Inhibition of transforming growth factor-beta-induced cataractous changes in lens explants by ocular media and alpha 2-macroglobulin.
OBJECTIVE
To investigate the ocular media for the presence of inhibitors of transforming growth factor-beta (TGF beta) using a lens epithelial explant system in which TGF beta induces cataractous changes. The effect of alpha 2-macroglobulin, an inhibitor of TGF beta in other systems, also was assessed.


METHODS
Explants prepared from 21-day-old rats were cultured with TGF beta 2 with and without 50% bovine aqueous or vitreous or alpha 2-macroglobulin. alpha 2-macroglobulin was added to an aqueous concentrate, shown to contain endogenous TGF beta activity by blocking with anti-TGF beta. Explants were monitored by phase-contrast microscopy for 5 days and assessed in terms of capsule wrinkling, spindle-cell formation, blebbing, and cell loss. alpha 2-macroglobulin in the ocular media was assessed by enzyme-linked immunosorbent assay and Western blot analysis.


RESULTS
At 50% strength, neither aqueous nor vitreous demonstrated TGF beta-like activity; however, aqueous partially and vitreous completely prevented cataractous changes induced by 25 and 100 pg/ml TGF beta 2, respectively. alpha 2-macroglobulin (50 to 200 micrograms/ml) also protected against these changes, with complete inhibition of TGF beta 2 or aqueous-derived TGF beta activity at the highest concentration. A threefold higher concentration of alpha 2-macroglobulin was detected in vitreous than aqueous.


CONCLUSIONS
Both aqueous and vitreous contain molecule(s) that inhibit TGF beta 2 activity. alpha 2-macroglobulin has been identified in the ocular media and shown to block cataractous changes induced by TGF beta. Maintaining appropriate levels of alpha 2-macroglobulin or similar molecules in the ocular media may protect lens cells from the damaging effects of TGF beta, and reduced levels may predispose to cataract.
Schulz
M W
MW
Department of Anatomy and Histology, University of Sydney, New South Wales, Australia.
Chamberlain
C G
CG
McAvoy
J W
JW
D000328:Adult; D000818:Animals; D001082:Aqueous Humor / Q000737:chemistry / Q000502:physiology*; D001685:Biological Factors / Q000494:pharmacology; D015153:Blotting, Western; D002386:Cataract / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D002417:Cattle; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D004848:Epithelium / Q000187:drug effects / Q000473:pathology; D006801:Humans; D007908:Lens, Crystalline / Q000187:drug effects* / Q000473:pathology; D008297:Male; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D014822:Vitreous Body / Q000737:chemistry / Q000502:physiology*; D000511:alpha-Macroglobulins / Q000494:pharmacology*
D001685:Biological Factors; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D000511:alpha-Macroglobulins