Guilpain Philippe, Servettaz Amélie, Goulvestre Claire, Barrieu Sandrine, Borderie Didier, Chéreau Christiane, Kavian Niloufar, Pagnoux Christian, Guillevin Loïc, Weill Bernard, Mouthon Luc, Batteux Frédéric
Université Paris Descartes, Hôpital Cochin, Assistance Publique Hôpitaux de Paris, Paris, France.
Arthritis Rheum. 2007 Jul;56(7):2455-63. doi: 10.1002/art.22741.
Microscopic polyangiitis (MPA) is a small-vessel vasculitis associated with antimyeloperoxidase (MPO) antibodies in 70% of patients. Anti-MPO antibodies can trigger the release of MPO by neutrophils and monocytes, but their involvement in the pathogenesis of MPA is still questioned. The aim of this study was to investigate whether anti-MPO antibodies can activate MPO to generate an oxidative stress that is potentially deleterious to the endothelium.
MPA sera, purified IgG from MPA sera, normal control sera, and purified IgG from normal sera were incubated with MPO coated onto microtitration plates. The peroxidase activity of MPO was evaluated by adding o-phenylenediamine. Production of hypochlorous acid (HOCl) was determined by chemiluminescence. The cytotoxic properties of byproducts of MPO activation were tested on endothelial cells in culture.
MPA sera with anti-MPO antibodies were found to activate MPO in vitro (P < 0.0001 versus normal sera) and to generate HOCl (P < 0.001), as did IgG purified from MPA sera (P < 0.05). MPA sera without anti-MPO antibodies and MPA IgG absorbed on MPO did not show these activities. The byproducts of MPO activation by MPA sera exerted a strong cytolytic activity on endothelial cells in culture (P < 0.01). Both HOCl production and endothelial lysis were abrogated by N-acetylcysteine (NAC), an antioxidant molecule (P < 0.05 and P < 0.0001, respectively).
Anti-MPO antibodies could play a pathogenic role in vivo by triggering an oxidative burst, leading to severe endothelial damage. Treatment of MPA patients with NAC might be proposed in an attempt to abrogate these deleterious phenomena.
显微镜下多血管炎（MPA）是一种小血管炎，70%的患者与抗髓过氧化物酶（MPO）抗体相关。抗MPO抗体可触发中性粒细胞和单核细胞释放MPO，但其在MPA发病机制中的作用仍存在疑问。本研究的目的是调查抗MPO抗体是否能激活MPO以产生对内皮细胞可能有害的氧化应激。
将MPA血清、从MPA血清中纯化的IgG、正常对照血清以及从正常血清中纯化的IgG与包被在微量滴定板上的MPO一起孵育。通过添加邻苯二胺评估MPO的过氧化物酶活性。通过化学发光法测定次氯酸（HOCl）的产生。在培养的内皮细胞上测试MPO激活副产物的细胞毒性特性。
发现含有抗MPO抗体的MPA血清在体外可激活MPO（与正常血清相比，P < 0.0001）并产生HOCl（P < 0.001），从MPA血清中纯化的IgG也有此作用（P < 0.05）。不含抗MPO抗体的MPA血清以及吸附在MPO上的MPA IgG未表现出这些活性。MPA血清激活MPO产生的副产物对培养的内皮细胞具有强烈的细胞溶解活性（P < 0.01）。抗氧化分子N - 乙酰半胱氨酸（NAC）可消除HOCl的产生和内皮细胞裂解（分别为P < 0.05和P < 0.0001）。
抗MPO抗体可能通过引发氧化爆发在体内发挥致病作用，导致严重的内皮损伤。或许可以考虑用NAC治疗MPA患者以消除这些有害现象。
