| AIM To explore the mechanism and realtionship between endothelial injury induced by homocysteine thiolactone (HTL) and peroxisome proliferator-activated receptorγ(PPARy).METHODS (1) Isolated aortic rings experiment:The isolated rat aortic rings were exposed to HTL (lOmmol/L) for 60 minutes after preincubating with rosiglitazone (0.1,0.3, 1mmol/L), captopril (0.03 mmol/L), apocynin (0.03mmol/L) for 30 minutes respectively. The endothelium-dependent relaxation (EDR) and endothelium-independent relaxation, the level of nitric oxide (NO) and malondialdehyde (MDA), the activity of superoxide dismutase in vascular tissue was measured. (2)Animal experiment in vivo:The rats were intragastric gavaged HTL (50 mg/kg/d), at the same time interfered with rosiglitazone (10,20,40 mg/kg/d), captopril (20mg/kg/d), apocynin (200mg/kg/d) respectively. After treatment of 8 weeks, the aortic rings were used to examine the EDR, endothlium-independent relaxation and the expression of PPARy mRNA. The content of NO and MDA, the activity of total nitric oxide synthase (TNOS), endothelial nitric oxide synthase (eNOS), induced nitric oxide synthase (iNOS) and paraoxonase 1 (PON1) in serum, the level of SOD in erythrocyte was detected. (3) Experiment on cells:The cultured human umbilical vein endothelial cells (HUVECs) were respectively preincubated with rosiglitazone (0.001,0.01, 0.1mmol/L), rosiglitazone+GW9662 (0.1mmol/L+0.01mmol/L), apocynin (0.1mmol /L), captopril (0.03mmol/L), PDTC (0.1mmol/L) for 1 hour, and then incubated with HTL (1mmol/L) for 24 hours. The cell viablity was measured by MTT;The level of ROS and the activity of nuclear factor-KB (NF-κB) were detected by fluorescence; The concentration of soluble intercelluar adhesion molecule-1 (sICAM-1) was determined by ELISA; The expression of PPARγmRNA was examined by RT-PCR.RESULTS (1) Isolated aortic rings experiment:HTL significantly inhibited EDR of isolated aortic rings, reduced the content of NO and increased the activity of SOD and content of MDA in vascular tissue (P<0.01 compared with normal control). Rosiglitazone (lmmol/L) significantly lessened the injuries of EDR, preserved NO content, recovered SOD activity and MDA content in aortic tissue induced by HTL (P<0.05 or P<0.01 compared with HTL). Captopril and apocynin also protected the vascular endothelium from injuries induced by HTL and improved the change of biochemical parameters in aortic tissue (P<0.05 or P<0.01 compared with HTL). (2) Animal experiment in vivo: HTL resulted in an inhibition on EDR and the expression of PPARy mRNA of aortic rings, increased the content of MDA, reduced the activity of PON1 and content of NO (P<0.01 compared with normal control), but had no effect on the activity of TNOS, eNOS, iNOS in serum and the activity of SOD in erythrocyte (P>0.05). Rosiglitazone dose-dependently protected the EDR from injuries induced by HTL, inhibited the down-regulated expression of PPARy mRNA of aortic rings and the elevated content of MDA, recovered the activity of PON1 and the content of NO in serum (P<0.05 or P＜0.01 compared with HTL).The treatment of capropril and apocynin also significantly inhibited the injuries of EDR and the decreased level of PPARy mRNA, improved the change of biochemical parameters in serum (P<0.05 or P<0.01 compared with HTL). The treatment of HTL both in vitro and vivo had no effect on the endothelium-independent relaxation (P>0.05). (3)Experiment on cells:HTL obviously decreased the HUVECs viability, enhanced the level of ROS and activation of NF-κB, increased the concentration of sICAM-1 and down-regulated the expression of PPARy mRNA (P<0.01 compared with normal control). Rosiglitazone dose-dependently increased the HUVECs viability, reduced the ROS level, NF-κB activation and sICAM-1 concentration, up-regulated the expression of PPARy mRNA (P<0.01 compared with HTL), while all the above protections could be cancelled by GW9662. Apocynin, captopril and PDTC had similar protective effects on the injuries of HUVECs induced by HTL.CONCLUSION (1) HTL significantly injured the vascular endothelium both in vitro and vivo; (2) Rosiglitazone could protect vascular endothelium from injuries induced by HTL; (3) Vascular endothelial injury induced by HTL in vivo was related to the inhibition of PON1 activity; (4) HTL-induced vascular endothelial dysfunction may involve the down-regulation of PPARy, which lead to increased oxidative stress by activating the NADPH oxidase.
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