OPA1 and Huntington disease: Together, these results indicate that 3-NPA disrupts the mitochondrial fission–fusion balance in HD cells by increasing Fis1, DRP1, and OPA1 levels, while MB pre-treatment mitigates these alterations in OPA1 and p62 expression, supporting a potential role of MB in normalizing mitochondrial dynamics during mitochondrial stress induced by 3-NPA.