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2017 ; 5
(2
): e00291
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Uricosuric targets of tranilast
#MMPMID28357121
Mandal AK
; Mercado A
; Foster A
; Zandi-Nejad K
; Mount DB
Pharmacol Res Perspect
2017[Apr]; 5
(2
): e00291
PMID28357121
show ga
Uric acid, generated from the metabolism of purines, has both proven and emerging
roles in human disease. Serum uric acid in humans is determined by production and
by the net balance of reabsorption and secretion in kidney and intestine. In the
human kidney, epithelial reabsorption dominates over secretion, such that in
normal subjects there is at least 90% net reabsorption of filtered urate
resulting in a fractional excretion of <10%. Tranilast, an anti-inflammatory drug
with pleiotropic effects, has a marked hypouricemic, uricosuric effect in humans.
We report here that tranilast is a potent inhibitor of [(14)C]-urate transport
mediated by the major reabsorptive urate transporters (URAT1, GLUT9, OAT4, and
OAT10) in Xenopus oocytes; this provides an unequivocal molecular mechanism for
the drug's uricosuric effect. Tranilast was found to inhibit urate transport
mediated by URAT1 and GLUT9 in a fully reversible and noncompetitive (mixed)
manner. In addition, tranilast inhibits the secretory urate transporters NPT1,
OAT1, and OAT3 without affecting the secretory efflux pump ABCG2. Notably, while
benzbromarone and probenecid inhibited urate as well as nicotinate transport,
tranilast inhibited the urate transport function of URAT1, GLUT9, OAT4, OAT10,
and NPT1, without significantly affecting nicotinate transport mediated by SMCT1
(IC (50) ~1.1 mmol/L), SMCT2 (IC (50) ~1.0 mmol/L), and URAT1 (IC (50)
~178 ?mol/L). In summary, tranilast causes uricosuria by inhibiting all the major
reabsorptive urate transporters, selectively affecting urate over nicotinate
transport. These data have implications for the treatment of hyperuricemia and
gout, the pharmacology of tranilast, and the structure-function analysis of urate
transport.