Hippocampal neuronal degeneration in the traumatic brain injury mouse: non-trivial effect of scalp incision

Pretreatment with troxerutin protects/improves neurological deficits in a mouse model of traumatic brain injury

Traumatic brain injury (TBI) is the major and leading cause of mortality and an alarming public health challenge. TBI leads to permanent cognitive, motor, sensory and psychotic disabilities. Patients suffering from the various and long-term repercussions of TBI currently have limited therapy choices. The current research work was designed to evaluate the beneficial and neuroprotective role of Troxerutin (Trox) (a natural flavonoid) in a closed brain injury mouse model. The male BALB/c 8-weeks old mice (n꞊150) were randomly distributed in three experimental groups. Control group of mice (n꞊50), TBI group (n꞊50) and Trox pre-treated mice group (Trox + TBI, n꞊50). The mice in Trox + TBI were pre-treated with Trox (150 mg/kg, 7 days) before TBI. The weight-drop mechanism was used to induce mild-moderate injury in mice in both the groups. Our results showed that the mice pre-treated with troxerutin significantly improved neurological severity score, blood glucose level, food intake and brain edema as compared to the mice in the TBI group. Furthermore, compared to the TBI group, the mice treated with troxerutin improved cognitive behavior as evaluated by Open field test, Shallow Water Maze and Y-Maze, decreased brain-infarct volume and blood-brain barrier (BBB) permeability, significantly decreased Reactive Oxygen Species (ROS), improved neuronal morphology and survival in the brain regions such as cortex and hippocampus. In summary, our data provided evidence that pre-treatment with troxerutin improved neurological functions, decreased the BBB permeability, improved behavior, reduced ROS and increased neuronal survival in the weight-drop close head traumatic injury mouse model.

A Systematic Review of Closed Head Injury Models of Mild Traumatic Brain Injury in Mice and Rats

Mild TBI (mTBI) is a significant health concern. Animal models of mTBI are essential for understanding mechanisms, and pathological outcomes, as well as to test therapeutic interventions. A variety of closed head models of mTBI that incorporate different aspects (i.e., biomechanics) of the mTBI have been reported. The aim of the current review was to compile a comprehensive list of the closed head mTBI rodent models, along with the common data elements, and outcomes, with the goal to summarize the current state of the field. Publications were identified from a search of PubMed and Web of Science and screened for eligibility following PRISMA guidelines. Articles were included that were closed head injuries in which the authors classified the injury as mild in rats or mice. Injury model and animal-specific common data elements, as well as behavioral and histological outcomes, were collected and compiled from a total of 402 articles. Our results outline the wide variety of methods used to model mTBI. We also discovered that female rodents and both young and aged animals are under-represented in experimental mTBI studies. Our findings will aid in providing context comparing the injury models and provide a starting point for the selection of the most appropriate model of mTBI to address a specific hypothesis. We believe this review will be a useful starting place for determining what has been done and what knowledge is missing in the field to reduce the burden of mTBI.

Modeling sports-related mild traumatic brain injury in animals-A systematic review

Sports-related head trauma has emerged as an important public health issue, as mild traumatic brain injuries (mTBIs) may result in neurodegenerative disorders such as chronic traumatic encephalopathy (CTE). Research into mTBI and CTE pathophysiology are difficult to undertake in athletes, with observational trials and post-mortem analysis the current mainstays. Thus, animal models play an important role in the study of mTBI, however, traditional animal models have focused on acute, severe injuries rather than the more typical mTBI's seen in sport injuries. Recently, a number of animal models have been developed that are both appropriately scaled and biomechanically relevant to the forces sustained by athletes. This review aimed to examine the literature for variables included in these animal models, and the resulting neurotrauma as evidenced by pathology and behavioral deficits. A systematic search of the literature was performed in multiple electronic databases. The inclusion criteria required mimicry of athlete mTBI conditions: freedom of head movement, lack of surgical alteration of the skull, and application of direct contact force. Studies were analyzed for variables including apparatus design features (impact force, change in animal head velocity, and kinetic energy transfer to the head), demonstrated pathology (phosphorylated tau, TDP-43 aggregation, diffuse axonal injury, gliosis, cytokine inflammation response, and genetic integrity), and behavioral changes. These studies suggested that appropriate animal models can assist in understanding the pathological and functional outcomes of athlete mTBI, and could be used as a platform for future studies of diagnostic/prognostic markers and in the development of treatment interventions.

Spontaneous resurgence of conditioned fear weeks after successful extinction in brain injured mice

Mild traumatic brain injury (TBI) is a major risk factor for post-traumatic stress disorder (PTSD), and both disorders share common symptoms and neurobiological defects. Relapse after successful treatment, known as long-term fear resurgence, is common in PTSD patients and a major therapeutic hurdle. We induced a mild focal TBI by controlled cortical impact (CCI) in male C57BL/6 J mice and used fear conditioning to assess PTSD-like behaviors and concomitant alterations in the fear circuitry. We found for the first time that mild TBI, and to a lesser extent sham (craniotomy), mice displayed a spontaneous resurgence of conditioned fear when tested for fear extinction memory recall, despite having effectively acquired and extinguished conditioned fear 6 weeks earlier in the same context. Other characteristic symptoms of PTSD are risk-taking behaviors and cognitive deficits. CCI mice displayed risk-taking behaviors, behavioral inflexibility and reductions in processing speed compared to naïve mice. In conjunction with these changes there were alterations in amygdala morphology 3 months post-trauma, and decreased myelin basic protein density at the primary lesion site and in distant secondary sites such as the hippocampus, thalamus, and amygdala, compared to sham mice. Furthermore, activity-dependent brain-derived neurotrophic factor (BDNF) transcripts were decreased in the prefrontal cortex, a key region for fear extinction consolidation, following fear extinction training in both TBI and, to a lesser extent, sham mice. This study shows for the first time that a mild brain injury can generate a spontaneous resurgence of conditioned fear associated with defective BDNF signalling in the prefrontal cortex, PTSD-like behaviors, and have enduring effects on the brain.

Effects of estrogen receptor GPR30 agonist G1 on neuronal apoptosis and microglia polarization in traumatic brain injury rats

PURPOSE

To investigate the effects of estrogen G protein-coupled receptor 30 (GPR30) agonist G1 on hippocampal neuronal apoptosis and microglial polarization in rat traumatic brain injury (TBI).

METHODS

Male SD rats were randomly divided into sham group, TBI + vehicle group, TBI + G1 group. Experimental moderate TBI was induced using Feeney's weigh-drop method. G1 (100μg/kg) or vehicle was intravenously injected from femoral vein at 30 min post-injury. Rats were sacrificed at 24 h after injury for detection of neuronal apoptosis and microglia polarization. Neuronal apoptosis was assayed by immunofluorescent staining of active caspase-3. M1 type microglia markers (iNOS and IL-1β) and M2 type markers (Arg1 and IL-4) were examined by immunoblotting or ELISA. Total protein level of Akt and phosphorylated Akt were assayed by immunoblotting.

RESULTS

G1 significantly reduced active caspase-3 positive neurons in hippocampus. Meanwhile G1 increased the ratio of Arg1/iNOS. IL-1β production was decreased but IL-4 was increased after G1 treatment. G1 treatment also increased the active form of Akt.

CONCLUSIONS

GPR30 agonist G1 inhibited neuronal apoptosis and favored microglia polarization to M2 type.