Genetic variability and outcome in the critically ill: avoiding SNP judgments

Tumor necrosis factor -308 polymorphism (rs1800629) is associated with mortality and ventilator duration in 1057 Caucasian patients

PURPOSE

Management of sepsis in critically ill patients remains difficult and requires prolonged intensive care. Genetic testing has been proposed as a strategy to identify patients at risk for adverse outcome of critical illnesses. Therefore, we wished to determine the influence of heredity on predisposition to poor outcome and on duration of ventilator support of intensive care unit (ICU) patients.

METHODS

A study was conducted from July 2001 to December 2005 in heterogeneous population of patients from 12 US ICUs represented by the Genetic Predisposition to Severe Sepsis (GenPSS) archive. In 1057 Caucasian critically ill patients with SAPS II probability of survival of >0.2 in the US, six functional single nucleotide polymorphisms in relation to inflammatory cytokines and innate immunity (rs1800629, rs16944, rs1800795, rs1800871, rs2569190, and rs909253) were evaluated in terms of mortality and ventilator free days.

RESULTS

The AA homozygote of TNF(-308) (rs1800629) was most over-represented in the deceased patient group (P=0.015 with recessive model). The carriage of the TNF(-308)*AA genotype showed significantly higher odds ratio of 2.67(1.29-5.55) (P=0.008) after adjustment with the covariates. However, the presence of 1, 2, or 3 acute organ dysfunctions was larger prognostic factors for the adverse outcome (OR(95%CI)=2.98(2.00-4.45), 4.01(2.07-7.77), or 19.95(4.99-79.72), P<0.001 for all). Kaplan-Mayer plot on ventilator duration of TNF(-308)*AA patient significantly diverged from that of TNF(-308)*(GG+GA) ((AA v GG+GA), Adjusted HR(95%CI)=2.53(1.11-5.79) with Cox regression, P=0.028).

CONCLUSIONS

TNF(-308)*AA is significantly associated with susceptibility to adverse outcome and to longer ventilator duration. Therefore, heredity likely affects both predisposition to ICU prognosis as well as the resource utilization.

Lipopolysaccharides up-regulate Kir6.1/SUR2B channel expression and enhance vascular KATP channel activity via NF-kappaB-dependent signaling

Sepsis is a severe medical condition causing a large number of deaths worldwide. Recent studies indicate that the septic susceptibility is attributable to the vascular ATP-sensitive K(+) (K(ATP)) channel. However, the mechanisms underlying the channel modulation in sepsis are still unclear. Here we show evidence for the modulation of vascular K(ATP) channel by septic pathogen lipopolysaccharides (LPS). In isolated mesenteric arterial rings, phenylephrine (PE) produced concentration-dependent vasoconstriction that was relaxed by pinacidil, a selective K(ATP) channel opener. The PE response was disrupted with a LPS treatment. In acutely dissociated aortic smooth myocytes the LPS treatment augmented K(ATP) channel activity, and hyperpolarized the cells. Quantitative PCR analysis showed that LPS raised Kir6.1 and SUR2B transcripts in a concentration-dependent manner, which was suppressed by transcriptional inhibition. Consistently, the same LPS treatment did not affect Kir6.1/SUR2B channels in a heterologous expression system. The LPS effect on Kir6.1 and SUR2B expression was abolished in the presence of NF-kappaB inhibitors. Several other Toll-like receptor ligands also stimulated Kir6.1 and SUR2B expression to a similar degree as LPS. Thus, the effect of LPS on vasodilation involves up-regulation of K(ATP) channel expression, in which the NF-kappaB-dependent signaling plays an important role.