NMDA-Type Glutamate Receptor Activation Promotes Vascular Remodeling and Pulmonary Arterial Hypertension

β-catenin mediates monocrotaline-induced pulmonary hypertension via glycolysis in rats

BACKGROUND

Metabolic abnormalities and immune inflammation are deeply involved in pulmonary vascular remodelling and the development of pulmonary hypertension (PH). However, the regulatory mechanisms of glycolysis in macrophages are still elusive. Cumulative evidence indicates that β-catenin plays a crucial role in metabolic reprogramming. This study aimed to investigate the effect of β-catenin on macrophage glycolysis in PH.

METHODS

LPS-induced BMDMs were generated via in vitro experiments. A monocrotaline (MCT)-induced PH rat model was established, and the β-catenin inhibitor XAV939 was administered in vivo. The role of β-catenin in glycolysis was analysed. The degree of pulmonary vascular remodelling was measured.

RESULTS

β-catenin was significantly increased in both in vitro and in vivo models. In LPS-induced BMDMs, β-catenin increased the levels of hexokinase 2 (HK2), phosphofructokinase (PFK), M2-pyruvate kinase (PKM2), lactate dehydrogenase (LDH), and lactate (LA) and the expression of inflammatory cytokines and promoted PASMC proliferation and migration in vitro. XAV939 decreased the level of glycolysis and downregulated the expression of inflammatory cytokines in vivo. MCT promoted pulmonary arterial structural remodelling and right ventricular hypertrophy, and XAV939 alleviated these changes.

CONCLUSIONS

Our findings suggest that β-catenin is involved in the development of PH by promoting glycolysis and the inflammatory response in macrophages. Inhibition of β-catenin could improve the progression of PH.

Unveiling the metabolic landscape of pulmonary hypertension: insights from metabolomics

Pulmonary hypertension (PH) is regarded as cardiovascular disease with an extremely poor prognosis, primarily due to irreversible vascular remodeling. Despite decades of research progress, the absence of definitive curative therapies remains a critical challenge, leading to high mortality rates. Recent studies have shown that serious metabolic disorders generally exist in PH animal models and patients of PH, which may be the cause or results of the disease. It is imperative for future research to identify critical biomarkers of metabolic dysfunction in PH pathophysiology and to uncover metabolic targets that could enhance diagnostic and therapeutic strategies. Metabolomics offers a powerful tool for the comprehensive qualitative and quantitative analysis of metabolites within specific organisms or cells. On the basis of the findings of the metabolomics research on PH, this review summarizes the latest research progress on metabolic pathways involved in processes such as amino acid metabolism, carbohydrate metabolism, lipid metabolism, and nucleotide metabolism in the context of PH.

The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review

Functional decline of physiological systems during ageing leads to age-related diseases. Dietary glycine increases healthy lifespan in model organisms and might decrease inflammation in humans, suggesting its geroprotective potential. This review summarises the evidence of glycine administration on the characteristics of eleven physiological systems in adult humans. Databases were searched using key search terms: 'glycine', 'adult', 'supplementation'/ 'administration'/ 'ingestion'/ 'treatment'. Glycine was administered to healthy and diseased populations (18 and 34 studies) for up to 14 days and 4 months, respectively. The nervous system demonstrated the most positive effects, including improved psychiatric symptoms from longer-term glycine administration in psychiatric populations. While longer-term glycine administration improved sleep in healthy populations, these studies had small sample sizes with a high risk of bias. Larger and long-term studies with more robust study designs in healthy populations to examine the effects of glycine administration on preventing, delaying or reversing the ageing process are warranted.

NMDARs activation regulates endothelial ferroptosis via the PP2A-AMPK-HMGB1 axis

N-methyl-D-aspartate receptors (NMDARs) are ligand-gated, voltage-dependent channels of the ionotropic glutamate receptor family. The present study explored whether NMDAR activation induced ferroptosis in vascular endothelial cells and its complicated mechanisms in vivo and in vitro. Various detection approaches were used to determine the ferroptosis-related cellular iron content, lipid reactive oxygen species (LOS), siRNA molecules, RNA-sequence, MDA, GSH, and western blotting. The AMPK activator Acadesine (AICAR), HMGB1 inhibitor glycyrrhizin (GLY), PP2A inhibitor LB-100, and NMDAR inhibitor MK801 were used to investigate the involved in vivo and in vitro pathways. The activation of NMDAR with L-glutamic acid (GLU) or NMDA significantly promoted cellular ferroptosis, iron content, MDA, and the PTGS2 expression, while decreasing GPX4 expression and GSH concentration in human umbilical vein endothelial cells (HUVECs), which was reversed by ferroptosis inhibitors Ferrostatin-1(Fer-1), Liproxstatin-1 (Lip-1), or Deferoxamine (DFO). RNA-seq revealed that ferroptosis and SLC7A11 participate in NMDA or GLU-mediated NMDAR activation. The PP2A-AMPK-HMGB1 pathway was majorly associated with NMDAR activation-induced ferroptosis, validated using the PP2A inhibitor LB-100, AMPK activator AICAR, or HMGB1 siRNA. The role of NMDAR in ferroptosis was validated in HUVECs induced with the ferroptosis activator errasin or RSL3 and counteracted by the NMDAR inhibitor MK-801. The in vivo results showed that NMDA- or GLU-induced ferroptosis and LOS production was reversed by MK-801, LB-100, AICAR, MK-801, and GLY, confirming that the PP2A-AMPK-HMGB1 pathway is involved in NMDAR activation-induced vascular endothelium ferroptosis. In conclusion, the present study demonstrated a novel role of NMDAR in endothelial cell injury by regulating ferroptosis via the PP2A-AMPK-HMGB1 pathway.

TIP60 mediates stress-induced hypertension via promoting glutamatedmPFC-to-vCA1 release

Hypertension is well-known to be influenced by genetic and environmental factors. Managing stress is one of the non-pharmacologic approaches to treating hypertension. It is, therefore, imperative to unravel the molecular mechanism by which stress conditions influence hypertension. In this study, TIP60 expressions in human blood samples and cell lines, glutamatedmPFC-to-vCA1 release, and receptor expressions in the Stress-induced hypertension mice were determined using western blotting, CSF (obtained by microdialysis), and ELISA. The study reports increased protein expressions of TIP60 in the peripheral blood of hypertensive patients and in cell lines representing hypertension. In Chronic restraint stress (CRS) conditions TIP60 expression and vCA1 glutamate release were found to be up-regulated, with high SBP and DSP indicating hypertension was induced. After electrical stimulation at the dmPFC, release of glutamate in the vCA1 increased, indicating that activity within the dmPFC drives the release of glutamate in the vCA1, which was blocked by injecting MG149 (a TIP60 inhibitor) into dmPFC. To further determine whether TIP60 was involved in glutamate release and eventually results in hypertension, MG149 was also injected i.p. alongside CRS modeling. The increased glutamate release, NR2B, and IL-18 expressions as well as the CRS-induced hypertension was therefore reversed by chronic application with MG149. Altogether, these results suggest that TIP60 influences the glutamatedmPFC-to-vCA1 release and receptor expressions. This study, therefore, proposes that stressful condition induces increased expression of TIP60 which lead to the transcription of genes that result in conditions that favors glutamate release and receptor expressions hence triggering hypertension.

NMDA Receptor Modulation in COVID-19-Associated Acute Respiratory Syndrome in both In Silico and In Vitro Approach

The normal function of the N-methyl D-aspartate receptors (NMDAR) in human lungs depends on precisely regulated synaptic glutamate levels. Pathophysiology of the lungs is brought on by the changes in homeostasis of glutamate in the synapsis that leads to abnormal NMDAR activity. Severe acute respiratory syndrome (SARS) primarily results in lung infections, particularly lung muscle stiffening, and NMDA receptor potentiation may increase calcium ion influx and support downstream signaling mechanisms. Hence, NMDAR modulators that depend on glutamate levels could be therapeutically useful medications with fewer unintended side effects. A compound called THP (tetrahydropalmatine) that amplifies Ca2+ influx and potentiates NMDA receptors has been identified in the current study. In asthmatic human airway smooth muscle (HASM) cells, THP regulates the NMDA receptor and helps in asthmatic ASM contraction, and the pharmacological stimulation of ASM depends on both brain and respiratory NMDA receptors. Glutamate potency is altered by this substance without any voltage-dependent side effects. Additionally, a GGPP (geranylgeranyl pyrophosphate)-dependent mechanism of THP reduced the production of pro-inflammatory cytokines in ASM. THP is distinctive in terms of its chemical makeup, functioning, and agonist concentration-dependent and allosteric modulatory activity. To treat COVID-19-related SARS, THP, or any future-related compounds will make good drug-like molecule candidates.

The role of N-methyl-D-aspartate glutamate receptors in Alzheimer's disease: From pathophysiology to therapeutic approaches

N-Methyl-D-aspartate glutamate receptors (NMDARs) are involved in multiple physiopathological processes, including synaptic plasticity, neuronal network activities, excitotoxic events, and cognitive impairment. Abnormalities in NMDARs can initiate a cascade of pathological events, notably in Alzheimer's disease (AD) and even other neuropsychiatric disorders. The subunit composition of NMDARs is plastic, giving rise to a diverse array of receptor subtypes. While they are primarily found in neurons, NMDAR complexes, comprising both traditional and atypical subunits, are also present in non-neuronal cells, influencing the functions of various peripheral tissues. Furthermore, protein-protein interactions within NMDAR complexes has been linked with Aβ accumulation, tau phosphorylation, neuroinflammation, and mitochondrial dysfunction, all of which potentially served as an obligatory relay of cognitive impairment. Nonetheless, the precise mechanistic link remains to be fully elucidated. In this review, we provided an in-depth analysis of the structure and function of NMDAR, investigated their interactions with various pathogenic proteins, discussed the current landscape of NMDAR-based therapeutics, and highlighted the remaining challenges during drug development.

FUT8-Mediated Core Fucosylation Promotes the Pulmonary Vascular Remodeling in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive cardiopulmonary disease with unclear underlying molecular mechanisms and limited therapeutic options. This study aimed to explore the role of core fucosylation and the only glycosyltransferase FUT8 in PAH. We observed increased core fucosylation in a monocrotaline (MCT)-induced PAH rat model and isolated rat pulmonary artery smooth muscle cells (PASMCs) treated with platelet-derived growth factor-BB (PDGF-BB). We found that 2-fluorofucose (2FF), a drug used to inhibit core fucosylation, improved hemodynamics and pulmonary vascular remodeling in MCT-induced PAH rats. In vitro, 2FF effectively restrains the proliferation, migration, and phenotypic switching of PASMCs and promotes apoptosis. Compared with controls, serum FUT8 concentration in PAH patients and MCT-induced rats was significantly elevated. FUT8 expression appeared increased in the lung tissues of PAH rats, and the co-localization of FUT8 with α-SMA was also observed. SiRNA was used to knockdown FUT8 in PASMCs (siFUT8). After effectively silencing FUT8 expression, phenotypic changes induced in PASMCs by PDGF-BB stimulation were alleviated. FUT8 activated the AKT pathway, while the admission of AKT activator SC79 could partially counteract the negative effect of siFUT8 on the proliferation, apoptotic resistance, and phenotypic switching of PASMCs, which may be involved in the core fucosylation of vascular endothelial growth factor receptor (VEGFR). Our research confirmed the critical role of FUT8 and its mediated core fucosylation in pulmonary vascular remodeling in PAH, providing a potential novel therapeutic target for PAH.

Human neutrophils communicate remotely via calcium-dependent glutamate-induced glutamate release

Neutrophils are white blood cells that are critical to acute inflammatory and adaptive immune responses. Their swarming-pattern behavior is controlled by multiple cellular cascades involving calcium-dependent release of various signaling molecules. Previous studies have reported that neutrophils express glutamate receptors and can release glutamate but evidence of direct neutrophil-neutrophil communication has been elusive. Here, we hold semi-suspended cultured human neutrophils in patch-clamp whole-cell mode to find that calcium mobilization induced by stimulating one neutrophil can trigger an N-methyl-D-aspartate (NMDA) receptor-driven membrane current and calcium signal in neighboring neutrophils. We employ an enzymatic-based imaging assay to image, in real time, glutamate release from neutrophils induced by glutamate released from their neighbors. These observations provide direct evidence for a positive-feedback inter-neutrophil communication that could contribute to mechanisms regulating communal neutrophil behavior.

Spatial and temporal resolution of metabolic dysregulation in the Sugen hypoxia model of pulmonary hypertension

Although PAH is partially attributed to disordered metabolism, previous human studies have mostly examined circulating metabolites at a single time point, potentially overlooking crucial disease biology. Current knowledge gaps include an understanding of temporal changes that occur within and across relevant tissues, and whether observed metabolic changes might contribute to disease pathobiology. We utilized targeted tissue metabolomics in the Sugen hypoxia (SuHx) rodent model to investigate tissue-specific metabolic relationships with pulmonary hypertensive features over time using regression modeling and time-series analysis. Our hypotheses were that some metabolic changes would precede phenotypic changes, and that examining metabolic interactions across heart, lung, and liver tissues would yield insight into interconnected metabolic mechanisms. To support the relevance of our findings, we sought to establish links between SuHx tissue metabolomics and human PAH -omics data using bioinformatic predictions. Metabolic differences between and within tissue types were evident by Day 7 postinduction, demonstrating distinct tissue-specific metabolism in experimental pulmonary hypertension. Various metabolites demonstrated significant tissue-specific associations with hemodynamics and RV remodeling. Individual metabolite profiles were dynamic, and some metabolic shifts temporally preceded the emergence of overt pulmonary hypertension and RV remodeling. Metabolic interactions were observed such that abundance of several liver metabolites modulated lung and RV metabolite-phenotype relationships. Taken all together, regression analyses, pathway analyses and time-series analyses implicated aspartate and glutamate signaling and transport, glycine homeostasis, lung nucleotide abundance, and oxidative stress as relevant to early PAH pathobiology. These findings offer valuable insights into potential targets for early intervention in PAH.

Mechanism of new optimized Sheng-Mai-San Formula to regulate cardiomyocyte apoptosis through NMDAR pathway

Background and objectives

Ischemic heart failure (HF) has become a disease that seriously endangers people's life and health. As a herbal formula widely used in clinical practice, new optimized Sheng-Mai-San (NO-SMS) has been shown to be significantly effective in improving cardiac function, increasing exercise tolerance, and slowing the progression of myocardial fibrosis in heart failure patients in multi-center clinical studies in various regions of China. In our previous pharmacodynamic and toxicological studies, we found that a medium-dose formulation (8.1 g of raw drug/kg) was the most effective in the treatment of heart failure, but its mechanism of action is still being investigated. The present study is exploring its relationship with cardiomyocyte apoptosis.

Materials and methods

We investigated and verified this through two parts of experiments, in vivo and in vitro. Firstly, we prepared male SD rats with heart failure models by ligating the left anterior descending branch of the coronary artery (EF ≤ 50%), which were treated with NO-SMS Formula (8.1 g of raw drug/kg/d), Ifenprodil (5.4 mg/kg/d) or Enalapril (0.9 mg/kg/d) prepared suspensions by gavage for 4 weeks. The cardiac and structural changes were evaluated by echocardiography, H&E, and MASSON staining. The apoptosis of cardiomyocytes in each group was detected by Western blot, qRT-PCR, and ELISA. In vitro cell experiments include H9c2 cardiomyocyte injury induced by H₂O₂ and NMDA respectively, and the groups were incubated with NO-SMS and Ifenprodil-containing serum for 24 h. Apoptosis was detected by Annexin V-FITC/PI double-staining method, and the rest of the assays were consistent with the in vivo experiments.

Results

Compared with the model group, the NO-SMS formula group and the Ifenprodil group could significantly improve cardiac function, delay myocardial fibrosis, reduce the expression of pro-apoptotic proteins, mRNA, and the concentration levels of Ca²⁺ and ROS in heart failure rats and H9c2 cardiomyocytes with H₂O₂ and NMDA-induced injury, which could significantly reduce the apoptosis rate of damaged cardiomyocytes and effectively inhibit the apoptosis of cardiomyocytes.

Conclusion

NO-SMS Formula improved cardiac function, inhibited ventricular remodeling and cardiomyocyte apoptosis in HF rats, and its mechanism may be related to the regulation of the NMDAR signaling pathway, inhibition of large intracellular Ca²⁺ inward flow, and ROS production in cardiomyocytes.

The Emerging Role of N-Methyl-D-Aspartate (NMDA) Receptors in the Cardiovascular System: Physiological Implications, Pathological Consequences, and Therapeutic Perspectives

N-methyl-D-aspartate receptors (NMDARs) are ligand-gated ion channels that are activated by the neurotransmitter glutamate, mediate the slow component of excitatory neurotransmission in the central nervous system (CNS), and induce long-term changes in synaptic plasticity. NMDARs are non-selective cation channels that allow the influx of extracellular Na⁺ and Ca²⁺ and control cellular activity via both membrane depolarization and an increase in intracellular Ca²⁺ concentration. The distribution, structure, and role of neuronal NMDARs have been extensively investigated and it is now known that they also regulate crucial functions in the non-neuronal cellular component of the CNS, i.e., astrocytes and cerebrovascular endothelial cells. In addition, NMDARs are expressed in multiple peripheral organs, including heart and systemic and pulmonary circulations. Herein, we survey the most recent information available regarding the distribution and function of NMDARs within the cardiovascular system. We describe the involvement of NMDARs in the modulation of heart rate and cardiac rhythm, in the regulation of arterial blood pressure, in the regulation of cerebral blood flow, and in the blood-brain barrier (BBB) permeability. In parallel, we describe how enhanced NMDAR activity could promote ventricular arrhythmias, heart failure, pulmonary artery hypertension (PAH), and BBB dysfunction. Targeting NMDARs could represent an unexpected pharmacological strategy to reduce the growing burden of several life-threatening cardiovascular disorders.

Mitochondrial Dysfunction in Pulmonary Hypertension

Pulmonary hypertension (PH) is a multi-etiological condition with a similar hemodynamic clinical sign and end result of right heart failure. Although its causes vary, a similar link across all the classifications is the presence of mitochondrial dysfunction. Mitochondria, as the powerhouse of the cells, hold a number of vital roles in maintaining normal cellular homeostasis, including the pulmonary vascular cells. As such, any disturbance in the normal functions of mitochondria could lead to major pathological consequences. The Warburg effect has been established as a major finding in PH conditions, but other mitochondria-related metabolic and oxidative stress factors have also been reported, making important contributions to the progression of pulmonary vascular remodeling that is commonly found in PH pathophysiology. In this review, we will discuss the role of the mitochondria in maintaining a normal vasculature, how it could be altered during pulmonary vascular remodeling, and the therapeutic options available that can treat its dysfunction.

Acquired disorders of mitochondrial metabolism and dynamics in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is an orphan disease of the cardiopulmonary unit that reflects an obstructive pulmonary vasculopathy and presents with hypertrophy, inflammation, fibrosis, and ultimately failure of the right ventricle (RVF). Despite treatment using pulmonary hypertension (PH)-targeted therapies, persistent functional impairment reduces the quality of life for people with PAH and death from RVF occurs in approximately 40% of patients within 5 years of diagnosis. PH-targeted therapeutics are primarily vasodilators and none, alone or in combination, are curative. This highlights a need to therapeutically explore molecular targets in other pathways that are involved in the pathogenesis of PAH. Several candidate pathways in PAH involve acquired mitochondrial dysfunction. These mitochondrial disorders include: 1) a shift in metabolism related to increased expression of pyruvate dehydrogenase kinase and pyruvate kinase, which together increase uncoupled glycolysis (Warburg metabolism); 2) disruption of oxygen-sensing related to increased expression of hypoxia-inducible factor 1α, resulting in a state of pseudohypoxia; 3) altered mitochondrial calcium homeostasis related to impaired function of the mitochondrial calcium uniporter complex, which elevates cytosolic calcium and reduces intramitochondrial calcium; and 4) abnormal mitochondrial dynamics related to increased expression of dynamin-related protein 1 and its binding partners, such as mitochondrial dynamics proteins of 49 kDa and 51 kDa, and depressed expression of mitofusin 2, resulting in increased mitotic fission. These acquired mitochondrial abnormalities increase proliferation and impair apoptosis in most pulmonary vascular cells (including endothelial cells, smooth muscle cells and fibroblasts). In the RV, Warburg metabolism and induction of glutaminolysis impairs bioenergetics and promotes hypokinesis, hypertrophy, and fibrosis. This review will explore our current knowledge of the causes and consequences of disordered mitochondrial function in PAH.

Lasso algorithm and support vector machine strategy to screen pulmonary arterial hypertension gene diagnostic markers

BACKGROUND

This study employs machine learning strategy algorithms to screen the optimal gene signature of pulmonary arterial hypertension (PAH) under big data in the medical field.

METHODS

The public database Gene Expression Omnibus (GEO) was used to analyze datasets of 32 normal controls and 37 PAH disease samples. The enrichment analysis was performed after selecting the differentially expressed genes. Two machine learning methods, the least absolute shrinkage and selection operator (LASSO) and support vector machine (SVM), were used to identify the candidate genes. The external validation data set further tests the expression level and diagnostic value of candidate diagnostic genes. The diagnostic effectiveness was evaluated by obtaining the receiver operating characteristic curve (ROC). The convolution tool CIBERSORT was used to estimate the composition pattern of the immune cell subtypes and to perform correlation analysis based on the combined training dataset.

RESULTS

A total of 564 differentially expressed genes (DEGs) were screened in normal control and pulmonary hypertension samples. The enrichment analysis results were found to be closely related to cardiovascular diseases, inflammatory diseases, and immune-related pathways. The LASSO and SVM algorithms in machine learning used 5 × cross-validation to identify 9 and 7 characteristic genes. The two machine learning algorithms shared Caldesmon 1 (CALD1) and Solute Carrier Family 7 Member 11 (SLC7A11) as genetic signals highly correlated with PAH. The results showed that the area under ROC (AUC) of the specific characteristic diagnostic genes were CALD1 (AUC = 0.924) and SLC7A11 (AUC = 0.962), indicating that the two diagnostic genes have high diagnostic value.

CONCLUSION

CALD1 and SLC7A11 can be used as diagnostic markers of PAH to obtain new insights for the further study of the immune mechanism involved in PAH.

Comprehensive analysis of long noncoding RNAs and lncRNA-mRNA networks in snakehead (Channa argus) response to Nocardia seriolae infection

Evidence has been demonstrated that lncRNAs are involved in a variety of immune responses in vertebrate. It has been demonstrated that immune-related lncRNAs play vital functions in immune regulation against infections in teleost. Nocardia seriolae, as one of the Gram-positive bacteria, can cause chronic systemic granulomatous disease for snakehead (Channa argus). However, how lncRNAs function in the immune regulation process once snakehead was infected with N. seriolae infection has not been studied so far. Accordingly, transcription landscapes of lncRNAs and mRNAs in snakehead were investigated. A total of 1,991 lncRNA were obtained. Totally, we predicted 57,584 co-expression and 16,047 co-location lncRNA-mRNA pairs. To further analyze the potential function of these lncRNAs, GO enrichment analysis and KEGG signal pathways were performed on the target mRNAs of these differently expressed lncRNAs, suggesting that lncRNAs may play essential roles in modulating mRNA expression levels, and subsequently trigger downstream immune signaling pathways to regulate the immune response in snakehead. In addition, 9 DEmRNA and 3 lncRNAs were randomly selected for qRT-PCR analyzed, which confirmed the accuracy of transcriptome data. These results can provide novel knowledge about lncRNAs in immune responses process in snakehead, and can serve as important resources for further investigating the roles of lncRNAs during pathogen infections in teleost.

Mitochondrial dysfunction in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by the increased pulmonary vascular resistance due to pulmonary vasoconstriction and vascular remodeling. PAH has high disability, high mortality and poor prognosis, which is becoming a more common global health issue. There is currently no drug that can permanently cure PAH patients. The pathogenesis of PAH is still not fully elucidated. However, the role of metabolic theory in the pathogenesis of PAH is becoming clearer, especially mitochondrial metabolism. With the deepening of mitochondrial researches in recent years, more and more studies have shown that the occurrence and development of PAH are closely related to mitochondrial dysfunction, including the tricarboxylic acid cycle, redox homeostasis, enhanced glycolysis, and increased reactive oxygen species production, calcium dysregulation, mitophagy, etc. This review will further elucidate the relationship between mitochondrial metabolism and pulmonary vasoconstriction and pulmonary vascular remodeling. It might be possible to explore more comprehensive and specific treatment strategies for PAH by understanding these mitochondrial metabolic mechanisms.

Hypertension risk is associated with elevated concentrations of rare earth elements in serum

BACKGROUND

Hypertension is a major contributor to cardiovascular morbidity and mortality, affecting over 17.1 million individuals worldwide. Environmental exposure such as toxic trace elements could be risk factors for hypertension, but the associations of toxic metal exposure with hypertension are not well understood.

METHODS

We recruited 400 volunteers consisting of 200 patients with hypertension (cases) and 200 healthy individuals without hypertension (controls). In the case or control group, half of the subjects came from the rare earth mining (REM) areas and the other half from non-REM areas. Serum levels of 8 rare earth elements (REEs) and 13 non-REEs were determined.

RESULTS

The concentrations of Ce and La were significant higher in the cases than in the controls in all comparisons. Serum concentrations of Mg, Mn, Dy, Ce and La were positively correlated with blood pressure, while those of concentrations K and Se were negatively correlated with blood pressure (p < 0.05). Compared with the lowest quartiles, participants in the highest quartiles of Sm, Gd, Dy, Yb, La and Ce had a 6.01-fold (95 % CI: 2.28, 15.8), 3.29-fold (95 % CI: 1.18, 9.16), 4.07-fold (95 % CI: 1.51,10.9), 7.83-fold (95 % CI: 2.78, 22.4), 20.00-fold (95 % CI: 5.48-72.9) and 6.13-fold (95 % CI: 2.13-17.6) increase in the probability of having hypertension respectively. Among all the detected metals, the univariate odds ratios (UORs) and adjusted odds ratios (AORs) of hypertension for highest vs. lowest quartile serum concentrations of Sm, Gd, Dy, Yb, La and Ce were significantly > 1 (p < 0.05), with the positive dose-response relationships observed between their serum levels and ORs associated with hypertension risk.

CONCLUSIONS

Collectively, there appears to be a positive correlation between hypertension and environmental exposure to REEs, especially La and Ce. Further studies are warranted to investigate the underlying mechanisms responsible for the risk.

Increased plasma glutamate in non-smokers with vasospastic angina pectoris is associated with plasma cystine and antioxidant capacity

Objectives. Endothelial dysfunction caused by oxidative stress plays an important role in the development of vasospastic angina pectoris (VSAP). Glutamate causes endothelial dysfunction by generating oxidative stress, and it inhibits cystine import into endothelial cells via the cystine/glutamate antiporter (X_C^-), which leads to depletion of antioxidant glutathione. However, whether glutamate and cystine are implicated in the pathogenesis of VSAP remains unclear. We investigated plasma glutamate and cystine levels, oxidative stress markers and antioxidant capacity in non-smoker patients with VSAP to determine whether glutamate and cystine are associated with the development of VSAP. We assessed 49 non-smokers assigned to groups with (n = 27) and without (n = 22) VSAP, and also measured plasma glutamate, cystine, nitrotyrosine, reactive oxygen metabolites and biological antioxidant potential. Results. Plasma glutamate and cystine values were significantly higher in the group with, than without VSAP (59.8 ± 25.7 vs. 43.5 ± 18.7 µmol/L, p = .016 and 35.3 ± 14.2 vs. 25.2 ± 9.1 µmol/L, p = .0056, respectively). Plasma glutamate and cystine values were significantly and positively associated (r = 0.32, p = .027). Levels of the oxidative stress markers nitrotyrosine and reactive oxygen metabolites, and biological antioxidant potential of as a measure of antioxidant capacity, did not significantly differ between the two groups. However, glutamate and biological antioxidant potential values were significantly and negatively associated (r = -0.3, p = .036). Conclusion. Plasma glutamate levels were increased in patients with VSAP who did not smoke, and they were positively associated with plasma cystine and negatively associated with the biological antioxidant potential levels.

Metabolic reprogramming: A novel metabolic model for pulmonary hypertension

Pulmonary arterial hypertension, or PAH, is a condition that is characterized by pulmonary artery pressures above 20 mmHg (at rest). In the treatment of PAH, the pulmonary vascular system is regulated to ensure a diastolic and contraction balance; nevertheless, this treatment does not prevent or reverse pulmonary vascular remodeling and still causes pulmonary hypertension to progress. According to Warburg, the link between metabolism and proliferation in PAH is similar to that of cancer, with a common aerobic glycolytic phenotype. By activating HIF, aerobic glycolysis is enhanced and cell proliferation is triggered. Aside from glutamine metabolism, the Randle cycle is also present in PAH. Enhanced glutamine metabolism replenishes carbon intermediates used by glycolysis and provides energy to over-proliferating and anti-apoptotic pulmonary vascular cells. By activating the Randle cycle, aerobic oxidation is enhanced, ATP is increased, and myocardial injury is reduced. PAH is predisposed by epigenetic dysregulation of DNA methylation, histone acetylation, and microRNA. This article discusses the abnormal metabolism of PAH and how metabolic therapy can be used to combat remodeling.

Vascular peroxidase 1 promotes phenotypic transformation of pulmonary artery smooth muscle cells via ERK pathway in hypoxia-induced pulmonary hypertensive rats

AIMS

Vascular peroxidase 1 (VPO1) plays an important role in mediation of vascular remodeling with pulmonary arterial hypertension (PAH). This study aims to determine whether VPO1 can promote phenotypic transformation of pulmonary artery smooth muscle cells (PASMCs) and the underlying mechanisms.

MAIN METHODS

Sprague-Dawley (SD) rats were exposed to 10 % O₂ for 21 days to establish the model of vascular remodeling in pulmonary arterial hypertension. PASMCs were incubated with 3 % O₂ for 48 h to induce phenotypic transformation. Western blot was performed to detect the expressions of target proteins. The 5-ethynyl-2'-deoxyuridine (EdU) assay was conducted to measure the proliferation of PASMCs.

KEY FINDINGS

In the rats exposed to hypoxia, there were increases in right ventricular systolic pressure, pulmonary vascular remodeling and phenotypic transformation of PASMCs (the down-regulated contractile proteins of α-smooth muscle actin, smooth muscle 22α while the up-regulated synthetic proteins of osteopontin, cyclinD1), accompanied by up-regulation of VPO1, increase of hypochlorous acid (HOCl) production and elevation of the phosphorylation of ERK. In the cultured PASMCs exposed to hypoxia, similar results were achieved but they were reversed by VPO1 small interfering RNA (VPO1 siRNA) or HOCl inhibitor. Replacement of hypoxia with NaOCl could induce PASMCs phenotypic transformation and activate the ERK signaling. Furthermore, ERK inhibitor (PD98059) could also attenuate hypoxia-induced PASMCs phenotypic transformation.

SIGNIFICANCE

VPO1 play a pivotal role in promotion of phenotypic transformation of PASMCs under hypoxic condition through activation of VPO1/HOCl/ERK pathway. It might serve as a potential target for prevention of pulmonary vascular remodeling.

Comprehensive Review on Novel Targets and Emerging Therapeutic Modalities for Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is the progressive increase in mean pulmonary arterial pressure (mPAP) (≥ 20 mmHg at rest). Current treatment strategies include the drugs targeting at nitric oxide pathway, endothelin receptors, prostaglandin receptors, thromboxane receptors and phosphodiesterase inhibitors, which provides the symptomatic relief. Despite of these treatments, the mortality amongst the PAH patients remains high due to non-reversal of the condition. This review primarily covers the introduction of PAH and the current treatments of the disease. This is followed by the newer disease targets expressed in the pathobiology of the disease like Rho Kinase Pathway, Vasoactive Intestinal Peptide Pathway, Receptor Tyrosine Kinases, Serotonin signalling pathway, Voltage-gated potassium (Kv) channel pathway. Newer formulation strategies for targeting at these specific receptors were covered and includes nano formulations like liposomes, Micelles, Polymeric Nanoparticles, Solid Lipid Nanoparticles (SLN), Bioresorbable stents, NONOates, Cell-Based Therapies, miRNA therapy for PAH. Novel targets were identified for their role in the pathogenesis of the PAH and needs to be targeted with new molecules or existing molecules effectively. Nanosystems have shown their potential as alternative carriers on the virtue of their better performance than traditional drug delivery systems.

Important Functions and Molecular Mechanisms of Mitochondrial Redox Signaling in Pulmonary Hypertension

Mitochondria are important organelles that act as a primary site to produce reactive oxygen species (ROS). Additionally, mitochondria play a pivotal role in the regulation of Ca²⁺ signaling, fatty acid oxidation, and ketone synthesis. Dysfunction of these signaling molecules leads to the development of pulmonary hypertension (PH), atherosclerosis, and other vascular diseases. Features of PH include vasoconstriction and pulmonary artery (PA) remodeling, which can result from abnormal proliferation, apoptosis, and migration of PA smooth muscle cells (PASMCs). These responses are mediated by increased Rieske iron–sulfur protein (RISP)-dependent mitochondrial ROS production and increased mitochondrial Ca²⁺ levels. Mitochondrial ROS and Ca²⁺ can both synergistically activate nuclear factor κB (NF-κB) to trigger inflammatory responses leading to PH, right ventricular failure, and death. Evidence suggests that increased mitochondrial ROS and Ca²⁺ signaling leads to abnormal synthesis of ketones, which play a critical role in the development of PH. In this review, we discuss some of the recent findings on the important interactive role and molecular mechanisms of mitochondrial ROS and Ca²⁺ in the development and progression of PH. We also address the contributions of NF-κB-dependent inflammatory responses and ketone-mediated oxidative stress due to abnormal regulation of mitochondrial ROS and Ca²⁺ signaling in PH.

Signal Transduction during Metabolic and Inflammatory Reprogramming in Pulmonary Vascular Remodeling

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by (mal)adaptive remodeling of the pulmonary vasculature, which is associated with inflammation, fibrosis, thrombosis, and neovascularization. Vascular remodeling in PAH is associated with cellular metabolic and inflammatory reprogramming that induce profound endothelial and smooth muscle cell phenotypic changes. Multiple signaling pathways and regulatory loops act on metabolic and inflammatory mediators which influence cellular behavior and trigger pulmonary vascular remodeling in vivo. This review discusses the role of bioenergetic and inflammatory impairments in PAH development.

Mitochondrial Metabolism, Redox, and Calcium Homeostasis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by elevated pulmonary arterial pressure due to increased pulmonary vascular resistance, secondary to sustained pulmonary vasoconstriction and excessive obliterative pulmonary vascular remodeling. Work over the last decade has led to the identification of a critical role for metabolic reprogramming in the PAH pathogenesis. It is becoming clear that in addition to its role in ATP generation, the mitochondrion is an important organelle that regulates complex and integrative metabolic- and signal transduction pathways. This review focuses on mitochondrial metabolism alterations that occur in deranged pulmonary vessels and the right ventricle, including abnormalities in glycolysis and glucose oxidation, fatty acid oxidation, glutaminolysis, redox homeostasis, as well as iron and calcium metabolism. Further understanding of these mitochondrial metabolic mechanisms could provide viable therapeutic approaches for PAH patients.

Research Progress on Pulmonary Arterial Hypertension and the Role of the Angiotensin Converting Enzyme 2-Angiotensin-(1-7)-Mas Axis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a complex aetiology and high mortality. Functional and structural changes in the small pulmonary arteries lead to elevated pulmonary arterial pressure, resulting in right heart failure. The pathobiology of PAH is not fully understood, and novel treatment targets in PAH are desperately needed. The renin-angiotensin system is critical for maintaining homeostasis of the cardiovascular system. The system consists of the angiotensin converting enzyme (ACE)-angiotensin (Ang) II-angiotensin type 1 receptor (AT₁R) axis and the ACE2-Ang-(1-7)-Mas receptor axis. The former, the ACE-Ang II-AT₁R axis, is involved in vasoconstrictive and hypertensive actions along with cardiac and vascular remodelling. The latter, the ACE2-Ang-(1-7)-Mas axis, generally mediates counterbalancing effects against those mediated by the ACE-Ang II-AT₁R axis. Based on established functions, the ACE2-Ang-(1-7)-Mas axis may represent a novel target for the treatment of PAH. This review focuses on recent advances in pulmonary circulation science and the role of the ACE2-Ang-(1-7)-Mas axis in PAH.

Urinary metabotype of severe asthma evidences decreased carnitine metabolism independent of oral corticosteroid treatment in the U-BIOPRED study

INTRODUCTION

Asthma is a heterogeneous disease with poorly defined phenotypes. Severe asthmatics often receive multiple treatments including oral corticosteroids (OCS). Treatment may modify the observed metabotype, rendering it challenging to investigate underlying disease mechanisms. Here, we aimed to identify dysregulated metabolic processes in relation to asthma severity and medication.

METHODS

Baseline urine was collected prospectively from healthy participants (n=100), mild-to-moderate asthmatics (n=87) and severe asthmatics (n=418) in the cross-sectional U-BIOPRED cohort; 12-18-month longitudinal samples were collected from severe asthmatics (n=305). Metabolomics data were acquired using high-resolution mass spectrometry and analysed using univariate and multivariate methods.

RESULTS

Ninety metabolites were identified, with 40 significantly altered (p<0.05, FDR<0.05) in severe asthma and 23 by OCS use. Multivariate modelling showed that observed metabotypes in healthy participants and mild-to-moderate asthmatics differed significantly from severe asthmatics (p=2.6×10^-20), OCS-treated asthmatics differed significantly from non-treated (p=9.5×10^-4), and longitudinal metabotypes demonstrated temporal stability. Carnitine levels evidenced the strongest OCS-independent decrease in severe asthma. Reduced carnitine levels were associated with mitochondrial dysfunction via decreases in pathway enrichment scores of fatty acid metabolism and reduced expression of the carnitine transporter SLC22A5 in sputum and bronchial brushings.

CONCLUSIONS

This is the first large-scale study to delineate disease- and OCS-associated metabolic differences in asthma. The widespread associations with different therapies upon the observed metabotypes demonstrate the necessity to evaluate potential modulating effects on a treatment- and metabolite-specific basis. Altered carnitine metabolism is a potentially actionable therapeutic target that is independent of OCS treatment, highlighting the role of mitochondrial dysfunction in severe asthma.

Peripherally active dextromethorphan derivatives lower blood glucose levels by targeting pancreatic islets

Dextromethorphan (DXM) acts as cough suppressant via its central action. Cell-protective effects of this drug have been reported in peripheral tissues, making DXM potentially useful for treatment of several common human diseases, such as type 2 diabetes mellitus (T2DM). Pancreatic islets are among the peripheral tissues that positively respond to DXM, and anti-diabetic effects of DXM were observed in two placebo-controlled, randomized clinical trials in humans with T2DM. Since these effects were associated with central side effects, we here developed chemical derivatives of DXM that pass the blood-brain barrier to a significantly lower extent than the original drug. We show that basic nitrogen-containing residues block central adverse events of DXM without reducing its anti-diabetic effects, including the protection of human pancreatic islets from cell death. These results show how to chemically modify DXM, and possibly other morphinans, as to exclude central side effects, while targeting peripheral tissues, such as pancreatic islets.

Serum metabolites of hypertension among Chinese adolescents aged 12-17 years

The regulatory mechanisms of hypertension in youth are incompletely understood. We aimed to identify potential serum metabolic alterations associated with hypertension in adolescents. A 1:1 age- and sex-matched case-control study including 30 hypertensive adolescents aged 12-17 years and 30 normotensive adolescents for the training set and 14 hypertensive adolescents and 14 normotensive adolescents for the test set was performed, which came from one cross-sectional study in Ningxia, China. Hypertension was defined based on blood pressure (BP) values measured on three different occasions according to the BP reference of Chinese children and adolescents. Untargeted ultra-high-performance liquid tandem chromatography quadrupole time of flight mass spectrometry was used to identify differential metabolites between hypertensive and normotensive adolescents. A total of 77 metabolites in positive mode and 101 in negative mode were identified (VIP > 1.0 and P < 0.05). After adjustment for the false discovery rate, 4 differential metabolites in positive mode and 10 in negative mode were found (Q value < 0.05). The logistic regression model adjusted for body mass index and lipid profile selected four significant metabolites (4-hydroxybutanoic acid, L-serine, acetone, and pterostilbene). The main metabolic pathways of amino acid metabolism, pantothenate and CoA biosynthesis, glyoxylate and dicarboxylate metabolism, fructose and mannose metabolism, and linoleic acid metabolism may contribute to the development of hypertension in Chinese adolescents. Based on the receiver operating characteristic plot, 4-hydroxybutanoic acid, L-serine, acetone, and pterostilbene may preliminarily help distinguish hypertension from normal BP in adolescents, with AUC values of 0.857 in the training set and 0.934 in the test set. The identified metabolites and pathways may foster a better understanding of hypertension pathogenesis in Chinese adolescents.

Emodin inhibits viability, proliferation and promotes apoptosis of hypoxic human pulmonary artery smooth muscle cells via targeting miR-244-5p/DEGS1 axis

OBJECTIVE

This study aimed to determine the effects of emodin on the viability, proliferation and apoptosis of human pulmonary artery smooth muscle cells (PASMCs) under hypoxia and to explore the underling molecular mechanisms.

METHODS

PASMCs were cultured in a hypoxic environment (1% oxygen) and then treated with emodin. Cell viability, proliferation and apoptosis were evaluated using CCK-8 assay, EdU staining assay, western blot and Mito-tracker red CMXRos and Annexin V-FITC apoptosis detection assay. The microRNA (miRNA)/mRNA and protein expression levels were assessed by quantitative real-time PCR and western blotting, respectively. Based on transcriptomics and proteomics were used to identify potential signaling pathways. Luciferase reporter assay was utilized to examine the interaction between miR-244-5p and DEGS1.

RESULTS

Emodin at 40 and 160 µM concentration-dependently suppressed cell viability, proliferation and migration, but enhanced cell apoptosis of PASMCs under hypoxia. Transcriptomic and proteomic analysis revealed that emodin could attenuate the activity of PI3K/Akt signaling in PASMCs under hypoxia. In addition, delta 4-desaturase, sphingolipid 1 (DEGS1) was found to be a direct target of miR-244-5p. Emodin could significantly up-regulated miR-244-5p expression and down-regulated DEGS1 expression in PASMCs under hypoxia. Furthermore, emodin-mediated effects on cell viability, migration, apoptosis and PI3K/Akt signaling activity of PASMCs under hypoxia were significantly attenuated by miR-244-5p knockdown.

CONCLUSIONS

Our results indicated that emodin suppressed cell viability, proliferation and migration, promoted cell apoptosis of PASMCs under hypoxia via modulating miR-244-5p-mediated DEGS1/PI3K/Akt signaling pathway. MiR-244-5p/DEGS1 axis was initially investigated in this current study, which is expected to further the understanding of the etiology of pulmonary arterial hypertension.

NMDAR in bladder smooth muscle is not a pharmacotherapy target for overactive bladder in mice

Overactive bladder (OAB) is a common condition that affects a significant patient population. The N-methyl-D-aspartate receptor (NMDAR) has a role in developing bladder overactivity, pharmacological inhibition of which inhibits bladder overactivity. The common pathogenesis of OAB involves bladder smooth muscle (BSM) overactivity. In this study, a smooth muscle-specific NMDAR knockout (SMNRKO) mouse model was generated. The bladders from SMNRKO mice displayed normal size and weight with an intact bladder wall and well-arranged BSM bundles. Besides, SMNRKO mice had normal voiding patterns and urodynamics and BSM contractility, indicating that NMDAR in BSM was not essential for normal physiological bladder morphology and function. Unexpectedly, cyclophosphamide (CYP)-treated SMNRKO and wild-type (WT) mice had similar pathological changes in the bladder. Furthermore, SMNRKO mice displayed similar altered voiding patterns and urodynamic abnormalities and impaired BSM contractility compared with WT mice after CYP treatment. MK801 partially reversed the pathological bladder morphology and improved bladder dysfunction induced by CYP, but did not cause apparent differences between WT mice and SMNRKO mice, suggesting that NMDAR in BSM was not involved in pathological bladder morphology and function. Moreover, the direct instillation of NMDAR agonists or antagonists into the CYP-induced OAB did not affect bladder urodynamic function, indicating that NMDAR in BSM was not the pharmacotherapy target of MK801 for CYP-induced cystitis. The findings indicated that NMDAR in BSM was not essential for normal physiological or pathological bladder morphology and function, and MK801 improving pathological bladder function was not mediated by an action on NMDAR in BSM.

[Spontaneous fibrinolysis and possibilities of its acceleration in pulmonary embolism]

This review contains the data concerning the mechanisms of spontaneous fibrinolysis in pulmonary vessels and possibilities of its acceleration in pulmonary embolism. The spontaneous fibrinolysis system is known to be sequential and multifactorial, with the interaction of accelerators (t-PA and u-PA) and inhibitors (alpha-2-antiplasmin, PAI-1, TAFI). The fibrinolytic processes take place in case of prevailing reactions of accelerating factors over inhibiting ones. The endothelium of pulmonary vessels possesses pronounced antithrombogenic and profibrinolytic properties, therefore, the processes of fibrinolysis in the pulmonary vascular bed normally occur more intensively than in the vessels of the systemic circulation. The membrane proteins of the endothelium annexins A2 activate plasminogen, whereas thrombomodulin inhibits the activity of PAI-1. The main approaches to increase the fibrinolysis intensity in conditions of pulmonary embolism may be aimed at elevating the activity of fibrinolytic enzymes (enhancing the synthesis of annexins A2, the use of NMDA-receptor antagonists) and suppressing its inhibitors (the use of monoclonal antibodies to alpha-2-antiplasmin, as well as plasminogen activator inhibitor-1 (PAI-1) and thrombin-activatable fibrinolysis inhibitor (TAFI). Promising directions for future research can be the synthesis of a new generation of tissue-type plasminogen activators, and investigations of the possibility of clinical application of antithrombin and thrombomodulin, angiotensin converting enzyme inhibitors and cortisol antagonists. To meet these challenges, it is necessary to develop new models of venous thrombosis and acute pulmonary embolism in different animal species, with the assessment of the changes in the venous haemodynamics and pulmonary microcirculation on the background of administration of a new class of fibrinolytic agents.

Simultaneous Pharmacologic Inhibition of Yes-Associated Protein 1 and Glutaminase 1 via Inhaled Poly(Lactic-co-Glycolic) Acid-Encapsulated Microparticles Improves Pulmonary Hypertension

Background Pulmonary hypertension (PH) is a deadly disease characterized by vascular stiffness and altered cellular metabolism. Current treatments focus on vasodilation and not other root causes of pathogenesis. Previously, it was demonstrated that glutamine metabolism, as catalyzed by GLS1 (glutaminase 1) activity, is mechanoactivated by matrix stiffening and the transcriptional coactivators YAP1 (yes-associated protein 1) and transcriptional coactivator with PDZ-binding motif (TAZ), resulting in pulmonary vascular proliferation and PH. Pharmacologic inhibition of YAP1 (by verteporfin) or glutaminase (by CB-839) improved PH in vivo. However, systemic delivery of these agents, particularly YAP1 inhibitors, may have adverse chronic effects. Furthermore, simultaneous use of pharmacologic blockers may offer additive or synergistic benefits. Therefore, a strategy that delivers these drugs in combination to local lung tissue, thus avoiding systemic toxicity and driving more robust improvement, was investigated. Methods and Results We used poly(lactic-co-glycolic) acid polymer-based microparticles for delivery of verteporfin and CB-839 simultaneously to the lungs of rats suffering from monocrotaline-induced PH. Microparticles released these drugs in a sustained fashion and delivered their payload in the lungs for 7 days. When given orotracheally to the rats weekly for 3 weeks, microparticles carrying this drug combination improved hemodynamic (right ventricular systolic pressure and right ventricle/left ventricle+septum mass ratio), histologic (vascular remodeling), and molecular markers (vascular proliferation and stiffening) of PH. Importantly, only the combination of drug delivery, but neither verteporfin nor CB-839 alone, displayed significant improvement across all indexes of PH. Conclusions Simultaneous, lung-specific, and controlled release of drugs targeting YAP1 and GLS1 improved PH in rats, addressing unmet needs for the treatment of this deadly disease.

N-methyl-d-aspartate receptor hyperfunction contributes to d-serine-mediated renal insufficiency

Glutamate N-methyl-d-aspartate receptor (NMDAR) hyperfunction is known to contribute to acute renal failure due to ischemia-reperfusion and endotoxemia. d-Serine is a coagonist for NMDAR activation, but whether NMDARs play a role in d-serine-mediated nephrotoxicity remains unclear. Here, we demonstrate that NMDAR blockade ameliorated d-serine-induced renal injury. In NMDAR-expressing LLC-PK1 cells, which were used as a proximal tubule model, d-serine but not l-serine induced cytotoxicity in a dose-dependent manner, which was abrogated by the selective NMDAR blockers MK-801 and AP-5. Time-dependent oxidative stress, evidenced by gradually increased superoxide and H2O2 production, was associated with d-serine-mediated cytotoxicity; these reactive oxygen species could be alleviated not only after NMDAR inhibition but also by NADPH oxidase (NOX) inhibition. Activation of protein kinase C (PKC)-δ and PKC-ζ is a downstream signal for NMDAR-mediated NOX activation because PKC inhibition diminishes the NOX activity that is induced by d-serine. Renal injury was further confirmed in male Wistar rats that intraperitoneally received d-serine but not l-serine. Peak changes in glucosuria, proteinuria, and urinary excretion of lactate dehydrogenase and malondialdehyde were found after 24 h of treatment. Persistent tubular damage was observed after 7 days of treatment. Cotreatment with the NMDAR blocker MK-801 for 24 h abolished d-serine-induced functional insufficiency and tubular damage. MK-801 attenuated renal superoxide formation by lowering NOX activity and protein upregulation of NOX4 but not NOX2. These results reveal that NMDAR hyperfunction underlies d-serine-induced renal injury via the effects of NOX4 on triggering oxidative stress.NEW & NOTEWORTHY Ionotropic N-methyl-d-aspartate receptors (NMDARs) are not only present in the nervous system but also expressed in the kidney. Overstimulation of renal NMDARs leads to oxidative stress via the signal pathway of calcium/protein kinase C/NADPH oxidase in d-serine-mediated tubular cell damage. Intervention of NMDAR blockade may prevent acute renal injury caused by d-serine.

Glutaminolysis: A Driver of Vascular and Cardiac Remodeling in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a decimating ailment described by chronic precapillary pulmonary hypertension, an elevated mean pulmonary arterial pressure with a normal pulmonary capillary wedge pressure, and a raised pulmonary vascular resistance resulting in increased right ventricular afterload culminating in heart failure and death. Current PAH treatments regulate the vasodilatory/vasoconstrictory balance of pulmonary vessels. However, these treatment options are unable to stop the progression of, or reverse, an already established disease. Recent studies have advanced a metabolic dysregulation, featuring increased glutamine metabolism, as a mechanism driving PAH progression. Metabolic dysregulation in PAH leads to increased glutaminolysis to produce substrate to meet the high-energy requirement by hyperproliferative and apoptosis-resistant pulmonary vascular cells. This article explores the role of glutamate metabolism in PAH and how it could be targeted as an anti-remodeling therapeutic strategy.

AMPA-Type Glutamate Receptors Associated With Vascular Smooth Muscle Cell Subpopulations in Atherosclerosis and Vascular Injury

Objectives and Aims: Vascular smooth muscle cells (VSMCs) are key constituents of both normal arteries and atherosclerotic plaques. They have an ability to adapt to changes in the local environment by undergoing phenotypic modulation. An improved understanding of the mechanisms that regulate VSMC phenotypic changes may provide insights that suggest new therapeutic targets in treatment of cardiovascular disease (CVD). The amino-acid glutamate has been associated with CVD risk and VSMCs metabolism in experimental models, and glutamate receptors regulate VSMC biology and promote pulmonary vascular remodeling. However, glutamate-signaling in human atherosclerosis has not been explored. Methods and Results: We identified glutamate receptors and glutamate metabolism-related enzymes in VSMCs from human atherosclerotic lesions, as determined by single cell RNA sequencing and microarray analysis. Expression of the receptor subunits glutamate receptor, ionotropic, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA)-type subunit 1 (GRIA1) and 2 (GRIA2) was restricted to cells of mesenchymal origin, primarily VSMCs, as confirmed by immunostaining. In a rat model of arterial injury and repair, changes of GRIA1 and GRIA2 mRNA level were most pronounced at time points associated with VSMC proliferation, migration, and phenotypic modulation. In vitro, human carotid artery SMCs expressed GRIA1, and selective AMPA-type receptor blocking inhibited expression of typical contractile markers and promoted pathways associated with VSMC phenotypic modulation. In our biobank of human carotid endarterectomies, low expression of AMPA-type receptor subunits was associated with higher content of inflammatory cells and a higher frequency of adverse clinical events such as stroke. Conclusion: AMPA-type glutamate receptors are expressed in VSMCs and are associated with phenotypic modulation. Patients suffering from adverse clinical events showed significantly lower mRNA level of GRIA1 and GRIA2 in their atherosclerotic lesions compared to asymptomatic patients. These results warrant further mapping of neurotransmitter signaling in the pathogenesis of human atherosclerosis.

Single-Cell Study of Two Rat Models of Pulmonary Arterial Hypertension Reveals Connections to Human Pathobiology and Drug Repositioning

Rationale: The cellular and molecular landscape and translational value of commonly used models of pulmonary arterial hypertension (PAH) are poorly understood. Single-cell transcriptomics can enhance molecular understanding of preclinical models and facilitate their rational use and interpretation.Objectives: To determine and prioritize dysregulated genes, pathways, and cell types in lungs of PAH rat models to assess relevance to human PAH and identify drug repositioning candidates.Methods: Single-cell RNA sequencing was performed on the lungs of monocrotaline (MCT), Sugen-hypoxia (SuHx), and control rats to identify altered genes and cell types, followed by validation using flow-sorted cells, RNA in situ hybridization, and immunofluorescence. Relevance to human PAH was assessed by histology of lungs from patients and via integration with human PAH genetic loci and known disease genes. Candidate drugs were predicted using Connectivity Map.Measurements and Main Results: Distinct changes in genes and pathways in numerous cell types were identified in SuHx and MCT lungs. Widespread upregulation of NF-κB signaling and downregulation of IFN signaling was observed across cell types. SuHx nonclassical monocytes and MCT conventional dendritic cells showed particularly strong NF-κB pathway activation. Genes altered in SuHx nonclassical monocytes were significantly enriched for PAH-associated genes and genetic variants, and candidate drugs predicted to reverse the changes were identified. An open-access online platform was developed to share single-cell data and drug candidates (http://mergeomics.research.idre.ucla.edu/PVDSingleCell/).Conclusions: Our study revealed the distinct and shared dysregulation of genes and pathways in two commonly used PAH models for the first time at single-cell resolution and demonstrated their relevance to human PAH and utility for drug repositioning.

Functional NMDA receptors are expressed by human pulmonary artery smooth muscle cells

N-methyl-d-aspartate (NMDA) receptors are widely expressed in the central nervous system. However, their presence and function at extraneuronal sites is less well characterized. In the present study, we examined the expression of NMDA receptor subunit mRNA and protein in human pulmonary artery (HPA) by quantitative polymerase chain reaction (PCR), immunohistochemistry and immunoblotting. We demonstrate that both GluN1 and GluN2 subunit mRNAs are expressed in HPA. In addition, GluN1 and GluN2 (A–D) subunit proteins are expressed by human pulmonary artery smooth muscle cells (HPASMCs) in vitro and in vivo. These subunits localize on the surface of HPASMCs and form functional ion channels as evidenced by whole-cell patch-clamp electrophysiology and reduced phenylephrine-induced contractile responsiveness of human pulmonary artery by the NMDA receptor antagonist MK801 under hypoxic condition. HPASMCs also express high levels of serine racemase and vesicular glutamate transporter 1, suggesting a potential source of endogenous agonists for NMDA receptor activation. Our findings show HPASMCs express functional NMDA receptors in line with their effect on pulmonary vasoconstriction, and thereby suggest a novel therapeutic target for pharmacological modulations in settings associated with pulmonary vascular dysfunction.

Dual-Functional MN-08 Attenuated Pulmonary Arterial Hypertension Through Vasodilation and Inhibition of Pulmonary Arterial Remodeling

[Figure: see text].

Activation of N-methyl-D-aspartate receptor regulates insulin sensitivity and lipid metabolism

RATIONALE

Although significant progress has been made in understanding the mechanisms of steatosis and insulin resistance, the physiological functions of regulators in these processes remain largely elusive. Evidence has suggested that the glutamate/N-methyl-D-aspartic acid receptor (NMDAR) axis contributes to acute lung injury, pulmonary arterial hypertension, and diabetes, but the specific metabolic contribution of the glutamate/NMDAR axis is not clear. Here we provide data at the animal, cellular, and molecular levels to support the role of the glutamate/NMDAR axis as a therapeutic target for metabolic syndrome in obesity. Methods: We examined the glutamate level in the obese mouse induced by a high-fat diet (HFD) for 12 weeks. To assess the role of NMDAR in insulin sensitivity and lipid metabolism, we tested the effects of Memantine (an NMDAR antagonist) and NMDA (an NMDAR agonist) on mice fed with HFD or standard chow diet. The in vitros NMDAR roles were analyzed in hepatocytes and potential mechanisms involved in regulating lipid metabolism were investigated. Results: Glutamate was increased in the serum of HFD-treated mice. The NMDAR blockade by Memantine decreased the susceptibility to insulin resistance and hepatic steatosis in obese mice. NMDA treatment for 6 months induced obesity in mice, characterized by hyperglycemia, hyperlipidemia, insulin resistance, and pathological changes in the liver. We provided in vitro evidence demonstrating that NMDAR activation facilitated metabolic syndrome in obesity through promoting lipid accumulation. NMDAR inhibition attenuated lipid accumulation induced by palmitic acid. Mechanistically, NMDAR activation impaired fatty acid oxidation by reducing PPARα phosphorylation and activity. The PPARα activity reduction induced by NMDAR activation was reversibly mediated by ERK1/2 signaling. Conclusion: These findings revealed that targeting NMDAR might be a promising therapeutic strategy for metabolic syndrome in obesity.

Plasma Amino Acid Concentrations at Birth and Patent Ductus Arteriosus in Very and Extremely Preterm Infants

Background: Amino acids are increasingly recognized as bioactive molecules in numerous physiological and pathophysiological pathways. The non-essential amino acid glutamate is vasoactive in the rat ductus arteriosus (DA) and a decrease in its levels within the 1st days of life has been associated with the presence of patent DA (PDA) in extremely preterm infants. However, these findings have not been confirmed in other studies. Objective: To investigate the possible association between amino acid concentrations in the 1st day of life and the presence of PDA in a cohort of 121 newborns with gestational age (GA) below 30 weeks and birth weight (BW) below 1,500 g. Methods: Plasma samples were collected 6-12 h after birth and amino acid concentrations were determined by tandem mass spectrometry. Besides PDA, we analyzed the potential association of amino acid concentrations with infant sex, small for GA (SGA, defined as BW < third percentile), antenatal corticosteroids, chorioamnionitis, and preeclampsia. Group differences were analyzed by ANOVA adjusted for GA and BW. A Bonferroni significance threshold of P < 0.0024 was used to correct for multiple testing. Results: PDA was found in 48 of the 121 infants examined. We observed higher mean levels of glutamate in infants with PDA (147.0 μmol/L, SD 84.0) as compared with those without (106.7 μmol/L, SD 49.1, P = 0.0006). None of the other amino acid concentrations in the PDA group reached the level of statistical significance that was pre-set to correct for multiple comparisons. Glutamate levels were not significantly affected by infant sex, being SGA, or by exposure to antenatal corticosteroids, clinical chorioamnionitis, or preeclampsia. Conclusion: Our study not only does not confirm the previous findings of low glutamate levels in preterm infants with PDA, but we have even found elevated glutamate concentrations associated with PDA. Nevertheless, despite the high statistical significance, the difference in glutamate levels may lack clinical significance or may be an epiphenomenon associated with the particular clinical condition of infants with PDA.

Targeted Drugs for Treatment of Pulmonary Arterial Hypertension: Past, Present, and Future Perspectives

Pulmonary arterial hypertension (PAH) is a devastating disease that can lead to right ventricular failure and premature death. Although approved drugs have been shown to be safe and effective, PAH remains a severe clinical condition, and the long-term survival of patients with PAH is still suboptimal. Thus, potential therapeutic targets and new agents to treat PAH are urgently needed. In recent years, a variety of related pathways and potential therapeutic targets have been found, which brings new hope for PAH therapy. In this perspective, not only are the marketed drugs used to treat PAH summarized but also the recently developed novel pharmaceutical therapies currently in clinical trials are discussed. Furthermore, the advances in natural products as potential treatment for PAH are also updated.

Ionotropic glutamate receptors in platelets: opposing effects and a unifying hypothesis

Ionotropic glutamate receptors include α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR), kainate receptors (KAR), and N-methyl-D-aspartate receptors (NMDAR). All function as cation channels; AMPAR and KAR are more permeable to sodium and NMDAR to calcium ions. Compared to the brain, receptor assemblies in platelets are unusual, suggesting distinctive functionalities.There is convincing evidence that AMPAR and KAR amplify platelet function and thrombus formation in vitro and in vivo. Transgenic mice lacking GluA1 and GluK2 (AMPAR and KAR subunits, respectively) have longer bleeding times and prolonged time to thrombosis in an arterial model. In humans, rs465566 KAR gene polymorphism associates with altered in vitro platelet responses suggesting enhanced aspirin effect. The NMDAR contribution to platelet function is less well defined. NMDA at low concentrations (≤10 μM) inhibits platelet aggregation and high concentrations (≥100 μM) have no effect. However, open NMDAR channel blockers interfere with platelet activation and aggregation induced by other agonists in vitro; anti-GluN1 antibodies interfere with thrombus formation under high shear rates ex vivo; and rats vaccinated with GluN1 develop iron deficiency anemia suggestive of mild chronic bleeding. In this review, we summarize data on glutamate receptors in platelets and propose a unifying model that reconciles some of the opposing effects observed.

Induced pluripotent stem cells as a platform to understand patient-specific responses to opioids and anaesthetics

Recent advances in human induced pluripotent stem cell (iPSC) technology may provide unprecedented opportunities to study patient-specific responses to anaesthetics and opioids. In this review, we will (1) examine the advantages and limitations of iPSC technology, (2) summarize studies using iPSCs that have contributed to our current understanding of anaesthetics and opioid action on the cardiovascular system and central nervous system (CNS), and (3) describe how iPSC technology can be used to further develop personalized analgesic and sedative pharmacotherapies with reduced or minimal detrimental cardiovascular effects.

N-Methyl-D-Aspartate (NMDA) receptor modulators: a patent review (2015-present)

INTRODUCTION

- The NMDA receptor is implicated in various diseases including neurodegenerative, neurodevelopmental and mood disorders. However, only a limited number of clinically approved NMDA receptor modulators are available. Today, apparent NMDA receptor drug development strategies entail 1) exploring the unknown chemical space to identify novel scaffolds; 2) using the clinically available NMDA receptor modulators to expand the therapeutic indication space; 3) and to trace physiological functions of the NMDA receptor.

AREAS COVERED

- The current review reflects on the functional and pharmacological facets of NMDA receptors and the current clinical status quo of NMDA receptor modulators. Patent literature covering 2015 till April 2020 is discussed with emphasis on new indications.

EXPERT OPINION

- Supporting evidence shows that subtype-selective NMDA receptor antagonists show an improved safety profile compared to broad-spectrum channel blockers. Although GluN2B-selective antagonists are by far the most extensively investigated subtype-selective modulators, they have shown only modest clinical efficacy so far. To overcome the limitations that have hampered the clinical development of previous subtype-selective NMDA receptor antagonists, future studies with improved animal models that better reflect human NMDA receptor pathophysiology are warranted. The increased availability of subtype-selective probes will allow target engagement studies and proper dose finding in future clinical trials.