Let-7b-TLR7 Signaling Axis Contributes to the Anesthesia/Surgery-Induced Cognitive Impairment

Perioperative neurocognitive disorders (PNDs) are severe and common neurological complications among elderly patients following anesthesia and surgery. As the first line of defense of the innate immune system, Toll-like receptors (TLRs) have been found to be involved in the occurrence of neurodegenerative diseases in recent years. However, the role of TLR7 in the pathology and development of PNDs remains largely unclear. In our current study, we hypothesized that increased microRNA let-7b (let-7b) during anesthesia and surgical operation would activate TLR7 signaling pathways and mediate PNDs. Using a mouse model of PNDs, 18-20 months wild-type (WT) mice were undergoing unilateral nephrectomy, and increased TLR7 and let-7b expression levels were found in the surgery group compared with the Sham group. Of note, increased TLR7 was found to be co-localized with let-7b in the hippocampal area CA1 in the PNDs model. In addition, TLR7 and let-7b inhibition could improve hippocampus-dependent memory and attenuate the production of inflammatory cytokines. Together, our results indicated that TLR7 activation and up-regulation might be triggered by increased let-7b under stressful conditions and initiated the downstream inflammatory signaling, playing a substantial role in the development of PNDs.

MicroRNA let-7b inhibits hepatitis C virus and induces apoptosis in human hepatoma cells

BACKGROUND

Small non-coding RNAs have emerged as essential modulators of viral infections such as hepatitis C virus (HCV). Cellular miRNAs directly regulate the viral infectivity and indirectly by targeting virus-host factors. The current study investigates the inhibitory effect of let-7b miRNA on HCV replication in the Hepatocarcinoma cell line (Huh7.5).

METHODS AND RESULTS

The algorithm-based search revealed that let-7b, a high score microRNA, has target sequences on the HCV genome. The Huh7.5 cells were stably transduced with let-7b lentiviral vectors (Huh7.5/let-7b) and mock (Huh7.5/scrambled). The expression of the let-7b level was assessed by real-time PCR assay and Red fluorescence microscope. A dual-luciferase assay was conducted to evaluate the liver-specific let-7b and HCV genome interaction. In the next step, for establishing HCVcc, Full-length HCV-RNA was transduced to naïve Huh7.5, Huh7.5/scrambled, and Huh7.5/let-7b cells. The results of in silico analysis and dual-luciferase reporter assay exhibited a specific interaction of HCV-NS5B and let-7b. Real-time PCR analysis revealed that in contrast to infected naïve Huh7.5 cells and Huh7.5/scrambled, a significant decrease in HCV-RNA load was seen in Huh7.5/let-7b cells. On the other hand, the Flow Cytometry test showed that let-7b could significantly induce the apoptosis pathway in Huh7.5/let-7b.

CONCLUSIONS

The results also suggest that let-7b, as a target of the HCV genome, potentially reduces HCV replication and raises cell apoptosis rate. We suggest that let-7b directly downregulates HCV replication and may serve as a unique antiviral therapy.

MicroRNA let-7b induces lens epithelial cell apoptosis by targeting leucine-rich repeat containing G protein-coupled receptor 4 (Lgr4) in age-related cataract

Owing to a rapidly aging population, vision impairment caused by age-related cataract has become very common. Age-related cataract has also become one of the principal causes of blindness, and apoptosis of lens epithelial cells contributes to non-congenital cataract development. Previous studies have reported that microRNA let-7b (let-7b) is upregulated in cataractous lens epithelial cells, and the expression level of let-7b is positively associated with N, C and P cataract scores. However, the role of let-7b in the development of age-related cataract remains unclear. Here, we observed that the expression level of let-7b in the anterior lens capsules of age-related cataract was significantly higher than that in the normal anterior lens capsules. We performed ultraviolet (UV) irradiation to induce lens epithelial cell apoptosis. The results showed that the expression level of let-7b in lens epithelial cells which were treated by UV irradiation was significantly higher than that in the control, and let-7b promoted UV irradiation-induced apoptosis. Furthermore, we showed that leucine-rich repeat containing G protein-coupled receptor 4 (Lgr4) was a direct target of let-7b, and let-7b modulated lens epithelial cell apoptosis by directly targeting Lgr4. These findings will offer new insights into our understanding of the molecular mechanisms underlying the pathogenesis of cataract.