Obesity has been suggested to be associated with an increased susceptibility to bacterial infection. However, few studies have examined the effect of obesity on the immune response to bacterial infections. In the present study, we investigated the effect of obesity on innate immune responses to Porphyromonas gingivalis infection, an infection strongly associated with periodontitis. Mice with dietinduced obesity (DIO) and lean control C57BL/6 mice were infected orally or systemically with P. gingivalis, and periodontal pathology and systemic immune responses were examined postinfection. After oral infection with P. gingivalis, mice with DIO had a significantly higher level of alveolar bone loss than the lean controls. Oral microbial sampling disclosed higher levels of P. gingivalis in mice with DIO vs. lean mice during and after infection. Furthermore, animals with DIO exposed to oral infection or systemic inoculation of live P. gingivalis developed a blunted inflammatory response with reduced expression of TNF-␣, IL-6, and serum amyloid A (SAA) at all time points compared with lean mice. Finally, peritoneal macrophages harvested from mice with DIO and exposed to P. gingivalis exhibited reduced levels of proinflammatory cytokines compared with lean mice and when exposed to P. gingivalis LPS treatment had a significantly reduced recruitment of NF-B to both TNF-␣ and IL-10 promoters 30 min after exposure. These data indicate that obesity interferes with the ability of the immune system to appropriately respond to P. gingivalis infection and suggest that this immune dysregulation participates in the increased alveolar bone loss after bacterial infection observed in mice with DIO.cytokine ͉ P. gingivalis ͉ inflammatory response ͉ macrophage ͉ chromatin immunoprecipitation

To characterize the roles of Porphyromonas gingivalis and its components in the disease processes, we investigated the cytokine profile induced by live P. gingivalis, its lipopolysaccharides (LPS), and its major fimbrial protein, fimbrillin (FimA). Using cytokine antibody arrays, we found that P. gingivalis LPS and FimA induced a similar profile of cytokine expression when exposed to mouse peritoneal macrophages but that this profile differed significantly in response to live P. gingivalis. In vitro, mouse peritoneal macrophages were stimulated to produce interleukin-6 (IL-6), granulocyte colony-stimulating factor, and lymphotactin by live P. gingivalis, but not by P. gingivalis LPS or FimA, while RANTES, gamma interferon, IL-17, vascular cell adhesion molecule 1 (VCAM-1), and vascular endothelial growth factor were induced by P. gingivalis LPS or FimA, but not by live P. gingivalis. In vivo, IL-6 mRNA was strongly induced only by live P. gingivalis while monocyte chemoattractant protein 1 mRNA was strongly induced only by P. gingivalis LPS and FimA in mouse calvarial scalp, further confirming the differences of cytokine profile induced in vitro. Cytokine antibody arrays using toll-like receptor 2 (TLR2)-and TLR4-deficient macrophages revealed that most of the cytokines induced by P. gingivalis LPS or FimA signal through TLR2, while most of cytokines induced by live P. gingivalis signal through both TLR2 and TLR4. Interestingly, the activation of TLR2 by live P. gingivalis inhibited the release of RANTES, VCAM-1, and IL-1␣ from mouse peritoneal macrophages. A tumor necrosis factor alpha enzyme-linked immunosorbent assay further confirmed that P. gingivalis LPS and FimA activate mouse peritoneal macrophages via TLR2. These results indicate that host immune cells sense live P. gingivalis and its components differently, which translates into the expression of different inflammatory cytokine profiles.

Porphyromonas gingivalis (P. gingivalis) can trigger an inflammatory condition leading to the destruction of periodontal tissues. However P. gingivalis LPS and its fimbriae (FimA) play different roles compared with the live bacteria in the context of intracellular molecule induction and cytokine secretion. To elucidate whether this difference results from different signaling pathways in host immune response to P. gingivalis, its LPS, or its FimA, we examined gene expression profile of human macrophages exposed to P. gingivalis, its LPS, or its FimA. A comparison of gene expression resulted in the identification of three distinct groups of expressed genes. Furthermore, computer-assisted promoter analysis of a subset of each group of differentially regulated genes revealed four putative transcriptional regulation models that associate with transcription factors NFκB, IRF7, and KLF4. Using gene knockout mice and siRNA to silence mouse genes, we showed that both TLR2 and TLR7 are essential for the induction of NFκB-containing genes and NFκB-IFN-sensitive response element (ISRE) cocontaining genes by either P. gingivalis or its purified components. The gene induction via either TLR2 or TLR7 is dependent on both MyD88 and p38 MAPK. However, the unique induction of IFN-β by P. gingivalis LPS requires TLR7 and IFNαβR cosignaling, and the induction of ISRE-containing gene is dependent on the activation of IFN-β autocrine loop. Taken together, these data demonstrate that P. gingivalis and its components induce NFκB-containing genes through either TLR2- or TLR7-MyD88-p38 MAPK pathway, while P. gingivalis LPS uniquely induces ISRE-containing genes, which requires IFNαβR signaling involving IRF7, KLF4, and pY701 STAT1.

Recent research links diet-induced obesity (DIO) with impaired immunity, although the underlying mechanisms remain unclear. We find that the induction of inducible NO synthase (iNOS) and cytokines is suppressed in mice with DIO and in bone marrow macrophages (BMM⌽) from mice with DIO exposed to an oral pathogen, Porphyromonas gingivalis. BMM⌽ from lean mice pretreated with free fatty acids (FFAs) and exposed to P. gingivalis also exhibit a diminished induction of iNOS and cytokines. BMM⌽ from lean and obese mice exposed to P. gingivalis and analyzed by a phosphorylation protein array show a reduction of Akt only in BMM⌽ from mice with DIO. This reduction is responsible for diminished NF-B activation and diminished induction of iNOS and cytokines. We next observed that Toll-like receptor 2 (TLR2) is suppressed in BMM⌽ from DIO mice whereas carboxy-terminal modulator protein (CTMP), a known suppressor of Akt phosphorylation, is elevated. This elevation stems from defective TLR2 signaling. In BMM⌽ from lean mice, both FFAs and TNF-␣-via separate pathways-induce an increase in CMTP. However, in BMM⌽ from DIO mice, TLR2 can no longer inhibit the TNF-␣-induced increase in CTMP caused by P. gingivalis challenge. This defect can then be restored by transfecting WT TLR2 into BMM⌽ from DIO mice. Thus, feeding mice a high-fat diet over time elevates the CTMP intracellular pool, initially via FFAs activating TLR2 and later when the defective TLR2 is unable to inhibit TNF-␣-induced CTMP. These findings unveil a link between obesity and innate immunity.O besity has been found to lead to diminished immune response. Several epidemiological studies of obese individuals found evidence of increased susceptibility to infections, including postoperative infectious complications (1), and a positive correlation between body weight index and the incidence of nosocomial infections (2). Diet-induced obesity (DIO) interferes with the ability of the immune system to appropriately respond to Porphyromonas gingivalis infection (3) and causes a higher mortality rate in mice following infection with influenza virus (4).Obesity is known to elevate TNF-␣ levels in the plasma of obese subjects (5, 6). However, macrophage functions are impaired in obese animals, with reduced phagocytic capacity and a defective oxidative burst (7,8). The reduced cytokine expression in response to infection observed in obese mice has been linked to a dysfunction in macrophages and/or a defect in maturation of monocytes (3,4,9). Moreover, the ability of mature macrophages from an obese individual to elicit an antimicrobial and cytotoxic response may be inhibited (10). Macrophages sense the presence of microorganisms via pattern recognition receptors, especially members of the Tolllike receptor (TLR) family, and subsequently activate proinflammatory signal pathways. TLR2 is an important receptor by which macrophages recognize P. gingivalis (11)(12)(13)(14), and mediates destructive chronic inflammatory reactions or confers host protection against P. gingivalis in acut...

The etiology of idiopathic Parkinson's disease (idPD) remains enigmatic despite recent successes in identification of genes (PARKs) that underlie familial PD. To find new keys to this incurable neurodegenerative disorder we focused on the poorly understood PARK14 disease locus (Pla2g6 gene) and the store-operated Ca2+ signalling pathway. Analysis of the cells from idPD patients reveals a significant deficiency in store-operated PLA2g6-dependent Ca2+ signalling, which we can mimic in a novel B6.Cg-Pla2g6ΔEx2-VB (PLA2g6 ex2KO) mouse model. Here we demonstrate that genetic or molecular impairment of PLA2g6-dependent Ca2+ signalling is a trigger for autophagic dysfunction, progressive loss of dopaminergic (DA) neurons in substantia nigra pars compacta and age-dependent L-DOPA-sensitive motor dysfunction. Discovery of this previously unknown sequence of pathological events, its association with idPD and our ability to mimic this pathology in a novel genetic mouse model opens new opportunities for finding a cure for this devastating neurodegenerative disease.