The mycotoxin fumonisin B1 inhibits eukaryotic protein synthesis: in vitro and in vivo studies

Inhibitory action of Fumonisin B₁ (FB₁) on eukaryotic protein synthesis was investigated, both in animal and plant system, and was compared with cycloheximide. Inhibitory effect of FB₁ was monitored in the TCA precipitable proteins of rabbit reticulocyte lysates exposed to various concentrations of the mycotoxin (0.0013–2.76 mM), using ³⁵ S-methionine as a tracer. FB₁ inhibited the protein synthesis by 6%, at 0.0013 mM and by 88%, at a higher concentration of 2.76 mM. Cycloheximide at a concentration of 0.355 mM was found to inhibit protein synthesis by 88%. Inhibitory action of FB₁ (1 mg kg⁻¹ body mass and a higher dose of 10 mg kg⁻¹ body mass) or cycloheximide (10 mg kg⁻¹ body mass; positive controls), injected intra-peritoneally into BALB/c mice was studied using ¹⁴C-l-Leucine as a tracer. FB₁ at lower dose of 1 mg kg⁻¹ body mass inhibited protein synthesis in liver by 8% and at a higher dose of 10 mg kg⁻¹ body mass by 38% in the BALB/c mice, when compared to cycloheximide which inhibited protein synthesis by 61%. The effects of FB₁ on protein synthesis in plant system was studied in germinated maize seedlings exposed to FB₁ at 0.9 μM, 0.009 mM and 0.09 mM concentrations, using ¹⁴C-l-Leucine as a tracer. Fumonisin B₁ at low, middle, and higher concentrations (0.9 μM, 0.009 mM, and 0.09 mM) inhibited protein synthesis in the seedlings by 4%, 12% and 22%, respectively. The inhibitory effects of FB₁ on the protein synthesis in the animal system in vitro and in vivo conditions, and in the plant system were found to be dose-dependent, though it was less potent compared to cycloheximide.