Immunomodulatory effects of fosfomycin in experimental human endotoxemia.

To evaluate the effect of fosfomycin on proinflammatory cytokines, a bolus of 2 ng of bacterial lipopolysaccharide/kg of body weight was injected intravenously into healthy volunteers. After 2 h, subjects received 8 g of fosfomycin or placebo in a randomized crossover study design. The resulting concentrations of tumor necrosis factor alpha, interleukin-1beta (IL-1beta), and IL-6 expressed as protein and mRNA levels were almost identical with and without fosfomycin.

The tumor necrosis factor alpha -308 G/A polymorphism does not influence inflammation and coagulation response in human endotoxemia.

Tumor necrosis factor (TNF)-alpha plays a major role in the immune system. Release of proinflammatory cytokines, such as TNF-alpha and interleukin 6, by macrophages and other cells occurs in response to bacterial products. It has been reported that the TNF-alpha -308 G/A polymorphism in the TNF-alpha gene determines basal TNF-alpha levels. We hypothesized that it may also be associated with the degree of inflammatory response in a well-standardized model of systemic inflammation. Eighty-seven young men (age range, 19-35 years) received 2 ng/kg i.v. endotoxin (lipopolysaccharide [LPS]). The TNF-alpha promoter genotype was analyzed on a TaqMan genomic analyzer. Inflammation markers (interleukin 6, TNF-alpha), temperature, and coagulation markers (prothrombin fragment F1+2, D-dimer) were measured at 0, 2, 6, and 24 h after LPS infusion. Tumor necrosis factor-alpha plasma concentrations increased from a baseline 1.3 ng/L (range, 0.8-3.1 ng/L) before LPS infusion to a peak of 57.5 ng/L (range, 10.8-131.4 ng/L) at 2 h after LPS and then decreased continually to 10.8 ng/L (range, 4.7-16.5 ng/L) after 6 h and returned to baseline values after 24 h (1.9 ng/L [range, 1.1-3.9 ng/L]). We observed no significant differences in TNF-alpha baseline levels or in response to LPS after stratification of the data according to TNF-alpha genotype. Basal and peak values of selected inflammatory and coagulation markers were not different between wild-type TNF-alpha -308 individuals (GG) and carriers of the TNF-alpha -308 mutant allele (GA and AA). The TNF-alpha -308 G/A polymorphism does not contribute significantly to the individual variability of systemic TNF-alpha plasma concentrations after endotoxin challenge. Thus, if any, the impact of the TNF-alpha -308 G/A polymorphism on systemic endotoxin-triggered inflammation seems to be limited.

High dose dexamethasone increases circulating P-selectin and von Willebrand factor levels in healthy men.

Although glucocorticoids are widely used in a number of inflammatory disorders associated with endothelial and platelet activation, their effect on the endothelium and platelets in humans remain poorly defined. Hence,we measured changes of a specific endothelial cell marker (von Willebrand factor [vWF]) and of a platelet marker (soluble P-selectin) by infusing therapeutic doses of dexamethasone (0.04 mg/kg and 1.0 mg/kg b.i.d on two days) or placebo into nine healthy men. Venous citrated plasma was obtained before infusion, and at 24 and 48 h. Compared to baseline levels, we found increased levels of vWF at both time points at the higher dose (p=0.011). Plasma levels of sP-selectin rose at 48 h after the high dose (p=0.017). Human umbilical endothelial cells were cultured in the presence or absence of dexamethasone (0, 0.01, 1 microM), to determine the possible mechanism for the increase in vWF. The vWF-mRNA levels as quantified by RT-PCR increased 2-fold (p<0.05), and the vWF-concentrations in cell lysates increased by 38% (p<0.05), whereas the vWF-concentrations in the supernatants were unaffected. In summary, high dose DEXA increases sP-selectin and vWF. The probable underlying mechanism for the latter was a DEXA induced up-regulation of vWF-mRNA transcription. Together, this indicates that high dose glucocorticoids may enhance haemostasis, which could be beneficial under certain conditions, but which may also contribute to adverse vascular events by increasing platelet activation and vWF dependent thrombosis.