Abstract
The lipid peroxidation product 4-hydroxynonenal (4-HNE) forms as a consequence of oxidative stress. By electrophilic attack on biological macromolecules, 4-HNE mediates signaling or may cause toxicity. A major route of 4-HNE disposal is via glutathione conjugation, in the mouse catalyzed primarily by glutathione transferase mGSTA4-4. Unexpectedly, mGsta4-null mice, in which 4-HNE detoxification is impaired, have an extended life span. This finding could be explained by the observed activation of the transcription factor Nrf2 in the knockout mice, which in turn leads to an induction of antioxidant and antielectrophilic defenses. Especially, the latter could provide a detoxification mechanism that contributes to enhanced longevity. We propose that disruption of 4-HNE conjugation elicits a hormetic response in which an initially increased supply of 4-HNE is translated into activation of Nrf2, leading to a new steady state in which the rise of 4-HNE concentrations is dampened, but life-extending detoxification mechanisms are concomitantly induced.