Medicinal Chemistry - Volume 5, Issue 1, 2009

Recently, we have demonstrated that substitution of 1,2,3,4 tetrahyidroisoquinoline-3- carboxylic acid (Tic) in place of Gly2 in dynorphin A-(1-13)-NH2 (DYN) analogue (A) decreased the affinity to the kappa, delta, and mu receptors, and kappa selectivity. The doubly substituted analogue [2',6apos;-dimethyl-L-tyrosine (Dmt1)-Tic2]DYN (B) exhibited high delta-affinity (Ki=0.39 nM) while mu- and kappa-affinities were only an order of magnitude less (4-5 nM). Bioactivity of [Tic2]DYN peptide (A) on guinea-pig ileum and rabbit jejunum revealed potent delta- and kappa-antagonism thus indicating that the conversion from a kappa-agonist to antagonist occurred with the inclusion of Tic into DYN analogues, similar to the appearance of antagonist properties with delta-opioid agonists containing a Tic2 residue. The present study was undertaken to compare the k- and δ-opioid antagonistic activity of two [Tic2] DYN peptides (A and B) with naloxone a well known non selective opioid receptor antagonist. This comparison was performed by using the model of opioid withdrawal in vitro. Following a 4 min in vitro exposure to U50-488 H (10-8 M), a selective k opioid receptor agonist, the guinea-pig isolated ileum exhibited a strong contracture after the addition of naloxone (10-5 M). Also, following a 4 min in vitro exposure to deltorphin II (10-8 M), a selective δ opioid receptor agonist, the rabbit jejunum exhibited a strong contracture after the addition of naloxone (10-5 M). Results are expressed as percent of Ach contractions. In our study, we showed that in guinea pig ileum the peptide A (k opioid receptor antagonist) was able to induce a strong contracture at a concentration of 10-9 M when injected 4 min after U50-488H (10-8 M). Also, in rabbit jejunum the peptide B (δ opioid receptor antagonist) was able to induce a strong contracture at a concentration of 10-10 M when injected 4 min after deltorphin II (10-8 M). The results of our experiments indicate that both peptide A (k receptor opiod antagonist) and peptide B (δ receptor opioid antagonist) showed an antagonistic activity higher than naloxone.

An investigation of the relationships between physicochemical features of ten antipsychotic drugs and previously reported influence of these drugs on neutrophil maturity was made. A quantitative structure-activity relations (QSAR) approach was adopted, in which several numerical parameters describing physicochemical characteristics of the antipsychotics were estimated. Possible connections between these parameters and neutrophil maturity were explored. Influence of drug physicochemistry on the incidence of agranulocytosis and neutropenia reported in the literature was documented. Overall it was found that drugs with the greatest tendency to induce neutrophil immaturity (chlorpromazine, clozapine and olanzapine) also showed the greatest tendency to cause agranulocytosis and neutropenia. Moreover marked induction of neutrophil immaturity occurred with compounds of moderately amphipathic character, whose amphipathic indices (AI) fell in the range 3-5; higher or lower AI values correlated with less immaturity. Consideration of the QSAR findings suggest that toxicity could be associated with selective uptake into the most fluid intracellular membranes, those of the endoplasmic reticulum and the outer mitochondrial membrane. The AI hazard zone (AI = 3-5) does constitute a predictive tool to assess risk of agranulocytosis and neutropenia arising from antipsychotic and other psychoactive drugs — and not only risk arising from medication but also from experimental or even proposed compounds.

An α1a- and α1d-adrenergic receptor (AR) selective antagonist may be a more efficacious treatment for BPH/LUTS patients and may have fewer side effects than the existing pharmaceuticals. A facile synthesis for a series of (2-cyclopropoxyphenyl)piperidine derivatives has been developed, in which aryl vinyl ether formation and subsequent cyclopropyl formation provide efficient access to key intermediate N-Boc-4-(2-cyclopropoxyphenyl)piperidine. The synthesized (2-cyclopropoxyphenyl)piperidine derivatives display high affinity and selectivity for α1a-AR and α1d-AR compared to α1b-AR and D2 receptor, Ki values for α1a-AR are 0.91 nM to 79.0 nM and α1d-AR are 2.0 nM to 57 nM; Ki values for α1b-AR are 107 nM to 839.8 nM and D2 receptor are 66.2 nM to 187.1 nM. The selectivity ratios of Ki(α1b)/Ki(α1a) are 11 to 155 fold, Ki(α1b)/Ki(α1d) are 6 to 171 fold, Ki(D2)/Ki(α1a) are 2 to 158 fold, and Ki(D2)/Ki(α1d) are 1.2 to 89 fold. Compound 17a shows improved stability in human liver microsome test (t1/2 = 18 minutes).

The causes of increased rates of myocardial infarctions and strokes by application of non-steroidal antiinflammatory agents (NSAIDs) are unclear. Here we present a biochemical model that the long-term vascular effects of NSAIDs can be consequences of their antiproliferative cellular mechanism. The analysis of the model suggests that the intramitochondrial uncoupling of oxidative phosphorylation induced by NSAIDs increases, through a reduced activity of ATP-dependent ionic pumps, the intra-cellular calcium x phosphate product with a consecutively increased formation and export of various calcium phosphate compounds. The latter cause, by chemical replication mechanisms of arterial hydroxyapatite deposits, a metatstatic calcifying vascular process. This sclerogenic vascular mineralization corresponds to an early arteriosclerotic development resembling the Monckeberg's media calcification. The mechanism shows direct analogies to the accelerated and metastatic calcification of coronary arteries seen in chronic kidney disease and dialysis. This appears an extra-cellular time-lapse version of the protracted cell model. The induction of this degenerative mechanism may explain the increased number of adverse cardiovascular, renovascular and cerebrovascular effects of NSAIDs as they are observed in long-term therapies.

Chronic viral hepatitis B and C are diseases worldwide. At present, the number of effective and safe drugs for treatment of HBV and HCV is still limited. In order to develop novel anti-viral hepatitis drug, a number of analogues of the active component schizandrin C from Fructus Schiznadrae, a Chinese herb used in the therapy of viral hepatitis, were synthesized. Bicyclol, one of the analogues, was demonstrated to have actions of anti-hepatitis virus replication in duck hepatitis model and 2.2.15 cell line, anti-experimental liver injury induced by hepatotoxins such as CCl4, acetaminophen and ConA, and anti-liver fibrosis in rats and mice. The active mechanism of bicyclol might be anti-apoptosis of hepatocytes through multiple signaling pathways mainly inducing the expressions of hepatic heat shock proteins (HSP27 and HSP70), molecular chaperons. Clinical trial was performed by double blind, randomized and positive control or placebo method in multi-medical centers in China. Patients received bicyclol 25mg thrice daily for six months, then stopped treatment and followed up for 3 months. Oral administration of bicyclol normalized the elevated serum transaminases (ALT, AST) by approximately 50% in chronic viral hepatitis B and C, and also showed certain level of inhibiting HBV and HCV replication. No noticeable adverse reaction has been observed. In combination therapy of bicyclol with interferon alpha, lamivudine and adefovir dipivoxil in HBV or HCV, bicyclol may potentiate the anti-viral efficacy and reduce YMDD mutant and side effects. In 2004 China FDA issued license to manufacture bicyclol. Since then bicyclol has been widely used to treat chronic HBV and HCV in China.

We investigated the effect of magnetic field stimulation (MS) on oxidative damage and skeletal muscle injury prompted by mepivacaine injection in the anterior tibial muscle of Wistar rats. The effects of mepivacaine and MS on oxidative stress were evaluated by lipid peroxidation, GSH levels and catalase activity. Muscle regeneration was analyzed by haematoxylin-eosin stained, NADH-TR histochemical reaction, desmin immunostaining as well as by morphometric parameters such as fibers density and fiber area were evaluated. Our data revealed that mepivacaine induced oxidative stress, that MS prevents the harmful effects induced by mepivacaine and that it facilitates the regeneration process of skeletal muscle. In conclusion, the results show the ability of MS to modify skeletal muscle response to mepivacaine.

Among neutral endopeptidase (NEP) inhibitors, mercaptoacyldipeptides implicated in cardiovascular diseases, are of great interest. Two groups, Coric et al. and Oefner et al. described two different binding preferences for mercaptoacyldipeptides at the active site of NEP. By focusing on both, 3D-QSAR studies were performed on mercaptoacyldipeptides, based on conformational alignment obtained by GOLD 3.2, using CoMFA and CoMSIA techniques. Statistically significant 3D-QSAR models were obtained with q2 of 0.580 and 0.559, and r2 of 0.996 and 0.991, respectively. Both the models were validated by an external test set of nine compounds giving highly predictive r2 (pred) of 0.929 and 0.928, respectively. The study will facilitate the rational design of more potent mercaptoacyldipeptides for the treatment of cardiovascular diseases.

Three-dimensional quantitative structure-activity relationships (3D-QSAR) were performed for a series of analgesic cyclic imides using the CoMFA and CoMSIA methods. Significant correlation coefficients (CoMFA, r2 = 0.95 and q2 = 0.72; CoMSIA, r2 = 0.96 and q2 = 0.76) were obtained, and the generated models were externally validated using test sets. The final QSAR models as well as the information gathered from 3D contour maps should be useful for the design of novel cyclic imides having improved analgesic activity.

Benzodiazepines are among the most frequently prescribed drugs and are often related with dry mouth. Pilocarpine is a cholinergic agonist that increases salivary flow rate and has been used to treat xerostomia. This study aimed to measure salivary flow rate of rats under chronic treatment with benzodiazepine (Diazepam®), to analyze by histomorphometry the effects of the drug in the parotids glands and to verify the effect of the pilocarpine in glandular parenchyma and in the salivary flow rate. Seventy-two male Wistar rats were allocated to four groups. Control groups received saline during 60 days (C60) and pilocarpine (Pilo) during 60 days. Experimental groups were dealt with Diazepam® associated with saline (DS), and Diazepam® associated with pilocarpine (DP) during 60 days. The stimulated salivary flow rate was obtained by using the gravimetric method. After the animals were killed, parotid glands were removed and mass and size were determined. The specimens were processed and stereological analysis revealed cell volume. Mean values of size and salivary flow rate varied from 9.007 mm and 0.015 mg/min in DS to 7.854 mm and 0.029 mg/min in DP, respectively. ANOVA showed statistically significant differences between groups for size (p=0.0028) and salivary flow rate (p=0.0003). Psychotropic drugs caused hyposalivation in rats and acinar hypertrophy in their parotid glands. Pilocarpine, a cholinergic agonist with topical appliance, showed significant secretagogue action in the treatment of hyposalivation induced by Diazepam® chronic use.

The activities of a series of benzothiazole derivatives, some Candida albicans N-myristoyltransferase (Nmt) inhibitors, were modeled through MIA-QSAR (multivariate image analysis applied to quantitative structure-activity relationship) by using two different regression methods: N-PLS, applied to the three-way array, and PLS, applied to the unfolded array. Both models demonstrated excellent predictive ability, with results comparable to those obtained through 3D approaches. In order to compare the results obtained through MIA descriptors with the predictions of a classical 2D QSAR, some representative physicochemical descriptors were calculated and regressed against the experimental pIC50 values through multiple linear regression, demonstrating that MIA-QSAR was superior for this series of compounds.

There has been an increasing interest in compounds that modulate potassium ion channels (K+-channels) since they can be developed as important therapeutic agents against ischemic heart diseases. Of the diverse family of K+- channels, the voltage-gated potassium channel Kv1.3 constitutes an attractive target for the selective suppression of effector memory T cells in autoimmune diseases. For the development of antiarrythmic drugs, the blockade of the rapidly activating delayed rectifier (IKr) and slowly activating delayed rectifier (IKs) potassium currents has been specifically studied. Since the discovery of IKs-channel, its blockers have been particularly more studied. In this communication, we present QSAR studies on a few series of Kv1.3-channel blockers and a series of IKs-channel blockers in order to provide some guidelines to the drug development.

Peptide conjugates derived from the SV 40 T antigen nuclear localisation sequence (NLS) have been successfully used to translocate both fluorescein isothiocyanate (FITC) and Gadolinium (Gd)-1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid (DOTA) into the cytoplasm and nucleus of glioma cells. However, uptake occurred only in up to 35% of cells. To improve cellular uptake, we designed three novel FITC-labelled Gd-DOTA conjugates. In the first conjugate, the commonly used Gd-DOTA-complex was coupled to the nuclear localization sequence (NLS) of the Simian Virus (SV) 40 T antigen alone as a control. In the second conjugate, the Gd-DOTA-coupled SV 40 T antigen NLS was elongated by the HIV-1 tat peptide (HIV-NLS). A third conjugate, in which the Gd-DOTA-complex was coupled to the SV 40 T antigen NLS elongated by a peptide containing seven arginines and six aminohexanoic acids (Ahx6R7) was also synthesized (AHX-NLS). By means of confocal laser scanning microscopy, fluorescence activated cell sorting, magnetic resonance imaging (MRI) and viability tests we were able to demonstrate that the first conjugate containing only the NLS of the SV 40 T antigen stained the nuclei of no more than 10-12% of U373 and LN18 glioma cells, resulting in low signal intensity in MRI. The stained cells remained viable. After incubation with conjugates HIV-NLS and AHX-NLS the nuclei of up to 73% of U373 and LN18 glioma cells were stained. This was associated with high signal intensity in MRI and cell death. As previously shown, the gadolinium ion reduces cellular uptake of DOTA conjugates. To confirm this, the conjugates were produced with or without gadolinium. The gadolinium-free DOTA conjugates showed a higher cellular uptake rate and an increased cytotoxic potential.