Reaction Cycles of Halogen Species in the Immune Defense: Implications for Human Health and Diseases and the Pathology and Treatment of COVID-19.

There is no vaccine or specific antiviral treatment for COVID-19, which is causing a global pandemic. One current focus is drug repurposing research, but those drugs have limited therapeutic efficacies and known adverse effects. The pathology of COVID-19 is essentially unknown. Without this understanding, it is challenging to discover a successful treatment to be approved for clinical use. This paper addresses several key biological processes of reactive oxygen, halogen and nitrogen species (ROS, RHS and RNS) that play crucial physiological roles in organisms from plants to humans. These include why superoxide dismutases, the enzymes to catalyze the formation of H2O2, are required for protecting ROS-induced injury in cell metabolism, why the amount of ROS/RNS produced by ionizing radiation at clinically relevant doses is ~1000 fold lower than the endogenous ROS/RNS level routinely produced in the cell and why a low level of endogenous RHS plays a crucial role in phagocytosis for immune defense. Herein we propose a plausible amplification mechanism in immune defense: ozone-depleting-like halogen cyclic reactions enhancing RHS effects are responsible for all the mentioned physiological functions, which are activated by H2O2 and deactivated by NO signaling molecule. Our results show that the reaction cycles can be repeated thousands of times and amplify the RHS pathogen-killing (defense) effects by 100,000 fold in phagocytosis, resembling the cyclic ozone-depleting reactions in the stratosphere. It is unraveled that H2O2 is a required protective signaling molecule (angel) in the defense system for human health and its dysfunction can cause many diseases or conditions such as autoimmune disorders, aging and cancer. We also identify a class of potent drugs for effective treatment of invading pathogens such as HIV and SARS-CoV-2 (COVID-19), cancer and other diseases, and provide a molecular mechanism of action of the drugs or candidates.

Characterization of Brain-Penetrant Pyrimidine-Containing Molecules with Differential Microtubule-Stabilizing Activities Developed as Potential Therapeutic Agents for Alzheimer's Disease and Related Tauopathies.

The microtubule (MT)-stabilizing protein tau disengages from MTs and forms intracellular inclusions known as neurofibrillary tangles in Alzheimer's disease and related tauopathies. Reduced tau binding to MTs in tauopathies may contribute to neuronal dysfunction through decreased MT stabilization and disrupted axonal transport. Thus, the introduction of brain-penetrant MT-stabilizing compounds might normalize MT dynamics and axonal deficits in these disorders. We previously described a number of phenylpyrimidines and triazolopyrimidines (TPDs) that induce tubulin post-translational modifications indicative of MT stabilization. We now further characterize the biologic properties of these small molecules, and our results reveal that these compounds can be divided into two general classes based on the cellular response they evoke. One group composed of the phenylpyrimidines and several TPD examples showed a bell-shaped concentration-response effect on markers of MT stabilization in cellular assays. Moreover, these compounds induced proteasome-dependent degradation of α- and ß-tubulin and caused altered MT morphology in both dividing cells and neuron cultures. In contrast, a second group comprising a subset of TPD molecules (TPD+) increased markers of stable MTs in a concentration-dependent manner in dividing cells and in neurons without affecting total tubulin levels or disrupting MT architecture. Moreover, an example TPD+ compound was shown to increase MTs in a neuron culture model with induced tau hyperphosphorylation and associated MT deficits. Several TPD+ compounds were shown to be both brain penetrant and orally bioavailable, and a TPD+ example increased MT stabilization in the mouse brain, making these compounds potential candidate therapeutics for neurodegenerative tauopathies such as Alzheimer's disease.

Deep brain stimulation in treatment-resistant depression in mice: comparison with the CRF1 antagonist, SSR125543.

Deep brain stimulation (DBS) has been demonstrated to represent a targeted therapeutic alternative for treatment-resistant depression. In this study, we used the unpredictable chronic mild stress (UCMS) test to validate high-frequency electrical stimulation of the cingulate cortex (CC) as a possible treatment to improve behavioral symptoms associated with a depressive-like state in treatment-resistant mice. The effects of DBS were compared with those of the CRF(1) antagonist, SSR125543. Mice were subjected to UCMS, which consisted of the sequential and unpredictable application of mild stressors for a total of 8 weeks. From week 4 until the end of week 6, mice received either a saline injection or were treated with the antidepressant, fluoxetine (10 mg/kg, i.p.). At the end of week 6, fluoxetine-treated mice were subdivided into two populations, that is one responding to fluoxetine, and one not responding, based on their fur coat state, an index of depressive-like state in this test. Non-responders were subsequently subjected to bilateral DBS (at 80 or 120 Hz, 1-h/day) or were treated with SSR125543 (20 mg/kg, i.p.) for two weeks. Stimulation of the CC at 120 Hz in treatment-resistant mice resulted in a normalization of motivated-like responses, anxiety-related behaviors, hyperactivity and aggressiveness. SSR125543 improved motivated-like and aggressive behaviors. These findings demonstrate that bilateral DBS of the CC and, to a lesser extent, pharmacological blockade of the CRF(1) receptor in treatment-resistant mice can attenuate several aspects of depressive-like behaviors, suggesting further that these approaches may represent valid alternatives for the treatment of drug-resistant depressed and/or anxious patients.

The γ-secretase inhibitor 2-[(1R)-1-[(4-chlorophenyl)sulfonyl](2,5-difluorophenyl) amino]ethyl-5-fluorobenzenebutanoic acid (BMS-299897) alleviates Aß1-42 seeding and short-term memory deficits in the Aß25-35 mouse model of Alzheimer's disease.

Alzheimer's disease pathomimetic toxicity could be induced in mice within one week after the intracerebroventricular (i.c.v.) injection of an aggregated preparation of the highly toxic and endogenous amyloid-ß fragment Aß(25-35). It was recently reported that Aß(25-35) also provokes a modification of APP processing with accumulation of endogenous Aß(1-42). We here analyzed whether a γ-secretase inhibitor, BMS-299897, attenuated this Aß(25-35)-induced Aß(1-42) seeding and toxicity. The compound was administered at 0.1-1 nmol/mouse, concomittantly with Aß(25-35) (9 nmol) in male Swiss mice. After one week, the contents in Aß(1-42) and Aß(1-40), and the levels in lipid peroxidation were analyzed in the mouse hippocampus. Mice were submitted to spontaneous alternation, passive avoidance and object recognition to analyze their short- and long-term memory abilities. Aß(25-35) increased Aß(1-42) content (+240%) but failed to affect Aß(1-40). BMS-299897 blocked the increase in Aß(1-42) content and decreased Aß(1-40) levels significantly. The compound did not affect Aß(25-35)-induced increase in hippocampal lipid peroxidation. Behaviorally, BMS-299897 blocked the Aß(25-35)-induced deficits in spontaneous alternation or novel object recognition, using a 1h intertrial time interval. BMS-299896 failed to affect the passive avoidance impairments or novel object recognition, using a 24h intertrial time interval. These results confirmed that Aß(25-35) injection provoked an accumulation in endogenous Aß(1-42), an effect blocked by γ-secretase inhibition. This Aß(1-42) accumulation marginally contributed to the toxicity or long-term memory deficits. However, since the seeded Aß(1-42) affected short-term memory, the rapid Aß(25-35) injection Alzheimer's disease model could be used to screen the activity of new secretase inhibitors.

Antidepressants recruit new neurons to improve stress response regulation.

Recent research suggests an involvement of hippocampal neurogenesis in behavioral effects of antidepressants. However, the precise mechanisms through which newborn granule neurons might influence the antidepressant response remain elusive. Here, we demonstrate that unpredictable chronic mild stress in mice not only reduces hippocampal neurogenesis, but also dampens the relationship between hippocampus and the main stress hormone system, the hypothalamo-pituitary-adrenal (HPA) axis. Moreover, this relationship is restored by treatment with the antidepressant fluoxetine, in a neurogenesis-dependent manner. Specifically, chronic stress severely impairs HPA axis activity, the ability of hippocampus to modulate downstream brain areas involved in the stress response, the sensitivity of the hippocampal granule cell network to novelty/glucocorticoid effects and the hippocampus-dependent negative feedback of the HPA axis. Remarkably, we revealed that, although ablation of hippocampal neurogenesis alone does not impair HPA axis activity, the ability of fluoxetine to restore hippocampal regulation of the HPA axis under chronic stress conditions, occurs only in the presence of an intact neurogenic niche. These findings provide a mechanistic framework for understanding how adult-generated new neurons influence the response to antidepressants. We suggest that newly generated neurons may facilitate stress integration and that, during chronic stress or depression, enhancing neurogenesis enables a dysfunctional hippocampus to restore the central control on stress response systems, then allowing recovery.

AVE1625, a cannabinoid CB1 receptor antagonist, as a co-treatment with antipsychotics for schizophrenia: improvement in cognitive function and reduction of antipsychotic-side effects in rodents.

RATIONALE: The psychotomimetic effects of cannabis are believed to be mediated via cannabinoid CB1 receptors. Furthermore, studies have implicated CB1 receptors in the pathophysiology of schizophrenia. OBJECTIVE: These studies investigated the effects of the CB1 receptor antagonist, AVE1625, in acute pharmacological and neurodevelopmental models of schizophrenia. AVE1625 was administered to rodents alone or as a co-treatment with clinically used antipsychotic drugs (APDs). METHODS: The antipsychotic potential of AVE1625 was tested using psychotomimetic-induced hyperactivity and latent inhibition (LI) deficit models. The procognitive profile was assessed using hole board, novel object recognition, auditory evoked potential, and LI techniques. In addition, the side-effect profile was established by measuring catalepsy, antipsychotic-induced weight gain, plasma levels of prolactin, and anxiogenic potential. RESULTS: AVE1625 (1, 3, and 10 mg/kg ip), reversed abnormally persistent LI induced by MK-801 or neonatal nitric oxide synthase inhibition in rodents, and improved both working and episodic memory. AVE1625 was not active in positive symptom models but importantly, it did not diminish the efficacy of APDs. It also decreased catalepsy and weight gain induced by APDs, suggesting that it may decrease APD-induced extrapyramidal side effects (EPS) and compliance. Unlike other CB1 antagonists, AVE1625 did not produce anxiogenic-like effects. CONCLUSIONS: These preclinical data suggest that AVE1625 may be useful to treat the cognitive deficits in schizophrenia and as a co-treatment with currently available antipsychotics. In addition, an improved side-effect profile was seen, with potential to ameliorate the EPS and weight gain issues with currently available treatments.

Profiling of energy metabolism in olanzapine-induced weight gain in rats and its prevention by the CB1-antagonist AVE1625.

This is the first study to examine the effect of subchronic olanzapine (OLZ) on energy homeostasis in rats, covering all aspects of energy balance, including energy intake as metabolizable energy, storage, and expenditure. We further analyzed whether, and by which mechanism, the CB1-antagonist AVE1625 might attenuate OLZ-induced body weight gain. For this purpose, we selected juvenile female Hanover Wistar rats that robustly and reproducibly demonstrated weight gain on OLZ treatment, accepting limitations to model the aberrations on lipid and carbohydrate metabolism. Rats received 2 mg/kg OLZ orally twice daily for 12 days. Body weight and body composition were analyzed. Moreover daily food intake, energy expenditure, and substrate oxidation were determined in parallel to motility and body core temperature. OLZ treatment resulted in substantial body weight gain, in which lean and fat mass increased significantly. OLZ-treated rats showed hyperphagia that manifested in increased carbohydrate oxidation and lowered fat oxidation (FO). Energy expenditure was increased, motility decreased, but there was no indication for hypothermia in OLZ-treated rats. Coadministration of OLZ and AVE1625 (10 mg/kg orally once daily) attenuated body weight gain, diminishing the enhanced food intake while maintaining increased energy expenditure and decreased motility. Our data reveal that energy expenditure was enhanced in OLZ-treated rats, an effect not critically influenced by motility. Energy uptake, however, exceeded energy expenditure and led to a positive energy balance, confirming hyperphagia as the major driving factor for OLZ-induced weight gain. Combination of OLZ treatment with the CB1-antagonist AVE1625 attenuated body weight gain in rats.

Cevipabulin (TTI-237): preclinical and clinical results for a novel antimicrotubule agent.

Antimitotic agents are among the most effective drugs for the treatment of solid tumors and metastatic cancer. These drugs promote cell death by interfering with the crucial structural and regulatory function of microtubules in cells. Most of the agents of clinical relevance are natural products or semisynthetic derivatives thereof, and they fall into two major classes: microtubule stabilizers such as the taxanes, which enhance tubulin polymerization, and microtubule destabilizers such as the Vinca alkaloids, which lead to the depolymerization of existing microtubules. While these drugs are effective in inhibiting the progression of certain types of tumors, their utility is limited in part by incomplete tumor responses and/or significant side effects. In addition, inherent resistance is encountered in many tumor types, or acquired resistance may occur as a result of multiple cycles of therapy. Cevipabulin (TTI-237) is a novel, small synthetic molecule with an unusual biological mode of action. It appears to bind at the vinca site, but exhibits some properties similar to those of taxane-site ligands, such as enhancing tubulin polymerization. The compound works against a variety of tumors, including those resistant to paclitaxel and vincristine. Furthermore, cevipabulin is stable and water-soluble, and can be administered i.v. or p.o. in saline. It can be synthesized in bulk quantities efficiently. Based on these properties, cevipabulin was selected for clinical development.

Corticolimbic transcriptome changes are state-dependent and region-specific in a rodent model of depression and of antidepressant reversal.

Gene microarrays may enable the elucidation of neurobiological changes underlying the pathophysiology and treatment of major depression. However, previous studies of antidepressant treatments were performed in healthy normal rather than 'depressed' animals. Since antidepressants are devoid of mood-changing effects in normal individuals, the clinically relevant rodent transcriptional changes could remain undetected. We investigated antidepressant-related transcriptome changes in a corticolimbic network of mood regulation in the context of the unpredictable chronic mild stress (UCMS), a naturalistic model of depression based on socio-environmental stressors. Mice subjected to a 7-week UCMS displayed a progressive coat state deterioration, reduced weight gain, and increased agonistic and emotion-related behaviors. Chronic administration of an effective (fluoxetine) or putative antidepressant (corticotropin-releasing factor-1 (CRF1) antagonist, SSR125543) reversed all physical and behavioral effects. Changes in gene expression differed among cingulate cortex (CC), amygdala (AMY) and dentate gyrus (DG) and were extensively reversed by both drugs in CC and AMY, and to a lesser extent in DG. Fluoxetine and SSR125543 also induced additional and very similar molecular profiles in UCMS-treated mice, but the effects of the same drug differed considerably between control and UCMS states. These studies established on a large-scale that the molecular impacts of antidepressants are region-specific and state-dependent, revealed common transcriptional changes downstream from different antidepressant treatments and supported CRF1 targeting as an effective therapeutic strategy. Correlations between UCMS, drug treatments, and gene expression suggest distinct AMY neuronal and oligodendrocyte molecular phenotypes as candidate systems for mood regulation and therapeutic interventions.

Spinal alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors may mediate the analgesic effects of emulsified halogenated anaesthetics.

1. The present study was designed to investigate the relationship between spinal cord alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and the analgesic effects of emulsified halogenated anaesthetics. 2. After having established the mouse model of analgesia by intraperitoneal or subcutaneous injections of appropriate doses of emulsified enflurane, isoflurane or sevoflurane, we injected different doses of AMPA intrathecally and observed effects on the pain threshold using the hot-plate and acetic acid-induced writhing tests. 3. The results showed that intrathecal injection of AMPA (0.25, 0.5 and 1.0 ng) did not affect the pain threshold on the hot-plate test or the writhing times in conscious mice. In contrast, AMPA (0.25, 0.5 and 1.0 ng intrathecally) significantly and dose-dependently decreased the pain threshold on the hot-plate test and increased the writhing times in mice treated with emulsified anaesthetics. 4. These results suggest that spinal AMPA receptors may be important targets for the analgesic effects of emulsified enflurane, isoflurane and sevoflurane.

Effects of the CRF1 receptor antagonist SSR125543 on energy balance and food deprivation-induced neuronal activation in obese Zucker rats.

The corticotropin-releasing factor (CRF) system is involved in numerous physiological and behavioral actions, including the regulation of energy balance. We examined the effects of the CRF(1) receptor antagonist, SSR125543, on energy balance and food deprivation-induced neuronal activation in obese rats. Lean (Fa/?) and obese (fa/fa) Zucker rats were treated orally with SSR125543 at a daily dose of 30 mg/kg for 21 days. Rats were killed either fed ad libitum or food deprived for 6 h in order to induce a mild stress response in obese rats. SSR125543 reduced plasma corticosterone levels in lean rats, prevented corticosterone response to fasting in obese rats, and increased CRF mRNA levels in the paraventricular hypothalamic nucleus (PVN) of both lean and obese rats, further confirming that the antagonist partially blocked CRF(1) receptors. SSR125543 increased protein gain in obese rats. Whole carcass analyses showed reduced energy and fat gains in lean rats. Consistent with reduced fat gain, circulating triglyceride and leptin levels were reduced in SSR125543-treated lean rats. In obese rats, circulating glucose levels and the homeostasis model assessment of insulin resistance index of insulin resistance were reduced by SSR125543 treatment. CRF(1) receptor blockade increased uncoupling protein-1 mRNA levels in interscapular brown adipose tissue of obese rats. The antagonist partly blocked the fasting-induced changes in c-fos mRNA levels in the PVN and arcuate nucleus of obese rats. Overall, these results suggest that although SSR125543 had relatively mild effects on energy balance, CRF(1) receptor blockade attenuated several metabolic effects of short-term fasting and improved plasma variables related to the metabolic syndrome and diabetes.

[Anaesthetic-induced myocardial preconditioning: fundamental basis and clinical implications]. / Préconditionnement myocardique induit par les agents anesthésiques halogénés: bases fondamentales et implications cliniques.

OBJECTIVE: Volatile halogenated anaesthetics offer a myocardial protection when they are administrated before a myocardial ischaemia. Cellular mechanisms involved in anaesthetic preconditioning are now better understood. The objectives of this review are to understand the anaesthetic-induced preconditioning underlying mechanisms and to know the clinical implications. DATA SOURCES: References were obtained from PubMed data bank (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi) using the following keywords: volatile anaesthetic, isoflurane, halothane, sevoflurane, desflurane, preconditioning, protection, myocardium. DATA SYNTHESIS: Ischaemic preconditioning (PC) is a myocardial endogenous protection against ischaemia. It has been described as one or several short ischaemia before a sustained ischemia. These short ischaemia trigger a protective signal against this longer ischaemia. An ischemic organ is able to precondition a remote organ. It is possible to replace the short ischaemia by a preadministration of halogenated volatile anaesthetic with the same protective effect, this is called anaesthetic PC (APC). APC and ischaemic PC share similar underlying biochemical mechanisms including protein kinase C, tyrosine kinase activation and mitochondrial and sarcolemnal K(ATP) channels opening. All halogenated anaesthetics can produce an anaesthetic PC effect. Myocardial protection during reperfusion, after the long ischaemia, has been shown by successive short ischaemia or volatile anaesthetic administration, this is called postconditioning. Ischaemic PC has been described in humans in 1993. Clinical studies in human cardiac surgery have shown the possibility of anaesthetic PC with volatile anaesthetics. These studies have shown a decrease of postoperative troponin in patient receiving halogenated anaesthetics.

Antidepressant-like effects of CRF1 receptor antagonist SSR125543 in an animal model of depression.

Much interest has been expressed in the antidepressant potential of nonpeptide, orally active corticotropin-releasing factor (CRF) receptor antagonists in recent years. Therefore, the present investigation examined the antidepressant-like effects of the novel CRF(1) receptor antagonist SSR125543 on the exaggerated swim test immobility in the Flinders Sensitive Line rat, a genetic animal model of depression. Chronic treatment with SSR125543 (3, 10, 20, 30 mg/kg, i.p.) for 14 days significantly increased swimming in the Flinders Sensitive Line rats. The reference serotonin reuptake inhibitor fluoxetine (5 mg/kg, i.p.) and the tricyclic antidepressant desipramine (5 mg/kg, i.p.) also significantly increased swimming, as expected. The higher doses of SSR125543 (20 and 30 mg/kg) also significantly increased the abnormally low level of social interaction behavior in the Flinders Sensitive Line rats. Together, these findings indicate that the CRF(1) receptor antagonist SSR125543 has both antidepressant- and anxiolytic-like effects in the Flinders Sensitive Line rats.

Cryoanalgesia with dichlorotetrafluoroethane lessens the pain of botulinum toxin injections for the treatment of palmar hyperhidrosis.

BACKGROUND: Hyperhidrosis is a troublesome problem that can be embarrassing in both social and professional situations. Botulinum toxin injections have proven efficacious in the treatment of hyperhidrosis. However, when treating palmar hyperhidrosis, pain at the injection site limits this therapy. We describe a method of cryoanalgesia using dichlorotetrafluoroethane to lessen the pain of botulinum toxin injections during the treatment of palmar hyperhidrosis. OBJECTIVE: To show the successful use of dichlorotetrafluoroethane or Frigiderm in the treatment of palmar hyperhidrosis. METHODS: This is a case report of a patient with a 20-year history of palmar hyperhidrosis who had previously tried several unsuccessful techniques to control pain during botulinum toxin injections to his palms. The left hand of the patient was pretreated with a spray of Frigiderm for 5 seconds before each of the botulinum injections. Two to 3 seconds of dichlorotetrafluoroethane at a distance of 2 to 4 inches were sprayed before each palmar injection. There was 1 to 2 seconds of frosting on the skin before the botulinum toxin was administered. After the botulinum toxin injection was administered, the patient was subjectively asked about pain during injection. RESULTS: The patient subjectively reported a 75% decrease in the intensity of pain with the Frigiderm application, which he said made the injections much more tolerable. No epidermal changes were noted at the time of treatment or at the telephone follow-up visit. The patient presented for follow-up 3 months later. He stated that the sweating had minimally returned but that he had not yet returned to baseline. CONCLUSION: The use of botulinum toxin for the treatment of palmar hyperhidrosis is often limited because of the pain of multiple injections. In this case report, we describe the successful use of cryoanalgesia with dichlorotetrafluoroethane or Frigiderm to lessen the pain of botulinum toxin injections during the treatment of palmar hyperhidrosis.

Lysophosphatidic acid acyltransferase-beta: a novel target for induction of tumour cell apoptosis.

Phosphatidic acid (PA) is a component of cellular membranes that is also a mediator of certain cell signalling functions associated with oncogenesis. These include ras/raf/Erk and Akt/mTor [1-3]. The authors have investigated whether it would be possible to interrupt these known oncogenic pathways through the inhibition of lysophosphatidic acid acyltransferase (LPAAT), an enzyme that catalyses the biosynthesis of PA. The expression and activity of the LPAAT-beta isoform are elevated in human tumours, and the respective gene displays transforming capacity when overexpressed in vitro. Inhibition by either genetic means or by isoform-specific small molecules results in a block to cell signalling pathways and apoptosis. Furthermore, the small-molecule inhibitors of LPAAT-beta are not cytotoxic to a number of normal cell types, including primary bone marrow progenitors, indicating a differential dependence of tumour cells on LPAAT-beta function. These discoveries indicate that LPAAT-beta represents a potential novel cancer therapy target.

Hepatoprotection by 3-bromo-6-(4-chlorophenyl)-4-methylthio-2H-pyran-2-one against experimentally induced liver injury in rats.

Hepatoprotective activity of 3-bromo-6-(4-chlorophenyl)-4-methylthio-2H-pyran-2-one, an isostere of dimethyl ricinine, was evaluated in adult male albino rats intoxicated with carbon tetrachloride, paracetamol or thioacetamide. The test compound showed significant hepatoprotection at 6.0 mg kg(-1) body mass daily dose, given to the rats for seven consecutive days. The carbon tetrachloride, paracetamol and thioacetamide were given, respectively, on days 3, 5, and 7, on day 6 and on day 6 post treatment with the test compound. The protective effect was evident in a battery of serum and liver biochemical parameters related to hepatotoxicity.

Relationships between reduction properties and cancer cell growth inhibitory activities of cis-dichloro- and cis-diiodo-Pt(IV)-ethylenediamines.

The chemical reactivities and cancer cell growth inhibitory activities of a new series of cis-diiodo-Pt(IV)-ethylenediamines were compared and contrasted with their cis-dichloro-Pt(IV)-counterparts, cis-Diiodo-Pt(IV)-ethylenediamines bearing various axial ligands (i.e., OH, OAc, OCOCF3, OSO2CH3) were prepared by oxidizing [PtI2(en)] with 30% H2O2 to yield trans,cis-[PtOH2I2(en)], which was then reacted with either Ac2O, (CF3CO)2O, or (SO2CH3)2O in CH2Cl2. The cis-diiodo-Pt(IV) complexes were readily reduced by biological thiols such as L-cysteine, glutathione (GSH), and bovine serum albumin (BSA) at pH 6.9 and 37 degrees C; the kinetics of reduction were second-order with respect to thiol concentration. In contrast, the cis-dichloro analogues were stable in the presence of GSH. The reduction potentials estimated by means of cyclovoltammetry for the Pt(IV) complexes are useful for obtaining a ranking order of reactivity towards biological thiols; however, the reduction potentials alone cannot be used to predict whether a Pt(IV) complex will be reduced by GSH at biologically relevant concentrations. GSH greatly facilitated the platination of calf thymus DNA by the diiodo-Pt(IV) complexes, which was > 90% complete after 24 h at 37 degrees C when the ratio of GSH to Pt(IV) was 2:1. DNA-platination by trans,cis-[Pt(OH)2I2(en)] and trans,cis-[Pt(OAc)2I2(en)] were dependent on the presence of GSH while trans,cis-[Pt(OSO2CH3)2I2(en)] showed 23% DNA platination after 24 h in the absence of GSH. In contrast, the dichloro analogues trans,cis-[Pt(OH)2Cl2(en)] and trans,cis-[Pt(OAc)2Cl2(en)] failed to react with DNA in the presence of either low (0.015 mM) to high (3.0 mM) concentrations of GSH. Cell culture experiments with four human cancer cell lines showed that the maximal growth inhibitory activity of the cis-diiodo-Pt(IV)-ethylenediamines was reached within a 24 h exposure to platinum complex, while the dichloro-Pt(IV) analogues required a much longer drug-exposure time (i.e., 96 h) to reach maximal activity.

[The technology for manufacturing antiparasitic preparations. 8. The preparation rilanid and its use for treating fascioliasis and intestinal nematodiases]. / Tekhnologiia proizvodstva protivoparazitarnykh preparatov. 8. Preparat rilanid i ego primenenie dlia lecheniia fastsioleza i kishechnykh nematodozov.

A procedure has been developed to prepare the anthelminthic Rilanide as a fine-dispersed formulation. The therapeutical dose of the agent in fascioliasis and intestinal nematodiasis is 60 mg/kg (for sheep), if given alone, and 100 mg/kg, if added to feed.

Empirical and rational approaches for development of inhibitors of the human immunodeficiency virus--HIV-1.

The human immunodeficiency virus, HIV-1, is generally accepted to be responsible for AIDS. It is imperative that all approaches, empirical and rational, be taken for development of a drug for therapy of this disease. These approaches are discussed, with emphasis on the direction being pursued in our laboratory. Empirically, we found 3'-deoxy-2',3'-didehydrothymidine, a compound first synthesized for potential anticancer activity by J. Horwitz in the 1960s, to be a potent inhibitor of HIV-1. It is now in Phase II/III clinical trials. We have also synthesized several 2,5'-anhydro pyrimidine nucleoside analogs, which have interesting chemical and biological properties. We have evaluated a natural product, gossypol and synthesized various derivatives for anti-HIV-1 activity, but none were appreciably more inhibitory than the parent compound. More recently, we have taken the rational approach and synthesized a boron-modified tetrapeptide, Ac-Thr-Leu-Asn-boro-Phe, which corresponds to the COOH-terminal of the Phe-Pro scissle bond of the gag/pol gene polyprotein product. Potent inhibition of the HIV-1 encoded protease was observed. These approaches and findings will be discussed.