Astaxanthin addition improves human neutrophils function: in vitro study

 
Journal Title (Medline/Pubmed accepted abbreviation):  Eur. J. Nutr.
Year: 2010
Volume: 49
Page numbers: 447-457
doi (if applicable):  10.1007/s00394-010-0103-1
 

Summary of Background and Research Design

Background:Astaxanthin (ASTA) is a red-orange carotenoid that is produced by aquatic microalgae and accumulates in sea creatures such as shrimp and lobster. ASTA has been touted for high antioxidant activity and other potential health benefits including anti-inflammation and anti-cancer. Neutrophils are an important part of the immune system; they engulf foreign pathogens and produce chemicals such as free radicals that are toxic to foreign invaders. However, too strong a response can be harmful to the host. Antioxidants help keep the level of free radicals low so that the neutrophils maintain the beneficial qualities yet the harmful properties are attenuated.
 
Phagocyte- a cell that can engulf pockets of its surrounding medium. Phagocytic leukocytes (white blood cells) engulf foreign bodies to prevent infection
 
Microbicidal- lethal to microbes
 
Cytokine- small molecules, often proteins, that cells secrete to communicate with other cells
 
Reactive oxygen species (ROS)- a molecule that can react readily with other molecules and cause further free radical formation, oxidation of proteins of lipids, or other detrimental effects 
 
Glutathione- a peptide produced in the body that reacts with free radicals and other oxidative species to prevent damage, i.e. an endogenous antioxidant
 
Hypothesis/Research Question:How does ASTA affect the phagocytic and microbicidal capacities, cytokine release, and ROS production in human neutrophils?
 
Subjects:About 30 healthy adults, men and women, age 27.0 ± 9.0 donated venous blood, from which neutrophils were cultured
 
Experimental design: in vitro
 
Treatments and protocol:Cultured neutrophils were treated with 5 µM ASTA at 95% O2 for 24 hrs at 37°C. Cells were assessed for toxicity; intracellular calcium (Ca2+) concentration (thought to modulate cellular functions); phagocytic and microbicidal activity (by incubating the cells with Candida albicans, a species of yeast); production of superoxide anion, nitric oxide, and hydrogen peroxide; activity of superoxide dismutase (an enzyme that catalyzes the reaction of superoxide, O2-, to hydrogen peroxide, H22, which is less reactive), glutathione peroxidase, and glutathione reductase; and oxidative lesions.
 
Summary of Research Findings
ASTA treatment increased the intracellular Ca2+ concentration 48% and nitric oxide production compared with the control group. These responses modulate cellular responses and possibly explain the other observed phenomena.    ASTA treatment increased the capacity of phagocytosis by 30% and was able to kill 28% more C. albanicans. ASTA reduced the amount of extracellular superoxide anion (free radical) compared to the control cells and ASTA reduced the amount of intracellular superoxide anions in stimulated cells but not control cells. Hydrogen peroxide (a compound that reacts to form free radicals) generation was significantly less in stimulated cells with ASTA treatment though was not different for untreated cells. Consequently, there were 35% fewer damages in biomolecules including a reduction in lipid oxidation. There was also less cytokine release, which implies that the inflammation pathway was less activated, leading to a reduced downstream response.
 
Interpretation of findings/Key practice applications:

ASTA is effective at increasing the antimicrobial capacity of white blood cells while reducing the responses that can be harmful to the host (production of oxidants).   Given the increased risk of upper respiratory tract and other infections that can occur in athletes after strenuous training and competitions, human studies of ASTA supplementation on immune markers in athletes may be warranted.
 
Limitations:

It is unlikely that ASTA concentrations will reach as high as 5 µM in human plasma. Because no other doses of ASTA were evaluated in this study, it is not known if lower, more physiological doses of ASTA could have the same effect. In addition, this was only an in vitro study and the results should be replicated in humans before ASTA supplementation is considered as an immune-boosting strategy.
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