RESUMO
The initiation or progression of periodontitis might involve a local renin-angiotensin system (RAS) in periodontal tissue. The aim of this study was to further characterize the local RAS in human and rat periodontal tissues between healthy and periodontally-affected tissue. Components of the RAS were investigated using in vitro, ex vivo and in vivo experiments involving both human and Wistar rat periodontium. Although not upregulated when challenged with P. gingivalis-lipopolysaccharide, human gingival and periodontal ligament fibroblasts expressed RAS components. Likewise, healthy and inflamed human gingiva expressed RAS components, some of which were shown to be functional, yet no differences in expression were found between healthy and diseased gingiva. However, in inflamed tissue the immunoreactivity was greater for the AT1R compared to AT2R in fibroblasts. When compared to healthy tissue, ACE activity was increased in human gingiva from volunteers with gingivitis. Human-gingiva homogenates generated Ang II, Ang 1-9 and Ang 1-7 when incubated with precursors. In gingiva homogenates, Ang II formation from Ang I was nearly abolished only when captopril and chymostatin were combined. Ang 1-7 formation was significantly greater when human gingiva homogenates were incubated with chymostatin alone compared to incubation without any inhibitor, only captopril, or captopril and chymostatin. In rat gingiva, RAS components were also found; their expression was not different between healthy and experimentally induced periodontitis (EP) groups. However, renin inhibition (aliskiren) and an AT1R antagonist (losartan) significantly blocked EP-alveolar-bone loss in rats. Collectively, these data are consistent with the hypothesis that a local RAS system is not only present but is also functional in both human and rat periodontal tissue. Furthermore, blocking AT1R and renin can significantly prevent periodontal bone loss induced by EP in rats.
Assuntos
Periodontite/imunologia , Periodontite/patologia , Periodonto/imunologia , Periodonto/patologia , Sistema Renina-Angiotensina , Adulto , Sequência de Aminoácidos , Angiotensina I/análise , Angiotensina I/imunologia , Angiotensina II/análise , Angiotensina II/imunologia , Animais , Células Cultivadas , Feminino , Gengiva/citologia , Gengiva/imunologia , Gengiva/patologia , Humanos , Inflamação/imunologia , Inflamação/patologia , Masculino , Pessoa de Meia-Idade , Fragmentos de Peptídeos/análise , Fragmentos de Peptídeos/imunologia , Ratos Wistar , Receptores de Angiotensina/análise , Receptores de Angiotensina/imunologia , Renina/imunologia , Adulto JovemRESUMO
It has been previously shown that besides its classical role in blood pressure control the renin-angiotensin system, mainly by action of angiotensin II on the AT(1) receptor, exerts pro-inflammatory effects such as by inducing the production of cytokines. More recently, alternative pathways to this system were described, such as binding of angiotensin-(1-7) to receptor Mas, which was shown to counteract some of the effects evoked by activation of the angiotensin II-AT(1) receptor axis. Here, by means of different molecular approaches we investigated the role of angiotensin-(1-7) in modulating inflammatory responses triggered in mouse peritoneal macrophages. Our results show that receptor Mas transcripts were up-regulated by eightfold in LPS-induced macrophages. Interestingly, macrophage stimulation with angiotensin-(1-7), following to LPS exposure, evoked an attenuation in expression of TNF-α and IL-6 pro-inflammatory cytokines; where this event was abolished when the receptor Mas selective antagonist A779 was also included. We then used heterologous expression of the receptor Mas in HEK293T cells to search for the molecular mechanisms underlying the angiotensin-(1-7)-mediated anti-inflammatory responses by a kinase array; what suggested the involvement of the Src kinase family. In LPS-induced macrophages, this finding was corroborated using the PP2 compound, a specific Src kinase inhibitor; and also by Western blotting when we observed that Ang-(1-7) attenuated the phosphorylation levels of Lyn, a member of the Src kinase family. Our findings bring evidence for an anti-inflammatory role for angiotensin-(1-7) at the cellular level, as well as show that its probable mechanism of action includes the modulation of Src kinases activities.