prostaglandin-d2 and 9-hydroxy-10-12-octadecadienoic-acid

Topics: Adipocytes; Cell Differentiation; Humans; Insulin Resistance; Ligands; Linoleic Acids; Linoleic Acids, Conjugated; Macrophage Activation; PPAR gamma; Prostaglandin D2

The gamma isoform of the peroxisome proliferator-activated receptor, PPAR gamma, regulates adipocyte differentiation and has recently been shown to be expressed in neoplasia of the colon and other tissues. We have found four somatic PPAR gamma mutations among 55 sporadic colon cancers: one nonsense, one frameshift, and two missense mutations. Each greatly impaired the function of the protein. c.472delA results in deletion of the entire ligand binding domain. Q286P and K319X retain a total or partial ligand binding domain but lose the ability to activate transcription through a failure to bind to ligands. R288H showed a normal response to synthetic ligands but greatly decreased transcription and binding when exposed to natural ligands. These data indicate that colon cancer in humans is associated with loss-of-function mutations in PPAR gamma.

Topics: Amino Acid Substitution; Binding Sites; Chromans; Colorectal Neoplasms; Dimerization; DNA-Binding Proteins; Exons; Genes, Tumor Suppressor; Humans; Hydroxyeicosatetraenoic Acids; Ligands; Linoleic Acids; Linoleic Acids, Conjugated; Mutation; Prostaglandin D2; Protein Binding; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Response Elements; Retinoid X Receptors; Rosiglitazone; Thiazoles; Thiazolidinediones; Transcription Factors; Transcriptional Activation; Troglitazone

Genes induced or suppressed by oxidized low-density lipoproteins (oxLDL) in human monocytic THP-1 cells were searched using differential display reverse transcriptase polymerase chain reactions (DDRT-PCR). Among the many differentially expressed cDNA fragments, one was dramatically stimulated by the oxLDL in a steady state level, which was later found to contain sequences corresponding to ferritin light chain (L-ferritin) in a sequence homology search. The stimulatory effect of the oxLDL on the level of L-ferritin mRNA in the THP-1 cells was both time- and dose-dependent. When the cells were allowed to differentiate in the presence of phorbol 12-myristate 13-acetate (PMA), the differentiated cells were generally less responsive to the oxLDL than the undifferentiated ones. An increase of L-ferritin mRNA was observed when the cells were treated with the lipid components in the oxLDL such as 9-HODE, 13-HODE, and 25-hydroxycholesterol. In addition, a stimulation of the L-ferritin gene expression was also observed when the cells were treated with an endogenous peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, 15d-PGJ2, in a time- and dose-dependent manner. These results suggest that oxLDL or its constituents are related to the stimulation of L-ferritin expression via PPARgamma.

Topics: Apoferritins; Base Sequence; Cell Differentiation; Cell Line; DNA Primers; Ferritins; Gene Expression Regulation; Humans; Hydroxycholesterols; Ligands; Linoleic Acids; Linoleic Acids, Conjugated; Lipoproteins, LDL; Monocytes; Prostaglandin D2; Receptors, Cytoplasmic and Nuclear; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Tetradecanoylphorbol Acetate; Transcription Factors

Macrophage uptake of oxidized low-density lipoprotein (oxLDL) is thought to play a central role in foam cell formation and the pathogenesis of atherosclerosis. We demonstrate here that oxLDL activates PPARgamma-dependent transcription through a novel signaling pathway involving scavenger receptor-mediated particle uptake. Moreover, we identify two of the major oxidized lipid components of oxLDL, 9-HODE and 13-HODE, as endogenous activators and ligands of PPARgamma. Our data suggest that the biologic effects of oxLDL are coordinated by two sets of receptors, one on the cell surface, which binds and internalizes the particle, and one in the nucleus, which is transcriptionally activated by its component lipids. These results suggest that PPARgamma may be a key regulator of foam cell gene expression.

Topics: Animals; CD36 Antigens; Cell Differentiation; Cells, Cultured; Dimerization; Fatty Acids, Unsaturated; Humans; Ligands; Linoleic Acids; Linoleic Acids, Conjugated; Lipopolysaccharide Receptors; Lipoproteins, LDL; Macrophages; Membrane Proteins; Monocytes; Oxidation-Reduction; Prostaglandin D2; Receptors, Cytoplasmic and Nuclear; Receptors, Immunologic; Receptors, Lipoprotein; Receptors, Retinoic Acid; Receptors, Scavenger; Recombinant Fusion Proteins; Retinoid X Receptors; Scavenger Receptors, Class B; Signal Transduction; Transcription Factors; Transcriptional Activation