Laboratory of Environmental Toxicology, Department of Biological Sciences, National School of Public Health, Oswaldo Cruz Foundation, Rio de Janeiro, RJ, Brazil.
Malar J. 2010 Mar 22;9:81. doi: 10.1186/1475-2875-9-81.
The mechanisms by which malaria up and down-regulates CYP activities are not understood yet. It is also unclear whether CYP activities are modulated during non-lethal malaria infections. This study was undertaken to evaluate the time course of CYP alterations in lethal (Plasmodium berghei ANKA) and non-lethal (Plasmodium chabaudi chabaudi) murine malaria. Additionally, hypotheses on the association of CYP depression with enhanced nitric oxide (NO) production, and of CYP2a5 induction with endoplasmic reticulum dysfunction, enhanced haem metabolism and oxidative stress were examined as well.
Female DBA-2 and C57BL/6 mice were infected with P.berghei ANKA or P. chabaudi and killed at different post-infection days. Infection was monitored by parasitaemia rates and clinical signs. NO levels were measured in the serum. Activities of CYP1a (ethoxyresorufin-O-deethylase), 2b (benzyloxyresorufin-O-debenzylase), 2a5 (coumarin-7-hydroxylase) and uridine-diphosphoglucuronyl-transferase (UGT) were determined in liver microsomes. Glutathione-S-transferase (GST) activity and concentrations of gluthatione (GSH) and thiobarbituric acid-reactive substances (TBARS) were determined in the liver. Levels of glucose-regulated protein 78 (GRP78) were evaluated by immunoblotting, while mRNAs of haemoxygenase-1 (HO-1) and inducible nitric oxide synthase (iNOS) were determined by quantitative RT-PCR.
Plasmodium berghei depressed CYP1a and 2b and induced 2a5 in DBA-2 mice. In P.berghei-infected C57BL/6 mice CYP activities remained unaltered. In both strains, GST and UGT were not affected by P.berghei. Plasmodium c. chabaudi depressed CYP1a and 2b and induced 2a5 activities on the day of peak parasitaemia or near this day. CYP2a5 induction was associated with over-expression of HO-1 and enhanced oxidative stress, but it was not associated with GRP78 induction, a marker of endoplasmic reticulum stress. Plasmodium chabaudi increased serum NO on days near the parasitaemia peak in both strains. Although not elevating serum NO, P.berghei enhanced iNOS mRNA expression in the liver.
Down-regulation of CYP1a and 2b and induction of 2a5 occurred in lethal and non-lethal infections when parasitaemia rates were high. A contribution of NO for depression of CYP2b cannot be ruled out. Results were consistent with the view that CYP2a5 and HO-1 are concurrently up-regulated and suggested that CYP2a5 induction may occur in the absence of enhanced endoplasmic reticulum stress.
疟疾上调和下调 CYP 活性的机制尚不清楚。在非致死性疟疾感染期间，CYP 活性是否受到调节也不清楚。本研究旨在评估致死性（伯氏疟原虫 ANKA）和非致死性（约氏疟原虫）鼠疟中 CYP 改变的时间过程。此外，还检验了 CYP 抑制与增强一氧化氮（NO）产生、CYP2a5 诱导与内质网功能障碍、增强血红素代谢和氧化应激之间关联的假设。
雌性 DBA-2 和 C57BL/6 小鼠感染伯氏疟原虫 ANKA 或约氏疟原虫，并在不同的感染后天数处死。通过寄生虫血症率和临床症状监测感染。在血清中测量 NO 水平。在肝微粒体中测定 CYP1a（乙氧基Resorufin-O-脱乙基酶）、2b（苄氧基Resorufin-O-脱苄基酶）、2a5（香豆素-7-羟化酶）和尿苷二磷酸葡萄糖醛酸转移酶（UGT）的活性。在肝脏中测定谷胱甘肽-S-转移酶（GST）活性以及谷胱甘肽（GSH）和硫代巴比妥酸反应物质（TBARS）的浓度。通过免疫印迹评估葡萄糖调节蛋白 78（GRP78）的水平，通过定量 RT-PCR 测定血红素加氧酶-1（HO-1）和诱导型一氧化氮合酶（iNOS）的 mRNA。
伯氏疟原虫在 DBA-2 小鼠中抑制 CYP1a 和 2b 并诱导 2a5。在感染伯氏疟原虫的 C57BL/6 小鼠中，CYP 活性未受影响。在两种菌株中，GST 和 UGT 不受疟原虫的影响。约氏疟原虫在寄生虫血症高峰或接近高峰时抑制 CYP1a 和 2b 并诱导 2a5 活性。2a5 诱导与 HO-1 的过表达和增强的氧化应激相关，但与内质网应激的标志物 GRP78 诱导无关。约氏疟原虫在两种菌株中寄生虫血症高峰附近增加了血清中的 NO。尽管没有升高血清中的 NO，但伯氏疟原虫在肝脏中增强了 iNOS mRNA 的表达。
当寄生虫血症率较高时，致死性和非致死性感染中会发生 CYP1a 和 2b 的下调和 2a5 的诱导。不能排除 NO 对 CYP2b 抑制的作用。结果与 CYP2a5 和 HO-1 同时上调的观点一致，并表明 CYP2a5 诱导可能发生在增强的内质网应激不存在的情况下。
