Phosphorylation of Nonmuscle Myosin Light Chain Promotes Endothelial Injury in Hyperlipidemic Rats Through a Mechanism Involving Downregulation of Dimethylarginine Dimethylaminohydrolase 2

Phosphoglycerate mutase 5 promotes necroptosis in trophoblast cells through activation of dynamin-related protein 1 in early-onset preeclampsia

OBJECTIVES

Placentae from patients with preeclampsia have increased susceptibility to necroptosis and phosphoglycerate mutase 5 (PGAM5) plays a role in many necrosis pathways. We determined whether PGAM5 promotes necroptosis of trophoblast cells and the underlying mechanisms in this study.

METHODS

The injury model was established by treating JEG3 cells with hypoxia for 24 h. The functional measurements were assessed by the cell counting kit-8, propidium iodide (PI)/Annexin V staining, JC-1 staining and firefly luciferase ATP assay. The expression of proteins in human placentae and JEG3 cells was measured Western blot. PGAM5 was knocked down to study its role in hypoxia-induced necroptosis.

RESULTS

The placentae from patients with preeclampsia showed up-regulation of PGAM5 and decreased levels of p-Drp1-S637, accompanied by increased necroptosis-relevant proteins expression. The expression of PGAM5 in JEG3 cells was up-regulated under hypoxia, which promoted dephosphorylation of Drp1 at Serine 637 residue, mitochondrial dysfunction (elevated ROS level and reduced mitochondrial membrane potential and ATP content) and cellular necroptosis (increased PI⁺ /Annexin V⁺ cells and decreased cell viability), accompanied by increased expression of necroptosis-relevant proteins; knockdown of PGAM5 attenuated these phenomena.

CONCLUSIONS

Our results indicate that PGAM5 can promote necroptosis in trophoblast cells through, at least in part, activation of Drp1. It may be used as a new therapeutic target to prevent trophoblast dysfunction in preeclampsia.

Liraglutide prevents high glucose induced HUVECs dysfunction via inhibition of PINK1/Parkin-dependent mitophagy

Functional loss of endothelial cells will lead to development and progression of atherosclerosis in diabetic patients. However, dysfunction of endothelial cells in diabetes has yet to be fully understood. We aimed to characterize the potential effects of liraglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, on preventing high glucose-induced endothelial dysfunction and excessive mitophagic response. Pretreatment with liraglutide prevented downregulation of eNOS phosphorylation and NO secretion, and reduced apoptosis and oxidative stress of the human umbilical vein endothelial cells (HUVECs) exposed to high glucose. We further demonstrated that liraglutide likely mediated such protective effects by reducing PINK1/Parkin mediated mitophagy. Liraglutide markedly decreased high glucose-induced mitochondrial ROS, lessened PINK1 expression and mitochondrial accumulation of Parkin, but recovered SIRT1 expression. Seahorse analysis revealed that liraglutide mitigated high glucose-induced reduction of basal and maximum respiration rates as well as spare respiration capacity. Inhibition of Parkin by RNA silencing not only resulted in increased mitochondrial and cytosolic ROS and reduced mitochondrial mass and mitochondrial membrane potential, but also led to increased apoptotic responses in high glucose treated HUVECs which were not preventable by liraglutide. Together, our study reveals that liraglutide acts upstream of the PINK1/Parkin pathway to effectively counteract high glucose induced cell dysfunction by suppression of the PINK1/Parkin-dependent mitophagy. Therefore, its use as an adjunct therapy for type 2 diabetes mellitus is warranted to reduce the risk of atherosclerosis. Further research is required to examine the exact molecules, including SIRT1, upstream of the PINK1/parkin pathway that liraglutide targets to maintain the mitochondrial homeostasis.

Nobiletin Regulates ROS/ADMA/DDAHII/eNOS/NO Pathway and Alleviates Vascular Endothelium Injury by Iron Overload

Iron overload is harmful to health and associates with intracellular excessive reactive oxygen species (ROS) generation. Nobiletin (Nob) is known to be antioxidant and anti-inflammatory. However, whether Nob can protect endothelial cells against iron overload has not been studied, and the specific mechanism has not yet been elucidated. In this study, we have identified the protective effects of Nob, and its underlying molecular mechanism in human umbilical vein endothelial cells (HUVECs) suffered from iron overload via ROS/ADMA/DDAHII/eNOS/NO pathway. We found that compared with 50 μM iron dextran treatment, co-treatment with 20 μM Nob increased cell viability and decreased lactate dehydrogenase activity. Besides, Nob could upregulate DDAHII expression and activity, promote eNOS phosphorylation to produce more NO, reduce ADMA content, and therefore increase superoxide dismutase, catalase, and glutathione peroxidase activities, and decrease malondialdehyde level and ROS generation. Nob also inhibited mitochondrial permeability transition pore (mPTP) openness and cleaved caspase-3 expression, and decreased apoptosis induced by iron overload. These results were consistent when Nob was replaced by the positive control reagents L-arginine (a competitive substrate of ADMA), cyclosporin A (an mPTP closing agent), or edaravone (a free radical scavenger). The addition of pAD/DDAHII-shRNA adenovirus reversed the above effects of Nob. These data suggested that the protective mechanism of Nob was to inhibit ROS burst, upregulate DDAHII expression and activity, promote eNOS phosphorylation, produce NO, reduce ADMA content, and ultimately alleviate iron overload damage in vascular endothelium.

Myosin light chain kinase inhibitor ML7 improves vascular endothelial dysfunction and permeability via the mitogen-activated protein kinase pathway in a rabbit model of atherosclerosis

Endothelial dysfunction (ED) and hyperpermeability are considered as the initiating steps in early atherosclerosis. Phosphorylation of myosin light chain (MLC) is key to cause vascular hyperpermeability via endothelial cell contraction. However, it is unclear whether MLC phosphorylation can also regulate the balance between contraction and relaxation of endothelial cells, thereby affecting endothelium-dependent diastolic function and leading to ED. The present study investigated relationships between ED and MLC phosphorylation and underlying mechanisms. Twenty-four male New Zealand white rabbits were randomly divided into three groups: control, AS, and ML7 (MLCK inhibitor) groups, and fed with normal diet, high-fat diet (HFD), and HFD plus oral ML7 (1 mg/kg daily) respectively. HFD-fed rabbits showed typical atheromatous lesions and endothelial hyperpermeability, and these lesions could be partly reversed following ML7 therapy. Western blotting revealed significant increased expression of myosin light chain kinase (MLCK) and phosphorylation of MLC, JNK, and ERK in the arterial wall of rabbits in the AS group compared with those of the control group (p < 0.05), whereas the ML7 group showed markedly decreased levels of these proteins compared with the AS group (p <  0.05). The endothelium-dependent relaxation rate was significantly reduced both in vitro and in vivo in AS group, and was improved using ML7 therapy. Taken together, these results indicate that MLCK expression and subsequent MLC phosphorylation increase vascular endothelial permeability and endothelium-dependent diastolic dysfunction by promoting endothelial cell contraction, which may be initiated by the activation of the MAP/ERK (MEK) and MAP/JNK (MEK) pathways.

Doxorubicin Induces Endotheliotoxicity and Mitochondrial Dysfunction via ROS/eNOS/NO Pathway

Background: Doxorubicin (Dox) can induce endotheliotoxicity and damage the vascular endothelium (VE). The most principle mechanism might be excess reactive oxygen species (ROS) generation. Nevertheless, the characteristics of ROS generation, downstream mechanisms, and target organelles in Dox-induced endotheliotoxicity have yet to be elucidated.

Methods and Results: In order to explore the related problems, the VE injury models were established in mice and human umbilical vein endothelial cells (HUVECs) by Dox-induced endotheliotoxicity. Results showed that the activities of lactate dehydrogenase (LDH) and creatine kinase of mice’s serum increased after injected Dox. The thoracic aortic strips’ endothelium-dependent dilation was significantly impaired, seen noticeable inflammatory changes, and brown TUNEL-positive staining in microscopy. After Dox-treated, HUVECs viability lowered, LDH and caspase-3 activities, and apoptotic cells increased. Both intracellular/mitochondrial ROS generation significantly increased, and intracellular ROS generation lagged behind mitochondria. HUVECs treated with Dox plus ciclosporin A (CsA) could basically terminate ROS burst, but plus edaravone (Eda) could only delay or inhibit, but could not completely cancel ROS burst. Meanwhile, the expression of endothelial nitric oxide synthase (eNOS) decreased, especially phosphorylation of eNOS significantly. Then nitric oxide content decreased, the mitochondrial function was impaired, mitochondrial membrane potential (MMP) impeded, mitochondrial swelled, mitochondrial permeability transition pore (mPTP) was opened, and cytochrome C was released from mitochondria into the cytosol.

Conclusion: Dox produces excess ROS in the mitochondria, thereby weakens the MMP, opens mPTP, activates the ROS-induced ROS release mechanism, induces ROS burst, and leads to mitochondrial dysfunction, which in turn damages VE. Therefore, interrupting any step of the cycles, as mentioned above can end the related vicious cycle and prevent the occurrence and development of injury.

Tetramethylpyrazine Attenuates the Endotheliotoxicity and the Mitochondrial Dysfunction by Doxorubicin via 14-3-3γ/Bcl-2

Doxorubicin (Dox) with cardiotoxicity and endotheliotoxicity limits its clinical application for cancer. The toxicitic mechanism involves excess ROS generation. 14-3-3s have the protective effects on various injured tissues and cells. Tetramethylpyrazine (TMP) is an alkaloid extracted from the rhizome of Ligusticum wallichii and has multiple bioactivities. We hypothesize that TMP has the protective effects on vascular endothelium by upregulating 14-3-3γ. To test the hypothesis, Dox-induced endotheliotoxicity was used to establish vascular endothelium injury models in mice and human umbilical vein endothelial cells. The effects of TMP were assessed by determining thoracic aortic strips' endothelium-dependent dilation (EDD), as well as LDH, CK, caspase-3, SOD, CAT, GSH-Px activities and MDA level in serum, apoptotic rate, and histopathological changes of vascular tissue (in vivo). Also, cell viability, LDH and caspase-3 activities, ROS generation, levels of NAD⁺/NADH and GSH/GSSG, MMP, mPTP opening, and apoptotic rate were evaluated (in vitro). The expression of 14-3-3γ and Bcl-2, as well as phosphorylation of Bad (S112), were determined by Western blot. Our results showed that Dox-induced injury to vascular endothelium was decreased by TMP via upregulating 14-3-3γ expression in total protein and Bcl-2 expression in mitochondria, activating Bad (S112) phosphorylation, maintaining EDD, reducing LDH, CK, and caspase-3 activities, thereby causing a reduction in apoptotic rate, and histopathological changes of vascular endothelium (in vivo). Furthermore, TMP increased cell viability and MMP levels, maintained NAD⁺/NADH, GSH/GSSG balance, decreased LDH and caspase-3 activities, ROS generation, mPTP opening, and apoptotic rate (in vitro). However, the protective effects to vascular endothelium of TMP were significantly canceled by pAD/14-3-3γ-shRNA, an adenovirus that caused knockdown 14-3-3γ expression, or ABT-737, a specific Bcl-2 inhibitor. In conclusion, this study is the first to demonstrate that TMP protects the vascular endothelium against Dox-induced injury via upregulating 14-3-3γ expression, promoting translocation of Bcl-2 to the mitochondria, closing mPTP, maintaining MMP, inhibiting RIRR mechanism, suppressing oxidative stress, improving mitochondrial function, and alleviating Dox-induced endotheliotoxicity.

Iron Overload Damages the Endothelial Mitochondria via the ROS/ADMA/DDAHII/eNOS/NO Pathway

It has been recognized that iron overload may harm the body's health. Vascular endothelial cells (VECs) are one of the main targets of iron overload injury, and the mechanism involved was thought to be related to the excessive generation of reactive oxygen species (ROS). However, the subcellular and temporal characteristics of ROS generation, potential downstream mechanisms, and target organelles in VECs injured by iron overload have not been expounded yet. In this study, we elucidated the abovementioned issues through both in vivo and in vitro experiments. Mice were fed pellet diets that were supplemented with iron for 4 consecutive months. Results showed that the thoracic aortic strips' endothelium-dependent dilation was significantly impaired and associated with inflammatory changes, noticeable under brown TUNEL-positive staining in microscopy analysis. In addition, the serum content of asymmetric dimethylarginine (ADMA) increased, whereas nitric oxide (NO) levels decreased. Furthermore, the dimethylarginine dimethylaminohydrolase II (DDAHII) expression and activity, as well as the phosphorylation of endothelial nitric oxide synthase (eNOS) in aortic tissue, were inhibited. Human umbilical vein endothelial cells were treated with 50 μM iron dextran for 48 hours, after which the cell viability, NO content, DDAHII expression and activity, and phosphorylation of eNOS decreased and lactate dehydrogenase and caspase-3 activity, ADMA content, and apoptotic cells significantly increased. After the addition of L-arginine (L-Arg) or pAD/DDAHII, the abovementioned changes were reversed. By dynamically detecting the changes of ROS generation in the cytoplasm and mitochondria and interfering with different aspects of signaling pathways, we have confirmed for the first time that excessive ROS originates from the cytoplasm and activates the ROS-induced ROS release (RIRR) mechanism, leading to mitochondrial dysfunction. Together, our data suggested that excessive free iron ions produced excess ROS in the cytoplasm. Thus, excess ROS create one vicious circle by activating the ADMA/eNOS/DDAHII/NO pathway and another vicious circle by activation of the RIRR mechanism, which, when combined, induce a ROS burst, resulting in mitochondrial dysfunction and damaged VECs.