Signal transducer and activator of transcription 3 in the heart transduces not only a hypertrophic signal but a protective signal against doxorubicin-induced cardiomyopathy - PubMed (original) (raw)

Signal transducer and activator of transcription 3 in the heart transduces not only a hypertrophic signal but a protective signal against doxorubicin-induced cardiomyopathy

K Kunisada et al. Proc Natl Acad Sci U S A. 2000.

Abstract

The signal transducer and activator of transcription (STAT) 3, a transcriptional factor downstream of several cytokines, is activated by Janus kinase families and plays a pivotal role in cardiac hypertrophy through gp130. To determine the physiological significance of STAT3 in vivo, transgenic mice with cardiac-specific overexpression of the Stat3 gene (STAT3-TG) were generated. STAT3-TG manifested myocardial hypertrophy at 12 wk of age with increased expression of the atrial natriuretic factor (ANF), beta-myosin heavy chain (MHC), and cardiotrophin (CT)-1 genes. The animals were injected i.p. with 15 mg/kg doxorubicin (Dox), an antineoplastic drug with restricted use because of its cardiotoxicity. The survival rates after 10 days were 25% (5/20) for control littermates (WT), but 80% (16/20) for STAT3-TG (P < 0.01). WT showed increased expression of beta-MHC and ANF mRNAs in the hearts 1 day after Dox treatment; this expression peaked at 3 days, suggesting that the WT suffered from congestive heart failure. Although the expression of these mRNAs was elevated in STAT3-TG hearts before Dox treatment, no additional increase was observed after the treatment. Dox administration significantly reduced the expression of the cardiac alpha-actin and Stat3 genes in WT hearts but not in STAT3-TG. These results provide direct evidence that STAT3 transduces not only a hypertrophic signal but also a protective signal against Dox-induced cardiomyopathy by inhibiting reduction of cardiac contractile genes and inducing cardiac protective factors.

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Figures

Figure 1

Figure 1

Transgene construct and STAT3 expression in the hearts. (A) Schematic representation of the transgene, a 2.3-kb murine Stat3 cDNA was ligated downstream of a 5.5-kb fragment of the murine α-myosin heavy chain (MHC) gene promoter and upstream of a 0.6-kb human growth hormone (hGH) poly(A). (B) Northern blot analysis was performed using a murine Stat3 cDNA as a probe. Hearts from transgene-positive animals (TG12 and TG22) showed abundant Stat3 mRNA expression. Equal RNA loadings were documented by 28S RNA (Lower). (C) gp130, JAK1, and STAT3 expressions in the hearts. The lysates from the hearts containing equal amounts of the protein (10 μg) were separated by SDS/PAGE and immunoblotted with rabbit anti-gp130, JAK1, or STAT3 Ab as described in Materials and Methods. WT, Control littermate; TG, STAT3-TG.

Figure 2

Figure 2

Histological analysis of the hearts. The sections obtained from the hearts of 3-mo-old control mice and STAT3-TG were stained with hematoxylin/eosin. (Magnification: ×20.)

Figure 3

Figure 3

Induction of the hypertrophy genes program in STAT3 transgenic mice. (A) Semiquantitative RT-PCR analysis. Equal volumes of the amplified PCR products were loaded onto a 1.5% agarose gel. (B) Northern blot analysis using a CT-1 cDNA as a probe. WT, Control littermate; TG, STAT3-TG.

Figure 4

Figure 4

Survival rates for the mice treated with Dox. Three-month-old STAT3-TG and WT mice weighing 21–23 g (n = 20) were injected i.p. with Dox at a single dose of 15 mg/kg and bred under normal condition. Kaplan–Meier survival curves represent significantly better survival (P < 0.01) in STAT3-TG than in WT.

Figure 5

Figure 5

Alteration of cardiac gene expressions after Dox treatment. WT and STAT3-TG were treated with single dose of 15 mg/kg Dox, and the hearts were excised after 2 days. Northern blot analysis was performed using a cardiac α-actin cDNA (A) or a murine Stat3 cDNA (B) as a probe. Equal RNA loadings were documented by 28S RNA and β-actin controls. WT, Control littermate; TG, STAT3-TG.

Figure 6

Figure 6

Expression of β-MHC and ANF mRNAs after Dox treatment. Semiquantitative RT-PCR was performed as described in Fig. 3. RNAs were obtained from the hearts at the indicated day after 15 mg/kg Dox treatment. WT, Control littermate; TG, STAT3-TG.

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