Severe acute respiratory syndrome CoV-2 (SARS-CoV-2) is currently causing a worldwide threat with its unusually high transmission rates and rapid evolution into diverse strains. Unlike typical respiratory viruses, SARS-CoV-2 frequently causes systemic infection by breaking the boundaries of the respiratory systems. The development of animal models recapitulating the clinical manifestations of COVID-19 is of utmost importance not only for the development of vaccines and antivirals but also for understanding the pathogenesis. However, there has not been developed an animal model for systemic infection of SARS-CoV-2 representing most aspects of the clinical manifestations of COVID-19 with systemic symptoms. Here we report that a Roborovski hamster strain SH101, a laboratory inbred hamster strain of
P. roborovskii
, displayed most symptoms of systemic infection upon SARS-CoV-2 infection as in the case of the human counterpart, unlike current COVID-19 animal models. Roborovski hamster strain SH101 post-infection of SARS-CoV-2 represented most clinical symptoms of COVID-19 such as snuffling, labored breathing, dyspnea, cough, hunched posture, progressive weight loss, ruffled fur, and high fever following shaking chills. Histological examinations also revealed initial right-predominated pneumonia as well as slight organ damages in the brain and liver, manifesting systemic COVID-19 cases. Considering the merit of a small animal as well as its clinical manifestations of SARS-CoV-2 infection in human, this hamster model seems to provide an ideal tool to investigate COVID-19.
Connexin 43 (Cx43) deficiency was found to increase mortality in a mouse model of bacterial peritonitis, and Cx43 is upregulated in macrophages by LPS treatment. In this study, we characterized a novel signaling pathway for LPS-induced Cx43 expression in RAW264.7 cells and thioglycolate-elicited peritoneal macrophages (TGEMs). LPS alone or LPS-containing conditioned medium (CM) upregulated Cx43. Overexpression or silencing of Cx43 led to the enhancement or inhibition, respectively, of CM-induced TGEM migration. This response involved the inducible NO synthase (iNOS)/focal adhesion kinase (FAK)/Src pathways. Moreover, CM-induced migration was compromised in TGEMs from Cx43 +/2 mice compared with TGEMs from Cx43 +/+ littermates. Cx43 was upregulated by a serum/glucocorticoid-regulated kinase 1 (SGK) activator and downregulated, along with inhibition of CMinduced TGEM migration, by knockdown of the SGK gene or blockade of the SGK pathway. LPS-induced SGK activation was abrogated by Torin2, whereas LPS-induced Cx43 was downregulated by both Torin2 and rapamycin. Analysis of the effects of FK506 and methylprednisolone, common immunosuppressive agents following organ transplantation, suggested a link between these immunosuppressive drugs and impaired macrophage migration via the Cx43/iNOS/Src/FAK pathway. In a model of Escherichia coli infectious peritonitis, GSK650349-, an SGK inhibitor, or Torin2-treated mice showed less accumulation of F4/80 + CD11b + macrophages in the peritoneal cavity, with a delay in the elimination of bacteria. Furthermore, following pretreatment with Gap19, a selective Cx43 hemichannel blocker, the survival of model mice was significantly reduced. Taken together, our study suggested that Cx43 in macrophages was associated with macrophage migration, an important immune process in host defense to infection.
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