Histone deacetylase (HDAC) 3, as a cofactor in co-repressor complexes containing silencing mediator for retinoid or thyroid-hormone receptors (SMRT) and nuclear receptor co-repressor (N-CoR), has been shown to repress gene transcription in a variety of contexts. Here, we reveal a novel role for HDAC3 as a positive regulator of IL-1-induced gene expression. Various experimental approaches involving RNAi-mediated knockdown, conditional gene deletion or small molecule inhibitors indicate a positive role of HDAC3 for transcription of the majority of IL-1-induced human or murine genes. This effect was independent from the gene regulatory effects mediated by the broad-spectrum HDAC inhibitor trichostatin A (TSA) and thus suggests IL-1-specific functions for HDAC3. The stimulatory function of HDAC3 for inflammatory gene expression involves a mechanism that uses binding to NF-κB p65 and its deacetylation at various lysines. NF-κB p65-deficient cells stably reconstituted to express acetylation mimicking forms of p65 (p65 K/Q) had largely lost their potential to stimulate IL-1-triggered gene expression, implying that the co-activating property of HDAC3 involves the removal of inhibitory NF-κB p65 acetylations at K122, 123, 314 and 315. These data describe a novel function for HDAC3 as a co-activator in inflammatory signaling pathways and help to explain the anti-inflammatory effects frequently observed for HDAC inhibitors in (pre)clinical use.

Interleukin (IL)2 -22 is a newly described member of the IL-10 family of cytokines that is produced by T and NK cells under conditions of immunoactivation. Initiation of the Jak1/Tyk2/ signal transducer and activator of transcription (STAT) 3 pathway appears to be the major mode of IL-22 signal transduction (1-4), although activation of STAT1 (5, 6), mitogen-activated protein kinases (5-7), nuclear factor B (NF-B) (8), activator protein-1 (8), and protein kinase B (6) has been related to this cytokine under specific conditions. IL-22 signaling is established by binding of the cytokine to its heterodimeric receptor complex consisting of IL-22R1 and IL-10R2 (2, 3). Because IL-10R2 is a ubiquitous protein, cellular IL-22 responsiveness is mainly determined by expression of the IL-22R1 receptor chain. Interestingly, IL-22R1 expression is restricted to nonleukocytic cells (9 -11). Therefore, IL-22 appears to be unique among a vast array of cytokines in that this protein is incapable of mediating autocrine or paracrine functions between leukocytes but is rather specialized to transmit information between leukocytes and the nonleukocytic cell compartment. This distinctive biological characteristic essentially discriminates IL-22 from another major activator of the STAT3 signaling system, namely IL-6 (12). Cell types identified to be responsive to IL-22 include synoviocytes (7), pancreatic acinar cells (11), hepatocytes (5, 13, 14), colonic epithelial myofibroblasts (8), and in particular cells of epithelial origin such as keratinocytes (10,15), lung carcinoma cells (16), and colon carcinoma cells (6,17). Proteins that have been reported to be inducible by IL-22 include pro-inflammatory and pro-angiogenic mediators such as IL-8 and enzymes that are involved in cell migration and tissue remodeling such as matrix metalloprotease-1 and -3 (6, 8), effector molecules of innate immunity such as ␤-defensins (10), and immunosuppressive modulators such as IL-10 (17) and SOCS proteins (17, 18). IL-22-induced STAT3 has been associated with induction of the acute phase response (13), with proliferation, and with protection from cell death (6, 14). Interestingly, constitutive activation of the STAT3 pathway is characteristic for numerous human malignancies. Based on the capabilities of this transcription factor to inhibit apoptosis and to promote cell proliferation, STAT3 is actually considered an oncogenic protein (12,19,20).Inducible nitric-oxide synthase (iNOS) and its volatile enzymatic product nitric oxide (NO) have been identified as potential promoters of tumor growth in a variety of human neoplasia, among other colorectal cancers (20 -24). The ability of iNOS to * This work was supported by Deutsche Forschungsgemeinschaft Grants GK1172 Biologicals and SFB 553. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C.