has been suggested to play an essential role in atherogenesis. There is a paucity of information about the association between H₂S and angiotensin converting enzyme 2 (ACE2), a novel homolog of ACE. Therefore, the aim of the study was to explore the role of H₂S in atherosclerosis with respect to ACE2 both in vitro and in vivo. Here, a murine model of acutely disturbed flow-induced atherosclerosis by left common carotid artery (LCA) partial ligation was utilized. We found that carotid partial ligation in high-fat fed apoE^−/− mice significantly inhibited endogenous H₂S synthesis in LCA. Application of NaHS, an H₂S donor considerably attenuated the severity of atherosclerosis with upregulating carotid expression of ACE2, thus converting pro-atherosclerotic angiotensin II (Ang II) to anti-atherosclerotic angiotensin 1-7 (Ang-(1-7)). The anti-atherosclerotic effect of NaHS was dramatically abolished by treatment with MLN-4760, an ACE2 inhibitor. In contrast, blockage of H₂S formation by DL-propargylglycine exacerbated the burden of atherosclerotic plaques accompanied by inhibiting carotid expression of ACE2. At the cellular level, NaHS dose-dependently promoted the expression of ACE2 and conversion from Ang II to Ang-(1-7) in unstimulated or LPS-stimulated endothelial cells, thus exerting anti-inflammatory properties. The anti-inflammatory effect of NaHS was abrogated by pretreatment with DX600, a selective ACE2 inhibitor. In conclusion, these data provide direct evidences that endogenous H₂S insufficiency exists in acute flow disturbance-induced atherosclerosis and that application of H₂S may protect against atherosclerosis via upregulating ACE2 expression in endothelial cells.

Beyond a Gasotransmitter: Hydrogen Sulfide and Polysulfide in Cardiovascular Health and Immune Response

SIGNIFICANCE

Hydrogen sulfide (H₂S) metabolism leads to the formation of oxidized sulfide species, including polysulfide, persulfide, and others. Evidence is emerging that many biological effects of H₂S may indeed be due to polysulfide and persulfide activation of signaling pathways and reactivity with discrete small molecules. Recent Advances: Exogenous oxidized sulfide species, including polysulfides, are more reactive than H₂S with a wide range of molecules. Importantly, endogenous polysulfide and persulfide formation has been reported to occur via transsulfuration enzymes, cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS).

CRITICAL ISSUES

In light of the recent understanding of oxidized sulfide metabolite formation and reactivity, comparatively few studies have been reported comparing cellular biological and in vivo effects of H₂S donors versus polysulfide and persulfide donors. Likewise, it is equally unclear when, how, and to what extent persulfide and polysulfide formation occurs in vivo under pathophysiological conditions.

FUTURE DIRECTIONS

Additional studies regarding persulfide and polysulfide formation and molecular reactions are needed in nearly all aspects of biology to better understand how sulfide metabolites contribute to key chemical biology reactions involved in cardiovascular health and immune responses. Antioxid. Redox Signal. 27, 634-653.