First-in-class, dual-action, 3,5-disubstituted indole derivatives having human nitric oxide synthase (nNOS) and norepinephrine reuptake inhibitory (NERI) activity for the treatment of neuropathic pain

In silico studies of bioactive compounds from selected African plants with inhibitory activity against nitric oxide synthase and arginase implicated in asthma

Background

It is a known fact that arginine is a common substrate for arginase and nitric oxide synthase (NOS). However, an imbalance between both enzymes could lead to a change in airway responses. Reports suggest that increased activities of both enzymes could lead to airway hyper-responsiveness. Thus, the requests for NOS inhibitors that can also inhibit arginase as the elevated activities of both enzymes have detrimental consequence on airways in asthma. Bioactive compounds from Azadirachta indica, Crinum glaucum, and Mangifera indica are documented for anti-inflammatory, immunomodulatory, anti-histaminic, smooth-muscle relaxants, and anti-allergic potentials. However, the mechanisms of action of these bioactive compounds in conferring the aforementioned protections are not well characterized. The objective of this present study is to assess in silico inhibitory potentials of these bioactive compounds against NOS and arginase via binding at their active sites. The crystal structures of NOS and arginase were retrieved from the protein database, while the bioactive compounds were retrieved from PubChem. Drug-likeness of the selected bioactive compounds was assessed using DruLiTo software. The successful compounds were docked with active sites of enzymes using AutoDock Vina docking software, and the docked complexes were analyzed using LigPlot and protein-ligand profiler web server.

Results

The findings of the study revealed that the bioactive compounds from A. indica, C. glaucum, and M. indica were able to interact with the active sites of NOS and arginase with the exception of gallic acid (from M. indica) and nimbandiol (from A. indica); these compounds showed differential binding energies (kcal/mol) and a number of them had higher binding energies than l-arginine when docked with NOS.

Conclusion

Conclusively, the in silico analysis proposes that these compounds could prove to be probable anti-asthmatic drugs.

Genipin Derivatives Protect RGC-5 from Sodium Nitroprusside-Induced Nitrosative Stress

CHR20 and CHR21 are a pair of stable diastereoisomers derived from genipin. These stereoisomers are activators of neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS). In the rat retinal ganglion (RGC-5) cell model these compounds are non-toxic. Treatment of RGC-5 with 750 μM of sodium nitroprusside (SNP) produces nitrosative stress. Both genipin derivatives, however, protect these cells against SNP-induced apoptic cell death, although CHR21 is significantly more potent than CHR20 in this regard. With Western blotting we showed that the observed neuroprotection is primarily due to the activation of protein kinase B (Akt)/eNOS and extracellular signal-regulated kinase (ERK1/2) signaling pathways. Therefore, LY294002 (a phosphatidylinositol 3-kinase (PI3K) inhibitor) or PD98059 (a MAPK-activating enzyme inhibitor) abrogated the protective effects of CHR20 and CHR21. Altogether, our results show that in our experimental setup neuroprotection by the diasteromeric pair is mediated through the PI3K/Akt/eNOS and ERK1/2 signaling pathways. Further studies are needed to establish the potential of these compounds to prevent ntric oxide (NO)-induced toxicity commonly seen in many neurodegenerative diseases.

Anti-allodynic Efficacy of NMDA Antagonist Peptide and Noradrenaline Alone and in Combination in Rodent Neuropathic Pain Model

Background

The present experiment was conducted to identify the cooperative effect of serine histogranin (SHG) and noradrenaline in alleviating peripheral neuropathic pain.

Methods

Chronic constriction injury of the right sciatic nerve was used to induce chronic neuropathic pain. For drug delivery, a PE10 tube was inserted into the subarachnoid space. Acetone drops and a 44℃ water bath were used to evaluate the cold and heat allodynia, respectively. Placing and grasping reflexes were used to assess the locomotor system.

Results

SHG at 0.5 and 1 µg significantly (P < 0.05) decreased the thermal allodynia. The cold allodynia was also significantly reduced by intrathecal injections of 0.5 (P < 0.05) and 1 µg (P < 0.001) of SHG. 1 µg of noradrenaline, but not 0.5 µg, significantly alleviated the cold (P < 0.01) and thermal (P < 0.05) allodynia. The ameliorating effect of noradrenaline or SHG disappeared when the two compounds were administrated in equal concentrations. A significant difference (P < 0.01 in the acetone and P < 0.05 in the heat) was observed in the groups under equal doses of the two compounds, with a lower effectiveness of the combination therapy.

Conclusions

Our findings suggest that the simultaneous administrations of noradrenaline and SHG do not result in synergistic analgesia, and combination therapy may not be a good approach to the treatment of chronic neuropathic pain syndrome.

Nitric oxide synthase inhibitors: a review of patents from 2011 to the present

INTRODUCTION

Nitric oxide synthases (NOSs) are a family of enzymes that play an essential role in synthesizing nitric oxide (NO) by oxidizing l-arginine. As previously reported, NO is a significant mediator in cellular signaling pathways. It serves as a crucial regulator in insulin secretion, vascular tone, peristalsis, angiogenesis, neural development and inflammation. Due to its important role, the inhibition of these vital enzymes provides, as tools, the opportunity to gain an insight into potential therapeutic applications targeting NOSs.

AREAS COVERED

This paper reviews the patent literature between 2011 and mid-2014 that specified inhibitors of NOS family members as the significant targets. Google and Baidu search engines were used to find relevant patents and clinical information using NOSs or NOS inhibitor as search terms.

EXPERT OPINION

Considerable recent progress has been made in the development of NOS inhibitors with pharmacodynamic and pharmacokinetic properties, and such development is likely to continue. The patented compounds attenuated mostly embodying evidence from in vitro and in vivo trials that demonstrate good potential for future clinical human trials and industrial applications. Furthermore, new techniques such as X-ray ligand crystallographic study and structure-activity relationship were popularly utilized, which give new insights for developing novel, safe, efficient and selective NOS inhibitors.

Development of nitric oxide synthase inhibitors for neurodegeneration and neuropathic pain

Nitric oxide (NO) is an important signaling molecule in the human body, playing a crucial role in cell and neuronal communication, regulation of blood pressure, and in immune activation. However, overproduction of NO by the neuronal isoform of nitric oxide synthase (nNOS) is one of the fundamental causes underlying neurodegenerative disorders and neuropathic pain. Therefore, developing small molecules for selective inhibition of nNOS over related isoforms (eNOS and iNOS) is therapeutically desirable. The aims of this review focus on the regulation and dysregulation of NO signaling, the role of NO in neurodegeneration and pain, the structure and mechanism of nNOS, and the use of this information to design selective inhibitors of this enzyme. Structure-based drug design, the bioavailability and pharmacokinetics of these inhibitors, and extensive target validation through animal studies are addressed.

The discovery of potentially selective human neuronal nitric oxide synthase (nNOS) Inhibitors: a combination of pharmacophore modelling, CoMFA, virtual screening and molecular docking studies

Neuronal nitric oxide synthase (nNOS) plays an important role in neurotransmission and smooth muscle relaxation. Selective inhibition of nNOS over its other isozymes is highly desirable for the treatment of neurodegenerative diseases to avoid undesirable effects. In this study, we present a workflow for the identification and prioritization of compounds as potentially selective human nNOS inhibitors. Three-dimensional pharmacophore models were constructed based on a set of known nNOS inhibitors. The pharmacophore models were evaluated by Pareto surface and CoMFA (Comparative Molecular Field Analysis) analyses. The best pharmacophore model, which included 7 pharmacophore features, was used as a search query in the SPECS database (SPECS^®, Delft, The Netherlands). The hit compounds were further filtered by scoring and docking. Ten hits were identified as potential selective nNOS inhibitors.

Recent advances toward improving the bioavailability of neuronal nitric oxide synthase inhibitors

Overproduction of nitric oxide by neuronal nitric oxide synthase (nNOS) has been highly correlated with numerous neurodegenerative diseases and stroke. Given its role in human diseases, nNOS is an important target for therapy that deserves further attention. During the last decade, a large number of organic scaffolds have been investigated to develop selective nNOS inhibitors, resulting in two principal classes of compounds, 2-aminopyridines and thiophene-2- carboximidamides. The former compounds were investigated in detail by our group, exhibiting great potency and excellent selectivity; however, they suffer from poor bioavailability, which hampers their therapeutic potential. Here we present a review of various strategies adopted by our group to improve the bioavailability of 2-aminopyridine derivatives and describe recent advances in thiophene-2-carboximidamide based nNOS-selective inhibitors, which exhibit promising pharmacological profiles.

Potent and selective double-headed thiophene-2-carboximidamide inhibitors of neuronal nitric oxide synthase for the treatment of melanoma

Selective inhibitors of neuronal nitric oxide synthase (nNOS) are regarded as valuable and powerful agents with therapeutic potential for the treatment of chronic neurodegenerative pathologies and human melanoma. Here, we describe a novel hybrid strategy that combines the pharmacokinetically promising thiophene-2-carboximidamide fragment and structural features of our previously reported potent and selective aminopyridine inhibitors. Two inhibitors, 13 and 14, show low nanomolar inhibitory potency (Ki = 5 nM for nNOS) and good isoform selectivities (nNOS over eNOS [440- and 540-fold, respectively] and over iNOS [260- and 340-fold, respectively]). The crystal structures of these nNOS-inhibitor complexes reveal a new hot spot that explains the selectivity of 14 and why converting the secondary to tertiary amine leads to enhanced selectivity. More importantly, these compounds are the first highly potent and selective nNOS inhibitory agents that exhibit excellent in vitro efficacy in melanoma cell lines.

Female reproductive tract pain: targets, challenges, and outcomes

Pain from the female reproductive tract (FRT) is a significant clinical problem for which there are few effective therapies. The complex neuroanatomy of pelvic organs not only makes diagnosis of pelvic pain disorders difficult but represents a challenge to development of targeted therapies. A number of potential therapeutic targets have been identified on sensory neurons supplying the FRT but our knowledge on the basic neurophysiology of these neurons is limited compared with other viscera. Until this is addressed we can only guess if the new experimental therapies proposed for somatic, gastrointestinal, or bladder pain will translate to the FRT. Once suitable therapeutic targets become clear, the next challenge is drug delivery. The FRT represents a promising system for topical drug delivery that could be tailored to act locally or systemically depending on formulation. Development of these therapies and their delivery systems will need to be done in concert with more robust in vivo and in vitro models of FRT pain.

Enantioselective inhibition of reverse transcriptase (RT) of HIV-1 by non-racemic indole-based trifluoropropanoates developed by asymmetric catalysis using recyclable organocatalysts

Herein, we report the development of efficient inhibitors of reverse transcriptase (RT) of HIV-1 based on indole-alkyl trifluoropyruvate derivatives by a TZM-bl cell assay. The inhibitory activities of the two enantiomers and the corresponding racemic mixture have been compared. TZM-bl cells exhibited strong enantioselective discrimination for the (R)-configuration, among these indole derivatives, the most active compound R-12, with a 5-NO2 substituent, gave the best result when tested in the TZM-bl cells on HIV virus type HIV-1IIIB, with an EC50 value of 0.019 μM, CC50 value of 210.697 μM and SI (selectivity index, CC50/EC50) value of 11,089, respectively. The cell test showed that, in most cases, the R-enantiomer was superior to the Rac-mixture, which was better than the corresponding S-enantiomer. The results indicated that the R-enantiomer is the most favorable configuration as an efficient HIV-1 inhibitor. Molecular modeling studies suggested a structural basis for the enantioselectivity of RT towards this class of molecules.