Inflammatory bowel disease (IBD) is a high-risk con-

The nuclear receptor peroxisome proliferator-activated receptor ␥ (PPAR␥) is a ligand-regulated nuclear receptor superfamily member. Liganded PPAR␥ exerts diverse biological effects, promoting adipocyte differentiation, inhibiting tumor cellular proliferation, and regulating monocyte/macrophage and anti-inflammatory activities in vitro. In vivo studies with PPAR␥ ligands showed enhancement of tumor growth, raising the possibility that reduced immune function and tumor surveillance may outweigh the direct inhibitory effects of PPAR␥ ligands on cellular proliferation. Recent findings that PPAR␥ ligands convey PPAR␥-independent activities through IB kinase (IKK) raises important questions about the specific mechanisms through which PPAR␥ ligands inhibit cellular proliferation. We investigated the mechanisms regulating the antiproliferative effect of PPAR␥. Herein PPAR␥, liganded by either natural (15d-PGJ 2 and PGD 2 ) or synthetic ligands (BRL49653 and troglitazone), selectively inhibited expression of the cyclin D1 gene. The inhibition of S-phase entry and activity of the cyclin D1-dependent serine-threonine kinase (Cdk) by 15d-PGJ 2 was not observed in PPAR␥-deficient cells. Cyclin D1 overexpression reversed the S-phase inhibition by 15d-PGJ 2 . Cyclin D1 repression was independent of IKK, as prostaglandins (PGs) which bound PPAR␥ but lacked the IKK interactive cyclopentone ring carbonyl group repressed cyclin D1. Cyclin D1 repression by PPAR␥ involved competition for limiting abundance of p300, directed through a c-Fos binding site of the cyclin D1 promoter. 15d-PGJ 2 enhanced recruitment of p300 to PPAR␥ but reduced binding to c-Fos. The identification of distinct pathways through which eicosanoids regulate anti-inflammatory and antiproliferative effects may improve the utility of COX2 inhibitors.The peroxisome proliferator-activated receptor ␥ (PPAR␥) is a member of the nuclear receptor superfamily that mediates adipocyte differentiation (61), exerts anti-inflammatory effects in monocyte/macrophages (29, 50), modulates insulin sensitivity, and inhibits cellular proliferation (5). PPAR␥ exhibits a modular structure with a central DNA-binding domain, an amino-terminal activation domain (AF-1), a carboxyl-terminal ligand-binding domain (LBD), and a ligand-dependent activation domain (AF-2). The natural ligands for PPAR␥ include a series of fatty acids such as linoleic acid, eicosanoid derivatives, and synthetic ligands called thiazolidinediones (TZDs) (22-34). The eicosanoid 15-deoxy-⌬ 12,14 prostaglandin J 2 (15d-PGJ 2 ) is a naturally occurring and potent PPAR␥ ligand, binding and activating PPAR␥ activity at micromolar concentrations. The TZDs were the first identified synthetic PPAR␥ ligands and bound with high affinity (K d of 40 nM). A serine residue within the N-terminal AF-1 domain (Ser 82 in PPAR␥1 and Ser 112 in PPAR␥2) is phosphorylated in vitro by mitogenactivated protein kinase (MAPK) (1,28,57). Mutation of this MAPK phosphorylation site negatively regulated the transcriptional and biological functi...

Choroidal thickness increases after short-term ortho-k treatment. Regional choroidal thickening after ortho-k treatment may be attributable to the altered retinal defocus profile associated with ortho-k lens wear.

Subjects with larger magnitude of corneal relative peripheral power change along specific axes after OK treatment experienced slower axial elongation by the end of 24 months. This effect might be mediated by the induction of greater amount of relative myopic defocus on the peripheral retina. Our study lends weight to potential OK lens designs for myopia control in children.

No abstract

ABSTRACT:UDP-glucuronosyltransferase (UGT) 1A4-catalyzed glucuronidation is an important drug elimination pathway. Although atypical kinetic profiles (nonhyperbolic, non-Michaelis-Menten) of UGT1A4-catalyzed glucuronidation have been reported occasionally, systematic kinetic studies to explore the existence of multiple aglycone binding sites in UGT1A4 have not been conducted. To this end, two positional isomers, dihydrotestosterone (DHT) and trans-androsterone (t-AND), were used as probe substrates, and their glucuronidation kinetics with HEK293-expressed UGT1A4 were evaluated both alone and in the presence of a UGT1A4 substrate [tamoxifen (TAM) or lamotrigine (LTG)]. Coincubation with TAM, a high-affinity UGT1A4 substrate, resulted in a concentrationdependent activation/inhibition effect on DHT and t-AND glucuronidation, whereas LTG, a low-affinity UGT1A4 substrate, noncompetitively inhibited both processes. The glucuronidation kinetics of TAM were then evaluated both alone and in the presence of different concentrations of DHT or t-AND. TAM displayed substrate inhibition kinetics, suggesting that TAM may have two binding sites in UGT1A4. However, the substrate inhibition kinetic profile of TAM became more hyperbolic as the DHT or t-AND concentration was increased. Various two-site kinetic models adequately explained the interactions between TAM and DHT or TAM and t-AND. In addition, the effect of TAM on LTG glucuronidation was evaluated. In contrast to the mixed effect of TAM on DHT and t-AND glucuronidation, TAM inhibited LTG glucuronidation. Our results suggest that multiple aglycone binding sites exist within UGT1A4, which may result in atypical kinetics (both homotropic and heterotropic) in a substrate-dependent fashion.

No abstract

Surfactant deficiency contributes to acute lung injury and may result from the elaboration of bioactive lipids such as oxysterols. We observed that the oxysterol 22-hydroxycholesterol (22-HC) in combination with its obligate partner, 9-cis-retinoic acid (9-cis-RA), decreased surfactant phosphatidylcholine (PtdCho) synthesis by increasing phosphorylation of the regulatory enzyme CTP:phosphocholine cytidylyltransferase-␣ (CCT␣). Phosphorylation of CCT␣ decreased its activity. 22-HC/ 9-cis-RA inhibition of PtdCho synthesis was blocked by PD98059 or dominant-negative ERK (p42 kinase). Overexpression of constitutively active MEK1, the kinase upstream of p42 kinase, increased CCT␣ phosphorylation. Expression of truncated CCT␣ mutants lacking prolinedirected sites within the C-terminal phosphorylation domain partially blocked oxysterol-mediated inhibition of PtdCho synthesis. Mutagenesis of Ser315 within CCT␣ was both required and sufficient to confer significant resistance to 22-HC/9-cis-RA inhibition of PtdCho synthesis. A novel putative ERK-docking domain N-terminal to this phosphoacceptor site was mapped within the CCT␣ membrane-binding domain (residues 287-300). The results are the first demonstration of a physiologically relevant phosphorylation site and docking domain within CCT␣ that serve as targets for ERKs, resulting in inhibition of surfactant synthesis.