Sphingosine kinase-1 is required for toll mediated beta-defensin 2 induction in human oral keratinocytes.
BACKGROUND
Host defense against invading pathogens is triggered by various receptors including toll-like receptors (TLRs). Activation of TLRs is a pivotal step in the initiation of innate, inflammatory, and antimicrobial defense mechanisms. Human beta-defensin 2 (HBD-2) is a cationic antimicrobial peptide secreted upon gram-negative bacterial perturbation in many cells. Stimulation of various TLRs has been shown to induce HBD-2 in oral keratinocytes, yet the underlying cellular mechanisms of this induction are poorly understood.


RESULTS
Here we demonstrate that HBD-2 induction is mediated by the Sphingosine kinase-1 (Sphk-1) and augmented by the inhibition of Glycogen Synthase Kinase-3beta (GSK-3beta) via the Phosphoinositide 3-kinase (PI3K) dependent pathway. HBD-2 secretion was dose dependently inhibited by a pharmacological inhibitor of Sphk-1. Interestingly, inhibition of GSK-3beta by SB 216763 or by RNA interference, augmented HBD-2 induction. Overexpression of Sphk-1 with concomitant inhibition of GSK-3beta enhanced the induction of beta-defensin-2 in oral keratinocytes. Ectopic expression of constitutively active GSK-3beta (S9A) abrogated HBD-2 whereas kinase inactive GSK-3beta (R85A) induced higher amounts of HBD-2.


CONCLUSIONS
These data implicate Sphk-1 in HBD-2 regulation in oral keratinocytes which also involves the activation of PI3K, AKT, GSK-3beta and ERK 1/2. Thus we reveal the intricate relationship and pathways of toll-signaling molecules regulating HBD-2 which may have therapeutic potential.
Benakanakere
Manjunatha R
MR
Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
Zhao
Jiawei
J
Galicia
Johnah C
JC
Martin
Michael
M
Kinane
Denis F
DF
D015153:Blotting, Western; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism*; D008094:Lithium / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D051195:Toll-Like Receptor 2 / Q000819:agonists / Q000378:metabolism*; D023083:beta-Defensins / Q000235:genetics / Q000378:metabolism*; D000099157:Sphingosine Kinase
D004791:Enzyme Inhibitors; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D007211:Indoles; D008094:Lithium; D008301:Maleimides; D017853:Phosphotransferases (Alcohol Group Acceptor); D051195:Toll-Like Receptor 2; D023083:beta-Defensins; D000099157:Sphingosine Kinase; C106641:DEFB4A protein, human; C417521:SB 216763; C495342:TLR2 protein, human; C000605506:GSK3B protein, human