Citrullination-Resistant LL-37 Is a Potent Antimicrobial Agent in the Inflammatory Environment High in Arginine Deiminase Activity

Human cathelicidin LL-37 exerts amelioration effects against EHEC O157:H7 infection regarding inflammation, enteric dysbacteriosis, and impairment of gut barrier function

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 infection impairs intestinal barrier function, causing intestinal inflammation and enteric dysbacteriosis. The human cathelicidin LL-37 can regulate excessive inflammatory responses, barrier function, and balance the intestinal microbial community; however, little is known about its effects on inflammation, intestinal barrier function, and microbiota disorders in EHEC O157:H7-infected mice. In this study, we investigated the protective effect of LL-37 against EHEC O157:H7 infection and elucidated the underlying mechanism using a mouse model. LL-37 treatment was found to inhibit body weight loss, restore edema and destruction of the intestinal villi, and significantly reduce epithelial apoptosis (P < 0.05) in EHEC O157:H7-infected mice. Furthermore, inflammatory infiltration of macrophages and neutrophils into the jejunum and colon was significantly decreased (P < 0.05). LL-37 significantly downregulated the production of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) (P < 0.05) and upregulated the anti-inflammatory cytokine (IL-10) during EHEC O157:H7 infection. LL-37 increased the expression of tight junction proteins (ZO-1, ZO-2, claudin-1, and occludin), which are associated with intestinal barrier function, and had a positive effect on EHEC O157:H7-induced microbial disorders, particularly in terms of the inflammation-related microbiota. LL-37 also significantly decreased the E. coli load in the liver and spleen (P < 0.01) and restored the structure of the liver and kidney. Taken together, LL-37 conferred protection in a EHEC O157:H7-induced mouse model by reducing intestinal inflammation, enhancing intestinal barrier function, and restoring the balance of the intestinal microbiota, which indicates the therapeutic potential of LL-37 against pathogen infection.

Efficacy of Oxymatrine Plus Antiviral in the Treatment of Sepsis and Its Effect on the Levels of Endotoxin and Inflammatory Factors

Objective

To assess the clinical efficacy of oxymatrine plus antiviral therapy in the treatment of sepsis and its effects on the levels of endotoxin and inflammatory factors. Methodology. 90 patients with sepsis were selected for retrospective analysis and were assigned to receive either conventional treatment (control group) or oxymatrine plus antiviral treatment (study group). The clinical endpoint was treatment efficacy.

Results

There were no significant differences in baseline patient profile between the two groups (P > 0.05). The study group showed a higher efficiency versus the control group (P < 0.05). Patients in the study group had a significantly shorter mechanical ventilation duration and ICU stay versus those in the control group (P < 0.05). Both groups had reduced Acute Physiology and Chronic Health Evaluation II (APACHE II) score, Marshall score, levels of endotoxin, tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-8, C-reactive protein (CRP), and procalcitonin (PCT) after treatment, with lower results in the study group versus the control group (P < 0.05).

Conclusion

Oxymatrine plus antiviral therapy effectively improves clinical efficacy, reduces the levels of endotoxin and inflammatory factors, protects organ function, and boosts recovery. Further clinical trials are, however, required prior to general application in clinical practice.

Cathelicidin LL-37 in Health and Diseases of the Oral Cavity

The mechanisms for maintaining oral cavity homeostasis are subject to the constant influence of many environmental factors, including various chemicals and microorganisms. Most of them act directly on the oral mucosa, which is the mechanical and immune barrier of the oral cavity, and such interaction might lead to the development of various oral pathologies and systemic diseases. Two important players in maintaining oral health or developing oral pathology are the oral microbiota and various immune molecules that are involved in controlling its quantitative and qualitative composition. The LL-37 peptide is an important molecule that upon release from human cathelicidin (hCAP-18) can directly perform antimicrobial action after insertion into surface structures of microorganisms and immunomodulatory function as an agonist of different cell membrane receptors. Oral LL-37 expression is an important factor in oral homeostasis that maintains the physiological microbiota but is also involved in the development of oral dysbiosis, infectious diseases (including viral, bacterial, and fungal infections), autoimmune diseases, and oral carcinomas. This peptide has also been proposed as a marker of inflammation severity and treatment outcome.

Biological Functions and Applications of Antimicrobial Peptides

Abstract:

Despite antimicrobial resistance, which is attributed to the misuse of broad-spectrum antibiotics, antibiotics can indiscriminately kill pathogenic and beneficial microorganisms. These events disrupt the delicate microbial balance in both humans and animals, leading to secondary infections and other negative effects. Antimicrobial peptides (AMPs) are functional natural biopolymers in plants and animals. Due to their excellent antimicrobial activities and absence of microbial resistance, AMPs have attracted enormous research attention. We reviewed the antibacterial, antifungal, antiviral, antiparasitic, as well as antitumor properties of AMPs and research progress on AMPs. In addition, we highlighted various recommendations and potential research areas for their progress and challenges in practical applications.

The Citrullination-Neutrophil Extracellular Trap Axis in Chronic Diseases

Citrullination of proteins is crucial for the formation of neutrophil extracellular traps (NETs) − strands of nuclear DNA expulsed in the extracellular environment along with antimicrobial proteins in order to halt the spread of pathogens. Paradoxically, NETs may be immunogenic and contribute to inflammation. It is known that for the externalization of DNA, a group of enzymes called peptidyl arginine deiminases (PADs) is required. Current research often looks at citrullination, NET formation, PAD overexpression, and extracellular DNA (ecDNA) accumulation in chronic diseases as separate events. In contrast, we propose that citrullination can be viewed as the primary mechanism of autoimmunity, for instance by the formation of anti-citrullinated protein antibodies (ACPAs) but also as a process contributing to chronic inflammation. Therefore, citrullination could be at the center, connecting and impacting multiple inflammatory diseases in which ACPAs, NETs, or ecDNA have already been documented. In this review, we aimed to highlight the importance of citrullination in the etiopathogenesis of a number of chronic diseases and to explore the diagnostic, prognostic, and therapeutic potential of the citrullination-NET axis.

Peptidylarginine deiminases 4 as a promising target in drug discovery

Peptidylarginine deaminase 4 (PAD4) is a crucial post-translational modifying enzyme catalyzing the conversion of arginine into citrulline residues, and mediating the formation of neutrophil extracellular traps (NETs). PAD4 plays a vital role in the occurrence and development of cardiovascular diseases, autoimmune diseases, and various tumors. Therefore, PAD4 is considered as a promising drug target for disease diagnosis and treatment. More and more efforts are devoted to developing highly efficient and selective PAD4 inhibitors via high-throughput screening, structure-based drug design and structure-activity relationship study. This article outlined the physiological and pathological functions of PAD4, and corresponding representative small molecule inhibitors reported in recent years.