Effects of Cyclophosphamide and/or Doxorubicin in a Murine Model of Postchemotherapy Cognitive Impairment

Cardioprotective role of a magnolol and honokiol complex in the prevention of doxorubicin-mediated cardiotoxicity in adult rats

Doxorubicin (DOXO) induces marked cardiotoxicity, though increased oxidative stress while there are some documents related with cardioprotective effects of some antioxidants against organ-toxicity during cancer treatment. Although magnolia bark has some antioxidant-like effects, its action in DOXO-induced heart dysfunction has not be shown clearly. Therefore, here, we aimed to investigate the cardioprotective action of a magnolia bark extract with active component magnolol and honokiol complex (MAHOC; 100 mg/kg) in DOXO-treated rat hearts. One group of adult male Wistar rats was injected with DOXO (DOXO-group; a cumulative dose of 15 mg/kg in 2-week) or saline (CON-group). One group of DOXO-treated rats was administered with MAHOC before DOXO (Pre-MAHOC group; 2-week) while another group was administered with MAHOC following the 2-week DOXO (Post-MAHOC group). MAHOC administration, before or after DOXO, provided full survival of animals during 12-14 weeks, and significant recoveries in the systemic parameters of animals such as plasma levels of manganese and zinc, total oxidant and antioxidant statuses, and also systolic and diastolic blood pressures. This treatment also significantly improved heart function including recoveries in end-diastolic volume, left ventricular end-systolic volume, heart rate, cardiac output, and prolonged P-wave duration. Furthermore, the MAHOC administrations improved the structure of left ventricles such as recoveries in loss of myofibrils, degenerative nuclear changes, fragmentation of cardiomyocytes, and interstitial edema. Biochemical analysis in the heart tissues provided the important cardioprotective effect of MAHOC on the redox regulation of the heart, such as improvements in activities of glutathione peroxidase and glutathione reductase, and oxygen radical-absorbing capacity of the heart together with recoveries in other systemic parameters of animals, while all of these benefits were observed in the Pre-MAHOC treatment group, more prominently. Overall, one can point out the beneficial antioxidant effects of MAHOC in chronic heart diseases as a supporting and complementing agent to the conventional therapies.

Endogenous FGF1 Deficiency Aggravates Doxorubicin-Induced Hepatotoxicity

Doxorubicin (DOX) is a broad-spectrum antineoplastic agent that widely used in clinic. However, its application is largely limited by its toxicity in multiple organs. Fibroblast growth factor 1 (FGF1) showed protective potential in various liver diseases, but the role of endogenous FGF1 in DOX-induced liver damage is currently unknown. Both wild-type (WT) and FGF1 knockout (FGF1-KO) mice were treated with DOX. DOX induced loss of body weight and liver weight and elevation of ALT and AST in WT mice, which were aggravated by FGF1 deletion. FGF1 deletion exacerbated hepatic oxidative stress mirrored by further elevated 3-nitrosative modification of multiple proteins and malondialdehyde content. These were accompanied by blunted compensatively antioxidative responses indicated by impaired upregulation of nuclear factor erythroid 2-related factor 2 and its downstream antioxidant gene expression. The aggravated oxidative stress was coincided with exacerbated cell apoptosis in DOX-treated FGF1-KO mice reflected by further increased TUNEL positive cell staining and BCL-2-associated X expression and caspase 3 cleavage. These detrimental changes in DOX-treated FGF1-KO mice were associated with worsened intestinal fibrosis and increased upregulation fibrotic marker connective tissue growth factor and α-smooth muscle actin expression. However, DOX-induced hepatic inflammatory responses were not further affected by FGF1 deletion. These results demonstrate that endogenous FGF1 deficiency aggravates DOX-induced liver damage and FGF1 is a potential therapeutic target for treatment of DOX-associated hepatoxicity.

A Review on the Neurotoxic Effects of Doxorubicin

Anthracyclines, a class of drugs considered as most effective anticancer drugs, used in the various regimens of cancer chemotherapy, induce long-term impairment of mitochondrial respiration, increase reactive oxygen species, and induce other mechanisms potentially leading to neurotoxicity. According to literature findings, one drug of this class - doxorubicin used to treat e.g. breast cancer, bladder cancer, lymphoma, and acute lymphocytic leukemia may induce such effects in the nervous system. Doxorubicin has poor penetration into the brain due to the lack of drug penetration through the blood-brain barrier, thus the toxicity of this agent is the result of its peripheral action. This action is manifested by cognitive impairment and anatomical changes in the brain and peripheral nervous system found in both preclinical and clinical studies in adult patients. Furthermore, more than 50% of children with cancer are treated with anthracyclines including doxorubicin, which may affect their nervous system, and lead to lifelong damage in many areas of their life. Despite ongoing research into the side effects of this drug, the mechanism of its neurotoxicity action on the central and peripheral nervous system is still not well understood. This review aims to summarize the neurotoxic effects of doxorubicin in preclinical (in vitro and in vivo) research and in clinical studies. Furthermore, it discusses the possible mechanisms of the toxic action of this agent on the nervous system.

L-carnitine Modulates Cognitive Impairment Induced by Doxorubicin and Cyclophosphamide in Rats; Insights to Oxidative Stress, Inflammation, Synaptic Plasticity, Liver/brain, and Kidney/brain Axes

Chemotherapy-induced cognitive impairment in cancer patients is known as "chemobrain". Doxorubicin and Cyclophosphamide are two chemotherapeutic agents used in combination to treat solid tumors. L-carnitine was reported for its anti-oxidant and anti-inflammatory activities. The goal of the present study was to elucidate the neuroprotective effect of L-carnitine against chemobrain induced by Doxorubicin and Cyclophosphamide in rats. Rats were divided into five groups: Control group; Doxorubicin (4mg/kg, IV) and Cyclophosphamide (40mg/kg, IV)-treated group; two L-carnitine-treated groups (150 and 300mg/kg, ip) with Doxorubicin and Cyclophosphamide; and L-carnitine alone-treated group (300mg/kg). Doxorubicin and Cyclophosphamide induced histopathological changes in rats' hippocampi and prefrontal cortices, as well as reduced memory as evidenced by behavioural testing. L-carnitine treatment showed opposite effects. In addition, chemotherapy treatment enhanced oxidative stress via reducing catalase and glutathione levels, and inducing lipid peroxidation. By contrast, L-carnitine treatment showed powerful antioxidant effects reversing chemotherapy-induced oxidative damage. Moreover, chemotherapy combination induced inflammation via their effect on nuclear factor kappa B (p65), interleukin-1β, and tumor necrosis factor-α. However, L-carnitine treatment corrected such inflammatory responses. Furthermore, Doxorubicin and Cyclophosphamide reduced synaptic plasticity via hindering expression of brain-derived neurotrophic factor, phosphorylated cyclase response element binding protein, synaptophysin, and postsynaptic density protein 95 whereas protein expression of such synaptic plasticity biomarkers was enhanced by L-carnitine treatment. Finally, acetylcholinesterase activity was found to be enhanced by chemotherapy treatment affecting rats' memory while L-carnitine treatment reduced acetylcholinesterase activity. L-carnitine also showed hepatoprotective and renal protective effects suggesting liver/brain and kidney/brain axes as possible mechanisms for its neuroprotective effects.

Biflavonoid quercetin protects against cyclophosphamide-induced organ toxicities via modulation of inflammatory cytokines, brain neurotransmitters, and astrocyte immunoreactivity

BACKGROUND

Cyclophosphamide use has been associated with increased oxidative stress in cells and tissues. Quercetin's antioxidative properties make it of potential benefit in such conditions of oxidative stress.

OBJECTIVE

To assess quercetin's ability to mitigate cyclophosphamide-induced organ toxicities in rats.

METHODS

Sixty rats were assigned into six groups. Groups A and D served as normal and cyclophosphamide control and were fed standard rat chow, groups B and E were fed quercetin supplemented diet (100 mg/kg of feed), while those in groups C and F were fed quercetin at 200 mg/kg of feed. Groups A-C received intraperitoneal (ip) normal saline on days 1 and 2, while D-F received ip cyclophosphamide (150 mg/kg/day on days 1 and 2). On day 21, behavioural tests were carried out, animals were sacrificed and blood samples taken. Organs were processed for histological study.

RESULTS

Quercetin reversed cyclophosphamide-induced decrease in body weight, food intake and total antioxidant capacity, and increase in lipid peroxidation (p = 0.001), It also reversed derangement in levels of liver transaminase, urea, creatinine and proinflammatory cytokines (p = 0.001). Improvement in working-memory and anxiety-related behaviours were also observed. Finally, quercetin reversed alterations in levels of acetylcholine, dopamine and brain-derived neurotropic factor (p = 0.021); while reducing serotonin levels and astrocyte immunoreactivity.

CONCLUSION

Quercetin shows significant ability to protect against cyclophosphamide-induced changes in rats.

An update on neurobiological mechanisms involved in the development of chemotherapy-induced cognitive impairment (CICI)

Cancer is the second leading cause of death worldwide despite efforts in early diagnosis of the disease and advances in treatment. The use of drugs that exert toxic effects on tumor cells or chemotherapy is one of the most widely used treatments against cancer. However, its low toxic selectivity affects both healthy cells and cancer cells. It has been reported that chemotherapeutic drugs may generate neurotoxicity that induces deleterious effects of chemotherapy in the central nervous system. In this sense, patients report decreased cognitive abilities, such as memory, learning, and some executive functions after chemotherapy. This chemotherapy-induced cognitive impairment (CICI) develops during treatment and persists even after chemotherapy. Here we present a review of the literature on the main neurobiological mechanisms involved in CICI using a Boolean formula following the steps of the PRISMA guidelines that were used to perform statements searches in various databases. The main mechanisms described in the literature to explain CRCI include direct and indirect mechanisms that induce neurotoxicity by chemotherapeutic agents. Therefore, this review provides a general understanding of the neurobiological mechanisms of CICI and the possible therapeutic targets to prevent it..

Hippocampal neuroinflammation following combined exposure to cyclophosphamide and naproxen in ovariectomized mice

Aim: Cancer patients undergoing chemotherapy report cognitive changes collectively termed "chemo brain." Neuroinflammation is among the factors believed to contribute to "chemo brain" suggesting a potential beneficial role for anti-inflammatory drugs in cancer patients undergoing chemotherapy. We investigated whether the non-steroidal anti-inflammatory drug naproxen influenced hippocampal inflammation in non-tumor bearing female mice receiving the chemotherapy drug cyclophosphamide (CP).Materials and methods: Intact and ovariectomized C57BL/6 mice were used to examine potential role of ovarian hormones on neuroinflammation. The mice were placed on naproxen (375 ppm) or control diet, and a week later CP (100 mg/kg; i.p.) was administered every 3 days for 2 weeks. We analyzed hippocampal inflammatory biomarkers, anxiety-like behavior, spatial working memory, exploratory behavior, spontaneous locomotor activity and depression-like behavior.Results: CP produced significant effects on anti-inflammatory but not pro-inflammatory biomarkers. However, CP and naproxen in combination produced significant effects on both pro- and anti- inflammatory biomarkers. Naproxen and ovariectomy individually produced significant effects on pro- and anti-inflammatory biomarkers as well. Working memory and depression-like behavior were not significantly influenced by CP, naproxen or ovariectomy individually although CP and ovariectomy produced significant interaction effects on depression-like behavior. Exploratory behavior and locomotor activity showed significant effects of CP, and interaction between CP and naproxen was significant for locomotor activity.Conclusions: Ovariectomy, naproxen and a combination of CP and naproxen upregulate hippocampal pro- and anti- inflammatory biomarkers. None of the factors individually produce significant behavioral changes that could be consistent with chemo brain, although CP and ovariectomy in combination produced significant effects on depression-like behavior, a co-morbidity of chemo brain.

Protective effect of low-dose radiation on doxorubicin-induced brain injury in mice

BACKGROUND

To investigate the protective effect of low-dose radiation (LDR) on brain injury in mice induced by doxorubicin (DOX).

METHODS

Sixty female BALB/C mice were randomly divided into the control (CTR) group, low-dose radiation (LDR) group, doxorubicin treatment (DOX) group and low-dose radiation before doxorubicin treatment (COM) group. After 72 h of exposure to 75 mGy, the mice were intraperitoneally injected with 7.5 mg/kg of doxorubicin and sacrificed 5 days later. Neuron-specific enolase (NSE), lactate dehydrogenase (LDH), adenosine triphosphate (ATP), neurotransmitters, inflammatory mediators, apoptosis- and oxidative stress-related mediators as well as mitochondrial dysfunction were examined.

RESULTS

Compared to the DOX group, the concentrations of DA, 5-HT, EPI and GABA in the COM group were significantly decreased, and the number of TUNEL-positive cells was decreased. In addition, the expression of proapoptotic proteins was downregulated in the COM group compared to the DOX group. Low-dose radiation in advance reduced reactive oxygen species and activated the SOD antioxidant defense system as indicated by significantly reduced GSH expression, increased GSSG expression, increased GPx expression and activation of the Nrf2 redox pathway. After low-dose radiation, the expression levels of ATP5f1, NDUFV1 and CYC1 were close to normal, and the mitochondrial respiratory control rate (RCR) and activity of respiratory chain complex enzymes also tended to be normal. Low-dose radiation upregulated the expression levels of IL-2 and IL-4 but downregulated the expression levels of IL-10 and TGF-β.

CONCLUSION

LDR has a protective effect on brain injury in mice treated with DOX. The mechanism is related to LDR alleviating mitochondrial dysfunction and oxidative stress, which promotes the production of antioxidant damage proteins, thus exerting an adaptive protective effect on cells.

Ameliorative effect of flavocoxid on cyclophosphamide-induced cardio and neurotoxicity via targeting the GM-CSF/NF-κB signaling pathway

Cyclophosphamide (Cyclo) is a chemotherapeutic agent used as an immunosuppressant and as a treatment for many cancerous diseases. Many previous pieces of literature proved the marked cardio and neurotoxicity of the drug. Thus, this research provides evidence on the alleviative effect of flavocoxid on the cardiac and brain toxicity of cyclophosphamide in mice and determines its underlying mechanisms. Flavocoxid (Flavo) is a potent antioxidant and anti-inflammatory agent that inhibits the peroxidase activity of cyclooxygenase (COX-1 and COX-2) enzymes and 5-lipooxygenase (5-LOX). Flavo was administered orally (20 mg/kg) for 2 weeks, followed by Cyclo (100 mg/kg, i.p.) on day 14. Higher heart and brain weight indices, serum lactate dehydrogenase (LDH), creatine kinase (CK-MB), and nitric oxide (NO) were mitigated following Flavo administration. Flavo modulated oxidative stress biomarkers (malonaldehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD)), tumor necrosis factor-α (TNF-α), and interleukin (IL)-1β. Additionally, cardiac troponin I (cTn-I), nuclear factor kappa B (NF-κB), brain amyloid precursor protein (APP), and granulocyte macrophage colony-stimulating factor (GM-CSF) were decreased by Flavo administration. Moreover, Flavo ameliorated heart and brain histopathological changes and caspase-3 levels. Collectively, Flavo (20 mg/kg) for 14 days showed significant cardio and neuroprotective effects due to its antioxidant, anti-inflammatory, and antiapoptotic activities via modulation of oxidative stress, inflammation, and the GM-CSF/NF-κB signaling pathway.

Chemobrain in Breast Cancer: Mechanisms, Clinical Manifestations, and Potential Interventions

Among the potential adverse effects of breast cancer treatment, chemotherapy-related cognitive impairment (CRCI) has gained increased attention in the past years. In this review, we provide an overview of the literature regarding CRCI in breast cancer, focusing on three main aspects. The first aspect relates to the molecular mechanisms linking individual drugs commonly used to treat breast cancer and CRCI, which include oxidative stress and inflammation, reduced neurogenesis, reduced levels of specific neurotransmitters, alterations in neuronal dendrites and spines, and impairment in myelin production. The second aspect is related to the clinical characteristics of CRCI in patients with breast cancer treated with different drug combinations. Data suggest the incidence rates of CRCI in breast cancer vary considerably, and may affect more than 50% of treated patients. Both chemotherapy regimens with or without anthracyclines have been associated with CRCI manifestations. While cross-sectional studies suggest the presence of symptoms up to 20 years after treatment, longitudinal studies confirm cognitive impairments lasting for at most 4 years after the end of chemotherapy. The third and final aspect is related to possible therapeutic interventions. Although there is still no standard of care to treat CRCI, several pharmacological and non-pharmacological approaches have shown interesting results. In summary, even if cognitive impairments derived from chemotherapy resolve with time, awareness of CRCI is crucial to provide patients with a better understanding of the syndrome and to offer them the best care directed at improving quality of life.

HDAC6 inhibition reverses long-term doxorubicin-induced cognitive dysfunction by restoring microglia homeostasis and synaptic integrity

Breast cancer is the most common female malignancy in both the developed and developing world. Doxorubicin is one of the most commonly used chemotherapies for breast cancer. Unfortunately, up to 60% of survivors report long-term chemotherapy-induced cognitive dysfunction (CICD) characterized by deficits in working memory, processing speed and executive function. Currently, no therapeutic standard for treating CICD exists. Here, we hypothesized that treatment with a blood-brain barrier permeable histone deacetylase 6 (HDAC6) inhibitor can successfully reverse long-term doxorubicin-induced cognitive dysfunction. Methods: The puzzle box test and novel object/place recognition test were used to assess cognitive function following a therapeutic doxorubicin dosing schedule in female mice. Mitochondrial function and morphology in neuronal synaptosomes were evaluated using the Seahorse XF24 extracellular flux analyzer and transmission electron microscopy, respectively. Hippocampal postsynaptic integrity was evaluated using immunofluorescence. Hippocampal microglia phenotype was determined using advanced imaging techniques and single-nucleus RNA sequencing. Results: A 14-day treatment with a blood-brain barrier permeable HDAC6 inhibitor successfully reversed long-term CICD in the domains of executive function, working and spatial memory. No significant changes in mitochondrial function or morphology in neuronal synaptosomes were detected. Long-term CICD was associated with a decreased expression of postsynaptic PSD95 in the hippocampus. These changes were associated with decreased microglial ramification and alterations in the microglia transcriptome that suggest a stage 1 disease-associated microglia (DAM) phenotype. HDAC6 inhibition completely reversed these doxorubicin-induced alterations, indicating a restoration of microglial homeostasis. Conclusion: Our results show that decreased postsynaptic integrity and a neurodegenerative microglia phenotype closely resembling stage 1 DAM microglia contribute to long-term CICD. Moreover, HDAC6 inhibition shows promise as an efficacious pharmaceutical intervention to alleviate CICD and improve quality of life of breast cancer survivors.

Motopsin deficiency imparts partial insensitivity to doxorubicin-induced hippocampal impairments in adult mice

Motopsin is a serine protease that plays a crucial role in synaptic functions. Loss of motopsin function causes severe intellectual disability in humans. In this study, we evaluated the role of motopsin in the neuropathological development of cognitive impairments following chemotherapy, also known as chemobrain. Motopsin knockout (KO) and wild-type (WT) mice were intravenously injected with doxorubicin (Dox) or saline four times every 8 days and were evaluated for open field, novel object recognition, and passive avoidance tests. Parvalbumin-positive neurons in the hippocampus were immunohistochemically analyzed. Dox administration significantly decreased the total distance in the open field test in both WT and motopsin KO mice without affecting the duration spent in the center square. A significant interaction between the genotype and drug treatment was detected in the recognition index (the rate to investigate a novel object) in the novel object recognition test, although Dox treatment did not affect the total investigation time. Additionally, Dox treatment significantly decreased the recognition index in WT mice, whereas it tended to increase the recognition index in motopsin KO mice. Dox treatment did not affect the latency to enter a dark compartment in either WT or motopsin KO mice in the passive avoidance test. Interestingly, Dox treatment increased the parvalbumin-positive neurons in the stratum oriens of the hippocampus CA1 region of only WT mice, not motopsin KO mice. Our data suggest that motopsin deficiency imparted partial insensitivity to Dox-induced hippocampal impairments. Alternatively, motopsin may contribute to the neuropathology of chemobrain.

Thymoquinone upregulates miR-125a-5p, attenuates STAT3 activation, and potentiates doxorubicin antitumor activity in murine solid Ehrlich carcinoma

In breast cancer, there has been evidence of atypical activation of signal transduction and activators of transcription 3 (STAT3). Thymoquinone (TQ) exerts its anti-neoplastic effect through diverse mechanisms, including STAT3 inhibition. The tumor suppressor, microRNA-125a-5p was reported to be downregulated in various breast cancer cells. Therefore, we investigated the influence of TQ and/or doxorubicin on microRNA-125a-5p and its correlation with STAT3 activation as well as tumor growth in mice bearing solid Ehrlich tumors. We found that TQ markedly suppressed inducible and constitutive phosphorylation of STAT3 in tumor tissue without affecting STAT5. Moreover, it attenuated tumor growth, downregulated STAT3 downstream target proteins, and increased the apoptotic activities of caspase-3 and -9. Interestingly, TQ-elicited synergism of doxorubicin anti-neoplastic activity was coupled with upregulation of tumoral microRNA-125a-5p. Taken together, the current findings raise the potential of TQ as a promising chemomodulatory adjuvant to augment mammary carcinoma sensitivity to doxorubicin.

Increasing dietary choline attenuates spatial memory deficits resulting from exposure to the chemotherapeutic agents cyclophosphamide and doxorubicin

BACKGROUND

Choline supplementation (+Ch) improves cognitive function in impaired animals and humans. Chemotherapy-related cognitive deficits (CRCDs) occur in cancer patients, and these deficits persist following treatment, adversely impacting quality of life. To date, there are no approved treatments for this condition.

AIM

Because +Ch improves impaired memory, it was of interest to determine whether +Ch can attenuate spatial memory deficits induced by the chemotherapeutic agents doxorubicin (DOX) and cyclophosphamide (CYP).

METHODS

Female BALB/C mice, 64 days of age, were trained in the Morris water maze and baseline performance determined on day 15. Following baseline assessment, mice were placed on +Ch diet (2.0% Ch) or remained on standard diet (0.12% Ch). Mice received intravenous injections of DOX (2.5 mg/kg) and CYP (25 mg/kg), or equivalent volumes of saline (0.9% NaCl), on days 16, 23, 30, and 37, and spatial memory was assessed weekly from day 22 to 71.

RESULTS

DOX and CYP produced a prolonged impairment in spatial memory as indicated by an increased latency to the correct zone (p < 0.05), and a decrease in time in the correct zone (p < 0.05), % of total swim distance in the correct zone (p < 0.05) and % entries to the correct zone (p < 0.05). These effects were attenuated by +Ch.

CONCLUSION

Although it remains to be determined whether this effect extends to other cognitive domains and whether +Ch is prophylactic or therapeutic, these findings suggest that +Ch may be an effective intervention for CRCDs.

Antinociceptive, Anti-Hyperalgesia and Antiallodynic Activities of Polyphenol Rich Extract from Shorea roxburghii against Cyclophosphamide Induced Peripheral Neuropathy

Cyclophosphamide (CYP) is a widely used antineoplastic and immunosuppressive drug, however, despite its efficacy, it has shown extensive multiple organ toxicities, including peripheral neuropathy which significantly affects the quality of life of cancer patients. This study elucidated the protective properties of Shorea roxburghii polyphenol extract (SLPE) in CYP-induced peripheral neuropathy. Rats were treated with SLPE (100 and 400 mg/kg) for five weeks plus CYP once a week from the second week of SLPE treatment. Using UHPLC-QTOF-MS, 54 polyphenolic compounds were identified in SLPE extract. After the treatment period the antinociceptive, anti-hyperalgesia and antiallodynic effects was evaluated using formalin paw edema, acetic acid abdominal writhing, hot plate, tail immersion and von Frey filament tests. While the locomotive and motor coordination effects were evaluated by open field and rotarod tests. The administration of CYP led to significant increases in mechanical and thermal hyperalgesia, in addition to hyper-nociceptive responses in the formalin and acetic acid writhing tests. CYP also significantly reduced locomotive activity and motor coordination. SLPE significantly protected against CYP-induced mechanical and thermal hyperalgesia. Furthermore, SLPE displayed robust antinociceptive effect by counteracting formalin and acetic acid induced hyper-nociception. In addition, SLPE increased the locomotive activity as well as the grip and motor coordination of the CYP treated rats. In conclusion, these results revealed the protective effects of SLPE against CYP-induced peripheral neuropathy and could be an effective therapeutic remedy for chemotherapy induced peripheral neuropathy.

Accelerated aging of the brain transcriptome by the common chemotherapeutic doxorubicin

Cancer is one of the most common age-related diseases, and over one-third of cancer patients will receive chemotherapy. One frequently reported side effect of chemotherapeutic agents like doxorubicin (Doxo) is impaired cognitive function, commonly known as "chemotherapy-induced cognitive impairment (CICI)", which may mimic accelerated brain aging. The biological mechanisms underlying the adverse effects of Doxo on the brain are unclear but could involve mitochondrial dysfunction. Here, we characterized brain (hippocampal) transcriptome and cognitive/behavioral changes in young mice treated with Doxo +/- the mitochondrial therapeutic MitoQ. We found that Doxo altered transcriptome/biological processes related to synaptic transmission and neurotransmitter function, neuronal health and behavior, and that these gene expression changes were: 1) similar to key differences observed in transcriptome data on brain aging; and 2) associated with related, aging-like behavioral differences, such as decreased exploration time and impaired novel object recognition test (NOR, an index of learning/memory) performance. Interestingly, MitoQ partially prevented Doxo-induced transcriptome changes in the brain, but it had no effect on behavior or cognitive function. Collectively, our findings are consistent with the idea that chemotherapeutic agents could induce neuronal/gene expression and behavioral changes similar to those that occur during brain aging. In this context, mitochondrial therapeutics may have potential as treatments for CICI at the biological level, but their effects on behavior/cognitive function require further investigation.

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.

Neuroimmune reactivity marker expression in rodent models of chemotherapy-induced cognitive impairment: A systematic scoping review

BACKGROUND

Chemotherapy-induced cognitive impairment (CICI) is a debilitating side effect arising from chemotherapy treatments. The condition is characterised by a range of cognitive deficits including impairment to memory, attention, and concentration. Whilst the underlying mechanisms that contribute to CICI remain unclear, neuroinflammation has been suggested as one key contributor.

METHOD

A comprehensive systematic search of EMBASE and Medline via PubMed was conducted to identify studies on neuroimmune reactivity marker expression changes and resulting cognitive changes in preclinical rodent models of CICI.

RESULTS

A total of twenty studies met the eligibility criteria and were included in the scoping review. There was significant heterogeneity in the methodology employed in the included studies. Our findings demonstrate that widespread changes in cytokines, chemokines, microglia reactivity, and astrocyte reactivity are observed in CICI in the brain regions expected to be affected, given the nature of the cognitive impairment observed in CICI.

CONCLUSIONS

Although there was considerable heterogeneity in study design that made comparisons between studies difficult, our findings suggest that neuroinflammation commonly occurs in CICI preclinical rodent models and shows an association with cognitive impairment.

Minimal effects from a single exposure to sevoflurane in adult male and female Sprague-Dawley rats

Many people undergo procedures requiring general anesthesia each day and adverse cognitive effects have been reported in response to that anesthesia. Postoperative Cognitive Dysfunction (POCD) may occur in as many as 80% of adults during the first post-surgical week and can have lasting effects. Here, the cognitive and motor effects of sevoflurane exposure in Sprague-Dawley rats was examined along with body weights, blood oxygen saturation, heart rate, and body temperature. Male and female rats were exposed to 2.5% sevoflurane or medical grade air for one hour at postnatal day 115. Beginning the following day, rats began a series of behavioral tests examining locomotor activity, motor coordination, novel object recognition, and spatial learning and memory in a water maze. Blood oxygen saturation, heart rate, and body temperature were not affected by the sevoflurane exposure. A slight effect on locomotor activity was detected, but no effects on motor coordination, novel object recognition, or spatial learning and memory were observed. Brain weights following behavioral testing did not differ. The results reported here along with existing literature suggest sevoflurane is largely without effects on later cognition in adult rodents when exposure is of a relatively short duration and at a relatively low concentration.

The Role of PGC-1α/UCP2 Signaling in the Beneficial Effects of Physical Exercise on the Brain

In understanding the pathology of neurological diseases, the role played by brain energy metabolism is gaining prominence. Animal models have demonstrated that regular physical exercise improves brain energy metabolism while also providing antidepressant, anxiolytic, antioxidant and neuroprotective functions. This review summarizes the latest evidence on the roles played by peroxisome proliferator-activated receptor gamma (PPAR-γ) coactivator 1-alpha (PGC-1α) and mitochondrial uncoupling protein (UCP) in this scenario. The beneficial effects of exercise seem to depend on crosstalk between muscles and nervous tissue through the increased release of muscle irisin during exercise.

Chronic Treatment with Combined Chemotherapeutic Agents Affects Hippocampal Micromorphometry and Function in Mice, Independently of Neuroinflammation

Chemotherapeutic agents induce long-term side effects, including cognitive impairment and mood disorders, particularly in breast cancer survivors who have undergone chemotherapy. However, the precise mechanisms underpinning chemotherapy-induced hippocampal dysfunction remain unknown. In this study, we investigated the detrimental effects of chronic treatment with a combination of adriamycin and cyclophosphamide (AC) on the neuronal architecture and functions of the hippocampi of female C57BL/6 mice. After chronic AC administration, mice showed memory impairment (measured using a novel object recognition memory task) and depression-like behavior (measured using the tail suspension test and forced swim test). According to Golgi staining, chronic AC treatment significantly reduced the total dendritic length, ramification, and complexity as well as spine density and maturation in hippocampal neurons in a sub-region-specific manner. Additionally, the AC combination significantly reduced adult neurogenesis, the extent of the vascular network, and the levels of hippocampal angiogenesis-related factors. However, chronic AC treatment did not increase the levels of inflammation-related signals (microglial or astrocytic distribution, or the levels of pro-inflammatory cytokines or M1/M2 macrophage markers). Thus, chronic AC treatment changed the neuronal architecture of the adult hippocampus, possibly by reducing neurogenesis and the extent of the vasculature, independently of neuroinflammation. Such detrimental changes in micromorphometric parameters may explain the hippocampal dysfunction observed after cancer chemotherapy.