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Purpose: More than 15 years have passed since the first description of the unbound brain-to-plasma partition coefficient (Kp,uu,brain) by Prof. Margareta Hammarlund-Udenaes, which was enabled by advancements in experimental methodologies including cerebral microdialysis. Since then, growing knowledge and data continue to support the notion that the unbound (free) concentration of a drug at the site of action, such as the brain, is the driving force for pharmacological responses. Towards this end, Kp,uu,brain is the key parameter to obtain unbound brain concentrations from unbound plasma concentrations. Methods: To understand the importance and impact of the Kp,uu,brain concept in contemporary drug discovery and development, a survey has been conducted amongst major pharmaceutical companies based in Europe and the USA. Here, we present the results from this survey which consisted of 47 questions addressing: 1) Background information of the companies, 2) Implementation, 3) Application areas, 4) Methodology, 5) Impact and 6) Future perspectives. Results and conclusions: From the responses, it is clear that the majority of the companies (93%) has established a common understanding across disciplines of the concept and utility of Kp,uu,brain as compared to other parameters related to brain exposure. Adoption of the Kp,uu,brain concept has been mainly driven by individual scientists advocating its application in the various companies rather than by a top-down approach. Remarkably, 79% of all responders describe the portfolio impact of Kp,uu,brain implementation in their companies as 'game-changing'. Although most companies (74%) consider the current toolbox for Kp,uu,brain assessment and its validation satisfactory for drug discovery and early development, areas of improvement and future research to better understand human brain pharmacokinetics/pharmacodynamics translation have been identified. [ABSTRACT FROM AUTHOR]

Protein kinase C (PKC) directly phosphorylated the beta-adrenergic receptor kinase (BetaARK) and catalyzed activation through membrane translocation. This direct effect indicated a cross-talk between PKC and BetaARK. BetaARK was regulated by alpha1B-AR through PKC activation. Substrate availability, membrane attachment and phosphorylation-mediated membrane translocation conditioned BetaARK regulation.

A mechanism-based biomarker model of TNFα-response, including different external provocations of LPS challenge and test compound intervention, was developed. The model contained system properties (such as kt, kout), challenge characteristics (such as ks, kLPS, Km, LPS, Smax, SC50) and test-compound-related parameters (Imax, IC50). The exposure to test compound was modelled by means of first-order input and Michaelis–Menten type of nonlinear elimination. Test compound potency was estimated to 20 nM with a 70% partial reduction in TNFα-response at the highest dose of 30 mg·kg−1. Future selection of drug candidates may focus the estimation on potency and efficacy by applying the selected structure consisting of TNFα system and LPS challenge characteristics. A related aim was to demonstrate how an exploratory (graphical) analysis may guide us to a tentative model structure, which enables us to better understand target biology. The analysis demonstrated how to tackle a biomarker with a baseline below the limit of detection. Repeated LPS-challenges may also reveal how the rate and extent of replenishment of TNFα pools occur. Lack of LPS exposure-time courses was solved by including a biophase model, with the underlying assumption that TNFα-response time courses, as such, contain kinetic information. A transduction type of model with non-linear stimulation of TNFα release was finally selected. Typical features of a challenge experiment were shown by means of model simulations. Experimental shortcomings of present and published designs are identified and discussed. The final model coupled to suggested guidance rules may serve as a general basis for the collection and analysis of pharmacological challenge data of future studies. [ABSTRACT FROM AUTHOR]

Neurotrophins bind to two structurally unrelated receptors, the trk tyrosine kinases and the neurotrophin receptor p75NTR. Ligand activation of these two types of receptor can lead to opposite actions, in particular the prevention or activation of programmed cell death. Many cells co-express trk receptors and p75NTR, and we found that p75NTR was co-precipitated with trkA, trkB and trkC in cells transfected with both receptor types. Co-precipitation of p75NTR was not observed with the epidermal growth factor receptor. Experiments with deletion constructs of trkB (the most abundant trk receptor in the brain) and p75NTR revealed that both the extracellular and intracellular domains of trkB and p75NTR contribute to the interaction. Blocking autophosphorylation of trkB substantially reduced the interactions between p75NTR and trkB constructs containing the intracellular, but not the extracellular, domains. We also found that co-expression of p75NTR with trkB resulted in a clear increase in the specificity of trkB activation by brain-derived neurotrophic factor, compared with neurotrophin-3 and neurotrophin-4/5. These results indicate a close proximity of the two neurotrophin receptors within cell membranes, and suggest that the signalling pathways they initiate may interact soon after their activation. [ABSTRACT FROM AUTHOR]