Amyotrophic lateral sclerosis (ALS) is a lethal motor neuron disorder characterized by a progressive loss of the upper and lower motor neurons at the spinal or bulbar levels. There are two forms of ALS, sporadic- and familiar-type.

The first type does not have a genetically inherited component. The mean age of onset varies from 50 to 65 years, while only in 5% of cases, the age of onset is less than 30 years.

However, the ALS incident is most pronounced in people 80 years or older. 5–10% of ALS cases have a genetic cause.

The most common cause of ALS is a gene mutation encoding Cu/Zn superoxide dismutase 1 (SOD1).

SOD1 is a ubiquitous dimeric enzyme mainly localized in the cytosol that catalyzes the dismutation of superoxide radical into hydrogen peroxide (H2O2) and molecular oxygen (O2); it plays a pivotal role in the cellular homeostasis of ROS. Mutant SOD1 has a structural instability that causes misfolds in the mutated enzyme, leading to aggregation in the motor neurons within the CNS.

More than 110 mutations of the SOD1 gene have been described. Many of these mutants retain their enzymatic activity, suggesting the possibility of a toxic functional gain of these forms of mutated SOD1 in ALS.

One of the proposed mechanisms of neuronal death in ALS is the free radical accumulation resulting from oxidative stress. This may lead to oxidative damage of lipid, proteins, and nucleic acids, causing cell death.

Free radicals are normally neutralized by antioxidant enzymes and nutrient-derived antioxidants, such as vitamin C, vitamin E, and astaxanthin. The effect of different antioxidants in treating people with ALS has been evaluated.

After investigating the use of antioxidants in cultured rat spinal neurons treated with the SOD1 inhibitor diethyldithiocarbamate (DDC), results demonstrated that the use of DDC induced an increase in endogenous oxidative stress, inhibiting thus neurite growth.

Antioxidants, such as L-ascorbic acid, L-histidine, α-tocopherol, β-carotene, and astaxanthin may rescue the motor neurons injured by SOD1 inhibition.

It is important to note that astaxanthin is the most potent carotenoid for this specific effect. Low concentrations of astaxanthin (100 nM) are needed to obtain a comparable effect to other antioxidant molecules (1 mM).