Circulating inflammatory cytokines and the risk of sepsis: a bidirectional mendelian randomization analysis

Sepsis is a life-threatening condition that is characterized by multiorgan dysfunction and caused by dysregulated cytokine networks, which are closely associated with sepsis progression and outcomes. However, currently available treatment strategies that target cytokines have failed. Thus, this study aimed to investigate the interplay between genetically predicted circulating concentrations of cytokines and the outcomes of sepsis and to identify potential targets for sepsis treatment.

Data related to 35 circulating cytokines in 31,112 individuals (including 11,643 patients with sepsis) were included in genome-wide association studies (GWASs) from the UK Biobank and FinnGen consortia. A bidirectional two-sample Mendelian randomization (MR) analysis was performed using single nucleotide polymorphisms (SNPs) to evaluate the causal effects of circulating cytokines on sepsis outcomes and other cytokines.

A total of 35 inflammatory cytokine genes were identified in the GWASs, and 11 cytokines, including Interleukin-1 receptor antagonist (IL-1ra), macrophage inflammatory protein 1 (MIP1α), IL-16, et al., were associated with sepsis outcome pairs according to the selection criteria of the cis-pQTL instrument. Multiple MR methods verified that genetically predicted high circulating levels of IL-1ra or MIP1α were negatively correlated with genetic susceptibility to risk of sepsis, including sepsis (28-day mortality), septicaemia, streptococcal and pneumonia-derived septicaemia (P ≤ 0.01). Furthermore, genetic susceptibility of sepsis outcomes except sepsis (28-day mortality) markedly associated with the circulating levels of five cytokines, including active plasminogen activator inhibitor (PAI), interleukin 7 (IL-7), tumour necrosis factor alpha (TNF-α), beta nerve growth factor (NGF-β), hepatic growth factor (HGF) (P < 0.05). Finally, we observed that the causal interaction network between MIP1α or IL-1ra and other cytokines (P < 0.05).

This comprehensive MR analysis provides insights into the potential causal mechanisms that link key cytokines, particularly MIP1α, with risk of sepsis, and the findings suggest that targeting MIP1α may be a potential strategy for preventing sepsis.