title: Glycoxidised LDL induced the upregulation of Axl receptor tyrosine kinase and its ligand in mouse mesangial cells.
abstract: OBJECTIVE
  Low-density lipoprotein (LDL) is subjected to glycoxidation in diabetes, and a novel signalling mechanism by which glycoxidised LDL functions in glomerular mesangial cells remains to be ascertained.
  
  
  METHODS
  We performed gene expression analysis in mouse glomerular mesangial cells treated with LDL modified by glycation and oxidation (GO-LDL, 100 µg/ml) for 48 h by using DNA microarray analysis and quantitative real-time PCR. We examined the GO-LDL-specific changes in gene and protein expression in mesangial cells and glomeruli of type 2 diabetic Zucker diabetic fatty (ZDF) rats.
  
  
  RESULTS
  By microarray profiling, we noted that GO-LDL treatment increased Axl receptor tyrosine kinase (Axl) mRNA expression (∼2.5-fold, p<0.05) compared with normal LDL (N-LDL) treatment in mesangial cells. Treatment with GO-LDL also increased the protein levels of Axl and its ligand Gas6 as measured by Western blotting. These increases were inhibited by neutralising Axl receptor-specific antibody. Silencing Gas6 by siRNA inhibited GO-LDL-induced Axl expression in mesangial cells. Axl and Gas6 protein were also increased in cells cultured in high glucose (30 mM) or methylglyoxal (200 µM). Gas6 treatment increased the expression and secretion of TGF-β1 protein, a key regulator of extracellular matrix expression in the glomeruli of diabetic kidneys. Immunohistochemical analyses of glomeruli from 20-week-old ZDF rats exhibited increased Axl protein expression. Rottlerin, a selective PKC-δ inhibitor, completely blocked Gas6-induced TGF-β1 expression.
  
  
  CONCLUSIONS
  These data suggest that LDL modified by glycoxidation may mediate Axl/Gas6 pathway activation, and this mechanism may play a significant role in the pathogenesis of diabetic nephropathy.
authors.affiliation: Korean Medicine-Based Herbal Drug Research Group, Herbal Medicine Research Division, Korea Institute of Oriental Medicine (KIOM), Daejeon, Republic of Korea.
authors.forename: Young Sook
authors.initials: YS
authors.lastname: Kim
authors.forename: Dong Ho
authors.initials: DH
authors.lastname: Jung
authors.forename: Eunjin
authors.initials: E
authors.lastname: Sohn
authors.forename: Junghyun
authors.initials: J
authors.lastname: Kim
authors.forename: Jin Sook
authors.initials: JS
authors.lastname: Kim
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D003928:Diabetic Nephropathies / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects*; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D006031:Glycosylation; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D050527:Mesangial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051379:Mice; D010084:Oxidation-Reduction; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D011765:Pyruvaldehyde / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D011924:Rats, Zucker; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D000094963:Axl Receptor Tyrosine Kinase; D000099255:Growth Arrest-Specific Protein 6
chemical_list: D000098:Acetophenones; D001578:Benzopyrans; D005947:Glucose; D036341:Intercellular Signaling Peptides and Proteins; D008077:Lipoproteins, LDL; D011518:Proto-Oncogene Proteins; D011765:Pyruvaldehyde; D034741:RNA, Small Interfering; D020794:Receptor Protein-Tyrosine Kinases; D053773:Transforming Growth Factor beta1; D000094963:Axl Receptor Tyrosine Kinase; D000099255:Growth Arrest-Specific Protein 6; C099252:oxidized low density lipoprotein; C085746:rottlerin