Microwave radiation injuries microvasculature through inducing endoplasmic reticulum stress.

OBJECTIVE: The study aimed to investigate the effect of microwave radiation on microvasculature as well as the underlying mechanisms. METHODS: Sprague Dawley rats were exposed to microwave radiation. Microvascular diameters, flow velocity, blood perfusion and permeability were measured. Cultured endothelial cells from microvessels were subjected to microwave radiation. Cytoskeleton, apoptosis, protein synthesis and the markers of endoplasmic reticulum stress including 78-kDa glucose-regulated protein and calreticulin in endothelial cells were examined. RESULTS: Microwave radiation decreased microvascular diameters and blood perfusion, increased the permeability of microvessles. And microwave radiation induced the formation of stress fibers, apoptosis, and LDH leakage from microvascular endothelial cells. Also, when microvascular endothelial cells were exposed to microwaves, protein synthesis was significantly elevated. We found that upon microwave radiation, the expression of 78-kDa glucose-regulated protein and calreticulin were greatly upregulated in microvascular endothelial cells. We also investigated possible signaling pathways for endoplasmic reticulum stress-initiated apoptosis. C/EBP homologous protein (CHOP) pathway was activated in microvascular endothelial cells exposed to microwaves. CONCLUSIONS: Microwave radiation induces microvascular injury by triggering the apoptotic pathway of endoplasmic reticulum stress. This article is protected by copyright. All rights reserved.

Hypoxic postconditioning inhibits endoplasmic reticulum stress-mediated cardiomyocyte apoptosis by targeting PUMA.

Postconditioning prevents cardiomyocytes from ischemia/reperfusion-induced apoptosis. However, little is known about the molecular mechanisms that mediate the cardioprotective effect of postconditioning. Here, we hypothesized that postconditioning targeted p53 upregulated modulator of apoptosis (PUMA) to protect cardiomyocytes against endoplasmic reticulum stress-mediated apoptosis. Our results demonstrated that postconditioning could inhibit GRP78 (78-kDa glucose-regulated protein) expression, caspase-12 activation, and cardiomyocyte apoptosis by regulating PUMA expression. In addition, p53 is involved in the regulatory role of postconditioning in PUMA expression. Our data reveal a cardioprotective pathway of postconditioning in which it represses PUMA.

MicroRNA-15a/b are up-regulated in response to myocardial ischemia/reperfusion injury.

OBJECTIVE: Several studies have indicated that miR-15a, miR-15b and miR-16 may be the important regulators of apoptosis. Since attenuate apoptosis could protect myocardium and reduce infarction size, the present study was aimed to find out whether these miRNAs participate in regulating myocardial ischemia reperfusion (I/R) injury. METHODS: Apoptosis in mice hearts subjected to I/R was detected by TUNEL assay in vivo, while flow cytometry analysis followed by Annexin V/PI double stain in vitro was used to detect apoptosis in cultured cardiomyocytes which were subjected to hypoxia/reoxygenation (H/R). Taqman real-time quantitative PCR was used to confirm whether miR-15a/15b/16 were involved in the regulation of cardiac I/R and H/R. RESULTS: Compared to those of the controls, I/R or H/R induced apoptosis of cardiomyocytes was significantly increased both in vivo (24.4% ± 9.4% vs. 2.2% ± 1.9%, P < 0.01, n = 5) and in vitro (14.12% ± 0.92% vs. 2.22% ± 0.08%). The expression of miR-15a and miR-15b, but not miR-16, was increased in the mice I/R model, and the results were consistent in the H/R model. CONCLUSIONS: Our data indicate miR-15 and miR-15b are up-regulated in response to cardiac I/R injury, therefore, down-regulation of miR-15a/b may be a promising strategy to reduce myocardial apoptosis induced by cardiac I/R injury.