Deficient DNASE1L3 facilitates neutrophil extracellular traps-induced invasion via cyclic GMP-AMP synthase and the non-canonical NF-κB pathway in diabetic hepatocellular carcinoma.

Objective: Diabetic hepatocellular carcinoma (HCC) patients have high mortality and metastasis rates. Diabetic conditions promote neutrophil extracellular traps (NETs) generation, which mediates HCC metastasis and invasion. However, whether and how diabetes-induced NETs trigger HCC invasion is largely unknown. Here, we aimed to observe the effects of diabetes-induced NETs on HCC invasion and investigate mechanisms relevant to a DNA sensor cyclic GMP-AMP synthase (cGAS). Methods: Serum from diabetic patients and healthy individuals was collected. Human neutrophil-derived NETs were isolated for stimulating HCC cell invasion. Data from the SEER and TCGA databases were used for bioinformatics analysis. In HCC cells and allograft models, NETs-triggered invasion was observed. Results: Diabetic HCC patients had poorer survival than non-diabetic ones. Either diabetic serum or extracted NETs caused HCC invasion. Induction of diabetes or NETosis elicited HCC allograft invasion in nude mice. HCC cell invasion was attenuated by the treatment with DNase1. In TCGA_LIHC, an extracellular DNase DNASE1L3 was downregulated in tumor tissues, while function terms (the endocytic vesicle membrane, the NF-κB pathway and extracellular matrix disassembly) were enriched. DNASE1L3 knockdown in LO2 hepatocytes or H22 cell-derived allografts facilitated HCC invasion in NETotic or diabetic nude mice. Moreover, exposure of HCC cells to NETs upregulated cGAS and the non-canonical NF-κB pathway and induced expression of metastasis genes (MMP9 and SPP1). Both cGAS inhibitor and NF-κB RELB knockdown diminished HCC invasion caused by NETs DNA. Also, cGAS inhibitor was able to retard translocation of NF-κB RELB. Conclusion: Defective DNASE1L3 aggravates NETs DNA-triggered HCC invasion on diabetic conditions via cGAS and the non-canonical NF-κB pathway.

Metabolic Reprogramming of Sulfur in Hepatocellular Carcinoma and Sulfane Sulfur-Triggered Anti-Cancer Strategy.

Metabolic reprogramming is a cancer hallmark. Although the reprogramming of central carbon has been well documented, the role of sulfur metabolism has been largely overlooked. Additionally, the effects of sulfur are sometimes contradictory in tumorigenesis. In this study, we aimed to investigate the gene expression profile in hepatocellular carcinoma (HCC) and the effects of reactive sulfur species (RSS) on HCC tumor cells. Furthermore, the cell imaging technology was applied to discover some potential anti-cancer compounds. Gene Set Enrichment Analysis (GSEA) of Gene Expression Omnibus (GEO) dataset (GSE102083) revealed that sulfur amino acid-related metabolism and vitamin B6 binding activity in HCC tissues were downregulated. Calculation of the interaction network identified nine hub genes, among which eight were validated by differential expression and survival analysis in the TCGA_LIHC cohort, and two (CSE and CBS) had the highest enrichment degree. The metabolomics analysis suggested that the hub genes were associated with RSS metabolism including H2S, H2S2, cystine, cysteine, homocysteine, cystathionine, and methionine. The cell viability assay demonstrated that H2S2 had significant anti-cancer effects in HCC SNU398 tumor cells. The cell imaging assay showed that treatment with H2S2 remarkably increased intracellular sulfane sulfur content. On this basis, the anti-cancer activity of some other sulfane sulfur compounds, such as DATS and DADS, was further verified. Lastly, according to the fact that HCC tumor cells preferentially take in cystine due to high expression of SLC7A11 (a cystine/glutamate transporter), persulfided cysteine precursor (PSCP) was tested for its sulfane sulfur release capability and found to selectively inhibit HCC tumor cell viability. Collectively, this study uncovered sulfur metabolism in HCC was reprogrammed, and provided a potential therapeutic strategy for HCC by donating sulfane sulfur.

Is Hydrogen Sulfide a Concern During Treatment of Lung Adenocarcinoma With Ammonium Tetrathiomolybdate?

Ammonium tetrathiomolybdate (ATTM) has been used in breast cancer therapy for copper chelation, as elevated copper promotes tumor growth. ATTM is also an identified H2S donor and endogenous H2S facilitates VitB12-induced S-adenosylmethionine (SAM) generation, which have been confirmed in m6A methylation and lung cancer development. The m6A modification was recently shown to participate in lung adenocarcinoma (LUAD) progression. These conflicting analyses of ATTM's anticancer vs. H2S's carcinogenesis suggest that H2S should not be ignored during LUAD's treatment with ATTM. This study was aimed to explore ATTM's effects on LUAD cells and mechanisms associated with H2S and m6A. It was found that treatment with ATTM inhibited cell growth at high concentrations, while enhanced cell growth at low concentrations in three LUAD cell lines (A549, HCC827, and PC9). However, another copper chelator triethylenetetramine, without H2S releasing activity, was not found to induce cell growth. Low ATTM concentrations also elevated m6A content in A549 cells. Analysis of differentially expressed genes in TCGA cohort indicated that m6A writer METTL3 and reader YTHDF1 were upregulated while eraser FTO was downregulated in LUAD tissues, consistent with the findings of protein expression in patient tissues. ATTM treatment of A549 cells significantly increased METTL3/14 and YTHDF1 while decreased FTO expression. Furthermore, inhibition of m6A with shMETTL3 RNA significantly attenuated eukaryotic translation initiation factor (eIF) expressions in A549 cells. Correlation analysis indicated that small nuclear ribonucleic protein PRPF6 was positively expressed with YTHDF1 in LUAD tissues. Knockdown of YTHDF1 partially blocked both basal and ATTM-induced PRPF6 expression, as well as A549 cell growth. Lastly, ATTM treatment not only raised intracellular H2S content but also upregulated H2S-producing enzymes. Exogenous H2S application mimicked ATTM's aforementioned effects, but the effects could be weakened by zinc-induced H2S scavenging. Collectively, H2S impedes ATTM-induced anticancer effects through YTHDF1-dependent PRPF6 m6A methylation in lung adenocarcinoma cells.

S-Persulfidation: Chemistry, Chemical Biology, and Significance in Health and Disease.

Significance: S-Persulfidation generates persulfide adducts (RSSH) on both small molecules and proteins. This process is believed to be critical in the regulation of biological functions of reactive sulfur species such as H2S, as well as in signal transduction. S-Persulfidation also plays regulatory roles in human health and diseases. Recent Advances: Some mechanisms underlying the generation of low-molecular-weight persulfides and protein S-persulfidation in living organisms have been uncovered. Some methods for the specific delivery of persulfides and the detection of persulfides in biological systems have been developed. These advances help to pave the road to better understand the functions of S-persulfidation. Critical Issues: Persulfides are highly reactive and unstable. Currently, their identification relies on trapping them by S-alkylation, but this is not always reliable due to rapid sulfur exchange reactions. Therefore, the presence, identity, and fates of persulfides in biological environments are sometimes difficult to track. Future Directions: Further understanding the fundamental chemistry/biochemistry of persulfides and development of more reliable detection methods are needed. S-Persulfidation in specific protein targets is essential in organismal physiological health and human disease states. Besides cardiovascular and neuronal systems, the roles of persulfidation in other systems need to be further explored. Contradictory results of persulfidation in biology, especially in cancer, need to be clarified.

Hydrogen Sulfide Mediated Tandem Reaction of Selenenyl Sulfides and Its Application in Fluorescent Probe Development.

A unique reaction between H2S and a selenenyl sulfide containing benzoate ester template was discovered. This reaction could be specifically triggered by H2S and lead to ester bond cleavage. The reaction was not affected by the presence of thiols such as glutathione and cysteine. With this reaction, a series of fluorescent probes were synthesized and evaluated. The probes exhibited high sensitivity/selectivity for H2S in both buffers and cells.

Data-Driven Identification of Hydrogen Sulfide Scavengers.

Hydrogen sulfide (H2 S) is an important signaling molecule whose up- and down-regulation have specific biological consequences. Although significant advances in H2 S up-regulation, by the development of H2 S donors, have been achieved in recent years, precise H2 S down-regulation is still challenging. The lack of potent/specific inhibitors for H2 S-producing enzymes contributes to this problem. We expect the development of H2 S scavengers is an alternative approach to address this problem. Since chemical sensors and scavengers of H2 S share the same criteria, we constructed a H2 S sensor database, which summarizes key parameters of reported sensors. Data-driven analysis led to the selection of 30 potential compounds. Further evaluation of these compounds identified a group of promising scavengers, based on the sulfonyl azide template. The efficiency of these scavengers in in vitro and in vivo experiments was demonstrated.

TRPC6 contributes to LPS-induced inflammation through ERK1/2 and p38 pathways in bronchial epithelial cells.

receptor potential canonical (TRPC) channels are presently an emerging target for airway disorders. Recent evidence has indicated that TRPC6 as a member of the TRPC family plays an important role in airway inflammation, but its precise function in bronchial epithelial cells remains unclear. The aim of this study was to investigate the role of TRPC6 in Toll-like receptor 4 (TLR4)-mediated inflammation in human bronchial epithelial cells stimulated by endotoxin [lipopolysaccharide (LPS)]. Hyp9 is a simplified phloroglucinol derivative of hyperforin that highly selectively activates TRPC6 channels. The results show that the activation of TRPC6 by Hyp9 induced the production of interleukin (IL)-8 and IL-6. LPS was also able to induce the release of IL-8 and IL-6, which was significantly aggravated by Hyp9 and reduced by knockdown of TRPC6. Treatment with LPS not only chronically induced the expression of TRPC6 mRNA and protein in a TLR4-dependent manner but also acutely increased Ca2+ influx through TRPC6 channels. In addition, LPS-induced overexpression of TRPC6 and Ca2+ influx were associated with the phosphorylation of phosphatidylinositol 3-kinase (PI3K) and Akt. Importantly, TRPC6 was required for the activation of ERK1/2, p38, and NF-κB. In conclusion, these data reveal that LPS induced the overexpression of TRPC6 and TRPC6-dependent Ca2+ influx via the TLR4/PI3K/Akt pathway resulting in Ca2+ mobilization, which subsequently promoted the activation of ERK1/2, p38, and NF-κB and the inflammatory response in bronchial epithelial cells.

Recent Development of Hydrogen Sulfide Releasing/Stimulating Reagents and Their Potential Applications in Cancer and Glycometabolic Disorders.

As an important endogenous gaseous signaling molecule, hydrogen sulfide (H2S) exerts various effects in the body. A variety of pathological changes, such as cancer, glycometabolic disorders, and diabetes, are associated with altered endogenous levels of H2S, especially decreased. Therefore, the supplement of H2S is of great significance for the treatment of diseases containing the above pathological changes. At present, many efforts have been made to increase the in vivo levels of H2S by administration of gaseous H2S, simple inorganic sulfide salts, sophisticated synthetic slow-releasing controllable H2S donors or materials, and using H2S stimulating agents. In this article, we reviewed the recent development of H2S releasing/stimulating reagents and their potential applications in two common pathological processes including cancer and glycometabolic disorders.

A novel pH-controlled hydrogen sulfide donor protects gastric mucosa from aspirin-induced injury.

Hydrogen sulphide (H2 S) serves as a vital gastric mucosal defence under acid condition. Non-steroidal anti-inflammatory drugs (NSAIDs) are among widely prescribed medications with effects of antipyresis, analgesia and anti-inflammation. However, their inappropriate use causes gastric lesions and endogenous H2 S deficiency. In this work, we reported the roles of a novel pH-controlled H2 S donor (JK-1) in NSAID-related gastric lesions. We found that JK-1 could release H2 S under mild acidic pH and increase solution pH value. Intragastrical administration of aspirin (ASP), one of NSAIDs, to mice elicited significant gastric lesions, evidenced by mucosal festering and bleeding. It also led to infiltration of inflammatory cells and resultant releases of IL-6 and TNF-α, as well as oxidative injury including myeloperoxidase (MPO) induction and GSH depletion. In addition, the ASP administration statistically inhibited H2 S generation in gastric mucosa, while up-regulated cyclooxygenase (COX)-2 and cystathionine gamma lyase (CSE) expression. Importantly, these adverse effects of ASP were prevented by the intragastrical pre-administration of JK-1. However, JK-1 alone did not markedly alter the property of mouse stomachs. Furthermore, in vitro cellular experiments showed the exposure of gastric mucosal epithelial (GES-1) cells to HClO, imitating MPO-driven oxidative injury, decreased cell viability, increased apoptotic rate and damaged mitochondrial membrane potential, which were reversed by pre-treatment with JK-1. In conclusion, JK-1 was proved to be an acid-sensitive H2 S donor and could attenuate ASP-related gastric lesions through reconstruction of endogenous gastric defence. This work indicates the possible treatment of adverse effects of NSAIDs with pH-controlled H2 S donors in the future.

Inhibition of Methylglyoxal-Induced AGEs/RAGE Expression Contributes to Dermal Protection by N-Acetyl-L-Cysteine.

BACKGROUND/AIM: Accumulation of advanced glycation end products (AGEs) is a major cause of diabetes mellitus (DM) skin complications. Methylglyoxal (MGO), a reactive dicarbonyl compound, is a crucial intermediate of AGEs generation. N-acetyl-L-cysteine (NAC), an active ingredient of some medicines, can induce endogenous GSH and hydrogen sulfide generation, and set off a condensation reaction with MGO. However, there is rare evidence to show NAC can alleviate DM-induced skin injury through inhibition of AGEs generation or toxicity. The present study aimed to observe the effects of NAC on MGO-induced inflammatory injury and investigate the roles of AGEs and its receptor (RAGE) in NAC's dermal protection in human HaCaT keratinocytes. METHODS: The cells were exposed to MGO to simulate a high MGO status in diabetic blood or tissues. The content of AGEs in serum or cell medium was measured with ELISA. The protective effects of NAC against MGO-induce injury were evaluated by administration before MGO one hour, in virtue of cell viability, mitochondrial membrane potential, inflammation reaction, nuclear factor (NF)-κB activation, matrix metalloproteinase (MMP)-9 expression, as well as cellular behavioral function. RESULTS: We found the AGEs levels of patients with DM were elevated comparing with healthy volunteers. The in vitro AGEs generation was also able to be enhanced by the exposure of HaCaT cells to MGO, which reduced dose-dependently cellular viability, damaged mitochondrial function, triggered secretion of interleukin (IL)-6 and IL-8, activated NF-κB and upregulated MMP-9 expression. Furthermore, the exposure caused cellular adhesion and migration dysfunction, as well as collagen type I inhibition. Importantly, before the exposure to MGO, the preconditioning with NAC significantly attenuated MGO-induced AGEs generation, improved cellular viability and mitochondrial function, partially reversed the overexpression of proinflammatory factors and MMP-9, as well as the activation of NF-κB. Lastly, NAC blocked MGO-induced RAGE upregulation, and inhibition of RAGE with its neutralizing antibody significantly alleviated MGO-induced NF-κB activation, MMP-9 upregulation and inflammatory injury in HaCaT cells. CONCLUSION: The present work indicates the administration of NAC can prevent MGO-induced dermal inflammatory injury through inhibition of AGEs/RAGE signal, which may provide a basal support for the treatment of diabetic skin complications with NAC-containing medicines in the future.

[N-acetyl-L-cysteine reduces the ozone-induced lung inflammation response in mice].

In this study, we investigated the protective effect of the antioxidant N-acetyl-L-cysteine (NAC) on the lung inflammation caused by ozone (O3) exposure in mice. Thirty-two C57BL/6 mice were randomly divided into control group, O3 group, O3+NAC group and NAC group. Mice were exposed to O3 (1.0 ppm) or fresh air for 3 h on the day 1, day 3 and day 5, respectively. NAC (100 mg/kg) was intraperitoneally applied to the mice 1 h before each exposure. At 24 h after the 3-time exposure, the alveolar wall structure was severely damaged and the infiltrated inflammatory cells were apparent perivascularly and peribronchiolarly. Significant increases in the total white blood cell count, macrophage, lymphocyte and neutrophil counts, as well as total protein concentration were observed in the bronchoalveolar lavage fluid (BALF) (P < 0.05). The IL-6, IL-8 (P < 0.01) and MDA levels (P < 0.05) in the lung homogenates were elevated coherently. Administration of NAC could attenuate the alveolar wall structure damage induced by O3 exposure and reduce the amount of infiltrated inflammatory cells, total and differential leukocyte counts (P < 0.05), as well as the IL-6, IL-8 (P < 0.01) and MDA release (P < 0.05). Western blotting results showed that the O3 exposure up-regulated the p38 MAPK and NF-κB p65 protein expression in the lung tissue of mice (P < 0.05), which could be alleviated by NAC (P < 0.05). These results indicated that NAC could protect against O3-induced pulmonary inflammation in mice. The beneficial effect of NAC might be related with the p38 MAPK and NF-κB p65 signal pathway.

Cytotoxic Diterpenoids from the Roots of Aralia melanocarpa.

Five new diterpenoids (1-5) were isolated from the roots of Aralia melanocarpa, together with four known compounds, 7ß-hydroxy-ent-pimara-8(14),15-diene-19-oic acid (6), 18-norpimara-8(14),15-dien-4-ol (7), ent-16ßH,17-isovalerate-kauran-19-oic acid (8), and ent-16α,17-dihydroxykauran-19-oic acid (9). Based on the MS, IR, and NMR spectral analysis, the structures of the five new diterpenoids (1-5) were elucidated. The cytotoxic activities of compounds 1-9 were assayed, and compounds 1 and 2 showed cytotoxicity in four cancer cell lines with IC50s from 4.2 to 8.2 µM.

Calcitriol prevents peripheral RSC96 Schwann neural cells from high glucose & methylglyoxal-induced injury through restoration of CBS/H2S expression.

A meta-analysis has suggested that vitamin D deficiency is involved in diabetic peripheral neuropathy (DPN) and the levels of hydrogen sulfide (H2S) are also decreased in type 2 diabetes. The injection of vitamin D induces cystathionine-ß-synthase (CBS) expression and H2S generation. However, it remains unclear whether the supplementation of vitamin D prevents DPN through improvement of CBS/H2S expression. In the present study, RSC96 cells, a rat Schwann cell line, were exposed to high glucose and methylglyoxal (HG&MG) to simulate diabetic peripheral nerve injury in vivo. Before the exposure to HG&MG, the cells were preconditioned with calcitriol (CCT), an active form of vitamin D, and then CCT-mediated neuroprotection was investigated in respect of cellular viability, superoxide anion (O2(-)) generation, inducible nitric oxide (NO) synthase (iNOS)/NO expression, mitochondrial membrane potential (MMP), as well as CBS expression and activity. It was found that both high glucose and MGO decreased cell viability and co-treatment with the two induced a more serious injury in RSC96 cells. Therefore, the exposure to HG&MG was used in the present study. The exposure to HG&MG markedly induced iNOS expression, NO and O2(-) generation, as well as MMP loss. In addition, the exposure to HG&MG depressed CBS expression and activity in RSC96 cells. However, the preconditioning with CCT significantly antagonized HG&MG-induced cell injury including the decreased viability, iNOS overexpression, NO and O2(-) accumulation, as well as MMP loss. CCT also partially restored the decreased CBS expression and activity triggered by HG&MG, while the inhibition of CBS with hydroxylamine attenuated CCT-mediated neuroprotection. Moreover, the exogenous donation of H2S produced similar cellular protective effects to CCT. The data indicate that the supplementation of vitamin D prevents HG&MG-induced peripheral nerve injury involving the restoration of endogenous H2S system, which may provide a basal support for the treatment of DPN with vitamin D clinically.

New clerodane diterpenes from Tinospora sagittata var. yunnanensis.

Four new clerodane diterpenes, namely sagittatayunnanosides A-D (1-4), were isolated from the roots of Tinospora sagittata var. yunnanensis, together with two known compounds, tinospinoside C (5) and tinospinoside E (6). The structures of the four new compounds were well elucidated by extensive analyses of the MS, IR, and 1D and 2D NMR data. The cytotoxic and antifouling activities of compounds 1-6 were evaluated.

Hydrogen sulfide prevents formaldehyde-induced neurotoxicity to PC12 cells by attenuation of mitochondrial dysfunction and pro-apoptotic potential.

Hydrogen sulfide (H(2)S) has been shown to act as a neuroprotectant and antioxidant. Numerous studies have demonstrated that exposure to formaldehyde (FA) causes neuronal damage and that oxidative stress is one of the most critical effects of FA exposure. Accumulation of FA is involved in the pathogenesis of Alzheimer's disease (AD). The aim of present study is to explore the inhibitory effects of H(2)S on FA-induced cytotoxicity and apoptosis and the molecular mechanisms underlying in PC12 cells. We show that sodium hydrosulfide (NaHS), a H(2)S donor, protects PC12 cells against FA-mediated cytotoxicity and apoptosis and that NaHS preserves the function of mitochondria by preventing FA-induced loss of mitochondrial membrane potential and release of cytochrome c in PC12 cells. Furthermore, NaHS blocks FA-exerted accumulation of intracellular reactive oxygen species (ROS), down-regulation of Bcl-2 expression, and up-regulation of Bax expression. These results indicate that H(2)S protects neuronal cells against neurotoxicity of FA by preserving mitochondrial function through attenuation of ROS accumulation, up-regulation of Bcl-2 level, and down-regulation of Bax expression. Our study suggests a promising future of H(2)S-based preventions and therapies for neuronal damage after FA exposure.

Interaction between ROS and p38MAPK contributes to chemical hypoxia-induced injuries in PC12 cells.

The present study investigated whether there is an interaction between reactive oxygen species (ROS) and p38 mitogen-activated protein kinase (MAPK) during chemical hypoxia-induced injury in PC12 cells. The results of the present study showed that cobalt chloride (CoCl2), a chemical hypoxia agent, markedly induced ROS generation and phosphorylation of p38MAPK, as well as neuronal injuries. N-acetylcysteine (NAC), a ROS scavenger, blocked CoCl2-induced phosphorylation of p38MAPK. In addition, SB203580, an inhibitor of p38MAPK attenuated not only CoCl2-induced activation of p38MAPK, but also ROS production. These results suggest that ROS and p38MAPK are capable of interacting positively during chemical hypoxia. Furthermore, NAC and SB203580 markedly prevented CoCl2-induced cytotoxicity, apoptosis and a loss of mitochondrial membrane potential. Taken together, our findings suggest that the positive interaction between CoCl2 induction of ROS and p38MAPK activation may play a significant role in CoCl2-induced neuronal injuries. We provide new insights into the mechanisms responsible for CoCl2-induced injuries in PC12 cells.

Inhibition of ROS-activated ERK1/2 pathway contributes to the protection of H2S against chemical hypoxia-induced injury in H9c2 cells.

Hydrogen sulfide (H(2)S) has been shown to exert cardioprotective effects. However, the roles of extracellular signal-regulated protein kinases 1/2 (ERK1/2) in H(2)S-induced cardioprotection have not been completely elucidated. In this study, cobalt chloride (CoCl(2)), a chemical hypoxia mimetic agent, was applied to treat H9c2 cells to establish a chemical hypoxia-induced cardiomyocyte injury model. The results showed that pretreatment with NaHS (a donor of H(2)S) before exposure to CoCl(2) attenuated the decreased cell viability, the increased apoptosis rate, the loss of mitochondrial membrane potential (ΔΨm), and the intracellular accumulation of reactive oxygen species (ROS) in H9c2 cells. Exposure of H9c2 cells to CoCl(2) or hydrogen peroxide (H(2)O(2)) upregulated expression of phosphorylated (p) ERK1/2, which was reduced by pretreatment with NaHS or N-acetyl-L-cysteine, a ROS scavenger. More importantly, U0126, a selective inhibitor of ERK1/2, mimicked the above cytoprotection of H(2)S against CoCl(2)-induced injury in H9c2 cells. In conclusion, these results indicate that H(2)S protects H9c2 cells against chemical hypoxia-induced injury partially by inhibiting ROS-mediated activation of ERK1/2.

Hydrogen sulfide protects H9c2 cells against doxorubicin-induced cardiotoxicity through inhibition of endoplasmic reticulum stress.

The roles of hydrogen sulfide (H(2)S) and endoplasmic reticulum (ER) stress in doxorubicin (DOX)-induced cardiotoxicity are still unclear. This study aimed to dissect the hypothesis that H(2)S could protect H9c2 cells against DOX-induced cardiotoxicity by inhibiting ER stress. Our results showed that exposure of H9c2 cells to DOX significantly inhibited the expression and activity of cystathionine-γ-lyase (CSE), a synthetase of H(2)S, accompanied by the decreased cell viability and the increased reactive oxygen species (ROS) accumulation. In addition, exposure of cells to H(2)O(2) (an exogenous ROS) mimicked the inhibitory effect of DOX on the expression and activity of CSE. Pretreatment with N-acetyl-L: -cysteine (NAC) (a ROS scavenger) attenuated intracellular ROS accumulation, cytotoxicity, and the inhibition of expression and activity of CSE induced by DOX. Notably, the ER stress-related proteins, including glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) were obviously upregulated in DOX-treated H9c2 cells. Pretreatment with sodium hydrosulfide (NaHS, a H(2)S donor) before DOX exposure markedly suppressed DOX-induced overexpressions of GRP78 and CHOP, cytotoxicity and oxidative stress. In conclusion, we have demonstrated that ROS-mediated inhibition of CSE is involved in DOX-induced cytotoxicity in H9c2 cells, and that exogenous H(2)S can confer protection against DOX-induced cardiotoxicity partly through inhibition of ER stress.

Heat shock protein 90 mediates cytoprotection by H2S against chemical hypoxia-induced injury in PC12 cells.

1. Increasing evidence indicates that hydrogen sulphide (H2S) may serve as an important biological cytoprotective agent. Heat shock protein (Hsp) 90 can attenuate stress-induced injury. However, whether Hsp90 mediates the cytoprotective effect of H2S against chemical hypoxia-induced injury in PC12 cells is not known. 2. In the present study, CoCl2 (a chemical hypoxia mimetic) was used to treat PC12 cells to create a model of chemical hypoxia. To explore the role of Hsp90 in the cytoprotection afforded by H2S against chemical hypoxia-induced injury, 2 µmol/L 17-allylaminogeldanamycin (17-AAG), a selective inhibitor of Hsp90, was administered for 30 min prior to preconditioning with 400 µmol/L NaHS, followed by chemical hypoxia. 3. Cobalt chloride reduced cell viability (by 52.7 ± 1.5%), increased PC12 cell apoptosis (by 42.1 ± 1.5%), induced reactive oxygen species (ROS) by 3.79% compared with control and induced the dissipation of mitochondrial membrane potential (MMP) by 2.56% compared with control. 4. Pretreatment of PC12 cells with 100-400 µmol/L sodium hydrosulphide (NaHS), an H2S donor, for 3 h prior to exposure to 600 µmol/L CoCl2 provided significant, concentration-dependant protection to PC12 cells against CoCl2-induced cytotoxicity. Specifically, pretreatment of PC12 cells with 400 µmol/L NaHS decreased apoptosis to 16.77 ± 1.77% and blocked the CoCl2-induced increase in ROS production and loss of MMP. 5. At 400 µmol/L, NaHS upregulated Hsp90 in a time-dependant manner (over the period 0-180 min). In addition to its effects on Hsp90 expression, NaHS pretreatment of PC12 cells augmented the overexpression of Hsp90 induced by 600 µmol/L CoCl2 by 1.38-fold (P < 0.01). 6. Treatment of PC12 cells with 2 µmol/L 17-AAG for 30 min prior to NaHS pretreatment blocked the overexpression of Hsp90 induced by NaHS preconditioning, as evidenced by decreased cell viability (by 54.2 + 1.2%; P < 0.01), increased PC12 cell apoptosis (by 36.6 ± 1.2%; P < 0.01) and increasing ROS production. 7. The findings of the present study provide novel evidence that Hsp90 mediates H2S-induced neuroprotection against chemical hypoxia-induced injury via anti-oxidant and anti-apoptotic effects.

Neuroprotective effect of asymmetric dimethylarginine against 1-methyl-4-phenylpyridinium ion-induced damage in PC12 cells.

1. Asymmetric dimethylarginine (ADMA) is a well-known endogenous nitric oxide synthase (NOS) inhibitor. Although it has been shown to be a novel risk marker in cardiovascular medicine and chronic kidney disease, we speculated that in some states associated with excess of nitric oxide (NO), such as 1-methyl-4-phenylpyridinium ion (MPP(+))-induced neuronal injury, ADMA might be protective by limiting the toxic effect of high concentrations of NO. 2. The aim of the present study is to explore the protection of ADMA against MPP(+)-induced apoptosis and the molecular mechanisms underlying in PC12 cells. 3. We found that exogenous application of ADMA obviously protected PC12 cells against MPP(+)-induced cytotoxicity and apoptosis not only by reducing the loss of mitochondrial membrane potential, but also by attenuating an increase in intracellular reactive oxygen species. Moreover, ADMA attenuated MPP(+)-induced excessive activation of nitric oxide synthase and overproduction of NO. 4. The results of the present study suggest that the protection caused by ADMA is related to preserving mitochondrial membrane potential and attenuating the MPP(+)-induced intracellular reactive oxygen species generation through inhibiting nitric oxide synthase activity and limiting NO generation.