Identifying chemokines as therapeutic targets in renal disease: Lessons from antagonist studies and knockout mice

Chemokines, in concert with cytokines and adhesion molecules, play multiple roles in local and systemic immune responses. In the kidney, the temporal and spatial expression of chemokines correlates with local renal damage and accumulation of chemokine receptor-bearing leukocytes. Chemokines play important roles in leukocyte trafficking and blocking chemokines can effectively reduce renal leukocyte recruitment and subsequent renal damage. However, recent data indicate that blocking chemokine or chemokine receptor activity in renal disease may also exacerbate renal inflammation under certain conditions. An increasing amount of data indicates additional roles of chemokines in the regulation of innate and adaptive immune responses, which may adversively affect the outcome of interventional studies. This review summarizes available in vivo studies on the blockade of chemokines and chemokine receptors in kidney diseases, with a special focus on the therapeutic potential of anti-chemokine strategies, including potential side effects, in renal disease. Copyright (C) 2004 S. Karger AG, Basel

The Expression and Regulation of Chemokines (CXCL9, CXCL10, CXCL11) in Urinary Bladder Inflammation of the Mouse

Interstitial cystitis is a serious chronic condition that causes bladder pain and increased voiding frequency in millions of adults in the US, most of them women. A possible biomarker that may be linked to bladder inflammation is the CXCL chemokine family, specifically CXCL9, CXCL10, and CXCL11. The goal of this project is to investigate the expression and regulation of these CXCL chemokines during acute and chronic inflammation of the urinary bladder. Wild-type C57BL/6J mice were injected with cyclophosphamide (CYP) to induce bladder inflammation. RT-PCR and ELISAs were used to determine mRNA and protein expression of CXCL9, CXCL10, and CXCL11 chemokines. During CYP-induced cystitis, the detrusor muscle exhibited more CXCL mRNA regulation in both males and females compared to the urothelium. CYP-induced cystitis significantly (p ≤ 0.05) upregulated CXCL10, while CXCL9 and CXCL11 were significantly (p ≤ 0.05) downregulated. CXCL chemokines were also more regulated during acute and intermediate inflammation versus chronic inflammation. Females had significantly (p ≤ 0.05) decreased CXCL9 and CXCL11 protein levels after chronic inflammation. There were no statistical differences between CXCL chemokine protein levels in males. Future research such as immunohistochemistry to focus on tissue distribution of chemokines and use of chemokine receptor antagonist should be performed to further explore the functional role of these chemokines in male and female urinary bladders

Chemokines (CCL3, CCL4, CCL5) inhibit ATP-induced release of IL-1beta by monocytic cells

ATP and chemokines are among the first inflammatory mediators that can enter the circulation via damaged blood vessels at the site of injury, leading to an activation of the host’s immune response. The main function of chemokines is leukocyte mobilization, guiding immune cells towards the injured tissue along a chemotactic concentration gradient. In monocytes, ATP typically triggers inflammasome assembly, a multiprotein complex necessary for the maturation and secretion of IL-1beta. IL-1beta is a potent inflammatory cytokine of innate immunity, essential for pathogen defense. However, excessive IL-1beta may cause life-threatening systemic inflammation. Here, we hypothesize that chemokines control ATP-dependent secretion of monocytic IL-1beta, by engaging a cholinergic signaling pathway. LPS-primed human monocytic U937 cells were treated with chemokines in the presence or absence of nAChR antagonists or iPLA2beta inhibitors and concomitantly stimulated with the P2X7 agonist BzATP. IL-1beta concentration was determined in the cell culture supernatants. Silencing of the chemokine receptor and iPLA2b gene expression was achieved by transfecting cells with the appropriate siRNA. CCL3, CCL4, and CCL5 dose-dependently inhibited BzATP-stimulated release of IL-1beta, whereas CXCL16 was ineffective. The effect of CCL3 was confirmed for primary mononuclear leukocytes. The inhibitory effect of CCL3 was blunted after silencing CCR1 or iPLA2beta gene expression by siRNA and was sensitive to antagonists of nAChRs containing subunits alpha7 and alpha9/alpha10. U937 cells secreted small factors in response to CCL3 that mediated the inhibition of IL-1beta release. We suggest that CCL chemokines inhibit ATP-induced release of IL-1beta from U937 cells by a triple-membrane-passing mechanism involving CCR, iPLA2, release of small mediators, and nAChR subunits alpha7 and alpha9/alpha10. We speculate that whenever chemokines and ATP enter the circulation concomitantly, systemic release of IL-1beta is minimized

A guide to chemokines and their receptors

The chemokines (or chemotactic cytokines) are a large family of small, secreted proteins that signal through cell surface G‐protein coupled heptahelical chemokine receptors. They are best known for their ability to stimulate the migration of cells, most notably white blood cells (leukocytes). Consequently, chemokines play a central role in the development and homeostasis of the immune system, and are involved in all protective or destructive immune and inflammatory responses. Classically viewed as inducers of directed chemotactic migration, it is now clear that chemokines can stimulate a variety of other types of directed and undirected migratory behaviour, such as haptotaxis, chemokinesis, and haptokinesis, in addition to inducing cell arrest or adhesion. However, chemokine receptors on leukocytes can do more than just direct migration, and these molecules can also be expressed on, and regulate the biology of, many non‐leukocytic cell types. Chemokines are profoundly affected by post‐translational modification, by interaction with the extracellular matrix (ECM), and by binding to heptahelical ‘atypical’ chemokine receptors that regulate chemokine localisation and abundance. This guide gives a broad overview of the chemokine and chemokine receptor families; summarises the complex physical interactions that occur in the chemokine network; and, using specific examples, discusses general principles of chemokine function, focussing particularly on their ability to direct leukocyte migration

Questions about Chemokine and Chemokine Receptor Antagonism in Renal Inflammation

Chemokines remain attractive therapeutic targets for modulating inflammatory diseases in all areas of medicine including acute and chronic kidney disease. Industry has launched huge programs for the development of chemokine antagonists, and clinical trials with chemokine and chemokine receptor antagonists are ongoing. However, chemokine biology remains an area of unexpected discoveries. Here we discuss a number of questions which need to be addressed to further explore the potential of chemokine antagonism in renal inflammation: Why does renal expression of chemokines and chemokine receptors not always correlate with their functional significance? Why does chemokine antagonism only partially reduce renal leukocyte counts? Will antagonist combinations be more effective in reducing renal inflammation? What are the functional roles of homeostatic chemokines and atypical, nonsignaling chemokine receptors in renal inflammation? And finally, what classes of chemokine antagonists are available to address these questions experimentally? Copyright (C) 2009 S. Karger AG, Base

Functional diversity of chemokines and chemokine receptors in response to viral infection of the central nervous system.

Encounters with neurotropic viruses result in varied outcomes ranging from encephalitis, paralytic poliomyelitis or other serious consequences to relatively benign infection. One of the principal factors that control the outcome of infection is the localized tissue response and subsequent immune response directed against the invading toxic agent. It is the role of the immune system to contain and control the spread of virus infection in the central nervous system (CNS), and paradoxically, this response may also be pathologic. Chemokines are potent proinflammatory molecules whose expression within virally infected tissues is often associated with protection and/or pathology which correlates with migration and accumulation of immune cells. Indeed, studies with a neurotropic murine coronavirus, mouse hepatitis virus (MHV), have provided important insight into the functional roles of chemokines and chemokine receptors in participating in various aspects of host defense as well as disease development within the CNS. This chapter will highlight recent discoveries that have provided insight into the diverse biologic roles of chemokines and their receptors in coordinating immune responses following viral infection of the CNS

Atypical chemokine receptor ACKR2 controls branching morphogenesis in the developing mammary gland

Macrophages are important regulators of branching morphogenesis during development and postnatally in the mammary gland. Regulation of macrophage dynamics during these processes can therefore have a profound impact on development. We demonstrate here that the developing mammary gland expresses high levels of inflammatory CC-chemokines, which are essential in vivo regulators of macrophage migration. We further demonstrate that the atypical chemokine receptor ACKR2, which scavenges inflammatory CC-chemokines, is differentially expressed during mammary gland development. We have previously shown that ACKR2 regulates macrophage dynamics during lymphatic vessel development. Here, we extend these observations to reveal a novel role for ACKR2 in regulating the postnatal development of the mammary gland. Specifically, we show that Ackr2−/− mice display precocious mammary gland development. This is associated with increased macrophage recruitment to the developing gland and increased density of the ductal epithelial network. These data demonstrate that ACKR2 is an important regulator of branching morphogenesis in diverse biological contexts and provide the first evidence of a role for chemokines and their receptors in postnatal development processes