Abstract
Neuroprostanes (nPs) are a series of isoprostane (IsoP)‐like compounds that are spontaneously formed in vivo and in vitro by free‐radical catalyzed peroxidation of the polyunsaturated fatty acid (PUFA), docosahexanoic acid. Although nPs are elevated in neurodegenerative conditions and in animal models of neuronal oxidative stress (Musiek et al., Brain Pathol. 15:149,2005), it is unknown whether nPs, like IsoPs, are endogenously produced in mammalian retina. We sought to measure endogenous production of the PUFA metabolites, A4‐nPs and F2‐IsoPs in bovine retinae, in vitro. Freshly isolated bovine retinae were exposed to hydrogen peroxide (H2O2) and cumene hydroperoxide (cuOOH) for up to 6h, in vitro. PUFA metabolites were measured by the stable isotope dilution methods employing GS/negative ion chemical ionization MS. Basal endogenous levels of A4‐nPs and F2‐IsoPs were found to be 35.0± 2.2 and 1.1± 0.001 ng/g tissue, respectively. Exposure of retina to H2O2 (1 mM) for 1h and 6h stimulated production of A4‐nP levels by 15% and 56% while bound F2‐IsoPs were elevated by 44% and 68%, respectively. Similarly, cuOOH (1 mM) enhanced (p<0.001) A4‐nP levels by 408% and 420% and F2‐IsoPs by 831% and 918% after 1h and 6h periods of treatment, respectively. In conclusion, basal levels of nPs exceed that of IsoPs in bovine retina. Furthermore, endogenous production of PUFA metabolites is enhanced by oxidant stress in retina.