Terapia fotodinâmica antimicrobiana (aPDT) com curcumina controla infecção intradérmica por Staphylococcus aureus resistente a meticilina em camundongos com Diabetes tipo 1

Abstract

Type 1 Diabetes Mellitus (T1DM) is a chronic non-communicable disease in which insulin is insufficiently produced due to the destruction of β cells in the pancreas. The changes generated by this condition increase the risk of infections for these individuals. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the main pathogens causing infections in individuals with diabetes. In this work, we aimed to investigate the effects of the application of photodynamic therapy (PDT), using curcumin as a photosensitizer (PS), in the treatment of intradermal infection in mice with T1DM. C57bl/6 mice were weighed and, in a fasting state, their blood glucose was measured. DMT1 was induced by intraperitoneal injection of a single dose of streptozotocin (STZ) (180 mg/kg). Five days after STZ administration, the animals' blood glucose was measured to confirm the establishment of DMT1. Fifteen days after DMT1 induction, the animals were weighed and then infected intradermally in the left ear. For infection, the concentration of 1.5 x 107 CFU of the MRSA ATCC 4330 strain was quantified. Twenty-four hours after infection, the animals were separated in three groups. A solution containing 100 μg of curcumin was photoactivated ex vivo using LED light (450 nm) obtaining a fluence of 13.5 J/cm2 which consists in experimental group. After photoactivation, the solution was inoculated at the infection site. Control treatments consisted of the application of non-photoactivated curcumin or sterile saline. The animals were euthanized 24 h after the treatments and the left ear and left retromaxillary lymph node were surgically collected. The lymph node was macerated in saline for analysis of bacterial load, measurement of cytokines by ELISA, measurement of nitrites and nitrates, and cell counts. The ear was used to make slides that were stained by H&E or stained with anti-myeloperoxidase (MPO) antibodies by immunohistochemistry. Slides were photomicrographed and cell counts and tissue MPO expression analyzes were performed. The PDT group had a lower bacterial load in the lymph node when compared to controls (p-value <0.05). In addition to the lower bacterial load, the PDT group also had higher levels of nitrates and nitrites in the lymph node when compared to controls (p-value < 0.001). Cell recruitment to the infectious site on ear was similar between the PDT group compared with the control groups, however, the expression of MPO in the PDT group was less intense compared to the saline group (p-value < 0.001). When analyzing the production of cytokines, the PDT group showed lower production of IL-1, IL-12, and IL-10 (p-value <0.01; p-value <0.05; p-value < 0.05, respectively), when compared to the saline group. This study shows, for the first time, the therapeutic potential of PDT using curcumin in the treatment of an intradermal infection caused by S. aureus in mice with T1DM.