Viability-Dependent and Structural Modulation of IL-10 Secretion in THP-1 Cells by Lactobacillus gasseri and Lacticaseibacillus rhamnosus.

Emerging evidence indicates that probiotic-mediated immunomodulation is not exclusively dependent on microbial viability, but is also significantly driven by structural components and postbiotic factors. This study systematically evaluated the viability-dependent versus structure-dependent regulation of Interleukin-10 (IL-10) in THP-1 monocytes by comparing alive, partially inactivated, and fully killed states of Lactobacillus gasseri and Lacticaseibacillus rhamnosus. Distinct bacterial preparations were generated via heat, ultraviolet (UV) irradiation, sonication, and chemical inactivation. We assessed IL-10 protein secretion (ELISA), transcriptional kinetics (RT-qPCR), and single-cell cytokine expression (flow cytometry), while ensuring cellular compatibility through MTT viability assays. The results demonstrate that both viable and non-viable preparations significantly induce IL-10 secretion. However, live preparations elicited a more robust and rapid transcriptional response, with peak IL-10 mRNA expression occurring at 16-20 h post-stimulation. Notably, mixed-strain conditions exhibited a pronounced combinatorial enhancement of IL-10 production at both the protein and single-cell levels. While structural microbial components are sufficient to trigger anti-inflammatory IL-10 responses, active microbial viability markedly amplifies the magnitude and kinetics of this regulation. These findings provide a mechanistic foundation for the rational design of precision paraprobiotic and probiotic formulations in immune-mediated therapies.