J Korean Neurol Assoc.  2006 Feb;24(1):66-75.

Selective Cytotoxic Mechanism of Homocysteine to Motor Neuronal Cells Expressing the Mutant Cu,Zn-superoxide Dismutase

• Sung JJ
• Kim HJ
• Kim SM
• Min JH
• Hong YH
• Park KS
• Kim M
• Lee SH
• Ho WK
• Lee KW

Abstract

BACKGROUND: Mutations in Cu, Zn-superoxide dismutase (SOD1) cause about 20% of familial amyotrophic lateral sclerosis (FALS) cases. The mechanism of late-onset disease manifestation despite the innate mutation has no clear explanation. The relationship between homocysteine (HC) and amyotrophic lateral sclerosis (ALS) has not been investigated fully, in spite of the similarity in their pathogenesis.
METHODS
We investigated the effect of HC on the motor neuronal cell-line (VSC4.1) transfected with SOD1 of either wild-type or mutant forms (G93A and A4V) using various methods including the MTT assay for the cytotoxic assay, the immunocytochemical staining using anti-SOD1 for the aggregation of SOD1, the western blotting using anti-nitrotyrosine and anti-DNPH for the oxidative protein damage, and the measurement of the intracellular Ca2+ concentration using Fura2-AM.
RESULTS
In the MTT assay, the HC induced significant cytotoxicity in the mutants, as compared with wild-type. This HC-induced cytotoxicity was inhibited by the trolox and the bathocuproinedisulfonate (BC). HC increased the carbonylation and nitrosylation of the mutant proteins. HC also increased significant SOD1-aggregation in mutants. This HC-induced SOD1-aggregation in mutants was inhibited by trolox, N-nitro-L-arginine methyl ester, BC, and z-VAD-FMK. HC did not change the intracellular concentration of Ca2+ in the mutants compared with the wild-type.
CONCLUSIONS
The authors showed that the vulnerability of the SOD1 mutant motor neuronal cells to HC involves the copper-mediated oxygen radical toxicity, and that HC may be a lifelong precipitating factor in some forms of FALS, suggesting a possible treatment modality with vitamin supplements.

Keyword

Amyotrophic Lateral Sclerosis (ALS); Superoxide dismutase (SOD); Homocysteine; Reactive oxygen species (ROS); Protein aggregation; Intracellular calcium concentration

MeSH Terms

Amyotrophic Lateral Sclerosis
Blotting, Western
Homocysteine*
Motor Neurons*
Mutant Proteins
Oxygen
Precipitating Factors
Vitamins
Homocysteine
Mutant Proteins
Oxygen
Vitamins