Photoinactivation of Leishmania amazonensis by Soranjidiol and White LED: Unraveling Photodynamic and Cell Death Mechanisms

Abstract

Leishmaniasis is a group of neglected diseases that pose significant health challenges worldwide. These infections are transmitted through the bites of hematophagous sandflies, which deposit Leishmania parasites into the skin. Despite the many years that have passed since the discovery of pentavalent antimonials, effective and low-cost therapies remain a challenge. Antimicrobial photodynamic therapy (aPDT) is a localized treatment that has successfully killed various pathogens without inducing resistance. Soranjidiol (Sor), a natural anthraquinone, has shown promising in vitro and in vivo results against Leishmania amazonensis. This study aims to elucidate the photodynamic and cell death mechanisms of Soranjidiol by evaluating two different concentrations in both promastigote and amastigote forms of Leishmania. Our results demonstrate that Soranjidiol is a versatile and effective photosensitizer (PS) capable of eliminating both parasite morphologies at low concentrations through reactive species, inducing either apoptosis or necrosis depending on the concentration used. Although both singlet oxygen and radicals are believed to be generated after PDT, our findings clearly indicate a predominance of type II reactions at low PS concentrations and type I reactions at the highest concentration tested. Finally, the application of serial PDT sessions appears to be a promising strategy for achieving complete lesion healing.