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Fike CD, Aschner JL, Avachat C, Birnbaum AK, Sherwin CMT. Multi-dose enteral L-citrulline administration in premature infants at risk of developing pulmonary hypertension associated with bronchopulmonary dysplasia. J Perinatol 2024; 44:280-287. [PMID: 37907796 PMCID: PMC10844094 DOI: 10.1038/s41372-023-01809-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 10/10/2023] [Accepted: 10/18/2023] [Indexed: 11/02/2023]
Abstract
OBJECTIVE Information is needed to guide the design of randomized controlled trials (RCTs) evaluating L-citrulline therapy for premature infants with pulmonary hypertension associated with bronchopulmonary dysplasia (BPD-PH). Based on our single-dose pharmacokinetic study, we evaluated the ability of a multi-dose enteral L-citrulline strategy to achieve a target trough steady-state L-citrulline plasma concentration and its tolerability in premature infants. STUDY DESIGN Plasma L-citrulline concentrations were measured in six premature infants receiving 60 mg/kg L-citrulline every 6 h for 72 h before the first and last L-citrulline doses. L-citrulline concentrations were compared to concentration-time profiles from our previous study. RESULTS Target trough plasma L-citrulline concentrations were achieved in 2/6 subjects. No serious adverse events occurred. CONCLUSIONS Multi-dose L-citrulline was well tolerated. These results will assist in the design of phase II RCTs evaluating L-citrulline dosage strategies to achieve target plasma L-citrulline concentrations in infants at risk for BPD-PH. CLINICAL TRIALS gov ID: NCT03542812.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, the University of Utah Health, Salt Lake City, UT, USA.
| | - Judy L Aschner
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, NY, USA
- Department of Pediatrics, Hackensack Meridian School of Medicine, Nutley, NJ, USA
| | - Charul Avachat
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, MN, USA
| | - Angela K Birnbaum
- Department of Pediatrics, the University of Utah Health, Salt Lake City, UT, USA
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, MN, USA
| | - Catherine M T Sherwin
- Department of Pediatrics, the University of Utah Health, Salt Lake City, UT, USA
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, MN, USA
- Dayton Children's Hospital, Dayton, OH, USA
- Department of Pediatrics, Wright State University Boonshoft School of Medicine, Dayton, OH, USA
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Douglass MS, Kaplowitz MR, Zhang Y, Fike CD. Impact of l-citrulline on nitric oxide signaling and arginase activity in hypoxic human pulmonary artery endothelial cells. Pulm Circ 2023; 13:e12221. [PMID: 37063746 PMCID: PMC10091859 DOI: 10.1002/pul2.12221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 03/28/2023] [Accepted: 03/30/2023] [Indexed: 04/18/2023] Open
Abstract
Impaired nitric oxide (NO) signaling contributes to the development of pulmonary hypertension (PH). The l-arginine precursor, l-citrulline, improves NO signaling and has therapeutic potential in PH. However, there is evidence that l-citrulline might increase arginase activity, which in turn, has been shown to contribute to PH. Our major purpose was to determine if l-citrulline increases arginase activity in hypoxic human pulmonary artery endothelial cells (PAECs). In addition, to avoid potential adverse effects from high dose l-citrulline monotherapy, we evaluated whether the effect on NO signaling is greater using co-treatment with l-citrulline and another agent that improves NO signaling, folic acid, than either alone. Arginase activity was measured in human PAECs cultured under hypoxic conditions in the presence of l-citrulline (0-1 mM). NO production and endothelial nitric oxide synthase (eNOS) coupling, as assessed by eNOS dimer-to-monomer ratios, were measured in PAECs treated with l-citrulline and/or folic acid (0.2 μM). Arginase activity increased in hypoxic PAECs treated with 1 mM but not with either 0.05 or 0.1 mM l-citrulline. Co-treatment with folic acid and 0.1 mM l-citrulline increased NO production and eNOS dimer-to-monomer ratios more than treatment with either alone. The potential to increase arginase activity suggests that there might be plasma l-citrulline concentrations that should not be exceeded when using l-citrulline to treat PH. Rather than progressively increasing the dose of l-citrulline as a monotherapy, co-therapy with l-citrulline and folic acid merits consideration, due to the possibility of achieving efficacy at lower doses and minimizing side effects.
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Affiliation(s)
| | | | - Yongmei Zhang
- Department of PediatricsUniversity of UtahSalt Lake CityUtahUSA
| | - Candice D. Fike
- Department of PediatricsUniversity of UtahSalt Lake CityUtahUSA
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Fike CD, Aschner JL. Pharmacotherapy for Pulmonary Hypertension in Infants with Bronchopulmonary Dysplasia: Past, Present, and Future. Pharmaceuticals (Basel) 2023; 16:503. [PMID: 37111262 PMCID: PMC10141152 DOI: 10.3390/ph16040503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 03/07/2023] [Accepted: 03/09/2023] [Indexed: 03/31/2023] Open
Abstract
Approximately 8-42% of premature infants with chronic lung disease of prematurity, bronchopulmonary dysplasia (BPD), develop pulmonary hypertension (PH). Infants with BPD-PH carry alarmingly high mortality rates of up to 47%. Effective PH-targeted pharmacotherapies are desperately needed for these infants. Although many PH-targeted pharmacotherapies are commonly used to treat BPD-PH, all current use is off-label. Moreover, all current recommendations for the use of any PH-targeted therapy in infants with BPD-PH are based on expert opinion and consensus statements. Randomized Control Trials (RCTs) are needed to determine the efficacy of PH-targeted treatments in premature infants with or at risk of BPD-PH. Prior to performing efficacy RCTs, studies need to be conducted to obtain pharmacokinetic, pharmacodynamic, and safety data for any pharmacotherapy used in this understudied and fragile patient population. This review will discuss current and needed treatment strategies, identify knowledge deficits, and delineate both challenges to be overcome and approaches to be taken to develop effective PH-targeted pharmacotherapies that will improve outcomes for premature infants with or at risk of developing BPD-PH.
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Affiliation(s)
- Candice D. Fike
- Department of Pediatrics, University of Utah Health, Salt Lake City, UT 84108, USA
| | - Judy L. Aschner
- Department of Pediatrics, Joseph M. Sanzari Children’s Hospital at Hackensack University Medical Center, Hackensack, NJ 07601, USA
- Department of Pediatrics, Hackensack Meridian School of Medicine, Nutley, NJ 07110, USA
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Fike CD, Avachat C, Birnbaum AK, Aschner JL, Sherwin CM. Pharmacokinetics of L-Citrulline in Neonates at Risk of Developing Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension. Paediatr Drugs 2023; 25:87-96. [PMID: 36316628 PMCID: PMC10039462 DOI: 10.1007/s40272-022-00542-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/02/2022] [Indexed: 11/06/2022]
Abstract
BACKGROUND Options to treat pulmonary hypertension (PH) in neonates with bronchopulmonary dysplasia (BPD) are few and largely ineffective. Improving the bioavailability of nitric oxide (NO) might be an efficacious treatment for BPD-PH. When administered orally, the NO-L-arginine precursor, L-citrulline, increases NO production in children and adults, however, pharmacokinetic (PK) studies of oral L-citrulline have not been performed in infants and children. OBJECTIVES This study characterized the PK of enterally administered L-citrulline in neonates at risk of developing BPD-PH to devise a model-informed dosing strategy. METHODS AND RESULTS Ten premature neonates (≤ 28 weeks gestation) were administered a single dose of 150 mg/kg (powder form solubilized in sterile water) oral L-citrulline at 32 ± 1 weeks postmenstrual age. Due to the need to limit blood draws, time windows were used to maximize the sampling over the dosing interval by assigning neonates to one of two groups (ii) samples collected pre-dose and at 1- and 2.5-h post-dose, and (ii) pre-dose and 0.25- and 3-h post-dose. The L-arginine concentrations (µmol/L) and the L-citrulline (µmol/L) plasma concentration-time data were evaluated using non-compartmental analysis (Phoenix WinNonlin version 8.1). Optimal dosage strategies were derived using a simulation-based methodology. Simulated doses of 51.5 mg or 37.5 mg/kg given four times a day produced steady-state concentrations close to a target of 50 µmol/L. The volume of distribution (V/F) and clearance (CL/F) were 302.89 ml and 774.96 ml/h, respectively, with the drug exhibiting a half-life of 16 minutes. The AUC from the time of dosing to the time of last concentration was 1473.3 h*μmol/L, with Cmax and Tmax of 799 μmol/L and 1.55 h, respectively. CONCLUSION This is the first PK study in neonates presenting data that can be used to inform dosing strategies in future randomized controlled trials evaluating enteral L-citrulline as a potential treatment to reduce PH associated with BPD in premature neonates. REGISTRATION Clinical trials.gov Identifier: NCT03542812.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, The University of Utah Health, Salt Lake City, UT, USA
| | - Charul Avachat
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, MN, USA
| | - Angela K Birnbaum
- Department of Pediatrics, The University of Utah Health, Salt Lake City, UT, USA
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, MN, USA
| | - Judy L Aschner
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, NY, USA
- Department of Pediatrics, Hackensack Meridian School of Medicine, Nutley, NJ, USA
| | - Catherine M Sherwin
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, MN, USA.
- Department of Pediatrics, Wright State University Boonshoft School of Medicine, Dayton, OH, USA.
- Dayton Children's Hospital, Dayton, OH, USA.
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Douglass M, Dikalova A, Kaplowitz MR, Zhang Y, Cunningham G, Summar M, Fike CD. Folic acid, either solely or combined with L-citrulline, improves NO signaling and ameliorates chronic hypoxia-induced pulmonary hypertension in newborn pigs. Physiol Rep 2021; 9:e15096. [PMID: 34762361 PMCID: PMC8582293 DOI: 10.14814/phy2.15096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 09/29/2021] [Accepted: 10/02/2021] [Indexed: 11/24/2022] Open
Abstract
Concomitant with developing pulmonary hypertension (PH), newborn piglets exposed to chronic hypoxia develop pulmonary vascular NO signaling impairments. PH is reduced and NO signaling is improved in chronically hypoxic piglets treated with the NO-arginine precursor, L-citrulline. Folic acid positively impacts NO signaling. We evaluated whether the effect on NO signaling and PH is greater using co-treatment with folic acid and L-citrulline than either alone. From day 3 to day 10 of hypoxia, piglets were treated solely with folic acid, solely with L-citrulline, or co-treated with both. Catheters were placed to measure in vivo hemodynamics. NO production was measured in vitro in dissected pulmonary arteries. Compared to normoxic piglets, pulmonary vascular resistance (PVR) was elevated and NO production was reduced in untreated hypoxic piglets. Regardless of treatment strategy, PVR was less in all three treated groups of hypoxic piglets when compared to the untreated hypoxic group. In addition, for all three groups of treated hypoxic piglets, NO production was higher than the untreated group. Improvements in PVR and NO production did not differ between piglets co-treated with folic acid and L-citrulline and those treated solely with either. Thus, the impact on NO production and PVR was not augmented by combining folic acid and L-citrulline treatments. Nonetheless, treatment with folic acid, either singly or when combined with L-citrulline, increases NO production and inhibits PH in chronically hypoxic newborn piglets. Folic acid merits consideration as a therapy for PH in human infants with chronic heart and lung conditions that are associated with chronic hypoxia.
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Affiliation(s)
- Matthew Douglass
- Department of PediatricsUniversity of Utah HealthSalt Lake CityUtahUSA
| | - Anna Dikalova
- Department of MedicineVanderbilt University Medical CenterNashvilleTennesseeUSA
| | - Mark R. Kaplowitz
- Department of PediatricsUniversity of Utah HealthSalt Lake CityUtahUSA
| | - Yongmei Zhang
- Department of PediatricsUniversity of Utah HealthSalt Lake CityUtahUSA
| | - Gary Cunningham
- Division of Genetics and MetabolismChildren’s National Medical CenterWashingtonDistrict of ColumbiaUSA
| | - Marshall Summar
- Division of Genetics and MetabolismChildren’s National Medical CenterWashingtonDistrict of ColumbiaUSA
| | - Candice D. Fike
- Department of PediatricsUniversity of Utah HealthSalt Lake CityUtahUSA
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6
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Douglass MS, Zhang Y, Kaplowitz MR, Fike CD. L-citrulline increases arginase II protein levels and arginase activity in hypoxic piglet pulmonary artery endothelial cells. Pulm Circ 2021; 11:20458940211006289. [PMID: 33948161 PMCID: PMC8053766 DOI: 10.1177/20458940211006289] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/08/2021] [Indexed: 11/15/2022] Open
Abstract
The L-arginine precursor, L-citrulline, re-couples endothelial nitric oxide synthase, increases nitric oxide production, and ameliorates chronic hypoxia-induced pulmonary hypertension in newborn pigs. L-arginine can induce arginase, which, in turn, may diminish nitric oxide production. Our major purpose was to determine if L-citrulline increases arginase activity in hypoxic piglet pulmonary arterial endothelial cells, and if so, concomitantly impacts the ability to increase endothelial nitric oxide synthase re-coupling and nitric oxide production. Piglet pulmonary arterial endothelial cells were cultured in hypoxic conditions with L-citrulline (0-3 mM) and/or the arginase inhibitor S-(2-boronoethyl)-L-cysteine. We measured arginase activity and nitric oxide production. We assessed endothelial nitric oxide synthase coupling by measuring endothelial nitric oxide synthase dimers and monomers. L-citrulline concentrations ≥0.5 mM increased arginase activity in hypoxic pulmonary arterial endothelial cells. L-citrulline concentrations ≥0.1 mM increased nitric oxide production and concentrations ≥0.5 mM elevated endothelial nitric oxide synthase dimer-to-monomer ratios. Co-treatment with L-citrulline and S-(2-boronoethyl)-L-cysteine elevated endothelial nitric oxide synthase dimer-to-monomer ratios more than sole treatment. Despite inducing arginase, L-citrulline increased nitric oxide production and endothelial nitric oxide synthase coupling in hypoxic piglet pulmonary arterial endothelial cells. However, these dose-dependent findings raise the possibility that there could be L-citrulline concentrations that elevate arginase to levels that negate improvements in endothelial nitric oxide synthase dysfunction. Moreover, our findings suggest that combining an arginase inhibitor with L-citrulline merits evaluation as a treatment for chronic hypoxia-induced pulmonary hypertension.
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Affiliation(s)
| | - Yongmei Zhang
- Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
| | - Mark R Kaplowitz
- Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
| | - Candice D Fike
- Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
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7
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McClellan EB, Wang Z, Albertine KH, Kaplowitz MR, Zhang Y, Fike CD. l-Citrulline treatment alters the structure of the pulmonary circulation in hypoxic newborn pigs. Pediatr Pulmonol 2020; 55:2762-2772. [PMID: 32662946 PMCID: PMC7719608 DOI: 10.1002/ppul.24960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 07/12/2020] [Indexed: 11/07/2022]
Abstract
BACKGROUND Dysregulated nitric oxide (NO) signaling contributes to chronic hypoxia (CH)-induced pulmonary hypertension (PH). NO signaling is improved and pulmonary vascular resistance (PVR) is reduced in CH piglets treated with the l-arginine-NO precursor, l-citrulline. We hypothesized that l-citrulline might cause structural changes in the pulmonary circulation that would contribute to the reduction in PVR and that the l-citrulline-induced structural changes would be accompanied by alterations in vascular endothelial growth factor (VEGF) signaling. METHODS We evaluated small pulmonary arterial (PA) wall thickness, lung capillary density, and protein abundances of VEGF, VEGFR2, and phospho (p)-VEGFR2 in PA and peripheral lung samples of piglets raised in the lab in CH (10%-12% O2 ) from the day of life (DOL) 2 until DOL 11 to 12 or raised in room air (normoxia) by the vendor and studied on arrival to the lab on DOL 11 to 12. Some CH piglets were treated with oral l-citrulline (1-1.5 g/kg/d) starting on the third day of hypoxia. RESULTS PA wall thickness was 32% less and lung capillary formation was nearly doubled in l-citrulline treated than untreated CH piglets. Both of these l-citrulline-induced structural changes in the pulmonary circulation were accompanied by altered amounts of VEGF protein but not by altered amounts of either VEGFR2 or p-VEGFR2 proteins. CONCLUSIONS Alterations in the structure of the pulmonary circulation in CH piglets by l-citrulline are unlikely to be mediated by overall VEGF signaling. Nonetheless, l-citrulline- induced structural changes should reduce PVR and thereby contribute to the amelioration of CH-induced PH.
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Affiliation(s)
- Eric B McClellan
- Department of Pediatrics, University of Utah Health, Salt Lake City, Utah
| | - Zhengming Wang
- Department of Pediatrics, University of Utah Health, Salt Lake City, Utah
| | - Kurt H Albertine
- Department of Pediatrics, University of Utah Health, Salt Lake City, Utah
| | - Mark R Kaplowitz
- Department of Pediatrics, University of Utah Health, Salt Lake City, Utah
| | - Yongmei Zhang
- Department of Pediatrics, University of Utah Health, Salt Lake City, Utah
| | - Candice D Fike
- Department of Pediatrics, University of Utah Health, Salt Lake City, Utah
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8
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Dikalova A, Aschner JL, Kaplowitz MR, Cunningham G, Summar M, Fike CD. Combined l-citrulline and tetrahydrobiopterin therapy improves NO signaling and ameliorates chronic hypoxia-induced pulmonary hypertension in newborn pigs. Am J Physiol Lung Cell Mol Physiol 2020; 318:L762-L772. [PMID: 32073878 PMCID: PMC7191483 DOI: 10.1152/ajplung.00280.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 02/05/2020] [Accepted: 02/12/2020] [Indexed: 01/21/2023] Open
Abstract
Newborn pigs with chronic hypoxia-induced pulmonary hypertension (PH) have evidence of endothelial nitric oxide synthase (eNOS) uncoupling. In this model, we showed that therapies that promote eNOS coupling, either tetrahydrobiopterin (BH4), a NOS cofactor, or l-citrulline, a NO-l-arginine precursor, inhibit PH. We wanted to determine whether cotreatment with l-citrulline and a BH4 compound, sapropterin dihydrochloride, improves NO signaling and chronic hypoxia-induced PH more markedly than either alone. Normoxic (control) and hypoxic piglets were studied. Some hypoxic piglets received sole treatment with l-citrulline or BH4, or were cotreated with l-citrulline and BH4, from day 3 through day 10 of hypoxia. Catheters were placed for hemodynamic measurements, and pulmonary arteries were dissected to assess eNOS dimer-to-monomer ratios and NO production. In untreated hypoxic piglets, pulmonary vascular resistance (PVR) was higher and NO production and eNOS dimer-to-monomer ratios were lower than in normoxic piglets. Compared with the untreated hypoxic group, PVR was lower in hypoxic piglets cotreated with l-citrulline and BH4 and in those treated with l-citrulline alone but not for those treated solely with BH4. NO production and eNOS dimer-to-monomer ratios were greater for all three treated hypoxic groups compared with the untreated group. Notably, greater improvements in PVR, eNOS dimer-to-monomer ratios, and NO production were found in hypoxic piglets cotreated with l-citrulline and BH4 than in piglets treated with either alone. Cotreatment with l-citrulline and BH4 more effectively improves NO signaling and inhibits chronic hypoxia-induced PH than either treatment alone. Combination therapies may offer enhanced therapeutic capacity for challenging clinical conditions, such as chronic neonatal PH.
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Affiliation(s)
- Anna Dikalova
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Judy L Aschner
- Department of Pediatrics, Albert Einstein College of Medicine, New York, New York
- Department of Pediatrics, Hackensack Meridian Health School of Medicine at Seton Hall University, Nutley, New Jersey
| | - Mark R Kaplowitz
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee
- Department of Pediatrics, University of Utah Health, Salt Lake City, Utah
| | - Gary Cunningham
- Division of Genetics and Metabolism, Children's National Medical Center, Washington, District of Columbia
| | - Marshall Summar
- Division of Genetics and Metabolism, Children's National Medical Center, Washington, District of Columbia
| | - Candice D Fike
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee
- Department of Pediatrics, University of Utah Health, Salt Lake City, Utah
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Dikalova AE, Aschner JL, Zhang Y, Kaplowitz MR, Fike CD. Reactive oxygen species modulate Na +-coupled neutral amino acid transporter 1 expression in piglet pulmonary arterial endothelial cells. Am J Physiol Heart Circ Physiol 2019; 316:H911-H919. [PMID: 30794434 DOI: 10.1152/ajpheart.00674.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have previously shown that Na+-coupled neutral amino acid transporter 1 (SNAT1) modulates nitric oxide (NO) production in pulmonary arterial endothelial cells (PAECs) from newborn piglets. Specifically, the ability to increase NO production in response to the l-arginine-NO precursor l-citrulline is dependent on SNAT1 expression. Elucidating factors that regulate SNAT1 expression in PAECs could provide new insights and therapeutic targets relevant to NO production. Our major goals were to determine if reactive oxygen species (ROS) modulate SNAT1 expression in PAECs from newborn piglets and to evaluate the role of NADPH oxidase 1 (NOX1) and uncoupled endothelial NO synthase, enzymatic sources of ROS, in hypoxia-induced increases in SNAT1 expression. Treatment with either H2O2 or xanthine plus xanthine oxidase increased SNAT1 expression in PAECs from newborn piglets cultured under normoxic conditions. Hypoxia-induced increases in SNAT1 expression were inhibited by treatments with the ROS-removing agents catalase and superoxide dismutase, NOX1 siRNA, and the NO synthase inhibitor NG-nitro-l-arginine methyl ester. Both tetrahydropbiopterin (BH4) and l-citrulline, two therapies that decrease ROS by recoupling endothelial NO synthase, reduced the hypoxia-induced increase in SNAT1 expression. BH4 and l-citrulline treatment improved NO production in hypoxic PAECs despite a reduction in SNAT1 expression. In conclusion, SNAT1 expression is modulated by ROS in PAECs from newborn piglets. However, ROS-mediated decreases in SNAT1 expression per se do not implicate a reduction in NO production. Although SNAT1 may be critical to l-citrulline-induced increases in NO production, therapies designed to alter SNAT1 expression may not lead to a concordant change in NO production. NEW & NOTEWORTHY Na+-coupled neutral amino acid transporter 1 (SNAT1) modulates nitric oxide (NO) production in piglet pulmonary arterial endothelial cells. Factors that regulate SNAT1 expression in pulmonary arterial endothelial cells are unclear. Here, we show that ROS-reducing strategies inhibit hypoxia-induced increases in SNAT1 expression. l-Citrulline and tetrahydropbiopterin decrease SNAT1 expression but increase NO production. Although SNAT1 is modulated by ROS, changes in SNAT1 expression may not cause a concordant change in NO production.
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Affiliation(s)
- Anna E Dikalova
- Department of Pediatrics, Vanderbilt University Medical Center , Nashville, Tennessee.,Department of Medicine, Vanderbilt University Medical Center , Nashville, Tennessee
| | - Judy L Aschner
- Department of Pediatrics, Albert Einstein College of Medicine, The Bronx, New York
| | - Yongmei Zhang
- Department of Pediatrics, Vanderbilt University Medical Center , Nashville, Tennessee.,Department of Pediatrics, University of Utah Health , Salt Lake City, Utah
| | - Mark R Kaplowitz
- Department of Pediatrics, Vanderbilt University Medical Center , Nashville, Tennessee.,Department of Pediatrics, University of Utah Health , Salt Lake City, Utah
| | - Candice D Fike
- Department of Pediatrics, Vanderbilt University Medical Center , Nashville, Tennessee.,Department of Pediatrics, University of Utah Health , Salt Lake City, Utah
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10
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Hemnes AR, Rathinasabapathy A, Austin EA, Brittain EL, Carrier EJ, Chen X, Fessel JP, Fike CD, Fong P, Fortune N, Gerszten RE, Johnson JA, Kaplowitz M, Newman JH, Piana R, Pugh ME, Rice TW, Robbins IM, Wheeler L, Yu C, Loyd JE, West J. A potential therapeutic role for angiotensin-converting enzyme 2 in human pulmonary arterial hypertension. Eur Respir J 2018; 51:13993003.02638-2017. [PMID: 29903860 DOI: 10.1183/13993003.02638-2017] [Citation(s) in RCA: 167] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 04/25/2018] [Indexed: 12/20/2022]
Abstract
Pulmonary arterial hypertension (PAH) is a deadly disease with no cure. Alternate conversion of angiotensin II (AngII) to angiotensin-(1-7) (Ang-(1-7)) by angiotensin-converting enzyme 2 (ACE2) resulting in Mas receptor (Mas1) activation improves rodent models of PAH. Effects of recombinant human (rh) ACE2 in human PAH are unknown. Our objective was to determine the effects of rhACE2 in PAH.We defined the molecular effects of Mas1 activation using porcine pulmonary arteries, measured AngII/Ang-(1-7) levels in human PAH and conducted a phase IIa, open-label pilot study of a single infusion of rhACE2 (GSK2586881, 0.2 or 0.4 mg·kg-1 intravenously).Superoxide dismutase 2 (SOD2) and inflammatory gene expression were identified as markers of Mas1 activation. After confirming reduced plasma ACE2 activity in human PAH, five patients were enrolled in the trial. GSK2586881 was well tolerated with significant improvement in cardiac output and pulmonary vascular resistance. GSK2586881 infusion was associated with reduced plasma markers of inflammation within 2-4 h and increased SOD2 plasma protein at 2 weeks.PAH is characterised by reduced ACE2 activity. Augmentation of ACE2 in a pilot study was well tolerated, associated with improved pulmonary haemodynamics and reduced markers of oxidant and inflammatory mediators. Targeting this pathway may be beneficial in human PAH.
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Affiliation(s)
- Anna R Hemnes
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.,These two authors are joint first authors
| | - Anandharajan Rathinasabapathy
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.,These two authors are joint first authors
| | - Eric A Austin
- Dept of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Evan L Brittain
- Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Erica J Carrier
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Xinping Chen
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Joshua P Fessel
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Candice D Fike
- Dept of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Peter Fong
- Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Niki Fortune
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Robert E Gerszten
- Division of Cardiovascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Jennifer A Johnson
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Mark Kaplowitz
- Dept of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - John H Newman
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Robert Piana
- Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Meredith E Pugh
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Todd W Rice
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Ivan M Robbins
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Lisa Wheeler
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Chang Yu
- Dept of Biostatistics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - James E Loyd
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - James West
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
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O'Connor MG, Suthar D, Vera K, Slaughter JC, Maitre NL, Steele S, Beller A, Fike CD, Aschner JL, Moore PE, Austin ED. Pulmonary hypertension in the premature infant population: Analysis of echocardiographic findings and biomarkers. Pediatr Pulmonol 2018; 53:302-309. [PMID: 29168320 PMCID: PMC5815883 DOI: 10.1002/ppul.23913] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 10/18/2017] [Accepted: 10/22/2017] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Extremely low gestational age neonates (ELGANs) are at risk for pulmonary hypertension (PH). We hypothesized that PH, defined by echocardiogram at 36 weeks gestational age (GA), would associate with respiratory morbidity, increased oxidant stress, and reduced nitric oxide production. STUDY DESIGN ELGANs in the Vanderbilt fraction of the Prematurity and Respiratory Outcomes Program (PROP) who had echocardiograms at 36 ± 1 weeks GA were studied. Echocardiogram features of PH were compared with clinical characteristics as well as markers of oxidant stress and components of the nitric oxide pathway. Biomarkers were obtained at enrollment (median day 3), 7, 14, and 28 days of life. RESULTS Sixty of 172 infants had an echocardiogram at 36 weeks; 11 had evidence of PH. Infants did not differ by PH status in regards to demographics, respiratory morbidity, or oxidant stress. However, odds of more severe PH were significantly higher in infants with higher nitric oxide metabolites (NOx) at enrollment and with a lower citrulline level at day 7. CONCLUSIONS Respiratory morbidity may not always associate with PH at 36 weeks among ELGANs. However, components of nitric oxide metabolism are potential biologic markers of PH in need of further study.
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Affiliation(s)
- Michael G O'Connor
- Division of Pediatric Pulmonary, Allergy, and Immunology, Vanderbilt University, Nashville, Tennessee
| | - Divya Suthar
- Division of Pediatric Cardiology, Vanderbilt University, Nashville, Tennessee
| | - Kimberly Vera
- Division of Pediatric Cardiology, Vanderbilt University, Nashville, Tennessee
| | - James C Slaughter
- Department of Biostatistics, Vanderbilt University, Nashville, Tennessee
| | | | - Steven Steele
- Division of Neonatology, Vanderbilt University, Nashville, Tennessee
| | - Amy Beller
- Division of Neonatology, Vanderbilt University, Nashville, Tennessee
| | - Candice D Fike
- Division of Neonatology, University of Utah, Salt Lake City, Utah
| | - Judy L Aschner
- Divisionof Neonatology, Albert Einstein College of Medicine, Bronx, New York
| | - Paul E Moore
- Division of Pediatric Pulmonary, Allergy, and Immunology, Vanderbilt University, Nashville, Tennessee
| | - Eric D Austin
- Division of Pediatric Pulmonary, Allergy, and Immunology, Vanderbilt University, Nashville, Tennessee
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Dikalova A, Aschner JL, Kaplowitz MR, Summar M, Fike CD. Tetrahydrobiopterin oral therapy recouples eNOS and ameliorates chronic hypoxia-induced pulmonary hypertension in newborn pigs. Am J Physiol Lung Cell Mol Physiol 2016; 311:L743-L753. [PMID: 27542807 PMCID: PMC5142125 DOI: 10.1152/ajplung.00238.2016] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 08/14/2016] [Indexed: 01/21/2023] Open
Abstract
We previously showed that newborn piglets who develop pulmonary hypertension during exposure to chronic hypoxia have diminished pulmonary vascular nitric oxide (NO) production and evidence of endothelial NO synthase (eNOS) uncoupling (Fike CD, Dikalova A, Kaplowitz MR, Cunningham G, Summar M, Aschner JL. Am J Respir Cell Mol Biol 53: 255-264, 2015). Tetrahydrobiopterin (BH4) is a cofactor that promotes eNOS coupling. Current clinical strategies typically invoke initiating treatment after the diagnosis of pulmonary hypertension, rather than prophylactically. The major purpose of this study was to determine whether starting treatment with an oral BH4 compound, sapropterin dihydrochloride (sapropterin), after the onset of pulmonary hypertension would recouple eNOS in the pulmonary vasculature and ameliorate disease progression in chronically hypoxic piglets. Normoxic (control) and hypoxic piglets were studied. Some hypoxic piglets received oral sapropterin starting on day 3 of hypoxia and continued throughout an additional 7 days of hypoxic exposure. Catheters were placed for hemodynamic measurements, and pulmonary arteries were dissected to assess eNOS dimer-to-monomer ratios (a measure of eNOS coupling), NO production, and superoxide (O2·-) generation. Although higher than in normoxic controls, pulmonary vascular resistance was lower in sapropterin-treated hypoxic piglets than in untreated hypoxic piglets. Consistent with eNOS recoupling, eNOS dimer-to-monomer ratios and NO production were greater and O2·- generation was less in pulmonary arteries from sapropterin-treated than untreated hypoxic animals. When started after disease onset, oral sapropterin treatment inhibits chronic hypoxia-induced pulmonary hypertension at least in part by recoupling eNOS in the pulmonary vasculature of newborn piglets. Rescue treatment with sapropterin may be an effective strategy to inhibit further development of pulmonary hypertension in newborn infants suffering from chronic cardiopulmonary conditions associated with episodes of prolonged hypoxia.
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Affiliation(s)
- Anna Dikalova
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Judy L Aschner
- Department of Pediatrics, Albert Einstein College of Medicine and the Children's Hospital at Montefiore, New York, New York
| | - Mark R Kaplowitz
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pediatrics, the University of Utah School of Medicine, Salt Lake City, Utah; and
| | - Marshall Summar
- Division of Genetics and Metabolism, Children's National Medical Center, Washington, District of Columbia
| | - Candice D Fike
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pediatrics, the University of Utah School of Medicine, Salt Lake City, Utah; and
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Fike CD, Dikalova A, Kaplowitz MR, Cunningham G, Summar M, Aschner JL. Rescue Treatment with L-Citrulline Inhibits Hypoxia-Induced Pulmonary Hypertension in Newborn Pigs. Am J Respir Cell Mol Biol 2015; 53:255-64. [PMID: 25536367 DOI: 10.1165/rcmb.2014-0351oc] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Infants with cardiopulmonary disorders associated with hypoxia develop pulmonary hypertension. We previously showed that initiation of oral L-citrulline before and continued throughout hypoxic exposure improves nitric oxide (NO) production and ameliorates pulmonary hypertension in newborn piglets. Rescue treatments, initiated after the onset of pulmonary hypertension, better approximate clinical strategies. Mechanisms by which L-citrulline improves NO production merit elucidation. The objective of this study was to determine whether starting L-citrulline after the onset of pulmonary hypertension inhibits disease progression and improves NO production by recoupling endothelial NO synthase (eNOS). Hypoxic and normoxic (control) piglets were studied. Some hypoxic piglets received oral L-citrulline starting on Day 3 of hypoxia and continuing throughout the remaining 7 days of hypoxic exposure. Catheters were placed for hemodynamic measurements, and pulmonary arteries were dissected to assess NO production and eNOS dimer-to-monomer ratios (a measure of eNOS coupling). Pulmonary vascular resistance was lower in L-citrulline-treated hypoxic piglets than in untreated hypoxic piglets but was higher than in normoxic controls. NO production and eNOS dimer-to-monomer ratios were greater in pulmonary arteries from L-citrulline-treated than from untreated hypoxic animals but were lower than in normoxic controls. When started after disease onset, oral L-citrulline treatment improves NO production by recoupling eNOS and inhibits the further development of chronic hypoxia-induced pulmonary hypertension in newborn piglets. Oral L-citrulline may be a novel strategy to halt or reverse pulmonary hypertension in infants suffering from cardiopulmonary conditions associated with hypoxia.
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Affiliation(s)
- Candice D Fike
- 1 Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee.,2 Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee
| | - Anna Dikalova
- 1 Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Mark R Kaplowitz
- 1 Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Gary Cunningham
- 3 Division of Genetics and Metabolism, Children's National Medical Center, Washington, District of Columbia; and
| | - Marshall Summar
- 3 Division of Genetics and Metabolism, Children's National Medical Center, Washington, District of Columbia; and
| | - Judy L Aschner
- 4 Department of Pediatrics, Albert Einstein College of Medicine and the Children's Hospital at Montefiore, New York, New York
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Aschner JL, Fike CD. Plasma asymmetric dimethylarginine in infants with bronchopulmonary dysplasia: a promising biomarker despite uncertain pathogenic significance. J Pediatr 2015; 166:222-4. [PMID: 25454308 DOI: 10.1016/j.jpeds.2014.10.039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 10/17/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Judy L Aschner
- Department of Pediatrics, Albert Einstein College of Medicine, Children's Hospital at Montefiore, Bronx, New York.
| | - Candice D Fike
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee
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Fike CD, Summar M, Aschner JL. L-citrulline provides a novel strategy for treating chronic pulmonary hypertension in newborn infants. Acta Paediatr 2014; 103:1019-26. [PMID: 24862864 DOI: 10.1111/apa.12707] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Revised: 03/23/2014] [Accepted: 05/23/2014] [Indexed: 02/05/2023]
Abstract
UNLABELLED Effective therapies are urgently needed for infants with forms of pulmonary hypertension that develop or persist beyond the first week of life. The L-arginine nitric oxide (NO) precursor, L-citrulline, improves NO signalling and ameliorates pulmonary hypertension in newborn animals. In vitro studies demonstrate that manipulating L-citrulline transport alters NO production. CONCLUSION Strategies that increase the supply and transport of L-citrulline merit pursuit as novel approaches to managing infants with chronic, progressive pulmonary hypertension.
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Affiliation(s)
- Candice D. Fike
- Department of Pediatrics; Vanderbilt University Medical Center; Nashville TN USA
- Monroe Carell Jr. Children's Hospital at Vanderbilt; Nashville TN USA
| | - Marshall Summar
- Division of Genetics and Metabolism; Children's National Medical Center; Washington DC USA
| | - Judy L. Aschner
- Department of Pediatrics; Albert Einstein College of Medicine and the Children's Hospital at Montefiore; New York NY USA
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Fike CD, Aschner JL, Kaplowitz MR, Zhang Y, Madden JA. Reactive oxygen species scavengers improve voltage-gated K(+) channel function in pulmonary arteries of newborn pigs with progressive hypoxia-induced pulmonary hypertension. Pulm Circ 2013; 3:551-63. [PMID: 24618540 DOI: 10.1086/674307] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Abstract Changes in voltage-gated K(+) (Kv) channel function contribute to the pathogenesis of pulmonary hypertension. Yet the mechanisms underlying Kv channel impairments in the pulmonary circulation remain unclear. We tested the hypothesis that reactive oxygen species (ROSs) contribute to the Kv channel dysfunction that develops in resistance-level pulmonary arteries (PRAs) of piglets exposed to chronic in vivo hypoxia. Piglets were raised in either room air (control) or hypoxia for 3 or 10 days. To evaluate Kv channel function, responses to the Kv channel antagonist 4-aminopyridine (4-AP) were measured in cannulated PRAs. To assess the influence of ROSs, PRAs were treated with the ROS-removing agent M40403 (which dismutates superoxide to hydrogen peroxide), plus polyethylene glycol catalase (which converts hydrogen peroxide to water). Responses to 4-AP were diminished in PRAs from both groups of hypoxic piglets. ROS-removing agents had no impact on 4-AP responses in PRAs from piglets exposed to 3 days of hypoxia but significantly increased the response to 4-AP in PRAs from piglets exposed to 10 days of hypoxia. Kv channel function is impaired in PRAs of piglets exposed to 3 or 10 days of in vivo hypoxia. ROSs contribute to Kv channel dysfunction in PRAs from piglets exposed to hypoxia for 10 days but are not involved with the Kv channel dysfunction that develops within 3 days of exposure to hypoxia. Therapies to remove ROSs might improve Kv channel function and thereby ameliorate the progression, but not the onset, of pulmonary hypertension in chronically hypoxic newborn piglets.
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Affiliation(s)
- Candice D Fike
- 1 Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; and Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee, USA
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Abstract
Abstract Infants with forms of pulmonary hypertension (PH) that persist or develop beyond the first week of life are an understudied group of patients with up to 40%-60% mortality. The clinical management of the progressive PH that develops in these infants is challenging because of the nonspecific signs and symptoms of clinical presentation, the limited diagnostic sensitivity of standard echocardiographic techniques, and the lack of proven therapies. The signaling mechanisms that underlie the structural and functional abnormalities in the pulmonary circulation of these infants are not yet clear. The ability to improve outcomes for these patients awaits technological advances to improve diagnostic capabilities and therapeutic discoveries made in basic science laboratories that can be tested in randomized clinical trials.
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Affiliation(s)
- Candice D Fike
- 1 Department of Pediatrics, Vanderbilt University School of Medicine, and Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee, USA
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Fike CD, Dikalova A, Slaughter JC, Kaplowitz MR, Zhang Y, Aschner JL. Reactive oxygen species-reducing strategies improve pulmonary arterial responses to nitric oxide in piglets with chronic hypoxia-induced pulmonary hypertension. Antioxid Redox Signal 2013; 18:1727-38. [PMID: 23244497 PMCID: PMC3619184 DOI: 10.1089/ars.2012.4823] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
AIMS There are no effective treatments for chronic pulmonary hypertension in infants with cardiopulmonary disorders associated with hypoxia, such as those with chronic lung disease. These patients often have poor or inconsistent pulmonary dilator responses to inhaled nitric oxide (iNO) therapy for unknown reasons. One possible explanation for poor responsiveness to iNO is reduced NO bioavailability caused by interactions between reactive oxygen species (ROS) and NO. Our major aim was to determine if strategies to reduce ROS improve dilator responses to the NO donor, S-nitroso-N-acetyl-penicillamine (SNAP), in resistance pulmonary arteries (PRAs) from a newborn piglet model of chronic pulmonary hypertension. RESULTS The dilation to SNAP was significantly impaired in PRAs from piglets with chronic hypoxia-induced pulmonary hypertension. ROS scavengers, including cell-permeable and impermeable agents to degrade hydrogen peroxide (H(2)O(2)), improved dilation to SNAP in PRAs from chronically hypoxic piglets. Treatment with agents to inhibit nitric oxide synthase and NADPH oxidase, potential enzymatic sources of ROS, also improved dilation to SNAP in PRAs from hypoxic piglets. INNOVATION Our studies are the first to utilize a newborn model of chronic pulmonary hypertension to evaluate the impact of a number of potential therapeutic strategies for ROS removal on responses to exogenous NO in the vessels most relevant to the regulation of pulmonary vascular resistance (PRA). CONCLUSIONS Strategies aimed at reducing ROS merit further evaluation and consideration as therapeutic approaches to improve responses to iNO in infants with chronic pulmonary hypertension.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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Fike CD, Sidoryk-Wegrzynowicz M, Aschner M, Summar M, Prince LS, Cunningham G, Kaplowitz M, Zhang Y, Aschner JL. Prolonged hypoxia augments L-citrulline transport by system A in the newborn piglet pulmonary circulation. Cardiovasc Res 2012; 95:375-84. [PMID: 22673370 DOI: 10.1093/cvr/cvs186] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
AIMS Pulmonary arterial endothelial cells (PAECs) express the enzymes needed for generation of l-arginine from intracellular l-citrulline but do not express the enzymes needed for de novo l-citrulline synthesis. Hence, l-citrulline levels in PAECs are dependent on l-citrulline transport. Once generated, l-arginine can be converted to l-citrulline and nitric oxide (NO) by the enzyme NO synthase. We sought to determine whether hypoxia, a condition aetiologically linked to pulmonary hypertension, alters the transport of l-citrulline and the expression of the sodium-coupled neutral amino acid transporters (SNATs) in PAECs from newborn piglets. METHODS AND RESULTS PAECs isolated from newborn piglets were cultured under normoxic and hypoxic conditions and used to measure SNAT1, 2, 3, and 5 protein expression and (14)C-l-citrulline uptake. SNAT1 protein expression was increased, while SNAT2, SNAT3, and SNAT5 expression was unaltered in hypoxic PAECs. (14)C-l-citrulline uptake was increased in hypoxic PAECs. Studies with inhibitors of System A (SNAT1/2) and System N (SNAT3/5) revealed that the increased (14)C-l-citrulline uptake was largely due to System A-mediated transport. Additional studies were performed to evaluate SNAT protein expression and l-citrulline levels in lungs of piglets with chronic hypoxia-induced pulmonary hypertension and comparable age controls. Lungs from piglets raised in chronic hypoxia exhibited greater SNAT1 expression and higher l-citrulline levels than lungs from controls. CONCLUSION Increased SNAT1 expression and the concomitant enhanced ability to transport l-citrulline in PAECs could represent an important regulatory mechanism to counteract NO signalling impairments known to occur during the development of chronic hypoxia-induced pulmonary hypertension in newborns.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, University School of Medicine, Vanderbilt University Medical Center, 2215 B Garland Ave., Nashville, TN 37232-0656, USA.
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Fike CD, Kaplowitz M, Zhang Y, Dantuma M, Madden JA. Effect of a phosphodiesterase 5 inhibitor on pulmonary and cerebral arteries of newborn piglets with chronic hypoxia-induced pulmonary hypertension. Neonatology 2012; 101:28-39. [PMID: 21791937 PMCID: PMC3151003 DOI: 10.1159/000326270] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 02/14/2011] [Indexed: 11/19/2022]
Abstract
BACKGROUND The use of phosphodiesterase 5 (PDE5) inhibitors to treat newborns with pulmonary hypertension is increasing. The effect of PDE5 inhibitors on the neonatal cerebral circulation remains unknown. The neonatal piglet model of chronic hypoxia-induced pulmonary hypertension allows the study of the effects of PDE5 inhibitors on both the pulmonary and cerebral circulations. OBJECTIVES To determine whether the PDE5 inhibitor, zaprinast, causes dilation in pulmonary and middle cerebral arteries (MCA) of normoxic newborn piglets and those with chronic hypoxia-induced pulmonary hypertension, and to evaluate whether zaprinast alters responses to increased pressure (autoregulatory ability) of the MCA. METHODS Two-day-old piglets were raised in normoxia or hypoxia for 3 or 10 days. Pulmonary arteries and MCA were isolated and pressurized, after which changes in diameter to zaprinast were measured. MCA pressure-diameter relationships were determined. RESULTS Dilation to zaprinast was similar in pulmonary arteries from normoxic and hypoxic piglets. Zaprinast dilated MCA from all groups but the response was diminished in MCA from piglets raised in hypoxia for 10 days. MCA pressure-diameter relationships (autoregulation) did not differ between the groups. CONCLUSIONS Pulmonary artery dilation to zaprinast supports the use of PDE5 inhibitors to treat pulmonary hypertension in neonates. PDE5 inhibitors function as MCA dilators but do not impair the pressure-diameter behavior of the cerebral circulation of either normoxic newborn piglets or those with chronic hypoxia-induced pulmonary hypertension. These findings suggest that cerebral autoregulation is likely to be intact with acute PDE5 inhibitor treatment in infants with pulmonary hypertension in conditions associated with chronic hypoxia.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, Vanderbilt University School of Medicine and the Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, TN 37232-0656, USA.
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Fike CD, Aschner JL, Slaughter JC, Kaplowitz MR, Zhang Y, Pfister SL. Pulmonary arterial responses to reactive oxygen species are altered in newborn piglets with chronic hypoxia-induced pulmonary hypertension. Pediatr Res 2011; 70:136-41. [PMID: 21516056 PMCID: PMC3131458 DOI: 10.1203/pdr.0b013e3182207ce7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Reactive oxygen species (ROS) have been implicated in the pathogenesis of pulmonary hypertension. ROS might mediate vascular responses, at least in part, by stimulating prostanoid production. Our goals were to determine whether the effect of ROS on vascular tone is altered in resistance pulmonary arteries (PRAs) of newborn piglets with chronic hypoxia-induced pulmonary hypertension and the role, if any, of prostanoids in ROS-mediated responses. In cannulated, pressurized PRA, ROS generated by xanthine (X) plus xanthine oxidase (XO) had minimal effect on vascular tone in control piglets but caused significant vasoconstriction in hypoxic piglets. Both cyclooxygenase inhibition with indomethacin and thromboxane synthase inhibition with dazoxiben significantly blunted constriction to X+XO in hypoxic PRA. X+XO increased prostacyclin production (70 ± 8%) by a greater degree than thromboxane production (50 ± 6%) in control PRA; this was not the case in hypoxic PRA where the increases in prostacyclin and thromboxane production were not statistically different (78 ± 13% versus 216 ± 93%, respectively). Thromboxane synthase expression was increased in PRA from hypoxic piglets, whereas prostacyclin synthase expression was similar in PRA from hypoxic and control piglets. Under conditions of chronic hypoxia, altered vascular responses to ROS may contribute to pulmonary hypertension by a mechanism that involves the prostanoid vasoconstrictor, thromboxane.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, Vanderbilt University School of Medicine and Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee 37232, USA.
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Fike CD, Pfister SL, Slaughter JC, Kaplowitz MR, Zhang Y, Zeng H, Frye NR, Aschner JL. Protein complex formation with heat shock protein 90 in chronic hypoxia-induced pulmonary hypertension in newborn piglets. Am J Physiol Heart Circ Physiol 2010; 299:H1190-204. [PMID: 20693398 DOI: 10.1152/ajpheart.01207.2009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Aberrant interactions between heat shock protein (Hsp)90 and its client proteins could contribute to pulmonary hypertension. We tested the hypotheses that 1) the interaction between Hsp90 and its known client protein, endothelial nitric oxide synthase (eNOS), is impaired in pulmonary resistance arteries (PRAs) from piglets with pulmonary hypertension caused by exposure to 3 or 10 days of hypoxia and 2) Hsp90 interacts with the prostanoid pathway proteins prostacyclin synthase (PGIS) and/or thromboxane synthase (TXAS). We also determined whether Hsp90 antagonism with geldanamycin alters the agonist-induced synthesis of prostacyclin and thromboxane or alters PRA responses to these prostaglandin metabolites. Compared with normoxic piglets, less eNOS coimmunoprecipitated with Hsp90 in PRAs from hypoxic piglets. Despite reduced Hsp90-eNOS interactions, dilation to ACh was enhanced in geldanamycin-treated PRAs from hypoxic, but not normoxic, piglets. In PRAs from all groups of piglets, PGIS and TXAS coimmunoprecipitated with Hsp90. Geldanamycin reduced the ACh-induced synthesis of prostacyclin and thromboxane and altered responses to the thromboxane mimetic U-46619 in PRAs from all groups. Although geldanamycin enhanced responses to prostacyclin in PRAs from both groups of hypoxic piglets, geldanamycin had no effect on prostacyclin responses in PRAs from either group of normoxic piglets. Our findings indicate that Hsp90 influences both prostanoid and eNOS signaling in the pulmonary circulation of newborn piglets and that the impact of pharmacological inhibition of Hsp90 on these signaling pathways is altered during exposure to chronic hypoxia.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, Vanderbilt University School of Medicine and Monroe Carell Jr. Children's Hospital, Vanderbilt, Nashville, TN 37232-0656, USA.
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Ananthakrishnan M, Barr FE, Summar ML, Smith HA, Kaplowitz M, Cunningham G, Magarik J, Zhang Y, Fike CD. L-Citrulline ameliorates chronic hypoxia-induced pulmonary hypertension in newborn piglets. Am J Physiol Lung Cell Mol Physiol 2009; 297:L506-11. [PMID: 19617312 DOI: 10.1152/ajplung.00017.2009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Newborn piglets develop pulmonary hypertension and have diminished pulmonary vascular nitric oxide (NO) production when exposed to chronic hypoxia. NO is produced by endothelial NO synthase (eNOS) in the pulmonary vascular endothelium using l-arginine as a substrate and producing l-citrulline as a byproduct. l-Citrulline is metabolized to l-arginine by two enzymes that are colocated with eNOS in pulmonary vascular endothelial cells. The purpose of this study was to determine whether oral supplementation with l-citrulline during exposure of newborn piglets to 10 days of chronic hypoxia would prevent the development of pulmonary hypertension and increase pulmonary NO production. A total of 17 hypoxic and 17 normoxic control piglets were studied. Six of the 17 hypoxic piglets were supplemented with oral l-citrulline starting on the first day of hypoxia. l-Citrulline supplementation was provided orally twice a day. After 10 days of hypoxia or normoxia, the animals were anesthetized, hemodynamic measurements were performed, and the lungs were perfused in situ. Pulmonary arterial pressure and pulmonary vascular resistance were significantly lower in hypoxic animals treated with l-citrulline compared with untreated hypoxic animals (P < 0.001). In vivo exhaled NO production (P = 0.03) and nitrite/nitrate accumulation in the perfusate of isolated lungs (P = 0.04) were significantly higher in l-citrulline-treated hypoxic animals compared with untreated hypoxic animals. l-Citrulline supplementation ameliorated the development of pulmonary hypertension and increased NO production in piglets exposed to chronic hypoxia. We speculate that l-citrulline may benefit neonates exposed to prolonged periods of hypoxia from cardiac or pulmonary causes.
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Affiliation(s)
- Madhumita Ananthakrishnan
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, Nashville, TN, USA
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Dennis KE, Aschner JL, Milatovic D, Schmidt JW, Aschner M, Kaplowitz MR, Zhang Y, Fike CD. NADPH oxidases and reactive oxygen species at different stages of chronic hypoxia-induced pulmonary hypertension in newborn piglets. Am J Physiol Lung Cell Mol Physiol 2009; 297:L596-607. [PMID: 19592458 DOI: 10.1152/ajplung.90568.2008] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recently, we reported that reactive oxygen species (ROS) generated by NADPH oxidase (NOX) contribute to aberrant responses in pulmonary resistance arteries (PRAs) of piglets exposed to 3 days of hypoxia (Am J Physiol Lung Cell Mol Physiol 295: L881-L888, 2008). An objective of the present study was to determine whether NOX-derived ROS also contribute to altered PRA responses at a more advanced stage of pulmonary hypertension, after 10 days of hypoxia. We further wished to advance knowledge about the specific NOX and antioxidant enzymes that are altered at early and later stages of pulmonary hypertension. Piglets were raised in room air (control) or hypoxia for 3 or 10 days. Using a cannulated artery technique, we found that treatments with agents that inhibit NOX (apocynin) or remove ROS [an SOD mimetic (M40403) + polyethylene glycol-catalase] diminished responses to ACh in PRAs from piglets exposed to 10 days of hypoxia. Western blot analysis showed an increase in expression of NOX1 and the membrane fraction of p67phox. Expression of NOX4, SOD2, and catalase were unchanged, whereas expression of SOD1 was reduced, in arteries from piglets raised in hypoxia for 3 or 10 days. Markers of oxidant stress, F(2)-isoprostanes, measured by gas chromatography-mass spectrometry, were increased in PRAs from piglets raised in hypoxia for 3 days, but not 10 days. We conclude that ROS derived from some, but not all, NOX family members, as well as alterations in the antioxidant enzyme SOD1, contribute to aberrant PRA responses at an early and a more progressive stage of chronic hypoxia-induced pulmonary hypertension in newborn piglets.
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Affiliation(s)
- Kathleen E Dennis
- Dept. of Pediatrics, Vanderbilt Univ. Medical Center, 2215 B Garland Ave., Nashville, TN 37232-0656, USA
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Aschner JL, Zeng H, Kaplowitz MR, Zhang Y, Slaughter JC, Fike CD. Heat shock protein 90-eNOS interactions mature with postnatal age in the pulmonary circulation of the piglet. Am J Physiol Lung Cell Mol Physiol 2009; 296:L555-64. [PMID: 19136580 DOI: 10.1152/ajplung.90456.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Binding of endothelial nitric oxide synthase (eNOS) to the chaperone protein, Hsp90, promotes coupled eNOS synthetic activity. Using resistance level pulmonary arteries (PRA) from 2-day-, 5- to 7-day-, and 12-day-old piglets, we tested the hypothesis that Hsp90-eNOS interactions are developmentally regulated in the early neonatal period. PRA were isolated for coimmunoprecipitation and immunoblot analyses or cannulated for continuous diameter measurements using the pressurized myography technique. NOS inhibition caused less constriction in PRA from 2-day- compared with 5- to 7-day- and 12-day-old piglets. No age-related differences were found in dilation responses to an NO donor or in protein expression of Hsp90, phospho-eNOS (Ser(1177)), Akt, phospho-Akt, or caveolin-1. Compared with the older animals, PRA from 2-day-old piglets had higher total eNOS expression but displayed less binding of eNOS to Hsp90 and Akt. Hsp90 antagonism with radicicol induced greatest constriction in PRA from 12-day-old piglets. ACh stimulation caused dilation in PRA from 5- to 7-day- and 12-day-old but not 2-day-old animals, despite rapid and equivalent ACh-mediated eNOS phosphorylation (Ser(1177)) in all three age groups. Hsp90 inhibition abolished ACh-mediated dilation in PRA from the older piglets. ACh failed to stimulate Hsp90-eNOS binding in 2-day-old but induced a significant increase in Hsp90-eNOS coimmunoprecipitation in PRA from the older age groups, which was blocked by Hsp90 antagonism. We conclude that physical interactions between Hsp90 and eNOS mature over the first weeks of life, likely contributing to the postnatal fall in pulmonary vascular resistance and changes in agonist-induced pulmonary vascular responses characteristic of the early neonatal period.
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Affiliation(s)
- Judy L Aschner
- Department of Pediatrics,Vanderbilt University Medical Center, Nashville, Tennessee, USA.
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Fike CD, Slaughter JC, Kaplowitz MR, Zhang Y, Aschner JL. Reactive oxygen species from NADPH oxidase contribute to altered pulmonary vascular responses in piglets with chronic hypoxia-induced pulmonary hypertension. Am J Physiol Lung Cell Mol Physiol 2008; 295:L881-8. [PMID: 18757525 DOI: 10.1152/ajplung.00047.2008] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Our main objective was to determine whether reactive oxygen species (ROS), such as superoxide (O(2)(-)) and hydrogen peroxide (H(2)O(2)), contribute to altered pulmonary vascular responses in piglets with chronic hypoxia-induced pulmonary hypertension. Piglets were raised in either room air (control) or hypoxia for 3 days. The effect of the cell-permeable superoxide dismutase mimetic (SOD; M40403) and/or PEG-catalase (PEG-CAT) on responses to acetylcholine (ACh) was measured in endothelium-intact and denuded pulmonary resistance arteries (PRAs; 90-to-300-microm diameter). To determine whether NADPH oxidase is an enzymatic source of ROS, PRA responses to ACh were measured in the presence and absence of a NADPH oxidase inhibitor, apocynin (APO). A Western blot technique was used to assess expression of the NADPH oxidase subunit, p67phox. A lucigenin-derived chemiluminescence technique was used to measure ROS production stimulated by the NADPH oxidase substrate, NADPH. ACh responses, which were dilation in intact control arteries but constriction in both intact and denuded hypoxic arteries, were diminished by M40403, PEG-CAT, the combination of M40403 plus PEG-CAT, as well as by APO. Although total amounts were not different, membrane-associated p67phox was greater in PRAs from hypoxic compared with control piglets. NADPH-stimulated lucigenin luminescence was nearly doubled in PRAs from hypoxic vs. control piglets. We conclude that ROS generated by NADPH oxidase contribute to the aberrant pulmonary arterial responses in piglets exposed to 3 days of hypoxia.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, Vanderbilt University Medical Center, 2215 B Garland Avenue, Nashville, TN 37232-0656, USA.
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Aschner JL, Foster SL, Kaplowitz M, Zhang Y, Zeng H, Fike CD. Heat shock protein 90 modulates endothelial nitric oxide synthase activity and vascular reactivity in the newborn piglet pulmonary circulation. Am J Physiol Lung Cell Mol Physiol 2007; 292:L1515-25. [PMID: 17337508 DOI: 10.1152/ajplung.00252.2006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Heat shock protein 90 (Hsp90) binding to endothelial nitric oxide synthase (eNOS) is an important step in eNOS activation. The conformational state of bound Hsp90 determines whether eNOS produces nitric oxide (NO) or superoxide (O(2)(*-)). We determined the effects of the Hsp90 antagonists geldanamycin (GA) and radicicol (RA) on basal and ACh-stimulated changes in vessel diameter, cGMP production, and Hsp90:eNOS coimmunoprecipitation in piglet resistance level pulmonary arteries (PRA). In perfused piglet lungs, we evaluated the effects of GA and RA on ACh-stimulated changes in pulmonary arterial pressure (Ppa) and perfusate accumulation of stable NO metabolites (NOx(-)). The effects of GA and RA on ACh-stimulated O(2)(*-) generation was investigated in cultured pulmonary microvascular endothelial cells (PMVEC) by dihydroethidine (DHE) oxidation and confocal microscopy. Hsp90 inhibition with GA or RA reduced ACh-mediated dilation, abolished the ACh-stimulated increase in cGMP, and reduced eNOS:Hsp90 coprecipitation. GA and RA also inhibited the ACh-mediated changes in Ppa and NOx(-) accumulation rates in perfused lungs. ACh increased the rate of DHE oxidation in PMVEC pretreated with GA and RA but not in untreated cells. The cell-permeable superoxide dismutase mimetic M40401 reversed GA-mediated inhibition of ACh-induced dilation in PRA. We conclude that Hsp90 is a modulator of eNOS activity and vascular reactivity in the newborn piglet pulmonary circulation. Uncoupling of eNOS with GA or RA inhibits ACh-mediated dilation by a mechanism that involves O(2)(*-) generation.
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Affiliation(s)
- Judy L Aschner
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
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Fike CD, Kaplowitz M, Zhang Y, Zeng H, Aschner J. HSP90/ENOS interactions contribute to maturational and chronic hypoxia‐induced changes in pulmonary vascular reactivity in newborn pigs. FASEB J 2007. [DOI: 10.1096/fasebj.21.6.a1437-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Candice D Fike
- PediatricsVanderbilt Univ. Med. Center2215 B Garland Ave., 1125 MRB IVNashvilleTN37232
| | - Mark Kaplowitz
- PediatricsVanderbilt Univ. Med. Center2215 B Garland Ave., 1125 MRB IVNashvilleTN37232
| | - Yongmei Zhang
- PediatricsVanderbilt Univ. Med. Center2215 B Garland Ave., 1125 MRB IVNashvilleTN37232
| | - Heng Zeng
- PediatricsVanderbilt Univ. Med. Center2215 B Garland Ave., 1125 MRB IVNashvilleTN37232
| | - Judy Aschner
- PediatricsVanderbilt Univ. Med. Center2215 B Garland Ave., 1125 MRB IVNashvilleTN37232
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Fike CD, Kaplowitz MR, Zhang Y, Madden JA. Voltage-gated K+ channels at an early stage of chronic hypoxia-induced pulmonary hypertension in newborn piglets. Am J Physiol Lung Cell Mol Physiol 2006; 291:L1169-76. [PMID: 16861383 DOI: 10.1152/ajplung.00117.2006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our purpose was to determine whether smooth muscle cell membrane properties are altered in small pulmonary arteries (SPA) of piglets at an early stage of pulmonary hypertension. Piglets were raised in either room air (control) or hypoxia for 3 days. A microelectrode technique was used to measure smooth muscle cell membrane potential ( Em) in cannulated, pressurized SPA (100- to 300-μm diameter). SPA responses to the voltage-gated K+ (KV) channel antagonist 4-aminopyridine (4-AP) and the KV1 family channel antagonist correolide were measured. Other SPA were used to assess amounts of KV1.2, KV1.5, and KV2.1 (immunoblot technique). Em was more positive in SPA of chronically hypoxic piglets than in SPA of comparable-age control piglets. The magnitude of constriction elicited by either 4-AP or correolide was diminished in SPA from hypoxic piglets. Abundances of KV1.2 were reduced, whereas abundances of both KV1.5 and KV2.1 were unaltered, in SPA from hypoxic piglets. At least partly because of reduced amounts of KV1.2, smooth muscle cell membrane properties are altered such that Em is depolarized and KV channel family function is impaired in SPA of piglets at an early stage of chronic hypoxia-induced pulmonary hypertension.
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Affiliation(s)
- Candice D Fike
- Department of Neurology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, NC, USA
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Abstract
Devising therapies that might prevent the onset or progression of pulmonary hypertension in newborns has received little attention. Our major objective was to determine whether sildenafil, a selective phosphodiesterase inhibitor, prevents the development of an early stage of chronic hypoxia-induced pulmonary hypertension in newborn pigs. Another objective was to determine whether sildenafil causes pulmonary vasodilation without systemic vasodilation in piglets with chronic pulmonary hypertension. Piglets were raised in room air (control, n = 5) or 10-11% O(2) (hypoxic, n = 17) for 3 days. Some piglets (n = 4) received oral sildenafil, 12 mg/kg/day, throughout exposure to hypoxia. All piglets were anesthetized and catheterized, and pulmonary arterial pressure (Ppa), pulmonary wedge pressure (Pw), aortic pressure (Ao), and cardiac output (CO) were measured. Then for some piglets raised in hypoxia for 3 days, a single oral sildenafil dose (3 mg/kg, n = 6) or placebo (n = 5) was given, and hemodynamic measurements were repeated. For piglets raised in hypoxia for 3 days, mean Ppa and calculated PVR were elevated above respective values in control piglets. Mean Ppa and PVR did not differ between piglets that received sildenafil throughout exposure to hypoxia and those that did not. For piglets with chronic hypoxia-induced pulmonary hypertension that received a single oral dose of sildenafil, mean Ppa and PVR decreased, while mean Pw, CO, mean Ao, and systemic vascular resistance remained the same. All hemodynamic measurements were unchanged after placebo. Oral sildenafil did not influence the early stage of chronic hypoxia-induced pulmonary hypertension in newborn piglets. However, a single oral dose of sildenafil caused pulmonary vasodilation, without systemic vasodilation, in piglets with chronic hypoxia-induced pulmonary hypertension, which may have therapeutic implications.
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MESH Headings
- Administration, Oral
- Animals
- Animals, Newborn
- Chronic Disease
- Cyclic GMP/metabolism
- Disease Models, Animal
- Disease Progression
- Dose-Response Relationship, Drug
- Hemodynamics/drug effects
- Humans
- Hypertension, Pulmonary/drug therapy
- Hypertension, Pulmonary/etiology
- Hypertension, Pulmonary/physiopathology
- Hypoxia/complications
- Infant, Newborn
- Infant, Newborn, Diseases/drug therapy
- Infant, Newborn, Diseases/physiopathology
- Lung/blood supply
- Piperazines/administration & dosage
- Pulmonary Artery/drug effects
- Pulmonary Artery/metabolism
- Purines
- Reference Values
- Sildenafil Citrate
- Sulfones
- Swine
- Treatment Outcome
- Vasodilator Agents/administration & dosage
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Affiliation(s)
- Karen M Binns-Loveman
- Division of Neonatology, Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
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Abstract
The pulmonary vasoconstrictor, thromboxane, may contribute to the development of pulmonary hypertension. Our objective was to determine whether a combined thromboxane synthase inhibitor-receptor antagonist, terbogrel, prevents pulmonary hypertension and the development of aberrant pulmonary arterial responses in newborn piglets exposed to 3 days of hypoxia. Piglets were maintained in room air (control) or 11% O(2) (hypoxic) for 3 days. Some hypoxic piglets received terbogrel (10 mg/kg po bid). Pulmonary arterial pressure, pulmonary wedge pressure, and cardiac output were measured in anesthetized animals. A cannulated artery technique was used to measure responses to acetylcholine. Pulmonary vascular resistance for terbogrel-treated hypoxic piglets was almost one-half the value of untreated hypoxic piglets but remained greater than values for control piglets. Dilation to acetylcholine in preconstricted pulmonary arteries was greater for terbogrel-treated hypoxic than for untreated hypoxic piglets, but it was less for pulmonary arteries from both groups of hypoxic piglets than for control piglets. Terbogrel may ameliorate pulmonary artery dysfunction and attenuate the development of chronic hypoxia-induced pulmonary hypertension in newborns.
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Affiliation(s)
- Candice D Fike
- Dept. of Pediatrics, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157, USA.
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Fike CD, Kaplowitz MR, Zhang Y, Pfister SL. Cyclooxygenase-2 and an early stage of chronic hypoxia-induced pulmonary hypertension in newborn pigs. J Appl Physiol (1985) 2004; 98:1111-8; discussion 1091. [PMID: 15516370 DOI: 10.1152/japplphysiol.00810.2004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our objective was to determine whether cyclooxygenase (COX)-2-dependent metabolites contribute to the altered pulmonary vascular responses that manifest in piglets with chronic hypoxia-induced pulmonary hypertension. Piglets were raised in either room air (control) or hypoxia for 3 days. The effect of the COX-2 selective inhibitor NS-398 on responses to arachidonic acid or acetylcholine (ACh) was measured in endothelium-intact and denuded pulmonary arteries (100- to 400-microm diameter). Pulmonary arterial production of the stable metabolites of thromboxane and prostacyclin was assessed in the presence and absence of NS-398. Dilation to arachidonic acid was greater for intact control than for intact hypoxic arteries, was unchanged by NS-398 in intact arteries of either group, and was augmented by NS-398 in denuded hypoxic arteries. ACh responses, which were dilation in intact control arteries but constriction in intact and denuded hypoxic arteries, were diminished by NS-398 treatment of all arteries. NS-398 reduced prostacyclin production by control pulmonary arteries and reduced thromboxane production by hypoxic pulmonary arteries. COX-2-dependent contracting factors, such as thromboxane, contribute to aberrant pulmonary arterial responses in piglets exposed to 3 days of hypoxia.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157, USA.
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Fike CD, Aschner JL, Zhang Y, Kaplowitz MR. Impaired NO signaling in small pulmonary arteries of chronically hypoxic newborn piglets. Am J Physiol Lung Cell Mol Physiol 2004; 286:L1244-54. [PMID: 14766668 DOI: 10.1152/ajplung.00345.2003] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We performed studies to determine whether chronic hypoxia impairs nitric oxide (NO) signaling in resistance level pulmonary arteries (PAs) of newborn piglets. Piglets were maintained in room air (control) or hypoxia (11% O2) for either 3 (shorter exposure) or 10 (longer exposure) days. Responses of PAs to a nonselective NO synthase (NOS) antagonist, Nω-nitro-l-arginine methylester (l-NAME), a NOS-2-selective antagonist, aminoguanidine, and 7-nitroindazole, a NOS-1-selective antagonist, were measured. Levels of NOS isoforms and of two proteins involved in NOS signaling, heat shock protein (HSP) 90 and caveolin-1, were assessed in PA homogenates. PAs from all groups constricted to l-NAME but not to aminoguanidine or 7-nitroindazole. The magnitude of constriction to l-NAME was similar for PAs from control and hypoxic piglets of the shorter exposure period but was diminished for PAs from hypoxic compared with control piglets of the longer exposure period. NOS-3, HSP90, and caveolin-1 levels were similar in hypoxic and control PAs. These findings indicate that NOS-3, but not-NOS 2 or NOS-1, is involved with basal NO production in PAs from both control and hypoxic piglets. After 10 days of hypoxia, NO function is impaired in PAs despite preserved levels of NOS-3, HSP90, and caveolin-1. The development of NOS-3 dysfunction in resistance level PAs may contribute to the progression of chronic hypoxia-induced pulmonary hypertension in newborn piglets.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157, USA.
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Turley JE, Nelin LD, Kaplowitz MR, Zhang Y, Fike CD. Exhaled NO is reduced at an early stage of hypoxia-induced pulmonary hypertension in newborn piglets. Am J Physiol Lung Cell Mol Physiol 2003; 284:L489-500. [PMID: 12426238 DOI: 10.1152/ajplung.00246.2002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Altered nitric oxide (NO) production could contribute to the pathogenesis of hypoxia-induced pulmonary hypertension. To determine whether parameters of lung NO are altered at an early stage of hypoxia-induced pulmonary hypertension, newborn piglets were exposed to room air (control, n = 21) or 10% O(2) (hypoxia, n = 19) for 3-4 days. Some lungs were isolated and perfused for measurement of exhaled NO output and the perfusate accumulation of nitrite and nitrate (NOx-), the stable metabolites of NO. Pulmonary arteries (20-600-microm diameter) and their accompanying airways were dissected from other lungs and incubated for NOx- determination. Abundances of the nitric oxide synthase (NOS) isoforms endothelial NOS and neural NOS were assessed in homogenates of PAs and airways. The perfusate NOx- accumulation was similar, whereas exhaled NO output was lower for isolated lungs of hypoxic, compared with control, piglets. The incubation solution NOx- did not differ between pulmonary arteries (PAs) of the two groups but was lower for airways of hypoxic, compared with control, piglets. Abundances of both eNOS and nNOS proteins were similar for PA homogenates from the two groups of piglets but were increased in airway homogenates of hypoxic compared with controls. The NO pathway is altered in airways, but not in PAs, at an early stage of hypoxia-induced pulmonary hypertension in newborn piglets.
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Affiliation(s)
- Joyce E Turley
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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Fike CD, Kaplowitz MR, Pfister SL. Arachidonic acid metabolites and an early stage of pulmonary hypertension in chronically hypoxic newborn pigs. Am J Physiol Lung Cell Mol Physiol 2003; 284:L316-23. [PMID: 12388340 DOI: 10.1152/ajplung.00228.2002] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our purpose was to determine whether production of arachidonic acid metabolites, particularly cyclooxygenase (COX) metabolites, is altered in 100-400-microm-diameter pulmonary arteries of piglets at an early stage of pulmonary hypertension. Piglets were raised in either room air (control) or hypoxia for 3 days. A cannulated artery technique was used to measure responses of 100-400-microm-diameter pulmonary arteries to arachidonic acid, a prostacyclin analog, or the thromboxane mimetic. Radioimmunoassay was used to determine pulmonary artery production of thromboxane B(2) (TxB(2)) and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)), the stable metabolites of thromboxane and prostacyclin, respectively. Assessment of abundances of COX pathway enzymes in pulmonary arteries was determined by immunoblot technique. Arachidonic acid induced less dilation in pulmonary arteries from hypoxic than in pulmonary arteries from control piglets. Pulmonary artery responses to prostacyclin and were similar for both groups. 6-Keto-PGF(1alpha) production was reduced, whereas TxB(2) production was increased in pulmonary arteries from hypoxic piglets. Abundances of both COX-1 and prostacyclin synthase were reduced, whereas abundances of both COX-2 and thromboxane synthase were unaltered in pulmonary arteries from hypoxic piglets. At least partly due to altered abundances of COX pathway enzymes, a shift in production of arachidonic acid metabolites, away from dilators toward constrictors, may contribute to the early phase of chronic hypoxia-induced pulmonary hypertension in newborn piglets.
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Affiliation(s)
- Candice D Fike
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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Fike CD, Pfister SL, Kaplowitz MR, Madden JA. Cyclooxygenase contracting factors and altered pulmonary vascular responses in chronically hypoxic newborn pigs. J Appl Physiol (1985) 2002; 92:67-74. [PMID: 11744644 DOI: 10.1152/jappl.2002.92.1.67] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulmonary hypertension and blunted pulmonary vascular responses to ACh develop when newborn pigs are exposed to chronic hypoxia for 3 days. To determine whether a cyclooxygenase (COX)-dependent contracting factor, such as thromboxane, is involved with altered pulmonary vascular responses to ACh, newborn piglets were raised in 11% O(2) (hypoxic) or room air (control) for 3 days. Small pulmonary arteries (100-400 microm diameter) were cannulated and pressurized, and their responses to ACh were measured before and after either the COX inhibitor indomethacin; a thromboxane synthesis inhibitor, dazoxiben or feregrelate; or the thromboxane-PGH(2)-receptor antagonist SQ-29548. In control arteries, indomethacin reversed ACh responses from dilation to constriction. In contrast, hypoxic arteries constricted to ACh before indomethacin and dilated to ACh after indomethacin. Furthermore, ACh constriction in hypoxic arteries was nearly abolished by either dazoxiben, feregrelate, or SQ-29548. These findings suggest that thromboxane is the COX-dependent contracting factor that underlies the constrictor response to ACh that develops in small pulmonary arteries of piglets exposed to 3 days of hypoxia. The early development of thromboxane-mediated constriction may contribute to the pathogenesis of chronic hypoxia-induced pulmonary hypertension in newborns.
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Affiliation(s)
- Candice D Fike
- Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
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Fike CD, Kaplowitz MR, Bousamra M. eNOS and prostanoid enzymes in lungs of newborn piglets with chronic aortopulmonary shunts. Am J Physiol Lung Cell Mol Physiol 2001; 281:L475-82. [PMID: 11435223 DOI: 10.1152/ajplung.2001.281.2.l475] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our purpose was to determine if abundance of proteins underlying nitric oxide (NO) and prostanoid production is altered in lungs of piglets with aortopulmonary shunts. We also evaluated whether shunted piglets exhibit abnormal pulmonary vascular responses to ACh, an endothelium-dependent agent that mediates dilation in part by NO and prostanoid release. At age 4-5 days, piglets underwent either a sham operation or placement of an aortopulmonary shunt. At age 5-6 wk, pulmonary arterial pressure (Ppa) and cardiac output by the thermodilution technique were measured in anesthetized piglets. Ppa responses to the endothelium-dependent agent, ACh, and to a non-endothelium-dependent agent, papaverine, were measured in perfused lungs. An immunoblot technique was applied to homogenates of whole lung tissue and two size groups of pulmonary arteries. In shunted piglets, Ppa and cardiac output were elevated, and Ppa responses to papaverine were reduced. ACh responses were not decreased when expressed relative to Ppa dilation with papaverine. Endothelial nitric oxide synthase (eNOS), cyclooxygenase-1, cyclooxygenase-2, prostacyclin synthase, and thromboxane synthase amounts were unaltered in all lung tissue homogenates. Altered abundance of eNOS and/or prostanoid enzymes does not contribute to the blunted dilation and the elevation in Ppa associated with aortopulmonary shunts in newborn piglets.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
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Fike CD, Kaplowitz MR, Rehorst-Paea LA, Nelin LD. L-Arginine increases nitric oxide production in isolated lungs of chronically hypoxic newborn pigs. J Appl Physiol (1985) 2000; 88:1797-803. [PMID: 10797144 DOI: 10.1152/jappl.2000.88.5.1797] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previously, our laboratory found that pulmonary hypertension developed and lung nitric oxide (NO) production was reduced when piglets were exposed to chronic hypoxia (Fike CD, Kaplowitz MR, Thomas CJ, and Nelin LD. Am J Physiol Lung Cell Mol Physiol 274: L517-L526, 1998). The purposes of this study were to determine whether L-arginine addition augments NO production and to evaluate whether L-arginine uptake is impaired in isolated lungs of chronically hypoxic newborn piglets. Studies were performed by using 1- to 3-day-old piglets raised in room air (control) or 10% O(2) (chronic hypoxia) for 10-12 days. Lung NO production was assessed in isolated lungs from both groups by measuring the perfusate accumulation of nitrites and nitrates (collectively termed NO(-)(x)) before and after addition of L-arginine (10(-2) M) to the perfusate. The rate of perfusate NO(-)(x) accumulation increased by 220% (from 0.8 +/- 0.4 to 2.5 +/- 0.5 nmol/min, P < 0.05) after L-arginine addition to chronic hypoxic lungs but remained unchanged (3.2 +/- 0. 8 before vs. 3.3 +/- 0.4 nmol/min after L-arginine) in control lungs. In the second series of studies, L-arginine uptake was evaluated by measuring the perfusate concentration of L-[(3)H]arginine at fixed time intervals. The perfusate concentration of L-[(3)H]arginine at each time point was less (P < 0.05) in control than in chronic hypoxic lungs. Thus L-arginine uptake was impaired and may underlie in part the reduction in lung NO production that occurs when piglets are exposed to 10-12 days of chronic hypoxia. Moreover, these findings in isolated lungs lead to the possibility that L-arginine supplementation might increase in vivo lung NO production in piglets with chronic hypoxia-induced pulmonary hypertension.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee 53226; and Research Services, Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin 53295, USA.
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Abstract
Therapies to prevent the onset or progression of pulmonary hypertension in newborns have received little study compared with those in adult models. We wanted to determine whether nifedipine treatment prevents the increased pulmonary vascular resistance, blunted pulmonary vascular responses to acetylcholine, and reduced lung endothelial nitric oxide synthase (eNOS) amounts that we have found in a newborn model of chronic hypoxia-induced pulmonary hypertension. Studies were performed with 1- to 3-day-old piglets raised in room air (control) or 10% O2 (hypoxia) for 10-12 days. Some piglets from each group were given nifedipine (3-5 mg/kg sublingually three times a day). Pulmonary arterial pressure, pulmonary wedge pressure, and cardiac output were measured in anesthetized animals. Pulmonary vascular responses to acetylcholine and eNOS amounts were assessed in excised lungs. The calculated value of the pulmonary vascular resistance for nifedipine-treated hypoxic piglets (0.09 +/- 0.01 cmH(2)O. ml(-1). min. kg) was almost one-half of the value for untreated hypoxic piglets (0.16 +/- 0.01 cmH(2)O. ml(-1). min. kg) and did not differ from the value for untreated control piglets (0.05 +/- 0.01 cmH(2)O. ml(-1). min. kg). Pulmonary arterial pressure responses to acetylcholine and whole lung homogenate eNOS amounts were less for both nifedipine-treated and untreated hypoxic piglets than for untreated control piglets. Nifedipine treatment attenuated pulmonary hypertension in chronically hypoxic newborn piglets despite the persistence of blunted responses to acetylcholine and reduced lung eNOS amounts.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Gordon JB, Halla TR, Fike CD, Madden JA. Mediators of alkalosis-induced relaxation in pulmonary arteries from normoxic and chronically hypoxic piglets. Am J Physiol 1999; 276:L155-63. [PMID: 9887068 DOI: 10.1152/ajplung.1999.276.1.l155] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Alkalosis-induced relaxation was measured in precontracted arterial rings from 1-wk-old piglets exposed to normoxia or to 3 days of chronic hypoxia. In normoxic piglet arteries, alkalosis-induced relaxation was blunted in arteries without functional endothelium and in arteries treated with nitric oxide synthase or guanylate cyclase inhibitors but not in arteries treated with cyclooxygenase inhibitors or Ca2+- and ATP-dependent K+-channel inhibitors. Inhibition of voltage-dependent K+ channels with 10(-3) M 4-aminopyridine also failed to block alkalosis-induced relaxation. 4-Aminopyridine at 10(-2) M did block the response, but this may have been due to sustained vascular smooth muscle depolarization. Arteries from hypoxic piglets exhibited greater contraction to the thromboxane mimetic U-46619, decreased endothelium-dependent relaxation, and blunted alkalosis-induced relaxation. The residual relaxation was eliminated by nitric oxide synthase but not by cyclooxygenase or voltage-dependent K+-channel inhibition. Alkalosis-induced relaxation of newborn piglet pulmonary arteries appears to be mediated by the nitric oxide-cGMP pathway and is attenuated after 3 days of hypoxia, likely because of decreased nitric oxide activity.
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Affiliation(s)
- J B Gordon
- Departments of Pediatrics and Neurology, Medical College of Wisconsin and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin 53226, USA
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Fike CD, Kaplowitz MR, Thomas CJ, Nelin LD. Chronic hypoxia decreases nitric oxide production and endothelial nitric oxide synthase in newborn pig lungs. Am J Physiol 1998; 274:L517-26. [PMID: 9575869 DOI: 10.1152/ajplung.1998.274.4.l517] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To examine the effect of chronic hypoxia on nitric oxide (NO) production and the amount of the endothelial isoform of nitric oxide synthase (eNOS) in lungs of newborn piglets, studies were performed using 1- to 3-day-old piglets raised in room air (control) or 10% O2 (chronic hypoxia) for 10-12 days. Exhaled NO output and plasma nitrites and nitrates (collectively termed NOx-) were measured in anesthetized animals. NOx- concentrations were measured in the perfusate of isolated lungs. eNOS amounts were assessed in whole lung homogenates. In the intact piglets, exhaled NO outputs and plasma NOx- were lower in the chronically hypoxic (exhaled NO output = 0.2 +/- 0.1 nmol/min; plasma NOx- = 10.3 +/- 3.7 nmol/ml) than in control animals (exhaled NO output = 0.8 +/- 0.2 nmol/min; plasma NOx- = 22.3 +/- 4.3 nmol/ml). In perfused lungs, the perfusate accumulation of NOx- was lower in chronic hypoxia (1.0 +/- 0.3 nmol/min) than in control (2.6 +/- 0.6 nmol/min) piglets. The amount of whole lung homogenate eNOS from the chronic hypoxia piglets was 40 +/- 8% less than that from the control piglets. The reduced NO production observed in anesthetized animals or perfused lungs of chronically hypoxic newborn piglets is consistent with the finding of reduced lung eNOS protein amounts. Decreased NO production might contribute to the development of chronic hypoxia-induced pulmonary hypertension in newborns.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee 53226, USA
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Abstract
Almost all of the studies evaluating the effect of chronic hypoxia on lung nitric oxide production have been performed in adult animals. Because results of studies in adult lungs should not be extrapolated to represent the newborn lung, we performed studies to determine whether decreased nitric oxide production might be involved in the pathogenesis of chronic hypoxia-induced pulmonary hypertension in newborns. We kept newborn pigs in chambers filled with room air (control) or 11-12% O2 for either 3-5 (short) or 10-12 (long) days. Using isolated lungs, we measured pulmonary vascular responses to agents that either stimulate or inhibit the synthesis of nitric oxide. To define the vascular sites of altered production of nitric oxide, we applied the micropuncture technique and measured small venular pressures before and after treatment with a nitric oxide synthesis inhibitor. Pulmonary vascular responses to acetylcholine were blunted in chronically hypoxic piglets of both the short and long groups. The nitric oxide synthesis inhibitor had a different effect in the lungs of control piglets than in those of chronically hypoxic piglets of the long but not of the short group. For the long group, the nitric oxide synthesis inhibitors caused constriction of both arteries and veins in lungs of control but not of chronically hypoxic piglets. These findings support the idea that decreased pulmonary vascular nitric oxide production occurs with chronic hypoxia in newborn pigs and might therefore contribute to the pathogenesis of pulmonary hypertension in newborns.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee 53201, USA
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Abstract
The normal switch from placental to pulmonary gas exchange at birth requires rapid removal of liquid from the lungs. Previous reports contend that vasopressin may be important in regulating this process, but this notion derives from studies in which fetal sheep received very large doses of vasopressin that yielded plasma concentrations at least 10 times greater than those that have been measured during normal labor. To study the physiologic effects of vasopressin on lung liquid volume in fetal sheep, we made three sets of experiments. First, we measured plasma vasopressin concentrations [VP] in 15 late-gestation fetal sheep, five of which were at various stages of spontaneous labor. [VP] in these fetuses ranged from < 1 (prelabor) to 31 (during labor) microU/mL; postmortem extravascular lung water (EVLW) ranged from 4.5 to 14.5 g/g dry lung tissue. In a second series of studies, we measured EVLW in five sets of near-term (138 +/- 1 d, term = 147 d) twin fetal sheep that received an 8-h i.v. infusion of either isotonic saline (control twin) or AVP (AVP-treated twin) at a rate of approximately 1 (mU/kg)/min. This dose was chosen to mimic [VP] measured in fetuses that had been studied during labor. [VP] did not change in the control twins, whereas [VP] increased from 1.8 +/- 1.0 to 27.7 +/- 3.5 microU/mL in treated twins. There was a small, statistically significant difference in EVLW between twins that received AVP and untreated twins (11.9 +/- 1.8 versus 14.6 +/- 2.8 g/g dry lung).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J J Cummings
- Cardiovascular Research Institute, University of California, San Francisco 94143, USA
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Abstract
Our purposes were to determine whether chronic alveolar hypoxia altered pulmonary vascular pressures in lungs of newborn pigs, evaluate the contribution of smooth muscle tone to alterations in pulmonary vascular pressures, and examine whether chronic hypoxia altered pulmonary vascular reactivity to acute hypoxia. We kept 24- to 72-h-old pigs in chambers filled with room air (control) or 11-12% O2 (chronic hypoxia) for either 3-5 (short) or 10-12 (long) days. We used isolated lungs and applied micropuncture and vascular occlusion techniques to measure pressure in 10- to 30-microns-diam venules and inflow occlusion and outflow occlusion pressures before and after the addition of the smooth muscle dilator papaverine or before and after inflation of the lungs with a hypoxic gas mixture. For pigs in both the short and long groups, pulmonary arterial pressure was the only vascular pressure that was greater in chronically hypoxic than in control lungs. Increased smooth muscle tone was the primary source of the change in pulmonary arterial pressure with short hypoxia, whereas morphometric changes contributed to the change in pulmonary arterial pressure with long hypoxia. Exposure of newborn pigs to different lengths of alveolar hypoxia is a useful model to study postnatal pulmonary hypertension in newborns and infants.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, University of Utah Medical Center, Salt Lake City 84132
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Abstract
Our purpose was to determine whether postnatal age and prostaglandins influence the sites of hypoxic vasoconstriction in lungs of rabbits. To do this, we used the micropuncture technique to measure pressures in 20- to 80-microns-diam subpleural arterioles and venules during sequential inflation of lungs of newborn and adult rabbits with normoxic (21% O2-7-10% CO2-69-72% N2) and hypoxic (90-93% N2-7-10% CO2) gas mixtures. Indomethacin (40 micrograms/ml) was added to the perfusate of some lungs of each age group. During hypoxia in untreated lungs of newborn rabbits, both pulmonary arterial and 20- to 80-microns-diam arteriolar pressure increased by 5%, whereas 20- to 80-microns-diam venular pressure remained the same. In contrast, during hypoxia in untreated lungs of adult rabbits, pulmonary arterial pressure increased by 48%, whereas 20- to 80-microns-diam arteriolar pressure decreased slightly and 20- to 80-microns-diam venular pressure did not change. Regardless of the presence of indomethacin, location of vessels used for micropuncture, or level of left atrial pressure, pulmonary arterial pressure was the only measured vascular pressure that increased with hypoxia in adult lungs. Thus, in adult lungs, the site of hypoxia-induced vasoconstriction was limited to arteries > 80 microns diam, whereas in newborn lungs the site of hypoxia-induced vasoconstriction included vessels both larger and smaller than 20- to 80-microns-diam arteries. This age-related difference in the sites of hypoxia-induced vasoconstriction was not found in indomethacin-treated lungs.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, University of Utah Medical Center, Salt Lake City 84132
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Abstract
We compared measurements made by vascular occlusion, double occlusion, and micropuncture techniques in isolated perfused lungs of 3- to 10-day-old lambs. After adding indomethacin to the perfusate of 16 lungs, we used the micropuncture technique to measure pressures in 20- to 80-microns-diam arterioles (Pa80), 20- to 50-microns-diam venules (Pv20), and 50- to 150-microns-diam venules (Pv150). The vascular occlusion and double occlusion techniques were used in these same lungs to measure inflow occlusion (Pao), outflow occlusion (Pvo), and double occlusion pressures (Pdo). In 14 other lungs without indomethacin added to the perfusate, we measured Pv20 and Pvo before and during alveolar hypoxia and/or before and after the addition of papaverine to the perfusate. In indomethacin-treated lungs, Pao was greater than Pa80, Pvo equaled Pv20 and Pv150, and Pdo was the same as Pa80, Pv20, and Pv150. In lungs without indomethacin treatment, Pvo was less than Pv20 both before and during hypoxia but Pvo equaled Pv20 after papaverine was added to the perfusate. Thus, in indomethacin-treated lungs of newborn lambs, Pao reflected pressure in arteries > 80 microns diam, Pdo reflected pressure between 80-microns-diam arteries and 150-microns-diam veins, and Pvo was similar to pressure in veins both as small as 20 microns diam and as large as 150 microns diam. However, without indomethacin there was a gradient between Pvo and Pv20 both before and during hypoxia but not after vasomotor tone was reduced with papaverine. Thus, the correlation between Pvo and micropuncture pressure in Pv20 and Pv150 was not constant and appeared related to vasomotor tone.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, University of Utah Medical Center, Salt Lake City 84132
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Fike CD, Kaplowitz MR. Effect of airway and left atrial pressures on microvascular and interstitial pressures in adult lungs. J Appl Physiol (1985) 1993; 74:2112-20. [PMID: 8335537 DOI: 10.1152/jappl.1993.74.5.2112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The purpose of this study was to determine the effect of lung inflation and left atrial pressure on the hydrostatic pressure gradient for fluid flux across 20- to 80-microns-diam arterioles and venules in isolated perfused lungs of adult rabbits. We used the micropuncture technique and measured microvascular or interstitial pressures at constant airway pressures of 5 and 15 cmH2O with left atrial pressure adjusted above (zone 3 conditions) or below (zone 2 conditions) airway pressure. Only in lungs inflated to the higher airway pressure did a reduction in left atrial pressure below airway pressure result in concomitant reductions in venular pressure. This suggests that the site of flow limitation in zone 2 shifted from venules > 80 microns diam toward vessels <20 microns diam with inflation from 5 to 15 cmH2O. With the lungs under zone 3 conditions, both transarteriolar and transvenular gradients (microvascular-interstitial pressures) were greater at the higher compared with the lower airway pressure. In contrast, transarteriolar and transvenular gradients changed in opposite directions when compared at the two inflation pressures under zone 2 conditions. Counteracting changes in transmicrovascular gradients make it difficult to predict the effect on fluid filtration from lung inflation under zone 2 conditions. When zone 3 conditions are maintained during inflation, the tendency for edema formation should increase.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, University of Utah Medical Center, Salt Lake City 84132
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Abstract
The purpose of this study was to determine whether pulmonary venous pressure increases during alveolar hypoxia in lungs of newborn pigs. We isolated and perfused with blood the lungs from seven newborn pigs, 6-7 days old. We maintained blood flow constant at 50 ml.min-1.kg-1 and continuously monitored pulmonary arterial and left atrial pressures. Using the micropuncture technique, we measured pressures in 10 to 60-microns-diam venules during inflation with normoxic (21% O2-69-74% N2-5-10% CO2) and hypoxic (90-95% N2-5-10% CO2) gas mixtures. PO2 was 142 +/- 21 Torr during normoxia and 20 +/- 4 Torr during hypoxia. During micropuncture we inflated the lungs to a constant airway pressure of 5 cmH2O and kept left atrial pressure greater than airway pressure (zone 3). During hypoxia, pulmonary arterial pressure increased by 69 +/- 24% and pressure in small venules increased by 40 +/- 23%. These results are similar to those obtained with newborn lambs and ferrets but differ from results with newborn rabbits. The site of hypoxic vasoconstriction in newborn lungs is species dependent.
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Affiliation(s)
- C D Fike
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030
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