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Exogenous toxicants (e.g. arsenic, cigarette smoke), trigger oxidative stress, and initiate the pathogenesis of many human diseases. Induction of nuclear factor E2-related factor 2 (Nrf2) counteracts exogenous toxicant-induced oxidative insults. Using a high-throughput screen, we firstly identified a citrus polymethoxyflavone, (2S)-5,6,7,3′,4′-pentamethoxyflavanone (PMF), to be an Nrf2 activator, and an investigation targeting Nrf2 pathway was performed. Our study indicated that: (i) PMF activated Nrf2 and its downstream genes, NQO1 and γ-GCS, and enhanced the stabilization of Nrf2 through inhibiting Nrf2 ubiquitination. (ii) Inhibition of PI3K, p38 MAPK, PKC and PERK by specific kinase inhibitors suppressed PMF-induced activation of Nrf2. (iii) PMF conferred Nrf2-dependent protection against sodium arsenite- and cigarette smoke extract- induced cytotoxicity in lung epithelial cells. Collectively, our data demonstrate that PMF is a novel Nrf2 activator with potential prevention against oxidative insults. The diverse pharmacological functions of citrus polymethoxyflavone might be related to their ability of activating Nrf2 pathway.

Human lung tissue, directly exposed to the environmental oxidants and toxicants, is apt to be harmed to bring about acute or chronic oxidative insults. The nuclear factor erythroid 2-related factor 2 (Nrf2) represents a central cellular defense mechanism, and is a target for developing agents against oxidative insult-induced human lung diseases. Our previous study found that the EtOH extract of Cinnamomum chartophyllum protected human bronchial epithelial cells against oxidative insults via Nrf2 activation. In this study, a systemic phytochemical investigation of the aerial parts of C. chartophyllum led to the isolation of thirty chemical constituents, which were further evaluated for their Nrf2 inducing potential using NAD(P)H: quinone reductase (QR) assay. Among these purified constituents, a sesquiterpenoid bearing α, β-unsaturated ketone group, 3S-(+)-9-oxonerolidol (NLD), and a diphenyl sharing phenolic groups, 3, 3â², 4, 4â²-tetrahydroxydiphenyl (THD) significantly activated Nrf2 and its downstream genes, NAD(P)H quinone oxidoreductase 1 (NQO-1), and γ-glutamyl cysteine synthetase (γ-GCS), and enhanced the nuclear translocation and stabilization of Nrf2 in human lung epithelial cells. Importantly, NLD and THD had no toxicities under the Nrf2 inducing doses. THD also demonstrated a potential of interrupting Nrf2-Keap1 proteinâprotein interaction (PPI). Furthermore, NLD and THD protected human lung epithelial cells against sodium arsenite [As(III)]-induced cytotoxicity. Taken together, we conclude that NLD and THD are two novel Nrf2 activators with potential application of preventing acute and chronic oxidative insults in human lung tissue. Keywords: Cinnamomum chartophyllum, Nrf2 activator, Arsenic, Oxidative insult

Background: Chronic obstructive pulmonary disease (COPD) is a major public health problem and gives arise to severe chronic morbidity and mortality in the world. Inflammatory response and oxidative stress play dominant roles in the pathological mechanism of COPD, and have been regarded to be two important targets for the COPD therapy. Traditional Chinese medicines (TCMs) possess satisfying curative effects on COPD under guidance of the TCM theory in China, and merit in-depth investigations as a resource of lead compounds. Methods: One hundred ninety-six of TCMs were collected, and extracted to establish a TCM extract library, and then further evaluated for their potency on inhibitions of oxidative stress and inflammatory response using NADP(H):quinone oxidoreductase (QR) assay and nitric oxide (NO) production assay, respectively. Results: Our investigation observed that 38 of the tested TCM extracts induced QR activity in hepa 1c1c7 murine hepatoma cells, and 55 of them inhibited NO production in RAW 264.7 murine macrophages at the tested concentrations. Noteworthily, 20 of TCM extracts simultaneously inhibited oxidative stress and inflammatory responses. Conclusion: The observed bioactive TCMs, particularly these 20 TCMs with dual inhibitory effects, might be useful for the treatment of COPD. More importantly, the results of the present research afford us an opportunity to discover new lead molecules as COPD therapeutic agents from these active TCMs. [ABSTRACT FROM AUTHOR]