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The unbridled dissemination of multidrug‐resistant pathogens is a major threat to global health and urgently demands novel therapeutic alternatives. Antimicrobial photodynamic therapy (aPDT) has been developed as a promising approach to treat localized infections regardless of drug resistance profile or taxonomy. Even though this technique has been known for more than a century, discussions and speculations regarding the biochemical mechanisms of microbial inactivation have never reached a consensus on what is the primary cause of cell death. Since photochemically generated oxidants promote ubiquitous reactions with various biomolecules, researchers simply assumed that all cellular structures are equally damaged. In this study, biochemical, molecular, biological and advanced microscopy techniques were employed to investigate whether protein, membrane or DNA damage correlates better with dose‐dependent microbial inactivation kinetics. We showed that although mild membrane permeabilization and late DNA damage occur, no correlation with inactivation kinetics was found. On the other hand, protein degradation was analyzed by three different methods and showed a dose‐dependent trend that matches microbial inactivation kinetics. Our results provide a deeper mechanistic understanding of aPDT that can guide the scientific community toward the development of optimized photosensitizing drugs and also rationally propose synergistic combinations with antimicrobial chemotherapy. [ABSTRACT FROM AUTHOR]

Osteoclasts are cells whose main function is the resorption of bone matrix. However, several factors, including medications, can interfere with the resorption process. Alendronate (ALN), a nitrogen-containing type of bisphosphonate, and dexamethasone (DEX), a glucocorticoid, are drugs that may affect the resorption activity. The aim of this study is to investigate the effects of ALN, and/or DEX on osteoclast gene expression and resorption activity in primary mouse marrow cultures stimulated with 1,25-dihydroxyvitamin D3, a model for the bone microenvironment. Cultures were treated only with ALN (10−5 M), DEX (10−6 M), and with a combination of both agents. Viability assays performed at days 5, 7, and 9 showed the highest number of viable cells at day 7. All the following assays were then performed at day 7 of cell culture: tartrate resistant acid phosphatase (TRAP) histochemistry, receptor activator of nuclear factor kappa B ligand (RANKL) immunofluorescence, osteoprotegerin (OPG), and RANKL gene expression by qPCR and resorption analysis by scanning electron microscopy. Treatment with ALN, DEX, and the combination of both did not promote significant changes in the number of TRAP+ cells, although larger giant cells were detected in groups treated with DEX. DEX treatment increased the gene expression of RANKL and reduced OPG. The treatment with ALN reduced the depth of the resorption pits, but their inhibitory effect was less effective when administered with DEX: [ABSTRACT FROM AUTHOR]

The unbridled dissemination of multidrug‐resistant pathogens is a major threat to global health and urgently demands novel therapeutic alternatives. Antimicrobial photodynamic therapy (aPDT) has been developed as a promising approach to treat localized infections regardless of drug resistance profile or taxonomy. Even though this technique has been known for more than a century, discussions and speculations regarding the biochemical mechanisms of microbial inactivation have never reached a consensus on what is the primary cause of cell death. Since photochemically generated oxidants promote ubiquitous reactions with various biomolecules, researchers simply assumed that all cellular structures are equally damaged. In this study, biochemical, molecular, biological and advanced microscopy techniques were employed to investigate whether protein, membrane or DNA damage correlates better with dose‐dependent microbial inactivation kinetics. We showed that although mild membrane permeabilization and late DNA damage occur, no correlation with inactivation kinetics was found. On the other hand, protein degradation was analyzed by three different methods and showed a dose‐dependent trend that matches microbial inactivation kinetics. Our results provide a deeper mechanistic understanding of aPDT that can guide the scientific community toward the development of optimized photosensitizing drugs and also rationally propose synergistic combinations with antimicrobial chemotherapy. [ABSTRACT FROM AUTHOR]

The unbridled dissemination of multidrug-resistant pathogens is a major threat to global health and urgently demands novel therapeutic alternatives. Antimicrobial photodynamic therapy (aPDT) has been developed as a promising approach to treat localized infections regardless of drug resistance profile or taxonomy. Even though this technique has been known for more than a century, discussions and speculations regarding the biochemical mechanisms of microbial inactivation have never reached a consensus on what is the primary cause of cell death. Since photochemically generated oxidants promote ubiquitous reactions with various biomolecules, researchers simply assumed that all cellular structures are equally damaged. In this study, biochemical, molecular, biological and advanced microscopy techniques were employed to investigate whether protein, membrane or DNA damage correlates better with dose-dependent microbial inactivation kinetics. We showed that although mild membrane permeabilization and late DNA damage occur, no correlation with inactivation kinetics was found. On the other hand, protein degradation was analyzed by three different methods and showed a dose-dependent trend that matches microbial inactivation kinetics. Our results provide a deeper mechanistic understanding of aPDT that can guide the scientific community toward the development of optimized photosensitizing drugs and also rationally propose synergistic combinations with antimicrobial chemotherapy., (© 2022 American Society for Photobiology.)