Unexpected role of stress as a possible resilience mechanism upon mild traumatic brain injury (mTBI) in mice.

INTRODUCTION: Mild traumatic brain injury (mTBI) is common and associated with cognitive impairment. Stress and mTBI are known to modulate the neural function. The present study aims at exploring the effect of prior stress exposure on cognitive function following mTBI. METHODS: Eight weeks old male ICR mice were subjected to either stress induced by forced swimming stress alone, stress followed by an immediate mTBI, or stress followed by 30 min break and then mTBI. We had two control groups: SHAM group - a control group which was not exposed to stress nor to mTBI and control mTBI group - a control group which was exposed only to TBI with no stress. Mice were weighed prior and at 12, 24 h and 1 week following interventions. Motor evaluation was conducted by rotarod. Behavioral changes were evaluated using open field, Y maze, elevated plus maze and staircase tests, at 12 h and 1 week following interventions. Brain levels of NMDAR subunits (R1, R2A, R2B), GABABR1, glucocorticoid and mineralocorticoid receptors (GR, MR) were evaluated using western blot. RESULTS: Stress alone, mTBI alone, and stress followed by immediate mTBI resulted in a significant weight loss compared to control (p < 0.05). Stress 30 min prior to mTBI had a protective effect on weight (p = 0.14 compared to control). The stress and mTBI alone groups showed reduced time at the center of the open field arena 1 week after intervention (p < 0.05 for both). Time in the novel arm of the Y maze was significantly shorter in the mTBI and stress followed by delayed mTBI (p = 0.02). Immediate stress prior to mTBI had normalized times in the novel arm (p = 0.95 compared to control). Combination of stress and mTBI significantly modified NMDAR subunits levels (increased NMDAR1, p < 0.008, decreased NMDAR2A p = 0.02) as well as increased MR levels (p = 0.04). CONCLUSION: Exposure to stress prior to mTBI may improve the cognitive consequences of mTBI. These data may point towards a novel, unexpected role of stress as a possible resilience mechanism in the setting of mTBI.

A Novel Highly Sensitive Method for Measuring Inflammatory Neural-Derived APC Activity in Glial Cell Lines, Mouse Brain and Human CSF.

BACKGROUND: Neural inflammation is linked to coagulation. Low levels of thrombin have a neuroprotective effect, mediated by activated protein C (APC). We describe a sensitive novel method for the measurement of APC activity at the low concentrations found in neural tissue. METHODS: APC activity was measured using a fluorogenic substrate, Pyr-Pro-Arg-AMC, cleaved preferentially by APC. Selectivity was assessed using specific inhibitors and activators. APC levels were measured in human plasma, in glia cell lines, in mice brain slices following mild traumatic brain injury (mTBI) and systemic lipopolysaccharide (LPS) injection, and in cerebrospinal fluid (CSF) taken from viral meningoencephalitis patients and controls. RESULTS: Selectivity required apixaban and alpha-naphthylsulphonylglycyl-4-amidinophenylalanine piperidine (NAPAP). APC levels were easily measurable in plasma and were significantly increased by Protac and CaCl2. APC activity was significantly higher in the microglial compared to astrocytic cell line and specifically lowered by LPS. Brain APC levels were higher in posterior regions and increased by mTBI and LPS. Highly elevated APC activity was measured in viral meningoencephalitis patients CSF. CONCLUSIONS: This method is selective and sensitive for the measurement of APC activity that significantly changes during inflammation in cell lines, animal models and human CSF.

Brain Protease Activated Receptor 1 Pathway: A Therapeutic Target in the Superoxide Dismutase 1 (SOD1) Mouse Model of Amyotrophic Lateral Sclerosis.

Glia cells are involved in upper motor neuron degeneration in amyotrophic lateral sclerosis (ALS). Protease activated receptor 1 (PAR1) pathway is related to brain pathologies. Brain PAR1 is located on peri-synaptic astrocytes, adjacent to pyramidal motor neurons, suggesting possible involvement in ALS. Brain thrombin activity in superoxide dismutase 1 (SOD1) mice was measured using a fluorometric assay, and PAR1 levels by western blot. PAR1 was localized using immunohistochemistry staining. Treatment targeted PAR1 pathway on three levels; thrombin inhibitor TLCK (N-Tosyl-Lys-chloromethylketone), PAR1 antagonist SCH-79797 and the Ras intracellular inhibitor FTS (S-trans-trans-farnesylthiosalicylic acid). Mice were weighed and assessed for motor function and survival. SOD1 brain thrombin activity was increased (p < 0.001) particularly in the posterior frontal lobe (p = 0.027) and hindbrain (p < 0.01). PAR1 levels were decreased (p < 0.001, brain, spinal cord, p < 0.05). PAR1 and glial fibrillary acidic protein (GFAP) staining decreased in the cerebellum and cortex. SOD1 mice lost weight (≥17 weeks, p = 0.047), and showed shorter rotarod time (≥14 weeks, p < 0.01). FTS 40mg/kg significantly improved rotarod scores (p < 0.001). Survival improved with all treatments (p < 0.01 for all treatments). PAR1 antagonism was the most efficient, with a median survival improvement of 10 days (p < 0.0001). Our results support PAR1 pathway involvement in ALS.

The association between video-nystagmography and sensory organization test of computerized dynamic posturography in patients with vestibular symptoms.

OBJECTIVE: Vertigo is a complex symptom which imposes diagnostic and treatment challenges. Laboratory evaluation of vertigo includes video-nystagmography (VNG) and computerized dynamic posturography (CDP) for the evaluation of different aspects of this complaint. There are vague indications for each test and potential disagreements between them. The aim of this study is to examine the association between the test results of the VNG and sensory organization test (SOT) of CDP in patients referred for both vestibular tests. METHODS: Retrospective data regarding 56 patients age 17-82 years were collected. Patients suffered vestibular complaints and were referred for VNG and CDP evaluation on the same day. The level of agreement between VNG (including caloric test) and the vestibular input of the SOT for each patient was calculated. RESULTS: Among the study group, 10 showed abnormal caloric test results, of which 3 (5.4%) had normal vestibular input in the SOT, and 7 (12.5%) had impaired input (p = 0.724). Spontaneous nystagmus was recorded in 13 patients by VNG, of which 2(3.6%) had normal vestibular input and 11(19.6%) had impaired vestibular input (p = 0.056). CONCLUSIONS: This study shows no statistically significant association between the VNG test and SOT test results. Our results emphasize the difference between the tested aspects in each laboratory test, and the need to define specific indications for each of them. There is a marginally significant association between impaired vestibular input and spontaneous nystagmus, demonstrating the non-localizing nature of this sign.

Clinical Characterization and Ancillary Tests in Susac Syndrome: A Systematic Review.

Susac syndrome (SuS) is an orphan microangiopathic disease characterized by a triad of encephalopathy, visual disturbances due to branch retinal artery occlusions, and sensorineuronal hearing loss. Our previous systematic review on all cases of SuS reported until 2012 allowed for a better understanding of clinical presentation and diagnostic findings. Based on these data, we suggested diagnostic criteria in 2016 to allow early diagnosis and treatment of SuS. In view of the accumulation of new SuS cases reported in the last 10 years and improved diagnostic tools, we here aimed at updating the demographic and clinical features of SuS and to review the updated ancillary tests being used for SuS diagnosis. Therefore, based on the 2016 criteria, we systematically collected and evaluated data on SuS published from January 2013 to March 2022.

The neuro-glial coagulonome: the thrombin receptor and coagulation pathways as major players in neurological diseases.

The neuro-glial interface extends far beyond mechanical support alone and includes interactions throu-gh coagulation cascade proteins. Here, we systematically review the evidence indicating that synaptic and node of Ranvier glia cell components modulate synaptic transmission and axonal conduction by a coagulation cascade protein system, leading us to propose the concept of the neuro-glial coagulonome. In the peripheral nervous system, the main thrombin receptor protease activated receptor 1 (PAR1) is located on the Schwann microvilli at the node of Ranvier and at the neuromuscular junction. PAR1 activation effects can be both neuroprotective or harmful, depending on thrombin activity levels. Low physiological levels of thrombin induce neuroprotective effects in the Schwann cells which are mediated by the endothelial protein C receptor. High levels of thrombin induce conduction deficits, as found in experimental autoimmune neuritis, the animal model for Guillaine-Barre syndrome. In the central nervous system, PAR1 is located on the peri-synaptic astrocyte end-feet. Its activation by high thrombin levels is involved in the pathology of primary inflammatory brain diseases such as multiple sclerosis, as well as in other central nervous system insults, including trauma, neoplasms, epilepsy and vascular injury. Following activation of PAR1 by high thrombin levels the seizure threshold is lowered. On the other hand, PAR1 activation by lower levels of thrombin in the central nervous system protects against a future ischemic insult. This review presents the known structure and function of the neuro-glial coagulonome, focusing on coagulation, thrombin and PAR1 in a pathway which may be either physiological (neuroprotective) or detrimental in peripheral nervous system and central nervous system diseases. Understanding the neuro-glial coagulonome may open opportunities for novel pharmacological interventions in neurological diseases.

Blocking Thrombin Significantly Ameliorates Experimental Autoimmune Neuritis.

Thrombin and its protease-activated receptor 1 (PAR1) are potentially important in peripheral nerve inflammatory diseases. We studied the role of thrombin and PAR1 in rat experimental autoimmune neuritis (EAN), a model of the human Guillain-Barré syndrome (GBS). EAN was induced by bovine peripheral myelin with complete Freund's adjuvant (CFA). Thrombin activity in the sciatic nerves, clinical scores and rotarod performance were measured. Thrombin activity in the sciatic nerve was elevated in EAN compared to CFA control rats (sham rats) (p ≤ 0.004). The effect of blocking the thrombin-PAR1 pathway was studied using the non-selective thrombin inhibitor N-Tosyl-Lys-chloromethylketone (TLCK), and the highly specific thrombin inhibitor N-alpha 2 naphtalenesulfonylglycyl 4 amidino-phenylalaninepiperidide (NAPAP). In-vitro TLCK and NAPAP significantly inhibited specific thrombin activity in EAN rats sciatics (p<0.0001 for both inhibitors). Treatment with TLCK 4.4 mg/kg and NAPAP 69.8 mg/kg significantly improved clinical and rotarod scores starting at day 12 and 13 post immunization (DPI12, DPI13) respectively (p < 0.0001) compared to the untreated EAN rats. In nerve conduction studies, distal amplitude was significantly lower in EAN compared to sham rats (0.76 ± 0.34 vs. 9.8 ± 1.2, mV, p < 0.0001). Nerve conduction velocity was impaired in EAN rats (23.6 ± 2.6 vs. sham 43 ± 4.5, m/s p = 0.01) and was normalized by TLCK (41.2 ± 7.6 m/s, p < 0.05). PAR1 histology of the sciatic node of Ranvier indicated significant structural damage in the EAN rats which was prevented by TLCK treatment. These results suggest the thrombin-PAR1 pathway as a possible target for future intervention in GBS.

The Association Between Vestibular Physical Examination, Vertigo Questionnaires, and the Electronystagmography in Patients With Vestibular Symptoms.

OBJECTS: Dizziness makes up a diagnostic and treatment challenge. The diagnostic accuracy of the medical history and vestibular physical examination in cases of vestibular symptoms is not clear. The aim of this study is to determine the association between vestibular physical examination, vestibular questionnaires, and electronystagmography (ENG) test in patients with vestibular symptoms. METHODS: This is a prospective study of 135 adults with vestibular symptoms. The subjects underwent targeted physical examination and filled vestibular questionnaires, including the Dizziness Handicap Inventory (DHI), before ENG testing. The results of the physical examination and questionnaires were compared with the final ENG findings. RESULTS: Of patients who had normal ENG results, 32.1% (17/52) showed abnormal physical examination, and 48.8% (40/82) of the patient who had normal physical examination showed abnormal ENG results ( P = .46). Among patients with severe disability by DHI, 46.4% (13/28) had an abnormal ENG, and 42.9% (12/28) had a normal ENG ( P = .39). CONCLUSIONS: This study did not demonstrate association between vestibular physical examination, vestibular questionnaires, and ENG results. Although history (augmented by questionnaires) and physical examination are the initial steps in the evaluation of vertigo, the current study suggests that they should be complemented by objective testing for evaluation of inner ear origin of vertigo.