title: Ethyl pyruvate-mediated Nrf2 activation and hemeoxygenase 1 induction in astrocytes confer protective effects via autocrine and paracrine mechanisms.
abstract: Ethyl pyruvate (EP), a simple ester of pyruvic acid, has been shown to act as an anti-inflammatory molecule under various pathological conditions, such as, during cerebral ischemia and sepsis in animal models. Here, the authors investigated the novel molecular mechanism underlying the anti-oxidative effect of EP in primary astrocyte cultures, particularly with respect to nuclear factor E2-related factor 2 (Nrf2) activation and hemeoxygenase 1 (HO-1) induction. EP was found to induce Nrf2 translocation and the inductions of various genes downstream of Nrf2 and these resulted in the amelioration of the oxidative damage of H(2)O(2). Furthermore, EP dose-dependently suppressed H(2)O(2)-induced astrocyte cell death (12h preincubation with 5mM EP increased cell survival after 1h exposure to 100 μM H(2)O(2) from 32.6±0.7% to 63±1.8%). HO-1 was markedly induced (4.9-fold) in EP-treated primary astrocyte cultures and Nrf2 was found to translocate from the cytosol to the nucleus and bind to the antioxidant response element (ARE) located on HO-1 promoter after EP treatment. siRNA-mediated HO-1 or Nrf2 knockdown and zinc protoporphyrin (ZnPP)-mediated inhibition of HO-1 activity showed that Nrf2 activation and HO-1 induction were responsible for the observed cytoprotective effect of EP, which was found to involve the ERK and Akt signaling pathways. Furthermore, EP-conditioned astrocyte culture media was found to have neuroprotective effects on primary neuronal cultures exposed to oxidative or excitotoxic stress, and this seemed to be mediated by glial cell line-derived neurotrophic factor (GDNF) and glutathione (GSH), which accumulated in EP-treated astrocyte culture media. Interestingly, we also found that in addition to HO-1, EP-induced Nrf2 activation increased the expressions of various anti-oxidant genes, including GST, NQO1, and GCLM. The study shows that EP-mediated Nrf2 activation and HO-1 induction in astrocytes act via autocrine and paracrine mechanisms to confer protective effects.
authors.affiliation: Department of Anatomy, Center for Advanced Medical Education (BK21 Project), Inha University School of Medicine, Inchon, Republic of Korea.
authors.forename: Joo-Hyun
authors.initials: JH
authors.lastname: Shin
authors.forename: Seung-Woo
authors.initials: SW
authors.lastname: Kim
authors.forename: Yinchuan
authors.initials: Y
authors.lastname: Jin
authors.forename: Il-Doo
authors.initials: ID
authors.lastname: Kim
authors.forename: Ja-Kyeong
authors.initials: JK
authors.lastname: Lee
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D003470:Culture Media; D004790:Enzyme Induction; D005978:Glutathione / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000096:biosynthesis*; D006801:Humans; D008297:Male; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D011773:Pyruvates / Q000494:pharmacology*; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
chemical_list: D003470:Culture Media; D051267:NF-E2-Related Factor 2; C495637:Nfe2l2 protein, rat; D011773:Pyruvates; C046522:ethyl pyruvate; D051547:Heme Oxygenase-1; D005978:Glutathione