Biology subjects

Das Sarma, J.

Publications and source records attributed to Das Sarma, J..

6 recordsLinked to original sources

bioRxiv2026

LIF-LIFR/gp130 Survival Signaling and Connexin 47 Dysregulation upon Murine-β-Coronavirus Infection: Discovery of a Novel ERK2 Phosphorylation Site at Cx47 C-Terminal Domain

Oligodendrocyte (OLG) injury and loss are increasingly recognized as major determinants of demyelination and remyelination failure in multiple sclerosis (MS), alongside conventional immune-mediated processes. However, the mechanism underlying OLG injury and remyelination failure remains incompletely understood. Astrocyte-oligodendrocyte interactions mediated by Connexin (Cx)-43-Cx47 gap junction (GJ) communication and leukemia inhibitory factor (LIF)-LIFR/gp130 signaling are critical for oligodendroglial survival, homeostasis, and myelination. Despite their established role, how these pathways are altered during neuroinflammatory diseases remains unclear. To address this, we integrated a murine {beta}-coronavirus (RSA59)-induced in vivo model with enriched primary oligodendrocyte precursor cell (OPC) and mature OLG cultures to investigate the effect of RSA59 infection on OLGs, Cx47-mediated GJ communication, and LIF-LIFR/gp130 Signaling. We observed that RSA59 directly targets oligodendroglial lineage cells, including OPCs and mature OLGs, and induces apoptosis in mature OLGs. Despite increased OPC abundance, RSA59 infection reduces the expression of mature and myelinating markers CNPase and MBP, raising the possibility of impaired oligodendrocyte maturation and myelination. RSA59 infection also differentially regulates Cx47-mediated GJ communication and LIF-LIFR/gp130 signaling, crucial for OLG survival and homeostasis. Furthermore, our studies demonstrate that extracellular signal-regulated kinase (ERK), a downstream effector of LIF signaling, phosphorylates the Cx47 C-terminal domain (Cx47CT) at Serine-372 residue, identifying a previously unreported mechanism. Collectively, these findings reveal that RSA59 infection disrupts interconnected oligodendroglial communication and survival pathways, providing mechanistic insights into virus-induced chronic demyelination pathology. The study further identifies Cx47-mediated GJ communication and LIF-LIFR/gp130 signaling as crucial therapeutic targets, and highlights ERK-dependent Cx47CT phosphorylation as a potential regulatory mechanism.

neuroscience↗

bioRxiv2026

CD40 Signaling Restricts Retrograde Viral Spread and Provides Neuroprotection to Retinal Ganglion Cells in a Murine β-Coronavirus Model of Optic Neuritis

CD40, a co-stimulatory receptor of the tumor necrosis factor receptor superfamily expressed on microglia and macrophages, is an upstream regulator of innate antiviral defense in coronavirus-induced neuroinflammation, but its specific role in the visual system remains undefined. Here, we demonstrate that CD40 signaling is essential for restricting retrograde axonal transport of the murine {beta}-coronavirus RSA59 from the brain to the retina and for preventing chronic neurodegeneration in a model of viral optic neuritis. Wild-type and CD40-/- mice were intracranially inoculated with RSA59, and viral burden, neuroinflammation, and neurodegeneration were assessed at acute (day 5), bridging (day 7), and chronic (day 30) stages. CD40-/- mice exhibited significantly increased clinical severity and [~]30% mortality by day 12 post-infection, compared to 100% survival in WT mice. CD40 deficiency resulted in elevated viral loads in the optic nerve and enhanced retrograde viral dissemination across all retinal layers, whereas in WT mice, the virus was largely confined to the ganglion cell layer. CD40-/- mice exhibited impaired early microglial activation and compensatory astrogliosis during the acute and bridging phases. By day 30 p.i., although viral-N protein was undetectable by immunohistochemistry in both genotypes, CD40-/- optic nerves retained significantly higher persistent viral RNA and exhibited extensive demyelination, oligodendrocyte loss, axonal depletion, and upregulation of phagocytic markers. Critically, CD40-/- retinas showed persistent astrogliosis, accumulation of phagocytic microglia/macrophages, and a significant loss of Brn3a+ retinal ganglion cells. These findings establish CD40 as a critical molecular node governing coronavirus optic neuritis, linking early innate immune regulation to long-term neuronal survival.

immunology↗

bioRxiv2024

4-Phenylbutyric acid modulates Connexin 43 expression restricting murine-β-coronavirus infectivity and virus-induced demyelination

Gap junction intercellular communication, particularly involving Connexin 43 and Connexin 47, plays a critical role in maintaining CNS homeostasis and has been implicated in Multiple Sclerosis (MS) pathology. Thus, warranting further studies in experimental animal models to understand how modulation of Cx43 expression can influence MS pathology. Intracranial infection with murine-{beta}-coronavirus Mouse Hepatitis Virus (MHV-A59) in mice results in acute pathology characterized by high viral titers, glial activation in the brain and chronic neuroinflammatory demyelination, effectively mimicking key pathological hallmarks of MS and serving as a robust model to investigate its viral etiology. MHV-A59 infection leads to a pronounced downregulation of Cx43 during the acute phase, emphasizing its critical role in virus-induced CNS pathology. In this study, we investigated the potential of in vivo 4-phenylbutyric acid (4-PBA) administration in modulating Cx43 expression in this MHV-induced model and its consequence on chronic virus-induced demyelination. Our results reveal that 4-PBA treatment reduced acute MHV-A59 infectivity and viral spread in the brain while modulating the glial cell response, mounting host immunity. Treatment with 4-PBA effectively preserved the expression of both Cx43 and Cx47 in infected CNS cells, counteracting their infection-induced downregulation. Furthermore, MHV-A59 infection downregulated the expression of ER-resident thioredoxin family protein (ERp29), a well-known molecular chaperone of Cx43, which was rescued by 4-PBA treatment. We further validated if such downregulation of ERp29 is also evident in MS demyelinating plaques. In human MS patient-derived brain tissue, reduced Cx43 and ERp29 staining was observed in demyelinating plaques. Our studies revealed that 4-PBA treatment not only limits viral replication and spread throughout the brain but also protects the mice against severe chronic neuroinflammatory demyelination. These findings suggest that targeting Cx43 with 4-PBA holds significant therapeutic potential for addressing virus-induced neuroinflammatory demyelination and MS by preserving gap junction intercellular communication.

neuroscience↗

bioRxiv2023

Human coronavirus OC43 infection remodels Connexin 43 mediated gap junction intercellular communication in vitro

{beta}-coronaviruses cause acute infection in the upper respiratory tract, resulting in various symptoms and clinical manifestations. OC43 is a human {beta}-coronavirus that induces mild clinical symptoms and can be safely studied in the BSL2 laboratory. Due to its low risk, OC43 can be a valuable and accessible model for understanding {beta}-coronavirus pathogenesis. One potential target for limiting virus infectivity could be gap junction-mediated communication. This study aims to unveil the status of cell-to-cell communications through gap junctions in human {beta}-coronavirus infection. Infection with OC43 leads to reduced expression of Cx43 in A549, a lung epithelial carcinoma cell line. Infection with this virus also showed a significant ER and oxidative stress increase. Internal localization of Cx43 is observed post OC43 infection in the ERGIC region, which impairs the gap junction communication between two adjacent cells, confirmed by Lucifer yellow dye transfer assay. It also affects hemichannel formation, as depicted by the EtBr uptake assay. Altogether, these results suggest that several physiological changes accompany OC43 infection in A549 cells and can be considered an appropriate model system for understanding the differences in gap junction communication post-viral infections. This model system can provide valuable insights for developing therapies against human {beta}-coronavirus infections. ImportanceThe enduring impact of the recent SARS-CoV-2 pandemic underscores the importance of studying human {beta}-coronaviruses, advancing our preparedness for future coronavirus infections. Due to SARS-CoV-2 being highly infectious, another human {beta}-coronavirus OC43 can be considered as an experimental model. One of the crucial pathways that can be considered is gap junction communication, as it is vital for cellular homeostasis. Our study seeks to understand the change in Cx43-mediated cell-to-cell communication during human {beta}-coronavirus OC43 infection. In vitro studies showed the downregulation of the gap junction protein Cx43 and the upregulation of endoplasmic reticulum and oxidative stress markers post-OC43 infection. Furthermore, OC43 infection causes impairment of functional hemichannel and gap junction formation. Overall, this current study infers that OC43 infection reshapes intercellular communication, suggesting that this pathway may be a promising target for designing highly effective therapeutics against human coronaviruses by regulating Cx43 expression.

pathology↗

bioRxiv2022

Ifit2 regulates murine-coronavirus spread to the spinal cord white matter and its associated myelin pathology

Ifit2, an interferon-induced protein with tetratricopeptide repeats 2, plays a critical role in restricting neurotropic murine {beta}-coronavirus RSA59 infection. RSA59 intracranial injection of Ifit2 deficient (-/-) compared to wild type (WT) mice results in impaired acute microglial activation, associated with reduced CX3CR1 expression, which consecutively limits migration of peripheral lymphocytes into the brain, leading to impaired virus control followed by severe morbidity and mortality. While the protective role of Ifit2 is established for acute viral encephalitis, less is known about its influence on demyelination during the chronic phase of RSA59 infection. Our current study demonstrates that Ifit2 deficiency causes extensive RSA59 viral spread throughout both the spinal cord grey and white matter and is associated with impaired CD4+ T cell infiltration. Cervical lymph nodes of RSA59 infected Ifit2-/- mice showed reduced activation of CD4+ T cells and impaired IFN{gamma} expression during acute encephalomyelitis. Furthermore, blood-brain-barrier integrity was preserved in the absence of Ifit2 as evidenced by integral, tight junction protein ZO-1 expression surrounding the meninges and blood vessels and decreased Texas red dye uptake. In contrast to WT mice exhibiting only sparse myelin loss, the chronic disease phase in Ifit2-/- mice was associated with severe demyelination and persistent viral load, even at low infection doses. Overall, our study highlights that Ifit2 provides antiviral functions by promoting acute neuroinflammation and thereby aiding virus control and limiting severe demyelination. Author SummaryThe role of interferons in providing protective immunity against viral spread and pathogenesis is well known. Interferons execute their function by inducing certain genes collectively called as interferon stimulated genes (ISGs) among which Interferon-induced protein with tetratricopeptide repeats 2, Ifit2, is known for restricting neurotropic viral replication and spread in the brain. So far, not much has been investigated about its role in viral spread to the spinal cord and its associated myelin pathology. Towards this our study using neurotropic murine-{beta}-coronavirus and Ifit2 deficient mice demonstrate that Ifit2 deficiency causes extensive viral spread throughout grey and white matter of spinal cord accompanied by impaired microglial activation and CD4+ T cell infiltration. Furthermore, infected Ifit2 deficient mice showed impaired activation of T cells in cervical lymph node and Blood-Brain-Barrier was relatively intact. Ifit2 deficient mice developed viral induced severe chronic neuroinflammatory demyelination accompanied by the presence of ameboid shaped phagocytotic microglia/macrophages.

neuroscience↗

bioRxiv2022

Inducible Nitric Oxide Synthase deficiency leads to early demyelination by altering the balance between pro- and anti-inflammatory responses against Murine-β-Coronavirus

The neurological disease Multiple sclerosis (MS) is characterized by neuroinflammation and demyelination orchestrated by the activated glial cells, the CNS infiltrating leukocytes, and their reciprocal interaction through inflammatory signals. Inducible nitric oxide synthase (iNOS), an enzyme that catalyzes sustained nitric oxide production in response to an inflammatory stimulus, is a pro-inflammatory marker expressed particularly by the microglia/macrophages (MG/M{varphi}) during neuroinflammation. In MS, iNOS has been reportedly associated with the disease pathology; however, studies dissecting its role in the underlying mechanisms, specifically demyelination, are limited. Therefore, we studied the role of iNOS in a recombinant beta-coronavirus-MHV-RSA59-induced neuroinflammation, which is a prototypic animal model used to investigate the pathological hallmarks of MS, neuroinflammatory demyelination, and axonal degeneration. During the acute phase of infection with RSA59, wildtype C57BL/6 (WT) mice had significantly upregulated iNOS expression in macrophages, natural killer cells, and natural killer T cells suggesting a role for iNOS in RSA59-induced neuroinflammation. Studies comparing RSA59-infected WT and iNOS-deficient mice revealed that iNOS deficiency aggravated the disease with increased CNS infiltration of macrophages and neutrophils and enhanced mortality. As early as 9-10 days after the infection, the CNS of iNOS-deficient mice had substantially higher demyelination marked with morphologically defined MG/M{varphi} in the demyelinating regions. Transcript analysis confirmed the significant upregulation of type2 macrophage (M2) markers-Arginase 1, CD206, and TREM2-in the CNS of iNOS-deficient mice. Corroborating to the phenotype, the iNOS-deficient mice showed a significantly higher expression of TGF{beta}-an anti-inflammatory cytokine- and increased T regulatory (Treg) cell infiltration, indicating an anti-inflammatory milieu established early after the infection. These observations highlight a protective role of iNOS in virus-induced neuroinflammation whereas its absence leads to MG/M{varphi} polarization towards a phenotype that may be involved in the exacerbated demyelination pathology. Author summaryContrary to the reported pathogenic role of inducible nitric oxide synthase (iNOS) in multiple sclerosis and related autoimmune animal models, we show that the mice deficient in iNOS show an exacerbated disease with accelerated demyelination accompanied by heightened production of an anti-inflammatory and phagocytic markers and more numbers of Tregs in a mouse model of a recombinant mouse hepatitis virus RSA59 infection. Therefore, iNOS may play protective and regulatory roles in this beta-coronavirus infection.

neuroscience↗