LAUSR

Objectives In addition to its role in hemostasis, vitamin K (VK) is involved in brain function through various proteins and sphingolipid metabolism. Warfarin (W), a widely prescribed anticoagulant drug, exerts its beneficial effect in coagulation by partially blocking the recycling of the vitamin. In previous studies, we provided evidence that, when administered in large doses, W leads to cognitive and exploratory behavior impairment, and alteration in the VK dependent proteins Gas6 and protein S (PS) and their downstream pro-survival extracellular signal-regulated (ERK) and serine-threonine (Akt) kinases pathways. In light of its widespread use as oral anticoagulant, the present study aimed to investigate the impact of W on cognition and behavior, Gas6 and PS and their signaling pathways when administered in doses comparable to those used in the clinical setting. Methods Male Wistar rats (n = 14/gp) were fed an AIN-93 based diet containing 750 mcg phylloquinone/kg/d and were randomly allocated to treatment with 0,1 mg W/kg/d (in drinking water) (W group) or not (C group), for 9 wks. Spatial memory (Morris Water Maze) and exploratory behavior (Open Field) were assessed. Gas6, PS, pAkt, pERK, caspases -3 and -12 (apoptosis), brain-derived neurotrophic factor (BDNF), and microglial CD11b/c protein (a marker of inflammation), were assessed by immunoblotting in hippocampus (HPP), frontal cortex (FC), and striatum (STR), three regions involved in cognition. VK contents were determined in these 3 brain regions by HPLC. Group difference was tested by unpaired Student t-test. Results Low dose W had no impact on brain VK concentrations, spatial memory, and exploratory behavior (all P > 0.05). In contrast, W treatment was associated with numerous cell-signaling modulations, namely increased PS, ERK and Akt activity, and caspase -3 and -12 expression, in HPP; increased BDNF in FC and STR; increased expression of CD11bc in STR, (all P < 0.05). Conclusions This study provides evidence that low dose W is not associated with cognitive and behavioral impairment despite numerous cell-signaling modulations that have the potential to be beneficial or detrimental to the brain. Whether these events represent compensatory mechanisms to maintain homeostasis deserves further investigation. Funding Sources Study funded by CIHR.