Increased muscle proteolysis after local trauma mainly reflects macrophage-associated lysosomal proteolysis

Abstract

. Increased muscle proteolysis after local trauma mainly reflects macrophage-associated lysosomal proteolysis. Am J Physiol Endocrinol Metab 282: E326-E335, 2002; 10.1152/ajpendo.00345.2001.-Rat gastrocnemius showed increased protein degradation (ϩ75-115%) at 48 h after traumatic injury. Injured muscle showed increased cathepsin B activity (ϩ327%) and mRNA encoding cathepsin B (ϩ670%), cathepsin L (ϩ298%), cathepsin H (ϩ159%), and cathepsin C (ϩ268%). In in situ hybridization, cathepsin B mRNA localized to the mononuclear cell infiltrate in injured muscle, and only background levels of hybridization were observed either over muscle cells in injured tissue or in uninjured muscle. Immunogold/electron microscopy showed specific staining for cathepsin B only in lysosome-like structures in cells of the mononuclear cell infiltrate in injured muscle. Muscle cells were uniformly negative in the immunocytochemistry. Matrix metalloproteinase-9 (granulocyte-macrophage gelatinase) mRNA and activity were not present in uninjured muscle but were expressed after trauma. There was no activation of the ATP-ubiquitinproteasome-dependent proteolytic pathway in injured muscle, by contrast to diverse forms of muscle wasting where the activity of this system and the expression of genes encoding ubiquitin and proteasome elements rise. These results suggest that proteolytic systems of the muscle cells remain unstimulated after local injury and that lysosomal enzymes of the inflammatory infiltrated cells are likely to be the major participant in protein catabolism associated with local trauma. injury; protein degradation IN A MODEL OF BLUNT TRAUMA TO MUSCLE, we demonstrated a period of degeneration lasting ϳ3 days, characterized by gross disruption of muscle cells, hemorrhage, inflammation, invasion of the injured site by mononuclear cells, and a 26% loss of previously existing muscle protein (12). A large increase in the process of protein catabolism occurs in injured muscle; however, it is not known which of the several distinct intracellular pro-

Effects on the ubiquitin proteasome system after closed soft-tissue trauma in rat skeletal muscle

“…While the initial reaction supports a common stimulus, slight differences seen in the time-dependent process of ligation and degradation activity potentially indicate uncoupled regulation of both systems. Increased ubiquitin mRNA levels seen under wasting conditions [1,12,30] were not observed until 48 h after the locally induced injury [38]. Therefore, it can be speculated that the elevated monomeric ubiquitin we detected 6 h after trauma was caused by accumulation rather than by increased gene expression.…”

“…Results revealed-in line with the present work-reduced ubiquitination activity after injury, but also proteasome activation. These controversial Studies of post-trauma ultrastructural events [33,34], changes in microcirculation [20,24,35], and metabolic effects of surgical trauma [36,37] are supplemented only by the work of Farges et al [38]. The results of this research supporting a lysosomal, UPP-independent protein breakdown by inflammatory infiltrated cells revealed a mechanism that was different from systemically induced muscle wasting.…”

“…Further investigations of other tissues like liver, heart and kidney must be made in order to fully understand the observed lung reaction and to explore potential effects in the plasma. Furthermore, the immediate reduction in the activity of the UPP after trauma initiation refers to a direct muscle cell response, in contrast to a macrophage-associated catabolic reaction [38]. Immune cell invasion is typically initiated by neutrophil infiltration 1 h after tissue injury, and this is followed by macrophage migration within 24 h of the trauma [44,45].…”

Myogenic and nonmyogenic cells differentially express proteinases, Hsc/Hsp70, and BAG-1 during skeletal muscle regeneration

“…Here, we report a new example of a condition under which cathepsin B/L enzyme activities are dramatically altered (22-fold increase) in skeletal muscle. A recent report (20) indicated that inflammatory cells expressed mainly lysosomal enzymes in response to local trauma. In agreement with that study, our histochemical analysis of lysosomal activity (acid phosphatase staining) showed that inflammatory cells were stained positively, whereas desmin-negative fibers did not react with the dye.…”

“…Myogenic cells (degenerating myofibers, myoblasts, regenerating myofibers, and growing mature myofibers) and nonmyogenic cells (inflammatory cells) are involved in the different stages of skeletal muscle regeneration and may thus participate in the expression of proteinases (17,20,49). In the present study, an immunohistochemical analysis was first performed to assess the relative proportion of myogenic and nonmyogenic cells over the course of muscle regeneration.…”