Neuroprotective effects of increasing levels of HSP70 against neuroinflammation in Parkinson's disease model by inhibition of NF-κB and STAT3

Regulatory mechanism of miR-20a-5p in neuronal damage and inflammation in lipopolysaccharide-induced BV2 cells and MPTP-HCl-induced Parkinson's disease mice

BACKGROUND

Parkinson's disease (PD) is a prevailing neurodegenerative disorder increasingly affecting the elderly population. The involvement of microRNAs (miRNAs) in PD has been confirmed. We sought to explore the molecular mechanism of miR-20a-5p in PD.

METHODS

Lipopolysaccharide (LPS)-induced BV2 cell model and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP-HCl)-induced PD mouse model were established. miR-20a-5p, inducible nitric oxide synthase (iNOS), interleukin (IL)-6, tumour necrosis factor (TNF)-α, transforming growth factor (TGF)-β1, and IL-10 expression in BV2 cells was examined by reverse transcription - quantitative polymerase chain reaction. Cell viability was assessed by MTT assay. The apoptotic rate and levels of Bcl-2, Bax, cleaved caspase-3, and signal transducer and activator of transmission (STAT)3 were examined by flow cytometry and Western blot. Bioinformatics software predicted the potential binding sites of miR-20a-5p and STAT3. Dual-luciferase experiment verified the binding relationship. Iba1-positive and tyrosine hydroxylase (TH)-positive cell numbers in substantia nigra pars compacta were detected by immunohistochemistry. The effect of miR-20a-5p on motor function in MPTP-induced PD mice was detected by Rota-rod test, Pole test, Traction test and Beam-crossing task.

RESULTS

miR-20a-5p was under-expressed in LPS-induced BV2 cells. Overexpression of miR-20a-5p increased the viability of LPS-induced BV2 cells and reduced apoptosis rates. Moreover, overexpression of miR-20a-5p reduced cleaved caspase-3, Bax, iNOS, IL-6, and TNF-α and increased Bcl-2 and TGF-β1, and IL-10. miR-20a-5p targeted STAT3. STAT3 overexpression partially reversed miR-20a-5p overexpression-mediated effects on LPS-induced BV2 cell viability, apoptosis, and inflammatory responses. miR-20a-5p overexpression inhibited MPTP-induced STAT3 and α-synuclein levels, microglia activation, and inflammatory response, and reduced the loss of TH-positive cells in mice. miR-20a-5p overexpression ameliorated MPTP-induced dyskinesia in PD model mice.

CONCLUSION

miR-20a-5p alleviates neuronal damage and suppresses inflammation by targeting STAT3 in PD.

6-Hydroxy-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline Demonstrates Neuroprotective Properties in Experimental Parkinson's Disease by Enhancing the Antioxidant System, Normalising Chaperone Activity and Suppressing Apoptosis

Parkinson's disease (PD) is a neurodegenerative disease, whereby disturbances within the antioxidant defence system, increased aggregation of proteins, and activation of neuronal apoptosis all have a crucial role in the pathogenesis. In this context, exploring the neuroprotective capabilities of compounds that sustain the effectiveness of cellular defence systems in neurodegenerative disorders is worthwhile. During this study, we assessed how 6-hydroxy-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline (HTHQ), which has antioxidant properties, affects the functioning of the antioxidant system, the activity of NADPH-generating enzymes and chaperones, and the level of apoptotic processes in rats with rotenone-induced PD. Six groups of animals were formed for our experiment, each with 12 animals. These were: a control group, animals with rotenone-induced PD, rats with PD given HTHQ at a dose of 50 mg/kg, rats with PD given HTHQ at a dose of 25 mg/kg, animals with pathology who were administered a comparison drug rasagiline, and control animals who were administered HTHQ at a dose of 50 mg/kg. The study results indicate that administering HTHQ led to a significant decrease in oxidative stress in PD rats. The enhanced redox status in animal tissues was linked with the recovery of antioxidant enzyme activities and NADPH-generating enzyme function, as well as an upsurge in the mRNA expression levels of antioxidant genes and factors Nrf2 and Foxo1. Administering HTHQ to rats with PD normalized the chaperone-like activity and mRNA levels of heat shock protein 70. Rats treated with the compound displayed lower apoptosis intensity when compared to animals with pathology. Therefore, owing to its antioxidant properties, HTHQ demonstrated a beneficial impact on the antioxidant system, resulting in decreased requirements for chaperone activation and the inhibition of apoptosis processes triggered in PD. HTHQ at a dose of 50 mg/kg had a greater impact on the majority of the examined variables compared to rasagiline.

Linking Heat Shock Protein 70 and Parkin in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disease that affects millions of elderly people worldwide and is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). The precise mechanisms underlying the pathogenesis of PD are still not fully understood, but it is well accepted that the misfolding, aggregation, and abnormal degradation of proteins are the key causative factors of PD. Heat shock protein 70 (Hsp70) is a molecular chaperone that participates in the degradation of misfolded and aggregated proteins in living cells and organisms. Parkin, an E3 ubiquitin ligase, participates in the degradation of proteins via the proteasome pathway. Recent studies have indicated that both Hsp70 and Parkin play pivotal roles in PD pathogenesis. In this review, we focus on discussing how dysregulation of Hsp70 and Parkin leads to PD pathogenesis, the interaction between Hsp70 and Parkin in the context of PD and their therapeutic applications in PD.

Modulating Stress Proteins in Response to Therapeutic Interventions for Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative illness characterized by the degeneration of dopaminergic neurons in the substantia nigra, resulting in motor symptoms and without debilitating motors. A hallmark of this condition is the accumulation of misfolded proteins, a phenomenon that drives disease progression. In this regard, heat shock proteins (HSPs) play a central role in the cellular response to stress, shielding cells from damage induced by protein aggregates and oxidative stress. As a result, researchers have become increasingly interested in modulating these proteins through pharmacological and non-pharmacological therapeutic interventions. This review aims to provide an overview of the preclinical experiments performed over the last decade in this research field. Specifically, it focuses on preclinical studies that center on the modulation of stress proteins for the treatment potential of PD. The findings display promise in targeting HSPs to ameliorate PD outcomes. Despite the complexity of HSPs and their co-chaperones, proteins such as HSP70, HSP27, HSP90, and glucose-regulated protein-78 (GRP78) may be efficacious in slowing or preventing disease progression. Nevertheless, clinical validation is essential to confirm the safety and effectiveness of these preclinical approaches.

Molecular Chaperones' Potential against Defective Proteostasis of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neuronal degenerative condition identified via a build-up of mutant aberrantly folded proteins. The native folding of polypeptides is mediated by molecular chaperones, preventing their pathogenic aggregation. The mutant protein expression in ALS is linked with the entrapment and depletion of chaperone capacity. The lack of a thorough understanding of chaperones' involvement in ALS pathogenesis presents a significant challenge in its treatment. Here, we review how the accumulation of the ALS-linked mutant FUS, TDP-43, SOD1, and C9orf72 proteins damage cellular homeostasis mechanisms leading to neuronal loss. Further, we discuss how the HSP70 and DNAJ family co-chaperones can act as potential targets for reducing misfolded protein accumulation in ALS. Moreover, small HSPB1 and HSPB8 chaperones can facilitate neuroprotection and prevent stress-associated misfolded protein apoptosis. Designing therapeutic strategies by pharmacologically enhancing cellular chaperone capacity to reduce mutant protein proteotoxic effects on ALS pathomechanisms can be a considerable advancement. Chaperones, apart from directly interacting with misfolded proteins for protein quality control, can also filter their toxicity by initiating strong stress-response pathways, modulating transcriptional expression profiles, and promoting anti-apoptotic functions. Overall, these properties of chaperones make them an attractive target for gaining fundamental insights into misfolded protein disorders and designing more effective therapies against ALS.

African Walnut (Tetracarpidium conophorum) Extract upregulates Glococerebrosidase activity and circumvents Parkinsonian changes in the Hippocampus via theActivation of Heatshock Proteins

BACKGROUND

Neurodegenerative illnesses like Parkinson's and Alzheimer's are largely caused by the accumulation of aggregated proteins. Heat shock proteins (HSPs), which are molecular chaperons, have been linked with the modulation of β-glucocerebrosidase (GCase) function encoded by GBA1 and Synucleinopathies. Herein, the chaperonic properties of African walnut ethanolic extract (WNE) in manganese-induced Parkinsonian neuropathology in the hippocampus was examined.

METHODOLOGY

48 adult male rats weighing 185g±10g were randomly assigned into 6 (A - F) groups (n=8) and treated orally as follows: A-PBS (1ml daily for 28 days), B-WNE (200mg/kg daily for 28 days), C- WNE (400mg/kg daily for 28 days), D-Mn (100mg/kg daily for 28 days), E-Mn plus WNE (100mg/kg Mn + 200mg/kg WNE daily concomitantly for 28 days), F-Mn plus WNE (100mg/kg Mn + 400mg/kg WNE daily concomitantly for 28 days).

RESULTS

Rats treated with WNE showed increased levels of HSP70 and HSP90 in comparison with the Mn-intoxicated group. GCase activity also increased significantly in animals treated with WNE. Our results further revealed the therapeutic tendencies of WNE against Mn toxicity by modulating oligomeric α-synuclein levels, redox activity, and glucose bioenergetics. Furthermore, immunohistochemical evaluation revealed reduced expression of neurofibrillary tangles, and reactive astrogliosis following WNE treatment.

CONCLUSION

The ethanolic extract of African Walnut induced the activation of HSPs and increased the expression of GBA1 gene in the hippocampus. Activated heat shock proteins suppressed neurodegenerative changes due to Manganese toxicity. WNE was also shown to modulate neuroinflammatory, bioenergetics and neural redox balance in Parkinson-like neuropathology. This study was limited to the use of crude walnut extract and the evaluation of non-motor cascades of Parkinson's disease.

Lyn attenuates sepsis-associated acute kidney injury by inhibition of phospho-STAT3 and apoptosis

Sepsis-associated acute kidney injury (SA-AKI) is a life-threatening condition associated with high mortality and morbidity. However, the underlying pathogenesis of SA-AKI is still unclear. Lyn belongs to Src family kinases (SFKs), which exert numerous biological functions including modulation in receptor-mediated intracellular signaling and intercellular communication. Previous studies demonstrated that Lyn gene deletion obviously aggravates LPS-induced lung inflammation, but the role and possible mechanism of Lyn in SA-AKI have not been reported yet. Here, we found that Lyn protected against renal tubular injury in cecal ligation and puncture (CLP) induced AKI mouse model by inhibition of signal transducer and activator of transcription 3 (STAT3) phosphorylation and cell apoptosis. Moreover, Lyn agonist MLR-1023 pretreatment improved renal function, inhibited STAT3 phosphorylation and decreased cell apoptosis. Thus, Lyn appears to play a crucial role in orchestrating STAT3-mediated inflammation and cell apoptosis in SA-AKI. Hence, Lyn kinase may be a promising therapeutic target for SA-AKI.

HSPA1A ameliorated spinal cord injury in rats by inhibiting apoptosis to exert neuroprotective effects

Traumatic spinal cord injury (TSCI) is a serious nervous system insult, and apoptosis in secondary injury is an important barrier to recovery from TSCI. Heat shock protein family A member 1A (HSPA1A) is a protective protein whose expression is elevated after stress. However, whether HSPA1A can inhibit apoptosis after spinal cord injury, and the potential mechanism of this inhibition, remain unclear. In this study, we established in vivo and in vitro models of TSCI and induced HSPA1A overexpression and silencing. HSPA1A upregulation promoted the recovery of neurological function and pathological morphology at the injury site, enhanced neurological cell survival, and inhibited apoptosis in rats following TSCI. In the in vitro model, HSPA1A overexpression inhibited H₂O₂-induced apoptosis, indicating that HSPA1A suppressed the expression of Bax, caspase-9, and cleaved-caspase-3, promoted the expression of Bcl-2. Furthermore, inhibition of HSPA1A expression can aggravate H₂O₂-induced apoptosis. We also found that HSPA1A overexpression activated the Wnt/β-catenin signaling pathway, and that inhibition of this pathway attenuated the inhibitory effect of HSPA1A overexpression on apoptosis. Together, these results indicate that HSPA1A has neuroprotective effects against TSCI that may be exerted through activation of the Wnt/β-catenin signaling pathway to inhibit apoptosis.

Therapeutic modulation of JAK-STAT, mTOR, and PPAR-γ signaling in neurological dysfunctions

The cytokine-activated Janus kinase (JAK)-signal transducer and activator of transcription (STAT) cascade is a pleiotropic pathway that involves receptor subunit multimerization. The mammalian target of rapamycin (mTOR) is a ubiquitously expressed serine-threonine kinase that perceives and integrates a variety of intracellular and environmental stimuli to regulate essential activities such as cell development and metabolism. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a prototypical metabolic nuclear receptor involved in neural differentiation and axon polarity. The JAK-STAT, mTOR, and PPARγ signaling pathways serve as a highly conserved signaling hub that coordinates neuronal activity and brain development. Additionally, overactivation of JAK/STAT, mTOR, and inhibition of PPARγ signaling have been linked to various neurocomplications, including neuroinflammation, apoptosis, and oxidative stress. Emerging research suggests that even minor disruptions in these cellular and molecular processes can have significant consequences manifested as neurological and neuropsychiatric diseases. Of interest, target modulators have been proven to alleviate neuronal complications associated with acute and chronic neurological deficits. This research-based review explores the therapeutic role of JAK-STAT, mTOR, and PPARγ signaling modulators in preventing neuronal dysfunctions in preclinical and clinical investigations.

Low doses of fumonisin B1 exacerbate ochratoxin A-induced renal injury in mice and the protective roles of heat shock protein 70

Fumonisin B1 (FB1) and ochratoxin A (OTA) possess nephrotoxicity to animals and widely co-exist in food and feedstuffs. FB1 rarely, while OTA often, causes toxicosis in animals. Heat shock protein 70 (Hsp70) resists lung injury induced by pneumolysin, but whether Hsp70 could remission mycotoxins-induced renal injury is still unknown. The present study aims to explore the impacts of nontoxic doses of FB1 on OTA-induced nephrotoxicity and the protective roles of Hsp70. In the mycotoxins-challenge experiment, ICR mice were co-exposed to nontoxic doses of FB1 (0, 0.2, 0.5, 1.0 mg/kg bw, IP) and toxic dose of OTA (0.4 mg/kg bw, IP) for 16 d. The results showed that the levels of BUN, Cr, MDA in serum, the Cyto C in renal tubes or glomerulus, pro-apoptosis genes and p-JNK protein expression in kidney were significantly increased. Histopathological results revealed the glomerular swelling. The above all indexes were dose-dependent. In the protection experiment, the mice were pretreated with the eukaryotic plasmid of pEGFP-C3-Hsp70, these increasing parameters in the mycotoxins-challenge experiment were reversed. In vitro, after pK-15 cells were treated with 8 μM FB1 and 5 μM OTA for 48 h, the mitochondrial membrane potential was significantly reduced, mitochondrial ROS was remarkably increased, more Cyto C was leaked from mitochondria into cytoplasm, and pro-apoptosis genes were significantly up-regulated. After the Hsp70 level was up-regulated by pEGFP-C3-Hsp70 or ML346 in pK-15 cells, these above indexes were reversed. However, activation of JNK by anisomycin significantly suppressed the protective effects of Hsp70. Our results demonstrate that the nontoxic doses of FB1 exacerbate the toxic dose of OTA-induced renal injury, while Hsp70 alleviates renal injury by inhibiting the JNK/MAPK signaling pathway. Hsp70 up-regulation may be an efficient strategy for protecting against tissue damage and bio-function impairment induced by co-exposure to FB1 and OTA.

Potential application of heat shock proteins as therapeutic targets in Parkinson's disease

Parkinson's disease (PD) is a common chronic neurodegenerative disease, and the heat shock proteins (HSPs) are proved to be of great value for PD. In addition, HSPs can maintain protein homeostasis, degrade and inhibit protein aggregation by properly folding and activating intracellular proteins in PD. This study mainly summarizes the important roles of HSPs in PD and explores their feasibility as targets. We introduced the structural and functional characteristics of HSPs and the physiological functions of HSPs in PD. HSPs can protect neurons from damage by degrading aggregates with three mechanisms, including the aggregation and removing α-Synuclein (α-Syn) aggregates, promotion the autophagy of abnormal proteins, and inhibition the apoptosis of degenerated neurons. This study underscores the importance of HSPs as targets in PD and helps to expand new mechanisms in PD treatment strategies.

Exogenous recombinant Hsp70 attenuates sevoflurane anesthesia-induced cognitive dysfunction in aged mice

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a severe postoperative neurological sequela in elderly patients, and there is currently no standard treatment for POCD. In this study, whether recombinant human heat shock protein 70 (rHsp70) could alleviate sevoflurane-induced cognitive impairment in aged mice is investigated.

METHODS

To determine the prophylactic effect of rHsp70 in sevoflurane-induced cognitive dysfunction, aged mice were pretreated with different concentrations of rHsp70 (29.4, 58.8, and 117.6 μg/kg; intranasal injected; N = 12) every day for 1 week; then, 3% sevoflurane was utilized to anesthetize the aged mice. Cognitive function, neurotoxicity, and serum and hippocampal Hsp70 levels in aged mice undergoing sevoflurane anesthesia were assessed by the Morris water maze test and enzyme-linked immunosorbent assay. The effects of rHsp70 on inflammatory response were assessed by proinflammatory cytokine production and nuclear factor-κB (NF-κB) activation assays.

RESULTS

We found that aged mice exposed to sevoflurane showed reduced learning and memory ability and reduced Hsp70 expression, which were both restored by rHsp70 pretreatment. RHsp70 also reversed sevoflurane-induced up-regulated Bax and Bcl-2 expression and interleukin-1, IL-6, and monocyte chemoattractant protein-1 overproduction. Finally, rHsp70 pretreatment suppressed sevoflurane-induced NF-κB activation. Our study indicated that rHsp70 was sufficient to suppress sevoflurane-induced cognitive decline and neurotoxicity.

CONCLUSION

Our important finding warrants further study on the clinical application of rHsp70 in elderly patients undergoing anesthesia.

Effects of overexpression of Hsp70 in neural stem cells on neurotoxicity and cognitive dysfunction in neonatal mice under sevoflurane exposure

As one of the commonly used inhalation anesthetics in clinical practice, sevoflurane is currently widely applied in surgery for children and the elderly due to its safety and efficacy. However, the neurotoxicity and cognitive impairment induced by sevoflurane exposure cannot be ignored. A recombinant adenovirus with green fluorescent protein-labeled heat shock protein 70 (Hsp70) was constructed and used to infect neural stem cells (NSCs) separated from neonatal mice. Quantitative real-time PCR and Western blot assays were used to evaluate the expression of certain genes. 5‑Ethynyl‑2'‑deoxyuridine staining and cell counting kit assay were used to detect the proliferation and differentiation ability of NSCs. The Morris water maze experiment was used to test the cognitive abilities of mice. Adv-Hsp70 induced the overexpression of Hsp70 in mouse NSCs. Upregulation of Hsp70 promoted the proliferation ability and differentiation of mouse NSCs. NSCs that overexpressed Hsp70 attenuated sevoflurane-induced neurotoxicity and protected cognitive dysfunction in mice under sevoflurane exposure. In summary, our findings demonstrate the potential of overexpression of Hsp70 in NSCs against sevoflurane-induced impairments.

Proteinopathies: Deciphering Physiology and Mechanisms to Develop Effective Therapies for Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are a cluster of diseases marked by progressive neuronal loss, axonal transport blockage, mitochondrial dysfunction, oxidative stress, neuroinflammation, and aggregation of misfolded proteins. NDs are more prevalent beyond the age of 50, and their symptoms often include motor and cognitive impairment. Even though various proteins are involved in different NDs, the mechanisms of protein misfolding and aggregation are very similar. Recently, several studies have discovered that, like prions, these misfolded proteins have the inherent capability of translocation from one neuron to another, thus having far-reaching implications for understanding the processes involved in the onset and progression of NDs, as well as the development of innovative therapy and diagnostic options. These misfolded proteins can also influence the transcription of other proteins and form aggregates, tangles, plaques, and inclusion bodies, which then accumulate in the CNS, leading to neuronal dysfunction and neurodegeneration. This review demonstrates protein misfolding and aggregation in NDs, and similarities and differences between different protein aggregates have been discussed. Furthermore, we have also reviewed the disposal of protein aggregates, the various molecular machinery involved in the process, their regulation, and how these molecular mechanisms are targeted to build innovative therapeutic and diagnostic procedures. In addition, the landscape of various therapeutic interventions for targeting protein aggregation for the effective prevention or treatment of NDs has also been discussed.

Pre-clinical Studies Identifying Molecular Pathways of Neuroinflammation in Parkinson's Disease: A Systematic Review

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by neuroinflammation, formation of Lewy bodies, and progressive loss of dopaminergic neurons in the substantia nigra of the brain. In this review, we summarize evidence obtained by animal studies demonstrating neuroinflammation as one of the central pathogenetic mechanisms of PD. We also focus on the protein factors that initiate the development of PD and other neurodegenerative diseases. Our targeted literature search identified 40 pre-clinical in vivo and in vitro studies written in English. Nuclear factor kappa B (NF-kB) pathway is demonstrated as a common mechanism engaged by neurotoxins such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), as well as the bacterial lipopolysaccharide (LPS). The α-synuclein protein, which plays a prominent role in PD neuropathology, may also contribute to neuroinflammation by activating mast cells. Meanwhile, 6-OHDA models of PD identify microsomal prostaglandin E synthase-1 (mPGES-1) as one of the contributors to neuroinflammatory processes in this model. Immune responses are used by the central nervous system to fight and remove pathogens; however, hyperactivated and prolonged immune responses can lead to a harmful neuroinflammatory state, which is one of the key mechanisms in the pathogenesis of PD.

Bone Marrow Stem Cell-Exo-Derived TSG-6 Attenuates 1-Methyl-4-Phenylpyridinium+-Induced Neurotoxicity via the STAT3/miR-7/NEDD4/LRRK2 Axis

Bone marrow mesenchymal stem cell-derived exosome (BMSCs-Exo)-derived TNF-stimulated gene-6 (TSG-6) has anti-inflammatory and antioxidative stress-related properties that may be beneficial in the treatment of Parkinson disease (PD) patients. To elucidate the mechanisms involved, we analyzed the effects of BMSCs-Exo-derived TSG-6 on in vitro models of PD induced with 1-methyl-4-phenylpyridinium (MPP+). TSG-6 was abundant in BMSCs-Exo and it attenuated MPP+-induced neurotoxicity. Moreover, BMSCs-Exo reversed the MPP+-induced toxicity accelerated by neural precursor cells expressed developmentally downregulated 4 (NEDD4) knockdown or miR-7 mimics. Further analysis indicated that NEDD4 combined with leucine-rich repeat kinase 2 (LRRK2) to accelerate ubiquitin degradation of LRRK2. Signal transducer and activator of transcription 3 (STAT3) bound to the miR-7 promoter and miR-7 targeted NEDD4. These data indicate that BMSCs-Exo-derived TSG-6 attenuated neurotoxicity via the STAT3-miR-7-NEDD4 axis. Our results define the specific mechanisms for BMSCs-Exo-derived TSG-6 regulation of MPP+-induced neurotoxicity that are relevant to understanding PD pathogenesis and developing therapies for PD patients.

Diosgenin revealed potential effect against cerebral ischemia reperfusion through HIKESHI/HSP70/NF-κB anti-inflammatory axis

BACKGROUND

It is a research hotspot to use natural compounds in treatment of cerebral ischemia reperfusion (I/R) for a refractory disease throughout the worldwide without available drugs or treatments at present. Our previous study has demonstrated that diosgenin (DIO), a starting material to synthesize various steroid anti-inflammatory drugs in medical industry, showed medicinal effect against I/R via inhibiting aberrant inflammatory reaction induced by I/R. However, the detailed anti-inflammatory network of DIO in treatment of I/R still remains to be further explored.

PURPOSE

HIKESHI was firstly identified as a novel target of DIO used for I/R by rat brain proteomic analysis, and mechanistic efforts were focused based on this gene. Hopefully, extensive detailed molecular mechanisms of DIO against I/R was established and confirmed.

METHODS

The effect of DIO against I/R was examined in vitro and in vivo, which cells (SH-SY5Y and PC12) and rats were experienced to ORD/RP and MCAO exposures, respectively, to establish I/R modes. Staining was used to evaluate the pathological procedure of DIO used for I/R. Protein changes including expression, interaction, and activity during DIO's anti-I/R effect were assessed with real time PCR, western blot, Co-IP, luciferase reporter assay.

RESULTS

In the current study, HIKESHI and HSP70 were both upregulated, when I/R cells and rats were treated with DIO in vitro and in vivo. Mechanistically, DIO stimulated the binding of HIKESHI to HSP70 and facilitated the translocation of HSP70 into nucleus. Subsequently, HSP70 blunted the transcription activity of NF-κB after physical interaction with this transcription factor, and therefore led to the suppression of its downstream pro-inflammatory cytokine (TNF-α, IL-1β, and IL-6) release into surrounding I/R lesion area. Conversely, HIKESHI or HSP70 knockdowns attenuated the nuclear translocation and restraint on NF-κB-mediated inflammation, finally resulting in the abolishment of DIO-induced anti-I/R effect. NF-κB activation also relieved the inhibitory inflammation and reversed DIO's effect against I/R, suggesting that NF-κB was the downstream target of HIKESHI and HSP70 in I/R treatment with DIO.

CONCLUSIONS

These findings established a novel HIKESHI/HSP70/NF-κB signaling pathway associated with DIO-treated I/R, which might be as therapeutic targets or drugs with potential implications for the therapeutic use of I/R in clinic.

SARM1 can be a potential therapeutic target for spinal cord injury

Injury to the spinal cord is devastating. Studies have implicated Wallerian degeneration as the main cause of axonal destruction in the wake of spinal cord injury. Therefore, the suppression of Wallerian degeneration could be beneficial for spinal cord injury treatment. Sterile alpha and armadillo motif-containing protein 1 (SARM1) is a key modulator of Wallerian degeneration, and its impediment can improve spinal cord injury to a significant degree. In this report, we analyze the various signaling domains of SARM1, the recent findings on Wallerian degeneration and its relation to axonal insults, as well as its connection to SARM1, the mitogen-activated protein kinase (MAPK) signaling, and the survival factor, nicotinamide mononucleotide adenylyltransferase 2 (NMNAT2). We then elaborate on the possible role of SARM1 in spinal cord injury and explicate how its obstruction could potentially alleviate the injury.

SIRT1 attenuates neuroinflammation by deacetylating HSPA4 in a mouse model of Parkinson's disease

As a deacetylase, SIRT1 plays essential roles in various physiological events, from development to lifespan regulation. SIRT1 has been shown neuroprotective effects in neurodegeneration disorders such as Parkinson's disease (PD). However, the underlying molecular mechanisms are still not well understood. Here, we generated transgenic mice with increased expression of Sirt1 in the brain and examined the potential roles of SIRT1 in PD. Our data showed that SIRT1 repressed proinflammatory cytokine expression both in microglia and astrocytes. In MPTP induced PD model mice, lower levels of microglia and astrocyte activation were observed in SIRT1 transgenic mice. Moreover, the tyrosine hydroxylase (TH) loss in the substantia nigra pars compacta (SNpc) and striatum induced by MPTP was also attenuated by SIRT1. As a consequence, the behavioral defects induced by MPTP were largely prevented in SIRT1 transgenic mice. Mechanistically, SIRT1 interacts with heat shock 70 kDa protein 4 (HSPA4) and deacetylates it at 305, 351 and 605 lysine residues. This deacetylation modification induces the nuclear translocation of HSPA4 and thus to repress proinflammatory cytokine expression. On the contrary, mutated HSPA4, in which 305/351/605 lysine residues were replaced with arginine, was mainly localized in the cytoplasm and losses its repression on proinflammatory cytokine expression. Taken together, our data indicate that SIRT1 plays beneficial roles in PD model mice, which is likely due to, at least in part, its anti-inflammation activity in glial cells by deacetylating HSPA4. Furthermore, HSPA4 might be a druggable target for developing novel agents for treating neuroinflammation associated disorders such as PD.

The heat shock response and small molecule regulators

The heat shock response (HSR) is a highly conserved cellular pathway that is responsible for stress relief and the refolding of denatured proteins [1]. When a host cell is exposed to conditions such as heat shock, ischemia, or toxic substances, heat shock factor-1 (HSF-1), a transcription factor, activates the genes that encode for the heat shock proteins (Hsps), which are a family of proteins that work alongside other chaperones to relieve stress and refold proteins that have been denatured (Burdon, 1986) [2]. Along with the refolding of denatured proteins, Hsps facilitate the removal of misfolded proteins by escorting them to degradation pathways, thereby preventing the accumulation of misfolded proteins [3]. Research has indicated that many pathological conditions, such as diabetes, cancer, neuropathy, cardiovascular disease, and aging have a negative impact on HSR function and are commonly associated with misfolded protein aggregation [4,5]. Studies indicate an interplay between mitochondrial homeostasis and HSF-1 levels can impact stress resistance, proteostasis, and malignant cell growth, which further support the role of Hsps in pathological and metabolic functions [6]. On the other hand, Hsp activation by specific small molecules can induce the heat shock response, which can afford neuroprotection and other benefits [7]. This review will focus on the modulation of Hsps and the HSR as therapeutic options to treat these conditions.

Effects of manganese on microglia M1/M2 polarization and SIRT1-mediated transcription of STAT3-dependent genes in mouse

Overexposure to manganese (Mn) can lead to neurological diseases, characterized by behavioral and motor impairments. Microglia-mediated neuroinflammation is involved in the pathogenesis and progression of neurodegenerative diseases. Microglial M1 and M2 phenotypes play pro-inflammatory and anti-inflammatory roles, respectively, in response to microenvironmental disturbances. Silent information regulator (SIRT1) has been demonstrated to play an important role in the neuroinflammatory response by deacetylating various transcription factors, such as proliferator-activated receptor γ coactivator 1α (PGC-1α), nuclear factor kappa B (NF-κB), and signal transducer and activator of transcription 3 (STAT3). In addition, PGC-1α and STAT3 have been implicated in microglial polarization and inflammatory response. In this study, Mn exposure (50, 100, 200 μmol/kg) induced neuroinflammatory injury and interfered with microglial M1/M2 polarization in mice, as indicated by the upregulated expression of M1 polarization marker mRNA (IL-1β, IL-6, TNF-α, and iNOS), whereas changes in M2 polarization markers (IL-4, TGF-β, and Arg1) varied, with some increasing and some decreasing, in response to increasing Mn doses, which was consistent with the flow cytometry results used to detect the percentages of each microglial type. We found that Mn could downregulate SIRT1 expression and activate NF-κB signaling. Following mice in the 200 μmol/kg Mn treatment, STAT3 and PGC-1α levels in the nuclear fraction both significantly decreased, and the interaction between the proteins decreased, affecting the transcription of STAT3-mediated genes. These findings provide new insights regarding the role played by Mn neurotoxicity in the suppression of neuroinflammation through the regulation of microglial polarization.

Intranasal HSP70 administration protects against dopaminergic denervation and modulates neuroinflammatory response in the 6-OHDA rat model

HSP70 is one of the main molecular chaperones involved in the cellular stress response. Besides its chaperone action, HSP70 also modulates the immune response. Increased susceptibility to toxic insults in intra- and extracellular environments has been associated with insufficient amounts of inducible HSP70 in adult neurons. On the other hand, exogenous HSP70 administration has demonstrated neuroprotective effects in experimental models of age-related disorders. In this regard, this study investigated the effects of exogenous HSP70 in an animal model of dopaminergic denervation of the nigrostriatal axis. After unilateral intrastriatal injection with 6-hydroxydopamine (6-OHDA), the animals received purified recombinant HSP70 through intranasal administration (2 μg/rat/day) for 15 days. Our results indicate a neuroprotective effect of intranasal HSP70 against dopaminergic denervation induced by 6-OHDA. Exogenous HSP70 improved motor impairment and reduced the loss of dopaminergic neurons caused by 6-OHDA. Moreover, HSP70 modulated neuroinflammatory response in the substantia nigra, an important event in Parkinson's disease pathogenesis. Specifically, HSP70 treatment reduced microglial activation and astrogliosis induced by 6-OHDA, as well as IL-1β mRNA expression in this region. Also, recombinant HSP70 increased the protein content of HSP70 in the substantia nigra of rats that received 6-OHDA. These data suggest the neuroprotection of HSP70 against dopaminergic neurons damage after cellular stress. Finally, our results indicate that HSP70 neuroprotective action against 6-OHDA toxicity is related to inflammatory response modulation.

Current Quest in Natural Bioactive Compounds for Alzheimer's Disease: Multi-Targeted-Designed-Ligand Based Approach with Preclinical and Clinical Based Evidence

Alzheimer's disease is a common and most chronic neurological disorder (NDs) associated with cognitive dysfunction. Pathologically, Alzheimer's disease (AD) is characterized by the presence of β-amyloid (Aβ) plaques, hyper-phosphorylated tau proteins, and neurofibrillary tangles, however, persistence oxidative-nitrative stress, endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory cytokines, pro-apoptotic proteins along with altered neurotransmitters level are common etiological attributes in its pathogenesis. Rivastigmine, memantine, galantamine, and donepezil are FDA approved drugs for symptomatic management of AD, whereas tacrine has been withdrawn because of hepatotoxic profile. These approved drugs only exert symptomatic relief and exhibit poor patient compliance. In the current scenario, the number of published evidence shows the neuroprotective potential of naturally occurring bioactive molecules via their antioxidant, anti-inflammatory, antiapoptotic and neurotransmitter modulatory properties. Despite their potent therapeutic implications, concerns have arisen in context to their efficacy and probable clinical outcome. Thus, to overcome these glitches, many heterocyclic and cyclic hydrocarbon compounds inspired by natural sources have been synthesized and showed improved therapeutic activity. Computational studies (molecular docking) have been used to predict the binding affinity of these natural bioactive as well as synthetic compounds derived from natural sources for the acetylcholine esterase, α/β secretase Nuclear Factor kappa- light-chain-enhancer of activated B cells (NF-kB), Nuclear factor erythroid 2-related factor 2(Nrf2) and other neurological targets. Thus, in this review, we have discussed the molecular etiology of AD, focused on the pharmacotherapeutics of natural products, chemical and pharmacological aspects and multi-targeted designed ligands (MTDLs) of synthetic and semisynthetic molecules derived from the natural sources along with some important on-going clinical trials.

SARM1 promotes neuroinflammation and inhibits neural regeneration after spinal cord injury through NF-κB signaling

Axonal degeneration is a common pathological feature in many acute and chronic neurological diseases such as spinal cord injury (SCI). SARM1 (sterile alpha and TIR motif-containing 1), the fifth TLR (Toll-like receptor) adaptor, has diverse functions in the immune and nervous systems, and recently has been identified as a key mediator of Wallerian degeneration (WD). However, the detailed functions of SARM1 after SCI still remain unclear.

Methods: Modified Allen's method was used to establish a contusion model of SCI in mice. Furthermore, to address the function of SARM1 after SCI, conditional knockout (CKO) mice in the central nervous system (CNS), SARM1^Nestin-CKO mice, and SARM1^GFAP-CKO mice were successfully generated by Nestin-Cre and GFAP-Cre transgenic mice crossed with SARM1^flox/flox mice, respectively. Immunostaining, Hematoxylin-Eosin (HE) staining, Nissl staining and behavioral test assays such as footprint and Basso Mouse Scale (BMS) scoring were used to examine the roles of SARM1 pathway in SCI based on these conditional knockout mice. Drugs such as FK866, an inhibitor of SARM1, and apoptozole, an inhibitor of heat shock protein 70 (HSP70), were used to further explore the molecular mechanism of SARM1 in neural regeneration after SCI.

Results: We found that SARM1 was upregulated in neurons and astrocytes at early stage after SCI. SARM1^Nestin-CKO and SARM1^GFAP-CKO mice displayed normal development of the spinal cords and motor function. Interestingly, conditional deletion of SARM1 in neurons and astrocytes promoted the functional recovery of behavior performance after SCI. Mechanistically, conditional deletion of SARM1 in neurons and astrocytes promoted neuronal regeneration at intermediate phase after SCI, and reduced neuroinflammation at SCI early phase through downregulation of NF-κB signaling after SCI, which may be due to upregulation of HSP70. Finally, FK866, an inhibitor of SARM1, reduced the neuroinflammation and promoted the neuronal regeneration after SCI.

Conclusion: Our results indicate that SARM1-mediated prodegenerative pathway and neuroinflammation promotes the pathological progress of SCI and anti-SARM1 therapeutics are viable and promising approaches for preserving neuronal function after SCI.

miR-124-3p Ameliorates Isoflurane-Induced Learning and Memory Impairment via Targeting STAT3 and Inhibiting Neuroinflammation

INTRODUCTION

Substantial evidence has indicated that isoflurane leads to learning and memory impairment. This study was designed to investigate the potential role of microRNA-124-3p (miR-124-3p) in isoflurane-induced learning and memory impairment in rats.

METHODS

Spatial learning and memory of rats were estimated by the Morris water maze (MWM) test after the construction of isoflurane-treated models. qRT-PCR was performed to assess the expression levels of miR-124-3p. The levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α in the hippocampal tissues were determined by enzyme-linked immunosorbent assay. The luciferase activity was determined by using a dual-luciferase reporter assay system.

RESULTS

The higher escape latency and lower time spent in the original quadrant were shown in isoflurane-treated rats compared with the control rats. Moreover, treatment with isoflurane could induce neuroinflammation, and miR-124-3p was poorly expressed in the hippocampal tissue of isoflurane-treated rats. Furthermore, STAT3 is a functional target of miR-124-3p, and inflammatory cytokine level was downregulated by miR-124-3p.

DISCUSSION/CONCLUSION

Combining the results of the current study demonstrates that miR-124-3p may have pivotal roles in improving isoflurane-induced learning and memory impairment via targeting STAT3 and inhibiting neuroinflammation.

Manganese increases Aβ and Tau protein levels through proteasome 20S and heat shock proteins 90 and 70 alteration, leading to SN56 cholinergic cell death following single and repeated treatment

Manganese (Mn) produces cholinergic neuronal loss in basal forebrain (BF) region that was related to cognitive dysfunction induced after single and repeated Mn treatment. All processes that generate cholinergic neuronal loss in BF remain to be understood. Mn exposure may produce the reduction of BF cholinergic neurons by increasing amyloid beta (Aβ) and phosphorylated Tau (pTau) protein levels, altering heat shock proteins' (HSPs) expression, disrupting proteasome P20S activity and generating oxidative stress. These mechanisms, described to be altered by Mn in regions different than BF, could lead to the memory and learning process alteration produced after Mn exposure. The research performed shows that single and repeated Mn treatment of SN56 cholinergic neurons from BF induces P20S inhibition, increases Aβ and pTau protein levels, produces HSP90 and HSP70 proteins expression alteration, and oxidative stress generation, being the last two effects mediated by NRF2 pathway alteration. The increment of Aβ and pTau protein levels was mediated by HSPs and proteasome dysfunction. All these mechanisms mediated the cell decline observed after Mn treatment. Our results are relevant because they may assist to reveal the processes leading to the neurotoxicity and cognitive alterations observed after Mn exposure.

Oxidative Stress and Neuroinflammation Potentiate Each Other to Promote Progression of Dopamine Neurodegeneration

Parkinson's disease (PD) is a chronic and complex disease of the central nervous system (CNS). Progressive loss of dopamine (DA) neurons in midbrain substantia nigra is considered to be the main cause of PD. The hallmark of PD pathology is the formation of Lewy bodies and the deposition of α-synuclein (α-syn). The mechanisms responsible for the progressive feature of DA neurodegeneration are not fully illustrated. Recently, oxidative stress and neuroinflammation have received extensive attention as two important entry points in the pathogenesis of PD. The occurrence of oxidative stress and neuroinflammation is usually derived from external influences or changes in internal environment, such as the accumulation of reactive oxygen species, exposure to a toxic environment, and the transformation of systemic inflammation. However, PD never results from a single independent factor and the simultaneous participation of oxidative stress and neuroinflammation contributed to PD development. Oxidative stress and neuroinflammation could potentiate each other to promote progression of PD. In this review, we briefly summarized the conditions of oxidative stress and neuroinflammation and the crosstalk between oxidative stress and neuroinflammation on the development of PD.

Bone marrow mesenchymal stem cells upregulate PI3K/AKT pathway and down-regulate NF-κB pathway by secreting glial cell-derived neurotrophic factors to regulate microglial polarization and alleviate deafferentation pain in rats

Deafferentation pain (DP), a typical neuropathic pain, occurs due to peripheral or central sensory nerve injury, which causes abnormal discharge of the upstream neurons or C fibers. Current treatment methods for DP have multiple side effects. Bone marrow mesenchymal stem cells (BMSC) have been used to treat neuropathic pain because of their ability to regulate neuroinflammation. Glial cell-derived neurotrophic factor (GDNF) is a neurotrophic mediator that exerts neuroprotective effects in neurological diseases. In this study, we investigated whether DP could be alleviated by BMSCs and the underlying mechanism. In vitro study, microglia was stimulated by lipopolysaccharide and then co-cultured with BMSC, GDNF or siRNA GDNF-BMSC. In vivo study, BMSC or siRNA GDNF-BMSC was transplanted intramedullarily on the 21st day after DP surgery. The expression of inflammatory-related factors were detected by RT-PCR and ELISA, RT-PCR,flow cytometry and immunofluorescence staining were performed to detect the expression of microglial surface markers, and Western blot was used to detect the expression levels of p-NF-kb, pPI3K, and pAKT. The pain-related behavioral changes were detected 7 days after transplantation. ELISA and RT-PCR results showed that the production of inflammatory cytokines in lipopolysaccharide-stimulated microglia and DP model plasma was downregulated, while anti-inflammatory mediators were upregulated significantly following pretreatment with BMSCs or GDNF. Flow cytometry, immunofluorescence staining, and RT-PCR results showed that BMSCs inhibited the microglial M1 phenotype and promoted the M2 phenotype by secreting GDNF. Furthermore, modulation functions of BMSCs involve inhibiting NF-κB while promoting PI3K /AKT signaling pathway activation. We found that our in vivo DP model was completely deafferent and BMSC administration clearly alleviated symptoms of DP. This function was also, at least partly, achieved by GDNF. The present studies demonstrate that BMSC can inhibit neuroinflammation by transforming microglial destructive M1 phenotype into regenerative M2 phenotype, and thus alleviate DP,likely by suppressing the NF-κB signaling pathway while promoting the PI3K/AKT signaling pathway activation through producing GDNF. The present findings are in support of the potential therapeutic application of BMSCs and the pharmaceutical application of GDNF for DP.

From cell lines to pluripotent stem cells for modelling Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder characterized by loss of dopaminergic (DAergic) neurons in the substantia nigra (SN) that contributes to the main motor symptoms of the disease. At present, even if several advancements have been done in the last decades, the molecular and cellular mechanisms involved in the pathogenesis are far to be fully understood. Accordingly, the establishment of reliable in vitro experimental models to investigate the early events of the pathogenesis represents a key issue in the field. However, to mimic and reproduce in vitro the complex neuronal circuitry involved in PD-associated degeneration of DAergic neurons still remains a highly challenging issue. Here we will review the in vitro PD models used in the last 25 years of research, ranging from cell lines, primary rat or mice neuronal cultures to the more recent use of human induced pluripotent stem cells (hiPSCs) and, finally, the development of 3D midbrain organoids.