(I-324) Impact of succinate-based nanoparticles on dendritic cells activation and metabolism

Immature dendritic cells (DCs), need to get activated to initiate immune responses. This activation requires metabolic changes in DCs, specifically transitioning from mitochondrial oxidative phosphorylation (OXPHOS) to glycolysis. Various intracellular and extracellular signals regulate DC metabolism, with multiple metabolic pathways playing a crucial role in their survival, growth, and function. In our previous studies, we demonstrated that succinate-based microparticles (1-3 μm) could be readily phagocytosed by DCs, leading to their activation and immune system activation in mice. Recent studies suggest that nanoparticles can elicit more robust responses in immune cells compared to microparticles.  Also, another study showed that nano- and micro-particles may have different immune induction profiles in the body. To study the effect of Succinate base nanoparticles on dendritic cell activation, we used the oil-in-water technique to create succinate-based nanoparticles. To the best of our knowledge, this study represents the first investigation into the efficacy of succinate-based nanoparticles in DCs activation.

Metabolite-based polymeric particles were generated through oil-in-water emulsions using 2% PVA and ethylene glycol Succinate polymer. The particles' characteristics, including particle size, were assessed using dynamic light scattering (DLS). Flow cytometry was performed using different concentrations of both succinate-based nanoparticles (PES NPs) and microparticles (PES MPs) to evaluate their ability to activate DCs. Seahorse XF Glycolysis Stress Test was conducted to assess the metabolic capacity and glycolytic reserve of DCs after exposure to PES NPs.

The results of our study are shown in Figure (1c-f). DLS measurement demonstrated that  PES NPs are approximately 200 nm in size (Fig1a). The activation of DCs in PES NPs was evaluated by the expression levels of CD80, CD86, MHC I, and MHC II (Fig1b,c). PES NPs induced higher expression levels of these activation markers at a concentration of 0.1 mg/mL, indicating a more activation of DCs compared to PES MPs. This enhanced activation suggests that PES NPs possess greater capacity to stimulate the immune response mediated by DCs. The concentration of 0.1 mg/mL PES NPs was used for further studies on the efficiency of PES NPs in DCs activation and glycolysis. DC's activation (CD86+ CD11c) was compared between 0.1 mg/mL PES NPs, Succinic acid and no treatment group (Figure.1d). The results demonstrated that PES NPs activate DCs better than no treatment and succinic acid monomer.

To further investigate the impact of PES NPs on DC metabolism, we conducted a Seahorse XF Glycolysis Stress Test. The results showed that PES NPs significantly increased the glycolytic reserve of DCs, but did not impact the metabolic capacity (fig 1e,f). Notably, it is shown that NPs increased cells’ glycolytic flux in response to energetic demand for ATP while maintaining their capacity to produce ATP when OXPHOS was interrupted. This finding suggests that PES NPs promote DCs towards glycolysis, a metabolic pathway known to be associated with immune cell activation.

The increased activation of DCs with succinate-based nanoparticles compared to microparticles suggests that nanoparticle size is a important factor in immune cell activation. The smaller size of PES NPs enhances their cellular uptake and interaction with DCs, leading to a more robust immune response. Future studies are exploring the impact of Succinate-based NPs on cytokine release and epigenetic changes in dendritic cells. Specifically, it is important to investigate the effect of succinate-based NPs on the release of cytokines such as interleukin-12 (IL-12) and Tumor Necrosis Factor-alpha (TNF-a) which play a key role in the immune response. Overall, these results supporting the hypothesis that succinate-based nanoparticles are more effective than macroparticles in activating dendritic cells.

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