Partial agonist activity of α1-adrenergic receptor antagonists for chemokine (C-X-C motif) receptor 4 and atypical chemokine receptor 3

Development of tolerance to chemokine receptor antagonists: current paradigms and the need for further investigation

Chemokine G-protein coupled receptors are validated drug targets for many diseases, including cancer, neurological, and inflammatory disorders. Despite much time and effort spent on therapeutic development, very few chemokine receptor antagonists are approved for clinical use. Among potential reasons for the slow progress in developing chemokine receptor inhibitors, antagonist tolerance, a progressive reduction in drug efficacy after repeated administration, is likely to play a key role. The mechanisms leading to antagonist tolerance remain poorly understood. In many cases, antagonist tolerance is accompanied by increased receptor concentration on the cell surface after prolonged exposure to chemokine receptor antagonists. This points to a possible role of altered receptor internalization and presentation on the cell surface, as has been shown for agonist (primarily opioid) tolerance. In addition, examples of antagonist tolerance in the context of other G-protein coupled receptors suggest the involvement of noncanonical signal transduction in opposing the effects of the antagonists. In this review, we summarize the available progress and challenges in therapeutic development of chemokine receptor antagonists, describe the available knowledge about antagonist tolerance, and propose new avenues for future investigation of this important phenomenon. Furthermore, we highlight the modern methodologies that have the potential to reveal novel mechanisms leading to antagonist tolerance and to propel the field forward by advancing the development of potent "tolerance-free" antagonists of chemokine receptors.

Atypical CXCL12 signaling enhances neutrophil migration by modulating nuclear deformability

To reach inflamed tissues from the circulation, neutrophils must overcome physical constraints imposed by the tissue architecture, such as the endothelial barrier or the three-dimensional (3D) interstitial space. In these microenvironments, neutrophils are forced to migrate through spaces smaller than their own diameter. One of the main challenges for cell passage through narrow gaps is the deformation of the nucleus, the largest and stiffest organelle in cells. Here, we showed that chemokines, the extracellular signals that guide cell migration in vivo, modulated nuclear plasticity to support neutrophil migration in restricted microenvironments. Exploiting microfabricated devices, we found that the CXC chemokine CXCL12 enhanced the nuclear pliability of mouse bone marrow–derived neutrophils to sustain their migration in 3D landscapes. This previously uncharacterized function of CXCL12 was mediated by the atypical chemokine receptor ACKR3 (also known as CXCR7), required protein kinase A (PKA) activity, and induced chromatin compaction, which resulted in enhanced cell migration in 3D. Thus, we propose that chemical cues regulate the nuclear plasticity of migrating leukocytes to optimize their motility in restricted microenvironments.

α1B/D-adrenoceptors regulate chemokine receptor-mediated leukocyte migration via formation of heteromeric receptor complexes

It is known that catecholamines regulate innate immune functions. The underlying mechanisms, however, are not well understood. Here we show that at least 20 members of the human chemokine receptor (CR) family heteromerize with one or more members of the α1-adrenergic receptor (AR) family in recombinant systems and that such heteromeric complexes are detectable in human monocytes and the monocytic leukemia cell line THP-1. Ligand binding to α1-ARs inhibited migration toward agonists of the CR heteromerization partners of α1B/D-ARs with high potency and 50 to 77% efficacy but did not affect migration induced by a noninteracting CR. Incomplete siRNA knockdown of α1B/D-ARs in THP-1 cells partially inhibited migration toward agonists of their CR heteromerization partners. Complete α1B-AR knockout via CRISPR-Cas9 gene editing in THP-1 cells (THP-1_ADRA1BKO) resulted in 82% reduction of α1D-AR expression and did not affect CR expression. Migration of THP-1_ADRA1BKO cells toward agonists of CR heteromerization partners of α1B/D-ARs was reduced by 82 to 95%. Our findings indicate that CR:α1B/D-AR heteromers are essential for normal function of CR heteromerization partners, provide a mechanism underlying neuroendocrine control of leukocyte trafficking, and offer opportunities to modulate leukocyte and/or cancer cell trafficking in disease processes.

Expression of colorectal neoplasia differentially expressed in anaplastic thyroid carcinoma and its effect on cancer cell proliferation

Background

The incidence of anaplastic thyroid cancer (ATC) is high among human cancers. Colorectal neoplasia differentially expressed (CRNDE) is highly expressed in common tumors, and is therefore a potential molecular target for anti-tumor therapy. However, the function of CRNDE in ATC remains elusive.

Methods

The Gene Expression Omnibus (GEO) database was used to screen the differential expression of long-noncoding RNA (lncRNA) in ATC tissues. The Cancer Genome Atlas (TCGA) database was used to analyze the expression of CRNDE in thyroid cancer (THCA) tissues and its impact on patient prognosis. Quantitative real-time PCR (qRT-PCR) was used to determine the expression level of CRNDE in tumor and control tissues. The biological function of CRNDE in THCA was explored using TCGA RNA sequencing (RNA-seq) data analysis. ATC cell lines with low and high CRNDE expression were selected for CRNDE siRNA transfection, and the proliferation of cells was detected in each group.

Results

The GEO and TCGA databases analysis results showed that CRNDE was highly expressed in ATC tissues, which is related to the poor prognosis of THCA patients. Also, the expression of CRNDE in the ATC cell line, ARO (human thyroid cancer cell line), was relatively high, while the expression in sw579 is relatively low. Therefore, ARO and sw579 were chosen for CRNDE small interfering RNA (siRNA) transfection. Compared with negative control (si-NC), the expression of CRNDE in si-CRNDE-1, si-CRNDE-2, and si-CRNDE-3 was reduced, indicating that the inhibitory effect was significantly enhanced and the cell proliferation ability was reduced, and the cell cycle is arrested in the G0/G1 phase. Finally, it was found that the wnt3a, β-catenin, and cyclinD1 protein expressions of si-CRNDE-1 and si-CRNDE-2 were significantly reduced.

Conclusions

The high expression of CRNDE in ATC tissues may promote the proliferation of ATC cells by regulating the Wnt/β-catenin signaling pathway. CRNDE may be a potential molecular target for the treatment of ATC.

Chemokine receptor antagonists with α1-adrenergic receptor blocker activity

OBJECTIVES

Chemokine receptor antagonists are being explored for their therapeutic potential in various disease processes. As the chemokine (C-C motif) receptor 2 (CCR2) antagonist RS504393 is known to compete with ligand binding to α₁-adrenoceptors, we tested a panel of 10 CCR antagonists for interactions with α₁-adrenoceptors to evaluate potential cardiovascular activities and side-effect profiles.

METHODS

The PRESTO-Tango β-arrestin recruitment assay was utilized to test whether the CCR antagonists interfere with α_1b-AR activation upon stimulation with phenylephrine. Pressure myography with isolated rat resistance arteries was employed to assess their effects on phenylephrine-induced vasoconstriction. The following antagonists were tested: CCR1-BX471, BX513, BI639667; CCR2-RS504393, INCB3284; CCR3-SB328437; and CCR4-AZD2098, and C021; CCR5-Maraviroc; CCR10-BI6901. The pan-α₁-adrenoceptor antagonist prazosin was used as control.

RESULTS

Among the CCR antagonists tested, RS504393, BX513, and C021 inhibited phenylephrine-induced β-arrestin recruitment to α_1b-adrenoceptor and phenylephrine-induced vasoconstriction. While RS504393 functioned as a competitive α₁-adrenoceptor blocker, BX513 and C021 functioned as noncompetitive α₁-adrenoceptor antagonists in both assay systems. Furthermore, RS504393, BX513, and C021 dose-dependently dilated arteries that were fully preconstricted with phenylephrine.

CONCLUSIONS

Our data suggest that CCR antagonists should be screened for cross-reactivity with α₁-adrenoceptors to exclude potential adverse cardiovascular effects when used as anti inflammatory drugs.

Regulation of the thrombin/protease-activated receptor 1 axis by chemokine (CXC motif) receptor 4

The chemokine receptor CXCR4, a G protein-coupled receptor (GPCR) capable of heteromerizing with other GPCRs, is involved in many processes, including immune responses, hematopoiesis, and organogenesis. Evidence suggests that CXCR4 activation reduces thrombin/protease-activated receptor 1 (PAR1)-induced impairment of endothelial barrier function. However, the mechanisms underlying cross-talk between CXCR4 and PAR1 are not well-understood. Using intermolecular bioluminescence resonance energy transfer and proximity ligation assays, we found that CXCR4 heteromerizes with PAR1 in the HEK293T expression system and in human primary pulmonary endothelial cells (hPPECs). A peptide analog of transmembrane domain 2 (TM2) of CXCR4 interfered with PAR1:CXCR4 heteromerization. In HTLA cells, the presence of CXCR4 reduced the efficacy of thrombin to induce β-arrestin-2 recruitment to recombinant PAR1 and enhanced thrombin-induced Ca²⁺ mobilization. Whereas thrombin-induced extracellular signal-regulated protein kinase 1/2 (ERK1/2) phosphorylation occurred more transiently in the presence of CXCR4, peak ERK1/2 phosphorylation was increased when compared with HTLA cells expressing PAR1 alone. CXCR4-associated effects on thrombin-induced β-arrestin-2 recruitment to and signaling of PAR1 could be reversed by TM2. In hPPECs, TM2 inhibited thrombin-induced ERK1/2 phosphorylation and activation of Ras homolog gene family member A. CXCR4 siRNA knockdown inhibited thrombin-induced ERK1/2 phosphorylation. Whereas thrombin stimulation reduced surface expression of PAR1, CXCR4, and PAR1:CXCR4 heteromers, chemokine (CXC motif) ligand 12 stimulation reduced surface expression of CXCR4 and PAR1:CXCR4 heteromers, but not of PAR1. Finally, TM2 dose-dependently inhibited thrombin-induced impairment of hPPEC monolayer permeability. Our findings suggest that CXCR4:PAR1 heteromerization enhances thrombin-induced G protein signaling of PAR1 and PAR1-mediated endothelial barrier disruption.