Low-level Laser Therapy to the Mouse Femur Enhances the Fungicidal Response of Neutrophils against Paracoccidioides brasiliensis

Abstract

Neutrophils (PMN) play a central role in host defense against the neglected fungal infection paracoccidioidomycosis (PCM), which is caused by the dimorphic fungus Paracoccidioides brasiliensis (Pb). PCM is of major importance, especially in Latin America, and its treatment relies on the use of antifungal drugs. However, the course of treatment is lengthy, leading to side effects and even development of fungal resistance. The goal of the study was to use low-level laser therapy (LLLT) to stimulate PMN to fight Pb in vivo. Swiss mice with subcutaneous air pouches were inoculated with a virulent strain of Pb or fungal cell wall components (Zymosan), and then received LLLT (780 nm; 50 mW; 12.5 J/cm2; 30 seconds per point, giving a total energy of 0.5 J per point) on alternate days at two points on each hind leg. The aim was to reach the bone marrow in the femur with light. Non-irradiated animals were used as controls. The number and viability of the PMN that migrated to the inoculation site was assessed, as well as their ability to synthesize proteins, produce reactive oxygen species (ROS) and their fungicidal activity. The highly pure PMN populations obtained after 10 days of infection were also subsequently cultured in the presence of Pb for trials of protein production, evaluation of mitochondrial activity, ROS production and quantification of viable fungi growth. PMN from mice that received LLLT were more active metabolically, had higher fungicidal activity against Pb in vivo and also in vitro. The kinetics of neutrophil protein production also correlated with a more activated state. LLLT may be a safe and non-invasive approach to deal with PCM infection.

Low‐level laser therapy stimulates the oxidative burst in human neutrophils and increases their fungicidal capacity

“…Nevertheless, we believe that although LLLT can reduce the influx of PMN into a given site of inflammation, somewhat paradoxically, LLLT may also be able to increase the individual activity levels of those PMN. In a recent study we were able to demonstrate that even though irradiated PMN were present in lower numbers, they were far more active against virulent forms of Paracoccidioides brasiliensis (Pb), which is the fungus responsible for a neglected tropical disease known as paracoccidioidomycosis (PCM) .…”

“…We have previously studied the effects of LLLT upon the behavior of PMN acting against an important fungal infection ( Paracoccidioides brasiliensis ), and observed that LLLT induced lesser PMN migration to the infection site; however, the PMN that did reach the site of infection were significantly more activated towards the fungal cells and could efficiently kill the microorganism due to higher PMN viability, and greater production of ROS as well as pro‐inflammatory proteins .…”

Effect of laser therapy on immune cells infiltrate after excisional wounds in diabetic rats

“…Studies with an arthritis model , and fungal disease model have found that laser therapy can improve the chemotaxis of neutrophils. However, the results in the literature on diabetic models are conflicting.…”

“…PBM is believed to promote angiogenesis, enhance neovascularization, increase collagen synthesis, and accelerate the healing of skin wounds . Recent studies have found that PBM at different wavelengths can modulate neutrophil chemotaxis and the cellular activation status of macrophages in inflammation processes .…”

Resistance to P. brasiliensis Experimental Infection of Inbred Mice Is Associated with an Efficient Neutrophil Mobilization and Activation by Mediators of Inflammation

“…Three other routes can also be mentioned, intravenous [ 23 ], intraoral [ 24 ], and intratracheal [ 25 ], and were not included in the present investigation. Nevertheless, the subcutaneous air-pouch technique that had already been shown to raise an almost pure pool of PMN, also being a local and controlled Pb infection [ 18 , 26 ], was now compared to other classical methods and did present the highest numbers of mature PMN in marrow, as well as recruited PMN in loco . Intraperitoneal injection of Pb , on the other hand, leads to an exsudate composed of 40–50% PMN [ 27 ].…”