Modulation of growth factor binding properties of alpha2-macroglobulin by enzyme therapy.
OBJECTIVE
To investigate the binding of transforming growth factor-beta (TGF-beta) to human alpha2-macroglobulin upon oral treatment of patients with proteases.


METHODS
Volunteers were given a cocktail of active proteinases (Phlogenzym) composed of trypsin, bromelain and the additive rutoside orally over a period of 7 days at low dose followed by a bolus application. Before and after medication plasma was immediately withdrawn and binding of 125I-TGF-beta to the proteinase inhibitor alpha2-macroglobulin was determined by electrophoresis and gamma-counting. Cell culture experiments were performed to study the effect of transformed alpha2-macroglobulin on TGF-beta-stimulated proliferation of skin fibroblasts.


RESULTS
Ingestion of proteinases was found to trigger the formation of intermediate forms of alpha2-macroglobulin displaying high affinity to TGF-beta. Maximum binding of TGF-beta was observed 1-2 h after bolus ingestion, and steadily levelled off with time. In vitro experiments demonstrated that complex formation of diverse proteinases (trypsin, alpha-chymotrypsin, bromelain and plasmin) with alpha2-macroglobulin conferred binding of 125I-TGF-beta, alpha2-Macroglobulin transformed by methylamine or proteinases was found to abolish the TGF-beta effect on fibroblasts in cell culture.


CONCLUSIONS
Intestinal absorption of proteinases triggers the formation of TGF-beta binding species of alpha2-macroglobulin in blood. Mediated by this process high concentrations of TGF-beta might be reduced via enhanced clearance of alpha2-macroglobulin-TGF-beta complexes. Thus, proteinase therapy may have beneficial effects in treatment of fibrosis and certain cancers accompanied by excessively high TGF-beta concentrations.
Lauer
D
D
Institute of Biochemistry, University of Leipzig, Germany.
Müller
R
R
Cott
C
C
Otto
A
A
Naumann
M
M
Birkenmeier
G
G
D000284:Administration, Oral; D001963:Bromelains / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D004338:Drug Combinations; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D006801:Humans; D007457:Iodine Radioisotopes; D008744:Methylamines / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D012431:Rutin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology*; D000511:alpha-Macroglobulins / Q000378:metabolism* / Q000494:pharmacology
D004338:Drug Combinations; D007457:Iodine Radioisotopes; D008744:Methylamines; C119937:Phlogenzym; D016212:Transforming Growth Factor beta; D000511:alpha-Macroglobulins; D012431:Rutin; D001963:Bromelains; C027451:methylamine; D014357:Trypsin