Induction of Heme Oxygenase-1 Expression in Macrophages by Diesel Exhaust Particle Chemicals and Quinones via the Antioxidant-Responsive Element

Abstract

Diesel exhaust particles (DEP) contain organic chemicals that contribute to the adverse health effects of inhaled particulate matter. Because DEP induce oxidative stress in the lung and in macrophages, effective antioxidant defenses are required. One type of defense is through the expression of the antioxidant enzyme, heme oxygenase I (HO-1). HO-1 as well as phase II detoxifying enzymes are induced via antioxidant response elements (ARE) in their promoters of that gene. We show that a crude DEP total extract, aromatic and polar DEP fractions, a benzo(a)pyrene quinone, and a phenolic antioxidant induce HO-1 expression in RAW264.7 cells in an ARE-dependent manner. N-acetyl cysteine and the flavonoid, luteolin, inhibited HO-1 protein expression. We also demonstrate that the same stimuli induce HO-1 mRNA expression in parallel with the activation of the SX2 enhancer of that gene. Mutation of the ARE core, but not the overlapping AP-1 binding sequence, disrupted SX2 activation. Finally, we show that biological agents, such as oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, could also induce HO-1 expression via an ARE-dependent mechanism. Prior induction of HO-1 expression, using cobalt-protoporphyrin, protected RAW264.7 cells against DEP-induced toxicity. Taken together, these data show that HO-1 plays an important role in cytoprotection against redox-active DEP chemicals, including quinones.

Comparison of the Pro-Oxidative and Proinflammatory Effects of Organic Diesel Exhaust Particle Chemicals in Bronchial Epithelial Cells and Macrophages

“…The combined extracts were concentrated by rotoevaporation, and asphaltenes were precipitated by exchanging into hexane. The supernatant was concentrated, dried over anhydrous sodium sulfate, and subjected to silica gel column chromatography (column size, 1 ϫ 30 cm) following the method of Venkatessan et al (11). Aliphatic, aromatic, and polar fractions were collected by elution with 20 ml hexane, 40 ml hexane/methylene chloride (3/2), and 30 ml methylene chloride/methanol (1/1), respectively.…”

“…Preparation of DEP fractions was conducted as previously described (11). Briefly, 1 g DEP was extracted with 60 ml methylene chloride five times using a VirTis homogenizer (Gardiner, NY).…”

“…Our interest lies with the PAH and their oxygenated derivatives (e.g., quinones), which are able to redox cycle and generate reactive oxygen species (ROS) in target cell populations such as macrophages (8, 14 -19). The pro-oxidative effects of intact DEP or crude DEP extracts can be reproduced with fractionated aromatic and polar chemical groups, which are enriched for PAH and quinones, respectively (11)(12)(13)(14)20). Similarly, intact DEP or organic DEP extracts induce pro-oxidative and proinflammatory effects in the respiratory tract, which can be negated by thiol antioxidants (10,16).…”

“…Thus, at low oxidative stress levels, as defined by no or minimal change in the cellular reduced glutathione (GSH)/glutathione disulfide (GSSG) ratios, these cells mount antioxidant and cytoprotective responses, e.g., heme oxygenase 1 (HO-1) and superoxide dismutase expression (24). HO-1 expression is dependent on the function of antioxidant response element (ARE) in its promoter (11) and is typically induced by 1-10 g/ml of the DEP extract (11,24). In contrast, extract doses of 10 -50 g/ml are required to activate intracellular pathways, such as the c-Jun N-terminal kinase (JNK) and NF-B cascades, which are responsible for proinflammatory effects (24).…”

Diesel exhaust particles disturb gene expression in mouse testis

“…The DEP consisted of large quantities of carbonaceous particles which absorbed a variety of organic compounds, such as polycyclic aromatic hydrocarbons (World Health Organization, 1996;Li et al, 2000). All the mice were divided into three groups: a high-DEPdose group (H-DEP), a low-DEP-dose group (L-DEP), and a control group.…”