enzymes [50] or by modulating immune responses against
tumor cells [51].
Astaxanthin in detoxification and liver function
The liver is a complex organ in which intense catabolism
and anabolism take place. Liver functions include active
oxidation of lipids to produce energy, detoxification of
contaminants, and destruction of pathogenic bacteria,
viruses and of dead red blood cells. These functions can
lead to significant release of free radicals and oxidation
byproducts and therefore it is important to have mechanisms
that protect liver cells against oxidative damage.
Astaxanthin is much more effective than vitamin E at
protecting mitochondria from rat liver cells against lipid
peroxidation [12]. Astaxanthin also induces xenobioticmetabolizing
enzymes in rat liver, a process that could
help prevent carcinogenesis [52]. Astaxanthin can
induce xenobiotic metabolizing enzymes in the lung
and kidney [50].
Astaxanthin and the immune response
Immune response cells are particularly sensitive to
oxidative stress and membrane damage by free radicals
because they rely heavily on cell-to-cell communications
via cell membrane receptors. Furthermore, the phagocytic
action of some of these cells releases free radicals that can
rapidly damage these cells if they are not neutralized by
antioxidants [53]. Astaxanthin significantly influences
immune function in several in vitro and in vivo assays
using animal models. Astaxanthin enhances in vitro
antibody production by mouse spleen cells [54] and can
also partially restore decreased humoral immune
responses in old mice [55]. Other evidence also points
to the immunomodulating activity of astaxanthin on
the proliferation and functions of murine immunocompetent
cells [56]. Finally, studies on human blood cells
in vitro have demonstrated enhancement by astaxanthin
of immunoglobulin production in response to
T-dependent stimuli [57].
Astaxanthin and neurodegenerative diseases
The nervous system is rich in both unsaturated fats (which
are prone to oxidation) and iron (which has strong
prooxidative properties). These, together with the intense
metabolic aerobic activity and rich irrigation with blood
vessels found in tissues of the nervous system, make
tissues particularly susceptible to oxidative damage [58].
There is substantial evidence that oxidative stress is a
causative or at least ancillary factor in the pathogenesis
of major neurodegenerative diseases (Alzheimer’s,
Huntington’s, Parkinson’s and amyotrophic lateral sclerosis,
ALS) and that diets high in antioxidants offer the
potential to lower the associated risks [59–62].
The above-mentioned study with rats fed natural
astaxanthin [19] demonstrated that astaxanthin can
cross the blood brain barrier in mammals and can extend
its antioxidant benefits beyond that barrier. Astaxanthin,
is therefore an excellent candidate for testing in
Alzheimer’s disease and other neurological diseases.