Endothelial Dysfunction in Murine Model of Systemic Sclerosis: Tight-skin Mice 1

We conducted this study to analyze endothelial cell function within intact thoracic aorta of the systemic sclerosis murine model, the heterozygous tight-skin mice 1: (i) assessing the distribution and activation intensity of endothelial cells, responsive to endothelium-dependent vasodilators (acetylcholine, adenosine triphosphate, bradykinin, and substance P) and Iloprost, using laser line confocal microscopy in combination with two Ca²⁺ fluorescent dyes; (ii) evaluating en-dothelium-dependent vasodilator- and Iloprostinduced relaxation, using isometric tension measurement; and (iii) investigating the role of nitric oxide in mediating relaxation to acetylcholine and adenosine triphosphate. The number of activated endothelial cells was significantly lower in heterozygous tight-skin mice 1, compared with controls, for adenosine triphosphate and Iloprost. Maximal increase of Ca²⁺ fluorescence intensity ratio in activated endothelial cells was decreased for adenosine triphosphate, bradykinin, and Iloprost, in heterozygous tight-skin mice 1. Adenosine triphosphate- and Iloprost-mediated aortic relaxation was further impaired in heterozygous tight-skin mice 1. Finally, aortic relaxation to acetylcholine and adenosine triphosphate was markedly decreased by nitric oxide synthase inhibitor in heterozygous tight-skin mice 1. This study suggests that endothelial cell receptors for endothelium-dependent vasodilators and Iloprost may not be homogeneously distributed or continuously expressed in thoracic aorta of heterozygous tight-skin mice 1, resulting in endothelium-dependent vasodilatation dysfunction. Moreover, because endothelium-dependent relaxation was highly dependent on nitric oxide release in heterozygous tight-skin mice 1, endothelium-dependent relaxation may differ from that of controls by increased production of nitric oxide. In turn, in heterozygous tight-skin mice 1, the resulting elevated nitric oxide levels may contribute to nitric oxide-mediated free radical endothelial cytotoxicity, although endothelium impairment may be related to other factors, particularly: Fbn-1 gene mutation and transforming growth factor-β.