Inhibition of astrocyte hemichannel improves recovery from spinal cord injury
Chao Zhang, … , Naomi L. Sayre, Jean X. Jiang
Chao Zhang, … , Naomi L. Sayre, Jean X. Jiang
Published March 8, 2021
Citation Information: JCI Insight. 2021;6(5):e134611. https://doi.org/10.1172/jci.insight.134611.
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Research Article Therapeutics

Inhibition of astrocyte hemichannel improves recovery from spinal cord injury

Abstract

Spinal cord injury (SCI) causes severe disability, and the current inability to restore function to the damaged spinal cord leads to lasting detrimental consequences to patients. One strategy to reduce SCI morbidity involves limiting the spread of secondary damage after injury. Previous studies have shown that connexin 43 (Cx43), a gap junction protein richly expressed in spinal cord astrocytes, is a potential mediator of secondary damage. Here, we developed a specific inhibitory antibody, mouse-human chimeric MHC1 antibody (MHC1), that inhibited Cx43 hemichannels, but not gap junctions, and reduced secondary damage in 2 incomplete SCI mouse models. MHC1 inhibited the activation of Cx43 hemichannels in both primary spinal astrocytes and astrocytes in situ. In both SCI mouse models, administration of MHC1 after SCI significantly improved hind limb locomotion function. Remarkably, a single administration of MHC1 30 minutes after injury improved the recovery up to 8 weeks post-SCI. Moreover, MHC1 treatment decreased gliosis and lesion sizes, increased white and gray matter sparing, and improved neuronal survival. Together, these results suggest that inhibition of Cx43 hemichannel function after traumatic SCI reduces secondary damage, limits perilesional gliosis, and improves functional recovery. By targeting hemichannels specifically with an antibody, this study provides a potentially new, innovative therapeutic approach in treating SCI.

Authors

Chao Zhang, Zhao Yan, Asif Maknojia, Manuel A. Riquelme, Sumin Gu, Grant Booher, David J. Wallace, Viktor Bartanusz, Akshay Goswami, Wei Xiong, Ningyan Zhang, Michael J. Mader, Zhiqiang An, Naomi L. Sayre, Jean X. Jiang

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Figure 2

MHC1 antibody inhibits hemichannel opening in astrocytes by cytokine, mechanical stimulation, and low extracellular Ca2+/Mg2+.

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MHC1 antibody inhibits hemichannel opening in astrocytes by cytokine, me...
(A) Primary astrocytes isolated from mouse spinal cord were treated with IL-1β (1 nM) for 24 hours. MHC1 (66.7 nM) or Cx43 (E2) antibody (6.7 nM) was then added 30 minutes prior to dye uptake assay with EtBr (50 μM) for 5 minutes. (B) Primary astrocytes isolated from mouse spinal cord were subjected to mechanical loading by Flexcell device in the absence or presence of MHC1 (66.7 nM) or Cx43E2 antibody (20 nM), and after loading, dye uptake assay was performed with EtBr (50 μM) for 5 minutes. (C) Primary astrocytes isolated from mouse spinal cord were incubated with or without EGTA to remove or maintain extracellular Ca2+/Mg2+ ([Ca2+ ]0) in the absence or presence of MHC1 (66.7 nM), Cx43E2 antibody (6.7 nM) or CBX (100 μM) for 30 minutes before dye uptake assay with EtBr (50 μM) for 15 minutes. Plus sign represents the presence of EGTA and absence of [Ca2+ ]0. Minus sign represents the absence of EGTA and presence of [Ca2+ ]0. The level of EtBr dye uptake was determined by fluorescence microcopy and quantified by NIH ImageJ software. The results are presented as mean ± SEM of 3 independent experiment, each experiment had 3–5 repeats (3–5 wells). Scale bar: 100 μm (A and B). General linear model was used in statistical analysis (A–C). **P < 0.01, ****P < 0.0001.