Phosphatidylcholine Specific PLC-Induced Dysregulation of Gap Junctions, a Robust Cellular Response to Environmental Toxicants, and Prevention by Resveratrol in a Rat Liver Cell Model.

UNLABELLED: Dysregulation of gap junctional intercellular communication (GJIC) has been associated with different pathologies, including cancer; however, molecular mechanisms regulating GJIC are not fully understood. Mitogen Activated Protein Kinase (MAPK)-dependent mechanisms of GJIC-dysregulation have been well-established, however recent discoveries have implicated phosphatidylcholine-specific phospholipase C (PC-PLC) in the regulation of GJIC. What is not known is how prevalent these two signaling mechanisms are in toxicant/toxin-induced dysregulation of GJIC, and do toxicants/toxins work through either signaling mechanisms or both, or through alternative signaling mechanisms. Different chemical toxicants were used to assess whether they dysregulate GJIC via MEK or PC-PLC, or both Mek and PC-PLC, or through other signaling pathways, using a pluripotent rat liver epithelial oval-cell line, WB-F344. Epidermal growth factor, 12-O-tetradecanoylphorbol-13-acetate, thrombin receptor activating peptide-6 and lindane regulated GJIC through a MEK1/2-dependent mechanism that was independent of PC-PLC; whereas PAHs, DDT, PCB 153, dicumylperoxide and perfluorodecanoic acid inhibited GJIC through PC-PLC independent of Mek. Dysregulation of GJIC by perfluorooctanoic acid and R59022 required both MEK1/2 and PC-PLC; while benzoylperoxide, arachidonic acid, 18ß-glycyrrhetinic acid, perfluorooctane sulfonic acid, 1-monolaurin, pentachlorophenol and alachlor required neither MEK1/2 nor PC-PLC. Resveratrol prevented dysregulation of GJIC by toxicants that acted either through MEK1/2 or PC-PLC. Except for alachlor, resveratrol did not prevent dysregulation of GJIC by toxicants that worked through PC-PLC-independent and MEK1/2-independent pathways, which indicated at least two other, yet unidentified, pathways that are involved in the regulation of GJIC. IN CONCLUSION: the dysregulation of GJIC is a contributing factor to the cancer process; however the underlying mechanisms by which gap junction channels are closed by toxicants vary. Thus, accurate assessments of risk posed by toxic agents, and the role of dietary phytochemicals play in preventing or reversing the effects of these agents must take into account the specific mechanisms involved in the cancer process.

Regulation of the alkaloid biosynthesis by miRNA in opium poppy.

Opium poppy (Papaver somniferum) is an important medicinal plant producing benzylisoquinoline alkaloids (BIA). MicroRNAs (miRNAs) are endogenous small RNAs (sRNAs) of approximately 21 nucleotides. They are noncoding, but regulate gene expression in eukaryotes. Although many studies have been conducted on the identification and functions of plant miRNA, scarce researches on miRNA regulation of alkaloid biosynthesis have been reported. In this study, a total of 316 conserved and 11 novel miRNAs were identified in opium poppy using second-generation sequencing and direct cloning. Tissue-specific regulation of miRNA expression was comparatively analysed by miRNA microarray assays. A total of 232 miRNAs were found to be differentially expressed among four tissues. Likewise, 1469 target transcripts were detected using in silico and experimental approaches. The Kyoto Encyclopedia of Genes and Genomes pathway analyses indicated that miRNA putatively regulates carbohydrate metabolism and genetic-information processing. Additionally, miRNA target transcripts were mostly involved in response to stress against various factors and secondary-metabolite biosynthesis processes. Target transcript identification analyses revealed that some of the miRNAs might be involved in BIA biosynthesis, such as pso-miR13, pso-miR2161 and pso-miR408. Additionally, three putatively mature miRNA sequences were predicted to be targeting BIA-biosynthesis genes.

Boron stress responsive microRNAs and their targets in barley.

Boron stress is an environmental factor affecting plant development and production. Recently, microRNAs (miRNAs) have been found to be involved in several plant processes such as growth regulation and stress responses. In this study, miRNAs associated with boron stress were identified and characterized in barley. miRNA profiles were also comparatively analyzed between root and leave samples. A total of 31 known and 3 new miRNAs were identified in barley; 25 of them were found to respond to boron treatment. Several miRNAs were expressed in a tissue specific manner; for example, miR156d, miR171a, miR397, and miR444a were only detected in leaves. Additionally, a total of 934 barley transcripts were found to be specifically targeted and degraded by miRNAs. In silico analysis of miRNA target genes demonstrated that many miRNA targets are conserved transcription factors such as Squamosa promoter-binding protein, Auxin response factor (ARF), and the MYB transcription factor family. A majority of these targets were responsible for plant growth and response to environmental changes. We also propose that some of the miRNAs in barley such as miRNA408 might play critical roles against boron exposure. In conclusion, barley may use several pathways and cellular processes targeted by miRNAs to cope with boron stress.