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

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.

[Fabry disease in Italy: first epidemiologic and collaborative study]. / Primo studio epidemiologico e collaborativo italiano sulla malattia di Fabry.

The authors sought to define the prevalence of Fabry disease and to establish the incidence and its natural history in Italy. The aim of this study was to point out the first clinical signs and symptoms to perform an early diagnosis and hence to start a specific therapeutic treatment. Fabry disease is an inborn error of metabolism caused by the deficiency of the lysosomal enzyme alpha-galactosidase A. Fabry disease is a severe X-linked disorder presenting with a higher morbidity between the third and the fourth decade of life. Fabry disease may be confused with other diseases or completely misdiagnosed: its frequency is estimated worldwide to be 1:117000. In Italy, 65 patients have been identified by several specialized institutions; age, sex, onset of first clinical signs and symptoms were analyzed and reported. In conclusion, this is the first Italian collaborative study that allows to delineate and point out the clinical signs of Fabry disease to perform a correct and early diagnosis. Enzyme replacement therapy is now available and its early beginning can prevent renal and cardiac failure, improve the quality of life and life expectancy in these patients.