Evaluation of anti-inflammatory and anti-adhesive effects of heparins in human endotoxemia

Sepsis results from a generalized inflammatory and pro-coagulant response to an infectious agent. Adhesion molecules and cytokines are of utmost importance for the development of early symptoms as well as the late sequela of endotoxemia.

Heparin is widely known as an antithrombotic agent. But beyond its well-understood anticoagulant activity heparin is able to influence immunologic responses. In addition, in vitro experiments and animal studies have shown that heparin inhibits P-selectin and L-selectin mediated adhesion.

Intravenous infusion of LPS into human volunteers provides a standardized model to study activation of inflammatory, pro-coagulant and adhesive cascades in humans.

It was recently demonstrated that heparin blunts endotoxin-induced coagulation activation in a human LPS-model. As pro-coagulant and inflammatory processes are intricately linked in sepsis, we used this LPS-model to elucidate whether clinically applied doses of unfractionated (UFH) or low-molecular weight heparin (LMWH) are able to affect early inflammatory responses in low grade human endotoxemia.

The trial was a randomized, double-blind, placebo-controlled study in three parallel groups of 30 healthy male subjects. A bolus of LPS 2 ng/kg was given i.v. to all subjects. Ten minutes later, study subjects received either 80 IU/kg heparin followed by a continuous infusion of 18 IU/kg/hour for 6 hours, 40 IU/kg dalteparin, followed by a continuous infusion of 15 IU/kg/hour for 6 hours, or placebo.

Following LPS infusion, TNF-α levels increased > 350-fold in the LMWH and placebo groups but only 150-fold in the UFH group (P < 0.01 vs LMWH group). Yet, IL-6, IL-8 and CRP levels were not different between treatment groups.

Plasma levels of sE-selectin increased by approximately 500% and sP-selectin levels doubled 6 hours after LPS infusion in all groups. Similarly, platelet leukocyte aggregates increased in all groups (P > 0.05 between treatments).

The changes in differential and absolute blood counts were not modified by any treatment. As expected, CD11b expression increased by 100% while L-selectin decreased by 41% 6 hours after LPS-infusion. Interestingly, both heparins (in particular UFH) decreased L-selectin down-modulation as compared to placebo (P < 0.01).

Heparin displayed little anti-inflammatory actions in low grade endotoxemia as measured by cytokine levels or endothelial/platelet activation markers. The heparin induced mitigation of L-selectin down-regulation on neutrophils is in good agreement with the blockade of L-selectin function observed in vitro and deserves further investigation.