Dysregulation of p38 and MKP-1 in response to NOD1/TLR4 stimulation in sarcoid bronchoalveolar cells.
BACKGROUND
Sarcoidosis is a systemic inflammatory disorder characterized by distinct up-regulation of Th1 cytokines, such as tumor necrosis factor (TNF)-α and IL-12. The mechanism underlying this up-regulation remains unclear. Recognition of microbial moieties through Toll-like or Nod-like receptors evokes sequential activation of mitogen-activated protein kinases (MAPKs), which plays a role in Th1-immune response.


OBJECTIVE
To test the hypothesis that dysregulation in MAPK signaling in response to microbial stimulation is important in mediating Th1 response in sarcoidosis.


METHODS
Ex vivo cultured bronchoalveolar lavage (BAL) cells isolated from patients with sarcoidosis and control subjects were stimulated with low-dose Toll-like receptor 4 (TLR4) and nucleotide-binding oligomerization domain 1 (NOD1) ligands as a model of microbial stimulation, and MAPK signaling and inflammatory response were analyzed.


RESULTS
BAL cells from patients with sarcoidosis exhibited higher basal p38 activity, greater p38 phosphorylation, and more robust production of TNF-α and IL-12/IL-23p40 on stimulation with NOD1 and TLR4 agonists than cells isolated from control subjects. In contrast, control BAL cells had greater basal extracellular signal-regulated kinase (ERK) activity and NOD1 and TLR4 agonists preferentially activated the ERK pathway. Inhibition of p38, but not ERK, attenuated production of both IL12/IL23p40 and TNF-α. Interestingly, stimulation of cells from patients with sarcoidosis with either NOD1 or TLR4 ligand failed to induce MAPK phosphatase 1 (MKP-1). Adenovirus-mediated overexpression of MKP-1 attenuated p38 activation and decreased the production of IL12/IL23p40 and TNF-α in sarcoid BAL cells.


CONCLUSIONS
Our results suggest that enhanced p38 signaling in response to microbial products is caused by abnormal regulation of MKP-1 and contributes to heightened inflammation in sarcoidosis.
Rastogi
Ruchi
R
Department of Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, Wayne State University School of Medicine and Detroit Medical Center, Detroit, Michigan, USA.
Du
Wenjin
W
Ju
Donhong
D
Pirockinaite
Gaila
G
Liu
Yusen
Y
Nunez
Gabriel
G
Samavati
Lobelia
L
D000328:Adult; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology*; D002478:Cells, Cultured; D015536:Down-Regulation / Q000276:immunology; D054638:Dual Specificity Phosphatase 1 / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D053474:Nod1 Signaling Adaptor Protein / Q000276:immunology / Q000378:metabolism*; D017565:Sarcoidosis, Pulmonary / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000276:immunology / Q000378:metabolism*
C119067:NOD1 protein, human; D053474:Nod1 Signaling Adaptor Protein; D051197:Toll-Like Receptor 4; D048051:p38 Mitogen-Activated Protein Kinases; D054638:Dual Specificity Phosphatase 1