Simvastatin suppresses the differentiation of C2C12 myoblast cells via a Rac pathway

Effects of Simvastatin on Gene Expression and Alkaline Phosphatase Activity in the MG-63 Cell Line Treated With Hyperglycemia for Bone Regeneration

Background Dental implants have become a widespread treatment option for replacing missing teeth. Adequate bone is required for the placement of dental implants, in the absence of which, augmentation by bone regeneration is done. Antiresorptive drugs are used as treatment procedures for bone regeneration. One such antiresorptive drug is simvastatin (SV), a 3-hydroxy-3-methylglutaryl coenzyme used to manage hyperlipidemia. It reduces serum cholesterol levels and has an advantageous effect on new bone formation. Various studies establish that SV stimulates bone morphogenetic protein (BMP)-2 expression and leads to bone formation. SV prevents the production of isoprenoids and mevalonate, which are essential for osteoclastogenesis and contribute to the bone-sparing effect.  Aim The aim of the study was to investigate the osteoregenerative activity of SV in the osteoblast-like cell models, MG-63 cell line, with hyperglycemic conditions. Methodology MG-63 cultures were established under high glucose concentrations during the experiments and cultured with SV concentrations of 1 µM and 3 µM. The quantification of the expression of the genes, namely, BMP-2 and osteocalcin (OCN) was done by real-time quantitative polymerase chain reaction (RTqPCR). The measurement of alkaline phosphatase activity in the SV-treated cells was also determined. Results According to the results of the study, SV had osteoprotective properties resulting from the inhibition of osteoclast stimulation and osteoinductive properties, facilitated by BMP-2 and OCN. In addition, SV at concentrations of 1 µM and 3 µM increased the gene expression of BMP-2 and OCN in the MG-63 cell line. Conclusion The results of this study demonstrated that SV had a significant and direct effect on osteogenesis in osteoblasts in vitro.

Targeting farnesylation as a novel therapeutic approach in HRAS-mutant rhabdomyosarcoma

Activating RAS mutations are found in a subset of fusion-negative rhabdomyosarcoma (RMS), and therapeutic strategies to directly target RAS in these tumors have been investigated, without clinical success to date. A potential strategy to inhibit oncogenic RAS activity is the disruption of RAS prenylation, an obligate step for RAS membrane localization and effector pathway signaling, through inhibition of farnesyltransferase (FTase). Of the major RAS family members, HRAS is uniquely dependent on FTase for prenylation, whereas NRAS and KRAS can utilize geranylgeranyl transferase as a bypass prenylation mechanism. Tumors driven by oncogenic HRAS may therefore be uniquely sensitive to FTase inhibition. To investigate the mutation-specific effects of FTase inhibition in RMS we utilized tipifarnib, a potent and selective FTase inhibitor, in in vitro and in vivo models of RMS genomically characterized for RAS mutation status. Tipifarnib reduced HRAS processing, and plasma membrane localization leading to decreased GTP-bound HRAS and decreased signaling through RAS effector pathways. In HRAS-mutant cell lines, tipifarnib reduced two-dimensional and three-dimensional cell growth, and in vivo treatment with tipifarnib resulted in tumor growth inhibition exclusively in HRAS-mutant RMS xenografts. Our data suggest that small molecule inhibition of FTase is active in HRAS-driven RMS and may represent an effective therapeutic strategy for a genomically-defined subset of patients with RMS.

Natural Compounds Attenuate Denervation-Induced Skeletal Muscle Atrophy

The weight of skeletal muscle accounts for approximately 40% of the whole weight in a healthy individual, and the normal metabolism and motor function of the muscle are indispensable for healthy life. In addition, the skeletal muscle of the maxillofacial region plays an important role not only in eating and swallowing, but also in communication, such as facial expressions and conversations. In recent years, skeletal muscle atrophy has received worldwide attention as a serious health problem. However, the mechanism of skeletal muscle atrophy that has been clarified at present is insufficient, and a therapeutic method against skeletal muscle atrophy has not been established. This review provides views on the importance of skeletal muscle in the maxillofacial region and explains the differences between skeletal muscles in the maxillofacial region and other regions. We summarize the findings to change in gene expression in muscle remodeling and emphasize the advantages and disadvantages of denervation-induced skeletal muscle atrophy model. Finally, we discuss the newly discovered beneficial effects of natural compounds on skeletal muscle atrophy.

MitoPlex: A targeted multiple reaction monitoring assay for quantification of a curated set of mitochondrial proteins

Mitochondria are the major source of cellular energy (ATP), as well as critical mediators of widespread functions such as cellular redox balance, apoptosis, and metabolic flux. The organelles play an especially important role in the maintenance of cardiac homeostasis; their inability to generate ATP following impairment due to ischemic damage has been directly linked to organ failure. Methods to quantify mitochondrial content are limited to low throughput immunoassays, measurement of mitochondrial DNA, or relative quantification by untargeted mass spectrometry. Here, we present a high throughput, reproducible and quantitative mass spectrometry multiple reaction monitoring based assay of 37 proteins critical to central carbon chain metabolism and overall mitochondrial function termed 'MitoPlex'. We coupled this protein multiplex with a parallel analysis of the central carbon chain metabolites (219 metabolite assay) extracted in tandem from the same sample, be it cells or tissue. In tests of its biological applicability in cells and tissues, "MitoPlex plus metabolites" indicated profound effects of HMG-CoA Reductase inhibition (e.g., statin treatment) on mitochondria of i) differentiating C2C12 skeletal myoblasts, as well as a clear opposite trend of statins to promote mitochondrial protein expression and metabolism in heart and liver, while suppressing mitochondrial protein and ii) aspects of metabolism in the skeletal muscle obtained from C57Bl6 mice. Our results not only reveal new insights into the metabolic effect of statins in skeletal muscle, but present a new high throughput, reliable MS-based tool to study mitochondrial dynamics in both cell culture and in vivo models.

The impact of statins on physical activity and exercise capacity: an overview of the evidence, mechanisms, and recommendations

PURPOSE

Statins are among the most widely prescribed medications worldwide. Considered the 'gold-standard' treatment for cardiovascular disease (CVD), statins inhibit HMG-CoA reductase to ultimately reduce serum LDL-cholesterol levels. Unfortunately, the main adverse event of statin use is the development of muscle-associated problems, referred to as SAMS (statin-associated muscle symptoms). While regular moderate physical activity also decreases CVD risk, there is apprehension that physical activity may induce and/or exacerbate SAMS. While much work has gone into identifying the epidemiology of SAMS, only recent research has focused on the extent to which these muscle symptoms are accompanied by functional declines. The purpose of this review is to provide an overview of possible mechanisms underlying SAMS and summarize current evidence regarding the relationship between statin treatment, physical activity, exercise capacity, and SAMS development.

METHODS

PubMed and Google Scholar databases were used to search the most relevant and up-to-date peer-reviewed research on the topic.

RESULTS

The mechanism(s) behind SAMS, including altered mitochondrial metabolism, reduced coenzyme Q10 levels, reduced vitamin D levels, impaired calcium homeostasis, elevated extracellular glutamate, and genetic polymorphisms, still lack consensus and remain up for debate. Our summation of the evidence leads us to suggest that the etiology of SAMS development is likely multifactorial. Our review also demonstrates that there is limited evidence for statins impairing exercise adaptations or reducing exercise capacity for the majority of the investigated populations.

CONCLUSION

The available evidence indicates that the benefits of engaging in physical activity while on statin medication largely outweigh the risks.

The glucocorticoid-induced leucine zipper mediates statin-induced muscle damage

Statins, the most prescribed class of drugs for the treatment of hypercholesterolemia, can cause muscle-related adverse effects. It has been shown that the glucocorticoid-induced leucine zipper (GILZ) plays a key role in the anti-myogenic action of dexamethasone. In the present study, we aimed to evaluate the role of GILZ in statin-induced myopathy. Statins induced GILZ expression in C2C12 cells, primary murine myoblasts/myotubes, primary human myoblasts, and in vivo in zebrafish embryos and human quadriceps femoris muscle. Gilz induction was mediated by FOXO3 activation and binding to the Gilz promoter, and could be reversed by the addition of geranylgeranyl, but not farnesyl, pyrophosphate. Atorvastatin decreased Akt phosphorylation and increased cleaved caspase-3 levels in myoblasts. This effect was reversed in myoblasts from GILZ knockout mice. Similarly, myofibers isolated from knockout animals were more resistant toward statin-induced cell death than their wild-type counterparts. Statins also impaired myoblast differentiation, and this effect was accompanied by GILZ induction. The in vivo relevance of our findings was supported by the observation that gilz overexpression in zebrafish embryos led to impaired embryonic muscle development. Taken together, our data point toward GILZ as an essential mediator of the molecular mechanisms leading to statin-induced muscle damage.

Geranylgeraniol-induced Myogenic Differentiation of C2C12 Cells

BACKGROUND

Geranylgeraniol (GGOH) is a C20 isoprenoid found in fruits, vegetables, and grains, including rice. As a food substance, GGOH is categorized as 'Generally Recognized as Safe'. GGOH is an intermediate product in the mevalonate pathway and acts as a precursor to geranylgeranyl pyrophosphate.

MATERIALS AND METHODS

C2C12 mouse myoblasts derived from muscle satellite cells were used. Quantitative reverse-transcriptase polymerase chain reaction, western blotting analysis, and immunocytochemical analysis were performed to respectively assess mRNA expression, protein levels, and the number of myofibers.

RESULTS

GGOH reduced the expression levels of skeletal muscle atrophy-related ubiquitin ligases in myofibers derived from C2C12 cells. GGOH induced myogenic differentiation of C2C12 cells via geranylgeranylation. GGOH did not adversely affect the proliferation of C2C12 cells.

CONCLUSION

GGOH induces myoblast differentiation in C2C12 cells.

Liver-type of tissue non-specific alkaline phosphatase is induced during mouse bone and tooth cell differentiation

BACKGROUND AND OBJECTIVE

Tissue non-specific alkaline phosphatase (TNSALP) contains two types-bone- and liver-type-which are produced from the same gene due to differences in splicing. These two differ in their promoter, but the amino acid sequences of the mature proteins are identical. In this study, we examined the relationship between the two types of TNSALP expression and osteoblast differentiation.

DESIGN

Gene expression of the two types of TNSALP was observed by reverse transcription-polymerase chain reaction. MC3T3-NM4 was sub-cloned from an established mouse osteoblastic cell line in which osteoblast characters do not appear without dexamethasone. The C2C12 mouse myoblastic cell line, which can be induced to osteoblasts with bone morphogenic protein 2, and organ-cultured tooth germs were also used in this work.

RESULTS

The gene expression of liver-type TNSALP was observed in only MC3T3-NM4 activated by dexamethasone. For C2C12, the gene expression of bone-type TNSALP was observed even in non-induced conditions where myotubes were formed, whereas the liver-type TNSALP mRNA was only expressed when C2C12 differentiated into osteoblasts by bone morphogenic protein 2. Furthermore, in the organ-cultured tooth germs, the liver-type TNSALP mRNA was expressed according to differentiation of tooth germs.

CONCLUSION

These results suggest that the liver-type TNSALP mRNA is induced according to differentiation of bone and tooth.

Molecular mechanisms linking geranylgeranyl diphosphate synthase to cell survival and proliferation

Geranylgeranyl diphosphate is a 20-carbon isoprenoid phospholipid whose lipid moiety can be post-translationally incorporated into proteins to promote membrane association. The process of geranylgeranylation has been implicated in anti-proliferative effects of clinical agents that inhibit enzymes of the mevalonate pathway (i.e. statins and nitrogenous bisphosphonates) as well as experimental agents that deplete geranylgeranyl diphosphate. Inhibitors of geranylgeranyl diphosphate synthase are an attractive way to block geranylgeranylation because they possess a calcium-chelating substructure to allow localization to bone and take advantage of a unique position of the enzyme within the biosynthetic pathway. Here, we describe recent advances in geranylgeranyl diphosphate synthase expression and inhibitor development with a particular focus on the molecular mechanisms that link geranylgeranyl diphosphate to cell proliferation via geranylgeranylated small GTPases.

Primary skeletal muscle myoblasts from chronic heart failure patients exhibit loss of anti-inflammatory and proliferative activity

BACKGROUND

Peripheral skeletal muscle wasting is a common finding with adverse effects in chronic heart failure (HF). Whereas its clinical relevance is beyond doubt, the underlying pathophysiological mechanisms are not yet fully elucidated. We aimed to introduce and characterize the primary culture of skeletal muscle cells from individual HF patients as a supportive model to study this muscle loss.

METHODS AND RESULTS

Primary myoblast and myotubes cultures were successfully propagated from the m. vastus lateralis of 6 HF patients with reduced ejection fraction (HFrEF; LVEF <45 %) and 6 age and gender-matched healthy donors. HFrEF cultures were not different from healthy donors in terms of morphology, such as myoblast size, shape and actin microfilament. Differentiation and fusion indexes were identical between groups. Myoblast proliferation in logarithmic growth phase, however, was attenuated in the HFrEF group (p = 0.032). In addition, HFrEF myoblasts are characterized by a reduced TNFR2 expression and IL-6 secretion (p = 0.017 and p = 0.016; respectively).

CONCLUSION

Biopsy derived primary skeletal muscle myoblasts of HFrEF patients produce similar morphological and myogenic differentiation responses as myoblasts of healthy donors, though demonstrate loss of anti-inflammatory and proliferative activity.

A new therapeutic effect of simvastatin revealed by functional improvement in muscular dystrophy

Duchenne muscular dystrophy (DMD) is a lethal, degenerative muscle disease with no effective treatment. DMD muscle pathogenesis is characterized by chronic inflammation, oxidative stress, and fibrosis. Statins, cholesterol-lowering drugs, inhibit these deleterious processes in ischemic diseases affecting skeletal muscle, and therefore have potential to improve DMD. However, statins have not been considered for DMD, or other muscular dystrophies, principally because skeletal-muscle-related symptoms are rare, but widely publicized, side effects of these drugs. Here we show positive effects of statins in dystrophic skeletal muscle. Simvastatin dramatically reduced damage and enhanced muscle function in dystrophic (mdx) mice. Long-term simvastatin treatment vastly improved overall muscle health in mdx mice, reducing plasma creatine kinase activity, an established measure of muscle damage, to near-normal levels. This reduction was accompanied by reduced inflammation, more oxidative muscle fibers, and improved strength of the weak diaphragm muscle. Shorter-term treatment protected against muscle fatigue and increased mdx hindlimb muscle force by 40%, a value comparable to current dystrophin gene-based therapies. Increased force correlated with reduced NADPH Oxidase 2 protein expression, the major source of oxidative stress in dystrophic muscle. Finally, in old mdx mice with severe muscle degeneration, simvastatin enhanced diaphragm force and halved fibrosis, a major cause of functional decline in DMD. These improvements were accompanied by autophagy activation, a recent therapeutic target for DMD, and less oxidative stress. Together, our findings highlight that simvastatin substantially improves the overall health and function of dystrophic skeletal muscles and may provide an unexpected, novel therapy for DMD and related neuromuscular diseases.

PKC-δ signalling pathway is involved in H9c2 cells differentiation

H9c2 are rat heart embryonic myoblasts, with skeletal muscle properties, which terminally differentiate by fusing and forming multinucleated myotubes. Here we investigated the possible involvement of Protein Kinases C (PKCs) in H9c2 cell differentiation and explored the interplay of these enzymes both with reactive oxygen species (ROS), upstream physiological mediators of cell differentiation, and with nitric oxide (NO), downstream target of PKC activation, known for being involved in apoptosis induction in differentiated myoblasts. Cells were induced to differentiate (6 days) under low serum culture conditions and assayed for the expression of cell cycle (cyclin A) and differentiation markers (morphology and myogenin). Both ROS and in vivo production of NO were found increased after 6 days of differentiation, when the activation of PKC-δ isoform was 14-fold increased compared with the undifferentiated control cells. The parallel analysis of apoptotic features demonstrated a small increase in Annexin-V+ cells and a concomitant increase in PARP cleavage and Bax expression. Interestingly, a reduced percentage of differentiated cells was obtained both in the presence of Rottlerin, a highly selective PKC-δ pharmacologic inhibitor, and, moreover, with the use of PKC-δ siRNA technology, further supporting the involvement of PKC-δ in switching on the events related to skeletal muscle myoblast differentiation.

Severe hypocholesterolaemia is often neglected in haematological malignancies

AIM OF THE STUDY

It is generally believed that high levels of cholesterol (hypercholesterolaemia) are life-threatening, while low levels seem to be positive. Unfortunately this assumption is far from true, and can be indicative of an underlying serious medical condition in most of the cases (i.e. cancer). However, the biological role of severe hypocholesterolaemia is poorly understood. Here, the possible biological process is being investigated. Cholesterol plays a key role in cell proliferation, hence it has been suggested that low cholesterol levels are probably linked to the high cellular cholesterol demands from neoplastic cells.

SUMMARY OF THE METHODS

We used serum and isolated T-lymphocytes from patients with acute lymphoblast leukaemia and human lymphoblast cell line to test this hypothesis.

RESULTS

We found that patients with low serum cholesterol levels have instead high levels of cholesterol in lymphocytes. These data were supported with in vitro studies. In fact we have demonstrated that low cholesterol level in the culture medium was related to the neoplastic cellular growth, suggesting a greater use by lymphoma cells for their proliferation. Therefore by inhibiting cholesterol synthesis by mevastatin, in vitro, we showed that cholesterol levels did not change significantly in culture medium and the cellular growth was inhibited.

CONCLUDING STATEMENT

Following these preliminary results, blood cholesterol levels could be potentially considered a good biological marker to follow up the neoplastic process.

Expression, localization, and pharmacological role of Kv7 potassium channels in skeletal muscle proliferation, differentiation, and survival after myotoxic insults

Changes in the expression of potassium channels regulate skeletal muscle development. The purpose of this study was to investigate the expression profile and pharmacological role of K(v)7 voltage-gated potassium channels in skeletal muscle differentiation, proliferation, and survival after myotoxic insults. Transcripts for all K(v)7 genes (K(v)7.1-K(v)7.5) were detected by polymerase chain reaction (PCR) and/or real-time PCR in murine C(2)C(12) myoblasts; K(v)7.1, K(v)7.3, and K(v)7.4 transcripts were up-regulated after myotube formation. Western blot experiments confirmed K(v)7.2, K(v)7.3, and K(v)7.4 subunit expression, and the up-regulation of K(v)7.3 and K(v)7.4 subunits during in vitro differentiation. In adult skeletal muscles from mice and humans, K(v)7.2 and K(v)7.3 immunoreactivity was mainly localized at the level of intracellular striations positioned between ankyrinG-positive triads, whereas that of K(v)7.4 subunits was largely restricted to the sarcolemmal membrane. In C(2)C(12) cells, retigabine (10 microM), a specific activator of neuronally expressed K(v)7.2 to K(v)7.5 subunits, reduced proliferation, accelerated myogenin expression, and inhibited the myotoxic effect of mevastatin (IC(50) approximately 7 microM); all these effects of retigabine were prevented by the K(v)7 channel blocker 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone (XE-991) (10 muM). These data collectively highlight neural K(v)7 channels as significant pharmacological targets to regulate skeletal muscle proliferation, differentiation, and myotoxic effects of drugs.

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.