Effect of simvastatin on expression of transforming growth factor-β and collagen type IV in rat mesangial cells.
ABSTRACT Diabetic nephropathy is characterized by the accumulation of extracellular matrix in the glomerular mesangium as a result of an imbalance between matrix synthesis and degradation. Since simvastatin has been proposed to decrease renal interstitial fibrosis, we hypothesized that the protective effect of statins was related to the expression of transforming growth factor-β (TGF-β) and type IV collagen (Col IV).
Cultured rat mesangial cells (RMC) were exposed to high glucose (HG), advanced glycosylation end products (AGE) or H(2)O(2) in the absence and presence of simvastatin. Expression of TGF-β and Col IV was determined by Western blotting.
Coincubation of RMC with HG, AGE or H(2)O(2) resulted in a significant increase of the expression of TGF-β and Col IV (p < 0.05). Simvastatin significantly inhibited HG-, AGE- or H(2)O(2)-induced expression of TGF-β and Col IV (p < 0.05). Moreover, simvastatin also inhibited HG-, AGE- and H(2)O(2)-induced activation of p38 mitogen-activated protein kinase, which indicated that the preventive effect of simvastatin on TGF-β and Col IV may be associated with p38.
These findings suggest that simvastatin can reduce HG-, AGE- and H(2)O(2)-induced expression of TGF-β and Col IV by inhibition of the p38 pathway.
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ABSTRACT: PURPOSE. Statins have been shown to increase aqueous outflow facility. The matricellular protein SPARC is a critical mediator of aqueous outflow and intraocular pressure (IOP). Here, we examine the effects of lovastatin on SPARC expression in trabecular meshwork (TM) cells, exploring the molecular mechanisms involved. METHODS. Primary cultured human TM cells were incubated for 24, 48, and 72 h with 10 μM lovastatin. In separate cultures, media was supplemented with either farnesyl pyrophosphate (FPP) or geranylgeranyl pyrophosphate (GGPP) for the duration of the 72 h time point experiment. TM cells were also pre-treated for 24 h with lovastatin followed by 24 h stimulation with 3 ng/mL TGF-β2. Cell lysates and media were harvested and relative mRNA and protein level changes were determined. Krüppel-like factor 4 (KLF4) localization in normal human anterior segments was examined by immunofluorescence. Adenovirus expressing human KLF4 was used and relative changes in SPARC mRNA and protein levels were assessed. RESULTS. Incubating TM cells with lovastatin suppressed SPARC mRNA and protein levels. This effect was reversed upon media supplementation with GGPP but not FPP. Pre-treating cells with lovastatin inhibited TGF-β2 induction of SPARC. The KLF4 transcription factor was expressed throughout the TM and the inner and outer walls of Schlemm's canal. Lovastatin treatment upregulated KLF4 mRNA and protein levels. Overexpression of KLF4 downregulated SPARC expression. CONCLUSIONS. Collectively, our data identify lovastatin as an important pharmacological suppressor of SPARC expression in TM cells, and provide further insight into the molecular mechanisms mediating statin enhancement of aqueous outflow facility.Investigative ophthalmology & visual science 01/2014; 55(3). DOI:10.1167/iovs.13-12712 · 3.66 Impact Factor