RP105 Protects Against Apoptosis in Ischemia/Reperfusion-Induced Myocardial Damage in Rats by Suppressing TLR4-Mediated Signaling Pathways

Abstract

Background: Myocardial apoptosis is heavily implicated in the myocardial damage caused by ischemia-reperfusion (I/R). Toll-like receptor 4 (TLR4) is a potent inducer of these apoptotic cascades. In contrast, the radioprotective 105 kDa protein (RP105) is a specific negative regulator of TLR4 signaling pathways. However, the precise mechanisms by which RP105 inhibits myocardium apoptosis via TLR4-associated pathways during I/R is not fully understood. Methods: We utilized a rat model of myocardial ischemic reperfusion injury (MIRI). Animals were pre-treated with Ad-EGFP adenovirus, Ad-EGFP-RP105 adenovirus, saline, or nothing (sham). After three days, rats underwent a 30min left anterior descending coronary artery occlusion and a 4h reperfusion. Mycardial tissue was assessed by immunohistochemistry, TUNEL-staining, Western blot, quantitative RT-PCR, and a morphometric assay. Results: RP105 overexpression resulted in a reduction in infarct size, fewer TUNEL-positive cardiomyocytes, and a reduction in mitochondrial-associated apoptosis cascade activity. Further, RP105 overexpression repressed I/R-induced myocardial injury by attenuating myocardial apoptosis. This was mediated by inhibiting TLR4 activation and the phosphorylation of P38MAPK and the downstream transcription factor AP-1. Conclusion: RP105 overexpression leads to the de-activation of TLR4, P38MAPK, and AP-1 signaling pathways, and subsequently represses apoptotic cascades and ensuing damage of myocardial ischemic reperfusion. These findings may become the basis of a novel therapeutic approach for reducing of cardiac damage caused by MIRI.

Troxerutin Protects Against Myocardial Ischemia/Reperfusion Injury Via Pi3k/Akt Pathway in Rats

“…Suppressing cell apoptosis attenuates cardiomyocyte loss and prevents I/R injury [37-40]. In the present study, the cardiomyocyte apoptotic rate decreased, and myocardial infarction size was reduced in the I/R+troxerutin group compared with the I/R group.…”

RNAi-Mediated Down-Regulation of CD47 Protects against Ischemia/Reperfusion-Induced Myocardial Damage via Activation of eNOS in a Rat Model

“…Therefore, this study was carried out to test the hypothesis that CD47 inhibition can attenuate MIRI. Unlike previous studies, which used CD47 knockouts or CD47 mAb, we used RNA interference technology to reduce the level of CD47 expression as we are experienced in the construction of mature viruses and the use of intramyocardial transduction technology [18,20,21]. Our results demonstrate that intramyocardial injection of adenovirus vector encoding RNAi targeting rat CD47 can successfully down-regulate CD47 mRNA and protein levels.…”

“…The expression of EGFP and CD47 were measured by immunofluorescence staining of tissue collected following I/R or sham treatment four days after the intramyocardial injection with adenovirus. Myocardial tissues were harvested, fixed in 4% paraformaldehyde, embedded in paraffin, and 4 um sections cut and mounted on glass slides [20]. Subsequently, sections were dewaxed using xylene and an alcohol gradient series, and antigen retrieval performed by microwave treatment.…”

The Opening of ATP-Sensitive K+ Channels Protects H9c2 Cardiac Cells Against the High Glucose-Induced Injury and Inflammation by Inhibiting the ROS-TLR4-Necroptosis Pathway

“…To date, 11 human and 13 mouse TLRs have been cloned [37]. Among the TLRs, TLR4 is one of the most expressed in cardiomyocytes [38, 39]. The TLR4 expression is increased in a plethora of inflammatory discovers, including atherosclerosis and diabetes [40, 41].…”