Chen L, Wang Y, Kairaitis L K, Wang Y, Zhang B H, Harris D C
Department of Renal Medicine, The University of Sydney at Westmead Hospital, Westmead, NSW, Australia.
Exp Nephrol. 2001;9(3):198-204. doi: 10.1159/000052612.
Nitric oxide (NO) levels are increased after exposure of cultured proximal tubule cells (PTC) to non-haem iron, potentially contributing to PTC injury in disease states associated with increased iron exposure, including proteinuric renal disease. The mechanisms underlying this observed increase were investigated. After 3 h exposure to 400 microM nitrilotriacetate (NTA)-Fe, inducible nitric oxide synthase (iNOS) mRNA expression was significantly increased, with a corresponding increase in iNOS protein after 12 h. The nuclear binding activity of NFkappaB with 400 microM NTA-Fe was increased, and pyrrolidine dithiocarbamate (PDTC), an antioxidant inhibitor of NFkappaB, prevented both activation of NFkappaB and NO production in response to NTA-Fe. Inhibition of protein tyrosine kinase reduced iNOS mRNA, iNOS protein levels and NO production in response to NTA-Fe. The effect of tyrosine kinase inhibition on NFkappaB activation was variable, with herbimycin but not genistein having an inhibitory effect. Activation of either protein kinase A or C increased iNOS mRNA and protein levels, and NO production in response to NTA-Fe, whereas only the protein kinase C activator phorbol dibutyrate (PDBu) had a stimulatory effect on NFkappaB activation. The protein kinase A activator forskolin did not alter iron-induced activation of NFkappaB. These data suggest that the observed increase in NO production by PTC in response to iron is due to increased transcription of iNOS. The transcriptional regulation of this response is complex and involves NFkappaB, protein tyrosine kinase and the protein kinases A and C.
将培养的近端肾小管细胞（PTC）暴露于非血红素铁后，一氧化氮（NO）水平会升高，这可能在与铁暴露增加相关的疾病状态（包括蛋白尿性肾病）中导致PTC损伤。对这种观察到的升高背后的机制进行了研究。在暴露于400微摩尔次氮基三乙酸（NTA）-铁3小时后，诱导型一氧化氮合酶（iNOS）mRNA表达显著增加，12小时后iNOS蛋白相应增加。400微摩尔NTA-铁使NFκB的核结合活性增加，吡咯烷二硫代氨基甲酸盐（PDTC）是一种NFκB的抗氧化抑制剂，可阻止NFκB的激活以及对NTA-铁的NO产生反应。蛋白酪氨酸激酶的抑制降低了对NTA-铁的iNOS mRNA、iNOS蛋白水平和NO产生。酪氨酸激酶抑制对NFκB激活的影响是可变的，除莠霉素有抑制作用而染料木黄酮没有。蛋白激酶A或C的激活增加了对NTA-铁的iNOS mRNA和蛋白水平以及NO产生，而只有蛋白激酶C激活剂佛波醇二丁酸酯（PDBu）对NFκB激活有刺激作用。蛋白激酶A激活剂福斯高林不会改变铁诱导的NFκB激活。这些数据表明，观察到的PTC对铁的NO产生增加是由于iNOS转录增加。这种反应的转录调控很复杂，涉及NFκB、蛋白酪氨酸激酶以及蛋白激酶A和C。
