Morphological and functional alterations of astrocytes responding to traumatic brain injury.

Astrocytes, one of the most abundant and heterogeneous types of glial cell in the brain and spinal cord, are responsible for various essential functions in the healthy central nervous system, including maintaining the blood brain barrier integrity, regulating neuron differentiation and supporting, nourishing, protecting, insulating and repairing neurons. They also fulfill a range of other homeostatic maintenance functions. Astrocytes are activated after traumatic brain injury. They then exhibit heterogeneous gene expression and changes in morphology, proliferative capacity and various functions in response either acute or chronic brain injury and associated secondary brain injury. Some biomarkers and imaging tools have been used to monitor astrogliosis after traumatic brain injury. Initially, morphological characteristics and the physiology of astrocytes are reviewed. Subsequently, alterations of astrocytes are described, which includes both the complex mechanisms and roles of reactive astrocytes. The roles of biomarkers and signaling pathways following traumatic brain injury have been summarized as well as the morphological and functional changes in astrocytes. In the latter case, by considering astrocytes as therapeutic targets of traumatic brain injury, the mechanisms of the latest drug treatments are explained. This review highlights the beneficial effects of astrogliosis according to some recent findings, which provides new insights for the treatment of traumatic brain injury.

Quantitative Proteomic Study Reveals Up-Regulation of cAMP Signaling Pathway-Related Proteins in Mild Traumatic Brain Injury.

Traumatic brain injury (TBI), as a neurological injury, becomes a leading cause of disability and mortality due to lacking effective therapy. About 75% of TBI is mild traumatic brain injury (mTBI). However, the complex molecular mechanisms underlying mTBI pathophysiology remains to be elucidated. In this study, iTRAQ-based quantitative proteomic approach was employed to measure temporal-global proteome changes of rat brain tissues from different time points (1 day, 7 day and 6 months) post single mTBI (smTBI) and repetitive mTBI (rmTBI). A total of 5169 proteins were identified, of which, 237 proteins were significantly changed between control rats and mTBI model rats. Fuzzy c-means (FCM) clustering analysis classified these 237 proteins into six clusters according to their temporal pattern of protein abundance. Functional bioinformatics analysis and protein-protein interaction (PPI) network mapping of these FCM clusters showed that phosphodiesterase 10A (Pde10a) and guanine nucleotide-binding protein G (olf) subunit alpha (Gnal) were the node proteins in the cAMP signaling pathway. Other biological processes, such as cell adhesion, autophagy, myelination, microtubule depolymerization and brain development, were also over-represented in FCM clusters. Further Western Blot experiments confirmed that Pde10a and Gnal were acutely up-regulated in severity-dependent manner by mTBI, but these two proteins could not be down-regulated to basal level at the time point of 6 months post repetitive mTBI. Our study demonstrated that different severity of mTBI cause significant temporal profiling change at the proteomic level and pointed out the cAMP signaling pathway-related proteins, Pde10a and Gnal, may play important roles in the pathogenesis and recovery of mTBI.

Erratum to: Vascular endothelial growth factor induces contralesional corticobulbar plasticity and functional neurological recovery in the ischemic brain.

Erratum to: Acta Neuropathol (2012) 123:273­284. DOI 10.1007/s00401­011­0914­z. The authors would like to correct Fig. 3 of the original manuscript, since the image in Fig. 3b does not correspond to a VEGF treated animal. Corrected Fig. 3 is shown below. We apologize for this mistake.

Expression of angiotensin II and its receptors in activated microglia in experimentally induced cerebral ischemia in the adult rats.

Expression of angiotensin II (Ang II) and its receptors (AT1/AT2) is undetected in the mature microglia in normal brain. We report here that the immunoexpression of Ang II and AT1/AT2 was altered in activated microglia notably at 1 week in rats subjected to middle cerebral artery occlusion (MCAO). Immunolabeled activated microglia were widely distributed in the infarcted cerebral tissue after MCAO. By enzyme immunoassay, Ang II protein expression levels of the ischemic tissues were decreased drastically at 12 h after ischemia, then rose rapidly at 3 days and 1 week after MCAO when compared with the control. On the other hand, AT1 and AT2 receptor mRNA and protein levels were up-regulated after MCAO, peaking at 12 h, but declined thereafter. Expression of tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) mRNA and protein levels was concomitantly increased. Edaravone significantly suppressed Ang II and AT1/AT2 receptor expression as well as that of TNF-α and IL-1ß suggesting that microglia-derived Ang II can act through an autocrine manner via its receptor that may be linked partly to the production of proinflammatory cytokines. We conclude that neuroinflammation in MCAO may be attenuated by Edaravone which acts through suppression of expression of Ang II and its receptors and proinflammatory cytokines in activated microglia.

Intracerebroventricularly delivered VEGF promotes contralesional corticorubral plasticity after focal cerebral ischemia via mechanisms involving anti-inflammatory actions.

Vascular endothelial growth factor (VEGF) has potent angiogenic and neuroprotective effects in the ischemic brain. Its effect on axonal plasticity and neurological recovery in the post-acute stroke phase was unknown. Using behavioral tests combined with anterograde tract tracing studies and with immunohistochemical and molecular biological experiments, we examined effects of a delayed i.c.v. delivery of recombinant human VEGF(165), starting 3 days after stroke, on functional neurological recovery, corticorubral plasticity and inflammatory brain responses in mice submitted to 30 min of middle cerebral artery occlusion. We herein show that the slowly progressive functional improvements of motor grip strength and coordination, which are induced by VEGF, are accompanied by enhanced sprouting of contralesional corticorubral fibres that branched off the pyramidal tract in order to cross the midline and innervate the ipsilesional parvocellular red nucleus. Infiltrates of CD45+ leukocytes were noticed in the ischemic striatum of vehicle-treated mice that closely corresponded to areas exhibiting Iba-1+ activated microglia. VEGF attenuated the CD45+ leukocyte infiltrates at 14 but not 30 days post ischemia and diminished the microglial activation. Notably, the VEGF-induced anti-inflammatory effect of VEGF was associated with a downregulation of a broad set of inflammatory cytokines and chemokines in both brain hemispheres. These data suggest a link between VEGF's immunosuppressive and plasticity-promoting actions that may be important for successful brain remodeling. Accordingly, growth factors with anti-inflammatory action may be promising therapeutics in the post-acute stroke phase.

Vascular endothelial growth factor induces contralesional corticobulbar plasticity and functional neurological recovery in the ischemic brain.

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor, which also has neuroprotective activity. In view of these dual actions on vessels and neurons, we were interested whether VEGF promotes long distance axonal plasticity in the ischemic brain. Herein, we show that VEGF promotes neurological stroke recovery in mice when delivered in a delayed way starting 3 days after middle cerebral artery occlusion. Using anterograde tract-tracing experiments that we combined with histochemical and molecular biological studies, we demonstrate that although VEGF promoted angiogenesis predominantly in the ischemic hemisphere, pronounced axonal sprouting was induced by VEGF in the contralesional, but not the ipsilesional corticobulbar system. Corticobulbar plasticity was accompanied by the deactivation of the matrix metalloproteinase MMP9 in the lesioned hemisphere and the transient downregulation of the axonal growth inhibitors NG2 proteoglycan and brevican and the guidance molecules ephrin B1/2 in the contralesional hemisphere. The regulation of matrix proteinases, growth inhibitors, and guidance molecules offers insights how brain plasticity is controlled in the ischemic brain.

Delayed melatonin administration promotes neuronal survival, neurogenesis and motor recovery, and attenuates hyperactivity and anxiety after mild focal cerebral ischemia in mice.

Melatonin is a potent antioxidant with neuroprotective activity in animal models of ischemic stroke, which based on its lack of serious toxicity has raised hopes that it might be used for human stroke treatment in the future. This study investigated how subacute delivery of melatonin, starting at 24 hr after stroke onset, and continuing for 29 days (4 mg/kg/day; via drinking water), influences neuronal survival, endogenous neurogenesis, motor recovery and locomotor activity in C57Bl6/j mice submitted to 30-min middle cerebral artery occlusion. Histologic studies showed that melatonin improved neuronal survival and enhanced neurogenesis, even when applied 1 day after stroke. Cell survival was associated with a long-lasting improvement of motor and coordination deficits, evaluated by the grip strength and RotaRod tests, as well as with attenuation of hyperactivity and anxiety of the animals as revealed in open field tests. The robust functional neurologic improvements encourage proof-of-concept studies with melatonin in human stroke patients.

[Coma criterion and classification standard of mild and moderate traumatic brain injury in rats].

OBJECTIVE: To set up a classification standard of mild and moderate traumatic brain injury, for the purpose of reliable data comparison derived from different laboratories. METHODS: Traumatic brain injury (TBI) in rats was prepared by using a metallic pendulum-striker device. After injury, five variable parameters including the time of apnea and the areflexia, time of corneal reflex, external auditory canal stung reaction, body-righting reflex and needling reaction were determined and scored by using rat coma criterion. These data were judged and classified into mild and moderate head injury by brain patho-anatomy changes. Then the data were used to set up a multivariate discriminate equation. RESULTS: The distinguished probability of mild and moderate TBI according to actual direct measured value and the criterion were 88.9% and 91.9%, respectively. CONCLUSION: This method is able to classify mild and moderate TBI in rats.

Human vascular endothelial growth factor protects axotomized retinal ganglion cells in vivo by activating ERK-1/2 and Akt pathways.

Based on its trophic effects on neurons and vascular cells, vascular endothelial growth factor (VEGF) is a promising candidate for the treatment of neurodegenerative diseases. To evaluate the therapeutic potential of VEGF, we here examined effects of this growth factor on the degeneration of axotomized retinal ganglion cells (RGCs), which, as CNS-derived neurons, offer themselves in an excellent way to study neuroprotection in vivo. Making use of a transgenic mouse line that constitutively expresses human VEGF under a neuron-specific enolase promoter, we show that (1) the VEGF-transgenic retina overexpresses human VEGF, (2) RGCs carry the VEGF receptor-2, and (3) vascular networks in normal and axotomized VEGF-transgenic (tg) retinas do not differ from control animals. After axotomy, RGCs of VEGF-tg mice were protected against delayed degeneration, as compared with wild-type littermates. Western blots revealed increased phosphorylated ERK-1/2 and Akt and reduced phosphorylated p38 and activated caspase-3 levels in axotomized VEGF-transgenic retinas. Intravitreous injections of pharmacological ERK-1/2 (PD98059) or Akt (LY294002) inhibitors showed that VEGF exerts neuroprotection by dual activation of ERK-1/2 and Akt pathways. In view that axotomy-induced RGC death occurs slowly and considering that RGCs are CNS-derived neurons, we predict the clinical implementation of VEGF in neurodegenerative diseases of both brain and retina.

Rosemary extract improves cognitive deficits in a rats model of repetitive mild traumatic brain injury associated with reduction of astrocytosis and neuronal degeneration in hippocampus.

In this study, we investigated whether Rosemary extract (RE) improved cognitive deficits in repetitive mild Traumatic brain injury (rmTBI) rats and its potential mechanisms. The present results showed that rmTBI caused cognitive deficits, such as increased latency to find platform and decreased time spent in target quadrant in Morris water maze (MWM). These behavioral alterations were accompanying with the increased neuronal degeneration and glial fibrillary acidic protein (GFAP)-positive cells, increased Reactive oxygen species (ROS) generation, decreased activity of Superoxide Dismutase (SOD), Glutathione Peroxidase (GPx) and Catalase (CAT), elevated protein level of IL-1ß, IL-6 and TNF-α in hippocampus. Treatment with RE prevented these changes above. Our findings confirmed the effect of rosemary extract on improvement of cognitive deficits and suggested its mechanisms might be mediated by anti-oxidative and anti-inflammatory. Therefore, rosemary extract may be a potential treatment to improve cognitive deficits in rmTBI patients.

[c-jun expression in spared dorsal root ganglion following partial dorsal root rhizotomy and acupuncture].

OBJECTIVE: To investigate the change of c-jun expression in spared dorsal root ganglion (DRG) following partial dorsal root rhizotomy and acupuncture. METHODS: Fifteen adult cats were divided into three groups with five cats in every group--sham operation, operation, and acupuncture following operation respectively. Animals of operation group were subjected to unilateral root rhizotomy (L1-L5, L7-S2 DRGs were sectioned, L6 DRG was spared). Electro-needling was performed alternatively at two sets of acupoints, including Zusanli and Xuanzhong, Futu and Sanyinjiao, located in the distribution area of spinal nerve L6 on the operated side, 30 min everyday for 7 days following unilateral root rhizotomy. The animals of sham operation group experienced only skin and muscle incisions. On the 7th day after operation, all animals were sacrificed. The L6 DRG on the disposal side of each animal was taken and made into frozen sections 20 micrograms in thickness. The sections were stained under the same condition using specific c-jun antibody (1:1000, Santa Cruz) by immunohistochemistry ABC method. The distribution and number as well as immunoreactive level of c-jun positive neurons in DRG were observed and measured. RESULTS: In the L6 DRG of sham operation group, only parts of neurons were stained. In contrast, the number of positive neurons and immunoreactive level for c-jun increased significantly in operation group (P < 0.05). Compared with the operation group, the operation plus acupuncture group had higher c-jun immunoreactive level of neurouns, but its number of c-jun positive neurons didn't change markedly. CONCLUSION: Partial dorsal root rhizotomy leads to the up-regulation of c-jun expression in neurons of spared DRG, and acupuncture enhances the up-regulation.

Role of Nogo-A in neuronal survival in the reperfused ischemic brain.

Nogo-A is an oligodendroglial neurite outgrowth inhibitor, the deactivation of which enhances brain plasticity and functional recovery in animal models of stroke. Nogo-A's role in the reperfused brain tissue was still unknown. By using Nogo-A(-/-) mice and mice in which Nogo-A was blocked with a neutralizing antibody (11C7) that was infused into the lateral ventricle or striatum, we show that Nogo-A inhibition goes along with decreased neuronal survival and more protracted neurologic recovery, when deactivation is constitutive or induced 24 h before, but not after focal cerebral ischemia. We show that in the presence of Nogo-A, RhoA is activated and Rac1 and RhoB are deactivated, maintaining stress kinases p38/MAPK, SAPK/JNK1/2 and phosphatase-and-tensin homolog (PTEN) activities low. Nogo-A blockade leads to RhoA deactivation, thus overactivating Rac1 and RhoB, the former of which activates p38/MAPK and SAPK/JNK1/2 via direct interaction. RhoA and its effector Rho-associated coiled-coil protein kinase2 deactivation in turn stimulates PTEN, thus inhibiting Akt and ERK1/2, and initiating p53-dependent cell death. Our data suggest a novel role of Nogo-A in promoting neuronal survival by controlling Rac1/RhoA balance. Clinical trials should be aware of injurious effects of axonal growth-promoting therapies. Thus, Nogo-A antibodies should not be used in the very acute stroke phase.