Protective effects of piperine on the retina of mice with streptozotocin-induced diabetes by suppressing HIF-1/VEGFA pathway and promoting PEDF expression

AIM:To evaluate the protective mechanisms of piperine in the retina of mice with streptozotocin-induced diabetes.METHODS:In experiments in vitro,stimulation by chemical hypoxia was established in ARPE-19 cells.Then,the expression of hypoxia-inducible factor-1α(HIF-1α),vascular endothelial growth factor A(VEGFA),and pigment epithelium-derived factor(PEDF)was assessed at the m RNA and protein levels.In experiments in vivo,diabetes mellitus was established by intraperitoneally injecting 150 mg/kg streptozotocin once.After 3 wk of the onset of diabetes,15 mg/kg piperine was intraperitoneally injected once daily for 1 or 3 wk.Then,the retinal morphology and m RNA and protein expression were assessed.RESULTS:In hypoxia,1-100μmol/L piperine significantly decreased the expression of VEGFA m RNA and increased the expression of PEDF m RNA without affecting HIF-1αm RNA.Meanwhile,100μmol/L piperine substantially decreased the protein level of VEGFA and increased the protein level of PEDF.The HIF-1αprotein level was also hampered by piperine.In the diabetic retina of mice,the morphological damage was alleviated by piperine.Likewise,the retinal vascular leakage was substantially decreased by piperine.Further,the protein levels of HIF-1αand VEGFA were significantly reduced by piperine.Moreover,the level of the antiangiogenic factor of PEDF dramatically increased by piperine.CONCLUSION:Piperine may exert protective effects on the retina of mice with diabetes via regulating the pro-antiangiogenic homeostasis composed of HIF-1/VEGFA and PEDF.

Inhibition of vascular endothelial growth factor expression by Chinese medicine of Hedyotis diffusa Willd herbal compounds

The Hedyotis diffusa Willd herbal compounds(HDWHCs)are commonly used as Chinese medicine to treat cancer patients with established clinical therapeutic efficacy in China.However,the underlying mechanisms remain to be elucidated.In this study,we used freeze-dried powder of the water extracts of HDWHCs to investigate the potential mechanisms of HDWHCs in cancer treatment.HDWHCs treatment significantly inhibited vascular endothelial growth factor(VEGF)mRNA levels and VEGF transcriptional activation in cancer cells.HDWHCs also had a remarkable inhibitory effect on the expression of hypoxia-inducible factor 1alpha(HIF-1alpha).Forced expression of HIF-1αrestored VEGF transcriptional activation inhibited by HDWHCs,indicating that HDWHCs suppressed VEGF expression through decreasing HIF-1alpha expression.Moreover,HDWHCs inhibited cyclooxygenase-2(COX-2)expression,and overexpression of HIF-1alpha restored HDWHCs’inhibitory effect on COX-2 at transcriptional level.These findings may provide better understanding of HDWHCs’anti-cancer mechanism in cancer treatment.