No abstract

Alpha7 nicotinic acetylcholine receptors (nAChRs) play an important role in learning and memory and are promising targets for pharmacological cognitive enhancement. Memantine, an approved substance for Alzheimer’s disease treatment, is an antagonist of the N-Methyl-D-aspartate receptor (NMDAR) and also acts as an alpha7 nAChR antagonist. Here, we tested the interaction between an alpha7 nAChR agonist (PHA-543613) and memantine. Efficacy of memantine, PHA-543613, and their co-administration were investigated on the spatial working memory of rats using the spontaneous alternation paradigm in T-maze. Scopolamine-induced transient amnesia was used to model cognitive impairment. First, the dose-response relationship was assessed for memantine, and its lowest effective dose was found to be 0.1 mg/kg. Then, co-administration treatments with subeffective doses of the alpha7 nAChR agonist PHA-543613 and different doses of memantine were tested. The co-administration of subeffective drug doses significantly improved memory performance of the rats and reversed scopolamine-induced deficits. Interestingly, a higher than effective (0.3 mg/kg) dose of memantine did not increase performance in monotreatment, only in co-administration with PHA-543613. However, the co-administration of PHA-543613 did not further increase the efficacy of the previously effective monotreatment doses of memantine. Thus, the efficacy of memantine monotreatment and its co-administration with PHA-543613 converged to create a common ceiling effect, with an additive interaction found in the behavioral effects. These results suggest that memantine and PHA-543613 may exert their cognitive enhancer effects on the same target, possibly on the alpha7 nAChRs. Results also suggest possible benefits of a combination therapy with memantine and alpha7 nAChR agonists.

Introduction: Wilms-tumor 1 antigen (WT1) expression in podocytes has the important role of maintaining their integrity and glomerular function. Vimentin also plays a role in preserving podocyte function and in morphologic changes observed after injury. Corticotropin releasing factor (CRF) is important in stress and in maintaining homeostasis. According to our previous studies, tyrosine (Tyr) isoforms (meta- and ortho-Tyr) may play a role in the development of many diseases. Introduction: Wilms-tumor 1 antigen (WT1) expression in podocytes has the important role of maintaining their integrity and glomerular function. Vimentin also plays a role in preserving podocyte function and in morphologic changes observed after injury. Corticotropin releasing factor (CRF) is important in stress and in maintaining homeostasis. According to our previous studies, tyrosine (Tyr) isoforms (meta- and ortho-Tyr) may play a role in the development of many diseases. Methods: Our aim was to investigate the expression of WT1, vimentin and CRF in human kidney and in HEK 293 cell cultures. Histological and clinical feature of 42 FSGS patients were evaluated and compared to patients with thin-basement membrane as a control group. Cells were cultured in medium containing para-, meta-, and ortho-tyrosine, and their expression of WT1, vimentin, and CRF were determined by immunocytochemistry. Podocyte foot process effacement was investigated by electron microscope (EM). Results: The intensity of WT1 staining in glomeruli was the same in focal segmental glomerulosclerosis (FSGS) and control groups, but it was lower in the tubulointerstitium of FSGS patients. Vimentin was lower in glomeruli of FSGS patients (p=0.009), and it was higher in the tubulointerstitium compared to the control group (p=0.003). CRF intensity was lower in the glomeruli (p=0.002). Podocyte foot process effacement determined by electron microscope (EM) showed correlation with vimentin and CRF in glomeruli. WT1 staining intensity was lower in meta- and ortho-Tyr group (p=0.001; p=0.009). Vimentin was lower in the meta-Tyr group (p=0.001). Discussion: Our observations on kidney biopsy samples support that the reduction of WT1 and vimentin could be characteristic for FSGS. Our results on HEK cells suggest that meta- and ortho-tyrosine may play a role in the development of FSGS.