Sol-Gel Nanocomposite Coatings for Preventing Biofilm Formation on Contact Lens Cases

Purpose

To evaluate the efficacy of a nanosilver-based sol–gel coating in preventing biofilm formation on contact lens cases.

Methods

An organic–inorganic hybrid silica–zirconia sol formulation with immobilized silver nanoparticles was deposited on contact lens case coupons. The coated and uncoated coupons were subjected to biofilm formation to Gram-negative and Gram-positive keratitis isolates and ATCC strains using a standard protocol. The biofilms were evaluated using crystal violet, MTT assay, and scanning electron microscope (SEM) examination. The duration of efficacy of the coating was evaluated by exposing the coated and uncoated coupons to a multipurpose lens cleaning solution for various durations up to 30 days and comparing their biofilm characteristics. The cytotoxicity of the coated surface was assessed using cell culture studies.

Results

Cross-hatch tests and SEM confirmed the presence of a uniform, well-adhered coating on the surface. The coating resulted in a nearly 95% reduction in biofilm formation of the tested bacteria and was effective despite exposures of up to 30 days to a multipurpose lens cleaning solution. The coating did not exhibit cytotoxicity to human corneal epithelial cells.

Conclusions

The silver nanoparticle-based coating exhibits a good antibiofilm property for both Gram-negative bacilli and Gram-positive cocci and is promising for commercial use in preventing contact lens-related infections.

Translational Relevance

Biofilm formation on lens cases continues to be an important concern. The proposed coating will help reduce such formations, thus reducing the risk of lens-associated microbial keratitis.

A Comparative Toxidrome Analysis of Human Organophosphate and Nerve Agent Poisonings Using Social Media

Here we utilized social media to compare the toxidrome of three lethal chemical exposures worldwide. YouTube videos were the main source from which the data were collected, but published reports and news were also utilized to fill in some gaps. All videos were organized in a database detailing symptoms and severity of each victim, along with demographics such as approximate age and gender. Each symptom was rated as mild, moderate, or severe and corresponding pie graphs for each incident were compared. The videos displayed symptoms ranging from mild to severe cholinergic toxicity and life‐threatening convulsions. Social media may represent an important resource in developing a viable approach to the early detection and identification of chemical exposure, reinforce our preparedness for better antidotes, long‐term follow up, and training about deadly chemical nerve agent attacks.

The Utility of Cannabidiol in the Treatment of Refractory Epilepsy

Cannabis-derived cannabinoids such as cannabidiol (CBD) have anticonvulsant properties. Recently, there has been an emerging interest in the use of CBD-enriched products for treatment of drug-resistant epilepsy. Some pilot trials of CBD have proved beneficial for refractory epilepsy, but its efficacy is yet to be confirmed by standard placebo-controlled trials. However, the mechanisms underlying the seizure protection efficacy claims of CBD remain unclear. This review briefly describes the clinical utility of CBD in the treatment of refractory epilepsy.

Current pharmacotherapy of attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a neurobehavioral developmental disorder in children and adults characterized by a persistent pattern of impulsiveness, inattention and hyperactivity. It affects about 3-10% of children and 2-5% of adolescents and adults and occurs about four times more commonly in boys than girls. The cause of ADHD is unknown, but it has strong genetic and environment components. The first-line treatment options for ADHD include behavioral therapy, pharmacotherapy with stimulants or both. Methylphenidate and amphetamine salts are the stimulant drugs of choice for ADHD treatment. Amphetamines act by increasing presynaptic release of dopamine and other biogenic amines in the brain. Methylphenidate inhibits the reuptake of dopamine and norepinephrine and therefore its pharmacology is identical to that of amphetamines. Lisdex-amfetamine is a prodrug of dextroamphetamine with low feasibility for abuse. Atomoxetine, a selective norepinephrine reuptake inhibitor, is an alternative, non-stimulant drug for ADHD but it is less efficacious than stimulants. Stimulants are generally safe but are associated with adverse effects including headache, insomnia, anorexia and weight loss. There is increased awareness about serious cardiovascular and psychiatric adverse events with ADHD drugs including concern for growth suppression in children. Stimulants have a high potential for abuse and dependence, and should be handled safely to prevent misuse and abuse.

Effect of Holostemma annularis on the progression of diabetes induced by a high fructose diet in rats and in diabetic C57BL/6J ob/ob mice

The roots of Holostemma annularis K. Schum (Asclepiadacae) are used in traditional medicine to treat diabetes. This medicinal plant, widely used in more than 34 ayurvedic preparations, was evaluated in a high fructose diet in induced insulin resistance and in C57BL/6J ob/ob diabetic mice for its antidiabetic activity. Graded doses of both chloroform and methanolic extracts of the roots of H. annularis were administered to normal and experimental diabetic rats for 21 days. Serum glucose, triglycerides, cholesterol levels and total protein in urine were analyzed. Significant results were observed in the estimated parameters. These data justify the use of the plant in the treatment of diabetes mellitus and is a potential source for the isolation of new active agents for diabetes mellitus.

Structural and optical investigation of semiconductor CdSe/CdS core-shell quantum dot thin films

Highly luminescent CdSe/CdS core-shell nanocrystals have been assembled on indium tin oxide (ITO) coated glass substrates using a wet synthesis route. The physical properties of the quantum dots (QD) have been investigated using X-ray diffraction, transmission electron microscopy and optical absorption spectroscopy techniques. These quantum dots showed a strong enhancement in the near band edge absorption. The in situ luminescence behavior has been interpreted in the light of the quantum confinement effect and induced strain in the core-shell structure.

Differential anesthetic activity of ketamine and the GABAergic neurosteroid allopregnanolone in mice lacking progesterone receptor A and B subtypes

Progesterone affects the function of the brain by multiple mechanisms. The physiological effects of progesterone are mediated by the interaction of the hormone with progesterone receptors (PRs), which are widely expressed in the hypothalamus, hippocampus and limbic areas. The PR is composed of two protein isoforms, PR-A and PR-B, which are expressed from a single PR gene. In addition, progesterone influences neuronal activity through its conversion to allopregnanolone, a neurosteroid that acts as a positive allosteric modulator of GABA(A) receptors. However, the role of PRs in the sedative-hypnotic action of neurosteroids is unclear. In this study, PR knockout (PRKO) mice were used as model to study the sedative-anesthetic actions of the progesterone-derived neurosteroid allopregnanolone and the noncompetitive NMDA receptor antagonist ketamine. Mice were confirmed to be PR deficient by genotyping and immunohistochemistry of PR expression in the brain. Anesthetic potency was evaluated by the loss of the righting reflex paradigm. Allopregnanolone-induced anesthetic activity was similar in PRKO mice and their wild-type littermates, suggesting that PRs are not involved in the anesthetic response to allopregnanolone. However, the noncompetitive NMDA receptor antagonist ketamine has significantly reduced anesthetic potency in PRKO mice, suggesting a possible developmental plasticity of glutamate receptors. There was no marked gender-related difference to ketamine response in both genotypes. In conclusion, these results suggest that the neurosteroid allopregnanolone and ketamine produce differential anesthetic response in mice lacking PRs.

Physiological role of adrenal deoxycorticosterone-derived neuroactive steroids in stress-sensitive conditions

Stress increases plasma and brain concentrations of corticosteroids and neuroactive steroids. Cortisol is the most important stress hormone in the hypothalamic pituitary adrenocortical system. However, significant amounts of the mineralocorticoid deoxycorticosterone are also released during stress. Deoxycorticosterone undergoes biotransformation to allotetrahydrodeoxycorticosterone, a neuroactive steroid with anxiolytic and anticonvulsant properties. Our studies indicate that the anticonvulsant activity of deoxycorticosterone is mediated by its conversion to allotetrahydrodeoxycorticosterone, which is a potent positive allosteric modulator of GABA(A) receptors. Although the role of allotetrahydrodeoxycorticosterone within the brain is undefined, recent studies indicate that stress induces increases in allotetrahydrodeoxycorticosterone to levels that can activate GABA(A) receptors. These results might have significant implications for human stress-sensitive conditions such as epilepsy, panic disorder, post-traumatic stress disorder, and major depression. In epilepsy, a role for adrenal allotetrahydrodeoxycorticosterone in seizure susceptibility has been suggested. Recent preclinical studies indicate a role of neuroactive steroids in ethanol actions. Although these studies provide a better understanding of the role of allotetrahydrodeoxycorticosterone and related neuroactive steroids in acute stress, further studies are clearly warranted to ascertain the specific role of neuroactive steroids in the pathophysiology of chronic stress and related brain conditions.

Pharmacology of catamenial epilepsy

Catamenial epilepsy is a menstrual cycle-related seizure disorder characterized by an increase in seizures at the time of menstruation. Catamenial epilepsy affects up to 70% of women with epilepsy. Catamenial seizures are common among women with focal or generalized epilepsy, which affects an estimated 1 million women in the United States. Presently, there is no specific, FDA-approved drug treatment for catamenial epilepsy. Despite the increased use of wide-ranging antiepileptic and hormonal drugs, catamenial seizures are often refractory to many treatments. Recent studies have provided an improved understanding of the pathophysiology of catamenial epilepsy. Cyclical changes of ovarian hormones estrogens and progesterone are now widely believed to be essential for the genesis of catamenial seizures. Generally, progesterone has antiseizure effects, while estrogens facilitate seizure susceptibility. The progesterone metabolite allopregnanolone has been identified as a key endogenous neurosteroid with powerful antiseizure activity. Allopregnanolone is a potent, positive allosteric modulator of GABA(A) receptors. Progesterone and allopregnanolone exposure and withdrawal affects GABA(A) receptor plasticity. In animal models, withdrawal from chronic progesterone and, consequently, of allopregnanolone levels in brain, has been shown to increase seizure susceptibility. Natural progesterone therapy is proven to be effective in women with epilepsy. Consequently, synthetic neurosteroids that are devoid of hormonal side effects represent a novel class of antiepileptic drugs for women with catamenial epilepsy. Our studies suggest that ganaxolone, a GABA(A) receptor-modulating synthetic neuroactive steroid, is a particularly promising treatment for catamenial epilepsy. Future studies are clearly warranted to determine the molecular pathophysiology and an effective treatment of catamenial epilepsy.

Anticonvulsant Activity of Progesterone and Neurosteroids in Progesterone Receptor Knockout Mice

Many of the biological actions of progesterone are mediated through the progesterone receptor (PR), a nuclear transcription factor. Progesterone is well recognized to protect against seizures in animal models. Although this activity has been attributed to the progesterone metabolite allopregnanolone, a GABAA receptor-modulating neurosteroid with anticonvulsant properties, PRs could also play a role. Here, we used PR knockout (PRKO(-/-)) mice bearing a targeted deletion of the PR gene that eliminates both isoforms of the PR to investigate the contribution of the PR to the anticonvulsant activity of progesterone. The protective activity of progesterone was examined in female and male homozygous PRKO mice and isogenic wild-type controls in the pentylenetetrazol (PTZ), maximal electroshock, and amygdala-kindling seizure models. In all three models, the anticonvulsant potency of progesterone was undiminished in PRKO mice compared with control mice. On the contrary, there was a substantial increase in the anticonvulsant potency of progesterone in the PTZ and kindling models. The antiseizure activity of progesterone in PRKO mice was reversed by pretreatment with finasteride, a 5alpha-reductase inhibitor that blocks the metabolism of progesterone to allopregnanolone. Unlike progesterone, the neurosteroids allopregnanolone and allotetrahydrodeoxycorticosterone exhibited comparable anticonvulsant potency in PRKO and wild-type mice. The basis for the heightened progesterone responsiveness of PRKO mice is not attributable to pharmacokinetic factors, because the plasma allopregnanolone levels achieved after progesterone administration were not greater in the PRKO mice. These studies provide strong evidence that the PR is not required for the antiseizure effects of progesterone, which mainly occurs through its conversion to the neurosteroid allopregnanolone.

Testosterone modulation of seizure susceptibility is mediated by neurosteroids 3α-androstanediol and 17β-estradiol

Testosterone modulates seizure susceptibility in animals and humans, but the underlying mechanisms are obscure. Here, testosterone modulation of seizure susceptibility is hypothesized to occur through its conversion to neurosteroids with "anticonvulsant" and "proconvulsant" actions, and hence the net effect of testosterone on neural excitability and seizure activity depends on the levels of distinct testosterone metabolites. Testosterone undergoes metabolism to neurosteroids via two distinct pathways. Aromatization of the A-ring converts testosterone into 17beta-estradiol. Reduction of testosterone by 5alpha-reductase generates 5alpha-dihydrotestosterone (DHT), which is then converted to 3alpha-androstanediol (3alpha-Diol), a powerful GABA(A) receptor-modulating neurosteroid with anticonvulsant properties. Systemic doses of testosterone decreased seizure threshold in rats and increased the incidence and severity of pentylenetetrazol (PTZ)-induced seizures in mice. These proconvulsant effects of testosterone were associated with increases in plasma 17beta-estradiol and 3alpha-Diol concentrations. Pretreatment with letrozole, an aromatase inhibitor that blocks the conversion of testosterone to 17beta-estradiol, significantly inhibited testosterone-induced exacerbation of seizures. The 5alpha-reductase inhibitor finasteride significantly reduced 3alpha-Diol levels and also blocked letrozole's ability to inhibit the proconvulsant effects of testosterone. The 5alpha-reduced metabolites of testosterone, DHT and 3alpha-Diol, had powerful anticonvulsant activity in the PTZ test. Letrozole or finasteride had no effect on seizure protection by DHT and 3alpha-Diol, but indomethacin partially reversed DHT actions. 3alpha-Diol but not 3beta-androstanediol, a GABA(A) receptor-inactive stereoisomer, suppressed 4-aminopyridine-induced spontaneous epileptiform bursting in rat hippocampal slices. Thus, testosterone-derived neurosteroids 3alpha-Diol and 17beta-estradiol could contribute to the net cellular actions of testosterone on neural excitability and seizure susceptibility.

Delayed presentation of traumatic popliteal artery pseudoaneurysms: a review of seven cases

OBJECTIVES

to examine the management and outcome of patients with traumatic popliteal artery pseudoaneurysms with delayed presentation.

MATERIALS

over a 2-year period 7 patients with traumatic popliteal pseudoaneurysms presenting to a tertiary referral unit after a delay of 1 month were reviewed.

METHODS

a retrospective review of clinical records.

RESULTS

the median interval between injury and presentation was 1.5 months (range 1-24 months). Penetrating trauma from gunshot wounds was the cause of the initial vascular injury in 6 patients and a stab wound in one. All patients had large pseudoaneurysms of more than 8 cm filling the popliteal fossa with variable degrees of fixed flexion deformity (FFD) of the knee. Severe FFD of more than 40 degrees was noted in 2 patients and 3 others had mild flexion deformities of 10 to 20 degrees. Six patients underwent repair of the pseudoaneurysm. One patient required an above knee amputation due to an infected false aneurysm. There were no deaths or graft related complications. Despite aggressive post-operative physiotherapy only 2 patients were able to completely straighten the leg at the time of discharge.

CONCLUSIONS

in patients with neglected popliteal artery pseudoaneurysms, morbidity is associated with the pre-operative degree of fixed flexion deformity of the knee.

Neurosteroid withdrawal model of perimenstrual catamenial epilepsy

PURPOSE

Perimenstrual catamenial epilepsy, the increase in seizure frequency that some women with epilepsy experience near the time of menstruation, may in part be related to withdrawal of the progesterone metabolite allopregnanolone, an endogenous anticonvulsant neurosteroid that is a potent positive allosteric gamma-aminobutyric acidA (GABA(A)) receptor modulator. The objective of this study was to develop an animal model of perimenstrual catamenial epilepsy for use in evaluating drug-treatment strategies.

METHODS

A state of prolonged high serum progesterone (pseudopregnancy) was induced in 26-day-old female rats by sequential injection of pregnant mares' serum gonadotropin and human chorionic gonadotropin. Neurosteroid withdrawal was induced by treatment with finasteride (100 mg/kg, i.p.), a 5alpha-reductase inhibitor that blocks the conversion of progesterone to allopregnanolone. Plasma progesterone and allopregnanolone levels were measured by gas chromatography/electron capture negative chemical ionization mass spectrometry. Seizure susceptibility was evaluated with the convulsant pentylenetetrazol (PTZ).

RESULTS

Plasma allopregnanolone levels were markedly increased during pseudopregnancy (peak level, 55.1 vs. control diestrous level, 9.3 ng/mL) and were reduced by 86% 24 h after finasteride treatment (6.4 ng/mL). Progesterone levels were unaffected by finasteride. After finasteride-induced withdrawal, rats showed increased susceptibility to PTZ seizures. There was a significant increase in the number of animals exhibiting clonic seizures when challenged with subcutaneous PTZ (60 mg/kg) compared with control pseudopregnant animals not undergoing withdrawal and nonpseudopregnant diestrous females. The CD50 (50% convulsant dose) was 46 mg/kg, compared with 73 mg/kg in nonwithdrawn pseudopregnant animals and 60 mg/kg in diestrous controls. The threshold doses for induction of various seizure signs, measured by constant intravenous infusion of PTZ, were reduced by 30-35% in neurosteroid-withdrawing animals compared with control diestrous females. No change in threshold was observed in pseudopregnant rats treated from days 7 to 11 with finasteride, demonstrating that high levels of progesterone alone do not alter seizure reactivity.

CONCLUSIONS

Neurosteroid withdrawal in pseudopregnant rats results in enhanced seizure susceptibility, providing an animal model of perimenstrual catamenial epilepsy that can be used for the evaluation of new therapeutic approaches.

Enhanced anticonvulsant activity of neuroactive steroids in a rat model of catamenial epilepsy

PURPOSE

Perimenstrual catamenial epilepsy may in part be due to withdrawal of the endogenous progesterone-derived neurosteroid allopregnanolone that potentiates gamma-aminobutyric acidA (GABA(A)) receptor-mediated inhibition. Here we sought to determine whether the anticonvulsant potencies of neuroactive steroids, benzodiazepines, phenobarbital (PB), and valproate (VPA) are altered during the heightened seizure susceptibility accompanying neurosteroid withdrawal in a rat model of perimenstrual catamenial epilepsy.

METHODS

Test drugs were evaluated for their ability to alter the convulsant activity of pentylenetetrazol (PTZ) in young adult female rats, in pseudopregnant rats with prolonged exposure to high levels of progesterone (and its neurosteroid metabolites), and in pseudopregnant rats 24 h after acute withdrawal of neurosteroids by treatment with the 5alpha-reductase inhibitor finasteride. Test drugs were administered at doses equivalent to twice their ED50 values for protection against PTZ-induced clonic seizures in naive young adult female rats.

RESULTS

The anticonvulsant activity of allopregnanolone (5 mg/kg, s.c.), pregnanolone (5 mg/kg, s.c.), allotetrahydrodeoxycorticosterone (15 mg/kg, s.c.), and tetrahydrodeoxycorticosterone (10 mg/kg, s.c.) were enhanced by 34-127% after neurosteroid withdrawal. The anticonvulsant activity of PB (65 mg/kg, i.p.) was also enhanced by 24% in neurosteroid-withdrawn animals. In contrast, the anticonvulsant activity of diazepam (4 mg/kg, i.p.), bretazenil (0.106 mg/kg, i.p.), and VPA (560 mg/kg, i.p.) were reduced or unchanged in neurosteroid-withdrawn animals.

CONCLUSIONS

The anticonvulsant activity of neuroactive steroids is potentiated after neurosteroid withdrawal, supporting the use of such agents in the treatment of perimenstrual catamenial epilepsy.

Chronic treatment with the neuroactive steroid ganaxolone in the rat induces anticonvulsant tolerance to diazepam but not to itself

Ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnane-20-one), an orally active synthetic analog of the neuroactive steroid allopregnanolone, is a positive allosteric modulator of gamma-aminobutyric acid(A) receptors with anticonvulsant properties. We sought to determine whether tolerance occurs to the anticonvulsant activity of ganaxolone in the pentylenetetrazol seizure test and whether there is cross-tolerance with diazepam. Rats were treated with two daily injections of a 2 x ED(50) dose of ganaxolone (7 mg/kg s.c.), diazepam (4 mg/kg i.p.), or vehicle for 3 or 7 days. On the day after the chronic treatment periods, the anticonvulsant potencies of ganaxolone and diazepam were determined. The ED(50) values for ganaxolone after 3- and 7-day treatment with ganaxolone were not significantly different from that in naive rats (ED(50) = 3.5 mg/kg). In contrast, in animals that were treated chronically with ganaxolone for 7 days, there was a significant reduction in the anticonvulsant potency of diazepam (ED(50) = 4.0 versus 1.9 mg/kg for naive controls). Chronic treatment with diazepam was not associated with a reduction in the potency of ganaxolone, but there was a reduction in the potency of diazepam (ED(50) = 3.7 mg/kg). Plasma ganaxolone determinations indicated that the pharmacokinetic properties of ganaxolone were unchanged after 7-day chronic ganaxolone treatment. The estimated equilibrium plasma concentrations of ganaxolone associated with threshold (750-950 ng/ml) and 50% seizure protection (1215-1295 ng/ml) were similar in naive and chronically treated rats. We conclude that there is no tolerance to the anticonvulsant activity of ganaxolone nor is there cross-tolerance to ganaxolone when tolerance develops to diazepam. However, there is cross-tolerance to diazepam with chronic ganaxolone treatment.

Functional laryngeal surgery - critical determinants of successful rehabilitation

This study addresses the functional outcome and rehabilitative process in 30 partial laryngectomies carried out for laryngeal (22) und hypoorpharyngeal (8) cancers at the department of H/N Surgery, The kidwai Memorial Institute of Oncology. Bangalore, India from 1985-1995, Special emphasis is directed towards post-surgical convalescence after various partial laryngeetomy techniques which include 6 vertical laryngectomies (V L / VPL). 17 supraglottic laryngectomies (SG L), and 7 supracricoid laryngectomies with Cricohyoidepexy (CHP). Rehabilitative success was measured with respect to the ease of dccannulation, resumption of normal deglutition and speech analysis - both objectively using standard speech analytical equipment in a speech laboratory and subjectively using the services of blinded judges to score recorded speech of patients. The speech analysis indicate that past SGL speech was the superior most followed by V L and C H P in that order. Aspiration was deemed as minimal and inconsequential after V L/VPL followed by CHP;and SGL, in the order of severity;the extended modifications to resect the arytenoid and / or basE of tongue and / or piriform fossa faring worse than classic standard technique.

Enhanced anticonvulsant activity of ganaxolone after neurosteroid withdrawal in a rat model of catamenial epilepsy

Perimenstrual catamenial epilepsy, the exacerbation of seizures in association with menstruation, may in part be due to withdrawal of the progesterone metabolite allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one), an endogenous anticonvulsant neurosteroid that is a positive allosteric modulator of gamma-aminobutyric acid(A) receptors. Neurosteroid replacement is a potential approach to therapy, but natural neurosteroids have poor bioavailability and may be converted to metabolites with undesired progestational activity. The synthetic neuroactive steroid ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnane-20-one) is an orally active analog of allopregnanolone that is not converted to the hormonally active 3-keto form. To assess the potential of ganaxolone in the treatment of catamenial seizure exacerbations, a state of persistently high serum progesterone (pseudopregnancy) was induced in 26-day-old female rats with gonadotropins, and neurosteroids were withdrawn on postnatal day 39 with finasteride, a 5alpha-reductase inhibitor that blocks the conversion of progesterone to allopregnanolone. Finasteride treatment during pseudopregnancy results in a reduction in the threshold for pentylenetetrazol seizures. During this state of enhanced seizure susceptibility, there was a 3-fold increase in the anticonvulsant potency of ganaxolone (control ED(50) = 3.5 mg/kg; withdrawn = 1.2 mg/kg) without a change in the potency for induction of motor toxicity in the rotarod test. The plasma concentrations of ganaxolone did not differ significantly in control and withdrawn animals; the estimated plasma concentrations of ganaxolone producing 50% seizure protection were approximately 500 and approximately 225 ng/ml in control and withdrawn rats, respectively. Unlike ganaxolone, neurosteroid withdrawal was associated with a decrease in the anticonvulsant potency of diazepam (control ED(50) = 1.9 mg/kg; withdrawn = 4.1 mg/kg) and valproate (control ED(50) = 279 mg/kg; withdrawn = 460 mg/kg). The enhanced anticonvulsant potency of ganaxolone after neurosteroid withdrawal supports the use of ganaxolone as a specific treatment for perimenstrual catamenial epilepsy.

Novel oral colon-specific drug delivery systems for pharmacotherapy of peptide and nonpeptide drugs

The increasing number of peptide and protein drugs being investigated demands the development of dosage forms which exhibit site-specific release. Delivery of drugs into systemic circulation through colonic absorption represents a novel mode of introducing peptide and protein drug molecules and drugs that are poorly absorbed from the upper gastrointestinal (GI) tract. Oral colon-specific drug delivery systems offer obvious advantages over parenteral administration. Colon targeting is naturally of value for the topical treatment of diseases of the colon such as Crohn's disease, ulcerative colitis and colorectal cancer. Sustained colonic release of drugs can be useful in the treatment of nocturnal asthma, angina and arthritis. Peptides, proteins, oligonucleotides and vaccines are the potential candidates of interest for colon-specific drug delivery. Sulfasalazine, ipsalazide and olsalazine have been developed as colon-specific delivery systems for the treatment of inflammatory bowel disease (IBD). The vast microflora and distinct enzymes present in the colon are being increasingly exploited to release drugs in the colon. Although the large intestine is a potential site for absorption of drugs, some difficulties are involved in the effective local delivery of drugs to the colon bypassing the stomach and small intestine. Furthermore, differential pH conditions and long transit time during the passage of drug formulations from mouth to colon create numerous technical difficulties in the safe delivery of drugs to the colon. However, recent developments in pharmaceutical technology, including coating drugs with pH-sensitive and bacterial degradable polymers, embedding in bacterial degradable matrices and designing into prodrugs, have provided renewed hope to effectively target drugs to the colon. The use of pH changes is analogous to the more common enteric coating and consists of employing a polymer with an appropriate pH solubility profile. The concept of using pH as a trigger to release a drug in the colon is based on the pH conditions that vary continuously down the GI tract. Polysaccharide and azopolymer coating, which is refractory in the stomach and small intestine yet degraded by the colonic bacteria, have been used as carriers for colon-specific targeting. Finally, the availability of optimal preclinical models and clinical methods fueled the rapid development and evaluation of colon-specific drug delivery systems for clinical use. Future studies may hopefully lead to further refinements in the technology of colon-specific drug delivery systems and improve the pharmacotherapy of peptide drugs.

Identification of a discrete intermediate in the assembly/disassembly of physalis mottle tymovirus through mutational analysis

Assembly intermediates of icosahedral viruses are usually transient and are difficult to identify. In the present investigation, site-specific and deletion mutants of the coat protein gene of physalis mottle tymovirus (PhMV) were used to delineate the role of specific amino acid residues in the assembly of the virus and to identify intermediates in this process. N-terminal 30, 34, 35 and 39 amino acid deletion and single C-terminal (N188) deletion mutant proteins of PhMV were expressed in Escherichia coli. Site-specific mutants H69A, C75A, W96A, D144N, D144N-T151A, K143E and N188A were also constructed and expressed. The mutant protein lacking 30 amino acid residues from the N terminus self-assembled to T=3 particles in vivo while deletions of 34, 35 and 39 amino acid residues resulted in the mutant proteins that were insoluble. Interestingly, the coat protein (pR PhCP) expressed using pRSET B vector with an additional 41 amino acid residues at the N terminus also assembled into T=3 particles that were more compact and had a smaller diameter. These results demonstrate that the amino-terminal segment is flexible and either the deletion or addition of amino acid residues at the N terminus does not affect T=3 capsid assembly. In contrast, the deletion of even a single residue from the C terminus (PhN188Delta1) resulted in capsids that were unstable. These capsids disassembled to a discrete intermediate with a sedimentation coefficent of 19.4 S. However, the replacement of C-terminal asparagine 188 by alanine led to the formation of stable capsids. The C75A and D144N mutant proteins also assembled into capsids that were as stable as the pR PhCP, suggesting that C75 and D144 are not crucial for the T=3 capsid assembly. pR PhW96A and pR PhD144N-T151A mutant proteins failed to form capsids and were present as heterogeneous aggregates. Interestingly, the pR PhK143E mutant protein behaved in a manner similar to the C-terminal deletion protein in forming unstable capsids. The intermediate with an s value of 19.4 S was the major assembly product of pR PhH69A mutant protein and could correspond to a 30mer. It is possible that the assembly or disassembly is arrested at a similar stage in pR PhN188Delta1, pR PhH69A and pR PhK143E mutant proteins.

Sex and estrous cycle-dependent changes in neurosteroid and benzodiazepine effects on food consumption and plus-maze learning behaviors in rats

Experiments were designed to investigate the influence of estrous cycle and gender of the rat on the effects of a gamma-aminobutyric acid type A (GABA(A)) receptor active neurosteroid, 3alpha-hydroxy-5alpha-pregnan-20-one (allopregnanolone), the benzodiazepine, triazolam, and a GABA(A) receptor antagonistic neurosteroid, delta5-androsten-3beta-ol-17-one sulfate (dehydroepiandrosterone sulfate), on food intake and elevated plus-maze learning behaviors. Allopregnanolone (0.25 mg/kg, s.c.) and triazolam (0.25 mg/kg, i.p.) produced a hyperphagic effect, while dehydroepiandrosterone sulfate (5 mg/kg, s.c.) elicited an anorectic effect. However, allopregnanolone was more potent in diestrous females, whereas triazolam exhibited significantly higher hyperphagic potency in estrus females. The extent of anorexia following dehydroepiandrosterone sulfate was alike in male and female rats. The triazolam- and allopregnanolone-induced hyperphagic effect was blocked by bicuculline (1 mg/kg, i.p.), a selective GABA(A) receptor antagonist. In contrast to triazolam, the hyperphagic effect of allopregnanolone was insensitive to flumazenil (5 mg/kg, i.p.), a benzodiazepine antagonist. Vehicle-treated diestrous rats displayed moderately higher latencies in the elevated plus-maze learning task than estrus or proestrus females. Although allopregnanolone and triazolam elicited equipotent learning deficits in plus-maze learning in male and female rats, the magnitude of impairment-induced by triazolam was significantly higher in diestrous females than proestrus females. Dehydroepiandrosterone sulfate enhanced memory performance only in male rats. Although the use of the elevated plus-maze as a learning paradigm with benzodiazepines and neurosteroids may be sensitive to changes in anxiety, the differential data suggest that neurosteroid-induced effects are at least partly specific to learning behavior. These results confirm the role of estrous cycle and sex of rats in modifying the potency of neurosteroids and benzodiazepines on food consumption and learning and memory processes.

Sigma (sigma1) receptor mediated anti-depressant-like effects of neurosteroids in the Porsolt forced swim test

This study examined the effects of neurosteroids dehydroepiandrosterone sulfate (DHEAS) and pregnenolone sulfate (PS) and progesterone on the Porsolt forced swim test of depression in mice, and investigated the possible involvement of delta receptors. The immobility time in the mouse forced swimming test was significantly reduced by DHEAS (5 and 20 mg/kg, s.c.) and PS (5 mg/kg) without accompanying changes in the ambulatory or open-field activity. Pretreatment with DHEAS (10 mg/kg) or PS (10 and 20 mg/kg), however, failed to modify the immobility. The relief of behavioral despair in the immobility test by DHEAS (5 and 20 mg/kg) was dose-dependently blocked by preadministration of NE-100 (N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl-ethylamine monohydrochloride; 0.5 and 1 mg/kg), a putative delta1 receptor antagonist, or progesterone (10 mg/kg), a delta receptor antagonistic neurosteroid. On the other hand, PS (5 mg/kg)-induced decrease in the immobility was significantly blocked by NE-100(0.5 mg/kg), but not by progesterone (10 mg/kg). Neither NE-100 nor progesterone influenced the immobility alone. These data suggest a role for central delta receptor in the antidepressant-like effects of neurosteroids, and reinforced their potential therapeutic use in depression.

Possible role of nitric oxide in the nootropic and antiamnesic effects of neurosteroids on aging- and dizocilpine-induced learning impairment

The ability of the nitric oxide (NO) synthase inhibitor, NG-nitro-l-arginine methyl ester (L-NAME), to modulate the attenuating effects of neurosteroids on the aging- and NMDA receptor antagonist dizocilpine-induced learning impairment, was tested in mice using two different behavioral models of long-term memory. The performance of aged mice (16 months old) in step-down type of passive-avoidance and elevated plus-maze paradigms was significantly impaired compared to that of young mice (3 months old). Neurosteroids pregnenolone sulfate (PS) and dehydroepiandrosterone sulfate (DHEAS), at 1-20 mg/kg, s.c., significantly improved the passive-avoidance and plus-maze performances in aged mice. Neurosteroids PS and DHEAS, at doses 1-20 mg/kg, s.c., significantly attenuated dizocilpine (0.1 mg/kg, i.p.)-induced amnesia, without producing any promnestic effects alone in adult mice. In both cognitive tasks, the effects exhibited by the neurosteroids tested had a bell-shaped curve. Preadministration of L-NAME (10 and 20 mg/kg, i.p.), at doses that did not disrupt cognition alone in either young or aged mice, significantly blocked the beneficial and antiamnesic effects of neurosteroids PS (5 mg/kg) and DHEAS (10 mg/kg). A selective action of L-NAME on the effects of neurosteroids was indicated, since the effects of L-NAME were completely reversed by L-arginine (300 mg/kg, i.p.), a competitive substrate for NO synthase. Neither L-NAME nor L-arginine alone affected the antinociception, locomotor activity or rota-rod performance of young or aged mice. These observations suggest that a NO-dependent mechanism may be involved in the beneficial and antiamnesic effects of neurosteroids PS and DHEAS on the aging- and dizocilpine-induced impairment of learning and memory processes.

Inhibition of neuronal nitric oxide synthase (n-cNOS) reverses the corticotrophin-induced behavioral effects in rats

The nitric oxide (NO) synthase inhibitor NG-monomethyl-L-arginine (N-NMMA) and the competitive substrate for NO synthase L-arginine were used to determine the role of endogenous NO on the behavioral and neuroendocrine responsiveness following systemic corticotrophin in dexamethasone-suppressed rats. Corticotrophin (50-200 mU/kg, s.c.) dose-dependently decreased behavioral activity in the actimeter and produced significant anxiolytic and anti-risk activity in the plus-maze behavior test, without affecting systolic blood pressure. Rats given corticotrophin showed significant increased plasma corticosterone and reduced adrenal ascorbic acid level. These behavioral and adrenal responses of corticotrophin were dose dependently blocked by metyrapone (20 and 50 mg/kg, i.p.), an inhibitor of steroid 11beta-hydroxylase in adrenal and neural tissues that block steroidogenesis. Intracerebroventricular administration of L-NMMA (20 microg/rat in 10 microl) significantly prevented the behavioral hypoactivity and anxiolytic-like responses of corticotrophin without influencing the adrenal responsiveness. The effect of L-NMMA was completely reversed by preadministration of L-arginine (300 mg/kg, i.p.). These results suggest that neuronal nitric oxide pathway plays an important modulating role in the behavioral effects of corticotrophin by mechanisms other than those involving cardiovascular effects.

The role of GABA-A and mitochondrial diazepam-binding inhibitor receptors on the effects of neurosteroids on food intake in mice

The present studies were undertaken to investigate the neuroactive steroidal modulation of feeding behavior and possible involvement of gamma-aminobutyric acid type-A (GABA-A) and mitochondrial diazepam binding inhibitor (DBI) receptors (MDR) in food-deprived male mice. Allopregnanolone (0.5-2 mg/kg), a neurosteroid, progesterone (1-10 mg/kg), a neurosteroid precursor, and 4'-chlordiazepam (0.25-1 mg/kg), a specific high affinity MDR agonist, produced a dose-dependent hyperphagic effects. In contrast, neurosteroids pregnenolone sulfate (PS) (1-10 mg/kg) and dehydroepiandrosterone sulfate (DHEAS) (1-10 mg/kg) produced a hypophagic effect, in a dose-dependent manner. The allopregnanolone-, progesterone- and 4'-chlordiazepam-induced hyperphagic effect was blocked by picrotoxin (1 mg/kg), a GABA-A chloride channel antagonist, but not by flumazenil (2 mg/kg), a benzodiazepine (BZD) antagonist. The 4'-chlordiazepam-induced hyperphagic effect was prevented by pretreatment with PK11195 (2 mg/kg), a selective partial MDR antagonist. The hypophagic effect of DHEAS (10 mg/kg) was reversed by dizocilpine (10 microg/kg), an NMDA receptor antagonist, but resistant to muscimol (0.1 mg/kg), a selective GABA-A receptor agonist. In contrast, the PS (10 mg/kg)-induced hypophagic response was resistant to dizocilpine, but sensitive to muscimol (0.1 mg/kg). Both the sulfated neurosteroids PS and DHEAS also reversed the hyperphagic effect of allopregnanolone. In addition, the BZD agonist triazolam (0.05-0.25 mg/kg) also produced a flumazenil- and picrotoxin-sensitive hyperphagic effects, thereby suggesting the changes in feeding behavior by neurosteroids represent GABA-A receptor mediated hyperphagic action. Although the possible antistress or anxiolytic actions of neurosteroids may confound the hyperphagia, behavioral effects observed were specific to food because the mice were adopted to the test environment and diet, and of a possible variation between various neurosteroids in the extent to which antistress or anxiolytic effect produced at hyperphagic doses. The hyperphagic effects of progesterone and 4'-chlordiazepam resembled that of neurosteroid allopregnanolone. Therefore, the effect of progesterone may be imputed to its metabolism to allopregnanolone, while the 4'-chlordiazepam-induced hyperphagic response is related to its MDR-stimulated neurosteroidogenesis and subsequent modulation of GABA-A receptors. The hypophagic response following DHEAS may, at least partly, involve an NMDA receptor mechanism. However, PS-induced hypophagia may be mediated by GABA-A or other receptor systems. These data suggest a pivotal role for GABA-A and mitochondrial DBI receptors in the hyperphagic effects of neurosteroids and reinforces a role for endogenous neurosteroids in regulating feeding behavior. Future studies may lead to the development of neurosteroid-based anorectic/hyperphagic agents for therapeutic use.

The effects of neurosteroids on acquisition and retention of a modified passive-avoidance learning task in mice

This study examined the effects of neurosteroids, pregnenolone sulfate (PS) and dehydroepiandrosterone sulfate (DHEAS), on learning and memory processes in a modified passive-avoidance task in mice. The two parameters measured are number of passive-avoidance step-down descents and the active escape latency to reach shock-free zone. Each neurosteroid was administered 60 min before or immediately after the training session, or 60 min before the retention test given 24 h after acquisition. Pretraining injection of PS (0.125-10 mg/kg, s.c.) and DHEAS (0.125-10 mg/kg, s.c.) decreased the number of mistakes committed on training day but had no effect on the latency measure. Both PS (0.125-10 mg/kg, s.c.) and DHEAS (0.125-10 mg/kg, s.c.) decreased the number of mistakes and latency to reach shock-free zone, in a dose-dependent and bell-shaped manner, following pretraining and posttraining administration schedules. Neurosteroids failed to improve memory performance when administered 60 min before retention testing. Injection of PS (0.5 and 1 mg/kg) or DHEAS (1 and 5 mg/kg) before both the training and test sessions, however, also significantly facilitated memory retention. In addition, the memory-facilitating effects of PS (0.5 mg/kg, s.c.) or DHEAS (1 mg/kg) when administered posttraining are blocked by concurrent administration of haloperidol (0.25 mg/kg, i.p.), a prototype sigma receptor antagonist. These results confirm that both PS and DHEAS facilitate retention of a modified learning task when given either pretraining or posttraining, but not prior to retention test. The pretraining neurosteroid-induced memory modulation do not involve state-dependent effects. These results suggest a role for central sigma receptor in the memory-modulating effects of neurosteroids.

Proconvulsant effects of neurosteroids pregnenolone sulfate and dehydroepiandrosterone sulfate in mice

We have investigated the effects of chronic treatment with the neurosteroids, pregnenolone sulfate and dehydroepiandrosterone sulfate, on the potential neurotoxicity in pentylenetetrazol seizure sensitivity test in mice. Four weeks of subcutaneous treatment with pregnenolone sulfate and dehydroepiandrosterone sulfate, at a dose of 10 mg kg(-1) day(-1), significantly shifted the pentylenetetrazol dose-percent convulsions and latency curves to the left, and markedly decreased the ED50 of pentylenetetrazol for tonic convulsions, indicating the increased sensitivity of mice to seizures. Chronic neurosteroid treatment significantly decreased the body weight of the animals. However, acute treatment of neurosteroids did not modify the seizure reactivity of mice to pentylenetetrazol. Furthermore, the dehydroepiandrosterone sulfate (10 mg kg(-1), s.c.)-induced proconvulsant effect was significantly prevented by chronic pretreatment with progesterone (5 mg kg(-1), s.c.), a precursor for GABA(A) receptor active neurosteroid, allopregnanolone, and dizocilpine (0.1 mg kg(-1), i.p.), a non-competitive NMDA receptor antagonist. These results suggest that long-term administration of neurosteroids pregnenolone sulfate or dehydroepiandrosterone sulfate produces proconvulsant effects.

Newer thrombolytic drugs for acute myocardial infarction

Arterial thrombosis is the underlying cause of a wide variety of cardiovascular diseases such as myocardial infarction, stroke and pulmonary thromboembolism. All the currently used thrombolytic agents are plasminogen activators, which are very efficient in restoring the blood flow. The fibrinolytic system comprises an inactive proenzyme plasminogen, that is converted by plasminogen activators to the enzyme plasmin, that degrades fibrin. Despite the widespread use of established thrombolytic agents such as streptokinase, tissue-plasminogen activator and urokinase, all these agents suffer from a number of inadequacies including resistance to reperfusion, occurrence of acute coronary reocclusion and bleeding complications. The quest continues for thrombolytic agents with a higher potency, specific thrombolytic activity and fibrin selectivity. Several lines of research towards improvement of thrombolytic agents are being explored including the construction of mutants and variants of plasminogen activators, chimeric plasminogen activators and conjugates of plasminogen activators with monoclonal antibodies. Newer molecules such as pro-urokinase, saruplase, alteplase, K1K2Pu and staphylokinase have shown promise in animal models of arterial and venous thrombosis and also in pilot scale clinical studies in patients with myocardial infarction. However, more clinical trials are needed to determine whether these novel recombinant thrombolytic agents shows improved efficacy and fibrin specificity with minimal bleeding tendencies.

Reversal of benzodiazepine inverse agonist FG 7142-induced anxiety syndrome by neurosteroids in mice

We have previously shown that neurosteroids produce GABA-A receptor mediated antistress, anxiolytic and other behavioral effects in rodents. In the present study, the effects of neuroactive steroids on benzodiazepine receptor inverse agonist FG 7142-induced anxiogenesis were investigated using mirrored chamber and elevated plus-maze paradigms in mice. FG 7142 (5-20 mg/kg) not only produced a dose-dependent reduction in the duration of open arm exploration and the total number of open arm entries, but also increased the latency to enter the mirrored chamber, decreased the number of entries and total time spent in the chamber, indicative of anxiogenic-like effects. Neurosteroids allopregnanolone (0.5 and 1.5 mg/kg) and pregnenolone sulfate (2 mg/kg) significantly reversed the FG 7142 (10 mg/kg)-induced anxiogenic response in both the paradigms, without producing any neurotoxicity. While dehydroepiandrosterone sulfate (1 and 2 mg/kg) failed to influence the anxiogenic effects of FG 7142. The neuroactive steroid progesterone (1-10 mg/kg), and the mitochondrial diazepam binding inhibitor (DBI) receptor agonist 4'-chlordiazepam (0.5 and 1 mg/kg) dose-dependently blocked the FG 7142-induced anxiogenesis in a flumazenil (2 mg/kg)-insensitive manner. The 4'-chlordiazepam-induced reversal response was, however, prevented by pretreatment with PK11195 (2 mg/kg), a selective mitochondrial DBI receptor antagonist. Further, at the anxiolytic doses, these neurosteroids did not produce locomotor inhibition and ataxia. These data suggest that neurosteroids allopregnanolone, pregnenolone sulfate, progesterone and the mitochondrial DBI receptor agonist 4'-chlordiazepam reverses the anxiogenic-like effects of benzodiazepine receptor inverse agonist FG 7142 in the mouse models of anxiety.

Chronic neurosteroid treatment prevents the development of morphine tolerance and attenuates abstinence behavior in mice

The effect of neurosteroids on the development of morphine tolerance and dependence was examined in mice. Development of tolerance to the antinociceptive effect of morphine sulfate (10 mg/kg, twice daily for 9 days) was measured in the tail-flick test and dependence was assessed from naloxone (2 mg/kg)-precipitated withdrawal jumps on day 10 of testing. Concomitant chronic administration of neurosteroids, allopregnanolone (0.5 mg/kg), pregnenolone sulfate (2 and 5 mg/kg) or dehydroepiandrosterone sulfate (2 and 5 mg/kg), followed by morphine (10 mg/kg) prevented the development of tolerance to the antinociceptive effect of morphine and suppressed the naloxone-precipitated withdrawal jumps. In contrast, dehydroepiandrosterone acetate (5 mg/kg) failed to modulate the morphine tolerance and dependence. The inhibitory effect was also seen upon concomitant administration of a neurosteroid precursor, progesterone (1-10 mg/kg), and a mitochondrial diazepam binding inhibitor receptor agonist, 4'-chlordiazepam (0.25-1 mg/kg), while an adrenocorticosteroid, hydrocortisone (1 and 10 mg/kg), failed to do so. However, acute treatment with these neurosteroids was not associated with any decrease in withdrawal jumping behavior in morphine-dependent mice. Neurosteroids themselves, at doses employed in the study, did not exert any effects on antinociception. These results support a role for neurosteroids in the development of tolerance to and dependence on morphine and suggest the potential utility of specific neuroactive steroids in its treatment.

Neurosteroid coadministration prevents development of tolerance and augments recovery from benzodiazepine withdrawal anxiety and hyperactivity in mice

Neurosteroids are potent and specific modulators of the GABAA receptors which regulate the neuronal activity through diverse neurotransmitter mechanisms. In the present study we investigated the effects of concomitant treatment with various neurosteroids on the development of tolerance and recovery from withdrawal anxiety and hyperactivity to chronic benzodiazepines. Long-term treatment of mice with full allosteric modulator (triazolam 0.25 mg/kg/day for 8 days) or selective allosteric modulator (diazepam 20 mg/kg/day for 21 days) of GABAA receptor induced tolerance to behavioral sedation on actimeter and anxiolytic effects on plus-maze, and produced a marked withdrawal anxiety and hyperactivity syndrome upon abrupt cessation of treatment, respectively. Concomitant progesterone (10 mg/kg, s.c.), a neurosteroid precursor, of 4'-chlordiazepam (0.25 mg/kg, i.p.), a mitochondrial diazepam binding inhibitor (DBI) receptor (MDR) ligand, prevented the development of tolerance and significantly augmented the recovery from withdrawal-induced anxiety and hyperlocomotion to diazepam. When administered alone for 21 days, neither progesterone nor 4'-chlordiazepam produced any per se effects on actimeter or plus-maze when tested on post-withdrawal days. Coadministration of neurosteroid allopregnanolone (AP) (0.25 and 0.5 mg/kg), or pregnenolone sulfate (PS) (2 mg/kg), but not dehydroepiandrosterone sulfate (2 mg/kg), abolished the development of tolerance and attenuated withdrawal-induced anxiety and hyperlocomotion due to triazolam, without producing any per se behavioral effects when tested at 1 and 2 days after the last injection. Coadministration of flumazenil (5 mg/kg), progesterone (10 mg/kg), 4'-chlordiazepam (0.25 mg/kg), hydrocortisone (100 mg/kg) or nifedipine (2 mg/kg) also prevented the development of tolerance and suppressed the triazolam withdrawal syndrome. However, pretreatment with PK11195 (2 mg/kg), a MDR partial antagonist, reversed the effects of 4'-chlordiazepam on triazolam tolerance and recovery from chronic triazolam. When injected simultaneously, nifedipine, a Ca2+ channel antagonist, potentiated the progesterone- and 4'-chlordiazepam-induced attenuation of triazolam tolerance and withdrawal behavior. These findings suggest that coadministration of neurosteroids allopregnanolone, pregnenolone sulfate and progesterone, and MDR ligand 4'-chlordiazepam prevents the development of tolerance to benzodiazepines and augments the recovery from chronic benzodiazepines. These results indicate that coadministration of neurosteroids may facilitate discontinuation of benzodiazepines in long-term therapy.

Differential anxiolytic effects of neurosteroids in the mirrored chamber behavior test in mice

This study examined the effects of neurosteroids on the behavior of mice in the mirrored chamber test of anxiety, and determined the potential mechanisms by which neurosteroids alter the behavior in animal models of anxiety. Allopregnanolone (AP) (0.5 and 1 mg/kg) and pregnenolone sulfate (PS) (0.5 and 2 mg/kg) significantly reduced the latency to enter the chamber, and increased both number of entries and total time spent in the chamber in a dose-dependent manner, without affecting the spontaneous locomotor activity. In contrast, dehydroepiandrosterone sulfate (DHEAS) (1 and 2 mg/kg) increased motor activity and caused an anxiogenic response, i.e., an increase in latency to enter the mirrored chamber, and a decrease in the number of entries and time spent in the chamber. Progesterone (PROG) (1-10 mg/kg), a neurosteroid precursor, and 4'-chlordiazepam (4'-CD) (0.25-1 mg/kg), a specific ligand for the mitochondrial diazepam binding inhibitor (DBI) receptor (MDR), produced a clear dose-dependent anxiolytic response in the mirrored chamber. The AP-, PROG- and 4'-CD-elicited anxiolytic behavior was blocked by picrotoxin (1 mg/kg), a GABA-A chloride channel antagonist, but not by flumazenil (2 mg/kg), a selective benzodiazepine (BZD) antagonist. In contrast, the anxiolytic effect of PS was not blocked by picrotoxin. The 4'-CD-induced anxiolytic effect was prevented by pretreatment with PK11195 (2 mg/kg), a selective partial MDR antagonist. Nifedipine (2 and 5 mg/kg), a dihydropyridine-type Ca2+ channel blocker, produced a flumazenil-resistant anxiolytic effect. Combined administration of nifedipine (2 and 5 mg/kg) and PS (0.5 and 2 mg/kg) exerted a significant additive effect in the mirrored chamber test. The potent anxiolytic effect of dizocilpine (0.5 and 1 mg/kg), an NMDA receptor antagonist, was blocked by pretreatment with DHEAS (2 mg/kg). Neurosteroids evoked changes in mirrored chamber activities resembling those elicited by triazolam (0.25 and 0.5 mg/kg). However, these effects were seen at doses that did not markedly affect locomotor activity, thereby suggesting these changes in behavior represent anxiolytic actions. Together, these results provide evidence for differential behavioral actions of the neurosteroids AP, PS and DHEAS in the mirrored chamber test of anxiety. The anxiolytic effect of PROG may be imputed to its metabolism to neurosteroid AP, while the 4'-CD-induced anxiolytic response is related to its MDR-stimulated neurosteroidogenesis and subsequent modulation of GABA-A receptor. Further, these differential effects reaffirm the contention that neurosteroids could be involved in the homeostasis of stress response.

Role of GABA-A and mitochondrial diazepam binding inhibitor receptors in the anti-stress activity of neurosteroids in mice

Neuroactive steroidal modulation of immobilization-stress and possible involvement of GABA-A and mitochondrial diazepam binding inhibitor (DBI) receptors (MDR) has been investigated in mice. Immobilization of mice for 2 h induced intense antinociception, anxiety state, and associated with a fall in adrenal ascorbic acid levels. Pretreatment with high dose of progesterone (10 mg/kg), a precursor of neurosteroids, significantly decreased the stress-induced antinociception, anxiety and fall in adrenal ascorbic acid, while low doses (1 and 5 mg/kg) or hydrocortisone (10 and 100 mg/kg) were ineffective. In contrast, progesterone (1 mg/kg, for 9 days) produced a significant antistress effect, which was blocked by GABA-A antagonists picrotoxin (1 mg/kg) and bicuculline (1 mg/kg), but not by flumazenil (2 mg/kg), a specific benzodiazepine (BZD) antagonist. 4'-chlordiazepam (0.1 and 0.25 mg/kg), a specific high affinity MDR agonist, produced significant anti-stress effect in a flumazenil-insensitive manner, but was blocked by pretreatment with PK11195 (1.5 mg/kg), a selective partial agonist of MDR, and with bicuculline (1 mg/kg), a potent GABA-A receptor antagonist. At higher doses, progesterone and 4'-chlordiazepam which are effective in immobilization stress also reduced locomotion. However, lower doses of progesterone (6.5 mg/kg) neither affected locomotion, nor produced any motor toxicity on rota-rod test. At the lower doses, the MDR ligand 4'-chlordiazepam (50 micrograms/kg) decreased locomotor activity, without altering motor toxicity on rota-rod test. Further, the per se effects of these treatments on unstressed mice were not significantly different from those of untreated controls, except for plus-maze test. The antistress profile of progesterone may be attributed to the in vivo production of neurosteroid allopregnanolone, thus resembled that of BZDs. Furthermore, the antistress actions are flumazenil-resistant, reaffirming that there may be an increase in the levels of pregnane neurosteroids in vivo, which may act on a specific allosteric site on GABA-A receptors distinct from BZD site. Because 4'-chlordiazepam binds to MDRs and stimulate mitochondrial neurosteroidogenesis, the anti-stress effects of 4'-chlordiazepam may be imputed to its MDR-induced neurosteroids, which then act on GABA-A receptors. These data suggest a pivotal role for GABA-A and mitochondrial DBI receptors in the antistress actions of neurosteroids and reinforces their ameliorative effect in physiological stress.

Comparative antioxidant effects of beta-adrenoceptor blockers, calcium antagonists and U-74500A against iron-dependent lipid peroxidation in murine ventricular microsomal membranes

Recently we have shown that ACE inhibitors and platelet activating factor antagonists inhibit iron-dependent lipid peroxidation in murine ventricular membranes and possess beneficial effects on ischemia and ischemia reperfusion-induced myocardial injury, which has been ascribed to their capacity to scavenge or impair oxygen free radical generation. In the present study we investigated the effects of beta-adrenoceptor blockers and calcium antagonists on iron-dependent lipid peroxidation (LPO) in murine ventricular membranes and compared them with the lazaroid U-74500A, a potent antioxidant. Fe(2+)-vitamin C induced LPO in a concentration- and time-dependent manner, measured as thiobarbituric acid reactive substances (TBARS) formation. Pretreatment of ventricular membranes with gallopamil, verapamil, propranolol and metaprolol at concentrations of 5 microM and higher inhibited Fe(2+)-vitamin C-induced LPO in a concentration-dependent manner with IC50 values of 192.8-208.3 microM; however, they were less potent than U-74500A (IC50 6.8 microM). In contrast, atenolol, timolol, diltiazem and nifedipine inhibited LPO at very high concentrations with IC50 values of 864.5-971.5 microM. Inhibition of LPO may not be due to the drugs' classical pharmacological actions, but rather to their characteristic chemical structures or physicochemical interactions with biological membranes. In view of the pathological importance of LPO in cardiac ischemic injury, inhibition of LPO by gallopamil, verapamil, propranolol and metaprolol may provide additional cardioprotective activity and thus reinforces their beneficial effects in the treatment of ischemic heart disease.

Effects of long-term hydralazine treatment on myocardial structure and expression of myosin isogenes in cardiac pressure overload in rats

The long-term effects of an arterial vasodilator, hydralazine, on myocardial structure and cardiac myosin isogene expression in pressure overload in rats were investigated. Portan rats were subjected to pressure overload by partial abdominal aortic constriction in order to study the effects of a 4-week treatment with hydralazine (15 mg/kg p.o.) on hemodynamics, ventricular structure, and ventricular total RNA, DNA, protein and myosin isoform expression pattern in sham (SO) and pressure-overloaded (p.o.) rats. P.o. increased the mean arterial pressure (MAP) and systolic blood pressure (SBP) and resulted in increased ventricular weight, LV wall thickness, total RNA and protein content; however, total DNA remained unchanged. The expression of fetal isogene beta-myosin heavy chain (beta-MHC) was markedly enhanced, whereas alpha-MHC was reduced. Hydralazine (15 mg/kg p.o.) normalized MAP and SBP, but did not modulate the hypertrophic changes of pressure-overloaded myocardium. It did not prevent an increase in ventricular total RNA and protein content and antithetical expression of myosin isoforms. Overall growth rate of rats was unaffected by hydralazine treatment. These results suggest that hydralazine has no direct effect in preventing the progression of cardiac hypertrophy and expression of beta-MHC, in spite of lowering blood pressure in pressure-overloaded rats. Thus, it further reaffirms that factors other than hemodynamics may play a pivotal role in the development of cardiac hypertrophy and induction of fetal isogene expression.

Role of cardiac renin-angiotensin system in the development of pressure-overload left ventricular hypertrophy in rats with abdominal aortic constriction

Possible involvement of cardiac renin-angiotensin system (RAS) in pressure overload induced left ventricular hypertrophy (LVH) was investigated. Rats were subjected to abdominal aortic constriction (AAC) and examined the effects of 4 weeks treatments with an angiotensin converting enzyme (ACE) inhibitor, captopril and a vasodilator, hydralazine on haemodynamics and ventricular RNA, DNA, protein and myosin isoform pattern in sham and hypertrophied rats. AAC increased the mean arterial pressure (MAP) and systolic blood pressure (SBP), and resulted in increased left ventricle/body weight ratio, LV thickness, RNA and protein content, however total DNA was not changed. The expression of fetal isogene, beta-myosin heavy chain (beta-MHC), was markedly enhanced where as alpha-MHC was reduced. High-dose captopril (100 mg/kg p.o.,) significantly prevented the increase in haemodynamics, development of LVH, LV remodeling, increase in total protein, RNA and antithetical expression of myosin isoforms. Hydralazine (15 mg/kg p.o.,), did not modulate hypertrophic changes and low-dose captopril (1.5 mg/kg p.o.,) which has not produced any marked fall in MAP and SBP also modulated favourably the development of LVH and its biochemical markers. Thus, the prevention of the development of LVH and induction of beta-MHC by non-hypotensive doses of captopril may be related to the blockade of intracardiac production of angiotensin II rather than circulating system. These results suggest that cardiac RAS may play an important role in pressure overload induced LVH.

Antiperoxidative effects of platelet activating factor antagonists against iron-dependent lipid peroxidation in murine ventricular membranes

Platelet activating factor (PAF) antagonists have been recently documented to possess beneficial effects on ischemia and ischemia-reperfusion-induced myocardial injury. Moreover, their ameliorative effect has been ascribed to their capacity to scavenge or impair oxygen free radical generation. In the present study, the effect of PAF antagonists BN 52021, BN 52030 and BN 52039 on iron-initiated lipid peroxidation (LPO) was investigated in murine ventricular membranes and compared with a potent antioxidant, U-74500A ( a lazaroid). Fe2+ -Vitamin C induced a concentration and time-dependent LPO, measured as thiobarbituric acid reactive substances (TBARS) by standard malondialdehyde (MDA) curve. PAF antagonists were pretreated to ventricular membranes in 5 microM and higher concentrations. All three agents inhibited Fe2+ -Vitamin C-initiated LPO in a concentration-dependent manner with an IC50 value ranging from 103.7 to 373.5 microM; however, they were less potent than U-74500A (IC50 6.8 microM). Inhibition of LPO may not be due to their classical pharmacological actions, but may be attributed to characteristic chemical structure or their physicochemical interactions with biological membranes. Inhibition of LPO may provide additional cardioprotective activity and thus reaffirms their use in ischemic heart disease.

Inactivation of clostridial ferredoxin and pyruvate-ferredoxin oxidoreductase by sodium nitrite

Clostridial ferredoxin and pyruvate-ferredoxin oxidoreductase activity was investigated after in vitro or in vivo treatment with sodium nitrite. In vitro treatment of commercially available Clostridium pasteurianum ferredoxin with sodium nitrite inhibited ferredoxin activity. Inhibition of ferredoxin activity increased with increasing levels of sodium nitrite. Ferredoxin was isolated from normal C. pasteurianum and Clostridium botulinum cultures and from cultures incubated with 1,000 micrograms of sodium nitrite per ml for 45 min. The activity of in vivo nitrite-treated ferredoxin was decreased compared with that of control ferredoxin. Pyruvate-ferredoxin oxidoreductase isolated from C. botulinum cultures incubated with 1,000 micrograms of sodium nitrite per ml showed less activity than did control oxidoreductase. It is concluded that the antibotulinal activity of nitrite is due at least in part to inactivation of ferredoxin and pyruvate-ferredoxin oxidoreductase.