The Study On Radiosensitive Effect And Mechanism To Tumor Cells Of Capsazepine

Transient receptor potential vanilloid 1(TRPVl) that also is known as capsaicin receptor is a non-selective cation ion channel. TRPV1 can regulate Ca2+ influx, and participate in a variety of physiological and pathological process of tumor. One such agent is Capsazepine(CPZ) that is now widely used as a selective vanilloid type 1 receptor(TRPV1) antagonist. CPZ can be directly actived on the capsaicin receptor, blocking its biological effects. CPZ also can abolish osteosarcoma-induced hyperalgesia and block calcium channels.Although studies have shown that CPZ has antitumor formation and the function of the resistance of tumor cell proliferation, but its role in the hepatocellular carcinoma Hep G2 cells, as well as Hep G2 cells radiation sensitivity function has not been reported. The study was to explore CPZ induced Hep G2 cell apoptosis and radiosensitivity; provide new targets for tumor prevention and radiotherapy. 1. CPZ induced apoptosis of Hep G2 cellsCPZ could inhibit the proliferation of Hep G2 cells in a dose dependent manner. Significantly morphological changes of cells including cytoplasm and nuclear condensation and partition of cytoplasm were observed by Hoechst 33258 staining. According to FCM analysis, Hep G2 cells were arrested in G0/G1 phase, and cell apoptotic rate increased. CPZ could inhibit TRPV1 expression in the m RNA and protein level. The protein expressions of Bax and p53 were up-regulated while Bcl-2 expression down-regulated. 2. Radiosensitive effect of CPZ on Hep G2 cellsRadiosensitive effect of CPZ on X-rays or 12C6+ ion irradiation was studied. Hep G2 cells were pretreated with 0.005 μmol/L CPZ for 6 h and irradiated with 2Gy X-rays or 12C6+ ion, the ratio of survival cells in the IR+CPZ group was significantly decreased(P< 0.05). The colony forming rate of IR+CPZ group was decreased from 100 % of control group and(35.56±3.60)% of IR group to(14.81±2.64)%(P< 0.05). Significantly morphological changes of cells including cytoplasm and nuclear condensation and partition of cytoplasm were observed by Hoechst 33258 staining. According to Western blot analysis, IR+CPZ could inhibit TRPV1 expression in the protein level. The protein expressions of p53, Bax and Caspase-3 were up-regulated while Bcl-2 expression down-regulated. CPZ plus 12C6 + ion beam irradiation caused mitochondrial cytochrome C release. The results showed that CPZ could significantly improve the radiosensitivity of Hep G2 cells by activating the mitochondria mediated intrinsic apoptotic signaling pathway.As expected, CPZ, a TRPV1 antagonist, can induce apoptosis of Hep G2 cells and enhance radiosensitivity on Hep G2 cells.