Hippocampal brain amines in methotrexate-induced learning and memory deficit

Effect of naringin on sodium fluoride‑induced neurobehavioral deficits in Wistar rats

There is a lack of treatment for the detrimental effects of fluorosis. Sodium fluoride at a concentration of 10 ppm induces stress, depression and memory impairment in adult Wistar rats. Naringin, a flavanone glycoside isolated from citrus fruits such as lemons and oranges, possesses anti-inflammatory, antioxidant and neuroprotective properties; therefore, it was used for treatment of fluoride induced toxicity in the present study. Adult Wistar rats were divided into eight groups (n=8). The normal control (NOR) group was provided with normal tap water. The sodium fluoride (FLU)10 group received water containing 10 ppm sodium fluoride for 60 days. The treatment groups (FLU10NAR100 and FLU10NAR50) received drinking water with 10 ppm sodium fluoride ad libitum along with Naringin 100 and 50 mg/kg body weight (bw) per oral gavage, respectively. The NAR100 and NAR50 groups received Naringin 100 and 50 mg/kg bw. The PRONAR100 and PRONAR50 groups received Naringin 100 and 50 mg/kg bw for the first 15 days and then subsequently received FLU10 ppm for 60 days (total of 75 days). All animals were subjected to behavioural tests consisting of the open field test (OFT), forced swim test (FST) and novel object recognition test (NORT). After euthanasia, the hippocampus and prefrontal cortex were stained with Cresyl violet. To measure the oxidative stress caused by fluoride and its effect on antioxidant levels, estimation of reduced glutathione (GSH) by Ellman's method, lipid peroxidation (LPO) measured in terms of the MDA:thiobarbituric acid reaction and catalase was performed. To evaluate the effect of fluoride on activity of acetylcholine, estimation of acetylcholinesterase (AChE) by Ellman's method was performed. In NORT and FST, significant changes (P<0.05) were present in the FLU10NAR100 and FLU10NAR50 groups compared with the FLU10 group, showing recovery from memory deficit and depression. The OFT results were insignificant. The LPO was reduced in all the other groups except the FLU10 group, with statistically significant changes. Catalase activity was significantly lower in FLU10 as compared with the NAR100, NAR50, PRONAR100 and PRONAR50 groups. GSH and AChE activities did not show significant changes as compared with the FLU10 group. The CA3 and prefrontal cortex viable and degenerated neuron count in the FLU10 group were insignificant compared with all other groups, except for the NAR100 and NAR50 groups. Thus, Naringin can be a useful drug to avoid the neurological effects of fluoride.

Natural products for the treatment of chemotherapy-related cognitive impairment and prospects of nose-to-brain drug delivery

Chemotherapy-related cognitive deficits (CRCI) as one of the common adverse drug reactions during chemotherapy that manifest as memory, attention, and executive function impairments. However, there are still no effective pharmacological therapies for the treatment of CRCI. Natural compounds have always inspired drug development and numerous natural products have shown potential therapeutic effects on CRCI. Nevertheless, improving the brain targeting of natural compounds in the treatment of CRCI is still a problem to be overcome at present and in the future. Accumulated evidence shows that nose-to-brain drug delivery may be an excellent carrier for natural compounds. Therefore, we reviewed natural products with potential anti-CRCI, focusing on the signaling pathway of these drugs' anti-CRCI effects, as well as the possibility and prospect of treating CRCI with natural compounds based on nose-to-brain drug delivery in the future. In conclusion, this review provides new insights to further explore natural products in the treatment of CRCI.

Effect of resveratrol and combination of resveratrol and donepezil on the expression of microglial cells and astrocytes in Wistar albino rats of colchicine-induced Alzheimer's disease

Aim

The goal was to evaluate the effect of resveratrol (RS) and combination therapy of RS and donepezil (DPZ), on the numerical expression of microglial cells and astrocytes, in the frontal cortex, regions of the hippocampus in colchicine-induced Alzheimer's disease (AD) model.

Methods

The study involved male albino Wistar rats of three months, age and consisted of 6 groups, with six animals each. The immunohistochemical staining with mouse monoclonal anti-human CD 68 and mouse monoclonal anti-GFAP was performed to assess the number of microglial cells and astrocytes, respectively.

Results

AD group showed an increase in the number of microglia, and the numbers declined in the treatment groups, RS 10, RS 20, RS10/10 and DPZ + RS (p < 0.001). Astrocyte count was increased in the treatment groups in contrast to the AD group (p < 0.05). The DPZ + RS combination group revealed substantial elevation in the number of astrocytes and decreased microglial number among all the groups (p < 0.001).

Conclusion

RS administration has diminished the microglial number and elevated the number of astrocytes. The elevated reactive astrocytes have decreased the microglial population. However, the limitation of our study is utilizing the colchicine for the induction of neurodegeneration. Using the transgenic models of AD may give a better insight into the pathogenesis and effect of RS. Another limitation of this study is the administration of RS and DPZ through different routes. The prospects of this research include studying the probiotic nature of RS and the effect of RS in other neurodegenerative disorders.

Neuroprotective effect by naringin against fluorosis-induced neurodegeneration in adult Wistar rats

Fluorosis is widespread in several areas of the world and including India leading to dental and skeletal fluorosis as well as neurological manifestations. With a limited number of treatment options available, we have tried to address the issue with a nutraceutical such as naringin which is an alkaloid derived from the citrus fruit. Naringin is a potent antioxidant and has neuroprotective action which can counteract the redox imbalance induced by sodium fluoride ingestion. Neurological effects of fluorosis were evaluated in Wistar rats by open field test (OFT) and novel object recognition test (NORT) along with lipid peroxidation (LPO) and glutathione estimation in brain homogenate and cresyl violet staining of CA3 neurons in the hippocampus. Animals were divided into groups namely, normal, vehicle, fluoride, naringin 100 mg/kg bd.wt group and fluoride with naringin (FLU-NAR) group. Fluorosis was induced by providing 100 ppm of sodium fluoride ad libitum in drinking water for 30 days and prophylactic treatment of naringin for 15 days per oral. OFT, NORT and forced swim test showed significant (P ≤ 0.05) changes in the FLU-NAR group as compared to the fluoride group indicating behavioral changes in the fluoride group and positive changes in the FLU-NAR group with attenuation of stress, fear, hyperactivity and memory impairment. The decrease in LPO and increase in glutathione levels in the treatment group compared to the fluoride group were supported by histological improvement as compared to the fluoride group. Prophylactic treatment of naringin showed its possible neuroprotective effect, thus giving an alternative treatment strategy to deal with neurological manifestations of fluorosis.

Effect of 2400 MHz mobile phone radiation exposure on the behavior and hippocampus morphology in Swiss mouse model

Electromagnetic field exposure to the nervous system can cause neurological changes. The effects of extremely low-frequency electromagnetic fields, such as second-generation and third-generation radiation, have been studied in most studies. The current study aimed to explore fourth-generation cellular phone radiation on hippocampal morphology and behavior in mice. Swiss albino male mice (n = 30) were randomly categorized into 3 groups; control, 40 min, and 60 min exposure to 2400 MHz radiofrequency electromagnetic radiation (RF-EMR) daily for 60 days. The control mice were housed in the same environments but were not exposed to anything. Anxiety-like behaviors were tested using the elevated plus-maze. For histological and stereological examination, the brain was dissected from the cranial cavity. On Cresyl violet stained brain slices, the number of pyramidal neurons in the cornu ammonis of the hippocampus were counted. In exposed mice compared to control mice, a significant increase in anxiety-like behavior has been observed. Histological observations have shown many black and dark blue cytoplasmic cells with shrunken morphology degenerative alterations in the neuronal hippocampus in the radiation exposed mice. In the RF-EMR mouse hippocampus, stereological analyses revealed a significant decrease in pyramidal and granule neurons compared to controls. Our findings suggest that 2400-MHz RF-EMR cell phone radiation affects the structural integrity of the hippocampus, which would lead to behavioral changes such as anxiety. However, it alerts us to the possible long-term detrimental effects of exposure to RF-EMR.

Association between systemic rheumatic diseases and dementia risk: A meta-analysis

BACKGROUND AND AIMS

Epidemiological studies have been conducted on the relationship between systemic rheumatic diseases (SRDs) and dementia. Therefore, we focused on determining the extent of alliances bounded by SRDs, along with the risk of dementia.

MATERIALS AND METHODS

Two independent reviewers assessed all studies retrieved from the PubMed, EMBASE, Scopus, and Web of Science databases between January 1, 2000 and November 30, 2021. Only observational studies that estimated the possibility of dementia in participants with SRD were considered. The random-effects model was applied to forecast pooled risk ratios (RRs) and 95% confidence intervals (CI). Heterogeneity among the studies was evaluated using the Q and I² statistics. The quality of the included studies was assessed using the Newcastle-Ottawa Scale. Funnel plots were used to calculate the risk of bias.

RESULTS

Seventeen observational studies with 17,717,473 participants were recruited. Our findings showed that among the participants with SRDs, those with osteoarthritis, systemic lupus erythematosus, and Sjogren's syndrome were highly related to an elevated risk of dementia (pooled RR: 1.31; 95% CI: 1.15-1.49, p<0.001; pooled RR: 1.43; 95% CI: 1.19-1.73, p<0.001; and pooled RR: 1.26; 95% CI: 1.14-1.39, p<0.001, respectively). However, participants with rheumatoid arthritis (RA) were not associated with an increased risk of dementia (pooled RR: 0.98; 95% CI: 0.90-1.07, p<0.001).

CONCLUSION

This systematic review and meta-analysis demonstrated an increased dementia risk among SRDs participants, except for RA.

A Bibliometric Analysis of Cyclophosphamide, Methotrexate, and Fluorouracil Breast Cancer Treatments: Implication for the Role of Inflammation in Cognitive Dysfunction

Inflammation is considered one of the possible mechanisms behind long-term cognitive dysfunction persistent after chemotherapy treatment. The chemotherapy combination of cyclophosphamide, methotrexate, and fluorouracil (CMF) was one of the older methods of treating breast cancer patients. Decades later, these patients still report experiencing cognitive side effects. In this present bibliometric review, we applied the VOSviewer tool to describe the existing landscape on literature concerning inflammation as it relates to CMF and cognitive dysfunctions. As time progressed, we saw an increase in interest in the topic. By the mid-2010s there were approximately 1,000 publications per year. Terms related to the brain and CNS did not appear until the later years, and terms related to inflammation and breast cancer were very prevalent throughout the three decades. Also, in more recent years, inflammatory markers and plant-derived compounds used to alleviate side effects of the inflammatory response appeared in the search results. The USA remained the most prolific producer of CMF-, inflammation-, and cognitive dysfunction-related papers throughout the three decades followed by Asia and Europe. As research of cognitive dysfunction caused by inflammation due to chemotherapy treatment progresses, more opportunities emerge for therapeutic methods to improve the quality of life for long-term survivors.

Comparison of malondialdehyde levels and superoxide dismutase activity in resveratrol and resveratrol/donepezil combination treatment groups in Alzheimer's disease induced rat model

The aim of this study was to determine the malondialdehyde (MDA) level and superoxide dismutase (SOD) activity in colchicine induced Alzheimer’s disease (AD), resveratrol (RS) treated and RS + donepezil (DPZ) treated rat models. The objective was to compare the MDA level and SOD activity among these rat models. The present study included 3 months old male albino Wistar rats, which were in-house bred and weighting about 220–250 g. The rats were divided into nine subgroups which included control, sham, AD induced, RS treated and DPZ treated groups in different doses and combinations. The lipid peroxidation product for MDA in the brain homogenate was measured by estimating the levels of thiobarbituric acid reactive substance. Estimation of SOD was done by the method of autoxidation of pyrogallol by Marklund and Marklund. There was a marked increase in the MDA levels in AD induced group in comparison to the control group (p < 0.05). The SOD activity was higher in the RS 10 and RS 20 treated groups in contrast to the AD group (p < 0.05). In DPZ + RS group, there was a substantial increase in the SOD activity (p < 0.05). It is also observed that the RS 20 treatment group showed higher SOD activity than the RS 10 group (p < 0.05). This study showed that, AD induced group had elevated levels of MDA, which indicates the poor oxidative stress–defence mechanism. The RS 10 and RS 20 groups showed higher SOD activity in comparison to the AD group, which indicated the improved oxidative stress–defence mechanism. The RS + DPZ group showed higher SOD activity, indicating a synergistic effect of DPZ and RS.

Early Effects of Cyclophosphamide, Methotrexate, and 5-Fluorouracil on Neuronal Morphology and Hippocampal-Dependent Behavior in a Murine Model

Breast cancer (BC) is the most common cancer among women. Fortunately, BC survival rates have increased because the implementation of adjuvant chemotherapy leading to a growing population of survivors. However, chemotherapy-induced cognitive impairments (CICIs) affect up to 75% of BC survivors and may be driven by inflammation and oxidative stress. Chemotherapy-induced cognitive impairments can persist 20 years and hinder survivors' quality of life. To identify early effects of CMF administration in mice, we chose to evaluate adult female mice at 2-week postchemotherapy. Mice received weekly IP administration of CMF (or saline) for 4 weeks, completed behavioral testing, and were sacrificed 2 weeks following their final CMF injection. Behavioral results indicated long-term memory (LTM) impairments postchemotherapy, but did not reveal short-term memory deficits. Dendritic morphology and spine data found increases in overall spine density within CA1 basal and CA3 basal dendrites, but no changes in DG, CA1 apical, or CA3 apical dendrites. Further analysis revealed decreases in arborization across the hippocampus (DG, CA1 apical and basal, CA3 apical and basal). These physiological changes within the hippocampus correlate with our behavioral data indicating LTM impairments following CMF administration in female mice 2-week postchemotherapy. Hippocampal cytokine analysis identified decreases in IL-1α, IL-1β, IL-3, IL-10, and TNF-α levels.

Protective effect of mangiferin on memory impairment: A systematic review

Memory impairment (MI) is one of the predominant criteria generally used to identify schizophrenia, dementia and amnesia that are associated with neurodegenerative disorders by evaluating patient’s cognitive symptoms. To date, there is no available treatment that can completely mitigate MI. Currently, there is a trend in recent investigations towards symptomatic therapy approaches using a variety of natural compounds. Mangiferin is one of them that have been investigated extensively. Mangiferin is a naturally occurring potent glucoxilxanthone and is mainly isolated from the Mangifera indica (Mango) plant. This review is aimed at providing a comprehensive overview on the efficacy of mangiferin on MI, based on in-vivo animal studies. After screening through articles identified from Scopus and PubMed based on the inclusion and exclusion criteria, a total of 11 articles between 2009 and 2019 were included. The minimum and maximum dose of mangiferin were 10 and 200 mg/kg respectively and administered over the period of 12–154 days. The results of 11 articles showed that mangiferin effectively improved spatial recognition, episodic aversive events, short- and long-term memories primarily occurring via its antioxidant and anti-inflammatory effects. The outcomes of the review revealed that mangiferin improves memory and cognitive impairment in different animal models, indicating that it has potential preventive and therapeutic roles in MI.

Chemotherapy-induced cognitive impairment (CICI): An overview of etiology and pathogenesis

Many cancer patients treated with chemotherapy develop chemotherapy-induced cognitive impairment (CICI), often referred to as chemo-brain, which manifest during or post-treatment with variable degrees, onset and duration thereby affecting the patients' quality of life. Several chemotherapeutic agents have been studied to determine its possible association with cognitive impairment and to fully comprehend their contribution to CICI. A vast number of studies have emerged proposing several candidate underlying mechanisms and etiologies contributing to CICI such as direct neurotoxicity, BBB disruption, decreased hippocampal neurogenesis, white matter abnormalities, secondary neuro-inflammatory response and increased oxidative stress; however, the exact underlying mechanisms are still not well defined. This review summarizes CICI associated with most commonly used chemotherapeutic agents with emphasizes the possible underlying pathogenesis in both animal and clinical studies.

Neuroprotective effects of hesperidin against methotrexate-induced changes in neurogenesis and oxidative stress in the adult rat

Methotrexate (MTX) induces the formation of reactive oxygen species (ROS) and leads to neurotoxicity. The drug also negatively impacts neurogenesis and memory. Hesperidin (Hsd) is a major flavanoid with multiple beneficial pharmacological effects such as anti-oxidation, anti-inflammation, and neuroprotective effects. The aim of our study was to investigate the neuroprotective effects of Hsd against MTX-induced alterations in oxidative stress and neurogenesis. Sprague Dawley rats were divided into four groups: 1) a vehicle group, which received saline and propylene glycol, 2) an Hsd group, which was orally administered with Hsd (100 mg/kg) for 21 days, 3) an MTX group, which received MTX (75 mg/kg) by intravenous injection on days 8 and 15, and 4) an MTX + Hsd group, which received both MTX and Hsd. After treatment with MTX, p21-positive cells had increased significantly and doublecortin (DCX) expression in the hippocampus had decreased significantly. Treatment with MTX also increased malondialdehyde (MDA) in both the hippocampus and prefrontal cortex and decreased levels of brain-derived neurotropic factor (BDNF) and nuclear factor erythroid 2-related factor 2 (Nrf2) in the hippocampus and prefrontal cortex. Additionally, there were significant decreases in superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) in the hippocampus and prefrontal cortex in the MTX group. However, co-treatment with Hsd ameliorated the negative effects of MTX on neurogenesis, oxidative stress, and antioxidant enzymes. These findings suggest that Hsd may be able to prevent neurotoxic effects of MTX by reducing oxidative stress and enhancing hippocampal neurogenesis.

Investigating Relationship between Pre- and Post- Chemotherapy Cognitive Performance with Levels of Depression and Anxiety in Breast Cancer Patients: A Cross-Sectional Study

INTRODUCTION

Evidence suggests that cancer and chemotherapy-related cognitive impairments are an important clinical issue that can have a negative impact on the quality of life (QOL) of many cancer patients during and after treatment. The aim of the current study was to investigate the relationship between cognitive performance before and after chemotherapy with levels of depression and anxiety in patients with breast cancer.

MATERIALS AND METHODS

This cross-sectional descriptive-analytical study was performed on 100 women with breast cancer in south of Iran. Patients included in the study were evaluated for cognitive performance before chemotherapy and 1, 3, and 6 months after chemotherapy. Patients' cognitive performance was assessed by Mini-Mental State Examination (MMSE). Patients were also assessed for their level of anxiety and depression using Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI). Descriptive tests (percentage, frequency and mean) and ANOVA test used for statistical analysis.

RESULTS

Results of ANOVA test showed a significant difference between the cognitive performance of patients with breast cancer at 1, 3, and 6 months after chemotherapy compared to pre- chemotherapy phase. The above test also revealed a significant relationship between cognitive performance of patients and anxiety and depression.

CONCLUSION

The results showed that, due to the decrease in cognitive performance and increased anxiety and depression after initiation of chemotherapy in patients with breast cancer, it is necessary to closely monitor the mental and psychological status of these patients by their family and the treatment staffs so that the patient be able to cope with the disease more optimally and to recover.

Rheumatoid arthritis and neurodegenerative dementia: a nested case-control study and a follow-up study using a national sample cohort

OBJECTIVES

The present study evaluated the associations between rheumatoid arthritis (RA) and neurodegenerative dementia using a Korean national sample cohort.

METHODS

We designed two studies using the Korean National Health Insurance Service-National Sample Cohort from 2002 to 2013. Study I included participants with dementia matched 1:4 with controls and analyzed the participants' history of RA. Study II included participants with RA matched 1:4 with controls and analyzed the occurrence of dementia. RA was defined by the presence of relevant ICD-10 codes (M05 or M06) and medication histories. Neurodegenerative dementia was defined using ICD-10 codes (G30 or F00). Crude and adjusted odds ratios (ORs) were analyzed using conditional logistic regression analyses. Crude and adjusted hazard ratios (HRs) were analyzed using the stratified Cox proportional hazard model. Subgroup analyses were performed on groups stratified by age and sex.

RESULTS

The adjusted ORs for RA were 0.96 (95% CI = 0.78-1.16, P = 0.644) in the dementia group in study I. The adjusted HRs for dementia were 0.91 (95% CI = 0.76-1.10, P = 0.319) in the RA group in study II. No subgroup analysis reached the statistical significance level.

CONCLUSION

We could not identify any significant relationship between RA and dementia.Key Points• Two studies were conducted to identify the relationship between rheumatoid arthritis and dementia using national cohort data.• Neither study showed any association between rheumatoid arthritis and dementia.

Effect of N-Acetyl Cysteine on Intracerebroventricular Colchicine Induced Cognitive Deficits, Beta Amyloid Pathology, and Glial Cells

Among the many factors responsible for the cognitive decline in Alzheimer's disease, beta amyloid protein and plaque formation is crucial. This amyloid pathology is associated with activation of glial cells and oxidative stress but whether oxidative stress activates beta amyloid protein in the neurons is not clear. Further the expression of microglia is also known to vary during pathogenesis of beta amyloid plaques. The aim of the present study is to evaluate the antioxidant effect of NAC on amyloid pathology and cognition and also to investigate the link between amyloid pathology and glial cells activation. Intracerebroventricular colchicine in rats known mimics human AD in many aspects including memory loss, oxidative stress, and hyper phosphorylation of tau protein. The animal groups consisted of age matched control, sham operated, AD, and NAC treated in AD models of rats. Cognitive function was evaluated in active avoidance test; beta amyloid protein, beta amyloid plaques, astrocytes, and microglia cells were quantified using immunohistochemistry in hippocampal and prefrontal cortices. Colchicine has resulted in significant cognitive loss, increased intraneuronal beta amyloid protein expression, increased reactive astrocytes, and activated microglia in all the regions of the hippocampus and prefrontal cortices. The antioxidant NAC has reversed the cognitive deficits and inhibited microglia activation but failed to inhibit BAP expression and astrocytosis. Intraneuronal BAP accumulation is deleterious and known to adversely affect cognition, but in this study in spite of intraneuronal BAP accumulation, the cognition is restored. It can be postulated that NAC might have reversed the effect of intraneuronal beta amyloid protein by acting on some downstream compensatory mechanisms which needs to be explored.

Methotrexate Affects Cerebrospinal Fluid Folate and Tau Levels and Induces Late Cognitive Deficits in Mice

Intravenous and/or intrathecal administration of the anti-folate drug methotrexate is a common chemotherapeutic procedure in childhood leukemia. Therapeutic and prophylactic efficacy of these procedures notwithstanding, the occurrence of late adverse effects remains a cause of clinical concern in leukemia survivors. We propose an experimental mouse model to mimic the impact of methotrexate exposure on brain biochemistry and cell proliferation, as well as behavioral and neurocognitive functioning at adult age. Female C57Bl6/J mouse pups received saline or methotrexate injection (20 mg/kg, i.p.). CSF and serum concentrations of folate metabolites and toxicity makers were analyzed at 4 h, 24 h, and 1 week following injection. Behavioral test battery performance was assessed at adult age (3-4 months). We found acute changes in serum and CSF levels of folate in exposed pups that coincided with increases in CSF Tau, whereas homocysteine in serum and CSF, and CSF levels of pTau were unchanged or remained below detection. In addition, methotrexate injection coincided with diminished hippocampal cell proliferation 1 week after methotrexate injection. At adult age, exposed mice displayed hippocampus-dependent deficits in the Morris water maze, whereas exploration and anxiety-related behaviors were largely unaffected. Particularly during the reference memory (probe) trial after reversal learning, methotrexate-exposed animals were less precise than controls. These findings demonstrate adult neurocognitive sequelae in a mouse model that can be attributed to the biochemical and cellular impact of early-life methotrexate exposure.

N-Acetyl Cysteine Supplement Minimize Tau Expression and Neuronal Loss in Animal Model of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by the accumulation of neurofibrillary tangles (NFT), deposition of beta amyloid plaques, and consequent neuronal loss in the brain tissue. Oxidative stress to the neurons is often attributed to AD, but its link to NFT and β-amyloid protein (BAP) still remains unclear. In an animal model of AD, we boosted the oxidative defense by N-Acetyl cysteine (NAC), a precursor of glutathione, a powerful antioxidant and free radical scavenger, to understand the link between oxidative stress and NFT. In mimicking AD, intracerebroventricular (ICV) colchicine, a microtubule disrupting agent also known to cause oxidative stress was administered to the rats. The animal groups consisted of an age-matched control, sham operated, AD, and NAC treated in AD models of rats. Cognitive function was evaluated in a passive avoidance test; neuronal degeneration was quantified using Nissl staining. NFT in the form of abnormal tau expression in different regions of the brain were evaluated through immunohistochemistry using rabbit anti-tau antibody. ICV has resulted in significant cognitive and neuronal loss in medial prefrontal cortex (MFC) and all the regions of the hippocampus. It has also resulted in increased accumulation of intraneuronal tau in the hippocampus and MFC. NAC treatment in AD model rats has reversed the cognitive loss and neuronal degeneration. The intraneuronal tau expression also minimized with NAC treatment in AD model rats. Thus, our findings suggest that an antioxidant supplement during the progression of AD is likely to prevent neuronal degeneration by minimizing the neurofibrillary degeneration in the form of tau accumulation.

DMARD use is associated with a higher risk of dementia in patients with rheumatoid arthritis: A propensity score-matched case-control study

BACKGROUND

Patients with rheumatoid arthritis (RA) exhibit an increased risk of dementia. Disease-modifying antirheumatic drugs (DMARDs) are commonly used to slow RA progression, but studies investigating the relationship between DMARDs and dementia in patients with RA are lacking. We investigated the relationship between DMARDs and dementia in patients with RA.

METHODS

Using the National Health Insurance Research Database, patients aged ≥20years, who were newly diagnosed with RA between 2000 and 2011 were identified. Patients with RA who had dementia comprised the dementia group, and patients with RA who did not have dementia comprised the control group. The groups were matched at a 1:1 ratio by the propensity score. DMARDs were categorized into conventional synthetic DMARDs (csDMARDs) and biological DMARDs (bDMARDs). Logistic regression models were used to calculate the odds ratio and 95% confidence interval (CI) to evaluate the association between DMARD use and the risk of dementia in patients with RA.

RESULTS

A total of 957 patients with RA and dementia, and 957 patients with RA but not dementia, were enrolled. The risk of dementia was determined to be 1.63-fold higher in patients with RA with csDMARD use than in those without csDMARD use (95% CI=1.33-2.00). No significant risk of dementia was observed in patients with RA who used bDMARDs compared with their counterparts. However, patients with RA who used hydroxychloroquine, methotrexate, and sulfasalazine exhibited significant risks of dementia, irrespective of cumulative exposure days.

CONCLUSION

Patients with RA who used csDMARDs exhibit significant association with dementia.

Decreased postural control in adult survivors of childhood cancer treated with chemotherapy

The objective of cancer treatment is to secure survival. However, as chemotherapeutic agents can affect the central and peripheral nervous systems, patients must undergo a process of central compensation. We explored the effectiveness of this compensation process by measuring postural behaviour in adult survivors of childhood cancer treated with chemotherapy (CTS). We recruited sixteen adults treated with chemotherapy in childhood for malignant solid (non-CNS) tumours and 25 healthy age-matched controls. Subjects performed posturography with eyes open and closed during quiet and perturbed standing. Repeated balance perturbations through calf vibrations were used to study postural adaptation. Subjects were stratified into two groups (treatment before or from 12 years of age) to determine age at treatment effects. Both quiet (p = 0.040) and perturbed standing (p ≤ 0.009) were significantly poorer in CTS compared to controls, particularly with eyes open and among those treated younger. Moreover, CTS had reduced levels of adaptation compared to controls, both with eyes closed and open. Hence, adults treated with chemotherapy for childhood cancer may suffer late effects of poorer postural control manifested as reduced contribution of vision and as reduced adaptation skills. These findings advocate development of chemotherapeutic agents that cause fewer long-term side effects when used for treating children.

Impaired Brain Dopamine and Serotonin Release and Uptake in Wistar Rats Following Treatment with Carboplatin

Chemotherapy-induced cognitive impairment, known also as “chemobrain”, is a medical complication of cancer treatment that is characterized by a general decline in cognition affecting visual and verbal memory, attention, complex problem solving skills, and motor function. It is estimated that one-third of patients who undergo chemotherapy treatment will experience cognitive impairment. Alterations in the release and uptake of dopamine and serotonin, central nervous system neurotransmitters that play important roles in cognition, could potentially contribute to impaired intellectual performance in those impacted by chemobrain. To investigate how chemotherapy treatment affects these systems, fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes was used to measure dopamine and serotonin release and uptake in coronal brain slices containing the striatum and dorsal raphe nucleus, respectively. Measurements were taken from rats treated weekly with selected doses of carboplatin and from control rats treated with saline. Modeling the stimulated dopamine release plots revealed an impairment of dopamine release per stimulus pulse (80% of saline control at 5 mg/kg and 58% at 20 mg/kg) after 4 weeks of carboplatin treatment. Moreover, V_max, the maximum uptake rate of dopamine, was also decreased (55% of saline control at 5 mg/kg and 57% at 20 mg/kg). Nevertheless, overall dopamine content, measured in striatal brain lysates by high performance liquid chromatography, and reserve pool dopamine, measured by FSCV after pharmacological manipulation, did not significantly change, suggesting that chemotherapy treatment selectively impairs the dopamine release and uptake processes. Similarly, serotonin release upon electrical stimulation was impaired (45% of saline control at 20 mg/kg). Measurements of spatial learning discrimination were taken throughout the treatment period and carboplatin was found to alter cognition. These studies support the need for additional neurochemical and behavioral analyses to identify the underlying mechanisms of chemotherapy-induced cognitive disorders.

Resveratrol for prenatal-stress-induced oxidative damage in growing brain and its consequences on survival of neurons

BACKGROUND

Prenatal-stress-induced neuronal damage in offspring is multifactorial, including oxidative damage in the developing brain. Resveratrol is known to exert its neuroprotective potentials by upregulating several antioxidant systems. Hence, the study was undertaken to evaluate the neuroprotective effect of resveratrol against prenatal-stress-induced hippocampal damage and oxidative damage in neonate rat brains.

METHODS

Pregnant rats were subjected to restraint stress during early or late gestational period. Another set of rats received resveratrol during the entire gestational period along with early or late gestational stress. The study parameters included several antioxidant studies directly from rat brain homogenate on the 40th postnatal day and hippocampal neuronal assay on the 21st postnatal day.

RESULTS

Early as well as late gestational stress resulted in a significant increase in lipid peroxidation and advanced oxidation protein products and decrease in total antioxidant activity and nitric oxide levels in rat brain homogenate. The neurons of the dentate gyrus were severely affected in early and late gestational stress, and only the neurons of the CA3 region were adversely affected in late gestational stress. Administration of resveratrol reversed the prenatal-stress-induced oxidative damage and neurons of dentate gyrus but not the CA3 hippocampal neurons.

CONCLUSIONS

These results show the neuroprotective abilities of resveratrol against prenatal-stress-induced oxidative damage in neonatal rat brain.

Clinical characteristics, pathophysiology, and management of noncentral nervous system cancer-related cognitive impairment in adults

Answer questions and earn CME/CNE Over the past few decades, a body of research has emerged confirming what many adult patients with noncentral nervous system cancer have long reported-that cancer and its treatment are frequently associated with cancer-related cognitive impairment (CRCI). The severity of CRCI varies, and symptoms can emerge early or late in the disease course. Nonetheless, CRCI is typically mild to moderate in nature and primarily involves the domains of memory, attention, executive functioning, and processing speed. Animal models and novel neuroimaging techniques have begun to unravel the pathophysiologic mechanisms underlying CRCI, including the role of inflammatory cascades, direct neurotoxic effects, damage to progenitor cells, white matter abnormalities, and reduced functional connectivity, among others. Given the paucity of research on CRCI with other cancer populations, this review synthesizes the current literature with a deliberate focus on CRCI within the context of breast cancer. A hypothetical case-study approach is used to illustrate how CRCI often presents clinically and how current science can inform practice. While the literature regarding intervention for CRCI is nascent, behavioral and pharmacologic approaches are discussed.

Cognitive impact of cytotoxic agents in mice

RATIONALE AND OBJECTIVES

Adjuvant chemotherapy is associated with changes in cognition in a subgroup of cancer patients. Chemotherapy is generally given as a combination of cytotoxic agents, which makes it hard to define the agent responsible for these observed changes. Literature on animal experiments has been difficult to interpret due to variance in experimental setup.

METHODS

We examined the effects of cytotoxic agents administered separately on various cognitive measures in a standardized animal model. Male C57Bl/6 mice received cyclophosphamide, docetaxel, doxorubicin, 5-fluorouracil, methotrexate, or topotecan. These agents represent different compound classes based on their working mechanism and are frequently prescribed in the clinic. A control group received saline. Behavioral testing started 2 or 15 weeks after treatment and included testing general measures of behavior and cognitive task performance: spontaneous behavior in an automated home cage, open field, novel location recognition (NLR), novel object recognition (NOR), Barnes maze, contextual fear conditioning, and a simple choice reaction time task (SCRTT).

RESULTS

Cyclophosphamide, docetaxel, and doxorubicin administration affected spontaneous activity in the automated home cage. All cytotoxic agents affected memory (NLR and/or NOR). Spatial memory measured in the Barnes maze was affected after administration with doxorubicin, 5-fluorouracil, and topotecan. Decreased inhibition in the SCRTT was observed after treatment with cyclophosphamide, docetaxel, and topotecan.

CONCLUSIONS

Our data show that, in mice, a single treatment with a cytotoxic agent causes cognitive impairment. Not all cytotoxic agents affected the same cognitive domains, which might be explained by differences in working mechanisms of the various agents.

Neurotoxicity of cancer chemotherapy

There is accumulating clinical evidence that chemotherapeutic agents induce neurological side effects, including memory deficits and mood disorders, in cancer patients who have undergone chemotherapeutic treatments. This review focuses on chemotherapy-induced neurodegeneration and hippocampal dysfunctions and related mechanisms as measured by in vivo and in vitro approaches. These investigations are helpful in determining how best to further explore the causal mechanisms of chemotherapy-induced neurological side effects and in providing direction for the future development of novel optimized chemotherapeutic agents.

Chemotherapy-related cognitive dysfunction: current animal studies and future directions

Cognitive impairment is a potential long-term side effect of adjuvant chemotherapy that can have a major impact on the quality of life of cancer survivors. There is a growing number of preclinical studies addressing this issue, thereby extending our knowledge of the mechanisms underlying chemotherapy-induced neurotoxicity. In this review, we will summarize the recent advances and important findings presented in these studies. Emerging challenges, such as the development of neuroprotective strategies, and the role of the blood-brain barrier on cognitive impairment will be described and future directions in this field of investigation will be outlined.

Oxidative stress and neurodegenerative disorders

Living cells continually generate reactive oxygen species (ROS) through the respiratory chain during energetic metabolism. ROS at low or moderate concentration can play important physiological roles. However, an excessive amount of ROS under oxidative stress would be extremely deleterious. The central nervous system (CNS) is particularly vulnerable to oxidative stress due to its high oxygen consumption, weakly antioxidative systems and the terminal-differentiation characteristic of neurons. Thus, oxidative stress elicits various neurodegenerative diseases. In addition, chemotherapy could result in severe side effects on the CNS and peripheral nervous system (PNS) of cancer patients, and a growing body of evidence demonstrates the involvement of ROS in drug-induced neurotoxicities as well. Therefore, development of antioxidants as neuroprotective drugs is a potentially beneficial strategy for clinical therapy. In this review, we summarize the source, balance maintenance and physiologic functions of ROS, oxidative stress and its toxic mechanisms underlying a number of neurodegenerative diseases, and the possible involvement of ROS in chemotherapy-induced toxicity to the CNS and PNS. We ultimately assess the value for antioxidants as neuroprotective drugs and provide our comments on the unmet needs.

Cognitive impairment in gynecologic cancers: a systematic review of current approaches to diagnosis and treatment

PURPOSE

To review the etiology and assessment of chemotherapy-related cognitive impairment (CRCI). To explore current treatment and prevention strategies for CRCI and propose future research goals in the field of gynecologic oncology.

METHODS

Computerized searches in PubMed of cognitive impairment in cancer between 2000 and 2012 were conducted. The inclusion criteria were randomized control trials evaluating treatment of CRCI and search terms 'cognitive function, cognitive impairment, cognitive decline, chemobrain, chemofog, and cancer'.

RESULTS

To date, numerous modalities have been utilized for assessing CRCI in patients undergoing therapy. It has been proposed to move towards web-based assessment modalities as a possible standard. Few studies have aimed to elucidate possible treatment and prevention options for CRCI; even less in the field of gynecologic oncology. Only seven of these studies were subjected to randomized control trials. Only one of these studies looked at treatment in patients with gynecologic cancers.

CONCLUSIONS

The etiology of CRCI is multi-factorial. Following from this, there is no consensus on the best way to assess CRCI although objective measures are more reliable. One must extrapolate data from the non-gynecologic cancer literature, even venturing to non-cancer literature, to explore the treatment and prevention of CRCI. The methods found in these areas of research have not yet been applied to CRCI in gynecologic oncology.

Effects of early chemotherapeutic treatment on learning in adolescent mice: implications for cognitive impairment and remediation in childhood cancer survivors

PURPOSE

Among children diagnosed with acute lymphoblastic leukemia (ALL) and given chemotherapy-only treatment, 40% to 70% of survivors experience neurocognitive impairment. The present study used a preclinical mouse model to investigate the effects of early exposure to common ALL chemotherapeutics methotrexate (MTX) and cytarabine (Ara-C) on learning and memory.

EXPERIMENTAL DESIGN

Preweanling mouse pups were treated on postnatal day (PND) 14, 15, and 16 with saline, MTX, Ara-C, or a combination of MTX and Ara-C. Nineteen days after treatment (PND 35), behavioral tasks measuring different aspects of learning and memory were administered.

RESULTS

Significant impairment in acquisition and retention over both short (1 hour) and long (24 hours) intervals, as measured by autoshaping and novel object recognition tasks, was found following treatment with MTX and Ara-C. Similarly, a novel conditional discrimination task revealed impairment in acquisition for chemotherapy-treated mice. No significant group differences were found following the extensive training component of this task, with impairment following the rapid training component occurring only for the highest MTX and Ara-C combination group.

CONCLUSIONS

Findings are consistent with those from clinical studies suggesting that childhood cancer survivors are slower at learning new information and primarily exhibit deficits in memory years after successful completion of chemotherapy. The occurrence of mild deficits on a novel conditional discrimination task suggests that chemotherapy-induced cognitive impairment may be ameliorated through extensive training or practice.

Cognitive impairments and cancer chemotherapy: translational research at a crossroads

Cancer chemotherapy is often associated with cognitive deficits which may remain after the treatment has ended. As more people survive cancer, concern is increasing about the impact of these problems with memory and executive function when they return to everyday life. When chemotherapeutic drugs are administered to healthy animals in dosing regimens modeling those used in humans, cognitive deficits also occur, and these preclinical studies can provide information about the biological mechanisms by which the cancer fighting drugs affect the brain. Evidence from animal studies points to damage to hippocampus, particularly a disruption of neurogenesis, whereas human studies emphasize cognitive deficits associated with impairments in frontal cortical function. This discrepancy may be due more to the tasks selected by researchers, and the choice of biochemical endpoints than inherently different effects of chemotherapy in humans and rodents. These differences in approach must be reconciled if common underlying mechanisms are to be identified, with the hope of leading to novel drug or non-pharmacological treatments. This may be achieved by broadening the scope of human and animal studies, and by looking outside the topic of chemotherapy-induced cancer deficits to learn from the advances being made by studying the effects of stress and somatic disease on brain function, and the cognitive impairments now recognized to result from a wide range of mental and physical illnesses.

Neuroprotective effect of resveratrol against prenatal stress induced cognitive impairment and possible involvement of Na(+), K(+)-ATPase activity

Resveratrol, an active ingredient of red wine extracts, has been shown to exhibit neuroprotective effects in several experimental models. Hence in the present study, the protective effects of resveratrol on cognitive deficits induced by prenatal stress were evaluated in offspring, and the possible involvement of Na(+), K(+)-ATPase in learning deficits were explored. Pregnant rats were subjected to restraint stress during early or late gestational period. Another set of rats received resveratrol during the entire gestational period along with early or late gestational stress. The study parameters included various behavioral tests like open field test and Morris water maze test. At the end of the behavioral tests (on 40th postnatal day), the offspring were sacrificed, and their brain homogenate was subjected to Na(+), K(+)-ATPase estimation. Early and late gestational stress affected spatial learning and memory and prenatal resveratrol has reversed these cognitive deficits. The Na(+), K(+)-ATPase activity in the offspring brain homogenate was reduced in the late gestational stress group; however prenatal resveratrol treatment has not affected this activity. These data suggest the neuroprotective efficacy of resveratrol against prenatal stress induced cognitive impairment. Though late gestational stress involves Na(+), K(+)-ATPase activity in rat brain homogenate, this would not be the primary cause in prenatal stress-induced cognitive dysfunction.

Effects of repeated administration of chemotherapeutic agents tamoxifen, methotrexate, and 5-fluorouracil on the acquisition and retention of a learned response in mice

RATIONALE

A number of cancer chemotherapeutic agents have been associated with a loss of memory in breast cancer patients although little is known of the causality of this effect.

OBJECTIVES

To assess the potential cognitive effects of repeated exposure to chemotherapeutic agents, we administered the selective estrogen receptor modulator tamoxifen or the antimetabolite chemotherapy, methotrexate, and 5-fluorouracil, alone and in combination to mice and tested them in a learning and memory assay.

METHODS

Swiss-Webster male mice were injected with saline, 32 mg/kg tamoxifen, 3.2 or 32 mg/kg methotrexate, 75 mg/kg 5-fluorouracil, 3.2 or 32 mg/kg methotrexate in combination with 75 mg/kg 5-fluorouracil once per week for 3 weeks. On days 23 and 24, mice were tested for acquisition and retention of a nose-poke response in a learning procedure called autoshaping. In addition, the acute effects of tamoxifen were assessed in additional mice in a similar procedure.

RESULTS

The chemotherapeutic agents alone and in combination reduced body weight relative to saline treatment over the course of 4 weeks. Repeated treatment with tamoxifen produced both acquisition and retention effects relative to the saline-treated group although acute tamoxifen was without effect except at a behaviorally toxic dose. Repeated treatment with methotrexate in combination with 5-fluorouracil produced effects on retention, but the magnitude of these changes depended on the methotrexate dose.

CONCLUSIONS

These data demonstrate that repeated administration of tamoxifen or certain combination of methotrexate and 5-fluorouracil may produce deficits in the acquisition or retention of learned responses which suggest potential strategies for prevention or remediation might be considered in vulnerable patient populations.

Preserved learning and memory following 5-fluorouracil and cyclophosphamide treatment in rats

Some patients experience enduring cognitive impairment after cancer treatment, a condition termed "chemofog". Animal models allow assessment of chemotherapy effects on learning and memory per se, independent of changes due to cancer itself or associated health consequences such as depression. The present study examined the long-term learning and memory effects of a chemotherapy cocktail used widely in the treatment of breast cancer, consisting of 5-fluorouracil (5FU) and cyclophosphamide (CYP). Eighty 5-month old male F344 rats received contextual and cued fear conditioning before treatment with saline, or a low or high dose drug cocktail (50mg/kg CYP and 75 mg/kg 5FU, or 75 mg/kg CYP and 120 mg/kg 5FU, i.p., respectively) every 30 days for 2 months. After a 2-month, no-drug recovery, both long-term retention and new task acquisition in the water maze and 14-unit T-maze were assessed. Neither dose of the CYP/5FU cocktail impaired retrograde fear memory despite marked toxicity documented by enduring weight loss and 50% mortality at the higher dose. Acquisition in the water maze and Stone maze was also normal relative to controls in rats treated with CYP/5FU. The results contribute to a growing literature suggesting that learning and memory mediated by the hippocampus can be relatively resistant to chemotherapy. Future investigation may need to focus on assessments of processing speed, executive function and attention, and the possible interactive contribution of cancer itself and aging to the post-treatment development of cognitive impairment.

Chemotherapy and cognitive impairment: treatment options

Chemotherapy has improved survival rates in patients with many of the common cancers. However, there is reliable evidence that, as a result of treatment, a subset of cancer survivors experience cognitive problems that can last for many years after the completion of chemotherapy. The etiology of this phenomenon is largely unknown, and currently there are no proven treatments. This article explores the clinical and preclinical literature on potential therapies for chemotherapy-induced cognitive impairments. Emerging results suggest that both pharmacological and behavioral approaches may offer patients some benefits. However, research in this area has been limited and is sometimes fraught with methodological flaws. As a result, it is difficult to draw definite conclusions regarding treatment efficacy. These issues, along with predictors of cognitive decline, are discussed in the light of possible interventions.

Disruption of learning processes by chemotherapeutic agents in childhood survivors of acute lymphoblastic leukemia and preclinical models

OBJECTIVE

With the survival rate of acute lymphoblastic leukemia (ALL) surpassing 90 percent within this decade, new research is emerging in the field of late effects. A review of the research investigating the relationship of treatment regimens for ALL to specific late effect deficits, underlying mechanisms, and possible remediation is warranted to support continued studies.

METHODS

The clinical literature was briefly surveyed to describe the occurrence and topography of late effects, specifically neurocognitive deficits. Additionally, the preclinical literature was reviewed to uncover potential underlying mechanisms of these deficits. The advantages of using rodent models to answer these questions are outlined, as is an assessment of the limited number of rodent models of childhood cancer treatment.

RESULTS

The literature supports that childhood survivors of ALL exhibit academic difficulties and are more likely to be placed in a special education program. Behavioral evidence has highlighted impairments in the areas of attention, working memory, and processing speed, leading to a decrease in full scale IQ. Neurophysiological and preclinical evidence for these deficits has implicated white matter abnormalities and acquired brain damage resulting from specific chemotherapeutic agents commonly used during treatment.

CONCLUSIONS

The exact role of chemotherapeutic agents in learning deficits remains mostly unknown. Recommendations for an improved rodent model of learning deficits in childhood cancer survivors are proposed, along with suggestions for future directions in this area of research, in hopes that forthcoming treatment regimens will reduce or eliminate these types of impairments.

Acute and late onset cognitive dysfunction associated with chemotherapy in women with breast cancer

BACKGROUND

Growing evidence supports cognitive dysfunction associated with standard dose chemotherapy in breast cancer survivors. We determined the incidence, nature, and chronicity of cognitive dysfunction in a prospective longitudinal randomized phase 3 treatment trial for patients with T1-3, N0-1, M0 breast cancer receiving 5-fluorouracil, doxorubicin, and cyclophosphamide with or without paclitaxel.

METHODS

Forty-two patients underwent a neuropsychological evaluation including measures of cognition, mood, and quality of life. Patients were scheduled to be assessed before chemotherapy, during and shortly after chemotherapy, and 1 year after completion of chemotherapy.

RESULTS

Before chemotherapy, 21% (9 of 42) evidenced cognitive dysfunction. In the acute interval, 65% (24 of 37) demonstrated cognitive decline. At the long-term evaluation, 61% (17 of 28) evidenced cognitive decline after cessation of treatment. Within this group of patients, 71% (12 of 17) evidenced continuous decline from the acute interval, and, notably, 29% (5 of 17) evidenced new delayed cognitive decline. Cognitive decline was most common in the domains of learning and memory, executive function, and processing speed. Cognitive decline was not associated with mood or other measured clinical or demographic characteristics, but late decline may be associated with baseline level of performance.

CONCLUSIONS

Standard dose systemic chemotherapy is associated with decline in cognitive function during and shortly after completion of chemotherapy. In addition, delayed cognitive dysfunction occurred in a large proportion of patients. These findings are consistent with a developing body of translational animal research demonstrating both acute and delayed structural brain changes as well as functional changes associated with common chemotherapeutic agents such as 5-fluorouracil.

Mesial temporal sclerosis associated with methotrexate-induced leukoencephalopathy

Mesial temporal sclerosis is a common form of symptomatic, localization-related epilepsy in children and adolescents, but its occurrence with acute lymphoblastic leukemia is rare. We present clinical records and neuroimaging results of a 13-year-old patient with acute lymphoblastic leukemia who developed recurrent partial seizures after an episode of leukoencephalopathy thought to be caused by methotrexate. Neuroradiologic images revealed hippocampal abnormalities consistent with the findings of mesial temporal sclerosis. Mesial temporal sclerosis was not previously reported in acute lymphoblastic leukemia patients with methotrexate-induced leukoencephalopathy. However, our case suggests that the pathogenesis of mesial temporal sclerosis may be associated with methotrexate-induced neurotoxicity.

Clinical patterns and biological correlates of cognitive dysfunction associated with cancer therapy

Standard oncological therapies, such as chemotherapy and cranial radiotherapy, frequently result in a spectrum of neurocognitive deficits that includes impaired learning, memory, attention, and speed of information processing. In addition to classical mechanisms of neurotoxicity associated with chemo- and radiotherapy, such as radiation necrosis and leukoencephalopathy, damage to dynamic progenitor cell populations in the brain is emerging as an important etiologic factor. Radiation- and chemotherapy-induced damage to progenitor populations responsible for maintenance of white matter integrity and adult hippocampal neurogenesis is now believed to play a major role in the neurocognitive impairment many cancer survivors experience.

Effects of chemotherapeutic agents 5-fluorouracil and methotrexate alone and combined in a mouse model of learning and memory

RATIONALE

The concern that adjuvant cancer chemotherapy agents cause cognitive impairment in a significant number of patients has been expressed by patients and healthcare providers, but clinical studies have yielded conflicting results to date.

OBJECTIVE

We directly tested two commonly used chemotherapeutic agents in a mouse model of learning and memory.

MATERIALS AND METHODS

In the present study, mice were conditioned to respond for a liquid reinforcer (Ensure solution) in the presence of an audible tone on day 1 as a measure of acquisition and were then required to perform the same response on day 2 as a measure of retrieval and retention. Methotrexate and 5-fluorouracil were administered prior to the day 1 session.

RESULTS

Methotrexate (1.0-32 mg/kg) alone failed to alter mean latency acquisition, retrieval, or reinforced response rates. Similar to scopolamine, a known amnesic in this assay, 5-fluorouracil (3-75 mg/kg) failed to alter response rates or acquisition latency on day 1 but significantly altered latency to retrieve a previously learned response on day 2. In combination, 3.2 mg/kg methotrexate plus 75 mg/kg 5-fluorouracil significantly increased day 1 and day 2 acquisition and retrieval latencies without altering response rates or motivation to respond as measured by progressive ratio responding.

CONCLUSION

Taken together, these data demonstrate that 5-fluorouracil causes increased latencies for retrieval of previously learned behavioral responses and that combination of chemotherapeutic agents may produce greater delays than either agent alone, including when neither agent alone does so.