Surplus spermine does not protect salmon cells against lipopolysaccharide (LPS)-induced stress, but excess spermine is eliminated through spermidine/spermine N1-acetyltransferase (SSAT)

The present trials tested the efficiency of surplus spermine to reduce inflammation and oxidative stress following LPS-induced stress using an in vitro model of head kidney and liver cells isolated from Atlantic salmon. Spermine did not protect cells from LPS-induced inflammatory response at either 0.3, 0.6 or 0.9 mM. However, as the gene expression of spermidine/spermine N1-acetyltransferase (SSAT) increased with increasing spermine concentration, we addressed possible oxidative effects of the increased SSAT using its activator DENSPM or inhibitor of polyamine oxidation of the acetylated polyamines using MDL72527 at a spermine concentration of 0.6 mM. There was no significant effect of DENSPM, but MDL72527 decreased gene expression of GPX-3 (p = .04), while gene expression of catalase and MnSOD was unaffected by treatment (p = .30 and p = .48, respectively). In conclusion, spermine did not protect cells from LPS-provoked inflammation. The higher the spermine concentration, the more SSAT producing acetylated spermine occurred. Inhibiting the acetylated polyamine oxidases by MDL72527 improved oxidation status as expected due to a lower endogenous production of H2O2 by polyamine and acetylated polyamine oxidases. Probably care should be taken using polyamines or arginine as functional ingredients to avoid any increased oxidation within cells.