Traumatic brain injury and immunological outcomes: the double-edged killer

Aquaporins: Gatekeepers of Fluid Dynamics in Traumatic Brain Injury

Aquaporins (AQPs), particularly AQP4, play a crucial role in regulating fluid dynamics in the brain, impacting the development and resolution of edema following traumatic brain injury (TBI). This review examines the alterations in AQP expression and localization post-injury, exploring their effects on brain edema and overall injury outcomes. We discuss the underlying molecular mechanisms regulating AQP expression, highlighting potential therapeutic strategies to modulate AQP function. These insights provide a comprehensive understanding of AQPs in TBI and suggest novel approaches for improving clinical outcomes through targeted interventions.

Reported head trauma and odds of acute ischemic stroke or transient ischemic attack: A population-based study (NEDICES)

BACKGROUND

Six previous observational studies have found a higher risk for stroke among traumatic head injury survivors. However, these studies have used record linkage systems, which could lead to underestimating stroke numbers. This study aims to reexamine the relationship between head trauma and the risk of ischemic stroke/transient ischemic attack (TIA) in an older population using data from the Neurological Disorders in Central Spain (NEDICES) study, a population-based study that includes rigorous clinical examinations for patients with suspected neurological diseases.

METHODS

We asked participants if they had ever experienced head trauma that was severe enough to warrant a consult with a physician, leading, among others, to visiting the emergency room, hospitalization, or resulting in loss of consciousness. The history of head trauma was evaluated in 196 (5.7%) acute ischemic stroke/TIA cases and 3256 controls in the NEDICES study.

RESULTS

Among the final sample of 3452 participants, 354 (10.3%) subjects had a history of head trauma. Twenty-nine (14.8%) of 196 acute ischemic stroke/TIA cases vs. 325 (10.0%) of 3256 controls reported a history of head trauma (p = 0.039). In a regression analysis that adjusted for several variables (age in years, sex, educational level, ever smoker, ever drinker, diabetes mellitus, arterial hypertension, and heart disease), the odds ratio was 1.54 (95% CI = 1.02-2.35, p = 0.042).

CONCLUSIONS

The reported head injury was associated with a 54% higher probability of acute ischemic stroke/TIA. More research is needed to confirm these findings, especially using population-based longitudinal studies.

Activation of CB2R by synthetic CB2R agonist, PM289, improves brain endothelial barrier properties, decreases inflammatory response and enhances endothelial repair

The Cannabinoid 2 Receptor (CB2R) has been found to provide immunological modulation in different cell types. More recently, detection of CB2R in the cerebral endothelium suggests a possible role in the resolution of inflammation at the level of the blood-brain-barrier (BBB). Here, the notion that CB2R upregulation in brain endothelial cells could be exploited to promote vascular protection and BBB integrity was evaluated. Targeting and activation of CB2R was accomplished by a novel and highly specific chromenopyrazole based CB2R agonist, PM289. This study demonstrates that CB2R upregulation is induced as early as 8 h in the cortical vasculature in an experimental mouse model of TBI. Unlike CB2R, CB1R was marginally detected and not significantly induced. In the human brain endothelial cell line, hCMEC/D3 cells, similar induction of CB2R was observed upon stimulation with TNFα. Analysis of transendothelial electrical resistance shows that PM289 markedly prevented the barrier-leakiness induced by TNFα. The BBB is also responsible for maintaining an immunological barrier. The five-fold increase in ICAM1 expression in stimulated endothelial cells was significantly diminished due to CB2R activation. Utilizing wounding assays, results showed that wound repair could be accomplished in nearly half the time when the novel CB2R agonist is present compared to the untreated control. Lastly, mechanistically, the effects of CB2R may be explained by the observed inhibition of the p65 NFκB subunit. Overall, these studies support the notion that targeting and activating CB2R in the brain vasculature could aid in BBB and vascular protection in the context of neuroinflammation.