Brain gray matter astroglia-specific connexin 43 ablation attenuates spinal cord inflammatory demyelination

Abstract

Background Brain astroglia are activated preceding the onset of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). We characterized the effects of brain astroglia on spinal cord inflammation, focusing on astroglial connexin (Cx)43, because we recently reported that Cx43 has a critical role in regulating neuroinflammation. Methods Because glutamate aspartate transporter (GLAST)+ astroglia are enriched in the brain gray matter, we generated Cx43fl/fl;GLAST-CreERT2/+ mice that were brain gray matter astroglia-specific Cx43 conditional knockouts (Cx43 icKO). EAE was induced by immunization with myelin oligodendroglia glycoprotein (MOG) 35–55 peptide 10 days after tamoxifen injection. Cx43fl/fl mice were used as controls. Results Acute and chronic EAE signs were significantly milder in Cx43 icKO mice than in controls whereas splenocyte MOG-specific responses were unaltered. Histologically, Cx43 icKO mice showed significantly less demyelination and fewer CD45+ infiltrating immunocytes, including F4/80+ macrophages, and Iba1+ microglia in the spinal cord than controls. Microarray analysis of the whole cerebellum revealed marked upregulation of anti-inflammatory A2-specific astroglia gene sets in the pre-immunized phase and decreased proinflammatory A1-specific and pan-reactive astroglial gene expression in the onset phase in Cx43 icKO mice compared with controls. Astroglia expressing C3, a representative A1 marker, were significantly decreased in the cerebrum, cerebellum, and spinal cord of Cx43 icKO mice compared with controls in the peak phase. Isolated Cx43 icKO spinal microglia showed more anti-inflammatory and less proinflammatory gene expression than control microglia in the pre-immunized phase. In particular, microglial expression of Ccl2, Ccl5, Ccl7, and Ccl8 in the pre-immunized phase and of Cxcl9 at the peak phase was lower in Cx43 icKO than in controls. Spinal microglia circularity was significantly lower in Cx43 icKO than in controls in the peak phase. Significantly lower interleukin (IL)-6, interferon-γ, and IL-10 levels were present in cerebrospinal fluid from Cx43 icKO mice in the onset phase compared with controls. Conclusions The ablation of Cx43 in brain gray matter astroglia attenuates EAE by promoting astroglia toward an anti-inflammatory phenotype and suppressing proinflammatory activation of spinal microglia partly through depressed cerebrospinal fluid proinflammatory cytokine/chemokine levels. Brain astroglial Cx43 might be a novel therapeutic target for MS.

Tetramethylpyrazine promotes stroke recovery by inducing the restoration of neurovascular unit and transformation of A1/A2 reactive astrocytes

“…Of greater interest, we found AQP4 and Cx43 levels were both strongly in positive correlation with C3 whereas in negative correlation with S100A10 expression, suggesting that AQP4 and Cx43 might be associated with polarization of astrocytes in cerebral ischemic rats. Previous studies have shown that Cx43 ablation was reported to be beneficial for A2 polarization of astrocytes in mice with multiple sclerosis (Une et al, 2021 ). Although far from being completely understood, the finding suggested that TMP induces the transformation of astrocytes into the neuroprotective A2 subtype at least in part, via regulating AQP4 and Cx43 after ischemic stroke.…”

“…A1/A2 reactive astrocytes were respectively visualized with complement C3 (C3)/glial fibrillary acidic protein (GFAP, label activated astrocytes) and S100 calcium binding protein A 10 (S100A10)/GFAP (Miyamoto et al, 2020 ). Functional proteins of astrocytes were visualized with, AQP4/GFAP (Liang et al, 2016 ), Cx43/GFAP (Une et al, 2021 ), and FGF2/GFAP (Shi et al, 2018 ).…”

Identification of potential regulatory long non-coding RNA-associated competing endogenous RNA axes in periplaque regions in multiple sclerosis

“…The expression of GJA1 (Cx43) is essential for maintaining K+ buffering and nutritional homeostasis in oligodendrocytes, CNS myelin, and oligodendrocyte function, according to previous research (Basu and Sarma, 2018;Une et al, 2021). Furthermore, ablation of Cx43 in brain gray matter astroglia reduces the severity of EAE, an animal model of MS, by promoting an antiinflammatory phenotype in astroglia and suppressing proinflammatory activation of spinal microglia partly through decreased cerebrospinal fluid pro-inflammatory cytokine/ chemokine levels (Une et al, 2021). Therefore, brain astroglial Cx43 may be a potential MS therapeutic target (Une et al, 2021).…”

“…Furthermore, ablation of Cx43 in brain gray matter astroglia reduces the severity of EAE, an animal model of MS, by promoting an anti-inflammatory phenotype in astroglia and suppressing pro-inflammatory activation of spinal microglia partly through decreased cerebrospinal fluid pro-inflammatory cytokine/chemokine levels ( Une et al, 2021 ). Therefore, brain astroglial Cx43 may be a potential MS therapeutic target ( Une et al, 2021 ). GJA1 expression was dramatically elevated in the spinal cord periplaques of progressive MS patients and in EAE mice, according to previous research.…”

Connexins and Pannexins: Important Players in Neurodevelopment, Neurological Diseases, and Potential Therapeutics

“…Astrocytes become reactive in response to the inflammatory environment seen in MS, and Cx43 gap junctions expressed in these astrocytes become activated hemichannels. The opening of hemichannels (especially Cx43) damages myelin via release of chemokines, further exacerbating inflammation [ 146 , 147 ] so much so that Cx43 deletion in astrocytes promotes CNS remyelination by modulation of local inflammation [ 148 , 149 ] in multiple sclerosis animal models.…”