Antrodia cinnamomea reduces obesity and modulates the gut microbiota in high-fat diet-fed mice.

BACKGROUND: Obesity is associated with gut microbiota dysbiosis, disrupted intestinal barrier and chronic inflammation. Given the high and increasing prevalence of obesity worldwide, anti-obesity treatments that are safe, effective and widely available would be beneficial. We examined whether the medicinal mushroom Antrodia cinnamomea may reduce obesity in mice fed with a high-fat diet (HFD). METHODS: Male C57BL/6J mice were fed a HFD for 8 weeks to induce obesity and chronic inflammation. The mice were treated with a water extract of A. cinnamomea (WEAC), and body weight, fat accumulation, inflammation markers, insulin sensitivity and the gut microbiota were monitored. RESULTS: After 8 weeks, the mean body weight of HFD-fed mice was 39.8±1.2 g compared with 35.8±1.3 g for the HFD+1% WEAC group, corresponding to a reduction of 4 g or 10% of body weight (P<0.0001). WEAC supplementation reduced fat accumulation and serum triglycerides in a statistically significant manner in HFD-fed mice. WEAC also reversed the effects of HFD on inflammation markers (interleukin-1ß, interleukin-6, tumor necrosis factor-α), insulin resistance and adipokine production (leptin and adiponectin). Notably, WEAC increased the expression of intestinal tight junctions (zonula occludens-1 and occludin) and antimicrobial proteins (Reg3g and lysozyme C) in the small intestine, leading to reduced blood endotoxemia. Finally, WEAC modulated the composition of the gut microbiota, reducing the Firmicutes/Bacteroidetes ratio and increasing the level of Akkermansia muciniphila and other bacterial species associated with anti-inflammatory properties. CONCLUSIONS: Supplementation with A. cinnamomea produces anti-obesogenic, anti-inflammatory and antidiabetic effects in HFD-fed mice by maintaining intestinal integrity and modulating the gut microbiota.

Pretreatment with a heat-killed probiotic modulates monocyte chemoattractant protein-1 and reduces the pathogenicity of influenza and enterovirus 71 infections.

It has been proposed that inactivated probiotics may modulate the host immune system and contribute to mitigation of viral infections. This study demonstrated that administration of heat-killed Enterococcus faecalis, a widely used probiotic, can protect host animals against viral infections. The influenza-mediated morbidity and lung inflammation in E. faecalis-treated mice decreased significantly compared with those of the control mice. Furthermore, we found that the protection is associated with production of monocyte chemoattractant protein-1 (MCP-1). The intratracheal injection of a recombinant mouse MCP-1 protein abrogated the antiviral effects elicited by pretreatment with E. faecalis. CC chemokine receptor 2 (CCR2) is a receptor for MCP-1, and the intraperitoneal administration of a CCR2 antagonist effectively inhibited viral pathogenicity. The reduced pathogenicity was also observed in CCR2-deficient mice. Finally, E. faecalis significantly attenuated neuropathogenicity induced by another RNA virus, enterovirus 71. This study demonstrates that killed probiotics can reduce viral disease severity and identify that the MCP-1 pathway might act as a key mediator in the improved antiviral immune response. Our findings suggest that MCP-1 and its related signaling pathway can serve as critical therapeutic targets for development of new antiviral strategies.

A Dual Role for P2X7 Receptor during Porphyromonas gingivalis Infection.

Emerging evidence suggests a role for purinergic signaling in the activation of multiprotein intracellular complexes called inflammasomes, which control the release of potent inflammatory cytokines, such as interleukin (IL) -1ß and -18. Porphyromonas gingivalis is intimately associated with periodontitis and is currently considered one of the pathogens that can subvert the immune system by limiting the activation of the NLRP3 inflammasome. We recently showed that P. gingivalis can dampen eATP-induced IL-1ß secretion by means of its fimbriae in a purinergic P2X7 receptor-dependent manner. Here, we further explore the role of this purinergic receptor during eATP-induced IL-1ß processing and secretion by P. gingivalis-infected macrophages. We found that NLRP3 was necessary for eATP-induced IL-1ß secretion as well as for caspase 1 activation irrespective of P. gingivalis fimbriae. Additionally, although the secretion of IL-1ß from P. gingivalis-infected macrophages was dependent on NLRP3, its adaptor protein ASC, or caspase 1, the cleavage of intracellular pro-IL-1ß to the mature form was found to occur independently of NLRP3, its adaptor protein ASC, or caspase 1. Our in vitro findings revealed that P2X7 receptor has a dual role, being critical not only for eATP-induced IL-1ß secretion but also for intracellular pro-IL-1ß processing. These results were relevant in vivo since P2X7 receptor expression was upregulated in a P. gingivalis oral infection model, and reduced IFN-γ and IL-17 were detected in draining lymph node cells from P2rx7(-/-) mice. Furthermore, we demonstrated that P2X7 receptor and NLRP3 transcription were modulated in human chronic periodontitis. Overall, we conclude that the P2X7 receptor has a role in periodontal immunopathogenesis and suggest that targeting of the P2X7/NLRP3 pathway should be considered in future therapeutic interventions in periodontitis.

Porphyromonas gingivalis infection sequesters pro-apoptotic Bad through Akt in primary gingival epithelial cells.

Porphyromonas gingivalis, a self-limiting oral pathogen, can colonize and replicate in gingival epithelial cells (GECs). P. gingivalis-infected GECs are protected from mitochondrion-dependent apoptosis, partially through activation of phosphatidyl inositol 3-kinase/Akt signaling. Biochemical events associated with P. gingivalis-induced inhibition of apoptosis include the blocking of mitochondrial membrane permeability and cytochrome-c release. We studied functional importance of Akt and the status of associated key mitochondrial molecules, pro-apoptotic Bad and caspase-9, during infection of GECs. We found that P. gingivalis infection caused significant phosphorylation of Bad progressively, while messenger RNA levels for Bad slowly decreased. Fluorescence microscopy showed translocation of the mitochondrial Bad to the cytosol post-infection. Conversely, P. gingivalis lost the ability to promote phosphorylation and translocation of Bad in Akt-deficient GECs. Caspase-9 activation induced by a chemical inducer of apoptosis was significantly inhibited by infection over time. However, Akt depletion by small interfering RNA did not reverse inhibition of caspase-9 activation by infection. Hence, P. gingivalis inactivates pro-apoptotic Bad through Akt. The inhibition of caspase-9 activation appears to be independent of Akt. Overall, our findings suggest that Akt is a key component of anti-apoptotic pathways stimulated by P. gingivalis. The P. gingivalis uses other mitochondrial pathways to protect host cells from cell-death and to ensure its survival in gingival epithelium.

Inflammasomes bridge signaling between pathogen identification and the immune response.

Microbial organisms express pathogen-associated molecular patterns (PAMPs) that can stimulate expression of proinflammatory mediators following ligation of pathogen recognition receptors. However, both commensal organisms and pathogens can express PAMPs. The immune system can distinguish between commensals and pathogens in part through secretion of the key inflammatory cytokines interleukin (IL)-1beta and IL-18. A PAMP such as lipopolysaccharide can induce production of intracellular pro-IL-1beta and pro-IL-18, but not their secretion. A second "danger signal", derived from host-cell molecules that are released from stressed or infected cells, or detected as a PAMP that is present in the cytosol, can stimulate assembly of an inflammasome that activates the protease caspase-1. Caspase-1, in turn, is responsible for processing and secretion of the mature IL-1beta and IL-18. Many diverse ligands leading to inflammasome activation have been identified, but the cell signaling pathways initiated by the ligands tend to converge on a small set of common mechanisms.

The tumor suppressor protein PML controls apoptosis induced by the HIV-1 envelope.

Promyelomonocytic leukemia (PML) is a prominent oncosuppressor whose inactivation is involved in the pathogenesis of hematological and epithelial cancers. Here, we report that PML aggregated in nuclear bodies in syncytia elicited by the envelope glycoprotein complex (Env) of human immunodeficiency virus-1 (HIV-1) in vitro. PML aggregation occurred after the fusion of nuclei (karyogamy) within syncytia but before the apoptotic program was activated. The aggregation of PML was detectable in syncytia present in the brain or lymph nodes from patients with HIV-1 infection, as well as in a fraction of blood leukocytes, correlating with viral status. Using a range of specific inhibitors of PML (the oncogenic PML/RARalpha fusion product or specific small interfering RNAs), we demonstrated that, in Env-elicited syncytia, PML was required for activating phosphorylation of ataxia telangiectasia mutated (ATM), which colocalized with PML in nuclear bodies, in a molecular complex that also involved topoisomerase IIbeta-binding protein 1. PML knockdown thus inhibited the ATM-dependent DNA damage response that culminates in the activation of p53, p53-dependent transcription of pro-apoptotic genes and cell death. Infection of CD4-expressing cells with HIV-1 also induced syncytial apoptosis, which could be suppressed by inhibiting PML. Altogether, these data indicate that PML activation is a critical early event that participates in the apoptotic demise of HIV-1-elicited syncytia.

Characterization of a monoclonal antibody reacting with antigen-4 domain of gp900 in Cryptosporidium parvum invasive stages.

Cryptosporidium parvum (Protozoa, Apicomplexa) infects the apical surface of intestinal epithelial cells, where it grows and divides within a membrane-bound parasitophorous vacuole. gp900, an abundant glycoprotein of C. parvum merozoites and sporozoites, is localized in micronemes and at the surface of invasive stages and participates in the invasion process. Here, we describe a new monoclonal antibody (mAb) against gp900. As shown by immunofluorescence of excysted parasites and immunoelectron microscopy of infected tissues, the mAb reacted with micronemes present in the apical pole of invasive stages. In immunoprecipitation experiments, the mAb was shown to react with a high molecular weight antigen co-migrating with gp900. Finally, three reactive clones were selected upon screening of a C. parvum genomic expression library with the mAb; and sequencing of the insert from one of them showed a 596 bp sequence identical to the DNA region encoding a domain of gp900 identified as antigen 4.

Modulation of P2Z/P2X(7) receptor activity in macrophages infected with Chlamydia psittaci.

Given the role that extracellular ATP (ATP(o))-mediated apoptosis may play in inflammatory responses and in controlling mycobacterial growth in macrophages, we investigated whether ATP(o) has any effect on the viability of chlamydiae in macrophages and, conversely, whether the infection has any effect on susceptibility to ATP(o)-induced killing via P2Z/P2X(7) purinergic receptors. Apoptosis of J774 macrophages could be selectively triggered by ATP(o), because other purine/pyrimidine nucleotides were ineffective, and it was inhibited by oxidized ATP, which irreversibly inhibits P2Z/P2X(7) purinergic receptors. Incubation with ATP(o) but not other extracellular nucleotides inhibits the growth of intracellular chlamydiae, consistent with previous observations on ATP(o) effects on growth of intracellular mycobacteria. However, chlamydial infection for 1 day also inhibits ATP(o)-mediated apoptosis, which may be a mechanism to partially protect infected cells against the immune response. Infection by Chlamydia appears to protect cells by decreasing the ability of ATP(o) to permeabilize macrophages to small molecules and by abrogating a sustained Ca(2+) influx previously associated with ATP(o)-induced apoptosis.

'Infectious web'.

Exhaustive information on the Epstein-Barr virus, a member of the herpes family, is described at the International Herpes Management Forum web-site. Cervical cancer associations, AIDS treatment projects, and the Los Alamos National Laboratories provide useful information on papillomavirus infections, as well as hyperlinks to recent international papillomavirus conferences. A private pharmaceutical company, in collaboration with the National Institutes of Health, has launched a lively web-site covering different aspects of microbial infections for the general public.

'Infectious web'.

Infections by Helicobacter pylori are responsible for duodenal and gastric ulcers and are a significant risk factor for the development of gastric adenocarcinoma. H. pylori was discovered in 1983, but many institutes in Canada, Europe, and the United States are already involved in programs to understand and treat the infections, as reflected by the growing number of internet sites devoted to this bacterium. Most AIDS patients and about 20% of children with acute lymphoblastic leukemia develop Pneumocystis carinii pneumoniae. Information on clinical symptoms and treatment, as well as the P. carinii genome sequencing project, are described at several web sites. Students and researchers wishing to understand the correlation between telomere length and AIDS may turn to web sites of the University of Colorado and Washington University School of Medicine for the latest on telomeres and telomerase, and their function in aging and cancer.

'Infectious web'.

This issue of 'Infectious Web' includes web-sites related to AIDS/HIV, pathogenic characteristics and resistance to Staphylococcus spp., diagnostic and clinical aspects of arthritis, and comprehensive information resources on malaria, cystic fibrosis and biological weapons.

Fluorescent labelling of intracellular bacteria in living host cells.

The fluorescent reagent, CellTracker, labels metabolically-active cells and was used here to label Chlamydia in vivo during their exponential phase of growth in infected cells. HeLa cells infected with C. psittaci were labelled with the CellTracker reagents between 15 and 48 h post-infection. The fluorescent label accumulated in the host-cell membrane compartment (inclusion) within which Chlamydia reside and replicate, and was also incorporated by the bacteria. Labelling with the CellTracker affected neither the growth nor the differentiation of the chlamydiae, and labelled chlamydiae isolated from infected cells were infectious. Our results demonstrate that the CellTracker could become a valuable tool for in vivo labelling of obligate intracellular parasites for which no genetic tools exist.

Effect of Chlamydia trachomatis infection and subsequent tumor necrosis factor alpha secretion on apoptosis in the murine genital tract.

The pathology observed during Chlamydia infection is due initially to localized tissue damage caused by the infection itself, followed by deleterious host inflammatory responses that lead to permanent scarring. We have recently reported that the infection by Chlamydia in vitro results in apoptosis of epithelial cells and macrophages and that infected monocytes secrete the proinflammatory cytokine interleukin-1beta. At the same time, proinflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha) can also trigger apoptosis of susceptible cells. To study the possible relationship between Chlamydia trachomatis infection and apoptosis in vivo, we used the terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling technique to determine whether infection may cause apoptosis in the genital tract of mice and, conversely, whether cytokines produced during the inflammatory response may modulate the level of apoptosis. Our results demonstrate that infected cells in the endocervix at day 2 or 7 after infection are sometimes apoptotic, although there was not a statistically significant change in the number of apoptotic cells in the endocervix. However, large clumps of apoptotic infected cells were observed in the lumen, suggesting that apoptotic cells may be shed from the endocervix. Moreover, there was a large increase in the number of apoptotic cells in the uterine horns and oviducts after 2 or 7 days of infection, which was accompanied by obvious signs of upper tract pathology. Interestingly, depletion of TNF-alpha led to a decrease in the level of apoptosis in the uterine horns and oviducts of animals infected for 7 days, suggesting that the inflammatory cytokines may exert part of their pathological effect via apoptosis in infected tissues.

'Infectious web'.

A comprehensive list of all known bacterial pathogens of humans is now available at various web-sites on the internet. The sites contain hyperlinks to original scientific literature, along with general information on laboratory testing, antibiotic resistance and clinical treatment. More specific sites highlight the fungus Pneumocystic carinii, arguably the main cause of pneumonia in immunosuppressed individuals.

Caspase-dependent apoptosis during infection with Cryptosporidium parvum.

The protozoan parasite Cryptosporidium parvum causes persistent diarrhea and malnutrition in children and the diarrhea-wasting syndrome in AIDS. No therapy exists for eliminating the parasite in the absence of a healthy immune response. Although it had been reported that infection of intestinal cell lines with C. parvum leads to host cell death, the mechanisms of cytolysis have not been characterized. We show here that infection with C. parvum leads to typical apoptotic nuclear condensation and DNA fragmentation in host cells. Both nuclear condensation and DNA fragmentation are inhibited by a caspase inhibitor, showing that caspases are involved in this type of apoptosis. Finally, blocking apoptosis with the caspase inhibitor increases the percentage of infected cells, suggesting that parasites may use apoptosis to exit from the infected cell or that the infected cells may eliminate the parasite through apoptosis. These results suggest that apoptosis could be involved in the pathogenesis of C. parvum infections in vivo, and raise the possibility that therapeutic interference with host cell death could alter the course of the pathology in vivo.

P2Z/P2X7 receptor-dependent apoptosis of dendritic cells.

Macrophages and thymocytes express P2Z/P2X7 nucleotide receptors that bind extracellular ATP. These receptors play a role in immune development and control of microbial infections, but their presence on dendritic cells has not been reported. We investigated whether extracellular ATP could trigger P2Z/P2X7 receptor-dependent apoptosis of dendritic cells. Apoptosis could be selectively triggered by tetrabasic ATP, since other purine/pyrimidine nucleotides were ineffective, and it was mimicked by the P2Z receptor agonist, benzoylbenzoyl ATP, and blocked by magnesium and the irreversible antagonist, oxidized ATP. RT-PCR analysis confirmed the mRNA expression of the P2Z/P2X7 receptor and the absence of P2X1. Caspase inhibitors and cycloheximide had only a partial effect on the apoptosis, suggesting that a caspase-independent mechanism may also be operative. Brief treatment with ATP led to an increase in the intracellular calcium concentration and permeabilization of the plasma membrane to Lucifer yellow, which diffused throughout the dendritic cell cytosol. Other small extracellular molecules may thus attain a similar intracellular distribution, perhaps activating endogenous proteases that contribute to initiation of apoptosis.

Chlamydia infection of epithelial cells expressing dynamin and Eps15 mutants: clathrin-independent entry into cells and dynamin-dependent productive growth.

Chlamydiae enter epithelial cells via a mechanism that still remains to be fully elucidated. In this study we investigated the pathway of entry of C. psittaci GPIC and C. trachomatis LGV/L2 into HeLa cells and demonstrated that it does not depend on clathrin coated vesicle formation. We used mutant cell lines defective in clathrin-mediated endocytosis due to overexpression of dominant negative mutants of either dynamin I or Eps15 proteins. When clathrin-dependent endocytosis was inhibited by overexpression of the dynK44A mutant of dynamin I (defective in GTPase activity), Chlamydia entry was not affected. However, in these cells there was a dramatic inhibition in the proliferation of Chlamydia and the growth of the chlamydia vacuole (inclusion). When clathrin-dependent endocytosis was inhibited by overexpression of an Eps15 dominant negative mutant, the entry and growth of Chlamydia was unaltered. These results indicate that the effect on the growth of Chlamydia in the dynK44A cells was not simply due to a deprivation of nutrients taken up by endocytosis. Instead, the dominant-negative mutant of dynamin most likely affects the vesicular traffic between the Chlamydia inclusion and intracellular membrane compartments. In addition, cytochalasin D inhibited Chlamydia entry by more than 90%, indicating that chlamydiae enter epithelial cells by an actin-dependent mechanism resembling phagocytosis. Finally, dynamin is apparently not involved in the formation of phagocytic vesicles containing Chlamydia.

Enhancement of endocytosis due to aminophospholipid transport across the plasma membrane of living cells.

Formation of intracellular vesicles is initiated by membrane budding. Here we test the hypothesis that the plasma membrane surface area asymmetry could be a driving force for vesicle formation during endocytosis. The inner layer phospholipid number was therefore increased by adding exogenous aminophospholipids to living cells, which were then translocated from the outer to the inner layer of the membrane by the ubiquitous flippase. Addition of either phosphatidylserine or phosphatidylethanolamine led to an enhancement of endocytosis, showing that the observed acceleration does not depend on the lipid polar head group. Conversely, a closely related aminophospholipid that is not recognized by the flippase, lyso-alpha-phosphatidylserine, inhibited endocytosis, and similar results were obtained with a cholesterol derivative that also remains in the plasma membrane outer layer. Thus an increase of lipid concentration in the inner layer enhanced internalization, whereas an increase of the lipid concentration in the outer layer inhibited internalization. These experiments suggest that transient asymmetries in lipid concentration might contribute to the formation of endocytic vesicles.