The roles of Kruppel-like factor 6 and peroxisome proliferator-activated receptor-γ in the regulation of macrophage inflammatory protein-3α at early onset of diabetes.
Macrophage inflammatory protein-3 alpha (MIP-3α) is known to be upregulated early in the development of diabetic nephropathy (DN). However, the transcriptional regulation of MIP-3α is unknown. We previously demonstrated that the transcription factors KLF6 and PPAR-γ play key roles in regulating renal fibrotic and inflammatory responses to factors inherent in diabetes mellitus. Hence we determined the role of these transcription factors in regulating MIP-3α expression. HK-2 cells and STZ-induced diabetic rats were used. siRNAs, over-expressing constructs and CHIP promoter binding assays were used to determine the role of KLF6 and PPAR-γ in MIP-3α transcriptional regulation. KLF6 overexpression increased MIP-3α which was inhibited by concurrent exposure to PPAR-γ agonists. PPAR-γ agonists attenuated high glucose-induced MIP-3α secretion. Furthermore, MIP-3α secretion was up-regulated in PPAR-γ silenced cells, suggesting both KLF6 and PPAR-γ antagonistically regulate high glucose-induced MIP-3α secretion. The CHIP promoter binding assay confirmed that PPAR-γ binds to the MIP-3α promoter and negatively regulates MIP-3α expression. PPAR-γ agonists increased the binding activity of the PPAR-γ-MIP-3α promoter. In contrast, promoter binding activity decreased in KLF6 over-expressing cells. PPAR-γ decreased in KLF6 over-expressing cells and increased in KLF6 silenced cells, while PPAR-γ siRNA had no effect on KLF6 expression, suggesting that KLF6 acted upstream of PPAR-γ in the regulation of MIP-3α. In diabetic rats, renal MIP-3α and the macrophage marker ED-1 expression increased, which was inhibited by exposure to PPAR-γ agonists. The recognition of MIP-3α as a significant pathogenic mediator in diabetic nephropathy reaffirms the increasingly recognized role of inflammation in the progression of DN. Targeting pro-inflammatory chemokine MIP-3α and its signaling pathways will provide novel strategy to treat diabetic kidney disease.
Kolling Institute, Dept of Medicine, Royal North Shore Hospital, University of Sydney, Sydney, Australia. wqi@med.usyd.edu.au
Weier
W
Qi
John
J
Holian
Christina Y R
CY
Tan
Darren J
DJ
Kelly
Xin-Ming
XM
Chen
Carol A
CA
Pollock
D000818:Animals; D054418:Chemokine CCL20 / Q000235:genetics* / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism*; D008297:Male; D047495:PPAR gamma / Q000819:agonists / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D045162:Thiazolidinediones / Q000494:pharmacology
D054418:Chemokine CCL20; C105465:KLF6 protein, human; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors; D047495:PPAR gamma; D011518:Proto-Oncogene Proteins; D045162:Thiazolidinediones; D005947:Glucose