title: ANP inhibits LPS-induced stimulation of rat microglial cells by suppressing NF-kappaB and AP-1 activations.
abstract: Atrial natriuretic peptide (ANP) contributes to the inhibition of such causes of inflammation as the lipopolysaccharide (LPS)-induced productions of nitric oxide (NO) and proinflammatory cytokines [including interleukin-1 (IL-1)] in macrophages. In the present study we used primary cultures of rat brain macrophage-like cells (i.e., microglial cells) to investigate whether ANP binding to its receptors inhibits LPS-induced microglial activation via effects on the activation of the proinflammatory transcription factors NF-kappaB and AP-1. The productions of NO and IL-1, as well as morphological changes, were examined to assess LPS-induced activation of microglial cells. Our RT-PCR study revealed that rat microglial cells express the mRNAs for ANP receptors (types A, B, and C) and that for the ANP molecule. LPS (100 ng/ml)-stimulated microglial cells showed increases in nitrite (a relatively stable metabolite of NO) and IL-1 concentrations, and in the expression of IL-1 mRNA, as well as a morphological change from an amoeboid shape to a multipolar (mostly bipolar, but sometimes tripolar) rod shape. These effects were all significantly inhibited by treatment with ANP (at 10(-6)M or less). The inhibition by ANP of the LPS-induced nitrite response was abrogated by a NP-receptor antagonist, HS-142-1 (100 ng/ml). NF-kappaB and AP-1 activities were enhanced in LPS-stimulated microglial cells, and these enhancements were significantly suppressed by ANP (10(-6)M). These results suggest that ANP inhibits LPS-stimulated activities in microglial cells through activation of microglial ANP receptors, leading to inhibitions of NF-kappaB and AP-1.
authors.affiliation: Division of Integrative Physiology, Department of Functional, Morphological and Regulatory Science, Tottori University Faculty of Medicine, Yonago, Tottori 683, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Moriyama
authors.forename: Makoto
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Kanako
authors.initials: K
authors.lastname: Miyano
authors.forename: Michio
authors.initials: M
authors.lastname: Miyoshi
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D002478:Cells, Cultured; D053583:Interleukin-1beta / Q000096:biosynthesis / Q000235:genetics; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors*; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017461:Receptors, Atrial Natriuretic Factor / Q000096:biosynthesis / Q000235:genetics; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D009569:Nitric Oxide; D009320:Atrial Natriuretic Factor; D017461:Receptors, Atrial Natriuretic Factor