[Role of myeloperoxidase in the host defense against fungal infection]

Critical Computational Evidence Regarding the Long-Standing Controversy Over the Main Electrophilic Species in Hypochlorous Acid Solution

Although hypochlorous acid (HOCl) solution has become a popular electrophilic reagent for industrial uses, the question of which molecule (HOCl or Cl₂) undergoes electrophilic addition with olefins remains a controversial issue in some literature and textbooks, and this problem has been largely underexplored in theoretical studies. In this work, we computationally studied the electrophilic addition mechanism of olefins using three experimentally predicted effective electrophilic chlorinating agents, i.e., HOCl, Cl₂, and Cl₂O molecules. Our results demonstrate that Cl₂ and Cl₂O are the main electrophilic agents in HOCl solution, whereas the HOCl molecule cannot be the electrophile since the energy barrier when directly adding HOCl molecule to olefins is too high to overcome and the “anti-Markovnikov” regioselectivity for tri-substituted olefin is not consistent with experiments. Notably, the HOCl molecule prefers to form oxonium ion intermediate with a double bond, rather than the generally believed chlorium ion intermediate. This work could benefit mechanistic studies of critical biological and chemical processes with HOCl solution and may be used to update textbooks.

Myiasis in Neglected Cutaneous Squamous Cell Carcinoma of the Head and Neck: Review of Management and Current Protocol Recommendations

OBJECTIVE

To propose a first-aid management protocol for myiasis in neglected cutaneous squamous cell carcinoma (SCC) in the ED based on a recent literature review.

DATA SOURCES

PubMed.

STUDY SELECTION

Inclusion criteria were all series and case reports of primary/secondary cutaneous SCC with myiasis of the head and neck, including orbital SCC cases, published after 2005.

DATA EXTRACTION

A total of 14 articles including 15 patients were included.

DATA SYNTHESIS

Demographics, socioeconomic situation, site of the lesion, larvae species with bacterial suprainfection, and first-aid treatment options were discussed. Two representative cases are described.

CONCLUSIONS

Large, ulcerated, necrotic, myiasis-burdened SCC lesions in the head and neck area present a challenge for treatment, and to date, no consensus regarding first-aid management exists. The authors' proposed four-pillar first-aid management scheme may be a valid option to rapidly improve wound condition through disinfection, pain relief, and malodor and discharge eradication as a bridge to surgery.

Neutrophil swarming delays the growth of clusters of pathogenic fungi

Neutrophils employ several mechanisms to restrict fungi, including the action of enzymes such as myeloperoxidase (MPO) or NADPH oxidase, and the release of neutrophil extracellular traps (NETs). Moreover, they cooperate, forming “swarms” to attack fungi that are larger than individual neutrophils. Here, we designed an assay for studying how these mechanisms work together and contribute to neutrophil's ability to contain clusters of live Candida. We find that neutrophil swarming over Candida clusters delays germination through the action of MPO and NADPH oxidase, and restricts fungal growth through NET release within the swarm. In comparison with neutrophils from healthy subjects, those from patients with chronic granulomatous disease produce larger swarms against Candida, but their release of NETs is delayed, resulting in impaired control of fungal growth. We also show that granulocyte colony-stimulating factors (GCSF and GM-CSF) enhance swarming and neutrophil ability to restrict fungal growth, even during treatment with chemical inhibitors that disrupt neutrophil function.

Neutrophils employ several mechanisms to control the growth of fungi, including enzymes, reactive oxygen species, extracellular traps, and formation of “swarms”. Here, Hopke et al. study how the different mechanisms work together, using an in vitro assay with human neutrophils and clusters of live Candida cells.

Response of Human Neutrophil Granulocytes to the Hyphae of the Emerging Fungal Pathogen Curvularia lunata

Curvularia lunata is an ascomycete filamentous fungus causing local and invasive phaeohyphomycoses in both immunocompromised and immunocompetent patients. Neutrophils are crucial participants of the first line host defense against fungal infections. They migrate to the infected site and eliminate the infectious agents by various mechanisms including phagocytoses, oxidative damage, or formation of neutrophil extracellular trap (NET). Neutropenia may be a risk factor for phaeohyphomycoses, and restoration of the neutrophil function can improve the outcome of the infection. In the present study, interaction of primary human neutrophil granulocytes with the hyphae C. lunata was examined and compared to that with the well characterized filamentous fungal pathogen Aspergillus fumigatus. Neutrophils could recognize the serum opsonized hyphae of C. lunata and attach to them. Myeloperoxidase release was also activated by a soluble factor present in the culture supernatant of the fungus. Induction of the oxidative burst was found to depend on serum opsonization of the hyphae. Although extracellular hydrogen peroxide production was induced, the fungus efficiently blocked the oxidative burst by acidifying the reaction environment. This blockage also affected the NET forming ability of the neutrophils.

The antimicrobial peptide cathelicidin modulates Clostridium difficile-associated colitis and toxin A-mediated enteritis in mice

BACKGROUND

Clostridium difficile mediates intestinal inflammation by releasing toxin A (TxA), a potent enterotoxin. Cathelicidins (Camp as gene name, LL-37 peptide in humans and mCRAMP peptide in mice) are antibacterial peptides that also posses anti-inflammatory properties.

OBJECTIVES

To determine the role of cathelicidins in models of Clostridium difficile infection and TxA-mediated ileal inflammation and cultured human primary monocytes.

DESIGN

Wild-type (WT) and mCRAMP-deficient (Camp(-/-)) mice were treated with an antibiotic mixture and infected orally with C difficile. Some mice were intracolonically given mCRAMP daily for 3 days. Ileal loops were also prepared in WT mice and treated with either saline or TxA and incubated for 4 h, while some TxA-treated loops were injected with mCRAMP.

RESULTS

Intracolonic mCRAMP administration to C difficile-infected WT mice showed significantly reduced colonic histology damage, apoptosis, tissue myeloperoxidase (MPO) and tumour necrosis factor (TNF)α levels. Ileal mCRAMP treatment also significantly reduced histology damage, tissue apoptosis, MPO and TNFα levels in TxA-exposed ileal loops. WT and Camp(-/-) mice exhibited similar intestinal responses in both models, implying that C difficile/TxA-induced endogenous cathelicidin may be insufficient to modulate C difficile/TxA-mediated intestinal inflammation. Both LL-37 and mCRAMP also significantly reduced TxA-induced TNFα secretion via inhibition of NF-κB phosphorylation. Endogenous cathelicidin failed to control C difficile and/or toxin A-mediated inflammation and even intestinal cathelicidin expression was increased in humans and mice.

CONCLUSION

Exogenous cathelicidin modulates C difficile colitis by inhibiting TxA-associated intestinal inflammation. Cathelicidin administration may be a new anti-inflammatory treatment for C difficile toxin-associated disease.

[Effect of oral administration of β-D-glucan from Aureobasidium pullulans ADK-34 on Candida and MRSA infections in immunosuppressed mice]

We examined the effect of the oral administration of β-D-glucan derived from Aureobasidium pullulans ADK-34 (AP-FBG) on Candida albicans or methicillin-resistant Staphylococcus aureus (MRSA) infection in immunosuppressed mice. Mice pretreated with cyclophosphamide (CY) were intraperitoneally administered AP-FBG for 4 days and then infected with 6×10(4) C. albicans cells. In a preliminary experiment, the survival time of the Candida-infected mice treated with AP-FBG was clearly prolonged. Similarly, the effect of the oral administration of AP-FBG was examined. Mice were orally given 2.5% AP-FBG in feed for 42 days from 14 days prior to 2×10(4) C. albicans cells infection. The survival time of mice treated with AP-FBG was significantly prolonged and the viable cell count in the kidneys of the survivors was significantly decreased at 30 days after infection. The effects of the oral administration of AP-FBG on intestinal MRSA infection were also examined. Mice were given 2.5% AP-FBG orally in feed for 30 days before and after oral MRSA infection and treated with CY 12 days after the infection. The number of viable MRSA cells or the IgA production in feces did not significantly change, while AP-FBG administration seemed to relieve temporally the loss of body weight of mice.

CONCLUSIONS

These results suggest that oral pre-administration of AP-FBG promoted resistance of CY-treated mice to C. albicans and lessened the weight reduction of CY-mice infected by MRSA.

Innate immunity and gut-microbe mutualism in Drosophila

Metazoan guts face a wide variety of microorganisms upon exposure to the environment, including beneficial symbionts, non-symbionts, food-borne microbes and life-threatening pathogens. Recent evidence has shown that the innate immunity of gut epithelia, such as anti-microbial peptide- and reactive oxygen species-based immune systems, actively participate in gut-microbe homeostasis by shaping the commensal community while efficiently eliminating unwanted bacteria. Therefore, elucidation of the regulatory mechanism by which gut innate immunity occurs at the molecular level will provide a novel perspective of gut-microbe mutualisms as well as of gut diseases caused by alterations in the innate immunity.