Abrogation of Insulin-like Growth Factor-I (IGF-I) and Insulin Action by Mevalonic Acid Depletion

N-deglycosylation targeting chimera (DGlyTAC): a strategy for immune checkpoint proteins inactivation by specifically removing N-glycan

Among the leading methods for triggering therapeutic anti-cancer immunity is the inhibition of immune checkpoint pathways. N-glycosylation is found to be essential for the function of various immune checkpoint proteins, playing a critical role in their stability and interaction with immune cells. Removing the N-glycans of these proteins seems to be an alternative therapy, but there is a lack of a de-N-glycosylation technique for target protein specificity, which limits its clinical application. Here, we developed a novel technique for specifically removing N-glycans from a target protein on the cell surface, named deglycosylation targeting chimera (DGlyTAC), which employs a fusing protein consisting of Peptide-N-glycosidase F (PNGF) and target-specific nanobody/affibody (Nb/Af). The DGlyTAC technique was developed to target a range of glycosylated surface proteins, especially these immune checkpoints-CD24, CD47, and PD-L1, which minimally affected the overall N-glycosylation landscape and the N-glycosylation of other representative membrane proteins, ensuring high specificity and minimal off-target effects. Importantly, DGlyTAC technique was successfully applied to lead inactivation of these immune checkpoints, especially PD-L1, and showed more potential in cancer immunotherapy than inhibitors. Finally, PD-L1 targeted DGlyTAC showed therapeutic effects on several tumors in vivo, even better than PD-L1 antibody. Overall, we created a novel target-specific N-glysocylation erasing technique that establishes a modular strategy for directing membrane proteins inactivation, with broad implications on tumor immune therapeutics.

Statin-Associated muscle symptoms and vitamin D supplementation

PURPOSE OF REVIEW

Statin medications play a pivotal role in the primary and secondary prevention and management of cardiovascular disease due to their potent lipid-lowering and anti-inflammatory effects. Nevertheless, the clinical application of statins is often hampered by statin-associated muscle symptoms (SAMS), which deter patient adherence and treatment efficacy considerably. SAMS currently affects 10-20% of statin users, thus understanding potential mitigation strategies is crucial. This review focuses on the role of vitamin D in mitigating SAMS, given the growing interest in vitamin D deficiency as a potentially modifiable risk factor.

RECENT FINDINGS

Despite observational suggestions linking vitamin D deficiency to heightened SAMS risk, recent studies have yielded conflicting results on the role of vitamin D supplementation in preventing SAMS. Some studies report an improvement in statin tolerance following vitamin D repletion. However, recent large-scale clinical trials, particularly the Vitamin D and Omega-3 trial (VITAL) report no significant benefit of vitamin D supplementation in preventing SAMS or reducing statin discontinuation rates, regardless of baseline vitamin D levels.

SUMMARY

Observational data provides evidence for the use of vitamin D supplementation in SAMS management, however conflicting evidence in recent clinical trials do not support its routine use for preventing or treating SAMS. To explore alternative strategies in improving statin tolerance and adherence, this discourse aims to elucidate the current understanding the complex mechanisms underlying SAMS, the influence of serum vitamin D levels, and the implications for clinical management.

The signaling landscape of insulin-like growth factor 1

The sheer amplitude of biological actions of insulin-like growth factor I (IGF-1) affecting all types of cells in all tissues suggests a vast signaling landscape for this ubiquitous humoral signal. While the canonical signaling pathways primarily involve the Ras/MAPK and PI3K/AKT cascades, the evolutionary conservation of insulin-like peptides (ILPs) and their pathways hints at the potential for novel functions to emerge over time. Indeed, the evolutionary trajectory of ILPs opens the possibility of either novel functions for these two pathways, novel downstream routes, or both. Evidence supporting this notion includes observations of neofunctionalization in bony fishes or crustaceans, and the involvement of ILPs pathways in invertebrate eusociality or in vertebrate bone physiology, respectively. Such evolutionary processes likely contribute to the rich diversity of ILPs signaling observed today. Moreover, the interplay between conserved signaling pathways, such as those implicated in aging (predominantly involving the PI3K-AKT route), and lesser known pathways, such as those mediated by biased G-protein coupled receptors and others even less known, may underpin the context-dependent actions characteristic of ILPs signaling. While canonical IGF-1 signaling is often assumed to account for the intracellular pathways utilized by this growth factor, a comprehensive analysis of all the pathways mediated by the IGF-1 receptor (IGF-1R) remains lacking. This review aims to explore both canonical and non-canonical routes of IGF-1R action across various cell types, offering a detailed examination of the mechanisms underlying IGF-1 signaling and highlighting the significant gaps in our current understanding.

Impaired myoblast differentiation and muscle IGF-1 receptor signaling pathway activation after N-glycosylation inhibition

The role of N-glycosylation in the myogenic process remains poorly understood. Here, we evaluated the impact of N-glycosylation inhibition by Tunicamycin (TUN) or by phosphomannomutase 2 (PMM2) gene knockdown, which encodes an enzyme essential for catalyzing an early step of the N-glycosylation pathway, on C2C12 myoblast differentiation. The effect of chronic treatment with TUN on tibialis anterior (TA) and extensor digitorum longus (EDL) muscles of WT and MLC/mIgf-1 transgenic mice, which overexpress muscle Igf-1Ea mRNA isoform, was also investigated. TUN-treated and PMM2 knockdown C2C12 cells showed reduced ConA, PHA-L, and AAL lectin binding and increased ER-stress-related gene expression (Chop and Hspa5 mRNAs and s/uXbp1 ratio) compared to controls. Myogenic markers (MyoD, myogenin, and Mrf4 mRNAs and MF20 protein) and myotube formation were reduced in both TUN-treated and PMM2 knockdown C2C12 cells. Body and TA weight of WT and MLC/mIgf-1 mice were not modified by TUN treatment, while lectin binding slightly decreased in the TA muscle of WT (ConA and AAL) and MLC/mIgf-1 (ConA) mice. The ER-stress-related gene expression did not change in the TA muscle of WT and MLC/mIgf-1 mice after TUN treatment. TUN treatment decreased myogenin mRNA and increased atrogen-1 mRNA, particularly in the TA muscle of WT mice. Finally, the IGF-1 production and IGF1R signaling pathways activation were reduced due to N-glycosylation inhibition in TA and EDL muscles. Decreased IGF1R expression was found in TUN-treated C2C12 myoblasts which was associated with lower IGF-1-induced IGF1R, AKT, and ERK1/2 phosphorylation compared to CTR cells. Chronic TUN-challenge models can help to elucidate the molecular mechanisms through which diseases associated with aberrant N-glycosylation, such as Congenital Disorders of Glycosylation (CDG), affect muscle and other tissue functions.

A phase 1 study of simvastatin in combination with topotecan and cyclophosphamide in pediatric patients with relapsed and/or refractory solid and CNS tumors

BACKGROUND

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) can inhibit tumor proliferation, angiogenesis, and restore apoptosis in preclinical pediatric solid tumor models. We conducted a phase 1 trial to determine the maximum tolerated dose (MTD) of simvastatin with topotecan and cyclophosphamide in children with relapsed/refractory solid and central nervous system (CNS) tumors.

METHODS

Simvastatin was administered orally twice daily on days 1-21, with topotecan and cyclophosphamide intravenously on days 1-5 of a 21-day cycle. Four simvastatin dose levels (DLs) were planned, 140 (DL1), 180 (DL2), 225 (DL3), 290 (DL4) mg/m2 /dose, with a de-escalation DL of 100 mg/m2 /dose (DL0) if needed. Pharmacokinetic and pharmacodynamic analyses were performed during cycle 1.

RESULTS

The median age of 14 eligible patients was 11.5 years (range: 1-23). The most common diagnoses were neuroblastoma (N = 4) and Ewing sarcoma (N = 3). Eleven dose-limiting toxicity (DLT)-evaluable patients received a median of four cycles (range: 1-6). There were three cycle 1 DLTs: one each grade 3 diarrhea and grade 4 creatine phosphokinase (CPK) elevations at DL1, and one grade 4 CPK elevation at DL0. All patients experienced at least one grade 3/4 hematologic toxicity. Best overall response was partial response in one patient with Ewing sarcoma (DL0) and stable disease for four or more cycles in four patients. Simvastatin exposure increased with higher doses and may have correlated with toxicity. Plasma interleukin 6 (IL-6) concentrations (N = 6) showed sustained IL-6 reductions with decrease to normal values by day 21 in all patients, indicating potential on-target effects.

CONCLUSIONS

The MTD of simvastatin with topotecan and cyclophosphamide was determined to be 100 mg/m2 /dose.

New dawn for cancer cell death: Emerging role of lipid metabolism

BACKGROUND

Resistance to cell death, a protective mechanism for removing damaged cells, is a "Hallmark of Cancer" that is essential for cancer progression. Increasing attention to cancer lipid metabolism has revealed a number of pathways that induce cancer cell death.

SCOPE OF REVIEW

We summarize emerging concepts regarding lipid metabolic reprogramming in cancer that is mainly involved in lipid uptake and trafficking, de novo synthesis and esterification, fatty acid synthesis and oxidation, lipogenesis, and lipolysis. During carcinogenesis and progression, continuous metabolic adaptations are co-opted by cancer cells, to maximize their fitness to the ever-changing environmental. Lipid metabolism and the epigenetic modifying enzymes interact in a bidirectional manner which involves regulating cancer cell death. Moreover, lipids in the tumor microenvironment play unique roles beyond metabolic requirements that promote cancer progression. Finally, we posit potential therapeutic strategies targeting lipid metabolism to improve treatment efficacy and survival of cancer patient.

MAJOR CONCLUSIONS

The profound comprehension of past findings, current trends, and future research directions on resistance to cancer cell death will facilitate the development of novel therapeutic strategies targeting the lipid metabolism.

Cardiac decompensation and promiscuous prenylation of small GTPases in cardiomyocytes in response to local mevalonate pathway disruption

Investigations of major mevalonate pathway enzymes have demonstrated the importance of local isoprenoid synthesis in cardiac homeostasis. Farnesyl diphosphate synthase (FPPS) synthesizes isoprenoid precursors needed for cholesterol biosynthesis and protein prenylation. Wang, Zhang, Chen et al, in a recently published article in The Journal of Pathology, elegantly elucidated the pathological outcomes of FPPS deficiency in cardiomyocytes, which paradoxically resulted in increased prenylation of the small GTPases Ras and Rheb. Cardiomyocyte FPPS depletion caused severe dilated cardiomyopathy that was associated with enhanced GTP-loading and abundance of Ras and Rheb in lipidated protein-enriched cardiac fractions and robust activation of downstream hypertrophic ERK1/2 and mTOR signaling pathways. Cardiomyopathy and activation of ERK1/2 and mTOR caused by loss of FPPS were ameliorated by inhibition of farnesyltransferase, suggesting that impairment of FPPS activity results in promiscuous activation of Ras and Rheb through non-canonical actions of farnesyltransferase. Here, we discuss the findings and adaptive signaling mechanisms in response to disruption of local cardiomyocyte mevalonate pathway activity, highlighting how alteration in a key branch point in the mevalonate pathway affects cardiac biology and function and perturbs protein prenylation, which might unveil novel strategies and intricacies of targeting the mevalonate pathway to treat cardiovascular diseases. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Defective IGF-1 prohormone N-glycosylation and reduced IGF-1 receptor signaling activation in congenital disorders of glycosylation

The insulin-like growth factor-1 (IGF-1) signaling pathway is crucial for the regulation of growth and development. The correct processing of the IGF-1Ea prohormone (proIGF-1Ea) and the IGF-1 receptor (IGF-1R) peptide precursor requires proper N-glycosylation. Deficiencies of N-linked glycosylation lead to a clinically heterogeneous group of inherited diseases called Congenital Disorders of Glycosylation (CDG). The impact of N-glycosylation defects on IGF-1/IGF-1R signaling components is largely unknown. In this study, using dermal fibroblasts from patients with different CDG [PMM2-CDG (n = 7); ALG3-CDG (n = 2); ALG8-CDG (n = 1); GMPPB-CDG (n = 1)], we analyzed the glycosylation pattern of the proIGF-1Ea, IGF-1 secretion efficiency and IGF-1R signaling activity. ALG3-CDG, ALG8-CDG, GMPPB-CDG and some PMM2-CDG fibroblasts showed hypoglycosylation of the proIGF-1Ea and lower IGF-1 secretion when compared with control (CTR). Lower IGF-1 serum concentration was observed in ALG3-CDG, ALG8-CDG and in some patients with PMM2-CDG, supporting our in vitro data. Furthermore, reduced IGF-1R expression level was observed in ALG3-CDG, ALG8-CDG and in some PMM2-CDG fibroblasts. IGF-1-induced IGF-1R activation was lower in most PMM2-CDG fibroblasts and was associated with decreased ERK1/2 phosphorylation as compared to CTR. In general, CDG fibroblasts showed a slight upregulation of Endoplasmic Reticulum (ER) stress genes compared with CTR, uncovering mild ER stress in CDG cells. ER-stress-related gene expression negatively correlated with fibroblasts IGF-1 secretion. This study provides new evidence of a direct link between N-glycosylation defects found in CDG and the impairment of IGF-1/IGF-1R signaling components. Further studies are warranted to determine the clinical consequences of reduced systemic IGF-1 availability and local activity in patients with CDG.

UBCH5 Family Members Differentially Impact Stabilization of Mutant p53 via RNF128 Iso1 During Barrett's Progression to Esophageal Adenocarcinoma

BACKGROUND & AIMS

TP53 mutations underlie Barrett's esophagus (BE) progression to dysplasia and cancer. During BE progression, the ubiquitin ligase (E3) RNF128/GRAIL switches expression from isoform 2 (Iso2) to Iso1, stabilizing mutant p53. However, the ubiquitin-conjugating enzyme (E2) that partners with Iso1 to stabilize mutant p53 is unknown.

METHODS

Single-cell RNA sequencing of paired normal esophagus and BE tissues identified candidate E2s, further investigated in expression data from BE to esophageal adenocarcinoma (EAC) progression samples. Biochemical and cellular studies helped clarify the role of RNF128-E2 on mutant p53 stability.

RESULTS

The UBE2D family member 2D3 (UBCH5C) is the most abundant E2 in normal esophagus. However, during BE to EAC progression, loss of UBE2D3 copy number and reduced expression of RNF128 Iso2 were noted, 2 known p53 degraders. In contrast, expression of UBE2D1 (UBCH5A) and RNF128 Iso1 in dysplastic BE and EAC forms an inactive E2-E3 complex, stabilizing mutant p53. To destabilize mutant p53, we targeted RNF128 Iso1 either by mutating asparagine (N48, 59, and 101) residues to block glycosylation to facilitate β-TrCP1-mediated degradation or by mutating proline (P54 and 105) residues to restore p53 polyubiquitinating ability. In addition, either loss of UBCH5A catalytic activity, or disruption of the Iso1-UBCH5A interaction promoted Iso1 loss. Consequently, overexpression of either catalytically dead or Iso1-binding-deficient UBCH5A mutants destabilized Iso1 to degrade mutant p53, thus compromising the clonogenic survival of mutant p53-dependent BE cells.

CONCLUSIONS

Loss of RNF128 Iso2-UBCH5C and persistence of the Iso1-UBCH5A complex favors mutant p53 stability to promote BE cell survival. Therefore, targeting of Iso1-UBCH5A may provide a novel therapeutic strategy to prevent BE progression.

Zebrafish as a Model for the Study of Lipid-Lowering Drug-Induced Myopathies

Drug-induced myopathies are classified as acquired myopathies caused by exogenous factors. These pathological conditions develop in patients without muscle disease and are triggered by a variety of medicaments, including lipid-lowering drugs (LLDs) such as statins, fibrates, and ezetimibe. Here we summarise the current knowledge gained via studies conducted using various models, such as cell lines and mammalian models, and compare them with the results obtained in zebrafish (Danio rerio) studies. Zebrafish have proven to be an excellent research tool for studying dyslipidaemias as a model of these pathological conditions. This system enables in-vivo characterization of drug and gene candidates to further the understanding of disease aetiology and develop new therapeutic strategies. Our review also considers important environmental issues arising from the indiscriminate use of LLDs worldwide. The widespread use and importance of drugs such as statins and fibrates justify the need for the meticulous study of their mechanism of action and the side effects they cause.

Targeting on glycosylation of mutant FLT3 in acute myeloid leukemia

Objective: To summarize the abnormal location of FLT3 caused by different glycosylation status which further leads to the distinguishing signaling pathways and discuss targeting on FLT3 glycosylation by drugs reported in recent literatures. Methods: We review FLT3 glycosylation in endoplasmic reticulum. The abnormal signal of mutant FLT3 with different glycosylation status is discussed. We also address potential FLT3 glycosylation-targeting strategies for the treatment. Results: Inhibition of FLT3 mutant cells by drugs reported in recent literatures involves the influence of glycosylation of FLT3: 2-deoxy-D-glucose, Tunicamycin and Fluvastatin are reported to inhibit N-glycosylation of FLT3; Pim-1 inhibitors are proved to block the inhibition of Pim-1 on FLT3 Oglycosylation; HSP90 inhibitors and Tyrosine Kinase Inhibitors are shown to increase fully glycosylated form of FLT3. Discussion: The FMS-like tyrosine kinase 3 (FLT3) gene expressed only in CD34+ progenitor cells in bone marrow is located on chromosome 13q12 encoding FLT3 protein. FLT3 is initially synthesized as a 110 KD protein, which glycosylated in the endoplasmic reticulum to a 130 KD immature protein rich in mannose, and further processed into a mature 160 KD protein in the Golgi apparatus, which could be transferred to the cell surface. Therapy targeting on FLT3 glycosylation is a promising direction for AML treatment. Conclusions: The abnormal location of FLT3 caused by different glycosylation status leads to the distinguishing signaling pathways. Targeting on FLT3 glycosylation may provide a new perspective for therapeutic strategies. Abbreviations: ABCG2: ATP-binding cassette transporter breast cancer resistance protein; ATF: activating transcription factor; AML: acute myeloid leukemia; CHOP: CCAAT-enhancer-binding protein homologous protein; 2-DG: 2-deoxy-D-glucose; EFS: event free survival; EPO: erythropoietin; EPOR: erythropoietin receptor; ERS: endoplasmic reticulum stress; FLT3: FMS-like tyrosine kinase 3; GPI: glycosylphosphatidylinositol; HSP: heat shock protein; ITD: internal tandem duplication; IRE1a: inositol-requiring enzyme 1 alpha; JNK: c-Jun N-terminal kinase; JMD: juxtamembrane domain; JAK: janus kinase; MAPK/ERK: mitogen activated protein kinase/extracellular signal-regulated protein kinase; OS: overall survival; PI3K/AKT: phosphatidylinositide 3-kinases/protein kinase B; PERK: RNA-activated protein kinase-like endoplasmic reticulum kinase; Pgp: P-glycoprotein; PTX3: human pentraxin-3; STAT: signal transducer and activator of transcriptions; TKD: tyrosine-kinase domain; TKI: tyrosine kinase inhibitor; TM: Tunicamycin; UPR: unfolded protein reaction.

Statins Induce a DAF-16/Foxo-dependent Longevity Phenotype via JNK-1 through Mevalonate Depletion in C. elegans

Statins belong to the most pre-scribed cholesterol lowering drugs in western countries. Their competitive inhibition of the HMG-CoA reductase causes a reduction in the mevalonate pool, resulting in reduced cholesterol biosynthesis, impaired protein prenylation and glycosylation. Recently, a cohort study showed a decreased mortality rate in humans between age 78-90 going along with statin therapy, which is independent of blood cholesterol levels. As C. elegans harbors the mevalonate pathway, but is cholesterol-auxotroph, it is particularly suitable to study cholesterol-independent effects of statins on aging-associated phenotypes. Here, we show that low doses of lovastatin or a mild HMG-CoA reductase knockdown via hmgr-1(RNAi) in C. elegans substantially attenuate aging pigment accumulation, which is a well-established surrogate marker for biological age. Consistently, for two statins we found dosages, which prolonged the lifespan of C. elegans. Together with an observed reduced fertility, slower developmental timing and thermal stress resistance this complex of outcomes point to the involvement of DAF-16/hFOXO3a, the master regulator of stress resistance and longevity. Accordingly, prolonged low-dose statin exposure leads to an increased expression of jnk-1, a known activator of DAF-16. Moreover, the beneficial effects of statins on aging pigments and lifespan depend on DAF-16 and JNK-1, as shown in epistasis analyses. These effects can be reverted by mevalonate supplementation. In conclusion, we describe a lifespan extension in C. elegans, which is conferred via two well-conserved stress-related factors (JNK-1, DAF-16) and results from mevalonate depletion.

Mitophagy protects against statin-mediated skeletal muscle toxicity

The deleterious effects of statins on skeletal muscle are well known, but the mechanism associated with these effects remains unresolved. Statins are associated with mitochondrial damage, which may contribute to muscle myopathy. Here we demonstrate that simvastatin induces mitophagy in skeletal muscle cells and hypothesized that attenuating this process by silencing the mitophagy adapter p62/sequestosome-1 (SQSTM1) might mitigate myotoxicity. Surprisingly, silencing p62/SQSTM1 in differentiated C2C12 muscle cells exacerbated rather than attenuated myotoxicity. This inhibition of mitophagy in the face of statin challenge correlated with increased release of cytochrome c to the cytosol, activation of caspase-3, and lactate dehydrogenase (LDH) release. Correspondingly, targeted knockdown of Parkin, a canonical E3 ubiquitin ligase important for mitophagy, mirrored the effects of p62/SQSTM1 silencing. To corroborate these findings in vivo, we treated Parkin knockout mice with simvastatin for 2 wk. In line with our findings in vitro, these mitophagy-compromised mice displayed reduced spontaneous activity, loss of grip strength, and increased circulating levels of muscle damage marker LDH. Our findings demonstrate that mitophagy is an important mechanism to resist statin-induced skeletal muscle damage.-Ramesh, M., Campos, J. C., Lee, P., Song, Y., Hernandez, G., Sin, J., Tucker, K. C., Saadaeijahromi, H., Gurney, M., Ferreira, J. C. B., Andres, A. M. Mitophagy protects against statin-mediated skeletal muscle toxicity.

Fatty acid desaturase 2 is up-regulated by the treatment with statin through geranylgeranyl pyrophosphate-dependent Rho kinase pathway in HepG2 cells

Statins have been reported to increase the plasma concentration of arachidonic acid (AA), an omega-6 long chain polyunsaturated fatty acid (LCPUFA) in several clinical studies indicating that statins affect the endogenous synthesis of LCUFAs. In the present study, we investigated the roles of the intrinsic mevalonate cascade and Rho-dependent pathway in LCPUFA synthesis, especially focusing on fatty acid desaturases (Fads) 2, using the human hepatocellular carcinoma cell line HepG2. Cell number and the activity of caspase-3 and 7 (caspase-3/7) was measured using a commercial kit. Gene expression was analyzed by quantitative real-time PCR. Protein expression was detected by Western blot analysis. Atorvastatin decreased cell viability and increased caspase-3/7 activity in a dose-dependent manner. At lower concentrations, atorvastatin stimulated both mRNA and protein expression of Fads2, and increased mRNA expression of FADS1 and ELVOL5. Both mevalonate and geranylgeranyl-pyrophosphate (GGPP), but not cholesterol, fully reversed atorvastatin-induced upregulation of Fads2, and mevalonate-effected reversal was inhibited by treatment with the Rho-associated protein kinase inhibitor Y-27632. These data clearly demonstrated that in human HepG2 cells, statins affect the endogenous synthesis of LCPUFAs by regulation of not only Fads2, but also Fads1 and Elovl5, through the GGPP-dependent Rho kinase pathway.

The Many Faces of Rap1 GTPase

This review addresses the issue of the numerous roles played by Rap1 GTPase (guanosine triphosphatase) in different cell types, in terms of both physiology and pathology. It is one among a myriad of small G proteins with endogenous GTP-hydrolyzing activity that is considerably stimulated by posttranslational modifications (geranylgeranylation) or guanine nucleotide exchange factors (GEFs), and inhibited by GTPase-activating proteins (GAPs). Rap1 is a ubiquitous protein that plays an essential role in the control of metabolic processes, such as signal transduction from plasma membrane receptors, cytoskeleton rearrangements necessary for cell division, intracellular and substratum adhesion, as well as cell motility, which is needed for extravasation or fusion. We present several examples of how Rap1 affects cells and organs, pointing to possible molecular manipulations that could have application in the therapy of several diseases.

Geranylgeraniol Prevents Statin-Dependent Myotoxicity in C2C12 Muscle Cells through RAP1 GTPase Prenylation and Cytoprotective Autophagy

The present study investigated the cytotoxic effects of statins (atorvastatin (ATR) and simvastatin (SIM), resp.) and methyl-beta-cyclodextrin (MβCD), at their respective IC₅₀ concentrations, on muscle regeneration in the in vitro model of murine C2C12 myoblasts. Cotreatment with mevalonate (MEV), farnesol (FOH), geranylgeraniol (GGOH), or water-soluble cholesterol (Chol-PEG) was employed to determine whether the statin-dependent myotoxicity resulted from the lower cholesterol levels or the attenuated synthesis of intermediates of mevalonate pathway. Our findings demonstrated that while GGOH fully reverted the statin-mediated cell viability in proliferating myoblasts, Chol-PEG exclusively rescued MβCD-induced toxicity in myocytes. Statins caused loss of prenylated RAP1, whereas the GGOH-dependent positive effect was accompanied by loss of nonprenylated RAP1. Geranylgeranyltransferases are essential for muscle cell survival as inhibition with GGTI-286 could not be reversed by GGOH cotreatment. The increase in cell viability correlated with elevated AKT 1(S463) and GSK-3β(S9) phosphorylations. Slight increase in the levels of autophagy markers (Beclin 1, MAP LC-3IIb) was found in response to GGOH cotreatment. Autophagy rose time-dependently during myogenesis and was inhibited by statins and MβCD. Statins and MβCD also suppressed myogenesis and neither nonsterol isoprenoids nor Chol-PEG could reverse this effect. These results point to GGOH as the principal target of statin-dependent myotoxicity, whereas plasma membrane cholesterol deposit is ultimately essential to restore viability of MβCD-treated myocytes. Overall, this study unveils for the first time a link found between the GGOH- and Chol-PEG-dependent reversal of statin- or MβCD-mediated myotoxicity and cytoprotective autophagy, respectively.

Interacting Cancer Machineries: Cell Signaling, Lipid Metabolism, and Epigenetics

Cancer-specific perturbations of signaling, metabolism, and epigenetics can be a cause and/or consequence of malignant transformation. Evidence indicates that these regulatory systems interact with each other to form highly flexible and robust cybernetic networks that promote malignant growth and confer treatment resistance. Deciphering these plexuses using holistic approaches known from systems biology can be instructive for the future design of novel anticancer strategies. In this review, I discuss novel findings elucidating the multiple molecular interdependence among cancer-specific signaling, cell metabolism, and epigenetics to provide an insightful understanding of how major cancer machineries interact with each other during cancer development and progression, and how this knowledge may be used for future co-targeting strategies.

Statin Therapy Negatively Impacts Skeletal Muscle Regeneration and Cutaneous Wound Repair in Type 1 Diabetic Mice

Those with diabetes invariably develop complications including cardiovascular disease (CVD). To reduce their CVD risk, diabetics are generally prescribed cholesterol-lowering 3-hydroxy-methylglutaryl coenzyme A reductase inhibitors (i.e., statins). Statins inhibit cholesterol biosynthesis, but also reduce the synthesis of a number of mevalonate pathway intermediates, leading to several cholesterol-independent effects. One of the pleiotropic effects of statins is the reduction of the anti-fibrinolytic hormone plasminogen activator inhibitor-1 (PAI-1). We have previously demonstrated that a PAI-1 specific inhibitor alleviated diabetes-induced delays in skin and muscle repair. Here we tested if statin administration, through its pleiotropic effects on PAI-1, could improve skin and muscle repair in a diabetic rodent model. Six weeks after diabetes onset, adult male streptozotocin-induced diabetic (STZ), and WT mice were assigned to receive control chow or a diet enriched with 600 mg/kg Fluvastatin. Tibialis anterior muscles were injured via Cardiotoxin injection to induce skeletal muscle injury. Punch biopsies were administered on the dorsal scapular region to induce injury of skin. Twenty-four days after the onset of statin therapy (10 days post-injury), tissues were harvested and analyzed. PAI-1 levels were attenuated in statin-treated diabetic tissue when compared to control-treated tissue, however no differences were observed in non-diabetic tissue as a result of treatment. Muscle and skin repair were significantly attenuated in Fluvastatin-treated STZ-diabetic mice as demonstrated by larger wound areas, less mature granulation tissue, and an increased presence of smaller regenerating muscle fibers. Despite attenuating PAI-1 levels in diabetic tissue, Fluvastatin treatment impaired cutaneous healing and skeletal muscle repair in STZ-diabetic mice.

Downregulation of monocytic differentiation via modulation of CD147 by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors

CD147 is an activation induced glycoprotein that promotes the secretion and activation of matrix metalloproteinases (MMPs) and is upregulated during the differentiation of macrophages. Interestingly, some of the molecular functions of CD147 rely on its glycosylation status: the highly glycosylated forms of CD147 induce MMPs whereas the lowly glycosylated forms inhibit MMP activation. Statins are hydroxy-methylglutaryl coenzyme A reductase inhibitors that block the synthesis of mevalonate, thereby inhibiting all mevalonate-dependent pathways, including isoprenylation, N-glycosylation and cholesterol synthesis. In this study, we investigated the role of statins in the inhibition of macrophage differentiation and the associated process of MMP secretion through modulation of CD147. We observed that differentiation of the human monocytic cell line THP-1 to a macrophage phenotype led to upregulation of CD147 and CD14 and that this effect was inhibited by statins. At the molecular level, statins altered CD147 expression, structure and function by inhibiting isoprenylation and N-glycosylation. In addition, statins induced a shift of CD147 from its highly glycosylated form to its lowly glycosylated form. This shift in N-glycosylation status was accompanied by a decrease in the production and functional activity of MMP-2 and MMP-9. In conclusion, these findings describe a novel molecular mechanism of immune regulation by statins, making them interesting candidates for autoimmune disease therapy.

Atorvastatin increases Fads1, Fads2 and Elovl5 gene expression via the geranylgeranyl pyrophosphate-dependent Rho kinase pathway in 3T3-L1 cells

Numerous clinical studies have reported that statins increase the plasma concentration of arachidonic acid, which is an ω-6 long-chain polyunsaturated fatty acid (LCPUFA), and decrease the concentrations of eicosapentaenoic acid and docosahexaenoic acid, which are ω‑3 LCPUFAs. These findings indicate that statins may affect the endogenous synthesis of LCPUFAs, which is regulated by fatty acid desaturases (FADSs) and elongation of very long‑chain fatty acids proteins (ELOVLs). The present study aimed to investigate the roles of the intrinsic mevalonate cascade and Rho‑dependent pathway in statin‑induced regulation of these desaturases and elongases, as well as cell viability using mouse 3T3‑L1 cells. mRNA expression was analyzed by quantitative polymerase chain reaction. Treatment with atorvastatin decreased cell viability and increased the mRNA expression levels of Fads1, Fads2 and ELOVL fatty acid elongase 5 (Elovl5) in a dose‑dependent manner. Mevalonate and geranylgeranyl pyrophosphate (GGPP), but not cholesterol, fully reversed the atorvastatin‑induced downregulation of cell viability and upregulation of gene expression; however, mevalonate itself did not affect cell viability and gene expression. The Rho‑associated protein kinase inhibitor Y‑27632 inhibited the mevalonate‑ and GGPP‑mediated reversal of atorvastatin‑induced upregulation of Fads1, Fads2 and Elovl5. These findings indicated that statins may affect the endogenous synthesis of LCPUFAs by regulating Fads1, Fads2 and Elovl5 gene expression via the GGPP‑dependent Rho kinase pathway in mouse 3T3-L1 cells.

Overexpression of Insulin-Like Growth Factor 1 Enhanced the Osteogenic Capability of Aging Bone Marrow Mesenchymal Stem Cells

Many studies have indicated that loss of the osteoblastogenic potential in bone marrow mesenchymal stem cells (bmMSCs) is the major component in the etiology of the aging-related bone deficit. But how the bmMSCs lose osteogenic capability in aging is unclear. Using 2-dimentional cultures, we examined the dose response of human bmMSCs, isolated from adult and aged donors, to exogenous insulin-like growth factor 1 (IGF-1), a growth factor regulating bone formation. The data showed that the mitogenic activity and the osteoblastogenic potential of bmMSCs in response to IGF-1 were impaired with aging, whereas higher doses of IGF-1 increased the proliferation rate and osteogenic potential of aging bmMSCs. Subsequently, we seeded IGF-1-overexpressing aging bmMSCs into calcium-alginate scaffolds and incubated in a bioreactor with constant perfusion for varying time periods to examine the effect of IGF-1 overexpression to the bone-forming capability of aging bmMSCs. We found that IGF-1 overexpression in aging bmMSCs facilitated the formation of cell clusters in scaffolds, increased the cell survival inside the cell clusters, induced the expression of osteoblast markers, and enhanced the biomineralization of cell clusters. These results indicated that IGF-1 overexpression enhanced cells' osteogenic capability. Thus, our data suggest that the aging-related loss of osteogenic potential in bmMSCs can be attributed in part to the impairment in bmMSCs' IGF-1 signaling, and support possible application of IGF-1-overexpressing autologous bmMSCs in repairing bone defect of the elderly and in producing bone graft materials for repairing large scale bone injury in the elderly.

A short-term statin treatment changes the contractile properties of fast-twitch skeletal muscles

Background

Cumulative evidence indicates that statins induce myotoxicity. However, the lack of understanding of how statins affect skeletal muscles at the structural, functional, and physiological levels hampers proper healthcare management. The purpose of the present study was to investigate the early after-effects of lovastatin on the slow-twitch soleus (Sol) and fast-twitch extensor digitorum longus (EDL) muscles.

Methods

Adult C57BL/6 mice were orally administrated with placebo or lovastatin [50 mg/kg/d] for 28 days. At the end of the treatment, the isometric ex vivo contractile properties of the Sol and EDL muscles were measured. Subtetanic and tetanic contractions were assessed and contraction kinetics were recorded. The muscles were then frozen for immunohistochemical analyses. Data were analyzed by two-way ANOVA followed by an a posteriori Tukey’s test.

Results

The short-term lovastatin treatment did not induce muscle mass loss, muscle fiber atrophy, or creatine kinase (CK) release. It had no functional impact on slow-twitch Sol muscles. However, subtetanic stimulations at 10 Hz provoked greater force production in fast-twitch EDL muscles. The treatment also decreased the maximal rate of force development (dP/dT) of twitch contractions and prolonged the half relaxation time (1/2RT) of tetanic contractions of EDL muscles.

Conclusions

An early short-term statin treatment induced subtle but significant changes in some parameters of the contractile profile of EDL muscles, providing new insights into the selective initiation of statin-induced myopathy in fast-twitch muscles.

Molecular mechanisms of statin intolerance

Statins reduce cardiovascular morbidity and mortality in primary and secondary prevention. Despite their efficacy, many persons are unable to tolerate statins due to adverse events such as hepatotoxicity and myalgia/myopathy. In the case of most patients, it seems that mild-to-moderate abnormalities in liver and muscle enzymes are not serious adverse effects and do not outweigh the benefits of coronary heart disease risk reduction. The risk for mortality or permanent organ damage ascribed to statin use is very small and limited to cases of myopathy and rhabdomyolysis. Statin-induced muscle-related adverse events comprise a highly heterogeneous clinical disorder with numerous, complex etiologies and a variety of genetic backgrounds. Every patient who presents with statin-related side effects cannot undergo the type of exhaustive molecular characterization that would include all of these mechanisms. Frequently the only solution is to either discontinue statin therapy/reduce the dose or attempt intermittent dosing strategies at a low dose.

Rosuvastatin: Beyond the cholesterol-lowering effect

Rosuvastatin is a fully synthetic statin wich acts by interfering with the endogenous synthesis of cholesterol through competitively inhibiting the 3-hydroxy-3-methylglutaryl coenzyme A reductase, a liver enzyme responsible of the rate-limiting step in cholesterol synthesis. When compared to other molecules of the same class, it shows high efficacy in the improvement of lipid profile, and, thanks to its non-cholesterol-lowering actions (anti-inflammatory, antioxidant and antithrombotic), represents a crucial tool for cardiovascular primary and secondary prevention. Moreover, recent data highlight rosuvastatin beneficial effects in several other fields. In this manuscript we analyzed literature sources in order to better define rosuvastatin features and discuss some critical issues.

The role of mitochondria in statin-induced myopathy

BACKGROUND

Statins inhibit hydroxymethylglutaryl-coenzyme A reductase, decrease plasma low-density lipoprotein cholesterol and reduce cardiovascular morbidity and mortality. They can also exert adverse effects, mostly affecting skeletal muscle, ranging from mild myalgia to rhabdomyolysis.

MATERIALS AND METHODS

Based on a PubMed search until December 2014, this review summarizes studies on statin effects on muscle mitochondrial morphology and function in the context of myopathy.

RESULTS

Possible mechanisms of statin-induced myopathy include lower cholesterol synthesis and production of prenylated proteins, reduced dolichols and increased atrogin-1 expression. Statin-treated patients frequently feature decreased muscle coenzyme Q10 (CoQ10) contents, suggesting that statins might impair mitochondrial function. In cell cultures, statins diminish muscle oxygen consumption, promote mitochondrial permeability transient pore opening and generate apoptotic proteins. Animal models confirm the statin-induced decrease in muscle CoQ10, but reveal no changes in mitochondrial enzyme activities. Human studies yield contradictory results, with decreased CoQ10, elevated lipids, decreased enzyme activities in muscle and impaired maximal oxygen uptake in several but not all studies. Some patients are susceptible to statin-induced myopathy due to variations in genes encoding proteins involved in statin uptake and biotransformation such as the solute carrier organic anion transporter family member 1B1 (SLCO1B1) or cytochrome P450 (CYP2D6, CYP3A4, CYP3A5). Carriers for carnitine palmitoyltransferase II deficiency and McArdle disease also present with higher prevalence of statin-induced myopathy.

CONCLUSIONS

Despite the widespread use of statins, the pathogenesis of statin-induced myopathy remains unclear, requiring prospective randomized controlled trials with intensive phenotyping also for identifying strategies for its risk assessment, prevention and treatment.

Inhibition of prenyltransferase activity by statins in both liver and muscle cell lines is not causative of cytotoxicity

As inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase, statins are an important first-line treatment for hypercholesterolemia. However, a recognized side-effect of statin therapy is myopathy, which in severe cases can present as potentially fatal rhabdomyolysis. This represents an important impediment to successful statin therapy, and despite decades of research the molecular mechanisms underlying this side-effect remain unclear. Current evidence supports a role for reduced levels of mevalonate pathway intermediates, with the most accepted hypothesis being a reduction in isoprenoids formation, leading to faulty post-translational modifications of membrane-associated proteins. We have undertaken a comprehensive analysis of the impact of nine statins on two human cell lines; Huh7 hepatoma and RD rhabdomyosarcoma. In both cell lines, concentration-dependent inhibition of prenylation was observed for cerivastatin and simvastatin, which could be rescued with the pathway intermediate mevalonate; in general, muscle cells were more sensitive to this effect, as measured by the levels of unprenylated Rap1A, a marker for prenylation by geranylgeranyl transferase I. Concentration-dependent toxicity was observed in both cell lines, with muscle cells again being more sensitive. Importantly, there was no correlation between inhibition of prenylation and cell toxicity, suggesting they are not causally linked. The lack of a causal relationship was confirmed by the absence of cytotoxicity in all cell lines following exposure to specific inhibitors of geranylgeranyl transferases I and II, and farnesyl transferase. As such, we provide strong evidence against the commonly accepted hypothesis linking inhibition of prenylation and statin-mediated toxicity, with the two processes likely to be simultaneous but independent.

Statins inhibit insulin-like growth factor action in first trimester placenta by altering insulin-like growth factor 1 receptor glycosylation

The rapid rise in obesity, metabolic syndrome and type 2 diabetes is one of the major healthcare problems of the Western world. Affected individuals are often treated with statins (3-hydroxy-3-methylglutaryl co-enzyme A [HMG CoA] reductase inhibitors) to reduce circulating cholesterol levels and the risk of developing cardiovascular disease; given the evolving demographic profile of these conditions, such drugs are increasingly prescribed to women of reproductive age. We have previously shown that exposure of placental tissue to statins inhibits the action of insulin-like growth factors (IGF)-I and -II which are key regulators of trophoblast proliferation and placental development. N-linked glycans in the IGF receptor, IGF1R, influence its presentation at the cell surface. This study aimed to determine whether statins, which are known to affect N-glycosylation, modulate IGF1R function in placenta. Treatment of first trimester villous tissue explants with statins (pravastatin or cerivastatin) or inhibitors of N-glycosylation (tunicamycin, deoxymannojirimycin or castanospermine) altered receptor distribution in trophoblast and attenuated proliferation induced by IGF-I or IGF-II (Ki67; P < 0.05, n = 5). Decreased binding of Phaseolus vulgaris lectin and phytohaemagglutinin to IGF1R immunoprecipitated from treated explants demonstrated reduced levels of complex N-linked glycans. Co-incubation of tissue explants with statins and farnesyl pyrophosphate (which increases the supply of dolichol intermediates), prevented statin-mediated disruption of IGF1R localization and reversed the negative effect on IGF-mediated trophoblast proliferation. These data suggest that statins attenuate IGF actions in the placenta by inhibiting N-linked glycosylation and subsequent expression of mature IGF1R at the placental cell surface.

In vitro and in vivo anticancer effects of mevalonate pathway modulation on human cancer cells

Background:

The increasing usage of statins (the 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) has revealed a number of unexpected beneficial effects, including a reduction in cancer risk.

Methods:

We investigated the direct anticancer effects of different statins approved for clinical use on human breast and brain cancer cells. We also explored the effects of statins on cancer cells using in silico simulations.

Results:

In vitro studies showed that cerivastatin, pitavastatin, and fluvastatin were the most potent anti-proliferative, autophagy inducing agents in human cancer cells including stem cell-like primary glioblastoma cell lines. Consistently, pitavastatin was more effective than fluvastatin in inhibiting U87 tumour growth in vivo. Intraperitoneal injection was much better than oral administration in delaying glioblastoma growth. Following statin treatment, tumour cells were rescued by adding mevalonate and geranylgeranyl pyrophosphate. Knockdown of geranylgeranyl pyrophosphate synthetase-1 also induced strong cell autophagy and cell death in vitro and reduced U87 tumour growth in vivo. These data demonstrate that statins main effect is via targeting the mevalonate synthesis pathway in tumour cells.

Conclusions:

Our study demonstrates the potent anticancer effects of statins. These safe and well-tolerated drugs need to be further investigated as cancer chemotherapeutics in comprehensive clinical studies.

Statin treatment and new-onset diabetes: a review of proposed mechanisms

New-onset diabetes has been observed in clinical trials and meta-analyses involving statin therapy. To explain this association, three major mechanisms have been proposed and discussed in the literature. First, certain statins affect insulin secretion through direct, indirect or combined effects on calcium channels in pancreatic β-cells. Second, reduced translocation of glucose transporter 4 in response to treatment results in hyperglycemia and hyperinsulinemia. Third, statin therapy decreases other important downstream products, such as coenzyme Q10, farnesyl pyrophosphate, geranylgeranyl pyrophosphate, and dolichol; their depletion leads to reduced intracellular signaling. Other possible mechanisms implicated in the effect of statins on new-onset diabetes are: statin interference with intracellular insulin signal transduction pathways via inhibition of necessary phosphorylation events and reduction of small GTPase action; inhibition of adipocyte differentiation leading to decreased peroxisome proliferator activated receptor gamma and CCAAT/enhancer-binding protein which are important pathways for glucose homeostasis; decreased leptin causing inhibition of β-cells proliferation and insulin secretion; and diminished adiponectin levels. Given that the magnitude of the risk of new-onset diabetes following statin use remains to be fully clarified and the well-established beneficial effect of statins in reducing cardiovascular risk, statins remain the first-choice treatment for prevention of CVD. Elucidation of the mechanisms underlying the development of diabetes in association with statin use may help identify novel preventative or therapeutic approaches to this problem and/or help design a new generation statin without such side-effects.

Mevalonate deprivation mediates the impact of lovastatin on the differentiation of murine 3T3-F442A preadipocytes

The statins competitively inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase activity and consequently the synthesis of mevalonate. The use of statins is associated with insulin resistance, presumably due to the impaired differentiation and diminished glucose utilization of adipocytes. We hypothesize that mevalonate is essential to adipocyte differentiation and adipogenic gene expression. Adipo-Red assay and Oil Red O staining showed that an eight-day incubation with 0-2.5 µmol/L lovastatin dose-dependently reduced the intracellular triglyceride content of murine 3T3-F442A adipocytes. Concomitantly, lovastatin downregulated the expression of peroxisome proliferator-activated receptor γ (Pparγ), leptin (Lep), fatty acid binding protein 4 (Fabp4), and adiponectin (AdipoQ) as measured by quantitative real-time polymerase chain reaction (real-time qPCR). The expression of sterol regulatory element binding protein 1 (Srebp-1), a transcriptional regulator of Pparγ and Lep genes, was also suppressed by lovastatin. Western-blot showed that lovastatin reduced the level of CCAAT/enhancer binding protein α (C/EBPα) while inducing a compensatory over-expression of HMG CoA reductase. The impact of lovastatin on intracellular triglyceride content and expression of the adipogenic genes was reversed by supplemental mevalonate. Mevalonate-derived metabolites have essential roles in promoting adipogenic gene expression and adipocyte differentiation.

Evaluation of atorvastatin and simvastatin for treatment of multiple sclerosis

Atorvastatin and simvastatin (members of the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor family) are widely prescribed as cholesterol-lowering agents. As they have been shown to exhibit potent immunomodulatory effects, they may become a future treatment option for autoimmune disease in general and multiple sclerosis (MS) in particular. Several recent reports have demonstrated that statins prevent and reverse chronic and relapsing experimental autoimmune encephalomyelitis, an animal model of MS. An open-label clinical trial assessing simvastatin in MS revealed a significant decrease in the number and volume of new MRI lesions and a favorable safety profile. The results of a large multicenter, placebo-controlled clinical trial assessing atorvastatin in patients with clinically isolated syndrome (a disease that predisposes to development MS) are expected soon. However, prospective placebo-controlled trials of atorvastatin or simvastatin in definite MS are difficult to perform due to ethical and financial objections. In this review, we discuss the backgrounds, mechanisms of action and future perspectives of atorvastatin and simvastatin as putative future treatment options in MS.

Atorvastatin administration is associated with dose-related changes in IGF bioavailability

OBJECTIVE

IGF levels, their binding proteins (IGFBPs) and high-dose statin therapy have been linked to the development of diabetes. We aimed to identify whether atorvastatin caused dose-related changes in IGF proteins.

DESIGN AND METHODS

We measured IGF1, IGF2, IGFBP1 and IGFBP3 concentrations at baseline, 6 and 12 months in Protection Against Nephropathy in Diabetes with Atorvastatin trial participants with type 2 diabetes randomised to 10 mg (n=59) vs 80 mg (n=60) of atorvastatin (n=119; mean (S.D.): age 64 (10) years; 83% male; HbA1c 61 (10) mmol/mol; blood pressure 131/73 mmHg).

RESULTS

Atorvastatin was associated with overall reductions in circulating IGF1, IGF2 and IGFBP3 concentrations (P<0.05 for all changes). The adjusted mean (95% CI) between-group differences that indicate dose-related changes in IGF proteins were not significant for IGF1: -3 (-21 to 14) ng/ml; IGF2: -23 (-65 to 18) ng/ml and IGFBP3: -0.34 (-0.71 to 0.03) μg/ml, negative values indicating numerically greater lowering with high dose. The IGFBP1 concentration did not change with atorvastatin therapy overall but the adjusted mean (95% CI) between-group difference indicating a dose-related change in log IGFBP1 was highly significant -0.41 (-0.69 to 0.13, P=0.004).

CONCLUSION

IGF1, IGF2 and IGFBP3 concentrations decreased following atorvastatin therapy. A differential effect of low- vs high-dose atorvastatin on IGFBP1 concentrations was observed with likely implications for IGF bioavailability. The dose-related differential impact of atorvastatin treatment on concentration of IGF proteins merits investigation as a mechanism to explain the worsening of glucose tolerance with statin therapy.

Fluvastatin inhibits FLT3 glycosylation in human and murine cells and prolongs survival of mice with FLT3/ITD leukemia

FLT3 is frequently mutated in acute myeloid leukemia (AML), but resistance has limited the benefit of tyrosine kinase inhibitors (TKI). We demonstrate that statins can impair FLT3 glycosylation, thus leading to loss of surface expression and induction of cell death, as well as mitigation of TKI resistance. Immunofluorescence microscopy confirms a reduction in surface localization and an increase in intracellular FLT3/internal tandem duplication (ITD) accumulation. This aberrant localization was associated with increased STAT5 activation but inhibition of both MAPK and AKT phosphorylation. Growth inhibition studies indicate that FLT3/ITD-expressing cells were killed with an IC(50) within a range of 0.2-2μM fluvastatin. Several mechanisms of resistance could be circumvented by fluvastatin treatment. An increase in the IC(50) for inhibition of phosphorylated FLT3/ITD by lestaurtinib caused by exogenous FLT3 ligand, resistance to sorafenib caused by the D835Y or FLT3/ITD N676K mutations, and activation of the IL-3 compensatory pathway were all negated by fluvastatin treatment. Finally, fluvastatin treatment in vivo reduced engraftment of BaF3 FLT3/ITD cells in Balb/c mice. These results demonstrate that statins, a class of drugs already approved by the US Food and Drug Administration, might be repurposed for the management of FLT3 mutant acute myeloid leukemia cases either alone or in conjunction with FLT3 TKI.

Modulation of h(2)s metabolism by statins: a new aspect of cardiovascular pharmacology

SIGNIFICANCE

Statins (3-hydroxy-3-methylglutarylcoenzyme A reductase inhibitors) are commonly used in the treatment of cardiovascular diseases. Statins reduce plasma low-density lipoproteins, inhibit inflammatory reaction, improve endothelial function, ameliorate oxidative stress, and reduce platelet activity. Consequently, statins markedly decrease the risk of acute cardiovascular events. H(2)S is synthesized in all layers of the vascular wall, including the endothelium, smooth muscle cells, and perivascular adipose tissue (PVAT).

RECENT ADVANCES

Recent studies demonstrate that PVAT-derived H(2)S decreases vascular tone by activating K(ATP) and/or KCNQ potassium channels in smooth muscle cells. Lipophilic atorvastatin, but not hydrophilic pravastatin, increases net H(2)S production in PVAT by inhibiting its mitochondrial oxidation, and augments the anticontractile effect of PVAT. Inhibition of H(2)S metabolism results from atorvastatin-induced decrease in coenzyme Q, which is a cofactor of H(2)S oxidation by sulfide:quinone oxidoreductase. In contrast to H(2)S, statins do not impair mitochondrial oxidation of organic substrates.

CRITICAL ISSUES

Taking into account antiatherosclerotic and anti-inflammatory effect of H(2)S, the gas may mediate some of the beneficial effects of statins on the cardiovascular system. In addition, specific statins differ in their ability to enhance H(2)S signaling.

FUTURE DIRECTIONS

Since both statins and H(2)S reduce ischemia-reperfusion injury, the possible effect of statins on H(2)S oxidation in other tissues such as the heart and the kidney needs to be examined. Inhibition of H(2)S metabolism may be a new therapeutic strategy to improve H(2)S signaling, especially in the mitochondrial compartment.

Pharmacological actions of statins: a critical appraisal in the management of cancer

Statins, among the most commonly prescribed drugs worldwide, are cholesterol-lowering agents used to manage and prevent cardiovascular and coronary heart diseases. Recently, a multifaceted action in different physiological and pathological conditions has been also proposed for statins, beyond anti-inflammation and neuroprotection. Statins have been shown to act through cholesterol-dependent and -independent mechanisms and are able to affect several tissue functions and modulate specific signal transduction pathways that could account for statin pleiotropic effects. Typically, statins are prescribed in middle-aged or elderly patients in a therapeutic regimen covering a long life span during which metabolic processes, aging, and concomitant novel diseases, including cancer, could occur. In this context, safety, toxicity, interaction with other drugs, and the state of health have to be taken into account in subjects treated with statins. Some evidence has shown a dichotomous effect of statins with either cancer-inhibiting or -promoting effects. To date, clinical trials failed to demonstrate a reduced cancer occurrence in statin users and no sufficient data are available to define the long-term effects of statin use over a period of 10 years. Moreover, results from clinical trials performed to evaluate the therapeutic efficacy of statins in cancer did not suggest statin use as chemotherapeutic or adjuvant agents. Here, we reviewed the pharmacology of the statins, providing a comprehensive update of the current knowledge of their effects on tissues, biological processes, and pathological conditions, and we dissected the disappointing evidence on the possible future use of statin-based drugs in cancer therapy.

Opposite effects of pravastatin and atorvastatin on insulin sensitivity in the rat: role of vitamin D metabolites

OBJECTIVE

Recent studies indicate that pravastatin improves whereas other statins impair glucose homeostasis in humans, but the underlying mechanisms are not clear. We examined the effect of pravastatin and atorvastatin on insulin sensitivity in a rat model.

METHODS

Pravastatin (40 mg/kg/day) or atorvastatin (20mg/kg/day) were administered for 3 weeks and insulin sensitivity was assessed by measuring fasting plasma insulin, HOMA-IR, non-esterified fatty acids (NEFA) and glycerol levels, as well as by the hyperinsulinemic euglycemic clamp.

RESULTS

Pravastatin had no effect on fasting insulin and HOMA-IR but significantly reduced plasma NEFA and glycerol levels and increased glucose infusion rate (GIR) during the hyperinsulinemic clamp. Increase in GIR induced by pravastatin was not abolished by NO synthase inhibitor, l-NAME, indicating that this effect did not result from the improvement of endothelial function. Atorvastatin increased fasting insulin, HOM-IR, NEFA and glycerol levels as well as reduced GIR. Statins had no effect on leptin, HMW adiponectin, resistin, visfatin, interleukin-6 and TNF-α. Pravastatin increased plasma concentrations of 25-hydroxy- and 1,25-dyhydroxyvitamin D(3) (25-OH-D(3) and 1,25-(OH)(2)-D(3)), and its effect on insulin sensitivity was mimicked by exogenous 1,25-(OH)(2)-D(3). Atorvastatin reduced plasma 25-OH-D(3) but had no effect on 1,25-(OH)(2)-D(3). Decrease in insulin sensitivity induced by atorvastatin was not corrected by supplementation of vitamin D(3) despite normalization of plasma 25-OH-D(3) level.

CONCLUSIONS

Pravastatin and atorvastatin have opposite effects on insulin sensitivity and vitamin D(3) status. Pravastatin-induced increase in insulin sensitivity is mediated by elevation of 1,25-(OH)(2)-D(3). In contrast, atorvastatin-induced decrease in insulin sensitivity is independent of lowering 25-OH-D(3).

Apposite insulin-like growth factor (IGF) receptor glycosylation is critical to the maintenance of vascular smooth muscle phenotype in the presence of factors promoting osteogenic differentiation and mineralization

Vascular calcification is strongly linked with increased morbidity and mortality from cardiovascular disease. Vascular calcification is an active cell-mediated process that involves the differentiation of vascular smooth muscle cells (VSMCs) to an osteoblast-like phenotype. Several inhibitors of this process have been identified, including insulin-like growth factor-I (IGF-I). In this study, we examined the role of the IGF receptor (IGFR) and the importance of IGFR glycosylation in the maintenance of the VSMC phenotype in the face of factors known to promote osteogenic conversion. IGF-I (25 ng/ml) significantly protected VSMCs from β-glycerophosphate-induced osteogenic differentiation (p < 0.005) and mineral deposition (p < 0.01). Mevalonic acid depletion (induced by 100 nm cerivastatin) significantly inhibited these IGF protective effects (p < 0.01). Mevalonic acid depletion impaired IGFR processing, decreased the expression of mature IGFRs at the cell surface, and inhibited the downstream activation of Akt and MAPK. Inhibitors of N-linked glycosylation (tunicamycin, deoxymannojirimycin, and deoxynojirimycin) also markedly attenuated the inhibitory effect of IGF-I on β-glycerophosphate-induced mineralization (p < 0.05) and activation of Akt and MAPK. These results demonstrate that alterations in the glycosylation of the IGFR disrupt the ability of IGF-I to protect against the osteogenic differentiation and mineralization of VSMCs by several interrelated mechanisms: decreased IGFR processing, reduced IGFR cell-surface expression, and reduced downstream signaling via the Akt and MAPK pathways. IGF-I thus occupies a critical position in the maintenance of normal VSMC phenotype and protection from factors known to stimulate vascular calcification.

Rosuvastatin, inflammation, C-reactive protein, JUPITER, and primary prevention of cardiovascular disease--a perspective

The major public health concern worldwide is coronary heart disease, with dyslipidemia as a major risk factor. Statin drugs are recommended by several guidelines for both primary and secondary prevention. Rosuvastatin has been widely accepted because of its efficacy, potency, and superior safety profile. Inflammation is involved in all phases of atherosclerosis, with the process beginning in early youth and advancing relentlessly for decades throughout life. C-reactive protein (CRP) is a well-studied, nonspecific marker of inflammation which may reflect general health risk. Considerable evidence suggests CRP is an independent predictor of future cardiovascular events, but direct involvement in atherosclerosis remains controversial. Rosuvastatin is a synthetic, hydrophilic statin with unique stereochemistry. A large proportion of patients achieve evidence-based lipid targets while using the drug, and it slows progression and induces regression of atherosclerotic coronary lesions. Rosuvastatin lowers CRP levels significantly. The Justification for Use of statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) trial was designed after the observation that when both low density lipoprotein and CRP were reduced, patients fared better than when only LDL was lowered. Advocates and critics alike acknowledge that the benefits of rosuvastatin in JUPITER were real. After a review, the US Food and Drug Administration extended the indications for rosuvastatin to include asymptomatic JUPITER-eligible individuals with one additional risk factor. The American Heart Association and Centers of Disease Control and Prevention had previously recognized the use of CRP in persons with "intermediate risk" as defined by global risk scores. The Canadian Cardiovascular Society guidelines went further and recommended use of statins in persons with low LDL and high CRP levels at intermediate risk. The JUPITER study focused attention on ostensibly healthy individuals with "normal" lipid profiles and high CRP values who benefited from statin therapy. The backdrop to JUPITER during this period was an increasing awareness of a rising cardiovascular risk burden and imperfect methods of risk evaluation, so that a significant number of individuals were being denied beneficial therapies. Other concerns have been a high level of residual risk in those who are treated, poor patient adherence, a need to follow guidelines more closely, a dual global epidemic of obesity and diabetes, and a progressively deteriorating level of physical activity in the population. Calls for new and more effective means of reducing risk for coronary heart disease are intensifying. In view of compelling evidence supporting earlier and aggressive therapy in people with high risk burdens, JUPITER simply offers another choice for stratification and earlier risk reduction in primary prevention patients. When indicated, and in individuals unwilling or unable to change their diet and lifestyles sufficiently, the benefits of statins greatly exceed the risks. Two side effects of interest are myotoxicity and an increase in the incidence of diabetes.

Statins can modulate effectiveness of antitumor therapeutic modalities

Despite significant, frequently very strong, antiproliferative and tumoricidal effects of statins demonstrated in vitro, their antitumor effects in animal models are modest, and their efficacy in clinical trials has not been proven. As such, statins seem unlikely to be ever regarded as antitumor agents. However, statins are regularly taken by many elderly cancer patients for the prevention of cardiovascular events. Owing to their pleiotropic effects in normal and tumor cells, statins interact in various ways with many antitumor treatment modalities, either potentiating or diminishing their effectiveness. Elucidation of these interactions might affect the choice of treatment to be planned in cancer patients as some combinations might be contraindicated, whereas others might elicit potentiated antitumor effects but at a cost of increased general toxicity. Some other combinations might induce either comparable or even stronger antitumor effects, but with a beneficial concomitant reduction of specific side effects. Most of the studies reviewed in this article have been carried in vitro or in experimental tumor models, but clinical relevance of the findings is also discussed.

Effect of simvastatin on cholesterol metabolism in C2C12 myotubes and HepG2 cells, and consequences for statin-induced myopathy

The mechanism of statin-induced skeletal muscle myopathy is poorly understood. We investigated how simvastatin affects cholesterol metabolism, ubiquinone levels, and the prenylation and N-linked glycosylation of proteins in C2C12 myotubes. We used liver HepG2 cells for comparison, as their responses to statins are well-characterized in terms of their cholesterol metabolism (in contrast to muscle cells), and statins are well-tolerated in the liver. Differences between the two cell lines could indicate the mechanism behind statin-induced myopathy. Simvastatin reduced de novo cholesterol production in C2C12 myotubes by 95% after 18h treatment. The reduction was 82% in the HepG2 cells. Total cholesterol pools, however, remained constant in both cell lines. Simvastatin treatment similarly did not affect total ubiquinone levels in the myotubes, unlike in HepG2 cells (22% reduction in CoQ10). Statin treatment reduced levels of Ras and Rap1 prenylation in both cell lines, whereas N-linked glycosylation was only affected in C2C12 myotubes (21% reduction in rate). From these observations, we conclude that total cholesterol and ubiquinone levels are unlikely to be involved in statin-mediated myopathy, but reductions in protein prenylation and especially N-linked glycosylation may play a role. This first comparison of the responses to simvastatin between liver and skeletal muscle cell lines may be important for future research directions concerning statin-induced myopathy.

Statin-induced muscle damage and atrogin-1 induction is the result of a geranylgeranylation defect

Statins are widely used to treat hypercholesterolemia but can lead to a number of side effects in muscle, including rhabdomyolysis. Our recent findings implicated the induction of atrogin-1, a gene required for the development of muscle atrophy, in statin-induced muscle damage. Since statins inhibit many biochemical reactions besides cholesterol synthesis, we sought to define the statin-inhibited pathways responsible for atrogin-1 expression and muscle damage. We report here that lovastatin-induced atrogin-1 expression and muscle damage in cultured mouse myotubes and zebrafish can be prevented in the presence of geranylgeranol but not farnesol. Further, inhibitors of the transfer of geranylgeranyl isoprene units to protein targets cause statin muscle damage and atrogin-1 induction in cultured cells and in fish. These findings support the concept that dysfunction of small GTP-binding proteins lead to statin-induced muscle damage since these molecules require modification by geranylgeranyl moieties for their cellular localization and activity. Collectively, our animal and in vitro findings shed light on the molecular mechanism of statin-induced myopathy and suggest that atrogin-1 may be regulated by novel signaling pathways.

Simvastatin suppresses leptin expression in 3T3-L1 adipocytes via activation of the cyclic AMP-PKA pathway induced by inhibition of protein prenylation

Simvastatin inhibits 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which catalyses conversion of HMG-CoA to mevalonate, a rate-limiting step in cholesterol synthesis. We demonstrated that simvastatin at 1 microM markedly inhibited adipocyte differentiation measured by Oil Red O staining in preadipocyte cells (3T3-L1), while expression of leptin, a marker of adipocyte differentiation, was suppressed by 1 muM simvastatin for up to 12 days of culture. Next, to elucidate mechanisms underlying the reduction of leptin expression induced by simvastatin, differentiated 3T3-L1 adipocytes were treated with various inhibitors with mevalonate or its metabolite in the presence or absence of simvastatin. Simvastatin time- and dose-dependently suppressed leptin mRNA expression. Heterogeneous nuclear RNA related to leptin mRNA was inhibited by 10 muM simvastatin, while stability of the mRNA was not changed by treatment with simvastatin in transcription-arrested 3T3-L1 cells. Simvastatin inhibition of leptin gene transcription was not abrogated by pre-treatment with cycloheximide, an inhibitor of protein synthesis. Addition of mevalonate or geranylgeranyl pyrophosphate (GGPP), a mevalonate metabolite, abolished simvastatin-induced inhibition of leptin expression in 3T3-L1 cells. Suppression of expression was observed upon addition of GGTI-298, a geranylgeranyl transferase I inhibitor, but not FTI-277, a farnesyl transferase inhibitor. Expression was suppressed by treatment with hydroxyfasudil, a protein prenylation inhibitor. Treatment with phosphatidylinositol 3-kinase (PI3K) inhibitors, LY294002 and wortmannin, reduced leptin expression in 3T3-L1 cells. Simvastatin dose-dependently increased intra-cellular cyclic AMP (cAMP) concentrations in 3T3-L1 cells, with maximal stimulation obtained at 10 muM. Addition of GGPP abolished simvastatin-induced stimulation of cAMP accumulation and protein kinase A (PKA) activity. H89, an inhibitor of PKA, completely abolished simvastatin-induced suppression of leptin expression. These results suggested that simvastatin reduced geranylgeranylprotein prenylation followed by deactivation of PI3K, leading to cAMP accumulation and subsequent activation of PKA in differentiated 3T3-L1 adipocytes. Finally, PKA inhibited leptin gene transcription without new protein synthesis.

HMG-CoA reductase inhibitors: do they have potential in the treatment of polycystic ovary syndrome?

Many women of reproductive age are affected by polycystic ovary syndrome (PCOS), a heterogeneous endocrinopathy characterized by androgen excess, chronic oligo-anovulation and/or polycystic ovarian morphology. In addition, PCOS is often associated with insulin resistance, systemic inflammation and oxidative stress, which, on one hand, lead to endothelial dysfunction and dyslipidaemia with subsequent cardiovascular sequelae and, on the other hand, to hyperplasia of the ovarian theca compartment with resultant hyperandrogenism and anovulation. Traditionally, HMG-CoA reductase inhibitors (statins) have been used to treat dyslipidaemia by blocking HMG-CoA reductase (the rate-limiting step in cholesterol biosynthesis); however, they also possess pleiotropic actions, resulting in antioxidant, anti-inflammatory and anti-proliferative effects. Statins offer a novel therapeutic approach to PCOS in that they address the dyslipidaemia associated with the syndrome, as well as hyperandrogenism or hyperandrogenaemia. These actions may be due to an inhibition of the effects of systemic inflammation and insulin resistance/hyperinsulinaemia. Evidence to date, both in vitro and in vivo, suggests that statins have potential in the treatment of PCOS; however, further clinical trials are needed before they can be considered a standard of care in the medical management of this common endocrinopathy.

Activation of ER stress and inhibition of EGFR N-glycosylation by tunicamycin enhances susceptibility of human non-small cell lung cancer cells to erlotinib

PURPOSE

The epidermal growth factor receptor (EGFR), an N-glycosylated transmembrane protein, is the target of erlotinib, an orally bioavailable agent approved for treatment of patients with non-small cell lung cancer (NSCLC). In this study, we examined whether inhibition of EGFR N-glycosylation and stimulation of endoplasmic reticulum (ER) stress by tunicamycin enhances erlotinib-induced growth inhibition in NSCLC cell lines.

METHODS

We examined the effects of tunicamycin and erlotinib on cytotoxicity of erlotinib-sensitive and resistant NSCLC cell lines, as well its effects on apoptotic pathways and on EGFR activation and subcellular localization.

RESULTS

A minimally cytotoxic concentration of tunicamycin (1 microM) resulted in approximatey 2.6-2.9 fold and approximatey 6.8-13.5 fold increase in erlotinib-induced antiproliferative effects in sensitive (H322 and H358) and resistant cell lines (A549 and H1650), respectively. We found that tunicamycin generated an aglycosylated form of 130 kDa EGFR. Tunicamycin additionally affected EGFR activation and subcellular localization. Interestingly, the combination of tunicamycin and erlotinib caused more inhibitory effect on EGFR phosphorylation than that of erlotinib alone. Moreover, the combination induced apoptosis in H1650 cells through induction of CHOP expression, activation of caspase-12 and caspase-3, cleavage of PARP and bak, and down-regulation of anti-apoptotic proteins bcl-xL and survivin.

CONCLUSIONS

Overall, our data demonstrate that tunicamycin significantly enhances the susceptibility of lung cancer cells to erlotinib, particularly sensitizing resistant cell lines to erlotinib, and that such sensitization may be associated with activation of the ER stress pathway and with inhibition of EGFR N-glycosylation.