Optimization of 5-vinylaryl-3-pyridinecarbonitriles as PKCtheta inhibitors

Synthesis, molecular modeling studies and bronchodilation properties of nicotinonitrile containing-compounds

Facile synthetic pathway for nicotinonitriles 5a‒o, 7a‒i was demonstrated through reaction of ketones 4a‒k, 6a‒f with ylidenemalononitrile 3 in the presence of sodium alkoxide. Meanwhile, nucleophilic attack of amines on 2-bromonicotinonitrile 9 (obtained through reaction of propenone 8 with malononitrile, followed by bromination with bromine in acetic acid) afforded 3-pyridinecarbonitriles 11a‒d. Single crystal X-ray of compound 7i reveals the monoclinic space group C2/c with 8 molecules per unit cell. Optimized structure of 7i [DFT/B3LYP, 6-31G(d,p)] shows close correlations to that of X-ray study. Compound 5l seems superior among all the synthesized analogues exhibiting bronchodilation properties about three folds potency compared to theophylline (standard reference) through pre-contracted tracheal rings with histamine standard method. Also compound 5a reveals promising observations (about two folds potency of the standard reference). Molecular modeling studies (3D-pharmacophore and 2D-QSAR) supported the observed biological properties.

Pharmacological Inhibition of PKCθ Counteracts Muscle Disease in a Mouse Model of Duchenne Muscular Dystrophy

Inflammation plays a considerable role in the progression of Duchenne Muscular Dystrophy (DMD), a severe muscle disease caused by a mutation in the dystrophin gene. We previously showed that genetic ablation of Protein Kinase C θ (PKCθ) in mdx, the mouse model of DMD, improves muscle healing and regeneration, preventing massive inflammation. To establish whether pharmacological targeting of PKCθ in DMD can be proposed as a therapeutic option, in this study we treated young mdx mice with the PKCθ inhibitor Compound 20 (C20). We show that C20 treatment led to a significant reduction in muscle damage associated with reduced immune cells infiltration, reduced inflammatory pathways activation, and maintained muscle regeneration. Importantly, C20 treatment is efficient in recovering muscle performance in mdx mice, by preserving muscle integrity. Together, these results provide proof of principle that pharmacological inhibition of PKCθ in DMD can be considered an attractive strategy to modulate immune response and prevent the progression of the disease.

Research in context

Duchenne muscular dystrophy (DMD) is a severe muscle disease affecting 1:3500 male births. DMD is caused by a mutation in dystrophin gene, coding for a protein required for skeletal and cardiac muscle integrity. Lack of a functional dystrophin is primarily responsible for the muscle eccentric contraction-induced muscle damage, observed in dystrophic muscle. However, inflammation plays a considerable role in the progression of DMD. Glucocorticoids, which have anti-inflammatory properties, are being used to treat DMD with some success; however, long term treatment with these drugs induces muscle atrophy and wasting, outweighing their benefit. The identification of specific targets for anti-inflammatory therapies is one of the ongoing therapeutic options. Although blunting inflammation would not be a “cure” for the disease, the emerging clue is that multiple strategies, addressing different aspects of the pathology, which may eventually converge, may be successful. In this context, we previously showed that genetic ablation of Protein Kinase C θ (PKCθ), an enzyme known to be involved in immune response, in mdx, the mouse model of DMD, improves muscle healing and regeneration, preventing massive inflammation. To establish whether pharmacological targeting of PKCθ in DMD can be proposed as a therapeutic option, in this study we treated young mdx mice with the PKCθ inhibitor Compound 20 (C20). We show that C20 treatment led to a significant reduction in muscle damage associated with reduced immune cells infiltration, reduced inflammatory pathways activation, and maintained muscle regeneration. Importantly, C20 treatment is efficient in recovering muscle performance in mdx mice, by preserving muscle integrity. Together, these results provide proof of principle that pharmacological inhibition of PKCθ in DMD can be considered an attractive strategy to modulate immune response and prevent the progression of the disease.

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Immune-cell intrinsic PKCθ activity might play a hitherto unrecognized role of in the development of DMD.

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Mdx dystrophic mice were treated with the PKCθ inhibitor C20.

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C20 treatment prevents damage and inflammation in dystrophic muscle, while improving muscle regeneration.

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C20 treatment prevents drop in force and ameliorates fatigue resistance in dystrophic mice.

Selective and efficient synthesis of trans-arylvinylboronates and trans-hetarylvinylboronates using palladium catalyzed cross-coupling

A versatile method of palladium catalyzed cross-coupling between pinacol vinylboronate and (het)arylbromides to obtain trans-(het)arylvinylboronates in excellent yields and selectivity.

Targeting PKCθ in skeletal muscle and muscle diseases: good or bad?

Protein kinase Cθ (PKCθ) is a member of the novel calcium-independent PKC family, with a relatively selective tissue distribution. Most studies have focused on its unique role in T-lymphocyte activation and suggest that inhibition of PKCθ could represent a novel therapeutic approach in the treatment of chronic inflammation, autoimmunity and allograft rejection. However, considering that PKCθ is also expressed in other cell types, including skeletal muscle cells, it is important to understand its function in different tissues before proposing it as a molecular target for the treatment of immune-mediated diseases. A number of studies have highlighted the role of PKCθ in mediating several intracellular pathways, regulating muscle cell development, homoeostasis and remodelling, although a comprehensive picture is still lacking. Moreover, we recently showed that lack of PKCθ in a mouse model of Duchenne muscular dystrophy (DMD) ameliorates the progression of the disease. In the present article, we review new developments in our understanding of the involvement of PKCθ in intracellular mechanisms regulating skeletal muscle development, growth and maintenance under physiological conditions and recent advances showing a hitherto unrecognized role of PKCθ in promoting muscular dystrophy.

Protein kinase C: a regulator of cytoskeleton remodelling and T-cell migration

Protein kinase C (PKC) is a family of ten serine/threonine kinases that have diverse roles in the signalling pathways regulating cellular proliferation, differentiation, apoptosis and immune responses. Elucidating roles for individual PKC isoforms in the immune responses of T-cells have long been a challenging prospect, because these cells are known to express nine of these isoforms. A variety of approaches including the use of knockout mice, overexpression of kinase-inactive mutants, cell-permeable peptides, pharmacological inhibitors and siRNAs have shown that PKCs regulate the production of inflammatory cytokines and the cytotoxic responses of various T-cell subsets. Central to the T-cell immune response is a requirement to migrate to various organs and tissues in search of pathogens and micro-organisms. T-cell migration is guided by specific sets of chemokines and integrin ligands that activate their cognate chemokine receptors and integrins on T-cells, resulting in remodelling of the cytoskeleton and the dynamic protrusive/contractile forces necessary for cell adhesion and motility. In the present article, we review the role of PKC in T-cell migration, with an emphasis on studies that have defined their roles in cytoskeletal remodelling, cell polarity and intracellular trafficking downstream of chemokine receptors and integrins.

The Novel PKCθ from Benchtop to Clinic

The protein kinases C (PKCs) are a family of serine/threonine kinases involved in regulating multiple essential cellular processes such as survival, proliferation, and differentiation. Of particular interest is the novel, calcium-independent PKCθ which plays a central role in immune responses. PKCθ shares structural similarities with other PKC family members, mainly consisting of an N-terminal regulatory domain and a C-terminal catalytic domain tethered by a hinge region. This isozyme, however, is unique in that it translocates to the immunological synapse between a T cell and an antigen-presenting cell (APC) upon T cell receptor-peptide MHC recognition. Thereafter, PKCθ interacts physically and functionally with downstream effectors to mediate T cell activation and differentiation, subsequently leading to inflammation. PKCθ-specific perturbations have been identified in several diseases, most notably autoimmune disorders, and hence the modulation of its activity presents an attractive therapeutic intervention. To that end, many inhibitors of PKCs and PKCθ have been developed and tested in preclinical and clinical studies. And although selectivity remains a challenge, results are promising for the future development of effective PKCθ inhibitors that would greatly advance the treatment of several T-cell mediated diseases.

Analysis of protein kinase C theta inhibitors for the control of HIV-1 replication in human CD4+ T cells reveals an effect on retrotranscription in addition to viral transcription

HIV-1 infection cannot be cured due to reservoirs formed early after infection. Decreasing the massive CD4+ T cell activation that occurs at the beginning of the disease would delay reservoir seeding, providing a better prognosis for patients. CD4+ T cell activation is mediated by protein kinase C (PKC) theta (θ), which is involved in T-cell proliferation, as well as NF-κB, NF-AT, and AP-1 activation. We found that PKCθ activity increased viral replication, but also that HIV-1 induced higher activation of PKCθ in infected CD4+ T cells, creating a feedback loop. Therefore, specific inhibition of PKCθ activity could contribute to control HIV-1 replication. We tested the efficacy of seven PKCθ specific inhibitors to control HIV-1 replication in CD4+ T cells and selected two of the more potent and safer: CGX1079 and CGX0471. They reduced PKCθ phosphorylation at T538 and its translocation to the plasma membrane, which correlated with decreased HIV-1 retrotranscription through partial inhibition of SAMHD1 antiviral activity, rendering lower proviral integration. CGX1079 and CGX0471 also interfered with viral transcription, which would reduce the production of new virions, as well as the subsequent spread and infection of new targets that would increase the reservoir size. CGX1079 and CGX0471 did not completely abrogate T-cell functions such as proliferation and CD8-mediated release of IFN-γ in PBMCs from HIV-infected patients, thereby avoiding general immunosuppresion. Consequently, using PKCθ inhibitors as adjuvant of antiretroviral therapy in recently infected patients would decrease the pool of activated CD4+ T cells, thwarting proviral integration and reducing the reservoir size.

2,6-Naphthyridines as potent and selective inhibitors of the novel protein kinase C isozymes

The present study describes a novel series of ATP-competitive PKC inhibitors based on the 2,6-naphthyridine template. Example compounds potently inhibit the novel Protein Kinase C (PKC) isotypes δ, ε, η, θ (in particular PKCε/η, and display a 10-100-fold selectivity over the classical PKC isotypes. The prototype compound 11 was found to inhibit PKCθ-dependent pathways in vitro and in vivo. In vitro, a-CD3/a-CD28-induced lymphocyte proliferation could be effectively blocked in 10% rat whole blood. In mice, 11 dose-dependently inhibited Staphylococcus aureus enterotoxin B-triggered IL-2 serum levels after oral dosing.

Protein kinase Ctheta is a specific target for inhibition of the HIV type 1 replication in CD4+ T lymphocytes

Integration of HIV-1 genome in CD4(+) T cells produces latent reservoirs with long half-life that impedes the eradication of the infection. Control of viral replication is essential to reduce the size of latent reservoirs, mainly during primary infection when HIV-1 infects CD4(+) T cells massively. The addition of immunosuppressive agents to highly active antiretroviral therapy during primary infection would suppress HIV-1 replication by limiting T cell activation, but these agents show potential risk for causing lymphoproliferative disorders. Selective inhibition of PKC, crucial for T cell function, would limit T cell activation and HIV-1 replication without causing general immunosuppression due to PKC being mostly expressed in T cells. Accordingly, the effect of rottlerin, a dose-dependent PKC inhibitor, on HIV-1 replication was analyzed in T cells. Rottlerin was able to reduce HIV-1 replication more than 20-fold in MT-2 (IC(50) = 5.2 μM) and Jurkat (IC(50) = 2.2 μM) cells and more than 4-fold in peripheral blood lymphocytes (IC(50) = 4.4 μM). Selective inhibition of PKC, but not PKCδ or -ζ, was observed at <6.0 μM, decreasing the phosphorylation at residue Thr(538) on the kinase catalytic domain activation loop and avoiding PKC translocation to the lipid rafts. Consequently, the main effector at the end of PKC pathway, NF-κB, was repressed. Rottlerin also caused a significant inhibition of HIV-1 integration. Recently, several specific PKC inhibitors have been designed for the treatment of autoimmune diseases. Using these inhibitors in combination with highly active antiretroviral therapy during primary infection could be helpful to avoid massive viral infection and replication from infected CD4(+) T cells, reducing the reservoir size at early stages of the infection.