Atorvastatin Regulates Notch Signaling Pathway And Improves Both Cerebral Vascular Regeneration And Neural Repair In Traumatic Brain Injury Rats

Objective:To explore whether atorvastatin administration improves the neural function, learning and memorizing ability, neuro-angiogenesis of the traumatic brain injury (TBI) rats and to investigate the related modulation mechanism in cellular and molecular levels.Methods:Wistar rats were randomly devided into sham injured, traumatic brain injury treated with saline-treated (TBI+Saline) and TBI treated with atorvastatin (TBI+Atorvastatin) groups. Each rat in the TBI+Atorvastatin group administered atorvastatin just after TBI at a dose of 1 mg/kg/day for 14 consecutive days. While the rats in the TBI+saline group only receive the saline injection with the eaual volumne compared of the one of the TBI+Atorvastatin group. At the same time, the mNSS was used to evaluate the functional recovery induced by atorvastatin at 1,4,7,14,21 day after TBI, and morris water maze was used for investigating the memory recovery at 21-25 days post-TBI. Then 1ml of blood was collected in EDTA tubes from retro-orbital venous plexus by glass capillary before and 1,4,7,14,25 day after TBI repectively, their EPCs levels were measured by flow cytometry. Aother 51 Wistar rats were randomly devided into sham injured, traumatic brain injury treated with saline (TBI+Saline) and TBI treated with atorvastatin (TBI+Atorvastatin) in order to collect the brain tissue at 1,4,7,14 and 21 days post-TBI respectively. The immnohistochemical staining, Real-time PCR, Western Blotting were all applied to evaluate the angiogenesis, the change of Notch signaling pathway and the regulation on Notch signaling pathway in TBI rats.Results:The mNSS was performed to assay the neuro-function status of the TBI rats to reveal that the atorvastatin-treating rats scored higher than the saline-treated ones at 14,21 and 25 days after TBI(P<0.05). Similarly, the spatial learning ability was significantly improved in atorvastatin-treated rats at the 24 and 25 day after TBI (P <0.05), compared with the saline-treated rats. In vivo studies showed that TBI induced a downregulation of the circulating EPCs level at 3 hours after TBI and then an sharp upregulation was observed to peak at 6 hours post-TBI(P<0.05), which then decreased gradually to the normal levle 24 hours later after TBI. While the level of the circulating EPCs was induced by the atorvastatin but not saline, which increased gradually and reaching a plateau around 7th day after atorvastatin treatment (P<0.05). The expression of Notch signaling pathway is diversity by Immunohistochemistry, Real-time PCR, western blotting in TBI rats. The peak of Notch1,Jagged1 expression appear after TBI, After the use of atorvastatin Notch1, Jagged1 expression was increased to, the expression of DLL4 reduced.Conclusion:Atorvastatin promates angiogenesis in the injured brain tissue, improves neurological function, learning and memorizing ability in TBI rats. A significant neurovascular regeneration was observed in the injured brain tissue after atorvastatin administration, which consisted well with an enhanced mobilization of the circulating endothelial progenitor cells from bone marrow The Notch signaling pathway was modulated and enhanced by the administration of atorvastatin too. It strongly implied that the modulation of Notch signal pathway be tightly associated with the neural regeneration and angiogenesis in the injured brain tissue.Thus a new strategy to targeting Notch signals is indicated in the TBI treatment.