Ghigo D, Todde R, Ginsburg H, Costamagna C, Gautret P, Bussolino F, Ulliers D, Giribaldi G, Deharo E, Gabrielli G, Pescarmona G, Bosia A
Department of Genetics, Biology and Medical Chemistry, University of Torino, Italy.
J Exp Med. 1995 Sep 1;182(3):677-88. doi: 10.1084/jem.182.3.677.
Nitric oxide (NO), a highly diffusible cellular mediator involved in a wide range of biological effects, has been indicated as one of the cytotoxic agents released by leukocytes to counteract malaria infection. On the other hand, NO has been implicated as a mediator of the neuropathological symptoms of cerebral malaria. In such circumstances NO production has been thought to be induced in host tissues by host-derived cytokines. Here we provide evidence for the first time that human red blood cells infected by Plasmodium falciparum (IRBC) synthesize NO. The synthesis of NO (measured as citrulline and nitrate production) appeared to be very high in comparison with human endothelial cells; no citrulline and nitrate production was detectable in noninfected red blood cells. The NO synthase (NOS) activity was very high in the lysate of IRBC (while not measurable in that of normal red blood cells) and was inhibited in a dose-dependent way by three different NOS inhibitors (L-canavanine, NG-amino-L-arginine, and NG-nitro-L-arginine). NOS activity in P. falciparum IRBC is Ca++ independent, and the enzyme shows an apparent molecular mass < 100 kD, suggesting that the parasite expresses an isoform different from those found in mammalian cells. IRBC release a soluble factor able to induce NOS in human endothelial cells. Such NOS-inducing activity is not tissue specific, is time and dose dependent, requires de novo protein synthesis, and is probably associated with a thermolabile protein having a molecular mass > 100 kD. Our data suggest that an increased NO synthesis in P. falciparum malaria can be directly elicited by soluble factor(s) by the blood stages of the parasite, without necessarily requiring the intervention of host cytokines.
一氧化氮（NO）是一种具有高度扩散性的细胞介质，参与多种生物学效应，已被指出是白细胞释放的用于对抗疟疾感染的细胞毒性因子之一。另一方面，NO被认为是脑型疟神经病理症状的介质。在这种情况下，人们认为宿主组织中由宿主来源的细胞因子诱导产生NO。在此，我们首次提供证据表明，被恶性疟原虫感染的人类红细胞（IRBC）能合成NO。与人类内皮细胞相比，NO的合成（以瓜氨酸和硝酸盐的产生量衡量）似乎非常高；在未感染的红细胞中未检测到瓜氨酸和硝酸盐的产生。IRBC裂解物中的一氧化氮合酶（NOS）活性非常高（而正常红细胞裂解物中无法检测到），并且被三种不同的NOS抑制剂（L-刀豆氨酸、NG-氨基-L-精氨酸和NG-硝基-L-精氨酸）以剂量依赖的方式抑制。恶性疟原虫IRBC中的NOS活性不依赖Ca++，且该酶的表观分子量<100 kD，这表明该寄生虫表达的一种同工型不同于在哺乳动物细胞中发现的同工型。IRBC释放一种可溶性因子，能够诱导人类内皮细胞中的NOS。这种诱导NOS的活性不是组织特异性的，具有时间和剂量依赖性，需要从头合成蛋白质，并且可能与一种分子量>100 kD的热不稳定蛋白有关。我们的数据表明，恶性疟原虫疟疾中NO合成的增加可由寄生虫血液阶段的可溶性因子直接引发，不一定需要宿主细胞因子的干预。
