Roflumilast and aquaporin‐2 regulation in rat renal inner medullary collecting duct

• Published in: Physiological reports Vol. 5; no. 2; pp. np - n/a
• Main Authors: Umejiego, Ezigbobiara N., Wang, Yanhua, Knepper, Mark A., Chou, Chung‐Lin
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.01.2017; John Wiley and Sons Inc
• Subjects: 1-Methyl-3-isobutylxanthine - administration & dosage; Aminopyridines - administration & dosage; Animals; Aquaporin 2 - metabolism; Benzamides - administration & dosage; cAMP phosphodiesterase; Capillary Permeability - drug effects; Cyclopropanes - administration & dosage; Diabetes; Dose-Response Relationship, Drug; Genetic Conditions Disorders and Treatments; kidney; Kidney Medulla - drug effects; Kidney Medulla - metabolism; Kidney Tubules, Collecting - drug effects; Kidney Tubules, Collecting - metabolism; Male; Mutation; nephrogenic diabetes insipidus; Original Research; Phosphodiesterase 4 Inhibitors - administration & dosage; Phosphorylation; Physiology; Protein Transport - drug effects; Rats; Rats, Sprague-Dawley; Regulatory Pathways; Renal Physiology; Signalling Pathways; Vasopressins - metabolism; Water - metabolism; X chromosome; X chromosome; cAMP phosphodiesterase; kidney; nephrogenic diabetes insipidus
• ISSN: 2051-817X; 2051-817X
• DOI: 10.14814/phy2.13121

Roflumilast is a cyclic nucleotide phosphodiesterase inhibitor that is FDA‐approved for treatment of chronic obstructive pulmonary disease. With a view toward possible use for treatment of patients with X‐linked nephrogenic diabetes insipidus (NDI) due to hemizygous mutations in the V2 vasopressin receptor, this study sought to determine the effect of roflumilast on aquaporin‐2 (AQP2) phosphorylation, AQP2 trafficking, and water permeability in the rat inner medullary collecting duct (IMCD). In the presence of the vasopressin analog dDAVP (0.1 nmol/L), both roflumilast and its active metabolite roflumilast N‐oxide (RNO) significantly increased phosphorylation at S256, S264, and S269, and decreased phosphorylation at S261 (immunoblotting) in IMCD suspensions in a dose‐dependent manner (3–3000 nmol/L). Another commonly used phosphodiesterase inhibitor, IBMX, affected phosphorylation only at the highest concentration in this range. However, neither roflumilast nor RNO had an effect on AQP2 phosphorylation in the absence of vasopressin. Furthermore, roflumilast alone did not increase AQP2 trafficking to the plasma membrane (immunofluorescence) or increase water permeability in freshly microdissected perfused IMCD segments. We conclude that roflumilast can be used to enhance vasopressin's action on AQP2 activity in the renal collecting duct, but has no detectable effect in the absence of vasopressin. These findings suggest that roflumilast may not have a beneficial effect in X‐linked NDI, but could find useful application in acquired NDI. The cyclic nucleotide phosphodiesterase inhibitor roflumilast, FDA‐approved for treatment of chronic obstructive pulmonary disease, could theoretically be used to treat X‐linked nephrogenic diabetes insipidus (NDI). To test the efficacy of the drug in the renal collecting duct, experiments were performed in inner medullary collecting ducts isolated from rat kidneys. Although roflumilast alone did not increase osmotic water permeability, alter subcellular distribution of aquaporin‐2, or alter phosphorylation of aquaporin‐2, it enhanced the collecting duct response to vasopressin. The authors conclude that roflumilast is unlikely to be effective in patients with X‐linked NDI, but has potential for use in acquired NDI, in which the vasopressin receptor is intact.