Upregulation of Respiratory Burst of Polymorphonuclear Leukocytes By A Bleomycin Derivative, Peplomycin

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 0.1μg/ml to 100μg/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-untrcated PMN was decreased to about 30% of the control by genislein, 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 50μg/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.     

Specificity of transport of bleomycin and cobalt-bleomycin in L5178Y cells

The mechanism of transport of [³H]peplomycin (PEP), a new member of bleomycin group antibiotics, was studied in cultured L5178Y mouse leukemic cells. Cobalt ions enhanced the uptake of PEP, but Cu, Zn, Fe(II) and Fe(III) had no effect. The initial rate of uptake of cobalt chelated PEP [PEP(Co)] was several times higher than that of free or Cu-chelated PEP and was temperature independent. A double reciprocal plot of the data demonstrated both saturable (K_m = 4.5 μM, V_max = 1.3 × 10^?18 mole/min/cell) and non-saturable components of the uptake of PEP(Co). The saturable component was inhibited specifically by cobalt chelated bleomycin analogs. PEP-chelates with metals other than cobalt, such as PEP(Cu) were metabolically unstable. These results suggest that bleomycin enters into cells as a metal chelate through a specific transport site.