A polymorphism upstream MIR1279 gene is associated with pericarditis development in Systemic Lupus Erythematosus and contributes to definition of a genetic risk profile for this complication.

Recently, a study has shown that a polymorphism in the region of MIR1279 modulates the expression of the TRAF3IP2 gene. Since polymorphisms in the TRAF3IP2 gene have been described in association with systemic lupus erithematosus (SLE) susceptibility and with the development of pericarditis, our aim is to verify if the MIR1279 gene variability could also be involved. The rs1463335 SNP, located upstream MIR1279 gene, was analyzed by allelic discrimination assay in 315 Italian SLE patients and 201 healthy controls. Moreover, the MIR1279 gene was full sequenced in 50 patients. A case/control association study and a genotype/phenotype correlation analysis were performed. We also constructed a pericarditis genetic risk profile for patients with SLE. The full sequencing of the MIR1279 gene in patients with SLE did not reveal any novel or known variation. The variant allele of the rs1463335 SNP was significantly associated with susceptibility to pericarditis ( P = 0.017 and OR = 1.67). A risk profile model for pericarditis considering the risk alleles of MIR1279 and three other genes (STAT4, PTPN2 and TRAF3IP2) showed that patients with 4 or 5 risk alleles have a higher risk of developing pericarditis ( OR = 4.09 with P = 0.001 and OR = 6.04 with P = 0.04 respectively). In conclusion, we describe for the first time the contribution of a MIR1279 SNP in pericarditis development in patients with SLE and a genetic risk profile model that could be useful to identify patients more susceptible to developing pericarditis in SLE. This approach could help to improve the prediction and the management of this complication.

Polymorphisms in STAT-4, IL-10, PSORS1C1, PTPN2 and MIR146A genes are associated differently with prognostic factors in Italian patients affected by rheumatoid arthritis.

Rheumatoid arthritis (RA) is a systemic autoimmune disease resulting in chronic inflammation of the synovium and consequent cartilage and bone erosion. RA is associated strongly with the presence of rheumatoid factor (RF), and consists of clinical subsets of anti-citrullinated protein antibody (ACPA)-positive and -negative patients. This study was designed to evaluate whether relevant single nucleotide polymorphisms (SNPs) associated with RA and other autoimmune disorders are related to RF, ACPA and clinical phenotype in a cohort of biologic drugs naive Italian RA patients; 192 RA patients and 278 age-matched healthy controls were included. Clinical and laboratory data were registered. We analysed a total of 12 single nucleotide polymorphisms (SNPs) in signal transducer and activator of transcription-4 (STAT-4), interleukin (IL)-10, psoriasis susceptibility 1 candidate 1 (PSORS1C1), protein tyrosine phosphatase, non-receptor type 2 (PTPN2), endoplasmic reticulum aminopeptidase 1 (ERAP1), tumour necrosis factor receptor-associated 3 interacting protein 2 (TRAF3IP2) and microRNA 146a (MIR146A) genes by allelic discrimination assays. Case-control association studies and genotype/phenotype correlation analyses were performed. A higher risk to develop RA was observed for rs7574865 in the STAT-4 gene, while the rs1800872 in the IL-10 gene showed a protective effect. The presence of RF was associated significantly with rs1800872 variant in IL-10, while rs2910164 in MIR146A was protective. ACPA were associated significantly with rs7574865 in STAT-4. The SNP rs2233945 in the PSORS1C1 gene was protective regarding the presence of bone erosions, while rs2542151 in PTPN2 gene was associated with joint damage. Our results confirm that polymorphisms in STAT-4 and IL-10 genes confer susceptibility to RA. For the first time, we described that SNPs in PSORS1C1, PTPN2 and MIR146A genes were associated differently with a severe disease phenotype in terms of autoantibody status and radiographic damage in an Italian RA population.

Miglustat Reverts the Impairment of Synaptic Plasticity in a Mouse Model of NPC Disease.

Niemann-Pick type C disease is an autosomal recessive storage disorder, characterized by abnormal sequestration of unesterified cholesterol within the late endolysosomal compartment of cells and accumulation of gangliosides and other sphingolipids. Progressive neurological deterioration and insurgence of symptoms like ataxia, seizure, and cognitive decline until severe dementia are pathognomonic features of the disease. Here, we studied synaptic plasticity phenomena and evaluated ERKs activation in the hippocampus of BALB/c NPC1-/- mice, a well described animal model of the disease. Our results demonstrated an impairment of both induction and maintenance of long term synaptic potentiation in NPC1-/- mouse slices, associated with the lack of ERKs phosphorylation. We then investigated the effects of Miglustat, a recent approved drug for the treatment of NPCD. We found that in vivo Miglustat administration in NPC1-/- mice was able to rescue synaptic plasticity deficits, to restore ERKs activation and to counteract hyperexcitability. Overall, these data indicate that Miglustat may be effective for treating the neurological deficits associated with NPCD, such as seizures and dementia.

Cholesterol depletion inhibits synaptic transmission and synaptic plasticity in rat hippocampus.

Several neurodegenerative disorders are associated with impaired cholesterol homeostasis in the nervous system where cholesterol is known to play a role in modulating synaptic activity and stabilizing membrane microdomains. In the present report, we investigated the effects of methyl-beta-cyclodextrin-induced cholesterol depletion on synaptic transmission and on the expression of 1) paired-pulse facilitation (PPF); 2) paired-pulse inhibition (PPI) and 3) long-term potentiation (LTP) in the CA1 hippocampal region. Results demonstrated that cyclodextrin strongly reduced synaptic transmission and blocked the expression of LTP, but did not affect PPF and PPI. The role of glutamatergic and GABAergic receptors in these cholesterol depletion-mediated effects was evaluated pharmacologically. Data indicate that, in cholesterol depleted neurons, modulation of synaptic transmission and synaptic plasticity phenomena are sustained by AMPA-, kainate-and NMDA-receptors but not by GABA-receptors. The involvement of AMPA-and kainate-receptors was confirmed by fluorimetric analysis of intracellular calcium concentrations in hippocampal cell cultures. These data suggest that modulation of receptor activity by manipulation of membrane lipids is a possible therapeutic strategy in neurodegenerative disease.

Effects of cyclotronic ion resonance on human metabolic processes: a clinical trial and one case report.

We studied the effects of ion cyclotron resonance (Seqex) magnetic therapy on the blood of thirty two healthy volunteers. They received 15 treatments each 27 minutes in length, distributed over 5 weeks. The concentrations of two blood components, malondialdehyde (MDA) and cholesterol were measured in each subject, immediately before and immediately after the 15 treatments as well as one month after the final treatment. Highly significant reductions in MDA concentrations, averaging 53.8% were noted just after the 15 treatments, tending to return to the original concentrations one month later. The effect on HDL and LDL cholesterol levels were not significant. The implication of this work is that this type of therapy may be useful in dealing with oxidative stress.

Evidence of domain formation in cardiolipin-glycerophospholipid mixed monolayers. A thermodynamic and AFM study.

The interaction of the three main components of the mitochondrial membrane, namely cardiolipin, phosphatidylcholine, and phosphatidylethanolamine, has been studied investigating mixed cardiolipin-phosphatidylcholine and cardiolipin-phosphatidylethanolamine monolayers at different cardiolipin molar fractions. The thermodynamic behavior of the mixed monolayers was investigated by means of surface pressure and surface potential measurements, and atomic force microscopy was employed to characterize the morphology of the monolayers. Langmuir isotherms and surface potential curves show a regular behavior with a progressive transition toward the isotherm of the pure component. Positive deviations from ideality in the excess Gibbs energies of mixing suggest the presence of repulsive interactions in both systems. Analysis of partial molecular dipole moment indicates a discontinuity at a definite cardiolipin/phosphatidylethanolamine molar fraction, suggesting the formation of a stoichiometric complex; as a consequence, in mixed cardiolipin-phosphatidylethanolamine monolayers, a phase separation is observed at phosphatidylethanolamine excess. AFM measurements indicate the presence of two domains: one made by phosphatidylethanolamine and the other by a regular arrangement of phosphatidylethanolamine and cardiolipin at a fixed molecular ratio.

Cytotoxic necrotizing factor 1 hinders skeletal muscle differentiation in vitro by perturbing the activation/deactivation balance of Rho GTPases.

The current knowledge assigns a crucial role to the Rho GTPases family (Rho, Rac, Cdc42) in the complex transductive pathway leading to skeletal muscle cell differentiation. Their exact function in myogenesis, however, remains largely undefined. The protein toxin CNF1 was herein employed as a tool to activate Rho, Rac and Cdc42 in the myogenic cell line C2C12. We demonstrated that CNF1 impaired myogenesis by affecting the muscle regulatory factors MyoD and myogenin and the structural protein MHC expressions. This was principally driven by Rac/Cdc42 activation whereas Rho apparently controlled only the fusion process. More importantly, we proved that a controlled balance between Rho and Rac/Cdc42 activation/deactivation state was crucial for the correct execution of the differentiation program, thus providing a novel view for the role of Rho GTPases in muscle cell differentiation. Also, the use of Rho hijacking toxins can represent a new strategy to pharmacologically influence the differentiative process.

Physical exercise intensity can be related to plasma glutathione levels.

The aim of the present study was to examine the effect of different kinds of physical exercise on plasma glutathione levels. Male Wistar rats were randomly divided into four groups: In walking group (W; n=6), rats were trained to walk 0.8 m/min for 45 min; slow running group (SR; n=6) were trained to run 4 m/min for 45 min; fast running group (FR; n=6) ran 8m/min for 60 min and control rats (C; n=6) remained in their home cages. All animals were sacrificed after exercise and the levels of reduced glutathione (GSH) in plasma samples determined by high performance liquid chromatography (HPLC) with a fluorescent detector. Compared to controls, exercise did not change GSH plasma levels of the W group. A tendency to decrease blood GSH was observed in plasma samples of the SR group and in the FR group, physical exercise resulted in a dramatic decrease in GSH plasma levels. These data suggest that during light physical exercise there is a low production of reactive oxygen species (ROS) with a low request for antioxidant defence such as oxidation of GSH. The dramatic decrease observed in GSH levels in FR rats would indicate the presence of oxidative stress able to modify blood antioxidant profiles. Our results suggest that GSH plays a central antioxidant role in blood during intensive physical exercise and that its modifications are closely related to exercise intensity.

Physical exercise intensity can be related to plasma glutathione levels.

The aim of the present study was to examine the effect of different kinds of physical exercise on plasma glutathione levels. Male Wistar rats were randomly divided into four groups: In walking group (W; n=6), rats were trained to walk 0.8 m/min for 45 min; slow running group (SR; n=6) were trained to run 4 m/min for 45 min; fast running group (FR; n=6) ran 8 m/min for 60 min and control rats (C; n=6) remained in their home cages. All animals were sacrificed after exercise and the levels of reduced glutathione (GSH) in plasma samples determined by high performance liquid chromatography (HPLC) with a fluorescent detector. Compared to controls, exercise did not change GSH plasma levels of the W group. A tendency to decrease blood GSH was observed in plasma samples of the SR group and in the FR group, physical exercise resulted in a dramatic decrease in GSH plasma levels. These data suggest that during light physical exercise there is a low production of reactive oxygen species (ROS) with a low request for antioxidant defence such as oxidation of GSH. The dramatic decrease observed in GSH levels in FR rats would indicate the presence of oxidative stress able to modify blood antioxidant profiles. Our results suggest that GSH plays a central antioxidant role in blood during intensive physical exercise and that its modifications are closely related to exercise intensity.

Zinc status in athletes: relation to diet and exercise.

Zinc is involved in the biochemical processes supporting life, such as cellular respiration, DNA reproduction, maintenance of cell membrane integrity and free radical scavenging. Zinc is required for the activity of more than 300 enzymes, covering all 6 classes of enzyme activity. Zinc binding sites in proteins are often of distorted tetrahedral or trigonal bipyramidal geometry, made up of the sulphur of cysteine, the nitrogen of histidine or the oxygen of aspartate and glutamate, or a combination. Zinc in proteins can either participate directly in chemical catalysis or be important for maintaining protein structure and stability. The nutritional habits of elite athletes during training and competition are quite different from the recommended diet in the majority of the population. Endurance athletes often adopt an unusual diet in an attempt to enhance performance: an excessive increase in carbohydrates and low intake of proteins and fat may lead to suboptimal zinc intake in 90% of athletes. Mild zinc deficiency is difficult to detect because of the lack of definitive indicators of zinc status. In athletes, zinc deficiency can lead to anorexia, significant loss in bodyweight, latent fatigue with decreased endurance and a risk of osteoporosis.

Beta-N-acetylhexosaminidase activity and isoenzyme profile in the kidney and urine of trained rats.

Lysosomes play an important role in the immune system functioning and are involved in different aspects of inflammatory reaction, repair processes and tissue damage at various levels. Among various effects, it is known that physical exercise influences the release of different lysosomal components. The aim of this study was to evaluate enzyme activity and isoenzymatic profile of beta-N-acetylhexosaminidase both in kidney and urine of normal and trained rats. Enzyme activity was measured by fluorimetric assay while beta-N-acetylhexosaminidase isoenzymes were separated using DEAE-cellulose chromatography. Hexosaminidase specific activity was significantly increased in urine of trained rats whereas there was no increase in the kidneys of trained rats. Indeed, no significant differences were observed in the isoenzyme profile of kidney and urine extracts from normal and trained rats. Our findings suggest the exercise-induced release of lysosomal enzymes is a functional effect and not due to disruption of lysosomal membranes.

2-Chloro-adenosine induces a glutamate-dependent calcium response in C2C12 myotubes.

Adenosine and its derivatives may induce acute changes, i.e., injury and death, in muscle cells. In the present work, we evaluated the intracellular calcium concentration in C2C12 myogenic cells differentiated in vitro to form myotubes and exposed to a metabolically stable analogue of adenosine, 2-chloro-adenosine. The compound was able to significantly modify ionic homeostasis by sensitizing muscle cells to the excitatory amino acid glutamate. A single exposure to glutamate led to a marked increase in intracellular calcium level. This is the first demonstration that adenosine analogues can regulate muscle cell integrity and function via an indirect increase of intracellular calcium ions.

N-acetylcysteine increases apoptosis induced by H(2)O(2) and mo-antiFas triggering in a 3DO hybridoma cell line.

N-Acetylcysteine (NAC) has been used as an antioxidant to prevent apoptosis triggered by different stimuli in different cell types. It is common opinion that cellular redox, which is largely determined by the ratio of oxidized and reduced glutathione (GSH), plays a significant role in the propensity of cells to undergo apoptosis. However, there are also contrasting opinions stating that intracellular GSH depletion or supplemented GSH alone are not sufficient to lead cells to apoptosis or conversely protect them. Unexpectedly, this study shows that NAC, even if it maintains the peculiar characteristics of an agent capable of reducing cell proliferation and increasing intracellular GSH content, increases apoptosis induced by H(2)O(2) treatment and mo-antiFas triggering in a 3DO cell line. We found that 24 h of NAC pre-treatment can shift cellular death from necrotic to apoptotic and determine an early expression of FasL in a 3DO cell line treated with H(2)O(2).

Adenosine- and 2-chloro-adenosine-induced cytopathic effects on myoblastic cells and myotubes: involvement of different intracellular mechanisms.

We recently suggested that, in muscular dystrophies, the excessive accumulation of adenosine as a result of an altered purine metabolism may contribute to progressive functional deterioration and muscle cell death. To verify this hypothesis, we have taken advantage of C2C12 myoblastic cells, which can be differentiated in vitro into multinucleated cells (myotubes). Exposure of both proliferating myoblasts and differentiated myotubes to adenosine or its metabolically-stable analog, 2-chloro-adenosine, resulted in apoptotic cell death and myotube disruption. Cytotoxicity by either nucleoside did not depend upon extracellular adenosine receptors, but, at least in part, by entry into cells via the membrane nitro-benzyl-thio-inosine-sensitive transporter. The adenosine kinase inhibitor, 5-iodotubercidin, prevented 2-chloro-adenosine-induced (but not adenosine-induced) effects, suggesting that an intracellular phosphorylation/activation reaction plays a key role in 2-chloro-adenosine-mediated cytotoxicity. Conversely, adenosine cytotoxicity was aggravated by the addition of homocysteine, suggesting that adenosine effects may be due to the accumulation of S-adenosyl-homocysteine, which blocks intracellular methylation-dependent reactions. Both nucleosides markedly disrupted the myotube structure via an effect on the actin cytoskeleton; however, also for myotubes, there were marked differences in the morphological alterations induced by these two nucleosides. These results show that adenosine and 2-chloro-adenosine induce apoptosis of myogenic cells via completely different metabolic pathways, and are consistent with the hypothesis that adenosine accumulation in dystrophic muscles may represent a novel pathogenetic pathway in muscle diseases.

Membrane-perturbing activity of Viperidae myotoxins: an electrostatic surface potential approach to a puzzling problem.

Phospholipase-like myotoxins are a class of proteins present in Viperidae venom. Despite the high level of amino acid and structural homology with soluble phospholipases A(2), myotoxins are devoid of enzymatic activity and share cytolytic activity by means of a totally unknown mechanism involving the lipid bilayer perturbation. The distribution of electrostatic surface potentials of four myotoxins and seven phospholipases A(2) has been compared. The charge distribution is similar in all active non-cytolytic phospholipases with a strongly positive side corresponding to the domain interacting with the micellar substrate and with the opposite side negatively charged. In contrast, all myotoxins examined are positively charged on both sides. Myotoxin III, the only known example of a myotoxin sharing enzymatic activity, displays the same electrostatic surface potential as other related toxins. Using liposomes made with non-hydrolysable phospholipids, we demonstrate that myotoxin III perturbs the lipid bilayer like other myotoxins. Based on these results, a molecular model for myotoxin-membrane perturbing activity is proposed. In this model, potential double-face binding of myotoxic phospholipases A(2) to lipid surfaces could trigger a lipid bilayer destabilization and could generate a stable fusion pore, probably because of the presence of hydrophobic moieties that flank the cationic sites.

PLA(2) stimulation of Na(+)/H(+) antiport and proliferation in rat aortic smooth muscle cells.

The proliferative properties and the ability to stimulate the Na(+)/H(+) antiport activity of a secretory phospholipase A(2) were studied in rat aortic smooth muscle cells in culture. The requirement of the enzymatic activity of phospholipase A(2) to elicit mitogenesis was assessed by the use of ammodytin L, a Ser(49) phospholipase A(2) from the venom of Vipera ammodytes, devoid of hydrolytic activity. We propose that the proliferative effect is mediated by the same transduction pathway for both proteins. In particular, 1) both secretory phospholipase A(2) and ammodytin L stimulated thymidine incorporation in a dose-dependent manner; 2) both proteins affected the cell cycle, as assessed by cell growth and fluorescence-activated cell sorting experiments; 3) both phospholipase A(2) and ammodytin L increased intracellular pH, a permissive factor for cell proliferation, through activation of the Na(+)/H(+) antiport; 4) ammodytin L was able to displace the (125)I-labeled phospholipase A(2) from specific binding sites in a concentration range consistent with that capable of eliciting a cellular response; and 5) the inhibition by heparin was similar for both proteins, taking into account the ratio of heparin to protein. In conclusion, the enzymatic activity of phospholipase A(2) is not required for the stimulation of mitogenesis. The inhibitory effect of heparin combined with its therapeutic potential could help to clarify the role of phospholipase A(2) in the pathogenesis of several preinflammatory situations.

Hyperhomocyst(e)inemia is associated with carotid atherosclerosis.

The atherogenicity of homocyst(e)ine--H(e) --emerged from many studies showing an association between moderately elevated levels and vascular occlusive disease. The aim of this study was to evaluate whether high homocyst(e)ine levels were associated with carotid atherosclerosis. Carotid atherosclerosis was defined as an intimal media thickness of internal and carotid bifurcation of at least 2 mm on the near and far walls as determined by B-mode ultrasonography. The study population included 91 patients: group 1 (61% males, mean age 64+/-10 years, 57% with history of hypertension) with ultrasound evidence of carotid atherosclerosis and 100 with normal carotid walls--group 2 (36% males, mean age 52+/-15 years, 27% with history of hypertension). Homocyst(e)ine levels (mol/L) were determined by high-performance liquid chromatography with a fluorescent detector. Body mass index, dyslipidemia, smoking, diabetes, serum creatinine, plasma folic acid and vitamin B12 were not significantly different in the two groups. Homocyst(e)ine levels (micromol/L) were significantly higher in patients with carotid ather osclerosis than in those with normal arteries (11.7+/-6.5 micromol/L, 95% CI 10.4-13.1 vs 8.07+/-4.4 micromol/L, 95% CI 7.2-8.9, p<0.0001). By multiple regression analysis H(e) levels were positively correlated with male gender (p<0.02), age (p<0.001), and negatively with folic acid (p<0.0001). By logistic regression the independent predictors of carotid atherosclerosis were male gender (OR 2.65), hypertension (OR 2.55), age (x10 years, OR 2.15) and H(e) levels (x1 micromol/L, OR 1.11). This study confirmed homocyst(e)ine is associated with carotid atherosclerosis. Consequently the authors recommend H(e) levels be screened in all patients at risk for atherosclerosis.

Zn(2+) ions selectively induce antimicrobial salivary peptide histatin-5 to fuse negatively charged vesicles. Identification and characterization of a zinc-binding motif present in the functional domain.

The salivary antimicrobial peptide histatin-5 is able to aggregate and fuse negatively charged small unilamellar vesicles, and this fusogenic activity is selectively induced by the presence of zinc ions. Circular dichroism spectroscopy shows that histatin-5, in the presence of negatively charged vesicles and zinc ions, undergoes a conformational change leading to the stabilization of an alpha-helical secondary structure. We attribute the specific action of the zinc ions to the presence of a consensus sequence, HEXXH, located in the C-terminal functional domain of histatin-5, a recognized zinc-binding motif in many proteins. Two-dimensional proton NMR spectroscopy of histatin-5 in a trifluoroethanol/water mixture (a membrane mimetic environment) has been performed and the results analyzed by means of distance geometry and restrained molecular dynamics simulations. Our results reveal that the peptide chain, including the Zn-binding consensus sequence corresponding to residues 15-19, is in a helicoidal conformation. Comparison of the chemical shifts of the individual amino acids in histatin-5 with those recently reported in other solvents indicates that trifluoroethanol/water has a structuring capability somewhere between water and dimethyl sulfoxide. The mechanism of action of this antimicrobial peptide is discussed on the basis of its structural characteristics with particular attention to the Zn-binding motif.

Comparative study of the cytolytic activity of myotoxic phospholipases A2 on mouse endothelial (tEnd) and skeletal muscle (C2C12) cells in vitro.

A rapid in vitro cytolytic effect of some myotoxic phospholipases A2 (PLA2s) isolated from the venoms of Viperidae snakes has been previously described. This study was undertaken to investigate if cytolytic activity is a common property of the myotoxic proteins from this group. Murine endothelial cells (tEnd) and skeletal muscle myotubes (C2C12) were utilized as targets. The release of lactic dehydrogenase was quantified as a measure of cell damage, 3 h after exposure of cells to the different PLA2s, including representatives from the genera Bothrops, Agkistrodon, Trimeresurus, Crotalus (family Viperidae), and Notechis (family Elapidae). All of the group II myotoxic PLA2s tested displayed rapid cytolytic activity when tested in the micromolar range of concentrations (8-32 microM). In contrast, the group I myotoxic PLA2 notexin was devoid of this activity. Aspartate-49 and lysine-49 PLA2 group II variants showed a comparable cytolytic effect. Skeletal muscle myotubes, obtained after fusion and differentiation of C2C12 myoblasts, were significantly more susceptible to the cytolytic action of myotoxins than endothelial cells, previously reported to be more susceptible than undifferentiated myoblasts under the same assay conditions. Cytolytic activity appears to be a common characteristic of group II myotoxic PLA2s of the Viperidae. Bee venom PLA2, a group III enzyme of known myotoxicity, also displayed cytotoxic activity on C2C12 myotubes, being devoid of activity on endothelial cells. These results suggest that in vitro differentiated skeletal muscle myotubes may represent a suitable model target for the study of myotoxic PLA2s of the structural group II found in snake venoms.

Actin cytoskeleton as a target for 2-chloro adenosine: evidence for induction of apoptosis in C2C12 myoblastic cells.

Recent results for various cell types have shown that adenosine is capable of inducing relevant cytophatological alterations which can eventually lead to apoptosis. No data are available regarding the involvement of adenosine in apoptosis of muscle cells. In this work, we studied the effect of the relatively hydrolysis-resistant adenosine analog 2-chloro adenosine on a cultured myogenic cell line, C2C12, which is able to differentiate in vitro, leading to the formation of syncythia, giant multinucleated cells called myotubes. Results indicated that 2-chloro adenosine induces apoptotic cell death in both myoblasts and myotubes; this was preceded by a derangement of actin microfilaments, which represent the main cytoskeletal component and play a pivotal role in the physiology of such cell line. The time-dependency of cytoskeletal alterations suggested a causal relationship between these changes and the induction of apoptosis. These results implicate adenosine as an endogenous regulator of apoptosis in muscle cells and validate this cell model system as a useful tool for studying human muscle cell pathologies.