4-Hydroxynonenal (4-HNE) is primarily studied for its role in cellular signaling and oxidative stress-related processes. It acts as a bioactive lipid mediator involved in the regulation of various cellular functions, including proliferation, apoptosis, and inflammation. Due to its reactivity, it is used as a marker for lipid peroxidation in research on oxidative damage linked to aging, neurodegenerative diseases (such as Alzheimer's and Parkinson's), atherosclerosis, and diabetes. In experimental biology, 4-HNE is applied to investigate stress response pathways and the impact of reactive aldehydes on protein function and gene expression. It modifies proteins through covalent adduct formation, which helps in studying post-translational modifications associated with disease mechanisms. Additionally, it is used in assays to evaluate antioxidant efficacy, as compounds that reduce 4-HNE formation or its adducts are considered potential therapeutic agents. Its presence in biological samples is also measured in clinical and toxicological studies to assess oxidative damage in tissues and fluids, supporting the development of diagnostic tools and interventions targeting oxidative stress.