Adenosine and adenosine receptors in the pathogenesis and treatment of rheumatic diseases

Treatment of Rheumatoid Arthritis Based on the Inherent Bioactivity of Black Phosphorus Nanosheets

Rheumatoid arthritis (RA) is an autoimmune disease that affects the living quality of patients, especially the elderly population. RA-related morbidity and mortality increase significantly with age, while current clinical drugs for RA are far from satisfactory and may have serious side effects. Therefore, the development of new drugs with higher biosafety and efficacy is demanding. Black phosphorus nanosheets (BPNSs) have been widely studied because of their excellent biocompatibility. Here, we focus on the inherent bioactivity of BPNSs, report the potential of BPNSs as a therapeutic drug for RA and elucidate the underlying therapeutic mechanism. We find that BPNSs inhibit autophagy at an early stage via the AMPK-mTOR pathway, switch the energy metabolic pathway to oxidative phosphorylation, increase intracellular ATP levels, suppress apoptosis, reduce inflammation and oxidative stress, and down-regulate senescence-associated secretory phenotype (SASP)-related genes in rheumatoid arthritis synovial fibroblasts (RA-SFs). Further, BPNSs induce the apoptosis of macrophages and promote their transition from the M1 to the M2 phenotype by regulating related cytokines. Significantly, the administration of BPNSs can alleviate key pathological features of RA in mice, revealing great therapeutic potential. This study provides a novel option for treating RA, with BPNSs emerging as a promising therapeutic candidate.

Adenosine and Its Receptors in the Pathogenesis and Treatment of Inflammatory Skin Diseases

Inflammatory skin diseases highlight inflammation as a central driver of skin pathologies, involving a multiplicity of mediators and cell types, including immune and non-immune cells. Adenosine, a ubiquitous endogenous immune modulator, generated from adenosine triphosphate (ATP), acts via four G protein-coupled receptors (A1, A2A, A2B, and A3). Given the widespread expression of those receptors and their regulatory effects on multiple immune signaling pathways, targeting adenosine receptors emerges as a compelling strategy for anti-inflammatory intervention. Animal models of psoriasis, contact hypersensitivity (CHS), and other dermatitis have elucidated the involvement of adenosine receptors in the pathogenesis of these conditions. Targeting adenosine receptors is effective in attenuating inflammation and remodeling the epidermal structure, potentially showing synergistic effects with fewer adverse effects when combined with conventional therapies. What is noteworthy are the promising outcomes observed with A2A agonists in animal models and ongoing clinical trials investigating A3 agonists, underscoring a potential therapeutic approach for the management of inflammatory skin disorders.

Label-free colorimetric detection platform based on catalytic hairpin self-assembly and G-quadruplex/hemin DNAzyme for comprehensive biomarker profiling

The expression level of human apurinic/apyrimidinic endonuclease 1 (APE1) is closely associated with the onset of various diseases, establishing it as a crucial clinical biomarker and a target in anti-cancer efforts. This study accomplished colorimetric and visual detection of APE1 by harnessing its endonuclease activity through catalytic hairpin self-assembly (CHA) and G-quadruplex/hemin DNAzyme. Optimization of the freedom degrees of the G-rich sequence significantly improved the detection performance of the strategy by influencing DNAzyme formation. Additionally, we replaced the signal reporting system with a molecular beacon to develop a fluorescence detection strategy, which served as an extension of the signal amplification system for validation and signal readout. The fluorescent probe method achieved a detection limit of 3.37 × 10-4 U/mL, while the colorimetric method yielded a detection limit of 6.5 × 10-3 U/mL, with a linear range spanning from 0.01 to 0.25 U/mL. Subsequently, the colorimetric approach effectively assessed APE1 activity in biological samples and facilitated the screening of APE1 activity inhibitors. Furthermore, this CHA/G-quadruplex/hemin DNAzyme strategy was adapted for the colorimetric detection of adenosine, showcasing its broad applicability across various biomarkers. The developed colorimetric analytical strategy represents a pivotal biosensing platform for diagnosing and treating diseases.

Anti-inflammatory effects of infliximab and methotrexate on peripheral blood and synovial fluid mononuclear cells: ex vivo study

OBJECTIVE

To investigate the effects of methotrexate (MTX) and the tumour necrosis factor inhibitor infliximab (IFX) on immune cells derived from peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) of inflammatory arthritis patients.

METHOD

Phytohaemagglutinin (PHA)-induced proliferation of healthy donors' PBMCs and synovial intermediate monocytes (CD14+CD16+ cells) in SFMCs derived from psoriatic arthritis (PsA) and rheumatoid arthritis (RA) patients was determined by flow cytometry following co-culture with IFX and MTX. PHA-induced interferon-γ (IFN-γ) production in PBMCs was measured by enzyme-linked immunosorbent assay. The drugs' effect on mRNA expression in SFMCs was determined by quantitative polymerase chain reaction.

RESULTS

The combination of IFX 10 μg/mL + MTX 0.1 μg/mL had the strongest inhibitory effect on PBMC proliferation (91%), followed by MTX 0.1 μg/mL (86%) and IFX 10 μg/mL (49%). In PHA-stimulated PBMCs, IFN-γ production was reduced by IFX 10 μg/mL, MTX 0.1 μg/mL, and IFX 10 μg/mL + MTX 0.1 μg/mL by 68%, 90%, and 85%, respectively. In SFMCs, IFX 10 µg/mL significantly reduced CD14+CD16+ cells compared to medium (PsA 54%, p < 0.01; RA 46%, p < 0.05), while MTX had no effect on this population. IFX + MTX led to a similar suppression of CD14+CD16+ cells as achieved by IFX alone. The drugs had different impacts on SFMC gene expression.

CONCLUSION

Both IFX and MTX effectively inhibited PBMC proliferation and IFN-γ production, but only IFX reduced synovial monocytes and pro-inflammatory gene expression in SFMCs, suggesting a differential impact of IFX and MTX on critical inflammatory cell populations ex vivo.

The inhibitory effect of adenosine on tumor adaptive immunity and intervention strategies

Adenosine (Ado) is significantly elevated in the tumor microenvironment (TME) compared to normal tissues. It binds to adenosine receptors (AdoRs), suppressing tumor antigen presentation and immune cell activation, thereby inhibiting tumor adaptive immunity. Ado downregulates major histocompatibility complex II (MHC II) and co-stimulatory factors on dendritic cells (DCs) and macrophages, inhibiting antigen presentation. It suppresses anti-tumor cytokine secretion and T cell activation by disrupting T cell receptor (TCR) binding and signal transduction. Ado also inhibits chemokine secretion and KCa3.1 channel activity, impeding effector T cell trafficking and infiltration into the tumor site. Furthermore, Ado diminishes T cell cytotoxicity against tumor cells by promoting immune-suppressive cytokine secretion, upregulating immune checkpoint proteins, and enhancing immune-suppressive cell activity. Reducing Ado production in the TME can significantly enhance anti-tumor immune responses and improve the efficacy of other immunotherapies. Preclinical and clinical development of inhibitors targeting Ado generation or AdoRs is underway. Therefore, this article will summarize and analyze the inhibitory effects and molecular mechanisms of Ado on tumor adaptive immunity, as well as provide an overview of the latest advancements in targeting Ado pathways in anti-tumor immune responses.

A meta-analysis of the association between the ATIC 347 C/G polymorphism and methotrexate responsiveness and toxicity in rheumatoid arthritis

OBJECTIVES

The purpose of this study was to determine whether the 347 C/G polymorphism in the 5-aminoimidazole-4-carboxamide ribonucleotide transformylase (ATIC) gene predicts the responsiveness to or toxicity of methotrexate (MTX) in patients with rheumatoid arthritis (RA).

METHOD

To identify relevant publications, we searched the Medline, Embase, Cochrane, and Web of Science databases. We performed a meta-analysis of studies on the relationship between the ATIC 347 C/G polymorphism and MTX toxicity or non-responsiveness in patients with RA.

RESULTS

Thirteen studies consisting of 3,185 patients with RA satisfied our inclusion criteria. The analysis included 10 studies on MTX responsiveness and seven studies on MTX toxicity in patients with RA in connection with ATIC 347C/G polymorphism. According to our meta-analysis, the ATIC 347 GG genotype and failure to respond to MTX treatment were significantly associated (OR = 0.741, 95% CI = 0.591-0.929, p=0.009). According to stratification by ethnicity, this genotype was significantly associated with non-responsiveness to MTX in Europeans (OR=0.548, 95% CI=0.377-0.796, p=0.002) but not in Asian populations (OR=0.882, 95% CI=0.665-1.1172, p=0.388). However, analyses employing allelic, dominant, and homozygous contrast models failed to detect any relationship between the polymorphism and the failure to respond to MXT. However, the ATIC 347GG genotype and MTX toxicity were not associated (OR=1.278, 95% CI=0.937-1.745, p=0.121). Asian and European populations showed no evidence of a relationship between the ATIC 347GG genotype and MTX toxicity (OR=1.252, 95% CI=0.905-1.732, p=0.175 and OR =1.617, 95% CI=0.549-4.765, p=0.383, respectively).

CONCLUSIONS

This meta-analysis revealed that ATIC 347 C/G polymorphism was related to non-responsiveness to MTX in European populations with RA. However, no significant correlation was found with MTX toxicity.

Effect of adenosine treatment on ionizing radiation toxicity in zebrafish early life stages

The danger of ionizing radiation exposure to human health is a concern. Since its wide use in medicine and industry, the development of radioprotectors has been very significant. Adenosine exerts anti-inflammatory actions and promotes tissue protection and repair, by activating the P1 receptors (A1, A2A, A2B, and A3). Zebrafish (Danio rerio) is an appropriate tool in the fields of toxicology and pharmacology, including the evaluation of radiobiological outcomes and in the search for radioprotector agents. This study aims to evaluate the effect of adenosine in the toxicity induced by radiation in zebrafish. Embryos were treated with 1, 10, or 100 µM adenosine, 30 min before the exposure to 15 Gy of gamma radiation. Adenosine potentiated the effects of radiation in heart rate, body length, and pericardial edema. We evaluated oxidative stress, tissue remodeling and inflammatory. It was seen that 100 µM adenosine reversed the inflammation induced by radiation, and that A2A2 and A2B receptors are involved in these anti-inflammatory effects. Our results indicate that P1R activation could be a promising pharmacological strategy for radioprotection.

Gene expression changes in conjunctival cells associated with contact lens wear and discomfort

PURPOSE

This study aimed to analyze the differences in the expression of pain-related genes in conjunctival epithelial cells among symptomatic contact lens (CL) wearers (SCLWs), asymptomatic CL wearers (ACLWs), and non-CL wearers (non-CLWs).

METHODS

For this study, 60 participants (20 non-CLWs, 40 CLWs) were enrolled. The CLW group comprised 20 ACLWs and 20 SCLWs according to the Contact Lens Dry Eye Questionnaire short form©. Conjunctival cells were collected using impression cytology, and RNA was isolated and used to determine the expression levels of 85 human genes involved in neuropathic and inflammatory pain. The effects of CL wear and discomfort were evaluated using mixed-effects ANOVA with partially nested fixed-effects model. Gene set enrichment analysis was performed to assign biological meaning to sets of differentially expressed genes.

RESULTS

Six genes (CD200, EDN1, GRIN1, PTGS1, P2RX7, and TNF) were significantly upregulated in CLWs compared to non-CLWs. Eleven genes (ADORA1, BDKRB1, CACNA1B, DBH, GRIN1, GRM1, HTR1A, PDYN, PTGS1, P2RX3, and TNF) were downregulated in SCLWs compared to ACLWs. These genes were mainly related to pain, synaptic transmission and signaling, ion transport, calcium transport and concentration, and cell-cell signaling.

CONCLUSIONS

CL wear modified the expression of pain- and inflammation-related genes in conjunctival epithelial cells. These changes may be in part, along with other mechanisms, responsible for CL discomfort in SCLWs.

Multi-Functional Small Molecule Alleviates Fracture Pain and Promotes Bone Healing

Bone injuries such as fractures are one major cause of morbidities worldwide. A considerable number of fractures suffer from delayed healing, and the unresolved acute pain may transition to chronic and maladaptive pain. Current management of pain involves treatment with NSAIDs and opioids with substantial adverse effects. Herein, we tested the hypothesis that the purine molecule, adenosine, can simultaneously alleviate pain and promote healing in a mouse model of tibial fracture by targeting distinctive adenosine receptor subtypes in different cell populations. To achieve this, a biomaterial-assisted delivery of adenosine is utilized to localize and prolong its therapeutic effect at the injury site. The results demonstrate that local delivery of adenosine inhibited the nociceptive activity of peripheral neurons through activation of adenosine A1 receptor (ADORA1) and mitigated pain as demonstrated by weight bearing and open field movement tests. Concurrently, local delivery of adenosine at the fracture site promoted osteogenic differentiation of mesenchymal stromal cells through adenosine A2B receptor (ADORA2B) resulting in improved bone healing as shown by histological analyses and microCT imaging. This study demonstrates the dual role of adenosine and its material-assisted local delivery as a feasible therapeutic approach to treat bone trauma and associated pain.

Cause analysis of conversion to biologics in spondyloarthritis patients with poor response to conventional treatment

OBJECTIVE

We sought to investigate the reasons why spondyloarthritis (SpA) patients failed to respond to non-steroidal anti-inflammatory drugs (NSAIDs) and conventional synthetic disease-modifying antirheumatic drugs (cDMARDs) and the influences of different initial cDMARDs on the likelihood of a switch to biologics.

METHODS

SpA patients were divided into a conventional drug maintenance group and a biologics conversion group to determine the causes of conversion to biologics. Then, we divided all patients into three groups according to different initial cDMARDs, NSAID monotherapy, NSAID + (sulfasalazine or thalidomide) double combination, and NSAID + sulfasalazine + thalidomide triple combination therapy groups, to clarify the influence of initial treatment on later conversion to biologics.

RESULTS

This study includes 202 patients, including 97 patients in the conventional drug maintenance group and 105 patients in the biologics conversion group. The mean age of the conventional drug maintenance group was higher than that of the biologics conversion group (40.8 ± 14.3 vs. 33.8 ± 12.3 years, P < 0.05). Uveitis (OR 5.356, P < 0.05) is positively correlated with conversion to biological therapy, while age (OR 0.940, P < 0.05) is negatively correlated. The proportion of NSAID monotherapy, double combination, and triple combination groups converted to biological agents was 80%, 51.1%, and 23.2%, respectively (P < 0.05).

CONCLUSION

Age and uveitis are related to conversion to biologics therapy. The early combination of sulfasalazine and thalidomide with NSAIDs may lower the probability of conversion to biologics therapy in the later stage and offer a new option for patients with limited use of biologics in SpA patients. Key Points • Patients' move to biologics may be caused mostly by inadequate disease control by conventional oral medications. • Regardless of axial vs. peripheral joint involvement, combination drug therapy was superior to single drug therapy in controlling SpA and decreasing the probability of conversion to a biological agent. • For SpA patients who are not candidates for biologics due to contraindications or other reasons, early combination application of NSAIDs, sulfasalazine, and thalidomide may be a new choice.

Prolonged administration of total glucosides of paeony improves intestinal immune imbalance and epithelial barrier damage in collagen-induced arthritis rats based on metabolomics-network pharmacology integrated analysis

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by synovial inflammation and joint damage with complex pathological mechanisms. In recent years, many studies have shown that the dysregulation of intestinal mucosal immunity and the damage of the epithelial barrier are closely related to the occurrence of RA. Total glucosides of paeony (TGP) have been used clinically for the treatment of RA in China for decades, while the pharmacological mechanism is still uncertain. The purpose of this study was to investigate the regulatory effect and mechanism of TGP on intestinal immunity and epithelial barrier in RA model rats. The results showed that TGP alleviated immune hyperfunction by regulating the ratio of CD3+, CD4+ and CD8+ in different lymphocyte synthesis sites of the small intestine, including Peyer's patches (PPs), intraepithelial lymphocytes (IELs), and lamina propria lymphocytes (LPLs). Specially, TGP first exhibited immunomodulatory effects on sites close to the intestinal lumen (IELs and LPLs), and then on PPs far away from the intestinal lumen as the administration time prolonged. Meanwhile, TGP restores the intestinal epithelial barrier by upregulating the ratio of villi height (V)/crypt depth (C) and expression of tight junction proteins (ZO-1, occludin). Finally, the integrated analysis of metabolomics-network pharmacology was also used to explore the possible regulation mechanism of TGP on the intestinal tract. Metabolomics analysis revealed that TGP reversed the intestinal metabolic profile disturbance in CIA rats, and identified 32 biomarkers and 163 corresponding targets; network pharmacology analysis identified 111 potential targets for TGP to treat RA. By intersecting the results of the two, three key targets such as ADA, PNP and TYR were determined. Pharmacological verification experiments showed that the levels of ADA and PNP in the small intestine of CIA rats were significantly increased, while TGP significantly decreased their ADA and PNP levels. In conclusion, purine metabolism may play an important role in the process of TGP improving RA-induced intestinal immune imbalance and impaired epithelial barrier.

[1,2,4]Triazolo[1,5-c]pyrimidines as Tools to Investigate A3 Adenosine Receptors in Cancer Cell Lines

The A3 adenosine receptor is an interesting target whose role in cancer is controversial. In this work, a structural investigation at the 2-position of the [1,2,4]triazolo[1,5-c]pyrimidine nucleus was performed, finding new potent and selective A3 adenosine receptor antagonists such as the ethyl 2-(4-methoxyphenyl)-5-(methylamino)-[1,2,4]triazolo[1,5-c]pyrimidine-8-carboxylate (20, DZ123) that showed a Ki value of 0.47 nM and an exceptional selectivity profile over the other adenosine receptor subtypes. Computational studies were performed to rationalize the affinity and the selectivity profile of the tested compounds at the A3 adenosine receptor and the A1 and A2A adenosine receptors. Compound 20 was tested on both A3 adenosine receptor positive cell lines (CHO-A3 AR transfected, THP1 and HCT16) and on A3 negative cancer cell lines, showing no effect in the latter and a pro-proliferative effect at a low concentration in the former. These interesting results pave the way to further investigation on both the mechanism involved and potential therapeutic applications.

Intervention Effects of Physical Activity on Type 2 Diabetic Patients Potentially Infected with COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has clearly had a great influence on the lifestyles of the population, especially on patients with type 2 diabetes mellitus. During the COVID-19 outbreak, many countries/regions implemented social-isolation measures, leading to an increase in negative behaviors and impairing the capability of diabetic patients to resist COVID-19, ultimately causing severe prognoses. Moreover, as the epidemic progressed, multiple studies emphasized the significance of physical exercise in the management of type 2 diabetic patients infected with COVID-19. In this study, we selected research from 1 December 2019 to 9 August 2023 that focused on COVID-19-infected diabetic patients to investigate the impact of type 2 diabetes on the immune functions, inflammation factor levels, lung injuries, and mental disorders of such patients, as well as to assess the risk of novel coronavirus pneumonia in these patients. Additionally, the effects of high-intensity, moderate-intensity, and low-intensity exercises on novel coronavirus pneumonia infection in type 2 diabetic patients and the mechanisms of the effects of such exercise were considered. We concluded that elderly diabetic patients with COVID-19 should perform low-intensity exercises to facilitate their recoveries. This study offers guidance for a proper understanding of the dangers of diabetes and the use of appropriate measures to reduce the risk of novel coronavirus pneumonia infections in type 2 diabetic patients.

Inhibitory effect of adenosine on adaptive antitumor immunity and intervention strategies

Tumors in which the microenvironment is characterized by lack of immune cell infiltration are referred as "cold tumors" and typically exhibit low responsiveness to immune therapy. Targeting the factors contributing to "cold tumors" formation and converting them into "hot tumors" is a novel strategy for improving the efficacy of immunotherapy. Adenosine, a hydrolysis product of ATP, accumulates with a significantly higher concentration in the tumor microenvironments compared with normal tissue and exerts inhibitory effects on tumor-specific adaptive immunity. Tumor cells, dendritic cells, macrophages, and T cells express abundant adenosine receptors on their surfaces. The binding of adenosine to these receptors initiates downstream signaling pathways that suppress tumor antigen presentation and immune cell activation, consequently dampening adaptive immune responses against tumors. Adenosine down-regulates the expression of major histocompatibility complex Ⅱ and co-stimulatory factors on dendritic cells and macrophages, thereby inhibiting antigen presentation to T cells. Adenosine also inhibits ligand-receptor binding and transmembrane signaling on T cells, concomitantly suppressing the secretion of anti-tumor cytokines and impairing T cell activation. Furthermore, adenosine hinders effector T cell trafficking to tumor sites and infiltration by inhibiting chemokine secretion and KCa3.1 channels. Additionally, adenosine promotes the secretion of immunosuppressive cytokines, increases immune checkpoint protein expression, and enhances the activity of immunosuppressive cells, collectively curbing cytotoxic T cell-mediated tumor cell killing. Given the immunosuppressive role of adenosine in adaptive antitumor immunity, several inhibitors targeting adenosine generation or adenosine receptor blockade are currently in preclinical or clinical development with the aim of enhancing the effectiveness of immunotherapies. This review provides an overview of the inhibitory effects of adenosine on adaptive antitumor immunity, elucidate the molecular mechanisms involved, and summarizes the latest advances in application of adenosine inhibition strategies for antitumor immunotherapy.

Interplay between inflammatory bowel disease therapeutics and the gut microbiome reveals opportunities for novel treatment approaches

Inflammatory bowel disease (IBD) is a complex heterogeneous disorder defined by recurring chronic inflammation of the gastrointestinal tract, attributed to a combination of factors including genetic susceptibility, altered immune response, a shift in microbial composition/microbial insults (infection/exposure), and environmental influences. Therapeutics generally used to treat IBD mainly focus on the immune response and include non-specific anti-inflammatory and immunosuppressive therapeutics and targeted therapeutics aimed at specific components of the immune system. Other therapies include exclusive enteral nutrition and emerging stem cell therapies. However, in recent years, scientists have begun to examine the interplay between these therapeutics and the gut microbiome, and we present this information here. Many of these therapeutics are associated with alterations to gut microbiome composition and functionality, often driving it toward a "healthier profile" and preclinical studies have revealed that such alterations can play an important role in therapeutic efficacy. The gut microbiome can also improve or hinder IBD therapeutic efficacy or generate undesirable metabolites. For certain IBD therapeutics, the microbiome composition, particularly before treatment, may serve as a biomarker of therapeutic efficacy. Utilising this information and manipulating the interactions between the gut microbiome and IBD therapeutics may enhance treatment outcomes in the future and bring about new opportunities for personalised, precision medicine.

Pharmacology of Adenosine Receptors: Recent Advancements

Adenosine receptors (ARs) are widely acknowledged pharmacological targets yet are still underutilized in clinical practice. Their ubiquitous distribution in almost all cells and tissues of the body makes them, on the one hand, excellent candidates for numerous diseases, and on the other hand, intrinsically challenging to exploit selectively and in a site-specific manner. This review endeavors to comprehensively depict the substantial advancements witnessed in recent years concerning the development of drugs that modulate ARs. Through preclinical and clinical research, it has become evident that the modulation of ARs holds promise for the treatment of numerous diseases, including central nervous system disorders, cardiovascular and metabolic conditions, inflammatory and autoimmune diseases, and cancer. The latest studies discussed herein shed light on novel mechanisms through which ARs exert control over pathophysiological states. They also introduce new ligands and innovative strategies for receptor activation, presenting compelling evidence of efficacy along with the implicated signaling pathways. Collectively, these emerging insights underscore a promising trajectory toward harnessing the therapeutic potential of these multifaceted targets.

In vivo phenotypic validation of adenosine receptor-dependent activity of non-adenosine drugs

Some non-adenosinergic drugs are reported to also act through adenosine receptors (ARs). We used mouse hypothermia, which can be induced by agonism at any of the four ARs, as an in vivo screen for adenosinergic effects. An AR contribution was identified when a drug caused hypothermia in wild type mice that was diminished in mice lacking all four ARs (quadruple knockout, QKO). Alternatively, an adenosinergic effect was identified if a drug potentiated adenosine-induced hypothermia. Four drugs (dipyridamole, nimodipine, cilostazol, cyclosporin A) increased the hypothermia caused by adenosine. Dipyridamole and nimodipine probably achieved this by inhibition of adenosine clearance via ENT1. Two drugs (cannabidiol, canrenoate) did not cause hypothermia in wild type mice. Four other drugs (nifedipine, ranolazine, ketamine, ethanol) caused hypothermia, but the hypothermia was unchanged in QKO mice indicating non-adenosinergic mechanisms. Zinc chloride caused hypothermia and hypoactivity; the hypoactivity was blunted in the QKO mice. Interestingly, the antidepressant amitriptyline caused hypothermia in wild type mice that was amplified in the QKO mice. Thus, we have identified adenosine-related effects for some drugs, while other candidates do not affect adenosine signaling by this in vivo assay. The adenosine-modulating drugs could be considered for repurposing based on predicted effects on AR activation.

Impact of methotrexate treatment on vaccines immunogenicity in adult rheumatological patients - Lessons learned from the COVID-19 pandemic

Despite the development of new biological and synthetic targeted therapies, methotrexate remains one of the most commonly used immunomodulatory drugs in rheumatology. However, its effect on the immunogenicity of vaccines has been studied only to a limited extent until recently, resulting in the lack of clear guidelines on the use of methotrexate during vaccination. Significant progress was made during the COVID-19 pandemic due to the dynamic development of research on vaccines, including patients with autoimmune inflammatory rheumatic diseases. In the following literature review, we present a summary of what we know so far on the impact of methotrexate on post-vaccination response in adult rheumatology patients, taking into account the lessons learned from the COVID-19 pandemic. Studies on the effect of methotrexate on the immunogenicity of influenza, pneumococcal, herpes zoster, tetanus/diphtheria/pertussis, hepatitis A, yellow fever, and COVID-19 vaccines are described in detail, including the effect of methotrexate on the humoral and cellular response of individual vaccines. The available evidence for recommendations for withholding methotrexate in the post-vaccination period is presented. Lastly, an overview of potential immunological mechanisms through which MTX modulates the immunogenicity of vaccinations is also provided.

Aceclofenac and methotrexate combination therapy could influence Th1/Th17 axis to modulate rheumatoid-arthritis-induced inflammation

Rheumatoid arthritis (RA) is an inflammatory, autoimmune and connective-tissue arthropathy. The methotrexate (MTX) and aceclofenac (ACL) combination drug regimen is known to regulate the immunological pathways. Also, RA-elicited inflammation is decreased by the combination drug treatment. ACL and MTX combination treatment has been shown to regulate the signaling pathway controlled by NF-κB and FOXO1. The present manuscript reviews the importance of the combination drug regimen to treat and/or manage RA. The combination drug regimen could affect the Th1/Th17 axis to switch the balance toward the immunoregulatory (Th1) phenotype for establishing immune homeostasis. In conclusion, we propose the study of the immunological signaling pathways in experimental humanized RA mice.

Determination of adenosine by CRISPR-Cas12a system based on duplexed aptamer and molecular beacon reporter linked to gold nanoparticles

Adenosine as a potential tumor marker is of great value for clinical disease diagnosis. Since the CRISPR-cas12a system is only capable of recognizing nucleic acid targets we expanded the CRISPR-cas12a system to determine small molecules by designing a duplexed aptamer (DA) converting g-RNA recognition of adenosine to recognition of aptamer complementary DNA strands (ACD). To further improve the sensitivity of determination, we designed a molecule beacon (MB)/gold nanoparticle (AuNP)-based reporter, which has higher sensitivity than traditional ssDNA reporter. In addition, the AuNP-based reporter enables more efficient and fast determination. The determination of adenosine under 488-nm excitation can be realized within 7 min, which is more than 4 times faster than traditional ssDNA reporter. The linear determination range of the assay to adenosine was 0.5-100 μM with the determination limit of 15.67 nM. The  assay was applied to recovery determination of adenosine in serum samples with satisfactory results. The recoveries were between 91 and 106% and the RSD values of different concertation were below  4.8%. This sensitive, highly selective, and stable sensing system is expected to play a role in the clinical determination of adenosine and other biomolecules.

Neuronal activity-induced, equilibrative nucleoside transporter-dependent, somatodendritic adenosine release revealed by a GRAB sensor

The purinergic signaling molecule adenosine (Ado) modulates many physiological and pathological functions in the brain. However, the exact source of extracellular Ado remains controversial. Here, utilizing a newly optimized genetically encoded GPCR-Activation-Based Ado fluorescent sensor (GRABAdo), we discovered that the neuronal activity-induced extracellular Ado elevation is due to direct Ado release from somatodendritic compartments of neurons, rather than from the axonal terminals, in the hippocampus. Pharmacological and genetic manipulations reveal that the Ado release depends on equilibrative nucleoside transporters but not the conventional vesicular release mechanisms. Compared with the fast-vesicular glutamate release, the Ado release is slow (~40 s) and requires calcium influx through L-type calcium channels. Thus, this study reveals an activity-dependent second-to-minute local Ado release from the somatodendritic compartments of neurons, potentially serving modulatory functions as a retrograde signal.

Enzyme Translocation-Mediated Signal Amplification for Spatially Selective Aptasensing of ATP in Inflammatory Cells

Amplified ATP imaging in inflammatory cells is highly desirable. However, the spatial selectivity of current amplification methods is limited, that is, signal amplification is performed systemically and not in a disease site-specific manner. Here we present a versatile strategy, termed enzymatically triggerable, aptamer-based signal amplification (ETA-SA), that enables inflammatory cell-specific imaging of ATP through spatially-resolved signal amplification. The ETA-SA leverages a translocated enzyme in inflammatory cells to activate DNA aptamer probes and further drive cascade reactions through the consumption of hairpin fuels, which, however, exerts no ATP response activity in normal cells, leading to a significantly improved sensitivity and spatial specificity for the inflammation-specific ATP imaging in vivo. Benefiting from the improved spatial selectivity, enhanced signal-to-background ratios were achieved for ATP imaging during acute hepatitis.

CD73: Friend or Foe in Lung Injury

Ecto-5′-nucleotidase (CD73) plays a strategic role in calibrating the magnitude and chemical nature of purinergic signals that are delivered to immune cells. Its primary function is to convert extracellular ATP to adenosine in concert with ectonucleoside triphosphate diphosphohydrolase-1 (CD39) in normal tissues to limit an excessive immune response in many pathophysiological events, such as lung injury induced by a variety of contributing factors. Multiple lines of evidence suggest that the location of CD73, in proximity to adenosine receptor subtypes, indirectly determines its positive or negative effect in a variety of organs and tissues and that its action is affected by the transfer of nucleoside to subtype-specific adenosine receptors. Nonetheless, the bidirectional nature of CD73 as an emerging immune checkpoint in the pathogenesis of lung injury is still unknown. In this review, we explore the relationship between CD73 and the onset and progression of lung injury, highlighting the potential value of this molecule as a drug target for the treatment of pulmonary disease.

Purinergic receptor: a crucial regulator of adipose tissue functions

Obesity is a public-health challenge resulting from an imbalance between energy expenditure and calorie intake. This health problem exacerbates a variety of metabolic complications worldwide. Adipose tissue is an essential regulator of energy homeostasis, and the functions within it are regulated by purinergic receptors. A₁R, P2X7R, and P2YR mainly mediate energy homeostasis primarily through regulating energy storage and adipokines secretion in white adipose tissue (WAT). P2X5R is a novel-specific cell surface marker in brown/beige adipocytes. A₂R is a promising therapeutic target for stimulating energy expenditure in brown adipose tissue (BAT) and also mediating WAT browning. Based on these features, purinergic receptors may be an appropriate target in treating obesity. In this review, the role of purinergic receptors in different types of adipose tissue is summarized. An improved understanding of purinergic receptor functions in adipose tissue may lead to more effective treatment interventions for obesity and its related metabolic disorders.

Efficacy of Polydeoxyribonucleotide in Promoting the Healing of Diabetic Wounds in a Murine Model of Streptozotocin-Induced Diabetes: A Pilot Experiment

We assessed the efficacy of polydeoxyribonucleotide (PDRN) in accelerating the healing of diabetic wounds in a murine model of streptozotocin (STZ)-induced diabetes. After the creation of diabetic wounds, the mice of the PDRN SC, PDRN IP and PBS groups received a subcutaneous, an intra-peritoneal injection of PDRN and a subcutaneous injection of PBS, respectively. After euthanasia, time-dependent changes in the wound diameter and histologic scores were measured and vascular endothelial growth factor (VEGF), transforming growth factor-β1 (TGF-β1) and collagen types I and III were assessed for their expression levels. The PDRN SC and the PDRN IP groups showed a significantly smaller diameter of diabetic wounds, significantly higher histologic scores, a significantly greater expression of VEGF, a significantly lower expression of TGF-β1 and a significantly greater expression of collagen types I and III as compared with the PBS group (p < 0.05 or 0.0001). In conclusion, PDRN might be effective in promoting the healing of diabetic wounds in a murine model of STZ-induced diabetes.

Current evidence and clinical relevance of drug-microbiota interactions in inflammatory bowel disease

Background

Inflammatory bowel disease (IBD) is a chronic relapsing-remitting disease. An adverse immune reaction toward the intestinal microbiota is involved in the pathophysiology and microbial perturbations are associated with IBD in general and with flares specifically. Although medical drugs are the cornerstone of current treatment, responses vary widely between patients and drugs. The intestinal microbiota can metabolize medical drugs, which may influence IBD drug (non-)response and side effects. Conversely, several drugs can impact the intestinal microbiota and thereby host effects. This review provides a comprehensive overview of current evidence on bidirectional interactions between the microbiota and relevant IBD drugs (pharmacomicrobiomics).

Methods

Electronic literature searches were conducted in PubMed, Web of Science and Cochrane databases to identify relevant publications. Studies reporting on microbiota composition and/or drug metabolism were included.

Results

The intestinal microbiota can both enzymatically activate IBD pro-drugs (e.g., in case of thiopurines), but also inactivate certain drugs (e.g., mesalazine by acetylation via N-acetyltransferase 1 and infliximab via IgG-degrading enzymes). Aminosalicylates, corticosteroids, thiopurines, calcineurin inhibitors, anti-tumor necrosis factor biologicals and tofacitinib were all reported to alter the intestinal microbiota composition, including changes in microbial diversity and/or relative abundances of various microbial taxa.

Conclusion

Various lines of evidence have shown the ability of the intestinal microbiota to interfere with IBD drugs and vice versa. These interactions can influence treatment response, but well-designed clinical studies and combined in vivo and ex vivo models are needed to achieve consistent findings and evaluate clinical relevance.

Cryo-EM structure of the human adenosine A2B receptor-Gs signaling complex

The human adenosine A_2B receptor (A_2BR) is a class A G protein-coupled receptor that is involved in several major physiological and pathological processes throughout the body. A_2BR recognizes its ligands adenosine and NECA with relatively low affinity, but the detailed mechanism for its ligand recognition and signaling is still elusive. Here, we present two structures determined by cryo-electron microscopy of A_2BR bound to its agonists NECA and BAY60-6583, each coupled to an engineered G_s protein. The structures reveal conserved orthosteric binding pockets with subtle differences, whereas the selectivity or specificity can mainly be attributed to regions extended from the orthosteric pocket. We also found that BAY60-6583 occupies a secondary pocket, where residues V250^6.51 and N273^7.36 were two key determinants for its selectivity against A_2BR. This study offers a better understanding of ligand selectivity for the adenosine receptor family and provides a structural template for further development of A_2BR ligands for related diseases.

Cupping alleviates lung injury through the adenosine/A2BAR pathway

Background

Acute lung injury (ALI) is a serious condition. Inflammation plays a crucial role in the pathogenesis of ALI. Cupping, as a part of traditional Chinese medicine, is still a popular complementary and alternative therapy for a variety of ailments including respiratory diseases. However, reliable scientific data about cupping therapy are scarce. Adenosine, a purine nucleoside produced under metabolic stress by the action of extracellular ectonucleotidases (i.e. CD39 and CD73), can attenuate ALI through the A_2BAR receptor. The aim of this study was to investigate the protective effect of cupping in a rat model of ALI and the role of adenosine in it.

Methods

Male adult rats were subjected to ALI by intratracheal LPS instillation (0.3 mg/kg). Immediately after intratracheal LPS instillation, vacuum pressure was applied to a sanitized plastic bell cup on the back of the rat by suction for 10 min. Pulmonary injury and inflammation were assessed at 4 h after LPS challenge. The role of adenosine and A_2BAR in cupping's protection after LPS instillation were evaluated.

Results

Cupping alleviated LPS-induced lung injury, reduced inflammation and inhibited NF-kB activation in rats. Cupping upregulated CD39 and CD73 mRNA expression of the skin tissue at the cupping site and increased circulating levels of adenosine. Administration of PSB1115, a specific adenosine A_2BAR receptor antagonist, abolished cupping's beneficial effects in LPS-induced ALI.

Conclusions

Cupping attenuates lung inflammation and injury through the adenosine/A_2BAR pathway. The current study provides evidence-based information about cupping therapy in ALI.

Extracellular Vesicles from Bothrops jararaca Venom Are Diverse in Structure and Protein Composition and Interact with Mammalian Cells

Snake venoms are complex cocktails of non-toxic and toxic molecules that work synergistically for the envenoming outcome. Alongside the immediate consequences, chronic manifestations and long-term sequelae can occur. Recently, extracellular vesicles (EVs) were found in snake venom. EVs mediate cellular communication through long distances, delivering proteins and nucleic acids that modulate the recipient cell's function. However, the biological roles of snake venom EVs, including possible cross-organism communication, are still unknown. This knowledge may expand the understanding of envenoming mechanisms. In the present study, we isolated and characterized the EVs from Bothrops jararaca venom (Bj-EVs), giving insights into their biological roles. Fresh venom was submitted to differential centrifugation, resulting in two EV populations with typical morphology and size range. Several conserved EV markers and a subset of venom related EV markers, represented mainly by processing enzymes, were identified by proteomic analysis. The most abundant protein family observed in Bj-EVs was 5'-nucleotidase, known to be immunosuppressive and a low abundant and ubiquitous toxin in snake venoms. Additionally, we demonstrated that mammalian cells efficiently internalize Bj-EVs. The commercial antibothropic antivenom partially recognizes Bj-EVs and inhibits cellular EV uptake. Based on the proteomic results and the in vitro interaction assays using macrophages and muscle cells, we propose that Bj-EVs may be involved not only in venom production and processing but also in host immune modulation and long-term effects of envenoming.

Update on the recent development of allosteric modulators for adenosine receptors and their therapeutic applications

Adenosine receptors (ARs) have been identified as promising therapeutic targets for countless pathological conditions, spanning from inflammatory diseases to central nervous system disorders, from cancer to metabolic diseases, from cardiovascular pathologies to respiratory diseases, and beyond. This extraordinary therapeutic potential is mainly due to the plurality of pathophysiological actions of adenosine and the ubiquitous expression of its receptors. This is, however, a double-edged sword that makes the clinical development of effective ligands with tolerable side effects difficult. Evidence of this is the low number of AR agonists or antagonists that have reached the market. An alternative approach is to target allosteric sites via allosteric modulators, compounds endowed with several advantages over orthosteric ligands. In addition to the typical advantages of allosteric modulators, those acting on ARs could benefit from the fact that adenosine levels are elevated in pathological tissues, thus potentially having negligible effects on normal tissues where adenosine levels are maintained low. Several A1 and various A3AR allosteric modulators have been identified so far, and some of them have been validated in different preclinical settings, achieving promising results. Less fruitful, instead, has been the discovery of A2A and A2BAR allosteric modulators, although the results obtained up to now are encouraging. Collectively, data in the literature suggests that allosteric modulators of ARs could represent valuable pharmacological tools, potentially able to overcome the limitations of orthosteric ligands.

Chinese Cordyceps: Bioactive Components, Antitumor Effects and Underlying Mechanism-A Review

Chinese Cordyceps is a valuable source of natural products with various therapeutic effects. It is rich in various active components, of which adenosine, cordycepin and polysaccharides have been confirmed with significant immunomodulatory and antitumor functions. However, the underlying antitumor mechanism remains poorly understood. In this review, we summarized and analyzed the chemical characteristics of the main components and their pharmacological effects and mechanism on immunomodulatory and antitumor functions. The analysis revealed that Chinese Cordyceps promotes immune cells' antitumor function by via upregulating immune responses and downregulating immunosuppression in the tumor microenvironment and resetting the immune cells' phenotype. Moreover, Chinese Cordyceps can inhibit the growth and metastasis of tumor cells by death (including apoptosis and autophagy) induction, cell-cycle arrest, and angiogenesis inhibition. Recent evidence has revealed that the signal pathways of mitogen-activated protein kinases (MAPKs), nuclear factor kappaB (NF-κB), cysteine-aspartic proteases (caspases) and serine/threonine kinase Akt were involved in the antitumor mechanisms. In conclusion, Chinese Cordyceps, one type of magic mushroom, can be potentially developed as immunomodulator and anticancer therapeutic agents.

May alcoholic and non-alcoholic drinks affect the rate of orthodontic tooth movement? A systematic review of animal studies

BACKGROUND

Humans may consume various beverages in everyday life. Previous research has shown that the administration of different substances (medicinal or not) may affect bone turnover and, thus, orthodontic tooth movement. It would be anticipated that the substances contained in beverages could have an impact on tooth movement, as well.

OBJECTIVE

To investigate in a systematic way and appraise the quality of the available evidence from animal studies regarding the impact of various drinks or the main ingredients included in beverages on the rate of orthodontic tooth movement.

SEARCH METHODS

Search without restriction in six databases (including grey literature) and hand searching were performed until March 2022.

SELECTION CRITERIA

We looked for controlled animal studies investigating the effect of drinks, or the main ingredients included in beverages, on the rate of orthodontic tooth movement.

DATA COLLECTION AND ANALYSIS

After study retrieval and selection, relevant data was extracted, and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. The quality of available evidence was assessed with the Grades of Recommendation, Assessment, Development, and Evaluation.

RESULTS

The initially identified records were finally reduced to nine studies conducted on animals. Carbonated soft drinks were shown to decrease the rate of tooth movement, but alcohol consumption did not have an impact. Exploratory meta-analysis showed that caffeine exhibited an acceleratory effect after 3 weeks of force application. Exploratory meta-regression results indicated that high dosages of caffeine reduced the rate of tooth movement.

CONCLUSIONS

The located animal experiments reported that caffeine accelerates, carbonated drinks decelerate, while alcohol does not affect the rate of orthodontic tooth movement. However, due to various limitations it remains unclear whether caffeine, alcohol, or carbonated drinks finally influence tooth movement in animal studies.

REGISTRATION

Open Science Framework (https://osf.io/jyhbd/).

Immune checkpoint modulators in cancer immunotherapy: recent advances and emerging concepts

The discovery of immune checkpoint inhibitors (ICIs) has now been universally acknowledged as a significant breakthrough in tumor therapy after the targeted treatment of checkpoint molecules: anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) and anti-cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) on several cancer types achieved satisfying results. However, there are still quite a lot of patients suffering from severe side effects and ineffective treatment outcomes. Although the current ICI therapy is far from satisfying, a series of novel immune checkpoint molecules with remarkable preclinical and clinical benefits are being widely investigated, like the V-domain Ig suppressor of T cell activation (VISTA), which can also be called PD-1 homolog (PD-1H), and ectonucleotidases: CD39, CD73, and CD38, which belong to the ribosyl cyclase family, etc. In this review, we systematically summarized and discussed these molecules' biological structures, molecular features, and the corresponding targeted drugs, aiming to help the in-depth understanding of immune checkpoint molecules and promote the clinical practice of ICI therapy.

Immune checkpoint modulators in cancer immunotherapy: recent advances and emerging concepts

The discovery of immune checkpoint inhibitors (ICIs) has now been universally acknowledged as a significant breakthrough in tumor therapy after the targeted treatment of checkpoint molecules: anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) and anti-cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) on several cancer types achieved satisfying results. However, there are still quite a lot of patients suffering from severe side effects and ineffective treatment outcomes. Although the current ICI therapy is far from satisfying, a series of novel immune checkpoint molecules with remarkable preclinical and clinical benefits are being widely investigated, like the V-domain Ig suppressor of T cell activation (VISTA), which can also be called PD-1 homolog (PD-1H), and ectonucleotidases: CD39, CD73, and CD38, which belong to the ribosyl cyclase family, etc. In this review, we systematically summarized and discussed these molecules' biological structures, molecular features, and the corresponding targeted drugs, aiming to help the in-depth understanding of immune checkpoint molecules and promote the clinical practice of ICI therapy.

Immune hallmarks of rheumatoid arthritis management: A brief review

The purpose of this review was to examine current evidence on immunomodulation mediated by conventional drugs and the use of novel biological agents for the treatment of rheumatoid arthritis (RA). Currently, treatment is focused on maximizing quality of life through sustained clinical remission and/or attenuating disease activity. To do so, disease-modifying antirheumatic drugs, especially methotrexate, are used alone or in combination with other drugs, including leflunomide, biological disease-modifying antirheumatic drugs (bDMARDs) and targeted synthetic disease-modifying antirheumatic drugs (tsDMARDs). The most recent strategies modulate the immune response of the individual RA patient using tsDMARDs such as JAK inhibitors and bDMARDs such as ig-CTLA-4, anti- IL6R, anti-TNF-α and anti-CD20. To better understand current immunopharmacological interventions, we also looked at documented mechanisms of RA-mediated immunomodulation, highlighting perspectives potentially boosting RA treatment.

The immunomodulatory function of adenosine in sepsis

Sepsis is an unsolved clinical condition with a substantial mortality rate in the hospital. Despite decades of research, no effective treatments for sepsis exists. The role of adenosine in the pathogenesis of sepsis is discussed in this paper. Adenosine is an essential endogenous molecule that activates the A1, A2a, A2b, and A3 adenosine receptors to regulate tissue function. These receptors are found on a wide range of immune cells and bind adenosine, which helps to control the immune response to inflammation. The adenosine receptors have many regulatory activities that determine the onset and progression of the disease, which have been discovered via the use of animal models. A greater understanding of the role of adenosine in modulating the immune system has sparked hope that an adenosine receptor-targeted treatment may be used one day to treat sepsis.

G-Protein-Coupled Receptors in Rheumatoid Arthritis: Recent Insights into Mechanisms and Functional Roles

Rheumatoid arthritis (RA) is a chronic inflammatory disease that leads to joint damage and even disability. Although there are various clinical therapies for RA, some patients still have poor or no response. Thus, the development of new drug targets remains a high priority. In this review, we discuss the role of G-protein-coupled receptors (GPCRs), including chemokine receptors, melanocortin receptors, lipid metabolism-related receptors, adenosine receptors, and other inflammation-related receptors, on mechanisms of RA, such as inflammation, lipid metabolism, angiogenesis, and bone destruction. Additionally, we summarize the latest clinical trials on GPCR targeting to provide a theoretical basis and guidance for the development of innovative GPCR-based clinical drugs for RA.

Istradefylline, an adenosine A2a receptor antagonist, inhibits the CD4+ T-cell hypersecretion of IL-17A and IL-8 in humans

Extracellular adenosine produced from ATP plays a role in energy processes, neurotransmission, and inflammatory responses. Istradefylline is a selective adenosine A2a receptor (A2aR) antagonist used for the treatment of Parkinson's disease. We previously showed using mouse models that adenosine primes hypersecretion of interleukin (IL)-17A via A2aR, which plays a role in neutrophilic inflammation models in mice. This finding suggests that adenosine is an endogenous modulator of neutrophilic inflammation. We, therefore, investigated the in vitro effect of istradefylline in humans. In the present study, using human peripheral blood mononuclear cells (PBMCs), we tested the effect of adenosine, adenosine receptor agonists and istradefylline on cytokine responses using mixed lymphocyte reaction (MLR), PBMCs, CD4⁺ T cells, and Candida albicans antigen (Ag)-stimulated PBMCs. We showed that adenosine and an A2aR agonist (PSB0777) promoted IL-17A and IL-8 production from human PBMCs, and istradefylline suppressed this response. In addition, istradefylline inhibited not only the IL-17A and IL-8 production induced by adenosine but also that from C. albicans Ag-stimulated PBMCs. These results indicate that adenosine-mediated IL-17A and IL-8 production plays a role in neutrophilic inflammation, against which istradefylline should be effective.

Application and pharmacological mechanism of methotrexate in rheumatoid arthritis

Methotrexate (MTX) has been used for the treatment of rheumatoid arthritis (RA) for about forty years and to date MTX remains the part of global standard of treatment for RA. The efficacy of MTX in RA is the result of multiple mechanisms of action. In order to summarize the possible pharmacological mechanisms of MTX in the treatment of RA, this review will elaborate on folate antagonism, promotion of adenosine accumulation, regulation of inflammatory signaling pathways, bone protection and maintenance of immune system function.

The effects of caffeine on bone mineral density and fracture risk

Caffeine is a regular part of the diet of many adults (coffee, tea, soft drinks, and energy drinks). Multiple molecular effects of caffeine suggest that it may promote bone loss. Given the extensive consumption of caffeine worldwide, any impact of caffeine consumption on bone strength and/or density would have large population health implications. The most well-established pharmacological effect of caffeine is non-specific antagonism of adenosine receptors. Adenosine regulates bone metabolism in a complex manner, with in vitro studies suggesting that direct stimulation of adenosine A_2A and A_2B receptors induces bone formation by activating osteoblasts and suppressing osteoclast differentiation and function. Thus, competitive inhibition of adenosine A₂ receptors by caffeine may inhibit bone formation and promote bone resorption. However, antagonism of adenosine A₁ receptors may have opposing effects. Caffeine has also been suggested to affect bone through derangement of calcium metabolism, alteration of vitamin D responses, and other mechanisms. In clinical and population-based studies, the impact of caffeine consumption on bone metabolism offers a mixed picture, with some but not all studies suggesting a potential link between caffeine intake and reduced bone mineral density or increased fracture risk. Differences in methodology, selected populations, and duration/timing of the studies may account for study outcome discrepancies. The in vitro effects of caffeine on cells involved in bone metabolism suggest that caffeine intake may promote osteoporosis, and some but not all clinical studies support a modest adverse caffeine impact. Herein, we describe the basic biology of caffeine as it pertains to bone, review the clinical literature to date, and consider the implications of the current data on clinical practice and future studies.

Muscle satellite cells are impaired in type 2 diabetic mice by elevated extracellular adenosine

Muscle regeneration is known to be defective under diabetic conditions. However, the underlying mechanisms remain less clear. Adult quiescent muscle satellite cells (MuSCs) from leptin-receptor-deficient (i.e., db/db) diabetic mice are defective in early activation in vivo, but not in culture, suggesting the involvement of pathogenic niche factors. Elevated extracellular adenosine (eAdo) and AMP (eAMP) are detected under diabetic conditions. eAdo and eAMP potently inhibit cell cycle re-entry of quiescent MuSCs and injury-induced muscle regeneration. Mechanistically, eAdo and eAMP engage the equilibrative Ado transporters (ENTs)-Ado kinase (ADK)-AMPK signaling axis in MuSCs to inhibit the mTORC1-dependent cell growth checkpoint. eAdo and eAMP also inhibit early activation of quiescent fibroadipogenic progenitors and human MuSCs by the same mechanism. Treatment of db/db diabetic mice with an ADK inhibitor partially rescues the activation defects of MuSCs in vivo. Thus, both ADK and ENTs represent potential therapeutic targets for restoring the regenerative functions of tissue stem cells in patients with diabetes.

Remote Conditioning by Rhythmic Compression of Limbs Ameliorated Myocardial Infarction by Downregulation of Inflammation via A2 Adenosine Receptors

Background

Remote ischemic conditioning (RIC) is a cardioprotective phenomenon, yet transient ischemia is not a requisite trigger for remote cardioprotection. In fact, RIC is a stimulus compound containing interruption of the blood vessel and tissue compression. In this study, we evaluate the effects of remote tissue compression on infarct size after myocardial infarction and explore its preliminary mechanisms.

Methods and Results

We used a murine model of myocardial infarction to assess ischemia injury and identified remote conditioning by rhythmic compression on forelimb as a novel cardioprotective intervention. We show that the cardioprotective signal transduction of remote conditioning from the trigger limb to the heart involves the release of adenosine. Our results demonstrate that A2a and A2b receptors are indispensable parts for cardioprotection of remote conditioning, which is linked to its anti-inflammatory properties by the subsequent activation of cAMP/PKA/NF-κB axis.

Conclusion

Our results establish a new connection between remote tissue compression and cardiovascular diseases, which enhances our cognition about the role of tissue compression on RIC cardioprotection.

Development of a hyperbranched polymer-based methotrexate nanomedicine for rheumatoid arthritis

Methotrexate (MTX) is an effective disease modifying anti-rheumatic drug, but can cause significant hepatotoxicity and liver failure in some individuals. The goal of this work was to develop a MTX-conjugated hyperbranched polymeric nanoparticle based on oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and examine its ability to selectively deliver MTX to rheumatic joints while sparing the liver. MTX was conjugated to the hyperbranched polymer via a matrix metalloproteinase-13 cleavable peptide linker. Two populations of nanoparticles were produced, with sizes averaging 20 and 200nm. Tri-peptide (FFK)-modified MTX was liberated in the presence of matrix metalloproteinase 13 (MMP-13)and showed 100 to 1000-fold lower antiproliferative capacity in monocytic THP-1 cells compared to unmodified MTX, depending on whether the gamma-carboxylate of MTX was functionalized with O-tert-butyl. Nanoparticles showed prolonged plasma exposure after intravenous injection with a terminal half-life of approximately 1 day, but incomplete (50%) absorption after subcutaneous administration. Nanoparticles selectively accumulated in inflamed joints in a rat model of rheumatoid arthritis and showed less than 5% biodistribution in the liver after 5 days. MTX-OtBu nanoparticles also showed no hepatocellular toxicity at 500 μM MTX equivalents. This work provides support for the further development of OEGMA-based hyperbranched polymers as MTX drug delivery systems for rheumatoid arthritis. STATEMENT OF SIGNIFICANCE: Nanomedicines containing covalently conjugated methotrexate offer the potential for selective accumulation of the potent hepatotoxic drug in rheumatic joints and limited liver exposure. One limitation of the high surface presentation of methotrexate on a nanoparticle surface, however, is the potential for enhanced liver uptake. We developed several OEGMA-based hyperbranched polymers containing alpha-carboxyl modified and unmodified methotrexate conjugated via an MMP-13 cleavable hexapeptide linker. The modified methotrexate polymer showed promising in vitro and in vivo behavior warranting further development and optimization as an anti-rheumatic nanomedicine. This work presents a new avenue for further research into the development of hyperbranched polymers for rheumatoid arthritis and suggests interesting approaches that may overcome some limitations associated with the translation of anti-rheumatic nanomedicines into patients.

International Union of Basic and Clinical Pharmacology. CXII: Adenosine Receptors: A Further Update

Our previous International Union of Basic and Clinical Pharmacology report on the nomenclature and classification of adenosine receptors (2011) contained a number of emerging developments with respect to this G protein-coupled receptor subfamily, including protein structure, protein oligomerization, protein diversity, and allosteric modulation by small molecules. Since then, a wealth of new data and results has been added, allowing us to explore novel concepts such as target binding kinetics and biased signaling of adenosine receptors, to examine a multitude of receptor structures and novel ligands, to gauge new pharmacology, and to evaluate clinical trials with adenosine receptor ligands. This review should therefore be considered a further update of our previous reports from 2001 and 2011. SIGNIFICANCE STATEMENT: Adenosine receptors (ARs) are of continuing interest for future treatment of chronic and acute disease conditions, including inflammatory diseases, neurodegenerative afflictions, and cancer. The design of AR agonists ("biased" or not) and antagonists is largely structure based now, thanks to the tremendous progress in AR structural biology. The A2A- and A2BAR appear to modulate the immune response in tumor biology. Many clinical trials for this indication are ongoing, whereas an A2AAR antagonist (istradefylline) has been approved as an anti-Parkinson agent.

Monocytes and Macrophages in Spondyloarthritis: Functional Roles and Effects of Current Therapies

Spondyloarthritis (SpA) is a family of chronic inflammatory diseases, being the most prevalent ankylosing spondylitis (AS) and psoriatic arthritis (PsA). These diseases share genetic, clinical and immunological features, such as the implication of human leukocyte antigen (HLA) class I molecule 27 (HLA-B27), the inflammation of peripheral, spine and sacroiliac joints and the presence of extra-articular manifestations (psoriasis, anterior uveitis, enthesitis and inflammatory bowel disease). Monocytes and macrophages are essential cells of the innate immune system and are the first line of defence against external agents. In rheumatic diseases including SpA, the frequency and phenotypic and functional characteristics of both cell types are deregulated and are involved in the pathogenesis of these diseases. In fact, monocytes and macrophages play key roles in the inflammatory processes characteristics of SpA. The aim of this review is analysing the characteristics and functional roles of monocytes and macrophages in these diseases, as well as the impact of different current therapies on these cell types.

The implication of adenosine receptor expression in prediction of methotrexate clinical response in Egyptian rheumatoid arthritis patients

Background

Adenosine signaling is now an accepted explanation for the therapeutic mechanism of Methotrexate (MTX) in rheumatoid arthritis (RA). Adenosine receptors categorized into four subclasses: adenosine A1 receptor (ADORA1), adenosine 2a receptor (ADORA2a), adenosine 2b receptor (ADORA2B), and adenosine 3 receptor (ADORA3). Our aim is to check the mRNA expression of two adenosine receptors; ADORA2a and ADORA3 in whole blood cell of RA patients and its relation in prediction of MTX clinical response in Egyptian patients.

Results

There was significant correlation between both ADORA2a and ADORA3 gene expression in RA patients as compared with healthy controls. The expression of ADORA2a and ADORA3 was increased in good and moderate response groups compared to no response group. There was significant correlation between both genes in mRNA expression before and after MTX treatment. Matrix metalloproteinase-3 (MMP3) concentration was significantly decreased after treatment in good and moderate response groups in comparison to non-responder group.

Conclusion

The inflammatory and clinical responses in RA patients which is demonstrated by DAS28 and suppression of MMP3 were regulated by ADORA2a and ADORA3. Their level of expression can predict MTX response and their agonists may offer a novel and effective therapeutic option for RA patients.