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

Non-nitrogen-containing bisphosphonates and nitrogen-containing bisphosphonates for the treatment of atherosclerosis and vascular calcification: A meta-analysis

BACKGROUND

The role of non-nitrogen-containing bisphosphonates (non-N-BPs) and nitrogen-containing bisphosphonates (N-BPs) in the treatment of atherosclerosis (AS) and vascular calcification (VC) is uncertain. This meta-analysis was conducted to evaluate the efficacy of non-N-BPs and N-BPs in the treatment of AS and VC.

METHODS

The PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, and Wanfang databases were searched from their inception to July 5th, 2023. Eligible studies comparing bisphosphonates (BPs) versus no BPs in the treatment of AS and VC were included. The data were analyzed using Review Manager Version 5.3.

RESULTS

Seventeen studies were included in this meta-analysis. Twelve were randomized control trials (RCTs), and 5 were nonrandomized studies. Overall, 813 patients were included in the BPs group, and 821 patients were included in the no BPs group. Compared with no BP treatment, non-N-BP or N-BP treatment did not affect serum calcium (P > .05), phosphorus (P > .05) or parathyroid hormone (PTH) levels (P > .05). Regarding the effect on serum lipids, non-N-BPs decreased the serum total cholesterol (TC) level (P < .05) and increased the serum triglyceride (TG) level (P < .01) but did not affect the serum low-density lipoprotein cholesterol (LDL-C) level (P > .05). N-BPs did not affect serum TC (P > .05), TG (P > .05) or LDL-C levels (P > .05). Regarding the effect on AS, non-N-BPs did not have a beneficial effect (P > .05). N-BPs had a beneficial effect on AS, including reducing the intima-media thickness (IMT) (P < .05) and plaque area (P < .01). For the effect on VC, non-N-BPs had a beneficial effect (P < .01), but N-BPs did not have a beneficial effect (P > .05).

CONCLUSION

Non-N-BPs and N-BPs did not affect serum calcium, phosphorus or PTH levels. Non-N-BPs decreased serum TC levels and increased serum TG levels. N-BPs did not affect serum lipid levels. Non-N-BPs had a beneficial effect on VC, and N-BPs had a beneficial effect on AS.

Increased Expression of Mevalonate Pathway-Related Enzymes in Angiotensin II-Induced Abdominal Aortic Aneurysms

Abdominal aortic aneurysm (AAA) is characterized by permanent luminal expansion and a high mortality rate due to aortic rupture. Despite the identification of abnormalities in the mevalonate pathway (MVA) in many diseases, including cardiovascular diseases, the potential impact of this pathway on AAA remains unclear. This study aims to investigate whether the expression of the MVA-related enzyme is altered during the progression of angiotensin II (Ang II) -induced AAA.Ang II 28D and Ang II 5D groups were continuously perfused with Ang II for 28 days and 5 days, respectively, and the Sham group was perfused with saline. The general and remodeling characteristics of AAA were determined by biochemical and histological analysis. Alteration of MVA-related enzyme expressions was revealed by western blot and single-cell RNA sequencing (scRNA-seq).The continuous Ang II infusion for 28 days showed significant aorta expansion and arterial remodeling. Although the arterial diameter slightly increased, the aneurysm formation was not found in Ang II induction for 5 days. MVA-related enzyme expression and activation of small GTP-binding proteins were significantly increased after Ang II-induced. As verified by scRNA-seq, the key enzyme gene expression was also higher in Ang II 28D. Similarly, it was detected that the expression levels of the above enzymes and the activity of small G proteins were elevated in the early stage of AAA as induced by Ang II infusion for 5 days.Continuous Ang II infusion-induced abdominal aortic expansion and arterial remodeling were accompanied by altered expression of key enzymes in the MVA.

Inhibition of farnesyl pyrophosphate synthase alleviates cardiomyopathy in diabetic rat

This study investigated the effects of ibandronate (IBN) on cardiomyopathy remodeling in diabetic rats. A rat model of diabetic cardiomyopathy (DCM) was established by supplementing them with a high-calorie diet combined with a low dose of streptozotocin (STZ). The diabetic rats received IBN (5 µg/kg per day) or normal saline subcutaneously for 16 weeks. The hematoxylin and eosin (H&E) and Masson's trichrome staining were performed for evaluating the myocardial morphologies of the rats. Echocardiography and cardiac catheter were performed to assess their cardiac functional parameters. The protein levels of connective tissue growth factor (CTGF), farnesyl pyrophosphate synthase (FPPS), and mitogen-activated protein kinase (MAPK) were determined using Western blot analysis. RhoA activation was detected using a small GTP protease-linked immunosorbent assay (GLISA). The diabetic rats showed the development of moderate hyperglycemia, insulin resistance, hyperlipidemia, myocardial fibrosis, FPPS overexpression, cardiac systolic, and diastolic dysfunction. Inhibiting the FPPS could ameliorate myocardial hypertrophy and fibrosis. These anatomical findings were accompanied by a significant improvement in heart function. Furthermore, the inhibition of FPPS, the increased activation of RhoA, and phosphorylation of p38 and extracellular signal-regulated kinase (ERK)1/2 in DCM decreased significantly with the treatment of IBN. This study for the first time demonstrated that the upregulation of FPPS expression might be involved in diabetic myocardial remodeling in diabetes mellitus (DM). In addition, IBN might exert its inhibitory effects on myocardial tissue remodeling by suppressing the RhoA/ERK1/2 and RhoA/p38 MAPK pathways in DCM.

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.

Inhibition of the mevalonate pathway improves myocardial fibrosis

The mevalonate (MVA) pathway serves an important role in ventricular remodeling. Targeting the MVA pathway has protective effects against myocardial fibrosis. The present study aimed to investigate the mechanism behind these effects. Primary cultured cardiac fibroblasts from C57BL/6 mice were treated in vitro in 5 groups: i) negative control; ii) angiotensin II (Ang II) model (1x10^-5 mol/l); iii) Ang II + rosuvastatin (ROS); iv) Ang II + alendronate (ALE); and v) Ang II + fasudil (FAS). Collagen and crystal violet staining were used to assess morphological changes in cardiac fibroblasts. Reverse transcription quantitative PCR and western blotting were used to analyze the expression of key signaling molecules involved in the MVA pathway. Collagen staining in the ALE, FAS, and ROS groups was weak compared with the Ang II group, while the rate of cell proliferation in the ROS, ALE, and FAS groups was slower compared with that in the Ang II group. In addition, the expression of key signaling molecules in the MVA pathway, including transforming growth factor-β1 (TGF-β1), heat shock protein 47 (HSP47), collagen type I α1 (COL1A1), vascular endothelial growth factor 2 (VEGF2) and fibroblast growth factor 2 (FGF2), was decreased in the FAS and ROS groups compared with the Ang II model. Compared with the Ang II group, 3-Hydroxy-3-Methylglutaryl-CoA reductase (HMGCR) gene expression was significantly lowered in the drug intervention groups, whereas farnesyl pyrophosphate synthase (FDPS) expression was downregulated in the ALE group, but elevated in the FAS and ROS groups. Compared with that in the Ang II group, ras homolog family member A (RhoA) expression was downregulated in the FAS and ROS groups, whilst mevalonate kinase expression was reduced in the ROS group. Protein expression of TGF-β1, COL1A1 and HSP47 were decreased following intervention with each of the three drugs compared with the Ang II group. Overall, rosuvastatin, aledronate and fasudil decreased the proliferation of myocardial fibroblasts and inhibited collagen synthesis. Rosuvastatin had the strongest protective effects against myocardial fibrosis compared with the other drugs tested, suggesting this to be a potential agent for the clinical treatment of cardiovascular disease.

Bisphosphonates and atrial fibrillation: revisiting the controversy

Bisphosphonates (BPs) are widely prescribed drugs used to treat osteoporosis, commonly arising in postmenopausal women and in chronic glucocorticoid use. Their mechanism of action is through inhibiting osteoclast-induced bone remodeling, and they also possess calcium sequestering properties. Common side effects involve the gastrointestinal system and rare but serious side effects, including osteonecrosis of the jaw. However, a link between BPs and atrial fibrillation (AF) has been proposed, with early clinical trials, such as the Fracture Intervention Trial and the HORIZON Pivotal Fracture Trial, reporting that BPs are associated with increased risk of AF. Nevertheless, subsequent studies have reported contrasting results, ranging from no effect of BPs to antiarrhythmic effects of BPs. Preclinical and electrophysiological studies on any proarrhythmic effect of BPs are limited in scope and number, but suggest possible mechanisms that include antiangionesis-related myocardial remodeling, calcium handling abnormalities, and inflammatory changes. Contrastingly, some studies indicate that BPs are antiarrhythmic by inhibiting fibrotic myocardial remodeling. In order to continue established clinical prescribing of BPs within absolute margins of safety, it will be necessary to systematically rule in/rule out these mechanisms. Thus, we discuss these studies and examine in detail the potential mechanistic links, with the aim of suggesting further avenues for research.

Farnesyl Pyrophosphate Synthase Blocker Ibandronate Reduces Thoracic Aortic Fibrosis in Diabetic Rats

BACKGROUND

This study assessed the effect of ibandronate (IBN), a farnesyl pyrophosphate synthase (FPPS) inhibitor, on vascular remodeling in diabetic rats.

METHODS

A rat model of diabetes was induced by a high-fat and high-sugar diet combined with a small dose of streptozotocin. The diabetic rats received 5 µg/kg of ibandronate solution or normal saline subcutaneously every morning for 16 weeks. The morphology of the thoracic aorta was assessed by hematoxylin and eosin and Masson's trichrome staining techniques. Gene expression levels of connective tissue growth factor (CTGF) and FPPS were assessed by quantitative real-time polymerase chain reaction (qRT-PCR) analysis. CTGF and FPPS protein levels were determined by Western blotting analysis.

RESULTS

Rats with diabetes mellitus showed moderate hyperglycemia, insulin resistance, hyperlipidemia and thoracic aortic fibrosis. FPPS was significantly upregulated in the thoracic aorta from diabetic animals. Interestingly, IBN treatment for 16 weeks alleviated the diabetes-induced histopathologic changes in the thoracic aortic wall and reduced CTGF protein and mRNA levels.

CONCLUSIONS

These findings provided evidence that FPPS is involved in thoracic aortic fibrosis in diabetic rats. Meanwhile, IBN could alleviate vascular remodeling in diabetic animals.

FPPS mediates TGF-β1-induced non-small cell lung cancer cell invasion and the EMT process via the RhoA/Rock1 pathway

Farnesyl pyrophosphate synthase (FPPS), a key enzyme in the mevalonate pathway, was recently shown to play a role in cancer progression. However, its role in non-small cell lung cancer (NSCLC) metastasis and the underlying mechanism remain unclear. In this study, FPPS expression was significantly correlated with TNM stage, and metastasis. Inhibition or knockdown of FPPS blocked TGF-β1-induced cell invasion and epithelial-to-mesenchymal transition (EMT) process. FPPS expression of FPPS was induced by TGF-β1 and FPPS promoted cell invasion and EMT via the RhoA/Rock1 pathway. In conclusion, FPPS mediates TGF-β1-induced lung cancer cell invasion and EMT via the RhoA/Rock1 pathway. These findings suggest new treatment strategies to reduce mortality associated with metastasis in patients with NSCLC.

β2-Adrenoceptor is involved in connective tissue remodeling in regenerating muscles by decreasing the activity of MMP-9

We investigated the role of β2-adrenoceptors in the connective tissue remodeling of regenerating muscles from β2-adrenoceptor knockout (β2KO) mice. Tibialis anterior muscles from β2KO mice were cryolesioned and analyzed after 3, 10, and 21 days. Regenerating muscles from β2KO mice showed a significant increase in the area density of the connective tissue and in the amount of collagen at 10 days compared with wild-type (WT) mice. A greater increase occurred in the expression levels of collagen I, III, and IV in regenerating muscles from β2KO mice evaluated at 10 days compared with WT mice; this increase continued at 21 days, except for collagen III. Matrix metalloproteinase (MMP-2) activity increased to a similar extent in regenerating muscles from both β2KO and WT mice at 3 and 10 days. This was also the case for MMP-9 activity in regenerating muscles from both β2KO and WT mice at 3 days; however, at 10 days post-cryolesion, this activity returned to baseline levels only in WT mice. MMP-3 activity was unaltered in regenerating muscles at 10 days. mRNA levels of tumor necrosis factor-α increased in regenerating muscles from WT and β2KO mice at 3 days and, at 10 days post-cryolesion, returned to baseline only in WT mice. mRNA levels of interleukin-6 increased in muscles from WT mice at 3 days post-cryolesion and returned to baseline at 10 days post-cryolesion but were unchanged in β2KO mice. Our results suggest that the β2-adrenoceptor contributes to collagen remodeling during muscle regeneration by decreasing MMP-9 activity.

Tribbles 3: A potential player in diabetic aortic remodelling

Tribbles 3, whose expression is up-regulated by insulin resistance, was confirmed to be involved in diabetic cardiomyopathy in our previous study. However, it is not known whether Tribbles 3 has a role on conduit arteries such as the aorta in diabetes. Type 2 diabetic rat model was induced by high-fat diet and low-dose streptozotocin. We evaluated the characteristics of diabetic rats by serial ultrasonography and histopathologic analyses of aortic wall architecture. Diabetic rats displayed increased aortic medial thickness, excessive collagen deposition, diminished elastic fibres and reduced vascular compliance together with Tribbles 3 overexpression. To further investigate the role of Tribbles 3 in aortic remodelling, we used Tribbles 3 gene silencing in vivo 12 weeks after onset of diabetes. Silence of Tribbles 3 significantly reversed pathological aortic remodelling without blood pressure modification. In Tribbles 3-small interfering RNA group, medial thickness and perivascular fibrosis were markedly decreased; moreover, there were prominent reductions in collagen content and collagen/elastin ratio, resulting in an improved arterial compliance. Additionally, with Tribbles 3 silencing, the diminished phosphorylation of PI3K/Akt was restored, and increased activation of MKK4/JNK was decreased. Silence of Tribbles 3 is potent in mediating reversal of aortic remodelling, implicating that Tribbles 3 is proposed to be a potential therapeutic target for vascular complication in diabetes.

Inhibitory effect of D1-like dopamine receptors on neuropeptide Y-induced proliferation in vascular smooth muscle cells

Proliferation of vascular smooth muscle cells (VSMCs) is thought to have a key role in the development of atherosclerotic lesions. Neuropeptide Y (NPY), norepinephrine and dopamine are sympathetic neurotransmitters. NPY has been particularly shown to stimulate proliferation of VSMCs. NPY, norepinephrine and dopamine are all sympathetic transmitters. In our previous study, we found that in the presence of the dopamine receptor, the α1-adrenergic receptor-mediated VSMC proliferation is reduced. We hypothesize that the activation of the D1-like receptor might inhibit the NPY-mediated VSMC proliferation. In our present study, we found that NPY, mainly via the Y1 receptor, increased VSMC proliferation. This was determined by [(3)H]-thymidine incorporation, in a concentration (10(-11) to 10(-8)  M)-dependent manner. In the presence of the D1-like receptor agonist, fenoldopam (10(-12) to 10(-5) M), the stimulatory effect of NPY on VSMC proliferation was reduced. The involvement of the D1-like receptor was confirmed when the inhibitory effect of fenoldopam was reversed in the presence of the D1-like receptor antagonist SCH-23390 (10(-8) M). Moreover, the inhibitory effect of fenoldopam on NPY-mediated VSMC proliferation was also blocked in the presence of the PKA inhibitor 14-22 (10(-6)  M). Protein kinase A activator 8-(4-chlorophenylthio) adenosine-3,5-cyclic monophosphorothioate, Sp-isomer sodium salt (10(-6)  M) could simulate the stimulatory effect of fenoldopam. It indicated that the inhibitory effect of D1-like receptors on NPY-mediated VSMC proliferation may have an important role in the regulation of blood pressure or prevention of atherosclerosis.

Blood pressure decrease in spontaneously hypertensive rats folowing renal denervation or dopamine β-hydroxylase inhibition with etamicastat

Overactivity of the sympathetic nervous system has an important role in the development and progression of arterial hypertension. Catheter-based renal nerve ablation for the treatment of drug-resistant hypertension has recently been developed. An alternative strategy for the modulation of sympathetic nerve function is to reduce the biosynthesis of noradrenaline (NA) by inhibiting dopamine β-hydroxylase (DβH), the enzyme that catalyzes the conversion of dopamine (DA) to NA in the sympathetic nerves. Renal denervation (RDN) surgery was performed in spontaneously hypertensive rats (SHR) to evaluate the effect of RDN on the DA and NA levels and on blood pressure over a 28-day period. The selective peripheral DβH inhibitor etamicastat (30 mg kg (-1)day(-1)) was administered to another cohort of SHR. RDN and etamicastat treatment had no effect on the renal function, as assessed by measuring the water balance response, renal function and urinary electrolyte levels. RDN significantly decreased the systolic blood pressure (SBP) and the diastolic blood pressure (DBP). A gradual return of the SBP and the DBP to the high baseline levels was observed over time. Conversely, treatment with etamicastat resulted in a significant decrease in the SBP and the DBP at all time points. On the last day of the assessment, NA levels in renal tissue were significantly decreased in both RDN and etamicastat-treated groups. In contrast, the NA levels in the left ventricle were decreased only in the etamicastat-treated group. Thus, RDN produces transitory decreases in blood pressure, whereas prolonged downregulation of sympathetic drive with the DβH inhibitor etamicastat results in a sustained decrease in the SBP and the DBP.

Alteration of mevalonate pathway in proliferated vascular smooth muscle from diabetic mice: possible role in high-glucose-induced atherogenic process

The proliferation of vascular smooth muscle cells (VSMCs) is one of the main features of atherosclerosis induced by high glucose. Mevalonate pathway is an important metabolic pathway that plays a key role in multiple cellular processes. The aim of this study was to define whether the enzyme expression in mevalonate pathway is changed in proliferated VSMCs during atherogenic process in diabetic mice. Diabetes was induced in BALB/c mice with streptozotocin (STZ, 50 mg/kg/day for 5 days). Induction of diabetes with STZ was associated with an increase of lesion area and media thickness after 8 and 16 weeks of diabetes. In aorta, there were overexpressions of some enzymes, including 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR), farnesyl pyrophosphate synthase (FPPS), geranylgeranyl pyrophosphate synthase (GGPPS), farnesyltransferase (FNT), and geranylgeranyltransferase-1 (GGT-1), and unchanged expression of squalene synthase (SQS) and phosphor-3-hydroxy-3-methylglutaryl-coenzyme A reductase (P-HMGR) in 8 and 16 weeks of diabetes. In vitro, VSMCs were cultured and treated with different glucose concentrations for 48 h. High glucose (22.2 mM) induced VSMC proliferation and upregulation of HMGR, FPPS, GGPPS, FNT, and GGT-1 but did not change the expressions of SQS and P-HMGR. In conclusion, altered expression of several key enzymes in the mevalonate pathway may play a potential pathophysiological role in atherogenic process of diabetes macrovascular complication.

Leucine supplementation accelerates connective tissue repair of injured tibialis anterior muscle

This study investigated the effect of leucine supplementation on the skeletal muscle regenerative process, focusing on the remodeling of connective tissue of the fast twitch muscle tibialis anterior (TA). Young male Wistar rats were supplemented with leucine (1.35 g/kg per day); then, TA muscles from the left hind limb were cryolesioned and examined after 10 days. Although leucine supplementation induced increased protein synthesis, it was not sufficient to promote an increase in the cross-sectional area (CSA) of regenerating myofibers (p > 0.05) from TA muscles. However, leucine supplementation reduced the amount of collagen and the activation of phosphorylated transforming growth factor-β receptor type I (TβR-I) and Smad2/3 in regenerating muscles (p < 0.05). Leucine also reduced neonatal myosin heavy chain (MyHC-n) (p < 0.05), increased adult MyHC-II expression (p < 0.05) and prevented the decrease in maximum tetanic strength in regenerating TA muscles (p < 0.05). Our results suggest that leucine supplementation accelerates connective tissue repair and consequent function of regenerating TA through the attenuation of TβR-I and Smad2/3 activation. Therefore, future studies are warranted to investigate leucine supplementation as a nutritional strategy to prevent or attenuate muscle fibrosis in patients with several muscle diseases.