The effects of peroxidase on the enzymatic and candidacidal activities of lysozyme

Effects of Zinc Compounds on Lysozyme, Peroxidase, and α-Amylase from the Perspective of Oral Health: a Scoping Review

Zinc has been proposed as a topical therapeutic agent for the prevention and treatment of various oral diseases. The purpose of this scoping review was to investigate the effects of zinc on the enzymatic activities of lysozyme, peroxidase, and α-amylase from the perspective of developing oral health care products and therapeutic agents for oral diseases. A comprehensive review of the scientific literature was conducted on the direct interactions of zinc with lysozyme, peroxidase, and α-amylase from various sources. Most of the reports on the effects of zinc on the enzymatic activities of lysozyme, peroxidase, and α-amylase involved enzymes derived from bacteria, fungi, animals, and plants. Studies of human salivary enzymes were scarce. Zinc was found to inhibit the enzymatic activities of lysozyme, peroxidase, and α-amylase under diverse experimental conditions. The suggested mechanism was ionic interactions between zinc and enzyme molecules. The possibility that zinc causes structural changes to enzyme molecules has also been suggested. In conclusion, for zinc to be used as an effective topical therapeutic agent for oral health, further studies on the activity of human salivary enzymes are warranted, and additional information regarding the type and concentration of effective zinc compounds is also required.

Immune Response of Galleria mellonella against Human Fungal Pathogens

In many aspects, the immune response against pathogens in insects is similar to the innate immunity in mammals. This has caused a strong interest in the scientific community for the use of this model in research of host⁻pathogen interactions. In recent years, the use of Galleria mellonella larvae, an insect belonging to the Lepidoptera order, has emerged as an excellent model to study the virulence of human pathogens. It is a model that offers many advantages; for example, it is easy to handle and establish in every laboratory, the larvae have a low cost, and they tolerate a wide range of temperatures, including human temperature 37 °C. The immune response of G. mellonella is innate and is divided into a cellular component (hemocytes) and humoral component (antimicrobial peptides, lytic enzymes, and peptides and melanin) that work together against different intruders. It has been shown that the immune response of this insect has a great specificity and has the ability to distinguish between different classes of microorganisms. In this review, we delve into the different components of the innate immune response of Galleria mellonella, and how these components manifest in the infection of fungal pathogens including Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans, and Histoplasma capsulatum.

Dose‑dependent effect of lysozyme upon Candida albicans biofilm

The present study investigated the in vitro effect of lysozyme (0-1,000 µg/ml) on Candida albicans (C. albicans) biofilm development. Investigations were conducted on C. albicans ATCC 10231 and on 10 clinical isolates from dentures. Strains were cultured aerobically at 37˚C in Sabouraud broth. Yeast growth was evaluated by turbidimetry. Biofilm biomass was quantified on a polystyrene support by crystal violet staining and on acrylic surfaces by counts of colony forming units. Lysozyme affected biofilm formation to a greater extent than it affected growth. For the ATCC 10231 reference strain, lysozyme acted as a biofilm promotor on polystyrene at the highest concentration tested (1,000 µg/ml, non‑physiological). When the reference strain was investigated on acrylic resin support, lysozyme acted as a significant biofilm promotor on rough resin, but less on smooth resin. The attached biomass in the presence of physiological concentrations of lysozyme (10‑30 µg/ml) was significantly decreased compared with the hypothetical value of 100% using a one‑sample t‑test, but a comparison between the different lysozyme conditions using analysis of variance and post hoc tests did not reveal significant differences. In 10 wild strains, different patterns of biofilm formation on polystyrene were observed in the presence of lysozyme. Some strains, characterized by large amounts of biofilm formation in the presence of 1,000 µg/ml lysozyme, were poor biofilm producers at low concentrations of lysozyme. In contrast, some strains that were poor biofilm producers with a high lysozyme concentration were more inhibited by low concentrations of lysozyme. The present study emphasizes the need to develop strategies for biofilm control based on in vitro experiments, and to implement these in clinical trials prior to approval of hygiene products enriched with exocrine proteins, such as lysozyme. Further studies will extend these investigations to other Candida species, and to fungi and bacteria present in oral biofilms.

Short term comparative evaluation of antimicrobial efficacy of tooth paste containing lactoferrin, lysozyme, lactoperoxidase in children with severe early childhood caries: a clinical study

BACKGROUND AND OBJECTIVES

The present study is conducted to compare the anti-microbial efficacy of tooth paste containing lactoferrin, lysozyme, lactoperoxidase (BioXtra ®), a 500ppm fluoride tooth paste, and a non fluoridated tooth paste in children with Severe Early Childhood Caries (S-ECC).

MATERIALS AND METHODS

Study group included 30 children with S-ECC aged 3-5 years. Subjects were randomly selected & divided into three groups of ten each. Group I: Non-fluoride tooth paste, Group II: 500 ppm fluoride tooth paste, Group III: tooth paste containing lactoferrin, lysozyme & lactoperoxidase. Estimation of salivary S. mutans and L. acidophilus levels was accomplished by collecting salivary samples and inoculated on Mitis Salivarius Bacitracin agar (MSB) and Rogosa SL media. Colony Forming Units (CFUs) were counted and the results were tabulated and subjected to statistical analysis.

RESULTS

Brushing with tooth paste containing lysozyme, lactoferrin and lactoperoxidase after a week showed highly significant reduction in the CFU counts of both salivary S. mutans and L. acidophilus (p<0.001), whereas 500ppm fluoride tooth paste showed a highly significant reduction in the S. mutans levels (p<0.001), but a significant reduction in L. acidophilus count (p<0.01). Non-fluoride tooth paste showed a highly significant reduction in S. mutans (p<0.001) only, but reduction in the L. acidophilus levels was insignificant (p<0.05).

CONCLUSION

The present study revealed that tooth paste containing lactoferrin, lysozyme, and lactoperoxidase was highly significant in reducing the salivary levels of mutans Streptococci and L. acidophilus in children with S-ECC.

Studies on the role of insect hemolymph polypeptides: Galleria mellonella anionic peptide 2 and lysozyme

The lysozymes are well known antimicrobial polypeptides exhibiting antibacterial and antifungal activities. Their antibacterial potential is related to muramidase activity and non-enzymatic activity resembling the mode of action of cationic defense peptides. However, the mechanisms responsible for fungistatic and/or fungicidal activity of lysozyme are still not clear. In the present study, the anti-Candida albicans activity of Galleria mellonella lysozyme and anionic peptide 2 (AP2), defense factors constitutively present in the hemolymph, was examined. The lysozyme inhibited C. albicans growth in a dose-dependent manner. The decrease in the C. albicans survival rate caused by the lysozyme was accompanied by a considerable reduction of the fungus metabolic activity, as revealed by LIVE/DEAD staining. In contrast, although AP2 reduced C. albicans metabolic activity, it did not influence its survival rate. Our results suggest fungicidal action of G. mellonella lysozyme and fungistatic activity of AP2 toward C. albicans cells. In the presence of AP2, the anti-C. albicans activity of G. mellonella lysozyme increased. Moreover, when the fungus was incubated with both defense factors, true hyphae were observed besides pseudohyphae and yeast-like C. albicans cells. Atomic force microscopy analysis of the cells exposed to the lysozyme and/or AP2 revealed alterations in the cell surface topography and properties in comparison with the control cells. The results indicate synergistic action of G. mellonella AP2 and lysozyme toward C. albicans. The presence of both factors in the hemolymph of naive larvae suggests their important role in the early stages of immune response against fungi in G. mellonella.

Hypochlorous acid-induced heme degradation from lactoperoxidase as a novel mechanism of free iron release and tissue injury in inflammatory diseases

Lactoperoxidase (LPO) is the major consumer of hydrogen peroxide (H₂O₂) in the airways through its ability to oxidize thiocyanate (SCN⁻) to produce hypothiocyanous acid, an antimicrobial agent. In nasal inflammatory diseases, such as cystic fibrosis, both LPO and myeloperoxidase (MPO), another mammalian peroxidase secreted by neutrophils, are known to co-localize. The aim of this study was to assess the interaction of LPO and hypochlorous acid (HOCl), the final product of MPO. Our rapid kinetic measurements revealed that HOCl binds rapidly and reversibly to LPO-Fe(III) to form the LPO-Fe(III)-OCl complex, which in turn decayed irreversibly to LPO Compound II through the formation of Compound I. The decay rate constant of Compound II decreased with increasing HOCl concentration with an inflection point at 100 µM HOCl, after which the decay rate increased. This point of inflection is the critical concentration of HOCl beyond which HOCl switches its role, from mediating destabilization of LPO Compound II to LPO heme destruction. Lactoperoxidase heme destruction was associated with protein aggregation, free iron release, and formation of a number of fluorescent heme degradation products. Similar results were obtained when LPO-Fe(II)-O₂, Compound III, was exposed to HOCl. Heme destruction can be partially or completely prevented in the presence of SCN⁻. On the basis of the present results we concluded that a complex bi-directional relationship exists between LPO activity and HOCl levels at sites of inflammation; LPO serve as a catalytic sink for HOCl, while HOCl serves to modulate LPO catalytic activity, bioavailability, and function.

A murine model for catheter-associated candiduria

Candiduria is a common finding in hospitalized patients with indwelling urine-draining devices. Animal models for candiduria are not well-developed and, despite its prevalence and associated mortality, candiduria is understudied. The presence of Candida in urine does not imply disease because it is also a commensal. Biofilm formation on catheters and the host-pathogen interaction are likely to be important factors that contribute to the pathogenesis. The objective of this study was to establish a candiduria model in mice with indwelling catheters. Our data demonstrate that biofilm formation on indwelling catheters and persistent candiduria can be established in mice. The study supports the concept that biofilm formation contributes to persistence. It also outlines differences between catheter-related candiduria in mice and humans. Specifically, mice exhibit higher levels of leukocyturia. In addition, mean daily fungal burden in urine in the murine model is 10- to 100-fold lower than that in humans. These important findings must be taken into consideration when using this model to study host-pathogen interaction in the setting of candiduria.