Phospholipids modulate the biophysical properties and vasoactivity of PACAP-(1—38)

2002 ◽  
Vol 93 (4) ◽  
pp. 1377-1383 ◽  
Author(s):  
Takaya Tsueshita ◽  
Salil Gandhi ◽  
Hayat Önyüksel ◽  
Israel Rubinstein
Keyword(s):  
Conformational Transition ◽  
Critical Micellar Concentration ◽  
Random Coil ◽  
Cheek Pouch ◽  
Hamster Cheek Pouch ◽  
Pituitary Adenylate Cyclase ◽  
Peripheral Microcirculation ◽  
Α Helix

The purpose of this study was to elucidate the interactions between pituitary adenylate cyclase-activating peptide (PACAP)-(1—38) and phospholipids in vitro and to determine whether these phenomena modulate, in part, the vasorelaxant effects of the peptide in the intact peripheral microcirculation. We found that the critical micellar concentration of PACAP-(1—38) was 0.4–0.9 μM. PACAP-(1—38) significantly increased the surface tension of a dipalmitoylphosphatidylcholine monolayer and underwent conformational transition from predominantly random coil in saline to α-helix in the presence of distearoyl-phosphatidylethanolamine-polyethylene glycol (molecular mass of 2,000 Da) sterically stabilized phospholipid micelles (SSM) ( P < 0.05). Using intravital microscopy, we found that aqueous PACAP-(1—38) evoked significant concentration-dependent vasodilation in the intact hamster cheek pouch that was significantly potentiated when PACAP-(1—38) was associated with SSM ( P < 0.05). The vasorelaxant effects of aqueous PACAP-(1—38) were mediated predominantly by PACAP type 1 (PAC1) receptors, whereas those of PACAP-(1—38) in SSM predominantly by PACAP/vasoactive intestinal peptide type 1 and 2 (VPAC1/VPAC2) receptors. Collectively, these data indicate that PACAP-(1—38) self-associates and interacts avidly with phospholipids in vitro and that these phenomena amplify peptide vasoactivity in the intact peripheral microcirculation.

scholarly journals Astrocytes Are More Vulnerable than Neurons to Silicon Dioxide Nanoparticle Toxicity in Vitro

Toxics ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 51
Author(s):  
Jorge Humberto Limón-Pacheco ◽  
Natalie Jiménez-Barrios ◽  
Alejandro Déciga-Alcaraz ◽  
Adriana Martínez-Cuazitl ◽  
Mónica Maribel Mata-Miranda ◽  
...  
Keyword(s):  
Nucleic Acids ◽  
Silicon Dioxide ◽  
Culture Media ◽  
Brain Cell ◽  
Attenuated Total Reflection ◽  
Random Coil ◽  
Silicon Dioxide Nanoparticles ◽  
Neurotoxic Effects ◽  
Α Helix

Some studies have shown that silicon dioxide nanoparticles (SiO2-NPs) can reach different regions of the brain and cause toxicity; however, the consequences of SiO2-NPs exposure on the diverse brain cell lineages is limited. We aimed to investigate the neurotoxic effects of SiO2-NP (0–100 µg/mL) on rat astrocyte-rich cultures or neuron-rich cultures using scanning electron microscopy, Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR), FTIR microspectroscopy mapping (IQ mapping), and cell viability tests. SiO2-NPs were amorphous particles and aggregated in saline and culture media. Both astrocytes and neurons treated with SiO2-NPs showed alterations in cell morphology and changes in the IR spectral regions corresponding to nucleic acids, proteins, and lipids. The analysis by the second derivative revealed a significant decrease in the signal of the amide I (α-helix, parallel β-strand, and random coil) at the concentration of 10 µg/mL in astrocytes but not in neurons. IQ mapping confirmed changes in nucleic acids, proteins, and lipids in astrocytes; cell death was higher in astrocytes than in neurons (10–100 µg/mL). We conclude that astrocytes were more vulnerable than neurons to SiO2-NPs toxicity. Therefore, the evaluation of human exposure to SiO2-NPs and possible neurotoxic effects must be followed up.

Cellular pathways of the conducted electrical response in arterioles of hamster cheek pouch in vitro

1995 ◽  
Vol 269 (6) ◽  
pp. H2031-H2038 ◽  
Author(s):  
J. Xia ◽  
T. L. Little ◽  
B. R. Duling
Keyword(s):  
Electrical Response ◽  
Electrical Current ◽  
Cell Types ◽  
Cheek Pouch ◽  
Resting Membrane Potential ◽  
Hamster Cheek Pouch ◽  
Cellular Pathways ◽  
Current Flows ◽  
Electrical Responses

We have previously shown that conducted vasomotor responses follow patterns that are consistent with a passive spread of electrical current along the length of the arterioles [(Xia and Duling, Am. J. Physiol. 269 (Heart Circ. Physiol. 38): H2022-H2030, 1995]. In this study, we define the cells through which the current flows. Isolated arterioles of hamster cheek pouch were used. The mean resting membrane potential (RMP) for randomly sampled arteriolar cells was -67 mV. When cell types were identified by dye injection, the RMPs were -68 and -67 mV for smooth muscle (SM) and endothelium (EC), respectively. Pulses of KCl induced transient, monophasic depolarizations at the site of stimulation (local), which were conducted decrementally along the length of the arteriole over several millimeters. During electrical conduction, three patterns of responses could be observed, but identical patterns of the conducted electrical responses were always observed in SM and EC. Phenylephrine stimulation also caused transient local and conducted depolarizations in both SM and EC. As with KCl stimuli, shapes of conducted electrical responses were identical in records made in both cell types. The results suggest that SM and EC are electrically coupled both homocellularly and heterocellularly.

scholarly journals Liposomal VIP attenuates phenylephrine- and ANG II-induced vasoconstriction in vivo

1998 ◽  
Vol 275 (2) ◽  
pp. R588-R595
Author(s):  
Hiroyuki Ikezaki ◽  
Hayat Önyüksel ◽  
Israel Rubinstein
Keyword(s):  
Calcium Ionophore ◽  
Cheek Pouch ◽  
Maximal Effect ◽  
Ang Ii ◽  
Hamster Cheek Pouch ◽  
Sterically Stabilized Liposomes ◽  
A 23187 ◽  
Α Helix

The purpose of this study was to determine whether vasoactive intestinal peptide (VIP) modulates vasoconstriction elicited by phenylephrine and ANG II in vivo and, if so, to begin to elucidate the mechanisms underlying this phenomenon. Using intravital microscopy, we found that suffusion of phenylephrine and ANG II elicits significant vasoconstriction in the in situ hamster cheek pouch that is potentiated by VIP-(10—28), a VIP receptor antagonist, but not by VIP-(1—12) ( P< 0.05). Aqueous VIP has no significant effects on phenylephrine- and ANG II-induced vasoconstriction. However, VIP on sterically stabilized liposomes (SSL), a formulation where VIP assumes a predominantly α-helix conformation, significantly attenuates this response. Maximal effect is observed within 30 min and is no longer seen after 60 min. Empty SSL are inactive. Indomethacin has no significant effects on responses induced by VIP on SSL. The vasodilators ACh, nitroglycerin, calcium ionophore A-23187, 8-bromo-cAMP, and isoproterenol have no significant effects on phenylephrine- and ANG II-induced vasoconstriction. Collectively, these data suggest that vasoconstriction modulates VIP release in the in situ hamster cheek pouch and that α-helix VIP opposes α-adrenergic- and ANG II-induced vasoconstriction in this organ in a reversible, prostaglandin-, NO-, cGMP-, and cAMP-independent fashion.

Exogenous calmodulin potentiates vasodilation elicited by phospholipid-associated VIP in vivo

1999 ◽  
Vol 276 (5) ◽  
pp. R1359-R1365 ◽  
Author(s):  
Hiroyuki Ikezaki ◽  
Manisha Patel ◽  
Hayat Önyüksel ◽  
Syed R. Akhter ◽  
Xiao-Pei Gao ◽  
...  
Keyword(s):  
Active Sites ◽  
Calcium Ionophore ◽  
Cheek Pouch ◽  
Induced Responses ◽  
Hamster Cheek Pouch ◽  
Sterically Stabilized Liposomes ◽  
Extracellular Calmodulin ◽  
Peripheral Microcirculation

The purpose of this study was to determine whether exogenous calmodulin potentiates vasoactive intestinal peptide (VIP)-induced vasodilation in vivo and, if so, whether this response is amplified by association of VIP with sterically stabilized liposomes. Using intravital microscopy, we found that calmodulin suffused together with aqueous and liposomal VIP did not potentiate vasodilation elicited by VIP in the in situ hamster cheek pouch. However, preincubation of calmodulin with liposomal, but not aqueous, VIP for 1 and 2 h and overnight at 4°C before suffusion significantly potentiated vasodilation ( P < 0.05). Calmodulin-induced responses were significantly attenuated by calmidazolium, trifluoperazine, and N G-nitro-l-arginine methyl ester (l-NAME) but notd-NAME. The effects ofl-NAME were reversed byl- but notd-arginine. Indomethacin had no significant effects on calmodulin-induced responses. Calmodulin had no significant effects on adenosine-, isoproterenol-, acetylcholine-, and calcium ionophore A-23187-induced vasodilation. Collectively, these data indicate that exogenous calmodulin amplifies vasodilation elicited by phospholipid-associated, but not aqueous, VIP in the in situ peripheral microcirculation in a specific, calmodulin active sites-, and nitric oxide-dependent fashion. We suggest that extracellular calmodulin, phospholipids, and VIP form a novel functionally coordinated class of endogenous vasodilators.

Ca2+ sensitivity of isolated arterioles from the hamster cheek pouch

1991 ◽  
Vol 260 (2) ◽  
pp. H355-H361 ◽  
Author(s):  
M. R. Hynes ◽  
B. R. Duling
Keyword(s):  
Smooth Muscle ◽  
Muscle Layer ◽  
Cheek Pouch ◽  
Maximum Diameter ◽  
Maximal Response ◽  
Bathing Solution ◽  
Hamster Cheek Pouch ◽  
Mean Time ◽  
Concentration Response Curve

When isolated from the hamster cheek pouch, cannulated, and perfused, 60- to 90-microns arterioles spontaneously contracted to 67 +/- 4% of maximum diameter. Vessel sensitivity to variations in extracellular Ca2+ was then evaluated. Tone, regardless of its source, was highly dependent on the concentration of Ca2+ in the bathing solution. The magnitude of responses to changing Ca2+ depended upon which vessel surface (luminal or abluminal) the change was made. For K(+)-induced tone the Ca2+ concentration-response curve was right shifted 60-fold for luminal vs. abluminal changes. These results suggest that restricted diffusion of Ca2+ from lumen to smooth muscle dramatically reduces smooth muscle Ca2+ concentration and that under standard in vitro conditions the smooth muscle layer is effectively isolated from luminal contents. Both the cytosolic and stored Ca2+ in these microvessels were dependent on the Ca2+ concentration in the bathing solution. Abrupt removal of Ca2+ from bath produced a rapid maximal dilation with a mean time to half-maximal response (t1/2 max) of 14 +/- 4 s. Ca2+ replacement induced a return to the previous level of tone with a mean t1/2 max of 8 +/- 3 s. The magnitude of transient responses to caffeine (10 mM) was inversely related to the time of exposure to zero Ca2+ with a rapid decay in magnitude (t1/2 max = 2.7 +/- 0.8 min). These data suggest that the smooth muscle cells of arterioles have a particularly rapid transmembrane Ca2+ flux that is tightly controlled by an intracellular regulatory mechanism, which may explain the generally increased dependence of smaller vessels on extracellular Ca2+.

Vasodilation elicited by liposomal VIP is unimpeded by anti-VIP antibody in hamster cheek pouch

1998 ◽  
Vol 275 (1) ◽  
pp. R56-R62 ◽  
Author(s):  
Hiroyuki Ikezaki ◽  
Sudhir Paul ◽  
Hayat Alkan-Önyüksel ◽  
Manisha Patel ◽  
Xiao-Pei Gao ◽  
...  
Keyword(s):  
Calcium Ionophore ◽  
Myeloma Cell ◽  
Cheek Pouch ◽  
Myeloma Cell Line ◽  
Hamster Cheek Pouch ◽  
High Affinity ◽  
Sterically Stabilized Liposomes

The purpose of this study was to determine whether a monoclonal anti-vasoactive intestinal peptide (VIP) antibody, which binds VIP with high affinity and specificity and catalyzes cleavage of the peptide in vitro, attenuates VIP vasorelaxation in vivo and, if so, whether insertion of VIP on the surface of sterically stabilized liposomes (SSL), which protects the peptide from trypsin- and plasma-catalyzed cleavage in vitro, curtails this response. Using intravital microscopy, we found that suffusion of monoclonal anti-VIP antibody (clone c23.5, IgG2ak), but not of nonimmune antibody (myeloma cell line UPC10, IgG2ak) or empty SSL, significantly attenuates VIP-induced vasodilation in the in situ hamster cheek pouch ( P < 0.05). By contrast, anti-VIP antibody has no significant effects on vasodilation elicited by isoproterenol, nitroglycerin, and calcium ionophore A-23187, agonists that activate intracellular effector systems in blood vessels that mediate, in part, VIP vasoreactivity. Suffusion of VIP on SSL, but not of empty SSL, restores the vasorelaxant effects of VIP in the presence of anti-VIP antibody. Collectively, these data suggest that VIP catalysis by high affinity and specific VIP autoantibodies displaying protease-like activity constitutes a novel mechanism whereby VIP vasoreactivity is regulated in vivo.

Ratiometric measurement of endothelial depolarization in arterioles with a potential-sensitive dye

1996 ◽  
Vol 270 (6) ◽  
pp. H2216-H2227 ◽  
Author(s):  
J. M. Beach ◽  
E. D. McGahren ◽  
J. Xia ◽  
B. R. Duling
Keyword(s):  
Membrane Potential ◽  
Fluorescence Emission ◽  
Cheek Pouch ◽  
Voltage Sensitivity ◽  
Hamster Cheek Pouch ◽  
Endothelial Cell Layer ◽  
Ratiometric Measurement ◽  
Length Constant

A fluorescence ratio technique based on the voltage-sensitive dye 1-(3-sulfonatopropyl)-8-[beta-[2-di-n-butylamino)-6-naphythyl++ +]vinyl] pyridinium betaine (di-8-ANEPPS)has been developed for recording membrane potential changes during vascular responses of arterioles. Perfusion of hamster cheek pouch arterioles with the dye labeled the endothelial cell layer. voltage responses from the endothelium of intact arterioles were determined by analysis of voltage-induced shifts in fluorescence emission wavelengths from dye spectra imaged from the vessel wall. Membrane depolarization caused the dye spectrum to shift toward blue wavelengths, with maximal fluorescence changes near 560 and 620 nm. In isolated nonperfused arterioles, comparison of continuous dual-wavelength recordings with simultaneous microelectrode recordings showed that the ratio of fluorescence intensities (fluorescence at 620 nm to fluorescence at 560 nm) accurately followed changes in membrane potential (6–21 mV) during vasoconstriction. The dye response was linear with respect to potential changes from -56 to -6 mV, with a voltage sensitivity of 9.7% change in the ratio per 100 mV. Membrane potential responses from in vitro and in vivo arterioles after potassium stimulation consisted of rapid ( < 0.5 -s) depolarization followed by slow repolarization over several seconds. Potassium-induced depolarizations were conducted along arterioles, and the values of the electrical length constant for conducted depolarization determined by optical and microelectrode methods were in agreement. We conclude that ratio analysis of di-8-ANEPPS fluorescence emission can be used to accurately record membrane potential changes on the time scale of seconds during vasomotor activity from arterioles.

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