Mechanism underlying the anti-apoptotic activity of pORF5 plasmid protein in Chlamydia trachomatis via high-mobility group box 1 protein: a preliminary study / 中华皮肤科杂志

ABSTRACT

Objective To explore the molecular mechanism underlying the anti-apoptotic activity of pORF5 plasmid protein of Chlamydia trachomatis,so as to provide an experimental basis for further clarifying the pathogenesis of Chlamydia trachomatis.Methods HeLa cells were divided into two groups:carbonyl cyanide m-chlorophenyl hydrazone (CCCP,an apoptosis inducer) group was stimulated by CCCP for 30 minutes,and pORF5 + CCCP group was pretreated with pORF5 plasmid protein for 18 hours followed by CCCP for 30 minutes.Then,Western blot analysis was performed to determine the expression of apoptosisrelated proteins Bcl-2,Bax and caspase-3,JC-1 fluorescent probe was used to detect changes in the mitochondrial membrane potential in HeLa cells,and cytochrome c release from mitochondria was analyzed by indirect immunofluorescence assay.To analyze whether high-mobility group box 1 (HMGB1) protein participated in the anti-apoptotic role of pORF5 plasmid protein,HMGB 1 shRNA and control RNA were separately transfected into the HeLa cells,which were then stimulated by pORF5 plasmid protein and CCCP.Then,the protein expression of Bcl-2,Bax,activated caspase-3 was determined,and cytochrome c release was analyzed.Data were compared between two groups by using paired t test.Results pORF5 plasmid protein could antagonize the CCCP-induced decrease of mitochondrial membrane potential,and the red/green fluorescence intensity ratio was significantly lower in the CCCP group (0.4 ± 0.1) than in the pORF5 + CCCP group (1.7 ± 0.3;t =6.95,P ＜ 0.01).The protein expression of Bcl-2 in the HeLa cells in the pORF5 + CCCP group was 5.3 ± 0.6 times more than that in the CCCP group (t =8.62,P ＜ 0.01),while the protein expression of Bax and activated caspase-3 in the pORF5 + CCCP group significantly decreased by 79％ ± 10％ (t =9.23,P ＜ 0.01) and 75％ ± 8％ (t =4.26,P ＜ 0.05) respectively compared with the CCCP group.Compared with the control RNA transfection group,the HMGB1 shRNA transfection group showed significantly decreased mitochondrial membrane potential in the HeLa cells (t =11.23,P ＜ 0.01),increased cytochrome c release,decreased Bcl-2 expresson (t =7.19,P ＜ 0.05) and increased Bax expression (t =13.06,P ＜ 0.01) after stimulation with pORF5 and CCCP.Conclusion Chlamydia trachomatis plasmid protein pORF5 plays an anti-apoptosis role by blocking the mitochondrial apoptotic pathway through HMGB1 protein.