Dynamin‐related protein 1‐mediated mitochondrial fission contributes to IR‐783‐induced apoptosis in human breast cancer cells

IR‐783 is a kind of heptamethine cyanine dye that exhibits imaging, cancer targeting and anticancer properties. A previous study reported that its imaging and targeting properties were related to mitochondria. However, the molecular mechanism behind the anticancer activity of IR‐783 has not been well demonstrated. In this study, we showed that IR‐783 inhibits cell viability and induces mitochondrial apoptosis in human breast cancer cells. Exposure of MDA‐MB‐231 cells to IR‐783 resulted in the loss of mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) depletion, mitochondrial permeability transition pore (mPTP) opening and cytochrome c (Cyto C) release. Furthermore, we found that IR‐783 induced dynamin‐related protein 1 (Drp1) translocation from the cytosol to the mitochondria, increased the expression of mitochondrial fission proteins mitochondrial fission factor (MFF) and fission‐1 (Fis1), and decreased the expression of mitochondrial fusion proteins mitofusin1 (Mfn1) and optic atrophy 1 (OPA1). Moreover, knockdown of Drp1 markedly blocked IR‐783‐mediated mitochondrial fission, loss of MMP, ATP depletion, mPTP opening and apoptosis. Our in vivo study confirmed that IR‐783 markedly inhibited tumour growth and induced apoptosis in an MDA‐MB‐231 xenograft model in association with the mitochondrial translocation of Drp1. Taken together, these findings suggest that IR‐783 induces apoptosis in human breast cancer cells by increasing Drp1‐mediated mitochondrial fission. Our study uncovered the molecular mechanism of the anti‐breast cancer effects of IR‐783 and provided novel perspectives for the application of IR‐783 in the treatment of breast cancer.     

Haemin attenuates intermittent hypoxia‐induced cardiac injury via inhibiting mitochondrial fission

Obstructive sleep apnoea (OSA) characterized by intermittent hypoxia (IH) is closely associated with cardiovascular diseases. IH confers cardiac injury via accelerating cardiomyocyte apoptosis, whereas the underlying mechanism has remained largely enigmatic. This study aimed to explore the potential mechanisms involved in the IH‐induced cardiac damage performed with the IH‐exposed cell and animal models and to investigate the protective effects of haemin, a potent haeme oxygenase‐1 (HO‐1) activator, on the cardiac injury induced by IH. Neonatal rat cardiomyocyte (NRC) was treated with or without haemin before IH exposure. Eighteen male Sprague‐Dawley (SD) rats were randomized into three groups: control group, IH group (PBS, ip) and IH + haemin group (haemin, 4 mg/kg, ip). The cardiac function was determined by echocardiography. Mitochondrial fission was evaluated by Mitotracker staining. The mitochondrial dynamics‐related proteins (mitochondrial fusion protein, Mfn2; mitochondrial fission protein, Drp1) were determined by Western blot. The apoptosis of cardiomyocytes and heart sections was examined by TUNEL. IH regulated mitochondrial dynamics‐related proteins (decreased Mfn2 and increased Drp1 expressions, respectively), thereby leading to mitochondrial fragmentation and cell apoptosis in cardiomyocytes in vitro and in vivo, while haemin‐induced HO‐1 up‐regulation attenuated IH‐induced mitochondrial fragmentation and cell apoptosis. Moreover, IH resulted in left ventricular hypertrophy and impaired contractile function in vivo, while haemin ameliorated IH‐induced cardiac dysfunction. This study demonstrates that pharmacological activation of HO‐1 pathway protects against IH‐induced cardiac dysfunction and myocardial fibrosis through the inhibition of mitochondrial fission and cell apoptosis.     

AKAP1 mediates high glucose-induced mitochondrial fission through the phosphorylation of Drp1 in podocytes

Increasing evidence suggests that mitochondrial dysfunction plays a critical role in the development of diabetic kidney disease (DKD), however, its specific pathomechanism remains unclear. A-kinase anchoring protein (AKAP) 1 is a scaffold protein in the AKAP family that is involved in mitochondrial fission and fusion. Here, we show that rats with streptozotocin (STZ)-induced diabetes developed podocyte damage accompanied by AKAP1 overexpression and that AKAP1 closely interacted with the mitochondrial fission enzyme dynamin-related protein 1 (Drp1). At the molecular level, high glucose (HG) promoted podocyte injury and Drp1 phosphorylation at Ser637 as proven by decreased mitochondrial membrane potential, elevated reactive oxygen species generation, reduced adenosine triphosphate synthesis, and increased podocyte apoptosis. Furthermore, the AKAP1 knockdown protected HG-induced podocyte injury and suppressed HG-induced Drp1 phosphorylation at Ser637. AKAP1 overexpression aggravated HG-induced mitochondrial fragmentation and podocyte apoptosis. The coimmunoprecipitation assay showed that HG-induced Drp1 interacted with AKAP1, revealing that AKAP1 could recruit Drp1 from the cytoplasm under HG stimulation. Subsequently, we detected the effect of drp1 phosphorylation on Ser637 by transferring several different Drp1 mutants. We demonstrated that activated AKAP1 promoted Drp1 phosphorylation at Ser637, which promoted the transposition of Drp1 to the surface of the mitochondria and accounts for mitochondrial dysfunction events. These findings indicate that AKAP1 is the main pathogenic factor in the development and progression of HG-induced podocyte injury through the destruction of mitochondrial dynamic homeostasis by regulating Drp1 phosphorylation in human podocytes.     

Ionizing radiation accelerates Drp1-dependent mitochondrial fission, which involves delayed mitochondrial reactive oxygen species production in normal human fibroblast-like cells

Ionizing radiation is known to increase intracellular level of reactive oxygen species (ROS) through mitochondrial dysfunction. Although it has been as a basis of radiation-induced genetic instability, the mechanism involving mitochondrial dysfunction remains unclear. Here we studied the dynamics of mitochondrial structure in normal human fibroblast like cells exposed to ionizing radiation. Delayed mitochondrial production was peaked 3 days after irradiation, which was coupled with accelerated mitochondrial fission. We found that radiation exposure accumulated dynamin-related protein 1 (Drp1) to mitochondria. Knocking down of Drp1 expression prevented radiation induced acceleration of mitochondrial fission. Furthermore, knockdown of Drp1 significantly suppressed delayed production of mitochondrial . Since the loss of mitochondrial membrane potential, which was induced by radiation was prevented in cells knocking down of Drp1 expression, indicating that the excessive mitochondrial fission was involved in delayed mitochondrial dysfunction after irradiation.     

Yap overexpression attenuates septic cardiomyopathy by inhibiting DRP1-related mitochondrial fission and activating the ERK signaling pathway

Context: Yes-associated protein (Yap) has been linked to several cardiovascular disorders, but the role of this protein in septic cardiomyocytes is not fully understood.

Objective: The aim of our study was to explore the influence of Yap in septic cardiomyopathy in vivo and in vitro.

Materials and methods: In the current study, Yap transgenic mice and Yap adenovirus-mediated gain-of-function assays were used in an LPS-established septic cardiomyopathy model. Mitochondrial function and mitochondrial fission were determined through western blotting, immunofluorescence analysis and ELISA.

Results: Our results demonstrated that Yap expression was downregulated by LPS, whereas Yap overexpression sustained cardiac function and attenuated cardiomyocyte death. The functional exploration revealed that LPS treatment induced cardiomyocyte mitochondrial stress, as manifested by mitochondrial superoxide overproduction, cardiomyocyte ATP deprivation, and caspase-9 apoptosis activation. Furthermore, we demonstrated that LPS-mediated mitochondrial damage was controlled by mitochondrial fission. However, Yap overexpression reduced mitochondrial fission and therefore improved mitochondrial function. A molecular investigation revealed that Yap overexpression inhibited mitochondrial fission by reversing ERK activity, and the inhibition of the ERK pathway promoted DRP1 upregulation and thereby mediated mitochondrial fission activation in the presence of Yap overexpression.

Conclusions: Overall, our results suggest that the cause of septic cardiomyopathy appears to be connected with Yap downregulation. The overexpression of Yap can attenuate myocardial inflammation injury through the reduction of DRP1-related mitochondrial fission in an ERK pathway activation-dependent manner.     

Knockdown of Mtfp1 can minimize doxorubicin cardiotoxicity by inhibiting Dnm1l‐mediated mitochondrial fission

The long‐term usage of doxorubicin (DOX) is largely limited due to the development of severe cardiomyopathy. Many studies indicate that DOX‐induced cardiac injury is related to reactive oxygen species generation and ultimate activation of apoptosis. The role of novel mitochondrial fission protein 1 (Mtfp1) in DOX‐induced cardiotoxicity remains elusive. Here, we report the pro‐mitochondrial fission and pro‐apoptotic roles of Mtfp1 in DOX‐induced cardiotoxicity. DOX up‐regulates the Mtfp1 expression in HL‐1 cardiac myocytes. Knockdown of Mtfp1 prevents cardiac myocyte from undergoing mitochondrial fission, and subsequently reduces the DOX‐induced apoptosis by preventing dynamin 1‐like (Dnm1l) accumulation in mitochondria. In contrast, when Mtfp1 is overexpressed, a suboptimal dose of DOX can induce a significant percentage of cells to undergo mitochondrial fission and apoptosis. These data suggest that knocking down of Mtfp1 can minimize the cardiomyocytes loss in DOX‐induced cardiotoxicity. Thus, the regulation of Mtfp1 expression could be a novel therapeutic approach in chemotherapy‐induced cardiotoxicity.     

A role for septin 2 in Drp1‐mediated mitochondrial fission

Mitochondria are essential eukaryotic organelles often forming intricate networks. The overall network morphology is determined by mitochondrial fusion and fission. Among the multiple mechanisms that appear to regulate mitochondrial fission, the ER and actin have recently been shown to play an important role by mediating mitochondrial constriction and promoting the action of a key fission factor, the dynamin‐like protein Drp1. Here, we report that the cytoskeletal component septin 2 is involved in Drp1‐dependent mitochondrial fission in mammalian cells. Septin 2 localizes to a subset of mitochondrial constrictions and directly binds Drp1, as shown by immunoprecipitation of the endogenous proteins and by pulldown assays with recombinant proteins. Depletion of septin 2 reduces Drp1 recruitment to mitochondria and results in hyperfused mitochondria and delayed FCCP‐induced fission. Strikingly, septin depletion also affects mitochondrial morphology in Caenorhabditis elegans, strongly suggesting that the role of septins in mitochondrial dynamics is evolutionarily conserved.     

RhoA/ROCK1 regulates the mitochondrial dysfunction through Drp1 induced by Porphyromonas gingivalis in endothelial cells

Porphyromonas gingivalis (P. gingivalis) is a pivotal pathogen of periodontitis. Our previous studies have confirmed that mitochondrial dysfunction in the endothelial cells caused by P. gingivalis was dependent on Drp1, which may be the mechanism of P. gingivalis causing endothelial dysfunction. Nevertheless, the signalling pathway induced the mitochondrial dysfunction remains unclear. The purpose of this study was to investigate the role of the RhoA/ROCK1 pathway in regulating mitochondrial dysfunction caused by P. gingivalis. P. gingivalis was used to infect EA.hy926 cells (endothelial cells). The expression and activation of RhoA and ROCK1 were assessed by western blotting and pull-down assay. The morphology of mitochondria was observed by mitochondrial staining and transmission electron microscopy. Mitochondrial function was measured by ATP content, mitochondrial DNA and mitochondrial permeability transition pore openness. The phosphorylation and translocation of Drp1 were evaluated using western blotting and immunofluorescence. The role of the RhoA/ROCK1 pathway in mitochondrial dysfunction was investigated using RhoA and ROCK1 inhibitors. The activation of RhoA/ROCK1 pathway and mitochondrial dysfunction were observed in P. gingivalis-infected endothelial cells. Furthermore, RhoA or ROCK1 inhibitors partly prevented mitochondrial dysfunction caused by P. gingivalis. The increased phosphorylation and mitochondrial translocation of Drp1 induced by P. gingivalis were both blocked by RhoA and ROCK1 inhibitors. In conclusion, we demonstrate that the RhoA/ROCK1 pathway was involved in mitochondrial dysfunction caused by P. gingivalis by regulating the phosphorylation and mitochondrial translocation of Drp1. Our research illuminated a possible new mechanism by which P. gingivalis promotes endothelial dysfunction.     

Aging shifts mitochondrial dynamics toward fission to promote germline stem cell loss

Changes in mitochondrial dynamics (fusion and fission) are known to occur during stem cell differentiation; however, the role of this phenomenon in tissue aging remains unclear. Here, we report that mitochondrial dynamics are shifted toward fission during aging of Drosophila ovarian germline stem cells (GSCs), and this shift contributes to aging‐related GSC loss. We found that as GSCs age, mitochondrial fragmentation and expression of the mitochondrial fission regulator, Dynamin‐related protein (Drp1), are both increased, while mitochondrial membrane potential is reduced. Moreover, preventing mitochondrial fusion in GSCs results in highly fragmented depolarized mitochondria, decreased BMP stemness signaling, impaired fatty acid metabolism, and GSC loss. Conversely, forcing mitochondrial elongation promotes GSC attachment to the niche. Importantly, maintenance of aging GSCs can be enhanced by suppressing Drp1 expression to prevent mitochondrial fission or treating with rapamycin, which is known to promote autophagy via TOR inhibition. Overall, our results show that mitochondrial dynamics are altered during physiological aging, affecting stem cell homeostasis via coordinated changes in stemness signaling, niche contact, and cellular metabolism. Such effects may also be highly relevant to other stem cell types and aging‐induced tissue degeneration.     

MiRNA‐30a inhibits AECs‐II apoptosis by blocking mitochondrial fission dependent on Drp‐1

Apoptosis of type II alveolar epithelial cells (AECs‐II) is a key determinant of initiation and progression of lung fibrosis. However, the mechanism of miR‐30a participation in the regulation of AECs‐II apoptosis is ambiguous. In this study, we investigated whether miR‐30a could block AECs‐II apoptosis by repressing mitochondrial fission dependent on dynamin‐related protein‐1 (Drp‐1). The levels of miR‐30a in vivo and in vitro were determined through quantitative real‐time PCR (qRT‐PCR). The inhibition of miR‐30a in AECs‐II apoptosis, mitochondrial fission and its dependence on Drp‐1, and Drp‐1 expression and translocation were detected using miR‐30a mimic, inhibitor‐transfection method (gain‐ and loss‐of‐function), or Drp‐1 siRNA technology. Results showed that miR‐30a decreased in lung fibrosis. Gain‐ and loss‐of‐function studies revealed that the up‐regulation of miR‐30a could decrease AECs‐II apoptosis, inhibit mitochondrial fission, and reduce Drp‐1 expression and translocation. MiR‐30a mimic/inhibitor and Drp‐1 siRNA co‐transfection showed that miR‐30a could inhibit the mitochondrial fission dependent on Drp‐1. This study demonstrated that miR‐30a inhibited AECs‐II apoptosis by repressing the mitochondrial fission dependent on Drp‐1, and could function as a novel therapeutic target for lung fibrosis.     

Chemerin‐induced mitochondrial dysfunction in skeletal muscle

Chemerin is a novel adipocyte‐derived factor that induces insulin resistance in skeletal muscle. However, the effect of chemerin on skeletal muscle mitochondrial function has received little attention. In the present study, we investigated whether mitochondrial dysfunction is involved in the pathogenesis of chemerin‐mediated insulin resistance. In this study, we used recombinant adenovirus to express murine chemerin in C57BL/6 mice. The mitochondrial function and structure were evaluated in isolated soleus muscles from mice. The oxidative mechanism of mitochondrial dysfunction in cultured C2C12 myotubes exposed to recombinant chemerin was analysed by western blotting, immunofluorescence and quantitative real‐time polymerase chain reaction. The overexpression of chemerin in mice reduced the muscle mitochondrial content and increased mitochondrial autophagy, as determined by the increased conversion of LC3‐I to LC3‐II and higher expression levels of Beclin1 and autophagy‐related protein‐5 and 7. The chemerin treatment of C2C12 myotubes increased the generation of mitochondrial reactive oxygen species, concomitant with a reduced mitochondrial membrane potential and increased the occurrence of mitochondrial protein carbonyls and mitochondrial DNA deletions. Knockdown of the expression of chemokine‐like receptor 1 or the use of mitochondria‐targeting antioxidant Mito‐TEMPO restored the mitochondrial dysfunction induced by chemerin. Furthermore, chemerin exposure in C2C12 myotubes not only reduced the insulin‐stimulated phosphorylation of protein kinase B (AKT) but also dephosphorylated forkhead box O3α (FoxO3α). Chemerin‐induced mitochondrial autophagy likely through an AKT‐FoxO3α‐dependent signalling pathway. These findings provide direct evidence that chemerin may play an important role in regulating mitochondrial remodelling and function in skeletal muscle.     

Reactive oxygen species modulate itraconazole-induced apoptosis via mitochondrial disruption in Candida albicans

Itraconazole (ITC), a well-known fungistatic agent, has potent fungicidal activity against Candida albicans. However, its mechanism of fungicidal activity has not been elucidated yet, and we aimed to identify the mechanism of ITC against C. albicans. ITC caused cell shrinkage via potassium leakage through the ion channel. Since shrunken cells could indicate apoptosis, we investigated apoptotic features. Annexin V-FITC and TUNEL assays indicated that fungicidal activity of ITC was involved in apoptosis. Subsequently, we confirmed an intracellular factor that could cause apoptosis. ITC treatment caused reactive oxygen species (ROS) accumulation. To confirm whether ROS is related with ITC-triggered cell death, cell viability was examined using the ROS scavenger N-acetylcysteine (NAC). NAC pretreatment recovered ITC-induced cell death, indicating that antifungal activity of ITC is associated with ROS, which is also confirmed by impaired glutathione-related antioxidant system and oxidized intracellular lipids. Moreover, ITC-induced mitochondrial dysfunction, in turn, triggered cytochrome c release and metacaspase activation, leading to apoptosis. Unlike the only ITC-treatment group, cells with NAC pretreatment did not show significant damage to mitochondria, and attenuated apoptotic features. Therefore, our results suggest that ITC induces apoptosis as fungicidal mechanism, and intracellular ROS is major factor to trigger the apoptosis by ITC in C. albicans.     

Human MIEF1 recruits Drp1 to mitochondrial outer membranes and promotes mitochondrial fusion rather than fission

Mitochondrial morphology is controlled by two opposing processes: fusion and fission. Drp1 (dynamin-related protein 1) and hFis1 are two key players of mitochondrial fission, but how Drp1 is recruited to mitochondria and how Drp1-mediated mitochondrial fission is regulated in mammals is poorly understood. Here, we identify the vertebrate-specific protein MIEF1 (mitochondrial elongation factor 1; independently identified as MiD51), which is anchored to the outer mitochondrial membrane. Elevated MIEF1 levels induce extensive mitochondrial fusion, whereas depletion of MIEF1 causes mitochondrial fragmentation. MIEF1 interacts with and recruits Drp1 to mitochondria in a manner independent of hFis1, Mff (mitochondrial fission factor) and Mfn2 (mitofusin 2), but inhibits Drp1 activity, thus executing a negative effect on mitochondrial fission. MIEF1 also interacts with hFis1 and elevated hFis1 levels partially reverse the MIEF1-induced fusion phenotype. In addition to inhibiting Drp1, MIEF1 also actively promotes fusion, but in a manner distinct from mitofusins. In conclusion, our findings uncover a novel mechanism which controls the mitochondrial fusion-fission machinery in vertebrates. As MIEF1 is vertebrate-specific, these data also reveal important differences between yeast and vertebrates in the regulation of mitochondrial dynamics.     

BI1 alleviates cardiac microvascular ischemia-reperfusion injury via modifying mitochondrial fission and inhibiting XO/ROS/F-actin pathways

Pathogenesis of cardiac microvascular ischemia-reperfusion (IR) injury is associated with excessive mitochondrial fission. However, the upstream mediator of mitochondrial fission remains obscure. Bax inhibitor 1 (BI1) is linked to multiple mitochondrial functions, and there have been no studies investigating the contribution of BI1 on mitochondrial fission in the setting of cardiac microvascular IR injury. This study was undertaken to establish the action of BI1 on the cardiac microvascular reperfusion injury and figure out whether BI1 sustained endothelial viability via inhibiting mitochondrial fission. Our observation indicated that BI1 was downregulated in reperfused hearts and overexpression of BI1 attenuated microvascular IR injury. Mechanistically, reperfusion injury elevated the levels of xanthine oxidase (XO), an effect that was followed by increased reactive oxygen species (ROS) production. Subsequently, oxidative stress mediated F-actin depolymerization and the latter promoted mitochondrial fission. Aberrant fission caused mitochondrial dysfunction and ultimately activated mitochondrial apoptosis in cardiac microvascular endothelial cells. By comparison, BI1 overexpression repressed XO expression and thus neutralized ROS, interrupting F-actin-mediated mitochondrial fission. The inhibitory effect of BI1 on mitochondrial fission sustained endothelial viability, reversed endothelial barrier integrity, attenuated the microvascular inflammation response, and maintained microcirculation patency. Altogether, we conclude that BI1 is essential in maintaining mitochondrial homeostasis and alleviating cardiac microvascular IR injury. Deregulated BI1 via the XO/ROS/F-actin pathways plays a causative role in the development of cardiac microvascular reperfusion injury.     

Knockdown of STIM1 inhibits 6-hydroxydopamine-induced oxidative stress through attenuating calcium-dependent ER stress and mitochondrial dysfunction in undifferentiated PC12 cells

Abstract

Stromal interaction molecule (STIM) proteins are parts of elaborate eukaryotic Ca²⁺ signaling systems and are considered to be important players in regulating neuronal Ca²⁺ homeostasis under normal ageing and pathological conditions. Here, we investigated the potential role of STIM1 in 6-hydroxydopamine (6-OHDA)-induced toxicity in undifferentiated PC12 cell lines. Cells exposed to 6-OHDA demonstrated alterations in the generation of reactive oxygen species (ROS) in a Ca²⁺-dependent manner. Downregulation of STIM1 expression by specific small interfering RNA (siRNA) attenuated apoptotic cell death, reduced intracellular ROS production, and partially prevented the impaired endogenous antioxidant enzyme activities after 6-OHDA treatment. Furthermore, STIM1 knockdown significantly attenuated 6-OHDA-induced intracellular Ca²⁺ overload by inhibiting endogenous store-operated calcium entry (SOCE). The effect of STIM1 siNRA on SOCE was related to orai1 and L-type Ca²⁺ channels, but not to transient receptor potential canonical type 1 (TRPC1) channel. In addition, silencing of STIM1 increased the Ca²⁺ buffering capacity of the endoplasmic reticulum (ER) in 6-OHDA-injured cells. ER vacuoles formed from the destruction of ER structural integrity and activation of ER-related apoptotic factors (CHOP and Caspase-12) were partially prevented by STIM1 knockdown. Moreover, STIM1 knockdown attenuated 6-OHDA-induced mitochondrial Ca²⁺ uptake and mitochondrial dysfunction, including the collapse of mitochondrial membrane potential (MMP) and the decrease of ATP generation. Taken together, our data provide the first evidence that inhibition of STIM1-meditated intracellular Ca²⁺ dyshomeostasis protects undifferentiated PC12 cells against 6-OHDA toxicity and indicate that STIM1 may be responsible for neuronal oxidative stress induced by ER stress and mitochondrial dysfunction in PD.     

Proinflammation effect of Mst1 promotes BV-2 cell death via augmenting Drp1-mediated mitochondrial fragmentation and activating the JNK pathway

Inflammation has been increasingly studied as part of the pathophysiology of neurodegenerative diseases. Mammalian Ste20-like kinase 1 (Mst1), a key factor of the Hippo pathway, is connected to cell death. Unfortunately, little study has been performed to detect the impact of Mst1 in neuroninflammation. The results indicated that Mst1 expression was upregulated because of LPS treatment. However, the loss of Mst1 sustained BV-2 cell viability and promoted cell survival in the presence of LPS treatment. Molecular investigation assay demonstrated that Mst1 deletion was followed by a drop in the levels of mitochondrial fission via repressing Drp1 expression. However, Drp1 adenovirus transfection reduced the protective impacts of Mst1 knockdown on mitochondrial stress and neuronal dysfunction. Finally, our results illuminated that Mst1 affected Drp1 content and mitochondrial fission in a JNK-dependent mechanism. Reactivation of the JNK axis inhibited Mst1 knockdown-mediated neuronal protection and mitochondrial homeostasis. Altogether, our results indicated that Mst1 upregulation and the activation of JNK-Drp1-mitochondrial fission pathway could be considered as the novel mechanism regulating the progression of neuroninflammation. This finding would pave a new road for the treatment of neurodegenerative diseases via modulating the Mst1-JNK-Drp1-mitochondrial fission axis.     

Zinc supplementation protects against diabetic endothelial dysfunction via GTP cyclohydrolase 1 restoration

This study explored whether zinc supplementation alleviates diabetic endothelial dysfunction and the possible mechanisms underlying. We found that high glucose exposure significantly increased reactive oxygen species (ROS) and decreased guanosine 5′-triphosphate cyclohydrolase 1 (GTPCH1) and tetrahydrobiopterin (BH4) levels in bovine aortic endothelial cells (BAECs) in a time-dependent manner. High glucose increased zinc release from GTPCH1 in a similar trend. Zinc supplementation restored GTPCH1 and BH4 levels and blocked ROS accumulation in both BACEs and wild type GTPCH1 transfected HEK293 cells, but not in the zinc-free C141R mutant of GTPCH1 transfected ones. In vivo experiments showed that exogenous supplementation of zinc to streptozotocin (STZ)-induced diabetic mice partially improved the impaired maximal endothelium-dependent vasorelaxation, reversed the aberrant reduction of GTPCH1 and BH4, and suppressed the elevation of ROS in the aortas. In conclusion, our study demonstrated a novel mechanism that via GTPCH1 restoration zinc supplementation exerts a protective benefit on diabetic endothelial dysfunction.