Alterations In Key Components Research Articles

Age-dependent alterations in key components of the nigrostriatal dopaminergic system and distinct motor phenotypes.

The nigrostriatal dopaminergic (DA) system, which includes DA neurons in the ventral and dorsal tiers of the substantia nigra pars compacta (vSNc, dSNc) and DA terminals in the dorsal striatum, is critically implicated in motor control. Accumulating studies demonstrate that both the nigrostriatal DA system and motor function are impaired in aged subjects. However, it is unknown whether dSNc and vSNc DA neurons and striatal DA terminals age in similar patterns, and whether these changes parallel motor deficits. To address this, we performed ex vivo patch-clamp recordings in dSNc and vSNc DA neurons, measured striatal dopamine release, and analyzed motor behaviors in rodents. Spontaneous firing in dSNc and vSNc DA neurons and depolarization-evoked firing in dSNc DA neurons showed inverse V-shaped changes with age. But depolarization-evoked firing in vSNc DA neurons increased with age. In the dorsal striatum, dopamine release declined with age. In locomotor tests, 12-month-old rodents showed hyperactive exploration, relative to 6- and 24-month-old rodents. Additionally, aged rodents showed significant deficits in coordination. Elevating dopamine levels with a dopamine transporter inhibitor improved both locomotion and coordination. Therefore, key components in the nigrostriatal DA system exhibit distinct aging patterns and may contribute to age-related alterations in locomotion and coordination.

Pleiotropic consequences of metabolic stress for the major histocompatibility complex class II molecule antigen processing and presentation machinery

Hyperglycemia and hyperlipidemia are often observed in individuals with type II diabetes (T2D) and related mouse models. One dysmetabolic biochemical consequence is the non-enzymatic reaction between sugars, lipids, and proteins, favoring protein glycation, glycoxidation, and lipoxidation. Here, we identified oxidative alterations in key components of the major histocompatibility complex (MHC) class II molecule antigen processing and presentation machinery invivo under conditions of hyperglycemia-induced metabolic stress. These modifications were linked to epitope-specific changes in endosomal processing efficiency, MHC class II-peptide binding, and DM editing activity. Moreover, we observed some quantitative and qualitative changes in the MHC class II immunopeptidome of Ob/Ob mice on a high-fat diet compared with controls, including changes in the presentation of an apolipoprotein B100 peptide associated previously with T2D and metabolic syndrome-related clinical complications. These findings highlight a link between glycation reactions and altered MHC class II antigen presentation that may contribute to T2D complications.

PTEN Expression, Not Mutation Status in TSC1, TSC2, or mTOR, Correlates with the Outcome on Everolimus in Patients with Renal Cell Carcinoma Treated on the Randomized RECORD-3 Trial.

Genomic alterations in key components of PI3K/mTOR pathway have been proposed as candidate predictive markers for rapalog therapy in renal cell carcinoma (RCC). We tested this hypothesis in patients from a randomized phase II trial of everolimus versus sunitinib. Archival specimens collected at baseline were analyzed with targeted next-generation sequencing (NGS). Focus of interest were alterations in key PI3K pathway components. PTEN expression was assessed by IHC. Association between molecular findings and treatment outcomes was investigated; same associations were tested for 2 everolimus-treated trial cohorts in gastric and hepatocellular carcinoma (HCC). Among 184 everolimus-treated patients with RCC with NGS data, mutation rates in genes of interest were 6% (TSC1), 4.4% (TSC2), and 8.2% (mTOR); 44% harbored alterations in ≥1 PI3K pathway component. For subjects with presence versus absence of mutations in TSC1, TSC2, or mTOR progression-free survival (PFS) neither differed on univariate analysis (HR, 1.0; P = 0.895) nor on multivariate testing stratified by MSKCC risk group and other established prognostic factors (HR, 1.1; P = 0.806). Everolimus-treated patients with retained (n = 50) versus lost (n = 50) PTEN IHC expression had median PFS of 5.3 months versus 10.5 months (HR, 2.5; P < 0.001). Such differences were not seen with sunitinib (10.9 months vs. 10.3 months; HR, 0.8; P = 0.475). Molecular findings did not correlate with outcomes in gastric and HCC cohorts. Association between mutation status for TSC1/TSC2/mTOR and therapeutic outcome on everolimus was not confirmed. Clinically meaningful differences in PFS were seen based on PTEN expression by IHC, lost in >50% of patients.

Dopamine homeostasis: brain functional connectivity in reward deficiency syndrome.

Reward deficiency syndrome (RDS) was first proposed by Kenneth Blum in 1995 to provide a clinically relevant and predictive term for conditions involving deficits in mesocorticolimbic dopamine function. Genetic, molecular, and neuronal alterations in key components of this circuitry contribute to a reward deficit state that can drive drug-seeking, consumption, and relapse. Among the dysfunctions observed in RDS are dysregulated resting state networks, which recently have been assessed in detail in chronic drug users by, positron emission tomography, functional magnetic resonance imaging, and functional connectivity analysis. A growing number of studies are helping to determine the putative roles of dopamine and glutamatergic neurotransmission in the regulation of activity in resting state networks, particularly in brain reward circuitry affected in drug use disorders. Indeed, we hypothesize in the present review that loss of homeostasis of these systems may lead to 'unbalanced' functional networks that might be both cause and outcome of disrupted synaptic communication between cortical and subcortical systems essential for controlling reward, emotional control, sensation seeking, and chronic drug use.

Mitogen-Activated Protein Kinase Pathway: Genetic Analysis of 95 Adrenocortical Tumors

Mitogen-activated protein kinase (MAPK) pathway is often deregulated in adrenocortical tumors (ACT) but with no concrete data confirming alteration rate. The objective of this study was to evaluate genetic alterations in key components of MAPK pathway. We found one BRAF mutation (p.V600E) and four HRAS silent mutations. No alteration was found in NRAS, KRAS, EGFR genes. The patient carrying BRAF mutation was further characterized by investigating his biomolecular and clinico-pathological findings. Therefore, even if MAPK signaling is activated in ACT, our results suggest that genetic alterations do not seem to represent a frequent mechanism of ACT tumorigenesis.

Subchronic glucocorticoid receptor inhibition rescues early episodic memory and synaptic plasticity deficits in a mouse model of Alzheimer's disease.

The early phase of Alzheimer's disease (AD) is characterized by hippocampus-dependent memory deficits and impaired synaptic plasticity. Increasing evidence suggests that stress and dysregulation of the hypothalamo-pituitary-adrenal (HPA) axis, marked by the elevated circulating glucocorticoids, are risk factors for AD onset. How these changes contribute to early hippocampal dysfunction remains unclear. Using an elaborated version of the object recognition task, we carefully monitored alterations in key components of episodic memory, the first type of memory altered in AD patients, in early symptomatic Tg2576 AD mice. We also combined biochemical and ex vivo electrophysiological analyses to reveal novel cellular and molecular dysregulations underpinning the onset of the pathology. We show that HPA axis, circadian rhythm, and feedback mechanisms, as well as episodic memory, are compromised in this early symptomatic phase, reminiscent of human AD pathology. The cognitive decline could be rescued by subchronic in vivo treatment with RU486, a glucocorticoid receptor antagonist. These observed phenotypes were paralleled by a specific enhancement of N-Methyl-D-aspartic acid receptor (NMDAR)-dependent LTD in CA1 pyramidal neurons, whereas LTP and metabotropic glutamate receptor-dependent LTD remain unchanged. NMDAR transmission was also enhanced. Finally, we show that, as for the behavioral deficit, RU486 treatment rescues this abnormal synaptic phenotype. These preclinical results define glucocorticoid signaling as a contributing factor to both episodic memory loss and early synaptic failure in this AD mouse model, and suggest that glucocorticoid receptor targeting strategies could be beneficial to delay AD onset.

Abscisic acid (ABA) regulation of Arabidopsis SR protein gene expression.

Serine/arginine-rich (SR) proteins are major modulators of alternative splicing, a key generator of proteomic diversity and flexible means of regulating gene expression likely to be crucial in plant environmental responses. Indeed, mounting evidence implicates splicing factors in signal transduction of the abscisic acid (ABA) phytohormone, which plays pivotal roles in the response to various abiotic stresses. Using real-time RT-qPCR, we analyzed total steady-state transcript levels of the 18 SR and two SR-like genes from Arabidopsis thaliana in seedlings treated with ABA and in genetic backgrounds with altered expression of the ABA-biosynthesis ABA2 and the ABA-signaling ABI1 and ABI4 genes. We also searched for ABA-responsive cis elements in the upstream regions of the 20 genes. We found that members of the plant-specific SC35-Like (SCL) Arabidopsis SR protein subfamily are distinctively responsive to exogenous ABA, while the expression of seven SR and SR-related genes is affected by alterations in key components of the ABA pathway. Finally, despite pervasiveness of established ABA-responsive promoter elements in Arabidopsis SR and SR-like genes, their expression is likely governed by additional, yet unidentified cis-acting elements. Overall, this study pinpoints SR34, SR34b, SCL30a, SCL28, SCL33, RS40, SR45 and SR45a as promising candidates for involvement in ABA-mediated stress responses.

Abstract 723: Anticancer ERK kinase inhibitor screening with molecular imaging.

Abstract Extracellular signal-regulated kinase (ERK, also known as the 42-/44-kDa MAPK) signaling pathway controls cell growth, differentiation and survival. ERK is activated by dual phosphorylation on tyrosine and threonine residues (pERK) as a result of genetic alterations in key components of the ERK pathway or upstream activators, or in response to signals from a variety of cell surface receptors. This pro-survival pathway is often upregulated in tumors and is a target for cancer therapy. To screen for ERK inhibitors in small molecule library, an ERK reporter molecule was used to determine ERK kinase activity by measuring bioluminescence with a Xenogen IVIS Optical Imaging System. ERK kinase inhibition was confirmed with Western Blot for pERK to validate ERK reporter. Drug-like small molecule compound libraries NCI Approved Oncology Drug Set (total 2 Plates, 101 compounds) and NCI Diversity Set II (total 18 Plates, 1364 compounds) were screened with an ERK reporter expressing cell line BxPC3-MBP by using bioluminescent assay at different time points and different dosages. Then top 15 candidates were further tested for cell toxicity IC50, ERK kinase inhibition, EGFR kinase inhibition, and combinational treatment response with chemotherapy agents in normal cell MRC-5, colorectal cancer cell SW480, and non-small cell lung cancer cell H460 and Calu6. ERK kinase inhibitor candidate number 6 was found to inhibit ERK kinase activity in a dose-dependent manner and have relatively lower toxicity to normal cells than cancer cells. Clinical trials of Sorafenib (an established small molecular inhibitor of several Tyrosine protein kinases and Raf kinases) combined with Cisplatin and Etoposide on small cell lung cancer and non-small cell lung cancer showed not favorable so Etoposide was compared with its similar structure Teniposide in our combination treatment. Combinational treatments were tested here are ERK kinase inhibitor candidate/Sorafenib combined with Cisplatin and Etoposide/Teniposide. Our results demonstrated that comparing with Sorafenib, ERK kinase inhibitor candidate number 6 was more efficient in killing non-small cell lung cancer cells in combinational treatment with Teniposide and Cisplatin. This ERK kinase inhibitor candidate has shown considerable promise for further in vivo study and clinical development. Citation Format: Lanlan Zhou, Shengliang Zhang, David T. Dicker, Alnawaz Rehemtulla, Wafik S. El-Deiry. Anticancer ERK kinase inhibitor screening with molecular imaging. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 723. doi:10.1158/1538-7445.AM2013-723

Are Drosophila a Useful Model for Understanding the Toxicity of Inhaled Oxidative Pollutants: A Review

Oxidative atmospheric pollutants represent a significant stress and cause injury to both vertebrate and invertebrate species. In both, the biosurfaces of their respiratory apparatus are directly exposed to oxidizing pollutant-induced stresses. Respiratory-tract surfaces contain integrated antioxidant systems that appear to provide a primary defense against environmental insults caused by inhaled atmospheric reactive oxygen species (ROS) and reactive nitrogen species (RNS), whether gaseous or particulate. When the biosurface antioxidant defenses are overwhelmed, oxidative and nitrosative stress to the acellular and cellular components of the exposed biosurfaces can ensue via direct chemical reactions that lead to the induction of inflammatory, adaptive, injurious, and reparative processes. The study of model invertebrates (e.g., Drosophila) has a long history of yielding valuable insights into both fundamental biology and pathobiology. Mutants and/or transgenic insects, with specific alterations in key components of innate and/or adaptive antioxidant defense systems and immune genes, offer opportunities to dissect the complex systems that maintain respiratory tract surface defenses against environmental oxidants and the ensuing host responses. In this article, we use a comparative absfont approach to consider interactions of atmospheric oxidant pollutants with selected biosystems. We focused primarily on ozone (O3 ) as the pollutant, vertebrate and invertebrate respiratory tracts as the exposed biosystems, and nonenzymatic micronutrient antioxidants as significant contributors to overall antioxidant defense strategies. We present parallels among these diverse organisms with regard to their protective strategies against environmental atmospheric oxidants, with particular focus given to using the invertebrate Drosophila as a potentially useful model for vertebrate respiratory-tract responses to inhaled oxidants specifically and pollutants in general. We conclude that the insect respiratory system has considerable promise toward understanding novel aspects of vertebrate respiratory tract responses to inhaled oxidative environmental challenges.

Targeting the ERK pathway: novel therapeutics for thyroid cancer.

Over the past two decades significant progress has been made in elucidating the pathogenesis of thyroid cancer. The ongoing identification of mutations in cellular signaling pathways has revolutionized the field of thyroid cancer biology and has led to the development of novel new therapeutic agents. One of the signaling cascades implicated in the oncogenic process is the ERK pathway that normally functions to transmit mitogenic signals from the cell membrane to the nucleus. Genetic alterations of key components of this cascade, namely RET, Ras and Raf, are thought to result in constitutive activation of the pathway and subsequent thyroid tumorigenesis. Targeting of these components with pharmaceutical agents holds the potential of providing newer and more effective treatment modalities for thyroid cancer. Several such drugs are currently being developed to inhibit RET, Ras, Raf, as well as other factors impacted by the ERK pathway. These include a vast array of agents such as antisense compounds, small molecule inhibitors as well as inhibitors of farnesyl transferase, heat shock proteins, matrix metalloproteinases and histone deacetylases. Some of these drugs have already entered preclinical and clinical testing with promising anti-tumor effects. These as well as even newer agents may offer exciting possibilities for the future treatment of thyroid cancer.

Environmental oxidant pollutant effects on biologic systems: a focus on micronutrient antioxidant-oxidant interactions.

Oxidative atmospheric pollutants represent a significant source of stress to both terrestrial plants and animals. The biosurfaces of plants and surface-living organisms are directly exposed to these pollutant stresses. These surfaces, including respiratory tract surfaces, contain integrated antioxidant systems that would be expected to provide a primary defense against environmental threats caused by atmospheric reactive oxygen species. When the biosurface antioxidant defenses are overwhelmed, oxidative stress to the cellular components of the exposed biosurfaces can be expected, inducing inflammatory, adaptive, injurious, and reparative processes. Studies of mutants and/or transformed plants and insects, with specific alterations in key components of antioxidant defense systems, offer opportunities to dissect the complex systems that maintain surface defenses against environmental oxidants. In this article, we use a comparative approach to consider interactions of atmospheric oxidant pollutants with selected biosystems, with focus on O3 as the pollutant; plants, flies, skin, and lungs as the exposed biosystems; and nonenzymatic micronutrient antioxidants as significant contributors to overall antioxidant defense strategies of these varied biosystems. Parallelisms among several living organisms, with regard to their protective strategies against environmental atmospheric oxidants, are presented.