Tetrahydrobiopterin Content Research Articles

Dietary supplementation with L-citrulline improves placental angiogenesis and embryonic survival in gilts.

This study was conducted with gilts as an animal model to test the hypothesis that dietary supplementation with L-citrulline (Cit) improves placental angiogenesis and embryonic survival. Between Days 14 and 25 of gestation, each gilt was fed a corn- and soybean-meal-based diet (2 kg/day) supplemented with 0.4% Cit or an isonitrogenous amount of L-alanine (Control). On Day 25 of gestation, gilts were hysterectomized to obtain conceptuses. Amniotic and allantoic fluids and placentae were analyzed for NOx [stable oxidation products of nitric oxide (NO)], polyamines, and amino acids (AAs). Placentae were also analyzed for syntheses of NO and polyamines; concentrations of AAs and related metabolites; and the expression of angiogenic factors and aquaporins (AQPs). Compared to the control group, Cit supplementation increased (P < 0.01) the number of viable fetuses by 2.0 per litter, the number and diameter of placental blood vessels (21% and 24%, respectively), placental weight (15%), and total allantoic and amniotic fluid volumes (20% and 47%, respectively). Cit supplementation also increased (P < 0.01) enzymatic activities of GTP-cyclohydrolase-1 (32%) and ornithine decarboxylase (27%) in placentae; syntheses of NO (29%) and polyamines (26%); concentrations of NOx (19%), tetrahydrobiopterin (28%), polyamines (22%), cAMP (26%), and cGMP (24%) in placentae; total amounts of NOx (22-40%), polyamines (23-40%), AAs (16-255%), glucose (22-44%), and fructose (22-43%) in allantoic and amniotic fluids. Furthermore, Cit supplementation increased (P < 0.05) placental mRNA levels for angiogenic factors (eNOS [84%], GTP-CH1 [55%], PGF [61%], VEGFA120 [26%], and VEGFR2 [137%], as well as AQPs - AQP1 [105%], AQP3 [53%], AQP5 [77%], AQP8 [57%], and AQP9 [31%]). Collectively, dietary Cit supplementation enhanced placental NO and polyamine syntheses as well as angiogenesis to improve conceptus development and survival.

Lonicerae japonicae flos ameliorates radiotherapy-induced mesenteric artery endothelial dysfunction through GTPCH1/BH4/eNOS pathway

BackgroundAs a traditional Chinese medicine, Lonicerae japonicae flos (LJF) and its main component chlorogenic acid (CGA) have anti-oxidant, anti-bacterial and anti-tumor effects. However, there is no research on the potential of LJF for vascular protection in radiotherapy. PurposeTo elucidate the potential and possible mechanisms of the LJF extract and CGA in alleviating endothelial dysfunction caused by abdominal radiotherapy. MethodsLJF was extracted with water and the CGA content was analyzed by HPLC. Male Sprague-Dawley rats received abdominal radiotherapy for 21 days. Seven days after irradiation, Laser Doppler and ex vivo vascular tension experiments were performed. Nitric oxide (NO), superoxide anion levels and tetrahydrobiopterin (BH4) content were detected. Western blot, flow cytometry and molecular docking were used. ResultsIn the radiotherapy group, the mesenteric arterial blood perfusion, NO, and superoxide anion levels were significantly reduced; rats treated with the LJF extract or CGA showed a certain extent of recovery of these indicators. Vascular tension experiments showed that CGA and the LJF extract improved the vasodilation of mesenteric arteries. Cell experiments demonstrated that CGA increased the NO content and reduce superoxide anion production and cell apoptosis. The expression levels of GTPCH1/BH4/eNOS signaling pathway were significantly increased due to the use of the LJF extract or CGA in vivo and in vitro. ConclusionsOur study demonstrated for the first time that LJF and its main component, CGA could prevent abdominal radiotherapy-induced vascular endothelial dysfunction via GTPCH1/BH4/eNOS pathway. LJF could be a potential therapeutic herbal agent.

Naringenin upregulates GTPCH1/eNOS to ameliorate high glucose-induced retinal endothelial cell injury.

Diabetic retinopathy (DR) is a microvascular complication of diabetes, while retinal endothelial cell (REC) dysfunction is considered the primary pathological process of DR. Naringenin, a natural flavonoid compound, exhibits therapeutic potential against multiple types of endothelial cell injury. To the best of our knowledge, however, its effect on REC injury has not been previously investigated. Therefore, the aim of the present study was to investigate the effect of naringenin on high glucose (HG)-induced REC injury and assess the underlying mechanism. To establish a retinal injury model, human (H)RECs were treated with 30 mM glucose. Cell Counting Kit-8 assay and TUNEL staining were used to assess the effects of naringenin on cell proliferation and apoptosis, respectively. Reactive oxygen species (ROS) levels and concentration of tetrahydrobiopterin (BH4), the essential cofactor of endothelial nitric oxide synthase (eNOS), were measured using a ROS detection kit and ELISA, respectively. The transfection efficiency of HRECs with guanosine triphosphate cyclohydrolase-1 (GTPCH1) interfering plasmid was examined by reverse transcription-quantitative PCR. The protein expression levels of Ki67, proliferative cell nuclear antigen (PCNA), eNOS and GTPCH1 were determined by western blot analysis. Compared with the HG-induced group alone, co-treatment with naringenin inhibited HG-induced HREC apoptosis in a dose-dependent manner, increased expression levels of the proliferation-associated proteins Ki67 and PCNA and effectively decreased intracellular ROS levels. Furthermore, naringenin upregulated GTPCH1/eNOS signaling and promoted release of BH4. However, GTPCH1 knockdown partially reversed the ameliorative effect of naringenin on HG-induced HREC injury. In summary, the present study suggested that naringenin effectively inhibited HG-induced HREC apoptosis and intracellular oxidative stress, which may be associated with naringenin-mediated GTPCH1/eNOS upregulation.

The Pah-R261Q mouse reveals oxidative stress associated with amyloid-like hepatic aggregation of mutant phenylalanine hydroxylase

Phenylketonuria (PKU) is caused by autosomal recessive variants in phenylalanine hydroxylase (PAH), leading to systemic accumulation of L-phenylalanine (L-Phe) that may reach neurotoxic levels. A homozygous Pah-R261Q mouse, with a highly prevalent misfolding variant in humans, reveals the expected hepatic PAH activity decrease, systemic L-Phe increase, L-tyrosine and L-tryptophan decrease, and tetrahydrobiopterin-responsive hyperphenylalaninemia. Pah-R261Q mice also present unexpected traits, including altered lipid metabolism, reduction of liver tetrahydrobiopterin content, and a metabolic profile indicative of oxidative stress. Pah-R261Q hepatic tissue exhibits large ubiquitin-positive, amyloid-like oligomeric aggregates of mutant PAH that colocalize with selective autophagy markers. Together, these findings reveal that PKU, customarily considered a loss-of-function disorder, can also have toxic gain-of-function contribution from protein misfolding and aggregation. The proteostasis defect and concomitant oxidative stress may explain the prevalence of comorbid conditions in adult PKU patients, placing this mouse model in an advantageous position for the discovery of mutation-specific biomarkers and therapies.

Nitric Oxide in the Spinal Cord Is Involved in the Hyperalgesia Induced by Tetrahydrobiopterin in Chronic Restraint Stress Rats.

It has been well recognized that exposure to chronic stress could increase pain responding and exacerbate pain symptoms, resulting in stress-induced hyperalgesia. However, the mechanisms underlying stress-induced hyperalgesia are not yet fully elucidated. To this end, we observed that restraint as a stressful event exacerbated mechanical and thermal hyperalgesia, accompanied with up-regulation of nitric oxide (NO) (P < 0.001), GTP cyclohydrolase 1 (GCH1) (GCH1 mRNA: P = 0.001; GCH1 protein: P = 0.001), and tetrahydrobiopterin (BH4) concentration (plasma BH4: P < 0.001; spinal BH4: P < 0.001) on Day 7 in restraint stress (RS) rats. Intrathecal injection of Nω-nitro-L-arginine methyl ester (L-NAME), a non-specific NO synthase inhibitor, or N-([3-(aminomethyl)phenyl]methyl) ethanimidamide, a special inhibitor of inducible NO synthase (iNOS), for seven consecutive days attenuated stress-induced hyperalgesia and decreased the production of NO (P < 0.001). Interestingly, 7-nitro indazole, a special inhibitor of neuronal NO synthase, alleviated stress-induced hyperalgesia but did not affect spinal NO synthesis. Furthermore, intrathecal injection of BH4 not only aggravated stress-induced hyperalgesia but also up-regulated the expression of spinal iNOS (iNOS mRNA: P = 0.015; iNOS protein: P < 0.001) and NO production (P < 0.001). These findings suggest that hyperalgesia induced by RS is associated with the modulation of the GCH1–BH4 system and constitutively expressed spinal iNOS. Thus, the GCH1–BH4–iNOS signaling pathway may be a new novel therapeutic target for pain relief in the spinal cord.

Neuronal vulnerability to fetal hypoxia-reoxygenation injury and motor deficit development relies on regional brain tetrahydrobiopterin levels

Hypertonia is pathognomonic of cerebral palsy (CP), often caused by brain injury before birth. To understand the early driving events of hypertonia, we utilized magnetic resonance imaging (MRI) assessment of early critical brain injury in rabbit fetuses (79% term) that will predict hypertonia after birth following antenatal hypoxia-ischemia. We examined if individual variations in the tetrahydrobiopterin cofactor in the parts of the brain controlling motor function could indicate a role in specific damage to motor regions and disruption of circuit integration as an underlying mechanism for acquiring motor disorders, which has not been considered before. The rabbit model mimicked acute placental insufficiency and used uterine ischemia at a premature gestation. MRI during the time of hypoxia-ischemia was used to differentiate which individual fetal brains would become hypertonic. Four brain regions collected immediately after hypoxia-ischemia or 48 h later were analyzed in a blinded fashion. Age-matched sham-operated animals were used as controls. Changes in the reactive nitrogen species and gene expression of the tetrahydrobiopterin biosynthetic enzymes in brain regions were also studied. We found that a combination of low tetrahydrobiopterin content in the cortex, basal ganglia, cerebellum, and thalamus brain regions, but not a unique low threshold of tetrahydrobiopterin, contributed etiologically to hypertonia. The biggest contribution was from the thalamus. Evidence for increased reactive nitrogen species was found in the cortex. By 48 h, tetrahydrobiopterin and gene expression levels in the different parts of the brain were not different between MRI stratified hypertonia and non-hypertonia groups. Sepiapterin treatment given to pregnant dams immediately after hypoxia-ischemia ameliorated hypertonia and death. We conclude that a developmental tetrahydrobiopterin variation is necessary with fetal hypoxia-ischemia and is critical for disrupting normal motor circuits that develop into hypertonia. The possible mechanistic pathway involves reactive nitrogen species.

MiR-124 inhibits spinal neuronal apoptosis through binding to GCH1.

To explore the effect of micro ribonucleic acid (miR)-124 on the spinal neuronal apoptosis and to explore its related mechanism. The rat model of spinal cord injury (SCI) was established, agomir-124 was injected intrathecally and the effect of agomir-124 on motor function recovery of rats was evaluated using the Basso-Beattie-Bresnahan (BBB) score. The gene expression levels of miR-124 and GTP-cyclohydrolase 1 (GCH1) in spinal cord tissues were detected via quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR), and the correlation between them was detected using the Pearson correlation coefficient. Then, the direct interaction between miR-124 and GCH1 mRNA was detected using the TargetScan software and luciferase reporter assay. The changes in apoptosis in each group were examined via flow cytometry and Western blotting. Moreover, the changes in the tetrahydrobiopterin (BH4) content in each group were detected via high-performance liquid chromatography, and the changes in the nitrite level in the supernatant in each group were detected using the Griess reagent. Finally, the changes in the activity of the inducible nitric oxide synthase (iNOS) protein were detected using the iNOS kit. Compared with that in the model group, the BBB score was significantly increased in agomir-124 group at 21, 28, 35 and 42 d. In the agomir-124 group, the relative expression level of miR 124 in spinal cord tissues was significantly increased at 7-28 d and reached the peak at 21 d, while the mRNA level of GCH1 in spinal cord tissues declined and touched the bottom at 21 d. According to the Pearson correlation coefficient, there was a significant negative correlation between the expression of miR-124 and mRNA expression of GCH1 (r =- 0.87, p = 1.5e-6). It was found in the prediction using TargetScan software that GCH1 might be a potential target for miR-124, which was further verified by the luciferase reporter assay. The results of flow cytometry and Western blotting showed that miR-124 significantly reduced the LPS-induced primary spinal neuronal apoptosis, while the miR-124 inhibitor remarkably increased the primary spinal neuronal apoptosis. Moreover, it was also found that the knockout of GCH1 reduced the LPS-induced spinal neuronal apoptosis. In addition, the GCH1 overexpression assay revealed that miR-124 inhibited spinal neuronal apoptosis by suppressing the GCH1 expression. LPS + miR-124 remarkably decreased the BH4 content, nitrite level, and iNOS activity while LPS + miR-124 + GCH1 remarkably increased the BH4 content, nitrite level, and iNOS activity. MiR-124 inhibits neuronal apoptosis in SCI by binding to GCH1. The results in the present study may provide a new mechanism for the therapeutic effect of miR-124, and miR-124 may have a potential therapeutic value in the treatment of SCI in the future.

Protective effect of Xin-Ji-Er-Kang on cardiovascular remodeling in high-salt induced hypertensive mice: Role ofoxidative stress and endothelial dysfunction

BackgroundXin-Ji-Er-Kang (XJEK) is a Chinese herbal formula that has beenreported to exert effective protection against cardiovascular diseases, such as hypertension and myocarditis. ObjectiveThe aim of the present study was to investigate the effect of XJEK on high-salt-induced hypertensive mice and its possible mechanism. MethodsThe model of hypertension was established through a high-salt diet. Sixty male Kunming mice were randomized into six groups, namely the Control, Model, Low-dose XJEK, Middle-dose XJEK, High-dose XJEK and Fosinopril groups (n=10 per group). Different steady interventions were given to each group: 0.9% Sodium chloride was added to the diet of the Control group and 8% sodium chloride to the diet of the other five groups from the very beginning. An additional 4, 8 and 12 g/kg/day XJEK were intragastrically administered to the Low-dose, Middle-dose and High-dose XJEK groups, respectively, and 2 mg/kg/day fosinopril to the fosinopril group, from the start of week 5. Systolic blood pressure (SBP) was measured weekly from weeks 1 to 8 using the tail-cuff method. At the end of week 8, left ventricular (LV) systolic pressure, LV end-diastolic pressure and rate of rise of LV pressure were examined using a TransonicScisense catheter (Transonic Systems Inc,Ithaca, NY,USA). Endothelium-dependent relaxations induced by acetylcholine were observed in an isolated thoracic aorta ring. Serum and heartsweresampled for the measurement of the following indexes:Serum nitric oxide (NO), superoxide dismutase (SOD) activity and malondialdehyde (MDA) content (determined by colorimetricanalysis); serum angiotensin II(Ang II), endothelin-1, endothelial NO synthase (eNOS), asymmetric dimethylarginine (ADMA), tetrahydrobiopterin (BH4) concentration and l-arginine (determined by enzyme-linked immunosorbent assay); heart to body weight (HW/BW) ratio; myocardial morphological change (determined by HE and VG staining); myocardial eNOS expression (determined by immunofluorescence), and myocardial endothelin receptor A (ETA) expression (determined by western blotting).Results:Statistical data showed that the HW/BW ratio was significantly decreased in the drug treatment group. XJEK treatment could improve the heart systolic and diastolic function and ameliorate hemodynamic parameters and vascular remodeling indexes. Colorimetric results showed that, compared with the model group, XJEK increased serum SOD, NOlevels, and decreased those of serum MDA and Ang II. XJEK reverted changes in cardiac pathology, decreased the myocardial cross-sectional area, collagen volume fraction and perivascular collagen area and improved endothelial dysfunction (ED) by promoting eNOS activity, enhancing NO bioavailability, increasing the expression of BH4 and decreasing ETA content. In addition, treatment with XJEK decreased ADMA content in the myocardium.Conclusion:In conclusion, XJEK mitigates cardiac remodeling in high-salt-induced hypertensive mice. The potential mechanism involves improved oxidative stress and endothelial dysfunction, independently of ameliorating BP.

Effect of (-)-epicatechin on the modulation of progression markers of chronic renal damage in a 5/6 nephrectomy experimental model

AimsTo evaluate the effects of (-)-epicatechin (Epi) in the progression of kidney damage. Material and methodsWe assessed the effects of Epi [0.01–20 mg/kg of body weight/day] during 14 days, in a 5/6 nephrectomy model in mice. Key findingsNephrectomy-induced systolic arterial hypertension was significantly reduced in a dose dependent manner with Epi treatment. Increased serum creatinine and urea were reduced almost to normal values. The concentration of tetrahydrobiopterin (BH4), used as subrogate of endothelial dysfunction, decreased in nephrectomyzed animals, Epi treatment increased BH4 levels almost reaching normal values. The expression of angiotensin II receptor (AT1-R) and NADPH oxidase-4 (NOX-4) and 3-nitrotyrosine levels increased with nephrectomy and were reduced with Epi treatment. Renal tissue morphology in the remaining tissue was conserved with Epi treatment in a dose dependent manner. Significance.Chronic kidney disease (CKD) is an independent cardiovascular risk factor associated with a mortality rate 10 to 20 times higher than that of the general population. High blood pressure, endothelial dysfunction and oxidative stress are important factors determining kidney damage progression. Findings of this study indicate that Epi is able to counteract the deleterious effects of subtotal nephrectomy and the structural and functional changes in the remnant kidney tissue, decreasing the progression of CKD. These results warrant the possibility of implement clinical trials to limit the progression of CKD in humans.

Exendin‑4 reverses endothelial dysfunction in mice fed a high‑cholesterol diet by a GTP cyclohydrolase‑1/tetrahydrobiopterin pathway.

The present study examined whether exendin-4 (Ex4) can improve the endothelial dysfunction of apolipoprotein E knockout (APOE-KO) mice fed a high-cholesterol diet and the potential mechanism by which it acts. Genetically wild-type (WT) C57BL/6 mice and APOE-KO mice of C57BL/6 background, were each randomly assigned to receive either Ex4 treatment (Ex4-treated, for 8 weeks) or not (control). The 4 groups were fed the same high-cholesterol diet for 8 weeks. The following were measured at the end of the eighth week: Endothelium-dependent vasodilation of the arteries; plasma nitric oxide (NO) and metabolic index; levels of endothelial NO synthase (eNOS); phosphorylated eNOS (p-eNOS; Ser-1,177); guanosine triphosphate cyclohydrolase-1 (GCH1); and tetrahydrobiopterin (THB). Ex4 treatment was associated with higher p-eNOS levels in the WT group and in the APOE-KO group, and higher vascular expression of GCH1 and higher arterial THB content, compared with baseline values. The results of the present study suggested that Ex4 may exert cardioprotective effects by reversing high-cholesterol diet-induced endothelial dysfunction in APOE-KO mice. The protective mechanism is probably associated with the promotion of the expression levels of GCH1 protein and THB that maintain the normal function of eNOS.

Vitamin C Deficiency Reduces Muscarinic Receptor Coronary Artery Vasoconstriction and Plasma Tetrahydrobiopterin Concentration in Guinea Pigs.

Vitamin C (vitC) deficiency is associated with increased cardiovascular disease risk, but its specific interplay with arteriolar function is unclear. This study investigates the effect of vitC deficiency in guinea pigs on plasma biopterin status and the vasomotor responses in coronary arteries exposed to vasoconstrictor/-dilator agents. Dunkin Hartley female guinea pigs (n = 32) were randomized to high (1500 mg/kg diet) or low (0 to 50 mg/kg diet) vitC for 10–12 weeks. At euthanasia, coronary artery segments were dissected and mounted in a wire-myograph. Vasomotor responses to potassium, carbachol, sodium nitroprusside (SNP), U46619, sarafotoxin 6c (S6c) and endothelin-1 (ET-1) were recorded. Plasma vitC and tetrahydrobiopterin were measured by HPLC. Plasma vitC status reflected the diets with deficient animals displaying reduced tetrahydrobiopterin. Vasoconstrictor responses to carbachol were significantly decreased in vitC deficient coronary arteries independent of their general vasoconstrictor/vasodilator capacity (p < 0.001). Moreover, in vitC deficient animals, carbachol-induced vasodilator responses correlated with coronary artery diameter (p < 0.001). Inhibition of cyclooxygenases with indomethacin increased carbachol-induced vasoconstriction, suggesting an augmented carbachol-induced release of vasodilator prostanoids. Atropine abolished carbachol-induced vasomotion, supporting a specific muscarinic receptor effect. Arterial responses to SNP, potassium, S6c, U46619 and ET-1 were unaffected by vitC status. The study shows that vitC deficiency decreases tetrahydrobiopterin concentrations and muscarinic receptor mediated contraction in coronary arteries. This attenuated vasoconstrictor response may be linked to altered production of vasoactive arachidonic acid metabolites and reduced muscarinic receptor expression/signaling.

Pretreatment with Astragaloside IV protects human umbilical vein endothelial cells from hydrogen peroxide induced oxidative stress and cell dysfunction via inhibiting eNOS uncoupling and NADPH oxidase - ROS - NF-κB pathway.

Endothelial cell injury caused by reactive oxygen species (ROS) plays a critical role in the pathogenesis of cardiovascular disorders. Astragaloside IV (AsIV) possesses potent antioxidant properties against oxidative stress through undefined mechanism(s). We sought to investigate whether AsIV protects human umbilical vein endothelial cells (HUVECs) from hydrogen peroxide (H2O2) induced oxidative stress focusing on eNOS uncoupling and the NADPH oxidase - ROS - NF-κB pathway. Compared with HUVECs incubated with H2O2 alone, pretreatment with AsIV significantly increased the viability of HUVECs, which was accompanied with apparent increase in nitric oxide (NO) production and decrease in intracellular superoxide anion production. Furthermore, pretreatment with AsIV increased endothelial nitric oxide synthase (eNOS) dimer/monomer ratio and its critical cofactor tetrahydrobiopterin (BH4) content, decreased Nox4 protein expression (the most abundant Nox isoform in HUVECs), inhibited translocation of NF-κB p65 subunit into nuclear fraction while enhanced the protein expression of IκB-α (the inhibitor of NF-κB p65), reduced the levels of IL-1β, IL-6, and TNF-α in HUVECs medium, and decreased iNOS protein expression. These results suggest that AsIV may protect HUVECs from H2O2-induced oxidative stress via inhibiting NADPH oxidase - ROS - NF-κB pathway and eNOS uncoupling.

Tetrahydrobiopterin Concentrations in Normal and Coronary Artery Diseased Heart Tissue

Background: Tetrahydrobiopterin (BH4) is a cofactor that plays a major role in cardiovascular health and disease. BH4 levels in the human heart have not been previously reported. Objective and Methods: Using a novel LC-MS/MS method we measured BH4 and BH2 levels in human heart tissue from subjects with (n=19) and without (n=19) coronary artery disease (CAD). Results: The concentration of BH4 was significantly lower in CAD subjects compared to controls (p=0.0006). There was a trend for a decrease in BH4/BH2 ratio (p=0.09). mRNA expression of GCH1, NOS3 and was not significantly different between CAD and controls. Conclusions: We conclude that the decrease in BH4 concentration in the left ventricular wall of subjects with CAD may be a causative factor or consequence of the failing heart.

Astragaloside IV improves the isoproterenol-induced vascular dysfunction via attenuating eNOS uncoupling-mediated oxidative stress and inhibiting ROS-NF-κB pathways

ObjectiveOxidative stress and inflammation are regarded as two important triggers of endothelial dysfunction and play pivotal role in progression of vascular damage associated with cardiac hypertrophy. Our previous studies demonstrated that astragaloside IV (AsIV) could protect against cardiac hypertrophy in rats induced by isoproterenol (Iso), but its effects on the aorta are not known. In present study, we aimed to assess the effects of AsIV on Isoinduced vascular dysfunction. MethodsSprague-Dawley (SD) rats were treated with Iso (10mg/kg/d) alone or in combination with AsIV (50mg/kg/d). ResultsCompared with Isotreated alone, AsIV significantly reduced the ratios of heart weight/body weight and left ventricular weight/body weight. AsIV ameliorated the increased vasoconstriction response to phenylephrine induced by Iso and suppressed superoxide anion generation in rat aorta, increased endothelial nitric oxide synthase (eNOS) dimer/monomer ratio and its critical cofactor tetrahydrobiopterin (BH4) content in aorta as well as the NO production in the serum, reduced the plasmatic peroxynitrite (ONOO–). Moreover, in contrast with Isotreatment alone, AsIV decreased the ratio of nuclear-to-cytosolic protein expression of the NF-κB p65 subunit while enhanced its inhibited protein expression of IκB-α, down-regulated mRNA expression of IL-1β, IL-6 and TNF-α of the aorta. ConclusionsThe present study suggested that AsIV protects against Isoinduced vascular dysfunction probably via attenuating eNOS uncoupling-mediated oxidative stress and inhibiting ROS-NF-κB pathways.

Tetrahydrobiopterin Role in human umbilical vein endothelial dysfunction in maternal supraphysiological hypercholesterolemia

Maternal physiological hypercholesterolemia (MPH) allows a proper foetal development; however, maternal supraphysiological hypercholesterolemia (MSPH) associates with foetal endothelial dysfunction and early development of atherosclerosis. MSPH courses with reduced endothelium-dependent dilation of the human umbilical vein due to reduced endothelial nitric oxide synthase activity compared with MPH. Whether MSPH modifies the availability of the nitric oxide synthase cofactor tetrahydrobiopterin is unknown. We investigated whether MSPH-associated lower umbilical vein vascular reactivity results from reduced bioavailability of tetrahydrobiopterin. Total cholesterol <7.2mmol/L was considered as maternal physiological hypercholesterolemia (n=72 women) and ≥7.2mmol/L as MSPH (n=35 women). Umbilical veins rings were used for vascular reactivity assays (wire myography), and primary cultures of human umbilical vein endothelial cells (HUVECs) to measure nitric oxide synthase, GTP cyclohydrolase 1, and dihydrofolate reductase expression and activity, as well as tetrahydrobiopterin content. MSPH reduced the umbilical vein rings relaxation caused by calcitonine gene-related peptide, a phenomenon partially improved by incubation with sepiapterin. HUVECs from MSPH showed lower nitric oxide synthase activity (l-citrulline synthesis from l-arginine) without changes in its protein abundance, as well as reduced tetrahydrobiopterin level compared with MPH, a phenomenon reversed by incubation with sepiapterin. Expression and activity of GTP cyclohydrolase 1 was lower in MSPH, without changes in dihydrofolate reductase expression. MSPH is a pathophysiological condition reducing human umbilical vein reactivity due to lower bioavailability of tetrahydrobiopterin leading to lower NOS activity in the human umbilical vein endothelium.

Chronic Co-Administration of Sepiapterin and L-Citrulline Ameliorates Diabetic Cardiomyopathy and Myocardial Ischemia/Reperfusion Injury in Obese Type 2 Diabetic Mice.

Diabetic heart disease is associated with tetrahydrobiopterin oxidation and high arginase activity, leading to endothelial nitric oxide synthase dysfunction. Sepiapterin (SEP) is a tetrahydrobiopterin precursor, and L-citrulline (L-Cit) is converted to endothelial nitric oxide synthase substrate, L-arginine. Whether SEP and L-Cit are effective at reducing diabetic heart disease is not known. The present study examined the effects of SEP and L-Cit on diabetic cardiomyopathy and ischemia/reperfusion injury in obese type 2 diabetic mice. Db/db and C57BLKS/J mice at 6 to 8 weeks of age received vehicle, SEP, or L-Cit orally alone or in combination for 8 weeks. Cardiac function was evaluated with echocardiography. Db/db mice displayed hyperglycemia, obesity, and normal blood pressure and cardiac function compared with C57BLKS/J mice at 6 to 8 weeks of age. After vehicle treatment for 8 weeks, db/db mice had reduced ejection fraction, mitral E/A ratio, endothelium-dependent relaxation of coronary arteries, tetrahydrobiopterin concentrations, ratio of endothelial nitric oxide synthase dimers/monomers, and nitric oxide levels compared with vehicle-treated C57BLKS/J mice. These detrimental effects of diabetes mellitus were abrogated by co-administration of SEP and L-Cit. Myocardial infarct size was increased, and coronary flow rate and ± dP/dt were decreased during reperfusion in vehicle-treated db/db mice subjected to ischemia/reperfusion injury compared with control mice. Co-administration of SEP and L-Cit decreased infarct size and improved coronary flow rate and cardiac function in both C57BLKS/J and db/db mice. Co-administration of SEP and L-Cit limits diabetic cardiomyopathy and ischemia/reperfusion injury in db/db mice through a tetrahydrobiopterin/endothelial nitric oxide synthase/nitric oxide pathway.

Selective Irreversible Inhibition of Neuronal and Inducible Nitric-oxide Synthase in the Combined Presence of Hydrogen Sulfide and Nitric Oxide

Citrulline formation by both human neuronal nitric-oxide synthase (nNOS) and mouse macrophage inducible NOS was inhibited by the hydrogen sulfide (H2S) donor Na2S with IC50 values of ∼2.4·10(-5) and ∼7.9·10(-5) m, respectively, whereas human endothelial NOS was hardly affected at all. Inhibition of nNOS was not affected by the concentrations of l-arginine (Arg), NADPH, FAD, FMN, tetrahydrobiopterin (BH4), and calmodulin, indicating that H2S does not interfere with substrate or cofactor binding. The IC50 decreased to ∼1.5·10(-5) m at pH 6.0 and increased to ∼8.3·10(-5) m at pH 8.0. Preincubation of concentrated nNOS with H2S under turnover conditions decreased activity after dilution by ∼70%, suggesting irreversible inhibition. However, when calmodulin was omitted during preincubation, activity was not affected, suggesting that irreversible inhibition requires both H2S and NO. Likewise, NADPH oxidation was inhibited with an IC50 of ∼1.9·10(-5) m in the presence of Arg and BH4 but exhibited much higher IC50 values (∼1.0-6.1·10(-4) m) when Arg and/or BH4 was omitted. Moreover, the relatively weak inhibition of nNOS by Na2S in the absence of Arg and/or BH4 was markedly potentiated by the NO donor 1-(hydroxy-NNO-azoxy)-l-proline, disodium salt (IC50 ∼ 1.3-2.0·10(-5) m). These results suggest that nNOS and inducible NOS but not endothelial NOS are irreversibly inhibited by H2S/NO at modest concentrations of H2S in a reaction that may allow feedback inhibition of NO production under conditions of excessive NO/H2S formation.

Effects of Xin-Ji-Er-Kang formula on 2K1C-induced hypertension and cardiovascular remodeling in rats

Ethnopharmacological relevanceXin-Ji-Er-Kang (XJEK), a Chinese herbal formula, is effective against hypertension induced coronary heart disease, viral myocarditis and toxic myocarditis. In this study, the effect of XJEK on cardiovascular system was investigated. To test the hypothesis that Xin-Ji-Er-Kang (XJEK) has an anti-hypertensive effect mediated through attenuation of cardiac remodeling, and amelioration of vascular endothelial dysfunction and oxidative stress. Materials and methodsHypertension was induced in Wistar rats by 2 kidney 1 clip (2K1C) treatment. The hypertensive rats were then randomly assigned into four groups and treated as follows: group 1 (Sham-operated [Sh-Op] group received only drinking water), group 2 (induced hypertensive model+no treatment), and group 3 (induced hypertensive+a single daily oral dose of 24gkg−1 XJEK treatment) and group 4 (induced hypertensive+a single oral dose of 15mgkg−1 Fosinopril treatment). The rats in all the defined groups were respectively treated for a period of 4 weeks. Cardiovascular parameter such as systolic blood pressure (SBP) was measured weekly by using tail-cuff apparatus; left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP) and the rate of the rise in left ventricular pressure (±dp/dt max) were measured by using a PowerLab 8/30 apparatus (AD Instruments, Australia) at the end of the 8th week; heart weight/body weight (HW/BW) was determined as an index of myocardial hypertrophy (MH). Hematoxylin and eosin (H&E) and Van Gieson (VG) stain were used to assess the cardio-histological changes. Colorimetric analysis was used to assay serum superoxide dismutase (SOD) activity, malondialdehyde (MDA), nitric oxide (NO), and hydroxyproline (Hyp) contents in cardiac tissue. Angiotensin II (Ang II) content in serum was assessed by radioimmunoassay; tetrahydrobiopterin (BH4) content in cardiac tissue, BNP and endothelial NOS (eNOS) in serum were determined by using ELISA, and the protein expressions of c-Jun NH2-terminal kinase (JNK), P-JNK, p38, P-p38, and NADPH oxidases-2 (Nox-2) were measured by western blot. ResultsXJEK therapy could impair the heart systolic and diastolic function, potently improve the heart weight index, inhibit the elevation of HW/BW ratio, and markedly ameliorate hemodynamic indices and vascular remodeling index. It has blunted the decrease of SOD, NO and the increase in MDA and Ang II serum contents, myocardial cross-section area (CSA), collagen volume fraction (CVF) and perivascular circumferential collagen area (PVCA) compared to the hypertensive model group. It also reduced the serum content of Hyp while increased BH4 levels in cardiac tissue. In addition, the expressions of Nox-2, P-JNK and P-p38MAPK were all suppressed compared to the hypertensive model group. Moreover, treatment with XJEK improved endothelial dysfunction (ED) manifested by promoting eNOS activities and enhancing the NO activity in serum. ConclusionThe results of the present study show that XJEK attenuates 2K1C-induced hypertension in rats, which confirms our hypothesis that XJEK has an anti-hypertensive and cardiovascular remodeling effect via attenuation of cardiac remodeling and improvement of endothelial dysfunction and oxidative stress.

Inhibition of proteasome-mediated glucocorticoid receptor degradation restores nitric oxide bioavailability in myocardial endothelial cells in vitro.

Glucocorticoids (GCs), including the synthetic GC derivate dexamethasone, are widely used as immunomodulators. One of the numerous side effects of dexamethasone therapy is hypertension arising from reduced release of the endothelium-derived vasodilator nitric oxide (NO). Herein, we described the role of dexamethasone and its glucocorticoid receptor (GR) in the regulation of NO synthesis in vitro using the mouse myocardial microvascular endothelial cell line, MyEND. GC treatment caused a firm decrease of extracellular NO levels, whereas the expression of endothelial NO synthase (eNOS) was not affected. However, GC application induced an impairment of tetrahydrobiopterin (BH4 ) concentrations as well as GTP cyclohydrolase-1 (GTPCH-1) expression, both essential factors for NO production upstream of eNOS. Moreover, dexamethasone stimulation resulted in a substantially decreased GR gene and protein expression in MyEND cells. Importantly, inhibition of proteasome-mediated proteolysis of the GR or overexpression of an ubiquitination-defective GR construct improved the bioavailability of BH4 and strengthened GTPCH-1 expression and eNOS activity. Summarising our results, we propose a new mechanism involved in the regulation of NO signalling by GCs in myocardial endothelial cells. We suggest that a sufficient GR protein expression plays a crucial role for the management of GC-induced harmful adverse effects, including deregulations of vasorelaxation arising from disturbed NO biosynthesis.

Increase in tetrahydrobiopterin concentration with aging in the cerebral cortex of the senescence-accelerated mouse prone 10 strain caused by abnormal regulation of tetrahydrobiopterin biosynthesis

6R-L-Erythro-5,6,7,8-tetrahydrobiopterin (BH4) is an essential cofactor for tyrosine hydroxylase (TH) activity and is a risk factor for cognitive decline and brain atrophy. Previous studies have shown that the decline in TH activity in the cerebral cortex of senescence-accelerated mouse prone 10 (SAMP10) mice is caused, at least in part, by a decrease in Fe, ferritin, and TH phosphorylation. We determined the concentrations of BH4 and the enzymes GTP cyclohydrolase-1,6-pyruvoyltetrahydropterin synthase and sepiapterin reductase (SPR) in the de novo pathway of BH4 biosynthesis. Dihydrofolate reductase (DHFR), which converts BH2 to BH4 in the salvage pathway of BH4 synthesis was also determined in the cerebral cortex of SAM mice at 3 and 12months of age. The BH4 concentration was measured by HPLC, and the protein levels of enzymes involved in BH4 synthesis were measured by western blot analysis. At 12months of age, BH4 concentration in the cerebral cortex of SAMP10 mice showed significantly higher values as compared to that of control mice. Further, the protein level of SPR in SAMP10 mice was significantly higher than that in SAMR1 mice at 3 and 12months of age. In contrast to SPR, the protein level of DHFR in SAMP10 mice was significantly lower than that in SAMR1 mice. These results indicate that abnormal regulation of BH4 metabolism occurs in the cerebral cortex of SAMP10 where the dysfunction of the salvage pathway of BH4 synthesis may cause overproduction of BH4 through the de novo pathway, which is considered characteristic in the cerebral cortex of SAMP10 with aging. Therefore, there is a possibility that the excess amounts of BH4 lead to age-related brain dysfunction in the cerebral cortex of SAMP10.