MicroRNA-21 (miR-21) is highly up-regulated during hypertrophic and cancerous cell growth. In contrast, we found that it declines in cardiac myocytes upon exposure to hypoxia. Thus, the objective was to explore its role during hypoxia. We show that miR-21 not only regulates phosphatase and tensin homologue deleted on chromosome 10 (PTEN), but also targets Fas ligand (FasL). During prolonged hypoxia, down-regulation of miR-21 proved necessary and sufficient for enhancing expression of both proteins. We demonstrate here for the first time that miR-21 is positively regulated via an AKT-dependent pathway, which is depressed during prolonged hypoxia. Accordingly, hypoxia-induced down-regulation of miR-21 and up-regulation of FasL and PTEN were reversed by activated AKT and reproduced by a dominant negative mutant, wortmannin, or PTEN. Moreover, the antiapoptotic function of AKT partly required miR-21, which was sufficient for inhibition of caspase-8 activity and mitochondrial damage. In consensus, overexpression of miR-21 in a transgenic mouse heart resulted in suppression of ischemia-induced up-regulation of PTEN and FasL expression, an increase in phospho-AKT, a smaller infarct size, and ameliorated heart failure. Thus, we have identified a unique aspect of the function of AKT by which it inhibits apoptosis through miR-21-dependent suppression of FasL. MicroRNA (miRNA)3 are molecules approximately twenty ribonucleotides long that specifically target mRNA through partial complementarity and, thereby, inhibit translation and/or induce their degradation. miR-21 is one of the most commonly and dramatically up-regulated miRNA in many cancers (1, 2) and has been implicated in the inhibition of programmed cell death (2). Some of its validated targets include tropomyosin 1 (3), PTEN (2, 4, 5), programmed cell death 4 (Pdcd4) (6, 7), TAp63 isoform of p53 family, and LRRFIP1, an inhibitor of NFB signaling (8). Similarly, miR-21 is one of the most highly and consistently up-regulated miRNA during cardiac hypertrophy (9 -12). Thum et al. (13) show that miR-21 is predominantly up-regulated in the myofibroblasts where it targets sprouty1 and enhances their survival and, thereby, fibrosis in the heart. Similarly, Roy et al. (14) show that miR-21 is elevated in the myofibroblast-infiltrated area 7 days after ischemia/ reperfusion and suppresses metalloprotease-2 via targeting PTEN. More recently, studies have shown that miR-21 exerts an antiapoptotic function in cardiac myocytes via inhibiting PDCD4 (15) and reduces infarct size via local viral delivery to the heart (16). However, the signaling pathway that regulates miR-21 has not been identified.Two of the molecules that play a major role in ischemic injury of the heart include PTEN and FasL. PTEN is a major negative regulator of AKT (17) whose activity is modulated by its abundance, oxidation, or phosphorylation (18). It is also targeted by miR-21, which provides a specific post-transcriptional mechanism for regulating its expression (2, 4, 5). PTEN has been regarded as the A...

Background and study aims: Qualified esophagogastroduodenoscopy (EGD) is a prerequisite for detecting upper gastrointestinal lesions especially early gastric cancer (EGC). Our previous report showed that artificial intelligence system could monitor blind spots during EGD. Here, we updated the system to a new one (named ENDOANGEL), verified its effectiveness on improving endoscopy quality and pre-tested its performance on detecting EGC in a multi-center randomized controlled trial. Patients and methods: ENDOANGEL was developed using deep convolutional neural networks and deep reinforcement learning. Patients undergoing EGD examination in 5 hospitals were randomly assigned to ENDOANGEL-assisted (EA) group or normal control (NC) group. The primary outcome was the number of blind spots. The second outcome includes performance of ENDOANGEL on predicting EGC in clinical setting. Results: 1,050 patients were recruited and randomized. 498 and 504 patients in EA and NC groups were respectively analyzed. Compared with NC, the number of blind spots was less (5.382±4.315 vs. 9.821±4.978, p<0.001) and the inspection time was prolonged (5.400±3.821 min vs. 4.379±3.907 min, p<0.001) in EA group. In the 498 patients from EA group, 196 gastric lesions with pathological results were identified. ENDOANGEL correctly predicted all 3 EGC (1 mucosal carcinoma and 2 high-grade neoplasia) and 2 advanced gastric cancer, with a per-lesion accuracy of 84.69%, sensitivity of 100% and specificity of 84.29% for detecting GC. Conclusions: The results of the multi-center study confirmed that ENDOANGEL is an effective and robust system to improve the quality of EGD and has the potential to detect EGC in real time.

Down-regulation of miR-26b in the heart is required for the up-regulation of GATA4 and the induction of pressure-induced cardiac hypertrophy. The results also underscore the functional relevance of miRNAs in regulating gene expression during cardiac hypertrophy.

Background:Transcriptional regulation plays an essential role in the development of cardiac hypertrophy. Results: Pol II and H3K9-acetyl chromatin immunoprecipitation reveal unique transcriptional patterns in the heart. Conclusion: Both de novo recruitment and promoter-pausing of pol II play critical roles in regulating specialized and housekeeping genes, respectively. Significance: Understanding transcriptional regulation helps in deciphering the mechanisms underlying hypertrophy.