Protective Effect of Raf-1 Kinase Inhibitory Protein on Diabetic Retinal Neurodegeneration through P38-MAPK Pathway

AR/RKIP pathway mediates the inhibitory effects of icariin on renal fibrosis and endothelial-to-mesenchymal transition in type 2 diabetic nephropathy

ETHNOPHARMACOLOGICAL RELEVANCE

Herba epimedium brevicornu maxim is traditionally known as a sexual enhancement, and has the effect of tonifying kidney yang. Icariin is a flavonoid extracted from epimedium brevicornu maxim, and has been shown to improve nephropathy disease.

AIM OF THE STUDY

This study investigated the possible role of icariin in regulating renal EndMT in type 2 diabetic nephropathy (T2DN).

MATERIALS AND METHODS

Male type 2 diabetic Sprague Dawley rats, Male D2.BKS(D)-Leprdb/J (db/db) mice, and mouse glomerular endothelial cells were utilized to evaluate the effect of icariin. Western blotting, Q-PCR, immunohistochemistry, H&E, Masson staining, immunofluorescence, and siRNA transfection, were performed in this study.

RESULTS

The inhibitory function of icariin in renal fibrosis and renal EndMT was verified in type 2 diabetic animals. Methyltestosterone suppressed renal fibrosis and EndMT in db/db mice. Androgen receptor (AR), the major receptor of testosterone, was upregulated by icariin. The AR antagonist MDV3100, blocked the inhibition by icariin in renal EndMT, revealing that icariin repressed renal EndMT by activating AR. In addition, icariin and methyltestosterone upregulated the Raf kinase inhibitor protein (RKIP) in db/db mice. Furthermore, siRNA-RKIP inhibited the effect of icariin on EndMT. The MEK/ERK pathway, as the downstream pathway of RKIP, was suppressed by icariin and methyltestosterone. Of note, the effect of icariin on the MEK/ERK pathway was abolished by MDV3100 or siRNA-RKIP.

CONCLUSIONS

These results supported that icariin targeted AR/RKIP/MEK/ERK pathway to suppress renal fibrosis and EndMT in T2DN.

MAPK Pathways in Ocular Pathophysiology: Potential Therapeutic Drugs and Challenges

Mitogen-activated protein kinase (MAPK) pathways represent ubiquitous cellular signal transduction pathways that regulate all aspects of life and are frequently altered in disease. Once activated through phosphorylation, these MAPKs in turn phosphorylate and activate transcription factors present either in the cytoplasm or in the nucleus, leading to the expression of target genes and, as a consequence, they elicit various biological responses. The aim of this work is to provide a comprehensive review focusing on the roles of MAPK signaling pathways in ocular pathophysiology and the potential to influence these for the treatment of eye diseases. We summarize the current knowledge of identified MAPK-targeting compounds in the context of ocular diseases such as macular degeneration, cataract, glaucoma and keratopathy, but also in rare ocular diseases where the cell differentiation, proliferation or migration are defective. Potential therapeutic interventions are also discussed. Additionally, we discuss challenges in overcoming the reported eye toxicity of some MAPK inhibitors.

Identification and Validation of Autophagy-Related Genes in Diabetic Retinopathy

BACKGROUND

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes, which is associated with damage of blood-retinal barrier and ischemia of retinal vasculature. It devastates visual acuity due to leakage of retinal vessels and aberrant pathological angiogenesis in diabetic patients. The etiology of DR is complex, accumulated studies have shown that autophagy plays an important role in the pathogenesis of DR, but its specific mechanism needs to be further studied.

METHODS

This study chose the online Gene Expression Omnibus (GEO) microarray expression profiling dataset GSE146615 to carry on the research. Autophagy-related genes that were potentially differentially expressed in DR were screened by R software. Then, the differentially expressed autophagy-related genes were analyzed by correlation analysis, tissue-specific gene expression, gene-ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and protein-protein interaction (PPI) network analysis. Finally, retinal pigment epithelial cell line (ARPE-19) incubated with high glucose (HG) was used to mimic the DR model, and the mRNA level of key genes was verified by quantitative real-time polymerase chain reaction (qRT-PCR) in vitro.

RESULTS

A total of 23 differentially expressed autophagy-related genes (9 up-regulated genes and 14 down-regulated genes) were identified by differential expression analysis. The analysis of tissue-specific gene expression showed that these differentially expressed autophagy-related genes were enriched in the retina. GO and KEGG enrichment analysis showed that differentially expressed autophagy-related genes were significantly enriched in autophagy-related pathways such as regulation of autophagy and macroautophagy. Then 10 hub genes were identified by PPI network analysis and construction of key modules. Finally, qRT-PCR confirmed that the expression of MAPK3 in the DR model was consistent with the results of bioinformatics analysis of mRNA chip.

CONCLUSION

Through bioinformatics analysis, we identified 23 potential DR autophagy-related genes, among which the down-regulated expression of MAPK3 may affect the occurrence and development of DR by regulating autophagy. It provides a novel insight into the pathogenesis of DR.