TGR5-mediated lateral hypothalamus-dCA3-dorsolateral septum circuit regulates depressive-like behavior in male mice.

Although bile acids play a notable role in depression, the pathological significance of the bile acid TGR5 membrane-type receptor in this disorder remains elusive. Using depression models of chronic social defeat stress and chronic restraint stress in male mice, we found that TGR5 in the lateral hypothalamic area (LHA) predominantly decreased in GABAergic neurons, the excitability of which increased in depressive-like mice. Upregulation of TGR5 or inhibition of GABAergic excitability in LHA markedly alleviated depressive-like behavior, whereas down-regulation of TGR5 or enhancement of GABAergic excitability facilitated stress-induced depressive-like behavior. TGR5 also bidirectionally regulated excitability of LHA GABAergic neurons via extracellular regulated protein kinases-dependent Kv4.2 channels. Notably, LHA GABAergic neurons specifically innervated dorsal CA3 (dCA3) CaMKIIα neurons for mediation of depressive-like behavior. LHA GABAergic TGR5 exerted antidepressant-like effects by disinhibiting dCA3 CaMKIIα neurons projecting to the dorsolateral septum (DLS). These findings advance our understanding of TGR5 and the LHAGABA→dCA3CaMKIIα→DLSGABA circuit for the development of potential therapeutic strategies in depression.

Neuroprotective effects of novel compound FMDB on cognition, neurogenesis and apoptosis in APP/PS1 transgenic mouse model of Alzheimer's disease.

Clinical and experimental studies have shown that the sharp reduction of estrogen is one of the important reasons for the high incidence of Alzheimer's disease (AD) in elderly women, but there is currently no such drug for treatment of AD. Our group first designed and synthesized a novel compound R-9-(4fluorophenyl)-3-methyl-10,10,-Hydrogen-6-hydrogen-benzopyran named FMDB. In this study, our aim is to investigate the neuroprotective effects and mechanism of FMDB in APP/PS1 transgenic mice. 6 months old APP/PS1 transgenic mice were intragastrical administered with FMDB (1.25, 2.5 and 5 mg/kg) every other day for 8 weeks. LV-ERß-shRNA was injected bilaterally into the hippocampus of APP/PS1 mice to knockdown estrogen receptor ß (ERß). We found that FMDB ameliorated cognitive impairment in the Morris water maze and novel object recognition tests, increased hippocampal neurogenesis and prevented hippocampal apoptotic responses in APP/PS1 mice. Importantly, FMDB activated nuclear ERß mediated CBP/p300, CREB and brain-derived neurotrophic factor (BDNF) signaling, and membrane ERß mediated PI3K/Akt, CREB and BDNF signaling in the hippocampus. Our study demonstrated the contributions and mechanism of FMDB to cognition, neurogenesis and apoptosis in APP/PS1 mice. These lay the experimental foundation for the development of new anti-AD drugs.

Deficiency of astrocyte CysLT1R ameliorates depression-like behaviors in mice by modulating glutamate synaptic transmission.

Our previous study suggests that hippocampal cysteinyl leukotriene receptor 1 (CysLT1R) could be involved in depression. Herein we hypothesize that CysLT1R may regulate depression by affecting synaptic glutamate cycling based on existence of CysLT1R in the astrocytes that participate in occurrence of depression. We found that CysLT1R expression was significantly increased in the astrocyte of chronic unpredictable mild stress (CUMS)-induced depression-like mice, CysLT1R astrocyte-specific conditional knockout (AcKO) significantly improved depression-like behaviors, as indicated by decreased immobility time in the forced swimming test and tail suspension test and increased sucrose preference in the sucrose preference test, and knockdown of CysLT1R in the astrocyte of dentate gyrus (DG), the region with the most significant increase of CysLT1R in the astrocyte of depression-like mice, produced similar effects. Correspondingly, overexpression of CysLT1R in the astrocyte of DG induced depression-like behaviors in mice. The further study showed that CysLT1R AcKO ameliorated synaptic plasticity impairment, as reflected by increased synapse, LTP and PSD95, and promoted glutamate transporter 1 (GLT-1) expression by inhibiting NF-κB p65 nuclear translocation mediated by ß-arestin2 and clatrhin, subsequently decreased glutamate in synaptic cleft and GluN2B on postsynaptic membrane in depression-like mice. The present study also showed that GLT-1 agonist or NF-κB inhibitor ameliorated depressive-like behaviors induced by overexpression of the astrocyte CysLT1R of DG. Our study demonstrated that astrocyte CysLT1R regulated depression by modulating glutamate synaptic transmission, suggesting that CysLT1R could be a potential target for developing novel drugs of anti-depression.

Neuroprotective effects of novel compound Tozan on cognition, neurogenesis and apoptosis in diabetes.

BACKGROUND: Cognitive impairment is a serious complication of diabetes that manifests as an impairment of spatial memory and learning ability. Its pathogenesis is unclear, and effective therapeutic drugs are very limited. Our group designed and synthesized a novel compound named 3-p-tolyl-9H-xanthen-9-one (Tozan). In this study, we sought to investigate the effects and mechanism of Tozan on diabetic cognitive impairment. METHODS: Methylglyoxal (MG)-induced SH-SY5Y cells and streptozotocin (STZ)-induced type 1 diabetic mice were treated with Tozan. Methyl thiazolul tetrazolium (MTT) and lactate dehydrogenase (LDH) were used to test cytotoxicity. Morris water maze (MWM) and Y-maze tests were used to evaluate cognitive function. Immunofluorescence and western blot analyses were used to evaluate neurogenesis, apoptosis, and signal transduction pathway-related proteins. In addition, Lentivirus (LV)-estrogen receptor beta (ERß)-ribonucleic acid interference (RNAi) was used to knockdown the ERß gene in SH-SY5Y cells. RESULTS: We found that Tozan ameliorated MG-induced cytotoxicity in SH-SY5Y cells, improved cognitive dysfunction in STZ-induced type 1 diabetic mice, increased neurogenesis, and prevented apoptotic responses in vitro and in vivo. Importantly, Tozan (2, 4, and 8 mg/kg) mediated phosphatidylinositol-3-kinase and protein kinase B cAMP-response element binding protein (PI3K/Akt-CREB) signaling by activating membrane ERß, and a high dose of Tozan (8 mg/kg) mediated CREB signaling by activating nuclear ERß in the hippocampus. Notably, Tozan did not have an anti-apoptosis and regeneration protective role in ERß gene knockdown cells. CONCLUSIONS: Our study demonstrates Tozan's contributions to and role in cognition, neurogenesis, and apoptosis in diabetes, and lays an experimental foundation for the development of new anti-diabetic cognitive impairment drugs.

Hippocampal CysLT1R overexpression or activation accelerates memory deficits, synaptic dysfunction, and amyloidogenesis in young APP/PS1 transgenic mice.

BACKGROUND: Our previous studies demonstrated that cysteinyl leukotrienes receptor 1 (CysLT1R) knockout, pharmacological blockade, or hippocampus knockdown produced beneficial effects against Alzheimer's disease (AD); however, whether CysLT1R upregulation has deleterious effects on AD remains elusive. METHODS: In this study, we investigated the changes in behaviors, hippocampal amyloidogenesis, and synapse plasticity after CysLT1R overexpression by microinfusion of the lentiviral vector, containing its coding sequence of mouse (LV-CysLT1R), into the bilateral dentate gyri (DG) of the hippocampus or CysLT1R activation by repeated systemic administration of its agonist YM-17690 (0.1 mg/kg, once a day, i.p., for 28 d). RESULTS: The behavior data showed that overexpression of CysLT1R in hippocampal DG or administration of YM-17690 deteriorated behavioral performance in Morris water maze (MWM), Y-maze tests, and novel object recognition (NOR) in young APP/PS1 mice. The further studies showed that these treatments significantly destroyed synaptic function, as evidenced by impaired hippocampal long-term potentiation (LTP), decreased spine density, low number of synapses, and decreased postsynaptic protein (PSD95), and promoted the generation of amyloid ß (Aß) through increased expression of BACE1 and PS1 in the hippocampus of young APP/PS1 mice. CONCLUSIONS: Together, our results indicate that CysLT1R upregulation accelerates memory impairment in young APP/PS1 mice, which is associated with promoting synaptic dysfunction and amyloidogenesis in the hippocampus.

Takeda G Protein-Coupled Receptor 5 Modulates Depression-like Behaviors via Hippocampal CA3 Pyramidal Neurons Afferent to Dorsolateral Septum.

BACKGROUND: Takeda G protein-coupled receptor 5 (TGR5) is recognized as a promising target for type 2 diabetes and metabolic syndrome; its expression has been demonstrated in the brain and is thought to be neuroprotective. Here, we hypothesize that dysfunction of central TGR5 may contribute to the pathogenesis of depression. METHODS: In well-established chronic social defeat stress (CSDS) and chronic restraint stress (CRS) models of depression, we investigated the functional roles of TGR5 in CA3 pyramidal neurons (PyNs) and underlying mechanisms of the neuronal circuit in depression (for in vivo studies, n = 10; for in vitro studies, n = 5-10) using fiber photometry; optogenetic, chemogenetic, pharmacological, and molecular profiling techniques; and behavioral tests. RESULTS: Both CSDS and CRS most significantly reduced TGR5 expression of hippocampal CA3 PyNs. Genetic overexpression of TGR5 in CA3 PyNs or intra-CA3 infusion of INT-777, a specific agonist, protected against CSDS and CRS, exerting significant antidepressant-like effects that were mediated via CA3 PyN activation. Conversely, genetic knockout or TGR5 knockdown in CA3 facilitated stress-induced depression-like behaviors. Re-expression of TGR5 in CA3 PyNs rather than infusion of INT-777 significantly improved depression-like behaviors in Tgr5 knockout mice exposed to CSDS or CRS. Silencing and stimulation of CA3 PyNs→somatostatin-GABAergic (gamma-aminobutyric acidergic) neurons of the dorsolateral septum circuit bidirectionally regulated depression-like behaviors, and blockade of this circuit abrogated the antidepressant-like effects from TGR5 activation of CA3 PyNs. CONCLUSIONS: These findings indicate that TGR5 can regulate depression via CA3 PyNs→somatostatin-GABAergic neurons of dorsolateral septum transmission, suggesting that TGR5 could be a novel target for developing antidepressants.

Mogrol attenuates lipopolysaccharide (LPS)-induced memory impairment and neuroinflammatory responses in mice.

This study aimed to evaluate whether mogrol, a main bioactive ingredient of Siraitia grosvenorii, could attenuate LPS-induced memory impairment in mice. The behavioral tests and immunohistochemical analysis and Western blot were performed. The present results showed that oral administration of mogrol (20, 40, 80 mg/kg) significantly improved LPS-induced memory impairment in mice. The results also indicated that mogrol treatment significantly reduced the number of Iba1-positive cells, the nuclear NF-κB p65 and levels of TNF-α, IL-1ß and IL-6 both in the hippocampus and frontal cortex of LPS-challenged mice. [Formula: see text].

Zileuton ameliorates depressive-like behaviors, hippocampal neuroinflammation, apoptosis and synapse dysfunction in mice exposed to chronic mild stress.

Our previous study has found that zileuton, a selective 5-lipoxygenase (5LO) inhibitor, abrogated lipopolysaccharide-induced depressive-like behaviors and hippocampal neuroinflammation. Herein, we further extended our curiosity to investigate effects of zileuton on stress-induced depressive-like behaviors. Our data indicated that zileuton significantly ameliorated depressive-like behaviors in mice subjected to chronic mild stress (CMS), as shown in the tail suspension test, forced swimming test and novelty-suppressed feeding test. The further studies indicated that zileuton suppressed hippocampal neuroinflammation, evidenced by lower levels of TNF-α, IL-1ß and nuclear NF-κB p65 as well as decreased number of Iba1-positive cells. It also significantly ameliorated hippocampal apoptosis, indicated by deceased number of TUNEL-positive cells, deceased ratio of cleaved caspase-3/procaspase-3 and increased ratio of Bcl-2/Bax. More importantly, zileuton increased the level of synaptic proteins PSD-95 and SYN and the number of NeuN+/BrdU+ cells in the hippocampus. Over all, zileuton alleviated CMS-induced depressive-like behaviors, neuroinflammatory and apoptotic responses, abnormalities of synapse and neurogenesis in the hippocampus, suggesting that it might has beneficial effects on depression.

1-Methylnicotinamide attenuates lipopolysaccharide-induced cognitive deficits via targeting neuroinflammation and neuronal apoptosis.

Alzheimer's disease (AD) is a neurodegenerative disease that affects cognition and behavior. The neuroinflammatory response in the brain is an important pathological characteristic in AD. In this study, we investigated the neuroprotective effects of 1-Methylnicotinamide (MNA), known as the main metabolite of nicotinamide, on reducing lipopolysaccharide (LPS)-induced cognitive deficits via targeting neuroinflammation and neuronal apoptosis. We found that the mice treated with LPS exhibited cognitive deficits in the novel object recognition, Morris water maze and Y-maze avoidance tests. However, intragastric administration of MNA (100 or 200 mg/kg) for 3 weeks significantly attenuated LPS-induced cognitive deficits in mice. Importantly, MNA treatment suppressed the protein expression of nuclear factor-kappa B p65 (NF-κB p65), pro-inflammatory cytokines (TNF-α, IL-6) and decreased the activation of microglia and astrocytes in the hippocampus and frontal cortex of LPS-induced mice. In addition, MNA treatment suppressed neuronal apoptosis by reducing the number of TUNEL-positive cells, caspase-3 activation and increasing the level of Bcl-2/Bax ratio in the hippocampus and frontal cortex. These findings indicate that MNA could be a potential neuroprotective drug in neurodegenerative diseases such as AD.

Protective effects of tauroursodeoxycholic acid on lipopolysaccharide-induced cognitive impairment and neurotoxicity in mice.

Accumulating evidence has shown that tauroursodeoxycholic acid (TUDCA) is neuroprotective in different animal models of neurological diseases. However, whether TGR5 agonist TUDCA can improve lipopolysaccharide (LPS)-induced cognitive impairment in mice is less clear. Using a model of cognitive impairment with LPS (2.0 µg) we investigated the effects of TUDCA (200 or 400 µg) on cognitive dysfunction and neurotoxicity in mice. Both Morris water maze and Y-maze avoidance tests showed that TUDCA treatment significantly alleviated LPS-induced behavioral impairments. More importantly, we found that TUDCA treatment reversed TGR5 down-regulation, prevented neuroinflammation via inhibiting NF-κB signaling in the hippocampus of LPS-treated mice. Additionally, TUDCA treatment decreased LPS-induced apoptosis through decreasing TUNEL-positive cells and the overexpression of caspase-3, increasing the ratio of Bcl-2/Bax. TUDCA treatment also ameliorated synaptic plasticity impairments by increasing the ratio of mBDNF/proBDNF, the number of dendritic spines and the expression of synapse-associated proteins in the hippocampus. Our results indicated that TUDCA can improve cognitive impairment and neurotoxicity induced by LPS in mice, which is involved in TGR5-mediated NF-κB signaling.

ERα and/or ERß activation ameliorates cognitive impairment, neurogenesis and apoptosis in type 2 diabetes mellitus mice.

Estrogen receptors (ERs) are thought to be associated with the onset and progression of neurodegenerative injuries and diseases, but the relationship and mechanisms underlying between ERs and cognition in type 2 diabetes remain elusive. In the current study, we investigated the effects of ERα and ERß on the cognition, neurogenesis and apoptosis in high-fat diet and streptozocin-induced diabetic mice. We found that ERα and/or ERß activation using their agonists (0.5 mg/kg E2, PPT or DPN) ameliorate memory impairment in the Morris water maze and Y-maze tests, increase hippocampal neurogenesis and prevent hippocampal apoptotic responses. Importantly, treatment with the pharmacologic ERs agonists caused significant increases in the membrane ERα and ERß expression and subsequent PI3K/Akt, CREB and BDNF activation in the hippocampus of type 2 diabetes mellitus mice. Our data indicate that ERα and ERß are involved in the cognitive impairment in type 2 diabetes, and that activated ERs, such as application of ERs agonists, could be a novel and promising strategy for the treatment of diabetic cognitive impairment.

Inhibitory effect of INT-777 on lipopolysaccharide-induced cognitive impairment, neuroinflammation, apoptosis, and synaptic dysfunction in mice.

Neuroinflammation plays an important role in the pathophysiology of Alzheimer's disease (AD) and memory impairment. Herein, we evaluated the neuroprotective effects of 6-ethyl-23(S)-methyl-cholic acid (INT-777), a specific G-protein coupled bile acid receptor 1 (TGR5) agonist, in the LPS-treated mouse model of acute neurotoxicity. Single intracerebroventricular (i.c.v.) injection of LPS remarkably induced mouse behavioral impairments in Morris water maze, novel object recognition, and Y-maze avoidance tests, which were ameliorated by INT-777 (1.5 or 3.0 µg/mouse, i.c.v.) treatment. Importantly, INT-777 treatment reversed LPS-induced TGR5 down-regulation, suppressed the increase of nuclear NF-κB p65, and mitigated neuroinflammation, evidenced by lower proinflammatory cytokines, less activation of microglia, and increased the ratio of p-CREB/CREB or mBDNF/proBDNF in the hippocampus and frontal cortex. In addition, INT-777 treatment also suppressed neuronal apoptosis, as indicated by the reduction of TUNEL-positive cells, decreased activation of caspase-3, increased the ratio of Bcl-2/Bax, and ameliorated synaptic dysfunction as evidenced by the upregulation of PSD95 and synaptophysin in the hippocampus and frontal cortex. Taken together, this study showed the potential neuroprotective effects of INT-777 against LPS-induced cognitive impairment, neuroinflammation, apoptosis, and synaptic dysfunction in mice.

Activation of ERα and/or ERß ameliorates cognitive impairment and apoptosis in streptozotocin-induced diabetic mice.

Estrogen receptors (ERs) are thought to be associated with the onset and progression of neurodegenerative injuries and diseases, but the relationship and mechanisms underlying between ERs and cognition in type 1 diabetes remain elusive. In the current study, we investigated the effects of ERα and ERß on the memory impairment and apoptosis in streptozotocin-induced diabetic mice. We found that ERα and/or ERß activation using their agonists (0.5 mg/kg E2, PPT or DPN) ameliorate memory impairment in the Morris water maze (MWM) and Y-maze tests and suppress apoptosis as evidenced by decreased caspase-3 activity and increased ratio of Bcl-2/Bax. Importantly, treatment with the pharmacologic ERs agonists caused significant increases in the membrane ERα and ERß expression and subsequent PI3K/Akt, CREB and BDNF activation in the hippocampus of diabetic mice. Our data indicate that ERα and ERß are involved in the cognitive impairment of type 1 diabetes and that activation of ERs via administration of ERs agonists could be a novel and promising strategy for the treatment of diabetic cognitive impairment.

Neuroprotective effects of INT-777 against Aß1-42-induced cognitive impairment, neuroinflammation, apoptosis, and synaptic dysfunction in mice.

Increasing evidence demonstrates that the neurotoxicity of amyloid-beta (Aß) deposition plays a causative role in Alzheimer's disease (AD). Herein, we evaluated the neuroprotective effects of 6α-ethyl-23(S)-methylcholic acid (S-EMCA, INT-777), a specific G-protein coupled bile acid receptor 1 (TGR5) agonist, in the Aß1-42-treated mouse model of acute neurotoxicity. Single intracerebroventricular (i.c.v.) injection of aggregated Aß1-42 (410 pmol/mouse; 5 µl) into the mouse brain induced cognitive impairment, neuroinflammation, apoptosis, and synaptic dysfunction. In contrast, INT-777 (1.5 or 3.0 µg/mouse, i.c.v.) significantly improved Aß1-42-induced cognitive impairment, as reflected by better performance in memory tests. Importantly, INT-777 treatment reversed Aß1-42-induced TGR5 down-regulation, suppressed the increase of nuclear NF-κB p65, and mitigated neuroinflammation, as evidenced by lower proinflammatory cytokines and less Iba1-positive cells in the hippocampus and frontal cortex. INT-777 treatment also pronouncedly suppressed apoptosis through the reduction of TUNEL-positive cells, decreased caspase-3 activation, increased the ratio of Bcl-2/Bax, and ameliorated synaptic dysfunction by promoting dendritic spine generation with the upregulation of postsynaptic and presynaptic proteins (PSD95 and synaptophysin) in Aß1-42-treated mice. Our results indicate that INT-777 has potent neuroprotective effects against Aß1-42-induced neurotoxicity. Taken together, these findings suggest that the activation of TGR5 could be a novel and promising strategy for the treatment of AD.

New views and possibilities of antidiabetic drugs in treating and/or preventing mild cognitive impairment and Alzheimer's Disease.

Mounting evidence suggests that diabetes mellitus (DM) is associated with mild cognitive impairment (MCI), vascular dementia and Alzheimer's disease (AD). Biological, clinical and epidemiological data support a close link between DM and AD. Increasingly, studies have found that several antidiabetic agents can promote neurogenesis, and clinically ameliorate cognitive and memory impairments in different clinical settings. Data has shown that these antidiabetic drugs positively affect mitochondrial and synaptic function, neuroinflammation, and brain metabolism. Evidence to date strongly suggests that these antidiabetic drugs could be developed as disease-modifying therapies for MCI and AD in patients with and without diabetes.

Antidepressant-like effect of zileuton is accompanied by hippocampal neuroinflammation reduction and CREB/BDNF upregulation in lipopolysaccharide-challenged mice.

BACKGROUND: Recent studies demonstrated beneficial effects of zileuton, a 5-lipoxygenase (5LO) inhibitor, on some brain diseases in animal models, but the role of zileuton in the depression remains unknown. METHODS: We investigated the effects of zileuton on depressive behaviors using tail suspension test (TST), forced swimming test (FST) and novelty-suppressed feeding test (NSFT) in mice injected with lipopolysaccharide (LPS). The 5LO level, activation of microglia, NF-κB p65, TNF-α, IL-1ß, brain-derived neurotrophic factor (BDNF), and c-AMP response element-binding protein (CREB) were determined in the mouse hippocampus. RESULTS: We firstly found that the expression of hippocampal 5LO was gradually increased over LPS exposure and was reversed by fluoxetine administration. Zileuton significantly suppressed LPS-induced depressive behaviors, evidenced by the decreases in immobility time in TST and FST, as well as the latency to feed in NSFT. This treatment pronouncedly alleviated LPS-induced neuroinflammatory response, characterized by decreased 5LO, suppressed activation of microglia, decreased NF-κB p65, TNF-α and IL-1ß, and significantly increased the ratio of p-CREB/CREB or mBDNF/proBDNF in the hippocampus of the LPS-challenged mice. CONCLUSIONS: Zileuton abrogates LPS-induced depressive-like behaviors and neuroinflammation, and enhances CREB/BDNF signaling in the hippocampus, suggesting that zileuton could have potential therapeutic value for depression.

Targeted inhibition of RAGE reduces amyloid-ß influx across the blood-brain barrier and improves cognitive deficits in db/db mice.

AIMS: To investigate restorative effects of the receptor for advanced glycation end products (RAGE)-specific inhibitor FPS-ZM1 on abnormal amyloid ß (Aß) influx across the blood brain-barrier (BBB) and cognitive deficits in db/db mice. METHODS: Aß influx across the BBB was determined by intra-arterial infusion of 125I-Aß1-40. Receptor for advanced glycation end products (RAGE), Aß, NF-κB p65, caspase-3, Bax, Bcl-2, PSD-95 and synaptophysin were assayed by Western blot, immunohistochemistry or RT-PCR. Apoptosis was quantified by TUNEL assay. In vivo hippocampal long term potentiation (LTP) recording, Golgi Staining, Morris water maze (MWM) task and Y-maze test were performed. RESULTS: FPS-ZM1 (1.0 mg/kg i.p.) inhibited Aß influx across the BBB and expression of RAGE participating in Aß influx, consequently decreased hippocampal Aß1-40 and Aß1-42 in db/db mice. After FPS-ZM1 treatment, NF-κB signaling was inhibited, and neuronal apoptosis was reduced, which revealed by less TUNEL + cells, reduced caspase-3 activity and higher ratio of Bcl-2/Bax. In addition, FPS-ZM1 improved hippocampal plasticity evidenced by enhanced in vivo LTP and the restoration of spine deficit and increased PSD-95 expression in hippocampal neuron. Further studies found that FPS-ZM1 treatment alleviated cognitive deficits shown by better performance in behavioral tests, without significant metabolic effects on blood glucose, insulin and cerebral AGEs. CONCLUSION: Downregulation of abnormal Aß influx across the BBB by FPS-ZM1 at higher dosage contributes to reduced neuronal apoptosis, improved hippocampal plasticity and cognitive impairment in db/db mice.

Simvastatin ameliorates memory impairment and neurotoxicity in streptozotocin-induced diabetic mice.

Diabetes comes with an additional burden of moderate to severe hyperlipidemia, but little is known about the effects of lipid-lowering therapy on diabetic complications such as diabetes-associated cognitive decline. Herein we investigated the effects of statins on memory impairment and neurotoxicity in streptozotocin-induced diabetic mice. Our data indicated that oral administration of simvastatin at 10 or 20mg/kg for 4weeks significantly ameliorated diabetes-associated memory impairment reflected by performance better in the Morris water maze and Y-maze tests. The further study showed that these treatments caused significant increase of peroxisome proliferator-activated receptors gamma and decrease of NF-κB p65 in nucleus of hippocampus and cortex, and ameliorated neuroinflammatory response as evidenced by less Iba-1-positive cells and lower inflammatory mediators including IL-1ß, IL-6 and TNF-α as well as suppressed neuronal apoptosis as indicated by decreased TUNEL-positive cells, increased ratio of Bcl-2/Bax and decreased caspase-3 activity in the hippocampus and cortex. Moreover, simvastatin pronouncedly attenuated amyloidogenesis by decreasing amyloid-ß, amyloid precursor protein (APP) and beta-site APP cleaving enzyme-1. As expected, treated with simvastatin, the diabetic mice exhibited significant improvement of hyperlipidemia rather than hyperglycemia. Our findings disclosed novel therapeutic potential of simvastatin for the diabetes-associated cognitive impairment.

Hippocampal CysLT1R knockdown or blockade represses LPS-induced depressive behaviors and neuroinflammatory response in mice.

Evidence suggests that neuroinflammation is involved in depression and that the cysteinyl leukotriene receptor 1 (CysLT1R) plays a potential pathophysiological role in several types of CNS disorders. Our previous study has shown that knockdown of hippocampal CysLT1R in mice prevents the depressive-like phenotype and neuroinflammation induced by chronic mild stress (CMS). Here, we examined the effects of hippocampal CysLT1R knockdown and CysLT1R blockade on LPS-induced depressive-like behavior in mice. We found that injection of LPS (0.5 mg/kg, ip) caused marked increase in hippocampal CysLT1R expression, which was reversed by pretreatment with fluoxetine (20 mg·kg-1·d-1 for 7 d, ig). Knockdown of hippocampal CysLT1R or blockade of CysLT1R by pretreatment with pranlukast (0.5 mg/kg, ip) significantly suppressed LPS-induced depressive behaviors, as evidenced by decreases in mouse immobility time in the forced swimming test (FST) and tail suspension test (TST) and latency to feed in the novelty-suppressed feeding (NSF) test. Moreover, both CysLT1R knockdown and CysLT1R blockade markedly prevented LPS-induced neuroinflammation, as shown by the suppressed activation of microglia and NF-κB signaling as well as the hippocampal levels of TNF-α and IL-1ß in mice. Our results suggest that CysLT1R may be involved in LPS-induced depressive-like behaviors and neuroinflammation, and that downregulation of CysLT1R could be a novel and potential therapeutic strategy for the treatment of depression, at least partially due to its role in neuroinflammation.

CysLT1R downregulation reverses intracerebroventricular streptozotocin-induced memory impairment via modulation of neuroinflammation in mice.

Our previous studies showed that cysteinyl leukotrienes receptor 1 (CysLT1R) is upregulated in amyloid-ß (Aß)-induced neurotoxicity and that administration of CysLT1R antagonists such as pranlukast or montelukast can ameliorate memory impairment in mice. In the current study, we sought to explore the role of CysLT1R in intracerebroventricular streptozotocin (STZ-ICV)-induced mouse model of memory impairment and neuroinflammation through shRNA-mediated knockdown of CysLT1R and also its pharmacological blockade by pranlukast. ICR mice were infused with STZ (3.0mg/kg) by a single bilateral stereotaxic ICV microinjection followed by administration of CysLT1R-shRNA (intra-hippocampal) or pranlukast (intragastric, IG). After 21days, a set of behavioral and biochemical tests were performed in order to assess the degree of memory impairment and neuroinflammation in mice. STZ-infused mice spent less time in the target quadrant of Morris water maze test and took more time to find the shock-free arm in modified Y-maze test, which were rescued in the CysLT1R-knockdowned or pranlukast-treated mice. STZ-induced memory impairment was also accompanied by an elevated level of hippocampal CysLT1R, microglial activation, increased IL-1ß, and TNF-α. Such elevation of these factors was found to be mediated through the classical NF-κB pathway and administration of CysLT1R-shRNA or pranlukast for 21days reversed all these parameters, suggesting a role of CysLT1R in STZ-induced memory deficit and neuroinflammation.