microRNA-182 Mediates Sirt1-Induced Diabetic Corneal Nerve Regeneration

Effects of microRNA-211 on proliferation and apoptosis of lens epithelial cells by targeting SIRT1 gene in diabetic cataract mice

Our study aimed at exploring the effects of miR-211 on the proliferation and apoptosis of lens epithelial cells in diabetic cataract mice by targetting NAD⁺-dependent histone deacetylase sirtulin 1 (SIRT1). Healthy male mice were assigned into normal and diabetic cataract groups. Blood glucose, lens turbidity, and apoptosis were measured. Lens epithelial cells were classified into the normal, blank, negative control (NC), miR-211 mimics, miR-211 inhibitors, siRNA-SIRT1, and miR-211 inhibitors + siRNA-SIRT1 groups. MiR-211, Bcl-2, Bax, p53, and SIRT1 expressions of each group were detected. Cell proliferation, cycle and apoptosis were tested by MTT assay and flow cytometry. MiR-211 can specifically bind to SIRT1 according to the luciferase system. SIRT1 protein concentration was strongly positive in normal mice and weakly positive in diabetic cataract mice. Apoptosis index of diabetic cataract mice was higher than the normal mice. Compared with normal mice, the expressions of miR-211, Bax, and p53 increased in diabetic cataract mice, while the Bcl-2 and SIRT1 expressions decreased. In comparison with the blank and NC groups, the expressions of miR-211, Bax, and p53 increased, while Bcl-2 and SIRT1 expressions decreased, and the proliferation decreased and apoptosis rate increased in the miR-211 mimics and siRNA-SIRT1 groups; the results were contradicting for the miR-211 inhibitor group. MiR-211 could promote apoptosis and inhibit proliferation of lens epithelial cells in diabetic cataract mice by targetting SIRT1.

MicroRNA-182-5p Regulates Nerve Injury–induced Nociceptive Hypersensitivity by Targeting Ephrin Type-b Receptor 1

Background

The authors and others have previously shown that the up-regulation of spinal ephrin type-b receptor 1 plays an essential role in the pathologic process of nerve injury–induced nociceptive hypersensitivity, but the regulatory mechanism remains unclear.

Methods

Radiant heat and von Frey filaments were applied to assess nociceptive behaviors. Real-time quantitative polymerase chain reaction, Western blotting, fluorescence in situ hybridization, immunofluorescence, immunohistochemistry, dual-luciferase reporter gene assays, recombinant lentivirus, and small interfering RNA were used to characterize the likely mechanisms.

Results

Periphery nerve injury induced by chronic constriction injury of the sciatic nerve significantly reduced spinal microRNA-182-5p (miR-182-5p) expression levels, which were inversely correlated with spinal ephrin type-b receptor 1 expression (R2 = 0.90; P < 0.05; n = 8). The overexpression of miR-182-5p in the spinal cord prevented and reversed the nociceptive behaviors induced by sciatic nerve injury, accompanied by a decreased expression of spinal ephrin type-b receptor 1 (recombinant lentiviruses containing pre-microRNA-182: 1.91 ± 0.34 vs. 1.24 ± 0.31, n = 4; miR-182-5p mimic: 2.90 ± 0.48 vs. 1.51 ± 0.25, n = 4). In contrast, the down-regulation of spinal miR-182-5p facilitated the nociceptive behaviors induced by sciatic nerve injury and increased the expression of spinal ephrin type-b receptor 1 (1.0 ± 0.26 vs. 1.74 ± 0.31, n = 4). Moreover, the down-regulation of miR-182-5p and up-regulation of ephrin type-b receptor 1 caused by sciatic nerve injury were mediated by the N-methyl-d-aspartate receptor.

Conclusions

Collectively, our findings reveal that the spinal ephrin type-b receptor 1 is regulated by miR-182-5p in nerve injury–induced nociceptive hypersensitivity.

MicroRNA-182 Regulates Neurite Outgrowth Involving the PTEN/AKT Pathway

MicroRNAs are implicated in neuronal development and maturation. Neuronal maturation, including axon outgrowth and dendrite tree formation, is regulated by complex mechanisms and related to several neurodevelopmental disorders. We demonstrated that one neuron-enriched microRNA, microRNA-182 (miR-182), played a significant role in regulating neuronal axon outgrowth and dendrite tree formation. Overexpression of miR-182 promoted axon outgrowth and complexity of the dendrite tree while also increasing the expression of neurofilament-M and neurofilament-L, which provide structural support for neurite outgrowth. However, a reduction of miR-182 inhibited neurite outgrowth. Furthermore, we showed that miR-182 activated the AKT pathway by increasing AKT phosphorylation on S473 and T308 and inhibiting PTEN activity by increasing phosphorylation on S380. Inhibition of AKT activity with the PI3-K inhibitor LY294002 could downregulate AKT and PTEN phosphorylation and suppress axon outgrowth. In addition, we showed that BCAT2 might be the target of miR-182 that takes part in the regulation of neuronal maturation; blockage of endogenous BCAT2 promotes axon outgrowth and AKT activity. These observations indicate that miR-182 regulates axon outgrowth and dendrite maturation involving activation of the PTEN/AKT pathway.

MicroRNA-27a promotes podocyte injury via PPARγ-mediated β-catenin activation in diabetic nephropathy

Podocyte injury has a pivotal role in the pathogenesis of diabetic nephropathy (DN). MicroRNA-27a (miR-27a), peroxisome proliferator-activated receptor γ (PPARγ) and β-catenin pathways have been involved in the pathogenesis of DN. Herein, we asked whether miR-27a mediates podocyte injury through PPARγ/β-catenin signaling in DN. The functional relevance of miR-27a, PPARγ and β-catenin were investigated in cultured podocytes and glomeruli of diabetic rats and patients using in vitro and in vivo approaches. Podocyte injury was assessed by migration, invasion and apoptosis assay. Biological parameters were analyzed using enzyme-linked immunosorbent assay. We found that high glucose stimulated miR-27a expression, which, by negatively targeting PPARγ, activated β-catenin signaling as evidenced by upregulation of β-catenin target genes, snail1 and α-smooth muscle actin (α-SMA) and downregulation of podocyte-specific markers podocin and synaptopodin. These changes caused podocyte injury as demonstrated by increased podocyte mesenchymal transition, disrupted podocyte architectural integrity and increased podocyte apoptosis. Furthermore, we provide evidence that miR-27a contributed to unfavorable renal function and increased podocyte injury in diabetic rats. Notably, miR-27a exhibited clinical and biological relevance as it was linked to elevated serum creatinine, proteinuria and reduced creatinine clearance rate. In addition, miR-27a upregulation and activation of PPARγ/β-catenin signaling were verified in renal biopsy samples from DN patients. We propose a novel role of the miR-27a/PPARγ/β-catenin axis in fostering the progression toward more deteriorated podocyte injury in DN. Targeting miR-27a could be a potential therapeutic approach for DN.

Neuronal Changes in the Diabetic Cornea: Perspectives for Neuroprotection

Diabetic neuropathy is associated with neurotrophic ulcerations of the skin and cornea. Decreased corneal sensitivity and impaired innervation lead to weakened epithelial wound healing predisposing patients to ocular complications such as corneal infections, stromal opacification, and surface irregularity. This review presents recent findings on impaired corneal innervation in diabetic individuals, and the findings suggest that corneal neuropathy might be an early indicator of diabetic neuropathy. Additionally, the recent findings for neuroprotective and regenerative therapy for diabetic keratopathy are presented.