15-Deoxy-Δ12,14-prostaglandin J2 modulates manganese-induced activation of the NF-κB, Nrf2, and PI3K pathways in astrocytes

Excessive exposure to manganese (Mn) increases levels of oxidative stressors and proinflammatory mediators, such as cyclooxygenase-2 and prostaglandin E-2. Mn also activates nuclear factor-kappa B (NF-kappa B), an important mediator of inflammation. The signaling molecule 15-deoxy-Delta 12,14-prostaglandin J(2) (15 d-PGJ(2)) is an anti-inflammatory prostaglandin. Here, we tested the hypothesis that 15 d-PGJ2 modulates Mn-induced activation of astrocytic intracellular signaling, including NF-kappa B and nuclear factor erythroid 2-related factor (Nrf2), a master regulator of antioxidant transcriptional responses. The results establish that 15 d-PGJ2 suppresses Mn-induced NF-kappa B activation by interacting with several signaling pathways. The PI3K/Akt pathway, which is upstream of NF-kappa B, plays a role in this activation, because (i) pretreatment with 15 d-PGJ2 (10 mu M for 1 h) significantly (p<0.01) inhibited Mn (500 mu M)-induced PI3K/Akt activation and (ii) inhibition of the PI3K/Akt pathway with LY29004 significantly (p<0.05) decreased NF-kappa B activation. 15 d-PGJ2 also significantly (p<0.05) attenuated Mn-induced astrocytic NF-kappa B activation by inhibiting the Mn-induced phosphorylation of I kappa B kinase and subsequent I kappa B-alpha degradation. Because Mn-induced oxidative stress is also associated with Nrf2 activation, additional studies addressed the ability of 15 d-PGJ(2) to modulate the Nrf2 pathway. 15 d-PGJ(2) significantly (p<0.01) increased Nrf2 expression in whole-cell lysates. Consistent with its pro-oxidant properties, Mn also increased Nr12 expression. Nevertheless, cotreatment of whole-cell lysates with both Mn and 15 d-PGJ(2) partially suppressed (p<0.01) the 15 d-PGJ(2)-induced increase in astrocytic Nrf2 protein expression. Mn treatment also decreased (p<0.001) expression of DJ-1, a Parkinson disease-associated protein and a stabilizer of Nrf2, and 15 d-PGJ(2) attenuated Mn-induced astrocytic inhibition of DJ-1 expression. Collectively, these results demonstrate that 15 d-PGJ(2) exerts a protective effect in astrocytes against Mn-induced inflammation and oxidative stress by modulating the activation of the NF-kappa B and Nrf2 signaling pathways. (C) 2011 Elsevier Inc. All rights reserved.