Effect of semax and its C-terminal peptide PGP on expression of neurotrophins and their receptors in rat brain during incomplete global ischemia

Neurotrophins regulate key functions of nervous tissue cells. Analysis of neurotrophin mRNA expression is an appropriate tool to assess therapeutic efficiency of antistroke drugs. We have analyzed the effect of synthetic peptide semax and its C-terminal Pro-Gly-Pro tripeptide on mRNA expression of neurotrophins Ngf, Bdnf, and Nt-3 and their receptors TrkA, TrkB, TrkC, and p75 in rat frontal cortex, hippocampus, and cerebellum after bilateral common carotid artery occlusion. The animals were decapitated at 30 min and 1, 2, 4, 8, 12, and 24 h after the operation. The mRNA expression of neurotrophins and their receptors was assessed by relative quantification using real-time RT-PCR. Our results demonstrated that ischemia caused a significant decrease in gene expression in the hippocampus. Semax and PGP treatment affected the expression of neurotrophins and their receptors predominantly in the frontal cortex and hippocampus of the ischemized animals. In the frontal cortex, Semax treatment resulted in a decrease of mRNA level of neurotrophin receptors, while PGP treatment increased the level of these mRNA. Maximal neuroprotective effect of both peptides was observed in the hippocampus 12 h after occlusion. A decrease of gene expression of neurotrophins and their receptors caused by the occlusion was overcome by Semax and PGP. These results clarify the mechanism of Semax action and reveal certain features of mRNA expression of neurotrophins and their receptors under experimental conditions.     

The effect of semax and its C-end peptide PGP on expression of the neurotrophins and their receptors in the rat brain during incomplete global ischemia

Neurotrophins regulate key function of nervous tissue cells. Analysis of neurotrophins mRNA expression is an appropriate tool to assess therapeutic efficiency of the anti-stroke drugs. We have analyzed the effect of synthetic peptide semax and its C-terminal Pro-Gly-Pro tripeptide upon mRNAs expression of neurotrophins Ngf, Bdrf, Nt-3 and their receptors TrkA, TrkB, TrkC, p75 in rat frontal lobes, hippocampus and cerebellum after bilateral common carotid artery occlusion. The animals were decapitated 30 min, 1, 2, 4, 8, 12, 24 h after the operation. The mRNA expression of neurotrophins and their receptors was assessed by relative quantification using real-time RT-PCR. Our showed that ischemia causes a significant decrease in gene expression in the hippocampus. Semax and PGP affected the expression of neurotrophins and their receptors predominantly in the frontal cortex and hippocampus of the ischemized animals. In the frontal cortex, Semax treatment resulted in a decrease of mRNA level of receptors, while PGP treatment increased the level of these mRNA. Maximal neuroprotective effect of both peptides has been observed in the hippocampus 12 h after occlusion. A decrease of gene expression of neurotrophins and their receptors caused by the occlusion was overcome by Semax and PGP. These results clarify the semax mechanism of and present certain features of mRNA's expression of neurotrophins and their receptors in experimental conditions.     

Effect of peptide Semax and its C-terminal fragment PGP on Vegfa gene expression during incomplete global cerebral ischemia in rats

Vascular endothelial growth factor (VEGF-A) is hypoxia-inducible signal glycoprotein. VEGF-A induces vascular endothelial cell proliferation, which leads to the reconstitution of the vascular network in brain regions damaged by ischemia. However, this protein is also involved in the processes of inflammation and edema in early stages of ischemia. The synthetic peptide Semax has neuroprotective and anti-inflammatory properties and is actively used in the treatment of cerebral ischemia. We have previously shown that Semax reduces vascular injury and activates the mRNA synthesis of neurotrophins and their receptors during global cerebral ischemia in rats. In this work, we studied the effect of Semax and its C-terminal Pro-Gly-Pro tripeptide on Vegfa mRNA expression in different regions of the rat brain after 0.5, 1, 2, 4, 8, 12 and 24 h, which is the irreversible occlusion of the common carotid arteries. It was shown that ischemia increases the levels of Vegfa mRNA in rat brains (4 h after occlusion in cerebellum, cerebral cortex, and hippocampus; 8 h after occlusion in the cortex and hippocampus; and 24 h after occlusion in the cortex). Treatment with Semax reduces the levels of Vegfa mRNA in the frontal cortex (4, 8 and 12 h after occlusion) and the hippocampus (2 and 4 h after occlusion). The effect of PGP on the Vegfa gene expression was almost negligible. It was shown that Semax prevents the activating effect of hypoxia on the expression of the Vegfa gene at early stages of global cerebral ischemia. In turn, an increase in the level of Vegfa mRNA in the hippocampus 24 h after occlusion and Semax administration apparently reflects the neuroprotective properties of the drug.     

Implication of TrkC-miR2 in neurotrophin signalling pathway regulation through NGFR transcript targeting

TrkC and NGFR neurotrophin receptors are associated with cell death, cancer and differentiation. TrkC-miR2, which is located in TrkC gene, is known to regulate Wnt signalling pathway, and its influence on other signalling pathways is under investigation. Here, through RT-qPCR, dual-luciferase assay and Western blotting we reveal that TrkC-miR2 targets NGFR. Overexpression of TrkC-miR2 also affected TrkA, TrkC, NFKB, BCL2 and Akt2 expressions involved in neurotrophin signalling pathway, and elevated survival rate of HEK293t and U87 cells was distinguished by flow cytometry and MTT assay. Consistently, an opposite expression correlation was obtained between TrkC-miR2 and NGFR or TrkC for the duration of NT2 differentiation. Meanwhile, TrkC-miR2 down-regulation attenuated NT2 differentiation into neural-like cells. Overall, here we present in silico and experimental evidence showing TrkC-miR2 as a new controller in regulation of neurotrophin signalling pathway.     

Neuroprotective Effect of Baicalin in a Rat Model of Permanent Focal Cerebral Ischemia

This investigation was performed to determine the neuroprotective effect of baicalin on permanent cerebral ischemia injury in rats and the potential mechanisms in this process. Adult male Sprague-Dawley rats underwent permanent middle cerebral artery occlusion (pMCAO). The rats were then received intraperitoneal injection with baicalin (10, 30 and 100 mg/kg) or vehicle. Morphological characteristic, neurological deficit scores, cerebral infarct volume and the enzymatic activity of myeloperoxidase (MPO) were measured 24 h after pMCAO. The mRNA expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were determined by RT-PCR. Neuronal apoptosis was determined by TUNEL staining and Western blot. Baicalin (30 and 100 mg/kg) reduced neurological deficit scores and cerebral infarct volume 24 h after pMCAO. Baicalin significantly decreased the enzymatic activity of MPO and the expression of iNOS mRNA and COX-2 mRNA in rat brain, it also significantly inhibited neuronal apoptosis and the expression of cleaved caspase-3 protein after pMCAO. Our results suggested that baicalin possesses potent anti-inflammatory and anti-apoptotic properties and attenuates cerebral ischemia injury. This protection might be associated with the downregulated expression of iNOS mRNA, COX-2 mRNA, and cleaved caspase-3 protein.     

The Binding of Semax, ACTH 4–10 Heptapeptide, to Plasma Membranes of the Rat Forebrain Basal Nuclei and Its Biodegradation

The binding characteristics of the peptide Semax (Met-Glu-His-Phe-Pro-Gly-Pro) to plasma membranes of basal nuclei of the rat forebrain and the dynamics of its degradation during its incubation with these membranes were studied. Binding of the homogeneously labeled [G-³H]Semax was shown to be time-dependent, specific, and reversible. Specific binding of the heptapeptide depended on calcium ions and was characterized by the dissociation constant of the ligand–receptor complex K _d 2.41 ± 1.02 × 10^–9 M and by the concentration of binding sites B _max 33.5 ± 7.9 × 10^–15 mol/mg of protein. A method of studying Semax biodegradation in the presence of plasma membranes of rat brain was developed. It is based on the use of the peptide homogeneously labeled with tritium and on an HPLC analysis with UV detection at 220 and 254 nm of the peptide fragments formed. The half-life of Semax in the presence of the plasma membranes was demonstrated to be longer than 1 h. Dipeptidylaminopeptidases are considered to be the main enzymes responsible for its biodegradation; they successively cleave Semax to the HFPGP pentapeptide and the PGP tripeptide.     

The Effect of Lactobacillus casei Consumption in Improvement of Obsessive–Compulsive Disorder: an Animal Study

Obsessive–compulsive disorder (OCD) is an important neuropsychiatric disorder worldwide. Common treatments of OCD include serotonergic antidepressants, which can cause potentially serious side effects. We assessed the effects of Lactobacillus casei (L. casei) Shirota consumption in an animal model of OCD. OCD-like symptoms were induced in rats by the chronic injection of the D2/D3 dopamine agonist quinpirole hydrochloride. Rats were classified into five groups of 6 rats. Four groups were injected chronically with quinpirole (0.5 mg/kg, twice weekly for 5 weeks). They were fed with L. casei Shirota (10⁹ CF/g, daily for 4 weeks) (group 1), fluoxetine (10 mg/kg, daily for 4 weeks) (group 2), combination of L. casei Shirota and fluoxetine (group 3), and normal saline (positive control group). The last group did not receive dopamine agonist and was only injected with saline (negative control group). Expression levels of brain-derived neurotrophic factor (Bdnf), solute carrier family 6 member 4 (Slc6a4), and 5-hydroxytryptamine receptor type 2A (Htr2a) were assessed in orbitofrontal cortex tissues of all rats. Behavioral tests showed improvement of OCD signs in rats treated with L. casei Shirota, fluoxetine, and a combination of drugs. Quantitative PCR analysis showed a remarkable decrease in the expression of Bdnf and an increase in the expression of Htr2a in quinpirole-treated rats. After treatment with L. casei Shirota and fluoxetine, the expression level of Bdnf was increased remarkably, whereas Htr2a expression was decreased. The current study showed the effectiveness of L. casei Shirota in the treatment of OCD in a rat model. The beneficial effects of this probiotic are possibly exerted through the modulation of serotonin-related genes expression.

     

Carbonic anhydrase inhibition for the management of cerebral ischemia: in vivo evaluation of sulfonamide and coumarin inhibitors

Ischemia of brain areas is a global health problem, causing death or long-term disability. Current pharmacological options have limited impact on ischemic damages. Recently, a relationship between hypoxia and carbonic anhydrase (CA) over-expression has been highlighted suggesting CA inhibition as a possible target. This study aimed to evaluate the pharmacological profile of sulfonamide and coumarin CA inhibitors in rats underwent permanent middle cerebral artery occlusion (pMCAO). The neurological score of pMCAO rats was dramatically reduced 24?h after occlusion. Repeated subcutaneous injections of the CA inhibitors 4 and 7 (1?mg kg^?1) were able to increase the neurological score by 40%. Compound 7 showed the tendency to reduce the volume of hemisphere infarction. The standard CA inhibitor acetazolamide was ineffective. The properties of novel CA inhibitors to improve neurological functionalities after cerebral ischemic insult are shown. The CA involvement in cerebral hypoxic phenomena deserves deeper investigations.     

Neuroprotective Effect of Scutellarin on Ischemic Cerebral Injury by Down-Regulating the Expression of Angiotensin-Converting Enzyme and AT1 Receptor

MethodsAdult Sprague–Dawley rats were administrated with different dosages of Scu by oral gavage for 7 days and underwent permanent middle cerebral artery occlusion (pMCAO). Blood pressure was measured 7 days after Scu administration and 24 h after pMCAO surgery by using a noninvasive tail cuff method. Cerebral blood flow (CBF) was determined by Laser Doppler perfusion monitor and the neuronal dysfunction was evaluated by analysis of neurological deficits before being sacrificed at 24 h after pMCAO. Histopathological change, cell apoptosis and infarct area were respectively determined by hematoxylin–eosin staining, terminal deoxynucleotidyl transfer-mediated dUTP nick end labeling (TUNEL) analysis and 2,3,5-triphenyltetrazolium chloride staining. Tissue angiotensin II (Ang II) and ACE activity were detected by enzyme-linked immunosorbent assays. The expression levels of ACE, Ang II type 1 receptor (AT1R), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) were measured by Western blot and real-time PCR. ACE inhibitory activity of Scu in vitro was detected by the photometric determination.ResultsScu treatment dose-dependently decreased neurological deficit score, infarct area, cell apoptosis and morphological changes induced by pMCAO, which were associated with reductions of ACE and AT1R expression and the levels of Ang II, TNF-α, IL-6, and IL-1β in ischemic brains. Scu has a potent ACE inhibiting activity.ConclusionScu protects brain from acute ischemic injury probably through its inhibitory effect on the ACE/Ang II/AT1 axis, CBF preservation and proinflammation inhibition.     

Effects of Exogenous Excitatory Amino Acid Neurotransmitters on Blood–Brain Barrier Disruption in Focal Cerebral Ischemia

This study was performed to determine whether exogenous N-methyl-d-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) would aggravate blood–brain barrier (BBB) disruption in focal cerebral ischemia in rats. Forty-five minutes after middle cerebral artery (MCA) occlusion, one of the following patches was applied to the exposed ischemic cerebral cortex of each rat: normal saline (control), 10⁻⁵ M AMPA, 10⁻⁴ M AMPA, 10⁻⁵ M NMDA, or 10⁻⁴ M NMDA. At 1 h after MCA occlusion, BBB permeability was determined by measuring the transfer coefficient (Ki) of ¹⁴C-α-aminoisobutyric acid (¹⁴C-AIB). In all experimental groups, the Ki of the ischemic cortex (IC) was higher than that of the corresponding contralateral cortex (CC). The Ki of the IC of the animals treated with 10⁻⁴ M AMPA or 10⁻⁴ M NMDA was higher (+41%: P < 0.05 and +33%: P < 0.05, respectively) than that of the control animals. Our data demonstrated that exogenous NMDA or AMPA could further aggravate the BBB disruption in focal cerebral ischemia. Any insult increasing the release of excitatory neurotransmitters could further aggravate BBB disruption and brain edema during the ischemic period.     

Synthesis and biological evaluation of novel hydrogen sulfide releasing nicotinic acid derivatives

Twelve novel hybrids of slowly releasing hydrogen sulfide donor ADT-OH combined with nicotinic acid were synthesized. All of their structures had been confirmed by ¹H NMR, ¹³C NMR and MS spectra. The target compounds were evaluated for their neuroprotective effects on hippocampal neuron HT22 cells against glutamate-induced injury at the concentrations of 1–100 μM with MTT assay, and their toxicity on HT22 cells untreated by glutamine at the concentration of 100 μM. The active compound was further investigated for its effect on ischemic infarct volume by intraperitoneal injection at 3 h after ischemia in mice models of permanent middle cerebral artery occlusion (pMCAO). The results showed that all the compounds significantly protected HT22 cells from glutamate-induced damage at most of the experimental concentrations, and had no or little neurotoxicity on normal HT22 cells at the high concentration. More importantly, compound A6 significantly reduced infarct volume in the pMCAO model. These results suggested that compound A6 may be promising for further evaluation for the intervention of cerebral ischemic injury.     

Characterizing Photothrombotic Distal Middle Cerebral Artery Occlusion and YAG Laser-Induced Reperfusion Model in the Izumo Strain of Spontaneously Hypertensive Rats

No study has systematically studied the relevance of original Izumo strain of spontaneously hypertensive rats (SHR/Izm) as a stroke model. Furthermore, both SHR/Izm and stroke-prone SHR/Izm (SHRSP/Izm) are commercially available, and recent progress in genetic studies allowed us to use several congenic strains of rats constructed with SHR/Izm and SHRSP/Izm as the genetic background strains. A total of 166 male SHR/Izm and 17 male SHRSP/Izm were subjected to photothrombotic middle cerebral artery (MCA) occlusion with or without YAG laser-induced reperfusion. The pattern of distal MCA was recorded. Infarct volumes were determined with 2,3,5-triphenyltetrazolium chloride. At 24 or 48 h after MCA occlusion, infarct volumes in the permanent occlusion and 2-h occlusion groups (88 ± 22 [SD] and 87 ± 25 mm³, respectively) were significantly larger than that in the 1-h occlusion group (45 ± 14 mm³), indicating the presence of sizeable zone of penumbra. Infarct size in SHRSP/Izm determined at 24 h after MCA occlusion was fairly large (124.0 ± 34.8 mm³, n = 10). Infarct volume in SHR/Izm with simple distal MCA was 76 ± 19 mm³, which was significantly smaller than 95 ± 22 mm³ in the other SHR/Izm with more branching MCA. These data suggest that this stroke model in SHR/Izm is useful in the preclinical testing of stroke therapies and elucidating the pathophysiology of cerebral ischemia/reperfusion.     

Gene expression and DNA methylation changes in the hypothalamus and hippocampus of adult rats developmentally exposed to bisphenol A or ethinyl estradiol: a CLARITY-BPA consortium study

Bisphenol A (BPA), an endocrine disrupting chemical (EDC), is a ubiquitous pollutant. As part of the Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA), we sought to determine whether exposure of Sprague-Dawley rats to 2,500 μg/kg/day BPA (BPA) or 0.5 μg/kg/day ethinyl estradiol (EE) from gestational day 6 through postnatal day 21 induces behavior-relevant gene expression and DNA methylation changes in hippocampus and hypothalamus at adulthood. RNA and DNA were isolated from both regions. Expression of ten genes (Dnmt1, Dnmt3a, Dnmt3b, Esr1, Esr2, Avp, Ar, Oxt, Otr, and Bdnf) presumably altered by early-life BPA/EE exposure was examined. Three genes (Bdnf, Dnmt3b, and Esr1) were studied for DNA methylation changes in their putative 5? promoter regions. Molecular changes in hippocampus were correlated to prior Barnes maze performance, including sniffing correct holes, distance traveled, and velocity. Exposure to BPA and/or EE disrupted patterns of sexually dimorphic gene expression/promoter DNA methylation observed in hippocampus and hypothalamus of controls. In the hippocampus of female offspring, BPA exposure resulted in hypermethylation of the putative 5? promoter region of Bdnf, while EE exposure induced hypomethylation. Bdnf methylation was weakly associated with Bdnf expression in hippocampi of female rats. Hippocampal Bdnf expression in females showed a weak negative association with sniffing correct hole in Barnes maze. Hippocampal expression of Avp, Esr2, Oxt, and Otr was strongly associated with velocity of control rats in Barnes maze. Findings suggest BPA exposure induced non-EE-like gene expression and epigenetic changes in adult rat hippocampi, a region involved in spatial navigation.     

Permanent Cerebral Vessel Occlusion via Double Ligature and Transection

Stroke is a leading cause of death, disability, and socioeconomic loss worldwide. The majority of all strokes result from an interruption in blood flow (ischemia) ¹. Middle cerebral artery (MCA) delivers a great majority of blood to the lateral surface of the cortex ², is the most common site of human stroke ³, and ischemia within its territory can result in extensive dysfunction or death ^1,4,5. Survivors of ischemic stroke often suffer loss or disruption of motor capabilities, sensory deficits, and infarct. In an effort to capture these key characteristics of stroke, and thereby develop effective treatment, a great deal of emphasis is placed upon animal models of ischemia in MCA.Here we present a method of permanently occluding a cortical surface blood vessel. We will present this method using an example of a relevant vessel occlusion that models the most common type, location, and outcome of human stroke, permanent middle cerebral artery occlusion (pMCAO). In this model, we surgically expose MCA in the adult rat and subsequently occlude via double ligature and transection of the vessel. This pMCAO blocks the proximal cortical branch of MCA, causing ischemia in all of MCA cortical territory, a large portion of the cortex. This method of occlusion can also be used to occlude more distal portions of cortical vessels in order to achieve more focal ischemia targeting a smaller region of cortex. The primary disadvantages of pMCAO are that the surgical procedure is somewhat invasive as a small craniotomy is required to access MCA, though this results in minimal tissue damage. The primary advantages of this model, however, are: the site of occlusion is well defined, the degree of blood flow reduction is consistent, functional and neurological impairment occurs rapidly, infarct size is consistent, and the high rate of survival allows for long-term chronic assessment.     

Neuroprotective Effect of DAHK Peptide in an Occlusive Model of Permanent Focal Ischemia in Rats

This study examined the neuroprotective ability of tetrapeptide l-Asp-Ala-His-Lys (DAHK) in permanent middle cerebral artery occlusion in rats. One DAHK dose (16 mg/kg) or saline solution were i.v. administered 30 min after occlusion and neurological deficit was evaluated at 2, 24, 48, 72 and 96 h using Longa scoring scale. The striatum infarction area was evaluated until 96 h after occlusion in both groups after staining with hematoxylin–eosin. DAHK-treated group showed a significant (P < 0.05) protection of 70% of neurological deficit at 96 h after occlusion, in comparison with the control-group that showed permanent neurological deficit. The DAHK-treated group showed a significant (P < 0.05) reduction of 52% infarction area in the striatum, as compared to control values. Results presented here support the possible therapeutic application of DAHK as a neuroprotective agent in human patients with stroke, as the peptide is part of human serum albumin, already being tested in clinical trials.