Biology subjects

Mansour, M. K.

Publications and source records attributed to Mansour, M. K..

8 recordsLinked to original sources

bioRxiv2024

Blocking HXA3-mediated neutrophil elastase release during S. pneumoniae lung infection limits pulmonary epithelial barrier disruption and bacteremia

Streptococcus pneumoniae (Sp), a leading cause of community-acquired pneumonia, can spread from the lung into the bloodstream to cause septicemia and meningitis, with a concomitant three-fold increase in mortality. Limitations in vaccine efficacy and a rise in antimicrobial resistance have spurred searches for host-directed therapies that target pathogenic immune processes. Polymorphonuclear leukocytes (PMNs) are essential for infection control but can also promote tissue damage and pathogen spread. The major Sp virulence factor, pneumolysin (PLY), triggers acute inflammation by stimulating the 12-lipoxygenase (12-LOX) eicosanoid synthesis pathway in epithelial cells. This pathway is required for systemic spread in a mouse pneumonia model and produces a number of bioactive lipids, including hepoxilin A3 (HXA3), a hydroxy epoxide PMN chemoattractant that has been hypothesized to facilitate breach of mucosal barriers. To understand how 12-LOX-dependent inflammation promotes dissemination during Sp lung infection and dissemination, we utilized bronchial stem cell-derived air-liquid interface (ALI) cultures that lack this enzyme to show that HXA3 methyl ester (HXA3-ME) is sufficient to promote basolateral-to-apical PMN transmigration, monolayer disruption, and concomitant Sp barrier breach. In contrast, PMN transmigration in response to the non-eicosanoid chemoattractant fMLP did not lead to epithelial disruption or bacterial translocation. Correspondingly, HXA3-ME but not fMLP increased release of neutrophil elastase (NE) from Sp-infected PMNs. Pharmacologic blockade of NE secretion or activity diminished epithelial barrier disruption and bacteremia after pulmonary challenge of mice. Thus, HXA3 promotes barrier disrupting PMN transmigration and NE release, pathological events that can be targeted to curtail systemic disease following pneumococcal pneumonia. ImportanceStreptococcus pneumoniae (Sp), a leading cause of pneumonia, can spread from the lung into the bloodstream to cause systemic disease. Limitations in vaccine efficacy and a rise in antimicrobial resistance have spurred searches for host-directed therapies that limit pathologic host immune responses to Sp. Excessive polymorphonuclear leukocyte (PMN) infiltration into Sp-infected airways promotes systemic disease. Using stem cell-derived respiratory cultures that reflect bona fide lung epithelium, we identified the eicosanoid hepoxilin A3 as a critical pulmonary PMN chemoattractant that is sufficient to drive PMN-mediated epithelial damage by inducing the release of neutrophil elastase. Inhibition of the release or activity of this protease in mice limited epithelial barrier disruption and bacterial dissemination, suggesting a new host-directed treatment for Sp lung infection.

microbiology↗

bioRxiv2024

Vimentin regulates mitochondrial ROS production and inflammatory responses of neutrophils

The intermediate filament vimentin is present in immune cells and is implicated in proinflammatory immune responses. Whether and how it supports antimicrobial activities of neutrophils is not well established. Here, we developed an immortalized neutrophil model to examine the requirement of vimentin. We demonstrate that vimentin restricts the production of proinflammatory cytokines and reactive oxygen species (ROS), but enhances phagocytosis and swarming. We observe that vimentin is dispensable for neutrophil extracellular trap (NET) formation, degranulation, and inflammasome activation. Moreover, gene expression analysis demonstrated that the presence of vimentin was associated with changes in expression of multiple genes required for mitochondrial function and ROS overproduction. Treatment of wild-type cells with rotenone, an inhibitor for complex I of the electron transport chain, increases the ROS levels. Likewise, treatment with mitoTEMPO, a SOD mimetic, rescues the ROS production in cells lacking vimentin. Together, these data show vimentin regulates neutrophil antimicrobial functions and alters ROS levels through regulation of mitochondrial activity.

immunology↗

bioRxiv2023

Self-extinguishing relay waves enable homeostaticcontrol of human neutrophil swarming

Neutrophils exhibit self-amplified swarming to sites of injury and infection. How swarming is controlled to ensure the proper level of neutrophil recruitment is unknown. Using an ex vivo model of infection, we find that human neutrophils use active relay to generate multiple pulsatile waves of swarming signals. Unlike classic active relay systems such as action potentials, neutrophil swarming relay waves are self-extinguishing, limiting the spatial range of cell recruitment. We identify an NADPH-oxidase-based negative feedback loop that is needed for this self-extinguishing behavior. Through this circuit, neutrophils adjust the number and size of swarming waves for homeostatic levels of cell recruitment over a wide range of initial cell densities. We link a broken homeostat to neutrophil over-recruitment in the context of human chronic granulomatous disease.

cell biology↗

bioRxiv2022

Predestined neutrophil heterogeneity in homeostasis varies in transcriptional and phenotypic response to Candida

Once perceived to be homogenous effector cells, neutrophils have since been shown to exhibit population heterogeneity. Here, we established an experimental model of clonal neutrophil heterogeneity using conditionally immortalized clonal granulocyte monocyte progenitors (GMPs) and their mature neutrophil progeny. Transcriptional and epigenetic profiling showed conserved genome-wide signatures of transcription and chromatin accessibility that were specific to individual GMP clones and their paired neutrophil progeny, suggesting that clone specificity is established as early as the GMP stage. Clone-specific genes in vital regulatory pathways were pre-programmed and exhibited delayed expression in the mature neutrophil stage. The clone-specific gene expression in the mature neutrophils paired to enhancer activation in their parental GMPs. To determine whether transcriptional heterogeneity predicted the response to fungal pathogens, neutrophil clones were functionally profiled. Clones demonstrated heterogeneous responses to fungal pathogens in vitro and revealed neutrophil subsets with evidence for tailored functional responses to Candida spp. as well as specific transcriptional and epigenetic patterns that may explain these differences. Together, this work establishes that heterogenous GMP and neutrophil compartments exist under homeostatic conditions and that these represent predefined clusters that are uniquely adapted to control invasive fungal pathogens. Short SummaryClonal neutrophil progenitors demonstrate heterogeneity in transcription and chromatin accessibility which may inform response to later fungal challenges.

immunology↗

bioRxiv2022

The C-type Lectin Receptor Dectin-2 is a receptor for Aspergillus fumigatus galactomannan

Aspergillus fumigatus is a ubiquitous environmental mold that causes significant mortality particularly amongst immunocompromised patients. The detection of the Aspergillus-derived carbohydrate galactomannan in patient sera and bronchoalveolar lavage fluid is the major biomarker used to detect A. fumigatus infection in clinical medicine. Despite the clinical relevance of this carbohydrate, we lack a fundamental understanding of how galactomannan is recognized by the immune system and its consequences. Galactomannan is composed of a linear mannan backbone with galactofuranose sidechains and is found both attached to the cell surface of Aspergillus and as a soluble carbohydrate in the extracellular milieu. In this study, we utilized fungal-like particles composed of highly purified Aspergillus galactomannan to identify a C-type lectin host receptor for this fungal carbohydrate. We identified a novel and specific interaction between Aspergillus galactomannan and the C-type lectin receptor Dectin-2. We demonstrate that galactomannan bound to Dectin-2 and induced Dectin-2 dependent signaling including activation of spleen tyrosine kinase and potent TNF production. Deficiency of Dectin-2 increased immune cell recruitment to the lungs but was dispensable for survival in a mouse model of pulmonary aspergillosis. Our results identify a novel interaction between galactomannan and Dectin-2 and demonstrate that Dectin-2 is a receptor for galactomannan which leads to a pro-inflammatory immune response in the lung. IMPORTANCEAspergillus fumigatus is a fungal pathogen that causes serious and often fatal disease in humans. The surface of Aspergillus is composed of complex sugar molecules. Recognition of these carbohydrates by immune cells by carbohydrate lectin receptos can lead to clearance of the infection or, in some cases, benefit the fungus by dampening the host response. Galactomannan is a carbohydrate that is part of the cell surface of Aspergillus but is also released during infection and is found in patient lungs as well as their bloodstreams. The significance of our research is that we have identified a mammalian immune cell receptor that recognizes, binds, and signals in response to galactomannan. These results enhance our understanding of how this carbohydrate interacts with the immune system at the site of infection and will lead to broader understanding of how release of galactomannan by Aspergillus effects the immune response in infected patients.

immunology↗

bioRxiv2021

Photoinactivation of catalase sensitizes Candida albicans and Candida auris to ROS-producing agents and immune cells

Nearly all organisms found in nature have evolved and developed their own specific strategies to cope with reactive oxygen species (ROS). Catalase, a heme-containing tetramer protein expressed in a broad range of aerobic fungi, has been utilized as an essential enzymatic ROS detoxifying mechanism, and shows remarkable efficiency in degrading hydrogen peroxide (H2O2) for fungal cell survival and host invasion. Here, we demonstrate that catalase inactivation with blue light renders fungal cells highly susceptible to ROS attack, thus resembling a strength-to-weakness optical switch. To unveil catalase as the underlying molecular target of blue light and its inactivation mechanism, we systematically compared wild-type Candida albicans to a catalase-deficient mutant strain for susceptibility to ROS in the absence/presence of 410 nm treatment. Upon testing on a wide range of fungal species and strains, we found that intracellular catalase could be effectively and universally inactivated by 410 nm blue light. We find that the photoinactivation of catalase in combination with ROS-generating agents is highly effective and potent in achieving full eradication of multiple fungal species and strains, including multiple clinical strains of Candida auris, the causative agent of the global fungal epidemic. In addition, photoinactivation of catalase is shown to facilitate macrophage killing of intracellular Candida albicans. The antifungal efficacy of catalase photoinactivation is further validated using a Candida albicans-induced mouse model of skin abrasion. Taken together, our findings offer a novel catalase-photoinactivation approach to address multidrug-resistant Candida infections.

microbiology↗

bioRxiv2021

tiRNA signaling via stress-regulated vesicle transfer in the hematopoietic niche

Extracellular vesicles transfer complex biologic material between cells, whose role in in-vivo organismal physiology is poorly defined. Here, we demonstrate that osteoblastic cells in the bone marrow elaborate extracellular vesicles that are taken up by hematopoietic progenitor cells in vivo. Genotoxic or infectious stress rapidly increased stromal-derived extracellular vesicle transfer to granulocyte-monocyte progenitors. Stimulating osteoblastic cells with parathyroid hormone or activating its receptor enhanced extracellular vesicle transfer, myeloid recovery post radiation and improved animal survival from Candida sepsis. The extracellular vesicles contained tiRNAs known to modulate protein translation. 5-ti-Pro-CGG-1 was preferentially abundant in osteoblast-derived extracellular vesicles and when transferred to granulocyte macrophage progenitors, increased protein translation, cell proliferation and myeloid differentiation. Therefore, EV-mediated tiRNA transfer provides a stress modulated signaling axis distinct from conventional cytokine-driven stress responses. One sentence summaryStress regulated tiRNA transfer alters hematopoiesis

cell biology↗

bioRxiv2021

Neutrophils require SKAP2 for reactive oxygen species production following C-type lectin and Candida stimulation

Signaling cascades that convert the recognition of pathogens to efficient inflammatory responses by immune cells, specifically neutrophils, are critical for host survival. SKAP2, an adaptor protein, is required for reactive oxygen species (ROS) generation following stimulation by integrins, formyl peptide receptors and gram-negative bacteria Klebsiella pneumoniae and Yersinia pseudotuberculosis in vitro (Nguyen et al., 2020, Shaban et al., 2020, Boras et al., 2017). SKAP2 is also required for the host defense against K. pneumoniae and{Delta} yopH Y. pseudotuberculosis infection in vivo in mouse models (Shaban et al., 2020, Nguyen et al., 2020). Another class of pattern recognition receptors (PRR) is the C-type lectin receptors (CLR), such as Dectin-1, Dectin-2 and Mincle, that are critical to trigger innate immune responses. Using neutrophils from murine HoxB8-immortalized progenitors, we show that SKAP2 is crucial for maximal ROS response to purified CLR agonists and to the fungal pathogens Candida glabrata and C. albicans, as well as for robust killing of C. glabrata. Skap2-/- murine neutrophils failed to generate ROS and exhibited reduced cellular adhesion in response to trehalose-6,6-dibehenate (TDB), furfurman, and curdlan, Mincle, Dectin-2, and Dectin-1 agonists, respectively. TDB, furfurman, and curdlan stimulation also led to SKAP2-independent integrin conformational changes, showing that inside-out signaling by these CLRs to integrin occurs in the absence of SKAP2. Pyk2 phosphorylation was significantly reduced after infection with C. glabrata in Skap2-/- neutrophils, while Syk phosphorylation was unaffected by the loss of SKAP2. These data strengthen the importance of SKAP2 in the activation of neutrophil ROS production by PRRs to include CLRs and extend the role of SKAP2 in host defense beyond antibacterial immunity to include Candida species.

immunology↗