AHP1251 recognises 4-hydroxynonenal (HNE). A 65 kDa, highly reactive aldehyde released upon oxidation of omega-6-insaturated fatty acids, often by free radicals. HNE acts to spread and increase the initial effects of free radical events. It binds nucleic acids, phospholipids and sulfhydryl, histidine and lysine groups. These conjugates cause the cytotoxic effects (including cell death) that occur during oxidative stress due to hydrogen peroxide, superoxide, UV, heat and oxidant chemicals. HNE plays a role in the pathogenesis of diseases, stimulating fibrogenesis and inflammation. It is thought to act as a sensor of external stimuli, inducing the stress response by modulating membrane receptors such as Epidermal growth factor receptor or Fas. It is thought that constitutive levels of HNE may be needed for normal cell functions as decreased HNE levels are associated with cell proliferation and increased HNE levels with elevated apoptosis.