HIF-1α expression in the hippocampus and peripheral macrophages after glutamate-induced excitotoxicity

VEGF and Neuronal Survival

Vascular endothelial growth factor (VEGF) is well known for its angiogenic activity, but recent evidence has revealed a neuroprotective action of this factor on injured or diseased neurons. In the present review, we summarize the most relevant findings that have contributed to establish a link between VEGF deficiency and neuronal degeneration. At issue, 1) mutant mice with reduced levels of VEGF show adult-onset muscle weakness and motoneuron degeneration resembling amyotrophic lateral sclerosis (ALS), 2) administration of VEGF to different animal models of motoneuron degeneration improves motor performance and ameliorates motoneuronal degeneration, and 3) there is an association between low plasmatic levels of VEGF and human ALS. Altogether, the results presented in this review highlight VEGF as an essential motoneuron neurotrophic factor endowed with promising therapeutic potential for the treatment of motoneuron disorders.

Transcriptomic Response of the Liver Tissue in Trachinotus ovatus to Acute Heat Stress

Trachinotus ovatus is a major economically important cultured marine fish in the South China Sea. However, extreme weather and increased culture density result in uncontrollable problems, such as increases in water temperature and a decline in dissolved oxygen (DO), hindering the high-quality development of aquaculture. In this study, liver transcriptional profiles of T. ovatus were investigated under acute high-temperature stress (31 °C and 34 °C) and normal water temperature (27 °C) using RNA sequencing (RNA-Seq) technology. Differential expression analysis and STEM analysis showed that 1347 differentially expressed genes (DEGs) and four significant profiles (profiles 0, 3, 4, and 7) were screened, respectively. Of these DEGs, some genes involved in heat shock protein (HSPs), hypoxic adaptation, and glycolysis were up-regulated, while some genes involved in the ubiquitin-proteasome system (UPS) and fatty acid metabolism were down-regulated. Our results suggest that protein dynamic balance and function, hypoxia adaptation, and energy metabolism transformation are crucial in response to acute high-temperature stress. Our findings contribute to understanding the molecular response mechanism of T. ovatus under acute heat stress, which may provide some reference for studying the molecular mechanisms of other fish in response to heat stress.

Inhibition of VEGFR-2 by SU5416 increases neonatally glutamate-induced neuronal damage in the cerebral motor cortex and hippocampus

Vascular endothelial growth factor (VEGF) exerts neuroprotective or proinflammatory effects, depending on what VEGF forms (A-E), receptor types (VEGFR1-3), and intracellular signaling pathways are involved. Neonatal monosodium glutamate (MSG) treatment triggers neuronal death by excitotoxicity, which is commonly involved in different neurological disorders, including neurodegenerative diseases. This study was designed to evaluate the effects of VEGFR-2 inhibition on neuronal damage triggered by excitotoxicity in the cerebral motor cortex (CMC) and hippocampus (Hp) after neonatal MSG treatment. MSG was administered at a dose of 4 g/kg of body weight (b.w.) subcutaneously on postnatal days (PD) 1, 3, 5, and 7, whereas the VEGFR-2 inhibitor SU5416 was administered at a dose of 10 mg/kg b.w. subcutaneously on PD 5 and 7, 30 min before the MSG treatment. Neuronal damage was assessed using hematoxylin and eosin staining, fluoro-Jade staining, and TUNEL assay. Additionally, western blot assays for some proteins of the VEGF-A/VEGFR-2 signaling pathway (VEGF-A, VEGFR-2, PI3K, Akt, and iNOS) were carried out. All assays were performed on PD 6, 8, 10, and 14. Inhibition of VEGFR-2 signaling by SU5416 increases the neuronal damage induced by neonatal MSG treatment in both the CMC and Hp. Moreover, neonatal MSG treatment increased the expression levels of the studied VEGF-A/VEGFR-2 signaling pathway proteins, particularly in the CMC. We conclude that VEGF-A/VEGFR-2 signaling pathway activation could be part of the neuroprotective mechanisms that attempt to compensate for neuronal damage induced by neonatal MSG treatment and possibly also in other conditions involving excitotoxicity.

Neuroprotective and Neurorestorative Effects of Epo and VEGF: Perspectives for New Therapeutic Approaches to Neurological Diseases

BACKGROUND

Erythropoietin (Epo) and vascular endothelial growth factor (VEGF) are two vasoactive molecules with essential trophic effects for brain development. The expression and secretion of both molecules increase in response to neuronal damage and they exert protective and restorative effects, which may also be accompanied by adverse side effects.

OBJECTIVE

We review the most relevant evidence on the neuroprotective and neurorestorative effects of Epo and VEGF in three of the most frequent neurological disorders, namely, stroke, epilepsy and Alzheimer's disease, to develop new therapeutic approaches.

METHODS

Several original scientific manuscripts and reviews that have discussed the evidence in critical way, considering both the beneficial and adverse effects of Epo and VEGF in the selected neurological disorders, were analysed. In addition, throughout this review, we propose several considerations to take into account in the design of therapeutic approaches based on Epo and VEGF signalling.

RESULTS

Although the three selected disorders are triggered by different mechanisms, they evolve through similar processes: excitotoxicity, oxidative stress, neuroinflammation, neuronal death, glial reactivity and vascular remodelling. Epo and VEGF exert neuroprotective and neurorestorative effects by acting on these processes due to their pleiotropism. In general, the evidence shows that both Epo and VEGF reduce neuronal death but that at the vascular level, their effects are contradictory.

CONCLUSION

Because the Epo and VEGF signalling pathways are connected in several ways, we conclude that more experimental studies, primarily studies designed to thoroughly assess the functional interactions between Epo and VEGF in the brain under both physiological and pathophysiological conditions, are needed.

The Involvement of Peripheral and Brain Insulin Resistance in Late Onset Alzheimer's Dementia

Nowadays, Alzheimer's disease (AD) is a severe sociological and clinical problem. Since it was first described, there has been a constant increase in its incidence and, for now, there are no effective treatments since current approved medications have only shown short-term symptomatic benefits. Therefore, it is imperative to increase efforts in the search for molecules and non-pharmacological strategies that are capable of slowing or stopping the progress of the disease and, ideally, to reverse it. The amyloid cascade hypothesis based on the fundamental role of amyloid has been the central hypothesis in the last 30 years. However, since amyloid-directed treatments have shown no relevant beneficial results other theories have been postulated to explain the origin of the pathology. The brain is a highly metabolically active energy-consuming tissue in the human body. It has an almost complete dependence on the metabolism of glucose and uses most of its energy for synaptic transmission. Thus, alterations on the utilization or availability of glucose may be cause for the appearance of neurodegenerative pathologies like AD. In this review article, the hypothesis known as Type 3 Diabetes (T3D) will be evaluated by summarizing some of the data that has been reported in recent years. According to published research, the adherence over time to low saturated fatty acids diets in the context of the Mediterranean diet would reduce the inflammatory levels in brain, with a decrease in the pro-inflammatory glial activation and mitochondrial oxidative stress. In this situation, the insulin receptor pathway would be able to fine tune the mitochondrial biogenesis in neuronal cells, regulation the adenosine triphosphate/adenosine diphosphate intracellular balance, and becoming a key factor involved in the preservation of the synaptic connexions and neuronal plasticity. In addition, new targets and strategies for the treatment of AD will be considered in this review for their potential as new pharmacological or non-pharmacological approaches.

Glutamate Neonatal Excitotoxicity Modifies VEGF-A, VEGF-B, VEGFR-1 and VEGFR-2 Protein Expression Profiles During Postnatal Development of the Cerebral Cortex and Hippocampus of Male Rats

Vascular endothelial growth factor (VEGF) exerts both neuroprotective and proinflammatory effects in the brain, depending on the VEGF (A-E) and VEGF receptor (VEGFR1-3) types involved. Neonatal monosodium glutamate (MSG) treatment triggers an excitotoxic degenerative process associated with several neuropathological conditions, and VEGF messenger RNA (mRNA) expression is increased at postnatal day (PD) 14 in rat hippocampus (Hp) following the treatment. The aim of this work was to establish the changes in immunoreactivity to VEGF-A, VEGF-B, VEGFR-1 and VEGFR-2 proteins induced by neonatal MSG treatment (4 g/kg, subcutaneous, at PD1, 3, 5 and 7) in the cerebral motor cortex (CMC) and Hp. Samples collected from PD2 to PD60 from control and MSG-treated male Wistar rats were assessed by western blotting for each protein. Considering that immunoreactivity measured by western blotting is related to the protein expression level, we found that each protein in each cerebral region has a specific expression profile throughout the studied ages, and all profiles were differentially modified by MSG. Specifically, neonatal MSG treatment significantly increased the immunoreactivity to the following: (1) VEGF-A at PD8-PD10 in the CMC and at PD6-PD8 in the Hp; (2) VEGF-B at PD2, PD6 and PD10 in the CMC and at PD8-PD9 in the Hp; and (3) VEGFR-2 at PD6-PD8 in the CMC and at PD21-PD60 in the Hp. Also, MSG significantly reduced the immunoreactivity to the following: (1) VEGF-B at PD8-PD9 and PD45-PD60 in the CMC; and (2) VEGFR-1 at PD4-PD6 and PD14-PD21 in the CMC and at PD4, PD9-PD10 and PD60 in the Hp. Our results indicate that VEGF-mediated signalling is involved in the excitotoxic process triggered by neonatal MSG treatment and should be further characterized.

Synergy of endothelial and neural progenitor cells from adipose-derived stem cells to preserve neurovascular structures in rat hypoxic-ischemic brain injury

Perinatal cerebral hypoxic-ischemic (HI) injury damages the architecture of neurovascular units (NVUs) and results in neurological disorders. Here, we differentiated adipose-derived stem cells (ASCs) toward the progenitor of endothelial progenitor cells (EPCs) and neural precursor cells (NPCs) via microenvironmental induction and investigated the protective effect by transplanting ASCs, EPCs, NPCs, or a combination of EPCs and NPCs (E+N) into neonatal HI injured rat pups. The E+N combination produced significant reduction in brain damage and cell apoptosis and the most comprehensive restoration in NVUs regarding neuron number, normal astrocytes, and vessel density. Improvements in cognitive and motor functions were also achieved in injured rats with E+N therapy. Synergistic interactions to facilitate transmigration under in vitro hypoxic microenvironment were discovered with involvement of the neuropilin-1 (NRP1) signal in EPCs and the C-X-C chemokine receptor 4 (CXCR4) and fibroblast growth factor receptor 1 (FGFR1) signals in NPCs. Therefore, ASCs exhibit great potential for cell sources in endothelial and neural lineages to prevent brain from HI damage.

Excitotoxicity triggered by neonatal monosodium glutamate treatment and blood-brain barrier function

It is likely that monosodium glutamate (MSG) is the excitotoxin that has been most commonly employed to characterize the process of excitotoxicity and to improve understanding of the ways that this process is related to several pathological conditions of the central nervous system. Excitotoxicity triggered by neonatal MSG treatment produces a significant pathophysiological impact on adulthood, which could be due to modifications in the blood-brain barrier (BBB) permeability and vice versa. This mini-review analyzes this topic through brief descriptions about excitotoxicity, BBB structure and function, role of the BBB in the regulation of Glu extracellular levels, conditions that promote breakdown of the BBB, and modifications induced by neonatal MSG treatment that could alter the behavior of the BBB. In conclusion, additional studies to better characterize the effects of neonatal MSG treatment on excitatory amino acids transporters, ionic exchangers, and efflux transporters, as well as the role of the signaling pathways mediated by erythropoietin and vascular endothelial growth factor in the cellular elements of the BBB, should be performed to identify the mechanisms underlying the increase in neurovascular permeability associated with excitotoxicity observed in several diseases and studied using neonatal MSG treatment.

Neuroprotective effect of pAkt and HIF-1 α on ischemia rats

OBJECTIVE

To explore the neuroprotective effect of pAkt and HIF-1 α on ischemia rats.

METHODS

The rat model of cerebral ischemia which induced by permanent middle cerebral artery occlusion was established, Silybin were given respectively. The behavior was measured by modified Longa method, brain water content were measured by the dry-wet method. Infarct volume was measured by image analysis method, Akt, HIF-1 α, Bcl-2, Bax, NF-κ B protein expressions were detected by Western blotting. The Akt, HIF-1 α, Bcl-2, Bax, NF-κ B mRNA expression were detected by RT-PCR.

RESULTS

The control group, low-dose silibinin group and high-dose silibinin group showed paralytic of the left body of rats in various degrees, the brain water content increased and different infarction size. There was no abnormal of the neurobehavioral assessment and no cerebral infarction in the blank group. Compared with the control group, there was no significant improvement of neurological function (t=1.341, P=0.188) or significant changes of the infarct volume (t=1.737, P=0.091) in the low-dose silibinin group, while there was significantly improvement of the neurological function in the high dose silibinin group (t=12.979, P<0.001), and the infarct volume was significantly reduced (t=23.503, P<0.001), the difference had statistically significant. The brain water content of lesion side of the control group increased (t=43.536, P<0.001), while the brain water content of lesion side of the low-dose silibinin group and the high-dose silybin group were significantly reduced (t=25.571, P<0.001; t= 42.426, P<0.001). The differences were statistical significance. The p-Akt 473, p-Akt 308, HIF-1 α, Bax, NF-κ B protein and the Akt, Bax, NF-κ B mRNA expression were increased of the control group, while the Bcl-2 protein and mRNA expression were decreased, the differences were statistically significant (P<0.05), there was no significant change of the Akt protein expression and HIF-1 α mRNA in the control group (P>0.05). In the high dose silybin group, the p-Akt 473, p-Akt 308, HIF-1α, Bcl-2 protein and Akt, Bcl-2 mRNA expression were increased, while the Bax, NF-κ B protein and Bax, NF-κ B mRNA expression were decreased, the differences were statistically significant (P<0.05), there was no significant change of the Akt protein expression and HIF-1 α mRNA in the high dose silybin group (P>0.05).

CONCLUSIONS

pAkt, HIF-1 α have neuroprotective effect on ischemia rats.

Cocaine potentiates cathepsin B secretion and neuronal apoptosis from HIV-infected macrophages

Substance abuse is a risk factor for HIV infection and progression to AIDS. Recent evidence establishes that cocaine use promotes brain perivascular macrophage infiltration and microglia activation. The lysosomal protease cathepsin B is increased in monocytes from patients with HIV dementia and its secretion induces 10-15% of neurotoxicity. Here we asked if cocaine potentiates cathepsin B secretion from HIV-infected monocyte-derived macrophages (MDM) and its effect in neuronal apoptosis. Samples of plasma, CSF, and post-mortem brain tissue from HIV positive patients that used cocaine were tested for cathepsin B and its inhibitors to determine the in vivo relevance of these findings. MDM were inoculated with HIV-1ADA, exposed to cocaine, and the levels of secreted and bioactive cathepsin B and its inhibitors were measured at different time-points. Cathepsin B expression (p < 0.001) and activity (p < 0.05) increased in supernatants from HIV-infected cocaine treated MDM compared with HIV-infected cocaine negative controls. Increased levels of cystatin B expression was also found in supernatants from HIV-cocaine treated MDM (p < 0.05). A significant increase in 30% of apoptotic neurons was obtained that decreased to 5% with the specific cathepsin B inhibitor (CA-074) or with cathepsin B antibody. Cathepsin B was significantly increased in the plasma and post-mortem brain tissue of HIV/cocaine users over non-drug users. Our results demonstrated that cocaine potentiates cathepsin B secretion in HIV-infected MDM and increase neuronal apoptosis. These findings provide new evidence that cocaine synergize with HIV-1 infection in increasing cathepsin B secretion and neurotoxicity.

Competitive HIF Prolyl Hydroxylase Inhibitors Show Protection against Oxidative Stress by a Mechanism Partially Dependent on Glycolysis

The hypoxia inducible factor 1 (HIF-1) is a central transcription factor involved in the cellular and molecular adaptation to hypoxia and low glucose supply. The level of HIF-1 is to a large degree regulated by the HIF prolyl hydroxylase enzymes (HPHs) belonging to the Fe(II) and 2-oxoglutarate-dependent dioxygenase superfamily. In the present study, we compared competitive and noncompetitive HPH-inhibitor compounds in two different cell types (SH-SY5Y and PC12). Although the competitive HPH-inhibitor compounds were found to be pharmacologically more potent than the non-competitive compounds at inhibiting HPH2 and HPH1, this was not translated into the cellular effects of the compounds, where the non-competitive inhibitors were actually more potent than the competitive in stabilizing and translocatingHIF1αto the nucleus (quantified with Cellomics ArrayScan technology). This could be explained by the high cellular concentrations of the cofactor 2-oxoglutarate (2-OG) as the competitive inhibitors act by binding to the 2-OG site of the HPH enzymes. Both competitive and non-competitive HPH inhibitors protected the cells against 6-OHDA induced oxidative stress. In addition, the protective effect of a specific HPH inhibitor was partially preserved when the cells were serum starved and exposed to 2-deoxyglucose, an inhibitor of glycolysis, indicating that other processes than restoring energy supply could be important for the HIF-mediated cytoprotection.

Effects of postnatal hyperoxia exposure on the rat dentate gyrus and subventricular zone

Premature newborns may be exposed to hyperoxia in the first postnatal period, but clinical and experimental works have raised the question of oxygen toxicity for the developing brain. However, specific analysis of hyperoxia exposure on neurogenesis is still lacking. Thus, the aim of the present study was to evaluate possible changes in the morphometric parameters of the main neurogenic sites in newborn rats exposed to 60 or 95 % oxygen for the first 14 postnatal days. The optical disector, a morphometric method based upon unbiased sampling principles of stereology, was applied to analyse cell densities, total volumes, and total cell numbers of the dentate gyrus (DG) and subventricular zone (SVZ). Apoptosis and proliferation were also studied by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling method and anti-ki67 immunohistochemistry, respectively. Severe hyperoxia increased the percentage of apoptotic cells in the DG. Moderate and severe hyperoxia induced a proliferative response both in the DG and SVZ, but the two neurogenic sites showed different changes in their morphometric parameters. The DG of both the hyperoxic groups showed lower volume and total cell number than that of the normoxic one. Conversely, the SVZ of newborn rats exposed to 95 % hyperoxia showed statistically significant higher volume and total cell number than SVZ of rats raised in normoxia. Our findings indicate that hyperoxia exposure in the first postnatal period affects both the neurogenic areas, although in different ways, i.e. reduction of DG and expansion of SVZ.

HIF-1α involves in neuronal apoptosis after traumatic brain injury in adult rats

Hypoxia-inducible factor-1α (HIF-1α), a well-identified hypoxia-related protein, is involved in regulating the biological functions of various cell types including neurons. The traditional biological function of HIF-1α is promoting the transcription of some pro-survival genes when exposing to low oxygen conditions. Meanwhile, some studies also point out that HIF-1α shows the detrimental role in several central nervous system (CNS) disorders. Up to now, the knowledge of HIF-1α function in CNS is still limited. To investigate whether HIF-1α is involved in CNS impairment and repair, we employed a traumatic brain injury model in adult rats. Upregulation of HIF-1α was observed in the injured brain cortex by western blot analysis and immunohistochemistry staining. Terminal deoxynucleotidyl transferase deoxy-UTP nick-end labeling (TUNEL) and 4',6-diamidino-2-phenylindole (DAPI) staining suggested that HIF-1α was relevant to neuronal apoptosis after brain injury. In addition, glutamate excitotoxic model of primary cortex neurons was introduced to further investigate the role of HIF-1α in neuronal apoptosis; the result implied HIF-1α was associated with the regulation of p53 and BNIP3 in the apoptotic neurons. Based on our data, we suggested that HIF-1α might play an important role in neuronal apoptosis after traumatic brain injury in rat, which might also provide a basis for the further study on its role in regulating the transcription of target genes in apoptotic neurons, and might gain a novel strategy for the clinical therapy for traumatic brain injury.

Decreased VEGF expression and microvascular density, but increased HIF-1 and 2α accumulation and EPO expression in chronic moderate hyperoxia in the mouse brain

Normal brain function is dependent on continuous and controlled oxygen delivery. Chronic moderate hypoxia leads to angiogenesis, suggesting a modulatory role for oxygen in determining capillary density. The objective of this study was to determine physiologic and brain angiogenic adaptational changes during chronic moderate normobaric hyperoxia in mice. Four-month old C56BL/6J mice were kept in a normobaric chamber at 50% O(2) for up to 3 weeks. Normoxic littermates were kept in the same room outside the chamber. Freshly collected or fixed brain specimens were analyzed by RT-PCR, Western blot analysis and immunohistochemistry. Results show accumulation of hypoxia inducible factors 1 and 2α (HIF-1 and 2α), and increased expression of erythropoietin (EPO), cyclooxygenase-2 (COX-2) and angiopoietin-2 (Ang-2). Conversely, vascular endothelial growth factor (VEGF), and VEGF receptor-2 (KDR/Flk-1), Peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) and prolylhydroxylase-2 (PHD-2) expressions were decreased. VEGF mRNA level was diminished but there was no change in HIF-1α mRNA and von Hippel Lindau E3 ubiquitin ligase (VHL) protein expression. Microvascular density was significantly diminished by the end of the 3rd week of hyperoxia. Overall, our results are: (1) increased expression of the potent neuroprotective molecule, EPO; (2) diminished expression of the potent angiogenic factor, VEGF; and (3) decreased microvascular density. We can, therefore, conclude that brain microvascular density can be controlled by HIF-independent mechanisms, and that brain capillary density is a continuously adjusted variable with tissue oxygen availability as one of the controlling modulators.

Fetal stress and programming of hypoxic/ischemic-sensitive phenotype in the neonatal brain: mechanisms and possible interventions

Growing evidence of epidemiological, clinical and experimental studies has clearly shown a close link between adverse in utero environment and the increased risk of neurological, psychological and psychiatric disorders in later life. Fetal stresses, such as hypoxia, malnutrition, and fetal exposure to nicotine, alcohol, cocaine and glucocorticoids may directly or indirectly act at cellular and molecular levels to alter the brain development and result in programming of heightened brain vulnerability to hypoxic-ischemic encephalopathy and the development of neurological diseases in the postnatal life. The underlying mechanisms are not well understood. However, glucocorticoids may play a crucial role in epigenetic programming of neurological disorders of fetal origins. This review summarizes the recent studies about the effects of fetal stress on the abnormal brain development, focusing on the cellular, molecular and epigenetic mechanisms and highlighting the central effects of glucocorticoids on programming of hypoxic-ischemic-sensitive phenotype in the neonatal brain, which may enhance the understanding of brain pathophysiology resulting from fetal stress and help explore potential targets of timely diagnosis, prevention and intervention in neonatal hypoxic-ischemic encephalopathy and other brain disorders.