Biology subjects

Beldi, G.

Publications and source records attributed to Beldi, G..

7 recordsLinked to original sources

bioRxiv2024

Released Bacterial ATP Shapes Local and Systemic Inflammation during Abdominal Sepsis

Sepsis causes millions of deaths per year worldwide and is a current global health priority declared by the WHO. Sepsis-related deaths are a result of dysregulated inflammatory immune responses indicating the need to develop strategies to target inflammation. An important mediator of inflammation is extracellular adenosine triphosphate (ATP) that is secreted by inflamed host cells and tissues, and also by bacteria in a strain-specific and growth phase-dependent manner. Here, we investigated the mechanisms by which bacteria release ATP. Using genetic mutant strains of Escherichia coli (E. coli), we demonstrate that ATP release is dependent on ATP synthase within the inner bacterial membrane. In addition, impaired integrity of the outer bacterial membrane and bacterial death notably contribute to ATP release. In a mouse model of abdominal sepsis, local effects of bacterial ATP were analysed using a transformed E. coli bearing an arabinose-inducible periplasmic apyrase hydrolyzing ATP to be released. Abrogating bacterial ATP release shows that bacterial ATP suppresses local immune responses, resulting in reduced neutrophil counts and impaired survival. In addition, bacterial ATP has systemic effects via its transport in outer membrane vesicles (OMV). ATP-loaded OMV are quickly distributed throughout the body and upregulated expression of genes activating degranulation in neutrophils, potentially contributing to the exacerbation of sepsis severity. This study reveals mechanisms of bacterial ATP release and its local and systemic roles in sepsis pathogenesis.

microbiology↗

bioRxiv2021

Primary infection by E. multilocularis induces distinct patterns of crosstalk between hepatic regulatory T and natural killer T cells in mice

The larval stage of the helminthic cestode Echinococcus multilocularis can inflict tumor-like hepatic lesions that cause the parasitic disease alveolar echinococcosis in humans, with high mortality in untreated patients. Recently, opportunistic properties of the disease have been proposed based on the increased incidence in immunocompromised patients and mouse models, indicating that an appropriate adaptive immune response is required for the control of the disease. However, little is known about how the local hepatic immune responses modulate the infection with E. multilocularis. In a mouse model of oral infection that mimics the normal infection route in human patients, the adaptive immune response in the liver was assessed using single-cell RNA sequencing of isolated hepatic CD3+ T cells at different infection stages. We observed an early significant increase in regulatory T and natural killer T cells in parallel with an active downregulation of CD4+ and CD8+ T cells. Early interactions between regulatory T cells and natural killer T cells indicate a promotion of the formation of hepatic lesions and later contribute to suppression of the resolution of parasite-induced pathology. The obtained data provides a fresh insight on the adaptive immune responses and local regulatory pathways at different infection stages of E. multilocularis in mice. Author summaryAlveolar echinococcosis is an endemic parasitic infection leading to slowly growing but potentially lethal liver lesions if untreated. Transmission by increasing populations of urban foxes and the raise of immunosuppressed patients in mainly industrializsed endemic zones are the main causes responsible for increased incidence of alveolar echinococcosis. Observations in humans and mice indicate that reactions of the adaptive immune system are required to control the disease and to protect from a chronic infection. Therefore, we analysed the responses of T cells in the liver at single-cell resolution in a murine model mimicking the typical route of infection in humans. This so called single-cell RNA sequencing revealed specific temporal changes of T cell subsets such as natural killer T cells and regulatory T cells, indicating that these two cell types are recruited in the early phase to try to protect from parasite proliferation and are subsequently inhibited in the late phase of infection thus indicating immune escape mechanisms of the parasite. This study shows temporal changes of the immune cell profile in the liver over the course of a natural infection with E. multilocularis at the single cell level and reveals putative targets for novel therapeutic approaches for human AE and possibly other (parasitic/helminthic) diseases.

immunology↗

bioRxiv2021

Single cell chronoatlas of regenerating mouse livers reveals early Kupffer cell proliferation

The liver is exemplar to study tissue regeneration due to its inherent ability of repair and regrowth. It replaces its lost or injured tissue by the proliferation, interaction and temporal coordination of multiple residential cell types. Until now we lacked a detailed description of the specific contributions of each cell type to the regenerative process, and therefore analyzed mouse livers 0, 3, 6, and 24 hours following two-thirds partial hepatectomy (PHx) by single cell RNA-sequencing (scRNA-seq) and mass cytometry. Our resulting genome wide temporal atlas contains the time dependent transcriptional changes in hepatocytes, endothelial cells, bone marrow-derived macrophages (BMDM) and Kupffer cells. In addition, it describes the cell specific contribution of mitogenic growth factors from biliary epithelial, endothelial and stellate cells as well as chemokines and cytokines from BMDM and granulocytes. And interestingly, Kupffer cells as opposed to hepatocytes emerged as the first cell to proliferate presenting a new dynamic in the liver following PHx. Here, we provide a robust data set at cellular resolution to uncover new elements and revisit current dogmas on the mechanisms underlying liver regeneration. To facilitate access to the data, we have launched the portal www.phxatlas.ch in which the scRNA-seq data can be visualized.

developmental biology↗

bioRxiv2021

Albendazole reduces endoplasmic reticulum stress induced by Echinococcus multilocularis in mice

BackgroundEchinococcus multilocularis causes alveolar echinococcosis (AE), a rising zoonotic disease in the northern hemisphere. Treatment of this fatal disease is limited to chemotherapy using benzimidazoles and surgical intervention, with relatively frequent disease recurrence in cases without radical surgery. Elucidating the molecular mechanisms underlying E. multilocularis infections and host-parasite interactions aids developing novel therapeutic options. This study explored an involvement of unfolded protein response (UPR) and endoplasmic reticulum-stress (ERS) during E. multilocularis infection in mice. MethodsE. multilocularis- and mock-infected C57BL/6 mice were subdivided six weeks after infection into vehicle and albendazole (ABZ) treated groups. Eight weeks later, liver tissue was collected to examine mRNA, microRNA (miR) and protein expression of UPR- and ERS-related genes. ResultsE. multilocularis infection upregulated UPR- and ERS-related proteins, including ATF6, CHOP, GRP78, ERP72, H6PD and calreticulin, whilst PERK and its target eIF2 were not affected, and IRE1 and ATF4 were downregulated. ABZ treatment in E. multilocularis infected mice reversed the increased ATF6 and calreticulin protein expression, tended to reverse increased CHOP, GRP78, ERP72 and H6PD expression, and decreased ATF4 and IRE1 expression to levels seen in mock-infected mice. The expression of miR-146a-5p (downregulated by IRE1) and miR-1839-5p (exhibiting a unique target site in the IRE1 3UTR) were significantly increased in E. multilocularis infected mice, an effect reversed by ABZ treatment. Other miRs analyzed were not altered in E. multilocularis infected mice. Conclusions and SignificanceAE causes UPR activation and ERS in mice. The E. multilocularis-induced ERS was ameliorated by ABZ treatment, indicating its effectiveness to inhibit parasite proliferation and downregulate its activity status. ABZ itself did not affect UPR in control mice. Identified miR-146a-5p and miR-1839-5p might represent biomarkers of E. multilocularis infection. Modulation of UPR and ERS, in addition to ABZ administration, could be exploited to treat E. multilocularis infection. Author summaryAlveolar echinococcosis is a zoonotic disease caused by the fox tapeworm Echinococcus multilocularis. Treatment of this fatal disease is limited to surgical intervention, preferably radical curative surgery if possible, and the use of parasitostatic benzimidazoles. It is not yet fully understood how the parasite can remain in the hosts tissue for prolonged periods, complicating the development of therapeutic applications. This work investigated an involvement of the unfolded protein response (UPR) and endoplasmic reticulum-stress (ERS) during E. multilocularis infection and upon treatment with albendazole (ABZ) in mice. The results revealed increased expression levels of the ERS sensor ATF6 and of downstream target genes in liver tissue of E. multilocularis- compared to mock-infected mice. Additionally, H6PD, generating NADPH within the endoplasmic reticulum, and the lectin-chaperone calreticulin were increased in E. multilocularis infected liver tissue while the expression of the ERS associated genes ATF4 and IRE1 were decreased. The miR-1839-5p and miR-146-p, linked to IRE1, were elevated upon E. multilocularis infection, offering potential as novel biomarkers of alveolar echinococcosis. The observed gene expression changes were at least partially reversed by ABZ treatment. Whether modulation of UPR and ERS targets can improve the therapy of alveolar echinococcosis remains to be investigated.

pathology↗

bioRxiv2019

Compartmentalization of intestinal bacteria by hepatic ILC3s prevents infections after surgery

Infections after surgical interventions are assumed to be caused by contamination. We show by analyzing multicentric data of 6561 patients that surgical infections as well as sepsis had a predominantly enteric microbial signature irrespective of the type of surgery, suggesting failure of intestinal bacterial compartmentalization. In mice, we reveal that hepatic surgery induced dysregulation of intestinal and hepatic type 3 innate lymphoid cells (ILC3s) and intestinal leakage resulting in enteric bacterial translocation via lymphatic vessels. In the absence of hepatic ILC3s, inflammasome activation and the induction of antimicrobial peptide encoding genes, bacteria colonized remote systemic organs and impaired surgical outcomes. Conversely, mammalian-microbial commensalism is required for the education of host immunity to ensure optimal hepatic healing responses. In fact, microbial-derived products were sufficient for the induction of proliferative transcriptional networks in the mouse liver, as illustrated by serum transfer experiments, mass spectrometry and RNA expression analysis, indicating that the balanced exposure of the host to commensals is essential for recovery. This study reveals the intestinal origin of microbes causing complications after surgical interventions and highlights host protective mechanisms of controlled commensalism that prevent infections.\n\nOne Sentence SummaryIntestinal bacteria cause surgical infections

immunology↗

bioRxiv2019

Bayesian Correlation is a robust similarity measure for single cell RNA-seq data

Assessing similarity is highly important for bioinformatics algorithms to determine correlations between biological information. A common problem is that similarity can appear by chance, particularly for low expressed entities. This is especially relevant in single cell RNA-seq (scRNA-seq) data because read counts are much lower compared to bulk RNA-seq.\n\nRecently, a Bayesian correlation scheme, that assigns low similarity to genes that have low confidence expression estimates, has been proposed to assess similarity for bulk RNA-seq. Our goal is to extend the properties of the Bayesian correlation in scRNA-seq data by considering 3 ways to compute similarity. First, we compute the similarity of pairs of genes over all cells. Second, we identify specific cell populations and compute the correlation in those populations. Third, we compute the similarity of pairs of genes over all clusters, by considering the total mRNA expression.\n\nWe demonstrate that Bayesian correlations are more reproducible than Pearson correlations. Compared to Pearson correlations, Bayesian correlations have a smaller dependence on the number of input cells. We show that the Bayesian correlation algorithm assigns high similarity values to genes with a biological relevance in a specific population.\n\nWe conclude that Bayesian correlation is a robust similarity measure in scRNA-seq data.

bioinformatics↗

bioRxiv2018

Connexin-43 dependent ATP release mediates macrophage activation during peritonitis

Peritonitis is the consequence of bacterial spillage into a sterile environment by gastrointestinal hollow-organ perforation that may lead to fulminant sepsis. Outcome of peritonitis-induced sepsis critically depends on macrophage activation by extracellular ATP release and associated para- and autocrine signaling via purinergic receptors. Mechanisms that mediate and control ATP release, however, are poorly understood. Here we show that TLR-2 and -4 agonists trigger ATP release via Connexin-43 (CX43) hemichannels in peritoneal macrophages leading to poor survival during sepsis. In humans, CX43 expression was upregulated on macrophages isolated from the peritoneal cavity in patients with intraperitoneal infection but not in healthy controls. Using a murine caecal ligation and puncture (CLP) model, we identified increased CX43 expression in activated infiltrating peritoneal, hepatic and pulmonary macrophages. Conditional MAC-CX43 KO Lyz2cre/creCx43flox/flox mice were developed to specifically assess the CX43 impact in macrophages. Both macrophage-specific CX43 deletion (using Lyz2cre/creCx43flox/flox mice) or pharmacological CX43 blockade were associated with reduced cytokine secretion by macrophages in response to LPS and CLP. This was ultimately resulting in increased survival in Lyz2cre/creCx43flox/flox mice and after pharmacological blockade. Specific inhibition of the purinergic receptor P2RY1 abrogated CX43 elicited cytokine responses. In conclusion, inhibition of autocrine ATP signaling via CX43 on macrophages and P2RY1 improves sepsis outcome in experimental peritonitis.\n\nBrief SummaryConnexin-43-mediated ATP release from macrophages in response to TLR-4 and -2 agonists modulates autocrine activation of macrophages in a P2Y1-dependent manner, ultimately determining sepsis survival.

immunology↗