An A2A adenosine receptor agonist, ATL313, reduces inflammation and improves survival in murine sepsis models

DAMPening COVID-19 Severity by Attenuating Danger Signals

COVID-19 might lead to multi-organ failure and, in some cases, to death. The COVID-19 severity is associated with a “cytokine storm.” Danger-associated molecular patterns (DAMPs) are proinflammatory molecules that can activate pattern recognition receptors, such as toll-like receptors (TLRs). DAMPs and TLRs have not received much attention in COVID-19 but can explain some of the gender-, weight- and age-dependent effects. In females and males, TLRs are differentially expressed, likely contributing to higher COVID-19 severity in males. DAMPs and cytokines associated with COVID-19 mortality are elevated in obese and elderly individuals, which might explain the higher risk for severer COVID-19 in these groups. Adenosine signaling inhibits the TLR/NF-κB pathway and, through this, decreases inflammation and DAMPs’ effects. As vaccines will not be effective in all susceptible individuals and as new vaccine-resistant SARS-CoV-2 mutants might develop, it remains mandatory to find means to dampen COVID-19 disease severity, especially in high-risk groups. We propose that the regulation of DAMPs via adenosine signaling enhancement might be an effective way to lower the severity of COVID-19 and prevent multiple organ failure in the absence of severe side effects.

Synapomorphic features of hepatic and pulmonary vasculatures include comparable purinergic signaling responses in host defense and modulation of inflammation

Hepatosplanchnic and pulmonary vasculatures constitute synapomorphic, highly comparable networks integrated with the external environment. Given functionality related to obligatory requirements of "feeding and breathing," these organs are subject to constant environmental challenges entailing infectious risk, antigenic and xenobiotic exposures. Host responses to these stimuli need to be both protective and tightly regulated. These functions are facilitated by dualistic, high-low pressure blood supply of the liver and lungs, as well as tolerogenic characteristics of resident immune cells and signaling pathways. Dysregulation in hepatosplanchnic and pulmonary blood flow, immune responses, and microbiome implicate common pathogenic mechanisms across these vascular networks. Hepatosplanchnic diseases, such as cirrhosis and portal hypertension, often impact lungs and perturb pulmonary circulation and oxygenation. The reverse situation is also noted with lung disease resulting in hepatic dysfunction. Others, and we, have described common features of dysregulated cell signaling during liver and lung inflammation involving extracellular purines (e.g., ATP, ADP), either generated exogenously or endogenously. These metabokines serve as danger signals, when released by bacteria or during cellular stress and cause proinflammatory and prothrombotic signals in the gut/liver-lung vasculature. Dampening of these danger signals and organ protection largely depends upon activities of vascular and immune cell-expressed ectonucleotidases (CD39 and CD73), which convert ATP and ADP into anti-inflammatory adenosine. However, in many inflammatory disorders involving gut, liver, and lung, these protective mechanisms are compromised, causing perpetuation of tissue injury. We propose that interventions that specifically target aberrant purinergic signaling might prevent and/or ameliorate inflammatory disorders of the gut/liver and lung axis.

Deletion of the adenosine A2A receptor increases the survival rate in a mice model of polymicrobial sepsis

We aim to investigate the role of A_2A receptor in peritonitis-related sepsis by injection of a fecal solution (FS) as a model of polymicrobial infection. C57/black J6 wild-type (WT) and A_2A-deficient mice (A_2AKO) were exposed to sepsis induced by intraperitoneal injection of a FS (FS-induced peritonitis) or instead was injected with saline buffer (Sham). Survival rate and sepsis score were measured up to 48 h. The presence of bacteria in tissue homogenates was analyzed. Telemetry and speckle laser Doppler were used for systemic blood pressure and peripheral blood perfusion analysis, respectively. Histological analysis and identification of active caspase 3 were performed in selected organs, including the liver. The survival rate of A_2AKO mice exposed to FS-induced peritonitis was significantly higher, and the sepsis score was lower than their respective WT counterpart. Injection of FS increases (50 to 150 folds) the number of colonies forming units in the liver, kidney, blood, and lung in WT mice, while these effects were significantly attenuated in A_2AKO mice exposed to FS-induced peritonitis. A significant reduction in both systolic and diastolic blood pressure, as well as in the peripheral perfusion was observed in WT and A_2AKO mice exposed to FS-induced peritonitis. Although, these last effects were significantly attenuated in A_2AKO mice. Histological analysis showed a large perivascular infiltration of polymorphonuclear in the liver of WT and A_2AKO mice exposed to FS-induced peritonitis, but again, this effect was attenuated in A_2AKO mice. Finally, high expression of active caspase 3 was found only in the liver of WT mice exposed to FS-induced peritonitis. The absence of the A_2A receptor increases the survival rate in mice exposed to polymicrobial sepsis. This outcome was associated with both hemodynamic compensation and enhanced anti-bacterial response.

Sustained reversal of central neuropathic pain induced by a single intrathecal injection of adenosine A2A receptor agonists

Central neuropathic pain is a debilitating outcome of spinal cord injury (SCI) and current treatments to alleviate this pain condition are ineffective. A growing body of literature suggests that activating adenosine A_2A receptors (A_2ARs) decreases the production of proinflammatory cytokines and increases the production of anti-inflammatory cytokines. Here, the effect of administering intrathecal A_2AR agonists on central neuropathic pain was measured using hindpaw mechanical allodynia in a rat model of SCI termed spinal neuropathic avulsion pain (SNAP). Other models of SCI cause extensive damage to the spinal cord, resulting in paralysis and health problems. SNAP rats with unilateral low thoracic (T13)/high lumbar (L1) dorsal root avulsion develop below-level bilateral allodynia, without concomitant motor or health problems. A single intrathecal injection of the A_2AR agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamido adenosine HCl (CGS21680) reversed SCI-induced allodynia for at least 6 weeks. The reversal is likely in part mediated by interleukin (IL)-10, as intrathecally administering neutralizing IL-10 antibodies 1 week after CGS21680 abolished the anti-allodynic effect of CGS21680. Dorsal spinal cord tissue from the ipsilateral site of SCI (T13/L1) was assayed 1 and 6 weeks after CGS21680 for IL-10, CD11b, and tumor necrosis factor (TNF) gene expression. CGS21680 treatment did not change IL-10 gene expression but did significantly decrease CD11b and TNF gene expression at both timepoints. A second A_2AR agonist, 4-(3-(6-amino-9-(5-cyclopropylcarbamoyl-3,4-dihydroxytetrahydrofuran-2-yl)-9H-purin-2-yl)prop-2-ynyl)piperidine-1-carboxylic acid methyl ester (ATL313), was also able to significantly prevent and reverse SCI-induced allodynia for several weeks after a single intrathecal injection, providing converging lines of evidence of A_2AR involvement. The enduring pain reversal after a single intrathecal injection of A_2AR agonists suggests that A_2AR agonists could be exciting new candidates for treating SCI-induced central neuropathic pain.

Anti-inflammatory effect of a novel locally acting A2A receptor agonist in a rat model of oxazolone-induced colitis

Adenosine represents a powerful modulating factor, which has been shown to orchestrate the scope, duration, and remission of the inflammatory response through the activation of four specific receptors, classified as A₁, A_2A, A_2B, and A₃, all being widely expressed in a variety of immune cells. Several selective A_2A receptor agonists have displayed anti-inflammatory effects, through the suppression of IL-12, TNF, and IFN-γ production by monocytes and lymphocytes, in the setting of chronic intestinal inflammation. However, the therapeutic application of A_2A receptor agonists remains hindered by the risk of serious cardiovascular adverse effects arising from the wide systemic distribution of A_2A receptors. The present study focused on evaluating the anti-inflammatory effects of the novel poorly absorbed A_2A receptor agonist PSB-0777 in a rat model of oxazolone-induced colitis as well as to evaluate its cardiovascular adverse effects, paying particular attention to the onset of hypotension, one of the main adverse effects associated with the systemic pharmacological activation of A_2A receptors. Colitis was associated with decreased body weight, an enhanced microscopic damage score and increased levels of colonic myeloperoxidase (MPO). PSB-0777, but not dexamethasone, improved body weight. PSB-0777 and dexamethasone ameliorated microscopic indexes of inflammation and reduced MPO levels. The beneficial effects of PSB-0777 on inflammatory parameters were prevented by the pharmacological blockade of A_2A receptors. No adverse cardiovascular events were observed upon PSB-0777 administration. The novel A_2A receptor agonist PSB-0777 could represent the base for the development of innovative pharmacological entities able to act in an event-specific and site-specific manner.

CD39 limits P2X7 receptor inflammatory signaling and attenuates sepsis-induced liver injury

BACKGROUND & AIMS

The severity of sepsis can be linked to excessive inflammatory responses resulting in hepatic injury. P2X7 receptor activation by extracellular ATP (eATP) exacerbates inflammation by augmenting cytokine production; while CD39 (ENTPD1) scavenges eATP to generate adenosine, thereby limiting P2X7 activation and resulting in A_2A receptor stimulation. We aim to determine how the functional interaction of P2X7 receptor and CD39 control the macrophage response, and consequently impact on sepsis and liver injury.

METHODS

Sepsis was induced by cecal ligation and puncture in C57BL/6 wild-type (WT) and CD39^-/- mice. Several in vitro assays were performed using peritoneal or bone marrow derived macrophages to determine CD39 ectonucleotidase activity and its role in sepsis-induced liver injury.

RESULTS

CD39 expression in macrophages limits ATP-P2X7 receptor pro-inflammatory signaling. P2X7 receptor paradoxically boosts CD39 activity. Inhibition and/or deletion of P2X7 receptor in LPS-primed macrophages attenuates cytokine production and inflammatory signaling as well as preventing ATP-induced increases in CD39 activity. Septic CD39^-/- mice exhibit higher levels of inflammatory cytokines and show more pronounced liver injury than WT mice. Pharmacological P2X7 blockade largely prevents tissue damage, cell apoptosis, cytokine production, and the activation of inflammatory signaling pathways in the liver from septic WT, while only attenuating these outcomes in CD39^-/- mice. Furthermore, the combination of P2X7 blockade with adenosine A_2A receptor stimulation completely inhibits cytokine production, the activation of inflammatory signaling pathways, and protects septic CD39^-/- mice against liver injury.

CONCLUSIONS

CD39 attenuates sepsis-associated liver injury by scavenging eATP and ultimately generating adenosine. We propose boosting of CD39 would suppress P2X7 responses and trigger adenosinergic signaling to limit systemic inflammation and restore liver homeostasis during the acute phase of sepsis. Lay summary: CD39 expression in macrophages limits P2X7-mediated pro-inflammatory responses, scavenging extracellular ATP and ultimately generating adenosine. CD39 genetic deletion exacerbates sepsis-induced experimental liver injury. Combinations of a P2X7 antagonist and adenosine A_2A receptor agonist are hepatoprotective during the acute phase of abdominal sepsis.

A New Class of Fluorinated A2A Adenosine Receptor Agonist with Application to Last-Step Enzymatic [18 F]Fluorination for PET Imaging

The A_2A adenosine receptor belongs to a family of G-coupled protein receptors that have been subjected to extensive investigation over the last few decades. Due to their prominent role in the biological functions of the heart, lungs, CNS and brain, they have become a target for the treatment of illnesses ranging from cancer immunotherapy to Parkinson's disease. The imaging of such receptors by using positron emission tomography (PET) has also been of interest, potentially providing a valuable tool for analysing and diagnosing various myocardial and neurodegenerative disorders, as well as offering support to drug discovery trials. Reported herein are the design, synthesis and evaluation of two new 5'-fluorodeoxy-adenosine (FDA)-based receptor agonists (FDA-PP1 and FDA-PP2), each substituted at the C-2 position with a terminally functionalised ethynyl unit. The structures enable a synthesis of ¹⁸ F-labelled analogues by direct, last-step radiosynthesis from chlorinated precursors using the fluorinase enzyme (5'-fluoro-5'-deoxyadenosine synthase), which catalyses a transhalogenation reaction. This delivers a new class of A_2A adenosine receptor agonist that can be directly radiolabelled for exploration in PET studies.

A2A adenosine receptor upregulation correlates with disease activity in patients with systemic lupus erythematosus

BACKGROUND

Adenosine is a purine nucleoside implicated in the regulation of the innate and adaptive immune systems, acting through its interaction with four cell surface receptors: A1, A2A, A2B, and A3. There is intense interest in understanding how adenosine functions in health and during disease, but surprisingly little is known about the actual role of adenosine-mediated mechanisms in systemic lupus erythematosus (SLE). With this background, the aim of the present study was to test the hypothesis that dysregulation of A1, A2A, A2B, and A3 adenosine receptors (ARs) in lymphocytes of patients with SLE may be involved in the pathogenesis of the disease and to examine the correlations between the status of the ARs and the clinical parameters of SLE.

METHODS

ARs were analyzed by performing saturation-binding assays, as well as messenger RNA and Western blot analysis, with lymphocytes of patients with SLE in comparison with healthy subjects. We tested the effect of A2AAR agonists in the nuclear factor kB (NF-kB) pathway and on the release of interferon (IFN)-α; tumor necrosis factor (TNF)-α; and interleukin (IL)-2, IL-6, IL-1β, and IL-10.

RESULTS

In lymphocytes obtained from 80 patients with SLE, A2AARs were upregulated compared with those of 80 age-matched healthy control subjects, while A1, A2B, and A3 ARs were unchanged. A2AAR density was inversely correlated with Systemic Lupus Erythematosus Disease Activity Index 2000 score disease activity through time evaluated according to disease course patterns, serositis, hypocomplementemia, and anti-double-stranded DNA positivity. A2AAR activation inhibited the NF-kB activation pathway and diminished inflammatory cytokines (IFN-α, TNF-α, IL-2, IL-6, IL-1β), but it potentiated the release of anti-inflammatory IL-10.

CONCLUSIONS

These data suggest the involvement of A2AARs in the complex pathogenetic network of SLE, acting as a modulator of the inflammatory process. It could represent a compensatory pathway to better counteract disease activity. A2AAR activation significantly reduced the release of proinflammatory cytokines while enhancing those with anti-inflammatory activity, suggesting a potential translational use of A2AAR agonists in SLE pharmacological treatment.

Purinergic regulation of the immune system

Cellular stress or apoptosis triggers the release of ATP, ADP and other nucleotides into the extracellular space. Extracellular nucleotides function as autocrine and paracrine signalling molecules by activating cell-surface P2 purinergic receptors that elicit pro-inflammatory immune responses. Over time, extracellular nucleotides are metabolized to adenosine, leading to reduced P2 signalling and increased signalling through anti-inflammatory adenosine (P1 purinergic) receptors. Here, we review how local purinergic signalling changes over time during tissue responses to injury or disease, and we discuss the potential of targeting purinergic signalling pathways for the immunotherapeutic treatment of ischaemia, organ transplantation, autoimmunity or cancer.

Adenosine and the adenosine A2A receptor agonist, CGS21680, upregulate CD39 and CD73 expression through E2F-1 and CREB in regulatory T cells isolated from septic mice

The number of regulatory T cells (Treg cells) and the expression of ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1; also known as CD39) and 5'-ectonucleotidase (NT5E; also known as CD73) on the Treg cell surface are increased during sepsis. In this study, to determine the factors leading to the high expression of CD39 and CD73, and the regulation of the CD39/CD73/adenosine pathway in Treg cells under septic conditions, we constructed a mouse model of sepsis and separated the Treg cells using a flow cytometer. The Treg cells isolated from the peritoneal lavage and splenocytes of the mice were treated with adenosine or the specific adenosine A2A receptor agonist, CGS21680, and were transfected with specific siRNA targeting E2F transcription factor 1 (E2F-1) or cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB), which are predicted transcription regulatory factors of CD39 or CD73. The regulatory relationships among these factors were then determined by western blot analysis and dual-luciferase reporter assay. In addition, changes in adenosine metabolism were measured in the treated cells. The results revealed that adenosine and CGS21680 significantly upregulated CD39 and CD73 expression (P<0.01). E2F-1 and CREB induced CD39 and CD73 expression, and were upregulated by adenosine and CGS21680. Adenosine triphosphate (ATP) hydrolysis and adenosine generation were inhibited by the knockdown of E2F-1 or CREB, and were accelerated in the presence of CGS21680. Based on these results, it can be inferred that adenosine, the adenosine A2A receptor agonist, E2F-1 and CREB are the possible factors contributing to the high expression of CD39 and CD73 on the Treg cell surface during sepsis. Adenosine and its A2A receptor agonist served as the signal transducer factors of the CD39/CD73/adenosine pathway, accelerating adenosine generation. Our study may benefit further research on adenosine metabolism for the treatment of sepsis.

Intestinal anti-inflammatory activity of the seeds of Raphanus sativus L. in experimental ulcerative colitis models

ETHNOPHARMACOLOGICAL RELEVANCE

Water extract of Raphanus sativus L. (RSL) seeds was traditionally used to treat digestive inflammatory complaints in Korean culture. RSL seeds exerted antioxidant, anti-inflammatory, and anti-septic functions, suggesting their pharmacological potential for the treatment of inflammatory pathologies associated with oxidative stress such as inflammatory bowel disease.

AIM OF THIS STUDY

We evaluated the intestinal anti-inflammatory effects of RSL seed water extract (RWE) in experimental rat models of trinitrobenzenesulphonic acid (TNBS)- or dextran sodium sulfate (DSS)-induced colitis.

MATERIALS AND METHODS

RWE was characterized by determining the content of sinapic acid as a reference material and then assayed in the DSS and TNBS models of rat colitis. Male Sprague-Dawley rats were divided into 10 groups (n=7/group): non-colitic control, DSS or TNBS control, DSS colitis groups treated with RWE (100mg/kg) or mesalazine (25mg/kg), and TNBS colitis groups treated with various doses (10, 40, 70, and 100mg/kg) of RWE or mesalazine (25mg/kg). RWE or mesalazine treatment started the same day of colitis induction and rats were sacrificed 24h after the last treatment followed by histological and biochemical analyses.

RESULTS

Oral administration with RWE suppressed intestinal inflammatory damages in both DSS- and TNBS-induced colitic rats. The treatment with 100mg/kg RWE recovered intestinal damages caused by TNBS or DSS to levels similar to that of mesalazine, decreasing the activity of myeloperoxidase activity and the secretion of tumor necrosis factor (TNF)-α and interleukin (IL)-1β. RWE treatment inhibited malondialdehyde production and glutathione reduction in colon of colitis rats. The administration of RWE at dose of 100mg/kg also suppressed the TNBS- or DSS-stimulated expression of TNF-α, IL-1β, monocyte chemotactic protein-1, inducible nitric oxide, and intercellular adhesion molecule-1. Furthermore, RWE inhibited p38 kinase and DNA-nuclear factor-κB binding activities, both of which were stimulated in the colitic rats.

CONCLUSIONS

The current findings show that RWE ameliorates intestinal oxidative and inflammatory damages in DSS and TNBS models of rat colitis, suggesting its beneficial use for the treatment of intestinal inflammatory disorders.

Adenosine 2A receptor agonism: A single intrathecal administration attenuates motor paralysis in experimental autoimmune encephalopathy in rats

A single intrathecal dose of adenosine 2A receptor (A2AR) agonist was previously reported to produce a multi-week reversal of allodynia in two different models of neuropathic pain in addition to downregulating glial activation markers in the spinal cord. We aimed to determine whether a single intrathecal administration of an A2AR agonist was able to attenuate motor symptoms induced by experimental autoimmune encephalopathy. Two A2AR agonists (CGS21680 and ATL313) significantly attenuated progression of motor symptoms following a single intrathecal administration at the onset of motor symptoms. OX-42, a marker of microglial activation, was significantly attenuated in the lumbar spinal cord following A2AR administration compared to vehicle. Therefore, A2AR agonists attenuate motor symptoms of EAE by acting on A2AR in the spinal cord.

Positive allosteric modulation of the adenosine A2a receptor attenuates inflammation

Background

Adenosine is produced at high levels at inflamed sites as a by-product of cellular activation and breakdown. Adenosine mediates its anti-inflammatory activity primarily through the adenosine A_2a receptor (A_2aR), a member of the G-protein coupled receptors. A_2aR agonists have demonstrated anti-inflammatory efficacy, however, their therapeutic utility is hindered by a lack of adenosine receptor subtype selectivity upon systemic exposure. We sought to harness the anti-inflammatory effects of adenosine by enhancing the responsiveness of A_2aR to endogenously produced adenosine through allosteric modulation. We have identified a family of positive allosteric modulators (PAMs) of the A_2aR. Using one member of this PAM family, AEA061, we demonstrate that A_2aRs are amenable to allosteric enhancement and such enhancement produces increased A_2aR signaling and diminished inflammation in vivo.

Methods

A_2aR activity was evaluated using a cell-based cAMP assay. Binding affinity of A_2aR was determined using [³H]CGS 21680. A_2aR-mediated G-protein activation was quantified using [³⁵S]GTP-γS. The effect of AEA061 on cytokine production was evaluated using primary monocytes and splenocytes. The anti-inflammatory effect of AEA061 was evaluated in the LPS-induced mouse model of inflammation.

Results

AEA061 had no detectable intrinsic agonist activity towards either rat or human A_2aRs. AEA061 enhanced the efficacy of adenosine to rat and human A_2aRs by 11.5 and 2.8 fold respectively. AEA061 also enhanced the maximal response by 4.2 and 2.1 fold for the rat and the human A_2aR respectively. AEA061 potentiated agonist-mediated Gα activation by 3.7 fold. Additionally, AEA061 enhanced both the affinity as well as the B_max at the human A_2aR by 1.8 and 3 fold respectively. Consistent with the anti-inflammatory role of the A_2aR, allosteric enhancement with AEA061 inhibited the production of TNF-α, MIP-1α, MIP-1β, MIP-2, IL-1α, KC and RANTES by LPS-stimulated macrophages and/or splenocytes. Moreover, AEA061 reduced circulating plasma TNF-α and MCP-1 levels and increased plasma IL-10 in endotoxemic A_2aR intact, but not in A_2aR deficient, mice.

Conclusions

AEA061 increases affinity and B_max of A_2aR to adenosine, thereby increasing adenosine potency and efficacy, which translates to enhanced A_2aR responsiveness. Since the A_2aR negatively regulates inflammation, PAMs of the receptor offer a novel means of modulating inflammatory processes.

The A2A adenosine receptor is a dual coding gene: a novel mechanism of gene usage and signal transduction

The A2A adenosine receptor (A2AR) is a G protein-coupled receptor and a major target of caffeine. The A2AR gene encodes alternative transcripts that are initiated from at least two independent promoters. The different transcripts of the A2AR gene contain the same coding region and 3'-untranslated region and different 5'-untranslated regions that are highly conserved among species. We report here that in addition to the production of the A2AR protein, translation from an upstream, out-of-frame AUG of the rat A2AR gene produces a 134-amino acid protein (designated uORF5). An anti-uORF5 antibody recognized a protein of the predicted size of uORF5 in PC12 cells and rat brains. Up-regulation of A2AR transcripts by hypoxia led to increased levels of both the A2AR and uORF5 proteins. Moreover, stimulation of A2AR increased the level of the uORF5 protein via post-transcriptional regulation. Expression of the uORF5 protein suppressed the AP1-mediated transcription promoted by nerve growth factor and modulated the expression of several proteins that were implicated in the MAPK pathway. Taken together, our results show that the rat A2AR gene encodes two distinct proteins (A2AR and uORF5) in an A2AR-dependent manner. Our study reveals a new example of the complexity of the mammalian genome and provides novel insights into the function of A2AR.

Methanol extract of the aerial parts of barley (Hordeum vulgare) suppresses lipopolysaccharide-induced inflammatory responses in vitro and in vivo

CONTEXT

Recently, there has been renewed interest in barley (Hordeum vulgare L. Poaceae) as a functional food and for its medicinal properties.

OBJECTIVE

This study examines the anti-inflammatory potential of the active fractions of barley and the mechanisms involved.

MATERIALS AND METHODS

The macrophages were exposed to 100 μg/mL of each of the barley extracts in the presence of 1 μg/mL lipopolysaccharide (LPS) and after 24 or 48 h of incubation, cells or culture supernatants were analyzed by various assays. The anti-inflammatory potential of barley fractions was also investigated using the LPS-injected septic mouse model. The active constituents in the fractions were identified using gas chromatography-mass spectrometry (GC-MS).

RESULTS

The active fractions, named F₄, F₇, F₉ and F₁₂, inhibited almost completely the LPS-induced production of nitric oxide (NO) and inducible NO synthase. Pre-treatment with these fractions at 100 μg/mL diminished the tumor necrosis factor-α (TNF-α) levels to 19.8, 3.5, 1.2 and 1.7 ng/mL, respectively, compared to LPS treatment alone (41.5 ng/mL). These fractions at 100 μg/mL also suppressed apparently the secretion of interleukin (IL)-6 and IL-1β and the DNA-binding activity of nuclear factor-κB in LPS-stimulated cells. Mice injected intraperitoneally with LPS (30 mg/kg BW) showed 20% survival at 48 h after injection, whereas oral administration of the fractions improved the survival rates to 80%. GC-MS analysis revealed the presence of the derivatives of benzoic and cinnamic acids and fatty acids in the fractions.

DISCUSSION AND CONCLUSION

The aerial parts of barley are useful as functional food to prevent acute inflammatory responses.

Chloroform extract of alfalfa (Medicago sativa) inhibits lipopolysaccharide-induced inflammation by downregulating ERK/NF-κB signaling and cytokine production

Alfalfa (Medicago sativa L.) is commonly used as a traditional medicine and functional food. This study investigated the anti-inflammatory potential of alfalfa and the mechanisms involved. The chloroform extract of alfalfa aerial parts inhibited lipopolysaccharide (LPS)-stimulated immune responses more than ether, butanol, or water soluble extracts. Treatment with 1 μg/mL LPS increased nitrite concentrations to 44.3 μM in RAW267.4 macrophages, but it was reduced to 10.6 μM by adding 100 μg/mL chloroform extract. LPS treatment also increased the concentrations of tumor necrosis factor-α, interleukin (IL)-6, and IL-1β to 41.3, 11.6, and 0.78 ng/mL in culture supernatants of the cells, but these cytokine levels decreased to 12.5, 3.1, and 0.19 ng/mL, respectively, by pretreating with 100 μg/mL of the extract. ICR mice injected with LPS (30 mg/kg body weight) alone showed a 0% survival rate after 48 h of the injection, but 48-h survival of the mice increased to 60% after oral administration of the extract. Subfractions of the chloroform extract markedly suppressed LPS-mediated activation of the extracellular signal-regulated kinase and nuclear factor kappa-B. Cinnamic acid derivatives and fatty acids were found to be active constituents of the extract. This research demonstrated that alfalfa aerial parts exert anti-inflammatory activity and may be useful as a functional food for the prevention of inflammatory disorders.

A(2A) adenosine receptors are differentially modulated by pharmacological treatments in rheumatoid arthritis patients and their stimulation ameliorates adjuvant-induced arthritis in rats

A_2A adenosine receptors (ARs) play a key role in the inhibition of the inflammatory process. The purpose of this study was to evaluate the modulation of A_2AARs in rheumatoid arthritis (RA) patients after different pharmacological treatments and to investigate the effect of A_2AAR stimulation in a rat model of arthritis. We investigated A_2AAR density and functionality in RA progression by using a longitudinal study in RA patients before and after methotrexate (MTX), anti-TNFα agents or rituximab treatments. A_2AARs were analyzed by saturation binding assays in lymphocytes from RA patients throughout the 24-month study timeframe. In an adjuvant-induced arthritis model in rats we showed the efficacy of the A_2AAR agonist, CGS 21680 in comparison with standard therapies by means of paw volume assessment, radiographic and ultrasonographic imaging. Arthritic-associated pain was investigated in mechanical allodynia and thermal hyperalgesia tests. IL-10 release following A_2AAR stimulation in lymphocytes from RA patients and in serum from arthritic rats was measured. In lymphocytes obtained from RA patients, the A_2AAR up-regulation was gradually reduced in function of the treatment time and the stimulation of these receptors mediated a significant increase of IL-10 production. In the same cells, CGS 21680 did not affected cell viability and did not produced cytotoxic effects. The A_2AAR agonist CGS 21680 was highly effective, as suggested by the marked reduction of clinical signs, in rat adjuvant-induced arthritis and associated pain. This study highlighted that A_2AAR agonists represent a physiological-like therapeutic alternative for RA treatment as suggested by the anti-inflammatory role of A_2AARs in lymphocytes from RA patients. The effectiveness of A_2AAR stimulation in a rat model of arthritis supported the role of A_2AAR agonists as potential pharmacological treatment for RA.

Adenosine A2A receptor activation reduces recurrence and mortality from Clostridium difficile infection in mice following vancomycin treatment

Background

Activation of the A_2A adenosine receptor (A_2AAR) decreases production of inflammatory cytokines, prevents C. difficile toxin A-induced enteritis and, in combination with antibiotics, increases survival from sepsis in mice. We investigated whether A_2AAR activation improves and A_2AAR deletion worsens outcomes in a murine model of C. difficile (strain VPI10463) infection (CDI).

Methods

C57BL/6 mice were pretreated with an antibiotic cocktail prior to infection and then treated with vancomycin with or without an A_2AAR agonist. A_2AAR^-/- and littermate wild-type (WT) mice were similarly infected, and IFNγ and TNFα were measured at peak of and recovery from infection.

Results

Infected, untreated mice rapidly lost weight, developed diarrhea, and had mortality rates of 50-60%. Infected mice treated with vancomycin had less weight loss and diarrhea during antibiotic treatment but mortality increased to near 100% after discontinuation of antibiotics. Infected mice treated with both vancomycin and an A_2AAR agonist, either ATL370 or ATL1222, had minimal weight loss and better long-term survival than mice treated with vancomycin alone. A_2AAR KO mice were more susceptible than WT mice to death from CDI. Increases in cecal IFNγ and blood TNFα were pronounced in the absence of A_2AARs.

Conclusion

In a murine model of CDI, vancomycin treatment resulted in reduced weight loss and diarrhea during acute infection, but high recurrence and late-onset death, with overall mortality being worse than untreated infected controls. The administration of vancomycin plus an A_2AAR agonist reduced inflammation and improved survival rates, suggesting a possible benefit of A_2AAR agonists in the management of CDI to prevent recurrent disease.

Adenosine A(2A) receptor activation supports an atheroprotective cholesterol balance in human macrophages and endothelial cells

The adenosine A(2A) receptor (A(2A)R) plays an important role in the regulation of inflammatory and immune responses. Our previous work has demonstrated that A(2A)R agonists exhibit atheroprotective effects by increasing expression of reverse cholesterol transport proteins in cultured human macrophages. This study explores the impact of pharmacologic activation/inhibition and gene silencing of A(2A)R on cholesterol homeostasis in both THP-1 human monocytes/macrophages and primary human aortic endothelial cells (HAEC). THP-1 human monocytes/macrophages and HAEC exposed to the A(2A)R-specific agonist ATL313 exhibited upregulation of proteins responsible for cholesterol efflux: the ABCA1 and G1 transporters. Further, activation of A(2A)R led to upregulation of the cholesterol metabolizing enzyme P450 27-hydroxylase, accompanied by intracellular changes in level of oxysterols. We demonstrate that anti-atherogenic properties of A(2A)R activation are not limited to the regulation of lipid efflux in vasculature, but include protection from lipid overload in macrophages, particularly via suppression of the CD36 scavenger receptor. The reduced lipid accumulation manifests directly as a diminution in foam cell transformation. In THP-1 macrophages, either A(2A)R pharmacological blockade or gene silencing promote lipid accumulation and enhance foam cell transformation. Our pre-clinical data provides evidence suggesting that A(2A)R stimulation by ATL313 has the potential to be a viable therapeutic strategy for cardiovascular disease prevention, particularly in patients with elevated risk due to immune/inflammatory disorders.

T-5224, a selective inhibitor of c-Fos/activator protein-1, attenuates lipopolysaccharide-induced liver injury in mice

The effect of T-5224, a selective inhibitor of c-Fos/activator protein (AP)-1, on lipopolysaccharide (LPS) induced liver injury was examined in mice. Administration of LPS (10 mg kg(-1), i.p.) markedly increased serum levels of tumor necrosis factor-alpha (TNFα), high mobility group box 1 (HMGB1), alanine aminotransferase/aspartate aminotransferase (ALT/AST), liver tissue levels of macrophage-inflammatory protein-1 alpha (MIP-1α) and monocyte chemoattractant protein-1 (MCP-1), as well as hepatic necrosis and inflammation, leading to 67 % lethality. Administration of T-5224 (300 mg kg(-1), p.o.) after intraperitoneal injection of LPS imparted appreciable protection against acute elevations in serum levels of TNFα, HMGB1, ALT/AST as well as in liver tissue levels of MIP-1α and MCP-1, and reduced the lethality (27 %). These data indicate that T-5224 ameliorates liver injury and improves survival through decreasing production of proinflammatory cytokines and chemokines in endotoxemic mice.

Regulation of lymphocyte function by adenosine

Adenosine regulates the interaction between lymphocytes and the vasculature, and is important for controlling lymphocyte trafficking in response to tissue injury or infection. Adenosine can blunt the effects of T cell receptor activation primarily by activating adenosine A(2A) receptors and signaling via cyclic AMP and protein kinase A. Protein kinase A reduces proximal T cell receptor signaling by phosphorylation of C-terminal Src kinase, nuclear factor of activated T cells and cyclic AMP response element-binding protein. Protein kinase A activation can either enhance or inhibit the survival of T cells depending on the strength and duration of signaling. Inducible enzymes such as CD73 and CD39 regulate adenosine formation and degradation in vivo. The extravasation of lymphocytes through blood vessels is influenced by A(2A) receptors-mediated suppression of intercellular adhesion molecule 1 expression on lymphocytes and diminished production of interferon γ and interferon γ-inducible chemokines that are chemotactic to activated lymphocytes. Adenosine also decreases the barrier function of vascular endothelium by activating A(2B)Rs. In sum, adenosine signaling is influenced by tissue inflammation and injury through induction of receptors and enzymes and has generally inhibitory effects on lymphocyte migration into inflamed tissues due to protein kinase A-mediated effects on adhesion molecules, interferon γ production, and endothelial barrier function.

Immunomodulatory therapy for sepsis: an update

Currently the treatment mainstay of sepsis is early and appropriate antibiotic therapy, accompanied by aggressive fluid administration, the use of vasopressors when needed and the prompt initiation of measures to support each failing organ. Activated protein C and hydrocortisone, when used accordingly can affect mortality. As the pathophysiologic events that take place during sepsis are being elucidated, new molecules that target each step of those pathways are being tested. However, a lot of those molecules affect various mediators of the sepsis cascade including inflammatory cytokines, cellular receptors, nuclear transcription factors, coagulation activators and apoptosis regulators. Over the last decade, a multitude of clinical trials and animal studies have investigated strategies that aimed to restore immune homeostasis either by reducing inflammation or by stimulating the innate and adaptive immune responses. Antibiotics, statins and other molecules with multipotent immunomodulatory actions have also been studied in the treatment of sepsis.

Effects of adenosine A₂A receptor activation and alanyl-glutamine in Clostridium difficile toxin-induced ileitis in rabbits and cecitis in mice

Background

Severe Clostridium difficile toxin-induced enteritis is characterized by exuberant intestinal tissue inflammation, epithelial disruption and diarrhea. Adenosine, through its action on the adenosine A_2A receptor, prevents neutrophillic adhesion and oxidative burst and inhibits inflammatory cytokine production. Alanyl-glutamine enhances intestinal mucosal repair and decreases apoptosis of enterocytes. This study investigates the protection from enteritis by combination therapy with ATL 370, an adenosine A_2A receptor agonist, and alanyl-glutamine in a rabbit and murine intestinal loop models of C. difficile toxin A-induced epithelial injury.

Methods

Toxin A with or without alanyl-glutamine was administered intraluminally to rabbit ileal or murine cecal loops. Animals were also given either PBS or ATL 370 parenterally. Ileal tissues were examined for secretion, histopathology, apoptosis, Cxcl1/KC and IL-10.

Results

ATL 370 decreased ileal secretion and histopathologic changes in loops treated with Toxin A. These effects were reversed by the A_2A receptor antagonist, SCH 58261, in a dose-dependent manner. The combination of ATL 370 and alanyl-glutamine significantly further decreased ileal secretion, mucosal injury and apoptosis more than loops treated with either drug alone. ATL 370 and alanyl-glutamine also decreased intestinal tissue KC and IL-10.

Conclusions

Combination therapy with an adenosine A_2A receptor agonist and alanyl-glutamine is effective in reversing C. difficile toxin A-induced epithelial injury, inflammation, secretion and apoptosis in animals and has therapeutic potential for the management of C. difficile infection.

The adenosine A₂A receptor - myocardial protectant and coronary target in endotoxemia

BACKGROUND

Cardiac injury and dysfunction are contributors to disease progression and mortality in sepsis. This study evaluated the cardiovascular role of intrinsic A₂A adenosine receptor (A₂AAR) activity during lipopolysaccharide (LPS)-induced inflammation.

METHODS

We assessed the impact of 24 h of LPS challenge (20 mg/kg, IP) on cardiac injury, coronary function and inflammatory mediator levels in Wild-Type (WT) mice and mice lacking functional A₂AARs (A₂AAR KO).

RESULTS

Cardiac injury was evident in LPS-treated WTs, with ~7-fold elevation in serum cardiac troponin I (cTnI), and significant ventricular and coronary dysfunction. Absence of A₂AARs increased LPS-provoked cTnI release at 24 h by 3-fold without additional demise of contraction function. Importantly, A₂AAR deletion per se emulated detrimental effects of LPS on coronary function, and LPS was without effect in coronary vessels lacking A₂AARs. Effects of A₂AAR KO were independent of major shifts in circulating C-reactive protein (CRP) and haptoglobin. Cytokine responses were largely insensitive to A₂AAR deletion; substantial LPS-induced elevations (up to 100-fold) in IFN-γ and IL-10 were unaltered in A₂AAR KO mice, as were levels of IL-4 and TNF-α. However, late elevations in IL-2 and IL-5 were differentially modulated by A₂AAR KO (IL-2 reduced, IL-5 increased). Data demonstrate that in the context of LPS-triggered cardiac and coronary injury, A₂AAR activity protects myocardial viability without modifying contractile dysfunction, and selectively modulates cytokine (IL-2, IL-5) release. A₂AARs also appear to be targeted by LPS in the coronary vasculature.

CONCLUSIONS

These experimental data suggest that preservation of A₂AAR functionality might provide therapeutic benefit in human sepsis.

Therapeutic potential of adenosine analogues and conjugates

This review summarizes current knowledge of adenosine analogues and conjugates with promising therapeutic properties. Adenosine is a signaling molecule that triggers numerous physiological responses. It acts through the adenosine receptors (ARs), belonging to the family of G-protein-coupled receptors and widely distributed throughout the body. Moreover, adenosine is involved in key biochemical processes as a part of ATP, the universal energy currency. Thus, compounds that are analogues of adenosine and its conjugates have been extensively studied as potential therapeutics. Many inhibitors of ARs are in clinical trials as promising agents in treatment of inflammation, type 2 diabetes, arrhythmia and as vasodilators used in the myocardial perfusion imaging (MPI) stress test. Furthermore, adenosine analogues revealed high efficacy as enzyme inhibitors, tested for antitrypanosomal action and as bivalent ligands and adenosine-oligoarginine conjugates as inhibitors of protein kinases.

Dipyridamole augments the antiinflammatory response during human endotoxemia

Introduction

In animal models of systemic inflammation, the endogenous nucleoside adenosine controls inflammation and prevents organ injury. Dipyridamole blocks the cellular uptake of endogenous adenosine and increases the extracellular adenosine concentration. We studied the effects of oral dipyridamole treatment on innate immunity and organ injury during human experimental endotoxemia.

Methods

In a randomized double-blind placebo-controlled study, 20 healthy male subjects received 2 ng/kg Escherichia coli endotoxin (lipopolysaccharide; LPS) intravenously after 7-day pretreatment with dipyridamole, 200 mg slow release twice daily, or placebo.

Results

Nucleoside transporter activity on circulating erythrocytes was reduced by dipyridamole with 89% ± 2% (P < 0.0001), and the circulating endogenous adenosine concentration was increased. Treatment with dipyridamole augmented the LPS-induced increase in the antiinflammatory cytokine interleukin (IL)-10 with 274%, and resulted in a more rapid decrease in proinflammatory cytokines tumor necrosis factor-α (TNF-α) and IL-6 levels directly after their peak level (P < 0.05 and < 0.01, respectively). A strong correlation was found between the plasma dipyridamole concentration and the adenosine concentration (r = 0.82; P < 0.01), and between the adenosine concentration and the IL-10 concentration (r = 0.88; P < 0.0001), and the subsequent decrease in TNF-α (r = -0.54; P = 0.02). Dipyridamole treatment did not affect the LPS-induced endothelial dysfunction or renal injury during experimental endotoxemia.

Conclusions

Seven-day oral treatment with dipyridamole increases the circulating adenosine concentration and augments the antiinflammatory response during experimental human endotoxemia, which is associated with a faster decline in proinflammatory cytokines.

Trial registration

ClinicalTrials (NCT): NCT01091571.

Immunological alterations mediated by adenosine during host-microbial interactions

Adenosine accumulates in inflammation and ischemia but it is more than an end-product of ATP catabolism. Signaling through different receptors with distinct, cell-specific cytoplasmic pathways, adenosine is now recognized as an inducible switch that regulates the immune system. By acting through the A(2A)AR, adenosine shapes T cell function, largely by conferring an anti-inflammatory tone on effector Th cells (Teff) and natural killer (NK)T cells. In contrast, both the A(2A)AR and A(2B)AR are expressed by antigen-presenting cells (APC) which have been shown to regulate innate responses and the transition to adaptive immunity. There is also emerging evidence that adenosine production is one mechanism that allows some pathogens as well as neoplasms to evade host defenses. This review discusses the immunoregulatory functions of adenosine and some of the interactions it may have in regulating host-microbial interactions.

Adenosine modulates Toll-like receptor function: basic mechanisms and translational opportunities

Adenosine is an endogenous purine metabolite whose concentration in human blood plasma rises from nanomolar to micromolar concentrations during the inflammatory process. Leukocytes express seven-transmembrane adenosine receptors whose engagement modulates Toll-like receptor-mediated cytokine responses, in part via modulation of intracellular cyclic adenosine monophosphate. Adenosine analogs are used clinically to treat arrhythmias and apnea of prematurity. Herein, we consider the potential of adenosine analogs as innate immune response modifiers to prevent and/or treat infection.

Segmental cholangitis impairs hepatic regeneration capacity after partial hepatectomy in rats

BACKGROUND

Patients with hilar cholangiocarcinoma or hepatolithiasis often develop segmental cholangitis (SC), but it is unclear whether hepatectomy for patients with SC can be performed safely.

METHODS

Rats were subjected to segmental bile duct ligation (SBDL) with LPS (SC group) or a saline (Sham group) infusion into the bile duct of the ligated lobes. The rats were sacrificed at 3, 24 and 48 h after the SBDL. For another experiment, the rats were subjected to partial hepatectomy (PHx) for the ligated lobes. Hepatic regeneration rates and the expression of regeneration-associated genes were evaluated.

RESULTS

In the SC group, severe parenchymal damage was observed in the acute phase (3 h). Altered gene expression in the liver in response to biliary infection occurred not only in the infected lobes but also in the non-infected lobes. In the rats of the SC group, both the hepatic regeneration rate and serum HGF levels were significantly lower than in the Sham group.

CONCLUSION

These results clearly demonstrate that SC impairs the regeneration capacity of the contralateral remnant liver. Therefore, hepatectomy should be avoided for patients with SC even if it occurs in the part of the liver to be resected.

Adenosine A(2A) receptors in early ischemic vascular injury after subarachnoid hemorrhage. Laboratory investigation

OBJECT

The role of adenosine A(2A) receptors in the early vascular response after subarachnoid hemorrhage (SAH) is unknown. In other forms of cerebral ischemia both activation and inhibition of A(2A) receptors is reported to be beneficial. However, these studies mainly used pharmacological receptor modulation, and most of the agents available exhibit low specificity. The authors used adenosine A(2A) receptor knockout mice to study the role of A(2A) receptors in the early vascular response to SAH.

METHODS

Subarachnoid hemorrhage was induced in wild-type mice (C57BL/6) and A(2A) receptor knockout mice by endovascular puncture. Cerebral blood flow, intracranial pressure, and blood pressure were recorded, and cerebral perfusion pressure was deduced. Animals were sacrificed at 1, 3, or 6 hours after SAH or sham surgery. Coronal brain sections were immunostained for Type IV collagen, the major protein of the basal lamina. The internal diameter of major cerebral arteries and the area fraction of Type IV collagen-positive microvessels (< 100 μm) were determined.

RESULTS

The initial increase in intracranial pressure and decrease in cerebral perfusion pressure at SAH induction was similar in both types of mice, but cerebral blood flow decline was significantly smaller in A(2A) receptor knockout mice as compared with wild-type cohorts. The internal diameter of major cerebral vessels decreased progressively after SAH. The extent of diameter reduction was significantly less in A(2A) receptor knockout mice than in wild-type mice. Type IV collagen immunostaining decreased progressively after SAH. This decrease was significantly less in A(2A) receptor knockout mice than in wild-type mice.

CONCLUSIONS

These results demonstrate that global inactivation of A(2A) receptors decreases the intensity of the early vascular response to SAH. Early inhibition of A(2A) receptors after SAH might reduce cerebral injury.

Differential recruitment of high affinity A1 and A2A adenosine receptors in the control of colonic neuromuscular function in experimental colitis

This study investigated the expression of A(1) and A(2A) receptors in the rat colonic neuromuscular compartment, and characterized their roles in the control of motility during inflammation. Colitis was induced by 2,4-dinitrobenzenesulfonic acid. A(1), A(2A) receptors, and ecto-5'-nucleotidase (CD73, adenosine producing enzyme) mRNA expression was examined by RT-PCR. The effects of DPCPX (A(1) receptor antagonist), CCPA (A(1) receptor agonist), 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (A(2A) receptor antagonist), 4-[2-[[6-amino-9-(N-ethyl-b-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid hydrochloride (A(2A) receptor agonist), AOPCP (CD73 inhibitor) were tested on electrically or carbachol-evoked contractions in colonic longitudinal muscle preparations. In normal colon, RT-PCR revealed the presence of A(1) receptors, A(2A) receptors and CD73, and an increased expression of A(2A) receptors and CD73 was detected in inflamed tissues. In normal colon, DPCPX or 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol enhanced electrically-induced contractions, while in inflamed preparations the effect of DPCPX no longer occurred. In normal colon, CCPA or 4-[2-[[6-amino-9-(N-ethyl-b-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl] benzenepropanoic acid hydrochloride decreased electrically-induced contractions. Under inflammation, 4-[2-[[6-amino-9-(N-ethyl-b-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl] benzenepropanoic acid hydrochloride reduced electrically evoked contractions with higher efficacy, while the inhibition by CCPA remained unchanged. A(1) and A(2A) receptor ligands did not affect carbachol-induced contractions. AOPCP enhanced electrically-induced contractions and prevented the contractile effects of 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol, without interfering with DPCPX, both in normal and inflamed colons. These results indicate that, in normal colon, both A(1) and A(2A) receptors contribute to the inhibitory control of motor functions at neuronal level. Under bowel inflammation, A(1) receptor loses its modulating actions, while the recruitment of A(2A) receptor by CD73-dependent endogenous adenosine drives an enhanced inhibitory control of colonic neuromotility.

Immunomodulatory properties of pentoxifylline are mediated via adenosine-dependent pathways

The phosphodiesterase inhibitor pentoxifylline (PTX) exerts multiple beneficial immunomodulatory effects in states of hyperinflammation. However, the exact mechanism of action still remains elusive, and the clinical effects of PTX cannot be reliably predicted. In immune cells, the G protein-coupled adenosine A2A receptor (A2AR) exerts strong anti-inflammatory effects. As PTX amplifies signaling pathways downstream of Gs protein-coupled receptors, the A2AR-signaling pathway might be involved in the mediation of immune-suppressive effects of PTX. Here, we investigated this assumption in LPS-stimulated human polymorphonuclear (PMN) leukocytes and in anti-CD3/CD28-stimulated human T cells. In stimulated PMN leukocytes, PTX treatment led to a 4.5-fold decrease of the 50% inhibitory concentrations of adenosine on the H2O2 production; i.e., for adenosine plus PTX (in clinically relevant concentrations), an overadditive increase of inhibitory effects from less than 20% (estimated for each) to 56% (+/-5%) was found. In T cells, adenosine plus PTX revealed similar synergistic inhibitory effects on proinflammatory cytokine production. Inhibition of interferon gamma and TNF-alpha production increased from 7% (+/-1%) and 31% (+/-6%) (PTX alone) to 49% (+/-2%) and 69% (+/-6%), respectively. In T cells and PMN leukocytes, mRNA transcription of the A2AR was significantly increased upon stimulation, which was not influenced by PTX. In human PMN leukocytes and T cells, clinically relevant anti-inflammatory effects of PTX can be achieved only in the presence of sufficient adenosine concentrations. Sufficient adenosine levels might be a prerequisite for the accessibility of sepsis patients to treatment with PTX.

Procession to pediatric bacteremia and sepsis: covert operations and failures in diplomacy

Despite advances in diagnosis and treatment, bacterial sepsis remains a major cause of pediatric morbidity and mortality, particularly among neonates, the critically ill, and the growing immunocompromised patient population. Sepsis is the end point of a complex and dynamic series of events in which both host and microbial factors drive high morbidity and potentially lethal physiologic alterations. In this article we provide a succinct overview of the events that lead to pediatric bloodstream infections (BSIs) and sepsis, with a focus on the molecular mechanisms used by bacteria to subvert host barriers and local immunity to gain access to and persist within the systemic circulation. In the events preceding and during BSI and sepsis, Gram-positive and Gram-negative pathogens use a battery of factors for translocation, inhibition of immunity, molecular mimicry, intracellular survival, and nutrient scavenging. Gaps in understanding the molecular pathogenesis of bacterial BSIs and sepsis are highlighted as opportunities to identify and develop new therapeutics.

Adenosine regulates thrombomodulin and endothelial protein C receptor expression in folliculostellate cells of the pituitary gland

Adenosine stimulates the release of interleukin 6 (IL-6) and vascular endothelial growth factor from folliculostellate cells of the anterior pituitary gland indicating that such cells are also involved in the communication between the immune and endocrine systems during stress and inflammation. In order to understand the precise actions of adenosine on folliculostellate cells, DNA microarray analysis was used to determine global changes in gene expression. Hierarchical clusters revealed, of the genes that had altered expression, the majority were suppressed and many, such as B cell translocation gene 2 and cyclin-dependent kinase inhibitor 2b were related to cell cycle arrest or inhibition of proliferation. Several of the up-regulated genes were associated with cytokine signalling or membrane receptor activity. The most notable of these being IL-6, sulfiredoxin 1, endothelial protein C receptor (EPCR) and thrombomodulin (THBD) which can all play a role in controlling inflammation. The EPCR and THBD pathway is well known in anti-coagulation but also has anti-inflammatory and anti-apoptotic properties. Up-regulation of EPCR and THBD in folliculostellate cells was confirmed by qRT-PCR and western blotting analysis and their expression were also demonstrated in many of the hormone-secreting cells of the anterior pituitary gland. Our findings suggest that adenosine can stimulate expression of stress and inflammation related genes from folliculostellate cells of the anterior pituitary gland. These genes include EPCR and THBD, neither of which has been previously identified in the pituitary gland.

15-deoxy-delta 12,14-prostaglandin J2 prevents inflammatory response and endothelial cell damage in rats with acute obstructive cholangitis

Acute obstructive cholangitis is a common disease with a high mortality rate. Ligands for peroxisome proliferator-activated receptor-gamma (PPARgamma), such as 15-deoxy-Delta(12,14)-prostaglandin J(2) (15D-PGJ(2)), have been proposed as a new class of anti-inflammatory compounds. This study investigated the effect of 15D-PGJ(2) treatment on lipopolysaccharide (LPS)-induced acute obstructive cholangitis. The rats were randomly assigned to five groups: sham operation (Sham; simple laparotomy), sham operation with intraperitoneal saline infusion (Sham+Saline), sham operation with intraperitoneal LPS infusion (Sham+LPS), bile duct ligation (BDL) with saline infusion into the bile duct (BDL+Saline), and BDL with LPS infusion into the bile duct (BDL+LPS). Biochemical assays of blood samples, histology of the liver, portal venous pressure, hyaluronic acid clearance, and expression of inflammation-associated genes in the liver were evaluated. Furthermore, the Sham+LPS and the BDL+LPS group were divided into two groups (with and without 15D-PGJ(2) treatment), and their survival rates were compared. Biochemical assays of blood samples, portal venous pressure, hyaluronic acid clearance, and expression of inflammation-associated genes in the liver were all significantly higher in the BDL+LPS group compared with those in the BDL+Saline group, indicating the presence of increased liver damage in the first group. However, preoperative administration of 15D-PGJ(2) significantly improved these outcomes. Furthermore, the survival rate after establishment of cholangitis was significantly improved by the administration of 15D-PGJ(2) in the BDL+LPS group. These results clearly demonstrate that 15D-PGJ(2) inhibits the inflammatory response and endothelial cell damage seen in acute obstructive cholangitis and could contribute to improve the outcome of this pathology.

Enduring reversal of neuropathic pain by a single intrathecal injection of adenosine 2A receptor agonists: a novel therapy for neuropathic pain

Previous studies of peripheral immune cells have documented that activation of adenosine 2A receptors (A(2A)Rs) decrease proinflammatory cytokine release and increase release of the potent anti-inflammatory cytokine, interleukin-10 (IL-10). Given the growing literature supporting that glial proinflammatory cytokines importantly contribute to neuropathic pain and that IL-10 can suppress such pain, we evaluated the effects of intrathecally administered A(2A)R agonists on neuropathic pain using the chronic constriction injury (CCI) model. A single intrathecal injection of the A(2A)R agonists 4-(3-(6-amino-9-(5-cyclopropylcarbamoyl-3,4-dihydroxytetrahydrofuran-2-yl)-9H-purin-2-yl)prop-2-ynyl)piperidine-1-carboxylic acid methyl ester (ATL313) or 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamido adenosine HCl (CGS21680), 10-14 d after CCI versus sham surgery, produced a long-duration reversal of mechanical allodynia and thermal hyperalgesia for at least 4 weeks. Neither drug altered the nociceptive responses of sham-operated controls. An A(2A)R antagonist [ZM241385 (4-(2-[7-amino-2-(2-furyl)(1,2,4)triazolo(2,3-a)(1,3,5)triazin-5-ylamino]ethyl)phenol)] coadministered intrathecally with ATL313 abolished the action of ATL313 in rats with neuropathy-induced allodynia but had no effect on allodynia in the absence of the A(2A)R agonist. ATL313 attenuated CCI-induced upregulation of spinal cord activation markers for microglia and astrocytes in the L4-L6 spinal cord segments both 1 and 4 weeks after a single intrathecal ATL313 administration. Neutralizing IL-10 antibodies administered intrathecally transiently abolished the effect of ATL313 on neuropathic pain. In addition, IL-10 mRNA was significantly elevated in the CSF cells collected from the lumbar region. Activation of A(2A)Rs after intrathecal administration may be a novel, therapeutic approach for the treatment of neuropathic pain by increasing IL-10 in the immunocompetent cells of the CNS.

A neurotransmitter system that regulates macrophage pro-inflammatory functions

Neurotransmitters released through peripheral and autonomic nerves play an important role in the signaling from the cells of the nervous system to lymphocytes, macrophages and other cells of the immune system. Macrophages are related to numerous physiological and pathological inflammatory processes since their cytokines play an important role in the defensive responses against invasive microorganisms, atherosclerosis progress, insulin resistance, behavior deviation, hematopoiesis feedback, degenerative chronic diseases and the stimulation of the hypothalamus-hypophysis-adrenal axis. Production of pro-inflammatory cytokines by macrophages is the main target for the modulatory activity of diverse neurotransmitters. In this brief review, we show how some neurotransmitters released by the central or the autonomic nervous systems down-regulate peripheral macrophages' inflammatory functions to balance immune protective mechanisms, although they can also promote the collateral progress of diverse diseases. The possible therapeutic uses of some neurotransmitters and the agonists or antagonist of their respective receptors are included as well.

Adenosine signaling and the regulation of chronic lung disease

Chronic lung diseases such as asthma, chronic obstructive pulmonary disease and interstitial lung disease are characterized by inflammation and tissue remodeling processes that compromise pulmonary function. Adenosine is produced in the inflamed and damaged lung where it plays numerous roles in the regulation of inflammation and tissue remodeling. Extracellular adenosine serves as an autocrine and paracrine signaling molecule by engaging cell surface adenosine receptors. Preclinical and cellular studies suggest that adenosine plays an anti-inflammatory role in processes associated with acute lung disease, where activation of the A(2A)R and A(2B)R has promising implications for the treatment of these disorders. In contrast, there is growing evidence that adenosine signaling through the A(1)R, A(2B)R and A(3)R may serve pro-inflammatory and tissue remodeling functions in chronic lung diseases. This review discusses the current progress of research efforts and clinical trials aimed at understanding the complexities of these signaling pathway as they pertain to the development of treatment strategies for chronic lung diseases.