Chromatinolysis refers to enzymatic degradation of nuclear
DNA and is regarded as one of the crucial events leading to cell death. Mixed-lineage
kinase domain-like
protein (MLKL) has been identified as a key executor of necroptosis, but it remains unclear whether MLKL contributes to necroptosis via regulation of chromatinolysis. In this study, we find that
shikonin induces MLKL activation and chromatinolysis in
glioma cells in vitro and in vivo, which are accompanied with nuclear translocation of AIF and γ-H2AX formation. In vitro studies reveal that inhibition of MLKL with its specific inhibitor NSA or knockdown of MLKL with
siRNA abrogates
shikonin-induced
glioma cell necroptosis, as well as chromatinolysis. Mechanistically, activated MLKL targets mitochondria and triggers excessive generation of mitochondrial
superoxide, which promotes AIF translocation into nucleus via causing mitochondrial depolarization and aggravates γ-H2AX formation via improving intracellular accumulation of ROS. Inhibition of nuclear level of AIF by knockdown of AIF with
siRNA or mitigation of γ-H2AX formation by suppressing ROS with
antioxidant NAC effectively prevents
shikonin-induced chromatinolysis. Then, we found that RIP3 accounts for
shikonin-induced activation of MLKL, and activated MLKL reversely up-regulates the
protein level of CYLD and promotes the activation of RIP1 and RIP3. Taken together, our data suggest that MLKL contributes to
shikonin-induced
glioma cell necroptosis via promotion of chromatinolysis, and
shikonin induces a positive feedback between MLKL and its upstream signals RIP1 and RIP3.