Involvement of NF-κB in High Glucose-induced Alteration of a-methyl-D-glucopyranoside (α-MG) Uptake in Renal Proximal Tubule Cells

Although recent data have shown that nuclear factor-kappa B (NF-kappaB) is activated in tubules and glomeruli in various experimental models of renal injury, biological significance of NF-kappaB activation in diabetic renal injury is not clear. Thus, this study performed to investigate involvement of NF-kappaB in high glucose-induced Na+/glucose cotransporters' dysfunction in primary cultured renal proximal tubules cells (PTCs). Treatment with 25 mM glucose for 48 hr increased NF-kappaB DNA binding activity by five times compared to 5 mM glucose (control). The specificity of the binding reaction was confirmed by competition studies. The level of NF-kappaB p65 protein by treatment with 25 mM glucose for 48 hr was increased by about 2-fold compared to 5 mM glucose in the nuclear extracts. Also, Western blot analysis of IkappaB-alpha protein showed that levels of IkappaB-alpha protein were clearly decreased after incubation with 25 mM glucose compare to 5 mM glucose. To examine the relationship of NF-kappaB and oxidative stress or PKC in the high glucose-induced inhibition of [14C]- alpha-methyl-D-glucopyranoside (alpha-MG) uptake, PKC inhibitors and antioxidants effectively blocked high glucose-induced activation of NF-kappaB although these themselves had no significant effects. In addition, high glucose-induced inhibition of alpha-MG uptake was prevented by NF-kappaB inhibitors. In conclusion, high glucose inhibits, in part, alpha-MG uptake through NF-kappaB activation mediated by oxidative stress and PKC activation in the primary cultured rabbit renal proximal tubule cells.