Increased neuroglobin levels in the cerebral cortex and serum after ischemia-reperfusion insults

Neuroglobin (NGB) is a newly discovered protein localized in neurons of the central and peripheral nervous systems in vertebrates. It functions to bind, store, and facilitate the utilization of oxygen in neuronal cells. Recent studies suggest that it may modulate hypoxic and ischemic injury. The major goal of the present study is to characterize the dynamic changes of NGB protein in the brain and serum in a global forebrain ischemia-reperfusion model using gerbils. The sensitivity and validity of serum NGB as a potential biomarker for brain injury were further evaluated. Global cerebral ischemia-reperfusion models were induced by bilateral carotid occlusion for 20 min followed with 2-, 8-, 16-, 24-, 48-, or 72-h reperfusion in forty-six Mongolian gerbils. Sham-operated and operated animals were sacrificed at the designated time after reperfusion. Brains were fixed for immunocytochemical study to evaluate the time-dependent expression of NGB, and the concentration of NGB in serum was measured by enzyme-linked immunosorbent assay. Our results showed that the expression of NGB was upregulated in the cerebral cortex but significantly downregulated in the hippocampus from 2 to 72 h of reperfusion after 20 min of bilateral common carotid arteries occlusion. The concentration of NGB in serum was significantly increased at 8 h and reached a peak at 48 h of reperfusion. There is a significant correlation between NGB levels in the serum and severity of neuronal damage in the gerbil brain. In summary, the upregulation of NGB in cerebral cortex and downregulation in hippocampus after reperfusion insults in the gerbil brain are consistent with the fact that cerebral cortex is more tolerant to hypoxic or ischemic injury than the hippocampus. Moreover, the changes of NGB levels in serum may be used to monitor the extent of brain damage in ischemic brain diseases.     

Quantitative analysis of the generation of different striatal neuronal subtypes in the adult brain following excitotoxic injury

Recent findings in adult rodents have provided evidence for the formation of new striatal neurons from subventricular zone (SVZ) precursors following stroke. Little is known about which factors determine the magnitude of striatal neurogenesis in the damaged brain. Here we studied striatal neurogenesis following an excitotoxic lesion to the adult rat striatum induced by intrastriatal quinolinic acid (QA) infusion. New cells were labeled with the thymidine-analogue 5-bromo-2'-deoxyuridine (BrdU) and their identity was determined immunocytochemically with various phenotypic markers. The unilateral lesion gave rise to increased cell proliferation mainly in the ipsilateral SVZ. At 2 weeks following the insult, there was a pronounced increase of the number of new neurons co-expressing BrdU and a marker of migrating neuroblasts, doublecortin, in the ipsilateral striatum, particularly its non-damaged medial parts. About 80% of the new neurons survived up to 6 weeks, when they expressed the mature neuronal marker NeuN and were preferentially located in the outer parts of the damaged area. Lesion-generated neurons expressed phenotypic markers of striatal medium spiny neurons (DARPP-32) and interneurons (parvalbumin or neuropeptide Y). The magnitude of neurogenesis correlated to the size of the striatal damage. Our data show for the first time that an excitotoxic lesion to the striatum can trigger the formation of new striatal neurons with phenotypes of both projection neurons and interneurons.     

Beneficial effects of sodium or ethyl pyruvate after traumatic brain injury in the rat

Sodium pyruvate (SP) treatment initiated within 5 min post-injury is neuroprotective in a rat model of unilateral cortical contusion injury (CCI). The current studies examined: (1) effects of delayed SP treatments (1000 mg/kg, i.p., at 1, 12 and 24 h), (2) effects of single (1 h) or multiple (1, 12 and 24 h) ethyl pyruvate treatments (EP; at 20 or 40 mg/kg, i.p.), and (3) mechanisms of action for pyruvate effects after CCI. In Experiment 1, both SP and EP treatment(s) significantly reduced the number of dead/dying cells in the ipsilateral hippocampus (dentate hilus + CA3_c and/or CA3_a-b regions) at 72 h post-CCI. Pyruvate treatment(s) attenuated CCI-induced reductions of cerebral cytochrome oxidase activity at 72 h, significantly improving activity in peri-contusional cortex after multiple SP or EP treatments. Optical density measures of ipsilateral CD11b immuno-staining were significantly increased 72 h post-CCI, but these measures of microglia activation were not different from sham injury values in SP and EP groups with three post-CCI treatments. In Experiment 2, three treatments (1, 12 and 24 h) of SP (1000 mg/kg) or EP (40 mg/kg) significantly improved recovery of beam-walking and neurological scores in the first 3 weeks after CCI, and EP treatments significantly improved spatial working memory 1 week post-CCI. Ipsilateral CA3_b neuronal loss, but not cortical tissue loss, was significantly reduced 1 month post-CCI with pyruvate treatments begun 1 h post-CCI. Thus, delayed pyruvate treatments after CCI are neuroprotective and improve neurobehavioral recovery; these effects may be mediated by improved metabolism and reduced inflammation.     

Potential mechanism of cell death in the developing rat brain induced by propofol anesthesia

Commonly used general anesthetics can have adverse effects on the developing brain by triggering apoptotic neurodegeneration, as has been documented in the rat. The rational of our study was to examine the molecular mechanisms that contribute to the apoptotic action of propofol anesthesia in the brain of 7-day-old (P7) rats. The down-regulation of nerve growth factor (NGF) mRNA and protein expression in the cortex and thalamus at defined time points between 1 and 24 h after the propofol treatment, as well as a decrease of phosphorylated Akt were observed. The extrinsic apoptotic pathway was induced by over-expression of tumor necrosis factor (TNF) which led to the activation of caspase-3 in both examined structures. Neurodegeneration was confirmed by Fluoro-Jade B staining. Our findings provide direct experimental evidence that the anesthetic dose (25 mg/kg) of propofol induces complex changes that are accompanied by cell death in the cortex and thalamus of the developing rat brain.     

The synthetic ceramide analog L-PDMP partially protects striatal dopamine levels but does not promote dopamine neuron survival in murine models of parkinsonism

Recent studies have examined the changes in the activity of cannabinoid signaling system in multiple sclerosis (MS), as a way to explain the efficacy of cannabinoid compounds to alleviate spasticity, pain, tremor and other signs of this autoimmune disease. In the present study, we have further explored this issue by examining density, mRNA expression and activation of GTP-binding proteins for the cannabinoid CB1 receptor subtype in several brain structures of mice with chronic relapsing experimental allergic encephalomyelitis (CREAE), a chronic model of MS that reproduces many of the pathological hallmarks of the human disease. CREAE animals were used at different phases in the progression of the disease (acute, remission and chronic) and compared to control mice. We observed several changes in the status of CB1 receptors that were region-specific and mainly circumscribed to motor-related regions, which is compatible with the symptomatology described for these animals that is preferentially of motor nature. We found a moderate decrease in the density of CB1 receptors in the caudate-putamen during the acute phase of CREAE. These reductions disappeared during the remission phase, but they were again observed, to a more marked extent, in the chronic phase. The same pattern for CB1 receptor density was observed in the cerebellum which, in this case, was accompanied by a progressive decrease in the capability of these receptors to activate GTP-binding proteins that was maximal in the chronic phase. The decrease in the density of CB1 receptors in the acute phase was also found in the globus pallidus but, in this case, the reduction was maintained during the further phases. No changes were observed in CB1 receptor-mRNA levels in any of the different regions examined. Finally, by contrast with the observations in motor structures, the status of CB1 receptors remained unaltered in cognition-related regions, such as the cerebral cortex and the hippocampus, during the different phases of CREAE. In summary, CB1 receptors were affected by the development of CREAE in mice exhibiting always down-regulatory responses that were circumscribed to motor-related regions and that were generally more marked during the acute and chronic phases. These observations may explain the efficacy of cannabinoid agonists to improve motor symptoms (spasticity, tremor, ataxia) typical of MS in both humans and animal models.     

Effects of perinatal exposure to low dose of bisphenol A on anxiety like behavior and dopamine metabolites in brain

Bisphenol A (BPA), an endocrine-disrupting chemical, is widely present in the environment. It has been reported that perinatal exposure to low doses of BPA that are less than the tolerable daily intake level (50 μg/kg/day) affects anxiety-like behavior and dopamine levels in the brain. Although the dopaminergic system in the brain is considered to be related to anxiety, no study has reported the effects of low-dose BPA exposure on the dopaminergic system in the brain and on anxiety-like behavior using the same methods of BPA exposure.