Antimicrobial peptides derived from hemoglobin are expressed in epithelium of channel catfish (Ictalurus punctatus, Rafinesque).
The beta-chain of the respiratory protein hemoglobin (Hbbeta), has recently been identified in novel sites, including mammalian macrophages and alveolar epithelium, as well as in gill microsomes of fish. However, the functional significance of extra-erythrocytically expressed hemoglobin has been unclear. Here we show inducible expression and upregulation of antimicrobial peptides (AMPs) homologous to Hbbeta in the gill epithelium of channel catfish (Ictalurus punctatus) in response to parasitic (Ichthyophthirius multifiliis, ich) infection. One peptide (HbbetaP-1), while having activity against some fish bacterial pathogens (e.g., Aeromonas hydrophila), had especially potent antiparasitic activity that was specifically lethal (lytic) to the feeding (trophont) stage of ich and also appeared to accelerate the differentiation of trophonts. However, it had no apparent effect on either the disseminative (theront) or reproductive (tomont) stages, nor was it lytic to channel catfish erythrocytes. Fish experimentally challenged with ich confirmed that the HbbetaP-1 sequence was both transcribed and translated in skin and gill epithelium, the target tissues for ich. The Hb AMP concentration expressed in vivo appeared to be well within the antiparasitic concentrations measured in vitro. Our findings suggest that hemoglobin-derived AMPs might play a significant role in the non-specific immune response.
Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606, USA.
Anirudh J
AJ
Ullal
R Wayne
RW
Litaker
Edward J
EJ
Noga
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology*; D000981:Antiprotozoal Agents / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D002397:Catfishes / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005880:Gills / Q000378:metabolism; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006454:Hemoglobins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology*; D006461:Hemolysis / Q000187:drug effects; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology*; D012867:Skin / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D015854:Up-Regulation
D000900:Anti-Bacterial Agents; D000981:Antiprotozoal Agents; D006454:Hemoglobins; D010455:Peptides