Platelet-activating factor stimulates cytoplasmic alkalinization and granule acidification in human eosinophils

Bankers-Fulbright, Jennifer L.; Kephart, Gail M.; Bartemes, Kathleen R.; Kita, Hirohito; O’Grady, Scott M.

doi:10.1242/jcs.01498

Cited by 34 publications

(29 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The pH calibration curve was generated as described previously. 55 Briefly, cells were trypsinized and labeled with 2 mM Lysosensor Yellow/Blue DND-160 for 30 min at 37 C in regular medium, and excessive dye was washed out using PBS. The labeled cells were treated for 10 min with 10 mM monensin (Sigma, M5273) and 10 M nigericin (Sigma, N7143) in 25 mM 2-(N-morpholino) ethanesulfonic acid (MES) calibration buffer, pH 3.5-6.0, containing 5 mM NaCl, 115 mM KCl and 1.2 mM MgSO 4 .…”

Section: Lysosomal Ph Measurementmentioning

confidence: 99%

Vacuolin-1 potently and reversibly inhibits autophagosome-lysosome fusion by activating RAB5A

et al. 2014

View full text Add to dashboard Cite

-l-phenylalanine 2-naphthylamide; LAMP1, lysosomal-associated membrane protein 1; Leup, leupeptin; MAP1LC3, microtubule-associated protein 1 light chain 3;MTOR, mechanistic target of rapamycin; RFP, red fluorescent protein; tfLC3, tandem fluorescence-tagged LC3.Autophagy is a catabolic lysosomal degradation process essential for cellular homeostasis and cell survival. Dysfunctional autophagy has been associated with a wide range of human diseases, e.g., cancer and neurodegenerative diseases. A large number of small molecules that modulate autophagy have been widely used to dissect this process and some of them, e.g., chloroquine (CQ), might be ultimately applied to treat a variety of autophagy-associated human diseases. Here we found that vacuolin-1 potently and reversibly inhibited the fusion between autophagosomes and lysosomes in mammalian cells, thereby inducing the accumulation of autophagosomes. Interestingly, vacuolin-1 was less toxic but at least 10-fold more potent in inhibiting autophagy compared with CQ. Vacuolin-1 treatment also blocked the fusion between endosomes and lysosomes, resulting in a defect in general endosomal-lysosomal degradation. Treatment of cells with vacuolin-1 alkalinized lysosomal pH and decreased lysosomal Ca 2C content. Besides marginally inhibiting vacuolar ATPase activity, vacuolin-1 treatment markedly activated RAB5A GTPase activity. Expression of a dominant negative mutant of RAB5A or RAB5A knockdown significantly inhibited vacuolin-1-induced autophagosome-lysosome fusion blockage, whereas expression of a constitutive active form of RAB5A suppressed autophagosome-lysosome fusion. These data suggest that vacuolin-1 activates RAB5A to block autophagosome-lysosome fusion. Vacuolin-1 and its analogs present a novel class of drug that can potently and reversibly modulate autophagy. IntroductionAmong 3 types of autophagy, including microautophagy, chaperone-mediated autophagy, and macroautophagy, in mammals, macroautophagy (hereafter referred as autophagy) is the most common type. Autophagy is an evolutionarily conserved catabolic degradation cellular process in which misfolded proteins or damaged organelles are first sequestered by a doublemembrane vesicle, called an autophagosome. Autophagosomes then fuse with lysosomes to form autolysosomes, inside which the sequestered contents are digested by lysosomal enzymes and recycled to maintain cellular homeostasis. Autophagy can also be markedly induced by a wide variety of stresses, e.g., nutrient starvation, infection, and aging, for cell survival. Dysfunctional autophagy has been associated with wide ranges of human diseases, e.g., cancer and neurodegenerative diseases. [1][2][3][4][5][6] Basal autophagy activity is essential for cell homeostasis, and it is tightly controlled by a complicated interplay among several key machineries, including ULK1 or ULK2 complexes and the class III phosphatidylinositol-3 kinase complexes. The MTOR (mechanistic target of rapamycin) Ser/Thr kinase suppresses autophagy by inhibiting the ULK1/2 comple...

show abstract

Section: Lysosomal Ph Measurementmentioning

confidence: 99%

Vacuolin-1 potently and reversibly inhibits autophagosome-lysosome fusion by activating RAB5A

et al. 2014

View full text Add to dashboard Cite

show abstract

“…A similar solution was used as test medium in most experiments after adjustment of the glucose concentration and the addition of the studied substances. When the concentration of KCl was increased to 30 Diazoxide was a gift from Schering-Plough. Fura PE3-AM, BCECF-AM, and Lysosensor Yellow/Blue DND-160 were obtained from Molecular Probes.…”

Section: Methodsmentioning

confidence: 99%

“…In the present study, we have used Lysosensor DND-160, a fluorescent probe that, unlike Lysosensor DND-189 used previously, permits ratioing measurement of pH and therefore, decreases potential problems linked to differences in loading or redistribution between cellular compartments (26). This probe has previously been instrumental to measure stimulus-induced pH changes in lysosomes (27), in intracellular canaliculi of parietal gastric cells (28,29), and in eosinophil granules (30). Our aims were to characterize the acute effects of glucose on granular pH in normal mouse islets, to establish the mechanisms of these effects, and to determine whether they are important for insulin secretion, in particular for its regulation via the amplifying pathway.…”

mentioning

confidence: 99%

Glucose Acutely Decreases pH of Secretory Granules in Mouse Pancreatic Islets

Stiernet¹,

Guiot²,

Gilon³

et al. 2006

Journal of Biological Chemistry

View full text Add to dashboard Cite

Glucose-induced insulin secretion requires a rise inomission. The amplification of insulin secretion by glucose was not suppressed. We conclude that an acidic granular pH is important for insulin secretion but that the acute further acidification produced by glucose is not essential for the augmentation of secretion via the amplifying pathway.Insulin secretion by pancreatic ␤-cells is finely regulated by the interaction of nutrients, hormones, and neurotransmitters.

show abstract

“…In addition, the Na + /H + exchanger on esophageal epithelial cell membranes can extrude intracellular protons that accumulate in the setting of injury, thereby acidifying the microenvironment. 76 Eosinophils and neutrophils can also release protons from their exocytic granules and lysosomes into the microenvironment, 77–79 and microenvironment acidification has been well documented in the setting of inflammation. 80–82 Thus, there are a number of plausible mechanisms whereby PPIs might be activated in the diseased esophagus of EoE.…”

Section: Potential Acid-independent Anti-inflammatory Effects Of Ppimentioning

confidence: 99%

Eosinophilic Esophagitis

Cheng

Souza

Spechler

2014

Gastroenterology Clinics of North America

View full text Add to dashboard Cite

Synopsis Early authorities on eosinophilic esophagitis (EoE) deemed it crucial to distinguish this disorder from gastroesophageal reflux disease (GERD). However, it has become clear that GERD and EoE are not mutually exclusive disorders, and that their interactions can be complex. The notion that GERD and EoE can be distinguished by the response to PPI treatment is based on the assumption that gastric acid suppression is the only important therapeutic effect of PPIs, and therefore only GERD can respond to PPIs. This assumption appears to be incorrect for two major reasons. First, there are multiple mechanisms whereby PPI-induced acid reduction might benefit patients with EoE. Second, PPIs have acid-independent, anti-inflammatory effects that might be beneficial both for GERD and for EoE. Since the PPIs have multiple effects that might benefit both diseases, for patients who have esophageal symptoms and esophageal eosinophilia, we feel that a clinical and/or histological response to PPIs does not rule in GERD, and does not rule out EoE. However, we do recommend a trial of PPI therapy for patients with symptomatic esophageal eosinophilia, even if the diagnosis of EoE seems clear-cut.

show abstract

Platelet-activating factor stimulates cytoplasmic alkalinization and granule acidification in human eosinophils

Cited by 34 publications

References 33 publications

Vacuolin-1 potently and reversibly inhibits autophagosome-lysosome fusion by activating RAB5A

Vacuolin-1 potently and reversibly inhibits autophagosome-lysosome fusion by activating RAB5A

Glucose Acutely Decreases pH of Secretory Granules in Mouse Pancreatic Islets

Eosinophilic Esophagitis

Contact Info

Product

Resources

About