Pinto-Almeida António, Mendes Tiago, Armada Ana, Belo Silvana, Carrilho Emanuel, Viveiros Miguel, Afonso Ana
Graduate Program in Areas of Basic and Applied Biology, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal; Medical Parasitology Unit, Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Lisbon, Portugal; Universidade de São Paulo, Instituto de Química de São Carlos, São Carlos, SP, Brazil.
Medical Parasitology Unit, Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Lisbon, Portugal; Institute of Biology, Universidade de Campinas, Campinas, SP, Brazil.
PLoS One. 2015 Oct 7;10(10):e0140147. doi: 10.1371/journal.pone.0140147. eCollection 2015.
Schistosomiasis is a neglected disease caused by a trematode of the genus Schistosoma that is second only to malaria in public health significance in Africa, South America, and Asia. Praziquantel (PZQ) is the drug of choice to treat this disease due to its high cure rates and no significant side effects. However, in the last years increasingly cases of tolerance to PZQ have been reported, which has caused growing concerns regarding the emergency of resistance to this drug.
METHODOLOGY/PRINCIPAL FINDINGS: Here we describe the selection of a parasitic strain that has a stable resistance phenotype to PZQ. It has been reported that drug resistance in helminths might involve efflux pumps such as members of ATP-binding cassette transport proteins, including P-glycoprotein and multidrug resistance-associated protein families. Here we evaluate the role of efflux pumps in Schistosoma mansoni resistance to PZQ, by comparing the efflux pumps activity in susceptible and resistant strains. The evaluation of the efflux activity was performed by an ethidium bromide accumulation assay in presence and absence of Verapamil. The role of efflux pumps in resistance to PZQ was further investigated comparing the response of susceptible and resistant parasites in the absence and presence of different doses of Verapamil, in an ex vivo assay, and these results were further reinforced through the comparison of the expression levels of SmMDR2 RNA by RT-PCR.
CONCLUSIONS/SIGNIFICANCE: This work strongly suggests the involvement of Pgp-like transporters SMDR2 in Praziquantel drug resistance in S. mansoni. Low doses of Verapamil successfully reverted drug resistance. Our results might give an indication that a combination therapy with PZQ and natural or synthetic Pgp modulators can be an effective strategy for the treatment of confirmed cases of resistance to PZQ in S. mansoni.
血吸虫病是一种由血吸虫属吸虫引起的被忽视的疾病，在非洲、南美洲和亚洲，其在公共卫生重要性方面仅次于疟疾。吡喹酮（PZQ）因其高治愈率且无明显副作用，是治疗该疾病的首选药物。然而，近年来，越来越多对PZQ耐受的病例被报道，这引发了人们对该药物耐药性出现的日益担忧。
方法/主要发现：在此，我们描述了一种对PZQ具有稳定耐药表型的寄生虫株的筛选。据报道，蠕虫中的耐药性可能涉及外排泵，如ATP结合盒转运蛋白家族的成员，包括P-糖蛋白和多药耐药相关蛋白家族。在此，我们通过比较易感和耐药株中外排泵的活性，评估外排泵在曼氏血吸虫对PZQ耐药性中的作用。外排活性的评估通过在有和没有维拉帕米的情况下进行溴化乙锭积累试验来进行。在体外试验中，通过比较在不同剂量维拉帕米存在和不存在时易感和耐药寄生虫的反应，进一步研究外排泵在对PZQ耐药性中的作用，并且通过逆转录聚合酶链反应（RT-PCR）比较SmMDR2 RNA的表达水平，进一步强化了这些结果。
结论/意义：这项工作有力地表明，类似Pgp的转运蛋白SMDR2参与了曼氏血吸虫对吡喹酮的耐药性。低剂量的维拉帕米成功逆转了耐药性。我们的结果可能表明，PZQ与天然或合成的Pgp调节剂联合治疗可能是治疗确诊的曼氏血吸虫对PZQ耐药病例的有效策略。
