Activation of Nrf2 by Lipid Peroxidation Products

Aldehydic products of lipid peroxidation, such as 4-hydroxy-trans-2-nonenal (HNE), are generated during oxidative stress and are associated with the onset and progression of cardiovascular disease. The transcription factor NF-E2 related factor (Nrf2) coordinates expression of antioxidant and detoxification genes (phase 2 genes) that constitute a cellular defense that scavenges reactive oxygen species, detoxifies electrophiles, and maintains intracellular reducing potential. Thus, we hypothesized that lipid peroxidation products, such as HNE, would feedback to stimulate the phase 2 response by activation of Nrf2. After rat aortic smooth muscle cells (RASMs) were exposed to HNE, the translocation of Nrf2 to the nucleus and the expression of genes that are transcriptionally driven by Nrf2 were measured by Western blot analysis. Exposure of RASMs to 25 µM HNE for 6h resulted in a two-fold increase in Nrf2 nuclear translocation and an 18-fold increase in production of the well-studied phase 2 response enzyme, heme oxygenase-1 (p\u3c0.05). Additionally, intracellular glutathione levels, as measured by spectrophotometric assay, were significantly increased after 6 h of stimulation. Inhibition of aldose reductase, an efficient HNE metabolizing enzyme, by tolrestat resulted in an increase in Nrf2 nuclear translocation, underscoring the sensitivity of the phase 2 response by lipid peroxidation products. Taken together, these data indicate that lipid peroxidation products are potent activators of the Nrf2-driven phase 2 response and, therefore, may play a role in the pathological development of cardiovascular disease