The effect of chronic exposure to high palmitic acid concentrations on the aerobic metabolism of human endothelial EA.hy926 cells

Endothelial dysfunction in vascular complications of diabetes: a comprehensive review of mechanisms and implications

Diabetic vascular complications are prevalent and severe among diabetic patients, profoundly affecting both their quality of life and long-term prospects. These complications can be classified into macrovascular and microvascular complications. Under the impact of risk factors such as elevated blood glucose, blood pressure, and cholesterol lipids, the vascular endothelium undergoes endothelial dysfunction, characterized by increased inflammation and oxidative stress, decreased NO biosynthesis, endothelial-mesenchymal transition, senescence, and even cell death. These processes will ultimately lead to macrovascular and microvascular diseases, with macrovascular diseases mainly characterized by atherosclerosis (AS) and microvascular diseases mainly characterized by thickening of the basement membrane. It further indicates a primary contributor to the elevated morbidity and mortality observed in individuals with diabetes. In this review, we will delve into the intricate mechanisms that drive endothelial dysfunction during diabetes progression and its associated vascular complications. Furthermore, we will outline various pharmacotherapies targeting diabetic endothelial dysfunction in the hope of accelerating effective therapeutic drug discovery for early control of diabetes and its vascular complications.

Coenzyme Q deficiency in endothelial mitochondria caused by hypoxia; remodeling of the respiratory chain and sensitivity to anoxia/reoxygenation

This study examined the effects of hypoxia on coenzyme Q (Q) levels and mitochondrial function in EA. hy926 endothelial cells, shedding light on their responses to changes in oxygen levels. Chronic hypoxia during endothelial cell culture reduced Q synthesis by reducing hydroxy-methylglutaryl-CoA reductase (HMGCR) levels via hypoxia-inducible factor 1α (HIF1α), leading to severe Q deficiency. In endothelial mitochondria, hypoxia led to reorganization of the respiratory chain through upregulation of supercomplexes (I+III2+IV), forming a complete mitochondrial Q (mQ)-mediated electron transfer pathway. Mitochondria of endothelial cells cultured under hypoxic conditions showed reduced respiratory rates and membrane potential, as well as increased production of mitochondrial reactive oxygen species (mROS) as a result of increased mQ reduction levels (mQH2/mQtot). Anoxia/reoxygenation (A/R) in vitro caused impairment of endothelial mitochondria, manifested by reduced maximal respiration, complex III activity, membrane potential, coupling parameters, and increased mQ reduction and mROS production. Weaker A/R-induced changes compared to control mitochondria indicated better tolerance of A/R stress by the mitochondria of hypoxic cells. Moreover, in endothelial mitochondria, hypoxia-induced increases in uncoupling protein 3 (UCP3) and mitochondrial large-conductance Ca2+-activated potassium channel (mitoBKCa) levels and activities appear to have alleviated reoxygenation injury after A/R. These results not only highlight hypoxia-induced changes in mQ redox homeostasis and related mitochondrial function, but also indicate that chronic hypoxia during endothelial cell culture leads to mitochondrial adaptations that help mitochondria better withstand subsequent oxygen fluctuations.

Stearoyl-CoA Desaturase Regulates Angiogenesis and Energy Metabolism in Ischemic Cardiomyocytes

New blood vessel formation is a key component of the cardiac repair process after myocardial infarction (MI). Hypoxia following MI is a major driver of angiogenesis in the myocardium. Hypoxia-inducible factor 1α (HIF1α) is the key regulator of proangiogenic signaling. The present study found that stearoyl-CoA desaturase (SCD) significantly contributed to the induction of angiogenesis in the hypoxic myocardium independently of HIF1α expression. The pharmacological inhibition of SCD activity in HL-1 cardiomyocytes and SCD knockout in an animal model disturbed the expression and secretion of proangiogenic factors including vascular endothelial growth factor-A, proinflammatory cytokines (interleukin-1β, interleukin-6, tumor necrosis factor α, monocyte chemoattractant protein-1, and Rantes), metalloproteinase-9, and platelet-derived growth factor in ischemic cardiomyocytes. These disturbances affected the proangiogenic potential of ischemic cardiomyocytes after SCD depletion. Together with the most abundant SCD1 isoform, the heart-specific SCD4 isoform emerged as an important regulator of new blood vessel formation in the murine post-MI myocardium. We also provide evidence that SCD shapes energy metabolism of the ischemic heart by maintaining the shift from fatty acids to glucose as the substrate that is used for adenosine triphosphate production. Furthermore, we propose that the regulation of the proangiogenic properties of hypoxic cardiomyocytes by key modulators of metabolic signaling such as adenosine monophosphate kinase, protein kinase B (AKT), and peroxisome-proliferator-activated receptor-γ coactivator 1α/peroxisome proliferator-activated receptor α depends on SCD to some extent. Thus, our results reveal a novel mechanism that links SCD to cardiac repair processes after MI.

Molecular mechanisms of coronary microvascular endothelial dysfunction in diabetes mellitus: focus on mitochondrial quality surveillance

Coronary microvascular endothelial dysfunction is both a culprit and a victim of diabetes, and can accelerate diabetes-related microvascular and macrovascular complications by promoting vasoconstrictive, pro-inflammatory and pro-thrombotic responses. Perturbed mitochondrial function induces oxidative stress, disrupts metabolism and activates apoptosis in endothelial cells, thus exacerbating the progression of coronary microvascular complications in diabetes. The mitochondrial quality surveillance (MQS) system responds to stress by altering mitochondrial metabolism, dynamics (fission and fusion), mitophagy and biogenesis. Dysfunctional mitochondria are prone to fission, which generates two distinct types of mitochondria: one with a normal and the other with a depolarized mitochondrial membrane potential. Mitochondrial fusion and mitophagy can restore the membrane potential and homeostasis of defective mitochondrial fragments. Mitophagy-induced decreases in the mitochondrial population can be reversed by mitochondrial biogenesis. MQS abnormalities induce pathological mitochondrial fission, delayed mitophagy, impaired metabolism and defective biogenesis, thus promoting the accumulation of unhealthy mitochondria and the activation of mitochondria-dependent apoptosis. In this review, we examine the effects of MQS on mitochondrial fitness and explore the association of MQS disorders with coronary microvascular endothelial dysfunction in diabetes. We also discuss the potential to treat diabetes-related coronary microvascular endothelial dysfunction using novel MQS-altering drugs.

Empagliflozin does not reverse lipotoxicity-induced impairment in human myeloid angiogenic cell bioenergetics

Background

Empagliflozin can curb inflammation and oxidative stress, through sodium-proton exchanger (NHE) inhibition, in a model of lipotoxicity in human myeloid angiogenic cells (MAC), which mediate endothelial repairing processes. Aim of this study is to assess in human MAC whether: (1) Stearic acid (SA) induced inflammation and increase in oxidant stress is accompanied by bioenergetic alterations; (2) empagliflozin anti-lipotoxic action is concomitant with coherent changes in bioenergetic metabolism, possibly via NHE blockade.

Methods

MAC were isolated from peripheral blood of healthy volunteers and incubated in the presence/absence of SA (100 μM for 3 h) with/without empagliflozin (EMPA 100 μM) or amiloride (Ami 100 μM) for 1 h. Cell respiration (oxygen consumption rate OCR) and anaerobic glycolysis (measured as proton production rate) were recorded in real-time by Seahorse technology, and ATP production (anaerobic glycolysis- and oxphos-derived) rates were calculated.

Results

SA, at the concentration causing inflammation and increased oxidant stress, altered cell bioenergetics of human MAC, with overall reductions in basal OCR and oxphos-derived ATP production (all p < 0.05), pointing to mitochondrial alterations. EMPA, at the concentration counteracting SA-induced lipotoxicity, both alone and in the presence of SA, caused NHE-independent extensive bioenergetic alterations (from p < 0.05 to p < 0.01), greater than those induced by SA alone.

Conclusions

In human MAC: (1) SA altered cell bioenergetics, concomitantly with inflammation and oxidant stress; (2) EMPA possibly inhibited mitochondrial respiration, (3) the protective effect of EMPA against SA-induced lipotoxicity was unlikely to be mediated through bioenergetic metabolism.

High metabolic substrate load induces mitochondrial dysfunction in rat skeletal muscle microvascular endothelial cells

The influence of glucose and palmitic acid (PA) on mitochondrial respiration and emission of hydrogen peroxide (H2 O2 ) was determined in skeletal muscle-derived microvascular endothelial cells. Measurements were assessed in intact and permeabilized (cells treated with 0.025% saponin) low passage endothelial cells with acute-or prolonged (3 days) incubation with regular (1.7 mM) or elevated (2.2 mM) PA concentrations and regular (5 mM) or elevated (11 mM) glucose concentrations. In intact cells, acute incubation with 1.7 mM PA alone or with 1.7 mM PA + 5 mM glucose (p < .001) led to a lower mitochondrial respiration (p < 0.01) and markedly higher H2 O2 /O2 emission (p < 0.05) than with 5 mM glucose alone. Prolonged incubation of intact cells with 1.7 mM PA +5 mM glucose led to 34% (p < 0.05) lower respiration and 2.5-fold higher H2 O2 /O2 emission (p < 0.01) than incubation with 5 mM glucose alone. Prolonged incubation of intact cells with elevated glucose led to 60% lower (p < 0.05) mitochondrial respiration and 4.6-fold higher H2 O2 /O2 production than incubation with 5 mM glucose in intact cells (p < 0.001). All effects observed in intact cells were present also in permeabilized cells (State 2). In conclusion, our results show that acute and prolonged lipid availability, as well as prolonged hyperglycemia, induces mitochondrial dysfunction as evidenced by lower mitochondrial respiration and enhanced H2 O2/ O2 emission. Elevated plasma substrate availability may lead to microvascular dysfunction in skeletal muscle by impairing endothelial mitochondrial function.

Coordinating Effect of VEGFC and Oleic Acid Participates to Tumor Lymphangiogenesis

Simple Summary

In cancer, the lymphatic system is hijacked by tumor cells that escape from primary tumor and metastasize to the sentinel lymph nodes. Tumor lymphangiogenesis is stimulated by the vascular endothelial growth factors-C (VEGFC) after binding to its receptor VEGFR-3. However, how VEGFC cooperates with other molecules to promote lymphatic neovessel growth has not been fully determined. Here, we showed that tumor lymphangiogenesis developed in tumoral lesions and in their surrounding adipose tissue (AT). Interestingly, lymphatic vessel density correlated with an increase in circulating free fatty acids (FFA) in the lymph from tumor-bearing mice. We showed that adipocyte-released FFA are uploaded by lymphatic endothelial cells (LEC) to stimulate their sprouting. Lipidomic analysis identified the monounsaturated oleic acid (OA) as the major circulating FFA in the lymph in a tumoral context. OA transporters FATP-3, -6 and CD36 were only upregulated on LEC in the presence of VEGFC showing a collaborative effect of these molecules. OA released from adipocytes is taken up by LECs to stimulate the fatty acid β-oxidation, leading to increased adipose tissue lymphangiogenesis. Our results provide new insights on the dialogue between tumors and adipocytes via the lymphatic system and identify a key role for adipocyte-derived FFA in the promotion of lymphangiogenesis, revealing novel therapeutic opportunities for inhibitors of lymphangiogenesis in cancer.

Abstract

In cancer, the lymphatic system is hijacked by tumor cells that escape from primary tumor and metastasize to the sentinel lymph nodes. Tumor lymphangiogenesis is stimulated by the vascular endothelial growth factors-C (VEGFC) after binding to its receptor VEGFR-3. However, how VEGFC cooperates with other molecules to promote lymphatics growth has not been fully determined. We showed that lymphangiogenesis developed in tumoral lesions and in surrounding adipose tissue (AT). Interestingly, lymphatic vessel density correlated with an increase in circulating free fatty acids (FFA) in the lymph from tumor-bearing mice. We showed that adipocyte-released FFA are uploaded by lymphatic endothelial cells (LEC) to stimulate their sprouting. Lipidomic analysis identified the monounsaturated oleic acid (OA) as the major circulating FFA in the lymph in a tumoral context. OA transporters FATP-3, -6 and CD36 were only upregulated on LEC in the presence of VEGFC showing a collaborative effect of these molecules. OA stimulates fatty acid β-oxidation in LECs, leading to increased AT lymphangiogenesis. Our results provide new insights on the dialogue between tumors and adipocytes via the lymphatic system and identify a key role for adipocyte-derived FFA in the promotion of lymphangiogenesis, revealing novel therapeutic opportunities for inhibitors of lymphangiogenesis in cancer.

Effect of docosahexaenoic acid plus insulin on atherosclerotic human endothelial cells

Background

Atherosclerosis is touted as one of the most critical consequences of diabetes mellitus indicated by local inflammation of endothelial cells. The Effect of Omega 3 fatty acids, mainly docosahexaenoic acid (DHA), has been investigated in cells after exposure to high doses of lipids. The current experiment aimed to address the modulatory effects of docosahexaenoic acid and insulin in palmitic-treated human endothelial cells.

Methods

Human umbilical vein endothelial cells were treated with 1 mM palmitic acid, 50 μM insulin, 50 μM docosahexaenoic acid, and their combination for 48 h. Cell survival rate and apoptosis were measured using MTT and flow cytometry assays. The Griess assay detected NO levels. Protein levels of TNF-α, IL-6, and NF-κB were studied using ELISA and immunofluorescence imaging. The expression of genes participating in atherosclerosis was monitored using PCR array analysis.

Results

Oil Red O staining showed the inhibitory effect of DHA and insulin to reduce the intracellular accumulation of palmitic acid. Both DHA and Insulin blunted palmitic acid detrimental effects on HUVECs indicated by an increased survival rate (p < 0.05). The percent of apoptotic cells was decreased in palmitic-treated cells received insulin and DHA compared to palmitic-treated group (p < 0.05). Based on our data, DHA and Insulin diminished the production of all inflammatory cytokines, TNF-α, IL-6, and NF-κB, in palmitic-treated cells (p < 0.05). Similar to these data, NO production was also decreased in all groups treated with insulin and DHA compared to the palmitic-treated cells (p < 0.05). PCR array analysis revealed the modulatory effect of DHA and insulin on the expression of atherosclerosis-related genes pre-treated with palmitic acid compared to the control group (p < 0.05).

Conclusion

DHA and Insulin could alter the dynamic growth and dysfunctional activity of human endothelial cells after treatment with palmitic acid. Taken together, Omega 3 fatty acids, along with insulin, could dictate specific cell behavior in endothelial cells in vitro.

Altered VDAC-HK association and apoptosis in mouse peripheral blood lymphocytes exposed to diabetic condition: an in vitro and in vivo study

Increased apoptotic lymphocytes have been correlated to a high incidence of infection in poorly controlled diabetes. This study aimed to determine whether altered voltage-dependent anion channel (VDAC)-hexokinase (HK) association contributes to the increase in apoptosis. Mouse peripheral blood lymphocytes (PBL) exposed to high glucose (Glc)/palmitic acid (PA) were used as the in vitro model, which was compared with PBL isolated from alloxan-induced diabetic mice (in vivo model). Our results showed a significant increase in apoptosis as indicated by the apoptotic index, caspase-3 activity, mitochondrial membrane potential and ultrastructural study. HK and glucose-6-phosphate dehydrogenase (G6PDH) activities were markedly reduced with a profound increase in glucose-6-phosphate level. Co-immunoprecipitation confirms HK interaction with VDAC, an outer mitochondrial membrane protein. Inhibited glycolytic enzyme, i.e. HK and reduced HK-VDAC interaction in our study could contribute to increased apoptosis in lymphocytes exposed to high Glc/PA. Targeting HK-VDAC interaction may therefore provide therapeutic potential for the treatment of diabetes-associated infection.

Lung mitochondria adaptation to endurance training in rats

We elucidated the impact of eight weeks of endurance training on the oxidative metabolism of rat lungs. Adult 3.5-month-old male rats were randomly allocated to a treadmill training group or a sedentary group as control. In the lungs, endurance training raised the expression level of the oxygen sensors hypoxia inducible factor 1α (HIF1α) and lysine-specific demethylase 6A (KDM6A) as well as stimulated mitochondrial oxidative capacity and mitochondrial biogenesis, while lactate dehydrogenase activity was reduced. Endurance training enhanced antioxidant systems (the coenzyme Q content and superoxide dismutase) in lung tissue but decreased them (and uncoupling protein 2) in lung mitochondria. In the lung mitochondria of trained rats, the decreased Q content and Complex I (CI) activity and the enhanced cytochrome pathway activity (CIII + CIV) may account for the diminished Q reduction level, resulting in a general decrease in H₂O₂ formation by mitochondria. Endurance training enhanced oxidation of glutamate and fatty acids and caused opposite effects in functional mitochondrial properties during malate and succinate oxidation, which were related to reduced activity of CI and increased activity of CII, respectively. In addition, endurance training downregulated CI in supercomplexes and upregulated CIII in the CIII₂+CIV supercomplex in the oxidative phosphorylation system. We concluded that the adaptive lung responses observed could be due to hypoxia and oxidative stress induced by strenuous endurance training.

Oleic Acid Counters Impaired Blastocyst Development Induced by Palmitic Acid During Mouse Preimplantation Development: Understanding Obesity-Related Declines in Fertility

Obesity is associated with altered fatty acid profiles, reduced fertility, and assisted reproductive technology (ART) success. The effects of palmitic acid (PA), oleic acid (OA), and their combination on mouse preimplantation development, endoplasmic reticulum (ER) stress pathway gene expression, lipid droplet formation, and mitochondrial reactive oxygen species (ROS) were characterized. Two-cell stage mouse embryos collected from superovulated and mated CD1 females were placed into culture with KSOMaa medium, or PA alone or in combination with OA for 46 h. PA significantly reduced blastocyst development in a concentration-dependent manner, which was prevented by co-treatment with OA. PA and OA levels in mouse reproductive tracts were assessed by liquid chromatography coupled to mass spectrometry (LC-MS). LC-MS indicated higher concentrations of PA in the mouse oviduct than the uterus. Transcript analysis revealed that PA alone groups had increased ER stress pathway (ATF3, CHOP, and XBP1 splicing) mRNAs, which was alleviated by OA co-treatment. OA co-treatment significantly increased lipid droplet accumulation and significantly decreased mitochondrial ROS from PA treatment alone. PA treatment for only 24 h significantly reduced its impact on blastocyst development from the 2-cell stage. Thus, PA affects ER stress pathway gene expression, lipid droplet accumulation, and mitochondrial ROS in treated preimplantation embryos. These mechanisms may serve to offset free fatty acid exposure effects on preimplantation development, but their protective ability may be overwhelmed by elevated PA.

The Influence of Statins on the Aerobic Metabolism of Endothelial Cells

Endothelial mitochondrial dysfunction is considered to be the main cause of cardiovascular disease. The aim of this research was to elucidate the effects of cholesterol-lowering statins on the aerobic metabolism of endothelial cells at the cellular and mitochondrial levels. In human umbilical vein endothelial cells (EA.hy926), six days of exposure to 100 nM atorvastatin (ATOR) induced a general decrease in mitochondrial respiration. No changes in mitochondrial biogenesis, cell viability, or ATP levels were observed, whereas a decrease in Coenzyme Q10 (Q10) content was accompanied by an increase in intracellular reactive oxygen species (ROS) production, although mitochondrial ROS production remained unchanged. The changes caused by 100 nM pravastatin were smaller than those caused by ATOR. The ATOR-induced changes at the respiratory chain level promoted increased mitochondrial ROS production. In addition to the reduced level of mitochondrial Q10, the activity of Complex III was decreased, and the amount of Complex III in a supercomplex with Complex IV was diminished. These changes may cause the observed decrease in mitochondrial membrane potential and an increase in Q10 reduction level as a consequence, leading to elevated mitochondrial ROS formation. The above observations highlight the role of endothelial mitochondria in response to potential metabolic adaptations related to the chronic exposure of endothelial cells to statins.

Mitigation of Glucolipotoxicity-Induced Apoptosis, Mitochondrial Dysfunction, and Metabolic Stress by N-Acetyl Cysteine in Pancreatic β-Cells

Glucolipotoxicity caused by hyperglycemia and hyperlipidemia are the common features of diabetes-induced complications. Metabolic adaptation, particularly in energy metabolism; mitochondrial dysfunction; and increased inflammatory and oxidative stress responses are considered to be the main characteristics of diabetes and metabolic syndrome. However, due to various fluctuating endogenous and exogenous stimuli, the precise role of these factors under in vivo conditions is not clearly understood. In the present study, we used pancreatic β-cells, Rin-5F, to elucidate the molecular and metabolic changes in glucolipotoxicity. Cells treated with high glucose (25 mM) and high palmitic acid (up to 0.3 mM) for 24 h exhibited increased caspase/poly-ADP ribose polymerase (PARP)-dependent apoptosis followed by DNA fragmentation, alterations in mitochondrial membrane permeability, and bioenergetics, accompanied by alterations in glycolytic and mitochondrial energy metabolism. Our results also demonstrated alterations in the expression of mammalian target of rapamycin (mTOR)/5′ adenosine monophosphate-activated protein kinase (AMPK)-dependent apoptotic and autophagy markers. Furthermore, pre-treatment of cells with 10 mM N-acetyl cysteine attenuated the deleterious effects of high glucose and high palmitic acid with improved cellular functions and survival. These results suggest that the presence of high energy metabolites enhance mitochondrial dysfunction and apoptosis by suppressing autophagy and adapting energy metabolism, mediated, at least in part, via enhanced oxidative DNA damage and mTOR/AMPK-dependent cell signaling.

Low-Level Saturated Fatty Acid Palmitate Benefits Liver Cells by Boosting Mitochondrial Metabolism via CDK1-SIRT3-CPT2 Cascade

Saturated fatty acids (SFAs) (the "bad" fat), especially palmitate (PA), in the human diet are blamed for potential health risks such as obesity and cancer because of SFA-induced lipotoxicity. However, epidemiological results demonstrate a latent benefit of SFAs, and it remains elusive whether a certain low level of SFAs is physiologically essential for maintaining cell metabolic hemostasis. Here, we demonstrate that although high-level PA (HPA) indeed induces lipotoxic effects in liver cells, low-level PA (LPA) increases mitochondrial functions and alleviates the injuries induced by HPA or hepatoxic agent carbon tetrachloride (CCl₄). LPA treatment in mice enhanced liver mitochondrial activity and reduced CCl₄ hepatotoxicity with improved blood levels of aspartate aminotransferase (AST), alanine transaminase (ALT), and mitochondrial aspartate transaminase (m-AST). LPA-mediated mitochondrial homeostasis is regulated by CDK1-mediated SIRT3 phosphorylation, which in turn deacetylates and dimerizes CPT2 to enhance fatty acid oxidation. Thus, an advantageous effect is suggested by the consumption of LPA that augments mitochondrial metabolic homeostasis via CDK1-SIRT3-CPT2 cascade.

Highly Glycolytic Immortalized Human Dermal Microvascular Endothelial Cells are Able to Grow in Glucose-Starved Conditions

Endothelial cells form the inner lining of blood vessels, in a process known as angiogenesis. Excessive angiogenesis is a hallmark of several diseases, including cancer. The number of studies in endothelial cell metabolism has increased in recent years, and new metabolic targets for pharmacological treatment of pathological angiogenesis are being proposed. In this work, we wanted to address experimental evidence of substrate (namely glucose, glutamine and palmitate) dependence in immortalized dermal microvascular endothelial cells in comparison to primary endothelial cells. In addition, due to the lack of information about lactate metabolism in this specific type of endothelial cells, we also checked their capability of utilizing extracellular lactate. For fulfilling these aims, proliferation, migration, Seahorse, substrate uptake/utilization, and mRNA/protein expression experiments were performed. Our results show a high glycolytic capacity of immortalized dermal microvascular endothelial cells, but an early independence of glucose for cell growth, whereas a total dependence of glutamine to proliferate was found. Additionally, in contrast with reported data in other endothelial cell lines, these cells lack monocarboxylate transporter 1 for extracellular lactate incorporation. Therefore, our results point to the change of certain metabolic features depending on the endothelial cell line.

Ilexgenin A inhibits mitochondrial fission and promote Drp1 degradation by Nrf2-induced PSMB5 in endothelial cells

Atherosclerosis (AS) is one of important events involving in the pathological process of coronary artery disease. Many traditional Chinese medicines have been widely used for the treatment of AS. Previous studies have demonstrated that Ilexgenin A (IA) obtained from Ilex hainanensis Merr. could improve AS development. However, its underlying mechanism is still unknown. This study was conducted to explore the possible targets and mechanisms involving in the anti-atheroclerosis effect of IA. The results showed IA significantly promoted NO production, reduced reactive oxygen species (ROS) generation, and inflammatory cytokine production induced by palmitate (PA) in endothelial cells, demonstrating IA could improve endothelial dysfunction. Meanwhile, IA dramatically inhibited dynamin-related protein 1 (Drp1) expression and mitochondrial fission induced by PA whereas proteasome inhibitor epoxomicin attenuated its effect on Drp1 expression, indicating IA decreased Drp1 expression with regulation of proteasome. Furthermore, IA also could increase the expression of proteasome subunit beta type5 (PSMB5) and activate nuclear factor-like 2 (Nrf2). Nrf2 knockdown eliminated the induction effect of IA on PSMB5 expression while abrogated its inhibition on ROS generation and mitochondrial fission stimulated by PA. These results demonstrated that IA could promote PSMB5 expression in an Nrf2-dependent manner, resulting in the suppression of mitochondrial fission, and thus improve endothelial dysfunction. These findings laid a foundation to the future development of IA as an agent to the prevention and treatment of AS.

Membrane-lipid therapy: A historical perspective of membrane-targeted therapies - From lipid bilayer structure to the pathophysiological regulation of cells

Our current understanding of membrane lipid composition, structure and functions has led to the investigation of their role in cell signaling, both in healthy and pathological cells. As a consequence, therapies based on the regulation of membrane lipid composition and structure have been recently developed. This novel field, known as Membrane Lipid Therapy, is growing and evolving rapidly, providing treatments that are now in use or that are being studied for their application to oncological disorders, Alzheimer's disease, spinal cord injury, stroke, diabetes, obesity, and neuropathic pain. This field has arisen from relevant discoveries on the behavior of membranes in recent decades, and it paves the way to adopt new approaches in modern pharmacology and nutrition. This innovative area will promote further investigation into membranes and the development of new therapies with molecules that target the cell membrane. Due to the prominent roles of membranes in the cells' physiology and the paucity of therapeutic approaches based on the regulation of the lipids they contain, it is expected that membrane lipid therapy will provide new treatments for numerous pathologies. The first on-purpose rationally designed molecule in this field, minerval, is currently being tested in clinical trials and it is expected to enter the market around 2020. However, it seems feasible that during the next few decades other membrane regulators will also be marketed for the treatment of human pathologies. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

WITHDRAWN: Membrane-lipid therapy: A historical perspective of membrane-targeted therapies-From lipid bilayer structure to the pathophysiological regulation of cells

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.bbamem.2017.05.017. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Hypoxia and aerobic metabolism adaptations of human endothelial cells

The goal of our study was to assess the influence of chronic exposure to hypoxia on mitochondrial oxidative metabolism in human umbilical vein endothelial cells (EA.hy926 line) cultured for 6 days at 1% O₂ tension. The hypoxia-induced effects were elucidated at the cellular and isolated mitochondria levels. Hypoxia elevated fermentation but did not change mitochondrial biogenesis or the aerobic respiratory capacity of endothelial cells. In endothelial cells, hypoxia caused a general decrease in mitochondrial respiration during carbohydrate, fatty acid, and amino acid oxidation but increased exclusively ketogenic amino acid oxidation. Hypoxia induced an elevation of intracellular and mitochondrial reactive oxygen species (ROS) formation, although cell viability was unchanged and antioxidant systems (superoxide dismutases SOD1 and SOD2, and uncoupling proteins (UCPs)) were not increased. In mitochondria from hypoxic cells, the opposite change was observed at the respiratory chain level, i.e., considerably elevated expression and activity of complex II, and decreased expression and activity of complex I were observed. The elevated activity of complex II resulted in an increase in succinate-sustained mitochondrial ROS formation, mainly through increased reverse electron transport. A hypoxia-induced decrease in UCP2 expression and activity was also observed. It can be concluded that the exposure to chronic hypoxia induces a shift from aerobic toward anaerobic catabolic metabolism. The hypoxia-induced increase in intracellular and mitochondrial ROS formation was not excessive and may be involved in endothelial signaling of hypoxic responses. Our results indicate an important role of succinate, complex II, and reverse electron transport in hypoxia-induced adjustments in endothelial cells.