Thesis (Ph. D.)--Virginia Commonwealth University, 2006. / Prepared for: Dept. of Biostatistics. Bibliography: leaves 173-177. Also available online.

Synthetic cathinones are stimulant drugs of abuse that act at monoamine transporters e.g. the dopamine transporter (DAT) as releasing agents or as reuptake inhibitors. More than >150 new synthetic cathinones have emerged on the clandestine market and have attracted considerable attention from the medical and law enforcement communities. threo-Methylphenidate (tMP) is an FDA approved drug for the treatment of ADHD and narcolepsy, which also acts as a DAT reuptake inhibitor and is widely abused. tMP and synthetic cathinones share some structural similarities and extensive structure-activity relationship (SAR) studies on tMP have been conducted. However, much less is known about the SAR of synthetic cathinones, and the available MP literature might assist in understanding it. The main focus of this research was to compare SAR between methylphenidate-cathinone hybrids and available methylphenidate SAR in order to identify some guiding principles that might allow
us to predict their abuse potential and to identify which cathinones should be
targeted for more extensive evaluation. In the present study, we evaluated eight 2-benzoylpiperidine analogs and a descarbonyl analog to determine if tMP SAR can be applied to cathinone SAR. We conducted molecular modeling and docking studies and predicted the order of potency to be tMP > 2-benzoylpiperidine > 2-benzylpiperidine based on the number of hydrogen bonds. The synthesized analogs were evaluated in a competition assay using live-cell imaging against APP+ in HEK293 cells stably expressing hDAT. All compounds were found to be DAT reuptake inhibitors and, as the modeling studies predicted, the order of potency in our functional studies was also found to be tMP > 2-benzoylpiperidine > 2- benzylpiperidine. A significant correlation was obtained between the potency of the benzoylpiperidines and tMP binding data (r = 0.91) suggesting that the SAR of tMP analogs might be applicable to the synthetic cathinones as DAT reuptake inhibitors.

Pharmacological magnetic resonance imaging (phMRI) is the use of functional MRI techniques to elucidate the effects that psychotropic drugs have on neural activity within the brain; it is an emerging field of research that holds great potential for the investigation of drugs that act on the central nervous system by revealing the changes in neural activity that mediate observable changes in behavior, cognition, and perception. However, the realization of this potential is hampered by several unanswered questions: Are the MRI measurements reliable surrogates of changing neural activity in the presence of pharmacological agents? Is it relevant to investigate psychiatric phenomena such as reward or anxiolysis in anesthetized, rather than conscious animals? What are the methods that yield reproducible and meaningful results from phMRI experiments, and are they consistent in the investigations of different drugs? The research presented herein addresses many of these questions with the specific aims of 1) Developing pharmacological MRI methodologies that can be used in the conscious animal, 2) Validating these methodologies with the investigation of a non-stimulant, psychoactive compound, and 3) Applying these methodologies to the investigation of typical and atypical antipsychotic drugs, classes of compounds with unknown mechanisms of therapeutic action Building on recent developments in the field of functional MRI research, we developed new techniques that enable the investigator to measure localized changes in metabolism commensurate with changing neural activity. We tested the hypothesis that metabolic changes are a more reliable surrogate of changes in neural activity in response to a cocaine challenge, than changes observed in the blood-oxygen-level-dependent (BOLD) signal alone. We developed a system capable of multi-modal imaging in the conscious rat, and we tested the hypothesis that the conscious brain exhibits a markedly different response to systemic morphine challenge than the anesthetized brain. We identified and elucidated several fundamental limitations of the imaging and analysis protocols used in phMRI investigations, and developed new tools that enable the investigator to avoid common pitfalls. Finally, we applied these phMRI techniques to the investigation of neuroleptic compounds by asking the question: does treatment with typical or atypical antipsychotic drugs modulate the systems in the brain which are direct or indirect (i.e. downstream) substrates for a dopaminergic agonist? The execution of this research has generated several new tools for the neuroscience and drug discovery communities that can be used in neuropsychiatric investigations into the action of psychotropic drugs, while the results of this research provide evidence that supports several answers to the questions that currently limit the utility of phMRI investigations. Specifically, we observed that metabolic change can be measured to resolve discrepancies between anomalous BOLD signal changes and underlying changes in neural activity in the case of systemically administered cocaine. We found clear differences in the response to systemically administered morphine between conscious and anesthetized rats, and observed that only conscious animals exhibit a phMRI response that can be explained by the pharmacodynamics of morphine and corroborated by behavioral observations. We identified fundamental and drug-dependent limitations in the protocols used to perform phMRI investigations, and designed tools and alternate methods to facilitate protocol development. By applying these techniques to the investigation of neuroleptic compounds, we have gained a new perspective of the alterations in dopaminergic signaling induced by treatment with antipsychotic medications, and have found effects in many nuclei outside of the pathways that act as direct substrates for dopamine. A clearer picture of how neuroleptics alter the intercommunication of brain nuclei would be an invaluable resource for the classification of investigational antipsychotic drugs, and would provide the basis for future studies that examine the neuroplastic changes that confer therapeutic efficacy following chronic treatment with antipsychotic medications.

In mammals a single receptor protein binds both insulin-like growth factor II (IGF-II) and mannose 6-phosphate (Man 6-P) containing ligands, most notably lysosomal enzymes. However, in chick embryo fibroblasts IGF-II binds predominantly to a type 1 IGF receptor, and no IGF-II/Man 6-P receptor has been identified in this species. In order to determine if chickens possess an IGF-II/Man 6-P receptor, an affinity resin (pentamannosyl 6-phosphate (PMP) Sepharose) was used to purify receptors from chicken membrane extracts by their ability to bind mannose 6-phosphate. Then 125I-IGF-II was used to evaluate their ability to bind IGF-II. These experiments demonstrate that nonmammalian Man 6-P receptors lack the ability to bind IGF-II, suggesting that the ability to bind IGF-II has been gained recently in evolution by the mammalian Man 6-P receptor. The second area of study involves the serum form of the IGF-II/Man 6-P receptor. This receptor had been detected in the serum of a number of mammalian species, yet its structure, function, regulation, and origin were unknown. Initial studies, done with Dr. R. G. MacDonald, showed that the serum receptor is truncated such that the C-terminal cytoplasmic domain of the cellular receptor is removed. These studies also demonstrate a regulation of serum receptor levels with age, similar to that seen for the cellular receptor, and that the serum form of the receptor existed in several forms which appeared intact under nonreducing conditions, but as multiple proteolytic products upon reduction. Finally, these studies demonstrated that both the cellular and serum IGF-II/Man 6-P receptors are capable of binding IGF-II and Man 6-P simultaneously. In studies on the serum form of the IGF-II/Man 6-P receptor that I have conducted independently, the regulation of the serum IGF-II/Man 6-P and transferrin receptors by insulin has been demonstrated. In these studies, insulin injected into rats subcutaneously resulted in a time and dose dependent increase in serum receptor levels. Finally, to investigate the relationship of the serum IGF- II/Man 6-P receptor to the cellular form of the receptor, pulse chase experiments were performed. These experiments demonstrate that the soluble (serum form released into the medium) receptor is a major degradation product of the cellular receptor. Furthermore, the lack of detectable amounts of the lower Mr soluble receptor intracellularly and the parallel relationship of cell surface and soluble receptor suggest that the proteolysis is occurring from the cell surface. Finally, a number of experiments suggest that the degradation rate depends upon the conformation state of the receptor: binding of IGF-II or Man 6-P makes the receptor more susceptible to proteolysis while the presence of lysosomal enzymes prevents receptor proteolysis. In summary, the serum form of the IGF-II receptor is a proteolytic product of the cellular form of the receptor. The rate of release depends upon the number of receptors at the cell surface and the binding state of the receptor. In circulation, the receptor retains the ability to bind both types of ligands, it thus may serve as an IGF binding protein and/or a lysosomal enzyme binding protein. These results suggest a model whereby the cellular receptor is proteolytically cleaved by a plasma membrane protease to produce a short membrane anchored fragment and the serum receptor. In vivo this pathway serves as the major degradative pathway of the IGF-II/Man 6-P receptor, with the serum form being cleared from circulation by further degradation and reuptake.

Cysteamine (CA), which is an aminothiol drug medically known as Cystagon® was studied in this thesis. Cysteamine was reacted with a binary toxin called peroxynitrite (PN) which is assembled spontaneously whenever nitric oxide and superoxide are produced together and the decomposition of peroxyinitrite was monitored. PN was able to nitrosate CA in highly acidic medium and excess CA to form S-nitrosocysteamine (CANO) in a 1:1 with the formation of one mole of CANO from one mole of ONOOH. In excess oxidant (PN) the following 1:2 stoichiometric ratio was obtained; ONOO- + 2CA → CA-CA + NO2- + H2O . In alkali medium the oxidation of CA went through a series of stages from sulfenic acid, sulfinic acid and then sulfonic acid which was followed by the cleavage of the C-S bond to form a reducing sulfur leaving group, which is easily oxidized to sulfate. The nitrosation reaction was first order in peroxynitrite, thus implicating it as a nitrosating agent in highly acidic pH conditions. Acid catalyzes nitrosation reaction, whitst nitrate catalyzed and increased the amount of CANO product, This means that the nitrosonium cation, NO+ which is produced from the protonation of nitrous acid(in situ) as also contributing to the nitrosation of CA species in highly acidic environments. The acid catalysis at constant peroxynitrite concentrations suggests that the protonated peroxynitrous acid nitrosates at a much higher rate than the peroxynitrite and peroxynitrous acid. Bimolecular rate constants for the nitrosation of CA, was deduced to be 10.23 M-1 s-1. A linear correlation was obtained between the initial rate constants and the pH. The oxidation of CA was modeled by a simple reaction scheme containing 12 reactions.

Schizophrenia affects about 1% of the population. A hallmark of the disorder is increased dopamine D2 receptor sensitivity in the brain. Studies have shown that schizophrenics smoke cigarettes at approximately 4 times the rate of the general population. It has been suggested that nicotine use is a form of self-medication for symptoms in schizophrenia. Smoking behaviors typically begin in adolescence. We assessed effects of nicotine on behavior and brain plasticity in an adolescent rodent model of schizophrenia with the goal of identifying targets for smoking cessation. Methods: Rats were neonatally treated with quinpirole (a D2/D3 agonist) or saline and sensitized to 0.3, 0.5, or 0.7 mg/kg (free base) nicotine or saline, every other day for 9 days, and locomotor activity was recorded. After behavioral testing, animals demonstrating sensitization to 0.5mg/kg nicotine were surgically implanted with a guide cannula, aimed at the nucleus accumbens core. After recovery, animals underwent microdialysis and in vivo samples were collected every 20 minutes for 300 minutes. Postmortem brains from animals exposed to 0.5mg/kg nicotine or saline were dissected and the nucleus accumbens and dorsal striatum were analyzed for brain-derived neurotrophic factor (BDNF), phosphorylated cAMP response element binding protein (pCREB), and glial-cell derived neurotrophic factor (GDNF), all proteins involved in neuronal plasticity. Results: Animals neonatally treated with quinpirole and administered nicotine showed robust increases in locomotor sensitization and a 400% increase in dopamine overflow from the accumbens core, which was greater than all other groups. Nicotine administration led to increased accumbal BDNF levels, which was enhanced by neonatal quinpirole pretreatment. GDNF levels were also increased in control animals given nicotine, which was attenuated to control levels by neonatal quinpirole. Finally, pCREB levels were robustly increased in animals neonatally treated with quinpirole, an effect that was partially attenuated by adolescent nicotine treatment. These data on pCREB suggest a possible biological marker of anhedonia. In conclusion, it is apparent that nicotine results in a robust increase in behavioral activity and changes in neural proteins of brain plasticity that may serve as possible pharmaceutical targets for smoking cessation in schizophrenia.

Iron is the 4th most abundant metal on the earth's crust and is required by most organisms as a cofactor for many enzymes; however, at physiological pH and aerobic conditions iron forms insoluble ferric oxyhydroxide polymers. Siderophores are low molecular weight compounds that scavenge ferric ions, bind with high affinity, and transport it into the cell via multicomponent transport systems. Rhizobia are soil dwelling organisms that form symbiotic relationships with host plants and fix atmospheric nitrogen, while the bacteria receive nutrients. R. leguminosarum IARI 917 produces a siderophore characterized as 'schizokinen'. In the present study, we have characterized the binding and transport kinetics of 'schizokinen' and have also attempted to identify the genes involved in its biosynthesis using mini Tn5 random mutagenesis. DNA sequence analysis of a non siderophore producing transconjugant revealed a gene involved in PAC/PAS signal transduction systems that respond to many extracellular cues.

The behavioral effects of nicotine on locomotor activity in a rodent model of psychosis were analyzed. This model is based on neonatal quinpriole treatment (a dopamine D2/D3 agonist) which causes increased D2 receptor sensitivity, a phenomenon known as D2 priming that is common in schizophrenia. D2-primed adolescent rats did not demonstrate nicotine-induced hypoactivity early in training, and males demonstrated more rapid sensitization to nicotine as compared to controls administered nicotine. D2-primed females administered nicotine demonstrated increased stereotypic behavior. D2-primed adult rats given nicotine demonstrated significantly more robust sensitization to nicotine than controls given nicotine. Brain-derived neurotrophic factor (BDNF) was analyzed in the nucleus accumbens. BDNF was significantly increased in nicotine treated adolescent females but was not affected in males. Nicotine alleviated BDNF deficits in D2-primed adults. These results suggest that sensitization to nicotine in D2-primed rats is age dependent, and nicotine induced changes in BDNF that is age and sexdependent.

Platinum compounds are widely used drugs in cancer treatments. Although DNA is the biological target, reaction of platinum compounds with proteins is also potentially significant. Our objective is to study the effects of leaving ligands on the relative reactivity between 5'-GMP (guanosine 5' phosphate), a key DNA target, and N-Acetyl - L-Methionine (N-AcMet), a key protein target. We have used NMR spectroscopy to monitor reactions with N-AcMet and 5'-GMP added to a platinum complex to see which products are formed preferentially. Previous research showed that both a non-bulky complex such as [Pt(en)(D2O)2]2+ [en=ethylenediamine], and a bulky complex such as [Pt(Me4en)(D2O)2]2+ [Me4en= N, N, N', N'-tetramethylethylenediamine] react more quickly with 5'-GMP than with N-AcMet. To improve the activity of platinum compounds in our current research, oxalates as leaving ligands are used. The results suggest that [Pt(en)(Ox)] [Ox= oxalate] reacts faster with N-AcMet than with 5'-GMP. Also, [Pt(Me4en)(Ox)] reacts slowly with 5'-GMP without N-AcMet and the reaction favors N-AcMet when both ligands are added simultaneously. Interestingly, the formation of the sulfur-oxygen chelate is slow enough to be observable in the oxalate reaction; but the mono product is not independently observed in the dinitrate complex.

Nanotechnology has become the most advanced type of drug delivery system within the last decade. This advancement shifted the focus on small carriers to increase the efficiency of the drugs. Among these, gold nanoparticles (GNPs) were found to have profound biomedical applications. In current research, kanamycin embedded GNPs were prepared in a single step, single phase, and bio-friendly (green synthesis) procedure. The synthesized Kanamycin-GNPs (Kan-GNPs) were spherical in shape and had a size range of 15 ± 3 nm. The chosen kanamycin is an aminoglycosidic antibiotic that is isolated from Streptomyces kanamyceticus. These special antibiotic GNPs are further characterized using several analytical methods like Transmission Electron Microscopy (TEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Ultra-Voilet/Visible spectroscopy (UV/Vis spectroscopy). The following research is a direct bio-friendly embedment of an antibiotic agent on the surface of the GNPs without any secondary capping agent or surface modification procedures.