Major Adverse Cardiovascular Events After Colchicine Administration Before Percutaneous Coronary Intervention: Follow-Up of the Colchicine-PCI Trial

Periprocedural inflammation is associated with major adverse cardiovascular events in patients who undergo percutaneous coronary intervention (PCI). In the contemporary era, 5% to 10% of patients develop restenosis, and in the acute coronary syndrome cohort, there remains a 20% major adverse cardiovascular events rate at 3 years, half of which are culprit-lesion related. In patients at risk of restenosis, colchicine has been shown to reduce restenosis when started within 24 hours of PCI and continued for 6 months thereafter, compared with placebo. The Colchicine-PCI trial, which randomized patients to a 1-time loading dose of colchicine or placebo 1 to 2 hours before PCI, showed a dampening of the inflammatory response to PCI but no difference in postprocedural myocardial injury. On mean follow-up of 3.3 years, the incidence of major adverse cardiovascular events did not differ between colchicine and placebo groups (32.5% vs 34.9%; hazard ratio 0.95 [0.68 to 1.34]).

Employing Indirect Adenosine 2A Receptors (A2AR) to Enhance Osseointegration of Titanium Devices: A Pre-Clinical Study

The present study aimed to evaluate the effect of dipyridamole, an indirect adenosine 2A receptors (A_2AR), on the osseointegration of titanium implants in a large, translational pre-clinical model. Sixty tapered, acid-etched titanium implants, treated with four different coatings ((i) Type I Bovine Collagen (control), (ii) 10 μM dipyridamole (DIPY), (iii) 100 μM DIPY, and (iv) 1000 μM DIPY), were inserted in the vertebral bodies of 15 female sheep (weight ~65 kg). Qualitative and quantitative analysis were performed after 3, 6, and 12 weeks in vivo to assess histological features, and percentages of bone-to-implant contact (%BIC) and bone area fraction occupancy (%BAFO). Data was analyzed using a general linear mixed model analysis with time in vivo and coating as fixed factors. Histomorphometric analysis after 3 weeks in vivo revealed higher BIC for DIPY coated implant groups (10 μM (30.42% ± 10.62), 100 μM (36.41% ± 10.62), and 1000 μM (32.46% ± 10.62)) in comparison to the control group (17.99% ± 5.82). Further, significantly higher BAFO was observed for implants augmented with 1000 μM of DIPY (43.84% ± 9.97) compared to the control group (31.89% ± 5.46). At 6 and 12 weeks, no significant differences were observed among groups. Histological analysis evidenced similar osseointegration features and an intramembranous-type healing pattern for all groups. Qualitative observation corroborated the increased presence of woven bone formation in intimate contact with the surface of the implant and within the threads at 3 weeks with increased concentrations of DIPY. Coating the implant surface with dipyridamole yielded a favorable effect with regard to BIC and BAFO at 3 weeks in vivo. These findings suggest a positive effect of DIPY on the early stages of osseointegration.

ATP transporters in the joints

Extracellular adenosine triphosphate (ATP) plays a central role in a wide variety of joint diseases. ATP is generated intracellularly, and the concentration of the extracellular ATP pool is determined by the regulation of its transport out of the cell. A variety of ATP transporters have been described, with connexins and pannexins the most commonly cited. Both form intercellular channels, known as gap junctions, that facilitate the transport of various small molecules between cells and mediate cell-cell communication. Connexins and pannexins also form pores, or hemichannels, that are permeable to certain molecules, including ATP. All joint tissues express one or more connexins and pannexins, and their expression is altered in some pathological conditions, such as osteoarthritis (OA) and rheumatoid arthritis (RA), indicating that they may be involved in the onset and progression of these pathologies. The aging of the global population, along with increases in the prevalence of obesity and metabolic dysfunction, is associated with a rising frequency of joint diseases along with the increased costs and burden of related illness. The modulation of connexins and pannexins represents an attractive therapeutic target in joint disease, but their complex regulation, their combination of gap-junction-dependent and -independent functions, and their interplay between gap junction and hemichannel formation are not yet fully elucidated. In this review, we try to shed light on the regulation of these proteins and their roles in ATP transport to the extracellular space in the context of joint disease, and specifically OA and RA.

Profiling Clinical Research Activity at an Academic Medical Center by Using Institutional Databases: Content Analysis

Background

It is important to monitor the scope of clinical research of all types, to involve participants of all ages and subgroups in studies that are appropriate to their condition, and to ensure equal access and broad validity of the findings.

Objective

We conducted a review of clinical research performed at New York University with the following objectives: (1) to determine the utility of institutional administrative data to characterize clinical research activity; (2) to assess the inclusion of special populations; and (3) to determine if the type, initiation, and completion of the study differed by age.

Methods

Data for all studies that were institutional review board–approved between January 1, 2014, and November 2, 2016, were obtained from the research navigator system, which was launched in November 2013. One module provided details about the study protocol, and another module provided the characteristics of individual participants. Research studies were classified as observational or interventional. Descriptive statistics were used to assess the characteristics of clinical studies across the lifespan, by type, and over time.

Results

A total of 22%-24% of studies included children (minimum age <18 years) and 4%-5% focused exclusively on pediatrics. Similarly, 64%-72% of studies included older patients (maximum age >65 years) but only 5%-12% focused exclusively on geriatrics. Approximately 85% of the studies included both male and female participants. Of the remaining studies, those open only to girls or women were approximately 3 times as common as those confined to boys or men. A total of 56%-58% of projects focused on nonvulnerable patients. Among the special populations studied, children (12%-15%) were the most common. Noninterventional trial types included research on human data sets (24%), observational research (22%), survey research (16%), and biospecimen research (8%). The percentage of projects designed to test an intervention in a vulnerable population increased from 17% in 2014 to 21% in 2015.

Conclusions

Pediatric participants were the special population that was most often studied based on the number of registered projects that included children and adolescents. However, they were much less likely to be successfully enrolled in research studies compared with adults older than 65 years. Only 20% of the studies were interventional, and 20%-35% of participants in this category were from vulnerable populations. More studies are exclusively devoted to women’s health issues compared with men’s health issues.

Effects of Acute Colchicine Administration Prior to Percutaneous Coronary Intervention: COLCHICINE-PCI Randomized Trial

BACKGROUND

Vascular injury and inflammation during percutaneous coronary intervention (PCI) are associated with increased risk of post-PCI adverse outcomes. Colchicine decreases neutrophil recruitment to sites of vascular injury. The anti-inflammatory effects of acute colchicine administration before PCI on subsequent myocardial injury are unknown.

METHODS

In a prospective, single-site trial, subjects referred for possible PCI (n=714) were randomized to acute preprocedural oral administration of colchicine 1.8 mg or placebo.

RESULTS

Among the 400 subjects who underwent PCI, the primary outcome of PCI-related myocardial injury did not differ between colchicine (n=206) and placebo (n=194) groups (57.3% versus 64.2%, P=0.19). The composite outcome of death, nonfatal myocardial infarction, and target vessel revascularization at 30 days (11.7% versus 12.9%, P=0.82), and the outcome of PCI-related myocardial infarction defined by the Society for Cardiovascular Angiography and Interventions (2.9% versus 4.7%, P=0.49) did not differ between colchicine and placebo groups. Among 280 PCI subjects in a nested inflammatory biomarker substudy, the primary biomarker end point, change in interleukin-6 concentrations did not differ between groups 1-hour post-PCI but increased less 24 hours post-PCI in the colchicine (n=141) versus placebo group (n=139; 76% [-6 to 898] versus 338% [27 to 1264], P=0.02). High-sensitivity C-reactive protein concentration also increased less after 24 hours in the colchicine versus placebo groups (11% [-14 to 80] versus 66% [1 to 172], P=0.001).

CONCLUSIONS

Acute preprocedural administration of colchicine attenuated the increase in interleukin-6 and high-sensitivity C-reactive protein concentrations after PCI when compared with placebo but did not lower the risk of PCI-related myocardial injury. Registration: URL: https://www.clinicaltrials.gov; Unique Identifiers: NCT02594111, NCT01709981.

Mécanisme d'action du méthotrexate dans le traitement de la polyarthrite rhumatoïde

Le méthotrexate est utilisé dans le traitement de la polyarthrite rhumatoïde (PR) depuis les années 1980 et est souvent à ce jour le médicament de première intention pour le traitement de la PR. Dans cette revue, nous examinons plusieurs hypothèses pour expliquer le mécanisme à l'origine de l'efficacité du méthotrexate dans la PR. Celles-ci comprennent l'antagonisme du folate, la signalisation par l'adénosine, la génération d'espèces réactives de l'oxygène (ROS), la diminution des molécules d'adhérence, la modification des profils cytokiniques et l'inhibition des polyamines, entre autres. Actuellement, la signalisation par l'adénosine est probablement l'explication la plus largement acceptée du mécanisme du méthotrexate dans la PR, car le méthotrexate augmente les taux d'adénosine et suite à l'engagement de l'adénosine avec ses récepteurs extracellulaires, une cascade intracellulaire est activée et favorise un état antiinflammatoire global. Outre ces hypothèses, nous examinons le mécanisme du méthotrexate dans la PR sous l'angle de ses effets indésirables et considérons certains des nouveaux marqueurs génétiques de l'efficacité et de la toxicité du méthotrexate dans la PR. Enfin, nous discutons brièvement du mécanisme du méthotrexate en association avec un traitement de la PR par un inhibiteur du TNF-. En fin de compte, en trouvant une explication claire de la voie et du mécanisme conduisant à l'efficacité du méthotrexate dans la PR, il pourrait exister un moyen de formuler des thérapies plus puissantes avec moins d'effets secondaires.

Tenofovir Causes Bone Loss via Decreased Bone Formation and Increased Bone Resorption, Which Can Be Counteracted by Dipyridamole in Mice

Osteopenia and fragility fractures have been associated with human immunodeficiency virus (HIV) infection. Tenofovir, a common antiviral in HIV treatment, also leads to increases in bone catabolism markers and decreased BMD in children and young adults. In murine models and human cell lines, tenofovir inhibits adenosine triphosphate release and decreases extracellular adenosine levels. Adenosine and adenosine A2A receptor inhibit osteoclast formation, and increase local adenosine concentration with dipyridamole, an agent that blocks adenosine cellular uptake and stimulates new bone formation as well as bone morphogenic protein 2. We hypothesized that tenofovir regulates bone resorption by diminishing endogenous adenosine levels and questioned whether dipyridamole may be a useful treatment to counteract the deleterous bone effects of tenofovir. Primary murine osteoclasts were induced by M-CSF/RANKL, and the number of TRAP-positive-cells was studied after challenge with tenofovir alone or in combination with dipyridamole. Differentiation markers were studied by RT-PCR and MAPK/NFkB expression by Western blot. Male C57Bl/6 mice were treated as follows: saline 0.9% (control), tenofovir 75 mg/kg/day, dipyridamole 25 mg/kg/day, combination tenofovir/dipyridamole (n = 10, 4 weeks). Calcein/Alizarin Red-labeling of newly formed bone was used, and long bones were prepared for micro-computed tomography (μCT)/histology. Tenofovir produced a dose-dependent increase in osteoclast differentiation (EC₅₀ = 44.5nM) that was reversed by dipyridamole (IC₅₀ = 0.3 μM). Tenofovir increased cathepsin K and NFATc1 mRNA levels and dipyridamole reversed the effect. Dipyridamole reversed the effect of tenofovir on pERK1/2, pp38, and NFkB nuclear translocation. Mice treated with tenofovir lost nearly 10% of their body weight (p < 0.001). μCT revealed decreased BMD and altered trabecular bone in tenofovir-treated mice, reversed by dipyridamole. TRAP-staining showed increased osteoclasts in tenofovir-treated mice (p < 0.005), an effect reversed by dipyridamole. Similar results were obtained for cathepsin K and CD68. RANKL-positive cells were increased in tenofovir-treated mice, whereas osteoprotegerin-positive cells were decreased; both effects were reversed by dipyridamole. These results suggest that treatment with agents that increase local adenosine concentrations, like dipyridamole, might prevent bone loss following tenofovir treatment. © 2019 American Society for Bone and Mineral Research.

Blockade of the Adenosine 2A Receptor Mitigates the Cardiomyopathy Induced by Loss of Plakophilin-2 Expression

Background: Mutations in plakophilin-2 (PKP2) are the most common cause of familial Arrhythmogenic Right Ventricular Cardiomyopathy, a disease characterized by ventricular arrhythmias, sudden death, and progressive fibrofatty cardiomyopathy. The relation between loss of PKP2 expression and structural cardiomyopathy remains under study, though paracrine activation of pro-fibrotic intracellular signaling cascades is a likely event. Previous studies have indicated that ATP release into the intracellular space, and activation of adenosine receptors, can regulate fibrosis in various tissues. However, the role of this mechanism in the heart, and in the specific case of a PKP2-initiated cardiomyopathy, remains unexplored.

Objectives: To investigate the role of ATP/adenosine in the progression of a PKP2-associated cardiomyopathy.

Methods: HL1 cells were used to study PKP2- and Connexin43 (Cx43)-dependent ATP release. A cardiac-specific, tamoxifen-activated PKP2 knock-out murine model (PKP2cKO) was used to define the effect of adenosine receptor blockade on the progression of a PKP2-dependent cardiomyopathy.

Results: HL1 cells silenced for PKP2 showed increased ATP release compared to control. Knockout of Cx43 in the same cells blunted the effect. PKP2cKO transcriptomic data revealed overexpression of genes involved in adenosine-receptor cascades. Istradefylline (an adenosine 2A receptor blocker) tempered the progression of fibrosis and mechanical failure observed in PKP2cKO mice. In contrast, PSB115, a blocker of the 2B adenosine receptor, showed opposite effects.

Conclusion: Paracrine adenosine 2A receptor activation contributes to the progression of fibrosis and impaired cardiac function in animals deficient in PKP2. Given the limitations of the animal model, translation to the case of patients with PKP2 deficiency needs to be done with caution.

The antiviral drug tenofovir, an inhibitor of Pannexin-1-mediated ATP release, prevents liver and skin fibrosis by downregulating adenosine levels in the liver and skin

Background

Fibrosing diseases are a leading cause of morbidity and mortality worldwide and, therefore, there is a need for safe and effective antifibrotic therapies. Adenosine, generated extracellularly by the dephosphorylation of adenine nucleotides, ligates specific receptors which play a critical role in development of hepatic and dermal fibrosis. Results of recent clinical trials indicate that tenofovir, a widely used antiviral agent, reverses hepatic fibrosis/cirrhosis in patients with chronic hepatitis B infection. Belonging to the class of acyclic nucleoside phosphonates, tenofovir is an analogue of AMP. We tested the hypothesis that tenofovir has direct antifibrotic effects in vivo by interfering with adenosine pathways of fibrosis using two distinct models of adenosine and A2AR-mediated fibrosis.

Methods

Thioacetamide (100mg/kg IP)-treated mice were treated with vehicle, or tenofovir (75mg/kg, SubQ) (n = 5–10). Bleomycin (0.25U, SubQ)-treated mice were treated with vehicle or tenofovir (75mg/kg, IP) (n = 5–10). Adenosine levels were determined by HPLC, and ATP release was quantitated as luciferase-dependent bioluminescence. Skin breaking strength was analysed and H&E and picrosirus red-stained slides were imaged. Pannexin-1expression was knocked down following retroviral-mediated expression of of Pannexin-1-specific or scrambled siRNA.

Results

Treatment of mice with tenofovir diminished adenosine release from the skin of bleomycin-treated mice and the liver of thioacetamide-treated mice, models of diffuse skin fibrosis and hepatic cirrhosis, respectively. More importantly, tenofovir treatment diminished skin and liver fibrosis in these models. Tenofovir diminished extracellular adenosine concentrations by inhibiting, in a dose-dependent fashion, cellular ATP release but not in cells lacking Pannexin-1.

Conclusions

These studies suggest that tenofovir, a widely used antiviral agent, could be useful in the treatment of fibrosing diseases.

Adenosine A2a Receptor Blockade Diminishes Wnt/β-Catenin Signaling in a Murine Model of Bleomycin-Induced Dermal Fibrosis

Adenosine A_2a receptor (A_2aR) stimulation promotes the synthesis of collagens I and III, and we have recently demonstrated that there is crosstalk between the A_2aR and WNT/β-catenin signaling pathway. In in vitro studies, A_2aR signaling for collagen III expression was mediated by WNT/β-catenin signaling in human dermal fibroblasts; we further verified whether the crosstalk between A_2aR and Wnt/β-catenin signaling was involved in diffuse dermal fibrosis in vivo. Wnt-signaling reporter mice (Tcf/Lef:H2B-GFP) were challenged with bleomycin and treated with the selective A_2aR antagonist istradefylline (KW6002) or vehicle. Dermal fibrosis was quantitated and nuclear translocation of β-catenin in fibroblasts was assessed by double-staining for Green fluorescent protein or dephosphorylated β-catenin or β-catenin phosphorylated at Ser552, and vimentin. KW6002 significantly reduced skin thickness, skinfold thickness, breaking tension, dermal hydroxyproline content, myofibroblast accumulation, and collagen alignment in bleomycin-induced dermal fibrosis. Also, there was increased expression of Tcf/Lef:H2B-GFP reporter in bleomycin-induced dermal fibrosis, an effect that was diminished by treatment with KW6002. Moreover, KW6002 significantly inhibited nuclear translocation of Tcf/Lef:H2B-GFP reporter, as well as dephosphorylated β-catenin and β-catenin phosphorylated at Ser552. Our work supports the hypothesis that pharmacologic blockade of A_2aR inhibits the WNT/β-catenin signaling pathway, contributing to its capacity to inhibit dermal fibrosis in diseases such as scleroderma.

Adenosine generation limits radiation-induced tumor immunogenicity by abrogating recruitment and activation of CD103+ DCs

Radiation therapy (RT) induces release of ATP in the tumor micro environment (TME) triggering recruitment and activation of dendritic cells (DCs), including CD103+ DCs, identified as the key DC subsetresponsible for cross-presentation of tumor antigens to CD8+ T cells. However, CD39 and CD73-expressing cells in the TME hydrolyze ATP into adenosine that potently inhibits DCs and CD8+ T cells. Here, we tested the hypothesis that adenosine generation limits the ability of RT totrigger anti-tumor immunity.

Wild type (WT) or BATF3−/− mice (CD103+DC-deficient) were inoculated s.c. with TSA tumor cells (day 0) and assigned to treatment with: (1) control Ab; (2) anti-CD73 Ab (100 μg) (3) RT (20 Gy); (4) RT + anti-CD73 Ab. Antibodies were administered i.p. on day 11, 14, 17 and 20. RT was given locally as single 20 Gy dose on day 12. On day 18, tumors were analyzed by flow cytometry for DC and T cell infiltration. Mice were monitored for tumor progression. DCs generated in vitro by culture of bone marrow from WT mice with Flt3L (&gt;90% CD103+) were labeled with CFSE and intravenously injected in BATF3−/− recipient mice. Tumors were harvested after 48h and analyzed by flow cytometry for infiltration of CFSE+ DCs.

In tumors of RT- but not sham-treated mice, anti-CD73 mAb increased infiltration of CD103+DCs and enhanced CD8+T cell/Treg ratio. Importantly, CD73 blockade had no anti-tumor effect by itself but significantly improved RT-induced tumor control. The therapeutic effect of RT + CD73 blockade was abrogated in BATF3−/− mice. Moreover, CD73 blockade increased recruitment of adoptively transferred CD103+DCs to irradiated tumors in BATF3−/− mice. Overall, data suggest that adenosine is a critical regulator of RT-induced immunogenicity.

Adenosine A2A receptor promotes collagen type III synthesis via β-catenin activation in human dermal fibroblasts

BACKGROUND AND PURPOSE

Adenosine A_2A receptor stimulation promotes the synthesis of collagen type I and type III (Col1 and Col3), mediators of fibrosis and scarring. The A_2A receptor modulates collagen balance via cAMP/PKA/p38-MAPK/Akt pathways. Wnt signalling is important in fibrosis and the cAMP and Wnt pathways converge. Because the A_2A receptor is Gs-linked and increases cAMP, we determined whether A_2A receptors and Wnt signalling interact.

EXPERIMENTAL APPROACH

Total β-catenin, de-phosphorylated β-catenin (canonical activation, de-phospho β-catenin) and phosphorylated β-catenin at Ser⁵⁵² (non-canonical activation, p-Ser⁵⁵² β-catenin) levels were determined in primary human dermal fibroblasts, cytosol and nucleus, by western blot analysis and fluorescence microscopy, before and after stimulation by A_2A receptor-selective agonist CGS21680, with/without A_2A receptor-selective antagonist (SCH56261) pretreatment. β-Catenin was knocked down by transfection with scrambled-siRNA or specific-siRNA, and Col1 and Col3 levels determined by western blots.

KEY RESULTS

CGS21680 stimulation rapidly (15 min) increased cellular β-catenin levels. Both de-phospho β-catenin and p-Ser⁵⁵² β-catenin levels were also increased. CGS21680 stimulated the translocation of total de-phospho and p-Ser⁵⁵² β-catenin to the nucleus. A_2A receptor-stimulation increased Col1 synthesis similarly in β-catenin knockeddown and scrambled cells. However, β-catenin knockdown abolished the increase in Col3 synthesis induced in A_2A receptor-stimulated fibroblasts.

CONCLUSIONS AND IMPLICATIONS

A_2A receptor stimulation promotes Col3 synthesis via the activation of canonical and non-canonical β-catenin, consistent with a role for A_2A receptors in dermal fibrosis and scarring.

Abstract 4033: Adenosine regulates radiation therapy-induced antitumor immunity

Radiation-induced immunogenic cell death (ICD) is a key mechanism whereby local radiation therapy (RT) can elicit anti-tumor immune responses and synergize with immune checkpoint inhibitors in enhancing tumor responses. ATP, which is an essential signal of ICD, activates tumor-resident dendritic cells (DCs) promoting their ability to cross-present tumor-derived antigens to T cells. Interestingly, while release of ATP by RT is dose-dependent (Golden et al., OncoImmunology 2014), a large RT dose of 20 Gy was not effective in inducing anti-tumor T cells and synergize with anti-CTLA-4 (Dewan et al., Clin Cancer Res 2009). Extracellular ATP is rapidly catabolized to adenosine (ADO) by ectonucleotidases CD39 and CD73, which are expressed on tumor cells and immune cells. ADO has immunosuppressive effects, inhibiting DC- and effector T cell-activation, while promoting regulatory T cells (Tregs). Here, we tested the hypothesis that conversion of ATP to ADO hinders generation of effective anti-tumor immunity by high dose RT.

Mice were inoculated s.c. with TSA breast cancer cells or MCA38 colon cancer cells on day 0 and assigned to treatment with: (1) control mAb; (2) anti-CD73 (TY/23); (3) RT (4) RT+TY/23. TY/23 (200 μg) was administered i.p. on day 11, 14, 17 and 20. RT was given locally as single 20 Gy dose on day 12. On day 18, some tumors were harvested for flow cytometry analysis of DC and T cells. Mice were monitored for tumor progression. HPLC was used to measure ADO levels in supernatants from 24 h co-cultures of bone marrow-derived DCs and irradiated TSA cells.In vitro, antibody blockade of CD73, the rate-limiting enzyme in the generation of ADO, reduced the levels of ADO in the supernatant and restored the activation of DCs cultured with irradiated TSA cells. In irradiated tumors, anti-CD73 reduced the percentage of Tregs within the tumor-infiltrating CD4+ T cell population (7.9±2.5% in RT+TY/23 vs 20±0.8% in RT, p&lt;0.01) while increasing CD8+ T cells (38.3±0.1% in RT+TY/23 vs 17.3±4% in RT, p&lt;0.05). Among intratumoral DCs, the CD8a+ DC subpopulation was increased after CD73-blockade (37.9±15.7% in TY/23+RT vs 11.3±4.9% in RT, p&lt;0.01). Importantly, in irradiated tumors, anti-CD73 enhanced expression of activation markers CD40 on CD8a+ DCs (MFI: 218±1 in RT+TY/23 vs 54±41 in RT, p&lt;0.05) and CD69 on CD8+ T cells (MFI: 513±126 in RT+TY/23 vs 148±59 in RT, p&lt;0.01). Furthermore, tumor-bearing mice treated with RT in combination with anti-CD73 had a significantly delayed tumor progression (p&lt;0.05) and prolonged survival (p&lt;0.01) compared to mice receiving RT alone. Anti-CD73 given alone had no effect on tumor growth.

Our data show that adenosinergic signaling regulates the ability of RT to induce anti-tumor immunity, affecting activation of both DCs and effector T cells. ADO blockade may represent a promising strategy to enhance the immunogenicity of irradiated tumors by improving the ability of RT to induce in situ tumor vaccination.

Citation Format: Erik Wennerberg, Aranzazu Mediero, Tuere Wilder, Silvia Formenti, Bruce Cronstein, Sandra Demaria. Adenosine regulates radiation therapy-induced antitumor immunity. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4033.

Signaling pathways involving adenosine A2A and A2B receptors in wound healing and fibrosis

Collagen and matrix deposition by fibroblasts is an essential part of wound healing but also contributes to pathologic remodeling of organs leading to substantial morbidity and mortality. Adenosine, a small molecule generated extracellularly from adenine nucleotides as a result of direct stimulation, hypoxia, or injury, acts via a family of classical seven-pass G protein-coupled protein receptors, A2A and A2B, leading to generation of cAMP and activation of downstream targets such as PKA and Epac. These effectors, in turn, lead to fibroblast activation and collagen synthesis. The regulatory actions of these receptors likely involve multiple interconnected pathways, and one of the more interesting aspects of this regulation is opposing effects at different levels of cAMP generated. Additionally, adenosine signaling contributes to fibrosis in organ-specific ways and may have opposite effects in different organs. The development of drugs that selectively target these receptors and their signaling pathways will disrupt the pathogenesis of fibrosis and slow or arrest the progression of the important diseases they underlie.

Purinergic signaling in scarring

Adenosine (ADO) and nucleotides such as ATP, ADP, and uridine 5'-triphosphate (UTP), among others, may serve as extracellular signaling molecules. These mediators activate specific cell-surface receptors-namely, purinergic 1 and 2 (P1 and P2)-to modulate crucial pathophysiological responses. Regulation of this process is maintained by nucleoside and nucleotide transporters, as well as the ectonucleotidases ectonucleoside triphosphate diphosphohydrolase [ENTPD; cluster of differentiation (CD)39] and ecto-5'-nucleotidase (5'-NT; CD73), among others. Cells involved in tissue repair, healing, and scarring respond to both ADO and ATP. Our recent investigations have shown that modulation of purinergic signaling regulates matrix deposition during tissue repair and fibrosis in several organs. Cells release adenine nucleotides into the extracellular space, where these mediators are converted by CD39 and CD73 into ADO, which is anti-inflammatory in the short term but may also promote dermal, heart, liver, and lung fibrosis with repetitive signaling under defined circumstances. Extracellular ATP stimulates cardiac fibroblast proliferation, lung inflammation, and fibrosis. P2Y2 (UTP/ATP) and P2Y6 [ADP/UTP/uridine 5'-diphosphate (UDP)] have been shown to have profibrotic effects, as well. Modulation of purinergic signaling represents a novel approach to preventing or diminishing fibrosis. We provide an overview of the current understanding of purinergic signaling in scarring and discuss its potential to prevent or decrease fibrosis.

Apremilast, a novel phosphodiesterase 4 (PDE4) inhibitor, regulates inflammation through multiple cAMP downstream effectors

Introduction

This work was undertaken to delineate intracellular signaling pathways for the PDE4 inhibitor apremilast and to examine interactions between apremilast, methotrexate and adenosine A_2A receptors (A_2AR).

Methods

After apremilast and LPS incubation, intracellular cAMP, TNF-α, IL-10, IL-6 and IL-1α were measured in the Raw264.7 monocytic murine cell line. PKA, Epac1/2 (signaling intermediates for cAMP) and A_2AR knockdowns were performed by shRNA transfection and interactions with A2AR and A2BR, as well as with methotrexate were tested in vitro and in the murine air pouch model. Statistical differences were determined using one or two-way ANOVA or Student’s t test. The alpha nominal level was set at 0.05 in all cases. A P value of < 0.05 was considered significant.

Results

In vitro, apremilast increased intracellular cAMP and inhibited TNF-α release (IC₅₀=104nM) and the specific A_2AR-agonist CGS21680 (1μM) increased apremilast potency (IC₅₀=25nM). In this cell line, apremilast increased IL-10 production. PKA, Epac1 and Epac2 knockdowns prevented TNF-α inhibition and IL-10 stimulation by apremilast. In the murine air pouch model, both apremilast and MTX significantly inhibited leukocyte infiltration, while apremilast, but not MTX, significantly inhibited TNF-α release. The addition of MTX (1 mg/kg) to apremilast (5 mg/kg) yielded no more inhibition of leukocyte infiltration or TNF-α release than with apremilast alone.

Conclusions

The immunoregulatory effects of apremilast appear to be mediated by cAMP through the downstream effectors PKA, Epac1, and Epac2. A2AR agonism potentiated TNF-α inhibition by apremilast, consistent with the cAMP-elevating effects of that receptor. Because the A2AR is also involved in the anti-inflammatory effects of MTX, the mechanism of action of both drugs involves cAMP-dependent pathways and is therefore partially overlapping in nature.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0771-6) contains supplementary material, which is available to authorized users.

Regulation of inflammation by adenosine

Adenosine, a purine nucleoside generated by the dephosphorylation of adenine nucleotides, is a potent endogenous physiologic and pharmacologic regulator of many functions. Adenosine was first reported to inhibit the inflammatory actions of neutrophils nearly 30 years ago and since then the role of adenosine and its receptors as feedback regulators of inflammation has been well established. Here we review the effects of adenosine, acting at its receptors, on neutrophil and monocyte/macrophage function in inflammation. Moreover, we review the role of adenosine in mediating the anti-inflammatory effects of methotrexate, the anchor drug in the treatment of Rheumatoid Arthritis and other inflammatory disorders.

Preparedness of the CTSA's structural and scientific assets to support the mission of the National Center for Advancing Translational Sciences (NCATS)

The formation of the National Center for Advancing Translational Sciences (NCATS) brings new promise for moving basic science discoveries to clinical practice, ultimately improving the health of the nation. The Clinical and Translational Science Award (CTSA) sites, now housed with NCATS, are organized and prepared to support in this endeavor. The CTSAs provide a foundation for capitalizing on such promise through provision of a disease-agnostic infrastructure devoted to clinical and translational (C&T) science, maintenance of training programs designed for C&T investigators of the future, by incentivizing institutional reorganization and by cultivating institutional support.

The roles of adenosine and adenosine receptors in bone remodeling

Adenosine regulates a wide variety of physiological processes including heart rate, vasodilation and inflammation through the activation of specific cell surface adenosine receptors. In addition to these well-established roles of adenosine, recent genetic and pharmacological research has implicated adenosine as an important regulator in bone remodeling. The secretion of adenosine and the presence of its four receptors in bone cells have been well documented. More recently, we provided the first evidence that adenosine regulates osteoclast formation and function through A1 receptor (A1R), and showed that A1R-knockout mice have significantly increased bone volume as a result of impaired osteoclast-mediated bone resorption. Moreover, adenosine A1R-knockout mice are protective from boss loss following ovariectomy further supporting the involvement of adenosine in osteoclast formation and function. This short review summarizes current knowledge related to the roles of adenosine and adenosine receptors in bone formation and remodeling. A deeper insight into the regulation of bone metabolism by adenosine receptors should assist in developing new therapies for osteoporosis.

Methylxanthines and inflammatory cells

Both caffeine and theophylline have a variety of roles in regulating inflammatory responses. At pharmacologically relevant concentrations most of the effects of these commonly used methylxanthines are attributable to adenosine receptor blockade and histone deacetylase activation. In addition, at higher concentrations methylxanthines can suppress inflammation by inhibiting phosphodiesterases, thereby elevating intracellular cyclic adenosine monophosphate levels. In summary, methylxanthines regulate inflammation by multiple mechanisms.

How does methotrexate suppress inflammation?

Methotrexate remains the most widely used agent for the treatment of rheumatoid arthritis and other chronic inflammatory diseases. Although introduced as a chemotherapeutic agent for the treatment of malignancies, it is clear that, in the doses used, the mechanism of action in the suppression of inflammation differs from simply suppression of purine and pyrimidine metabolism, resulting in inhibition of proliferation. Here we review the proposed mechanisms of action of methotrexate.

Adenosine receptors: therapeutic aspects for inflammatory and immune diseases

Adenosine is a key endogenous molecule that regulates tissue function by activating four G-protein-coupled adenosine receptors: A1, A2A, A2B and A3. Cells of the immune system express these receptors and are responsive to the modulatory effects of adenosine in an inflammatory environment. Animal models of asthma, ischaemia, arthritis, sepsis, inflammatory bowel disease and wound healing have helped to elucidate the regulatory roles of the various adenosine receptors in dictating the development and progression of disease. This recent heightened awareness of the role of adenosine in the control of immune and inflammatory systems has generated excitement regarding the potential use of adenosine-receptor-based therapies in the treatment of infection, autoimmunity, ischaemia and degenerative diseases.

Synergistic up-regulation of vascular endothelial growth factor expression in murine macrophages by adenosine A(2A) receptor agonists and endotoxin

Under normoxic conditions, macrophages from C57BL mice produce low levels of vascular endothelial growth factor (VEGF). Hypoxia stimulates VEGF expression by approximately 500%; interferon-gamma (IFN-gamma) with endotoxin [lipopolysaccharide (LPS)] also stimulates VEGF expression by approximately 50 to 150% in an inducible nitric oxide synthase (iNOS)-dependent manner. Treatment of normoxic macrophages with 5'-N-ethyl-carboxamido-adenosine (NECA), a nonselective adenosine A(2) receptor agonist, or with 2-[p-(2-carboxyethyl)-phenylethyl amino]-5'-N-ethyl-carboxamido-adenosine (CGS21680), a specific adenosine A(2A) receptor agonist, modestly increases VEGF expression, whereas 2-chloro-N(6)-cyclopentyl adenosine (CCPA), an adenosine A(1) agonist, does not. Treatment with LPS (0 to 1000 ng/ml), or with IFN-gamma (0 to 300 U/ml), does not affect VEGF expression. In the presence of LPS (EC(50) < 10 ng/ml), but not of IFN-gamma, both NECA and CGS21680 synergistically up-regulate VEGF expression by as much as 10-fold. This VEGF is biologically active in vivo in the rat corneal bioassay of angiogenesis. Inhibitors of iNOS do not affect this synergistic induction of VEGF, and macrophages from iNOS-/- mice produce similar levels of VEGF as wild-type mice, indicating that NO does not play a role in this induction. Under hypoxic conditions, VEGF expression is slightly increased by adenosine receptor agonists but adenosine A(2) or A(1) receptor antagonists 3,7-dimethyl-1-propargyl xanthine (DMPX), ZM241385, and 8-cyclopentyl-1,3-dipropylxanthine (DCPCX) do not modulate VEGF expression. VEGF expression is also not reduced in hypoxic macrophages from A(3)-/- and A(2A)-/- mice. Thus, VEGF expression by hypoxic macrophages does not seem to depend on endogenously released or exogenous adenosine. VEGF expression is strongly up-regulated by LPS/NECA in macrophages from A(3)-/- but not A(2A)-/- mice, confirming the role of adenosine A(2A) receptors in this pathway. LPS with NECA strongly up-regulates VEGF expression by macrophages from C(3)H/HeN mice (with intact Tlr4 receptors), but not by macrophages from C(3)H/HeJ mice (with mutated, functionally inactive Tlr4 receptors), implicating signaling through the Tlr4 pathway in this synergistic up-regulation. Finally, Western blot analysis of adenosine A(2A) receptor expression indicated that the synergistic interaction of LPS with A(2A) receptor agonists does not involve up-regulation of A(2A) receptors by LPS. These results indicate that in murine macrophages there is a novel pathway regulating VEGF production, that involves the synergistic interaction of adenosine A(2A) receptor agonists through A(2A) receptors with LPS through the Tlr4 pathway, resulting in the strong up-regulation of VEGF expression by macrophages in a hypoxia- and NO-independent manner.

Mycobacterium tuberculosis alters expression of adhesion molecules on monocytic cells

The host response to Mycobacterium tuberculosis is characterized by interactions between mononuclear cells, with recruitment and fusion of these cells culminating in granuloma formation. In addition, the host response to M. tuberculosis requires CD4+ T-cell reactivity, mediated by antigen-independent as well as antigen-dependent mechanisms. Thus, we hypothesized that cell adhesion molecules such as intercellular adhesion molecule 1 (ICAM-1; CD54) would participate in the response to infection with M. tuberculosis. Exposure of THP-1 cells derived from a monocyte/macrophage cell line to M. tuberculosis (1:1 bacterium/cell ratio) elicited a sustained increase (660% +/- 49% above resting level) in the expression of ICAM-1 that continued for at least 72 h. Neither the expression of vascular cell adhesion molecule 1 (VCAM-1; CD106) nor that of the integrins lymphocyte function-associated antigen 1 (LFA-1; CD11a/CD18) or CR3 (CD11b/CD18) was increased to a similar extent at corresponding time points. The increase in ICAM-1 protein expression was accompanied by an increase in steady-state mRNA (Northern [RNA] analysis). Neutralizing monoclonal antibodies directed against tumor necrosis factor alpha but not interleukin 1 alpha or interleukin 1 beta substantially abrogated the response to M. tuberculosis consistent with a paracrine or autocrine response. Continuous upregulation of the expression of ICAM-1 on mononuclear phagocytes induced by M. tuberculosis may mediate the recruitment of monocytes and enhance the antigen presentation of M. tuberculosis, thus permitting the generation and maintenance of the host response.

Acute syphilitic meningitis in a patient with systemic lupus erythematosus

A man with systemic lupus erythematosus receiving chronic steroid therapy presented with headache, fever and panophthalmitis. Cerebrospinal fluid analysis was consistent with syphilitic meningitis. This represents the first reported case of syphilitic meningitis in a lupus patient. Our case report highlights the need to remain alert for unusual manifestations of syphilis in immunosuppressed patients.

Correlation of the conformation of a modified ribonuclease octapeptide, homologous to peptide T, with its ability to induce CD4-dependent monocyte chemotaxis

Peptide T, from the human immunodeficiency virus (HIV), whose sequence is Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr, has been shown to inhibit attachment of this virus to T cells and neural cells bearing the CD4 receptor. This peptide shares extensive homology with the 19-26 segment of ribonuclease A (RNase A), whose sequence is Ala-Ala-Ser-Ser-Ser-Asn-Tyr-Cys. Based on comparison of the structures of peptides occurring in proteins of known structure that are homologous to peptide T, viz, RNase A and endothiapepsin and on conformational energy calculations, we predicted that peptide T adopts a structure much like that for residues 19-26 in RNase A. A critical feature is a bend involving residues Thr 4-Asn 7 in peptide T corresponding to Ser 22-Tyr 25 in the RNase A peptide. Our proposed structure for peptide T has recently been confirmed by Cotelle et al. (Biochem. Biophys. Res. Commun. 171, 596-602). We now show directly that the RNase A peptide, with Met replacing Cys 26 to prevent disulfide exchange reactions, strongly induces monocyte-chemotaxis that is blocked by anti-CD4 monoclonal antibody. Both peptide T and RNase A fail to induce chemotaxis, however, in neutrophils which do not express surface CD4 receptors. These results suggest that both peptides interact with the CD4 receptor in inducing monocyte chemotaxis. We have also prepared cyclo-RNase A peptide with Met 26. Using molecular dynamics and conformational energy calculations, we find that the cyclic peptide cannot form a bend structure involving Ser 22-Tyr 25 that is superimposable on the RNase A bend.(ABSTRACT TRUNCATED AT 250 WORDS)