The effects of swainsonine on the activity and expression of α-mannosidase in BRL-3A cells

Swainsonine (SW) is the principal toxic ingredient of locoweeds, which can cause intensive vacuolar degeneration because of α-mannosidase inhibition after animal ingestion. While SW can lead to obvious liver damage in vivo, the mechanism of hepatotoxic damage caused by SW is not clear. Therefore, BRL-3A cells were treated for 24, 48, and 72 h with SW at various concentrations (0, 700, 900, 1100 μg/mL). The α-mannosidase (AMAN) activity was determined in BRL-3A cells using an enzyme substrate technique. The expression of mRNA and proteins of GM II (MAN2A1) and LAM (MAN2B1) in BRL-3A cells was detected by qPCR and Western-blot. The results showed that SW could significantly reduce the activity of AMAN in a time-dose effect relationship. Compared with the control group, the activity of AMAN significantly decreased only in the group treated with 1100 μg/mL SW for 24 h (P < 0.01), but the activity decreased significantly (P < 0.05 or P < 0.01) in all experimental groups treated for 48 or 72 h. SW also significantly reduced the expression of MAN2A1 and MAN2B1 mRNA and proteins in a time-dose effect relationship (P < 0.05 or P < 0.01), while the inhibition of SW was stronger for MAN2B1 than for MAN2A1. These results suggest that SW can significantly reduce the activity and expression of α-mannosidase thus causing SW-induced hepatotoxic damage.