Redox regulation of the immune response

The Relationship of Kynurenine and Neopterin Levels and Their Association with a Selection of Other Immune Markers in Chronic Myeloid Leukaemia Patients

Among malignant diseases, chronic myeloid leukaemia (CML) is one of the best suited candidates for immunotherapy. For this purpose it is necessary to broaden the present knowledge on the immunology of this disease. As a part of such a project, the levels of kynurenine (KYN) and neopterin (NPT) were studied in 28 CML patients and in the same number of healthy subjects. At diagnosis, both KYN and NPT levels were found to be elevated in a significant portion of the patients and dependent on their leukocyte count. As in the case of KYN, increased NPT levels dropped after achieving remission. When correlating KYN and NPT levels with a selection of other markers tested, significant association was revealed only in the case of CRP and IL-6. However, there were several patients with increased KYN levels in whom NPT was not detected, and vice versa. The relapse of the disease observed in two patients was accompanied by an increased level of NPT in both cases, but by an increased level of KYN in only one of them. No significant correlation was found between KYN and NPT levels in sera taken at diagnosis. However, when the whole set of sera was taken into consideration, the association became statistically significant. Although the data obtained revealed a number of similarities between KYN and NPT production in CML patients, it also suggested a difference in the kinetics of these two biomarkers' production.

Mood, food, and cognition: role of tryptophan and serotonin

PURPOSE OF REVIEW

Food is not only necessary as a metabolic fuel for the body, it becomes more and more evident that there exists an association between food and brain functions like mood and cognition. Tryptophan represents a key element for brain functioning, because of its role as a precursor for production of neurotransmitter serotonin (5-hydroxytryptamine). In clinical conditions, which involve chronic immune system activation or under cytokine therapy, lower tryptophan levels because of high catabolism of tryptophan as indicated by the kynurenine to tryptophan ratio are common and often associate with depressive mood.

RECENT FINDINGS

Studies in the in vitro model of mitogen-stimulated peripheral blood mononuclear cells revealed that several phytocompounds, mainly antioxidants like polyphenols and vitamins, can interfere with inflammatory signaling cascades including tryptophan breakdown. If extrapolated to the in vivo situation, such compounds could increase blood and brain tryptophan availability for serotonin production. Although there is some in vivo evidence for the effect of such compounds, outcomes are hardly predictable and most likely depend on the individual's immunological state.

SUMMARY

Not only a diet rich in tryptophan but also a diet rich in antioxidants can have a positive impact on mood and cognition. This could be of special relevance for individuals who present with low grade inflammation conditions.

DAMPs, ageing, and cancer: The 'DAMP Hypothesis'

Ageing is a complex and multifactorial process characterized by the accumulation of many forms of damage at the molecular, cellular, and tissue level with advancing age. Ageing increases the risk of the onset of chronic inflammation-associated diseases such as cancer, diabetes, stroke, and neurodegenerative disease. In particular, ageing and cancer share some common origins and hallmarks such as genomic instability, epigenetic alteration, aberrant telomeres, inflammation and immune injury, reprogrammed metabolism, and degradation system impairment (including within the ubiquitin-proteasome system and the autophagic machinery). Recent advances indicate that damage-associated molecular pattern molecules (DAMPs) such as high mobility group box 1, histones, S100, and heat shock proteins play location-dependent roles inside and outside the cell. These provide interaction platforms at molecular levels linked to common hallmarks of ageing and cancer. They can act as inducers, sensors, and mediators of stress through individual plasma membrane receptors, intracellular recognition receptors (e.g., advanced glycosylation end product-specific receptors, AIM2-like receptors, RIG-I-like receptors, and NOD1-like receptors, and toll-like receptors), or following endocytic uptake. Thus, the DAMP Hypothesis is novel and complements other theories that explain the features of ageing. DAMPs represent ideal biomarkers of ageing and provide an attractive target for interventions in ageing and age-associated diseases.

Protection from Radiation-Induced Pulmonary Fibrosis by Peripheral Targeting of Cannabinoid Receptor-1

Radiation-induced pulmonary fibrosis (RIF) is a severe complication of thoracic radiotherapy that limits its dose, intensity, and duration. The contribution of the endocannabinoid signaling system in pulmonary fibrogenesis is not known. Using a well-established mouse model of RIF, we assessed the involvement of cannabinoid receptor-1 (CB1) in the onset and progression of pulmonary fibrosis. Female C57BL/6 mice and CB1 knockout mice generated on C57BL/6 background received 20 Gy (2 Gy/min) single-dose thoracic irradiation that resulted in pulmonary fibrosis and animal death within 15 to 18 weeks. Some C57BL/6 animals received the CB1 peripherally restricted antagonist AM6545 at 1 mg/kg intraperitoneally three times per week. Animal survival and parameters of pulmonary inflammation and fibrosis were evaluated. Thoracic irradiation (20 Gy) was associated with marked pulmonary inflammation and fibrosis in mice and high mortality within 15 to 18 weeks after exposure. Genetic deletion or pharmacological inhibition of CB1 receptors with a peripheral CB1 antagonist AM6545 markedly attenuated or delayed the lung inflammation and fibrosis and increased animal survival. Our results show that CB1 signaling plays a key pathological role in the development of radiation-induced pulmonary inflammation and fibrosis, and peripherally restricted CB1 antagonists may represent a novel therapeutic approach against this devastating complication of radiotherapy/irradiation.

Berberine attenuates CCN2-induced IL-1β expression and prevents cartilage degradation in a rat model of osteoarthritis

Connective tissue growth factor (CTGF; also known as CCN2) is an inflammatory mediator that is abundantly expressed in osteoarthritis (OA). Interleukin-1β (IL-1β) plays a pivotal role in OA pathogenesis. Berberine exhibits an anti-inflammatory effect, but the mechanisms by which it modulates CCN2-induced IL-1β expression in OA synovial fibroblasts (OASFs) remain unknown. We showed that CCN2-induced IL-1β expression is mediated by the activation of αvβ3/αvβ5 integrin-dependent reactive oxygen species (ROS) generation, and subsequent activation of apoptosis signal-regulating kinase 1 (ASK1), p38/JNK, and nuclear factor-κB (NF-κB) signaling pathways. This IL-1β expression in OASFs is attenuated by N-acetylcysteine (NAC), inhibitors of ASK1, p38, or JNK, or treatment with berberine. Furthermore, berberine also reverses cartilage damage in an experimental model of collagenase-induced OA (CIOA). We observed that CCN2 increased IL-1β expression via αvβ3/αvβ5 integrins, ROS, and ASK1, p38/JNK, and NF-κB signaling pathways. Berberine was found to inhibit these signaling components in OASFs in vitro and prevent cartilage degradation in vivo. We suggest a novel therapeutic strategy of using berberine for managing OA.

Anopheles stephensi p38 MAPK signaling regulates innate immunity and bioenergetics during Plasmodium falciparum infection

Background

Fruit flies and mammals protect themselves against infection by mounting immune and metabolic responses that must be balanced against the metabolic needs of the pathogens. In this context, p38 mitogen-activated protein kinase (MAPK)-dependent signaling is critical to regulating both innate immunity and metabolism during infection. Accordingly, we asked to what extent the Asian malaria mosquito Anopheles stephensi utilizes p38 MAPK signaling during infection with the human malaria parasite Plasmodium falciparum.

Methods

A. stephensi p38 MAPK (AsP38 MAPK) was identified and patterns of signaling in vitro and in vivo (midgut) were analyzed using phospho-specific antibodies and small molecule inhibitors. Functional effects of AsP38 MAPK inhibition were assessed using P. falciparum infection, quantitative real-time PCR, assays for reactive oxygen species and survivorship under oxidative stress, proteomics, and biochemical analyses.

Results

The genome of A. stephensi encodes a single p38 MAPK that is activated in the midgut in response to parasite infection. Inhibition of AsP38 MAPK signaling significantly reduced P. falciparum sporogonic development. This phenotype was associated with AsP38 MAPK regulation of mitochondrial physiology and stress responses in the midgut epithelium, a tissue critical for parasite development. Specifically, inhibition of AsP38 MAPK resulted in reduction in mosquito protein synthesis machinery, a shift in glucose metabolism, reduced mitochondrial metabolism, enhanced production of mitochondrial reactive oxygen species, induction of an array of anti-parasite effector genes, and decreased resistance to oxidative stress-mediated damage. Hence, P. falciparum-induced activation of AsP38 MAPK in the midgut facilitates parasite infection through a combination of reduced anti-parasite immune defenses and enhanced host protein synthesis and bioenergetics to minimize the impact of infection on the host and to maximize parasite survival, and ultimately, transmission.

Conclusions

These observations suggest that, as in mammals, innate immunity and mitochondrial responses are integrated in mosquitoes and that AsP38 MAPK-dependent signaling facilitates mosquito survival during parasite infection, a fact that may attest to the relatively longer evolutionary relationship of these parasites with their invertebrate compared to their vertebrate hosts. On a practical level, improved understanding of the balances and trade-offs between resistance and metabolism could be leveraged to generate fit, resistant mosquitoes for malaria control.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1016-x) contains supplementary material, which is available to authorized users.

Affect of Early Life Oxygen Exposure on Proper Lung Development and Response to Respiratory Viral Infections

Children born preterm often exhibit reduced lung function and increased severity of response to respiratory viruses, suggesting that premature birth has compromised proper development of the respiratory epithelium and innate immune defenses. Increasing evidence suggests that premature birth promotes aberrant lung development likely due to the neonatal oxygen transition occurring before pulmonary development has matured. Given that preterm infants are born at a point of time where their immune system is also still developing, early life oxygen exposure may also be disrupting proper development of innate immunity. Here, we review current literature in hopes of stimulating research that enhances understanding of how the oxygen environment at birth influences lung development and host defense. This knowledge may help identify those children at risk for disease and ideally culminate in the development of novel therapies that improve their health.

Curdlan-Conjugated PLGA Nanoparticles Possess Macrophage Stimulant Activity and Drug Delivery Capabilities

PURPOSE

There is significant interest in the application of nanoparticles to deliver immunostimulatory signals to cells. We hypothesized that curdlan (immune stimulating polymer) could be conjugated to PLGA and nanoparticles from this copolymer would possess immunostimulatory activity, be non-cytotoxic and function as an effective sustained drug release system.

METHODS

Carbodiimide chemistry was employed to conjugate curdlan to PLGA. The conjugate (C-PLGA) was characterized using (1)H and (13)C NMR, FTIR, DSC and TGA. Nanoparticles were synthesized using an emulsion-solvent evaporation technique. Immunostimulatory activity was characterized in THP-1 derived macrophages. MTT assay and real-time impedance measurements were used to characterize polymer and nanoparticle toxicity and uptake in macrophages. Drug delivery capability was assessed across Caco-2 cells using rifampicin as a model drug.

RESULTS

Spectral characterization confirmed successful synthesis of C-PLGA. C-PLGA nanoparticles enhanced phosphorylated ERK production in macrophages indicating cell stimulation. Nanoparticles provided slow release of rifampicin across Caco-2 cells. Polymers but not nanoparticles altered the adhesion profiles of the macrophages. Impedance measurements suggested Ca(2+) dependent uptake of nanoparticles by the macrophages.

CONCLUSIONS

PLGA nanoparticles with macrophage stimulating and sustained drug delivery capabilities have been prepared. These nanoparticles can be used to stimulate macrophages and concurrently deliver drug in infectious disease therapy.

The cellular immunity and oxidative stress markers in early pregnancy loss

OBJECTIVE

We investigated whether changes in cellular immunity and oxidative stress in pregnancy have any association with spontaneous miscarriage.

MATERIAL AND METHODS

Circulating adenosine deaminase (ADA) activity as a marker of cellular immunity and malondialdehyde (MDA) and catalase (CAT), glutathione peroxidase (GPx) as markers of T lymphocyte activation and parameters of oxidative stress and antioxidant defense were compared between 40 women with early pregnancy loss and another 40 women with ungoing healthy pregnancy.

RESULTS

Women with miscarriage had higher serum ADA and GPx levels when compared with women with normal pregnancy (p = 0.034 and p < 0.001, respectively). Although serum MDA level was slightly higher in women with miscarriage, the difference was not significant (p = 0.083). CAT levels were alike in both groups.

CONCLUSION

We have demonstrated an increased cellular immunity and perhaps a compensated oxidative stress related to increased antioxidant activation in women with early spontaneous pregnancy loss.

A Pterin-Dependent Signaling Pathway Regulates a Dual-Function Diguanylate Cyclase-Phosphodiesterase Controlling Surface Attachment in Agrobacterium tumefaciens

The motile-to-sessile transition is an important lifestyle switch in diverse bacteria and is often regulated by the intracellular second messenger cyclic diguanylate monophosphate (c-di-GMP). In general, high c-di-GMP concentrations promote attachment to surfaces, whereas cells with low levels of signal remain motile. In the plant pathogen Agrobacterium tumefaciens, c-di-GMP controls attachment and biofilm formation via regulation of a unipolar polysaccharide (UPP) adhesin. The levels of c-di-GMP in A. tumefaciens are controlled in part by the dual-function diguanylate cyclase-phosphodiesterase (DGC-PDE) protein DcpA. In this study, we report that DcpA possesses both c-di-GMP synthesizing and degrading activities in heterologous and native genetic backgrounds, a binary capability that is unusual among GGDEF-EAL domain-containing proteins. DcpA activity is modulated by a pteridine reductase called PruA, with DcpA acting as a PDE in the presence of PruA and a DGC in its absence. PruA enzymatic activity is required for the control of DcpA and through this control, attachment and biofilm formation. Intracellular pterin analysis demonstrates that PruA is responsible for the production of a novel pterin species. In addition, the control of DcpA activity also requires PruR, a protein encoded directly upstream of DcpA with a predicted molybdopterin-binding domain. PruR is hypothesized to be a potential signaling intermediate between PruA and DcpA through an as-yet-unidentified mechanism. This study provides the first prokaryotic example of a pterin-mediated signaling pathway and a new model for the regulation of dual-function DGC-PDE proteins.

IMPORTANCE

Pathogenic bacteria often attach to surfaces and form multicellular communities called biofilms. Biofilms are inherently resilient and can be difficult to treat, resisting common antimicrobials. Understanding how bacterial cells transition to the biofilm lifestyle is essential in developing new therapeutic strategies. We have characterized a novel signaling pathway that plays a dominant role in the regulation of biofilm formation in the model pathogen Agrobacterium tumefaciens. This control pathway involves small metabolites called pterins, well studied in eukaryotes, but this is the first example of pterin-dependent signaling in bacteria. The described pathway controls levels of an important intracellular second messenger (cyclic diguanylate monophosphate) that regulates key bacterial processes such as biofilm formation, motility, and virulence. Pterins control the balance of activity for an enzyme that both synthesizes and degrades the second messenger. These findings reveal a complex, multistep pathway that modulates this enzyme, possibly identifying new targets for antibacterial intervention.

Glucose 6-phosphate dehydrogenase knockdown enhances IL-8 expression in HepG2 cells via oxidative stress and NF-κB signaling pathway

Background

This study was designed to investigate the effect of glucose 6-phosphate dehydrogenase (G6PD) deficiency on pro-inflammatory cytokine secretion using a palmitate-induced inflammation HepG2 in vitro model. The modulation of cellular pro-inflammatory cytokine expression under G6PD deficiency during chronic hepatic inflammation has never been investigated before.

Methods

The culture medium of untreated and palmitate-treated G6PD-scramble (Sc) and G6PD-knockdown (Gi) HepG2 cells were subjected to cytokine array analysis, followed by validation with ELISA and qRT-PCR of the target cytokine. The mechanism of altered cytokine secretion in palmitate-treated Sc and Gi HepG2 cells was examined in the presence of anti-oxidative enzyme (glutathione peroxidase, GPX), anti-inflammatory agent (curcumin), NF-κB inhibitor (BAY11-7085) and specific SiRNA against NF-κB subunit p65.

Results

Cytokine array analysis indicated that IL-8 is most significantly increased in G6PD-knockdown HepG2 cells. The up-regulation of IL-8 caused by G6PD deficiency in HepG2 cells was confirmed in other G6PD-deficient cells by qRT-PCR. The partial reduction of G6PD deficiency-derived IL-8 due to GPX and NF-κB blockers indicated that G6PD deficiency up-regulates pro-inflammatory cytokine IL-8 through oxidative stress and NF-κB pathway.

Conclusions

G6PD deficiency predisposes cells to enhanced production of pro-inflammatory cytokine IL-8. Mechanistically, G6PD deficiency up-regulates IL-8 through oxidative stress and NF-κB pathway. The palmitate-induced inflammation in G6PD-deficient HepG2 cells could serve as an in vitro model to study the role of altered redox homeostasis in chronic hepatic inflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-015-0078-z) contains supplementary material, which is available to authorized users.

Immune-metabolic profiling of anorexic patients reveals an anti-oxidant and anti-inflammatory phenotype

CONTEXT

Anorexia nervosa (AN) is an excessive form of calorie restriction (CR) associated with pathological weight loss and alterations of the immune system. However, AN patients seem to be protected from common viral infections.

OBJECTIVES

To investigate the metabolic and molecular adaptations induced by sustained extreme CR in the peripheral blood mononuclear cells (PBMCs) of patients with restrictive alimentary AN.

DESIGN

Inflammatory cytokines and adipokines were measured in 15 young (age range, 15-24 years) AN female patients and 20 age-matched healthy controls. Isolated PBMCs were immunophenotyped by flow cytometry, and glycolysis and mitochondrial respiration were determined by measuring the extracellular acidification and oxygen consumption rate. Stress resistance to H2O2 and the antioxidant transcriptional profile of PBMCs and human fibroblasts incubated with sera from AN patients were also determined.

RESULTS

Compared with controls, AN patients (BMI, 15.9±0.4 kg/m(2)) had significantly fewer leucocytes, lymphocytes and NK cells, lower serum concentrations of leptin, IGF-1 and sTNFR1, and higher levels of adiponectin, sCD40L and sICAM-1 (p<0.05). IL-1β, TNFα, and IL-6 produced by PBMC cultured with autologous serum for 48 h were significantly lower in AN patients than in controls (p<0.01). Moreover, glycolysis and mitochondrial respiration were lower, and the antioxidant transcriptional profile was higher in the PBMCs of AN patients. Fibroblasts cultured in serum from AN patients showed a 24% increase in resistance to H2O2 damage.

CONCLUSIONS

Extreme CR in AN patients is associated with a reduction in several immune cell populations, but with higher antioxidant potential, stress resistance and an anti-inflammatory status.

The good and bad of antioxidant foods: An immunological perspective

Maintenance of redox homeostasis plays a central role in health and disease prevention, and antioxidant foods are thought to exert protective effects by counteracting oxidative stress. The term "dietary antioxidant" implies a classical reducing or radical-scavenging capacity, but more data on the in vivo bioactivity of such compounds are needed. Indeed, several dietary antioxidants activate signaling cascades that lead to effects that extend beyond radical scavenging, such as the induction of endogenous cytoprotective mechanisms and detoxification. Currently, the overall uptake of antioxidants with diet exceeds actual needs, as food additives that include vitamins, colorants, flavoring agents, and preservatives are often also relatively strong antioxidants. Chronic antioxidative stress favors adverse effects, such as the suppression of T helper (Th) type 1 immune responses and consequent activation of Th2 reactions that support the development of asthma, allergies, and obesity. In this context, we discuss the immunoregulatory pathway of tryptophan breakdown by enzyme indoleamine 2,3-dioxygenase (IDO), which represents a central regulatory hub for immune, metabolic, and neuroendocrine processes. Activation of IDO-mediated tryptophan metabolism is strongly redox-sensitive and is therefore susceptible to modulation by dietary components, phytochemicals, preservatives, and drugs.

The potential of targeting indoleamine 2,3-dioxygenase for cancer treatment

INTRODUCTION

Degradation of the essential amino acid tryptophan via indoleamine 2,3-dioxygenase (IDO1) represents an important antiproliferative strategy of the cellular immune response. Tryptophan shortage and accumulation of kynurenine downstream products also affect T-cell responses, providing a negative feedback control of immune activation. IDO1 activity can promote a regulatory phenotype in both T cells and dendritic cells. These phenomena can support tumor immune escape.

AREAS COVERED

IDO1 activity reflects the course of several malignancies, and determination of kynurenine to tryptophan ratio in serum/plasma can be used to assess immune activation. Moreover, the accelerated breakdown of tryptophan has been correlated with the development of cancer-associated disturbances such as anemia, weight loss and depression. Tumoral IDO1 expression was correlated with a poor prognosis in several types of tumors, which makes it to an interesting target for immunotherapy. In addition, according to recent data, a role of trytptophan 2,3-dioxygenase (TDO) in tumorigenesis cannot be excluded.

EXPERT OPINION

Tryptophan metabolism is critical for cell proliferation, inflammation and immunoregulation. Accelerated tryptophan breakdown favors tumor immune escape. Accordingly, targeting IDO1 by immunotherapy may represent a favorable approach; however, blocking crucial immunoregulatory pathways could also introduce the risk of immune system overactivation, finally leading to unresponsiveness.

T cell tyrosine phosphorylation response to transient redox stress

Reactive Oxygen Species (ROS) are crucial to multiple biological processes involved in the pathophysiology of inflammation, and are also involved in redox signaling responses. Although previous reports have described an association between oxidative events and the modulation of innate immunity, a role for redox signaling in T cell mediated adaptive immunity has not been described yet. This work aims at assessing if T cells can sense redox stress through protein sulfhydryl oxidation and respond with tyrosine phosphorylation changes. Our data show that Jurkat T cells respond to -SH group oxidation with specific tyrosine phosphorylation events. The release of T cell cytokines TNF, IFNγ and IL2 as well as the expression of a number of receptors are affected by those changes. Additionally, experiments with spleen tyrosine kinase (Syk) inhibitors showed a major involvement of Syk in these responses. The experiments described herein show a link between cysteine oxidation and tyrosine phosphorylation changes in T cells, as well as a novel mechanism by which Syk inhibitors exert their anti-inflammatory activity through the inhibition of a response initiated by ROS.

The role of physiological elements in future therapies of rheumatoid arthritis. III. The role of the electromagnetic field in regulation of redox potential and life cycle of inflammatory cells

Each material consisting of charged particles can be influenced by a magnetic field. Polarized particles play an essential role in almost all physiological processes. Locally generated electromagnetic fields several physiological processes within the human body, for example: stimulation of nerves, muscles, and cardiac electrical activity. This phenomenon is used today in many medical applications. In this article, we discuss ways in which electromagnetic field affects the physiological and pathological processes in cells and tissues. This knowledge will help to better understand the electrophysiological phenomenon in connective tissue diseases and can bring new therapeutic strategies (in the form of “invisible drugs”) for the treatment of rheumatic diseases?

Cross-talk between HPA-axis-increased glucocorticoids and mitochondrial stress determines immune responses and clinical manifestations of patients with sepsis

Various stressors activate the hypothalamo-pituitary-adrenal axis (HPA-axis) that stimulates adrenal secretion of glucocorticoids, thereby playing critical roles in the modulation of immune responses. Transcriptional regulation of nuclear genes has been well documented to underlie the mechanism of glucocorticoid-dependent modulation of cytokine production and immune reactions. Glucocorticoids also regulate inflammatory responses via non-genomic pathways in cytoplasm and mitochondria. Recent studies have revealed that glucocorticoids modulate mitochondrial calcium homeostasis and generation of reactive oxygen species (ROS). Although redox status and ROS generation in inflammatory cells have been well documented to play important roles in defense against pathogens, the roles of glucocorticoids and mitochondria in the modulation of immunological responses remain obscure. This review describes the role of stress-induced activation of the HPA-axis and glucocorticoid secretion by the adrenal gland in mitochondria-dependent signaling pathways that modulate endotoxin-induced inflammatory reactions and innate immunity.

Inference of the oxidative stress network in Anopheles stephensi upon Plasmodium infection

Ookinete invasion of Anopheles midgut is a critical step for malaria transmission; the parasite numbers drop drastically and practically reach a minimum during the parasite's whole life cycle. At this stage, the parasite as well as the vector undergoes immense oxidative stress. Thereafter, the vector undergoes oxidative stress at different time points as the parasite invades its tissues during the parasite development. The present study was undertaken to reconstruct the network of differentially expressed genes involved in oxidative stress in Anopheles stephensi during Plasmodium development and maturation in the midgut. Using high throughput next generation sequencing methods, we generated the transcriptome of the An. stephensi midgut during Plasmodium vinckei petteri oocyst invasion of the midgut epithelium. Further, we utilized large datasets available on public domain on Anopheles during Plasmodium ookinete invasion and Drosophila datasets and arrived upon clusters of genes that may play a role in oxidative stress. Finally, we used support vector machines for the functional prediction of the un-annotated genes of An. stephensi. Integrating the results from all the different data analyses, we identified a total of 516 genes that were involved in oxidative stress in An. stephensi during Plasmodium development. The significantly regulated genes were further extracted from this gene cluster and used to infer an oxidative stress network of An. stephensi. Using system biology approaches, we have been able to ascertain the role of several putative genes in An. stephensi with respect to oxidative stress. Further experimental validations of these genes are underway.

Gene targeting RhoA reveals its essential role in coordinating mitochondrial function and thymocyte development

Thymocyte development is regulated by complex signaling pathways. How these signaling cascades are coordinated remains elusive. RhoA of the Rho family small GTPases plays an important role in actin cytoskeleton organization, cell adhesion, migration, proliferation, and survival. Nonetheless, the physiological function of RhoA in thymocyte development is not clear. By characterizing a conditional gene targeting mouse model bearing T cell deletion of RhoA, we show that RhoA critically regulates thymocyte development by coordinating multiple developmental events. RhoA gene disruption caused a strong developmental block at the pre-TCR checkpoint and during positive selection. Ablation of RhoA led to reduced DNA synthesis in CD4(-)CD8(-), CD4(+)CD8(-), and CD4(-)CD8(+) thymocytes but not in CD4(+)CD8(+) thymocytes. Instead, RhoA-deficient CD4(+)CD8(+) thymocytes showed an impaired mitosis. Furthermore, we found that abrogation of RhoA led to an increased apoptosis in all thymocyte subpopulations. Importantly, we show that the increased apoptosis was resulted from reduced pre-TCR expression and increased production of reactive oxygen species (ROS), which may be because of an enhanced mitochondrial function, as manifested by increased oxidative phosphorylation, glycolysis, mitochondrial membrane potential, and mitochondrial biogenesis in RhoA-deficient thymocytes. Restoration of pre-TCR expression or treatment of RhoA-deficient mice with a ROS scavenger N-acetylcysteine partially restored thymocyte development. These results suggest that RhoA is required for thymocyte development and indicate, to our knowledge, for the first time that fine-tuning of ROS production by RhoA, through a delicate control of metabolic circuit, may contribute to thymopoiesis.

Dose-dependent hepatic transcriptional responses in Atlantic salmon (Salmo salar) exposed to sublethal doses of gamma radiation

Due to the production of free radicals, gamma radiation may pose a hazard to living organisms. The high-dose radiation effects have been extensively studied, whereas the ecotoxicity data on low-dose gamma radiation is still limited. The present study was therefore performed using Atlantic salmon (Salmo salar) to characterize effects of low-dose (15, 70 and 280 mGy) gamma radiation after short-term (48h) exposure. Global transcriptional changes were studied using a combination of high-density oligonucleotide microarrays and quantitative real-time reverse transcription polymerase chain reaction (qPCR). Differentially expressed genes (DEGs; in this article the phrase gene expression is taken as a synonym of gene transcription, although it is acknowledged that gene expression can also be regulated, e.g., at protein stability and translational level) were determined and linked to their biological meanings predicted using both Gene Ontology (GO) and mammalian ortholog-based functional analyses. The plasma glucose level was also measured as a general stress biomarker at the organism level. Results from the microarray analysis revealed a dose-dependent pattern of global transcriptional responses, with 222, 495 and 909 DEGs regulated by 15, 70 and 280 mGy gamma radiation, respectively. Among these DEGs, only 34 were commonly regulated by all radiation doses, whereas the majority of differences were dose-specific. No GO functions were identified at low or medium doses, but repression of DEGs associated with GO functions such as DNA replication, cell cycle regulation and response to reactive oxygen species (ROS) were observed after 280mGy gamma exposure. Ortholog-based toxicity pathway analysis further showed that 15mGy radiation affected DEGs associated with cellular signaling and immune response; 70mGy radiation affected cell cycle regulation and DNA damage repair, cellular energy production; and 280mGy radiation affected pathways related to cell cycle regulation and DNA repair, mitochondrial dysfunction and immune functions. Twelve genes representative of key pathways found in this study were verified by qPCR. Potential common MoAs of low-dose gamma radiation may include induction of oxidative stress, DNA damage and disturbance of oxidative phosphorylation (OXPHOS). Although common MoAs were proposed, a number of DEGs and pathways were still found to be dose-specific, potentially indicating multiple mechanisms of action (MOAs) of low-dose gamma radiation in fish. In addition, plasma glucose displayed an apparent increase with increasing radiation doses, although the results were not significantly different from the control. These findings suggested that sublethal doses of gamma radiation may cause dose-dependent transcriptional changes in the liver of Atlantic salmon after short-term exposure. The current study predicted multiple MoA for gamma radiation and may aid future impact assessment of environmental radioactivity in fish.

Amino acids and immune response: a role for cysteine, glutamine, phenylalanine, tryptophan and arginine in T-cell function and cancer?

While proteins are critical for immunity, T-cells constitute a critical component of adaptive immunity by clearing cancerous cells among other abnormal cells. However, cancer cells exhibit a potential to escape T-cell control by employing mechanisms not completely delineated. Interesting work has investigated how certain amino acids affect the proliferation rate of T-cells as well as their effectiveness in clearing tumors. The role of amino acids cysteine, glutamine, phenylalanine, tryptophan and arginine in immunomodulation and particularly regarding T-cell proliferation and activation is discussed. The redox balance is reported to affect T-cell proliferation via modulation of cysteine availability. In addition antigen presenting cells (APCs), similar to myeloid cells determine the availability of amino acids in the extracellular microenvironment affecting T-cell proliferation and activation. A better mechanistic understanding of T-cell function modulation via amino acid signaling or metabolic properties may be helpful towards optimization of adaptive immunity with implications for cancer prognosis and treatment.

Deception and manipulation: the arms of leishmania, a successful parasite

Leishmania spp. are intracellular parasitic protozoa responsible for a group of neglected tropical diseases, endemic in 98 countries around the world, called leishmaniasis. These parasites have a complex digenetic life cycle requiring a susceptible vertebrate host and a permissive insect vector, which allow their transmission. The clinical manifestations associated with leishmaniasis depend on complex interactions between the parasite and the host immune system. Consequently, leishmaniasis can be manifested as a self-healing cutaneous affliction or a visceral pathology, being the last one fatal in 85–90% of untreated cases. As a result of a long host–parasite co-evolutionary process, Leishmania spp. developed different immunomodulatory strategies that are essential for the establishment of infection. Only through deception and manipulation of the immune system, Leishmania spp. can complete its life cycle and survive. The understanding of the mechanisms associated with immune evasion and disease progression is essential for the development of novel therapies and vaccine approaches. Here, we revise how the parasite manipulates cell death and immune responses to survive and thrive in the shadow of the immune system.

Antioxidants, inflammation and cardiovascular disease

Multiple factors are involved in the etiology of cardiovascular disease (CVD). Pathological changes occur in a variety of cell types long before symptoms become apparent and diagnosis is made. Dysregulation of physiological functions are associated with the activation of immune cells, leading to local and finally systemic inflammation that is characterized by production of high levels of reactive oxygen species (ROS). Patients suffering from inflammatory diseases often present with diminished levels of antioxidants either due to insufficient dietary intake or, and even more likely, due to increased demand in situations of overwhelming ROS production by activated immune effector cells like macrophages. Antioxidants are suggested to beneficially interfere with diseases-related oxidative stress, however the interplay of endogenous and exogenous antioxidants with the overall redox system is complex. Moreover, molecular mechanisms underlying oxidative stress in CVD are not fully elucidated. Metabolic dybalances are suggested to play a major role in disease onset and progression. Several central signaling pathways involved in the regulation of immunological, metabolic and endothelial function are regulated in a redox-sensitive manner. During cellular immune response, interferon γ-dependent pathways are activated such as tryptophan breakdown by the enzyme indoleamine 2,3-dioxygenase (IDO) in monocyte-derived macrophages, fibroblasts, endothelial and epithelial cells. Neopterin, a marker of oxidative stress and immune activation is produced by GTP-cyclohydrolase I in macrophages and dendritic cells. Nitric oxide synthase (NOS) is induced in several cell types to generate nitric oxide (NO). NO, despite its low reactivity, is a potent antioxidant involved in the regulation of the vasomotor tone and of immunomodulatory signaling pathways. NO inhibits the expression and function of IDO. Function of NOS requires the cofactor tetrahydrobiopterin (BH₄), which is produced in humans primarily by fibroblasts and endothelial cells. Highly toxic peroxynitrite (ONOO^-) is formed solely in the presence of superoxide anion (O₂^-). Neopterin and kynurenine to tryptophan ratio (Kyn/Trp), as an estimate of IDO enzyme activity, are robust markers of immune activation in vitro and in vivo. Both these diagnostic parameters are able to predict cardiovascular and overall mortality in patients at risk. Likewise, a significant association exists between increase of neopterin concentrations and Kyn/Trp ratio values and the lowering of plasma levels of vitamin-C, -E and -B. Vitamin-B deficiency is usually accompanied by increased plasma homoycsteine. Additional determination of NO metabolites, BH₄ and plasma antioxidants in patients with CVD and related clinical settings can be helpful to improve the understanding of redox-regulation in health and disease and might provide a rationale for potential antioxidant therapies in CVD.

Evaluation of oxidative stress biomarkers in patients with fixed orthodontic appliances

AIM

The aim of this study was to examine the changes in the levels of interleukine-1 beta (IL-1 β ), tumor necrosis factor alpha (TNF- α ), malondialdehyde (MDA), nitric oxide (NO), and 8-hydroxydeoxyguanosine (8-OHdG) in saliva and IL-1 β , TNF- α , and NO in gingival crevicular fluid (GCF) samples of patients with fixed orthodontic appliances.

MATERIAL AND METHOD

The subject population consisted of 50 volunteers who were in need of orthodontic treatment with fixed orthodontic appliances. GCF and saliva samples were obtained from all individuals before treatment, at 1st month of treatment and at 6th month of treatment. Periodontal clinical parameters were measured. Samples were investigated to detect IL-1 β , TNF- α , and 8-OHdG levels using ELISA method and NO and MDA levels using spectrophotometric method.

RESULTS

Since IL-1 β level detected in GCF at the 6th month of orthodontic treatment is statistically significant according to baseline (P < 0.05), all other biochemical parameters detected both in saliva and in GCF did not show any significant change at any measurement periods.

CONCLUSION

Orthodontic tooth movement and orthodontic materials used in orthodontic treatment do not lead to a change above the physiological limits that is suggestive of oxidative damage in both GCF and saliva.

Neopterin is associated with cardiovascular events and all-cause mortality in renal transplant patients

BACKGROUND

Inflammatory markers show significant associations with cardiovascular events and all-cause mortality after kidney transplantation. Neopterin, reflecting interferon-γ-release, may better reflect the proinflammatory state of recipients than less specific markers.

METHODS

Kidney transplant recipients in the Assessment of LEscol in Renal Transplant (ALERT) trial were examined and investigated for an association between serum neopterin and subsequent clinical events: graft loss, major cardiovascular events (MACE) and all-cause mortality.

RESULTS

After adjustment for established and emerging risk factors neopterin expressed as neopterin-to-creatinine ratio was significantly associated with MACE (p = 0.009) and all-cause mortality (p = 0.002). Endpoints were more frequent with increasing quartiles of neopterin-to-creatinine ratio. The incidence rates of MACE and all-cause mortality were significantly increased in the upper quartiles compared with the first.

CONCLUSIONS

This long-term prospective analysis in stable kidney allograft recipients suggests that neopterin is associated with long-term risk of cardiovascular events and all-cause mortality, but not renal outcomes.

Oxidative stress induced by HIV-1 reverse transcriptase modulates the enzyme's performance in gene immunization

HIV-1 infection induces chronic oxidative stress. The resultant neurotoxicity has been associated with Tat protein. Here, we for the first time describe the induction of oxidative stress by another HIV-1 protein, reverse transcriptase (RT). Expression of HIV-1 RT in human embryonic kidney cells generated potent production of the reactive oxygen species (ROS), detected by the fluorescence-based probes. Quantitative RT-PCR demonstrated that expression of RT in HEK293 cells induced a 10- to 15-fold increased transcription of the phase II detoxifying enzymes human

NAD(P)H

quinone oxidoreductase (Nqo1) and heme oxygenase 1 (HO-1), indicating the induction of oxidative stress response. The capacity to induce oxidative stress and stress response appeared to be an intrinsic property of a vast variety of RTs: enzymatically active and inactivated, bearing mutations of drug resistance, following different routes of processing and presentation, expressed from viral or synthetic expression-optimized genes. The total ROS production induced by RT genes of the viral origin was found to be lower than that induced by the synthetic/expression-optimized or chimeric RT genes. However, the viral RT genes induced higher levels of ROS production and higher levels of HO-1 mRNA than the synthetic genes per unit of protein in the expressing cell. The capacity of RT genes to induce the oxidative stress and stress response was then correlated with their immunogenic performance. For this, RT genes were administered into BALB/c mice by intradermal injections followed by electroporation. Splenocytes of immunized mice were stimulated with the RT-derived and control antigens and antigen-specific proliferation was assessed by IFN-γ/IL-2 Fluorospot. RT variants generating high total ROS levels induced significantly stronger IFN-γ responses than the variants inducing lower total ROS, while high levels of ROS normalized per unit of protein in expressing cell were associated with a weak IFN-γ response. Poor gene immunogenicity was also associated with a high (per unit of protein) transcription of antioxidant response element (ARE) dependent phase II detoxifying enzyme genes, specifically HO-1. Thus, we have revealed a direct link between the propensity of the microbial proteins to induce oxidative stress and their immunogenicity.