Influence of RARα gene on MDR1 expression and P-glycoprotein function in human leukemic cells

BACKGROUND: Multidrug resistance (MDR) phenotype of malignant cells is the major problem in the chemotherapy of neoplasia. The treatment of leukemia with retinoids is aimed on the induction of leukemic cells differentiation. However the interconnections between retinoid regulated differentiation of leukemic cells and regulation of MDR remains unclear. METHODS: Four lines of cultured leukemic cells of diverse types of differentiation were infected with RARα gene and stable transfectants were isolated. We investigated the differentiation of these cells as well as the expression of RARα and MDR1 genes and P-glycoprotein (Pgp, MDR protein) functional activity in these cells. RESULTS: All RARα transfected sublines demonstrated the increase in the quantity of RARα mRNA. All these sublines became more differentiated. Intrinsic activity of MDR1 gene (but not Pgp functional activity) was increased in one of the transfectants. All-trans-retinoic acid (ATRA) induced Pgp activity in two of three infectants to a larger extent than in parental cells. CONCLUSION: The data show that RARα regulates MDR1/ Pgp activity in human leukemic cells, in the first place, Pgp activity induced by ATRA. These results show that RARα overexpression in leukemic cells could result in MDR

Arc/Arg3.1 expression in the brain tissues during the learning process in Alzheimer's disease animal models

Introduction. Arc/Arg3.1 is a common marker of neuronal activation for learning and memorizing. Some experimental data show the Arc/Arg3.1 expression in the post-mitotic neurons of the neurogenic niches. At the same time, we still have to understand the importance of such an expression for neurogenesis induced by the learning or memorizing processes, in health and in disease. Objective: to evaluate the changes in Arc/Arg3.1 expression in the post-mitotic neurons and to assess the proliferative activity of the neurogenic niche cells in Alzheimer's disease animal models. Materials and methods. We divided the C57Bl/6В mice into 2 groups: experimental (n = 15) and control (n = 15). The experimental group were injected with the amyloid- oligomers 2535 in their CA1 hippocampal region while the control mice received normal saline injections in the same region. Passive Avoidance Test (PAT) was used to assess the cognitive functions from the day 9 after the intervention. One hour after each test session we collected the samples of brain tissues to immunohistochemically assess them for the Arc/Arg3.1 expression and PCNA cell proliferation marker. Results. At day 11 the count of Arc/Arg3.1+NeuN+ cells in the subgranular zone had significantly increased. In animal neurodegeneration models the 1st and 2nd PAT sessions were associated with a significant increase in Arc/Arg3.1+NeuN+ cells, although by the day 11 their count significantly decreased. The count of Arc/Arg3.1+ cells in the subventricular and subgranular zones had increased after the 3rd PAT session in the control group while in Alzheimer's disease animal models this was observed only after the 2nd PAT session. Preserved Arc/Arg3.1 expression in the subventricular zone is associated with the increased PCNA cell prolifera- tion marker expression. At the same time, the toxic effect of the amyloid- oligomers suppressed the cells' proliferative activity in the subgranular zone at day 9. Conclusions. Despite the toxic effect of the amyloid- oligomers 2535, the post-mitotic neurons of the neurogenic niches retained the ability to express Arc/Arg3.1 in vivo. The obtained results show a transient increase in sensitivity of the post-mitotic neurons of the neurogenic niches for the learning stimuli in the early stages of the Alzheimer-type neurodegeneration

Cognitive function and metabolic features in male Sprague-Dawley rats receiving high-fat and low-calorie diets

Background: Obesity is a risk factor for cognitive disorders. However, it is still unknown whether low-calorie diet will improve cognitive function in obese patients. Aim: To evaluate cognitive function and metabolic features in male Sprague-Dawley rats receiving high-fat and low-calorie diets. Materials and methods: The work was carried out on Sprague Dawley male rats (n = 32), which were divided into 2 groups with 16 animals in each group: Control (normal / low-calorie diet) and Obesity (high-fat diet). In 90 days the rats of the Control group were transferred to a low-calorie diet, the rats of the Obesity group continued to receive high-fat diet. To assess motor activity and cognitive functions at the end of the study (180 days), following behavioral tests were conducted: "open field", "tapering beam", "elevated plus-maze" (EPM) and "passive avoidance reaction". During the study glucose tolerance test were performed: at baseline (GTT 1) and in 30 days (GTT 2). Results: Obesity group rats gained weight significantly faster than the control animals (547.69 ± 11.32 g against 442.8 ± 19.8 g at study end, p = 0.0001). GTT 2 showed normal carbohydrate metabolism in control group, postprandial hyperglycemia in obesity group. Testing in the open field showed that the rats of the obesity group moved more actively across the installation area than the control ones: the total distance covered was 9.352 ± 0.932 m against 6.781 ± 0.951 m, p = 0.046. The results of a tapering beam test showed that the number of hind limb extrusions in obese rats significantly exceeded this parameter in control group (33.7 ± 3 vs. 15.7 ± 2.7, p = 0.0001), test time in both groups did not differ. When testing in EPM, there was no significant difference in any of the key test parameters between the groups. However, the number of looking out from the closed arms in animals of the obesity group was significantly higher than in the control group (4.19 ± 0.6 vs. 2.30 ± 0.58, p = 0.044). When testing the reproduction of conditional reactions of passive avoidance it was shown that after day 1 of the pain stimulation application the latent period of transition to the dark compartment in the obesity group was significantly higher than that of the control group (180.0 ± 0.0 vs. 128 86 ± 21.45, p = 0.008). This indicates a better preservation of the memorial trail compared to the "control" rats. By the end of the study 30% of animals in the control group died. Conclusions: Rats on high-fat diet were more active, less anxious and showed better results in training tests comparing to animals on low-calorie diet. Adherence to low-calorie diet may be harmful for cognitive functions

Morphological Changes in Neural Progenitors Derived from Human Induced Pluripotent Stem Cells and Transplanted into the Striatum of a Parkinson's Disease Rat Model

Introduction. Development of cell therapy for Parkinson's disease (PD) requires protocols based on transplantation of neurons derived from human induced pluripotent stem cells (hiPSCs) into the damaged area of the brain. Objective: to characterize neurons transplanted into a rat brain and evaluate neural transplantation efficacy using a PD animal model. Materials and methods. Neurons derived from hiPSCs (IPSRG4S line) were transplanted into the striatum of rats after intranigral injection of 6-hydroxydopamine (6-OHDA). Immunostaining was performed to identify expression of glial and neuronal markers in the transplanted cells within 224 weeks posttransplant. Results. 4 weeks posttransplant we observed increased expression of mature neuron markers, decreased expression of neural progenitor markers, and primary pro-inflammatory response of glial cells in the graft. Differentiation and maturation of neuronal cells in the graft lasted over 3 months. At 3 and 6 months we detected 2 graft zones: one mainly contained the transplanted neurons and the other human astrocytes. We detected human neurites in the corpus callosum and surrounding striatal tissue and large human tyrosine hydroxylase-expressing neurons in the graft. Conclusion. With graft's morphological characteristics identified at different periods we can better understand pathophysiology and temporal patterns of new dopaminergic neurons integration and striatal reinnervation in a rat PD model in the long-term postoperative period