geranylgeranyl-pyrophosphate and Disease-Models--Animal

The mevalonate synthesis inhibitors, statins, are mainstay therapeutics for cholesterol management and cardiovascular health. Thirty years of research have uncovered supportive roles for the mevalonate pathway in numerous cellular processes that support oncogenesis, most recently macropinocytosis. Central to the diverse mechanisms of statin sensitivity is an acquired dependence on one mevalonate pathway output, protein geranylgeranylation. New chemical prenylation probes and the discovery of a novel geranylgeranyl transferase hold promise to deepen our understanding of statin mechanisms of action. Further, insights into statin selection and the counterproductive role of dietary geranylgeraniol highlight how we should assess statins in the clinic. Lastly, rational combination strategies preview how statins will enter the oncology toolbox.

Topics: Alkyl and Aryl Transferases; Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Cell Proliferation; Cell Survival; Disease Models, Animal; Diterpenes; Farnesyltranstransferase; Feeding Behavior; Food-Drug Interactions; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Metabolic Networks and Pathways; Mevalonic Acid; Mice; Neoplasms; Pinocytosis; Polyisoprenyl Phosphates; Prenylation

High serum/plasma cholesterol levels have been suggested as a risk factor for Alzheimer's disease (AD). Some reports, mostly retrospective epidemiological studies, have observed a decreased prevalence of AD in patients taking the cholesterol lowering drugs, statins. The strongest evidence causally linking cholesterol to AD is provided by experimental studies showing that adding/reducing cholesterol alters amyloid precursor protein (APP) and amyloid beta-protein (Ab) levels. However, there are problems with the cholesterol-AD hypothesis. Cholesterol levels in serum/plasma and brain of AD patients do not support cholesterol as a causative factor in AD.Prospective studies on statins and AD have largely failed to show efficacy. Even the experimental data are open to interpretation given that it is well-established that modification of cholesterol levels has effects on multiple proteins, not only amyloid precursor protein and Ab. The purpose of this review, therefore, was to examine the above-mentioned issues, discuss the pros and cons of the cholesterol-AD hypothesis, involvement of other lipids in the mevalonate pathway, and consider that AD may impact cholesterol homeostasis.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Apolipoproteins E; Astrocytes; Cell Membrane; Cells, Cultured; Cholesterol; Cholesterol, Dietary; Disease Models, Animal; Humans; Hydroxycholesterols; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hypercholesterolemia; Mice; Models, Biological; Neurons; Polyisoprenyl Phosphates; Rabbits; Sesquiterpenes

Previous studies have suggested that metabolites in the mevalonate pathway are involved in hepatic bile acid metabolism, yet the details of this relationship remain unknown. In this study, we found that the hepatic farnesyl pyrophosphate (FPP) level and the ratio of FPP to geranylgeranyl pyrophosphate (GGPP) were increased in mice with acute obstructive cholestasis compared with mice that underwent a sham operation. In addition, the livers of the mice with acute obstructive cholestasis showed lower expression of geranylgeranyl diphosphate synthase (GGPPS), which synthesizes GGPP from FPP. When Ggps1 was conditionally deleted in the liver, amelioration of liver injury, as shown by downregulation of the hepatic inflammatory response and decreased hepatocellular apoptosis, was found after ligation of the common bile duct and cholecystectomy (BDLC). Subsequently, liquid chromatography/mass spectrometry analysis showed that knocking out Ggps1 decreased the levels of hepatic bile acids, including hydrophobic bile acids. Mechanistically, the disruption of Ggps1 increased the levels of hepatic FPP and its metabolite farnesol, thereby resulting in farnesoid X receptor (FXR) activation, which modulated hepatic bile acid metabolism and reduced hepatic bile acids. It was consistently indicated that digeranyl bisphosphonate, a specific inhibitor of GGPPS, and GW4064, an agonist of FXR, could also alleviate acute obstructive cholestatic liver injury in vivo. In general, GGPPS is critical for modulating acute obstructive cholestatic liver injury, and the inhibition of GGPPS ameliorates acute obstructive cholestatic liver injury by decreasing hepatic bile acids, which is possibly achieved through the activation of FXR-induced bile acid metabolism.

Topics: Animals; Apoptosis; Bile Acids and Salts; Cholestasis; Disease Models, Animal; Farnesyltranstransferase; Hepatocytes; Liver Diseases; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Multienzyme Complexes; Polyisoprenyl Phosphates; Sesquiterpenes

Farnesyl pyrophosphate synthase (FPPS) is a key enzyme in the mevalonate pathway. In our previous study, we found that inhibition of FPPS attenuates cardiac hypertrophy in spontaneously hypertensive rats (SHRs) and prevents angiotensin (Ang) II-induced hypertrophy in cardiomyocytes. Here, we further investigate the role of FPPS in cardiac hypertrophy and heart failure (HF) using a transgenic (Tg) model, and its mechanisms.. Tg mice with cardiac-specific expression of FPPS were studied as an experimental model. The results showed that Tg mice with overexpression of FPPS exhibited cardiac hypertrophy, fibrosis, and HF, as well as increased synthesis of farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate in heart tissue. These pathological changes were associated with the activation of RhoA and other known kinases in the hypertrophic signalling pathway, such as extracellular signal-related kinases 1/2 and p38. Adenoviral infection of FPPS in cultured neonatal cardiomyocytes induced a hypertrophic response characterized by an 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. Further investigation showed a marked increase of FPPS protein levels in hypertrophic ventricles of patients with valvular heart disease.. Taken together, these results suggest that FPPS may function as a potent regulator in myocardial remodelling. The FPPS-regulated signalling pathway is relevant to the pathological changes in cardiac hypertrophy and HF.

Topics: Adenoviridae; Animals; Cardiomegaly; Cells, Cultured; Disease Models, Animal; Female; Gene Expression; Geranyltranstransferase; Heart Failure; Heart Valve Diseases; Humans; In Vitro Techniques; Male; MAP Kinase Signaling System; Mice; Mice, Inbred C57BL; Mice, Inbred CBA; Mice, Transgenic; Myocardium; Myocytes, Cardiac; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Polyisoprenyl Phosphates; rhoA GTP-Binding Protein; Signal Transduction; Ventricular Dysfunction, Left

Parathyroid hormone-related protein (PTHrP) is overexpressed in atherosclerotic plaques by unknown mechanisms. We have examined here the putative mechanism(s) responsible for this overexpression in the atherosclerotic lesion and its potential modulation by simvastatin, both in vitro and in vivo.. Atherosclerosis was induced in rabbits by femoral endothelial dessication and atherogenic diet. After 2 weeks, animals were randomized to receive either 5mg/(kgd) simvastatin (n=7) or no treatment (n=6) during 4 additional weeks. An increase in PTHrP immunostaining was observed in atherosclerotic lesions of hyperlipidemic rabbits, which was significantly reduced by simvastatin. However, PTH/PTHrP type 1 receptor staining was similar in both groups. In cultured vascular smooth muscle cells (VSMCs), atherogenic concentrations of native LDL (0.125-0.5mg/mL) increased PTHrP expression. This effect was prevented by preincubation with simvastatin (1micromol/L) and was reversed by mevalonate, geranylgeranylpyrophosphate and, to a lesser extent, by farnesylpyrophosphate. Moreover, in transfection studies, we showed that RhoA appears to participate in the mechanism whereby LDL induces PTHrP in VSMC. Finally, native LDL-induced VSMC growth and this mitogenic effect was blocked by PTHrP silencing.. LDL might be responsible for PTHrP overexpression in atherosclerotic plaques of hyperlipidemic rabbits. The inhibition of this effect by simvastatin provides further insights into the mechanisms of action of statins.

Topics: Animals; Atherosclerosis; Cells, Cultured; Disease Models, Animal; Femoral Artery; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Lipoproteins, LDL; Macrophages; Male; Mevalonic Acid; Muscle Cells; Muscle, Smooth, Vascular; Parathyroid Hormone-Related Protein; Polyisoprenyl Phosphates; Rabbits; Receptor, Parathyroid Hormone, Type 1; RNA, Small Interfering; Simvastatin; Tunica Intima; Up-Regulation

Hydroxymethyl glutaryl (HMG)-coenzyme A (CoA) reductase inhibitors (statins) protect the myocardium against ischemia-reperfusion injury via a mechanism unrelated to cholesterol lowering. Statins may inhibit isoprenylation and thereby prevent activation of proteins such as RhoA. We hypothesized that statins protect the myocardium against ischemia-reperfusion injury via a mechanism involving inhibition of geranylgeranyl pyrophosphate synthesis and translocation of RhoA to the plasma membrane. Sprague-Dawley rats were given either the HMG-CoA reductase inhibitor rosuvastatin, geranylgeranyl pyrophosphate dissolved in methanol, the combination of rosuvastatin and geranylgeranyl pyrophosphate, rosuvastatin and methanol, or distilled water (control) by intraperitoneal injection for 48 h before ischemia-reperfusion. Animals were anesthetized and either subjected to 30 min of coronary artery occlusion followed by 2 h of reperfusion where at infarct size was determined, or the expression of RhoA protein was determined in cytosolic and membrane fractions of nonischemic myocardium. There were no significant differences in hemodynamics between the control group and the other groups before ischemia or during ischemia and reperfusion. The infarct size was 80 +/- 3% of the area at risk in the control group. Rosuvastatin reduced infarct size to 64 +/- 2% (P<0.001 vs. control). Addition of geranylgeranyl pyrophosphate (77 +/- 2%, P<0.01 vs. rosuvastatin) but not methanol (65 +/- 2%, not significant vs. rosuvastatin) abolished the cardioprotective effect of rosuvastatin. Geranylgeranyl pyrophosphate alone did not affect infarct size per se (84 +/- 2%). Rosuvastatin increased the cytosol-to-membrane ratio of RhoA protein in the myocardium (P<0.05 vs. control). These changes were abolished by addition of geranylgeranyl pyrophosphate. We conclude that the cardioprotection and the increase of the RhoA cytosol-to-membrane ratio induced by rosuvastatin in vivo are blocked by geranylgeranyl pyrophosphate. The inhibition of geranylgeranyl pyrophosphate formation and subsequent modulation of cytosol/membrane-bound RhoA are of importance for the protective effect of statins against myocardial ischemia-reperfusion injury.

Topics: Animals; Cardiovascular Agents; Cell Membrane; Cytosol; Disease Models, Animal; Fluorobenzenes; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Male; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Polyisoprenyl Phosphates; Protein Transport; Pyrimidines; Rats; Rats, Sprague-Dawley; rhoA GTP-Binding Protein; Rosuvastatin Calcium; Sulfonamides

This study emphasizes the importance of Rho/ROCK pathway in lovastatin-induced apoptosis as replenishment with exogenous isoprenoid, geranylgeranylpyrophosphate (GGPP), resulted in inhibition of apoptosis in cultured tumor cells. Treatment of C6 glioma cells with Toxin B and exoenzyme C3 resulted in cell death suggesting the role of geranylgeranylated protein(s) in the survival of glioma cells. Relative apoptotic death observed in cells transfected with dominant negative constructs of RhoA, Rac, and cdc42 imply Rho A as playing the major role in cell survival. Furthermore, the inhibition of Rho A kinase (ROCK), a direct downstream effector of Rho A, by Y-27632 or dominant negative of ROCK, induced apoptosis in glioma cells. These findings indicate that RhoA/ROCK pathway is involved negatively in the regulation of glioma cell death pathway. Moreover, in vivo studies of lovastatin treatment in animals implanted with C6 glioma cell tumors also resulted in smaller tumor size and induced apoptosis in the tumor tissue. The implantation of stably transfected C6 glioma cells with expression vector of C3 exoenzyme, dominant negative of RhoA and ROCK, resulted in significant smaller tumor mass, further establishing the importance of geranylgeranylated proteins, specifically RhoA and its downstream effecter ROCK, in cell survival and tumor genesis.

Topics: Amides; Animals; Antineoplastic Agents; Apoptosis; Blotting, Southern; Blotting, Western; Caspases; Cell Survival; Disease Models, Animal; DNA Fragmentation; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Inhibitors; Flow Cytometry; Humans; Immunohistochemistry; In Situ Nick-End Labeling; Intracellular Signaling Peptides and Proteins; Lovastatin; Male; Mevalonic Acid; Mice; Neoplasms; Neoplasms, Experimental; Polyisoprenyl Phosphates; Protein Serine-Threonine Kinases; Pyridines; Rats; Rats, Wistar; rho-Associated Kinases; rhoA GTP-Binding Protein; Signal Transduction; Tetrazolium Salts; Thiazoles; Time Factors; Tumor Cells, Cultured

Human immunodeficiency virus (HIV)-1 infectivity requires actin-dependent clustering of host lipid raft-associated receptors, a process that might be linked to Rho guanosine triphosphatase (GTPase) activation. Rho GTPase activity can be negatively regulated by statins, a family of drugs used to treat hypercholesterolemia in man. Statins mediate inhibition of Rho GTPases by impeding prenylation of small G proteins through blockade of 3-hydroxy-3-methylglutaryl coenzyme A reductase. We show that statins decreased viral load and increased CD4+ cell counts in acute infection models and in chronically HIV-1-infected patients. Viral entry and exit was reduced in statin-treated cells, and inhibition was blocked by the addition of l-mevalonate or of geranylgeranylpyrophosphate, but not by cholesterol. Cell treatment with a geranylgeranyl transferase inhibitor, but not a farnesyl transferase inhibitor, specifically inhibited entry of HIV-1-pseudotyped viruses. Statins blocked Rho-A activation induced by HIV-1 binding to target cells, and expression of the dominant negative mutant RhoN19 inhibited HIV-1 envelope fusion with target cell membranes, reducing cell infection rates. We suggest that statins have direct anti-HIV-1 effects by targeting Rho.

Topics: Acquired Immunodeficiency Syndrome; Animals; CD4 Lymphocyte Count; Cells, Cultured; Cholesterol; Cytoskeleton; Disease Models, Animal; Down-Regulation; Electrophoresis, Polyacrylamide Gel; HIV-1; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Leukocytes, Mononuclear; Mevalonic Acid; Mice; Mice, SCID; Polyisoprenyl Phosphates; Precipitin Tests; rho GTP-Binding Proteins; RNA

Apolipoprotein E (ApoE) genotype modulates the risk of Alzheimer's disease. ApoE has been shown essential for amyloid beta-peptide fibrillogenesis and deposition, a defining pathological feature of this disease. Because astrocytes and microglia represent the major source of extracellular apoE in brain, we investigated apoE secretion by glia. We determined that protein prenylation is required for apoE release from a continuous microglial cell line, primary mixed glia, and from organotypic hippocampal cultures. Using selective protein prenylation inhibitors, apoE secretion was found to require protein geranylgeranylation. This prenylation involved a protein critical to apoE secretion, not apoE proper. ApoE secretion could also be suppressed by inhibiting synthesis of mevalonate, the precursor to both types of protein prenylation, using hydroxyl-3-methylglutaryl coenzyme A reductase inhibitors (statins). Recent reports have described the beneficial effects of statins on the risk of dementia. Our finding that protein geranylgeranylation is required for apoE secretion in the brain parenchyma provides another contributing mechanism to explain the effective properties of statins against the development of dementia. In this model, statin-mediated inhibition of mevalonate synthesis, an essential reaction in forming geranylgeranyl lipid, would lower extracellular levels of parenchymal apoE. Because apoE has been found necessary for plaque development in transgenic models of Alzheimer's disease, suppressing apoE secretion by statins could reduce plaques and, in turn, improve cognitive function.

Topics: Alkyl and Aryl Transferases; Alzheimer Disease; Amyloid beta-Peptides; Animals; Animals, Newborn; Apolipoproteins E; Astrocytes; Brain; Cells, Cultured; Disease Models, Animal; Dose-Response Relationship, Drug; Farnesyltranstransferase; Hippocampus; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Lovastatin; Mevalonic Acid; Mice; Mice, Transgenic; Microglia; Neuroglia; Polyisoprenyl Phosphates; Protein Prenylation