Disruption of calcium (Ca2+) homeostasis in neurons is a hallmark of neurodegenerative diseases. Here, we investigate the mechanisms leading to Ca2+ dysregulation and ask whether altered Ca2+ dynamics impinge on neuronal stress and circuit dysfunction. Using two-photon microscopy, we show that ocular hypertension, a major risk factor in glaucoma, and optic nerve crush injury disrupt the capacity of retinal neurons to clear cytosolic Ca2+ leading to impaired light-evoked responses. Gene- and protein expression analysis reveal the loss of the sarco-endoplasmic reticulum (ER) Ca2+-ATPase2 pump (SERCA2/ATP2A2) in injured retinal neurons from mice and patients with primary open-angle glaucoma. Pharmacological activation or neuron-specific gene delivery of SERCA2 is sufficient to rescue single-cell Ca2+ dynamics and promote robust survival of damaged neurons. Furthermore, SERCA2 gene supplementation reduces ER stress, reestablishes circuit balance, and restores visual behaviors. Our findings reveal that enhancing the Ca2+ clearance capacity of vulnerable neurons alleviates organelle stress and promotes neurorecovery.
Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.

Intestinal epithelial expression of the tight junction protein claudin-2, which forms paracellular cation and water channels, is precisely regulated during development and in disease. Here, we show that small intestinal epithelial claudin-2 expression is selectively upregulated in septic patients. Similar changes occurred in septic mice, where claudin-2 upregulation coincided with increased flux across the paracellular pore pathway. In order to define the significance of these changes, sepsis was induced in claudin-2 knockout (KO) and wild-type (WT) mice. Sepsis-induced increases in pore pathway permeability were prevented by claudin-2 KO. Moreover, claudin-2 deletion reduced interleukin-17 production and T cell activation and limited intestinal damage. These effects were associated with reduced numbers of neutrophils, macrophages, dendritic cells, and bacteria within the peritoneal fluid of septic claudin-2 KO mice. Most strikingly, claudin-2 deletion dramatically enhanced survival in sepsis. Finally, the microbial changes induced by sepsis were less pathogenic in claudin-2 KO mice as survival of healthy WT mice injected with cecal slurry collected from WT mice 24 h after sepsis was far worse than that of healthy WT mice injected with cecal slurry collected from claudin-2 KO mice 24 h after sepsis. Claudin-2 upregulation and increased pore pathway permeability are, therefore, key intermediates that contribute to development of dysbiosis, intestinal damage, inflammation, ineffective pathogen control, and increased mortality in sepsis. The striking impact of claudin-2 deletion on progression of the lethal cascade activated during sepsis suggests that claudin-2 may be an attractive therapeutic target in septic patients.

Insulin resistance is a compromised response to insulin in target tissues such as liver. Emerging evidence shows that vascular endothelial cells (ECs) are critical in mediating glucose metabolism. However, how liver ECs can regulate inflammation in the setting of insulin resistance is still unknown. Using genome-wide transcriptome analysis of ECs isolated from diabetic mice, we found enrichment of the genes involved in epidermal growth factor receptor (Egfr) signaling. In line with this, hepatic sinusoidal ECs in diabetic mice had elevated levels of Egfr expression. Interestingly, we found an increased number of hepatic myeloid cells, especially macrophages, and systemic glucose intolerance in Cdh5Cre/+Egfrfl/fl mice lacking Egfr in ECs compared with littermate control mice with type II diabetes. Egfr deficiency upregulated the expression of MCP-1 in hepatic sinusoidal ECs. This resulted in augmented monocyte recruitment and macrophage differentiation in Cdh5Cre/+Egfrfl/fl mice compared with littermate control mice as determined by a mouse model of parabiosis. Finally, MCP-1 neutralization and hepatic macrophage depletion in Cdh5Cre/+Egfrfl/fl mice resulted in a reduced number of hepatic macrophages and ameliorated glucose intolerance compared with the control groups. Collectively, these results demonstrate a protective endothelial Egfr signaling in reducing monocyte-mediated hepatic inflammation and glucose intolerance in type II diabetic mice.
Copyright © 2023 by The American Association of Immunologists, Inc.

The intestinal immune system must concomitantly tolerate food and commensals and protect against pathogens. Dendritic cells (DCs) orchestrate these immune responses by presenting luminal antigens and inducing functional differentiation of CD4 + T cells into regulatory (pTreg) or pro-inflammatory (Th) subsets. However, the exact nature of the DCs inducing tolerance or inflammation to dietary antigens has been difficult to define. Using an intestine-adapted Labeling Immune Partnerships by SorTagging Intercellular Contacts (LIPSTIC) combined with single-cell transcriptomics, we characterized DCs presenting dietary antigens in the context of tolerance or infection. At steady-state, migratory cDC1 and cDC2 DCs, but not resident DCs, were found to present dietary antigen to cognate CD4 + T cells. Whereas cDC2s promoted T cell activation, only cDC1s induced their differentiation into pTregs. Infection with the helminth Strongyloides venezuelensis abrogated cDC1 presentation of dietary antigens, preventing pTreg and oral tolerance induction. In contrast, Heligmosomoides polygyrus infection only partially affected cDC1s, allowing oral tolerance to be maintained. An expanded population of cDC2s that induced type-2 immunity during both helminth infections did not present dietary antigens, demonstrating that compartmentalized presentation of luminal antigens can prevent food-specific Th2 responses during inflammatory conditions. Our data uncover novel cellular mechanisms by which tolerance to food is induced and can be disrupted during infections.

IgG4 is the least potent human IgG subclass for the FcγR-mediated antibody effector function. Paradoxically, IgG4 is also the dominant IgG subclass of pathogenic autoantibodies in IgG4-mediated diseases. Here, we show that the IgG subclass and Fc-FcγR interaction have a distinct impact on the pathogenic function of autoantibodies in different IgG4-mediated diseases in mouse models. While IgG4 and its weak Fc-FcγR interaction have an ameliorative role in the pathogenicity of anti-ADAMTS13 autoantibodies isolated from thrombotic thrombocytopenic purpura (TTP) patients, they have an unexpected exacerbating effect on anti-Dsg1 autoantibody pathogenicity in pemphigus foliaceus (PF) models. Strikingly, a non-pathogenic anti-Dsg1 antibody variant optimized for FcγR-mediated effector function can attenuate the skin lesions induced by pathogenic anti-Dsg1 antibodies by promoting the clearance of dead keratinocytes. These studies suggest that IgG effector function contributes to the clearance of autoantibody-Ag complexes, which is harmful in TTP, but beneficial in PF and may provide new therapeutic opportunity.
© 2022, Bi et al.