Novel antimicrobial cecropins derived from O. curvicornis and D. satanas dung beetles.

Antibiotic resistance is an increasing global problem and therapeutic alternatives to traditional antibiotics are needed. Antimicrobial and host defense peptides represent an attractive source for new therapeutic strategies, given their wide range of activities including antimicrobial, antitumoral and immunomodulatory. Insects produce several families of these peptides, including cecropins. Herein, we characterized the sequence, structure, and biological activity of three cecropins called satanin 1, 2, and curvicin, found in the transcriptome of two dung beetle species Dichotomius satanas and Onthophagus curvicornis. Sequence and circular dichroism analyses show that they have typical features of the cecropin family: short length (38-39 amino acids), positive charge, and amphipathic α-helical structure. They are active mainly against Gram-negative bacteria (3.12-12.5 µg/mL), with low toxicity on eukaryotic cells resulting in high therapeutic indexes (TI > 30). Peptides also showed effects on TNFα production in LPS-stimulated PBMCs. The biological activity of Satanin 1, 2 and Curvicin makes them interesting leads for antimicrobial strategies.

Steroid hormone modulates the production of cathelicidin and human ß-defensins in lung epithelial cells and macrophages promoting Mycobacterium tuberculosis killing.

Several studies have documented the interaction between the immune and endocrine systems as an effective defense strategy against tuberculosis, involving the production of several molecules and immunological processes. In this study, we determined the effect of cortisol and dehydroepiandrosterone (DHEA) on the production of antimicrobial peptides such as cathelicidin and human ß-defensin (HBD) -2, and HBD-3 and their effect on intracellular growth of Mycobacterium tuberculosis (Mtb) in lung epithelial cells and macrophages. Our results showed that DHEA promotes the production of these antimicrobial peptides in infected cells, correlating with the decrease of Mtb bacilli loads. These results suggest the use of exogenous DHEA as an adjuvant for tuberculosis therapy.

Nicotine promotes the intracellular growth of Mycobacterium tuberculosis in epithelial cells.

Several epidemiological studies have identified the cigarette smoke as a risk factor for the infection and development of tuberculosis. Nicotine is considered the main immunomodulatory molecule of the cigarette. In the present study, we evaluated the effect of nicotine in the growth of M. tuberculosis. Lung epithelial cells and macrophages were infected with M. tuberculosis and/or treated with nicotine. The results show that nicotine increased the growth of M. tuberculosis mainly in type II pneumocytes (T2P) but not in airway basal epithelial cells nor macrophages. Further, it was observed that nicotine decreased the production of ß-defensin-2, ß-defensin-3, and the cathelicidin LL-37 in all the evaluated cells at 24 and 72 h post-infection. The modulation of the expression of antimicrobial peptides appears to be partially mediated by the nicotinic acetylcholine receptor α7 since the blockade of this receptor partially reverted the production of antimicrobial peptides. In summary, it was found that nicotine decreases the production of HBD-2, HBD-3, and LL-37 in T2P during the infection with M. tuberculosis promoting its intracellular growth.

Host Defense Peptide RNase 7 Is Down-regulated in the Skin of Diabetic Patients with or without Chronic Ulcers, and its Expression is Altered with Metformin.

BACKGROUND: Diabetic foot ulcers (DFUs) are one of the main complications in patients with type 2 diabetes mellitus (DM2), previous studies have reported that DM2 patients have lower production of host defense peptides (HDP). AIM OF THE STUDY: To investigate the expression of RNase 7, cathelicidin, HBD-2, and psoriasin in biopsies obtained from DM2 patients with or without DFU. METHODS: Biopsies from DFU patients grade 3 according to Wagner's classification, from diabetic patients without ulcer and from healthy donors were obtained. qPCR, immunohistochemistry and cell line cultures were performed. To assess whether L-isoleucine, calcitriol, phenyl butyrate, metformin, glyburide or insulin induced RNase 7, keratinocytes were stimulated, and RNase 7 expression was evaluated. RESULTS: Our data showed that RNase 7 levels were decreased in both diabetic groups when were compared with skin from healthy donors. Since most of the DM2 patients are treated with drugs to reduce glycemia, we investigated whether glyburide, metformin or insulin were able to induce any change regarding RNase 7 production. Results showed that metformin reduces the expression of RNase 7 in in vitro treated keratinocytes, suggesting that the chronic use of metformin should be evaluated in DFU patients, whereas calcitriol, phenyl butyrate and L-isoleucine did not increase the RNase 7 production. CONCLUSIONS: Due RNase 7 has antimicrobial activity, its downregulation can make prone to DM2 patients to develop infections and impaired wound healing.

Evidence that changes in antimicrobial peptides during tuberculosis are related to disease severity, clinical presentation, specific therapy and levels of immune-endocrine mediators.

Given the role of host defense peptides (HDPs) in the defensive response against mycobacteria, we analyzed the circulating levels of LL-37, ß-defensin-2 and -3 in newly diagnosed patients with pulmonary (PTB) or pleural tuberculosis (PLTB) in whom measurements of pleural fluids were also performed. Severe PTB patients displayed higher circulating amounts of ß-defensin-3, statistically different from controls, further decreasing upon antimycobacterial treatment. LL-37 concentrations appeared within the normal range at diagnosis, but tended to increase during treatment, becoming statistically upon its completion in moderate cases. PLTB patients revealed decreased levels of ß-defensin-2 in presence of increased amounts of ß-defensin-3 and LL-37; in their plasma or pleural fluids. Considering the immune-endocrine dysregulation of tuberculosis, we also performed correlation analysis detecting positive associations between levels of cortisol, IL-6 and ß-defensin-3 in plasma from untreated severe patients as did their dehydroepiandrosterone and LL-37 values. Increased presence of ß-defensins, may represent an attempt to improve defensive mechanisms; which also take part in the inflammatory reaction accompanying TB, reinforced by the association with immune-endocrine mediators. The divergent profile of PLTB patients, decreased ß-defensin-2 but increased ß-defensin-3 and LL-37 levels, suggests a differential role of these HDPs in a situation characterized for its better protective response.