Effects of α and β-adrenergic signaling on innate immunity and Porphyromonas gingivalis virulence in an invertebrate model.

To investigate the role of adrenergic signalling (AS) in the host immune response and virulence, we compared norepinephrine (NE) and isoproterenol (ISO) responses in . infection was evaluated by survival; humoral immune responses (i.e. melanization and and mRNA expression); cellular immune responses (i.e. haemocyte count, nodulation by histology); and recovery (CFU/mL). was cultivated in the presence of ISO (PgISO) or NE and injected into the larvae for survival evaluation. Finally, we co-injected ISO and PgISO to evaluate the concomitant effects on the immune response and bacterial virulence. None of the ligands were toxic to the larvae; ISO increased haemocyte number, even after infection, by mobilizing sessile haemocytes in a β-adrenergic-specific manner, while NE showed the opposite effect. ISO treatment reduced larval mortality and the number of recovered bacteria, while NE increased mortality and showed no effect on bacterial recovery. ISO and NE had similar effects on melanization and decreased the expression of cecropin. Although co-cultivation with NE and ISO increased the gene expression of bacterial virulence factors , only the injection of PgISO increased larval death, which was partially reversed by circulating ISO. Therefore, α- and β-adrenergic signalling had opposite effects after infection. Ultimately, the catecholamine influence on the immune response overcame the effect of more virulent strains. The effect of AS directly on the pathogen found did not translate to the setting.