Vibrio vulnificus induces acute necrosis of dendritic cells via toll-like receptor 2 and 4 pathways / 中华传染病杂志

ABSTRACT

Objective To explore how Vibrio vulnificus (Vv) invades dendritic cells (DC) and induces acute necrosis of DC via toll-like receptor (TLR) 2 and 4 pathways.Methods Vv 1.1758 strain and DC 2.4 mixed culture model was established,observed the infection rates of DC with optical microscope,the location of Vv and structural changes of DC by transmission electron microscope.The expression levels of TLR2 and TLR4 mRNA were determined by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and tumor necrosis factor-α (TNFα) protein titers were measured by enzyme-linked immunosorbent assay (ELISA).DNA ladder qualitative test was used to detect cell apoptosis,while flow cytometry was used to quantify cell apoptosis and necrosis rates.Statistical analysis was done by chi-square test and one-way ANOVE.Results The infection rates of DC after 0.5,1,2,4 and 6 h of mixed culture were (7.8±0.8) ％,(13.9± 1.1) ％,(34.6±4.9) ％,(77.8± 10.2)％ and (95.8 ± 13.1)％,respectively.Vv was generally located in the internal cell membrane of DC 2.4.After 2 h co-culture,nuclear chromatins of DC became active and intranuclear apoptosis bodies appeared.After 4 h,cytoplasmic vacuoles appeared,chromatin gathered,and cell membranes were seriously damaged.After 6 h,mitochondria was highly swelled and distorted,and cell apoptosis and necrosis occurred.TLR2 and TLR4 mRNA levels reached peak values after co-culture for 0.5 h; TNF-α level began to increase at 1 h (P＜0.05) and reached peak values at 2 h.DNA Ladder electrophoresis presented scouring necrosis after 2 h culture and apoptotic bands appeared between 720 bp and 900 bp after 4 to 5 h culture.Early apoptosis rates of DC after 2,4 and 6 h culture were (3.1±3.8)％,(7.8±4.7)％ and (12.7±8.2)％,and necrosis rates of DC were (16.7±12.5)％,(41.6±25.9)％ and (75.5±33.6)％,higher than that of control group (all P＜0.05).Conclusions Vv infects DC and induce DNA degradation through up-regulated expression of TLR2 and TLR4 and increasing of TNF-α inflammatory mediators.During cell degradation,apoptosis and necrosis coexist,while necrosis is predominant.