Elevated glucocorticoid damages gap junction structure and function in rat prefrontal cortex / 药学学报

In this article, we exogenously administered glucocorticoids to rats, observed changes in the structure and function of gap junctions in the prefrontal cortex (PFC) and studied the effects of glucocorticoid receptor (GR) inhibitor mifepristone on these changes. Subcutaneous injection of corticosterone (CORT) was used to increase glucocorticoid levels in rats, intragastric administration of mifepristone antagonist GR. Sucrose preference test was conducted to evaluate anhedonia. Dye transfer assay and electron microscopy were used to analyze the function and ultrastructural changes of gap junctions in astrocytes of PFC. Immunofluorescence was used to detect the expression of connexin 43 (Cx43). Animals exposed to CORT showed behavioral deficits in sucrose preference test, exhibited significant decreases in diffusion of gap junction channel-permeable dye and abnormal gap junctional ultrastructure, as well as reductions in Cx43 puncta density in the PFC. The behavioral and cellular alterations induced by CORT were reversed or blocked by treatment with the GR antagonist mifepristone. The results suggest that mifepristone can improve the gap junction function and structural damage of astrocytes in the PFC of depressive rats induced by CORT. In conclusion, the activation of the GR receptor may contribute to gap junction dysfunction in the PFC.

Protective effects of ginsenoside Rg1 against corticosterone-induced primary astrocytes injury / 药学学报

The study was designed to explore the effects and the underlying mechanism of ginsenoside Rg1 on corticosterone (CORT)-induced astrocytes injury. The primary hippocampal and prefrontal cortical astrocytes from rats were cultured and purified. CORT was used to stimulate stress condition. Western blot was used to detect the effects of ginsenoside Rg1 on the phosphorylation of Cx43. Cell Counting Kit (CCK8) was used to detect the effects of ginsenoside Rg1 on astrocytes viability. The roles of ginsenoside Rg1 was reversed by protein kinase inhibitors in the change of astrocytes morphology. Our results showed that ginsenoside Rg1 reversed the phosphorylation of Cx43 induced by CORT; ginsenoside Rg1 significantly upregulated the cell viability of astrocytes against CORT; the role of ginsenoside Rg1 was obviously inhibited by Src protein kinase inhibitors PP2 and Akt protein kinase inhibitors BAY1125976 in prefrontal cortical astrocytes; in hippocampal astrocytes, Src protein kinase inhibitor PP2, p38 protein kinase inhibitor SB203580, Akt protein kinase inhibitor BAY1125976 significantly inhibited the cell protective effects of ginsenoside Rg1. In conclusion, ginsenoside Rg1 improved the activity of Cx43 gap junctions in astrocytes exposed to CORT; ginsenoside Rg1 protected astrocytes against that CORT activated the Src, p38 and Akt signaling pathways, and the mechanism was different in prefrontal cortical and hippocampal astrocytes.