The spreading of HIV-1 infection in the human organism is caused by fractalkine trafficking of the infected lymphocytes—a review, hypothesis and implications for treatment

Alterations in CX3CL1 Levels and Its Role in Viral Pathogenesis

CX3CL1, also named fractalkine or neurotactin, is the only known member of the CX3C chemokine family that can chemoattract several immune cells. CX3CL1 exists in both membrane-anchored and soluble forms, with each mediating distinct biological activities. CX3CL1 signals are transmitted through its unique receptor, CX3CR1, primarily expressed in the microglia of the central nervous system (CNS). In the CNS, CX3CL1 acts as a regulator of microglia activation in response to brain disorders or inflammation. Recently, there has been a growing interest in the role of CX3CL1 in regulating cell adhesion, chemotaxis, and host immune response in viral infection. Here, we provide a comprehensive review of the changes and function of CX3CL1 in various viral infections, such as human immunodeficiency virus (HIV), SARS-CoV-2, influenza virus, and cytomegalovirus (CMV) infection, to highlight the emerging roles of CX3CL1 in viral infection and associated diseases.

Progression of radio-labeled molecular imaging probes targeting chemokine receptors

Chemokine receptors are significantly expressed in the surface of most inflammatory cells and tumor cells. Guided by chemokines, inflammatory cells which express the relevant chemokine receptors migrate to inflammatory lesions and participate in the evolution of inflammation diseases. Similarly, driven by chemokines, immune cells infiltrate into tumor lesions not only induces alterations in the tumor microenvironment, disrupting the efficacy of tumor therapies, but also has the potential to selectively target tumoral cells and diminish tumor progression. Chemokine receptors, which are significantly expressed on the surface of tumor cell membranes, are regulated by chemokines and initiate tumor-associated signaling pathways within tumor cells, playing a complex role in tumor progression. Based on the antagonists targeting chemokine receptors, radionuclide-labeled molecular imaging probes have been developed for the emerging application of molecular imaging in diseases such as tumors and inflammation. The value and limitations of molecular probes in disease imaging are worth reviewing.

Practical Management of Patients with Atopic Dermatitis on Dupilumab

INTRODUCTION

Dupilumab is approved to treat moderate-to-severe atopic dermatitis (AD) in several countries in patients as young as 6 years of age. Since its approval, practical issues related to the use of dupilumab for AD have arisen, with particular interest in transitioning from current therapies and managing medication overlap, considerations for special populations of patients with AD, and management of potential adverse events.

METHODS

This article aims to review the literature addressing several practical management issues related to dupilumab use for AD and to provide a framework for clinical decision-making in these circumstances and sub-populations. Each statement was reviewed, revised and voted on by authors to provide their level of agreement and degree of uncertainty for each statement.

RESULTS

An agreement level > 80% was achieved for all of the statements.

CONCLUSION

The expert panel provides statements considering the practical management of patients with AD taking dupilumab to inform clinical decision-making in specific but frequently encountered clinical situations.

Influence of chemokines on the endothelial permeability and cellular transmigration during dengue

During a pathogenic infection, an inflammatory process is triggered in which several inflammatory mediators, such as cytokines, chemokines, growth factors, complement system components, nitric oxide, and others induce integrity alteration on the endothelial barrier. Chemokines are responsible for regulating leukocyte trafficking under homeostatic conditions as well as activating immune system cells under inflammatory conditions. They are crucial molecules in the early stages of infection, leading to the recruitment of immune cells, namely neutrophils, monocytes, natural killer (NK) cells, natural killer T cells (NKT), dendritic cells (DC), T lymphocytes and all cells expressing chemokine receptors for inflammatory sites. Other functions, such as collagen production, tissue repair, a proliferation of hematopoietic precursors and angiogenesis, are also performed by these molecules. Chemokines, amongst inflammatory mediators, play a key role in dengue immunopathogenesis. Dengue fever is a disease caused by the dengue virus (DENV). It is characterized by a broad spectrum of clinical manifestations ranging from asymptomatic cases to mild and severe symptomatic ones. As for the latter, the appearance of hemorrhagic manifestations and changes in vascular permeability may lead the patient to develop cavitary effusions, organ involvement, and even death. As chemokines exert an influence on various homeostatic and inflammatory processes, acting vigorously on vascular endothelial activation and cell migration, the main purpose of this chapter is to discuss the influence of chemokines on the alteration of endothelial permeability and migration of T lymphocytes in DENV infection.

Association of chemokine receptor gene variants with HIV-1 genotype predicted tropism

OBJECTIVES

As a switch from chemokine (C-C motif) receptor 5 [CCR5 (R5)] to chemokine (C-X-C motif) receptor 4 [CXCR4 (X4)] HIV-1 tropism is associated with symptomatic and AIDS stages of infection, while chemokine receptor gene variants modify the tempo of HIV disease progression, we aimed to analyse the association between pretreatment HIV-1 tropism and chemokine polymorphisms known to restrict disease progression.

METHODS

V3 genotype tropism prediction was performed in a group of 221 treatment-naïve patients, with subsequent CCR5 Δ32 (rs333), CCR2 V64I (rs1799864), CCR5 promoter (-627 C/T; rs1799988) and CX3CR1 V249I (rs3732378) genotyping performed in 206 patients. Alleles with a protective effect were assigned positive values while risk alleles were assigned negative values to calculate genetic scores. χ(2) tests, Mann-Whitney U-tests and logistic and linear regression models were used for statistical analyses.

RESULTS

R5 tropism was found in 85.5% of patients (n = 189) using a false positive rate (FPR) of 5.75% and in 72.8% of patients (n = 161) using an FPR of 10%. A higher frequency of the 5.75% FPR predicted R5 tropism was associated with the CX3CR1 A allele (P = 0.027). Lower additive genetic scores were associated with an increased frequency of 5.75% FPR predicted R5 tropism (P = 0.0059), with the trend confirmed by logistic regression [odds ratio (OR) 0.5819; 95% confidence interval (CI) 0.3457-0.9795; P = 0.0416]. Viral load tended to increase with decreasing genetic score in the logistic regression analysis (slope = -0.127 ± 0.076; P = 0.095; r(2)  = 0.161).

CONCLUSIONS

The CX3CR1 A allele and lower genetic scores may restrict the switch of HIV-1 tropism from R5 to X4. This effect may be associated with the amount of co-receptor on the cell surface. Chemokine receptor gene polymorphisms influence both disease progression and tropism variability.

Exposure of human astrocytes to leukotriene C4 promotes a CX3CL1/fractalkine-mediated transmigration of HIV-1-infected CD4⁺ T cells across an in vitro blood-brain barrier model

Eicosanoids, including cysteinylleukotrienes (cysLTs), are found in the central nervous system (CNS) of individuals infected with HIV-1. Few studies have addressed the contribution of cysLTs in HIV-1-associated CNS disorders. We demonstrate that conditioned medium from human astrocytes treated with leukotriene C4 (LTC4) increases the transmigration of HIV-1-infected CD4(+) T cells across an in vitro blood-brain barrier (BBB) model using cultured brain endothelial cells. Additional studies indicate that the higher cell migration is linked with secretion by astrocytes of CX3CL1/fractalkine, a chemokine that has chemoattractant activity for CD4(+) T cells. Moreover, we report that the enhanced cell migration across BBB leads to a more important CD4(+) T cell-mediated HIV-1 transfer toward macrophages. Altogether data presented in the present study reveal the important role that LTC4, a metabolite of arachidonic acid, may play in the HIV-1-induced neuroinvasion, neuropathogenesis and disease progression.

CB2 receptor agonists protect human dopaminergic neurons against damage from HIV-1 gp120

Despite the therapeutic impact of anti-retroviral therapy, HIV-1-associated neurocognitive disorder (HAND) remains a serious threat to AIDS patients, and there currently remains no specific therapy for the neurological manifestations of HIV-1. Recent work suggests that the nigrostriatal dopaminergic area is a critical brain region for the neuronal dysfunction and death seen in HAND and that human dopaminergic neurons have a particular sensitivity to gp120-induced damage, manifested as reduced function (decreased dopamine uptake), morphological changes, and reduced viability. Synthetic cannabinoids inhibit HIV-1 expression in human microglia, suppress production of inflammatory mediators in human astrocytes, and there is substantial literature demonstrating the neuroprotective properties of cannabinoids in other neuropathogenic processes. Based on these data, experiments were designed to test the hypothesis that synthetic cannabinoids will protect dopaminergic neurons against the toxic effects of the HIV-1 protein gp120. Using a human mesencephalic neuronal/glial culture model, which contains dopaminergic neurons, microglia, and astrocytes, we were able to show that the CB1/CB2 agonist WIN55,212-2 blunts gp120-induced neuronal damage as measured by dopamine transporter function, apoptosis and lipid peroxidation; these actions were mediated principally by the CB2 receptor. Adding supplementary human microglia to our cultures enhances gp120-induced damage; WIN55,212-2 is able to alleviate this enhanced damage. Additionally, WIN55,212-2 inhibits gp120-induced superoxide production by purified human microglial cells, inhibits migration of human microglia towards supernatants generated from gp120-stimulated human mesencephalic neuronal/glial cultures and reduces chemokine and cytokine production from the human mesencephalic neuronal/glial cultures. These data suggest that synthetic cannabinoids are capable of protecting human dopaminergic neurons from gp120 in a variety of ways, acting principally through the CB2 receptors and microglia.

Serum selenium and skin diseases among Nigerians with human immunodeficiency virus/acquired immune deficiency syndrome

Background

The role of selenium as an antioxidant micronutrient has garnered the unprecedented focus of researchers in recent times. No clinical study has related serum selenium concentration to skin diseases in human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) patients.

Methods

In this study, 134 newly diagnosed HIV patients that satisfied the inclusion criteria were included. Skin diseases were clinically diagnosed and fasting venous blood was taken for assessment of serum selenium using an atomic absorption spectrophotometer.

Results

The mean age of HIV subjects with and without skin disease were not significantly different: 32.72 ± 9.21 versus 35.86 ± 8.55 years, P = 0.077, respectively. The mean of serum selenium (0.51 ± 0.48 versus 0.81 ± 0.39), CD4+ count (228.06 ± 212.89 versus 446.41 ± 182.87), and body mass index (BMI; 21.09 ± 3.58 versus 23.53 ± 3.35) were significantly lower (P < 0.001) for HIV/AIDS participants with skin disease than those without skin disease. We found significant clustering of symptoms and signs: fever (P = 0.037), weight loss (P = 0.009), oral candidiasis (P = 0.038), pallor (P = 0.037) among HIV/AIDS subjects with skin diseases than those without. Low serum selenium concentration was significantly associated with primary skin disease of HIV/AIDS, such as pruritic papular eruption of AIDS (P = 0.003), xeroderma (P = 0.030), fluffy hair (P = 0.021), blue-black nail hyperpigmentation (P = 0.033) and secondary skin disease, such as oral candidiasis (P = 0.002). There was a significant association between low serum selenium concentration and increasing frequency of skin diseases (P = 0.002), but serum selenium was not significantly related to extents of distribution of skin diseases (P > 0.05).

Conclusion

serum selenium concentration was lower among HIV subjects with skin diseases than those without skin disease. Pruritic papular eruption, xeroderma, fluffy hair, blue-black nail hyper pigmentation, and oral candidiasis were significantly associated with low serum selenium concentration.

Sulfur-containing amino acids in 7TMRs: molecular gears for pharmacology and function

Seven-transmembrane receptors (7TMRs) mediate the majority of physiological responses to hormones and neurotransmitters in higher organisms. Tertiary structure stability and activation of these versatile membrane proteins require formation or disruption of complex networks of well-recognized interactions (such as H-bonds, ionic, or aromatic-aromatic) but also of other type of interactions which have been less studied. In this review, we compile evidence from crystal structure, biophysical, and site-directed mutagenesis data that indicate or support the importance of interactions involving Met and Cys in 7TMRs in terms of pharmacology and function. We show examples of Met/Cys-aromatic and Met-Met interactions participating in ligand binding, in tuning the orientation of functionally important aromatic residues during activation or even in modulating the type of signaling response. Collectively, data presented enlarge the repertoire of interactions governing 7TMR functioning.

Host factor transcriptional regulation contributes to preferential expression of HIV type 1 in IL-4-producing CD4 T cells

HIV type 1 (HIV-1) replicates preferentially in IL-4-producing CD4 T cells for unclear reasons. We show increased HIV-1 expression is irrespective of viral tropism for chemokine receptors as previously suggested, but rather transcription of the HIV-1 long terminal repeat (LTR) is increased in IL-4-producing CD4 T cells. Increased expression of HIV-1 message is also confirmed in IL-4-producing CD4 T cells from HIV-1-infected individuals ex vivo. In exploring a transcriptional mechanism, we identify a novel c-maf (required for IL-4 expression) transcription factor binding site just upstream of the dual NF-κB/NFAT binding sites in the proximal HIV-1 LTR. We demonstrate that c-maf binds this site in vivo and synergistically augments HIV-1 transcription in cooperation with NFAT2 and NF-κB p65, but not NFAT1 or NF-κB p50. Conversely, small interfering RNA inhibition of c-maf reduces HIV-1 transcription in IL-4-producing T cells. Thus, c-maf increases HIV-1 expression in IL-4-producing CD4 T cells by binding the proximal HIV-1 LTR and augmenting HIV-1 transcription in partnership with NFAT2 and NF-κB p65 specifically. This has important implications for selective targeting of transcription factors during HIV-1 infection because, over the course of HIV-1 progression/AIDS, IL-4-producing T cells frequently predominate and substantially contribute to disease pathology.

Increased levels of circulating cytokines with HIV-related immunosuppression

Cytokines may contribute to the severity of CD4 cell depletion with human immunodeficiency virus (HIV) infection, but quantitative relationships are not well defined. Serum and plasma from 181 HIV-infected individuals were tested with Millipore 30-plex Luminex cytokine assays. Within-individual correlations among cytokines were summarized by two-dimensional hierarchical cluster analysis. Associations with age, sex, race, CD4 count, and HIV viral load were determined with linear regression models. Tests for statistical significance were corrected for multiple comparisons, using a false discovery rate of 0.1. African-Americans had significantly higher levels than whites of six cytokines (IL-2, IL-5, IL-7, IL-15, fractalkine, and IFN-γ), and lower levels of MCP-1. Females had higher fractalkine levels than males. Age was not associated with levels of any cytokine. Six cytokines, including the T-helper (Th) type 1 cytokine IL-15, the Th2 cytokines IL-1ra and IL-10, the chemokines fractalkine and MCP-1, and the growth factor G-CSF were each inversely associated with CD4 count; no cytokine was directly associated with CD4 count. Fractalkine was directly associated with HIV viral load, adjusted for CD4 count. Cytokines clustered by primary function (e.g., Th1, Th2, proinflammatory, chemokines, or growth factors) whereas individuals clustered according to cytokine levels (generally high, intermediate, or low) had significantly different CD4 counts [medians (interquartile range) of 60 (17-162), 131 (62-321), and 155 (44-467), respectively; p<0.0001]. CD4 deficiency is associated with generalized increases in cytokines of various functions. Racial differences in cytokine response to HIV infection could contribute to disparities in disease progression.

Opiate drug use and the pathophysiology of neuroAIDS

Opiate abuse and HIV-1 have been described as interrelated epidemics, and even in the advent of combined anti-retroviral therapy, the additional abuse of opiates appears to result in greater neurologic and cognitive deficits. The central nervous system (CNS) is particularly vulnerable to interactive opiate-HIV-1 effects, in part because of the unique responses of microglia and astroglia. Although neurons are principally responsible for behavior and cognition, HIV-1 infection and replication in the brain is largely limited to microglia, while astroglia and perhaps glial progenitors can be latently infected. Thus, neuronal dysfunction and injury result from cellular and viral toxins originating from HIV-1 infected/exposed glia. Importantly, subsets of glial cells including oligodendrocytes, as well as neurons, express µ-opioid receptors and therefore can be direct targets for heroin and morphine (the major metabolite of heroin in the CNS), which preferentially activate µ-opioid receptors. This review highlights findings that neuroAIDS is a glially driven disease, and that opiate abuse may act at multiple glial-cell types to further compromise neuron function and survival. The ongoing, reactive cross-talk between opiate drug and HIV-1 co-exposed microglia and astroglia appears to exacerbate critical proinflammatory and excitotoxic events leading to neuron dysfunction, injury, and potentially death. Opiates enhance synaptodendritic damage and a loss of synaptic connectivity, which is viewed as the substrate of cognitive deficits. We especially emphasize that opioid signaling and interactions with HIV-1 are contextual, differing among cell types, and even within subsets of the same cell type. For example, astroglia even within a single brain region are heterogeneous in their expression of µ-, δ-, and κ-opioid receptors, as well as CXCR4 and CCR5, and Toll-like receptors. Thus, defining the distinct targets engaged by opiates in each cell type, and among brain regions, is critical to an understanding of how opiate abuse exacerbates neuroAIDS.

Pathological role of fractalkine/CX3CL1 in rheumatic diseases: a unique chemokine with multiple functions

Understanding rheumatic diseases from the perspective of chemokine biology has shaped and will continue to shape our approach for targeted drug design. Among different kinds of chemokines, fractalkine/CX3CL1 has been found to play an important role in inflammation, portraying unique functional, and structural characteristics. This review summarizes the emerging role of fractalkine/CX3CL1 from a functional and clinical perspective and provides evidence to validate it as a potential therapeutic target in rheumatic diseases such as rheumatoid arthritis, Sjögren's syndrome, systemic lupus erythematosus, scleroderma, as well as diseases related to vascular inflammation. From this, recent studies investigating potential therapeutic agents against fractalkine/CX3CL1's role in pathology have shown promise.

Fractalkine/CX3CL1 protects striatal neurons from synergistic morphine and HIV-1 Tat-induced dendritic losses and death

BACKGROUND

Fractalkine/CX3CL1 and its cognate receptor CX3CR1 are abundantly expressed in the CNS. Fractalkine is an unusual C-X3-C motif chemokine that is important in neuron-microglial communication, a co-receptor for HIV infection, and can be neuroprotective. To assess the effects of fractalkine on opiate-HIV interactive neurotoxicity, wild-type murine striatal neurons were co-cultured with mixed glia from the striata of wild-type or Cx3cr1 knockout mice ± HIV-1 Tat and/or morphine. Time-lapse digital images were continuously recorded at 20 min intervals for up to 72 h using computer-aided microscopy to track the same cells repeatedly.

RESULTS

Co-exposure to Tat and morphine caused synergistic increases in neuron death, dendritic pruning, and microglial motility as previously reported. Exogenous fractalkine prevented synergistic Tat and morphine-induced dendritic losses and neuron death even though the inflammatory mediator TNF-α remained significantly elevated. Antibody blockade of CX3CR1 mimicked the toxic effects of morphine plus Tat, but did not add to their toxicity; while fractalkine failed to protect wild-type neurons co-cultured with Cx3cr1-/--null glia against morphine and Tat toxicity. Exogenous fractalkine also normalized microglial motility, which is elevated by Tat and morphine co-exposure, presumably limiting microglial surveillance that may lead to toxic effects on neurons. Fractalkine immunofluorescence was expressed in neurons and to a lesser extent by other cell types, whereas CX3CR1 immunoreactivity or GFP fluorescence in cells cultured from the striatum of Cx3cr1-/- (Cx3cr1GFP/GFP) mice were associated with microglia. Immunoblotting shows that fractalkine levels were unchanged following Tat and/or morphine exposure and there was no increase in released fractalkine as determined by ELISA. By contrast, CX3CR1 protein levels were markedly downregulated.

CONCLUSIONS

The results suggest that deficits in fractalkine-CX3CR1 signaling contribute to the synergistic neurotoxic effects of opioids and Tat. Importantly, exogenous fractalkine can selectively protect neurons from the injurious effects of chronic opioid-HIV-1 Tat co-exposure, and this suggests a potential therapeutic course for neuroAIDS. Although the cellular mechanisms underlying neuroprotection are not certain, findings that exogenous fractalkine reduces microglial motility and fails to protect neurons co-cultured with Cx3cr1-/- mixed glia suggest that fractalkine may act by interfering with toxic microglial-neuron interactions.

Administration of exogenous fractalkine, a CX3C chemokine, is capable of modulating inflammatory response in cecal ligation and puncture-induced sepsis

Fractalkine (FTK) is a unique member of the CX3C chemokine family by acting through the CX3CR1 receptor. Membrane-bound FTK acts like an adhesion molecule, whereas soluble FTK (sFTK) acts as a classic chemokine ligand. Whether this chemokine plays a role in sepsis is still not clear. Using a mouse model of cecal ligation and puncture (CLP)-induced sepsis, we found that FTK levels were elevated in plasma 24 h after CLP. Reverse transcription-polymerase chain reaction results showed that FTK messenger RNA levels were upregulated, whereas CX3CR1 messenger RNA levels were downregulated in lungs after CLP procedure. To study the role of FTK in lung injury during sepsis, we injected exogenous sFTK into the mice before the CLP procedure. We found that plasma FTK levels were further elevated by sFTK. Mice that were injected with FTK had a lower myeloperoxidase activity in lungs compared with the CLP group. Furthermore, macrophage inflammatory protein 2, IL-1beta, and IL-6 levels in lungs were reduced after the injection of FTK. Treatment with sFTK also attenuated lung morphological changes in histological sections. To find out whether sFTK had an effect on leukocyte rolling and adherence, intravital microscope was used. Results showed that sFTK significantly attenuated leukocyte adhesion but had little effect on leukocyte rolling in mesenteric microcirculation. Taken together, our findings suggest that FTK may be a novel chemokine that modulates neutrophil infiltration and chemokine and cytokine production during sepsis.

Evolution of viruses and their impact on human life: HIV-1 subgroup M

The history of mankind over many millennia has been marred by many epidemics caused by viruses which infect the human respiratory system and alimentary tract. The current HIV-1/AIDS pandemic, however, is caused by one virus mutant, HIV-1M, which has evolved to infect humans through the genitals. The virus is able to use the innate system cells of the infected individual to inactivate the adaptive immune system, causing AIDS. The mechanisms used by HIV-1M to inhibit the immune system are presented. Understanding the viral mechanisms is leading to novel antiviral treatments and an approach to an HIV-1 vaccine.

MAIDS resistance-associated gene expression patterns in secondary lymphoid organs

Murine acquired immunodeficiency syndrome (MAIDS) is caused by exposure to murine leukemia virus and serves as a model to study human AIDS. In MAIDS-susceptible C57BL/6 mice, virus exposure leads to progressive immune deficiency, while resistant strains such as BALB/c recover from infection and develop protective immunity. The goal of this study was to identify early gene expression patterns that may be important in establishing this strain-specific differential response. Total RNA was isolated from spleens and pooled lymph nodes of both mouse strains at 3 and 7 days post virus infection. The complementary DNA generated from this RNA was hybridized to mouse oligonucleotide DNA microarrays using a strategy that controlled for inherent variability and highlighted only virus-induced changes. Fluorescent intensities were normalized and analyzed for statistically significant differential expression between strains across both time points and lymphoid organs. The majority of the resistance-associated genes was identified at day 3 post-infection and demonstrated the highest fold differences between strains, while more susceptibility-associated sequences were seen at 7 days post-infection. Among the most highly differentially expressed sequences seen at the earlier time point were genes related to protein metabolism, especially serine proteases. Differential patterns of chemokine-related genes were observed at the later time point. The overall pattern of expression suggests strain-specific differences in proteases and chemokines within secondary lymphoid organs shortly after infection influence the likelihood of disease progression.

Cytokine expression profiling of the myocardium reveals a role for CX3CL1 (fractalkine) in heart failure

Several lines of evidence suggest that inflammatory processes mediated by cytokines are involved in the pathogenesis of heart failure (HF). However, the regulation of cytokine expression and the role of cytokines during HF development are not well understood. To address this issue, we have examined alterations in gene expression during HF progression by microarray technology in non-infarcted left ventricular (LV) murine tissue at various time points after myocardial infarction (MI). The highest number of regulated genes was found five days after MI. In total, we identified 14 regulated genes encoding cytokines with no previous association to HF. The strongest up-regulation was found for the chemokine fractalkine (CX3CL1). In human failing hearts we detected a 3-fold increase in CX3CL1 protein production, and both cardiomyocytes and fibrous tissue revealed immunoreactivity for CX3CL1 and its specific receptor CX3CR1. We also found that the circulating level of CX3CL1 was increased in patients with chronic HF in accordance with disease severity (1.6-fold in NYHA II, 2.2-fold in NYHA III and 2.9-fold in NYHA IV). In vitro experiments demonstrated that CX3CL1 production could be induced by inflammatory cytokines known to be highly expressed in HF. CX3CL1 itself induced the expression of markers of cardiac hypertrophy and protein phosphatases in neonatal cardiomyocytes. Given the increased CX3CL1 production in both an experimental HF model and in patients with chronic HF as well as its direct effects on cardiomyocytes, we suggest a role for CX3CL1 and its receptor CX3CR1 in the pathogenesis of HF.