Shikonin Suppresses Trophoblast Cell Growth via Regulation of GLI1, and p62 Mediated Caspase 8 Activation

Unruptured ectopic pregnancy (UEP) is a common cause of morbidity and, occasionally, of mortality in women of reproductive age. Pharmacological intervention is a common therapeutic approach for early-stage UEP. Herein, we investigated the cytotoxic effect and novel mechanism of shikonin, a natural naphthoquinone pigment purified from Lithospermum erythrorhizon, in human trophoblast cells. These data demonstrated that shikonin suppressed proliferation and induced apoptosis in a time-dependent manner in HTR-8/SVneo cells. Shikonin blocked autophagic flux and promoted p62 interaction with caspase 8, resulting in caspase 8 activation. Moreover, shikonin suppressed GLI1 expression, and GLI1 overexpression attenuated shikonin-induced cell apoptosis. Although silencing GLI1 slightly promoted cell apoptosis, p62 overexpression enhanced GLI1 silencing-induced cell apoptosis by activating caspase 8. Furthermore, rapamycin increased shikonin-induced cell apoptosis in HTR-8/SVneo cells, whereas 3-MA attenuated the cytotoxic effect of shikonin. In conclusion, shikonin suppressed trophoblast cell growth by silencing GLI1 and increasing p62 co-mediated activation of caspase 8, which suggested a potential novel therapeutic target for UEP.

Keywords: Caspase 8; GLI1; Shikonin; Unruptured ectopic pregnancy; p62.