Effect of macrophage migration inhibitory factor on pulmonary vein arrhythmogenesis through late sodium current.

AIMS: Macrophage migration inhibitory factor (MIF), a pleiotropic inflammatory cytokine, is highly expressed in patients with atrial fibrillation (AF). Inflammation increases the risk of AF and is primarily triggered by pulmonary vein (PV) arrhythmogenesis. This study investigated whether MIF can modulate the electrical activity of the PV and examined the underlying mechanisms of MIF. METHODS AND RESULTS: A conventional microelectrode, a whole-cell patch clamp, western blotting, and immunofluorescent confocal microscopy were used to investigate electrical activity, calcium (Ca2+) regulation, protein expression, ionic currents, and cytosolic reactive oxygen species (ROS) in rabbit PV tissue and isolated single cardiomyocytes with and without MIF incubation (100 ng/mL, treated for 6 h). The MIF (100 ng/mL)-treated PV tissue (n = 8) demonstrated a faster beating rate (1.8 ± 0.2 vs. 2.6 ± 0.1 Hz, P < 0.05), higher incidence of triggered activity (12.5 vs. 100%, P < 0.05), and premature atrial beat (0 vs. 100%, P < 0.05) than the control PV tissue (n = 8). Compared with the control PV cardiomyocytes, MIF-treated single PV cardiomyocytes had larger Ca2+ transients (0.6 ± 0.1 vs. 1.0 ± 0.1, ΔF/F0, P < 0.05), sarcoplasmic reticulum Ca2+ content (0.9 ± 0.20 vs. 1.7 ± 0.3 mM of cytosol, P < 0.05), and cytosolic ROS (146.8 ± 5.3 vs. 163.7 ± 3.8, ΔF/F0, P < 0.05). Moreover, MIF-treated PV cardiomyocytes exhibited larger late sodium currents (INa-Late), L-type Ca2+ currents, and Na+/Ca2+ exchanger currents than the control PV cardiomyocytes. KN93 [a selective calcium/calmodulin-dependent protein kinase II (CaMKII) blocker, 1 µM], ranolazine (an INa-Late inhibitor, 10 µM), and N-(mercaptopropionyl) glycine (ROS inhibitor, 10 mM) reduced the beating rates and the incidence of triggered activity and premature captures in the MIF-treated PV tissue. CONCLUSION: Macrophage migration inhibitory factor increased PV arrhythmogenesis through Na+ and Ca2+ dysregulation through the ROS activation of CaMKII signalling, which may contribute to the genesis of AF during inflammation. Anti-CaMKII treatment may reverse PV arrhythmogenesis. Our results clearly reveal a key link between MIF and AF and offer a viable therapeutic target for AF treatment.

Vascular endothelial growth factor on Runt-related transcript factor-2 in aortic valve cells.

BACKGROUND: Calcific aortic valve disease is associated with ageing and high mortality. However, no effective pharmacological treatment has been developed. Vascular endothelial growth factor (VEGF) and its receptor are overexpressed in the calcified aortic valve tissue. However, the role of VEGF in calcific aortic valve disease pathogenesis and its underlying mechanisms remain unclear. MATERIALS AND METHODS: Runt-related transcription factor 2 expression and calcium-related signalling were investigated in porcine valvular interstitial cells with or without human VEGF-A recombinant protein (VEGF165 , 1-100 ng/mL) treatment and/or calmodulin-dependent kinase II (CaMKII) inhibitor (KN93, 10 µmol/L) and inositol triphosphate receptor inhibitor (2-aminoethyldiphenyl borate, 30 µmol/L) for 5 days. RESULTS: VEGF165 -treated cells had higher Runt-related transcription factor 2 expression and CaMKII/ adenosine 3',5'-monophosphate response element-binding protein (CREB) signalling activation than did control cells. KN93 reduced Runt-related transcription factor 2 expression and CREB phosphorylation in VEGF165 -treated cells. The 2-aminoethyldiphenyl borate also reduced Runt-related transcription factor 2 expression in VICs treated with VEGF165 . CONCLUSION: VEGF upregulated Runt-related transcription factor 2 expression in VICs by activating the IP3R/CaMKII/CREB signalling pathway.

The Role of EREG/EGFR Pathway in Tumor Progression.

Aberrant activation of the epidermal growth factor receptor (EGFR/ERBB1) by erythroblastic leukemia viral oncogene homolog (ERBB) ligands contributes to various tumor malignancies, including lung cancer and colorectal cancer (CRC). Epiregulin (EREG) is one of the EGFR ligands and is low expressed in most normal tissues. Elevated EREG in various cancers mainly activates EGFR signaling pathways and promotes cancer progression. Notably, a higher EREG expression level in CRC with wild-type Kirsten rat sarcoma viral oncogene homolog (KRAS) is related to better efficacy of therapeutic treatment. By contrast, the resistance of anti-EGFR therapy in CRC was driven by low EREG expression, aberrant genetic mutation and signal pathway alterations. Additionally, EREG overexpression in non-small cell lung cancer (NSCLC) is anticipated to be a therapeutic target for EGFR-tyrosine kinase inhibitor (EGFR-TKI). However, recent findings indicate that EREG derived from macrophages promotes NSCLC cell resistance to EGFR-TKI treatment. The emerging events of EREG-mediated tumor promotion signals are generated by autocrine and paracrine loops that arise from tumor epithelial cells, fibroblasts, and macrophages in the tumor microenvironment (TME). The TME is a crucial element for the development of various cancer types and drug resistance. The regulation of EREG/EGFR pathways depends on distinct oncogenic driver mutations and cell contexts that allows specific pharmacological targeting alone or combinational treatment for tailored therapy. Novel strategies targeting EREG/EGFR, tumor-associated macrophages, and alternative activation oncoproteins are under development or undergoing clinical trials. In this review, we summarize the clinical outcomes of EREG expression and the interaction of this ligand in the TME. The EREG/EGFR pathway may be a potential target and may be combined with other driver mutation targets to combat specific cancers.

Empagliflozin and Liraglutide Differentially Modulate Cardiac Metabolism in Diabetic Cardiomyopathy in Rats.

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 inhibitors (SGLT2is) are antihyperglycemic agents with cardioprotective properties against diabetic cardiomyopathy (DCM). However, the distinctive mechanisms underlying GLP-1RAs and SGLT2is in DCM are not fully elucidated. The purpose of this study was to investigate the impacts of GLP1RAs and/or SGLT2is on myocardial energy metabolism, cardiac function, and apoptosis signaling in DCM. Biochemistry and echocardiograms were studied before and after treatment with empagliflozin (10 mg/kg/day, oral gavage), and/or liraglutide (200 µg/kg every 12 h, subcutaneously) for 4 weeks in male Wistar rats with streptozotocin (65 mg/kg intraperitoneally)-induced diabetes. Cardiac fibrosis, apoptosis, and protein expression of metabolic and inflammatory signaling molecules were evaluated by histopathology and Western blotting in ventricular cardiomyocytes of different groups. Empagliflozin and liraglutide normalized myocardial dysfunction in diabetic rats. Upregulation of phosphorylated-acetyl coenzyme A carboxylase, carnitine palmitoyltransferase 1ß, cluster of differentiation 36, and peroxisome proliferator-activated receptor-gamma coactivator, and downregulation of glucose transporter 4, the ratio of phosphorylated adenosine monophosphate-activated protein kinase α2 to adenosine monophosphate-activated protein kinase α2, and the ratio of phosphorylated protein kinase B to protein kinase B in diabetic cardiomyocytes were restored by treatment with empagliflozin or liraglutide. Nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3, interleukin-1ß, tumor necrosis factor-α, and cleaved caspase-1 were significantly downregulated in empagliflozin-treated and liraglutide-treated diabetic rats. Both empagliflozin-treated and liraglutide-treated diabetic rats exhibited attenuated myocardial fibrosis and apoptosis. Empagliflozin modulated fatty acid and glucose metabolism, while liraglutide regulated inflammation and apoptosis in DCM. The better effects of combined treatment with GLP-1RAs and SGLT2is may lead to a potential strategy targeting DCM.

Pitx2c inhibition increases atrial fibroblast activity: Implications in atrial arrhythmogenesis.

BACKGROUND: A Pitx2c deficiency increases the risk of atrial fibrillation (AF). Atrial structural remodelling with fibrosis blocks electrical conduction and leads to arrhythmogenesis. A Pitx2c deficiency enhances profibrotic transforming growth factor (TGF)-ß expression and calcium dysregulation, suggesting that Pitx2c may play a role in atrial fibrosis. The purposes of this study were to evaluate whether a Pitx2c deficiency modulates cardiac fibroblast activity and study the underlying mechanisms. MATERIALS AND METHODS: A migration assay, proliferation analysis, Western blot analysis and calcium fluorescence imaging were conducted in Pitx2c-knockdown human atrial fibroblasts (HAFs) using short hairpin (sh)RNA or small interfering (si)RNA. RESULTS: Compared to control HAFs, Pitx2c-knockdown HAFs had a greater migration but a similar proliferative ability. Pitx2c-knockdown HAFs had a higher calcium influx with enhanced phosphorylation of calmodulin kinase II (CaMKII), α-smooth muscle actin and matrix metalloproteinase-2. In the presence of a CaMKII inhibitor (KN-93, 0.5 µmol/L), control and Pitx2c-knockdown HAFs exhibited similar migratory abilities. CONCLUSION: These findings suggest that downregulation of Pitx2c may regulate atrial fibrosis through modulating calcium homeostasis, which may contribute to its role in anti-atrial fibrosis, and Pitx2c downregulation may change the atrial electrophysiology and AF occurrence through modulating fibroblast activity.

Hepatoma cell functions modulated by NEK2 are associated with liver cancer progression.

NEK2 (NIMA-related expressed kinase 2) is a serine/threonine centrosomal kinase that acts as a critical regulator of centrosome structure and function. Aberrant NEK2 activities lead to failure in regulating centrosome duplication. NEK2 overexpression promotes tumorigenesis and is associated with poor prognosis in several cancers. Increased NEK2 expression during the late pathological stage has been detected in the Oncomine liver dataset and hepatocellular carcinoma (HCC) specimens. Elevated NEK2 protein is associated with poor overall survival in patients with HCC. However, the precise roles and mechanisms of NEK2 in liver cancer progression remain largely unknown. An earlier functional study revealed that NEK2 mediates drug resistance (cisplatin or lipo-doxorubicin) via expression of an ABCC10 transporter. Active angiogenesis and metastasis underlie the rapid recurrence and poor survival of HCC. Results from the current study showed that NEK2 mediates tumor growth, metastasis and angiogenesis in vivo. NEK2-mediated drug resistance was blocked by a specific PI3K or AKT inhibitor. Moreover, NEK2 mediated liver cancer cell migration via pAKT/NF-κB signaling and matrix metalloproteinase (MMP) activation. Angiogenesis was induced via the same signaling pathway and IL-8 stimulation. Our findings collectively indicate that NEK2 modulates hepatoma cell functions, including growth, drug resistance, metastasis and angiogenesis via downstream genes activation.

Silencing A7-nAChR levels increases the sensitivity of gastric cancer cells to ixabepilone treatment.

Gastric cancer is an important health issue worldwide. Currently, improving the therapeutic efficacy of chemotherapy drugs is an important goal of cancer research. Alpha-7 nicotine acetylcholine receptor (A7-nAChR) is the key molecule that mediates gastric cancer progression, metastasis, and therapy responses; however, the role of A7-nAChR in the therapeutic efficacy of ixabepilone remains unclear. A7-nAChR expression was silenced by small interfering RNA (siRNA) technology. The cytotoxicity of ixabepilone was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and ixabepilone-induced apoptosis was analyzed by flow cytometry and annexin V/propidium iodide (PI) apoptotic assay. The expression patterns of anti-apoptotic proteins (AKT, phospho-AKT, Mcl-1, and Bcl-2) and pro-apoptotic proteins (Bad and Bax) were determined by western blot. Our study found that A7-nAChR knockdown (A7-nAChR-KD) AGS cells were more sensitive to ixabepilone administration than scrambled control AGS cells. We found that A7-nAChR knockdown enhanced ixabepilone-induced cell death as evidenced by the increased number of annexin V-positive (apoptotic) cells. After scrambled control and A7-nAChR-KD cells were treated with ixabepilone, we found that pAKT and AKT levels were significantly reduced in both groups of cells. The levels of Bcl-2 and the anti-apoptotic Mcl-1 isoform increased dramatically after ixabepilone treatment in scrambled control cells but not in A7-nAChR-KD cells. Bad and Bax levels did not change between the treatment group and vehicle group in both A7-nAChR-KD and scrambled control cells, whereas cleaved PARP levels dramatically increased in ixabepilone-treated A7-nAChR-KD cells. Our results demonstrated that knockdown of A7-nAChR enhanced the sensitivity of gastric cancer cells to ixabepilone administration. Thus, the A7-nAChR expression level in patients with gastric cancer may be a good indicator of ixabepilone sensitivity.

The α7-nicotinic acetylcholine receptor mediates the sensitivity of gastric cancer cells to taxanes.

Gastric cancer is difficult to cure because most patients are diagnosed at an advanced disease stage. Systemic chemotherapy remains an important therapy for gastric cancer, but both progression-free survival and disease-free survival associated with various combination regimens are limited because of refractoriness and chemoresistance. Accumulating evidence has revealed that the homomeric α7-nicotinic acetylcholine receptor (A7-nAChR) promotes human gastric cancer by driving cancer cell proliferation, migration, and metastasis. Therefore, A7-nAChR may serve as a potential therapeutic target for gastric cancer. However, the role of A7-nAChR in taxane therapy for gastric cancer was unclear. Cells were subjected to A7-nAChR knockdown (A7-nAChR KD) using short interfering RNA (siRNA). The anti-proliferative effects of taxane were assessed via 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL), and cell cycle distribution assays. A7-nAChR-KD cells exhibited low resistance to docetaxel and paclitaxel treatment, as measured by the MTT assay. Following paclitaxel treatment, the proportion of apoptotic cells was higher among A7-nAChR-KD cells than among scrambled control cells, as measured by cell cycle distribution and TUNEL assays. Further molecular analyses showed a reduction in the pAKT levels and a dramatic increase in the Bad levels in paclitaxel-treated A7-nAChR-KD cells but not in scrambled control cells. Following paclitaxel treatment, the level of Bax was slightly increased in both cell populations, whereas Poly (ADP-ribose) polymerase (PARP) cleavage was increased only in A7-nAChR-KD cells. These findings indicate that A7-nAChR-KD cells are more sensitive to paclitaxel treatment. We conclude that A7-nAChR may be a key biomarker for assessing the chemosensitivity of gastric cancer cells to taxane.

Glucose-regulated protein 94 mediates cancer progression via AKT and eNOS in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a crucial health issue worldwide. High glucose-regulated protein 94 (GRP94) expression has been observed in different types of cancer, suggesting a link between tumor progression and GRP94 expression. However, the mechanisms underlying the role of GRP94 in HCC progression remain unclear. We used specific small hairpin RNA (shRNA) to manipulate GRP94 expression in HCC cells. Tissue arrays, MTT assays, xCELLigence assays, and in vivo xenograft model were performed to identify clinicopathological correlations and to analyze cell growth. We found that high GRP94 expression reflected a poor response and a lower survival rate. In vitro and in vivo studies showed that silencing GRP94 suppressed cancer progression. Mechanistically, GRP94 knockdown reduced AKT, phospho-AKT, and eNOS levels but did not influence the AMPK pathway. Our results demonstrated that GRP94 is a key molecule in HCC progression that modulates the AKT pathway and eNOS levels. Our findings suggest that GRP94 may be a new prognostic and therapeutic target for HCC.

Glucose-regulated protein 94 mediates metastasis by CCT8 and the JNK pathway in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide. Cancer metastasis is a major obstacle in clinical cancer therapy. The mechanisms underlying the metastasis of HCC remain unclear. Glucose-regulated protein 94 (GRP94) is a key protein involved in mediating cancer progression, and it is highly expressed in HCC specimens. However, the role of GRP94 in cancer metastasis is unclear. A specific short hairpin RNA (shRNA) was employed to knock down GRP94 gene expression in HCC cell lines. Wound-healing migration, transwell migration, and invasion assays were performed to determine the migration and invasive ability of HCC cells. We demonstrated that silencing GRP94 inhibited HCC cell wound healing, migration, and invasion. Furthermore, our findings indicated that GRP94 knockdown might attenuate HCC cell metastasis by inhibiting CCT8/c-Jun/EMT signaling. Our study indicated that silencing GRP94 significantly reduced the migration and invasion abilities of HCC cells. Moreover, depleting GRP94 inhibited cell migration and invasion by downregulating CCT8/c-Jun signaling. Thus, our data suggest that the GRP94/CCT8/c-Jun/EMT signaling cascade might be a new therapeutic target for HCC.

Negative modulation of the epigenetic regulator, UHRF1, by thyroid hormone receptors suppresses liver cancer cell growth.

The thyroid hormone, 3,3',5-triiodo-l-thyronine (T3 ), mediates several physiological processes, including embryonic development, cellular differentiation, metabolism and regulation of cell proliferation. Thyroid hormone (T3 ) and its receptor (TR) are involved in metabolism and growth. In addition to their developmental and metabolic functions, TRs play a tumor suppressor role, and therefore, their aberrant expression can lead to tumor transformation. Aberrant epigenetic silencing of tumor suppressor genes promotes cancer progression. The epigenetic regulator, Ubiquitin-like with PHD and ring finger domains 1 (UHRF1), is overexpressed in various cancers. In our study, we demonstrated that T3 negatively regulates UHRF1 expression, both in vitro and in vivo. Our results further indicate that UHRF1 regulation by T3 is indirect and mediated by Sp1. Sp1-binding elements of UHRF1 were identified at positions -664/-505 of the promoter region using the luciferase and chromatin immunoprecipitation assays. Notably, UHRF1 and Sp1 levels were elevated in subgroups of hepatocellular carcinoma patients and inversely correlated with TRα1 expression. Knockdown of UHRF1 expression should therefore provide a means to inhibit hepatoma cell proliferation. Expression of UHRF1 was downregulated by TRs, in turn, relieving silencing of the UHRF1 target gene, p21. Based on the collective findings, we propose that T3 /TR signaling induces hepatoma cell growth inhibition via UHRF1 repression.

Glucose-regulated protein 78 mediates the anticancer efficacy of shikonin in hormone-refractory prostate cancer cells.

Glucose-regulated protein 78 (GRP78) is a key modulator of prostate cancer progression and therapeutic resistance. Prostate cancer is a worldwide health problem, and therapeutic resistance is a critical obstacle for the treatment of hormone-refractory prostate cancer patients. Shikonin inhibits prostate cancer proliferation and metastasis. However, the role of GRP78 in the cytotoxic effect of shikonin in prostate cancer cells remains unclear. GRP78 expression was abolished using small interfering RNA (siRNA), and the anticancer effects of shikonin were assessed using MTT assays, the XCELLigence biosensor, flow cytometric cell cycle analysis, and Annexin V-PI apoptotic assays. PC-3 cells expressed more GRP78 than DU-145 cells, and the MTT assays revealed that DU-145 cells were more sensitive to shikonin than PC-3 cells. GRP78 knockdown (GRP78KD) PC-3 cells were more sensitive to shikonin treatment than scrambled siRNA control cells. Based on cell cycle analysis and AnnexinV-PI apoptotic assays, apoptosis dramatically increased in GRP78KD cells compared with the control PC-3 in response to shikonin. Finally, in response to shikonin treatment, Mcl-1 and Bcl-2 levels increased in the scrambled control cells treated with shikonin, whereas Bcl-2 decreased and Mcl-1 slightly increased in the GRP78KD PC-3 cells. The levels of Bax and Bad did not change in the scrambled control or GRP78KD cells after shikonin treatment. These results are consistent with the increased sensitivity to shikonin after knockdown of GRP78. GRP78 expression may determine the therapeutic efficacy of shikonin against prostate cancer cells.

Alpha 7-nicotinic acetylcholine receptor mediates the sensitivity of gastric cancer cells to 5-fluorouracil.

Gastric cancer is the second most common cause of cancer mortality worldwide. Most gastric cancer patients are asymptomatic until the advanced stages, for which current therapeutic treatments are suboptimal. 5-Fluorouracil (5-FU), an antimetabolite agent, is widely used in gastric cancer therapy. However, the presence of drug resistance in gastric cancer patients reduces the cytotoxic activity of 5-FU. In gastric cancer, no research has yet been conducted to analyze the effect of alpha 7-nicotinic acetylcholine receptor (A7-nAChR) on the therapeutic response to 5-FU. In this study, we generated A7-nAChR knockdown (A7-nAChR-KD) AGS cells by a small interfering RNA (siRNA) technique in gastric cancer cells. The anti-proliferative effects of 5-FU were determined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, a terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay, and cell cycle determination. We found that A7-nAChR-KD cells were more resistant to 5-FU treatment compared with the scrambled control cells according to the MTT assay. The apoptotic cell population was increased more in scrambled control cells treated with 5-FU than A7-nAChR-KD cells according to the cell cycle distribution and TUNEL assays. We analyzed expression levels of survival and apoptosis-associated proteins (pAkt, Akt, Mcl-1, Bcl-2, Bad, and Bax) altered by 5-FU treatment. Survival and antiapoptosis signaling (pAkt, Akt, Mcl-1 and Bcl-2) was downregulated, and the proapoptotic proteins (Bad and Bax) were upregulated in 5-FU-treated control cells but expression levels of Bcl-2, Bad, and Bad were not altered in 5-FU-treated A7-nAChR-KD cells. This is consistent with A7-nAChR-KD cells exhibiting more resistance to 5-FU treatment. In our study, we carried out an in vitro study on AGS gastric cancer cell line to elucidate the anticancer efficacy and molecular mechanisms of A7-nAChR silencing on 5-FU-induced cell death. The results clearly showed that depletion of A7-nAChR suppressed the drug sensitivity of gastric cancer cells to 5-FU treatment.

Thyroid hormone actions in liver cancer.

The thyroid hormone 3,3',5-triiodo-L-thyronine (T3) mediates several physiological processes, including embryonic development, cellular differentiation, metabolism, and the regulation of cell proliferation. Thyroid hormone receptors (TRs) generally act as heterodimers with the retinoid X receptor (RXR) to regulate target genes. In addition to their developmental and metabolic functions, TRs have been shown to play a tumor suppressor role, suggesting that their aberrant expression can lead to tumor transformation. Conversely, recent reports have shown an association between overexpression of wild-type TRs and tumor metastasis. Signaling crosstalk between T3/TR and other pathways or specific TR coregulators appear to affect tumor development. Since TR actions are complex as well as cell context-, tissue- and time-specific, aberrant expression of the various TR isoforms has different effects during diverse tumorigenesis. Therefore, elucidation of the T3/TR signaling mechanisms in cancers should facilitate the identification of novel therapeutic targets. This review provides a summary of recent studies focusing on the role of TRs in hepatocellular carcinomas (HCCs).

The relationship between typhoons' peripheral circulation and ground-level ozone concentrations in central Taiwan.

Surface data of meteorological parameters (wind speed, wind direction, and mixing height) and air pollutant concentrations (O3, NO, and NO2) were collected for a 92-day period associated with typhoon formation in 2005. The influence of typhoons on O3 concentration were defined by azimuth and distance from Taiwan, and Types A, B, and C correspond to typhoons less than 1,500 km from Taiwan and located between azimuths 45° and 135°, 135° and 225°, and 225° and 45°, respectively. Type D corresponds to typhoons more than 1,500 km from Taiwan. Titration reactions were conducted at three temporal phases: 2000-0700, 0800-1100, and 1200-1400 LST (Local Standard Time). The air pollution model (TAPM) was used to simulate wind fields and trajectories of air masses. It was determined that typhoon position affected O3 concentration, temporal and spatial patterns of O3 titration and vertical meteorological characteristics, which were not all at the statistically significant level.

Engineering Glucosamine-6-Phosphate Synthase to Achieve Efficient One-Step Biosynthesis of Glucosamine.

As an important functional monosaccharide, glucosamine (GlcN) is widely used in fields such as medicine, food nutrition, and health care. Here, we report a distinct GlcN biosynthesis method that utilizes engineered Bacillus subtilis glucosamine-6-phosphate synthase (BsGlmS) to convert D-fructose to directly generate GlcN. The best variant obtained by using a combinatorial active-site saturation test/iterative saturation mutagenesis (CAST/ISM) strategy was a quadruple mutant S596D/V597G/S347H/G299Q (BsGlmS-BK19), which has a catalytic activity 1736-fold that of the wild type toward D-fructose. Upon using mutant BK19 as a whole-cell catalyst, D-fructose was converted into GlcN with 65.32% conversion in 6 h, whereas the wild type only attained a conversion rate of 0.31% under the same conditions. Molecular docking and molecular dynamics simulations were implemented to provide insights into the mechanism underlying the enhanced activity of BK19. Importantly, the BsGlmS-BK19 variant specifically catalyzes D-fructose without the need for phosphorylated substrates, representing a significant advancement in GlcN biosynthesis.

Dickkopf 4 positively regulated by the thyroid hormone receptor suppresses cell invasion in human hepatoma cells.

UNLABELLED: Thyroid hormone (T(3)) mediates cellular growth, development, and differentiation by binding to the nuclear thyroid hormone receptor (TR). Recent studies suggest that long-term hypothyroidism is associated with human hepatocellular carcinoma (HCC) independent from other major HCC risk factors. Dickkopf (DKK) 4, a secreted protein, antagonizes the Wnt signal pathway. In this study, we demonstrate that T(3) may play a suppressor role by inducing DKK4 expression in HCC cells at both the messenger RNA (mRNA) and protein levels. DKK4 was down-regulated in 67.5% of HCC cancerous tissues. The decrease in DKK4 levels was accompanied by a concomitant decrease in TR protein levels in the matched cancerous tissues in 31% of tissues compared by immunoblotting with the adjacent noncancerous tissues. Further, TR and DKK4 expression levels were positively correlated in both normal and cancerous specimens by tissue array analysis. In function assays, stable DKK4 transfected into J7 or HepG2 cells decreased cell invasion in vitro. Conversely, knocking down DKK4 restores cell invasiveness. DKK4-expressing J7 clones showed increased degradation of ß-catenin, but down-regulation of CD44, cyclin D1, and c-Jun. To investigate the effect of DKK4 and TR on tumor growth in vivo, we established a xenograft of J7 cells in nude mice. J7-DKK4 and J7-TRα1 overexpressing mice, which displayed growth arrest, lower lung colony formation index, and smaller tumor size than in control mice, supporting an inhibitory role of DKK4 in tumor progression. CONCLUSION: Taken together, these data suggest that the TR/DKK4/Wnt/ß-catenin cascade influences the proliferation and migration of hepatoma cells during the metastasis process and support a tumor suppressor role of the TR.

Overexpression of ADP-ribosylation factor 1 in human gastric carcinoma and its clinicopathological significance.

Gastric cancer is the sixth leading cause of cancer-related death in Taiwan, and the identification of related factors is essential to increase patient survival. ADP-ribosylation factor 1 (ARF1) was initially identified using 2-D electrophoresis combined with MALDI-time-of-flight mass spectrometry. ADP-ribosylation factor 1 belongs to the Ras superfamily or GTP-binding protein family and has been shown to enhance cell proliferation. In the current study, we evaluated the potential of ARF1 as a biomarker for gastric cancer detection. ADP-ribosylation factor 1 mRNA was upregulated in tumor tissues (compared with adjacent non-tumor tissues, n = 55) in approximately 67.2% of gastric cancer patients. Expression of ARF1 protein was additionally observed using Western blot and immunohistochemistry (IHC) analyses. The clinicopathological correlations of ARF1 were further evaluated. Elevated ARF1 expression was strongly correlated with lymph node metastasis (P = 0.008), serosal invasion (P = 0.046), lymphatic invasion (P = 0.035), and pathological staging (P = 0.010). Moreover, the 5-year survival rate for the lower ARF1 expression group (n = 50; IHC score < 90) was higher than that of the higher expression group (n = 60; IHC score ≥ 90) (P = 0.0228, log-rank test). To establish the specific function of ARF1 in human gastric cancer, isogenic ARF1-overexpressing cell lines were prepared. Our results showed that ARF1-overexpressing clones display enhanced cell proliferation, migration, and invasion. Furthermore, ARF1-overexpression might contribute to poor prognosis of patients. These findings collectively support the utility of ARF1 as a novel prognostic marker for gastric cancer and its role in cell invasion.

Melatonin Inhibits NF-κB/CREB/Runx2 Signaling and Alleviates Aortic Valve Calcification.

Calcific aortic valve disease (CAVD) is linked to high mortality. Melatonin inhibits nuclear factor-kappa B (NF-κB)/cyclic AMP response element-binding protein (CREB), contributing to CAVD progression. This study determined the role of melatonin/MT1/MT2 signaling in valvular interstitial cell (VIC) calcification. Western blotting and Alizarin red staining were used to analyze NF-κB/CREB/runt-related transcription factor 2 (Runx2) signaling in porcine VICs treated with an osteogenic (OST) medium without (control) or with melatonin for 5 days. Chromatin immunoprecipitation (ChIP) assay was used to analyze NF-κB's transcription regulation of NF-κB on the Runx2 promoter. OST medium-treated VICs exhibited a greater expression of NF-κB, CREB, and Runx2 than control VICs. Melatonin treatment downregulated the effects of the OST medium and reduced VIC calcification. The MT1/MT2 antagonist (Luzindole) and MT1 receptor neutralized antibody blocked the anticalcification effect of melatonin, but an MT2-specific inhibitor (4-P-PDOT) did not. Besides, the NF-κB inhibitor (SC75741) reduced OST medium-induced VIC calcification to a similar extent to melatonin at 10 nmol/L. The ChIP assay demonstrated that melatonin attenuated OST media increased NF-κB binding activity to the promoter region of Runx2. Activation of the melatonin/MT1-axis significantly reduced VIC calcification by targeting the NF-κB/CREB/Runx2 pathway. Targeting melatonin/MT1 signaling may be a potential therapeutic strategy for CAVD.

Galectin-3 enhances atrial remodelling and arrhythmogenesis through CD98 signalling.

AIM: Galectin-3 (Gal-3) is a biomarker of atrial fibrillation (AF) that mediates atrial inflammation. CD98 is the membrane surface receptor for Gal-3. Nevertheless, the role of the Gal-3/CD98 axis in atrial arrhythmogenesis is unclear. In this study, we investigated the effects of Gal-3/CD98 signalling on atrial pathogenesis. METHODS: Whole cell patch clamp and western blotting were used to analyse calcium/potassium homeostasis and calcium-related signalling in Gal-3-administrated HL-1 atrial cardiomyocytes with/without CD98 neutralized antibodies. Telemetry electrocardiographic recording, Masson's trichrome staining and immunohistochemistry staining of atrium were obtained from mice having received tail-vein injections with Gal-3. RESULTS: Gal-3-treated HL-1 myocytes had a shorter action potential duration, smaller L-type calcium current, increased sarcoplasmic reticulum (SR) calcium content, Na+ /Ca2+ exchanger (NCX) current, transient outward potassium current, and ultrarapid delayed rectifier potassium current than control cells had. Gal-3-treated HL-1 myocytes had greater levels of SR Ca2+ ATPase, NCX, Nav1.5, and NLR family pyrin domain containing 3 (NLRP3) expression and increased calcium/calmodulin-dependent protein kinase II (CaMKII), ryanodine receptor 2 (RyR2), and nuclear factor kappa B (NF-κB) phosphorylation than control cells had. Gal-3-mediated activation of CaMKII/RyR2 pathway was diminished in the cotreatment of anti-CD98 antibodies. Mice that were injected with Gal-3 had more atrial ectopic beats, increased atrial fibrosis, and activated NF-κB/NLRP3 signalling than did control mice (nonspecific immunoglobulin) or mice treated with Gal-3 and anti-CD98 antibodies. CONCLUSION: Gal-3 recombinant protein administration increases atrial fibrosis and arrhythmogenesis through CD98 signalling. Targeting Gal-3/CD98 axis might be a novel therapeutic strategy for patients with AF and high Gal-3 levels.