Genetic disruption of NRF2 promotes the development of necroinflammation and liver fibrosis in a mouse model of HFE-hereditary hemochromatosis.
Redox Biol 2016;
11:157-169. [PMID:
27936457 PMCID:
PMC5149069 DOI:
10.1016/j.redox.2016.11.013]
[Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 11/16/2016] [Accepted: 11/28/2016] [Indexed: 12/18/2022] Open
Abstract
Background and Aims
In hereditary hemochromatosis, iron deposition in the liver parenchyma may lead to fibrosis, cirrhosis and hepatocellular carcinoma. Most cases are ascribed to a common mutation in the HFE gene, but the extent of clinical expression is greatly influenced by the combined action of yet unidentified genetic and/or environmental modifying factors. In mice, transcription factor NRF2 is a critical determinant of hepatocyte viability during exposure to acute dietary iron overload. We evaluated if the genetic disruption of Nrf2 would prompt the development of liver damage in Hfe-/- mice (an established model of human HFE-hemochromatosis).
Methods
Wild-type, Nrf2-/-, Hfe-/- and double knockout (Hfe/Nrf2-/-) female mice on C57BL/6 genetic background were sacrificed at the age of 6 (young), 12–18 (middle-aged) or 24 months (old) for evaluation of liver pathology.
Results
Despite the parenchymal iron accumulation, Hfe-/- mice presented no liver injury. The combination of iron overload (Hfe-/-) and defective antioxidant defences (Nrf2-/-) increased the number of iron-related necroinflammatory lesions (sideronecrosis), possibly due to the accumulation of toxic oxidation products such as 4-hydroxy-2-nonenal-protein adducts. The engulfment of dead hepatocytes led to a gradual accumulation of iron within macrophages, featuring large aggregates. Myofibroblasts recruited towards the injury areas produced substantial amounts of collagen fibers involving the liver parenchyma of double-knockout animals with increased hepatic fibrosis in an age-dependent manner.
Conclusions
The genetic disruption of Nrf2 promotes the transition from iron accumulation (siderosis) to liver injury in Hfe-/- mice, representing the first demonstration of spontaneous hepatic fibrosis in the long term in a mouse model of hereditary hemochromatosis displaying mildly elevated liver iron.
Despite the parenchymal iron overload, single Hfe-/- mice present no liver injury.
Hfe and Nrf2 double knockout mice develop liver fibrosis with aging.
Fibrosis is triggered by iron-related hepatocellular death (sideronecrosis).
Nrf2 genetic disruption increases susceptibility to oxidative/electrophilic stress.
NRF2 status is a potential determinant of liver injury in hemochromatosis.
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