Deletion of PPARα results in more pronounced cardiac hypertrophy in response to chronic pressure overload

S130

ABSTRACTS / Journal of Molecular and Cellular Cardiology 42 (2007) S129–S144

Fibroblast growth factor-2 (FGF-2) is a multifunctional and ubiquitous protein. Cells accumulate both low molecular weight (lo) as well as high molecular weight (hi) FGF-2 isoforms. We recently demonstrated that hi- (but not lo-) FGF-2, acting from ‘the outside-in’, induces cardiac and myocyte hypertrophy. We have now investigated if hi-FGF-2 can be exported by cardiac fibroblasts, since these cells are a major source of FGF-2 and are known to integrate pro-hypertrophic signals to cardiac myocytes. We examined the identity as well as extracellular destination of FGF-2 isoforms released by early passaged cardiac (human; rat) fibroblasts, in response to a pro-hypertrophic stimulus, Angiotensin II (Ang-II). Two possible destinations of cell-exported FGF-2 were examined: the conditioned medium (simulating systemic release) and a 2 M salt gentle wash, representing cell-surface and matrix-bound FGF-2. Western blotting of heparin-column-enriched fractions was used for detection of FGF-2 isoforms. We found that Ang-II promoted preferential release of the 34 kDa human hi-FGF-2, or the 23 kDa rat hi-FGF2 into the conditioned medium. Lo-FGF-2 was the predominant isoform detected in the 2 M salt wash, in the presence or absence of Ang-II stimulation. Our data suggest that fibroblast-released hi-FGF-2 may have both long-range (systemic) as well as local (cell and matrix-associated) effects, while lo-FGF-2 may be more involved with local auto- and paracrine actions. Keywords: Fibroblast growth factor-2; Cardiac hypertrophy; Cardiac fibroblasts doi:10.1016/j.yjmcc.2007.03.368

Deletion of PPARα results in more pronounced cardiac hypertrophy in response to chronic pressure overload Pascal J.H. Smeets, Peter H. Willemsen, Agnieszka E. Brouns, Ben J. Janssen, Ger J. van der Vusse, Marc van Bilsen. Dept. Physiology, Maastricht Univ., NL Peroxisome proliferator-activated receptor-α (PPARα) is a nuclear receptor regulating cardiac metabolism and has antiinflammatory as well as anti-fibrotic effects. Given these properties it is anticipated that PPARα modulates cardiac remodeling. Therefore, we studied the role of PPARα in pressure-overload induced hypertrophy using PPARα−/− (KO) and PPARα+/+ (WT) mice subjected to transverse aortic constriction (TAC) for 28 days. Sham-operated KO and WT mice served as controls (N ≥ 9 in all groups). KO mice had slightly lower blood pressure than WT mice (111 vs. 122 mm Hg, p< 0.05). Nevertheless, TAC resulted in more pronounced posterior and anterior left ventricular (LV) wall thickness and LV/body weight ratio in KO-TAC than in WT-TAC (LVW/BW: +37% vs. +20%, p< 0.05). LV ejection fraction and maximal LV contractility (+dP/dtmax) were significantly lower in KO-TAC compared to sham (−19.4% and −19.2%, respectively, p <0.05), but not in WT-TAC. Moreover, in KO-TAC mice LV mRNA levels of hypertrophic (ANF), fibrotic (Collagen 1, MMP2) and inflammatory (Interleukin-6, TNF-α) genes were significantly higher relative to WT-TAC. Thus, absence of PPARα results in a more pronounced hypertrophic growth response, indicating that

PPARα attenuates pathological cardiac remodeling following pressure overload. Acknowledgments Supported by grants EU No. LSHM-CT-2005-018833/ EUGeneHeart and NWO No. 912-04-017. Keywords: Cardiac hypertrophy; Cardiac remodeling doi:10.1016/j.yjmcc.2007.03.369

Differential regulation of components of the AM/IMD receptor system in nitric oxide-deficient cardiomyocytes Y.Y. Zhao, D. Bell, F. McCoy, B. McDermott. Centre for Vascular Medicine, Queen's University Belfast, UK In myocardial ischemia and remodeling produced by NO synthase inhibition, upregulation of adrenomedullin (AM) and receptor components, RAMP2 and 3, in hypertrophied cardiomyocytes is prevented by blood pressure (BP) lowering (hydralazine + thiazide); that of RAMP1 and intermedin (IMD) is not. The hypothesis is that IMD/RAMP1 are regulated by hypoxia. Effects were examined of (i) anti-oxidant intervention; (ii) intervention to alleviate pressure loading and ischemic injury concurrently. L-NAME (35 mg/kg/day) was given to rats for 8 weeks ± (in mg/kg/day) (i) vitamin C (25)+ Tempol (25) [VT] or (ii) atenolol (25) + nifedipine (20) [AN]. [VT] did not reduce systolic BP but in cardiomyocytes: (i) abolished a 3.6-fold increase in membrane protein oxidation and normalized augmented mRNA expression of components of pro-oxidant NADPH oxidase and compensatory increases in anti-oxidant GPx, SOD1 but not SOD3; (ii) attenuated (by 42%) increased cell width and normalized mRNA expression of hypertrophic markers, sk-α-actin, prepro-ET1 but not BNP; (iii) normalized mRNA expression of prepro-IMD, RAMP-1, but not prepro-AM, RAMP2, 3. [AN] normalized: (i) systolic BP; (ii) increased cell width and mRNA expression of sk-αactin, prepro-ET-1 and BNP; (iii) augmented membrane protein oxidant status and mRNA expression of NADPH oxidase components, GPx, SOD1 and SOD3; (iv) mRNA expression of prepro-AM, prepro-IMD and RAMPs 1–3. It is concluded that in contrast to AM/RAMP2 and 3, IMD/RAMP1 expression is induced by oxidative stress; IMD may act in a negative feedback manner to reduce ischemic injury and hypertrophic remodeling. Keywords: Nitric oxide; Cardiac peptides; Hypertrophy doi:10.1016/j.yjmcc.2007.03.370

Captopril improves MCT-induced rat right ventricular hypertrophy through inhibition of matrix metalloproteinases Yukio Hara, Hirokazu Naruse, Keiichiro Kizaki*, Mune-yoshi Okada, Hideyuki Yamawaki. Vet Pharmacol, Kitasato Univ., Japan. *Vet Physiol, Iwate Univ., Japan