Dimethyl sulphoxide enhances the effects of P(i) in myofibrils and inhibits the activity of rabbit skeletal muscle contractile proteins

Synchronized, Spontaneous, and Oscillatory Detachment of Eukaryotic Cells: A New Tool for Cell Characterization and Identification

Despite the importance of cell characterization and identification for diagnostic and therapeutic applications, developing fast and label-free methods without (bio)-chemical markers or surface-engineered receptors remains challenging. Here, we exploit the natural cellular response to mild thermal stimuli and propose a label- and receptor-free method for fast and facile cell characterization. Cell suspensions in a dedicated sensor are exposed to a temperature gradient, which stimulates synchronized and spontaneous cell-detachment with sharply defined time-patterns, a phenomenon unknown from literature. These patterns depend on metabolic activity (controlled through temperature, nutrients, and drugs) and provide a library of cell-type-specific indicators, allowing to distinguish several yeast strains as well as cancer cells. Under specific conditions, synchronized glycolytic-type oscillations are observed during detachment of mammalian and yeast-cell ensembles, providing additional cell-specific signatures. These findings suggest potential applications for cell viability analysis and for assessing the collective response of cancer cells to drugs.

Single molecule turnover of fluorescent ATP by myosin and actomyosin unveil elusive enzymatic mechanisms

Benefits of single molecule studies of biomolecules include the need for minimal amounts of material and the potential to reveal phenomena hidden in ensembles. However, results from recent single molecule studies of fluorescent ATP turnover by myosin are difficult to reconcile with ensemble studies. We found that key reasons are complexities due to dye photophysics and fluorescent contaminants. After eliminating these, through surface cleaning and use of triple state quenchers and redox agents, the distributions of ATP binding dwell times on myosin are best described by 2 to 3 exponential processes, with and without actin, and with and without the inhibitor para-aminoblebbistatin. Two processes are attributable to ATP turnover by myosin and actomyosin respectively, whereas the remaining process (rate constant 0.2–0.5 s⁻¹) is consistent with non-specific ATP binding to myosin, possibly accelerating ATP transport to the active site. Finally, our study of actin-activated myosin ATP turnover without sliding between actin and myosin reveals heterogeneity in the ATP turnover kinetics consistent with models of isometric contraction.

With fluorescence based-TIRF microspectroscopy, Ušaj et al. unveil mechanistic details about the ATP turnover rates by myosin and actomyosin with enzymatic reaction pathways that were not possible to obtain from ensemble studies. This study could be important to the field of molecular motors.

Role of cardiac troponin I carboxy terminal mobile domain and linker sequence in regulating cardiac contraction

Inhibition of striated muscle contraction at resting Ca(2+) depends on the C-terminal half of troponin I (TnI) in thin filaments. Much focus has been on a short inhibitory peptide (Ip) sequence within TnI, but structural studies and identification of disease-associated mutations broadened emphasis to include a larger mobile domain (Md) sequence at the C-terminus of TnI. For Md to function effectively in muscle relaxation, tight mechanical coupling to troponin's core-and thus tropomyosin-is presumably needed. We generated recombinant, human cardiac troponins containing one of two TnI constructs: either an 8-amino acid linker between Md and the rest of troponin (cTnILink8), or an Md deletion (cTnI1-163). Motility assays revealed that Ca(2+)-sensitivity of reconstituted thin filament sliding was markedly increased with cTnILink8 (∼0.9 pCa unit leftward shift of speed-pCa relation compared to WT), and increased further when Md was missing entirely (∼1.4 pCa unit shift). Cardiac Tn's ability to turn off filament sliding at diastolic Ca(2+) was mostly (61%), but not completely eliminated with cTnI1-163. TnI's Md is required for full inhibition of unloaded filament sliding, although other portions of troponin-presumably including Ip-are also necessary. We also confirm that TnI's Md is not responsible for superactivation of actomyosin cycling by troponin.

Effects of therapeutic pulsed ultrasound and dimethylsulfoxide phonophoresis on oxidative stress parameters after injury induced by eccentric exercise

INTRODUCTION

The aim of the study was to evaluate the effects of TPU together with DMSO on oxidative stress parameters after eccentric exercise.

METHODS

Thirty and six animals were divided in control; eccentric exercise (EE); EE+saline gel 0.9%; EE+TPU 0.8 W/cm(2); EE+DMSO gel; EE+TPU+DMSO gel and submitted to one 90-min downhill run (1.0 km h(-1)). TPU was used 2, 12, 24, 46 h after exercise session and 48 h after the animals were killed and the gastrocnemius muscles were surgically removed. Production of superoxide anion, creatine kinase (CK) levels, lipoperoxidation, carbonylation, and antioxidants enzymes were analyzed.

RESULTS

Showed that TPU and gel-DMSO improved muscle healing. Moreover, superoxide anion production, TBARS level and protein carbonyls levels, superoxide dismutase and catalase activity were all decreased in the group TPU plus gel-DMSO.

DISCUSSION

Our results show that DMSO is effective in the reduction of the muscular lesion and in the oxidative stress after eccentric exercise only when used with TPU.

Effects of therapeutic pulsed ultrasound and dimethylsulfoxide (DMSO) phonophoresis on parameters of oxidative stress in traumatized muscle

Many studies have demonstrated an increase in reactive oxygen species (ROS) and oxidative damage markers after muscle damage. Phonophoresis aims to achieve therapeutically relevant concentrations of the transdermally introduced drug in the tissues subjected to the procedure by the use ultrasound waves. The aim of the study was to evaluate the effects on the therapeutic pulsed ultrasound (TPU) together with gel-dimethylsulfoxide (DMSO) in the parameters of muscular damage and oxidative stress. Male Wistar rats were divided randomly into six groups (n=6): sham (uninjured muscle); muscle injury without treatment; muscle injury and treatment with gel-saline (0.9%); muscle injury and treatment with gel-DMSO (15mg/kg); muscle injury and TPU plus gel-saline; and muscle injury and TPU plus gel-DMSO. Gastrocnemius injury was induced by a single impact blunt trauma. TPU (6min duration, frequency of 1.0MHz, intensity of 0.8W/cm(2)) was used 2, 12, 24, 48, 72, 96 and 120h after muscle trauma. The CK and acid phosphatase activity in serum was used as an indicator of skeletal muscle injury. Superoxide anion, TBARS, protein carbonyls, superoxide dismutase (SOD) and catalase (CAT) activity was used as indicators of stress oxidative. Results showed that TPU and gel-DMSO improved muscle healing. Moreover, superoxide anion production, TBARS level and protein carbonyls levels, superoxide dismutase (SOD) and catalase (CAT) activity were all decreased in the group TPU plus gel-DMSO. Our results show that DMSO is effective in the reduction of the muscular lesion and in the oxidative stress after mechanical trauma only when used with TPU. (E-mail: silveira_paulo2004@yahoo.com.br).

Experimental vasoprotection by a novel erythrocyte-derived depressing factor in rats with arterial calcinosis

Erythrocyte-derived depressing factor (EDDF) shows significant protective effects on blood vessels from hypertensive rats, by regulating vascular reactivity, calcium homeostasis, DNA synthesis, and cell cycle progression in vascular smooth muscles (VSMCs). Arteries from hypertensive and aging people have high levels of accumulated calcium. However, in the life span of experimental animals commonly used, arterial calcium content does not reach cytotoxic levels observed in human. An overdose of vitamin D(3) results in a rapid arterial calcium overload. Using rats with arterial calcinosis and age- and gender-matched Wistar controls, we investigated whether EDDF has beneficial effect on blood vessels from animals with arterial calcinosis. Blood vessel functions were impaired in rats with arterial calcinosis, as indicated by decreased Ca(2+)-ATPase activity, increased vasoconstrictor responses to alpha1 adrenoceptor agonist phenylephrine and increased ERK1/2 phosphorylation. Arterial calcium overload also impaired the morphological integrity of VSMCs. EDDF restored the abovementioned abnormalities caused by arterial calcinosis, and inhibited cell cycle progression of VSMCs induced by angiotensin II. In conclusion, EDDF may protect blood vessels from animals with arterial calcinosis, which is mediated by regulating calcium homeostasis, vascular reactivity and cell cycle progression as well as by improving morphological integrity of VSMCs.

Dimethyl sulphoxide relaxes rabbit detrusor muscle by decreasing the Ca2+ sensitivity of the contractile apparatus

BACKGROUND AND PURPOSE

The intravesical administration of dimethyl sulphoxide (DMSO) is used to alleviate the symptoms of interstitial cystitis. We investigated the relaxant effect of DMSO and its underlying mechanism in the detrusor muscle.

EXPERIMENTAL APPROACH

The effects of DMSO on contraction, on Ca2+ sensitivity of myofilaments, and on myosin light chain (MLC) phosphorylation were investigated in both intact and alpha-toxin-permeabilized strips of rabbit detrusor muscle.

KEY RESULTS

In fura-PE3-loaded strips, DMSO (>1%) induced a significant relaxation during sustained contractions induced by 60 mM K+-depolarization or 10 microM carbachol, while having no effect on the [Ca2+](i) level. DMSO decreased the level of MLC phosphorylation during the contractions induced by 60 mM K+ and 10 microM carbachol. DMSO also inhibited both the contraction and MLC phosphorylation induced by calyculin-A in intact strips. In the alpha-toxin-permeabilized preparations, DMSO relaxed the Ca2+-induced contraction and also inhibited the tension development induced by a stepwise increment of Ca2+ concentrations. Such a relaxant effect of DMSO was enhanced in the presence of phosphate.

CONCLUSIONS AND IMPLICATIONS

DMSO relaxes rabbit detrusor muscle by decreasing the Ca2+ sensitivity of myofilaments. Inhibition of the kinase activities involved in myosin phosphorylation may play a major role in DMSO-induced Ca2+ desensitization. Inhibition of the cross-bridge cycling at the step of phosphate release may also contribute to the relaxant effect of DMSO. Such relaxant effects of DMSO could be linked to the therapeutic effect of DMSO in interstitial cystitis.

Probing actomyosin interactions with 2,4-dinitrophenol

Access to different intermediates that follow ATP cleavage in the catalytic cycle of skeletal muscle actomyosin is a major goal of studies that aim toward an understanding of chemomechanical coupling in muscle contraction. 2,4-Dinitrophenol (DNP, 10(-2) M) inhibits muscle contraction, even though it accelerates the ATPase activity of isolated myosin. Here we used myosin subfragment 1 (S1), acto-S1 and mammalian skinned fibers to investigate the action of DNP in the presence of actin. DNP increases acto-S1 affinity and at the same time reduces the maximum rate of turnover as [actin]-->infinity. In skinned fibers, isometric force is reduced to the same extent (K0.5 approximately equal to 6 mM). Although actin activates Pi release from S1 at all DNP concentrations tested, the combination of enhanced S1 activity and reduced acto-S1 activity leads to a reduction in the ratio of these two rates by a factor of 30 at the highest DNP concentration tested. This effect is seen at low as well as at high actin concentrations and is less pronounced with the analog meta-nitrophenol (MNP), which does not inhibit the acto-S1 ATPase. Arrhenius plots for acto-S1 are parallel and linear between 5 and 30 degrees C, indicating no abrupt shifts in rate-limiting step with either DNP or MNP. Analysis of the reduction in isometric force with increasing Pi concentrations suggests that DNP and MNP stabilize weakly bound cross-bridges (AM.ADP.Pi). In addition, MNP (10(-2) M) increases the apparent affinity for Pi.