Molecular determinants and intracellular targets of taurine signalling in pancreatic islet ß-cells.

AIM: Despite its abundance in pancreatic islets of Langerhans and proven antihyperglycemic effects, the impact of the essential amino acid, taurine, on islet ß-cell biology has not yet received due consideration, which prompted the current studies exploring the molecular selectivity of taurine import into ß-cells and its acute and chronic intracellular interactions. METHODS: The molecular aspects of taurine transport were probed by exposing the clonal pancreatic BRIN BD11 ß-cells and primary mouse and human islets to a range of the homologs of the amino acid (assayed at 2-20 mM), using the hormone release and imaging of intracellular signals as surrogate read-outs. Known secretagogues were employed to profile the interaction of taurine with acute and chronic intracellular signals. RESULTS: Taurine transporter TauT was expressed in the islet ß-cells, with the transport of taurine and homologs having a weak sulfonate specificity but significant sensitivity to the molecular weight of the transporter. Taurine, hypotaurine, homotaurine, and ß-alanine enhanced insulin secretion in a glucose-dependent manner, an action potentiated by cytosolic Ca2+ and cAMP. Acute and chronic ß-cell insulinotropic effects of taurine were highly sensitive to co-agonism with GLP-1, forskolin, tolbutamide, and membrane depolarization, with an unanticipated indifference to the activation of PKC and CCK8 receptors. Pre-culturing with GLP-1 or KATP channel inhibitors sensitized or, respectively, desensitized ß-cells to the acute taurine stimulus. CONCLUSION: Together, these data demonstrate the pathways whereby taurine exhibits a range of beneficial effects on insulin secretion and ß-cell function, consistent with the antidiabetic potential of its dietary low-dose supplementation.

NKCC transport mediates the insulinotropic effects of taurine and other small neutral amino acids.

AIMS: Despite its high concentration in pancreatic islets of Langerhans and broad range of antihyperglycemic effects, the route facilitating the import of dietary taurine into pancreatic ß-cell and mechanisms underlying its insulinotropic activity are unclear. We therefore studied the impact of taurine on beta-cell function, alongside that of other small neutral amino acids, L-alanine and L-proline. MAIN METHODS: Pharmacological profiling of insulin secretion was conducted using clonal BRIN BD11 ß-cells, the impact of taurine on the metabolic fate of glucose carbons was assessed using NMR and the findings were verified by real-time imaging of Ca2+ dynamics in the cytosol of primary mouse and human islet beta-cells. KEY FINDINGS: In our hands, taurine, alanine and proline induced secretory responses that were dependent on the plasma membrane depolarisation, import of Ca2+, homeostasis of K+ and Na+ as well as on cell glycolytic and oxidative metabolism. Taurine shifted the balance between the oxidation and anaplerosis towards the latter, in BRIN BD11 beta-cells. Furthermore, the amino acid signalling was significantly attenuated by inhibition of Na+-K+-Cl- symporter (NKCC). SIGNIFICANCE: These data suggest that taurine, like L-alanine and L-proline, acutely induces glucose-dependent insulin-secretory responses by modulating electrogenic Na+ transport, with potential role of intracellular K+ and Cl- in the signal transduction. The acute action delineated would be consistent with antidiabetic potential of dietary taurine supplementation.

Urinary bladder recurrences following ureteroscopic biopsies of upper tract urothelial cancers: a multi-centre observational study with genomic assessment for clonality.

BACKGROUND AND AIMS: Urinary bladder recurrences (UBRs) after radical nephroureterectomy (RNUx) are a known challenge in patients with upper-tract urothelial cancers (UTUCs). We aim to assess factors associated with UBR and clonal-relatedness with resected UTUC. METHODS: Patients who underwent RNUx for UTUC between 1998 and 2015 in five institutions were identified. Clonal relatedness between primary UTUC and subsequent UBR in a sub-cohort was assessed using next-generation sequencing. A Kaplan-Meier curve was used to assess differences in UBR between two groups (with or without ureteroscopic biopsy). RESULTS: Of 267 patients with complete records, 73 (27.3%) had UBR during follow-up. The five-year UBR-free survival in all patients was 64.7%. The five-year UBR-free-survival was inferior in patients who underwent URS biopsy compared with patients who did not undergo ureteroscopic biopsy (49.9% vs 76.4%, p < 0.001). History of bladder tumour (HR, 95% CI; 2.94, 1.73-5.00, p < 0.001), ureteroscopic biopsy (HR, 95% CI; 2.21, 1.38-3.53, p = 0.001) and preoperative urine cytology ≥C3 (HR, 95% CI; 2.06, 1.24-3.40, p = 0.005) were independently associated with UBR. Patients with ureteroscopic biopsy (n = 3/5) showed identical mutational changes for common genes (TP53 and FGFR3) between primary UTUC and subsequent UBR. CONCLUSIONS: Ureteroscopic biopsy of UTUC is a significant risk factor for UBR. Qualitative clonality assessment showed identical mutational signatures between primary UTUC and UBR.

Interactions between anti-EGFR therapies and cytotoxic chemotherapy in oesophageal squamous cell carcinoma: why clinical trials might have failed and how they could succeed.

PURPOSE: Oesophageal squamous cell carcinoma (ESCC) has a poor prognosis. Advanced tumours are treated with fluoropyrimidine/platinum chemotherapy followed by irinotecan or taxane monotherapy, but resistance is common and new treatments are needed. Approximately 20% of ESCCs carry copy number gain (CNG) of the epidermal growth factor receptor (EGFR) gene. Previous trials show that while anti-EGFR monotherapy benefits biomarker-selected patients with EGFR CNG and/or high EGFR expression, combining anti-EGFR therapies with platinum fluoropyrimidine chemotherapies is not effective, and uncertainty remains regarding the optimal cytotoxic chemotherapy partner for anti-EGFR therapies in ESCC. METHODS: The effects of EGFR CNG on fluoropyrimidine/platinum chemotherapy sensitivity in a cohort of gastroesophageal cancer patients (n = 302) was evaluated. Drug combination studies using the EGFR inhibitor gefitinib with cytotoxic chemotherapies, docetaxel, cisplatin, oxaliplatin and irinotecan, on cell proliferation and cell death of EGFR CNG ESCC cell lines were assessed. RESULTS: EGFR CNG in gastroesophageal cancer patients was associated with improved overall survival following fluoropyrimidine/platinum chemotherapy. However, co-administration of gefitinib and oxaliplatin or cisplatin was frequently antagonistic in cell-based assays in EGFR CNG ESCC, whereas the combination of gefitinib with docetaxel or irinotecan was more efficacious. Co-administration of gefitinib/docetaxel and sequential administration of docetaxel before gefitinib showed synergy, but docetaxel given after gefitinib was antagonistic. CONCLUSION: Gefitinib/platinum co-administration demonstrated antagonism suggesting a possible explanation for the lack of benefit from addition of anti-EGFR therapies to fluoropyrimidine/platinum chemotherapy in trials. Gefitinib/docetaxel co-administration demonstrated synergy suggesting taxanes could be the most effective cytotoxic partner for anti-EGFR therapies in EGFR CNG-positive ESCC, but careful consideration of drug scheduling is required.

Nonagenarians from the Swedish NONA Immune Study have increased plasma antioxidant capacity and similar levels of DNA damage in peripheral blood mononuclear cells compared to younger control subjects.

The results of previous work from our laboratories have suggested that free radical damage to T cells as they age may contribute to the age-related decline in the T cell-mediated immune response. The aims of this investigation were to assess the efficiency of in vivo antioxidant capacity through determining the antioxidant capacity of plasma using the ferric reducing ability of plasma assay, and to assess the levels and types of DNA damage (as a measure of in vivo antioxidant efficiency) using the alkaline comet assay and two enzymatic modifications of the comet assay, in peripheral blood mononuclear cells (PBMCs) from nonagenarian subjects drawn from the Swedish NONA Immune Study. The results obtained were compared with those from middle-aged (40-60 years) controls to identify potential anti-immunosenescent effects of in vivo antioxidants. The results revealed a significantly higher plasma antioxidant capacity in NONA subjects compared to controls, and these results support a relationship between longevity and intact immune function, which may be underpinned by antioxidant defences which reduce free radical damage to PBMC, thus helping to maintain cell function. The NONA subjects were found to have similar levels of DNA damage in their PBMCs to those found in middle aged controls.