Chemerin triggers migration of a CD8 T cell subset with natural killer cell functions

The recruitment of cells with effector functions into the tumor microenvironment holds potential for delaying cancer progression. We show that subsets of human CD28-effector CD8 T cells, CCR7- CD45RO+ effector memory, and CCR7- CD45RO- effector memory RA phenotypes, express the chemerin receptor CMKLR1 and bind chemerin via the receptor. CMKLR1-expressing human CD8 effector memory T cells present gene, protein, and cytotoxic features of NK cells. Active chemerin promotes chemotaxis of CMKLR1-expressing CD8 effector memory cells and triggers activation of the α4β1 integrin. In an experimental prostate tumor mouse model, chemerin expression is downregulated in the tumor microenvironment, which is associated with few tumor-infiltrating CD8+ T cells, while forced overexpression of chemerin by mouse prostate cancer cells leads to an accumulation of intra-tumor CD8+ T cells. Furthermore, α4 integrin blockade abrogated the chemerin-dependent recruitment of CD8+ T effector memory cells into implanted prostate tumors in vivo. The results identify a role for chemerin:CMKLR1 in defining a specialized NK-like CD8 T cell, and suggest the use of chemerin-dependent modalities to target effector CMKLR1-expressing T cells to the tumor microenvironment for immunotherapeutic purposes.

The expression and regulation of chemerin in the epidermis

Chemerin is a protein ligand for the G protein-coupled receptor CMKLR1 and also binds to two atypical heptahelical receptors, CCRL2 and GPR1. Chemerin is a leukocyte attractant, adipokine, and antimicrobial protein. Although chemerin was initially identified as a highly expressed gene in healthy skin keratinocytes that was downregulated during psoriasis, the regulation of chemerin and its receptors in the skin by specific cytokines and microbial factors remains unexplored. Here we show that chemerin, CMKLR1, CCRL2 and GPR1 are expressed in human and mouse epidermis, suggesting that this tissue may be both a source and target for chemerin mediated effects. In human skin cultures, chemerin is significantly downregulated by IL-17 and IL-22, key cytokines implicated in psoriasis, whereas it is upregulated by acute phase cytokines oncostatin M and IL-1β. Moreover, we show that human keratinocytes in vitro and mouse skin in vivo respond to specific microbial signals to regulate expression levels of chemerin and its receptors. Furthermore, in a cutaneous infection model, chemerin is required for maximal bactericidal effects in vivo. Together, our findings reveal previously uncharacterized regulators of chemerin expression in skin and identify a physiologic role for chemerin in skin barrier defense against microbial pathogens.

Robust expansion of dendritic cells in vivo by hydrodynamic FLT3L-FC gene transfer

Due to low numbers of endogenous dendritic cells (DCs) in vivo, exogenous DC-poietin Fms-like tyrosine kinase 3-ligand (FLT3L) is routinely used to generate DC for subsequent studies. We engineered a novel FLT3L-FC DNA construct that, when combined with hydrodynamic gene transfer (HDT), induced robust DC expansion in mice. DC generated in vivo by FLT3L-FC HDT produced cytokines in response to stimulation by an array of TLR agonists and promoted T cell proliferation. The FLT3L-FC protein produced in vivo spontaneously homodimerized to enable effective FLT signaling and the FC-domain enhanced its plasma half-life, providing an improved reagent and method to boost DC numbers.

Canonical and noncanonical Wnt proteins program dendritic cell responses for tolerance

Ag-presenting dendritic cells (DCs) interpret environmental signals to orchestrate local and systemic immune responses. They govern the balance between tolerance and inflammation at epithelial surfaces, where the immune system must provide robust pathogen responses while maintaining tolerance to commensal flora and food Ags. The Wnt family of secreted proteins, which control epithelial and hematopoietic development and homeostasis, is emerging as an important regulator of inflammation. In this study, we show that canonical and noncanonical Wnts directly stimulate murine DC production of anti-inflammatory cytokines. Wnt3A triggers canonical β-catenin signaling and preferentially induces DC TGF-β and VEGF production, whereas Wnt5A induces IL-10 through alternative pathways. The Wnts also alter DC responses to microbe- or pathogen-associated molecular patterns, inhibiting proinflammatory cytokine induction in response to TLR ligands and promoting DC generation of Foxp3(+) regulatory T cells. Moreover, although both Wnts suppress proinflammatory responses to bacterial endotoxin and to TLR1/2, TLR7, and TLR9 ligands, Wnt5A, but not Wnt3A, inhibits IL-6 production in response to the viral mimic, polyinosinic:polycytidylic acid. Thus, Wnt family members directly and differentially regulate DC functions, an ability that may contribute to the balance between tolerance and inflammation at epithelial sites of exposure to microbes and environmental Ags.

HuR protein is involved in S49 thymoma cell proliferation and is regulated by cAMP/PKA signaling (88.20)

The RNA binding protein human antigen R (HuR) participates in the post transcriptional regulation of many mRNAs bearing AU rich and U rich elements by influencing stabilization and translation. Based on the types of mRNAs regulated by HuR, the cellular role of HuR can be identified as pro-survival and pro-inflammatory. Using the S49 thymoma cell line, we recently showed that cAMP treatment, which triggers apoptotic signaling events, leads to a decrease in the effectiveness of HuR function. In this work, we investigate if there is a relationship between cAMP mediated cell death and HuR activity by utilizing small interfering RNA-mediated suppression of HuR in S49 cells. We found that knockdown of HuR protein decreases normal cell growth, and increases cAMP mediated apoptosis. qPCR analysis of mRNAs important in inflammation, cell growth, and apoptosis reveal that knockdown of HuR downregulates TNF-α mRNA and upregulates IL-10 and Bim mRNAs in untreated cells, and upregulates p27, and Bim mRNAs upon treatment with cAMP. Furthermore, cAMP treatment causes a PKA dependent decrease in HuR cytoplasmic levels. These results suggest that a pro-inflammatory and pro-survival role for HuR in S49 thymoma cells exists and may be compromised upon the elevation of cAMP by decreasing cytoplasmic HuR protein and allowing the expression of apoptotic factors.