P339	The contraction of smooth muscle cells is inhibited by interleukin-1, as detected in a three dimensional collagen gel assay.
Y.Shi, B.Li, U.Müller-Werdan, K.Werdan, H.Loppnow
Martin-Luther-Universität Halle-Wittenberg, Universitätsklinik und Poliklinik für Innere Medizin III, Halle/Saale, DE.

The contraction of human vascular smooth muscle cells (SMC) is important for maintaining blood pressure in health and disease. In septic patients the blood pressure is reduced, partly due to vasodilatation of the blood vessels. Cytokines can mediate vasodilatory effects. It has been shown previously in animal experiments with rat aortic rings that interleukin-1 (IL-1) can inhibit the phenylephrine-induced contraction of the rat vessels. In order to investigate cytokine effects on contraction of human SMC, as well as patient samples, we established a method to measure the contraction of these cells in a three dimensional collagen system. For this purpose we used cultured saphenous vein or aortic SMC. The cells were incubated in 12-well culture dishes in the presence of collagen and finally formed a three dimensional matrix. The test system was first evaluated by test substances (fetal calf serum (FCS); angiotensin) commonly used in contraction measurements as a standard. Both induced the contraction of the cultured cells in a dose dependent manner, as measured at various time points by the reduction of collagen gel area. FCS was a little more potent in induction of contraction than angiotensin. Among the cytokines tested in the assay, namely IL-1, IL-6, IL-18, cardiotrophin, fractalkine, interferon-gamma, transforming growth factor, tumor necrosis factor-α, and VEGF, only IL-1, TGF and TNF interferred with contraction. Both, IL-1 and TNF inhibited the contraction of the SMC. The inhibition of contraction by IL-1 was reversed by addition of IL-1 receptor antagonist. Endotoxin (LPS) may be causative of vasodilatation in sepsis. However, LPS by itself did not influence contraction of the SMC. In contrast, supernatants of LPS-stimulated whole blood inhibited contraction of SMC as compared to supernatants of unstimulated cells, pointing to the induction of cytokines by LPS. Furthermore, preliminary experiments showed that plasma samples of critically ill patients caused less contraction as compared to samples of healthy persons. These data show the establishment of a 3-D-system capable of measuring the effects of cytokines and patient samples on contraction of human vascular smooth muscle cells.

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