title: Regulation of central melanocortin signaling by interleukin-1 beta.
abstract: Anorexia and involuntary weight loss are common and debilitating complications of a number of chronic diseases and inflammatory states. Proinflammatory cytokines, including IL-1 beta, are hypothesized to mediate these responses through direct actions on the central nervous system. However, the neural circuits through which proinflammatory cytokines regulate food intake and energy balance remain to be characterized. Here we report that IL-1 beta activates the central melanocortin system, a key neuronal circuit in the regulation of energy homeostasis. Proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC) were found to express the type I IL-1 receptor. Intracerebroventricular injection of IL-1 beta induced the expression of Fos protein in ARC POMC neurons but not in POMC neurons in the commissural nucleus of the tractus solitarius. We further show that IL-1 beta increases the frequency of action potentials of ARC POMC neurons and stimulates the release of alpha-MSH from hypothalamic explants in a dose-dependent fashion. Collectively, our data support a model in which IL-1 beta increases central melanocortin signaling by activating a subpopulation of hypothalamic POMC neurons and stimulating their release of alpha-MSH.
authors.affiliation: Center for the Study of Weight Regulation and Associated Disorders, Oregon Health and Science University, 3181 Southwest Sam Jackson Park Road, Portland, Oregon 97239, USA.
authors.forename: Jarrad M
authors.initials: JM
authors.lastname: Scarlett
authors.forename: Erin E
authors.initials: EE
authors.lastname: Jobst
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: Enriori
authors.forename: Darren D
authors.initials: DD
authors.lastname: Bowe
authors.forename: Ayesha K
authors.initials: AK
authors.lastname: Batra
authors.forename: Wilmon F
authors.initials: WF
authors.lastname: Grant
authors.forename: Michael A
authors.initials: MA
authors.lastname: Cowley
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Marks
mesh_terms: D000818:Animals; D000855:Anorexia / Q000503:physiopathology; D002452:Cell Count; D016207:Cytokines / Q000502:physiology; D005123:Eye / Q000166:cytology; D017930:Genes, Reporter; D007249:Inflammation / Q000503:physiopathology; D053583:Interleukin-1beta / Q000502:physiology*; D008297:Male; D053486:Melanocortins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011333:Pro-Opiomelanocortin / Q000235:genetics; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology*; D015431:Weight Loss / Q000502:physiology
chemical_list: D016207:Cytokines; D053583:Interleukin-1beta; D053486:Melanocortins; D016760:Proto-Oncogene Proteins c-fos; D011333:Pro-Opiomelanocortin