TGF-beta1 induces IL-8 and MCP-1 through a connective tissue growth factor-independent pathway.
Transforming growth factor-beta(1) (TGF-beta(1)) functions as an important immunomodulatory cytokine in human kidney. Evidence suggests that connective tissue growth factor (CTGF) is an important downstream mediator of the profibrotic effects of TGF-beta(1). However, the role of CTGF in TGF-beta(1)-induced chemokine production remains unknown. This study was undertaken to determine whether CTGF is involved in mediating TGF-beta(1)-induced chemokine production in renal proximal tubular (HK-2) cells. Interleukin-8 (IL-8) and macrophage chemoattractant protein-1 (MCP-1) were measured. TGF-beta(1) induced an increase in IL-8 and MCP-1 (both P < 0.05) compared with control levels. CTGF was effectively silenced using small interference RNA (siRNA) in HK-2 cells. RT-PCR and real-time PCR confirmed a 94% reduction in CTGF mRNA. In the CTGF-silenced cells, TGF-beta(1)-stimulated IL-8 and MCP-1 secretion was not altered compared with control cells. Similarly, basal secretion of IL-8 and MCP-1 was not changed in CTGF-silenced cells. The direct effect of CTGF (20, 200, and 400 ng/ml) on IL-8 and MCP-1 was assessed at 24-, 48-, and 72-h time points and no stimulation was observed. Our studies further demonstrate that in the CTGF gene-silenced cells, CTGF partially mediates TGF-beta(1)-induced fibronectin and collagen IV secretion. These data suggest that TGF-beta(1) induced IL-8 and MCP-1 via CTGF-independent pathway. TGF-beta mediates both fibrosis and chemokine production in the proximal tubule of the kidney. However, CTGF plays a more specific role as a downstream mediator of TGF-beta(1)-induced fibrosis.
Qi
Weier
W
Department of Medicine, Kolling Institute, University of Sydney, Royal North Shore Hospital, St. Leonards, NSW 2065, Australia.
Chen
Xinming
X
Polhill
Tania S
TS
Sumual
Siska
S
Twigg
Stephen
S
Gilbert
Richard E
RE
Pollock
Carol A
CA
D001483:Base Sequence; D002460:Cell Line; D018932:Chemokine CCL2 / Q000235:genetics*; D055513:Connective Tissue Growth Factor; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D017874:Immediate-Early Proteins / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D016209:Interleukin-8 / Q000235:genetics*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D011994:Recombinant Proteins / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
C111835:CCL2 protein, human; C526317:CCN2 protein, human; D018932:Chemokine CCL2; D017931:DNA Primers; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D016209:Interleukin-8; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D055513:Connective Tissue Growth Factor