A family of antimicrobial and immunomodulatory peptides related to the frenatins from skin secretions of the Orinoco lime frog Sphaenorhynchus lacteus (Hylidae).
Peptidomic analysis of norepinephrine-stimulated skin secretions of the Orinoco lime tree frog Sphaenorhynchus lacteus (Hylidae, Hylinae) revealed the presence of three structurally related host-defense peptides with limited sequence similarity to frenatin 2 from Litoria infrafrenata (Hylidae, Pelodryadinae) and frenatin 2D from Discoglossus sardus (Alytidae). Frenatin 2.1S (GLVGTLLGHIGKAILG.NH2) and frenatin 2.2S (GLVGTLLGHIGKAILS.NH2) are C-terminally α-amidated but frenatin 2.3S (GLVGTLLGHIGKAILG) is not. Frenatin 2.1S and 2.2S show potent bactericidal activity against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MIC ≤16μM) but are less active against a range of Gram-negative bacteria. Frenatin 2.1S (LC50=80±6 μM) and 2.2S (LC50=75±5 μM) are cytotoxic against non-small cell lung adenocarcinoma A549 cells but are less hemolytic against human erythrocytes (LC50=167±8 μM for frenatin 2.1S and 169±7 μM for 2.2S). Weak antimicrobial and cytotoxic potencies of frenatin 2.3S demonstrate the importance of C-terminal α-amidation for activity. Frenatin 2.1S and 2.2S significantly (P<0.05) increased production of proinflammatory cytokines IL-1β and IL-23 by lipopolysaccharide (LPS)-stimulated mouse peritoneal macrophages and frenatin 2.1S also enhanced production of TNF-α. Effects on IL-6 production were not significant. Frenatin 2.2S significantly downregulated production of the anti-inflammatory cytokine IL-10 by LPS-stimulated cells. The data support speculation that frenatins act on skin macrophages to produce a cytokine-mediated stimulation of the adaptive immune system in response to invasion by microorganisms. They may represent a template for the design of peptides with therapeutic applications as immunostimulatory agents.
Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, 17666 Al Ain, United Arab Emirates. Electronic address: jmconlon@uaeu.ac.ae.
J Michael
JM
Conlon
Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, 17666 Al Ain, United Arab Emirates.
Milena
M
Mechkarska
Center for Molecular Medicine, Faculty of Medicine, University of Kragujevac, Kragujevac, Serbia.
Gordana
G
Radosavljevic
Department of Pharmacology, College of Medicine and Health Sciences, United Arab Emirates University, 17666 Al Ain, United Arab Emirates.
Samir
S
Attoub
Rare Species Conservatory Foundation, St. Louis, MO 63110, USA.
Jay D
JD
King
Center for Molecular Medicine, Faculty of Medicine, University of Kragujevac, Kragujevac, Serbia.
Miodrag L
ML
Lukic
School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, Northern Ireland BT52 1SA, UK.
Stephen
S
McClean
D029845:Amphibian Proteins / Q000737:chemistry; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D007155:Immunologic Factors / Q000737:chemistry / Q000494:pharmacology*; D016753:Interleukin-10 / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D053759:Interleukin-23 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects; D051379:Mice; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology*; D012867:Skin / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D029845:Amphibian Proteins; D000890:Anti-Infective Agents; D000970:Antineoplastic Agents; D007155:Immunologic Factors; D053583:Interleukin-1beta; D053759:Interleukin-23; D008070:Lipopolysaccharides; D010455:Peptides; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10
Antimicrobial; Cytokine; Frenatin; Frog skin; Hylidae; Immunomodulatory