RETINOL AND RETINALDEHYDE SPECIFICALLY INCREASE ALPHA-1-PROTEINASE INHIBITOR IN THE HUMAN CORNEA

alpha 1-Proteinase inhibitor is a serpin and can inhibit most serine p roteinases. The cornea is one of several extrahepatic tissues that syn thesizes this inhibitor. In the presence of retinol, corneal alpha 1-p roteinase inhibitor levels were increased 3.8-fold. The maximal respon se was achieved 2 h after the addition of retinol (1 mu M final concen tration) to the culture medium. A similar increase in alpha 1-proteina se inhibitor was observed with retinaldehyde (1 nM final concentration ). Concentrations of alpha 1-proteinase inhibitor in other tested cell s (Hep G2, CaCo 2, MCF-7, monocytes and macrophages) remained unchange d in the presence of retinol. Retinoic acid did not affect alpha 1-pro teinase inhibitor levels in the cornea or the other cells tested. The acute-phase cytokine, interleukin-6, increased alpha 1-proteinase inhi bitor levels in all tested tissues/cells except the cornea. These resu lts demonstrate that alpha 1-proteinase inhibitor levels are controlle d differently in the cornea compared with other tissues/cells. alpha 1 -Proteinase inhibitor is the first protein identified whose levels are regulated by a mechanism supported by retinol and retinaldehyde but n ot retinoic acid.