Oncostatin M regulates SOCS3 mRNA stability via the MEK-ERK1/2-pathway independent of p38(MAPK)/MK2

The induction of suppressor of cytokine signalling (SOCS)3 expression context dependently involves regulation of SOCS3 transcript stability as previously demonstrated for MAPK activated protein kinase (MK)2-dependent regulation of SOCS3 expression by TNFα (Ehlting et al., 2007). In how far the IL-6-type cytokine OSM, which in contrast to IL-6 is a strong activator of p38(MAPK)/MK2 signalling, also involves regulation of transcript stability and activation of MK2 to induce SOCS3 expression is unclear. In contrast to IL-6, OSM induces SOCS3 expression in murine fibroblasts and in primary human and murine hepatocytes, but not in macrophages because the latter lack the OSM receptor (OSMR)β subunit. Evidence is provided that regulation of OSM-induced expression of SOCS3 involves MEK1- and Erk1/2-mediated stabilization of the SOCS3 transcript. Consistently, OSM-induced stabilization of the SOCS3 transcript is impaired in the presence of inhibitors that specifically block activation of MEK1/2 (U0126) and ERK1/2 (FR180204) or upon knock-down of ERK1/2 expression using specific siRNA. As a potential target site that integrates the stability regulating effect of OSM and OSM-induced activation of MEK1/2 and ERK1/2 a region containing three copies of a pentameric AUUUA motif located within position 2422 and 2541 in closed proximity to the 3' UTR of the SOCS3 transcript has been identified. Unexpectedly, activation of the p38(MAPK)/MK2 pathway, which apart from STAT3 and ERK1/2, is also strongly activated by OSM in human and murine hepatocytes and murine fibroblasts is dispensable for stabilization of the SOCS3 transcript as suggested from inhibitor studies using the p38(MAPK) inhibitor SB203580 or from the analysis of MK2-deficient hepatocytes. However, analysis of MK2-deficient macrophages and hepatocytes revealed that, although MK2 is dispensable for regulation of OSM-induced SOCS3 expression, MK2 is essential for LPS-induced OSM production in macrophages and limits the overall availability of the OSMRβ subunit in hepatocytes. Thus MK2 plays a role for the induction and sensing of OSM-mediated intercellular signalling between macrophages and hepatocytes during LPS-induced inflammation.

A sensory neuron-expressed IL-31 receptor mediates T helper cell-dependent itch: Involvement of TRPV1 and TRPA1

BACKGROUND

Although the cytokine IL-31 has been implicated in inflammatory and lymphoma-associated itch, the cellular basis for its pruritic action is yet unclear.

OBJECTIVE

We sought to determine whether immune cell-derived IL-31 directly stimulates sensory neurons and to identify the molecular basis of IL-31-induced itch.

METHODS

We used immunohistochemistry and quantitative real-time PCR to determine IL-31 expression levels in mice and human subjects. Immunohistochemistry, immunofluorescence, quantitative real-time PCR, in vivo pharmacology, Western blotting, single-cell calcium imaging, and electrophysiology were used to examine the distribution, functionality, and cellular basis of the neuronal IL-31 receptor α in mice and human subjects.

RESULTS

Among all immune and resident skin cells examined, IL-31 was predominantly produced by TH2 and, to a significantly lesser extent, mature dendritic cells. Cutaneous and intrathecal injections of IL-31 evoked intense itch, and its concentrations increased significantly in murine atopy-like dermatitis skin. Both human and mouse dorsal root ganglia neurons express IL-31RA, largely in neurons that coexpress transient receptor potential cation channel vanilloid subtype 1 (TRPV1). IL-31-induced itch was significantly reduced in TRPV1-deficient and transient receptor channel potential cation channel ankyrin subtype 1 (TRPA1)-deficient mice but not in c-kit or proteinase-activated receptor 2 mice. In cultured primary sensory neurons IL-31 triggered Ca(2+) release and extracellular signal-regulated kinase 1/2 phosphorylation, inhibition of which blocked IL-31 signaling in vitro and reduced IL-31-induced scratching in vivo.

CONCLUSION

IL-31RA is a functional receptor expressed by a small subpopulation of IL-31RA(+)/TRPV1(+)/TRPA1(+) neurons and is a critical neuroimmune link between TH2 cells and sensory nerves for the generation of T cell-mediated itch. Thus targeting neuronal IL-31RA might be effective in the management of TH2-mediated itch, including atopic dermatitis and cutaneous T-cell lymphoma.