• Tuberculosis and Respiratory Diseases
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• v.39 no.3
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• pp.228-235
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• 1992

Background: Although polymorphonuclear leukocytes (PMN) are important in protecting the airways and alveolar surfaces, there is evidence that they can also injure the lung while exercising their defensive role. However it has been unclear whether PMN-induced pneumocyte injury is mediated by their direct cytotoxic effect on target cells or by PMN-derived cytotoxic mediators. On the other hand histamine was known not only to act as an important chemical mediator participated in the pathogenesis of some atotic and allegic disorders, but also to have an inhibitory effect on normal PMN functions. Method: To study the mechanism by which PMN induce pneumocyte injury, we cocultured PMN from four healthy nonsmokers or their PMN-derived supernatants (PMN-SPN) with monolayers of $^{51}Cr$-labeled human A549 pneumocytes and compared PMN-and PMN-SPN-mediated pneumocyte injuries measured by $^{51}Cr$ release assay. We also compared the effects of histamine on each pneumocyte injury. Results: 1) PMN-SPN showed more injurious effect on A549 pneumocytes than that of PMN itself regardless histamine pretreatment of PMN. 2) Pneumocyte injury by PMN with histamine pretreatment was increased or decreased compared with that by PMN without histamine pretreatment, according to histamine concentrations, and PMN stimulating agents and their concentrations. 3) Pneumocyte injury by PMN-SPN with histamine pretreatment tended to be decreased compared with that by PMN-SPN without histamine pretreatment. Conclusion: Our results suggest that PMN-SPN may play more important role in mediating pneumocyte injury than PMN itself and that histamine may partially play a protective role on PMN-induced pneumocyte injury. Alternatively we conclude that the effects of histamine on PMN-induced pneumocyte injury may be affected by microenvironment in vivo.