Arsenic-Induced Inflammatory Response via ROS-Dependent Activation of ERK/NF-kB Signaling Pathways: Protective Role of Natural Polyphenol Tannic Acid.

Abstract

Arsenic (As), a highly toxic metalloid, is present throughout our environment as a result of both natural and human-related activities. Furthermore, As exposure could lead to a persistent inflammatory response, which may facilitate the pathogenesis of several diseases in various organs. This study was performed to investigate the As-induced inflammatory response and the underlying molecular mechanisms in vitro. Further, the anti-inflammatory effects of a natural dietary polyphenol tannic acid (TA) were also explored. In human normal bronchial (BEAS-2B), adenocarcinoma alveolar basal (A549), and murine macrophages (J774) cell lines, a trivalent form of As (as As³⁺) exposure markedly induced the expression of various pro-inflammatory mediators (cytokines and chemokines). Additionally, it was found that As³⁺ exposure induced reactive oxygen species (ROS) generation and activation of the nuclear factor-kappa B (NF-kB) p65 and extracellular signal-regulated kinase (ERK)1/2 pathways in BEAS-2B cells. As expected, the blockade of either ERK1/2 (PD98059) or NF-kB p65 (IMD0354), or both pathways attenuated As³⁺-induced pro-inflammatory mediators release. Interestingly, pre-treatment with ROS inhibitor N-acetylcysteine (NAC) attenuated activation of ERK/NF-kB pathways, suggesting that ROS have a critical role in pathway's activation and subsequent inflammatory response. Further, TA pre-treatment effectively attenuated As³⁺-induced inflammatory response by suppressing ROS production and ERK/NF-kB signaling pathways activation. Therefore, this study provides scientific evidence for the anti-inflammatory activities of TA and the underlying molecular mechanisms.