Rapid radiosynthesis of [11C] and [14C]azelaic,suberic, and sebacic acids for in vivo mechanistic studies of systemic acquired resistance in plants

A recent report that the aliphatic dicarboxylic acid, azelaic acid (1,9‐nonanedioic acid) but not related acids, suberic acid (1,8‐octanedioic acid) or sebacic (1,10‐decanedioic acid) acid induces systemic acquired resistance to invading pathogens in plants stimulated the development of a rapid method for labeling these dicarboxylic acids with ¹¹C and ¹⁴C for in vivo mechanistic studies in whole plants. ¹¹C‐labeling was performed by reaction of ammonium [¹¹C]cyanide with the corresponding bromonitrile precursor followed by hydrolysis with aqueous sodium hydroxide solution. Total synthesis time was 60 min. Median decay‐corrected radiochemical yield for [¹¹C]azelaic acid was 40% relative to trapped [¹¹C]cyanide, and specific activity was 15 GBq/µmol. Yields for [¹¹C]suberic and sebacic acids were similar. The ¹⁴C‐labeled version of azelaic acid was prepared from potassium [¹⁴C]cyanide in 45% overall radiochemical yield. Radiolabeling procedures were verified using ¹³C‐labeling coupled with ¹³C‐NMR and liquid chromatography–mass spectrometry analysis. The ¹¹C and ¹⁴C‐labeled azelaic acid and related dicarboxylic acids are expected to be of value in understanding the mode‐of‐action, transport, and fate of this putative signaling molecule in plants. Copyright © 2011 John Wiley & Sons, Ltd.     

Serotonin and the 5‐HT7 receptor: The link between hepatocytes,IGF‐1 and small intestinal neuroendocrine tumors

Platelet‐derived serotonin (5‐HT) is involved in liver regeneration. The liver is also the metastatic site for malignant enterochromaffin (EC) cell “carcinoid” (neuroendocrine) neoplasms, the principal cellular source of 5‐HT. We hypothesized that 5‐HT produced by metastatic EC cells played a role in the hepatic tumor‐microenvironment principally via 5‐HT₇ receptor‐mediated activation of hepatocyte IGF‐1 synthesis and secretion. Using isolated rat hepatocytes, we evaluated 5‐HT₇ receptor expression (using PCR, sequencing and western blot). ELISA, cell transfection and western blots delineated 5‐HT‐mediated signaling pathways (pCREB, AKT and ERK). IGF‐1 synthesis/secretion was evaluated using QPCR and ELISA. IGF‐1 was tested on small intestinal neuroendocrine neoplasm proliferation, while IGF‐1 production and 5‐HT₇ expression were examined in an in vivo SCID metastasis model. Our results demonstrated evidence for a functional 5‐HT₇ receptor. 5‐HT activated cAMP/PKA activity, pCREB (130–205%, P < 0.05) and pERK/pAKT (1.2–1.75, P < 0.05). Signaling was reversed by the 5‐HT₇ receptor antagonist SB269970. IGF‐1 significantly stimulated proliferation of two small intestinal neuroendocrine neoplasm cell lines (EC₅₀: 7–70 pg/mL) and could be reversed by the small molecule inhibitor BMS‐754807. IGF‐1 and 5‐HT were elevated (40–300×) in peri‐tumoral hepatic tissue in nude mice, while 5‐HT₇ was increased fourfold compared to sham‐operated animals. We conclude that hepatocytes express a cAMP‐coupled 5‐HT₇ receptor, which, at elevated 5‐HT concentrations that occur in liver metastases, signals via CREB/AKT and is linked to IGF‐1 synthesis and secretion. Because IGF‐1 regulates NEN proliferation, identification of a role for 5‐HT₇ in the hepatic metastatic tumor microenvironment suggests the potential for novel therapeutic strategies for amine‐producing mid‐gut tumors.