Diallyl disulfide and diallyl trisulfide protect endothelial nitric oxide synthase against damage by oxidized low-density lipoprotein

Protective role of perivascular adipose tissue in the cardiovascular system

This review provides an overview of the key role played by perivascular adipose tissue (PVAT) in the protection of cardiovascular health. PVAT is a specific type of adipose tissue that wraps around blood vessels and has recently emerged as a critical factor for maintenance of vascular health. Through a profound exploration of existing research, this review sheds light on the intricate structural composition and cellular origins of PVAT, with a particular emphasis on combining its regulatory functions for vascular tone, inflammation, oxidative stress, and endothelial function. The review then delves into the intricate mechanisms by which PVAT exerts its protective effects, including the secretion of diverse adipokines and manipulation of the renin-angiotensin complex. The review further examines the alterations in PVAT function and phenotype observed in several cardiovascular diseases, including atherosclerosis, hypertension, and heart failure. Recognizing the complex interactions of PVAT with the cardiovascular system is critical for pursuing breakthrough therapeutic strategies that can target cardiovascular disease. Therefore, this review aims to augment present understanding of the protective role of PVAT in cardiovascular health, with a special emphasis on elucidating potential mechanisms and paving the way for future research directions in this evolving field.

Reactive Sulfur Species in Human Diseases

Significance: Reactive sulfur species (RSS) have been recently recognized as redox molecules no less important than reactive oxygen species or reactive nitrogen species. They possess regulatory and protective properties and are involved in various metabolic processes, thereby contributing to the maintenance of human health. It has been documented that many disorders, including neurological, cardiovascular, and respiratory diseases, diabetes mellitus (DM), and cancer, are related to the disruption of RSS homeostasis. Recent Advances: There is still a growing interest in the role of RSS in human diseases. Since a decrease in hydrogen sulfide or other RSS has been reported in many disorders, safe and efficient RSS donors have been developed and tested under in vitro conditions or on animal models. Critical Issues: Cardiovascular diseases and DM are currently the most common chronic diseases worldwide due to stressful and unhealthy lifestyles. In addition, because of high prevalence and aging of the population, neurological disorders including Parkinson's disease and Alzheimer's disease as well as respiratory diseases are a formidable challenge for health care systems. From this point of view, the knowledge of the role of RSS in these disorders and RSS modulation options are important and could be useful in therapeutic strategies. Future Directions: Improvement and standardization of analytical methods used for RSS estimation are crucial for the use of RSS as diagnostic biomarkers. Finding good, safe RSS donors applicable for therapeutic purposes could be useful as primary or adjunctive therapy in many common diseases. Antioxid. Redox Signal. 39, 1000-1023.

Investigation of Potential cGMP-Specific PDE V and Aminopeptidase N Inhibitors of Allium ampeloprasum L. and Its Bioactive Components: Kinetic and Molecular Docking Studies

The primary objectives of this study were to assess the inhibitory effects of Allium ampeloprasum L. extract (AAE) and its derived organosulfur and polyphenolic compounds on the enzymatic activities of cGMP-specific PDE V (PDE5) and aminopeptidase N (APN). Additionally, the study aimed to investigate their potential as inhibitors against these two target enzymes through kinetic analyses and molecular docking studies. The in vitro enzyme assays demonstrated that both AAE and its derived compounds significantly decreased the activity of PDE5 and APN. Further analyses involving kinetics and molecular docking provided insights into the specific inhibitor types of AAE and its derived compounds along with the proposed molecular docking models illustrating the interactions between the ligands (the compounds) and the enzymes (PDE5 and APN). In particular, AAE-derived polyphenolic compounds showed relatively stable binding affinity (-7.2 to -8.3 kcal/mol) on PDE5 and APN. Our findings proved the potential as an inhibitor against PDE5 and APN of AAE and AAE-derived organosulfur and polyphenolic compounds as well as a functional material for erectile dysfunction improvement.

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.

Role of the renin-angiotensin system in the pathophysiology of coronary heart disease and heart failure: Diagnostic biomarkers and therapy with drugs and natural products

The renin-angiotensin system (RAS) plays a pivotal role in blood pressure regulation. In some cases, this steering mechanism is affected by various deleterious factors (mainly via the overactivation of the RAS) causing cardiovascular damage, including coronary heart disease (CHD) that can ultimately lead to chronic heart failure (CHF). This not only causes cardiovascular disability and absenteeism from work but also imposes significant healthcare costs globally. The incidence of cardiovascular diseases has escalated exponentially over the years with the major outcome in the form of CHD, stroke, and CHF. The involvement of the RAS in various diseases has been extensively researched with significant limelight on CHD. The RAS may trigger a cascade of events that lead to atherosclerotic mayhem, which causes CHD and related aggravation by damaging the endothelial lining of blood vessels via various inflammatory and oxidative stress pathways. Although there are various diagnostic tests and treatments available in the market, there is a constant need for the development of procedures and therapeutic strategies that increase patient compliance and reduce the associated side effects. This review highlights the advances in the diagnostic and treatment domains for CHD, which would help in subjugating the side effects caused by conventional therapy.

Natural Products in Cardiovascular Diseases: The Potential of Plants from the Allioideae Subfamily (Ex-Alliaceae Family) and Their Sulphur-Containing Compounds

Cardiovascular diseases (CVDs) are the leading cause of mortality worldwide and, together with associated risk factors such as diabetes, hypertension, and dyslipidaemia, greatly impact patients' quality of life and health care systems. This burden can be alleviated by fomenting lifestyle modifications and/or resorting to pharmacological approaches. However, due to several side effects, current therapies show low patient compliance, thus compromising their efficacy and enforcing the need to develop more amenable preventive/therapeutic strategies. In this scenario, medicinal and aromatic plants are a potential source of new effective agents. Specifically, plants from the Allioideae subfamily (formerly Alliaceae family), particularly those from the genus Allium and Tulbaghia, have been extensively used in traditional medicine for the management of several CVDs and associated risk factors, mainly due to the presence of sulphur-containing compounds. Bearing in mind this potential, the present review aims to gather information on traditional uses ascribed to these genera and provide an updated compilation of in vitro and in vivo studies validating these claims as well as clinical trials carried out in the context of CVDs. Furthermore, the effect of isolated sulphur-containing compounds is presented, and whenever possible, the relation between composition and activity and the mechanisms underlying the beneficial effects are pointed out.

Progress and perspective on hydrogen sulfide donors and their biomedical applications

Following the discovery of nitric oxide (NO) and carbon monoxide (CO), hydrogen sulfide (H₂ S) has been identified as the third gasotransmitter in humans. Increasing evidence have shown that H₂ S is of preventive or therapeutic effects on diverse pathological complications. As a consequence, it is of great significance to develop suitable approaches of H₂ S-based therapeutics for biomedical applications. H₂ S-releasing agents (H₂ S donors) play important roles in exploring and understanding the physiological functions of H₂ S. More importantly, accumulating studies have validated the theranostic potential of H₂ S donors in extensive repertoires of in vitro and in vivo disease models. Thus, it is imperative to summarize and update the literatures in this field. In this review, first, the background of H₂ S on its chemical and biological aspects is concisely introduced. Second, the studies regarding the H₂ S-releasing compounds are categorized and described, and accordingly, their H₂ S-donating mechanisms, biological applications, and therapeutic values are also comprehensively delineated and discussed. Necessary comparisons between related H₂ S donors are presented, and the drawbacks of many typical H₂ S donors are analyzed and revealed. Finally, several critical challenges encountered in the development of multifunctional H₂ S donors are discussed, and the direction of their future development as well as their biomedical applications is proposed. We expect that this review will reach extensive audiences across multiple disciplines and promote the innovation of H₂ S biomedicine.

Biological Functions of Diallyl Disulfide, a Garlic-Derived Natural Organic Sulfur Compound

Garlic is widely accepted as a functional food and an excellent source of pharmacologically active ingredients. Diallyl disulfide (DADS), a major bioactive component of garlic, has several beneficial biological functions, including anti-inflammatory, antioxidant, antimicrobial, cardiovascular protective, neuroprotective, and anticancer activities. This review systematically evaluated the biological functions of DADS and discussed the underlying molecular mechanisms of these functions. We hope that this review provides guidance and insight into the current literature and enables future research and the development of DADS for intervention and treatment of multiple diseases.

Diallyl Trisulfide Prevents Obesity and Decreases miRNA-335 Expression in Adipose Tissue in a Diet-Induced Obesity Rat Model

SCOPE

Diallyl trisulfide (DATS), an organosulfur compound generates in crushed garlic, has various beneficial health effects. A growing body of evidence indicates that miRNAs are involved in the pathology of lifestyle diseases including obesity. The anti-obesogenic effect of garlic is previously reported; however, the effects of DATS on obesity, and the relationship between garlic compounds and the involvement of miRNA remains unclear. Here, the anti-obesogenic activity of DATS and the potential role of miRNA in a diet-induced obesity rat model are investigated.

METHODS AND RESULTS

Oral administration of DATS suppressed body and white adipose tissue (WAT) weight gain in rats fed a high-fat diet compared with vehicle-administered rats. DATS lowered the plasma and liver triglyceride levels in obese rats, and decreased lipogenic mRNA levels including those of Srebp1c, Fasn, and Scd1 in the liver. DATS also suppressed de novo lipogenesis in the liver. Transcriptomic analyses of miRNA and mRNA in the epididymal WAT of obese rats using microarrays revealed that DATS decreased miRNA-335 expression and normalized the obesity-related mRNA transcriptomic signatures in epididymal WAT.

CONCLUSION

The potent anti-obesogenic effects of DATS and its possible mechanism of action was clearly demonstrated in this study.

Diallyl disulfide improves lipid metabolism by inhibiting PCSK9 expression and increasing LDL uptake via PI3K/Akt-SREBP2 pathway in HepG2 cells

BACKGROUND AND AIM

Diallyl disulfide (DADS), a volatile sulfide extracted from garlic, has been suggested as a chemical of anti-atherosclerotic drugs, while its molecular mechanism for this benefit has not fully been understood. The aim of the present study was to investigate the effects of DADS on lipid metabolism and its potential mechanisms in HepG2 cells induced by lipopolysaccharides (LPS).

METHODS AND RESULTS

HepG2 cells were treated with LPS with or without different concentrations of DADS (0, 20, 40, 80, 160 μg/ml) for 24 h. The cell activity was detected by CCK8, and Dil-LDL uptake assay was used to examine the LDL uptake. Real-time PCR and Western blot were used to detect the expression of LDLR, PCSK9 SREBP2 and HMGCR. In addition, we examined the effect of the combination of DADS with atorvastatin on PCSK9 expression. The results showed that LPS significantly increased PCSK9 and SREBP2 expressions in a dose-dependent manner in HepG2 cells. DADS attenuated PCSK9, SREBP2 and HMGCR expressions and up-regulated the expression of LDLR. Moreover, DADS reversed the expressions of PCSK9, SREBP2, HMGCR and LDLR induced by LPS and DADS could promote the LDL uptake in HepG2 cells. Furthermore, DADS decreased the expression of PCSK9 by activating the PI3K/Akt-SREBP2 signal pathway. Notably, DADS could reduce PCSK9 expression induced by atorvastatin in HepG2 cells.

CONCLUSION

DADS could significantly attenuated PCSK9 expression in a dose-dependent manner induced by LPS and increased the LDLR expression in HepG2 cells, which was associated with the activation of PI3K/Akt-SREBP2 signaling pathway.

H2 S donor improves heart function and vascular relaxation in diabetes

BACKGROUND AND AIMS

Diabetes dramatically increases the risk of cardiovascular complications and mortality. Hydrogen sulphide plays an important role in reducing oxidative stress. Several studies demonstrated that hydrogen sulphide protects islet beta cells from oxidant stress damage and decreases apoptosis. The aim of the work is to investigate the effect of hydrogen sulphide donor on heart functions and endothelium-dependent relaxation of aortic smooth muscle in diabetes.

MATERIALS AND METHODS

Rats were divided into control and diabetic groups. Diabetes mellitus was induced with a single intraperitoneally injection of streptozotocin (60 mg kg^-1 ). The functional cardiohemodynamic indicators were registered via microcatheter and Pressure-Volume System. The sodium hydrosulphide NaHS (15.8 mg kg^-1 ) was administered intraperitoneally. The contractile activity of the muscle preparations of the thoracic aorta was recorded using a strain gauge.

RESULTS

We demonstrate that the NaHS improves pumping function and restores diastolic heart function in streptozotocin-induced (STZ) diabetes rats. We show that pretreatment with NaHS increased the stroke volume by 43.1%, and the ejection fraction increased by 48.64%. NaHS improves the ventriculo-arterial coupling and increases by 3.4 times acetylcholine-induced relaxation of the aorta in diabetic rats. The inhibition of NOS activity by blocker L-NAME abolished NaHS-mediated vasodilatation in the intact endothelium of the aorta in diabetes. It indicates that the NaHS caused vasodilatation by a NOS-dependent mechanism.

CONCLUSION

The exogenous hydrogen sulphide can improve pumping function and restore diastolic heart function in diabetes. The pretreatment with NaHS can prevent endothelial dysfunction in diabetes due to the NOS-dependent mechanism.

Role of hydrogen sulfide in endothelial dysfunction: Pathophysiology and therapeutic approaches

BACKGROUND

The vascular endothelium represents a fundamental mechanical and biological barrier for the maintenance of vascular homeostasis along the entire vascular tree. Changes in its integrity are associated to several cardiovascular diseases, including hypertension, atherosclerosis, hyperhomocysteinemia, diabetes, all linked to the peculiar condition named endothelial dysfunction, which is referred to the loss of endothelial physiological functions, comprehending the regulation of vascular relaxation and/or cell redox balance, the inhibition of leukocyte infiltration and the production of NO. Among the endothelium-released vasoactive factors, in the last years hydrogen sulfide has been viewed as one of the main characters involved in the regulation of endothelium functionality, and many studies demonstrated that H2S behaves as a vasoprotective gasotransmitter in those cardiovascular diseases where endothelial dysfunction seems to be the central issue.

AIM

The role of hydrogen sulfide in endothelial dysfunction-related cardiovascular diseases is discussed in this review.

KEY SCIENTIFIC CONCEPTS

Possible therapeutic approaches using molecules able to release H2S.

A comprehensive understanding about the pharmacological effect of diallyl disulfide other than its anti-carcinogenic activities

Diallyl disulfide (DADS), an oil-soluble sulfur compound that is responsible for the biological effects of garlic, displays numerous biological activities, among which its anti-cancer activities are the most famous ones. In recent years, the pharmacological effects of DADS other than its anti-carcinogenic activities have attracted numerous attentions. For example, it has been reported that DADS can prevent the microglia-mediated neuroinflammatory response and depression-like behaviors in mice. In the cardiovascular system, DADS administration was found to ameliorate the isoproterenol- or streptozotocin-induced cardiac dysfunction via the activation of the nuclear factor E2-related factor 2 (Nrf2) and insulin-like growth factor (IGF)-phosphatidylinositol-3-kinase (PI3K)-protein kinase B (Akt) signaling. DADS administration can also produce neuroprotective effects in animal models of Alzheimer's disease and protect the heart, endothelium, liver, lung, and kidney against cellular or tissue damages induced by various toxic factors, such as the oxidized-low density lipoprotein (ox-LDL), carbon tetrachloride (CCl₄), ethanol, acetaminophen, Cis-Diammine Dichloroplatinum (CisPt), and gentamicin. The major mechanisms of action of DADS in disease prevention and/or treatment include inhibition of inflammation, oxidative stress, and cellular apoptosis. Mechanisms, including the activation of Akt, extracellular signal-regulated kinase 1/2 (ERK1/2), protein kinase A (PKA), and cyclic adenosine monophosphate-response element binding protein (CREB) and the inhibition of histone deacetylases (HDACs), can also mediate the cellular protective effects of DADS in different tissues and organs. In this review, we summarize and discuss the pharmacological effects of DADS other than its anti-carcinogenic activities, aiming to reveal more possibilities for DADS in disease prevention and/or treatment.

Modulation of hydrogen sulfide synthesis improves heart function and endothelium-dependent vasorelaxation in diabetes

Diabetes dramatically increases the risk of cardiovascular complications. The endothelial dysfunction and diastolic heart dysfunction are associated with a decreasing level of hydrogen sulfide (H₂S) and inhibition of the activity of endothelial nitric oxide synthase (NOS) in diabetes. The aim of this study is to investigate the effect of modulation of H₂S synthesis on heart functions and vasorelaxation in diabetes. The dl-propargylglycine and l-cysteine were administered intraperitoneally. H₂S content in the heart tissue, markers of oxidative stress, inducible NOS and constitutive NOS (cNOS) activities, endothelium-dependent vasorelaxation of the aortic rings, and heart function were studied. We demonstrate that our combination increased H₂S synthesis 13 times and cNOS activity 5 times in the heart tissue of diabetic rats. Increasing NO and H₂S production caused improvement and restoration of endothelium-dependent relaxation of aorta, effective arterial elastance, and diastolic heart function in diabetic rats. The endothelium-dependent relaxation increased 2.4 times; effective arterial elastance decreased by 47%. The end-diastolic myocardial stiffness decreased 2.2 times. Thus, modulation of H₂S synthesis leads to increased cNOS activity by up to 5 times in the cardiovascular system. Increasing NO and H₂S production restored endothelium-dependent relaxation of aorta and improved heart function in diabetes.

Role of hydrogen sulfide in cardiovascular ageing

Cardiovascular diseases are the main cause of morbidity and mortality in the Western society and ageing is a relevant non-modifiable risk factor. Morphological and functional alterations at endothelial level represent first events of ageing, inevitably followed by vascular dysfunction and consequent atherosclerosis that deeply influences cardiovascular health. Indeed, myocardial hypertrophy and fibrosis typically occur and contribute to compromise overall cardiac output. As regards the intracellular molecular mechanisms involved in the cardiovascular ageing, an intricate network is emerging, revealing a role for many mediators, including SIRT1/AMPK/PCG1α pathway, anti-oxidants factors (i.e. Nrf-2 and FOXOs) and pro-inflammatory cytokines. Thus, the search for pharmacological and non-pharmacological strategies that can promote a "healthy ageing", in order to slow down age-related machinery, are currently an exciting challenge for the biomedical research. Interestingly, hydrogen sulfide (H₂S) has been recently recognized as a new player capable to influence intracellular machinery involved in ageing and then it is view as a potential target for preventing cardiovascular diseases. Therefore, this review is focused on the role of H₂S in cardiovascular ageing, and on the evidence of the relationship between progressive decline in endogenous H₂S levels and the onset of various cardiovascular age-related diseases.

Potential application of nanoemulsified garlic oil blend in mitigating the progression of type 2 diabetes-mediated nephropathy in Wistar rats

The renoprotective potential of nanoemulsified garlic oil blend (GNE) in alleviating the progressive stages of hyperlipidemia-mediated diabetic nephropathy was examined. The study was carried out in high fat-fed, streptozotocin-induced type 2 diabetic Wistar rats for five months. The diabetic rats showed a significant increase of area under the curve in OGTT (p < 0.01) and IPITT (p < 0.01), increased urinary albumin (p < 0.01), urinary microprotein (p < 0.001), total cholesterol (p < 0.01), triglycerides (p < 0.001) and LDL cholesterol (p < 0.001), with decreased serum albumin (p < 0.01), serum protein (p < 0.001) and HDL-cholesterol levels (p < 0.05) than the control rats. The histopathological analysis evidenced mesangial expansion and hypercellularity at the end of the first and third month, and glomerulosclerosis and tubular atrophy at the end of the fifth month in diabetic rats. Moreover, on disease progression, increase in urinary podocalyxin, NGAL and CD36 was observed, and the renal mRNA and protein expression of podocalyxin decreased significantly with a concomitant increase in NGAL and CD36 expression from first till fifth month end. The treatment with GNE (20 mg/kg) significantly ameliorated the serum albumin (p < 0.001) and urine albumin (p < 0.01) from the end of the third month with significant attenuation in the lipid profile than GO (20 mg/kg) or Ator (8 mg/kg). Moreover, GNE reverted the histopathological alterations and attenuated the aberrant mRNA, protein expression and urinary excretion level of renal CD36, podocalyxin and NGAL in diabetic rats from an early stage of disease till the end of the study period. This study demonstrated the enhanced efficacy of GO in nanoemulsified form in mitigating the progression of nephropathy in type 2 diabetic rats.

The effect of garlic on vascular function: A systematic review of randomized clinical trials

BACKGROUNDS AND AIMS

Atherosclerosis and its associated cardiovascular disease (CVD) represent a major global health problem worldwide and vascular dysfunction is important in its pathogenesis. Clinical trials investigating the effect of garlic on vascular function measured by several non-invasive methods and their results are inconsistent. This study aimed to summarize the current evidence regarding the effectiveness of garlic as one of the world's most ancient medicines on measures of vascular reactivity and/or stiffness in adults.

METHODS

All published RCTs in English were systematically searched on PubMed, Scopus and Google Scholar search engines up to Oct 2019. The exposure and outcome variable of interest were garlic and vascular function measurements. Ten trials which met inclusion criteria were included in this study.

RESULTS

A total of 45 studies were found through search databases. After excluding duplicates, the 25 remaining studies were screened by title and abstract which 15 of them excluded. Finally, ten trials were included in this review study, which were published between 2004 and 2018.

CONCLUSIONS

Findings were inconsistent. However, garlic has the potential to improve vascular function, particularly in subjects with cardiovascular risk factors. Additional human studies on garlic and its constituents should consider the population and the specific type of garlic preparation.

Regulation of carbohydrate metabolism by nitric oxide and hydrogen sulfide: Implications in diabetes

Nitric oxide (NO) and hydrogen sulfide (H₂S) are two gasotransmitters that are produced in the human body and have a key role in many of the physiological activities of the various organ systems. Decreased NO bioavailability and deficiency of H₂S are involved in the pathophysiology of type 2 diabetes and its complications. Restoration of NO levels have favorable metabolic effects in diabetes. The role of H₂S in pathophysiology of diabetes is however controversial; H₂S production is decreased during development of obesity, diabetes, and its complications, suggesting the potential therapeutic effects of H₂S. On the other hand, increased H₂S levels disturb the pancreatic β-cell function and decrease insulin secretion. In addition, there appear to be important interactions between NO and H₂S at the levels of both biosynthesis and signaling pathways, yet clear an insight into this relationship is lacking. H₂S potentiates the effects of NO in the cardiovascular system as well as NO release from its storage pools. Likewise, NO increases the activity and the expression of H₂S-generating enzymes. Inhibition of NO production leads to elimination/attenuation of the cardioprotective effects of H₂S. Regarding the increasing interest in the therapeutic applications of NO or H₂S-releasing molecules in a variety of diseases, particularly in the cardiovascular disorders, much is to be learned about their function in glucose/insulin metabolism, especially in diabetes. The aim of this review is to provide a better understanding of the individual and the interactive roles of NO and H₂S in carbohydrate metabolism.

Garlic and Gaseous Mediators

Garlic (Allium sativum) and allied plant species are rich sources of sulfur compounds. Major roles for garlic and its sulfur constituents include the regulation of vascular homeostasis and the control of metabolic systems linked to nutrient metabolism. Recent studies have indicated that some of these sulfur compounds, such as diallyl trisulfide (DATS), alter the levels of gaseous signalling molecules including nitric oxide (NO), hydrogen sulfide (H₂S), and perhaps carbon monoxide (CO) in mammalian tissues. These gases are important in cellular processes associated with the cardiovascular system, inflammation, and neurological functions. Importantly, these studies build on the known biological effects of garlic and associated sulfur constituents. This review highlights our current understanding of the health benefits attributed to edible plants like garlic.

Regulation of vascular tone homeostasis by NO and H2S: Implications in hypertension

Nitric oxide (NO) and hydrogen sulfide (H2S) are two gasotransmitters that are produced in the vasculature and contribute to the regulation of vascular tone. NO and H2S are synthesized in both vascular smooth muscle and endothelial cells; NO functions primarily through the sGC/cGMP pathway, and H2S mainly through activation of the ATP-dependent potassium channels; both leading to relaxation of vascular smooth muscle cells. A deficit in the NO/H2S homeostasis is involved in the pathogenesis of various cardiovascular diseases, especially hypertension. It is now becoming increasingly clear that there are important interactions between NO and H2S and that have a profound impact on vascular tone and this may provide insights into the new therapeutic interventions. The aim of this review is to provide a better understanding of individual and interactive roles of NO and H2S in vascular biology. Overall, available data indicate that both NO and H2S contribute to vascular (patho)physiology and in regulating blood pressure. In addition, boosting NO and H2S using various dietary sources or donors could be a hopeful therapeutic strategy in the management of hypertension.

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.

Garlic-Derived Organic Polysulfides and Myocardial Protection

For centuries, garlic has been shown to exert substantial medicinal effects and is considered to be one of the best disease-preventative foods. Diet is important in the maintenance of health and prevention of many diseases including cardiovascular disease (CVD). Preclinical and clinical evidence has shown that garlic reduces risks associated with CVD by lowering cholesterol, inhibiting platelet aggregation, and lowering blood pressure. In recent years, emerging evidence has shown that hydrogen sulfide (H2S) has cardioprotective and cytoprotective properties. The active metabolite in garlic, allicin, is readily degraded into organic diallyl polysulfides that are potent H2S donors in the presence of thiols. Preclinical studies have shown that enhancement of endogenous H2S has an impact on vascular reactivity. In CVD models, the administration of H2S prevents myocardial injury and dysfunction. It is hypothesized that these beneficial effects of garlic may be mediated by H2S-dependent mechanisms. This review evaluates the current knowledge concerning the cardioprotective effects of garlic-derived diallyl polysulfides.

H2S, a novel gasotransmitter, involves in gastric accommodation

H₂S is produced mainly by two enzymes:cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE), using L-cysteine (L-Cys) as the substrate. In this study, we investigated the role of H₂S in gastric accommodation using CBS^+/− mice, immunohistochemistry, immunoblot, methylene blue assay, intragastric pressure (IGP) recording and electrical field stimulation (EFS). Mouse gastric fundus expressed H₂S-generating enzymes (CBS and CSE) and generated detectable amounts of H₂S. The H₂S donor, NaHS or L-Cys, caused a relaxation in either gastric fundus or body. The gastric compliance was significantly increased in the presence of L-Cys (1 mM). On the contrary, AOAA, an inhibitor for CBS, largely inhibited gastric compliance. Consistently, CBS^+/− mice shows a lower gastric compliance. However, PAG, a CSE inhibitor, had no effect on gastric compliances. L-Cys enhances the non-adrenergic, non-cholinergic (NANC) relaxation of fundus strips, but AOAA reduces the magnitude of relaxations to EFS. Notably, the expression level of CBS but not CSE protein was elevated after feeding. Consistently, the production of H₂S was also increased after feeding in mice gastric fundus. In addition, AOAA largely reduced food intake and body weight in mice. Furthermore, a metabolic aberration of H₂S was found in patients with functional dyspepsia (FD). In conclusion, endogenous H₂S, a novel gasotransmitter, involves in gastric accommodation.

Diallyl disulfide attenuated carbon ion irradiation-induced apoptosis in mouse testis through changing the ratio of Tap73/ΔNp73 via mitochondrial pathway

Diallyl disulfide (DADS), a major organosulfur compound derived from garlic, has various biological properties, including anti-cancer effects. However, the protective mechanism of DADS against radiation-induced mouse testis cell apoptosis has not been elucidated. In this study, the magnitude of radiation effects evoked by carbon ion irradiation was marked by morphology changes, significant rise in apoptotic cells, activation expression of p53, up regulation the ratio of pro-apoptotic Tap73/anti-apoptotic ΔNp73, as well as alterations of crucial mediator of the mitochondrial pathway. Interestingly, pretreatment with DADS attenuated carbon ion irradiation-induced morphology damages and apoptotic cells. Additionally, DADS elevated radiation-induced p53 and p21 expression, suggesting that p53 might be involved in the inhibition of cell cycle progression through up regulation of p21. Furthermore, administration with DADS prevented radiation-induced Tap73/ΔNp73 expression and consequently down regulated Bax/Bcl-2 ratio, cytochrome c release and caspase-3 expression, indicating that the balance between Tap73 and ΔNp73 had potential to activate p53 responsive genes. Thus, our results showed that radio protection effect of DADS on mouse testis is mediated by blocking apoptosis through changing the ratio of Tap73/ΔNp73 via mitochondrial pathway, suggesting that DADS could be used as a potential radio protection agent for the testis against heavy-ion radiation.

The Cardioprotective Effects of Hydrogen Sulfide in Heart Diseases: From Molecular Mechanisms to Therapeutic Potential

Hydrogen sulfide (H₂S) is now recognized as a third gaseous mediator along with nitric oxide (NO) and carbon monoxide (CO), though it was originally considered as a malodorous and toxic gas. H₂S is produced endogenously from cysteine by three enzymes in mammalian tissues. An increasing body of evidence suggests the involvement of H₂S in different physiological and pathological processes. Recent studies have shown that H₂S has the potential to protect the heart against myocardial infarction, arrhythmia, hypertrophy, fibrosis, ischemia-reperfusion injury, and heart failure. Some mechanisms, such as antioxidative action, preservation of mitochondrial function, reduction of apoptosis, anti-inflammatory responses, angiogenic actions, regulation of ion channel, and interaction with NO, could be responsible for the cardioprotective effect of H₂S. Although several mechanisms have been identified, there is a need for further research to identify the specific molecular mechanism of cardioprotection in different cardiac diseases. Therefore, insight into the molecular mechanisms underlying H₂S action in the heart may promote the understanding of pathophysiology of cardiac diseases and lead to new therapeutic targets based on modulation of H₂S production.

Chemical and biochemical mechanisms underlying the cardioprotective roles of dietary organopolysulfides

Foods that are rich in organosulfides are highly regarded for their broad range of functions in disease prevention and health promotion since ancient time yet modern scientific study, particularly clinical studies could not agree with traditional wisdom. One of the complexities is due to the labile nature of organosulfides, which are often transformed to different structures depending on the processing conditions. The recent evidence on polysulfides as H₂S donors may open up a new avenue for establishing structure and health promotion activity relationship. To put this development into perspective, we carried out a review on the recent progress on the chemistry and biochemistry of organopolysulfides with emphasis on their cardioprotective property. First, we briefly surveyed the foods that are rich in polysulfides and their structural diversity. This is followed by in-depth discussion on the chemical transformations of polysulfides under various processing conditions. We further reviewed the potential action mechanisms of polysulfides in cardioprotection through: (a) hydrogen sulfide releasing activity; (b) radical scavenging activity; and (c) activity in enzyme inhibition and intervention of gene regulation pathways. Based on the literature trend, we can conclude that the emerging concept of organopolysulfides as naturally occurring H₂S donors is intriguing and warrants further research to establish the structure and activity relationship of the organopolysulfides as H₂S donors.

H2S regulation of nitric oxide metabolism

Nitric oxide (NO) and hydrogen sulfide (H2S) are two major gaseous signaling molecules that regulate diverse physiological functions. Recent publications indicate the regulatory role of H2S on NO metabolism. In this chapter, we discuss the latest findings on H2S-NO interactions through formation of novel chemical derivatives and experimental approaches to study these adducts. This chapter also addresses potential H2S interference on various NO detection techniques, along with precautions for analyzing biological samples from various sources. This information will facilitate critical evaluation and clearer insight into H2S regulation of NO signaling and its influence on various physiological functions.

Medicinal Chemistry: Insights into the Development of Novel H2S Donors

Hydrogen sulfide (H2S) was traditionally considered as a toxic gas. However, recent studies have demonstrated H2S is an endogenously generated gaseous signaling molecule (gasotransmitter) with importance on par with that of two other well-known endogenous gasotransmitters, nitric oxide (NO) and carbon monoxide (CO). Although H2S's exact mechanisms of action are still under investigation, the production of endogenous H2S and the exogenous administration of H2S have been demonstrated to elicit a wide range of physiological responses including modulation of blood pressure and protection of ischemia reperfusion injury, exertion of anti-inflammatory effects, and reduction of metabolic rate. These results strongly suggest that modulation of H2S levels could have potential therapeutic values. In this regard, synthetic H2S-releasing agents (i.e., H2S donors) are not only important research tools, but also potential therapeutic agents. This chapter summarizes the knowledge of currently available H2S donors. Their preparation, H2S releasing mechanisms, and biological applications are discussed.

Ameliorative effect of diallyl trisulphide on arsenic-induced oxidative stress in rat erythrocytes and DNA damage in lymphocytes

BACKGROUND

Arsenic (As) is a naturally occurring semimetallic element that is classified as a toxicant and a human carcinogen. Diallyl trisulphide (DATS), an organosulphur compound, is an antioxidative substance that is extracted from garlic (Allium sativum). Erythrocytes are very expedient models to understand the susceptibility of membrane to oxidative damage induced by different xenobiotic compounds. Arsenic has been reported to induce oxidative stress to erythrocytes due to lipid peroxidation and alteration in defence mechanism as erythrocytes are the first target that arsenic compounds attack in the body after systemic absorption. In the light of this fact, the purpose of this study is to characterise the ameliorative effect of DATS on arsenic-induced oxidative stress in rat erythrocytes.

METHODS

Experimental rats were randomly divided into four groups and treated orally for 28 days: control, As [5 mg/kg body weight (BW)] treated, As+DATS (80 mg/kg BW) treated, DATS (80 mg/kg BW) treated and As+vitamin C (100 mg/kg BW) treated. Oxidative stress in erythrocytes was recorded by estimating plasma marker enzymes, plasma and erythrocyte membrane oxidative stress markers, erythrocyte membrane antioxidant enzymes and non-antioxidant enzymes, etc.

RESULTS

Oral administration of arsenic at 5 mg/kg BW per day elevated the levels of plasma marker enzymes, namely, aspartate transaminase (AST), alanine transaminase (ALT), acid phosphatase (ACP), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and γ-glutamyl transferase (γGT) (U/L) with significantly increased lipid peroxidation markers such as thiobarbituric acid reactive substances (TBARS), malondialdehyde (MDA), lipid hydroperoxides (LH), conjugated dienes (CD), and protein carbonyl (PC) contents were also elevated in As-treated rat plasma and erythrocytes. The levels of non-enzymatic antioxidants (reduced glutathione, vitamins C and E) and enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR), and glucose-6-phosphate dehydrogenase (G6PD) were also decreased in As-treated rats. The toxic effect of As significantly decreased the activities of membrane-bound ATPases (Na+/K+-ATPase, Mg2+-ATPase, and Ca2+-ATPase), with a significant increase in% tail DNA of rat lymphocytes measured by means of a single-cell gel electrophoresis assay. Administration of DATS for 28 days significantly reduced the levels of plasma markers. The levels of TBARS, MDA, LH, CD, and PC were significantly decreased and there was a significant increase in ATPase activities and non-enzymatic and enzymatic antioxidants on treatment with DATS in a dose-related manner.

CONCLUSIONS

All these changes were supported by reduction of DNA damage in lymphocytes with DATS treatment. DATS at a dose of 80 mg/kg BW was found to be most effective and the results revealed the same. The results of the study showed that DATS shows a protective effect against As-induced oxidative stress in rat erythrocytes and lymphocytes.

Hydrogen sulfide in signaling pathways

For a long time hydrogen sulfide (H₂S) was considered a toxic compound, but recently H₂S (at low concentrations) has been found to play an important function in physiological processes. Hydrogen sulfide, like other well-known compounds - nitric oxide (NO) and carbon monoxide (CO) is a gaseous intracellular signal transducer. It regulates the cell cycle, apoptosis and the oxidative stress. Moreover, its functions include neuromodulation, regulation of cardiovascular system and inflammation. In this review, I focus on the metabolism of hydrogen sulfide (including enzymatic pathways of H₂S synthesis from l- and d-cysteine) and its signaling pathways in the cardiovascular system and the nervous system. I also describe how hydrogen sulfide may be used as therapeutic agent, i.e. in the cardiovascular diseases.

Diallyl disulfide inhibits proliferation and transdifferentiation of lung fibroblasts through induction of cyclooxygenase and synthesis of prostaglandin E₂

Platelet-derived growth factor-BB (PDGF-BB) and transforming growth factor-β1 (TGF-β1) are critically involved in idiopathic pulmonary fibrosis by inducing the proliferation and transdifferentiation of lung fibroblasts. In the present study, we examined the impact of diallyl disulfide (DADS), a garlic-derived compound, on such pathological conditions. DADS showed profound inhibitory effects on the PDGF-BB-induced proliferation of human and mouse lung fibroblasts. DADS also abrogated the TGF-β1-induced expression of α-smooth muscle actin, type I collagen and fibronectin. Following treatment with DADS, the expression of cyclooxygenase-2 (COX-2) and the synthesis of prostaglandin E₂ (PGE₂) were found to be markedly enhanced, which in turn led to elevated cAMP levels in lung fibroblasts. Notably, the effect of DADS was largely abolished in the presence of either COX inhibitor indomethacin or siRNA-targeting COX-2, or in the absence of the PGE₂ receptor EP2, supporting an essential role for the COX-2-PGE₂-cAMP autocrine loop. Furthermore, we demonstrated that the upregulated expression of COX-2 was a result of increased level of histone 3 acetylation at COX-2 locus in DADS-treated cells. Together, these results suggest that DADS, by inducing COX-2 expression, may have therapeutic potential in treating lung fibrosis.

A role for diallyl trisulfide in mitochondrial antioxidative stress contributes to its protective effects against vascular endothelial impairment

Persistent hyperglycemia increases a systemic oxidative stress, causing the onset of vascular endothelial dysfunction and atherosclerosis. Diallyl trisulfide (DAT), a natural organosulfur compound in garlic, has been reported to have actions of dilating blood vessels and antibacteria, etc. In this study, models of obese diabetic rat in vivo and high glucose concentration (HG)-induced endothelial cell injury in vitro were used to investigate the protective effects of DAT on vascular endothelial injury and its underlying mechanisms. In the in vivo model, the obese diabetic rats were injected venously with DAT (5.0 mg kg(-1)d(-1)) and Vitamin E (1.0 mg kg(-1)d(-1)) respectively, once daily for 7 consecutive days. In the in vitro model, HG-injured HUVEC were treated with or without DAT (25 µmol L(-1), 50 µmol L(-1), 100 µmol L(-1)) or Vitamin E (25 µmol L(-1)) respectively for 24h. The extents of vascular endothelial injury and protective effects of DAT were evaluated. The results both in vivo and in vitro displayed that DAT-treatment significantly attenuated the endothelial cell impairments. Besides, DAT-treatment markedly decreased the levels of malondialdehyde (MDA) and reactive oxygen species, whereas elevated the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in mitochondrium. Moreover, DAT-treatment considerably improved mitochondrial respiration function. Taken together, our results suggest that DAT protects vascular endothelium from HG or hyperglycemia induced-injury by reducing mitochondrial oxidative stress. The findings provide a novel insight for DAT to potentially treat the oxidative stress diseases, i.e., atherosclerosis, diabetes, and neurodegenerative diseases.

An outlook on vascular hydrogen sulphide effects, signalling, and therapeutic potential

Hydrogen sulphide (H(2)S) is the most recently discovered gasotransmitter. It is endogenously generated in mammalian vascular cells and attracts substantial interest by its function as physiological relevant signalling mediator, and by its dysfunction in metabolic diseases like obesity, type 2 diabetes and their associated complications. The purpose of this review is to highlight the novel findings on vascular H(2)S homeostasis, pathology-associated dysregulation, cell signalling, and therapeutic potential. The data bases searched were Medline and PubMed, from 2008 to 2012 (terms: hydrogen sulphide, sulfhydration). The new reports definitely assess the vasculoprotectant role of H(2)S in health, and its reduced biosynthesis/systemic levels in obesity, diabetes, atherosclerosis and hypertension. One of the mechanisms of H(2)S signalling discussed here is S-sulfhydration of catalytic cysteine residue of PTP1B, a negative regulator of insulin and leptin signalling. Finally, the review critically evaluates the compounds able to regulate vascular H(2)S bioavailability, and with potential in therapeutic exploitation.

Hydrogen sulfide chemical biology: pathophysiological roles and detection

Hydrogen sulfide (H2S) is the most recent endogenous gasotransmitter that has been reported to serve many physiological and pathological functions in different tissues. Studies over the past decade have revealed that H2S can be synthesized through numerous pathways and its bioavailability regulated through its conversion into different biochemical forms. H2S exerts its biological effects in various manners including redox regulation of protein and small molecular weight thiols, polysulfides, thiosulfate/sulfite, iron-sulfur cluster proteins, and anti-oxidant properties that affect multiple cellular and molecular responses. However, precise measurement of H2S bioavailability and its associated biochemical and pathophysiological roles remains less well understood. In this review, we discuss recent understanding of H2S chemical biology, its relationship to tissue pathophysiological responses and possible therapeutic uses.

A tale of two gases: NO and H2S, foes or friends for life?

Nitric oxide (NO) and hydrogen sulfide (H₂S) have emerged as dominant redox regulators of numerous aspects of cellular and physiological functions within several organ systems included cardiovascular, immune and neurological tissues. Recent studies have begun to reveal that these two gaseous molecules may have redundant or overlapping pathophysiological functions often involving similar molecular targets. However, it remains less clear when and how NO and H₂S may interact under biological and disease processes. In this graphical review, we discuss the current understanding of NO and H₂S interactions and how they may functionally influence each other and what this may mean for biology and mechanisms of disease.

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H₂S and NO are important gaseous regulators of numerous physiological responses.

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H₂S and NO may target both similar and divergent signaling and molecular pathways.

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H₂S and NO react with protein free thiols that differentially affect protein function.

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H₂S and NO metabolites can react together to yield novel biochemical products.

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The presence and physiological importance of these novel products remains unknown.

Dietary Nrf2 activators inhibit atherogenic processes

Dietary Nrf2 activators increase expression of phase 2 protein genes in cells undergoing oxidative stress resulting in a lowering of oxidative stress. Oxidative stress promotes atherogenic processes through oxidizing low density lipoproteins and promotion of inflammation through activation of nuclear factor kappa B and activation of mitogen-activated protein kinases. Nrf2 activators by decreasing oxidative stress decrease the probability of developing atherosclerotic lesions.

Beneficial effects of aged garlic extract and coenzyme Q10 on vascular elasticity and endothelial function: the FAITH randomized clinical trial

OBJECTIVE

Aged garlic extract (AGE) is associated with a significant decrease in atherosclerotic plaque progression and endothelial function improvement. Similarly, coenzyme Q10 (CoQ10) has significant beneficial effects on endothelial function. A stressful lifestyle is a well-known risk factor for the presence and progression of atherosclerosis. This study investigated the effect of AGE plus CoQ10 on vascular elasticity measured by pulse-wave velocity (PWV) and endothelial function measured by digital thermal monitoring (DTM) in firefighters.

METHODS

Sixty-five Los-Angeles County firefighters who met the eligibility criteria were enrolled in this placebo-controlled, double-blinded randomized trial. The firefighters were randomized to four tablets of AGE (300 mg/tablet) plus CoQ10 (30 mg/tablet) or placebo. The participants underwent quarterly visits and 1-year follow-up. PWV and DTM were measured at baseline and at the 1-year follow-up.

RESULTS

There were no significant differences in age, cardiovascular risk factors, PWV, and DTM between the AGE/CoQ10 and placebo groups at baseline (P > 0.5). At 1-y, PWV and DTM significantly improved in the AGE/CoQ10 compared with the placebo group (P < 0.05). After an adjustment for cardiovascular risk factors and statin therapy, the mean decrease in vascular stiffness (PWV) was 1.21 m/s in the AGE/CoQ10 compared with the placebo group (P = 0.005). Similarly, the mean increase in the area under the temperature curve, the DTM index of endothelial function, was 31.3 in the AGE/CoQ10 compared with the placebo group (P = 0.01).

CONCLUSION

The combination of AGE and CoQ10 was independently associated with significant beneficial effects on vascular elasticity and endothelial function in firefighters with high occupational stress, highlighting the important role of AGE and CoQ10 in atherosclerotic prevention of such individuals.

The polysulfide diallyl trisulfide protects the ischemic myocardium by preservation of endogenous hydrogen sulfide and increasing nitric oxide bioavailability

Diallyl trisulfide (DATS), a polysulfide constituent found in garlic oil, is capable of the release of hydrogen sulfide (H(2)S). H(2)S is a known cardioprotective agent that protects the heart via antioxidant, antiapoptotic, anti-inflammatory, and mitochondrial actions. Here, we investigated DATS as a stable donor of H(2)S during myocardial ischemia-reperfusion (MI/R) injury in vivo. We investigated endogenous H(2)S levels, infarct size, postischemic left ventricular function, mitochondrial respiration and coupling, endothelial nitric oxide (NO) synthase (eNOS) activation, and nuclear E2-related factor (Nrf2) translocation after DATS treatment. Mice were anesthetized and subjected to a surgical model of MI/R injury with and without DATS treatment (200 μg/kg). Both circulating and myocardial H(2)S levels were determined using chemiluminescent gas chromatography. Infarct size was measured after 45 min of ischemia and 24 h of reperfusion. Troponin I release was measured at 2, 4, and 24 h after reperfusion. Cardiac function was measured at baseline and 72 h after reperfusion by echocardiography. Cardiac mitochondria were isolated after MI/R, and mitochondrial respiration was investigated. NO metabolites, eNOS phosphorylation, and Nrf2 translocation were determined 30 min and 2 h after DATS administration. Myocardial H(2)S levels markedly decreased after I/R injury but were rescued by DATS treatment (P < 0.05). DATS administration significantly reduced infarct size per area at risk and per left ventricular area compared with control (P < 0.001) as well as circulating troponin I levels at 4 and 24 h (P < 0.05). Myocardial contractile function was significantly better in DATS-treated hearts compared with vehicle treatment (P < 0.05) 72 h after reperfusion. DATS reduced mitochondrial respiration in a concentration-dependent manner and significantly improved mitochondrial coupling after reperfusion (P < 0.01). DATS activated eNOS (P < 0.05) and increased NO metabolites (P < 0.05). DATS did not appear to significantly induce the Nrf2 pathway. Taken together, these data suggest that DATS is a donor of H(2)S that can be used as a cardioprotective agent to treat MI/R injury.

Diallyl trisulfide suppresses the adipogenesis of 3T3-L1 preadipocytes through ERK activation

Garlic and its organosulfur compounds display hypolipidemic effects by inhibiting fatty acid and cholesterol synthesis. We investigated the anti-adipogenic effect of diallyl trisulfide (DATS), the second most abundant organosulfide in garlic oil. We studied the effects of DATS in 3T3-L1 preadipocytes and the mechanism involved in its action. DATS (0-75 μM) inhibited CCAAT/enhancer-binding protein (C/EBP) α and β and peroxisome proliferator-activated receptor (PPAR) γ mRNA and protein levels in a dose- and time-dependent manner, leading to a decrease of fatty acid synthase (FAS) expression and lipid accumulation in 3T3-L1 cells. Insulin treatment induced a transient increase in ERK phosphorylation in 3T3-L1 preadipocytes, and maximal induction was observed at 5 min and then declined. DATS, however, sustained ERK phosphorylation up to 120 min. In the presence of PD98059, the phosphorylation of ERK and suppression of PPARγ expression and DNA binding activity of PPARγ by DATS were reversed, and lipid accumulation was restored. In conclusion, these results indicate that DATS inhibits the differentiation of 3T3-L1 preadipocytes into adipocytes. DATS is likely to act by prolonging ERK activation, which leads to the down-regulation of adipogenic transcription factor expression during adipogenesis. Our results suggest that garlic may have potential as an anti-obesity agent.

Hydrogen sulfide-mediated cardioprotection: mechanisms and therapeutic potential

H2S (hydrogen sulfide), viewed with dread for more than 300 years, is rapidly becoming a ubiquitously present and physiologically relevant signalling molecule. Knowledge of the production and metabolism of H2S has spurred interest in delineating its functions both in physiology and pathophysiology of disease. Although its role in blood pressure regulation and interaction with NO is controversial, H2S, through its anti-apoptotic, anti-inflammatory and antioxidant effects, has demonstrated significant cardioprotection. As a result, a number of sulfide-donor drugs, including garlic-derived polysulfides, are currently being designed and investigated for the treatment of cardiovascular conditions, specifically myocardial ischaemic disease. However, huge gaps remain in our knowledge about this gasotransmitter. Only by additional studies will we understand more about the role of this intriguing molecule in the treatment of cardiovascular disease.