Hypoxia/reoxygenation alters essential fatty acids metabolism in cultured rat cardiomyocytes: protection by antioxidants

The bioinformatics and metabolomics research on anti-hypoxic molecular mechanisms of Salidroside via regulating the PTEN mediated PI3K/Akt/NF-κB signaling pathway

Salidroside (SAL), a major bioactive compound of Rhodiola crenulata, has significant anti-hypoxia effect, however, its underlying molecular mechanism has not been elucidated. In order to explore the protective mechanism of SAL, the lactate dehydrogenase (LDH), reactive oxygen species (ROS), superoxide dismutase (SOD) and hypoxia-induced factor 1α (HIF-1α) were measured to establish the PC12 cell hypoxic model. Cell staining and cell viability analyses were performed to evaluate the protective effects of SAL. The metabolomics and bioinformatics methods were used to explore the protective effects of salidroside under hypoxia condition. The metabolite-protein interaction networks were further established and the protein expression level was examined by Western blotting. The results showed that 59 endogenous metabolites changed and the expression of the hub proteins of CK2, p-PTEN/PTEN, PI3K, p-Akt/Akt, NF-κB p65 and Bcl-2 were increased, suggesting that SAL could increase the expression of CK2, which induced the phosphorylation and inactivation of PTEN, reduced the inhibitory effect on PI3K signaling pathways and activated the PI3K/Akt/NF-κB survival signaling pathway. Our study provided an important insight to reveal the protective molecular mechanism of SAL as a novel drug candidate.

PUFA and oxidative stress. Differential modulation of the cell response by DHA

Although an increased dietary intake of long-chain n-3 PUFA is considered an effective preventive strategy, a theoretical concern related to the possible increase of lipid peroxidation induced by a PUFA-rich diet still remains a problem. In this study, the effects of different PUFA (linoleic, α-linolenic, arachidonic, eicosapentaenoic and docosahexaenoic acid) on cytotoxicity, lipid oxidation, and modulation of antioxidant defenses were evaluated in HepG2 cells submitted to an oxidative stress (H2O2). Results clearly evidenced that all supplemented PUFA, but DHA, enhanced cell susceptibility to H2O2. Overall, our results underline that PUFA cannot be considered as a single category but as individual compounds, and research on mechanisms of action and preventive effects should deal with the individual fatty acids, particularly in the case of DHA.

Circadian (about 24-hour) variation in malondialdehyde content and catalase activity of mouse erythrocytes

Lipid peroxidation is a part of normal metabolism that may cause biological molecule damage leading to the formation of several specific metabolites that include aldehydes of variable chains, such as malondialdehyde (MDA). These biological effects are controlled in vivo by a wide spectrum of enzymatic and non-enzymatic defense mechanisms among which catalase (CAT) is considered as an important regulator of oxidative stress. The present study aimed to investigate the possible relationship between the temporal patterns of the formation of MDA and the activity of CAT in the erythrocytes of mice. Twenty-four-hour studies were performed on male Swiss albino mice, 12 weeks old, synchronized to a 12:12 light: dark cycle for 3 weeks. Different and comparable groups of animals (n = 10) were sacrificed at an interval of 4 hours (1, 5, 9, 13, 17, and 21 hours after light onset (HALO)). The levels of erythrocyte MDA concentration and CAT activity both significantly (analysis of variance: F = 6.4, P < 0.002) varied according to the time of sampling under non-stressed conditions. The characteristics of the waveform describing the temporal patterns differed between the two studied variables, e.g. MDA content showing one peak (≅21 HALO) and CAT activity showing three peaks (≅9, 17, and 21 HALO). Cosinor analysis revealed a significant (adjusted Cosinor: P ≤ 0.018) circadian (τ ≅ 24 hours) rhythm in MDA level and no statistically significant rhythmicity in CAT activity. The differences and the absence of correlation between the curve patterns of erythrocyte MDA content and CAT activity under physiological conditions are hypothesized to explain that variation in lipid peroxidation may depend on several factors. Moreover, the identification of peak/trough levels of MDA accumulation in erythrocytes may reflect the degree of oxidative stress in these blood cells. In addition, the observed significant time-of-day effect suggests that, in both clinical and scientific settings, appropriate comparison of MDA production and CAT activity levels can only be achieved on data obtained at the same time of day.

Molecular identification for epigallocatechin-3-gallate-mediated antioxidant intervention on the H2O2-induced oxidative stress in H9c2 rat cardiomyoblasts

Background

Epigallocatechin-3-gallate (EGCG) has been documented for its beneficial effects protecting oxidative stress to cardiac cells. Previously, we have shown the EGCG-mediated cardiac protection by attenuating reactive oxygen species and cytosolic Ca²⁺ in cardiac cells during oxidative stress and myocardial ischemia. Here, we aimed to seek a deeper elucidation of the molecular anti-oxidative capabilities of EGCG in an H₂O₂-induced oxidative stress model of myocardial ischemia injury using H9c2 rat cardiomyoblasts.

Results

Proteomics analysis was used to determine the differential expression of proteins in H9c2 cells cultured in the conditions of control, 400 μM H₂O₂ exposure for 30 min with and/or without 10 to 20 μM EGCG pre-treatment. In this model, eight proteins associated with energy metabolism, mitochondrial electron transfer, redox regulation, signal transduction, and RNA binding were identified to take part in EGCG-ameliorating H₂O₂-induced injury in H9c2 cells. H₂O₂ exposure increased oxidative stress evidenced by increases in reactive oxygen species and cytosolic Ca²⁺ overload, increases in glycolytic protein, α-enolase, decreases in antioxidant protein, peroxiredoxin-4, as well as decreases in mitochondrial proteins, including aldehyde dehydrogenase-2, ornithine aminotransferase, and succinate dehydrogenase ubiquinone flavoprotein subunit. All of these effects were reversed by EGCG pre-treatment. In addition, EGCG attenuated the H₂O₂-induced increases of Type II inositol 3, 4-bisphosphate 4-phosphatase and relieved its subsequent inhibition of the downstream signalling for Akt and glycogen synthase kinase-3β (GSK-3β)/cyclin D1 in H9c2 cells. Pre-treatment with EGCG or GSK-3β inhibitor (SB 216763) significantly improved the H₂O₂-induced suppression on cell viability, phosphorylation of pAkt (S473) and pGSK-3β (S9), and level of cyclin D1 in cells.

Conclusions

Collectively, these findings suggest that EGCG blunts the H₂O₂-induced oxidative effect on the Akt activity through the modulation of PIP3 synthesis leading to the subsequent inactivation of GSK-3β mediated cardiac cell injury.

n-3 PUFA as regulators of cardiac gene transcription: a new link between PPAR activation and fatty acid composition

The fatty acids regulate gene expression directly binding to nuclear receptors or affecting the protein content of transcription factors. In this work, supplementing primary cultures of neonatal rat cardiomyocytes with 60 microM EPA or DHA, we demonstrated by an ELISA assay an increased PPAR beta/delta binding to DNA. n-3 PUFA supplementation deeply changed the acyl composition of both cytosolic and nuclear fractions. The high content of total fatty acids, particularly EPA and DHA, and its increase following supplementation suggested a selective accumulation of n-3 PUFAs in the nucleus, supporting the direct interaction of n-3 PUFA with PPAR. The activity of acyl-CoA thioesterase (ACOT), catalyzing the reaction leading to NEFA from acyl-CoA, increased in n-3 PUFA supplemented cells. The NEFA/acyl-CoA ratio is an important regulator of the fatty acid transport to the nucleus and consequent modulation of gene transcription, and although ACOT activity is not the only parameter of this ratio, it is important for the control of the NEFA pool composition. Our data further clarify what happens in cardiomyocytes following n-3 PUFA supplementation, linking the modification of acyl composition to ACOT activity and PPAR activation.

n-3 and n-6 Polyunsaturated fatty acids suppress sterol regulatory element binding protein activity and increase flow of non-esterified cholesterol in HepG2 cells

The plasma lipid-lowering effect of PUFA, one of their main beneficial effects, is considered to be related to the regulation of lipid biosynthesis through transcription factors including sterol regulatory element binding proteins (SREBP). In the present study, we compared the effect of different PUFA on SREBP activity in HepG2 cells, using a sterol regulatory element–luciferase reporter construct as a probe. Supplementation with different fatty acids reduced SREBP activity in the order 20 : 5n-3 = 18 : 2n-6 = 20 : 4n-6≫18 : 3n-3 = 22 : 6n-3 = 22 : 5n-6≫18 : 1n-9. The suppression of SREBP activity greatly depended on the degree of incorporation of the supplemented PUFA into cellular lipids, and correlated positively with the unsaturation index (r 0·831; P < 0·01) of total cell lipids. Supplemented PUFA were also metabolised to longer and more unsaturated species. These processing activities were higher for n-3 than n-6 PUFA (P < 0·01). We studied the effect of PUFA on the intracellular distribution of non-esterified cholesterol, using filipin staining and fluorescence microscopy with or without the cholesterol traffic blocker U18666A. The data show that the incorporation of PUFA increases non-esterified cholesterol flow from the plasma membrane to intracellular membranes. We conclude that suppression of SREBP activity by PUFA depends on the degree of incorporation into cellular lipids, and is associated with increased flow of non-esterified cholesterol between the plasma membrane and intracellular membranes.

High throughput lipidomic profiling of schizophrenia and bipolar disorder brain tissue reveals alterations of free fatty acids, phosphatidylcholines, and ceramides

A mass spectrometry based high throughput approach was employed to profile white and gray matter lipid levels in the prefrontal cortex (Brodmann area 9) of 45 subjects including 15 schizophrenia and 15 bipolar disorder patients as well as 15 controls samples. We found statistically significant alterations in levels of free fatty acids and phosphatidylcholine in gray and white matter of both schizophrenia and bipolar disorder samples compared to controls. Also, ceramides were identified to be significantly increased in white matter of both neuropsychiatric disorders as compared to control levels. The patient cohort investigated in this study includes a number of drug naive as well as untreated patients, allowing the assessment of drug effects on lipid levels. Our findings indicate that while gray matter phosphatidylcholine levels were influenced by antipsychotic medication, this was not the case for phosphatidylcholine levels in white matter. Changes in free fatty acids or ceramides in either white or gray matter also did not appear to be influenced by antipsychotic treatment. To assess lipid profiles in the living patient, we also profiled lipids of 40 red blood cell samples, including 7 samples from drug naive first onset patients. We found significant alterations in the concentrations of free fatty acids as well as ceramide. Overall, our findings suggest that lipid abnormalities may be a disease intrinsic feature of both schizophrenia and bipolar disorder reflected by significant changes in the central nervous system as well as peripheral tissues.

Pericardial delivery of omega-3 fatty acid: a novel approach to reducing myocardial infarct sizes and arrhythmias

Basic and clinical evidence suggests that omega-3 (n-3) polyunsaturated fatty acids (PUFAs) decrease fatal arrhythmias and infarct sizes. This study investigated if pericardial delivery of n-3 PUFAs would protect the myocardium from ischemic damages and arrhythmias. Acute myocardial infarctions were induced in 23 pigs with either 45 min balloon inflations or clamp occlusions of the left anterior descending coronary arteries and 180 min reperfusion. Docosahexaenoic acid (C22:6n-3, DHA, 45 mg), one of the main n-3 PUFAs in fish oil, was infused within the pericardial space only during the 40-min stabilizing phase, 45 min ischemia and initial 5 min reperfusion. Hemodynamics and cardiac functions were very similar between the DHA-treated and control groups. However, DHA therapy significantly reduced infarct sizes from 56.8 ± 4.9% for controls ( n = 12) to 28.8 ± 7.9% ( P < 0.01) for DHA-treated animals ( n = 11). Compared with controls, DHA-treated animals significantly decreased heart rates and reduced ventricular arrhythmia scores during ischemia. Furthermore, three (25%) control animals experienced eight episodes of ventricular fibrillation (VF), and two died subsequent to unsuccessful defibrillation. In contrast, only 1 (9%) of 11 DHA-treated pigs elicited one episode of VF that was successfully converted via defibrillation to normal rhythm; thus, mortality was reduced from 17% in the controls to 0% in the DHA-treated animals. These data demonstrate that pericardial infusion of n-3 PUFA DHA can significantly reduce both malignant arrhythmias and infarct sizes in a porcine infarct model. Pericardial administration of n-3 PUFAs could represent a novel approach to treating or preventing myocardial infarctions.

Increased shear stress with upregulation of VEGF-A and its receptors and MMP-2, MMP-9, and TIMP-1 in venous stenosis of hemodialysis grafts

Venous injury and subsequent venous stenosis formation are responsible for hemodialysis graft failure. Our hypothesis is that these pathological changes are in part related to changes in wall shear stress (WSS) that results in the activation of matrix regulatory proteins causing subsequent venous stenosis formation. In the present study, we examined the serial changes in WSS, blood flow, and luminal vessel area that occur subsequent to the placement of a hemodialysis graft in a porcine model of chronic renal insufficiency. We then determined the corresponding histological, morphometric, and kinetic changes of several matrix regulatory proteins including VEGF-A, its receptors, matrix metalloproteinase (MMP)-2, MMP-9, tissue inhibitor of matrix metalloproteinase (TIMP)-1, and TIMP-2. WSS was estimated by obtaining blood flow and luminal vessel area by performing phase-contrast MRI with magnetic resonance angiography in 21 animals at 1 day after graft placement and prior to death on day 3 (n = 7), day 7 (n = 7), and day 14 (n = 7). At all time points, the mean WSS at the vein-to-graft anastomosis was significantly higher than that at the control vein (P < 0.05). WSS had a bimodal distribution with peaks on days 1 and 7 followed by a significant reduction in WSS by day 14 (P < 0.05 compared with day 7) and a decrease in luminal vessel area compared with control vessels. By day 3, there was a significant increase in VEGF-A and pro-MMP-9 followed by, on day 7, increased pro-MMP-2, active MMP-2, and VEGF receptor (VEGFR)-2 (P < 0.05) and, by day 14, increased VEGFR-1 and TIMP-1 (P < 0.05) at the vein-to-graft anastomosis compared with control vessels. Over time, the neointima thickened and was composed primarily of alpha-smooth muscle actin-positive cells with increased cellular proliferation. Our data suggest that hemodialysis graft placement leads to early increases in WSS, VEGF-A, and pro-MMP-9 followed by subsequent increases in pro-MMP-2, active MMP-2, VEGFR-1, VEGFR-2, and TIMP-1, which may contribute to the development of venous stenosis.

Hypoxia-related lipid peroxidation: Evidences, implications and approaches

Hypoxia may be intensified by concurrent oxidative stress. Lack of oxygen in relation to aerobic ATP requirements, as hypoxia has been defined, goes along with an increased generation of reactive oxygen species (ROS). Polyunsaturated fatty acids (PUFAs) range among the molecules most susceptible to ROS. Oxidative breakdown of n-3 PUFAs may compromise not only membrane lipid matrix dynamics, and hence structure and function of membrane-associated proteins like enzymes, receptors, and transporters, but also gene expression. Eicosapentaenoic acid depletion, products of lipid peroxidation (LP), as well as, lack of oxygen may combine in exacerbating activity of nuclear factor kappa B (NFkappaB), an ubiquitous pro-inflammatory and anti-apoptotic transcription factor. Field studies at high altitude show malondialdehyde (MDA) content in exhaled breath condensate (EBC) of mountaineers to correlate with Lake Louis score of acute mountain sickness. A pathogenic role of LP in hypoxia can therefore be expected. By control of LP, some species seem to cope more efficiently than others with naturally occurring hypoxia. Limitation of potential pro-inflammatory effects of hypoxia-related LP by an adequate provision of n-3 PUFAs and antioxidants may contribute to increase survival under conditions where oxygen is lacking in relation to aerobic ATP requirements. A need for antioxidant intervention, however, should be weighed against the ROS requirement for triggering adaptive processes in response to an increased demand of oxygen.