In vivo and in vitro evidences that carotenoids could modulate the neutrophil respiratory burst during dietary manipulation

Summary

Background

The primary role of polymorphonuclear neutrophils (PMNs) is to destroy pathogenic microorganisms after phagocytosis by producing reactive oxygen species (ROS) and toxic molecules. However, PMNs produce sufficient amounts of ROS during an oxidative burst to be autotoxic and detrimental to their own functions and to possibly cause DNA damage, protein and lipid oxidation and cell membrane destructuration.

Objective

The aim of this study was to investigate in vivo the role of the antioxidant capacities of carotenoids in modulating ROS content in PMNs during oxidative burst. Moreover to investigate the direct or indirect effect of carotenoids, the modification of PMN ROS content was explored after in vitro supplementation with β-carotene or lycopene, chosen taking account of their vitamin A and no vitamin A precursor effect, respectively.

Design

In vivo study: Venous blood was collected from 10 healthy male volunteers and ROS production from phorbol myristate acetate (PMA)-stimulated PMNs was determined, by flow cytometry using the fluorescent dye dihydrorhodamine 123, at baseline, after 3 weeks of carotenoid depletion (carotenoid intake limited to 25% of usual intake) and after 5 weeks of carotenoid repletion (30 mg β-carotene, 15 mg lycopene and 9mg lutein per day). In vitro study: ROS content in PMA-stimulated PMNs isolated from carotenoid depleted subjects and controls was quantified after an in vitro enrichment with β-carotene (1 µmol/L) or lycopene (0.3 µmol/L).

Results

In vivo carotenoid depletion increased PMN H₂O₂ content after PMA activation by 38% (p < 0.05 vs baseline),while supplementation for 5 weeks restored basal H₂O₂ generation (p < 0.05 vs depletion). Although H₂O₂ measurement in PMNs from non-depleted subjects was not affected by an in vitro supply with β-carotene or lycopene, a significant decrease in H₂O₂ content by 78.9 % and 81.2%, respectively, was observed in PMNs from carotenoid depleted subjects (p < 0.01 vs depleted control subjects).

Conclusions

The carotenoid ROS quenching capacities control both in vivo and in vitro the PMNs ROS generation and probably protect these cells against DNA, membrane lipid and protein damages during oxidative burst. Moreover, these effects appear independent from the metabolic conversion of carotenoids to vitamin A.