ALTERATIONS IN SERUM THROMBOSPONDIN IN PATIENTS WITH AMYOTROPHIC-LATERAL-SCLEROSIS

Thrombospondin (TSP), an endogenous extracellular matrix (ECM) glycopr otein, is secreted from platelet ct-granules after thrombin stimulatio n. Alterations in blood TSP levels occur in different pathologic condi tions, suggesting it is a marker for certain disorders. We previously found a marked increase in TSP deposition in the muscle ECM of patient s with amyotrophic lateral sclerosis (ALS) in comparison with controls . Because the mechanism for this increase is unknown, we compared seru m TSP levels in 11 patients to 15 controls using three different site- specific monoclonal antibodies (MA-I, MA-II and A6.1). We found mean s erum TSP concentrations by indirect ELISA to be significantly decrease d in the ALS patients. Using laser densitometry we calculated the rati o of fragmented to native TSP from Western immunoblots probed with A6. 1, where a higher ratio corresponds to increased fragments. Mean value s for this ratio were 6.3 +/- 4.9 and 18.3 +/- 8.2 for controls and pa tients, respectively. Thus significant decrease in native TSP and incr ease in its proteolytic fragments in ALS is consistent with increased proteolytic enzyme activity. Dysregulation of the protease: inhibitor balance in this degenerative condition may be reflected in the quantit ative and qualitative changes in TSP.