Effect of MRSA on CYP450: dynamic changes of cytokines, oxidative stress, and drug-metabolizing enzymes in mice infected with MRSA

Antimicrobial activity of novel symmetrical antimicrobial peptides centered on a hydrophilic motif against resistant clinical isolates: in vitro and in vivo analyses

Antibiotic resistance poses a significant public health threat worldwide. The rise in antibiotic resistance and the sharp decline in effective antibiotics necessitate the development of innovative antibacterial agents. Based on the central symmetric structure of glycine-serine-glycine, combined with tryptophan and arginine, we designed a range of antimicrobial peptides (AMPs) that exhibited broad-spectrum antibacterial activity. Notably, AMP W5 demonstrated a rapid and effective sterilization against methicillin-resistant Staphylococcus aureus (MRSA), displaying both a minimum inhibitory concentration and a minimum bactericidal concentration of 8 µM. Mechanistic studies revealed that AMP W5 killed bacterial cells by disrupting the cytoplasmic membrane integrity, triggering leakage of cell contents. AMP W5 also exhibited excellent biocompatibility in both in vitro and in vivo safety evaluations. AMP W5 treatment significantly reduced skin bacterial load in our murine skin infection model. In conclusion, we designed a novel centrosymmetric AMP representing a promising medical alternative to conventional antibiotics for treating MRSA infections.

IMPORTANCE

Increasing antibiotic resistance and the paucity of effective antibiotics necessitate innovative antibacterial agents. Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen causing bacterial infections with high incidence and mortality rates, showing increasing resistance to clinical drugs. Antimicrobial peptides (AMPs) exhibit significant potential as alternatives to traditional antibiotics. This study designed a novel series of AMPs, characterized by a glycine-serine-glycine-centered symmetrical structure, and our results indicated that AMP W5 exhibited a rapid and effective bactericidal effect against MRSA. AMP W5 also demonstrated excellent biocompatibility and a bactericidal mechanism that disrupted membrane integrity, leading to leakage of cellular contents. The notable reduction in skin bacterial load observed in mouse models reinforced the clinical applicability of AMP W5. This study provides a promising solution for addressing the increasing threat of antibiotic-resistant bacteria and heralds new prospects for clinical applications.

Tea tree oil inhibits hydrogen sulfide-induced oxidative damage in chicken lungs through CYP450s/ROS pathway

A large amount of hydrogen sulfide (H2S) is produced in the process of chicken breeding, which can cause serious inflammation and oxidative damage to the respiratory system of chickens. Tea tree oil (TTO) has antioxidant and anti-inflammatory properties. No studies have been reported on the use of TTO in H2S-induced lung injury in chickens. Therefore, in this study, 240 one-day-old Roman pink laying hens were randomly and equally divided into 3 groups: control group (CON), H2S exposure group (AVG, containing H2S), and TTO treatment group (TTG, containing H2S and 0.02 mL/L TTO) to establish an experimental model of TTO treatment with H2S exposure for a period of 42 d. Hematoxylin and eosin (H&E) staining was used to detect lung histopathology. Gene expression profiles were analyzed using transcriptomics. The underlying mechanism of the amelioration of lung injury by TTO was further revealed by antioxidant enzyme assays and qRT-PCR. The results showed that H2S exposure induced significant gene expression of CYP450s (CYP1B1 and CYP1C1) (P < 0.05), and caused intense oxidative stress, apoptosis and inflammation compared with CON. TTO could reduce ROS production and enhance antioxidant capacity (SOD, CAT, T-AOC, and GSH-PX) by regulating the CYP450s/ROS pathway (P < 0.05). Compared with the control group, the treatment group showed significantly decreased expression of apoptotic (Caspase-8, Caspase-3, Bid and Fas) (P < 0.05) and inflammatory (IL-4, IL-16, NF-κB, TNF-α and IFN-γ) (P < 0.05) factors in the lung. This study revealed that TTO regulated CYP450s/ROS pathway to alleviate H2S-induced lung injury in chickens. These results enrich the theory of the action mechanism of TTO on H2S-exposed chicken lungs and are of great value for the treatment of H2S-exposed animals.

Catharanthus roseus (L.) G. Don counteracts the ampicillin resistance in multiple antibiotic-resistant Staphylococcus aureus by downregulation of PBP2a synthesis

It is essential to revisit the global biodiversity, search for ethnopharmacologically relevant plants, and unveil their untapped potential to overcome the complications associated while treating infections triggered by multiple antibiotic-resistant Staphylococcus aureus. Catharanthus roseus (L.) G. Don of the Apocynaceae family is a medicinal plant used for remedial purposes against infectious diseases from ancient times. In this study, we intended to evaluate the mechanism by which the ethanolic extract of C. roseus root (EECRR) causes the reversal of ampicillin resistance in S. aureus. To achieve this goal, we have stained EECRR-treated S. aureus with acridine orange, analysed DNA damage by comet assay, and studied the alteration of plasmid band pattern and expression of penicillin-binding protein 2a (PBP2a) protein. Experiments revealed better S. aureus killing efficiency of EECRR at its minimum inhibitory concentration (MIC) doses due to DNA damage and reducing plasmid band intensities along with a decline in the expression of PBP2a in EECRR-treated cells at half-MIC dose. EECRR proved to be an efficient growth inhibitor of S. aureus that reduces the expression of PBP2a. Therefore, EECRR can also render ampicillin-resistant S. aureus susceptible to the antibiotic.

Development and characterization of catechin-in-cyclodextrin-in-phospholipid liposome to eradicate MRSA-mediated surgical site infection: Investigation of their anti-infective efficacy through in vitro and in vivo studies

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the prime pathogens responsible for surgical site infection (SSI). Treatment of SSI remains challenging because of resistant nature of MRSA, which is a major threat in recent years. Our previous work revealed the antibacterial potential of catechin isolated from cashewnut shell against MRSA. However, the application of catechin to treat MRSA-mediated SSI is hampered because of its poor solubility and low trans-dermal delivery. Hence, the present study focused on developing catechin-in-cyclodextrin-in-phospholipid liposome (CCPL) and evaluating its physicochemical characteristics and anti-infective efficacy through in vitro and in vivo models. Encapsulation of catechin with β-cyclodextrin and soybean lecithin was confirmed through UV-Vis spectroscopy, FTIR, and XRD techniques, while TEM imaging revealed the size of CCPL (206 nm). The CCPL displayed a higher level of water solubility (25.13%) and in vitro permeability (42.14%) compared to pure catechin. A higher level of encapsulation efficiency (98.9%) and antibacterial activity (19.8 mm of ZOI and 31.25 μg/mL of MIC) were noted in CCPL compared to the catechin/cyclodextrin complex. CCPL recorded significant and dose-dependent healing of the incision, significant reduction of bacterial count, improved epithelization, and effective prevention of inflammation in skin samples of SSI-induced Balb/c mice. Data of the present work suggest that the CCPL could be considered as a novel and potential candidate to mitigate MRSA-mediated SSI after clinical trials.

Distinct Effects of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus Cell Wall Component-Induced Inflammation on the Iron Metabolism of THP-1 Cells

Macrophages are essential immune cells of the innate immune system. They participate in the development and regulation of inflammation. Macrophages play a fundamental role in fighting against bacterial infections by phagocytosis of bacteria, and they also have a specific role in immunomodulation by secreting pro-inflammatory cytokines. In bacterial infection, macrophages decrease the serum iron concentration by removing iron from the blood, acting as one of the most important regulatory cells of iron homeostasis. We examined whether the Gram-positive and Gram-negative cell wall components from various bacterial strains affect the cytokine production and iron transport, storage and utilization of THP-1 monocytes in different ways. We found that S. aureus lipoteichoic acid (LTA) was less effective in activating pro-inflammatory cytokine expression that may related to its effect on fractalkine production. LTA-treated cells increased iron uptake through divalent metal transporter-1, but did not elevate the expression of cytosolic and mitochondrial iron storage proteins, suggesting that the cells maintained iron efflux via the ferroportin iron exporter. E. coli and P. aeruginosa lipopolysaccharides (LPSs) acted similarly on THP-1 cells, but the rates of the alterations of the examined proteins were different. E. coli LPS was more effective in increasing the pro-inflammatory cytokine production, meanwhile it caused less dramatic alterations in iron metabolism. P. aeruginosa LPS-treated cells produced a smaller amount of pro-inflammatory cytokines, but caused remarkable elevation of both cytosolic and mitochondrial iron storage proteins and intracellular iron content compared to E. coli LPS. These results prove that LPS molecules from different bacterial sources alter diverse molecular mechanisms in macrophages that prepossess the outcome of the bacterial infection.

Effects of infection of MRSA on the expression and activity of renal cytochrome P450s in mice

Methicillin-resistant Staphylococcus aureus (MRSA) leads to serious infections, but it is not known whether it changes the expression of kidney drug metabolizing enzymes during infection. The mice were infected with different doses of MRSA and the oxidative stress and inflammation levels in the kidney were examined. The mRNA expression and activity of cytochrome P450 enzyme was analysed. Mice infected with high levels of MRSA showed a decrease in renal antioxidant capability and an elevated level of oxidative metabolites, which was accompanied by the release of inflammatory cytokines. The levels of interleukin 1β, tumour necrosis factor alpha, and macrophage inflammatory protein-1α were significantly increased along with the levels of nitric oxide and malondialdehyde. On day 7, mRNA expression of Cyp1a2, 2d22, and 3a11 were decreased by the high level of MRSA, but the low level of MRSA increased their expressions. Cyp2e1 mRNA expression was increased by MRSA in the kidney of mice. High dose of MRSA infection increased the oxidative stress and inflammatory response in mouse kidney, leading to the decrease in the expression of renal drug-metabolizing enzymes and no recovery within 7 days.

Effect and mechanism of citral against methicillin-resistant Staphylococcus aureus in vivo

BACKGROUND

Citral is an active component of many plant extracts, and it is a safe additive used in food and cosmetics. A previous study showed that citral has a good antibacterial effect against methicillin-resistant Staphylococcus aureus (MRSA) in vitro, but its in vivo anti-infective activity has not been studied. Anti-MRSA activity and the preliminary mechanism of citral against MRSA were investigated in MRSA-infected KM mice. The ED₅₀ was calculated using Karber's method. Groups were selected for inflammatory and oxidative stress level tests, and lung and liver tissues were counterstained with HE for detection of pathological changes. Cytokines and oxidative factors were evaluated using the ELISA method (one-way ANOVA computed using SPSS 19.0.).

RESULTS

With the increase in the concentration of citral, the survival rate of MRSA-infected mice increased accordingly. The ED₅₀ values of citral for intramuscular injection and intragastric administration were 0.09 and 0.26 g kg^-1 respectively. Citral significantly reduced cytokines (IL-1β, IL-6, TNF-α) and oxidative factors (malondialdehyde and hydroxyl radicals) of MRSA-infected mice, whereas it increased gluthtione and superoxide dismutase levels. Citral can reduce the lung inflammatory infiltrates infected by MRSA.

CONCLUSIONS

Citral exerted a dose-dependent anti-MRSA effect and ameliorated MRSA-induced abnormal changes in inflammation and oxidative stress. This indicates that citral has the potential for development as a new anti-MRSA drug. © 2019 Society of Chemical Industry.

Nasal colonization with methicillin-resistant Staphylococcus aureus associated with elevated homocysteine levels in the general US adults

Given the emergence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) as a global health threat, understanding the risk factors for MRSA infection in the community may be a reasonable strategy to prevent it. We investigated the associations between serum homocysteine levels and prevalence of nasal colonization with S aureus and MRSA among United States adults. We conducted a cross-sectional analysis of a nationally representative sample of 7832 adults (20 years or older). The main outcome variables were nasal colonization with S aureus and MRSA. Percentages of colonization with S aureus and MRSA were calculated by the quartiles of serum homocysteine. A total of 7832 of 2051 subjects (26.2%) were culture positive for S aureus, 98 (4.8%) of whom had nasal colonization with MRSA. In comparison with subjects having the lowest serum homocysteine, the odds of nasal colonization with MRSA were significantly higher in those with the highest homocysteine (odds ratio, 3.09; 95% confidence interval, 1.11-8.61) in multivariate analysis, adjusted for all confounding variables. By contrast, homocysteine elevation was not significantly associated with S aureus colonization. Nasal colonization with MRSA in the general community was significantly associated with increases in serum homocysteine levels.