Regulatory role of endoplasmic reticulum resident chaperone protein ERp29 in anti-murine ß-coronavirus host cell response.

Gap junctional intercellular communication (GJIC) involving astrocytes is important for proper CNS homeostasis. As determined in our previous studies, trafficking of the predominant astrocyte GJ protein, Connexin43 (Cx43), is disrupted in response to infection with a neurotropic murine ß-coronavirus (MHV-A59). However, how host factors are involved in Cx43 trafficking and the infection response is not clear. Here, we show that Cx43 retention due to MHV-A59 infection was associated with increased ER stress and reduced expression of chaperone protein ERp29. Treatment of MHV-A59-infected astrocytes with the chemical chaperone 4-sodium phenylbutyrate increased ERp29 expression, rescued Cx43 transport to the cell surface, increased GJIC, and reduced ER stress. We obtained similar results using an astrocytoma cell line (delayed brain tumor) upon MHV-A59 infection. Critically, delayed brain tumor cells transfected to express exogenous ERp29 were less susceptible to MHV-A59 infection and showed increased Cx43-mediated GJIC. Treatment with Cx43 mimetic peptides inhibited GJIC and increased viral susceptibility, demonstrating a role for intercellular communication in reducing MHV-A59 infectivity. Taken together, these results support a therapeutically targetable ERp29-dependent mechanism where ß-coronavirus infectivity is modulated by reducing ER stress and rescuing Cx43 trafficking and function.

Gap junction-mediated cell-cell interaction between transplanted mesenchymal stem cells and vascular endothelium in stroke.

We have shown previously that transplanted bone marrow mononuclear cells (BM-MNC), which are a cell fraction rich in hematopoietic stem cells, can activate cerebral endothelial cells via gap junction-mediated cell-cell interaction. In the present study, we investigated such cell-cell interaction between mesenchymal stem cells (MSC) and cerebral endothelial cells. In contrast to BM-MNC, for MSC we observed suppression of vascular endothelial growth factor uptake into endothelial cells and transfer of glucose from endothelial cells to MSC in vitro. The transfer of such a small molecule from MSC to vascular endothelium was subsequently confirmed in vivo and was followed by suppressed activation of macrophage/microglia in stroke mice. The suppressive effect was absent by blockade of gap junction at MSC. Furthermore, gap junction-mediated cell-cell interaction was observed between circulating white blood cells and MSC. Our findings indicate that gap junction-mediated cell-cell interaction is one of the major pathways for MSC-mediated suppression of inflammation in the brain following stroke and provides a novel strategy to maintain the blood-brain barrier in injured brain. Furthermore, our current results have the potential to provide a novel insight for other ongoing clinical trials that make use of MSC transplantation aiming to suppress excess inflammation, as well as other diseases such as COVID-19 (coronavirus disease 2019).

Chloroquine differentially modulates coronary vasodilation in control and diabetic mice.

BACKGROUND AND PURPOSE: Chloroquine is a traditional medicine to treat malaria. There is increasing evidence that chloroquine not only induces phagocytosis but regulates vascular tone. Few reports investigating the effect of chloroquine on vascular responsiveness of coronary arteries have been made. In this study, we examined how chloroquine affected endothelium-dependent relaxation in coronary arteries under normal and diabetic conditions. EXPERIMENTAL APPROACH: We isolated coronary arteries from mice and examined endothelium-dependent relaxation (EDR). Human coronary endothelial cells and mouse coronary endothelial cells isolated from control and diabetic mouse (TALLYHO/Jng [TH] mice, a spontaneous type 2 diabetic mouse model) were used for the molecular biological or cytosolic NO and Ca2+ measurements. KEY RESULTS: Chloroquine inhibited endothelium-derived NO-dependent relaxation but had negligible effect on endothelium-derived hyperpolarization (EDH)-dependent relaxation in coronary arteries of control mice. Chloroquine significantly decreased NO production in control human coronary endothelial cells partly by phosphorylating eNOSThr495 (an inhibitory phosphorylation site of eNOS) and attenuating the rise of cytosolic Ca2+ concentration after stimulation. EDR was significantly inhibited in diabetic mice in comparison to control mice. Interestingly, chloroquine enhanced EDR in diabetic coronary arteries by, specifically, increasing EDH-dependent relaxation due partly to its augmenting effect on gap junction activity in diabetic mouse coronary endothelial cells. CONCLUSIONS AND IMPLICATIONS: These data indicate that chloroquine affects vascular relaxation differently under normal and diabetic conditions. Therefore, the patients' health condition such as coronary macrovascular or microvascular disease, with or without diabetes, must be taken account into the consideration when selecting chloroquine for the treatment of malaria.