Role Of Rarnesylpyrophosphate Synthase In Cardiac Remodeling

Background:Cardiac hypertrophy and heart failure are leading causes of morbidity and mortality worldwide. Cardiac hypertrophy is thought to be an adaptive response to pressure and/or volume overload, which enables the heart to normalize ventricular-wall tension and improve pump function. However, a sustained or excessive hypertrophic response is considered to be maladaptive on the basis of the progression towards heart failure. Farnesyl pyrophosphate synthase (FPPS) is a key enzyme in the mevalonate pathway. FPPS catalyzes the synthesis of farnesyl pyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP). The latter is essential for geranylgeranylation and activation of RhoA. In our previous study we find that inhibition of FPPS attenuates cardiac hypertrophy in spontaneously hypertensive rats (SHRs) and prevents angiotensin (Ang) Ⅱ-induced hypertrophy in cardiomyocytes.Aims:We further investigate the role of FPPS in cardiac hypertrophy and heart failure (HF) using transgenic (Tg) model, and its mechanisms. Methods:Tg mice with cardiac-specific expression of FPPS were studied as an experimental model.(1) FPPS expression was measured in Tg mice by quantitative real-time polymerase chain reaction (qRT-PCR), western blot and immunohistochemistry.(2) FPP and GGPP levels in Tg mice were measured by HPLC as well as cholesterol concentrations were measured by enzymatic determination.(3) Cardiac function and morphological changes of Tg mice were investigated by echocardiography, pathological analysis, and cardiac catheterization.(4) ANP, BNP, β-MHC and TGF-β, CTGF mRNA expression in Tg mice were measured by qRT-PCR.(5) RhoA, Rac1, Cdc42and Ras activation in Tg mice were measured by G-Lisa method. Besides, the activities of Erkl/2, P38mitogen-activated protein kinases (MAPK) and Akt/GSK3β were detected by western blot analysis.(6) Areas of cultured neonatal cardiomyocytes infected by adenovirus were detected by immunofluorescence. Alendronate and C3exoenzyme, FTS were added after infection.(7) RhoA and Ras activation in cardiomyocytes were measured by G-Lisa method. Besides, the activities of Erk1/2, P38MAPK and Akt/GSK3β were detected by western blot analysis.(8) FPP and GGPP levels in cardiomyocytes were measured by HPLC as well as cholesterol concentration in cardiomyocytes was measured by enzymatic determination.Results:(1) FPPS expression was increased in Tg heart.(2) FPP, GGPP and cholesterol levels were increased in Tg heart.(3) Tg mice with overexpression of FPPS exhibited cardiac hypertrophy, fibrosis and heart failure as well as enhanced expression of ANP, BNP, β-MHC and TGF-β, CTGF. (4) These pathological changes were associated with activation of RhoA and other known kinases in the hypertrophic signaling pathways, such as extracellular signal-related kinases1/2(ERK1/2) and p38.(5) Adenoviral infection of FPPS in cultured neonatal cardiomyocytes induced a hypertrophic response characterized by increased cell size and an increased extent of sarcomeric organization, as well as an increased activation profile of small GTPases and downstream protein kinases concordant with those seen in vivo. Alendronate attenuated the increase in cell-surface area and BNP mRNA expression induced by Ad-FPPS infection. Additionally, the increased BNP mRNA expression induced by Ad-FPPS infection was attenuated by a RhoA inhibitor C3exoenzyme, but not by FTS.Conclusions:Taken together, these results suggest that FPPS may function as a potent regulator in myocardial remodeling. The FPPS-regulated signaling pathway is relevant to the pathological changes in cardiac hypertrophy and HF. Background:Angiotensin II (Ang II) is a vasopressor, octapeptide hormone intermediate of the renin-angiotensin system (RAS). Considerable evidence demonstrates Ang II plays a pivotal role in cardiac hypertrophy and fibrosis. In the previous study, we find that the expression level of FPPS is significantly increased in Ang II-treated cardiomyocytes, suggesting that FPPS may play an important role in cardiac hypertrophy induced by Ang II. Our previous work also prove that knockdown of FPPS expression with small interfering RNA or inhibition of FPPS with alendronate prevents Ang II-induced hypertrophy in cultured cardiomyocytes.Aims:In this study, we evaluated the effects of FPPS inhibition in Ang II-mediated cardiac hypertrophy and fibrosis in vivo.Methods:(1) Wild type mice were separately treated with saline, Ang II (2.88mg/kg per day), FPPS inhibitor alendronate (0.1mg/kg per day), or the combination of Ang II (2.88mg/kg per day) and alendronate (0.1mg/kg per day) for4weeks.(2) FPPS expression was measured in mice by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot.(3) FPP and GGPP levels in mice were measured by HPLC.(4) Cardiac function and morphological changes of mice were investigated by echocardiography, pathological analysis.(5) ANP, BNP and TGF-β1, Procollagen Ⅰ/Ⅲ mRNA expression in mice were measured by qRT-PCR and ANP and TGF-β1, collagen Ⅰ/Ⅲ protein expression were measured by western blot analysis. (6) RhoA, Ras activation in mice were measured by G-Lisa method. Besides, the activity of P38mitogen-activated protein kinases (MAPK) was detected by western blot analysis.Results:(1) Ang Ⅱ induced cardiac hypertrophy and fibrosis in mice.(2) Inhibition of FPPS decreased cardiac hypertrophy and fibrosis in Ang Ⅱ-infused mice.(3) Ang Ⅱ increased FPPS expression and FPPS inhibition decreased p-38MAPK activity in Ang Ⅱ-treated mice.(4) Inhibition of FPPS decreased ANP, BNP, TGF-β1expression in Ang Ⅱ-infused mice.(5) Inhibition of FPPS decreased FPP and GGPP levels in Ang Ⅱ-infused mice.(6) Inhibition of FPPS decreased RhoA activity in Ang Ⅱ-infused mice.Conclusions:In conclusion, FPPS might play an important role in Ang Ⅱ-induced cardiac hypertrophy and fibrosis in vivo, at least in part through RhoA, p-38MAPK and TGF-β1.