title: The renal phenotype of allopurinol-treated HPRT-deficient mouse.
abstract: Excess of uric acid is mainly treated with xanthine oxidase (XO) inhibitors, also called uricostatics because they block the conversion of hypoxanthine and xanthine into urate. Normally, accumulation of upstream metabolites is prevented by the hypoxanthine-guanine phosphoribosyltransferase (HPRT) enzyme. The recycling pathway, however, is impaired in the presence of HPRT deficiency, as observed in Lesch-Nyhan disease. To gain insights into the consequences of purine accumulation with HPRT deficiency, we investigated the effects of the XO inhibitor allopurinol in Hprt-lacking (HPRT-/-) mice. Allopurinol was administered in the drinking water of E12-E14 pregnant mothers at dosages of 150 or 75 μg/ml, and mice sacrificed after weaning. The drug was well tolerated by wild-type animals and heterozygous HPRT+/- mice. Instead, a profound alteration of the renal function was observed in the HPRT-/- model. Increased hypoxanthine and xanthine concentrations were found in the blood. The kidneys showed a yellowish appearance, diffuse interstitial nephritis, with dilated tubules, inflammatory and fibrotic changes of the interstitium. There were numerous xanthine tubular crystals, as determined by HPLC analysis. Oil red O staining demonstrated lipid accumulation in the same location of xanthine deposits. mRNA analysis showed increased expression of adipogenesis-related molecules as well as profibrotic and proinflammatory pathways. Immunostaining showed numerous monocyte-macrophages and overexpression of alpha-smooth muscle actin in the tubulointerstitium. In vitro, addition of xanthine to tubular cells caused diffuse oil red O positivity and modification of the cell phenotype, with loss of epithelial features and appearance of mesenchymal characteristics, similarly to what was observed in vivo. Our results indicate that in the absence of HPRT, blockade of XO by allopurinol causes rapidly developing renal failure due to xanthine deposition within the mouse kidney. Xanthine seems to be directly involved in promoting lipid accumulation and subsequent phenotype changes of tubular cells, with activation of inflammation and fibrosis.
authors.affiliation: Department of Medical, Surgery and Health Sciences, Università degli Studi di Trieste, Trieste, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Zennaro
authors.affiliation: Department of Medical, Surgery and Health Sciences, Università degli Studi di Trieste, Trieste, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Tonon
authors.affiliation: Department of Life Sciences, Università degli Studi di Trieste, Trieste, Trieste, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Zarattini
authors.affiliation: Department of Pathology and Legal Medicine, Azienda Sanitaria Universitaria Integrata di Trieste, Trieste, Italy.
authors.forename: Milan
authors.initials: M
authors.lastname: Clai
authors.affiliation: Unit of Bio-imaging, Department of Cardiovascular Research, IRCCS Mario Negri Institute for Pharmacological Research, Milano, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Corbelli
authors.affiliation: Department of Medical, Surgery and Health Sciences, Università degli Studi di Trieste, Trieste, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Carraro
authors.affiliation: Department of Life Sciences, University of Parma, Parma, Italy.
authors.forename: Marialaura
authors.initials: M
authors.lastname: Marchetti
authors.affiliation: Department of Neurosciences, University of Parma, Parma, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Ronda
authors.affiliation: Department of Pharmacy and SITEIA, PARMA Interdepartmental Center, University of Parma, Parma, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Paredi
authors.affiliation: Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy.
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Rastaldi
authors.affiliation: Department of Life Sciences, University of Parma, Parma, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Percudani
mesh_terms: D000493:Allopurinol / Q000494:pharmacology*; D000818:Animals; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D007926:Lesch-Nyhan Syndrome / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D009393:Nephritis / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D019820:Xanthine / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D019820:Xanthine; D000493:Allopurinol; D014969:Xanthine Oxidase; D007041:Hypoxanthine Phosphoribosyltransferase