The Role Of JAK/STAT3 Signal Pathway In Inhibition Host Cellapotosis Induced By Chlamydophila Psittaci

Objective: To investigate the role and mechanisms of JAK/STAT3 signal pathway in host cell apoptosis induced by Chlamydophila psittaci infection.Methods: HeLa Cells were infected with C.psittaci with a multiplicity of infection(MOI) of 3. After treated with 1.5 mol/L Staurosporine for 4h, the apoptosis of cells were measured by DNA ladder and fluorescent hoechst 32258 staining. The levels of mRNA transcript and proteins expression of JAK1, JAK2 and STAT3 were detected by RT-qPCR and western blot respectively.After the specific inhibitor of JAK/STAT3 signal pathway AG490 was added, the apoptosis of C. psittaci infected cells were measured by FITC-Annexin V/PI Flow cytometric assay and fluorescent hoechst32258 staining. Then the protein expression levels of Bcl-2, Bax,Caspase-3, Caspase-7, Caspase-9 and PARP were detected by western blot.Results: Compared with the control group, the DNA bands were obviously weakened, and there were no ladder bands in cells infected with C.psittaci with or without Staurosporine treatment. And after fluorescent hoechst 32258 staining, apoptotic bodies were barely detected in infected cells, which indicated that C.psittaci are profoundly resistant to diverse apoptotic stimuli. The mRNA level of STAT3 was significantly up-regulated at 6h and 12 h, JAK1 at 4h and JAK2 at 2h post C.psittaci infection. The total and phosphorylated STAT3 and JAK1 were also significantly up-regulated in HeLa cells infected with C.psittaci.The results of Flow cytometric assay and fluorescent hoechst 32258 staining showed that the number of apoptosis cells in AG490 treated C.psittaci infected cells was much higher than that in AG490 un-treated infected cells. And the ration of Bax & Bcl-2, the total and cleaved Caspase-3, Caspase-7, Caspase-9 and PARP in AG490 treated C.psittaci infected cells was much lower than that in AG490 treated un-infected HeLa cells, but significantly higher than that in AG490 un-treated infected cells.Conclusions: 1, C. psittaci antiapoptotic activity involves activation of the JAK/STAT3 signaling pathway.2, JAK/STAT3 signal pathway may regulate C.psittaci anti-apoptotic activity via down-regulating the ratio of Bax&Bcl-2 and the activation of Caspase-3, Caspase-7, Caspase-9 and PARP.