Browsing by Subject "inhibition"

Now showing 1 - 5 of 5
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    Composite Functional Genetic and Comedication CYP2D6 Activity Score in Predicting Tamoxifen Drug Exposure Among Breast Cancer Patients
    (Wiley, 2010-04) Borges, Silvana; Desta, Zeruesenay; Jin, Yan; Faouzi, Azzouz; Robarge, Jason D.; Philip, Santosh; Nguyen, Anne; Stearns, Vered; Hayes, Daniel; Rae, James M.; Skaar, Todd C.; Flockhart, David A.; Li, Lang
    Accurate assessment of CYP2D6 phenotypes from genotype is inadequate in patients taking CYP2D6 substrate together with CYP2D6 inhibitors. A novel CYP2D6 scoring system is proposed that incorporates the impact of concomitant medications with the genotype in calculating the CYP2D6 activity score. Training (n = 159) and validation (n = 81) data sets were obtained from a prospective cohort tamoxifen pharmacogenetics registry. Two inhibitor factors were defined: 1 genotype independent and 1 genotype based. Three CYP2D6 gene scoring systems, and their combination with the inhibitor factors, were compared. These 3 scores were based on Zineh, Zanger, and Gaedigk's approaches. Endoxifen/NDM-Tam plasma ratio was used as the phenotype. The overall performance of the 3 gene scoring systems without consideration of CYP2D6-inhibiting medications in predicting CYP2D6 phenotype was poor in both the training set (R(2) = 0.24, 0.22, and 0.18) and the validation set (R(2) = 0.30, 0.24, and 0.15). Once the CYP2D6 genotype-independent inhibitor factor was integrated into the score calculation, the R(2) values in the training and validation data sets were nearly twice as high as the genotype-only scoring model: (0.44, 0.43, 0.38) and (0.53, 0.50, 0.41), respectively. The integration of the inhibitory effect of concomitant medications with the CYP2D6 genotype into the composite CYP2D6 activity score doubled the ability to predict the CYP2D6 phenotype. However, endoxifen phenotypes still varied substantially, even with incorporation of CYD2D6 genotype and inhibiting factors, suggesting that other, as yet unidentified factors must be involved in tamoxifen activation.
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    Decreased Prefrontal Activity During a Cognitive Inhibition Task Following Violent Video Game Play: A Multi-Week Randomized Trial
    (APA, 2019) Hummer, Tom A.; Kronenberger, William G.; Wang, Yang; Mathews, Vincent P.; Psychiatry, School of Medicine
    There is substantial evidence that exposure to violent media increases aggressive thoughts and behaviors, potentially due in part to alterations to inhibitory mechanisms mediated by prefrontal cortex. Past research has demonstrated that playing a violent video game for short periods decreases subsequent prefrontal activity during inhibition, yet the impact of long-term game play is unclear. To assess how extensive video game play impacts brain activity, young adult males (n = 49; ages 18–29) with limited video game experience performed a go/no-go task during fMRI for 3 consecutive weeks. Following a baseline scan, these men were randomly assigned to extensively play a violent video game (VG) or avoid all video game play (control) during the subsequent week. After 1 week, inhibition-related activity decreased in right inferior frontal gyrus and right cerebellum in the VG group, compared to the control sample, and self-reported executive functioning problems were higher. VG participants assigned to a second week of game play had similarly reduced bilateral prefrontal activity during inhibition, relative to the control group. However, VG participants assigned to avoid game play or play a cognitive training game during the second week demonstrated similar overall changes from baseline as the control group. This research provides preliminary evidence indicating how long-term video game play may impact brain function during inhibition, which may impair control of aggressive behavior.
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    Early Sexual Trauma Exposure and Neural Response Inhibition in Adolescence and Young Adults: Trajectories of Frontal Theta Oscillations During a Go/No-Go Task
    (Elsevier, 2019) Meyers, Jacquelyn; McCutcheon, Vivia V.; Pandey, Ashwini K.; Kamarajan, Chella; Subbie, Stacey; Chorlian, David; Salvatore, Jessica; Pandey, Gayathri; Almasy, Laura; Anokhin, Andrey; Bauer, Lance; Bender, Annah; Dick, Danielle M.; Edenberg, Howard J.; Hesselbrock, Victor; Kramer, John; Kuperman, Samuel; Agrawal, Arpana; Bucholz, Kathleen; Porjesz, Bernice; Biochemistry and Molecular Biology, School of Medicine
    Objective Trauma, particularly when experienced early in life, can alter neurophysiologic and behavioral development, thereby increasing risk for substance use disorders and related psychopathology. However, few studies have empirically examined trauma using well-characterized developmental samples that are followed longitudinally. Method The association of assaultive, non-assaultive, and sexual assaultive experiences before 10 years of age with developmental trajectories of brain function during response inhibition was examined by measuring electrophysiologic theta and delta oscillations during no-go and go conditions in an equal probability go/no-go task. Data were drawn from the Collaborative Study of the Genetics of Alcoholism (COGA) prospective cohort, composed of offspring from high-risk and comparison families who were 12 to 22 years old at enrollment, with follow-ups at 2-year intervals since 2004. In addition, other important predictors of neurophysiologic functioning (eg, substance use, impulsivity, and parental alcohol use disorders) were investigated. Moreover, associations of neurophysiologic functioning with alcohol and cannabis use disorder symptom counts and externalizing and internalizing psychopathology were examined. Results Individuals exposed to sexual assaultive trauma before 10 years of age had slower rates of change in developmental trajectories of no-go frontal theta during response inhibition. Importantly, effects remained significant after accounting for exposure to other traumatic exposures, such as parental history of alcohol use disorder and participants’ substance use, but not measures of impulsivity. Further, slower rates of change in no-go frontal theta adolescent and young adult development were associated with increased risk for alcohol use disorder symptoms and internalizing psychopathology, but not for cannabis use disorder symptoms or externalizing psychopathology. Conclusion Childhood sexual assault is associated with atypical frontal neurophysiologic development during response inhibition. This could reflect alterations in frontal lobe development, synaptic pruning, and/or cortical maturation involving neural circuits for inhibitory control. These same areas could be associated with increased risk for young adult alcohol use disorder symptoms and internalizing psychopathology. These findings support the hypothesis that changes in neurocognitive development related to early sexual trauma exposure could increase the risk for mental health and substance use problems in young adulthood.
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    Inhibition of the Aldehyde Dehydrogenase 1/2 Family by Psoralen and Coumarin Derivatives
    (ACS, 2017-03-23) Buchman, Cameron D.; Hurley, Thomas D.; Biochemistry and Molecular Biology, School of Medicine
    Aldehyde dehydrogenase 2 (ALDH2), one of 19 ALDH superfamily members, catalyzes the NAD+-dependent oxidation of aldehydes to their respective carboxylic acids. In this study, we further characterized the inhibition of four psoralen and coumarin derivatives toward ALDH2 and compared them to the ALDH2 inhibitor daidzin for selectivity against five ALDH1/2 isoenzymes. Compound 2 (Ki = 19 nM) binds within the aldehyde-binding site of the free enzyme species of ALDH2. Thirty-three structural analogs were examined to develop a stronger SAR profile. Seven compounds maintained or improved upon the selectivity toward one of the five ALDH1/2 isoenzymes, including compound 36, a selective inhibitor for ALDH2 (Ki = 2.4 μM), and compound 32, which was 10-fold selective for ALDH1A1 (Ki = 1.2 μM) versus ALDH1A2. Further medicinal chemistry on the compounds’ basic scaffold could enhance the potency and selectivity for ALDH1A1 or ALDH2 and generate chemical probes to examine the unique and overlapping functions of the ALDH1/2 isoenzymes.
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    Kinetic and pH Studies on Human Phenylethanolamine N-Methyltransferase
    (Elsevier, 2013-11) Wu, Qian; McLeish, Michael J.; Department of Chemistry & Chemical Biology, IU School of Science
    Phenylethanolamine N-methyltransferase (PNMT) catalyzes the conversion of norepinephrine (noradrenaline) to epinephrine (adrenaline) while, concomitantly, S-adenosyl-l-methionine (AdoMet) is converted to S-adenosyl-l-homocysteine. This reaction represents the terminal step in catecholamine biosynthesis and inhibitors of PNMT have been investigated, inter alia, as potential antihypertensive agents. At various times the kinetic mechanism of PNMT has been reported to operate by a random mechanism, an ordered mechanism in which norepinephrine binds first, and an ordered mechanism in which AdoMet binds first. Here we report the results of initial velocity studies on human PNMT in the absence and presence of product and dead end inhibitors. These, coupled with isothermal titration calorimetry and fluorescence binding experiments, clearly shown that hPNMT operates by an ordered sequential mechanism in which AdoMet binds first. Although the log V pH-profile was not well defined, plots of log V/K versus pH for AdoMet and phenylethanolamine, as well as the pKi versus pH for the inhibitor, SK&F 29661, were all bell-shaped indicating that a protonated and an unprotonated group are required for catalysis.