Involvement of NF-κB in high glucose-induced alteration of α-methyl-D-glucopyranoside (α-MG) uptake in renal proximal tubule cells

Although recent data have shown that nuclear factor-kappa B (NF-κB) is activated in tubules and glomeruli in various experimental models of renal injury, biological significance of NF-κB activation in diabetic renal injury is not clear. Thus, this study performed to investigate involvement of NF-κB 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-κB 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-κB 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 IκB-α protein showed that levels of IκB-α protein were clearly decreased after incubation with 25 mM glucose compare to 5 mM glucose. To examine the relationship of NF-κB and oxidative stress or PKC in the high glucose-induced inhibition of [ ¹⁴ C]-α-methyl-D- glucopyranoside (α-MG) uptake, PKC inhibitors and antioxidants effectively blocked high glucose-induced activation of NF-κB although these themselves had no significant effects. In addition, high glucose-induced inhibition of α-MG uptake was prevented by NF-κB inhibitors. In conclusion, high glucose inhibits, in part, α-MG uptake through NF-κB activation mediated by oxidative stress and PKC activation in the primary cultured rabbit renal proximal tubule cells.