Hypoxia Inducible Factor 1α Promotes Endogenous Adaptive Response in Rat Model of Chronic Cerebral Hypoperfusion

Danggui-Shaoyao San alleviates cognitive impairment via enhancing HIF-1α/EPO axis in vascular dementia rats

ETHNOPHARMACOLOGICAL RELEVANCE

Invigorating blood circulation to remove blood stasis is a primary strategy in TCM for treating vascular dementia (VaD). Danggui-Shaoyao San (DSS), as a traditional prescription for neuroprotective activity, has been proved to be effective in VaD treatment. However, its precise molecular mechanisms remain incompletely understood.

AIM OF THE STUDY

The specific mechanism underlying the therapeutic effects of DSS on VaD was explored by employing network pharmacology as well as in vivo and in viro experiment validation.

MATERIALS AND METHODS

We downloaded components of DSS from the BATMAN-TCM database for target prediction. The intersection between the components of DSS and targets, PPI network, as well as GO and KEGG enrichment analysis were then performed. Subsequently, the potential mechanism of DSS predicted by network pharmacology was assessed and validated through VaD rat model induced by 2VO operation and CoCl2-treated PC12 cells. Briefly, the DSS extract were first quantified by HPLC. Secondly, the effect of DSS on VaD was studied using MWM test, HE staining and TUNEL assay. Finally, the molecular mechanism of DSS against VaD was validated by Western blot and RT-QPCR experiments.

RESULTS

Through network analysis, 137 active ingredients were obtained from DSS, and 67 potential targets associated with DSS and VaD were identified. GO and KEGG analysis indicated that the action of DSS on VaD primarily involves hypoxic terms and HIF-1 pathway. In vivo validation, cognitive impairment and neuron mortality were markedly ameliorated by DSS. Additionally, DSS significantly reduced the expression of proteins related to synaptic plasticity and neuron apoptosis including PSD-95, SYP, Caspase-3 and BCL-2. Mechanistically, we confirmed DSS positively modulated the expression of HIF-1α and its downstream proteins including EPO, p-EPOR, STAT5, EPOR, and AKT1 in the hippocampus of VaD rats as well as CoCl2-induced PC12 cells. HIF-1 inhibitor YC-1 significantly diminished the protection of DSS on CoCl2-induced PC12 cell damage, with decreased HIF-1α, EPO, EPOR expression.

CONCLUSION

Our results initially demonstrated DSS could exert neuroprotective effects in VaD. The pharmacological mechanism of DSS may be related to its positive regulation on HIF-1α/EPO pathway.

Early hyperbaric oxygen therapy through regulating the HIF-1α signaling pathway attenuates Neuroinflammation and behavioral deficits in a mouse model of Sepsis-associated encephalopathy

BACKGROUND

Sepsis-associated encephalopathy (SAE) presents a significant clinical challenge, associated with increased mortality and healthcare expenses. Hyperbaric oxygen therapy (HBOT), involving inhaling pure or highly concentrated oxygen under pressures exceeding one atmosphere, has demonstrated neuroprotective effects in various conditions. However, the precise mechanisms underlying its protective actions against sepsis-associated brain injury remain unclear. This study aimed to determine whether HBOT protects against SAE and to elucidate the impact of the hypoxia-inducible factor-1α (HIF-1α) signaling pathway on SAE.

METHODS

The experiment consisted of two parts. In the first part, C57BL/6 J male mice were divided into five groups using a random number table method: control group, sham surgery group, sepsis group, HBOT + sepsis group, and HBOT + sham surgery group. In the subsequent part, C57BL/6 J male mice were divided into four groups: sepsis group, HBOT + sepsis group, HIF-1α + HBOT + sepsis group, and HIF-1α + sepsis group. Sepsis was induced via cecal ligation and puncture (CLP). Hyperbaric oxygen therapy was administered at 1 h and 4 h post-CLP. After 24 h, blood and hippocampal tissue were collected for cytokine measurements. HIF-1α, TNF-α, IL-1β, and IL-6 expression were assessed via ELISA and western blotting. Microglial expression was determined by immunofluorescence. Blood-brain barrier permeability was quantified using Evans Blue. Barnes maze and fear conditioning were conducted 14 days post-CLP to evaluate learning and memory.

RESULTS

Our findings reveal that CLP-induced hippocampus-dependent cognitive deficits coincided with elevated HIF-1α and increased TNF-α, IL-1β, and IL-6 levels in both blood and hippocampus. Observable activation of microglial cells in the hippocampus and increased blood-brain barrier (BBB) permeability were also evident. HBOT mitigated HIF-1α, TNF-α, IL-1β, and IL-6 levels, attenuated microglial activation in the hippocampus, and significantly improved learning and memory deficits in CLP-exposed mice. Additionally, these outcomes were corroborated by injecting a lentivirus that overexpressed HIF-1α into the hippocampal region of the mice.

CONCLUSION

HIF-1α escalation induced peripheral and central inflammatory factors, promoting microglial activation, BBB impairment, and cognitive dysfunction. However, HBOT ameliorated these effects by reducing HIF-1α levels in Sepsis-Associated Encephalopathy.

Insight into the Effects of High-Altitude Hypoxic Exposure on Learning and Memory

The earth land area is heterogeneous in terms of elevation; about 45% of its land area belongs to higher elevation with altitude above 500 meters compared to sea level. In most cases, oxygen concentration decreases as altitude increases. Thus, high-altitude hypoxic stress is commonly faced by residents in areas with an average elevation exceeding 2500 meters and those who have just entered the plateau. High-altitude hypoxia significantly affects advanced neurobehaviors including learning and memory (L&M). Hippocampus, the integration center of L&M, could be the most crucial target affected by high-altitude hypoxia exposure. Based on these points, this review thoroughly discussed the relationship between high-altitude hypoxia and L&M impairment, in terms of hippocampal neuron apoptosis and dysfunction, neuronal oxidative stress disorder, neurotransmitters and related receptors, and nerve cell energy metabolism disorder, which is of great significance to find potential targets for medical intervention. Studies illustrate that the mechanism of L&M damaged by high-altitude hypoxia should be further investigated based on the entire review of issues related to this topic.

Maternal Vit D supplementation in AMA mice and the role of Vit D/VDR signaling in the offspring's cognition

OBJECTIVE

To explore the molecular mechanism underlying the effect of maternal vitamin D (Vit D) supplementation before pregnancy in advanced maternal age (AMA) mice on the offspring's cognitive function.

METHODS

Thirty-two-week-old female mice either received 10 IU/g body weight vitamin D₃ dissolved in 200 μl corn oil (32W+VD group), or 200 μl corn oil (32W group) per day for one week. Another group of eight-week-old female mice received the same amount of corn oil as 32W group was set as normal reproductive age control (8W group). Then the three groups of female mice were mating with ten-week-old male mice at 2:1 ratio, the offspring were weaned at the age of 3 weeks and housed until the age of 6 weeks. Vit D metabolites and enzymes involved in Vit D metabolism were measured in both mothers and their offspring. Vit D receptor (VDR) and synaptic markers were determined in the offspring hippocampus. Vit D response elements in HIF-1α promoter were predicted, and VDR transcriptional target genes and related signaling molecules were also detected.

RESULTS

Vit D intervention markedly improved the serum 1,25 dihydroxy vitamin D₃ (1,25(OH)₂D₃) concentration in early pregnancy, middle pregnancy and late pregnancy stages in AMA mice. The hippocampal 1,25(OH)₂D₃ levels in the offspring showed the similar pattern. Subsequently, the expression of Cyp27b1, the gene encoding enzyme that converts 25(OH)D₃ to 1,25(OH)₂D₃, in the hippocampus of the offspring from AMA mice was significantly lower than that of the offspring from normal female mice, and was restored by Vit D supplementation. VDR (Vit D receptor), which mediates the cellular actions of active 1,25(OH)₂D₃, was also rescued by Vit D supplementation, especially in dentate gyrus (DG) region of hippocampus. Concurrently, the synaptic markers NR1, NR2A, and PSD-93 in the hippocampus were reversed in 32W+VD group. Finally, we found that Vit D supplementation may affect PI3K-AKT, PLC-ERK1/2, and p38-MAPK signaling molecules by mediating HIF1α expression via VDR.

CONCLUSION

Our findings highlight the biological significance of maternal Vit D supplementation before pregnancy on Vit D metabolism, and signaling molecules in the offspring, underlying the potential mechanism of the cognitive impairment in the offspring born to AMA mice.

miRNA-132/212 Gene-Deletion Aggravates the Effect of Oxygen-Glucose Deprivation on Synaptic Functions in the Female Mouse Hippocampus

Cerebral ischemia and its sequelae, which include memory impairment, constitute a leading cause of disability worldwide. Micro-RNAs (miRNA) are evolutionarily conserved short-length/noncoding RNA molecules recently implicated in adaptive/maladaptive neuronal responses to ischemia. Previous research independently implicated the miRNA-132/212 cluster in cholinergic signaling and synaptic transmission, and in adaptive/protective mechanisms of neuronal responses to hypoxia. However, the putative role of miRNA-132/212 in the response of synaptic transmission to ischemia remained unexplored. Using hippocampal slices from female miRNA-132/212 double-knockout mice in an established electrophysiological model of ischemia, we here describe that miRNA-132/212 gene-deletion aggravated the deleterious effect of repeated oxygen-glucose deprivation insults on synaptic transmission in the dentate gyrus, a brain region crucial for learning and memory functions. We also examined the effect of miRNA-132/212 gene-deletion on the expression of key mediators in cholinergic signaling that are implicated in both adaptive responses to ischemia and hippocampal neural signaling. miRNA-132/212 gene-deletion significantly altered hippocampal AChE and mAChR-M1, but not α7-nAChR or MeCP2 expression. The effects of miRNA-132/212 gene-deletion on hippocampal synaptic transmission and levels of cholinergic-signaling elements suggest the existence of a miRNA-132/212-dependent adaptive mechanism safeguarding the functional integrity of synaptic functions in the acute phase of cerebral ischemia.

High VCAM-1 Predicts Poor Prognosis and is Associated with Chemotherapy Resistance in Nasopharyngeal Carcinoma

Purpose

Nasopharyngeal carcinoma (NPC) is a malignant tumor endemic in southern China and Southeast Asia with a poor prognosis. Vascular cell adhesion protein 1 (VCAM-1) is highly expressed in NPC; however, it is unclear whether VCAM-1 is correlated with chemotherapy resistance and prognosis in NPC.

Patients and Methods

To further explore the role of VCAM-1 in chemotherapy resistance and prognosis in NPC, we examined the expression of VCAM-1, the sensitivity of chemotherapy drugs, and clinical follow-up data from 73 patients with NPC. Then, the results of VCAM-1 expression were analyzed in response to chemotherapy drugs, progression-free survival (PFS), and overall survival (OS).

Results

The expression of VCAM-1 protein in NPC was significantly higher than that in chronic inflammatory tissue. No significant differences in the expression of VCAM-1 among gender, age, pathologic classification, tumor classification, lymph node status, metastasis status, and overall clinical stage were found. The periods of PFS and OS in patients with high VCAM-1 expression were significantly shorter than those in patients with low VCAM-1 expression. The sensitivity rates of NPC to eight chemotherapy drugs were different; carboplatin and docetaxel showed the highest chemotherapy sensitivity and resistance rates, respectively. The resistance rates to paclitaxel were different between the patients with high VCAM-1 expression and those with low VCAM-1 expression.

Conclusion

Our data indicated that VCAM-1 was highly expressed in NPC. Patients with high VCAM-1 expression were more prone to shorter periods of PFS and OS. VCAM-1 could be a prognostic marker of NPC patients. The detection of VCAM-1 expression in NPC may be valuable for chemotherapy drug evaluation and management of patients with NPC in the clinic.

Exosome-transferred hsa_circ_0014235 promotes DDP chemoresistance and deteriorates the development of non-small cell lung cancer by mediating the miR-520a-5p/CDK4 pathway

BACKGROUND

Circular RNAs (circRNAs) play crucial roles in the development and progression of human cancers, including non-small cell lung cancer (NSCLC). However, most of these circRNAs, such as hsa_circ_0014235, are not fully identified in functions and mechanisms.

METHODS

The isolated exosomes from serum specimens were identified using transmission electron microscopy (TEM). The expression of hsa_circ_0014235, miR-520a-5p and cyclin-dependent kinase 4 (CDK4) was detected by real-time quantitative polymerase chain reaction (qPCR). For functional assays, cell proliferation, colony formation ability, migration, invasion, cell apoptosis and cell cycle progression were determined using cell counting kit-8 (CCK-8) assay, colony formation assay, wound healing assay, transwell assay and flow cytometry assay, respectively. The expression of CDK4 and other indicated marker proteins was detected by western blot. The predicted target relationship between miR-520a-5p and hsa_circ_0014235 or cyclin-dependent kinase 4 (CDK4) was verified by dual-luciferase reporter assay or RNA immunoprecipitation (RIP) assay.

RESULTS

The expression of hsa_circ_0014235 was notably elevated in NSCLC serum-derived exosomes, tumor tissues and cells. NSCLC serum-derived exosomes promoted NSCLC cell resistance to cisplatin (DDP), cell proliferation, migration and invasion in vitro, as well as tumor growth and DDP resistance in vivo. Hsa_circ_0014235 overexpression enhanced DDP resistance and facilitated cell malignant behaviors. MiR-520a-5p was a target of hsa_circ_0014235, and rescue experiments showed that miR-520a-5p restoration reversed the effects of hsa_circ_0014235 overexpression. Moreover, CDK4 was a target of miR-520a-5p, and rescue experiments showed that CDK4 knockdown reversed the aggressive effects of miR-520a-5p inhibition on NSCLC progression.

CONCLUSIONS

Exosome-transmitted hsa_circ_0014235 promoted NSCLC malignant development by mediating the miR-520a-5p/CDK4 regulatory axis.

Microglial Responses to Brain Injury and Disease: Functional Diversity and New Opportunities

As an integral part of the innate immune system of the brain, resident microglia must react rapidly to the onset of brain injury and neurological disease. These dynamic cells then continue to shift their phenotype along a multidimensional continuum with overlapping pro- and anti-inflammatory states, allowing them to adapt to microenvironmental changes during the progression of brain disorders. However, the ability of microglia to shift phenotype through nimble molecular, structural, and functional changes comes at a cost, as the extreme pro-inflammatory states may prevent these professional phagocytes from clearing toxic debris and secreting tissue-repairing neurotrophic factors. Evolution has strongly favored heterogeneity in microglia in both the spatial and temporal dimensions-they can assume diverse roles in different brain regions, throughout the course of brain development and aging, and during the spatiotemporal progression of brain injuries and neurological diseases. Age and sex differences add further diversity to microglia functional status under physiological and pathological conditions. This article reviews recent advances in our knowledge of microglia with emphases on molecular mediators of phenotype shifts and functional diversity. We describe microglia-targeted therapeutic opportunities, including pharmacologic modulation of phenotype and repopulation of the brain with fresh microglia. With the advent of powerful new tools, research on microglia has recently accelerated in pace and may translate into potential therapeutics against brain injury and neurological disease.

Neuronal Nitric Oxide Inhibitor 7-Nitroindazole Improved Brain-Derived Neurotrophic Factor and Attenuated Brain Tissues Oxidative Damage and Learning and Memory Impairments of Hypothyroid Juvenile Rats

Hypothyroidism-associated learning and memory impairment is reported to be connected to oxidative stress and reduced levels of brain-derived neurotrophic factor (BDNF). The effects of neuronal nitric oxide inhibitor 7-nitroindazole (7NI) on brain tissues oxidative damage, nitric oxide (NO), BDNF and memory impairments in hypothyroid juvenile rats were investigated. Male Wistar juvenile rats (20 days old) were divided into five groups, including Martinez et al. (J Neurochem 78 (5):1054-1063, 2001). Control in which vehicle was injected instead of 7NI, (Jackson in Thyroid 8 (10):951-956, 1998) Propylthiouracil (PTU) where 0.05% PTU was added in drinking water and vehicle was injected instead of 7NI, (Gong et al. in BMC Neurosci 11 (1):50, 2010; Alva-Sánchez et al. in Brain Res 1271:27-35, 2009; Anaeigoudari et al. in Pharmacol Rep 68 (2): 243-249, 2016) PTU-7NI 5, PTU-7NI 10 and PTU-7NI 20 in which 5, 10, or 20 mg/kg7NI was injected intraperitoneally (i.p.). Following 6 weeks, Morris water maze (MMW) and passive avoidance learning (PAL) tests were used to evaluate the memory. Finally, the hippocampus and the cortex of the rats were removed after anesthesia by urethane to be used for future analysis. The escape latency and traveled path in MWM test was increased in PTU group (P < 0.001). PTU also reduced the latency to enter the dark box of PAL and the time spent and the distance in the target quadrant in MWM test (P < 0.001 and P < 0.01). Treatment with 7NI attenuated all adverse effects of PTU (P < 0.05 to P < 0.001). PTU lowered BDNF and thiol content and superoxide dismutase (SOD) and catalase (CAT) activities in the brain but increased malondialdehyde (MDA) and nitric oxide (NO) metabolites. In addition, 7NI improved thiol, SOD, CAT, thiol, and BDNF but attenuated MDA and NO metabolites. The results of the current study showed that 7NI improvement in the learning and memory of the hypothyroid juvenile rats, which was accompanied with improving of BDNF and attenuation of NO and brain tissues oxidative damage.

Decreased overall mortality rate with Chinese herbal medicine usage in patients with decompensated liver cirrhosis in Taiwan

Background

Liver cirrhosis is one of the main causes of the morbidity and mortality in liver diseases. Chinese herbal medicine (CHM) has long been used for the clinical treatment of liver diseases. This study was designed to explore the usage frequency and prescription patterns of CHM for patients with decompensated liver cirrhosis and to evaluate the long-term effects of CHM on overall mortality.

Methods

Two thousand four hundred sixty-seven patients with decompensated liver cirrhosis (ICD-9-CM code: 571.2, 571.5, and 571.6) diagnosed between 2000 and 2009 in Taiwan were identified from the registry for catastrophic illness patients. Of these, 149 CHM users and 298 CHM non-users were matched for age, gender, and Charlson comorbidity index score. The chi-squared test, paired Student’s t-test, Cox proportional hazard model, and Kaplan–Meier method were applied for various comparisons between these groups of patients.

Results

CHM-treated patients showed a lower overall mortality risk compared with non-treated patients (Multivariable: p < 0.0001; HR: 0.54, 95% CI: 0.42–0.69). The cumulative incidence of overall mortality was lower in the CHM-treated group (stratified log-rank test, p = 0.0002). The strongest CHM co-prescription pattern- Yin-Chen-Hao-Tang (YCHT) → Long-Dan-Xie-Gan-Tang (LDXGT) had the highest support, followed by Zhi-Zi (ZZ) → Yin-Chen-Wu-Ling-San (YCWLS) and Bai-Hua-She-She-Cao (BHSSC) → Da-Huang (DaH).

Conclusion

CHM, as adjunct therapy, might decrease the risk of overall mortality in patients with decompensated liver cirrhosis. CHM co-prescription patterns and network analysis showed that comprehensive herbal medicines have a protective role against liver fibrosis. Further studies are required to enhance the knowledge of safety and efficacy of CHM in patients with decompensated liver cirrhosis.

Mfsd2a Reverses Spatial Learning and Memory Impairment Caused by Chronic Cerebral Hypoperfusion via Protection of the Blood-Brain Barrier

Disruption of the blood–brain barrier (BBB) can lead to cognitive impairment. Major facilitator superfamily domain-containing protein 2a (Mfsd2a) is a newly discovered protein that is essential for maintaining BBB integrity. However, the role of Mfsd2a in vascular cognitive impairment has not been explored yet. In this study, a rat model of chronic cerebral hypoperfusion (CCH) was established by producing permanent bilateral common carotid artery occlusion (2VO) in rats. We found that after the 2VO procedure, the rats exhibited cognitive impairment, showed increased BBB leakage within the hippocampus, and had reduced expression of the Mfsd2a protein. The overexpression of Mfsd2a in the rat hippocampus reversed these changes. Further investigations using transmission electron microscopy revealed a significantly increased rate of vesicular transcytosis in the BBB of the hippocampus of the CCH rats; the rate reduced after overexpression of Mfsd2a. Moreover, Mfsd2a overexpression did not cause changes in the expression of tight junction-associated proteins and in the ultrastructures of the tight junctions. In conclusion, Mfsd2a attenuated BBB damage and ameliorated cognitive impairment in CCH rats, and its protective effect on the BBB was achieved via inhibition of vesicular transcytosis.

Electroacupuncture Improved Chronic Cerebral Hypoperfusion-Induced Anxiety-Like Behavior and Memory Impairments in Spontaneously Hypertensive Rats by Downregulating the ACE/Ang II/AT1R Axis and Upregulating the ACE2/Ang-(1-7)/MasR Axis

Electroacupuncture (EA) can effectively alleviate anxiety disorders and memory impairments caused by various neurodegenerative diseases; however, the molecular mechanisms underlying its neuroprotective effects are unclear. Previous studies have shown that the renin-angiotensin system (RAS) comprises of two axes with mutual antagonism: the classical angiotensin converting enzyme/angiotensin II/angiotensin II type 1 receptor (ACE/Ang II/AT1R) axis and the protective angiotensin converting enzyme 2/angiotensin-(1-7)/Mas receptor (ACE2/Ang-(1-7)/MasR) axis. In this study, we observed that chronic cerebral hypoperfusion (CCH) mediated anxiety-like behavior and memory impairments in spontaneously hypertensive rats (SHR) via upregulation of the hippocampal classical axis (ACE/Ang II/AT1R) and the partial hippocampal protective axis (ACE2/Ang-(1-7)). However, Ang II levels were much higher than those of Ang-(1–7), indicating that the ACE/Ang II/AT1R axis plays a dominant role in the comorbidity of CCH and hypertension. Moreover, candesartan cilexetil (Canc) and perindopril (Peril) were used as positive control drugs. We found that EA, Canc, and Peril attenuated CCH-induced anxiety-like behavior and memory impairments in SHR, potentially via downregulation of the hippocampal classical axis (ACE/Ang II/AT1R) and upregulation of the whole hippocampal protective axis (ACE2/Ang-(1-7)/MasR). These results suggest that EA therapy for CCH with hypertension may be mediated by two hippocampal RAS axes.

Small Vessel Disease-Related Dementia: An Invalid Neurovascular Coupling?

The arteriosclerosis-dependent alteration of brain perfusion is one of the major determinants in small vessel disease, since small vessels have a pivotal role in the brain's autoregulation. Nevertheless, as far as we know, endothelium distress can potentiate the flow dysregulation and lead to subcortical vascular dementia that is related to small vessel disease (SVD), also being defined as subcortical vascular dementia (sVAD), as well as microglia activation, chronic hypoxia and hypoperfusion, vessel-tone dysregulation, altered astrocytes, and pericytes functioning blood-brain barrier disruption. The molecular basis of this pathology remains controversial. The apparent consequence (or a first event, too) is the macroscopic alteration of the neurovascular coupling. Here, we examined the possible mechanisms that lead a healthy aging process towards subcortical dementia. We remarked that SVD and white matter abnormalities related to age could be accelerated and potentiated by different vascular risk factors. Vascular function changes can be heavily influenced by genetic and epigenetic factors, which are, to the best of our knowledge, mostly unknown. Metabolic demands, active neurovascular coupling, correct glymphatic process, and adequate oxidative and inflammatory responses could be bulwarks in defense of the correct aging process; their impairments lead to a potentially catastrophic and non-reversible condition.

Development of Novel N-hydroxypyridone Derivatives as Potential Anti-Ischemic Stroke Agents

Our previous study had identified ciclopirox (CPX) as a promising lead compound for treatment of ischemic stroke. To find better neuroprotective agents, a series of N-hydroxypyridone derivatives based on CPX were designed, synthesized, and evaluated in this study. Among these derivatives, compound 11 exhibits significant neuroprotection against oxygen glucose deprivation and oxidative stress-induced injuries in neuronal cells. Moreover, compound 11 possesses good blood-brain barrier permeability and superior antioxidant capability. In addition, a complex of compound 11 with olamine-11·Ola possesses good water solubility, negligible hERG inhibition, and superior metabolic stability. The in vivo experiment demonstrates that 11·Ola significantly reduces brain infarction and alleviates neurological deficits in middle cerebral artery occlusion rats. Hence, compound 11·Ola is identified in our research as a prospective prototype in the innovation of stroke treatment.

Intracellular Neuroprotective Mechanisms in Neuron-Glial Networks Mediated by Glial Cell Line-Derived Neurotrophic Factor

Glial cell line-derived neurotrophic factor (GDNF) has a pronounced neuroprotective effect in various nervous system pathologies, including ischaemic brain damage and neurodegenerative diseases. In this work, we studied the effect of GDNF on the ultrastructure and functional activity of neuron-glial networks during acute hypoxic exposure, a key damaging factor in numerous brain pathologies. We analysed the molecular mechanisms most likely involved in the positive effects of GDNF. Hypoxia modelling was performed on day 14 of culturing primary hippocampal cells obtained from mouse embryos (E18). GDNF (1 ng/ml) was added to the culture medium 20 min before oxygen deprivation. Acute hypoxia-induced irreversible changes in the ultrastructure of neurons and astrocytes led to the loss of functional Сa²⁺ activity and neural network disruption. Destructive changes in the mitochondrial apparatus and its functional activity characterized by an increase in the basal oxygen consumption rate and respiratory chain complex II activity during decreased stimulated respiration intensity were observed 24 hours after hypoxic injury. At a concentration of 1 ng/ml, GDNF maintained the functional metabolic network activity in primary hippocampal cultures and preserved the structure of the synaptic apparatus and number of mature chemical synapses, confirming its neuroprotective effect. GDNF maintained the normal structure of mitochondria in neuronal outgrowth but not in the soma. Analysis of the possible GDNF mechanism revealed that RET kinase, a component of the receptor complex, and the PI3K/Akt pathway are crucial for the neuroprotective effect of GDNF. The current study also revealed the role of GDNF in the regulation of HIF-1α transcription factor expression under hypoxic conditions.

Dl-3-n-Butylphthalide Reduces Cognitive Impairment Induced by Chronic Cerebral Hypoperfusion Through GDNF/GFRα1/Ret Signaling Preventing Hippocampal Neuron Apoptosis

Hippocampal neuron death is a key factor in vascular dementia (VD) induced by chronic cerebral hypoperfusion (CCH). Dl-3-n-butylphthalide (NBP) is a multiple-effects drug. Therefore, the potential molecular mechanisms underlying CCH and its feasible treatment should be investigated. This study had two main purposes: first, to identify a potential biomarker in a rat model of CCH induced VD using antibody microarrays; and second, to explore the neuroprotective role of NBP at targeting the potential biomarker. Glial cell line-derived neurotrophic factor (GDNF)/GDNF family receptor alpha-1 (GFRα1)/receptor tyrosine kinase (Ret) signaling is altered in the hippocampus of CCH rats; however, NBP treatment improved cognitive function, protected against hippocampal neuron apoptosis via regulation of GDNF/GFRα1/Ret, and activated the phosphorylation AKT (p-AKT) and ERK1/2 (p-ERK1/2) signaling. We also found that 1 h oxygen-glucose deprivation (OGD) followed by 48 h reperfusion (R) in cultured hippocampal neurons led to downregulation of GDNF/GFRα1/Ret. NBP upregulated the signaling and increased neuronal survival. Ret inhibitor (NVP-AST487) inhibits Ret and downstream effectors, including p-AKT and p-ERK1/2. Additionally, both GDNF and GFRα1 expression are markedly inhibited in hippocampal neurons by coincubation with NVP-AST487, particularly under conditions of OGD/R. GDNF/GFRα1/Ret signaling and neuronal viability can be maintained by NBP, which activates p-AKT and p-ERK1/2, increases expression of Bcl-2, and decreases expression of Bax and cleaved caspase-3. The current study showed that GDNF/GFRα1/Ret signaling plays an essential role in the CCH induced VD. NBP was protective against hippocampal neuron apoptosis, and this was associated with regulation of GDNF/GFRα1/Ret and AKT/ERK1/2 signaling pathways, thus reducing cognitive impairment.

Genetic polymorphisms in ABCG2 and CYP1A2 are associated with imatinib dose reduction in patients treated for gastrointestinal stromal tumors

Imatinib has a mild toxicity profile, although severe adverse events may develop. In this pharmacogenetic pathway analysis the need for dose reduction and cessation of therapy was tested for an association with single nucleotide polymorphisms (SNPs) in genes related to imatinib pharmacology. Retrospective data from 315 patients with a gastrointestinal stromal tumor who received imatinib 400 mg o.d. was associated with 36 SNPs. SNPs that showed a trend in univariate testing were tested in a multivariate model with clinical factors and correction for multiple testing was performed. Dose reduction was associated with carriership of the A-allele in rs2231137 in ABCG2 (OR 7.35, p = 0.0002) and two C-alleles in rs762551 in CYP1A2 (OR 7.12, p = 0.001). Results remained significant after correction for multiple testing. Therapy cessation did not show an association with any of the tested SNPs. These results may help identifying patients at increased risk for toxicity who could benefit from intensified follow-up.

Transient receptor potential vanilloid-4 channels are involved in diminished myogenic tone in brain parenchymal arterioles in response to chronic hypoperfusion in mice

AIM

Adaptive responses of brain parenchymal arterioles (PAs), a target for cerebral small vessel disease, to chronic cerebral hypoperfusion are largely unknown. Previous evidence suggested that transient receptor potential vanilloid 4 channels may be involved in the regulation of cerebrovascular tone. Therefore, we investigated the role of TRPV4 in adaptations of PAs in a mouse model of chronic hypoperfusion.

METHODS

TRPV4 knockout (^-/- ) and wild-type (WT) mice were subjected to unilateral common carotid artery occlusion (UCCAo) for 28 days. Function and structure of PAs ipsilateral to UCCAo were studied isolated and pressurized in an arteriograph.

RESULTS

Basal tone of PAs was similar between WT and TRPV4^-/- mice (22 ± 3 vs 23 ± 5%). After UCCAo, active inner diameters of PAs from WT mice were larger than control (41 ± 2 vs 26 ± 5 μm, P < 0.05) that was due to decreased tone (8 ± 2 vs 23 ± 5%, P < 0.05), increased passive inner diameters (46 ± 3 vs 34 ± 2 μm, P < 0.05), and decreased wall-to-lumen ratio (0.104 ± 0.01 vs 0.137 ± 0.01, P < 0.05). However, UCCAo did not affect vasodilation to a small- and intermediate-conductance calcium-activated potassium channel agonist NS309, the nitric oxide (NO) donor sodium nitroprusside, or constriction to a NO synthase inhibitor L-NNA. Wall thickness and distensibility in PAs from WT mice were unaffected. In TRPV4^-/- mice, UCCAo had no effect on active inner diameters or tone and only increased passive inner diameters (53 ± 2 vs 43 ± 3 μm, P < 0.05).

CONCLUSION

Adaptive response of PAs to chronic cerebral hypoperfusion includes myogenic tone reduction and outward remodelling. TRPV4 channels were involved in tone reduction but not outward remodelling in response to UCCAo.

Hypoxia Mimetic Agents for Ischemic Stroke

Every year stroke claims more than 6 million lives worldwide. The majority of them are ischemic stroke. Small molecule-based therapeutics for ischemic stroke has attracted a lot of attention, but none has been shown to be clinically useful so far. Hypoxia-inducible factor-1 (HIF-1) plays a crucial role in the transcriptional adaptation of cells to hypoxia. Small molecule-based hypoxia-mimetic agents either stabilize HIF-1α via HIF-prolyl hydroxylases (PHDs) inhibition or through other mechanisms. In both the cases, these agents have been shown to confer ischemic neuroprotection in vitro and in vivo. The agents which act via PHD inhibition are mainly classified into iron chelators, iron competitors, and 2 oxoglutarate (2OG) analogs. This review discusses HIF structure and key players in the HIF-1 degradation pathway as well as the genes, proteins and chemical molecules that are connected to HIF-1 and how they affect cell survival following ischemic injury. Furthermore, this review gives a summary of studies that used PHD inhibitors and other HIF-1α stabilizers as hypoxia-mimetic agents for the treatment of ischemic injury.

TRPM2 Channel Aggravates CNS Inflammation and Cognitive Impairment via Activation of Microglia in Chronic Cerebral Hypoperfusion

Chronic cerebral hypoperfusion is a characteristic seen in widespread CNS diseases, including neurodegenerative and mental disorders, and is commonly accompanied by cognitive impairment. Recently, several studies demonstrated that chronic cerebral hypoperfusion can induce the excessive inflammatory responses that precede neuronal dysfunction; however, the precise mechanism of cognitive impairment due to chronic cerebral hypoperfusion remains unknown. Transient receptor potential melastatin 2 (TRPM2) is a Ca²⁺-permeable channel that is abundantly expressed in immune cells and is involved in aggravation of inflammatory responses. Therefore, we investigated the pathophysiological role of TRPM2 in a mouse chronic cerebral hypoperfusion model with bilateral common carotid artery stenosis (BCAS). When male mice were subjected to BCAS, cognitive dysfunction and white matter injury at day 28 were significantly improved in TRPM2 knock-out (TRPM2-KO) mice compared with wild-type (WT) mice, whereas hippocampal damage was not observed. There were no differences in blood-brain barrier breakdown and H₂O₂ production between the two genotypes at 14 and 28 d after BCAS. Cytokine production was significantly suppressed in BCAS-operated TRPM2-KO mice compared with WT mice at day 28. In addition, the number of Iba1-positive cells gradually decreased from day 14. Moreover, daily treatment with minocycline significantly improved cognitive perturbation. Surgical techniques using bone marrow chimeric mice revealed that activated Iba1-positive cells in white matter could be brain-resident microglia, not peripheral macrophages. Together, these findings suggest that microglia contribute to the aggravation of cognitive impairment by chronic cerebral hypoperfusion, and that TRPM2 may be a potential target for chronic cerebral hypoperfusion-related disorders.SIGNIFICANCE STATEMENT Chronic cerebral hypoperfusion is manifested in a wide variety of CNS diseases, including neurodegenerative and mental disorders that are accompanied by cognitive impairment; however, the underlying mechanisms require clarification. Here, we used a chronic cerebral hypoperfusion mouse model to investigate whether TRPM2, a Ca²⁺-permeable cation channel highly expressed in immune cells, plays a destructive role in the development of chronic cerebral hypoperfusion-induced cognitive impairment, and propose a new hypothesis in which TRPM2-mediated activation of microglia, not macrophages, specifically contributes to the pathology through the aggravation of inflammatory responses. These findings shed light on the understanding of the mechanisms of chronic cerebral hypoperfusion-related inflammation, and are expected to provide a novel therapeutic molecule for cognitive impairment in CNS diseases.

Hypoxia-inducible factor 1a induces phenotype switch of human aortic vascular smooth muscle cell through PI3K/AKT/AEG-1 signaling

To date, hypoxia-inducible factor 1a (HIF-1a) and astrocyte elevated gene-1 (AEG-1) have been involved in the proliferation, migration and morphological changes of vascular smooth muscle cells. However, the potential relationship of HIF-1a-AEG-1 pathway in human aortic smooth muscle cell (HASMC) has not been reported. In the present study, in-vitro assays were utilized to explore the potential impact of HIF-1a-AEG-1 signaling on HASMC phenotype. Here, we found that HIF-1a expression was up-regulated in the media of thoracic aortic dissection tissues as compared with normal aortic tissues, and was associated with increased apoptotic SMCs and decreased AEG-1 expression. Mechanically, hypoxia promoted the expression of HIF-1a by PI3K-AKT pathway in HASMCs; HIF-1a further suppressed the expressions of AEG-1, a-SMA and SM22a, and promoted osteopontin (OPN) expression. Functionally, HIF-1a inhibited the proliferation and migration of HASMCs. However, si-HIF-1a or Akt inhibitor abrogated HIF-1a-mediated related expressions and biological effects above. In conclusion, HIF-1a induces HASMC phenotype switch, and closely related to PI3K/AKT and AEG-1 signaling, which may provide new avenues for the prevention and treatment of aortic dissection diseases.

Vascular tight junction disruption and angiogenesis in spontaneously hypertensive rat with neuroinflammatory white matter injury

Vascular cognitive impairment is a major cause of dementia caused by chronic hypoxia, producing progressive damage to white matter (WM) secondary to blood-brain barrier (BBB) opening and vascular dysfunction. Tight junction proteins (TJPs), which maintain BBB integrity, are lost in acute ischemia. Although angiogenesis is critical for neurovascular remodeling, less is known about its role in chronic hypoxia. To study the impact of TJP degradation and angiogenesis during pathological progression of WM damage, we used the spontaneously hypertensive/stroke prone rats with unilateral carotid artery occlusion and Japanese permissive diet to model WM damage. MRI and IgG immunostaining showed regions with BBB damage, which corresponded with decreased endothelial TJPs, claudin-5, occludin, and ZO-1. Affected WM had increased expression of angiogenic factors, Ki67, NG2, VEGF-A, and MMP-3 in vascular endothelial cells and pericytes. To facilitate the study of angiogenesis, we treated rats with minocycline to block BBB disruption, reduce WM lesion size, and extend survival. Minocycline-treated rats showed increased VEGF-A protein, TJP formation, and oligodendrocyte proliferation. We propose that chronic hypoxia disrupts TJPs, increasing vascular permeability, and initiating angiogenesis in WM. Minocycline facilitated WM repair by reducing BBB damage and enhancing expression of TJPs and angiogenesis, ultimately preserving oligodendrocytes.

Nrdp1 Increases Ischemia Induced Primary Rat Cerebral Cortical Neurons and Pheochromocytoma Cells Apoptosis Via Downregulation of HIF-1α Protein

Neuregulin receptor degradation protein-1 (Nrdp1) is an E3 ubiquitin ligase that targets proteins for degradation and regulates cell growth, apoptosis and oxidative stress in various cell types. We have previously shown that Nrdp1 is implicated in ischemic cardiomyocyte death. In this study, we investigated the change of Nrdp1 expression in ischemic neurons and its role in ischemic neuronal injury. Primary rat cerebral cortical neurons and pheochromocytoma (PC12) cells were infected with adenoviral constructs expressing Nrdp1 gene or its siRNA before exposing to oxygen-glucose deprivation (OGD) treatment. Our data showed that Nrdp1 was upregulated in ischemic brain tissue 3 h after middle cerebral artery occlusion (MCAO) and in OGD-treated neurons. Of note, Nrdp1 overexpression by Ad-Nrdp1 enhanced OGD-induced neuron apoptosis, while knockdown of Nrdp1 with siRNA attenuated this effect, implicating a role of Nrdp1 in ischemic neuron injury. Moreover, Nrdp1 upregulation is accompanied by increased protein ubiquitylation and decreased protein levels of ubiquitin-specific protease 8 (USP8) in OGD-treated neurons, which led to a suppressed interaction between USP8 and HIF-1α and subsequently a reduction in HIF-1α protein accumulation in neurons under OGD conditions. In conclusion, our data support an important role of Nrdp1 upregulation in ischemic neuronal death, and suppressing the interaction between USP8 and HIF-1α and consequently the hypoxic adaptive response of neurons may account for this detrimental effect.