Melatonin protects cardiac microvasculature against ischemia/reperfusion injury via suppression of mitochondrial fission-VDAC1-HK2-mPTP-mitophagy axis

NR4A1 Promotes Cerebral Ischemia Reperfusion Injury by Repressing Mfn2-Mediated Mitophagy and Inactivating the MAPK-ERK-CREB Signaling Pathway

Mitochondrial dysfunction has been acknowledged as the key pathogenic mechanism in cerebral ischemia-reperfusion (IR) injury. Mitophagy is the protective system used to sustain mitochondrial homeostasis. However, the upstream regulator of mitophagy in response to brain IR injury is not completely understood. Nuclear receptor subfamily 4 group A member 1 (NR4A1) has been found to be associated with mitochondrial protection in a number of diseases. The aim of our study is to explore the functional role of NR4A1 in cerebral IR injury, with a particular focus on its influence on mitophagy. Wild-type mice and NR4A1-knockout mice were used to generate cerebral IR injury in vivo. Mitochondrial function and mitophagy were detected via immunofluorescence assays and western blotting. Cellular apoptosis was determined via MTT assays, caspase-3 activity and western blotting. Our data revealed that NR4A1 was significantly increased in the reperfused brain tissues. Genetic ablation of NR4A1 reduced the cerebral infarction area and repressed neuronal apoptosis. The functional study demonstrated that NR4A1 modulated cerebral IR injury by inducing mitochondrial damage. Higher NR4A1 promoted mitochondrial potential reduction, evoked cellular oxidative stress, interrupted ATP generation, and initiated caspase-9-dependent apoptosis. Mechanistically, NR4A1 induced mitochondrial damage by disrupting Mfn2-mediated mitophagy. Knockdown of NR4A1 elevated Mfn2 expression and therefore reversed mitophagic activity, sending a prosurvival signal for mitochondria in the setting of cerebral IR injury. Further, we demonstrated that NR4A1 modulated Mfn2 expression via the MAPK-ERK-CREB signaling pathway. Blockade of the ERK pathway could abrogate the permissive effect of NR4A1 deletion on mitophagic activation, contributing to neuronal mitochondrial apoptosis. Overall, our results demonstrate that the pathogenesis of cerebral IR injury is closely associated with a drop in protective mitophagy due to increased NR4A1 through the MAPK-ERK-CREB signaling pathway.

Responses of Transgenic Melatonin-Enriched Goats on LPS Stimulation and the Proteogenomic Profiles of Their PBMCs

The anti-inflammatory activity of melatonin (MT) has been well documented; however, little is known regarding endogenously occurring MT in this respect, especially for large animals. In the current study, we created a MT-enriched animal model (goats) overexpressing the MT synthetase gene Aanat. The responses of these animals to lipopolysaccharide (LPS) stimulation were systematically studied. It was found that LPS treatment exacerbated the inflammatory response in wild-type (WT) goats and increased their temperature to 40 °C. In addition, their granulocyte counts were also significantly elevated. In contrast, these symptoms were not observed in transgenic goats with LPS treatment. The rescue study with MT injection into WT goats who were treated with LPS confirmed that the protective effects in transgenic goats against LPS were attributed to a high level of endogenously produced MT. The proteomic analysis in the peripheral blood mononuclear cells (PBMCs) isolated from the transgenic animals uncovered several potential mechanisms. MT suppressed the lysosome formation as well as its function by downregulation of the lysosome-associated genes Lysosome-associated membrane protein 2 (LAMP2), Insulin-like growth factor 2 receptor (IGF2R), and Arylsulfatase B (ARSB). A high level of MT enhanced the antioxidant capacity of these cells to reduce the cell apoptosis induced by the LPS. In addition, the results also uncovered previously unknown information that showed that MT may have protective effects on some human diseases, including tuberculosis, bladder cancer, and rheumatoid arthritis, by downregulation of these disease-associated genes. All these observations warranted further investigations.

TAZ inhibition promotes IL-2-induced apoptosis of hepatocellular carcinoma cells by activating the JNK/F-actin/mitochondrial fission pathway

Background

Cytokine-based cancer therapies have attracted a great deal of attention in recent years. Unfortunately, resistance to treatment limits the efficacy of these therapeutics. Therefore, the aim of our study was to explore the mechanism of IL-2-based therapy for hepatocellular carcinoma in an attempt to increase the efficiency of this treatment option.

Methods

HepG2 cells were treated with IL-2. Then, siRNA against TZA was used to transfected into HepG2 cells. Cellular apoptosis was measured via MTT assay, TUNEL assay and caspase-3 activity. Cellular proliferation was evaluated via EdU assay and western blotting. Cellular migration was detected via Transwell assay. Mitochondrial function was monitored by mitochondrial potential analysis, ROS staining, immunofluorescence and western blotting. Pathway blocker and activator were used to establish the role of JNK/F-actin/mitochondrial fission signaling pathway in HepG2 cells stress response.

Results

Our study found that IL-2 treatment significantly reduced the viability, mobility and proliferation of HepG2 cells in vitro. We also demonstrated that IL-2 treatment was accompanied by an increase in the expression of transcriptional co-activator with PDZ-binding motif (TAZ). Interestingly, genetic ablation of TAZ in the presence of IL-2 further promoted apoptosis, inhibited mobility, and arrested proliferation in HepG2 cells. At the molecular level, IL-2 administration activated excessive mitochondrial fission via the JNK/F-actin pathway; these effects were further enhanced by TAZ deletion. Mechanistically, TAZ knockdown further increased the expression of mitochondrial fission-related proteins such as Drp1, Mff and Fis. The augmented mitochondrial fission stimulated ROS overproduction, mediated redox imbalance, interrupted mitochondrial energy generation, reduced mitochondrial membrane potential, promoted leakage of the pro-apoptotic molecule cyt-c into the nucleus, and initiated caspase-9-related mitochondrial death. Further, we demonstrated that the anti-proliferative and anti-metastatic effects of IL-2 in HepG2 cells were enhanced by TAZ deletion, suggesting that IL-2 sensitizes HepG2 cells to IL-2-based cytokine therapy. However, JNK/F-actin pathway blockade could abrogate the inhibitory effects of TAZ deletion on HepG2 migration, proliferation and survival.

Conclusions

Taken together, our data indicate that the anti-tumor effects of IL-2-based therapies may be enhanced by TAZ deletion in a JNK/F-actin pathway-dependent manner. This finding provides a novel combinatorial therapeutic approach for treating hepatocellular carcinoma that might significantly increase the efficacy of cytokine-based therapies in a clinical setting.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0615-y) contains supplementary material, which is available to authorized users.

Melatonin and cardioprotection against ischaemia/reperfusion injury: What's new? A review

Melatonin is a pleiotropic hormone with several functions. It binds to specific receptors and to a number of cytosolic proteins, activating a vast array of signalling pathways. Its potential to protect the heart against ischaemia/reperfusion damage has attracted much attention, particularly in view of its possible clinical applications. This review will focus mainly on the possible signalling pathways involved in melatonin-induced cardioprotection. In particular, the role of the melatonin receptors and events downstream of receptor activation, for example, the reperfusion injury salvage kinase (RISK), survivor activating factor enhancement (SAFE) and Notch pathways, the sirtuins, nuclear factor E2-related factor 2 (Nrf2) and translocases in the outer membrane (TOM70) will be discussed. Particular attention is given to the role of the mitochondrion in melatonin-induced cardioprotection. In addition, a brief overview will be given regarding the status quo of the clinical application of melatonin in humans.

Tanshinone IIA regulates colorectal cancer apoptosis via attenuation of Parkin‑mediated mitophagy by suppressing AMPK/Skp2 pathways

Mitophagy is important for cancer development. Notably, the role of Parkin‑mediated mitophagy in colorectal cancer (CRC) mortality has not been fully determined. Therefore, the present study aimed to investigate the effect of Parkin‑mediated mitophagy on CRC apoptosis. In addition, the present study investigated the therapeutic effects of Tanshinone IIA (Tan IIA) on the regulation of CRC cell death via mitophagy. Cellular apoptosis was measured following Tan IIA treatment. In addition, mitophagy activity was evaluated by immunofluorescence and western blotting. The results of the present study revealed that Tan IIA may enhance CRC cell death. In addition, the results demonstrated that Tan IIA enhanced mitochondrial apoptosis, as demonstrated by reduced mitochondrial membrane potential, elevated mitochondrial permeability transition pore opening, and increased oxidative stress, mitochondrial energy disorder and proapoptotic factor expression. Furthermore, the results of the present study demonstrated that Tan IIA induced mitochondrial apoptosis via inhibition of mitophagy. In addition, it was revealed that mitophagy could suppress mitochondrial apoptosis. Functional assays revealed that Tan IIA suppressed the adenosine monophosphate‑activated protein kinase (AMPK) pathway, resulting in the inactivation of S‑phase kinase associated protein 2 (Skp2). Furthermore, reduced levels of Skp2 failed to activate Parkin, thus resulting in inhibition of mitophagy. Conversely, reactivation of AMPK and overexpression of Skp2 rescued mitophagy activity and thus attenuated the Tan IIA‑induced apoptosis of CRC cells. In conclusion, the results of the present study demonstrated the beneficial role of mitophagy in CRC cell survival and suggested that Tan IIA may be an effective therapeutic agent, which suppresses mitophagy activity and enhances CRC apoptosis.

Therapeutic effect of Sirtuin 3 on ameliorating nonalcoholic fatty liver disease: The role of the ERK-CREB pathway and Bnip3-mediated mitophagy

Increased mitochondrial damage is related to the progression of a diet-induced nonalcoholic fatty liver disease. The aim of our study is to investigate the role of Sirtuin 3 (Sirt3) in treating nonalcoholic fatty liver disease with a focus on mitophagy and the ERK-CREB pathway. Our data indicated that Sirt3 was downregulated in liver tissue in response to chronic HFD treatment. Interestingly, re-introduction of Sirt3 protected hepatic function, attenuated liver fibrosis, alleviated the inflammatory response, and prevented hepatocyte apoptosis. Molecular investigations demonstrated that lipotoxicity was associated with an increase in mitochondrial apoptosis as evidenced by reduced mitochondrial potential, augmented ROS production, increased cyt-c leakage into the nucleus, and activated caspase-9 apoptotic signalling. Additionally, Sirt3 overexpression protected hepatocytes against mitochondrial apoptosis via promoting Bnip3-required mitophagy. Functional studies showed that Sirt3 reversed Bnip3 expression and mitophagy activity via the ERK-CREB signalling pathway. Blockade of the ERK-CREB axis repressed the promotive effects of Sirt3 on Bnip3 activation and mitophagy augmentation, finally negating the anti-apoptotic influences of Sirt3 on hepatocytes in the setting of high-fat-stress. Collectively, our data show that high-fat-mediated liver damage is associated with Sirt3 downregulation, which is followed by ERK-CREB pathway inactivation and Bnip3-mediated inhibition of mitophagy, causing hepatocytes to undergo mitochondria-dependent cell death. Based on this, strategies for enhancing Sirt3 activity and activating the ERK-CREB-Bnip3-mitophagy pathways could be used to treat nonalcoholic fatty liver disease.

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Sirt3 overexpression prevents diet-mediated fatty liver disease.

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Sirt3 blocks hepatocyte mitochondrial apoptosis in the setting of high-fat injury.

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Bnip3-mediated mitophagy protects mitochondria against high-fat-mediated damage.

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Sirt3 controls Bnip3-mediated mitophagy via the ERK-CREB signalling pathway.

PTEN enhances nasal epithelial cell resistance to TNFα‑induced inflammatory injury by limiting mitophagy via repression of the TLR4‑JNK‑Bnip3 pathway

Nasal epithelial cell inflammatory injury is associated with chronic obstructive pulmonary disease development. However, the mechanism by which inflammation triggers nasal epithelial cell damage remains unclear. In the present study, tumor necrosis factor (TNF)α was used to induce an inflammatory injury and explore the underlying pathogenesis for nasal epithelial cell apoptosis in vitro, with a focus on mitochondrial homeostasis. Then, cellular apoptosis was detected via a terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labeling assay and western blotting. Mitochondrial function was evaluated via JC‑1 staining, mPTP opening measurement and western blotting. The results demonstrated that TNFα treatment induced nasal epithelial cell apoptosis, proliferation arrest and migration inhibition via downregulating phosphatase and tensin homolog (PTEN) levels. Increased PTEN expression was associated with reduce Toll‑like receptor (TLR)4‑c‑Jun kinase (JNK)‑Bcl2‑interacting protein 3 (Bnip3) pathway signaling, leading to reductions in mitophagy activity. Excessive mitophagy resulted in ATP deficiencies, mitochondrial dysfunction, caspase‑9 activation and cellular apoptosis. By contrast, PTEN overexpression in nasal epithelial cells alleviated the mitochondrial damage and cellular apoptosis via inhibiting the TLR4‑JNK‑Bnip3 pathway, favoring the survival of nasal epithelial cells under inflammatory injury. Therefore, this data uncovered a potential molecular basis for nasal epithelial cell apoptosis in response to inflammatory injury, and PTEN was identified as the endogenous defender of nasal epithelial cell survival via controlling lethal mitophagy by inhibiting the TLR4‑JNK‑Bnip3 pathway, suggesting that this pathway may be a potential target for clinically treating chronic nasal and sinus inflammatory injury.

NR4A1 contributes to high-fat associated endothelial dysfunction by promoting CaMKII-Parkin-mitophagy pathways

Parkin-related mitophagy is vital for endothelial cell viability and the development of atherosclerosis, although the upstream regulatory factor underlying Parkin-mediated mitophagy in endothelial apoptosis and atherosclerosis progression remains unknown. In the present study, we demonstrated that nuclear receptor subfamily 4 group A member 1 (NR4A1) is actually expressed in aortic endothelial cells (AECs) under oxidized low-density lipoprotein (ox-LDL) treatment in vitro or isolated from high-fat treated mice in vivo. Higher NR4A1 levels were associated with AEC apoptosis, mitochondrial dysfunction, and energy disorder. At the molecular level, ox-LDL stimulation increased NR4A1 expression, which evoked Parkin-mediated mitophagy. Excessive mitophagy overtly consumed mitochondrial mass, leading to an energy shortage and mitochondrial dysfunction. However, loss of NR4A1 protected AECs against ox-LDL induced apoptosis by inhibiting excessive mitophagy. Furthermore, we also identified that NR4A1 regulated Parkin activation via post-transcriptional modification by Ca2+/calmodulin-dependent protein kinase II (CaMKII). Activated CaMKII via NR4A1 induced the phosphorylated activation of Parkin. In summary, our data support the role of NR4A1/CaMKII/Parkin/mitophagy in AEC apoptosis and atherosclerosis formation and provide new insights into treating atherosclerosis with respect to endothelial viability, mitophagy, and NR4A1.

ER-Mitochondria Microdomains in Cardiac Ischemia-Reperfusion Injury: A Fresh Perspective

The mitochondrial and endoplasmic reticulum (ER) homeostasis is pivotal to the maintenance of an array of physiological processes. The physical contact and association between ER and mitochondria, known as the ER–mitochondria microdomains or mitochondria-associated ER membrane (MAM), temporally and spatially regulates the mitochondria/ER structure and function. More evidence suggests a role for MAMs in energy production, cellular contraction and mobility, and normal extracellular signal transmission. In pathological states, such as cardiac ischemia–reperfusion (I/R injury), this ER–mitochondria microdomains may act to participate in the cellular redox imbalance, ER stress, mitochondrial injury, energy deletion, and programmed cell death. From a therapeutic perspective, a better understanding of the cellular and molecular mechanisms of the pathogenic ER–mitochondria contact should help to identify potential therapeutic target for cardiac I/R injury and other cardiovascular diseases and also pave the road to new treatment modalities pertinent for the treatment of reperfusion damage in clinical practice. This review will mainly focus on the possible signaling pathways involved in the regulation of the ER–mitochondria contact. In particular, we will summarize the downstream signaling modalities influenced by ER–mitochondria microdomains, for example, mitochondrial fission, mitophagy, calcium balance, oxidative stress, and programmed cell death in details.

Bcl-2/E1B-19KD-Interacting Protein 3/Light Chain 3 Interaction Induces Mitophagy in Spinal Cord Injury in Rats Both In Vivo and In Vitro

Autophagy and mitophagy have been shown to occur in spinal cord injury (SCI). Bcl-2/E1B-19KD-interacting protein 3 (BNIP3) and its homologue, NIX, have been implicated in the regulation of mitophagy. The aim of this work was to characterize the mechanisms and role of BNIP3 in SCI-associated mitophagy. Our data showed that BNIP3, targeted to mitochondria, interacted with microtubule-associated protein 1A/1B-light chain 3 (LC3), which is targeted to autophagosomes, thus forming a mitochondria-BNIP3-LC3-autophagosome complex and resulting in mitophagy. Downregulation of BNIP3 by RNA interference strengthened the mitochondrial function and decreased cell death in spinal cord neurons under hypoxia. Particularly, BNIP3 knockdown significantly improved neurological recovery and the number of neuronal nuclei-positive cells post-SCI in rats. The present study demonstrated that BNIP3 interacts with LC3 to induce mitophagy, whereas its inhibition provided protective neuronal effects in SCI rat models both in vivo and in vitro.

Mst1 regulates post-infarction cardiac injury through the JNK-Drp1-mitochondrial fission pathway

Background

Post-infarction cardiac injury is closely associated with cardiac remodeling and heart dysfunction. Mammalian STE20-like kinase 1 (Mst1), a regulator of cellular apoptosis, is involved in cardiac remodeling in post-infarction heart, but the mechanisms remain poorly defined. We aimed to explore the role of Mst1 in regulating chronic post-infarction cardiac injury, with a focus on mitochondrial homoeostasis.

Methods

Wild-type (WT) and Mst1-knockout mice were as the cardiac myocardial infarction model. Cardiac fibrosis, myocardial inflammation response, heart dysfunction and cardiomyocyte death were measured in vivo using immunohistochemistry, immunofluorescence, western blot, qPCR and TUNEL assays. Cardiomyocytes were isolated from WT and Mst1-knockout mice, and a chronic hypoxia model was used to induce damage. Mitochondrial function was determined via JC1 staining, ROS measurement, cyt-c leakage detection and mitochondrial apoptotic pathways analysis. Mitochondrial fission was observed using immunofluorescence. A pathway activator and inhibitor were applied to establish the signaling pathways involved in regulating mitochondrial homeostasis.

Results

Our study demonstrated that Mst1 expression was significantly upregulated in the heart post-infarction. Activated Mst1 induced cardiac fibrosis, an excessive inflammatory response, and cardiomyocyte death, whereas the genetic ablation of Mst1 protected the myocardium against chronic post-infarction injury. Function assays showed that upregulation of Mst1 activity contributed to JNK pathway activation, which led to Drp1 migration from the cytoplasm onto the surface of the mitochondria, indicative of mitochondrial fission activation. Excessive mitochondrial fission caused mitochondrial fragmentation, resulting in mitochondrial potential collapse, ROS overproduction, mitochondrial pro-apoptotic leakage into the cytoplasm, and the initiation of caspase-9-mediated mitochondrial apoptosis. By contrast, Mst1 deletion helped to maintain mitochondrial structure and function, sending pro-survival signals to the cardiomyocytes.

Conclusions

Our results identify Mst1 as a malefactor in the development of post-infarction cardiac injury and that it acts through the JNK-Drp1-mitochondrial fission pathway.

Ripk3 regulates cardiac microvascular reperfusion injury: The role of IP3R-dependent calcium overload, XO-mediated oxidative stress and F-action/filopodia-based cellular migration

Ripk3-mediated cellular apoptosis is a major contributor to the pathogenesis of myocardial ischemia reperfusion (IR) injury. However, the mechanisms by which Ripk3 influences microvascular homeostasis and endothelial apoptosis are not completely understood. In this study, loss of Ripk3 inhibited endothelial apoptosis, alleviated luminal swelling, maintained microvasculature patency, reduced the expression of adhesion molecules and limited the myocardial inflammatory response. In vitro, Ripk3 deficiency protected endothelial cells from apoptosis and migratory arrest induced by HR injury. Mechanistically, Ripk3 had the ability to migrate onto the endoplasmic reticulum (ER), leading to ER damage, as evidenced by increased IP3R and XO expression. The higher IP3R content was associated with cellular calcium overload, and increased XO expression was involved in cellular oxidative injury. Furthermore, IP3R-mediated calcium overload and XO-dependent oxidative damage were able to initiate cellular apoptosis. More importantly, IP3R and XO also caused F-actin degradation into G-actin via post-transcriptional modification of cofilin, impairing the formation of the filopodia and limiting the migratory response of endothelial cells. Altogether, our data confirmed that Ripk3 was involved in microvascular IR injury via regulation of IP3R-mediated calcium overload, XO-dependent oxidative damage and filopodia-related cellular migration, ultimately leading to endothelial apoptosis and migratory inhibition. These findings provide a potential target for treating cardiac microcirculatory IR injury.

Melatonin attenuated retinal neovascularization and neuroglial dysfunction by inhibition of HIF-1α-VEGF pathway in oxygen-induced retinopathy mice

Retinopathy of prematurity (ROP) is a retinopathy characterized by retinal neovascularization (RNV) occurring in preterm infants treated with high concentrations of oxygen and may lead to blindness in severe cases. Currently, anti-VEGF therapy is a major treatment for ROP, but it is costly and may cause serious complications. The previous study has demonstrated that melatonin exerted neuroprotective effect against retinal ganglion cell death induced by hypoxia in neonatal rats. However, whether melatonin is anti-angiogenic and neuroglial protective in the progression of ROP remains unknown. Thus, this study was to investigate the effect of melatonin on RNV and neuroglia in the retina of oxygen-induced retinopathy (OIR) mice. The results showed a reduction in retinal vascular leakage in OIR mice after melatonin treatment. Besides, the size of retinal neovascular and avascular areas, the number of preretinal neovascular cell nuclei, and the number of proliferative vascular endothelial cells within the neovascular area were significantly decreased in mice treated with melatonin. After oxygen-induced injury, the density of astrocytes was decreased, accompanied by morphologic and functional changes of astrocytes. Besides, retinal microglia were also activated. Meanwhile, the levels of inflammatory factors were elevated. However, these pathologic processes were all hindered by melatonin treatment. Furthermore, HIF-1α-VEGF pathway was activated in the retina of OIR mice, yet was suppressed in melatonin-treated OIR mice retinas. In conclusion, melatonin prevented pathologic neovascularization, protected neuroglial cells, and exerts anti-inflammation effect via inhibition of HIF-1α-VEGF pathway in OIR retinas, suggesting that melatonin could be a promising therapeutic agent for ROP.

Empagliflozin rescues diabetic myocardial microvascular injury via AMPK-mediated inhibition of mitochondrial fission

Impaired cardiac microvascular function contributes to diabetic cardiovascular complications although effective therapy remains elusive. Empagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor recently approved for treatment of type 2 diabetes, promotes glycosuria excretion and offers cardioprotective actions beyond its glucose-lowering effects. This study was designed to evaluate the effect of empagliflozin on cardiac microvascular injury in diabetes and the underlying mechanism involved with a focus on mitochondria. Our data revealed that empagliflozin improved diabetic myocardial structure and function, preserved cardiac microvascular barrier function and integrity, sustained eNOS phosphorylation and endothelium-dependent relaxation, as well as improved microvessel density and perfusion. Further study suggested that empagliflozin exerted its effects through inhibition of mitochondrial fission in an adenosine monophosphate (AMP)-activated protein kinase (AMPK)-dependent manner. Empagliflozin restored AMP-to-ATP ratio to trigger AMPK activation, suppressed Drp1S616 phosphorylation, and increased Drp1S637 phosphorylation, ultimately leading to inhibition of mitochondrial fission. The empagliflozin-induced inhibition of mitochondrial fission preserved cardiac microvascular endothelial cell (CMEC) barrier function through suppressed mitochondrial reactive oxygen species (mtROS) production and subsequently oxidative stress to impede CMEC senescence. Empagliflozin-induced fission loss also favored angiogenesis by promoting CMEC migration through amelioration of F-actin depolymerization. Taken together, these results indicated the therapeutic promises of empagliflozin in the treatment of pathological microvascular changes in diabetes.

miR-125a induces apoptosis, metabolism disorder and migrationimpairment in pancreatic cancer cells by targeting Mfn2-related mitochondrial fission

Mitochondrial fission is important for the development and progression of pancreatic cancer (PC). However, little is known regarding its role in pancreatic cancer apoptosis, metabolism and migration. In the current study, the mechanism by which mitochondrial fission modifies the biological characteristics of PC was explored. MicroRNA-125a (miR-125a) had the ability to inhibit mitochondrial fission and contributed to cellular survival. Suppressed mitochondrial fission led to a reduction in mitochondrial debris, preserved the mitochondrial membrane potential, inhibited mitochondrial permeability transition pore opening, ablated cytochrome c leakage into the cytoplasm and reduced the pro-apoptotic protein contents, finally blocking mitochondria related apoptosis pathways. Furthermore, defective mitochondrial fission induced by miR-125a enhanced mitochondria-dependent energy metabolism by promoting activity of electron transport chain complexes. Furthermore, suppressed mitochondrial fission also contributed to PANC-1 cell migration by preserving the F-actin balance. Furthermore, mitofusin 2 (Mfn2), the key defender of mitochondrial fission, is involved in inhibition of miR125a-mediated mitochondrial fission. Low contents of miR-125a upregulated Mfn2 transcription and expression, leading to inactivation of mitochondrial fission. Ultimately, the current study determined that miR-125a and Mfn2 are regulated by hypoxia-inducible factor 1 (HIF1). Knockdown of HIF1 reversed miR-125a expression, and therefore, inhibited Mfn2 expression, leading to activation of mitochondrial fission. Collectively, the present study demonstrated mitochondrial fission as a tumor suppression process that is regulated by the HIF/miR-125a/Mfn2 pathways, acting to restrict PANC-1 cell survival, energy metabolism and migration, with potential implications for novel approaches for PC therapy.

Mitochonic acid 5 activates the MAPK-ERK-yap signaling pathways to protect mouse microglial BV-2 cells against TNFα-induced apoptosis via increased Bnip3-related mitophagy

BACKGROUND

The regulation of microglial function via mitochondrial homeostasis is important in the development of neuroinflammation. The underlying mechanism for this regulatory function remains unclear. In this study, we investigated the protective role of mitochonic acid 5 (MA-5) in microglial mitochondrial apoptosis following TNFα-induced inflammatory injury.

METHODS

TNFα was used to induce inflammatory injury in mouse microglial BV-2 cells with and without prior MA-5 treatment. Cellular apoptosis was assessed using the MTT and TUNEL assays. Mitochondrial functions were evaluated via mitochondrial membrane potential JC-1 staining, ROS flow cytometry analysis, mPTP opening assessment, and immunofluorescence of cyt-c. Mitophagy was examined using western blots and immunofluorescence. The pathways analysis was carried out using western blots and immunofluorescence with a pathway blocker.

RESULTS

Our results demonstrated that TNFα induced apoptosis in the microglial BV-2 cell line by activating the caspase-9-dependent mitochondrial apoptotic pathway. Mechanistically, inflammation reduced mitochondrial potential, induced ROS production, and contributed to the leakage of mitochondrial pro-apoptotic factors into the cytoplasm. The inflammatory response reduced cellular energy metabolism and increased oxidative stress. By contrast, treatment with MA-5 reduced mitochondrial apoptosis via upregulation of mitophagy. Increased mitophagy degraded damaged mitochondria, disrupting mitochondrial apoptosis, neutralizing ROS overproduction, and improving cellular energy production. We also identified that MA-5 regulated mitophagy via Bnip3 through the MAPK-ERK-Yap signaling pathway. Inhibiting this signaling pathway or knocking down Bnip3 expression prevented MA-5 from having beneficial effects on mitochondrial homeostasis and increased microglial apoptosis.

CONCLUSIONS

After TNFα-induced inflammatory injury, MA-5 affects microglial mitochondrial homeostasis in a manner mediated via the amplification of protective, Bnip3-related mitophagy, which is mediated via the MAPK-ERK-Yap signaling pathway.

Protective role of melatonin in cardiac ischemia-reperfusion injury: From pathogenesis to targeted therapy

Acute myocardial infarction (MI) is a major cause of mortality and disability worldwide. In patients with MI, the treatment option for reducing acute myocardial ischemic injury and limiting MI size is timely and effective myocardial reperfusion using either thombolytic therapy or primary percutaneous coronary intervention (PCI). However, the procedure of reperfusion itself induces cardiomyocyte death, known as myocardial reperfusion injury, for which there is still no effective therapy. Recent evidence has depicted a promising role of melatonin, which possesses powerful antioxidative and anti-inflammatory properties, in the prevention of ischemia-reperfusion (IR) injury and the protection against cardiomyocyte death. A number of reports explored the mechanism of action behind melatonin-induced beneficial effects against myocardial IR injury. In this review, we summarize the research progress related to IR injury and discuss the unique actions of melatonin as a protective agent. Furthermore, the possible mechanisms responsible for the myocardial benefits of melatonin against reperfusion injury are listed with the prospect of the use of melatonin in clinical application.

Yap regulates gastric cancer survival and migration via SIRT1/Mfn2/mitophagy

Gastric cancer is the fifth most common cancer worldwide and Hippo-Yap is the novel signaling pathway which plays an important role in gastric cancer tumor development and progression. However, little insight is available to date regarding the specific role of Yes-associated protein (Yap) in gastric cancer. In the present study, we identified the mechanism through which Yap sustains gastric cancer viability and migration. Yap was greatly upregulated in gastric cancer cells and its expression promoted cellular migration and survival. Functional studies found that knockdown of Yap reduced the mitophagy activity, which subsequently caused mitochondrial apoptosis and cellular oxidative stress. The latter impaired adhesive protein expression, alleviated F-actin expression, blunted lamellipodium formation, leading to inhibition of cancer cell motility. Mechanistically, Yap preserved Sirtuin 1 (SIRT1) activity which manipulated mitofusin 2 (Mfn2) expression and subsequent mitophagy. Loss of Yap reduced SIRT1 expression and inhibited Mfn2-mediated mitophagy. Collectively, our results identified Hippo-Yap as a tumor promoter in gastric cancer that was mediated via activation of the SIRT1/Mfn2/mitophagy axis, with potential applications to gastric cancer therapy involving cancer survival and migration.

Zearalenone regulates endometrial stromal cell apoptosis and migration via the promotion of mitochondrial fission by activation of the JNK/Drp1 pathway

Increased endometrial stromal cell (ESC) survival and migration is responsible for the development and progression of endometriosis. However, little is known about the mechanisms underlying ESC survival and migration, and limited therapeutic strategies that are able to reverse these abnormalities are available. The present study investigated the effects of zearalenone (ZEA) on ESC survival and migration, particularly focusing on mitochondrial fission and the c‑Jun N‑terminal kinase (JNK)/dynamin‑related protein 1 (Drp1) pathway. The results revealed that ZEA induced ESC apoptosis in a dose‑dependent manner. Furthermore, ZEA treatment triggered excessive mitochondrial fission resulting in structural and functional mitochondrial damage, leading to the collapse of the mitochondrial membrane potential and subsequent leakage of cytochrome c into the cytoplasm. This triggered the mitochondrial pathway of apoptosis. Additionally, ZEA‑induced mitochondrial fission decreased ESC migration through F‑actin/G‑actin homeostasis dysregulation. ZEA also increased JNK phosphorylation and subsequently Drp1 phosphorylation at the serine 616 position, resulting in Drp1 activation. JNK/Drp1 pathway inhibition abolished the inhibitory effects of ZEA on ESC survival and migration. In summary, the present study demonstrated that ZEA reduced ESC survival and migration through the stimulation of mitochondrial fission by activation of the JNK/Drp1 pathway.

Pathogenesis of cardiac ischemia reperfusion injury is associated with CK2α-disturbed mitochondrial homeostasis via suppression of FUNDC1-related mitophagy

Disturbed mitochondrial homeostasis contributes to the pathogenesis of cardiac ischemia reperfusion (IR) injury, although the underlying mechanism remains elusive. Here, we demonstrated that casein kinase 2α (CK2α) was upregulated following acute cardiac IR injury. Increased CK2α was shown to be instrumental to mitochondrial damage, cardiomyocyte death, infarction area expansion and cardiac dysfunction, whereas cardiac-specific CK2α knockout (CK2α^CKO) mice were protected against IR injury and mitochondrial damage. Functional assay indicated that CK2α enhanced the phosphorylation (inactivation) of FUN14 domain containing 1 (FUNDC1) via post-transcriptional modification at Ser13, thus effectively inhibiting mitophagy. Defective mitophagy failed to remove damaged mitochondria induced by IR injury, resulting in mitochondrial genome collapse, electron transport chain complex (ETC) inhibition, mitochondrial biogenesis arrest, cardiolipin oxidation, oxidative stress, mPTP opening, mitochondrial debris accumulation and eventually mitochondrial apoptosis. In contrast, loss of CK2α reversed the FUNDC1-mediated mitophagy, providing a survival advantage to myocardial tissue following IR stress. Interestingly, mice deficient in both CK2α and FUNDC1 failed to show protection against IR injury and mitochondrial damage through a mechanism possible attributed to lack of mitophagy. Taken together, our results confirmed that CK2α serves as a negative regulator of mitochondrial homeostasis via suppression of FUNDC1-required mitophagy, favoring the development of cardiac IR injury.

HIF1α deletion facilitates adipose stem cells to repair renal fibrosis in diabetic mice

Adipose stem cell (ASC) transplantation is a promising therapeutic strategy for diabetic renal fibrosis. Hypoxia-inducible factor 1α (HIF1α) is a negative regulatory factor of mitochondrial function. In the current study, we aimed to explore if HIF1α deletion protects against hyperglycemia-induced ASC damage and enhances the therapeutic efficiency of ASCs in diabetic renal fibrosis. Our data indicated that HIF1α was upregulated in ASCs in response to high glucose stimulation. Higher HIF1α expression was associated with ASC apoptosis and proliferation arrest. Loss of HIF1α activated mitophagy protecting ASCs against high glucose-induced apoptosis via preserving mitochondrial function. Transplanting HIF1α-deleted ASCs in db/db mice improved the abnormalities in glucose metabolic parameters, including the levels of glucose, insulin, C-peptide, HbA1c, and inflammatory markers. In addition, the engraftment of HIF1α-modified ASCs also reversed renal function, decreased renal hypertrophy, and ameliorated renal histological changes in db/db mice. Functional studies confirmed that HIF1α-modified ASCs reduced renal fibrosis. Collectively, our results demonstrate that ASCs may be a promising therapeutic treatment for ameliorating diabetes and the development of renal fibrosis and that the loss of HIF1α in ASCs may further increase the efficiency of stem cell-based therapy. These findings provide a new understanding about the protective effects of HIF1α silencing on ASCs and offer a new strategy for promoting the therapeutic efficacy of ASCs in diabetic renal fibrosis.

Liraglutide repairs the infarcted heart: The role of the SIRT1/Parkin/mitophagy pathway

Liraglutide is glucagon‑like peptide‑1 receptor agonist used for treating patients with type 2 diabetes mellitus. The present study aimed to investigate the role and mechanism of liraglutide in repairing the infarcted heart following myocardial infarction. The results of the present study demonstrated that amplification of the dose of liraglutide for ~28 days was able to reduce cardiac fibrosis, inflammatory responses and myocardial death in the post‑infarcted heart. In vitro, liraglutide protected cardiomyocyte mitochondria against the chronic hypoxic damage, inhibiting the mitochondrial apoptosis pathways. Mechanistically, liraglutide elevated the expression of NAD‑dependent protein deacetylase sirtuin‑1 (SIRT1), which increased the expression of Parkin, leading to mitophagy activation. Protective mitophagy reversed cellular adenosine 5'‑triphosphate production, reduced cellular oxidative stress and balanced the redox response, sustaining mitochondrial homeostasis. Notably, following blockade of glucagon‑like peptide 1 receptor or knockdown of Parkin, the beneficial effects of liraglutide on mitochondria disappeared. In conclusion, the results of the present study illustrated the protective role of liraglutide in repairing the infarcted heart via regulation of the SIRT1/Parkin/mitophagy pathway.

Melatonin alleviates inflammation-induced apoptosis in human umbilical vein endothelial cells via suppression of Ca2+-XO-ROS-Drp1-mitochondrial fission axis by activation of AMPK/SERCA2a pathway

Endothelia inflammation damage is vital to the development and progression of chronic venous disease. In the present study, we explored the protective effect of melatonin on endothelia apoptosis induced by LPS, particularly focusing on the mitochondrial fission. We demonstrated that human umbilical vein endothelial cells (HUVEC) subjected to LPS for 12 h exhibited a higher apoptotic rate. However, melatonin (1-20 μM) treatment 12 h before LPS had the ability to protect HUVEC cell against LPS-mediated apoptosis in a dose-dependent manner. Furthermore, LPS induced the cytoplasmic calcium overload which was responsible for the upregulation of calcium-dependent xanthine oxidase (XO). Higher XO expression was associated with reactive oxygen species (ROS) overproduction, leading to the Drp1 phosphorylation at the Ser616 site and migration on the surface of mitochondria. Furthermore, phosphorylated Drp1 initiated the mitochondrial fission contributing to the caspase9-dependent mitochondrial apoptosis as evidenced by lower membrane potential, more cyt-c leakage into the nuclear, and higher expression of proapoptotic proteins. However, melatonin treatment could trigger the AMPK pathway, which was followed by the increased SERCA2a expression. Activation of AMPK/SERCA2a by melatonin inhibited the calcium overload, XO-mediated ROS outburst, Drp1-required mitochondrial fission, and final mitochondrial apoptosis. In summary, this study confirmed that LPS induced HUVEC apoptosis through Ca2+-XO-ROS-Drp1-mitochondrial fission axis and that melatonin reduced the apoptosis of HUVEC through activation of the AMPK/SERCA2a pathway.

Ripk3 promotes ER stress-induced necroptosis in cardiac IR injury: A mechanism involving calcium overload/XO/ROS/mPTP pathway

Receptor-interacting protein 3 (Ripk3)-mediated necroptosis contributes to cardiac ischaemia-reperfusion (IR) injury through poorly defined mechanisms. Our results demonstrated that Ripk3 was strongly upregulated in murine hearts subjected to IR injury and cardiomyocytes treated with LPS and H₂O₂. The higher level of Ripk3 was positively correlated to the infarction area expansion, cardiac dysfunction and augmented cardiomyocytes necroptosis. Function study further illustrated that upregulated Ripk3 evoked the endoplasmic reticulum (ER) stress, which was accompanied with an increase in intracellular Ca²⁺ level ([Ca²⁺]c) and xanthine oxidase (XO) expression. Activated XO raised cellular reactive oxygen species (ROS) that mediated the mitochondrial permeability transition pore (mPTP) opening and cardiomyocytes necroptosis. By comparison, genetic ablation of Ripk3 abrogated the ER stress and thus blocked the [Ca²⁺]c overload-XO-ROS-mPTP pathways, favouring a pro-survival state that ultimately resulted in the inhibition of cardiomyocytes necroptosis in the setting of cardiac IR injury. In summary, the present study helps to elucidate how necroptosis is mediated by ER stress, via the calcium overload /XO/ROS/mPTP opening axis.

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ER stress is activated by Ripk3 in cardiac IR injury.

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ER stress induces calcium overload which triggers XO-dependent ROS overproduction.

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ROS outburst promotes mPTP opening that accounts for the necroptosis.

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Inhibiting ER stress favors cardiomyocytes survival and protects cardiac function.

Correlation between Changes in Local Earth's Magnetic Field and Cases of Acute Myocardial Infarction

The impact of changes in the geomagnetic field on the human body remains the subject of studies across the world, yet there is no consensus. Current studies are observing effects that require further work by researchers in order to find out the mechanisms that would allow a proper assessment of the correlations between the Earth‘s magnetic field variations and changes in human organisms. The main purpose of this study was to investigate possible correlations between the strength of time-varying aspects of the local Earth’s magnetic field and incidence of myocardial infarctions. Study participants included 435 males and 268 females who had diagnosis of myocardial infarction during the period of 1 January 2016 to 31 December 2016 and attended the Department of Cardiology at the Hospital of Lithuanian University of Health Sciences (LUHS), Kauno klinikos. Time varying magnetic field data was collected at the magnetometer site located in Lithuania. After mathematical analysis, the results support the hypothesis that the Earth’s magnetic field has a relationship between the number of acute myocardial infarction with ST segment elevation (STEMI) cases per week and the average weekly geomagnetic field strength in different frequency ranges. Correlations varied in different age groups as well as in males and females, which may indicate diverse organism sensitivity to the Earth’s magnetic field.

Pineal Calcification, Melatonin Production, Aging, Associated Health Consequences and Rejuvenation of the Pineal Gland

The pineal gland is a unique organ that synthesizes melatonin as the signaling molecule of natural photoperiodic environment and as a potent neuronal protective antioxidant. An intact and functional pineal gland is necessary for preserving optimal human health. Unfortunately, this gland has the highest calcification rate among all organs and tissues of the human body. Pineal calcification jeopardizes melatonin's synthetic capacity and is associated with a variety of neuronal diseases. In the current review, we summarized the potential mechanisms of how this process may occur under pathological conditions or during aging. We hypothesized that pineal calcification is an active process and resembles in some respects of bone formation. The mesenchymal stem cells and melatonin participate in this process. Finally, we suggest that preservation of pineal health can be achieved by retarding its premature calcification or even rejuvenating the calcified gland.

Melatonin protected cardiac microvascular endothelial cells against oxidative stress injury via suppression of IP3R-[Ca2+]c/VDAC-[Ca2+]m axis by activation of MAPK/ERK signaling pathway

The cardiac microvascular reperfusion injury is characterized by the microvascular endothelial cells (CMECs) oxidative damage which is responsible for the progression of cardiac dysfunction. However, few strategies are available to reverse such pathologies. This study aimed to explore the mechanism by which oxidative stress induced CMECs death and the beneficial actions of melatonin on CMECs survival, with a special focused on IP3R-[Ca2+]c/VDAC-[Ca2+]m damage axis and the MAPK/ERK survival signaling. We found that oxidative stress induced by H2O2 significantly activated cAMP response element binding protein (CREB) that enhanced IP3R and VDAC transcription and expression, leading to [Ca2+]c and [Ca2+]m overload. High concentration of [Ca2+]m suppressed ΔΨm, opened mPTP, and released cyt-c into cytoplasm where it activated mitochondria-dependent death pathway. However, melatonin could protect CMECs against oxidative stress injury via stimulation of MAPK/ERK that inactivated CREB and therefore blocked IP3R/VDAC upregulation and [Ca2+]c/[Ca2+]m overload, sustaining mitochondrial structural and function integrity and ultimately blockading mitochondrial-mediated cellular death. In summary, these findings confirmed the mechanisms by which oxidative injury induced CMECs mitochondrial-involved death and provided an attractive and effective way to enhance CMECs survival.

Dynamin-related protein 1-mediated mitochondrial fission contributes to post-traumatic cardiac dysfunction in rats and the protective effect of melatonin

Mechanical trauma (MT) causes myocardial injury and cardiac dysfunction. However, the underlying mechanism remains largely unclear. This study investigated the role of mitochondrial dynamics in post-traumatic cardiac dysfunction and the protective effects of melatonin. Adult male Sprague Dawley rats were subjected to 5-minute rotations (200 revolutions at a rate of 40 rpm) to induce MT model. Melatonin was administrated intraperitoneally 5 minute after MT. Mitochondrial morphology, myocardial injury, and cardiac function were determined in vivo. There was smaller size of mitochondria and increased number of mitochondria per μm² in the hearts after MT when the secondary myocardial injury was induced. Melatonin treatment at the dose of 30 mg/kg reduced serine 616 phosphorylation of Drp1 and inhibited mitochondrial Drp1 translocation and mitochondrial fission in the hearts of rats subjected to MT, which contributed to the reduction of myocardial injury and the improvement of cardiac function. In vitro, H9c2 cells cultured in 20% traumatic plasma (TP) for 12 hour showed enhanced mitochondrial fission, mitochondrial membrane potential (∆Ψm) loss, mitochondrial cytochrome c release, and decreased mitochondrial complex I-IV activities. Pretreatment with melatonin (100 μmol/L) efficiently inhibited TP-induced mitochondrial fission, ∆Ψm loss, cytochrome c release, and improved mitochondrial function. Melatonin's protective effects were attributed to its role in suppressing plasma TNF-α overproduction, which was responsible for Drp1-mediated mitochondrial fission. Taken together, our results demonstrate for the first time that abnormal mitochondrial dynamics is involved in post-traumatic cardiac dysfunction. Melatonin has significant pharmacological potential in protecting against MT-induced cardiac dysfunction by preventing excessive mitochondrial fission.

Effects of melatonin on fatty liver disease: The role of NR4A1/DNA-PKcs/p53 pathway, mitochondrial fission, and mitophagy

Mitochondrial dysfunction has been implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) through poorly defined mechanisms. Melatonin supplementation has been found to protect liver function in diabetes and obesity. Here, we intensively explored the role and mechanism of melatonin in the development of NAFLD. We demonstrated that the onset of diet-induced NAFLD greatly caused NR4A1 upregulation in hepatocytes, leading to the activation of DNA-PKcs and p53. On the one hand, p53 aided Drp1 migration in the mitochondria and consequently drove mitochondrial fission. On the other hand, p53 repressed Bnip3 transcription and expression, resulting in mitophagy arrest. The excessive fission and deficient mitophagy dramatically mediated mitochondrial dysfunction, including extensive mPTP opening, reduction in mitochondrial potential, oxidative stress, calcium overload, mitochondrial respiratory collapse, and ATP shortage. However, genetic deletion of NR4A1 or DNA-PKcs could definitively reverse NAFLD progression and the mitochondrial dysfunction. Similarly, melatonin supplementation could robustly reduce the damage to liver and mitochondrial structure and function in NAFLD. Mechanistically, melatonin halted fission but recovered mitophagy via blockade of NR4A1/DNA-PKcs/p53 pathway, finally improving mitochondrial and liver function in the setting of NAFLD. Our results identify NR4A1/DNA-PKcs/p53 pathway as the novel molecular mechanism underlying the pathogenesis of NAFLD via regulation of Drp1-mediated mitochondrial fission and Bnip3-related mitophagy. Meanwhile, we also confirm that melatonin has the ability to cut off the NR4A1/DNA-PKcs/p53 pathway, which confers a protective advantage to hepatocytes and mitochondria. The manipulation of NR4A1/DNA-PKcs/p53 pathway by melatonin highlights a new entry point for treating NAFLD.

DUSP1 alleviates cardiac ischemia/reperfusion injury by suppressing the Mff-required mitochondrial fission and Bnip3-related mitophagy via the JNK pathways

Mitochondrial fission and selective mitochondrial autophagy (mitophagy) form an essential axis of mitochondrial quality control that plays a critical role in the development of cardiac ischemia-reperfusion (IR) injury. However, the precise upstream molecular mechanism of fission/mitophagy remains unclear. Dual-specificity protein phosphatase1 (DUSP1) regulates cardiac metabolism, but its physiological contribution in the reperfused heart, particularly its influence on mitochondrial homeostasis, is unknown. Here, we demonstrated that cardiac DUSP1 was downregulated following acute cardiac IR injury. In vivo, compared to wild-type mice, DUSP1 transgenic mice (DUSP1^TG mice) demonstrated a smaller infarcted area and the improved myocardial function. In vitro, the IR-induced DUSP1 deficiency promoted the activation of JNK which upregulated the expression of the mitochondrial fission factor (Mff). A higher expression level of Mff was associated with elevated mitochondrial fission and mitochondrial apoptosis. Additionally, the loss of DUSP1 also amplified the Bnip3 phosphorylated activation via JNK, leading to the activation of mitophagy. Increased mitophagy overtly consumed mitochondrial mass resulting into the mitochondrial metabolism disorder. However, the reintroduction of DUSP1 blunted Mff/Bnip3 activation and therefore alleviated the fatal mitochondrial fission/mitophagy by inactivating the JNK pathway, providing a survival advantage to myocardial tissue following IR stress. The results of our study suggest that DUSP1 and its downstream JNK pathway are therapeutic targets for conferring protection against IR injury by repressing Mff-mediated mitochondrial fission and Bnip3-required mitophagy.

Melatonin suppresses platelet activation and function against cardiac ischemia/reperfusion injury via PPARγ/FUNDC1/mitophagy pathways

Platelet activation is a major (patho-) physiological mechanism that underlies ischemia/reperfusion (I/R) injury. In this study, we explored the molecular signals for platelet hyperactivity and investigated the beneficial effects of melatonin on platelet reactivity in response to I/R injury. After reperfusion, peroxisome proliferator-activated receptor γ (PPARγ) was progressively downregulated in patients with acute myocardial infarction undergoing coronary artery bypass grafting (CABG) surgery and in mice with I/R injury model. Loss of PPARγ was closely associated with FUN14 domain containing 1 (FUNDC1) dephosphorylation and mitophagy activation, leading to increased mitochondrial electron transport chain complex (ETC.) activity, enhanced mitochondrial respiratory function, and elevated ATP production. The improved mitochondrial function strongly contributed to platelet aggregation, spreading, expression of P-selectin, and final formation of micro-thromboses, eventually resulting in myocardial dysfunction and microvascular structural destruction. However, melatonin powerfully suppressed platelet activation via restoration of the PPARγ content in platelets, which subsequently blocked FUNDC1-required mitophagy, mitochondrial energy production, platelet hyperactivity, and cardiac I/R injury. In contrast, genetic ablation of PPARγ in platelet abolished the beneficial effects of melatonin on mitophagy, mitochondrial ATP supply, and platelet activation. Our results lay the foundation for the molecular mechanism of platelet activation in response to I/R injury and highlight that the manipulation of the PPARγ/FUNDC1/mitophagy pathway by melatonin could be a novel strategy for cardioprotection in the setting of cardiac I/R injury.

Melatonin increases human cervical cancer HeLa cells apoptosis induced by cisplatin via inhibition of JNK/Parkin/mitophagy axis

Considering that chemotherapy resistance is vital to the progression of cervical carcinoma, emerging researchers are focused on developing anti-tumor drugs to assist the treatment efficiency of chemotherapy. Melatonin has anti-tumor activity via several mechanisms including its anti-proliferative and pro-apoptotic effects as well as its potent pro-oxidant action in tumor cells. Therefore, melatonin may be useful for the treatment of tumors in association with chemotherapy drugs. Here, we studied the effect and mechanism of melatonin on HeLa cells apoptosis under cisplatin (CIS) treatment, particularly focusing on the caspase-9-related apoptosis pathway and mitophagy-mediated anti-apoptotic mechanism. The result indicated that co-stimulation of HeLa cells with CIS in the presence of melatonin further increased cellular apoptosis. Furthermore, concomitant treatments with melatonin and CIS significantly enhanced the mitochondrial structure and function damage, substantially augmented the caspase-9-dependent mitochondrial apoptosis with evidenced by lower mitochondria membrane potential, higher mitochondria ROS, and more pro-apoptotic proteins compared to the treatment with CIS alone. Mechanistically, melatonin inactivated mitophagy via blockade of JNK/Parkin, leading to the inhibition of anti-apoptotic mitophagy. The mitophagy had the ability to clear and remove damaged mitochondria, impairing CIS-mediated mitochondrial apoptosis. Activation of JNK/Parkin could alleviate the lethal effect of melatonin on HeLa cells. In summary, this study confirmed that melatonin sensitizes human cervical cancer HeLa cells to CIS-induced apoptosis through inhibition of JNK/Parkin/mitophagy pathways.

Ripk3 induces mitochondrial apoptosis via inhibition of FUNDC1 mitophagy in cardiac IR injury

Ripk3-required necroptosis and mitochondria-mediated apoptosis are the predominant types of cell death that largely account for the development of cardiac ischemia reperfusion injury (IRI). Here, we explored the effect of Ripk3 on mitochondrial apoptosis. Compared with wild-type mice, the infarcted area in Ripk3-deficient (Ripk3-/-) mice had a relatively low abundance of apoptotic cells. Moreover, the loss of Ripk3 protected the mitochondria against IRI and inhibited caspase9 apoptotic pathways. These protective effects of Ripk3 deficiency were relied on mitophagy activation. However, inhibition of mitophagy under Ripk3 deficiency enhanced cardiomyocyte and endothelia apoptosis, augmented infarcted area and induced microvascular dysfunction. Furthermore, ischemia activated mitophagy by modifying FUNDC1 dephosphorylation, which substantively engulfed mitochondria debris and cytochrome-c, thus blocking apoptosis signal. However, reperfusion injury elevated the expression of Ripk3 which disrupted FUNDC1 activation and abated mitophagy, increasing the likelihood of apoptosis. In summary, this study confirms the promotive effect of Ripk3 on mitochondria-mediated apoptosis via inhibition of FUNDC1-dependent mitophagy in cardiac IRI. These findings provide new insight into the roles of Ripk3-related necroptosis, mitochondria-mediated apoptosis and FUNDC1-required mitophagy in cardiac IRI.

Yap promotes hepatocellular carcinoma metastasis and mobilization via governing cofilin/F-actin/lamellipodium axis by regulation of JNK/Bnip3/SERCA/CaMKII pathways

Despite the increasingly important role of Hippo-Yap in hepatocellular carcinoma (HCC) development and progression, little insight is available at the time regarding the specifics interaction of Yap and cancer cells migration. Here, we identified the mechanism by which tumor-intrinsic Yap deletion resulted in HCC migratory inhibition. Yap was greatly upregulated in HCC and its expression promoted the cells migration. Functional studies found that knockdown of Yap induced JNK phosphorylation which closely bound to the Bnip3 promoter and contributed to Bnip3 expression. Higher Bnip3 employed excessive mitophagy leading to mitochondrial dysfunction and ATP shortage. The insufficient ATP inactivated SERCA and consequently triggered intracellular calcium overload. As the consequence of calcium oscillation, Ca/calmodulin-dependent protein kinases II (CaMKII) was signaled and subsequently inhibited cofilin activity via phosphorylated modification. The phosphorylated cofilin failed to manipulate F-actin polymerization and lamellipodium formation, resulting into the impairment of lamellipodium-based migration. Collectively, our results identified Hippo-Yap as the tumor promoter in hepatocellular carcinoma that mediated via activation of cofilin/F-actin/lamellipodium axis by limiting JNK-Bnip3-SERCA-CaMKII pathways, with potential application to HCC therapy involving cancer metastasis.

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Yap is upregulated in the hepatocellular carcinoma and promotes cancer cell migration.

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Loss of Yap impairs cell mobility via inhibiting cofilin/F-actin/lamellipodium by activation of JNK-Bnip3-SERCA-CaMKII.

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Loss of Yap enhances JNK phosphorylation which triggers Bnip3-required mitophagy.

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Excessive mitophagy induces mitochondrial energy disorder which blunts SERCA and causes calcium overload.

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The calcium overload drives CaMKII which inactivates cofilin, leading to F-actin degradation and lamellipodium collapse.

Melatonin protects cardiac microvasculature against ischemia/reperfusion injury via suppression of mitochondrial fission-VDAC1-HK2-mPTP-mitophagy axis

The cardiac microvascular system, which is primarily composed of monolayer endothelial cells, is the site of blood supply and nutrient exchange to cardiomyocytes. However, microvascular ischemia/reperfusion injury (IRI) following percutaneous coronary intervention is a woefully neglected topic, and few strategies are available to reverse such pathologies. Here, we studied the effects of melatonin on microcirculation IRI and elucidated the underlying mechanism. Melatonin markedly reduced infarcted area, improved cardiac function, restored blood flow, and lower microcirculation perfusion defects. Histological analysis showed that cardiac microcirculation endothelial cells (CMEC) in melatonin-treated mice had an unbroken endothelial barrier, increased endothelial nitric oxide synthase expression, unobstructed lumen, reduced inflammatory cell infiltration, and less endothelial damage. In contrast, AMP-activated protein kinase α (AMPKα) deficiency abolished the beneficial effects of melatonin on microvasculature. In vitro, IRI activated dynamin-related protein 1 (Drp1)-dependent mitochondrial fission, which subsequently induced voltage-dependent anion channel 1 (VDAC1) oligomerization, hexokinase 2 (HK2) liberation, mitochondrial permeability transition pore (mPTP) opening, PINK1/Parkin upregulation, and ultimately mitophagy-mediated CMEC death. However, melatonin strengthened CMEC survival via activation of AMPKα, followed by p-Drp1^S616 downregulation and p-Drp1^S37 upregulation, which blunted Drp1-dependent mitochondrial fission. Suppression of mitochondrial fission by melatonin recovered VDAC1-HK2 interaction that prevented mPTP opening and PINK1/Parkin activation, eventually blocking mitophagy-mediated cellular death. In summary, this study confirmed that melatonin protects cardiac microvasculature against IRI. The underlying mechanism may be attributed to the inhibitory effects of melatonin on mitochondrial fission-VDAC1-HK2-mPTP-mitophagy axis via activation of AMPKα.

[Empagliflozin alleviates cardiac microvascular ischemia/reperfusion injury by maintaining myocardial mitochondrial homeostasis]

OBJECTIVE

To evaluate the effect of empagliflozin (EMPA) in mitigating microvascular and endothelial damage induced by myocardial ischemia-reperfusion (I/R) injury.

METHODS

Fifteen male C57BL/6J mice were randomized into shamoperated group, I/R group and I/R+EMPA group, and in the latter two groups, myocardial I/R injury was induced by ligating the left anterior descending coronary artery followed by reperfusion for 2 h. EMPA treatment was administered at the daily dose of 10 mg/kg for 7 days. After the treatment, the changes in myocardial microvascular structure of the mice were observed under electron microscopy. In the cell experiment, cultured human coronary artery endothelial cells (HCAECs) were treated with 10 μmol/L EMPA before exposure to hypoxia for 45 min followed normoxic culture for 2 h. Western blotting and immunofluorescence assay were performed to observe fibrin accumulation and endothelial cell protein expressions in the myocardial tissues of the mice and in HCAECs, and RT-qPCR was used to detect the expressions of pro-inflammatory cytokines.

RESULTS

Electron microscopy revealed significant myocardial microvascular wall thickening and lumen narrowing in mice with myocardial I/R injury. Fibrin accumulation and ICAM1 expression in the microvessels were more pronounced in I/R group than in the sham-operated and I/R + EMPA groups (P < 0.05). EMPA treatment obviously alleviated microvascular occlusion and microthrombus formation induced by I/R injury. At the cellular level, the protein levels of p-eNOS, Fak, and Src kinases in hypoxic exposure group were significantly lower than those in the control and EMPA treatment groups (P < 0.05). Hypoxic exposure significantly reduced mitochondrial DNA replication and transcription and lowered the expression levels of Cox-Ⅰ and Cox-Ⅱ in HCAECs, and these changes were obviously improved by EMPA treatment (P < 0.05).

CONCLUSION

EMPA can alleviate myocardial I/R injury by maintaining mitochondrial homeostasis to protect the microvascular system.