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Chemokines are the principal regulators of leukocyte migration and are essential for initiation and maintenance of inflammation. Atypical chemokine receptor 2 (ACKR2) binds and scavenges proinflammatory CC-chemokines, regulates cutaneous T-cell positioning, and limits the spread of inflammation in vivo. Altered ACKR2 function has been implicated in several inflammatory disorders, including psoriasis, a common and debilitating T-cell–driven disorder characterized by thick erythematous skin plaques. ACKR2 expression is abnormal in psoriatic skin, with decreased expression correlating with recruitment of T-cells into the epidermis and increased inflammation. However, the molecular mechanisms that govern ACKR2 expression are not known. Here, we identified specific psoriasis-associated microRNAs (miRs) that bind ACKR2, inhibit its expression, and are active in primary cultures of human cutaneous cells. Using both in silico and in vitro approaches, we show that miR-146b and miR-10b directly bind the ACKR2 3′-UTR and reduce expression of ACKR2 transcripts and protein in keratinocytes and lymphatic endothelial cells, respectively. Moreover, we demonstrate that ACKR2 expression is further down-regulated upon cell trauma, an important trigger for the development of new plaques in many psoriasis patients (the Koebner phenomenon). We found that tensile cell stress leads to rapid ACKR2 down-regulation and concurrent miR-146b up-regulation. Together, we provide, for the first time, evidence for epigenetic regulation of an atypical chemokine receptor. We propose a mechanism by which cell trauma and miRs coordinately exacerbate inflammation via down-regulation of ACKR2 expression and provide a putative mechanistic explanation for the Koebner phenomenon in psoriasis.

Diabetes mellitus type 2 (T2DM) is a serious and frequent disease, characterized by deregulation of glucose metabolism as a consequence of dysfunction of the insulin signaling system. The relevance of the IGF1 receptor (IGF1R) in compensating functions of the structurally closely related insulin receptor (IR) was subject to several studies but has not been clarified so far. To investigate a possible redundant function of both receptors two strategies were pursued to obtain the simultaneous RNAi-mediated knockdown (KD) of both receptors in transgenic mice. The first strategy based on the generation of a ES cell line bearing two alleles prepared for recombinase mediated cassette exchange (RMCE) in the loci of Rosa 26 (R26) and Collagen, type I, α1 (Col1a1) facilitating the integration of two shRNA expression cassettes. The Functionality of double RMCE was demonstrated, although expression properties of the Collagen locus did not meet our requirements. As a second strategy two shRNA expression units allowing tet-repressor (tetR)-mediated temporal control of RNAi, were combined in a tandem construct, integrated into the Rosa26 locus of ES cells using RMCE technologie. Transgenic mice harbouring this tandem construct displayed temporal controllable RNAi, reducing IR expression to 15-25% and IGF1R expression to 20-45%. Simultaneous whole body silencing of both receptors did not cause an enhanced middle-term diabetic phenotype in semi adult mice, displaying disturbance of glucose and lipid metabolism to the same degree as mice with single ablation of the IR. A faster initial increase of blood glucose was observed in double KD mice, possibly a consequence of a rudimental ability of the IGF1R or IGF1R/IR hybrids to adopt functions of the IR, also demonstrated by a lowered response of IGF1R single KD mice on insulin challenge. Certainly this effect seems not to be distinct enough to appear after complete silencing of IR, since neither the magnitude of hyperglycaemia, nor peripheral glucose disposal were distinguishable between double KD mice and IR KD mice after the initial phase. These findings indicate that IGF1R might in part compensate loss of IR function in marginal or pre-diabetic insulin resistance but is not crucial in severe loss of IR function in semi adult mice.