Abstract
BACKGROUND: Previous studies have identified critical roles of IL-27 in the pathological mechanisms of sepsis, and blockade of IL-27 may be a promising alternative therapy for sepsis. The purpose of this study was to evaluate the clinical relevance of IL-27 genetic polymorphisms in sepsis and to further characterize their effect on IL-27 expression and inflammatory processes following sepsis. METHODS: A total of 885 septic patients and 1101 healthy controls were enrolled and genotyped for IL-27 genetic variants (rs153109/-964A > G and rs17855750/2905 T > G). Quantitative real-time PCR and enzyme-linked immunosorbent assays were performed to detect IL-27 expression and cytokine production. The effect of the rs153109 polymorphism on IL-27 promoter activity was evaluated using a luciferase reporter assay, and THP-1 cell apoptosis was calculated using an annexin V apoptosis assay. RESULTS: No significant differences in the genotype/allele frequencies were observed between patients with sepsis and healthy controls, suggesting that these two IL-27 polymorphisms may not influence susceptibility to sepsis. The -964AA genotype was overrepresented in patients with severe sepsis/septic shock relative to patients with the sepsis subtype, and the A allele was significantly associated with 28-mortality in sepsis. Patients carrying the -964AA genotype exhibited significantly higher expression levels of IL-27 than the GA/GG genotype carriers. The results of an in vitro (lipopolysaccharide (LPS))-stimulated experiment showed that this sepsis-associated high-risk AA genotype significantly increased IL-27 levels and enhanced TNF-α and IL-1β production in the peripheral blood mononuclear cells (PBMCs) upon exposure to LPS in vitro. Furthermore, luciferase reporter assays indicated that the high-risk -964A allele resulted in increased promoter activities compared to the non-risk allele in THP-1 and 293 T cells. Additionally, IL-27 treatment significantly enhanced TNF-α and IL-6 secretion and apoptosis of THP-1 cells upon LPS stimulation. CONCLUSIONS: These results provided evidence that the IL-27 -964A > G polymorphism functionally enhanced IL-27 expression and promoted sepsis-induced inflammatory responses, which ultimately resulted in promoting the progression of sepsis and poor prognosis.