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The lung is an attractive target for drug delivery due to noninvasive administration via inhalation aerosols, avoidance of first-pass metabolism, direct delivery to the site of action for the treatment of respiratory diseases, and the availability of a huge surface area for local drug action and systemic absorption of drug. Colloidal carriers (ie, nanocarrier systems) in pulmonary drug delivery offer many advantages such as the potential to achieve relatively uniform distribution of drug dose among the alveoli, achievement of improved solubility of the drug from its own aqueous solubility, a sustained drug release which consequently reduces dosing frequency, improves patient compliance, decreases incidence of side effects, and the potential of drug internalization by cells. This review focuses on the current status and explores the potential of colloidal carriers (ie, nanocarrier systems) in pulmonary drug delivery with special attention to their pharmaceutical aspects. Manufacturing processes, in vitro/in vivo evaluation methods, and regulatory/toxicity issues of nanomedicines in pulmonary delivery are also discussed.

This study examines the various equilibrium in situ secondary structures of the pharmaceutical heteropolypeptide, KL 4, in the solid state, in solution, and in the monolayer state alone and mixed with dipalmitoylphosphatidylcholine (DPPC) and palmitoyloleoylphosphatidylglycerol (POPG). In situ surface circular dichroism spectroscopy, using a method first reported by Damodaran (Damodaran, S. Anal. Bioanal. Chem. 2003, 376, 182-188), of equilibrated KL 4, DPPC/KL 4, POPG/KL 4, and DPPC/POPG/KL 4 monolayers at the air-water interface was used to examine the in situ two-dimensional conformation of KL 4. Gravimetric vapor sorption by solid KL 4 was used to analyze the effects of water molecules on the conformation of KL 4 when confined as a monolayer at the surface of water. Solid-state KL 4 conformation was determined by X-ray powder diffraction (XRPD). The equilibrium interfacial and spreading properties were measured at 25 degrees C, 37 degrees C, and 45 degrees C using the Wilhelmy plate method and Langmuir film balance. Equilibrium phase transition temperatures were measured using differential scanning calorimetry (DSC). It was found that solid-state KL 4, which takes up very little water, exhibits beta-sheet and alpha-helix secondary structures, whereas KL 4 in solution appears to exist only as an alpha-helix. KL 4 forms a stable, insoluble monolayer, exhibiting beta-sheet and aperiodic structures. These structures provide KL 4, when confined in two-dimensions, the structural flexibility to maximize favorable cationic lysine-water interactions and favorable leucine-leucine hydrophobic and van der Waals interactions; while effectively "shielding" the leucine residues away from water. In DPPC/KL 4 monolayers, KL 4 retains its native beta-sheet and aperiodic structures, consistent with phase separation of DPPC and KL 4 in bilayers and monolayers. In POPG/KL 4 monolayers, KL 4 exhibits an increase in aperiodic secondary structures (loss of beta-sheet) to maximize favorable electrostatic interactions, consistent with the observed negative deviations from ideal monolayer mixing.

This review presents an introduction to Raman scattering and describes the various Raman spectroscopy, Raman microscopy, and chemical imaging techniques that have demonstrated utility in biocolloidal self-assemblies, pharmaceutical drug delivery systems, and pulmonary research applications. Recent Raman applications to pharmaceutical aerosols in the context of pulmonary inhalation aerosol delivery are discussed. The "molecular fingerprint" insight that Raman applications provide includes molecular structure, drug-carrier/excipient interactions, intramolecular and intermolecular bonding, surface structure, surface and interfacial interactions, and the functional groups involved therein. The molecular, surface, and interfacial properties that Raman characterization can provide are particularly important in respirable pharmaceutical powders, as these particles possess a higher surface-area-to-volume ratio; hence, understanding the nature of these solid surfaces can enable their manipulation and tailoring for functionality at the nanometer level for targeted pulmonary delivery and deposition. Moreover, Raman mapping of aerosols at the micro- and nanometer level of resolution is achievable with new, sophisticated, commercially available Raman microspectroscopy techniques. This noninvasive, highly versatile analytical and imaging technique exhibits vast potential for in vitro and in vivo molecular investigations of pulmonary aerosol delivery, lung deposition, and pulmonary cellular drug uptake and disposition in unfixed living pulmonary cells.

The performance of dry powder aerosols for the delivery of drugs to the lungs has been studied extensively in the last decade. The focus for different research groups has been on aspects of the powder formulation, which relate to solid state, surface and interfacial chemistry, bulk properties (static and dynamic) and measures of performance. The nature of studies in this field, tend to be complex and correlations between specific properties and performance seem to be rare. Consequently, the adoption of formulation approaches that on a predictive basis lead to desirable performance has been an elusive goal but one that many agree is worth striving towards. The purpose of this paper is to initiate a discussion of the use of a variety of techniques to elucidate dry particle behavior that might guide the data collection process. If the many researchers in this field can agree on this, or an alternative, guide then a database can be constructed that would allow predictive models to be developed. This is the first of two papers that discuss static and dynamic methods of characterizing dry powder inhaler formulations.

Characteristics of particles included in dry powder inhalers is extended from our previous report (in this journal) to include properties related to their dynamic performance. The performance of dry powder aerosols for pulmonary delivery is known to depend on fluidization and dispersion which reflects particle interactions in static powder beds. Since the solid state, surface/interfacial chemistry and static bulk properties were assessed previously, it remains to describe dynamic performance with a view to interpreting the integrated database. These studies result in complex data matrices from which correlations between specific properties and performance may be deduced. Lactose particles were characterized in terms of their dynamic flow, powder and aerosol electrostatics, and aerodynamic performance with respect to albuterol aerosol dispersion. There were clear correlations between flow properties and aerosol dispersion that would allow selection of lactose particles for formulation. Moreover, these properties can be related to data reported earlier on the morphological and surface properties of the carrier lactose particles. The proposed series of analytical approaches to the evaluation of powders for inclusion in aerosol products has merit and may be the basis for screening and ultimately predicting particle performance with a view to formulation optimization.

The intricate interplay between the bilayer and monolayer properties of phosphatidylcholine (PC), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE) phospholipids, in relation to their polar headgroup properties, and the effects of chain permutations on those polar headgroup properties have been demonstrated for the first time with a set of time-independent bilayer-monolayer equilibria studies. Bilayer and monolayer phase behavior for PE is quite different than that observed for PC and PG. This difference is attributed to the characteristic biophysical PE polar headgroup property of favorable intermolecular hydrogen-bonding and electrostatic interactions in both the bilayer and monolayer states. This characteristic hydrogen-bonding ability of the PE polar headgroup is reflected in the condensed nature of PE monolayers and a decrease in equilibrium monolayer collapse pressure at temperatures below the monolayer critical temperature, T(c) (whether above or below the monolayer triple point temperature, T(t)). This interesting phenomena is compared to equilibrated PC and PG monolayers which collapse to form bilayers at 45 mN/m at temperatures both above and below monolayer T(c). Additionally, it has been demonstrated by measurements of the equilibrium spreading pressure, pie, that at temperatures above the bilayer main gel-to-liquid-crystalline phase-transition temperature, T(m), all liquid-crystalline phospholipid bilayers spread to form monolayers with pie around 45 mN/m, and spread liquid-expanded equilibrated monolayers collapse at 45 mN/m to form their respective thermodynamically stable liquid-crystalline bilayers. At temperatures below bilayer T(m), PC and PG gel bilayers exhibit a drop in bilayer pi(e) values < or =0.2 mN/m forming gaseous monolayers, whereas the value of pic of spread monolayers remains around 45 mN/m. This suggests that spread equilibrated PC and PG monolayers collapse to a metastable liquid-crystalline bilayer structure at temperatures below bilayer T(m) (where the thermodynamically stable bilayer liquid-crystalline phase does not exist) and with a surface pressure of 45 mN/m, a surface chemical property characteristically observed at temperatures above bilayer T(m) (monolayer T(c)). In contrast, PE gel bilayers, which exist at temperatures below bilayer T(m) but above bilayer T(s) (bilayer crystal-to-gel phase-transition temperature), exhibit gel bilayer spreading to form equilibrated monolayers with intermediate pie values in the range of 30-40 mN/m; however, bilayer pie and monolayer pic values remain equal in value to one another. Contrastingly, at temperatures below bilayer T(s), PE crystalline bilayers exhibit bilayer pie values < or =0.2 mN/m forming equilibrated gaseous monolayers, whereas spread monolayers collapse at a value of pic remaining around 30 mN/m, indicative of metastable gel bilayer formation.

Water vapor absorption and desorption at 25 degrees C and phase transition temperatures of phospholipid bilayers were measured as a function of relative humidity (RH) to better understand how the patterns of water vapor absorption and desorption are linked to corresponding phase changes induced by the level of hydration. Comparisons were made of the dipalmitoyl and palmitoyloleyol esters of glycerol derivatized with phosphatidyl-choline, -glycerol, -ethanolamine and with phosphatidic acid. The results suggest that the extent of water vapor absorption and desorption at a given RH reflects the combined effects of water-polar group interaction and access of water to the polar region as controlled by intra- and interbilayer molecular packing and intermolecular attractive and repulsive interactions. The results further suggest that the extent of water vapor absorption and desorption over a range of relative humidities reflects the combined effects of the polar group's ability to interact with water, the access that water has to the polar groups as determined by molecular size and various intermolecular and intrabilayer forces of attraction and repulsion, and interbilayer interactions which influence the degree of order/disorder present in the overall solid-state structure. This behavior is also reflected in the changes observed in the various bilayer phase transition temperatures as a function of RH. Analyses of absorption isotherms suggests that after exceeding a critical RH, water initially interacting with these phospholipids most likely forms either stoichiometric or nonstoichiometric crystal hydrates, as with the disaturated derivatives, or hydrated mesophases, as with the gel states of the monounsaturated derivatives.

Oligomers incorporating the tetrapeptide MSH4, the minimum active sequence of melanocyte stimulating hormone, were synthesized by an A2 + B2 strategy involving microwave-assisted copper-catalyzed azide-alkyne cycloaddition. A2 contained an MSH4 core while B2 contained a (Pro-Gly)3 spacer. Soluble mixtures containing compounds with up to eight MSH4 units were obtained from oligomerizations at high monomer concentrations. The avidities of several oligomeric mixtures were evaluated by means of a competitive binding assay using HEK293 cells engineered to overexpress the melanocortin 4 receptor. When based on total MSH4 concentrations, avidities were only minimally enhanced compared with a monovalent control. The lack of variation in the effect of ligands on probe binding is consistent with high off rates for MSH4 in both monovalent and oligomeric constructs relative to that of the competing probe.

PURPOSE:
Mutations in BEST1, encoding Bestrophin-1 (Best1), cause Best vitelliform macular dystrophy (BVMD) and other inherited retinal degenerative diseases. Best1 is an integral membrane protein localized to the basolateral plasma membrane of the retinal pigment epithelium (RPE). Data from numerous in vitro and in vivo models have demonstrated that Best1 regulates intracellular Ca(2+) levels. Although it is known from in vitro and crystal structure data that Best1 is also a calcium-activated anion channel, evidence for Best1 functioning as a channel in human RPE is lacking. To assess Best1-associated channel activity in the RPE, we examined the transepithelial electrical properties of fetal human RPE (fhRPE) cells, which express endogenous Best1.

METHODS:
Using adenovirus-mediated gene transfer, we overexpressed Best1 and the BVMD mutant Best1(W93C) in fhRPE cells and assessed resting transepithelial potential (TEP), transepithelial resistance, short circuit current (Isc), and intracellular Ca(2+) levels. Cl(-) currents were directly measured in transfected HEK293 cells using whole-cell patch clamp.

RESULTS:
Best1(W93C) showed ablated Cl(-) currents and, when co-expressed, suppressed the channel activity of Best1 in HEK293 cells. In fhRPE, overexpression of Best1 increased TEP and Isc, while Best1(W93C) diminished TEP and Isc. Substitution of Cl(-) in the bath media resulted in a significant reduction of Isc in monolayers overexpressing Best1, but no significant Isc change in monolayers expressing Best1(W93C). We removed Ca(2+) as a limit on transepithelial electrical properties by treating cells with ionomycin, and found that changes in Isc and TEP for monolayers expressing Best1 were absent in monolayers expressing Best1(W93C). Similarly, inhibition of calcium-activated anion channels with niflumic acid reduced both Isc and TEP of control and Best1 monolayers, but did not notably affect Best1(W93C) monolayers. Stimulation with extracellular ATP induced an increase in TEP in control monolayers that was greater than that observed in those expressing Best1(W93C). Examination of [Ca(2+)]i following ATP stimulation demonstrated that the expression of Best1(W93C) impaired intracellular Ca(2+) signaling.

CONCLUSIONS:
These data indicate that Best1 activity strongly influences electrophysiology and Ca(2+) signaling in RPE cells, and that a common BVMD mutation disrupts both of these parameters. Our findings support the hypothesis that Best1 functions as an anion channel in human RPE.

NHE8 is a newly identified NHE isoform expressed in rat intestine. To date, the kinetic characteristics and the intestinal segmental distribution of this NHE isoform have not been studied. This current work was performed to determine the gene expression pattern of the NHE8 transporter along the gastrointestinal tract, as well as its affinity for Na(+), H(+), and sensitivity to known NHE inhibitors HOE694 and S3226. NHE8 was differentially expressed along the GI tract. Higher NHE8 expression was seen in stomach, duodenum, and ascending colon in human, while higher NHE8 expression was seen in jejunum, ileum and colon in adult mouse. Moreover, the expression level of NHE8 is much higher in the stomach and jejunum in young mice compared with adult mice. To evaluate the functional characterictics of NHE8, the pH indicator SNARF-4 was used to monitor the rate of intra-cellular pH (pH(i)) recovery after an NH(4)Cl induced acid load in NHE8 cDNA transfected PS120 cells. The NHE8 cDNA transfected cells exhibited a sodium-dependent proton exchanger activity having a Km for pH(i) of approximately pH 6.5, and a Km for sodium of approximately 23 mM. Low concentration of HOE694 (1 microM) had no effect on NHE8 activity, while high concentration (10 microM) significantly reduced NHE8 activity. In the presence of 80 microM S3226, the NHE8 activity was also inhibited significantly. In conclusion, our work suggests that NHE8 is expressed along the gastrointestinal tract and NHE8 is a functional Na(+)/H(+) exchanger with kinetic characteristics that differ from other apically expressed NHE isoforms.

No abstract given.

Fluorescent probes offer insight into the highly localized and rapid molecular events that underlie cell function. However, methods are required that can efficiently transform the limited signals from such probes into high-resolution images. An algorithm has now been developed that produces highly accurate images of fluorescent probe distribution inside cells with minimal light exposure and a conventional light microscope. This method provides resolution nearly four times greater than that currently available from any fluorescence microscope and was used to study several biological problems.

Mammalian cells generally regulate their intracellular pH (pHi) via collaboration between Na(+)-H+ exchanger and HCO3- transport. In addition, a number of normal mammalian cells have been identified that express H(+)-adenosinetriphosphatases (ATPases) in their plasma membranes. Because tumor cells often maintain a high pHi, we hypothesized that they might functionally express H(+)-ATPases in their plasma membranes. In the first phase of the present study, we screened 19 normal and tumorigenic human cell lines for the presence of plasmalemmal H(+)-ATPase activity using bafilomycin A1 to inhibit V-type H(+)-ATPase and Sch-28080 to inhibit P-type H(+)-K(+)-ATPase. Bafilomycin A1 decreased pHi in the six tumor cell lines with the highest resting pHi in the absence of HCO3-. Sch-28080 did not affect pHi in any of the human cells. Simultaneous measurement of pH in the cytoplasm and in the endosomes/lysosomes localized the activity of bafilomycin to the plasma membrane in three cell lines. In the second phase of this study, these three cell lines were shown to recover from NH4(+)-induced acid loads in the absence of Na+. This recovery was inhibited by N-ethylmaleimide, bafilomycin A1, and ATP depletion and was not significantly affected by vanadate, Sch-28080, or hexamethyl amiloride. These results indicate that a vacuolar type H(+)-ATPase is expressed in the plasma membrane of some tumor cells.

Hexokinase isozyme I is proposed to be associated with mitochondria in vivo. Moreover, it has been suggested that this association is modulated in coordination with changes in cell metabolic state. To test these hypotheses, we analyzed the subcellular distribution of hexokinase relative to mitochondria in paraformaldehyde-fixed astrocytes using immunocytochemistry and quantitative three-dimensional confocal microscopy. Analysis of the extent of colocalization between hexokinase and mitochondria revealed that approximately 70% of cellular hexokinase is associated with mitochondria under basal metabolic conditions. In contrast to the immunocytochemical studies, between 15 to 40% of cellular hexokinase was found to be associated with mitochondria after fractionation of astrocyte cultures depending on the exact fractionation conditions. The discrepancy between fractionation studies and those based on imaging of distributions in fixed cells indicates the usefulness of using techniques that can evaluate the distributions of "cytosolic" enzymes in cells whose subcellular ultrastructure is not severely disrupted. To determine if hexokinase distribution is modulated in concert with changes in cell metabolism, the localization of hexokinase with mitochondria was evaluated after inhibition of glucose metabolism with 2-deoxyglucose. After incubation with 2-deoxyglucose there was an approximate 35% decrease in the amount of hexokinase associated with mitochondria. These findings support the hypothesis that hexokinase is bound to mitochondria in rat brain astrocytes in vivo, and that this association is sensitive to cell metabolic state.

Thyroid hormone, specifically thyroxine, alters cytoskeletal organization in astrocytes by modulating actin polymerization and, in turn, regulates the turnover of the short-lived membrane protein, type II iodothyronine 5'-deiodinase. In the absence of thyroxine, approximately 35% of the total cellular actin is depolymerized, and greater than 90% of the deiodinase is found in the plasma membrane and not associated with the cytoskeleton. Addition of thyroxine promotes actin polymerization and decreases the depolymerized actin to approximately 10% of the total actin pool, induces binding of the deiodinase to F-actin, and promotes rapid internalization of the enzyme. These data provide direct evidence that the actin cytoskeleton participates in the inactivation pathway of the deiodinase by translocating this short-lived plasma membrane protein to an internal membrane pool.

To study the regulation of glycogen utilization in vascular smooth muscle, we measured the content of glycogen and glucose 6-phosphate and the activity of the glycogen phosphorylase and glycogen debrancher enzymes in porcine carotid artery. During active contraction, the rates of glycogen phosphorylase and glycogenolysis were as high as expected. Despite this, glycogen content did not decrease to less than approximately 50% of control levels even after sustained contractions. The activity of glycogen debrancher enzyme was found to be limiting glycogen utilization at this point. Although glycogenolysis is closely coordinated with increases in oxidative metabolism concomitant with active contraction, the maximal level of tension obtained after stimulation was not substantially reduced under conditions where glycogen debrancher enzyme was limiting glycogen utilization. On the other hand, the rate of tension generation was increased in these tissues. Thus glycogen utilization is not necessary for maximal force generation per se, but may influence other muscle contractile properties. Finally, during steady-state tension maintenance, glycogen utilization is likely to be regulated by the intracellular concentrations of metabolic intermediates (glucose, glucose 6-phosphate), as it is in skeletal muscle.

Nicotinamide adenine dinucleotide (NADH) plays a critical role in oxidative phosphorylation as the primary source of reducing equivalents to the respiratory chain. Using a modified fluorescence microscope, we have obtained spectra and images of the blue autofluorescence from single rat cardiac myocytes. The optical setup permitted rapid acquisition of fluorescence emission spectra (390-595 nm) or intensified digital video images of individual myocytes. The spectra showed a broad fluorescence centered at 447 +/- 0.2 nm, consistent with mitochondrial NADH. Addition of cyanide resulted in a 100 +/- 10% increase in fluorescence, while the uncoupler FCCP resulted in a 82 +/- 4% decrease. These two transitions were consistent with mitochondrial NADH and implied that the myocytes were 44 +/- 6% reduced under the resting control conditions. Intracellular fluorescent structures were observed that correlated with the distribution of a mitochondrial selective fluorescent probe (DASPMI), the mitochondrial distribution seen in published electron micrographs, and a metabolic digital subtraction image of the cyanide fluorescence transition. These data are consistent with the notion that the blue autofluorescence of rat cardiac myocytes originates from mitochondrial NADH.

The relation between the activity of the Na+-K+-ATPase and the metabolic source of ATP was investigated in suspensions of MDCK cells. The pump activity of Na+-K+-ATPase was estimated from the initial rate of ouabain-sensitive K+ uptake into K+-depleted cells. Uptake was initiated by the reintroduction of K+ to the medium in which the cells were suspended. The metabolic source of ATP was varied by changing the substrates supplied to the suspension. Cells respiring on glutamine produced ATP from oxidative metabolism alone, whereas cells incubated with glucose and glutamine produced ATP via glycolysis and oxidative phosphorylation. Over a wide range of extracellular K+ concentrations, the initial rate of K+ uptake was faster in cells incubated with glucose and glutamine when compared with cells incubated with glutamine alone. Kinetic analysis together with ouabain-binding data demonstrated that this increase in K+ uptake was due to an increase in maximal velocity (Vmax) at a constant number of Na+-K+-ATPase transport sites. In addition, steady-state studies revealed that the addition of glucose to K+-depleted cells respiring on glutamine alone resulted in a net ouabain-sensitive influx of K+. These data demonstrate that in MDCK cells the maximal capacity for transport via the Na+-K+-ATPase is greater when ATP is produced from both glycolysis and oxidative phosphorylation than when ATP is produced from oxidative phosphorylation alone.(ABSTRACT TRUNCATED AT 250 WORDS)

In vascular smooth muscle, oxidative phosphorylation and glycolysis are independently regulated. Previous studies indicated that the independent regulation of these pathways was related to a compartmentation of carbohydrate metabolism. To further study carbohydrate metabolism, glucose transport and the incorporation of radiolabel from glucose into glycogen and lactate were measured after the oxidative and glycolytic pathways were independently altered. Ouabain stimulated mechanical activity, oxygen consumption, and glycogenolysis, whereas lactate production was decreased. Although glycogenolysis was substantial, glucose was the only substrate for lactate, indicating that intermediates derived from glycogen do not mix with those from glucose uptake. Thus glycogenolysis and glycolysis are carried out by independent enzymatic pathways. Insulin-stimulated lactate production and glucose transport without affecting the other parameters. Again, lactate was produced only from glucose. Phenytoin decreased isometric tension and oxygen consumption, whereas stimulating lactate production and glycogenolysis. Glycogen was the primary substrate for the lactate produced. Our findings indicate that the compartmentation of substrate utilization is ascribable to the coordination of glycogenolysis with increases in oxygen consumption and the coupling of glycolysis to the Na-K-adenosine triphosphatase. The coupling of independent energy providing pathways to specific endergonic processes indicates a mechanism by which cellular energetic efficiency may be optimized.

The energy metabolism of two continuous cell lines of renal origin, MDCK (Madin-Darby dog kidney) and A6 (toad kidney), was investigated by measuring the oxygen consumption (QO2) and lactate production (Jlac) by cells taken into suspension from monolayer cultures. Cells suspended from fully differentiated monolayers produce approximately 80% of their ATP requirements from oxidative metabolism. The interrelationship between ion transport and metabolism was determined by analyzing the ouabain sensitive components of intermediary metabolism under control conditions and after the stimulation of active Na-K transport with nystatin. In both cell lines, approximately 25% of the net rate of ATP production was inhibited by ouabain. Ouabain inhibited Jlac by 40% in MDCK and 45% in A6 cells, whereas QO2 was decreased by only 20% in both cell lines. In the presence of 0.05 mg nystatin/mg cell protein, ouabain sensitive Jlac increased by 75% in MDCK and was more than doubled in A6, whereas the ouabain-sensitive QO2 was not statistically different than control. This preferential stimulation of glycolysis with nystatin was not due to a limited capacity of mitochondrial oxidative phosphorylation since nystatin treatment of cells incubated without glucose (no glycolysis) significantly elevated the rate of QO2. These data demonstrate that aerobic glycolysis is more sensitive than is QO2 to changes in hydrolytic activity of the Na-K-adenosine triphosphatase (ATPase), in both cell lines.

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