Targeted activation of Nrf2 at sites of oxidative stress reverses doxorubicin-induced cognitive impairments in mice.

While cancer survivorship has increased due to advances in treatments, chemotherapy often carries long-lived neurotoxic side effects which reduce quality of life. Commonly affected domains include memory, executive function, attention, processing speed and sensorimotor function, colloquially known as chemotherapy-induced cognitive impairment (CICI) or “chemobrain”. Oxidative stress and neuroimmune signaling in the brain have been mechanistically linked to the deleterious effects of chemotherapy on cognition and sensorimotor function. With this in mind, we tested if activation of the master regulator of antioxidant response nuclear factor E2-related factor 2 (Nrf2) alleviates cognitive and sensorimotor impairments induced by doxorubicin. The FDA-approved systemic Nrf2 activator, diroximel fumarate (DRF) was used, along with our recently developed prodrug 1c which has the advantage of specifically releasing monomethyl fumarate at sites of oxidative stress. DRF and 1c both reversed doxorubicin-induced deficits in executive function, spatial and working memory, as well as decrements in fine motor coordination and grip strength, across both male and female mice. Both treatments reversed doxorubicin-induced loss of synaptic proteins and microglia phenotypic transition in the hippocampus. Doxorubicin-induced myelin damage in the corpus callosum was reversed by both Nrf2 activators. These results demonstrate the therapeutic potential of Nrf2 activators to reverse doxorubicin-induced cognitive impairments, motor incoordination, and associated structural and phenotypic changes in the brain. The localized release of monomethyl fumarate by 1c has the potential to diminish unwanted effects of fumarates while retaining efficacy.

: Recent population studies have suggested that children with multiple exposures to anesthesia and surgery at an early age are at an increased risk of cognitive impairment. The authors therefore have established an animal model with single versus multiple exposures of anesthetic(s) in young versus adult mice, aiming to distinguish the role of different types of anesthesia in cognitive impairment. : Six- and 60-day-old mice were exposed to various anesthesia regimens. The authors then determined the effects of the anesthesia on learning and memory function, levels of proinflammatory cytokine interleukin-6 and tumor necrosis factor-α in brain tissues, and the amount of ionized calcium-binding adaptor molecule 1-positive cells, the marker of microglia activation, in the hippocampus. : In this article, the authors show that anesthesia with 3% sevoflurane for 2 h daily for 3 days induced cognitive impairment and neuroinflammation (e.g., increased interleukin-6 levels, 151 ± 2.3% [mean ± SD] vs. 100 ± 9.0%, P = 0.035, n = 6) in young but not in adult mice. Anesthesia with 3% sevoflurane for 2 h daily for 1 day and 9% desflurane for 2 h daily for 3 days induced neither cognitive impairment nor neuroinflammation. Finally, an enriched environment and antiinflammatory treatment (ketorolac) ameliorated the sevoflurane-induced cognitive impairment. : Anesthesia-induced cognitive impairment may depend on developmental stage, anesthetic agent, and number of exposures. These findings also suggest the cellular basis and the potential prevention and treatment strategies for anesthesia-induced cognitive impairment, which may ultimately lead to safer anesthesia care and better postoperative outcomes for children.

The transcription factor nuclear factor erythroid 2–related factor 2 (NRF2) is a master regulator of the antioxidant response and an attractive target for treating diseases driven by oxidative stress, particularly neuropathy. While activation of NRF2 by monomethyl fumarate (MMF) is well established in rodent models, this mechanism is not confirmed as the primary mode of action in its approved use for relapsing-remitting multiple sclerosis (RRMS). Nevertheless, the systemic exposure and broad side-effect profile of MMF and its two FDA approved prodrugs, Vumerity and Tecfidera, limit broader therapeutic utility. These side effects may be acceptable in debilitating neurodegenerative disorders, such as RRMS, but are not for other indications, such as neuropathic pain. Here, we report the synthesis, in vitro and in vivo evaluation of a series of α-keto ester-functionalized prodrugs of MMF (1–23), designed to release the therapeutically active MMF selectively at sites of oxidative stress. These prodrugs were designed to exploit elevated pathological levels of reactive oxygen species (ROS), which trigger Baeyer-Villiger oxidation of the 1,2-dicarbonyl moiety, resulting in rapid hydrolysis of the generated anhydride and localized MMF release. Interestingly, structure-property relationship (SPR) analysis revealed that prodrugs with simple alkyl α-keto esters demonstrated the highest levels of NRF2 activation and therapeutic efficacy. Specifically, compounds 4, 5, and 6, with trideuteromethyl, ethyl, and iso-propyl esters, respectively, exhibit strong tissue-specific NRF2 activation, and 4 in particular demonstrated full reversal of mechanical allodynia in a mouse model of neuropathy.

Downregulation of Nrf2 deteriorates cognitive impairment in APP/PS1 mice by inhibiting mitochondrial biogenesis through the PPARγ/PGC1α signaling pathway.

Pathology activated prodrugs targeting Nrf2 to treat neuropathic pain

Chemotherapy‐induced cognitive impairment (CICI) is an emerging concern among cancer patients undergoing chemotherapy treatment. Several mechanisms including neuronal oxidative stress and mitochondrial dysfunction have been proposed as the underlying mechanisms of CICI. While a few synthetic and natural compounds with different mechanisms of action have been proposed for targeting the CICI, their beneficial effects are outweighed by severe adverse effects including reduced efficacy of chemotherapy drugs. Therefore, search for novel and safer neuroprotective avenues to target CICI is needed. We sought to determine whether Oroxylum indicum extract (OIE, Sabroxy®) prevents CICI in a rodent model by suppressing chemotherapy induced neuronal oxidative stress and mitochondrial dysfunction. Male C57BL/6J mice were injected intraperitoneally with saline or doxorubicin (2mg/kg) and cyclophosphamide (50mg/kg) once a week for 4 weeks. While control mice received powdered rodent food alone, OIE treatment group received the powdered rodent food mixed with OIE (250 or 500mg/kg) daily for 4 weeks. After the treatment period, the mice were assessed for cognitive function using novel object recognition, Y‐maze, and Morris water maze analyses. Biochemical assays were performed using brain tissues to determine the underlying mechanisms of CICI. While the chemotherapy treatment impaired the performance of the mice in the novel object recognition, Y‐maze and Morris water maze tests, OIE significantly prevented the chemotherapy impaired performance in these tests. Additionally, OIE treatment prevented the chemotherapy‐induced changes in oxidative stress and mitochondrial dysfunction in the cortex and rest of the brain. Mechanistically, OIE enhanced mitochondrial function and counteracted chemotherapy‐increased reactive oxygen species formation and lipid peroxidation. Furthermore, OIE treatment increased the monoamine oxidase activity in the cortex and rest of the brain. Our results support the hypothesis that neuronal mitochondrial dysfunction induced by doxorubicin and cyclophosphamide treatment is an underlying cause of CICI, and that OIE may be offered as an adjuvant therapeutic strategy to treat CICI.Support or Funding InformationOIE (Sabroxy®) and funding was provided by Sabinsa Corporation.

Children with multiple exposures to anesthesia and surgery may have an increased risk of developing cognitive impairment. Sevoflurane is a commonly used anesthetic in children. Tau phosphorylation contributes to cognitive dysfunction. The authors therefore assessed the effects of sevoflurane on Tau phosphorylation and the underlying mechanisms in young mice. Six-day-old wild-type and Tau knockout mice were exposed to sevoflurane. The authors determined the effects of sevoflurane anesthesia on Tau phosphorylation, levels of the kinases and phosphatase related to Tau phosphorylation, interleukin-6 and postsynaptic density protein-95 in hippocampus, and cognitive function in both young wild-type and Tau knockout mice. Anesthesia with 3% sevoflurane 2 h daily for 3 days induced Tau phosphorylation (257 vs. 100%, P = 0.0025, n = 6) and enhanced activation of glycogen synthase kinase 3β, which is the kinase related to Tau phosphorylation in the hippocampus of postnatal day-8 wild-type mice. The sevoflurane anesthesia decreased hippocampus postsynaptic density protein-95 levels and induced cognitive impairment in the postnatal day-31 mice. Glycogen synthase kinase 3β inhibitor lithium inhibited the sevoflurane-induced glycogen synthase kinase 3β activation, Tau phosphorylation, increased levels of interleukin-6, and cognitive impairment in the wild-type young mice. Finally, the sevoflurane anesthesia did not induce an increase in interleukin-6 levels, reduction in postsynaptic density protein-95 levels in hippocampus, or cognitive impairment in Tau knockout young mice. These data suggested that sevoflurane induced Tau phosphorylation, glycogen synthase kinase 3β activation, increase in interleukin-6 and reduction in postsynaptic density protein-95 levels in hippocampus of young mice, and cognitive impairment in the mice. Future studies will dissect the cascade relation of these effects.

Chronic kidney disease accelerates cognitive impairment in a mouse model of Alzheimer's disease, through angiotensin II

The protective role of Nrf2 on cognitive impairment in chronic intermittent hypoxia and sleep fragmentation mice

BackgroundAnesthesia may induce neurotoxicity and neurocognitive impairment in young mice. However, the underlying mechanism remains largely to be determined. Meanwhile, autophagy is involved in brain development and contributes to neurodegenerative diseases. We, therefore, set out to determine the effects of sevoflurane on autophagy in the hippocampus of young mice and on cognitive function in the mice.MethodsSix day-old mice received 3% sevoflurane, for two hours daily, on postnatal days (P) 6, 7 and 8. We then decapitated the mice and harvested the hippocampus of the young mice at P8. The level of LC3, the ratio of LC3-II to LC3-I, and SQSTM1/p62 level associated with the autophagy in the hippocampus of the mice were assessed by using Western blotting. We used different groups of mice for behavioral testing via the Morris Water Maze from P31 to P37.ResultsThe anesthetic sevoflurane increased the level of LC3-II and ratio of LC3-II/LC3-I, decreased the p62 level in the hippocampus of the young mice, and induced cognitive impairment in the mice. 3-Methyladenine, the inhibitor of autophagy, attenuated the activation of autophagy and ameliorated the cognitive impairment induced by sevoflurane in the young mice.ConclusionThese data showed that sevoflurane anesthesia might induce cognitive impairment in the young mice via activation of autophagy in the hippocampus of the young mice. These findings from the proof of concept studies have established a system and suggest the role of autophagy in anesthesia neurotoxicity and cognitive impairment in the young mice, pending further investigation.

Risperidone ameliorated 1,2-Diacetylbenzene-induced cognitive impairments in mice via activating prolactin signaling pathways

IL-6 gene expression is controlled by a promoter region containing multiple regulatory elements such as NF-κB, NF-IL6, CRE, GRE, and TRE. In this study, we demonstrated that TRE, found within the IL-6 promoter, is embedded in a functional antioxidant response element (ARE) matching an entire ARE consensus sequence. Further, point mutations of the ARE consensus sequence in the IL-6 promoter construct selectively eliminate ARE but not TRE activity. Nrf2 is a redox-sensitive transcription factor which provides cytoprotection against electrophilic and oxidative stress and is the most potent activator of ARE-dependent transcription. Using Nrf2 knock-out mice we demonstrate that Nrf2 is a potent activator of IL-6 gene transcription in vivo. Moreover, we show evidence that Nrf2 is the transcription factor that activates IL6 expression in a cholestatic hepatitis mouse model. Our findings suggest a possible role of IL-6 in oxidative stress defense and also give indication about an important function for Nrf2 in the regulation of hematopoietic and inflammatory processes.

Protective effect and mechanism of Lycium barbarum L. polyphenol on cognitive impairment induced by ethanol in mice

We isolated a polypeptide PNP2 from Corn Cervi Pantotrichum and investigated its effect and mechanism on cognitive impairment in Alzheimer's disease (AD) mice. Morris water maze was used to assess the degree of cognitive impairment in mice. Histopathological changes were detected by H&E staining; the expressions of inflammatory cytokines were assayed by ELISA. Western blotting was employed to detect the protein expressions. PNP2 could improve cognitive impairment, central inflammatory response, and NLRP3 signaling in AD mice. In vitro experiments revealed that PNP2 could suppress the inflammatory response of microglial cells and reduce the activation of NLRP3 in microglial cells, while MCC950 could antagonize the effects of PNP2. Polypeptide component PNP2 in Corn Cervi Pantotrichum can ameliorate central nervous inflammation and cognitive impairment in AD mice by suppressing NLRP3 signaling.

Tau phosphorylation is associated with cognitive impairment in young mice. However, the underlying mechanism and targeted interventions remain mostly unknown. We set out to determine the potential interactions of Tau, interleukin 6 (IL-6) and mitochondria following treatment of anesthetic sevoflurane and to assess their influences on synapse number and cognition in young mice. Sevoflurane (3% for 2 ​h) was given to wild-type, Tau knockout, IL-6 knockout, and cyclophilin D (CypD) knockout mice on postnatal (P) day 6, 7 and 8. We measured amounts of phosphorylated Tau, IL-6, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), ATP, postsynaptic density 95 (PSD-95), synaptophysin, N-cadherin, synapse number, and cognitive function in the mice, employing Western blot, electron microscope and Morris water maze among others. Here we showed that sevoflurane increased Tau phosphorylation and caused IL-6 elevation, mitochondrial dysfunction, synaptic loss and cognitive impairment in young wild-type, but not Tau knockout, mice. In young IL-6 knockout mice, sevoflurane increased Tau phosphorylation but did not cause mitochondrial dysfunction, synaptic loss or cognitive impairment. Finally, sevoflurane increased Tau phosphorylation and IL-6 amount, but did not induce synaptic loss and cognitive impairment, in young CypD knockout mice or WT mice pretreated with idebenone, an analog of co-enzyme Q10. In conclusion, sevoflurane increased Tau phosphorylation, which caused IL-6 elevation, leading to mitochondrial dysfunction in young mice. Such interactions caused synaptic loss and cognitive impairment in the mice. Idebenone mitigated sevoflurane-induced cognitive impairment in young mice. These studies would promote more research to study Tau in young mice.