Pharmacological characterisation of the recombinant human CRF binding protein using a simple assay

The pharmacology of CP-154,526, a non-peptide antagonist of the CRH1 receptor: a review

Since CRH has been shown to mediate stress-induced physiological and behavioral changes, it has been hypothesized that CRH receptor antagonists may have therapeutic potential in disorders that involve excessive CRH activity. CP-154,526 and its close analog antalarmin are potent, brain-penetrable, selective nonpeptide CRH1 receptor antagonists that were discovered in an effort to develop compounds with efficacy in CNS disorders precipitated by stress. Since its discovery many investigators have used CP-154,526 as a tool to study the pharmacology of CRH and its receptors and to evaluate its therapeutic potential in a variety of CNS and peripheral disorders. Systemically-administered CP-154,526 has been demonstrated to antagonize CRH- and stress-induced neuroendocrine, neurochemical, electrophysiological, and behavioral effects. These findings support the hypothesis that CRH1 receptor antagonists may have therapeutic utility in a number of neuropsychiatric disorders. CP-154,526, as well as other CRH1 receptor antagonists that have since been discovered, have also shown activity in several preclinical models of anxiety, depression, and substance abuse, while having little effect on locomotor activity and motor function. Although these effects are on occasion inconsistent among different laboratories, clinical evaluation of CRH1 antagonists appears justified on the basis of these and clinical data implicating the involvement of CRH in several CNS disorders. The effects of CRH1 antagonists on cognition, neurodegeneration, inflammation, and the gastrointestinal system have not been as extensively characterized and additional studies will be necessary to evaluate their therapeutic potential in these areas.

The corticotropin-releasing factor family of peptides and CRF receptors: their roles in the regulation of energy balance

The corticotropin-releasing factor (CRF) system could play a significant role in the regulation of energy balance. This system, which includes CRF, CRF-related peptides and CRF receptors, is part of a huge network of cells connected to central and peripheral pathways modulating energy metabolism. CRF and CRF-related peptides, which elicit their effects through G-protein-coupled receptors known in mammals as CRF(1) receptor and CRF(2) receptor, are capable of strong anorectic and thermogenic effects. Also supporting a role for the CRF system in the regulation of energy balance are findings demonstrating alterations in this system in obese and food-deprived animals that concur to facilitate energy deposition. In recent years, great progress has been made in understanding the specific physiological roles of the CRF system. In that respect, the discovery of urocortins II and III, two endogenous ligands of the CRF(2) receptor, and the development of selective and long-acting antagonists for the CRF receptors, have led to a better comprehension of the role of the CRF system in the regulation of energy balance. Although there are still important unresolved issues in the field of CRF research, the progress made recently warrants investigations aimed at evaluating the CRF system as a potential target for anti-obesity drugs.

Selective stimulatory actions of corticotropin-releasing factor ligands on correlates of energy balance

Acute administration of corticotropin-releasing factor (CRF) results in anorexic and sympathomimetic effects that suggest efficacy in chronic models of energy balance. The present studies employed a broad spectrum energy balance indices in lean and genetically obese Zucker rats in order to fully characterize the pharmacological efficacy of CRF and a CRF binding protein (CRF-BP) ligand inhibitor, CRF(6-33), which is thought to liberate CRF from CRF-BP. Acute administration of CRF(6-33) significantly increased CRF(2) receptor density by 10% within the ventromedial hypothalamic (VMH) nucleus of Zucker lean rats and decreased density by 10% in Zucker obese rats. A single infusion of CRF(6-33) increased nonshivering thermogenesis by 25-30% as measured by proton conductance in brown adipose tissue of both lean and obese rats. Chronic CRF(6-33) infusion suppressed body weight gain and elevated core temperature irrespective of genotype while increasing motor activity in obese rats without altering heart rate or blood pressure. Taken together, these results document strain-dependent, long-term effects of a CRF-BP ligand inhibitor on a select subset of physiological and behavioral measures of increased energy expenditure.

Corticotropin-releasing factor (CRF) or CRF binding-protein ligand inhibitor administration suppresses food intake in mice and elevates body temperature in rats

Corticotropin-releasing factor (CRF) receptor agonist and CRF binding-protein (CRF-BP) ligand inhibitor peptides both activate CRF systems but exert very distinct functional profiles in animal models of arousal, energy balance and emotionality. The present studies were designed to extend the dissimilar efficacy profiles of central administration of a CRF agonist, r/h CRF(1-41), versus a CRF-BP ligand inhibitor, r/h CRF(6-33), into mouse and rat models of energy balance in order to further explore in vivo efficacy of these ligands in two separate animal species. In CD-1 mice, food intake was significantly attenuated 3 h after acute administration of CRF(1-41) (0.007-0.2 nmol), but not CRF(6-33). In obese Ob/Ob mice, both CRF(1-41) (0.007-0.2 nmol) and CRF(6-33) (0.02-2.3 nmol) significantly attenuated basal feeding over 3 h following acute peptide administration. In rats, CRF(1-41) (1 nmol) and CRF(6-33) (1.5-7.7 nmol) infusion significantly increased rectal temperature. In studies employing a telemetry apparatus, core temperature was also increased by CRF(1-41) (1 nmol) and CRF(6-33) (1.5 nmol), whereas only CRF(1-41) increased locomotor activity and heart rate. These results suggest that CRF receptor agonist administration is capable of producing a global profile of negative energy balance by reducing food intake in mice and increasing energy expenditure in rats. In contrast, CRF-BP ligand inhibitor administration appears to suppress food intake in a mouse strain selective manner and to elevate rectal and core temperature in rats without accompanying cardiovascular activation.

Pharmacological characterization of recombinant rat corticotropin releasing factor binding protein using different sauvagine analogs

Little is known on the structural ligand requirements for corticotropin-releasing factor binding protein (CRFBP) of the rat used as an important experimental animal. To obtain such information recombinant rat CRFBP was produced in stably transfected HEK 293 cells. The primary structure and posttranslational processing of purified rat CRFBP was established by peptide mapping using HPLC combined with mass spectrometric analysis. Rat CRFBP was pharmacologically characterized employing a competition binding assay with tritium-labeled rat urocortin. The rank order of declining affinity of various CRF analogs was urotensin-I, human/rat CRF (h/rCRF), rat urocortin, sauvagine (Svg), and ovine CRF in agreement with the rank order found for human CRFBP. In contrast to astressin, the CRF receptor 2-selective antagonist anti-sauvagine-30 did not show any detectable specific binding to rat CRFBP. The significance of residues 10 to 12 and 21 to 24 of Svg for its low affinity binding was established by changing these residues of Svg to those of h/rCRF. The corresponding residues 22 to 25 of h/rCRF represented the ARAE motif determined to be crucial for binding in agreement with reported data on human CRFBP. Residues 11 to 13 of CRF introduced into Svg also enhanced the affinity to rat CRFBP.

The role of corticotropin-releasing factor and urocortin in the modulation of ingestive behavior

Participation of the hypothalamo-pituitary-adrenocortical axis, and its primary brain trigger, corticotropin-releasing factor (CRF) in the control of ingestive behavior can be inferred from data suggesting that CRF and its homologue urocortin act in brain to limit appetite following administration in rodents. Moreover, levels of endogenous CRF, CRF(1)and CRF(2)receptors and CRF-binding protein, which sequesters CRF and urocortin, are altered by changes in nutritional status brought about by food restriction/repletion. Mediation of the anorexic effects of CRF and urocortin appear not to privilege CRF(1)receptors, unlike the anxiogenic effects of CRF which are primarily a consequence of CRF(1)receptor activation. Such fear-like consequences of CRF system activation constitute a non-specific mechanism whereby the emergence of behaviors incompatible with food intake may appear to suppress appetite without affecting hunger per se. However, enhanced appetite following administration of CRF receptor antagonists and the involvement of CRF systems in sexual appetite and drug-seeking behavior all suggest a role for CRF in ingestive behavior. In particular, available evidence suggests that physiologically relevant suppression of appetite may accompany CRF system activation occurring as a consequence of stressor exposure induced by nutrient imbalance, for example, or under conditions of excessive intake or consumption of unfamiliar foodstuffs.

Urocortin: slower dissociation than corticotropin releasing factor from the CRF binding protein

We report on a comparison of the kinetics of [125I][Tyr0]corticotropin releasing factor (CRF) and [125I][Tyr0]urocortin binding to the CRF binding protein (CRF-BP) at physiological temperature. The association rates of [125I][Tyr0]urocortin or [125I][Tyr0]CRF binding to the CRF-BP were similar. The half time of association for [125I][Tyr0]urocortin was 3.2 min and for [125I][Tyr0]CRF, 2.6 min. [125I][Tyr0]urocortin dissociated from the CRF-BP but the rate of dissociation was slower than for [125I][Tyr0]CRF. The half time for dissociation of [125I][Tyr0]urocortin was 131 min and for [125I][Tyr0]CRF, 64 min. This slower dissociation indicates that the CRF-BP may be more effective in clearing urocortin than CRF.