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Mitochondrial dysfunctions contribute to brain injury in ischemic stroke while disturbance of mitochondrial dynamics results in mitochondrial dysfunction. Mitochondrial E3 ubiquitin ligase 1 (Mul1) involves in regulation of mitochondrial fission and fusion. This study aims to explore whether Mul1 contributes to brain injury in ischemic stroke and the underlying mechanisms. First, a rat ischemic stroke model was established by middle cerebral artery occlusion (MCAO), which showed ischemic injuries (increase in neurological deficit score and infarct volume) and upregulation of Mul1 in brain tissues. Next, Mul1 siRNAs were injected intracerebroventricularly to knockdown Mul1 expression, which evidently attenuated brain injuries (decrease in neurological deficit score, infarct volume and caspase-3 activity), restored mitochondrial dynamics and functions (decreases in mitochondrial fission and cytochrome c release while increase in ATP production), and restored protein levels of dynamin-related protein 1 (Drp1, a mitochondrial fission protein) and mitofusin2 (Mfn2, a mitochondrial fusion protein) through suppressing their sumoylation and ubiquitination, respectively. Finally, PC12 cells were cultured under hypoxic condition to mimic the ischemic stroke. Consistently, knockdown of Mul1 significantly reduced hypoxic injuries (decrease in apoptosis and LDH release), restored protein levels of Drp1 and Mfn2, recovered mitochondrial dynamics and functions (decreases in mitochondrial fission, mitochondrial membrane potential, reactive oxygen species production and cytochrome c release while increase in ATP production). Based on these observations, we conclude that upregulation of Mul1 contributes to brain injury in ischemic stroke rats and disturbs mitochondrial dynamics through sumoylation of Drp1 and ubiquitination of Mfn2.

Initiation of necroptosis has been considered as a promising strategy for anticancer therapies, especially for eradicating apoptosis-resistant malignant cells. Jujubisode B is a natural saponins extracted from the seeds of Zizyphi Spinosi Semen, and possesses multiple pharmacological activities, including antianxiety, anti-inflammation, antiplatelet aggregation and induction of apoptosis. This study aims to explore the effect of jujuboside B on acute leukemic cells and the underlying mechanisms. Our results showed that jujuboside B inhibited leukemia cell growth in a dose-dependent manner and attenuated the clonogenic ability of U937 cells, concomitant with activation of RIPK1/RIPK3/MLKL pathway; these phenomena were evidently blocked by necroptosis inhibitor (Nec-1). With the help of Molecular Operating Environment (MOE) program, we identified that RIPK1, RIPK3 and MLKL are potential targets of jujuboside B. To the best of our knowledge, this is the first study to provide evidence that jujuboside B possesses antileukemic activity via a mechanism involving activation of RIPK1/RIPK3/MLKL pathway.

Methyl protodioscin (MPD) is reported to relieve angina pectoris and myocardial ischemia, and mitochondrial E3 ubiquitin ligase 1 (Mul1) plays a key role in maintaining mitochondrial functions. Bioinformatic analysis shows potential interactions between MPD and Mul1. This study aims to explore whether MPD could protect rat brain against ischemia/reperfusion (I/R) injury through regulation of Mul1/ superoxide dismutase 2 (SOD2) pathway. The SD rat brains were subjected to 2 h of ischemia following by 24 h of reperfusion, which showed I/R injury (increase in neurological deficit score and infarct volume), up-regulation of Mul1 and down regulation of SOD2, these phenomena were attenuated by MPD treatment (3 or 10 mg/kg, i.g.). Consistently, in cultured HT22 cells, hypoxia-reoxygenation (H/R) treatment induced cellular injury (apoptosis and LDH release) concomitant with up-regulation of Mul1 and down regulation of SOD2, these phenomena were blocked in the presence of MPD (5 μM). Knockdown of Mul1 could also decrease SOD2 protein levels in HT22 cells accompanied by alleviation of H/R injury (reduction of apoptosis and LDH release). In agreement with the change of SOD2, reactive oxygen species generation was increased in H/R-treated HT22 cells while decreased in the presence of MPD. Based on these observations, we conclude that upregulation of Mul1 in rat brain contributes to cerebral I/R injury via suppression of SOD2 and that MPD protects rat brain from I/R injury through a mechanism involving regulation of Mul1/SOD2 pathway.