Dual specificity phosphatase 1 is a crucial negative

Dusp1 regulates inflammatory
osteolysis and therapeutic effects of
dexamethasone in CIA
Youridies Vattakuzhi
Kennedy Institute of Rheumatology
Presenter Disclosure Information:
no conflicts of interest

Dual Specificity Phosphatase 1 (DUSP1)
• DUSP1 (MKP-1) inactivates MAPKs by dephosphorylation
of threonine and tyrosine residues in the activation loop of
p38 MAPK and JNK
• MAPK activation triggers pro-inflammatory cytokines
• Enhanced inflammation in Dusp1 -/- mice
• Zymosan induced inflammation (Abraham et al. 2006)
• LPS challenge (Carlson et al. 2009)
• Periodontal disease (Yu et al. 2010)

DUSP1 activation in osteoclasts
• RANKL activates p38 MAPK
• RANKL induces Dusp1 expression (Carlson et al. 2009)
Dusp1 +/+ Dusp1 -/- DUSP1
Carlson et al. 2009

Resorption area (mm 2 /slice)
TRAP positive mnc/well
Enhanced osteoclastogenesis in Dusp1 -/-
mice
Dusp1 +/+
M-CSF
RANKL
M-CSF
RANKL
TNFα
400
300
200
Dusp1 +/+
Dusp1 -/-
*
n.s.
***
***
100
Dusp1 -/-
0
M-CSF (25ng/ml)
RANKL (5ng/ml)
TNF (2pg/ml)
0.20
0.15
Dusp1 +/+
0.10
0.05
Dusp1 -/-
0.00
M-CSF (25ng/ml)
200µm RANKL (5ng/ml)
TNF (2pg/ml)
+ +
+ +
n.s.
+ +
+ +
n.s.
*
+ +
+ +
+ +
**
+ +
+ +
+ +

Collagen Induced Arthritis
• TNFα drives inflammation and bone resorption in RA
• Enhanced osteoclast activity is a debilitating feature of
rheumatoid arthritis (RA)
• Immunization with chicken collagen type 2 and
complete Freund’s adjuvant

Early onset and increased incidence of
CIA in Dusp1 -/- mice

Increased severity in Dusp1 -/- mice
• Synovial hyperplasia
• Inflammatory infiltrate
• Bone erosions
• Cartilage damage

Increased bone resorption in Dusp1 -/- mice
Dusp1 +/+ Dusp1 -/-
Naive
CIA
Naive
CIA

Adaptive immune responses in CIA
• TNFα and IL-17 promote osteoclast activity in CIA
• Th17
• Th1
• Th2
• Secretion of pro-inflammatory IL-17
• Secretion of IFNγ
• Promote collagen specific Ab production by B cells (IgG2a)
• Promote collagen specific Ab production by B cells (IgG1)

Increased IL-17 production in Dusp1 -/-
mice
0.152%
Dusp1 +/+
0.358%
CD4 +
IL-17 + Dusp1 -/-

elative to control
Decreased anti-collagen IgG2a in
Dusp1 -/- mice
5 Dusp1 +/+ (PBS)
4
Dusp1 -/- (PBS)
**
3
n.s.
2
1
0
IgG1
IgG2a
• Reduced Th1 cell activity
• Enhanced IL-17 production from Th17 cells

Can dexamethasone reduce
inflammation in arthritic Dusp1 -/- mice?
• Glucocorticoids are potent anti-inflammatory drugs (e.g.
inactivates MAPKs)
• Expression of Dusp1 can be induced by glucocorticoids
(Lasa et al. 2002)
• Dexamethasone (Dex) induced inactivation of MAPK is
partly mediated by activation of DUSP1
• i.p. injection of 0.5mg/kg Dex every 2 days after onset of
disease

Dex treatment reduced clinical scores in
arthritic Dusp1 +/+ mice
↓42%
↓17%

Reduced effect of Dex on T cell
proliferation in Dusp1 -/- mice
• Dex had no effect on IFNγ, IL-17 or collagen-specific Ab
production
in vitro
in vivo
n.s.

DUSP1 regulates bone resorption and
inflammation in CIA
Dusp1 -/-
↓p38 MAPK
Dexamethasone
↑ TNFα ↑ resorption ↑ ↓ activation proliferation
Macrophage Osteoclast T h17 T cell
Abraham et al. 2006 Vattakuzhi et al. 2012
↑ TNFα
Dusp1 -/- Dusp1 -/-
↑ IL-17
↓p38 MAPK
Dexamethasone
↑↑ RESORPTION
INFLAMMATION

Acknowledgements
• Nikki Horwood and Andy Clark
• Richard Williams
• Andrew Freidin
Original Dusp1 -/- mice from: