Modulation of Keratinocyte Gene Expression and Differentiation by PPAR-Selective Ligands and Tetradecylthioacetic Acid

Abstract

Peroxisome proliferator-activated receptors (PPARs) are pleiotropic regulators of growth and differentiation of many cell types. We have performed a comprehensive analysis of the expression of PPARs, transcriptional cofactors, and marker genes during differentiation of normal human keratinocytes using a combination of reverse transcriptase polymerase chain reaction, Northern and Western blotting, and immunohistochemistry. PPARdelta was the predominant PPAR subtype in human keratinocytes and highly expressed in basal cells and suprabasal cells. Induction of PPARalpha and PPARgamma expression was linked to differentiation, and accordingly, expression of PPARalpha and PPARgamma was in essence confined to suprabasal cells. Differentiation was not accompanied by significant changes in the expression of the coactivators CREB-binding protein, p300, steroid receptor coactivator 1, or the corepressors nuclear receptor corepressor and silence mediator for retinoid and thyroid hormone receptors. We critically evaluated the effects of selective PPAR ligands and a synthetic fatty acid analog, tetradecylthioacetic acid. Tetradecylthioacetic acid activated all human PPAR subtypes in the ranking order PPARdelta >> PPARalpha > PPARgamma. All selective PPAR ligands marginally induced transglutaminase-1 expression with the PPARdelta-selective ligand L165041 being the most potent. The PPARalpha- and PPARgamma-selective ligands Wy14643 and BRL49653 had negligible effect on involucrin expression, whereas a dose-dependent induction was observed with L165041. Simultaneous addition of L165041 and BRL49653 synergistically induced strong involucrin expression. Additionally, L165041 potently induced CD36 mRNA expression. Administration of tetradecylthioacetic acid resulted in a dramatic decrease in proliferation and a robust upregulation of the expression of involucrin and transglutaminase. Our results indicate that tetradecylthioacetic acid may affect keratinocyte gene expression and differentiation via PPAR-dependent and PPAR-independent pathways, and that the latter play an important role.

Peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) ligands inhibit growth of UACC903 and MCF7 human cancer cell lines

“…These observations are consistent with recent findings made in other human cancer cell lines (Hollingshead et al 2007a), as well as numerous reports linking PPARβ/δ with inducing terminal differentiation and/or inhibiting cell growth (Ali et al 2005;Aung et al 2006;Burdick et al 2007;Fukumoto et al 2005;Hollingshead et al 2007a;Kim et al 2004;Kim et al 2006;Kim et al 2005;Man et al 2007;Marin et al 2006;Martinasso et al 2006;Matthiessen et al 2005;Michalik et al 2001;Müller-Brüsselbach et al 2007;Nadra et al 2006;Ou et al 2007;Peters et al 2000;Planavila et al 2005;Schmuth et al 2004;Tan et al 2001;Teunissen et al 2007;Varnat et al 2006;Westergaard et al 2001). The relatively modest activation of PPARβ/δ in both UACC903 and MCF7 cells as shown by increased mRNA encoding ANGPTL4 shows that these cells are not highly responsive to PPARβ/δ ligands as compared to other cells such as keratinocytes.…”

“…Anti-inflammatory activity of PPARβ/δ and/or PPARβ/δ ligands has been shown in a number of different models including immune cells, colon epithelium, macrophages, cardiomyocytes, keratinocytes, myoblasts, endothelial cells, nerve tissue and hepatocytes Graham et al 2005;Hollingshead et al 2007b;Jakobsen et al 2006;Kim et al 2006;Nagasawa et al 2006;Peters et al 2000;Polak et al 2005;Rival et al 2002;Schmuth et al 2004;Welch et al 2003;Woo et al 2006). There is also strong evidence that ligand activation of PPARβ/δ promotes terminal differentiation in intestinal epithelium, breast and colon cancer cell lines, trophoblasts and primary keratinocytes (Aung et al 2006;Burdick et al 2007;Kim et al 2006;Marin et al 2006;Nadra et al 2006;Schmuth et al 2004;Tan et al 2001;Varnat et al 2006;Westergaard et al 2001). Evidence from a large number of independent laboratories also shows that cell growth is inhibited by PPARβ/δ and its ligands in colonocytes, keratincytes, cardiomyocytes, fibroblasts, endothelial cells and a variety of cancer cell lines (Ali et al 2005;Aung et al 2006;Burdick et al 2007;Fukumoto et al 2005;Hollingshead et al 2007a;Kim et al 2004;Kim et al 2006;Kim et al 2005;Man et al 2007;Marin et al 2006;Martinasso et al 2006;Matthiessen et al 2005;Michalik et al 2001;Müller-Brüsselbach et al 2007;Nadra et al 2006;O...…”

“…There is also strong evidence that ligand activation of PPARβ/δ promotes terminal differentiation in intestinal epithelium, breast and colon cancer cell lines, trophoblasts and primary keratinocytes (Aung et al 2006;Burdick et al 2007;Kim et al 2006;Marin et al 2006;Nadra et al 2006;Schmuth et al 2004;Tan et al 2001;Varnat et al 2006;Westergaard et al 2001). Evidence from a large number of independent laboratories also shows that cell growth is inhibited by PPARβ/δ and its ligands in colonocytes, keratincytes, cardiomyocytes, fibroblasts, endothelial cells and a variety of cancer cell lines (Ali et al 2005;Aung et al 2006;Burdick et al 2007;Fukumoto et al 2005;Hollingshead et al 2007a;Kim et al 2004;Kim et al 2006;Kim et al 2005;Man et al 2007;Marin et al 2006;Martinasso et al 2006;Matthiessen et al 2005;Michalik et al 2001;Müller-Brüsselbach et al 2007;Nadra et al 2006;Ou et al 2007;Peters et al 2000;Planavila et al 2005;Schmuth et al 2004;Tan et al 2001;Teunissen et al 2007;Varnat et al 2006;Westergaard et al 2001). Given the potential of PPARβ/δ ligands as therapeutic agents, it is of great importance to determine the effect of ligand activation of PPARβ/δ on cell growth in vitro and in vivo.…”

Various peroxisome proliferator‐activated receptor (PPAR)‐γ agonists differently induce differentiation of cultured human keratinocytes

“…Interestingly, telmisartan tended to have similar effects to those of troglitazone; increased expression of filaggrin but not loricrin. In contrast, PPAR-c agonists showed no significant changes in undifferentiated NHKs, indicating that PPAR-c agonists act only on differentiated keratinocytes with PPAR-c expression, as shown previously (14).…”

Peroxisome proliferator-activated receptor-β/δ protects against chemically induced liver toxicity in mice

“…[9][10][11]21,24,35,41,[52][53][54][55][56][57][58][59][60][61][62] It is possible that PPAR␤/␦-dependent regulation of kinase signaling as found in skin cells, 24 is also critical in liver cells, and thus protects against enhanced cell proliferation. This putative PPAR␤/␦-dependent process could ultimately contribute to preventing liver cancer, as PPAR␤/␦-dependent regulation of cell proliferation is known to influence skin and colon cancer.…”