Stochastic analysis of the VEGF receptor response curve

Recently, an analysis of the response curve of the vascular endothelial growth factor (VEGF) receptor and its application to cancer therapy was described in [T. Alarcón, and K. Page, J. R. Soc. Lond. Interface 4, 283–304 (2007)]. The analysis is significantly extended here by demonstrating that an alternative computational strategy, namely the Krylov FSP algorithm for the direct solution of the chemical master equation, is feasible for the study of the receptor model. The new method allows us to further investigate the hypothesis of symmetry in the stochastic fluctuations of the response. Also, by augmenting the original model with a single reversible reaction we formulate a plausible mechanism capable of realizing a bimodal response, which is reported experimentally but which is not exhibited by the original model. The significance of these findings for mechanisms of tumour resistance to antiangiogenic therapy is discussed.

Transglutaminases and receptor tyrosine kinases

Transglutaminases are confounding enzymes which are known to play key roles in various cellular processes. In this paper, we aim to bring together several pieces of evidence from published research and literature that suggest a potentially vital role for transglutaminases in receptor tyrosine kinases (RTK) signalling. We cite literature that confirms and suggests the formation of integrin:RTK:transglutaminase complexes and explores the occurrence and functionality of these complexes in a large fraction of the RTK family.

Pharmacological consequence of the A118G μ opioid receptor polymorphism on morphine-and fentanyl-mediated modulation of Ca2+ channels in humanized mouse sensory neurons

Background: The most common functional single nucleotide polymorphism of the human OPRM1 gene, A118G, has been shown to be associated with interindividual differences in opioid analgesic requirements, particularly with morphine, in patients with acute postoperative pain. The purpose of this study was to examine whether this polymorphism would modulate the morphine and fentanyl pharmacological profile of sensory neurons isolated from a humanized mouse model homozygous for either the 118A or 118G allele. Methods: The coupling of wild-type and mutant μ opioid receptors to voltage-gated Ca channels after exposure to either ligand was examined by employing the whole cell variant of the patch-clamp technique in acutely dissociated trigeminal ganglion neurons. Morphine-mediated antinociception was measured in mice carrying either the 118AA or 118GG allele. RESULTS:: The biophysical parameters (cell size, current density, and peak current amplitude potential) measured from both groups of sensory neurons were not significantly different. In 118GG neurons, morphine was approximately fivefold less potent and 26% less efficacious than that observed in 118AA neurons. On the other hand, the potency and efficacy of fentanyl were similar for both groups of neurons. Morphine-mediated analgesia in 118GG mice was significantly reduced compared with the 118AA mice. Conclusions: This study provides evidence to suggest that the diminished clinical effect observed with morphine in 118G carriers results from an alteration of the receptor's pharmacology in sensory neurons. In addition, the impaired analgesic response with morphine may explain why carriers of this receptor variant have an increased susceptibility to become addicted to opioids. © 2011 the American Society of Anesthesiologists, Inc. Lippincott Williams & Wilkins. Anesthesiology.

Investigation of the expression of the EphB4 receptor tyrosine kinase in prostate carcinoma

Background: The EphB4 receptor tyrosine kinase has been reported as increased in tumours originating from several different tissues and its expression in a prostate cancer xenograft model has been reported. Methods: RT-PCR, western blotting and immunohistochemical techniques were used to examine EphB4 expression and protein levels in human prostate cancer cell lines LNCaP, DU145 and PC3. Immunohistochemistry was also used to examine localisation of EphB4 in tissue samples from 15 patients with prostate carcinomas. Results: All three prostate cancer cell lines expressed the EphB4 gene and protein. EphB4 immunoreactivity in vivo was significantly greater in human prostate cancers as compared with matched normal prostate epithelium and there appeared to be a trend towards increased expression with higher grade disease. Conclusions: EphB4 is expressed in prostate cancer cell lines with increased expression in human prostate cancers when compared with matched normal tissue. EphB4 may therefore be a useful anti-prostate cancer target. © 2005 Lee et al., licensee BioMed Central Ltd.

Delta opioid-receptor function in the dorsal striatum plays a role in high levels of ethanol consumption in rats

Binge-like patterns of excessive drinking during young adulthood increase the propensity for alcohol use disorders (AUDs) later in adult life; however, the mechanisms that drive this are not completely understood. Previous studies showed that the δ-opioid peptide receptor (DOP-R) is dynamically regulated by exposure to ethanol and that the DOP-R plays a role in ethanol-mediated behaviors. The aim of this study was to determine the role of the DOP-R in high ethanol consumption from young adulthood through to late adulthood by measuring DOP-R-mediated [(35)S]GTPγS binding in brain membranes and DOP-R-mediated analgesia using a rat model of high ethanol consumption in Long Evans rats. We show that DOP-R activity in the dorsal striatum and DOP-R-mediated analgesia changes during development, being highest during early adulthood and reduced in late adulthood. Intermittent access to ethanol but not continuous ethanol or water from young adulthood leads to an increase in DOP-R activity in the dorsal striatum and DOP-R-mediated analgesia into late adulthood. Multiple microinfusions of naltrindole into the dorsal striatum or multiple systemic administration of naltrindole reduces ethanol consumption, and following termination of treatment, DOP-R activity in the dorsal striatum is attenuated. These findings suggest that DOP-R activity in the dorsal striatum plays a role in high levels of ethanol consumption and suggest that targeting the DOP-R is an alternative strategy for the treatment of AUDs.

The delta opioid receptor antagonist, SoRI-9409, decreases yohimbine stress-induced reinstatement of ethanol-seeking

A major problem in treating alcohol use disorders (AUDs) is the high rate of relapse due to stress and re-exposure to cues or an environment previously associated with alcohol use. Stressors can induce relapse to alcohol-seeking in humans or reinstatement in rodents. Delta opioid peptide receptors (DOP-Rs) play a role in cue-induced reinstatement of ethanol-seeking; however, their role in stress-induced reinstatement of ethanol-seeking is not known. The objective of this study was to determine the role of DOP-Rs in yohimbine-stress-induced reinstatement of ethanol-seeking. Male, Long-Evans rats were trained to self-administer 10% ethanol in daily 30-minute operant self-administration sessions using a FR3 schedule of reinforcement, followed by extinction training. Once extinction criteria were met, we examined the effects of the DOP-R antagonist, SoRI-9409 (0–5 mg/kg, i.p.) on yohimbine (2 mg/kg, i.p.) stress-induced reinstatement. Additionally, DOP-R-stimulated [35S]GTPS binding was measured in brain membranes and plasma levels of corticosterone (CORT) were determined. Pre-treatment with SoRI-9409 decreased yohimbine stress-induced reinstatement of ethanol-seeking but did not affect yohimbine-induced increases in plasma CORT levels. Additionally, yohimbine increased DOP-R-stimulated 35[S]GTPS binding in brain membranes of ethanol-trained rats, an effect that was inhibited by SoRI-9409. This suggests that the DOP-R plays an important role in yohimbine-stress-induced reinstatement of ethanol-seeking behavior, and DOP-R antagonists may be promising candidates for further development as a treatment for AUDs.