Modulation of Tubular pH by Acetazolamide in a Ca2+ Transport Deficient Mice Facilitates Calcium Nephrolithiasis |
| |
| Authors: | Eugenia Awuah Boadi Samuel Shin Samuel Yeroushalmi Bok-Eum Choi Peijun Li Bidhan C Bandyopadhyay |
| |
| Affiliation: | 1.Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, 50 Irving Street, NW, Washington, DC 20422, USA; (E.A.B.); (S.S.); (S.Y.); (B.-E.C.); (P.L.);2.Division of Renal Diseases & Hypertension, Department of Medicine, The George Washington University, Washington, DC 20037, USA;3.Department of Biomedical Engineering, The Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064, USA |
| |
| Abstract: | Proximal tubular (PT) acidosis, which alkalinizes the urinary filtrate, together with Ca2+ supersaturation in PT can induce luminal calcium phosphate (CaP) crystal formation. While such CaP crystals are known to act as a nidus for CaP/calcium oxalate (CaOx) mixed stone formation, the regulation of PT luminal Ca2+ concentration (Ca2+]) under elevated pH and/or high Ca2+] conditions are unknown. Since we found that transient receptor potential canonical 3 (TRPC3) knockout (KO; -/-) mice could produce mild hypercalciuria with CaP urine crystals, we alkalinized the tubular pH in TRPC3-/- mice by oral acetazolamide (0.08%) to develop mixed urinary crystals akin to clinical signs of calcium nephrolithiasis (CaNL). Our ratiometric (λ340/380) intracellular Ca2+] measurements reveal that such alkalization not only upsurges Ca2+ influx into PT cells, but the mode of Ca2+ entry switches from receptor-operated to store-operated pathway. Electrophysiological experiments show enhanced bicarbonate related current activity in treated PT cells which may determine the stone-forming phenotypes (CaP or CaP/CaOx). Moreover, such alkalization promotes reactive oxygen species generation, and upregulation of calcification, inflammation, fibrosis, and apoptosis in PT cells, which were exacerbated in absence of TRPC3. Altogether, the pH-induced alteration of the Ca2+ signaling signature in PT cells from TRPC3 ablated mice exacerbated the pathophysiology of mixed urinary stone formation, which may aid in uncovering the downstream mechanism of CaNL. |
| |
| Keywords: | acetazolamide renal tubular pH proximal tubule Ca2+ signaling oxidative stress inflammation fibrosis apoptosis calcium nephrolithiasis urinary stones |
|
|
