Effects of methylene blue-mediated photodynamic inactivation associated to NO-releasing chitosan nanoparticles on cutaneous leishmaniasis in mice

Abstract

Cutaneous leishmaniasis (C L) is a ehronie disease developed by parasites of the genus Leishmania that promotes destruetive.and ulcerated lesions. The available treatments are limited beeause of side effeets, resistanee and toxieity. Reaetive oxygen speeies and nitrie oxide (NO) are potentially toxic to these parasites; Photodynamie inaetivation (PDI) involves the generation af oxidative stress and has been explored as an altemative treatment once it is less expensive and no reports about resistanee have been describedY Additionally, several studies indicate that the administration of exogenous NO donors represents an interesting strategy against CL.3 The aim of this work was to explore the effects Df methylene blue (MB)-mediated PDI in assoeiation with encapsulated NO donors (S-nitroso-MSA) in chitosan nanoparticles (CSNPs) on CL in BALB/e mice using real time bioluminescence. Promastigotes of L. (L) amazonensis transgenie line expressing luciferase were used. Sixteen BALB/e miee were infected in the left footpad with 1.106 promastigotes. After 4 weeks, mice were randomly assigned to experimental groups (n=4): Control (non-treated), PDI (treated only with PDI), PDI+CSNP (submitted to PDI and S-nitroso-MSA-CSNPs) and CSNP (treated only with S-nitroso-MSA-CSNPs). PDI was administered in two sessions separated by 24 h and CSNPs (80 eM) were applied immediately after the second PDI session. PDI was performed using a red LED (0= 660 ± 22 nm), MB (100 IlM), irradiance of 100 mW/cm2 and radiant exposure of 150 J/cm2 • parasite burden was analyzed through luciferase deteetion by bioimaging in the first 96 h following treatment and every week during 4 weeks. Statistically significant differences were considered when p < 0.05. Test groups presented significant reduction in parasite load compared to control during all experimental period. Twenty-four-h after treatments, parasite burden was lower for PDI+CSNP group but no statistically signifieant difference was observed when compared to other test groups. After 48 h, all test groups were similar. Besides, parasite load in test groups remained lower than control following 1, 2,3 and 4 weeks post-treatment. Under conditions used in this study, we conclude that CSNPs were not able to enhance MBmediated PDI efficiency in L. (L) amazonensis-induced CL in mice.