4‑Hydroxy-7-oxo-5-heptenoic Acid (HOHA) Lactone is a Biologically Active Precursor for the Generation of 2‑(ω-Carboxyethyl)pyrrole (CEP) Derivatives of Proteins and Ethanolamine Phospholipids Hua Wang Mikhail Linetsky Junhong Guo Jaewoo Choi Li Hong Amanda S. Chamberlain Scott J. Howell Andrew M. Howes Robert G. Salomon 10.1021/acs.chemrestox.5b00001.s001 https://acs.figshare.com/articles/journal_contribution/4_Hydroxy_7_oxo_5_heptenoic_Acid_HOHA_Lactone_is_a_Biologically_Active_Precursor_for_the_Generation_of_2_Carboxyethyl_pyrrole_CEP_Derivatives_of_Proteins_and_Ethanolamine_Phospholipids/2166202 2-(ω-Carboxyethyl)­pyrrole (CEP) derivatives of proteins were previously shown to have significant pathological and physiological relevance to age-related macular degeneration, cancer and wound healing. Previously, we showed that CEPs are generated in the reaction of ε-amino groups of protein lysyl residues with 1-palmityl-2-(4-hydroxy-7-oxo-5-heptenoyl)-<i>sn</i>-glycero-3-phosphatidylcholine (HOHA-PC), a lipid oxidation product uniquely generated by oxidative truncation of docosahexanenate-containing phosphatidylcholine. More recently, we found that HOHA-PC rapidly releases HOHA-lactone and 2-lyso-PC (<i>t</i><sub>1/2</sub> = 30 min at 37 °C) by nonenzymatic transesterification/deacylation. Now we report that HOHA-lactone reacts with Ac-Gly-Lys-OMe or human serum albumin to form CEP derivatives in vitro. Incubation of human red blood cell ghosts with HOHA-lactone generates CEP derivatives of membrane proteins and ethanolamine phospholipids. Quantitative analysis of the products generated in the reaction HOHA-PC with Ac-Gly-Lys-OMe showed that HOHA-PC mainly forms CEP-dipeptide that is not esterified to 2-lysophosphatidycholine. Thus, the HOHA-lactone pathway predominates over the direct reaction of HOHA-PC to produce the CEP-PC-dipeptide derivative. Myleoperoxidase/H<sub>2</sub>O<sub>2</sub>/NO<sub>2</sub><sup>–</sup> promoted in vitro oxidation of either 1-palmityl-2-docosahexaneoyl-<i>sn</i>-glycero-3-phosphatidylcholine (DHA-PC) or docosahexaenoic acid (DHA) generates HOHA-lactone in yields of 0.45% and 0.78%, respectively. Lipid oxidation in human red blood cell ghosts also releases HOHA-lactone. Oxidative injury of ARPE-19 human retinal pigmented epithelial cells by exposure to H<sub>2</sub>O<sub>2</sub> generated CEP derivatives. Treatment of ARPE-19 cells with HOHA-lactone generated CEP-modified proteins. Low (submicromolar), but not high, concentrations of HOHA-lactone promote increased vascular endothelial growth factor (VEGF) secretion by ARPE-19 cells. Therefore, HOHA-lactone not only serves as an intermediate for the generation of CEPs but also is a biologically active oxidative truncation product from docosahexaenoate lipids. 2015-05-18 00:00:00 lipid oxidation product oxidative truncation product ARPE protein lysyl residues VEGF CEP derivatives blood cell ghosts HOHA 2O form CEP derivatives DHA