Could Metformin act through the lysosomal Ragulator complex to coordinate TOR inhibition in Echinococcus sp.?

LOOS JULIA .A.; DÁVILA VALERIA A.; D´ANTONI CECILIA; CUMINO ANDREA C.

Lima

Congreso; XXVIII World Congress on Echinococcosis; 2019

Asociación Internacional de Hidatología y Ministerio de Salud de Perú

Metformin (Met) is an anti-hyperglycemic agent, which also exerts antiproliferativeeffects. Recent data reveal that Met activates AMPK and inhibits TOR (the catalyticsubunit of TORC1) by multiple, mutually nonexclusive mechanisms that do notnecessarily depend on the inhibition of electron transport chain and the cellular ATPlevel. Among these, the assembly of the v-ATPase-Ragulator-AXIN/LKB1-AMPKcomplex on the lysosome surface appears to be of greatest significance at therapeuticallyachievable concentrations of this drug. We have previously shown that Met exhibitsconsiderable in vitro and in vivo activity against E. granulosus larval stage. Here, weextended the study and evaluated the effect of the drug on E. multilocularis. Metforminpartially arrested the in vitro differentiation of protoscoleces into metacestode vesiclesand exerted a dose-dependent effect on the viability of parasite primary cells. At themolecular level, the drug induced depolarization of the mitochondrial membrane,activation of AMPK (increased Em-AMPKɑ-P176), suppression of Em-TOR (decreasedEm-TOR-P3122) and overexpression of the autophagic marker Em-Atg8 in the germinallayer of in vitro cultivated metacestode vesicles. Besides, while insulin increased thelevels of active Em-TOR, rapamycin reduced them in larval vesicles. Based on our invitro results, we then examined the in vivo effect of Met on the growth of E.multilocularis larval stage in mice. Oral administration of Met (50 mg/kg/day for 8weeks) was effective in achieving a significant reduction of parasite weight (1.5 ± 1.1 g)compared to untreated group (3.14 ± 1.1 g). Finally, by in silico assays, the presence ofthe key lysosomal pathway components were confirmed in the parasite. These resultssuggest that Met inhibits the development of Echinococcus spp. through AMPKactivation and TOR inhibition and raise the question of whether this occurs indirectly, asa consequence of ATP synthesis inhibition, and/or directly, by the lysosomal pathway.