p38 MAPK inhibition in nucleus pulposus cells: a potential target for treating intervertebral disc degeneration.
METHODS
Human nucleus pulposus cells were cultured in alginate beads and activated with IL-1 beta or TNF-alpha, with and without inhibition of p38 mitogen activated protein kinase (p38 MAPK) activity. Cell production of factors modulating the anabolic/catabolic balance of the disc was determined.


OBJECTIVE
To determine the role of signaling through p38 MAPK in nucleus pulposus cell's response to inflammatory cytokines and whether it might be a valid target for the development of molecular therapies for disc degeneration.


BACKGROUND
Multiple factors contribute to intervertebral disc degeneration (IDD), and development of effective therapies depends on understanding the underlying cellular pathophysiology. Interleukin-1 beta and tumor necrosis factor-alpha are implicated in the development of IDD, and p38 MAPK is part of cytokine and mechanical stress signal pathways in other cells. These studies determine whether inhibiting p38 MAPK can decrease factors that negatively affect the metabolic balance and viability of nucleus pulposus cells.


METHODS
Degenerated intervertebral disc tissue was obtained from patients undergoing elective surgical procedures. Nucleus pulposus cells in alginate bead culture were exposed to IL-1 or TNF-alpha, with or without p38 MAPK inhibition, and conditioned media analyzed for accumulation of nitric oxide (NO), prostaglandin E2 (PGE2), IL-6, matrix metalloproteinase-3 (MMP-3), and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) through 10 days.


RESULTS
Inhibition of p38 MAPK decreased PGE2 in conditioned medium of control, unstimulated cells while not affecting TIMP-1 accumulation. Blocking cytokine activation of p38 MAPK reduced IL-1 and TNF-alpha induced PGE2 and IL-6 accumulation. p38 MAPK inhibition increased the ratio of TIMP-1 to MMP-3 in conditioned medium of cells activated by IL-1 or TNF-alpha.


CONCLUSIONS
Inhibition of p38 MAPK in cytokine-activated disc cells blunts production of factors associated with inflammation, pain, and disc matrix catabolism. The data support further analysis of these effects on the anabolic/catabolic balance of nucleus pulposus cells and suggest that molecular techniques blocking this signal could provide a therapeutic approach to slow the course of intervertebral disc degeneration.
Studer
Rebecca K
RK
VA Pittsburgh Healthcare System, Pittsburgh, PA 15240, USA. rstuder@pitt.edu
Aboka
Alex M
AM
Gilbertson
Lars G
LG
Georgescu
Helga
H
Sowa
Gwendolyn
G
Vo
Nam
N
Kang
James D
JD
D000328:Adult; D000464:Alginates; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D005260:Female; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology* / Q000627:therapeutic use; D053583:Interleukin-1beta / Q000378:metabolism; D007403:Intervertebral Disc / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D008297:Male; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D011725:Pyridines / Q000494:pharmacology* / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects*; D013122:Spinal Diseases / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D013997:Time Factors; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism
D000464:Alginates; D017077:Culture Media, Conditioned; D006603:Hexuronic Acids; D007093:Imidazoles; D053583:Interleukin-1beta; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D019715:Tissue Inhibitor of Metalloproteinase-1; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D020723:Glucuronic Acid; D048051:p38 Mitogen-Activated Protein Kinases; C511768:MMP3 protein, human; D019278:Matrix Metalloproteinase 3; D015232:Dinoprostone; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole