The inhibition of spontaneous and tumor necrosis factor-alpha induced neutrophil apoptosis by crystals of calcium pyrophosphate dihydrate and monosodium urate monohydrate
C. Tudan et al., The inhibition of spontaneous and tumor necrosis factor-alpha induced neutrophil apoptosis by crystals of calcium pyrophosphate dihydrate and monosodium urate monohydrate, J RHEUMATOL, 27(10), 2000, pp. 2463-2472
Objective. Spontaneous neutrophil apoptosis may be inhibited by various pro
inflammatory stimuli, which may result in prolonged lifetimes and responses
of these phagocytic cells with the potential for extended inflammation. We
investigated the effect of short term incubation of opsonized crystals of
monosodium urate monohydrate (MSUM) or calcium pyrophosphate dihydrate (CPP
D) on both spontaneous and tumor necrosis fator-alpha (TNF-alpha) induced n
eutrophil apoptosis.
Methods. Peripheral neutrophils were incubated with plasma opsonized crysta
ls of CPPD or MSUM in the presence or absence of TNF-alpha for 4 h at 37 de
grees C. Apoptosis was determined using 3 separate assays: (1) an agrarose
DNA fragmentation assay, (2) a cytoplasmic histone associated DNA fragmenta
tion assay, and (3) a caspase 3 fluorometric assay.
Results. All 3 assays showed similar results. Both MSUM and CPPD crystals i
nhibited spontaneous apoptosis in neutrophils. TNF-alpha induced high level
s of apoptosis in neutrophils. However, co-incubation of the cells with TNF
-alpha and crystals resulted in the inhibition of apoptosis to levels below
those of control cells. Pretreatment of neutrophils with the protein synth
esis inhibitor cycloheximide prevented the inhibition of apoptosis by cryst
als.
Conclusion. These data support the concept of crystal induced inhibition of
neutrophil apoptosis as part of the pathophysiology of the diseases collec
tively known as crystal induced arthritis.