Regulation of nuclear factor kappaB by corticosteroids in rat mesangial cells.
Nuclear factor kappaB (NF-kappaB) is one of the most important proinflammatory transcription factors. The anti-inflammatory activity of steroids in leukocytes is partly due to inhibition of signaling by NF-kappaB, but it is not known whether steroids inhibit NF-kappaB in kidney cells. Since the mesangial cell is important in several kidney diseases, especially mesangial proliferative glomerulonephritis, the aims of this study were: (1) to define the mechanism of NF-kappaB activation in rat glomerular mesangial cells; and (2) to determine whether steroids inhibit activation of NF-kappaB in these cells. Electrophoretic mobility shift assays (EMSA) showed that interleukin-1beta and tumor necrosis factor-alpha activated NF-kappaB from 15 min to 48 h after stimulation. Supershift EMSA demonstrated that p65 and p50 were the predominant subunits involved. Degradation of the inhibitory subunit IkappaB-alpha was first observed 15 min after stimulation by Western blot, was maximal at 15 to 30 min (>90% by densitometry), and had returned to near normal levels at 90 min. In contrast, IkappaB-beta was maximally degraded at 60 to 120 min and was still reduced at 48 h (<50% of the untreated level). Although treatment of mesangial cells with dexamethasone increased IkappaB-alpha mRNA by 1.92x and protein by 1.45x over controls, pretreatment did not inhibit degradation of IkappaB-alpha or -beta in response to stimulation, or prevent the increase in NF-kappaB binding activity shown by EMSA. However, dexamethasone significantly inhibited the increase in monocyte chemoattractant protein-1 mRNA seen after stimulation with interleukin 1beta, although this was not complete. It did not reduce transcription of an NF-kappaB reporter. In comparison, the pyrrolidine derivative of dithiocarnamate (PDTC), a known inhibitor of NF-kappaB, prevented the increase in NF-kappaB binding activity and significantly reduced transcription of the NF-kappaB reporter. These studies suggest that steroids can partially inhibit transcriptional activation by NF-kappaB in mesangial cells but not through an increase in IkappaB-alpha protein alone. Their effect must occur at the promoter and may be restricted to some NF-kappaB-responsive genes. Therapies that block NF-kappaB more effectively than steroids in mesangial cells, therefore, may be useful in the treatment of mesangial proliferative glomerulonephritis.
Auwardt
R B
RB
Immunology Research Centre, St. Vincent's Hospital, Melbourne, Victoria, Australia.
Mudge
S J
SJ
Chen
C G
CG
Power
D A
DA
D000305:Adrenal Cortex Hormones / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000032:analysis; D003907:Dexamethasone / Q000494:pharmacology; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005938:Glucocorticoids / Q000494:pharmacology; D007375:Interleukin-1 / Q000378:metabolism / Q000494:pharmacology; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012680:Sensitivity and Specificity; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
D000305:Adrenal Cortex Hormones; D018076:DNA, Complementary; D005938:Glucocorticoids; D007375:Interleukin-1; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone