Phorbol ester treatment inhibits proliferation and differentiation of cultured human skeletal muscle satellite cells by differentially acting on protein kinase C isoforms.

We have previously shown that cultured human skeletal muscle cells express five protein kinase C (PKC) isoforms (PKCalpha, -gamma, -eta, -theta, and -zeta) and that expression levels of various PKC isozymes differentially change during differentiation. In this study we investigated the effects of the PKC activator phorbol 12-myristate 13-acetate (PMA) on differentiation and on PKC isozymes of human skeletal muscle satellite cells. PMA inhibited the growth and fusion of cultured human myoblasts in a dose-dependent manner. In addition, prolonged treatment of cells with PMA suppressed the expression of the myogenic differentiation marker desmin showing similar dose-response characteristics. Furthermore, PMA also induced the intracellular translocation of PKCgamma, -eta, and -theta, whereas cellular localization of PKCalpha and -zeta were not altered. These changes in subcellular localization patterns were of great importance since only those PKC isoforms were translocated that possessed alterations in their expression levels during differentiation. Our findings, therefore, suggest that the PMA-induced inhibition of differentiation of human skeletal muscle cells is mediated by certain PKC isoforms. Moreover, these data strongly argue for differential and isozyme-specific roles of various PKC isoforms in these processes.

Differential expressions of protein kinase C isozymes during proliferation and differentiation of human skeletal muscle cells in vitro.

The mechanism of skeletal muscle regeneration in vivo can be well modeled in vitro by culturing skeletal muscle cells. In these cultures mononuclear satellite cells fuse to form polynuclear myotubes by proliferation and differentiation. The aim of this study was to determine how the different protein kinase C (PKC) isozymes were expressed during differentiation of human skeletal muscle in vitro. The expressions of desmin, used as a muscle-specific intermediate filament protein marker of differentiation, and of different PKC isozymes were detected by single and double immunohistochemical labeling, and by Western blot analysis. In skeletal muscle cells we could identify five PKC isozymes (PKC alpha, -gamma, -etha, -theta and -zeta). The expressions of PKC alpha and -zeta did not change significantly during differentiation; their levels of expression were high in the early immature cells and remained unchanged in later phases. In contrast, the expression levels of PKC gamma and -etha increased with differentiation. Furthermore, the cellular localization of PKC gamma markedly altered during differentiation, with a perinuclear-nuclear to cytoplasmic translocation. The change in the level of expression of PKC theta during differentiation showed different pattern; its expression was high during the early phases, but a decreased immunostaining was detected in the matured, well-differentiated myotubes. We conclude, therefore, that cultured human skeletal muscle cells possess a characteristic PKC isozyme pattern, and that the different phases of differentiation are accompanied by different expression patterns of the various isozymes. These data suggest the possible functional and differential roles of PKC isozymes in human skeletal muscle differentiation.

Evaluation by integrated thermography of the beneficial effect of cyclofenil in severe subcutaneous arterial insufficiency.

Integrated thermographic measurements were made in a patient suffering from a complex syndrome which included scleroderma, Osler-Weber-Rendu disease and a marked atherosclerotic circulatory insufficiency. A new anti-estrogenic drug, cyclofenil, elicited a rapid and prolonged curative effect against the entire syndrome. The circulatory amelioration was registered periodically by integrated thermography of the face and both hands. This method enables temperature distribution functions to be calculated and seems to hold considerable promise for the evaluation of circulatory changes and in particular those changes evoked by therapeutic agents.

Effect of cyclofenil treatment on arterial insufficiency demonstrated in a patient by colour thermography.

Cyclofenil, 200 mg t.i.d., was administered for four months to a 67-year-old woman, who suffered from a combination of scleroderma, Osler-Weber-Rendu disease and a severe atherosclerotic circulatory insufficiency. The effects on the severely impaired skin circulation in the face and hands were followed and recorded by colour isothermograms, using the AGA monitor system. The treatment resulted in a marked improvement of the arterial circulation with disappearance of the Raynaud phenomenon, complete arrest of gastrointestinal bleeding, disappearance of malabsorption, and relief of the joint stiffness.