Hennariikka Koivisto

The impact of Bdnf gene deficiency to the memory impairment and brain pathology of APPswe/PS1dE9 mouse model of Alzheimer's disease.

Brain-derived neurotrophic factor (BDNF) importantly regulates learning and memory and supports the survival of injured neurons. Reduced BDNF levels have been detected in the brains of Alzheimer’s disease (AD) patients but the exact role of BDNF in the pathophysiology of the disorder remains obscure. We have recently shown that reduced signaling of BDNF receptor TrkB aggravates memory impairment in APPswe/PS1dE9 (APdE9) mice, a model of AD. The present study examined the influence of Bdnf gene deficiency (heterozygous knockout) on spatial learning, spontaneous exploratory activity and motor coordination/balance in middle-aged male and female APdE9 mice. We also studied brain BDNF protein levels in APdE9 mice in different ages showing progressive amyloid pathology. Both APdE9 and Bdnf mutations impaired spatial learning in males and showed a similar trend in females. Importantly, the effect was additive, so that double mutant mice performed the worst. However, APdE9 and Bdnf mutations influenced spontaneous locomotion in contrasting ways, such that locomotor hyperactivity observed in APdE9 mice was normalized by Bdnf deficiency. Obesity associated with Bdnf deficiency did not account for the reduced hyperactivity in double mutant mice. Bdnf deficiency did not alter amyloid plaque formation in APdE9 mice. Before plaque formation (3 months), BDNF protein levels where either reduced (female) or unaltered (male) in the APdE9 mouse cortex. Unexpectedly, this was followed by an age-dependent increase in mature BDNF protein. Bdnf mRNA and phospho-TrkB levels remained unaltered in the cortical tissue samples of middle-aged APdE9 mice. Immunohistological studies revealed increased BDNF immunoreactivity around amyloid plaques indicating that the plaques may sequester BDNF protein and prevent it from activating TrkB. If similar BDNF accumulation happens in human AD brains, it would suggest that functional BDNF levels in the AD brains are even lower than reported, which could partially contribute to learning and memory problems of AD patients.

Special lipid-based diets alleviate cognitive deficits in the APPswe/PS1dE9 transgenic mouse model of Alzheimer's disease independent of brain amyloid deposition ☆

Dietary fish oil, providing n3 polyunsaturated fatty acids like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), associates with reduced dementia risk in epidemiological studies and reduced amyloid accumulation in Alzheimer mouse models. We now studied whether additional nutrients can improve the efficacy of fish oil in alleviating cognitive deficits and amyloid pathology in APPswe/PS1dE9 transgenic and wild-type mice. We compared four isocaloric (5% fat) diets. The fish oil diet differed from the control diet only by substituted fish oil. Besides fish oil, the plant sterol diet was supplemented with phytosterols, while the Fortasyn diet contained as supplements precursors and cofactors for membrane synthesis, viz. uridine-monophosphate; DHA and EPA; choline; folate; vitamins B6, B12, C and E; phospholipids and selenium. Mice began the special diets at 5 months and were sacrificed at 14 months after behavioral testing. Transgenic mice, fed with control chow, showed poor spatial learning, hyperactivity in exploring a novel cage and reduced preference to explore novel odors. All fish-oil-containing diets increased exploration of a novel odor over a familiar one. Only the Fortasyn diet alleviated the spatial learning deficit. None of the diets influenced hyperactivity in a new environment. Fish-oil-containing diets strongly inhibited β- and γ-secretase activity, and the plant sterol diet additionally reduced amyloid-β 1-42 levels. These data indicate that beneficial effects of fish oil on cognition in Alzheimer model mice can be enhanced by adding other specific nutrients, but this effect is not necessarily mediated via reduction of amyloid accumulation.

chronic Pyruvate supplementation increases exploratory activity and Brain energy reserves in Young and Middle- aged Mice

Numerous studies have reported neuroprotective effects of pyruvate when given in systemic injections. Impaired glucose uptake and metabolism are found in Alzheimer’s disease (AD) and in AD mouse models. We tested whether dietary pyruvate supplementation is able to provide added energy supply to brain and thereby attenuate aging- or AD-related cognitive impairment. Mice received ~800 mg/kg/day Na-pyruvate in their chow for 2–6 months. In middle-aged wild-type mice and in 6.5-month-old APP/PS1 mice, pyruvate facilitated spatial learning and increased exploration of a novel odor. However, in passive avoidance task for fear memory, the treatment group was clearly impaired. Independent of age, long-term pyruvate increased explorative behavior, which likely explains the paradoxical impairment in passive avoidance. We also assessed pyruvate effects on body weight, muscle force, and endurance, and found no effects. Metabolic postmortem assays revealed increased energy compounds in nuclear magnetic resonance spectroscopy as well as increased brain glycogen storages in the pyruvate group. Pyruvate supplementation may counteract aging-related behavioral impairment, but its beneficial effect seems related to increased explorative activity rather than direct memory enhancement.

Lipid-based diets improve muscarinic neurotransmission in the hippocampus of transgenic APPSwe/PS1dE9 mice

Transgenic APPswe/PS1dE9 mice modeling Alzheimers disease demonstrate ongoing accumulation of β-amyloid fragments resulting in formation of amyloid plaques that starts at the age of 4-5 months. Buildup of β-amyloid fragments is accompanied by impairment of muscarinic transmission that becomes detectable at this age, well before the appearance of cognitive deficits that manifest around the age of 12 months. We have recently demonstrated that long-term feeding of trangenic mice with specific isocaloric fish oil-based diets improves specific behavioral parameters. Now we report on the influence of short-term feeding (3 weeks) of three isocaloric diets supplemented with Fortasyn (containing fish oil and ingredients supporting membrane renewal), the plant sterol stigmasterol together with fish oil, and stigmasterol alone on markers of cholinergic neurotransmission in the hippocampus of 5-month-old transgenic mice and their wild-type littermates. Transgenic mice fed normal diet demostrated increase in ChAT activity and attenuation of carbachol-stimulated GTP-γ(35)S binding compared to wild-type mice. None of the tested diets compared to control diet influenced the activities of ChAT, AChE, BuChE, muscarinic receptor density or carbachol-stimulated GTP-γ(35)S binding in wild-type mice. In contrast, all experimental diets increased the potency of carbachol in stimulating GTP-γ(35)S binding in trangenic mice to the level found in wild-type animals. Only the Fortasyn diet increased markers of cholinergic synapses in transgenic mice. Our data demonstrate that even short-term feeding of transgenic mice with chow containing specific lipid-based dietary supplements can influence markers of cholinergic synapses and rectify impaired muscarinic signal transduction that develops in transgenic mice.

Effects of intermediate frequency magnetic fields on male fertility indicators in mice

Abstract Human exposure to intermediate frequency (IF) fields is increasing due to new applications such as electronic article surveillance systems, wireless power transfer and induction heating cookers. However, limited data is available on effects of IF magnetic fields (MF) on male fertility function. This study was conducted to assess possible effects on fertility indicators from exposure to IF MF. Male C57BL/6J mice were exposed continuously for 5 weeks to 7.5 kHz MF at 12 and 120 &mgr;T. Sperm cells from cauda epididymis were analysed for motility, total sperm counts, and head abnormalities. Motile sperm cells were classified as progressive or non‐progressive. Testicular spermatid heads were counted as well. The body weight development and reproductive tissue weights were not affected. No exposure‐related differences were observed in sperm counts or sperm head abnormalities. Proportion of non‐motile cells was significantly decreased in the 120 &mgr;T group, and a corresponding increase was seen in the percentage of motile cells (significant in non‐progressive motile cells). In conclusion, no adverse effects on fertility indicators were observed. Increased sperm motility is an interesting finding that needs to be confirmed in further studies. HighlightsHuman exposure to intermediate frequency magnetic fields is increasing.Mice were exposed to 7.5 kHz magnetic fields to evaluate possible effects on male fertility.No adverse effects on fertility indicators were observed.Sperm motility was increased in the highest exposure group.

Behavioral testing of mice exposed to intermediate frequency magnetic fields indicates mild memory impairment

Human exposure to intermediate frequency magnetic fields (MF) is increasing due to applications like electronic article surveillance systems and induction heating cooking hobs. However, limited data is available on their possible health effects. The present study assessed behavioral and histopathological consequences of exposing mice to 7.5 kHz MF at 12 or 120 μT for 5 weeks. No effects were observed on body weight, spontaneous activity, motor coordination, level of anxiety or aggression. In the Morris swim task, mice in the 120 μT group showed less steep learning curve than the other groups, but did not differ from controls in their search bias in the probe test. The passive avoidance task indicated a clear impairment of memory over 48 h in the 120 μT group. No effects on astroglial activation or neurogenesis were observed in the hippocampus. The mRNA expression of brain-derived neurotrophic factor did not change but expression of the proinflammatory cytokine tumor necrosis factor alpha mRNA was significantly increased in the 120 μT group. These findings suggest that 7.5 kHz MF exposure may lead to mild learning and memory impairment, possibly through an inflammatory reaction in the hippocampus.

Special lipid-based diets alleviate cognitive deficits in the APPswe/PS1dE9 transgenic mouse model of Alzheimer's disease independent of brain amyloid deposition

cerebellum and thalamus were collected to measure exposure levels of test compounds by liquid chromatography/mass spectroscopy (LC-MS/MS). Results: ZW-104 concentrations in thalamus and cerebellum were dose dependently decreasing in all compound treated groups. The sigmoidal dose response curves for % a4ß2 receptor occupancy was reveals that ABT0594 is a potent compound which requires 0.001 mg/kg of dose to induce 50% receptor occupancy than other compounds. The linear increases in brain and plasma concentration were found for all compounds with respect to dose. Conclusions: The unlabelled ZW-104 was successfully employed for assessing in vivo receptor occupancy for neuronal nicotinic acetylcholine receptor containing a4ß2 in rat by using LC-MS/MS based method. The distribution of ZW-104 in rat brain was consistent with 18F-ZW-104 distribution in baboons. ZW-104 was found faster elimination, less nonspecific binding with high brain penetration than 2FA-85380.

Behavioural phenotypes in mice after prenatal and early postnatal exposure to intermediate frequency magnetic fields

Abstract Electromagnetic fields are ubiquitous in the environment. Human exposure to intermediate frequency (IF) fields is increasing due to applications like electronic article surveillance systems, wireless power transfer, and induction heating cooking hobs. However, there are limited data on possible health effects of exposure to IF magnetic fields (MF). In the present study, we set out to assess cognitive and behavioural effects of IF MF in mice exposed during prenatal and early postnatal periods. Pregnant female mice were exposed continuously to 7.5 kHz MFs at 12 and 120 &mgr;T, from mating until weaning of pups. Sham exposed pregnant mice were used as a control group. A behavioural teratology study was conducted on the male offspring at two months of age to detect possible effects on the developing nervous system. Body weight development did not differ between the exposure groups. The exposure did not alter spontaneous motor activity when exploring a novel cage or anxiety in novelty‐suppressed feeding or marble burying tests. Improved performance in the Rotarod task was observed in the 12 &mgr;T group, while the 120 &mgr;T exposure group swam more slowly than the sham exposed group in the Morris swim navigation task. However, indices of learning and memory (path length and escape latency during task acquisition and search bias during the probe test) did not differ between the exposure groups. Furthermore, the passive avoidance task did not indicate any impairment of long‐term memory over a 48 h interval in the exposed groups. In a post‐mortem histopathological analysis, there was no evidence for an effect of IF MF exposure on astroglial reactivity or hippocampal neurogenesis. The results suggest that the IF MF used did not have detrimental effects on spatial learning and memory or histological markers of tissue reaction. The two statistically significant findings that were observed (improved performance in the Rotarod task in the 12 &mgr;T group and decreased swimming speed in the 120 &mgr;T group) are likely to be chance findings, as they do not form an internally consistent, dose‐dependent pattern indicative of specific developmental effects. HighlightsHuman exposure to intermediate frequency magnetic fields (MF) is increasing.We exposed prenatal and early postnatal male mice to 7.5 kHz MFs at 12 and 120 &mgr;T.A behavioural teratology study focused on the developing nervous system.No consistent adverse effects were observed.

Genotoxicity of intermediate frequency magnetic fields in vitro and in vivo

ABSTRACT We assessed genotoxic effects of intermediate frequency magnetic fields (MF) in vitro and in vivo. Rat primary astrocytes were exposed for 24 h to a 7.5 kHz MF at a magnetic flux density of 30 or 300 &mgr;T. Male C57BL/6 J mice were exposed continuously for 5 weeks to a 7.5 kHz MF at 12 or 120 &mgr;T, and blood samples were collected for the genotoxicity assays. To evaluate possible co‐genotoxicity, the in vitro experiments included combined exposure with menadione (an agent that induces mitochondrial superoxide production and DNA damage) and methyl methanesulfonate (an alkylating agent). DNA damage and DNA repair (in vitro) were measured using the alkaline Comet assay and formation of micronuclei was assessed microscopically (in vivo) or using flow cytometry (in vitro). The results did not support genotoxicity or co‐genotoxicity of 7.5 kHz MFs at magnetic flux densities up to 300 &mgr;T in vitro or in vivo. On the contrary, there was some evidence that exposure to 7.5 kHz MFs might reduce the level of genetic damage. Strongest indication of any biological effects was obtained from measurements of relative cell number, which was significantly and consistently increased after MF exposure in all in vitro experiments. Health implications of this finding are unclear, but it suggests that 7.5 kHz MFs may stimulate cell proliferation or suppress cell death. HighlightsHuman exposure to intermediate frequency magnetic fields is increasing.7.5 kHz magnetic fields were not genotoxic in animals or in vitro.Magnetic field exposure did not enhance effects of genotoxic chemicals.There was some evidence of protection against genotoxicity.The number of cells was increased in the exposed cultures.