Antisense inhibition of secretory and cytosolic phospholipase A2 reduces the mortality in rats with sepsis

OBJECTIVE:Phospholipase A2 has been implicated to play a pivotal role in the pathogenesis of sepsis syndrome. The two major forms of phospholipase A2 isoenzymes, secretory phospholipase A2 and cytosolic phospholipase A2, are overexpressed during sepsis. The objective of this study was to test the hypothesis that inhibition of the overexpressed secretory phospholipase A2 and cytosolic phospholipase A2 during sepsis benefits the disease’s eventual outcome. DESIGN:Short-chain antisense oligonucleotide molecules were designed with the aid of computer software programs, and their in vitro efficacies were assessed in cell culture systems based on inhibition of target protein expression. The in vivo efficacies were determined in intact sepsis rats using 35-day survival rate as a primary efficacy end point. SETTING:Animal research laboratory at a university. SUBJECTS:Male Sprague-Dawley rats (180–200 g). INTERVENTIONS:Sepsis was induced by cecal ligation and puncture. Antibiotics were administered subcutaneously once daily at 12 mg/kg, for 20 days. Oligonucleotides (antisense or mismatch) were administered intravenously once daily at 2 mg/kg to 0.8 mg/kg in a decreasing order, for 20 days. MEASUREMENTS AND MAIN RESULTS:In cell culture systems, 21 of the 105 antisense constructs were found to be efficacious in inhibiting secretory phospholipase A2 IIa and cytosolic phospholipase A2 IVa protein expression. In sepsis rats, antisense oligonucleotides were capable of reducing their target protein expression by 18%–61% in major organs such as liver, heart, and kidney. In animal experiments, sepsis without any treatment (Group 1) had a median survival time of 2 days and a zero (0) percent survival rate at day 14. Sepsis with antibiotic treatment (Group 2) had a median survival time of 6 days and a 35-day survival rate of 28%. Sepsis with cotreatment of antibiotics and antisense oligonucleotides (one against secretory phospholipase A2 IIa and the other against cytosolic phospholipase A2 IVa) (Group 4) increased the median survival time from 6 to 35 days and the 35-day survival rate from 28% to 58.8% as compared with antibiotics alone (Group 4 vs. Group 2; p .05). CONCLUSIONS:The results demonstrate that antisense strategy against secretory phospholipase A2 IIa an