Porphyromonas gingivalis, Gamma Interferon, and a Proapoptotic Fibronectin Matrix Form a Synergistic Trio That Induces c-Jun N-Terminal Kinase 1-Mediated Nitric Oxide Generation and Cell Death

Abstract

During infection and inflammation, bacterial and inflammatory proteases break down extracellular matrices into macromolecular fragments. Fibronectin fragments are associated with disease severity in arthritis and periodontitis. The mechanisms by which these fragments contribute to disease pathogenesis are unclear. One likely mechanism is that fibronectin fragments induce apoptosis of resident cells, which can be further modulated by nitric oxide. Nitric oxide levels are increased at inflammatory sites in periodontitis patients. The aim of this study was to examine whether a proapoptotic fibronectin matrix (AFn) exerts its action by inducing nitric oxide and whether priming by bacterial and inflammatory components exacerbates this mechanism. Our data demonstrate that AFn increased the levels of nitric oxide and inducible nitric oxide synthase (iNOS) dose and time dependently in periodontal ligament (PDL) cells. These effects and apoptosis were inhibited by iNOS suppression and enhanced by iNOS overexpression. Nitric oxide and iNOS induction were paralleled by increased c-Jun N-terminal kinase 1 (JNK-1) phosphorylation. JNK-1 overexpression enhanced the expression of nitric oxide and iNOS, whereas inhibiting JNK-1 by small interfering RNA or a kinase mutant reversed these findings. Priming PDL cells with Porphyromonas gingivalis, its lipopolysaccharide (LPS), or gamma interferon (IFN-␥) further increased nitric oxide levels and apoptosis. Escherichia coli and Streptococcus mutans induced lesser effects. Gingival fibroblasts and neutrophils responded to a lesser degree to these stimuli, whereas keratinocytes were resistant to apoptosis. Thus, proapoptotic matrices trigger nitric oxide release via JNK-1, promoting further apoptosis in host cells. LPS and IFN-␥ accentuate this mechanism, suggesting that during inflammation, the affected matrices and bacterial and inflammatory components combined exert a greater pathogenic effect on host cells.

Treponema denticolaincreases MMP-2 expression and activation in the periodontium via reversible DNA and histone modifications

“…MMP-2 production and activation is a major event in the pathogenesis of these diseases via its role in extracellular matrix destruction. The T. denticola dentilisin protease plays an important role in the up-regulation and activation of MMP-2 in PDL cells (Miao et al , 2011, Miao et al , 2014), thereby promoting further ECM destruction and release of fibronectin fragments, which have deleterious effects on the periodontal environment (Kapila et al , 1996, Kapila et al , 1999, Kapila et al , 2002, Jee et al , 2004, Dai et al , 2005, Tafolla et al , 2005, Ghosh et al , 2008, Joo et al , 2008, Joseph et al , 2010, Miao et al , 2011, Miao et al , 2014, Pereira et al , 2014). The oral spirochete T. lecithinolyticum is also reported to activate MMP-2, as are P. gingivalis and A. actinomycetemcomitans (Choi et al , 2001, Chang et al , 2002, Song et al , 2003).…”

“…Destruction of the ECM in periodontitis results in the release of fibronectin (FN) fragments, which are considered markers of periodontal disease status (Huynh et al , 2002). Evidence from in vitro studies further indicate that these FN fragments, induce several detrimental effects, including induction of apoptosis and suppression of osteoblast differentiation of periodontal ligament cells (Kapila et al , 1996, Kapila et al , 1998, Kapila et al , 1999, Jee et al , 2004, Dai et al , 2005, Ghosh et al , 2008, Joseph et al , 2010), thereby further potentiating disease progression.…”

Neutrophils in Periodontal Inflammation

“…Furthermore, the uptake of apoptotic neutrophils induces the production of anti-inflammatory cytokines, such as TGFβ, in the phagocytosing cell (17, 46). Several periodontal pathogens have been shown to induce phagocytosis-induced cell death in innate cells, including Fusobacterium nucleatum and P. gingivalis , as well as other bacteria known to inhabit the oral cavity, such as Neisseria gonorrhoeae (17, 47–48). Induction of apoptosis presumably benefits periodontal pathogens by preventing phagocytosis.…”

Resposta imune inata na estomatite protética: interação in vitro entre células epiteliais de palato humano e Candida albicans

“…O óxido nítrico (NO), um radical livre de meia-vida curta (GHOSH et al, 2008), é sintetizado em células de mamíferos com a participação da enzima NO sintase (NOS), que converte o aminoácido arginina e oxigênio em citrulina e NO (SEO et al, 2002). Esta enzima pode ser encontrada sob as formas constitutiva (cNOS) e indutiva (iNOS), sendo cNOS expressa em duas isoformas diferentes, uma presente em endotélio vascular (eNOS) e outra em células nervosas (nNOS) (SEO et al, 2002).…”

“…Normalmente, a forma indutiva da enzima não está presente nas células (GHOSH et al, 2008). iNOS são expressos em resposta à infecção microbiana, citocinas inflamatórias e agressões ambientais em diversas células, incluindo os queratinócitos, além dos hepatócitos, macrófagos, neutrófilos e condrócitos (SEO et al, 2002).…”