Activation of melanocortin 4 receptors reduces the inflammatory response and prevents apoptosis induced by lipopolysaccharide and interferon-γ in astrocytes

α-MSH exerts an immunomodulatory action in the brain and may play a neuroprotective role acting through melanocortin 4 receptors (MC4Rs). In the present study, we show that MC4Rs are constitutively expressed in astrocytes as determined by immunocytochemistry, RT-PCR, and Western blot analysis. α-MSH (5 μM) reduced the nitric oxide production and the expression of inducible nitric oxide synthase (iNOS) induced by bacterial lipopolysaccharide (LPS, 1 μg/ml) plus interferon-γ (IFN-γ, 50 ng/ml) in cultured astrocytes after 24 h. α-MSH also attenuated the stimulatory effect of LPS/IFN-γ on prostaglandin E2 release and cyclooxygenase-2 (COX-2) expression. Treatment with HS024, a selective MC4R antagonist, blocked the antiinflammatory effects of α-MSH, suggesting a MC4R-mediated mechanism in the action of this melanocortin. In astrocytes, LPS/IFN-γ treatment reduced cell viability, increased the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells and activated caspase-3. α-MSH prevented these apoptotic events, and this cytoprotective effect was abolished by HS024. LPS/IFN-γ decreased Bcl-2, whereas it increased Bax protein expression in astrocytes, thus increasing the Bax/Bcl-2 ratio. α-MSH produced a shift in Bax/Bcl-2 ratio toward astrocyte survival because it increased Bcl-2 expression and also prevented the effect of LPS/IFN-γ on Bax and Bcl-2 expression. In summary, these findings suggest that α-MSH, through MC4R activation, attenuates LPS/IFN-γ-induced inflammation by decreasing iNOS and COX-2 expression and prevents LPS/ IFN-γ-induced apoptosis of astrocytes by modulating the expression of proteins of the Bcl-2 family.Fil: Caruso, Carla Mariana. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Durand, Daniela Elizabeth. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schiöth, Helgi Birgir. Uppsala Universitet; SueciaFil: Rey, Rodolfo Alberto. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; ArgentinaFil: Seilicovich, Adriana. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lasaga, Mercedes Isabel. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin