Toll-like receptor 4 promotes tubular inflammation in diabetic nephropathy.
Inflammation contributes to the tubulointerstitial lesions of diabetic nephropathy. Toll-like receptors (TLRs) modulate immune responses and inflammatory diseases, but their role in diabetic nephropathy is not well understood. In this study, we found increased expression of TLR4 but not of TLR2 in the renal tubules of human kidneys with diabetic nephropathy compared with expression of TLR4 and TLR2 in normal kidney and in kidney disease from other causes. The intensity of tubular TLR4 expression correlated directly with interstitial macrophage infiltration and hemoglobin A1c level and inversely with estimated glomerular filtration rate. The tubules also upregulated the endogenous TLR4 ligand high-mobility group box 1 in diabetic nephropathy. In vitro, high glucose induced TLR4 expression via protein kinase C activation in a time- and dose-dependent manner, resulting in upregulation of IL-6 and chemokine (C-C motif) ligand 2 (CCL-2) expression via IκB/NF-κB activation in human proximal tubular epithelial cells. Silencing of TLR4 with small interfering RNA attenuated high glucose-induced IκB/NF-κB activation, inhibited the downstream synthesis of IL-6 and CCL-2, and impaired the ability of conditioned media from high glucose-treated proximal tubule cells to induce transmigration of mononuclear cells. We observed similar effects using a TLR4-neutralizing antibody. Finally, streptozotocin-induced diabetic and uninephrectomized TLR4-deficient mice had significantly less albuminuria, renal dysfunction, renal cortical NF-κB activation, tubular CCL-2 expression, and interstitial macrophage infiltration than wild-type animals. Taken together, these data suggest that a TLR4-mediated pathway may promote tubulointerstitial inflammation in diabetic nephropathy.
Division of Nephrology, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong.
Miao
M
Lin
Wai Han
WH
Yiu
Hao Jia
HJ
Wu
Loretta Y Y
LY
Chan
Joseph C K
JC
Leung
Wo Shing
WS
Au
Kwok Wah
KW
Chan
Kar Neng
KN
Lai
Sydney C W
SC
Tang
D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D015214:Antigens, Differentiation, Myelomonocytic / Q000032:analysis; D016022:Case-Control Studies; D002478:Cells, Cultured; D002633:Chemotaxis; D003921:Diabetes Mellitus, Experimental / Q000276:immunology / Q000378:metabolism; D003928:Diabetic Nephropathies / Q000276:immunology / Q000378:metabolism*; D005947:Glucose; D024243:HMGB1 Protein / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D007672:Kidney Cortex / Q000378:metabolism*; D008264:Macrophages / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009000:Monocytes / Q000502:physiology; D016328:NF-kappa B / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation; D000097382:CD68 Molecule
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D005947:Glucose; D024243:HMGB1 Protein; D018840:HSP70 Heat-Shock Proteins; D051550:I-kappa B Kinase; D016328:NF-kappa B; D011493:Protein Kinase C; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C495342:TLR2 protein, human; C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse