Effect of Signaling Inhibitors on the Release of Lysozyme from Human Neutrophils Activated by Sambucus nigra Agglutinin

I. V. Gorudko¹ and A. V. Timoshenko^2*

¹Department of Biophysics, Belarusian State University, pr. F. Skaryny 4, Minsk, 220050 Belarus; fax: (017) 220-7465; E-mail: gorudko@phys.bsu.unibel.by

²Institute of Photobiology, National Academy of Sciences of Belarus, ul. Akademicheskaya 27, Minsk, 220072 Belarus; E-mail: timoshenko@phys.bsu.unibel.by

^* To whom correspondence should be addressed.

Received September 14, 1999; Revision received December 22, 1999

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The effect of alpha-NeuAc(2-->6)Gal/GalNAc-specific lectin from Sambucus nigra (SNA) on the release of lysozyme from human neutrophils was studied in vitro. Interaction of cells with the lectin was accompanied by dose-dependent release of lysozyme, which was increased in the presence of cytochalasin B. The involvement of intracellular signaling pathways in the lectin-induced degranulation of neutrophils was determined using a panel of specific inhibitors tested at concentrations in the range of 10-100 µM. Aristolochic acid (a phospholipase A₂ inhibitor), indomethacin (a cyclooxygenase inhibitor), neomycin sulfate (a phospholipase C inhibitor), trifluoperazine (a calmodulin antagonist/protein kinase C inhibitor), N-ethylmaleimide (a sulfhydryl reagent), and guanosine-5´-O-(2-thiodiphosphate) (a G-protein inhibitor) were found to reduce SNA-induced lysozyme release from neutrophils by 20-45%. The treatment of cells with bisindolylmaleimide (a protein kinase C inhibitor), H-8 (an inhibitor of protein kinases A, C, G and of myosin light chain kinase), PD 98059 (a MAP kinase inhibitor), and (±)-methoxyverapamil (a Ca²⁺-channel blocker) failed to affect the release of lysozyme. These results indicate that only selective intracellular pathways associated with activation of G-proteins and phospholipid metabolism as well as the thiol-dependent signaling systems are apparently involved in the realization of the SNA-induced degranulation response of human neutrophils.

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KEY WORDS: Sambucus nigra, lectin, signaling, degranulation, human neutrophils

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