Immunomodulatory and Antimicrobial Effects of Pd(II)-Pincer-Type Complex

Background: The newly synthesized palladium(II) complex [Pd(L1)Cl]Cl (where L1 = N²,N⁶-bis(5-methylhthiazol-2-yl)pyridine-2,6-dicarboxamide) has demonstrated significant in vitro antitumor activity. In this study, the effects of this complex on the immune response and its antimicrobial potential were evaluated. Methods: Splenocytes isolated from mice were treated with lipopolysaccharide (LPS)/Concanavalin A (ConA) along with the Pd(II) complex. The concentrations of IFN-γ, IL-17, IL-4, TNF-α, IL-1β, and IL-10 were measured using commercial ELISA kits. The antimicrobial effect was tested against reference strains of Gram-positive and Gram-negative bacteria, as well as yeast. The Minimal Inhibitory Concentration (MIC) was determined via the broth microdilution method, followed by the determination of Minimal Bactericidal/Fungicidal concentrations (MBC/MFC). Results: The Pd(II) complex induced an increase in the concentration of all tested cytokines compared to untreated cells. Co-treatment with Pd(II) complex and LPS significantly increased the levels of IFN-γ, IL-1β, and IL-17 compared to the LPS-only-stimulated group. Co-treatment with ConA and the Pd(II) complex resulted in a significant increase in TNF-α and IL-17 levels, whereas a significant decrease was observed in the concentrations of IL-10, IL-4, and IFN-γ compared to the ConA-only-stimulated group. The tested complex showed weak to moderate antimicrobial activity, Gram-positive bacteria showed better susceptibility to the examined complex compared to Gram-negative. Conclusions: Results of the study indicate that the Pd(II) complex exhibits a significant immunomodulatory effect on splenocytes, alongside weak to moderate antimicrobial activity.