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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 on hypoxia-induced remodeling of pulmonary arterioles, right ventricular pressure and hypertrophy.(A) Representative pictures, and (B) quantified data of wall thickness of pulmonary arterioles in mice exposed to normoxia (NX) or in mice exposed to 21 days of hypoxia (HX 21d) which were treated or not with sepiapterin (30 mg/kg, one day before exposure to hypoxia and every other day during hypoxia). (C) Right ventricular systolic pressure and (D) weight ratio right ventricle / (left ventricle + septum) in mice exposed to normoxia (NX) or in mice exposed to 21 days of hypoxia (HX 21d) which were treated or not with sepiapterin (30 mg/kg, one day before exposure to hypoxia and every other day during hypoxia). Results are expressed as mean ± SEM from all the arteries on each lung section from 4 to 7 mice for wall thickness, from 6-14 mice for right ventricular systolic pressure and from at least 8 experiments for weight ratio right ventricle / (left ventricle + septum). * p<0.05, *** p<0.001, compared to NX ; #p<0.05, ###p<0.001 compared to 21 days hypoxia.
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pone-0082594-g006: Effect of sepiapterin on hypoxia-induced remodeling of pulmonary arterioles, right ventricular pressure and hypertrophy.(A) Representative pictures, and (B) quantified data of wall thickness of pulmonary arterioles in mice exposed to normoxia (NX) or in mice exposed to 21 days of hypoxia (HX 21d) which were treated or not with sepiapterin (30 mg/kg, one day before exposure to hypoxia and every other day during hypoxia). (C) Right ventricular systolic pressure and (D) weight ratio right ventricle / (left ventricle + septum) in mice exposed to normoxia (NX) or in mice exposed to 21 days of hypoxia (HX 21d) which were treated or not with sepiapterin (30 mg/kg, one day before exposure to hypoxia and every other day during hypoxia). Results are expressed as mean ± SEM from all the arteries on each lung section from 4 to 7 mice for wall thickness, from 6-14 mice for right ventricular systolic pressure and from at least 8 experiments for weight ratio right ventricle / (left ventricle + septum). * p<0.05, *** p<0.001, compared to NX ; #p<0.05, ###p<0.001 compared to 21 days hypoxia.

Mentions: As expected, chronic hypoxia (21 days) significantly increased medial thickness in intrapulmonary arterioles (Figures 6A and B), to a similar extend than in previous mice studies [27,28]. Chronic oral treatment with sepiapterin, wich tended to increase lung BH4 content from 23.4 ± 0.2 to 28.5 ± 2.4 pmol / mg protein (p = 0.10), did not prevent hypoxia-induced increase in pulmonary arterioles wall thickness (Figures 6A and B). However, sepiapterin prevented hypoxia-induced increase in right ventricular systolic pressure (Figure 6C) and right ventricular hypertrophy (Figure 6D). In normoxic WT mice, both wall thickness of pulmonary arterioles and weight ratio right ventricle / (left ventricle + septum) were not modified by chronic oral treatment with sepiapterin (data not shown).


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 on hypoxia-induced remodeling of pulmonary arterioles, right ventricular pressure and hypertrophy.(A) Representative pictures, and (B) quantified data of wall thickness of pulmonary arterioles in mice exposed to normoxia (NX) or in mice exposed to 21 days of hypoxia (HX 21d) which were treated or not with sepiapterin (30 mg/kg, one day before exposure to hypoxia and every other day during hypoxia). (C) Right ventricular systolic pressure and (D) weight ratio right ventricle / (left ventricle + septum) in mice exposed to normoxia (NX) or in mice exposed to 21 days of hypoxia (HX 21d) which were treated or not with sepiapterin (30 mg/kg, one day before exposure to hypoxia and every other day during hypoxia). Results are expressed as mean ± SEM from all the arteries on each lung section from 4 to 7 mice for wall thickness, from 6-14 mice for right ventricular systolic pressure and from at least 8 experiments for weight ratio right ventricle / (left ventricle + septum). * p<0.05, *** p<0.001, compared to NX ; #p<0.05, ###p<0.001 compared to 21 days hypoxia.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0082594-g006: Effect of sepiapterin on hypoxia-induced remodeling of pulmonary arterioles, right ventricular pressure and hypertrophy.(A) Representative pictures, and (B) quantified data of wall thickness of pulmonary arterioles in mice exposed to normoxia (NX) or in mice exposed to 21 days of hypoxia (HX 21d) which were treated or not with sepiapterin (30 mg/kg, one day before exposure to hypoxia and every other day during hypoxia). (C) Right ventricular systolic pressure and (D) weight ratio right ventricle / (left ventricle + septum) in mice exposed to normoxia (NX) or in mice exposed to 21 days of hypoxia (HX 21d) which were treated or not with sepiapterin (30 mg/kg, one day before exposure to hypoxia and every other day during hypoxia). Results are expressed as mean ± SEM from all the arteries on each lung section from 4 to 7 mice for wall thickness, from 6-14 mice for right ventricular systolic pressure and from at least 8 experiments for weight ratio right ventricle / (left ventricle + septum). * p<0.05, *** p<0.001, compared to NX ; #p<0.05, ###p<0.001 compared to 21 days hypoxia.
Mentions: As expected, chronic hypoxia (21 days) significantly increased medial thickness in intrapulmonary arterioles (Figures 6A and B), to a similar extend than in previous mice studies [27,28]. Chronic oral treatment with sepiapterin, wich tended to increase lung BH4 content from 23.4 ± 0.2 to 28.5 ± 2.4 pmol / mg protein (p = 0.10), did not prevent hypoxia-induced increase in pulmonary arterioles wall thickness (Figures 6A and B). However, sepiapterin prevented hypoxia-induced increase in right ventricular systolic pressure (Figure 6C) and right ventricular hypertrophy (Figure 6D). In normoxic WT mice, both wall thickness of pulmonary arterioles and weight ratio right ventricle / (left ventricle + septum) were not modified by chronic oral treatment with sepiapterin (data not shown).

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