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.

Background: Fibroblasts are considered important cells in periodontitis. When challenged by different agents, they respond through the release of cytokines that participate in the inflammatory process. The aim of this study is to evaluate and compare the expression and production of macrophage inflammatory protein (MIP)‐1α, stromal‐derived factor (SDF)‐1, and interleukin (IL)‐6 by human cultured periodontal ligament and gingival fibroblasts challenged with lipopolysaccharide (LPS) from Porphyromonas gingivalis.Methods: Fibroblasts were cultured from biopsies of gingival tissue and periodontal ligament of the same donors and used on the fourth passage. After confluence in 24‐well plates, the culture medium alone (control) or with 0.1 to 10 μg/ml of LPS from P. gingivalis was added to the wells, and after 1, 6, and 24 hours, the supernatant and the cells were collected and analyzed by enzyme‐linked immunosorbent assay and real‐time polymerase chain reaction, respectively.Results: MIP‐1α, SDF‐1, and IL‐6 protein production was significantly greater in gingival fibroblasts compared to periodontal ligament fibroblasts. IL‐6 was upregulated in a time‐dependent manner, mainly in gingival fibroblasts (P <0.05), which secreted more MIP‐1α in the lowest concentration of LPS used (0.1 μg/ml). In contrast, a basal production of SDF‐1 that was inhibited with the increase of LPS concentration was detected, especially after 24 hours (P <0.05).Conclusion: The distinct ability of the gingival and periodontal ligament fibroblasts to secrete MIP‐1α, SDF‐1, and IL‐6 emphasizes that these cells may differently contribute to the balance of cytokines in the LPS‐challenged periodontium.

Background: Fibroblasts are now seen as active components of the immune response because these cells express Toll‐like receptors (TLRs), recognize pathogen‐associated molecular patterns, and mediate the production of cytokines and chemokines during inflammation. The innate host response to lipopolysaccharide (LPS) from Porphyromonas gingivalis is unusual inasmuch as different studies have reported that it can be an agonist for Toll‐like receptor 2 (TLR2) and an antagonist or agonist for Toll‐like receptor 4 (TLR4). This study investigates and compares whether signaling through TLR2 or TLR4 could affect the secretion of interleukin (IL)‐6, IL‐8, and stromal derived factor‐1 (SDF‐1/CXCL12) in both human gingival fibroblasts (HGF) and human periodontal ligament fibroblasts (HPDLF).Methods: After small interfering RNA‐mediated silencing of TLR2 and TLR4, HGF and HPDLF from the same donors were stimulated with P. gingivalis LPS or with two synthetic ligands of TLR2, Pam2CSK4 and Pam3CSK4, for 6 hours. IL‐6, IL‐8, and CXCL12 mRNA expression and protein secretion were evaluated by quantitative polymerase chain reaction and enzyme‐linked immunosorbent assay, respectively.Results: TLR2 mRNA expression was upregulated in HGF but not in HPDLF by all the stimuli applied. Knockdown of TLR2 decreased IL‐6 and IL‐8 in response to P. gingivalis LPS, or Pam2CSK4 and Pam3CSK4, in a similar manner in both fibroblasts subpopulations. Conversely, CXCL12 remained unchanged by TLR2 or TLR4 silencing.Conclusion: These results suggest that signaling through TLR2 by gingival and periodontal ligament fibroblasts can control the secretion of IL‐6 and IL‐8, which contribute to periodontal pathogenesis, but do not interfere with CXCL12 levels, an important chemokine in the repair process.

BACKGROUND AND PURPOSE Independent studies in experimental models of Trypanosoma cruzi appointed different roles for endothelin‐1 (ET‐1) and bradykinin (BK) in the immunopathogenesis of Chagas disease. Here, we addressed the hypothesis that pathogenic outcome is influenced by functional interplay between endothelin receptors (ET_AR and ET_BR) and bradykinin B₂ receptors (B₂R).EXPERIMENTAL APPROACH Intravital microscopy was used to determine whether ETR/B₂R drives the accumulation of rhodamine‐labelled leucocytes in the hamster cheek pouch (HCP). Inflammatory oedema was measured in the infected BALB/c paw of mice. Parasite invasion was assessed in CHO over‐expressing ETRs, mouse cardiomyocytes, endothelium (human umbilical vein endothelial cells) or smooth muscle cells (HSMCs), in the presence/absence of antagonists of B₂R (HOE‐140), ET_AR (BQ‐123) and ET_BR (BQ‐788), specific IgG antibodies to each GPCRs; cholesterol or calcium‐depleting drugs. RNA interference (ET_AR or ET_BR genes) in parasite infectivity was investigated in HSMCs.KEY RESULTS BQ‐123, BQ‐788 and HOE‐140 reduced leucocyte accumulation in HCP topically exposed to trypomastigotes and blocked inflammatory oedema in infected mice. Acting synergistically, ET_AR and ET_BR antagonists reduced parasite invasion of HSMCs to the same extent as HOE‐140. Exogenous ET‐1 potentiated T. cruzi uptake by HSMCs via ETRs/B₂R, whereas RNA interference of ET_AR and ET_BR genes conversely reduced parasite internalization. ETRs/B₂R‐driven infection in HSMCs was reduced in HSMC pretreated with methyl‐β‐cyclodextrin, a cholesterol‐depleting drug, or in thapsigargin‐ or verapamil‐treated target cells.CONCLUSIONS AND IMPLICATIONS Our findings suggest that plasma leakage, a neutrophil‐driven inflammatory response evoked by trypomastigotes via the kinin/endothelin pathways, may offer a window of opportunity for enhanced parasite invasion of cardiovascular cells.LINKED ARTICLE This paper is commented on by D'Orléans‐Juste et al., pp. 1330–1332 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476‐5381.2011.01636.x

Pyroptosis is a lytic type of programmed cell death that was traditionally associated with the involvement of inflammatory caspases, such as caspase-1. These inflammatory caspases are activated within multi-protein complexes called inflammasomes that are assembled in response to invading pathogens and/or danger signals. Pyroptotic cell death was suggested to evolve via the formation of pores in the plasma membrane, but the exact mechanism underlying the formation of these pores remained unclear. Recently, gasdermin D, a member of the gasdermin protein family was identified as a caspase substrate and essential effector of pyroptosis, being identified as the protagonist of membrane pore formation. Gasdermins have emerged as a family of new class of cell death inducers, but many questions remain unanswered. Here, we present an overview of recent work being done in the area of programmed cell death and the latest evidence regarding the role and participation of gasdermin D as an effector of pyroptosis.