Gene Expression and Localization of the Epinecidin-1 Antimicrobial Peptide in the Grouper (Epinephelus coioides), and Its Role in Protecting Fish Against Pathogenic Infection

Abstract

Epinecidin-1 is an antimicrobial peptide and plays a vital role in protecting fish against pathogenic infection. As a mimic of a grouper epinecidin-1 peptide, it has tertiary structures that closely resemble those of pleurocidin found in the winter flounder (Pleuronectes americanus). The tissue-specific, lipopolysaccharide (LPS)-stimulation-specific, and poly(I):poly(C)-stimulation-specific expressions of the grouper (Epinephelus coioides) epinecidin-1 antimicrobial peptide were determined using a comparative reverse-transcription polymerase chain reaction. Results of the tissue distribution analysis revealed high levels of epinecidin-1 messenger RNA (mRNA) in the head kidneys, intestines, and skin. Expression of epinecidin-1 mRNA was dose-dependently stimulated by both LPS and poly(I):poly(C). Immunohistochemical analysis with the polyclonal antiserum of a grouper epinecidin-1 peptide (rabbit polyclonal antibody) showed that the peptide was localized with the epinecidin-1 antibody in the gills and intestines. Two synthetic peptides of the grouper epinecidin-1 peptide (g-ple 22-51 and g-ple 22-42) and one winter flounder pleurocidin as a control exhibited high antimicrobial activities against gram-negative or gram-positive bacteria. In addition, peptide treatment was effective in promoting a significant increase in fish survival after the injection of Vibrio vulnificus in tilapia (Oreochromis mossambicus) and grouper. These results are relevant to the design of prophylactic and therapeutic strategies to counter bacterial infections, especially for preventing or ameliorating immune defects in fish during bacterial infections.

Inducible Resistance of Fish Bacterial Pathogens to the Antimicrobial Peptide Cecropin B

“…V. anguillarum is known to enter its fish host through the portals of the skin, the gut, and the gills and has been shown to move by chemotaxis toward mucus secretions from multiple epithelial tissues, including the skin and the intestine (27). Fish epithelial tissues secrete innate immune effectors, including AMPs (10,28). The increase in the cumulative mortality of medaka following challenge with V. anguillarum that was previously exposed to cecropin B suggests that successful colonization of the fish by V. anguillarum depends on its ability to resist the actions of AMPs.…”

Epinecidin-1 Has Immunomodulatory Effects, Facilitating Its Therapeutic Use in a Mouse Model of Pseudomonas aeruginosa Sepsis

“…The blood samples were centrifuged, and sera were collected. The concentration of epinecidin-1 in sera was determined by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS), following a previously published protocol and procedure (23).…”

“…The central role of AMPs in host defense makes them potential candidates for the treatment of infections (21)(22)(23), and the effects of several AMPs on P. aeruginosa infection have been analyzed in vitro (21). Recently, we identified a cDNA sequence from Epinephelus coioides that encodes a peptide named epinecidin-1; we found that epinecidin-1 is active against Gram-negative and -positive bacteria, viruses, Candida albicans, and Trichomonas vaginalis in vitro and in vivo (23)(24)(25)(26).…”

“…Recently, we identified a cDNA sequence from Epinephelus coioides that encodes a peptide named epinecidin-1; we found that epinecidin-1 is active against Gram-negative and -positive bacteria, viruses, Candida albicans, and Trichomonas vaginalis in vitro and in vivo (23)(24)(25)(26). Morphological changes in bacteria treated with epinecidin-1 suggest that the peptide disrupts membranes (24) and may thus prevent or delay the development of microbial resistance.…”

Importance of Fish Antimicrobial Peptides for Aquaculture and Biomedicine

“…A large number of AMPs have been isolated from a wide number of fish species during last years, among which pleurocidin from winter flounder (Pleuronectes americanus) [2], cathelicidins from rainbow trout (Oncorhynchus mykiss) [3], defensins from zebrafish (Danio rerio) [4], piscidins from hybrid striped bass (white bass, Morone chrysops, female, x striped bass, Morone saxatilis, male) [5], dicentracin from sea bass (Dicentrarchus labrax) [6], and hepcidin from channel catfish (Ictalurus punctatus) [7], epinecidin from the grouper (Epinephelus coiodes) [8] (for a review see [9]). The activity of fish AMPs have been tested not only against the more common fish bacterial pathogens [8,10] but either against other pathogens like nervous necrosis virus [11]. Moreover, some AMPs have shown dual functional aspects, like hepcidins that have been indicated to be involved in iron regulation [12].…”