Plasma fluorescent oxidation products and risk of estrogen receptor-negative breast cancer in the Nurses' Health Study and Nurses' Health Study II

A study of the oxidative processes in human plasma by time-resolved fluorescence spectroscopy

The aim of this study was to examine the usefulness of time-resolved fluorescence spectroscopy in the evaluation of the oxidative processes in human plasma. To investigate the impact of oxidative stress on the fluorescence of plasma, five studied markers (thiobarbituric acid-reactive substances, ischemia modified albumin, carbonyl groups, hydrogen peroxide, advanced oxidation protein products) were chosen as oxidative damage approved markers. Our method presents several advantages over traditional methods as it is a direct, non-time-consuming, repeatable, and non-invasive technique that requires only simple pre-treatment of samples without additional reagents and the sample size needed for analysis is small. In principle, each modification of the protein in plasma can be expected to modify its fluorescence properties and hence its lifetime or intensity. The study involved 59 blood donors with no evidence of disease. The research was conducted at excitation wavelengths of 280 nm and 360 nm, and emission was measured at wavelengths of 350 nm and 440 nm, respectively. Our results, although preliminary, suggest that the application of fluorescence measurements can be considered as an effective marker of oxidative stress. Regression analyses showed that a notable growth in fluorescence intensity at 440 nm and a simultaneous decrease in fluorescence intensity and mean fluorescence lifetime at 350 nm are associated with higher levels of oxidative stress.

Oxidative Stress and Breast Cancer Risk in Premenopausal Women

BACKGROUND

Detrimental effects of oxidative stress are widely recognized, but induction of apoptosis and senescence may also have benefits for cancer prevention. Recent studies suggest oxidative stress may be associated with lower breast cancer risk before menopause.

METHODS

We conducted a nested case-control study (N = 457 cases, 910 controls) within the NIEHS Sister Study cohort of 50,884 women. Premenopausal women ages 35-54 were eligible for selection. We matched controls 2:1 to cases on age and enrollment year and were breast cancer-free at the time of the corresponding case's diagnosis. Oxidative stress was measured by urinary F2-isoprostane and metabolite (15-F2t-isoprostane-M) concentrations. Odds ratios (OR) and 95% confidence intervals (CIs) were calculated with multivariable conditional logistic regression.

RESULTS

After multivariable adjustment for body mass index (BMI) and other potential confounders, the OR for breast cancer comparing the >90th (≥2.94 ng/mgCr) to <25th percentile (1.01 ng/mgCr) was 1.1 (CI: 0.65, 1.7) for F2-isoprostane and 0.70 (CI: 0.43, 1.1) for the metabolite. Higher metabolite concentrations were associated with lower breast cancer risk among women who were also premenopausal (353 cases, OR: 0.59, CI: 0.34, 1.0) or <46 years (82 cases, OR: 0.15, CI: 0.06, 0.42) at diagnosis. ORs for the metabolite and breast cancer were inverse among women with BMI 18.5-24.9 kg/m (OR: 0.47, CI: 0.18, 1.2, 208 cases) and >30 kg/m (OR: 0.71, CI: 0.30, 1.7, 107 cases), but not among women with BMI 25-29.9 kg/m (OR: 0.98, CI: 0.39, 2.5, 138 cases).

CONCLUSIONS

Together with other studies, our results support a possible inverse association between oxidative stress and premenopausal breast cancer risk.