Astrocytes play a key role in modulating synaptic transmission by controlling extracellular gamma-aminobutyric acid (GABA) levels via GAT-1 and GAT-3 GABA transporters (GATs). Using primary cultures of rat astrocytes, we show here that a further level of regulation of GABA uptake occurs via modulation of the GATs by the adenosine A 1 (A 1 R) and A 2A (A 2A R) receptors. This regulation occurs through A 1 R-A 2A R heteromers that signal via two different G proteins, G s and G i/0 , and either enhances (A 2A R) or inhibits (A 1 R) GABA uptake. These results provide novel mechanistic insight into how GPCR heteromers signal. Furthermore, we uncover a previously unknown mechanism where adenosine, in a concentrationdependent manner, acts via a heterocomplex of adenosine receptors in astrocytes to significantly contribute to neurotransmission at the tripartite (neuron-glia-neuron) synapse.

Background: Transport of GABA into astrocytes is crucial for excitability control. Results: The neurotrophin BDNF, through TrkB-t receptor activation, enhances GABA transport into astrocytes, which requires adenosine A 2A receptor signaling. Conclusion: BDNF plays an active role in the synaptic clearance of GABA. Significance: This new regulatory role for TrkB-t receptors discloses their relevance for excitability control at the tripartite synapse.

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Neurotransmitter transporters are regulated by phosphorylation but little is known about endogenous substances and receptors that regulate this process. Adenosine is an ubiquitous neuromodulator operating G‐protein coupled receptors, which affect the activity of several kinases. We therefore evaluated the influence of adenosine upon the GABA transporter 1 (GAT‐1) mediated GABA uptake into hippocampal synaptosomes. Removal of endogenous adenosine (adenosine deaminase, 1 U/mL) decreased GABA uptake, an effect mimicked by blockade of A2A receptors (2‐(2‐furanyl)‐7‐(2‐phenylethyl)‐7H‐pyrazolo[4,3‐e][1,2,4]triazolo[1,5‐c]pyrimidin‐5‐amine, 50 nM) but not A1 or A2B receptors. A2A receptor activation (4‐[2‐[[6‐amino‐9‐(N‐ethyl‐β‐d‐ribofuranuronamidosyl)‐9H‐purin‐yl]amino]ethyl]benzenepropanoic acid hydrochloride, 3–100 nM) enhanced GABA uptake by increasing the transporter Vmax without change of KM. This was mimicked by adenylate cyclase activation (forskolin, 10 μM) and prevented by protein kinase A (PKA) inhibition (N‐[2‐(p‐bromocinnamylamino) ethyl]‐5‐isoquinolinesulfonamide dihydrochloride, 1 μM), which per se did not influence GABA transport. Blockade of protein kinase C (PKC) (2‐[1‐(3‐dimethylaminopropyl)indol‐3‐yl]‐3‐(indol‐3‐yl) maleimide, 1 μM) facilitated GABA transport whereas PKC activation (4‐β‐phorbol‐didecanoate, 250 nM) inhibited it. PKA blockade did not affect the facilitatory action of the PKC inhibitor or the inhibitory action of the PKC activator. However, when adenylate cyclase was activated neither activation nor inhibition of PKC affected GABA uptake. It is concluded that A2A receptors, through activation of the adenylate cyclase/cAMP/PKA transducing pathway facilitate GAT‐1 mediated GABA transport into nerve endings by restraining tonic PKC‐mediated inhibition.

The external globus pallidus (GP) is a key GABAergic hub in the basal ganglia (BG) circuitry, a neuronal network involved in motor control. In Parkinson's disease (PD), the rate and pattern of activity of GP neurons are profoundly altered and contribute to the motor symptoms of the disease. In rodent models of PD, the striato-pallidal pathway is hyperactive, and extracellular GABA concentrations are abnormally elevated in the GP, supporting the hypothesis of an alteration of neuronal and/or glial clearance of GABA. Here, we discovered the existence of persistent GABAergic tonic inhibition in GP neurons of dopamine-depleted (DD) rodent models. We showed that glial GAT-3 transporters are downregulated while neuronal GAT-1 function remains normal in DD rodents. Finally, we showed that blocking GAT-3 activity in vivo alters the motor coordination of control rodents, suggesting that GABAergic tonic inhibition in the GP contributes to the pathophysiology of PD.

Background/methods: Although the prognosis of metastatic breast cancer (BC) has improved, some patients still develop high burden metastases or visceral crisis (VC) and polychemotherapy is commonly used in these cases. Data reporting the real effectiveness of this strategy are scanty. Therefore, the outcomes of patients with metastatic BC treated with platinum-based chemotherapy (P-ChT) at the Jules Bordet Institute during the period of January 2008 and December 2018 were retrospectively reviewed. The presence of VC was defined according to ABC 4 criteria. Results 441 patients were identified: visceral metastases were observed in 430 (97.5%) while 261 (59.2%) presented VC. As for metastatic BC subtype, 255 (57.8%) had ER-positive/HER2-negative, 41 (9.3%) ER-positive/HER2-positive, 34 (7.7%) ER-negative/HER2-positive and 111 (25.1%) triple-negative BC. Median number of prior treatment lines was 3.8 (0–12). Median OS with P-ChT in the entire cohort was 6.13 months. Patients with VC had lower OS than patients without VC (8.6 vs 3.7 months; p < 0.001). On multivariate analysis, the variables correlated with worse OS were hyperbilirubinemia (HR 1.90; 95% CI 1.34–2.75), ECOG ≥2 (HR 1.77; 95% CI 1.13–2.78) and ECOG ≥3 (HR 2.52; 95% CI 1.48–4.28), and >3 previous treatment lines (HR 2.27; 95% CI 1.53–3.21). Of the 261 patients with VC, 106 (40.5%) presented a resolution of the VC which correlated with better OS (9.3 vs 2.0 months, HR 0.27; 95% CI 0.21–0.36). Conclusion Patients who overcome VC benefit from P-ChT with OS similar to patients without VC. In this analysis, hyperbilirubinemia, poor ECOG and >3 previous treatment lines were significant prognostic factors in the overall study population.

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Breast cancer is the deadliest female malignancy worldwide and, while much is known about phenotype and function of infiltrating immune cells, the same attention has not been paid to the peripheral immune compartment of breast cancer patients. To obtain faster, cheaper, and more precise monitoring of patients’ status, it is crucial to define and analyze circulating immune profiles. This review compiles and summarizes the disperse knowledge on the peripheral immune profile of breast cancer patients, how it departs from healthy individuals and how it changes with disease progression. We propose this data to be used as a starting point for validation of clinically relevant biomarkers of disease progression and therapy response, which warrants more thorough investigation in patient cohorts of specific breast cancer subtypes. Relevant clinical findings may also be explored experimentally using advanced 3D cellular models of human cancer–immune system interactions, which are under intensive development. We review the latest findings and discuss the strengths and limitations of such models, as well as the future perspectives. Together, the scientific advancement of peripheral biomarker discovery and cancer–immune crosstalk in breast cancer will be instrumental to uncover molecular mechanisms and putative biomarkers and drug targets in an all-human setting.