Role of ecto‐5′‐nucleotidase in bladder function

• Published in: The FASEB journal 2024-01, Vol.38 (2), p.e23416-n/a
• Main Authors: Barge, Sagar, Wu, Ali, Zhang, Lanlan, Robson, Simon C., Olumi, Aria, Alper, Seth L., Zeidel, Mark L., Yu, Weiqun
• Format: Article
• Language: English
• Subjects: 5'-Nucleotidase - genetics; Adenosine; Alkaline Phosphatase; Animals; bladder smooth muscle; Cholinergic Agents; ecto‐5′‐nucleotidase; lower urinary tract symptoms; Mice; Mice, Knockout; purinergic signaling; Urinary Bladder
• ISSN: 0892-6638; 1530-6860; 1530-6860
• DOI: 10.1096/fj.202301393R

Purinergic signaling plays an important role in regulating bladder contractility and voiding. Abnormal purinergic signaling is associated with lower urinary tract symptoms (LUTS). Ecto‐5′‐nucleotidase (NT5E) catalyzes dephosphorylation of extracellular AMP to adenosine, which in turn promotes adenosine‐A2b receptor signaling to relax bladder smooth muscle (BSM). The functional importance of this mechanism was investigated using Nt5e knockout (Nt5eKO) mice. Increased voiding frequency of small voids revealed by voiding spot assay was corroborated by urodynamic studies showing shortened voiding intervals and decreased bladder compliance. Myography indicated reduced contractility of Nt5eKO BSM. These data support a role for NT5E in regulating bladder function through modulation of BSM contraction and relaxation. However, the abnormal bladder phenotype of Nt5eKO mice is much milder than we previously reported in A2b receptor knockout (A2bKO) mice, suggesting compensatory response(s) in Nt5eKO mouse bladder. To better understand this compensatory mechanism, we analyzed changes in purinergic and other receptors controlling BSM contraction and relaxation in the Nt5eKO bladder. We found that the relative abundance of muscarinic CHRM3 (cholinergic receptor muscarinic 3), purinergic P2X1, and A2b receptors was unchanged, whereas P2Y12 receptor was significantly downregulated, suggesting a negative feedback response to elevated ADP signaling. Further studies of additional ecto‐nucleotidases indicated significant upregulation of the nonspecific urothelial alkaline phosphatase ALPL, which might mitigate the degree of voiding dysfunction by compensating for Nt5e deletion. These data suggest a mechanistic complexity of the purinergic signaling network in bladder and imply a paracrine mechanism in which urothelium‐released ATP and its rapidly produced metabolites coordinately regulate BSM contraction and relaxation. Nt5e knockout (Nt5eKO) mice exhibited increased voiding frequency of small voids. The bladder compliance is decreased with the voiding interval shortened. Bladder smooth muscle has decreased contractile forces. Mechanistically, deletion of Nt5e likely impaired the adenosine A2b receptor‐mediated smooth muscle relaxation of the bladder. Significant compensatory changes in Alpl, Entpd1/2, and P2y12 were noticed which might mitigate the degree of voiding dysfunction in Nt5eKO mice. These data suggest a mechanistic complexity of the purinergic signaling network in