Nephrotoxicity of Different Formulations of Amphotericin B: Summarizing Evidence by Network Meta-analysis

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GPR35 Activation Reduces Ca2+ Transients and Contributes to the Kynurenic Acid-Dependent Reduction of Synaptic Activity at CA3-CA1 Synapses

Limited information is available on the brain expression and role of GPR35, a Gi/o coupled receptor activated by kynurenic acid (KYNA). In mouse cultured astrocytes, we detected GPR35 transcript using RT-PCR and we found that KYNA (0.1 to 100 µM) decreased forskolin (FRSK)-induced cAMP production (p<0.05). Both CID2745687 (3 µM, CID), a recently described GPR35 antagonist, and GPR35 gene silencing significantly prevented the action of KYNA on FRSK-induced cAMP production. In these cultures, we then evaluated whether GPR35 activation was able to modulate intracellular Ca(2+) concentration ([Ca(2+)]i ) and [Ca(2+)]i fluxes. We found that both KYNA and zaprinast, a phosphodiesterase (PDE) inhibitor and GPR35 agonist, did not modify either basal or peaks of [Ca(2+)]i induced by challenging the cells with ATP (30 µM). However, the [Ca(2+)]i plateau phase following peak was significantly attenuated by these compounds in a store-operated Ca(2+) channel (SOC)-independent manner. The activation of GPR35 by KYNA and zaprinast was also studied at the CA3-CA1 synapse in the rat hippocampus. Evoked excitatory post synaptic currents (eEPSCs) were recorded from CA1 pyramidal neurons in acute brain slices. The action of KYNA on GPR35 was pharmacologically isolated by using NMDA and α7 nicotinic receptor blockers and resulted in a significant reduction of eEPSC amplitude. This effect was prevented in the presence of CID. Moreover, zaprinast reduced eEPSC amplitude in a PDE5- and cGMP-independent mechanism, thus suggesting that glutamatergic transmission in this area is modulated by GPR35. In conclusion, GPR35 is expressed in cultured astrocytes and its activation modulates cAMP production and [Ca(2+)]i. GPR35 activation may contribute to KYNA effects on the previously reported decrease of brain extracellular glutamate levels and reduction of excitatory transmission

Zaprinast reduces eEPSC amplitude at CA3→CA1 synapse in a PDE5-and cGMP-indipendent manner.

<p><b>A</b> and <b>C</b>) Time course of the zaprinast-induced decrease in eEPSC amplitude alone (<i>A</i>) and in the presence of Rp-8-Br (a cGMP-dependent protein kinase-PKG- inhibitor). EPSCs are normalized to pre-application amplitude values. Sample traces (at <i>top</i>) were obtained before (<i>left</i>) and during (<i>right</i>) zaprinast application and represent averages of 5 traces. Rp-8-Br was pre incubated for at least 10 min before zaprinast application. <b>B</b>) Time course of the effect of sildenafil (a PDE5 inhibitor) showing no effect on EPSC amplitude. Sample traces (at <i>top</i>) were obtained before (<i>left</i>) and during (<i>right</i>) sildenafil application and represent averages of 5 traces. <b>D</b>) Bar graph of maximal effect of zaprinast application, with or without Rp-8-Br, and sildenafil.</p