The first evaluation of the in vitro effects of silver(I)-N-heterocyclic carbene complexes on Encephalitozoon intestinalis and Leishmania major promastigotes

Abstract

Encephalitozoon intestinalis is an opportunistic microsporidian parasite that primarily infects immunocompromised individuals, such as those with HIV/AIDS or undergoing organ transplantation. Leishmaniasis is responsible for parasitic infections, particularly in developing countries. The disease has not been effectively controlled due to the lack of an effective vaccine and affordable treatment options. Current treatment options for E. intestinalis infection and leishmaniasis are limited and often associated with adverse side effects. There is no previous study in the literature on the antimicrosporidial activities of Ag(I)-N-heterocyclic carbene compounds. In this study, the in vitro antimicrosporidial activities of previously synthesized Ag(I)-N-heterocyclic carbene complexes were evaluated using E. intestinalis spores cultured in human renal epithelial cell lines (HEK-293). Inhibition of microsporidian replication was determined by spore counting. In addition, the effects of the compounds on Leishmania major promastigotes were assessed by measuring metabolic activity or cell viability using a tetrazolium reaction. Statistical analysis was performed to determine significant differences between treated and control groups. Our results showed that the growth of E. intestinalis and L. major promastigotes was inhibited by the tested compounds in a concentration-dependent manner. A significant decrease in parasite viability was observed at the highest concentrations. These results suggest that the compounds have potential anti-microsporidial and anti-leishmanial activity. Further research is required to elucidate the underlying mechanisms of action and to evaluate the efficacy of the compounds in animal models or clinical trials.

Keywords: Encephalitozoon intestinalis; Leishmania; Microsporidia; N-heterocyclic carbene; Silver.

Fig. 1

Treatment drugs for Leishmaniasis and Microsporidia infections

Scheme 1

Synthesis of Ag(I)-NHC complexes, 2a–d

Fig. 2

In vitro cytotoxicity of 10⁻⁴, 10⁻⁵, 10⁻⁶, and 10⁻⁷ M concentrations of Ag(I)-NHC complexes (2a–d) on human renal epithelial cells (HEK-293) by XTT method. *p < 0.05 vs. control

Fig. 3

In vitro activity of 10⁻⁵, 10⁻⁶ and 10⁻⁷ M concentrations of Ag(I)-NHC complexes (2a–d) against E. intestinalis spores (A) and L. major promastigotes (B). *p < 0.05 vs control. Data are expressed as mean ± SD

Fig. 4

On day 10, the appearance of host cells and E. intestinalis spores were treated with three different concentrations of the Ag(I)–NHC complexes (2a–d) and stained with Trichrom stain (× 100). Spores are seen dispersed intracellularly and extracellularly (arrows)