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PPARδ agonist prevents endothelial dysfunction via induction of dihydrofolate reductase gene and activation of tetrahydrobiopterin salvage pathway
Author(s) -
Zhang Zihui,
Xie Xinya,
Yao Qinyu,
Liu Jia,
Tian Ying,
Yang Chunmiao,
Xiao Lei,
Wang Nanping
Publication year - 2019
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.14745
Subject(s) - dihydrofolate reductase , endothelial dysfunction , myograph , tetrahydrobiopterin , agonist , chemistry , peroxisome proliferator activated receptor , biology , endothelium , pharmacology , biochemistry , endocrinology , nitric oxide synthase , receptor , enzyme
Background and Purpose Impaired endothelium‐dependent relaxation (EDR) is a hallmark of endothelial dysfunction. A deficiency of tetrahydrobiopterin (BH 4 ) causes endothelial NOS to produce ROS rather than NO. PPARδ is an emerging target for pharmacological intervention of endothelial dysfunction. Thus, the present study examined the role of PPARδ in the regulation of dihydrofolate reductase (DHFR), a key enzyme in the BH 4 salvage pathway. Experimental Approach Gene expression was measured by using qRT‐PCR and western blotting. Biopterins and ROS were determined by using HPLC. NO was measured with fluorescent dye and electron paramagnetic resonance spectroscopy. Vasorelaxation was measured by Multi Myograph System. Key Results The PPARδ agonist GW501516 increased DHFR and BH 4 levels in endothelial cells (ECs). The effect was blocked by PPARδ antagonist GSK0660. Chromatin immunoprecipitation identified PPAR‐responsive elements within the 5′‐flanking region of the human DHFR gene. The promoter activity was examined with luciferase assays using deletion reporters. Importantly, DHFR expression was suppressed by palmitic acid (PA, a saturated fatty acid) but increased by docosahexaenoic acid (DHA, a polyunsaturated fatty acid). GSK0660 prevented DHA‐induced increased DHFR expression. Conversely, the suppressive effect of PA was mitigated by GW501516. In mouse aortae, GW501516 ameliorated the PA‐impaired EDR. However, this vasoprotective effect was attenuated by DHFR siRNA or methotrexate. In EC‐specific Ppard knockout mice, GW501516 failed to improve vasorelaxation. Conclusion and Implications PPARδ prevented endothelial dysfunction by increasing DHFR and activating the BH 4 salvage pathway. These results provide a novel mechanism for the protective roles of PPARδ against vascular diseases.

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