Mdivi-1: Effective but complex mitochondrial fission inhibitor

Mdivi-1, Mitochondrial DIVIsion inhibitor 1, has been widely employed in research under the assumption that it exclusively influences mitochondrial fusion, but effects other than mitochondrial dynamics have been underinvestigated. This paper provides transcriptome and DNA methylome-wide analysis for Mdivi-1 treated SH-SY5Y human neuroblastoma cells using RNA sequencing (RNA-seq) and methyl capture sequencing (MC-seq) methods. Gene ontology analysis of RNA sequences revealed that p53 transcriptional gene network and DNA replication initiation-related genes were significantly up and down-regulated, respectively, showing the correlation with the arrest cell cycle in the G1 phase. MC-seq, a powerful sequencing method for capturing DNA methylation status in CpG sites, revealed that although Mdivi-1 does not induce dramatic DNA methylation change, the subtle alterations were concentrated within the CpG island. Integrative analysis of both sequencing data disclosed that the p53 transcriptional network was activated while the Parkinson's disease pathway was halted. Next, we investigated several changes in mitochondria in response to Mdivi-1. Copy number and transcription of mitochondrial DNA were suppressed. ROS levels increased, and elevated ROS triggered mitochondrial retrograde signaling rather than inducing direct DNA damage. In this study, we could better understand the molecular network of Mdivi-1 by analyzing DNA methylation and mRNA transcription in the nucleus and further investigating various changes in mitochondria, providing inspiration for studying nuclear-mitochondrial communications.

Decreasing mitochondrial fission ameliorates HIF-1α-dependent pathological retinal angiogenesis

Angiogenesis plays a critical role in many pathological processes, including irreversible blindness in eye diseases such as retinopathy of prematurity. Endothelial mitochondria are dynamic organelles that undergo constant fusion and fission and are critical signalling hubs that modulate angiogenesis by coordinating reactive oxygen species (ROS) production and calcium signalling and metabolism. In this study, we investigated the role of mitochondrial dynamics in pathological retinal angiogenesis. We showed that treatment with vascular endothelial growth factor (VEGF; 20 ng/ml) induced mitochondrial fission in HUVECs by promoting the phosphorylation of dynamin-related protein 1 (DRP1). DRP1 knockdown or pretreatment with the DRP1 inhibitor Mdivi-1 (5 μM) blocked VEGF-induced cell migration, proliferation, and tube formation in HUVECs. We demonstrated that VEGF treatment increased mitochondrial ROS production in HUVECs, which was necessary for HIF-1α-dependent glycolysis, as well as proliferation, migration, and tube formation, and the inhibition of mitochondrial fission prevented VEGF-induced mitochondrial ROS production. In an oxygen-induced retinopathy (OIR) mouse model, we found that active DRP1 was highly expressed in endothelial cells in neovascular tufts. The administration of Mdivi-1 (10 mg·kg-1·d-1, i.p.) for three days from postnatal day (P) 13 until P15 significantly alleviated pathological angiogenesis in the retina. Our results suggest that targeting mitochondrial fission may be a therapeutic strategy for proliferative retinopathies and other diseases that are dependent on pathological angiogenesis.

Metabolic reprogramming of immune cells by mitochondrial division inhibitor-1 to prevent post-vascular injury neointimal hyperplasia

BACKGROUND AND AIMS

New treatments are needed to prevent neointimal hyperplasia that contributes to post-angioplasty and stent restenosis in patients with coronary artery disease (CAD) and peripheral arterial disease (PAD). We investigated whether modulating mitochondrial function using mitochondrial division inhibitor-1 (Mdivi-1) could reduce post-vascular injury neointimal hyperplasia by metabolic reprogramming of macrophages from a pro-inflammatory to anti-inflammatory phenotype.

METHODS AND RESULTS

In vivo Mdivi-1 treatment of Apoe-/- mice fed a high-fat diet and subjected to carotid-wire injury decreased neointimal hyperplasia by 68%, reduced numbers of plaque vascular smooth muscle cells and pro-inflammatory M1-like macrophages, and decreased plaque inflammation, endothelial activation, and apoptosis, when compared to control. Mdivi-1 treatment of human THP-1 macrophages shifted polarization from a pro-inflammatory M1-like to an anti-inflammatory M2-like phenotype, reduced monocyte chemotaxis and migration to CCL2 and macrophage colony stimulating factor (M-CSF) and decreased secretion of pro-inflammatory mediators. Finally, treatment of pro-inflammatory M1-type-macrophages with Mdivi-1 metabolically reprogrammed them to an anti-inflammatory M2-like phenotype by inhibiting oxidative phosphorylation and attenuating the increase in succinate levels and correcting the decreased levels of arginine and citrulline.

CONCLUSIONS

We report that treatment with Mdivi-1 inhibits post-vascular injury neointimal hyperplasia by metabolic reprogramming macrophages towards an anti-inflammatory phenotype thereby highlighting the therapeutic potential of Mdivi-1 for preventing neointimal hyperplasia and restenosis following angioplasty and stenting in CAD and PAD patients.

Multiomics Reveals Induction of Neuroblastoma SK-N-BE(2)C Cell Death by Mitochondrial Division Inhibitor 1 through Multiple Effects

Mitochondrial division inhibitor 1 (Mdivi-1) is a well-known synthetic compound aimed at inhibiting dynamin-related protein 1 (Drp1) to suppress mitochondrial fission, making it a valuable tool for studying mitochondrial dynamics. However, its specific effects beyond Drp1 inhibition remain to be confirmed. In this study, we employed integrative proteomics and phosphoproteomics to delve into the molecular responses induced by Mdivi-1 in SK-N-BE(2)C cells. A total of 3070 proteins and 1945 phosphorylation sites were identified, with 880 of them represented as phosphoproteins. Among these, 266 proteins and 97 phosphorylation sites were found to be sensitive to the Mdivi-1 treatment. Functional enrichment analysis unveiled their involvement in serine biosynthesis and extrinsic apoptotic signaling pathways. Through targeted metabolomics, we observed that Mdivi-1 enhanced intracellular serine biosynthesis while reducing the production of C24:1-ceramide. Within these regulated phosphoproteins, dynamic dephosphorylation of proteasome subunit alpha type 3 serine 250 (PSMA3-S250) occurred after Mdivi-1 treatment. Further site-directed mutagenesis experiments revealed that the dephosphorylation-deficient mutant PSMA3-S250A exhibited a decreased cell survival. This research confirms that Mdivi-1's inhibition of mitochondrial division leads to various side effects, ultimately influencing cell survival, rather than solely targeting Drp1 inhibition.

Mdivi-1 Rescues Memory Decline in Scopolamine-Induced Amnesic Male Mice by Ameliorating Mitochondrial Dynamics and Hippocampal Plasticity

Memory loss, often known as amnesia, is common in the elderly population and refers to forgetting facts and experiences. It is associated with increased mitochondrial fragmentation, though the contribution of mitochondrial dynamics in amnesia is poorly understood. Therefore, the present study is aimed at elucidating the role of Mdivi-1 in mitochondrial dynamics, hippocampal plasticity, and memory during scopolamine (SC)-induced amnesia. The findings imply that Mdivi-1 significantly increased the expression of Arc and BDNF proteins in the hippocampus of SC-induced amnesic mice, validating improved recognition and spatial memory. Moreover, an improved mitochondrial ultrastructure was attributed to a decline in the percentage of fragmented and spherical-shaped mitochondria after Mdivi-1 treatment in SC-induced mice. The significant downregulation of p-Drp1 (S616) protein and upregulation of Mfn2, LC3BI, and LC3BII proteins in Mdivi-1-treated SC-induced mice indicated a decline in fragmented mitochondrial number and healthy mitochondrial dynamics. Mdivi-1 treatment alleviated ROS production and Caspase-3 activity and elevated mitochondrial membrane potential, Vdac1 expression, ATP production, and myelination, resulting in reduced neurodegeneration in SC mice. Furthermore, the decline of pro-apoptotic protein cytochrome-c and increase of anti-apoptotic proteins Procaspase-9 and Bcl-2 in Mdivi-1-treated SC-induced mice suggested improved neuronal health. Mdivi-1 also increased the dendritic arborization and spine density, which was further corroborated by increased expression of synaptophysin and PSD95. In conclusion, the current study suggests that Mdivi-1 treatment improves mitochondrial ultrastructure and function through the regulation of mitochondrial dynamics. These changes further improve neuronal cell density, myelination, dendritic arborization, and spine density, decrease neurodegeneration, and improve recognition and spatial memory. Schematic presentation depicts that Mdivi-1 rescues memory decline in scopolamine-induced amnesic male mice by ameliorating mitochondrial dynamics and hippocampal plasticity.

Mitochondrial dynamics modulate the allergic inflammation in a murine model of allergic rhinitis

OBJECTIVE

Allergic rhinitis (AR) is a common allergic disorder, afflicting thousands of human beings. Aberrant mitochondrial dynamics are important pathological elements for various immune cell dysfunctions and allergic diseases. However, the connection between mitochondrial dynamics and AR remains poorly understood. This study aimed to determine whether mitochondrial dynamics influence the inflammatory response in AR.

METHODS

In the present study, we established a murine model of AR by sensitization with ovalbumin (OVA). Then, we investigated the mitochondrial morphology in mice with AR by transmission electron microscopy and confocal fluorescence microscopy, and evaluated the role of Mdivi-1 (an inhibitor of mitochondrial fission) on allergic symptoms, inflammatory responses, allergic-related signals, and reactive oxygen species formation.

RESULTS

There was a notable enhancement in mitochondrial fragmentation in the nasal mucosa of mice following OVA stimulation, whereas Mdivi-1 prevented aberrant mitochondrial morphology. Indeed, Mdivi-1 alleviated the rubbing and sneezing responses in OVA-sensitized mice. Compared with vehicle-treated ones, mice treated with Mdivi-1 exhibited a reduction in interleukin (IL)-4, IL-5, and specific IgE levels in both serum and nasal lavage fluid, and shown an amelioration in inflammatory response of nasal mucosa. Meanwhile, Mdivi-1 treatment was associated with a suppression in JAK2 and STAT6 activation and reactive oxygen species generation, which act as important signaling for allergic response.

CONCLUSION

Our findings reveal mitochondrial dynamics modulate the allergic responses in AR. Mitochondrial dynamics may represent a promising target for the treatment of AR.

Inhibition of DRP1-dependent mitochondrial fission by Mdivi-1 alleviates atherosclerosis through the modulation of M1 polarization

BACKGROUND

Inflammation and immune dysfunction with classically activated macrophages(M1) infiltration are important mechanisms in the progression of atherosclerosis (AS). Dynamin-related protein 1 (DRP1)-dependent mitochondrial fission is a novel target for alleviating inflammatory diseases. This study aimed to investigate the effects of DRP1 inhibitor Mdivi-1 on AS.

METHODS

ApoE-/- mice were fed with a high-fat diet supplemented with or without Mdivi-1. RAW264.7 cells were stimulated by ox-LDL, pretreated with or without MCC950, Mito-TEMPO, or Mdivi-1. The burden of plaques and foam cell formation were determined using ORO staining. The blood lipid profles and inflammatory cytokines in serum were detected by commercial kits and ELISA, respectively. The mRNA expression of macrophage polarization markers, activation of NLRP3 and the phosphorylation state of DRP1 were detected. Mitochondrial reactive oxygen species (mito-ROS), mitochondrial staining, ATP level and mitochondrial membrane potential were detected by mito-SOX, MitoTracker, ATP determination kit and JC-1 staining, respectively.

RESULTS

In vivo, Mdivi-1 reduced the plaque areas, M1 polarization, NLRP3 activation and DRP1 phosphorylation at Ser616. In vitro, oxidized low-density lipoprotein (ox-LDL) triggered M1 polarization, NLRP3 activation and abnormal accumulation of mito-ROS. MCC950 and Mito-TEMPO suppressed M1 polarization mediated foam cell formation. Mito-TEMPO significantly inhibited NLRP3 activation. In addition, Mdivi-1 reduced foam cells by inhibiting M1 polarization. The possible mechanisms responsible for the anti-atherosclerotic effects of Mdivi-1 on reducing M1 polarization were associated with suppressing mito-ROS/NLRP3 pathway by inhibiting DRP1 mediated mitochondrial fission. In vitro, similar results were observed by DRP1 knockdown.

CONCLUSION

Inhibition of DRP1-dependent mitochondrial fission by Mdivi-1 alleviated atherogenesis via suppressing mito-ROS/NLRP3-mediated M1 polarization, indicating DRP1-dependent mitochondrial fission as a potential therapeutic target for AS.

Role of KLF4/NDRG1/DRP1 axis in hypoxia-induced pulmonary hypertension

N-myc downstream regulated gene 1 (NDRG1) has recently drawn increasing attention because of its involvement in angiogenesis, cell proliferation, and differentiation. We used in vitro [human pulmonary artery smooth muscle cells (hPASMCs)] and in vivo (rat) models under hypoxic conditions and found a vital role of NDRG1 in reducing apoptosis and increasing proliferation and migration by overexpressing and knocking down NDRG1. We also proved that hypoxia induced the protein expression of dynamin-related protein 1 (DRP1) and stimulated The phosphatidylinositol-3-kinase (PI3K)/ Protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathways, and these effects were reversed by NDRG1 knockdown. The relationship between NDRG1 and DRP1 and the PI3K/Akt/mTOR pathway was further evaluated by adding mdivi-1 (DRP1 inhibitor) or LY294002 (PI3K inhibitor). NDRG1 was found to regulate the proliferation, apoptosis, and migration of hypoxia-treated hPASMCs via DRP1 and PI3K/Akt/mTOR signaling pathways. We explored the upstream regulators of NDRG1 using in vivo and in vitro hypoxia models. Hypoxia was found to upregulate and downregulate KLF transcription factor 4 (KLF4) protein expression in the cytoplasm and nucleus, respectively. Further, we showed that KLF4 regulated the proliferation and migration of hypoxia-treated hPASMCs via NDRG1. These results indicated a link between KLF4, NDRG1, and DRP1 for the first time, providing new ideas for treating hypoxic pulmonary hypertension.

Effects of Mdivi-1 on Extending the Golden Treatment Time following Hemorrhagic Shock in Hot Environment in Rats

It is found that a hot environment aggravates hemorrhagic shock-induced internal environment and organ dysfunction. Meanwhile mitochondria show over-fission. Whether inhibition of mitochondrial fission benefits from the early treatment of hemorrhagic shock under a hot environment is unclear. An uncontrolled hemorrhagic shock model in rats is used, and the effects of mitochondrial fission inhibitor mdivi-1 on mitochondrial function, organ function, and survival rate of rats are measured. The results show that 0.1-3 mg/kg mdivi-1 antagonizes hemorrhagic shock-induced mitochondrial fragment. In addition, mdivi-1 improves mitochondrial function, and alleviates hemorrhagic shock-induced oxidative stress and inflammation under a hot environment. Further studies show that 0.1-3 mg/kg Mdivi-1 reduces blood loss, and maintains a mean artery pressure (MAP) of 50-60 mmHg before bleeding-stops after hemorrhagic shock, compared with single Lactate Ringer's (LR) resuscitation. Notably, 1 mg/kg of Mdivi-1 extends the time of hypotensive resuscitation to 2-3 h. During 1 or 2 h of ligation, Mdivi-1 prolongs survival time and protects vital organ function by rescuing mitochondrial morphology and improving mitochondrial function. These results suggest Mdivi-1 is suitable for the early treatment of hemorrhagic shock under a hot environment and can extend the golden treatment time to 2-3 hour for hemorrhagic shock under a hot environment.

Mitochondrial division inhibitor (mdivi-1) inhibits proliferation and epithelial-mesenchymal transition via the NF-κB pathway in thyroid cancer cells

Excessively fragmented mitochondria have been reported in thyroid cancer (TC). Mitochondrial division inhibitor (mdivi-1), a putative inhibitor of dynamin-related protein 1 (Drp1), prevents mitochondrial fission and thereby restricts cell proliferation across several types of primary cancer. However, the role of mdivi-1 on TC has not been sufficiently studied. This research is intended to explore the therapeutic effect of mdivi-1 in TC cells. Results demonstrated that highly invasive TC cells displayed excessive mitochondrial fission with more fragmented mitochondria. Treatment with mdivi-1 inhibited mitochondrial fission in 8505C cells as indicated by transmission electron microscope (TEM). It also impaired the proliferation and increased apoptosis in 8505C and K1 cells as shown by plate cloning assay, cell viability assay, and apoptosis assay. Mdivi-1 treatment also attenuated migratory and invasive abilities in 8505C and K1 cells as shown by the transwell assay and the wound healing assay. And we noticed the same inhibition of mdivi-1 in cell migration and cell viability after the knockdown of Drp1 in 8505C cells. This demonstrated that mdivi-1 exerted an anti-tumor effect independently of Drp1 in 8505C cells. Moreover, mdivi-1 treatment reversed epithelial-mesenchymal transition (EMT) by inhibiting the NF-κB pathway in 8505C cells. The present findings demonstrate that mdivi-1 has a therapeutic role in thyroid carcinoma.

Mito-TEMPO protects preimplantation porcine embryos against mitochondrial fission-driven apoptosis through DRP1/PINK1-mediated mitophagy

AIMS

Mdivi-1 (Md-1) is a well-known inhibitor of mitochondrial fission and mitophagy. The mitochondrial superoxide scavenger Mito-TEMPO (MT) exerts positive effects on the developmental competence of pig embryos. This study aimed to explore the adverse effects of Md-1 on developmental capacity in porcine embryos and the protective effects of MT against Md-1-induced injury.

MAIN METHODS

We exposed porcine embryos to Md-1 (10 and 50 μM) for 2 days after in vitro fertilization (IVF). MT (0.1 μM) treatment was applied for 4 days after exposing embryos to Md-1. We assessed blastocyst development, DNA damage, mitochondrial superoxide production, and mitochondrial distribution using TUNEL assay, Mito-SOX, and Mito-tracker, respectively. Subsequently, the expression of PINK1, DRP1, and p-DRP1Ser616 was evaluated via immunofluorescence staining and Western blot analysis.

KEY FINDINGS

Md-1 compromised the developmental competence of blastocysts. Apoptosis and mitochondrial superoxide production were significantly upregulated in 50 μM Md-1-treated embryos, accompanied by a downregulation of p-DRP1Ser616, PINK1, and LC3B levels and lower mitophagy activity at the blastocyst stage. We confirmed the protective effects of MT against the detrimental effect of Md-1 on blastocyst developmental competence, mitochondrial fission, and DRP1/PINK1-mediated mitophagy activation. Eventually, MT recovered DRP1/PINK1-mediated mitophagy and mitochondrial fission by inhibiting superoxide production in Md-1-treated embryos.

SIGNIFICANCE

MT protects against detrimental effects of Md-1 on porcine embryos by suppressing superoxide production. These findings expand available scientific knowledge on improving outcomes of IVF.

Mdivi-1 improves postoperative neurocognitive disorders in aged rats undergoing splenectomy by inhibiting dynamin-related protein-1

Background

The regulatory role of mitochondria in the inflammatory response of the nervous system postoperatively remains unclear. This study explored the relationship between mitochondria and postoperative neurocognitive dysfunction (PNCD) by regulating mitochondrial function in aged rats undergoing splenectomy.

Methods

A total of 120 aged rats were randomly divided into five groups (n=24) as follows: Control group (not subjected to any form of treatment), Sham group (subjected only to sham-splenectomized operation after anesthesia), Splenectomy group (only underwent splenectomy after anesthesia), Synonyms Mitochondrial division inhibitor 1 (Mdivi-1) group [treated with Mdivi-1, a dynamin-relatedprotein 1 (Drp1) inhibitor], and Dimethyl Sulfoxide (DMSO) group (treated with DMSO, a solvent). Inflammatory markers, namely interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α), were measured in the plasma and brains of the rats. Cognitive function was assessed using the Morris water maze test.

Results

During the perioperative period, the physiological parameters did not differ among the five groups (P>0.05). The results of the Morris water maze experiments showed that the memory of the rats was significantly impaired after splenectomy, which was alleviated by Mdivi-1 administration (P=0.04). Postoperatively, the proinflammatory cytokine levels in the serum and hippocampus tissue were upregulated, while Mdivi-1 administration reduced this increase. The electron microscopy and hematoxylin-eosin (HE) staining results indicated that the structure of neurons and mitochondria was minimally impaired in the Mdivi-1 group.

Conclusions

Aged rats that underwent splenectomy exhibited significant postoperative cognitive impairments. The selective inhibitor of Drp1, Mdivi-1, exerted protective effects against PNCD by ameliorating mitochondrial dysfunction and reducing the inflammatory response.

Regulation of mitochondrial fusion and mitophagy by intra-tumoral delivery of membrane-fused mitochondria or Midiv-1 enhances sensitivity to doxorubicin in triple-negative breast cancer

Increasing mitochondrial fusion by intra-tumoral grafting of membrane-fused mitochondria created with Pep-1 conjugation (P-Mito) contributes to breast cancer treatment, but it needs to be validated. Using mitochondrial division inhibitor-1 (Mdivi-1, Mdi) to disturb mitochondrial dynamics, we showed that the antitumor action of P-Mito in a mouse model of triple-negative breast cancer depends upon mitochondrial fusion and that Mdi treatment alone is ineffective. P-Mito significantly enhanced Doxorubicin (Dox) sensitivity by inducing mitochondrial fusion and mitophagy, and the same efficiency was also achieved with Mdi by inhibiting mitophagy. Cell death was induced via the p53 pathway and AIF nuclear translocation in the case of P-Mito, versus the caspase-dependent pathway for Mdi. Notably, both mitochondrial treatments reduced oxidative stress and blood vessel density of xenograft tumors, especially P-Mito, which was accompanied by inhibition of nuclear factor kappa-B activation. Furthermore, through enrichment analysis, four microRNAs in serum microvesicles induced by P-Mito caused expression of predicted targets via the PI3K-Akt pathway, and significantly impacted regulation of nuclear processes and myeloid cell differentiation. Clustering of gene-sets implicated a major steroid catabolic network. This study showed diverse roles of mitochondria in breast cancer and revealed effective adjuvant therapy targeting mitochondrial fusion and mitophagy.

Therapeutic Effect of Mitochondrial Division Inhibitor-1 (Mdivi-1) on Hyperglycemia-Exacerbated Early and Delayed Brain Injuries after Experimental Subarachnoid Hemorrhage

Background: Neurological deficits following subarachnoid hemorrhage (SAH) are caused by early or delayed brain injuries. Our previous studies have demonstrated that hyperglycemia induces profound neuronal apoptosis of the cerebral cortex. Morphologically, we found that hyperglycemia exacerbated late vasospasm following SAH. Thus, our previous studies strongly suggest that post-SAH hyperglycemia is not only a response to primary insult, but also an aggravating factor for brain injuries. In addition, mitochondrial fusion and fission are vital to maintaining cellular functions. Current evidence also shows that the suppression of mitochondrial fission alleviates brain injuries after experimental SAH. Hence, this study aimed to determine the effects of mitochondrial dynamic modulation in hyperglycemia-related worse SAH neurological prognosis. Materials and methods: In vitro, we employed an enzyme-linked immunosorbent assay (ELISA) to detect the effect of mitochondrial division inhibitor-1 (Mdivi-1) on lipopolysaccharide (LPS)-induced BV-2 cells releasing inflammatory factors. In vivo, we produced hyperglycemic rats via intraperitoneal streptozotocin (STZ) injections. Hyperglycemia was confirmed using blood-glucose measurements (>300 mg/dL) 7 days after the STZ injection. The rodent model of SAH, in which fresh blood was instilled into the craniocervical junction, was used 7 days after STZ administration. We investigated the mechanism and effect of Mdivi-1, a selective inhibitor of dynamin-related protein (Drp1) to downregulate mitochondrial fission, on SAH-induced apoptosis in a hyperglycemic state, and evaluated the results in a dose−response manner. The rats were divided into the following five groups: (1) control, (2) SAH only, (3) Diabetes mellitus (DM) + SAH, (4) Mdivi-1 (0.24 mg/kg) + DM + SAH, and (5) Mdivi-1 (1.2 mg/kg) + DM + SAH. Results: In vitro, ELISA revealed that Mdivi-1 inhibited microglia from releasing inflammatory factors, such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6. In vivo, neurological outcomes in the high-dose (1.2 mg/kg) Mdivi-1 treatment group were significantly reduced compared with the SAH and DM + SAH groups. Furthermore, immunofluorescence staining and ELISA revealed that a high dose of Mdivi-1 had attenuated inflammation and neuron cell apoptosis by inhibiting Hyperglycemia-aggravated activation, as well as microglia and astrocyte proliferation, following SAH. Conclusion: Mdivi-1, a Drp-1 inhibitor, attenuates cerebral vasospasm, poor neurological outcomes, inflammation, and neuron cell apoptosis following SAH + hyperglycemia.

Mdivi-1 alleviates cardiac fibrosis post myocardial infarction at infarcted border zone, possibly via inhibition of Drp1-Activated mitochondrial fission and oxidative stress

Mitochondrial division inhibitor 1(Mdivi-1) has been shown to play a beneficial role in a variety of diseases, mainly by inhibiting Drp1-mediated mitochondrial fission. The effects of Mdivi-1 on cardiac fibrosis at infarcted border zone area and its possible mechanism remain unclear. This study aimed to investigate the effects of Mdivi-1 on reactive cardiac fibrosis and cardiac function post myocardial infarction and its potential mechanisms. Mice were randomly divided into six groups(n = 9 for each group): Sham; Mdivi-1; MI 7d; MI 14d; MI 28d; MI 28d + Mdivi-1. The MI model was induced by ligation of LAD coronary artery. Mdivi-1 (1mg/kg) was administered to mice every other day at a time from the second day until the sacrifice of the mice (total 14 injection of Mdivi-1). In vitro experiments, the effect of Mdivi-1 on TGF-β1-induced fibrosis-related pathophysiological changes of fibroblasts was examined in NIH3T3 cells. We found that Mdivi-1 significantly attenuated fibroblast activation, collagen production and fibrosis at infarcted border zone after MI, improved impaired heart function. Mechanistically, we observed that Mdivi-1 reduced the protein expression of P-Drp1-S616 and abnormal mitochondrial fission of cardiac fibroblasts in the infarcted border zone area. In addition, we found that the effects of Mdivi-1 partially relied on increasing the expression of Hmox1 and inhibiting oxidative stress. In conclusion, Mdivi-1 could attenuate cardiac fibrosis at infarcted border zone and improve impaired heart function partially through attenuation of Drp1-mediated mitochondrial fission. Moreover, inhibition of oxidative stress, which is possible due to the up-regulation of Hmox1, may be another potential mechanism of action of Mdivi-1.

Modulating mitochondrial dynamics attenuates cardiac ischemia-reperfusion injury in prediabetic rats

Mitochondria are extraordinarily dynamic organelles that have a variety of morphologies, the status of which are controlled by the opposing processes of fission and fusion. Our recent study shows that inhibition of excessive mitochondrial fission by Drp1 inhibitor (Mdivi-1) leads to a reduction in infarct size and left ventricular (LV) dysfunction following cardiac ischemia-reperfusion (I/R) injury in high fat-fed induced pre-diabetic rats. In the present study, we investigated the cardioprotective effects of a mitochondrial fusion promoter (M1) and a combined treatment (M1 and Mdivi-1) in pre-diabetic rats. Wistar rats were given a high-fat diet for 12 weeks to induce prediabetes. The rats then subjected to 30 min-coronary occlusions followed by reperfusion for 120 min. These rats were intravenously administered M1 (2 mg/kg) or M1 (2 mg/kg) combined with Mdivi-1 (1.2 mg/kg) prior to ischemia, during ischemia or at the onset of reperfusion. We showed that administration of M1 alone or in combination with Mdivi-1 prior to ischemia, during ischemia or at the onset of reperfusion all significantly attenuated cardiac mitochondrial ROS production, membrane depolarization, swelling and dynamic imbalance, leading to reduced arrhythmias and infarct size, resulting in improved LV function in pre-diabetic rats. In conclusion, the promotion of mitochondrial fusion at any time-points during cardiac I/R injury attenuated cardiac mitochondrial dysfunction and dynamic imbalance, leading to decreased infarct size and improved LV function in pre-diabetic rats.

Effects of Mdivi-1 on Neural Mitochondrial Dysfunction and Mitochondria-Mediated Apoptosis in Ischemia-Reperfusion Injury After Stroke: A Systematic Review of Preclinical Studies

This systematic review sought to determine the effects of Mitochondrial division inhibitor-1 (Mdivi-1) on neural mitochondrial dysfunction and neural mitochondria-mediated apoptosis in ischemia/reperfusion (I/R) injury after ischemic stroke. Pubmed, Web of Science, and EMBASE databases were searched through July 2021. The studies published in English language that mentioned the effects of Mdivi-1 on neural mitochondrial dysfunction and neural mitochondria-mediated apoptosis in I/R-induced brain injury were included. The CAMARADES checklist (for in vivo studies) and the TOXRTOOL checklist (for in vitro studies) were used for study quality evaluation. Twelve studies were included (median CAMARADES score = 6; TOXRTOOL scores ranging from 16 to 18). All studies investigated neural mitochondrial functions, providing that Mdivi-1 attenuated the mitochondrial membrane potential dissipation, ATP depletion, and complexes I-V abnormalities; enhanced mitochondrial biogenesis, as well as inactivated mitochondrial fission and mitophagy in I/R-induced brain injury. Ten studies analyzed neural mitochondria-mediated apoptosis, showing that Mdivi-1 decreased the levels of mitochondria-mediated proapoptotic factors (AIF, Bax, cytochrome c, caspase-9, and caspase-3) and enhanced the level of antiapoptotic factor (Bcl-2) against I/R-induced brain injury. The findings suggest that Mdivi-1 can protect neural mitochondrial functions, thereby attenuating neural mitochondria-mediated apoptosis in I/R-induced brain injury. Our review supports Mdivi-1 as a potential therapeutic compound to reduce brain damage in ischemic stroke (PROSPERO protocol registration ID: CRD42020205808). Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/], identifier [CRD42020205808].

Mdivi-1 Modulates Macrophage/Microglial Polarization in Mice with EAE via the Inhibition of the TLR2/4-GSK3β-NF-κB Inflammatory Signaling Axis

Macrophage/microglial modulation plays a critical role in the pathogenesis of multiple sclerosis (MS), which is an inflammatory disorder of the central nervous system. Dynamin-related protein 1 is a cytoplasmic molecule that regulates mitochondrial fission. It has been proven that mitochondrial fission inhibitor 1 (Mdivi-1), a small molecule inhibitor of Drp1, can relieve experimental autoimmune encephalomyelitis (EAE), a preclinical animal model of MS. Whether macrophages/microglia are involved in the pathological process of Mdivi-1-treated EAE remains to be determined. Here, we studied the anti-inflammatory effect of Mdivi-1 on mice with oligodendrocyte glycoprotein peptide_35-55 (MOG_35-55)-induced EAE. We found that Drp1 phosphorylation at serine 616 in macrophages/microglia was decreased with Mdivi-1 treatment, which was accompanied by decreased antigen presentation capacity of the macrophages/microglia in the EAE mouse spinal cord. The Mdivi-1 treatment caused macrophage/microglia to produce low levels of proinflammatory molecules, such as CD16/32, iNOS, and TNF-α, and high levels of anti-inflammatory molecules, such as CD206, IL-10, and Arginase-1, suggesting that Mdivi-1 promoted the macrophage/microglia shift from the inflammatory M1 phenotype to the anti-inflammatory M2 phenotype. Moreover, Mdivi-1 was able to downregulate the expression of TRL2, TRL4, GSK-3β, and phosphorylated NF-κB-p65 and prevent NF-κB-mediated IL-1β and IL-6 production. In conclusion, these results indicate that Mdivi-1 significantly alleviates inflammation in mice with EAE by promoting M2 polarization by inhibiting TLR2/4- and GSK3β-mediated NF-κB activation.

Protective Effects of Inhibition of Mitochondrial Fission on Organ Function After Sepsis

Sepsis-associated organ dysfunction plays a critical role in its high mortality, mainly in connection with mitochondrial dysfunction. Whether the inhibition of mitochondrial fission is beneficial to sepsis-related organ dysfunction and underlying mechanisms are unknown. Cecal ligation and puncture induced sepsis in rats and dynamic related protein 1 knockout mice, lipopolysaccharide-treated vascular smooth muscle cells and cardiomyocytes, were used to explore the effects of inhibition of mitochondrial fission and specific mechanisms. Our study showed that mitochondrial fission inhibitor Mdivi-1 could antagonize sepsis-induced organ dysfunction including heart, vascular smooth muscle, liver, kidney, and intestinal functions, and prolonged animal survival. The further study showed that mitochondrial functions such as mitochondrial membrane potential, adenosine-triphosphate contents, reactive oxygen species, superoxide dismutase and malonaldehyde were recovered after Mdivi-1 administration via improving mitochondrial morphology. And sepsis-induced inflammation and apoptosis in heart and vascular smooth muscle were alleviated through inhibition of mitochondrial fission and mitochondrial function improvement. The parameter trends in lipopolysaccharide-stimulated cardiomyocytes and vascular smooth muscle cells were similar in vivo. Dynamic related protein 1 knockout preserved sepsis-induced organ dysfunction, and the animal survival was prolonged. Taken together, this finding provides a novel effective candidate therapy for severe sepsis/septic shock and other critical clinical diseases.

Melatonin Protects Against Mdivi-1-Induced Abnormal Spindle Assembly and Mitochondrial Superoxide Production During Porcine Oocyte Maturation

Mitochondrial division inhibitor 1 (Mdivi-1) reportedly provides a close connection between oocyte maturation and mitochondrial function in pigs. N-acetyl-5-methoxy-tryptamine (melatonin) is known to be a representative antioxidant with the ability to rehabilitate meiotic maturation of porcine oocytes. However, the ability of melatonin to recover Mdivi-1-mediated disruption of spindle formation during meiotic maturation of porcine oocytes during in vitro maturation (IVM) has not been studied. Here, we first investigated changes in mitochondrial length, such as fragmentation and elongation form, in mature porcine oocytes during IVM. Mature oocytes require appropriate mitochondrial fission for porcine oocyte maturation. We identified a dose-dependent reduction in meiotic maturation in porcine oocytes following Mdivi-1 treatment (50, 75, and 100 μM). We also confirmed changes in mitochondrial fission protein levels [dynamin-related protein 1 phosphorylation at serine 616 (pDRP1-Ser616) and dynamin-related protein 1 (DRP1)], mitochondrial membrane potential, and ATP production in 75 μM Mdivi-1-treated oocytes. As expected, Mdivi-1 significantly reduced mitochondrial function and DRP1 protein levels and increased spindle abnormalities in porcine oocytes. In addition, we confirmed that melatonin restores abnormal spindle assembly and reduces meiotic maturation rates by Mdivi-1 during porcine oocyte maturation. Interestingly, the expression levels of genes that reduce DNA damage and improve tubulin formation were enhanced during porcine meiotic maturation. Taken together, these results suggest that melatonin has direct beneficial effects on meiotic maturation through tubulin formation factors during porcine oocyte maturation.

Mdivi-1, a mitochondrial fission inhibitor, reduces angiotensin-II- induced hypertension by mediating VSMC phenotypic switch

Vascular smooth muscle cell (VSMC) phenotypic switch plays an essential role in the pathogenesis of hypertension. Mitochondrial dynamics, such as mitochondrial fission, can also contribute to VSMC phenotypic switch. Whether mitochondrial fission act as a novel target for anti-hypertensive drug development remains unknown. In the present study, we confirmed that angiotensin II (AngII) rapidly and continuously induced mitochondrial fission in VSMCs. We also detected the phosphorylation status of dynamin-related protein-1 (Drp1), a key protein involved in mitochondrial fission, at Ser616 site; and observed Drp1 mitochondrial translocation in VSMCs or arteries of AngII-induced hypertensive mice. The Drp1 inhibitor mitochondrial division inhibitor-1 (Mdivi-1) dramatically reversed AngII-induced Drp1 phosphorylation, mitochondrial fission, and reactive oxidative species generation. Treatment with Mdivi-1 (20 mg/kg/every other day) significantly attenuated AngII-induced hypertension (22 mmHg), arterial remodeling, and cardiac hypertrophy, in part by preventing VSMC phenotypic switch. In addition, Mdivi-1 treatment was not associated with liver or renal functional injury. Collectively, these results indicate that Mdivi-1 inhibited mitochondrial fission, recovered mitochondrial activity, and prevented AngII-induced VSMC phenotypic switch, resulting in reduced hypertension.

Preservation of mitochondrial homeostasis is responsible for the ameliorative effects of Suhuang antitussive capsule on non-resolving inflammation via inhibition of NF-κB signaling and NLRP3 inflammasome activation

ETHNOPHARMACOLOGICAL RELEVANCE

Suhuang antitussive capsule (Suhuang), one of traditional antitussive Chinese patent medicines, has been used for the treatment of post-infectious cough and cough variant asthma in clinical practice. It has been demonstrated to show numerous biological actions including antitussive and anti-inflammatory effects.

AIM OF THE STUDY

This study aims to investigate the effects of Suhuang on non-resolving inflammation and its underlying molecular mechanism.

MATERIAL AND METHODS

In vitro, mitochondrial membrane potential and ROS were detected by flow cytometry analysis. mtDNA release and mPTP fluorescence were determined by Q-PCR and fluorescence microplate reader analysis. Cytochrome C release and 8-OHdG levels were evaluated by ELISA. Additionally, the effects of Suhuang on Drp1, MMP9, IκBα/NF-κB and NLRP3/ASC/Caspase-1 expression were determined by Q-PCR, gelatin zymography or immunoblot analysis. In vivo, C57/BL6 mice were orally administrated for 2 weeks with Suhuang, then lung injury was induced by LPS. Inflammatory mediators mRNA, histological assessment and NF-κB/Caspase-1/IL-1β levels were evaluated by Q-PCR, H&E staining and immunoblot analysis. Two sepsis models of mice were further used to evaluate its anti-inflammatory effects.

RESULTS

Suhuang restored mitochondrial homeostasis by inhibiting Drp1 activation and mitochondrial fission. Besides, Suhuang reduced mPTP opening, mitochondrial membrane potential collapse, ROS overproduction and mtDNA release. Moreover, Suhuang down-regulated MMP9 expression. As a consequence of preserved mitochondrial homeostasis, Suhuang inhibited NF-κB pathway activation by prevention of NF-κB-p65 phosphorylation and IκBα degradation. Suhuang also limited NLRP3 inflammasome activation by blocking NLRP3-ASC interaction and promoting NLRP3 ubiquitination degradation. Drp1 knockdown in vitro diminished the inhibitory effects of Suhuang on inflammatory responses, indicating the essential role of Drp1 in the Suhuang's activity. Consistently, the therapeutic effects of Suhuang were confirmed in LPS-inhaled mice, which recapitulated the protective actions of Suhuang in mitochondrial homeostasis in vitro. Additionally, two sepsis models of mice confirmed the inhibitory effects of Suhuang on uncontrolled inflammation.

CONCLUSIONS

Altogether, our work reveals that Suhuang inhibits non-resolving inflammation through inhibition of NF-κB signaling and NLRP3 inflammasome activation by preserving mitochondrial homeostasis, providing new pharmacological data for the clinical use of Suhuang. Our study also suggests mitochondrial homeostasis as a potential intrinsic regulatory strategy for treating inflammatory diseases.

CFTR chloride channel activity modulates the mitochondrial morphology in cultured epithelial cells

The impairment of the CFTR channel activity, a cAMP-activated chloride (Cl^-) channel responsible for cystic fibrosis (CF), has been associated with a variety of mitochondrial alterations such as modified gene expression, impairment in oxidative phosphorylation, increased reactive oxygen species (ROS), and a disbalance in calcium homeostasis. The mechanisms by which these processes occur in CF are not fully understood. Previously, we demonstrated a reduced MTND4 expression and a failure in the mitochondrial complex I (mCx-I) activity in CF cells. Here we hypothesized that the activity of CFTR might modulate the mitochondrial fission/fusion balance, explaining the decreased mCx-I. The mitochondrial morphology and the levels of mitochondrial dynamic proteins MFN1 and DRP1 were analysed in IB3-1 CF cells, and S9 (IB3-1 expressing wt-CFTR), and C38 (IB3-1 expressing a truncated functional CFTR) cells. The mitochondrial morphology of IB3-1 cells compared to S9 and C38 cells showed that the impaired CFTR activity induced a fragmented mitochondrial network with increased rounded mitochondria and shorter branches. Similar results were obtained by using the CFTR pharmacological inhibitors CFTR(inh)-172 and GlyH101 on C38 cells. These morphological changes were accompanied by modifications in the levels of the mitochondrial dynamic proteins MFN1, DRP1, and p(616)-DRP1. IB3-1 CF cells treated with Mdivi-1, an inhibitor of mitochondrial fission, restored the mCx-I activity to values similar to those seen in S9 and C38 cells. These results suggest that the mitochondrial fission/fusion balance is regulated by the CFTR activity and might be a potential target to treat the impaired mCx-I activity in CF.

Mdivi-1 alleviates brain damage and synaptic dysfunction after intracerebral hemorrhage in mice

As a selective inhibitor of mitochondrial fission protein dynamin-related protein-1 (Drp1), mitochondrial division inhibitor 1 (mdivi-1) can cross the blood-brain barrier (BBB) and exert neuroprotection. However, it remains unclear whether mdivi-1 can attenuate intracerebral hemorrhage (ICH)-induced secondary brain injury. This study was undertaken to characterize the roles of mdivi-1 in short-term and long-term behavioral outcomes, along with synaptic plasticity changes in mice after ICH. The results indicated mdivi-1 reversed Drp1 translocation and the morphologic changes of mitochondria, as well as ameliorated short-term neurobehavioral deficits, the BBB disruption and brain edema remarkably. In addition, mdivi-1 could rescue ICH-induced motor and memory dysfunctions. Mdivi-1 could also prevent ICH-induced reductions in synaptic proteins (synapsin I, PSD95) and phosphorylated cAMP-response element binding (p-CREB). In vitro, mdivi-1 inhibited hemin-induced hippocampal neuron death and improved neurite outgrowth. In conclusion, we found that mdivi-1 can alleviate short-term and long-term neurological deficits, synaptic dysfunction. These findings demonstrate that mdivi-1 may be beneficial in the treatment of secondary brain injury, synaptic dysfunction and neurological outcomes caused by ICH.

Inhibition of Drp1 Sensitizes Cancer Cells to Cisplatin-Induced Apoptosis through Transcriptional Inhibition of c-FLIP Expression

Mitochondrial fragmentation occurs during the apoptosis. Dynamin-related protein 1 (Drp1) acts as an important component in mitochondrial fission machinery and can regulate various biological processes including apoptosis, cell cycle, and proliferation. The present study demonstrates that dysfunction of mitochondrial dynamics plays a pivotal role in cisplatin-induced apoptosis. Inhibiting the mitochondrial fission with the specific inhibitor (Mdivi-1) did not affect apoptotic cell death in low concentrations (<10 μM). Interestingly, mdivi-1 enhanced cisplatin-induced apoptosis in cancer cells, but not in normal cells. Particularly in the presence of mdivi-1, several human cancer cell lines, including renal carcinoma cell line Caki-1, became vulnerable to cisplatin by demonstrating the traits of caspase 3-dependent apoptosis. Combined treatment induced downregulation of c-FLIP expression transcriptionally, and ectopic expression of c-FLIP attenuated combined treatment-induced apoptotic cell death with mdivi-1 plus cisplatin. Collectively, our data provide evidence that mdivi-1 might be a cisplatin sensitizer.

Mdivi-1 attenuates oxidative stress and exerts vascular protection in ischemic/hypoxic injury by a mechanism independent of Drp1 GTPase activity

Vascular dysfunctions such as vascular hyporeactivity following ischemic/hypoxic injury are a major cause of death in injured patients. In this study, we showed that treatment with mitochondrial division inhibitor 1 (Mdivi-1), a selective inhibitor of dynamin-related protein 1 (Drp1), significantly improved vascular reactivity in ischemic rats by attenuating oxidative stress. The antioxidative effects of Mdivi-1 were relatively Drp1-independent, and possibly due to an increase in the levels of the antioxidant enzymes, SOD1 and catalase, as well as to enhanced Nrf2 expression. In addition, we found that while Mdivi-1 had little effect on Drp1 GTPase activity in vascular smooth muscle cells, it inhibited hypoxia-induced Drp1 phosphorylation at Ser-616, reducing excessive mitochondrial fission and slightly enhancing mitochondrial fusion. These effects possibly contributed to vascular protection at an early stage of ischemic/hypoxic injury. Finally, Mdivi-1 stabilized hemodynamics, increased vital organ perfusion, and improved rat survival after ischemic/hypoxic injury, proving a promising therapeutic agent for ischemic/hypoxic injury.

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Mdivi-1 improved vascular contractility in ischemic rats.

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Mdivi-1 attenuated hypoxia-induced oxidative stress and mitochondrial changes.

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Drp1 recruitment to mitochondria, not GTPase activity, involved in Mdivi-1 effects.

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Mdivi-1 has therapeutic potential against ischemic injury.

Echinacoside attenuates inflammatory response in a rat model of cervical spondylotic myelopathy via inhibition of excessive mitochondrial fission

Cervical spondylotic myelopathy (CSM) is a leading cause of spinal cord dysfunction with few treatment options. Although mitochondrial dynamics are linked to a wide range of pathological changes in neurodegenerative diseases, a connection between aberrant mitochondrial dynamics and CSM remains to be illuminated. In addition, mechanisms underlying the emerging anti-inflammatory and neuroprotective effects of echinacoside (ECH), the main active ingredient of Cistanche salsa, are poorly understood. We hypothesized that excessive mitochondrial fission plays a critical role in regulating inflammatory responses in CSM, and ECH might alleviate such responses by regulating mitochondrial dynamics. To this end, we assessed the effects of ECH and Mdivi-1, a selective inhibitor of dynamin-related protein (Drp1), in a rat model of chronic cervical cord compression and activated BV2 cells. Our results showed that rats with Mdivi-1 intervention had improved motor function compared with vehicle-treated rats. Indeed, Mdivi-1 treatment attenuated pro-inflammatory cytokine expression, as well as activation of the nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, nuclear transcription factor-κB (NF-κB), and Drp1 in lesions. Compared with vehicle-treated rats, compression sites of Mdivi-1-treated animals exhibited elongated mitochondrial morphologies and reduced reactive oxygen species (ROS). Similarly, ECH-treated rats exhibited neurological recovery and suppression of inflammatory response or related signals in the lesion area after treatment. Interestingly, ECH treatment partly reversed aberrant mitochondrial fragmentation and oxidative stress within the lesion area. In vitro data suggested that ECH suppressed activated microglia by modulating activation of the NLRP3 inflammasome and NF-κB signaling. Furthermore, we observed that ECH markedly inhibited Drp1 translocation onto mitochondria, whereby it regulated mitochondrial dynamics and ROS production, which act as regulators of NLRP3 inflammasome activation and NF-κB signaling. Thus, our findings reveal that mitochondrial dynamics modulate inflammatory responses during CSM. Moreover, ECH may attenuate neuroinflammation in rats subjected to chronic cervical cord compression by regulating Drp1-dependent mitochondrial fission and activation of downstream signaling.

Increased mitochondrial fragmentation in polycystic kidney disease acts as a modifier of disease progression

Autosomal dominant polycystic kidney disease (ADPKD) is a common monogenic disorder, characterized by bilateral renal cyst formation. Multiple pathways are de-regulated in cystic epithelia offering good opportunities for therapy. Others and we have previously reported that metabolic reprogramming, including alterations of the TCA cycle, are prominent features of ADPKD. Several lines of evidence suggest that mitochondrial impairment might be responsible for the metabolic alterations. Here, we performed morphologic and morphometric evaluation of mitochondria by TEM in an orthologous mouse model of PKD caused by mutations in the Pkd1 gene (Ksp-Cre;Pkd1^flox/- ). Furthermore, we measured mitochondrial respiration by COX and SDH enzymatic activity in situ. We found several alterations including reduced mitochondrial mass, altered structure and fragmentation of the mitochondrial network in cystic epithelia of Ksp-Cre;Pkd1^flox/- mice. At the molecular level, we found reduced expression of the pro-fusion proteins OPA1 and MFN1 and up-regulation of the pro-fission protein DRP1. Importantly, administration of Mdivi-1, which interferes with DRP1 rescuing mitochondrial fragmentation, significantly reduced kidney/body weight, cyst formation, and improved renal function in Ksp-Cre;Pkd1^flox/- mice. Our data indicate that impaired mitochondrial structure and function play a role in disease progression, and that their improvement can significantly modify the course of the disease.

Mitochondrial Fission-Mediated Lung Development in Newborn Rats With Hyperoxia-Induced Bronchopulmonary Dysplasia With Pulmonary Hypertension

Background: Bronchopulmonary dysplasia (BPD) is the most common chronic respiratory disease in premature infants. Oxygen inhalation and mechanical ventilation are common treatments, which can cause hyperoxia-induced lung injury, but the underlying mechanism is not yet understood. Mitochondrial fission is essential for mitochondrial homeostasis. The objective of this study was to determine whether mitochondrial fission (dynamin-related protein 1, Drp1) is an important mediator of hyperoxia lung injury in rats. Methods: The animal model of BPD was induced with high oxygen (80-85% O₂). Pulmonary histological changes were observed by hematoxylin-eosin (HE) staining. Pulmonary microvessels were observed by immunofluorescence staining of von Willebrand Factor (vWF). Protein expression levels of Drp1 and p-Drp1 (Ser616) were observed using Western Blot. We used echocardiography to measure pulmonary artery acceleration time (PAT), pulmonary vascular resistance index (PVRi), peak flow velocity of the pulmonary artery (PFVP), pulmonary arteriovenous diameter, and pulmonary vein peak velocity. Mitochondrial division inhibitor-1 (Mdivi-1) was used as an inhibitor of Drp1, and administered through intraperitoneal injection (25 mg/kg). Results: Pulmonary artery resistance of the hyperoxide-induced neonatal rat model of BPD increased after it entered normoxic convalescence. During the critical stage of alveolar development in neonatal rats exposed to high oxygen levels for an extended period, the expression and phosphorylation of Drp1 increased in lung tissues. When Drp1 expression was inhibited, small pulmonary vessel development improved and PH was relieved. Conclusion: Our study shows that excessive mitochondrial fission is an important mediator of hyperoxia-induced pulmonary vascular injury, and inhibition of mitochondrial fission may be a useful treatment for hyperoxia-induced related pulmonary diseases.

Mdivi-1, a mitochondrial fission inhibitor, modulates T helper cells and suppresses the development of experimental autoimmune encephalomyelitis

Background

Unrestrained activation of Th1 and Th17 cells is associated with the pathogenesis of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). While inactivation of dynamin-related protein 1 (Drp1), a GTPase that regulates mitochondrial fission, can reduce EAE severity by protecting myelin from demyelination, its effect on immune responses in EAE has not yet been studied.

Methods

We investigated the effect of Mdivi-1, a small molecule inhibitor of Drp1, on EAE. Clinical scores, inflammation, demyelination and Drp1 activation in the central nervous system (CNS), and T cell responses in both CNS and periphery were determined.

Results

Mdivi-1 effectively suppressed EAE severity by reducing demyelination and cellular infiltration in the CNS. Mdivi-1 treatment decreased the phosphorylation of Drp1 (ser616) on CD4⁺ T cells, reduced the numbers of Th1 and Th17 cells, and increased Foxp3⁺ regulatory T cells in the CNS. Moreover, Mdivi-1 treatment effectively inhibited IFN-γ⁺, IL-17⁺, and GM-CSF⁺ CD4⁺ T cells, while it induced CD4⁺ Foxp3⁺ regulatory T cells in splenocytes by flow cytometry.

Conclusions

Together, our results demonstrate that Mdivi-1 has therapeutic potential in EAE by modulating the balance between Th1/Th17 and regulatory T cells.

Mdivi-1 and mitochondrial fission: recent insights from fungal pathogens

Mitochondrial fission shows potential as a therapeutic target in non-infectious human diseases. The compound mdivi-1 was identified as a mitochondrial fission inhibitor that acts against the evolutionarily conserved mitochondrial fission GTPase Dnm1/Drp1, and shows promising data in pre-clinical models of human pathologies. Two recent studies, however, found no evidence that mdivi-1 acts as a mitochondrial fission inhibitor and proposed other mechanisms. In mammalian cells, Bordt et al. showed that mdivi-1 inhibits complex I in mitochondria (Dev Cell 40:583, 2017). In a second study, we have recently demonstrated that mdivi-1 does not trigger a mitochondrial morphology change in the human yeast pathogen Candida albicans, but impacts on endogenous nitric oxide (NO) levels and inhibits the key virulence property of hyphal formation (Koch et al., Cell Rep 25:2244, 2018). Here we discuss recent insights into mdivi-1’s action in pathogenic fungi and the potential and challenges for repurposing it as an anti-infective. We also outline recent findings on the roles of mitochondrial fission in human and plant fungal pathogens, with the goal of starting the conversation on whether the research field of fungal pathogenesis can benefit from efforts in other disease areas aimed at developing therapeutic inhibitors of mitochondrial division.

Mitochondrial division inhibitor-1 potentiates cisplatin-induced apoptosis via the mitochondrial death pathway in cholangiocarcinoma cells

AIMS

Mdivi-1, a selective Drp-1 inhibitor, impedes mitochondrial dynamics and suppresses cancer proliferation and progression. Cholangiocarcinoma (CCA) is a very aggressive malignancy which is refractory to chemotherapy. The study investigated the mechanism of the chemosensitizing effect of mdivi-1 in cholangiocarcinoma.

MAIN METHODS

CCA cells and HEK293 T cells were employed in the study. Cell viability and induction of apoptotic cell death were determined by the MTT and acridine orange-ethidium bromide methods. Cellular glutathione content and reactive oxygen species (ROS) formation were assessed using thiol green and 2',7'-dichlorofluorescin diacetate fluorescent probes, respectively. Mitochondrial transmembrane potential and autophagy were detected by JC-1 dye and autophagy assay. Cell cycle progression was analyzed by flow cytometry. Cell migration was measured using the wound healing assay. Proteins involved in cell proliferation and cell cycle were analyzed by western immunoblotting.

KEY FINDINGS

Mdivi-1 enhanced cisplatin-induced cytotoxicity in CCA cells but not in HEK293 T cells. Mdivi-1 enhanced cisplatin induced glutathione redox stress, ROS formation, and loss of mitochondrial transmembrane potential. Moreover, mdivi-1 also inhibited autophagic flux and suppressed CCA cell migration.

SIGNIFICANCE

Mdivi-1 sensitized CCA cells to cytotoxicity of cisplatin in association with increases of oxidative stress and autophagosomes, and induced cell death via the mitochondrial pathway. Disruption of mitochondrial dynamics may be a novel strategy to improve the efficacy of chemotherapy to treat CCA.

Mitochondrial regulation of diabetic vascular disease: an emerging opportunity

Diabetes-related vascular complication rates remain unacceptably high despite guideline-based medical therapies that are significantly more effective in individuals without diabetes. This critical gap represents an opportunity for researchers and clinicians to collaborate on targeting mechanisms and pathways that specifically contribute to vascular pathology in patients with diabetes mellitus. Dysfunctional mitochondria producing excessive mitochondrial reactive oxygen species (mtROS) play a proximal cell-signaling role in the development of vascular endothelial dysfunction in the setting of diabetes. Targeting the mechanisms of production of mtROS or mtROS themselves represents an attractive method to reduce the prevalence and severity of diabetic vascular disease. This review focuses on the role of mitochondria in the development of diabetic vascular disease and current developments in methods to improve mitochondrial health to improve vascular outcomes in patients with DM.

Inhibiting crosstalk between MET signaling and mitochondrial dynamics and morphology: a novel therapeutic approach for lung cancer and mesothelioma

The receptor tyrosine kinase MET is frequently involved in malignant transformation and inhibiting its activity in MET-dependent cancers is associated with improved clinical outcomes. Emerging evidence also suggests that mitochondria play an essential role in tumorigenesis and Dynamin Related Protein (DRP1), a key component of the mitochondrial fission machinery, has emerged as an attractive therapeutic target. Here, we report that inhibiting MET activity with the tyrosine kinase inhibitor MGCD516 attenuates viability, migration, and invasion of non-small cell lung cancer (NSCLC) and malignant pleural mesothelioma (MPM) cell lines in vitro, and significantly retards tumor growth in vivo. Interestingly, MGCD516 treatment also results in altered mitochondrial morphology in these cell lines. Furthermore, inhibiting MET pharmacologically or knocking down its expression using siRNA, decreases DRP1 activity alluding to possible crosstalk between them in these two cancers. Consistently, a combination of MGCD516 and mdivi-1, a quinazolinone reported to inhibit mitochondrial fission, is more effective in attenuating proliferation of NSCLC and MPM cell lines than either drug alone. Considered together, the present study has uncovered a novel mechanism underlying mitochondrial regulation by MET that involves crosstalk with DRP1, and suggests that a combination therapy targeting both MET and DRP1 could be a novel strategy for NSCLC and MPM.

Differential Roles of Mitochondrial Translocation of Active Caspase-3 and HMGB1 in Neuronal Death Induced by Status Epilepticus

Under pathophysiological conditions, aberrant mitochondrial dynamics lead to the different types of neuronal death: excessive mitochondrial fission provokes apoptosis and abnormal mitochondrial elongation induces necrosis. However, the underlying mechanisms how the different mitochondrial dynamics result in the distinct neuronal death patterns have been elusive. In the present study, status epilepticus (SE) evoked excessive mitochondrial fission in parvalbumin (PV) cells (one of GABAergic interneurons) and abnormal mitochondrial elongation in CA1 neurons in the rat hippocampus. These impaired mitochondrial dynamics were accompanied by mitochondrial translocations of active caspase-3 and high mobility group box 1 (HMGB1) in PV cells and CA1 neurons, respectively. WY14643 (an activator of mitochondrial fission) aggravated SE-induced PV cell loss by enhancing active caspase-3 induction and its mitochondrial translocation, which were attenuated by Mdivi-1 (an inhibitor of mitochondrial fission). Mitochondrial HMGB1 import was not observed in PV cell. In contrast to PV cells, Mdivi-1 deteriorated SE-induced CA1 neuronal death concomitant with mitochondrial HMGB1 translocation, which was abrogated by WY14643. These findings suggest that SE-induced aberrant mitochondrial dynamics may be involved in translocation of active caspase-3 and HMGB1 into mitochondria, which regulate neuronal apoptosis and necrosis, respectively.

Mdivi-1 pretreatment mitigates isoflurane-induced cognitive deficits in developmental rats

Accumulating evidence indicates that general anesthetics can cause acute neuroapoptosis and long-term cognitive deficit in models exposed to anesthetics during the brain growth-spurt period. Anesthetics-induced imbalance of mitochondrial fusion and fission preceded and contributed to developmental neuroapoptosis. Accordingly, the imbalance was accompanied by activation of dynamin-related protein (Drp)1 which was closely associated with synaptic degeneration in neurodegenerative diseases. Based on the neuroprotective role of mitochondrial division inhibitor-1 (mdivi-1) in neurodegeneration and stroke, we set out to examine whether mdivi-1 can mitigate developmental neurotoxicity induced by isoflurane. In the present study, we showed that 2% isoflurane exposure for 2 h triggered Drp1 dephosphorylation at serine 656 and increased translocation of Drp1 and Bax from cytosol to mitochondria, concomitant with cytochrome C leakage into the cytosol. Remarkably, pretreatment with mdivi-1 not only alleviated isoflurane-induced disturbed mitochondrial translocation of Drp1 and Bax and almost restored morphological changes, but also inhibited cytochrome C release, caspase9 and caspase3 activation in hippocampi. Furthermore, mdivi-1 mitigated the loss of synaptic proteins and long-lasting cognitive deficit in later life of rats neonatally exposed to isoflurane. Taken together, isoflurane-induced Drp1 activation and translocation led to excessive mitochondrial fission and subsequently contributed to the synaptic injury and long-term cognitive impairment. However, mdivi-1 pretreatment prevented Drp1-dependent excessive mitochondrial fission and mitigated neuro-apoptosis and synaptic injury, and improved the long-term cognitive function. Thus mdivi-1 holds far-reaching insight for prophylaxis of developmental neurotoxicity induced by isoflurane.

Mitochondrial dynamics and protective effects of a mitochondrial division inhibitor, Mdivi-1, in lipopolysaccharide-induced brain damage

Sepsis is one of the most common reasons for mortality in Intensive Care Units. As a common but severe neurological complication, sepsis associated encephalopathy (SAE) has always been ignored and there is no generally accepted treatment. In this study, we demonstrated that Mdivi-1 ameliorated brain damage assessed by Nissl staining. Furthermore, Mdivi-1 reduced TUNEL-positive cells in hippocampus, and inhibited S100 calcium binding protein B (S100B) and neuron-specific enolase (NSE) release into plasma. Biochemical analysis also showed that Mdivi-1 protected hippocampus from oxidative stresses. Western blot analysis revealed that Mdivi-1, as a Drp1 inhibitor, inhibited LPS induced dynamin-related GTPase (Drp1) increase. Interestingly, it can also attenuate LPS induced optic atrophy 1 (OPA1) and phosphorylated Drp1 (p-Drp1) decrease. Thus Mdivi-1 protected rats from SAE, and this protective effect could be associated with its inhibition of Drp1 and its activation of p-Drp1 and OPA1. Mitochondrial dynamics may be a potential pharmacological therapeutic target for treating SAE.

Mdivi-1 Protects Human W8B2+ Cardiac Stem Cells from Oxidative Stress and Simulated Ischemia-Reperfusion Injury

Cardiac stem cell (CSC) therapy is a promising approach to treat ischemic heart disease. However, the poor survival of transplanted stem cells in the ischemic myocardium has been a major impediment in achieving an effective cell-based therapy against myocardial infarction. Inhibiting mitochondrial fission has been shown to promote survival of several cell types. However, the role of mitochondrial morphology in survival of human CSC remains unknown. In this study, we investigated whether mitochondrial division inhibitor-1 (Mdivi-1), an inhibitor of mitochondrial fission protein dynamin-related protein-1 (Drp1), can improve survival of a novel population of human W8B2⁺ CSCs in hydrogen peroxide (H₂O₂)-induced oxidative stress and simulated ischemia-reperfusion injury models. Mdivi-1 significantly reduced H₂O₂-induced cell death in a dose-dependent manner. This cytoprotective effect was accompanied by an increased proportion of cells with tubular mitochondria, but independent of mitochondrial membrane potential recovery and reduction of mitochondrial superoxide production. In simulated ischemia-reperfusion injury model, Mdivi-1 given as a pretreatment or throughout ischemia-reperfusion injury significantly reduced cell death. However, the cytoprotective effect of Mdivi-1 was not observed when given at reperfusion. Moreover, the cytoprotective effect of Mdivi-1 in the simulated ischemia-reperfusion injury model was not accompanied by changes in mitochondrial morphology, mitochondrial membrane potential, or mitochondrial reactive oxygen species production. Mdivi-1 also did not affect mitochondrial bioenergetics of intact W8B2⁺ CSCs. Taken together, these experiments demonstrated that Mdivi-1 treatment of human W8B2⁺ CSCs enhances their survival and can be employed to improve therapeutic efficacy of CSCs for ischemic heart disease.

Mdivi-1 ameliorates early brain injury after subarachnoid hemorrhage via the suppression of inflammation-related blood-brain barrier disruption and endoplasmic reticulum stress-based apoptosis

Aberrant modulation of mitochondrial dynamic network, which shifts the balance of fusion and fission towards fission, is involved in brain damage of various neurodegenerative diseases including Parkinson's disease, Huntington's disease and Alzheimer's disease. A recent research has shown that the inhibition of mitochondrial fission alleviates early brain injury after experimental subarachnoid hemorrhage, however, the underlying molecular mechanisms have remained to be elucidated. This study was undertaken to characterize the effects of the inhibition of dynamin-related protein-1 (Drp1, a dominator of mitochondrial fission) on blood-brain barrier (BBB) disruption and neuronal apoptosis following SAH and the potential mechanisms. The endovascular perforation model of SAH was performed in adult male Sprague Dawley rats. The results indicated Mdivi-1(a selective Drp1 inhibitor) reversed the morphologic changes of mitochondria and Drp1 translocation, reduced ROS levels, ameliorated the BBB disruption and brain edema remarkably, decreased the expression of MMP-9 and prevented degradation of tight junction proteins-occludin, claudin-5 and ZO-1. Mdivi-1 administration also inhibited the nuclear translocation of nuclear factor-kappa B (NF-κB), leading to decreased expressions of TNF-ɑ, IL-6 and IL-1ß. Moreover, Mdivi-1 treatment attenuated neuronal cell death and improved neurological outcome. To investigate the underlying mechanisms further, we determined that Mdivi-1 reduced p-PERK, p-eIF2α, CHOP, cleaved caspase-3 and Bax expression as well as increased Bcl-2 expression. Rotenone (a selective inhibitor of mitochondrial complexes I) abolished both the anti-BBB disruption and anti-apoptosis effects of Mdivi-1. In conclusion, these data implied that excessive mitochondrial fission might inhibit mitochondrial complex I to become a cause of oxidative stress in SAH, and the inhibition of Drp1 by Mdivi-1 attenuated early brain injury after SAH probably via the suppression of inflammation-related blood-brain barrier disruption and endoplasmic reticulum stress-based apoptosis.

Inhibition of Drp1-mediated mitochondrial fission improves mitochondrial dynamics and bioenergetics stimulating neurogenesis in hippocampal progenitor cells from a Down syndrome mouse model

Functional and structural damages to mitochondria have been critically associated with the pathogenesis of Down syndrome (DS), a human multifactorial disease caused by trisomy of chromosome 21 and associated with neurodevelopmental delay, intellectual disability and early neurodegeneration. Recently, we demonstrated in neural progenitor cells (NPCs) isolated from the hippocampus of Ts65Dn mice -a widely used model of DS - a severe impairment of mitochondrial bioenergetics and biogenesis and reduced NPC proliferation. Here we further investigated the origin of mitochondrial dysfunction in DS and explored a possible mechanistic link among alteration of mitochondrial dynamics, mitochondrial dysfunctions and defective neurogenesis in DS. We first analyzed mitochondrial network and structure by both confocal and transmission electron microscopy as well as by evaluating the levels of key proteins involved in the fission and fusion machinery. We found a fragmentation of mitochondria due to an increase in mitochondrial fission associated with an up-regulation of dynamin-related protein 1 (Drp1), and a decrease in mitochondrial fusion associated with a down-regulation of mitofusin 2 (Mnf2) and increased proteolysis of optic atrophy 1 (Opa1). Next, using the well-known neuroprotective agent mitochondrial division inhibitor 1 (Mdivi-1), we assessed whether the inhibition of mitochondrial fission might reverse alteration of mitochondrial dynamics and mitochondrial dysfunctions in DS neural progenitors cells. We demonstrate here for the first time, that Mdivi-1 restores mitochondrial network organization, mitochondrial energy production and ultimately improves proliferation and neuronal differentiation of NPCs. This research paves the way for the discovery of new therapeutic tools in managing some DS-associated clinical manifestations.

Mitochondrial Fission Inhibitors Suppress Endothelin-1-Induced Artery Constriction

BACKGROUND/AIMS

Endothelin-1 is implicated in the pathogenesis of hypertension, but the underlying mechanisms remained elusive. Our previous study found that inhibition of mitochondrial fission of smooth muscle cells suppressed phenylephrine- and high K+-induced artery constriction. Here, we studied the effects of mitochondrial fission inhibitors on endothelin-1-induced vasoconstriction.

METHODS

The tension of rat mesenteric arteries and thoracic aorta was measured by using a multi-wire myograph system. Mitochondrial morphology of aortic smooth muscle cells was observed by using transmission electron microscopy.

RESULTS

Dynamin-related protein-1 selective inhibitor mdivi-1 relaxed endothelin-1-induced constriction, and mdivi-1 pre-treatment prevented endothelin-1-induced constriction of rat mesenteric arteries with intact and denuded endothelium. Mdivi-1 had a similar inhibitory effect on rat thoracic aorta. Another mitochondrial fission inhibitor dynasore showed similar effects as mdivi-1 in rat mesenteric arteries. Mdivi-1 inhibited endothelin-1-induced increase of mitochondrial fission in smooth muscle cells of rat aorta. Rho-associated protein kinase inhibitor Y-27632 which relaxed endothelin-1-induced vasoconstriction inhibited endothelin-1-induced mitochondrial fission in smooth muscle cells of rat aorta.

CONCLUSION

Endothelin-1 increases mitochondrial fission in vascular smooth muscle cells, and mitochondrial fission inhibitors suppress endothelin-1-induced vasoconstriction.

Salidroside inhibits high-glucose induced proliferation of vascular smooth muscle cells via inhibiting mitochondrial fission and oxidative stress

The mitochondria are highly dynamic organelles, carefully maintaining network homeostasis by regulating mitochondrial fusion and fission. Mitochondrial dynamics are involved in the regulation of a variety of pathophysiological processes, including cell proliferation. Oxidative stress serves an important role in the remodeling of arterial vascular tissue in diabetic patients by affecting the proliferation of vascular smooth muscle cells (VSMCs). Salidroside is the primary active component of Rhodiola rosea and has been demonstrated to be an antioxidant with cardio- and vascular-protective effects, in addition to improving glucose metabolism. Therefore, the present study aimed to examine the impact of Salidroside on VSMC proliferation, reactive oxygen species (ROS) generation and mitochondrial dynamics under high glucose conditions and the potential mechanisms involved. The current study used Salidroside and a mitochondrial division inhibitor, specifically of Drp1 (Mdivi-1) to treat VSMCs under high glucose conditions for 24 h and assessed VSMCs proliferation, the state of mitochondrial fission and fusion and the expression level of proteins related to mitochondrial dynamics including dynamin-related protein (Drp1) and mitofusin 2 (Mfn2), ROS level and nicotinamide adenine dinucleotide phosphate oxidase activity. The results of the present study indicate that Salidroside and Mdivi-1 inhibit VSMC proliferation, Drp1 expression and oxidative stress and upregulate Mfn2 expression (all P<0.05). The inhibitive effect on VSMC proliferation may be partly reversed by exogenous ROS. In addition, the inhibitive effect on VSMCs proliferation and oxidative stress may also be in part reversed by Mfn2-siRNA. Collectively, these data suggest that Salidroside inhibits VSMCs proliferation induced by high-glucose and may perform its therapeutic effect via maintaining mitochondrial dynamic homeostasis and regulating oxidative stress level, with Mfn2 as a therapeutic target.

Ischemia-induced Drp1 and Fis1-mediated mitochondrial fission and right ventricular dysfunction in pulmonary hypertension

Right ventricular (RV) function determines prognosis in pulmonary arterial hypertension (PAH). We hypothesize that ischemia causes RV dysfunction in PAH by triggering dynamin-related protein 1 (Drp1)-mediated mitochondrial fission. RV function was compared in control rats (n = 50) versus rats with monocrotaline-induced PAH (MCT-PAH; n = 60) both in vivo (echocardiography) and ex vivo (RV Langendorff). Mitochondrial membrane potential and morphology and RV function were assessed before or after 2 cycles of ischemia-reperfusion injury challenge (RV-IR). The effects of Mdivi-1 (25 μM), a Drp1 GTPase inhibitor, and P110 (1 μM), a peptide inhibitor of Drp1-Fis1 interaction, were studied. We found that MCT caused RV hypertrophy, RV vascular rarefaction, and RV dysfunction. Prior to IR, the mitochondria in MCT-PAH RV were depolarized and swollen with increased Drp1 content and reduced aconitase activity. RV-IR increased RV end diastolic pressure (RVEDP) and mitochondrial Drp1 expression in both control and MCT-PAH RVs. IR depolarized mitochondria in control RV but did not exacerbate the basally depolarized MCT-PAH RV mitochondria. During RV IR mdivi-1 and P110 reduced Drp1 translocation to mitochondria, improved mitochondrial structure and function, and reduced RVEDP. In conclusion, RV ischemia occurs in PAH and causes Drp1-Fis1-mediated fission leading to diastolic dysfunction. Inhibition of mitochondrial fission preserves RV function in RV-IR.

KEY MESSAGES

Right ventricular ischemia reperfusion (RV-IR) causes RV diastolic dysfunction. IR-induced mitochondrial fission causes RV diastolic dysfunction. In RV-IR Drp1 translocates to mitochondria, binds Fis1 and causes fission and injury. A baseline RV mitochondriopathy in MCT PAH resembles IR-induced mitochondrial injury. Drp1 inhibitors (Mdivi-1 and P110) preserve RV diastolic function post RV-IR.

Dynamin-Related Protein 1 Promotes Mitochondrial Fission and Contributes to The Hippocampal Neuronal Cell Death Following Experimental Status Epilepticus

AIMS

Prolonged seizure activity may result in mitochondrial dysfunction and lead to cell death in the hippocampus. Mitochondrial fission may occur in an early stage of neuronal cell death. This study examined the role of the mitochondrial fission protein dynamin-related protein 1 (Drp1) in the hippocampus following status epilepticus.

METHODS

Kainic acid (KA) was microinjected unilaterally into the hippocampal CA3 area in Sprague Dawley rats to induce prolonged seizure activity. Biochemical analysis, electron microscopy, and immunofluorescence staining were performed to evaluate the subsequent molecular and cellular events. The effects of pretreatment with a mitochondrial fission protein inhibitor, Mdivi-1 (2 nmol), were also evaluated.

RESULTS

Phosphorylation of Drp1 at serine 616 (p-Drp1(Ser616)) was elevated from 1 to 24 h after the elicited seizure activity. Pretreatment with Mdivi-1 decreased the Drp1 phosphorylation at Ser616 and limited the mitochondrial fission. Mdivi-1 rescued the Complex I dysfunction, decreased the levels of oxidized proteins, decreased the activation of cytochrome c/caspase-3 signaling, and blunted cell death in CA3 neurons.

CONCLUSION

Our findings suggest that activation of p-Drp1(Ser616) is related to seizure-induced neuronal damage. Modulation of p-Drp1(Ser616) expression is accompanied by decreases in mitochondrial fission, mitochondrial dysfunction, and oxidation, providing a neuroprotective effect against seizure-induced hippocampal neuronal damage.

Dynamin-related protein inhibitor downregulates reactive oxygen species levels to indirectly suppress high glucose-induced hyperproliferation of vascular smooth muscle cells

Hyperproliferation of vascular smooth muscle cells is a pathogenic mechanism common in diabetic vascular complications and is a putatively important therapeutic target. This study investigated multiple levels of biology, including cellular and organellar changes, as well as perturbations in protein synthesis and morphology. Quantitative and qualitative analysis was utilized to assess the effect of mitochondrial dynamic changes and reactive oxygen species(ROS) levels on high-glucose-induced hyperproliferation of vascular smooth muscle cells. The data demonstrated that the mitochondrial fission inhibitor Mdivi-1 and downregulation of ROS levels both effectively inhibited the high-glucose-induced hyperproliferation of vascular smooth muscle cells. Downregulation of ROS levels played a more direct role and ROS levels were also regulated by mitochondrial dynamics. Increased ROS levels induced excessive mitochondrial fission through dynamin-related protein (Drp 1), while Mdivi-1 suppressed the sensitivity of Drp1 to ROS levels, thus inhibiting excessive mitochondrial fission under high-glucose conditions. This study is the first to propose that mitochondrial dynamic changes and ROS levels interact with each other and regulate high-glucose-induced hyperproliferation of vascular smooth muscle cells. This finding provides novel ideas in understanding the pathogenesis of diabetic vascular remodeling and intervention.

Mdivi-1 Protects Epileptic Hippocampal Neurons from Apoptosis via Inhibiting Oxidative Stress and Endoplasmic Reticulum Stress in Vitro

Mitochondrial division inhibitor 1 (mdivi-1), a selective inhibitor of the mitochondrial fission protein dynamin-related protein 1, has been proposed to have a neuroprotective effect on hippocampal neurons in animal models of epilepsy. However, the effect of mdivi-1 on epileptic neuronal death in vitro remains unknown. Therefore, we investigated the effect of mdivi-1 and the underlying mechanisms in the hippocampal neuronal culture (HNC) model of acquired epilepsy (AE) in vitro. We found that mitochondrial fission was increased in the HNC model of AE and inhibition of mitochondrial fission by mdivi-1 significantly decreased neuronal apoptosis induced by AE. In addition, mdivi-1 pretreatment significantly attenuated oxidative stress induced by AE characterized by decrease of reactive oxygen species (ROS) production and malondialdehyde level and by increase of superoxide dismutase activity. Moreover, mdivi-1 pretreatment significantly decreased endoplasmic reticulum (ER) stress markers glucose-regulated protein 78, C/EBP homologous protein expression and caspase-3 activation. Altogether, our findings suggest that mdivi-1 protected against AE-induced hippocampal neuronal apoptosis in vitro via decreasing ROS-mediated oxidative stress and ER stress.

Inhibition of Drp1 by Mdivi-1 attenuates cerebral ischemic injury via inhibition of the mitochondria-dependent apoptotic pathway after cardiac arrest

Mitochondrial fission is predominantly controlled by the activity of dynamin-related protein1 (Drp1), which has been reported to be involved in mitochondria apoptosis pathways. However, the role of Drp1 in a rat model of cardiac arrest remains unknown. In this study, we found that activation of Drp1 in the mitochondria was increased after cardiac arrest and inhibition of Drp1 by 1.2 mg/kg of mitochondrial division inhibitor-1 (Mdivi-1) administration after the restoration of spontaneous circulation (ROSC) significantly protected against cerebral ischemic injury, shown by the increased 72-h survival rate and improved neurological function. Moreover, the increase of the vital neuron and the reduction of cytochrome c (CytC) release, apoptosis-inducing factor (AIF) translocation and caspase-3 activation in the brain indicate that this protection might result from the suppression of neuron apoptosis. Altogether, these results indicated that Drp1 is activated after cardiac arrest and the inhibition of Drp1 is protective against cerebral ischemic injury in a rat of cardiac arrest model via inhibition of the mitochondrial apoptosis pathway.

The mitochondrial division inhibitor mdivi-1 attenuates spinal cord ischemia-reperfusion injury both in vitro and in vivo: Involvement of BK channels

Mitochondrial division inhibitor (mdivi-1), a selective inhibitor of a mitochondrial fission protein dynamin-related protein 1 (Drp1), has been shown to exert protective effects in heart and cerebral ischemia-reperfusion models. The present study was designed to investigate the beneficial effects of mdivi-1 against spinal cord ischemia-reperfusion (SCIR) injury and its associated mechanisms. SCIR injury was induced by glutamate treatment in cultured spinal cord neurons and by descending thoracic aorta occlusion for 20 min in rats. We found that mdivi-1 (10 μM) significantly attenuated glutamate induced neuronal injury and apoptosis in spinal cord neurons. This neuroprotective effect was accompanied by decreased expression of oxidative stress markers, inhibited mitochondrial dysfunction and preserved activities of antioxidant enzymes. In addition, mdivi-1 significantly increased the expression of the large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels, and blocking BK channels by paxilline partly ablated mdivi-1 induced protection. The in vivo experiments showed that mdivi-1 treatment (1 mg/kg) overtly mitigated SCIR injury induced spinal cord edema and neurological dysfunction with no organ-related toxicity in rats. Moreover, mdivi-1 increased the expression of BK channels in spinal cord tissues, and paxilline pretreatment nullified mdivi-1 induced protection after SCIR injury in rats. Thus, mdivi-1 may be an effective therapeutic agent for SCIR injury via activation of BK channels as well as reduction of oxidative stress, mitochondrial dysfunction and neuronal apoptosis. This article is part of a Special Issue entitled SI: Spinal cord injury.

The combination of thioxodihydroquinazolinones and platinum drugs reverses platinum resistance in tumor cells by inducing mitochondrial apoptosis independent of Bax and Bak

The effective management of tumors resistant to platinum drugs-based anticancer therapies is a critical challenge in current clinical practices. The proapoptotic Bcl-2 family proteins Bax and Bak are essential for cisplatin-induced apoptosis. Unfortunately, Bax and its related upstream endogenous apoptotic signaling pathways are often dysregulated in cancer cells. Strategies that are able to bypass Bax- and Bak-dependent apoptotic pathways will thus provide opportunities to overcome platinum drug resistance. We have identified the thioxodihydroquinazolinone mdivi-1 as a member of a novel class of small molecules that are able to induce Bax- and Bak-independent mitochondrial outer membrane permeabilization when combined with cisplatin, thereby efficiently triggering apoptosis in platinum-resistant tumor cells. In the present structure activity relationship (SAR) study of a computationally selected library of mdivi-1 related small molecules, we established a pharmacophore model that can lead to the enhancement of platinum drug efficacy and Bax/Bak-independent mitochondrial apoptosis. Specifically, we found that a thiourea function is necessary but not sufficient for the synergism of this class of thioxodihydroquinazolinones with cisplatin. We were also able to identify more potent mdivi-1 analogs through this SAR study, which will guide future designs with the goal to develop novel combination regimens for the treatment of platinum- and multidrug-resistant tumors.

Mdivi-1 Protects Against Ischemic Brain Injury via Elevating Extracellular Adenosine in a cAMP/CREB-CD39-Dependent Manner

This study aimed to examine whether the neuroprotective effects of Mdivi-1 are attributable to extracellular ATP and adenosine. Mdivi-1 was administered prior to or post middle cerebral artery occlusion (MCAO). The extracellular adenosine was measured by in vivo microdialysis and high-pressure liquid chromatography (HPLC) in MCAO mouse model. Western blot was done to determine the influence of Mdivi-1 on the expression of CD39 and CREB phosphorylation both in vivo and in the cultured astrocytes. Intracellular cAMP and protein kinase A (PKA) activity were detected in primary astrocytes. Results showed that Mdivi-1 significantly reduced infarct volume and neurological scores when administered either prior to or post MCAO. Interestingly, pretreatment with Mdivi-1 resulted in marked increase of extracellular adenosine and concomitant decrease in ATP. The expression of CD39, but not CD73, was upregulated by Mdivi-1, which was associated with the elevated phosphorylated cAMP response element-binding protein (CREB), a transcription factor potentially regulating CD39 expression. In primary astrocytes, Mdivi-1 treatment induced increases in intracellular cAMP, PKA activity and CREB phosphorylation, and PKA-specific inhibitor completely reversed Mdivi-1-induced CD39 expression. Our results demonstrate that Mdivi-1 protects against ischemic brain injury through increasing extracellular adenosine, a process involving elevated CD39 expression that is likely modulated by cAMP/PKA/CREB cascade. Figure Potential mechanisms by which Mdivi-1 mediates the neuroprotection on cerebral ischemic stroke. Results from the present study indicate that Mdivi-1 protects against ischemic brain injury through increasing extracellular adenosine, a process involving elevated CD39 expression that is likely modulated by the cAMP/PKA/CREB cascades.