Mitogen-activated protein kinase kinase 3 is a pivotal pathway regulating p38 activation in inflammatory arthritis.
p38 mitogen-activated protein kinase (MAPK) regulates cytokines in arthritis and is, in turn, regulated by MAPK kinase (MKK) 3 and MKK6. To modulate p38 function but potentially minimize toxicity, we evaluated the utility of targeting MKK3 by using MKK3(-/-) mice. These studies showed that TNF-alpha increased phosphorylation of p38 in WT cultured synoviocytes but that p38 activation, IL-1beta, and IL-6 expression were markedly lower in MKK3(-/-) synoviocytes. In contrast, IL-1beta or LPS-stimulated p38 phosphorylation and IL-6 production by MKK3(-/-) synoviocytes were normal. Detailed signaling studies showed that NF-kappaB also contributes to IL-6 production and that TNF-alpha-induced NF-kappaB activation is MKK3-dependent. In contrast, LPS-mediated activation of NF-kappaB does not require MKK3. To determine whether this dichotomy occurs in vivo, two inflammation models were studied. In K/BxN passive arthritis, the severity of arthritis was dramatically lower in MKK3(-/-) mice. Phospho-p38, phospho-MAPK activator protein kinase 2, IL-1beta, CXC ligand 1, IL-6, and matrix metalloproteinase (MMP) 3 levels in the joints of MKK3(-/-) mice were significantly lower than in controls. Exogenous IL-1beta administered during the first 4 days of the passive model restored arthritis to the same severity as in WT mice. In the second model, IL-6 production after systemic LPS administration was similar in WT and MKK3(-/-) mice. Therefore, selective MKK3 deficiency can suppress inflammatory arthritis and cytokine production while Toll-like receptor 4-mediated host defense remains intact.
Division of Rheumatology, Allergy, and Immunology, University of California at San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093-0656, USA.
Tomoyuki
T
Inoue
David L
DL
Boyle
Maripat
M
Corr
Deepa
D
Hammaker
Roger J
RJ
Davis
Richard A
RA
Flavell
Gary S
GS
Firestein
D000818:Animals; D001169:Arthritis, Experimental / Q000201:enzymology*; D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D047468:Immunoprecipitation; D007375:Interleukin-1 / Q000096:biosynthesis; D015850:Interleukin-6 / Q000096:biosynthesis; D048371:MAP Kinase Kinase 3 / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D007375:Interleukin-1; D015850:Interleukin-6; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; C482531:Map2k3 protein, mouse