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.

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.

Morphine treatment enhances extracellular ATP enzymolysis and adenosine generation in rat astrocytes.

Recent studies have shown that astrocytes play important roles in ATP degradation and adenosine (a well known analgesic molecule) generation, which are closely related to pain signaling pathway. The aim of this study was to investigate whether morphine, a well known analgesic drug, could affect the speeds of ATP enzymolysis and adenosine generation in rat astrocytes. Intracellular calcium concentration ([Ca(2+)](i)) of astrocyte was measured by flow cytometry, and the time points that morphine exerted notable effects were determined for subsequent experiments. Cultured astrocytes were pre-incubated with morphine (1 µmol/L) and then were incubated with substrates, ATP and AMP, for 30 min. The speeds of ATP enzymolysis and adenosine generation were measured by high performance liquid chromatography (HPLC). The results showed that both 1.5 and 48 h of morphine pre-incubation induced maximal ATP enzymolysis speed in astrocytes among all the time points, and there was no statistical difference of ATP enzymolysis speed between morphine treatments for 1.5 and 48 h. As to adenosine, morphine pre-incubation for 1.5 h statistically increased adenosine generation, which was degraded from AMP, in cultured astrocytes compared with control group. However, no difference of adenosine generation was observed after 48 h of morphine pre-incubation. These results indicate that treatment of morphine in vitro dynamically changes the concentrations of ATP and adenosine in extracellular milieu of astrocytic cells. In addition, astrocyte can be regarded as at least one of the target cells of morphine to induce changes of ATP and adenosine levels in central nervous system.

[Reactive oxygen species scavenger protects cardiac cells against injuries induced by chemical hypoxia].

OBJECTIVE: To investigate the protective effect of reactive oxygen species (ROS) scavenger, N-acetyl-L-cysteine (NAC), against H9c2 cardiomyocytes from injuries induced by chemical hypoxia. METHODS: H9c2 cells were treated with cobalt chloride (CoCl2), a chemical hypoxia-mimetic agent, to establish the chemical hypoxia-induced cardiomyocyte injury model. NAC was added into the cell medium 60 min prior to CoCl2 exposure. The cell viability was evaluated using cell counter kit (CCK-8), and the intercellular ROS level was measured by 2', 7'- dichlorfluorescein-diacetate (DCFH-DA) staining and photofluorography. Mitochondrial membrane potential (MMP) of the cells was observed by Rhodamine123 (Rh123) staining and photofluorography, and the ratio of GSSG/ (GSSG+GSH) was calculated according to detection results of the GSSG kit. RESULTS: Exposure of H9c2 cardiomyocytes to 600 micromol/L CoCl2 for 36 h resulted in significantly reduced cell viability. Pretreatment with NAC at the concentrations ranging from 500 to 2000 micromol/L 60 min before CoCl2 exposure dose-dependently inhibited CoCl2-induced H9c2 cell injuries, and obviously increased the cell viability. NAC at 2000 micromol/L obviously inhibited the oxidative stress induced by CoCl2, decreased the ratio of GSSG/(GSSG+GSH), increased ROS level, and antagonized CoCl2-induced inhibition on MMP. CONCLUSION: NAC offers obvious protective effect on H9c2 cardiomyocytes against injuries induced by chemical hypoxia by decreasing in the ratio of GSSG/(GSSG+GSH) and ROS level and ameliorating MMP.