MMP2-A2M interaction increases ECM accumulation in aged rat kidney and its modulation by calorie restriction.

Age-associated renal fibrosis is related with renal function decline during aging. Imbalance between accumulation and degradation of extracellular matrix is key feature of fibrosis. In this study, RNA-sequencing (RNA-Seq) results based on next-generation sequencing (NGS) data were analyzed to identify key proteins that change during aging and calorie restriction (CR). Among the changed genes, A2M and MMP2, which are known to interact, exhibited the highest between centrality (BC) and degree values when analyzed by protein-protein interaction (PPI). Both mRNA and protein levels of MMP2 and A2M were increased during aging. Furthermore, the interaction between MMP2 and A2M was verified by immunoprecipitation and immunohistochemistry. MMP2 activity was further measured under the presence or absence of A2M-MMP2 interaction. MMP2 activity, which was increased under the absence of A2M-MMP2 interaction, was significantly decreased under the presence of interactions in aged kidney. We further hypothesized that the interaction between A2M-MMP2 played a role in the inactivation of MMP2 leading to accumulation of ECM including collagen type I and IV. Aged kidney showed highly accumulated MMP2 substrate proteins despite of increased MMP2 protein expression and CR blunted these accumulation. Additional in vivo analysis revealed that the signal transducer and activator of transcription (STAT) 3 transcriptional factor was significantly increased thus increasing A2M expression during aging. STAT3 activating cytokines were also highly increased in aged kidney. In conclusion, the results of the present study indicate that A2M-MMP2 interaction has a role in age-associated renal ECM accumulation and in the suppression such fibrosis by CR.

Evaluation of Antimelanogenic Activity and Mechanism of Galangin in Silico and in Vivo.

Abnormal pigmentation owing to excessive melanin synthesis can result in serious problems such as freckles, age-spots, and melanoma. Tyrosinase inhibitors have been an interesting target for the treatment of hyperpigmentation because tyrosinase is the rate-limiting enzyme in melanin synthesis. The screening for strong tyrosinase inhibitors led to the finding of the flavonoid galangin, which showed notable inhibitory effects on mushroom tyrosinase. The IC50 value of galangin (3.55±0.39 µM) was lower than that of kojic acid (48.55±1.79 µM), which was used as a positive control. In silico docking simulation and mechanistic studies demonstrated that galangin interacted with the catalytic sites of tyrosinase and competed with tyrosine. In B16F10 melanoma cells stimulated with α-melanocyte stimulating hormone, galangin inhibited tyrosinase activity as well as melanin production. Although high doses of galangin were cytotoxic, no cytotoxic effects were observed at low doses. In addition, the in vivo efficacy of galangin was evaluated in HRM2 melanin-possessing hairless mice. As measured by the skin-whitening index and melanin staining, repeated UVB exposure increased skin melanin synthesis. Galangin application significantly reduced melanogenesis induced by UVB exposure. Collectively, our data indicates that galangin shows strong tyrosinase inhibition activity, which suggests that it may be an effective skin-whitening agent.

Involvement of NF-κBIZ and related cytokines in age-associated renal fibrosis.

Chronic inflammation is a major contributor to age-related nephropathic changes, including renal fibrosis. In this study, various experimental paradigms were designed to delineate the role played by NF-κBIZ (also known as IκBζ) in age-associated renal fibrosis. Analyses based on RNA-sequencing findings obtained by next generation sequencing (NGS) revealed the upregulations of NF-κBIZ and of IL-6 and MCP-1 (both known to be regulated by NF-κBIZ) during aging. The up-regulation of NF-κBIZ in aged rat kidneys coincided with increased macrophage infiltration. In LPS-treated macrophages, oxidative stress was found to play a pivotal role in NF-κBIZ expression, suggesting age-related oxidative stress is associated with NF-κBIZ activation. Furthermore, these in vitro findings were confirmed in LPS-treated old rats, which showed higher levels of oxidative stress and NF-κBIZ in kidneys than LPS-treated young rats. Additional in vitro experiments using macrophages and kidney fibroblasts demonstrated NF-κBIZ and related cytokines participate in fibrosis. In particular, increased levels of NF-κBIZ-associated cytokines in macrophages significantly up-regulated TGF-ß induced kidney fibroblast activation. Moreover, experiments with NF-κBIZ knocked down macrophages showed reduced TGF-ß-induced kidney fibroblast activation. The findings of the present study provide evidence regarding an involvement of NF-κBIZ in age-associated progressive renal fibrosis and provides potential targets for its prevention.

Short-term calorie restriction ameliorates genomewide, age-related alterations in DNA methylation.

DNA methylation plays major roles in many biological processes, including aging, carcinogenesis, and development. Analyses of DNA methylation using next-generation sequencing offer a new way to profile and compare methylomes across the genome in the context of aging. We explored genomewide DNA methylation and the effects of short-term calorie restriction (CR) on the methylome of aged rat kidney. Whole-genome methylation of kidney in young (6 months old), old (25 months old), and OCR (old with 4-week, short-term CR) rats was analyzed by methylated DNA immunoprecipitation and next-generation sequencing (MeDIP-Seq). CpG islands and repetitive regions were hypomethylated, but 5'-UTR, exon, and 3'-UTR hypermethylated in old and OCR rats. The methylation in the promoter and intron regions was decreased in old rats, but increased in OCR rats. Pathway enrichment analysis showed that the hypermethylated promoters in old rats were associated with degenerative phenotypes such as cancer and diabetes. The hypomethylated promoters in old rats related significantly to the chemokine signaling pathway. However, the pathways significantly enriched in old rats were not observed from the differentially methylated promoters in OCR rats. Thus, these findings suggest that short-term CR could partially ameliorate age-related methylation changes in promoters in old rats. From the epigenomic data, we propose that the hypermethylation found in the promoter regions of disease-related genes during aging may indicate increases in susceptibility to age-related diseases. Therefore, the CR-induced epigenetic changes that ameliorate age-dependent aberrant methylation may be important to CR's health- and life-prolonging effects.