Polyunsaturated fatty acids modulate NOX 4 anion superoxide production in human fibroblasts

Geometrical isomerization of arachidonic acid during lipid peroxidation interferes with ferroptosis

Geometrical mono-trans isomers of arachidonic acid (mtAA) are endogenous products of free radical-induced cis-trans double bond isomerization occurring to natural fatty acids during cell metabolism, including lipid peroxidation (LPO). Very little is known about the functional roles of mtAA and in general on the effects of mono-trans isomers of polyunsaturated fatty acids (mtPUFA) in various types of programmed cell death, including ferroptosis. Using HT1080 and MEF cell cultures, supplemented with 20 μM PUFA (i.e., AA, EPA or DHA) and their mtPUFA congeners, ferroptosis occurred in the presence of RSL3 (a direct inhibitor of glutathione peroxidase 4) only with the PUFA in their natural cis configuration, whereas mtPUFA showed an anti-ferroptotic effect. By performing the fatty acid-based membrane lipidome analyses, substantial differences emerged in the membrane fatty acid remodeling of the two different cell fates. In particular, during ferroptosis mtPUFA formation and their incorporation, together with the enrichment of SFA, occurred. This opens new perspectives in the role of the membrane composition for a ferroptotic outcome. While pre-treatment with AA promoted cell death for treatment with H₂O₂ and RSL3, mtAA did not. Cell death by AA supplementation was suppressed also in the presence of either ferroptosis inhibitors, such as the lipophilic antioxidant ferrostatin-1, or NADPH oxidase (NOX) inhibitors, including diphenyleneiodonium chloride and apocynin. Our results confirm a more complex scenario for ferroptosis than actually believed. While LPO processes are active, the importance of environmental lipid levels, balance among SFA, MUFA and PUFA in lipid pools and formation of mtPUFA influence the membrane phospholipid turnover, with crucial effects in the occurrence of cell death by ferroptosis.

DHA Induces Cell Death through the Production of ROS and the Upregulation of CHOP in Fibroblast-like Synovial Cells from Human Rheumatoid Arthritis Patients

Rheumatoid arthritis (RA) is an inflammatory disease marked by a massive proliferation of synovial cells in the joints. In this study, we investigated the pro-apoptotic effects of docosahexaenoic acid (DHA) in human fibroblast-like synovial cells from RA patients (RA-FLS). An in vitro study using MH7A cells showed that DHA treatment induced caspase-8-dependent apoptosis in a dose-dependent manner and reduced the TNF-α-mediated induction of MMP-9 and IL-1β. DHA also induced the phosphorylation of eIF2α, the expression of the ER stress markers ATF4 and C/EBP homologous protein (CHOP), and death receptor 5 (DR5). The knockdown of CHOP or DR5 increased cell viability and reduced apoptosis in DHA-treated cells. Furthermore, the knockdown of CHOP reduced DHA-mediated DR5 expression, while the overexpression of CHOP increased DR5 expression. We also found that DHA treatment induced the accumulation of reactive oxygen species (ROS), and pretreatment with the anti-oxidant Tiron effectively abrogated not only the expression of CHOP and DR5, but also DHA-induced apoptosis. Under this condition, cell viability was increased, while PARP-1 cleavage and caspase-8 activation were reduced. All the findings were reproduced in human primary synovial cells obtained from RA patients. These results suggest that the DHA-mediated induction of ROS and CHOP induced apoptosis through the upregulation of DR5 in RA-FLSs, and that CHOP could be used as a therapy for RA.

NADPH Oxidase 4: A Potential Therapeutic Target of Malignancy

Reactive oxygen species (ROS) play a crucial role in the regulation of tumor occurrence and development. As a main source of ROS, NADPH oxidases are key enzymes that mediate electron transport within intracellular membranes. Of the NOX members that have been reported to be dysregulated in a wide variety of tumors, NOX4 is the member to be most frequently expressed. Numerous studies have elucidated that NOX4 gets involved in the regulation of tumor proliferation, metastasis, therapy resistance, tumor-stromal interaction and dysregulated tumor metabolism. In this review, we primarily discussed the biological function of NOX4 in tumorigenesis and progression of multiple cancer models, including its role in activating oncogenic signaling pathways, rewiring the metabolic phenotype and mediating immune response. Besides, the development of NOX4 inhibitors has also been unraveled. Herein, we discussed the interplay between NOX4 and tumorigenesis, proposing NOX4 as a promising therapeutic target waiting for further exploration.

Cardiomyocyte-specific miR-100 overexpression preserves heart function under pressure overload in mice and diminishes fatty acid uptake as well as ROS production by direct suppression of Nox4 and CD36

MicroRNAs are key regulators of the cardiac response to injury. MiR-100 has recently been suggested to be involved in different forms of heart failure, but functional studies are lacking. In the present study, we examined the impact of transgenic miR-100 overexpression on cardiac structure and function during physiological aging and pathological pressure-overload-induced heart failure in mice after transverse aortic constriction surgery. MiR-100 was moderately upregulated after induction of pressure overload in mice. While in our transgenic model the cardiomyocyte-specific overexpression of miR-100 did not result in an obvious cardiac phenotype in unchallenged mice, the transgenic mouse strain exhibited less left ventricular dilatation and a higher ejection fraction than wildtype animals, demonstrating an attenuation of maladaptive cardiac remodeling by miR-100. Cardiac transcriptome analysis identified a repression of several regulatory genes related to cardiac metabolism, lipid peroxidation, and production of reactive oxygen species (ROS) by miR-100 overexpression, possibly mediating the observed functional effects. While the modulation of ROS-production seemed to be indirectly affected by miR-100 via Alox5-and Nox4-downregulation, we demonstrated that miR-100 induced a direct repression of the scavenger protein CD36 in murine hearts resulting in a decreased uptake of long-chain fatty acids and an alteration of mitochondrial respiratory function with an enhanced glycolytic state. In summary, we identified miR-100 as a modulator of cardiac metabolism and ROS production without an apparent cardiac phenotype at baseline but a protective effect under conditions of pressure-overload-induced cardiac stress, providing new insight into the mechanisms of heart failure.

Schizochytrium sp. Dietary supplementation modify Toll-like receptor 4 (TLR4) transcriptional regulation in monocytes and neutrophils of dairy goats

Animals protect themselves against pathogens or abiotic factors by innate or adaptive mechanisms. Long-chain polyunsaturated fatty acids (ω3) of microalgae modify both human and mice' immune systems resulting in a beneficial balance between pro-inflammatory and anti-inflammatory pathways. However, scarce information exists on their impact on lactating animals' immunity. The objective of this study was to investigate the impact of dietary inclusion of Schizochytrium sp. (rich in docosapentaenoic and docosahexaenoic acid), on the expression of several genes involved in the innate immunity of goats. Twenty-four dairy goats were divided into four homogeneous sub-groups (n = 6). All goats were fed individually with alfalfa hay and concentrate. The concentrate of the control group (CON) had no microalgae while those of the treated groups were supplemented daily with 20 (ALG20), 40 (ALG40), and 60 (ALG60) g Schizochytrium sp. Monocytes and neutrophils were isolated from goats' blood in the 20th, 40th^, and 60th days from the beginning of the experimental period. The relative transcript levels of TLR4, MYD88, MAPK, IRF3, IFNG, and pro-inflammatory cytokines (IL1B, IL2, IL8, TNF), and chemokines (CCL5 and CXCL16) were decreased in monocytes of microalgae treated goats compared to the CON. In contrast, MAPK and IL1B relative transcript levels were increased in neutrophils of ALG40 and ALG60 groups. In conclusion, the supplementation of goats' diet with 20 g Schizochytrium sp. resulted in a downregulation of the pro-inflammatory transcriptions, and following further research could be considered as a sustainable alternative strategy to improve immune function.

Docosahexaenoic Acid Supplemented Diet Influences the Orchidectomy-Induced Vascular Dysfunction in Rat Mesenteric Arteries

Over the past few decades, the cardiovascular benefits of a high dietary intake of long-chain polyunsaturated fatty acids (PUFAs), like docosahexaenoic acid (DHA), have been extensively studied. However, many of the molecular mechanisms and effects exerted by PUFAs have yet to be well explained. The lack of sex hormones alters vascular tone, and we have described that a DHA-supplemented diet to orchidectomized rats improve vascular function of the aorta. Based on these data and since the mesenteric artery importantly controls the systemic vascular resistance, the objective of this study was to analyze the effect of a DHA-supplemented diet on the mesenteric vascular function from orchidectomized rats. For this purpose mesenteric artery segments obtained from control, orchidectomized or orchidectomized plus DHA-supplemented diet were utilized to analyze: (1) the release of prostanoids, (2) formation of NO and ROS, (3) the vasodilator response to acetylcholine (ACh), as well as the involvement of prostanoids and NO in this response, and (4) the vasoconstrictor response to electrical field stimulation (EFS), analyzing also the effect of exogenous noradrenaline (NA), and the NO donor, sodium nitroprusside (SNP). The results demonstrate beneficial effects of DHA on the vascular function in orchidectomized rats, which include a decrease in the prostanoids release and superoxide formation that were previously augmented by orchidectomy. Additionally, there was an increase in endothelial NO formation and the response to ACh, in which NO involvement and the participation of vasodilator prostanoids were increased. DHA also reversed the decrease in EFS-induced response caused by orchidectomy. All of these findings suggest beneficial effects of DHA on vascular function by reversing the neurogenic response and the endothelial dysfunction caused by orchidectomy.

Anti-inflammatory effects of docosahexaenoic acid: Implications for its cancer chemopreventive potential

The implication of inflammatory tissue damage in pathophysiology of human cancer as well as some metabolic disorders has been under intense investigation. Numerous studies have identified a series of critical signaling molecules involved in cellular responses to inflammatory stimuli. These include nuclear factor κB, peroxisome proliferator-activated receptor γ, nuclear factor erythroid 2 p45-related factor 2 and sterol regulatory element-binding protein 1. The proper regulation of these transcription factors mediating pro- and anti-inflammatory signaling hence provides an important strategy for the chemoprevention of inflammation-associated cancer. There is compelling evidence supporting that dietary supplementation with fish oil-derived ω-3 polyunsaturated fatty acids including docosahexaenoic acid (DHA) ameliorates symptomatic inflammation associated with cancer as well as other divergent human disorders. Acute or physiologic inflammation is an essential body's first line of defence to microbial infection and tissue injuries, but it must be properly completed by a process termed 'resolution'. Failure of resolution mechanisms can result in persistence of inflammation, leading to chronic inflammatory conditions and related malignancies. The phagocytic engulfment of apoptotic neutrophils and clearance of their potentially histotoxic contents by macrophages, called efferocytosis is an essential component in resolving inflammation. Of note, DHA is a precursor of endogenous proresolving lipid mediators which regulate the leukocyte trafficking and recruitment and thereby facilitate efferocytosis. Therefore, DHA and its metabolites may have a preventive potential in the management of human cancer which arises as a consequence of impaired resolution of inflammation as well as chronic inflammation.

Impact of Arachidonic Acid and the Leukotriene Signaling Pathway on Vasculogenesis of Mouse Embryonic Stem Cells

Embryonic stem (ES) cells can differentiate into various kinds of cells, such as endothelial and hematopoietic cells. In addition, some evidence suggests that inflammatory mediators such as leukotrienes (LTs), which include the 5-lipoxygenase (LOX) family, can regulate endothelial cell differentiation. In the present study, the eicosanoid precursor arachidonic acid (AA) stimulated vasculogenesis of ES cells by increasing the number of fetal liver kinase-1+ vascular progenitor cells as well as vascular structures positive for platelet endothelial cell adhesion protein-1 and vascular endothelial cadherin. The stimulation of vasculogenesis and expression of the rate-limiting enzyme in the LT signaling pathway, 5-LOX-activating protein (FLAP), was blunted upon treatment with the FLAP inhibitors AM643 and REV5901. Vasculogenesis was significantly restored upon exogenous addition of LTs. Downstream of FLAP, the LTB4 receptor (BLT1) blocker U75302, the BLT2 receptor blocker LY255283 as well as the cysteinyl LT blocker BAY-u9773 inhibited vasculogenesis of ES cells. AA treatment of differentiating ES cells increased reactive oxygen species (ROS) generation, which was not affected upon either FLAP or cyclooxygenase-2 inhibition. Prevention of ROS generation by either the free radical scavengers vitamin E and N-(2-mercaptopropionyl)glycine or the NADPH oxidase inhibitor VAS2870 downregulated vasculogenesis of ES cells and blunted the provasculogenic effect of AA. In summary, our data demonstrate that proinflammatory AA stimulates vasculogenesis of ES cells via the LT pathway by mechanisms involving ROS generation.

Cordycepin, a Natural Antineoplastic Agent, Induces Apoptosis of Breast Cancer Cells via Caspase-dependent Pathways

Cordycepin, a major compound separated from Cordyceps sinensis, is known as a potential novel candidate for cancer therapy. Breast cancer, the most typical cancer diagnosed among women, remains a global health problem. In this study, the anti-breast cancer property of cordycepin and its underlying mechanisms was investigated. The direct effects of cordycepin on breast cancer cells both in in vitro and in vivo experiments were evaluated. Cordycepin exerted cytotoxicity in MCF-7 and MDA-MB-231 cells confirmed by reduced cell viability, inhibition of cell proliferation, enhanced lactate dehydrogenase release and reactive oxygen species accumulation, induced mitochondrial dysfunction and nuclear apoptosis in human breast cancer cells. Cordycepin increased the activation of pro-apoptotic proteins, including caspase-8, caspase-9, caspase-3 and Bax, and suppressed the expression of the anti-apoptotic protein, B-cell lymphoma 2 (Bcl-2). The inhibition on MCF-7-xenografted tumor growth in nude mice further confirmed cordycepin's anti-breast cancer effect. These aforementioned results reveal that cordycepin induces apoptosis in human breast cancer cells via caspase-dependent pathways. The data shed light on the possibility of cordycepin being a safe agent for breast cancer treatment.

Omega-3 fatty acids differentially modulate enzymatic anti-oxidant systems in skeletal muscle cells

During physical activity, increased reactive oxygen species production occurs, which can lead to cell damage and in a decline of individual's performance and health. The use of omega-3 polyunsaturated fatty acids as a supplement to protect the immune system has been increasing; however, their possible benefit to the anti-oxidant system is not well described. Thus, the aim of this study was to evaluate whether the omega-3 fatty acids (docosahexaenoic acid and eicosapentaenoic acid) can be beneficial to the anti-oxidant system in cultured skeletal muscle cells. C2C12 myocytes were differentiated and treated with either eicosapentaenoic acid or docosahexaenoic acid for 24 h. Superoxide content was quantified using the dihydroethidine oxidation method and superoxide dismutase, catalase, and glutathione peroxidase activity, and expression was quantified. We observed that the docosahexaenoic fatty acids caused an increase in superoxide production. Eicosapentaenoic acid induced catalase activity, while docosahexaenoic acid suppressed superoxide dismutase activity. In addition, we found an increased protein expression of the total manganese superoxide dismutase and catalase enzymes when cells were treated with eicosapentaenoic acid. Taken together, these data indicate that the use of eicosapentaenoic acid may present both acute and chronic benefits; however, the treatment with DHA may not be beneficial to muscle cells.

Immunonutrition stimulates immune functions and antioxidant defense capacities of leukocytes in radiochemotherapy-treated head & neck and esophageal cancer patients: A double-blind randomized clinical trial

BACKGROUND

Immunonutrition has been reported to improve the immune status of perioperative cancer patients, thereby reducing complications and length of hospital stay.

AIM

This study aimed to assess whether immunonutrition enriched in arginine, EPA & DHA and nucleotides could impact the immune cells responses in head & neck and esophageal cancer patients treated by radiochemotherapy (RCT).

METHODS

A double-blind clinical trial was carried out in 28 patients randomized into two groups, receiving either an immunomodulating enteral nutrition formula (IEN, n = 13, Impact(®), Nestlé) or an isoenergetic isonitrogenous standard enteral nutrition formula (SEN, n = 15) throughout RCT (5-7 weeks). After isolation from whole blood, immune cells metabolism and functions were assessed at the beginning (Db) and at the end (De) of RCT.

RESULTS

Immunonutrition maintained CD4(+)/CD8(+) T-lymphocyte counts ratio and CD3 membrane expression between Db and De. Polymorphonuclear cells CD62L and CD15 densities and ROS production were increased in IEN patients. Peripheral blood mononuclear cells (PBMC) production of pro-inflammatory prostaglandin-E2 was stable in IEN patients and lower than in SEN patients at De. Genes coding for immune receptors, antioxidant enzymes and NADPH oxidase subunits were overexpressed in the PBMC of IEN vs SEN patients at De.

CONCLUSION

Immunonutrition can enhance immune cell responses through the modulation of their phenotypes and functions. By modulating the gene expression of immune cells, immunonutrition could make it easier for the organism to adapt to the systemic inflammation and oxidative stress induced by RCT.

CLINICAL TRIAL REGISTRATION

This clinical trial has been registered on ClinicalTrial.gov website: NCT00333099.

Effect of conjugated linoleic Acid, vitamin e, alone or combined on immunity and inflammatory parameters in adults with active rheumatoid arthritis: a randomized controlled trial

BACKGROUND

Little information about the effects of conjugated linoleic acids (CLAs) on inflammation and immune function in humans is available. This study investigated the effects of CLAs, with and without Vitamin E on immunity and inflammatory parameters in adults with active rheumatoid arthritis (RA).

METHODS

In a double-blind clinical trial, 78 patients were randomly divided into four groups, each group receiving one of the following daily supplement for 3 months; group C: 2.5 g CLAs, group E: 400 mg Vitamin E, group CE: CLAs plus Vitamin E, group P: Placebo. Cytokines, matrix metalloproteinase 3 (MMP-3) and citrullinated antibody (CCP-A) were measured by ELISA method and Vitamin E by high-performance liquid chromatography.

RESULTS

Consider statistical methods there were no significant differences between groups in cytokines interleukin-2 (IL-2), IL-4, tumor necrosis factor-α (TNF-α), IL-1β, IL-2/IL-4, CCP-A white blood cells and neutrophils, lymphocyte, monocytes, and eosinophils numbers. TNF-α decreased in all groups, but its reduction was significant in group CE. IL-1β increased in groups P (P = 0.004) and E (P = 0.041) but the difference between group P and CE was significant. IL-4 decreased in groups C, CE and E (P = 0.03, P = 0.03, P = 0.07 respectively). IL2 did not change significantly within groups. CCP-A increased in groups P (P = 0.035) and E (P = 0.05), while it decreased in groups CE (P = 0.034). CCP-A and MMP-3 decrease were significant between groups P and CE. MMP-3 reduction was significant in group CE.

CONCLUSIONS

Co-supplementation CLAs and Vitamin E may be effective in the level of inflammatory markers in RA patients.

Plumbagin ameliorates diabetic nephropathy via interruption of pathways that include NOX4 signalling

NADPH oxidase 4 (Nox4) is reported to be the major source of reactive oxygen species (ROS) in the kidneys during the early stages of diabetic nephropathy. It has been shown to mediate TGFβ1-induced differentiation of cardiac fibroblasts into myofibroblasts. Despite TGFβ1 being recognised as a mediator of renal fibrosis and functional decline role in diabetic nephropathy, the renal interaction between Nox 4 and TGFβ1 is not well characterised. The aim of this study was to investigate the role of Nox4 inhibition on TGFβ1-induced fibrotic responses in proximal tubular cells and in a mouse model of diabetic nephropathy. Immortalised human proximal tubular cells (HK2) were incubated with TGFβ1 ± plumbagin (an inhibitor of Nox4) or specific Nox4 siRNA. Collagen IV and fibronectin mRNA and protein expression were measured. Streptozotocin (STZ) induced diabetic C57BL/6J mice were administered plumbagin (2 mg/kg/day) or vehicle (DMSO; 50 µl/mouse) for 24 weeks. Metabolic, physiological and histological markers of nephropathy were determined. TGFβ1 increased Nox4 mRNA expression and plumbagin and Nox4 siRNA significantly inhibited TGF-β1 induced fibronectin and collagen IV expression in human HK2 cells. STZ-induced diabetic C57BL/6J mice developed physiological features of diabetic nephropathy at 24 weeks, which were reversed with concomitant plumbagin treatment. Histologically, plumbagin ameliorated diabetes induced upregulation of extracellular matrix protein expression compared to control. This study demonstrates that plumbagin ameliorates the development of diabetic nephropathy through pathways that include Nox4 signalling.

NADPH oxidase as a therapeutic target for oxalate induced injury in kidneys

A major role of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase family of enzymes is to catalyze the production of superoxides and other reactive oxygen species (ROS). These ROS, in turn, play a key role as messengers in cell signal transduction and cell cycling, but when they are produced in excess they can lead to oxidative stress (OS). Oxidative stress in the kidneys is now considered a major cause of renal injury and inflammation, giving rise to a variety of pathological disorders. In this review, we discuss the putative role of oxalate in producing oxidative stress via the production of reactive oxygen species by isoforms of NADPH oxidases expressed in different cellular locations of the kidneys. Most renal cells produce ROS, and recent data indicate a direct correlation between upregulated gene expressions of NADPH oxidase, ROS, and inflammation. Renal tissue expression of multiple NADPH oxidase isoforms most likely will impact the future use of different antioxidants and NADPH oxidase inhibitors to minimize OS and renal tissue injury in hyperoxaluria-induced kidney stone disease.

Quinone compounds regulate the level of ROS production by the NADPH oxidase Nox4

NADPH oxidase Nox4 is expressed in a wide range of tissues and plays a role in cellular signaling by providing reactive oxygen species (ROS) as intracellular messengers. Nox4 oxidase activity is thought to be constitutive and regulated at the transcriptional level; however, we challenge this point of view and suggest that specific quinone derivatives could modulate this activity. In fact, we demonstrated a significant stimulation of Nox4 activity by 4 quinone derivatives (AA-861, tBuBHQ, tBuBQ, and duroquinone) observed in 3 different cellular models, HEK293E, T-REx™, and chondrocyte cell lines. Our results indicate that the effect is specific toward Nox4 versus Nox2. Furthermore, we showed that NAD(P)H:quinone oxidoreductase (NQO1) may participate in this stimulation. Interestingly, Nox4 activity is also stimulated by reducing agents that possibly act by reducing the disulfide bridge (Cys226, Cys270) located in the extracellular E-loop of Nox4. Such model of Nox4 activity regulation could provide new insight into the understanding of the molecular mechanism of the electron transfer through the enzyme, i.e., its potential redox regulation, and could also define new therapeutic targets in diseases in which quinones and Nox4 are implicated.

Nephrogenic systemic fibrosis: evidence for oxidative stress and bone marrow-derived fibrocytes in skin, liver, and heart lesions using a 5/6 nephrectomy rodent model

Nephrogenic systemic fibrosis (NSF) is associated with gadolinium-based magnetic resonance imaging (MRI) contrast exposure in the setting of acute or chronic renal compromise. It has been proposed that circulating fibrocytes mediate the disease. A study was conducted to determine whether bone marrow-derived fibroblast precursors are involved in contributing to organ fibrosis in MRI contrast-treated rodents with renal insufficiency. Rats status post 5/6 nephrectomy underwent bone marrow transplant from human placental alkaline phosphatase (hPAP)-expressing donors. After engraftment, animals were treated with gadolinium-based MRI contrast (2.5 mmol/kg IP), during weekdays for 4 weeks, or an equivalent volume of normal saline. Dermal cellularity in the contrast-treated group was fourfold that of control. Skin cells from the contrast-treated group demonstrated greater hPAP expression with co-expression of pro-collagen I and α-smooth muscle actin-positive stress fibers. Donor and host cells expressed CD34. Dihydroethidium staining of skin was greater in the contrast-treated animals, indicating oxidative stress. This was abrogated when the animals were co-administered the superoxide dismutase mimetic tempol. In conclusion, a bone marrow-derived cell population is increased in the dermis of MRI contrast-treated rodents. The cell markers are consistent with fibrocytes mediating the disease. These changes correlate with oxidative stress and expression of Nox4, suggestive of a novel therapeutic target. Elucidation of the mechanisms of MRI contrast-induced fibrosis may aid in discovering therapies to this devastating disease.

The NADPH oxidase family and its inhibitors

The classical nicotinamide adenine dinucleotide phosphate (NADPH) oxidase was originally detected in neutrophils as a multicomponent enzyme that catalyzes the generation of superoxide from oxygen and the reduced form of NADPH. This enzyme is composed of two membrane-bound subunits (p22phox and gp91phox), three cytosolic subunits (p67phox, p47phox, and p40phox) and a small G-protein Rac (Rac1 and Rac2). Recently, it has been demonstrated that there are several isoforms of nonphagocytic NADPH oxidase. Endothelial cells, vascular smooth muscle cells or adventitial fibroblasts possess multiple isoforms of this enzyme. The new homologs, along with gp91phox are now designated the Nox family of NADPH oxidases and are key sources of reactive oxygen species in the vasculature. Reactive oxygen species play a significant role in regulating endothelial function and vascular tone. However, besides the participation in the processes of physiological cell, these enzymes can also be the perpetrator of oxidative stress that causes endothelial dysfunction. This review summarizes the current state of knowledge of the structure and functions of NADPH oxidase and NADPH oxidase inhibitors in the treatment of disorders with endothelial damage.

NADPH oxidases as regulators of tumor angiogenesis: current and emerging concepts

SIGNIFICANCE

Reactive oxygen species (ROS) such as superoxide, hydrogen peroxide, and peroxynitrite are generated ubiquitously by all mammalian cells and have been understood for many decades as inflicting cell damage and as causing cancer by oxidation and nitration of macromolecules, including DNA, RNA, proteins, and lipids.

RECENT ADVANCES

A current concept suggests that ROS can also promote cell signaling pathways triggered by growth factors and transcription factors that ultimately regulate cell proliferation, differentiation, and apoptosis, all of which are important hallmarks of tumor cell proliferation and angiogenesis. Moreover, an emerging concept indicates that ROS regulate the functions of immune cells that infiltrate the tumor environment and stimulate angiogenesis, such as macrophages and specific regulatory T cells.

CRITICAL ISSUES

In this article, we highlight that the NADPH oxidase family of ROS-generating enzymes are the key sources of ROS and, thus, play an important role in redox signaling within tumor, endothelial, and immune cells thereby promoting tumor angiogenesis.

FUTURE DIRECTIONS

Knowledge of these intricate ROS signaling pathways and identification of the culprit NADPH oxidases is likely to reveal novel therapeutic opportunities to prevent angiogenesis that occurs during cancer and which is responsible for the revascularization after current antiangiogenic treatment.

Protective effect of 4,4'-diaminodiphenylsulfone against paraquat-induced mouse lung injury

Although 4,4'-diaminodiphenylsulfone (DDS, dapsone) has been used to treat several dermatologic conditions, including Hansen disease, for the past several decades, its mode of action has remained a topic of debate. We recently reported that DDS treatment significantly extends the lifespan of the nematode C. elegans by decreasing the generation of reactive oxygen species. Additionally, in in vitro experiments using non-phagocytic human fibroblasts, we found that DDS effectively counteracted the toxicity of paraquat (PQ). In the present study, we extended our work to test the protective effect of DDS against PQ in vivo using a mouse lung injury model. Oral administration of DDS to mice significantly attenuated the lung tissue damage caused by subsequent administration of PQ. Moreover, DDS reduced the local expression of mRNA transcripts encoding inflammation-related molecules, including endothelin-1 (ET-1), macrophage inflammatory protein-1α (MIP-1α), and transforming growth factor-β (TGF-β). In addition, DDS decreased the PQ-induced expression of NADPH oxidase mRNA and activation of protein kinase Cμ (PKCμ). DDS treatment also decreased the PQ-induced generation of superoxide anions in mouse lung fibroblasts. Taken together, these data suggest the novel efficacy of DDS as an effective protective agent against oxidative stress-induced tissue damages.

Combating oxidative stress in vascular disease: NADPH oxidases as therapeutic targets

NADPH oxidases are a family of enzymes that generate reactive oxygen species (ROS). The NOX1 (NADPH oxidase 1) and NOX2 oxidases are the major sources of ROS in the artery wall in conditions such as hypertension, hypercholesterolaemia, diabetes and ageing, and so they are important contributors to the oxidative stress, endothelial dysfunction and vascular inflammation that underlies arterial remodelling and atherogenesis. In this Review, we advance the concept that compared to the use of conventional antioxidants, inhibiting NOX1 and NOX2 oxidases is a superior approach for combating oxidative stress. We briefly describe some common and emerging putative NADPH oxidase inhibitors. In addition, we highlight the crucial role of the NADPH oxidase regulatory subunit, p47phox, in the activity of vascular NOX1 and NOX2 oxidases, and suggest how a better understanding of its specific molecular interactions may enable the development of novel isoform-selective drugs to prevent or treat cardiovascular diseases.

Suppression of ROS generation by 4,4-diaminodiphenylsulfone in non-phagocytic human diploid fibroblasts

The action mode of 4,4-diaminodiphenylsulfone (DDS) is still under debate, although it has long been used in treatment of several dermatologic diseases including Hansens disease. In this study, we tested the effect of DDS as an antioxidant on paraquat-induced oxidative stress in non-phagocytic human diploid fibroblasts (HDFs). Overall, preincubation of HDFs with DDS prevented the oxidative stress and the resulting cytotoxic damages caused by paraquat in these cells. The specific effects of DDS in paraquat-treated HDFs are summarized as follows: a) reducing the expression of NADPH oxidase 4 (NOX4) by inhibiting paraquat-induced activation of PKC; b) inhibiting paraquat-induced decreases in mitochondrial complex protein levels as well as in membrane potentials; c) consequently, inhibiting the generation of cytosolic and mitochondrial superoxide anions. Taken together, these findings suggest that DDS would suppress the radical generation in non-phagocytic HDFs during oxidative stress, and that DDS might have the extended potential to be used further in prevention of other oxidative stress-related pathologies.

Hydroethidine- and MitoSOX-derived red fluorescence is not a reliable indicator of intracellular superoxide formation: another inconvenient truth

Hydroethidine (HE; or dihydroethidium) is the most popular fluorogenic probe used for detecting intracellular superoxide radical anion. The reaction between superoxide and HE generates a highly specific red fluorescent product, 2-hydroxyethidium (2-OH-E(+)). In biological systems, another red fluorescent product, ethidium, is also formed, usually at a much higher concentration than 2-OH-E(+). In this article, we review the methods to selectively detect the superoxide-specific product (2-OH-E(+)) and the factors affecting its levels in cellular and biological systems. The most important conclusion of this review is that it is nearly impossible to assess the intracellular levels of the superoxide-specific product, 2-OH-E(+), using confocal microscopy or other fluorescence-based microscopic assays and that it is essential to measure by HPLC the intracellular HE and other oxidation products of HE, in addition to 2-OH-E(+), to fully understand the origin of red fluorescence. The chemical reactivity of mitochondria-targeted hydroethidine (Mito-HE, MitoSOX red) with superoxide is similar to the reactivity of HE with superoxide, and therefore, all of the limitations attributed to the HE assay are applicable to Mito-HE (or MitoSOX) as well.

Involvement of reactive oxygen species in TGF-beta1-induced tropoelastin expression by human dermal fibroblasts

Chronic exposure to solar UV radiation causes marked changes in the dermal extracellular matrix that underlie the loss of resiliency and increased laxity observed in photoaged skin. In particular, the dermal elastin content increases substantially and the normal, well-organized elastic fibers are replaced by amorphous elastotic material. Transforming growth factor-beta1 (TGF-beta1) stimulates synthesis of elastin by dermal fibroblasts and may mediate the increase in elastin in chronically photodamaged skin. We investigated pathways involved in the TGF-beta1-induced increase in tropoelastin (TE), the soluble elastin monomer and assessed the role of reactive oxygen species (ROS) in the regulation of TE mRNA. Antioxidants and an inhibitor of NADPH oxidase blocked TGF-beta1-induced TE mRNA increase even when added 1.5 h after TGF-beta1, although ROS were detected for only 30 min. The TE mRNA increase required activation of Smad4, shown using Smad4 siRNA, and also involved the ERK1/2, p38 and JNK MAP kinases but not PI3K. ROS did not enhance signaling through Smad2 but did enhance activation of p38 and ERK1/2 at 10 min after TGF-beta1. These results indicate that Smad and MAPK pathways mediate TGF-beta1-induced TE expression and that ROS are required for both early signal transduction and later steps that increase elastin.

5-hydroxy-2-methyl-1,4-naphthoquinone, a vitamin K3 analogue, suppresses STAT3 activation pathway through induction of protein tyrosine phosphatase, SHP-1: potential role in chemosensitization

The activation of signal transducers and activators of transcription 3 (STAT3) has been linked with carcinogenesis through survival, proliferation, and angiogenesis of tumor cells. Agents that can suppress STAT3 activation have potential not only for prevention but also for treatment of cancer. In the present report, we investigated whether 5-hydroxy-2-methyl-1,4-naphthoquinone (plumbagin), an analogue of vitamin K, and isolated from chitrak (Plumbago zeylanica), an Ayurvedic medicinal plant, can modulate the STAT3 pathway. We found that plumbagin inhibited both constitutive and interleukin 6-inducible STAT3 phosphorylation in multiple myeloma (MM) cells and this correlated with the inhibition of c-Src, Janus-activated kinase (JAK)1, and JAK2 activation. Vanadate, however, reversed the plumbagin-induced downregulation of STAT3 activation, suggesting the involvement of a protein tyrosine phosphatase. Indeed, we found that plumbagin induced the expression of the protein tyrosine phosphatase, SHP-1, and silencing of the SHP-1 abolished the effect of plumbagin. This agent also downregulated the expression of STAT3-regulated cyclin D1, Bcl-xL, and vascular endothelial growth factor; activated caspase-3; induced poly (ADP ribose) polymerase cleavage; and increased the sub-G(1) population of MM cells. Consistent with these results, overexpression of constitutive active STAT3 significantly reduced the plumbagin-induced apoptosis. When compared with AG490, a rationally designed STAT3/JAK2 inhibitor, plumbagin was found more potent in suppressing the proliferation of cells. Plumbagin also significantly potentiated the apoptotic effects of thalidomide and bortezomib in MM cells. Overall, these results suggest that the plumbagin inhibits STAT3 activation pathway through the induction of SHP-1 and this may mediate the sensitization of STAT3 overexpressing cancers to chemotherapeutic agents.

Omacor, n-3 polyunsaturated fatty acid, attenuated albuminuria and renal dysfunction with decrease of SREBP-1 expression and triglyceride amount in the kidney of type II diabetic animals

BACKGROUND

We assumed that n-3 polyunsaturated fatty acid (n-3 PUFA) would attenuate the tissue dyslipidemic condition through suppression of sterol regulatory element-binding protein (SREBP-1) in the kidney and would prevent renal progression in diabetic animals.

METHODS

We gavaged Omacor, composed of docosahexaenoic acid and eicosapentaenoic acid, to db/db mice for 2 weeks (0.2 g/100 g/day). We measured the markers of renal function, triglyceride amount and expressions of SREBP-1, liver X-activated receptor alpha (LXRalpha), collagen IV and TGFbeta-1 in kidney lysate, and performed immunohistochemical staining for SREBP-1, desmin and WT-1 in the renal sections. We measured collagen IV in primary mesangial cells cultured with high glucose media (25 mM), both with and without a transient transfection of small interfering RNA (siRNA) SREBP-1.

RESULTS

Omacor decreased the concentration of serum free fatty acid, and the amount of renal triglyceride, which was associated with decreased expression of SREBP-1 in the kidney, albuminuria and renal dysfunction in db/db mice. Omacor attenuated the expansion of mesangial matrix and the expression of desmin, preserved the WT-1 positive cells, and inhibited the phosphorylation of nuclear factor kappaB in renal tissue. In mesangial cells cultured in high glucose media, the suppression of SREBP-1 expression decreased the collagen IV in the cells.

CONCLUSIONS

Our study results demonstrated that n-3 PUFA prevented renal progression with attenuation of SREBP-1 and reduction of triglyceride in the diabetic kidney. This suggests that the regulation of dyslipidemic signals in the kidney could be a possible mechanism by which PUFA preserves renal function in the diabetic condition.

NOX and inflammation in the vascular adventitia

Vascular inflammation has traditionally been thought to be initiated at the luminal surface and progress through the media toward the adventitial layer. In recent years, however, evidence has emerged suggesting that the vascular adventitia is activated early in a variety of cardiovascular diseases and that it plays an important role in the initiation and progression of vascular inflammation. Adventitial fibroblasts have been shown to produce substantial amounts of NAD(P)H oxidase-derived reactive oxygen species (ROS) in response to vascular injury. Additionally, inflammatory cytokines, lipids, and various hormones, implicated in fibroblast proliferation and migration, lead to recruitment of inflammatory cells to the adventitial layer and impairment of endothelium-dependent relaxation. Early in the development of vascular disease, there is clear evidence for progression toward a denser vasa vasorum which delivers oxygen and nutrients to an increasingly hypoxic and nutrient-deficient media. This expanded vascularization appears to provide enhanced delivery of inflammatory cells to the adventitia and outer media. Combined adventitial fibroblast and inflammatory cell-derived ROS therefore are expected to synergize their local effect on adventitial parenchymal cells, leading to further cytokine release and a feed-forward propagation of adventitial ROS production. In fact, data from our laboratory and others suggest a broader paracrine positive feedback role for adventitia-derived ROS in medial smooth muscle cell hypertrophy and neointimal hyperplasia. A likely candidate responsible for the adventitia-derived paracrine signaling across the vessel wall is the superoxide anion metabolite hydrogen peroxide, which is highly stable, cell permeant, and capable of activating downstream signaling mechanisms in smooth muscle cells, leading to phenotypic modulation of smooth muscle cells. This review addresses the role of adventitial NAD(P)H oxidase-derived ROS from a nontraditional, perivascular vantage of promoting vascular inflammation and will discuss how ROS derived from adventitial NAD(P)H oxidases may be a catalyst for vascular remodeling and dysfunction.

Antioxidant therapy in multiple sclerosis

Reactive oxygen species (ROS) play an important role in various events underlying multiple sclerosis pathology. In the initial phase of lesion formation, ROS are known to mediate the transendothelial migration of monocytes and induce a dysfunction in the blood-brain barrier. Although the pathogenesis of MS is not completely understood, various studies suggest that reactive oxygen species contribute to the formation and persistence of multiple sclerosis lesions by acting on distinct pathological processes. The detrimental effects of ROS in the central nervous system are endowed with a protective mechanism consisting of enzymatic and non-enzymatic antioxidant. Antioxidant therapy may therefore represent an attractive treatment of MS. Several studies have shown that antioxidant therapy is beneficial in vitro and in vivo in animal models for MS. Since oxidative damage has been known to be involved in inflammatory and autoimmune-mediated tissue destruction in which, modulation of oxygen free radical production represents a new approach to the treatment of inflammatory and autoimmune diseases. Several experimental studies have been performed to see whether dietary intake of several antioxidants can prevent and or reduce the progression of EAE or not. Although a few antioxidants showed some efficacy in these studies, little information is available on the effect of treatments with such compounds in patients with MS. In this review, our aim is to clarify the therapeutic efficacy of antioxidants in MS disease.

Inhibition of insulin-stimulated hydrogen peroxide production prevents stimulation of sodium transport in A6 cell monolayers

Insulin-stimulated sodium transport across A6 cell (derived from amphibian distal nephron) monolayers involves the activation of a phosphatidylinositol (PI) 3-kinase. We previously demonstrated that exogenous addition of H2O2 to the incubation medium of A6 cell monolayers provokes an increase in PI 3-kinase activity and a subsequent rise in sodium transport (Markadieu N, Crutzen R, Blero D, Erneux C, Beauwens R. Am J Physiol Renal Physiol 288: F1201-F1212, 2005). We therefore questioned whether insulin would produce an intracellular burst of H2O2 leading to PI 3-kinase activation and subsequent increase in sodium transport. An acute production of reactive oxygen species (ROS) in A6 cells incubated with the oxidation-sensitive fluorescent probe 5,6-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate was already detected after 2 min of insulin stimulation. This fluorescent signal and the increase in sodium transport were completely inhibited in monolayers incubated with peggylated catalase, indicating that H2O2 is the main intracellular ROS produced upon insulin stimulation. Similarly, preincubation of monolayers with different chelators of either superoxide (O2(*-); nitro blue tetrazolium, 100 microM) or H2O2 (50 microM ebselen), or blockers of NADPH oxidase (Nox) enzymes (diphenyleneiodonium, 5 microM; phenylarsine oxide, 1 microM and plumbagin, 30 microM) prevented both insulin-stimulated H2O2 production and insulin-stimulated sodium transport. Furthermore, diphenyleneiodonium pretreatment inhibited the recruitment of the p85 PI 3-kinase regulatory subunit in an anti-phosphotyrosine immunoprecipitate in insulin-stimulated cells. In contrast, PI-103, an inhibitor of class IA PI 3-kinase, inhibited insulin-stimulated sodium transport but did not significantly reduce insulin-stimulated H2O2 production. Taken together, our data suggest that insulin induces an acute burst of H2O2production which participates in an increase in phosphatidylinositol 3,4,5-trisphosphate production and subsequently stimulation of sodium transport.

Protective effects of EPA and deleterious effects of DHA on eNOS activity in Ea hy 926 cultured with lysophosphatidylcholine

Oxidized low density lipoprotein (Ox-LDL) is a well-established risk factor in atherosclerosis and lysophosphatidylcholine (LysoPtdCho) is considered to be one of the major atherogenic component of Ox-LDL. The purpose of this work was to investigate the effects of two membrane n-3 long chain polyunsaturated fatty acids (n-3 PUFAs), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) compared to n-6 PUFA, ARA (arachidonic acid), on the activation of endothelial NO synthase (eNOS) by histamine in Ea hy 926 endothelial cells incubated during 24 h in the presence or the absence of LysoPtdCho. DHA (50 muM) produced a ROS induction in cells and aggravated the LysoPtdCho-induced oxidative stress. It did not modify the basal eNOS activity but impaired the stimulation of eNOS induced by histamine and was unable to correct the deleterious effect of LysoPtdCho on histamine-stimulated eNOS activity or phosphorylation of Ser 1177. In contrast, EPA (90 muM) did not modify the ROS level produced in the presence or absence of LysoPtdCho or basal eNOS activity and the stimulating effect of histamine on eNOS. However, it diminished the deleterious effect of LysoPtdCho as well as on the histamine-stimulated eNOS activity on the phosphorylation on Ser 1177 of eNOS. The beneficial effect of EPA but not DHA on endothelial eNOS activity in Ea hy 926 could be also partially due to a slight decrease in membrane DHA content in EPA-treated cells. Consequently, the equilibrium between NO generated by eNOS and ROS due to oxidative stress could explain, in part, the beneficial effect of EPA on the development of cardiovascular diseases. By contrast ARA an n-6 PUFA was devoid of any effect on ROS generation or eNOS activity in the basal state or after histamine-induced stimulation. In vivo experiments should be undertaken to confirm these results.

HPLC study of oxidation products of hydroethidine in chemical and biological systems: ramifications in superoxide measurements

Methods for the detection and quantitation of hydroethidine (HE) and its oxidation products by HPLC analysis are described. Synthetic methods for preparation of authentic standards (2-hydroxyethidium and diethidium) are provided. Potential applications of the HPLC methods to chemical and biological systems are discussed. Specific examples of chromatograms obtained using UV-Vis absorption, fluorescence, electrochemical, and mass spectrometry detectors are provided. The development of a dual electrochemical and fluorescence detection methodology and its applications are described. The HPLC-based method enables analyses of HE and its oxidation products such as ethidium and the dimeric products of HE. The ramifications of HPLC measurement of HE and its oxidation products in the detection and quantitation of 2-hydroxyethidium, the diagnostic marker product of superoxide and HE, in the intracellular milieu are discussed. Similarly, mitochondria-targeted HE conjugated to a triphenylphosphonium group (Mito-HE or Mito-SOX) also forms oxidation products (dimers of Mito-HE and Mito-E+) that can affect the detection and quantitation of 2-hydroxy-mito-ethidium, the diagnostic marker product of Mito-HE and superoxide in mitochondria.

Oxidative imbalance in nonstimulated X-adrenoleukodystrophy-derived lymphoblasts

X-Adrenoleukodystrophy (X-ALD) is a peroxisomal disorder characterized by accumulation of very-long-chain (VLC) fatty acids, which induces inflammatory disease and alterations in cellular redox, both of which are reported to play a role in the pathogenesis of the severe form of the disease (childhood cerebral ALD). Here, we report on the status of oxidative stress (NADPH oxidase activity) and inflammatory mediators in an X-ALD lymphoblast cell line under nonstimulated conditions. X-ALD lymphoblasts contain nearly 7 times higher levels of the C(26:0) fatty acid compared to controls; these levels were downregulated by treatment with sodium phenylacetate (NaPA), lovastatin or the combination of both drugs. In addition, free-radicals synthesis was elevated in X-ALD lymphoblasts, and protein levels of the NADPH oxidase gp91(PHOX) membrane subunit were significantly upregulated, but no changes were observed in the p47(PHOX) and p67(PHOX) cytoplasmic subunits. Unexpectedly, there was no increase in gp91(PHOX) mRNA levels in X-ALD lymphoblasts. Furthermore, X-ALD lymphoblasts produced higher levels of nitric oxide (NO) and cytokines (tumor necrosis factor-alpha and interleukin 1 beta), and treatment with NaPA or lovastatin decreased the synthesis of NO. Our data indicate that X-ALD lymphoblasts are significantly affected by the accumulation of VLC fatty acids, which induces changes in the cell membrane properties/functions that may, in turn, play a role in the development/progression of the pathogenesis of X-ALD disease.

Role of NADPH oxidase in the apoptotic death of cultured cerebellar granule neurons

Cerebellar granule neurons (CGN) cultured in a medium containing 25 mM KCl and treated with staurosporine (ST) or transferred to a medium with 5 mM KCl (K5) die apoptotically. CGN death is mediated by an increase in reactive oxygen species (ROS) production. When CGN are treated with antioxidants all apoptotic parameters and cell death are markedly diminished, showing a central role for ROS in this process. Recently, it has been suggested that a possible ROS source involved in cell death is a NADPH oxidase. In that regard, we found expression in CGN of the components of NADPH proteins, p40phox, p47phox and p67phox, and p22phox, as well as three homologues of the catalytic subunit of this complex, NOX1, 2, and 4. The inhibition of NADPH oxidase with diphenylene iodonium or 4-(2-aminoethyl)benzenesulfonyl fluoride significantly reduced ROS production, NADPH oxidase activity, all the apoptotic events, and cell death induced by both K5 and ST. We conclude that ROS could be an early signal of apoptotic neuronal death and that NADPH oxidase, including NOX1, 2, and/or 4, could have a central role in apoptotic death induced by different conditions in these neurons.

Fatty acids as modulators of the cellular production of reactive oxygen species

Long-chain nonesterified ("free") fatty acids (FFA) and some of their derivatives and metabolites can modify intracellular production of reactive oxygen species (ROS), in particular O(2)(-) and H(2)O(2). In mitochondria, FFA exert a dual effect on ROS production. Because of slowing down the rate of electron flow through Complexes I and III of the respiratory chain due to interaction within the complex subunit structure, and between Complexes III and IV due to release of cytochrome c from the inner membrane, FFA increase the rate of ROS generation in the forward mode of electron transport. On the other hand, due to their protonophoric action on the inner mitochondrial membrane ("mild uncoupling effect"), FFA strongly decrease ROS generation in the reverse mode of electron transport. In the plasma membrane of phagocytic neutrophils and a number of other types of cells, polyunsaturated FFA stimulate O(2)(-) generation by NADPH oxidase. These effects of FFA can modulate signaling functions of ROS and be, at least partly, responsible for their proapoptotic effects in several types of cells.

NOX enzymes as novel targets for drug development

The members of the NOX/DUOX family of NADPH oxidases mediate such physiologic functions as host defense, cell signaling, and thyroid hormone biosynthesis through the generation of reactive oxygen species (ROS), including superoxide anion and hydrogen peroxide. Moreover, ROS are involved in a broad range of fundamental biochemical and cellular processes, and data accumulated in recent years indicate that the NOX enzymes comprise one of the most important biological sources of ROS. Given the high biochemical reactivity of ROS, it is not surprising that they have been implicated in a wide variety of pathologies and diseases. Prominent among the settings that feature ROS-mediated tissue injury are disorders associated with inflammation, aging, and progressive degenerative changes in cells and organ systems, and it appears that essentially no organ system is exempt. Among the disorders currently believed to be mediated at least in part by NOX-derived ROS are hypertension, aortic aneurysm, myocardial infarction (and other ischemia-reperfusion disorders), pulmonary fibrosis and hypertension, amyotropic lateral sclerosis, Alzheimer's disease, Parkinson's disease, ischemic stroke, diabetic nephropathy, and renal cell carcinoma. Several small-molecule and peptide inhibitors of the NOX enzymes have been useful in experimental studies, but issues of specificity, potency, and toxicity militate against any of the existing published compounds as candidates for drug development. Given the broad array of disease targets documented in recent work, the time is here for vigorous efforts to develop clinically useful inhibitors of the NOX enzymes. As most (though not all) NOX-related diseases appear to be mediated by a single member of the NOX family, agents with isoform specificity will be preferred, although broadly active NOX inhibitors may prove to be useful in some settings.

Composition and functions of vascular nicotinamide adenine dinucleotide phosphate oxidases

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases are important sources of reactive oxygen species (ROS) and are expressed in at least three different homologues in the vasculature. The enzymes consist of a membrane complex of one of the large catalytically active Nox proteins and p22phox and different cytosolic subunits. Reactive oxygen species formation by the nicotinamide adenine dinucleotide phosphate oxidases Nox1 and Nox2 in arteries is a consequence of an activation of the enzymes by different stimuli such as growth factors, cytokines, and cardiovascular risk factors (cigarette smoke, high blood pressure, oxidized lipids). Nox4, in contrast, is constitutively active, and therefore, ROS formation by this enzyme is controlled on the expression level of the protein. The negative vascular effects of ROS, such as endothelial dysfunction, vascular hypertrophy, aneurysm formation, and inflammatory activation, appear to be the consequence of an activation of Nox1 and Nox2. Nox4, in contrast, potentially elicits positive effects because it promotes differentiation and reduces proliferation of cells. Consequently, selective pharmacologic inhibition of Nox proteins has a potential to interfere with cardiovascular disease initiation and progression.

Prevention of atrial fibrillation following cardiac surgery: basis for a novel therapeutic strategy based on non-hypoxic myocardial preconditioning

Atrial fibrillation is the most common complication of cardiac surgical procedures performed with cardiopulmonary bypass. It contributes to increased hospital length of stay and treatment costs. At present, preventive strategies offer only suboptimal benefits, despite improvements in anesthesia, surgical technique, and medical therapy. The pathogenesis of postoperative atrial fibrillation is considered to be multifactorial. However oxidative stress is a major contributory factor representing the unavoidable consequences of ischemia/reperfusion cycle occurring in this setting. Considerable evidence suggests the involvement of reactive oxygen species (ROS) in the pathogenic mechanism of this arrhythmia. Interestingly, the deleterious consequences of high ROS exposure, such as inflammation, cell death (apoptosis/necrosis) or fibrosis, may be abrogated by a myocardial preconditioning process caused by previous exposure to moderate ROS concentration known to trigger survival response mechanisms. The latter condition may be created by n-3 PUFA supplementation that could give rise to an adaptive response characterized by increased expression of myocardial antioxidant enzymes and/or anti-apoptotic pathways. In addition, a further reinforcement of myocardial antioxidant defenses could be obtained through vitamins C and E supplementation, an intervention also known to diminish enzymatic ROS production. Based on this paradigm, this review presents clinical and experimental evidence supporting the pathophysiological and molecular basis for a novel therapeutic approach aimed to diminish the incidence of postoperative atrial fibrillation through a non-hypoxic preconditioning plus a reinforcement of the antioxidant defense system in the myocardial tissue.