Mast cell granule enhancement of neutrophil chemiluminescence responses

Cutaneous mast cell degranulation in rats results in tissue inflammation, and this species has therefore provided a useful model to study the pathogenesis of late phase reactions (LPRs). The mast cell dependency of LPRs has been confirmed by the demonstration that isolated rat mast cell granules (MCGs), when injected intradermally into rat skin, induce patterns of tissue inflammation similar to those seen after skin testing with anti-IgE antibody. Rat LPRs are neutrophil dependent, and, further, MCG-derived inflammatory factors can chemically attract rat neutrophils in vitro. To further study the relationships among MCGs, tissue inflammation, and neutrophil function, luminol-dependent chemiluminescence (CL) responses of rat peritoneal-elicited neutrophils in response to opsonized zymosan and phorbol myristate acetate (PMA) in the presence and absence of MCGs were analyzed. When MCGs (1.0, 10, and 100 micrograms/ml) alone were added to neutrophil suspensions, a rapid concentration-dependent increase in baseline CL responses was observed; these increases (maximum of sixfold) were modest, varied with cell concentrations, and followed different time courses compared with those seen after addition of preopsonized zymosan (0.5 mg/ml) (50-fold increases that peaked in 4 to 8 minutes). However, if neutrophils were preincubated (15 minutes) in the presence of MCGs, the CL response to opsonized zymosan (1.25 mg/ml) was significantly and synergistically enhanced compared with the response seen with MCGs alone. Similar but less pronounced effects were also noted after cell activation with PMA (2.5 and 25 ng/ml). To determine which component of the MCG was responsible for this enhancing activity, additional experiments were performed. Enhancement was still observed, albeit less intense, if MCGs were prepared membrane free and washed free of readily dissociable mediators such as histamine. Histamine (10(-6) and 10(-5) mol/L) had no enhancing effect nor did preparations of MCG membranes. MCG solubilization (3 mol/L NH4HCO3) revealed that the enhancing activity resided completely in the high molecular weight (greater than 10,000 daltons) fraction. Heat treatment of the granules and sodium azide preincubation completely abolished the enhancing effect. Exogenous horseradish peroxidase, at peroxidase activity levels contained within the MCGs (1 x 10(-4) to 10(-2) U/ml), reproduced the enhancing effect. After opsonized zymosan activation, neutrophils generated less H2O2 and superoxide anion in the presence of MCGs.(ABSTRACT TRUNCATED AT 400 WORDS)