Concurrent activation of β2-adrenergic receptor and blockage of GPR55 disrupts pro-oncogenic signaling in glioma cells

A comprehensive pharmacological analysis of fenoterol and its derivatives to unravel the role of β2-adrenergic receptor in zebrafish

β-adrenergic receptors (βARs) belong to a key molecular targets that regulate the most important processes occurring in the human organism. Although over the last decades a zebrafish model has been developed as a model complementary to rodents in biomedical research, the role of β₂AR in regulation of pathological and toxicological effects remains to elucidate. Therefore, the study aimed to clarify the role of β₂AR with a particular emphasis on the distinct role of subtypes A and B of zebrafish β₂AR. As model compounds selective β₂AR agonists - (R,R)-fenoterol ((R,R)-Fen) and its new derivatives: (R,R)-4'-methoxyfenoterol ((R,R)-MFen) and (R,R)-4'-methoxy-1-naphtylfenoterol ((R,R)-MNFen) - were tested. We described dose-dependent changes observed after fenoterols exposure in terms of general toxicity, cardiotoxicity and neurobehavioural responses. Subsequently, to better characterise the role of β₂-adrenergic stimulation in zebrafish, we have performed a series of molecular docking simulations. Our results indicate that (R,R)-Fen displays the highest affinity for subtype A of zebrafish β₂AR and β_2AAR might be involved in pigment depletion. (R,R)-MFen shows the lowest affinity for zebrafish β₂ARs out of the tested fenoterols and this might be associated with its cardiotoxic and anxiogenic effects. (R,R)-MNFen displays the highest affinity for subtype B of zebrafish β₂AR and modulation of this receptor might be associated with the development of malformations, increases locomotor activity and induces a negative chronotropic effect. Taken together, the presented data offer insights into the functional responses of the zebrafish β₂ARs confirming their intraspecies conservation, and support the translation of the zebrafish model in pharmacological and toxicological research.

Disorders of cancer metabolism: The therapeutic potential of cannabinoids

Abnormal energy metabolism, as one of the important hallmarks of cancer, was induced by multiple carcinogenic factors and tumor-specific microenvironments. It comprises aerobic glycolysis, de novo lipid biosynthesis, and glutamine-dependent anaplerosis. Considering that metabolic reprogramming provides various nutrients for tumor survival and development, it has been considered a potential target for cancer therapy. Cannabinoids have been shown to exhibit a variety of anticancer activities by unclear mechanisms. This paper first reviews the recent progress of related signaling pathways (reactive oxygen species (ROS), AMP-activated protein kinase (AMPK), mitogen-activated protein kinases (MAPK), phosphoinositide 3-kinase (PI3K), hypoxia-inducible factor-1alpha (HIF-1α), and p53) mediating the reprogramming of cancer metabolism (including glucose metabolism, lipid metabolism, and amino acid metabolism). Then we comprehensively explore the latest discoveries and possible mechanisms of the anticancer effects of cannabinoids through the regulation of the above-mentioned related signaling pathways, to provide new targets and insights for cancer prevention and treatment.

Nuclear size rectification: A potential new therapeutic approach to reduce metastasis in cancer

Research on metastasis has recently regained considerable interest with the hope that single cell technologies might reveal the most critical changes that support tumor spread. However, it is possible that part of the answer has been visible through the microscope for close to 200 years. Changes in nuclear size characteristically occur in many cancer types when the cells metastasize. This was initially discarded as contributing to the metastatic spread because, depending on tumor types, both increases and decreases in nuclear size could correlate with increased metastasis. However, recent work on nuclear mechanics and the connectivity between chromatin, the nucleoskeleton, and the cytoskeleton indicate that changes in this connectivity can have profound impacts on cell mobility and invasiveness. Critically, a recent study found that reversing tumor type-dependent nuclear size changes correlated with reduced cell migration and invasion. Accordingly, it seems appropriate to now revisit possible contributory roles of nuclear size changes to metastasis.

Chemical Interrogation of Nuclear Size Identifies Compounds with Cancer Cell Line-Specific Effects on Migration and Invasion

Background: Lower survival rates for many cancer types correlate with changes in nuclear size/scaling in a tumor-type/tissue-specific manner. Hypothesizing that such changes might confer an advantage to tumor cells, we aimed at the identification of commercially available compounds to guide further mechanistic studies. We therefore screened for Food and Drug Administration (FDA)/European Medicines Agency (EMA)-approved compounds that reverse the direction of characteristic tumor nuclear size changes in PC3, HCT116, and H1299 cell lines reflecting, respectively, prostate adenocarcinoma, colonic adenocarcinoma, and small-cell squamous lung cancer. Results: We found distinct, largely nonoverlapping sets of compounds that rectify nuclear size changes for each tumor cell line. Several classes of compounds including, e.g., serotonin uptake inhibitors, cyclo-oxygenase inhibitors, β-adrenergic receptor agonists, and Na⁺/K⁺ ATPase inhibitors, displayed coherent nuclear size phenotypes focused on a particular cell line or across cell lines and treatment conditions. Several compounds from classes far afield from current chemotherapy regimens were also identified. Seven nuclear size-rectifying compounds selected for further investigation all inhibited cell migration and/or invasion. Conclusions: Our study provides (a) proof of concept that nuclear size might be a valuable target to reduce cell migration/invasion in cancer treatment and (b) the most thorough collection of tool compounds to date reversing nuclear size changes specific to individual cancer-type cell lines. Although these compounds still need to be tested in primary cancer cells, the cell line-specific nuclear size and migration/invasion responses to particular drug classes suggest that cancer type-specific nuclear size rectifiers may help reduce metastatic spread.

Deprogramming metabolism in pancreatic cancer with a bi-functional GPR55 inhibitor and biased β2 adrenergic agonist

Metabolic reprogramming contributes to oncogenesis, tumor growth, and treatment resistance in pancreatic ductal adenocarcinoma (PDAC). Here we report the effects of (R,S′)-4′-methoxy-1-naphthylfenoterol (MNF), a GPR55 antagonist and biased β₂-adrenergic receptor (β₂-AR) agonist on cellular signaling implicated in proliferation and metabolism in PDAC cells. The relative contribution of GPR55 and β₂-AR in (R,S′)-MNF signaling was explored further in PANC-1 cells. Moreover, the effect of (R,S′)-MNF on tumor growth was determined in a PANC-1 mouse xenograft model. PANC-1 cells treated with (R,S′)-MNF showed marked attenuation in GPR55 signal transduction and function combined with increased β₂-AR/Gα_s/adenylyl cyclase/PKA signaling, both of which contributing to lower MEK/ERK, PI3K/AKT and YAP/TAZ signaling. (R,S′)-MNF administration significantly reduced PANC-1 tumor growth and circulating l-lactate concentrations. Global metabolic profiling of (R,S′)-MNF-treated tumor tissues revealed decreased glycolytic metabolism, with a shift towards normoxic processes, attenuated glutamate metabolism, and increased levels of ophthalmic acid and its precursor, 2-aminobutyric acid, indicative of elevated oxidative stress. Transcriptomics and immunoblot analyses indicated the downregulation of gene and protein expression of HIF-1α and c-Myc, key initiators of metabolic reprogramming in PDAC. (R,S′)-MNF treatment decreased HIF-1α and c-Myc expression, attenuated glycolysis, shifted fatty acid metabolism towards β-oxidation, and suppressed de novo pyrimidine biosynthesis in PANC-1 tumors. The results indicate a potential benefit of combined GPR55 antagonism and biased β₂-AR agonism in PDAC therapy associated with the deprogramming of altered cellular metabolism.

Structural Insights into Ligand-Receptor Interactions Involved in Biased Agonism of G-Protein Coupled Receptors

G protein-coupled receptors (GPCRs) are versatile signaling proteins that mediate complex cellular responses to hormones and neurotransmitters. Ligand directed signaling is observed when agonists, upon binding to the same receptor, trigger significantly different configuration of intracellular events. The current work reviews the structurally defined ligand – receptor interactions that can be related to specific molecular mechanisms of ligand directed signaling across different receptors belonging to class A of GPCRs. Recent advances in GPCR structural biology allow for mapping receptors’ binding sites with residues particularly important in recognition of ligands’ structural features that are responsible for biased signaling. Various studies show particular role of specific residues lining the extended ligand binding domains, biased agonists may alternatively affect their interhelical interactions and flexibility what can be translated into intracellular loop rearrangements. Studies on opioid and angiotensin receptors indicate importance of residues located deeper within the binding cavity and direct interactions with receptor residues linking the ortosteric ligand binding site with the intracellular transducer binding domain. Collection of results across different receptors may suggest elements of common molecular mechanisms which are responsible for passing alternative signals from biased agonists.

Heterodimerization With 5-HT2BR Is Indispensable for β2AR-Mediated Cardioprotection

RATIONALE

The β2-adrenoceptor (β2-AR), a prototypical GPCR (G protein-coupled receptor), couples to both Gs and Gi proteins. Stimulation of the β2-AR is beneficial to humans and animals with heart failure presumably because it activates the downstream Gi-PI3K-Akt cell survival pathway. Cardiac β2-AR signaling can be regulated by crosstalk or heterodimerization with other GPCRs, but the physiological and pathophysiological significance of this type of regulation has not been sufficiently demonstrated.

OBJECTIVE

Here, we aim to investigate the potential cardioprotective effect of β2-adrenergic stimulation with a subtype-selective agonist, (R,R')-4-methoxy-1-naphthylfenoterol (MNF), and to decipher the underlying mechanism with a particular emphasis on the role of heterodimerization of β2-ARs with another GPCR, 5-hydroxytryptamine receptors 2B (5-HT2BRs).

METHODS AND RESULTS

Using pharmacological, genetic and biophysical protein-protein interaction approaches, we studied the cardioprotective effect of the β2-agonist, MNF, and explored the underlying mechanism in both in vivo in mice and cultured rodent cardiomyocytes insulted with doxorubicin, hydrogen peroxide (H2O2) or ischemia/reperfusion. In doxorubicin (Dox)-treated mice, MNF reduced mortality and body weight loss, while improving cardiac function and cardiomyocyte viability. MNF also alleviated myocardial ischemia/reperfusion injury. In cultured rodent cardiomyocytes, MNF inhibited DNA damage and cell death caused by Dox, H2O2 or hypoxia/reoxygenation. Mechanistically, we found that MNF or another β2-agonist zinterol markedly promoted heterodimerization of β2-ARs with 5-HT2BRs. Upregulation of the heterodimerized 5-HT2BRs and β2-ARs enhanced β2-AR-stimulated Gi-Akt signaling and cardioprotection while knockdown or pharmacological inhibition of the 5-HT2BR attenuated β2-AR-stimulated Gi signaling and cardioprotection.

CONCLUSIONS

These data demonstrate that the β2-AR-stimulated cardioprotective Gi signaling depends on the heterodimerization of β2-ARs and 5-HT2BRs.

β adrenergic receptor modulated signaling in glioma models: promoting β adrenergic receptor-β arrestin scaffold-mediated activation of extracellular-regulated kinase 1/2 may prove to be a panacea in the treatment of intracranial and spinal malignancy and extra-neuraxial carcinoma

Neoplastically transformed astrocytes express functionally active cell surface β adrenergic receptors (βARs). Treatment of glioma models in vitro and in vivo with β adrenergic agonists variably amplifies or attenuates cellular proliferation. In the majority of in vivo models, β adrenergic agonists generally reduce cellular proliferation. However, treatment with β adrenergic agonists consistently reduces tumor cell invasive potential, angiogenesis, and metastasis. β adrenergic agonists induced decreases of invasive potential are chiefly mediated through reductions in the expression of matrix metalloproteinases types 2 and 9. Treatment with β adrenergic agonists also clearly reduce tumoral neoangiogenesis, which may represent a putatively useful mechanism to adjuvantly amplify the effects of bevacizumab. Bevacizumab is a monoclonal antibody targeting the vascular endothelial growth factor receptor. We may accordingly designate βagonists to represent an enhancer of bevacizumab. The antiangiogenic effects of β adrenergic agonists may thus effectively render an otherwise borderline effective therapy to generate significant enhancement in clinical outcomes. β adrenergic agonists upregulate expression of the major histocompatibility class II DR alpha gene, effectively potentiating the immunogenicity of tumor cells to tumor surveillance mechanisms. Authors have also demonstrated crossmodal modulation of signaling events downstream from the β adrenergic cell surface receptor and microtubular polymerization and depolymerization. Complex effects and desensitization mechanisms of the β adrenergic signaling may putatively represent promising therapeutic targets. Constant stimulation of the β adrenergic receptor induces its phosphorylation by β adrenergic receptor kinase (βARK), rendering it a suitable substrate for alternate binding by β arrestins 1 or 2. The binding of a β arrestin to βARK phosphorylated βAR promotes receptor mediated internalization and downregulation of cell surface receptor and contemporaneously generates a cell surface scaffold at the βAR. The scaffold mediated activation of extracellular regulated kinase 1/2, compared with protein kinase A mediated activation, preferentially favors cytosolic retention of ERK1/2 and blunting of nuclear translocation and ensuant pro-transcriptional activity. Thus, βAR desensitization and consequent scaffold assembly effectively retains the cytosolic homeostatic functions of ERK1/2 while inhibiting its pro-proliferative effects. We suggest these mechanisms specifically will prove quite promising in developing primary and adjuvant therapies mitigating glioma growth, angiogenesis, invasive potential, and angiogenesis. We suggest generating compounds and targeted mutations of the β adrenergic receptor favoring β arrestin binding and scaffold facilitated activation of ERK1/2 may hold potential promise and therapeutic benefit in adjuvantly treating most or all cancers. We hope our discussion will generate fruitful research endeavors seeking to exploit these mechanisms.

The presence and distribution of G protein-coupled receptor 35 (GPR35) in the human cornea - Evidences from in silico gene expression analysis and immunodetection

We provide the evidence for G protein-coupled receptor 35 (GPR35) presence and distribution in the human cornea. The initial data on GPR35 gene expression were retrieved from microarray repositories and were further confirmed by western blotting and immunohistochemical analysis. Immunoblotting suggested that GPR35 exists predominantly as a dimer in corneal tissue. Moreover, corneal tissues were significantly richer in GPR35 compared to the adjacent sclera. Immunoreactivity for GPR35 was detected in normal corneas, keratoconus and Fuchs' dystrophy, mainly in the corneal epithelium and endothelium. In corneas with Fuchs' dystrophy, less intensive immunoreactivity for GPR35 in endothelium was revealed. The physiological relevance of this phenomenon requires further investigation.

GPR55 receptor antagonist decreases glycolytic activity in PANC-1 pancreatic cancer cell line and tumor xenografts

The Warburg effect is a predominant metabolic pathway in cancer cells characterized by enhanced glucose uptake and its conversion to l-lactate and is associated with upregulated expression of HIF-1α and activation of the EGFR-MEK-ERK, Wnt-β-catenin, and PI3K-AKT signaling pathways. (R,R')-4'-methoxy-1-naphthylfenoterol ((R,R')-MNF) significantly reduces proliferation, survival, and motility of PANC-1 pancreatic cancer cells through inhibition of the GPR55 receptor. We examined (R,R')-MNF's effect on glycolysis in PANC-1 cells and tumors. Global NMR metabolomics was used to elucidate differences in the metabolome between untreated and (R,R')-MNF-treated cells. LC/MS analysis was used to quantify intracellular concentrations of β-hydroxybutyrate, carnitine, and l-lactate. Changes in target protein expression were determined by Western blot analysis. Data was also obtained from mouse PANC-1 tumor xenografts after administration of (R,R')-MNF. Metabolomics data indicate that (R,R')-MNF altered fatty acid metabolism, energy metabolism, and amino acid metabolism and increased intracellular concentrations of β-hydroxybutyrate and carnitine while reducing l-lactate content. The cellular content of phosphoinositide-dependent kinase-1 and hexokinase 2 was reduced consistent with diminished PI3K-AKT signaling and glucose metabolism. The presence of the GLUT8 transporter was established and found to be attenuated by (R,R')-MNF. Mice treated with (R,R')-MNF had significant accumulation of l-lactate in tumor tissue relative to vehicle-treated mice, together with reduced levels of the selective l-lactate transporter MCT4. Lower intratumoral levels of EGFR, pyruvate kinase M2, β-catenin, hexokinase 2, and p-glycoprotein were also observed. The data suggest that (R,R')-MNF reduces glycolysis in PANC-1 cells and tumors through reduced expression and function at multiple controlling sites in the glycolytic pathway.