Terry C M, Clikeman J A, Hoidal J R, Callahan K S
Department of Pharmacology and Toxicology,University of Utah, Salt Lake City, Utah 84148, USA.
Am J Physiol. 1999 May;276(5):H1493-501. doi: 10.1152/ajpheart.1999.276.5.H1493.
Heme oxygenase-1 (HO-1), an enzyme important in protection against oxidant stress, is induced in human vascular endothelial cells by the cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-1alpha (IL-1alpha). However, the signaling mediators that regulate the induction are not known. This study examined the involvement of protein kinase C (PKC), phospholipase A2 (PLA2), calcium, and oxidants in cytokine induction of HO-1. Acute exposure to the PKC activator phorbol 12-myristate 13-acetate (PMA) stimulated HO-1 mRNA. However, prolonged exposure, which downregulates most PKC isoforms, blocked induction of HO-1 mRNA by IL-1alpha and TNF-alpha. Additionally, the phosphatase inhibitors okadaic acid and calyculin enhanced cytokine induction of HO-1. Mepacrine, a PLA2 inhibitor, prevented HO-1 induction by cytokine, suggesting a role for arachidonate, the product of PLA2 hydrolysis of phospholipids, in HO-1 expression. The intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) blocked cytokine induction of HO-1. Paradoxically, the calcium ionophore A-23187 prevented HO-1 induction by cytokine but not by PMA. Finally, the oxidant scavenger N-acetylcysteine inhibited HO-1 induction by cytokines. These results demonstrate that TNF-alpha and IL-1alpha induction of HO-1 requires PKC-mediated phosphorylation and PLA2 activation as well as oxidant generation.
血红素加氧酶-1（HO-1）是一种在抵御氧化应激中起重要作用的酶，可被细胞因子肿瘤坏死因子-α（TNF-α）和白细胞介素-1α（IL-1α）在人血管内皮细胞中诱导产生。然而，调节这种诱导作用的信号介质尚不清楚。本研究检测了蛋白激酶C（PKC）、磷脂酶A2（PLA2）、钙和氧化剂在细胞因子诱导HO-1过程中的作用。急性暴露于PKC激活剂佛波酯12-肉豆蔻酸13-乙酸酯（PMA）可刺激HO-1 mRNA的表达。然而，长时间暴露会下调大多数PKC同工型，从而阻断IL-1α和TNF-α对HO-1 mRNA的诱导。此外，磷酸酶抑制剂冈田酸和花萼海绵诱癌素可增强细胞因子对HO-1的诱导作用。PLA2抑制剂米帕林可阻止细胞因子诱导HO-1，这表明磷脂经PLA2水解产生的花生四烯酸在HO-1表达中起作用。细胞内钙螯合剂1,2-双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸乙酰甲酯（BAPTA-AM）可阻断细胞因子对HO-1的诱导。矛盾的是，钙离子载体A-23187可阻止细胞因子诱导HO-1，但不能阻止PMA诱导HO-1。最后，氧化剂清除剂N-乙酰半胱氨酸可抑制细胞因子诱导HO-1。这些结果表明，TNF-α和IL-1α诱导HO-1需要PKC介导的磷酸化、PLA2激活以及氧化剂的产生。
