Inhibition of P2X4 and P2X7 receptors improves histological and behavioral outcomes after experimental traumatic brain injury in rats

Masato Kobayashi; Nobuhiro Moro; Atsuo Yoshino; Takahiro Kumagawa; Katsunori Shijo; Takeshi Maeda; Hideki Oshima

doi:10.3892/etm.2023.12077

Inhibition of P2X4 and P2X7 receptors improves histological and behavioral outcomes after experimental traumatic brain injury in rats

Exp Ther Med. 2023 Jun 23;26(2):378. doi: 10.3892/etm.2023.12077. eCollection 2023 Aug.

Authors

Masato Kobayashi¹, Nobuhiro Moro^{1

2}, Atsuo Yoshino¹, Takahiro Kumagawa¹, Katsunori Shijo¹, Takeshi Maeda¹, Hideki Oshima¹

Affiliations

¹ Division of Neurosurgery, Department of Neurological Surgery, Nihon University School of Medicine, Tokyo 173-8610, Japan.
² Department of Neurological Surgery, Honjo-General Hospital, Saitama 367-0031, Japan.

Abstract

Release of large amounts of adenosine triphosphate (ATP), a gliotransmitter, into the extracellular space by traumatic brain injury (TBI) is considered to activate the microglia followed by release of inflammatory cytokines resulting in excessive inflammatory response that induces secondary brain injury. The present study investigated whether antagonists of ATP receptors (P2X4 and/or P2X7) on microglia are beneficial for reducing the post-injury inflammatory response that leads to secondary injury, a prognostic aggravation factor of TBI. Adult male Sprague-Dawley rats were subjected to cortical contusion injury (CCI) and randomly assigned to injury and drug treatment conditions, as follows: i) No surgical intervention (naïve group); ii) dimethyl sulfoxide treatment after CCI (CCI-control group); iii) 5-BDBD (antagonist of P2X4 receptor) treatment after CCI (CCI-5-BDBD group); iv) CCI-AZ11645373 (antagonist of P2X7 receptor) treatment after CCI (CCI-AZ11645373 group); v) or 5-BDBD and AZ11645373 treatment after CCI (CCI-5-BDBD + AZ11645373 group). In the CCI-5-BDBD, CCI-AZ11645373, and CCI-5-BDBD + AZ11645373 groups, expression of activated microglia was suppressed in the ipsilateral cortex and hippocampus 3 days after the CCI. Western blotting with ionized calcium-binding adaptor molecule 1 antibody revealed that administration of CCI-5-BDBD and/or CCI-AZ11645373 suppressed expression of microglia and reduced expression of inflammatory cytokine mRNA 3 days after the CCI. Furthermore, the plus maze test, which reflects the spatial memory function and involves the hippocampal function, showed improvement 28 days after secondary injury to the hippocampus. These findings confirmed that blocking the P2X4 and P2X7 receptors, which are ATP receptors central in gliotransmission, suppresses microglial activation and subsequent cytokine expression after brain injury, and demonstrates the potential as an effective treatment for reducing secondary brain injury.

Keywords: adenosine triphosphate; gliotransmitter; microglia; purinergic receptors; traumatic brain injury.

Grants and funding

Funding: This work was supported in part by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (grant no. 25861292).