Carcinogenesis 2015 December 17 [Epub ahead of print] [Link]
Pietrofesa RA, Velalopoulou A, Arguiri E, Menges CW, Testa JR, Hwang WT, Albelda SM, Christofidou-Solomidou M.
Malignant mesothelioma (MM), linked to asbestos exposure, is a highly lethal form of thoracic cancer with a long latency period, high mortality and poor treatment options. Chronic inflammation and oxidative tissue damage caused by asbestos fibers are linked to MM development. Flaxseed lignans, enriched in secoisolariciresinol diglucoside (SDG), have antioxidant, anti-inflammatory and cancer chemopreventive properties. As a prelude to chronic chemoprevention studies for MM development, we tested the ability of flaxseed lignan component (FLC) to prevent acute asbestos-induced inflammation in MM-prone Nf2+/mu mice. Mice (n=16-17 per group) were placed on control (CTL) or FLC-supplemented diets initiated 7 days prior to a single intraperitoneal bolus of 400 μg of crocidolite asbestos. Three days post-asbestos exposure, mice were evaluated for abdominal inflammation, proinflammatory/profibrogenic cytokine release, WBC gene expression changes, and oxidative and nitrosative stress in peritoneal lavage fluid (PLF). Asbestos-exposed mice fed CTL diet developed acute inflammation, with significant (p<0.0001) elevations in WBCs and proinflammatory/profibrogenic cytokines (IL-1β, IL-6, TNFα, HMGB1 and active TGFβ1) relative to baseline (BL) levels. Alternatively, asbestos-exposed FLC-fed mice had a significant (p<0.0001) decrease in PLF WBCs and proinflammatory/profibrogenic cytokine levels relative to CTL-fed mice. Importantly, PLF WBC gene expression of cytokines (IL-1β, IL-6, TNFα, HMGB1 and TGFβ1) and cytokine receptors (TNFαR1, and TGFβR1) were also down-regulated by FLC. FLC also significantly (p<0.0001) blunted asbestos-induced nitrosative and oxidative stress. FLC reduces acute asbestos-induced peritoneal inflammation, nitrosative and oxidative stress, and may thus prove to be a promising agent in the chemoprevention of MM.