Muthusamy Ramesh

Development of animal model for vasculatic neuropathy: Induction by ischemic-reperfusion in the rat femoral artery

Ischemic-reperfusion (I/R) is common in various pathological conditions like diabetic complication, complex regional pain syndrome type II (CRPS II), necrotizing vascular occlusive disease and trauma. We have developed an animal model of ischemic-reperfusion injury induced nociceptive sensory neuropathy in rats. The model was validated after 2, 4 and 6h of ischemia followed by prolonged reperfusion. The sensory behavioral assessment revealed thermal and mechanical hyperalgesia in paw and in tail which expressed the peripheral and central neuropathic pain respectively. We observed a decrease in the serum IL-10 and nerve conduction velocity and increase in the serum nitrate, malondialdehyde (MDA) and TNF-alpha levels in the 4 and 6h I/R groups in biochemical and electrophysiological evaluations. Histopathological study had revealed the decrease in nerve fiber density in the moderate and severe I/R groups. We selected the moderate (4h) ischemic-reperfusion injury as beneficial model because of the good correlation with clinical status for the development of neuropathy in human associated with severe pain disorders. This model can be used to explore pathophysiological mechanisms implied in the genesis of neuropathic pain and also to evaluate the new analgesic agents, peripheral neuro-vasoactive substances and neuroprotective drugs.

Recent advancements in the development of anti-tuberculosis drugs

Modern chemotherapy has significantly improved patient outcomes against drug-sensitive tuberculosis. However, the rapid emergence of drug-resistant tuberculosis, together with the bacteriums ability to persist and remain latent present a major public health challenge. To overcome this problem, research into novel anti-tuberculosis targets and drug candidates is thus of paramount importance. This review article provides an overview of tuberculosis highlighting the recent advances and tools that are employed in the field of anti-tuberculosis drug discovery. The predominant focus is on anti-tuberculosis agents that are currently in the pipeline, i.e. clinical trials.

Drug Therapy of Neuropathic Pain: Current Developments and Future Perspectives

Understanding mechanism of neuropathic pain is too complex and involves both peripheral and central pathophysiological phenomenon. Accordingly the treatment of neuropathic pain is also very complex and is unsatisfactory. The present review attempts to discuss the currently employed pharmacological agents for the management of neuropathic pain including anti-depressants, anti-convulsants, NMDA receptor antagonists, topical & local anesthetics, and upload analgesics. However, the existing pharmacotherapy has marginal efficacy and significant side effects. The review also gives an insight into various pharmacological agents with potential neuropathic pain attenuating properties in experimental models that include NSAIDs, corticosteroids, ion channel blockers (Ca(2+), Na(+), K(+), and TRP channel); ion exchange modulators (NCE and NHE); ion/molecule transport modulators (NKCC-1 and glycine); receptor modulators (kinin, histamine, 5-HT1A, dopamine, alpha & beta adrenergic, purinergic, excitatory amino acid, sigma, ORL1, endothelin, melanocortin, ephrin and PAR); enzyme inhibitors (cytosolic kinase, metalloproteinase, protease, vasopeptidase, D-amino acid oxidase, fatty acid amide hydrolase, aldose reductase and sorbitol dehydrogenase); other ligands (AGE, RAGEs, neuropeptides, neurotrophic factor, complement cascade, cytokine, glial cell & gap junction, nitrous oxide, growth factor, cell adhesion molecule and neuronal sprouting molecule). Moreover, some advanced therapeutic approaches such as neuronal cell transplantation, stem cell therapy, anti-sense oligonucleotide and recombinant therapy have also been dicussed.

Ameliorative potential of montelukast on ischemia–reperfusion injury induced vasculitic neuropathic pain in rat

AIMS Ischemia-reperfusion (I/R) event in vascular and nervous system has been documented to rising ischemic and vasculitic neuropathic pain, clinically resembles the complex regional pain syndrome (CRPS). The present study evaluated the effect of montelukast, a cysteinyl leukotriene receptor (Cys-LTC(4) and Cys-LTD(4)) antagonist on ischemia -reperfusion (I/R) induced vasculitic neuropathic pain in rats. MAIN METHODS Behavioral parameters were assessed at different time intervals (i.e. 0, 1, 7, 14 and 21st day) and biochemical analysis in sciatic nerve tissue samples were also performed along with histopathological studies. KEY FINDINGS Behavioral pain assessment has shown increase in paw and tail withdrawal threshold in montelukast treated groups against thermal and mechanical stimuli as compared to I/R control group. We observed a decrease in the total calcium, thiobarbituric acid reactive substance (TBARS) and myeloperoxidase (MPO) activity levels, whereas there is rise in reduced glutathione level in montelukast treated groups as compared to I/R control group. However, significant behavioral and biochemical results were observed only in medium and high dose of treated groups which were comparable to normal control group. Moreover, histopathological study has revealed the reduction of I/R induced neuronal edema and axonal degeneration due to montelukast. SIGNIFICANCE Montelukast has ameliorated I/R induced vasculitic neuropathic pain, these effects may be due to inhibition of lipid peroxidation, reduction of oxidative stress, release of inflammatory mediators and neuroprotective actions. Hence, it could be used as a novel therapeutic agent for the management of vasculitic inflammation related neuropathic pain.

Per-residue energy decomposition pharmacophore model to enhance virtual screening in drug discovery: a study for identification of reverse transcriptase inhibitors as potential anti-HIV agents

A novel virtual screening approach is implemented herein, which is a further improvement of our previously published “target-bound pharmacophore modeling approach”. The generated pharmacophore library is based only on highly contributing amino acid residues, instead of arbitrary pharmacophores, which are most commonly used in the conventional approaches in literature. Highly contributing amino acid residues were distinguished based on free binding energy contributions obtained from calculation from molecular dynamic (MD) simulations. To the best of our knowledge; this is the first attempt in the literature using such an approach; previous approaches have relied on the docking score to generate energy-based pharmacophore models. However, docking scores are reportedly unreliable. Thus, we present a model for a per-residue energy decomposition, constructed from MD simulation ensembles generating a more trustworthy pharmacophore model, which can be applied in drug discovery workflow. This work is aimed at introducing a more rational approach to the field of drug design, rather than comparing the validity of this approach against those previously reported. We recommend additional computational and experimental work to further validate this approach. This approach was used to screen for potential reverse transcriptase inhibitors using the pharmacophoric features of compound GSK952. The complex was subjected to docking, thereafter, MD simulation confirmed the stability of the system. Experimentally determined inhibitors with known HIV-reverse transcriptase inhibitory activity were used to validate the protocol. Two potential hits (ZINC46849657 and ZINC54359621) showed a significant potential with regard to free binding energy. Reported results obtained from this work confirm that this new approach is favorable in the future of the drug design industry.

Adenosine Monophosphate-Activated Protein Kinase (AMPK) as a Diverse Therapeutic Target: A Computational Perspective.

AbstractAdenosine monophosphate-activated protein kinase (AMPK) is viewed as a privileged therapeutic target for several diseases such as cancer, diabetes, inflammation, obesity, etc. In addition, AMPK has entered the limelight of current drug discovery with its evolution as a key metabolic regulator. AMPK also plays a key role in the maintenance of cellular energy homeostasis. Structurally, AMPK is a heterotrimeric protein, which consists of three protein subunits (α, β, and γ). The crystal structure of AMPK was solved, and several computational studies including homology modeling, molecular docking, molecular dynamics, and QSAR have been reported in order to explore the structure and function of this diverse therapeutic target. In this review, we present a comprehensive up-to-date overview on the computational and molecular modeling approaches that have been carried out on AMPK in order to understand its structure, function, dynamics, and its drug binding landscape. Information provided in this review would be of great interest to a wide pool of researchers involved in the design of new molecules against various diseases where AMPK plays a predominant role. Graphical Abstractᅟ

γ-Cyclodextrin capped silver nanoparticles for molecular recognition and enhancement of antibacterial activity of chloramphenicol.

Computational studies were conducted to identify the favourable formation of the inclusion complex of chloramphenicol with cyclodextrins. The results of molecular docking and molecular dynamics predicted the strongest interaction of chloramphenicol with γ-cyclodextrin. Further, the inclusion complex of chloramphenicol with γ-cyclodextrin was experimentally prepared and a phenomenon of inclusion was verified by using different characterization techniques such as thermogravimetric analysis, differential scanning calorimetry, (1)H nuclear magnetic resonance (NMR) and two dimensional nuclear overhauser effect spectroscopy (NOESY) experiments. From these results it was concluded that γ-cyclodextrins could be an appropriate cyclodextrin polymer which can be used to functionalize chloramphenicol on the surface of silver nanoparticles. In addition, γ-cyclodextrin capped silver nanoparticles were synthesized and characterized using UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR) and zeta potential analysis. Molecular recognition of chloramphenicol by these cyclodextrin capped silver nanoparticles was confirmed by surface enhanced raman spectroscopy (SERS) experiments. Synergistic antibacterial effect of chloramphenicol with γ-cyclodextrin capped silver nanoparticles was evaluated against Pseudomonas aeruginosa (ATCC 27853), Enterococcus faecalis (ATCC 5129), Klebsiella pneumoniae (ATCC 700603) and Staphylococcus aureus (ATCC 43300). The results from the antibacterial experiment were favourable thus allowing us to conclude that the approach of modifying organic drug molecules with cyclodextrin capped inorganic silver nanoparticles could help to enhance the antibacterial activity of them.

Ligand and structure based in silico studies to identify kinesin spindle protein (KSP) inhibitors as potential anticancer agents

Kinesin spindle protein (KSP) belongs to the kinesin superfamily of microtubule-based motor proteins. KSP is responsible for the establishment of the bipolar mitotic spindle which mediates cell division. Inhibition of KSP expedites the blockade of the normal cell cycle during mitosis through the generation of monoastral MT arrays that finally cause apoptotic cell death. As KSP is highly expressed in proliferating/cancer cells, it has gained considerable attention as a potential drug target for cancer chemotherapy. Therefore, this study envisaged to design novel KSP inhibitors by employing computational techniques/tools such as pharmacophore modelling, virtual database screening, molecular docking and molecular dynamics. Initially, the pharmacophore models were generated from the data-set of highly potent KSP inhibitors and the pharmacophore models were validated against in house test set ligands. The validated pharmacophore model was then taken for database screening (Maybridge and ChemBridge) to yield hits, which were further filtered for their drug-likeliness. The potential hits retrieved from virtual database screening were docked using CDOCKER to identify the ligand binding landscape. The top-ranked hits obtained from molecular docking were progressed to molecular dynamics (AMBER) simulations to deduce the ligand binding affinity. This study identified MB-41570 and CB-10358 as potential hits and evaluated these experimentally using in vitro KSP ATPase inhibition assays.

Sequence, Structural Analysis and Metrics to Define the Unique Dynamic Features of the Flap Regions Among Aspartic Proteases

Aspartic proteases are a class of hydrolytic enzymes that have been implicated in a number of diseases such as HIV, malaria, cancer and Alzheimer’s. The flap region of aspartic proteases is a characteristic unique structural feature of these enzymes; and found to have a profound impact on protein overall structure, function and dynamics. Flap dynamics also plays a crucial role in drug binding and drug resistance. Therefore, understanding the structure and dynamic behavior of this flap regions is crucial in the design of potent and selective inhibitors against aspartic proteases. Defining metrics that can describe the flap motion/dynamics has been a challenging topic in literature. This review is the first attempt to compile comprehensive information on sequence, structure, motion and metrics used to assess the dynamics of the flap region of different aspartic proteases in “one pot”. We believe that this review would be of critical importance to the researchers from different scientific domains.

Therapeutic, Molecular and Computational Aspects of Novel Monoamine Oxidase (MAO) Inhibitors

Background Due to the limited number of MAO inhibitors in the clinics, several research efforts are aimed at the discovery of novel MAO inhibitors. At present, a high specificity and a reversible mode of inhibition of MAO-A/B are cited as desirable traits in drug discovery process. This will help to reduce the probability of causing target disruption and may increase the duration of action of drug. AIM Most of the existing MAO inhibitors lead to side effects due to the lack of affinity and selectivity. Therefore, there is an urgent need to design novel, potent, reversible and selective inhibitors for MAO-A/B. Selective inhibition of MAO-A results in the elevated level of serotonin and noradrenaline. Hence, MAO-A inhibitors can be used for improving the symptoms of depression. The selective MAO-B inhibitors are used with L-DOPA and/or dopamine agonists in the symptomatic treatment of Parkinsons disease. The present study was aimed to describe the recently developed hits of MAO inhibitors. METHOD At present, CADD techniques are gaining an attention in rationale drug discovery of MAO inhibitors, and several research groups employed CADD approaches on various chemical scaffolds to identify novel MAO inhibitors. These computational techniques assisted in the development of lead molecules with improved pharmacodynamics / pharmacokinetic properties toward MAOs. Further, CADD techniques provided a better understanding of structural aspects of molecular targets and lead molecules. CONCLUSIONS The present review describes the importance of structural features of potential chemical scaffolds as well as the role of computational approaches like ligand docking, molecular dynamics, QSAR and pharmacophore modeling in the development of novel MAO inhibitors.