Beta-3 adrenoceptor signaling pathways in urothelial and smooth muscle cells in the presence of succinate

• Published in: The Journal of pharmacology and experimental therapeutics 2018-11, Vol.367 (2), p.252-259
• Main Authors: Mossa, Abubakr H, Velasquez Flores, Monica, Nguyen, Hieu, Cammisotto, Philippe, Campeau, Lysanne
• Format: Article
• Language: English
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.118.249979

Succinate, an intermediate metabolite of the Krebs cycle, can alter the metabolomics response to certain drugs, and controls an array of molecular responses in the urothelium through activation of its receptor GPR91. Mirabegron, a β3-adrenergic receptor (β3-AR) agonist used to treat overactive bladder syndrome, increases intracellular cyclic AMP (cAMP) in the detrusor smooth muscle cells (SMCs), leading to relaxation. We have previously shown that succinate inhibits forskolin-stimulated cAMP production in urothelium. To determine whether succinate interferes with mirabegron-mediated bladder relaxation, we examined their individual and synergistic effect in urothelial and SMC signaling. We first confirmed β3-AR involvement in the mirabegron response by quantifying receptor abundance by immunoblotting in cultured urothelial and SMCs and cellular localization by immunohistochemistry in rat bladder tissue. Mirabegron increased cAMP levels in SMCs but not in urothelial cells, an increase that was inhibited by succinate, suggesting that it impairs cAMP-mediated bladder relaxation by mirabegron. Succinate and mirabegron increased iNOS synthesis and nitric oxide (NO) secretion only in urothelial cells, suggesting that its release can indirectly induces SMC relaxation. Succinate exposure decreased the expression of β3-AR protein in whole bladder in vivo and in SMCs in vitro, indicating that this metabolite may lead to impaired pharmacodynamics of the bladder. Together, our results demonstrate that increased levels of succinate in settings of metabolic stress, e.g. metabolic syndrome, may lead to impaired mirabegron and β3-AR interaction, inhibition of cAMP production, and ultimately requiring mirabegron dose adjustment for its treatment of overactive bladder syndrome related with these conditions.