TGF-ß regulates TGFBIp expression in corneal fibroblasts via miR-21, miR-181a, and Smad signaling.

Transforming growth factor-ß (TGF-ß)-induced gene (TGFBI) protein (TGFBIp) is associated with granular corneal dystrophy type 2 (GCD2). TGFBIp levels can affect GCD2 phenotypes, but the underlying molecular mechanisms have not been fully elucidated. We investigated the involvement of microRNA (miRNA) and TGF-ß in the regulation of TGFBIp expression in corneal fibroblasts. Ectopic expression of miR-9, miR-21, and miR-181a significantly decreased TGFBIp levels. Conversely, expression of miR-21 and miR-181a was induced by TGF-ß1. Expression of miR-21 was 10-fold higher than that of miR-9 and miR-181a in corneal fibroblasts. Additionally, TGF-ß1 expression was significantly higher than that of TGF-ß2 and TGF-ß3 in corneal fibroblasts, whereas expression of all three TGF-ß forms was not significantly different between wild-type (WT) and GCD2 homozygotes (HO) corneal fibroblasts. Taken together, these data indicate that TGFBIp expression is positively regulated by TGF-ß, whereas TGF-ß-induced miR-21 and miR-181a negatively regulate TGFBIp expression. In conclusion, TGFBIp levels in corneal fibroblasts are controlled via the coordinated activity of miR-21 and miR-181a and by Smad signaling. Pharmacologic modulation of these miRNAs and TGF-ß signaling could have therapeutic potential for TGFBI-associated corneal dystrophy, including GCD2.

Lithium chloride suppresses LPS-mediated matrix metalloproteinase-9 expression in macrophages through phosphorylation of GSK-3ß.

Abnormal degradation of matrix components due to dysregulated expression of matrix metalloproteinase (MMP)-9 in macrophages has been linked to progression of acute cerebral ischemia and atherosclerosis. We report that lithium chloride (LiCl) or CHIR99021, inhibitors of Wnt signaling pathway, enhance phosphorylation of glycogen synthase kinase-3beta and suppress lipopolysaccharide-mediated upregulation of MMP-9 expression in murine macrophage RAW264.7 cells in a dose-dependent manner. Suppression of MMP-9 expression by LiCl or CHIR99021 did not result after inhibition of kinases involved in NFκB or AP-1 family proteins, but from changes in the activity of histone deacetylases. Beneficial effects on atherosclerosis or cerebral ischemia in animal studies caused by LiCl may be in part explained by the suppression of MMP-9 gene expression.

Melatonin induces autophagy via an mTOR-dependent pathway and enhances clearance of mutant-TGFBIp.

The hallmark of granular corneal dystrophy type 2 (GCD2) is the deposit of mutant transforming growth factor-ß (TGF-ß)-induced protein (TGFBIp) in the cornea. We have recently shown that there is a delay in autophagic degradation of mutant-TGFBIp via impaired autophagic flux in GCD2 corneal fibroblasts. We hypothesized that melatonin can specifically induce autophagy and consequently eliminate mutant-TGFBIp in GCD corneal fibroblasts. Our results show that melatonin activates autophagy in both wild-type (WT) and GCD2-homozygous (HO) corneal fibroblast cell lines via the mammalian target of rapamycin (mTOR)-dependent pathway. Melatonin treatment also led to increased levels of beclin 1, which is involved in autophagosome formation and maturation. Furthermore, melatonin significantly reduced the amounts of mutant- and WT-TGFBIp. Treatment with melatonin counteracted the autophagy-inhibitory effects of bafilomycin A1, a potent inhibitor of autophagic flux, demonstrating that melatonin enhances activation of autophagy and increases degradation of TGFBIp. Cotreatment with melatonin and rapamycin, an autophagy inducer, had an additive effect on mutant-TGFBIp clearance compared to treatment with either drug alone. Treatment with the selective melatonin receptor antagonist luzindole did not block melatonin-induced autophagy. Given its ability to activate autophagy, melatonin is a potential therapeutic agent for GCD2.

Atorvastatin and simvastatin, but not pravastatin, up-regulate LPS-induced MMP-9 expression in macrophages by regulating phosphorylation of ERK and CREB.

Statins suppress expression of pro-inflammatory cytokines in endothelial cells, whereas they enhance it in immune cells. Pro-inflammatory cytokines and lipopolysaccharide (LPS) induce matrix metalloproteinase (MMP)-9 gene expression in macrophages, which has been linked to progress of various inflammatory diseases. The aim of this study was to identify effects of various statins on LPS-induced MMP-9 gene expression in macrophages and microglia. MMP-9 expression was analyzed by real-time PCR or zymography. Effect of statins on activation of signaling pathways was analyzed by time-dependent phosphorylation of signaling molecules. Atorvastatin and simvastatin, but not pravastatin, up-regulated LPS-induced MMP-9 expression in murine RAW 264.7 macrophages and BV2 microglia. The phosphorylation duration of extracellular signal regulated kinases was extended by simvastatin, but not by atorvastatin or pravastatin. The up-regulation of LPS-induced MMP-9 gene expression by the statins was dependent on extracellular calcium ions and mediated by enhancing phosphorylation of cAMP-responsive element binding protein. Geranylgeranyl pyrophosphate, a precursor for cholesterol synthesis, could suppress up-regulation of LPS-mediated MMP-9 gene expression by atorvastatin and simvastatin. Atorvastatin and simvastatin-mediated up-regulation of LPS-induced MMP-9 gene expression in macrophages and microglia in vitro raises an important concern about use of the widely-prescribed statins in certain inflammatory conditions that are mediated by LPS.

Uncoupling by (--)-epigallocatechin-3-gallate of ATP-sensitive potassium channels from phosphatidylinositol polyphosphates and ATP.

Of green tea catechins, (--)-epigallocatechin-3-gallate (EGCG) and (--)-epicatechin-3-gallate (ECG), but not (--)-epicatechin and (--)-epigallocatechin, inhibit the activity of ATP-sensitive potassium (K(ATP)) channels at tens of micromolar concentrations, ECG being three times more effective than EGCG. Further, we found that by using cloned beta cell-type K(ATP) channels, only EGCG at 1 microM, a readily achievable plasma concentration by oral intake in humans, but not other epicatechins, significantly blocked channel reactivation after ATP wash-out, suggesting that interaction of phosphatidylinositol polyphosphates (PIP) with the channel was impaired by EGCG. In addition, a 10-fold higher concentration of EGCG reduced the channel sensitivity to ATP, but not AMP and ADP. This effect of EGCG was greater in the channel with the sulfonylurea receptor (SUR) than with the inwardly rectifying K(+) channel (Kir6.2) alone. Neomycin, a polycation, profoundly suppressed the effect of EGCG. Expectedly, glucose-stimulated cytosolic Ca(2+) elevation in rat pancreatic beta cells, and insulin secretory responses to high glucose loading in vivo were impaired by EGCG. In rabbit cardiac myocytes, dinitrophenol-induced opening of the channel was delayed by 1 microM EGCG. These results suggest that EGCG may interact with PIP-binding sites on the Kir6.2 subunit. SUR further endows EGCG with an ability to interfere with an interaction of the gamma-phosphate tail of ATP with Kir6.2. The specificity of EGCG possibly implies that 5'-OH of the B-ring on the pyrogallol moiety in the EGCG molecule may be critical for these actions of EGCG on the K(ATP) channel.