The Orphan G Protein-coupled Receptors GPR41 and GPR43 Are Activated by Propionate and Other Short Chain Carboxylic Acids

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Specific Inhibition of Orai1-mediated Calcium Signalling Resolves Inflammation and Clears Bacteria in an ARDS Model

Rationale: Acute Respiratory Distress Syndrome (ARDS) has an unacceptably high mortality rate (35%) and is without effective therapy. Orai1 is a Ca 2+ channel involved in store operated Ca 2+ entry (SOCE), a process that exquisitely regulates inflammation. Orai1 is considered a druggable target, but to date, no Orai1-specific inhibitors exist. Objectives: To evaluate whether ELD607, a first-in-class Orai1 antagonist, can treat ARDS caused by bacterial pneumonia in preclinical models.  Methods: ELD607 pharmacology was evaluated in HEK293T cells and freshly-isolated ARDS patient immune cells. A murine acute lung injury model caused by bacterial pneumonia was then used. Mice were infected with P. aeruginosa, S. aureus, methicillin-resistant S. aureus (MRSA) or multidrug-resistant P. aeruginosa (MDR- Pa) and then treated with ELD607 intranasally. Measurements and Main Results: ELD607 specifically inhibited SOCE in HEK293T cells with an IC50 of 9 nM. ELD607 was stable in ARDS airway secretions and inhibited SOCE in ARDS immune cells. In vivo, inhaled ELD607 significantly reduced neutrophilia and improved survival. Surprisingly, Orai1 inhibition by ELD607 caused a significant reduction in lung bacteria, including MRSA. ELD607 worked as an immunomodulator that reduced cytokine levels, lowered neutrophilia and promoted both macrophage-mediated resolution of inflammation and clearance of bacteria. Indeed, when alveolar macrophages were depleted with inhaled clodronate, ELD607 was no longer able to resolve inflammation or clear bacteria. Conclusions: These data indicate that specific Orai1 inhibition by ELD607 may be a novel approach to reduce multi-organ inflammation and treat antibiotic-resistant bacteria. </p

Pharmacological regulation of insulin secretion in MIN6 cells through the fatty acid receptor GPR40: identification of agonist and antagonist small molecules

1. Long chain fatty acids have recently been identified as agonists for the G protein-coupled receptors GPR40 and GPR120. Here, we present the first description of GW9508, a small-molecule agonist of the fatty acid receptors GPR40 and GPR120. In addition, we also describe the pharmacology of GW1100, a selective GPR40 antagonist. These molecules were used to further investigate the role of GPR40 in glucose-stimulated insulin secretion in the MIN6 mouse pancreatic β-cell line. 2. GW9508 and linoleic acid both stimulated intracellular Ca(2+) mobilization in human embryonic kidney (HEK)293 cells expressing GPR40 (pEC(50) values of 7.32±0.03 and 5.65±0.06, respectively) or GPR120 (pEC(50) values of 5.46±0.09 and 5.89±0.04, respectively), but not in the parent HEK-293 cell line. 3. GW1100 dose dependently inhibited GPR40-mediated Ca(2+) elevations stimulated by GW9508 and linoleic acid (pIC(50) values of 5.99±0.03 and 5.99±0.06, respectively). GW1100 had no effect on the GPR120-mediated stimulation of intracellular Ca(2+) release produced by either GW9508 or linoleic acid. 4. GW9508 dose dependently potentiated glucose-stimulated insulin secretion in MIN6 cells, but not in primary rat or mouse islets. Furthermore, GW9508 was able to potentiate the KCl-mediated increase in insulin secretion in MIN6 cells. The effects of GW9508 on insulin secretion were reversed by GW1100, while linoleic acid-stimulated insulin secretion was partially attenuated by GW1100. 5. These results add further evidence to a link between GPR40 and the ability of fatty acids to acutely potentiate insulin secretion and demonstrate that small-molecule GPR40 agonists are glucose-sensitive insulin secretagogues