Maraviroc promotes recovery from traumatic brain injury in mice by suppression of neuroinflammation and activation of neurotoxic reactive astrocytes

Neuroinflammation and the NACHT,LRR,and PYD domains-containing protein 3 inflammasome play crucial roles in secondary tissue damage following an initial insult in patients with traumatic brain injury(TBI).Maraviroc,a C-C chemokine receptor type 5 antagonist,has been viewed as a new therapeutic strategy for many neuroinflammatory diseases.We studied the effect of maraviroc on TBI-induced neuroinflammation.A moderate-TBI mouse model was subjected to a controlled cortical impact device.Maraviroc or vehicle was injected intraperitoneally 1 hour after TBI and then once per day for 3 consecutive days.Western blot,immunohistochemistry,and TUNEL(terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling)analyses were performed to evaluate the molecular mechanisms of maraviroc at 3 days post-TBI.Our results suggest that maraviroc administration reduced NACHT,LRR,and PYD domains-containing protein 3 inflammasome activation,modulated microglial polarization from M1 to M2,decreased neutrophil and macrophage infiltration,and inhibited the release of inflammatory factors after TBI.Moreover,maraviroc treatment decreased the activation of neurotoxic reactive astrocytes,which,in turn,exacerbated neuronal cell death.Additionally,we confirmed the neuroprotective effect of maraviroc using the modified neurological severity score,rotarod test,Morris water maze test,and lesion volume measurements.In summary,our findings indicate that maraviroc might be a desirable pharmacotherapeutic strategy for TBI,and C-C chemokine receptor type 5 might be a promising pharmacotherapeutic target to improve recovery after TBI.

Dexmedetomidine attenuates traumatic brain injury: action pathway and mechanisms

Traumatic brain injury induces potent inflammatory responses that can exacerbate secondary blood-brain barrier（BBB） disruption, neuronal injury, and neurological dysfunction. Dexmedetomidine is a novel α2-adrenergic receptor agonist that exert protective effects in various central nervous system diseases. The present study was designed to investigate the neuroprotective action of dexmedetomidine in a mouse traumatic brain injury model, and to explore the possible mechanisms. Adult male C57 BL/6 J mice were subjected to controlled cortical impact. After injury, animals received 3 days of consecutive dexmedetomidine therapy（25 μg/kg per day）. The modified neurological severity score was used to assess neurological deficits. The rotarod test was used to evaluate accurate motor coordination and balance. Immunofluorescence was used to determine expression of ionized calcium binding adapter molecule-1, myeloperoxidase, and zonula occluden-1 at the injury site. An enzyme linked immunosorbent assay was used to measure the concentration of interleukin-1β（IL-1β）, tumor necrosis factor α, and IL-6. The dry-wet weight method was used to measure brain water content. The Evans blue dye extravasation assay was used to measure BBB disruption. Western blot assay was used to measure protein expression of nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3（NLRP3）, caspase-1 p20, IL-1β, nuclear factor kappa B（NF-κB） p65, occluding, and zonula occluden-1. Flow cytometry was used to measure cellular apoptosis. Results showed that dexmedetomidine treatment attenuated early neurological dysfunction and brain edema. Further, dexmedetomidine attenuated post-traumatic inflammation, up-regulated tight junction protein expression, and reduced secondary BBB damage and apoptosis. These protective effects were accompanied by down-regulation of the NF-κB and NLRP3 inflammasome pathways. These findings suggest that dexmedetomidine exhibits neuroprotective effects against acute（3 days） post-traumatic inflammatory responses, potentially via suppression of NF-κB and NLRP3 inflammasome activation.

Cold water swimming pretreatment reduces cognitive deficits in a rat model of traumatic brain injury

A moderate stress such as cold water swimming can raise the tolerance of the body to potentially injurious events. However, little is known about the mechanism of beneficial effects induced by moderate stress. In this study, we used a classic rat model of traumatic brain injury to test the hypothesis that cold water swimming preconditioning improved the recovery of cognitive functions and explored the mechanisms. Results showed that after traumatic brain injury, pre-conditioned rats（cold water swimming for 3 minutes at 4℃） spent a significantly higher percent of times in the goal quadrant of cold water swim, and escape latencies were shorter than for non-pretreated rats. The number of circulating endothelial progenitor cells was significantly higher in pre-conditioned rats than those without pretreatment at 0, 3, 6 and 24 hours after traumatic brain injury. Immunohistochemical staining and Von Willebrand factor staining demonstrated that the number of CD34~＋ stem cells and new blood vessels in the injured hippocampus tissue increased significantly in pre-conditioned rats. These data suggest that pretreatment with cold water swimming could promote the proliferation of endothelial progenitor cells and angiogenesis in the peripheral blood and hippocampus. It also ameliorated cognitive deficits caused by experimental traumatic brain injury.

Cognitive impairment after traumatic brain injury is associated with reduced long-term depression of excitatory postsynaptic potential in the rat hippocampal dentate gyrus

Traumatic brain injury can cause loss of neuronal tissue, remote symptomatic epilepsy, and cognitive deficits. However, the mechanisms underlying the effects of traumatic brain injury are not yet clear. Hippocampal excitability is strongly correlated with cognitive dysfunction and remote symptomatic epilepsy. In this study, we examined the relationship between traumatic brain injury-induced neuronal loss and subsequent hippocampal regional excitability. We used hydraulic percussion to generate a rat model of traumatic brain injury. At 7 days after injury, the mean modified neurological severity score was 9.5, suggesting that the neurological function of the rats was remarkably impaired. Electrophysiology and immunocytochemical staining revealed increases in the slope of excitatory postsynaptic potentials and long-term depression（indicating weakened long-term inhibition）, and the numbers of cholecystokinin and parvalbumin immunoreactive cells were clearly reduced in the rat hippocampal dentate gyrus. These results indicate that interneuronal loss and changes in excitability occurred in the hippocampal dentate gyrus. Thus, traumatic brain injury-induced loss of interneurons appears to be associated with reduced long-term depression in the hippocampal dentate gyrus.