Administration of NaHS Attenuates Footshock-Induced Pathologies and Emotional and Cognitive Dysfunction in Triple Transgenic Alzheimer's Mice

Protective Roles of Hydrogen Sulfide in Alzheimer's Disease and Traumatic Brain Injury

The gaseous signaling molecule hydrogen sulfide (H₂S) critically modulates a plethora of physiological processes across evolutionary boundaries. These include responses to stress and other neuromodulatory effects that are typically dysregulated in aging, disease, and injury. H₂S has a particularly prominent role in modulating neuronal health and survival under both normal and pathologic conditions. Although toxic and even fatal at very high concentrations, emerging evidence has also revealed a pronounced neuroprotective role for lower doses of endogenously generated or exogenously administered H₂S. Unlike traditional neurotransmitters, H₂S is a gas and, therefore, is unable to be stored in vesicles for targeted delivery. Instead, it exerts its physiologic effects through the persulfidation/sulfhydration of target proteins on reactive cysteine residues. Here, we review the latest discoveries on the neuroprotective roles of H₂S in Alzheimer's disease (AD) and traumatic brain injury, which is one the greatest risk factors for AD.

Hydrogen Sulfide Attenuates the Cognitive Dysfunction in Parkinson's Disease Rats via Promoting Hippocampal Microglia M2 Polarization by Enhancement of Hippocampal Warburg Effect

Identification of innovative therapeutic targets for the treatment of cognitive impairment in Parkinson's disease (PD) is urgently needed. Hydrogen sulfide (H₂S) plays an important role in cognitive function. Therefore, this work is aimed at investigating whether H₂S attenuates the cognitive impairment in PD and the underlying mechanisms. In the rotenone- (ROT-) established PD rat model, NaHS (a donor of H₂S) attenuated the cognitive impairment and promoted microglia polarization from M1 towards M2 in the hippocampus of PD rats. NaHS also dramatically upregulated the Warburg effect in the hippocampus of PD rats. 2-Deoxyglucose (2-DG, an inhibitor of the Warburg effect) abolished NaHS-upregulated Warburg effect in the hippocampus of PD rats. Moreover, the inhibited hippocampal Warburg effect by 2-DG abrogated H₂S-excited the enhancement of hippocampal microglia M2 polarization and the improvement of cognitive function in ROT-exposed rats. Our data demonstrated that H₂S inhibits the cognitive dysfunction in PD via promoting microglia M2 polarization by enhancement of hippocampal Warburg effect.

Lactobacillus plantarum PS128 prevents cognitive dysfunction in Alzheimer's disease mice by modulating propionic acid levels, glycogen synthase kinase 3 beta activity, and gliosis

Background

According to recent evidence, psychobiotics exert beneficial effects on central nervous system-related diseases, such as mental disorders. Lactobacillus plantarum PS128 (PS128), a novel psychobiotic strain, improves motor function, depression, and anxiety behaviors. However, the psychobiotic effects and mechanisms of PS128 in Alzheimer’s disease (AD) remain to be explored.

Objectives

The goal of the current study was to evaluate the beneficial effects of PS128 and to further elucidate its mechanism in AD mice.

Methods

PS128 (10¹⁰ colony-forming unit (CFU)/ml) was administered via oral gavage (o.g.) to 6-month-old male wild-type B6 and 3 × Tg-AD mice (harboring the PS1M146V, APPswe and TauP30IL transgenes) that received an intracerebroventricular injection of streptozotocin (icv-STZ, 3 mg/kg) or vehicle (saline) for 33 days. After serial behavioral tests, fecal short-chain fatty acid levels and AD-related pathology were assessed in these mice.

Results

Our findings show that intracerebroventricular injection of streptozotocin accelerated cognitive dysfunction associated with increasing levels of glycogen synthase kinase 3 beta (GSK3β) activity, tau protein phosphorylation at the T231 site (pT231), amyloid-β (Aβ) deposition, amyloid-β protein precursor (AβPP), β-site AβPP-cleaving enzyme (BACE1), gliosis, fecal propionic acid (PPA) levels and cognition-related neuronal loss and decreasing postsynaptic density protein 95 (PSD95) levels in 3 × Tg-AD mice. PS128 supplementation effectively prevented the damage induced by intracerebroventricular injection of streptozotocin in 3 × Tg-AD mice.

Conclusions

Based on the experimental results, intracerebroventricular injection of streptozotocin accelerates the progression of AD in the 3 × Tg-AD mice, primarily by increasing the levels of gliosis, which were mediated by the propionic acid and glycogen synthase kinase 3 beta pathways. PS128 supplementation prevents damage induced by intracerebroventricular injection of streptozotocin by regulating the propionic acid levels, glycogen synthase kinase 3 beta activity, and gliosis in 3 × Tg-AD mice. Therefore, we suggest that PS128 supplementation is a potential strategy to prevent and/or delay the progression of AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03426-8.

A novel small-molecule PROTAC selectively promotes tau clearance to improve cognitive functions in Alzheimer-like models

Intracellular accumulation of tau is a hallmark pathology in Alzheimer disease (AD) and the related tauopathies, thus targeting tau could be promising for drug development. Proteolysis Targeting Chimera (PROTAC) is a novel drug discovery strategy for selective protein degradation from within cells. Methods: A novel small-molecule PROTAC, named as C004019 with a molecular mass of 1,035.29 dalton, was designed to simultaneously recruite tau and E3-ligase (Vhl) and thus to selectively enhance ubiquitination and proteolysis of tau proteins. Western blotting, immunofluoresence and immunohistochemical staining were employed to verify the effects of C004019 in cell models (HEK293 and SH-SY5Y) and mouse models (hTau-transgenic and 3xTg-AD), respectively. The cognitive capacity of the mice was assessed by a suite of behavior experiments. Electrophysiology and Golgi staining were used to evaluate the synaptic plasticity. Results: C004019 induced a robust tau clearance via promoting its ubiquitination-proteasome-dependent proteolysis in HEK293 cells with stable or transient overexpression of human tau (hTau), and in SH-SY5Y that constitutively overexpress hTau. Furthermore, intracerebral ventricular infusion of C004019 induced a robust tau clearance in vivo. Most importantly, both single-dose and multiple-doses (once per 6 days for a total 5 times) subcutaneous administration of C004019 remarkably decreased tau levels in the brains of wild-type, hTau-transgenic and 3xTg-AD mice with improvement of synaptic and cognitive functions. Conclusions: The PROTAC (C004019) created in the current study can selectively and efficiently promote tau clearance both in vitro and in vivo, which provides a promising drug candidate for AD and the related tauopathies.

Prebiotic Lactulose Ameliorates the Cognitive Deficit in Alzheimer's Disease Mouse Model through Macroautophagy and Chaperone-Mediated Autophagy Pathways

Lactulose, as a prebiotic, can be utilized by human gut microbiota and stimulate their growth. Although microbiota modulation has become an emerging approach to manage many diseases and can be achieved by the administration of prebiotics, fewer investigations have been carried out on the therapeutic mechanism of lactulose. Two trehalose analogs, lactulose and melibiose, were identified as having a neuroprotective effect in polyglutamine and Parkinson disease models. In this study, we examined lactulose and melibiose in a mouse primary hippocampal neuronal culture under the toxicity of oligomeric Aβ_25-35. Lactulose was further tested in vivo because its effective concentration is lower than that of melibiose. Lactulose and trehalose were applied individually to mice before a bilateral intrahippocampal CA1 injection of oligomeric Aβ_25-35. The administration of lactulose and trehalose attenuated the short-term memory and the learning retrieval of Alzheimer's disease (AD) mice. From a pathological analysis, we found that the pretreatment of lactulose and trehalose decreased neuroinflammation and increased the levels of the autophagic pathways. These results suggest that the neuroprotective effects of both lactulose and trehalose are achieved through anti-inflammation and autophagy. In addition, lactulose was better than trehalose in the enhancement of the synaptic protein expression level in AD mice. Therefore, lactulose could potentially be developed into a preventive and/or therapeutic disaccharide for AD.

Autophagy Plays a Protective Role in Sodium Hydrosulfide-Induced Acute Lung Injury by Attenuating Oxidative Stress and Inflammation in Rats

Sodium hydrosulfide (NaHS), as an exogenous hydrogen sulfide (H₂S) donor, has been used in various pathological models. NaHS is usually considered to be primarily protective, however, the toxic effect of NaHS has not been well elucidated. The aim of this study was to investigate whether NaHS (1 mg/kg) can induce acute lung injury (ALI is a disease process characterized by diffuse inflammation of the lung parenchyma) and define the mechanism by which NaHS-induced ALI involves autophagy, oxidative stress, and inflammatory response. Wistar rats were randomly divided into three groups (control group, NaHS group, and 3-MA + NaHS group), and samples from each group were collected from 2, 6, 12, and 24 h. We found that intraperitoneal injection of NaHS (1 mg/kg) increased the pulmonary levels of H₂S and oxidative stress-related indicators (reactive oxygen species, myeloperoxidase, and malondialdehyde) in a time-dependent manner. Intraperitoneal injection of NaHS (1 mg/kg) induced histopathological changes of ALI and inhibition of autophagy exacerbated the lung injury. This study demonstrates that administration of NaHS (1 mg/kg) induces ALI in rats and autophagy in response to ROS is protective in NaHS-induced ALI by attenuating oxidative stress and inflammation.

Chronic low dose of AM404 ameliorates the cognitive impairment and pathological features in hyperglycemic 3xTg-AD mice

RATIONALE

Hyperglycemia accelerates the progression of Alzheimer's disease (AD), and GSK3β plays a potential link between AD and hyperglycemia. Therefore, a direct or indirect GSK3β inhibition may have potential to delay the progression of AD. Our previous biochemical assay identified AM404 as a GSK3β inhibitor at high dose (IC50 = 5.353 μM); however, other study suggests that AM404 impaired synaptic plasticity of hippocampus at high dose (10 mg/kg; i.p.). Therefore, the dose and duration of treatment are crucial for the effects of AM404.

OBJECTIVE

The effects and molecular mechanisms of AM404 at low dose were evaluated from in vitro to in vivo models.

METHODS

AM404 (0.1-0.5 μM) was tested on tau hyperphosphorylated mouse hippocampal primary cultures treated with Wortmannin (WT) and GF109203X (GFX). Hyperglycemic triple transgenic AD (3×Tg-AD) mice at 6 months old were intraperitoneally injected with AM404 (0.25 mg/kg) for 4 weeks. The spatial learning and memory of mice were measured using the Morris water maze. Mouse brain and serum samples were collected for pathological analyses.

RESULTS

AM404 (0.5 μM) exhibited significantly augmented neuroprotection toward tau hyperphosphorylation in primary cultures. The chronic systemic administration of AM404 (0.25 mg/kg) attenuated cognitive deficits in hyperglycemic 3×Tg-AD mice. Moreover, chronic low dose of AM404 significantly attenuated Aβ production, tau protein phosphorylation, and inflammation associated with an increase of pS473Akt and pS9-GSK3β. Therefore, AM404 at low dose, not only increased neuroprotection, but also ameliorated cognitive deficit, could be partly by regulating the Akt/GSK3β signaling, which may contribute to downregulation of Aβ, tau hyperphosphorylation, and inflammation in hyperglycemic 3×Tg-AD mice.

CONCLUSIONS

These results highlight that chronic administration of AM404 at low dose may be through the Akt/GSK3β pathway to ameliorate the impairment in hyperglycemic 3×Tg-AD mice.

Administration of Momordica charantia Enhances the Neuroprotection and Reduces the Side Effects of LiCl in the Treatment of Alzheimer's Disease

Recently, the use of natural food supplements to reduce the side effects of chemical compounds used for the treatment of various diseases has become popular. Lithium chloride (LiCl) has some protective effects in neurological diseases, including Alzheimer’s disease (AD). However, its toxic effects on various systems and some relevant interactions with other drugs limit its broader use in clinical practice. In this study, we investigated the in vitro and in vivo pharmacological functions of LiCl combined with Momordica charantia (MC) in the treatment of AD. The in vitro results show that the order of the neuroprotective effect is MC5, MC3, MC2, and MC5523 under hyperglycemia or tau hyperphosphorylation. Therefore, MC5523 (80 mg/kg; oral gavage) and/or LiCl (141.3 mg/kg; intraperitoneal injection) were applied to ovariectomized (OVX) 3×Tg-AD female and C57BL/6J (B6) male mice that received intracerebroventricular injections of streptozotocin (icv-STZ, 3 mg/kg) for 28 days. We found that the combined treatment not only increased the survival rate by reducing hepatotoxicity but also increased neuroprotection associated with anti-gliosis in the icv-STZ OVX 3×Tg-AD mice. Furthermore, the cotreatment with MC5523 and LiCl prevented memory deficits associated with reduced neuronal loss, gliosis, oligomeric Aβ level, and tau hyperphosphorylation and increased the expression levels of synaptic-related protein and pS9-GSK3β (inactive form) in the icv-STZ B6 mice. Therefore, MC5523 combined with LiCl could be a potential strategy for the treatment of AD.

MGCD0103, a selective histone deacetylase inhibitor, coameliorates oligomeric Aβ25-35 -induced anxiety and cognitive deficits in a mouse model

AIMS

Recently, histone deacetylase (HDAC) inhibitors are considered a possible therapeutic strategy in Alzheimer's disease (AD). However, HDACi treatments exhibit diverse functions with unfavorable effects in AD. Thus, the development of selective HDACi without side effects is urgently needed.

METHODS

HDACi, namely, BML210, MGCD0103, PXD101, and Droxinostat, were screened in mouse hippocampal primary cultures incubated with oligomeric Aβ_25-35 (50 μmol/L). MGCD0103 was chosen for in vivo tests and was intraperitoneally injected into C57BL/6J mice (0.5 mg/kg, once per day) for 4 weeks following an intrahippocampal CA1 injection of oligomeric Aβ_25-35 . Brain samples were collected for pathological analyses after the behavioral analyses including open- field test (OFT), elevated plus maze (EPM), Y-maze, and Morris water maze (MWM).

RESULTS

Among the HDACi, MGCD0103 exhibited significant neuroprotection against the Aβ toxicity in primary cultures. MGCD0103 coattenuated cognitive deficits and anxiety against Aβ damage in mice. MGCD0103 further ameliorated pathological features such as the levels of acetylated histone 3 at Lys 9 site (H3K9) and α-tubulin, synaptophysin, Aβ, tau protein phosphorylation, and serotonergic neuron loss against Aβ toxicity. Furthermore, chronic MGCD0103 treatment did not show liver or kidney toxicity in mice.

CONCLUSIONS

These results reveal MGCD0103 could be a potential therapeutic agent against AD.

The Potential of Indole/Indolylquinoline Compounds in Tau Misfolding Reduction by Enhancement of HSPB1

BACKGROUND

Neurofibrillary tangles formed from tau misfolding have long been considered one of the pathological hallmarks of Alzheimer's disease (AD). The misfolding of tau in AD correlates with the clinical progression of AD and inhibition or reversal of tau misfolding may protect the affected neurons.

METHODS

We generated 293 and SH-SY5Y cells expressing DsRed-tagged pro-aggregation mutant of repeat domain of tau (ΔK280 tau_RD ) to test indole/indolylquinoline derivatives for reducing tau misfolding and neuroprotection.

RESULTS

Four of the 10 derivatives tested displayed good misfolding-inhibitory effects on Tet-On 293 cells. Among them, NC009-1 and NC009-7 enhanced heat-shock 27 kDa protein 1 (HSPB1) expression to increase ∆K280 tau_RD -DsRed solubility and promoted neurite outgrowth in Tet-On SH-SY5Y cells. Knockdown of HSPB1 resulted in decreased ∆K280 tau_RD -DsRed solubility and reduced neurite outgrowth, which were rescued by addition of NC009-1/NC009-7. Treatment with indole/indolylquinoline derivatives also improved neuronal cell viability and neurite outgrowth in mouse hippocampal primary culture under tau cytotoxicity.

CONCLUSION

Our results demonstrate how indole/indolylquinoline derivatives are likely to work in tau misfolding reduction, providing insight into the possible working mechanism of indole and indolylquinoline derivatives in AD treatment.