Chronic pravastatin but not atorvastatin treatment impairs cognitive function in two rodent models of learning and memory

Impact of micronutrients and nutraceuticals on cognitive function and performance in Alzheimer's disease

Alzheimer's disease (AD) is a major global health problem today and is the most common form of dementia. AD is characterized by the formation of β-amyloid (Aβ) plaques and neurofibrillary clusters, leading to decreased brain acetylcholine levels in the brain. Another mechanism underlying the pathogenesis of AD is the abnormal phosphorylation of tau protein that accumulates at the level of neurofibrillary aggregates, and the areas most affected by this pathological process are usually the cholinergic neurons in cortical, subcortical, and hippocampal areas. These effects result in decreased cognitive function, brain atrophy, and neuronal death. Malnutrition and weight loss are the most frequent manifestations of AD, and these are also associated with greater cognitive decline. Several studies have confirmed that a balanced low-calorie diet and proper nutritional intake may be considered important factors in counteracting or slowing the progression of AD, whereas a high-fat or hypercholesterolemic diet predisposes to an increased risk of developing AD. Especially, fruits, vegetables, antioxidants, vitamins, polyunsaturated fatty acids, and micronutrients supplementation exert positive effects on aging-related changes in the brain due to their antioxidant, anti-inflammatory, and radical scavenging properties. The purpose of this review is to summarize some possible nutritional factors that may contribute to the progression or prevention of AD, understand the role that nutrition plays in the formation of Aβ plaques typical of this neurodegenerative disease, to identify some potential therapeutic strategies that may involve some natural compounds, in delaying the progression of the disease.

A mild impairment in reversal learning in a bowl-digging substrate deterministic task but not other cognitive tests in the Dlg2+/- rat model of genetic risk for psychiatric disorder

Variations in the Dlg2 gene have been linked to increased risk for psychiatric disorders, including schizophrenia, autism spectrum disorders, intellectual disability, bipolar disorder, attention deficit hyperactivity disorder, and pubertal disorders. Recent studies have reported disrupted brain circuit function and behaviour in models of Dlg2 knockout and haploinsufficiency. Specifically, deficits in hippocampal synaptic plasticity were found in heterozygous Dlg2+/- rats suggesting impacts on hippocampal dependent learning and cognitive flexibility. Here, we tested these predicted effects with a behavioural characterisation of the heterozygous Dlg2+/- rat model. Dlg2+/- rats exhibited a specific, mild impairment in reversal learning in a substrate deterministic bowl-digging reversal learning task. The performance of Dlg2+/- rats in other bowl digging task, visual discrimination and reversal, novel object preference, novel location preference, spontaneous alternation, modified progressive ratio, and novelty-suppressed feeding test were not impaired. These findings suggest that despite altered brain circuit function, behaviour across different domains is relatively intact in Dlg2+/- rats, with the deficits being specific to only one test of cognitive flexibility. The specific behavioural phenotype seen in this Dlg2+/- model may capture features of the clinical presentation associated with variation in the Dlg2 gene.

Statins Use in Alzheimer Disease: Bane or Boon from Frantic Search and Narrative Review

Alzheimer’s disease (AD) was used to describe pre-senile dementia to differentiate it from senile dementia, which develops in the adult age group of more than 65 years. AD is characterized by the deposition of amyloid beta (Aβ) plaque and tau-neurofibrillary tangles (TNTs) in the brain. The neuropathological changes in AD are related to the deposition of amyloid plaques, neurofibrillary tangles, and progression of neuroinflammation, neuronal mitochondrial dysfunction, autophagy dysfunction, and cholinergic synaptic dysfunction. Statins are one of the main cornerstone drugs for the management of cardiovascular disorders regardless of dyslipidemia status. Increasing the use of statins, mainly in the elderly groups for primary and secondary prevention of cardiovascular diseases, may affect their cognitive functions. Extensive and prolonged use of statins may affect cognitive functions in healthy subjects and dementia patients. Statins-induced cognitive impairments in both patients and health providers had been reported according to the post-marketing survey. This survey depends mainly on sporadic cases, and no cognitive measures were used. Evidence from prospective and observational studies gives no robust conclusion regarding the beneficial or detrimental effects of statins on cognitive functions in AD patients. Therefore, this study is a narrative review aimed with evidences to the beneficial, detrimental, and neutral effects of statins on AD.

Sinomenine Attenuates Trimethyltin-Induced Cognitive Decline via Targeting Hippocampal Oxidative Stress and Neuroinflammation

Sinomenine is the main bioactive ingredient of the medicinal plant Sinomenium acutum with neuroprotective potential. This study was designed to assess beneficial effect of sinomenine in alleviation of trimethyltin (TMT)-induced cognitive dysfunction. TMT was administered i.p. (8 mg/kg, once) and sinomenine was daily given p.o. 1 h after TMT for 3 weeks at doses of 25 or 100 mg/kg. Cognitive performance was assessed in various behavioral tests. In addition, oxidative stress- and inflammation-associated factors were measured and histochemical evaluation of the hippocampus was conducted. Sinomenine at a dose of 100 mg/kg significantly and partially increased discrimination index in novel object recognition (NOR), improved alternation in short-term Y maze, increased step-through latency in passive avoidance paradigm, and also reduced probe trial errors and latency in the Barnes maze task. Moreover, sinomenine somewhat prevented inappropriate hippocampal changes of malondialdehyde (MDA), reactive oxygen species (ROS), protein carbonyl, nitrite, superoxide dismutase (SOD), tumor necrosis factor α (TNFα), interleukin 6 (IL 6), acetylcholinesterase (AChE) activity, beta secretase 1 (BACE 1) activity, and mitochondrial membrane potential (MMP) with no significant effect on glutathione (GSH), catalase, glutathione reductase, glutathione peroxidase, and myeloperoxidase (MPO). In addition, lower reactivity (IRA) for glial fibrillary acidic protein (GFAP) as an index of astrocyte activity was observed and loss of CA1 pyramidal neurons was attenuated following sinomenine treatment. This study demonstrated that sinomenine could lessen TMT-induced cognitive dysfunction which is partly due to its attenuation of hippocampal oxidative stress and neuroinflammation.

Paeonol Ameliorates Cognitive Deficits in Streptozotocin Murine Model of Sporadic Alzheimer's Disease via Attenuation of Oxidative Stress, Inflammation, and Mitochondrial Dysfunction

Intracerebroventricular (ICV) microinjection of diabetogenic drug streptozotocin (STZ) in rodents consistently produces a model of sporadic Alzheimer's disease (sAD) which is characterized by tau pathology and concomitant cognitive decline, insulin resistance, neuroinflammation, oxidative stress, and mitochondrial malfunction. Paeonol is an active phenolic component in some medicinal plants like Cortex Moutan with neuroprotective efficacy via exerting anti-inflammatory and anti-oxidative effects. This study was conducted to assess beneficial effect of paeonol in amelioration of cognitive deficits in ICV STZ rat model of sAD. STZ (3 mg/kg) was microinjected into the lateral ventricles on days 0 and 2, and paeonol was given p.o. at two doses of 25 (low) or 100 (high) mg/kg from day 0 (post-surgery) till day 24 post-STZ. Cognitive performance was evaluated in different tasks, and oxidative stress- and inflammation-related parameters were measured in addition to immunohistochemical assessment of glial fibrillary acidic protein (GFAP) as a marker of astrocytes. Paeonol at the higher dose ameliorated cognitive deficits in Barnes maze, novel object recognition (NOR) task, Y maze, and passive avoidance test. In addition, paeonol partially reversed hippocampal malondialdehyde (MDA), reactive oxygen species (ROS), total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase, glutathione reductase, tumor necrosis factor α (TNFα), interleukin 6 (IL-6), mitochondrial membrane potential (MMP), myeloperoxidase (MPO), and acetylcholinesterase (AChE) activity. Paeonol treatment was also associated with lower hippocampal immunoreactivity for GFAP. This study showed that paeonol can alleviate cognitive disturbances in ICV STZ rat model of sAD via ameliorating neuroinflammation, oxidative stress, mitochondrial dysfunction, and also through its attenuation of astrogliosis.

Diosgenin Attenuates Cognitive Impairment in Streptozotocin-Induced Diabetic Rats: Underlying Mechanisms

OBJECTIVE

Prolonged diabetes mellitus causes impairments of cognition and attentional dysfunctions. Diosgenin belongs to a group of steroidal saponins with reported anti-diabetic and numerous protective properties. This research aimed to assess the effect of diosgenin on beneficially ameliorating learning and memory decline in a rat model of type 1 diabetes caused by streptozotocin (STZ) and to explore its modes of action including involvement in oxidative stress and inflammation.

METHODS

Rats were assigned to one of four experimental groups, comprising control, control under treatment with diosgenin, diabetic, and diabetic under treatment with diosgenin. Diosgenin was given daily p.o. (40 mg/kg) for 5 weeks.

RESULTS

The administration of diosgenin to the diabetic group reduced the deficits of functional performance in behavioral tests, consisting of Y-maze, passive avoidance, radial arm maze, and novel object discrimination tasks (recognitive). Furthermore, diosgenin treatment attenuated hippocampal acetylcholinesterase activity and malon-dialdehyde, along with improvement of antioxidants such as superoxide dismutase and glutathione. Meanwhile, the hippocampal levels of inflammatory indicators, namely interleukin 6, nuclear factor-κB, toll-like receptor 4, tumor necrosis factor α, and astrocyte-specific biomarker glial fibrillary acidic protein, were lower and, on the other hand, tissue levels of nuclear factor (erythroid-derived 2)-related factor 2 were elevated upon diosgenin administration. Besides, the mushroom-like spines of the pyramidal neurons of the hippocampal CA1 area decreased in the diabetic group, and this was alleviated following diosgenin medication.

CONCLUSIONS

Taken together, diosgenin is capable of ameliorating cognitive deficits in STZ-diabetic animals, partly due to its amelioration of oxidative stress, inflammation, astrogliosis, and possibly improvement of cholinergic function in addition to its neuroprotective potential.

Deficiency of Endothelial Nitric Oxide Synthase (eNOS) Exacerbates Brain Damage and Cognitive Deficit in A Mouse Model of Vascular Dementia

Vascular Dementia (VaD) accounts for nearly 20% of all cases of dementia. eNOS plays an important role in neurovascular remodeling, anti-inflammation, and cognitive functional recovery after stroke. In this study, we investigated whether eNOS regulates brain damage, cognitive function in mouse model of bilateral common carotid artery stenosis (BCAS) induced VaD. Late-adult (6-8 months) C57BL/6J and eNOS knockout (eNOS-/-) mice were subjected to BCAS (n=12/group) or sham group (n=8/group). BCAS was performed by applying microcoils to both common carotid arteries. Cerebral blood flow (CBF) and blood pressure were measured. A battery of cognitive functional tests was performed, and mice were sacrificed 30 days after BCAS. Compared to corresponding sham mice, BCAS in wild-type (WT) and eNOS-/- mice significantly: 1) induces short term, long term memory loss, spatial learning and memory deficits; 2) decreases CBF, increases ischemic cell damage, including apoptosis, white matter (WM) and axonal damage; 3) increases blood brain barrier (BBB) leakage, decreases aquaporin-4 (AQP4) expression and vessel density; 4) increases microglial, astrocyte activation and oxidative stress in the brain; 5) increases inflammatory factor interleukin-1 receptor-associated kinase-1(IRAK-1) and amyloid beta (Aβ) expression in brain; 6) increases IL-6 and IRAK4 expression in brain. eNOS-/-sham mice exhibit increased blood pressure, decreased iNOS and nNOS in brain compared to WT-sham mice. Compared to WT-BCAS mice, eNOS-/-BCAS mice exhibit worse vascular and WM/axonal damage, increased BBB leakage and inflammatory response, increased cognitive deficit, decreased iNOS, nNOS in brain. eNOS deficit exacerbates BCAS induced brain damage and cognitive deficit.

Melatonin reverses cognitive deficits in streptozotocin-induced type 1 diabetes in the rat through attenuation of oxidative stress and inflammation

Uncontrolled diabetes mellitus (DM) is linked to attentional deficits and cognition deterioration. The neurohormone melatonin is an endogenous synchronizer of circadian rhythms with multiple protective properties. This research was designed to assess its effect against learning and memory decline in streptozotocin (STZ)-induced diabetic rats. Rats were assigned to control, melatonin-treated control, diabetic, and melatonin-treated diabetic groups. Melatonin was administered i.p. at a dose of 10 mg/kg/day for 47 days. Treatment of diabetic rats with melatonin reversed decline of spatial recognition memory in Y maze, performance of rats in novel object discrimination, and retention and recall in passive avoidance tasks. Furthermore, melatonin appropriately attenuated hippocampal malondialdehyde (MDA) and reactive oxygen species (ROS) and improved superoxide dismutase (SOD) activity and improved mitochondrial membrane potential (MMP) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) with no significant effect on nitrite, glutathione (GSH) and catalase activity. Besides, hippocampal level of acetylcholinesterase (AChE), glial fibrillary acidic protein (GFAP), nuclear factor-kappaB (NF-κB), interleukin 6 (IL-6) and tumor necrosis factor α (TNFα) decreased following melatonin treatment. There was also a reduction of dendritic spines of pyramidal neurons of hippocampal CA1 area in diabetic group that was significantly alleviated upon melatonin treatment. Melatonin could ameliorate learning and memory disturbances in diabetic rats through mitigation of cholinesterase activity, astrocytes, oxidative stress and inflammation and also via upregulation of some antioxidants in addition to its prevention of dendritic spine loss.

High dose simvastatin and rosuvastatin impair cognitive abilities of healthy rats via decreasing hippocampal neurotrophins and irisin

BACKGROUND

Statins are cholesterol lowering drugs that decrease the risk of cardiovascular events, but they are related with a few unfavorable symptoms in skeletal muscle including myopathy, and mild to moderate fatigue. Additionally, there has been discrepancies about the impacts of statins on brain and cognition. This study aimed to examine the impacts of two different statins, lipophilic simvastatin and hydrophilic rosuvastatin on cognitive functions in normal healthy rats. Simultaneously, we investigated the alterations of neurotropins and irisin levels in hippocampus and myokine levels in skeletal muscle.

METHODS

The rats were dosed with 88 mg kg body weight^-1 day^-1 simvastatin (n = 8), 150 mg kg body weight^-1 day^-1 rosuvastatin (n = 8) or vehicle (n = 8) for 18 days via oral gavage. After that behavioral assessment was performed and hippocampus and skeletal muscle samples were taken for the analysis of neurotrophins and irisin levels.

RESULTS

Locomotion and learning and memory functions were lower, but anxiety levels were higher in the simvastatin and rosuvastatin groups than in the control group (P < 0.05). Hippocampal neurotrophins and irisin levels were lower, but skeletal muscle brain-derived neurotrophic factor (BDNF) and irisin levels were higher in the simvastatin and rosuvastatin groups than in the control group (P < 0.05).

CONCLUSION

These findings suggest that high dose simvastatin and rosuvastatin impair cognitive functions via decreasing BDNF, NGF and irisin levels in the hippocampus.

HUCBC Treatment Improves Cognitive Outcome in Rats With Vascular Dementia

Background and purpose: Vascular dementia (VaD) is the second common cause of dementia after Alzheimer's disease in older people. Yet, there are no FDA approved drugs specifically for VaD. In this study, we have investigated the therapeutic effects of human umbilical cord blood cells (HUCBC) treatment on the cognitive outcome, white matter (WM) integrity, and glymphatic system function in rats subject to a multiple microinfarction (MMI) model of VaD. Methods: Male, retired breeder rats were subjected to the MMI model (800 ± 100 cholesterol crystals/300 μl injected into the internal carotid artery), and 3 days later were treated with phosphate-buffered saline (PBS) or HUCBC (5 × 10⁶, i.v.). Sham rats were included as naïve control. Following a battery of cognitive tests, rats were sacrificed at 28 days after MMI and brains extracted for immunohistochemical evaluation and Western blot analysis. To evaluate the glymphatic function, fluorescent tracers (Texas Red dextran, MW: 3 kD and FITC-dextran, MW: 500 kD) was injected into the cisterna magna over 30 min at 14 days after MMI. Rats (3-4/group/time point) were sacrificed at 30 min, 3 h, and 6 h, and the tracer movement analyzed using laser scanning confocal microscopy. Results: Compared to control MMI rats, HUCBC treated MMI rats exhibit significantly improved short-term memory and long-term memory exhibited by increased discrimination index in novel object recognition task with retention delay of 4 h and improved novel odor recognition task with retention delay of 24 h, respectively. HUCBC treatment also improves spatial learning and memory as measured using the Morris water maze test compared to control MMI rats. HUCBC treatment significantly increases axon and myelin density increases oligodendrocyte and oligodendrocyte progenitor cell number and increases Synaptophysin expression in the brain compared to control MMI rats. HUCBC treatment of MMI in rats significantly improves glymphatic function by reversing MMI induced delay in the penetration of cerebrospinal fluid (CSF) into the brain parenchyma via glymphatic pathways and reversing delayed clearance from the brain. HUCBC treatment significantly increases miR-126 expression in serum, aquaporin-4 (AQP4) expression around cerebral vessels, and decreases transforming growth factor-β (TGF-β) protein expression in the brain which may contribute to HUCBC induced improved glymphatic function. Conclusions: HUCBC treatment of an MMI rat model of VaD promotes WM remodeling and improves glymphatic function which together may aid in the improvement of cognitive function and memory. Thus, HUCBC treatment warrants further investigation as a potential therapy for VaD.

Deficiency of tPA Exacerbates White Matter Damage, Neuroinflammation, Glymphatic Dysfunction and Cognitive Dysfunction in Aging Mice

Tissue plasminogen activator (tPA) is a serine protease primarily involved in mediating thrombus breakdown and regulating catabolism of amyloid-beta (Aβ). The aim of this study is to investigate age-dependent decline of endogenous tPA and the effects of tPA decline on glymphatic function and cognitive outcome in mice. Male, young (3m), adult (6m) and middle-aged (12m) C57/BL6 (wild type) and tPA knockout (tPA^-/-) mice were subject to a battery of cognitive tests and white matter (WM) integrity, neuroinflammation, and glymphatic function were evaluated. Adult WT mice exhibit significantly decreased brain tPA level compared to young WT mice and middle-aged WT mice have significantly lower brain tPA levels than young and adult WT mice. Middle-aged WT mice exhibit significant neuroinflammation, reduced WM integrity and increased thrombin deposition compared to young and adult mice, and increased blood brain barrier (BBB) permeability and reduced cognitive ability compared to young WT mice. In comparison to adult WT mice, adult tPA^-/- mice exhibit significant BBB leakage, decreased dendritic spine density, increased thrombin deposition, neuroinflammation, and impaired functioning of the glymphatic system. Compared to age-matched WT mice, adult and middle-aged tPA^-/- mice exhibit significantly increased D-Dimer expression and decreased perivascular Aquaporin-4 expression. Compared to age-matched WT mice, young, adult and middle-aged tPA^-/- mice exhibit significant cognitive impairment, axonal damage, and increased deposition of amyloid precursor protein (APP), Aβ, and fibrin. Endogenous tPA may play an important role in contributing to aging induced cognitive decline, axonal/WM damage, BBB disruption and glymphatic dysfunction in the brain.

Trigonelline protects hippocampus against intracerebral Aβ(1-40) as a model of Alzheimer's disease in the rat: insights into underlying mechanisms

Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the most common phenotype of dementia. Trigonelline is an alkaloid found in medicinal plants such as fenugreek seeds and coffee beans with neuroprotective potential and according to existing evidences, a favorable agent for treatment of neurodegenerative disorders. In this study, the possible protective effect of trigonelline against intracerebral Aβ(1-40) as a model of AD in the rat was investigated. For induction of AD, aggregated A(1-40) (10 μg/2 휇l for each side) was bilaterally microinjected into the hippocampal CA1 area. Trigonelline was administered p.o. at a dose of 100 mg/kg. The results showed that trigonelline pretreatment of Aβ-microinjected rats significantly improves spatial recognition memory in Y maze and performance in novel object recognition (NOR) task, mitigates hippocampal malondialdehyde (MDA), protein carbonyl, lactate dehydrogenase (LDH), and improves mitochondrial membrane potential (MMP), glutathione (GSH), and superoxide dismutase (SOD) with no significant change of catalase activity, nitrite level, caspase 3 activity, and DNA fragmentation. Additionally, trigonelline ameliorated hippocampal levels of glial fibrillary acidic protein (GFAP), S100b, cyclooxygenase 2 (Cox2), tumor necrosis factor α (TNFα), and interleukin 6 (IL-6) with no significant alteration of inducible nitric oxide synthase (iNOS). In addition, trigonelline pretreatment prevented loss of hippocampal CA1 neurons in Aβ-microinjected group. Therefore, our results suggest that trigonelline pretreatment in Aβ model of AD could improve cognition and is capable to alleviate neuronal loss through suppressing oxidative stress, astrocyte activity, and inflammation and also through preservation of mitochondrial integrity.

Berberine ameliorates lipopolysaccharide-induced learning and memory deficit in the rat: insights into underlying molecular mechanisms

Systemic lipopolysaccharide (LPS) triggers neuroinflammation with consequent development of behavioral and cognitive deficits. Neuroinflammation plays a crucial role in the pathogenesis of neurodegenerative disorders including Alzheimer's disease (AD). Berberine is an isoquinoline alkaloid in Berberis genus with antioxidant and anti-inflammatory property and protective effects in neurodegenerative disorders. In this research, beneficial effect of this alkaloid against LPS-induced cognitive decline was assessed in the adult male rats. LPS was intraperitoneally administered at a dose of 1 mg/kg to induce neuroinflammation and berberine was given via gavage at doses of 10 or 50 mg/kg, one h after LPS, for 7 days. Treatment of LPS group with berberine at a dose of 50 mg/kg (but not at a dose of 10 mg/kg) improved spatial recognition memory in Y maze, performance in novel object recognition task (NORT), and prevented learning and memory dysfunction in passive avoidance tasks. Furthermore, berberine lowered hippocampal activity of acetylcholinesterase (AChE), malondialdehyde (MDA), protein carbonyl, activity of caspase 3, and DNA fragmentation and improved antioxidant capacity through enhancing glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase, and glutathione (GSH). Besides, berberine attenuated inflammation-related indices, as was evident by lower levels of nuclear factor-kappa B (NF-κB), toll-like receptor 4 (TLR4), tumor necrosis factor α (TNFα), and interleukin 6 (IL-6). Berberine also appropriately restored hippocampal 3-nitrotyrosine (3-NT), cyclooxygenase 2 (Cox 2), glial fibrillary acidic protein (GFAP), sirtuin 1, and mitogen-activated protein kinase (p38 MAPK) with no significant alteration of brain-derived neurotrophic factor (BDNF). In summary, berberine could partially ameliorate LPS-induced cognitive deficits via partial suppression of apoptotic cascade, neuroinflammation, oxido-nitrosative stress, AChE, MAPK, and restoration of sirtuin 1.

Substituted Aminobenzothiazole Derivatives of Tacrine: Synthesis and Study on Learning and Memory Impairment in Scopolamine-Induced Model of Amnesia in Rat

BACKGROUND

Currently, there is no conclusive cure for Alzheimer's disease (AD) and existing treatments mainly offer symptomatic relief. Dysfunction of the cholinergic system plays an important role in the pathogenesis of AD. Tacrine (1, 2, 3, 4-tetrahydroacridin-9-amine, III) was the first approved agent for the palliative therapy of AD but its use is associated with some complications. Development of novel multi target derivatives of Tacrine with lower complications is strongly warranted. In this study, new aminobenzothiazole (1-5, with many useful biological and pharmacological properties) analogues (IV-VIII) were synthesized by changing of amine moiety of III. Then, the effects of these new compounds on learning and memory impairment in scopolamine-induced model of amnesia were studied and the outcomes were compared with control and Tacrine groups in rat.

MATERIAL AND METHODS

The rats received Tacrine or its derivatives (IV-VIII) i.p. for two weeks at a dose of 10 mg/kg. For induction of amnesia, scopolamine at a dose of 1 mg/kg was daily administered i.p. started on day-8 till the end of the study. Behavioral experiments including Y-maze, novel object recognition (discrimination) and passive avoidance paradigms were conducted at week 2.

RESULTS

Data analysis showed that some Tacrine derivatives, especially VII with 2-amino, 6-nitrobenzothiazole moiety, could markedly and significantly improve alternation score, discrimination ratio and step through latency compared to control and Tacrine groups.

CONCLUSION

These findings indicated that some of these derivatives (especially compounds VI and VII) are capable to mitigate learning and memory deficits in scopolamine-induced model of amnesia in rats and may have potential benefit in management of patients with AD.

Cerebrolysin Reduces Astrogliosis and Axonal Injury and Enhances Neurogenesis in Rats After Closed Head Injury

BACKGROUND

Cerebrolysin is a neuropeptide preparation with neuroprotective and neurotrophic properties. Our previous study demonstrates that cerebrolysin significantly improves functional recovery in rats after mild traumatic brain injury (mTBI).

OBJECTIVE

To determine histological outcomes associated with therapeutic effects of cerebrolysin on functional recovery after TBI.

METHODS

In this prospective, randomized, blinded, and placebo-controlled study, adult Wistar rats with mild TBI induced by a closed head impact were randomly assigned to one of the cerebrolysin dose groups (0.8, 2.5, 7.5 mL/kg) or placebo, which were administered 4 hours after TBI and then daily for 10 consecutive days. Functional tests assessed cognitive, behavioral, motor, and neurological performance. Study end point was day 90 after TBI. Brains were processed for histological tissue analyses of astrogliosis, axonal injury, and neurogenesis.

RESULTS

Compared with placebo, cerebrolysin significantly reduced amyloid precursor protein accumulation, astrogliosis, and axonal damage in various brain regions and increased the number of neuroblasts and neurogenesis in the dentate gyrus. There was a significant dose effect of cerebrolysin on functional outcomes at 3 months after injury compared with saline treatment. Cerebrolysin at a dose of ⩾0.8 mL/kg significantly improved cognitive function, whereas at a dose of ⩾2.5 mL/kg, cerebrolysin also significantly improved sensorimotor function at various time points. There were significant correlations between multiple histological and functional outcomes 90 days after mTBI.

CONCLUSIONS

Our findings demonstrate that cerebrolysin reduces astrogliosis and axonal injury and promotes neurogenesis, which may contribute to improved functional recovery in rats with mTBI.

Prospective, randomized, blinded, and placebo-controlled study of Cerebrolysin dose-response effects on long-term functional outcomes in a rat model of mild traumatic brain injury

OBJECTIVE

Cerebrolysin is a neuropeptide preparation that mimics the properties of neurotrophic factors and has had beneficial effects in the treatment of neurodegenerative diseases, stroke, and traumatic brain injury (TBI). To further evaluate treatment schemes, the authors assessed the dose-response of Cerebrolysin on functional improvement in a rat model of mild TBI (mTBI).

METHODS

This dose-response study was a prospective, randomized, blinded, and placebo-controlled preclinical experiment. Male Wistar adult rats, subjected to mTBI induced by a closed head impact, were treated randomly with 0 (saline as placebo), 0.8, 2.5, or 7.5 ml/kg of Cerebrolysin 4 hours after mTBI and daily for a total of 10 consecutive days. A battery of cognitive and sensorimotor functional tests was performed over 90 days.

RESULTS

The primary outcome was functional improvement over the 90 days; animal weight and death were the secondary and safety outcomes, respectively. A significant (p < 0.001) dose effect of Cerebrolysin on cognitive recovery 3 months after injury was found. Cerebrolysin at a dose of ≥ 0.8 ml/kg significantly (p < 0.001) improved cognitive outcome. The higher dose (7.5 ml/kg) resulted in significantly better cognitive recovery than the lowest doses (0.8 ml/kg) but not relative to the 2.5-ml/kg dose. Cerebrolysin at a dose of 2.5 or 7.5 ml/kg also caused different onset times of significant improvement in sensorimotor function. No differences in body weight or mortality rate among the groups were found.

CONCLUSIONS

This preclinical randomized, placebo-controlled, and blinded study with a clinically relevant treatment scheme revealed that Cerebrolysin at doses of 0.8–7.5 ml/kg, administered 4 hours after mTBI and then once daily for a total of 10 consecutive days, improved functional outcomes 3 months after injury. A dose of 2.5 ml/kg is likely an optimal dose for the treatment of experimental mTBI.

Influence of Sex on Cognition and Peripheral Neurovascular Function in Diabetic Mice

Cognition impairment and peripheral neuropathy (DPN) are two major complications of diabetes. The aim of the present study is to investigate the effect of sex differences on cognition and DPN in diabetic mice. Male and female BKS.Cg-m+/+Leprdb/J (db/db) and db/m mice were used. At ages of 20 and 30 weeks, all animals were subjected to learning, memory and neurological function tests. Regional blood flow in footpad and sciatic nerves were measured using laser Doppler flowmetry. Our data showed that male db/db mice aged 20 weeks and 30 weeks spent significantly more time to locate the hidden platform in the correct quadrant and spent significantly less time exploring the cage with a new stranger mouse compared to aged-matched female db/db mice. Electrophysiological recordings showed that male db mice aged 30 weeks had significantly reduced motor and sensory nerve conduction velocity compared with females. Hot plate and tactile allodynia tests revealed that males exhibited significantly higher thermal and mechanical latency than females. Male db mice aged 30 weeks displayed significantly reduced blood perfusion in sciatic nerve and footpad tissues compared with females. In addition, compared with male and female non-diabetic db/m mice, db/db mice exhibited increased time spent on locating the hidden platform, decreased time spent on exploring the novel odor bead and an unfamiliar mouse, as well as showed significantly lower levels of blood flow, lower velocity of MCV and SCV, higher thermal and mechanical latencies. Blood glucose levels and body weight were not significantly different between male and female diabetic animals (age 30 weeks), but male db mice showed a higher serum total cholesterol content. Together, our data suggest that males develop a greater extent of diabetes-induced cognition deficits and peripheral neurovascular dysfunction than females.

A Small Molecule Spinogenic Compound Enhances Functional Outcome and Dendritic Spine Plasticity in a Rat Model of Traumatic Brain Injury

The tetra (ethylene glycol) derivative of benzothiazole aniline (SPG101) has been shown to improve dendritic spine density and cognitive memory in the triple transgenic mouse model of Alzheimer disease (AD) when administered intraperitoneally. The present study was designed to investigate the therapeutic effects of SPG101 on dendritic spine density and morphology and sensorimotor and cognitive functional recovery in a rat model of traumatic brain injury (TBI) induced by controlled cortical impact (CCI). Young adult male Wistar rats with CCI were randomly divided into the following two groups (n = 7/group): (1) Vehicle, and (2) SPG101. SPG101 (30 mg/kg) dissolved in vehicle (1% dimethyl sulfoxide in phosphate buffered saline) or Vehicle were intraperitoneally administered starting at 1 h post-injury and once daily for the next 34 days. Sensorimotor deficits were assessed using a modified neurological severity score and adhesive removal and foot fault tests. Cognitive function was measured by Morris water maze, novel object recognition (NOR), and three-chamber social recognition tests. The animals were sacrificed 35 days after injury, and their brains were processed for measurement of dendritic spine density and morphology using ballistic dye labeling. Compared with the vehicle treatment, SPG101 treatment initiated 1 h post-injury significantly improved sensorimotor functional recovery (days 7-35, p < 0.0001), spatial learning (days 32-35, p < 0.0001), NOR (days 14 and 35, p < 0.0001), social recognition (days 14 and 35, p < 0.0001). Further, treatment significantly increased dendritic spine density in the injured cortex (p < 0.05), decreased heterogeneous distribution of spine lengths in the injured cortex and hippocampus (p < 0.0001), modifications that are associated with the promotion of spine maturation in these brain regions. In summary, treatment with SPG101 initiated 1 h post-injury and continued for an additional 34 days improves both sensorimotor and cognitive functional recovery, indicating that SPG101 acts as a spinogenic agent and may have potential as a novel treatment of TBI.

Trigonelline mitigates lipopolysaccharide-induced learning and memory impairment in the rat due to its anti-oxidative and anti-inflammatory effect

Brain inflammation is associated with cognitive dysfunction, especially in elderly. Trigonelline is a plant alkaloid and a major component of coffee and fenugreek with anti-diabetic, antioxidant, anti-inflammatory, and neuroprotective effects. In this study, the beneficial effect of trigonelline against lipopolysaccharide (LPS)-induced cognitive decline was assessed in the rat. LPS was injected i.p. at a dose of 500 μg/kg to induce neuroinflammation and trigonelline was administered p.o. at doses of 20, 40, or 80 mg/kg/day 1 h after LPS that continued for one week. Trigonelline-treated LPS-challenged rats showed improved spatial recognition memory in Y maze, discrimination ratio in novel object discrimination test, and retention and recall in passive avoidance paradigm. Additionally, trigonelline lowered hippocampal malondialdehyde (MDA) and acetylcholinesterase (AChE) activity and improved superoxide dismutase (SOD), catalase, and glutathione (GSH). Furthermore, trigonelline depressed hippocampal nuclear factor-kappaB (NF-κB), toll-like receptor 4 (TLR4), and tumor necrosis factor α (TNF α) in LPS-challenged rats. All of the effects of trigonelline followed a dose-dependent pattern and in some aspects, it acted even better than the routinely-used anti-inflammatory drug dexamethasone. Collectively, trigonelline is capable to diminish LPS-induced cognitive decline via suppression of hippocampal oxidative stress and inflammation and appropriate modulation of NF-κB/TLR4 and AChE activity.

Soy isoflavone genistein attenuates lipopolysaccharide-induced cognitive impairments in the rat via exerting anti-oxidative and anti-inflammatory effects

Systemic inflammation during infectious disorders usually accompanies chronic complications including cognitive dysfunction. Neuroinflammation and cognitive deficit are also observed in some debilitating neurological disorders like Alzheimer's and Parkinson's diseases. Genistein is a soy isoflavone with multiple beneficial effects including anti-inflammatory, anti-oxidative, and protective properties. In this research study, the effect of genistein in prevention of lipopolysaccharide (LPS)-induced cognitive dysfunction was investigated. LPS was given i.p. (500 μg/kg/day) and genistein was orally given (10, 50, or 100 mg/kg) for one week. Findings showed that genistein could dose-dependently attenuate spatial recognition, discrimination, and memory deficits. Additionally, genistein treatment of LPS-challenged group lowered hippocampal level of malondialdehyde (MDA) and increased activity of superoxide dismutase (SOD) and catalase and glutathione (GSH) level. Furthermore, genistein ameliorated hippocampal acetylcholinesterase (AChE) activity in LPS-challenged rats. Furthermore, genistein administration to LPS-injected group lowered hippocampal level of interleukin 6 (IL-6), nuclear factor-kappaB (NF-κB) p65, toll-like receptor 4 (TLR4), tumor necrosis factor α (TNFα), cyclooxygenase-2 (COX2), inducible nitric oxide synthase (iNOS), glial fibrillary acidic protein (GFAP), and increased hippocampal level of antioxidant element nuclear factor (erythroid-derived 2)-like 2 (Nrf2). In conclusion, genistein alleviated LPS-induced cognitive dysfunctions and neural inflammation attenuation of oxidative stress and AChE activity and appropriate modulation of Nrf2/NF-κB/IL-6/TNFα/COX2/iNOS/TLR4/GFAP.

Ellagic acid ameliorates learning and memory deficits in a rat model of Alzheimer's disease: an exploration of underlying mechanisms

RATIONALE

Alzheimer's disease (AD) is a neurodegenerative disorder with irreversible loss of intellectual abilities. Current therapies for AD are still insufficient.

OBJECTIVE

In this study, the effect of ellagic acid on learning and memory deficits was evaluated in intrahippocampal amyloid beta (Aβ_25-35)-microinjected rats and its modes of action were also explored.

METHODS

AD rat model was induced by bilateral intrahippocampal microinjection of Aβ_25-35 and ellagic acid was daily administered (10, 50, and 100 mg/kg), and learning, recognition memory, and spatial memory were evaluated in addition to histochemical assessment, oxidative stress, cholinesterases activity, and level of nuclear factor-kappaB (NF-κB), Toll-like receptor 4 (TLR4), and nuclear factor (erythroid-derived 2)-like 2 (Nrf2).

RESULTS

The amyloid beta-microinjected rats showed a lower discrimination ratio in novel object and alternation score in Y maze tasks and exhibited an impairment of retention and recall capability in passive avoidance paradigm and higher working and reference memory errors in radial arm maze (RAM). In addition, amyloid beta group showed a lower number of Nissl-stained neurons in CA1 area in addition to enhanced oxidative stress, higher activity of cholinesterases, greater level of NF-κB and TLR4, and lower level of nuclear/cytoplasmic ratio for Nrf2 and ellagic acid at a dose of 100 mg/kg significantly prevented most of these abnormal alterations.

CONCLUSIONS

Ellagic acid pretreatment of intrahippocampal amyloid beta-microinjected rats could dose-dependently improve learning and memory deficits via neuronal protection and at molecular level through mitigation of oxidative stress and acetylcholinesterase (AChE) activity and modulation of NF-κB/Nrf2/TLR4 signaling pathway.

Reciprocal regulation of eNOS, H2S and CO-synthesizing enzymes in human atheroma: Correlation with plaque stability and effects of simvastatin

The molecular and cellular mechanisms underlying plaque destabilization remain obscure. We sought to elucidate the correlation between NO, H₂S and CO-generating enzymes, nitro-oxidative stress and plaque stability in carotid arteries. Carotid atherosclerotic plaques were collected from 62 patients who had undergone endarterectomy due to internal artery stenosis. Following histological evaluation the plaques were divided into stable and unstable ones. To investigate the impact of simvastatin we divided patients with stable plaques, into those receiving and to those not receiving simvastatin. Expression and/or levels of p-eNOS/eNOS, pAkt/t-Akt, iNOS, cystathionine beta synthase (CBS), cystathionine gamma lyase (CSE), heme oxygenase-1(HO-1), soluble guanyl cyclase sGCα1, sGCβ1, NOX-4 and HIF-1α were evaluated. Oxidative stress biomarkers malondialdehyde (MDA) and nitrotyrosine (NT) were measured. NT levels were decreased in stable plaques with a concomitant increase of eNOS phosphorylation and expression and Akt activation compared to unstable lesions. An increase in HIF-1α, NOX-4, HO-1, iNOS, CBS and CSE expression was observed only in unstable plaques. 78% of patients under simvastatin were diagnosed with stable plaques whereas 23% of those not receiving simvastatin exhibited unstable plaques. Simvastatin decreased iNOS, HO-1, HIF-1α and CSE whilst it increased eNOS phosphorylation. In conclusion, enhanced eNOS and reduced iNOS and NOX-4 were observed in stable plaques; CBS and CSE positively correlated with plaque vulnerability. Simvastatin, besides its known effect on eNOS upregulation, reduced the HIF-1α and its downstream targets. The observed changes might be useful in developing biomarkers of plaque stability or could be targets for pharmacothepary against plaque vulnerability.

Serum Cholesterol Levels within the High Normal Range Are Associated with Better Cognitive Performance among Chinese Elderly

OBJECTIVES

The association between cognitive function and cholesterol levels is poorly understood and inconsistent results exist among the elderly. The purpose of this study is to investigate the association of cholesterol level with cognitive performance among Chinese elderly.

DESIGN

A cross-sectional study was implemented in 2012 and data were analyzed using generalized additive models, linear regression models and logistic regression models.

SETTING

Community-based setting in eight longevity areas in China.

SUBJECTS

A total of 2000 elderly aged 65 years and over (mean 85.8±12.0 years) participated in this study.

MEASUREMENTS

Total cholesterol (TC), triglycerides (TG), low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) concentration were determined and cognitive impairment was defined as Mini-Mental State Examination (MMSE) score ≤23.

RESULTS

There was a significant positive linear association between TC, TG, LDL-C, HDL-C and MMSE score in linear regression models. Each 1 mmol/L increase in TC, TG, LDL-C and HDL-C corresponded to a decreased risk of cognitive impairment in logistic regression models. Compared with the lowest tertile, the highest tertile of TC, LDL-C and HDL-C had a lower risk of cognitive impairment. The adjusted odds ratios and 95% CI were 0.73(0.62-0.84) for TC, 0.81(0.70-0.94) for LDL-C and 0.81(0.70-0.94) for HDL-C. There was no gender difference in the protective effects of high TC and LDL-C levels on cognitive impairment. However, for high HDL-C levels the effect was only observed in women. High TC, LDL-C and HDL-C levels were associated with lower risk of cognitive impairment in the oldest old (aged 80 and older), but not in the younger elderly (aged 65 to 79 years).

CONCLUSIONS

These findings suggest that cholesterol levels within the high normal range are associated with better cognitive performance in Chinese elderly, specifically in the oldest old. With further validation, low cholesterol may serve a clinical indicator of risk for cognitive impairment in the elderly.

S-allyl cysteine ameliorates cognitive deficits in streptozotocin-diabetic rats via suppression of oxidative stress, inflammation, and acetylcholinesterase

Diabetes mellitus (DM) is associated with learning, memory, and cognitive deficits. S-allyl cysteine (SAC) is the main organosulfur bioactive molecule in aged garlic extract with anti-diabetic, antioxidant, anti-inflammatory and nootropic property. This research was conducted to evaluate the efficacy of SAC on alleviation of learning and memory deficits in streptozotocin (STZ)-diabetic rats and to explore involvement of toll-like receptor 4 (TLR4), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), nuclear factor-kappa B (NF-κB), and heme oxygenase 1 (HO-1) signaling cascade. Male Wistar rats were divided into control, diabetic, SAC-treated diabetic, and glibenclamide-treated diabetic (positive control) groups. SAC was administered at a dose of 150mg/kg for seven weeks. Treatment of diabetic rats with SAC lowered serum glucose, improved spatial recognition memory in Y maze, discrimination ratio in novel object recognition task, and restored step-through latency (STL) in passive avoidance paradigm. In addition, SAC reduced acetylcholinesterase activity, lipid peroxidation marker malondialdehyde (MDA) and augmented antioxidant defensive system including superoxide dismutase (SOD), catalase and reduced glutathione (GSH) in hippocampal lysate. Meanwhile, SAC lowered hippocampal NF-kB, TLR4, and TNFα and prevented reduction of Nrf2 and heme oxygenase-1 (HO-1) in diabetic rats. Taken together, chronic SAC treatment could ameliorate cognitive deficits in STZ-diabetic rats through modulation of Nrf2/NF-κB/TLR4/HO-1, and acetylcholinesterase and attenuation of associated oxidative stress and neuroinflammation.

White matter damage and glymphatic dysfunction in a model of vascular dementia in rats with no prior vascular pathologies

We investigated cognitive function, axonal/white matter (WM) changes and glymphatic function of vascular dementia using a multiple microinfarction (MMI) model in retired breeder (RB) rats. The MMI model induces significant (p < 0.05) cognitive decline that worsens with age starting at 2 weeks, which persists until at least 6 weeks after MMI. RB rats subjected to MMI exhibit significant axonal/WM damage identified by decreased myelin thickness, oligodendrocyte progenitor cell numbers, axon density, synaptic protein expression in the cortex and striatum, cortical neuronal branching, and dendritic spine density in the cortex and hippocampus compared with age-matched controls. MMI evokes significant dilation of perivascular spaces as well as water channel dysfunction indicated by decreased Aquaporin-4 expression around blood vessels. MMI-induced glymphatic dysfunction with delayed cerebrospinal fluid penetration into the brain parenchyma via paravascular pathways as well as delayed waste clearance from the brain. The MMI model in RB rats decreases Aquaporin-4 and induces glymphatic dysfunction which may play an important role in MMI-induced axonal/WM damage and cognitive deficits.

Simvastatin-induced cognitive dysfunction: two case reports

Background

Simvastatin is commonly prescribed for hypercholesterolemia to reduce vascular risk in patients. Some of these patients have dementia with cognitive defects of several domains. Although protective effects seem to be present, there is emerging evidence that statins cause cognitive impairment.

The role of cholesterol in cognitive function is complex. This is reflected in the effects that statins show on cognition functions. The reduction in cholesterol levels seen with statins is effective in improving learning and memory in some patients. However, there is emerging evidence that statins may worsen cognitive function. Similarly, there are major concerns over whether statins alleviate or worsen cognitive problems. The correlation between cholesterol levels and cognitive function is still controversial, mainly due to a lack of robust evidence.

Case presentation

We report the cases of two Asian patients who developed cognitive deficits after starting simvastatin. A 32-year-old man and a 54-year-old woman developed different but clear cognitive deficits that reversed after stopping simvastatin.

Conclusions

The possibility of new-onset cognitive dysfunction and the deterioration of existing cognitive deficits should be considered when prescribing simvastatin to patients.

[Statins Use in Elderly Patients]

The risk of cardiovascular disease in elderly is significantly higher than in young subjects; paradoxically some treatments that have proven their efficacy in reducing cardiovascular risk are often under prescribed in this age group. The benefits of statins in secondary cardiovascular prevention are well established in patients <80 years. In primary prevention, these drugs reduce the risk of myocardial infarction and stroke, but their effects on cardiovascular mortality remain uncertain. In very elderly patients, there are no randomized trials relative to the impact of statins on morbi-mortality in primary prevention as well in secondary prevention. Adverse effects in the elderly seem to be statistically similar to those occurring in young people , but the prescription in very old people should be individualized, taking into account the life expectancy, the life quality, the comorbidities, and especially the risk of drug interactions.

Dietary cholesterol concentration affects synaptic plasticity and dendrite spine morphology of rabbit hippocampal neurons

Previous studies have shown dietary cholesterol can enhance learning but retard memory which may be partly due to increased cholesterol levels in hippocampus and reduced afterhyperpolarization (AHP) amplitude of hippocampal CA1 neurons. This study explored the dose-dependent effect of dietary cholesterol on synaptic plasticity of rabbit hippocampal CA1 neurons and spine morphology, the postsynaptic structures responsible for synaptic plasticity. Field potential recordings revealed a low concentration of dietary cholesterol increased long-term potentiation (LTP) expression while high concentrations produced a pronounced reduction in LTP expression. Dietary cholesterol facilitated basal synaptic transmission but did not influence presynaptic function. DiI staining showed dietary cholesterol induced alterations in dendrite spine morphology characterized by increased mushroom spine density and decreased thin spine density, two kinds of dendritic spines that may be linked to memory consolidation and learning acquisition. Dietary cholesterol also modulated the geometric measures of mushroom spines. Therefore, dietary cholesterol dose-dependently modulated both synaptic plasticity and dendrite spine morphologies of hippocampal CA1 neurons that could mediate learning and memory changes previously seen to result from feeding a cholesterol diet.

Models and mechanisms of vascular dementia

Vascular dementia (VaD) is the second leading form of dementia after Alzheimer's disease (AD) plaguing the elderly population. VaD is a progressive disease caused by reduced blood flow to the brain, and it affects cognitive abilities especially executive functioning. VaD is poorly understood and lacks suitable animal models, which constrain the progress on understanding the basis of the disease and developing treatments. This review article discusses VaD, its risk factors, induced cognitive disability, various animal (rodent) models of VaD, pathology, and mechanisms of VaD and treatment options.

Do statins impair cognition? A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

In 2012, the United States Food and Drug Administration (FDA) issued a warning regarding potential adverse effects of HMG-CoA reductase inhibitors (statins) on cognition, based on the Adverse Events Reporting System and a review of the medical literature. We aimed to synthesize randomized clinical trial (RCTs) evidence on the association between statin therapy and cognitive outcomes.

METHODS

We searched MEDLINE, EMBASE, and Cochrane CENTRAL through December 2012, and reviewed published systematic reviews of statin treatment. We sought RCTs that compared statin treatment versus placebo or standard care, and reported at least one cognitive outcome (frequency of adverse cognitive events or measurements using standard neuropsychological cognitive test scores). Studies reporting sufficient information to calculate effect sizes were included in meta-analyses. Standardized and unstandardized mean differences were calculated for continuous outcomes for global cognition and for pre-specified cognitive domains. The main outcome was change in cognition measured by neuropsychological tests; an outcome of secondary interest was the frequency of adverse cognitive events observed during follow-up.

RESULTS

We identified 25 RCTs (all placebo-controlled) reporting cognitive outcomes in 46,836 subjects, of which 23 RCTs reported cognitive test results in 29,012 participants. Adverse cognitive outcomes attributable to statins were rarely reported in trials involving cognitively normal or impaired subjects. Furthermore, meta-analysis of cognitive test data (14 studies; 27,643 participants) failed to show significant adverse effects of statins on all tests of cognition in either cognitively normal subjects (standardized mean difference 0.01, 95% confidence interval, CI, -0.01 to 0.03, p = 0.42) or Alzheimer's disease subjects (standardized mean difference -0.05, 95% CI -0.19 to 0.10, p = 0.38).

CONCLUSIONS

Statin therapy was not associated with cognitive impairment in RCTs. These results raise questions regarding the continued merit of the FDA warning about potential adverse effects of statins on cognition.

Cognitive Impairment and Age-Related Vision Disorders: Their Possible Relationship and the Evaluation of the Use of Aspirin and Statins in a 65 Years-and-Over Sardinian Population

Neurological disorders (Alzheimer’s disease, vascular and mixed dementia) and visual loss (cataract, age-related macular degeneration, glaucoma, and diabetic retinopathy) are among the most common conditions that afflict people of at least 65 years of age. An increasing body of evidence is emerging, which demonstrates that memory and vision impairment are closely, significantly, and positively linked and that statins and aspirin may lessen the risk of developing age-related visual and neurological problems. However, clinical studies have produced contradictory results. Thus, the intent of the present study was to reliably establish whether a relationship exist between various types of dementia and age-related vision disorders, and to establish whether statins and aspirin may or may not have beneficial effects on these two types of disorders. We found that participants with dementia and/or vision problems were more likely to be depressed and displayed worse functional ability in basic and instrumental activities of daily living than controls. Mini mental state examination scores were significantly lower in patients with vision disorders compared to subjects without vision disorders. A closer association with macular degeneration was found in subjects with Alzheimer’s disease than in subjects without dementia or with vascular dementia, mixed dementia, or other types of age-related vision disorders. When we considered the associations between different types of dementia and vision disorders and the use of statins and aspirin, we found a significant positive association between Alzheimer’s disease and statins on their own or in combination with aspirin, indicating that these two drugs do not appear to reduce the risk of Alzheimer’s disease or improve its clinical evolution and may, on the contrary, favor its development. No significant association in statin use alone, aspirin use alone, or the combination of these was found in subjects without vision disorders but with dementia, and, similarly, none in subjects with vision disorders but without dementia. Overall, these results confirm the general impression so far; namely, that macular degeneration may contribute to cognitive disorders (Alzheimer’s disease in particular). In addition, they also suggest that, while statin and aspirin use may undoubtedly have some protective effects, they do not appear to be magic pills against the development of cognitive impairment or vision disorders in the elderly.

Up-regulation of matrix metallopeptidase 12 in motor neurons undergoing synaptic stripping

Axotomy of the rodent facial nerve represents a well-established model of synaptic plasticity. Post-traumatic "synaptic stripping" was originally discovered in this system. We report upregulation of matrix metalloproteinase MMP12 in regenerating motor neurons of the mouse and rat facial nucleus. Matrix metalloproteinases (matrix metallopeptidases, MMPs) are zinc-binding proteases capable of degrading components of the extracellular matrix and of regulating extracellular signaling networks including within synapses. MMP12 protein expression in facial motor neurons was enhanced following axotomy and peaked at day 3 after the operation. The peak of neuronal MMP12 expression preceded the peak of experimentally induced synaptic plasticity. At the same time, MMP12 redistributed intracellularly and became predominantly localized beneath the neuronal somatic cytoplasmic membrane. Both findings point to a role of MMP12 in the neuronal initiation of the synaptic stripping process. MMP12 is the first candidate molecule for such a trigger function and has potential as a therapeutic target. Moreover, since statins have been shown to increase the expression of MMP12, interference with synaptic stability may represent one mechanism by which these widely used drugs exert their side effects on higher CNS functions.

Cognitive effects of statin medications

The demonstrated benefits of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) for cardiovascular and cerebrovascular disease are well established in the medical literature, and this class of medications is among those most commonly prescribed in the USA. In 2012, the US Food and Drug Administration issued updated recommendations regarding statin medications, and the panel's comments regarding memory impairment fostered clinical confusion (in part because of the lay media's amplification). Cognitive data from several large epidemiological studies have not reliably demonstrated a robust association between incident cognitive impairment and statin use, with some studies reporting a protective effect, some reporting an increased risk and others finding no association. Although several interventional studies have evaluated statins as a possible adjunctive treatment for Alzheimer's disease, none have clearly demonstrated a benefit. A small number of case series have reported infrequent memory difficulties associated with statin use. In these series, the patients' cognitive symptoms resolved after statin discontinuation. The existing medical literature does not suggest that cognitive considerations should play a major role in medical decision making to prescribe statins for the large majority of patients. As with any medication prescribed for older adults, careful clinical monitoring for side effects should be exercised. If a patient is suspected of having idiosyncratic memory impairment associated with use of a statin medication, the drug can be discontinued. The patient should then be followed with careful clinical observation for 1-3 months for resolution of the cognitive symptoms.

Suppression of memory acquisition following co-administration of lithium and atorvastatin through nitric oxide pathway in mice

PURPOSE

The aim of this study was to investigate the interactive effect of lithium and atorvastatin on cognitive performance and the role of NO as a potential mechanism involved in this interaction.

MATERIALS AND METHODS

Memory performance was evaluated in a two-trial recognition Y-maze test and a step-through passive avoidance task in mice. Lithium (5, 10, 20 or 40 mg/kg, i.p.) and atorvastatin (1 mg/kg, p.o.) were administered 1 h before each trial, L-NAME, a non-specific NO synthase inhibitor (3, 10 mg/kg, i.p.); aminoguanidine, a specific inducible NO synthase (iNOS) inhibitor (100 mg/kg); and L-arginine, a NO precursor (750 mg/kg) were administered 30 min before training sessions. The level of plasma NO end-products (NOx) was determined using Griess reagent protocol.

RESULTS

1) Lithium (40 mg/kg) impaired the acquisition of spatial recognition memory; 2) lithium did not affect the retrieval phase of spatial memory; 3) atorvastatin (1 mg/kg) significantly impaired the memory performance, when co-administered with the sub-effective dose of lithium (10 mg/kg), but did not affect the status when administered with lithium (5 mg/kg); 4) L-NAME (10 mg/kg) and aminoguanidine (100 mg/kg) dramatically decreased memory performance in mice received sub-effective doses of both lithium (5 mg/kg) and atorvastatin (1 mg/kg); 5) L-arginine (750 mg/kg) improved the memory acquisition in mice administered lithium (10 mg/kg) and atorvastatin (1 mg/kg); 6) lithium did not affect the cognitive performance in the passive avoidance test. All results were compatible and confirmed with in vitro determination of plasma NOx levels.

CONCLUSIONS

Lithium, dose dependently, impaired acquisition phase of spatial recognition memory. Lithium and atorvastatin co-administration impaired spatial recognition memory mediating by nitrergic pathway. In addition to L-arginine, our data from L-NAME and aminoguanidine also support the involvement of NO pathway in this interaction.