Overexpression of acetyl-coenzyme A carboxylase beta increases proinflammatory cytokines in cultured human renal proximal tubular epithelial cells.
BACKGROUND
We have identified the acetyl-coenzyme A carboxylase beta gene (ACACB) as a strong susceptibility gene to diabetic nephropathy in individuals with type 2 diabetes. To elucidate the mechanism by which ACACB contributes to conferring susceptibility to diabetic nephropathy, we examined the role of ACACB in human renal proximal tubular epithelial cells (RPTECs).


METHODS
RPTECs were infected with adenovirus vectors encoding ACACB or LacZ (control), and messenger RNA (mRNA) expression profiles were evaluated with a microarray analysis. We determined the mRNA expressions of proinflammatory cytokines by real-time quantitative reverse transcription (RT) polymerase chain reaction (PCR) and secretion of these cytokines from cells by enzyme-linked immunosorbent assay (ELISA).


RESULTS
Among 54,613 transcripts analyzed in the microarray analysis, genes encoding proinflammatory cytokines, including interleukin (IL)-6, chemokine (C-X-C motif) ligands (CXCL) 1, 2, 5, and 6, were remarkably up-regulated (>20-fold) in the ACACB-overexpressing cells. The increased expression of these inflammatory cytokines was reversed by the addition of a synthetic inhibitor of acetyl-coenzyme A carboxylase beta. Overexpression of ACACB could increase IL-6 mRNA expression and IL-6 protein secretion in a time-dependent manner. We further found that IL-6 mRNA stability and expression had significantly increased in ACACB-overexpressing RPTECs, and a treatment of the cells with p38 mitogen-activated protein kinase (MAPK) inhibitor partially but significantly reversed these effects.


CONCLUSIONS
An excess of ACACB results in increased proinflammatory cytokine expression, such as IL-6, at least partly by increasing mRNA stability through a p38 MAPK-dependent pathway.
Kobayashi
Masa-aki
MA
RIKEN Center for Genomic Medicine, Tsurumi-ku, Yokohama, Kanagawa, Japan.
Watada
Hirotaka
H
Kawamori
Ryuzo
R
Maeda
Shiro
S
D000103:Acetyl-CoA Carboxylase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000367:Age Factors; D000818:Animals; D002478:Cells, Cultured; D019743:Chemokines, CXC / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000201:enzymology / Q000276:immunology; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D020869:Gene Expression Profiling / Q000379:methods; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors; D014161:Transduction, Genetic; D014475:Uncoupling Agents / Q000494:pharmacology; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D019743:Chemokines, CXC; D016207:Cytokines; C508600:IL6 protein, human; D018836:Inflammation Mediators; D015850:Interleukin-6; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D014475:Uncoupling Agents; D013482:Superoxide Dismutase; D048051:p38 Mitogen-Activated Protein Kinases; C520105:ACACB protein, human; C498191:Acacb protein, mouse; D000103:Acetyl-CoA Carboxylase