In vivo imaging of reactive oxygen and nitrogen species in inflammation using the luminescent probe L-012

Anti-inflammatory and antioxidant activities of methanol extracts and alkaloid fractions of four Mexican medicinal plants of Solanaceae

BACKGROUND

Methanol extracts and alkaloid fractions of different parts of four plant species belonging to Solanaceae family and used in Mexican traditional medicine were investigated for their total phenolic contents, anti-inflammatory and antioxidant properties.

MATERIALS AND METHODS

The total phenolic compounds of each extract was determined according to the Folin-Ciocalteu method, while the in vitro radical scavenging activities of the extracts were assessed using the DPPH and ABTS radicals. The in vivo anti-inflammatory activity was determined using the TPA-induced mouse ear edema model.

RESULTS

The methanol extracts contained the highest concentrations of phenolic compounds and also exhibited the best reducing power on the DPPH and ABTS radicals, in a concentration-dependent fashion. However, the anti-inflammatory activity did not follow the same trend, as some alkaloid fractions that showed low radical reducing power exhibited the strongest anti-inflammatory activity.

CONCLUSION

The methanol extract obtained from the flowers of Nicotiana glauca presented the best overall performance with the largest amount of phenolic compounds (111 µg garlic acid equivalents/g of extract), the best antioxidant activity (94.80% inhibition of DPPH and 97.57% of ABTS) and the highest anti-inflammatory activity (81.93% inhibition of the inflammation).

Nanoparticles with dual responses to oxidative stress and reduced ph for drug release and anti-inflammatory applications

Oxidative stress and reduced pH are involved in many inflammatory diseases. This study describes a nanoparticle-based system that is responsive to both oxidative stress and reduced pH in an inflammatory environment to effectively release its encapsulated curcumin, an immune-modulatory agent with potent anti-inflammatory and antioxidant capabilities. Because of the presence of Förster resonance energy transfer between curcumin and the carrier, this system also allowed us to monitor the intracellular release behavior. The curcumin released upon triggering could efficiently reduce the excess oxidants produced by the lipopolysaccharide (LPS)-stimulated macrophages. The feasibility of using the curcumin-loaded nanoparticles for anti-inflammatory applications was further validated in a mouse model with ankle inflammation induced by LPS. The results of these studies demonstrate that the proposed nanoparticle system is promising for treating oxidative stress-related diseases.

Periarticular bone loss in antigen-induced arthritis

Objective

Bone loss in arthritis is a complex process characterized by bone erosions and periarticular and generalized bone loss. The antigen-induced arthritis (AIA) model is mainly used to study synovitis and joint destruction, including bone erosions; however, periarticular bone loss has been less extensively investigated. The objectives of this study were to characterize and establish AIA as a model for periarticular bone loss, and to determine the importance of NADPH oxidase 2 (NOX-2)–derived reactive oxygen species (ROS) in periarticular bone loss.

Methods

Arthritis was induced in mice by local injection of antigen in one knee; the other knee was used as a nonarthritis control. At study termination, the knees were collected for histologic assessment. Periarticular bone mineral density (BMD) was investigated by peripheral quantitative computed tomography. Flow cytometric analyses were performed using synovial and bone marrow cells.

Results

AIA resulted in decreased periarticular trabecular BMD and increased frequencies of preosteoclasts, neutrophils, and monocytes in the arthritic synovial tissue. Arthritis induction resulted in an increased capability to produce ROS. However, induction of arthritis in Ncf1*^/* mice, which lack NOX-2–derived ROS, and control mice resulted in similar reductions in periarticular trabecular BMD.

Conclusion

The initiation of AIA resulted in periarticular bone loss associated with local effects on inflammatory cells and osteoclasts. Furthermore, based on our observations using this model, we conclude that NOX-2–derived ROS production is not essential for inflammation-mediated periarticular bone loss. Thus, AIA can be used as a model to investigate the pathogenesis of local inflammation–mediated bone loss.

In vitro and in vivo demonstrations of Fluorescence by Unbound Excitation from Luminescence (FUEL)

Bioluminescence imaging is a powerful technique that allows for deep-tissue analysis in living, intact organisms. However, in vivo optical imaging is compounded by difficulties due to light scattering and absorption. While light scattering is relatively difficult to overcome and compensate, light absorption by biological tissue is strongly dependent upon wavelength. For example, light absorption by mammalian tissue is highest in the blue-yellow part of the visible energy spectrum. Many natural bioluminescent molecules emit photonic energy in this range, thus in vivo optical detection of these molecules is primarily limited by absorption. This has driven efforts for probe development aimed to enhance photonic emission of red light that is absorbed much less by mammalian tissue using either direct genetic manipulation, and/or resonance energy transfer methods. Here we describe a recently identified alternative approach termed Fluorescence by Unbound Excitation from Luminescence (FUEL), where bioluminescent molecules are able to induce a fluorescent response from fluorescent nanoparticles through an epifluorescence mechanism, thereby significantly increasing both the total number of detectable photons as well as the number of red photons produced.

Measurement of respiratory burst products, released or retained, during activation of professional phagocytes

Activation of professional phagocytes, potent microbial killers of our innate immune system, is associated with an increase in cellular consumption of molecular oxygen (O2). The consumed O2 is utilized by an NADPH-oxidase to generate highly reactive oxygen species (ROS) by a one electron reduction, initially generating superoxide anion (O2 (-)) that then dismutates to hydrogen peroxide (H2O2). The ROS are strongly bactericidal molecules but may also cause tissue destruction, and are capable of driving immune competent cells of both the innate and the adaptive immune systems into apoptosis. The development of basic techniques to measure/quantify ROS generation by phagocytes during activation of the respiratory burst is of great importance, and a large number of methods have been used for this purpose. A selection of methods, including chemiluminescence amplified by luminol or isoluminol, the absorbance change following reduction of cytochrome c, and the fluorescence increase upon oxidation of PHPA, are described in detail in this chapter with special emphasis on how to distinguish between ROS that are released extracellularly, and those that are retained within intracellular organelles. These techniques can be valuable tools in research spanning from basic phagocyte biology to more clinically oriented research on innate immune mechanisms and inflammation.

Diagnostic assays for chronic granulomatous disease and other neutrophil disorders

Inasmuch as neutrophils are the primary cellular defense against bacterial and fungal infections, disorders that affect these white cells typically predispose individuals to severe and recurrent infections. Therefore, diagnosis of such disorders is an important first step in directing long-term treatment/care for the patient. Herein, we describe methods to identify chronic granulomatous disease, leukocyte adhesion deficiency, and neutropenia. The assays are relatively simple to perform and cost effective and can be performed with equipment available in most laboratories.

Commensal bacteria control cancer response to therapy by modulating the tumor microenvironment

The gut microbiota influences both local and systemic inflammation. Inflammation contributes to development, progression, and treatment of cancer, but it remains unclear whether commensal bacteria affect inflammation in the sterile tumor microenvironment. Here, we show that disruption of the microbiota impairs the response of subcutaneous tumors to CpG-oligonucleotide immunotherapy and platinum chemotherapy. In antibiotics-treated or germ-free mice, tumor-infiltrating myeloid-derived cells responded poorly to therapy, resulting in lower cytokine production and tumor necrosis after CpG-oligonucleotide treatment and deficient production of reactive oxygen species and cytotoxicity after chemotherapy. Thus, optimal responses to cancer therapy require an intact commensal microbiota that mediates its effects by modulating myeloid-derived cell functions in the tumor microenvironment. These findings underscore the importance of the microbiota in the outcome of disease treatment.

On the use of L-012, a luminol-based chemiluminescent probe, for detecting superoxide and identifying inhibitors of NADPH oxidase: a reevaluation

L-012, a luminol-based chemiluminescent (CL) probe, is widely used in vitro and in vivo to detect NADPH oxidase (Nox)-derived superoxide (O2(*-)) and identify Nox inhibitors. Yet understanding of the free radical chemistry of the L-012 probe is still lacking. We report that peroxidase and H2O2 induce superoxide dismutase (SOD)-sensitive, L-012-derived CL in the presence of oxygen. O2(*-) alone does not react with L-012 to emit luminescence. Self-generated O2(*-) during oxidation of L-012 and luminol analogs artifactually induce CL inhibitable by SOD. These aspects make assays based on luminol analogs less than ideal for specific detection and identification of O2(*-) and NOX inhibitors.

In vivo imaging method to distinguish acute and chronic inflammation

Inflammation is a fundamental aspect of many human diseases. In this video report, we demonstrate non-invasive bioluminescence imaging techniques that distinguish acute and chronic inflammation in mouse models. With tissue damage or pathogen invasion, neutrophils are the first line of defense, playing a major role in mediating the acute inflammatory response. As the inflammatory reaction progresses, circulating monocytes gradually migrate into the site of injury and differentiate into mature macrophages, which mediate chronic inflammation and promote tissue repair by removing tissue debris and producing anti-inflammatory cytokines. Intraperitoneal injection of luminol (5-amino-2,3-dihydro-1,4-phthalazinedione, sodium salt) enables detection of acute inflammation largely mediated by tissue-infiltrating neutrophils. Luminol specifically reacts with the superoxide generated within the phagosomes of neutrophils since bioluminescence results from a myeloperoxidase (MPO) mediated reaction. Lucigenin (bis-N-methylacridinium nitrate) also reacts with superoxide in order to generate bioluminescence. However, lucigenin bioluminescence is independent of MPO and it solely relies on phagocyte NADPH oxidase (Phox) in macrophages during chronic inflammation. Together, luminol and lucigenin allow non-invasive visualization and longitudinal assessment of different phagocyte populations across both acute and chronic inflammatory phases. Given the important role of inflammation in a variety of human diseases, we believe this non-invasive imaging method can help investigate the differential roles of neutrophils and macrophages in a variety of pathological conditions.

Casein hydrolysate diet controls intestinal T cell activation, free radical production and microbial colonisation in NOD mice

AIMS/HYPOTHESIS

Dietary and microbial factors and the gut immune system are important in autoimmune diabetes. We evaluated inflammatory activity in the whole gut in prediabetic NOD mice using ex vivo imaging of reactive oxygen and nitrogen species (RONS), and correlated this with the above-mentioned factors.

METHODS

NOD mice were fed a normal diet or an anti-diabetogenic casein hydrolysate (CH) diet. RONS activity was detected by chemiluminescence imaging of the whole gut. Proinflammatory and T cell cytokines were studied in the gut and islets, and dietary effects on gut microbiota and short-chain fatty acids were determined.

RESULTS

Prediabetic NOD mice displayed high RONS activity in the epithelial cells of the distal small intestine, in conjunction with a proinflammatory cytokine profile. RONS production was effectively reduced by the CH diet, which also controlled (1) the expression of proinflammatory cytokines and colonisation-dependent RegIIIγ (also known as Reg3g) in ileum; (2) intestinal T cell activation; and (3) islet cytokines. The CH diet diminished microbial colonisation, increased the Bacteroidetes:Firmicutes ratio, and reduced lactic acid and butyric acid production in the gut.

CONCLUSIONS/INTERPRETATION

Epithelial RONS production and proinflammatory T cell activation appears in the ileum of NOD mice after weaning to normal laboratory chow, but not after weaning to an anti-diabetogenic CH diet. Our data suggest a link between dietary factors, microbial colonisation and mucosal immune activation in NOD mice.

ROS production in phagocytes: why, when, and where?

In the phagocytosis field, ROS production by the phagocyte NOX has been associated with pathogen killing for the last 50 years. Since the discovery of nonphagocyte NOX, numerous other roles for ROS production have been identified. Oxidative stress and ROS-mediated signaling have received much attention in recent years. Much lower concentrations of ROS may be required for signaling compared with microbial killing. Based on the discoveries in nonphagocytic cells, it became logical to look for ROS functions distinct from pathogen killing, even in phagocytes. ROS are now linked to various forms of cell death, to chemotaxis, and to numerous modifications of cellular processes, including the NOX itself. ROS functions are clearly concentration-dependent over a wide range of concentrations. How much is required for which function? Which species are required for how much time? Is ROS signaling only a side effect of bactericidal ROS production? One major obstacle to answer these questions is the difficulty of reliable quantitative ROS detection. Signal transduction often takes place on a subcellular scale over periods of seconds or minutes, so the detection methods need to provide appropriate time and space resolution. We present examples of local ROS production, decreased degradation, signaling events, and potentially ROS-sensitive functions. We attempt to illustrate the current limitations for quantitative spatiotemporal ROS detection and point out directions for ongoing development. Probes for localized ROS detection and for combined detection of ROS, together with protein localization or other cellular parameters, are constantly improved.

Hydrogen peroxide as an immunological transmitter regulating autoreactive T cells

SIGNIFICANCE

An unexpected finding, revealed by positional cloning of genetic polymorphisms controlling models for rheumatoid arthritis, exposed a new function of Ncf1 and NADPH oxidase (NOX) 2 controlled oxidative burst.

RECENT ADVANCES

A decreased capacity to produce ROS due to a natural polymorphism was found to be the major factor leading to more severe arthritis and increased T cell-dependent autoimmunity.

CRITICAL ISSUES

In the vein of this finding, we here review a possible new role of ROS in regulating inflammatory cell and autoreactive T cell activity. It is postulated that peroxide is an immunologic transmitter secreted by antigen-presenting cells that downregulate the responses by autoreactive T cells.

FUTURE DIRECTIONS

This may operate at different levels of T cell selection and activation: during negative selection in the thymus, priming of T cells in draining lymph nodes, and while interacting with macrophages in peripheral target tissues.

Exon array analysis of alternative splicing of genes in SOD1G93A transgenic mice

Alternative splicing is a common strategy for creating functional diversities of proteins. While conventional identification of splice variants generally targets individual genes in amyotrophic lateral sclerosis, we present a novel exon-centric array that allows genome-wide identification of splice variants and concurrently provides analysis of gene expression. Compare 1 was asymptomatic SOD1G93A transgenic mice with nontransgenic littermates; compare 2 was symptomatic with asymptomatic transgenic mice. RT-PCR was performed to validate. Pathway and GO analysis were performed on abnormal genes. These findings could guide us to demonstrated the potential influence of mutant human CuZn-SOD1 and of splicing regulation in pathological processes.

Detection of reactive oxygen species derived from the family of NOX NADPH oxidases

NADPH oxidases (NOX) are superoxide anion radical (O(2)(-•))-generating enzymes. They form a family of seven members, each with a specific tissue distribution. They function as electron transport chains across membranes, using NADPH as electron donor to reduce molecular oxygen to O(2)(-•). NOX have multiple biological functions, ranging from host defense to inflammation and cellular signaling. Measuring NOX activity is crucial in understanding the roles of these enzymes in physiology and pathology. Many of the methods used to measure NOX activity are based on the detection of small molecules that react with NOX-generated O(2)(-•) or its direct dismutation product hydrogen peroxide (H(2)O(2)) to form fluorescent, luminescent, or colored products. Initial techniques were developed to measure the activity of the phagocyte isoform NOX2 during the oxidative burst of stimulated polymorphonuclear leukocytes, which generate large quantities of O(2)(-•). However, other members of the NOX family generate much less O(2)(-•) and hence H(2)O(2), and their activity is difficult to distinguish from other sources of these reactive species. In addition, O(2)(-•) and H(2)O(2) are reactive molecules and most probes are prone to artifacts and therefore should be used with appropriate controls and the data carefully interpreted. This review gives an overview of current methods used to measure NOX activity and NOX-derived O(2)(-•) and H(2)O(2) in cells, tissues, isolated systems, and living organisms, describing the advantages and caveats of many established methods with emphasis on more recent technologies and future perspectives.

Bioluminescence imaging of NADPH oxidase activity in different animal models

NADPH oxidase is a critical enzyme that mediates antibacterial and antifungal host defense. In addition to its role in antimicrobial host defense, NADPH oxidase has critical signaling functions that modulate the inflammatory response (1). Thus, the development of a method to measure in "real-time" the kinetics of NADPH oxidase-derived ROS generation is expected to be a valuable research tool to understand mechanisms relevant to host defense, inflammation, and injury. Chronic granulomatous disease (CGD) is an inherited disorder of the NADPH oxidase characterized by severe infections and excessive inflammation. Activation of the phagocyte NADPH oxidase requires translocation of its cytosolic subunits (p47(phox), p67(phox), and p40(phox)) and Rac to a membrane-bound flavocytochrome (composed of a gp91(phox) and p22(phox) heterodimer). Loss of function mutations in any of these NADPH oxidase components result in CGD. Similar to patients with CGD, gp91(phox) -deficient mice and p47(phox)-deficient mice have defective phagocyte NADPH oxidase activity and impaired host defense (2, 13). In addition to phagocytes, which contain the NADPH oxidase components described above, a variety of other cell types express different isoforms of NADPH oxidase. Here, we describe a method to quantify ROS production in living mice and to delineate the contribution of NADPH oxidase to ROS generation in models of inflammation and injury. This method is based on ROS reacting with L-012 (an analogue of luminol) to emit luminescence that is recorded by a charge-coupled device (CCD). In the original description of the L-012 probe, L-012-dependent chemiluminescence was completely abolished by superoxide dismutase, indicating that the main ROS detected in this reaction was superoxide anion (14). Subsequent studies have shown that L-012 can detect other free radicals, including reactive nitrogen species (15, 16). Kielland et al. (16) showed that topical application of phorbol myristate acetate, a potent activator of NADPH oxidase, led to NADPH oxidase-dependent ROS generation that could be detected in mice using the luminescent probe L-012. In this model, they showed that L-012-dependent luminescence was abolished in p47(phox)-deficient mice. We compared ROS generation in wildtype mice and NADPH oxidase-deficient p47(phox-/-) mice (2) in the following three models: 1) intratracheal administration of zymosan, a pro-inflammatory fungal cell wall-derived product that can activate NADPH oxidase; 2) cecal ligation and puncture (CLP), a model of intra-abdominal sepsis with secondary acute lung inflammation and injury; and 3) oral carbon tetrachloride (CCl4), a model of ROS-dependent hepatic injury. These models were specifically selected to evaluate NADPH oxidase-dependent ROS generation in the context of non-infectious inflammation, polymicrobial sepsis, and toxin-induced organ injury, respectively. Comparing bioluminescence in wildtype mice to p47(phox-/-) mice enables us to delineate the specific contribution of ROS generated by p47(phox)-containing NADPH oxidase to the bioluminescent signal in these models. Bioluminescence imaging results that demonstrated increased ROS levels in wildtype mice compared to p47(phox-/-) mice indicated that NADPH oxidase is the major source of ROS generation in response to inflammatory stimuli. This method provides a minimally invasive approach for "real-time" monitoring of ROS generation during inflammation in vivo.

Imaging inflammation: molecular strategies to visualize key components of the inflammatory cascade, from initiation to resolution

Dysregulation of inflammation is central to the pathogenesis of innumerable human diseases. Understanding and tracking the critical events in inflammation are crucial for disease monitoring and pharmacological drug discovery and development. Recent progress in molecular imaging has provided novel insights into spatial associations, molecular events and temporal sequelae in the inflammatory process. While remaining a burgeoning field in pre-clinical research, increasing application in man affords researchers the opportunity to study disease pathogenesis in humans in situ thereby revolutionizing conventional understanding of pathophysiology and potential therapeutic targets. This review provides a description of commonly used molecular imaging modalities, including optical, radionuclide and magnetic resonance imaging, and details key advances and translational opportunities in imaging inflammation from initiation to resolution.

Apocynin reduces reactive oxygen species concentrations in exhaled breath condensate in asthmatics

Asthma is an inflammatory airway disease, and oxidative stress was proven to be involved in its pathogenesis. Apocynin effectively inhibits the main source of reactive oxygen species (ROS)-nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-by blocking its activation. The aim of this study was to investigate the effect of inhaled apocynin on ROS and RNS (reactive nitrogen species) concentration in 14 nonsmoking mild asthmatics. Effects of nebulized apocynin (0.5 mg/mL) were assessed in exhaled breath condensate (EBC) after 30, 60, and 120 minutes, and safety parameters have been analyzed. Apocynin significantly decreased H2O2 concentration in EBC in comparison with placebo after 60 and 120 minutes. Moreover, apocynin significantly reduced NO(-2) concentration 30 and 60 minutes after nebulization and caused a significant decrease of NO(-3) concentration in EBC 60 and 120 minutes after administration, comparing with placebo. No adverse events have been observed throughout the study. This research confirmed anti-inflammatory properties of nebulized apocynin, which might be an effective and safe drug in bronchial asthma.

Enhancement of antibody-induced arthritis via Toll-like receptor 2 stimulation is regulated by granulocyte reactive oxygen species

The suppressive role of phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX2) complex-derived reactive oxygen species (ROS) in adaptive immunity-driven arthritis models is well established. In this study, we aimed to investigate the role of NOX2 complex-derived ROS in a model of innate immunity-driven arthritis and to identify the ROS-regulated innate receptors that control arthritis. We used collagen antibody-induced arthritis (CAIA), which is a T and B lymphocyte-independent model of the effector phase of arthritis and is induced by well-defined monoclonal arthritogenic antibodies and enhanced by injection of lipopolysaccharide (LPS). CAIA was induced in both wild-type and Ncf1 mutant mice that lack phagocyte oxidative burst, and stimulated with LPS and other agents to activate innate immune responses. We found that both LPS and lipomannan enhanced CAIA more potently in the presence of functional phagocyte ROS production than in its absence. The ROS-dependent enhancement of CAIA was regulated by TLR2, but not by TLR4 stimulation, and was driven by granulocytes, whereas macrophages did not contribute to the phenotype. In addition, we report that collagen-induced arthritis was not affected by the functionality of the TLR4. We report that TLR2 signaling as an important ROS-regulated proinflammatory pathway leads to severe neutrophil-dependent inflammation in murine CAIA and conclude that the TLR2 pathway is modulated by phagocyte ROS to stimulate the development of arthritis.

Reactive oxygen species produced by the NADPH oxidase 2 complex in monocytes protect mice from bacterial infections

Chronic granulomatous disease (CGD) is an inherited disorder characterized by recurrent life-threatening bacterial and fungal infections. CGD results from defective production of reactive oxygen species by phagocytes caused by mutations in genes encoding the NADPH oxidase 2 (NOX2) complex subunits. Mice with a spontaneous mutation in Ncf1, which encodes the NCF1 (p47(phox)) subunit of NOX2, have defective phagocyte NOX2 activity. These mice occasionally develop local spontaneous infections by Staphylococcus xylosus or by the common CGD pathogen Staphylococcus aureus. Ncf1 mutant mice were more susceptible to systemic challenge with these bacteria than were wild-type mice. Transgenic Ncf1 mutant mice harboring the wild-type Ncf1 gene under the human CD68 promoter (MN(+) mice) gained the expression of NCF1 and functional NOX2 activity specifically in monocytes/macrophages, although minimal NOX2 activity was also detected in some CD11b(+)Ly6G(+) cells defined as neutrophils. MN(+) mice did not develop spontaneous infection and were more resistant to administered staphylococcal infections compared with MN(-) mice. Most strikingly, MN(+) mice survived after being administered Burkholderia cepacia, an opportunistic pathogen in CGD patients, whereas MN(-) mice died. Thus, monocyte/macrophage expression of functional NCF1 protected against spontaneous and administered bacterial infections.

Superoxide dismutase 3 limits collagen-induced arthritis in the absence of phagocyte oxidative burst

Extracellular superoxide dismutase (SOD3), an enzyme mediating dismutation of superoxide into hydrogen peroxide, has been shown to reduce inflammation by inhibiting macrophage migration into injured tissues. In inflamed tissues, superoxide is produced by the phagocytic NOX2 complex, which consists of the catalytic subunit NOX2 and several regulatory subunits (e.g., NCF1). To analyze whether SOD3 can regulate inflammation in the absence of functional NOX2 complex, we injected an adenoviral vector overexpressing SOD3 directly into the arthritic paws of Ncf1^∗/∗ mice with collagen-induced arthritis. SOD3 reduced arthritis severity in both oxidative burst-deficient Ncf1^∗/∗ mice and also in wild-type mice. The NOX2 complex independent anti-inflammatory effect of SOD3 was further characterized in peritonitis, and SOD3 was found to reduce macrophage infiltration independently of NOX2 complex functionality. We conclude that the SOD3-mediated anti-inflammatory effect on arthritis and peritonitis operates independently of NOX2 complex derived oxidative burst.

Carotenoid intake does not affect immune-stimulated oxidative burst in greenfinches

Carotenoid-based integument colouration is extremely widespread in the animal kingdom. It has been hypothesized that carotenoid colouration is used for communicating the health status of the bearers because carotenoids are efficient immunomodulators or antioxidants. However, the latter argument has been recently debated and the mechanisms by which carotenoids modulate immunity or oxidative balance are poorly known. We performed an experiment on wild-caught captive greenfinches, passerine birds with carotenoid-based plumage colouration, in order to test whether dietary carotenoid supplementation affects immune-stimulated oxidative burst of phagocytes in the whole blood and humoral immune response to a novel antigen, Brucella abortus (BA). Additionally, we tested whether immune stimulation with bacterial lipopolysaccharide (LPS) affects blood carotenoid levels. We thus tested the effects of carotenoids on the oxidative burst of phagocytes under neutral conditions and during in vivo immune challenge. LPS injection depleted plasma carotenoids, indicating involvement of these phytochemicals in the immune response. However, we did not find any evidence that manipulation of carotenoid intake had modulated anti-BA antibody production, LPS-stimulated oxidative burst of phagocytes, or basal levels of circulating reactive oxygen species. This indicates that carotenoid intake does not affect endogenous production of reactive oxygen species by immune cells. This finding is consistent with the view that carotenoids are unlikely to provide a direct link between oxidative stress and colouration. However, it remains to be tested whether the oxidative burst of phagocytes induced in our experiment actually inflicts oxidative damage and whether carotenoids play a role in the attenuation of such potential damages.

Noninvasive assessment of localized inflammatory responses

Inflammatory diseases are associated with the accumulation of activated inflammatory cells, particularly polymorphonuclear neutrophils (PMNs), which release reactive oxygen species (ROS) to eradicate foreign bodies and microorganisms. To assess the location and extent of localized inflammatory responses, L-012, a highly sensitive chemiluminescent probe, was employed to noninvasively monitor the production of ROS. We found that L-012-associated chemiluminescence imaging can be used to identify and to quantify the extent of inflammatory responses. Furthermore, regardless of differences among animal models, there is a good linear relationship between chemiluminescence intensity and PMN numbers surrounding inflamed tissue. Depletion of PMNs substantially diminished L-012-associated chemiluminescence in vivo. Finally, L-012-associated chemiluminescence imaging was found to be a powerful tool for assessing implant-mediated inflammatory responses by measuring chemiluminescence intensity at the implantation sites. These results support the use of L-012 for monitoring the kinetics of inflammatory responses in vivo via the detection and quantification of ROS production.

Therapeutic effect of Withania somnifera on pristane-induced model of SLE

Systemic lupus erythematosus commonly known as lupus is an intricate disorder with multiple organ involvement characterized primarily by inflammation caused due to deposition of immune-complexes formed by production of autoantibodies against nuclear, nucleolar as well as cytoplasmic self-antigens. Lack of availability of suitable treatments or treatments that are only symptomatic calls for investigation of possible modalities. Withania somnifera with its immunomodulatory properties is prescribed for arthritis in ayurveda. In the present study, the therapeutic effect of Withania somnifera pure root powder (at 1,000 and 500 mg/kg body weight) on pristane-induced Balb/c model of lupus was investigated to elucidate its remedial outcome on SLE. SLE-like symptoms are produced in the model of lupus: production of autoantibodies, proteinuria, nephritis as well as immune-complex deposition along with various other inflammatory markers such as formation of lipogranuloma, production of pro-inflammatory cytokines including interleukin-6 and tumor necrosis factor-α, nitric oxide and reactive oxygen species. Withania somnifera was found to have potent inhibitory effect on proteinuria, nephritis and other inflammatory markers. Humoral response, however, was found to be impervious. The potent reduction in inflammation in the present model of lupus suggests further investigation of this herb for its possible therapeutic use in SLE.

NOX2 complex-derived ROS as immune regulators

Reactive oxygen species (ROS) are a heterogeneous group of highly reactive molecules that oxidize targets in a biologic system. During steady-state conditions, ROS are constantly produced in the electron-transport chain during cellular respiration and by various constitutively active oxidases. ROS production can also be induced by activation of the phagocyte NADPH oxidase 2 (NOX2) complex in a process generally referred to as an oxidative burst. The induced ROS have long been considered proinflammatory, causing cell and tissue destruction. Recent findings have challenged this inflammatory role of ROS, and today, ROS are also known to regulate immune responses and cell proliferation and to determine T-cell autoreactivity. NOX2-derived ROS have been shown to suppress antigen-dependent T-cell reactivity and remarkably to reduce the severity of experimental arthritis in both rats and mice. In this review, we discuss the role of ROS and the NOX2 complex as suppressors of autoimmunity, inflammation, and arthritis.

NADPH oxidase subunit 4-mediated reactive oxygen species contribute to cycling hypoxia-promoted tumor progression in glioblastoma multiforme

BACKGROUND

Cycling and chronic tumor hypoxia are involved in tumor development and growth. However, the impact of cycling hypoxia and its molecular mechanism on glioblastoma multiforme (GBM) progression remain unclear.

METHODOLOGY

Glioblastoma cell lines, GBM8401 and U87, and their xenografts were exposed to cycling hypoxic stress in vitro and in vivo. Reactive oxygen species (ROS) production in glioblastoma cells and xenografts was assayed by in vitro ROS analysis and in vivo molecular imaging studies. NADPH oxidase subunit 4 (Nox4) RNAi-knockdown technology was utilized to study the role of Nox4 in cycling hypoxia-mediated ROS production and tumor progression. Furthermore, glioblastoma cells were stably transfected with a retroviral vector bearing a dual reporter gene cassette that allowed for dynamic monitoring of HIF-1 signal transduction and tumor cell growth in vitro and in vivo, using optical and nuclear imaging. Tempol, an antioxidant compound, was used to investigate the impact of ROS on cycling hypoxia-mediated HIF-1 activation and tumor progression.

PRINCIPAL FINDINGS

Glioblastoma cells and xenografts were compared under cycling hypoxic and normoxic conditions; upregulation of NOX4 expression and ROS levels were observed under cycling hypoxia in glioblastoma cells and xenografts, concomitant with increased tumor cell growth in vitro and in vivo. However, knockdown of Nox4 inhibited these effects. Moreover, in vivo molecular imaging studies demonstrated that Tempol is a good antioxidant compound for inhibiting cycling hypoxia-mediated ROS production, HIF-1 activation, and tumor growth. Immunofluorescence imaging and flow cytometric analysis for NOX4, HIF-1 activation, and Hoechst 3342 in glioblastoma also revealed high localized NOX4 expression predominantly in potentially cycling hypoxic areas with HIF-1 activation and blood perfusion within the endogenous solid tumor microenvironment.

CONCLUSIONS

Cycling hypoxia-induced ROS via Nox4 is a critical aspect of cancer biology to consider for therapeutic targeting of cycling hypoxia-promoted HIF-1 activation and tumor progression in GBM.

Highly selective in-vivo imaging of tumor as an inflammation site by ROS detection using hydrocyanine-conjugated, functional nano-carriers

Previously, the optical imaging of chitosan-functionalized, Pluronic-based nano-carriers by Cy5.5 conjugation revealed a good tumor targeting characteristic of the nano-carriers in vivo [J. Control. Release, 147 (2010) 109-117]. However, in spite of the relatively strong signal from tumor site, they also showed strong fluorescence signals from other organs, especially liver. Thus, for the detection of pathological sites, the direct use of the Cy5.5-conjugated nano-carriers is limited due to significant background signals associated with non-specific delivery of the probes. To overcome this limitation, in this study, we prepared hydrocyanine-conjugated and chitosan-functionalized Pluronic-based nano-carriers (Hydrocyanine-NC) that can detect ROS in pathological sites. The reduction of cyanine to hydrocyanine of the nano-carriers resulted in complete disappearance of fluorescence emission, and the fluorescence could be recovered by ROS-induced re-oxidization. Hydrocyanine-NC could detect various ROS including superoxide anion (O(2)(-)) and hydroxyl radical (OH(-)) in a dose-dependent manner. Hydrocyanine-NC was also stable in serum-containing media and did not show acute cytotoxicity. Hydrocyanine-NC developed strong fluorescence by the intracellular ROS formation in LPS-stimulated macrophage cells in vitro. As an in-vivo inflammation site imaging, SCC7 tumor-bearing mice were optically monitored after the i.v. injection of the dye-conjugated nano-carriers. When non-reduced, cyanine-conjugated and chitosan-functionalized Pluronic-based nano-carriers (Cyanine-NC) were injected, strong fluorescence emission was observed from the abdominal area as well as from the tumor site, and it remained over 2days. In contrast, in the case of Hydrocyanine-NC, the initially very weak fluorescence emission from the abdominal area disappeared over time whereas the fluorescence emission from the tumor site was similar to that of Cyanine-NC. Therefore, the re-oxidation of Hydrocyanine-NC by ROS in vivo specifically eliminated the background signals from non-specific delivery of the probes, but it produced fluorescence emission strong enough to monitor the target inflammation site selectively.

Comparison of fluorescence reagents for simultaneous determination of hydroxylated phenylalanine and nitrated tyrosine by high-performance liquid chromatography with fluorescence detection

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are well-known and important contributors to oxidative and nitrosative stress in several diseases. Hydroxylated phenylalanine and nitrated tyrosine products appear to be particularly susceptible targets of oxidative and nitrosative stress. We compared fluorescence reagents for their potential use in the analysis of hydroxylated phenylalanine and nitrated tyrosine products with a high-sensitivity and high-specificity HPLC-UV-FL technique. The analytes were extracted from serum via solid-phase extraction on Waters Oasis MCX cartridges. Chromatographic separation was achieved on an ODS column (Capcell Pak MG II; 150 × 2.0 mm) using a gradient mobile phase consisting of 20 mm sodium phosphate buffer (adjusted to pH 3.0) and acetonitrile. The method quantification limit for 4-nitrophenylalanine, m-tyrosine, and 3-nitrotyrosine was 0.1 μm. The relative standard deviation of the precision and accuracy was acceptable at the spiked concentration of 0.1 μm for 4-nitrophenylalanine, m-tyrosine and 3-nitrotyrosine. The method could be used for the in vitro analysis of serum samples.

Effects of pharmacological inhibition of NADPH oxidase or iNOS on pro-inflammatory cytokine, palmitic acid or H2O2-induced mouse islet or clonal pancreatic β-cell dysfunction

Various pancreatic β-cell stressors including cytokines and saturated fatty acids are known to induce oxidative stress, which results in metabolic disturbances and a reduction in insulin secretion. However, the key mechanisms underlying dysfunction are unknown. We investigated the effects of prolonged exposure (24 h) to pro-inflammatory cytokines, H(2)O(2) or PA (palmitic acid) on β-cell insulin secretion, ATP, the NADPH oxidase (nicotinamide adenine dinucleotide phosphate oxidase) component p47phox and iNOS (inducible nitric oxide synthase) levels using primary mouse islets or clonal rat BRIN-BD11 β-cells. Addition of a pro-inflammatory cytokine mixture [IL-1β (interleukin-1β), TNF-α (tumour necrosis factor-α) and IFN-γ (interferon-γ)] or H(2)O(2) (at sub-lethal concentrations) inhibited chronic (24 h) levels of insulin release by at least 50% (from islets and BRIN-BD11 cells), while addition of the saturated fatty acid palmitate inhibited acute (20 min) stimulated levels of insulin release from mouse islets. H(2)O(2) decreased ATP levels in the cell line, but elevated p47phox and iNOS levels as did cytokine addition. Similar effects were observed in mouse islets with respect to elevation of p47phox and iNOS levels. Addition of antioxidants SOD (superoxide dismutase), Cat (catalase) and NAC (N-acetylcysteine) attenuated H(2)O(2) or the saturated fatty acid palmitate-dependent effects, but not cytokine-induced dysfunction. However, specific chemical inhibitors of NADPH oxidase and/or iNOS appear to significantly attenuate the effects of cytokines, H(2)O(2) or fatty acids in islets. While pro-inflammatory cytokines are known to increase p47phox and iNOS levels in β-cells, we now report that H(2)O(2) can increase levels of the latter two proteins, suggesting a key role for positive-feedback redox sensitive regulation of β-cell dysfunction.

Real-time in vivo detection of biomaterial-induced reactive oxygen species

The non-specific host response to implanted biomaterials is often a key challenge of medical device design. To evaluate biocompatibility, measuring the release of reactive oxygen species (ROS) produced by inflammatory cells in response to biomaterial surfaces is a well-established method. However, the detection of ROS in response to materials implanted in vivo has not yet been demonstrated. Here, we develop a bioluminescence whole animal imaging approach to observe ROS released in response to subcutaneously-implanted materials in live animals. We compared the real-time generation of ROS in response to two representative materials, polystyrene and alginate, over the course of 28 days. High levels of ROS were observed near polystyrene, but not alginate implants, and persisted throughout the course of 28 days. Histological analysis revealed that high levels of ROS correlated not only with the presence of phagocytic cells at early timepoints, but also fibrosis at later timepoints, suggesting that ROS may be involved in both the acute and chronic phase of the foreign body response. These data are the first in vivo demonstration of ROS generation in response to implanted materials, and describe a novel technique to evaluate the host response.

Molecular imaging of transcriptional regulation during inflammation

Molecular imaging enables non-invasive visualization of the dynamics of molecular processes within living organisms in vivo. Different imaging modalities as MRI, SPECT, PET and optic imaging are used together with molecular probes specific for the biological process of interest. Molecular imaging of transcription factor activity is done in animal models and mostly in transgenic reporter mice, where the transgene essentially consists of a promoter that regulates a reporter gene. During inflammation, the transcription factor NF-κB is widely involved in orchestration and regulation of the immune system and almost all imaging studies in this field has revolved around the role and regulation of NF-κB. We here present a brief introduction to experimental use and design of transgenic reporter mice and a more extensive review of the various studies where molecular imaging of transcriptional regulation has been applied during inflammation.