4-Hydroxy-2-nonenal is a powerful endogenous inhibitor of endothelial response

Autoantibodies to the C-terminal subunit of RLIP76 induce oxidative stress and endothelial cell apoptosis in immune-mediated vascular diseases and atherosclerosis

Although detection of autoantibodies in the peripheral blood from patients with immune-mediated endothelial dysfunctions has so far failed to provide tools of diagnostic or pathogenetic value, putative bioindicators include anti-endothelial cell antibodies, a heterogeneous family of antibodies that react with autoantigens expressed by endothelial cells. In this study, to identify endothelial autoantigens involved in the autoimmune processes causing endothelial damage, we screened a human microvascular endothelial cell cDNA library with sera from patients with Behçet's disease. We identified antibodies to the C-terminus of Ral binding protein1 (RLIP76), a protein that catalyzes the ATP-dependent transport of glutathione (GSH) conjugates including GSH-4-hydroxy-t-2,3-nonenal, in the serum of a significant percentage of patients with various diseases characterized by immune-mediated endothelial dysfunction, including Behçet disease, systemic sclerosis, systemic lupus erythematosus and carotid atherosclerosis. These autoantibodies increased intracellular levels of 4-hydroxy-t-2,3-nonenal, decreased levels of GSH and activated C-Jun NH2 Kinase signaling (JNK), thus inducing oxidative stress-mediated endothelial cell apoptosis. The dietary antioxidant alpha-tocopherol counteracted endothelial cell demise. These findings suggest that autoantibodies to RLIP76 play a pathogenetic role in immune-mediated vascular diseases and represent a valuable peripheral blood bioindicator of atherosclerosis and immune-mediated vascular diseases.

Redox regulation of 4-hydroxy-2-nonenal-mediated endothelial barrier dysfunction by focal adhesion, adherens, and tight junction proteins

4-Hydroxy-2-nonenal (4-HNE), one of the major biologically active aldehydes formed during inflammation and oxidative stress, has been implicated in a number of cardiovascular and pulmonary disorders. 4-HNE has been shown to increase vascular endothelial permeability; however, the underlying mechanisms are unclear. Hence, in the current study, we tested our hypothesis that 4-HNE-induced changes in cellular thiol redox status may contribute to modulation of cell signaling pathways that lead to endothelial barrier dysfunction. Exposure of bovine lung microvascular endothelial cells (BLMVECs) to 4-HNE induced reactive oxygen species generation, depleted intracellular glutathione, and altered cell-cell adhesion as measured by transendothelial electrical resistance. Pretreatment of BLM-VECs with thiol protectants, N-acetylcysteine and mercaptopropionyl glycine, attenuated 4-HNE-induced decrease in transendothelial electrical resistance, reactive oxygen species generation, Michael protein adduct formation, protein tyrosine phosphorylation, activation of ERK, JNK, and p38 MAPK, and actin cytoskeletal rearrangement. Treatment of BLMVECs with 4-HNE resulted in the redistribution of FAK, paxillin, VE-cadherin, beta-catenin, and ZO-1, and intercellular gap formation. Western blot analyses confirmed the formation of 4-HNE-derived Michael adducts with the focal adhesion and adherens junction proteins. Also, 4-HNE decreased tyrosine phosphorylation of FAK without affecting total cellular FAK contents, suggesting the modification of integrins, which are natural FAK receptors. 4-HNE caused a decrease in the surface integrin in a time-dependent manner without altering total alpha5 and beta3 integrins. These results, for the first time, revealed that 4-HNE in redox-dependent fashion affected endothelial cell permeability by modulating cell-cell adhesion through focal adhesion, adherens, and tight junction proteins as well as integrin signal transduction that may lead dramatic alteration in endothelial cell barrier dysfunction during heart infarction, brain stroke, and lung diseases.

The clinical and pathophysiological features of malarial anaemia

This review will focus on the principal clinical and pathophysiological features of the anaemia of falciparum malaria, including the problems of treating malarial anaemia, and also will suggest how recent advances in genomics may help our understanding of cellular and molecular mechanisms underlying this syndrome.

Induction of endothelial cell apoptosis by lipid hydroperoxide-derived bifunctional electrophiles

Endothelial dysfunction is considered to be the earliest event in atherogenesis. Oxidative stress, inflammation, and apoptosis play critical roles in its progression and onset. Lipid peroxidation, which occurs during oxidative stress, results in the formation of lipid hydroperoxide-derived bifunctional electrophiles such as 4-hydroxy-2(E)-nonenal that induce apoptosis. In this study, recently identified lipid hydroperoxide-derived bifunctional electrophiles 4-oxo-2(E)-nonenal (ONE; 5-30 microm) and 4,5-epoxy-2(E)-decenal (EDE; 10-20 microM) were shown to cause a dose- and time-dependent apoptosis in EA.hy 926 endothelial cells. This was manifest by morphological changes, caspase-3 activation, and poly(ADP-ribose) polymerase cleavage. Bifunctional electrophiles caused cytochrome c release from mitochondria into the cytosol, implicating a mitochondrial pathway of apoptosis in the endothelial cells. The novel carboxylate-containing lipid hydroperoxide-derived bifunctional electrophile 9,12-dioxo-10(E)-dodecenoic acid was inactive because it could not translocate across the plasma membrane. However, its less polar methyl ester derivative (2-10 microM) was the most potent inducer of apoptosis of any bifunctional electrophile that has been tested. An acute decrease in intracellular glutathione (GSH) preceded the onset of apoptosis in bifunctional electrophile-treated cells. The ability of ONE and EDE to deplete GSH was directly correlated with their predicted reactivity toward nucleophilic amino acids. Liquid chromatography/mass spectrometry methodology was developed in order to examine the intracellular and extracellular concentrations of bifunctional electrophile-derived GSH adducts. Relative intracellular/extracellular ratios of the GSH adducts were identical with the rank order of potency for inducing caspase 3 activation. This suggests that there may be a role for the bifunctional electrophile-derived GSH adducts in the apoptotic response. N-Acetylcysteine rescued bifunctional electrophile-treated cells from apoptosis, whereas the GSH biosynthesis inhibitor d,l-buthionine-(R,S)-sulfoximine sensitized the cells to apoptosis. These data suggest that lipid hydroperoxide-derived bifunctional electrophiles may play an important role in cardiovascular pathology through their ability to induce endothelial cell apoptosis.

Mechanisms for the induction of HNE- MDA- and AGE-adducts, RAGE and VEGF in retinal pigment epithelial cells

Pathological features of age-related macular degeneration such as the formation of extracellular deposits and neovascularization are frequently viewed as outcomes of compromising processes within retinal pigment epithelial cells, but the initiating circumstances are poorly understood. Here we tested the hypothesis that photooxidation events initiated by A2E, a blue light-excitable aging fluorophore of the retinal pigment epithelium, can set the stage for altered cellular signaling and changes in the expression of genes that can impact the extracellular milieu. Proteins modified by lipid peroxidation products (4-hydroxynonenal; malondialdhyde) and advanced glycation end products were detected at sites of blue light irradiation both in association with the cultured A2E-laden retinal pigment epithelial cells and within the fibronectin substrate on which the cells were grown. RAGE, the cell surface receptor that transduces the effects of advanced glycation end products, was also upregulated, and RAGE expression co-localized with the deposition of advanced glycation end products. Blue light triggered alterations in gene expression was also evidenced by elevations in both transcripts and protein for vascular endothelial growth factor, a potent angiogenic and permeability-enhancing factor. These findings indicate that cell associated and extracellular modification of proteins by lipid peroxidation products and advanced glycation end products together with increased expression of RAGE and vascular endothelial growth factor may be induced consequent to blue light illumination of A2E-burdened retinal pigment epithelial cells. Thus, photooxidative events that are not an immediate threat to retinal pigment epithelial cell viability may nevertheless elicit sustained perturbation that could ultimately alter neighboring tissues and impact retinal pigment epithelial cell function.

Induction of endothelial apoptosis by 4-hydroxyhexenal

Lipid peroxidation and its products such as 4-hydroxy-2-nonenal (HNE) and 4-hydroxyhexenal (HHE) are known to affect redox balance during aging and various degenerative processes, including vascular dysfunction. Deterioration of the endothelial cells that line the vascular wall is known to be an underlying cause of vascular dysfunction. At present, little is known about the mechanism by which HHE induces endothelial cell death (i.e. apoptosis), although HNE-induced apoptotic cell death has been reported. The aim of this study was to determine whether apoptosis induced by HHE in endothelial cells involves peroxynitrite (ONOO(-)). Our results show that in endothelial cells HHE triggers apoptotic cell death by inducing apoptotic Bax coupled with a decrease in anti-apoptotic Bcl-2. Results show that HHE induces reactive oxygen species (ROS), nitric oxide, and ONOO(-) generation, leading to redox imbalance. Furthermore, the antioxidant N-acetyl cysteine, ROS scavenger, and penicillamine, an ONOO(-) scavenger, were found to block HHE-mediated apoptosis. We used confocal laser microscopy to estimate the ability of these inhibitors to attenuate HHE-induced intracellular ONOO(-) levels thus confirming the oxidative mediation of apoptosis in endothelial cells. These findings strongly suggest that accumulated HHE triggers reactive species-mediated endothelial apoptosis, leading to vascular dysfunction as well as vascular aging. During aging, increased lipid peroxidation and its associated production of HHE may exacerbate the weakened redox balance, leading to various chronic degenerative processes including vascular dysfunction.

Role of mitogen-activated protein kinases in 4-hydroxy-2-nonenal-induced actin remodeling and barrier function in endothelial cells

In vivo and in vitro studies indicate that 4-hydroxy-2-nonenal (4-HNE), generated by cellular lipid peroxidation or after oxidative stress, affects endothelial permeability and vascular tone. However, the mechanism(s) of 4-HNE-induced endothelial barrier function is not well defined. Here we provide evidence for the first time on the involvement of mitogen-activated protein kinases (MAPKs) in 4-HNE-mediated actin stress fiber formation and barrier function in lung endothelial cells. Treatment of bovine lung microvascular endothelial cells with hydrogen peroxide (H(2)O(2)), as a model oxidant, resulted in accumulation of 4-HNE as evidenced by the formation of 4-HNE-Michael protein adducts. Exposure of cells to 4-HNE, in a dose- and time-dependent manner, decreased endothelial cell permeability measured as transendothelial electrical resistance. The 4-HNE-induced permeability changes were not because of cytotoxicity or endothelial cell apoptosis, which occurred after prolonged treatment and at higher concentrations of 4-HNE. 4-HNE-induced changes in transendothelial electrical resistance were calcium independent, as 4-HNE did not alter intracellular free calcium levels as compared with H(2)O(2) or diperoxovanadate. Stimulation of quiescent cells with 4-HNE (1-100 microm) resulted in phosphorylation of ERK1/2, JNK, and p38 MAPKs, and actin cytoskeleton remodeling. Furthermore, pretreatment of bovine lung microvascular endothelial cells with PD 98059 (25 microm), an inhibitor of MEK1/2, or SP 600125 (25 microm), an inhibitor of JNK, or SB 202190 (25 microm), an inhibitor of p38 MAPK, partially attenuated 4-HNE-mediated barrier function and cytoskeletal remodeling. These results suggest that the activation of ERK, JNK, and p38 MAP kinases is involved in 4-HNE-mediated actin remodeling and endothelial barrier function.

Intracellular Ca2+ homeostatic regulation and 4-hydroxynonenal-induced aortic endothelial dysfunction

The aldehydic lipid peroxidation product 4-hydroxynonenal (HNE) is known to compromise erythrocyte passive Ca2+ permeability and to irreversibly inhibit the plasma membrane (Ca2+ + Mg2+)-ATPase and Ca2+-transport. To measure the effects of HNE on passive and active Ca2+ transport in endothelial cells, we first characterized 45Ca2+ uptake and efflux in cultured porcine aortic endothelial cells (PAEC). PAEC exchanged 45Ca2+ to a cumulative near-isotopic equilibrium of about 4.5 pmole 45Ca2+/10(6) cells in 120 min at 37 degrees C. This Ca2+ pool was diminished by thapsigargin, cyclopiazonic acid, oligomycin B, and sodium azide. In contrast, ouabain enhanced Ca2+ uptake capacity from 5.17 to 5.77 pmole/10(6) cells. Accumulated 45Ca2+ was extruded at rate of 8.7 fmole 45Ca2+/10(6) cells/min or shunted rapidly by the ionophore A23187. HNE increased total 45Ca2+ accumulation in a time- and concentration-dependent manner by as much as 562% with an EC50 of 64.0 wM. Concomitant morphological analysis of PAEC revealed vacuolization, nuclear swelling, cell shrinking, and cell detachment. Initial structural changes, such as vacuolization, began well before any changes in Ca2+ accumulation were observed. These functional and morphological changes indicate that HNE significantly increases intracellular Ca2+ accumulation in vascular endothelium, which may explain the cytotoxic effects associated with HNE exposure and provide further evidence that atherogenic effects of HNE may, in part, be caused by disturbances in Ca2+ homeostasis.

4-Hydroxy-2-nonenal: a product and mediator of oxidative stress

The onset of lipid peroxidation within cellular membranes is associated with changes in their physiochemical properties and with the impairment of enzymatic functions located in the membrane environment. There is increasing evidence that aldehydic molecules generated endogenously during the process of lipid peroidation are causally involved in most of the pathophysiological effects associated with oxidative stress in cells and tissues. 4-Hydroxy-2-nonenal (HNE), among them, is believed to be largely responsible for cytopathological effects observed during oxidative stree in vivo and has achieved the status of one of the best recognized and most studied of the cytotoxic products of lipid peroxidation. In the present review, I provide a comprehensive summary of HNE, as the product and mediator or oxidative stress.

Polymorphisms in the von Willebrand factor gene are not associated with proliferative retinopathy in non-insulin-dependent diabetes mellitus

Von Willebrand factor, a multimeric glycoprotein synthesized mainly by endothelial cells, is involved in platelet adhesion and aggregation and has an important role in the process of angiogenesis. Increased levels of von Willebrand factor, reflecting activation or damage of endothelial cells, have been described in association with proliferative diabetic retinopathy (PDR). We investigated the relationships of two polymorphisms (-1793G/C and Thr789Ala) in the von Willebrand factor gene with PDR. Genotypes were detected by polymerase chain reactions with subsequent restrictions with specific endonucleases. Allele frequencies were determined in an association study (n = 371) comprising three groups of subjects (diabetics with and without retinopathy and nondiabetics). Allele frequencies of the -1793G/C and Thr789Ala did not differ between the non-insulin-dependent diabetes mellitus (NIDDM) + PDR and the NIDDM non-PDR groups (p > 0.05). However, a statistically significant difference in allele and genotype frequencies of the -1793G/C was proved between all NIDDM versus nondiabetic subjects (p = 0.024 and 0.0065, respectively) with allele G and genotype GG being significantly more frequent in the NIDDM group. Calculated odds ratio for the GG genotype was 1.20 (95% CI, 0.77-1.86). Although significantly higher plasma von Willebrand factor antigen levels in NIDDM patients with PDR have been described in several studies, our findings indicate that no association exists between the two polymorphisms and PDR. However, the -1793G/C polymorphism might affect the risk of NIDDM.

N-acetylcysteine and celecoxib lessen cadmium cytotoxicity which is associated with cyclooxygenase-2 up-regulation in mouse neuronal cells

In many neurodegenerative disorders, aggregates of ubiquitinated proteins are detected in neuronal inclusions, but their role in neurodegeneration remains to be defined. To identify intracellular mechanisms associated with the appearance of ubiquitin-protein aggregates, mouse neuronal HT4 cells were treated with cadmium. This heavy metal is a potent cell poison that mediates oxidative stress and disrupts the ubiquitin/proteasome pathway. In the current studies, the following intracellular events were found to be also induced by cadmium: (i) a specific rise in cyclooxygenase-2 (COX-2) gene expression but not COX-1; (ii) an increase in the extracellular levels of the proinflammatory prostaglandin E2, a product of COX-2; and (iii) production of 4-hydroxy-2-nonenal-protein adducts, which result from lipid peroxidation. In addition, cadmium treatment led to the accumulation of high molecular weight ubiquitin-COX-2 conjugates and perturbed COX-2 glycosylation. The thiol-reducing antioxidant N-acetylcysteine, and, to a lesser extent, the COX-2 inhibitor celecoxib, attenuated the loss of cell viability induced by cadmium demonstrating that oxidative stress and COX-2 activation contribute to cadmium cytotoxicity. These findings establish that disruption of the ubiquitin/proteasome pathway is not the only event triggered by cadmium. This oxidative stressor also activates COX-2 function. Both events could be triggered by formation of 4-hydroxy-2-nonenal as a result of cadmium-induced lipid peroxidation. Proinflammatory responses stimulated by oxidative stressors that mimic the cadmium effects may, therefore, be important initiators of the neurodegenerative process and exacerbate its progress.