RESUMO
AIM: To investigate the biological characteristics and effect of TNF-alpha binding peptide (TBP) and TNFR blocking peptide (TRBP) in vitro. METHODS: The binding specificity of TBP or TRBP was tested by competition experiment using GFP-TNF fusion protein and detected by FCM and fluorescent microscope. The interaction between TBP and TRBP was determined by non-denatured PAGE and the inhibitory effect of TBP and TRBP on TNF-alpha cytotoxicity against U937 was carried out by MTT colorimetry. The effects of TBP and TRBP on the functions of human monocytes activated by TNF-alpha and IFN-gamma in vitro were detected by nitrotetrazolium blue chloride (NBT) reduction assay for evaluating respiratory burst and by RT-PCR for evaluating IL-1beta and IL-8 mRNA transcription. RESULTS: It was showed that TBP and TRBP was able to block the GFP-TNF binding to the TNFR on the surface of cells and no binding interaction took place between TBP and TRBP. Both TBP and TRBP were able to inhibit the TNF-alpha cytotoxicity against U937 and this inhibitory effect was dose-dependent and the combination of TBP and TRBP (pep.38+X4) was able to inhibit the TNF-alpha cytotoxicity more efficiently than the individual peptide at all tested concentrations. The combination of TBP and TRBP was able to obviously inhibit both respiratory burst of monocytes induced by TNF-alpha and IFN-gamma and transcription level of IL-1beta and IL-8 mRNA induced by TNF-alpha. CONCLUSION: TBP or TRBP can bind with their ligands specifically and don't interact with each other. They can also block the biological activity of the TNF-alpha in vitro, and the combination of TBP and TRBP is able to inhibit the biological activity of the TNF-alpha more efficiently. This research will provide an experimental basis for the clinical treatment of the inflammatory disease.
Assuntos
Monócitos/efeitos dos fármacos , Peptídeos/metabolismo , Peptídeos/farmacologia , Fator de Necrose Tumoral alfa/metabolismo , Linhagem Celular Tumoral , Células Cultivadas , Colorimetria , Citometria de Fluxo , Humanos , Interferon gama/farmacologia , Interleucina-1beta/genética , Interleucina-8/genética , Microscopia de Fluorescência , Monócitos/metabolismo , Ligação Proteica , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
AIM: To compare the changes of free calcium concentration in target cells killed by transmembrane tumor necrosis factor-alpha(TM-TNF-alpha) and secretory TNF-alpha(S-TNF-alpha). METHODS: The cytotoxicity of two types of TNF-alpha was tested by bioassay. The intracellular Ca(2+) concentration was determined by Frua-2. RESULTS: TM-TNF-alpha had cytotoxic effect on all 6 kinds of target cells, whereas S-TNF-alpha could kill only two of them. The cytotoxic activity of both types of TNF-alpha was accompanied by a dramatically increase of intracellular free Ca(2+) concentration. The intracellular Ca(2+) concentration in the target cells treated with S-TNF-alpha was obviously reduced by pretreating target cells with 10 micromol/L calcium chelator EGTA for 30 minutes (P<0.01) and the cytotoxicity of S-TNF-alpha was significantly inhibited (P<0.01), while the pretreatment with EGTA had no effect on the intracellular Ca(2+) concentration in the target cells treated with TM-TNF-alpha and the cytotoxicity of TM-TNF-alpha. CONCLUSION: These results suggest that both types of TNF-alpha increase Ca(2+) concentration in target cells by promoting the redistribution of intracellular free calcium and only S-TNF-alpha seems to be able to accelerate the influx of extracellular calcium into the target cells.
