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Cloning and functional studies of a splice variant of CYP26B1 expressed in vascular cells
Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
Computational Chemistry and Biology Group, Facultad de Química, UdelaR, Montevideo, Uruguay.
Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
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2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 5, e36839Article in journal (Refereed) Published
Abstract [en]

Background: All-trans retinoic acid (atRA) plays an essential role in the regulation of gene expression, cell growth and differentiation and is also important for normal cardiovascular development but may in turn be involved in cardiovascular diseases, i.e. atherosclerosis and restenosis. The cellular atRA levels are under strict control involving several cytochromes P450 isoforms (CYPs). CYP26 may be the most important regulator of atRA catabolism in vascular cells. The present study describes the molecular cloning, characterization and function of atRA-induced expression of a spliced variant of the CYP26B1 gene.

Methodology/Principal Findings: The coding region of the spliced CYP26B1 lacking exon 2 was amplified from cDNA synthesized from atRA-treated human aortic smooth muscle cells and sequenced. Both the spliced variant and full length CYP26B1 was found to be expressed in cultured human endothelial and smooth muscle cells, and in normal and atherosclerotic vessel. atRA induced both variants of CYP26B1 in cultured vascular cells. Furthermore, the levels of spliced mRNA transcript were 4.5 times higher in the atherosclerotic lesion compared to normal arteries and the expression in the lesions was increased 20-fold upon atRA treatment. The spliced CYP26B1 still has the capability to degrade atRA, but at an initial rate one-third that of the corresponding full length enzyme. Transfection of COS-1 and THP-1 cells with the CYP26B1 spliced variant indicated either an increase or a decrease in the catabolism of atRA, probably depending on the expression of other atRA catabolizing enzymes in the cells.

Conclusions/Significance: Vascular cells express the spliced variant of CYP26B1 lacking exon 2 and it is also increased in atherosclerotic lesions. The spliced variant displays a slower and reduced degradation of atRA as compared to the fulllength enzyme. Further studies are needed, however, to clarify the substrate specificity and role of the CYP26B1 splice variant in health and disease.

Place, publisher, year, edition, pages
San Francisco, USA: Public Library Science , 2012. Vol. 7, no 5, e36839
National Category
Medical and Health Sciences Cell and Molecular Biology
Research subject
URN: urn:nbn:se:oru:diva-23025DOI: 10.1371/journal.pone.0036839ISI: 000305349600006PubMedID: 22666329ScopusID: 2-s2.0-84861551190OAI: diva2:529456
Available from: 2012-05-31 Created: 2012-05-30 Last updated: 2016-06-03Bibliographically approved
In thesis
1. CYP26B1 as regulator of retinoic acid in vascular cells and atherosclerotic lesions
Open this publication in new window or tab >>CYP26B1 as regulator of retinoic acid in vascular cells and atherosclerotic lesions
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cardiovascular disease (CVD), currently the most common cause of morbidity and mortality worldwide, is caused mainly by atherosclerosis. Atherosclerosis is a chronic multifocal, immunoinflammatory, fibroproliferative disease of medium and large arteries. Atherosclerotic lesions and vascular cells express different genes, among these are genes regulated by retinoic acid. Retinoids have pleiotropic effects and are able to modulate gene expression involved in growth, function and adaptation. During atherosclerosis development, there is endothelial perturbation, lipid accumulation, attraction of immune cells, smooth muscle cell migration and extracellular matrix remodeling and eventually fibrous cap formation which results in plaques. Retinoids have been demonstrated to either inhibit or modulate the above processes, resulting in amelioration of atherosclerosis. So far, retinoids are known to have impact on cellular processes in SMC, vascular injury and atherosclerosis. However, little is known about catabolism of retinoids in vascular cells and lesions and the effects of alteration of retinoic catabolizing enzymes on retinoids’ status. Therefore, we investigated the expression of Cytochrome P450 26 (CYP26) which is thought to be dedicated to retinoid catabolism. In vascular SMCs and atherosclerotic lesions, we found that CYP26B1 was the only member of the CYP26 family expressed, and it was highly inducible by atRA. Our data revealed that blocking CYP26B1 by chemical inhibition, or by targeted siRNA knock-down, resulted in significantly increased cellular retinoid levels. This indicates that CYP26B1 is an important modulator of endogenous retinoic acid levels. Therefore, we studied the effect of the CYP26B1 nonsynonymous polymorphism rs224105 on retinoic acid availability and found that the minor allele was associated with an enhanced retinoic acid catabolism rate and also with a slightly larger area of atherosclerotic lesions. The expression of CYP26B1 in human atherosclerotic lesions was localized to macrophage rich areas, suggesting retinoic acid activity in macrophages. Furthermore, we demonstrated that a CYP26B1 splice variant, that lack exon two, is expressed in vascular cells and in vessels walls. It is functional, with a reduced catabolic activity to around 70%, inducible by atRA in vascular cells and expressed 4.5 times more in atherosclerotic lesions compared to normal arteries. Moreover, the statins simvastatin and rosuvastatin reduced CYP26B1 mediated atRA catabolism in a concentration-dependent manner, and in vascular cells increased the mRNA expression of the atRA-responsive genes CYP26B1 and RARβ. This could lead to statins indirectly augmenting retinoic acid action in vascular cells which mimic statins roles. In conclusion, CYP26B1 is a major retinoic acid modulator in vascular cells and atherosclerotic lesions. Blocking of CYP26B1 could provide an advantageous therapeutic alternative to exogenous retinoid administration for treatment of vascular disorders.

Place, publisher, year, edition, pages
Örebro: Örebro universitet, 2012. 62 p.
Örebro Studies in Medicine, ISSN 1652-4063 ; 71
CYP26B1, alternative splice, vascular cells, atherosclerosis, alltrans-retinoic acid, gene polymorphism, inflammation, statins
National Category
Medical and Health Sciences Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Research subject
urn:nbn:se:oru:diva-22799 (URN)978-91-7668-877-9 (ISBN)
Public defence
2012-06-07, Hörsal HSP1, Prismahuset, Örebro universietet, Fakultetsgatan 1, Örebro, 13:15 (Swedish)
Available from: 2012-05-10 Created: 2012-05-10 Last updated: 2016-06-30Bibliographically approved

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