C1q/TNF-related protein-3 represents a novel and endogenous lipopolysaccharide antagonist of the adipose tissue.
Proteins secreted by adipocytes (adipokines) play an important role in the pathophysiology of type 2 diabetes mellitus and the associated chronic and low-grade state of inflammation. It was the aim to characterize the antiinflammatory potential of the new adipocytokine, C1q/TNF-related protein-3 (CTRP-3), which shows structural homologies to the pleiotropic adipocytokine adiponectin. mRNA and protein expression of CTRP-3 was analyzed by RT-PCR and Western blot. Recombinant CTRP-3 and small interfering RNA-based strategies were used to investigate the effect of CTRP-3 on toll-like receptor (TLR) ligand, lipopolysaccharide (LPS)-, and lauric acid-induced chemokine release of monocytes and adipocytes. Together with complex ELISA-based techniques, a designed TLR4/myeloid differentiation protein-2 fusion molecule shown to bind LPS was used to prove the ability of CTRP-3 to act as endogenous LPS antagonist. CTRP-3 is synthesized in monocytes and adipocytes. The recombinant protein dose-dependently inhibits the release of chemokines in monocytes and adipocytes that were induced by lauric acid, LPS, and other TLR ligands in vitro and ex vivo. CTRP-3 inhibits monocyte chemoattractant protein-1 release in adipocytes, whereas small interfering RNA-mediated knockdown of CTRP-3 up-regulates monocyte chemoattractant protein-1 release, reduces lipid droplet size, and decreases intracellular triglyceride concentration in adipocytes, causing a dedifferentiation into a more proinflammatory and immature phenotype. By using a designed TLR4/MD-2 fusion molecule, it is shown by different techniques that CTRP-3 specifically and effectively inhibits the binding of LPS to its receptor, TLR4/MD-2. CTRP-3 inhibits three basic and common proinflammatory pathways involved in obesity and type 2 diabetes mellitus (adipo-inflammation) by acting as an endogenous LPS antagonist of the adipose tissue.
Kopp
Andrea
A
Department of Internal Medicine I, University of Regensburg, D-93042 Regensburg, Germany.
Bala
Margarita
M
Buechler
Christa
C
Falk
Werner
W
Gross
Philipp
P
Neumeier
Markus
M
Schölmerich
Jürgen
J
Schäffler
Andreas
A
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000328:Adult; D000818:Animals; D015153:Blotting, Western; D018932:Chemokine CCL2 / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007249:Inflammation / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D008875:Middle Aged; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D051193:Toll-Like Receptors / Q000378:metabolism; D014162:Transfection; D048069:Tumor Necrosis Factors / Q000378:metabolism*
C506069:C1QTNF3 protein, human; D018932:Chemokine CCL2; D016207:Cytokines; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D051193:Toll-Like Receptors; D048069:Tumor Necrosis Factors