Regulation of Lysozyme Activity by Human Hormones

Background

Lysozyme is a part of human and animal noncellular immunity. The regulation of its activity by hormones is poorly studied. The aim of this study was to test the in vitro activity of lysozyme in the presence of catecholamines, natriuretic hormones, and estradiol (E2).

Methods

Hormones were incubated with lysozyme, and the activity of lysozome was further determined using a test culture of Micrococcus luteus in the early exponential growth stage. The activity of lysozyme was assessed based on the rate of change in the OD of the test culture. Molecular docking was performed using SwissDock server http://www.swissdock.ch/docking), and molecular structures were further analyzed and visualized in the UCSF Chimera 1.15rc software.

Results

According to the results, epinephrine and norepinephrine increased lysozyme activity up to 180% compared to the hormone-free enzyme. Changing the pH of the medium from 6.3 to 5.5, increased the lysozyme activity in the presence of E2 up to 150-200 %. The results also showed that exposure to hormones could modify lysozyme ctivity, and this effect depends on the temperature and pH value. The molecular docking revealed a decrease in the activation energy of the active site of enzyme during the interaction of catecholamines with the amino acid residues, asp52 and glu35 of the active site.

Conclusion

Our findings demonstrate an additional mechanism for the involvement of lysozyme in humoral regulation of nonspecific immunity with respect to human pathogenic microflora and bacterial skin commensals by direct modulation of its activity using human hormones.

The use of 4-Hexylresorcinol as antibiotic adjuvant

Ever decreasing efficiency of antibiotic treatment due to growing antibiotic resistance of pathogenic bacteria is a critical issue in clinical practice. The two generally accepted major approaches to this problem are the search for new antibiotics and the development of antibiotic adjuvants to enhance the antimicrobial activity of known compounds. It was therefore the aim of the present study to test whether alkylresorcinols, a class of phenolic lipids, can be used as adjuvants to potentiate the effect of various classes of antibiotics. Alkylresorcinols were combined with 12 clinically used antibiotics. Growth-inhibiting activity against a broad range of pro- and eukaryotic microorganisms was determined. Test organisms did comprise 10 bacterial and 2 fungal collection strains, including E. coli and S. aureus, and clinical isolates of K. pneumoniae. The highest adjuvant activity was observed in the case of 4-hexylresorcinol (4-HR), a natural compound found in plants with antimicrobial activity. 50% of the minimal inhibitory concentration (MIC) of 4-HR caused an up to 50-fold decrease in the MIC of antibiotics of various classes. Application of 4-HR as an adjuvant revealed its efficiency against germination of bacterial dormant forms (spores) and prevented formation of antibiotic-tolerant persister cells. Using an in vivo mouse model of K. pneumoniae-induced sepsis, we could demonstrate that the combination of 4-HR and polymyxin was highly effective. 75% of animals were free of infection after treatment as compared to none of the animals receiving the antibiotic alone. We conclude that alkylresorcinols such as 4-HR can be used as an adjuvant to increase the efficiency of several known antibiotics. We suggest that by this approach the risk for development of genetically determined antibiotic resistance can be minimized due to the multimodal mode of action of 4-HR.

Botulinum Toxin Conjugated With Silk Fibroin and 4-Hexylresorcinol

PURPOSE

The objective of this study was to evaluate whether silk fibroin (SF) incorporated into 4-hexylresorcinol (4HR) could increase botulinum toxin-A (BTX-A) activity.

MATERIAL AND METHODS

In total, 30 rats were used for this study. The animals were divided into 6 groups according to the injected materials (SA: saline only; SF; 4HR; B2: 2 units of BTX-A; B2 + SF + 4HR: combination of B2, SF, and 4HR; B5: 5 units of BTX-A). Serial sonography was used for the evaluation of muscle thickness after injection. Immunohistochemical staining was used for the evaluation of myosin type II (myo2) and Bcl-2 protein expression.

RESULTS

The relative thickness of the masseter muscle in B2 group was 66.14% ± 4.55% to the preinjection level; in B2 + SF + 4HR group was 54.59% ± 4.83%, and in B5 group was 56.19% ± 8.28%. Any BTX-injected group showed significantly lower value of the relative muscle thickness compared to SA, SF, or 4HR group (P < 0.001 for all). The difference of relative muscle thickness between B2 group and B2 + SF + 4HR group was statistically significant (P < 0.001). The intensity of myo2 immunostaining in B5, B2, and B2 + SF + 4HR group was significantly higher than those in the other groups (P < 0.05).

CONCLUSIONS

When 2 units of BTX was incorporated to SF and 4HR, combination formula showed similar activity to those of 5 units of BTX.

Accelerated biodegradation of silk sutures through matrix metalloproteinase activation by incorporating 4-hexylresorcinol

Silk suture material is primarily composed of silk fibroin and regarded as a non-resorbable material. It is slowly degraded by proteolysis when it is implanted into the body. 4-Hexylresorcinol (4HR) is a well-known antiseptic. In this study, the biodegradability of 4HR-incorporated silk sutures were compared to that of untreated silk sutures and polyglactin 910 sutures, a commercially available resorbable suture. 4HR-incorporated silk sutures exhibited anti-microbial properties. Matrix metalloproteinase (MMP) can digest a wide spectrum of proteins. 4HR increased MMP-2, -3, and -9 expression in RAW264.7 cells. MMP-2, -3, and -9 were able to digest not only silk fibroin but also silk sutures. Consequently, 59.5% of the 4HR-incorporated silk suture material remained at 11 weeks after grafting, which was similar to that of polyglactin 910 degradation (56.4% remained). The residual amount of bare silk suture material at 11 weeks after grafting was 91.5%. The expression levels of MMP-2, -3 and -9 were high in the 4HR-incorporated silk suture-implanted site 12 weeks after implantation. In conclusion, 4HR-treated silk sutures exhibited anti-microbial properties and a similar level of bio-degradation to polyglactin 910 sutures and induced higher expression of MMP-2, -3, and -9 in macrophages.