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PAR-1 signaling on macrophages is required for effective in vivo delayed-type hypersensitivity responses.

ABSTRACT: Delayed-type hypersensitivity (DTH) responses underpin chronic inflammation. Using a model of oxazolone-induced dermatitis and a combination of transgenic mice, adoptive cell transfer, and selective agonists/antagonists against protease activated receptors, we show that that PAR-1 signaling on macrophages by thrombin is required for effective granuloma formation. Using BM-derived macrophages (BMMs) in vitro, we show that thrombin signaling induced (a) downregulation of cell membrane reverse cholesterol transporter ABCA1 and (b) increased expression of IFN? receptor and enhanced co-localization within increased areas of cholesterol-rich membrane microdomains. These two key phenotypic changes combined to make thrombin-primed BMMs sensitive to M1 polarization by 1000-fold less IFN?, compared to resting BMMs. We confirm that changes in ABCA1 expression were directly responsible for the exquisite sensitivity to IFN? in vitro and for the impact on granuloma formation in vivo. These data indicate that PAR-1 signaling plays a hitherto unrecognized and critical role in DTH responses.

SUBMITTER: Wilkinson H

PROVIDER: S-EPMC7797913 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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PAR-1 signaling on macrophages is required for effective in vivo delayed-type hypersensitivity responses.

Wilkinson Hannah H Leonard Hugh H Chen Daxin D Lawrence Toby T Robson Michael M Goossens Pieter P McVey John H JH Dorling Anthony A

iScience 20210105 1

Delayed-type hypersensitivity (DTH) responses underpin chronic inflammation. Using a model of oxazolone-induced dermatitis and a combination of transgenic mice, adoptive cell transfer, and selective agonists/antagonists against protease activated receptors, we show that that PAR-1 signaling on macrophages by thrombin is required for effective granuloma formation. Using BM-derived macrophages (BMMs) <i>in vitro</i>, we show that thrombin signaling induced (a) downregulation of cell membrane rever ...[more]

PMID: 33458623

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Project description:Decorin, a small leucine-rich proteoglycan, regulates extracellular matrix organization, growth factor-mediated signaling, and cell growth. Because decorin may directly modulate immune responses, we investigated its role in a mouse model of contact allergy (oxazolone-mediated delayed-type hypersensitivity [DTH]) in decorin-deficient (Dcn(-/-)) and wild-type mice. Dcn(-/-) mice showed a reduced ear swelling 24 h after oxazolone treatment with a concurrent attenuation of leukocyte infiltration. These findings were corroborated by reduced glucose metabolism, as determined by (18)fluordeoxyglucose uptake in positron emission tomography scans. Unexpectedly, polymorphonuclear leukocyte numbers in Dcn(-/-) blood vessels were significantly increased and accompanied by large numbers of flattened leukocytes adherent to the endothelium. Intravital microscopy and flow chamber and static adhesion assays confirmed increased adhesion and reduced transmigration of Dcn(-/-) leukocytes. Circulating blood neutrophil numbers were significantly increased in Dcn(-/-) mice 24 h after DTH elicitation, but they were only moderately increased in wild-type mice. Expression of the proinflammatory cytokine TNF-? was reduced, whereas syndecan-1 and ICAM-1 were overexpressed in inflamed ears of Dcn(-/-) mice, indicating that these adhesion molecules could be responsible for increased leukocyte adhesion. Decorin treatment of endothelial cells increased tyrosine phosphorylation and reduced syndecan-1 expression. Notably, absence of syndecan-1 in a genetic background lacking decorin rescued the attenuated DTH phenotype of Dcn(-/-) mice. Collectively, these results implicated a role for decorin in mediating DTH responses by influencing polymorphonuclear leukocyte attachment to the endothelium. This occurs via two nonmutually exclusive mechanisms that involve a direct antiadhesive effect on polymorphonuclear leukocytes and a negative regulation of ICAM-1 and syndecan-1 expression.

Project description:It is widely recognized that innate macrophage immune reactions to implant debris are central to the inflammatory responses that drive biologic implant failure over the long term. Less common, adaptive lymphocyte immune reactions to implant debris, such as delayed type hypersensitivity (DTH), can also affect implant performance. It is unknown which key patient factors, if any, mediate these adaptive immune responses that potentiate particle/macrophage mediated osteolysis. The objective of this investigation was to determine to what degree known adaptive immune responses to metal implant debris can affect particle-induced osteolysis (PIO); and if this pathomechanism is dependent on: 1) innate immune danger signaling, i.e., NLRP3 inflammasome activity, 2) sex, and/or 3) age. We used an established murine calvaria model of PIO using male and female wild-type C57BL/6 vs. Caspase-1 deficient mice as well as young (12-16 weeks old) vs. aged (18-24 months old) female and male C57BL/6 mice. After induction of metal-DTH, and Cobalt-alloy particle (ASTM F-75, 0.4um median diameter) calvaria challenge, bone resorption was assessed using quantitative micro-computed tomography (micro-CT) analysis and immune responses were assessed by measuring paw inflammation, lymphocyte transformation test (LTT) reactivity and adaptive immune cytokines IFN-gamma and IL-17 (ELISA). Younger aged C57BL/6 female mice exhibited the highest rate and severity of metal sensitivity lymphocyte responses that also translated into higher PIO compared to any other experimental group. The absence of inflammasome/caspase-1 activity significantly suppressed DTH metal-reactivity and osteolysis in both male and female Caspase-1 deficient mice. These murine model results indicate that young female mice are more predisposed to metal-DTH augmented inflammatory responses to wear debris, which is highly influenced by active NLRP3 inflammasome/caspase-1 danger signaling. If these results are clinically meaningful for orthopedic patients, then younger female individuals should be appropriately assessed and followed for DTH derived peri-implant complications.

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PAR-1 signaling on macrophages is required for effective in vivo delayed-type hypersensitivity responses.

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PAR-1 signaling on macrophages is required for effective in vivo delayed-type hypersensitivity responses.

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