Antigiardial Effect of Kramecyne in Experimental Giardiasis

Abstract

A variety of drugs are used in giardiasis treatment with different levels of efficiency, presence of side effects, and even formation of resistant strains, so that it is important to search new only-one-dose treatments with high efficiency and less side effects. Kramecyne, an anti-inflammatory compound isolated from methanolic extract of Krameria cytisoides, does not present toxicity, even at doses of 5,000 mg/kg. The objective was to determine the antigiardial effect of kramecyne over Giardia intestinalis in vitro and in vivo and analyze the expression of genes ERK1, ERK2, and AK on kramecyne treated trophozoites by Real Time Polymerase Chain Reaction (RTPCR). The median lethal dose (LD₅₀) was 40 μg/mL and no morphological changes were observed by staining with blue trypan and light microscopy; experimental gerbil infection was eliminated with 320 μg/Kg of weight. After treatment there were no differences between intestines from treated and untreated gerbils. Kramecyne did not have significant effect over ERK1 and AK, but there are differences in ERK2 expression (p = 0.04). Results show antigiardial activity of kramecyne; however the mode of action is still unclear and the evaluation of ultrastructural damage and expressed proteins is an alternative of study to understand the action mechanism.

Figure 1

Chemical structure of (a) kramecyne (cyclic polymer) and (b) monomer [12].

Figure 2

Trophozoites after treatment with 80 μg/mL of kramecyne stained with trypan blue dye. Preparation allows differentiating dead cells (in blue; SC) and transparent living cells (NSC). No structural damage is observed caused by contact with kramecyne. Olympus BH (40x).

Figure 3

Results of effect in vitro, percentage of inhibition of two strains (P-I and WB ) of Giardia intestinalis axenically cultured treated with different concentrations of kramecyne (K), LD₅₀2 value = 40 μg/mL for both strains. Percentages of inhibition of P-I and P-I(r) are also observed (LD₅₀1 = 12 and LD₅₀3 = 70 μg/mL, resp.).

Figure 4

Graph of kramecyne concentration versus Ct values showing results of the expression determined by Real Time PCR reaction for the genes ERK1 (z = 0.5), ERK2 (z = 0.04), and AK (z = 0.99).