Cytokines and growth factors modify the upregulation of contractile endothelin ETA and ETB receptors in rat cerebral arteries after organ culture

Aim: Experimental cerebral ischaemia and organ culture of cerebral arteries induce an increased endothelin ETB receptormediated contraction. The aim of this study was to examine whether cytokines and growth factors, known to be activated in ischaemia, can influence the expression and function of endothelin receptors after organ culture. Methods: Rat middle cerebral arteries were cultured for 24h at 37 degrees C in humidified 5% CO2 and air in culture medium alone, or with tumour necrosis factor-a (TNF-alpha), interleukin-1 beta (IL-1 beta), platelet-derived growth factor (PDGF), epidermal growth factor (EGF) or basic fibroblast growth factor (bFGF). Concentrationresponse curves were obtained for sarafotoxin 6c (ETB receptor agonist) and endothelin-1 (here ETA receptor agonist, because of ETB receptor desensitization). The receptor mRNA expression was examined by real-time PCR and the protein expression by immunohistochemistry and Western blot. Results: Tumour necrosis factor-a (100ngmL-1) and EGF (20ngmL-1) potentiated the ETB receptormediated contraction (increase in pEC50 without change in Emax). bFGF (10ngmL-1) and IL-1 beta (10ngmL-1) induced an enhanced ETA receptormediated contraction. bFGF (10ngmL-1) significantly increased the ETB mRNA level, and EGF (20ngmL-1) increased the ETA receptor protein. Increased ETB receptor mRNA and protein level also were observed after treatment with IL-1 beta (10ngmL-1). Conclusion: This study shows that TNF-a, IL-1 beta, EGF and bFGF can modify the expression and function of endothelin receptors during organ culture. Because there is similar receptor upregulation in experimental stroke, the effect of cytokines and growth factors on endothelin receptor upregulation is an interesting aspect to study in vivo.