Investigation of the memory impairment in rats fed with oxidized-cholesterol-rich diet employing passive avoidance test.

See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/261104933

Investigation of the Memory Impairment in Rats Fed with Oxidized-Cholesterol-Rich Diet Employing Passive Avoidance Test ARTICLE · MARCH 2014 DOI: 10.1055/s-0034-1370950 · Source: PubMed

CITATION

DOWNLOADS

VIEWS

1

69

75

6 AUTHORS, INCLUDING: Arash Khorrami

Saeed Ghanbarzadeh

Tabriz University of Medical Sciences


30 PUBLICATIONS 37 CITATIONS


SEE PROFILE

SEE PROFILE

Javad Mahmoudi

Alireza Mohajjel Nayebi





SEE PROFILE

SEE PROFILE

Available from: Arash Khorrami Retrieved on: 17 June 2015

Original Article 1

DrugRes/2013-12-0514/28.2.2014/MPS DrugRes/2013-12-0514/28.2.2014/MPS

Investigation of the Memory Impairment in Rats Fed with Oxidized-Cholesterol-Rich Diet Employing Passive Avoidance Test

Authors Affiliations

Key words ▶ cholesterol ● ▶ oxidized cholesterol ● ▶ coenzyme Q10 ● ▶ memory impairment ●

A. Khorrami1, 2, 4, S. Ghanbarzadeh2, 3, 4, J. Mahmoudi1, A. M. Nayebi1, N. Maleki-Dizaji1, A. Garjani1 1

Department of Pharmacology & Toxicology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran Research Center for Pharmaceutical Nanotechnology, Tabriz University of Medical Sciences, Tabriz, Iran 3 Department of Pharmaceutics, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran 4 Student Research Committee, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran 2

Abstract

▼

Background: Recent studies have shown that hypercholesterolemia, besides being a risk factor for cardiovascular diseases, has also toxic effects on central nervous system. The design of the present study was to investigate the effects of dietary cholesterol and oxidized cholesterol on cognitive function. Methods: Male Wistar rats were randomly divided into 3 groups. The animals were fed with three normal, 2 % cholesterol-rich, and 2 % oxidized cholesterol-rich diets for 14 weeks. Memory impairment was analyzed by passive avoidance test. Coenzyme Q10 content was also measured by a validate RP-HPLC method. Besides, lipid peroxidation in serum and brain tissue was determined by malondialdehyde concentration measurement. Results: The results showed that feeding rats with high oxidized cholesterol diet for 14 weeks

significantly impaired the cognitive function compared to the normal (P < 0.001) and high cholesterol-fed groups (P < 0.01). The memory impairment was positively correlated to the serum level of the oxidized LDL; it was significantly associated with the increased malondialdehyde concentration on the brain tissue of both groups (P < 0.05 and P < 0.001, respectively). The total antioxidant level in the serum was also decreased in rats fed with the oxidized cholesterol (P < 0.05). Moreover, the brain coenzyme Q10 content was significantly declined in the animals fed with the oxidized cholesterol-rich diet compared to the animals fed with the normal (P < 0.01) and cholesterol-rich diets (P < 0.05). Conclusion: The results suggested that the high dietary intake of the oxidized-cholesterol might impair the memory that could be correlated to the oxidative stress and declined the coenzyme Q10 content of the brain tissue.

received 11.12.2013 accepted 13.02.2014 Bibliography DOI http://dx.doi.org/ 10.1055/s-0034-1370950 Drug Res 2014; 64: 1–7 © Georg Thieme Verlag KG Stuttgart · New York ISSN 2194-9379 Correspondence Dr. A. Garjani Department of Pharmacology Professor of Pharmacology Faculty of Pharmacy Daneshgah Street Tabriz University of Medical Sciences Tabriz Iran Tel.: + 98/411/3341 315 Fax: + 98/411/3344 798 [email protected] [email protected]

Introduction

▼

Dementia is an acquired decline in the cognitive capabilities that impairs the successful performance of daily life activities. In more than half of demented patients, Alzheimer Disease (AD) is the cause of the dementia [1–3]. The metabolic cardiovascular syndrome includes hypertension, glucose intolerance, obesity, and dyslipidemia; it may be a preclinical condition that increases the risk of the dementia [4–6]. Furthermore, the elevated concentration of cholesterol on the serum is an important risk factor for the cardiovascular diseases. Today, it is suggested that the metabolism of cholesterol plays an important role in the pathogenesis of the Alzheimer disease [7–10]. In this regard, statin therapy shows 60–73 % lower prevalence rate of the AD in human [11]. In addition, other studies have shown that lipidlowering agents are associated with the decreased risk of the dementia and hyperlipi-

demia is associated with the increased risk of the non-Alzheimer type of the dementia [12–14]. It is worth noting that cholesterol is an essential component of the central nervous system and cellular membranes; it is also a precursor in oxysterols, steroid hormones, and bile acids formation. Although cholesterol is a major constituent of the brain (the central nervous system accounting for 20–25 % of the total-body cholesterol), it is efficiently isolated from other reservoirs of cholesterol in the body through the efficient Blood Brain Barrier (BBB) [15–17]. Defects in the cholesterol metabolism also lead to structural and functional central nervous system diseases including Smith-Lemli-Opitz syndrome, Niemann-Pick type C disease, and Huntington disease [17–23]. The cells provide their required cholesterol through uptake of lipoprotein cholesterol and de novo synthesis. In contrast, the demanded brain cholesterol is primarily covered by the de novo synthesis. The intact BBB

■ Proof copy for correction only. All forms of publication, duplication or distribution prohibited under copyright law. ■ Khorrami A et al. Oxidized LDL and Memory Impairment … Drug Res 2014; 64: 1–7

2 Original Article

in vertebrates inhibits the lipoproteins entry from the circulation to the Central Nervous System (CNS) [24, 25]. In contrast with the unchanged cholesterol, the side-chain oxidized cholesterol metabolites such as 24(S)-hydroxy cholesterol and 27-hydroxycholesterol are able to cross lipophilic membranes such as the BBB at a much faster rate than cholesterol itself. In this regard, the entry of the additional 27-hydroxycholesterol of cerebral metabolite from the circulation into the brain is shown and 5 mg daily entry of the 27-hydroxycholesterol into the brain is predictable. The amount of the entry is associated with the 27-hydroxycholesterol concentration on the circulation and the integrity of the BBB [26]. In addition, the existence of a hydroxyl group in the side chain of cholesterol leads to the transfer of the oxidized cholesterol across the membrane greater than that of the unchanged cholesterol [17, 19, 27]. Although cholesterol is constantly present in the most peripheral tissues and circulation in a large quantity compared to the oxysterols with the ratio of cholesterol to any oxysterol being 1 000:1 to 100 000:1, the ratio is much lower in the brain and varies between 500:1 and 1 000:1 [28]. The oxysterols can incorporate in the membrane; they can be extracted by the cholesterol acceptors such as the lipoproteins. Reactive Oxygen Species (ROS) induced by the impaired cholesterol metabolism lead to mitochondrial damage, apoptotic cell death, and oxidative stress. Recent studies have shown the oxidative stress connection to the mitochondrial dysfunction in neurodegeneration [29–31]. In this respect, Coenzyme Q10 (CoQ10), an important cofactor of the electron transport chain, as a dietary supplement has recently gained attention for its potential role in the treatment of the neurodegenerative disease. The coenzyme Q10 protects the neuronal cells against the oxidative stress in the neurodegenerative diseases. It acts through preserving mitochondrial membrane potential, supporting Adenosine Tri-Phosphate (ATP) synthesis, and obstructing ROS generation [32–34]. Controlled trials suggest that reducing the disease progress is possible with early diagnosis and with the treatment in the dementia stage of the Alzheimer disease. Management of the hyperlipidemia may be more helpful in the dementia and the AD prevention [35, 36]. The present study examines the effects of the dietary cholesterol and the oxidized cholesterol on the memory impairment and its correlation with the oxidative stress and the Coenzyme Q10 content of the brain tissue.


terol-fed group) were fed with the second group’s diet except for 2 % oxidized cholesterol instead of 2 % cholesterol. Oxidized cholesterol was prepared by the method described by Ilona Staprans [37]. Following 14 weeks feeding with these diets, the abdominal cavity of anesthetized rats was opened through the skin and the abdominal wall. A gauge needle (25 G) was inserted into the vein and blood was drawn slowly. The blood samples were centrifuged at 2 500 rpm and low temperature (10 °C) for 10 min, and separated serum samples were stored at − 80 °C for subsequent analysis. Brain samples were excised, frozen in liquid nitrogen for 10 s and then stored at − 80 °C for later measurement of CoQ10 content.

Serum biochemical analysis To evaluate the effect of the high-fat diets on biochemical parameters’ levels in the blood, serum samples were analyzed using enzymatic colorimetric methods for total cholesterol (TC), triglycerides (TGs), LDL and HDL using commercially available kits (Pars Azmoon Laboratories, Iran). The assays were performed according to the manufacturer’s instructions in duplicate. Glory OxLDL kits (USA), work upon a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) was utilized to evaluate the levels of OxLDL in samples.

Determination of lipid peroxidation in brain The concentration of malondialdehyde (MDA), a thiobarbiturate reactive substance, was measured as a marker of oxidative stress in the brain tissue homogenates and serum using the method prescribed by Satoh [38]. The lipid peroxidation has been expressed as nano moles of MDA per grams of brain tissue and per milliliter of serum which was measured spectrophotometrically.

Determination of total antioxidant status

Material and Method

Serum total antioxidant status (TAS) was measured by a commercially available kit from Randox Laboratories. This technique involves the incubation of ABTS® (2,2′-Azino-di-[3–ethylbenzthiazolinesulphonate]) with hydrogen peroxide and a peroxidase (metmyoglobin), resulting in the production of the stable radical cation, ABTS + , which has a measurable relatively stable blue-green color at 600 nm. Antioxidants addition to samples causes a concentration relevant suppression in color production. The suppression degree of the radical generation in the samples, indicating the presence of antioxidant activity, was quantified through comparison with a standard.

Experimental protocol

Determination of CoQ10 in brain tissue

Male Wistar rats (body weight 220–250 g, 10 months of age) were housed in the temperature and humidity controlled rooms with a 12 h day and night light cycle with free access to the food and water during the entire experiment. The Body weight, food consumption and water intake were monitored weekly. All of these experiments were approved by the animal care committee at Tabriz University of Medical Sciences (National Institutes of Health Publication No. 85–23, revised 1985). Rats were randomly divided into 3 groups. In control group, animals were fed with the standard rat chow diet. In second group (cholesterol-fed group) animals were fed with the diet containing following ingredients: rodent chow powder (62.75 %), lard oil (15 %), cholesterol (2 %), cholic acid (0.25 %), wheat flour (10 %) and sucrose (10 %). The animals in third group (oxidized choles-

To evaluate the CoQ10 content, brain tissues were sampled and subjected in to the extraction process of CoQ10 which was performed according to the our previously described method [39]. Briefly, ethanol was added to the samples to remove proteins by partitioning and denaturation of enzymes. 100 mg of freezeclamped tissue was accurately weighed and homogenized with 1 mL of water. 50 μL of ethanolic solution of butylated hydroxy toluene (10 mg/mL) was added to each sample for prevention of auto-oxidation. Then, 1 mL of sodium dodecyl sulfate (0.1 M) was added to the samples and after brief homogenization were transferred to a glass tube fitted with a PTFE-lined screw cap. Subsequently, 2 mL of ethanol was added to the mixture, mixed for 30 s, and after addition of 2 mL of hexane mixed vigorously again for 2 min. Finally, mixtures were centrifuged for 5 min

▼


Original Article 3


(2 200 rpm) and supernatant organic layer was collected. In order to ensure to maximal extraction, the extraction process was performed twice. The solvent of extracts were evaporated under reduced pressure using an evaporator (Buchi, rotavapor R-215, Switzerland). Samples were injected in to high performance liquid chromatography (HPLC) instrument after reconstitution with 100 μL of mobile phase. Quantitative analysis of CoQ10 content was done by reverse phase HPLC system (RP-HPLC) (Knauer, smartline 2 500), using C-18 column (250 × 4.6 mm, 5 μm). The mobile phase, consisted of a mixture of ethanol and methanol (80:20), was eluted at flow rate of 1.2 mL/min. The UV detector was set at 275 nm. All analyses were performed at room temperature in triplicate.

Table 1 Total cholesterol, LDL, HDL, triglyceride and oxidized LDL serum levels in the rats fed with the normal diet (Control), cholesterol (Chol) and oxidized cholesterol (OxChol)-rich diets. Variable

Control

Chol

OxChol

Total cholesterol (mg/dL) ± SEM LDL (mg/dL) ± SEM Total triglycerides (mg/dL) ± SEM HDL (mg/dL) ± SEM

64.3 ± 4.8

122.2 ± 8.2***

125.5 ± 8.3***

20.2 ± 1.1 55.3 ± 4

54.8 ± 3.8*** 98.1 ± 7.3***

56.2 ± 3.9 *** 101.5 ± 8.7***

34 ± 3.8

45 ± 3.1

43.1 ± 2.9*

The results were analyzed to be statistically significant at *P < 0.05 and ***P < 0.001 compared to the control group. Values were expressed as mean ± SEM of each group

Passive avoidance test The apparatus consisted of an illuminate chamber connected to dark chamber by a guillotine door. The examination was based on the natural instinct of rats to stay in dark compartment. The test was performed in 4 days. On the first and second day, after 5 min of habituation to the apparatus, the rats were placed on a bright compartment, allowed to enter the dark compartment. In the third day, an acquisition trial was performed and the rats were separately placed in the illuminated chamber. After a habituation period (2 min), the guillotine door was opened and after the rat entering to the dark chamber, the door was closed and the rats were received an inescapable foot shock (1 mA, 50 HZ, 3 s) through the grill floor of the dark compartment (learning trial). In this trial, the latency time (LT) of entrance into the dark chamber was recorded and the rats with LT more than 60 s were disqualified from the study. The passive avoidance reaction was checked 24 h later again. Afterwards, the rats were placed on the illuminated compartment once more and the latency time to enter the dark compartment was measured during 720 s. This test was conducted during the 40th, 70th and 100th days after feeding with high fat diets initiation and each rat was tested only once for measurement of long-term memory. Experiments were performed at the same time of the day and under similar conditions and therefore, the results of all groups were comparable.

Data analysis The quantitative variables were presented as mean ± SEM. The statistical analysis was performed using Analysis Of Variance (ANOVA) followed by post-hoc Tukey HSD test to compare variables among the different groups. A value of P < 0.05 was considered significant. All statistical analyses were performed by SPSS software version 17 (IBM corp, USA). The correlations between LDL and oxidized LDL content with passive avoidance test results were determined using Pearson test.

Results and Discussion

▼

Effects of dietary cholesterol and oxidized cholesterol on the lipid profile ▶ Table 1 shows the lipid profile in the serum of rats in 3 groups ● following 14 weeks feeding with high fat and normal diets. The levels of serum LDL, total cholesterol, and triglycerides were significantly increased (2–3 folds) in both groups fed with the cholesterol-rich and oxidized cholesterol-rich diets compared to the ▶ Fig. 1, the serum control group (P < 0.001). As it is shown in ● concentrations of the oxidized cholesterol were significantly

Fig. 1 The comparison of the LDL (columns) and oxidized LDL level (linear) in serum of rats fed with normal (Control), cholesterol (Chol) and oxidized cholesterol (OxChol)-rich diets. The results were analyzed to be statistically significant at *P < 0.05, ***P < 0.001 compared to the control group and #P < 0.05, ###P < 0.001 compared to the Chol group. Values were expressed as mean ± SEM of each group.

higher in both the cholesterol and oxidized cholesterol-fed rats. However, the increase in the oxidized cholesterol-fed animals was much higher than the cholesterol-fed group (P < 0.001).

Effects of cholesterol and oxidized cholesterol on the memory impairment The latency time was assessed in rats fed with normal, choles▶ Fig. terol, and oxidized cholesterol-rich diets. As it is shown in ● 2, in the 70th day, the latency time of the oxidized cholesterolfed rats was significantly lower than the control group (P < 0.05). However, in the 100th day, the latency time of both the cholesterol-fed and oxidized cholesterol-fed rats showed significant reduction (P < 0.05 and P < 0.001, respectively). At the same time, the difference between the latency time of the cholesterol-fed and oxidized cholesterol-fed rats was also significant (P < 0.01). The brain cholesterol is mostly involved in cell membrane structure, signal transduction, neurotransmitter release, synaptogenesis, and membrane trafficking. Several reports showed a relation between the high dietary exposure to cholesterol and the oxidative stress in the brains of mice and rats [19, 40]. These studies also showed an up-regulation of markers of lipid peroxidation, ROS generation, oxidized nucleosides, and proteins, reflecting the increased oxidative stress in the brain in response to the high cholesterol diet [41]. In this regard, Crisby et al. revealed that a diet containing high fat and cholesterol induced the expression of the antioxidant enzyme NAD(P)H: the quinone oxidoreductase (NQO1) in mouse brain [42]. Montilla et al. also reported that a cholesterol-rich diet reduced the activities of several key antioxidant enzymes such as catalase and SOD [43].


4 Original Article

Fig. 2 Effects of normal, cholesterol and oxidized cholesterol-rich diets on latency time (Sec) in different days. The results were analyzed to be statistically significant at *P < 0.05 and ***P < 0.001 compared to the control group and #P < 0.05 and ###P < 0.001 compared to the cholesterol-fed group. Values were expressed as mean ± SEM of each group. The interval between the placement in the illuminated chamber and the entry into the dark chamber was measured as latency time.

Fig. 3 Effects of normal, cholesterol and oxidized cholesterol-rich diets on malondialdehyde (MDA) level in serum and brain tissue. The results were analyzed to be statistically significant at *P < 0.05 and ***P < 0.001 compared to the control group and ##P < 0.01 compared to the cholesterol-fed group. Values were expressed as mean ± SEM of each group.

The increased levels and decreased activity of the antioxidant enzymes are often seen throughout the extended states of the oxidative stress such as in the Alzheimer disease. Furthermore, there are strong evidences supporting the essential role of the oxysterols in the neurotoxicity compared to the unchanged cholesterol. First, the BBB efficiently prevents the cholesterol uptake from the circulation into the brain, and the de novo synthesis is responsible for almost all cholesterol present there. The significant flux of the neurotoxic oxysterols such as the 27-hydroxycholesterol from the circulation across the BBB is well described [17, 44]. Second, the deleterious effects of the oxysterol ranged from the Aβ accumulation to the oxidative cell damage have been investigated in recent studies [45]. Third, a modest accumulation of the 27-hydroxycholesterol in the brains of patients with the sporadic Alzheimer disease consistent with a role of the 27-hydroxycholesterol as a primary pathogenetic factor has been shown [46, 47]. Fourth, the impairment of the brain cholesterol metabolism has been described in the neurodegenerative diseases such as Multiple Sclerosis, Alzheimer, and Huntington diseases [17, 48, 49]. Due to the association between


the oxysterols and cholesterol in the circulation and the lipoprotein-bound, cholesterol cannot pass from the BBB. Therefore, it is suggested that the oxysterols may mediate the effects of the hypercholesterolemia on the brain tissue and function. The influential effect of the diet on the brain function has been known for quite some time. However, the precise mechanisms through which cholesterol and oxidized cholesterol influence the brain function are less well defined. The present study verified that the oxidized cholesterol-rich diet aggravated the memory of the male rats compared to the rats fed with the high cholesterol diet. The effects of cholesterol might be related to the conversion of cholesterol to the oxidized cholesterol in tissues, which was well defined in the atherosclerosis. Therefore, the present study revealed that the oxidized cholesterol significantly increased the latency time compared to the cholesterol-fed group.

Effects of dietary cholesterol and oxidized cholesterol on lipid peroxidation The malondialdehyde (MDA) concentration was measured in the brain tissue homogenates and serum so as to determine the lipid ▶ Fig. 3, feeding with the cholesperoxidation. As it is shown in ● terol and oxidized cholesterol-rich diets significantly (P < 0.05 and P < 0.001) increased the lipid peroxidation in the brain tissue and serum compared to the control group. However, the elevation in the MDA level in the oxidized cholesterol-fed animals was significantly (P < 0.01) higher than that of the cholesterolfed group. In addition, the MDA level in the animals’ serum between the control group and the cholesterol-rich diet fed group was not significantly different (P > 0.05), whereas the difference between the MDA level in the animals fed with the cholesterol-rich diet and the oxidized cholesterol-rich diet was significant (P < 0.01). The imbalance between the reactive oxygen species production and the detoxification leads to the oxidative stress generation that has an important role in the brain aging, the neurodegenerative diseases, and other related adverse conditions such as movement defect [50, 51]. Although the physiologic levels of the ROS serve as signaling molecules, an extreme amount causes the oxidative modification of nucleic acids, proteins, and lipids [52]. The brain neurons, depending on the neurons type, show different degrees of responsiveness to the oxidative stress to the occurrence of injuries [53]. Although many brain neurons can tolerate the oxidative stress, small amount of neurons are vulnerable. This vulnerability causes functional decline and cell death in these neurons during normal aging or in the age-related neurodegenerative diseases such as the Alzheimer disease [54–56].

Effects of cholesterol and oxidized cholesterol on the total antioxidant status The obtained data showed that the total antioxidant level in the oxidized cholesterol group was significantly lower than the control group (P < 0.05). However, feeding with the cholesterol-rich ▶ Fig. 4). diet did not decrease the total antioxidant level (●

Effects of cholesterol and oxidized Cholesterol on the brain CoQ10 content Although there was a significant negative correlation between the oxidized LDL levels in the serum with the CoQ10 content in the brain tissues, the cholesterol-rich diet feeding did not affect the brain CoQ10 content. The total CoQ10 concentration on the brain tissue in the control group (1.45 ± 0.12 μg/100 mg tissue)


Original Article 5


Fig. 4 Serum antioxidant status of rats fed with normal (Control), cholesterol-rich (Chol) and oxidized cholesterol-rich (OxChol) diets. The results were analyzed to be statistically significant at *P < 0.05 compared to the control group. Data were represented as mean ± SEM of each group.

Fig. 6 Correlation between serum OxLDL levels and latency time.

in humans and may be promising for therapeutic trials in the Alzheimer disease.

The correlation of serum oxidized LDL level with latency time There was a significant and positive correlation between the ▶ Fig. serum oxidized LDL concentration and the latency time (● 6) in the oxidized cholesterol-fed animals (r2 = 0.76, P < 0.01). There was also the same correlation between the serum oxidized LDL level with the latency time in the cholesterol-fed rats (r2 = 0.66, P < 0.05). The present study indicated the association of memory loss and the brain CoQ10 content in the animals fed with the cholesterol and oxidized cholesterol-rich diets. The results revealed that the serum oxidized LDL level was related to the memory in the male rats. However, there was not the same correlation between the serum cholesterol concentration and the latency time. Fig. 5 The brain tissue CoQ10 content in rats fed with normal diet, high cholesterol and high oxidized cholesterol-rich (OxChol) diets. The results were analyzed to be statistically significant at **P < 0.01 compared to the control group; #P < 0.05 compared to the Chol group.

was significantly (P < 0.01) higher than the oxidized cholesterolfed group (0.82 ± 0.06 μg/100 mg tissue). In addition, the oxidized cholesterol-rich diet significantly decreased the brain CoQ10 content compared to the cholesterol-rich diet (P < 0.05) ▶ Fig. 5). (● The oxidative stress is involved in the pathogenesis of the Alzheimer disease. Increasing evidences suggest that the Amyloid-β (Aβ) deposition is followed by the mitochondrial dysfunction and increased reactive oxygen species [57, 58]. The Coenzyme Q10, a lipid soluble antioxidant, is well described as a neuroprotective antioxidant in the animal’s models and human trials of the Alzheimer disease [33, 59]. Following feeding with the cholesterol and oxidized cholesterol-rich diets, the CoQ10 content of the brain is decreased. It may be used for the reactive oxygen species detoxification. Previous studies showed that the CoQ10 reduced the oxidative stress markers such as the protein carbonyls and the MDA level in the brain. The CoQ10 supplementation also decreased the brain Aβ42 levels [60]. The CoQ10-treated mice highly show improved cognitive performance during Morris water maze testing [61]. The Coenzyme Q10 is well tolerated

Conclusion

▼

Cholesterol and oxidized cholesterol in diet increased the MDA and decreased the CoQ10 content of the brain tissue indicating the oxidative stress increment. The oxidized cholesterol was more potent oxidative stress inducer that was associated with the oxidized LDL level in the serum. The serum oxidized LDL level was positively correlated with the latency time in the passive avoidance test. The memory impairment might be due to the high reactive oxygen species, and the oxidative stress injuries occurred in the brain tissue. The moderate effect of cholesterol could be related to the conversion of cholesterol to the oxidized cholesterol in tissues. However, further investigation is necessary to explain the exact mechanism(s) of the cholesterol and oxidized cholesterol effects on the cognition.

Acknowledgments

▼

The present study was supported by a grant from the Research Vice Chancellors of Tabriz University of Medical Sciences; Tabriz, Iran. This article is based on a thesis submitted for Ph.D. degree (No. 75) in Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.


6 Original Article Conflict of Interest

▼

The authors declare that there are no conflicts of interest.

References 1 Bäckman L, Small BJ. Cognitive deficits in preclinical Alzheimer’s disease and vascular dementia: Patterns of findings from the Kungsholmen Project. Physiology & Behavior 2007; 92: 80–86 2 Ishrat T, Parveen K, Khan MM et al. Selenium prevents cognitive decline and oxidative damage in rat model of streptozotocin-induced experimental dementia of Alzheimer’s type. Brain Research 2009; 1281: 117–127 3 Stopford CL, Thompson JC, Neary D et al. Working memory, attention, and executive function in Alzheimer’s disease and frontotemporal dementia. Cortex 2012; 48: 429–446 4 Kerola T, Kettunen R, Nieminen T. The complex interplay of cardiovascular system and cognition: How to predict dementia in the elderly? International Journal of Cardiology 2011; 150: 123–129 5 Kling MA, Trojanowski JQ, Wolk DA et al. Vascular disease and dementias: Paradigm shifts to drive research in new directions. Alzheimer’s & Dementia 2013; 9: 76–92 6 Mattson MP. Roles of the lipid peroxidation product 4-hydroxynonenal in obesity, the metabolic syndrome, and associated vascular and neurodegenerative disorders. Experimental Gerontology 2009; 44: 625–633 7 Castello MA, Soriano S. Rational heterodoxy: Cholesterol reformation of the amyloid doctrine. Ageing Research Reviews 2013; 12: 282–288 8 Liu J-P, Tang Y, Zhou S et al. Cholesterol involvement in the pathogenesis of neurodegenerative diseases. Molecular and Cellular Neuroscience 2010; 43: 33–42 9 Mathew A, Yoshida Y, Maekawa T et al. Alzheimer’s disease: Cholesterol a menace? Brain Research Bulletin 2011; 86: 1–12 10 Khorrami A, Ghanbarzadeh S, Ziaee M et al. Effects of LDL and Oxidized LDL on Cardiac Function in Isoproterenol-induced Myocardial Infarction in Rat. Drug Research 2014; In Press 11 Wolozin B, Kellman W, Ruosseau P et al. Decreased prevalence of Alzheimer disease associated with 3-hydroxy-3-methyglutaryl coenzyme A reductase inhibitors. Arch Neurol 2000; 57: 1439–1443 12 Almuti K, Rimawi R, Spevack D et al. Effects of statins beyond lipid lowering: Potential for clinical benefits. International Journal of Cardiology 2006; 109: 7–15 13 DeKosky ST. Statin therapy in the treatment of Alzheimer disease: what is the rationale? The American Journal of Medicine 2005; 118: 48–53 14 Green RC, McNagny SE, Jayakumar P et al. Statin use and the risk of Alzheimer’s disease: The MIRAGE Study. Alzheimer’s & Dementia 2006; 2: 96–103 15 Björkhem I. Five decades with oxysterols. Biochimie 2013; 95: 448–454 16 Gosselet F, Saint-Pol J, Fenart L. Effects of oxysterols on the blood–brain barrier: Implications for Alzheimer’s disease. Biochemical and Biophysical Research Communications 2013; In press: In press 17 Leoni V, Caccia C. Oxysterols as biomarkers in neurodegenerative diseases. Chemistry and Physics of Lipids 2011; 164: 515–524 18 Block RC, Dorsey ER, Beck CA et al. Altered cholesterol and fatty acid metabolism in Huntington disease. Journal of Clinical Lipidology 2010; 4: 17–23 19 Leoni V, Caccia C. 24S-hydroxycholesterol in plasma: A marker of cholesterol turnover in neurodegenerative diseases. Biochimie 2013; 95: 595–612 20 Pfrieger FW, Ungerer N. Cholesterol metabolism in neurons and astrocytes. Progress in Lipid Research 2011; 50: 357–371 21 Quan G, Xie C, Dietschy JM et al. Ontogenesis and regulation of cholesterol metabolism in the central nervous system of the mouse. Developmental Brain Research 2003; 146: 87–98 22 Schreurs BG. The effects of cholesterol on learning and memory. Neuroscience & Biobehavioral Reviews 2010; 34: 1366–1379 23 Valenza M, Cattaneo E. Emerging roles for cholesterol in Huntington’s disease. Trends in Neurosciences 2011; 34: 474–486 24 Andersson M, Elmberger PO, Edlund C et al. Rates of cholesterol, ubiquinone, dolichol and dolichyl-P biosynthesis in rat brain slices. FEBS Letters 1990; 269: 15–18 25 Thelen KM, Falkai P, Bayer TA et al. Cholesterol synthesis rate in human hippocampus declines with aging. Neuroscience Letters 2006; 403: 15–19 26 Leoni V, Masterman T, Patel P et al. Side chain oxidized oxysterols in cerebrospinal fluid and the integrity of blood-brain and bloodcerebrospinal fluid barriers. Journal of Lipid Research 2003; 44: 793–799


27 Cartagena CM, Burns MP, Rebeck GW. 24S-hydroxycholesterol effects on lipid metabolism genes are modeled in traumatic brain injury. Brain Research 2010; 1319: 1–12 28 Lütjohann D, Breuer O, Ahlborg G et al. Cholesterol homeostasis in human brain: evidence for an age-dependent flux of 24S-hydroxycholesterol from the brain into the circulation. Proc Natl Acad Sci USA 1996; 93: 9799–9804 29 Nilsen J. Estradiol and neurodegenerative oxidative stress. Frontiers in Neuroendocrinology 2008; 29: 463–475 30 Yan MH, Wang X, Zhu X. Mitochondrial defects and oxidative stress in Alzheimer disease and Parkinson disease. Free Radical Biology and Medicine 2013; 62: 90–101 31 Ghanbarzadeh S, Garjani A, Ziaee M et al. CoQ10 and L-Carnitine Attenuate the Effect of High LDL and Oxidized LDL on Spermatogenesis in Male Rats. Drug Research 2014; In Press 32 Choi H, Park H-H, Koh S-H et al. Coenzyme Q10 protects against amyloid beta-induced neuronal cell death by inhibiting oxidative stress and activating the P13K pathway. NeuroToxicology 2012; 33: 85–90 33 Somayajulu M, McCarthy S, Hung M et al. Role of mitochondria in neuronal cell death induced by oxidative stress; neuroprotection by Coenzyme Q10. Neurobiology of Disease 2005; 18: 618–627 34 Ghanbarzadeh S, Garjani A, Ziaee M et al. Effects of L-Carnitine and Coenzyme Q10 on Impaired Spermatogenesis Caused by Isoproterenol in Male Rats. Drug Research 2014; In Press 35 Kamat SM, Kamat AS, Grossberg GT. Dementia Risk Prediction: Are We There Yet? Clinics in Geriatric Medicine 2010; 26: 113–123 36 Patterson C, Feightner J, Garcia A et al. Primary prevention of dementia. Alzheimer’s & Dementia 2007; 3: 348–354 37 Staprans I, Pan XM, Rapp JH et al. Oxidized Cholesterol in the Diet Accelerates the Development of Atherosclerosis in LDLReceptor – and Apolipoprotein E-Deficient Mice Arterioscler. Thromb Vasc Biol 2000; 20: 708–714 38 Satoh K. Serum lipid peroxide in cerebrovascular disorders determined by a new colorimetric method. Clin Chim Acta 1978; 90: 37–43 39 Khorrami A, Ghanbarzadeh S, garjani A et al. Reduction of Coenzyme Q10 Content: A Possible Effect of Isoproterenol on Heart Failure and Myocardial Infarction in Rat. Drug Research 2014; In Press 40 Waseem TV, Kolos VA, Lapatsina LP et al. Influence of cholesterol depletion in plasma membrane of rat brain synaptosomes on calcium-dependent and calcium-independent exocytosis. Neuroscience Letters 2006; 405: 106–110 41 Pensalfini A, Zampagni M, Liguri G et al. Membrane cholesterol enrichment prevents Aβ-induced oxidative stress in Alzheimer’s fibroblasts. Neurobiology of Aging 2011; 32: 210–222 42 Crisby M, Rahman SMA, Sylvén C et al. Effects of high cholesterol diet on gliosis in apolipoprotein E knockout mice: Implications for Alzheimer’s disease and stroke. Neuroscience Letters 2004; 369: 87–92 43 Montilla P, Espejo I, Muñoz MC et al. Protective effect of red wine on oxidative stress and antioxidant enzyme activities in the brain and kidney induced by feeding high cholesterol in rats. Clinical Nutrition 2006; 25: 146–153 44 Gosselet F, Saint-Pol J, Fenart L. Effects of oxysterols on the blood– brain barrier: Implications for Alzheimer’s disease. Biochemical and Biophysical Research Communications 2013; In press 45 Poli G, Biasi F, Leonarduzzi G. Oxysterols in the pathogenesis of major chronic diseases. Redox Biology 2013; 1: 125–130 46 Emanuelsson I, Norlin M. Protective effects of 27- and 24-hydroxycholesterol against staurosporine-induced cell death in undifferentiated neuroblastoma SH-SY5Y cells. Neuroscience Letters 2012; 525: 44–48 47 Kölsch H, Heun R, Kerksiek A et al. Altered levels of plasma 24S- and 27-hydroxycholesterol in demented patients. Neuroscience Letters 2004; 368: 303–308 48 Leoni V, Caccia C. 24S-hydroxycholesterol in plasma: A marker of cholesterol turnover in neurodegenerative diseases. Biochimie 2013; In Press: In Press 49 Tan C-C, Yu J-T, Tan M-S et al. Autophagy in aging and neurodegenerative diseases: implications for pathogenesis and therapy. Neurobiology of Aging 2013; In press 50 Floyd RA, Hensley K. Oxidative stress in brain aging: Implications for therapeutics of neurodegenerative diseases. Neurobiology of Aging 2002; 23: 795–807 51 Mariani E, Polidori MC, Cherubini A et al. Oxidative stress in brain aging, neurodegenerative and vascular diseases: An overview. Journal of Chromatography B 2005; 827: 65–75 52 Gamaley IA, Klyubin IV. Roles of Reactive Oxygen Species: Signaling and Regulation of Cellular Functions. Academic Press 1999;



53 Yuan Y, Bian JC, Liu XZ et al. Oxidative Stress and Apoptotic Changes of Rat Cerebral Cortical Neurons Exposed to Cadmium in Vitro. Biomedical and Environmental Sciences 2012; 25: 172–181 54 Brasnjevic I, Hof PR, Steinbusch HWM et al. Accumulation of nuclear DNA damage or neuron loss: Molecular basis for a new approach to understanding selective neuronal vulnerability in neurodegenerative diseases. DNA Repair 2008; 7: 1087–1097 55 Saxena S, Caroni P. Selective Neuronal Vulnerability in Neurodegenerative Diseases: from Stressor Thresholds to Degeneration. Neuron 2011; 71: 35–48 56 Surmeier DJ. Calcium, ageing, and neuronal vulnerability in Parkinson’s disease. The Lancet Neurology 2007; 6: 933–938 57 Butterfield DA, Galvan V, Lange MB et al. In vivo oxidative stress in brain of Alzheimer disease transgenic mice: Requirement for methionine 35 in amyloid β-peptide of APP. Free Radical Biology and Medicine 2010; 48: 136–144

Original Article 7

58 Butterfield DA, Reed T, Newman SF et al. Roles of amyloid β-peptideassociated oxidative stress and brain protein modifications in the pathogenesis of Alzheimer’s disease and mild cognitive impairment. Free Radical Biology and Medicine 2007; 43: 658–677 59 Li G, Zou L, Jack CR Jr et al. Neuroprotective effect of Coenzyme Q10 on ischemic hemisphere in aged mice with mutations in the amyloid precursor protein. Neurobiology of Aging 2007; 28: 877–882 60 Moreira PI, Santos MS, Sena C et al. CoQ10 therapy attenuates amyloid β-peptide toxicity in brain mitochondria isolated from aged diabetic rats. Experimental Neurology 2005; 196: 112–119 61 Ishrat T, Khan MB, Hoda MN et al. Coenzyme Q10 modulates cognitive impairment against intracerebroventricular injection of streptozotocin in rats. Behavioural Brain Research 2006; 171: 9–16


Learning and memory impairment in rats fed a high saturated fat diet.

Cerebellum and memory: an experimental study in the rat using a passive avoidance conditioning test.

Pregnene-type steroids and impairment of passive avoidance behavior in rats.

Verapamil Blocks Scopolamine Enhancement Effect on Memory Consolidation in Passive Avoidance Task in Rats.

Dextrorphan blocks long- but not short-term memory in a passive avoidance task in rats.

Oxiracetam prevents haloperidol-induced passive avoidance impairment in mice.

Halothane anaesthesia and DMS performance in rats: memory impairment or avoidance behaviour?

Cycloheximide and passive avoidance memory in mice: time-response, dose-response and short-term memory.

Less body fat accumulation in rats fed a safflower oil diet than in rats fed a beef tallow diet.

Preventive effect of baicalein on methamphetamine-induced amnesia in the passive avoidance test in mice.

Effects of delta9-tetrahydrocannabinol on active avoidance acquisition and passive avoidance retention in rats with amygdaloid lesions.

Effects of NIK-247 on CO-induced impairment of passive avoidance in mice.

Impairment of hippocampal-dependent memory induced by juvenile high-fat diet intake is associated with enhanced hippocampal inflammation in rats.

Effects of amygdaloid lesions on the performance of rats in four passive avoidance tasks.

Cue-induced recall of a passive avoidance response by rats with hippocampal lesions.

The effect of lithium chloride on one-trial passive avoidance learning in rats.

The effect of ethanol on a passive avoidance task in rats [proceedings].

Reduced carotid baroreceptor distensibility-induced baroreflex resetting contributes to impairment of sodium regulation in rats fed a high-fat diet.

The effects of atrial natriuretic peptide on passive avoidance behaviour in rats.

Effect of tempol on the passive avoidance and novel object recognition task in diabetic rats.

Ascorbic acid metabolism in rats fed high fat cholesterol diet.

A Memory of Early Life Physical Activity Is Retained in Bone Marrow of Male Rats Fed a High-Fat Diet.

Antagonism by propyl-beta-carboline-3-carboxylate of passive avoidance impairment induced by diazepam.

Immunohistochemical and ultrastructural investigation of acinar cells in submandibular and sublingual glands of rats fed a liquid diet.