Reprogramming of Lipopolysaccharide-Primed Macrophages Is Controlled by a Counterbalanced Production of IL-10 and IL-12

Abstract

We studied the potential role of a cytokine regulatory mechanism(s) in LPS-dependent reprogramming and modulation of TNF-α and nitric oxide (NO) responses in mouse peritoneal macrophages. Reciprocal regulation of TNF-α and NO production by LPS-primed and LPS-stimulated macrophages was found to be dependent on the presence of soluble secretory products released by the cells during the initial LPS priming interaction. Pretreatment of naïve macrophages with different mouse recombinant cytokines such as rIL-10, rIL-12, and rIFN-γ dose dependently and differentially regulated subsequent LPS-induced production of TNF-α, IL-6, and NO by cytokine-primed cells. Analysis of IL-12 and IL-10 levels present in culture supernatants of LPS-primed and LPS-stimulated macrophages revealed a high degree of correlation between the profiles of TNF-α and IL-12 as well as NO and IL-10. Furthermore, LPS priming of macrophages in the presence of anti-IL-12-neutralizing mAb attenuated TNF-α responses while at the same time up-regulated NO production. In contrast, neutralization of endogenous IL-10 with anti-IL-10 mAb resulted in considerable TNF-α response at LPS priming doses under conditions that would otherwise strongly inhibit TNF-α production. We also found that the initial LPS priming of naïve macrophages differentially and dose dependently regulates expression of mRNAs for IL-10, IL-12, and IFN-γ in LPS-primed macrophages. Collectively, our data provide experimental support for the hypothesis that a cytokine regulatory network, most probably autocrine, tightly controls the reciprocal modulation of TNF-α and NO responses in LPS-primed macrophages.

Oral epithelial-derived mediators suppress RANKL expression in human mandibular-derived bone cells

“…Numerous studies have shown the epithelial secretes potent antimicrobial peptides and many cytokines/chemokines (18,19,(50)(51)(52) that act as host defense molecules to combat infection and control the balance between normal flora and pathogens in the oral cavity. Oral epithelial cells act as a physical protective barrier to defense with pathogen and their virulence factors including the outer membrane of P.gingivalis LPS (PgLPS), one of the most important periodontal pathogenic bacteria (86), by secreting several proinflammatory cytokines, anti-inflammatory cytokines and chemokines to maintain oral mucosal homeostasis (87).…”

“…These cytokines also secreted by macrophages, fibroblast, dendritic cells, mast cells and lymphocytes in the oral mucosa. Oral commensals play an important role in stimulating immune responses which are down regulated and reprogrammed such as by induction of oral tolerance(18). Induction of immune tolerance toward commensals combined with responsiveness to pathogens is essential to sustaining immune homeostasis while preventing life-threatening infections (Figure2.6).…”