Differential Regulation of Chemokine Production in Human Peritoneal Mesothelial Cells: IFN-γ Controls Neutrophil Migration Across the Mesothelium In Vitro and In Vivo

Abstract

Leukocyte recruitment into the infected peritoneal cavity consists of an early, predominant polymorphonuclear leukocyte (PMN) influx and subsequent, prolonged mononuclear cell migration phase. Although chemokine secretion by resident peritoneal cells plays a primary role in mediating this migration, the mechanisms involved in controlling the switch in phenotype of cell infiltrate remain unclear. The present study investigates a potential role for the Th1-type cytokine IFN-γ in the process of leukocyte recruitment into the peritoneal cavity. Stimulation of cultured human peritoneal mesothelial cells with IFN-γ (1–100 U/ml) alone or in combination with IL-1β (100 pg/ml) or TNF-α (1000 pg/ml) resulted in significant up-regulation of monocyte chemoattractant protein-1 and RANTES protein secretion. In contrast, IFN-γ inhibited basal and IL-1β-, and TNF-α-induced production of IL-8. The modulating effects of IFN-γ on chemokine production occurred at the level of gene expression, and the degree of regulation observed was dependent on the doses of IL-1β and TNF-α used. Analysis of the functional effects of IFN-γ on IL-1β-induced transmesothelial PMN migration with an in vitro human transmigration system and an in vivo murine model of peritoneal inflammation demonstrated that IFN-γ was able to down-regulate PMN migration induced by optimal doses of IL-1β. These effects were mediated in vivo via down-regulation of CXC chemokine synthesis. These findings suggest that IFN-γ may play a role in controlling the phenotype of infiltrating leukocyte during the course of an inflammatory response, in part via regulation of resident cell chemokine synthesis.

Interferon‐γ protects against the development of structural damage in experimental arthritis by regulating polymorphonuclear neutrophil influx into diseased joints

“…These observations parallel those made in cultured human mesothelial cells, in which IFN␥ reduced IL-1␤-and TNF␣-driven CXCL8 production at a transcriptional and translational level (47). Interestingly, in that study, the reduction in CXCL8 production was accompanied by reduced migration of PMNs across mesothelial cell monolayers.…”

“…In our RA FLS model, both IL-1␤ and TNF␣ induced CCL2 production; however, in contrast to CXCL8 production, IFN␥ synergistically increased IL-1␤-driven CCL2 production, once again paralleling observations made in other stromal cells (47). These data suggest a potential mechanism by which IFN␥ differentially controls CXC and CC chemokine secretion, culminating in the removal of inflammatory PMNs from the joint space and promoting the resolution of inflammation.…”

“…To define the mechanism by which IFN␥ might regulate this process, we used an in vitro model system using the structural cells that constitute the inflammatory pannus, namely, FLS cultured from human RA synovial tissue specimens. In these experiments, we observed that while both IL-1␤ and TNF␣ were potent activators of CXCL8 production, a phenomenon demonstrated previously in many cell types (42)(43)(44)(45)(46)(47), coincubation with IFN␥ (which did not itself induce CXCL8) significantly reduced RA FLS CXCL8 production.…”

“…Synovial tissue and synovial fluid from RA patients contain increased concentrations of several chemokines produced by resident synoviocytes and infiltrating cells alike (53)(54)(55). At the level of chemokine production, the potential of different chemokines to be induced (or repressed) with differing kinetics may be one mechanism involved in controlling the magnitude, time dependency, and phenotype of specific leukocyte subsets recruited to sites of inflammation (47)(48)(49). In other stromal cells, CCL2 production supersedes that of CXCL8 (47); if the time course of events was paralleled in RA FLS, then the effects of IFN␥ deficiency on monocyte recruitment may be secondary to effects on PMNs.…”

“…At the level of chemokine production, the potential of different chemokines to be induced (or repressed) with differing kinetics may be one mechanism involved in controlling the magnitude, time dependency, and phenotype of specific leukocyte subsets recruited to sites of inflammation (47)(48)(49). In other stromal cells, CCL2 production supersedes that of CXCL8 (47); if the time course of events was paralleled in RA FLS, then the effects of IFN␥ deficiency on monocyte recruitment may be secondary to effects on PMNs. This theory was borne out in murine AIA, in which joint sections taken from IFN␥ Ϫ/Ϫ mice within 8 hours of arthritis induction contained a mild synovial CXCR2ϩ infiltrate; F4/80 monocyte/macrophage lineage cells were absent.…”