Systemic administration of a calpain inhibitor reduces behavioral deficits and blood-brain barrier permeability changes after experimental subarachnoid hemorrhage in the rat

The Cell Permeant Phosphopetpide mimetic of VASP Alleviates Motor Function Deficits After Experimental Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) due to the rupture of an intracranial aneurysm leads to delayed vasospasm and neuroischemia, which can result in profound neurologic deficit and death. Therapeutic options after SAH are currently limited to hemodynamic optimization and nimodipine, which have limited clinical efficacy. Experimental SAH results in cerebral vasospasm have demonstrated the downregulation of nitric oxide (NO)-protein kinase G (PKG) signaling elements. VP3 is a novel cell permeant phosphopeptide mimetic of VASP, a substrate of PKG and an actin-associated protein that modulates vasorelaxation in vascular smooth muscle cells. In this study, we determined that intravenous administration of high doses of VP3 did not induce systemic hypotension in rats except at the maximal soluble dose, implying that VP3 is well-tolerated and has a wide therapeutic window. Using a single cisterna magna injection rat model of SAH, we demonstrated that intravenous administration of low-dose VP3 after SAH improved neurologic deficits for up to 14 days as determined by the rotarod test. These findings suggest that strategies aimed at targeting the cerebral vasculature with VP3 may improve neurologic deficits associated with SAH.

Calpastatin peptide attenuates early brain injury following experimental subarachnoid hemorrhage

Calpain activation may have an important role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). The present study investigated the effects of the calpastatin peptide, a cell-permeable peptide that functions as a potent inhibitor of calpain, on EBI in a rat SAH model. It was revealed that calpastatin peptide treatment significantly reduced SAH-induced body weight loss and neurological deficit at 72 h when compared with untreated SAH controls. Furthermore, the quantification of brain water content and the extravasation of Evans blue dye revealed a significant reduction in SAH-induced brain edema and blood-brain barrier permeability at 72 h due to treatment with the calpastatin peptide when compared with untreated SAH controls. Finally, calpastatin peptide treatment significantly attenuated the protein levels of Bax, cytochrome c, cleaved caspase-9 and cleaved caspase-3, and reduced the number of terminal deoxynucleotidyl transferase dUTP nick end labelling-positive cells in the basal cortex at 72 h after SAH when compared with untreated SAH controls. These results indicated that the calpastatin peptide may ameliorate EBI following SAH in rat models.

Effects of a high concentration of hydrogen on neurological function after traumatic brain injury in diabetic rats

Reactive oxygen species, inflammation, and apoptosis are major contributors to secondary injuries that follow traumatic brain injury (TBI) in diabetic patients. Hydrogen (H₂) can selectively neutralize reactive oxygen species and downregulate inflammatory and apoptotic factors. Therefore, we investigated the effects of inhaled high and low concentrations of hydrogen on neurological function after TBI in diabetic rats and the potential mechanism. We found that the inhalation of high concentrations of H₂ significantly improved outcomes following TBI in diabetic rats. The inhalation of 42% H₂ for one hour per day for 48 h significantly reduced brain edema, decreased the extravasation of sodium fluorescein, and reduced oxidative stress markers (p < 0.05). In addition, the inhalation of a high concentration of H₂ (42% for one hour per day for 7 days) improved neurological deficits (p < 0.05) and reduced the expression of apoptotic protein markers (p < 0.05). However, the inhalation of 3% H₂ did not yield significant effects. These results showed that the inhalation of 42% H₂ can alleviate nerve damage and improve neurological function after TBI in diabetic rats. Therefore, the inhalation of a high concentration of H₂ may be associated with the treatment of traumatic brain injuries.

Blood-brain barrier function, cell viability, and gene expression of tight junction-associated proteins in the mouse are disrupted by crude oil, benzo[a]pyrene, and the dispersant COREXIT

Exposure to crude oil, its components, and oil dispersants during a major crude oil spill, such as the Deepwater Horizon Oil Spill, can elicit behavioral changes in animals and humans. However, the underlying mechanisms by which oil spill-related compounds alters behavior remains largely unknown. A major cause of behavioral changes generally is dysfunction of the blood-brain barrier (BBB). We investigated the impact of a crude oil high energy water accommodated fraction (HEWAF), benzo[a] pyrene (BaP; a major component of crude oil), and the oil dispersant COREXIT, on BBB function. BBB function was assessed by measuring transendothelial electrical resistance (TEER) of mouse brain microvascular endothelial cells (BMECs). Within 3 h after treatment, TEER was significantly reduced by exposure to high concentrations of all test compounds. TEER remained reduced in response to COREXIT after 48 h, but this effect waned in BMECs treated with HEWAF and BaP, with low-mid range concentrations inducing increased TEER compared to vehicle controls. At 48 h of treatment, BMEC viability was significantly reduced in response to 2% HEWAF, but was increased in response to BaP (25 and 50 μM). BMEC viability was increased with 80 ppm COREXIT, but was reduced with 160 ppm. Gene expression of tight junction-associated proteins (claudin-5 and tight junction protein-1), and cell adhesion receptor (vascular cell adhesion molecule-1) was reduced in response to HEWAF and COREXIT, but not BaP. Taken together, these data suggest that oil spill-related compounds markedly affect BBB function, and that these changes may underlie the observed behavioral changes due to crude oil exposure.

TAT-mGluR1 Attenuation of Neuronal Apoptosis through Prevention of MGluR1α Truncation after Experimental Subarachnoid Hemorrhage

Excessive glutamate-mediated overactivation of metabotropic glutamate receptor 1 (mGluR1) plays a leading role in neuronal apoptosis following subarachnoid hemorrhage (SAH). TAT-mGluR1, a fusion peptide consisting of a peptide spanning the calpain cleavage site of mGluR1α and the trans-activating regulatory protein (TAT) of HIV, effectively blocks mGluR1α truncation and protects neurons against excitotoxic damage. This study investigated the effects of TAT-mGluR1 on neuronal apoptosis in the rat SAH model. Here, we report that SAH caused activation of calpain and truncation of mGluR1α; intraperitoneally administered TAT-mGluR1 did not affect calpain activity, while it blocked truncation of mGluR1α after SAH. Intraperitoneally administered FITC-labeled TAT-mGluR1 was colocalized with mGluR1α in thecortex after SAH. Furthermore, TAT-mGluR1 significantly improved the neurological deficit, increased p-PI3K, p-Akt, and p-GSK3β, downregulated Bax, upregulated Bcl-2, and reduced cortical apoptosis in the basal cortex at 24 h after SAH. These findings indicated that TAT-mGluR1 acted against SAH-induced cell apoptosis through preventing mGluR1α truncation.

Calpeptin Reduces Neurobehavioral Deficits and Neuronal Apoptosis Following Subarachnoid Hemorrhage in Rats

BACKGROUND

Inhibition of calpain activity provides neuroprotection in multiple central nervous system injury, but the role and mechanism of calpain in subarachnoid hemorrhage (SAH) remain unclear. This study was undertaken to determine the effects of inhibition of calpain on neurological deficit and neuronal apoptosis following experimental SAH.

METHODS

The endovascular perforation model of SAH was produced in male Sprague-Dawley rats. Rats were administered calpeptin 50 μg, intracerebroventricular injection, 30 minutes before induction of SAH. After 72 hours, the method of Evans blue dye extravasation and wet/dry method were used for determination of blood-brain barrier permeability and brain edema, Western blot analysis and immunohistological staining were used to evaluate neuronal apoptosis.

RESULTS

The intracellular Ca²⁺ level and calpain activity was significantly elevated in basal cortex after SAH. Calpain inhibitor calpeptin reduces brain water content and Evans blue dye extravasation, improves neurobehavioral deficits after SAH. Importantly, calpeptin treatment significantly reduces activation of caspase-3, caspase-9, caspase-12 and poly ADP ribose polymerase and the number of apoptotic neurons in basal cortex after SAH.

CONCLUSION

The present study suggested that calpeptin is neuroprotective in early brain injury after SAH through antiapoptotic effect.

Attenuation of Blood-Brain Barrier Breakdown and Hyperpermeability by Calpain Inhibition

Blood-brain barrier (BBB) breakdown and the associated microvascular hyperpermeability followed by brain edema are hallmark features of several brain pathologies, including traumatic brain injuries (TBI). Recent studies indicate that pro-inflammatory cytokine interleukin-1β (IL-1β) that is up-regulated following traumatic injuries also promotes BBB dysfunction and hyperpermeability, but the underlying mechanisms are not clearly known. The objective of this study was to determine the role of calpains in mediating BBB dysfunction and hyperpermeability and to test the effect of calpain inhibition on the BBB following traumatic insults to the brain. In these studies, rat brain microvascular endothelial cell monolayers exposed to calpain inhibitors (calpain inhibitor III and calpastatin) or transfected with calpain-1 siRNA demonstrated attenuation of IL-1β-induced monolayer hyperpermeability. Calpain inhibition led to protection against IL-1β-induced loss of zonula occludens-1 (ZO-1) at the tight junctions and alterations in F-actin cytoskeletal assembly. IL-1β treatment had no effect on ZO-1 gene (tjp1) or protein expression. Calpain inhibition via calpain inhibitor III and calpastatin decreased IL-1β-induced calpain activity significantly (p < 0.05). IL-1β had no detectable effect on intracellular calcium mobilization or endothelial cell viability. Furthermore, calpain inhibition preserved BBB integrity/permeability in a mouse controlled cortical impact model of TBI when studied using Evans blue assay and intravital microscopy. These studies demonstrate that calpain-1 acts as a mediator of IL-1β-induced loss of BBB integrity and permeability by altering tight junction integrity, promoting the displacement of ZO-1, and disorganization of cytoskeletal assembly. IL-1β-mediated alterations in permeability are neither due to the changes in ZO-1 expression nor cell viability. Calpain inhibition has beneficial effects against TBI-induced BBB hyperpermeability.

The neuro-behavioral profile in rats after subarachnoid hemorrhage

Despite significant advancements in the understanding of the pathophysiological mechanisms of subarachnoid hemorrhage (SAH), little is known about the emotional consequences. The primary goal of this study was to describe the locomotor and behavioral patterns in rats following both a single-injection and double-injection model of SAH. In 48 rats, SAH was induced by injecting 0.3 ml of autologous arterial blood into the cisterna magnum (single-hemorrhagic model). In 24 of these rats, post-SAH vasospasm was induced by a repeated injection of blood into the cisterna magnum 24h later (double-hemorrhagic model). In 24 additional rats, 0.3 ml of saline was injected into the cisterna magnum (sham group). Neurological performance was assessed at 24, 48 h, 1, 2 and 3 weeks after SAH. Four behavioral tests were performed for 3 weeks after SAH for the duration of 6 consequent days, in the following order: open field test, sucrose preference test, elevated plus maze test and forced swimming test. Following both, a single and double-hemorrhagic models of SAH, rats were found to have significant behavioral abnormalities on the open field test, sucrose preference test, elevated plus maze test, and forced swimming test. A more prominent disability was found in rats that underwent the double-hemorrhagic model of SAH than rats that underwent the single-hemorrhagic model. Both a single and double injection model of rats SAH are associated with significant behavioral disturbances including locomotor abnormalities, depressive behavior and increased anxiety, even as early as 3 weeks after SAH.

Nimodipine attenuation of early brain dysfunctions is partially related to its inverting acute vasospasm in a cisterna magna subarachnoid hemorrhage (SAH) model in rats

Subarachnoid hemorrhage (SAH)-induced brain injury is highly related to neurological deficits and mortality. Regional cerebral blood flow (rCBF) changes and vasoconstriction are two complications that occur soon after SAH experimentally. In this study we investigated the changes in rCBF and vertebro-basilar arterial diameter in a cisterna megna SAH model in Sprague-Dawley rats and intended to explore whether improving early rCBF reduction and cerebral vasospasm could contribute to alleviating blood-brain barrier (BBB) dysfunction. In rats for rCBF, vasospasm and BBB permeability assessments, nimodipine (NDP) or saline was administered intravenously 5 minutes after SAH. rCBF within the first 60 minutes after SAH was measured by laser Doppler flowmetry. BBB permeability indexed by Evans Blue extravasation was assessed 4 hours after SAH. Angiography for the caliber changes of the vertebro-basilar artery were conducted 30 minutes post SAH. Pronounced rCBF reduction and vasospasm were observed soon after SAH, followed by BBB permeability increment. NDP administration could improve rCBF and attenuate vasospasm, followed by the alleviation of BBB permeability. Our results demonstrate that early improvement of cerebral circulation by NDP may contribute to the reduction in brain injury indexed by BBB disruption.

The importance of early brain injury after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a medical emergency that accounts for 5% of all stroke cases. Individuals affected are typically in the prime of their lives (mean age 50 years). Approximately 12% of patients die before receiving medical attention, 33% within 48 h and 50% within 30 days of aSAH. Of the survivors 50% suffer from permanent disability with an estimated lifetime cost more than double that of an ischemic stroke. Traditionally, spasm that develops in large cerebral arteries 3-7 days after aneurysm rupture is considered the most important determinant of brain injury and outcome after aSAH. However, recent studies show that prevention of delayed vasospasm does not improve outcome in aSAH patients. This finding has finally brought in focus the influence of early brain injury on outcome of aSAH. A substantial amount of evidence indicates that brain injury begins at the aneurysm rupture, evolves with time and plays an important role in patients' outcome. In this manuscript we review early brain injury after aSAH. Due to the early nature, most of the information on this injury comes from animals and few only from autopsy of patients who died within days after aSAH. Consequently, we began with a review of animal models of early brain injury, next we review the mechanisms of brain injury according to the sequence of their temporal appearance and finally we discuss the failure of clinical translation of therapies successful in animal models of aSAH.

Neurological and neurobehavioral assessment of experimental subarachnoid hemorrhage

About 50% of humans with aneurysmal subarachnoid hemorrhage (SAH) die and many survivors have neurological and neurobehavioral dysfunction. Animal studies usually focused on cerebral vasospasm and sometimes neuronal injury. The difference in endpoints may contribute to lack of translation of treatments effective in animals to humans. We reviewed prior animal studies of SAH to determine what neurological and neurobehavioral endpoints had been used, whether they differentiated between appropriate controls and animals with SAH, whether treatment effects were reported and whether they correlated with vasospasm. Only a few studies in rats examined learning and memory. It is concluded that more studies are needed to fully characterize neurobehavioral performance in animals with SAH and assess effects of treatment.

Neurological impairment in rats after subarachnoid hemorrhage--a comparison of functional tests

Functional outcome has become a key parameter for the determination of the efficacy of therapeutic interventions. Unfortunately, functional tests are not established for filament perforation induced subarachnoid hemorrhage (SAH). Therefore, we evaluated generally applied functional tasks for their potential to discriminate between various degrees of neuronal damage. Rats were subjected to SAH by an endovascular filament and were randomly assigned to controls treated with 0.9% NaCl, moderately neuroprotective therapy with 7.5% NaCl, and highly effective neuroprotection by 7.5% NaCl+6% dextran 70 (HSD). Functional deficit was quantified daily using beam balance task, prehensile traction task, rotarod, a 6-point motor function score and a general neurological 100-point score. Only the HSD group exhibited significantly more surviving neurons at postoperative day 7. Despite significant variations in histomorphometry, beam balance, prehensile traction and rotarod failed to distinguish between groups. On the other hand, the 100-point neuroscore showed improved neurological recovery on postoperative day 1 for HSD. The 100-point neuroscore failed to discriminate between treatment arms at later time points and therefore seems to reflect predominantly early neurological dysfunction. In conclusion, the results of pure motor tasks after experimental SAH in rats should be carefully interpreted. The integration of a test regimen to examine long term cognitive deficits after rat SAH might be valuable to gain additional information about the functional consequences of morphological damage.

Alpha-II spectrin breakdown products in aneurysmal subarachnoid hemorrhage: a novel biomarker of proteolytic injury

OBJECT

Aneurysmal subarachnoid hemorrhage (ASAH) is a serious event with grave consequences. Delayed ischemic neurological deficits caused by cerebral arterial vasospasm contribute significantly to death and disability. Biomarkers may reflect brain injury and provide an early warning of impending neurological decline and stroke from ASAH-induced vasospasm. Alpha-II spectrin is a cytoskeletal protein whose breakdown products are candidate surrogate markers of injury magnitude, treatment efficacy, and outcome. In addition, all spectrin breakdown products (SBDPs) can provide information on the proteolytic mechanisms of injury.

METHODS

Twenty patients who received a diagnosis of Fisher Grade 3 ASAH were enrolled in this study to examine the clinical utility of SBDPs in the detection of cerebral vasospasm in patients with ASAH. All patients underwent placement of a ventriculostomy for continual cerebrospinal fluid drainage within 72 hours of ASAH onset. Cerebrospinal fluid samples were collected every 6 hours and analyzed using Western Blotting for SBDPs. Onset of vasospasm was defined as an acute onset of a focal neurological deficit or a change in Glasgow Coma Scale score of two or more points. All suspected cases of vasospasm were confirmed on imaging studies.

RESULTS

Both calpain- and caspase-mediated SBDP levels are significantly increased in patients suffering ASAH. The concentration of SBDPs was found to increase significantly over baseline level up to 12 hours before the onset of cerebral arterial vasospasm.

CONCLUSIONS

Differential expression of SBDPs suggests oncotic necrotic proteolysis may be predominant in acute brain injury after ASAH and cerebral arterial vasospasm.

NMDA receptor antagonist felbamate reduces behavioral deficits and blood-brain barrier permeability changes after experimental subarachnoid hemorrhage in the rat

Increased levels of glutamate and aspartate have been detected after subarachnoid hemorrhage (SAH) that correlate with neurological status. The NMDA receptor antagonist felbamate (FBM; 2-phenyl-1,3-propanediol dicarbamate) is an anti-epileptic drug that elicits neuroprotective effects in different experimental models of hypoxia-ischemia. The aim of this dose-response study was to evaluate the effect of FBM after experimental SAH in rats on (1) behavioral deficits (employing a battery of assessment tasks days 1-5 post-injury) and (2) blood-brain barrier (BBB) permeability changes (quantifying microvascular alterations according to the extravasation of protein-bound Evans Blue by a spectrophotofluorimetric technique 2 days post-injury). Animals were injected with 400 muL of autologous blood into the cisterna magna. Within 5 min, rats received daily oral administration of FBM (15, 30, or 45 mg/kg) for 2 or 5 days. Results were compared with sham-injured controls treated with oral saline or FBM (15, 30, or 45 mg/kg). FBM administration significantly ameliorated SAH-related changes in Beam Balance scores on days 1 and 2 and Beam Balance time on days 1-3, Beam Walking performance on days 1 and 2, and Body Weight on days 3-5. FBM also decreased BBB permeability changes in frontal, temporal, parietal, occipital, and cerebellar cortices; subcortical and cerebellar gray matter; and brainstem. This study demonstrates that, in terms of behavioral and microvascular effects, FBM is beneficial in a dose-dependent manner after experimental SAH in rats. These results reinforce the concept that NMDA excitotoxicity is involved in the cerebral dysfunction that follows SAH.

Moderate hypothermia, but not calpain inhibitor 2, attenuates the proteolysis of microtubule-associated protein 2 in the hippocampus following traumatic brain injury in rats

BACKGROUND AND OBJECTIVE

The degradation of the cytoskeletal protein microtubule-associated protein 2 (MAP2), by calpain has been known to occur following traumatic brain injury. We examined the therapeutic potential of calpain inhibitor 2, compared with that of moderate hypothermia in traumatic brain injury produced by weight drop in rats.

METHODS

An inhibitor treated group (n = 8) received calpain inhibitor 2 intravenously (i.v.) for 5 min before and for 6 h after injury (total 2 micromol); a hypothermic (HT) group (n = 8) was maintained at 30 degrees C (temporalis muscle temperature) for 45 min prior to and 60 min after injury; an untreated (UT) group (n = 8) received an infusion of inactive vehicle. Eight rats (sham group) underwent surgery without brain injury. Histopathological (haematoxylin and eosin staining) and MAP2 (immunohistchemistry and western blotting) evaluations were performed at 6 h after injury.

RESULTS

Ipsilateral cortical damage was marked in the injured groups. In the hippocampus, marked pyramidal neuronal damage was observed in the UT and calpain inhibitor treated (CI) groups, while these neurons were better preserved in the HT group. The hippocampal MAP2 levels in the UT, CI and HT groups were significantly decreased to 13 +/- 9%, 28 +/- 33% and 62 +/- 25% of the sham contol, respectively. MAP2 concentration in the HT group was significantly higher than in UT and CI groups (P < 0.05).

CONCLUSION

The results suggest that moderate hypothermia, but not calpain inhibitor 2 with the tested regime, attenuates cytoskeletal damage in the ipsilateral hippocampus at 6 h after traumatic brain injury.