Role Of Tumor Necrosis Factor α And Nitric Oxide In Pathogenesis Of Cerebral Malaria

Cerebral malaria (CM) is the most severe complication of Plasmodium falciparum infection, whose mortality is as high as 20%~50%. The death roll of CM is 50% of malaria mortality. Falciparum malaria is prevalent in the south areas of 33ç™— in China, especially in Hainan province and Yunnan province. CM is often happened and threatens the life of people in these areas. There are many difficulties in the prevention and treatment of CM because its pathophysiology is still poorly understood. It is of high significance to investigate the pathogenesis of CM.There are many difficulties in studying CM on humans because of the restriction of ethics. It is the important method and tool for the study of CM to set up experimental CM animal model. Some strains of mice infected with Plasmodium berghei may develop CM. The pathological changes and clinical manifestations in mice CM are similar to human CM.Tumor necrosis factor a (TNF- a ) is a cytokine produced mainly by macrophages in blood and tissues. It is considered that TNF- a may play an important role in the development of CM. There is no correlative report ofTNF- a level in brain tissue Nitric oxide(NO) is a lively gas with comprehensive biological functions Nitric oxide synthase(NOS)is the enzyme to synthesize NO. It is inferred that TNF- a may mediate CM through stimulating the production of NO recently, but there is no experimental evidence. In this study, C57BL/6J mice were used to infect with P. berghei K173 to set up CM animal model. Levels of TNF- a , NO and NOS in serum and brain tissue were measured in the course of infection. The influences of dexamethasone, an inhibitor of TNF- a production and N-nitro-L-arginine (L-NNA), an inhibitor of NO production on CM were observed. The purpose of this study is to investigate the pamogenesis of CM and to explore new methods for treatment of CM.Materials and methodsA hundred female C57BL/6J mice, aged 6-8 weeks were divided into 5 groups randomly and each group contained 20 mice. The first group was normal control group. Mice were injected intraperitoneally(ip) with saline; The second group was infection control group. Mice were infected with Plasmodium yoelli. The third group was CM model group. Mice were infected with P.berghei. The fourth group was dexamethasone group. Mice were infected with P.berghei. Dexamethasone was added to the drinking water of the mice (lOmg/L ) before day 1 of infection .The fifth group was L-NNA group. Mice were infected with P.berghei. Infected mice were injected ip daily with 5 mg L-NNA from the infection day. Ten mice of each group were killed on day 5 after infection. Mice of CM model group were killed when mice displayed the first sign of CM. Mice of other groups were killed on day 10 after infection. Blood and brain were taken when mice were killed. The levels of TNF- a ,NO,NOS of serum and brain tissue were detected. Water content of brain tissue was detected at the same time. Other 40 C57BL/6J mice were divided into 4 groups and each group contained 10 mice. All mice were infected with P.berghei. The first group was CM model. Mice of the second group were given drinking water containing dexamethasone. Mice of the third group were injected ip daily with 5 mg L-NNA from the day of infection . Mice of the fourth group were injected ip with 15 u g lipopolysaccharide (LPS) on day 8 after infection. The survival time and the development of CM in mice were observed. The experimental data were treated by SPSS software. Analysis of variance was adopted to analyze the differences, a =0.05 a was the level of test. The experimental results were presented as mean + SD.Results1. The development of CM in mice after infection. The mice infected with P.yoelli didn't develop CM. The mice infected with P.berghei developed CM and died between day 9 and 11 after infection. The P.berghei- infected mice treated with dexamethasone or treated with L-NNA did not develop CM till day 10 after infection.2. Comparing the mice developed CM with those on day 5 after infection The levels o...