IADR Abstract Archives
Oral LPS: Macrophage subsets are differentially sensitive to endotoxin tolerance
Objectives: Mucosal macrophages (MΦs) play an important role in immune function; determining responsiveness to pathogenic challenge, effectively driving immune activation or suppression/tolerance-fate decisions. This on/off switch is dependent on pathogen recognition and MΦ subset; dysfunctions in which contribute to mucosal pathology. Prior endotoxin challenge renders MΦs refractory to re-exposure. This endotoxin tolerance (ET) effectively suppresses inflammatory responses resulting in quiescence, characteristic of the relapsing-remitting nature of mucosal inflammatory diseases such as chronic periodontitis and Crohn’s disease. The objective of this study was to characterise MΦ subset-specific ET mechanisms associated with responses to LPS from the enteropathogenic E.coli K12 and compare to those driven by LPS from the oral pathogen, Porphyromonas gingivalis (PG).
Methods: M1- and M2-like MΦs were generated in vitro from the THP-1 monocyte cell line by differentiation with PMA and Vitamin D3, respectively. Sensitivity to ET was measured by cytokine secretion by ELISA and mRNA expression of cytokines, TLR4 and the endogenous TLR signal regulators, IRAK-M and Tollip by RT-PCR.
Results: PG-LPS differentially tolerised M1 and M2 subset cytokine responses, where TNFα and IL-1β were suppressed in M2 MΦs and augmented in M1s. In the case of E.coli K12-LPS, TNFα and IL-1β were suppressed in both subsets, as was TLR4. Both Tollip and IRAK-M expression were up-regulated in tolerised M1 MΦs and less so in M2s. Only tolerised M2 MΦs however, displayed an augmentation in IRAK-M protein. Finally, IL-10 differentially suppressed TNFα secretion; K12-LPS-induced TNFα was suppressed in both MΦ subsets whereas PG-LPS-induced TNFα was only suppressed in M2 MΦs.
Conclusions: PG-LPS and E. coli K12-LPS differentially suppress MΦ cytokine production; dependent on subset, sensitivity to IL-10 anti-inflammatory effects and the expression of TLR negative regulators, IRAK-M and Tollip. Manipulation of which may offer future therapeutic regimens for the control of mucosal inflammatory pathology.
Methods: M1- and M2-like MΦs were generated in vitro from the THP-1 monocyte cell line by differentiation with PMA and Vitamin D3, respectively. Sensitivity to ET was measured by cytokine secretion by ELISA and mRNA expression of cytokines, TLR4 and the endogenous TLR signal regulators, IRAK-M and Tollip by RT-PCR.
Results: PG-LPS differentially tolerised M1 and M2 subset cytokine responses, where TNFα and IL-1β were suppressed in M2 MΦs and augmented in M1s. In the case of E.coli K12-LPS, TNFα and IL-1β were suppressed in both subsets, as was TLR4. Both Tollip and IRAK-M expression were up-regulated in tolerised M1 MΦs and less so in M2s. Only tolerised M2 MΦs however, displayed an augmentation in IRAK-M protein. Finally, IL-10 differentially suppressed TNFα secretion; K12-LPS-induced TNFα was suppressed in both MΦ subsets whereas PG-LPS-induced TNFα was only suppressed in M2 MΦs.
Conclusions: PG-LPS and E. coli K12-LPS differentially suppress MΦ cytokine production; dependent on subset, sensitivity to IL-10 anti-inflammatory effects and the expression of TLR negative regulators, IRAK-M and Tollip. Manipulation of which may offer future therapeutic regimens for the control of mucosal inflammatory pathology.