Targeting multiple response regulators of Mycobacterium tuberculosis augments the host immune response to infection.

The genome of M. tuberculosis (Mtb) encodes eleven paired two component systems (TCSs) consisting of a sensor kinase (SK) and a response regulator (RR). The SKs sense environmental signals triggering RR-dependent gene expression pathways that enable the bacterium to adapt in the host milieu. We demonstrate that a conserved motif present in the C-terminal domain regulates the DNA binding functions of the OmpR family of Mtb RRs. Molecular docking studies against this motif helped to identify two molecules with a thiazolidine scaffold capable of targeting multiple RRs, and modulating their regulons to attenuate bacterial replication in macrophages. The changes in the bacterial transcriptome extended to an altered immune response with increased autophagy and NO production, leading to compromised survival of Mtb in macrophages. Our findings underscore the promise of targeting multiple RRs as a novel yet unexplored approach for development of new anti-mycobacterial agents particularly against drug-resistant Mtb.

Structural Models for the Design of PKMzeta Inhibitors with Neurobiological Indications.

An atypical protein kinase C, PKMzeta has become an attractive target for various neurological disorders including long term potentiation, cognition, neuropathic pain and cancer. Drug discovery efforts have been hindered due to the non-availability of the protein structure and hence in the present study we attempted to build the open and closed models of the protein PKMzeta using homology modeling. The models were then used to identify PKMzeta inhibitors utilizing a high-throughput virtual screening protocol from a large commercial chemical database. Compounds were selected based on the binding interactions and Glide score. Compounds were then subjected to in vitro luminescent based kinase assay for their inhibitory activity on targeted protein. Seven compounds exhibited IC50 s less than or equal to 10 µM. Cell based assays revealed that Lead C3 and Lead C6 exhibited selectivity towards methylmercury treated neuroblastoma growth inhibition and suppressed reactive oxygen species with IC50 s of 0.89 and 0.17 µM, respectively. Furthermore, Lead C3 exhibited attenuation of proinflammatory response with least energy in dynamic simulation studies and thus emerged as a prototypical lead for further development as novel inhibitor of PKMzeta for neurological implications.

Design of dual inhibitors of ROCK-I and NOX2 as potential leads for the treatment of neuroinflammation associated with various neurological diseases including autism spectrum disorder.

Inhibition of both Rho kinase (ROCK-I) and NADPH oxidase (NOX2) to treat neuroinflammation could be very effective in the treatment of progressive neurological diseases like Alzheimer's disease, autism spectral disorder, and fragile X syndrome. NOX2 being a multi-enzyme component is activated during host defense in phagocytes such as microglia, to catalyze the production of superoxide from oxygen, while ROCK is an important mediator of fundamental cell processes like adhesion, proliferation and migration. Phosphorylated ROCK was found to activate NOX2 assembly via Ras related C3 botulinum toxin substrate (Rac) in disease conditions. Overexpression of ROCK-I and NOX2 in innate immune cells like microglial cells contribute to progressive neuronal damage early in neurological disease development. In the present study we employed a computer-aided methodology combining pharmacophores and molecular docking to identify new chemical entities that could inhibit ROCK-I as well as NOX2 (p47 phox). Among the huge dataset of a commercial database, top 18 molecules with crucial binding interactions were selected for biological evaluation. Seven among the lead molecules exhibited inhibitory potential against ROCK-I and NOX2 with IC50s ranging from 1.588 to 856.2 nM and 0.8942 to 10.24 µM, respectively, and emerged as potential hits as dual inhibitors with adequate selectivity index (SI = CC50/GIC50) in cell-based assays. The most active compound 3 was further found to show reduction of the pro-inflammatory mediators such as TNFα, interleukin-6 (IL-6) and interleukin-1beta (IL-1ß) mRNA expression levels in activated (MeHg treated) human neuroblastoma (IMR32) cell lines. Hence the present work documented the utility of these dual inhibitors as prototypical leads to be useful for the treatment of neurological disorders including autism spectrum disorder and Alzheimer's disease.

Design of novel rho kinase inhibitors using energy based pharmacophore modeling, shape-based screening, in silico virtual screening, and biological evaluation.

Rho-associated protein kinase (ROCK) plays a key role in regulating a variety of cellular processes, and dysregulation of ROCK signaling or expression is implicated in numerous diseases and infections. ROCK proteins have therefore emerged as validated targets for therapeutic intervention in various pathophysiological conditions such as diabetes-related complications or hepatitis C-associated pathogenesis. In this study, we report on the design and identification of novel ROCK inhibitors utilizing energy based pharmacophores and shape-based approaches. The most potent compound 8 exhibited an IC50 value of 1.5 µM against ROCK kinase activity and inhibited methymercury-induced neurotoxicity of IMR-32 cells at GI50 value of 0.27 µM. Notably, differential scanning fluorometric analysis revealed that ROCK protein complexed with compound 8 with enhanced stability relative to Fasudil, a validated nanomolar range ROCK inhibitor. Furthermore, all compounds exhibited ≥96 µM CC50 (50% cytotoxicity) in Huh7 hepatoma cells, while 6 compounds displayed anti-HCV activity in HCV replicon cells. The identified lead thus constitutes a prototypical molecule for further optimization and development as anti-ROCK inhibitor.

Discovery and structure optimization of a series of isatin derivatives as Mycobacterium tuberculosis chorismate mutase inhibitors.

In this study, the crystal structure of the Mycobacterium tuberculosis (MTB) enzyme chorismate mutase (CM) bound to transition state analogue (PDB: 2FP2) was used as a framework for virtual screening of the BITS-Pilani in-house database (2500 compounds) to identify new scaffold. We identified isatin as novel small molecule MTB CM inhibitors; further twenty-four isatin derivatives were synthesized and evaluated in vitro for their ability to inhibit MTB CM, and activity against M. tuberculosis as steps towards the derivation of structure-activity relationships (SAR) and lead optimization. Compound 3-(4-nitrobenzylidene)indolin-2-one, 24 emerged as the most promising lead with an IC50 of 1.01 ± 0.22 µm for purified CM and MIC of 23.5 µm for M. tuberculosis, with little or no cytotoxicity.

Identification and structure-activity relationship study of carvacrol derivatives as Mycobacterium tuberculosis chorismate mutase inhibitors.

In the present study, we identified carvacrol, a major phenolic component of oregano oil as a novel small molecule inhibitor of Mycobacterium tuberculosis (MTB) chorismate mutase (CM) enzyme with IC50 of 1.06 ± 0.4 µM. Virtual screening of the BITS-Pilani in-house database using the crystal structure of the MTB CM bound transition state intermediate (PDB: 2FP2) as framework identified carvacrol as a potential lead. Further various carvacrol derivatives were evaluated in vitro for their ability to inhibit MTB CM enzyme, whole cell MTB and cytotoxicity as steps toward the derivation of structure-activity relationships (SAR) and lead optimization.

Potential role of Rho kinase inhibitors in combating diabetes-related complications including diabetic neuropathy--a review.

The worldwide epidemic scale of diabetes mellitus has been underestimated for a long time. Currently every 10 seconds one patient dies of diabetes-related pathologies. Given the high risk and prevalence of secondary complications as well as individual predisposition to target organ injury, diabetes is one of the major risk factors for various organ and tissue dysfunctions including nerves. The present review outlines the role of Rho Kinase (ROCK) in various diabetic indications: diabetic neuropathy, erectile dysfunction, cardiomyopathy, sexual dysfunction, nephropathy, cardiomyopathy, retinopathy, cerebro-vascular disease and cystopathy. We found that ROCK is involved in various pathophysiological mechanisms, leading to a number of unique diabetic complications. Recent studies have indicated an increasing interest in the use of ROCK inhibitors like Y-27632, H1152 and fasudil not only for the treatment of diabetic neuropathy, but also for the treatment of sexual dysfunction, cardiomyopathy and other diabetic complications. The pathophysiological mechanism has been extensively analyzed and the current status of ROCK inhibitors has been discussed in the review.