RESUMO
This study was purposed to investigate the inhibitory effect of macrocalin A (MA) on proteasome of multiple myeloma U266 cells in vitro and molecular mechanism of MA-inducing apoptosis. U266 cells in vitro were incubated with different concentrations (2, 4, 8 µg/mL) of MA, the Hochest staining and Annexin-V/PI double staining were used to detect the apoptosis of U266 cells. The expressions of protein β1, β1i, β2, β2i, β5, β5i, ubiquitous, 19S subunit S6', and BAD,BCL-2, FAS, FAS-L,MAPK, PARP, Pro-caspase 3, cleaved-caspase 3 were detected by Western blot technique. The results showed that along with time prolonging and dose increasing of MA, the small and compact fluorescent particles were observed in cytoplasm and nucleus of U266 cells stained with Hoechst 33258, the Annexin V(+)/PI(-) cells and the total apoptosis cells (Annexin V(+)/PI(-) and Annexin V(+)/PI(+)) increased. MA could elevate the ubiquitylation level in U266 cells, suppress the expression of β1i,β2, β5i and 19S subunit S6', meanwhile the expression of BCJ-2, MAPK, PARP and pro-caspase 3 were down-regulated along with increasing of drug concentrations, but the expressions of BAD, FAS, FAS-L cleaved-caspase 3 were enhanced. It is concluded that MA can inhibit the effect of proteasome, and the mitochondrial pathway and death receptor pathway may play important roles in apoptosis of U266 cells induced by MA.