Evidence for widespread distribution of piscidin antimicrobial peptides in teleost fish

Abstract

Antimicrobial peptides (AMPs) are increasingly recognized as a critical component of the host's defense against infection. Several types of AMPs have been recently identified from mucosal tissues or immune cells of a number of teleosts. Among these are the piscidins, which are 22 residue, α-helical AMPs that were originally isolated from mast cells of hybrid striped bass Morone saxatilis male × Morone chrysops female. Using an antibody specific for the conserved N-terminal amino acid sequence of piscidin 1, we used immunohistochemistry to probe skin, gill, and gastrointestinal tract of 39 teleosts representing 7 different orders. Nine fish species were piscidin-positive, with all of these species being in the Perciformes, the largest and most evolutionarily advanced order of teleosts. Piscidin-positive cells were identified in species belonging to the families Moronidae, Serranidae, Sciaenidae, Siganidae and Belontidae. Immunopositive cells were usually most consistent with mast cells, although in some species, the granule appearance and tinctorial properties diverged somewhat from those of a typical piscine mast cell. In addition, rodlet cells were piscidin-positive in one member of the family Cichlidae; to our knowledge, it is the first time that a host-associated chemical biomarker has been identified in rodlet cells. Our data suggest that piscidins are present in many evolutionarily advanced teleosts. Piscidin-immunoreactive cells were most common at sites of pathogen entry, including the skin, gill and gastrointestinal tract. These results strongly suggest that piscidins are a widespread and important component of many fishes' defense against disease. KEY WORDS: Piscidins · Mast cells · Rodlet cells · Innate immunity · Pisces Resale or republication not permitted without written consent of the publisherDis Aquat Org 72: [241][242][243][244][245][246][247][248][249][250][251][252] 2006 tissues of hybrid striped bass; the parental stocks of hybrid striped bass (white bass Morone chrysops and striped bass M. saxatilis) are in the family Moronidae, and similar appearing cells were positive in members of the family Sciaenidae (spot Leistomus xanthurus and Atlantic croaker Micropogonias undulatus). This prompted us to hypothesize that piscidins are present in other teleosts. To answer this question, we immunochemically examined tissues from 7 different orders of teleosts. Presumptively healthy, subadult to adult, farm-raised fish, as well as wild-caught individuals, were examined in the present study. MATERIALS AND METHODSPeptide synthesis. Piscidin 1 (both the entire peptide and an 11-mer fragment) and Magainin 2 peptides were synthesized using Fmoc chemistry on a Rainin Symphony instrument that provides on-instrument cleavage of the peptide from the resin. After synthesis, peptides were purified via analytical reverse phase HPLC using a YMC C-18 column (4 × 50 mm, 3 µm particle size, 120 Å pore size support) using an acetonitrile gradient that was eluted at 1 ml min -1 where Buffer A was 0.05% trif...

An Overview of the Immunological Defenses in Fish Skin

“…In addition, rodlet cells have also been identified as piscidin-positive in one member of the family Cichlidae. This study was the first one which identified in rodlet cells a host-associated chemical biomarker [157]. All piscidins show broad-spectrum antimicrobial activity, probably killing cells via toroidal-pore formation [151,170,171].…”

“…However, several types of AMPs have been identified from mucosal tissues or immune cells of a number of teleosts, and they are, at present, considered a very important part of the mucus and skin barrier function ( [114,157], reviewed by [158]). …”

“…S30 from skin secretions of Oncorhynchus mykiss [148] and three ribosomal-derived proteins and peptides (namely, L40, L36A, and L35) isolated from the epidermal mucus of Atlantic cod (Gadus morhua) [114]. Piscidins are 22-residue AMPs that were originally isolated from mast cells of hybrid striped bass Morone saxatilis male × Morone chrysops female and now known to be present in other fish species [148,157,163,164]. Using an antibody specific for the conserved N-terminal amino acid sequence of piscidin 1, an immunohistochemical study has been carried out on skin, gill, and gastrointestinal tract of thirty-nine teleost fish species representing seven different orders.…”

“…Nine fish species were piscidin-positive, with all of these species being in the Perciformes, the largest and most evolutionarily advanced order of teleosts. Piscidin-positive cells were identified in species belonging to the families Moronidae, Serranidae, Sciaenidae, Siganidae, and Belontidae [157]. Examples of piscidins are also dicentracin from the European bass (Dicentrarchus labrax) [165], chrysophsins from red sea bream (Chrysophrys major) [166], and epinecidin from the orange-spotted grouper (Epinephelus coioides) [167].…”

Histamine is stored in mast cells of most evolutionarily advanced fish and regulates the fish inflammatory response

“…It is possible that although the storage of histamine in MCs and its use as an inflammatory messenger was established in primitive reptiles (Lepidosauria) Ϸ276 mya (44), this same feature developed independently in Perciform fish in the Lower Eocene, between 55 and 45 mya, a short period during which the great majority of Percomorph families appeared (47). It is striking that piscidins had a similar evolutionary history, because only the MCs of Perciformes are endowed with these antimicrobial peptides (48). However, a related family of antimicrobial peptides, called pleurocidins, are synthesized by MCs of the Atlantic halibut (49), a flat fish belonging to the order Pleuronectiformes and the family Pleuronectidae.…”