Inhibition of a p38/Stress-Activated Protein Kinase-2-Dependent Phosphatase Restores Function of IL-1 Receptor-Associated Kinase-1 and Reverses Toll-Like Receptor 2- and 4-Dependent Tolerance of Macrophages

Abstract

Pretreatment of macrophages with Toll-like receptor (TLR)2 or TLR4 agonists leads to a stage of cell hyporesponsiveness to a second stimulation with TLR agonists. This tolerance state is accompanied by the repression of IL-1 receptor-associated kinase-1, mitogen-activated protein kinases, and IκB phosphorylation and expression of genes encoding proinflammatory cytokines, like IL-1β and TNF-α. In this report, we demonstrated that mucin-like glycoprotein (tGPI-mucin) of Trypanosoma cruzi trypomastigotes (TLR2 agonist) and LPS (TLR4 agonist) induce cross-tolerance in macrophages and we addressed the role of phosphatase activity in this process. Analysis of the kinetic of phosphatase activity induced by tGPI-mucin or LPS revealed maximum levels between 12 and 24 h, which correlate with the macrophage hyporesponsiveness stage. The addition of okadaic acid, an inhibitor of phosphatase activity, reversed macrophage hyporesponsiveness after exposure to either LPS or tGPI-mucin, allowing phosphorylation of IL-1R-associated kinase-1, mitogen-activated protein kinases, and ΙκB and leading to TNF-α gene transcription and cytokine production. Furthermore, pretreatment with either the specific p38/stress-activated protein kinase-2 inhibitor (SB203580) or the NF-κB translocation inhibitor (SN50) prevented the induction of phosphatase activity and hyporesponsiveness in macrophage, permitting cytokine production after restimulation with LPS. These results indicate a critical role of p38/stress-activated protein kinase-2 and NF-κB-dependent phosphatase in macrophage hyporesponsiveness induced by microbial products that activate TLR2 and TLR4.

Dual Receptors and Distinct Pathways Mediate Interleukin-1 Receptor-associated Kinase Degradation in Response to Lipopolysaccharide

“…It was recently reported that IRAK degradation in murine macrophages in response to either LPS or mucin-like glycoprotein from Trypanosoma cruzi may involve activation of serine/threonine phosphatases such as PP1 and PP2A (59). However, using okadaic acid pretreatment to inhibit serine/threonine phosphatase activity, we have thus far been unable to block either early or late-phase IRAK degradation in response to LPS.…”

Intraspecies Variation in Trypanosoma cruzi GPI-Mucins: Biological Activities and Differential Expression of α-Galactosyl Residues

“…16,31,37 Furthermore, the molecular mechanisms of this induction were reported to involve members of the nuclear factor κB (NF-κB) pathway, including TLR2/TLR6, 17,18 MyD88, 54 extracellular signal-related (ERK) -1/ERK2 kinases, mitogen-activated protein kinase (MAPK), stress-activated protein kinase (SAPK-2/p38), and inhibitor of κB (IκB). 55,56 However, an unknown aspect of T. cruzi glycobiology is how tGPI-mucins from different strains/DTUs would trigger different responses in murine macrophages. Here, a higher production of NO and IL-12 was observed for BZR-Y followed by BZS-Y, CL, and Colombiana.…”

Synergistic Activation of Macrophages via CD40 and TLR9 Results in T Cell Independent Antitumor Effects

“…All these hybridomas were obtained from American Type Culture Collection. Depletion of T cells and PMN was confirmed by flow cytometry (FC), and depletion of NK cells was determined in the 4-h 51 Cr cytotoxicity assay against YAC-1 cells. M were inactivated by i.p.…”