Protopine promotes the proteasomal degradation of pathological tau in Alzheimer's disease models via HDAC6 inhibition

Protopine Exerts Neuroprotective Effects on Neonatal Hypoxic-Ischemic Brain Damage in Rats via Activation of the AMPK/PGC1α Pathway

Introduction

Neonatal hypoxic-ischemic encephalopathy (HIE), caused by perinatal asphyxia, is characterized by high morbidity and mortality, but there are still no effective therapeutic drugs. Mitochondrial biogenesis and apoptosis play key roles in the pathogenesis of HIE. Protopine (Pro), an isoquinoline alkaloid, has anti-apoptotic and neuro-protective effects. However, the protective roles of Pro on neonatal hypoxic-ischemic brain injury remain unclear.

Methods

In this study, we established a CoCl2-induced PC12 cell model in vitro and a neonatal rat hypoxic-ischemic (HI) brain damage model in vivo to explore the neuro-protective effects of Pro and try to elucidate the potential mechanisms.

Results

Our results showed that Pro significantly reduced cerebral infarct volume, alleviated brain edema, inhibited glia activation, improved mitochondrial biogenesis, relieved neuron cell loss, decreased cell apoptosis and reactive oxygen species (ROS) after HI damage. In addition, Pro intervention upregulated the levels of p-AMPK/AMPK and PGC1α as well as the downstream mitochondrial biogenesis related factors, such as nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM), but the AMPK inhibitor compound c (CC) could significantly reverse these effects of Pro.

Discussion

Pro may exert neuroprotective effects on neonatal hypoxic-ischemic brain damage via activation of the AMPK/PGC1α pathway, suggesting that Pro may be a promising therapeutic candidate for HIE, and our study firstly demonstrate the neuro-protective roles of Pro in HIE models.

HDAC6 modulates the cognitive behavioral function and hippocampal tissue pathological changes of APP/PS1 transgenic mice through HSP90-HSF1 pathway

The aim of this study was to investigate histone deacetylase 6 (HDAC6) modifies the heat shock protein 90 (HSP90) and heat shock transcription factor 1 (HSF1) affect the levels of pathological markers such as Aβ oligomers (Aβo) and Tau phosphorylation (p-Tau) in APP/PS1 double transgenic mice hippocampal tissues or HT22 neurons as well as the changes in cognitive behavioral functions of mice. (1) APP/PS1 transgenic mice (6 months old, 25 ~ 30 g) were randomly assigned to 5 experimental groups, C57BL/6J mice (6 months old, 25 ~ 30 g) were used as 4 control groups, with 8 mice in each group. All mice underwent intracerebroventricular (i.c.v.) cannulation, and the experimental groups were administered with normal saline (APP + NS group), HDAC6 agonist tubastatin A hydrochloride (TSA) (APP + TSA group) or HDAC6 agonist theophylline (Theo) (APP + Theo group), HSP90 inhibitor Ganetespib (Gane) (APP + Gane group), or a combination of pre-injected Gane by TSA (APP + Gane + TSA group); the control group received i.c.v. injections of Gane (Gane group), TSA (TSA group), Theo (Theo group) or NS (NS group), respectively. (2) Mouse hippocampal neurons HT22 were randomly divided into a control group (Control) and an Aβ1-42 intervention group (Aβ). Within the Aβ group, further divisions were made for knockdown HSP90 (Aβ + siHSP90 group), overexpression HSP90 (Aβ + OE-HSP90 group), knockdown HSF1(Aβ + siHSF1 group) and knockdown HSF1 followed by overexpression HSP90 (Aβ + siHSF1 + OE-HSP90 group), resulting in a total of 6 groups. Morris water maze test was used to evaluate the cognitive behavior of the mice. Western blot and immunohistochemistry or immunofluorescence were performed to detect the levels of HDAC6, HSP90, HSF1, Aβ1-42, Tau protein, and p-Tau in the hippocampal tissue or HT22 cells. qRT-PCR was used to measure the levels of hdac6, hsp90, and hsf1 mRNA in the hippocampus or nerve cells. (1) The levels of HDAC6, Aβ1-42 and p-Tau were elevated, while HSP90 and HSF1 were decreased in the hippocampal tissue of APP/PS1 transgenic mice (all P < 0.01). Inhibiting HDAC6 upregulated the expressions of HSP90 and HSF1 in the hippocampal tissue of APP/PS1 mice, while decreasing the levels of Aβ1-42 and p-Tau as well as improving the spatial cognitive behavior in mice (P < 0.05 or P < 0.01). The opposite effects were observed upon HDAC6 activation. However, inhibiting HSP90 reduced the expression of HSF1 (P < 0.01) and increased the levels of Aβ1-42 and p-Tau (P < 0.05 or P < 0.01) but did not significantly affect the expression of HDAC6 (P > 0.05). No significant changes were observed in the aforementioned indicators in the 4 control groups (P > 0.05). (2) In the Aβ1-42 intervention group, HDAC6 and Aβ1-42, p-Tau expression levels were elevated, while HSP90 and HSF1 expressions were all decreased, and cell viability was reduced (P < 0.05 or P < 0.01). Overexpression of HSP90 upregulated HSF1 expression, decreased the levels of Aβ1-42 and p-Tau, and increased cell viability (P < 0.05 or P < 0.01). Knocking down HSP90 had the opposite effect; and knocking down HSF1 increased the levels of Aβ1-42 and p-Tau and decreased cells viability (all P < 0.01), but did not result in significant changes in the expression levels of HSP90 (P > 0.05). Inhibiting HDAC6 can upregulate the expressions of HSP90 and HSF1 but reduce the levels of Aβ1-42 and p-Tau in the hippocampus of APP/PS1 mice and improvement of cognitive behavioral function in mice; Overexpression of HSP90 can increase HSF1 but decrease Aβ1-42 and p-Tau levels in the hippocampal neurons and increase cell activity. It is suggested that HDAC6 may affect the formation of Aβ oligomers and the changes in Tau protein phosphorylation levels in the hippocampus of AD transgenic mouse as well as the alterations in cognitive behavioral functions by regulating the HSP90-HSF1 pathway.

Unveiling the impact of aging on BBB and Alzheimer's disease: Factors and therapeutic implications

Alzheimer's disease (AD) is a highly prevalent neurodegenerative condition that has devastating effects on individuals, often resulting in dementia. AD is primarily defined by the presence of extracellular plaques containing insoluble β-amyloid peptide (Aβ) and neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau protein (P-tau). In addition, individuals afflicted by these age-related illnesses experience a diminished state of health, which places significant financial strain on their loved ones. Several risk factors play a significant role in the development of AD. These factors include genetics, diet, smoking, certain diseases (such as cerebrovascular diseases, obesity, hypertension, and dyslipidemia), age, and alcohol consumption. Age-related factors are key contributors to the development of vascular-based neurodegenerative diseases such as AD. In general, the process of aging can lead to changes in the immune system's responses and can also initiate inflammation in the brain. The chronic inflammation and the inflammatory mediators found in the brain play a crucial role in the dysfunction of the blood-brain barrier (BBB). Furthermore, maintaining BBB integrity is of utmost importance in preventing a wide range of neurological disorders. Therefore, in this review, we discussed the role of age and its related factors in the breakdown of the blood-brain barrier and the development of AD. We also discussed the importance of different compounds, such as those with anti-aging properties, and other compounds that can help maintain the integrity of the blood-brain barrier in the prevention of AD. This review builds a strong correlation between age-related factors, degradation of the BBB, and its impact on AD.

Protopine protects chondrocytes from undergoing ferroptosis by activating Nrf2 pathway

Osteoarthritis is a highly prevalent joint disease; however, effective treatments are lacking. Protopine (PTP) is an isoquinoline alkaloid with potent anti-inflammatory and antioxidant properties; however, it has not been studied in osteoarthritis. This study aimed to investigate whether PTP can effectively protect chondrocytes from ferroptosis. Primary mouse chondrocytes were treated with tert-butyl hydroperoxide (TBHP) to simulate oxidative stress in an in vitro model of osteoarthritis. Two concentrations of PTP (10 and 20 μg/mL) were validated for in vitro experiments. Cellular inflammation and metabolism were detected using RT-qPCR and western blotting (WB). Ferroptosis was assessed via WB, qPCR, reactive oxygen species (ROS) levels, lipid ROS, and immunofluorescence staining. In vitro, PTP significantly ameliorated chondrocyte inflammation and cytolytic metabolism and significantly suppressed chondrocyte ferroptosis through the activation of the Nrf2 pathway. The anterior cruciate ligament transection (ACLT) mouse model was used to validate the in vivo effects of PTP. The joint cartilage was assessed using the Osteoarthritis Research Society International (OARSI) score, Safranin O staining, and immunohistochemistry. The intra-articular administration of PTP alleviated cartilage inflammation and ferroptosis, as evidenced by the expression of MMP3, MMP13, COL2A1, GPX4, and Nrf2. Overall, we find that PTP exerted anti-ferroptosis and anti-inflammatory effects on chondrocytes to protect the articular cartilage.

Modulation of Tau Pathology in Alzheimer's Disease by Dietary Bioactive Compounds

Tau is a microtubule-associated protein essential for microtubule assembly and stability in neurons. The abnormal intracellular accumulation of tau aggregates is a major characteristic of brains from patients with Alzheimer's disease (AD) and other tauopathies. In AD, the presence of neurofibrillary tangles (NFTs), which is composed of hyperphosphorylated tau protein, is positively correlated with the severity of the cognitive decline. Evidence suggests that the accumulation and aggregation of tau cause synaptic dysfunction and neuronal degeneration. Thus, the prevention of abnormal tau phosphorylation and elimination of tau aggregates have been proposed as therapeutic strategies for AD. However, currently tau-targeting therapies for AD and other tauopathies are limited. A number of dietary bioactive compounds have been found to modulate the posttranslational modifications of tau, including phosphorylation, small ubiquitin-like modifier (SUMO) mediated modification (SUMOylation) and acetylation, as well as inhibit tau aggregation and/or promote tau degradation. The advantages of using these dietary components over synthetic substances in AD prevention and intervention are their safety and accessibility. This review summarizes the mechanisms leading to tau pathology in AD and highlights the effects of bioactive compounds on the hyperphosphorylation, aggregation and clearance of tau protein. The potential of using these bioactive compounds for AD prevention and intervention is also discussed.

Takinib inhibits microglial M1 polarization and oxidative damage after subarachnoid hemorrhage by targeting TAK1-dependent NLRP3 inflammasome signaling pathway

Transforming growth factor-β-activated kinase 1 (TAK1) positively regulates oxidative stress and inflammation in different diseases. Takinib, a novel and specific TAK1 inhibitor, has beneficial effects in a variety of disorders. However, the effects of takinib on early brain injury (EBI) after subarachnoid hemorrhage (SAH) and the underlying molecular mechanisms remain unknown. Our study showed that takinib administration significantly inhibited phosphorylated TAK1 expression after SAH. In addition, takinib suppressed M1 microglial polarization and promoted M2 microglial polarization. Furthermore, blockade of TAK1 by takinib reduced neuroinflammation, oxidative damage, brain edema, and neuronal apoptosis, and improved neurological behavior after SAH. Mechanistically, we revealed that TAK1 inhibition by takinib mitigated reactive oxygen species (ROS) production and ROS-mediated nod-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome activation. In contrast, NLRP3 activation by nigericin abated the neuroprotective effects of takinib against EBI after SAH. In general, our study demonstrated that takinib could protect against EBI by targeting TAK1-ROS-NLRP3 inflammasome signaling. Inhibition of TAK1 might be a promising option in the management of SAH.

The composition, pharmacological effects, related mechanisms and drug delivery of alkaloids from Corydalis yanhusuo

Corydalis yanhusuo W. T. Wang, also known as yanhusuo, yuanhu, yanhu and xuanhu, is one of the herb components of many Chinese Traditional Medicine prescriptions such as Jin Ling Zi San and Yuanhu-Zhitong priscription. C. yanhusuo was traditionally used to relieve pain and motivate blood and Qi circulation. Now there has been growing interest in pharmacological effects of alkaloids, the main bioactive components of C. yanhusuo. Eighty-four alkaloids isolated from C. yanhusuo are its important bioactive components and can be characterized into protoberberine alkaloids, aporphine alkaloids, opiate alkaloids and others and proper extraction or co-administration methods modulate their contents and efficacy. Alkaloids from C. yanhusuo have various pharmacological effects on the nervous system, cardiovascular system, cancer and others through multiple molecular mechanisms such as modulating neurotransmitters, ion channels, gut microbiota, HPA axis and signaling pathways and are potential treatments for many diseases. Plenty of novel drug delivery methods such as autologous red blood cells, self-microemulsifying drug delivery systems, nanoparticles and others have also been investigated to better exert the effects of alkaloids from C. yanhusuo. This review summarized the alkaloid components of C. yanhusuo, their pharmacological effects and mechanisms, and methods of drug delivery to lay a foundation for future investigations.

The behavioral, pathological and therapeutic features of the triple transgenic Alzheimer's disease (3 × Tg-AD) mouse model strain

As a classic animal model of Alzheimer's disease (AD), the 3 × Tg-AD mouse not only recapitulates most of anatomical hallmarks observed in AD pathology but also displays cognitive alterations in memory and learning tasks. The 3 × Tg-AD can better show the two characteristics of AD, amyloid β (Aβ) and neurofibrillary tangles (NFT). Therefore, 3 × Tg-AD strain is widely used in AD pathogenesis research and new drug development of AD. In this paper, the construction methods, pathological changes, and treatment characteristics of 3 × Tg-AD mouse models commonly used in AD research are summarized and commented, hoping to provide reference for researchers to choose and establish experimental patterns.

PPARɑ Ligand Caudatin Improves Cognitive Functions and Mitigates Alzheimer's Disease Defects By Inducing Autophagy in Mice Models

The autophagy-lysosomal pathway (ALP) is a major cellular machinery involved in the clearance of aggregated proteins in Alzheimer disease (AD). However, ALP is dramatically impaired during AD pathogenesis via accumulation of toxic amyloid beta (Aβ) and phosphorylated-Tau (phospho-Tau) proteins in the brain. Therefore, activation of ALP may prevent the increased production of Aβ and phospho-Tau in AD. Peroxisome proliferator-activated receptor alpha (PPARα), a transcription factor that can activate autophagy, and transcriptionally regulate transcription factor EB (TFEB) which is a key regulator of ALP. This suggests that targeting PPARα, to reduce ALP impairment, could be a viable strategy for AD therapy. In this study, we investigated the anti-AD activity of Caudatin, an active constituent of Cynanchum otophyllum (a traditional Chinese medicinal herb, Qing Yang Shen; QYS). We found that Caudatin can bind to PPARα as a ligand and augment the expression of ALP in microglial cells and in the brain of 3XTg-AD mice model. Moreover, Caudatin could activate PPARα and transcriptionally regulates TFEB-augmented lysosomal degradation of Aβ and phosphor-Tau aggregates in AD cell models. Oral administration of Caudatin decreased AD pathogenesis and ameliorated the cognitive dysfunction in 3XTg-AD mouse model. Conclusively, Caudatin can be a potential AD therapeutic agent via activation of PPARα-dependent ALP.

Sanwei DouKou Decoction ameliorate Alzheimer disease by increasing endogenous neural stem cells proliferation through the Wnt/β-catenin signalling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Sanwei DouKou decoction (SDKD) is a traditional Chinese medicine (TCM) prescription derived from the Tibetan medical book "Si Bu Yi Dian" and is clinically used for the treatment of Alzheimer's disease (AD). However, the potential mechanism of SDKD treatment for AD remains elusive.

AIM OF THE STUDY

This study aims to explore the potential mechanism by which SDKD alleviates AD.

MATERIALS AND METHODS

Extracts of SDKD were identified with Gas chromatograph-mass spectrometer (GC-MS). 5 × FAD mice were treated with SDKD for 8 weeks. The efficacy of SDKD against AD was evaluated by in-vivo experiments. Morris water maze and contextual fear conditioning tests were used to detect the learning and memory ability of mice. Hematoxylin-eosin staining (H&E) staining was used to observe the pathological changes of brain tissue. Immunohistochemistry was used to detect the positive expression of Nestin in hippocampus. In in-vitro experiments, the Cell Counting Kit 8 (CCK-8) technique was used to detect cell viability, the proliferation of neural stem cells was detected by immunofluorescence staining, the intracellular protein expression was detected by Western Blot.

RESULTS

The results of this study suggested that SDKD may ameliorate AD. SDKD significantly shortened the escape latency of mice in the Morris water maze experiment, increased the number of times the mice crossed the target quadrant, and prolonged freezing time in the contextual fear memory experiment. SDKD also improved neuronal pathology in the hippocampus, decreased neuronal loss, and increased Nestin protein levels. Furthermore, in in-vitro experiments, SDKD could significantly increase Neural stem cells (NSCs) viability, promoted NSCs proliferation, and also effectively activated the Wnt/β-catenin signalling pathway, increased Wnt family member 3A (Wnt3a), β-catenin and CyclinD1 protein levels, activated the NSCs proliferation pathways in AD model mouse brain tissue.

CONCLUSIONS

The present study demonstrated that sanwei doukou decoction can ameliorate AD by increasing endogenous neural stem cells proliferation through the Wnt/β-catenin signalling pathway. Our observations justify the traditional use of SDKD for a treatment of AD in nervous system.

Elaboration of the Effective Multi-Target Therapeutic Platform for the Treatment of Alzheimer's Disease Based on Novel Monoterpene-Derived Hydroxamic Acids

Novel monoterpene-based hydroxamic acids of two structural types were synthesized for the first time. The first type consisted of compounds with a hydroxamate group directly bound to acyclic, monocyclic and bicyclic monoterpene scaffolds. The second type included hydroxamic acids connected with the monoterpene moiety through aliphatic (hexa/heptamethylene) or aromatic linkers. An in vitro analysis of biological activity demonstrated that some of these molecules had powerful HDAC6 inhibitory activity, with the presence of a linker area in the structure of compounds playing a key role. In particular, it was found that hydroxamic acids containing a hexa- and heptamethylene linker and (-)-perill fragment in the Cap group exhibit excellent inhibitory activity against HDAC6 with IC₅₀ in the submicromolar range from 0.56 ± 0.01 µM to 0.74 ± 0.02 µM. The results of the study of antiradical activity demonstrated the presence of moderate ability for some hydroxamic acids to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2ROO^• radicals. The correlation coefficient between the DPPH radical scavenging activity and oxygen radical absorbance capacity (ORAC) value was R² = 0.8400. In addition, compounds with an aromatic linker based on para-substituted cinnamic acids, having a monocyclic para-menthene skeleton as a Cap group, 35a, 38a, 35b and 38b, demonstrated a significant ability to suppress the aggregation of the pathological β-amyloid peptide 1-42. The 35a lead compound with a promising profile of biological activity, discovered in the in vitro experiments, demonstrated neuroprotective effects on in vivo models of Alzheimer's disease using 5xFAD transgenic mice. Together, the results obtained demonstrate a potential strategy for the use of monoterpene-derived hydroxamic acids for treatment of various aspects of Alzheimer's disease.

Natural bioactive compounds in Alzheimer's disease: From the perspective of type 3 diabetes mellitus

There is a close relationship between Alzheimer's disease (AD) and diabetes mellitus (DM), and the link between the two is often referred to as type 3 diabetes mellitus (T3DM). Many natural bioactive compounds have shown the potential to treat AD and diabetes. We mainly review the polyphenols represented by resveratrol (RES) and proanthocyanidins (PCs) and alkaloids represented by berberine (BBR) and Dendrobium nobile Lindl. alkaloids (DNLA) from the perspective of T3DM to review the neuroprotective effects and molecular mechanisms of natural compounds in AD.

Computational Evaluation of N-Based Transannular Interactions in Some Model Fused Medium-Sized Heterocyclic Systems and Implications for Drug Design

As part of a project on fused medium-sized ring systems as potential drugs, we have previously demonstrated the usefulness of Density Functional Theory (DFT) to evaluate amine nitrogen-based transannular interactions across the central 10-membered ring in the bioactive dibenzazecine alkaloid, protopine. A range of related hypothetical systems have been investigated, together with transannular interactions involving ring-embedded imino or azo group nitrogens and atoms or groups (Y) across the ring. Electrostatic potential energies mapped onto electron density surfaces in the different ring conformations were evaluated in order to characterise these conformations. Unexpectedly, the presence of sp² hybridised nitrogen atoms in the medium-sized rings did not influence the conformations appreciably. The strength and type of the N^…Y interactions are determined primarily by the nature of Y. This is also the case when the substituent on the interacting nitrogen is varied from CH₃ (protopine) to H or OH. With Y = BOH, very strong interactions were observed in protopine analogues, as well as in rings incorporating imino or azo groups. Strong to moderate interactions were observed with Y = CS, CO and SO in all ring systems. Weaker interactions were observed with Y = S, O and weaker ones again with an sp³ hybridised carbon (Y = CH₂). The transannular interactions can influence conformational preferencing and shape and change electron distributions at key sites, which theoretically could modify properties of the molecules while providing new or enhanced sites for biological target interactions, such as the H or OH substituent. The prediction of new strong transannular interaction types such as with Y = BOH and CS should be helpful in informing priorities for synthesis and other experimental studies.

Frankincense-Myrrh treatment alleviates neuropathic pain via the inhibition of neuroglia activation mediated by the TLR4/MyD88 pathway and TRPV1 signaling

BACKGROUND

Neuroglia are important modulators of neuronal functionality, and thus play an integral role in the pathogenesis and treatment of neuropathic pain (NP). According to traditional Chinese medicine, Frankincense-Myrrh is capable of "activating blood and dissipating blood stasis", and as such these two biological compounds are commonly used to treat NP, however, the mechanisms underlying the efficacy of such treatment are unclear.

PURPOSE

This study aimed to further elucidate the protective effects associated with the Frankincense-Myrrh treatment of NP.

METHODS

A chronic sciatic nerve compression injury (CCI) model of NP was established, after which animals were gavaged with Frankincense, Myrrh, Frankincense-Myrrh, or the positive control drug pregabalin for 14 days. Network pharmacology approaches were used to identify putative pathways and targets associated with the Frankincense-Myrrh-mediated treatment of NP, after which these targets were subjected to in-depth analyses. The impact of TLR4 blockade on NP pathogenesis was assessed by intrathecally administering a TLR4 antagonist (LRU) or the MyD88 homodimerization inhibitory peptide (MIP).

RESULTS

Significant alleviation of thermal and mechanical hypersensitivity in response to Frankincense and Myrrh treatment was observed in NP model mice, while network pharmacology analyses suggested that the pathogenesis of NP may be related to TLR4/MyD88-mediated neuroinflammation. Consistently, Frankincense-Myrrh treatment was found to reduce TLR4, MyD88, and p-p65 expression in spinal dorsal horn neuroglia from treated animals, in addition to inhibiting neuronal TRPV1 and inflammatory factor expression. Intrathecal LRU and MIP delivery were sufficient to alleviate thermal and mechanical hyperalgesia in these CCI model mice, with concomitant reductions in neuronal TRPV1 expression and neuroglial activation in the spinal dorsal horn.

CONCLUSION

These data suggest that Frankincense-Myrrh treatment was sufficient to alleviate NP in part via inhibiting TLR4/MyD88 pathway and TRPV1 signaling activity. Blocking TLR4 and MyD88 activation may thus hold value as a means of treating NP.

Pterostilbene Attenuates Subarachnoid Hemorrhage-Induced Brain Injury through the SIRT1-Dependent Nrf2 Signaling Pathway

Neuroinflammatory injury, oxidative insults, and neuronal apoptosis are major causes of poor outcomes after subarachnoid hemorrhage (SAH). Pterostilbene (PTE), an analog of resveratrol, has been verified as a potent sirtuin 1 (SIRT1) activator. However, the beneficial actions of PTE on SAH-induced brain injury and whether PTE regulates SIRT1 signaling after SAH remain unknown. We first evaluated the dose-response influence of PTE on early brain impairment after SAH. In addition, EX527 was administered to suppress SIRT1 signaling. The results revealed that PTE significantly attenuated microglia activation, oxidative insults, neuronal damage, and early neurological deterioration. Mechanistically, PTE effectively enhanced SIRT1 expression and promoted nuclear factor-erythroid 2-related factor 2 (Nrf2) accumulation in nuclei. Furthermore, EX527 pretreatment distinctly repressed PTE-induced SIRT1 and Nrf2 activation and deteriorated these beneficial outcomes. In all, our study provides the evidence that PTE protects against SAH insults by activating SIRT1-dependent Nrf2 signaling pathway. PTE might be a therapeutic alternative for SAH.

Role of autophagy in lysophosphatidylcholine-induced apoptosis in mouse Leydig cells

Lysophosphatidylcholine (LPC), a major class of glycerophospholipids ubiquitously present in most tissues, plays a dominant role in many diseases, while it is still unknown about the potential mechanism of LPC affecting the testicular Leydig cells. In the present study, mouse TM3 Leydig cells in vitro were treated with LPC for 48 h. LPC was found to significantly induce apoptosis and oxidative stress of mouse TM3 Leydig cells; while inhibition of oxidative stress by N-acetyl-L-cysteine, an inhibitor of oxidative stress, could rescue the induction of apoptosis, indicating that LPC induced apoptosis of mouse TM3 Leydig cells via oxidative stress. Interestingly, LPC was showed to inhibit autophagy; however, induction of autophagy by rapamycin significantly alleviated the induction of apoptosis by LPC. Taken together, oxidative stress was involved in LPC-induced apoptosis of mouse TM3 Leydig cells, and autophagy might play a protective role in LPC-induced apoptosis.

Protopine alleviates lipopolysaccharide-triggered intestinal epithelial cell injury through retarding the NLRP3 and NF-κB signaling pathways to reduce inflammation and oxidative stress

BACKGROUND

Inflammatory bowel disease (IBD) is a common chronic intestinal disease. Protopine isolated from different plants has been investigated to understand its special functions on varied diseases. However, the regulatory effects of protopine on the progression of IBD remain unclear. Our study is aimed to explore the effects of protopine on the progression of IBD and its underlying regulatory mechanism of action.

METHODS

The cell viability was assessed through MTT colorimetric assay. The protein expressions of genes were examined by Western blot analysis. The cell apoptosis and reactive oxygen species level were measured using flow cytometry. The levels of inflammation and oxidative stress-related proteins were tested through enzyme-linked-immunosorbent serologic assay. The intracellular Ca²⁺ concentration and mitochondrial membrane potential were measured through immunofluorescence assay.

RESULTS

First, different concentrations of lipopolysaccharide (LPS) were treated with NCM460 cells to establish IBD cell model, and 5-μg/mL LPS was chosen for followed experiments. In this study, we discovered that protopine relieved the LPS-induced inhibited intestinal epithelial cell viability and enhanced cell apoptosis. Moreover, protopine attenuated LPS-stimulated inflammation activation and oxidative stress. Further experiments illustrated that the increased intracellular Ca²⁺ concentration and decreased mitochondrial membrane potential stimulated by LPS were reversed by protopine treatment. Finally, through Western blot analysis, it was demonstrated that protopine retarded the activated NLR family pyrin domain containing 3 (NLRP3) and nuclear factor kappa B (NF-κB) signaling pathways mediated by LPS.

CONCLUSION

Protopine alleviated LPS-triggered intestinal epithelial cell injury by inhibiting NLRP3 and NF-κB signaling pathways to reduce inflammation and oxidative stress. This discovery may provide a useful drug for treating IBD.

Patchouli alcohol ameliorates the learning and memory impairments in an animal model of Alzheimer's disease via modulating SIRT1

BACKGROUND

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases. Patchouli alcohol (PA), a major active ingredient isolated from Pogostemonis Herba, exhibits extensive bioactivity in the central nervous system (CNS) and exerts neuroprotective effects.

PURPOSE

This study aimed to investigate the anti-AD effects of PA in an animal model of AD and to elucidate the underlying molecular mechanisms.

METHODS

The gas chromatography (GC) was used to determine the ability of PA to pass the blood-brain barrier (BBB) in rats after oral administration. The sporadic AD rat model was established by intracerebroventricularly (ICV) injection with streptozotocin (STZ). PA (25 and 50 mg/kg) was given to rat orally once daily for 42 consecutive days. Morris water maze (MWM) test was performed to determine the learning and memory functions of the STZ-induced AD rats. EX527, a silent information regulator 1 (SIRT1) selective inhibitor, was used to investigate the involvement of SIRT1 in the anti-AD effects of PA in rats.

RESULTS

PA could penetrate the BBB. MWM test results showed that PA could significantly ameliorate the learning and memory deficits induced by STZ in rats. Meanwhile, PA enhanced the expression of SIRT1, and markedly alleviated the tau pathology by inhibiting the hyperacetylation (at the site of Lys174) and hyperphosphorylation (at the sites of Thr181, Thr205, Ser396 and Ser404) of tau protein. PA also efficiently suppressed the activation of microglia and astrocytes, and the beta-amyloid (Aβ) expression and the deacetylation of nuclear factor-kappa B (NF-κB) at Lys 310 (K310) in the STZ-treated AD rats. EX527, a SIRT1 selective inhibitor, could partially abolish the cognitive deficits improving effect of PA and inhibit the down-regulation of acetylated tau and acetylated NF-κB p65, suggesting that PA exhibited neuroprotective effects against AD via upregulating SIRT1.

CONCLUSION

This study reported for the first time that PA could penetrate the BBB to exert its protective effects on the brain after a single-dose oral administration. The current experimental findings also amply demonstrated that PA could improve the cognitive and memory impairments in the STZ-induced AD rat model. The underlying mechanisms involve the alleviations of neuroinflammation, tau pathology and Aβ deposition via modulating of SIRT1 and NF-κB pathways. All these findings strongly suggest that PA is a promising naturally occurring compound worthy of further development into an anti-AD pharmaceutical.

Bromo-protopine, a novel protopine derivative, alleviates tau pathology by activating chaperone-mediated autophagy for Alzheimer’s disease therapy

Emerging evidence from Alzheimer’s disease (AD) patients suggests that reducing tau pathology can restore cognitive and memory loss. To reduce tau pathology, it is critical to find brain-permeable tau-degrading small molecules that are safe and effective. HDAC6 inhibition has long been considered a safe and effective therapy for tau pathology. Recently, we identified protopine as a dibenzazecine alkaloid with anti-HDAC6 and anti-AD activities. In this study, we synthesized and tested novel protopine derivatives for their pharmacological action against AD. Among them, bromo-protopine (PRO-Br) demonstrated a two-fold increase in anti-HDAC6 activity and improved anti-tau activities compared to the parent compound in both in vitro and in vivo AD models. Furthermore, molecular docking results showed that PRO-Br binds to HDAC6, with a ∆G value of −8.4 kcal/mol and an IC₅₀ value of 1.51 µM. In neuronal cell lines, PRO-Br reduced pathological tau by inducing chaperone-mediated autophagy (CMA). In 3xTg-AD and P301S tau mice models, PRO-Br specifically decreased the pathogenic hyperphosphorylated tau clumps and led to the restoration of memory functions. In addition, PRO-Br treatment promoted the clearance of pathogenic tau by enhancing the expression of molecular chaperones (HSC70) and lysosomal markers (LAMP2A) via CMA in AD models. Our data strongly suggest that administration of the brain-permeable protopine derivative PRO-Br, could be a viable anti-tau therapeutic strategy for AD.

Reduction of kinesin I heavy chain decreases tau hyperphosphorylation, aggregation, and memory impairment in Alzheimer's disease and tauopathy models

Many neurodegenerative diseases, such as Alzheimer's disease (AD) and frontotemporal dementia with Parkinsonism linked to chromosome 17, are characterized by tau pathology. Numerous motor proteins, many of which are involved in synaptic transmission, mediate transport in neurons. Dysfunction in motor protein-mediated neuronal transport mechanisms occurs in several neurodegenerative disorders but remains understudied in AD. Kinesins are the most important molecular motor proteins required for microtubule-dependent transport in neurons, and kinesin-1 is crucial for neuronal transport among all kinesins. Although kinesin-1 is required for normal neuronal functions, the dysfunction of these motor domains leading to neurodegenerative diseases is not fully understood. Here, we reported that the kinesin-I heavy chain (KIF5B), a key molecular motor protein, is involved in tau homeostasis in AD cells and animal models. We found that the levels of KIF5B in P301S tau mice are high. We also found that the knockdown and knockout (KO) of KIFf5B significantly decreased the tau stability, and overexpression of KIF5B in KIF5B-KO cells significantly increased the expression of phosphorylated and total tau levels. This suggested that KIF5B might prevent tau accumulation. By conducting experiments on P301S tau mice, we showed that partially reducing KIF5B levels can reduce hyperphosphorylation of the human tau protein, formation of insoluble aggregates, and memory impairment. Collectively, our results suggested that decreasing KIF5B levels is sufficient to prevent and/or slow down abnormal tau behavior of AD and other tauopathies.

Isoliquiritigenin mitigates oxidative damage after subarachnoid hemorrhage in vivo and in vitro by regulating Nrf2-dependent Signaling Pathway via Targeting of SIRT1

BACKGROUND

Oxidative stress is a crucial factor leading to subarachnoid hemorrhage (SAH)-induced early brain injury (EBI). Isoliquiritigenin has been verified as a powerful anti-oxidant in a variety of diseases models and can activate sirtuin 1 and nuclear factor-erythroid 2-related factor 2 (Nrf2) pathways. However, the effects of isoliquiritigenin against EBI after SAH and the underlying mechanisms remain elusive.

PURPOSE

The primary goal of this study is to verify the therapeutic effects of isoliquiritigenin on EBI after SAH and the possible molecular mechanisms.

STUDY DESIGN

A prechiasmatic cistern SAH model in rats and a hemoglobin incubation SAH model in primary neurons were established. Isoliquiritigenin was administered after SAH induction. EX527 was employed to inhibit sirtuin 1 activation and ML385 was used to suppress Nrf2 signaling.

METHODS

In our study, neurological scores, brain edema, biochemical estimation, western blotting, and histopathological study were performed to explore the therapeutic action of isoliquiritigenin against SAH.

RESULTS

Our data revealed that isoliquiritigenin significantly mitigated oxidative damage after SAH as evidenced by decreased reactive oxygen species overproduction and enhanced intrinsic anti-oxidative system. Concomitant with the reduced oxidative insults, isoliquiritigenin improved neurological function and reduced neuronal death in the early period after SAH. Additionally, isoliquiritigenin administration significantly enhanced Nrf2 and sirtuin 1 expressions. Inhibition of Nrf2 by ML385 reversed the anti-oxidative and neuroprotective effects of isoliquiritigenin against SAH. Moreover, inhibiting sirtuin 1 by EX527 pretreatment suppressed isoliquiritigenin-induced Nrf2-dependent pathway and abated the cerebroprotective effects of isoliquiritigenin. In primary cortical neurons, isoliquiritigenin treatment also ameliorated oxidative insults and repressed neuronal degeneration. The beneficial aspects of isoliquiritigenin were attributed to the promotion of sirtuin 1 and Nrf2 signaling pathways and were counteracted by EX527.

CONCLUSION

Our findings suggest that isoliquiritigenin exerts cerebroprotective effects against SAH-induced oxidative insults by modulating the Nrf2-mediated anti-oxidant signaling in part through sirtuin 1 activation. Isoliquiritigenin might be a new potential drug candidate for SAH.

Acute, chronic, and genotoxic studies on the protopine total alkaloids of the Macleaya cordata (willd.) R. Br. in rodents

The protopine alkaloids are widely distributed within the opium poppy family and have a wide range of pharmacological effects. MPTA is a product of the protopine total alkaloids extracted from the Macleaya cordata (Willd.) R. Br. Previously, we reported good anti-inflammatory activity of MPTA as well as oral acute and sub-chronic toxicity studies in rats. In order to perform a systematic toxicological safety assessment of MPTA, oral acute toxicity, genotoxicity (bone marrow cell chromosome aberration test, sperm abnormality test, bone marrow cell micronucleus test, and rat teratogenicity test), and chronic toxicity in mice were performed in this study. In the oral acute toxicity test, the LD₅₀ in ICR mice was 481.99 mg/kg, with 95% confidence limits ranging from 404.27 to 574.70 mg/kg. All three mutagenicity tests tested negative in the range of 60.25–241.00 mg/kg. The results of the teratogenicity test in rats showed no reproductive or embryonic developmental toxicity at only 7.53 mg/kg, which can be considered as a no observed effect level (NOEL) for the teratogenicity test. Therefore, MPTA is safe for use at the doses tested, but attention should be paid to the potential risk to pregnant animals and the safety evaluation and toxicity mechanisms in target animals should be further investigated.

Synaptamide Modulates Astroglial Activity in Mild Traumatic Brain Injury

At present, the study of the neurotropic activity of polyunsaturated fatty acid ethanolamides (N-acylethanolamines) is becoming increasingly important. N-docosahexaenoylethanolamine (synaptamide, DHEA) is a highly active metabolite of docosahexaenoic acid (DHA) with neuroprotective, synaptogenic, neuritogenic, and anti-inflammatory properties in the nervous system. Synaptamide tested in the present study was obtained using a chemical modification of DHA isolated from squid Berryteuthis magister liver. The results of this study demonstrate the effects of synaptamide on the astroglial response to injury in the acute (1 day) and chronic (7 days) phases of mild traumatic brain injury (mTBI) development. HPLC-MS study revealed several times increase of synaptamide concentration in the cerebral cortex and serum of experimental animals after subcutaneous administration (10 mg/kg/day). Using immunohistochemistry, it was shown that synaptamide regulates the activation of GFAP- and S100β-positive astroglia, reduce nNOS-positive immunostaining, and stimulates the secretion of neurotrophin BDNF. Dynamics of superoxide dismutase production in synaptamide treatment confirm the antioxidant efficacy of the test compound. We found a decrease in TBI biomarkers such as GFAP, S100β, and IL-6 in the blood serum of synaptamide-treated experimental animals using Western blot analysis. The results indicate the high therapeutic potential of synaptamide in reducing the severity of the brain damage consequences.

QbD-based rivastigmine tartrate-loaded solid lipid nanoparticles for enhanced intranasal delivery to the brain for Alzheimer's therapeutics

Alzheimer's disease (AD) is a neurodegenerative disease that affects a wide range of populations and is the primary cause of death in various countries. The treatment of AD is still restricted to oral conventional medicines that act only superficially. Fabrication of intranasal solid lipid nanoparticulate system for the uptake of therapeutic agents will act as a convincing approach with limited off-site toxicity and increased pharmacological activity. The objective of this study was to formulate, optimize, and evaluate the efficiency of rivastigmine tartrate (RT)-loaded intranasal solid lipid nanoparticles (SLNs) employing the solvent-evaporation diffusion method. To optimize the formulation parameters, the central composite design (CCD) was used. Lipid concentration (X1) and surfactant concentration (X2) were considered to be independent variables, while particle size (Y1), percentage entrapment efficiency (Y2), and percentage drug release (Y3) were considered as responses. The solid lipid was glyceryl monostearate, while the surfactant was polysorbate 80. The optimized formulation has a particle size of 110.2 nm, % entrapment efficiency of 82.56%, and % drug release of 94.86%. The incompatibility of drug excipients was established by differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Nasal histopathology tests on sheep mucosa revealed that the developed SLNs were safe to utilize for intranasal delivery with no toxicity. Ex vivo permeation investigations revealed that the flux and diffusion coefficients for RT solid lipid nanoparticles and RT solution were 3.378 g/cm2 /h and 0.310-3 cm2 /h, respectively. Stability studies demonstrated that the developed SLNs were stable when stored under various storage conditions. The viability and vitality of adopting a lipid particle delivery system for improved bioavailability via the intranasal route were also established in the in vivo pharmacokinetic investigations. According to the histopathological and pharmacokinetic investigations, the developed formulations were safe, non-lethal, efficient, and robust. These results suggest the potentiality provided by rivastigmine tartrate-loaded solid lipid nanoparticles for nasal delivery.

Prospective Evaluation of an Amide-Based Zinc Scaffold as an Anti-Alzheimer Agent: In Vitro, In Vivo, and Computational Studies

Alzheimer's disease is the most common progressive neurodegenerative mental disorder associated with loss of memory, decline in cognitive function, and dysfunction of language. The prominent pathogenic causes of this disease involve deposition of amyloid-β plaques, acetylcholine neurotransmitter deficiency, and accumulation of neurofibrillary tangles. There are multiple pathways that have been targeted to treat this disease. The inhibition of the intracellular cyclic AMP regulator phosphodiesterase IV causes the increase in CAMP levels that play an important role in the memory formation process. Organometallic chemistry works in a different way in treating pharmacological disorders. In the field of medicinal chemistry and pharmaceuticals, zinc-based amide carboxylates have been shown to be a preferred pharmacophore. The purpose of this research work was to investigate the potential of zinc amide carboxylates in inhibition of phosphodiesterase IV for the Alzheimer's disease management. Swiss Albino mice under controlled conditions were divided into seven groups with 10 mice each. Group I was injected with carboxymethylcellulose (CMC) at 1 mL/100 g dose, group II was injected with Streptozotocin (STZ) at 3 mg/kg dose, group III was injected with Piracetam acting as a standard drug at 200 mg/kg dosage, while groups IV-VII were injected with a zinc scaffold at the dose regimen of 10, 20, 40, and 80 mg/kg through intraperitoneal injection. All groups except group I were injected with Streptozotocin on the first day and third day of treatment at the dose of 3 mg/kg through an intracerebroventricular route to induce Alzheimer's disease. Afterward, respective treatment was continued for all groups for 23 days. In between the treatment regimen, groups were analyzed for memory and learning improvement through various behavioral tests such as open field, elevated plus maze, Morris water maze, and passive avoidance tests. At the end of the study, different biochemical markers in the brain were estimated like neurotransmitters (dopamine, serotonin and adrenaline), oxidative stress markers (superoxide dismutase, glutathione, and catalase), acetylcholinesterase (AchE), tau proteins, and amyloid-β levels. A PCR study was also performed. Results showed that the LD₅₀ of the zinc scaffold is greater than 2000 mg/kg. Research indicated that the zinc scaffold has the potential to improve the memory impairment and learning behavior in Alzheimer's disease animal models in a dose-dependent manner. At the dose of 80 mg/kg, a maximum response was observed for the zinc scaffold. Maximum reduction in the acetylcholinesterase enzyme was observed at 80 mg/kg dose, which was further strengthened and verified by the PCR study. Oxidative stress was restored by the zinc scaffold due to the significant activation of the endogenous antioxidant enzymes. This research ended up with the conclusion that the zinc-based amide carboxylate scaffold has the potential to improve behavioral disturbances and vary the biochemical markers in the brain.

Design, Synthesis, and Bioactivity of Novel Bifunctional Small Molecules for Alzheimer's disease

The abnormal phosphorylation of the τ-protein is a typical early pathological feature of Alzheimer's disease (AD). The excessive phosphorylation of the τ-protein in the brain causes the formation of neurofibrillary tangles (NFTs) and increases the neurotoxicity of amyloid-β (Aβ). Thus, targeting the τ-protein is considered a promising strategy for treating AD. Herein, we designed and synthesized a series of molecules containing bifunctional groups to recognize the τ-protein and the E3 ligase. The molecules were examined in vitro, and their effects were tested on PC12 cells. In addition, we further studied the pharmacokinetics of compound I3 in healthy rats. Our data showed that compound I3 could effectively degrade τ-protein, reduce Aβ-induced cytotoxicity, and regulate the uneven distribution of mitochondria, which may open a new therapeutic strategy for the treatment of AD.

Signal pathways in the treatment of Alzheimer's disease with traditional Chinese medicine

AIM OF THE REVIEW

This study aimed to reveal the classical signal pathways and important potential targets of traditional Chinese medicine (TCM) for treating Alzheimer's disease (AD), and provide support for further investigation on TCM and its active ingredients.

MATERIALS AND METHODS

Literature survey was conducted using PubMed, Web of Science, Google Scholar, CNKI, and other databases, with "Alzheimer's disease," "traditional Chinese medicine," "medicinal herb," "Chinese herb," and "natural plant" as the primary keywords.

RESULTS

TCM could modulate signal pathways related to AD pathological progression, including NF-κB, Nrf2, JAK/STAT, ubiquitin-proteasome pathway, autophagy-lysosome pathway-related AMPK/mTOR, GSK-3/mTOR, and PI3K/Akt/mTOR, as well as SIRT1 and PPARα pathway. It could regulate crosstalk between pathways through a multitarget, thus maintaining chronic inflammatory interaction balance, inhibiting oxidative stress damage, regulating ubiquitin-proteasome system function, modulating autophagy, and eventually improving cognitive impairment in patients with AD.

CONCLUSION

TCM could be multilevel, multitargeted, and multifaceted to prevent and treat AD. In-depth research on the prevention and treatment of AD with TCM could provide new ideas for exploring the pathogenesis of AD and developing new anti-AD drugs.

Exploring the Anti-inflammatory Effects of Protopine Total Alkaloids of Macleaya Cordata (Willd.) R. Br

Macleaya cordata (Willd). R. Br. is a Chinese medicinal plant commonly used externally to treat inflammatory-related diseases such as arthritis, sores, and carbuncles. This study aimed to evaluate the anti-inflammatory activity of protopine total alkaloids (MPTAs) in Macleaya cordata (Willd.) R. Br. in vivo tests in rats with acute inflammation showed that MPTA (2.54 and 5.08 mg/kg) showed significant anti-inflammatory activity 6 h after carrageenan injection. Similarly, MPTA (3.67 and 7.33 mg/kg) showed significant anti-inflammatory activity in the mouse ear swelling test. In addition, the potential mechanisms of the anti-inflammatory effects of MPTA were explored based on network pharmacology and molecular docking. The two main active components of MPTA, protopine and allocryptopine, were identified, and the potential targets and signaling pathways of MPTA's anti-inflammatory effects were initially revealed using tools and databases (such as SwissTargetPrediction, GeneCards, and STRING) combined with molecular docking results. This study provides the basis for the application of MPTA as an anti-inflammatory agent.

Phosphate in the Context of Cognitive Impairment and Other Neurological Disorders Occurrence in Chronic Kidney Disease

The nervous system and the kidneys are linked under physiological states to maintain normal body homeostasis. In chronic kidney disease (CKD), damaged kidneys can impair the central nervous system, including cerebrovascular disease and cognitive impairment (CI). Recently, kidney disease has been proposed as a new modifiable risk factor for dementia. It is reported that uremic toxins may have direct neurotoxic (astrocyte activation and neuronal death) and/or indirect action through vascular effects (cerebral endothelial dysfunction, calcification, and inflammation). This review summarizes the evidence from research investigating the pathophysiological effects of phosphate toxicity in the nervous system, raising the question of whether the control of hyperphosphatemia in CKD would lower patients’ risk of developing cognitive impairment and dementia.

Theranostic F-SLOH mitigates Alzheimer's disease pathology involving TFEB and ameliorates cognitive functions in Alzheimer's disease models

Accumulation of amyloid-β (Aβ) oligomers and phosphorylated Tau aggregates are crucial pathological events or factors that cause progressive neuronal loss, and cognitive impairments in Alzheimer's disease (AD). Current medications for AD have failed to halt, much less reverse this neurodegenerative disorder; therefore, there is an urgent need for the development of effective and safe drugs for AD therapy. In the present study, the in vivo therapeutic efficacy of an Aβ-oligomer-targeted fluorescent probe, F-SLOH, was extensively investigated in 5XFAD and 3XTg-AD mouse models. We have shown that F-SLOH exhibits an efficient inhibitory activity against Aβ aggregation in vivo, and acts as an effective theranostic agent for the treatment of multiple neuropathological changes in AD mouse models. F-SLOH has been found to significantly reduce not only the levels of Aβ oligomers, Tau aggregates and plaques but also the levels of amyloid precursor protein (APP) and its metabolites via autophagy lysosomal degradation pathway (ALP) in the brains of 5XFAD and 3XTg-AD mice. It also reduces astrocyte activation and microgliosis ultimately alleviating neuro-inflammation. Furthermore, F-SLOH mitigates hyperphosphorylated Tau aggregates, synaptic deficits and ameliorates synaptic memory function, and cognitive impairment in AD mouse models. The mechanistic studies have shown that F-SLOH promotes the clearance of C-terminal fragment 15 (CTF15) of APP and Paired helical filaments of Tau (PHF1) in stable cell models via the activation of transcription factor EB (TFEB). Moreover, F-SLOH promotes ALP and lysosomal biogenesis for the clearance of soluble, insoluble Aβ, and phospho Tau. Our results unambiguously reveal effective etiological capabilities of theranostic F-SLOH to target and intervene multiple neuropathological changes in AD mouse models. Therefore, F-SLOH demonstrates tremendous therapeutic potential for treating AD in its early stage.

Mechanistic Insights into Selective Autophagy Subtypes in Alzheimer's Disease

Eukaryotic cells possess a plethora of regulatory mechanisms to maintain homeostasis and ensure proper biochemical functionality. Autophagy, a central, conserved self-consuming process of the cell, ensures the timely degradation of damaged cellular components. Several studies have demonstrated the important roles of autophagy activation in mitigating neurodegenerative diseases, especially Alzheimer's disease (AD). However, surprisingly, activation of macroautophagy has not shown clinical efficacy. Hence, alternative strategies are urgently needed for AD therapy. In recent years, selective autophagy has been reported to be involved in AD pathology, and different subtypes have been identified, such as aggrephagy, mitophagy, reticulophagy, lipophagy, pexophagy, nucleophagy, lysophagy and ribophagy. By clarifying the underlying mechanisms governing these various subtypes, we may come to understand how to control autophagy to treat AD. In this review, we summarize the latest findings concerning the role of selective autophagy in the pathogenesis of AD. The evidence overwhelmingly suggests that selective autophagy is an active mechanism in AD pathology, and that regulating selective autophagy would be an effective strategy for controlling this pathogenesis.

Klotho an Autophagy Stimulator as a Potential Therapeutic Target for Alzheimer’s Disease: A Review

Alzheimer’s disease (AD) is an age-associated neurodegenerative disease; it is the most common cause of senile dementia. Klotho, a single-pass transmembrane protein primarily generated in the brain and kidney, is active in a variety of metabolic pathways involved in controlling neurodegeneration and ageing. Recently, many studies have found that the upregulation of Klotho can improve pathological cognitive deficits in an AD mice model and have demonstrated that Klotho plays a role in the induction of autophagy, a major contributing factor for AD. Despite the close association between Klotho and neurodegenerative diseases, such as AD, the underlying mechanism by which Klotho contributes to AD remains poorly understood. In this paper, we will introduce the expression, location and structure of Klotho and its biological functions. Specifically, this review is devoted to the correlation of Klotho protein and the AD phenotype, such as the effect of Klotho in upregulating the amyloid-beta clearance and in inducing autophagy for the clearance of toxic proteins, by regulating the autophagy lysosomal pathway (ALP). In summary, the results of multiple studies point out that targeting Klotho would be a potential therapeutic strategy in AD treatment.