Our previous studies demonstrated that simvastatin reduced neuronal death, increased neurogenesis, and promoted functional recovery after TBI. Objective: To investigate the effect of simvastatin on angiogenesis after TBI, and the related signaling pathways.
Saline or simvastatin (1 mg/kg) was administered orally to rats starting at day 1 after TBI or sham surgery and then daily for 14 days. Rats were sacrificed at 3 and 14 days after treatment. Brain sections and tissues were prepared for immunohistochemical staining, ELISA, and Western blot analysis, respectively. Cultured rat brain microvascular endothelial cells (RBMVECs) were subjected to oxygen-glucose deprivation (OGD) followed by immunocytochemical staining with phallotoxins and vascular endothelial growth factor receptor-2 (VEGFR-2). Western blot analysis was carried out to examine the simvastatin-induced activation of the v-akt murine thymoma viral oncogene homolog (Akt) signaling pathway. The expression of VEGFR-2 was detected by ELISA.
Simvastatin significantly increased the length of vascular perimeter, promoted the proliferation of endothelial cells, and improved the sensorimotor function after TBI. Simvastatin stimulated endothelial cell tube formation after OGD in vitro. VEGFR-2 expression in both brain tissues and cultured RBMVECs was enhanced after simvastatin treatment, which may be modulated by activation of Akt. Akt-dependent endothelial nitric oxide synthase (eNOS) phosphorylation was also induced by simvastatin in vivo and in vitro.
Simvastatin augments TBI-induced angiogenesis in the lesion boundary zone and hippocampus and improves functional recovery. Simvastatin also promotes angiogenesis in vitro. These beneficial effects on angiogenesis may be related to simvastatin-induced activation of the VEGFR-2/Akt/eNOS signaling pathway.
Angiogenesis; Simvastatin; Traumatic brain injury; VEGFR-2
In this study, we examined the effect of chronic administration of simvastatin immediately after status epilepticus (SE) on rat brain with temporal lobe epilepsy (TLE). First, we evaluated cytokines expression at 3 days post KA-lesion in hippocampus and found that simvastatin-treatment suppressed lesion-induced expression of interleukin (IL)-1β and tumor necrosis factor-α (TNF-α). Further, we quantified reactive astrocytosis using glial fibrillary acidic protein (GFAP) staining and neuron loss using Nissl staining in hippocampus at 4–6 months after KA-lesion. We found that simvastatin suppressed reactive astrocytosis demonstrated by a significant decrease in GFAP-positive cells, and attenuated loss of pyramidal neurons in CA3 and interneurons in dentate hilar (DH). We next assessed aberrant mossy fiber sprouting (MFS) that is known to contribute to recurrence of spontaneous seizure in epileptic brain. In contrast to the robust MFS observed in saline-treated animals, the extent of MFS was restrained by simvastatin in epileptic rats. Attenuated MFS was related to decreased neuronal loss in CA3 and DH, which is possibly a mechanism underlying decreased hippocampal susceptibility in animal treated with simvastatin. Electronic encephalography (EEG) was recorded during 4 to 6 months after KA-lesion. The frequency of abnormal spikes in rats with simvastatin-treatment decreased significantly compared to the saline group. In summary, simvastatin treatment suppressed cytokines expression and reactive astrocytosis and decreased the frequency of discharges of epileptic brain, which might be due to the inhibition of MFS in DH. Our study suggests that simvastatin administration might be a possible intervention and promising strategy for preventing SE exacerbating to chronic epilepsy.
Our previous studies demonstrated that simvastatin treatment promotes neuronal survival and reduces inflammatory cytokine release from astrocytes after traumatic brain injury (TBI) in rats. Since reactive astrocytes produce inflammation mediators, in the current study we investigated the effect of simvastatin on astrocyte activation after TBI and its underlying signaling mechanisms.
Saline or simvastatin (1 mg/kg) was orally administered to rats starting at Day 1 after TBI and then daily for 14 days. Rats were sacrificed at 1, 3, 7, 14 days after treatment. Brain sections and tissues were prepared for immunohistochemical staining and Western blot analysis, respectively. Cultured astrocytes were subjected to oxygen-glucose deprivation (OGD) and followed by immunocytochemical staining with GFAP/caveolin-1 and Western blot analysis. Lipid rafts were isolated from the cell lysate and Western blot was carried out to detect the changes in epidermal growth factor receptor (EGFR) expression and phosphorylation in the lipid rafts.
Simvastatin significantly promoted neuronal survival after TBI and attenuated activation of astrocytes. Simvastatin modified the caveolin-1 expression in lipid rafts in astrocyte cell membrane, suppressed the phosphorylation of EGFR in lipid rafts of astrocytes after OGD, and inhibited the OGD-induced interleukin-1 (IL-1) production.
These data suggest that simvastatin reduces reactive astrogliosis and rescues neuronal cells after TBI. These beneficial effects of simvastatin may be mediated by inhibiting astrocyte activation after TBI through modifying the caveolin-1 expression in lipid rafts and the subsequent modulation of EGFR phosphorylation in lipid rafts.
simvastatin; EGFR; lipid rafts; astrocyte; traumatic brain injury
Increased neurogenesis in feeding centers of the murine hypothalamus is associated with weight loss in diet-induced obese rodents (Kokoeva et al., 2005 and Matrisciano et al., 2010), but this relationship has not been examined in other species. Postmortem hippocampal neurogenesis rates and premortem metabolic parameters were statistically analyzed in 8 chow-fed colony-reared adult bonnet macaques. Dentate gyrus neurogenesis, reflected by the immature neuronal marker, doublecortin (DCX), and expression of the antiapoptotic gene factor, B-cell lymphoma 2 (BCL-2), but not the precursor proliferation mitotic marker, Ki67, was inversely correlated with body weight and crown-rump length. DCX and BCL-2 each correlated positively with blood glucose level and lipid ratio (total cholesterol/high-density lipoprotein). This study demonstrates that markers of dentate gyrus neuroplasticity correlate with metabolic parameters in primates.
This study was designed to investigate the long-term effects of simvastatin treatment after traumatic brain injury (TBI) in rats.
Adult female Wistar rats (n=24) were injured with controlled cortical impact and divided into three groups. The first two groups were treated with simvastatin 0.5 mg/kg or 1 mg/kg administered orally for 14 days starting one day after TBI. The third group (control) received phosphate-buffered saline (PBS) orally for 14 days. Neurological functional outcome was measured with modified neurological severity scores (mNSS) performed 1 day before TBI and after TBI on Days 1, 4, 7, 14 and biweekly thereafter. All animals were sacrificed 3 months after TBI. Brain tissues of half of the animals were processed for preparation of paraffin-embedded sections for immunohistological studies. The remaining half was frozen for ELISA studies for quantification of brain-derived neurotrophic factor (BDNF) in hippocampus and cortex.
Results showed that both doses of simvastatin significantly improved functional outcome compared to control with no difference between the two doses. Simvastatin treatment of 1 mg/kg increased the number of morphologically intact neurons in hippocampus with 0.5 mg/kg having no significant effect. ELISA studies showed that 0.5 mg/kg of simvastatin significantly increased BDNF levels within hippocampus with 1 mg/kg having no significant effect; neither dose had any effect on BDNF levels within the cortex.
Simvastatin treatment provides long-lasting functional improvement after TBI in rats. It also enhances neuronal survival in the hippocampus and increases BDNF levels in the hippocampus secondary to simvastatin treatment.
Simvastatin; Traumatic brain injury; Long term; Newly generated cells
Our previous studies demonstrated that simvastatin promotes neurological functional recovery after traumatic brain injury (TBI) in rat; however, the underlying mechanisms remain poorly understood. The purpose of this study was to investigate the anti-inflammatory effect of simvastatin by measuring the level of cytokines and activation of glial cells.
Controlled cortical impact injury was performed in adult male Wistar rats. The rats were randomly divided into three groups: sham, saline control group and simvastatin treatment group. Simvastatin was administered orally starting at day 1 after TBI until sacrifice. Animals were sacrificed at 1, 3, 7, 14, and 35 days after treatment. Functional outcome was measured using modified neurological severity scores (mNSS). ELISA and immunohistochemical staining were employed to measure the expression of IL-1β, IL-6 and TNF-α, and to identify activated microglia and astrocytes.
At days 1 and 3 after simvastatin or saline treatment, cytokine levels in the lesion boundary zone were significantly higher in the simvastatin-treated rats and saline-treated rats compared to the sham group, peaking at day 3. Simvastatin only reduced the level of IL-1 β but not IL-6 and TNF-α compared with the saline group. Also, simvastatin reduced significantly the number of activated microglia and astrocytes compared to the saline control animals. There was also a trend towards improvement of mNSS score, reaching statistical significance (P=0.003) towards the end of the trial.
Our data demonstrate that TBI causes inflammatory reaction, including increased levels of IL-1β, IL-6 and TNF-α, as well as activated microglia. Simvastatin selectively reduces IL-1β expression and inhibits the activation of microglia and astrocytes after TBI, which may be one of the mechanisms underlying the therapeutic benefits of simvastatin treatment of TBI.
Astrocyte; Interleukin 1 beta; Microglia; Simvastatin; Traumatic brain injury
This study was designed to investigate the beneficial effects of combination therapy of simvastatin and marrow stromal cells (MSCs) in improving functional outcome after traumatic brain injury (TBI) in rats. Adult female Wistar rats (n = 72 and 8, per group) were injured with controlled cortical impact and treated either with monotherapy of MSCs or simvastatin or a combination therapy of these two agents. Different combination doses were tested, and nine groups of animals were studied. Neurological function was evaluated using Modified Neurological Severity Score (MNSS), and animals were sacrificed 3 months after injury. Coronal brain sections were stained with standard hematoxylin and eosin immunohistochemistry. Our results showed that, though functional improvement was seen with monotherapies of MSCs and simvastatin, the combination therapy when used in optimal doses was significantly better in improving functional outcome. This improvement was long lasting and persisted until the end of the trial (3 months). The optimum combination dose was 0.5 mg of simvastatin combined with 2 × 106 MSCs. Post mortem analysis showed the presence of donor MSCs within the injured cortex. Endogenous cellular proliferation induced by the neurorestorative treatments was also observed in the lesion boundary zone. Our data show that MSCs and simvastatin have a synergistic effect in improving functional outcome after TBI.
combination therapy; marrow stromal cells (MSCs); simvastatin; traumatic brain injury (TBI)
This study was designed to investigate the beneficial effects of combination therapy of simvastatin and marrow stromal cells (MSCs) in improving functional outcome after traumatic brain injury (TBI) in rats. Adult female Wistar rats (n = 72 and 8, per group) were injured with controlled cortical impact and treated either with monotherapy of MSCs or simvastatin or a combination therapy of these two agents. Different combination doses were tested, and nine groups of animals were studied. Neurological function was evaluated using Modified Neurological Severity Score (MNSS), and animals were sacrificed 3 months after injury. Coronal brain sections were stained with standard hematoxylin and eosin immunohistochemistry. Our results showed that, though functional improvement was seen with monotherapies of MSCs and simvastatin, the combination therapy when used in optimal doses was significantly better in improving functional outcome. This improvement was long lasting and persisted until the end of the trial (3 months). The optimum combination dose was 0.5 mg of simvastatin combined with 2×106 MSCs. Post mortem analysis showed the presence of donor MSCs within the injured cortex. Endogenous cellular proliferation induced by the neurorestorative treatments was also observed in the lesion boundary zone. Our data show that MSCs and simvastatin have a synergistic effect in improving functional outcome after TBI.
combination therapy; marrow stromal cells (MSCs); simvastatin; traumatic brain injury (TBI)
Erythropoietin (EPO) and its receptor (EPOR), essential for erythropoiesis, are expressed in the nervous system. Recombinant human EPO treatment promotes functional outcome after traumatic brain injury (TBI) and stroke, suggesting that the endogenous EPO/EPOR system plays an important role in neuroprotection and neurorestoration. This study was designed to investigate effects of the EPOR on histological and functional outcomes after TBI. Experimental TBI was induced in adult EPOR-null and wild-type mice by controlled cortical impact. Neurological function was assessed using the modified Morris Water Maze and footfault tests. Animals were sacrificed 35 days after injury and brain sections stained for immunohistochemistry. As compared to the wild-type injured mice, EPOR-null mice did not exhibit higher susceptibility to TBI as exemplified by tissue loss in the cortex, cell loss in the dentate gyrus, impaired spatial learning, angiogenesis and cell proliferation. We observed that less cortical neurogenesis occurred and that sensorimotor function (i.e., footfault) was more impaired in the EPOR-null mice after TBI. Co-accumulation of amyloid precursor protein (axonal injury marker) and calcium was observed in the ipsilateral thalamus in both EPOR-null and wild-type mice after TBI with more calcium deposits present in the wild-type mice. This study demonstrates for the first time that EPOR null in the nervous system aggravates sensorimotor deficits, impairs cortical neurogenesis and reduces thalamic calcium precipitation after TBI.
cell proliferation; erythropoietin receptor null; mouse; sensorimotor; spatial learning; traumatic brain injury
The aim of this study was to investigate the role of gender in histological and functional outcome, angiogenesis, neurogenesis and therapeutic effects of recombinant human erythropoietin (rhEPO) in mice after traumatic brain injury (TBI). TBI caused both tissue loss in the cortex and cell loss in the dentate gyrus (DG) in the injured hemisphere at day 35 post TBI without a significant gender difference. After TBI, sensorimotor deficits were significantly larger in male mice compared to females, while similar spatial learning deficits were present in both genders. TBI alone significantly stimulated angiogenesis and neurogenesis in the cortex and in the DG of injured hemispheres in both genders. rhEPO at a dose of 5,000 Units/kg body weight administered intraperitoneally at 6 h, and 3 and 7 days after injury significantly reduced lesion volume and DG cell loss examined at day 35 after TBI as well as dramatically improved sensorimotor and spatial learning performance without an obvious gender proclivity. rhEPO significantly enhanced neurogenesis in the cortex and the DG of the ipsilateral hemisphere in male TBI mice. rhEPO did not affect angiogenesis in the ipsilateral cortex and DG in both genders after TBI. The present data demonstrate that posttraumatic administration of rhEPO improves histological and functional outcome in both genders, which may be mediated by reducing cortical tissue damage and DG cell loss in the ipsilateral hemisphere. In addition, the major gender propensity observed in the present study with mice after TBI without treatment is limited to sensorimotor deficits and cell proliferation.
behavior; erythropoietin; gender; mouse; neurogenesis; traumatic brain injury
This study was designed to investigate the effects of human bone marrow stromal cell (hMSC) administration in rats for three months after traumatic brain injury (TBI).
Adult male Wistar rats (n = 60) were injured with controlled cortical impact and divided into four groups. The three treatment groups (n = 10 each) were injected with 2 × 106, 4 × 106, and 8 × 106 hMSCs intravenously, whereas the control group (n = 30), received phosphate buffered saline (PBS). All injections were performed 1 day after injury into the tail veins of rats. Neurological functional evaluation of animals was performed before and after injury using Neurological Severity Scores (NSS). Animals were sacrificed 3 months after TBI and brain sections were stained by immunohistochemistry.
Statistically significant improvement in functional outcome was observed in all three treatment groups when compared with control (p < 0.05). This benefit was visible 14 days after TBI and persisted until 3 months (end of trial). There was no difference in functional outcome among the three treatment groups. Histological analysis showed that hMSCs were present in the lesion boundary zone at 3 months with all three doses tested.
hMSCs injected in rats after TBI survive until 3 months and provide long-lasting functional benefit. Functional improvement may be attributed to stimulation of endogenous neurorestorative functions such as neurogenesis and synaptogenesis.
functional improvement; human marrow stromal cells; traumatic brain injury
Traumatic brain injury (TBI) causes extensive loss of cerebral parenchyma; however, no strategy for reconstruction has been clinically effective. We and others have employed human marrow stromal cells (hMSCs) to treat rats subjected to TBI and found no significant changes in the lesion volume, although functional outcome was improved significantly. To identify new ways of delivering hMSCs into the injured brain and to maximize the therapeutic benefits of hMSC treatment, we investigated the use of collagen scaffolds implanted with hMSCs as a cell delivery system for treatment of TBI.
Collagen scaffolds populated with 3 × 106 hMSCs were transplanted into the lesion cavity of the injured cortex 4 days after TBI, and the rats were sacrificed 35 days after TBI. Sensorimotor function and spatial learning were measured using an array of function tests, and the brain tissue was processed for histopathology analysis.
The data show that scaffolds populated by hMSCs improve spatial learning and sensorimotor function, reduce the lesion volume, and foster the migration of hMSCs into the lesion boundary zone after TBI in rats. hMSC-populated scaffolds may be a new way to reconstruct injured brain and improve neurological function after TBI.
Scaffold; Human marrow stromal cells; Lesion volume; Traumatic brain injury
Traumatic brain injury (TBI) remains a major public health problem globally. Presently, there is no way to restore cognitive deficits caused by TBI. In this study, we seek to evaluate the effect of statins (simvastatin and atorvastatin) on the spatial learning and neurogenesis in rats subjected to controlled cortical impact. Rats were treated with atorvastatin and simvastatin 1 day after TBI and daily for 14 days. Morris water maze tests were performed during weeks 2 and 5 after TBI. Bromodeoxyuridine (BrdU; 50 mg/kg) was intraperitoneally injected 1 day after TBI and daily for 14 days. Brain tissue was processed for immunohistochemical staining to identify newly generated cells and vessels. Our data show that (1) treatment of TBI with statins improves spatial learning on days 31–35 after onset of TBI; (2) in the non-neurogenic region of the hippocampal CA3 region, statin treatment reduces the neuronal loss after TBI, demonstrating the neuroprotective effect of statins; (3) in the neurogenic region of the dentate gyrus, treatment of TBI with statins enhances neurogenesis; (4) statin treatment augments TBI-induced angiogenesis; and (5) treatment with simvastatin at the same dose provides a therapeutic effect superior to treatment with atorvastatin. These results suggest that statins may be candidates for treatment of TBI.
neurogenesis; rat; spatial learning; statins