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Validating the GTP-cyclohydrolase 1-feedback regulatory complex as a therapeutic target using biophysical and in vivo approaches.

Hussein D, Starr A, Heikal L, McNeill E, Channon KM, Brown PR, Sutton BJ, McDonnell JM, Nandi M - Br. J. Pharmacol. (2015)

Bottom Line: Therefore, orally bioavailable pharmacological activators of endogenous BH4 biosynthesis hold significant therapeutic potential.We investigated the effects of L-phe on the biophysical interactions of GCH1 and GFRP and its potential to alter BH4 levels in vivo.In vivo, L-phe challenge induced a sustained elevation of aortic BH4 , an effect absent in GCH1(fl/fl)-Tie2Cre mice.

View Article: PubMed Central - PubMed

Affiliation: Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College London, London, UK.

No MeSH data available.


Related in: MedlinePlus

Effects of oral L-phe challenge on systemic and vascular biopterin levels in wild-type mice and GCH1(fl/fl)-Tie2Cre (KO) mice. (A) Plasma L-phenylalanine, (B) plasma total biopterins, (C) aortic total biopterins and (D) aortic 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) levels detected by HPLC, over an 8 h time course, following 100 mg·kg−1 oral L-phe challenge in wild-type mice. n = 6–12 for plasma and n = 4–8 aorta, mean ± SEM. ***P < 0.001, **P < 0.01, *P < 0.05: significantly different from saline control. (E) Aortic total biopterins and (F) aortic BH4 levels in GCH1(fl/fl)-Tie2Cre (KO) mice and wild-type littermates, 1 and 4 h after 100 mg·kg−1 oral L-phe challenge. n = 6–8, mean ± SEM. **P < 0.01, significantly different from WT saline.
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fig04: Effects of oral L-phe challenge on systemic and vascular biopterin levels in wild-type mice and GCH1(fl/fl)-Tie2Cre (KO) mice. (A) Plasma L-phenylalanine, (B) plasma total biopterins, (C) aortic total biopterins and (D) aortic 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) levels detected by HPLC, over an 8 h time course, following 100 mg·kg−1 oral L-phe challenge in wild-type mice. n = 6–12 for plasma and n = 4–8 aorta, mean ± SEM. ***P < 0.001, **P < 0.01, *P < 0.05: significantly different from saline control. (E) Aortic total biopterins and (F) aortic BH4 levels in GCH1(fl/fl)-Tie2Cre (KO) mice and wild-type littermates, 1 and 4 h after 100 mg·kg−1 oral L-phe challenge. n = 6–8, mean ± SEM. **P < 0.01, significantly different from WT saline.

Mentions: Oral L-phe challenge (100 mg·kg−1 bolus) in C57BL/6 mice led to a peak plasma L-phe concentration at 20 min which normalized to baseline by 4 h (Figure 4A). Similarly, the peak increase in plasma biopterin was rapid and normalized by 8 h (Figure 4B). In contrast, biopterin in aortic tissue followed a different profile, showing a more gradual and continual rise over the 8 h period (Figure 4C). Importantly, the functionally important pterin, BH4 (which behaves as an NOS cofactor and has vaso-protective properties), was also significantly elevated in aorta 4 h after administration of L-phe, normalizing by 8 h (Figure 4D). Finally, whilst administration of L-phe to GCH1 wild-type littermates stimulated biopterin/BH4 production in a similar manner to that observed in commercially purchased C57BL/6 mice (Figure 4B, E and F), L-phe had no significant effect in mice lacking endothelial GCH1 [GCH1(fl/fl)-Tie2Cre] (Figure 4E and F). These data suggest that L-phe stimulates endothelial GCH1, leading to a rise in BH4 in the aorta.


Validating the GTP-cyclohydrolase 1-feedback regulatory complex as a therapeutic target using biophysical and in vivo approaches.

Hussein D, Starr A, Heikal L, McNeill E, Channon KM, Brown PR, Sutton BJ, McDonnell JM, Nandi M - Br. J. Pharmacol. (2015)

Effects of oral L-phe challenge on systemic and vascular biopterin levels in wild-type mice and GCH1(fl/fl)-Tie2Cre (KO) mice. (A) Plasma L-phenylalanine, (B) plasma total biopterins, (C) aortic total biopterins and (D) aortic 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) levels detected by HPLC, over an 8 h time course, following 100 mg·kg−1 oral L-phe challenge in wild-type mice. n = 6–12 for plasma and n = 4–8 aorta, mean ± SEM. ***P < 0.001, **P < 0.01, *P < 0.05: significantly different from saline control. (E) Aortic total biopterins and (F) aortic BH4 levels in GCH1(fl/fl)-Tie2Cre (KO) mice and wild-type littermates, 1 and 4 h after 100 mg·kg−1 oral L-phe challenge. n = 6–8, mean ± SEM. **P < 0.01, significantly different from WT saline.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4543619&req=5

fig04: Effects of oral L-phe challenge on systemic and vascular biopterin levels in wild-type mice and GCH1(fl/fl)-Tie2Cre (KO) mice. (A) Plasma L-phenylalanine, (B) plasma total biopterins, (C) aortic total biopterins and (D) aortic 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) levels detected by HPLC, over an 8 h time course, following 100 mg·kg−1 oral L-phe challenge in wild-type mice. n = 6–12 for plasma and n = 4–8 aorta, mean ± SEM. ***P < 0.001, **P < 0.01, *P < 0.05: significantly different from saline control. (E) Aortic total biopterins and (F) aortic BH4 levels in GCH1(fl/fl)-Tie2Cre (KO) mice and wild-type littermates, 1 and 4 h after 100 mg·kg−1 oral L-phe challenge. n = 6–8, mean ± SEM. **P < 0.01, significantly different from WT saline.
Mentions: Oral L-phe challenge (100 mg·kg−1 bolus) in C57BL/6 mice led to a peak plasma L-phe concentration at 20 min which normalized to baseline by 4 h (Figure 4A). Similarly, the peak increase in plasma biopterin was rapid and normalized by 8 h (Figure 4B). In contrast, biopterin in aortic tissue followed a different profile, showing a more gradual and continual rise over the 8 h period (Figure 4C). Importantly, the functionally important pterin, BH4 (which behaves as an NOS cofactor and has vaso-protective properties), was also significantly elevated in aorta 4 h after administration of L-phe, normalizing by 8 h (Figure 4D). Finally, whilst administration of L-phe to GCH1 wild-type littermates stimulated biopterin/BH4 production in a similar manner to that observed in commercially purchased C57BL/6 mice (Figure 4B, E and F), L-phe had no significant effect in mice lacking endothelial GCH1 [GCH1(fl/fl)-Tie2Cre] (Figure 4E and F). These data suggest that L-phe stimulates endothelial GCH1, leading to a rise in BH4 in the aorta.

Bottom Line: Therefore, orally bioavailable pharmacological activators of endogenous BH4 biosynthesis hold significant therapeutic potential.We investigated the effects of L-phe on the biophysical interactions of GCH1 and GFRP and its potential to alter BH4 levels in vivo.In vivo, L-phe challenge induced a sustained elevation of aortic BH4 , an effect absent in GCH1(fl/fl)-Tie2Cre mice.

View Article: PubMed Central - PubMed

Affiliation: Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College London, London, UK.

No MeSH data available.


Related in: MedlinePlus