4-Hydroxynonenal

4-Hydroxynonenal, or 4-hydroxy-2-nonenal or 4-HNE or HNE, (C₉H₁₆O₂), is an α,β-unsaturated hydroxyalkenal which is produced by lipid peroxidation in cells. 4-HNE is the primary alpha,beta-unsaturated hydroxyalkenal formed in this process.

4-HNE has 3 reactive groups: an aldehyde, a double-bond at carbon 2, and a hydroxy group at carbon 4.

It is found throughout animal tissues, and in higher quantities during oxidative stress due to the increase in the lipid peroxidation chain reaction, due to the increase in stress events.

4-HNE has been hypothesized by several researchers to play a key role in cell signal transduction, in a variety of pathways from cell cycle events to cellular adhesion.