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Biopterin metabolism and eNOS expression during hypoxic pulmonary hypertension in mice.

Dubois M, Delannoy E, Duluc L, Closs E, Li H, Toussaint C, Gadeau AP, Gödecke A, Freund-Michel V, Courtois A, Marthan R, Savineau JP, Muller B - PLoS ONE (2013)

Bottom Line: In lungs, chronic hypoxia increased BH4 levels and eNOS expression, without modifying dihydrobiopterin (BH2, the oxidation product of BH4) levels, GTP cyclohydrolase-1 or dihydrofolate reductase expression (two key enzymes regulating BH4 availability).In intrapulmonary arteries, chronic hypoxia also increased expression of eNOS, but did not induce destabilisation of eNOS dimers into monomers.In hypoxic mice, sepiapterin prevented increase in right ventricular systolic pressure and right ventricular hypertrophy, whereas it modified neither remodelling nor alteration in vasomotor responses (hyper-responsiveness to phenylephrine, decrease in endothelium-dependent relaxation to acetylcholine) in intrapulmonary arteries.

View Article: PubMed Central - PubMed

Affiliation: University Bordeaux, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France ; INSERM, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France.

ABSTRACT
Tetrahydrobiopterin (BH4), which fosters the formation of and stabilizes endothelial NO synthase (eNOS) as an active dimer, tightly regulates eNOS coupling / uncoupling. Moreover, studies conducted in genetically-modified models demonstrate that BH4 pulmonary deficiency is a key determinant in the pathogenesis of pulmonary hypertension. The present study thus investigates biopterin metabolism and eNOS expression, as well as the effect of sepiapterin (a precursor of BH4) and eNOS gene deletion, in a mice model of hypoxic pulmonary hypertension. In lungs, chronic hypoxia increased BH4 levels and eNOS expression, without modifying dihydrobiopterin (BH2, the oxidation product of BH4) levels, GTP cyclohydrolase-1 or dihydrofolate reductase expression (two key enzymes regulating BH4 availability). In intrapulmonary arteries, chronic hypoxia also increased expression of eNOS, but did not induce destabilisation of eNOS dimers into monomers. In hypoxic mice, sepiapterin prevented increase in right ventricular systolic pressure and right ventricular hypertrophy, whereas it modified neither remodelling nor alteration in vasomotor responses (hyper-responsiveness to phenylephrine, decrease in endothelium-dependent relaxation to acetylcholine) in intrapulmonary arteries. Finally, deletion of eNOS gene partially prevented hypoxia-induced increase in right ventricular systolic pressure, right ventricular hypertrophy and remodelling of intrapulmonary arteries. Collectively, these data demonstrate the absence of BH4/BH2 changes and eNOS dimer destabilisation, which may induce eNOS uncoupling during hypoxia-induced pulmonary hypertension. Thus, even though eNOS gene deletion and sepiapterin treatment exert protective effects on hypoxia-induced pulmonary vascular remodelling, increase on right ventricular pressure and / or right ventricular hypertrophy, these effects appear unrelated to biopterin-dependent eNOS uncoupling within pulmonary vasculature of hypoxic wild-type mice.

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Effect of sepiapterin and L-NAME on hypoxia-induced alterations of contraction to phenylephrine in intrapulmonary arteries.Contractile response to phenylephrine in intrapulmonary arteries from mice exposed to (A) normoxia (NX), (B) 10 days, (C) 21 days, and (D) 40 days of hypoxia (HX 10d, HX 21d and HX 40d, respectively), in the presence or absence of sepiapterin (10-4 M) or L-NAME (3.10-4 M). Results are expressed as mean ± SEM from 6 to 9 experiments. * p<0.05 compared to control.
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pone-0082594-g005: Effect of sepiapterin and L-NAME on hypoxia-induced alterations of contraction to phenylephrine in intrapulmonary arteries.Contractile response to phenylephrine in intrapulmonary arteries from mice exposed to (A) normoxia (NX), (B) 10 days, (C) 21 days, and (D) 40 days of hypoxia (HX 10d, HX 21d and HX 40d, respectively), in the presence or absence of sepiapterin (10-4 M) or L-NAME (3.10-4 M). Results are expressed as mean ± SEM from 6 to 9 experiments. * p<0.05 compared to control.

Mentions: Phenylephrine-induced contraction was exacerbated following chronic hypoxia (Figure 5). The NO-synthase inhibitor L-NAME exacerbated hypoxia-induced hyper-reactivity to phenylephrine in intrapulmonary arteries (Figure 5), indicating that contractile responses were modulated by NOS-derived NO. Sepiapterin also failed to normalize hypoxia-induced impaired contraction to phenylephrine (Figure 5).


Biopterin metabolism and eNOS expression during hypoxic pulmonary hypertension in mice.

Dubois M, Delannoy E, Duluc L, Closs E, Li H, Toussaint C, Gadeau AP, Gödecke A, Freund-Michel V, Courtois A, Marthan R, Savineau JP, Muller B - PLoS ONE (2013)

Effect of sepiapterin and L-NAME on hypoxia-induced alterations of contraction to phenylephrine in intrapulmonary arteries.Contractile response to phenylephrine in intrapulmonary arteries from mice exposed to (A) normoxia (NX), (B) 10 days, (C) 21 days, and (D) 40 days of hypoxia (HX 10d, HX 21d and HX 40d, respectively), in the presence or absence of sepiapterin (10-4 M) or L-NAME (3.10-4 M). Results are expressed as mean ± SEM from 6 to 9 experiments. * p<0.05 compared to control.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3842263&req=5

pone-0082594-g005: Effect of sepiapterin and L-NAME on hypoxia-induced alterations of contraction to phenylephrine in intrapulmonary arteries.Contractile response to phenylephrine in intrapulmonary arteries from mice exposed to (A) normoxia (NX), (B) 10 days, (C) 21 days, and (D) 40 days of hypoxia (HX 10d, HX 21d and HX 40d, respectively), in the presence or absence of sepiapterin (10-4 M) or L-NAME (3.10-4 M). Results are expressed as mean ± SEM from 6 to 9 experiments. * p<0.05 compared to control.
Mentions: Phenylephrine-induced contraction was exacerbated following chronic hypoxia (Figure 5). The NO-synthase inhibitor L-NAME exacerbated hypoxia-induced hyper-reactivity to phenylephrine in intrapulmonary arteries (Figure 5), indicating that contractile responses were modulated by NOS-derived NO. Sepiapterin also failed to normalize hypoxia-induced impaired contraction to phenylephrine (Figure 5).

Bottom Line: In lungs, chronic hypoxia increased BH4 levels and eNOS expression, without modifying dihydrobiopterin (BH2, the oxidation product of BH4) levels, GTP cyclohydrolase-1 or dihydrofolate reductase expression (two key enzymes regulating BH4 availability).In intrapulmonary arteries, chronic hypoxia also increased expression of eNOS, but did not induce destabilisation of eNOS dimers into monomers.In hypoxic mice, sepiapterin prevented increase in right ventricular systolic pressure and right ventricular hypertrophy, whereas it modified neither remodelling nor alteration in vasomotor responses (hyper-responsiveness to phenylephrine, decrease in endothelium-dependent relaxation to acetylcholine) in intrapulmonary arteries.

View Article: PubMed Central - PubMed

Affiliation: University Bordeaux, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France ; INSERM, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France.

ABSTRACT
Tetrahydrobiopterin (BH4), which fosters the formation of and stabilizes endothelial NO synthase (eNOS) as an active dimer, tightly regulates eNOS coupling / uncoupling. Moreover, studies conducted in genetically-modified models demonstrate that BH4 pulmonary deficiency is a key determinant in the pathogenesis of pulmonary hypertension. The present study thus investigates biopterin metabolism and eNOS expression, as well as the effect of sepiapterin (a precursor of BH4) and eNOS gene deletion, in a mice model of hypoxic pulmonary hypertension. In lungs, chronic hypoxia increased BH4 levels and eNOS expression, without modifying dihydrobiopterin (BH2, the oxidation product of BH4) levels, GTP cyclohydrolase-1 or dihydrofolate reductase expression (two key enzymes regulating BH4 availability). In intrapulmonary arteries, chronic hypoxia also increased expression of eNOS, but did not induce destabilisation of eNOS dimers into monomers. In hypoxic mice, sepiapterin prevented increase in right ventricular systolic pressure and right ventricular hypertrophy, whereas it modified neither remodelling nor alteration in vasomotor responses (hyper-responsiveness to phenylephrine, decrease in endothelium-dependent relaxation to acetylcholine) in intrapulmonary arteries. Finally, deletion of eNOS gene partially prevented hypoxia-induced increase in right ventricular systolic pressure, right ventricular hypertrophy and remodelling of intrapulmonary arteries. Collectively, these data demonstrate the absence of BH4/BH2 changes and eNOS dimer destabilisation, which may induce eNOS uncoupling during hypoxia-induced pulmonary hypertension. Thus, even though eNOS gene deletion and sepiapterin treatment exert protective effects on hypoxia-induced pulmonary vascular remodelling, increase on right ventricular pressure and / or right ventricular hypertrophy, these effects appear unrelated to biopterin-dependent eNOS uncoupling within pulmonary vasculature of hypoxic wild-type mice.

Show MeSH
Related in: MedlinePlus