Adenosine 2A receptor and TIM3 suppress cytolytic killing of tumor cells via cytoskeletal polarization

Tumors generate an immune-suppressive environment that prevents effective killing of tumor cells by CD8+ cytotoxic T cells (CTL). It remains largely unclear upon which cell type and at which stage of the anti-tumor response mediators of suppression act. We have combined an in vivo tumor model with a matching in vitro reconstruction of the tumor microenvironment based on tumor spheroids to identify suppressors of anti-tumor immunity that directly act on interaction between CTL and tumor cells and to determine mechanisms of action. An adenosine 2A receptor antagonist, as enhanced by blockade of TIM3, slowed tumor growth in vivo. Engagement of the adenosine 2A receptor and TIM3 reduced tumor cell killing in spheroids, impaired CTL cytoskeletal polarization ex vivo and in vitro and inhibited CTL infiltration into tumors and spheroids. With this role in CTL killing, blocking A2AR and TIM3 may complement therapies that enhance T cell priming, e.g. anti-PD-1 and anti-CTLA-4.

Attenuation of Tumor Development in Mammary Carcinoma Rats by Theacrine, an Antagonist of Adenosine 2A Receptor

Caffeine has been reported to induce anti-tumor immunity for attenuating breast cancer by blocking the adenosine 2A receptor. Molecular modeling showed that theacrine, a purine alkaloid structurally similar to caffeine, might be an antagonist of the adenosine 2A receptor equivalent to or more effective than caffeine. Theacrine was further demonstrated to be an effective antagonist of the adenosine 2A receptor as its concurrent supplementation significantly reduced the elevation of AMPK phosphorylation level in MCF-7 human breast cells induced by CGS21680, an agonist of adenosine 2A receptors. In an animal model, the development of mammary carcinoma induced by 7,12-Dimethylbenz[a]anthracene in Sprague–Dawley rats could be attenuated by daily supplement of theacrine of 50 or 100 mg/kg body weight. Both expression levels of cleaved-caspase-3/pro-caspase-3 and granzyme B in tumor tissues were significantly elevated when theacrine was supplemented, indicating the induction of programmed cell death in tumor cells might be involved in the attenuation of mammary carcinoma. Similar to the caffeine, significant elevation of interferon-γ and tumor necrosis factor-α was observed in the serum and tumor tissues of rats after the theacrine supplement of 50 mg/kg body weight. Taken together, theacrine is an effective antagonist of adenosine 2A receptors and possesses great potential to be used to attenuate breast cancer.

Simultaneous administration of coffee and rasagiline/l-dopa protects against paraquat-induced neurochemical and motor behavior impairments in vivo

Background Caffeine is a natural alkaloid present in a variety of highly consumed popular drinks such as coffee, tea and soft drinks as well as chocolate. Its consumption elicits beneficiary psychostimulant that has been linked to a reduced risk of developing Parkinson’s disease (PD). The aim of the present study is to investigate the possible synergistic neuroprotective effects of co-administration of caffeine (CAF) or coffee (COF) with rasagiline (R) or l-dopa against paraquat (PQ)-induced neurochemical and motor behavior impairments in mice. Results In behavioral tests, R + COF increased the locomotor activity in rotarod test compared to l-dopa + COF. l-Dopa combinations decreased the immobility time in FST compared to rasagiline combinations; l-dopa + CAF provided a similar increase in locomotor activity compared to R + CAF. Combination of CAF or COF with l-dopa or rasagiline resulted in a substantial improvement in brain neurotransmitter and antioxidant levels as they significantly increased dopamine and super oxide dismutase but significantly decreased nitric oxide levels as compared to l-dopa or rasagiline, respectively. Furthermore, they also exerted a protective effect against the neurodegenerative histopathological changes induced by PQ. Conclusions Our findings demonstrated co-administration of COF or CAF, adenosine 2A receptor antagonists, along with l-dopa or rasagiline possesses a new therapeutic strategy for the management of PD neurochemical disturbances and motor behavior impairments through preservation of the brain dopamine and serotonin content, antioxidants level and histological features.

Combined Deficiency of the Melanocortin 5 Receptor and Adenosine 2A Receptor Unexpectedly Provides Resistance to Autoimmune Disease in a CD8+ T Cell-Dependent Manner

Regulatory immunity that provides resistance to relapse emerges during resolution of experimental autoimmune uveitis (EAU). This post-EAU regulatory immunity requires a melanocortin 5 receptor (MC5r)-dependent suppressor antigen presenting cell (APC), as shown using a MC5r single knock-out mouse. The MC5r-dependent APC activates an adenosine 2A receptor (A2Ar)-dependent regulatory Treg cell, as shown using an A2Ar single knock-out mouse. Unexpectedly, when MC5r-/- post-EAU APC were used to activate A2Ar-/- post-EAU T cells the combination of cells significantly suppressed EAU, when transferred to EAU mice. In contrast, transfer of the reciprocal activation scheme did not suppress EAU. In order to explain this finding, MC5r-/-A2Ar-/- double knock-out (DKO) mice were bred. Naïve DKO mice had no differences in the APC populations, or inflammatory T cell subsets, but did have significantly more Treg cells. When we examined the number of CD4 and CD8 T cell subsets, we found significantly fewer CD8 T cells in the DKO mice compared to WT and both single knock-out mice. DKO mice also had significantly reduced EAU severity and accelerated resolution. In order to determine if the CD8 T cell deficiency contributed to the resistance to EAU in the DKO mice, we transferred naïve CD8 T cells from WT mice, that were immunized for EAU. Susceptibility to EAU was restored in DKO mice that received a CD8 T cell transfer. While the mechanism that contributed to the CD8 T cell deficiency in the DKO mice remains to be determined, these observations indicate an importance of CD8 T cells in the initiation of EAU. The involvement of CD4 and CD8 T cells suggests that both class I and class II antigen presentation can trigger an autoimmune response, suggesting a much wider range of antigens may trigger autoimmune disease.

Role of Adenosine Receptors in Rare Neurodegenerative Diseases with Motor Symptoms

: The approval of istradefylline, an adenosine 2A receptor (A2AR) antagonist, as an add-on treatment in adult patients with Parkinson’s disease by the Food and Drug Administration (FDA) and European Medicines Agency (EMA), is the latest proof of the importance of the adenosinergic system in the nervous system. Adenosine is an endogenous purine nucleoside with a role as a modulator of both neurotransmission and the inflammatory response. As such, the expression pattern of the 4 adenosine receptors (A1R, A2AR, A2BR and A3R) and the extracellular adenosine levels have attracted great interest in the pathogenesis and possible treatment of rare neurodegenerative diseases with motor symptoms. These include Huntington’s disease (HD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), restless legs syndrome (RLS) and Machado-Joseph disease (MJD, also known as spinocerebellar ataxia type 3, SCA3). In this review, we shall focus on the role of the different adenosine receptor subtypes in the development and possible treatment of the aforementioned rare neurodegenerative diseases with motor symptoms using the currently available data. The last section discusses the possibility of a role for the adenosine receptors in the treatment of other rare diseases based on the available molecular pathology knowledge.

Contribution of the Adenosine 2A Receptor to Behavioral Effects of Tetrahydrocannabinol, Cannabidiol and PECS-101

The cannabis-derived molecules, ∆9 tetrahydrocannabinol (THC) and cannabidiol (CBD), are both of considerable therapeutic interest for a variety of purposes, including to reduce pain and anxiety and increase sleep. In addition to their other pharmacological targets, both THC and CBD are competitive inhibitors of the equilibrative nucleoside transporter-1 (ENT-1), a primary inactivation mechanism for adenosine, and thereby increase adenosine signaling. The goal of this study was to examine the role of adenosine A2A receptor activation in the effects of intraperitoneally administered THC alone and in combination with CBD or PECS-101, a 4′-fluorinated derivative of CBD, in the cannabinoid tetrad, elevated plus maze (EPM) and marble bury assays. Comparisons between wild-type (WT) and A2AR knock out (A2AR-KO) mice were made. The cataleptic effects of THC were diminished in A2AR-KO; no other THC behaviors were affected by A2AR deletion. CBD (5 mg/kg) potentiated the cataleptic response to THC (5 mg/kg) in WT but not A2AR-KO. Neither CBD nor THC alone affected EPM behavior; their combination produced a significant increase in open/closed arm time in WT but not A2AR-KO. Both THC and CBD reduced the number of marbles buried in A2AR-KO but not WT mice. Like CBD, PECS-101 potentiated the cataleptic response to THC in WT but not A2AR-KO mice. PECS-101 also reduced exploratory behavior in the EPM in both genotypes. These results support the hypothesis that CBD and PECS-101 can potentiate the cataleptic effects of THC in a manner consistent with increased endogenous adenosine signaling.

The adenosine 2a receptor and TIM3 directly inhibit killing of tumor cells by cytotoxic T lymphocytes through interference with cytoskeletal polarization

Tumors generate an immune-suppressive environment that prevents effective killing of tumor cells by CD8+ cytotoxic T cells (CTL). It remains largely unclear upon which cell type and at which stage of the anti-tumor response mediators of suppression act. We have combined an in vivo tumor model with a matching in vitro reconstruction of the tumor microenvironment based on tumor spheroids to identify suppressors of anti-tumor immunity that directly act on interaction between CTL and tumor cells and to determine mechanisms of action. An adenosine 2a receptor antagonist, as enhanced by blockade of TIM3, slowed tumor growth in vivo. Engagement of the adenosine 2a receptor and TIM3 reduced tumor cell killing in spheroids, impaired CTL cytoskeletal polarization ex vivo and in vitro and inhibited CTL infiltration into tumors and spheroids. With this focus on CTL killing, blocking A2aR and TIM3 complements therapies that enhance T cell priming, e.g. anti-PD1 and anti-CTLA-4.