IL-10 and toll-like receptor-4 polymorphisms and the in vivo and ex vivo response to endotoxin

To determine to what extent lipopolysaccharide-induced IL-10 production capacity is determined by polymorphisms in toll-like receptor-4 (TLR4) and the IL-10 promoter region, we measured in vivo IL-10 and TNF-α production in patients undergoing elective cardiopulmonary bypass surgery, a major surgical trauma associated with ischemia-reperfusion injury that triggers an endotoxemia and profound inflammatory response in most patients. Ex vivo the IL-10 and TNF-α production was measured in a whole blood stimulation assay, using 3 LPS concentrations. Positive correlations were found between TNF-α and IL-10 production ex vivo, upon stimulation with each of the LPS concentrations. Also, the estimated TNF-α and IL-10 EC50, and TNF-αmax and IL-10max were positively correlated (r = 0.203; p = 0.023 and r = 0.287; p = 0.001, respectively), indicating that these parameters describing LPS sensitivity and maximal production capacity, respectively, can be estimated by measuring either TNF-α or IL-10. Interleukin-10 concentrations in patients experiencing endotoxemia in vivo negatively correlated with the IL-10 levels produced upon stimulation with 1000 ng/mL LPS as well as the estimated IL-10max ex vivo. In vivo, a positive correlation between the TNF-α concentration at time-point 2 and the IL-10 concentration at time-point 3 was found, consistent with an important contribution of the magnitude of TNF-α release upon the subsequent IL-10 production. Carriers of the IL-10 promoter −1330G, −1082A, −819T, −592A (GATA) haplotype had lower IL-10 production ex vivo upon stimulation with 10 and 100 ng/mL LPS and higher EC50 values (the estimated LPS concentration at which 50% of the maximal IL-10 response is reached) as compared to carriers of the other haplotypes combined, indicating decreased LPS sensitivity ex vivo. These individuals did not differ from the others in interleukin-10 production capacity upon stimulation with a high LPS concentration (i.e., 1000 ng/mL) and the estimated IL-10max values, were similar, indicating unimpaired maximal IL-10 production capacity ex vivo. Carriers of the IL-10 promoter AGCC haplotype had lower EC50 values as compared to carriers of the other haplotypes combined, indicating increased LPS sensitivity ex vivo. In accordance with this finding, carriers of the AGCC haplotype had higher circulating IL-10 levels in vivo. The common TLR4 polymorphisms (Asp299Gly and Thr399Ile) were associated with slightly higher IL-10 production capacity ex vivo and in vivo, however, this was not statistically significant. Our results indicate that polymorphisms in the proximal IL-10 promoter region are associated with in vivo and ex vivo LPS sensitivity. The contribution to the inter-individual variation, however, is limited since the variation between individuals in LPS sensitivity and IL-10 production capacity can only partly be attributed to these IL-10 promoter polymorphisms.