Cannabinoid Receptors Reduced Early Brain Damage by Regulating NOX-2 and the NLRP3 Inflammasome in an Animal Model of Intracerebral Hemorrhage

Background

Intracerebral hemorrhage (ICH) is a leading cause of death and disability worldwide. Following the initial mechanical injury caused by hematoma expansion, a secondary injury occurs, characterized by the production of reactive oxygen species (ROS) generated by NOX-2 and neuroinflammation, which is exacerbated by the upregulation of the NLRP3 inflammasome. These conditions collectively aggravate brain damage. The endocannabinoid system (ECS), through the activation of the cannabinoid receptors, has demonstrated neuroprotective properties in various models of brain injury. However, the role of the ECS during ICH remains poorly understood, particularly regarding the action of the CB1 receptor in the activation of NOX-2 and the inflammasome. The present study investigates the neuroprotective effects of the cannabinoid receptor agonist WIN55,212-2 in an ICH animal model, specifically examining the roles of NLRP3 and NOX-2.

Methods

Male C57BL/6 mice were subjected to ICH through an intracerebral injection of collagenase, followed by intraperitoneal administration of WIN55,212-2 and/or MCC950, a selective NLRP3 inhibitor. Various outcome measures were employed, including assessments of motor activity, hematoma volume, brain water content, and blood–brain barrier (BBB) permeability, which was evaluated using Evans blue assay. Additionally, the activity of NOX and the protein levels of crucial markers such as CB1, gp91phox, NLRP3, AQP4, and caspase-1 were measured via western blot analysis.

Result

The findings demonstrate that ICH induced a significant brain lesion characterized by hematoma formation, edema, BBB disruption, and subsequent motor impairments in the affected mice. Notably, these detrimental effects were markedly reduced in animals treated with WIN55,212-2. The study also revealed an activation of both NOX-2 and NLRP3 in response to ICH, which was reduced by cannabinoid receptor activation. Furthermore, the pharmacological inhibition of NLRP3 using MCC950 also led to a reduction in hematoma size, edema, and motor impairment secondary to ICH.

Conclusions

These results support a neuroprotective role of the cannabinoid receptor activation during ICH and suggest the involvement of NOX-2 and NLRP3.