Fatty acyl-CoAs inhibit retinoic acid-induced apoptosis in Hep3B cells

Retinoic acid (RA) induces apoptosis in Hep3B human hepatoma cells. 9-Cis-R A (c-RA) had a similar effect as all-trans-RA (t-RA) in inducing cell death in Hep3B cells. RA-induced Hep3B-cell death was associated with inhibited expression of the hepatocyte nuclear factor 4 (HNF-4) gene. Palmitoyl-CoA ( (C16:0)-CoA), the reported HNF-4 ligand, prevented RA-induced apoptosis. Th e effect of (C16:0)-CoA was specific, since palmitic acid and co-enzyme A h ad no effect in preventing RA-induced apoptosis. Bovine serum albumin (BSA) also prevented RA-induced apoptosis. However, in contrast to BSA, which in duced cell growth, (C16:0)-CoA alone had no effect on cell growth. Investig ating the possible role of HNF-4 in apoptosis, the reported HNF-4 antagonis t (C18:0)-CoA was employed, and it also prevented RA-induced apoptosis. By transient transfection, overexpression of HNF-4 did not prevent RA-induced apoptosis. The induction and prevention of apoptosis caused by RA and (C16: 0)-CoA were associated, respectively with the induction and inhibition of t he expression of transforming growth factor beta (TGF beta). which is known to play a role in apoptosis. Furthermore, RA and (C16:0)-CoA can regulate AP-1, which is a key regulator of the TGF beta gene. Our data indicate that fatty acyl-CoAs can prevent RA-induced apoptosis and that TGF beta, rather than HNF-4, may play a role in these regulatory processes. Our data also s uggest that (C16:0)-CoA and (C18:0)-CoA are not the agonist and antagonist fur HNF4, respectively in the Hep3B cell system. (C) 2000 Elsevier Science ireland Ltd. All rights reserved.