The role of interleukin-1 in mesangial proliferation

Interleukin-1β induces hyaluronan and CD44-dependent cell protrusions that facilitate fibroblast-monocyte binding

Persistent inflammation is a well-known determinant of progressive tissue fibrosis; however, the mechanisms underlying this process remain unclear. There is growing evidence indicating a role of the cytokine IL-1β in profibrotic responses. We previously demonstrated that fibroblasts stimulated with IL-1β increased their generation of the polysaccharide hyaluronan (HA) and increased their expression of the HA synthase enzyme (HAS-2). The aim of this study was to determine the significance of IL-1β-induced changes in HA and HAS-2 generation. In this study, we found that stimulation of fibroblasts with IL-1β results in the relocalization of HA associated with the cell to the outer cell membrane, where it forms HAS2- and CD44-dependent cell membrane protrusions. CD44 is concentrated within the membrane protrusions, where it co-localizes with the intracellular adhesion molecule 1. Furthermore, we have identified that these cell protrusions enhance IL-1β-dependent fibroblast-monocyte binding through MAPK/ERK signaling. Although previous data have indicated the importance of the HA-binding protein TSG-6 in maintaining the transforming growth factor β1-dependent HA coat, TSG-6 was not essential for the formation of the IL-1β-dependent HA protrusions, thus identifying it as a key difference between IL-1β- and transforming growth factor β1-dependent HA matrices. In summary, these data suggest that IL-1β-dependent HA generation plays a role in fibroblast immune activation, leading to sequestration of monocytes within inflamed tissue and providing a possible mechanism for perpetual inflammation.

Growth factors and proinflammatory cytokines in the renal involvement of POEMS syndrome

The POEMS syndrome is a multisystemic syndrome associated with plasma cell dyscrasia, characterized by the combination of polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes. Renal involvement in POEMS syndrome is rare (26 reported cases). It has been described as membranoproliferative glomerulonephritis-like lesions (MPGN-like), mesangiolytic glomerulonephritis, or thrombotic microangiopathy. Proinflammatory cytokines (TNF-alpha, IL-1, IL-6) have been implicated in the physiopathogenesis of POEMS syndrome, particularly when there is renal involvement. Growth factors (FGF-beta, TGF-beta, PDGF) have been implicated in renal lesions of the same histological type but of different origins. An increase in serum vascular endothelial growth factor (VEGF) has been reported in POEMS syndrome (20 of 22 cases). Circulating levels of these factors were determined in 4 patients with POEMS and renal involvement (3 MPGN-like, 1 MPGN-like, and mesangiolysis) and compared with those obtained in 4 patients with POEMS without clinical renal involvement and in 4 patients with primitive membranoproliferative glomerulonephritis (MPGN). TNF-alpha, IL-1beta, and IL-6 were determined with an immunoradiometric assay, and VEGF, PDGF, FGF-beta, and TGF-beta with an enzyme-linked immunosorbent assay. Among the patients with POEMS syndrome, there was no difference in proinflammatory cytokines and growth factors between those with or without renal involvement. VEGF is the only growth factor that differentiates MPGN in POEMS syndrome from primitive MPGN.