Studies on the nitric oxide radical-based system for prevention of malaria infection in gene knockout mice

为探讨一氧化氮自由基(NO-)在预防红细胞性疟疾原虫感染中的作用，将查鲍迪疟原虫注射到干扰素-γ受体基因敲除小鼠(干扰素-γR-/-)和诱导型一氧化氮合酶基因敲除小鼠(诱导型一氧化氮合酶-/-)，比较两种基因敲除小鼠的存活率、外周血红细胞计数和寄生虫血症，并与野生型(干扰素-γR+/+、诱导型一氧化氮合酶R+/+)进行比较。这种感染实验也是在中性粒细胞耗竭的小鼠身上进行的，这些小鼠已经用抗小鼠粒细胞单抗(RB6-8C5)进行了耗竭处理。结果显示，两组患者在红细胞计数和寄生虫血症方面的变化无显著差异。另一方面，对于感染小鼠的存活率，非计量生存分析的Kaplan-Meter方法的logrank(Mantel-Cox)检验结果如下。1)当中性粒细胞耗尽时，携带干扰素-γR+/+的雄性小鼠比携带干扰素-γR-/-的雄性小鼠存活时间更长(P=0.0614)。2)去中性粒细胞干扰素-γR+/+小鼠较去中性粒细胞干扰素-γR-/-小鼠寿命更长，自愈频率更高，雌鼠P=0.0148，雄鼠P=0.0236。3)给iNOS-/-和iNOS+/+小鼠注射2.5×105-106的感染红细胞后，iNOS+/+小鼠的存活时间和自愈频率均高于iNOS-/-小鼠。4)iNOS-/-小鼠和iNOS+/+小鼠的中性粒细胞去除实验结果无明显差异。结果表明，NO-对红细胞疟原虫的感染没有直接或显著的预防作用，而感染小鼠的存活率似乎受到干扰素-γ、中性粒细胞相关的各种细胞因子、NO-、活性氧等因素的影响。

To investigate the role of the nitric oxide radical (NO-) in the prevention of infection by erythrocytic malaria parasite, murine malaria parasite (Plasmodium chabaudi chabaudi AS) was injected into the abdominal cavity of interferon-γ receptor gene knockout mice (IFN-γ R-/-) and inducible Nitric Oxide Synthase gene knockout mice (iNOS-/-) to compare survival rate, peripheral red blood cell (RBC) counts, and parasitemia between the knockout mice and wild type mice (IFN-γ R+/+, iNOS+/+). Such infection experiments were also carried out with neutrophil-depleted mice which had been treated with monoclonal anti-mouse granulocyte antibodies (RB6-8C5) for depletion. Results did not show any significant difference in the changes of RBC counts nor parasitemia between them. On the other hand, as for the survival rate of the infected mice, the Logrank (Mantel-Cox) test of the Kaplan-Meter method of Nonmetric Survival Analysis suggested the following results. 1) Male mice of IFN-γ R+/+ lived loner than IFN-γ R-/- male mice when neutrophils were depleted and self-healing was observed with some of the neutrophil-depleted IFN-γ R-/- mice (P=0.0614). 2) The neutrophil-depleted IFN-γ R+/+ mice lived longer and self-healing was observed more often than in the neutrophil-depleted IFN-γ R-/- mice, namely, P=0.0148 for female and P=0.0236 for male mice. 3) When 2.5×10^5-10^6 of infected RBC were administered to iNOS-/- and iNOS+/+ mice, the iNOS+/+ mice lived longer and self-healing was observed more often than in the iNOS-/- mice. 4) The results of the neutrophil-depletion experiment did not differ between the iNOS-/- mice and the iNOS+/+ mice. The results suggested that the NO- did not directly nor significantly prevent infection of the erythrocytic malaria parasite, while the survival rate of the infected mice appeared to be somehow influenced by IFN-γ, neutrophil related various cytokines, the NO-, active oxygen, etc.