Erin Terry

Oxidative Stress and Matrix Metalloproteinase-9 in Acute Ischemic Stroke: The Biomarker Evaluation for Antioxidant Therapies in Stroke (BEAT-Stroke) Study

Background and Purpose— Experimental stroke studies indicate that oxidative stress is a major contributing factor to ischemic cerebral injury. Oxidative stress is also implicated in activation of matrix metalloproteinases (MMPs) and blood-brain barrier injury after ischemia-reperfusion. Plasma biomarkers of oxidative stress may have utility as early indicators of efficacy in Phase 2 trials of antioxidant therapies in human stroke. To date, a valid biomarker has been unavailable. We measured F2-isoprostanes (F2IPs), free-radical induced products of neuronal arachadonic acid peroxidation, in acute ischemic stroke. We aimed to determine the change in plasma F2IP levels over time and relationship with plasma MMP-9 in tPA-treated and tPA-untreated stroke patients. Methods— We performed a case–control study of consecutive ischemic stroke patients (25 tPA-treated and 27 tPA-untreated) presenting within 8 hours of stroke onset. Controls were individuals without prior stroke from a primary care clinic network serving the source population from which cases were derived. Infarct volume was determined on acute diffusion-weighted MRI (DWI) performed within 48 hours using a semi-automated computerized segmentation algorithm. Phlebotomy was performed at <8 hours, 24 hours, 2 to 5 days, and 4 to 6 weeks. F2IPs were measured by gas chromatography/mass spectrometry and MMP-9 by ELISA. Prestroke antioxidant dietary intake was measured by the 24-hour recall method. Results— In 52 cases and 27 controls, early (median 6 hours postonset) F2IPs were elevated in stroke cases compared with controls (medians 0. 041 versus 0.0295pg/mL, P=0.012). No difference in F2IPSs was present at later time points. Early plasma F2IPs correlated with MMP-9 in all patients (P=0.01) and the tPA-treated subgroup (P=0.02). No correlation was found with NIHSS, DWI infarct volume, 90-day Rankin score, or C-reactive protein (P>0.05 for all). Conclusions— In early human stroke we found evidence of increased oxidative stress and a relationship with MMP-9 expression, supporting findings from experimental studies.

Peripheral F2‐isoprostanes and F4‐neuroprostanes are not increased in Alzheimer's disease

Quantitative biomarkers of oxidative damage, such as the F2‐isoprostanes (IsoPs) and F4‐neuroprostanes (F4‐NeuroPs), may be useful in assessing progression and response to therapeutics in patients with Alzheimers disease. F2‐IsoPs and F4‐NeuroPs are reproducibly increased in brain and cerebrospinal fluid of Alzheimers disease patients; however, results in blood and urine have been conflicting. We tested the hypothesis that F2‐IsoPs and F4‐NeuroPs in plasma or urine quantitatively reflect oxidative damage to the central nervous system. Our results showed that urine levels of F2‐IsoPs or their major metabolite were not significantly different between 56 Alzheimers disease patients and 34 controls. In addition, urine and cerebrospinal fluid F2‐IsoP levels in 32 Alzheimers disease patients did not correlate. Supporting these conclusions, elevated rat cerebral F2‐IsoPs and F4‐NeuroPs after systemic exposure to kainic acid were not associated with a significant change in their plasma or urine levels. These results show that plasma and urine F2‐IsoPs and F4‐NeuroPs do not accurately reflect central nervous system levels of these biomarkers and are not reproducibly elevated in body fluids outside of central nervous system in Alzheimers disease patients. These results should guide the organization of clinical trials now being planned for patients with Alzheimers disease.

Measurement of F2- isoprostanes and isofurans using gas chromatography-mass spectrometry.

F2-Isoprostanes (IsoPs) are isomers of prostaglandin F2α formed from the nonenzymatic free radical-catalyzed peroxidation of arachidonic acid. Since discovery of these molecules by Morrow and Roberts in 1990, F2-IsoPs have been shown to be excellent biomarkers as well as potent mediators of oxidative stress in vivo in humans. Isofurans (IsoFs) are also oxidation products generated from the nonenzymatic oxidation of arachidonic acid. IsoFs are preferentially formed instead of F2-IsoPs in settings of increased oxygen tension. The protocol presented herein is the current methodology that our laboratory uses to quantify F2-IsoPs and IsoFs in biological tissues and fluids using gas chromatography/mass spectrometry (GC/MS). A variety of analytical procedures to measure F2-IsoPs, including other GC/MS methods and liquid chromatography/MS and immunological approaches, are reported in the literature. This method provides a very low limit of quantitation and is suitable for analysis of both F2-IsoPs and IsoFs from a variety of biological sources including urine, plasma, tissues, cerebral spinal fluid, exhaled breath condensate, and amniotic fluid, among others.

Improved assay for the quantification of the major urinary metabolite of the isoprostane 15-F2t-isoprostane (8-iso-PGF2α) by a stable isotope dilution mass spectrometric assay

BACKGROUND The F(2)-isoprostanes (IsoPs) are a series of novel prostaglandin (PG)-like compounds generated from the free radical catalyzed peroxidation of arachidonic acid. One IsoP, 15-F(2t)-IsoP (8-iso-PGF(2alpha)), has been shown to be formed in abundance in vivo and to exert potent biological activity. METHODS As a means to assess the endogenous production of this compound, we previously developed a method to quantify the major urinary metabolite of 15-F(2t)-IsoP, 2,3-dinor-5,6-dihydro-15-F(2t)-IsoP (2,3-dinor-5,6-dihydro-8-iso-PGF(2alpha), 15-F(2t)-IsoP-M ), by gas chromotography (GC)/negative ion chemical ionization mass spectrometry (MS) employing stable isotope dilution methodology. While useful, we found that the assay occasionally suffered from the presence of impurities that co-elute on GC with 15-F(2t)-IsoP-M, making the measurement of this compound difficult. We now report a modified assay for the quantification of 15-F(2t)-IsoP-M employing GC/MS that alleviates this problem. RESULTS Precision of the assay is +/-7% and the accuracy is 96%. The lower limit of sensitivity is approximately 8 pg. Normal concentrations of this metabolite in urine were found to be 0.46+/-0.09 ng/mg creatinine (mean+/-1 S.D.) Urinary excretion of 15-F(2t)-IsoP-M is markedly altered in situations associated with increased or decreased oxidant stress in vivo. CONCLUSIONS This assay provided a sensitive and accurate method to assess endogenous IsoP generation and can be used to further explore the role of oxidant injury in human disease.

Antioxidants significantly affect the formation of different classes of isoprostanes and neuroprostanes in rat cerebral synaptosomes

Lipid peroxidation has been implicated in the pathogenesis of a number of diseases, including neurodegenerative disorders. Evidence that antioxidants can affect the clinical course of neurodegenerative diseases is limited. In the present study, we examined the ability of five common antioxidants or antioxidant combinations, alpha-tocopherol, gamma-tocopherol, ascorbic acid, GSH ethyl ester, and a combination of ascorbate and alpha-tocopherol, to modulate lipid peroxidation in peroxidizing rat cerebral synaptosomes, a well-characterized model of oxidant injury. In these studies, we quantified isoprostanes (IsoPs) derived from arachidonic acid as an index of whole tissue oxidation and neuroprostanes (NeuroPs) formed from docosahexaenoic acid as a marker of selective neuronal peroxidation. We report that these various antioxidants displayed markedly different capacities to inhibit IsoP and NeuroP formation with the most potent effects on IsoPs observed for ascorbate, GSH ethyl ester, and the alpha-tocopherol-ascorbate combination. alpha-Tocopherol was slightly less potent and gamma-tocopherol significantly less effective. The concentration-response relationships were significantly different for NeuroP formation with the antioxidants being significantly less potent than for IsoP generation. In particular, alpha-tocopherol did not inhibit NeuroP formation at concentrations up to 100 microM. We also determined that tocopherols, in particular alpha-tocopherol, act in vitro as reducing agents to convert IsoP and NeuroP endoperoxides to reduced F-ring compounds, a finding we have observed previously in vivo in brain. These studies are of importance because they have further defined the role of antioxidants to modulate the formation of lipid peroxidation products in peroxidizing brain tissue. In addition, they suggest that alpha-tocopherol may not be a particularly effective agent to inhibit oxidant stress in the terminal compartment of neurons in the central nervous system.

Oxidant stress and peripheral neuropathy during antiretroviral therapy: an AIDS clinical trials group study.

Background: Peripheral neuropathy that complicates HIV nucleoside reverse transcriptase inhibitor (NRTI) therapy is likely caused by mitochondrial injury. Mitochondria play a central role in regulating oxidant stress. We explored the relationships between oxidant stress and NRTI-induced peripheral neuropathy. Methods: The AIDS Clinical Trials Group (ACTG) studied the cases of 384 antiretroviral-naive individuals randomized to receive didanosine/stavudine or zidovudine/lamivudine, plus efavirenz, nelfinavir, or both. The participants were followed for up to 3 years. Peripheral neuropathy was ascertained by signs and symptoms. We performed a case-control study of ACTG 384 participants. Peripheral neuropathy cases and nonneuropathy control subjects were selected from didanosine/stavudine recipients. Alternate control subjects were selected from zidovudine/lamivudine recipients who developed peripheral neuropathy. Oxidant stress was assessed by quantifying F2-isoprostanes (F2-IsoPs) in cryopreserved plasma. Results: Seventy-five cases, 71 control subjects, and 18 alternate control subjects were identified. The median baseline F2-IsoP values were 53 (interquartile range [IQR], 40-85), 57 (IQR, 41-77), and 53 (IQR, 47-101) pg/mL, respectively, and did not differ between cases and control subjects (P = 0.78) or alternate control subjects (P = 0.60). Changes in F2-IsoPs from baseline to time of peripheral neuropathy did not differ significantly between cases (median, 10 [IQR, −17 to 26] pg/mL) and control subjects (median, 4 [IQR, −11 to 17] pg/mL; P = 0.48) or alternate control subjects (median, 1 [IQR, −48 to 10] pg/mL; P = 0.21). Conclusions: Peripheral neuropathy that complicates antiretroviral therapy with NRTIs was not associated with increased systemic oxidant stress assessed by plasma F2-IsoPs.