Knockdown of farnesylpyrophosphate synthase prevents angiotensin II-mediated cardiac hypertrophy

Key Enzymes for the Mevalonate Pathway in the Cardiovascular System

ABSTRACT

Isoprenylation is an important post-transcriptional modification of small GTPases required for their activation and function. Isoprenoids, including farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate, are indispensable for isoprenylation by serving as donors of a prenyl moiety to small G proteins. In the human body, isoprenoids are mainly generated by the mevalonate pathway (also known as the cholesterol-synthesis pathway). The hydroxymethylglutaryl coenzyme A reductase catalyzes the first rate-limiting steps of the mevalonate pathway, and its inhibitor (statins) are widely used as lipid-lowering agents. In addition, the FPP synthase is also of critical importance for the regulation of the isoprenoids production, for which the inhibitor is mainly used in the treatment of osteoporosis. Synthetic FPP can be further used to generate geranylgeranyl pyrophosphate and cholesterol. Recent studies suggest a role for isoprenoids in the genesis and development of cardiovascular disorders, such as pathological cardiac hypertrophy, fibrosis, endothelial dysfunction, and fibrotic responses of smooth-muscle cells. Furthermore, statins and FPP synthase inhibitors have also been applied for the management of heart failure and other cardiovascular diseases rather than their clinical use for hyperlipidemia or bone diseases. In this review, we focus on the function of several critical enzymes, including hydroxymethylglutaryl coenzyme A reductase, FPP synthase, farnesyltransferase, and geranylgeranyltransferase in the mevalonate pathway which are involved in regulating the generation of isoprenoids and isoprenylation of small GTPases, and their pathophysiological role in the cardiovascular system. Moreover, we summarize recent research into applications of statins and the FPP synthase inhibitors to treat cardiovascular diseases, rather than for their traditional indications respectively.

Intermittent Parathyroid Hormone Accelerates Stress Fracture Healing More Effectively Following Cessation of Bisphosphonate Treatment

Parathyroid hormone (PTH) and bisphosphonates (BPs), including alendronate (ALN), have opposing effects on bone dynamics. The extent to which PTH remains effective in the treatment of stress fracture (SFx) in the presence of an ongoing BP treatment has not been tested. SFx was induced in 150 female Wistar rats, divided into five equal groups (n = 30). All rats were pretreated with ALN (1 μg/kg^-1/day^-1) for 14 days prior to SFx induction, followed by ALN cessation or continuation for the duration of the experiment; this was combined with daily PTH (8 μg/100 g^-1/day^-1) on SFx induction for 14 days, followed by cessation or continuation of ALN after SFx induction or an equivalent vehicle as a control. Ulnas were examined 2 weeks or 6 weeks following SFx. Two toluidine blue- and two tartrate-resistant acid phosphatase-stained sections were examined for histomorphometric analysis using Osteomeasure software. There was a significant interaction between the effects of time and treatment type on the woven bone width and apposition rate, as well as an improvement in the woven bone architecture. However, woven bone variables remained unaffected by the cessation or continuation of ALN. Cessation of ALN increased osteoclast number when compared with the ALN-PTH continuation group (p = 0.006), and vehicle (p = 0.024) after 2 weeks. There was a significant interaction between the effects of time and treatment type on the number of osteoclasts per unit BMU area and length. The number of osteoclasts per unit BMU area and length was significantly greater in ALN cessation groups. It was concluded that intermittent short-duration iPTH treatment effectively increased remodeling of SFx with a concurrent BP treatment, provided that BP was ceased at the time of SFx. Our results could help develop shorter iPTH treatment protocols for the clinical management of SFxs and guide clinical decision-making to cease BP treatment in cases of SFx. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Once-yearly zoledronic acid and change in abdominal aortic calcification over 3 years in postmenopausal women with osteoporosis: results from the HORIZON Pivotal Fracture Trial

This study evaluated whether zoledronic acid (ZA) inhibited the progression of abdominal aortic calcification (AAC) over 3 years in 502 postmenopausal women with osteoporosis. AAC progressed in a similar proportion of participants in the ZA (29%) and placebo (31%) groups, suggesting no effect of ZA on AAC progression.

INTRODUCTION

Bisphosphonate use is associated with reduced risk of all-cause mortality and cardiovascular events. The underlying mechanisms are uncertain but may include effects on vascular calcification. This study aimed to evaluate the effect of zoledronic acid (ZA) on abdominal aortic calcification (AAC) in postmenopausal women with osteoporosis.

METHODS

This was a post hoc analysis of the HORIZON Pivotal Fracture Trial that included 502 postmenopausal women (mean age 72.5 years) with osteoporosis (234 received ZA and 268 placebo). AAC scores (range, 0-8) were assessed from paired spine X-rays at baseline and after 3 years. Progression of AAC was defined as any increase in AAC score. The association between change in hip and femoral neck bone mineral density and change in AAC score was also assessed.

RESULTS

At baseline, 292 (58.2%) participants had AAC (i.e., AAC score > 0), with AAC scores similar in the two intervention groups (median [interquartile range], 1 [0 to 2] for both; p = 0.98). Over 3 years, AAC progressed in a similar proportion of participants in both groups (ZA 29% and placebo 31%; p = 0.64). Change in bone mineral density and change in AAC score were not correlated.

CONCLUSION

Once-yearly zoledronic acid did not affect progression of AAC over 3 years in postmenopausal women with osteoporosis.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00049829.

Cardioprotective cytokine interleukin-33 is up-regulated by statins in human cardiac tissue

Interleukin (IL)‐33 is a member of the IL‐1 family and is able to act cardioprotective. The aim of this study was to investigate the regulation of IL‐33 by 3‐hydroxy‐3‐methylglutaryl‐coenzyme‐A (HMG‐CoA) reductase inhibitors (statins) and bisphosphonates (BPs) in human cardiac tissue. The lipophilic fluvastatin, simvastatin, atorvastatin, and lovastatin as well as the nitrogenous BPs alendronate and ibandronate, but not hydrophilic pravastatin increased IL‐33 mRNA and intracellular IL‐33 protein levels in both human adult cardiac myocytes (HACM) and fibroblasts (HACF). Additionally, fluvastatin reduced soluble ST2 secretion from HACM. IL‐33 was also up‐regulated by the general inhibitor of prenylation perillic acid, a RhoA kinase inhibitor Y‐27632, and by latrunculin B, but statin‐induced IL‐33 expression was inhibited by mevalonate, geranylgeranyl pyrophosphate (GGPP) and RhoA activator U‐46619. The IL‐33 promoter was 2.3‐fold more accessible in statin‐treated HACM compared to untreated cells (P = 0.037). In explanted hearts of statin‐treated patients IL‐33 protein was up‐regulated as compared with the hearts of non‐statin‐treated patients (P = 0.048). As IL‐33 was previously shown to exert cardioprotective effects, one could speculate that such up‐regulation of IL‐33 expression in human cardiac cells, which might happen mainly through protein geranylgeranylation, could be a novel mechanism contributing to known cardioprotective effects of statins and BPs.

Risks and Benefits of Bisphosphonate Therapies

Bisphosphonates are the mainstay of osteoporosis treatment but also play a fundamental role in treating other bone diseases such as Osteogenesis Imperfecta, Pagets' disease, and in the prevention of adverse skeletal effects in certain cancers such as prostate cancer or multiple myeloma. In the last decades, the refinement of bisphosphonates and an increase in the number of new bisphosphonates commercialized has altered the clinical management of these diseases. Despite differences between randomized controlled trials and observational studies, overall all bisphosphonates licensed have proven to reduce the risk of fracture through the inhibition of bone resorption. Other beneficial effects include pain reduction in bone metastasis and potentially a decrease in mortality. However, the chronic nature of most of these disorders implies long-term treatments, which can be associated with long-term adverse effects. Some of the adverse effects identified include an increased risk of atypical femur fractures, osteonecrosis of the jaw, gastrointestinal side effects, or atrial fibrillation. The harm/benefit thinking and the constant update regarding these medications are vital in the day-to-day decision-making in clinical practices. The aims of this review are to compile the basic characteristics of these drugs and outline the most important benefits and side effects and provide a clinical context as well as a research agenda to fill the gaps in our knowledge.

Lentiviral-mediated silencing of farnesyl pyrophosphate synthase through RNA interference in mice

Farnesyl pyrophosphate synthase (FPPS) plays a vital role in the mevalonate pathway and has been shown to be involved in hypertrophy and cardiovascular diseases. Lentivirus-mediated RNA interference (RNAi) to knock down a gene of interest has become a promising new tool for the establishment of transgenic animals. The interfering fragment, named pLVT202, was chosen from cardiomyocytes tested in vitro and was microinjected into the perivitelline space of zygotes from C57BL/6J mice via a lentivirus vehicle; 20 were identified as carrying copies of the transgene using the polymerase chain reaction (PCR). Real-time PCR and western blotting analysis showed that FPPS was downregulated in multiple tissues in the transgenic mice. The transgenic mouse model provides a novel means of studying the gene function of FPPS.

Inhibition of farnesyl pyrophosphate synthase prevents angiotensin II-induced cardiac fibrosis in vitro

Farnesyl pyrophosphate synthase (FPPS)-catalysed isoprenoid intermediates are important for the activation of Ras homologue gene family, member A (RhoA) in angiotensin (Ang) II-induced cardiac fibrosis. This study was designed to investigate the specific role of FPPS in the development of cardiac fibrosis. We demonstrated that FPPS expression was elevated in both in-vivo and in-vitro models of Ang II-mediated cardiac fibrosis. FPPS inhibition by zolendronate and FPPS knock-down by a silencing lentivirus decreased the expression of cardiac fibrosis marker genes, including collagen I, collagen III and transforming growth factor (TGF)-β1. FPPS inhibition was reversed by geranylgeraniol (GGOH) and mimicked by RhoA knock-down with siRhoA. The antagonistic effect of GGOH on the zolendronate-mediated modulation of RhoA activation in Ang II-stimulated cardiac fibroblasts was demonstrated by a pull-down assay. Furthermore, FPPS knock-down also prevented RhoA activation by Ang II in vitro. In conclusion, FPPS and RhoA may be part of a signalling pathway that plays an important role in Ang II-induced cardiac fibrosis in vitro.

Heart failure in patients treated with bisphosphonates

OBJECTIVES

The aim of this study was to investigate the occurrence of heart failure in patients treated with bisphosphonates.

DESIGN

In this nationwide retrospective cohort study from Denmark, all users of bisphosphonates and raloxifene between 1996 and 2006 (n = 102 342) were included in the 'exposed' group and three age- and gender-matched subjects (n = 307.026) from the general population comprised the control group. The risk of heart failure was estimated by Cox proportional hazard analyses.

RESULTS

The mean follow-up times were 2.8, 5.5 and 4.9 years for alendronate-, etidronate- and raloxifene-treated patients, respectively. The absolute risk of heart failure was 4.4% in the exposed group and 3.7% in the control group (P < 0.01). The relative risk (RR) of heart failure was significantly increased in users of bisphophonates: crude RR 1.71 [95% confidence interval (CI) 1.63-1.79]; adjusted hazard ratio (HR) 1.41 (95% CI 1.34-1.48). By comparison, raloxifene, which is used for the same indication but has a different mechanism of action, was not associated with an increased risk of heart failure: adjusted HR 1.07 (95% CI 0.76-1.50). When the two most commonly used bisphosphonates, alendronate and etidronate, were analysed separately, significant trends in the risk of heart failure were observed across refill compliance strata. The risk of heart failure increased significantly with increasing refill compliance for etidronate (P for trend < 0.01), whereas it decreased for alendronate (P for trend < 0.01).

CONCLUSIONS

Bisphosphonate users were at increased risk of heart failure compared to age- and gender-matched control subjects. However, users of alendronate showed a dose-dependent reduction in this risk, suggesting that alendronate may reduce the risk of heart failure.

Inhibition of farnesyl pyrophosphate synthase prevents norepinephrine-induced fibrotic responses in vascular smooth muscle cells from spontaneously hypertensive rats

Both norepinephrine (NE) and connective tissue growth factor (CTGF) contribute to vascular fibrosis during hypertension. Recent studies indicate that farnesyl pyrophosphate synthase (FPPS) plays an important role in cardiac remodeling in hypertension. However, the role of FPPS in NE-induced fibrotic responses and related molecular mechanisms is unknown. Vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were stimulated with NE. The fibrotic responses were assessed by measuring CTGF, hydroxyproline (hyp), and α-1 procollagen I levels using Western blot, a hydroxyproline test kit, and real-time quantitative PCR assays, respectively. Ras activity was determined by a pull-down assay using a Ras activation assay kit and detected by Western blot. NE dose-dependently increased fibrosis in SHR-VSMCs, and this increase was significantly reduced by ibandronate, an inhibitor of FPPS. The addition of farnesol, but not geranylgeraniol, partially reversed the inhibitory effects of ibandronate. Furthermore, the anti-fibrotic effects of ibandronate could be mimicked by FTI-276 but not by GGTI-286. A pull-down assay showed that ibandronate reduced the NE-induced Ras activation. Moreover, ibandronate inhibited the NE-induced activation of p38, JNK, and ERK1/2. Only SB203580 (specific inhibitor of p38) diminished the NE-induced CTGF production. These results demonstrated that inhibiting FPPS prevents NE-induced fibrotic responses in SHR-VSMCs and that the Ras kinase and p38 pathways were the underlying mechanisms involved in this process.

Inhibition of farnesyl pyrophosphate synthase attenuates angiotensin II-induced cardiac hypertrophy and fibrosis in vivo

Farnesyl pyrophosphate synthase (FPPS), as a key branchpoint of the mevalonate pathway, catalyzes the synthesis of isoprenoid intermediates. The isoprenoid intermediates are needed for protein isoprenylation to participate in cardiac remodeling. We have previously demonstrated that both knockdown of FPPS with small interfering RNA and inhibition of FPPS by alendronate could prevent Ang II-induced hypertrophy in cultured cardiomyocytes. In this study, we evaluated the effects of FPPS inhibition in Ang II-mediated cardiac hypertrophy and fibrosis in vivo. Wild type mice were separately treated with saline, Ang II (2.88 mg/kg per day), FPPS inhibitor alendronate (0.1 mg/kg per day), or the combination of Ang II (2.88 mg/kg per day) and alendronate (0.1 mg/kg per day) for 4 weeks. The results showed that Ang II increased FPPS expression, and the increases of Ang II-induced synthesis of the isoprenoid intermediates, FPP and GGPP, were significantly inhibited by FPPS inhibitor. In the meantime, FPPS inhibition attenuated Ang II-mediated cardiac hypertrophy and fibrosis as indexed by the heart weight to body weight ratio, echocardiographic parameters, histological examinations and expression of ANP and BNP mRNA. Furthermore, it was also found that FPPS inhibitor attenuated Ang II-induced increases of RhoA activity and p-38 MAPK phosphorylation and TGF-β1 mRNA expression. 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-38 MAPK and TGF-β1.

Attenuation of microRNA-22 derepressed PTEN to effectively protect rat cardiomyocytes from hypertrophy

Cardiac hypertrophy, which is characterized by the enlargement of cell size, reactivation of fetal genes, remains one of the most important triggers to heart failure. Increasing evidence shows that microRNA (miRNA) is extensively involved in the pathogenesis of cardiac hypertrophy. But the effects of miRNAs on cardiomyocyte hypertrophy have not been completely solved yet. Here, we showed that a collection of miRNAs was aberrantly expressed in hypertrophic cardiomyocytes induced by phenylephrine (PE) or angiotensin II (Ang II). Among them, miR-22 was the most strikingly up-regulated miRNA. To investigate the role of miR-22 in hypertrophy, both over-expression and knock-down assays were performed on cardiomyocytes. The results showed that up-regulation of miR-22 significantly increased the cell size and markedly influenced the expression of hypertrophic markers, including induction of nppa and reduction of myh6. In contrast, reduction of miR-22 level attenuated either PE- or Ang II-induced hypertrophic reaction. Furthermore, several genes, including PTEN, were identified as potential targets of miR-22 by bioinformatic algorithms. Using luciferase analysis, miR-22 could significantly suppress the luciferase activity of reporter fused with 3' untranslated region of PTEN mRNA. Furthermore, up-regulation of miR-22 could suppress the protein level of PTEN and reduction of miR-22 level markedly increased the protein level of PTEN in cardiomyocytes by Western blot analysis, suggesting that the contribution of miR-22 to cardiomyocyte hypertrophy may be partially through targeting PTEN. Taken together, miRNAs were dynamically regulated in cardiomyocyte hypertrophy and attenuation of miR-22 in rat cardiomyocytes efficiently protected from hypertrophic effects through derepressing PTEN.

Fasudil, a Rho-kinase inhibitor, protects against excessive endurance exercise training-induced cardiac hypertrophy, apoptosis and fibrosis in rats

Excessive endurance exercise training (EEET) is accompanied by cardiac remodeling, changes in ventricular function and increased heart failure risk. Fasudil, a potent Rho-kinase inhibitor, has been demonstrated to blunt cardiomyocyte hypertrophy, cardiac remodeling, and heart failure progression in pre-clinical trials and has been approved for clinical use in Japan. We examined the in vivo bioefficacy of fasudil against EEET-induced cardiac remodeling and the underlying molecular mechanisms. Male Sprague-Dawley rats were randomly divided into three groups: sedentary control (SC), EEET, and EEET with fasudil treatment (EEET-F). Rats in EEET and EEET-F groups ran on a motorized treadmill for 12 weeks. The results revealed that EEET increased myocardial hypertrophy (LV weight/tibial length), myocyte cross-sectional area, hypertrophy-related pathways (IL6/STAT3-MEK5-ERK5, calcineurin-NFATc3, p38 and JNK MAPK), hypertrophic markers (ANP/BNP), pro-apoptotic molecules (cytochrome C, cleaved caspase-3 and PARP), and fibrosis-related pathways (FGF-2-ERK1/2) and fibrosis markers (uPA, MMP-9 and -2). These pathways were then expressed lower in the EEET-F group when compared with the EEET group. The cardiac hypertrophic level, apoptotic pathway and fibrosis signaling were further inhibited in the fasudil-treated group. We systematically investigated the possible signaling pathways leading to EEET-induced cardiac hypertrophy, apoptosis and fibrosis. We also provide evidence for the novel function of fasudil in suppressing EEET-induced cardiac remodeling and impairment by multiple mechanisms, which suggests that the RhoA signaling pathway contributes to EEET-induced cardiac remodeling and dysfunction.

Establishment of transgenic mice carrying the gene for farnesyl pyrophosphate synthase

Farnesyl pyrophosphate synthase (FPPS) is an essential enzyme in the mevalonate pathway and might be relevant to hypertension and other cardiovascular diseases. FPPS transgenic mice were produced by microinjecting a construct with the FPPS gene into fertilized eggs derived from an inbred C57BL/6 strain. Three mice were identified as carrying copies of the transgene using the PCR. Reverse transcription PCR and Western blotting showed that the transgene was expressed in heart, liver, lung, ear, brain, thymus, and blood vessels in the transgenic mouse. Pathological analysis (hematoxylin and eosin staining) showed that FPPS expression did not cause obvious pathological changes in multiple tissues of 6-week-old transgenic mice. This FPPS transgenic mouse model, may therefore, facilitate the investigation of the biological functions of FPPS in vivo.