Genetic contribution of suppressor of cytokine signalling polymorphisms to the susceptibility to infection after traumatic injury

Abstract

Suppressor of cytokine signalling (SOCS) proteins are crucial negative regulators in many signalling pathways and are implicated in the pathogenesis of infectious diseases. The purpose of this study was to uncover possible associations of common polymorphisms within SOCS genes with infectious outcomes after traumatic injury. A total of 1087 trauma patients (Chongqing cohort 806 and Yunnan cohort 281) were recruited and followed-up for the development of infectious outcomes, such as sepsis and multiple organ dysfunction syndrome (MODS). Twelve selected single nucleotide polymorphisms (SNPs) were screened by pyrosequencing to determine their genotypes and associations with infectious complications. Among the 12 selected SNPs, only the cytokine-inducible Src homology (SH2) domain protein (CISH) promoter rs414171 polymorphism was found consistently to be associated statistically with the incidence of sepsis and MOD score in the two cohorts, despite analysing the SNPs independently or in combination. Further, patients with a T allele had significantly lower CISH expression and lower production of tumour necrosis factor (TNF)-α, but higher production of interleukin (IL)-10. Luciferase assay confirmed that the A→T variant in the rs414171 polymorphism inhibited the transcriptional activities of the CISH gene significantly. The CISH rs414171 polymorphism is associated significantly with susceptibility to sepsis and MODS in traumatic patients, which might prove to be a novel biomarker for indicating risk of infectious outcomes in critically injured patients.

Keywords: MODS; SOCS proteins; polymorphisms; sepsis; trauma.

© 2018 British Society for Immunology.

Figures

Figure 1

Effect of the rs414171 polymorphism on cytokine‐inducible Src homology (SH2) domain protein (CISH) promoter activity. Relative luciferase activity (RLA) was measured in human embryonic kidney cells (HEK)293T cells transfected with rs414171‐237AA or TT constructed plasmid. Luciferase activity was normalized for transfection efficiency by using a control plasmid, cytomegalovirus (CMV) immediate early enhancer/promoter region (pRL‐CMV)]. The A→T variation significantly attenuated promoter activities (TT versus AA: P = 0·001, Student’s t‐test).

Figure 2

Association of the rs414171 polymorphism with lipopolysaccharide (LPS)‐induced expression of cytokine‐inducible Src homology (SH2) domain protein (CISH) in the healthy cohort. Expression levels of CISH mRNA in human peripheral blood leucocytes with different genotypes in the rs414171 polymorphism were normalized to glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) expression, shown as the mean and standard deviation. Significant differences were observed among AA, AT and TT genotypes under LPS stimulation (TT+AT versus AA: P = 0·033, Student’s t‐test).

Figure 3

Association of the rs414171 polymorphism on lipopolysaccharide (LPS)‐induced cytokine production by peripheral blood leucocytes. The whole‐blood samples collected immediately from trauma patients were incubated with 100 ng/ml LPS (Escherichia coli O55:B5) at 37°C for 4 h. The levels of interleukin (IL)‐10 (a) and tumour necrosis factor (TNF)‐α (b) in the plasma were assayed by a sandwich enzyme‐linked immunosorbent assay. Student’s t‐test was used to assess statistical significance. #Dominant effect (TT + AT versus AA), #P = 0·031, *recessive effect (TT versus AT + AA), *P = 0·013.