Hydrophilic cyclodextrin derivatives enable effective oral administration of steroidal hormones

Unveiling the dynamic and thermodynamic interactions of hydrocortisone with β-cyclodextrin and its methylated derivatives through insights from molecular dynamics simulations

Cyclodextrins (CDs) can enhance the stability and bioavailability of pharmaceutical compounds by encapsulating them within their cavities. This study utilized molecular dynamics simulations to investigate the interaction mechanisms between hydrocortisone (HC) and various methylated CD derivatives. The results reveal that the loading of HC into CD cavities follows different mechanisms depending on the degree and position of methylation. Loading into βCD and 6-MeβCD was more complete, with the hydroxyl groups of HC facing the primary hydroxyl rim (PHR) and the ketone side facing the secondary hydroxyl rim (SHR). In contrast, 2,3-D-MeβCD and 2,6-D-MeβCD showed a different loading mechanism, with the ketone side facing the PHR and the hydroxyl groups facing the SHR. The root mean square fluctuation (RMSF) analysis demonstrated that methylation increases the flexibility of CD heavy atoms, with 3-MeβCD and 2,3-D-MeβCD exhibiting the highest flexibility. However, upon inclusion of HC, 3-MeβCD, 2,3-D-MeβCD, 2-MeβCD, and 6-MeβCD showed a significant reduction in flexibility, suggesting a more rigid structure that effectively retains HC within their cavities. The radial distribution function revealed a significant reduction in the number of water molecules within the innermost layer of the methylated CD cavities, particularly in TMeβCD, indicating a decrease in polarity. The presence of HC led to the release of high-energy water molecules, creating more favorable conditions for HC loading. Conformational analysis showed that methylation caused a partial decrease in the area of the PHR, a significant decrease in the area of the middle rim, and a notable decrease in the area of the SHR. The loading of HC increased the area of the PHR in most derivatives, with the most pronounced increase observed in 2,6-D-MeβCD and 6-MeβCD. The analysis of interaction energies and binding free energies demonstrated that the binding of HC to methylated CD derivatives is thermodynamically more favorable than to βCD, with the strongest association observed for 6-MeβCD, 2-MeβCD, and 2,3-D-MeβCD.

Dissolution Improvement of Progesterone and Testosterone via Impregnation on Mesoporous Silica Using Supercritical Carbon Dioxide

Progesterone (PRG) and testosterone (TST) were impregnated on mesoporous silica (ExP) particles via supercritical carbon dioxide (scCO2) processing at various pressures (10–18 MPa), temperatures (308.2–328.2 K), and time (30–360 min). The impact of a co-solvent on the impregnation was also studied at the best determined pressure and temperature. The properties of the drug embedded in silica particles were analysed via gas chromatography (GC), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and nitrogen adsorption. An impregnation of 1 to 82 mg/g for PRG and 0.1 to 16 mg/g for TST was obtained depending on the processing parameters. There was a significant effect of pressure, time, and co-solvent on the impregnation efficiency. Generally, an increase in time and pressure plus the use of co-solvent led to an improvement in drug adsorption. Conversely, a rise in temperature resulted in lower impregnation of both TST and PRG on ExP. There was a substantial increase in the dissolution rate (> 90% drug release within the first 2 min) of both TST and PRG impregnated in silica particles when compared to the unprocessed drugs. This dissolution enhancement was attributed to the amorphisation of both drugs due to their adsorption on mesoporous silica.

Graphical Abstract

Implementation of Water-Soluble Cyclodextrin-Based Polymers in Biomedical Applications: How Far are we?

Cyclodextrin-based polymers can be prepared starting from the naturally occurring monomers following green and low-cost procedures. They can be selectively derivatized pre- or post-polymerization allowing to fine-tune functionalities of ad hoc customized polymers. Preparation nowadays has reached the 100 g scale thanks also to the interest of industries in these extremely versatile compounds. During the last 15 years these macromolecules have been the object of intense investigations in view of possible biomedical applications as the ultimate goal and large amounts of scientific data are now available. Compared to their monomeric models, already used in the formulation of various therapeutic agents, they display superior behavior in terms of their solubility in water and solubilizing power towards drugs incompatible with biological fluids. Moreover, they allow the combination of more than one type of therapeutic agent in the polymeric system. In this review we provide a complete state-of-the-art on the knowledge and potentialities of water-soluble cyclodextrin-based polymers as therapeutic agents as well as carrier systems for different types of therapeutics to implement combination therapy. Finally, we give a perspective on their assets for innovation in disease treatment as well as their limits that still need to be addressed. This article is protected by copyright. All rights reserved.

Comparative bioavailability study following a single dose intravenous and buccal administration of remdesivir in rabbits

As remdesivir, the first FDA-approved drug for SARS-CoV-2 infection, can be used only for hospitalized patients due to intravenous administration, there is an urgent need of effective oral antiviral formulations to be used at early stage of infection in an outpatient setting. The present paper reports on the comparative pharmacokinetics of the electrospun nanofiber remdesivir/sulfobutyl ether beta-cyclodextrin formulation after intravenous and buccal administration. It was postulated that oral transmucosal administration avoids remdesivir from metabolic transformation and intact remdesivir can be detected in plasma, but only the active metabolite GS-441524 could be experimentally detected at a significantly lower plasma level, than that provided by the intravenous route. In buccally treated animals, the metabolite GS-441524 appeared only at 1  h after treatment, while in intravenously treated animals, GS-441524 was possible to quantify even at the first time-point of blood collection. Further optimization of formulation is required to improve pharmacokinetics of remdesivir-sulfobutyl ether beta-cyclodextrin formulation upon buccal administration.

History of cyclodextrin-based polymers in food and pharmacy: a review

Cyclodextrins are glucose macrocycles whose inclusional capabilities towards non-polar solutes can be modulated with the help of other macrostructures. The incorporation of cyclodextrin moieties into larger structures produces five types of new materials: crosslinked networks, functionalized chains, amphiphilic cyclodextrins, polyrotaxanes and nanocomposites. This review presents crosslinking and grafting to prepare covalently-attached cyclodextrins, and applications in the food and pharmaceutical sectors, from an historical point of view. In food science, applications include debittering of juices, retention of aromas and release of preservatives from packaging. In biomedical science, cyclodextrin polymers are applied classically to drug release, and more recently to gene delivery and regenerative medicine. The remarkable points are: 1) epichlorohydrin and diisocyanates have been extensively used as crosslinkers since the 1960s, but during the last two decades more complex cyclodextrin polymeric structures have been designed. 2) The evolution of cyclodextrin polymers matches that of macromolecular materials with regard to complexity, functionality and capabilities. 3) The use of cyclodextrin polymers as sorbents in the food sector came first, but smart packaging is now an active challenge. Cyclodextrins have also been recently used to design treatments against the coronavirus disease 2019 (COVID-19).

Glabrescione B delivery by self-assembling micelles efficiently inhibits tumor growth in preclinical models of Hedgehog-dependent medulloblastoma

Aberrant activation of the Hedgehog (Hh) pathway leads to the development of several tumors, including medulloblastoma (MB), the most common pediatric brain malignancy. Hh inhibitors acting on GLI1, the final effector of Hh signaling, offer a valuable opportunity to overcome the pitfalls of the existing therapies to treat Hh-driven cancers. In this study, the toxicity, delivery, biodistribution, and anticancer efficacy of Glabrescione B (GlaB), a selective GLI1 inhibitor, were investigated in preclinical models of Hh-dependent MB. To overcome its poor water solubility, GlaB was formulated with a self-assembling amphiphilic polymer forming micelles, called mPEG_5kDa-cholane. mPEG_5kDa-cholane/GlaB showed high drug loading and stability, low cytotoxicity, and long permanence in the bloodstream. We found that mPEG_5kDa-cholane efficiently enhanced the solubility of GlaB, thus avoiding the use of organic solvents. mPEG_5kDa-cholane/GlaB possesses favorable pharmacokinetics and negligible toxicity. Remarkably, GlaB encapsulated in mPEG_5kDa-cholane micelles was delivered through the blood-brain barrier and drastically inhibited tumor growth in both allograft and orthotopic models of Hh-dependent MB. Our findings reveal that mPEG_5kDa-cholane/GlaB is a good candidate for the treatment of Hh-driven tumors and provide relevant implications for the translation of GlaB into clinical practice.

Selective modifications at the different positions of cyclodextrins: a review of strategies

Cyclodextrins (CDs) are natural, nontoxic, and biodegradable macrocyclic oligosaccharides. As supramolecular hosts, CDs have numerous applications in many aspects. However, nonsubstituted CDs have the disadvantages of solubility, unspecific recognition sites, and weak interactions with guest molecules. Therefore, new CD-based derivatives are successfully designed, synthesized, and widely used in various fields. This contribution outlines the research progress in CD derivatives. In particular, this review emphasizes the synthesis and application of CDs modified through functionalization in definite positions, random substitution, and reconstruction of the skeleton. At the end of this review, a summary and future directions are presented.

Synthesis and in vitro evaluation of cyclodextrin hyaluronic acid conjugates as a new candidate for intestinal drug carrier for steroid hormones

Steroid hormones became increasingly interesting as active pharmaceutical ingredients for the treatment of endocrine disorders. However, medical applications of many steroidal drugs are inhibited by their very low aqueous solubilities giving rise to low bioavailabilities. Therefore, the prioritized oral administration of steroidal drugs remains problematic. Cyclodextrins are promising candidates for the development of drug delivery systems for oral route applications, since they solubilize hydrophobic steroids and increase their rate of transport in aqueous environments. In this study, the synthesis and characterization of polymeric β-cyclodextrin derivates is described, which result from the attachment of a hydrophilic β-CD-thioether to hyaluronic acid. Host-guest complexes of the synthesized β-cyclodextrin hyaluronic acid conjugates were formed with two poorly soluble model steroids (β-estradiol, dexamethasone) and compared to monomeric β-cyclodextrin derivates regarding solubilization and complexation efficiency. The β-cyclodextrin-drug (host-guest) complexes were evaluated in vitro for their suitability (cytotoxicity and transport rate) as intestinal drug carriers for steroid hormones. In case of β-estradiol, higher solubilities could be achieved by complexation with both synthesized β-cyclodextrin derivates, leading to significantly higher intestinal transport rates in vitro. However, this success could not be shown for dexamethasone, which namely solubilized better, but could not enhance the transport rate significantly. Thus, this study demonstrates the biocompatibility of the synthesized and characterized β-cyclodextrin derivates and shows their potential as new candidate for intestinal drug carrier for steroid hormones like β-estradiol.

Dorsal Hippocampal Actin Polymerization Is Necessary for Activation of G-Protein-Coupled Estrogen Receptor (GPER) to Increase CA1 Dendritic Spine Density and Enhance Memory Consolidation

Activation of the membrane estrogen receptor G-protein-coupled estrogen receptor (GPER) in ovariectomized mice via the GPER agonist G-1 mimics the beneficial effects of 17β-estradiol (E₂) on hippocampal CA1 spine density and memory consolidation, yet the cell-signaling mechanisms mediating these effects remain unclear. The present study examined the role of actin polymerization and c-Jun N-terminal kinase (JNK) phosphorylation in mediating effects of dorsal hippocampally infused G-1 on CA1 dendritic spine density and consolidation of object recognition and spatial memories in ovariectomized mice. We first showed that object learning increased apical CA1 spine density in the dorsal hippocampus (DH) within 40 min. We then found that DH infusion of G-1 increased both CA1 spine density and phosphorylation of the actin polymerization regulator cofilin, suggesting that activation of GPER may increase spine morphogenesis through actin polymerization. As with memory consolidation in our previous work (Kim et al., 2016), effects of G-1 on CA1 spine density and cofilin phosphorylation depended on JNK phosphorylation in the DH. Also consistent with our previous findings, E₂-induced cofilin phosphorylation was not dependent on GPER activation. Finally, we found that infusion of the actin polymerization inhibitor, latrunculin A, into the DH prevented G-1 from increasing apical CA1 spine density and enhancing both object recognition and spatial memory consolidation. Collectively, these data demonstrate that GPER-mediated hippocampal spinogenesis and memory consolidation depend on JNK and cofilin signaling, supporting a critical role for actin polymerization in the GPER-induced regulation of hippocampal function in female mice.SIGNIFICANCE STATEMENT Emerging evidence suggests that G-protein-coupled estrogen receptor (GPER) activation mimics effects of 17β-estradiol on hippocampal memory consolidation. Unlike canonical estrogen receptors, GPER activation is associated with reduced cancer cell proliferation; thus, understanding the molecular mechanisms through which GPER regulates hippocampal function may provide new avenues for the development of drugs that provide the cognitive benefits of estrogens without harmful side effects. Here, we demonstrate that GPER increases CA1 dendritic spine density and hippocampal memory consolidation in a manner dependent on actin polymerization and c-Jun N-terminal kinase phosphorylation. These findings provide novel insights into the role of GPER in mediating hippocampal morphology and memory consolidation, and may suggest first steps toward new therapeutics that more safely and effectively reduce memory decline in menopausal women.

Mechanisms underlying the rapid effects of estradiol and progesterone on hippocampal memory consolidation in female rodents

Contribution to Special Issue on Fast effects of steroids. Although rapid effects of 17β‑estradiol (E₂) and progesterone on cellular functions have been observed for several decades, a proliferation of data in recent years has demonstrated the importance of these actions to cognition. In particular, an emerging literature has demonstrated that these hormones promote the consolidation of spatial and object recognition memories in rodents via rapid activation of numerous cellular events including cell signaling, histone modifications, and local protein translation in the hippocampus. This article provides an overview of the evidence demonstrating that E₂ and progesterone enhance hippocampal memory consolidation in female rodents, and then discusses numerous molecular mechanisms thus far shown to mediate the beneficial effects of these hormones on memory formation.

New Polyfunctional Derivatives of β-Cyclodextrin Suited for the Formulation of Drug Release Systems

New functional derivatives of β-cyclodextrin were obtained by grafting β-cyclodextrin with epoxides of protected polyols, such as glycidyliso propylideneglycerol, glycidyldiisopropylidenexylitol and glycidyldiisopropyl idenearabitol. The glycidyl ether of 2-pyrrolidone was also used. The reaction products have a degree of substitution per glucose residue included between 0.5 and 1. Selective removal of protecting groups from cyclodextrin substituents, carried out under conditions not affecting the integrity of the cyclodextrin ring, gave rise to hydrosoluble cyclodextrin derivatives whose hydrophilic/hydropho bic balance was modulated by controlling the extent of deprotection. The un usual solubility in water, greater than 350%, for both protected and depro tected derivatives, represents a breakthrough for a wide variety of applications requiring polymeric materials with remarkable water solubility.

Amorphous Soluble Cyclodextrins: Pharmaceutical and Therapeutic Uses

Amorphous water soluble derivatives of cyclodextrins are potent, nontoxic solubilizers of drugs and lipids. Their use as excipients which enable effective oral administration of sex hormones is described. Furthermore, these com pounds were used intravenously as an active drug to assist an organism in unloading a toxic lipophile.

Sex steroid hormones matter for learning and memory: estrogenic regulation of hippocampal function in male and female rodents

Ample evidence has demonstrated that sex steroid hormones, such as the potent estrogen 17β-estradiol (E2), affect hippocampal morphology, plasticity, and memory in male and female rodents. Yet relatively few investigators who work with male subjects consider the effects of these hormones on learning and memory. This review describes the effects of E2 on hippocampal spinogenesis, neurogenesis, physiology, and memory, with particular attention paid to the effects of E2 in male rodents. The estrogen receptors, cell-signaling pathways, and epigenetic processes necessary for E2 to enhance memory in female rodents are also discussed in detail. Finally, practical considerations for working with female rodents are described for those investigators thinking of adding females to their experimental designs.

Formulation and evaluation of buccoadhesive quetiapine fumarate tablets

The aim of present study was to develop and evaluate buccoadhesive Quetiapine Fumarate (QF) tablets, which is extensively metabolised by liver. Buccoadhesive tablets of QF were prepared using HPMC K4M, HPMC K15M and combination of carbopol and HPC as mucoadhesive polymers by direct compression method. Sodium deoxycholate was added to formulation to improve the permeation of drug. The formulations were tested for bioadhesion strength, ex vivo residence time, swelling time and in vitro dissolution studies and ex vivo permeation studies. Optimized formulation (F3) showed 92% in vitro release in 8 h and 67% permeation of drug through porcine buccal mucosa and followed fickian release mechanism with zero order kinetics. FTIR studies of optimized formulation showed no evidence of interaction between the drug and polymers. In vivo mucoadhesive behaviour of optimized formulation was performed and subjective parameters were evaluated.

The progesterone-induced enhancement of object recognition memory consolidation involves activation of the extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin (mTOR) pathways in the dorsal hippocampus

Although much recent work has elucidated the biochemical mechanisms underlying the modulation of memory by 17β-estradiol, little is known about the signaling events through which progesterone (P) regulates memory. We recently demonstrated that immediate post-training infusion of P into the dorsal hippocampus enhances object recognition memory consolidation in young ovariectomized female mice (Orr et al., 2009). The goal of the present study was to identify the biochemical alterations that might underlie this mnemonic enhancement. We hypothesized that the P-induced enhancement of object recognition would be dependent on activation of the ERK and mTOR pathways. In young ovariectomized mice, we found that bilateral dorsal hippocampal infusion of P significantly increased levels of phospho-p42 ERK and the mTOR substrate S6K in the dorsal hippocampus 5 min after infusion. Phospho-p42 ERK levels were downregulated 15 min after infusion and returned to baseline 30 min after infusion, suggesting a biphasic effect of P on ERK activation. Dorsal hippocampal ERK and mTOR activation were necessary for P to facilitate memory consolidation, as suggested by the fact that inhibitors of both pathways infused into the dorsal hippocampus immediately after training blocked the P-induced enhancement of object recognition. Collectively, these data provide the first demonstration that the ability of P to enhance memory consolidation depends on the rapid activation of cell signaling and protein synthesis pathways in the dorsal hippocampus.

Dorsal hippocampal progesterone infusions enhance object recognition in young female mice

The effects of progesterone on memory are not nearly as well studied as the effects of estrogens. Although progesterone can reportedly enhance spatial and/or object recognition in female rodents when given immediately after training, previous studies have injected progesterone systemically, and therefore, the brain regions mediating this enhancement are not clear. As such, this study was designed to determine the role of the dorsal hippocampus in mediating the beneficial effect of progesterone on object recognition. Young ovariectomized C57BL/6 mice were trained in a hippocampal-dependent object recognition task utilizing two identical objects, and then immediately or 2 h afterwards, received bilateral dorsal hippocampal infusions of vehicle or 0.01, 0.1, or 1.0 microg/microl water-soluble progesterone. Forty-eight hours later, object recognition memory was tested using a previously explored object and a novel object. Relative to the vehicle group, memory for the familiar object was enhanced in all groups receiving immediate infusions of progesterone. Progesterone infusion delayed 2 h after training did not affect object recognition. These data suggest that the dorsal hippocampus may play a critical role in progesterone-induced enhancement of object recognition.

Formulation and evaluation of bioadhesive buccal drug delivery of tizanidine hydrochloride tablets

The study aim was concerned with formulation and evaluation of bioadhesive buccal drug delivery of tizanidine hydrochloride tablets, which is extensively metabolized by liver. The tablets were prepared by direct compression using bioadhesive polymers such as hydroxylpropyl methylcellulose K4M, sodium carboxymethyl cellulose alone, and a combination of these two polymers. In order to improve the permeation of drug, different permeation enhancers like beta-cyclodextrin (beta-CD), hydroxylpropyl beta-cyclodextrin (HP-beta-CD), and sodium deoxycholate (SDC) were added to the formulations. The beta-CD and HP-beta-CD were taken in 1:1 molar ratio to drug in formulations. Bioadhesion strength, ex vivo residence time, swelling, and in vitro dissolution studies and ex vivo permeation studies were performed. In vitro release of optimized bioadhesive buccal tablet was found to be non-Fickian. SDC was taken in 1%, 2%, and 3% w/w of the total tablet weight. Stability studies in natural saliva indicated that optimized formulation has good stability in human saliva. In vivo mucoadhesive behavior of optimized formulation was performed in five healthy male human volunteers and subjective parameters were evaluated.

Dose-dependent effects of post-training estradiol plus progesterone treatment on object memory consolidation and hippocampal extracellular signal-regulated kinase activation in young ovariectomized mice

Previous work from our laboratory has shown that the ability of estradiol to enhance object memory consolidation in young ovariectomized mice is dependent on dorsal hippocampal activation of the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) signaling pathway [Fernandez SM, Lewis MC, Pechenino AS, Harburger LL, Orr PT, Gresack JE, Schafe GE, Frick KM (2008) Estradiol-induced enhancement of object memory consolidation involves hippocampal extracellular signal-regulated kinase activation and membrane-bound estrogen receptors. J Neurosci 28:8660-8667]. However, it is unclear if estradiol modulates memory or ERK activation similarly in the presence of progesterone. Therefore, the present study investigated effects of combined estradiol and progesterone treatment on object memory consolidation and dorsal hippocampal ERK activation in young ovariectomized C57BL/6 mice. Object memory was tested in a novel object recognition task. Immediately after training, mice received intraperiotoneal (i.p.) injections of vehicle, 17beta-estradiol (E(2); 0.2 mg/kg), or E(2) plus 5, 10, or 20 mg/kg progesterone (P). Forty-eight hours later, mice receiving E(2) alone or E(2) plus 10 or 20 mg/kg P exhibited significantly enhanced memory for the novel object relative to chance, whereas those receiving vehicle or E(2) plus 5 mg/kg P spent no more time than chance with the novel object. Two weeks later, ERK phosphorylation was measured in the dorsal hippocampus 1 h after i.p. injection of vehicle, E(2), or E(2) plus P. Consistent with our previous work [Fernandez SM, Lewis MC, Pechenino AS, Harburger LL, Orr PT, Gresack JE, Schafe GE, Frick KM (2008) Estradiol-induced enhancement of object memory consolidation involves hippocampal extracellular signal-regulated kinase activation and membrane-bound estrogen receptors. J Neurosci 28:8660-8667], E(2) alone significantly increased phospho-p42 ERK protein levels in the dorsal hippocampus relative to vehicle controls. In contrast, no combination of E(2) and P affected dorsal hippocampal phospho-ERK levels. These data indicate that, unlike E(2) alone, the beneficial effects of combined E(2) plus P treatment on memory are not associated with ERK activation in the dorsal hippocampus 1 h after treatment, and suggest that E(2) alone and combined E(2) plus P may influence ERK activation in different time frames or enhance memory through different mechanisms.

Estrogens and age-related memory decline in rodents: what have we learned and where do we go from here?

The question of whether ovarian hormone therapy can prevent or reduce age-related memory decline in menopausal women has been the subject of much recent debate. Although numerous studies have demonstrated a beneficial effect of estrogen and/or progestin therapy for certain types of memory in menopausal women, recent clinical trials suggest that such therapy actually increases the risk of cognitive decline and dementia. Because rodent models have been frequently used to examine the effects of age and/or ovarian hormone deficiency on mnemonic function, rodent models of age-related hormone and memory decline may be useful in helping to resolve this issue. This review will focus on evidence suggesting that estradiol modulates memory, particularly hippocampal-dependent memory, in young and aging female rats and mice. Various factors affecting the mnemonic response to estradiol in aging females will be highlighted to illustrate the complications inherent to studies of estrogen therapy in aging females. Avenues for future development of estradiol-based therapies will also be discussed, and it is argued that an approach to drug development based on identifying the molecular mechanisms underlying estrogenic modulation of memory may lead to promising future treatments for reducing age-related mnemonic decline.

The effects of acute 17beta-estradiol treatment on gene expression in the young female mouse hippocampus

Previous studies have demonstrated that treatment with 17beta-estradiol (E(2)) improves both spatial and nonspatial memory in young female mice. Still unclear, however, are the molecular mechanisms underlying the beneficial effects of E(2) on memory. We have previously demonstrated that a single post-training intraperitoneal (i.p.) injection of 0.2 mg/kg E(2) can enhance hippocampal-dependent spatial and object memory consolidation (e.g., Gresack & Frick, 2006b). Therefore, in the present study, we performed a microarray analysis on the dorsal hippocampi of 4-month-old female mice injected i.p. with vehicle or 0.2 mg/kg E(2). Genes were considered differentially expressed following E(2) treatment if they showed a greater than 2-fold change in RNA expression levels compared to controls. Overall, out of a total of approximately 25,000 genes represented on the array, 204 genes showed altered mRNA expression levels upon E(2) treatment, with 111 up-regulated and 93 down-regulated. Of these, 17 of the up-regulated and 6 of the down-regulated genes are known to be involved in learning and memory. mRNA expression changes in 5 of the genes were confirmed by real-time quantitative PCR analysis, and protein changes in these same genes were confirmed by Western blot analysis: Hsp70, a heat shock protein known to be estrogen responsive; Igfbp2, an IGF-I binding protein; Actn4, an actin binding protein involved in protein trafficking; Tubb2a, the major component of microtubules; and Snap25, a synaptosome-specific protein required for neurotransmitter release. The types of genes altered indicate that E(2) may induce changes in the structural mechanics of cells within the dorsal hippocampus that could be conducive to promoting memory consolidation.

Differential effects of acute progesterone administration on spatial and object memory in middle-aged and aged female C57BL/6 mice

The present study examined the effects of acute progesterone administration on hippocampal-dependent memory consolidation in ovariectomized middle-aged (16 months old) and aged (22 months old) female mice. Spatial memory was tested in a 2-day Morris water-maze task and object memory was tested using an object recognition task with 24- and 48-h delays. Immediately after water-maze training, mice received i.p. injections of vehicle, or 5.0, 10.0, or 20.0 mg/kg of water-soluble progesterone. Twenty-four hours later, retention of the platform location was tested. No overnight forgetting of the platform location was observed in middle-aged vehicle-treated mice. Acute progesterone administration had no effect on spatial memory in middle-aged mice. However, aged vehicle-treated mice demonstrated impaired memory for the platform location on Day 2 relative to Day 1. Twenty mg/kg, but not 5 or 10 mg/kg, progesterone reversed these deficits, suggesting that 20 mg/kg progesterone can improve spatial memory in aged females. In the object recognition task, mice explored two identical objects and then immediately received vehicle or progesterone injections. In middle-aged mice, 10 and 20 mg/kg progesterone enhanced object memory consolidation, relative to chance, after 24-h, but all doses were ineffective after 48-h. In aged mice, 10 mg/kg progesterone enhanced object memory consolidation, relative to chance, after 24 h, whereas both 5 and 10 mg/kg progesterone enhanced memory after 48 h. Together, these results indicate that acute progesterone differentially enhances hippocampal-dependent memory in middle-aged and aged females.

Post-training progesterone dose-dependently enhances object, but not spatial, memory consolidation

The aim of this study was to determine if progesterone modulates object and spatial memory consolidation in young ovariectomized C57BL/6 mice. Object memory was tested in an object recognition task using 24- and 48-h delays. Spatial memory was tested in a 2-day version of the Morris water maze in which retention was tested 24 or 48 h after training. Immediately after training in each task, mice received a single intraperitoneal injection of vehicle or 5, 10, or 20mg/kg water-soluble progesterone. Mice were then tested 24 or 48 h later in the absence of circulating progesterone. Post-training injections of 10 and 20mg/kg progesterone enhanced object recognition, but not memory in the spatial water maze. These findings suggest that object memory consolidation in young female mice is more sensitive to the modulatory effects of progesterone than spatial memory consolidation, at least using the tasks, doses, and delays tested. As such, these findings may have important implications for the design of progesterone therapies intended to reduce age-related memory decline.

Life-long environmental enrichment differentially affects the mnemonic response to estrogen in young, middle-aged, and aged female mice

The present study was designed to examine whether life-long exposure to standard or enriched housing affects the ability of estrogen to improve spatial and object memory throughout the lifespan. Three-week-old female mice were maintained in standard or enriched housing up to and through ovariectomy and behavioral testing at 5, 17, or 22 months of age. Spatial memory was tested in the Morris water maze and object memory was tested using an object recognition task. Immediately after training each day, mice were injected intraperitoneally with vehicle or 0.2 mg/kg 17beta-estradiol. Among young females, object recognition was enhanced by estradiol alone, an effect that was reduced by enrichment. In contrast, spatial water maze performance was impaired by estradiol alone, but improved by the combination of both estradiol and enrichment. At middle-age, object recognition was enhanced by estradiol or enrichment alone, and the combination of both treatments. Spatial memory in the water maze was also improved by both treatments at middle-age, but the beneficial effects of estradiol were limited to standard-housed females. Finally, whereas enrichment in aged females significantly enhanced performance in both tasks, estradiol had no effect at this age in either task. In total, the data indicate that life-long enrichment can significantly alter the extent to which estradiol affects memory in mice throughout the lifespan. Importantly, the interaction between these treatments is highly dependent on age and type of memory tested.

Rise of testosterone, nortestosterone, and 17ß-estradiol concentrations in peripheral blood plasma of pigs after sublingual application in vivo

Application of endogenous anabolic steroids to meat producing animals is not allowed in the EU. In other countries application is practised due to a low oral activity based on an efficient first liver passage. This contrasts with pharmacological investigations where steroids were readily absorbed by the buccal and sublingual mucosa using absorption enhancers. An in vivo study was performed to clarify possible absorption after sublingual applications of one milligram portions of either testosterone (T), 17beta-estradiol (E), or nortestosterone (NT) in sesame oil to castrated male pigs (n=5) without specific delivery systems during anaesthesia. Blood samples were drawn using jugular vein catheters for 15 min before and 3h after application. Hormone concentrations were determined by Radioimmunoassay for T and E or Enzymeimmunoassay for NT. For all steroids a slight increase was measurable one minute after application. Maximal values for T, E, and NT were 2.5 ng/ml, 1.5 ng/ml and 4.2 ng/ml, respectively, and were observed after 10 min. The concentrations of the three steroids decreased slowly thereafter but were still significantly elevated 1-3h after application. Oral absorption of steroids without enhancers should be considered in risk analysis.

Solubility and dissolution rate of progesterone-cyclodextrin-polymer systems

This contribution focused on the solubility improvement of the poorly water-soluble steroid hormone progesterone which, in its natural state, presents a reduced oral bioavailability. In the first part of this study, two simple, reproducible methods that were candidates for use in the preparation of inclusion complexes with cyclodextrins were investigated. Solubility capacities of the progesterone complex with hydroxypropyl-beta-CD (HPbeta-CD), hydoxypropyl-gamma-CD (HPgamma-CD), permethyl-beta-CD (PMbeta-CD), and sulfobutylether-beta-CD (SBEbeta-CD), prepared by the freeze-drying and precipitation methods, were evaluated by Higuchi phase solubility studies. The results showed that HPbeta-CD and PMbeta-CD were the most efficient among the four cyclodextrins for the solubilization of progesterone, with the highest apparent stability constants. Therefore, dissolution studies were conducted on these latest progesterone/cyclodextrin complexes and physical mixtures. Two additional natural cyclodextrins, beta-CD and gamma-CD, were taken as references. Hence, the influence of more highly soluble derivatives of beta-CD (HPbeta-CD, PMbeta-CD) on the progesterone dissolution rate, in comparison to pristine beta-CD, alongside an increase in the cavity width for gamma-CD versus beta-CD, were investigated. The dissolution kinetics of progesterone dissolved from HPbeta-CD, PMbeta-CD, and gamma-CD revealed higher constant rates in comparison to beta-CD. Therefore, the aim of the second part of this study was to investigate the possibility of improving the dissolution rate of progesterone/beta-CD binary systems upon formation of ternary complexes with the hydrophilic polymer, PEG 6000, as beta-CD had the smallest progesterone solubility and dissolution capacity among the four cyclodextrins studied (beta-CD, HPbeta-CD, HPgamma-CD and PMbeta-CD). The results indicated that dissolution constant rates were considerably enhanced for the 5% and 10% progesterone/beta-CD complexes in PEG 6000. The interaction of progesterone with the cyclodextrins of interest on the form of the binary physical mixtures, complexes, or ternary complexes were investigated by differential scanning calorimetry (DSC) and Fourier transformed-infrared spectroscopy (FT-IR). The results proved that progesterone was diffused into the cyclodextrin cavity, replacing the water molecules and, in case of ternary systems, that the progesterone beta-cyclodextrin was well dispersed into PEG, thus improving progesterone bioavailability for subsequent oral delivery in the same way as derivatized cyclodextrins. The present work proves that ternary complexes are promising systems for drug encapsulation.

Limited brain diffusion of the glucocorticoid receptor agonist RU28362 following i.c.v. administration: implications for i.c.v. drug delivery and glucocorticoid negative feedback in the hypothalamic-pituitary-adrenal axis

The experiments described herein present a method for tracking diffusion of the glucocorticoid receptor agonist RU28362 in brain following i.c.v. drug administration. A useful property of glucocorticoid receptor is that it is primarily cytoplasmic when unbound and rapidly translocates to the nucleus when bound by ligand. Thus, removal of endogenous glucocorticoids by adrenalectomy allows us to identify brain regions with activated glucocorticoid receptor after i.c.v. glucocorticoid receptor agonist treatment by examining the presence or absence of nuclear glucocorticoid receptor immunostaining. We have previously demonstrated that an i.p. injection of 150 microg/kg RU28362 1 h prior to restraint stress is sufficient to suppress stress-induced hypothalamic-pituitary-adrenal axis hormone secretion [Ginsberg AB, Campeau S, Day HE, Spencer RL (2003) Acute glucocorticoid pretreatment suppresses stress-induced hypothalamic-pituitary-adrenal axis hormone secretion and expression of corticotropin-releasing hormone hnRNA but does not affect c-fos mRNA or fos protein expression in the paraventricular nucleus of the hypothalamus. J Neuroendocrinol 15:1075-1083]. We report here, however, that in rats i.c.v. treatment with a high-dose of RU28362 (1 microg) 1 h prior to stressor onset does not suppress stress-induced hypothalamic-pituitary-adrenal axis activity. We then performed a series of experiments to examine the possible differences in glucocorticoid receptor activation patterns in brain and pituitary after i.c.v. or i.p. treatment with RU28362. In a dose-response study we found that 1 h after i.c.v. injection of RU28362 (0.001, 0.1 and 1.0 microg) glucocorticoid receptor nuclear immunoreactivity was only evident in brain tissue immediately adjacent to the lateral or third ventricle, including the medial but not more lateral portion of the medial parvocellular paraventricular nucleus of the hypothalamus. In contrast, i.p. injection of RU28362 produced a uniform predominantly nuclear glucocorticoid receptor immunostaining pattern throughout all brain tissue. I.c.v. injection of the endogenous glucocorticoid receptor agonist, corticosterone (1 microg) also had limited diffusion into brain tissue. Time-course studies indicated that there was not a greater extent of nuclear glucocorticoid receptor immunostaining present in brain after shorter (10 or 30 min) or longer (2 or 3 h) intervals of time after i.c.v. RU28362 injection. Importantly, time-course studies found that i.c.v. RU28362 produced significant increases in nuclear glucocorticoid receptor immunostaining in the anterior pituitary that were evident within 10 min after injection and maximal after 1 h. These studies support an extensive literature indicating that drugs have very limited ability to diffuse out of the ventricles into brain tissue after i.c.v. injection, while at the same time reaching peripheral tissue sites. In addition, these studies indicate that significant occupancy of some glucocorticoid receptor within the paraventricular nucleus of the hypothalamus and pituitary is not necessarily sufficient to suppress stress-induced hypothalamic-pituitary-adrenal axis activity.

Post-training estrogen enhances spatial and object memory consolidation in female mice

The present study was designed to determine if post-training injections of a water-soluble form of 17beta-estradiol could enhance spatial and object memory consolidation in young female mice. Young ovariectomized female mice were trained in Morris water maze and object recognition tasks, injected with 0.1, 0.2, or 0.4 mg/kg cyclodextrin-encapsulated 17beta-estradiol or cyclodextrin-conjugated vehicle, and then re-tested after a delay. In the water maze, mice were trained in eight consecutive trials, injected, and memory for the platform location was re-tested after 24 h. All mice learned to find the platform on Day 1, but only mice receiving 0.2 mg/kg estradiol remembered the platform location on Day 2. In the object recognition task, mice were first presented with two identical objects, injected, and then presented with a familiar and novel object after a 24- or 48-h delay. For both delays, the 0.2 and 0.4 mg/kg doses enhanced memory for the familiar object. These data demonstrate that a 0.2 mg/kg dose of estradiol can enhance multiple types of memory consolidation in female mice, and suggest a narrower effective dose range for spatial memory than for object memory.

Effects of estrogen and progesterone on spatial memory consolidation in aged females

Interpretation of data illustrating that estrogen, with or without progestin, is detrimental to memory in post-menopausal women is complicated by the fact that little is known about the effects of progestins on memory. The present study examined if estrogen, alone or with progesterone, affects spatial memory consolidation in ovariectomized aged female mice. Mice received eight training trials in a spatial Morris water maze followed immediately by injection of water-soluble 17beta-estradiol (E(2); 0.2 mg/kg) or vehicle. Mice were re-tested 24 h later. All mice learned to find the platform on Day 1. On Day 2, the performance of control, but not E(2) mice, deteriorated, suggesting that E(2) enhanced memory for the platform location. In a second experiment, mice were injected with E(2) and 10 or 20 mg/kg water-soluble progesterone. The 10 mg/kg dose of progesterone did not affect estrogen's ability to enhance spatial memory consolidation, but 20 mg/kg blocked this effect. These data indicate that estrogen can improve spatial memory consolidation in aged females and that this effect can be attenuated by progesterone.

Delivery systems for hormone replacement therapy

The steroid hormones used for hormone replacement therapy in the menopausal transition and postmenopause can be administered by several different routes using a variety of delivery systems. The conventional approach to administration has been oral, and this is still the standard against which other routes are compared. However, there is a steadily increasing research development and popularity for alternative systems. Such systems can be geared to ultra low-dose delivery for local vaginal effect or higher dosages for systemic effect. Different delivery systems have a range of attributes with varying appeal to different individual women. Such a range of choices can be important for acceptability and compliance. One of the most important attributes of many newer delivery systems is the potential to deliver hormones in a controlled manner over prolonged periods of time, allowing constant low dosages, as well as constant blood and tissue levels. They also have the potential for reducing side effects and metabolic effects. Transdermal, subdermal, intravaginal and intrauterine systems are particularly likely to undergo refinement and further development in the foreseeable future with subsequent increases in popularity.

Cyclodextrins in drug delivery: an updated review

The purpose of this review is to discuss and summarize some of the interesting findings and applications of cyclodextrins (CDs) and their derivatives in different areas of drug delivery, particularly in protein and peptide drug delivery and gene delivery. The article highlights important CD applications in the design of various novel delivery systems like liposomes, microspheres, microcapsules, and nanoparticles. In addition to their well-known effects on drug solubility and dissolution, bioavailability, safety, and stability, their use as excipients in drug formulation are also discussed in this article. The article also focuses on various factors influencing inclusion complex formation because an understanding of the same is necessary for proper handling of these versatile materials. Some important considerations in selecting CDs in drug formulation such as their commercial availability, regulatory status, and patent status are also summarized. CDs, because of their continuing ability to find several novel applications in drug delivery, are expected to solve many problems associated with the delivery of different novel drugs through different delivery routes.

Effects of RM-β-CD on sublingual bioavailability of Δ9-tetrahydrocannabinol in rabbits

The purpose of the present study was to develop novel cyclodextrin-containing sublingual formulations of cannabinoids. Complexation of model cannabinoids, Delta(9)-tetrahydrocannabinol (THC) and cannabidiol (CBD), with randomly methylated beta-cyclodextrin (RM-beta-CD) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD), were studied by the phase-solubility method. Due to better complexation efficiency, RM-beta-CD was selected for further studies. Solid THC/RM-beta-CD and CBD/RM-beta-CD complexes were prepared by freeze-drying. The dissolutions of both THC and CBD in the presence and absence of RM-beta-CD were determined. THC was selected for in vivo studies: the pharmacokinetics of THC after both sublingual and oral administrations of ethanolic THC and THC/RM-beta-CD complex solutions were studied in rabbits. The aqueous solubility of CBD and THC increased as a function of CD concentration, showing A(L)- and A(P)-type diagrams for HP-beta-CD and RM-beta-CD, respectively. Dissolution rates of THC/RM-beta-CD and CBD/RM-beta-CD complexes were significantly (p < 0.05) higher than those of plain THC and plain CBD, respectively. The absolute bioavailability (F) of THC decreased in the following order: sublingual THC/RM-beta-CD solution (F = 12.1+/-1.4%; mean+/-S.D.; n = 4) > oral THC/RM-beta-CD solution (F = 4.0+/-6.0%) > or = sublingual ethanolic THC solution (F = 3.8+/-2.8%) > oral ethanolic THC solution (F = 1.3+/-1.4%). These results demonstrate that RM-beta-CD increases both the aqueous solubility and dissolution rate of these cannabinoids, making the development of novel sublingual formulation possible. These results also suggest that the sublingual administration of a THC/RM-beta-CD complex substantially increases the bioavailability of THC in rabbits.

Influence of hydroxypropyl-beta-cyclodextrin complexation on piroxicam release from buccoadhesive tablets

Interaction of piroxicam (PX) and hydroxypropyl-beta-cyclodextrin (HPbetaCD) was investigated in solution and in the solid state. Solubility studies demonstrated the formation of the PX-HPbetaCD inclusion complex with 1:1 stoichiometry. Equimolecular PX-HPbetaCD solid systems were prepared and characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray diffractometry. Modification of the release of a sparingly water-soluble drug, PX, from hydrophilic matrices using cyclodextrin complexation was evaluated. The buccoadhesive controlled release tablets for the delivery of PX were prepared by direct compression of hydroxypropylmethyl cellulose (HPMC) and Carbopol 940 (C940), which showed superior bioadhesion properties compared to HPMC. The tablets were evaluated for their dissolution, swelling and mucoadhesive properties. The in vitro release results demonstrated that matrix tablets containing the PX-HPbetaCD solid complex displayed faster PX release compared to those containing a physical mixture or "free" drug. Differences in release rates of PX from the tablets could be attributed to the presence of the polymers and to cyclodextrin complexation. The effect of the polymers on PX release can affect the drug solubility (complexation) and polymer water uptake (swelling). Higher polymer water uptake may result in higher drug solubility and diffusivity in a hydrated polymeric environment. Drug complexation affected also its diffusivity through the semipermeable membrane.

The physicochemical characteristics and bioavailability of indomethacin from β-cyclodextrin, hydroxyethyl-β-cyclodextrin, and hydroxypropyl-β-cyclodextrin complexes

In an effort to improve the bioavailability of the insoluble drug indomethacin, three complexes were prepared with indomethacin and the soluble complexing agents beta-, hydroxyethyl-beta-, and hydroxypropyl-beta-cyclodextrin. The indomethacin content was similar among the complexes (P</=0.05). To confirm complex formation, each complex was characterized by ultraviolet, infrared, nuclear-magnetic resonance, powder X-ray diffraction, and differential-scanning calorimetry techniques. Powder diffraction studies show the beta-cyclodextrin complex was polycrystalline, and the hydroxyethyl- and hydroxypropyl-beta-cyclodextrin complexes were amorphous. Phase-solubility analysis confirmed the formation of complexes and suggested the three complexes were bound similarly. Solubility studies show complexation increased indomethacin solubility, and the hydroxyethyl- and hydroxypropyl-beta-cyclodextrin complexes were more soluble than the beta-cyclodextrin complex in 0.1 N hydrochloric acid and distilled water. Dosage forms were prepared by encapsulating the complexes without the addition of excipients. Dissolution studies show the encapsulated beta- and hydroxyethyl-beta-cyclodextrin complexes had superior dissolution when compared to the hydroxypropyl-beta-cyclodextrin and Indocin (50 mg) capsules. Bioavailability studies were performed by administering the indomethacin complex or Indocin capsules to male-albino, New Zealand rabbits. Indomethacin plasma-time concentration data fit best to a compartment-independent model for all capsule formulations. Bioavailability comparisons by ANOVA show no significant difference (P</=0.10) in the peak-plasma time and peak concentration among the capsule formulations. The area-under-the-curve for the beta-cyclodextrin complex capsules was found to be significantly higher (P</=0.10) than all other capsule formulations. In conclusion, the bioavailabilty of indomethacin was improved by complexation with only beta-cyclodextrin. No correlations were found among the bioavailability, solubility, and dissolution results.

Inclusion complexes of ketosteroids with beta-cyclodextrin

Inclusion complexes of several steroid derivatives with beta-cyclodextrin (7) were studied in dimethylsulfoxide solution. The investigated molecules were ketosteroids with different functional groups on the skeleton: 3beta-acetoxypregn-5-en-20-one (1), 3beta-acetoxypregna-5,16-dien-20-one (2), 3beta-acetoxyandrost-5-en-17-one (3), 3beta-hydroxyandrost-5-en-17-one (4), 5alpha-androstane-3,17-dione (5) and 17beta-hydroxyandrost-4-en-3-one (6). Complex formation was monitored by two-dimensional ROESY experiments through the detection of intermolecular dipolar interactions. In case of inclusion complex formation, the steroid molecule penetrates the cavity of the cyclodextrin and dipole-dipole interactions (ROEs) can be detected between the glucose H-3 and H-5 protons inside the cyclodextrin cavity and the steroid skeletal protons. Intermolecular interactions were detected in all six cases. However, ROESY experiments provided data indicating only partial immersion (A and B ring of the steroid skeleton) in case of 1, 2 and 6. On the contrary, compounds 3 and 5, showing the most correlation rich spectra, seem to fully immerse in the beta-cyclodextrin cavity.

Determination of second-order association constants by global analysis of 1H and 13C NMR chemical shifts. Application to the complexation of sodium fusidate and potassium helvolate by beta- and gamma-cyclodextrin

The host-guest interaction between the steroid antibiotics sodium fusidate and potassium helvolate as guests and the hosts beta- and gamma-cyclodextrin was studied by 13C and 1H NMR techniques. The analysis of chemical shifts of individual nuclei leads to inconsistent values of the association constants and fails generally in the case of mixtures of 1:1 and 1:2 stoichiometries. The problem of parameter correlation is identified and the global analysis of two or more nuclei is proposed as a very effective method for the detection of complexes of higher stoichiometries and for the precise determination of the involved association constants. A matrix formulation of global analysis and the determination of confidence intervals is described. An analytical solution of the cubic equation, necessary for the description of higher order complexes, is presented in detail and its use together with commercial fitting software is compared with dedicated implementations. gamma-Cyclodextrin forms with both studied steroids, sodium fusidate and potassium helvolate, 1:1 complexes with high values of the association constants, K(1)=(60+/-24)x10(3)lmol(-1), and K(2)=(22+/-9)x10(3)lmol(-1), respectively. To the contrary, beta-cyclodextrin forms 1:1 and 1:2 (guest:host) complexes with both steroids, with moderate K(1) and low K(2) values (K(1)=(0.74+/-0.13)x10(3)lmol(-1), K(2)=(0.210+/-0.075)x10(3)lmol(-1)), and (K(1)=(2.42+/-0.87)x10(3)lmol(-1), K(2)=(0.06+/-0.09)x10(3)lmol(-1)), respectively.