• Parasites, Hosts and Diseases
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• 제54권4호
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• pp.415-421
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• 2016

The drug-resistance of malaria parasites is the main problem in the disease control. The huge Brazilian biodiversity promotes the search for new compounds, where the animal kingdom is proving to be a promising source of bioactive compounds. The main objective of this study was to evaluate the antiplasmodial and cytotoxic activity of the compounds obtained from the toad venoms of Brazilian Amazon. Toad venoms were collected from the secretion of Rhinella marina and Rhaebo guttatus in Mato Grosso State, Brazil. The powder was extracted at room temperature, yielding 2 extracts (RG and RM) and a substance ('1') identified as a bufadienolide, named telocinobufagin. Growth inhibition, intraerythrocytic development, and parasite morphology were evaluated in culture by microscopic observations of Giemsa-stained thin blood films. Cytotoxicity was determined against HepG2 and BGM cells by MTT and neutral red assays. The 2 extracts and the pure substance ('1') tested were active against chloroquine-resistant Plasmodium falciparum strain, demonstrating lower $IC_{50}$ values. In cytotoxic tests, the 2 extracts and substance '1' showed pronounced lethal effects on chloroquine-resistant P. faciparum strain and low cytotoxic effect, highlighting toad parotoid gland secretions as a promising source of novel lead antiplasmodial compounds.

• Parasites, Hosts and Diseases
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• 제53권4호
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• pp.421-430
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• 2015

The parasite Plasmodium falciparum causes severe malaria and is the most dangerous to humans. However, it exhibits resistance to their drugs. Farnesyltransferase has been identified in pathogenic protozoa of the genera Plasmodium and the target of farnesyltransferase includes Ras family. Therefore, the inhibition of farnesyltransferase has been suggested as a new strategy for the treatment of malaria. However, the exact functional mechanism of this agent is still unknown. In addition, the effect of farnesyltransferase inhibitor (FTIs) on mitochondrial level of malaria parasites is not fully understood. In this study, therefore, the effect of a FTI R115777 on the function of mitochondria of P. falciparum was investigated experimentally. As a result, FTI R115777 was found to suppress the infection rate of malaria parasites under in vitro condition. It also reduces the copy number of mtDNA-encoded cytochrome c oxidase III. In addition, the mitochondrial membrane potential (${\Delta}{\Psi}m$) and the green fluorescence intensity of MitoTracker were decreased by FTI R115777. Chloroquine and atovaquone were measured by the mtDNA copy number as mitochondrial non-specific or specific inhibitor, respectively. Chloroquine did not affect the copy number of mtDNA-encoded cytochrome c oxidase III, while atovaquone induced to change the mtDNA copy number. These results suggest that FTI R115777 has strong influence on the mitochondrial function of P. falciparum. It may have therapeutic potential for malaria by targeting the mitochondria of parasites.

• Parasites, Hosts and Diseases
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• 제47권2호
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• pp.139-144
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• 2009

The aim of the present study was to investigate antimalarial drug pressure resulting from the clinical use of different antimalarials in Thailand. The phenotypic diversity of the susceptibility profiles of antimalarials, i.e., chloroquine (CQ), quinine (QN), mefloquine (MQ), and artesunate (ARS) in Plasmodium falciparum isolates collected during the period from 1988 to 2003 were studied. P. falciparum isolates from infected patients were collected from the Thai-Cambodian border area at different time periods (1988-1989, 1991-1992, and 2003), during which 3 different patterns of drug use had been implemented: MQ+sulphadoxine (S)+pyrimethamine (P), MQ alone and MQ+ARS, respectively. The in vitro drug susceptibilities were investigated using a method based on the incorporation of $[^3H]$ hypoxanthine. A total of 50 isolates were tested for susceptibilities to CQ, QN, MQ, and ARS. Of these isolates, 19, 16, and 15 were adapted during the periods 1988-1989, 1991-1993, and 2003, respectively. P. falciparum isolates collected during the 3 periods were resistant to CQ. Sensitivities to MQ declined from 1988 to 2003. In contrast, the parasite was sensitive to QN, and similar sensitivity profile patterns were observed during the 3 time periods. There was a significantly positive but weak correlation between the $IC_{50}$ values of CQ and QN, as well as between the $IC_{50}$, values of QN and MQ. Drug pressure has impact on sensitivity of P. falciparum to MQ. A combination therapy of MQ and ARS is being applied to reduce the parasite resistance, and also increasing the efficacy of the drug.

• Journal of Korean Neurosurgical Society
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• 제38권1호
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• pp.47-53
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• 2005

Objective : Anti-malaria drugs may modulate tumor resistance to chemotherapeutic agents, but it has not been proven effective in the treatment of malignant gliomas. The aim of this study was to determine whether adequate pre-clinical data on co-administration of chemotherapeutic agents with anti-malaria drugs on malignant cell lines could be obtained that would warrant its further potential consideration for use in a clinical trial for malignant gliomas. Methods : Two malignant glioma cell lines [U87MG, T98G] were treated with chemotherapeutic agents alone or with anti-malaria drugs. Cells were incubated with drugs for 4 days. Following the 4-day incubation, drug sensitivity assays were performed using 3-[4,5-dimethyl-2-thiazol-2-yl] 2,5-diphenyltetrazolium bromide [MTT] assay following optimization of experimental conditions for each cell lines and cell viability was calculated. Results : In all of four chemotherapeutic agents[doxorubicin. vincrisitne, nimustine, and cisplatin], the cell viability was found to be markedly decreased when hydroxychloroquine was co-administered on both U87MG and T98G cell lines. The two way analysis of variance[ANOVA] yielded a statistically significant two-sided p-value of 0.0033[doxorubicin], 0.0005[vincrisitne], 0.0007[nimustine], and 0.0003[cisplatin] on U87MG cell lines and 0.0006[doxorubicin], 0.0421[vincrisitne], 0.0317[nimustine], and 0.0001[cisplatin] on T98G cell lines, respectively. However, treatment with chloroquine and primaquine did not induce a decrease in cell viability on both U87MG and T98G cell lines. Conclusion : Our data support further consideration of the use of hydroxychloroquine prior to systemic chemotherapy to maximize its tumoricidal effect for patients with malignant gliomas.

• Journal of Digestive Cancer Research
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• 제4권1호
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• pp.1-9
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• 2016

The abundance of multi-drug resistance ATPase binding cassette and deranged self-renewal pathways shown in cancer stem cells (CSCs) played a crucial role in tumorigenesis, tumor resistance, tumor recurrence, and tumor metastasis. Therefore, elucidation of CSCs biology can improve diagnosis, enable targeted treatment, and guide the follow up of GI cancer patients. In order to achieve chemoquiescence, seizing cancer through complete ablation of CSCs, CSCs are rational targets for the design of interventions that will enhance responsiveness to traditional therapeutic strategies and contribute in the prevention of local recurrence as well as metastasis. However, current cancer treatment strategies fail to either detect or differentiate the CSCs from their non-tumorigenic progenies mostly due to the absence of specific biomarkers and potent agents to kill CSCs. Recent advances in knowledge of CSCs enable to produce several candidates to ablate CSCs in gastrointestinal (GI) cancers, especially cancers originated from inflammation-driven mutagenesis such as Barrett's esophagus (BE), Helicobacter pylori-associated gastric cancer, and colitis-associated cancer (CAC). Our research teams elucidated through revisiting old drugs that proton pump inhibitor (PPI) and potassium competitive acid blocker (p-CAB) beyond authentic acid suppression, chloroquine for autophage inhibition, sonic hedgehog (SHH) inhibitors, and Wnt/β-catenin/NOTCH inhibitor can ablate CSCs specifically and efficiently. Furthermore, nanoformulations of these molecules could provide an additional advantage for more selective targeting of the pathways existing in CSCs just like current molecular targeted therapeutics and sustained action, while normal stem cells intact. In this review article, the novel approach specifically to ablate CSCs existing in GI cancers will be introduced with the introduction of explored mode of action.

• 동의생리병리학회지
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• 제23권2호
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• pp.494-498
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• 2009

The emergence and spread of drug-resistant malaria parasites is a serious public health problem in the tropical world. Useful antimalarial drugs such as chloroquine have resistance in the world now. Moreover, other antimalarialdrugs such as mefloquine, halofantrine, atovaquone, proguanil, artemether and lumefantrine retain efficacy but have limitations, one of which is their high cost. New antimalarial drugs are clearly needed now. Cytotoxicity assay and susceptibility assay were performed for the selectivity of herb extracts in vitro. On the basis of high selectivity, 4-day suppressive test and survival test were progressed in Plasmodium berghei-infected mice. The selectivity of Areca catechu L. (ACL) and butanol extract of ACL (ACL-BuOH extract) were 3.4 and 3.0 in vitro, respectively. Moreover in vivo, 4-day suppressive test showed 39.1 % inhibition effect after treated with 150 mg/kg/day ACL-BuOH to P. berghei-infected mice. Survival test also showed 60% survival rate with ACL-BuOH-treated group while all other group mice died. In this study, ACL and ACL-BuOH were investigated for antimalarial activity in vitro and in vivo and they showed a potent antimalarial activity. In particular,ACL-BuOH could specifically lead higher survival rate of mice in vivo. Therefore ACL-BuOH would be a candidate of antimalarial drugs.

• Parasites, Hosts and Diseases
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• 제36권2호
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• pp.143-146
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• 1998

최근 primaquine으로 완치 (radicalcure)된 후에도 재발하는 삼일열 말라리아 보고가 많아지면 서 primaquine에 대한 내성 가능성이 언급되고 있다. 저자들은 해외여행 중에 감염된 삼일열 말라리아를 hydroxychloroquine과 primaquine으로 치료한 후 재발한 예를 경험하였기에 문헌고찰과 함께 보고한다. 35세 남자 환자가 내원 34일 전부터 15일간 인도 뭄바이와 중국 쉬천에 출장 다녀왔고 귀국 3일 후부터 고열이 발생하여 발열 17일째 본원에 입원하였다. 말초혈액 도말검사에 서 분열체 내의 분열소체의 수가 14개 이상 되고 세포질 형태가 불규칙적인 영양형이 보여 삼일열 말라리아로 진단한 후 hydrouychloroquine를 투여하고 열이 떨어진 후 primaquine (15 mg/일, 14일간)을 투여하였다. 치료 후 55일째까지 말라리아 재발의 증상이 없었고 말초혈액 도말에서도 말라리아 원충이 없음을 확인하였다. 6개월 후 다시 발열이 생기고 말초혈액 도말검사에서 분열소 체와 영양형이 보여 재발로 진단하였다 처음 입원 때와 같은 방법으로 치료하였고 현재까지 10개월간 경과 관찰 중이며 증상의 재발은 없었다.