Suppression of Human Liver Cancer Cell Migration and Invasion via the GABAA Receptor

Regulation of neutrophil migration in acute pulmonary inflammation by extraneuronal α1 gamma-aminobutyric acidA receptors

Acute pulmonary inflammation is a common disease on intensive care. Due to the lack of specific treatments, lethality is still very high. The ionotropic GABAA-receptors are known from the central nervous system (CNS) and have recently been detected in the lung. These receptors have been shown to influence inflammatory processes. Opposing data has been reported, where both, GABA site agonists and antagonists achieved anti-inflammatory effects. The distribution of the 19 known GABAA-receptor subunits (α1-6, β1-3, γ1-3, δ, ε, π, θ and ρ1-3) and their role in inflammation remain unclear. In murine models of LPS- and bacteria-induced inflammation, Muscimol (GABAA-receptor agonist) and Bicuculline (antagonist) were administered before the onset of inflammation. Transcription of GABAA-receptor subunits was evaluated by real-time polymerase chain reaction. Neutrophil counts and adhesion molecule expression in wild type and GABAα1 knock-in mice were determined by flow-cytometry. Myeloperoxidase, neutrophil extracellular traps and cytokines were determined. In a model of ventilator-induced lung injury, blood gas analysis was performed using arterial blood. A multiplex western blot was done to assess signaling proteins. Muscimol and Bicuculline inhibited neutrophil influx in the bronchoalveolar lavage but did not change neutrophil activation. Both altered surface expression of adhesion molecules on neutrophils and reduced release of interleukin-6 (IL-6). The increased α1 subunit expression on lung epithelium and endothelium after inflammation was abolished by Muscimol and Bicuculline. In GABAα1-knock-in mice the protective effects of both agents were no longer observed. Only Muscimol lowered protein extravasation, improved blood gas analysis and lung function. A multiplex assay ascribed these anti-inflammatory effects to the influence of the IL-6 and phosphoinositide 3-kinase signaling pathways. In conclusion, Muscimol and Bicuculline exert various protective effects in two murine models of acute pulmonary inflammation. The multiple effects of Muscimol were linked to the inhibition of the proinflammatory signaling pathways IL-6 and PI3K.

Heat-killed Prevotella intermedia promotes the progression of oral squamous cell carcinoma by inhibiting the expression of tumor suppressors and affecting the tumor microenvironment

BACKGROUND

Oral microbial dysbiosis contributes to the development of oral squamous cell carcinoma (OSCC). Our previous study showed that Prevotella intermedia (P. intermedia) were enriched in the oral mucosal surface, plaque, and saliva of patients with OSCC. Intratumoral microbiome could reshape the immune system and influence the development of various tumors. However, the invasion status of human OSCC tissues by P. intermedia and the pathway through which intratumoral P. intermedia potentiates tumor progression remain unexplored.

METHODS

P. intermedia in human OSCC or normal tissues was detected by FISH. A mouse OSCC cell line SCC7 was adopted to investigate the effects of heat-killed P. intermedia treatment on cell proliferation, invasion, and cytokine release by using CCK-8 assay, transwell invasion assay and ELISA. Moreover, we established a mouse transplanted tumor model by using SCC7 cells, injected heat-killed P. intermedia into tumor tissues, and investigated the effects of heat-killed P. intermedia on tumor growth, invasion, cytokine levels, immune cell infiltrations, and expression levels by using gross observation, H&E staining, ELISA, immunohistochemistry, mRNA sequencing, and transcriptomic analysis.

RESULTS

Our results indicated that P. intermedia were abundant in OSCC and surrounding muscle tissues. Heat-killed P. intermedia promoted SCC7 cell proliferation, invasion and proinflammatory cytokine secretions, accelerated transplanted tumor growth in mice, exacerbate muscle and perineural invasion of OSCC, elevated the serum levels of IL-17A, IL-6, TNF-α, IFN-γ, and PD-L1, induced Treg cells M2 type macrophages in mouse transplanted tumors. The data of transcriptomic analysis revealed that heat-killed P. intermedia increased the expression levels of inflammatory cytokines and chemokines while reduced the expression levels of some tumor suppressor genes in mouse transplanted tumors. Additionally, IL-17 signaling pathway was upregulated whereas GABAergic system was downregulated by heat-killed P. intermedia treatment.

CONCLUSIONS

Taken together, our results suggest that P. intermedia could inhibit the expression of tumor suppressors, alter the tumor microenvironment, and promote the progression of OSCC.

γ-aminobutyric acid B2 receptor: A potential therapeutic target for cholangiocarcinoma in patients with diabetes mellitus

BACKGROUND

The association between diabetes mellitus (DM) and the increased risk and progression of cholangiocarcinoma (CCA) has been reported with unclear underlying mechanisms. Previous studies showed that γ-aminobutyric acid (GABA) B2 receptor (GABBR2) was upregulated in CCA cells cultured in high glucose (HG) conditions. Roles of GABA receptors in CCA progression have also been studied, but their association with DM and hyperglycemia in CCA remains unclarified.

AIM

To investigate the effects of hyperglycemia on GABBR2 expression and the potential use of GABBR2 as a CCA therapeutic target.

METHODS

CCA cells, KKU-055 and KKU-213A, were cultured in Dulbecco Modified Eagle's Medium supplemented with 5.6 mmol/L (normal glucose, NG) or 25 mmol/L (HG) glucose and assigned as NG and HG cells, respectively. GABBR2 expression in NG and HG cells was investigated using real-time quantitative polymerase chain reaction and western blot. Expression and localization of GABBR2 in CCA cells were determined using immunocytofluorescence. GABBR2 expression in tumor tissues from CCA patients with and without DM was studied using immunohistochemistry, and the correlations of GABBR2 with the clinicopathological characteristics of patients were analyzed using univariate analysis. Effects of baclofen, a GABA-B receptor agonist, on CCA cell proliferation and clonogenicity were tested using the MTT and clonogenic assays. Phospho-kinases arrays were used to screen the affected signaling pathways after baclofen treatment, and the candidate signaling molecules were validated using the public transcriptomic data and western blot.

RESULTS

GABBR2 expression in CCA cells was induced by HG in a dose- and time-dependent manner. CCA tissues from patients with DM and hyperglycemia also showed a significantly higher GABBR2 expression compared with tumor tissues from those with euglycemia (P < 0.01). High GABBR2 expression was significantly associated with a poorer non-papillary histological subtype but with smaller sizes of CCA tumors (P < 0.05). HG cells of both tested CCA cell lines were more sensitive to baclofen treatment. Baclofen significantly suppressed the proliferation and clonogenicity of CCA cells in both NG and HG conditions (P < 0.05). Phospho-kinase arrays suggested glycogen synthase kinase 3 (GSK3), β-catenin, and the signal transducer and activator of transcription 3 (STAT3) as candidate signaling molecules under the regulation of GABBR2, which were verified in NG and HG cells of the individual CCA cell lines. Cyclin D1 and c-Myc, the common downstream targets of GSK3/β-catenin and STAT3 involving cell proliferation, were accordingly downregulated after baclofen treatment.

CONCLUSION

GABBR2 is upregulated by HG and holds a promising role as a therapeutic target for CCA regardless of the glucose condition.

High mRNA expression of GABA receptors in human sperm with oligoasthenoteratozoospermia and teratozoospermia and its association with sperm parameters and intracytoplasmic sperm injection outcomes

Objective

This study investigated the mRNA expression of gamma-aminobutyric acid (GABA) receptors in the sperm of oligoasthenoteratozoospermic (OAT) and teratozoospermic (TER) men compared to normozoospermic (NOR) men, as well as the relationships between GABA receptor expression and sperm parameters, fertilization rate, and embryo quality.

Methods

The mRNA expression of GABA A-α1 and GABA B-R2 receptors in sperm was examined using reverse transcription–polymerase chain reaction in three groups of patients: NOR (n=32), OAT (n=22), and TER (n=45). The fertilization rate and embryo quality were assessed in 35 patients undergoing intracytoplasmic sperm injection (ICSI; 10 NOR, 10 OAT, and 15 TER men).

Results

OAT men had significantly higher mRNA expression of GABA A-α1 and GABA B-R2 receptors in sperm than NOR men; however, the difference between TER and NOR men was not significant. High levels of these receptors were significantly correlated with low sperm concentration, motility, and morphology, as well as the rate of good-quality embryos (GQEs) at the cleavage stage after ICSI. Patients whose female partners had a >50% GQE rate at the cleavage stage had significantly lower levels of GABA A-α1 receptor expression than those whose partners had a ≤50% GQE rate.

Conclusion

Our findings indicate that mRNA levels of GABA receptors in human sperm are correlated with poor sperm quality and associated with embryo development after ICSI treatment. The GABA A-α1 receptor in sperm has a stronger relationship with embryo quality at the cleavage stage than the GABA B-R2 receptor.

Distinct diagnostic and prognostic values of γ-aminobutyric acid type A receptor family genes in patients with colon adenocarcinoma

In the present study, the significance of GABA_A genes in colon adenocarcinoma (COAD) were investigated from the view of diagnosis and prognosis. All data were achieved from The Cancer Genome Atlas. Overall survival was analyzed by the Kaplan-Meier analyses and Cox regression model and the hazard ratios and 95% confidence interval were calculated for computation. The Database for Annotation, Visualization and Integrated Discovery, and the Biological Networks Gene Ontology (BiNGO) softwares were applied to assess the biological processes and Kyoto Encyclopedia of Genes and Genomes (KEGG) was used for pathway analysis to predict the biological function of GABA_A genes. The associated Gene Ontology and KEGG pathways were conducted by Gene Set Enrichment Analysis (GSEA). From receiver operating characteristics curves analysis, it was found that the expression of GABR, γ-aminobutyric acid type A receptor GABRA2, GABRA3, GABRB2, GABRB3, GABRG2, GABRG3, GABRD, GABRE were correlated with COAD occurrence [P<0.0001, area under the curve (AUC)>0.7]. The low expression of the GABRB1, GABRD, GABRP and GABRQ in genes after tumor staging adjustment were positively correlated with the overall survival rate [P=0.049, hazard ratio (HR)=1.517, 95% confidence interval (CI)=1.001–2.297; P=0.006, HR=1.807, 95% CI=1.180–2.765; P=0.005, HR=1.833, 95% CI=1.196–2.810; P=0.034, HR=1.578, 95% CI=1.036–2.405). GSEA showed enrichment of cell matrix adhesion, integrin binding, angiogenesis, endothelial growth factor and endothelial migration regulation in patients with COAD with GABRD overexpression. GABRB1, GABRD, GABRP and GABRQ were associated with the prognostic factors of COAD. The expression levels of GABRA2, GABRA3, GABRB2, GABRB3, GABRG2, GABRD and GABRE may allow differentiation between tumor tissues and adjacent normal tissues.

Unique and independent role of the GABAB1 subunit in embryo implantation and uterine decidualization in mice

Embryo implantation and decidualization are crucial for successful pregnancy, which include multiple genes and signaling pathways, while the precise mechanism regarding embryo implantation and decidualization has yet to be explored. The GABA which activates GABA_A or GABA_B receptors has been found playing an important role in early pregnancy. Here we seek to investigate whether GABA_B receptors participate in embryo implantation in mice. This study first characterized the spatiotemporal expression pattern of GABA_B receptors in the uterus during the peri-implantation period and found that GABA_B1 expression was drastically upregulated in stromal cells on days 4–6, a period of embryo implantation and early stages of decidualization. Embryo delayed implantation and oil-induced decidualization models were further used to confirm that the GABA_B1 was associated with embryo implantation and decidualization. We also found estrogen or progesterone had no directly effect on expression of GABA_B1 in ovariectomized model. Because we were unable to detect significant GABA_B2 which couples with GABA_B1 to form whole GABA_B receptors, and the agonist and antagonist of whole GABA_B receptors had weak effect on the proliferation and differentiation of stromal cells as well, we excluded the possibility whole GABA_B receptors function, and concluded it should be non-classical signals of GABA_B1 involving in embryo implantation and decidualization. Future studies should focus on investigating the roles and mechanisms of GABA_B1 during embryo implantation and decidualization.

An Updated Review on Pharmaceutical Properties of Gamma-Aminobutyric Acid

Gamma-aminobutyric acid (Gaba) is a non-proteinogenic amino acid that is widely present in microorganisms, plants, and vertebrates. So far, Gaba is well known as a main inhibitory neurotransmitter in the central nervous system. Its physiological roles are related to the modulation of synaptic transmission, the promotion of neuronal development and relaxation, and the prevention of sleeplessness and depression. Besides, various pharmaceutical properties of Gaba on non-neuronal peripheral tissues and organs were also reported due to anti-hypertension, anti-diabetes, anti-cancer, antioxidant, anti-inflammation, anti-microbial, anti-allergy, hepato-protection, reno-protection, and intestinal protection. Therefore, Gaba may be considered as potential alternative therapeutics for prevention and treatment of various diseases. Accordingly, this updated review was mainly focused to describe the pharmaceutical properties of Gaba as well as emphasize its important role regarding human health.

Role of the nervous system in cancer metastasis

Cancer remains as one of the leading cause of death worldwide. The development of cancer involves an intricate process, wherein many identified and unidentified factors play a role. Although most studies have focused on the genetic abnormalities which initiate and promote cancer, there is overwhelming evidence that tumors interact within their environment by direct cell-to-cell contact and with signaling molecules, suggesting that cancer cells can influence their microenvironment and bidirectionally communicate with other systems. However, only in recent years the role of the nervous system has been recognized as a major contributor to cancer development and metastasis. The nervous system governs functional activities of many organs, and, as tumors are not independent organs within an organism, this system is integrally involved in tumor growth and progression.

Aberrant epigenetic regulation of GABRP associates with aggressive phenotype of ovarian cancer

Metastasis is a major cause of therapeutic failure in ovarian cancer. To elucidate molecular mechanisms of ovarian cancer metastasis, we previously established a metastatic xenograft mouse model using human ovarian carcinoma SK-OV-3 cells. Using gene expression profiling, we found that γ-aminobutyric acid (GABA)_A receptor π subunit (GABRP) expression was upregulated (>4-fold) in metastatic tissues from our xenograft mice compared with SK-OV-3 cells. Importantly, GABRP knockdown diminished the migration and invasion of SK-OV-3 cells, and reduced extracellular signal-regulated kinase (ERK) activation while overexpression of GABRP exhibited significantly increased cell migration, invasion and ERK activation. Moreover, treatment with the mitogen-activated protein kinase (MAPK)/ERK kinase (MEK) inhibitor U0126 similarly suppressed the migration and invasion of SK-OV-3 cells, implying that GABRP promotes these cellular behaviors by activating the MAPK/ERK pathway. Using genome-wide DNA methylation profiling, we identified hypomethylated CpG sites in the GABRP promoter in metastatic tissues from the xenograft mice compared with SK-OV-3 cells. Treatment with a DNA methyltransferase inhibitor demonstrated that methylation at −963 bp from the GABRP transcription start site (−963 CpG site) was critical for the epigenetic regulation of GABRP. Finally, we analyzed human ovarian cancer patient samples and showed DNA hypomethylation at the GABRP −963 CpG site in advanced stage, but not early-stage, primary tumors compared with their paired normal tissues. These findings suggest that GABRP enhances the aggressive phenotype of ovarian cancer cells, and that the DNA methylation status of the GABRP −963 CpG site may be useful for predicting the metastatic potential in ovarian cancer patients.

RBBP6: a potential biomarker of apoptosis induction in human cervical cancer cell lines

Overexpression of RBBP6 in cancers of the colon, lung, and esophagus makes it a potential target in anticancer therapy. This is especially important because RBBP6 associates with the tumor suppressor gene p53, the inactivation of which has been linked to over 50% of all cancer types. However, the expression of RBBP6 in cancer and its interaction with p53 are yet to be understood in order to determine whether or not RBBP6 is cancer promoting and therefore a potential biomarker. In this study, we manipulated RBBP6 expression levels followed by treatment with either camptothecin or γ-aminobutyric acid in cervical cancer cells to induce apoptosis or cell cycle arrest. We began by staining human cervical cancer tissue sections with anti-RBBP6 monoclonal antibody to evaluate the extent of expression of RBBP6 in patients’ specimens. We followed on with silencing the overexpression of RBBP6 and treatment with anticancer agents to evaluate how the specimens respond to combinational therapy. Apoptosis induction was evaluated through confocal microscope, and flow cytometry using annexin V staining, and also by checking the mitochondrial and caspase-3/7 activity. Cell cycle arrest was evaluated using flow cytometry through staining with propidium iodide. RBBP6 was highly expressed in cervical cancer tissue sections that were in stage II or III of development. Silencing RBBP6 followed by treatment with γ-aminobutyric acid and camptothecin seems to sensitize cells to apoptosis induction rather than cell cycle arrest. Overexpression of RBBP6 seems to promote S-phase in cell cycle and cell proliferation. These results predict a proliferative role of RBBP6 in cancer progression rather than as a cancer-causing gene. Furthermore, sensitization of cells to camptothecin-induced apoptosis by RBBP6 targeting suggests a promising tool for halting cervical cancer progression.

Modulatory role of garlicin in migration and invasion of intrahepatic cholangiocarcinoma via PI3K/AKT pathway

Increasing evidences have indicated the role of garlicin in inhibiting the progression of various tumors including glioma, pulmonary carcinoma and pancreatic carcinoma, via mediating cell apoptosis or cell cycle. The regulatory effect and related molecular mechanism of garlicin in intrahepatic cholangiocarcinoma, however, remained unknown. This study thus aimed to investigate this scientific issue. HCCC-9810 cell line was treated with serially diluted garlicin, followed by cell proliferation assay using MTT approach. Transwell migration and invasion assays were further employed the regulatory effect of garlicin. The expression level of p-AKT and AKT proteins in tumor cells was quantified by Western blot. The growth of tumor cells was significantly inhibited by high concentration of garlicin (> 1.5 μM). Lower concentration of garlicin showed dose-dependent inhibition of tumor cell invasion and migration. After using specific agonist IGF-1 (50 ng/mL) of PI3K/AKT signaling pathway, such facilitating effects of garlicin were depressed (P < 0.05). Western blotting showed significantly decreased phosphorylation level of AKT after treated with gradient concentrations of garlicin, while leaving the total AKT protein level unchanged. Garlicin may inhibit the invasion and migration of intrahepatic cholangiocarcinoma cells via inhibiting PI3K/AKT signaling pathway.