Functional Local Renin-Angiotensin System in Human and Rat Periodontal Tissue

Abstract

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.

Angiotensin II Type 1 Receptor Knockdown Impairs Interleukin‐1β‐Induced Cytokines in Human Periodontal Fibroblasts

“…A recent study demonstrated that renin inhibitor aliskiren and AT1R antagonist losartan significantly blocked experimental ligature‐induced periodontitis in rats 29 . In addition, this study showed that HGFs and periodontal ligament cells expressed RAS components and that they were functional in human‐derived gingival tissue.…”

“…Results of this study show for the first time, to the best of the authors’ knowledge, the role of AT1R in modulating secretion of IL‐6 and IL‐8 induced by IL‐1β in fibroblasts, the resident and most abundant cells of periodontal connective tissue. Use of this cytokine as proinflammatory stimulus was based on a previous study in which greater AT1R fluorescence intensity was observed in HGF and HPLF stimulated by IL‐1β compared with P. gingivalis– or Escherichia coli –derived lipopolysaccharide (LPS) 29 . It was previously shown that proinflammatory cytokines such as IL‐1β and TNF‐α induce expression of AT1R in different cell types 33 , 34 .…”

“…β‐actin (4333762T) was used as the reference gene. All experiments were performed in a high‐productivity qPCR system ¶¶ using the comparative cycle threshold (Ct) method (ΔΔCt) as previously described 29 …”

“…A previous study in human gingival tissue demonstrated presence of ACE, angiotensinogen, and AT1R mRNA and protein in cultured HGFs 26 . In addition, AT1R antagonist losartan was able to prevent Aggregatibacter actinomycetemcomitans– induced alveolar bone loss associated with rheumatoid arthritis in mice, 27 therefore emphasizing a possible role for RAS in development and progression of periodontal disease 28 , 29 …”

Efeitos do ramipril sobre a doença periodontal induzida experimentalmente em ratos

“…Para a análise histológica foram utilizados os parâmetros inflamatórios segundo Santos et al (2015). Um pesquisador cegado pontuou a inflamação de ratos com 14 dias de doença periodontal induzida experimentalmente.…”