Induction of heme oxygenase-1 by chamomile protects murine macrophages against oxidative stress

Aims: Protection of cells from oxidative insult may be possible through direct scavenging of reactive oxygen species, or through stimulation of intracellular antioxidant defense mechanisms by induction of antioxidant gene expression. In this study we investigated the cytoprotective effect of chamomile and elucidated the underlying mechanisms. Main methods: The cytoprotective effect of chamomile was examined on H2O2-induced cellular stress in RAW 264.7 murine macrophages. Key findings: RAW 264.7 murine macrophages treated with chamomile were protected from cell death caused by H2O2. Treatment with 50 mu M H2O2 for 6 h caused significant increase in cellular stress accompanied by cell death in RAW 264.7 macrophages. Pretreatment with chamomile at 10-20 mu g/mL for 16 h followed by H2O2 treatment protected the macrophages against cell death. Chamomile exposure significantly increased the expression of antioxidant enzymes viz. heme oxygenase-1 (HO-1), peroxiredoxin-1 (Prx-1), and thioredoxin-1 (Trx-1) in a dose-dependent manner, compared with their respective controls. Chamomile increased nuclear translocation of Nrf2 with increased phosphorylated Nrf2 levels, and binding to the antioxidant response element in the nucleus. Significance: These molecular findings for the first time provide insights into the mechanisms underlying the induction of phase 2 enzymes through the Keap1-Nr12 signaling pathway by chamomile, and provide evidence that chamomile possesses antioxidant and cytoprotective properties. (c) 2012 Elsevier Inc. All rights reserved.