Kenyon, L. C. | bioRxiv Science

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↗

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↗