CONICET | Buscador de Institutos y Recursos Humanos

Toxic substances accumulation in the tubular lumen and their association with the increase in intracellular damaged components is a physiopathological contributor to diabetic nephropathy (DN) development, but the mechanisms associated with disease progression are not well known. We studied, in the proximal tubule, autophagy and protein endocytic transport in a mouse model (C57BKSdb+/- y C57BKSdb/db) of diabetic nephropathy induced by type 2 diabetes mellitus (T2DM). Male mice were sacrificed at 32 weeks old and, at this age; they showed albuminuria and signs of cellular damage (enzymuria -GGT and ALP-, and histological signs of cell injury). About autophagy, we found an increase in the number of vesicles marked with LBPA (late endosomes) by immunofluorescence. We also observed, by transmission electronic microscopy, the presence of larger autophagic vesicles than the observed in the control group. Western Blot analysis showed a ratio of both LC3 isoforms (LC3II/ LC3I) significantly decreased when compared to control group. Furthermore, p62 protein was significantly decreased in T2DM animals, compared to control animals. Related to protein transporters, we observed increased urinary levels of albumin and Vitamin D binding protein. This protein is specifically endocytosed by proximal tubule transporters megalin and cubilin. Both endocytic transporters did not show alterations in tubule localization (confocal microscopy analysis), but the expression of megalin was significantly decreased compared with the control group (Western Blot analysis). At the beginnings of DN, hyperfiltration induces a rise in toxic substances into proximal tubule lumen, like glycation end products and other toxic albumin-bound compounds. These substances could be introduced in the cell and affect physiological homeostatic mechanisms like the endocytic recycling pathway of surface protein transporters and may cause cellular injury and apoptosis, contributing to DN progression.