capsazepine and 2-aminoethoxydiphenyl-borate

Scanning probe techniques enable direct imaging of morphology changes associated with cellular processes at life specimen. Here, glutaraldehyde-fixed and living alveolar type II (ATII) cells were investigated by atomic force microscopy (AFM), and the obtained topographical data were correlated with results obtained by scanning electron microscopy (SEM) and confocal microscopy (CM). We show that low-force contact mode AFM at glutaraldehyde-fixed cells provides complementary results to SEM and CM. Both AFM and SEM images reveal fine structures at the surface of fixed cells, which indicate microvilli protrusions. If ATII cells were treated with Ca(2+) channel modulators known to induce massive endocytosis, changes of the cell surface topography became evident by the depletion of microvilli. Low force contact mode AFM imaging at fixed ATII cells revealed a significant reduction of the surface roughness for capsazepine and 2-aminoethoxydiphenyl-borate (CPZ/2-APB)-treated cells compared to untreated control cells (Rc of 99.7 ± 6.8 nm vs. Rc of 71.9 ± 4.6 nm for N = 22), which was confirmed via SEM studies. CM of microvilli marker protein Ezrin revealed a cytoplasmic localization of Ezrin in CPZ/2-APB-treated cells, whereas a submembranous Ezrin localization was observed in control cells. Furthermore, in situ AFM investigations at living ATII cells using low force contact mode imaging revealed an apparent decrease in cell height of 17% during stimulation experiments. We conclude that a dynamic reorganization of the microvillous cell surface occurs in ATII cells at conditions of stimulated endocytosis.

Topics: Alveolar Epithelial Cells; Animals; Boron Compounds; Calcium; Capsaicin; Cell Membrane; Cells, Cultured; Cytoskeletal Proteins; Endocytosis; Glutaral; Imaging, Three-Dimensional; Lung; Male; Microscopy, Atomic Force; Microscopy, Confocal; Microscopy, Electron, Scanning; Microvilli; Rats; Rats, Sprague-Dawley

Calcium as a second messenger influences many cellular and physiological processes. In lung, alveolar type II (ATII) cells sense mechanical stress and respond by Ca(2+) dependent release of surfactant, which is essential for respiratory function. Nevertheless, Ca(2+) signaling mechanisms in these cells--in particular Ca(2+) entry pathways are still poorly understood. Herein, we investigated pharmacological properties of non-voltage-gated Ca(2+) channel modulators in ATII and NCI-H441 cells and demonstrate that 2-Aminoethoxydiphenyl-borinate (2-APB) and capsazepine (CPZ) activate Ca(2+) entry with pharmacologically distinguishable components. Surprisingly, 2-APB and CPZ activated clathrin dependent endocytosis in ATII and NCI-H441 cells, which was dependent on Ca(2+) entry. The internalized material accumulated in non-acidic granules distinct from surfactant containing lamellar bodies (LB). LB exocytosis was not observed under these conditions. Our study demonstrates that 2-APB/CPZ induces Ca(2+) entry which unlike ATP- or stretch-induced Ca(2+) entry in ATII cells does not activate exocytosis but an opposing endocytotic mechanism.

Topics: Alveolar Epithelial Cells; Animals; Boron Compounds; Calcium; Capsaicin; Cell Line; Cells, Cultured; Clathrin; Endocytosis; Male; Rats; Rats, Sprague-Dawley

Hyperthermia has been shown to sensitize vagal pulmonary C-fibers in anesthetized rats. However, it was not clear whether the effect was due to a direct action of hyperthermia on these sensory neurons. To answer this question, we carried out this study to determine the effect of increasing temperature on the responses to various chemical stimuli in isolated nodose and jugular ganglion neurons innervating the rat lungs. In the whole cell perforated patch-clamp study, when the temperature was increased from normal (approximately 36 degrees C) to hyperthermic (approximately 40.6 degrees C) level of the rat body temperature, the inward currents evoked by capsaicin, a selective activator of the transient receptor potential vanilloid type 1 (TRPV1), and 2-aminoethoxydiphenyl borate (2-APB), a nonselective activator of TRPV1-3 receptors, were both significantly increased. This potentiating effect was clearly present even at a moderate level of hyperthermia (approximately 39 degrees C). However, only the slow, sustained component of acid-evoked current mediated through the TRPV1 receptor was potentiated by hyperthermia, whereas the rapid, transient component was inhibited. In contrast, the currents evoked by adenosine 5'-triphosphate and acetylcholine, neither of which is known to activate the TRPV1 channel, did not increase when the same temperature elevation was applied. Furthermore, the hyperthermia-induced potentiation of the cell response to 2-APB was significantly attenuated by either capsazepine or AMG 9810, selective TRPV1 antagonists. In conclusion, increasing temperature within the physiological range exerts a potentiating effect on the response to TRPV1 activators in these neurons, which is probably mediated through a positive interaction between hyperthermia and these chemical activators at the TRPV1 channel.

Topics: Acrylamides; Animals; Boron Compounds; Bridged Bicyclo Compounds, Heterocyclic; Capsaicin; Evoked Potentials; Hexamethonium; Hydrogen-Ion Concentration; Hyperthermia, Induced; Lung; Male; Neurons, Afferent; Rats; Rats, Sprague-Dawley; Temperature; TRPV Cation Channels; Vagus Nerve

This study was carried out to determine the effect of 2-aminoethoxydiphenyl borate (2-APB), a common activator of transient receptor potential vanilloid (TRPV) type 1, 2, and 3 channels, on cardiorespiratory reflexes, pulmonary C fiber afferents, and isolated pulmonary capsaicin-sensitive neurons. In anesthetized, spontaneously breathing rats, intravenous bolus injection of 2-APB elicited the pulmonary chemoreflex responses, characterized by apnea, bradycardia, and hypotension. After perineural treatment of both cervical vagi with capsaicin to block the conduction of C fibers, 2-APB no longer evoked any of these reflex responses. In open-chest and artificially ventilated rats, 2-APB evoked an abrupt and intense discharge in vagal pulmonary C fibers in a dose-dependent manner. The stimulation of C fibers by 2-APB was attenuated but not abolished by capsazepine, a selective antagonist of the TRPV1, which completely blocked the response to capsaicin in these C fiber afferents. In isolated pulmonary capsaicin-sensitive neurons, 2-APB concentration dependently evoked an inward current that was partially inhibited by capsazepine but almost completely abolished by ruthenium red, an effective blocker of all TRPV channels. In conclusion, 2-APB evokes a consistent and distinct stimulatory effect on pulmonary C fibers in vivo and on isolated pulmonary capsaicin-sensitive neurons in vitro. These results establish the functional evidence demonstrating that TRPV1, V2, and V3 channels are expressed on these sensory neurons and their terminals.

Topics: Animals; Blood Pressure; Boron Compounds; Capsaicin; Cation Transport Proteins; Coloring Agents; Heart Rate; Ion Channels; Lung; Nerve Fibers, Unmyelinated; Nodose Ganglion; Rats; Rats, Sprague-Dawley; Receptors, Drug; Reflex; Respiratory Mechanics; Ruthenium Red; TRPV Cation Channels