Cytokine interactions promote synergistic fibronectin accumulation by mesangial cells.
BACKGROUND
The development of glomerulosclerosis has been associated with the presence of the cytokines transforming growth factor-beta 1 (TGF-beta 1), tumor necrosis factor-alpha (TNF-alpha) and/or interleukin-1 beta (IL-1 beta), at some stage in the glomerulus. To better understand the role of these cytokines in the scarring process their effect on rat mesangial cell fibronectin production was investigated.


METHODS
Mesangial cells were exposed to 10 ng/ml of either TGF-beta 1, TNF-alpha, or IL-1 beta or to TGF-beta 1 in combination with TNF-alpha or IL-1 beta. Tissue culture supernatants and cell lysates were assayed for fibronectin. Supernatants were also assayed for TGF-beta 1. Northern blot analyses probing for fibronectin, transin, TIMP-1 and TGF-beta 1 were carried out on RNA extracted from mesangial cells exposed to individual and combinations of cytokines.


RESULTS
Individually these cytokines were only able to induce modest increases in fibronectin protein levels. However, when mesangial cells were exposed to TGF-beta 1 in combination with either TNF-alpha or IL-1 beta then fibronectin levels were synergistically up-regulated approximately fivefold over unstimulated levels. Northern analysis demonstrated that fibronectin mRNA levels in the combination were also synergistically increased. In contrast, rat transin gene expression in the combinations was reduced to well below levels induced by TNF-alpha and IL-1 beta individually. In addition, synergistic up-regulation of both TGF-beta 1 protein and message by the cytokine combinations was also observed. TGF-beta 1: TNF-alpha and TGF-beta 1: IL-1 beta induced additive increases in TIMP-1 (tissue inhibitor of metalloproteinases-1) mRNA levels.


CONCLUSIONS
These data illustrate that complex interactions can occur between cytokines within the glomerulus modulating both matrix synthetic and degradation pathways. These could initiate the scarring process and the development of glomerulosclerosis.
Pawluczyk
I Z
IZ
Department of Nephrology, Leicester General Hospital, England, United Kingdom.
Harris
K P
KP
D000818:Animals; D015415:Biomarkers; D015152:Blotting, Northern; D002921:Cicatrix / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004797:Enzyme-Linked Immunosorbent Assay; D005353:Fibronectins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D005920:Glomerular Mesangium / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D007375:Interleukin-1 / Q000494:pharmacology; D019278:Matrix Metalloproteinase 3 / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics; D017186:Titrimetry; D014158:Transcription, Genetic / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D015415:Biomarkers; D016207:Cytokines; D005353:Fibronectins; D007375:Interleukin-1; D012333:RNA, Messenger; D019715:Tissue Inhibitor of Metalloproteinase-1; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D019278:Matrix Metalloproteinase 3