Levosimendan has two main mechanisms of action: calcium sensitization of contractile proteins through increased ca2+ binding by troponin C and opening of ATP-dependent K+ channels in smooth muscle vascular cells, causing arteriolar and venous dilation. In large randomised trials, no positive effect on levosimendan outcomes compared to placebo or dobutamine was demonstrated. In placebo-controlled studies, levosimendan was associated with an improvement in the compound`s primary clinical endpoint, with fewer episodes of CI deterioration and a greater decrease in BNP.109 However, levosimendan was associated with more frequent hypotension (50% versus 36%; ventricular tachycardia, 25% versus 17%; and atrial fibrillation, 9% vs. 2%).109 In the study comparing levosimendan with dobutamine in 1327 patients with ADH, mortality at 180 days was similar between the two study groups (26% with levosimendan versus 28% with dobutamine, P = 0.40). The decrease in BNP was greater in patients assigned to levosimendan and the rate of worsening of CI was higher in the dobutamine group, while the rate of newly emerged atrial fibrillation was higher in the levosimendan group.110 The 2DGE systematic separation of protein isoforms of skeletal muscle subtypes, combined with MS analysis, led to the identification of different myosin isoforms. Actins, troponins and tropomyosins as well as many associated proteins of the sarcomeric structure [10,42]. Based on the results of the first skeletal muscle proteome gel studies [96,97,98], high-resolution 2DGE was applied to the cataloguing of vastus lateralis, deltoidus and human laryngeal muscles [99,100,101,102] and a variety of animal species such as rats, rabbits, cows and fish [103,104,105,106,107,108,109,110]. Differential expression patterns of contractile proteins in skeletal muscles with mainly rapid contractions compared to slow muscles have been established for various muscle subtypes such as gastrocnemius muscles, digitorium longus extensors, longissimus dorsi, semitendinosus and soleus using 2DGE [111,112,113,114,115]. Gel-based fiber specification maps are consistent with the distribution of fast and slow muscle protein isoforms determined by stable isotopic labeling with amino acids in the SILAC mouse model [116].
Figure 3 shows representative 1DGE and 2DGE images of distinct muscle protein populations. These approaches are commonly used for proteomic identification of various proteoforms of contractile components. Muscle atrophy – protein degradation (loss of contractile proteins, increase in non-contractile tissue, e.B collagen) and cytokine activity. Reduction of strength, especially of the antigravitational muscles of the lower limbs (i.e. those related to transfer and the ability to walk). Inactivity improves the catabolic response of skeletal muscles to cortisol, resulting in more pronounced atrophy after trauma or disease. Especially important in groups of patients with low relative muscle mass, e.B. the elderly. Nutritional countermeasures should be considered and carefully titrated to best meet the requirements Contractile protein studies in trained animals were conducted on floating rats and rats and dogs trained on treadmills.
The results obtained in the floating rat compared to the rat trained on the treadmill and the dog are different and this difference may be the result of the type of training or the load associated with the training. The data are therefore discussed first for the floating rat, then for the animals trained on treadmills, and little effort is made to match the measurements. Despite the lack of effect on the production of contractile protein strength, HF modifies other aspects of contractile protein function; In particular, the kinetics of myosin-actin-cross-bridge interaction in RF patients was slowed down compared to age- and activity-appropriate controls.7 Although such changes in myosin-actin-actin-actin cross-bridge function may be potentially beneficial in maintaining the energy-producing capacity of muscle fibers, 7 may have adverse consequences. Slowing down the kinetics of the transverse bridge would likely slow down the contractile velocity,64 which in turn could reduce muscle power. In fact, there is evidence from preclinical models for reduced contractile velocity with HF.65 A reduction in muscle contractile velocity would contribute to an overall reduction in muscle strength performance.51 Thus, some of the reduced working capacity of skeletal muscle in patients with CI, which would directly affect performance in a peak load test, could result in a deceased contractile velocity that is due to impaired transverse bridge function (see Fig. 16.3). In fact, drugs that improve the protein function of myofilament improve muscle contractility and power delivery, and in turn increase physical performance.66 At rest, the plasma membrane of smooth vascular muscle cells is relatively impermeable to Ca2+. However, upon activation, Ca2+ channels are opened in the plasma membrane, allowing Ca2+ to flow along its concentration gradient into the cell. Two types of calcium channels have been proposed: potential- or voltage-driven channels, which are regulated by changes in membrane potential, and channels operated by receptors, which are controlled by ligand-receptor interactions. Modulation of these channels by various pharmacological agents affects the contractile capacity of smooth vascular muscles.1–3 Protein acetylation is involved in regulating protein stability and function during various cellular and physiological processes [218,219], including skeletal muscle atrophy [220] and age-related fiber waste [221]. Acetylation of lysine residues on histone and non-histone proteins is a reversible dynamic protein modification that is regulated by lysine acetyltransferases and deacetylases and controls a number of different biological functions, including protein-protein interactions, protein-DNA interactions, enzyme activity and subcellular localization. High concentrations of residual acetyltransferase dihydrolipoyllysine were detected in the nucleus of the triceps muscle of the elderly rat by fluorescence 2D DIGE analysis and were shown to be associated with increased protein acetylation [221].
Acetylation of lysine residues removes the positive charge from the side chain and thus directly affects the electrostatic state of the modified protein, allowing separation associated with isoelectric focusing. Protein pI changes due to PTMs showed that the theoretical pI of the non-acetylated form of tropomyosin-beta is close to the pI of its experimentally acetylated counterpart, while the additional acetylation of tropomyosin (LEKTIDDLEETLASAK + acetyl (K); Acetyl (term N)) does not significantly affect iCp [222]. Interestingly, a variety of contractile proteins are impaired in chronic Chagas disease, an often fatal outcome of trypanosoma cruzi infection characterized by severe cardiomyopathy and chronic skeletal muscle myositis and vasculitis [223,224]. Protein changes were assessed using 2DGE from samples from patients with chronic end-stage Chagas disease to better understand their pathophysiology [225]. Several gel stains with different pI values and comparable molecular weight were identified by peptide mass imprint as proteoforms of important structural and contractile proteins, including various forms of actin (ACTA1, ACTA2, ACTC, ACTG2, ACTN2), desmin, myosin (MYL3 and MYL7) and vimentin. Variations in their position within 2D brammengeles could be due to PTMs such as acetylation or other processes. An increase in the cytoplasmic concentration of Ca2+, which activates the contractile process in smooth vascular muscle cells, may be due to increased permeability of the cell membrane for extracellular calcium (i.e. calcium influx) or mobilization of Ca2+ from cell reserves (e.B. sarcoplasmic reticulum and mitochondria). The source of the activation ion differs depending on the anatomical origin of the smooth vascular muscles, the contractile stimulus or the experimental conditions to which the tissues are exposed (Fig. .