Amaryllidaceae alkaloids in skin cancer management: Photoprotective effect on human keratinocytes and anti-proliferative activity in melanoma cells.

Skin cancer has high rates of mortality and therapeutic failure. In this study, to develop a multi-agent strategy for skin cancer management, the selective cytotoxicity of several alkaloid fractions and pure alkaloids isolated from Amaryllidaceae species was evaluated in melanoma cells. In addition, UVB-stimulated keratinocytes (HaCaT) were exposed to seven alkaloid fractions characterized by GC-MS, and the production of intracellular reactive oxygen species (ROS) and IL-6, were measured to evaluate their photoprotection effects. The Eucharis caucana (bulb) alkaloid fraction (20 µg/ml) had a clear effect on the viability of melanoma cells, reducing it by 45.7% without affecting healthy keratinocytes. This alkaloid fraction and tazettine (both at 2.5 µg/ml) suppressed UVB-induced ROS production by 31.6% and 29.4%, respectively. The highest anti-inflammatory potential was shown by the Zephyranthes carinata (bulb) alkaloid fraction (10 µg/ml), which reduced IL-6 production by 90.8%. According to the chemometric analysis, lycoramine and tazettine had a photoprotective effect on the UVB-exposed HaCaT cells, attenuating the production of ROS and IL-6. These results suggest that Amaryllidaceae alkaloids have photoprotective and therapeutic potential in skin cancer management, especially at low concentrations.

Phosphorylation of Histone Deacetylase 8: Structural and Mechanistic Analysis of the Phosphomimetic S39E Mutant.

Histone deacetylase (HDAC) enzymes that catalyze removal of acetyl-lysine post-translational modifications are frequently post-translationally modified. HDAC8 is phosphorylated within the deacetylase domain at conserved residue serine 39, which leads to decreased catalytic activity. HDAC8 phosphorylation at S39 is unique in its location and function and may represent a novel mode of deacetylation regulation. To better understand the impact of phosphorylation of HDAC8 on enzyme structure and function, we performed crystallographic, kinetic, and molecular dynamics studies of the S39E HDAC8 phosphomimetic mutant. This mutation decreases the level of deacetylation of peptides derived from acetylated nuclear and cytoplasmic proteins. However, the magnitude of the effect depends on the peptide sequence and the identity of the active site metal ion [Zn(II) vs Fe(II)], with the value of kcat/KM for the mutant decreasing 9- to >200-fold compared to that of wild-type HDAC8. Furthermore, the dissociation rate constant of the active site metal ion increases by ∼10-fold. S39E HDAC8 was crystallized in complex with the inhibitor Droxinostat, revealing that phosphorylation of S39, as mimicked by the glutamate side chain, perturbs local structure through distortion of the L1 loop. Molecular dynamics simulations of both S39E and phosphorylated S39 HDAC8 demonstrate that the perturbation of the L1 loop likely occurs because of the lost hydrogen bond between D29 and S39. Furthermore, the S39 perturbation causes structural changes that propagate through the protein scaffolding to influence function in the active site. These data demonstrate that phosphorylation plays an important regulatory role for HDAC8 by affecting ligand binding, catalytic efficiency, and substrate selectivity.

[Effectiveness and safety of generic version of lamivudine/tenofovir and efavirenz in treatment naïve HIV-infected patients: a nonrandomized, open-label, phase IV study in Cali-Colombia, 2012-2014]. / Efectividad y seguridad del esquema genérico lamivudina/tenofovir y efavirenz en pacientes con VIH/SIDA naïve: estudio fase IV no aleatorizado, Cali-Colombia 2012-2014.

BACKGROUND: Clinical studies aimed to evaluating the quality of generic drugs may be useful to strengthen policies of access to combined antiretroviral therapy (cART). AIM: To describe the effectiveness and safety of the generic schema lamivudine/tenofovir/efavirenz (3TC/TDF/EFV) in patients with HIV/AIDS naive, belonging to a comprehensive care program. METHODS: A nonrandomized, open-label, phase IV study, during 2012 to 2014 naive HIV-infected patients 18 years or older with indication to receive cART were recruited. Patients were treated with generic scheme 3TC/TDF/EFV and were followed-up during 12 months. Clinical, immunological and laboratory parameters were assessed at baseline, 3, 6 and 12 months of treatment. RESULTS: Of the 40 patients, 30 (75%) met the 12 months of treatment; of them, 80% achieved undetectable viral load (< 40 copies/mL) and 83.3% viral load < 50 copies/mL. Additionally, there was a significant increase (173 cells/mm3) in the median for CD4 T lymphocyte count. Moreover, the results of the whole blood count, creatinine and transaminases were preserved in normal ranges and did not generate changes in the cART. Potential side effects of antiretroviral drugs occurred in less than 10% of patients and had no serious implications. CONCLUSIONS: In this small group of patients, the generic scheme 3TC/TDF/EFV is effective and safe in the treatment of patients with HIV/AIDS naïve, and its effectiveness and safety profile is similar to show by innovator scheme 3TC/TDF/EFV in patients with similar clinical conditions. Registro Estudio: Registro Público Cubano de Ensayos Clínicos (RPCEC) ID: RPCEC00000134. Registered 20 July 2012.

Efectividad y seguridad del esquema genérico lamivudina/tenofovir y efavirenz en pacientes con VIH/SIDA naïve: estudio fase IV no aleatorizado, Cali-Colombia 2012-2014 / Effectiveness and safety of generic version of lamivudine/tenofovir and efavirenz in treatment naïve HIV-infected patients: a nonrandomized, open-label, phase IV study in Cali-Colombia, 2012-2014

Resumen Antecedentes: Los estudios clínicos orientados a evaluar la calidad de medicamentos genéricos pueden ser útiles para fortalecer políticas de acceso a terapia anti-retroviral combinada (TARc). Objetivo: Describir la efectividad y seguridad del esquema genérico lamivudina/tenofovir/efavirenz (3TC/TDF/EFV) en pacientes con infección por VIH/SIDA naïve, pertenecientes a un programa de atención integral. Materiales/Métodos: Estudio clínico prospectivo fase IV abierto y sin grupo control. Entre 2012-2014, se incluyeron y siguieron 40 pacientes con infección por VIH/SIDA naïve y con indicación para iniciar tratamiento. Los pacientes fueron tratados con el esquema genérico 3TC/TDF/EFV y fueron seguidos durante 12 meses. El seguimiento incluyó valoración clínica, parámetros inmunovirológicos y de laboratorio, al inicio del tratamiento y a los 3, 6 y 12 meses. Resultados: De los 40 pacientes, 30 (75%) cumplieron los doce meses de tratamiento; de ellos, 80% alcanzó CV indetectable (< 40 copias/mL) y 83,3% CV < 50 copias/mL. Adicionalmente, en el grupo hubo un incremento en la mediana de 173 linfocitos TCD4/mm3. Por su parte, los resultados del hemograma completo, creatininemia y transaminasas hepáticas se conservaron en rangos normales y no generaron cambios del TARc. Los efectos adversos reconocidos para estos medicamentos se presentaron en menos de 10% de los pacientes y no tuvieron implicaciones graves. Conclusiones: En este grupo pequeño de pacientes, el esquema genérico 3TC/TDF/EFV es efectivo y seguro en el tratamiento de pacientes con infección por VIH/SIDA naïve, y su perfil de efectividad y seguridad es similar al del esquema 3TC/TDF/EFV innovador en pacientes con condiciones clínicas similares.

Background: Clinical studies aimed to evaluating the quality of generic drugs may be useful to strengthen policies of access to combined antiretroviral therapy (cART). Aim: To describe the effectiveness and safety of the generic schema lamivudine/tenofovir/efavirenz (3TC/TDF/EFV) in patients with HIV/AIDS naive, belonging to a comprehensive care program. Methods: A nonrandomized, open-label, phase IV study, during 2012 to 2014 naive HIV-infected patients 18 years or older with indication to receive cART were recruited. Patients were treated with generic scheme 3TC/TDF/EFV and were followed-up during 12 months. Clinical, immunological and laboratory parameters were assessed at baseline, 3, 6 and 12 months of treatment. Results: Of the 40 patients, 30 (75%) met the 12 months of treatment; of them, 80% achieved undetectable viral load (< 40 copies/mL) and 83.3% viral load < 50 copies/mL. Additionally, there was a significant increase (173 cells/mm3) in the median for CD4 T lymphocyte count. Moreover, the results of the whole blood count, creatinine and transaminases were preserved in normal ranges and did not generate changes in the cART. Potential side effects of antiretroviral drugs occurred in less than 10% of patients and had no serious implications. Conclusions: In this small group of patients, the generic scheme 3TC/TDF/EFV is effective and safe in the treatment of patients with HIV/AIDS naïve, and its effectiveness and safety profile is similar to show by innovator scheme 3TC/TDF/EFV in patients with similar clinical conditions. Registro Estudio: Registro Público Cubano de Ensayos Clínicos (RPCEC) ID: RPCEC00000134. Registered 20 July 2012.

Amaryllidaceae alkaloids as agents with protective effects against oxidative neural cell injury.

AIMS: Determine a relationship between the neuroprotective activity and the antioxidant capacity of the Amaryllidaceae alkaloids in a model of Glu excitotoxicity in rat cortical neurons. MATERIALS AND METHODS: Was evaluated several alkaloidal fractions isolated from Amaryllidaceae species, a family known to contain neuroprotective alkaloids, in a model of Glu excitotoxicity in rat cortical neurons. In addition, several mechanisms of antioxidant activity were used, and a theoretical study of the antioxidants was performed. KEY FINDINGS: The results of this study suggest that a possible neuroprotective mode of action of the alkaloidal fractions of Eucharis bonplandii (Kunth) Traub bulbs, Eucharis caucana Meerow bulbs, and Clivia miniata Regel leaves, is through their antioxidant activity and ability to stabilize free radicals generated from an excitotoxic process mediated by Glu. The chemical structure characterization and antioxidant activity of the fractions suggest that the phenol and enol groups in the structures of the alkaloids are critical for the stabilization of ROS and RNS. Additionally, the pair of free electrons on the N is spatially close to a hydroxyl group, which benefits the cleavage of this group and, consequently, the stabilization of the generated O. SIGNIFICANCE: The versatility of the structures of the studied Amaryllidaceae alkaloids suggests that they have potential as neuroprotective agents against an oxidative stimulus.

HDAC8 substrate selectivity is determined by long- and short-range interactions leading to enhanced reactivity for full-length histone substrates compared with peptides.

Histone deacetylases (HDACs) catalyze deacetylation of acetyl-lysine residues within proteins. To date, HDAC substrate specificity and selectivity have been largely estimated using peptide substrates. However, it is unclear whether peptide substrates accurately reflect the substrate selectivity of HDAC8 toward full-length proteins. Here, we compare HDAC8 substrate selectivity in the context of peptides, full-length proteins, and protein-nucleic acid complexes. We demonstrate that HDAC8 catalyzes deacetylation of tetrameric histone (H3/H4) substrates with catalytic efficiencies that are 40-300-fold higher than those for corresponding peptide substrates. Thus, we conclude that additional contacts with protein substrates enhance catalytic efficiency. However, the catalytic efficiency decreases for larger multiprotein complexes. These differences in HDAC8 substrate selectivity for peptides and full-length proteins suggest that HDAC8 substrate preference is based on a combination of short- and long-range interactions. In summary, this work presents detailed kinetics for HDAC8-catalyzed deacetylation of singly-acetylated, full-length protein substrates, revealing that HDAC8 substrate selectivity is determined by multiple factors. These insights provide a foundation for understanding recognition of full-length proteins by HDACs.

Active Site Metal Identity Alters Histone Deacetylase 8 Substrate Selectivity: A Potential Novel Regulatory Mechanism.

Histone deacetylase 8 (HDAC8) is a well-characterized member of the class I acetyl-lysine deacetylase (HDAC) family. Previous work has shown that the efficiency of HDAC8-catalyzed deacetylation of a methylcoumarin peptide varies depending on the identity of the divalent metal ion in the HDAC8 active site. Here we demonstrate that both HDAC8 activity and substrate selectivity for a diverse range of peptide substrates depend on the identity of the active site metal ion. Varied deacetylase activities of Fe(II)- and Zn(II)-HDAC8 toward an array of peptide substrates were identified using self-assembled monolayers for matrix-assisted laser desorption ionization (SAMDI) mass spectrometry. Subsequently, the metal dependence of deacetylation of peptides of biological interest was measured using an in vitro peptide assay. While Fe(II)-HDAC8 is generally more active than Zn(II)-HDAC8, the Fe(II)/Zn(II) HDAC8 activity ratio varies widely (from 2 to 150) among the peptides tested. These data provide support for the hypothesis that HDAC8 may undergo metal switching in vivo that, in turn, may regulate its activity. However, future studies are needed to explore the identity of the metal ion bound to HDAC8 in cells under varied conditions.

Therapeutic blockade of TCR signal transduction and co-stimulation in autoimmune disease.

Autoimmune diseases are initiated and maintained by presentation of self antigen through complex interactions between different cells of the immune system. In most autoimmune disorders, autoantigen-specific responses are induced by the activation of specific T cells with self peptides displayed on activated antigen presenting cells (APCs). These T cells may then activate and drive B cell responses that either initiate or contribute to chronic disease pathogenesis. In order to activate the T cell, two signals are required: T cell receptor (TCR) engagement by autoantigen presented in the context of self MHC class II and costimulation (CD28-CD80/CD86 interactions). Feedback must also be provided to the APC through MHC class II engagement by the TCR and through costimulatory events controlling T cell differentiation and effector function (CD154-CD40 interactions, among others). With this in mind, numerous strategies have been developed to block the engagement and activation of self-reactive cells. We review and discuss recent progress in understanding the efficacy and underlying molecular mechanisms of three separate immunotherapeutic strategies targeting the TCR and costimulatory molecules: i) blocking TCR signaling (using non-mitogenic anti-CD3 monoclonal antibody); ii) blocking CD28 costimulation (anti-B7 monoclonal antibody blockade); and iii) blocking CD40 engagement on APCs (anti-CD154 monoclonal antibody blockade).

Microglia are activated to become competent antigen presenting and effector cells in the inflammatory environment of the Theiler's virus model of multiple sclerosis.

Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD) is a well-characterized murine model of the chronic-progressive form of human multiple sclerosis (MS) characterized by the activation of myelin-specific autoreactive CD4 Th1 cells via epitope spreading. To gain an understanding of the potential role of central nervous system (CNS)-resident cells in the presentation of endogenous myelin epitopes, we determined the individual antigen presentation and effector potential of resident microglia vs. infiltrating macrophages in the CNS of mice with ongoing TMEV-IDD by performing functional analysis of these populations separated to high purity by flow cytometric sorting based on their level of CD45 expression. Unlike microglia from nai;ve mice, peptide-pulsed CD45(lo) microglia isolated at the onset of clinical disease were as efficient as CNS-infiltrating CD45(hi) macrophages in activating proliferation and IFN-gamma production by myelin-peptide specific Th1 cells. In contrast, during the chronic stages of TMEV-IDD, CNS-infiltrating macrophages were more highly activated than the resident microglia as reflected both by higher expression of cell surface molecules associated with APC function and enhanced functional ability of spinal cord-infiltrating macrophages to stimulate T cell proliferation in vitro. Interestingly, both microglia and infiltrating macrophages expressed similar profiles of effector molecules such as IL-1, IL-6, IL-12 p40, TNF-alpha, and iNOS. Collectively, this is the first report comparing the antigen-presenting phenotype and function of microglia and infiltrating macrophages in a virus-induced model of CNS demyelination demonstrating that the resident microglia are capable APCs and may play an important role in antigen presentation at the onset of clinical disease and contribute to effector myelin destruction.