Sensing of Fatty Acids for Octanoylation of Ghrelin Involves a Gustatory G-Protein

Ghrelin is an important regulator of energy--and glucose homeostasis. The octanoylation at Ser(3) is essential for ghrelin's biological effects but the mechanisms involved in the octanoylation are unknown. We investigated whether the gustatory G-protein, α-gustducin, and the free fatty acid receptors GPR40 and GPR120 are involved in the fatty acid sensing mechanisms of the ghrelin cell.Wild-type (WT) and α-gustducin knockout (gust(-/-)) mice were fed a glyceryl trioctanoate-enriched diet (OD) during 2 weeks. Ghrelin levels and gastric emptying were determined. Co-localization between GPR40, GPR120 and ghrelin or α-gustducin/α-transducin was investigated by immunofluorescence staining. The role of GPR120 in the effect of medium and long chain fatty acids on the release of ghrelin was studied in the ghrelinoma cell line, MGN3-1. The effect of the GPR40 agonist, MEDICA16, and the GPR120 agonist, grifolic acid, on ghrelin release was studied both in vitro and in vivo.Feeding an OD specifically increased octanoyl ghrelin levels in the stomach of WT mice but not of gust(-/-) mice. Gastric emptying was accelerated in WT but not in gust(-/-) mice. GPR40 was colocalized with desoctanoyl but not with octanoyl ghrelin, α-gustducin or α-transducin positive cells in the stomach. GPR120 only colocalized with ghrelin in the duodenum. Addition of octanoic acid or α-linolenic acid to MGN3-1 cells increased and decreased octanoyl ghrelin levels, respectively. Both effects could not be blocked by GPR120 siRNA. MEDICA16 and grifolic acid did not affect ghrelin secretion in vitro but oral administration of grifolic acid increased plasma ghrelin levels.This study provides the first evidence that α-gustducin is involved in the octanoylation of ghrelin and shows that the ghrelin cell can sense long- and medium-chain fatty acids directly. GPR120 but not GPR40 may play a role in the lipid sensing cascade of the ghrelin cell

ATP release via anion channels

ATP serves not only as an energy source for all cell types but as an ‘extracellular messenger-for autocrine and paracrine signalling. It is released from the cell via several different purinergic signal efflux pathways. ATP and its Mg2+ and/or H+ salts exist in anionic forms at physiological pH and may exit cells via some anion channel if the pore physically permits this. In this review we survey experimental data providing evidence for and against the release of ATP through anion channels. CFTR has long been considered a probable pathway for ATP release in airway epithelium and other types of cells expressing this protein, although non-CFTR ATP currents have also been observed. Volume-sensitive outwardly rectifying (VSOR) chloride channels are found in virtually all cell types and can physically accommodate or even permeate ATP4- in certain experimental conditions. However, pharmacological studies are controversial and argue against the actual involvement of the VSOR channel in significant release of ATP. A large-conductance anion channel whose open probability exhibits a bell-shaped voltage dependence is also ubiquitously expressed and represents a putative pathway for ATP release. This channel, called a maxi-anion channel, has a wide nanoscopic pore suitable for nucleotide transport and possesses an ATP-binding site in the middle of the pore lumen to facilitate the passage of the nucleotide. The maxi-anion channel conducts ATP and displays a pharmacological profile similar to that of ATP release in response to osmotic, ischemic, hypoxic and salt stresses. The relation of some other channels and transporters to the regulated release of ATP is also discussed

Hypertonicity counteracts MCL 1 and renders BCL XL a synthetic lethal target in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is an aggressive and difficult‐to‐treat cancer entity. Current therapies ultimately aim to activate the mitochondria‐controlled (intrinsic) apoptosis pathway, but complex alterations in intracellular signaling cascades and the extracellular microenvironment hamper treatment response. On the one hand, proteins of the BCL‐2 family set the threshold for cell death induction and prevent accidental cellular suicide. On the other hand, controlling a cell's readiness to die also determines whether malignant cells are sensitive or resistant to anticancer treatments. Here, we show that HNSCC cells upregulate the proapoptotic BH3‐only protein NOXA in response to hyperosmotic stress. Induction of NOXA is sufficient to counteract the antiapoptotic properties of MCL‐1 and switches HNSCC cells from dual BCL‐XL/MCL‐1 protection to exclusive BCL‐XL addiction. Hypertonicity‐induced functional loss of MCL‐1 renders BCL‐XL a synthetically lethal target in HNSCC, and inhibition of BCL‐XL efficiently kills HNSCC cells that poorly respond to conventional therapies. We identify hypertonicity‐induced upregulation of NOXA as link between osmotic pressure in the tumor environment and mitochondrial priming, which could perspectively be exploited to boost efficacy of anticancer drugs

Comparison of Scolicidal Effects of Amphotricin B, Silver Nanoparticles,_and Foeniculum vulgare Mill on Hydatid Cysts Protoscoleces

BACKGROUND: Surgery is the preferred treatment for hydatid cyst (cystic echinococcosis, CE). At present, various scolicidal agents have been used for inactivation of protoscoleces during surgery, but they are associated with adverse side effects. The aim of the present study was to evaluate the scolicidal effects of amphotricin B, Silver nano particles, Foeniculum vulgare Mill, essential oil and hypertonic saline against protoscoleces of hydatid cyst on an in vitro model. METHODS: Protoscoleces were aseptically aspirated from the naturally infected livers of sheep and goats. Various concentrations of AmB (2.5-20 mg/ml), Ag-NPs (0.5-4 mg/ml), F. vulgare essential oil (0.125-1 mg/ml) and hypertonic saline (10-20%) were used for 5-60 min. Eosin exclusion test was used to determine the viability of protoscoleces. RESULTS: Maximum protoscolicidal effect of AmB and Ag-NPs was found at concentrations of 20 and 4 mg/mL, resulting in only 82.3% and 71.6% of the protoscoleces after 60 min of incubation, respectively. In contrast, F. vulgare essential oil at concentration of 1 mg/ml and hypertonic saline 20% killed 100% protoscoleces after 5 and 10 min of exposure, respectively. CONCLUSION: The results indicated weak scolicidal activity of AmB and Ag-NPs; whereas F. vulgare essential oil had potent scolicidal activity against protoscoleces of hydatid cyst that revealed the potential of F. vulgare as a natural source for the production of new scolicidal agent for use in hydatid cyst surgery. However, further studies will be needed to confirm these results by checking the essential oil and its active component in the in vivo model