Mycophenolate Acid Inhibits Endothelial NAD(P)H Oxidase Activity and Superoxide Formation by a Rac1-Dependent Mechanism

Increased levels of a mycophenolic acid metabolite in patients with kidney failure negatively affect cardiomyocyte health

Chronic kidney disease (CKD) significantly increases cardiovascular risk and mortality, and the accumulation of uremic toxins in the circulation upon kidney failure contributes to this increased risk. We thus performed a screening for potential novel mediators of reduced cardiovascular health starting from dialysate obtained after hemodialysis of patients with CKD. The dialysate was gradually fractionated to increased purity using orthogonal chromatography steps, with each fraction screened for a potential negative impact on the metabolic activity of cardiomyocytes using a high-throughput MTT-assay, until ultimately a highly purified fraction with strong effects on cardiomyocyte health was retained. Mass spectrometry and nuclear magnetic resonance identified the metabolite mycophenolic acid-β-glucuronide (MPA-G) as a responsible substance. MPA-G is the main metabolite from the immunosuppressive agent MPA that is supplied in the form of mycophenolate mofetil (MMF) to patients in preparation for and after transplantation or for treatment of autoimmune and non-transplant kidney diseases. The adverse effect of MPA-G on cardiomyocytes was confirmed in vitro, reducing the overall metabolic activity and cellular respiration while increasing mitochondrial reactive oxygen species production in cardiomyocytes at concentrations detected in MMF-treated patients with failing kidney function. This study draws attention to the potential adverse effects of long-term high MMF dosing, specifically in patients with severely reduced kidney function already displaying a highly increased cardiovascular risk.

Kidney Transplant Recipients Show Limited Lung Diffusion Capacity but Similar Hydrogen Peroxide Exhalation as Healthy Matched Volunteers: A Pilot Study

Patients with end-stage chronic kidney disease show higher systemic oxidative stress and exhale more hydrogen peroxide (H2O2) than healthy controls. Kidney transplantation reduces oxidative stress and H2O2 production by blood polymorphonuclear leukocytes (PMNs). Kidney transplant recipients (KTRs) may be predisposed to an impairment of lung diffusing capacity due to chronic inflammation. Lung function and H2O2 concentration in the exhaled breath condensate (EBC) were compared in 20 KTRs with stable allograft function to 20 healthy matched controls. Serum interleukin eight (IL-8) and C-reactive protein (CRP), blood cell counts, and spirometry parameters did not differ between groups. However, KTRs showed lower total lung diffusing capacity for carbon monoxide, corrected for hemoglobin concentration (TLCOc), in comparison to healthy controls (92.1 ± 11.5% vs. 102.3 ± 11.9% of predicted, p = 0.009), but similar EBC H2O2 concentration (1.63 ± 0.52 vs. 1.77 ± 0.50 µmol/L, p = 0.30). The modality of pre-transplant renal replacement therapy had no effect on TLCOc and EBC H2O2. TLCOc did not correlate with time after transplantation. In this study, TLCOc was less reduced in KTRs in comparison to previous reports. We suggest this fact and the non-elevated H2O2 exhalation exhibited by KTRs, may result perhaps from the evolution of the immunosuppressive therapy.

Cardiovascular effects of immunosuppression agents

Immunosuppressive medications are widely used to treat patients with neoplasms, autoimmune conditions and solid organ transplants. Key drug classes, namely calcineurin inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and purine synthesis inhibitors, have direct effects on the structure and function of the heart and vascular system. In the heart, immunosuppressive agents modulate cardiac hypertrophy, mitochondrial function, and arrhythmia risk, while in vasculature, they influence vessel remodeling, circulating lipids, and blood pressure. The aim of this review is to present the preclinical and clinical literature examining the cardiovascular effects of immunosuppressive agents, with a specific focus on cyclosporine, tacrolimus, sirolimus, everolimus, mycophenolate, and azathioprine.

Comparison of PREDICTS atherosclerosis biomarker changes after initiation of new treatments in patients with SLE

Objective

Patients with SLE have an increased risk of atherosclerosis (ATH) that is not adequately explained by traditional risk factors. We previously described the Predictors of Risk for Elevated Flares, Damage Progression, and Increased Cardiovascular disease in PaTients with SLE (PREDICTS) atherosclerosis-risk panel, which includes proinflammatory HDL (piHDL), leptin, soluble tumour necrosis factor-like weak inducer of apoptosis (sTWEAK) and homocysteine, as well as age and diabetes. A high PREDICTS score confers 28-fold increased odds for future atherosclerosis in SLE. The aim of this study is to determine whether PREDICTS biomarkers are modifiable by common lupus therapies.

Methods

This prospective observational study included SLE subjects started on new lupus treatments. Leptin, sTWEAK, homocysteine and antioxidant function of HDL were measured at baseline (prior to drug initiation), 6 weeks and 12 weeks.

Results

16 subjects started mycophenolate (MMF), 18 azathioprine (AZA) and 25 hydroxychloroquine (HCQ). In MMF-treated subjects, HDL function progressively improved from 2.23 ± 1.32 at baseline to 1.37±0.81 at 6 weeks (p=0.02) and 0.93±0.54 at 12 weeks (p=0.009). sTWEAK levels also improved in MMF-treated subjects from 477.5±447.1 to 290.3±204.6 pg/mL after 12 weeks (p=0.04), but leptin and homocysteine levels were not significantly changed. In HCQ-treated subjects, only HDL function improved from 1.80±1.29 at baseline to 1.03±0.74 after 12 weeks (p=0.05). There were no changes in the AZA group. MMF treatment was still associated with significant improvements in HDL function after accounting for potential confounders such as total prednisone dose and changes in disease activity. Overall, the mean number of high-risk PREDICTS biomarkers at week 12 significantly decreased in the entire group of patients started on a new lupus therapy (2.1±0.9 to 1.8±0.9, p=0.02) and in the MMF-treated group (2.4±0.8 vs 1.8±0.9, p=0.003), but not in the AZA or HCQ groups. In multivariate analysis, the odds of having a high PREDICTS atherosclerosis risk score at 12 weeks were lower with MMF treatment (OR 0.002, 95% CI 0.000 to 0.55, p=0.03).

Conclusions

12 weeks of MMF therapy improves the overall PREDICTS atherosclerosis biomarker profile. Further studies will determine whether biomarker changes reflect decreases in future cardiovascular events.

Beneficial effects of mycophenolate mofetil on cardiotoxicity induced by tacrolimus in wistar rats

The immunosuppressive drug tacrolimus (TAC) is used clinically to reduce the rejection rate in transplant patients. TAC has contributed to an increased prevalence of cardiovascular disease in patients receiving solid organ transplantation. Mycophenolate mofetil (MMF), a potent inhibitor of de novo purine synthesis, is known to prevent ongoing rejection in combination with TAC. In the present study, we investigated the antioxidant and antigenotoxic effect of MMF on TAC-induced cardiotoxicity in rats. Oral administration of TAC at 2.4, 24, and 60 mg/kg b.w. corresponding, respectively, to 1, 10, and 25% of LD50 for 24 h caused cardiac toxicity in a dose-dependant manner. TAC increased significantly DNA damage level in hearts of treated rats. Furthermore, it increased malondialdehyde (MDA) and protein carbonyl (PC) levels and decreased catalase (CAT) and superoxide dismutase (SOD) activities. The oral administration of MMF at 50 mg/kg b.w. simultaneously with TAC at 60 mg/kg b.w. proved a significant cardiac protection by decreasing DNA damage, MDA, and PC levels, and by increasing the antioxidant activities of CAT and SOD. Thus, our study showed, for the first time, the protective effect of MMF against cardiac toxicity induced by TAC. This protective effect was mediated via an antioxidant process.

Excess reactive oxygen species production mediates monoclonal antibody-induced human embryonic stem cell death via oncosis

Antibody-mediated cell killing has significantly facilitated the elimination of undesired cells in therapeutic applications. Besides the well-known Fc-dependent mechanisms, pathways of antibody-induced apoptosis were also extensively studied. However, with fewer studies reporting the ability of antibodies to evoke an alternative form of programmed cell death, oncosis, the molecular mechanism of antibody-mediated oncosis remains underinvestigated. In this study, a monoclonal antibody (mAb), TAG-A1 (A1), was generated to selectively kill residual undifferentiated human embryonic stem cells (hESC) so as to prevent teratoma formation upon transplantation of hESC-derived products. We revealed that A1 induces hESC death via oncosis. Aided with high-resolution scanning electron microscopy (SEM), we uncovered nanoscale morphological changes in A1-induced hESC oncosis, as well as A1 distribution on hESC surface. A1 induces hESC oncosis via binding-initiated signaling cascade, most likely by ligating receptors on surface microvilli. The ability to evoke excess reactive oxygen species (ROS) production via the Nox2 isoform of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is critical in the cell death pathway. Excess ROS production occurs downstream of microvilli degradation and homotypic adhesion, but upstream of actin reorganization, plasma membrane damage and mitochondrial membrane permeabilization. To our knowledge, this is the first mechanistic model of mAb-induced oncosis on hESC revealing a previously unrecognized role for NAPDH oxidase-derived ROS in mediating oncotic hESC death. These findings in the cell death pathway may potentially be exploited to improve the efficiency of A1 in eliminating undifferentiated hESC and to provide insights into the study of other mAb-induced cell death.

Nox Inhibitors & Therapies: Rational Design of Peptidic and Small Molecule Inhibitors

Oxidative stress-related diseases underlie many if not all of the major leading causes of death in United States and the Western World. Thus, enormous interest from both academia and pharmaceutical industry has been placed on the development of agents which attenuate oxidative stress. With that in mind, great efforts have been placed in the development of inhibitors of NADPH oxidase (Nox), the major enzymatic source of reactive oxygen species and oxidative stress in many cells and tissue. The regulation of a catalytically active Nox enzyme involves numerous protein-protein interactions which, in turn, afford numerous targets for inhibition of its activity. In this review, we will provide an updated overview of the available Nox inhibitors, both peptidic and small molecules, and discuss the body of data related to their possible mechanisms of action and specificity towards each of the various isoforms of Nox. Indeed, there have been some very notable successes. However, despite great commitment by many in the field, the need for efficacious and well-characterized, isoform-specific Nox inhibitors, essential for the treatment of major diseases as well as for delineating the contribution of a given Nox in physiological redox signalling, continues to grow.

NOX Modifiers-Just a Step Away from Application in the Therapy of Airway Inflammation?

SIGNIFICANCE

NADPH oxidase (NOX) enzymes, which are widely expressed in different airway cell types, not only contribute to the maintenance of physiological processes in the airways but also participate in the pathogenesis of many acute and chronic diseases. Therefore, the understanding of NOX isoform regulation, expression, and the manner of their potent inhibition might lead to effective therapeutic approaches.

RECENT ADVANCES

The study of the role of NADPH oxidases family in airway physiology and pathophysiology should be considered as a work in progress. While key questions still remain unresolved, there is significant progress in terms of our understanding of NOX importance in airway diseases as well as a more efficient way of using NOX modifiers in human settings.

CRITICAL ISSUES

Agents that modify the activity of NADPH enzyme components would be considered useful tools in the treatment of various airway diseases. Nevertheless, profound knowledge of airway pathology, as well as the mechanisms of NOX regulation is needed to develop potent but safe NOX modifiers.

FUTURE DIRECTIONS

Many compounds seem to be promising candidates for development into useful therapeutic agents, but their clinical potential is yet to be demonstrated. Further analysis of basic mechanisms in human settings, high-throughput compound scanning, clinical trials with new and existing molecules, and the development of new drug delivery approaches are the main directions of future studies on NOX modifiers. In this article, we discuss the current knowledge with regard to NOX isoform expression and regulation in airway inflammatory diseases as well as the aptitudes and therapeutic potential of NOX modifiers.

Tacrolimus and mycophenolate mofetil associations

Gastrointestinal risk factors after organ transplantation are prevalent, due to the chronic use of immunosuppressant. The immunosuppressive drugs such as tacrolimus/mycophenolate mofetil (TAC/MMF) association are the most commonly used therapy. TAC and MMF have been implicated in gastrotoxicity, but their direct effects, alone and combined, on intestinal cells are not completely elucidated. This study investigated the effect of TAC and MMF alone and combined on human colon carcinoma cells. Our results demonstrated that TAC and MMF individually inhibit clearly cells proliferation, enhanced free radicals, lipid peroxidation production, induced DNA lesions and reduced mitochondrial membrane potential. In this study, we also showed that the two molecules TAC and MMF combined at high concentrations amplified the cell damage. Furthermore, the TAC (5 µM) prevented cell death induced by MMF (half maximal inhibitory concentration (IC50)). Also, MMF (50 µM) induced cytoprotection in HCT116 cells against TAC (IC50) toxicity. Our findings provide additional evidence that oxidative damage is the major contribution of TAC and MMF combined toxicities. In fact, MMF and TAC exert a gastroprotective effect by modulating reactive oxygen species production. These data underscore the pleiotropic effect of TAC and MMF on HCT116 cells that play a preventive and critical role on intestinal function.

The quest for selective nox inhibitors and therapeutics: challenges, triumphs and pitfalls

SIGNIFICANCE

Numerous studies in animal models and human subjects corroborate that elevated levels of reactive oxygen species (ROS) play a pivotal role in the progression of multiple diseases. As a major source of ROS in many organ systems, the NADPH oxidase (Nox) has become a prime target for therapeutic development.

RECENT ADVANCES

In recent years, intense efforts have been dedicated to the development of pan- and isoform-specific Nox inhibitors as opposed to antioxidants that proved ineffective in clinical trials. Over the past decade, an array of compounds has been proposed in an attempt to fill this void.

CRITICAL ISSUES

Although many of these compounds have proven effective as Nox enzyme family inhibitors, isoform specificity has posed a formidable challenge to the scientific community. This review surveys the most prominent Nox inhibitors, and discusses potential isoform specificity, known mechanisms of action, and shortcomings. Some of these inhibitors hold substantial promise as targeted therapeutics.

FUTURE DIRECTIONS

Increased insight into the mechanisms of action and regulation of this family of enzymes as well as atomic structures of key Nox subunits are expected to give way to a broader spectrum of more potent, efficacious, and specific molecules. These lead molecules will assuredly serve as a basis for drug development aimed at treating a wide array of diseases associated with increased Nox activity.

Hirschsprung-like disease is exacerbated by reduced de novo GMP synthesis

Hirschsprung disease (HSCR) is a partially penetrant oligogenic birth defect that occurs when enteric nervous system (ENS) precursors fail to colonize the distal bowel during early pregnancy. Genetic defects underlie HSCR, but much of the variability in the occurrence and severity of the birth defect remain unexplained. We hypothesized that nongenetic factors might contribute to disease development. Here we found that mycophenolate, an inhibitor of de novo guanine nucleotide biosynthesis, and 8 other drugs identified in a zebrafish screen impaired ENS development. In mice, mycophenolate treatment selectively impaired ENS precursor proliferation, delayed precursor migration, and induced bowel aganglionosis. In 2 different mouse models of HSCR, addition of mycophenolate increased the penetrance and severity of Hirschsprung-like pathology. Mycophenolate treatment also reduced ENS precursor migration as well as lamellipodia formation, proliferation, and survival in cultured enteric neural crest–derived cells. Using X-inactivation mosaicism for the purine salvage gene Hprt, we found that reduced ENS precursor proliferation most likely causes mycophenolate-induced migration defects and aganglionosis. To the best of our knowledge, mycophenolate is the first medicine identified that causes major ENS malformations and Hirschsprung-like pathology in a mammalian model. These studies demonstrate a critical role for de novo guanine nucleotide biosynthesis in ENS development and suggest that some cases of HSCR may be preventable.

The cooperative roles of inflammation and oxidative stress in the pathogenesis of hypertension

SIGNIFICANCE

Innate and adaptive immunity play fundamental roles in the development of hypertension and its complications. As effectors of the cell-mediated immune response, myeloid cells and T lymphocytes protect the host organism from infection by attacking foreign intruders with bursts of reactive oxygen species (ROS).

RECENT ADVANCES

While these ROS may help to preserve the vascular tone and thereby protect against circulatory collapse in the face of overwhelming infection, aberrant elaboration of ROS triggered by immune cells in the absence of a hemodynamic insult can lead to pathologic increases in blood pressure. Conversely, misdirected oxidative stress in cardiovascular control organs, including the vasculature, the kidney, and the nervous system potentiates inflammatory responses, augmenting blood pressure elevation and inciting target organ damage.

CRITICAL ISSUES

Inflammation and oxidative stress thereby act as cooperative and synergistic partners in the pathogenesis of hypertension.

FUTURE DIRECTIONS

Pharmacologic interventions for hypertensive patients will need to exploit this robust bidirectional relationship between ROS generation and immune activation in cardiovascular control organs to maximize therapeutic benefit, while limiting off-target side effects.

Mycophenolic acid attenuates the tumour necrosis factor-α-mediated proinflammatory response in endothelial cells by blocking the MAPK/NF-κB and ROS pathways

BACKGROUND

Mycophenolate mofetil (MMF) has beneficial effects in cardiac transplant patients beyond the suppression of tissue rejection. Moreover, mycophenolic acid (MPA), its active metabolite, has been associated with positive effects on atherosclerosis in animal models. The attachment of leukocytes to the vascular endothelium and the subsequent migration of these cells into the vessel wall are early events in inflammation and atherosclerosis. The aim of this study was to investigate the effects of MPA on tumour necrosis-α (TNF-α)-induced, endothelial cell proinflammatory responses and the underlying mechanisms.

METHODS AND RESULTS

Human aortic endothelial cells (HAECs) were treated with different concentrations (primarily 50 μM) of MPA before treatment with TNF-α. The surface protein and mRNA expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were determined by flow cytometry and real-time RT-PCR, respectively. Adhesion of leukocytes to TNF-α-treated HAECs was evaluated by an adhesion assay. Activation of mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) was evaluated by measuring the levels of their phosphorylation using flow cytometry. NF-κB p65 translocation was detected by Western blotting. The production of reactive oxygen species (ROS) was determined by reduction in fluorescent 2',7'-dichlorofluorescein diacetate (H2 DCFH-DA). MPA significantly inhibits TNF-α-induced ICAM-1, VCAM-1 surface protein and mRNA expression as well as adhesion of mononuclear leukocytes to HAEC. ICAM-1 and VCAM-1 expressions were also reduced by antioxidants such as pyrrolidine dithiocarbamate, diphenylene iodonium and apocynin. MPA inhibited TNF-α-stimulated ROS generation similarly to apocynin. TNF-α increased ICAM-1 and VCAM-1 expression via c-Jun NH2 -terminal kinase (JNK), extracellular signal-regulated kinase (ERK1/2) and p38 MAPK. MPA and apocynin inhibited TNF-α-induced phosphorylation of all three MAP kinases. Furthermore, TNF-α-induced NF-κB activation was attenuated by SP600125 (JNK inhibitor), PD98059 (ERK1/2 inhibitor, SB203580 (p38 MAPK inhibitor) and MPA. MPA also inhibited TNF-α-induced nuclear translocation of NF-κB p65.

CONCLUSION

These results suggest that, in addition to the prevention of rejection, MPA may be a promising approach for the treatment of inflammatory vascular disease.

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.

Immunosuppression preserves renal autoregulatory function and microvascular P2X(1) receptor reactivity in ANG II-hypertensive rats

Autoregulation is critical for protecting the kidney against arterial pressure elevation and is compromised in some forms of hypertension. Evidence indicates that activated lymphocytes contribute importantly to cardiovascular injury in hypertension. We hypothesized that activated lymphocytes contribute to renal vascular dysfunction by impairing autoregulation and P2X(1) receptor signaling in ANG II-infused hypertensive rats. Male Sprague-Dawley rats receiving ANG II infusion were treated with a lymphocyte proliferation inhibitor, mycophenolate mofetil (MMF) for 2 wk. Autoregulation was assessed in vitro and in vivo using the blood-perfused juxtamedullary nephron preparation and anesthetized rats, respectively. ANG II-treated rats exhibited impaired autoregulation. At the single vessel level, pressure-mediated afferent arteriolar vasoconstriction was significantly blunted (P < 0.05 vs. control rats). At the whole kidney level, renal blood flow passively decreased as renal perfusion pressure was reduced. MMF treatment did not alter the ANG II-induced hypertensive state; however, MMF did preserve autoregulation. The autoregulatory profiles in both in vitro or in vivo settings were similar to the responses from control rats despite persistent hypertension. Autoregulatory responses are linked to P2X(1) receptor activation. Accordingly, afferent arteriolar responses to ATP and the P2X(1) receptor agonist β,γ-methylene ATP were assessed. ATP- or β,γ-methylene ATP-induced vasoconstriction was significantly attenuated in ANG II-infused hypertensive rats but was normalized by MMF treatment. Moreover, MMF prevented elevation of plasma transforming growth factor-β1 concentration and lymphocyte and macrophage infiltration in ANG II-infused kidneys. These results suggest that anti-inflammatory treatment with MMF prevents lymphocyte infiltration and preserves autoregulation in ANG II-infused hypertensive rats, likely by normalizing P2X(1) receptor activation.

Dietary immunosuppressants do not enhance UV-induced skin carcinogenesis, and reveal discordance between p53-mutant early clones and carcinomas

Immunosuppressive drugs are thought to cause the dramatically increased risk of carcinomas in sun-exposed skin of organ transplant recipients. These drugs differ in local effects on skin. We investigated whether this local impact is predictive of skin cancer risk and may thus provide guidance on minimizing the risk. Immunosuppressants (azathioprine, cyclosporine, tacrolimus, mycophenolate mofetil, and rapamycin) were assessed on altering the UV induction of apoptosis in human skin models and of p53 mutant cell clones (putative tumor precursors) and ensuing skin carcinomas (with mutant p53) in the skin of hairless mice. Rapamycin was found to increase apoptosis (three-fold), whereas cyclosporine decreased apoptosis (three-fold). Correspondingly, a 1.5- to five-fold reduction (P = 0.07) or a two- to three-fold increase (P < 0.001) was found in cell clusters overexpressing mutant p53 in chronically UV-exposed skin of mice that had been fed rapamycin or cyclosporine, respectively. Deep sequencing showed, however, that the allelic frequency (∼5%) of the hotspot mutations in p53 (codons 270 and 275) remained unaffected. The majority of cells with mutated p53 seemed not to overexpress the mutated protein. Unexpectedly, none of the immunosuppressants admixed in high dosages to the diet accelerated tumor development, and cyclosporine even delayed tumor onset by approximately 15% (P < 0.01). Thus, in contrast to earlier findings, the frequency of p53-mutant cells was not predictive of the incidence of skin carcinoma. Moreover, the lack of any accelerative effect on tumor development suggests that immunosuppressive medication is not the sole cause of the dramatic increase in skin cancer risk in organ transplant recipients.

Mycophenolic acid regulates spleen tyrosine kinase to repress tumour necrosis factor-alpha-induced monocyte chemotatic protein-1 production in cultured human aortic endothelial cells

Atherosclerosis develops from cascades of inflammatory processes. Spleen tyrosine kinase (Syk) and monocyte chemotatic protein-1 (MCP-1) play important roles in the pathogenesis of atherosclerosis. Mycophenolic acid (MPA) has an anti-inflammatory effect. We have investigated whether MPA regulates Syk to repress tumour necrosis factor-α (TNF-α)-induced MCP-1 production in cultured human aortic endothelial cells. Expression of MCP-1 mRNA and its protein were measured by real time RT-PCR and ELISA, respectively. Reactive oxygen species (ROS) production were measured using 2'7'-dichlorofluorescein diacetate. Activation of AP-1 and NF-κB were assessed by electrophoretic mobility shift assay. Tyrosine phosphorylation of Syk was examined by Western blot analysis. TNF-α increased MCP-1 at both mRNA and protein levels. TNF-α-induced MCP-1 mRNA expression was inhibited by N-acetylcysteine (NAC), Syk inhibitor, Syk-siRNA and MPA. TNF-α-induced MCP-1 protein production was also inhibited by Syk inhibitor and MPA. TNF-α increased DNA binding activity of AP-1 and NF-κB, whereas both AP-1 and NF-κB decoy oligodeoxynucleotides downregulated TNF-α-induced MCP-1 mRNA expression. TNF-α increased ROS generation, which was inhibited by NAC and MPA, but not by Syk inhibitor. TNF-α increased tyrosine phosphorylation of Syk, which was attenuated by NAC and MPA. MPA and Syk inhibitor attenuated TNF-α-induced DNA binding activity of NF-κB and AP-1. TNF-α induced MCP-1 expression via activation of AP-1 and NF-κB. AP-1 and NF-κB were mediated through ROS, followed by Syk. MPA exerts anti-inflammatory effect by inhibiting MCP-1 expression via suppression of ROS and Syk.

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 oxidase inhibitors: a decade of discovery from Nox2ds to HTS

NADPH oxidases (Nox) are established as major sources of reactive oxygen species (ROS). Over the past two decades, Nox-derived ROS have emerged as pivotal in the development of myriad diseases involving oxidative stress. In contrast, Nox are also involved in signaling mechanisms necessary for normal cell function. The study of these enzymes in physiological and pathophysiological conditions is made considerably more complex by the discovery of 7 isoforms: Nox1 through 5 as well as Duox1 and 2, each with its own specific cytosolic components, regulatory control mechanisms, subcellular localization and/or tissue distribution. A clear understanding of the role individual isoforms play in a given system is hindered by the lack of isoform-specific inhibitors. In animal models, knockdown or knockout methodologies are providing definitive answers to perplexing questions of the complex interplay of multiple Nox isoforms in cell and tissue signaling. However, the complex structures and interactions of these heteromeric isozymes predict pleiotropic actions of the Nox subunits and thus suppression of these proteins is almost certain to have untoward effects. Thus, as both therapies and pharmacological tools, molecule-based inhibitors continue to prove extremely useful and rational in design. Unfortunately, many of the available inhibitors have proven non-specific, falling into the category of scavengers or inhibitors of more than one source of ROS. Here, we will review some of the efforts that have been undertaken to develop specific inhibitors of NADPH oxidase over the past decade, from the peptidic inhibitor Nox2ds-tat to more recent small molecule inhibitors that have emerged from high-throughput screening campaigns.

Antibody-induced nonapoptotic cell death in human lymphoma and leukemia cells is mediated through a novel reactive oxygen species-dependent pathway

Monoclonal antibodies (mAbs) have revolutionized the treatment of B-cell malignancies. Although Fc-dependent mechanisms of mAb-mediated tumor clearance have been extensively studied, the ability of mAbs to directly evoke programmed cell death (PCD) in the target cell and the underlying mechanisms involved remain under-investigated. We recently demonstrated that certain mAbs (type II anti-CD20 and anti-HLA DR mAbs) potently evoked PCD through an actin-dependent, lysosome-mediated process. Here, we reveal that the induction of PCD by these mAbs, including the type II anti-CD20 mAb GA101 (obinutuzumab), directly correlates with their ability to produce reactive oxygen species (ROS) in human B-lymphoma cell lines and primary B-cell chronic lymphocytic leukemia cells. ROS scavengers abrogated mAb-induced PCD indicating that ROS are required for the execution of cell death. ROS were generated downstream of mAb-induced actin cytoskeletal reorganization and lysosome membrane permeabilization. ROS production was independent of mitochondria and unaffected by BCL-2 overexpression. Instead, ROS generation was mediated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. These findings provide further insights into a previously unrecognized role for NADPH oxidase-derived ROS in mediating nonapoptotic PCD evoked by mAbs in B-cell malignancies. This newly characterized cell death pathway may potentially be exploited to eliminate malignant cells, which are refractory to conventional chemotherapy and immunotherapy.

Immunosuppressant regimen based on sirolimus decreases aortic stiffness in renal transplant recipients in comparison to cyclosporine

Whether or not a cyclosporine A (CsA)-free immunosuppressant regimen based on sirolimus (SRL) prevents aortic stiffening and improves central hemodynamics in renal recipients remains unknown. Forty-four patients (48 ± 2 years) enrolled in the CONCEPT trial were randomized at week 12 (W12) to continue CsA or switch to SRL, both associated with mycophenolate mofetil. Carotid systolic blood pressure (cSBP), pulse pressure (cPP), central pressure wave reflection (augmentation index, AIx) and carotid-to-femoral pulse-wave velocity (PWV: aortic stiffness) were blindly assessed at W12, W26 and W52 together with plasma endothelin-1 (ET-1), thiobarbituric acid-reactive substances (TBARS) and superoxide dismutase (SOD) and catalase erythrocyte activities. At W12, there was no difference between groups. At follow-up, PWV, cSBP, cPP and AIx were lower in the SRL group. The difference in PWV remained significant after adjustment for blood pressure and eGFR. In parallel, ET-1 decreased in the SRL group, while TBARS, SOD and catalase erythrocyte activities increased in both groups but to a lesser extent in the SRL group. Our results demonstrate that a CsA-free regimen based on SRL reduces aortic stiffness, plasma endothelin-1 and oxidative stress in renal recipients suggesting a protective effect on the arterial wall that may be translated into cardiovascular risk reduction.

Phagocyte-like NADPH oxidase generates ROS in INS 832/13 cells and rat islets: role of protein prenylation

Recent evidence suggests that an acute increase in the generation of phagocyte-like NADPH-oxidase (Nox)-mediated reactive oxygen species (ROS) may be necessary for glucose-stimulated insulin secretion. Using rat islets and INS 832/13 cells, we tested the hypothesis that activation of specific G proteins is necessary for nutrient-mediated intracellular generation of ROS. Stimulation of β-cells with glucose or a mixture of mitochondrial fuels (mono-methylsuccinate plus α-ketoisocaproic acid) markedly elevated intracellular accumulation of ROS, which was attenuated by selective inhibitors of Nox (e.g., apocynin or diphenyleneiodonium chloride) or short interfering RNA-mediated knockdown of p47(phox), one of the subunits of Nox. Selective inhibitors of protein prenylation (FTI-277 or GGTI-2147) markedly inhibited nutrient-induced ROS generation, suggesting that activation of one (or more) prenylated small G proteins and/or γ-subunits of trimeric G proteins is involved in this signaling axis. Depletion of endogenous GTP levels with mycophenolic acid significantly reduced glucose-induced activation of Rac1 and ROS generation in these cells. Other immunosuppressants, like cyclosporine A or rapamycin, which do not deplete endogenous GTP levels, failed to affect glucose-induced ROS generation, suggesting that endogenous GTP is necessary for glucose-induced Nox activation and ROS generation. Treatment of INS 832/13 cells or rat islets with pertussis toxin (Ptx), which ADP ribosylates and inhibits inhibitory class of trimeric G proteins (i.e., G(i) or G(o)), significantly attenuated glucose-induced ROS generation in these cells, implicating activation of a Ptx-sensitive G protein in these signaling cascade. Together, our findings suggest a prenylated Ptx-sensitive signaling step couples Rac1 activation in the signaling steps necessary for glucose-mediated generation of ROS in the pancreatic β-cells.

Early and late effects of the immunosuppressants rapamycin and mycophenolate mofetil on UV carcinogenesis

Increased skin cancer risk in organ transplant recipients has been experimentally emulated with enhanced UV carcinogenesis from administering conventional immunosuppressants. However, newer generation immunosuppressive drugs, rapamycin (Rapa) and mycophenolate mofetil (MMF), have been shown to impair angiogenesis and outgrowth of tumor implants. To ascertain the overall effect on UV carcinogenesis, Rapa and MMF were admixed into the food pellets of hairless SKH1 mice receiving daily sub-sunburn UV dosages. With immunosuppressive blood levels neither of the drugs affected onset of tumors (<2 mm), but in contrast to MMF, Rapa significantly increased latency of large tumors (>or=4 mm, medians of 190 vs 125 days) and reduced their multiplicity (1.6 vs 4.5 tumors per mouse at 200 days). Interestingly, tumors (>2 mm) from the Rapa-fed group showed a reduction in UV-signature p53 mutations (39% vs 90%) in favor of mutations from putative base oxidation. This shift in mutation spectrum was not essentially linked to the reduction in large tumors because it was absent in large tumors similarly reduced in number when feeding Rapa in combination with MMF, possibly owing to an antioxidant effect of MMF. Significantly fewer tumor cells were Vegf-positive in the Rapa-fed groups, but a correspondingly reduced expression of Hif1alpha target genes (Vegf, Ldha, Glut1, Pdk1) that would indicate altered glucose metabolism with increased oxidative stress was not found. Remarkably, we observed no effect of the immunosuppressants on UV-induced tumor onset, and with impaired tumor outgrowth Rapa could therefore strongly reduce skin carcinoma morbidity and mortality rates in organ transplant recipients.

Cyclosporine A-induced nitration of tyrosine 34 MnSOD in endothelial cells: role of mitochondrial superoxide

AIMS

Cyclosporine A (CsA) has represented a fundamental therapeutic weapon in immunosuppression for the past three decades. However, its clinical use is not devoid of side effects, among which hypertension and vascular injury represent a major drawback. Endothelial cells are able to generate reactive oxygen and nitrogen species upon exposure to CsA, including formation of peroxynitrite. This may result in endothelial cell toxicity and increased tyrosine nitration. We have now studied the subcellular origin of superoxide formation in endothelial cells treated with CsA and the biochemical consequences for the function of mitochondrial enzymes.

METHODS AND RESULTS

By using electron spin resonance and endothelial cells lacking functional mitochondria, we showed that superoxide anion is generated in mitochondria. This was associated with an effect of CsA on bioenergetic parameters: increased mitochondrial membrane potential and inhibition of cellular respiration. In addition, CsA inhibited the activity of the mitochondrial enzymes aconitase and manganese superoxide dismutase (MnSOD). The use of murine lung endothelial cells deficient in endothelial nitric oxide synthase (eNOS) and NOS/peroxynitrite inhibitors allowed us to establish that the presence of eNOS and concomitant NO synthesis and peroxynitrite formation were essential for CsA induced nitration and inhibition of MnSOD activity. As the latter has been shown to become inactivated by nitration, we sought to identify this modification by mass spectrometry analysis. We found that CsA induced specific MnSOD tyrosine 34 nitration both in the recombinant protein and in endothelial cells overexpressing MnSOD.

CONCLUSION

We propose that CsA induced endothelial damage may be related to increased mitochondrial superoxide formation and subsequent peroxynitrite-dependent nitroxidative damage, specifically targeting MnSOD. The inactivation of this key antioxidant enzyme by tyrosine nitration represents a pathophysiological cellular mechanism contributing to self-perpetuation and amplification of CsA-related vascular toxicity.

Mycophenolic acid attenuates tumor necrosis factor-alpha-induced endothelin-1 production in human aortic endothelial cells

AIMS

Atherosclerotic cardiovascular disease is the major cause of morbidity and mortality in solid organ transplant recipients. Endothelin-1 (ET-1) is implicated in the pathogenesis of atherosclerosis and is one of the potential therapeutic targets. This study was conducted to evaluate the effect of mycophenolic acid (MPA), an immunosuppressant for the transplant recipients, on tumor necrosis factor-alpha (TNF-alpha)-induced ET-1 production in aortic endothelial cells.

METHODS AND RESULTS

In cultured human aortic endothelial cells, TNF-alpha increased ET-1 through AP-1 and NF-kappaB, whereas MPA attenuated it by reducing both AP-1 and NF-kappaB DNA-binding activities. TNF-alpha increased ET-1 via c-Jun NH2-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), but not extracellular signal-regulated kinase. N-acetylcysteine that downregulated TNF-alpha-induced reactive oxygen species (ROS) inhibited JNK activation, but not p38 MAPK. N-acetylcysteine, SP600125 (JNK inhibitor) and SB203580 (p38 MAPK inhibitor) attenuated TNF-alpha-induced DNA-binding activities of both AP-1 and NF-kappaB. MPA inhibited JNK and p38 MAPK activations as well as ROS generation. N-acetylcysteine, SP600125, SB203580 and MPA had no effect on either TNF-alpha-induced IkappaBalpha degradation or p65 nuclear translocation, but attenuated p65 Ser276 phosphorylation.

CONCLUSION

MPA attenuated TNF-alpha-induced ET-1 production through inhibitions of ROS-dependent JNK and ROS-independent p38 MAPK that regulated NF-kappaB as well as AP-1. These findings suggest that MPA could have an effect of amelioration of atherosclerosis.

Small-molecule NOX inhibitors: ROS-generating NADPH oxidases as therapeutic targets

NOX NADPH oxidases are electron-transporting membrane enzymes whose primary function is the generation of reactive oxygen species (ROS). ROS produced by NOX enzymes show a variety of biologic functions, such as microbial killing, blood pressure regulation, and otoconia formation. Strong evidence suggests that NOX enzymes are major contributors to oxidative damage in pathologic conditions. Blocking the undesirable actions of NOX enzymes, therefore, is a therapeutic strategy for treating oxidative stress-related pathologies, such as ischemia/reperfusion tissue injury, and neurodegenerative and metabolic diseases. Most currently available NOX inhibitors have low selectivity, potency, and bioavailability, precluding a pharmacologic demonstration of NOX as therapeutic targets in vivo. This review has two main purposes. First, we describe a systematic approach that we believe should be followed in the search for truly selective NOX inhibitors. Second, we present a critical review of small-molecule NOX inhibitors described over the last two decades, including recently published patents from the pharmaceutical industry. Structures, activities, and in vitro/in vivo specificity of these NOX inhibitors are discussed. We conclude that NOX inhibition is a pertinent and promising novel pharmacologic concept, but that major efforts will be necessary to develop specific NOX inhibitors suited for clinical application.

Antioxidant effects of mycophenolate mofetil in a murine pleurisy model

Generation of oxidative stress induced by reactive oxygen species (ROS) and nitrogen (RNS) is believed to be a primary factor in the etiology of various inflammatory diseases. Although, the process of generation of oxygen species is a physiological event, in the inflammatory process this event is increased and produces large amounts of reactive species that leads to lipid peroxidation and to cell death. Mycophenolate mofetil (MMF) is a drug effective in protecting against chronic allograft failure and recently was introduced as an alternative for the treatment of various inflammatory diseases such as glomerulopathies, systemic lupus erythematosus and systemic vasculitis. Based on studies of the anti-inflammatory effect of MMF the aim of this study was to evaluate the effects of MMF on the inhibition of leukocytes and exudation, as well as myeloperoxidase and some antioxidant enzyme activities using carrageenan-induced pleurisy in mice. Our results showed that MMF significantly decreased leukocyte influx (P<0.01), exudation (P<0.01), superoxide dismutase (P<0.05), catalase (P<0.05), glutathione peroxidase (P<0.01), glutathione S-transferase (P<0.01) activities, levels of lipid peroxidation (P<0.05), as well as myeloperoxidase activity (P<0.05) on both phases (4h and 48h) of the inflammatory response induced by carrageenan into the mice pleural cavity. In conclusion, the anti-inflammatory effect of MMF may be, at least in part, via inhibition of ROS and/or NRS overgeneration, and consequently, attenuating the related oxidative stress.

Elevated serum uric acid levels following heart transplantation predict all-cause and cardiac mortality

AIMS

We evaluated the relationship between elevated serum uric acid (SUA) and mortality as well as cardiac allograft vasculopathy (CAV) among 184 heart transplant (HTx) recipients. We also measured inflammatory, neurohormonal, and oxidative stress markers to explore pathophysiological mechanisms.

METHODS AND RESULTS

There were 28 (15%) deaths, patients with SUA > or = 502 micromol/L (upper quartile) at 1 year post-HTx had an increased risk of total mortality (adjusted HR 2.21, P = 0.03) and cardiac mortality (adjusted HR 4.38, P = 0.03). Elevated SUA was a significant risk factor for development of moderate/severe angiographic CAV (adjusted HR 4.79, P = 0.01). A smaller decline in SUA (<97 micromol/L) during the first year post-HTx was also associated with an increased risk of mortality (P = 0.02). Patients with elevated SUA had significantly higher levels of high-sensitivity C-reactive protein (P = 0.008) and N-terminal probrain natriuretic peptide (P = 0.022), but there was no significant difference in oxidative stress parameters.

CONCLUSION

Elevated SUA at 1 year post-HTx, or a modest rather than a marked decline in SUA levels during the first year post-HTx, is associated with an increased risk of mortality. Although the pathophysiological mechanism is unclear, our data indicate a potential relationship between SUA and inflammation which should be explored further.

Reduced post-operative neutrophil activation in liver transplant recipients suffering from post-hepatitic cirrhosis

BACKGROUND

It has been supposed that liver transplant recipients with hepatitis C virus infection have a higher incidence of infectious complications after transplantation. This study was designed to investigate whether neutrophil function is immediately affected by liver transplantation.

METHODS

Biochemical values, plasma levels of myeloperoxidase (MPO), hydrogen peroxide production of neutrophils and neutrophil-platelet complexes were analyzed in 32 patients who underwent liver transplantation and 20 healthy volunteers.

RESULTS

MPO levels were significantly increased 24 h after reperfusion. In post-hepatitic patients levels were significantly lower three d up to one wk post-transplant than in patients due to other liver diseases. One wk post-operatively the respiratory burst activity following N-formyl-methionyl-leucylphenylalanine (fMLP) or (tumor necrosis factor-alpha) TNF-alpha/fMLP stimulation was depressed in post-hepatitic recipients. Respiratory burst stimulated with phorbol 12-myristate 13-acetate in these patients was increased one wk after transplantation. One d after transplantation the neutrophil-platelet complexes decreased significantly throughout the post-operative period.

CONCLUSIONS

The results of this study suggest a reduced post-operative neutrophil activation in liver transplant recipients suffering from post-hepatitic cirrhosis compared to cirrhosis due to other causes. We hypothesized that neutrophil dysfunction in those patients depends on the underlying disease with an increased susceptibility to bacterial or fungal infections.

Role of rho-kinase in the regulation of vascular tone in hypertensive renal transplant recipients

Activation of rho-kinase (ROK) is involved in the development of hypertension as it is a potent regulator of vascular smooth muscle cell (VSMC) contractility. Here we evaluated whether activation of ROK is present in hypertensive kidney transplant recipients (NTX). We tested the effect of the ROK-inhibitor fasudil on the regulation of forearm blood flow (FBF) in NTX and in healthy control subjects (CTL). In addition potential modulating effects of ROK-inhibition on local vascular nitric oxide (NO) release were studied. The effect of intra-arterial infusion of fasudil on FBF was studied by venous-occlusion plethysmography in NTX and CTL. To unmask the role of NO fasudil was infused with/without clamping of vascular NO in NTX and CTL. To unravel the basal NO-mediated tone the NO-synthase inhibitor l-NMMA was infused. Fasudil markedly but comparably increased FBF in NTX and CTL. The vascular response to fasudil was blunted during NO-clamp in CTL (104+/-18% vs. 244+/-48% for NO-clamp+fasudil vs. fasudil alone; baseline=0%, P<0.05) but not in NTX. The l-NMMA-induced vasoconstriction was impaired in NTX compared to CTL. In NTX and CTL basal vascular tone equally depends on ROK. Fasudil-induced vasodilatation is partly mediated by vascular NO in CTL but not in NTX. The greater NO-insensitive fasudil-induced increase in FBF in NTX suggests an increased ROK-mediated VSMC constrictor tone in these patients. Basal NO-mediated tone is attenuated in hypertensive NTX.

Mycophenolic acid inhibits oleic acid-induced mesangial cell activation through both cellular reactive oxygen species and inosine monophosphate dehydrogenase 2 pathways

The synthesis of extracellular matrix (ECM) in mesangial cells (MCs) plays important roles in the development and progression of renal diseases, including chronic allograft nephropathy. Mycophenolic acid (MPA), an inhibitor of inosine monophosphate dehydrogenase 2 (IMPDH2), suppresses MC proliferation and ECM synthesis. However, the exact inhibitory mechanism of MPA on MCs has not been clearly elucidated. In this study we compared the inhibitory effects of MPA and IMPDH2 reduction [by using small interfering RNA (siRNA)] on oleic acid (OA)-induced fibronectin secretion and cellular reactive oxygen species (ROS) in mouse MCs. Growth-arrested MCs were stimulated with OA in the presence or absence of MPA, IMPDH2 siRNA, N-acetylcysteine (NAC), transforming growth factor beta (TGF-beta) antibody or exogenous guanosine. Fibronectin secretion into the medium was examined by Western blot, dichlorodihydrofluorescein (DCF)-sensitive cellular ROS by fluorescence-activated cell scanning (FACS), TGF-beta levels in the media by enzyme-linked immunosorbent assay (ELISA). OA increased fibronectin secretion, TGF-beta and cellular ROS levels. A TGF-beta neutralizing antibody effectively suppressed OA-induced fibronectin secretion. NAC and MPA completely suppressed OA-induced fibronectin secretion and decreased the levels of TGF-beta and cellular ROS. However, IMPDH2 siRNA partly inhibited OA-induced MC activation. Exogenous guanosine successfully reversed the inhibitory effects of IMPDH2 siRNA on OA-induced MC activation. Pleiotropic inhibitory effect of MPA on OA-induced mouse MC activation was mediated via its antioxidant effect on cellular ROS production and partly via inhibition of IMPDH2 itself. Our results implicate ROS as an alternative therapeutic target for the prevention of hyperlipidemia-related glomerulopathy, chronic allograft nephropathy, and subsequent graft loss.

Mycophenolic acid inhibits PMA-induced activation of the neutrophil respiratory burst

Mycophenolate mofetil (MMF) is commonly used in immunosuppressive regimens for solid organ transplantation. There is evidence that the hydrolyzed active agent mycophenolic acid (MPA) causes the endothelial depletion of intracellular guanosine 5'-triphosphate (GTP) levels. This depletion may cause inactivation of nicotinamide adenine dinucleotide phosphate oxidase. The purpose of the present study was to examine the impact of MPA on the neutrophil respiratory burst and phagocytic activity using flow cytometry. In whole blood of healthy volunteers, 2 different doses of MPA (1 and 10 mumol/L) did not alter hydrogen peroxide production of neutrophils induced by receptor-dependent activators. In contrast, MPA inhibits the protein kinase C (PKC)-mediated hydrogen peroxide production by phorbol 12-myristate 13-acetate (PMA) in a time-dependent manner (negative: 21.17 +/- 1.64 vs. 120 min: 14.46 +/- 1.28 mean fluorescence intensity, incubation with 1 mumol/L MPA). In conclusion, our results corroborated that the neutrophil respiratory burst activity of healthy volunteers, induced by either formyl-methionyl-leucylphenylalanine (fMLP), priming with tumor necrosis factor alpha followed by fMLP or Escherichia coli and neutrophil phagocytic capacity, were not significantly affected after MPA treatment. We also could demonstrate that the hydrogen peroxide production of neutrophils decreased in response to the PKC activator PMA in a time-dependent manner.

Effects of mycophenolic Acid on high glucose-induced fibronectin secretion and cellular reactive oxygen species in rat vascular smooth muscle cells

Vascular smooth muscle cell (VSMC) proliferation, migration, and matrix protein accumulation play important roles in the development and progression of vascular disease including diabetic vascular complications and chronic allograft vasculopathy. Mycophenolic acid (MPA) inhibits various mesenchymal cell proliferation and matrix protein accumulation and reactive oxygen species (ROS). In this study, we investigated the effects of MPA on high glucose (HG)-induced fibronectin secretion and the role of ROS in rat VSMCs. Primary cultured rat VSMCs from Sprague-Dawley rats were exposed for 1 hour before stimulation with media containing 5.6 mmol/L glucose (low glucose [LG]), 30 mmol/L mannitol (M), or 30 mmol/L glucose (HG) with or without MPA (0.1-10 micromol/L) or N-acetylcysteine (NAC; 5 mmol/L). Fibronectin secretion was measured by Western blot analysis and dichlorofluorescein (DCF)-sensitive cellular ROS by flow cytometry. HG significantly increased fibronectin secretion by 1.7-fold. The increment of DCF-sensitive cellular ROS was 1.5-fold at 1 hour by HG. MPA at concentrations above 1 micromol/L effectively inhibited HG-induced fibronectin secretion and cellular ROS in a dose-dependent manner. NAC at 5 mmol/L also inhibited HG-induced rat VSMC activation. These results suggested that MPA inhibits HG-induced VSMC activation partially through inhibiting cellular ROS.

Oxidative stress and 'monocyte reprogramming' after kidney transplant: a longitudinal study

Uremia has been implicated in increased oxidative stress (OS) and decreased monocyte HLA-DR expression in chronic kidney disease (CKD) patients. Thus, one would expect normalization of these parameters after successful kidney transplant (KTx). Our aim was to describe patterns of OS and HLA-DR expression after KTx and to explore the effect of renal function and different immunosuppression regimens. 30 KTx patients (20 male; 48 +/- 11 years) were enrolled and compared with 20 healthy controls. We measured advanced oxidation protein products (AOPP) and the percentage of monocytes expressing HLA-DR (%DR+) before (preKTx) and after KTx (on days 2, 30, 90, 180 and after 1 year). Compared to controls, patients had a higher preKTx AOPP (152.6 vs. 69.3 micromol/l; p < 0.001). AOPP decreased at 48 h after KTx, achieving values similar to controls. Thereafter, it increased again and remained significantly higher compared to controls, returning to preKTx levels at 90 days. Prior to KTx there was a trend for lower %DR+ in KTx patients compared to controls (96 vs. 98%; NS). Following KTx, patients had a lower %DR+ in the 1st month; then it gradually returned to preKTx levels during the 1st year; at no time did it reach a value similar to controls. Cyclosporine (CyA)-treated patients had a significantly higher AOPP (161.5 vs. 99.5 micromol/l; p = 0.03) and a lower %DR+ (91.7 vs. 96.4; p < 0.05) at 30 days than patients on tacrolimus (FK). Patients on mycophenolate mofetil (MMF) showed a low AOPP (106.9 vs. 168.1 micromol/l; p = 0.05) and a high %DR+ (96.7 vs. 88.2%; p = 0.001) than those on everolimus. After 3 months, CyA-treated patients had a non-significant increase in AOPP levels, whereas those on FK showed a decrease (p < 0.05) as did those treated with MMF (p < 0.05). Successful KTx reduced but did not normalize AOPP, suggesting ongoing OS, perhaps due to persistent mild renal dysfunction and the effects of immunosuppression. HLA-DR expression remained low after KTx, which may be a possible contributing factor to infectious complications after transplantation. Immunosuppressive agents appear to have diverse effects on OS and HLA-DR expression.

Mechanism of homocysteine-induced Rac1/NADPH oxidase activation in mesangial cells: role of guanine nucleotide exchange factor Vav2

We have demonstrated that homocysteine (Hcys) stimulates de novo ceramide synthesis and thereby induces NADPH oxidase activation by increase of Rac GTPase activity in rat mesangial cells (RMCs). However, which isofrom of Rac GTPases is involved in Hcys-induced NADPH oxidase activity and what mechanism mediates Hcys-induced Rac GTPase activation remain unknown. The present study first addressed the role of Rac1 and then determined the contribution of a subfamily of Guanine Nucleotide Exchange Factors (GEFs), Vav, to the action of Hcys on Rac and NADPH oxidase activities in RMCs. By small interfering RNA (siRNA), it was found that Rac1-siRNA attenuated Hcys-induced superoxide (O(2)(-)) production. To explore the mechanism activating Rac by Hcys, GEF-Vav was examined. Vav2 was found to be a predominant isoform among Vav family in RMCs. In Vav2-siRNA transfected RMCs, Hcys-induced Rac activity was blocked, which was accompanied by significant reduction of Hcys-induced O(2)(-). production. This Vav2-siRNA also blocked Rac activation induced by C16-Ceramide (C16-Cer), an intermediate lipid product stimulated by Hcys. Furthermore, we found that Hcys induced Vav2 phosphorylation in a time-dependent manner, which could be induced by C16-Cer and blocked by inhibition of de novo ceramide synthesis. These results suggest that Vav2 importantly contributes to Hcys-induced increase in Rac1 activity and consequent activation of NADPH oxidase in RMCs via ceramide-associated tyrosine phosphorylation.

Mycophenolic acid inhibits oleic acid-induced vascular smooth muscle cell activation by inhibiting cellular reactive oxygen species

BACKGROUND

Vascular smooth muscle cell (VSMC) proliferation and matrix protein accumulation play important roles in the development and progression of chronic allograft vasculopathy. Mycophenolic acid (MPA) inhibits various types of mesenchymal cell proliferation and cellular reactive oxygen species (ROS) are involved in the anti-proliferative effect of MPA. In this study, we investigated the effects of MPA on oleic acid (OA)-induced VSMC proliferation and the role of ROS in this process.

METHODS

Primary VSMCs from Sprague-Dawley rats were stimulated with 100 microM OA, with or without MPA (0.1- 10 microM) or 5 mM N-acetylcysteine (NAC) for one hour prior to the addition of OA. Cell proliferation was measured by methylthiazoletetrazolium (MTT) assays, proliferating cell nuclear antigen (PCNA) expression, and fibronectin secretion by Western blot analysis, and dichlorofluorescein (DCF)-sensitive cellular ROS by fluorescence-activated cell scanning (FACS).

RESULTS

OA (100 microM) increased cell proliferation, as measured by MTT (by 1.6-fold), PCNA expression, fibronectin secretion, and cellular ROS (by 1.6-fold). Treatment with MPA dose-dependently inhibited OA-induced VSMC proliferation, fibronectin secretion, and cellular ROS. Treatment with 5 mM NAC also inhibited OA-induced rat VSMC activation.

CONCLUSIONS

These results suggest that MPA inhibits OA-induced VSMC proliferation and matrix protein synthesis partially by inhibiting cellular ROS.

Dietary sesamin suppresses aortic NADPH oxidase in DOCA salt hypertensive rats

1. Dietary sesamin, a sesame lignan, is known to suppress the development of experimental hypertension in rats partly through its inhibitory effect on vascular O(2)(-) production. Therefore, in the present study, we examined whether sesamin feeding had any effect on vascular NADPH oxidase using aortas from deoxycorticosterone acetate (DOCA) salt hypertensive rats. 2. After a 5 week feeding and treatment period, aortic O(2)(-) production and NADPH oxidase activity were measured using the lucigenin assay. Reverse transcription-polymerase chain reaction was performed to analyse aortic expression of NADPH oxidase subunit (p22phox, gp91phox, Nox1 and Nox4) mRNA. 3. Sesamin feeding markedly suppressed DOCA salt-induced hypertension and significantly decreased aortic O(2)(-) production. DOCA salt treatment increased NADPH oxidase activity and elevated aortic mRNA expression of p22phox, gp91phox, Nox1 and Nox4. Sesamin feeding abolished the increase in NADPH oxidase activity and, furthermore, significantly suppressed increases in p22phox, gp91phox and Nox1 mRNA expression. 4. In conclusion, dietary sesamin prevented DOCA salt-induced increases in NADPH oxidase activity and subunit mRNA expression. These effects seem to be involved in the anti-oxidant and antihypertensive effects of sesamin.

Angiotensin II-induced reactive oxygen species and the kidney

Angiotensin II (AngII) is an important mediator in renal injury. Accumulating evidence suggests that AngII stimulates intracellular formation of reactive oxygen species (ROS) such as the superoxide anion and hydrogen peroxide. AngII activates several subunits of the membrane-bound multicomponent NAD(P)H oxidase and also increases ROS formation in the mitochondria. Some of these effects may be induced by aldosterone and not directly by AngII. The superoxide anion and hydrogen peroxide influence other downstream signaling pathways, such as transcription factors, tyrosine kinases/phosphatases, ion channels, and mitogen-activated protein kinases. Through these signaling pathways, ROS have distinct functional effects on renal cells. They are transducers of cell growth, apoptosis, and cell migration and affect expression of inflammatory and extracellular matrix genes. For example, AngII-mediated expression of p27(Kip1), a cell-cycle regulatory protein, and induction of tubular hypertrophy depend on the generation of ROS. The effects of ROS generated within different renal cells ultimately depend on the locally generated concentrations and the balance of pro- and antioxidant pathways. Although the concept that AngII mediates oxidative stress in the kidney has been validated in experimental models, the exact role is still incompletely understood in human renal diseases.

Cytotoxicity of paraquat in microglial cells: Involvement of PKCdelta- and ERK1/2-dependent NADPH oxidase

Excess production of reactive oxygen species (ROS) is an important mechanism underlying the pathogenesis of a number of neurodegenerative diseases including Parkinson's disease (PD) which is characterized by a progressive loss of dopaminergic neurons in the substantia nigra. Exposure to paraquat, an herbicide with structure similar to the dopaminergic neurotoxin, 1-methyl-4-phenylpyridinium (MPP+), has been shown to produce PD-like symptoms. Despite previous focus on the dopaminergic neurons and signaling pathways involved in their cell death, recent studies have implicated microglial cells as a major producer of ROS for damaging neighboring neurons. In this study, we examined the source of ROS and the underlying signaling pathway for paraquat-induced cytotoxicity to BV-2 microglial cells. Paraquat-induced ROS production (including superoxide anions) in BV-2 cells was accompanied by translocation of the p67phox cytosolic subunit of NADPH oxidase to the membrane. Paraquat-induced ROS production was inhibited by NADPH oxidase inhibitors, apocynin and diphenylene iodonium (DPI), but not the xanthine/xanthine oxidase inhibitor, allopurinol. Apocynin and DPI also rescued cells from paraquat-induced toxicity. The inhibitors for protein kinase C delta (PKCdelta) or extracellular signal-regulated kinases (ERK1/2) could partially attenuate paraquat-induced ROS production and cell death. Rottlerin, a selective PKCdelta inhibitor, also inhibited paraquat-induced translocation of p67phox. Taken together, this study demonstrates the involvement of ROS from NADPH oxidase in mediating paraquat cytotoxicity in BV-2 microglial cells and this process is mediated through PKCdelta- and ERK-dependent pathways.