Increased expression of IL-6 and LIF in the hypertrophied left ventricle of TGR(mRen2)27 and SHR rats

Cytokines from the interleukin-6 ( IL-6) family have been reported to play an important synergistic role with angiotensin II in the development of pathological cardiac hypertrophy. Whether their expression pattern changes in vivo, in an angiotensin II-dependent hypertrophied myocardium has not been reported. In this study, we addressed that issue using two animal models of angiotensin II-dependent cardiac hypertrophy. Heterozygous transgenic TGR(mRen2)27 (TGR) with an overactive cardiac renin angiotensin system and the closely related spontaneously hypertensive rats (SHR) were compared to their respective control rats. The mRNA levels of IL-6, leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF) and cardiotrophin-1 (CT-1) as well as their receptor subunits, glycoprotein 130 (gp130), IL-6 receptor (IL-6R), LIFR, and CNTFR, were measured by semi-quantitative RT-PCR. The protein levels of IL-6, LIF and CT-1 were investigated by western blot. TGR and SHR both displayed significant over expression of mRNA and protein levels for IL-6 and LIF. In TGR, the increased level of LIF was accompanied by a decrease in mRNA levels for LIFR and CNTFR. In SHR, a higher level of mRNA IL-6R was observed. By contrast, the mRNA and protein levels for CT-1 and the mRNA level for gp130 did not vary in these two models. These findings suggest that IL-6 and LIF, but not CT-1, contribute to angiotensin II-dependent left ventricular hypertrophy in the two hypertensive rat models, TGR(mRen2)27 and SHR.