Lysine triggers apoptosis through a NADPH oxidase-dependent mechanism in human renal tubular cells

Daniela Verzola, Annamaria Famà, Barbara Villaggio, Maia Di Rocco, Alchiede Simonato, Elena D'Amato, Fabio Gianiorio, Giacomo Garibotto

Research output: Contribution to journalArticlepeer-review


Progressive chronic kidney disease (CKD) is common in lysinuric protein intolerance (LPI), a primary inherited aminoaciduria characterized by massive Lysine excretion in urine. However, by which mechanisms Lysine may cause kidney damage to tubule cells is still not understood. This study determined whether Lysine overloading of human proximal tubular cells (HK-2) in culture enhances apoptotic cell loss and its associated mechanisms. Overloading HK-2 with Lysine levels reproducing those observed in urine of patients affected by LPI (10 mM) increased apoptosis (+30%; p <0.01 vs.C), as well as Bax and Apaf-1 expressions (+30-50% p <0.05), while downregulated Bcl-2 (-40% p <0.05). Apoptosis induced by high Lysine was no longer observed after addition of caspase-9 and caspase-3 inhibitors while caspase-8 inhibitor had no protective effect. High Lysine induced elevations in ROS generation and NADPH oxidase subunits mRNAs (p22 phox +106±23%, p67 phox +108±22% and gp91 phox +75±4% p <0.05-0.01). In addition, the NADPH oxidase inhibitor DPI prevented both ROS production and apoptosis. Treating HK-2 with antioxidants, such as Cysteine and its analog, N-acetyl-l-cysteine (NAC), rescued the HK-2 from apoptosis induced by Lysine. In summary, our data show that high Lysine in vitro increases the permissiveness of proximal tubule kidney cells to apoptosis by triggering a pathway involving NADPH oxidase signaling. This event may represent a key cellular effect in the increasing the susceptibility of human tubular cells to apoptosis when the tubules cope with a high Lysine load. This effect is instrumental to renal damage and disease progression in patients with LPI.

Original languageEnglish
Pages (from-to)1011-1019
Number of pages9
JournalJournal of Inherited Metabolic Disease
Issue number6
Publication statusPublished - Nov 2012

ASJC Scopus subject areas

  • Genetics(clinical)
  • Genetics


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