Epigallocatechin-3-Gallate Upregulates miR-221 to Inhibit Osteopontin-Dependent Hepatic Fibrosis.

Osteopontin (OPN) promotes hepatic fibrosis, and developing therapies targeting OPN expression in settings of hepatic injury holds promise. The polyphenol epigallocatechin-3-gallate (EGCG), found in high concentrations in green tea, downregulates OPN expression through OPN mRNA degradation, but the mechanism is unknown. Previous work has shown that microRNAs can decrease OPN mRNA levels, and other studies have shown that EGCG modulates the expression of multiple microRNAs. In our study, we first demonstrated that OPN induces hepatic stellate cells to transform into an activated state. We then identified three microRNAs which target OPN mRNA: miR-181a, miR-10b, and miR-221. In vitro results show that EGCG upregulates all three microRNAs, and all three microRNAs are capable of down regulating OPN mRNA when administered alone. Interestingly, only miR-221 is necessary for EGCG-mediated OPN mRNA degradation and miR-221 inhibition reduces the effects of EGCG on cell function. In vivo experiments show that thioacetamide (TAA)-induced cell cytotoxicity upregulates OPN expression; treatment with EGCG blocks the effects of TAA. Furthermore, chronic treatment of EGCG in vivo upregulates all three microRNAs equally, suggesting that in more chronic treatment all three microRNAs are involved in modulating OPN expression. We conclude that in in vitro and in vivo models of TAA-induced hepatic fibrosis, EGCG inhibits OPN-dependent injury and fibrosis. EGCG works primarily by upregulating miR-221 to accelerate OPN degradation. EGCG may therefore have utility as a protective agent in settings of liver injury.

Contribution of TNF-α to the development of retinal neurodegenerative disorders.

During the late 1970s, tumor necrosis factor alpha (TNF-α) was initially recognized as an endotoxin-induced substance that was mainly produced by macrophages, and able to cause the lysis of certain tumor cells. Subsequent research demonstrated that TNF-α mediates a broad range of cellular activities, including proliferation, survival, differentiation and apoptosis. It is also considered to be essential for the induction and maintenance of the inflammatory immune responses. Meanwhile, visual impairment imposes a substantial disease burden on society. It is associated with both significant economic impact and reduction in quality of life. Visual impairment raises serious social challenges for both patients and their families, interfering with day-to-day life, and can limit employment possibilities. Many of the most common, irreversible blinding pathologies involve neuronal loss from the retina, which is the light-sensing tissue of the eye. The retina, being part of the central nervous system, is unable to regenerate neurons lost to disease. Therefore, in the current review we will discuss the association between increased expression of TNF-α with neurodegenerative disorders, downstream cellular signaling mechanisms following interaction of TNF-α with its receptors, and the role of TNF-α as a possible target in the treatment of retinal neurodegenerative disorders.