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Disruption of C5a/C5aR1 axis confers protection against hookworm infection in lung

ABSTRACT: Hookworms are soil-transmitted parasitic nematodes that penetrate the host skin before migrating to the lungs. With an estimated 500-700 million people infected worldwide, hookworm infections are a neglected tropical disease and a significant cause of morbidity, particularly in children, pregnant women, and immunocompromised individuals. Although there is ample evidence that complement activation is pivotal to elicit a protective host immune response against invasive pathogens, its role in hookworm infection remains insufficiently explored. Here, we investigated the complement anaphylatoxin, C5a, during the early lung stage of infection with Nippostrongylus brasiliensis in C57BL/6J wild type and C5aR1-/- mice. Despite the previously reported ability of lung larvae to evade complement activation, C5a was detectable locally in lung tissue and broncho-alveolar lavages. Surprisingly, C5aR1 presence directly contributed to the pathogenicity of hookworm infection. The burden of viable parasites in the lungs was mitigated in C5aR1-/- mice, compared to C57BL/6J mice 48 hours post-infection. Additionally, C5aR1-/- mice showed significantly reduced lung injury, lower cytokine release, attenuated alveolar hemorrhage, and limited alveolar-capillary barrier disruption. Neutrophils were the most abundant and highest C5aR1-expressing cell type in the alveolar space after infection. Deficiency of C5aR1 reduced the influx of neutrophils, monocytes, and eosinophils to the pulmonary airways. RNA sequencing of alveolar neutrophils revealed C5aR1-dependent regulation of the novel nuclear protein, DEDD2. In conclusion, our findings highlight the impact of C5aR1 signaling in neutrophils during hookworm infection uncovering an unexpected downside of complement activation in parasitic infection.

ORGANISM(S): Mus musculus

PROVIDER: GSE272613 | GEO | 2024/08/29

REPOSITORIES: GEO

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Project description:The complement system is part of the innate immune system that works to clear pathogens and cellular debris. In the central nervous system (CNS) complement activation can promote synaptic pruning clearance of neuronal blebs recruitment of phagocytes and protection from pathogens. However in a neuropathologic environment complement activation may contribute to inflammatory pathways neuronal dysfunction and in the Alzheimer’s disease (AD) brain cognitive decline. If complement activation proceeds to the cleavage of C5 and thus generation of C5a engagement of C5a with the receptor C5aR1 can instigate a feed-forward loop of inflammation injury and neuronal death thus making this molecule a potential target for modulation in AD therapeutics. The Arctic (Arc) AD mouse model known to rapidly accumulate fibrillar amyloid plaques was crossed to a model that lacks the receptor for C5a (ArcC5aR1KO) or to a transgenic mouse that generates C5a under the GFAP promoter (ArcC5a+). ArcticC5a+ mice showed accelerated loss of spatial memory compared to Arc mice. While eliminating C5aR1 did not alter amyloid plaque accumulation in this AD model C5aR1KO delayed or prevented the expression of important AD-associated genes in the hippocampus indicating a separation between those genes induced by amyloid plaques and those influenced by C5a-C5aR1 signaling. C5ar1 deletion also reduced/delayed the expression of select pan-reactive and A1 reactive astrocyte genes. ArcC5aR1KO showed delayed expression of genes enriched for biological processes that are significant in the AD context such as regulation of inflammatory signaling microglial cell activation astrocyte migration and lysosome pathway. Interestingly overexpression of C5a also delayed the increase of some AD- complement and astrocyte-associated genes perhaps mediated by C5aR2 and emphasizing the importance of selectively suppressing C5aR1. Immunohistochemical investigation further confirmed that modulation of C5a-C5aR1 either delayed or reduced some reactive microglial markers in the Arc hippocampus including CD11b and CD11c. These results suggest that C5a-C5aR1 signaling in the context of AD largely exerts its effects by suppressing those microglial activation pathways that accelerate disease enhancing pathways. Given the highly focused modulation of a common driver of neurotoxicity pharmacological inhibition of this C5aR1 signaling pathway is a promising therapeutic strategy to treat AD.

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Disruption of C5a/C5aR1 axis confers protection against hookworm infection in lung

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