[Protective effects of recombinant trichinella spiralis-53 000 protein combining with imipenem on polymicrobial septic mice].

OBJECTIVE

To observe the protective effects of recombinant trichinella spiralis-53 000 protein (rTsP53 protein) combining with imipenem (IMP) on septic mice and their underlying mechanisms. .

METHODS

Male BALB/c mice were divided into five groups randomly. Cecal ligature and puncture (CLP) operation was used for building polymicrobial septic model (CLP group).Mice in sham group were only subjected to laparoromy and abdominal closure without cecum ligation. At 6 hours post CLP, mice in CLP+IMP,CLP+rTsP53,and CLP+IMP+rTsP53 groups were injected intraperitoneally with IMP (20 mg/kg) + 0.1 mL albumin,rTsP53 protein (6 mg/kg) + 0.1 mL normal saline (NS),IMP (20 mg/kg) + rTsP53 protein (6 mg/kg) respectively, mice in sham group and CLP group were injected intraperitoneally with 0.1 mL albumin + 0.1 mL NS, then these therapies were repeated every 12 hours until the experiment ended. Twenty mice were extracted randomly from each group for surveying 72-hour survival rate.At 0,6,12,24,36,48,72 hours post CLP,3 mice in each group were collected and cytokines in serum were tested by enzyme-linked immunosorbent assay (ELISA).Whole blood was cultured, then the numbers of bacteria colony-forming units (CFU) were counted. Mice were executed at 24 hours, then the epithelial cells ultrastructures of the mice small intestinal mucosa were observed by transmission electron microscope (TEM).

RESULTS

① Compared with CLP,CLP+IMP or CLP+rTsP53 group,72-hour survival rate of the mice in CLP+IMP+rTsP53 group was significantly elevated (85％ vs.20％,55％,25％,all P ＜ 0.05).② No bacteria was found in cultured whole blood of mice in sham group at all time-points. At 6 hours post CLP operation, the number of bacterial clone of all experimental groups was rose significantly. The changed trend of bacterial number in CLP group was rising at the beginning, then declining, and the bacterial number reached the peak at 24 hours (× 106 cfu/L:12.74± 2.33).From 12 hours, the bacterial numbers of CLP+rTsP53 group were higher than those of CLP group, and reached the peak at 36 hours (× 106 cfu/L:22.13 ± 4.28),then declined gradually. The bacterial numbers of CLP+IMP and CLP+IMP+rTsP53 groups reached the peak at 6 hours (× 106 cfu/L:5.72 ± 0.50,5.49 ± 0.59),then declined. They were significantly less than those of CLP group from 12 hours.③ From 6 hours after CLP,the cytokines levels of mice in all experimental groups were higher than those in sham group. The tumor necrosis factor-α (TNF-α) levels in CLP group showed a trend of elevation in the beginning, and decrease thereafter. It reached the peak at 36 hours (ng/L:1 422.67 ±72.19).The TNF-α level peak time of CLP+IMP group,CLP+rTsP53 group,CLP+IMP+rTsP53 group was advanced to 12 hours post CLP (ng/L:1376.29±44.67,929.36±40.42,809.61±22.61).At 24 hours post CLP, the interleukin-6 (IL-6) level of CLP group and CLP+IMP group reached the peak (ng/L:215.39 ± 16.05,191.63 ± 8.99).The peak time of CLP+rTsP53 group and CLP+IMP+rTsP53 was advanced to 12 hours post CLP (ng/L:113.01 ± 12.11,92.43±6.11).The level of IL-4,IL-10 in CLP group raised gradually to the highest at 72 hours (ng/L:366.25 ±24.25,923.14±30.36).The IL-4 and IL-10 levels of CLP+IMP group raised to their maximum value at 12 hours and 24 hours respectively (ng/L:281.47±16.33,555.67±13.57),then declined. The IL-4 and IL-10 levels of CLP+rTsP53 group and CLP+IMP+rTsP53 group gradually ascended their peak value at 72 hours [IL-4 (ng/L) was 453.14±18.53,410.43 ± 15.75,IL-10 (ng/L) was 1 185.61 ± 16.74,1 006.77 ± 36.91,respectively].From 12 hours, the pro-inflammatory cytokines levels of CLP+IMP+rTsP53 group were significantly less than those of CLP+IMP group and CLP+rTsP53 group.④ At 24 hours post CLP, compared with mice in CLP,CLP+IMP, or CLP+rTsP53 group, mice in CLP+IMP+rTsP53 group had slighter ultra structure injuries in the microvilli, cell junction and mitochondria of small intestinal mucosa epithelial cells.

CONCLUSIONS

The levels of pro-inflammatory cytokines were reduced and the levels of anti-inflammatory eytokines were escalated by intervention of rTsP53 protein combining with IMP boosted in polymierobial septic mice serum, and enhanced the survival rate of the mice. The injection of rTsP53 protein alone had no protective effects on polymicrobial septic mice,because the amount of bacteria in mice blood was augmented