Effect of bitter compounds on amylase secretion in murine submandibular glands: Signaling pathway mechanisms.

BACKGROUND: Amylase is synthesized in submandibular glands (SMG) and released into the oral cavity to degrade carbohydrates in the mouth. Bitter taste receptors (T2R) belong to the G-protein coupled receptor (GPCR) family and are expressed in the taste cells and also in the digestive tract. METHODS: The activity of amylase secreted by murine SMG was measured, detecting maltose by Bernfeld's method. Amylase and T2R6 were detected by imunohistochemistry and Western blot. The expression of Ggustducin, Gi, and phospholipase Cß2 was also studied by Western blot. cAMP levels were measured by radioimmunoassay and inositol monophosphate production was quantified by ELISA. RESULTS: Theophylline, denatonium and cycloheximide exerted a dose-dependent inhibition on amylase secretion. This effect was reverted by preincubating SMG with an anti-Gαi antibody. cAMP production was increased by the same compounds, an effect that was also abrogated by an anti-Gαi antibody. Bitter compounds reduced inositol monophosphate formation in SMG and H-89, a protein kinase A inhibitor, reverted this action, revealing that this protein kinase down regulates phospholipase C activity. GENERAL SIGNIFICANCE: We demonstrated that theophylline, denatonium and cycloheximide inhibit salivary amylase secretion, activating an intracellular signaling pathway that involves cAMP and phospholipase C, that cross talks via protein kinase A.

Increasing The Genetic Admixture of Available Lines of Human Pluripotent Stem Cells.

Human pluripotent stem cells (hPSCs) may significantly improve drug development pipeline, serving as an in vitro system for the identification of novel leads, and for testing drug toxicity. Furthermore, these cells may be used to address the issue of differential drug response, a phenomenon greatly influenced by genetic factors. This application depends on the availability of hPSC lines from populations with diverse ancestries. So far, it has been reported that most lines of hPSCs derived worldwide are of European or East Asian ancestries. We have established 23 lines of hPSCs from Brazilian individuals, and we report the analysis of their genomic ancestry. We show that embryo-derived PSCs are mostly of European descent, while induced PSCs derived from participants of a national-wide Brazilian cohort study present high levels of admixed European, African and Native American genomic ancestry. Additionally, we use high density SNP data and estimate local ancestries, particularly those of CYP genes loci. Such information will be of key importance when interpreting variation among cell lines with respect to cellular phenotypes of interest. The availability of genetically admixed lines of hPSCs will be of relevance when setting up future in vitro studies of drug response.

Muscarinic regulation of SCA-9 cell proliferation via nitric oxide synthases, arginases and cyclooxygenases. Role of the nuclear translocation factor-κB.

The submandibular gland-derived tumor cell line SCA-9 is considered a useful tool to study the signaling pathways involved in proliferation, and their regulation, triggered by different stimuli. It is proposed that the non neuronal cholinergic system: acethylcholine, the enzymes that synthesize and degrade it, and the nicotinic and muscarinic receptors, play a key role in tumorigenesis. Here, we investigate the role of muscarinic receptors in SCA-9 cell proliferation, and the modulation of cholinergic signaling pathways exerted by the nuclear transcription factor κB (NF-κB). The activation of cholinergic receptors by carbachol (10⁻9M) increased cell proliferation (P<0.001). This was prevented by preincubating cells with the muscarinic antagonist atropine but not by mecamylamine, a nicotinic receptor blocker. Phospholipase C (PLC)/nitric oxide synthase (NOS)/arginase pathway is involved in this effect, since carbachol stimulated nitric oxide production, increased NOS2 and NOS3 expressions, urea production, and arginase II expression (P<0.001). Also, phospholipase A2 (PLA2)/cyclooxygenase (COX) pathway is up-regulated in carbachol-induced SCA-9 cell proliferation, because prostaglandin E2 liberation (P<0.001) is increased and COX-1 expression is turned up (P<0.001). Interactions between PLC/NOS/arginases and PLA2/COX pathways via its metabolites were detected. SCA-9 cells exhibit a constitutive activation of NF-κB, which regulates carbachol-induced NOS2 and 3, arginase II and COX-1 expressions. In addition, protein kinase C is involved in the up-regulation of NOS2 and arginase II enzymes induced by carbachol via NF-κB. In conclusion, the activation of cholinergic receptors in SCA-9 tumor cells promotes proliferation via muscarinic effector enzymes, and reveals the participation of NF-κB at this step of tumorigenesis.