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AIM：To investigate the role of NF-κB in the activation of inducible nitric oxide synthase (iNOS) gene by tumor necrosis factor alpha (TNF α) and lipopolysaccharide (LPS) in endothelial cells and effect of antioxidant on the induction of iNOS. METHODS：Rat pulmonary microvascular endothelial cell (RPMEC) was cultured and the cells were identified with antiendothelial cell antibody CD31 using immunohistochemistry(ABC). The concentration of nitrite in the culture media was determined based on Griess reaction. iNOS mRNA was analyzed using RT-PCR and Northern blot. NF-κB in cell nuclei was detected with electrophoresis mobility shift assay (EMSA). RESULTS：A marked production of nitrite in RPMECs was found after 24 hours treatment with TNF α(105 U/L) and LPS (1 mg/L) (P＜0.01). The level of iNOS mRNA increased significantly after adding TNF α(105 U/L) and LPS (1 mg/L) to the cell media for 2 hours (P＜0.05). Pretreatment with cycloheximide (CHX, 10 mg/L) or antioxidant, PDTC (0.1 mmol/L) or NAC (20 mmol/L) significantly decreased nitrite production and iNOS mRNA expression induced by TNF α(105 U/L) and LPS (1 mg/L) (P＜0.05). Furthermore, there was a dose-effect relationship between PDTC/NAC and inhibitory effect. TNF α (105 U/L) and LPS (1 mg/L) triggered the activation and translocation of NF-κB. This effect was blocked by adding PDTC (0.1 mmol/L) or NAC (20 mmol/L) to the cell media for 1.5 hours.CONCLUSION：1.TNFα and LPS may induce iNOS gene expression at transcriptional or posttranscriptional level. The upregulation of iNOS depends on new protein synthesis. 2. The induction of iNOS gene expression by TNFα and LPS is dependent on the activation of NF-κB. 3. Antioxidants may inhibit the induction of iNOS gene through the inhibition of NF-κB activation.
RESUMO
Microvascular endothelial cell (MVEC) is one of the target cells of TNFα (TNF effect). The dysfunction of MVEC induced by TNF plays an important role in some cardio-cerebral vascular diseases. ① Cell proliferation kinetic: Using flow cytometry, we found cell count ［(4.30±0.34)×107／L)］ in TNF group (4×105 U/L) was obviously less than that in control ［(5.23±0.50)×107／L, P＜0.01］. The cells of G1 phase were more than those of the control, while the cells of G2, S and M phase became less (P＜0.05). ② Coagulant and anticoagulant: 72 h after MVEC cultued in the media, the content of 6-keto-PGF1α (RIA) and activity of PAI decreased significantly in TNF (4×105 U/L) group (P＜0.01, vs control). The difference between TXB2 content and t-PA activity in groups was not significant (P＞0.05). ③ Adhesive molecule: The effect of low concentration TNF (＜4×105 U/L) on adhesion between cultured MVEC and leukocytes was not signficant, but when the concentration of TNF reached 8×105 U/L or more, 12 h after culture the adhesion rate between MVEC and neutrophil increased 30.8%±4.5%. If adding monoclonal antibody of ICAM-1/CD11 into media, the adhesion rate of leukocytes decreased significantly (from 31.2% to 63.4%). ④ NO: The level of nitrite in culture media (Griess reaction) was higher than that of control (P＜0.05) after pretreatment of TNF (2×106 U/L) for 6 h. Adding L-NMMA, Dexamethasone or Cycloheximide in media could block the increase of nitrite induced by TNF, while L-Arg could enhance it. The expression of iNOS mRNA of PMVEC increased significantly after treated with TNF (2×106 U/L) for 24 h (quantitative RT/PCR). Pretreatment with Dexamethasone or Cycloheximide could block the increase (P＜0.05). Meanwhile, the expression of eNOS mRNA decreased significantly compared with control, the decrease can be blocked by Cycloheximide but not by Dexamethasone. So that TNF can induce the expression of iNOS mRNA in PMVEC, but inhibited the expression of eNOS mRNA. NO production in PMVEC can be time-dependently induced by TNF. ⑤ Apoptosis: Adding high concentration TNF(＞1.2×106 U/L) in culture media for 12 h can induce apoptosis of PMVEC with electron microscopy, flow cytometry (PI/AnnexinV stain), TUNEL and DNA ladder eletrophoresis. Meanwhile, expression of apoptosis-associated gene Bcl-2 mRNA decreased and that of Fas mRNA increased (Northern blot). The expression of FADD, caspase 3 and caspase 8 enhanced too. So that signal of apoptosis induced by TNF may be transmitted following the cascade of Fas→FADD→caspase8→caspase3. In conclusion, it should be paid attention to metabolism inability and dysfunction induced by TNF which can not found easyily using light microscope. High concentration TNF can induce apoptosis of endothelial cells regulated by apoptosis-associated genes. The changes mentioned above are common pathway in pathogenesis of some diseases related to TNF.
RESUMO
AIM:To investigate the role of nuclear factor ?B (NF ?B) in the induction of iNOS gene by TNF? and LPS in endothelial cells and the effect of antioxidant on the induction of iNOS. METHODS:Nitrite was determined based on Griess reaction. iNOS mRNA was analyzed using Northern blot. NF ?B in the cell nucleole was detected with electrophoretic mobility shift assay.RESULTS:(1)NO production and iNOS mRNA expression induced by LPS and TNF? was blocked by pyrrolidine dithiocarbamate(PDTC) or N-acetylcysteine(NAC). (2)LPS and TNF? triggered the activation and translocation of NF ?B, and PDTC or NAC inhibited the activation of NF ?B induced by LPS and TNF?.CONCLUSIONS:(1)The induction of iNOS gene by TNF? and LPS is dependent on the activation of NF ?B.(2)Antioxidants may inhibit the induction of iNOS gene through the inhibition of NF ?B activation.
