Pharmacological evaluation of non-nucleotide purine derivatives as P2X7 antagonists for the treatment of neuroinflammation in traumatic brain injury.

Abstract

Background and purpose: Traumatic brain injury (TBI) is considered to be a leading cause of mortality and disability worldwide. After TBI, innate immunity is rapidly activated in response to damage-associated molecular patterns, such as ATP release, recognised by P2X7 receptors. The P2X7-NLRP3 inflammasome axis has been identified as one of the main players in neuroinflammation. This study aimed to validate P2X7 receptors as therapeutic target for traumatic brain injury.

Experimental approach: P2X7 receptors were studied by genetic and pharmacological approaches. Six non-nucleotide purine derivatives were evaluated as P2X7 antagonists. Compounds that prevented LPS + ATP-induced IL-1β release from primary glial cultures were investigated in the closed-head injury TBI model in vivo in male mice. Finally, we evaluated soluble (s)P2X7 receptor plasmatic levels in a cohort of TBI patients.

Key results: P2rx7^-/- mice showed an exaggerated inflammatory response 24 h post-TBI compared to control mice. However, animals treated with the selective P2X7 antagonist JNJ-47965567 (30 mg kg^-1 i.p.) 30 min post-TBI showed improved neurological and inflammatory parameters. The purine derivative ITH15004 was the most potent compound reducing IL-1β production in vitro. When administered in vivo 30 min post-TBI, ITH15004 (1 mg kg^-1 i.p.) improved both neuro-behavioural and inflammatory markers at 24 h. In TBI patients, we showed a tendency towards increase in circulating sP2X7 receptor levels at 24 and 72 h post-TBI.

Conclusions and implications: These results highlight the importance of P2X7 receptors in the acute phase of TBI and present ITH15004 as a promising pharmacological tool to counteract P2X7 receptor-dependent neuroinflammation in vivo.