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Introduction: Melittin is a potent antimicrobial peptide from bee venom that is effective against both Gram-positive and Gram-negative bacteria. However, it is extremely toxic to mammalian cells and, as yet, has no clinical use. Modifications to its amino acid sequence, cyclization, truncation, and dimerization have been attempted in order to reduce its toxicity whilst maintaining its antimicrobial activity. Methods: In this study, we targeted the three lysine residues present in melittin and substituted them with lysine homologs containing shorter side chains (ornithine, Orn, diaminobutyric acid, Dab, and diaminopropanoic acid, Dap) and made both parallel and antiparallel melittin dimers to observe how lysine substitution and dimerization affects its activity and toxicity. The antibacterial activity of melittin and its analogs was tested against S. aureus (Gram-positive bacteria) and E. coli (Gram-negative bacteria), and cytotoxicity was tested against the mammalian cell lines HEK293 and H4IIE. Results: Overall, dimerization and lysine substitution exhibited improved antimicrobial activity toward E. coli and limited improvement toward S. aureus. However, mammalian cell toxicity was only marginally reduced compared to native melittin. Interestingly, the parallel dimer was found to be marginally more active than the antiparallel dimer, indicating orientation maybe important for activity, although both dimers were less effective than the native and Lys-analog peptides toward S. aureus. Of the Lys substitutions, Dab and Dap improved melittin's activity toward E. coli. Discussion: Dimerization and Lys substitution of melittin improved the antimicrobial activity toward Gram-negative bacteria but did not significantly improve its activity toward Gram-positive bacteria. Some analogs also displayed reduced toxicity toward HEK293 and H4IIE cells but overall remained toxic at bactericidal concentrations. Our data indicates that although highly antibacterial, melittin's toxicity is the major drawback in its potential use. [ABSTRACT FROM AUTHOR]

Background: Invasive dental treatment in patients exposed to antiresorptive and antiangiogenic drugs can cause medication-related osteonecrosis of the jaw (MRONJ). Currently, the exact pathogenesis of this disease is unclear. Methods: In March 2022, Medline (Ovid), Embase (Ovid), Scopus, and Web of Science were screened to identify eligible in vitro studies investigating the effects of antiresorptive and antiangiogenic compounds on orally derived cells. Results: Fifty-nine articles met the inclusion criteria. Bisphosphonates were used in 57 studies, denosumab in two, and sunitinib and bevacizumab in one. Zoledronate was the most commonly used nitrogen-containing bisphosphonate. The only non-nitrogen-containing bisphosphonate studied was clodronate. The most frequently tested tissues were gingival fibroblasts, oral keratinocytes, and alveolar osteoblasts. These drugs caused a decrease in cell proliferation, viability, and migration. Conclusions: Antiresorptive and antiangiogenic drugs displayed cytotoxic effects in a dose and time-dependent manner. Additional research is required to further elucidate the pathways of MRONJ. [ABSTRACT FROM AUTHOR]

Background: Oropharyngeal Neisseria gonorrhoeae (NG) infections are common, increasing, and have a higher treatment failure compared with other infection sites. Due to antimicrobial resistance, NG has become a global public health threat as available treatments remain scarce. Little is known about where NG colonizes in the oral mucosa and therefore, where antibiotics need to be distributed to cure infection. A recent review also highlighted the lack of oral cell models available for investigating NG infection. We recently started creating an in-vitro co-culture model for NG strains with human oral epithelial cells to understand patterns of NG growth in the mouth and examine antibiotic uptake by oral cell types supporting NG growth. Methods: NG strains were grown on Chocolate agar with IsoVitaleX and in modified Fastidious broth media in optimised conditions. NG colonies were assessed using a colony counter (Scan1200, Interscience technology). In a 2D model, NG were cocultured with 4 human oral keratinocyte cell lines isolated from different anatomical subsites of the oral cavity. Intra- and extra-cellular NG was quantified, and intracellular spatial distribution was assessed with confocal microscopy and immunocytochemistry. Invasion into 3D spheroids was characterised with penetration depth assessed via histological analysis (haematoxylin and eosin staining) and immunocytochemistry with images taken on a Zeiss Axioscan7 slide scanner or LSM800 confocal microscope. Real time invasion into spheroids was imaged using a MuviCyte live-cell imaging system. Lastly, host cell viability in response to NG infection was also assessed. Results: We created the first-of-its-kind in-vitro model for NG oral infection demonstrating that it is possible to co-culture NG with oral derived cells. NG survives and infects oral cells in an in vitro setting in both 2D and 3D models. Different strains of NG infected oral cells to significantly different degrees. Conclusion: Our presented model can be used to explore the interactions of NG with oral tissues and to investigate current and new therapeutics against oropharyngeal gonorrhoea. [ABSTRACT FROM AUTHOR]