Schistosomiasis-associated pulmonary hypertension unveils disrupted murine gut-lung microbiome and reduced endoprotective Caveolin-1/BMPR2 expression.

Schistosomiasis-associated Pulmonary Arterial Hypertension (Sch-PAH) is a life-threatening complication of chronic S. mansoni infection that can lead to heart failure and death. During PAH, the expansion of apoptosis-resistant endothelial cells (ECs) has been extensively reported; however, therapeutic approaches to prevent the progression or reversal of this pathological phenotype remain clinically challenging. Previously, we showed that depletion of the anti-apoptotic protein Caveolin-1 (Cav-1) by shedding extracellular vesicles contributes to shifting endoprotective bone morphogenetic protein receptor 2 (BMPR2) towards transforming growth factor beta (TGF-ß)-mediated survival of an abnormal EC phenotype. However, the mechanism underlying the reduced endoprotection in PAH remains unclear. Interestingly, recent findings indicate that, similar to the gut, healthy human lungs are populated by diverse microbiota, and their composition depends significantly on intrinsic and extrinsic host factors, including infection. Despite the current knowledge that the disruption of the gut microbiome contributes to the development of PAH, the role of the lung microbiome remains unclear. Thus, using a preclinical animal model of Sch-PAH, we tested whether S. mansoni infection alters the gut-lung microbiome composition and causes EC injury, initiating the expansion of an abnormal EC phenotype observed in PAH. Indeed, in vivo stimulation with S. mansoni eggs significantly altered the gut-lung microbiome profile, in addition to promoting injury to the lung vasculature, characterized by increased apoptotic markers and loss of endoprotective expression of lung Cav-1 and BMPR2. Moreover, S. mansoni egg stimulus induced severe pulmonary vascular remodeling, leading to elevated right ventricular systolic pressure and hypertrophy, characteristic of PAH. In vitro, exposure to the immunodominant S. mansoni egg antigen p40 activated TLR4/CD14-mediated transient phosphorylation of Cav-1 at Tyr14 in human lung microvascular EC (HMVEC-L), culminating in a mild reduction of Cav-1 expression, but failed to promote death and shedding of extracellular vesicles observed in vivo. Altogether, these data suggest that disruption of the host-associated gut-lung microbiota may be essential for the emergence and expansion of the abnormal lung endothelial phenotype observed in PAH, in addition to S. mansoni eggs and antigens.

Dysbiosis in Inflammatory Bowel Disease: Pathogenic Role and Potential Therapeutic Targets.

Microbe-host communication is essential to maintain vital functions of a healthy host, and its disruption has been associated with several diseases, including Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel disease (IBD). Although individual members of the intestinal microbiota have been associated with experimental IBD, identifying microorganisms that affect disease susceptibility and phenotypes in humans remains a considerable challenge. Currently, the lack of a definition between what is healthy and what is a dysbiotic gut microbiome limits research. Nevertheless, although clear proof-of-concept of causality is still lacking, there is an increasingly evident need to understand the microbial basis of IBD at the microbial strain, genomic, epigenomic, and functional levels and in specific clinical contexts. Recent information on the role of diet and novel environmental risk factors affecting the gut microbiome has direct implications for the immune response that impacts the development of IBD. The complexity of IBD pathogenesis, involving multiple distinct elements, suggests the need for an integrative approach, likely utilizing computational modeling of molecular datasets to identify more specific therapeutic targets.

MSU Crystals induce sterile IL-1ß secretion via P2X7 receptor activation and HMGB1 release.

BACKGROUD: The mechanism by which monosodium urate (MSU) crystals induce inflammation is not completely understood. Few studies have shown that MSU is capable of stimulating the release of IL-1ß in the absence of LPS treatment. The purinergic P2X7 receptor is involved in the release of IL-1ß in inflammatory settings caused by crystals, as is the case in silicosis. METHODS: We investigated the role of P2X7 receptor in sterile MSU-induced inflammation by evaluating peritonitis and paw edema. In in vitro models, we performed the experiments using peritoneal macrophages and THP-1 cells. We measured inflammatory parameters using ELISA and immunoblotting. We measured cell recruitment using cell phenotypic identification and hemocytometer counts. RESULTS: Our in vivo data showed that animals without P2X7 receptors generated less paw edema, less cell recruitment, and lower levels of IL-1ß release in a peritonitis model. In the in vitro model, we observed that MSU induced dye uptake by the P2X7 receptor. In the absence of the receptor, or when it was blocked, MSU crystals induced less IL-1ß release and this effect corresponded to the concentration of extracellular ATP. Moreover, MSU treatment induced HMGB1 release; pre-treatment with P2X7 antagonist reduced the amount of HMGB1 in cell supernatants. CONCLUSIONS: IL-1ß secretion induced by MSU depends on P2X7 receptor activation and involves HMGB1 release. GENERAL SIGNIFICANCE: We propose that cell activation caused by MSU crystals induces peritoneal macrophages and THP-1 cells to release ATP and HMGB1, causing IL-1ß secretion via P2X7 receptor activation.

P2X7 receptor-mediated leukocyte recruitment and Porphyromonas gingivalis clearance requires IL-1ß production and autocrine IL-1 receptor activation.

The Gram-negative bacterium Porphyromonas gingivalis is strongly associated with periodontitis. We previously demonstrated that P2X7 receptor activation by extracellular ATP (eATP) triggers elimination of intracellular pathogens, such as Leishmania amazonensis, Toxoplasma gondii and Chlamydia trachomatis. We also showed that eATP-induced IL-1ß secretion via the P2X7 receptor is impaired by P. gingivalis fimbriae. Furthermore, enhanced P2X7 receptor expression was detected in the maxilla of P. gingivalis-orally infected mice as well as in human periodontitis patients. Here, we examined the effect of P2X7-, caspase-1/11- and IL-1 receptor-mediated responses during P. gingivalis infection. P2X7 receptor played a large role in controlling P. gingivalis infection and P. gingivalis-induced recruitment of inflammatory cells, especially neutrophils. In addition, IL-1ß secretion was detected at different time points only when P2X7 receptor was expressed and in the presence of eATP treatment ex vivo. Activation of P2X7 receptor and IL-1 receptor by eATP and IL-1ß, respectively, promoted P. gingivalis elimination in macrophages. Interestingly, eATP-induced P. gingivalis killing was inhibited by the IL-1 receptor antagonist (IL-1RA), consistent with autocrine activation of the IL-1 receptor for P. gingivalis elimination. In vivo, caspase-1/11 and IL-1 receptor were also required for bacterial clearance, leukocyte recruitment and IL-1ß production after P. gingivalis infection. Our data demonstrate that the P2X7-IL-1 receptor axis activation is required for effective innate immune responses against P. gingivalis infection.

Pyrimidinergic Receptor Activation Controls Toxoplasma gondii Infection in Macrophages.

Infection by the protozoan parasite Toxoplasma gondii is highly prevalent worldwide and may have serious clinical manifestations in immunocompromised patients. T. gondii is an obligate intracellular parasite that infects almost any cell type in mammalian hosts, including immune cells. The immune cells express purinergic P2 receptors in their membrane--subdivided into P2Y and P2X subfamilies--whose activation is important for infection control. Here, we examined the effect of treatment with UTP and UDP in mouse peritoneal macrophages infected with T. gondii tachyzoites. Treatment with these nucleotides reduced parasitic load by 90%, but did not increase the levels of the inflammatory mediators NO and ROS, nor did it modulate host cell death by apoptosis or necrosis. On the other hand, UTP and UDP treatments induced early egress of tachyzoites from infected macrophages, in a Ca2+-dependent manner, as shown by scanning electron microscopy analysis, and videomicroscopy. In subsequent infections, prematurely egressed parasites had reduced infectivity, and could neither replicate nor inhibit the fusion of lysosomes to the parasitophorous vacuole. The use of selective agonists and antagonists of the receptor subtypes P2Y2 and P2Y4 and P2Y6 showed that premature parasite egress may be mediated by the activation of these receptor subtypes. Our results suggest that the activity of P2Y host cell receptors controls T. gondii infection in macrophages, highlighting the importance of pyrimidinergic signaling for innate immune system response against infection. Finally the P2Y receptors should be considered as new target for the development of drugs against T. gondii infection.