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Upregulation of respiratory burst of polymorphonuclear leukocytes by a bleomycin derivative, peplomycin
Abstract:
The influence of peplomycin (PLM) on the respiratory burst of peripheral blood polymorphonuclear leukocytes (PMN) was investigated. Short-term (5 min) treatment of human PMN with 0.1mu g/ml to 100mu g/ml of PLM increased phorbol myristate acetate (PMA)- and formyl-methionyl-leucyl-phenylalanine (FMLP)-induced luminol-dependent chemiluminescence. PMN, as well as alveolar macrophages from rabbits treated with 0.5 to 1.0 mg/kg of peplomycin per day for 5 days, generated more superoxide (O2-) than the cells from untreated rabbits. In both PLM-treated and untreated PMN, chemiluminescence induced by FMLP and PMA was decreased to less than 50% of the control by staurosporine, superoxide dismutase (SOD) and catalase. However, the peak intensity in PLM-untreated PMN was decreased to about 30% of the control by genistein, while this agent induced a slight decrease in peak intensity in the PLM-treated PMN. Inositol triphosphate and diacyl glycerol levels were not clearly increased by PLM, but an increase of intracellular Ca++ and a shift of protein kinase C (PKC) to the membrane occurred in PMN within 1 min after PLM treatment. Western blotting revealed that the tyrosine phosphorylation of a 115 kDa protein was upregulated by 5 to 50mu g/ml of PLM. While, PLM suppressed SOD activity in alveolar macrophages and PMN. These results seem to indicate that PLM increases the respiratory burst of PMN and macrophages both by way of direct PKC activation and by the upregulation of protein tyrosine phosphorylation. This increased reactive oxygen generation, together with the suppression of SOD activity seems to be tissue-impairing.
Insights
Peplomycin (PLM) enhances the respiratory burst in immune cells like polymorphonuclear leukocytes (PMN) and macrophages. This occurs through protein kinase C (PKC) activation and increased tyrosine phosphorylation, potentially impairing tissues by boosting reactive oxygen species and suppressing superoxide dismutase (SOD).
Area of Science:
- Immunology
- Cellular Biology
- Pharmacology
Background:
- The respiratory burst in polymorphonuclear leukocytes (PMN) and macrophages is crucial for immune responses.
- Peplomycin (PLM) is an anticancer drug whose effects on immune cell function require further elucidation.
Purpose of the Study:
- To investigate the influence of peplomycin (PLM) on the respiratory burst activity of peripheral blood PMN and rabbit alveolar macrophages.
- To explore the underlying molecular mechanisms of PLM-induced changes in immune cell respiratory burst.
Main Methods:
- Luminol-dependent chemiluminescence assays were used to measure respiratory burst in human PMN treated with varying concentrations of PLM.
- Superoxide generation was assessed in PMN and alveolar macrophages from PLM-treated rabbits.
- Western blotting was employed to analyze protein tyrosine phosphorylation and kinase C (PKC) translocation.
Main Results:
- PLM treatment significantly increased phorbol myristate acetate (PMA)- and formyl-methionyl-leucyl-phenylalanine (FMLP)-induced chemiluminescence in human PMN.
- PLM-exposed PMN and macrophages exhibited enhanced superoxide (O2-) generation compared to controls.
- PLM induced rapid intracellular Ca++ increase and PKC translocation to the membrane in PMN, alongside upregulated tyrosine phosphorylation of a 115 kDa protein.
Conclusions:
- Peplomycin enhances the respiratory burst of PMN and macrophages via direct PKC activation and upregulation of protein tyrosine phosphorylation.
- PLM also suppresses superoxide dismutase (SOD) activity in these immune cells.
- The combined effects of increased reactive oxygen generation and suppressed SOD activity suggest a potential for tissue impairment.