Hypoxia-inducible Factor-1α (HIF-1α) Protein Diminishes Sodium Glucose Transport 1 (SGLT1) and SGLT2 Protein Expression in Renal Epithelial Tubular Cells (LLC-PK1) under Hypoxia

Othir G. Galicia-Cruz,Juan R. Zapata-Morales,Martha Franco,Flavio Martinez y Morales

doi:10.1074/jbc.m113.526814

Abstract

In this work, we demonstrated the regulation of glucose transporters by hypoxia inducible factor-1α (HIF-1α) activation in renal epithelial cells. LLC-PK1 monolayers were incubated for 1, 3, 6, or 12 h with 0% or 5% O2 or 300 μm cobalt (CoCl2). We evaluated the effects of hypoxia on the mRNA and protein expression of HIF-1α and of the glucose transporters SGLT1, SGLT2, and GLUT1. The data showed an increase in HIF-1α mRNA and protein expression under the three evaluated conditions (p < 0.05 versus t = 0). An increase in GLUT1 mRNA (12 h) and protein expression (at 3, 6, and 12 h) was observed (p < 0.05 versus t = 0). SGLT1 and SGLT2 mRNA and protein expression decreased under the three evaluated conditions (p < 0.05 versus t = 0). In conclusion, our results suggest a clear decrease in the expression of the glucose transporters SGLT1 and SGLT2 under hypoxic conditions which implies a possible correlation with increased expression of HIF-1α.

Highlights

Hypoxia regulates the transport systems expression in kidney cells
We demonstrated the regulation of glucose transporters by hypoxia inducible factor-1␣ (HIF-1␣) activation in renal epithelial cells
We evaluated the effects of hypoxia on the mRNA and protein expression of HIF-1␣ and of the glucose transporters SGLT1, SGLT2, and glucose transporter 1 (GLUT1)

Summary

Background

Hypoxia regulates the transport systems expression in kidney cells. Results: Expression of SGLT1 and SGLT2 is diminished in LLC-PK1 cells exposed to low oxygen concentrations. Under chemical hypoxia induced with cobalt chloride (CoCl2) or dimethyloxalylglycine, the rodent kidney expresses HIF-1␣ in the renal cortex and inner and outer medulla This HIF-1␣ expression is accompanied by the co-detection of HIF-1-regulated proteins, such as vascular endothelial growth factor (VEGF) and glucose transporter 1 (GLUT1) [16, 19, 20] in streptozotocin-induced diabetic rats, high levels of HIF-1␣ were found in the outer medullary region, including the medullary thick ascending limb [9]. HIF-1 regulates glucose transport via GLUT1 and GLUT3, and glucose metabolism mediated by enzymes such as fructose-2, 6-biphosphatase and hexokinase 2, resulting in a high rate of glucose turnover and increased oxidative metabolism [21] Cytokines such as IL-1␤ in human proximal tubule cells induce HIF-1 and VEGF activities, as evidenced by measuring their mRNA and protein expression, as well as the increased expression of genes that are up-regulated by HIF [22]. We propose that HIF-1␣ regulates glucose transporter expression in the cultured epithelial renal cell line LLC-PK1 subjected to hypoxia

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION