Toll-like receptor adaptor signaling molecule MyD88 on intervertebral disk homeostasis: in vitro, ex vivo studies.
MyD88 is an adapter protein that links toll-like receptors (TLRs) and Interleukin-1 receptors (IL-1Rs) with downstream signaling molecules. The MyD88 has been found to be an essential mediator in the development of osteoarthritis in articular cartilage. However, the role of the MyD88 pathway has yet to be elucidated in the intervertebral disk (IVD). Using in vitro techniques, we analyzed the effect of MyD88 pathway-specific inhibition on the potent inflammatory and catabolic mediator LPS and IL-1 in bovine and human nucleus pulposus (NP) cells by assessing matrix-degrading enzyme expression, including matrix metalloproteases (MMPs) and a disintegrin-like and metalloprotease with thrombospondin motifs (ADAMTS family). We also analyzed inhibition of MyD88 in the regulation of inducible nitric oxide synthase and TLR-2. Finally, we used an ex vivo organ culture model to assess the effects of MyD88 inhibitor (MyD88i) on catabolic factor-induced disk degeneration in mice lumbar disks. In bovine NP cells, MyD88i potently antagonizes LPS- or IL-1-mediated induction of cartilage-degrading enzyme production, including MMP-1, MMP-13, ADAMTS-4, and ADAMTS-5. MyD88i also attenuates the LPS- or IL-1-mediated induction of iNOS and TLR-2 gene expression. Our ex vivo findings reveal inhibition of MyD88 via counteraction of IL-1-mediated proteoglycan depletion. The findings from this study demonstrate the potent anti-inflammatory and anti-catabolic effects of inhibition of MyD88 pathway inhibition on IVD homeostasis, suggesting a potential therapeutic benefit of a MyD88i in degenerative disk disease in the future.
Department of Biochemistry, Rush University Medical Center, Chicago, IL 606124, USA.
Michael B
MB
Ellman
Jae-Sung
JS
Kim
Howard S
HS
An
Di
D
Chen
Ranjan
R
KC
Jennifer
J
An
Teju
T
Dittakavi
Andre J
AJ
van Wijnen
Gabriella
G
Cs-Szabo
Xin
X
Li
Guozhi
G
Xiao
Steven
S
An
Su-Gwan
SG
Kim
Hee-Jeong
HJ
Im
D051722:ADAM Proteins / Q000378:metabolism; D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D015870:Gene Expression / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D007403:Intervertebral Disc / Q000187:drug effects*; D055959:Intervertebral Disc Degeneration / Q000188:drug therapy / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D020782:Matrix Metalloproteinases / Q000378:metabolism; D051379:Mice; D053594:Myeloid Differentiation Factor 88 / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D009924:Organ Culture Techniques; D015398:Signal Transduction / Q000187:drug effects*; D051195:Toll-Like Receptor 2 / Q000378:metabolism
D007375:Interleukin-1; D008070:Lipopolysaccharides; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D051195:Toll-Like Receptor 2; D052247:Nitric Oxide Synthase Type II; D051722:ADAM Proteins; D020782:Matrix Metalloproteinases