Human target validation of phosphoinositide 3‐kinase (PI3K)β: effects on platelets and insulin sensitivity,using AZD6482 a novel PI3Kβ inhibitor

Nylander S, Kull B, Björkman JA, Ulvinge JC, Oakes N, Emanuelsson BM, Andersson M, Skärby T, Inghardt T, Fjellström O, Gustafsson D. Human target validation of phosphoinositide 3‐kinase (PI3K)β:effects on platelets and insulin sensitivity, using AZD6482 a novel PI3Kβ inhibitor. J Thromb Haemost 2012; 10: 2127–36. See also Jackson SP, Schoenwaelder SM. Antithrombotic phosphoinositide 3‐kinase β inhibitors in humans – a ‘shear’ delight! This issue, pp 2123–6. Summary. Background: Based on in vitro and animal data, PI3Kβ is given an important role in platelet adhesion and aggregation but its role in insulin signaling is unclear. Objective: To strengthen the PI3Kβ target validation using the novel, short‐acting inhibitor AZD6482. Methods and results: AZD6482 is a potent, selective and ATP competitive PI3Kβ inhibitor (IC₅₀ 0.01 μm ). A maximal anti‐platelet effect was achieved at 1 μm in the in vitro and ex vivo tests both in dog and in man. In dog, in vivo AZD6482 produced a complete anti‐thrombotic effect without an increased bleeding time or blood loss. AZD6482 was well tolerated in healthy volunteers during a 3‐h infusion. The ex vivo anti‐platelet effect and minimal bleeding time prolongation in the dog model translated well to data obtained in healthy volunteers. AZD6482 inhibited insulin‐induced human adipocyte glucose uptake in vitro (IC₅₀ of 4.4 μm ). In the euglycemic hyperinsulinemic clamp model, in rats, glucose infusion rate was not affected at 2.3 μm but reduced by about 60% at a plasma exposure of 27 μm . In man, the homeostasis model analysis (HOMA) index increased by about 10–20% at the highest plasma concentration of 5.3 μm . Conclusions: This is the first human target validation for PI3Kβ inhibition as anti‐platelet therapy showing a mild and generalized antiplatelet effect attenuating but not completely inhibiting multiple signaling pathways with an impressive separation towards primary hemostasis. AZD6482 at ‘supratherapeutic’ plasma concentrations may attenuate insulin signaling, most likely through PI3Kα inhibition.     

Stable size distribution of amyloid plaques over the course of Alzheimer disease

Amyloid β plaques are a key pathologic feature of Alzheimer disease (AD), but whether plaque sizes increase or stabilize over the course of AD is unknown. We measured the size distribution of total immunoreactive (10D5-positive) and dense-core (Thioflavin S-positive) plaques in the temporal neocortex of a large group of subjects with AD and age-matched plaque-bearing subjects without dementia to test the hypothesis that amyloid plaques continue to grow along with the progression of the disease. The size of amyloid β (10D5)-positive plaques did not differ between groups, whereas dense-core plaques from the group with AD were slightly larger than those from the group without dementia (～25%-30%, p = 0.01). Within the group with AD, dense-core plaque size did not independently correlate with duration of clinical disease (from 4 to 21 years, p = 0.68), whereas 10D5-positive plaque size correlated negatively with disease duration (p = 0.01). By contrast, an earlier age of symptom onset strongly predicted a larger postmortem plaque size; this effect was independent of disease duration and the presence of the APOE[Latin Small Letter Open E]4 allele (p = 0.0001). We conclude that plaques vary in size among patients, with larger size distributions correlating with an earlier age of onset, but plaques do not substantially increase in size over the clinical course of the disease.     

Dendrodendritic and dendrosomatic contacts between oculomotor and trochlear motoneurons of the frog, Rana esculenta

Gaze fixation requires very fast movements of the eye during body displacement. The morphological and physiological background of the very fine and continuous tuning of gaze fixation is not yet fully understood. In a previous study we have shown that the dendrites of oculomotor neurons form bundles which invade the trochlear nucleus, and vice versa, trochlear dendritic bundles invade the oculomotor nucleus. Earlier physiological observations demonstrating electrotonic coupling between dendrites of spinal motoneurons in the frog suggest a similar mechanism between the oculomotor and trochlear motoneurons. We studied a possible morphological basis of gaze fixation. The experiments were carried out on common water frogs, Rana esculenta. The trochlear and oculomotor nerves were cut, and their proximal stumps were labeled simultaneously with different retrograde fluorescent tracers. Using confocal laser scanning microscope we detected a large number of close contacts in both nuclei, the majority of them were dendrodendritic apposition. The distance between the adjacent profiles suggested close membrane appositions without intercalating glial or neuronal elements. At the ultrastructural level, the dendrodendritic and dendrosomatic contacts did not show any morphological specialization; the long membrane appositions may provide ephaptic interactions between the neighboring profiles. This electrotonic coupling between the oculomotor and trochlear nerve motoneurons may promote the co-activation of the muscles responsible for vertical eye movements.     

Endometrial perfusion across the normal human menstrual cycle assessed by laser Doppler fluxmetry

This study investigated variations in microvascular perfusion of human endometrium across the menstrual cycle, using a laser Doppler technique to assess red blood cell (RBC) flux. Endometrial RBC flux was monitored by laser Doppler fluxmetry via a fibre optic probe inserted transvaginally into the uteri of 19 conscious normal volunteer women, on four occasions at weekly intervals over one menstrual cycle. Regional variation in RBC flux was investigated in 16 surgical patients under general anaesthesia and in five excised uteri. Endometrial perfusion exhibited short-term temporal variations consistent with the cardiac cycle and often also showed vasomotion (5-12 cycles/min). Mean endometrial perfusion differed between phases of the menstrual cycle in conscious women, being highest during early proliferative and early follicular phases. There were no significant regional differences in local mean endometrial perfusion in anaesthetized patients. No evidence of endometrial ischaemia/reperfusion episodes was found in any subject using this technique. This study provides benchmark data of variations in RBC flux per unit volume of tissue in the luminal approximately 1 mm of endometrium, across the normal human menstrual cycle. Flux values were highest at times associated with endometrial growth and preparation for implantation, indicating that RBC flux may be a useful parameter for assessment of endometrial physiology.