Altered Ca2+ signalling in human neutrophils from inflammatory sites

To determine whether the intracellular store release of Ca2+ in neutrophils from patients with rheumatoid arthritis, other joint disease and active leg ulceration was different from normal neutrophils.

The release into the cytosol of Ca2+ from stores within individual neutrophils was determined using ratiometric imaging of fura2. The size of the elevated Ca2+ 'cloud' and its concentration were quantified in neutrophils from the circulation of patients with rheumatoid arthritis, other joint diseases, and leg ulcers and from the joints of those with joint disease.

In neutrophils isolated from both the synovial fluid of patients with rheumatoid arthritis and other joint conditions, and also arising from leg ulcers, the amount of the cell cytosol occupied by elevated Ca2+ was significantly increased compared with neutrophils from healthy subjects; for neutrophils from rheumatoid, non-rheumatoid joints and leg ulcers p values were 0.0006, < 0.0001, 0.016 respectively (Student's t test). There was also a significant increase in Ca2+ release from circulating neutrophils from patients with rheumatoid arthritis (p = 0.09), but not in circulating neutrophils from patients with leg ulcers or non-rheumatoid joint conditions.

It is proposed that the increased release of free Ca2+ into the cytosol of neutrophil at inflammatory sites results in increased oxidase activation.