Simultaneous measurements of cytoplasmic Ca2+ responses and intracellular pH in neutrophils of localized aggressive periodontitis (LAP) patients

Abstract

In view of the reports that polymorphonuclear leukocytes (PMN) of patients with localized aggressive periodontitis (LAP) exhibit hyper-responsiveness to stimulation, it has been suggested that such abnormalities could lead to PMN-mediated tissue damage during inflammation. To determine whether these abnormalities include signal transduction, we compared cytoplasmic calcium concentration (Delta[Ca2+](i)) and cytoplasmic pH (DeltapH(i)) changes, early stimulus responses to chemotactic agents, of LAP versus control (C)-PMN and explored whether these could be modulated by sensitizing cytokines or calcium channel-blocking agents. PMN responses of LAP patients were compared with age- and gender-matched controls. Delta[Ca2+](i) and DeltapH(i) were measured fluorimetrically using 1H-indole-6-carboxylic acid, 2-[4-[bis[2-[(acetyloxy)methoxy]-2-oxoethyl]amino]-3-[2-[2-[bis[2-[(acetyloxy)methoxy]-2-oxoethyl]amino]-5-methylphenoxy]ethoxy]phenyl]-1 and 2',7'-bis-(carboxyethyl)-5(6)-carboxyfluorescein as respective probes. Not only was the maximal calcium response to chemoattractants higher in LAP-PMN, but also their subsequent intracellular calcium redistribution was significantly slower. The slower calcium redistribution of LAP-PMN, but not their higher maximal calcium response, was successfully mimicked in C-PMN treated with Nifedipine or 1-[b-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole-HCl, both known to be inhibitors of membrane-associated calcium influx, but this redistribution was not affected when inhibitors of other calcium influx mechanisms, Diltiazem or Verapamil, were used. Taken together, our findings indicate that certain early stimulus responses are aberrant in LAP-PMN, that internal redistribution of cytoplasmic-free calcium is compromised, and, additionally, that a membrane-associated Ca2+ transport defect may be present.