Probes for INS

The atypical chemokine receptor 2 (ACKR2), also named D6, regulates local levels of inflammatory chemokines by internalization and degradation. To explore potential anti-inflammatory functions of ACKR2 in glomerulonephritis, we induced autologous nephrotoxic nephritis in C57/BL6 wild-type and Ackr2-deficient mice. Renal ACKR2 expression increased and localized to interstitial lymphatic endothelium during nephritis. At two weeks Ackr2–/–mice developed increased albuminuria and urea levels compared to wild-type mice. Histological analysis revealed increased structural damage in the glomerular and tubulointerstitial compartments within Ackr2−/− kidneys. This correlated with excessive renal leukocyte infiltration of CD4+ T cells and mononuclear phagocytes with increased numbers in the tubulointerstitium but not glomeruli in knockout mice. Expression of inflammatory mediators and especially markers of fibrotic tissue remodeling were increased along with higher levels of ACKR2 inflammatory chemokine ligands like CCL2 in nephritic Ackr2–/– kidneys. In vitro, Ackr2 deficiency in TNF-stimulated tubulointerstitial tissue but not glomeruli increased chemokine levels. These results are in line with ACKR2 expression in interstitial lymphatic endothelial cells, which also assures efflux of activated leukocytes into regional lymph nodes. Consistently, nephritic Ackr2–/– mice showed reduced adaptive cellular immune responses indicated by decreased regional T-cell activation. However, this did not prevent aggravated injury in the kidneys of Ackr2–/– mice with nephrotoxic nephritis due to simultaneously increased tubulointerstitial chemokine levels, leukocyte infiltration and fibrosis. Thus, ACKR2 is important in limiting renal inflammation and fibrotic remodeling in progressive nephrotoxic nephritis. Hence, ACKR2 may be a potential target for therapeutic interventions in immune complex glomerulonephritis.

Patients with primary solid malignancies frequently exhibit signs of systemic inflammation. Notably, elevated levels of neutrophils and their associated soluble mediators are regularly observed in cancer patients, and correlate with reduced survival and increased metastasis formation. Recently, we demonstrated a mechanistic link between mammary tumor-induced IL17-producing γδ T cells, systemic expansion of immunosuppressive neutrophils and metastasis formation in a genetically engineered mouse model for invasive breast cancer. How tumors orchestrate this systemic inflammatory cascade to facilitate dissemination remains unclear. Here we show that activation of this cascade relies on CCL2-mediated induction of IL1β in tumor-associated macrophages. In line with these findings, expression of CCL2 positively correlates with IL1Β and macrophage markers in human breast tumors. We demonstrate that blockade of CCL2 in mammary tumor-bearing mice results in reduced IL17 production by γδ T cells, decreased neutrophil expansion and enhanced CD8+ T cell activity. These results highlight a new role for CCL2 in facilitating the breast cancer-induced pro-metastatic systemic inflammatory γδ T cell – IL17 – neutrophil axis.

Following renal ischemia-reperfusion injury (IRI) resolution of inflammation allows tubular regeneration, whereas ongoing inflammatory injury mediated by infiltrating leukocytes leads to nephron loss and renal fibrosis, typical hallmarks of chronic kidney disease. The atypical chemokine receptor 2 (ACKR2) is a chemokine decoy receptor, that binds and scavenges inflammatory CC-chemokines and reduces local leukocyte accumulation. We hypothesized that ACKR2 limits leukocyte infiltration, inflammation, and fibrotic tissue remodeling after renal IRI, thus preventing progression to chronic kidney disease. Compared to wild-type, Ackr2 deficiency increased CC chemokine ligand 2 levels in tumor necrosis factor-stimulated tubulointerstitial tissue in vitro. In Ackr2-deficient mice with early IRI one or five days after transient renal pedicle clamping tubular injury was similar to wild-type, although accumulation of mononuclear phagocytes increased in postischemic Ackr2-/-kidneys. Regarding long-term outcomes, Ackr2-/- kidneys displayed more tubular injury five weeks after IRI, which was associated with persistently increased renal infiltrates of mononuclear phagocytes, T cells, Ly6Chigh inflammatory macrophages, and inflammation. Moreover, Ackr2 deficiency resulted in substantially aggravated renal fibrosis in Ackr2-/- kidneys five weeks after IRI, as revealed by increased expression of matrix molecules, renal accumulation of αSMA+ myofibroblasts, and bone marrow-derived fibrocytes. ACKR2 plays an important role in limiting persistent inflammation, tubular loss, and renal fibrosis after ischemic acute kidney injury, and thus can prevent progression to chronic renal disease.

Inflammatory disorders of the CNS are frequently accompanied by synaptic loss, which is thought to involve phagocytic microglia and complement components. However, the mechanisms accounting for aberrant synaptic connectivity in the context of CD8+ T cell-driven neuronal damage are poorly understood. Here, we profiled the neuronal translatome in a murine model of encephalitis caused by CD8+ T cells targeting antigenic neurons. Neuronal STAT1 signaling and downstream CCL2 expression were essential for apposition of phagocytes, ensuing synaptic loss and neurological disease. Analogous observations were made in the brains of Rasmussen’s encephalitis patients. In this devastating CD8+T cell-driven autoimmune disease, neuronal STAT1 phosphorylation and CCL2 expression co-clustered with infiltrating CD8+ T cells as well as phagocytes. Taken together, our findings uncover an active role of neurons in coordinating phagocyte-mediated synaptic loss and highlight neuronal STAT1 and CCL2 as critical steps in this process that are amenable to pharmacological interventions.

The contributions of the innate immune system to the development of pancreatic cancer are still ill defined. Inflammatory macrophages can initiate metaplasia of pancreatic acinar cells to a duct-like phenotype (acinar-to-ductal metaplasia [ADM]), which then gives rise to pancreatic intraepithelial neoplasia (PanIN) when oncogenic KRas is present. However, it remains unclear when and how this inflammatory macrophage population is replaced by tumor-promoting macrophages. Here, we demonstrate the presence of interleukin-13 (IL-13), which can convert inflammatory into Ym1+ alternatively activated macrophages, at ADM/PanIN lesions. We further show that Ym1+ macrophages release factors, such as IL-1ra and CCL2, to drive pancreatic fibrogenesis and tumorigenesis. Treatment of mice expressing oncogenic KRas under an acinar cell-specific promoter with a neutralizing antibody for IL-13 significantly decreased the accumulation of alternatively activated macrophages at these lesions, resulting in decreased fibrosis and lesion growth.