MAP Kinase Cascades Are Activated in Astrocytes and Preadipocytes by 15-Deoxy-Δ12–14-prostaglandin J2 and the Thiazolidinedione Ciglitazone through Peroxisome Proliferator Activator Receptor γ-independent Mechanisms Involving Reactive Oxygenated Species

Abstract

15-Deoxy-⌬12-14 -prostaglandin J 2 (dPGJ2) and thiazolidinediones are known as ligands for the peroxisome proliferator activator receptor ␥ (PPAR␥) a member of the nuclear receptor superfamily. Herein, we show that dPGJ2 activates, in cultured primary astrocytes, Erk, Jnk, p38 MAP kinase, and ASK1, a MAP kinase kinase kinase, which can be involved in the activation of Jnk and p38 MAP kinase. The activation kinetic is similar for the three MAP kinase. The activation of the MAP kinases is detectable around 0.5 h. The activation increases with dPGJ2 in a dose dependent manner (0 -15 M). A scavenger of reactive oxygenated species (ROS), N-acetylcysteine (NAC) at 20 mM, completely suppresses the activation of MAP kinases and ASK1, suggesting a role for oxidative stress in the activation mechanism. Other prostaglandin cyclopentenones than dPGJ2, A 2 , and to a lesser degree, A 1 also stimulate the MAP kinases, although they do not bind to PPAR␥. Ciglitazone (20 M), a thiazolidinedione that mimics several effects of dPGJ2 in different cell types, also activates the three MAP kinase families and ASK1 in cultured astrocytes. However the activation is more rapid (it is detectable at 0.25 h) and more sustained (it is still strong after 4 h). NAC prevents the activation of the three MAP kinase families by ciglitazone. Another thiazolidinedione that binds to PPAR␥, rosiglitazone, does not activate MAP kinases, indicating that the effect of ciglitazone on MAP kinases is independent of PPAR ␥. Ciglitazone and less strongly dPGJ2 activate Erk in undifferentiated cells of the adipocyte cell line 1B8. Ciglitazone also activates Jnk and p38 MAP kinase in these preadipocytes. Our findings suggest that a part of the biological effects of dPGJ2 and ciglitazone involve the activation of the three MAP kinase families probably through PPAR␥-independent mechanisms involving ROS. 15-Deoxy-⌬12-14 -prostaglandinJ2 (dPGJ2) 1 has been shown to bind and to activate peroxisome proliferator-activated receptor ␥ (PPAR␥). This receptor, a member of the ligand-regulated nuclear receptor family, is a molecular target of the thiazolidinedione class of antidiabetic drugs (1, 2), including ciglitazone, pioglitazone, and rosiglitazone. This receptor has a critical role in adipogenesis, glucose metabolism, placental function, and macrophage functions (3-5). It has been suggested that much of the effects of dPGJ2 and thiazolidinediones may be mediated by this receptor. However, Rossi et al. (6) have shown that dPGJ2 also can directly inhibit the IKK␤ subunit of IKK, the protein kinase responsible for the activation of NFB by proinflammatory stimuli. This effect of dPGJ2 can be mimicked by other prostaglandin cyclopentenones and is clearly independent of PPAR␥. dPGJ2 also activates Erk cascade in mesangial cells in a manner probably independent of PPAR␥ as ciglitazone does not mimic this effect (7).In the cellular model studied by our group, rat cultured astrocytes, which express PPAR␥, we observed (this paper) 2 that dPGJ2 promotes apoptosis and prevents...

15-PGJ2, but not thiazolidinediones, inhibits cell growth, induces apoptosis, and causes downregulation of Stat3 in human oral SCCa cells

“…Similarly, Ward et al (2002) recently showed that 15-PGJ 2 exploits PPARg-independent inhibition of NF-kB activation to induce caspase-dependent apoptosis in granulocytes. Other mediators that have been implicated in PPARg-independent properties of 15-PGJ 2 and can potentially have a similar function in cancer cells include AP-1 (Boyault et al, 2001), MAP kinase (Harris et al, 2002;Lennon et al, 2002), and reactive oxygen species (Li et al, 2001;Lennon et al, 2002). The latter has been shown to act as intermediates for the induction of apoptosis caused by 15-PGJ 2 in human myofibroblasts (Li et al, 2001).…”

Troglitazone inhibits cell proliferation by attenuation of epidermal growth factor receptor signaling independent of peroxisome proliferator-activated receptor γ

“…Previous studies have shown that PPARγ agonists can cause rapid MAPKs activation or Akt inhibition in multiple cell types [25,[39][40][41]], yet their interrelationship has not been fully addressed. We have demonstrated that, like many other non-natural ligands that transactivate EGFR signaling [42], TGZ can cause rapid, EGFRdependent transient Erk1/2 activation, which has an absolute requirement for Grb2 binding to EGFR.…”

Ciglitazone mediates COX-2 dependent suppression of PGE2 in human non-small cell lung cancer cells

“…However while TZDs are widely known as ligands for PPARγ, they may mediate receptorindependent effects as previously demonstrated [28]. For example, by utilizing the embryonic stem cells from PPARγ null mice, Chawla et al found that neither macrophage differentiation nor anti-inflammatory effects of synthetic PPARγ ligands are PPARγ receptor dependent [29].…”

“…For example, by utilizing the embryonic stem cells from PPARγ null mice, Chawla et al found that neither macrophage differentiation nor anti-inflammatory effects of synthetic PPARγ ligands are PPARγ receptor dependent [29]. In addition ciglitazone was found to activate MAP kinase cascades in astrocytes and preadipocytes through PPARγ independent mechanisms [28]. In order to understand whether the suppression of COX-2 and PGE2 by ciglitazone is PPARγ dependent in NSCLC, we performed experiments utilizing a dn.…”