5. Gossypol acetate reduced mHTT level and rescued HD-relevant phenotypes in vivo
Having demonstrated that gossypol acetate protected HD neurons by inducing autophagy-mediated degradation of mHTT, we assessed whether gossypol acetate had beneficial effect in vivo onDrosophila HD models expressing HTT-16Q, HTT-128Q, HTTexon1-25Q or HTTexon1-72Q fragments (33 ). As shown by HTRF assays, gossypol acetate significantly reduced mHTT level in the HTT-128Q model as well as in HTTexon1-72Q model without reducing wtHTT level in transgenicDrosophila model with HTT-16Q or HTTexon1-25Q (Fig. 4A). In HTT-128Q flies,feeding with food containing 10 μM gossypol acetate significantly rescued the climbing deficits in Huntington’s disease flies (Fig. 4B). Flies expressing HTTexon1-72Q exhibited similar climbing deficits and a shorter lifespan and were also rescued by feeding the flies with gossypol acetate, while little effects after GA treatment were observed in flies expressing wtHTT (HTT-16Q or HTTexon1-25Q) (Fig. 4C, 4D). The results suggested that gossypol acetate was effective in reducing mHTT level and rescuing HD phenotypes inDrosophila models.
To further confirm its neuronal protective effects and therapeutic potential, we examined the effects of gossypol acetate in the HD knock-in mouse model expressing endogenous mHTT proteins with 140Q (HdhQ140/Q140). Consistent with previous reports, we observed several motor function-related deficits in the homozygous HD (HdhQ140/Q140) mice (Fig. 5A-D) , including decrease of the activity in the rearing test, deficits in the open-field tests, and reduced latency to fall in the rotarod tests. Intraperitoneal injection of gossypol acetate significantly rescued all these behavioral phenotypes (Figure 5A-C). Consistently, homozygous HD mice treated with gossypol acetate showed significantly reduced mHTT levels in the cortex and striata (Fig. 5D). All results confirmed that gossypol acetate treatment reduced mHTT levels in vivo and rescued HD relevant phenotypes.