Defensins

Naturally occurring antimicrobial cationic polypeptides play a major role in innate and adaptive immunity, defensins.

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Defensins

Federal government websites often end in. The site is secure. Defensins are a major family of host defense peptides expressed predominantly in neutrophils and epithelial cells. Their broad antimicrobial activities and multifaceted immunomodulatory functions have been extensively studied, cementing their role in innate immunity as a core host-protective component against bacterial, viral and fungal infections. This mini review summarizes the latest findings on the potential pathogenic properties of defensins against the backdrop of their protective roles in antiviral and antibacterial immunity. Further, a succinct description of both tumor-proliferative and -suppressive activities of defensins is also given to highlight their functional and mechanistic complexity in antitumor immunity. The first mammalian defensin, also termed microbicidal cationic protein, was isolated in by Lehrer and colleagues from rabbit lung macrophages 1 , 2. It was not until when the same lab discovered homologous peptides in human neutrophils did Lehrer coin the term defensin 3 , 4 to describe disulfide-stabilized cationic peptides of mammalian origins with broad antimicrobial activity against bacteria, viruses and fungi. HNPs-containing granules normally undergo restricted secretion and are commonly directed for fusion with phagolysosomes, where high concentrations of HNPs directly kill phagocytosed microbes 16 , Upon holocrine secretion and neutrophil infiltration during inflammation, HNPs are released into the extracellular milieu through degranulation of activated neutrophils 17 —

Paneth cell alpha-defensin synthesis and function.

Defensins are small cysteine -rich cationic proteins across cellular life, including vertebrate [1] and invertebrate [2] animals, plants , [3] [4] and fungi. They are variously active against bacteria , fungi and many enveloped and nonenveloped viruses. They are typically amino acids in length, with three or four highly conserved disulphide bonds. In animals, they are produced by cells of the innate immune system and epithelial cells , whereas in plants and fungi they are produced by a wide variety of tissues. An organism usually produces many different defensins, some of which are stored inside the cells e.

Naturally occurring antimicrobial cationic polypeptides play a major role in innate and adaptive immunity. These polypeptides are found to be either linear and unstructured or structured through disulfide bonds. Among the structured antimicrobial polypeptides, defensins comprise a family of cysteine-rich cationic polypeptides that contribute significantly to host defense against the invasion of microorganisms in animals, humans, insects and plants. Their wide-spread occurrence in various tissues of these diverse organisms, and their importance in innate and adaptive immunity have led to their identification, isolation and characterization. Much has also been published regarding their antimicrobial, antiviral and chemoattractive properties, and their molecular and cellular interactions. In this review, we describe the current status of our knowledge of defensins with respect to their molecular, cellular and structural biology, their role in host defense, future research paradigms and the possibility of their utilization as a new class of non-toxic antimicrobial agents and immuno-modulators.

Defensins

Defensins are a major family of host defense peptides expressed predominantly in neutrophils and epithelial cells. Their broad antimicrobial activities and multifaceted immunomodulatory functions have been extensively studied, cementing their role in innate immunity as a core host-protective component against bacterial, viral and fungal infections. This mini review summarizes the latest findings on the potential pathogenic properties of defensins against the backdrop of their protective roles in antiviral and antibacterial immunity. Further, a succinct description of both tumor-proliferative and -suppressive activities of defensins is also given to highlight their functional and mechanistic complexity in antitumor immunity. The first mammalian defensin, also termed microbicidal cationic protein, was isolated in by Lehrer and colleagues from rabbit lung macrophages 1 , 2. It was not until when the same lab discovered homologous peptides in human neutrophils did Lehrer coin the term defensin 3 , 4 to describe disulfide-stabilized cationic peptides of mammalian origins with broad antimicrobial activity against bacteria, viruses and fungi.

Disc-o-bed

Care Med. Cryptdin-3 induces novel apical conductance s in Cl—secretory, including cystic fibrosis, epithelia. Innate Immun. An artificial human theta-defensin, [40] retrocyclin , was created by 'fixing' the pseudogene , and it was shown to be effective against HIV [41] and other viruses, including herpes simplex virus and influenza A. The role of protegrins and other elastase-activated polypeptides in the bactericidal properties of porcine inflammatory fluids. Enteric defensins: antibiotic peptide components of intestinal host defense. Oral Oncol. Liu, C. Also interesting is the effect of alpha-defensins on the exotoxin produced by anthrax Bacillus anthracis. In pigs, caprylic acid and nonanoic acid, both medium-chain fatty acids, significantly increase pBD and pBD expression, respectively, in porcine intestinal enterocytes IPEC-J2 and decrease bacterial translocation, with augmented antibacterial activity , Fig. The same can be said about the antimicrobial insect defensins, which show striking structural similarity to certain toxic peptides found in scorpion venom Cociancich et al. They are typically amino acids in length, with three or four highly conserved disulphide bonds. Genome Research. Oxford University Press is a department of the University of Oxford. The direct antibacterial activity requires high local concentrations, and many defensins exhibit specific cytotoxicity and inflammatory responses at high concentrations, 17 as described in the Regulation of Cell Death section.

Enteric alpha-defensins are potent effectors of innate immunity that are abundantly expressed in the small intestine. Certain enteric bacteria and viruses are resistant to defensins and even appropriate them to enhance infection despite neutralization of closely related microbes.

Antimicrobial peptides are widely distributed in nature and represent an ancient mechanism of host defense. Oncol Rep. The mouse genome encodes a single homolog of the antimicrobial peptide human beta-defensin 1. Evans, E. Lehrer RI, Lu W. MacLeod, R. Secretion of type II phospholipase A2 and cryptdin by rat small intestinal Paneth cells. Immunity 54 , — In such cases apoptotic epithelial cells will not be able to continue to express hBD2. Miani, M. SLPI is synthesized as a aa prepropeptide with a aa signal peptide. However, the beneficial effects of probiotics in adjusting abnormal defensin levels, be it an increase or decrease, have been fairly consistent in aiding host recovery. Avian host defense cathelicidins: structure, expression, biological functions, and potential therapeutic applications.