ABSTRACT
The catabolic cytokine interleukin-1 (IL-1) and endotoxin lipopolysaccharide (LPS) are well-known inflammatory mediators involved in degenerative disc disease, and inhibitors of IL-1 and LPS may potentially be used to slow or prevent disc degeneration in vivo. Here, we elucidate the striking anti-catabolic and anti-inflammatory effects of bovine lactoferricin (LfcinB) in the intervertebral disc (IVD) via antagonism of both IL-1 and LPS-mediated catabolic activity using in vitro and ex vivo analyses. Specifically, we demonstrate the biological counteraction of LfcinB against IL-1 and LPS-mediated proteoglycan (PG) depletion, matrix-degrading enzyme production, and enzyme activity in long-term (alginate beads) and short-term (monolayer) culture models using bovine and human nucleus pulposus (NP) cells. LfcinB significantly attenuates the IL-1 and LPS-mediated suppression of PG production and synthesis, and thus restores PG accumulation and pericellular matrix formation. Simultaneously, LfcinB antagonizes catabolic factor mediated induction of multiple cartilage-degrading enzymes, including MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5, in bovine NP cells at both mRNA and protein levels. LfcinB also suppresses the catabolic factor-induced stimulation of oxidative and inflammatory factors such as iNOS, IL-6, and toll-like receptor-2 (TLR-2) and TLR-4. Finally, the ability of LfcinB to antagonize IL-1 and LPS-mediated suppression of PG is upheld in an en bloc intradiscal microinjection model followed by ex vivo organ culture using both mouse and rabbit IVD tissue, suggesting a potential therapeutic benefit of LfcinB on degenerative disc disease in the future.
Subject(s)
Interleukin-1/metabolism , Intervertebral Disc/metabolism , Lactoferrin/metabolism , Lipopolysaccharides/toxicity , Low Back Pain/drug therapy , Animals , Cattle , Cell Survival/drug effects , Gene Expression Regulation/drug effects , Humans , Interleukin-1/antagonists & inhibitors , Intervertebral Disc/cytology , Intervertebral Disc/physiopathology , Lactoferrin/chemistry , Lactoferrin/pharmacology , Low Back Pain/physiopathology , Mice , Organ Culture Techniques , Proteoglycans/biosynthesis , Proteoglycans/drug effects , RabbitsABSTRACT
OBJECTIVE: Protein kinase Cδ (PKCδ) activation has been shown to be a principal rate-limiting step in matrix-degrading enzyme production in human articular chondrocytes. The aim of this study was to assess the role of the PKC pathways, specifically PKCδ, in intervertebral disc tissue homeostasis. METHODS: Using in vitro, ex vivo, and in vivo techniques, we evaluated the pathophysiologic role of the PKCδ pathway by examining 1) proteoglycan deposition, 2) matrix-degrading enzyme production and activity, 3) downstream signaling pathways regulated by PKCδ, and 4) the effect on in vivo models of disc degeneration in genetically engineered PKCδ-knockout mice. RESULTS: Studies of pathway-specific inhibitors revealed a vital role of the PKCδ/MAPK (ERK, p38, JNK) axis and NF-κB in disc homeostasis. Accordingly, in an in vivo model of disc injury, PKCδ-knockout mice were markedly resistant to disc degeneration. CONCLUSION: Suppression of the PKCδ pathway may be beneficial in the prevention and/or treatment of disc degeneration. The results of this study provide evidence for a potential therapeutic role of pathway-specific inhibitors of the PKCδ cascade in the future.
