The role of the CCL25-CCR9 axis in beta-cell function: potential for therapeutic intervention in type 2 diabetes

The Role of G Protein-Coupled Receptors and Receptor Kinases in Pancreatic β-Cell Function and Diabetes

Type 2 diabetes (T2D) mellitus has emerged as a major global health concern that has accelerated in recent years due to poor diet and lifestyle. Afflicted individuals have high blood glucose levels that stem from the inability of the pancreas to make enough insulin to meet demand. Although medication can help to maintain normal blood glucose levels in individuals with chronic disease, many of these medicines are outdated, have severe side effects, and often become less efficacious over time, necessitating the need for insulin therapy. G protein-coupled receptors (GPCRs) regulate many physiologic processes, including blood glucose levels. In pancreatic β cells, GPCRs regulate β-cell growth, apoptosis, and insulin secretion, which are all critical in maintaining sufficient β-cell mass and insulin output to ensure euglycemia. In recent years, new insights into the signaling of incretin receptors and other GPCRs have underscored the potential of these receptors as desirable targets in the treatment of diabetes. The signaling of these receptors is modulated by GPCR kinases (GRKs) that phosphorylate agonist-activated GPCRs, marking the receptor for arrestin binding and internalization. Interestingly, genome-wide association studies using diabetic patient cohorts link the GRKs and arrestins with T2D. Moreover, recent reports show that GRKs and arrestins expressed in the β cell serve a critical role in the regulation of β-cell function, including β-cell growth and insulin secretion in both GPCR-dependent and -independent pathways. In this review, we describe recent insights into GPCR signaling and the importance of GRK function in modulating β-cell physiology. SIGNIFICANCE STATEMENT: Pancreatic β cells contain a diverse array of G protein-coupled receptors (GPCRs) that have been shown to improve β-cell function and survival, yet only a handful have been successfully targeted in the treatment of diabetes. This review discusses recent advances in our understanding of β-cell GPCR pharmacology and regulation by GPCR kinases while also highlighting the necessity of investigating islet-enriched GPCRs that have largely been unexplored to unveil novel treatment strategies.

Protein-centric omics integration analysis identifies candidate plasma proteins for multiple autoimmune diseases

It remains challenging to translate the findings from genome-wide association studies (GWAS) of autoimmune diseases (AIDs) into interventional targets, presumably due to the lack of knowledge on how the GWAS risk variants contribute to AIDs. In addition, current immunomodulatory drugs for AIDs are broad in action rather than disease-specific. We performed a comprehensive protein-centric omics integration analysis to identify AIDs-associated plasma proteins through integrating protein quantitative trait loci datasets of plasma protein (1348 proteins and 7213 individuals) and totally ten large-scale GWAS summary statistics of AIDs under a cutting-edge systematic analytic framework. Specifically, we initially screened out the protein-AID associations using proteome-wide association study (PWAS), followed by enrichment analysis to reveal the underlying biological processes and pathways. Then, we performed both Mendelian randomization (MR) and colocalization analyses to further identify protein-AID pairs with putatively causal relationships. We finally prioritized the potential drug targets for AIDs. A total of 174 protein-AID associations were identified by PWAS. AIDs-associated plasma proteins were significantly enriched in immune-related biological process and pathways, such as inflammatory response (P = 3.96 × 10-10). MR analysis further identified 97 protein-AID pairs with potential causal relationships, among which 21 pairs were highly supported by colocalization analysis (PP.H4 > 0.75), 10 of 21 were the newly discovered pairs and not reported in previous GWAS analyses. Further explorations showed that four proteins (TLR3, FCGR2A, IL23R, TCN1) have corresponding drugs, and 17 proteins have druggability. These findings will help us to further understand the biological mechanism of AIDs and highlight the potential of these proteins to develop as therapeutic targets for AIDs.

β-cell function is regulated by metabolic and epigenetic programming of islet-associated macrophages, involving Axl, Mertk, and TGFβ receptor signaling

We have exploited islet-associated macrophages (IAMs) as a model of resident macrophage function, focusing on more physiological conditions than the commonly used extremes of M1 (inflammation) versus M2 (tissue remodeling) polarization. Under steady state, murine IAMs are metabolically poised between aerobic glycolysis and oxidative phosphorylation, and thereby exert a brake on glucose-stimulated insulin secretion (GSIS). This is underpinned by epigenetic remodeling via the metabolically regulated histone demethylase Kdm5a. Conversely, GSIS is enhanced by engaging Axl receptors on IAMs, or by augmenting their oxidation of glucose. Following high-fat feeding, efferocytosis is stimulated in IAMs in conjunction with Mertk and TGFβ receptor signaling. This impairs GSIS and potentially contributes to β-cell failure in pre-diabetes. Thus, IAMs serve as relays in many more settings than currently appreciated, fine-tuning insulin secretion in response to dynamic changes in the external environment. Intervening in this nexus might represent a means of preserving β-cell function during metabolic disease.

Quantification of changes in human islet G protein-coupled receptor mRNA expression in obesity

BACKGROUND

G protein-coupled receptors (GPCRs) play crucial roles in regulating islet function, with Gαs- and Gαq-coupled receptors being linked to the stimulation of insulin secretion. We have quantified the mRNA expression of 384 non-olfactory GPCRs in islets isolated from lean and obese organ donors to determine alterations in islet GPCR mRNA expression in obesity.

METHODS

RT-qPCR was used to quantify GPCR mRNAs relative to five reference genes (ACTB, GAPDH, PPIA, TBP, and TFRC) in human islets isolated from lean (BMI = 22.6 ± 0.5) and obese (BMI = 32.0 ± 0.8) donors.

RESULTS

Overall, 197 and 256 GPCR mRNAs were detected above trace level in islets from lean and obese donors, respectively, with 191 GPCR mRNAs being common to the lean and obese groups. 40.9% (n = 157) and 27.1% (n = 104) of the mRNAs were expressed at trace level whilst 7.8% and 6.3% were absent in islets from lean and obese donors, respectively. Hundred and seventeen GPCR mRNAs were upregulated at least twofold in islets from obese donors, and there was >twofold downregulation of 21 GPCR mRNAs. Of particular interest, several receptors signalling via Gαs or Gαq showed significant mRNA upregulation in islets from obese donors (fold increase: PTH2R: 54.0 ± 14.6; MC2R: 34.3 ± 11.5; RXFP1: 8.5 ± 2.1; HTR2B: 6.0 ± 2.0; GPR110: 3.9 ± 1.2; PROKR2: 3.9 ± 0.7).

CONCLUSIONS

Under conditions of obesity, human islets showed significant alterations in mRNAs encoding numerous GPCRs. The increased expression of Gαs- and Gαq-coupled receptors that have not previously been investigated in β-cells opens up possibilities of novel therapeutic candidates that may lead to the potentiation of insulin secretion and/or β-cell mass to regulate glucose homeostasis.

CCL25/CCR9 interaction promotes the malignant behavior of salivary adenoid cystic carcinoma via the PI3K/AKT signaling pathway

Background

CC chemokine receptor 9 (CCR9), an organ-specific chemokine receptor, interacts with its exclusive ligand CCL25 to promote tumor proliferation and metastasis. However, the effect of CCR9 on salivary adenoid cystic carcinoma (SACC) malignant behavior remains unknown. This study aimed to investigate the specific molecular mechanism by which CCR9/CCL25 modulates malignant progression in SACC.

Methods

Immunohistochemistry staining and RT-qPCR analyses were performed to detect the correlation of CCR9 expression and tumor progression-associated markers in SACC. In vitro, SACC cell proliferation and apoptosis were evaluated using Cell Counting Kit-8 and colon formation, and cell migration and invasion were detected by wound healing and transwell assays. Vercirnon was used as an inhibitor of CCR9, and LY294002 was used as an inhibitor of the PI3K/AKT pathway in this study. Western blot and RT-qPCR assays were carried out to measure the downstream factors of the interaction of CCL25 and CCR9. The effect of CCL25 on the development of SACC in vivo was examined by a xenograft tumor model in nude mice following CCL25, Vercirnon and LY294002 treatment.

Results

CCR9 was highly expressed in SACC compared with adjacent salivary gland tissues, and its level was associated with tumor proliferation and metastases. CCL25 enhanced cell proliferation, migration, and invasion through its interaction with CCR9 and exerted an antiapoptotic effect on SACC cells. Targeting CCR9 via Vercirnon significantly reduced the phosphorylation level of AKT induced by CCL25. CCL25/CCR9 could activate its downstream factors through the PI3K/AKT signaling pathway, such as cyclin D1, BCL2 and SLUG, thus promoting SACC cell proliferation, antiapoptosis, invasion and metastasis. The in vivo data from the xenograft mouse models further proved that CCL25 administration promoted malignant tumor progression by activating the PI3K/AKT pathway.

Conclusion

The interaction of CCL25 and CCR9 promotes tumor growth and metastasis in SACC by activating the PI3K/AKT signaling pathway, offering a promising strategy for SACC treatment.

CCL25 Inhibition Alleviates Sepsis-Induced Acute Lung Injury and Inflammation

Purpose

Acute lung injury (ALI) is a common clinical syndrome with high mortality. The chemokine ligand 25 (CCL25) is involved in inflammation, leukocyte trafficking and immunoregulation. However, the role and mechanism of CCL25 in ALI are not fully understood yet. The aim of this study was to explore the relationship between acute lung injury and CCL25.

Patients and Methods

In this study, we first examined chemokine expression in sepsis patients and found that serum CCL25 expression levels were relatively high in sepsis patients compared to healthy individuals. Based on this, we designed in vitro and in vivo experiments to verify the validity of the theory. In vitro, we used lipopolysaccharide-stimulated human pulmonary microvascular endothelial cells (HPMECs). In vivo, we established male C57BL/6 mice cecal ligation puncture (CLP) model of sepsis.

Results

In vitro, we used lipopolysaccharide-stimulated human pulmonary microvascular endothelial cells (HPMECs) and found significantly higher expression of CCL25 by enzyme-linked immunosorbent assay. Inhibition of CCL25 resulted in a significant decrease in the expression of inflammatory cytokines in HPMECs. In addition, we found that CCL25 promoted increased endothelial permeability by reducing the expression of tight junction proteins and was associated with activation of the P38 MAPK pathway by measuring the transepithelial electrical resistance and fluorescence intensity of fluorescein isothiocyanate. Results from luciferase assays and chromatin immunoprecipitation assays showed that inhibition of NF-κB activity in HPMECs decreased CCL25 expression, but addition of recombinant CCL25 increased cell permeability and inflammatory cytokine expression. In vivo, we established male C57BL/6 mice cecal ligation puncture (CLP) model of sepsis. We found that inhibition of CCL25 significantly reduced inflammatory cytokine expression in a CLP-induced sepsis model, thereby alleviating lung tissue damage in mice.

Conclusion

Our study suggests that CCL25 contributed to the development of ALI by modulating the functions of microvascular endothelial cells.

Inflammatory Chemokines Expression Variations and Their Receptors in APP/PS1 Mice

BACKGROUND

In Alzheimer's disease (AD), an increase in inflammation is distinctive. Amyloid precursor protein plus presenilin-1 (APP/PS1 mice) is a model for this illness. Chemokines secreted by central nervous system (CNS) cells could play multiple important roles in AD. Data looking for the chemokines involved in inflammatory mechanisms are lacking. To understand the changes that occur in the inflammation process in AD, it is necessary to improve strategies to act on specific inflammatory targets.

OBJECTIVE

Chemokines and their receptors involved in phagocytosis, demyelination, chemotaxis, and coagulation were the objective of our study.

METHODS

Female APPswe/PS1 double-transgenic mice (B6C3-Tg) were used and cortex brain from 20-22-month-old mice obtained and used to quantify chemokines and chemokine receptors expression using RT-PCR technique.

RESULTS

Significant inflammatory changes were detected in APP/PS1 compared to wild type mice. CCR1, CCR3, CCR4, and CCR9 were elevated, and CCR2 were decreased compared with wild type mice. Their ligands CCL7, CCL11, CCL17, CCL22, CCL25, and CXCL4 showed an increase expression; however, changes were not observed in CCL2 in APP/PS1 compared to wild type mice.

CONCLUSION

This change in expression could explain the differences between AD patients and elderly people without this illness. This would provide a new strategy for the treatment of AD, with the possibility to act in specific inflammatory targets.

Transcriptome analysis of islets from diabetes-resistant and diabetes-prone obese mice reveals novel gene regulatory networks involved in beta-cell compensation and failure

The mechanisms underpinning beta-cell compensation for obesity-associated insulin resistance and beta-cell failure in type 2 diabetes remain poorly understood. We used a large-scale strategy to determine the time-dependent transcriptomic changes in islets of diabetes-prone db/db and diabetes-resistant ob/ob mice at 6 and 16 weeks of age. Differentially expressed genes were subjected to cluster, gene ontology, pathway and gene set enrichment analyses. A distinctive gene expression pattern was observed in 16 week db/db islets in comparison to the other groups with alterations in transcriptional regulators of islet cell identity, upregulation of glucose/lipid metabolism, and various stress response genes, and downregulation of specific amino acid transport and metabolism genes. In contrast, ob/ob islets displayed a coordinated downregulation of metabolic and stress response genes at 6 weeks of age, suggestive of a preemptive reconfiguration in these islets to lower the threshold of metabolic activation in response to increased insulin demand thereby preserving beta-cell function and preventing cellular stress. In addition, amino acid transport and metabolism genes were upregulated in ob/ob islets, suggesting an important role of glutamate metabolism in beta-cell compensation. Gene set enrichment analysis of differentially expressed genes identified the enrichment of binding motifs for transcription factors, FOXO4, NFATC1, and MAZ. siRNA-mediated knockdown of these genes in MIN6 cells altered cell death, insulin secretion, and stress gene expression. In conclusion, these data revealed novel gene regulatory networks involved in beta-cell compensation and failure. Preemptive metabolic reconfiguration in diabetes-resistant islets may dampen metabolic activation and cellular stress during obesity.

Obesity-induced changes in human islet G protein-coupled receptor expression: Implications for metabolic regulation

G protein-coupled receptors (GPCRs) are a large family of cell surface receptors that are the targets for many different classes of pharmacotherapy. The islets of Langerhans are central to appropriate glucose homeostasis through their secretion of insulin, and islet function can be modified by ligands acting at the large number of GPCRs that islets express. The human islet GPCRome is not a static entity, but one that is altered under pathophysiological conditions and, in this review, we have compared expression of GPCR mRNAs in human islets obtained from normal weight range donors, and those with a weight range classified as obese. We have also considered the likely outcomes on islet function that the altered GPCR expression status confers and the possible impact that adipokines, secreted from expanded fat depots, could have at those GPCRs showing altered expression in obesity.

Development of Anti-Human CC Chemokine Receptor 9 Monoclonal Antibodies for Flow Cytometry

CC chemokine receptor 9 (CCR9) belongs to the beta chemokine receptor family and is mainly distributed on the surface of immature T lymphocytes and enterocytes. This receptor is highly expressed in rheumatoid arthritis, colitis, type 2 diabetes, and various tumors. Therefore, more sensitive monoclonal antibodies (mAbs) need to be developed to predict the prognosis of many high CCR9 expression diseases. Because CCR9 is a structurally unstable G protein-coupled receptor, it has been difficult to develop anti-CCR9 mAbs using the traditional method. This study developed anti-human CCR9 (hCCR9) mAbs for flow cytometry using a Cell-Based Immunization and Screening (CBIS) method. Two mice were immunized with hCCR9-overexpressed Chinese hamster ovary (CHO)-K1 cells (CHO/hCCR9), and hybridomas showing strong signals from CHO/hCCR9 and no signals from CHO-K1 cells were selected by flow cytometry. We established an anti-hCCR9 mAb, C₉Mab-1 (IgG₁, kappa), which detected hCCR9 in MOLT-4 leukemia T lymphoblast cells and CHO/hCCR9 cells by flow cytometry. Our study showed that an anti-hCCR9 mAb was developed more rapidly by the CBIS method than the previous method.

qPCR Analysis Reveals Association of Differential Expression of SRR, NFKB1, and PDE4B Genes With Type 2 Diabetes Mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a heterogeneous, metabolic, and chronic condition affecting vast numbers of the world's population. The related variables and T2DM associations have not been fully understood due to their diverse nature. However, functional genomics can facilitate understanding of the disease. This information will be useful in drug design, advanced diagnostic, and prognostic markers.

AIM

To understand the genetic causes of T2DM, this study was designed to identify the differentially expressed genes (DEGs) of the disease.

METHODS

We investigated 20 publicly available disease-specific cDNA datasets from Gene Expression Omnibus (GEO) containing several attributes including gene symbols and clone identifiers, GenBank accession numbers, and phenotypic feature coordinates. We analyzed an integrated system-level framework involving Gene Ontology (GO), protein motifs and co-expression analysis, pathway enrichment, and transcriptional factors to reveal the biological information of genes. A co-expression network was studied to highlight the genes that showed a coordinated expression pattern across a group of samples. The DEGs were validated by quantitative PCR (qPCR) to analyze the expression levels of case and control samples (50 each) using glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as the reference gene.

RESULTS

From the list of 50 DEGs, we ranked three T2DM-related genes (p < 0.05): SRR, NFKB1, and PDE4B. The enriched terms revealed a significant functional role in amino acid metabolism, signal transduction, transmembrane and intracellular transport, and other vital biological functions. DMBX1, TAL1, ZFP161, NFIC (66.7%), and NR1H4 (33.3%) are transcriptional factors associated with the regulatory mechanism. We found substantial enrichment of insulin signaling and other T2DM-related pathways, such as valine, leucine and isoleucine biosynthesis, serine and threonine metabolism, adipocytokine signaling pathway, P13K/Akt pathway, and Hedgehog signaling pathway. The expression profiles of these DEGs verified by qPCR showed a substantial level of twofold change (FC) expression (2-ΔΔCT) in the genes SRR (FC ≤ 0.12), NFKB1 (FC ≤ 1.09), and PDE4B (FC ≤ 0.9) compared to controls (FC ≥ 1.6). The downregulated expression of these genes is associated with pathophysiological development and metabolic disorders.

CONCLUSION

This study would help to modulate the therapeutic strategies for T2DM and could speed up drug discovery outcomes.