Thymosin β4 alleviates renal fibrosis and tubular cell apoptosis through TGF-β pathway inhibition in UUO rat models

Background: Thymosin beta 4 (T beta 4) is closely associated with the cytoskeleton, inflammation, wound healing, angiogenesis, apoptosis, and myocardial regeneration, but the effects of T beta 4 treatment on chronic renal tubular interstitial fibrosis (CRTIF) are poorly known. This study aimed to examine the effects of T beta 4 on the renal apoptosis and the expression of transforming growth factor (TGF-beta), E-cadherin, and a-smooth muscle actin (alpha-SMA) in CRTIF rat models. Methods: Male SD rats were randomized into four groups (sham group, unilateral ureteral obstruction (UUO) group, UUO + low-dose T beta 4 group, and UUO + high-dose T beta 4 group). The pathological changes of kidney tissue and its function were assessed two weeks after UUO. In renal interstitial tissue, TGF-beta, E-cadherin and a-SMA expression was detected by western blot. In tubular epithelial cells, E-cadherin and alpha-SMA expression was detected using Real-time qPCR and western blot. Cell apoptosis of rat renal interstitial tissue and tubular epithelial cells was evaluated by immunofluorescence and western blot. Results: Two weeks after UUO, no differences in blood urea nitrogen and creatinine were observed between the four groups (P > 0.05). Compared to the UUO group, T beta 4 treatment decreased the 24-h proteinuria (P < 0.001) and reduced the area of pathological change (P < 0.01); this effect was more apparent in the UUO + high-dose T beta 4 group. Compared to the UUO group, a significant decrease in TGF-beta and alpha-SMA protein expression was observed in the high-dose T beta 4 group. The level of E-cadherin protein was lower in the UUO group than the T beta 4 groups, and high-dose T beta 4 treatment further increased E-cadherin expression and improved cell apoptosis in the renal interstitial tissue. Analysis of in vitro tubular epithelial cells showed that a-SMA mRNA and protein expression decreased, while E-cadherin mRNA and protein expression increased by T beta 4 treatment. Similarly, these changes were more significant in the UUO + high-dose T beta 4 group. T beta 4 treatment improved the apoptosis of In vitro tubular epithelial cells compared with pure TGF-beta stimulation, and equally, the decrease of apoptosis was more apparent in the TGF-beta + high-dose T beta 4 group. Conclusions: T beta 4 treatment might alleviate the renal fibrosis and apoptosis of tubular epithelial cells through TGF-beta pathway inhibition in UUO rats with CRTIF.