MMP-8 genotypes influence the inflammatory response in human endotoxemia.

Clinical studies have reported associations between MMP-8 genotypes and clinical outcomes without exploring underlying mechanisms. This study aims to understand the influence of the rs1940475 SNP on downstream chemokine and cytokine response in human endotoxemia. Rs1940475 was genotyped in 44 healthy Caucasian males, who were challenged with an intravenous bolus of 2 ng/kg lipopolysaccharide (LPS). Plasma levels of tumor necrosis factor (TNF), interleukin (IL)-6, IL-8, and macrophage inflammatory protein (MIP)-1α were measured at baseline and 2, 4, 6, and 24 h after LPS infusion with high-sensitivity enzyme immunoassays. Peak TNF levels at 2 h after LPS infusion were significantly higher in subjects with AA genotype compared to subjects with AG or GG genotypes (185 pg/mL [IQR, 154-234] vs. 94 pg/mL [IQR, 65-125] vs. 107 pg/mL [IQR, 80-241], respectively; p = 0.03 between groups). Peak IL-6 levels were trend-wise higher in subjects with AA genotype compared to those with AG or GG genotypes (566 pg/mL [IQR, 294-644] vs. 278 pg/mL [IQR, 184-539] and 329 pg/mL [IQR, 240-492], respectively; p = 0.15 between groups). In contrast, peak MIP-1α at 2 h was highest in GG genotype carriers compared to those with AG or AA genotypes (602 pg/mL [IQR, 449-727] vs. 389 pg/mL [IQR, 375-490] and 510 pg/mL [425-813], respectively; p < 0.03 between groups). AA genotype carriers had highest peak TNF and IL-6 levels after LPS challenge, whereas peak MIP-1α levels were highest in GG carriers. This indicates that the rs1940475 SNP modifies the host response to inflammatory stimuli, which may in part explain previously shown associations with clinical outcomes.

Continuous thrombin infusion leads to a bleeding phenotype in sheep.

BACKGROUND: In addition to a recognized role in the coagulation cascade and haemostasis, thrombin is known to have multiple functions. We aimed to establish an ovine model to study thrombin effects in vivo. METHODS: Thrombin (0.0004-0.42 IU/kg/min) was continuously infused in Austrian Mountain Sheep over five hours in the dose escalation study (n=5 animals; 15 experiments). In the dose verification study animals received 0.42 IU/kg/min of thrombin vs. saline solution in a cross-over design (n=3 animals; 7 experiments). RESULTS: Thrombin at an infusion rate of 0.42 IU/kg/min decreased fibrinogen levels by 75% (p<0.001) and increased degradation products of the fibrinogen beta-chain as shown in a proteomic analysis. Thrombin decreased platelet counts by 36% (p=0.006), prolonged thrombin time by 70% (p=0.012) and activated partial thromboplastin time by 32%. Interestingly, thrombin infusion significantly increased the activity of coagulation factors V and X (p<0.05) and decreased the activity of the coagulation factors VIII and XIII (p<0.05). Accordingly, thrombin displayed predominantly anti-coagulant and anti-platelet effects: 1) thrombin prolonged clotting time/clot formation time 7-fold (p=0.019) and induced a 65% decrease in maximal clot firmness (p<0.001); 2) thrombin reduced collagen- induced platelet aggregation by 85% and prolonged collagen/adenosine diphosphate closure time 3-fold; and 3) thrombin caused lung haemorrhage but not thromboembolism. CONCLUSION: Protracted intravenous infusion of thrombin over a period of five hours offers a new experimental model to study thrombin effects in a large animal species.