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Antimicrobial peptides from marine invertebrates are known not only to act like cytotoxic agents, but they also can display some additional activities in mammalian organisms. In particular, these peptides can modulate the complement system as was described for tachyplesin, a peptide from the horseshoe crab. In this work, we investigated the influence on complement activation of the antimicrobial peptide arenicin-1 from the marine polychaete Arenicola marina. To study effects of arenicin on complement activation in human blood serum, we used hemolytic assays of two types, with antibody sensitized sheep erythrocytes and rabbit erythrocytes. Complement activation was also assessed, by the level of C3a production that was measured by ELISA. We found that the effect of arenicin depends on its concentration. At relatively low concentrations the peptide stimulates complement activation and lysis of target erythrocytes, whereas at higher concentrations arenicin acts as a complement inhibitor. A hypothetical mechanism of peptide action is proposed, suggesting its interaction with two complement proteins, C1q and C3. The results lead to the possibility of the development of new approaches for therapy of diseases connected with complement dysregulation, using peptide regulators derived from natural antimicrobial peptides of invertebrates.

Antimicrobial peptides (AMPs) are not only cytotoxic towards host pathogens or cancer cells but also are able to act as immunomodulators. It was shown that some human and non-human AMPs can interact with complement proteins and thereby modulate complement activity. Thus, AMPs could be considered as the base for complement-targeted therapeutics development. Arenicins from the sea polychaete Arenicola marina, the classical example of peptides with a β-hairpin structure stabilized by a disulfide bond, were shown earlier to be among the most prospective regulators. Here, we investigate the link between arenicins’ structure and their antimicrobial, hemolytic and complement-modulating activities using the derivative Ar-1-(C/A) without a disulfide bond. Despite the absence of this bond, the peptide retains all important functional activities and also appears less hemolytic in comparison with the natural forms. These findings could help to investigate new complement drugs for regulation using arenicin derivatives.

initiate apoptosis in target cells, though its action was slower than that of the native ChBac3.4. Its antitumor effectiveness was successfully verified in vivo in a murine Ehrlich ascites carcinoma model. The obtained results demonstrate the potential of structural modification to manage caprine bactenecins' selectivity and activity spectrum and confirm that they are promising prototypes for antimicrobial and anticancer drugs design.

Антимикробные белки и пептиды нейтрофильных гранулоцитов как модуляторы системы комплементаФедеральное государственное бюджетное научное учреждение «Институт экспериментальной медицины» Министерства науки и высшего образования Российской Федерации, 197376, г. Санкт-Петербург, Российская Федерация Резюме Нейтрофильные гранулоциты (нейтрофилы) и система комплемента -важные факторы врожденного иммунитета позвоночных. Вследствие длительной коэволюции между ними сформировались разнообразные отношения. Накоплены данные о действии антимикробных белков и пептидов нейтрофилов на комплемент. В данной работе кратко рассматривается биология нейтрофилов и комплемента, систематизируются работы, посвященные действию миелопероксидазы, активных форм кислорода, лизоцима, антимикробных пептидов, лактоферрина, нейтрофильных внеклеточных ловушек, фрагментов нейтрофилов и тотального вещества гранул на комплемент человека. Акцент делается на физиологической и патофизиологической роли такой модуляции.

The interaction between arenicin-1, that is an antimicrobial peptide from polychaeta Arenicola marina, and human complement system protein C1q was studied using enzyme-linked receptor sorbent assay and ELISA. We revealed that arenicin-1 and C1q form complex that is stable in high ionic strength condition 0.5 M NaCl. The ability of C1q to interact with arenicin-1 is comparable with the binding activity of C1q towards another antimicrobial peptide, porcine cathelicidin protegrin-1, which has a similar spatial arrangement with arenicin-1. Namely, both arenicin-1 and protegrin-1 form cystine-stabilized antiparallel β-hairpin structure.

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