The influence of succinic acid on the apoptosis of polymorphonuclear neutrophil in peripheral blood

Objective To investigate the influence of succinic acid on the apoptosis of polymorphonu- clear neutrophil(PMN)in human peripheral blood,and to explore its role in infection.Methods PMNs were incubated in vitro,and its concentration was adjusted to 5×10~6/mL.Then the ceils were divided into normal control group and 5,10,20,30 mmol/L succinic acid groups according to different concentrations of succinic acid added into the medium.The supernatant of the cultures in each groups were collected to deter- mine the superoxide content.1 mL cell suspension was collected from 5,20 mmol/L succinic acid groups be- fore treatment and at 2,4,6,8,10 post-treatment hours(PTH)for the determination of caspase-3 activity and the apoptosis rate.Results The content of superoxide in 5,10,20,30 mmol/L succinic acid groups (0.437±0.056,0.432±0.024,0.395±0.049,0.386±0.010)was significantly lower than that in control group(0.505±0.028,P0.05).The caspase-3 activity in each group increased along with the in- cubation time,but was in lower concentration in 5mmol/L succinic acid group and in higher concentration in 20 mmol/L succinic acid group when compared with that in control group(P0.05).The apoptosis rate of PMN in control group was(6.1±1.1)% before incubation,and it reached(13.2±2.0)% at 2 PTH,and (27.7±3.7)% at 10 PTH.The apoptosis rate of PMN in 5mmol/L succinic acid group was lower than that in control group except that at 4 PTH(P0.05).On the other hand,the apoptosis rate in 20 mmol/L suc- cinic acid group(during 4-10 PTH)were obviously higher at each time points compared with the control group (P0.05).Conclusion Low concentration of succinic acid can suppress the apoptosis of PMN,while high concentration of suceiuic acid has an opposite effect.It is known that bacteria can produce succinic acid.