Secoisolariciresinol diglucoside reduces cell death and upregulates antioxidants in cardiac iron overload

Abstract

Iron is essential to many biological and metabolic processes used in all organisms, but excess iron can result in complications such as cirrhosis, diabetes, and heart failure. Cardiac iron overload has been linked to increased oxidative stress and cell death. Oxidative stress has been shown to play a role in cardiovascular diseases. Antioxidants can counter the effect of oxidative stress by scavenging reactive oxygen species. Protein kinase B (Akt) promotes cell survival by regulating growth, antioxidant production, and cell death in cardiomyoctes. The aim of this study was to examine the cardioprotective role of secoisolariciresinol diglucoside (SDG), a phytochemical extracted from flax seeds, in an in vitro cardiac iron overload condition. H9c2 cardiac cells were incubated with 50 μM iron for either 6, 12 or 24 hours and/or received a SDG pretreatment of 250 μM or 500 μM for 24 hours. Flow cytometry was used to assess necrotic cells and changes in the mitochondrial membrane potential. Western blot was used to determine the protein expression of antioxidants (manganese superoxide dismutase and catalase) and redox sensitive proteins, 5’AMP-activated protein kinase (AMPK), signal transducer and activator of transcription 3 (STAT3), Akt, and the mammalian target of rapamycin (mTOR). Pretreatment of SDG reduced the amount of necrotic cells (24.3%) after iron treatment. Pretreatment of SDG resulted in increased protein expression of catalase after 24 hours of iron treatment, and increased activity of AMPK and STAT3 after 12 hours of iron treatment. Akt activity and 4-hydroxynonenal (4HNE) levels were decreased after 6 hours of iron treatment when pretreated with SDG. This study demonstrates that SDG can act as an antioxidant by attenuating cell death, oxidative stress, and increasing the level of intrinsic antioxidants.