Targeted inhibition of CX3CL1 limits podocytes ferroptosis to ameliorate cisplatin-induced acute kidney injury.

BACKGROUND: It is widely acknowledged that cisplatin-induced nephrotoxicity hinders its efficacy during clinical therapy. Effective pharmaceutical interventions for cisplatin-induced acute kidney injury (Cis-AKI) are currently lacking. Prior studies have implicated the chemokine CX3CL1 in the development of lipopolysaccharide-induced AKI; however, its specific role in Cis-AKI remains uncertain. This research aimed to comprehensively characterize the therapeutic impact and mechanism of CX3CL1 inhibition on Cis-AKI. METHODS: This study employed an in vivo Cis-AKI mouse model and in vitro cisplatin-treated podocytes. Kidney pathological changes were assessed using hematoxylin-eosin (HE) and Periodic-Schiff (PAS) staining. Transcriptome changes in mouse kidney tissue post-cisplatin treatment were analyzed through RNA sequencing (RNA-seq) datasets. Evaluation parameters included the expression of inflammatory markers, intracellular free iron levels, ferroptosis-related proteins-solute carrier family 7 member 11 (SLC7A11/XCT) and glutathione peroxidase 4 (GPX4)-as well as lipid peroxidation markers and mitochondrial function proteins. Mitochondrial morphological changes were visualized through transmission electron microscopy. The impact of CX3CL1 on the glucose-regulated protein 78/eukaryotic translation initiation factor 2A/CCAAT enhancer binding protein-homologous protein (GRP78/eIF2α/CHOP) and hypoxia-inducible factor 1-alpha/heme oxygenase-1 (HIF1A/HO-1) pathways in Cis-AKI was assessed via Western Blot and Immunofluorescence experiments, both in vivo and in vitro. RESULTS: Kidney CX3CL1 levels were elevated following cisplatin injection in wild-type (WT) mice. Cisplatin-treated CX3CL1-Knockout mice exhibited reduced renal histological changes, lowered blood creatinine (Cre) and blood urea nitrogen (BUN) levels, and decreased expression of inflammatory mediators compared to cisplatin-treated WT mice. RNA-seq analysis revealed the modulation of markers associated with oxidative stress and lipid metabolism related to ferroptosis in the kidneys of mice with Cis-AKI. Both the in vivo Cis-AKI mouse model and in vitro cisplatin-treated podocytes demonstrated that CX3CL1 inhibition could mitigate ferroptosis. This effect was characterized by alleviated intracellular iron overload, malondialdehyde (MDA) content, and reactive oxygen species (ROS) production, alongside increased glutathione/glutathione disulfide ratio, superoxide dismutase (SOD), XCT, and GPX4 activity. CX3CL1 inhibition also ameliorated mitochondrial dysfunction and upregulated expression of mitochondrial biogenesis proteins-uncoupling protein (UCP), mitofusin 2 (Mfn2), and peroxisome proliferators-activated receptor γ coactivator l-alpha (PGC1α)-both in vivo and in vitro. Furthermore, CX3CL1 inhibition attenuated cisplatin-induced endoplasmic reticulum (ER) stress in podocytes. Notably, CX3CL1 inhibition reduced cisplatin-induced expression of HIF-1α and HO-1 in vivo and in vitro. CONCLUSION: Our findings suggest that CX3CL1 inhibition exerts therapeutic effects against Cis-AKI by suppressing podocyte ferroptosis.

Bujing Yishi tablets alleviate photoreceptor cells death via the P2X7R/CX3CL1/CX3CR1 pathway in Retinitis Pigmentosa rats.

BACKGROUND: Retinitis pigmentosa (RP) refers to a group of progressive photoreceptor degenerative diseases. The activation of microglia has been reported to play an important role in the photoreceptor degeneration in RP retinal. Bujing Yishi tablets (BJYS), a Chinese herbal medicine, has been used to treat retinal diseases in China with desirable effect in improving visual function. However, the mechanisms underlying the efficacy of BJYS treatment in RP are not yet fully understood. PURPOSE: Based on the preliminary experiments, this study aimed to investigate the therapeutic mechanism involved in treating N-Methyl-N-Nitrosourea (MNU)-induced retinal degeneration of RP with BJYS. METHODS: To explore the efficacy of BJYS, a rat experimental RP model was established through intraperitoneal injection of MNU (50 mg/kg). Two experiment was carried out. After the treatment, we conducted H&E, TUNEL, retinal cytokine levels and IBA-1 expression in microglia to confirm the impact on RP model. The specific mechanism of action of BJYS tablet was assessed by western blot, real-time polymerase chain reaction (RT-PCR), and immunofluorescence to determine the mRNA and protein expression levels involved in clarifying the effectiveness of BJYS exerted through P2X7R/CX3CL1/CX3CR1 pathway. RESULTS: Significant alleviation of retinal morphological structure and photoreceptor degeneration by BJYS treatment was observed in the retinal of MNU-induced RP rats, BJYS prevented the reduction of ONL thickness and decreased the level of apoptotic cells in ONL. It also inhibited microglia overactivation and reduced retinal levels of IL-1ß, IL-6, TNF-α. In addition, BJYS decreased the protein expression and mRNA expression of P2X7, CX3CL1 and CX3CR1 and reduced the phosphorylation of p38 MAPK. CONCLUSION: In summary, this study suggested that BJYS treatment could alleviate photoreceptors degeneration of RP by inhibiting microglia overactivation and inflammation through the P2X7R/CX3CL1/CX3CR1 pathway. These effects suggest that BJYS tablets may serve as a promising oral therapeutic agent for RP.

Resveratrol improves myocardial ischemia and ischemic heart failure in mice by antagonizing the detrimental effects of fractalkine*.

OBJECTIVES: To test the hypothesis that resveratrol would improve cardiac remodeling by inhibiting the detrimental effects of fractalkine. We previously reported that fractalkine exacerbates heart failure. Furthermore, this study sought to determine whether resveratrol targets fractalkine to improve myocardial ischemia and cardiac remodeling. DESIGN: Randomized and controlled laboratory investigation. SETTING: Research laboratory. SUBJECTS: Neonatal rat cardiac cells and C57BL/6 mice. INTERVENTIONS: Cardiac cells were treated with recombinant mouse soluble fractalkine for 24 hrs or pretreated with 25 µM resveratrol. Cardiomyocytes were exposed to anoxia/reoxygenation, H2O2, or pretreatment with resveratrol. Ex vivo murine hearts were perfusioned with soluble fractalkine or pretreated with resveratrol after global ischemia. Mice were subjected to the left coronary artery ligation to induce myocardial infarction and randomized to treatment with resveratrol or vehicle alone for 42 days. MEASUREMENTS AND MAIN RESULTS: In a murine myocardial infarction model, we found that resveratrol increased survival and delayed the progression of cardiac remodeling evaluated by serial echocardiography. At 6 wks, the heart weight/body weight ratio, lung weight/body weight ratio, and old infarct size were significantly smaller in resveratrol-treated mice than in untreated myocardial infarction mice. In cultures of neonatal rat cells, exposure to soluble fractalkine increased the atrial natriuretic peptide expression by cardiomyocytes, matrix metalloproteinase-9 and procollagen expression by fibroblasts, and intercellular adhesion molecule-1 expression by microvascular endothelial cells, while it decreased autophagy in cardiomyocytes. All these effects were blocked by coculture with resveratrol. The methyl thiazolyl tetrazolium assay showed that soluble fractalkine reduced the viability of cultured cardiomyocytes during exposure to anoxia/reoxygenation or H2O2, while pretreatment with resveratrol blocked this effect. Perfusion of ex vivo murine hearts with soluble fractalkine after global ischemia led to an increase of infarct size, which was prevented by pretreatment with resveratrol. CONCLUSION: Resveratrol alleviates the deleterious effects of fractalkine on myocardial ischemia and thus reduces subsequent cardiac remodeling.

New evidences for fractalkine/CX3CL1 involved in substantia nigral microglial activation and behavioral changes in a rat model of Parkinson's disease.

Activated microglia are instrumental to neurodegeneration in Parkinson's disease (PD). Fractalkine, as an exclusive ligand for CX3CR1 expressed on microglia, has recently been reported to be released out by neurons, and induce microglial activation as a neuron-to-glia signal in the spinal cord. However, the role of fractalkine-induced microglial activation in PD remains unknown. In our study, we injected 1-methyl-4-phenylpyridinium (MPP(+)) into unilateral substantia nigra (SN) which induced ipsilateral endogenous fractalkine expression on neuron and observe the increase of CX3CR1 expression in response to MPP(+) by Western blotting analysis. Moreover, pre-administration of anti-CX3CR1 neutralizing antibody which potentially blocked microglial activation can promote rotation behaviors. To further investigate the role of fractalkine in PD, we injected exogenous fractalkine in unilateral SN, and observed microglial activation, dopaminergic cell depletion, and motor dysfunction. All these effects can be totally abolished by cerebroventricular administration of anti-CX3CR1. Intracerebroventricular administration of minocycline, a selective microglia inhibitor, can prevent fractalkine-induced rotation behaviors, and inhibit dopaminergic neurons from degeneration in the way of dose-dependent. Our studies demonstrate that fractalkine-induced microglial activation plays an important role in the development of PD, and provide an evidence of fractalkine and CX3CR1 as new therapeutic targets for PD treatment.

Altered fractalkine cleavage potentially promotes local inflammation in NOD salivary gland.

INTRODUCTION: In the nonobese diabetic (NOD) mouse model of Sjögren's syndrome, lymphocytic infiltration is preceded by an accumulation of dendritic cells in the submandibular glands (SMGs). NOD mice also exhibit an increased frequency of mature, fractalkine receptor (CX3C chemokine receptor [CX3CR]1) expressing monocytes, which are considered to be precursors for tissue dendritic cells. To unravel further the role played by fractalkine-CX3CR1 interactions in the salivary gland inflammation, we studied the expression of fractalkine in NOD SMGs. METHODS: We studied protein expression using Western blot analysis of whole tissue lysates. Protease activity was measured in salivary gland tissue lysates using fluorimetric substrates. Digestive capacity of enzymes was determined by in vitro incubation of recombinant enzyme and fractalkine, followed by protein staining and Western blot. RESULTS: Fractalkine was detected in salivary glands of both NOD and control mice at all ages. Western blot analysis showed fractalkine cleavage with increasing age, which was more pronounced in NOD mice. This cleavage resulted in a decrease in the 31 kDa form of the protein, and the generation of an approximately 19 kDa band. Furthermore, in NOD animals older than 15 weeks, we noted the presence of a unique approximately 17 kDa fragment. This cleavage was organ specific, because it did not occur in brain or pancreas. Increased gelatinase and alpha-secretase activity were detected in NOD SMG and contributed to cleavage of the 31 kDa protein. Because aberrant cleavage products may induce autoimmunity, we studied the presence of autoantibodies against fractalkine. Indeed, NOD mice exhibited significantly more antibodies against fractalkine than did control animals. CONCLUSION: These data indicate that aberrant proteolytic activity in the NOD SMG results in increased fractalkine cleavage and generation of a unique fractalkine fragment. This specific cleavage may contribute to autoimmunity.