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-β-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.