In Vitro Effects of Certain Membrane-acting Agents on Superoxide and Hydrogen Peroxide Production,Protein Synthesis and Membrane ATPase Activity in Buffalo PMN Cells

Abstract

Polymorphonuclear (PMN) cells play a key role in innate immunity, due to their ability to produce reactive oxidants such as superoxide (O^2–) and hydrogen peroxide (H₂O₂), and to release antimicrobial proteins and peptides stored in their lysosomal granules. In the present study, the effects of the activation of buffalo PMN cells with various membrane-acting agents were evaluated in terms of O^2– and H₂O₂ production, the activities of membrane ATPases, and protein synthesis. Studies involving the incorporation of ³⁵S-methionine revealed significant protein-synthesising ability in resting PMN cells and in cells treated with lipopolysaccharide (LPS), as well as with opsonised zymosan (OZ). Protein synthesis, as judged by fluorography of the cytosolic fraction, showed more than 12 bands, whilst the cytoskeletal fraction showed 2–3 bands. PMN activation with concanavalin A (ConA), digitonin and sodium nitroprusside (SNP) resulted in increased O^2– and H₂O₂ production. However, in the presence of anti-inflammatory agents such as indomethacin and cortisol, the production of O^2– and H₂O₂ by these cells was found to decline. Studies pertaining to membrane ATPases revealed that verapamil hydrochloride (VpHCl) significantly increased total ATPase and Na⁺K⁺ATPase activity. ConA treatment yielded only a moderate level of activity. Similarly, digitonin up to 24μM also caused a significant increase in ATPase activity. Our observations indicate that these membrane-acting agents influenced oxygen-dependent and oxygen-independent microbicidal mechanisms in buffalo PMN cells.