A novel cyclic squamosamide analogue compound FLZ improves memory impairment in artificial senescence mice induced by chronic injection of D-galactose and NaNO2

BaZiBuShen alleviates cognitive deficits and regulates Sirt6/NRF2/HO-1 and Sirt6/P53-PGC-1α-TERT signaling pathways in aging mice

ETHNOPHARMACOLOGICAL RELEVANCE

BaZiBuShen formula (BZBS) is clinically used to counteract mental fatigue and to retard the aging process. Brain aging echoes in major risks of human sufferings and has become one of the main challenges to our societies and the health-care systems.

AIM OF THE STUDY

To investigate the effect and mode of action of BZBS on aging-associated cognitive impairments.

MATERIALS AND METHODS

BZBS was orally administered to D-galactose and NaNO2-induced aging mice. Premature senescence was assessed using the Morris water maze, step-down type passive avoidance, and pole-climbing tests. Telomere length was examined by qPCR analysis. Telomerase activity was assessed using PCR ELISA assay. Mitochondrial complex IV activity was examined by biochemical test. The levels of redox and immune status were determined by ELISA or biochemical assay. The expressions of sirtuin 6 (Sirt6), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), P53, telomerase reverse transcriptase (TERT), heme oxygenase-1 (HO-1), phospho(p)-nuclear factor erythroid-2 related factor 2 (NRF2), caspase-3, Bcl-2 associated x (Bax), and B-cell lymphoma-2 (Bcl-2) in the cerebral cortex were examined by Western blot and/or immunohistochemical staining.

RESULTS

BZBS intervention ameliorated reduced brain performances in aging mice, including memory, cognitive, and motor functions. In addition, BZBS administration to aging mice preserved redox homeostasis, attenuated immunosenescence, and maintained telomerase activity and telomere length. Moreover, BZBS treatment were associated with a declines in P53, caspase-3, Bax expressions and an increase in Sirt6, p-HO-1, p-NRF2, PGC-1α, and Bcl-2 expressions in the brains of this rapid aging mouse.

CONCLUSIONS

BZBS attenuates premature senescence possibly via the preservation of redox homeostasis and telomere integrity, and inhibition of apoptosis in rapid aging mouse. The mechanism governing the alterations may be associated with through the activation of Sirt6/NRF2/HO-1 and Sirt6/P53-PGC-1α-TERT signaling pathways. The results suggest that BZBS may provide a novel strategy for confronting aging and age-associated diseases.

Racemic oleracein E increases the survival rate and attenuates memory impairment in D-galactose/NaNO₂-induced senescent mice

BACKGROUND

Compounds that possess a pyrrolidone skeleton are a rich resource for the discovery of nootropic drugs. Oleracein E (OE), which possesses both tetrahydroisoquinoline and pyrrolidone skeletons, was first isolated from the medicinal plant Portulaca oleracea L. and was thought to be an active component in the cognition-improvement effect induced by this herb. The aim of this study was to investigate the effect of OE on cognitive impairment in senescent mice and its underlying mechanism of action.

METHOD

Senescent Kunming mice were established by the intraperitoneal injection of D-galactose (D-gal, 1250 mg/kg/d) and NaNO2 (90 mg/kg/d) for 8 weeks. OE (3 mg/kg/d, 15 mg/kg/d) was orally administered for 8 weeks, and the nootropic drug piracetam (PA, 400 mg/kg/d) was used as a positive control. A Morris water maze was used to assess cognitive ability. GSH and MDA levels and T-AOC, SOD, and CAT activities in the brain or plasma were determined. Hippocampal morphology was observed by HE staining, and expression of the anti-apoptotic protein Bcl-2 and the pro-apoptotic proteins Bax and Caspase-3 was observed by immunohistochemical staining.

RESULTS

Large-dosage treatments with D-gal/NaNO2 for 8 weeks significantly reduced survival, impaired spatial memory capacity, compensatorily up-regulated GSH level and T-AOC and SOD activities, decreased CAT activity, and induced hippocampal neuronal damage and apoptosis as reflected by the apparent low expression of Bcl-2 and high expression of Bax and Caspase-3. OE significantly prolonged lifespan and was more potent than PA. Similar to PA, OE at 15 mg/kg/d improved memory capacity. The underlying mechanism of action was related to the reversal of abnormal brain antioxidant biomarkers (GSH, T-AOC, and SOD) to normal levels and the inhibition of hippocampal neuronal apoptosis.

CONCLUSION

OE from P. oleracea is an active compound for improving cognitive function and is also a candidate nootropic drug for the treatment of age-related dementia.

An in vivo microdialysis study of FLZ penetration through the blood-brain barrier in normal and 6-hydroxydopamine induced Parkinson's disease model rats

FLZ (N-[2-(4-hydroxy-phenyl)-ethyl]-2-(2,5-dimethoxy-phenyl)-3-(3-methoxy-4-hydroxy-phenyl)-acrylamide) is a novel synthetic squamosamide derivative and a potential anti-Parkinson's disease (PD) agent. The objective of the present study was to investigate the penetration of free FLZ across the BBB and the effects of P-gp inhibition on FLZ transport in normal and 6-hydroxydopamine (6-OHDA) induced PD model rats. In vivo microdialysis was used to collect FLZ containing brain and blood dialysates following intravenous (i.v.) drug administration either with or without pretreatment with the specific P-gp inhibitor, zosuquidar trihydrochloride (zosuquidar·3HCl). A sensitive, rapid, and reliable ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) technique was developed and validated to quantitate free FLZ levels in the dialysates. No significant differences were observed in the brain/blood FLZ area under the concentration-time curve (AUC) ratio between normal and PD model rats. However, pretreatment with zosuquidar·3HCl markedly increased the AUC ratio in both rat models. In addition, FLZ penetration was similar in zosuquidar·3HCl-pretreated normal and PD rats. These results suggest that P-gp inhibition increases BBB permeability to FLZ, thereby supporting the hypothesis that P-gp normally restricts FLZ transfer to the brain. These findings could provide reference data for future clinical trials and may aid investigation of the BBB permeability of other CNS-active substances.

Hippocampal neurochemical changes in senescent mice induced with chronic injection of D-galactose and NaNO₂: an in vitro high-resolution NMR spectroscopy study at 9.4T

Proton magnetic resonance spectroscopy (¹H-MRS) has been used to provide useful information about the neurochemical changes reflecting early pathological alterations in Alzheimer's disease (AD) brain. In this study, we have longitudinally measured the hippocampal neurochemical profile in vitro in senescent mice induced with chronic injection of D-Galactose and NaNO₂, at different time point from day 30 to day 70 with a 10-day interval. Pathological brain alterations induced by D-Galactose and NaNO₂ were monitored through hematoxylin and eosin (HE) staining, Congo red staining and bielschowsky silver staining, and the cognition deficits were assessed via Morris Water Maze (MWM) test. This D-galactose and NaNO₂ treated mouse model, characterized by an early-onset memory dysfunction, a robust neuronal loss, amyloid plaques and neurofibrillary tangles in hippocampal subdivision, well mimics a prodromal Alzheimer's phenotype. Consistent with previously published in vivo ¹H MRS findings in human AD patients and AD transgenic mice, our in vitro ¹H MRS on the perchloric acid extractions of hippocampus in senescent mice observed significant decreases of N-acetylaspartate (NAA) and Glutamate (Glu) but an increase in Myo-inositol (mIns). Elevated mIns occurred prior to the reduction of NAA and Glu during the progression of aging. In addition, changes in mIns, NAA and Glu were found to precede pathological abnormalities. Overall, our in vitro findings in senescent mice validated the concept that hippocampal neurochemical alternations preceded the pathological changes of the brain, and could serve as potential markers of AD progression. Reductions of NAA and Glu can be interpreted in terms of neuronal degeneration and dysfunctions in glutamatergic activity that may contribute to the pathophysiological mechanisms underlying AD. Elevated mIns might be related to glial activation. Further experiments are needed to explore the potential value of mIns in the early diagnosis of AD, to verify whether glial cell proliferation occurs earlier than neuronal changes.

FLZ alleviates the memory deficits in transgenic mouse model of Alzheimer's disease via decreasing beta-amyloid production and tau hyperphosphorylation

Alzheimer’s disease (AD) is the most common cause of dementia worldwide and mainly characterized by the aggregated β-amyloid (Aβ) and hyperphosphorylated tau. FLZ is a novel synthetic derivative of natural squamosamide and has been proved to improve memory deficits in dementia animal models. In this study, we aimed to investigate the mechanisms of FLZ’s neuroprotective effect in APP/PS1 double transgenic mice and SH-SY5Y (APPwt/swe) cells. The results showed that treatment with FLZ significantly improved the memory deficits of APP/PS1 transgenic mice and decreased apoptosis of SH-SY5Y (APPwt/swe) cells. FLZ markedly attenuated Aβ accumulation and tau phosphorylation both in vivo and in vitro. Mechanistic study showed that FLZ interfered APP processing, i.e., FLZ decreased β-amyloid precursor protein (APP) phosphorylation, APP-carboxy-terminal fragment (APP-CTF) production and β-amyloid precursor protein cleaving enzyme 1 (BACE1) expression. These results indicated that FLZ reduced Aβ production through inhibiting amyloidogenic pathway. The mechanistic study about FLZ’s inhibitory effect on tau phosphorylation revealed t the involvement of Akt/glycogen synthase kinase 3β (GSK3β) pathway. FLZ treatment increased Akt activity and inhibited GSK3β activity both in vivo and in vitro. The inhibitory effect of FLZ on GSK3β activity and tau phosphorylation was suppressed by inhibiting Akt activity, indicating that Akt/GSK3β pathway might be the possible mechanism involved in the inhibitory effect of FLZ on tau hyperphosphorylation. These results suggested FLZ might be a potential anti-AD drug as it not only reduced Aβ production via inhibition amyloidogenic APP processing pathway, but also attenuated tau hyperphosphoylation mediated by Akt/GSK3β.

FLZ inhibited γ-secretase selectively and decreased Aβ mitochondrial production in APP-SH-SY5Y cells

Amyloid precursor protein (APP) metabolism is a key factor in the pathogenesis of Alzheimer's disease (AD). Amyloid-beta (Aβ) in mitochondria comes from APP mitochondrial metabolism or from the uptake Aβ from outside of mitochondria. It has been recently proposed that mitochondria are involved in the biochemical pathways through which Aβ causes neuronal dysfunction. The accumulated Aβ in mitochondria decreases the level of cytochrome c oxidase (COX IV) and attenuates the ATP production consequently. FLZ is a synthetic cyclic derivative of squamosamide from Annona glabra. In this study, the effect of FLZ on APP processing in mitochondria was investigated in SH-SY5Y cells over-expressing APP695 (wt/Swe). FLZ treatment attenuated APP processing and decreased Aβ production in mitochondria. The mitochondrial function was increased with the upregulation of COX IV both at protein and activity levels. ATP production was also increased after FLZ treatment. The mechanistic study showed that FLZ inhibited γ-secretase activity by decreasing C-terminal fragment protein level of presenilin, the active center of γ-secretase. The effect of FLZ differs from DAPT (a non-selective γ-secretase inhibitor), suggesting FLZ is a selective γ-secretase inhibitor. FLZ selectively inhibited γ-secretase in the cleavage of recombinant C terminus of APP in vitro, without specifically modulating the processing of recombinant Notch intracellular domain. These results indicate that FLZ decreases Aβ accumulation in mitochondria by selectively inhibiting γ-secretase. We propose that FLZ is a potential anti-AD drug candidate, and its mechanism may be improving mitochondrial function by reducing the Aβ burden in mitochondria.

Rutin, a Flavonoid That Is a Main Component of Saussurea involucrata, Attenuates the Senescence Effect in D-Galactose Aging Mouse Model

Saussurea involucrata (Kar. et Kir.), known as the snow lotus, grows in the Tian Shan and A'er Tai areas of China. It has recently been reported that the ethyl acetate extract of S. involucrata (SI-2) can inhibit proliferation and induce apoptosis in PC-3 human prostate cancer cells. This study investigated the protective effect of ethyl acetate extract of S. involucrata (SI-2) or rutin, a flavonoid extracted from ethyl acetate extract of S. involucrata (SI-2), on D-galactose- (D-gal-) induced brain injury in mice. Administering SI-2 or rutin (30 mg/kg/d and 30 mg/kg/d) for 6 weeks, concomitant with D-gal injection, significantly increased superoxide dismutase and glutathione peroxidase activities and decreased the MDA level in plasma. Furthermore, the result showed that the percentages of cleaved caspase-3 and PARP in the D-gal-treated mice were much higher than those in the control. Pretreatment using SI-2 or rutin decreased the expression of cyclooxygenase-2 via downregulation of NF-kappaB, resulting in a decrease in lipid peroxidation. Furthermore, our results also showed that oral administration of rutin to these mice significantly improved behavioral performance in a step-through passive avoidance task and these results suggest that SI-2 or rutin exerts potent antiaging effects on D-gal in mice via antioxidative mechanisms.

Ethanol extract of Scutellaria baicalensis Georgi prevents oxidative damage and neuroinflammation and memorial impairments in artificial senescense mice

Aging is a progressive process related to the accumulation of oxidative damage and neuroinflammation. We tried to find the anti-amnesic effect of the Scutellaria baicalens Georgia (SBG) ethanol extract and its major ingredients. The antioxidative effect of SBG on the mice model with memory impairment induced by chronic injection of D-galactose and sodium nitrate was studied. The Y-maze test was used to evaluate the learning and memory function of mice. The activities of superoxide dismutase, catalase and the content of malondialdehyde in brain tissue were used for the antioxidation activities. Neuropathological alteration and expression of bcl-2 protein were investigated in the hippocampus by immunohistochemical staining. ROS, neuroinflammation and apoptosis related molecules expression such as Cox-2, iNOS, procaspase-3, cleaved caspase-3, 8 and 9, bcl-2 and bax protein and the products of iNOS and Cox-2, NO, PGE2, were studied using LPS-activated Raw 264.7 cells and microglia BV2 cells. The cognition of mice was significantly improved by the treatment of baicalein and 50 and 100 mg/kg of SBG in Y-maze test. Both SBG groups showed strong antioxidation, antiinflammation effects with significantly decreased iNOS and Cox-2 expression, NO and PGE2 production, increased bcl-2 and decreased bax and cleaved caspase-3 protein expression in LPS induced Raw 264.7 and BV2 cells. We also found that apoptotic pathway was caused by the intrinsic mitochondrial pathway with the decreased cleaved caspase-9 and unchanged cleaved caspase-8 expression. These findings suggest that SBG, especially high dose, 100 mg/kg, improved the memory impairments significantly and showed antioxidation, antiinflammation and intrinsic caspase-mediated apoptosis effects.

Isochaihulactone protects PC12 cell against H(2)O(2) induced oxidative stress and exerts the potent anti-aging effects in D-galactose aging mouse model

AIM

to investigate the effect of isochaihulactone (also known as K8), a lignan compound of Bupleurum scorzonerifolium, on H(2)O(2)-induced cytotoxicity in neuronally differentiated PC12 cells (nPC12).

METHODS

viability of neuronal PC12 cells was measured using MTT assay. Protein expression was determined by Western blot. Apoptotic cells was determined using TUNEL assay. D-galactose aging mice were used as a model system to study the anti-oxidant effects of isochaihulactone in vivo.

RESULTS

pretreatment with isochaihulactone (5-10 micromol/L) increased cell viability and decreased membrane damage, generation of reactive oxygen species and degradation of poly (ADP-ribose) polymerase in H(2)O(2)-treated nPC12 cells and also decreased the expression of cyclooxygenase-2, via downregulation of NF-kappaB, resulting in a decrease in lipid peroxidation. The results suggest that isochaihulactone is a potential antioxidant agent. In a murine aging model, in which chronic systemic exposure to D-galactose (D-gal) causes the acceleration of senescence, administration of isochaihulactone (10 mgxkg(-1)xd(-1), sc) for 7 weeks concomitant with D-gal injection significantly increased superoxide dismutase and glutathione peroxidase activities and decreased the MDA level in plasma. Furthermore, H&E staining to quantify cell death within hippocampus showed that percentage of pyknotic nuclei in the D-gal-treated mice were much higher than in control.

CONCLUSION

the results suggest that isochaihulactone exerts potent anti-aging effects against D-gal in mice possibly via antioxidative mechanisms.

The novel squamosamide derivative FLZ enhances BDNF/TrkB/CREB signaling and inhibits neuronal apoptosis in APP/PS1 mice

AIM

The aim of this study was to study the effects of compound FLZ, a novel cyclic derivative of squamosamide from Annona glabra, on brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB)/cAMP response element-binding protein (CREB) signaling and neuronal apoptosis in the hippocampus of the amyloid precursor protein (APP)/presenilin-1 (PS1) double transgenic mice.

METHODS

APP/PS1 mice at the age of 5 months and age-matched wild-type mice (WT) were intragastrically administered FLZ (150 mg/kg) or vehicle [0.05% carboxymethyl cellulose sodium (CMC-Na)] daily for 20 weeks. The levels of BDNF in the hippocampus of WT and APP/PS1 mice were then measured by immunohistochemistry and Western blot analysis. Neuronal apoptosis in mouse hippocampus was detected by Nissl staining. Expression of NGF, NT3, pTrkB (Tyr515)/TrkB, pAkt (Ser473)/Akt, pERK/ERK, pCREB (Ser133)/CREB, Bcl-2/Bax, and active caspase-3 fragment/caspase-3 in the hippocampus of WT and APP/PS1 mice was detected by Western blot analysis.

RESULTS

Compared with vehicle-treated APP/PS1 mice, FLZ (150 mg/kg) significantly increased BDNF and NT3 expression in the hippocampus of APP/PS1 mice. In addition, FLZ promoted BDNF high-affinity receptor TrkB phosphorylation and activated its downstream ERK, thus increasing phosphorylation of CREB at Ser133 in the hippocampus of APP/PS1 mice. Moreover, FLZ showed neuroprotective effects on neuronal apoptosis by increasing the Bcl-2/Bax ratio and decreasing the active caspase-3 fragment/caspase-3 ratio in the hippocampus of APP/PS1 mice.

CONCLUSION

FLZ exerted neuroprotection at least partly through enhancing the BDNF/TrkB/CREB pathway and inhibiting neuronal apoptosis in APP/PS1 mice, which suggests that FLZ can be explored as a potential therapeutic agent in long-term Alzheimer's disease therapy.