The cardioprotection induced by lipopolysaccharide involves phosphoinositide 3-kinase/Akt and high mobility group box 1 pathways

Toll-Like Receptor 4 Activation Prevents Rat Cardiac Fibroblast Death Induced by Simulated Ischemia/Reperfusion

Death of cardiac fibroblasts (CFs) by ischemia/reperfusion (I/R) has major implications for cardiac wound healing. In in vivo models of myocardial infarction, toll-like receptor 4 (TLR4) activation has been reported as a cardioprotector; however, it remains unknown whether TLR4 activation can prevent CF death triggered by simulated I/R (sI/R). In this study, we analyzed TLR4 activation in neonate CFs exposed to an in vitro model of sI/R and explored the participation of the pro-survival kinases Akt and ERK1/2. Simulated ischemia was performed in a free oxygen chamber in an ischemic medium, whereas reperfusion was carried out in normal culture conditions. Cell viability was analyzed by trypan blue exclusion and the MTT assay. Necrotic and apoptotic cell populations were evaluated by flow cytometry. Protein levels of phosphorylated forms of Akt and ERK1/2 were analyzed by Western blot. We showed that sI/R triggers CF death by necrosis and apoptosis. In CFs exposed only to simulated ischemia or only to sI/R, blockade of the TLR4 with TAK-242 further reduced cell viability and the activation of Akt and ERK1/2. Preconditioning with lipopolysaccharide (LPS) or treatment with LPS in ischemia or reperfusion was not protective. However, LPS incubation during both ischemia and reperfusion periods prevented CF viability loss induced by sI/R. Furthermore, LPS treatment reduced the sub-G1 population, but not necrosis of CFs exposed to sI/R. On the other hand, the protective effects exhibited by LPS were abolished when TLR4 was blocked and Akt and ERK1/2 were inhibited. In conclusion, our results suggest that TLR4 activation protects CFs from apoptosis induced by sI/R through the activation of Akt and ERK1/2 signaling pathways.

Protective effects of p-nitro caffeic acid phenethyl ester on acute myocardial ischemia-reperfusion injury in rats

Myocardial ischemia-reperfusion (IR) causes widespread cardiomyocyte dysfunction, including apoptosis and necrosis. The present study aimed to investigate the possible cardioprotective effects of p-nitro caffeic acid phenethyl ester (CAPE-NO₂) on myocardial IR-induced injury in vivo. To generate a rat model of myocardial IR, the left anterior descending coronary artery was occluded for 30 min, followed by reperfusion for 2 h. The rats were administered either the sham treatment (the sham and IR control groups) or the therapeutic agents [the caffeic acid phenethyl ester (CAPE) and CAPE-NO₂ groups] 10 min prior to the occlusion. Myocardial IR-induced injury is characterized by: A significant increase in the levels of myocardial enzymes, including creatine kinase, lactate dehydrogenase and aspartate transaminase; a marked increase in intercellular adhesion molecule 1 expression levels, lipid peroxidation products and inflammatory mediators; and a significant decrease in myocardial antioxidants, including catalase, total superoxide dismutase and glutathione peroxidase. In the present study, pretreatment with CAPE-NO₂ significantly ameliorated these changes, and decreased the infarct size, as compared with the IR control group (10.32±3.8 vs. 35.65±5.4%). Furthermore, western blotting demonstrated that pretreatment with CAPE-NO₂ downregulated the myocardial IR-induced protein expression levels of B-cell lymphoma-2 (Bcl-2)-associated X protein (Bax), cleaved caspase-3, P38 and the Bax/Bcl-2 ratio. CAPE-NO₂ also upregulated the myocardial IR-induced expression levels of Bcl-2, phosphoinositide-3-kinase, phosphorylated Akt and mammalian target of rapamycin. In conclusion, the results of the present study indicated that CAPE-NO₂ demonstrated improved cardioprotective effects, as compared with CAPE; therefore, CAPE-NO₂ may represent a novel approach to pharmacological cardioprotection.

Neferine, a bisbenzylisoquinoline alkaloid, offers protection against cobalt chloride-mediated hypoxia-induced oxidative stress in muscle cells

Background

Neferine, a bisbenzylisoquinoline alkaloid, isolated from Nelumbo nucifera has a wide range of biological activities. Cobalt chloride (CoCl₂) was known to mimic hypoxic condition. In the present study, we assessed the cytoprotective effect of neferine against CoCl₂-induced oxidative stress in muscle cells.

Methods

Rhabdomyosarcoma cells were exposed to different concentrations of CoCl₂, and the IC₅₀ value was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Lactate dehydrogenase and NO assays were performed in order to determine the cytotoxic effect of CoCl₂. Reactive oxygen species generation and cellular antioxidant status were determined for evaluating oxidative stress. For analyzing the effect of neferine on CoCl₂-induced apoptosis, propidium iodide staining was performed.

Results

The results of the present study indicate that CoCl₂ induces cell death in a dose-dependent manner. Neferine pretreatment at 700 nM concentration offers better cytoprotection in the cells exposed to CoCl₂. Lactate dehydrogenase and NO release in the culture medium were restored after neferine pretreatment. CoCl₂ triggers time-dependent reactive oxygen species generation in muscle cells. Further, results of propidium iodide staining, mitochondrial membrane potential, and intracellular calcium accumulation confirm that neferine offers protection against CoCl₂-induced hypoxic injury. Depleted activities of antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase due to CoCl₂ exposure were also reinstated in the group that received neferine pretreatment.

Conclusion

Our study suggests that neferine from N. nucifera offers protection to muscle cells by counteracting the oxidative stress induced by CoCl₂.

Heart protective effects and mechanism of quercetin preconditioning on anti-myocardial ischemia reperfusion (IR) injuries in rats

In this study, we investigated the effects and mechanism of quercetin preconditioning on anti-myocardial ischemia reperfusion (IR) injuries in vivo. Meanwhile, their potential anti-oxidative stress and anti-inflammation effect were assessed. SD rats were orally given quercetin 250 mg/kg. Myocardium apoptosis was determined with TUNEL staining. The biomarkers related to myocardial ischemia injury were determined. Simultaneously, hemodynamic parameters were monitored as left ventricular systolic pressure (LVSP), LV end-diastolic pressure (LVEDP) and maximal rate of increase and decrease of left ventricular pressure (dP/dtmax). The oxidative stress indicators and inflammatory factors were also evaluated. Western blot method was used for analysis of PI3K, Akt, p-Akt, Bax and Bcl-2 protein expressions. The results showed that quercetin significantly reduced apoptosis rate, improved cardiac function, decreased levels of creatine kinase (CK), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH). Quercetin also restrained the oxidative stress related to myocardial ischemia injury as evidenced by decreased malondialdehyde (MDA), and elevated GSH, superoxide dismutase (SOD), catalase (CAT), glutathione-peroxidase (GSH-Px), glutathione reductase (GR) activity. Meanwhile, the inflammatory cascade was inhibited as evidenced by decreased cytokines such as tumor necrosis factor-α (TNF-α), C-reactive protein (CRP) and interleukin-1β (IL-1β). Our results still showed that quercetin pretreatment significantly inhibited the apoptosis by decreasing the number of apoptotic cells, decreasing the level of cleaved Bax, and increasing the level of Bcl-2 in rats subjected to I/R injury. Simultaneously, quercetin pretreatment markedly increased the phosphorylation of Akt. Blockade of PI3K activity by LY294002, dramatically abolished its anti-apoptotic effect and lowered Akt phosphorylation level. It can be concluded that quercetin pretreatment was protected against myocardium IR injury by decreasing oxidative stress, repressing inflammatory cascade, inhibiting apoptosis in vivo and PI3K/Akt pathway involved in the anti-apoptotic effect.