Time dependent changes of striatal interneurons after focal cerebral ischemia in rats

Apitherapy in Post-Ischemic Brain Neurodegeneration of Alzheimer's Disease Proteinopathy: Focus on Honey and Its Flavonoids and Phenolic Acids

Neurodegeneration of the brain after ischemia is a major cause of severe, long-term disability, dementia, and mortality, which is a global problem. These phenomena are attributed to excitotoxicity, changes in the blood-brain barrier, neuroinflammation, oxidative stress, vasoconstriction, cerebral amyloid angiopathy, amyloid plaques, neurofibrillary tangles, and ultimately neuronal death. In addition, genetic factors such as post-ischemic changes in genetic programming in the expression of amyloid protein precursor, β-secretase, presenilin-1 and -2, and tau protein play an important role in the irreversible progression of post-ischemic neurodegeneration. Since current treatment is aimed at preventing symptoms such as dementia and disability, the search for causative therapy that would be helpful in preventing and treating post-ischemic neurodegeneration of Alzheimer's disease proteinopathy is ongoing. Numerous studies have shown that the high contents of flavonoids and phenolic acids in honey have antioxidant, anti-inflammatory, anti-apoptotic, anti-amyloid, anti-tau protein, anticholinesterase, serotonergic, and AMPAK activities, influencing signal transmission and neuroprotective effects. Notably, in many preclinical studies, flavonoids and phenolic acids, the main components of honey, were also effective when administered after ischemia, suggesting their possible use in promoting recovery in stroke patients. This review provides new insight into honey's potential to prevent brain ischemia as well as to ameliorate damage in advanced post-ischemic brain neurodegeneration.

TSPO Expression Modulatory Effect of Acetylcholinesterase Inhibitor in the Ischemic Stroke Rat Model

We performed in vivo PET imaging with 3-[¹⁸F]F-CP118,954 (1) for acetylcholinesterase (AChE) and [¹⁸F]fluoromethyl-PBR28-d₂ (2) for translocator protein 18-kDa (TSPO) to investigate the inflammatory brain response after stroke. Imaging studies were performed in the middle cerebral artery occlusion (MCAO) Sprague-Dawley rat model for a period of three weeks. The percentage injected dose per tissue weight (%ID/g) of striatum of 1, and cortex of 2 were obtained, respectively. To trace the sequential inflammatory responses, AChE imaging of 1 was done on post-MCAO day 2, after giving cold PK-11195 for 1 day, and TSPO imaging of 2 was carried out on post-MCAO day 11, after giving donepezil for 10 days. AChE activity in the MCAO-lesioned side were significantly higher than that of the contralateral side on day one, and TSPO activity was highest on day 11. TSPO inhibitor, PK-11195 did not affect AChE activity on day two, while AChE inhibitor, donepezil significantly lowered TSPO binding on day 12. Our study demonstrates that AChE level is elevated in the early course of brain ischemia as a trigger for the inflammatory response, and TSPO level is elevated persistently throughout the post-ischemic injury in the brain. Also, the AChE inhibitor may be able to inhibit or delay neurotoxic inflammatory responses and serve as a beneficial treatment option.

Mechanistic evaluation of Ursolic acid against rotenone induced Parkinson's disease- emphasizing the role of mitochondrial biogenesis

Parkinson's disease (PD) is an age associated, progressive and a second most common neurodegenerative disease. It is caused due to degeneration of dopaminergic neurons in substantia nigra (SN). Various studies implicate mitochondrial dysfunction, oxidative stress, altered degradation of misfolded proteins in PD pathogenesis. Ursolic acid (UA), a natural pentacyclic triterpenoid carboxylic acid, is reported to possess a number of biological activities viz. anti-oxidant, anti-inflammatory etc. The focus of our study was to assess the neuroprotective potential of UA against the rotenone induced pathophysiological alterations. In this study rats were subjected to stereotaxic bilateral injection of rotenone (12 μg/μl) in SN. Further, they were treated per-orally with UA (5 and 10 mg/kg) for 30 days. During the study, neurobehavioral tests comprising Rota-rod, Open field and Barnes maze (BMT) were conducted. At the end of 30 days, the antioxidant (Reduced glutathione, superoxide dismutase, catalase and lipid peroxidation), inflammatory (TNF-α) parameters, mitochondrial complex I, mitochondrial biogenesis (MB) and immunohistochemical analysis (TH positive neurons, Glial Fibrillary Acidic Protein (GFAP)) was performed. The results exhibited significant amelioration in the motor deficits by UA which can be attributed to the protection of TH positive neurons from degeneration. A significant improvement in the cognitive function due to UA was observed in BMT. Biochemically, the oxidative stress and inflammation triggered by rotenone was significantly diminished by UA. It also significantly obviated the complex I inhibition and promoted MB. The preliminary results thus firmly advocate the neuroprotective potential of UA to prevent rotenone induced neurotoxicity in rats.

Restoring brain function after stroke - bridging the gap between animals and humans

Stroke is the leading cause of complex adult disability in the world. Recovery from stroke is often incomplete, which leaves many people dependent on others for their care. The improvement of long-term outcomes should, therefore, be a clinical and research priority. As a result of advances in our understanding of the biological mechanisms involved in recovery and repair after stroke, therapeutic opportunities to promote recovery through manipulation of poststroke plasticity have never been greater. This work has almost exclusively been carried out in preclinical animal models of stroke with little translation into human studies. The challenge ahead is to develop a mechanistic understanding of recovery from stroke in humans. Advances in neuroimaging techniques now enable us to reconcile behavioural accounts of recovery with molecular and cellular changes. Consequently, clinical trials can be designed in a stratified manner that takes into account when an intervention should be delivered and who is most likely to benefit. This approach is expected to lead to a substantial change in how restorative therapeutic strategies are delivered in patients after stroke.

Inhibited Expression of α4β2 Nicotinic Acetylcholine Receptor in Blood Leukocytes of Chinese Patients with Vascular Dementia and in Blood Leukocytes as Well as the Hippocampus of Brain from Ischemic Rats

Our present aim was to investigate whether changes in the expression of α₄β₂ nicotinic acetylcholine receptor (nAChR) in patients with vascular dementia (VaD) and ischemic rats are related to cognitive scores. Blood leukocytes for 59 Chinese patients with VaD (diagnosed on the basis of clinical guidelines) and 31 cases as age-matched controls were examined, and the animal model established employing Pulsinelli's four-vessel occlusion. The levels of α₄ and β₂ subunit mRNA in leukocytes and the hippocampus were analyzed by real-time PCR, and the protein level in the hippocampus by Western blotting. The mini-mental state examination was utilized to characterize the intellectual capacity of the patients with reference to the DSM IV diagnosis and Hachinski Ischemic Scale score, and the Morris Water Maze test to assess the ability of learning and memory of the rats. In patients, the level of α₄ mRNA, but not β₂, in blood leukocytes was clearly lowered, which was significantly correlated to their clinical cognitive test scores. Smoking exerted no impact on the level of α₄ mRNA in the present study. In the blood leukocytes and the hippocampus of the brains of the ischemic rats, the levels of both α₄ and β₂ mRNA were lowered, and the proteins of these subunits in the hippocampus were decreased. The changes of α₄ and β₂ mRNA in blood leukocytes, and their protein levels in the hippocampus were significantly correlated with impaired learning and memory. These findings indicate that alterations in expression of the α₄β₂ subtype of nAChR may be involved in the molecular mechanism(s) underlying the cognitive deficit associated with VaD.

Cholinergic control of the cerebral vasculature in humans

Despite growing evidence of autonomic nervous system involvement in the regulation of cerebral blood flow, the specific contribution of cholinergic vasodilatation to cerebral autoregulation remains unknown. We examined cerebral and forearm blood flow responses to augmented arterial pressure oscillations with and without cholinergic blockade. Oscillatory lower body negative pressure was applied at six frequencies from 0.03 to 0.08 Hz in nine healthy subjects with and without cholinergic blockade via glycopyrrolate. Cholinergic blockade increased cross-spectral coherence between arterial pressure and cerebral flow at all frequencies except 0.03 Hz and increased the transfer function gain at frequencies above 0.05 Hz. In contrast, gain between pressure and forearm flow increased only at frequencies below 0.06 Hz. These data demonstrate that the cholinergic system plays an active and unique role in cerebral autoregulation. The frequency region and magnitude of effect is very similar to what has been seen with sympathetic blockade, indicating a possible balance between the two reflexes to most effectively respond to rising and falling pressure. These findings might have implications for the role of dysfunction in autonomic control of the vasculature in cerebrovascular disease states.

Neural differentiation of transplanted neural stem cells in a rat model of striatal lacunar infarction: light and electron microscopic observations

The increased risk and prevalence of lacunar stroke and Parkinson's disease (PD) makes the search for better experimental models an important requirement for translational research. In this study we assess ischemic damage of the nigrostriatal pathway in a model of lacunar stroke evoked by damaging the perforating arteries in the territory of the substantia nigra (SN) of the rat after stereotaxic administration of endothelin-1 (ET-1), a potent vasoconstrictor peptide. We hypothesized that transplantation of neural stem cells (NSCs) with the capacity of differentiating into diverse cell types such as neurons and glia, but with limited proliferation potential, would constitute an alternative and/or adjuvant therapy for lacunar stroke. These cells showed neuritogenic activity in vitro and a high potential for neural differentiation. Light and electron microscopy immunocytochemistry was used to characterize GFP-positive neurons derived from the transplants. 48 h after ET-1 injection, we characterized an area of selective degeneration of dopaminergic neurons within the nigrostriatal pathway characterized with tissue necrosis and glial scar formation, with subsequent behavioral signs of Parkinsonism. Light microscopy showed that grafted cells within the striatal infarction zone differentiated with a high yield into mature glial cells (GFAP-positive) and neuron types present in the normal striatum. Electron microscopy revealed that NSCs-derived neurons integrated into the host circuitry establishing synaptic contacts, mostly of the asymmetric type. Astrocytes were closely associated with normal small-sized blood vessels in the area of infarct, suggesting a possible role in the regulation of the blood brain barrier and angiogenesis. Our results encourage the use of NSCs as a cell-replacement therapy for the treatment of human vascular Parkinsonism.

Damage to neurons and oligodendrocytes in the hippocampal CA1 sector after transient focal ischemia in rats

Focal brain lesions such as transient focal cerebral ischemia can lead to neuronal damage in remote areas, including the ipsilateral substantia nigra and hippocampus, as well as in the ischemic core. In this study, we investigated acute changes in the ipsilateral hippocampus from 1 up to 7 days after 90 min of transient focal cerebral ischemia in rats, using anti-NeuN (neuronal nuclei), anti-Cu/Zn-superoxide dismutase (Cu/Zn-SOD), anti-Mn-SOD, anti-neuronal nitric oxide synthase (nNOS), anti-inducible NOS (iNOS), anti-glial fibrillary acidic protein (GFAP), anti-ionized calcium-binding adaptor molecule 1(Iba 1) and anti-2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) antibodies. In our western blot and histochemical analyses, present results show that transient focal cerebral ischemia in rats can cause a severe and acute damage of neurons and oligodendrocytes in the ipsilateral hippocampal CA1 sector. The present findings also demonstrate that the expression of iNOS produced by Iba 1-immunopositive microglia precedes the damage of neurons and oligodendrocytes in the ipsilateral hippocampal CA1 sector after transient focal cerebral ischemia. In contrast, our results suggest that increased reactive oxygen species (ROS) production during reperfusion cannot lead to damage of neurons and oligodendrocytes in the ipsilateral hippocampal CA1 sector after transient focal cerebral ischemia, because of an insufficient expression of Cu/Zn-SOD and Mn-SOD. Our double-labeled immunohistochemical study demonstrates that the overexpression of iNOS produced by Iba 1-immunopositive microglia may play a pivotal role in the damage of neurons and oligodendrocytes in the ipsilateral hippocampal CA1 sector at an acute stage after transient focal cerebral ischemia.

Poly(ADP-ribose)polymerase inhibitor can attenuate the neuronal death after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity in mice

An excessive expression of poly(ADP-ribose)polymerase (PARP) has been demonstrated to play a key role in the pathogenesis of Parkinson's disease (PD). Here we investigated the therapeutic effect of the PARP inhibitor benzamide against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in mice. In our HPLC and Western blot analysis, pretreatment with benzamide showed a neuroprotective effect against MPTP neurotoxicity in mice. Posttreatment with benzamide also attenuated MPTP neurotoxicity in mice. Furthermore, our immunohistochemical study showed that posttreatment with benzamide significantly prevented neuronal damage by suppressing overexpression of neuronal, microglial, and astroglial PARP after MPTP treatment. These findings have important implications for the therapeutic time window and choice of PARP inhibitors in PD patients. Our present findings provide further evidence that PARP inhibitor may offer a novel therapeutic strategy for PD.

Delayed gastric emptying and disruption of the interstitial cells of Cajal network after gastric ischaemia and reperfusion

BACKGROUND

Gastrointestinal tract is one of the most susceptible organ systems to ischaemia. Not only mucosal injury but also alterations of the intestinal motility and loss of interstitial cells of Cajal (ICC) have been reported in response to ischaemia and reperfusion (I/R). However, there are few reports on the changes in the gastric motility after gastric I/R. The present study was designed to investigate the alterations in gastric emptying, the ICC and enteric nerves that regulate smooth muscle function in response to gastric I/R.

METHODS

Seven-week-old male Wistar rats were exposed to gastric I/R, and the gastric emptying rates at 12 and 48 h after I/R were evaluated by the phenol red method. Expressions of gene product of c-kit receptor tyrosine kinase (c-Kit), a marker of ICC, and of neuronal proteins were also examined.

KEY RESULTS

Gastric emptying was transiently delayed at 12 h after I/R, but returned to normal by 48 h. Expression of c-Kit protein as assessed by Western blotting and immunofluorescent staining of the smooth muscle layer, as well as expression of the mRNA of stem cell factor, the ligand for c-Kit, were reduced at both 12 and 48 h after I/R. The expression of neuronal nitric oxide synthase (nNOS) protein as assessed by Western blotting and immunofluorescent staining was also decreased at 12 h after I/R, but was restored to normal by 48 h.

CONCLUSIONS & INFERENCES

Gastric I/R evokes transient gastroparesis with delayed gastric emptying, associated with disruption of the ICC network and nNOS-positive neurons.

Alterations of interneurons in the striatum and frontal cortex of mice during postnatal development

We investigated the postnatal alterations of neuronal nuclei (NeuN)-positive neurons, parvalbumin (PV)-positive interneurons, neuronal nitric oxide synthase (nNOS)-positive interneurons, and neurotrophic factors in the mouse striatum and frontal cortex using immunohistochemistry. NeuN, PV, nNOS, nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF) immunoreactivity were measured in 1-, 2-, 4- and 8-week-old mice. Total number of NeuN-positive neurons was unchanged in the mouse striatum and frontal cortex from 1 up to 8 weeks of age. In contrast, a significant decrease in the number of PV-positive interneurons was observed in the striatum and frontal cortex of 1-, 2- and 4-week-old mice. Furthermore, a significant increase of nNOS-positive interneurons was found in the striatum and frontal cortex of 1- and/or 2-week-old mice. NGF-positive neurons were unchanged in the mouse striatum from 1 up to 8 weeks of age. In the frontal cortex, a significant increase in the number of NGF-positive neurons was observed only in 1-week-old mice. In contrast, a significant increase in the number of NGF-positive glia 1 cells was found in the striatum and frontal cortex of 4-week-old mice. Our double-labeled immunostaining showed that nNOS immunoreactivity was not found in PV-immunopositive interneurons. Furthermore, BDNF immunoreactivity was observed in both nNOS-positive and PV-positive interneurons in the striatum of 1- or 2-week-old mice. These results show that the maturation of nNOS-immunopositive interneurons precedes the maturation of PV-immunopositive interneurons in the striatum and frontal cortex during postnatal development. Furthermore, our results demonstrate that the expression of BDNF may play some role in the maturation of interneurons in the striatum and frontal cortex during postnatal development. Moreover, our findings suggest that the expression of NGF in glia cells may play some role in the maturation of glial cells and PV-positive interneurons in the striatum and frontal cortex during postnatal development.

Long-term changes in the ipsilateral substantia nigra after transient focal cerebral ischaemia in rats

Transient focal cerebral ischaemia can cause neuronal damage in remote areas, including the ipsilateral thalamus and subsutantia nigra, as well as in the ischaemic core. In the present study, we investigated long-term changes in the ipsilateral substantia nigra from 1 up to 20 weeks after 90 min of transient focal cerebral ischaemia in rats, using tyrosine hydroxylase (TH), neuronal nuclei (NeuN), Iba-1, glial fibrillary acidic protein (GFAP) and brain-derived neurotrophic factor (BDNF) immunostaining. These results show that transient focal cerebral ischaemia in rats can cause a severe and prolonged neuronal damage in the ipsilateral striatum. Our results with TH and NeuN immunostaining also demonstrate that the atrophy of the ipsilateral substantia nigra after transient focal cerebral ischaemia was not static but progressive. Furthermore, our double-labelled immunohistochemical study suggests that BDNF released by GFAP-positive astrocytes may play a key role in the survival of dopaminergic neurones in the ipsilateral substantia nigra at the chronic stage after transient focal cerebral ischaemia, although the areas of the ipsilateral substantia nigra are decreased progressively after ischaemia. Thus our study provides further valuable information for the pathogenesis of neuronal damage after transient focal cerebral ischaemia.

Increased acetylcholinesterase and capase-3 expression in the brain and peripheral immune system of focal cerebral ischemic rats

Cerebral ischemia induces rapid neuro-immunological injury as demonstrated by changes in inflammatory factors, cytokines and chemokines in the circulation and peripheral immune system. In addition, elevated acetylcholinesterase (AChE) activity was reported in ischemic brain tissue. Here, we evaluated the time dependent changes in AChE levels and cytokines and NK activity, as well as the relationship of AChE to apoptosis in the brain, spleen and thymus at different time points after focal cerebral ischemia. The data show an elevated level of immunoreactive AChE in the cortex of ischemic brains. This sustained elevated level of AChE in the brain, thymus and spleen activates capase-3 in response to cerebral ischemia. We propose that this pro-apoptotic activity may result in a T helper cell (Th1/Th2) imbalance and impaired immune function in ischemia.

Glial damage after transient focal cerebral ischemia in rats

We investigated the immunohistochemical changes of 8-hydroxy-2'-deoxyguanosine (8-OHdG) immunoreactivity as a marker of DNA damage and single-strand DNA (ssDNA) immunoreactivity as a marker of apoptosis in the striatum from 1 up to 15 days after 90 min of focal cerebral ischemia caused by middle cerebral artery occlusion in rats. In the present study, marked loss of MAP2 immunostaining was observed in the ipsilateral striatum 3 days after focal cerebral ischemia. A significant increase in the number of ssDNA-immunoreactive apoptotic neurons was observed in the ipsilateral striatum 1 and 3 days after focal cerebral ischemia. In contrast, a significant increase in densities of 8-OHdG-immunopositive cells was observed in the ipsilateral striatum from 3 up to 15 days after focal cerebral ischemia. Our double-labeled immunochemical study showed that 8-OHdG immunoreactivity was observed in both isolectin B(4)-positive microglia and glial fibrillary acidic protein-immunopositive astrocytes in the ipsilateral striatum 7 days after focal cerebral ischemia. These results suggest that focal cerebral ischemia can cause a marked increase in the number of microglia and astrocytes with oxidative DNA damage in the ipsilateral striatum. Furthermore, our results show that most microglia and astrocytes in the ipsilateral striatum after focal cerebral ischemia may not die by apoptosis. Thus, our findings provide novel evidence that focal cerebral ischemia can cause oxidative DNA damage in most microglia and astrocytes.