15-PGDH/15-KETE plays a role in hypoxia-induced pulmonary vascular remodeling through ERK1/2-dependent PAR-2 pathway

Omega-6 polyunsaturated fatty acids and their metabolites: a potential targeted therapy for pulmonary hypertension

Pulmonary hypertension (PH) is a progressive and life-threatening cardiopulmonary disease that is not uncommon. The modulation of the pulmonary artery (PA) involves various fatty acids, including omega-6 polyunsaturated fatty acids (ω-6 PUFAs) and ω-6 PUFAs-derived oxylipins. These lipid mediators are produced through cyclooxygenase (COX), lipoxygenase (LOX), cytochrome P450 (CYP450), and non-enzymatic pathways. They play a crucial role in the occurrence and development of PH by regulating the function and phenotype of pulmonary artery endothelial cells (PAECs), pulmonary artery smooth muscle cells (PASMCs), pulmonary fibroblasts, alveolar macrophages, and inflammatory cells. The alterations in ω-6 PUFAs and oxylipins are pivotal in causing vasoconstriction, pulmonary remodeling, and ultimately leading to right heart failure in PH. Despite the limited understanding of the PH pathophysiology, there is potential for novel interventions through dietary and pharmacological approaches targeting ω-6 PUFAs and oxylipins. The aim of this review is to summarize the significant advances in clinical and basic research on omega-6 PUFAs and oxylipins in pulmonary vascular disease, particularly PH, and to propose a potential targeted therapeutic modality against omega-6 PUFAs.

Presenilin 1 Is a Therapeutic Target in Pulmonary Hypertension and Promotes Vascular Remodeling

Small muscular pulmonary artery remodeling is a dominant feature of pulmonary arterial hypertension (PAH). PSEN1 affects angiogenesis, cancer, and Alzheimer's disease. We aimed to determine the role of PSEN1 in the pathogenesis of vascular remodeling in pulmonary hypertension (PH). Hemodynamics and vascular remodeling in the Psen1-knockin and smooth muscle-specific Psen1-knockout mice were assessed. The functional partners of PSEN1 were predicted by bioinformatics analysis and biochemical experiments. The therapeutic effect of PH was evaluated by administration of the PSEN1-specific inhibitor ELN318463. We discovered that both the mRNA and protein levels of PSEN1 were increased over time in hypoxic rats, monocrotaline rats, and Su5416/hypoxia mice. Psen1 transgenic mice were highly susceptible to PH, whereas smooth muscle-specific Psen1-knockout mice were resistant to hypoxic PH. STRING analysis showed that Notch1/2/3, β-catenin, Cadherin-1, DNER (delta/notch-like epidermal growth factor-related receptor), TMP10, and ERBB4 appeared to be highly correlated with PSEN1. Immunoprecipitation confirmed that PSEN1 interacts with β-catenin and DNER, and these interactions were suppressed by the catalytic PSEN1 mutations D257A, D385A, and C410Y. PSEN1 was found to mediate the nuclear translocation of the Notch1 intracellular domains and activated RBP-Jκ. Octaarginine-coated liposome-mediated pharmacological inhibition of PSEN1 significantly prevented and reversed the pathological process in hypoxic and monocrotaline-induced PH. PSEN1 essentially drives the pathogenesis of PAH and interacted with the noncanonical Notch ligand DNER. PSEN1 can be used as a promising molecular target for treating PAH. PSEN1 inhibitor ELN318463 can prevent and reverse the progression of PH and can be developed as a potential anti-PAH drug.

Aldicarb disturbed bile acid, steroid hormone and oxylipin homeostasis in C57BL/6 J mice

Mounting evidence has shown that the gut microbiota plays a key role in human health. The homeostasis of the gut microbiota could be affected by many factors, including environmental chemicals. Aldicarb is a carbamate insecticide used to control a variety of insects and nematode pests in agriculture. Aldicarb is highly toxic and its wide existence has become a global public health concern. In our previous study, we have demonstrated that aldicarb disturbed the gut microbial community structure and composition. However, the impacts of aldicarb on gut microbiota-derived metabolites, bile acids, remain elusive. In present study, we performed targeted metabolomics analysis to explore the effects of aldicarb exposure on bile acids, as well as steroid hormones and oxylipins in the serum, feces and liver of C57BL/6 J mice. Our results showed that aldicarb exposure disturbed the level of various bile acids, steroid hormones and oxylipins in the serum and feces of C57BL/6 J mice. In the liver, the level of cortisol was decreased, meanwhile 15,16-dihydroxyoctadeca-9,12-dienoic acid was increased in aldicarb-treated mice. Metagenomic sequencing analysis showed that the relative abundance of a bile salt hydrolase, choloylglycine hydrolase (EC:3.5.1.24) and a sulfatase enzyme involved in steroid hormone metabolism, arylsulfatase, was significantly increased by aldicarb exposure. Furthermore, correlations were found between gut microbiota and various serum metabolites. The results from this study are helpful to improve the understanding of the impact of carbamate insecticides on host and microbial metabolism.

Coagulation-independent effects of thrombin and Factor Xa: role of protease-activated receptors in pulmonary hypertension

AIMS

Pulmonary arterial hypertension (PAH) is a devastating disease with limited therapeutic options. Vascular remodelling of pulmonary arteries, characterized by increased proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), is a hallmark of PAH. Here, we aimed to systematically characterize coagulation-independent effects of key coagulation proteases thrombin and Factor Xa (FXa) and their designated receptors, protease-activated receptor (PAR)-1 and -2, on PASMCs in vitro and experimental PAH in vivo.

METHODS AND RESULTS

In human and murine PASMCs, both thrombin and FXa were identified as potent mitogens, and chemoattractants. FXa mediated its responses via PAR-1 and PAR-2, whereas thrombin signalled through PAR-1. Extracellular-signal regulated kinases 1/2, protein kinase B (AKT), and sphingosine kinase 1 were identified as downstream mediators of PAR-1 and PAR-2. Inhibition of FXa or thrombin blunted cellular responses in vitro, but unexpectedly failed to protect against hypoxia-induced PAH in vivo. However, pharmacological inhibition as well as genetic deficiency of both PAR-1 and PAR-2 significantly reduced vascular muscularization of small pulmonary arteries, diminished right ventricular systolic pressure, and right ventricular hypertrophy upon chronic hypoxia compared to wild-type controls.

CONCLUSION

Our findings indicate a coagulation-independent pathogenic potential of thrombin and FXa for pulmonary vascular remodelling via acting through PAR-1 and PAR-2, respectively. While inhibition of single coagulation proteases was ineffective in preventing experimental PAH, our results propose a crucial role for PAR-1 and PAR-2 in its pathobiology, thus identifying PARs but not their dedicated activators FXa and thrombin as suitable targets for the treatment of PAH.

Investigation of 15-hydroxyprostaglandin dehydrogenase catalytic reaction mechanism by molecular dynamics simulations

15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a prostaglandin metabolizing enzyme that oxidizes the hydroxyl group at carbon 15 (C15). The aim of the present work is to propose the main amino acids that catalyze the reaction through studying the intermolecular interaction between the ligand and the enzyme inside the active site using molecular dynamics simulation (MD). Therefore, MD simulations for two 15-PGDH systems bound with a substrate (PGE₂) or an inhibitor (compound 4) were performed to investigate the importance of ligand interaction on the behavior of amino acids in the active site. Findings from this work proposed the amino acids: Tyr151, Gln148 & Asn95 to act as a catalytic triad for the reaction as hydrogen bond interactions, dihedral rotation analysis and MM-GBSA free energy calculations revealed.

Maternal DHA supplementation protects rat offspring against impairment of learning and memory following prenatal exposure to valproic acid

Docosahexaenoic acid (22:6n-3; DHA) is known to play a critical role in postnatal brain development. However, there have been no studies investigating the preventive effect of DHA on prenatal valproic acid (VPA)-induced behavioral and molecular alterations in offspring. The present study was to evaluate the neuroprotective effects in offspring using maternal feeding of DHA to rats exposed to VPA in pregnancy. In the present study, rats were exposed to VPA on day 12.5 of pregnancy; DHA was administered at the dosages of 100, 300 and 500 mg/kg/day for 3 weeks from day 1 to 21 of pregnancy. The results showed that maternal feeding of DHA to the prenatal exposed to VPA (1) prevented VPA-induced learning and memory impairment but did not change social-related behavior, (2) increased total DHA content in offspring plasma and hippocampus, (3) rescued VPA-induced neuronal loss and apoptosis of pyramidal cells in hippocampal CA1, (4) influenced the content of malondialdehyde and glutathione and the activities of superoxide dismutase and glutathione in the hippocampus, (5) altered levels of apoptosis-related proteins (Bcl-2, Bax and caspase-3) and inhibited the activity of caspase-3 in offspring hippocampus and (6) enhanced relative levels of p-CaMKII and p-CREB proteins in the hippocampus. These findings suggest that maternal feeding with DHA may prevent prenatal VPA-induced impairment of learning and memory, normalize several different molecules associated with oxidative stress and apoptosis in the hippocampus of offspring, and exert preventive effects on prenatal VPA-induced brain dysfunction.

Reverse Regulatory Pathway (H2S / PGE2 / MMP) in Human Aortic Aneurysm and Saphenous Vein Varicosity

Hydrogen sulfide (H₂S) is a mediator with demonstrated protective effects for the cardiovascular system. On the other hand, prostaglandin (PG)E₂ is involved in vascular wall remodeling by regulating matrix metalloproteinase (MMP) activities. We tested the hypothesis that endogenous H₂S may modulate PGE₂, MMP-1 activity and endogenous tissue inhibitors of MMPs (TIMP-1/-2). This regulatory pathway could be involved in thinning of abdominal aortic aneurysm (AAA) and thickening of saphenous vein (SV) varicosities. The expression of the enzyme responsible for H₂S synthesis, cystathionine-γ-lyase (CSE) and its activity, were significantly higher in varicose vein as compared to SV. On the contrary, the endogenous H₂S level and CSE expression were lower in AAA as compared to healthy aorta (HA). Endogenous H₂S was responsible for inhibition of PGE₂ synthesis mostly in varicose veins and HA. A similar effect was observed with exogenous H₂S and consequently decreasing active MMP-1/TIMP ratios in SV and varicose veins. In contrast, in AAA, higher levels of PGE₂ and active MMP-1/TIMP ratios were found versus HA. These findings suggest that differences in H₂S content in AAA and varicose veins modulate endogenous PGE₂ production and consequently the MMP/TIMP ratio. This mechanism may be crucial in vascular wall remodeling observed in different vascular pathologies (aneurysm, varicosities, atherosclerosis and pulmonary hypertension).

Plasma 12- and 15-hydroxyeicosanoids are predictors of survival in pulmonary arterial hypertension

This study aimed to characterize alterations in select eicosanoids in experimental and human pulmonary arterial hypertension (PAH) and to assess their potential utility as predictors of outcome. Using liquid chromatography-mass spectrometry, we performed targeted lipidomic analyses of the lungs and right ventricles (RVs) of chronically hypoxic rats and plasma of consecutive PAH patients and healthy controls. In rat lungs, chronic hypoxia was associated with significantly decreased lung prostacyclin (PGI2)/thromboxane B2 (TXB2) ratio and elevated lung 8-hydroxyeicosanoid (HETE) acid concentrations. RV eicosanoids did not exhibit any changes with chronic hypoxia. PAH treatment-naïve patients had significantly increased plasma concentrations of TXB2 and 5-, 8-, 12-, and 15-HETE. The PGI2/TXB2 ratio was lower in PAH patients than in controls, especially in the treatment-naïve cohort (median: 2.1, 0.3, and 1.3 in controls, treatment-naïve, and treated patients, respectively, P = 0.001). Survival was significantly worse in PAH patients with 12-HETEhigh (≥57 pg/mL) and 15-HETEhigh (≥256 pg/mL) in unadjusted and adjusted analyses (hazard ratio [HR]: 2.8 [95% confidence interval (CI): 1.1-7.3], P = 0.04 and HR: 4.3 [95% CI: 1.6-11.8], P = 0.004, respectively; adjustment was performed with the REVEAL [Registry to Evaluate Early and Long-Term PAH Disease Management] risk score). We demonstrate significant alterations in eicosanoid pathways in experimental and human PAH. We found that 12- and 15-HETE were independent predictors of survival in human PAH, even after adjusting for the REVEAL score, suggesting their potential role as novel biomarkers.

Notoginsenoside Rb1 inhibits activation of ERK and p38 MAPK pathways induced by hypoxia and hypercapnia

The aim of the present study was to investigate the effect of notoginsenoside Rb1 (Rb1) on the ERK and p38 MAPK pathways in primary cultured pulmonary arterial smooth muscle cells (PASMCs) exposed to hypoxia and hypercapnia, in order to elucidate the mechanism underlying the effect of Rb1 on hypoxia and hypercapnia-induced pulmonary vasoconstriction (HHPV). PASMCs were isolated from Sprague-Dawley rats. The cells were divided into five groups: Normal (N), hypoxia and hypercapnia (H), Rb_L, Rb_M and Rb_H groups. N group cells were cultured under 5% CO₂ and 21% O₂. H, Rb_L, Rb_M and Rb_H groups were cultured under 6% CO₂ and 1% O₂. Prior to the hypoxia and hypercapnia exposure, Rb_L, Rb_M and Rb_H groups were treated with 8, 40 and 100 mg/ml Rb1 for 30 min, respectively. Phosphorylated extracellular signal-regulated kinase (P-ERK) and P-p38 protein, and ERK1/2 and p38 mRNA expression levels were detected using western blot and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) analyses, respectively. The correlations between P-ERK protein and ERK1/2 mRNA, and between P-p38 protein and p38 mRNA were evaluated. Results of western blot and RT-PCR showed hypoxia and hypercapnia increased P-ERK and P-p38 protein, and ERK1/2 mRNA, respectively (P<0.05). Rb1 suppressed the increased P-ERK and P-p38 protein, and ERK1/2 and p38 mRNA by hypoxia and hypercapnia (P<0.05). P-ERK protein was positively correlated with ERK1 (r=0.5, P<0.01) and ERK2 mRNA (r=0.977, P<0.01). P-p38 protein was positively correlated with p38 mRNA (r=0.884, P<0.01). Thus, the present results indicate that Rb1 may ameliorate HHPV by suppressing ERK and p38 pathways. The study provides an experimental basis for investigating the clinical use of Rb1 in the management of HHPV-related disorders.

A hybrid strategy using global analysis of oxidized fatty acids and bioconversion by Bacillus circulans

RATIONALE

Targeted oxidized fatty acid analysis has been widely used to understand the roles of fatty acids in the development of diseases. However, because of the extensive structural diversity of fatty acids, it is considered that unknown lipid metabolites will remain undetected. Here, to discover and identify unknown lipid metabolites in biological samples, a global analytical system and a method of synthesizing lipid standards were investigated.

METHODS

Oxidized fatty acids in mouse lung tissues were extracted using mixed-mode spin columns. Separation was achieved via ultra-high-performance liquid chromatography, mass spectrometric (MS) analysis was conducted in full scan mode using a Q Exactive Plus instrument equipped with an electrospray ionization probe, and structure analysis was carried out by high-resolution data-dependent tandem mass spectrometry (dd-MS(2)). In addition, lipid standards, which are not commercially available, were synthesized by bioconversion using Bacillus circulans.

RESULTS

Oxidized fatty acids in mouse lung tissues were analyzed by high-resolution accurate-mass analysis, and multiple unknown molecules were discovered and tentatively identified using high-resolution dd-MS(2). Among these molecules, 21-hydroxydocosahexaenoic acid (21-HDoHE) and 22-HDoHE, which are not commercially available, were synthesized by bioconversion. By comparing the exact masses, retention times, and characteristic fragment ions of the synthesized standards, 21-HDoHE and 22-HDoHE were definitively identified in the mouse lung tissue.

CONCLUSIONS

Our strategy of global analysis and bioconversion can be used for the discovery and identification of unknown lipid molecules.

Key Role of ROS in the Process of 15-Lipoxygenase/15-Hydroxyeicosatetraenoiccid-Induced Pulmonary Vascular Remodeling in Hypoxia Pulmonary Hypertension

We previously reported that 15-lipoxygenase (15-LO) and its metabolite 15-hydroxyeicosatetraenoic acid (15-HETE) were up-regulated in pulmonary arterial cells from both pulmonary artery hypertension patients and hypoxic rats and that these factors mediated the progression of pulmonary hypertension (PH) by affecting the proliferation and apoptosis of pulmonary arterial (PA) cells. However, the underlying mechanisms of the remodeling induced by 15-HETE have remained unclear. As reactive oxygen species (ROS) and 15-LO are both induced by hypoxia, it is possible that ROS are involved in the events of hypoxia-induced 15-LO expression that lead to PH. We employed immunohistochemistry, tube formation assays, bromodeoxyuridine (BrdU) incorporation assays, and cell cycle analyses to explore the role of ROS in the process of 15-HETE-mediated hypoxic pulmonary hypertension (HPH). We found that exogenous 15-HETE facilitated the generation of ROS and that this effect was mainly localized to mitochondria. In particular, the mitochondrial electron transport chain and nicotinamide-adenine dinucleotide phosphate oxidase 4 (Nox4) were responsible for the significant 15-HETE-stimulated increase in ROS production. Moreover, ROS induced by 15-HETE stimulated endothelial cell (EC) migration and promoted pulmonary artery smooth muscle cell (PASMC) proliferation under hypoxia via the p38 MAPK pathway. These results indicated that 15-HETE-regulated ROS mediated hypoxia-induced pulmonary vascular remodeling (PVR) via the p38 MAPK pathway.

Activation of ERK pathway is required for 15-HETE-induced angiogenesis in human umbilical vascular endothelial cells

Angiogenesis plays a critical role in the progression of cardiovascular disease, retinal ischemia, or tumorigenesis. The imbalance of endothelial cell proliferation and apoptosis disturbs the establishment of the vasculogenesis, which is affected by several arachidonic acid metabolites. 15-Hydroxyeicosatetraenoic acid (15-HETE) is one of the metabolites. However, the underlying mechanisms of angiogenesis induced by 15-HETE in human umbilical vascular endothelial cells (HUVECs) are still poorly understood. Since extracellular signal-regulated kinase (ERK) is a critical regulator of cell proliferation, there may be a crosstalk between 15-HETE-regulating angiogenic process and ERK-proliferative effect in HUVECs. To test this hypothesis, we study the effect of 15-HETE on cell proliferation, angiogenesis, and apoptosis using cell viability measurement, cell cycle analysis, western blot, scratch-wound, tube formation assay, and nuclear morphology determination. We found that 15-HETE promoted HUVEC angiogenesis, which were mediated by ERK. Moreover, 15-HETE-induced proliferation and cell cycle transition from the G(0)/G(1) phase to the G(2)/M + S phase. All these effects were reversed after blocking ERK with PD98059 (an ERK inhibitor). In addition, HUVEC apoptosis was relieved by 15-HETE through the ERK pathway. Thus, ERK is necessary for the effects of 15-HETE in the regulation of HUVEC angiogenesis, which may be a novel potential target for the treatment of angiogenesis-related diseases.