Topical and Intradermal Efficacy of Photodynamic Therapy with Methylene Blue and Light-Emitting Diode in the Treatment of Cutaneous Leishmaniasis Caused by Leishmania braziliensis

Antimicrobial Resistance: Is There a 'Light' at the End of the Tunnel?

In recent years, with the increases in microorganisms that express a multitude of antimicrobial resistance (AMR) mechanisms, the threat of antimicrobial resistance in the global population has reached critical levels. The introduction of the COVID-19 pandemic has further contributed to the influx of infections caused by multidrug-resistant organisms (MDROs), which has placed significant pressure on healthcare systems. For over a century, the potential for light-based approaches targeted at combatting both cancer and infectious diseases has been proposed. They offer effective killing of microbial pathogens, regardless of AMR status, and have not typically been associated with high propensities of resistance development. To that end, the goal of this review is to describe the different mechanisms that drive AMR, including intrinsic, phenotypic, and acquired resistance mechanisms. Additionally, the different light-based approaches, including antimicrobial photodynamic therapy (aPDT), antimicrobial blue light (aBL), and ultraviolet (UV) light, will be discussed as potential alternatives or adjunct therapies with conventional antimicrobials. Lastly, we will evaluate the feasibility and requirements associated with integration of light-based approaches into the clinical pipeline.

Effectiveness of two photosensitizer-mediated photodynamic therapy for treating moderate peri-implant infections in type-II diabetes mellitus patients: A randomized clinical trial

PURPOSE

This study evaluated the impact of Fox Green (FG) against methylthioninium chloride (MTC)-facilitated photodynamic therapy (PDT) as an adjunctive to manual scaling (MS) on the peri‑implant clinical and cytokine parameters in type-2 diabetes mellitus (DM) patients with peri‑implantitis.

METHODS

Patients were divided into group-A comprising 13 patients who received adjunctive FG-PDT using a diode laser (wavelength: 810 nm; irradiation power: 300 mW; irradiation time: 30 s; fluence: 56 Jcm-2), group-B comprising 12 patients who received adjunctive MTC-PDT using a diode laser (wavelength: 660 nm; irradiation power: 100 mW; irradiation time: 120 s/site; fluence: 30 Jcm-2), and group-C comprising 13 patients who received MS alone [control group]). After diagnosing the diabetics with peri‑implantitis (established on eligibility criteria), a structured questionnaire was used to gather the information of the participants. Plaque (PS) and bleeding scores (BS), along with peri‑implant probing scores (PPS) and peri‑implant bone loss (PIBL), together with immunological variables (interleukin [IL]-6, tumor necrosis factor-alpha [TNF-α], and advanced glycation end products [AGEs]) were measured in all study group participants at baseline, 3-month, and 6-month follow-ups.

RESULTS

A significant reduction was observed for PS, BS, and PPS within all tested groups at each follow-up visits compared from their baseline values (p<0.05). However, a substantial decrease in PIBL was observed in all study group patients at 6-month follow-up as compared to 3-month follow-up (p<0.05). Regarding the levels of IL-6 and TNF-α, a substantial reduction was observed in all study groups until 6-month from their baseline scores (p<0.05). However, no changes were observed in the levels of AGEs in any group at either visit (p>0.05).

CONCLUSION

In DM patients with periimplantitis, adjunctive FG-PDT and MTC-PDT exhibited comparable outcomes in terms of peri‑implant clinical as well as pro-inflammatory characteristics than MS alone among peri‑implantitis patients with DM.

Antileishmanial activity of tetra-cationic porphyrins with peripheral Pt(II) and Pd(II) complexes mediated by photodynamic therapy approaches

Leishmaniasis is a seriously neglected disease that impacts more than one billion people in endemic areas of the globe. Several drawbacks are associated with the currently existing drugs for the treatment as low effectiveness, toxicity, and the emergence of resistant strains that demonstrates the importance of looking for novel therapeutic alternatives. Photodynamic therapy (PDT) is a promising novel alternative for cutaneous leishmaniasis treatment because its topical application avoids potential side effects generally associated with oral/parenteral application. A light-sensitive compound known as photosensitizer (PS) interacts with light and molecular oxygen to generate reactive oxygen species (ROS), which promote cell death by oxidative stress through PDT approaches. Here, for the first time, we demonstrate the antileishmanial effect of tetra-cationic porphyrins with peripheral Pt(II)- and Pd(II)-polypyridyl complexes using PDT. The isomeric tetra-cationic porphyrins in the meta positions, 3-PtTPyP, and 3-PdTPyP, exhibited the highest antiparasitic activity against promastigote (IC_50-pro = 41.8 nM and 46.1 nM, respectively) and intracellular amastigote forms (IC_50-ama = 27.6 nM and 38.8 nM, respectively) of L. amazonensis under white light irradiation (72 J cm^-2) with high selectivity (SI > 50) for both forms of parasites regarding mammalian cells. In addition, these PS induced the cell death of parasites principally by a necrotic process in the presence of white light by mitochondrial and acidic compartments accumulation. This study showed that porphyrins 3-PtTPyP and 3-PdTPyP displayed a promising antileishmanial-PDT activity with potential application for cutaneous leishmaniasis treatment.

The role of the light source in antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (APDT) is a promising approach to fight the growing problem of antimicrobial resistance that threatens health care, food security and agriculture. APDT uses light to excite a light-activated chemical (photosensitiser), leading to the generation of reactive oxygen species (ROS). Many APDT studies confirm its efficacy in vitro and in vivo against bacteria, fungi, viruses and parasites. However, the development of the field is focused on exploring potential targets and developing new photosensitisers. The role of light, a crucial element for ROS production, has been neglected. What are the main parameters essential for effective photosensitiser activation? Does an optimal light radiant exposure exist? And finally, which light source is best? Many reports have described the promising antibacterial effects of APDT in vitro, however, its application in vivo, especially in clinical settings remains very limited. The restricted availability may partially be due to a lack of standard conditions or protocols, arising from the diversity of selected photosensitising agents (PS), variable testing conditions including light sources used for PS activation and methods of measuring anti-bacterial activity and their effectiveness in treating bacterial infections. We thus sought to systematically review and examine the evidence from existing studies on APDT associated with the light source used. We show how the reduction of pathogens depends on the light source applied, radiant exposure and irradiance of light used, and type of pathogen, and so critically appraise the current state of development of APDT and areas to be addressed in future studies. We anticipate that further standardisation of the experimental conditions will help the field advance, and suggest key optical and biological parameters that should be reported in all APDT studies. More in vivo and clinical studies are needed and are expected to be facilitated by advances in light sources, leading to APDT becoming a sustainable, alternative therapeutic option for bacterial and other microbial infections in the future.

Progress in the photodynamic therapy treatment of Leishmaniasis

Leishmaniasis is a serious and endemic infectious disease that has been reported in more than 90 countries and territories. The classical treatment presents a series of problems ranging from difficulty in administration, development of resistance, and a series of side effects. Photodynamic therapy (PDT) has already shown great potential for use as a treatment for leishmaniasis that is effective and non-invasive, with very minor side effects. PDT can also be inexpensive and easy to administer. In this review, we will report the most recent developments in the field, starting with the chemical diversity of photosensitizers, highlighting important mechanistic aspects, and noting information that may assist in designing and developing new and promising photosensitizer molecules.

Photodynamic therapy for leishmaniasis: Recent advances and future trends

Leishmaniasis has infected more than 12 million people worldwide. This neglected tropical disease, causing 20,000-30,000 deaths per year, is a global health problem. The emergence of resistant parasites and serious side effects of conventional therapies has led to the search for less toxic and non-invasive alternative treatments. Photodynamic therapy is a promising therapeutic strategy to produce reactive oxygen species for the treatment of leishmaniasis. In this regard, natural and synthetic photosensitizers such as curcumin, hypericin, 5-aminolevulinic acid, phthalocyanines, phenothiazines, porphyrins, chlorins and nanoparticles have been applied. In this review, the recent advances on using photodynamic therapy for treating Leishmania species have been reviewed.

An appraisal of the scientific current situation and new perspectives in the treatment of cutaneous leishmaniasis

Leishmaniasis is a Neglected Tropical Diseases caused by protozoan parasites of the genus Leishmania. It is a major health problem in many tropical and subtropical regions of the world and can produce three different clinical manifestations, among which cutaneous leishmaniasis has a higher incidence in the world than the other clinical forms. There are no recognized and reliable means of chemoprophylaxis or vaccination against infections with different forms of leishmaniasis. In addition, chemotherapy, unfortunately, remains, in many respects, unsatisfactory. Therefore, there is a continuing and urgent need for new therapies against leishmaniasis that are safe and effective in inducing a long-term cure. This review summarizes the latest advances in currently available treatments and improvements in the development of drug administration. In addition, an analysis of the in vivo assays was performed and the challenges facing promising strategies to treat CL are discussed. The treatment of leishmaniasis will most likely evolve into an approach that uses multiple therapies simultaneously to reduce the possibility of developing drug resistance. There is a continuous effort to discover new drugs to improve the treatment of leishmaniasis, but this is mainly at the level of individual researchers. Undoubtedly, more funding is needed in this area, as well as greater participation of the pharmaceutical industry to focus efforts on the development of chemotherapeutic agents and vaccines for this and other neglected tropical diseases.

Towards effective cutaneous leishmaniasis treatment with light-based technologies. A systematic review and meta-analysis of preclinical studies

Cutaneous leishmaniasis (CL) is a neglected disease that represents a serious global public health concern. We performed a systematic review with meta-analysis targeting the use of light-based therapies on CL in preclinical studies since they are essential to identify the benefits, challenges, and limitations of proposing new technologies to fight CL. We searched Pubmed and Web of Science to include original preclinical researches in English that used light-based technologies to fight CL. Inclusion criteria encompassed any animal model for CL induction, an untreated infected group as the comparator, reliable and consistent methodology to develop and treat CL, focus on an antimicrobial therapeutic approach, and data for lesion size and/or parasite load in the infection site. We identified eight eligible articles, and all of them used photodynamic therapy (PDT). For the meta-analysis, three studies were included regarding the parasite load in the infection site and four comprised the lesion size. No overall statistically significant differences were observed between untreated control and PDT groups for parasite load. Differently, PDT significantly reduced the lesion size regardless of the protocol used to treat CL (in mm, SMD: -1.90; 95% CI: -3.74 to -0.07, p = 0.04). This finding is particularly encouraging since CL promotes disfiguring lesions that profoundly affect the quality of life of patients. We conclude that PDT is a new promising technology able to be topically used against CL if applied in more than one session, making it a promising ally for the management of CL.

Efficacy of photodynamic therapy using TiO2 nanoparticles doped with Zn and hypericin in the treatment of cutaneous Leishmaniasis caused by Leishmania amazonensis

Since Leishmania parasites exhibit resistance outbreaks to drugs conventionally used in medical treatments, research of new antileishmanial compounds or alternative treatment therapies are essential. A focus of interest has been the implementation of light-based therapies such as photodynamic therapy, where inorganic compounds such as titanium dioxide have shown promising results as drug delivery carriers. In this work, nanoparticles of TiO₂ doped with Zn (TiO₂/Zn) were synthesized through solution combustion route and with hypericin (HY) in order to enhance its photodynamic activity in the visible light region. Scanning (SEM) and transmission (TEM) electron microscopy analyses showed particles of (TiO₂/Zn) with sizes smaller than 20 nm and formation of aggregates smaller than 1 μm, whilst electron diffraction spectroscopy (EDS) analysis ensured the presence of Zn in the system. The association of the TiO₂/Zn with HY (TiO₂/Zn-HY) was further confirmed by fluorescence spectrometry. Measurements of its cellular uptake showed the presence of smaller molecules into promastigotes after 120 min incubation. TiO₂/Zn-HY showed good antileishmanial activity (EC₅₀ of 17.5 ± 0.2 μg mL^-1) and low cytotoxicity against murine macrophages (CC₅₀ 35.2 ± 0.3 μg mL^-1) in the visible light (22 mW cm^-2; 52.8 J cm^-2). Moreover, in the in vivo analysis, TiO₂/Zn-HY decreased the parasite load of L. amazonensis - BALB/c infected mice by 43% - 58% after a combination of blue and red light presenting 22 mW cm^-2 of intensity and 52.8 J cm^-2 of fluency delivered. All together, these data indicate a new combined system of nanoparticles associated with a photosensitizer and PDT as alternative to amphotericin B for the treatment of cutaneous leishmaniasis.

Chlorin, Phthalocyanine, and Porphyrin Types Derivatives in Phototreatment of Cutaneous Manifestations: A Review

Recent scientific research has shown the use of chlorin, phthalocyanines, and porphyrins derivatives as photosensitizers in photodynamic therapy in the treatment of various pathologies, including some of the major skin diseases. Thus, the main goal of this critical review is to catalog the papers that used these photosensitizers in the treatment of acne vulgaris, psoriasis, papillomavirus infections, cutaneous leishmaniasis, and skin rejuvenation, and to explore the photodynamic therapy mechanisms against these conditions alongside their clinical benefits.

Study of the efficacy of N-methyl glucamine antimoniate (SbV) associated with photodynamic therapy using liposomal chloroaluminium phthalocyanine in the treatment of cutaneous leishmaniasis caused by Leishmania (L.) amazonensis in C57BL6 mice

BACKGROUND

Pentavalent antimonials remain first-line drugs in the treatment of cutaneous leishmaniasis (CL); however, adverse effects and drug resistance have led to the search for less toxic and more effective treatments. As an alternative, topical phthalocyanine has been studied and its efficacy and low toxicity demonstrated. We aimed to study the in vivo efficacy of N-methyl glucamine antimoniate (NMG) associated with photodynamic therapy (PDT) with topical liposomal chloroaluminium phthalocyanine (AlClPC) in the treatment of experimental CL by L. amazonensis.

METHODS

Experimental study with 54 C57BL6 isogenic mice divided into 9 groups including uninfected control, untreated control, PDT with AlClPC + NMG at doses of 10 and 20 mgSb^V/Kg/day. The criteria to evaluate the treatment efficacy were: paw diameter, amastigote count, culture, viability test and parasite counts using MTT (3-bromo-4,5-dimethylthiazol-2,5-diphenyl-tetrazolium bromide).

RESULTS

Treatment of CL with the association of NMG20 + PDT with AlClPC showed significant reduction of paw diameter, amastigote count, cultures, viability test and parasite counts. Parasite reduction occurred at the 10th and 20th days of treatment and 60 days after treatment ended, indicating that parasites did not multiply again. The NMG10 + PDT group with AlClPC presented results equivalent to gold-standard treatment (20 mgSb^V/kg/day). Biochemical and histopathological evaluation showed minor changes.

CONCLUSION

Treatment of CL caused by L. amazonensis with NMG20 mgSb^V/kg/day + PDT with AlClPC was more effective than the traditional NMG20 mgSb^V/kg/day.

Photodynamic Therapy for the Treatment of American Tegumentary Leishmaniasis: Evaluation of Therapies Association in Experimentally Infected Mice With Leishmania (Leishmania) amazonensis

Introduction: American tegumentary leishmaniasis (ATL) is a zoonotic disease caused by protozoan parasites of the genus Leishmania that affects the skin and mucous membrane. Currently, the available drugs for the treatment are injectable, with side effects, long-term treatment regimen and there is the possibility of drug resistance. Thus, alternative therapies have been tested, including photodynamic therapy (PDT). We evaluated the efficacy of PDT on its own and associated with the prescribed ATL treatment. Methods: BALB/c mice were infected with Leishmania (Leishmania) amazonensis and divided into 6 groups: Gluc+PDT, treated with Glucantime® and photodynamic therapy (PDT) with methylene blue (MB)/red LED (light-emitting diode); Gluc, treated with Glucantime®; PDT, treated with PDT with MB/red LED; Ampho+PDT, treated with amphotericin and PDT with MB/red LED; Ampho, treated with amphotericin; and control, which were infected but not treated. Two treatment cycles were performed. After 165 days of infection, the parasite load was determined. Results: Statistical differences were not found (P>0.05) between measures of volume and thickness of the infected footpads in the treated groups when compared with the control group. However, there was a significant reduction (P<0.05) in the parasitic load of the popliteal lymph nodes of the Gluc+PDT, Gluc, PDT and Ampho groups when compared to the control group. In the histological analysis of the infected footpads, the Gluc+PDT group presented a smaller amount of amastigote nests and lower intensity of the mononuclear infiltrate when compared to the Gluc and PDT groups. Conclusion: The results showed that although there is no significant difference in the evaluations of footpad size (thickness and volume), there is a downward measurement tendency in the Gluc+PDT group, as it can be observed by volume data and corroborated by parasite negative load.

The photodynamic action of pheophorbide a induces cell death through oxidative stress in Leishmania amazonensis

Leishmaniasis is a disease caused by hemoflagellate protozoa, affecting millions of people worldwide. The difficulties of treating patients with this parasitosis include the limited efficacy and many side effects of the currently available drugs. Therefore, the search for new compounds with leishmanicidal action is necessary. Photodynamic therapy has been studied in the medical field because of its selectivity, utilizing a combination of visible light, a photosensitizer compound, and singlet oxygen to reach the area of treatment. The continued search for selective alternative treatments and effective targets that impact the parasite and not the host are fundamentally important for the development of new drugs. Pheophorbide a is a photosensitizer that may be promising for the treatment of leishmaniasis. The present study evaluated the in vitro biological effects of pheophorbide a and its possible mechanisms of action in causing cell death in L. amazonensis. Pheophorbide a was active against promastigote and amastigote forms of the parasite. After treatment, we observed ultrastructural alterations in this protozoan. We also observed changes in promastigote macromolecules and organelles, such as loss of mitochondrial membrane potential [∆Ψ_m], lipid peroxidation, an increase in lipid droplets, DNA fragmentation, phosphatidylserine exposure, an increase in caspase-like activity, oxidative imbalance, and a decrease in antioxidant defense systems. These findings suggest that cell death occurred through apoptosis. The mechanism of cell death in intracellular amastigotes appeared to involve autophagy, in which we clearly observed an increase in reactive oxygen species, a compromised ∆Ψ_m, and an increase in the number of autophagic vacuoles. The present study contributes to the development of new photosensitizers against L. amazonensis. We also elucidated the mechanism of action of pheophorbide a, mainly in intracellular amastigotes, which is the most clinically relevant form of this parasite.

Evaluation of methylene blue as photosensitizer in promastigotes of Leishmania major and Leishmania braziliensis

The cutaneous leishmaniasis is caused by the protozoan of the genus Leishmania. It is considered by WHO as a public health issue and a neglected disease, which affects rural workers and it is also a risk to travelers in endemic areas. The conventional treatment is toxic and leads to severe side effects. The photodynamic therapy has been studied as an alternative treatment to cutaneous leishmaniasis. This study aimed to evaluate the methylene blue internalization and the impact of the PDT in the viability and morphology of Leishmania major and Leishmania braziliensis promastigote in culture medium. The fluorescence microscopy was used to determine the MB localization. To evaluate the mitochondrial activity (MTT), viability (Trypan blue test) and the morphological alterations both species were incubated with the MB in concentrations starting in 500μg/ml, in serial dilution, until 7,8μg/ml. The fluorescence microscopy demonstrated that the MB is internalized by both species after one hour of incubation. The MB presented low toxicity at the dark and the PDT was capable of decreasing the viability in more than 70% in the higher concentrations tested. The PDT also triggered significant morphological alterations in the Leishmania promastigotes. The results presented in this study are an indicative that the MB is a photosensitizer with promising potential to clinical application, besides its low cost.

Photodynamic Therapy With Bengal Rose and Derivatives Against Leishmania amazonensis

Introduction: The treatment of cutaneous leishmaniasis (CL) is based primarily on the use of pentavalent antimonials, which may lead to many side effects limiting their use. Photodynamic therapy (PDT) is an alternative for the treatment of CL, and some xanthene dyes have the potential for use in PDT. Methods: The xanthenes rose bengal B (RB) and its derivatives rose bengal methyl ester (RBMET), and butyl ester (RBBUT) were analyzed for leishmanicidal activity against promastigotes and intracellular amastigotes of Leishmania amazonensis. Cytotoxicity was assessed in J774.A1 macrophages. Results: RB derivates RBMET (IC₅₀ 9.83 μM), and RBBUT (IC₅₀ 45.08 μM) showed leishmanicidal activity, however, were toxic to J774.A1 macrophages, resulting in low selectivity index. Conclusion: The RBMET and RBBUT showed to be effective against the L. amazonensis and the low selectivity index presented may not be a limitation for their use in PDT to CL treatment.