Stimuli that enhance cAMP levels (e.g., prostaglandin E2 or PDE4 inhibitors) suppress SIK2 activity and robustly potentiate IL-10 production by macrophages and dendritic cells (DCs), a phenotype that can be mimicked by small molecules that directly inhibit SIK2 [ 24••, 25 and 26]. Whereas recombinant IL-10 supplementation is ineffective in Crohn’s disease (CD) patients [ 27], perhaps due to insufficient delivery to the gut mucosa [ 28], these data suggest that SIK2 inhibition may be effective at increasing IL-10 levels directly in this tissue. The additional ability of SIK2 inhibitors to suppress production of IL-12 and other inflammatory cytokines
makes this kinase a promising target for further investigation CDK inhibitor review in IBD [ 24,26]. Studies from genetics, physiology and chemical biology continue to implicate kinases as potential targets for restoring normal cytokine function in disease (Table Entinostat 1). Novel polymorphisms in leucine-rich repeat kinase 2 (LRRK2, a gene previously linked to Parkinson’s disease)
confer increased risk of IBD [ 29]. Functional studies suggest that LRRK2 regulates production of reactive oxygen species and inflammatory cytokines by macrophages [ 30 and 31]. In addition, SNPs near IRAK1, which encodes a kinase required for production of interferons (IFNs) following viral infection, confer increased risk of systemic lupus erythematosus [ 32]. The serum/glucocorticoid-regulated kinase 1 (SGK1) regulates differentiation of TH17 cells, a CD4+ T cell subset that produces IL-17A and other inflammatory cytokines, in response to environmental factors including NaCl; small-molecule inhibition of SGK1 suppresses high salt-induced TH17 development [ 33 and 34]. Mechanism-of-action studies have implicated the phoshatidylinositol kinase PIKfyve as the target of the clinical candidate apilimod, an inhibitor of IL-12/23 production discovered through phenotypic screening [ 35• and 36]. Targeting kinases implicated
in cytokine regulation, Lepirudin with novel inhibitors or those repurposed from other indications, is a critical step for testing novel therapeutic hypotheses and may yield valuable starting points for drug development. Signaling cascades downstream of immune receptors converge on transcription factors to regulate cytokine expression. The clinical success of calcineurin inhibitors, which suppress IL-2 production following T cell receptor stimulation by preventing dephosphorylation of NFAT , demonstrates the utility of small molecules that target transcriptional regulation in immune cells. In addition to acute transcriptional responses, activation of immune cells leads to chromatin modifications that can promote acquisition of distinct effector states [6, 7, 8 and 9].