Angiotensin type 1 receptor antagonist inhibits lipopolysaccharide-induced stimulation of rat microglial cells by suppressing nuclear factor kappaB and activator protein-1 activation.
We investigated whether angiotensin (ANG) II and its receptors contribute to lipopolysaccharide (LPS)-induced microglial activation through activation of the proinflammatory transcription factors nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1). Using primary microglial cell cultures, we examined whether losartan [ANG type 1 receptor (AT(1)) antagonist] alters the effects of LPS on: the production of interleukin-1 (IL-1) and nitric oxide, cell morphology, and NF-kappaB and AP-1 activities. Reverse transcription-polymerase chain reaction revealed that LPS-stimulated microglial cells exhibited marked mRNA expression for AT(1), ANG type 2 receptor (AT(2)) and the ANG II precursor angiotensinogen, whereas non-stimulated microglial cells expressed only those for AT(2) and angiotensinogen. We further demonstrated marked peptide/protein expression for AT(1) and ANG II in LPS-activated microglial cells. LPS (100 ng/mL)-stimulated microglial cells showed increased concentrations of IL-1 and nitrite (a relatively stable metabolite of nitric oxide), and increased 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 losartan treatment (10(-5) M or less). NF-kappaB and AP-1 activities were enhanced in LPS-stimulated microglial cells, effects that were significantly suppressed by losartan (10(-5) M). ANG II application enhanced the LPS-induced increases in IL-1 and nitrite concentrations, as well as the LPS-induced morphological changes and AP-1 activation, and these enhancements were inhibited by losartan (10(-5) M). These results suggest that endogenous ANG II enhances LPS-induced microglial activities through stimulation of the microglial AT(1), which itself evokes activation of the transcription factors NF-kappaB and AP-1.
Miyoshi
Michio
M
Division of Integrative Physiology, Department of Functional, Morphological and Regulatory Science, Tottori University, Yonago, Tottori 683, Japan.
Miyano
Kanako
K
Moriyama
Naoki
N
Taniguchi
Makoto
M
Watanabe
Tatsuo
T
D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D005260:Female; D008070:Lipopolysaccharides / Q000494:pharmacology*; D019808:Losartan / Q000494:pharmacology; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors* / Q000378:metabolism
D047228:Angiotensin II Type 1 Receptor Blockers; D008070:Lipopolysaccharides; D016328:NF-kappa B; D044140:Receptor, Angiotensin, Type 1; D018808:Transcription Factor AP-1; D019808:Losartan