title: Expression of the Cardiac Maintenance and Survival Factor FGF-16 Gene Is Regulated by Csx/Nkx2.5 and Is an Early Target of Doxorubicin Cardiotoxicity.
abstract: The fibroblast growth factor (FGF) 16 gene (Fgf-16) is preferentially expressed by neonatal cardiomyocytes after birth, with levels increasing into adulthood. Null mice and isolated heart studies suggest a role for FGF-16 in cardiac maintenance and survival, including increased resistance to doxorubicin (DOX)-induced injury. However, the effect of DOX on endogenous FGF-16 synthesis and specifically regulation of cardiac Fgf-16 expression has not been reported. Here we assess the effect of DOX on FGF-16 RNA levels and stability as well as promoter activity and use sequence analysis, knockdown, and overexpression to investigate the role of cardiac transcription factor(s) implicated in the response. Endogenous FGF-16 RNA levels were reduced >70% in 8-week-old rats treated with 15 mg DOX/kg for 6 h. This was modeled in neonatal rat cardiomyocyte cultures, where an equivalent decrease was also seen within 6 h of 1 μM DOX treatment. Six kilobases of mouse Fgf-16 upstream flanking and promoter DNA was also assessed for DOX responsiveness in transfected cardiomyocytes. A decrease in FGF-16 promoter activity was seen with only 747 base pairs containing the Fgf-16 TATA box that includes a putative and highly conserved binding site for the cardiac transcription factor Csx/Nkx2.5. There was also no effect of DOX on FGF-16 RNA stability, consistent with transcriptional control. Levels and binding of Csx/Nkx2.5 to the FGF-16 promoter were reduced with DOX treatment. Knockdown of Csx/Nkx2.5 specifically decreased endogenous FGF-16 RNA and protein levels, whereas Csx/Nkx2.5 overexpression stimulated levels, and increased resistance to the rapid DOX-induced depletion of FGF-16. These observations indicate that Fgf-16 expression is directly regulated by Csx/Nkx2.5 in neonatal cardiomyocytes, and a negative effect of DOX on Csx/Nkx2.5 and, thus, endogenous FGF-16 synthesis may contribute indirectly to its cardiotoxic effects. Targeting FGF-16 levels could, however, offer increased resistance to cardiac injury.
authors.affiliation: Department of Physiology & Pathophysiology, University of Manitoba , Winnipeg, Canada .
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Physiology & Pathophysiology, University of Manitoba , Winnipeg, Canada .
authors.forename: Yan
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Department of Physiology & Pathophysiology, University of Manitoba , Winnipeg, Canada .
authors.forename: Peter A
authors.initials: PA
authors.lastname: Cattini
mesh_terms: D000818:Animals; D066126:Cardiotoxicity / Q000235:genetics / Q000378:metabolism; D004317:Doxorubicin / Q000009:adverse effects*; D005346:Fibroblast Growth Factors / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects*; D055785:Gene Knockdown Techniques; D000072576:Homeobox Protein Nkx-2.5 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D013997:Time Factors
chemical_list: C110776:Fgf16 protein, rat; D000072576:Homeobox Protein Nkx-2.5; D005346:Fibroblast Growth Factors; D004317:Doxorubicin
keywords: Csx/Nkx2.5; FGF-16; doxorubicin; neonatal rat cardiac myocytes