Human beta-defensin-2 increases cholinergic response in colon epithelium.
The human beta-defensin-2 (hBD-2) is expressed in epithelial cells of skin and respiratory and gastrointestinal tracts. Defensins are arginine-rich small cationic peptides with six intramolecular disulfide bonds and are antimicrobially active against a broad spectrum of pathogens. In addition, they have cytokine-like immunomodulatory properties. We hypothesized that hBD-2 also might influence epithelial cells themselves, thereby altering fluid composition in the gastrointestinal tract. We therefore tested its impact on electrogenic ion transport properties of distal colon in Ussing chamber experiments. Application of hBD-2 did not affect transepithelial voltage or resistance in cAMP-stimulated distal colon. However, it increased cholinergic Ca(2+)-dependent Cl(-) secretion. After 20 min of incubation with hBD-2, the effect of carbachol (CCh) on the equivalent short circuit current (I'(sc)) was enhanced twofold compared to vehicle-treated colon. Modulation of Ca(2+) signaling by hBD-2 was validated by Fura-2 measurements in human colon carcinoma HT29 cells. Twenty-minute incubation with hBD-2 increased the CCh-induced Ca(2+) transient by 20-30% compared to either vehicle-treated cells or cells treated with the defensins hBD-1, hBD-3, or HD-5. This effect was concentration-dependent, with an EC(50) of 0.043 microg/ml, and still present in the absence of extracellular Ca(2+). Also, the ionomycin-induced Ca(2+) transient was increased by hBD-2 treatment. We conclude that hBD-2 facilitates cholinergic Ca(2+)-regulated epithelial Cl(-) secretion. These findings contribute to the concept of a specific interaction of antimicrobial peptides with epithelial function.
Physiologisches Institut der Christian-Albrechts-Universität, Kiel, Germany. n.himmerkus@physiologie.uni-kiel.de
Nina
N
Himmerkus
Veit
V
Vassen
Birte
B
Sievers
Boeren
B
Goerke
Qixian
Q
Shan
Jürgen
J
Harder
Jens-Michael
JM
Schröder
Markus
M
Bleich
D000109:Acetylcholine / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002217:Carbachol / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism; D018679:Cholinergic Agonists / Q000494:pharmacology; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D017097:Electric Impedance; D019073:HT29 Cells; D006801:Humans; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D051381:Rats; D013997:Time Factors; D023083:beta-Defensins / Q000378:metabolism*
D002712:Chlorides; D018679:Cholinergic Agonists; C422950:DEFB103A protein, human; C465593:DEFB105A protein, human; C106641:DEFB4A protein, human; D007476:Ionophores; D023083:beta-Defensins; D015759:Ionomycin; D002217:Carbachol; D000109:Acetylcholine; D002118:Calcium