[Translocation of MuRF isoforms to nuclei in postural muscle during gravitational unloading].

Ubiquitin-proteasomal proteolytic pathway is one of the key signaling pathways determining protein degradation in muscle fibers. Among the E3 ubiquitin ligases, rate limiting enzymes of the ubiquitin-proteasomal pathway, the most interesting ones are the MuRF isoforms: MuRF-1 and MuRF-2. There are some pieces of evidence that these enzymes are also involved in the regulation of gene expression in skeletal muscle under some specific conditions (i. e. muscle disuse). We supposed that it was disuse that brought about to altered localization of MuRFs in postural muscle fibers and their translocation to nuclei. In the study using the conventional simulation model of the gravitational unloading (rat hindlimb suspension according to Ilyin and Novikov modified by Morey-Holton) we found that from the 3rd day till 14th day of unloading the content of MuRF-1 and MuRF-2 in the nuclear fraction 4-5 fold increased in unloaded soleus as compared to the control values. These data obtained by means of electrophoresis and western blot of the nuclear fraction of rat soleus were confirmed in the immunohistochemical study of co-localization of MuRF-1 and MuRF-2 antibodies and DAPI nuclear stain on transverse frozen sections of soleus muscle. Thus in the present study we observed the phenomenon of MuRF isoforms accumulation in nuclei of soleus muscle fibers during simulated gravitational unloading.

[Effect of 30-day space flight and subsequent readaptation on the signaling processes in m. longissimus dorsi of mice].

Some steps of anabolic and catabolic signaling pathways were investigated in postural/tonic m. longissimus dorsi of mice following the 30-day orbital flight of biosatellite "Bion-M1" and 8-day recovery. Western blotting was used for determining insulin receptor substrate 1 (IRS-1) and AMR-activated protein kinase (AMPK) involved in reciprocal regulation of anabolic and catabolic pathways, as well as E3-ligase MURF-1, and elongation factor eEF2. Functioning of the IGF-1-dependent IRS-1 signaling pathway was activated in the recovery period only. Though the content of ubiquitinligase MURF-1 showed an increase after flight, on completion of the recovery period it did not exceed the pre-flight level unambiguously.

[Neuronal NO-synthase as the molecular guard of myofiber stability. NO-dependent signaling pathways in the active and unloaded muscle].

The review is dedicated to the signaling pathways triggered by the nitric oxide II in skeletal muscle. Analysis of the current literature shows that during physical exercise of various intensity and regimen the nitric oxide is an essential trigger of the signaling pathways, leading to the alteration of the structural and metabolic myofiber profile and enhancement of its functional capacity. At the same time during the elevated muscle contractile activity (for instance, eccentric activity), NO serves as a protective and stabilizing agent, preventing from the intensification of the proteolytic processes. Data obtained from the experiments with the modulation of the NO at the background of the functional (gravitational) unloading give evidence that neuronal NO synthase activation in this experimental conditions allows to stabilize the degradation pathways and prevent from disuse atrophy development.

[Proteolytic signaling mechanisms in skeletal muscles in patients with alcohol-induced muscle disease].

Chronic alcoholic myopathy is one of most numerous and profound manifestations of chronic alcohol intoxication. This disease is characterized by the pronounced atrophy of the locomotor muscles, which involves predominantly those fibers expressing myosin isoforms of the I "fast" type. In early experiments with alcohol-fed rats and studies of patients it was shown the impairment of the anabolic intracellular signaling pathways and decrease in protein synthesis rate. We were the first to analyze the signaling pathways involved in the pathogenesis of alcoholic myopathy with different fiber atrophy levels. At the early stages of the pathogenesis we observed also the sufficient increase of mRNA of E3 ubiquitin ligases. However the ubiquitinylation level was not altered in patients as compared to the control subjects. This phenomenon could be associated with the increased expression of the heat-shock proteins, known for their protective action.

[Expression of splice-variants of the insulin-like growth factor I and the condition of the cell-myosatellite pool in the rat m. soleus under conditions of gravitation relief and passive stretching].

We suggested that satellite proliferation with subsequent incorporation of their nuclei in the fibres was essential for enhancement of the protein synthesis in the rat relieved m. soleus. In passive stretch of the muscle, the number of labelled cells exceeded 2.5-fold their number in hung out animals and 1.7-fold in the control animals. The expression level of the insulin-like growth factor I (IF-1) was determined in the m. soleus after hanging out with stretching, and no changes were revealed as compared with hanging out without stretching in the control group. We believe that the muscle IF-1 and satellite cell incorporation are not essential for preventing atrophy of relieved soleus muscle in stretching.

[Protective effect of nitric oxide on cytoskeletal proteins in skeletal muscles under eccentric exercise].

The protective effect of nitric oxide (NO) on the cytoskeletal muscle proteins desmin and dystrophin has been studied under eccentric exercise. Experiments were performed on 28 male Wistar rats, which were divided into four groups: cage control (C, n = 7); group of eccentric exercise (running down a motor-driven treadmill, inclination 16 degrees) (20 m/min, 40 min running) (R, n = 7); eccentric exercise + L-arginine group (RA, n = 7) (with a daily supplementation of 500 mg/kg wt L-arginine for 3 days before the running); and eccentric exercise + L-NAME group (RN, n = 7) (with a daily supplementation of 90 mg/kg wt L-NAME (Nomega-nitro-L-arginine methyl ester, nNOS blocker) for 3 days before the running). It was found that increasing the NO concentration (in RA group) prevents the disruption of the dystrophin layer and decreases the loss of desmin in m. soleus under eccentric contraction, whereas in the R and RN groups the level of damage to dystrophin and desmin was significantly higher compared to the control rats. The inhibition of nNOS (by L-NAME) increases the nNOS mRNA level in the m. soleus, whereas increasing the NO concentration in m. soleus (L-arginine administration) does not affect the level of nNOS mRNA during the eccentric running. It was concluded that NO has a protective action on the cytoskeletal proteins desmin and dystrophin in skeletal muscle under eccentric contraction-induced damage.