Inhibition of apoptosis in neuronal cells infected with Chlamydophila (Chlamydia) pneumoniae

Background Chlamydophila (Chlamydia) pneumoniae is an intracellular bacterium that has been identified within cells in areas of neuropathology found in Alzheimer disease (AD), including endothelia, glia, and neurons. Depending on the cell type of the host, infection by C. pneumoniae has been shown to influence apoptotic pathways in both pro- and anti-apoptotic fashions. We have hypothesized that persistent chlamydial infection of neurons may be an important mediator of the characteristic neuropathology observed in AD brains. Chronic and/or persistent infection of neuronal cells with C. pneumoniae in the AD brain may affect apoptosis in cells containing chlamydial inclusions. Results SK-N-MC neuroblastoma cells were infected with the respiratory strain of C. pneumoniae, AR39 at an MOI of 1. Following infection, the cells were either untreated or treated with staurosporine and then examined for apoptosis by labeling for nuclear fragmentation, caspase activity, and membrane inversion as indicated by annexin V staining. C. pneumoniae infection was maintained through 10 days post-infection. At 3 and 10 days post-infection, the infected cell cultures appeared to inhibit or were resistant to the apoptotic process when induced by staurosporine. This inhibition was demonstrated quantitatively by nuclear profile counts and caspase 3/7 activity measurements. Conclusion These data suggest that C. pneumoniae can sustain a chronic infection in neuronal cells by interfering with apoptosis, which may contribute to chronic inflammation in the AD brai

cIAP-1 Controls Innate Immunity to C. pneumoniae Pulmonary Infection

The resistance of epithelial cells infected with Chlamydophila pneumoniae for apoptosis has been attributed to the induced expression and increased stability of anti-apoptotic proteins called inhibitor of apoptosis proteins (IAPs). The significance of cellular inhibitor of apoptosis protein-1 (cIAP-1) in C. pneumoniae pulmonary infection and innate immune response was investigated in cIAP-1 knockout (KO) mice using a novel non-invasive intra-tracheal infection method. In contrast to wildtype, cIAP-1 knockout mice failed to clear the infection from their lungs. Wildtype mice responded to infection with a strong inflammatory response in the lung. In contrast, the recruitment of macrophages was reduced in cIAP-1 KO mice compared to wildtype mice. The concentration of Interferon gamma (IFN-γ) was increased whereas that of Tumor Necrosis Factor (TNF-α) was reduced in the lungs of infected cIAP-1 KO mice compared to infected wildtype mice. Ex vivo experiments on mouse peritoneal macrophages and splenocytes revealed that cIAP-1 is required for innate immune responses of these cells. Our findings thus suggest a new immunoregulatory role of cIAP-1 in the course of bacterial infection

Porins and lipopolysaccharide from Salmonella typhimurium regulate the expression of CD80 and CD86 molecules on B cells and macrophages but not CD28 and CD152 on T cells

ObjectiveThe aim of this study was to evaluate the effect of porins from Salmonella typhimurium on costimulatory molecules such as CD80/CD86 and CD28/CD152. The interactions between these molecules are able to influence the immune response through the regulation of cytokines release which, on their own, are able to regulate the immunological response by a feedback mechanism.MethodsS. typhimurium strain SH5014 (a rough lipopolysaccharide (LPS) producing strain) was used as the source of porins and LPS. Peripheral blood mononuclear cells were obtained from healthy adult donors. THP1 cells were obtained from ATCC (Rockville, MD, USA). Immunofluorescence and flow cytometry were performed using a FACS IV (Becton–Dickinson, Mountain View, CA, USA).ResultsOur results show that porins of S. typhimurium increase the expression of CD86 and the expression of CD80 both on B lymphocytes and macrophages, while the expression of CD28 and CD152 on T lymphocytes was unaltered. The expression of CD80 and CD86 is dose-dependent and starts after 24 h post treatment, peaks at 48 h and goes back to the basal value after 72 h.ConclusionsS. typhimurium porins are able to induce a high expression of costimulatory molecules (CD80 and CD86) on lymphocytes and macrophages

Antimicrobial effect of natural polyphenols with or without antibiotics on Chlamydia pneumoniae infection in vitro.

Abstract Chlamydia pneumoniae is a human pathogen that causes multiple diseases worldwide. Despite appropriate therapy with antichlamydial antibiotics, chronic exacerbated diseases often occur and lead to serious sequelae. The use of the macrolide clarithromycin and the fluoroquinolone ofloxacin has improved the treatment of chlamydial infection, but therapy failure is still a major problem. In this work, we studied the pretreatment with natural polyphenols and subsequent treatment with clarithromycin or ofloxacin. The phenolic compounds resveratrol and quercetin improved the antichlamydial effect of clarithromycin and ofloxacin. In particular, resveratrol at 40 μM and quercetin at 20 μM exhibited significant growth inhibition on C. pneumoniae in presence of clarithromycin or ofloxacin compared to controls. In addition, we demonstrated that both resveratrol and quercetin decreased IL-17 and IL-23 production in a time-dependent manner in C. pneumoniae-infected cells. The results showed a particularly strong inhibition of the IL-23 levels released with combined treatment of resveratrol or quercetin and ofloxacin or clarithromycin, suggesting that the combined treatment may afford a synergistic effect in controlling Chlamydia infections

Effect of nitric oxide on the growth of Chlamydophila pneumoniae.

Chlamydophila pneumoniae is an important human intracellular pathogen; however, the pathogenesis of C. pneumoniae infection is poorly understood and the immune control mechanism versus host cells is not completely known. The role of the nitric oxide (NO) synthase pathway in inhibiting the ability of C. pneumoniae to infect macrophage J774 cells and the ability of NO to damage isolated C. pneumoniae were investigated. Exposure of infected cultures to recombinant murine gamma interferon (MurIFN-gamma) resulted in increased production of NO and reduced viability. Addition of 2-(N,N-diethylamino)-diazenolase-2-oxide before infection of J774 cells or during chlamydial cultivation released NO, both resulting in a reduction in the viability of C. pneumoniae in a dose-dependent way. These results indicate that immune control of chlamydial growth in murine macrophage cells may trigger a mechanism that includes NO release with effects on the multiplication of the microorganism, thus suggesting that NO may play a role in preventing the systemic spread of Chlamydia

Immunological response in mice after long-term stimulation with cell wall antigens from Brucella melitensis.

The continuous stimulation of the immune system using cell wall antigens from Brucella melitensis was found to cause both quantitative and qualitative changes in circulating lymphocyte populations in mice. Animals were inoculated in the hind legs with antigens on alternate days for varying lengths of time. During a two-month period, we saw a higher number of circulating lymphocytes, with an increase in the number of CD4+ cells (L3T4+) and B lymphocytes (I-Ad). After two months, a drop in the overall number of circulating lymphocytes occurred, with a decrease in CD4+ cells and an increase in CD8+ cells. During the first two months, we observed a size increase in popliteal lymph nodes and an elevated humoral response. The response then waned with the declining CD4+ cells. In the first two months, the treated animals also showed an in vitro response to two mitogens, concanavalin A and lipopolysaccharide and to the cell wall fraction, after which the treated animals showed a decreased response