Mito-TIPTP Increases Mitochondrial Function by Repressing the Rubicon-p22phox Interaction in Colitis-Induced Mice

The run/cysteine-rich-domain-containing Beclin1-interacting autophagy protein (Rubicon) is essential for the regulation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase by interacting with p22phox to trigger the production of reactive oxygen species (ROS) in immune cells. In a previous study, we demonstrated that the interaction of Rubicon with p22phox increases cellular ROS levels. The correlation between Rubicon and mitochondrial ROS (mtROS) is poorly understood. Here, we report that Rubicon interacts with p22phox in the outer mitochondrial membrane in macrophages and patients with human ulcerative colitis. Upon lipopolysaccharide (LPS) activation, the binding of Rubicon to p22phox was elevated, and increased not only cellular ROS levels but also mtROS, with an impairment of mitochondrial complex III and mitochondrial biogenesis in macrophages. Furthermore, increased Rubicon decreases mitochondrial metabolic flux in macrophages. Mito-TIPTP, which is a p22phox inhibitor containing a mitochondrial translocation signal, enhances mitochondrial function by inhibiting the association between Rubicon and p22phox in LPS-primed bone-marrow-derived macrophages (BMDMs) treated with adenosine triphosphate (ATP) or dextran sulfate sodium (DSS). Remarkably, Mito-TIPTP exhibited a therapeutic effect by decreasing mtROS in DSS-induced acute or chronic colitis mouse models. Thus, our findings suggest that Mito-TIPTP is a potential therapeutic agent for colitis by inhibiting the interaction between Rubicon and p22phox to recover mitochondrial function.

The MAP4 Projection Domain Accelerates Hypoxia-Induced Mitophagy Disruption through LIR Motif in Cardiomyocytes

Previously, we and other investigators have demonstrated that phosphorylated microtubule-associated protein 4 (p-MAP4) impacts myocardial hypertrophy and ischemic heart failure. However, the detailed mechanism behind this remains under elucidated. Published studies have suggested that impaired mitophagy contributes to hypoxia-induced myocardial damage, hence the involvement of p-MAP4 in mitophagy in cardiomyocytes was investigated. The results herein revealed that there was increased degradation of mitochondria, accumulated mitophagosomes and disrupted autophagic flux in both neonatal and adult ones of MAP4-knockin (KI) mice. This indicated that p-MAP4 persistently degraded mitochondria through activating mitophagy. Next, Tom70 was found as the importer of p-MAP4 in the context of mitochondrial translocation. And, the LC3-interacting region (LIR) motif (47–50aa) caused p-MAP4-induced mitochondrial engulfment, and the ubiquitin-interacting motif (UIM) domain determined the characteristics of p-MAP4-induced mitophagosomes, which were structure and membrane potential-independent. Moreover, p-MAP4 enhanced hypoxia-induced mitophagic flux impairment, and p-MAP4 LIR (47–50aa) mutation decreased hypoxia-induced autophagy both in MAP4 knockout and wildtype cardiomyocytes. Overall, this study identified that p-MAP4 as a novel mediator and cargo receptor in mitophagy, and that the degradation of the MAP4 PJ domain as a promising therapeutic target for improving the cardiac function of hypoxia-related heart failure or cardiac remodelling.

Parkin Dependent Mitophagy Protects Macrophage Against Oxidative Injury And Inflammation During Atherogenesis

Mitochondrial oxidative injury induces macrophage inflammatory activation and apoptosis during atherogenesis. Timely clearance of dysfunctional mitochondria may therefore be beneficial for the survival of macrophages. Based on these principles, our working hypothesis was therefore that mitophagy mediated by the E3 ubiquitin ligase Parkin could have an important role in reducing both oxidative injury and the apoptosis of macrophages under atherogenic conditions. To examine this proposal, in the present study oxidative low-density lipoprotein (ox-LDL) treated THP-1 macrophages were used for the in vitro experiments, and high-cholesterol-fed male apolipoprotein E knockout (ApoE−/−) mice were used for the in vivo investigations. The results demonstrated that mitophagy was activated both in oxidatively stimulated THP-1 macrophages and in aortic plaque macrophages of high-cholesterol-fed ApoE−/− mice. In ox-LDL treated THP-1 macrophages, both the expression level and mitochondrial translocation of Parkin were increased following oxidative stimulation, whereas silencing Parkin led to impaired mitophagy, which exacerbated macrophage oxidative injury, NF-κB activation and apoptosis. Taken together, these results have demonstrated that mitophagy exerts a protective role in macrophages under atherogenic conditions, and that Parkin is a key mediator in this process.

Ginsenoside Re Protects against Serotonergic Behaviors Evoked by 2,5-Dimethoxy-4-iodo-amphetamine in Mice via Inhibition of PKCδ-Mediated Mitochondrial Dysfunction

It has been recognized that serotonin 2A receptor (5-HT2A) agonist 2,5-dimethoxy-4-iodo-amphetamine (DOI) impairs serotonergic homeostasis. However, the mechanism of DOI-induced serotonergic behaviors remains to be explored. Moreover, little is known about therapeutic interventions against serotonin syndrome, although evidence suggests that ginseng might possess modulating effects on the serotonin system. As ginsenoside Re (GRe) is well-known as a novel antioxidant in the nervous system, we investigated whether GRe modulates 5-HT2A receptor agonist DOI-induced serotonin impairments. We proposed that protein kinase Cδ (PKCδ) mediates serotonergic impairments. Treatment with GRe or 5-HT2A receptor antagonist MDL11939 significantly attenuated DOI-induced serotonergic behaviors (i.e., overall serotonergic syndrome behaviors, head twitch response, hyperthermia) by inhibiting mitochondrial translocation of PKCδ, reducing mitochondrial glutathione peroxidase activity, mitochondrial dysfunction, and mitochondrial oxidative stress in wild-type mice. These attenuations were in line with those observed upon PKCδ inhibition (i.e., pharmacologic inhibitor rottlerin or PKCδ knockout mice). Furthermore, GRe was not further implicated in attenuation mediated by PKCδ knockout in mice. Our results suggest that PKCδ is a therapeutic target for GRe against serotonergic behaviors induced by DOI.

DRP1 Inhibition Rescues Mitochondrial Integrity and Excessive Apoptosis in CS-A Disease Cell Models

Cockayne syndrome group A (CS-A) is a rare recessive progeroid disorder characterized by sun sensitivity and neurodevelopmental abnormalities. Cells derived from CS-A patients present as pathological hallmarks excessive oxidative stress, mitochondrial fragmentation and apoptosis associated with hyperactivation of the mitochondrial fission dynamin related protein 1 (DRP1). In this study, by using human cell models we further investigated the interplay between DRP1 and CSA and we determined whether pharmacological or genetic inhibition of DRP1 affects disease progression. Both reactive oxygen and nitrogen species are in excess in CS-A cells and when the mitochondrial translocation of DRP1 is inhibited a reduction of these species is observed together with a recovery of mitochondrial integrity and a significant decrease of apoptosis. This study indicates that the CSA-driven modulation of DRP1 pathway is key to control mitochondrial homeostasis and apoptosis and suggests DRP1 as a potential target in the treatment of CS patients.

Ropivacaine induces cell cycle arrest in the G0/G1 phase and apoptosis of PC12 cells via inhibiting mitochondrial STAT3 translocation

STAT3 has neuroprotective effect via non-canonical activation and mitochondrial translocation, but its effects on ropivacaine-induced neurotoxicity remain unclear. Our previous study revealed that apoptosis was an important mechanism of ropivacaine-induced neurotoxicity, this study is to illustrate the relationship between STAT3 with ropivacaine-induced apoptosis. Those results showed that ropivacaine treatment decreased cell viability, induced cell cycle arrest in the G0/G1 phase, apoptosis, oxidative stress, and mitochondrial dysfunction in PC12 cells. Besides, ropivacaine decreased the phosphorylated levels of STAT3 at Ser727 and downregulated the expression of STAT3 upstream gene IL-6. The mitochondrial translocation of STAT3 was also hindered by ropivacaine. To further illustrate the connection of STAT3 protein structure with ropivacaine, the autodock-vina was used to examine the interaction between STAT3 and ropivacaine, and the results showed that ropivacaine could bind to STAT3’s proline site and other sites. In addition, the activator and inhibitor of mitoSTAT3 translocation were used to demonstrate it was involved in ropivacaine-induced apoptosis, the results showed that enhancing the mitochondrial STAT3 translocation could prevent ropivacaine-induced apoptosis. Finally, the expression of p-STAT3 and the levels of apoptosis in the spinal cord were also detected, the results were consistent with the cell experiment, ropivacaine decreased the expression of p-STAT3 protein and increased the levels of apoptosis in the spinal cord. We demonstrated that ropivacaine induced apoptosis by inhibiting the phosphorylation of STAT3 at Ser727 and the mitochondrial STAT3 translocation. This effect was reversed by the activation of the mitochondrial STAT3 translocation.

Ischemic post-conditioning promotes mitochondrial translocation of DJ-1 and stabilizes binding to Bcl- xL to attenuate myocardial ischemic-reperfusion injury in STZ-induced diabetic rats

Background Ischemic post-conditioning (IPO) is a strategy in reducing myocardial ischemic-reperfusion (I/R) injury, but its specific molecular mechanism is incompletely understood. Deletions or mutations in the DJ-1 gene are directly linked to the cardiovascular system. DJ-1 plays a critical role in regulating mitochondrial homeostasis in response to stress through translocation of DJ-1 from the cytoplasm into the nucleus. Meanwhile, how the DJ-1 is removed in myocardial I/R injury and regulating apoptosis is needed to further verified. Given the discovery mentioned above, we hypothesize that DJ-1 translocate to mitochondria recover IPO induced cardioprotection in STZ-induced diabetic rats. To evaluate our hypothesis, we overexpressed the DJ-1 protein under high glucose condition, subjected IPO or not. And then measure the expression of DJ-1 in mitochondria and cytoplasm after myocardial I/R. Results We found that DJ-1 translocated to mitochondria combined with Bcl-xL was reduced cardiomyocyte injury and apoptosis in diabetic myocardial I/R heart. Additionally, the binding of DJ-1 and Bcl-xL is dependent on the oxidative state of DJ-1(oxidation of DJ-1 at Cys-106 is important for its protective effect). Conclusions If our hypothesis is correct, promote DJ-1 mitochondrial transfer may be critical with respect to restoring myocardial responsiveness to IPO in diabetes.