Insulin-stimulated production of nitric oxide is inhibited by wortmannin. Direct measurement in vascular endothelial cells

Hypertension is associated with insulin-resistant states such as diabetes and obesity. Nitric oxide (NO) contributes to regulation of blood pressure. To gain insight into potential mechanisms linking hypertension with insulin resistance we directly measured and characterized NO production from human umbilical vein endothelial cells (HUVEC) in response to insulin using an amperometric NO-selective electrode. Insulin stimulation of HUVEC resulted in rapid, dose-dependent production of NO with a maximal response of approximately 100 nM NO (200,000 cells in 2 ml media; ED50 approximately 500 nM insulin). Although HUVEC have many more IGF-1 receptors than insulin receptors (approximately 400,000, and approximately 40,000 per cell respectively), a maximally stimulating dose of IGF-1 generated a smaller response than insulin (40 nM NO; ED50 approximately 100 nM IGF-1). Stimulation of HUVEC with PDGF did not result in measurable NO production. The effects of insulin and IGF-1 were completely blocked by inhibitors of either tyrosine kinase (genestein) or nitric oxide synthase (L-NAME). Wortmannin (an inhibitor of phosphatidylinositol 3-kinase [PI 3-kinase]) inhibited insulin-stimulated production of NO by approximately 50%. Since PI 3-kinase activity is required for insulin-stimulated glucose transport, our data suggest that NO is a novel effector of insulin signaling pathways that are also involved with glucose metabolism.

Roles for insulin receptor, PI3-kinase, and Akt in insulin-signaling pathways related to production of nitric oxide in human vascular endothelial cells

BACKGROUND

Previously, we demonstrated that insulin stimulates production of nitric oxide (NO) in endothelial cells. However, specific insulin-signaling pathways mediating production of NO have not been elucidated.

METHODS AND RESULTS

We developed methods for transfection of human umbilical vein endothelial cells (HUVECs) and direct measurement of NO to begin defining insulin-signaling pathways related to NO production. HUVECs were cotransfected with enhanced Green Fluorescent Protein (eGFP) and another gene of interest. Transfection efficiencies >95% were obtained by selecting cells expressing eGFP. Overexpression of insulin receptors in HUVECs resulted in an approximately 3-fold increase in production of NO in response to insulin. In contrast, HUVECs overexpressing a tyrosine kinase-deficient mutant insulin receptor had a dose-response curve similar to that of control cells. Overexpression of inhibitory mutants of either phosphatidylinositol 3-kinase (PI3K) or Akt resulted in nearly complete inhibition of insulin-stimulated production of NO. Overexpression of an inhibitory mutant of Ras had a much smaller effect.

CONCLUSIONS

Receptor kinase activity is necessary to mediate production of NO through the insulin receptor. Both PI3K and Akt contribute importantly to this process, whereas the contribution of Ras is small.

Age-related changes in the default mode network are more advanced in Alzheimer disease

OBJECTIVE

To investigate age-related default mode network (DMN) connectivity in a large cognitively normal elderly cohort and in patients with Alzheimer disease (AD) compared with age-, gender-, and education-matched controls.

METHODS

We analyzed task-free-fMRI data with both independent component analysis and seed-based analysis to identify anterior and posterior DMNs. We investigated age-related changes in connectivity in a sample of 341 cognitively normal subjects. We then compared 28 patients with AD with 56 cognitively normal noncarriers of the APOE ε4 allele matched for age, education, and gender.

RESULTS

The anterior DMN shows age-associated increases and decreases in fontal lobe connectivity, whereas the posterior DMN shows mainly age-associated declines in connectivity throughout. Relative to matched cognitively normal controls, subjects with AD display an accelerated pattern of the age-associated changes described above, except that the declines in frontal lobe connectivity did not reach statistical significance. These changes survive atrophy correction and are correlated with cognitive performance.

CONCLUSIONS

The results of this study indicate that the DMN abnormalities observed in patients with AD represent an accelerated aging pattern of connectivity compared with matched controls.

Role of tumor-associated gangliosides in cancer progression

Neuroectodermic tumors can mostly be characterized by the presence of tumor-associated glycosphingolipid antigens, such as gangliosides, defined by monoclonal antibodies. Recently, cumulative evidence indicates that gangliosides modify the biological effects of several trophic factors, in vitro and in vivo, as well as the mitogenic signaling cascade that these factors generate. The functional roles of gangliosides in tumor progression can be revisited: (i) ganglioside antigens on the cell surface, or shed from the cells, act as immunosuppressors, as typically observed for the suppression of cytotoxic T cells and dendritic cells, (ii) certain gangliosides, such as GD3 or GM2, promote tumor-associated angiogenesis, (iii) gangliosides strongly regulate cell adhesion/motility and thus initiate tumor metastasis, (iv) ganglioside antigens are directly connected with transducer molecules in microdomains to initiate adhesion coupled with signaling, and (v) ganglioside antigens and their catabolites are modulators of signal transduction through interaction with tyrosine kinases associated with growth factor receptors or other protein kinases. Given the potential importance of these sialylated gangliosides and their modulating biological behavior in vivo, further studies on the role of gangliosides are warranted.

Transgenic animals with inducible, targeted gene expression in brain

Several inducible gene expression systems have been developed in vitro in recent years to overcome limitations with traditional transgenic mice. One of these, the tetracycline-regulated system, has been used successfully in vivo. Nevertheless, concerns remain about the ability of this system to direct high levels of transgene expression in vivo and to enable such expression to be turned on and off effectively. We report here the generation, using a modified tetracycline-regulated system under the control of the neuron-specific enolase promoter, of several lines of mice that direct transgene expression to specific brain regions, including the striatum, cerebellum, CA1 region of the hippocampus, or deep layers of cerebral neocortex. Transgene expression in these mice can be turned off completely with low doses of doxycycline (a tetracycline derivative) and driven to very high levels in the absence of doxycycline. We demonstrate this tissue-specific, inducible expression for three transgenes: those that encode luciferase (a reporter protein) or DeltaFosB or the cAMP-response element binding protein (CREB) (two transcription factors). The various lines of transgenic mice demonstrate an inducible system that generates high levels of transgene expression in specific brain regions and represent novel and powerful tools with which to study the functioning of these (or potentially any other) genes in the brain.

CD4(+) T cell recognition of MHC class II-restricted epitopes from NY-ESO-1 presented by a prevalent HLA DP4 allele: association with NY-ESO-1 antibody production

NY-ESO-1 is a tumor-specific shared antigen with distinctive immunogenicity. Both CD8(+) T cells and class-switched Ab responses have been detected from patients with cancer. In this study, a CD4(+) T cell line was generated from peripheral blood mononuclear cells of a melanoma patient and was shown to recognize NY-ESO-1 peptides presented by HLA-DP4, a dominant MHC class II allele expressed in 43--70% of Caucasians. The ESO p157--170 peptide containing the core region of DP4-restricted T cell epitope was present in a number of tumor cell lines tested and found to be recognized by both CD4(+) T cells as well as HLA-A2-restricted CD8(+) T cells. Thus, the ESO p157--170 epitope represents a potential candidate for cancer vaccines aimed at generating both CD4(+) and CD8(+) T cell responses. More importantly, 16 of 17 melanoma patients who developed Ab against NY-ESO-1 were found to be HLA-DP4-positive. CD4(+) T cells specific for the NY-ESO-1 epitopes were generated from 5 of 6 melanoma patients with NY-ESO-1 Ab. In contrast, no specific DP4-restricted T cells were generated from two patients without detectable NY-ESO-1 Ab. These results suggested that NY-ESO-1-specific DP4-restricted CD4(+) T cells were closely associated with NY-ESO-1 Ab observed in melanoma patients and might play an important role in providing help for activating B cells for NY-ESO-1-specific Ab production.

Senolytic agent Quercetin ameliorates intervertebral disc degeneration via the Nrf2/NF-κB axis

OBJECTIVE

Intervertebral disc degeneration (IDD) represents major cause of low back pain. Quercetin (QUE) is one of the approved senolytic agents. In this study, we evaluated the protective effects of QUE on IDD development and its underlying mechanism.

METHODS

Effects of senolytic agent QUE on the viability of nucleus pulposus cells (NPCs) were measured by CCK-8 assays and EdU staining. The senescence associated secreted phenotype (SASP) factors expressions were measured by qPCR, western blot, and ELISA; and NF-κB pathway was detected by immunofluorescence and western blot. Molecular docking was applied to predict the interacting protein of QUE; while Nrf2 was knocked down by siRNAs to confirm its role in QUE regulated senescence phenotype. X-ray, MRI, Hematoxylin-Eosin and Safranin O-Fast green staining were performed to evaluate the therapeutic effects of QUE on IDD in the puncture-induced rat model.

RESULTS

In in vitro experiments, QUE inhibited SASP factors expression and senescence phenotype in IL-1β-treated NPCs. Mechanistically, QUE suppressed IL-1β induced activation of the NF-κB pathway cascades; it was also demonstrated in molecular docking and knock down studies that QUE might bind to Keap1-Nrf2 complex to suppress NF-κB pathway. In vivo, QUE ameliorated the IDD process in the puncture-induced rat model.

CONCLUSIONS

Together the present work suggests that QUE inhibits SASP factors expression and senescence phenotype in NPCs and ameliorates the progression of IDD via the Nrf2/NF-κB axis, which supports senolytic agent QUE as a potential therapeutic agent for the treatment of IDD.

Geographic distribution, virologic and clinical characteristics of hepatitis B virus genotypes in China

The significance of hepatitis B virus (HBV) genotypes for the heterogeneity of chronic HBV infection and severity of liver disease is not well understood. The aim of this study was to determine the distribution and virologic characteristics of HBV genotypes in China and possible association with the diversity of liver disease. The study includes 1096 chronic HBV carriers from nine provinces in China. We collected clinical and laboratory data and analysed the HBV strains in sera by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and nucleotide sequencing techniques. The most common HBV genotypes were B (41%) and C (53%), while genotypes A and D were also found. A North-South divide was identified in genotype B and C distribution - genotype C was predominant in northern China, while genotype B was more prevalent in southern provinces. Patients with genotype B were younger than those with genotype C, and had a lower prevalence of HBeAg - 65%vs 72%, respectively (P = 0.03). However, the severity of liver disease did not differ significantly between patients infected with genotype B or C - neither when comparing liver function tests (1024 patients), nor hepatic inflammation and fibrosis (264 patients). Amongst 47 patients with genotype D (by PCR-RFLP), 37 (79%) were infected with a new subtype (designated Dc), having a recombination fragment from genotype C precore/core region. This is the first large-scale HBV genotype study from China and convincing documentation of the North-to-South gradient of genotypes C vs B in this country. HBV DNA recombination over the surface and precore/core genes increases the diversity of HBV strains and may have diagnostic and clinical implications.

Identification of CD4+ T cell epitopes from NY-ESO-1 presented by HLA-DR molecules

In previous studies, the shared cancer-testis Ag, NY-ESO-1, was demonstrated to be recognized by both Abs and CD8+ T cells. Gene expression of NY-ESO-1 was detected in many tumor types, including melanoma, breast, and lung cancers, but was not found in normal tissues, with the exception of testis. In this study, we describe the identification of MHC class II-restricted T cell epitopes from NY-ESO-1. Candidate CD4+ T cell peptides were first identified using HLA-DR4 transgenic mice immunized with the NY-ESO-1 protein. NY-ESO-1-specific CD4+ T cells were then generated from PBMC of a patient with melanoma stimulated with the candidate peptides in vitro. These CD4+ T cells recognized NY-ESO-1 peptides or protein pulsed on HLA-DR4+ EBV B cells, and also recognized tumor cells expressing HLA-DR4 and NY-ESO-1. A 10-mer peptide (VLLKEFTVSG) was recognized by CD4+ T cells. These studies provide new opportunities for developing more effective vaccine strategies by using tumor-specific CD4+ T cells. This approach may be applicable to the identification of CD4+ T cell epitopes from many known tumor Ags recognized by CD8+ T cells.

Duplex ultrasonography scanning for chronic venous disease: patterns of venous reflux

PURPOSE

Patterns of flow in superficial and deep veins and outward flow in medial calf perforators were studied by duplex ultrasonography scanning in 1653 lower limbs in 1114 consecutive patients. This study compares results in 776 limbs with primary uncomplicated varicose veins with those in 166 limbs with the complications of lipodermatosclerosis or past venous ulceration.

METHODS

Duplex scanning determined whether superficial and deep veins were occluded or showed reflux and whether outward flow occurred in medial calf perforators with calf muscle contraction.

RESULTS

Two proximal deep veins were occluded. When limbs with primary uncomplicated varicose veins, lipodermatosclerosis, or past ulceration were compared, superficial reflux alone was seen in 55%, 39%, and 38%, deep reflux alone was seen in 2%, 7%, and 8%, and combined superficial and deep reflux was seen in 18%, 34%, and 48%, respectively. Superficial reflux affected the long saphenous system alone in 58%, 57%, and 40%, the short saphenous system alone in 18%, 18%, and 26%, and both the long and short saphenous systems in 24%, 25%, and 34%, respectively. Limbs with ulceration more frequently showed superficial reflux (p < 0.05), and all limbs with complications more frequently showed short saphenous reflux (p < 0.05) and deep reflux (p < 0.01) specifically in the posterior tibial veins (p < 0.01). Outward flow was seen in medial calf perforators in 57%, 67%, and 66%, respectively; it occurred more frequently in all limbs with complications (p < 0.05). Isolated outward flow in perforators without superficial or deep reflux was seen in 10%, 10%, and 2%, respectively.

CONCLUSIONS

Most limbs with complications had superficial reflux either alone or combined with deep reflux, and few had deep reflux alone. Reflux was more frequent in posterior tibial veins for limbs with complications compared with those with uncomplicated primary varicose veins. Outward flow in perforators was common in limbs with complications and with uncomplicated primary varicose veins, but isolated outward flow in perforators was uncommon. Treatment directed to the superficial veins alone may be sufficient for most patients with complications.

Characterization of a 12-kilodalton rhodanese encoded by glpE of Escherichia coli and its interaction with thioredoxin

Rhodaneses catalyze the transfer of the sulfane sulfur from thiosulfate or thiosulfonates to thiophilic acceptors such as cyanide and dithiols. In this work, we define for the first time the gene, and hence the amino acid sequence, of a 12-kDa rhodanese from Escherichia coli. Well-characterized rhodaneses are comprised of two structurally similar ca. 15-kDa domains. Hence, it is thought that duplication of an ancestral rhodanese gene gave rise to the genes that encode the two-domain rhodaneses. The glpE gene, a member of the sn-glycerol 3-phosphate (glp) regulon of E. coli, encodes the 12-kDa rhodanese. As for other characterized rhodaneses, kinetic analysis revealed that catalysis by purified GlpE occurs by way of an enzyme-sulfur intermediate utilizing a double-displacement mechanism requiring an active-site cysteine. The K(m)s for SSO(3)(2-) and CN(-) were 78 and 17 mM, respectively. The apparent molecular mass of GlpE under nondenaturing conditions was 22.5 kDa, indicating that GlpE functions as a dimer. GlpE exhibited a k(cat) of 230 s(-1). Thioredoxin 1 from E. coli, a small multifunctional dithiol protein, served as a sulfur acceptor substrate for GlpE with an apparent K(m) of 34 microM when thiosulfate was near its K(m), suggesting that thioredoxin 1 or related dithiol proteins could be physiological substrates for sulfurtransferases. The overall degree of amino acid sequence identity between GlpE and the active-site domain of mammalian rhodaneses is limited ( approximately 17%). This work is significant because it begins to reveal the variation in amino acid sequences present in the sulfurtransferases. GlpE is the first among the 41 proteins in COG0607 (rhodanese-related sulfurtransferases) of the database Clusters of Orthologous Groups of proteins (http://www.ncbi.nlm.nih.gov/COG/) for which sulfurtransferase activity has been confirmed.

Regulation of the actin cytoskeleton organization in yeast by a novel serine/threonine kinase Prk1p

Normal actin cytoskeleton organization in budding yeast requires the function of the Pan1p/ End3p complex. Mutations in PAN1 and END3 cause defects in the organization of actin cytoskeleton and endocytosis. By screening for mutations that can suppress the temperature sensitivity of a pan1 mutant (pan1-4), a novel serine/threonine kinase Prk1p is now identified as a new factor regulating the actin cytoskeleton organization in yeast. The suppression of pan1-4 by prk1 requires the presence of mutant Pan1p. Although viable, the prk1 mutant is unable to maintain an asymmetric distribution of the actin cytoskeleton at 37 degreesC. Consistent with its role in the regulation of actin cytoskeleton, Prk1p localizes to the regions of cell growth and coincides with the polarized actin patches. Overexpression of the PRK1 gene in wild-type cells leads to lethality and actin cytoskeleton abnormalities similar to those exhibited by the pan1 and end3 mutants. In vitro phosphorylation assays demonstrate that Prk1p is able to phosphorylate regions of Pan1p containing the LxxQxTG repeats, including the region responsible for binding to End3p. Based on these findings, we propose that the Prk1 protein kinase regulates the actin cytoskeleton organization by modulating the activities of some actin cytoskeleton-related proteins such as Pan1p/End3p.

Porphyromonas gingivalis Promotes Oral Squamous Cell Carcinoma Progression in an Immune Microenvironment

Increasing evidence has revealed a significant association between microorganisms and oral squamous cell carcinoma (OSCC). Porphyromonas gingivalis, the keystone pathogen in chronic periodontitis, is considered an important potential etiologic agent of OSCC, but the underlying immune mechanisms through which P. gingivalis mediates tumor progression of the oral cancer remain poorly understood. Our cohort study showed that the localization of P. gingivalis in tumor tissues was related to poor survival of patients with OSCC. Moreover, P. gingivalis infection increased oral lesion multiplicity and size and promoted tumor progression in a 4-nitroquinoline-1 oxide (4NQO)–induced carcinogenesis mouse model by invading the oral lesions. In addition, CD11b+ myeloid cells and myeloid-derived suppressor cells (MDSCs) showed increased infiltration of oral lesions. Furthermore, in vitro observations showed that MDSCs accumulated when human-derived dysplastic oral keratinocytes (DOKs) were exposed to P. gingivalis, and CXCL2, CCL2, interleukin (IL)–6, and IL-8 may be potential candidate genes that facilitate the recruitment of MDSCs. Taken together, our findings suggest that P. gingivalis promotes tumor progression by generating a cancer-promoting microenvironment, indicating a close relationship among P. gingivalis, tumor progression of the oral cancer, and immune responses.

Regulation of yeast actin cytoskeleton-regulatory complex Pan1p/Sla1p/End3p by serine/threonine kinase Prk1p

The serine/threonine kinase Prk1p is known to be involved in the regulation of the actin cytoskeleton organization in budding yeast. One possible function of Prk1p is the negative regulation of Pan1p, an actin patch regulatory protein that forms a complex in vivo with at least two other proteins, Sla1p and End3p. In this report, we identified Sla1p as another substrate for Prk1p. The phosphorylation of Sla1p by Prk1p was established in vitro with the use of immunoprecipitated Prk1p and in vivo with the use of PRK1 overexpression, and was further supported by the finding that immunoprecipitated Sla1p contained PRK1- and ARK1-dependent kinase activities. Stable complex formation between Prk1p and Sla1p/Pan1p in vivo could be observed once the phosphorylation reaction was blocked by mutation in the catalytic site of Prk1p. Elevation of Prk1p activities in wild-type cells resulted in a number of deficiencies, including those in colocalization of Pan1p and Sla1p, endocytosis, and cell wall morphogenesis, likely attributable to a disintegration of the Pan1p/Sla1p/End3p complex. These results lend a strong support to the model that the phosphorylation of the Pan1p/Sla1p/End3p complex by Prk1p is one of the important mechanisms by which the organization and functions of the actin cytoskeleton are regulated.

Endogenous TGF-beta activity is modified during cellular aging: effects on metalloproteinase and TIMP-1 expression

In culture, nontransformed human diploid fibroblasts divide a limited number of times, resulting in a nonproliferating senescent cell culture which exhibits an altered pattern of gene expression. Previously we reported that an early event in the process of replicative senescence was an increase in the synthesis of two connective tissue degrading metalloproteinases, collagenase and stromelysin, and a decrease in the synthesis of the physiological inhibitor of those enzymes, tissue inhibitor of metalloproteinases-1 (TIMP-1). The cytokine TGF-beta1 is known to regulate the expression of each of these three genes and to be synthesized and secreted by cultured human fibroblasts. This suggested the hypothesis that the age-specific modulation of collagenase, stromelysin, and TIMP-1 expression is the result of a change in TGF-beta1 activity during replicative senescence. To test this hypothesis, the responses of early, mid, and late passage (presenescent) fibroblast cell cultures to a TGF-beta neutralizing antibody were evaluated. In early passage cell cultures, exposure to TGF-beta neutralizing antibody resulted in a significant increase in the expression of collagenase and stromelysin and decreased TIMP-1 expression. The antibody did not affect expression of either of those genes by late passage cell cultures, although late passage cultures did respond to added TGF-beta1. Quantification of the levels of active TGF-beta, using a growth inhibition assay, indicates that the level of active TGF-beta1 is decreased during replicative senescence, supporting the conclusion that the modulation of collagenase, stromelysin, and TIMP-1 expression results from diminished TGF-beta activity.

Repressor for the sn-glycerol 3-phosphate regulon of Escherichia coli K-12: primary structure and identification of the DNA-binding domain

The nucleotide sequence of the glpEGR operon of Escherichia coli was determined. The translational reading frame at the beginning, middle, and end of each gene was verified. The glpE gene encodes an acidic, cytoplasmic protein of 108 amino acids with a molecular weight of 12,082. The glpG gene encodes a basic, cytoplasmic membrane-associated protein of 276 amino acids with a molecular weight of 31,278. The functions of GlpE and GlpG are unknown. The glpR gene encodes the repressor for the glycerol 3-phosphate regulon, a protein predicted to contain 252 amino acids with a calculated molecular weight of 28,048. The amino acid sequence of the glp repressor was similar to several repressors of carbohydrate catabolic systems, including those of the glucitol (GutR), fucose (FucR), and deoxyribonucleoside (DeoR) systems of E. coli, as well as those of the lactose (LacR) and inositol (IolR) systems of gram-positive bacteria and agrocinopine (AccR) system of Agrobacterium tumefaciens. These repressors constitute a family of related proteins, all of which contain approximately 250 amino acids, possess a helix-turn-helix DNA-binding motif near the amino terminus, and bind a sugar phosphate molecule as the inducing signal. The DNA recognition helix of the glp repressor and the nucleotide sequence of the glp operator were very similar to those of the deo system. The presumptive recognition helix of the glp repressor was changed by site-directed mutagenesis to match that of the deo repressor or, in a separate construct, to abolish DNA binding. Neither altered form of the glp repressor recognized the glp or deo operator, either in vivo or in vitro. However, both altered forms of the glp repressor were negatively dominant to the wild-type glp repressor, indicating that the inability to bind DNA with high affinity was due to alteration of the DNA-binding domain, not to an inability to oligomerize or instability of the altered repressors. For the first time, analysis of repressors with altered DNA-binding domains has verified the assignment of the helix-turn-helix motif of the transcriptional regulators in the deoR family.

Commercially available immunoglobulins contain virus neutralizing antibodies against all major genotypes of polyomavirus BK

Neutralizing antibodies (NAbs) form the basis of immunotherapeutic strategies against many important human viral infections. Accordingly, we studied the prevalence, titer, genotype-specificity, and mechanism of action of anti-polyomavirus BK (BKV) NAbs in commercially available human immune globulin (IG) preparations designed for intravenous (IV) use. Pseudovirions (PsV) of genotypes Ia, Ib2, Ic, II, III, and IV were generated by co-transfecting a reporter plasmid encoding luciferase and expression plasmids containing synthetic codon-modified VP1, VP2, and VP3 capsid protein genes into 293TT cells. NAbs were measured using luminometry. All IG preparations neutralized all BKV genotypes, with mean EC50 titers as high as 254 899 for genotype Ia and 6,666 for genotype IV. Neutralizing titers against genotypes II and III were higher than expected, adding to growing evidence that infections with these genotypes are more common than currently appreciated. Batch to batch variation in different lots of IG was within the limits of experimental error. Antibody mediated virus neutralizing was dose dependent, modestly enhanced by complement, genotype-specific, and achieved without effect on viral aggregation, capsid morphology, elution, or host cell release. IG contains potent NAbs capable of neutralizing all major BKV genotypes. Clinical trials based on sound pharmacokinetic principles are needed to explore prophylactic and therapeutic applications of these anti-viral effects, until effective small molecule inhibitors of BKV replication can be developed.

The global atmospheric environment for the next generation

Air quality, ecosystem exposure to nitrogen deposition, and climate change are intimately coupled problems: we assess changes in the global atmospheric environment between 2000 and 2030 using 26 state-of-the-art global atmospheric chemistry models and three different emissions scenarios. The first (CLE) scenario reflects implementation of current air quality legislation around the world, while the second (MFR) represents a more optimistic case in which all currently feasible technologies are applied to achieve maximum emission reductions. We contrast these scenarios with the more pessimistic IPCC SRES A2 scenario. Ensemble simulations for the year 2000 are consistent among models and show a reasonable agreement with surface ozone, wet deposition, and NO2 satellite observations. Large parts of the world are currently exposed to high ozone concentrations and high deposition of nitrogen to ecosystems. By 2030, global surface ozone is calculated to increase globally by 1.5 +/- 1.2 ppb (CLE) and 4.3 +/- 2.2 ppb (A2), using the ensemble mean model results and associated +/-1 sigma standard deviations. Only the progressive MFR scenario will reduce ozone, by -2.3 +/- 1.1 ppb. Climate change is expected to modify surface ozone by -0.8 +/- 0.6 ppb, with larger decreases over sea than over land. Radiative forcing by ozone increases by 63 +/- 15 and 155 +/- 37 mW m(-2) for CLE and A2, respectively, and decreases by -45 +/- 15 mW m(-2) for MFR. We compute that at present 10.1% of the global natural terrestrial ecosystems are exposed to nitrogen deposition above a critical load of 1 g N m(-2) yr(-1). These percentages increase by 2030 to 15.8% (CLE), 10.5% (MFR), and 25% (A2). This study shows the importance of enforcing current worldwide air quality legislation and the major benefits of going further. Nonattainment of these air quality policy objectives, such as expressed by the SRES-A2 scenario, would further degrade the global atmospheric environment.