Activities of psilostachyin A and cynaropicrin against Trypanosoma cruzi in vitro and in vivo

Abstract

In vitro and in vivo activities against Trypanosoma cruzi were evaluated for two sesquiterpene lactones: psilostachyin A and cynaropicrin. Cynaropicrin had previously been shown to potently inhibit African trypanosomes in vivo, and psilostachyin A had been reported to show in vivo effects against T. cruzi, albeit in another test design. In vitro data showed that cynaropicrin was more effective than psilostachyin A. Ultrastructural alterations induced by cynaropicrin included shedding events, detachment of large portions of the plasma membrane, and vesicular bodies and large vacuoles containing membranous structures, suggestive of parasite autophagy. Acute toxicity studies showed that one of two mice died at a cynaropicrin dose of 400 mg/kg of body weight given intraperitoneally (i.p.). Although no major plasma biochemical alterations could be detected, histopathology demonstrated that the liver was the most affected organ in cynaropicrin-treated animals. Although cynaropicrin was as effective as benznidazole against trypomastigotes in vitro, the treatment (once or twice a day) of T. cruzi-infected mice (up to 50 mg/kg/day cynaropicrin) did not suppress parasitemia or protect against mortality induced by the Y and Colombiana strains. Psilostachyin A (0.5 to 50 mg/kg/day given once a day) was not effective in the acute model of T. cruzi infection (Y strain), reaching 100% animal mortality. Our data demonstrate that although it is very promising against African trypanosomes, cynaropicrin does not show efficacy compared to benznidazole in acute mouse models of T. cruzi infection.

Fig 1

Structures of cynaropicrin and psilostachyin A.

Fig 2

Transmission electron microscopy analysis of cynaropicrin's effects on bloodstream trypomastigotes. BT were left untreated (A and B) or exposed to this STL (EC₅₀/24 h) for 2 h (C to F). Untreated parasites displayed typical morphology, while cynaropicrin-treated parasites showed vacuolization (*), swelling of the mitochondrion and endoplasmic reticulum (white arrows), and plasma membrane shedding (black arrows). M, mitochondrion; G, Golgi complex; N, nucleus.

Fig 3

Histopathologic analysis of untreated female mice (A) and female mice treated with 200 (B)- and 400 (C)-mg/kg doses of cynaropicrin. (A) Liver section from an untreated animal, stained with hematoxylin-eosin and showing characteristic morphology. (B) Liver section from a treated mouse, exhibiting an inflammatory infiltrate (white arrow) in addition to the occurrence of hepatocyte vacuolization (black stars). (C) Liver regeneration area (circle) with binucleated cells (black arrows). Original magnification, ×400.

Fig 4

In vivo effects of psilostachyin A (A and B) and cynaropicrin (C to F) in acute mouse models of infection using different T. cruzi strains: Y (A to D) and Colombiana (E and F). Parasitemia (A, C, and E) and cumulative mortality (B, D, and F) data are shown. (A and B) The effects of psilostachyin A (Psilo) (i.p.) and Bz (p.o.) were followed using doses of up to 50 mg/kg/day, administered at 5 and 8 dpi. (C and D) The effects of cynaropicrin (cyna) and Bz were followed using doses of up to 50 mg/kg/day for cynaropicrin (i.p.) and 100 mg/kg/day for Bz (p.o.), administered at 5 and 8 dpi. (E and F) The effects of cynaropicrin and Bz were followed using doses of 25 mg/kg/day for cynaropicrin (i.p., b.i.d.) and 100 mg/kg/day for Bz (p.o.), administered for 2 consecutive days starting at the onset of parasitemia (11 dpi).