Hydroxyethyl starch (130 kD) inhibits Toll-like receptor 4 signaling pathways in rat lungs challenged with lipopolysaccharide

Abstract

Background: A number of studies have shown that hydroxyethyl starch (HES) solutions are able to down-regulate the expression of inflammatory mediators and inhibit neutrophil-mediated tissue injuries when they are used in patients with sepsis or other diseases with severe inflammatory responses. However, our knowledge about the underlying mechanisms is limited. Toll-like receptor 4 (TLR4) signaling has a pivotal role in inflammatory processes. In this study, we examined the possible involvement of TLR4 signaling in the antiinflammatory effects of HES.

Methods: Male Sprague-Dawley rats were exposed to lipopolysaccharide (LPS) (10 mg/kg, IV) and received IV saline (30 mL/kg) or HES 130/0.4 (15 or 30 mL/kg). Six hours after LPS challenge, rats were killed and their lungs harvested. Lung injury was examined by hematoxylin and eosin staining. TLR4 mRNA expression, p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinases 1/2 MAPK activation, and activator protein 1 (AP-1) activity in the lungs were detected with quantitative polymerase chain reaction, Western blotting, and electrophoretic mobility shift assay, respectively.

Results: Compared with saline, HES profoundly attenuated the histological changes induced by LPS in the lungs at both dose levels. Molecular analysis showed that both 15 and 30 mL/kg HES significantly decreased TLR4 mRNA levels and inhibited activation of p38 MAPK and AP-1 in rats challenged with LPS, whereas activation of extracellular signal-regulated kinases 1/2 MAPK was not affected by either dose of HES.

Conclusions: These findings indicate that the beneficial effects of HES 130/0.4 on inflammation are mediated at least in part by inhibiting the TLR4/p38 MAPK/AP-1 pathway in lungs from rats challenged with LPS.