Analysis Of Drug Effects Research Articles

Identification of Ionizing Irradiation Damage Mitigators by Evaluation of Clonogenic Survival of Human Umbilical Cord Blood Progenitor Cells

Evaluation of the effectiveness of small molecule radiation protectors and mitigators requires in vitro assays for clonogenic survival and analyses of drug effects on apoptosis and DNA damage repair. Application of novel mitigators for potential use in normal tissue protection during clinical radiation therapy and radiation counter terrorism mandates animal testing which, in the LD 50/30 assay for the effects of TBI on the hematopoietic syndrome, involves significant expense. We tested the hypothesis that early evaluation of candidate drugs in human cord blood clonogenic assay could potentially identify drugs which, while effective in the murine system, might be ineffective in humans.

Immunotoxicity, Flow Cytometry, and Chemoinformatics: Review, Bibliometric Analysis, and New QSAR Model of Drug Effects Over Macrophages

Immunotoxicity, Flow Cytometry, and Chemoinformatics: Review, Bibliometric Analysis, and New QSAR Model of Drug Effects Over Macrophages

In Vitro Synergistic Interaction between DTA0100 and Radiation in Human Cancer Cell Lines

DTA0100 is a new catalytic inhibitor of the human DNA topoisomerase IIα that induces G2/M phase cell cycle arrest in human solid tumor cells lines from various malignancies. In our study, we investigated the effectiveness of the combined treatment of ionizing radiation with DTA0100 on the survival of three representative human solid tumor cell lines: HeLa (cervix), WiDr (colon) and SW1573 (non-small cell lung cancer). The concomitant treatment of DTA0100 and irradiation showed a synergistic and antagonistic effect in the three cell lines tested. A synergistic cytotoxic effect of the combination of DTA0100 and radiation was confirmed by the median drug effect analysis method. It was found that in those protocols where the drug was administered after radiation the most synergistic effect was achieved. Our study constitutes the first in vitro evidence for synergistic effects between DTA0100 and radiation. This combination therapy might thus be expected to be more effective than either treatment alone in patients with cervical, colon and non-small cell lung cancer cells.

Modulation of non‐voiding activity by the muscarinergic antagonist tolterodine and the β3‐adrenoceptor agonist mirabegron in conscious rats with partial outflow obstruction

Experimental urethral obstruction in rats alters micturition patterns with non-voiding activity (NVA) during filling cystometry, showing similarity to that observed in human detrusor overactivity. Several drug classes with therapeutic potential in overactive bladder in humans have been tested in this model in rats, rabbits or guinea pigs, but no detailed analysis of drug effects on cystometric patterns has been published. The present study uses a rat model of overactivity with partial bladder outflow obstruction (BOO) in combination with the procedures to analyse NVA to study the effects of the anticholinergic drug tolterodine and the novel β(3)-adrenoceptor agonist mirabegron. The current data for the first time show that NVA in rats with BOO is sensitive to both the muscarinergic antagonist tolterodine and the β(3)-adrenoceptor agonist mirabegron, but with clear differences between the two drugs: during progression of bladder filling, tolterodine affected both the amplitude and frequency of NVA whereas mirabegron affected primarily the frequency. In addition, tolterodine dose-dependently reduced voiding contractions, while mirabegron did not. A model is proposed to account for these observations where both agents act on a 'pacemaker-like' mechanism which is sensitive to cholinergic excitatory and beta-adrenergic inhibitory inputs. Such concepts could provide insights into the nature of overactive bladder and the site of action of key therapeutic drugs. To investigate the hypothesis that tolterodine and the β(3)-adrenoceptor agonist mirabegron exert their actions on the motor component of the motor/sensory system in the bladder wall: non-voiding activity (NVA). The present study used standard cystometric techniques and a conscious rat model of partial bladder outflow obstruction (BOO). A single dose of either tolterodine (0.01, 0.1 0.3 or 1.0 mg/kg) or mirabegron (0.03, 0.1, 0.3, 1.0 or 3.0 mg/kg) was given i.v. to each animal. In the dose ranges used, tolterodine reduced the voiding contraction amplitude, whereas mirabegron did not. Non-voiding activity consisted of small (<0.6 mmHg) and large (>0.6 mmHg) transients. As a fill progressed, both tolterodine and mirabegron reduced the cumulative activity of the large non-voiding contractions, but had little effect on the small transients. Tolterodine affected both the amplitude and frequency of NVA, whereas mirabegron affected primarily the frequency. Non-voiding activity is sensitive to muscarinergic antagonists and β(3)-adrenoceptor agonists, but there are clear differences between the two drugs. A model is proposed to account for these observations where both agents act on a 'pacemaker-like' mechanism with cholinergic excitatory and adrenergic inhibitory inputs. Such concepts may provide insights into the nature of overactive bladder and the site of action of key therapeutic drugs.

Celecoxib Enhances the Radiosensitizing Effect of 7-Hydroxystaurosporine (UCN-01) in Human Lung Cancer Cell Lines

7-Hydroxystaurosporine (UCN-01), a Chk1-specific inhibitor, showed promising in vitro and in vivo chemo- or radiosensitizing activity. However, there have been concerns about its limited therapeutic efficacy and risk of side effects. A method of enhancing the treatment efficacy of UCN-01 while not increasing its side effects on normal tissue may therefore be required to apply this drug in clinical settings. Celecoxib is a cyclooxygenase-2 (COX-2)-specific inhibitor that downregulates ataxia telangiectasia and rad3-related (ATR) protein, an upstream kinase of Chk1. In this study, we investigated whether the addition of celecoxib can potentiate the radiosensitizing effect of UCN-01. The cooperative radiosensitizing effects and the underlying molecular mechanisms of UCN-01 plus celecoxib were determined by clonogenic assay, tumor growth delay assay, flow cytometry, and Western blotting. Synergism of the three agents combined (UCN-01 plus celecoxib plus radiation) were evaluated using median drug effect analysis and drug-independent action model analysis. The combination of UCN-01 and celecoxib could induce synergistic cytotoxicity and radiosensitizing effects in in vitro and in vivo systems. The combination of both drugs also cooperatively inhibited IR-induced G(2)/M arrest, and increased the G(2) to mitotic transition. Combined treatment with UCN-01 and celecoxib can exert synergistically enhanced radiosensitizing effects via cooperative inhibition of the ionizing radiation-activated G(2) checkpoint. We propose that this combination strategy may be useful in clinical applications of UCN-01 for radiotherapy of cancer patients.

Central respiratory effects on motor nerve activities after organophosphate exposure in a working heart brainstem preparation of the rat

The impact of organophosphorus compound (OP) intoxication on the activity of central respiratory circuitry, causing acetylcholinesterase (AChE) inhibition and accumulation of acetylcholine in the respiratory brainstem circuits, is not understood. We investigated the central effect of the OP Crotylsarin (CRS) on respiratory network activity using the working heart brainstem preparation, which specifically allows for the analysis of central drug effects without changes in brainstem oxygenation possibly caused by drug effects on peripheral cardio-respiratory activity. Respiratory network activity was determined from phrenic and hypoglossal or vagal nerve activities (PNA, HNA, VNA). To investigate combined central and peripheral CRS effects hypo-perfusion was used mimicking additional peripheral cardiovascular collapse. Systemic CRS application induced a brief central apnea and complete AChE-inhibition in the brainstem. Subsequently, respiration was characterised by highly significant reduced PNA minute activity, while HNA showed expiratory related extra bursting indicative for activation of un-specified oro-pharyngeal behaviour. During hypo-perfusion CRS induced significantly prolonged apnoea. In all experiments respiratory activity fully recovered after 1 h. We conclude that CRS mediated AChE inhibition causes only transient central breathing disturbance. Apparently intrinsic brainstem mechanisms can compensate for cholinergic over activation. Nevertheless, combination of hypo-perfusion and CRS exposure evoke the characteristic breathing arrests associated with OP poisoning.

Abstract 5454: Drug effect analysis of methoxyamine through quantifying the drug on its therapeutic target

Abstract Methoxyamine (MX) is the first DNA base-excision-repair (BER) inhibitor evaluated in humans. MX potentiates the cytotoxicity of alkylating and antimetabolic agents by condensing with DNA apurinic/pymidinic (AP) sites which are produced through the removal of alkylated or abnormal nucleobases from DNA backbone by DNA glycosylases. The formation of AP-MX complex blocks the BER pathway, and hence reverses tumor resistance to the chemotherapeutic agents. The further repair of MX-bound DNA by topoisomerase II results in ds-DNA breaks, and induces tumor cell death. In this work, we developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantitative analysis of AP-MX complex released from MX-bound DNA by a multi-enzyme system. The enzyme-released AP-MX (i.e., deoxyribose-MX, or dR-MX) was first separated from the enzyme digestion matrix on a Hypercarb® column, and then quantitated by a triple quadrupole mass analyzer using multiple-reaction-monitoring (MRM) mode with a mass transition of m/z 164 &amp;gt; 117. The calibration curve which corresponds to 3.55 to 227 AP-MX complexes/107 bases was established using AP-MX calibrators obtained by serial dilution of DNA oligomer containing known amount of AP-MX complex in blank calf thymus DNA. The method developed has been applied to AP-MX analysis of DNA extracts from T98G cells treated with temozolomide with MX, and blood samples from an ongoing Phase I study of methoxyamine and temozolomide in patient with advanced solid tumors. The dose, AP-MX complex, and time profiles have been obtained. This method provides a quantitative measure of methoxyamine at its proposed target sites. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5454. doi:10.1158/1538-7445.AM2011-5454

Expression of p16 and Retinoblastoma Determines Response to CDK4/6 Inhibition in Ovarian Cancer

PD-0332991 is a selective inhibitor of the CDK4/6 kinases with the ability to block retinoblastoma (Rb) phosphorylation in the low nanomolar range. Here we investigate the role of CDK4/6 inhibition in human ovarian cancer. We examined the effects of PD-0332991 on proliferation, cell-cycle, apoptosis, and Rb phosphorylation using a panel of 40 established human ovarian cancer cell lines. Molecular markers for response prediction, including p16 and Rb, were studied using gene expression profiling, Western blot, and array CGH. Multiple drug effect analysis was used to study interactions with chemotherapeutic drugs. Expression of p16 and Rb was studied using immunohistochemistry in a large clinical cohort of ovarian cancer patients. Concentration-dependent antiproliferative effects of PD-0332991 were seen in all ovarian cancer cell lines, but varied significantly between individual lines. Rb-proficient cell lines with low p16 expression were most responsive to CDK4/6 inhibition. Copy number variations of CDKN2A, RB, CCNE1, and CCND1 were associated with response to PD-0332991. CDK4/6 inhibition induced G0/G1 cell cycle arrest, blocked Rb phosphorylation in a concentration-and time-dependent manner, and enhanced the effects of chemotherapy. Rb-proficiency with low p16 expression was seen in 97/262 (37%) of ovarian cancer patients and was independently associated with poor progression-free survival (adjusted relative risk 1.49, 95% CI 1.00-2.24, P = 0.052). PD-0332991 shows promising biologic activity in ovarian cancer cell lines. Assessment of Rb and p16 expression may help select patients most likely to benefit from CDK4/6 inhibition in ovarian cancer.

Use of DNA Microarray and Small Animal Positron Emission Tomography in Preclinical Drug Evaluation of RAF265, a Novel B-Raf/VEGFR-2 Inhibitor

Positron emission tomography (PET) imaging has become a useful tool for assessing early biologic response to cancer therapy and may be particularly useful in the development of new cancer therapeutics. RAF265, a novel B-Raf/vascular endothelial growth factor receptor-2 inhibitor, was evaluated in the preclinical setting for its ability to inhibit the uptake of PET tracers in the A375M(B-Raf(V600E)) human melanoma cell line. RAF265 inhibited 2-deoxy-2-[(18)F]fluoro-d-glucose (FDG) accumulation in cell culture at 28 hours in a dose-dependent manner. RAF265 also inhibited FDG accumulation in tumor xenografts after 1 day of drug treatment. This decrease persisted for the remaining 2 weeks of treatment. DNA microarray analysis of treated tumor xenografts revealed significantly decreased expression of genes regulating glucose and thymidine metabolism and revealed changes in apoptotic genes, suggesting that the imaging tracers FDG, 3-deoxy-3-[(18)F]fluorothymidine, and annexin V could serve as potential imaging biomarkers for RAF265 therapy monitoring. We concluded that RAF265 is highly efficacious in this xenograft model of human melanoma and decreases glucose metabolism as measured by DNA microarray analysis, cell culture assays, and small animal FDG PET scans as early as 1 day after treatment. Our results support the use of FDG PET in clinical trials with RAF265 to assess early tumor response. DNA microarray analysis and small animal PET studies may be used as complementary technologies in drug development. DNA microarray analysis allows for analysis of drug effects on multiple pathways linked to cancer and can suggest corresponding imaging tracers for further analysis as biomarkers of tumor response.

MentalSquares: A generic bipolar Support Vector Machine for psychiatric disorder classification, diagnostic analysis and neurobiological data mining

MentalSquares (MSQs)--an equilibrium-based dimensional approach is presented for the classification and diagnostic analysis of psychological conditions with Bipolar Disorders (BPDs) as an example. While a Support Vector Machine (SVM) is defined in Hilbert space. A MSQ can be considered as a generic SVM for improved classification. Different from the traditional categorical model of BPDs, the generic approach focuses on the balance of two poles of mental equilibrium. Preliminary results show that this new approach has a number of advantages over existing models. The generic model is analytically illustrated with public domain clinical examples and well-known empirical clinical knowledge. Its clinical and computerised operability is illustrated. Its potential of being a practical method for the classification and analysis of neurobiological patterns and drug effects is discussed.

Improved Visualization and Quantitative Analysis of Drug Effects Using Micropatterned Cells

To date, most HCA (High Content Analysis) studies are carried out with adherent cell lines grown on a homogenous substrate in tissue-culture treated micro-plates. Under these conditions, cells spread and divide in all directions resulting in an inherent variability in cell shape, morphology and behavior. The high cell-to-cell variance of the overall population impedes the success of HCA, especially for drug development. The ability of micropatterns to normalize the shape and internal polarity of every individual cell provides a tremendous opportunity for solving this critical bottleneck 1-2. To facilitate access and use of the micropatterning technology, CYTOO has developed a range of ready to use micropatterns, available in coverslip and microwell formats. In this video article, we provide detailed protocols of all the procedures from cell seeding on CYTOOchip micropatterns, drug treatment, fixation and staining to automated acquisition, automated image processing and final data analysis. With this example, we illustrate how micropatterns can facilitate cell-based assays. Alterations of the cell cytoskeleton are difficult to quantify in cells cultured on homogenous substrates, but culturing cells on micropatterns results in a reproducible organization of the actin meshwork due to systematic positioning of the cell adhesion contacts in every cell. Such normalization of the intracellular architecture allows quantification of even small effects on the actin cytoskeleton as demonstrated in these set of protocols using blebbistatin, an inhibitor of the actin-myosin interaction.

Improved Visualization and Quantitative Analysis of Drug Effects Using Micropatterned Cells

To date, most HCA (High Content Analysis) studies are carried out with adherent cell lines grown on a homogenous substrate in tissue-culture treated micro-plates. Under these conditions, cells spread and divide in all directions resulting in an inherent variability in cell shape, morphology and behavior. The high cell-to-cell variance of the overall population impedes the success of HCA, especially for drug development. The ability of micropatterns to normalize the shape and internal polarity of every individual cell provides a tremendous opportunity for solving this critical bottleneck (1-2). To facilitate access and use of the micropatterning technology, CYTOO has developed a range of ready to use micropatterns, available in coverslip and microwell formats. In this video article, we provide detailed protocols of all the procedures from cell seeding on CYTOOchip micropatterns, drug treatment, fixation and staining to automated acquisition, automated image processing and final data analysis. With this example, we illustrate how micropatterns can facilitate cell-based assays. Alterations of the cell cytoskeleton are difficult to quantify in cells cultured on homogenous substrates, but culturing cells on micropatterns results in a reproducible organization of the actin meshwork due to systematic positioning of the cell adhesion contacts in every cell. Such normalization of the intracellular architecture allows quantification of even small effects on the actin cytoskeleton as demonstrated in these set of protocols using blebbistatin, an inhibitor of the actin-myosin interaction.

Gender-based effect of statins on functional decline in amyotrophic lateral sclerosis

Recently an association between statins and the onset and more rapid disease course of amyotrophic lateral sclerosis (ALS) was reported, while other studies rejected such a link. The role of gender in that controversy is unclear. We evaluated the gender-specific effect of statins on the rate of functional decline in patients with ALS, based on data retrieved from the medical records of all ALS patients who participated in two previously reported clinical trials on the efficacy of topiramate and of celecoxib in ALS. The topiramate trial enrolled 294 patients, 28 (9.5%) of whom were statin users (20 males). The celecoxib trial enrolled 300 patients, 25 (8.3%) of whom were statin users (17 males). Statins had no effect on the functional decline in the celecoxib trial, but they did have a negative impact on disease course in the topiramate trial. When males and females were analyzed separately, the functional decline of females taking statins was significantly greater than that of males in both trials. Our results indicate that statins affect possibly negatively ALS progression among females but not males. They emphasize the need to consider gender in future analyses of drug effects.

Proteomics accelerating the identification of the target molecule of bioactive small molecules

Failures in many drug development programs in the past decades were related to unspecified mechanism of action and poor pharmacokinetic (PK) properties. Recent developments are focused on well defined targets, improved PK profiles, however, not much is known about off-target effects, especially those responsible for diminishing drug activity. Steadily increasing application of proteomics in drug development should expose clinically relevant proteins for the analysis of drug effects, to show what group of patients will respond and who should not be treated with an agent.

Drug effects analysis on cells using a high throughput microfluidic chip

Usually cell-based assay is performed using titer plates. Because of the large library of chemical compounds, robust and rapid methods are required to find, refine and test a potential drug candidate in an efficient manner. In this article, the drug effects analysis on human breast cancer cells with a droplet microfluidic chip is reported. Each droplet serves as a nanoliter-volume titer plate and contains a human breast cancer cell MDA-MB-231, Cytochalasin D drug solution and cell viability indicator such as Calcein AM, which emits cytoplasmic green fluorescence. The drug effects on each cell are monitored in real time using a fluorescence microscope and by analyzing the fluorescence image of each cell. Clear change of the cell shape and size has been observed after the drug treatment, which is similar to that of conventional petri dish technique, suggesting this approach is a potential viable technical platform for drug effect analysis and for high throughput drug screen and discovery.

Abstract 2391: Hsp90-Dependent Regulation of HIF and angiogenic potential in clear-cell renal cell carcinoma

Abstract Tumor vascularization is a critical component of cancer progression, malignancy, and metastasis and hypoxia inducible factor (HIF) is a key regulator of these processes. HIF transcriptional activity regulates numerous pro-angiogenic cytokines that act upon cancer cells and the surrounding tumor stroma to cooperatively stimulate tumor vascularization. HIF is constitutively activated in clear cell renal cell carcinoma (CCRCC), the most lethal and angiogenic type of kidney cancer, due to genetic or functional loss of the HIF-targeting VHL ubiquitin ligase protein. In the absence of VHL-dependent HIF degradation, pharmacologic targeting of HIF may be exploited as a means to suppress HIF-dependent signaling. HIF is also a client protein for Hsp90, a molecular chaperone regulating a number of substrates that support cancer progression. Hsp90 inhibitors possess anti-tumorigenic and anti-angiogenic properties, due in part to their ability to inhibit HIF function. However, clinical trials with the prototypic Hsp90 inhibitor 17-AAG have been unsuccessful in CCRCC and other solid tumors, highlighting the need to further evaluate the role of Hsp90 in CCRCC angiogenic processes and HIF signaling. Approach: We compared the molecular and functional effects of 3 Hsp90 inhibitors, using VHL replaced cells as HIF suppressed controls. We examined the prototypic Hsp90 inhibitor 17-AAG, a newer, more potent totally synthetic small molecule derivative (EC154), and LBH589, an HDAC inhibitor in clinical use that also impairs Hsp90 function. Our assays consisted of analysis of drug effects on 1) genome wide HIF ChIP and RT-PCR 2) cytokine profiles, 3) endothelial cell tubule assays, and 4) limited phospho-proteomic analysis of signaling proteins. Results: These inhibitors exhibit variable suppression of HIF target genes, illustrating the complexity associated with these pathways. Cytokine arrays indicated that while VEGF expression decreased in response to all drugs, a number of proteins unexpectedly increased. In addition, these changes did not always correlate with VHL-dependent HIF suppression. Although Hsp90 inhibitors initiate the destruction of a number of proteins and impact upon numerous signaling cascades, the protein-centric effects of Hsp90 inhibition in cancer cells remain unknown. To explore this, we utilized a commercial phosphoproteome array to examine the effects of Hsp90 inhibition upon the activation status of over 1300 key signaling proteins. Finally, to understand how alterations in these signaling profiles modulate angiogenic potential, conditioned medium from untreated cells, VHL replaced cells, or drug treated cells was evaluated in a tubule assay. Collectively, the results of these studies will further define the role of HIF in CCRCC tumor angiogenesis, add to our understanding of molecular events that contribute to clinical failure of Hsp90 inhibitors, and shed light on alternative approaches for CCRCC treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2391.

Abstract 3650: In Vitro and in vivo synergistic anticancer effect of HDAC inhibitor panobinostat (LBH589) plus zoledronic acid in human prostate, breast and multiple myeloma tumor models

Abstract Prostate cancer (PCa), multiple myeloma (MM) as well as triple-negative breast cancers (TNBCa) (lacking ER, PR, and ErbB2 receptor) are associated with aggressive behaviour, poor prognosis, and limited response to conventional chemotherapy as well as to molecular targeted drugs, in advanced disease. On this regards, the recent availability of agents able to regulate many signaling pathways, such as HDAC inhibitors (HDAC-Is) as well as bisphosphonates (BPs), can help to overcome the existence limited activity of anticancer strategies. The HDAC-I Panobinostat (LBH589) has shown significant preclinical and clinical anticancer activity in both haematological and solid malignancies, and is currently in phase III for relapsed MM. BPs, such as zoledronic acid (ZOL), inhibit osteoclast-mediated bone resorption and are indicated for the treatment of cancer bone metastasis. In addition a direct and indirect anticancer activity of ZOL in several preclinical models and clinical studies have been observed. In our study, we sought to define preclinically, the potential anticancer effect of Panobinostat in combination with ZOL in several cell models. We showed a potent synergistic antiproliferative effect of Panobinostat/ZOL treatment in PC3, LNCAP and DU145 PCa cells, independently of p53/KRAS status as well as androgen dependency, whatever schedule of administration (simultaneous vs sequential) we used, as demonstrated by median drug effect analysis calculating combination index (CI) according to the method of Chou and Talalay (CI&amp;lt;1). Similar results were obtained in MM cells (RPMI and U266 and LP1, KMS12BM, KMS21BM). Moreover, consistent preliminary results showed sequence-dependent synergistic/additive effect in TNBCa cells. We also demonstrated that the combination of Panobinostat and ZOL, compared to single agents treatment, increased apoptotic cell death as demonstrated by Annexin V-FITC staining, and PARP cleavage, in both PCa and MM cells. The oxidative injury may play a functional role in the observed increase cell death, because co-administration of the antioxidant N-acetyl-L-cystein blocked reactive oxygen species generation and apoptosis. Furthermore, a synergistic inhibition of cancer cell migration and invasion in the combination setting compared to single drug treatment were observed. At the molecular level the observed anticancer synergistic effect could be, at least in part, related to the ability of Panobinostat to downregulate the activation of p38MAPK induced by ZOL, which has been described as a mechanism of resistance to aminoBPs treatment. The synergistic anticancer effect of Panobinostat/ZOL combination was confirmed in vivo in PCa DU145 cells xenograft model, where we observed a marked inhibition of tumor growth in the combination-treated group compared to controls and single agents treated group. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3650.

Parametric approaches towards understanding the effects of the preferential D3 receptor agonist pramipexole on prepulse inhibition in rats

The preferential dopamine D3 receptor agonist pramipexole (PRA) disrupts prepulse inhibition (PPI) of acoustic startle, an operational measure of sensorimotor gating, in rats. Drug effects on PPI are sensitive to numerous experimental variables; proceeding with in-depth analyses of drug effects without a clear understanding of these variables is inefficient. The present studies characterized the impact on PRA-induced PPI deficits by a range of experimental parameters. As shown previously, PRA reduced both PPI and startle magnitude beginning 5–15 min post-injection; PRA effects on PPI were statistically significant through 35 min post-injection, while those on startle magnitude were still significant 65 min post-injection. PRA-induced PPI deficits were evident under conditions that matched startle magnitude in vehicle and PRA conditions and were independent of PRA-induced changes in prepulse-elicited motor activity. Additionally, PRA-induced PPI deficits did not differ significantly between uni- vs. cross-modal stimuli or between male vs. female rats, with no robust effect of estrous phase in females. These findings demonstrate that PRA effects on PPI are observed across several different experimental conditions and are dissociable from changes in startle magnitude or prepulse-elicited responses. Recommendations are made regarding “optimal” experimental conditions for studying the neurobiology of PRA-induced changes in PPI in rats.

Analysis of individual drug use as a time-varying determinant of exposure in prospective population-based cohort studies

In pharmaco-epidemiology, the use of drugs is the determinant of interest when studying exposure-outcome associations. The increased availability of computerized information about drug use on an individual basis has greatly facilitated analyses of drug effects on a population-based scale. It seems likely that many negative findings in the early days of pharmaco-epidemiology can be explained by non-differential misclassification because of too simple (yes/no) exposure measures. In this paper, the authors discuss the importance of an adequate definition of drug exposure in pharmaco-epidemiological research and how this time-varying determinant can be analyzed in cohort studies. To reduce the risk of non-differential misclassification, a precise definition of exposure is mandatory and it is important to distinguish the complete follow-up period of a population into mutually exclusive episodes of non-use, past use and current use for each individual. By analyzing exposure to drugs as a time-dependent variable in a Cox regression model, cohort studies with complete coverage of all filled prescriptions can provide us with valid and precise risk estimates of drug-outcome associations. However, such estimates may be biased in the presence of time-dependent confounders which are themselves affected by prior exposure.

Remarkable interference with telomeric function by a G-quadruplex selective bisantrene regioisomer

The use of small molecules able to induce and stabilize selected G-quadruplex arrangements can cause telomerase inhibition and telomere dysfunction in cancer cells, thus providing very selective therapeutic approaches. Effective stabilizers usually comprise a planar aromatic portion to grant effective stacking onto the G-quartet and positively charged side chains to exploit the highly negative charge density on the quadruplex grooves. Since the relative position of these two pharmacophoric moieties is expected to play an important role in DNA folding stabilization, we evaluated a series of anthracene derivatives substituted with one or two 4,5-dihydro-1 H-imidazol-2-yl-hydrazonic groups (the bisantrene side chain) at different positions of the aromatic system. Indeed, the various regioisomers showed distinct binding affinities for telomeric G-quadruplex, and the most effective was the 1,5 and 1,7 bis-substituted analogues. On turn, the 1,8 regioisomer was poorly effective. Interestingly, G-quadruplex binding is clearly related to telomerase inhibition in this class of compounds, thus confirming their ability to shift the nucleic acid conformational equilibrium upon binding and consequently produce interference with the telomere processing enzyme. Additionally, the 1,5 regioisomer was shown to inhibit telomerase activity at lower concentrations than those required to reduce tumor cell proliferation. Comparative analysis of drug effects in telomerase-positive and telomerase-negative cancer cells showed consistent cell growth impairment, as a consequence of activation of the senescence pathway, which was mainly attributable to anthracene-mediated telomere dysfunction.