title: Angiotensin II-induced upregulation of AT(1) receptor expression: sequential activation of NF-kappaB and Elk-1 in neurons.
abstract: It has been clearly established that increased circulating angiotensin II (ANG II) with concurrent upregulation of brain and peripheral ANG II type 1 receptors (AT(1)R) are important mediators in the pathophysiology of several diseases characterized by sympatho-excitation. In an effort to further understand the regulation of AT(1)R expression in neurons, we determined the role of sequential activation of the transcription factors nuclear factor-kappaB (NF-kappaB) and Ets-like protein 1 (Elk-1) in AT(1)R upregulation. We used CATH.a neurons as our neuronal cell model. Cells were treated with ANG II (100 nM) over a preset time course. Following ANG II activation, there was a temporal increase in the p65 subunit of NF-kappaB that was observed at 30 min, peaked at 1 h, and was sustained up to 24 h. There was a concomitant decrease of IkappaB and increased IkappaK expression. We also observed an increase in AT(1)R expression which followed the temporal increase of NF-kappaB. The activation of NF-kappaB was blocked by using the inhibitors parthenolide or p65 small interfering RNA (siRNA) which both led to a decrease in AT(1)R expression. The expression of Elk-1 was upregulated over a time period following ANG II activation and was decreased following NF-kappaB inhibition. p65-DNA binding was assessed using electrophoretic mobility shift assay, and it was shown that there was a time-dependent increased binding that was inhibited by means of parthenolide pretreatment or siRNA-mediated p65 gene silencing. Therefore, our results suggest a combined role for the transcription factors NF-kappaB and Elk-1 in the upregulation of AT(1)R in the CATH.a cell neuronal model. These data imply a positive feedback mechanism that may impact neuronal discharge sensitivity in response to ANG II.
authors.affiliation: Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska, USA.
authors.forename: Amit K
authors.initials: AK
authors.lastname: Mitra
authors.forename: Lie
authors.initials: L
authors.lastname: Gao
authors.forename: Irving H
authors.initials: IH
authors.lastname: Zucker
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D044140:Receptor, Angiotensin, Type 1 / Q000096:biosynthesis*; D012717:Sesquiterpenes / Q000494:pharmacology; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors / Q000235:genetics; D014158:Transcription, Genetic; D015854:Up-Regulation; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism*
chemical_list: C494113:Elk1 protein, mouse; D016328:NF-kappa B; D034741:RNA, Small Interfering; D044140:Receptor, Angiotensin, Type 1; D012717:Sesquiterpenes; D051996:Transcription Factor RelA; D050807:ets-Domain Protein Elk-1; D000804:Angiotensin II; C002669:parthenolide; D004247:DNA