结合代谢的抗疟药溶血毒性体外检测法

以苯巴比妥i.p.60mg/kg×3d及单剂苯并黄酮i.p.80mg/kg诱导雄性Sprague-Dawley大鼠,摘肝制微粒体,加氧化型辅酶Ⅱ(NADP)等辅助因子,组成体外代谢系统。选取6-磷酸葡萄糖脱氢酶(G6PD)偏低的兔血,制成1％红细胞悬液。不同剂量的伯喹、氯喹或三氟乙酰伯喹(M8506)分别于体外和肝微粒体代谢系统在37℃共同温育后,再取其上清液与1％红细胞悬液共同温育,测定温育后各管上清液的OD值。结果表明,在3×10~1～3×10~3μmol/L的浓度范围内,伯喹和M8506均可测出明显的溶血毒性,并呈一定的剂量一反应关系;而氯喹则无溶血毒性。提示本方法可用作抗疟药溶血毒性的快速初筛试验。     

抗疟化合物三氟乙酰伯氨喹的毒性及诱变性

三氟乙酰伯氨喹(M 8506)对小鼠、大鼠与犬的毒性明显低于伯氨喹(PQ)。小鼠 igM 8506的LD50为 PQ 的3倍。大鼠 igM 8506 30mg/(kg·d)×28d,犬 ig 2mg/(kg·d)×28d 无不良反应。犬 ig量≥5mg/(kg·d)时有消化道反应,肝、肾与心等受损。6只犬 igM 8506 10mg/(kg·d),3只犬完成21d疗程;2只犬 ig 同剂量 PQ 1～2剂后均死亡。M 8506无诱变性。     

Retail supply of malaria-related drugs in rural Tanzania: risks and opportunities

OBJECTIVES: To characterize availability of fever and malaria medicines within the retail sector in rural Tanzania, assess the likely public health implications, and identify opportunities for policy interventions to increase the coverage of effective treatment. METHODS: A census of retailers selling drugs was undertaken in the areas under demographic surveillance in four Tanzanian districts, using a structured questionnaire. RESULTS: Drugs were stocked by two types of retailer: a large number of general retailers (n = 675) and a relatively small number of drug shops (n = 43). Almost all outlets stocked antipyretics/painkillers. One-third of general retailers stocking drugs had antimalarials, usually chloroquine alone. Almost all drug shops stocked antimalarials (98%): nearly all had chloroquine, 42% stocked quinine, 37% sulphadoxine-pyrimethamine and 30% amodiaquine. A large number of antimalarial brands were available. Population ratios indicate the relative accessibility of retail drug providers compared with health facilities. Drug shop staff generally travelled long distances to buy from drugs wholesalers or pharmacies. General retailers bought mainly from local general wholesalers, with a few general wholesalers accounting for a high proportion of all sources cited. CONCLUSIONS: Drugs were widely available from a large number of retail outlets. Potential negative implications include provision of ineffective drugs, confusion over brand names, uncontrolled use of antimalarials, and the availability of components of potential combination therapy regimens as monotherapies. On the other hand, this active and highly accessible retail market provides opportunities for improving the coverage of effective antimalarial treatment. Interventions targeted at all drug retailers are likely to be costly to deliver and difficult to sustain, but two promising points for targeted intervention are drug shops and selected general wholesalers. Retail quality may also be improved through consumer education, and modification of the chemical quality, packaging and price of products entering the retail distribution chain.     

胍丁胺对伯氏疟原虫K173株的抗疟作用(英文)

AIM: To study the antimalarial effect of agmatine (Agm) on chloroquine-susceptible Plasmodium berghei K173strain (S strain) and the P berghei K173 resistant strain (R strain). METHODS: The antimalarial effects of Agm onP berghei K173 S strain and R strain were evaluated by Peters 4-d suppression test in mice. RESULTS: Agm(12.5-200 mg/kg,ig,daily) decreased the parasitemia for both P berghei K173 S strain (IC50=139 mg/kg) and Rstrain (IC50=126mg/kg) in mice. Subcutaneous injection (sc) of Agm (5-40mg/kg,tid) showed relatively strongerantimalarial effect than intragastric gavage (IC50=30 mg/kg) in P berghei K 173 S strain. Spermidine antagonized theantimalarial effect of Agm for P berghei K173 S strain and R strain. Agm did not reverse the chloroquine resistanceof P berghei K173 S strain, dl-α-Difluoromethylornithine (DFMO, sc) decreased the parasitemia of P BergheiK173 S strain and this effect was antagonized by spermidine. CONCLUSION: Agm has an antimalarial effect andthe mechanism is related to its inhibition of polyamine synthesis.     

口服青蒿琥酯对伯氏鼠疟和诺氏猴疟的杀灭效果

目的:研究青蒿琥酯口服对伯氏鼠疟和诺氏猴疟的血液裂殖体杀灭效果。方法:分别在鼠疟和猴疟模型上采用“4-day试验法”、“28-day试验法”和“7-day试验法”检测了青蒿琥酯和氯喹的药效。结果:口服青蒿琥酯对伯氏鼠疟民K_(173)株的抑制效果低于氯喹,但其原虫血症下降50％、90％和转阴的时间比氯喹快10-15h,对抗株RC/K_(173)的疗效优于氯喹,无交叉抗性,I_(90)仅为1.4。青蒿琥酯和氯喹对诺氏猴疟在31.6,10.0和3.16mg·kg~(-1)剂量组的试验猴全部治愈。结论:口服青蒿琥酯在鼠、猴疟模型上的药效研究为临床研究提供有益参考。     

Melatonin action in Plasmodium infection: Searching for molecules that modulate the asexual cycle as a strategy to impair the parasite cycle

Half of the world's population lives in countries at risk of malaria infection, which results in approximately 450,000 deaths annually. Malaria parasites infect erythrocytes in a coordinated manner, with cycle durations in multiples of 24 hours, which reflects a behavior consistent with the host's circadian cycle. Interference in cycle coordination can help the immune system to naturally fight infection. Consequently, there is a search for new drugs that interfere with the cycle duration for combined treatment with conventional antimalarials. Melatonin appears to be a key host hormone responsible for regulating circadian behavior in the parasite cycle. In addition to host factors, there are still unknown factors intrinsic to the parasite that control the cycle duration. In this review, we present a series of reports of indole compounds and melatonin derivatives with antimalarial activity that were tested on several species of Plasmodium to evaluate the cytotoxicity to parasites and human cells, in addition to the ability to interfere with the development of the erythrocytic cycle. Most of the reported compounds had an IC50 value in the low micromolar range, without any toxicity to human cells. Triptosil, an indole derivative of melatonin, was able to inhibit the effect of melatonin in vitro without causing changes to the parasitemia. The wide variety of tested compounds indicates that it is possible to develop a compound capable of safely eliminating parasites from the host and interfering with the life cycle, which is promising for the development of new combined therapies against malaria.     

Therapy of systemic lupus erythematosus: new agents and new evidence

Systemic lupus erythematosus (SLE) is a disease of relatively low prevalence with a wide range of clinical manifestations. Due in part to these two facts, there is little new evidence on the treatment of lupus. In fact, randomised controlled studies and prospective series are few and usually involve a small number of patients. Despite this, some therapies have shown to be beneficial within the last five years, while others emerge as possibilities in the near future. Among the former, antimalarials appear to be the treatment of choice for maintaining mild to moderate disease in remission. Methotrexate may be an alternative to other corticosteroid-sparing drugs, especially in patients with active arthritis and skin disease. Cyclosporin can be of use in proteinuric nephritis, although the incidence of hypertension with this drug is high. Thalidomide is useful for refractory skin lesions, but the efficacy of lower, less toxic doses is still to be studied. Immunoglobulins should probably be limited to selected patients with manifestations such as thrombocytopoenia. Experience is more limited with cladribine, fludarabine, tacrolimus, danazol and pentoxifylline. New therapies for severe SLE include mycophenolate mofetil, a potent immunosuppressive drug with a reasonable safety profile and immunoablative therapy with or without stem cell transplantation, in highly resistant cases or those with a poor prognosis. Other recently developed molecules, including anti-CD40L monoclonal antibodies (mAbs), are still under investigation.     

The η-class carbonic anhydrases as drug targets for antimalarial agents

Introduction: The η-class of carbonic anhydrases (CAs, EC 4.2.1.1) was recently discovered as the sixth genetic family of this metalloenzyme superfamily, and seems to be present only in various Plasmodium species, the malaria-provoking pathogens. The present review through detailed biochemical, kinetic and phylogenetic studies afford a clear view regarding the differences between η- and the other CA families.

Areas covered: In this review, the authors underlined as the η-CAs, like α-, γ- and δ-class enzymes, have the Zn(II) ion coordinated by three histidine residues and a water molecule. They seem to be more closely related to the α-CAs, but there are notable differences between them, such as the lack of the proton shuttle residue (His64) and gatekeeper residues, Glu106 and Thr199 in the η-CAs, which are conserved in all α-CAs.

Expert opinion: Plasmodium falciparum η-CA showed a moderate but significant activity for the CO₂ hydration reaction, with a k_cat of 1.4 × 10⁵s^-1 and a k_cat/K_m of 5.4 × 10⁶ M^-1 × s^-1. Several inhibition studies with anions and sulfonamides/sulfamates, allowed the identification of interesting lead compounds. The discovery of η-CA-specific inhibitors may lead to novel such agents with a new mechanism of action.     

Antimalarial drugs and drug targets specific to fatty acid metabolic pathway of Plasmodium falciparum

Plasmodium falciparum, a causitive agent of malaria, is the third most prevalent factor for mortility in the world. Falciparum malaria is an example of evolutionary and balancing selection. Because of mutation and natural selection, the parasite has developed resistance to most of the existing drugs. Under such circumstances, there is a growing need to develop new molecular targets in P. falciparum. A four membrane bound organelles called apicoplast, very much similar to that of chloroplast of plants, have been found in parasite. Therefore, the proteins involved in metabolic pathways of apicoplasts are important drug targets. Among the pathways in apicoplast, fatty acid biosynthetic pathway is the most important metabolic pathway in P. falciparum. Several studies have explored the role of different proteins involved in this pathway and antimalarial compounds against this target. In this review, we have studied the role of different proteins in fatty acid metabolism and designing, synthesis and evaluation of compounds against the targets identified in fatty acid metabolic pathway.     

Falsified antimalarials: a minireview

Malaria is a curable disease, provided timely access to efficacious drugs is sought. Poor quality and, in particular, falsified antimalarial drugs harm the population of malaria endemic areas; they put lives in peril, cause economic losses to patients, families, industry, and generally undermine the trust in health systems. The extent of the problem is not easily assessed, and although a prevalence of up to 35% of poor-quality antimalarials has been reported, this number should be interpreted with caution given the heterogeneity of methods used to measure it. The trade in falsified antimalarials can be curtailed by putting in place drug quality surveillance, better legislation and improving the access and affordability of these essential drugs.