Endothelin-receptor gene-expression in rat endotoxemia

Abstract.

Objective: The reduced vascular response to endothelin-1 has focused interest onto the regulation of the endothelin-receptor subtypes ET_A and ET_B during severe sepsis. Design and setting: Prospective animal trial followed by a controlled cell culture study in the laboratory of the Department of Anesthesiology. Subjects: Male Sprague-Dawley rats weighing 200–250 g, aortic vascular smooth muscle cell line A7r5. Interventions: Rats were injected with lipopolysaccharide to induce severe experimental endotoxemia. ET_A/ET_B receptor gene expression was investigated by specific RNase protection assay, and abundance of tumor necrosis factor α was determined in the lung and kidney. Aortic vascular smooth muscle cells were incubated with the proinflammatory cytokines interleukin-1β, tumor necrosis factor α, and interferon γ or with the nitric oxide donor S-nitroso-N-acetylpenicillamine to investigate the regulation of ET_A receptor gene expression during severe inflammation. Measurements and results: ET_A/ET_B receptor gene expression was markedly downregulated in the lung but was unchanged in the kidney during endotoxemia. ET_A receptor gene expression was downregulated in aortic vascular smooth muscle cells by tumor necrosis factor α but not by interleukin 1β, interferon γ, or nitric oxide. In vivo there seems to be a correlation between the tissue concentration of tumor necrosis factor α and gene expression of ET_A receptors in the lung and kidney. Conclusions: Our data show that sepsis causes downregulation of ET_A receptors at the level of gene expression, and provide correlative evidence that this effect can be mediated by tumor necrosis factor α. This downregulation of ET_A receptors possibly contributes to the attenuated vascular response to endothelin-1 in the pulmonary circulation.