Pro-inflammatory cytokines increase reactive oxygen species through mitochondria and NADPH oxidase in cultured RPE cells

Influence of IL-1RN intron 2 variable number of tandem repeats (VNTR) polymorphism on the age at onset of neuropsychiatric symptoms in Wilson's disease

ABSTRACT Wilson's disease (WND) is an autosomal recessive copper storage disease characterized with diverse clinical pictures with the hepatic and/or neuropsychiatric symptoms manifesting at variable age. On the basis of the existing knowledge on possible copper-proinflammatory cytokines interactions, we hypothesized that in WND hereditary, over-/underexpression of PC or anti-inflammatory cytokines may have an impact on the course of the disease. We analyzed the clinical manifestations of WND in relationship to polymorphisms within genes for interleukin-1 receptor antagonist (IL1RN intron 2 VNTR polymorphism), interleukin-1α (IL1A G4845T), IL-1β (IL1B C-511T), IL-6 (IL6 G-174C), and tumor necrosis factor (TNF G-308A) in a total sample of 332 patients. The IL1B C-511T and IL1RN VNTR polymorphisms had an impact on copper metabolism parameters. None of the studied gene polymorphisms had effect on the mode of WND manifestation (neuropsychiatric vs. hepatic). Carriership of the IL1RN *2 allele was related to earlier WND onset, especially among patients with neuropsychiatric form of the disease (median 27.5 vs. 32.0 years, p = .003). Because of the crucial modulatory role of IL1ra on IL-1α and IL-1β proinflammatory functions, IL1ra and its interactions may play a role in the pathogenesis of the neurodegenerative process in WND; our results need to be replicated, possibly in different ethnic groups.

RETRACTED: REDOX regulation of IL-13 signaling in intestinal epithelial cells: usage of alternate pathways mediates distinct gene expression patterns

In the classic view interleukin-13 (IL-13) binds to a heterodimer protein complex of the IL-13Ralpha1 and IL-4Ralpha chains and signals through a Janus kinase 1 (JAK1)-signal transducer and activator of transcription 6 (STAT6) mechanism. We recently reported that IL-13 also signals through the IL-13Ralpha2 chain initiating all three mitogen activated protein kinase (MAPK) pathways, and the relative expression of IL-13Ralpha1 and IL-13Ralpha2 modulates one another's transduction pathway. Therefore we investigated whether generation of reactive oxygen species (ROS) as second messengers may serve as a common nexus between these two pathways emanating from the individual IL-13 receptor chains in intestinal epithelial cells (IEC). IL-13 stimulates intracellular ROS synthesis within 5min via IL-13Ralpha1-JAK1-STAT6- and IL-13Ralpha2-MEK1/2-ERK1/2-dependent activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-1 (NOX-1). IL-13-induced ROS generation in turn positively regulates phosphorylation of ERK1/2 and STAT6, yielding a feed forward amplification loop. IL-13 also stimulates the stable, long-term gene expression of two other NADPH oxidases, NOX-4 and DUOX-2, which along with constitutive NOX-1, might facilitate elevated, continuous production of ROS in IL-13-activated IEC. The contribution of each signal transduction pathway initiated by IL-13 engagement to such biological functions as wound healing, inflammation, and apoptosis was mapped for representative, responsive genes. Distinct usage patterns were observed, demonstrating not only that IL-13 signal transduction through STAT6, MAPK, and ROS is regulated in both an antagonistic and cyclic fashion, but also that each pathway plays a specific role in modulating the wound healing and anti-apoptotic capabilities of the intestinal epithelium.

p53 represses class switch recombination to IgG2a through its antioxidant function

Ig class switch recombination (CSR) occurs in activated mature B cells, and causes an exchange of the IgM isotype for IgG, IgE, or IgA isotypes, which increases the effectiveness of the humoral immune response. DNA ds breaks in recombining switch (S) regions, where CSR occurs, are required for recombination. Activation-induced cytidine deaminase initiates DNA ds break formation by deamination of cytosines in S regions. This reaction requires reactive oxygen species (ROS) intermediates, such as hydroxyl radicals. In this study we show that the ROS scavenger N-acetylcysteine inhibits CSR. We also demonstrate that IFN-gamma treatment, which is used to induce IgG2a switching, increases intracellular ROS levels, and activates p53 in switching B cells, and show that p53 inhibits IgG2a class switching through its antioxidant-regulating function. Finally, we show that p53 inhibits DNA breaks and mutations in S regions in B cells undergoing CSR, suggesting that p53 inhibits the activity of activation-induced cytidine deaminase.

Pro-angiogenic effect of IFNgamma is dependent on the PI3K/mTOR/translational pathway in human retinal pigmented epithelial cells

PURPOSE

To investigate the molecular signaling pathway of Interferon gamma (IFNgamma) contributing to angiogenesis in retinal pigmented epithelial (RPE) cells and the role of Phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) in this process.

METHODS

Human adult and fetal RPE cells were used in this study. Real-time polymerase chain reaction was used to detect human vascular endothelial growth factor (VEGF) mRNA expression. Thiazolyl blue tetrazolium bromide (MTT) assay was used to detect cell viability. VEGF expression from cell supernatant was measured using enzyme-linked immunosorbent assay (ELISA). Small interfering RNA (SiRNA) of signal transducers and activators of transcription 1 (stat1) and protein kinases B (akt) were transfected into ARPE-19 cells to directly study the roles of these molecules in VEGF expression. Sodium dodecyl sulfate PAGE (SDS-PAGE) and western blot analysis were used to detect the expression of signaling molecules.

RESULTS

IFNgamma promoted human VEGF expression in both adult and fetal RPE cells. The PI-3K/Akt/mTOR/p70 S6 kinase pathway is required for IFNgamma-induced VEGF expression in retinal cells. The mTOR inhibitor, rapamycin, along with the SiRNA targeted to akt and the PI3K inhibitor, LY294002, decreased hVEGF secretion from RPE cells. Moreover, IFNgamma-induced hVEGF expression was not affected by SiRNA targeted to Stat1, implying that the classic Jak-Stat1 pathway of IFNgamma may not be involved in this process.

CONCLUSIONS

We provide evidence that IFNgamma induces VEGF expression in human retinal pigment epithelial cells. Our work emphasizes that the activation of the PI-3K/mTOR/translational pathway is important for IFNgamma-mediated VEGF expression in RPE cells. By elucidating molecular signaling involved in this process, our findings provide further mechanistic insight into the successful clinical application of rapamycin therapy for choroidal neovascularization in age-related macular degeneration (AMD) and uveitis.

Pro-angiogenic effect of IFNgamma is dependent on the PI3K/mTOR/translational pathway in human retinal pigmented epithelial cells

Background

Mutations in COL8A2 gene which encodes the collagen alpha-2 (VIII) chain have been identified in both familial and sporadic cases of Fuchs endothelial corneal dystrophy (FECD). Heterozygous mutations in the SLC4A11 gene are also known to cause late-onset FECD. Therefore we screened for COL8A2, SLC4A11 gene variants in Indian FECD patients.

Methods

Eighty patients with clinically diagnosed FECD and 100 age matched normal individuals were recruited. Genomic DNA was isolated from peripheral blood leukocytes. Mutations in COL8A2, SLC4A11 coding regions were screened using bi-directional sequencing. Fischer's exact test or Pearson's chi squared test were used to predict the statistical association of genotypes with the phenotype.

Results

Screening of COL8A2 gene revealed 2 novel c.1610G>A, c.1643A>G and 3 reported variations c.112G>A, c.464G>A and c.1485G>A. In SLC4A11 gene, novel c.1659C>T, c.1974C>T and reported c.405G>A, c.481A>C and c.639G>A variants were identified. However all the variations in both the genes were also present in unaffected controls.

Conclusions

This is the first study analysing COL8A2 gene in Indian patients with FECD. No pathogenic mutations were identified in COL8A2. Merely silent changes, which showed statistically insignificant association with FECD, were identified in the screening of SLC4A11 gene. These results suggest that COL8A2, SLC4A11 genes may not be responsible for FECD in patients examined in this study.

Gene modulation and immunoregulatory roles of interferon gamma

Interferon-gamma (IFNgamma) is a central regulator of the immune response and signals via the Janus Activated Kinase (JAK)-Signal Transducer and Activator of Transcription (STAT) pathway. Phosphorylated STAT1 homodimers translocate to the nucleus, bind to Gamma Activating Sequence (GAS) and recruit additional factors to modulate gene expression. A bioinformatics analysis revealed that greater number of putative promoters of immune related genes and also those not directly involved in immunity contain GAS compared to response elements (RE) for Interferon Regulatory Factor (IRF)1, Nuclear factor kappa B (NFkappaB) and Activator Protein (AP)1. GAS is present in putative promoters of well known IFNgamma-induced genes, IRF1, GBP1, CXCL10, and other genes identified were TLR3, VCAM1, CASP4, etc. Analysis of three microarray studies revealed that the expression of a subset of only GAS containing immune genes were modulated by IFNgamma. As a significant correlation exists between GAS containing immune genes and IFNgamma-regulated gene expression, this strategy may identify novel IFNgamma-responsive immune genes. This analysis is integrated with the literature on the roles of IFNgamma in mediating a plethora of functions: anti-microbial responses, antigen processing, inflammation, growth suppression, cell death, tumor immunity and autoimmunity. Overall, this review summarizes our present knowledge on IFNgamma mediated signaling and functions.

Microarray analysis identifies changes in inflammatory gene expression in response to amyloid-beta stimulation of cultured human retinal pigment epithelial cells

PURPOSE

Age-related macular degeneration (AMD) is a common cause of irreversible vision loss in the elderly. The hypothesis was that in vitro stimulation of RPE cells with Abeta(1-40), a constituent of drusen, promotes changes in gene expression and cellular pathways associated with the pathogenesis of AMD, including oxidative stress, inflammation, and angiogenesis.

METHODS

Confluent human RPE cells were stimulated with Abeta(1-40), or the reverse peptide Abeta(40-1), and genome wide changes in gene expression were studied with gene microarrays. Selected genes were verified by qRT-PCR and ELISA. Pathway analysis with gene set enrichment analysis (GSEA) and ingenuity revealed top functional pathways in RPE after Abeta(1-40) stimulation.

RESULTS

RPE cells stimulated with Abeta(1-40) (0.3 microM) for 24 hours resulted in 63 upregulated and 22 downregulated previously known genes. The upregulated genes were predominantly in inflammatory and immune response categories, but other categories were also represented, including apoptosis, cell signaling, cell proliferation, and signal transduction. Categories of downregulated genes included immune response, transporters, metabolic functions and transcription factors. ELISA confirmed that secreted levels of IL-8 were two times higher than control levels. GSEA and ingenuity analysis confirmed that the top affected pathways in RPE cells after Abeta(1-40) stimulation were inflammation and immune response related. Surprisingly, few angiogenic pathways were activated at the doses and exposure times studied.

CONCLUSIONS

Abeta(1-40) promotes RPE gene expression changes in pathways associated with immune response, inflammation, and cytokine and interferon signaling pathways. Results may relate to in vivo mechanisms associated with the pathogenesis of AMD.

Expression of glutaredoxin-1 in nasal polyps and airway epithelial cells

BACKGROUND

Glutaredoxins (GRX)-1 is glutathione-dependent oxidoreductase. However, the role of these enzymes remains unknown in airway inflammatory diseases. Therefore, we aimed to establish the expression pattern of GRX-1 in the nasal polyps (NPs) and to assess the regulatory mechanisms associated with GRX-1 expression in interleukin (IL)-1 beta-treated airway epithelial cells.

METHODS

The expression of GRX-1 in NPs and normal nasal mucosa were analyzed by reverse-transcription polymerase chain reaction and immunohistochemical staining. IL-1 beta-induced reactive oxygen species (ROS) formation and GRX-1 expression in the airway epithelial cells was determined by flow cytometry and immunoassay.

RESULTS

The expression level of GRX-1 in NPs was significantly higher than in the normal nasal mucosa (p < 0.05). GRX-1 was highly expressed in the surface epithelial cells and the submucosal glandular cells in the NPs. IL-1 beta increased the intracellular ROS formation and GRX-1 expression in airway epithelial cells. The inhibition of IL-1 beta-induced ROS production by N-acetyl-cystein, an ROS scavenger, reduced GRX-1 expression. Diphenyleneiodonium and apocynin, NADPH oxidase inhibitors, did not abolish IL-1 beta-induced ROS formation and GRX-1 expression, whereas budesonide attenuated it.

CONCLUSION

High GRX-1 expression in NPs might be a primary defense against chronic inflammatory oxidative stress in nasal mucosa. IL-1 beta-induced up-regulation of GRX-1 in airway epithelial cells is probably mediated by ROS. Glucocorticoids can regulate IL-1 beta-induced ROS formation and GRX-1 expression.

Dynamics of liver GH/IGF axis and selected stress markers in juvenile gilthead sea bream (Sparus aurata) exposed to acute confinement: differential stress response of growth hormone receptors

The time courses of liver GH/IGF axis and selected stress markers were analyzed in juvenile gilthead sea bream (Sparus aurata) sampled at zero time and at fixed intervals (1.5, 3, 6, 24, 72 and 120 h) after acute confinement (120 kg/m(3)). Fish remained unfed throughout the course of the confinement study, and the fasting-induced increases in plasma growth hormone (GH) levels were partially masked by the GH-stress inhibitory tone. Hepatic mRNA levels of growth hormone receptor-I (GHR-I) were not significantly altered by confinement, but a persistent 2-fold decrease in GHR-II transcripts was found at 24 and 120 h. A consistent decrease in circulating levels of insulin-like growth factor-I (IGF-I) was also found through most of the experimental period, and the down-regulated expression of GHR-II was positively correlated with changes in hepatic IGF-I and IGF-II transcripts. This stress-specific response was concurrent with plasma increases in cortisol and glucose levels, reflecting the cortisol peak (60-70 ng/mL), the intensity and duration of the stressor when data found in the literature were compared. Adaptive responses against oxidative damage were also found, and a rapid enhanced expression was reported in the liver tissue for mitochondrial heat-shock proteins (glucose regulated protein 75). At the same time, the down-regulated expression of proinflammatory cytokines (tumour necrosis factor-alpha) and detoxifying enzymes (cytochrome P450 1A1) might dictate the hepatic depletion of potential sources of reactive oxygen species. These results provide suitable evidence for a functional partitioning of hepatic GHRs under states of reduced IGF production and changing cellular environment resulting from acute confinement.

Association of superoxide anions with retinal pigment epithelial cell apoptosis induced by mononuclear phagocytes

PURPOSE

Oxidative stress of the retinal pigment epithelium by reactive oxygen species and monocytic infiltration have been implicated in age-related macular degeneration. The purpose of this study was to determine the role of superoxide anions (O(2)(-)) in mononuclear phagocyte-induced RPE apoptosis.

METHODS

Mouse RPE cell cultures were established from wild-type and heterozygous superoxide dismutase 2-knockout (Sod2(+/-)) mice. The intracellular reactive oxygen species, O(2)(-) and hydrogen peroxide, were measured by using dihydroethidium assay and 5-(and 6)-chloromethyl-2',7'-dichlorodihydrofluorescence diacetate, acetyl ester assay, respectively. RPE apoptosis was evaluated by Hoechst staining and terminal deoxynucleotidyltransferase dUTP nick-end labeling assay. Changes in mitochondrial membrane potential were detected by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide dye. Activated caspases and caspase-3 were detected in situ by FITC-VAD-fmk staining and caspase-3 substrate, respectively.

RESULTS

Mononuclear phagocytes and interferon-gamma-activated mononuclear phagocytes induced the production of intracellular RPE O(2)(-), a decrease in RPE mitochondrial membrane potential, caspase activation, and apoptosis of mouse RPE cells. All theses changes were significantly enhanced in the Sod2(+/-) RPE cells. Activated mononuclear phagocytes induced more of these oxidative and apoptotic changes in RPE cells than did unstimulated mononuclear phagocytes.

CONCLUSIONS

The authors have shown that the decreased expression of SOD2 and increased superoxide production correlate with RPE apoptosis induced by unstimulated and activated mononuclear phagocytes. The authors suggest that elevated O(2)(-) levels due to genetic abnormalities of SOD2 or immunologic activation of mononuclear phagocytes lead to greater levels of RPE apoptosis. The present study could serve as a useful model to characterize RPE/phagocyte interaction in AMD and other retinal diseases.

Age-related macular degeneration: activation of innate immunity system via pattern recognition receptors

Age-related macular degeneration (AMD) is the most common cause of irreversible loss of central vision. Histopathological studies have demonstrated that inflammation is the key player in the pathogenesis of AMD. Genetic studies have revealed that complement factor H is a strong risk factor for the development of AMD. However, innate immunity defence involves several other pattern recognition receptors (PRRs) which can trigger inflammatory responses. Retinal pigment epithelial (RPE) cells have the main role in the immune defence in macula. In this study, we examine in detail the endogenous danger signals which can activate different PRRs in RPE cells, such as Toll-like, NOD-like and scavenger receptors along with complement system. We also characterise the signalling pathways triggered by PRRs in evoking inflammatory responses. In addition, we will discuss whether AMD pathology could represent the outcome of chronic activation of the innate immunity defence in human macula.

Downregulation of p22phox in retinal pigment epithelial cells inhibits choroidal neovascularization in mice

Choroidal neovascularization (CNV) occurs in a variety of chorioretinal diseases including age-related macular degeneration (AMD), and is the major cause of severe visual loss in patients with AMD. Oxidative stress has been thought to play an important role in the development of CNV. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is one of the major intracellular sources of reactive oxygen species (ROS) in the vascular system. In this study, we examined the expression of p22phox, an integral subunit in the NADPH oxidase complex, in the mouse eye. We determined that p22phox is expressed in the retinal pigment epithelial (RPE) cells and inner retinal neurons. A small-interfering RNA (siRNA) designed against p22phox efficiently reduced the expression of the protein in the eye when delivered by means of recombinant adeno-associated virus (AAV) vector. Vector treatment inhibited CNV in the mouse when delivered into the subretinal space where RPE cells were transduced. These results suggest that NADPH oxidase-mediated ROS production in RPE cells may play an important role in the pathogenesis of neovascular AMD, and that this pathway may represent a new target for therapeutic intervention in AMD.

Role of bone marrow renin-angiotensin system in the pathogenesis of atherosclerosis

The renin-angiotensin system (RAS) has been considered to be a circulating hormonal system that regulates blood pressure, blood flow, fluid volume and electrolyte balance. A growing body of evidence indicates local effects of an activated RAS, particularly in the cardiac, vascular, and renal systems. It is now well established that RAS, especially angiotensin II (Ang II) and Ang II type 1 receptor (AT1R) pathway, has significant pro-inflammatory actions on the vessel wall, leading to progression of atherosclerosis. Recent reports suggest that an activated RAS has local effects in bone marrow (BM), which contributes to the regulation of normal and malignant hematologic processes. We reported that AT1aR in BM cells participate in the pathogenesis of atherosclerosis by analyzing several BM chimeric mice whose BM cells were positive or negative for AT1aR. These results suggest that blockade of AT1R not only in vascular cells but also in BM could be an important strategy to prevent atherosclerosis. In this review, we overview recent findings on a role of RAS in the pathogenesis of atherosclerosis, and discuss functional contribution of a local RAS in BM to progression and destabilization of atherosclerotic plaque.

Retinal flavoprotein autofluorescence as a measure of retinal health

PURPOSE

To establish that increased autofluorescence of mitochondrial flavoproteins, an indicator of mitochondrial oxidative stress, correlates with retinal cell dysfunction.

METHODS

Retinal flavoprotein autofluorescence (FA) was imaged in humans with a fundus camera modified with 467DF8-nm excitation and 535-nm emission filters and a back-illuminated, electron-multiplying, charge-coupled device camera interfaced with a computer equipped with customized image capture software. Multiple digital images, centered on the fovea, were obtained from each eye. Histograms of pixel intensities in grayscale units were analyzed for average intensity and average curve width. Adults with diabetes mellitus, age-related macular degeneration (ARMD), central serous retinopathy, and retinal dystrophies, as well as healthy control volunteers, were imaged. Monolayers of cultured human retinal pigment epithelial (HRPE) cells, HRPE cells exposed to sublethal doses of H2O2, and HRPE cells exposed to H2O2 in the presence of antioxidants were imaged for FA using fluorescent photomicroscopy.

RESULTS

Control patients demonstrated low levels of retinal FA, which increased progressively with age. Diabetics without visible retinopathy demonstrated increased FA levels compared to control volunteers (P < .001). Diabetics with retinopathy demonstrated significantly higher FA values than those without retinopathy (P < .04). Patients with ARMD, central serous retinopathy, or retinal dystrophies also demonstrated significantly increased FA. Compared to control RPE cells, cells oxidatively stressed with H2O2 had significantly elevated FA (P < .05), which was prevented by antioxidants (P < .05).

CONCLUSIONS

Retinal FA is significantly increased with age and diseases known to be mediated by oxidative stress. Retinal FA imaging may provide a novel, noninvasive method of assessing retinal health and retinal dysfunction prior to retinal cell death.