4-Hydroxynonenal (4-HNE) is primarily known for its role in cellular signaling and oxidative stress pathways. It acts as a mediator in various physiological and pathological processes due to its reactivity with proteins, DNA, and phospholipids. In research, 4-HNE is used as a biomarker for lipid peroxidation, helping scientists assess oxidative damage in cells and tissues, particularly in studies related to aging, neurodegenerative diseases (like Alzheimer's and Parkinson's), atherosclerosis, and diabetes. Its ability to modulate signal transduction pathways makes it valuable in studying apoptosis, inflammation, and cell proliferation. Researchers also investigate its dual nature—acting as a toxic byproduct at high concentrations and as a signaling molecule at low levels—providing insights into redox biology and potential therapeutic targets. Due to its involvement in disease mechanisms, 4-HNE is a focus in developing strategies to mitigate oxidative damage through antioxidants and protective agents.