Activity of Chitosan and Its Derivatives against Leishmania major and Leishmania mexicana In Vitro

Abstract

There is an urgent need for safe, efficacious, affordable, and field-adapted drugs for the treatment of cutaneous leishmaniasis, which newly affects around 1.5 million people worldwide annually. Chitosan, a biodegradable cationic polysaccharide, has previously been reported to have antimicrobial, antileishmanial, and immunostimulatory activities. We investigated the in vitro activity of chitosan and several of its derivatives and showed that the pH of the culture medium plays a critical role in antileishmanial activity of chitosan against both extracellular promastigotes and intracellular amastigotes of Leishmania major and Leishmania mexicana. Chitosan and its derivatives were approximately 7 to 20 times more active at pH 6.5 than at pH 7.5, with high-molecular-weight chitosan being the most potent. High-molecular-weight chitosan stimulated the production of nitric oxide and reactive oxygen species by uninfected and Leishmania-infected macrophages in a time-and dose-dependent manner at pH 6.5. Despite the in vitro activation of bone marrow macrophages by chitosan to produce nitric oxide and reactive oxygen species, we showed that the antileishmanial activity of chitosan was not mediated by these metabolites. Finally, we showed that rhodamine-labeled chitosan is taken up by pinocytosis and accumulates in the parasitophorous vacuole of Leishmaniainfected macrophages.

Activity of Amphotericin B-Loaded Chitosan Nanoparticles against Experimental Cutaneous Leishmaniasis

“…In our previous study (Riezk et al 2020), we described how chitosan (HMW) was active in vitro against intracellular L. major amastigotes [ 21 ]. To translate this activity into an in vivo model of L. major infection, we used chitosan nanoparticles prepared by the ionotropic gelation method as a drug delivery vehicle for AmB because chitosan nanoparticles: (i) potentially reduce the toxicity of AmB, improve its efficacy, modulate AmB pharmacokinetics, permit sustainable AmB release at the site of infection and protect the drug from degradation [ 15 , 33 , 38 ], (ii) have promising features for DDS due to their biocompatibility, biodegradability, controlled drug release, mucoadhesiveness, wound healing and antimicrobial properties [ 11 , 12 , 39 ] and (iii) have high stability at different temperatures and a simple preparation process [ 40 , 41 ] while other drug carriers, such as liposomal formulations, need the cold chain for stability, have a complex preparation process and can be costly which limits their use [ 22 , 27 , 29 ].…”

“…Similar findings have been reported for AmB-loaded chitosan-chondroitin sulphate nanoparticles, which showed less toxicity against RBC and murine macrophages than AmB solution [ 15 ]. Lowering the pH of RPMI medium from 7.5 to 6.5 increased the anti-leishmanial activity of chitosan solution and CH-TPP nanoparticles against L. major and L. mexicana promastigotes and amastigotes by 7–20× due to the greater chitosan ionisation at lower pH for both chitosan solution and CH-TPP nanoparticles (positive surface charge) [ 21 ]. AmB-loaded chitosan nanoparticles showed a similar activity against L. major and L. mexicana promastigotes and amastigotes to AmB solution and significantly higher activity than AmBisome ® at the two pH values.…”

“…We have previously demonstrated that chitosan solution (high molecular weight (HMW)) has a pH-dependent anti-leishmanial activity and this activity was not due to immune activation. Instead, the anti-leishmanial activity was related to direct chitosan pinocytic uptake into the parasitophorous vacuole (PV) in the host cell [ 21 ].…”

Chitosan Contribution to Therapeutic and Vaccinal Approaches for the Control of Leishmaniasis

“…Thus, low molecular weight chitosan, with 95% degree of deacetylation, was completely effective at concentrations of 100 μg/mL on promastigotes of L. major after 180 min of application [ 27 ]. In vitro activities of chitosan and some of its derivatives have also been studied in depth against L. major and L. mexicana , showing that the pH of the culture medium is critical for the activity against both promastigotes and intramacrophage amastigotes [ 28 ]. Thus, chitosan and its derivatives appeared approximately 7 to 20 times more efficient at pH 6.5 than at pH 7.5, and high-molecular-weight chitosan was the most active.…”

“…Although the production of nitric oxide and reactive oxygen species was stimulated by high-molecular-weight chitosan in both uninfected and Leishmania -infected macrophages in a time- and dose-dependent manner at pH 6.5, the antileishmanial activity of chitosan was found not to be mediated by these metabolites. Analysis of the mechanism of action, based upon confocal imaging showed that rhodamine-labeled chitosan was taken up by pinocytosis and accumulated in the parasitophorous vacuole of Leishmania -infected macrophages [ 28 ]. This is the first demonstration of the mechanism of chitosan uptake by Leishmania -infected macrophages and of its location within the parasitophorous vacuole.…”