Cyclopentenone prostaglandins.(PGs), such as 15-deoxy-12,13-didehydro-14,15-didehydro-PGJ(2) (15d-Delta(12,14)-PGJ(2)), 12,13-didehydro-PGJ(2) (Delta(12)-PGJ(2)) and PGA(2), are actively transported into cells and promote the expression of a variety of genes. The ultimate metabolite of PGD(2), 15d-Delta(12,14)- PGJ(2), specifically binds to a nuclear receptor, they isoform of the peroxisome proliferator-activated receptor, thereby promoting adipogenesis. Cyclopentenone PGs also induce the expression of various stress genes, such as heat shock proteins (HSPs), the immunoglobulin heavy chain binding protein (BiP) and protein disulfide isomerase by acting through heat shock element or unfolded protein response element. Overall, cyclopentenone PGs regulate cell growth, cell differentiation and stress responses by regulating various gene expression. (C) 2002 Elsevier Science Inc. All rights reserved.