Swainsonine Induces Apoptosis through Mitochondrial Pathway and Caspase Activation in Goat Trophoblasts

The indolizidine alkaloid swainsonine (SW) has been reported to impair placentae and ultimately cause abortion in pregnant goats. Up to now, however, the precise effects of SW on goat trophoblast cells (GTCs) are still unclear. In this study, the cytotoxicity effects of SW on GTCs were detected and evaluated by MTT assay, AO/EB double staining, DNA fragmentation assay and flow cytometry analysis. Results showed that SW treatment significantly suppressed GTCs viability and induced typical apoptotic features in a time- and concentration-dependent manner. SW treatment increased Bax protein levels, reduced Bcl-2 protein levels, induced Bax translocation to mitochondria, and triggered the release of cytochrome c from mitochondria into cytosol, which in turn activated caspase-9 and caspase-3, and cleaved PARP, resulting in GTCs apoptosis. However, caspase-8 activity and the level of Bid did not exhibit significant changes in the process of SW-induced apoptosis. In addition, TUNEL assay suggested that SW induced GTCs apoptosis but not other cells in goat placenta cotyledons. Taken together, these data suggest that SW selectively induces GTCs apoptosis via the activation of mitochondria-mediated apoptosis pathway in goat placenta cotyledons, which might contribute to placentae impairment and abortion in pregnant goats fed with SW-containing plants. These findings may provide new insights to understand the mechanisms involved in SW-caused goat's abortion.