L. Jackson Roberts

Formation of Isoprostane-like Compounds (Neuroprostanes) in Vivo from Docosahexaenoic Acid

F2-isoprostanes are prostaglandin F2-like compounds that are formed nonenzymatically by free radical-induced oxidation of arachidonic acid. We explored whether oxidation of docosahexaenoic acid (C22:6ω3), which is highly enriched in the brain, led to the formation of F2-isoprostane-like compounds, which we term F4-neuroprostanes. Oxidation of docosahexaenoic acidin vitro yielded a series of compounds that were structurally established to be F4-neuroprostanes using a number of mass spectrometric approaches. The amounts formed exceeded levels of F2-isoprostanes generated from arachidonic acid by 3.4-fold. F4-neuroprostanes were detected esterified in normal whole rat brain and newborn pig cortex at a level of 7.0 ± 1.4 ng/g and 13.1 ± 8 ng/g, respectively. Furthermore, F4-neuroprostanes could be detected in normal human cerebrospinal fluid and levels in patients with Alzheimer’s disease (110 ± 12 pg/ml) were significantly higher than age-matched controls (64 ± 8 pg/ml) (p < 0.05). F4-neuroprostanes may provide a unique marker of oxidative injury to the brain and could potentially exert biological activity. Furthermore, the formation of F4-neuroprostane-containing aminophospholipids might adversely effect neuronal function as a result of alterations they induce in the biophysical properties of neuronal membranes.

Isoprostanes as Markers of Lipid Peroxidation in Atherosclerosis

Cardiovascular disease is one of the leading causes of morbidity and mortality in the United States. Central to the process of atherogenesis is the uptake of LDL by macrophages resulting in formation of foam cells in the vascular wall. Thus, insights into the mechanism that leads to the uptake of LDL by macrophages are key to understanding the pathogenesis of atherosclerosis. Native LDL is not internalized by macrophages. However, chemical modification of LDL apolipoprotein B-100 converts the LDL into a ligand for scavenger receptors on macrophages, which leads to rapid uptake of the modified LDL (1–3). Because the scavenger pathway of LDL uptake lacks feedback inhibition by intracellular cholesterol content, massive accumulation of modified LDL can occur, resulting in foam cell formation.

Quantification of F-ring and D-/E-ring isoprostanes and neuroprostanes in Alzheimer's disease

Numerous in vitro cell culture, animal, and tissue homogenate studies have implicated free radical damage in the pathogenesis of Alzheimer’s disease (AD) 1,2. A variety of methods have been employed to assess the free radical damage; however, most of these methods suffer from either non-quantitative results, a lack of information about cellular localization, or both3- 10.

Reactive Products of the Isoprostane Pathway: Isoketals and Cyclopentenone A2/J2-Isoprostanes

Isoprostanes (IsoPs) are prostaglandin-like compounds that are formed non-enzymatically by free radical catalyzed peroxidation of arachidonic acid. The archetypical compounds discovered to be formed by this pathway were prostaglandin F2-like compounds, F2-IsoPs [1]. An important facet of the formation of IsoPs is that, unlike prostaglandins, they are initially formed in situ esterified to phospholipids and then released preformed [2]. Key intermediates in the formation of IsoPs, analogous to the formation of prostaglandins via the cyclooxygenase pathway, are bicyclic endoperoxides PGH2-like compounds (H2-IsoPs). H2-IsoPs are reduced to form F2-IsoPs. However, we have found that this reduction is not completely efficient such that the H2-IsoPs undergo rearrangement in vivo to form prostaglandin E2-like and D2-like compounds (E2/D2-IsoPs) and thromboxane-like compounds (isothromboxanes) [3,4].