T N Usenko | PubMed Health

PubMed2001

Neutrophil antiserum response to decrease in proteolytic activity in loaded rat muscle.

The leukocytes that are found in skeletal muscles after intense muscular activity have been shown to infiltrate areas of injury in skeletal muscle tissue. We believe that leukocyte enzymes, which appear in the tissue after the degranulation or destruction of leukocytes, could play a role in tissue enzyme activities. Neutrophil proteinases were investigated. Histological data provided evidence of rat muscular tissue infiltration by leukocytes after intense physical loading. To reduce the influx of leukocytes in rat muscles, a rabbit antiserum against rat peritoneal leukocytes was injected into rats after muscle loading. This resulted in a reduction in muscle cytosol proteolytic activity as compared to control animals (who received saline injections). The levels of proteolytic activities of media conditioned by the soleus muscle isolated from antiserum-treated rats were also reduced. These data provide evidence that the increase in proteolytic activity observed in rat skeletal muscles after physical loading is partially induced by neutrophil proteinases.

Animals↗

PubMedDate not supplied

[Transformation with the E1A + cHa-ras oncogenes enhances the trans-repressor function of the Elk-1 transcription factor].

Rat embryo fibroblasts (REF) transformed with the complementing E1A and cHa-ras oncogenes show a down-regulation of the c-fos early response gene, which is transcribed with the participation of Elk-1. The role of Elk-1 was studied with constructs coding for the full-length factor or its N- or C-terminal fragment fused with Gal. The trans-activating effect of each construct on the Gal4-Luc reporter plasmid was estimated in contransfected REF52 and E1A + cHa-ras cells stimulated with serum or treated with sodium butyrate, a histone deacetylase inhibitor. In E1A + cHa-ras cells, serum activated the expression of C-terminal Gal-Elk(206-428) but not that of full-length Gal-Elk(1-428). The serum-induced activation of Gal-Elk(206-428) was suppressed by PD98059, a MEK/ERK inhibitor, and enhanced by SB203580, an inhibitor of the p38-kinase cascade. It was assumed that p38 negatively affects the MEK/ERK cascade, which plays the major role in the Elk-1 activation in response to serum. Sodium butyrate enhanced the Gal-Elk(1-428) activity both in serum-stimulated and in starving E1A - cHa-ras cells, suggesting a high activity of Elk-1-phosphorylating kinases in the latter. The butyrate-mediated activation of Gal-Elk(206-428) and Gal-Elk(1-428) was suppressed by PD98059 and, therefore, depended on the MEK/ERK cascade. Thus, Elk-1 acted not only as a positive, but also as a negative transcription regulator. Possibly, to suppress transcription, Elk-1 binds with histone deacetylases and thereby contributes to the inactive chromatin state in E1A + cHa-ras cells.

Adenovirus E1A Proteins↗