Blockage of C-X-C Motif Chemokine Receptor 2 (CXCR2) Suppressed Uric Acid (UA)-Induced Cardiac Remodeling

Hyperuricemia-induced cardiac remodeling is at least in part via pressure-dependent mechanisms, yet the pressure-independent mechanisms are not well understood. C-X-C motif chemokine ligand 1 (CXCL1) was upregulated in renal tubules from mice subjected to uric acid (UA)-induced nephropathy. Given that CXCL1 is a master chemokine responsible for the recruitment of macrophage by binding with its receptor C-X-C motif chemokine receptor 2 (CXCR2), we thus hypothesized that UA-induced cardiac injury is via promoting the recruitment of CXCR2 + macrophages into the heart, which enhances cardiac inflammation. Within a mouse model of UA injection (500 mg/kg, twice/day, 14 days), we measured the level of cardiac CXCL1. We also tested the efficacy of the CXCR2 antagonist on UA-induced cardiac inflammation and remodeling. We found a high plasma level of UA-induced upregulation of CXCL1 in heart tissues. CXCR2 antagonist relieved UA-induced cardiac hypertrophy and suppressed cardiac inflammation and fibrosis. The silencing of CXCR2 in human monocytes abolished the migration of UA-induced monocyte. Thus, the interventions against CXCL1/CXCR2 may be effective for the prevention and treatment of UA-induced cardiac hypertrophy and inflammatory responses.

CXCL2-CXCR2 axis mediates αV integrin-dependent peritoneal metastasis of colon cancer cells

Peritoneal metastasis is an insidious aspect of colorectal cancer. The aim of the present study was to define mechanisms regulating colon cancer cell adhesion and spread to peritoneal wounds after abdominal surgery. Mice was laparotomized and injected intraperitoneally with CT-26 colon carcinoma cells and metastatic noduli in the peritoneal cavity was quantified after treatment with a CXCR2 antagonist or integrin-αV-antibody. CT-26 cells expressed cell surface chemokine receptors CXCR2, CXCR3, CXCR4 and CXCR5. Stimulation with the CXCR2 ligand, CXCL2, dose-dependently increased proliferation and migration of CT-26 cells in vitro. The CXCR2 antagonist, SB225002, dose-dependently decreased CXCL2-induced proliferation and migration of colon cancer cells in vitro. Intraperitoneal administration of CT-26 colon cancer cells resulted in wide-spread growth of metastatic nodules at the peritoneal surface of laparotomized animals. Laparotomy increased gene expression of CXCL2 at the incisional line. Pretreatment with CXCR2 antagonist reduced metastatic nodules by 70%. Moreover, stimulation with CXCL2 increased CT-26 cell adhesion to extracellular matrix (ECM) proteins in a CXCR2-dependent manner. CT-26 cells expressed the αV, β1 and β3 integrin subunits and immunoneutralization of αV abolished CXCL2-triggered adhesion of CT-26 to vitronectin, fibronectin and fibrinogen. Finally, inhibition of the αV integrin significantly attenuated the number of carcinomatosis nodules by 69% in laparotomized mice. These results were validated by use of the human colon cancer cell line HT-29 in vitro. Our data show that colon cancer cell adhesion and growth on peritoneal wound sites is mediated by a CXCL2-CXCR2 signaling axis and αV integrin-dependent adhesion to ECM proteins.

CXCR2 As a Novel Target for Overcoming Resistance to Tyrosine Kinase Inhibitors in Chronic Myelogenous Leukemia Cells

Background: Chronic myeloid leukemia (CML) is a reciprocal translocation disorder driven by a breakpoint cluster region (BCR)-Abelson leukemia virus (ABL) fusion gene that stimulates abnormal tyrosine kinase activity. Tyrosine kinase inhibitors (TKIs) are effective in the treatment of Philadelphia chromosome (Ph)+ CML patients. However, the appearance of TKI-resistant CML cells is a hurdle in CML treatment. Therefore, it is necessary to identify novel treatments that could target a different mechanism than that of tyrosine kinases.Methods: The study was designed to verify whether C-X-C chemokine receptor 2 (CXCR2) could be a novel target for TKI-resistant CML treatment. We examined CXCR2 ligands from CML patient samples and TKI-resistant CML cell lines. Then, we inhibited CXCR2 and examined the effects on cell proliferation and apoptosis using immunoblotting and flow cytometry. The CXCR2 inhibition effect was also confirmed using a mouse xenograft model with TKI-sensitive and -resistant CML cells.Results: Interleukin 8 (IL-8), a CXCR2 ligand, was significantly increased in the bone marrow serum of initially diagnosed CML patients. CML cell lines expressed CXCR2, regardless of their sensitivity to TKIs. IL-8 stimulated CXCR2, mTOR, and c-Myc mRNA expression in CML cell lines. CXCR2 antagonists suppressed the proliferation of CML cells via cell cycle arrest in the G2/M phase. In addition, CXCR2 inhibition attenuated mTOR, c-Myc, and BCR-ABL expression, leading to CML cell apoptosis, irrespective of TKI responsiveness. Moreover, SB225002, a CXCR2 antagonist, caused higher cell death in CML cells than TKIs. Using a mouse xenograft model, we confirmed that SB225002 suppresses CML cells, with a prominent effect on TKI-resistant CML cells.Conclusions: Taken together, our findings demonstrate that IL-8 is a prognostic factor to the progress of CML. Inhibiting the CXCR2-mTOR-c-Myc cascade is a promising therapeutic strategy to overcome TKI-sensitive and -insensitive CML. Thus, CXCR2 blockade is a novel therapeutic strategy to treat CML, and SB225002, a commercially available CXCR2 antagonist, might be a drug candidate to treat TKI-resistant CML.

The protective effect of CXC chemokine receptor 2 antagonist on experimental bronchopulmonary dysplasia induced by postnatal systemic inflammation

Background: Animal studies have shown that a leukocyte influx precedes the development of bronchopulmonary dysplasia (BPD) in premature sheep. The CXC chemokine receptor 2 (CXCR2) pathway has been implicated in the pathogenesis of BPD because of the predominance of CXCR2 ligands in tracheal aspirates of preterm infants who later developed BPD.Purpose: To test the effect of CXCR2 antagonist on postnatal systemic and pulmonary inflammation and alveolarization in a newborn Sprague-Dawley rat model of BPD.Methods: Lipopolysaccharide (LPS) was injected intraperitoneally (i.p.) into the newborn rats on postnatal day 1 (P1), P3, and P5 to induce systemic inflammation and inhibit alveolarization. In the same time with LPS administration, CXCR2 antagonist (SB-265610) or vehicle was injected i.p. to investigate whether CXCR2 antagonist can alleviate the detrimental effect of LPS on alveolarization by attenuating inflammation. On P7 and P14, bronchoalveolar lavage fluid (BALF) and peripheral blood (PB) were collected from the pups. To assess alveolarization, mean cord length and alveolar surface area were measured on 4 random nonoverlapping fields per animal in 2 distal lung sections at ×100 magnification.Results: Early postnatal LPS administration significantly increased neutrophil counts in BALF and PB and inhibited alveolarization, which was indicated by a greater mean cord length and lesser alveolar surface area. CXCR2 antagonist significantly attenuated the increase of neutrophil counts in BALF and PB and restored alveolarization as indicated by a decreased mean cord length and increased alveolar surface area in rat pups exposed to early postnatal systemic LPS.Conclusion: CXCR2 antagonist preserved alveolarization by alleviating pulmonary and systemic inflammation induced by early postnatal systemic LPS administration. These results suggest that CXCR2 antagonist can be considered a potential therapeutic agent for BPD that results from disrupted alveolarization induced by inflammation.

The neuroprotection of hyperbaric oxygen therapy against traumatic brain injury via NF-κB/MAPKs-CXCL1 signaling pathway

Background It is well known that hyperbaric oxygen (HBO) therapy achieves neuroprotective effects by suppressing or relieving neuroinflammatory responses. However, its underlying therapeutic mechanisms are not yet fully elucidated. Based on our previous studies, we further investigated whether HBO therapy exerts neuroprotective effects in vivo by regulating the NF-κB/ MAPKs-CXCL1 inflammatory pathway. Methods A rat model of traumatic brain injury (TBI) was established by controlled cortical impact (CCI). The cellular distribution of CXCL1 and CXCR2 was observed by double immunofluorescence labeling. The neurological function of TBI rats was assessed by modified neurological severity scores and Morris water maze methods. TUNEL staining was performed to observe apoptosis of neuronal cells in the injured cortical area. The changes in neural function, neuronal apoptosis, and expression of CXCL1, CXCR2, NF-κB, and MAPKs (ERK and JNK) were observed in TBI rats treated with CXCR2 antagonist, ERK, JNK, and NF-κB inhibitor or HBO therapy. Results The expression of CXCL1 and CXCR2 increased after TBI, and cell localization analysis revealed that CXCL1 was mainly expressed in astrocytes, while CXCR2 was mainly expressed in neurons. Increased apoptosis of cortical neurons in the injury area was also found after TBI. Reduced neuronal apoptosis with improved neurological function was observed after application of a CXCR2 antagonist. The expression of p-ERK, p-JNK and p-NF-κB increased after TBI, and application of ERK, JNK and NF-κB inhibitors decreased expression of CXCL1 and CXCR2 in rats. We further found that HBO therapy down-regulated the expression of p-ERK, p-JNK, p-NF-κB, CXCL1, and CXCR2, and reduced neuronal apoptosis, improved the neurological function of TBI rats, and ultimately alleviated the secondary injury. Conclusions CXCL1- CXCR2 mediates the interaction of activated astrocytes and neurons, exacerbating secondary injury after TBI. HBO therapy exerts neuroprotective effects by regulating the NF-κB/ MAPKs (JNK and ERK)- CXCL1 inflammatory pathway to control neuroinflammation after TBI, which provides the theoretical and experimental basis for the clinical application of HBO therapy in the treatment of TBI.

Cxcl5/Cxcr2 Modulates Inflammation-Mediated Neural Repair After Optic Nerve Injury

BackgroundPrevious studies reported that mild inflammation promotes retinal ganglion cell (RGC) survival and axonal regeneration after optic nerve (ON) injury with involvement of infiltrating macrophages and neutrophils. Here we aimed to evaluate the involvement and regulation of the main inflammatory chemokine pathway Cxcl5/Cxcr2 in the inflammation-mediated RGC survival and axonal regeneration in mice after ON injury.MethodsThe expressions and cellular locations of Cxcl5 and Cxcr2 were confirmed in mouse retina. Treatment effects of recombinant Cxcl5 and Cxcr2 antagonist SB225002 were studied in the explant culture and the ON injury model with or without lens injury. The number of RGCs, regenerating axons, and inflammatory cells were determined, and the activation of Akt and Stat3 signaling pathways evaluated. ResultsCxcr2 and Cxcl5 expressions were increased after ON and lens injury. Addition of recombinant Cxcl5 promoted RGC survival and neurite outgrowth in retinal explant culture with increase in the number of activated microglia, which was inhibited by SB225002 or clodronate liposomes. Recombinant Cxcl5 also alleviated RGC death and promoted axonal regeneration in mice after ON injury, and promoted the lens injury-induced RGC protection with increase in the number of activated microglia. SB225002 inhibited lens injury-induced cell infiltration and activation, and attenuated the promotion effect on RGC survival and axonal regeneration through reduction of lens injury-induced Akt activation.ConclusionsCxcl5 promotes RGC survival and axonal regeneration after ON injury and further enhances RGC protection induced by lens injury through microglia activation, which is attenuated by Cxcr2 antagonist. Cxcl5/Cxcr2 should be a potential therapeutic target for RGC survival promotion after ON injury.