(848) Green-synthesized gold nanoparticles derived from Spirulina and Leptolyngbya, modulate innate immune response via M1 polarization of THP-1 macrophages

Introduction/Rationale: Macrophage polarization plays a pivotal role in regulating immune responses against infections and cancer. Cyanobacteria such as Spirulina and Leptolyngbya are rich in immunomodulatory metabolites; however, their mechanistic roles in macrophage polarization remain unexplored. This study investigates whether cyanobacterial extracts and their green-synthesized gold nanoparticles (AuNPs) modulate human macrophage polarization.

Methods: Methanolic extracts of Spirulina and Leptolyngbya and their AuNPs were characterized by UV–Vis, DLS, TEM, and FTIR. THP-1 macrophages were treated with extracts or AuNPs. Expression of M1/M2 gene markers (TNF, IL1β, IL8, CXCL10, CD163, TGFβ, and STAB1) was analyzed by qRT-PCR, while surface markers (CD80 and CD86) were assessed using both qRT-PCR and flow cytometry. Agonist–antagonist assays were conducted to trace the potential pathway. Statistical significant difference was observed using Student t-test and ANOVA (n=3).

Results: THP-1 macrophages treated with extracts or AuNPs exhibited significant upregulation of M1 markers TNF-α (p < 0.01), IL-8 (p < 0.01), and IL-1β (p < 0.01), along with a moderate increase in CXCL10 (p < 0.05). Conversely, there was significant downregulation of M2 markers CD163 (p < 0.01), TGFβ (p < 0.05), and STAB1 (p < 0.01). Algal extract-induced polarization occurred via the TLR2 pathway, as it was significantly reversed by TLR2 blockade via a specific antagonist. In contrast, algal-derived AuNPs retained their M1-polarizing capability even after TLR2 inhibition, suggesting activation of TLR2-independent pathways.

Conclusion: The immunostimulatory response induced by cyanobacterial extracts is partly dependent on TLR-2 signaling. However, extracts AuNps appear to evade TLR2-mediated signaling by internalizing into the macrophages, suggesting activation of alternative pathways leading to M1 polarization. The M1 polarizing ability of extracts and AuNPs highlights their potential as promising therapeutic candidates for cancer immunotherapy.