Promotion Of Fusion Research Articles

Endochondral Ossification for Spinal Fusion: A Novel Perspective from Biological Mechanisms to Clinical Applications.

Degenerative scoliosis (DS), encompassing conditions like spondylolisthesis and spinal stenosis, is a common type of spinal deformity. Lumbar interbody fusion (LIF) stands as a conventional surgical intervention for this ailment, aiming at decompression, restoration of intervertebral height, and stabilization of motion segments. Despite its widespread use, the precise mechanism underlying spinal fusion remains elusive. In this review, our focus lies on endochondral ossification for spinal fusion, a process involving vertebral development and bone healing. Endochondral ossification is the key step for the successful vertebral fusion. Endochondral ossification can persist in hypoxic conditions and promote the parallel development of angiogenesis and osteogenesis, which corresponds to the fusion process of new bone formation in the hypoxic region between the vertebrae. The ideal material for interbody fusion cages should have the following characteristics: (1) Good biocompatibility; (2) Stable chemical properties; (3) Biomechanical properties similar to bone tissue; (4) Promotion of bone fusion; (5) Favorable for imaging observation; (6) Biodegradability. Utilizing cartilage-derived bone-like constructs holds promise in promoting bony fusion post-operation, thus warranting exploration in the context of spinal fusion procedures.

An old dog with new tricks: TFEB promotes syncytin expression and cell fusion in the human placenta.

In the human placenta, cell fusion is crucial for forming the syncytiotrophoblast, a multinucleated giant cell essential for maintaining pregnancy and ensuring fetal health. The formation of the syncytiotrophoblast is catalyzed by the evolutionarily modern fusogens syncytin-1 and syncytin-2. In this issue of Genes & Development, Esbin and colleagues (doi:10.1101/gad.351633.124) reveal a critical role for the transcription factor TFEB in the regulation of syncytin expression and the promotion of trophoblast fusion. Notably, TFEB's pro-fusion role operates independently of its well-known functions in lysosome biogenesis and autophagy, suggesting that TFEB has acquired additional functions to promote cell fusion in the human placenta.

Mitochondrial dynamics regulate cell morphology in the developing cochlea.

In multicellular tissues, the size and shape of cells are intricately linked with their physiological functions. In the vertebrate auditory organ, the neurosensory epithelium develops as a mosaic of sensory hair cells (HCs), and their glial-like supporting cells, which have distinct morphologies and functional properties at different frequency positions along its tonotopic long axis. In the chick cochlea, the basilar papilla (BP), proximal (high-frequency) HCs, are larger than their distal (low-frequency) counterparts, a morphological feature essential for sound perception. Mitochondrial dynamics, which constitute the equilibrium between fusion and fission, regulate differentiation and functional refinement across a variety of cell types. We investigate this as a potential mechanism for regulating the shape of developing HCs. Using live imaging in intact BP explants, we identify distinct remodelling of mitochondrial networks in proximal compared with distal HCs. Manipulating mitochondrial dynamics in developing HCs alters their normal morphology along the proximal-distal (tonotopic) axis. Inhibition of the mitochondrial fusion machinery decreased proximal HC surface area, whereas promotion of fusion increased the distal HC surface area. We identify mitochondrial dynamics as a key regulator of HC morphology in developing inner ear epithelia.

Cationic Glucan Dendrimer Gel-Mediated Local Delivery of Anti-OC-STAMP-siRNA for Treatment of Pathogenic Bone Resorption.

Osteoclast stimulatory transmembrane protein (OC-STAMP) plays a pivotal role in the promotion of cell fusion during osteoclast differentiation (osteoclastogenesis) in the context of pathogenic bone resorption. Thus, it is plausible that the suppression of OC-STAMP through a bioengineering approach could lead to the development of an effective treatment for inflammatory bone resorptive diseases with minimum side effects. Here, we synthesized two types of spermine-bearing (Spe) cationic glucan dendrimer (GD) gels (with or without C12) as carriers of short interfering RNA (siRNA) to silence OC-STAMP. The results showed that amphiphilic C12-GD-Spe gel was more efficient in silencing OC-STAMP than GD-Spe gel and that the mixture of anti-OC-STAMP siRNA/C12-GD-Spe significantly downregulated RANKL-induced osteoclastogenesis. Also, local injection of anti-OC-STAMP-siRNA/C12-GD-Spe could attenuate bone resorption induced in a mouse model of periodontitis. These results suggest that OC-STAMP is a promising target for the development of a novel bone regenerative therapy and that C12-GD-Spe gel provides a new nanocarrier platform of gene therapies for osteolytic disease.

Human periodontal ligament stem cell sheets activated by graphene oxide quantum dots repair periodontal bone defects by promoting mitochondrial dynamics dependent osteogenic differentiation

BackgroundBone defects in the maxillofacial region restrict the integrity of dental function, posing challenges in clinical treatment. Bone tissue engineering (BTE) with stem cell implants is an effective method. Nanobiomaterials can effectively enhance the resistance of implanted stem cells to the harsh microenvironment of bone defect areas by promoting cell differentiation. Graphene oxide quantum dots (GOQDs) are zero-dimensional nanoscale derivatives of graphene oxide with excellent biological activity. In the present study, we aimed to explore the effects of GOQDs prepared by two methods (Y-GOQDs and B-GOQDs) on the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs), as well as the effect of gelatin methacryloyl (GelMA)-encapsulated GOQD-induced hPDLSC sheets on the repair of mandibular periodontal defects in rats. We also explored the molecular biological mechanism through which GOQD promotes bone differentiation.ResultsThere were significant differences in oxygen-containing functional groups, particle size and morphology between Y-GOQDs and B-GOQDs. Y-GOQDs promoted the osteogenic differentiation of hPDLSCs more effectively than did B-GOQDs. In addition, GelMA hydrogel-encapsulated Y-GOQD-induced hPDLSC cell sheet fragments not only exhibited good growth and osteogenic differentiation in vitro but also promoted the repair of mandibular periodontal bone defects in vivo. Furthermore, the greater effectiveness of Y-GOQDs than B-GOQDs in promoting osteogenic differentiation is due to the regulation of hPDLSC mitochondrial dynamics, namely, the promotion of fusion and inhibition of fission.ConclusionsOverall, Y-GOQDs are more effective than B-GOQDs at promoting the osteogenic differentiation of hPDLSCs by regulating mitochondrial dynamics, which ultimately contributes to bone regeneration via the aid of the GelMA hydrogels in vivo.Graphical

QueryTrack: Joint-Modality Query Fusion Network for RGBT Tracking.

Existing RGB-Thermal trackers usually treat intra-modal feature extraction and inter-modal feature fusion as two separate processes, therefore the mutual promotion of extraction and fusion is neglected. Then, the complementary advantages of RGB-T fusion are not fully exploited, and the independent feature extraction is not adaptive to modal quality fluctuation during tracking. To address the limitations, we design a joint-modality query fusion network, in which the intra-modal feature extraction and the inter-modal fusion are coupled together and promote each other via joint-modality queries. The queries are initialized based on the multimodal features of the current frame, making the subsequent fusion adaptive to modal quality fluctuation during tracking. Then the joint-modality query fusion (JQF) utilizes the queries to interact with RGB-T features, allowing the intra-modal enhancement and the inter-modal interactions to be unified for mutual promotion. In this way, JQF can distinguish and enhance the complementary modality features, while filtering out redundant information. For real-time tracking, we propose regional cross-attention for cross-modal interactions to reduce computational cost. Our end-to-end tracker sets a new state-of-the-art performance on multiple RGBT tracking benchmarks including LasHeR, VTUAV, RGBT234 and GTOT, while running at a real-time speed.

Pharmacologically targeted mitochondrial fission/fusion performs neuroprotection against trastuzumab‐induced cognitive deficits in rats via suppressing mitochondrial dysfunction and oxidative stress

AbstractBackgroundTrastuzumab (TRZ) has been utilized primarily as a chemotherapeutic treatment for advanced human epidermal growth factor receptor type 2‐expressing malignant tumors. Regardless, TRZ‐associated neurotoxicity has emerged as an adverse clinical complication of oncologic therapy by increasing oxidative stress and damaging mitochondrial function. As the neuroprotective effects of mitochondrial fission inhibitor (MDV) and fusion promoter (M1) have been illustrated for a variety of neurological pathologies, the anti‐neurotoxic mechanisms of MDV and M1 against TRZ are unknown.MethodTwenty male Wistar rats were randomly divided into either the TRZ group (4 mg/kg/day for 7 days, I.P., n = 15) or the control group (CON, n = 5). In the TRZ group, rats also received one of the following co‐treatments: 1) vehicle (VEH, n = 5), 2) MDV (1.2 mg/kg/day, n = 5), or 3) M1 (2 mg/kg/day, n = 5) via I.P. injection for 7 days. Subsequently, novel object location (NOL) and novel object recognition (NOR) tests for long‐term learning and memory were performed. Then, the brain tissue was used for determining mitochondrial functions, and the blood serum was also used to measure the oxidative stress levels.ResultTRZ (the VEH group) increased brain mitochondrial dysfunction and systemic oxidative stress via increasing reactive oxygen species (ROS) production, mitochondrial depolarization, mitochondrial swelling, and serum malondialdehyde levels, respectively, when compared to the CON group (p<0.05, Figure 1). TRZ (the VEH group) impaired long‐term learning and memory, as indicated by the attenuated percentage preference index of NOL and NOR tests, compared to the CON group (p<0.05, Figure 1). MDV and M1 co‐therapies exerted neuroprotection by rescuing brain mitochondrial function and systemic oxidative stress, resulting in the restoration of long‐term cognitive parameters (p<0.05, Figure 1).ConclusionTargeting brain mitochondrial dynamics could be an effective remedy against TRZ‐induced cognitive impairment in rats via suppressing mitochondrial dysfunction and oxidative stress. Therefore, pharmacological inhibition of mitochondrial fission and promotion of mitochondrial fusion could be a novel anti‐neurotoxicity‐induced by TRZ.

Upregulation of mitochondrial fusion as potential cardioprotective strategies against trastuzumab-induced cardiotoxicity in rats

Abstract Background Trastuzumab (TRZ) is a commonly used chemotherapeutic drug for treating advanced malignancies that express human epidermal growth factor receptor type 2. However, TRZ has been linked with cardiotoxicity, which is an unfavourable clinical side effect of cancer treatment. Alterations in mitochondrial dynamic mechanisms, particularly reduced fusion, have been shown to be a key mechanistic insight into the progression of chemotherapy-induced cardiotoxicity. Despite the cardioprotective benefits of a mitochondrial fusion promoter (M1) that have been established in various cardiovascular settings, its ability to counteract the cardiotoxicity caused by TRZ remains unknown. Purpose To examine the effect of M1 treatment on mitochondrial fusion, myocardial oxidative stress, apoptosis, and cardiac injury biomarker in TRZ-induced cardiotoxicity rats. Methods Male Wistar rats (n=18) were divided into the TRZ group (4 mg/kg/day for 7 days, I.P., n=12) and the control group (CON, n=6). In the TRZ group, at the time of first TRZ injection all rats also received the intervention with either the vehicle injection (VEH, n=6) or M1 (M1, 2 mg/kg/day, n=6) via I.P. injection for 7 days. The left ventricular ejection fraction (LVEF) was measured using echocardiography, and troponin-I levels were determined using blood serum. Then, the cardiac tissue was processed to assess the levels of malondialdehyde (MDA) for oxidative stress, mitochondrial fusion, and apoptotic proteins. Results TRZ induced cardiotoxicity via downregulation of mitochondrial fusion along with upregulation of myocardial oxidative stress and apoptosis, as indicated by decreasing Mfn1 protein expression and increasing the levels of MDA and Bax to Bcl-2 ratio, respectively (Fig. 1A, B, C, and E). TRZ also showed markedly higher levels of serum Troponin-I (Fig. 1D) and impaired LV function (77% LVEF for TRZ vs. 89% LVEF for CON). M1 co-treatment promoted Mfn1-mediated mitochondrial fusion, resulting in a reduction in MDA-associated oxidative stress, apoptosis, Troponin-I, and cardiac dysfunction (16% improvement over the TRZ group) (Fig. 1A-E). Conclusion M1 effectively protected the heart against TRZ-induced cardiotoxicity by promoting mitochondrial fusion and preventing oxidative stress and apoptosis-mediated myocardial injury. These findings suggest that the pharmacological promotion of mitochondrial fusion could be a novel anti-cardiotoxicity strategy in TRZ-induced cardiotoxicity.

The role of RIM in neurotransmitter release: promotion of synaptic vesicle docking, priming, and fusion.

There are many special sites at the end of a synapse called active zones (AZs). Synaptic vesicles (SVs) fuse with presynaptic membranes at these sites, and this fusion is an important step in neurotransmitter release. The cytomatrix in the active zone (CAZ) is made up of proteins such as the regulating synaptic membrane exocytosis protein (RIM), RIM-binding proteins (RIM-BPs), ELKS/CAST, Bassoon/Piccolo, Liprin-α, and Munc13-1. RIM is a scaffold protein that interacts with CAZ proteins and presynaptic functional components to affect the docking, priming, and fusion of SVs. RIM is believed to play an important role in regulating the release of neurotransmitters (NTs). In addition, abnormal expression of RIM has been detected in many diseases, such as retinal diseases, Asperger's syndrome (AS), and degenerative scoliosis. Therefore, we believe that studying the molecular structure of RIM and its role in neurotransmitter release will help to clarify the molecular mechanism of neurotransmitter release and identify targets for the diagnosis and treatment of the aforementioned diseases.

Chronic mitochondrial fusion promotor as a novel pharmacological intervention to alleviate left ventricular dysfunction in rats with chronic myocardial infarction

Abstract Background Decreased cardiac mitochondrial fusion associated with increased mitochondrial dysfunction has been demonstrated in acute myocardial infarction pathology. However, whether this pathophysiologic process is associated with myocardial injury in chronic myocardial infarction (CMI) is still unclear. Recently, a novel pharmacological intervention to promote mitochondrial fusion using mitochondrial fusion promotor-M1 (M1) has been shown to exert cardioprotection against myocardial ischemia and reperfusion injury. However, the roles of M1 in CMI has never been investigated. Purpose We investigated the potential cardioprotective benefits of chronic treatment with mitochondrial fusion promotor-M1 in rats with chronic MI model. Methods Adult male Wistar rats were assigned to the sham group (n=5) and the CMI group (n=15), which was induced by a permanent left anterior descending coronary occlusion. After 1 week of operation, rats in the CMI group were randomly divided into 3 subgroups which was treated with one of the followings: 1) vehicle (3% DMSO/day, ip, CON, n=5), 2) enalapril (10 mg/kg/day, po, ENA, n=5), or 3) mitochondrial fusion promotor-M1 (2 mg/kg/day, ip, M1, n=5) once daily for 4 weeks. In the end, echocardiography for the left ventricular (LV) function was performed, and the heart was removed to determine the mitochondrial function and malondialdehyde (MDA) level for oxidative stress. Results CMI rats that received vehicle showed significantly impaired LV function and cardiac mitochondrial function as evidenced by a 60% reduction in LV ejection fraction (LVEF) along with increased mitochondrial reactive oxygen species (ROS) production, mitochondrial depolarization and mitochondrial swelling, respectively, when compared with the sham rats (Fig. 1A–D). The CMI rats also exhibited a higher cardiac tissue MDA level than those of sham rats, further indicating cardiac oxidative stress (Fig. 1E). Interestingly, chronic treatment with either enalapril or M1 effectively attenuated CMI-induced mitochondrial dysfunction and oxidative stress upregulation, thus increasing LVEF (27% improvement for both ENA and M1), when compared with the vehicle group (Fig. 1A). Conclusion Long-term promotion of mitochondrial fusion mitigated cardiac mitochondrial dysfunction and oxidative stress, eventually culminating in improved LV function in rats with CMI. These findings suggest that chronic modulation of mitochondrial fusion could be a promising pharmacological intervention to improve LV function in CMI. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1. The National Science and Technology Development Agency Thailand2. The Thailand Research Fund (RGJ)

Representation learning for knowledge fusion and reasoning in Cyber–Physical–Social Systems: Survey and perspectives

The digital deep integration of cyber space, physical space and social space facilitates the formation of Cyber–Physical–Social Systems (CPSS). Knowledge empowers CPSS to be capable of solving complex tasks and providing intelligent services. Knowledge representation, fusion, and reasoning are complementary in the knowledge graph and worthy of continuous exploration and in-depth research. Since the concept of knowledge representation learning has been proposed, various models have been developed and demonstrated their superior ability in knowledge fusion and reasoning. In this paper, we investigate the progress and function of representation learning models adopted in knowledge fusion and reasoning, and extract their commonalities and characteristics, which is a perspective that has never been developed before, to provide new ideas for scholars and realize the mutual promotion of knowledge fusion and reasoning. This paper comprehensively reviews classic methods and investigates advanced and emerging works, which are published in authoritative journals or conferences. Furthermore, to overcome the limitations of existing methods, we propose an integrated knowledge representation learning and application framework for CPSS and a series of tensor-based knowledge fusion and reasoning models. Finally, four future directions are discussed in this paper, we analyze the challenges faced by them and suggest promising solutions.

Pyrroloquinoline quinone (PQQ) protects mitochondrial function of HEI-OC1 cells under premature senescence

The aim of this study was to investigate the effects of pyrroloquinoline quinone (PQQ), an oxidoreductase cofactor, on the H2O2-induced premature senescence model in HEI-OC1 auditory cells and to elucidate its mechanism of action in vitro. Cells were treated with PQQ for 1 day before H2O2 (100 μM) exposure. Mitochondrial respiratory capacity was damaged in this premature senescence model but was restored in cells pretreated with PQQ (0.1 nM or 1.0 nM). A decrease in mitochondrial potential, the promotion of mitochondrial fusion and the accelerated movement of mitochondria were all observed in PQQ-pretreated cells. The protein expression of sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) were significantly decreased under H2O2 exposure while they were increased with PQQ pretreatment, and PGC-1α acetylation was significantly decreased. In conclusion, PQQ has a protective effect on the premature senescence model of HEI-OC1 auditory cells and is associated with the SIRT1/PGC-1α signaling pathway, mitochondrial structure, and mitochondrial respiratory capacity.

Nicotinamide riboside promotes Mfn2-mediated mitochondrial fusion in diabetic hearts through the SIRT1-PGC1α-PPARα pathway

Myocardial dysfunction is associated with an imbalance in mitochondrial fusion/fission dynamics in patients with diabetes. However, effective strategies to regulate mitochondrial dynamics in the diabetic heart are still lacking. Nicotinamide riboside (NR) supplementation ameliorated mitochondrial dysfunction and oxidative stress in both cardiovascular and aging-related diseases. This study investigated whether NR protects against diabetes-induced cardiac dysfunction by regulating mitochondrial fusion/fission and further explored the underlying mechanisms. Here, we showed an evident decrease in NAD+ (nicotinamide adenine dinucleotide) levels and mitochondrial fragmentation in the hearts of leptin receptor-deficient diabetic (db/db) mouse models. NR supplementation significantly increased NAD+ content in the diabetic hearts and promoted mitochondrial fusion by elevating Mfn2 level. Furthermore, NR-induced mitochondrial fusion suppressed mitochondrial H2O2 and O2•− production and reduced cardiomyocyte apoptosis in both db/db mice hearts and neonatal primary cardiomyocytes. Mechanistically, chromatin immunoprecipitation (ChIP) and luciferase reporter assay analyses revealed that PGC1α and PPARα interdependently regulated Mfn2 transcription by binding to its promoter region. NR treatment elevated NAD+ levels and activated SIRT1, resulting in the deacetylation of PGC1α and promoting the transcription of Mfn2. These findings suggested the promotion of mitochondrial fusion via oral supplementation of NR as a potential strategy for delaying cardiac complications in patients with diabetes.

Chronic Pharmacological Modulation of Mitochondrial Dynamics Alleviates Prediabetes-Induced Myocardial Ischemia-Reperfusion Injury by Preventing Mitochondrial Dysfunction and Programmed Apoptosis.

There is an increasing body of evidence to show that impairment in mitochondrial dynamics including excessive fission and insufficient fusion has been observed in the pre-diabetic condition. In pre-diabetic rats with cardiac ischemia-reperfusion (I/R) injury, acute treatment with a mitochondria fission inhibitor (Mdivi-1) and a fusion promoter (M1) showed cardioprotection. However, the potential preventive effects of chronic Mdivi-1 and M1 treatment in a pre-diabetic model of cardiac I/R have never been elucidated. Male Wistar rats (n = 40) were fed with a high-fat diet (HFD) for 12weeks to induce prediabetes. Then, all pre-diabetic rats received the following treatments daily via intraperitoneal injection for 2weeks: (1) HFDV (Vehicle, 0.1% DMSO); (2) HFMdivi1 (Mdivi-1 1.2mg/kg); (3) HFM1 (M1 2mg/kg); and (4) HFCom (Mdivi-1 + M1). At the end of treatment protocols, all rats underwent 30min of coronary artery ligation followed by reperfusion for 120min. Chronic Mdivi-1, M1, and the combined treatment showed markedly improved cardiac mitochondrial function and dynamic control, leading to a decrease in cardiac arrhythmias, myocardial cell death, and infarct size (49%, 42%, and 51% reduction for HFMdivi1, HFM1, and HFCom, respectively vs HFDV). All of these treatments improved cardiac function following cardiac I/R injury in pre-diabetic rats. Chronic inhibition of mitochondrial fission and promotion of fusion exerted cardioprevention in prediabetes with cardiac I/R injury through the relief of cardiac mitochondrial dysfunction and dynamic alterations, and reduction in myocardial infarction, thus improving cardiac function.

Paeonol promotes Opa1-mediated mitochondrial fusion via activating the CK2α-Stat3 pathway in diabetic cardiomyopathy

Diabetes disrupts mitochondrial function and often results in diabetic cardiomyopathy (DCM). Paeonol is a bioactive compound that has been reported to have pharmacological potential for cardiac and mitochondrial protection. This study aims to explore the effects of paeonol on mitochondrial disorderes in DCM and the underlying mechanisms. We showed that paeonol promoted Opa1-mediated mitochondrial fusion, inhibited mitochondrial oxidative stress, and preserved mitochondrial respiratory capacity and cardiac performance in DCM in vivo and in vitro. Knockdown of Opa1 blunted the above protective effects of paeonol in both diabetic hearts and high glucose-treated cardiomyocytes. Mechanistically, inhibitor screening, siRNA knockdown and chromatin immunoprecipitation experiments showed that paeonol-promoted Opa1-mediated mitochondrial fusion required the activation of Stat3, which directly bound to the promoter of Opa1 to upregulate its transcriptional expression. Moreover, pharmmapper screening and molecular docking studies revealed that CK2α served as a direct target of paeonol that interacted with Jak2 and induced the phosphorylation and activation of Jak2-Stat3. Knockdown of CK2α blunted the promoting effect of paeonol on Jak2-Stat3 phosphorylation and Opa1-mediated mitochondrial fusion. Collectively, we have demonstrated for the first time that paeonol is a novel mitochondrial fusion promoter in protecting against hyperglycemia-induced mitochondrial oxidative injury and DCM at least partially via an Opa1-mediated mechanism, a process in which paeonol interacts with CK2α and restores its kinase activity that subsequently increasing Jak2-Stat3 phosphorylation and enhancing the transcriptional level of Opa1. These findings suggest that paeonol or the promotion of mitochondrial fusion might be a promising strategy for the treatment of DCM.

Augmenting ATG14 alleviates atherosclerosis and inhibits inflammation via promotion of autophagosome-lysosome fusion in macrophages

ABSTRACT Dysfunction of macroautophagy/autophagy in macrophages contributes to atherosclerosis. Impaired autophagy-lysosomal degradation system leads to lipid accumulation, facilitating atherosclerotic plaque. ATG14 is an essential regulator for the fusion of autophagosomes with lysosomes. Whether ATG14 plays a role in macrophage autophagy dysfunction in atherosclerosis is unknown. To investigate the effects of ATG14 on macrophage autophagy, human atherosclerotic plaque, apoe−/- mice and cultured mouse macrophages were evaluated. Overexpression of ATG14 by adenovirus was used to reveal its function in autophagy, inflammation and atherosclerotic plaque formation. Results showed that impaired autophagy function with reduction of ATG14 expression existed in macrophages of human and mouse atherosclerotic plaques. Ox-LDL impaired autophagosome-lysosome fusion with reduction of ATG14 expression in macrophages. Overexpression of ATG14 in macrophages enhanced fusion of autophagosomes with lysosomes and promoted lipid degradation, decreasing Ox-LDL-induced apoptosis and inflammatory response. Augmenting ATG14 expression reversed the autophagy dysfunction in macrophages of apoe−/- mice plaque, blunted SQSTM1/p62 accumulation, inhibited inflammation, and upregulated the population of Treg cells, resulting in alleviating atherosclerotic lesions. Abbreviations: ABCC1: ATP-binding cassette, sub-family C (CFTR/MRP), member 1; ABCA1: ATP-binding cassette, sub-family A (ABC1), member 1; Ad-Atg14: adenovirus vector carrying the mouse Atg14 gene; Ad-LacZ: adenovirus vector carrying the gene for bacterial β-galactosidase; apoe−/- : apolipoprotein E knockout; ATG14: autophagy-related 14; CD68: CD68 antigen; DAPI: 4ʹ,6-diamidino-2-phenylindole; Dil-ox-LDL: Dil-oxidized low density lipoprotein; ELISA: enzyme-linked immunosorbent assay; HFD: high-fat diet (an atherogenic diet); IL: interleukin; LAMP2: lysosomal-associated membrane protein 2; LDL-C: low density lipoprotrein cholesterol; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; ND: normal diet; Ox-LDL: oxidized low density lipoprotein; PBMC: peripheral blood mononuclear cells; SQSTM1/p62: sequestosome 1; SREBF1/SREBP1c: sterol regulatory element binding transcription factor 1; SREBF2/SREBP2: sterol regulatory element binding factor 2; STX17: syntaxin 17; TC: serum total cholesterol; TG: triglyceride; TNF: tumor necrosis factor; IFN: interferon; Treg cell: regulatory T cell

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 toischemia, 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.

Extracellular matrix stiffness regulates mitochondrial dynamics through PINCH-1- and kindlin-2-mediated signalling

Proper control of mitochondrial morphology is crucial for many vital cellular processes including energy production, cell cycle and apoptosis. We show here that extracellular matrix (ECM) stiffness regulates mitochondrial morphology through integrin-dependent signaling pathways. ECM stiffening promotes mitochondrial fusion and concomitantly suppressed DRP1 expression and mitochondrial fission. Depletion of kindlin-2, an integrin-binding protein, inhibits ECM stiffening-induced mitochondrial fusion but fails to release ECM stiffening-induced suppression of DRP1 expression and mitochondrial fission. On the other hand, depletion of PINCH-1, a focal adhesion protein whose level is increased in response to ECM stiffening, does not significantly affect mitochondrial fusion but abolishes ECM stiffening-induced suppression of DRP1 expression and mitochondrial fission. Finally, overexpression of PINCH-1 is sufficient to override ECM softening-induced up-regulation of DRP1 expression and mitochondrial fission. Our results demonstrate a crucial role of ECM mechanics in regulation of mitochondrial dynamics and suggest that this regulation is mediated through two distinct signaling mechanisms, namely kindlin-2-dependent up-regulation of mitochondrial fusion and PINCH-1-dependent suppression of DRP1 expression and mitochondrial fission. • Mitochondrial morphology is influenced by extracellular matrix (ECM) stiffness. • ECM stiffening promotes mitochondrial fusion and suppresses mitochondrial fission. • Kindlin-2 mediates ECM stiffening-induced promotion of mitochondrial fusion. • PINCH-1 mediates ECM stiffening-induced suppression of mitochondrial fission. • PINCH-1 suppresses mitochondrial fission through inhibition of DRP1 expression.

Cardiopreventive effects of mitochondrial dynamics modulators in pre-diabetic rats subjected to cardiac ischaemia-reperfusion injury

Abstract Background Chronic exposure to a high-fat diet (HFD) consumption causes alteration of cardiac mitochondrial dynamics and function, leading to the abnormal left ventricular (LV) function. Since excessive mitochondrial fission and reduced mitochondrial fusion are correlated with both obesity and myocardial ischaemia, targeting mitochondrial fission and fusion could be an effective cardioprotective strategy. We previously showed that acute inhibition of mitochondrial fission and promotion of mitochondrial fusion exerted cardioprotection in obese rats. However, the chronic treatment with mitochondrial fission inhibitor (Mdivi-1) and mitochondrial fusion promoter (M1) in pre-diabetic rats subjected to cardiac ischaemia-reperfusion (I/R) injury has never been investigated. Purpose We investigated the cardiopreventive effects of chronic Mdivi-1 and M1 treatment in pre-diabetic rats with cardiac I/R injury on infarct size, mitochondrial function, and LV contractility. Methods Wistar rats (n=32, male) were fed with HFD for 12 weeks, then randomly divided into: 1) HFV (Vehicle, 0.1% DMSO), 2) HFMdivi1 (Mdivi-1, 1.2 mg/kg), and 3) HFM1 (M1, 2 mg/kg) with intraperitoneal injection. After 2 weeks of drugs administration, all rats underwent 30 min of left anterior descending coronary artery occlusion followed by reperfusion for 120 min. LV function was monitored throughout the experiment. At the end, the heart was removed to determine infarct size and mitochondrial function. Results Chronic treatment with Mdivi-1 and M1 similarly showed a decrease in mitochondrial reactive oxygen species and infarct size, leading to an improvement in LV function in HFD rats, as indicated by increased ejection fraction, when compared to HFV rats (Figure). Conclusion Mitochondrial fission inhibitor and fusion promoter exerted similar efficacy in protecting pre-diabetic rat hearts against cardiac I/R injury through attenuating mitochondrial dysfunction, reducing infarct size and increasing LV contractility. Figure 1 Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): The National Science and Technology Development Agency Thailand

Blockade of HCN2 Channels Provides\xa0Neuroprotection\xa0Against Ischemic Injury via Accelerating Autophagic\xa0Degradation in Hippocampal Neurons

In the central nervous system, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are essential to maintain normal neuronal function. Recent studies have shown that HCN channels may be involved in the pathological process of ischemic brain injury, but the mechanisms remain unclear. Autophagy is activated in cerebral ischemia, but its role in cell death/survival remains controversial. In this study, our results showed that the HCN channel blocker ZD7288 remarkably decreased the percentage of apoptotic neurons and corrected the excessive autophagy induced by oxygen-glucose deprivation followed by reperfusion (OGD/R) in hippocampal HT22 neurons. Furthermore, in the OGD/R group, p-mTOR, p-ULK1 (Ser757), and p62 were significantly decreased, while p-ULK1 (Ser317), atg5, and beclin1 were remarkably increased. ZD7288 did not change the expression of p-ULK1 (Ser757), ULK1 (Ser317), p62, Beclin1, and atg5, which are involved in regulating autophagosome formation. Besides, we found that OGD/R induced a significant increase in Cathepsin D expression, but not LAMP-1. Treatment with ZD7288 at 10 μmol/L in the OGD/R group did not change the expression of cathepsin D and LAMP-1. However, chloroquine (CQ), which decreases autophagosome-lysosome fusion, eliminated the correction of excessive autophagy and neuroprotection by ZD7288. Besides, shRNA knockdown of HCN2 channels significantly reduced the accumulation of LC3-II and increased neuron survival in the OGD/R and transient global cerebral ischemia (TGCI) models, and CQ also eliminated the effects of HCN2-shRNA. Furthermore, we found that the percentage of LC3-positive puncta that co-localized with LAMP-1-positive lysosomes decreased in Con-shRNA-transfected HT22 neurons exposed to OGD/R or CQ. In HCN2-shRNA-transfected HT22 neurons, the percentage of LC3-positive puncta that co-localized with LAMP-1-positive lysosomes increased under OGD/R; however, the percentage was significantly decreased by the addition of CQ to HCN2-shRNA-transfected HT22 neurons. The present results demonstrated that blockade of HCN2 channels provides neuroprotection against OGD/R and TGCI by accelerating autophagic degradation attributable to the promotion of autophagosome and lysosome fusion.