[Interaction of Arenicin-1 with C1q Protein]

Marine Invertebrate Antimicrobial Peptides and Their Potential as Novel Peptide Antibiotics

Marine invertebrates constantly interact with a wide range of microorganisms in their aquatic environment and possess an effective defense system that has enabled their existence for millions of years. Their lack of acquired immunity sets marine invertebrates apart from other marine animals. Invertebrates could rely on their innate immunity, providing the first line of defense, survival, and thriving. The innate immune system of marine invertebrates includes various biologically active compounds, and specifically, antimicrobial peptides. Nowadays, there is a revive of interest in these peptides due to the urgent need to discover novel drugs against antibiotic-resistant bacterial strains, a pressing global concern in modern healthcare. Modern technologies offer extensive possibilities for the development of innovative drugs based on these compounds, which can act against bacteria, fungi, protozoa, and viruses. This review focuses on structural peculiarities, biological functions, gene expression, biosynthesis, mechanisms of antimicrobial action, regulatory activities, and prospects for the therapeutic use of antimicrobial peptides derived from marine invertebrates.

Tachyplesin I and its derivatives: A pharmaco-chemical perspective on their antimicrobial and antitumor potential

INTRODUCTION

Increasing evidence suggests that intratumor microbiota are an intrinsic component in the tumor microenvironment across multiple cancer types, and that there is a close relationship between microbiota and tumor progression. Therefore, how to address the interaction between bacteria and malignances has become a growing concern. Tachyplesin I (TPI), a peptide with dual antimicrobial and antitumor effects, holds great promise as a therapeutic alternative for the aforementioned diseases, with the advantage of broad-spectrum activities, quick killing efficacy, and a low tendency to induce resistance.

AREAS COVERED

This review comprehensively summarizes the pharmacological mechanisms of TPI with an emphasis on its antimicrobial and antitumor potential. Furthermore, it presents advances in TPI derivatives and gives a perspective on their future development. The article is based on literature searches using PubMed and SciFinder to retrieve the most up-to-date information of TPI.

EXPERT OPINION

Bacterial infections and cancer both pose a serious threat to health due to their symbiotic interactions and drug resistance. TPI is anticipated to be a novel agent to control pathogenic bacteria and various tumors through multiple mechanisms of action. Indeed, the continuous advancements in chemical modification and innovative applications of TPI give hope for future improvements in therapeutic efficacy.

Antimicrobial Peptide Arenicin-1 Derivative Ar-1-(C/A) as Complement System Modulator

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.

Human antimicrobial peptides in autoimmunity

Antimicrobial peptides (AMPs) were firstly discovered as cytotoxic substances that killed bacteria. Later they were described as biologically active peptides that are able not only to kill invaders but also to modulate host immunity. In particular, it is shown that human antimicrobial peptides are able to influence the activity of different innate and adaptive immunity components, thus, obviously, they also participate in autoimmune processes. In this review we discuss the nature of human AMPs and analyze their role in such autoimmune disorders like type 1 diabetes mellitus, rheumatoid arthritis, systemic lupus erythematosus, psoriasis, Crohn's disease and sarcoidosis. These peptides were shown to have a "double-sided" influence on the autoimmune disease pathogenesis. Thus, described facts should be taken into account for the development of new pharmaceutical agents to cure patients with autoimmune disorders. These agents could derive from natural antimicrobial peptides that in some cases modulate immune response. For example, it was shown that human AMPs are able to modulate complement system dysregulation of which is known to be one of the most dangerous pathogenic factors during autoimmune processes.

Modulation of Human Complement System by Antimicrobial Peptide Arenicin-1 from Arenicola marina

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.