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Hum Mol Genet. 2015 Dec 15;24(24):7049-59. doi: 10.1093/hmg/ddv405. Epub 2015 Sep 29.

Molecular and biochemical alterations in tubular epithelial cells of patients with isolated methylmalonic aciduria.

Author information

1
Department of General Pediatrics, Division of Neuropediatrics and Metabolic Medicine, University Children's Hospital Heidelberg, D-69120 Heidelberg, Germany.
2
Department of General Pediatrics, Division of Neuropediatrics and Metabolic Medicine, University Children's Hospital Heidelberg, D-69120 Heidelberg, Germany, Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland, Institute of Physiology, Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland and.
3
Department of Cellular and Molecular Pathology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
4
Department of General Pediatrics, Division of Neuropediatrics and Metabolic Medicine, University Children's Hospital Heidelberg, D-69120 Heidelberg, Germany, sven.sauer@med.uni-heidelberg.de.

Abstract

Methylmalonic acidurias (MMAurias) are a group of inherited disorders in the catabolism of branched-chain amino acids, odd-chain fatty acids and cholesterol caused by complete or partial deficiency of methylmalonyl-CoA mutase (mut(0) and mut(-) subtype respectively) and by defects in the metabolism of its cofactor 5'-deoxyadenosylcobalamin (cblA, cblB or cblD variant 2 type). A long-term complication found in patients with mut(0) and cblB variant is chronic tubulointerstitial nephritis. The underlying pathomechanism has remained unknown. We established an in vitro model of tubular epithelial cells from patient urine (hTEC; 9 controls, 5 mut(0), 1 cblB). In all human tubular epithelial cell (hTEC) lines we found specific tubular markers (AQP1, UMOD, AQP2). Patient cells showed disturbance of energy metabolism in glycolysis, mitochondrial respiratory chain and Krebs cycle in concert with increased reactive oxygen species (ROS) formation. Electron micrographs indicated increased autophagosome production and endoplasmic reticulum stress, which was supported by positive acridine orange staining and elevated levels of LC3 II, P62 and pIRE1. Screening mTOR signaling revealed a release of inhibition of autophagy. Patient hTEC produced and secreted elevated amounts of the pro-inflammatory cytokine IL8, which was highly correlated with the acridine orange staining. Summarizing, hTEC of MMAuria patients are characterized by disturbed energy metabolism and ROS production that lead to increased autophagy and IL8 secretion.

PMID:
26420839
DOI:
10.1093/hmg/ddv405
[Indexed for MEDLINE]
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