Comparison of Gene Expression Profiling in Pressure and Volume
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1029 Hypertens Res Vol.29 (2006) No.12 p.1029-1045 Original Article Comparison of Gene Expression Profiling in Pressure and Volume Overload–Induced Myocardial Hypertrophies in Rats Hiroshi MIYAZAKI1), Naoki OKA1), Akimasa KOGA1), Haruya OHMURA1), Tamenobu UEDA1), and Tsutomu IMAIZUMI1),2) Gene expression profiling has been conducted in rat hearts subjected to pressure overload (PO). However, pressure and volume overload produce morphologically and functionally distinct forms of cardiac hypertro- phy. Surprisingly, gene expression profiling has not been reported for in an animal model of volume over- load (VO). We therefore compared the gene expression profiles in the hypertrophied myocardium of rats subjected to PO and VO using DNA chip technology (Affymetrix U34A). Constriction of the abdominal aorta and abdominal aortocaval shunting were used to induce PO and VO, respectively. The gene expression pro- files of the left ventricle (LV) 4 weeks after the procedure were analyzed by DNA chips. There were compa- rable increases in the left ventricular weight/body weight ratio in rats subjected to PO and VO. Echocardiography revealed concentric hypertrophy in the PO animals, but eccentric hypertrophy in the rats subjected to VO. The expressions of many genes were altered in VO, PO, or both. Among the genes that were upregulated in both forms of hypertrophy, greatly increased expressions of B-type natriuretic peptide, lysyl oxidase–like protein 1 and metallothionein-1 (MT) were confirmed by real-time reverse transcription– polymerase chain reaction (RT-PCR). Because free radicals are increased in the hypertrophied heart and may contribute to apoptosis, we examined the role of MT, a free radical scavenger, in apoptosis. The over- expression of MT in H9c2 cells inhibited norepinephrine-induced apoptosis, suggesting that MT may act as an anti-apoptotic molecule in cardiac hypertrophy. In conclusion, we found that many genes were regulated in VO, PO, or both. In addition, a novel role of MT in the hypertrophied myocardium was suggested. (Hyper- tens Res 2006; 29: 1029–1045) Key Words: gene expression, hypertrophy, DNA chip, metallothionein-1, apoptosis phy whereas VO produces eccentric hypertrophy. At the cel- Introduction lular level, cardiomyocytes grow vertically in PO and longitudinally in VO. The molecular mechanisms of these Pressure and volume overload (PO and VO, respectively) differences have been unknown. Changes of some specific produce morphologically and functionally distinct forms of genes have been reported in the hearts of PO and VO, i.e., the cardiac hypertrophy (1–4); PO produces concentric hypertro- expressions of collagen isoforms (5, 6) and matrix metallo- From the 1)Department of Medicine, Division of Cardio-Vascular Medicine and 2)Cardiovascular Research Institute, Kurume University School of Med- icine, Kurume, Japan. This study was supported in part by a grant from the Kimura Memorial Heart Foundation/Pfizer Grant for Research on Autonomic Nervous System and Hypertension (to N.O.), and a grant for Science Frontier Research Promotion Centers and a Grant-in-Aid for the Encouragement of Young Scientists (to H.M. and N.O.) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. Address for Reprints: Naoki Oka, M.D., Ph.D., Department of Medicine, Division of Cardio-Vascular Medicine, Kurume University School of Medi- cine, 67 Asahi-machi, Kurume 830–0011, Japan. E-mail: [email protected] Received February 27, 2006; Accepted in revised form September 4, 2006. 1030 Hypertens Res Vol. 29, No. 12 (2006) A ** ** B ** ** 10 2.5 8 ) 2 m m 6 ( 1.5 T 4 S 1 V I LVDd (mm) 2 0.5 0 0 Sham VO PO Sham VO PO C D ** 60 6 ** 50 ) 5 m 40 m 4 ( 30 D 3 A L Shortening 20 2 % Fractional 10 1 0 0 Sham VO PO SOham V PO Fig. 1. Echocardiographic measurements of the hypertrophied rat heart. Echocardiography was performed 28 days after hemo- dynamic overload as described in Methods. VO, volume overload group; PO, pressure overload group; LVDd, end-diastolic diameter of the left ventricle; IVST, interventricular septal wall thickness; %FS, percent fractional shortening; LAD, left atrial diameter. Values are the mean±SD. **p<0.01 vs. the sham group. proteinases (7), the expression of β myosin heavy chain (8), pentobarbital, then examined by echocardiography with an the transcriptional regulation of adrenomedullin (9), and the SSD 5500 and a 7.5 MHz probe (Aloka, Tokyo, Japan). expressions of growth factors (10, 11) and β-tubulin (12). Based on these previous reports, it is anticipated that some DNA Chip Analysis specific genes are regulated similarly or differentially in PO and VO, but the regulation of genes other than those listed DNA chips (GeneChip Rat Genome U34A arrays) were pur- above has not been clarified. Microarray analysis is a useful chased from Affymetrix (Santa Clara, USA). Poly (A) RNA method to analyze the behavior of many genes. With this was extracted from the left ventricle (LV) by using a FAST method, gene profiling has been conducted in animal hearts track RNA purification kit (Invitrogen, Carlsbad, USA). We subjected to PO (13, 14). Surprisingly, however, gene expres- mixed poly (A) RNAs prepared from the LV of five rats and sion profiling has not been conducted in hearts subjected to the samples were analyzed by three DNA chips in each group. VO. Accordingly, we compared the gene expression profiles DNA chip analysis was performed according to the manufac- in the hypertrophied myocardium of rats subjected to PO and turer’s recommended protocol. Each of the groups was com- VO using the DNA chip technology. pared with each of the other groups, resulting in 27 comparison tests. Average intensity values for each probe set p Methods were obtained from the Affymetrix MicroArray Suite 4.0. A value less than 0.01 was arbitrarily assigned as the level of statistical significance. We considered genes that were ele- Animal Models vated by >2 fold compared with controls as “upregulated,” Male Wistar rats were used for the experiments. PO was pro- genes that were reduced to <0.5 as “downregulated,” and duced in rats by abdominal aortic banding (15), and VO by genes that were altered by 0.8–1.2 fold as showing “no aortocaval shunting (16). The rats were sacrificed 28 days change.” The genes that were expressed at very low levels after the procedure. All animal procedures were conducted (those with a signal intensity less than 100) or genes that were according to the guidelines provided by the Kurume Univer- considered not to be present based on low signal intensity by sity Institutional Animal Care and Use Committee under an the Affymetrix software under all conditions were omitted. approved protocol. For clustering analysis, the CEL files were converted into DCP files using dCHIP analysis software (www.biostat.har vard.edu/compalab/cdhip/), as described previously by Li and Echocardiography Wong (17). Genechips were normalized, and model-based At the day before sacrifice, rats were lightly anesthetized with expression values were generated. We used hierarchical clus- Miyazaki et al: Gene Expression Profiling in Cardiac Hypertrophy 1031 A * B * ** ** 4 7 6 3 5 4 2 3 2 1 HW/BW (mg/g) LVW/ BW (mg/g) 1 0 0 Sham VO PO Sham VO PO Fig. 2. Left ventricular weight and heart weight 28 days after hemodynamic overload. A: LVW/BW. B: HW/BW. VO, volume overload group; PO, pressure overload group; LVW/BW, left ventricular weight normalized to body weight; HW/BW, heart weight normalized to body weight. Values are the mean±SD, *p<0.05, **p<0.01 vs. the sham group. A Genes upregulated D Genes behaved differentially PO 52 33 88 VO PO 80 5 72 VO B Genes downregulated E Genes behaved differentially PO 41 31 46 VO PO 61 11 110 VO C Genes unaltered PO 118 8304 77 VO Fig. 3. Comparisons of differentially regulated genes. Venn diagrams were produced to compare the number of genes altered in the volume overload (VO), pressure overload (PO), and sham groups. A: Genes differentially upregulated between the sham group and the VO group, PO group, or both. B: Genes differentially downregulated between the sham group and the VO group, PO group, or both. C: Genes unaltered between the sham group and the VO group, PO group, or both. D: Genes upregulated in the PO group, downregulated in the VO group, or both. E: Genes upregulated in the VO group, downregulated in the PO group, or both. tering with the average linkage method. The functions of somal RNA (TaqMan ribosomal RNA control reagents; these altered genes were classified by clusters of orthologous Applied Biosystems). The primers and TaqMan probes used groups analysis. in these experiments were as follows: guanosine monophos- phate (GMP) reductase TaqMan probe, CTCTGACGG AAGCTGCACATGTCCA; GMP reductase sense-primer, Real-Time Reverse Transcription–Polymerase GGCCTCAAGGGACACATCA; GMP reductase antisense- Chain Reaction primer, AAAGGCTTTGGCGACATCTC; metallothionein-1 Total RNA was prepared with an RNeasy Midi Kit (MT) TaqMan probe, TGCAAAGGTGCCTCGGACAAG (QIAGEN, Tokyo, Japan) from LV. Real-time reverse tran- TGC; MT sense-primer, GTGGGCTGCTCCAAATGTG; scription–polymerase chain reaction (RT-PCR) was per- MT antisense-primer, GGTCCGGAAATTATTTACACC formed by a GeneAmp 5700 and a TaqMan One-Step RT- TGA; B-type natriuretic peptide (BNP) TaqMan Probe, PCR Master Mix Reagents Kit (Applied Biosystems, Foster CGGCGCAGTCAGTCGCTTGG; BNP sense-primer, TGG City, USA) according to the manufacturer’s instruction. GCAGAAGATAGACCGGA; BNP antisense-primer, ACA Expression values for each gene were