Identification of highly potent and selective PI3Kδ inhibitors

Selective PI3Kδ inhibitors have recently been hypothesized to be appropriate immunosuppressive agents for the treatment of immunological disorders such as rheumatoid arthritis. However, few reports have highlighted molecules that are highly selective for PI3Kδ over the other PI3K isoforms. In this letter, isoform and kinome selective PI3Kδ inhibitors are presented. The Structural Activity Relationship leading to such molecules is outlined.     

Discovery of 7-(3-(piperazin-1-yl)phenyl)pyrrolo[2,1-f][1,2,4]triazin-4-amine derivatives as highly potent and selective PI3Kδ inhibitors

As demonstrated in preclinical animal models, the disruption of PI3Kδ expression or its activity leads to a decrease in inflammatory and immune responses. Therefore, inhibition of PI3Kδ may provide an alternative treatment for autoimmune diseases, such as RA, SLE, and respiratory ailments. Herein, we disclose the identification of 7-(3-(piperazin-1-yl)phenyl)pyrrolo[2,1-f][1,2,4]triazin-4-amine derivatives as highly potent, selective and orally bioavailable PI3Kδ inhibitors. The lead compound demonstrated efficacy in an in vivo mouse KLH model.     

Recombinant expression and characterization of Lucilia cuprina CYP6G3: Activity and binding properties toward multiple pesticides

The Australian sheep blowfly, Lucilia cuprina, is a primary cause of sheep flystrike and a major agricultural pest. Cytochrome P450 enzymes have been implicated in the resistance of L. cuprina to several classes of insecticides. In particular, CYP6G3 is a L. cuprina homologue of Drosophila melanogaster CYP6G1, a P450 known to confer multi-pesticide resistance. To investigate the basis of resistance, a bicistronic Escherichia coli expression system was developed to co-express active L. cuprina CYP6G3 and house fly (Musca domestica) P450 reductase. Recombinant CYP6G3 showed activity towards the high-throughput screening substrates, 7-ethoxycoumarin and p-nitroanisole, but not towards p-nitrophenol, coumarin, 7-benzyloxyresorufin, or seven different luciferin derivatives (P450-Glo™ substrates). The addition of house fly cytochrome b₅ enhanced the k_cat for p-nitroanisole dealkylation approximately two fold (17.8 ± 0.5 vs 9.6 ± 0.2 min⁻¹) with little effect on K_M (13 ± 1 vs 10 ± 1 μM). Inhibition studies and difference spectroscopy revealed that the organochlorine compounds, DDT and endosulfan, and the organophosphate pesticides, malathion and chlorfenvinphos, bind to the active site of CYP6G3. All four pesticides showed type I binding spectra with spectral dissociation constants in the micromolar range suggesting that they may be substrates of CYP6G3. While no significant inhibition was seen with the organophosphate, diazinon, or the neonicotinoid, imidacloprid, diazinon showed weak binding in spectral assays, with a Kd value of 23 ± 3 μM CYP6G3 metabolised diazinon to the diazoxon and hydroxydiazinon metabolites and imidacloprid to the 5-hydroxy and olefin metabolites, consistent with a proposed role of CYP6G enzymes in metabolism of phosphorothioate and neonicotinoid insecticides in other species.     

Ral GTPase interacts with the N-terminal in addition to the C-terminal region of PLC-δ1

Previously, we have shown that RalA, a calmodulin (CaM)-binding protein, binds to the C2 region in the C-terminal of PLC-δ1, and increases its enzymatic activity. Since PLC-δ1 contains a CaM-like region in its N-terminus, we have investigated if RalA can also bind to the N-terminus of PLC-δ1. Therefore, we created a GST-PLC-δ1 construct consisting of the first 294 amino acids of PLC-δ1 (GST-PLC-δ1_1-294). In vitro binding experiments confirmed that PLC-δ1_1-294 was capable of binding directly to RalA. W-7 coupled to polyacrylamide beads bound pure PLC-δ1, demonstrating that PLC-δ1 contains a CaM-like region. Competition assays with W-7, peptides representing RalA and the newly identified RalB CaM-binding regions, or the IQ peptide from PLC-δ1 were able to inhibit RalA binding to PLC-δ1_1-294. This study demonstrates that there are two binding sites for RalA in PLC-δ1 and provides further insight into the role of Ral GTPase in the regulation of PLC-δ1 function.     

Role of proteolytic activation of protein kinase Cδ in the pathogenesis of prion disease

Prion diseases are infectious and inevitably fatal neurodegenerative diseases characterized by prion replication, widespread protein aggregation and spongiform degeneration of major brain regions controlling motor function. Oxidative stress has been implicated in prion-related neuronal degeneration, but the molecular mechanisms underlying prion-induced oxidative damage are not well understood. In this study, we evaluated the role of oxidative stress-sensitive, pro-apoptotic protein kinase Cδ (PKCδ) in prion-induced neuronal cell death using cerebellar organotypic slice cultures (COSC) and mouse models of prion diseases. We found a significant upregulation of PKCδ in RML scrapie-infected COSC, as evidenced by increased levels of both PKCδ protein and its mRNA. We also found an enhanced regulatory phosphorylation of PKCδ at its two regulatory sites, Thr505 in the activation loop and Tyr311 at the caspase-3 cleavage site. The prion infection also induced proteolytic activation of PKCδ in our COSC model. Immunohistochemical analysis of scrapie-infected COSC revealed loss of PKCδ positive Purkinje cells and enhanced astrocyte proliferation. Further examination of PKCδ signaling in the RML scrapie adopted in vivo mouse model showed increased proteolytic cleavage and Tyr 311 phosphorylation of the kinase. Notably, we observed a delayed onset of scrapie-induced motor symptoms in PKCδ knockout (PKCδ^−/−) mice as compared with wild-type (PKCδ^+/+) mice, further substantiating the role of PKCδ in prion disease. Collectively, these data suggest that PKCδ signaling likely plays a role in the neurodegenerative processes associated with prion diseases.     

Kinetics and pathway of biodegradation of dibutyl phthalate by Pleurotus ostreatus

Dibutyl phthalate (DBP) is a plasticizer, whose presence in the environment as a pollutant has attained a great deal of attention due to its reported association with endocrine system disturbances on animals. Growth parameters, glucose uptake, percentage of removal efficiency (%E) of DBP, biodegradation constant of DBP (k) and half-life of DBP biodegradation (t_1/2) were evaluated for Pleurotus ostreatus grown on media containing glucose and different concentrations of DBP (0, 500 and 1000 mg l^?1). P. ostreatus degraded 99.6 % and 94 % of 500 and 1000 mg of DBP l^?1 after 312 h and 504 h, respectively. The k was 0.0155 h^?1 and 0.0043 h^?1 for 500 and 1000 mg of DBP l^?1, respectively. t_1/2 was 44.7 h and 161 h for 500 and 1000 mg of DBP l^?1, respectively. Intermediate compounds of biodegraded DBP were identified by GC-MS and a DBP biodegradation pathway was proposed using quantum chemical calculation. DBP might be metabolized to benzene and acetyl acetate, the first would be oxidated to muconic acid and the latter would enter into the Krebs cycle. P. ostreatus has the ability to degrade DBP and utilizes it as source of carbon and energy.     

Sweet Killing in Obesity and Diabetes: The Metabolic Role of the BH3-only Protein BIM

Diabetes is a metabolic disorder affecting more than 400 million individuals and their families worldwide. The major forms of diabetes (types 1 and 2) are characterized by pancreatic β-cell dysfunction and, in some cases, loss of β-cell mass causing hyperglycemia due to absolute or relative insulin deficiency. The BCL-2 homology 3 (BH3)-only protein BIM has a wide role in apoptosis induction in cells. In this review, we describe the apoptotic mechanisms mediated by BIM activation in β cells in obesity and both forms of diabetes. We focus on molecular pathways triggered by inflammation, saturated fats, and high levels of glucose. Besides its role in cell death, BIM has been implicated in the regulation of mitochondrial oxidative phosphorylation and cellular metabolism in hepatocytes. BIM is both a key mediator of pancreatic β-cell death and hepatic insulin resistance and is thus a potential therapeutic target for novel anti-diabetogenic drugs. We consider the implications and challenges of targeting BIM in the treatment of the disease.     

Calmodulin-dependent protein kinase II (CaMKII) mediates radiation-induced mitochondrial fission by regulating the phosphorylation of dynamin-related protein 1 (Drp1) at serine 616

Mitochondrial dynamics are suggested to be indispensable for the maintenance of cellular quality and function in response to various stresses. While ionizing radiation (IR) stimulates mitochondrial fission, which is mediated by the mitochondrial fission protein, dynamin-related protein 1 (Drp1), it remains unclear how IR promotes Drp1 activation and subsequent mitochondrial fission. Therefore, we conducted this study to investigate these concerns. First, we found that X-irradiation triggered Drp1 phosphorylation at serine 616 (S616) but not at serine 637 (S637). Reconstitution analysis revealed that introduction of wild-type (WT) Drp1 recovered radiation-induced mitochondrial fission, which was absent in Drp1-deficient cells. Compared with cells transfected with WT or S637A Drp1, the change in mitochondrial shape following irradiation was mitigated in S616A Drp1-transfected cells. Furthermore, inhibition of CaMKII significantly suppressed Drp1 S616 phosphorylation and mitochondrial fission induced by IR. These results suggest that Drp1 phosphorylation at S616, but not at S637, is prerequisite for radiation-induced mitochondrial fission and that CaMKII regulates Drp1 phosphorylation at S616 following irradiation.     

Discovery and biological evaluation of novel pyrazolopyridine derivatives as potent and orally available PI3Kδ inhibitors

Phosphatidylinositol-3-kinase (PI3K)δ inhibition is one of the most attractive approaches to the treatment of autoimmune diseases and leukocyte malignancies. Through the exploration of pyrazolopyridine derivatives as potential PI3Kδ inhibitors, compound 12a was identified as a potent PI3Kδ inhibitor but suffered from poor oral exposure in mice. With a modified amide linkage group, compound 15a was developed as an orally available PI3Kδ inhibitor with reduced selectivity against other PI3Ks. To improve the trade-off between selectivity and PK profile, structure–activity relationship (SAR) studies of terminal substituents on the pyrolidine ring were conducted. As a result, we developed potent PI3Kδ inhibitors with good oral availability. In particular, the representative compound 15j showed excellent selectivity for PI3Kδ over other PI3Ks with good oral exposure in mice.