Neuroprotective Role of Intermittent Hypobaric Hypoxia in Unpredictable Chronic Mild Stress Induced Depression in Rats

Protective Effects of Long-Term Escitalopram Administration on Memory and Hippocampal BDNF and BCL-2 Gene Expressions in Rats Exposed to Predictable and Unpredictable Chronic Mild Stress

Stress and escitalopram (an anti-stress medication) can affect brain functions and related gene expression. This study investigated the protective effects of long-term escitalopram administration on memory, as well as on hippocampal BDNF and BCL-2 gene expressions in rats exposed to predictable and unpredictable chronic mild stress (PCMS and UCMS, respectively). Male rats were randomly assigned to different groups: control (Co), sham (Sh), predictable and unpredictable stress (PSt and USt, respectively; 2 h/day for 21 consecutive days), escitalopram (Esc; 10 mg/kg for 21 days), and predictable and unpredictable stress with escitalopram (PSt-Esc and USt-Esc, respectively). The passive avoidance test was used to assess behavioral variables. The expressions of the BDNF and BCL-2 genes were assessed using real-time quantitative PCR. Latency significantly decreased in the PSt and USt groups. Additionally, latency showed significant improvement in the PSt-Esc group compared to the PSt group. The expression of the BDNF gene significantly decreased only in the USt group. BDNF gene expression significantly increased in the PSt-Esc and USt-Esc groups compared to their respective stress-related groups, whereas the expression of the BCL-2 gene did not change significantly in both PSt-Esc and USt-Esc groups. PCMS and UCMS had devastating effects on memory. Escitalopram improved memory only under PCMS conditions. PCMS and UCMS exhibited fundamental differences in hippocampal BDNF and BCL-2 gene expressions. Furthermore, escitalopram increased hippocampal BDNF gene expression in the PCMS and UCMS subjects. Hence, neurogenesis occurred more significantly than anti-apoptosis under both PCMS and UCMS conditions with escitalopram.

Lactobacillus brevis-Fermented Gamma-Aminobutyric Acid Ameliorates Depression- and Anxiety-Like Behaviors by Activating the Brain-Derived Neurotrophic Factor-Tropomyosin Receptor Kinase B Signaling Pathway in BALB/C Mice

This study investigated the effects of Lactobacillus brevis-fermented gamma-aminobutyric acid (LB-GABA) on depressive and anxiety-like behaviors with the underlying molecular mechanism in a chronic stress model of BALB/c mice. LB-GABA attenuates both neuronal cell death and the increase of monoamine oxidase activity induced by hydrogen peroxide. Behavioral tests revealed that GABA significantly increased sucrose preference and reduced immobility time in both tail suspension and forced swimming tests. LB-GABA increased exploration of the open arms in the elevated plus maze and restored activity in the open field. Moreover, LB-GABA lowered stress hormone and inflammatory mediator levels. Mechanistically, LB-GABA increased protein levels of BDNF and TrkB, activating downstream targets (AKT, ERK, and CREB), crucial for neuronal survival and plasticity. Furthermore, LB-GABA protected hippocampal neurons from stress-induced cell death and increased serotonin and dopamine levels. Overall, LB-GABA has the potential to alleviate stress-induced depression and anxiety-like symptoms and neuroinflammation by activating the BDNF-TrkB signaling pathway.

Enhancing HIF-1α-P2X2 signaling in dorsal raphe serotonergic neurons promotes psychological resilience

Major depressive disorder (MDD) is a devastating condition. Although progress has been made in the past seven decades, patients with MDD continue to receive an inadequate treatment, primarily due to the late onset of first-line antidepressant drugs and to their acute withdrawal symptoms. Resilience is the ability to rebound from adversity in a healthy manner and many people have psychological resilience. Revealing the mechanisms and identifying methods promoting resilience will hopefully lead to more effective prevention strategies and treatments for depression. In this study, we found that intermittent hypobaric hypoxia training (IHHT), a method for training pilots and mountaineers, enhanced psychological resilience in adult mice. IHHT produced a sustained antidepressant-like effect in mouse models of depression by inducing long-term (up to 3 months after this treatment) overexpression of hypoxia-inducible factor (HIF)-1α in the dorsal raphe nucleus (DRN) of adult mice. Moreover, DRN-infusion of cobalt chloride, which mimics hypoxia increasing HIF-1α expression, triggered a rapid and long-lasting antidepressant-like effect. Down-regulation of HIF-1α in the DRN serotonergic (DRN5-HT) neurons attenuated the effects of IHHT. HIF-1α translationally regulated the expression of P2X2, and conditionally knocking out P2rx2 (encodes P2X2 receptors) in DRN5-HT neurons, in turn, attenuated the sustained antidepressant-like effect of IHHT, but not its acute effect. In line with these results, a single sub-anesthetic dose of ketamine enhanced HIF-1α-P2X2 signaling, which is essential for its rapid and long-lasting antidepressant-like effect. Notably, we found that P2X2 protein levels were significantly lower in the DRN of patients with MDD than that of control subjects. Together, these findings elucidate the molecular mechanism underlying IHHT promoting psychological resilience and highlight enhancing HIF-1α-P2X2 signaling in DRN5-HT neurons as a potential avenue for screening novel therapeutic treatments for MDD.

Neurogenesis, A Potential Target for Intermittent Hypoxia Leading to Cognitive Decline

As a sleep breathing disorder, characterized by intermittent hypoxia (IH) and Obstructive sleep apnea (OSA), is believed to decrease the cognitive function of patients. Many factors are thought to be responsible for cognitive decline in OSA patients. Neurogenesis, a process by which neural stem cells (NSCs) differentiate into new neurons in the brain, is a major determinant affecting cognitive function. However, there is no clear relationship between IH or OSA and neurogenesis. In recent years, increasing numbers of studies on IH and neurogenesis are documented. Therefore, this review summarizes the effects of IH on neurogenesis; then discusses the influencing factors that may cause these effects and the potential signaling pathways that may exist. Finally, based on this impact, we discuss potential methods and future directions for improving cognition.

Mechanisms underlying the health benefits of intermittent hypoxia conditioning

Intermittent hypoxia (IH) is commonly associated with pathological conditions, particularly obstructive sleep apnoea. However, IH is also increasingly used to enhance health and performance and is emerging as a potent non-pharmacological intervention against numerous diseases. Whether IH is detrimental or beneficial for health is largely determined by the intensity, duration, number and frequency of the hypoxic exposures and by the specific responses they engender. Adaptive responses to hypoxia protect from future hypoxic or ischaemic insults, improve cellular resilience and functions, and boost mental and physical performance. The cellular and systemic mechanisms producing these benefits are highly complex, and the failure of different components can shift long-term adaptation to maladaptation and the development of pathologies. Rather than discussing in detail the well-characterized individual responses and adaptations to IH, we here aim to summarize and integrate hypoxia-activated mechanisms into a holistic picture of the body's adaptive responses to hypoxia and specifically IH, and demonstrate how these mechanisms might be mobilized for their health benefits while minimizing the risks of hypoxia exposure.

Sestrin-2 and hypoxia-ınducible factor-1 alpha levels in major depressive disorder and its subtypes

BACKGROUND

The objective of this study is to measure the levels of sestrin-2 (SESN2) and hypoxia-inducible factor-1 alpha (HIF-1α), which can be determinants in the relevant physiopathology and etiology, assessment of the clinical severity, and identification of new treatment targets in major depressive disorder (MDD) and its subtypes.

METHODS

A total of 230 volunteers, including 153 patients diagnosed with MDD according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), and 77 healthy controls, were included in the study. Of the MDD patients included in the study, 40 had melancholic features, 40 had anxious distress features, 38 had atypical features, and the remaining 35 had psychotic features. All participants were administered the Beck's Depression Inventory (BDI) and Clinical Global Impressions-Severity (CGI-S) scale. Serum SESN2 and HIF-1α levels of the participants were measured using the enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

The HIF-1α and SESN2 values of the patient group were found to be significantly lower than those of the control group (p < 0.05). The HIF-1α and SESN2 values were significantly lower in patients with melancholic, anxious distress, and atypical features compared to the control group (p < 0.05). The HIF-1α and SESN2 levels did not differ significantly between patients with psychotic features and the control group (p > 0.05).

CONCLUSION

The findings of the study suggested that knowledge of SESN2 and HIF-1α levels may contribute to the explanation of the etiology of MDD, objective assessment of the severity of the disease, and identification of new treatment targets.

Tobacco use modify exon IV BDNF gene methylation levels in depression

This study aimed to investigate BDNF gene methylation in individuals with depression based on tobacco use. Therefore, 384 adults from southeastern Brazil were recruited to assess depression, socioeconomic status, lifestyle, and methylation by pyrosequencing exon IV promoter region of the BDNF gene. The Generalized Linear Model (GzLM) was used to check the effect of depression, tobacco, and the interaction between depression and tobacco use in methylation levels. In addition, the Kruskal-Wallis test, followed by Dunn's post hoc test, was used to compare methylation levels. Interaction between depression and tobacco use was significant at levels of BDNF methylation in the CpG 5 (p = 0.045), 8 (p = 0.016), 9 (p = 0.042), 10 (p = 0.026) and mean 5-11 (p < 0.001). Dunn's post hoc test showed that individuals with depression and tobacco use compared to those with or without depression who did not use tobacco had lower levels of BDNF methylation in CpG 5, 6, 7, 8, 9, 11, and mean 5-11. Therefore, we suggest that tobacco use appears to interfere with BDNF gene methylation in depressed individuals.

Negative relationship between brain-derived neurotrophic factor (BDNF) and attention: A possible elevation in BDNF level among high-altitude migrants

Objective

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophic family that plays a vital role in regulating neuronal activity and synaptic plasticity in the brain, affects attention. However, studies investigating the association between BDNF and attention in long-term high-altitude (HA) migrants are limited in the literature. As HA affects both BDNF and attention, the relationship between these factors becomes more complex. Therefore, this study aimed to evaluate the relationship between peripheral blood concentrations of BDNF and the three attentional networks in both behavioral and electrical aspects of the brain in long-term HA migrants.

Materials and methods

Ninety-eight Han adults (mean age: 34.74 ± 3.48 years, 51 females and 47 males, all have lived at Lhasa for 11.30 ± 3.82 years) were recruited in this study. For all participants, the serum BDNF levels were assessed using enzyme-linked immunosorbent assay; event-related potentials (N1, P1, and P3) were recorded during the Attentional Networks Test, which was used as the measure of three attentional networks.

Results

Executive control scores were negatively correlated with P3 amplitude (r = -0.20, p = 0.044), and serum BDNF levels were positively correlated with executive control scores (r = 0.24, p = 0.019) and negatively correlated with P3 amplitude (r = -0.22, p = 0.027). Through grouping of BDNF levels and three attentional networks, executive control was found to be significantly higher in the high BDNF group than in the low BDNF group (p = 0.010). Different BDNF levels were associated with both orienting scores (χ² = 6.99, p = 0.030) and executive control scores (χ² = 9.03, p = 0.011). The higher the BDNF level, the worse was the executive function and the lower was the average P3 amplitude and vice versa. Females were found to have higher alerting scores than males (p = 0.023).

Conclusion

This study presented the relationship between BDNF and attention under HA. The higher the BDNF level, the worse was the executive control, suggesting that after long-term exposure to HA, hypoxia injury of the brain may occur in individuals with relatively higher BDNF levels, and this higher BDNF level may be the result of self-rehabilitation tackling the adverse effects brought by the HA environment.

Occlusion preconditioned mice are resilient to hypobaric hypoxia-induced myocarditis and arrhythmias due to enhanced immunomodulation, metabolic homeostasis, and antioxidants defense

Background

Sea-level residents experience altitude sickness when they hike or visit altitudes above ~2,500 m due to the hypobaric hypoxia (HH) conditions at such places. HH has been shown to drive cardiac inflammation in both ventricles by inducing maladaptive metabolic reprogramming of macrophages, which evokes aggravated proinflammatory responses, promoting myocarditis, fibrotic remodeling, arrhythmias, heart failure, and sudden deaths. The use of salidroside or altitude preconditioning (AP) before visiting high altitudes has been extensively shown to exert cardioprotective effects. Even so, both therapeutic interventions have geographical limitations and/or are inaccessible/unavailable to the majority of the population as drawbacks. Meanwhile, occlusion preconditioning (OP) has been extensively demonstrated to prevent hypoxia-induced cardiomyocyte damage by triggering endogenous cardioprotective cascades to mitigate myocardial damage. Herein, with the notion that OP can be conveniently applied anywhere, we sought to explore it as an alternative therapeutic intervention for preventing HH-induced myocarditis, remodeling, and arrhythmias.

Methods

OP intervention (6 cycles of 5 min occlusion with 200 mmHg for 5 min and 5 min reperfusion at 0 mmHg - applying to alternate hindlimb daily for 7 consecutive days) was performed, and its impact on cardiac electric activity, immunoregulation, myocardial remodeling, metabolic homeostasis, oxidative stress responses, and behavioral outcomes were assessed before and after exposure to HH in mice. In humans, before and after the application of OP intervention (6 cycles of 5 min occlusion with 130% of systolic pressure and 5 min reperfusion at 0 mmHg - applying to alternate upper limb daily for 6 consecutive days), all subjects were assessed by cardiopulmonary exercise testing (CPET).

Results

Comparing the outcomes of OP to AP intervention, we observed that similar to the latter, OP preserved cardiac electric activity, mitigated maladaptive myocardial remodeling, induced adaptive immunomodulation and metabolic homeostasis in the heart, enhanced antioxidant defenses, and conferred resistance against HH-induce anxiety-related behavior. Additionally, OP enhanced respiratory and oxygen-carrying capacity, metabolic homeostasis, and endurance in humans.

Conclusions

Overall, these findings demonstrate that OP is a potent alternative therapeutic intervention for preventing hypoxia-induced myocarditis, cardiac remodeling, arrhythmias, and cardiometabolic disorders and could potentially ameliorate the progression of other inflammatory, metabolic, and oxidative stress-related diseases.

The interplay of hypoxic and mental stress: Implications for anxiety and depressive disorders

Adequate oxygen supply is essential for the human brain to meet its high energy demands. Therefore, elaborate molecular and systemic mechanism are in place to enable adaptation to low oxygen availability. Anxiety and depressive disorders are characterized by alterations in brain oxygen metabolism and of its components, such as mitochondria or hypoxia inducible factor (HIF)-pathways. Conversely, sensitivity and tolerance to hypoxia may depend on parameters of mental stress and the severity of anxiety and depressive disorders. Here we discuss relevant mechanisms of adaptations to hypoxia, as well as their involvement in mental stress and the etiopathogenesis of anxiety and depressive disorders. We suggest that mechanisms of adaptations to hypoxia (including metabolic responses, inflammation, and the activation of chemosensitive brain regions) modulate and are modulated by stress-related pathways and associated psychiatric diseases. While severe chronic hypoxia or dysfunctional hypoxia adaptations can contribute to the pathogenesis of anxiety and depressive disorders, harnessing controlled responses to hypoxia to increase cellular and psychological resilience emerges as a novel treatment strategy for these diseases.

High-Fat Diet and Short-Term Unpredictable Stress Increase Long-Chain Ceramides Without Enhancing Behavioral Despair

Clinical and preclinical studies suggest that increases in long-chain ceramides in blood may contribute to the development of depressive-like behavior. However, which factors contribute to these increases and whether the increases are sufficient to induce depressive-like behaviors is unclear. To begin to address this issue, we examined the effects of high fat diet (HFD) and short-term unpredictable (STU) stress on long-chain ceramides in the serum of male and female rats. We found that brief exposure to HFD or unpredictable stress was sufficient to induce selective increases in the serum concentrations of long-chain ceramides, associated with depression in people. Furthermore, combined exposure to HFD and unpredictable stress caused a synergistic increase in C16:0, C16:1, and C18:0 ceramides in both sexes and C18:1 and C24:1 in males. However, the increased peripheral long-chain ceramides were not associated with increases in depressive-like behaviors suggesting that increases in serum long-chain ceramides may not be associated with the development of depressive-like behaviors in rodents.

Reparative effects of chronic intermittent hypobaric hypoxia pre‑treatment on intervertebral disc degeneration in rats

Previous studies have indicated that chronic intermittent hypobaric hypoxia (CIHH) preconditioning can inhibit TNF-α and other related inflammatory cytokines and exerts protective effect on intervertebral disc degeneration disease (IDD) in rats; however, the mechanism is still unclear. The present study aimed to explore the repair mechanisms of CIHH on IDD in rats. In the experiment, 48 adult Sprague-Dawley rats were selected and randomly divided into an experimental group (CIHH-IDD), a degenerative group (IDD) and a control group (CON). The CIHH-IDD group of rats (n=16) were treated with CIHH (simulated 3000 m altitude, 5 h per day, 28 days; P_O2=108.8 mmHg) before disc degeneration surgery. The IDD group of rats (n=16) underwent tail-vertebral intervertebral disc surgery to establish a model of intervertebral disc degeneration. The CON group of rats (n=16) did not receive any treatments. After surgery, the disc height index was calculated using X-ray analysis of rat tail vertebrae, the degeneration process was observed and repair was evaluated by chemically staining degenerative intervertebral disc tissue slices. The expression levels of basic fibroblast growth factor (bFGF), TGFβ1, Collagen I and Collagen II were measured in the intervertebral disc tissue using western blotting; while the expression levels of bFGF, TGFβ1 and hypoxia-inducible factor 1-α (HIF-1α) were measured in rat serum using ELISA. The results demonstrated that: i) The degree of intervertebral disc height degeneration in CIHH-IDD rats was significantly lower compared with that in IDD rats (P<0.05); ii) the expression levels of bFGF, TGFβ1 and HIF-1α were higher in CIHH-IDD rat serum compared with those in IDD rat serum (P<0.05); iii) optical microscopy revealed that the degree of disc degeneration was relatively mild in CIHH-IDD rats; and iv) the protein expression levels of bFGF, TGFβ1 and collagen II were increased in CIHH-IDD rat intervertebral disc tissues compared with those of IDD rats, while the overexpression of collagen I protein was inhibited. Overall, after CIHH pre-treatment, the expression levels of bFGF and TGFβ1 were up-regulated, which play notable roles in repairing degenerative intervertebral discs in rats.

Brain Activity after Intermittent Hypoxic Brain Condition in Rats

Hypoxic brain injury is accompanied by a decrease in various functions. It is also known that obstructive sleep apnea (OSA) can cause hypoxic brain injury. This study aimed to produce a model of an intermittent hypoxic brain condition in rats and determine the activity of the brain according to the duration of hypoxic exposure. Forty male Sprague–Dawley rats were divided into four groups: the control group (n = 10), the 2 h per day hypoxia exposure group (n = 10), the 4 h per day hypoxia exposure group (n = 10), and the 8 h per day hypoxia exposure group (n = 10). All rats were exposed to a hypoxic chamber containing 10% oxygen for five days. Positron emission tomography–computed tomography (PET-CT) brain images were acquired using a preclinical PET-CT scanner to evaluate the activity of brain metabolism. All the rats were subjected to normal conditions. After five days, PET-CT was performed to evaluate the recovery of brain metabolism. Western blot analysis and immunohistochemistry were performed with vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF). The mean SUV was elevated in the 2 h per day and 4 h per day groups, and all brain regions showed increased metabolism except the amygdala on the left side, the auditory cortex on the right side, the frontal association cortex on the right side, the parietal association cortex on the right side, and the somatosensory cortex on the right side immediately after hypoxic exposure. However, there was no difference between 5 days rest after hypoxic exposure and control group. Western blot analysis revealed the most significant immunoreactivity for VEGF in the 2, 4, and 8 h per day groups compared with the control group and quantification of VEGF immunohistochemistry showed more expression in 2 and 4 h per day groups compared with the control group. However, there was no significant difference in immunoreactivity for BDNF among the groups. The duration of exposure to hypoxia may affect the activity of the brain due to angiogenesis after intermittent hypoxic brain conditions in rats.

The role of hypoxia in stem cell regulation of the central nervous system: From embryonic development to adult proliferation

Hypoxia is involved in the regulation of various cell functions in the body, including the regulation of stem cells. The hypoxic microenvironment is indispensable from embryonic development to the regeneration and repair of adult cells. In addition to embryonic stem cells, which need to maintain their self-renewal properties and pluripotency in a hypoxic environment, adult stem cells, including neural stem cells (NSCs), also exist in a hypoxic microenvironment. The subventricular zone (SVZ) and hippocampal dentate gyrus (DG) are the main sites of adult neurogenesis in the brain. Hypoxia can promote the proliferation, migration, and maturation of NSCs in these regions. Also, because most neurons in the brain are non-regenerative, stem cell transplantation is considered as a promising strategy for treating central nervous system (CNS) diseases. Hypoxic treatment also increases the effectiveness of stem cell therapy. In this review, we firstly describe the role of hypoxia in different stem cells, such as embryonic stem cells, NSCs, and induced pluripotent stem cells, and discuss the role of hypoxia-treated stem cells in CNS diseases treatment. Furthermore, we highlight the role and mechanisms of hypoxia in regulating adult neurogenesis in the SVZ and DG and adult proliferation of other cells in the CNS.

Temporal exposure to chronic unpredictable stress induces precocious neurobehavioral deficits by distorting neuromorphology and glutathione biosynthesis in zebrafish brain

Modelling of chronic stress conditions in experimental animals and its neuropsychiatric outcomes has been well documented in literature. Zebrafish (Danio rerio) by exhibiting significant genetic and epidemiological similarities with human beings, has now emerged as a promising animal model of translational research. In this line, risk assessment following exposure to chronic unpredictable stress (CUS) towards neurobehavioral response and neuromorphology of sensitive brain region in zebrafish is the prime objective of the present study. With the existing knowledge on CUS in affecting diverse neurobehavioral aspects, we were primarily interested in whether this neurobehavioral transformation is an outcome of altered glutathione biosynthesis in zebrafish. We were also concerned about whether the precocious neurobehavioral transformation has been linked to altered neuromorphology in the periventricular grey zone (PGZ) of the zebrafish brain. Our basic findings showed that CUS itself represented as a universal factor in altering native bottom-dwelling and scototaxis behaviour of zebrafish. Our findings also backing the argument that CUS itself represented a collective stress regimen by altering the brain glutathione biosynthesis in zebrafish. Correspondingly, a temporal transformation in CUS instigated augmentation in neuronal pyknosis and chromatin condensation were observed in PGZ of the zebrafish brain. Collectively, these findings designate that CUS induced temporal neurobehavioral transformation is an outcome of augmented oxidative stress and neuromorphological alteration in the zebrafish brain. However, the underlying mechanism of such neuropathological manifestation associated with CUS might provide novel insight towards the development of prophylactic/therapeutic intervention to counter such co-morbid behavioral alteration.

Ginkgo biloba L. Prevents Hypobaric Hypoxia-Induced Spatial Memory Deficit Through Small Conductance Calcium-Activated Potassium Channel Inhibition: The Role of ERK/CaMKII/CREB Signaling

Hypobaric hypoxia (HH) is a stressful condition, which is more common at high altitudes and can impair cognitive functions. Ginkgo biloba L. leaf extract (GBE) is widely used as herbal medicine against different disorders. Its ability to improve cognitive functions, reduce oxidative stress, and promote cell survival makes it a putative therapeutic candidate against HH. The present study has been designed to explore the effect of GBE on HH-induced neurodegeneration and memory impairment as well as possible signaling mechanisms involved. 220–250 gm (approximately 6- to 8-week-old) Sprague Dawley rats were randomly divided into different groups. GBE was orally administered to respective groups at a dose of 100 mg/kg/day throughout the HH exposure, i.e., 14 days. Memory testing was performed followed by hippocampus isolation for further processing of different molecular and morphological parameters related to cognition. The results indicated that GBE ameliorates HH-induced memory impairment and oxidative damage and reduces apoptosis. Moreover, GBE modulates the activity of the small conductance calcium-activated potassium channels, which further reduces glutamate excitotoxicity and apoptosis. The exploration of the downstream signaling pathway demonstrated that GBE administration prevents HH-induced small conductance calcium-activated potassium channel activation, and that initiates pro-survival machinery by activating extracellular signal–regulated kinase (ERK)/calmodulin-dependent protein kinase II (CaMKII) and the cAMP response element–binding protein (CREB) signaling pathway. In summary, the current study demonstrates the beneficial effect of GBE on conditions like HH and provides various therapeutic targets involved in the mechanism of action of GBE-mediated neuroprotection.

Effect of Acute Normobaric Hypoxia Exposure on Executive Functions among Young Physically Active Males

Background: On the one hand, hypoxic exposure may result in progressive brain metabolism disturbance, causing subsequent cognitive impairments. On the other hand, it might also enhance neurogenesis and brain vascularization as well as accelerate cerebral blood flow, leading to cognitive function improvement. The aim of this study was to investigate whether progressive stages of normobaric hypoxia (NH) (FIO₂ = 13%, FIO₂ = 12%, and FIO₂ = 11%) differentially affect post-exposure cognitive performance. Methods: Fifteen physically active men (age = 23.1 ± 2.1) participated in the study. The Stroop test (ST) was applied to assess cognitive function. To generate NH conditions, a hypoxic normobaric air generator was used. Results: We observed an executive function impairment (“naming” interference p < 0.05) after NH exposure (FIO₂ = 13%). After exposure at FIO₂ = 12% and FIO₂ = 11%, no changes were observed in the Stroop test. Also, changes in SpO₂ during subsequent NH exposure were observed. Conclusions: The current investigation shows that executive functions deteriorate after acute NH exposure and this post-exposure deterioration is not proportional to the normobaric hypoxia stages among young physically active males.

Elucidating the role of hypoxia/reoxygenation in hippocampus-dependent memory impairment: do SK channels play role?

Professionals and mountaineers often face the problem of reperfusion injury due to re-oxygenation, upon their return to sea-level after sojourn at high altitude. Small conductance calcium-activated potassium channels (SK channels) have a role in regulating hippocampal synaptic plasticity. However, the role of SK channels under hypoxia-reoxygenation (H/R) is unknown. The present study hypothesized that SK channels play a significant role in H/R induced cognitive dysfunction. Sprague-Dawley rats were exposed to simulated HH (25,000 ft) continuously for 7 days followed by reoxygenation periods 3, 6, 24, 48, 72 and 120 h. It was observed that H/R exposure caused impairment in spatial memory as indicated by increased latency (p < 0.001) and pathlength (p < 0.001). The SK1 channel expression increased upon HH exposure (102.89 ± 7.055), which abrogated upon reoxygenation. HH exposure results in an increase in SK2 (CA3, 297.67 ± 6.69) and SK3 (CA1, 246 ± 5.13) channels which continued to increase gradually upon reoxygenation. The number of pyknotic cells (24 ± 2.03) (p < 0.01) and the expression of caspase-3 increased with HH exposure, which continued in the reoxygenation group (177.795 ± 1.264). Similar pattern was observed in lipid peroxidation (p < 0.001), LDH activity (p < 0.001) and ROS production (p < 0.001). A positive correlation of memory, cell death and oxidative stress indicates that H/R exposure increases oxidative stress coupled with SK channel expression, which may play a role in H/R-induced cognitive decline and neurodegeneration.

The Association Between Hypoxia Improvement and Electroconvulsive Therapy for Major Depressive Disorder

BACKGROUND

The occurrence of depression was related with a state of mild hypoxia for a long time. Hypoxia-inducible factor-2α (HIF-2α) modulates the process from acute to chronic hypoxia, consequently regulating changes in inducible nitric oxide synthase (iNOS). Increasing levels of iNOS combined with major depressive disorder (MDD) have been associated with the concentration of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), which increase the severity of depression.

OBJECTIVE

The aim was to investigate whether depressive symptoms might be improved by regulating HIF-2α levels to decrease the degree of oxidative stress and inflammation using electroconvulsive therapy (ECT).

METHODS

In this observational study, 49 MDD patients were divided into the ECT group (n=32) and control group (n=17). The Hamilton Depression Rating Scale (HAMD) was used to evaluate depressive symptoms of patients at enrollment and after 2 weeks of treatment. The levels of HIF-2α, NOS, IL-6, and TNF-α in plasma were analyzed accordingly.

RESULTS

The total score in each dimension of HAMD decreased more efficiently in the ECT group than in the control group (p < 0.05). The plasma levels of IL-6 in the ECT group were notably decreased after the 2-week treatment (t = 3.596, p = 0.001). The decreased trend to statistical significance of HIF-2α was observed after treatment in the ECT group (p = 0.091).

CONCLUSION

The present study demonstrated that the therapeutic effects of long-term ECT therapy for MDD may further benefit from and contribute to the improvement of MDD-associated chronic hypoxia.

Venlafaxine Inhibits the Apoptosis of SHSY-5Y Cells Through Active Wnt/β-Catenin Signaling Pathway

OBJECTIVE

This study aimed to explore the mechanism of venlafaxine in regulating the apoptosis of SHSY-5Y cells induced by hypoxia.

METHODS

The CoCl2-induced neuronal hypoxia model was established based on SHSY-5Y cells. The morphology and related protein expression of SHSY-5Y cells were detected by qPCR, ELISA and Western blot.

RESULTS

Under the condition of hypoxia-induced by CoCl2, the expression of HIF-1α in SHSY-5Y cells was up-regulated and the expression of β-catenin was down-regulated. After adding siRNA targeting HIF-1 α to the culture cell system, down-regulation of β -catenin expression in SHSY-5Y cells was restored. This confirmed the existence of the "hypoxia-HIF-1α-Wnt/β-catenin-depression" axis. Further studies have shown that venlafaxine can alleviate neuronal apoptosis induced by hypoxia by upregulating the Wnt/β-catenin signaling pathway.

CONCLUSION

Venlafaxine regulates apoptosis induced by hypoxia through the Wnt/β-catenin signaling pathway, which provides a new theoretical basis for the treatment of depression.

Elevating the level of hypoxia inducible factor may be a new potential target for the treatment of depression

Hypoxia inducible factor-1 (HIF-1) is a transcriptional factor that regulates gene expressions in response to decreased oxygen levels in the tissue, or hypoxia. HIF-1 exerts protective effects against hypoxia by mediating mitochondrial metabolism and consequently reducing oxidative stress. Recently, increased levels of oxidative stress and abnormal energy metabolism in the brain have been suggested to play essential roles in the pathogenesis of depression. Given that HIF-1 activates creatine metabolism and increases phosphocreatine levels in the intestinal epithelial cells, we assume that HIF-1 may induce similar processes in the brain. Elevated phosphocreatine levels in the brain, as measured by magnetic resonance spectroscopy, were associated with better treatment response to the antidepressants in individuals with depression. In addition, oral creatine supplements, which led to increased phosphocreatine levels in the brain, also enhanced the effects of antidepressants in individuals with depression. As such, we hypothesized that increasing the HIF-1, which potentially facilitates creatine metabolism in the brain, might be a new therapeutic target in depression. With this regard, we suggested that interventions to elevate the HIF-1 levels in the brain, including the intermittent hypoxia conditioning and hyperbaric oxygen therapy, might be considered as new additional treatments for depression.

Targeting Oxidative Stress Reduction and Inhibition of HDAC1, MECP2, and NF-kB Pathways in Rats With Experimentally Induced Hyperglycemia by Administration of Thymus marshallianus Willd. Extracts

The effects of two lyophilized extracts obtained from the aerial parts of Thymus marschallianus Willd. and harvested from wild flora (TMW) and obtained from culture (TMC) were evaluated in Wistar rats with experimentally induced hyperglycemia. The hyperglycemia was induced by streptozotocin (STZ) administration and the obtained results were evaluated in comparison for TMW and TMC. The polyphenolic composition of extracts was evaluated by spectrophotometrical and LC-MS methods. In vitro antioxidant capacity assays (DPPH, FRAP, EPR) were performed in order to preliminary establish the ability of tested samples to protect against free radical induced damage. Afterwards, the effects of these extracts were assessed in vivo on rats with experimental-induced hyperglycemia. Oxidative stress biomarkers (e.g. malondialdehyde—MDA), phosphorylated transcription factor subunit of nuclear kappaB (NF-kB) p65, methyl CpG binding protein (MECP) 2 and histone deacetylase 1 (HDAC1) expressions in hippocampus and frontal lobe were assessed. Open Field Test (OFT) and Elevated Plus Maze (EPM) were conducted on tested animals. Malondialdehyde (MDA) levels and HDAC1and MeCP2 expressions increased significantly in hippocampus (p<0.05) and frontal lobe (p<0.001) of diabetes group compared to the control group in parallel with decreasing of GSH/GSSG ratio. TMW and TMC administration reduced blood glucose levels and diminished lipid peroxidation, HDAC1 expression and enhanced antioxidant capacity in frontal lobe. TMW improved central locomotion of rats, increased phospho-NFkB p65 and diminished MECP2 expressions in hippocampus. Both tested samples exerted a beneficial effect by increasing the antioxidant defense. Our findings indicate that the administration of these extracts might represent a good option in the treatment of diabetes and its complications.

The Modulatory Effect of Metformin on Ethanol-Induced Anxiety, Redox Imbalance, and Extracellular Matrix Levels in the Brains of Wistar Rats

The study investigated the potential neuroprotective effects of metformin (MET) on alcohol-induced neurotoxicity in adult Wistar rats. The animals were randomized in four groups (n = 10): control, alcohol (ALC), ALC + MET, and MET. ALC (2 g/kg b.w.) and MET (200 mg/kg b.w.) were orally administered for 21 days, once daily. For the ALC + MET group, MET was administered 2 h after ALC treatment. On day 22, the open field test (OFT) and elevated plus maze (EPM) were performed. MET improved global activity and increased the time spent in unprotected open arms, decreased oxidative stress, both in the frontal lobe and in the hippocampus, and increased neuroglobin expression in the frontal cortex. Histopathologically, an increased neurosecretory activity in the frontal cortex in the ALC + MET group was noticed. Thus, our findings suggest that metformin has antioxidant and anxiolytic effects and may partially reverse the neurotoxic effects induced by ethanol.

Polysaccharide extracted from Potentilla anserina L ameliorate acute hypobaric hypoxia-induced brain impairment in rats

High altitude cerebral edema (HACE) is a high altitude malady caused by acute hypobaric hypoxia (AHH), in which pathogenesis is associated with oxidative stress and inflammatory cytokines. Potentilla anserina L is mainly distributed in Tibetan Plateau, and its polysaccharide possesses many physiological and pharmacological properties. In the present study, the protective effect and potential treatment mechanism of Potentilla anserina L polysaccharide (PAP) in HACE were explored. First, we measured the brain water content and observed the pathological changes in brain tissues, furthermore, malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), and glutathione (GSH) were evaluated by kits. Finally, the protein contents and mRNA expressions of pro-inflammatory (IL-1β, IL-6, TNF-α, vascular endothelial cell growth factor [VEGF], NF-κB, and hypoxia inducible factor-1 α [HIF-1α]) were detected by ELISA kits, RT-PCR, and western blotting. The results demonstrated that PAP reduced the brain water content, alleviated brain tissue injury, reduce the levels of MDA and NO, and increased the activity of SOD and GSH level. In addition, PAP blocking the NF-κB and HIF-1α signaling pathway activation inhibited the generation of downstream pro-inflammatory cytokines (IL-1β, IL-6, TNF-α, and VEGF). Therefore, PAP has a potential to treat and prevent of HACE by suppression of oxidative stress and inflammatory response.

FG-4592 Improves Depressive-Like Behaviors through HIF-1-Mediated Neurogenesis and Synapse Plasticity in Rats

Depression, plus the accompanying memory impairment, is one of the leading causes of disability worldwide. Thus, there is a critical need to develop new drugs based on distinct strategies. FG-4592, an inhibitor of prolyl hydroxylase, activates the hypoxia-inducible factor-1 (HIF-1) pathway, to produce multiple effects on cell properties. Here, we examined whether FG-4592 has antidepressant effects, using a chronic unpredictable mild stress (CUMS) procedure to establish rodent depression models. We found that FG-4592 not only reversed depressive behaviors but also improved CUMS-induced memory impairment. Mechanistically, FG-4592 could play an important role in promoting hippocampal neurogenesis and synaptic plasticity. At the molecular level, FG-4592 was found to activate HIF-1 and cAMP-responsive element-binding protein/brain-derived neurotrophic factor signaling pathways in vivo, as well as promote the expression of postsynaptic density (PSD) proteins, PSD95 and Homer1. An examination of primary hippocampal neurons showed that FG-4592 promoted dendritic growth. Taken together, our results not only provide an experimental basis for the future application of FG-4592 in clinical treatment of depression but also support the argument that the HIF-1 signaling pathway is a promising target for the treatment of depression.

Primer for Mainstreaming Mind-Body Techniques for Extreme Climates-Insights and Future Directions

Background: The deprivation of oxygen reaching the tissues (also termed as hypoxia) affects the normal functioning of the body. This results in development of many diseases like ischemia, glaucoma, MCI (Mild Cognitive Impairment), pulmonary and cerebral edema, stress and depression. There are no effective drugs that can treat such diseases. Despite such failure, alternative interventions such as mind-body techniques (MBTs) have not been adequately investigated. Methods: The first part of this review has been focused on philosophical aspects of various MBTs besides evolving an ayurgenomic perspective. The potential of MBTs as a preventive non-pharmacological intervention in the treatment of various general and hypoxic pathologies has been further described in this section. In the second part, molecular, physiological, and neuroprotective roles of MBTs in normal and hypoxic/ischemic conditions has been discussed. Results: In this respect, the importance of and in vivo studies has also been discussed. Conclusions: Although several studies have investigated the role of protective strategies in coping with the hypoxic environment, the efficacy of MBTs at the molecular level has been ignored.

Intermittent Hypoxic Conditioning Alleviates Post-Traumatic Stress Disorder-Induced Damage and Dysfunction of Rat Visceral Organs and Brain

Posttraumatic stress disorder (PTSD) causes mental and somatic diseases. Intermittent hypoxic conditioning (IHC) has cardio-, vaso-, and neuroprotective effects and alleviates experimental PTSD. IHC’s ability to alleviate harmful PTSD effects on rat heart, liver, and brain was examined. PTSD was induced by 10-day exposure to cat urine scent (PTSD rats). Some rats were then adapted to 14-day IHC (PTSD+IHC rats), while PTSD and untreated control rats were cage rested. PTSD rats had a higher anxiety index (AI, X-maze test), than control or PTSD+IHC rats. This higher AI was associated with reduced glycogen content and histological signs of metabolic and hypoxic damage and of impaired contractility. The livers of PTSD rats had reduced glycogen content. Liver and blood alanine and aspartate aminotransferase activities of PTSD rats were significantly increased. PTSD rats had increased norepinephrine concentration and decreased monoamine oxidase A activity in cerebral cortex. The PTSD-induced elevation of carbonylated proteins and lipid peroxidation products in these organs reflects oxidative stress, a known cause of organ pathology. IHC alleviated PTSD-induced metabolic and structural injury and reduced oxidative stress. Therefore, IHC is a promising preventive treatment for PTSD-related morphological and functional damage to organs, due, in part, to IHC’s reduction of oxidative stress.

Antidepressant-like effects of dietary gardenia blue pigment derived from genipin and tyrosine

Gardenia blue pigments derived from genipin reacting with amino acids have been used as natural food colorants for nearly 30 years in East Asia. However, their pharmacological effects, especially antidepressant-like effects, have not been reported so far. In this study, one of the gardenia blue pigments, was obtained from the reaction of genipin with tyrosine (genipin-tyrosine derivant (GTD)), and its antidepressant-like effects were investigated in lipopolysaccharide (LPS) or chronic unpredictable mild stress (CUMS) models. The results showed that GTD could attenuate depressive-like behaviors in both animal models. GTD reversed the LPS-induced cytokine increase of TNF-α, IL-6, and corticosterone (CORT) in mice plasma and hippocampus. In CUMS rats, GTD treatment significantly reduced hypothalamic-pituitary-adrenal (HPA) axis-related stress hormone levels in plasma including those of CORT, adrenocorticotropic hormone (ACTH), and corticotropin-releasing hormone (CRH). Besides, GTD increased plasma testosterone and hippocampal brain-derived neurotrophic factor (BDNF) levels in CUMS rats. GTD increased serotonin (5-HT), dopamine (DA), and norepinephrine (NE) in rat hippocampus and corpus striatum. Consistently, hippocampal metabolomic analysis demonstrated that GTD restored monoamine neurotransmitter metabolism, mitochondrial oxidative function, and membrane structural integrity. Our data suggested that GTD produced antidepressant-like activity through the restoration of the HPA axis hormone balance and the regulation of neurotransmitter release.

The Benefits of Using New Tools for Behavioral Investigations in Animal Experimental Models

The animal experimental models of emotional disorders attempt to reproduce features of human psychiatric disorders in laboratory animals by correlating the physiological and behavioral changes associated with specific emotional states, the etiology of disorders, and responses on drug treatments. Animal experimental models that accurately recapitulate clinical pathology are indispensable for understanding molecular mechanisms and advancing preclinical studies. Behavioral tests on animal models have been developed over time in two directions: to enable the acquisition of as many valid behavior data as possible, and constructing experimental models and procedures that represent a parallel with certain conditions in humans. In this review we discuss more information for the new tools in behavioral investigations in animal experimental models. Here we described evoked beam-walking (EBW) test as a new test for estimation of anxiety levels. The reliability of that test was confirmed in our studies by using nandrolone decanoate (ND) and testosterone enanthate (TE) in supraphysiological doses. Also, we defined a new approach to estimation of exploratory activity by using these tests and an improvement of detectability in standard evaluation of depressive state levels. Taking into account that behavioral investigation in animal models still has to remain indispensable in conducting of preclinical studies, we assume that new tools that can be applied in this field may improve the quality of research.

Chronic mild hypoxia promotes hippocampal neurogenesis involving Notch1 signaling in epileptic rats

Cognitive impairment is one of the most common and disabling co-morbidities of epilepsy. It is therefore imperative to find novel treatment approaches to rescue cognitive function among epilepsy patients. Adult neurogenesis is strongly implicated in cognitive function, and mild hypoxia is known to promote the proliferation and differentiation of both embryonic and adult neural stem cells (NSCs). In the present study, we investigated the effect of mild hypoxia on cognitive function and hippocampal neurogenesis of rats with pilocarpine-induced chronic epilepsy. Chronic epilepsy induced marked spatial learning and memory deficits in the Morris water maze that were rescued by consecutively 28 days mild hypoxia exposure (6 h/d at 3000 m altitude equivalent) during the chronic phase. Moreover, mild hypoxia reversed the suppression of hippocampal neurogenesis and the downregulation of NT-3 and BDNF expression in hippocampus and cortex of epileptic rats. Mild hypoxia in vitro also promoted hippocampus-derived NSC proliferation and neuronal differentiation. In addition, mild hypoxia enhanced Notch1 and Hes1 expression, suggesting that Notch1 signaling may be involved in neuroprotection of hypoxia. Our data may help to pave the way for identifying new therapeutic targets for rescuing cognition conflicts in epileptic patients by using hypoxia to promote hippocampus neurogenesis.

Intermittent hypoxia improves behavioral and adrenal gland dysfunction induced by posttraumatic stress disorder in rats

Nonpharmacological treatments of stress-induced disorders are promising, since they enhance endogenous stress defense systems, are free of side effects, and have few contraindications. The present study tested the hypothesis that intermittent hypoxia conditioning (IHC) ameliorates behavioral, biochemical, and morphological signs of experimental posttraumatic stress disorder (PTSD) induced in rats with a model of predator stress (10-day exposure to cat urine scent, 15 min daily followed by 14 days of stress-free rest). After the last day of stress exposure, rats were conditioned in an altitude chamber for 14 days at a 1,000-m simulated altitude for 30 min on day 1 with altitude and duration progressively increasing to 4,000 m for 4 h on day 5. PTSD was associated with decreased time spent in open arms and increased time spent in closed arms of the elevated X-maze, increased anxiety index, and increased rate of freezing responses. Functional and structural signs of adrenal cortex degeneration were also observed, including decreased plasma concentration of corticosterone, decreased weight of adrenal glands, reduced thickness of the fasciculate zone, and hydropic degeneration of adrenal gland cells. The thickness of the adrenal fasciculate zone negatively correlated with the anxiety index. IHC alleviated both behavioral signs of PTSD and morphological evidence of adrenal cortex dystrophy. Also, IHC alone exerted an antistress effect, which was evident from the increased time spent in open arms of the elevated X-maze and a lower number of rats displaying freezing responses. Therefore, IHC of rats with experimental PTSD reduced behavioral signs of the condition and damage to the adrenal glands.

NEW & NOTEWORTHY Intermittent hypoxia conditioning (IHC) has been shown to be cardio-, vaso-, and neuroprotective. For the first time, in a model of posttraumatic stress disorder (PTSD), this study showed that IHC alleviated both PTSD-induced behavioral disorders and functional and morphological damage to the adrenal glands. Also, IHC alone exerted an antistress effect. These results suggest that IHC may be a promising complementary treatment for PTSD-associated disorders.

Low Oxygen Post Conditioning as an Efficient Non-pharmacological Strategy to Promote Motor Function After Stroke

Low oxygen post conditioning (LOPC) has shown promising results in terms of neuroprotection after stroke, but the effects on motor function have not been considered. Cortical stroke targeting the motor and sensory cortex was induced by photothrombotic occlusion and after 48 h allocated to LOPC (11% O₂) for 2 weeks. Motor impairment was assessed using the cylinder and grid walk tests during the exposure period and for two further weeks upon completion of the intervention. Neuroprotection was evaluated by histological and molecular analysis at two time points. Two weeks of LOPC was sufficient to significantly reduce motor deficits and tissue loss after stroke. This functional improvement was associated with increased capillary density, enhanced levels of BDNF, decreased neuronal loss and decreased microglia activation. These improvements, in most instances, were maintained up to 2 weeks after the end of the treatment. To our knowledge, this is the first study to demonstrate that LOPC induces a persistent improvement in motor function and neuroprotection after stroke, and in doing so provides evidence to support a case for considering taking LOPC forward to early stage clinical research.

Physiological and Biological Responses to Short-Term Intermittent Hypobaric Hypoxia Exposure: From Sports and Mountain Medicine to New Biomedical Applications

In recent years, the altitude acclimatization responses elicited by short-term intermittent exposure to hypoxia have been subject to renewed attention. The main goal of short-term intermittent hypobaric hypoxia exposure programs was originally to improve the aerobic capacity of athletes or to accelerate the altitude acclimatization response in alpinists, since such programs induce an increase in erythrocyte mass. Several model programs of intermittent exposure to hypoxia have presented efficiency with respect to this goal, without any of the inconveniences or negative consequences associated with permanent stays at moderate or high altitudes. Artificial intermittent exposure to normobaric hypoxia systems have seen a rapid rise in popularity among recreational and professional athletes, not only due to their unbeatable cost/efficiency ratio, but also because they help prevent common inconveniences associated with high-altitude stays such as social isolation, nutritional limitations, and other minor health and comfort-related annoyances. Today, intermittent exposure to hypobaric hypoxia is known to elicit other physiological response types in several organs and body systems. These responses range from alterations in the ventilatory pattern to modulation of the mitochondrial function. The central role played by hypoxia-inducible factor (HIF) in activating a signaling molecular cascade after hypoxia exposure is well known. Among these targets, several growth factors that upregulate the capillary bed by inducing angiogenesis and promoting oxidative metabolism merit special attention. Applying intermittent hypobaric hypoxia to promote the action of some molecules, such as angiogenic factors, could improve repair and recovery in many tissue types. This article uses a comprehensive approach to examine data obtained in recent years. We consider evidence collected from different tissues, including myocardial capillarization, skeletal muscle fiber types and fiber size changes induced by intermittent hypoxia exposure, and discuss the evidence that points to beneficial interventions in applied fields such as sport science. Short-term intermittent hypoxia may not only be useful for healthy people, but could also be considered a promising tool to be applied, with due caution, to some pathophysiological states.

Adenosine A2A receptor involves in neuroinflammation-mediated cognitive decline through activating microglia under acute hypobaric hypoxia

Hypobaric hypoxia (HH) at high altitudes leads to a wide range of cognitive impairments which can handicap human normal activities and performances. However, the underlying mechanism is still unclear. Adenosine A_2A receptors (A_2ARs) of the brain are pivotal to synaptic plasticity and cognition. Besides, insult-induced up-regulation of A_2AR regulates neuroinflammation and therefore induces brain damages in various neuropathological processes. The present study was designed to determine whether A_2AR-mediate neuroinflammation involves in cognitive impairments under acute HH. A_2AR knock-out and wild-type male mice were exposed to a simulated altitude of 8000 m for 7 consecutive days in a hypobaric chamber and simultaneously received behavioral tests including Morris water maze test and open filed test. A_2AR expression, the activation of microglia and the production of TNF-α were evaluated in the hippocampus by immunohistochemistry and ELISA, respectively. Behavioral tests showed that acute HH exposure caused the dysfunction of spatial memory and mood, while genetic inactivation of A_2AR attenuated the impairment of spatial memory but not that of mood. Double-labeled immunofluorescence showed that A_2ARs were mainly expressed on microglia and up-regulated in the hippocampus of acute HH model mice. Acute HH also induced the accumulation of microglia and increased production of TNF-α in the hippocampus, which could be markedly inhibited by A_2AR inactivation. These findings indicate that microglia-mediated neuroinflammation triggered by A_2AR activation involves in acute HH-induced spatial memory impairment and that A_2AR could be a new target for the pharmacotherapy of cognitive dysfunction at high altitudes.

Curcumin Reverses the Diazepam-Induced Cognitive Impairment by Modulation of Oxidative Stress and ERK 1/2/NF-κB Pathway in Brain

Oxidative stress and inflammation can be involved in cognitive dysfunction associated with neurodegenerative disorders. Diazepam (DZP) administration has been chosen to simulate the memory impairment. The aim of this study was to evaluate the effects of curcumin (CUR) on spatial cognition, ambulatory activity, and blood and brain oxidative stress levels. The ERK/NF-κB signaling pathway and the histopathological changes in the hippocampus and frontal lobe, in diazepam-treated rats, were also analyzed. The animals were divided into 4 groups: control, carboxymethylcellulose (CMC) + CUR, CMC + DZP, and CUR + CMC + DZP. CUR (150 mg/kg b.w.) was orally administered for 28 days. DZP (2 mg/kg b.w.) was intraperitoneally administered 20 minutes before the behavioral tests (open field test, Y-maze, and elevated plus maze). CUR improved the spontaneous alternation behavior, decreased the oxidative stress levels, both in the blood and in the hippocampus, and downregulated the extracellular signal-regulated kinase (ERK 1/2)/nuclear transcription factor- (NF-) κB/pNF-κB pathway in the hippocampus and the iNOS expression in the hippocampus and frontal lobe of the DZP-treated rats. Histopathologically, no microscopic changes were found. The immunohistochemical signal of iNOS decreased in the DZP and CUR-treated group. Thus, our findings suggest that curcumin administration may improve the cognitive performance and may also have an antioxidant effect.

Hypoxic conditioning and the central nervous system: A new therapeutic opportunity for brain and spinal cord injuries?

Central nervous system diseases are among the most disabling in the world. Neuroprotection and brain recovery from either acute or chronic neurodegeneration still represent a challenge in neurology and neurorehabilitation as pharmacology treatments are often insufficiently effective. Conditioning the central nervous system has been proposed as a potential non-pharmacological neuro-therapeutic. Conditioning refers to a procedure by which a potentially deleterious stimulus is applied near to but below the threshold of damage to the organism to increase resistance to the same or even different noxious stimuli given above the threshold of damage. Hypoxic conditioning has been investigated in several cellular and preclinical models and is now recognized as inducing endogenous mechanisms of neuroprotection. Ischemic, traumatic, or chronic neurodegenerative diseases can benefit from hypoxic conditioning strategies aiming at preventing the deleterious consequences or reducing the severity of the pathological condition (preconditioning) or aiming at inducing neuroplasticity and recovery (postconditioning) following central nervous system injury. Hypoxic conditioning can consist in single (sustained) or cyclical (intermittent, interspersed by short period of normoxia) hypoxia stimuli which duration range from few minutes to several hours and that can be repeated over several days or weeks. This mini-review addresses the existing evidence regarding the use of hypoxic conditioning as a potential innovating neuro-therapeutic modality to induce neuroprotection, neuroplasticity and brain recovery. This mini-review also emphasizes issues which remain to be clarified and future researches to be performed in the field. Impact statement Neuroprotection and brain recovery from either acute or chronic neurodegeneration still represent a challenge in neurology and neurorehabilitation. Hypoxic conditioning may represent a harmless and efficient non-pharmacological new therapeutic modality in the field of neuroprotection and neuroplasticity, as supported by many preclinical data. Animal studies provide clear evidence for neuroprotection and neuroplasticity induced by hypoxic conditioning in several models of neurological disorders. These studies show improved functional outcomes when hypoxic conditioning is applied and provides important information to translate this intervention to clinical practice. Some studies in humans provide encouraging data regarding the tolerance and therapeutic effects of hypoxic conditioning strategies. The main issues to address in future research include the definition of the appropriate hypoxic dose and pattern of exposure, the determination of relevant physiological biomarkers to assess the effects of the treatment and the evaluation of combined strategies involving hypoxic conditioning and other pharmacological or non-pharmacological treatments.

Effect of XingPiJieYu decoction on spatial learning and memory and cAMP-PKA-CREB-BDNF pathway in rat model of depression through chronic unpredictable stress

BACKGROUND

Depression is a mental disorder characterized by a pervasive low mood and loss of pleasure or interest in usual activities, and often results in cognitive dysfunction. The disturbance of cognitive processes associated with depression, especially the impairment of learning and memory, exacerbates illness and increases recurrence of depression. XingPiJieYu (XPJY) is one of the most widely clinical formulas of traditional Chinese medicine (TCM) and can improve the symptoms of depression, including learning and memory. However, its regulatory effects haven't been comprehensively studied so far. Recently, some animal tests have indicated that the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA)-cAMP response element-binding protein (CREB)-brain derived neurotrophic factor (BDNF) signaling pathway in hippocampus is closely related to depression and the pathogenesis of cognitive function impairments. The present study was performed to investigate the effect and mechanism of XPJY on depression and learning and memory in animal model.

MATERIALS

The rat model of depression was established by chronic unpredictable stress (CUS) for 21 days. The rats were randomly divided into six groups: control group, CUS group, CUS + XPJY (1.4 g/kg, 0.7 g/kg and 0.35 g/kg) groups, and CUS + sertraline (10 mg/kg) group. The sucrose preference, open field exploration and Morris water maze (MWM) were tested. The expression of cAMP, CREB, PKA and BDNF protein in hippocampus was examined with Elisa and Western Blot. The mRNA level of CREB and BDNF in hippocampus was measured with PCR.

RESULTS

The results demonstrated that rats subjected to CUS exhibited decreases in sucrose preference, total ambulation, percentage of central ambulation, rearing in the open field test and spatial performance in the MWM. CUS reduced the expression of cAMP, PKA, CREB and BDNF in hippocampus of model rats. These effects could be reversed by XPJY.

CONCLUSION

The results indicated that XPJY can improve depression and related learning and memory and the effect of XPJY is partly exerted through the cAMP-PKA-CREB-BDNF signaling pathway.

Tobacco use is associated with increased plasma BDNF levels in depressed patients

Since serum Brain Derived Neurotrophic Factor (BDNF) levels are higher in tobacco smokers than in non-smokers and since Major Depressive Disorder (MDD) is associated with a 2-fold increased risk of smoking, we assessed the association of smoking and plasma BDNF levels in 359 depressed MDD patients. Plasma BDNF levels were positively correlated with the magnitude of tobacco consumption (current number of cigarettes/day and number of packs/year). Accordingly, current tobacco users had significantly higher plasma BDNF levels than non-users. In further studies of MDD, peripheral measures of BDNF should take into account tobacco use.