CX3CL1 Action on Microglia Protects from Diet-Induced Obesity by Restoring POMC Neuronal Excitability and Melanocortin System Activity Impaired by High-Fat Diet Feeding.

Both hypothalamic microglial inflammation and melanocortin pathway dysfunction contribute to diet-induced obesity (DIO) pathogenesis. Previous studies involving models of altered microglial signaling demonstrate altered DIO susceptibility with corresponding POMC neuron cytological changes, suggesting a link between microglia and the melanocortin system. We addressed this hypothesis using the specific microglial silencing molecule, CX3CL1 (fractalkine), to determine whether reducing hypothalamic microglial activation can restore POMC/melanocortin signaling to protect against DIO. We performed metabolic analyses in high fat diet (HFD)-fed mice with targeted viral overexpression of CX3CL1 in the hypothalamus. Electrophysiologic recording in hypothalamic slices from POMC-MAPT-GFP mice was used to determine the effects of HFD feeding and microglial silencing via minocycline or CX3CL1 on GFP-labeled POMC neurons. Finally, mice with hypothalamic overexpression of CX3CL1 received central treatment with the melanocortin receptor antagonist SHU9119 to determine whether melanocortin signaling is required for the metabolic benefits of CX3CL1. Hypothalamic overexpression of CX3CL1 increased leptin sensitivity and POMC gene expression, while reducing weight gain in animals fed an HFD. In electrophysiological recordings from hypothalamic slice preparations, HFD feeding was associated with reduced POMC neuron excitability and increased amplitude of inhibitory postsynaptic currents. Microglial silencing using minocycline or CX3CL1 treatment reversed these HFD-induced changes in POMC neuron electrophysiologic properties. Correspondingly, blockade of melanocortin receptor signaling in vivo prevented both the acute and chronic reduction in food intake and body weight mediated by CX3CL1. Our results show that suppressing microglial activation during HFD feeding reduces DIO susceptibility via a mechanism involving increased POMC neuron excitability and melanocortin signaling.

Tetrahydroxy stilbene glycoside regulates TGF-ß/fractalkine/CX3CR1 based on network pharmacology in APP/PS1 mouse model.

Alzheimer's disease (AD) is a serious, progressive neurodegenerative disease that involves irreversible neuronal death. Tetrahydroxy stilbene glycoside (TSG) is an active compound extracted from P. multiflorum, a traditional Chinese herbal medicine, but its role in neuroprotection is unclear. Herein, we aimed to validate the effects of TSG on APP/PS1 model mice and the underlying mechanism. RNA-seq was performed to identify differentially expressed genes in APP/PS1 mouse, with PCR and immunohistochemistry used for validation. Experiments were performed after bioinformatic analysis for verification. Neuronal damage was observed by H&E staining. Key proteins involved in the pathway such as CX3CR1, Iba1 and TGF-ß were examined by immunohistochemical analysis. The KEGG analysis suggested that these genes might act by multiple pathways to build the pharmacological network of TSG in AD progression. These data provide the credible evidence that TSG improved neuronal damage and regulated neuroprotective mechanisms. Together, our work has detailed the whole and major genes in APP/PS1 model mouse regulated by TSG, and highlighted the anti-inflammatory function of TSG in mediating CX3CR1 and TGF-ß as the TGF-ß/fractalkine/CX3XR1 signaling pathway, especially in microglia. Moreover, TSG has potential value in synaptic transmission and neurotrophic action on neurodegenerative diseases. In summary, TSG is a promising candidate for preventing and treating the progression of AD.

Jinfukang inhibits lung cancer metastasis by upregulating CX3CL1 to recruit NK cells to kill CTCs.

ETHNOPHARMACOLOGICAL RELEVANCE: Circulating tumor cells (CTCs) play an important role in tumor metastasis and may be a target for metastasis prevention. The traditional Chinese medicine Jinfukang functions to improve immunity, prevent metastasis, and prolong lung cancer patient survival periods. Yet, whether Jinfukang prevents metastasis by regulating immune cells to clearance CTCs is still unknown. AIM OF THE STUDY: To explore the anti-metastasis mechanism of Jinfukang from the perspective of regulating NK cells to clear CTCs. MATERIALS AND METHODS: CTC-TJH-01 cell was treated with Jinfukang. Cytokine chip was used to detect cytokines in cell culture supernatant. Lymphocyte recruitment assay was detected by Transwell and flow cytometry. Protein expression was analysis by Western blot. LDH kit was used to detect cytotoxicity. NOD-SCID mice used for tail vein injection to study lung metastasis. RESULTS: Jinfukang could promote the expression and secretion of the chemokine CX3CL1 by CTCs. In addition, Jinfukang could promote the recruitment of natural killer (NK) cells by CTCs and significantly increase the cytotoxic effect of NK cells on CTCs. Moreover, Jinfukang could upregulate the expression of FasL and promote the secretion of TNF-α by NK cells and that NK cells could induce the apoptosis of CTCs through the Fas/FasL signaling pathway. Finally, we confirmed that Jinfukang could promote NK cells to kill CTCs and then inhibit lung cancer metastasis in vivo. The above effects of Jinfukang could be partially reversed by an anti-CX3CL1 mAb. CONCLUSIONS: These results suggest that Jinfukang may prevent lung cancer metastasis by enhancing the clearance of CTCs in the peripheral blood by NK cells, providing evidence for the anti-metastasis effect of Jinfukang.

Comparative Analysis of the Occurrence and Role of CX3CL1 (Fractalkine) and Its Receptor CX3CR1 in Hemophilic Arthropathy and Osteoarthritis.

OBJECTIVE: Hemophilic arthropathy is characterized by recurrent bleeding episodes in patients with hemophilia leading to irreversible joint degeneration. The involvement of CX3CL1 (fractalkine) and its receptor CX3CR1 was observed in the pathogenesis of numerous arthritis-associated diseases. Taking this into account, we have presented a study investigating the role of the CX3CL1/CX3XR1 axis in the course of hemophilic arthropathy, including the CX3CL1-dependent expression of CD56+, CD68+, and CD31+ cells along with evaluation of articular cartilage and synovial membrane morphology. METHODS: The study was carried out using cases (n = 20) of end-stage hemophilic arthropathy with a severe type of hemophilia A and control cases (n = 20) diagnosed with osteoarthritis. The biofluids including blood serum and synovial fluid were obtained intraoperatively for the evaluation of CX3CL1 using the ELISA test. Tissue specimens including articular cartilage and synovial membrane were similarly collected during surgery and stained immunohistologically using selected antibodies including anti-CX3CR1, anti-CD56, anti-CD68, and anti-CD31. Additionally, the analysis included the assessment of articular cartilage, synovial membrane, and blood vessel morphology. RESULTS: In our study, we have documented increased average concentration of CX3CL1 in the blood serum of the study group (7.16 ± 0.53 ng/ml) compared to the control group (5.85 ± 0.70 ng/ml) without statistically significant difference in synovial fluid concentration at the same time. We have observed an increased macrophage presence with more marked proliferation and fibrosis of the synovial membrane in the study group. Remaining results such as expression of CX3CR1 presence of NK cells and larger surface area of blood vessels within the synovial membrane were noted also without statistical significance. CONCLUSIONS: This study has demonstrated collective CX3CL1/CX3CR1 axis involvement in hemophilic arthropathy pathogenesis introducing new interesting diagnostics and a therapeutic target.

Effect of curcumin supplementation on serum expression of select cytokines and chemokines in a female rat model of nonalcoholic steatohepatitis.

OBJECTIVE: We recently reported that curcumin supplementation in a metabolically (i.e., Western diet [WD]) and chemically (i.e., CCl4) induced female rat model of non-alcoholic steatohepatitis (NASH) was associated with lower liver pathology scores and molecular markers of inflammation. This occurred when curcumin was given during induction of disease (preventative arm; 8-week WD with or without curcumin [8WD + C vs. 8WD]) as well as when given after disease development (treatment arm; 12-week WD with or without curcumin during weeks 9-12 [12WD + C vs. 12WD]). Herein, we sought to extend our findings from that study by determining the effects of curcumin supplementation on cytokine/chemokine expression in serum collected from these same rats. RESULTS: 24 cytokines/chemokines were assayed. IL-2 (+ 80%) and IL-13 (+ 83%) were greater with curcumin supplementation in the prevention arm. IL-2 (+ 192%), IL-13 (+ 87%), IL-17A (+ 81%) and fractalkine (+ 121%) were higher while RANTES was lower (- 22%) with curcumin supplementation in the treatment arm (p < 0.05 for all). RANTES concentrations also correlated significantly with hepatic pathology scores of inflammation (r = 0.417, p = 0.008). Select serum cytokines/chemokines were affected with curcumin supplementation in this female rat model of NASH. Moreover, curcumin's effect(s) on RANTES and its association with liver disease pathogenesis and progression may warrant further investigation.

Naringin Protects Against High Glucose-Induced Human Endothelial Cell Injury Via Antioxidation and CX3CL1 Downregulation.

BACKGROUND/AIMS: The induction of endothelial injury by hyperglycemia in diabetes has been widely accepted. Naringin is a bio-flavonoid. Some studies showed that naringin alleviates diabetic complications, but the exact mechanisms by which naringin improves diabetic anomalies are not yet fully understood. The aim of this research was to study the protective effect of naringin on high glucose-induced injury of human umbilical vein endothelial cells (HUVECs). METHODS: HUVECs were cultured with or without high glucose in the absence or presence of naringin for 5 days. The expression of CX3CL1 was determined by quantitative real-time RT-PCR (qPCR) and western blot. The cellular bioenergetic analysis oxygen consumption rate (OCR) was measured with a Seahorse Bioscience XF analyzer. RESULTS: The production of reactive oxygen species (ROS), the expression of CX3CL1 and the level of AKT phosphorylation were increased in HUVECs cultured with high glucose compared with controls. However, naringin rescued these increases in ROS production, CX3CL1 expression and AKT phosphorylation. Nitric oxide (NO) production and OCR were lower in the high glucose group, and naringin restored the changes induced by high glucose. Molecular docking results suggested that Naringin might interact with the CX3CL1 protein. CONCLUSION: Naringin protects HUVECs from high-glucose-induced damage through its antioxidant properties by downregulating CX3CL1 and by improving mitochondrial function.

(-)-Epigallocatechin-3-Gallate Antihyperalgesic Effect Associates With Reduced CX3CL1 Chemokine Expression in Spinal Cord.

(-)-Epigallocatechin-3-gallate (EGCG) is a major polyphenol in green tea with beneficial effects on the neuropathic pain alleviation in animal models. Because chemokine fractalkine (CX3CL1) has been suggested as an important signal during neuropathic pain development, this study aimed to investigate whether CX3CL1 expression may be modulated by EGCG treatment reducing hyperalgesia in chronic constriction injured mice. To this end, Balb/c mice were subjected to a chronic constriction injury of sciatic nerve (CCI) and treated with EGCG or vehicle once a day during the first week following surgery. Thermal hyperalgesia was tested at 7 and 14 days post-surgery, and the expression of CX3CL1 and its mRNA were analyzed in spinal cord at the end of the experimental period. Results revealed that EGCG treatment significantly reduced thermal hyperalgesia in CCI-injured mice at short time, and this antihyperalgesic effect was associated with a down-regulation of CX3CL1 protein expression in the spinal cord. On the other hand, EGCG treatment did not affect the CX3CL1 transcription. Overall, our results suggest a new role of EGCG-treatment in an experimental model of neuropathic pain as a mediator of nociceptive signaling cross talk between neurons and glial cells in the dorsal horn of the spinal cord. Copyright © 2016 John Wiley & Sons, Ltd.

The impact of chronic blackberry intake on the neuroinflammatory status of rats fed a standard or high-fat diet.

Neuroinflammation has been suggested as a central mediator of central nervous system dysfunction, including in dementia and neurodegenerative disease. Flavonoids have emerged as promising candidates for the prevention of neurodegenerative diseases and are thought to be capable of antiinflammatory effects in the brain. In the present study, the impact of a chronic intake of an anthocyanin extract from blackberry (BE) on brain inflammatory status in the presence or absence of a high-fat diet was investigated. Following intake of the dietary regimes for 17 weeks neuroinflammatory status in Wistar rat cortex, hippocampus and plasma were assessed using cytokine antibody arrays. In the cortex, intake of the high-fat diet resulted in an increase of at least 4-fold, in expression of the cytokine-induced neutrophil chemoattractant CINC-3, the ciliary neurotrophic factor CNTF, the platelet-derived growth factor PDGF-AA, IL-10, the tissue inhibitor of metalloproteinase TIMP-1 and the receptor for advanced glycation end products RAGE. BE intake partially decreased the expression of these mediators in the high-fat challenged brain. In standard-fed animals, BE intake significantly increased cortical levels of fractalkine, PDGF-AA, activin, the vascular endothelial growth factor VEGF and agrin expression, suggesting effects as neuronal growth and synaptic connection modulators. In hippocampus, BE modulates fractalkine and the thymus chemokine TCK-1 expression independently of diet intake and, only in standard diet, increased PDGF-AA. Exploring effects of anthocyanins on fractalkine transcription using the neuronal cell line SH-SY5Y suggested that other cell types may be involved in this effect. This is the first evidence, in in vivo model, that blackberry extract intake may be capable of preventing the detrimental effects of neuroinflammation in a high-fat challenged brain. Also, fractalkine and TCK-1 expression may be specific targets of anthocyanins and their metabolites on neuroinflammation.

Fractalkine (CX3CL1) is involved in the early activation of hypothalamic inflammation in experimental obesity.

Hypothalamic inflammation is a common feature of experimental obesity. Dietary fats are important triggers of this process, inducing the activation of toll-like receptor-4 (TLR4) signaling and endoplasmic reticulum stress. Microglia cells, which are the cellular components of the innate immune system in the brain, are expected to play a role in the early activation of diet-induced hypothalamic inflammation. Here, we use bone marrow transplants to generate mice chimeras that express a functional TLR4 in the entire body except in bone marrow-derived cells or only in bone marrow-derived cells. We show that a functional TLR4 in bone marrow-derived cells is required for the complete expression of the diet-induced obese phenotype and for the perpetuation of inflammation in the hypothalamus. In an obesity-prone mouse strain, the chemokine CX3CL1 (fractalkine) is rapidly induced in the neurons of the hypothalamus after the introduction of a high-fat diet. The inhibition of hypothalamic fractalkine reduces diet-induced hypothalamic inflammation and the recruitment of bone marrow-derived monocytic cells to the hypothalamus; in addition, this inhibition reduces obesity and protects against diet-induced glucose intolerance. Thus, fractalkine is an important player in the early induction of diet-induced hypothalamic inflammation, and its inhibition impairs the induction of the obese and glucose intolerance phenotypes.

The cardiovascular actions of fractalkine/CX3CL1 in the hypothalamic paraventricular nucleus are attenuated in rats with heart failure.

The paraventricular nucleus (PVN) of the hypothalamus plays an important role in the regulation of sympathetic nerve activity, which is significantly elevated in chronic heart failure (CHF). Fractalkine (FKN) and its cognate receptor, CX3CR1, are constitutively expressed in the central nervous system, but their role and physiological significance are not well known. The aims of the present study were to determine whether FKN plays a cardiovascular role within the PVN and to investigate how the actions of FKN might be altered in CHF. We show that both FKN and CX3CR1 are expressed on neurons in the PVN of rats, suggesting that they may have a physiological function in this brain nucleus. Unilateral microinjection of FKN directly into the PVN of anaesthetized rats elicited a significant dose-related decrease in blood pressure (1.0 nmol, -5 ± 3 mmHg; 2.5 nmol, -13 ± 2 mmHg; 5.0 nmol, -22 ± 3 mmHg; and 7.5 nmol, -32 ± 3 mmHg) and a concomitant increase in heart rate (1.0 nmol, 6 ± 3 beats min(-1); 2.5 nmol, 11 ± 3 beats min(-1); 5 nmol, 18 ± 4 beats min(-1); and 7.5 nmol, 27 ± 5 beats min(-1)) compared with control saline microinjections. In order to determine whether FKN signalling is altered in rats with CHF, we first performed quantitative RT-PCR and Western blot analysis and followed these experiments with functional studies in rats with CHF and sham-operated control rats. We found a significant increase in CX3CR1 mRNA and protein expression, as determined by quantitative RT-PCR and Western blot analysis, respectively, in the PVN of rats with CHF compared with sham-operated control rats. We also found that the blood pressure effects of FKN (2.5 nmol in 50 nl) were significantly attenuated in rats with CHF (change in mean arterial pressure, -6 ± 3 mmHg) compared with sham-operated control rats (change in mean arterial pressure, -16 ± 6 mmHg). These data suggest that FKN and its receptor, CX3CR1, modulate cardiovascular function at the level of the PVN and that the actions of FKN within this nucleus are altered in heart failure.

Total flavonoids of Bidens bipinnata L. a traditional Chinese medicine inhibits the production of inflammatory cytokines of vessel endothelial cells stimulated by sera from Henoch-Schönlein purpura patients.

OBJECTIVES: Bidens bipinnata L. is well known as a traditional antipyretic, anti-inflammatory and anti-rheumatic medicine in China. This study was designed to evaluate the role of total extracted flavonoids from B. bipinnata (TFB) in inhibiting the production of inflammatory cytokines. METHODS: Human umbilical vein endothelial cells (HUVEC) were used to examine the effect of TFB on the production of inflammatory cytokines. The supernatant interleukin (IL)-8, tumour necrosis factor (TNF)-α and nitric oxide (NO) levels of HUVEC were measured with ELISA methods. Nuclear factor-kappaB (NF-κB) and fractalkine expression was evaluated by RT-PCR and Western blot methods, respectively. KEY FINDINGS: We observed that IL-8, TNF-α and NO release of HUVEC incubated with sera from active Henoch-Schönlein purpura (HSP) was significantly increased. TFB intervention may significantly suppressed the supernatant IL-8, TNF-α and NO levels of HUVEC. Similarly, TFB obviously suppressed the NF-κB and fractalkine mRNA and protein expression. CONCLUSIONS: These results suggested that TFB may be useful for improving microvascular inflammation in HSP patients.

[Variabilities of the impacts of cold pathogen and cold-dampness pathogen on fractalkine mRNA expression in lung tissues of rats].

OBJECTIVE: To study the variabilities of the effects of cold pathogen and cold-dampness pathogen on the fractalkine (FKN) mRNA expression in lung tissues of rats. METHODS: Twenty-four Wistar rats of SPF grade were randomly divided into 3 groups: normal temperature group, cold pathogen group and cold-dampness pathogen group. There were 8 rats in each group. Rats in normal temperature group were bred at (20+/-2)degrees centigrade and under normal humidity (50%-55%) for 2 h. Rats in cold pathogen group were bred at -10 degrees centigrade and under normal humidity (50%-55%) for 2 h, and the rats in cold-dampness pathogen group were bred at -10 degrees centigrade and under high humidity (90%-100%) for 2 h. Rats in the three groups were bred in thermostats under the corresponding conditions on the first day of experiment, and then the rats in different groups were all bred at normal temperature. Lung specimens in 3 groups were gathered four days later. The behavior and the pathological changes in the lung tissues of rats in different groups were observed. The content of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) in lung homogenate was detected by radioimmunoassay (RIA) method. Expression of FKN mRNA in lung homogenate was detected by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: The lung tissues of rats in both cold pathogen group and cold-dampness pathogen group had various degrees of pathological changes. Compared with normal temperature group, the content of IL-6 and TNF-alpha was increased obviously in lung homogenate of rats in both cold pathogen group and cold-dampness pathogen group (P<0.01). The content of IL-6 and TNF-alpha in lung homogenate of rats in cold-dampness pathogen group was obviously higher than that in cold pathogen group (P<0.01). The RT-PCR results showed a low expression of FKN mRNA in lung tissues of rats in normal temperature group. If the injured lung tissues were aggravated, the expression of FKN mRNA in the lung tissues was elevated. Compared with normal temperature group, FKN mRNA expressions in both cold pathogen group and cold-dampness pathogen group were increased obviously (P<0.01). FKN mRNA expression in lung homogenate of rats in cold-dampness pathogen group was also obviously higher than that in cold pathogen group (P<0.01). CONCLUSION: Cold pathogen can induce lung injury and up-regulate the FKN mRNA expression in lung tissue. Dampness pathogen can up-regulate the FKN mRNA expression through aggravating the injury of lung tissues caused by cold pathogen. FKN has a close relationship with the lung injury.

[Effect of Shenqi Fuzheng injection on fractalkine expression in lung tissue of rats with lipopolysaccharide-induced acute lung injury].

OBJECTIVE: To observe dynamically the Fractalkine (FKN) expression in lung tissue of rats with lipopolysaccharide (LPS)-induced acute lung injury (ALI) and the effect of Shenqi Fuzheng Injection (SFI) on it. METHODS: Rat model of ALI was established by intravenous injection of 4 mg/kg of LPS. Forty-two Wistar rats were randomly divided into 7 groups, the normal group, the model group and the SFI group, the latter two were separated respectively into three time phases (the 1 h, 2 h and 4 h after modeling ) groups, 6 rats in each group. Pathological changes and wet/dry weight ratio (W/D) of lung were observed, serum TNF-alpha and FKN mRNA expression in the lung tissue were examined by ELISA and RT-PCR respectively. RESULTS: Severe pathological changes of lung presented in the model groups of all three time phases with a higher W/D ratio, as well as increased serum TNF-alpha level and FKN mRNA expression in lung tissue. The peak of abnormality of serum TNF-alpha level and FKN mRNA expression was shown in the 2 h time phase group. All the above-mentioned abnormal changes were alleviated after treatment in the SFI group (P<0.05). In addition, the level of FKN mRNA expression was found to be positively correlated to the serum TNF-alpha concentration. CONCLUSION: SFI treatment in early stage could relieve the pathological changes and edema in lung tissue, decrease serum TNF-alpha and down-regulate FKN mRNA expression, playing a protective role in LPS-induced ALI rats.