Purinergic receptor P2X7: a novel target for anti-inflammatory therapy.

Purinergic receptors, also known as purinoceptors, are ligand gated membrane ion channels involved in many cellular functions. Among all identified purinergic receptors, P2X7 subform is unique since it induces the caspase activity, cytokine secretion, and apoptosis. The distribution of P2X7 receptors, and the need of high concentration of ATP required to activate this receptor exhibited its ability to function as 'danger' sensor associated with tissue inflammation and damage. Further, the modulation of other signalling pathways associated with P2X7 has also been proposed to play an important role in the control of macrophage functions and inflammatory responses, especially towards lipopolysaccharides. Experimentally, researchers have also observed the decreased severity of inflammatory responses in P2X7 receptor expressing gene (P2RX7) knockout (KO) phenotypes. Therefore, newly developed potent antagonists of P2X7 receptor would serve as novel therapeutic agents to combat various inflammatory conditions. In this review article, we tried to explore various aspects of P2X7 receptors including therapeutic potential, and recent discoveries and developments of P2X7 receptor antagonists.

Receptor guided 3D-QSAR analysis of thieno[2,3-b]pyridine-5- carbonitrile inhibitors of protein kinase C theta (PKC-θ).

In the present study, receptor induced 3D-QSAR model was developed for a set of 46 thieno[2,3-b]pyridine-5- carbonitrile PKC-θ inhibitors, to explore the structural requirements of the molecules necessary for PKC-θ inhibition. Since the chemical nature of the studied molecules was different from the crystal ligand of the selected protein, induced fit docking (IFD) protocol was employed to induce the conformational changes in the active site of the selected protein. Thereafter, all molecules were docked into the newly generated active site environment of the selected protein using glide docking program, and the 3D-QSAR analysis was performed in PHASE program utilizing the docking based alignment of the molecules. The best 3D-QSAR model was selected on the basis of the highest value of Q(2)test (0.600), and the selected model also showed high values of R(2)train , 0.915, Pearson-r, 0.801 and low value of SD, 0.241. The contour maps corresponding to the selected 3D-QSAR model, in combination with docking analysis, helped to explore the essential amino acid residues involved in binding, and structural requirements of the ligand molecules necessary for complementary fit with the active site of the protein. Therefore, the information revealed from the generated model can further be explored as a novel tool for the designing of new congener molecules that can serve as potential therapeutics for the treatment of various disease conditions associated with abnormal PKC-θ signalling.

Protein kinase C-theta inhibitors: a novel therapy for inflammatory disorders.

PKC-θ is a serine/threonine specific protein kinase and its activation depends upon the concentration of diacylglycerol (DAG) and phospholipids (phosphatidylserine). PKC-θ phosphorylates a variety of proteins that are known to be involved in the diverse cellular signaling pathways. It is predominantly expressed in the T-cells and localized in the center of immunological synapse upon T-cell receptor (TCR) and CD28 signaling. Activation of PKC-θ leads to the activation of various transcription factors in the nuclei of T-cells, e.g. NF-κB, NFAT, c-Jun, c-Fos and AP-1 that further control the proliferation and differentiation of T-cells. Defective T-cell activation in turn leads to the aberrant expression of apoptosis related proteins that cause the poor T-cell survival. Researchers have found that T-cells deficient in PKC-θ exhibit reduced interleukin-2 (IL-2) production. Apart from this role on IL-2 expression, it also plays crucial roles in the proliferation, differentiation and survival of the T-cells, which make it an attractive therapeutic target for a variety of immunological and T-cell mediated diseases. Hence, new molecules capable of modulating the expression or biological activity of PKC-θ are being developed and tested for their potential as novel therapy for several T-cells mediated disease conditions such as multiple sclerosis, rheumatoid arthritis, asthma, inflammatory bowel disease and organ transplantation, etc. In the present review, we tried to integrate the recent discoveries on PKC-θ including its pharmacology and therapeutic potential, along with brief update on its inhibitor molecules.

Structural Basis of Amino Pyrimidine Derivatives for Inhibitory Activity of PKC-θ: 3D-QSAR and Molecular Docking Studies.

In the present study, 3D-QSAR analysis was performed on a set of 56 amino pyrimidine PKC-θ inhibitors utilizing docking based alignment. The best 3D-QSAR model exhibited the highest value of Q(2) (0.825) and also displayed high values of R(2) (0.937), F (184.600) and low SD (0.240). The selected model was validated by determining the Pearson-r (0.915) for test set molecules. Docking simulation was carried out to explore the binding interactions of the molecules with active site amino acid residues of the receptor and subsequently to validate the generated 3D-QSAR model. The results of 3D-QSAR and docking analysis exerted complementary fit that strengthen the stability and reliability of the generated model. Therefore, the combined study of 3D-QSAR and docking analysis may successfully be used for the rational designing of new potent congeners.