Ristic B, Sivaprakasam S, Narayanan M, Ganapathy V. Hereditary hemochromatosis disrupts uric acid homeostasis and causes hyperuricemia via altered expression/activity of xanthine oxidase and ABCG2.
Biochem J 2020;
477:1499-1513. [PMID:
32239172 PMCID:
PMC7200644 DOI:
10.1042/bcj20190873]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 03/30/2020] [Accepted: 04/01/2020] [Indexed: 12/20/2022]
Abstract
Hereditary hemochromatosis (HH) is mostly caused by mutations in the iron-regulatory gene HFE. The disease is associated with iron overload, resulting in liver cirrhosis/cancer, cardiomegaly, kidney dysfunction, diabetes, and arthritis. Fe2+-induced oxidative damage is suspected in the etiology of these symptoms. Here we examined, using Hfe-/- mice, whether disruption of uric acid (UA) homeostasis plays any role in HH-associated arthritis. We detected elevated levels of UA in serum and intestine in Hfe-/- mice compared with controls. Though the expression of xanthine oxidase, which generates UA, was not different in liver and intestine between wild type and Hfe-/- mice, the enzymatic activity was higher in Hfe-/- mice. We then examined various transporters involved in UA absorption/excretion. Glut9 expression did not change; however, there was an increase in Mrp4 and a decrease in Abcg2 in Hfe-/- mice. As ABCG2 mediates intestinal excretion of UA and mutations in ABCG2 cause hyperuricemia, we examined the potential connection between iron and ABCG2. We found p53-responsive elements in hABCG2 promoter and confirmed with chromatin immunoprecipitation that p53 binds to this promoter. p53 protein was reduced in Hfe-/- mouse intestine. p53 is a heme-binding protein and p53-heme complex is subjected to proteasomal degradation. We conclude that iron/heme overload in HH increases xanthine oxidase activity and also promotes p53 degradation resulting in decreased ABCG2 expression. As a result, systemic UA production is increased and intestinal excretion of UA via ABCG2 is decreased, causing serum and tissue accumulation of UA, a potential factor in the etiology of HH-associated arthritis.
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