Salidroside Protects Against 6-Hydroxydopamine-Induced Cytotoxicity by Attenuating ER Stress

Effect of salidroside on neuroprotection and psychiatric sequelae during the COVID-19 pandemic: A review

The coronavirus disease 2019 (COVID-19) pandemic has affected the mental health of individuals worldwide, and the risk of psychiatric sequelae and consequent mental disorders has increased among the general population, health care workers and patients with COVID-19. Achieving effective and widespread prevention of pandemic-related psychiatric sequelae to protect the mental health of the global population is a serious challenge. Salidroside, as a natural agent, has substantial pharmacological activity and health effects, exerts obvious neuroprotective effects, and may be effective in preventing and treating psychiatric sequelae and mental disorders resulting from stress stemming from the COVID-19 pandemic. Herein, we systematically summarise, analyse and discuss the therapeutic effects of salidroside in the prevention and treatment of psychiatric sequelae as well as its roles in preventing the progression of mental disorders, and fully clarify the potential of salidroside as a widely applicable agent for preventing mental disorders caused by stress; the mechanisms underlying the potential protective effects of salidroside are involved in the regulation of the oxidative stress, neuroinflammation, neural regeneration and cell apoptosis in the brain, the network homeostasis of neurotransmission, HPA axis and cholinergic system, and the improvement of synaptic plasticity. Notably, this review innovatively proposes that salidroside is a potential agent for treating stress-induced health issues during the COVID-19 pandemic and provides scientific evidence and a theoretical basis for the use of natural products to combat the current mental health crisis.

The Therapeutic Potential of Salidroside for Parkinson's Disease

Parkinson's disease (PD), a neurological disorder, is characterized by the progressive loss of dopaminergic (DA) neurons in the substantia nigra. Its incidence increases with age. Salidroside, a phenolic compound extracted from Sedum roseum, reportedly has multiple biological and pharmacological activities in the nervous system. However, its effects on PD remain unclear. In this review, we summarize the effects of salidroside on PD with regard to DA metabolism, neuronal protection, and glial activation. In addition, we summarize the susceptibility genes and their underlying mechanisms related to antioxidation, inflammation, and autophagy by regulating mitochondrial function, ubiquitin, and multiple signaling pathways involving NF-κB, mTOR, and PI3K/Akt. Although recent studies were based on animal and cellular experiments, this review provides evidence for further clinical utilization of salidroside for PD.

Chaperone-Dependent Mechanisms as a Pharmacological Target for Neuroprotection

Modern pharmacotherapy of neurodegenerative diseases is predominantly symptomatic and does not allow vicious circles causing disease development to break. Protein misfolding is considered the most important pathogenetic factor of neurodegenerative diseases. Physiological mechanisms related to the function of chaperones, which contribute to the restoration of native conformation of functionally important proteins, evolved evolutionarily. These mechanisms can be considered promising for pharmacological regulation. Therefore, the aim of this review was to analyze the mechanisms of endoplasmic reticulum stress (ER stress) and unfolded protein response (UPR) in the pathogenesis of neurodegenerative diseases. Data on BiP and Sigma1R chaperones in clinical and experimental studies of Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease are presented. The possibility of neuroprotective effect dependent on Sigma1R ligand activation in these diseases is also demonstrated. The interaction between Sigma1R and BiP-associated signaling in the neuroprotection is discussed. The performed analysis suggests the feasibility of pharmacological regulation of chaperone function, possibility of ligand activation of Sigma1R in order to achieve a neuroprotective effect, and the need for further studies of the conjugation of cellular mechanisms controlled by Sigma1R and BiP chaperones.

Unveiling sex-based differences in Parkinson's disease: a comprehensive meta-analysis of transcriptomic studies

BACKGROUND

In recent decades, increasing longevity (among other factors) has fostered a rise in Parkinson's disease incidence. Although not exhaustively studied in this devastating disease, the impact of sex represents a critical variable in Parkinson's disease as epidemiological and clinical features differ between males and females.

METHODS

To study sex bias in Parkinson's disease, we conducted a systematic review to select sex-labeled transcriptomic data from three relevant brain tissues: the frontal cortex, the striatum, and the substantia nigra. We performed differential expression analysis on each study chosen. Then we summarized the individual differential expression results with three tissue-specific meta-analyses and a global all-tissues meta-analysis. Finally, results from the meta-analysis were functionally characterized using different functional profiling approaches.

RESULTS

The tissue-specific meta-analyses linked Parkinson's disease to the enhanced expression of MED31 in the female frontal cortex and the dysregulation of 237 genes in the substantia nigra. The global meta-analysis detected 15 genes with sex-differential patterns in Parkinson's disease, which participate in mitochondrial function, oxidative stress, neuronal degeneration, and cell death. Furthermore, functional analyses identified pathways, protein-protein interaction networks, and transcription factors that differed by sex. While male patients exhibited changes in oxidative stress based on metal ions, inflammation, and angiogenesis, female patients exhibited dysfunctions in mitochondrial and lysosomal activity, antigen processing and presentation functions, and glutamic and purine metabolism. All results generated during this study are readily available by accessing an open web resource ( http://bioinfo.cipf.es/metafun-pd/ ) for consultation and reuse in further studies.

CONCLUSIONS

Our in silico approach has highlighted sex-based differential mechanisms in typical Parkinson Disease hallmarks (inflammation, mitochondrial dysfunction, and oxidative stress). Additionally, we have identified specific genes and transcription factors for male and female Parkinson Disease patients that represent potential candidates as biomarkers to diagnosis.

A Cecropin-4 Derived Peptide C18 Inhibits Candida albicans by Disturbing Mitochondrial Function

Global burden of fungal infections and related health risk has accelerated at an incredible pace, and multidrug resistance emergency aggravates the need for the development of new effective strategies. Candida albicans is clinically the most ubiquitous pathogenic fungus that leads to high incidence and mortality in immunocompromised patients. Antimicrobial peptides (AMPs), in this context, represent promising alternatives having potential to be exploited for improving human health. In our previous studies, a Cecropin-4-derived peptide named C18 was found to possess a broader antibacterial spectrum after modification and exhibit significant antifungal activity against C. albicans. In this study, C18 shows antifungal activity against C. albicans or non-albicans Candida species with a minimum inhibitory concentration (MIC) at 4∼32 μg/ml, and clinical isolates of fluconazole (FLZ)-resistance C. tropicalis were highly susceptible to C18 with MIC value of 8 or 16 μg/ml. Additionally, C18 is superior to FLZ for killing planktonic C. albicans from inhibitory and killing kinetic curves. Moreover, C18 could attenuate the virulence of C. albicans, which includes damaging the cell structure, retarding hyphae transition, and inhibiting biofilm formation. Intriguingly, in the Galleria mellonella model with C. albicans infection, C18 could improve the survival rate of G. mellonella larvae to 70% and reduce C. albicans load from 5.01 × 107 to 5.62 × 104 CFU. For mechanistic action of C18, the level of reactive oxygen species (ROS) generation and cytosolic Ca2 + increased in the presence of C18, which is closely associated with mitochondrial dysfunction. Meanwhile, mitochondrial membrane potential (△Ψm) loss and ATP depletion of C. albicans occurred with the treatment of C18. We hypothesized that C18 might inhibit C. albicans via triggering mitochondrial dysfunction driven by ROS generation and Ca2 + accumulation. Our observation provides a basis for future research to explore the antifungal strategies and presents C18 as an attractive therapeutic candidate to be developed to treat candidiasis.

Mini review ATF4 and GRP78 as novel molecular targets in ER-Stress modulation for critical COVID-19 patients

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has resulted in more than 4.4 million deaths worldwide as of August 24, 2021. Viral infections such as SARS-CoV2 are associated with endoplasmic reticulum (ER) stress and also increased the level of reactive oxygen species. Activating transcription factor 4 (ATF4) is preferentially translated under integrated stress conditions and controls the genes involved in protein homeostasis, amino acid transport and metabolism, and also protection from oxidative stress. The GRP78, regulated either directly or indirectly by ATF4, is an essential chaperone in the ER and overexpressed and appears on the surface of almost all cells during stress and function as a SARS-CoV2 receptor. In this mini-review article, we briefly discuss the effects of SARS-CoV2 infection on the ER stress, and then the stress modulator functions of ATF4 and GRP78 as novel therapeutic targets were highlighted. Finally, the effects of GRP78 inhibitory components as potential factors for targeted therapies for COVID-19 critical cases were discussed.

Endoplasmic reticulum stress associates with the development of intervertebral disc degeneration

Endoplasmic reticulum (ER) is an important player in various intracellular signaling pathways that regulate cellular functions in many diseases. Intervertebral disc degeneration (IDD), an age-related degenerative disease, is one of the main clinical causes of low back pain. Although the pathological development of IDD is far from being fully elucidated, many studies have been shown that ER stress (ERS) is involved in IDD development and regulates various processes, such as inflammation, cellular senescence and apoptosis, excessive mechanical loading, metabolic disturbances, oxidative stress, calcium homeostasis imbalance, and extracellular matrix (ECM) dysregulation. This review summarizes the formation of ERS and the potential link between ERS and IDD development. ERS can be a promising new therapeutic target for the clinical management of IDD.

Plant-microbial interaction: The mechanism and the application of microbial elicitor induced secondary metabolites biosynthesis in medicinal plants

Plants and microbes interact with each other via different chemical signaling pathways. At the risophere level, the microbes can secrete molecules, called elicitors, which act on their receptors located in plant cells. The so-called elicitor molecules as well as their actions differ according to the mcirobes and induce different bilogical responses in plants such as the synthesis of secondary metabolites. Microbial compounds induced phenotype changes in plants are known as elicitors and signaling pathways which integrate elicitor's signals in plants are called elicitation. In this review, the impact of microbial elicitors on the synthesis and the secretion of secondary metabolites in plants was highlighted. Moreover, biological properties of these bioactive compounds were also highlighted and discussed. Indeed, several bacteria, fungi, and viruses release elicitors which bind to plant cell receptors and mediate signaling pathways involved in secondary metabolites synthesis. Different phytochemical classes such as terpenoids, phenolic acids and flavonoids were synthesized and/or increased in medicinal plants via the action of microbial elicitors. Moreover, these compounds compounds exhibit numerous biological activities and can therefore be explored in drugs discovery.

Potential therapeutic compounds from traditional Chinese medicine targeting endoplasmic reticulum stress to alleviate rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease which affects about 0.5-1% of people with symptoms that significantly impact a sufferer's lifestyle. The cells involved in propagating RA tend to display pro-inflammatory and cancer-like characteristics. Medical drug treatment is currently the main avenue of RA therapy. However, drug options are limited due to severe side effects, high costs, insufficient disease retardation in a majority of patients, and therapeutic effects possibly subsiding over time. Thus there is a need for new drug therapies. Endoplasmic reticulum (ER) stress, a condition due to accumulation of misfolded proteins in the ER, and subsequent cellular responses have been found to be involved in cancer and inflammatory pathologies, including RA. ER stress protein markers and their modulation have therefore been suggested as therapeutic targets, such as GRP78 and CHOP, among others. Some current RA therapeutic drugs have been found to have ER stress-modulating properties. Traditional Chinese Medicines (TCMs) frequently use natural products that affect multiple body and cellular targets, and several medicines and/or their isolated compounds have been found to also have ER stress-modulating capabilities, including TCMs used in RA treatment by Chinese Medicine practitioners. This review encourages, in light of the available information, the study of these RA-treating, ER stress-modulating TCMs as potential new pharmaceutical drugs for use in clinical RA therapy, along with providing a list of other ER stress-modulating TCMs utilized in treatment of cancers, inflammatory diseases and other diseases, that have potential use in RA treatment given similar ER stress-modulating capacity.

Salidroside: A review of its recent advances in synthetic pathways and pharmacological properties

Salidroside has been identified as one of the most potent compounds isolated from various Rhodiola plants, which have been used for a long time as adaptogens in traditional Chinese medicine. However, due to the severe growing environment of herbal medicine and large-scale excavation, the content of natural salidroside is extremely small. Most of the previous studies focused on herbal medicine, and there were few reviews on the synthesis of its main active ingredient salidroside. This paper presents different synthetic routes of salidroside to resolve the contradiction between supply and demand and lays the foundation for new drug research and development. Furthermore, emerging evidence indicates that salidroside, a promising environmentally-adapted drug with low toxicity and few side effects, possesses a wide spectrum of pharmacological properties, including activities on the cardiovascular system and central nervous system, anti-hypoxia, anti-fatigue and anti-aging activities, anticancer activity, anti-inflammatory activity, antioxidant activity, antivirus and immune stimulation activities, antidiabetic activity, anti-osteoporotic activity, and so on. Although the former researches have summarized the pharmacological effects of salidroside, focusing on the central nervous system, diabetes, and cancer, the overall pharmacological aspects of it have not been analyzed. This review highlights biological characteristics and mechanisms of action from 2009 to now as well as toxicological and pharmacokinetic data of the analyzed compound reported so far, with a view to providing a reference for further development and utilization of salidroside.

Salidroside alleviated hypoxia-induced liver injury by inhibiting endoplasmic reticulum stress-mediated apoptosis via IRE1α/JNK pathway

Endoplasmic reticulum (ER) stress and subsequent apoptosis played vital role in liver injury and dysfunction. The aim of this study was to investigate the protective effect and mechanism of salidroside on hypoxia induced liver injury both in vivo and in vitro. Male SD rats were exposed to hypobaric chamber to simulate high altitude hypoxia model. High altitude hypoxia led to significant liver injury and apoptosis, increased the expression levels of p-JNK, BAX and ER stress markers. Salidroside treatment significantly inhibited hypoxia induced ER stress by decreasing the protein expression of glucose-regulated protein 78 (GRP78), CCAAT/enhancer binding protein homologous protein (CHOP) and phosphorylated inositol-requiring enzyme 1α (p-IRE1α). In addition, salidroside treatment also restrained the ER stress-mediated apoptotic pathway, as indicated by decreased pro-apoptotic proteins p-JNK, TRAF2, BAX, and cleaved caspase 9 and caspase 12, as well as upregulation of Bcl-2. Furthermore, in vitro study found that blocking IRE1α pathway using specific inhibitor STF-083010 subsequently reversed the protective effect of salidroside on liver apoptosis. Taken together, our findings revealed that salidroside exerts protective effects against hypoxia induced liver injury through inhibiting ER stress mediated apoptosis via IRE1α/JNK pathway.

Protective Evaluation of Compounds Extracted from Root of Rhodiola rosea L. against Methylglyoxal-Induced Toxicity in a Neuronal Cell Line

Rhodiola rosea L. (R. rosea) is one of the most beneficial medicinal plants and it is studied as an adaptogen. This study aims to evaluate the neuroprotective activity of compounds extracted from the root of R. rosea against methylglyoxal (MG)-induced apoptosis in neuro-2A (N2A) cells. The root of R. rosea was extracted with ethanol and partitioned with water, ethyl acetate, and n-butanol fractions to evaluate acetylcholinesterase (AChE) inhibitory activity and neuroprotective activity. The ethyl acetate fraction exhibited the highest values of AChE inhibitory activity (49.2% ± 3%) and cell viability (50.7% ± 4.8%) for neuroprotection. The structure identification of the most potential fraction (ethyl acetate fraction) revealed 15 compounds, consisting of three tannins, five flavonoids, and seven phenolics by infrared spectroscopy, nuclear magnetic resonance, and mass spectroscopy. All compounds were evaluated for their neuroprotective activity. Salidroside had the most potential neuroprotective activity. Gallic acid and methyl gallate had potential cytotoxicity in N2A cells. This study showed that R. rosea might have potential neuroprotective activities.

Salidroside suppresses the metastasis of hepatocellular carcinoma cells by inhibiting the activation of the Notch1 signaling pathway

Salidroside (SDS) is a phenylpropanoid glycoside isolated from Rhodiola rosea L. It exhibits multiple pharmacological properties in clinical medicine and has been commonly used in traditional Chinese medicine. The present study investigated the inhibitory effects of SDS on tumor invasion and migration, and the expression of metastasis‑related genes in highly metastatic hepatocellular carcinoma (HCC) cells (MHCC97H) in vitro. The underlying mechanisms of SDS on the tumor metastasis were also explored. SDS was found to significantly reduce wound closure areas and inhibit cell migration. In addition, SDS markedly inhibited the invasion of these cells into Matrigel‑coated membranes. SDS markedly downregulated the expression of Notch1, Snail, COX‑2, MMP‑2, MMP‑9 genes and upregulated the expression of E‑cadherin in a dose‑dependent manner. Furthermore, SDS inhibited the expression of the Notch signaling target genes, Hey1, Hes1 and Hes5. On the whole, the findings of this study suggest that SDS inhibits HCC cell metastasis by modulating the activity of the Notch1 signaling pathway.

GRP78/BIP/HSPA5 as a Therapeutic Target in Models of Parkinson's Disease: A Mini Review

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by selective loss of dopamine neurons in the substantia nigra pars compacta of the midbrain. Reports from postmortem studies in the human PD brain, and experimental PD models reveal that endoplasmic reticulum (ER) stress is implicated in the pathogenesis of PD. In times of stress, the unfolded or misfolded proteins overload the folding capacity of the ER to induce a condition generally known as ER stress. During ER stress, cells activate the unfolded protein response (UPR) to handle increasing amounts of abnormal proteins, and recent evidence has demonstrated the activation of the ER chaperone GRP78/BiP (78 kDa glucose-regulated protein/binding immunoglobulin protein), which is important for proper folding of newly synthesized and partly folded proteins to maintain protein homeostasis. Although the activation of this protein is essential for the initiation of the UPR in PD, there are inconsistent reports on its expression in various PD models. Consequently, this review article aims to summarize current knowledge on neuroprotective agents targeting the expression of GRP78/BiP in the regulation of ER stress in experimental PD models.

Salidroside stimulates the Sirt1/PGC-1α axis and ameliorates diabetic nephropathy in mice

BACKGROUND

Salidroside, an active component from Traditional Chinese Medicine Rhodiola rosea L., has various pharmacological functions including anti-inflammatory, anti-cancer and anti-oxidative properties. However, whether salidroside plays a beneficial role in diabetic nephropathy is still unclear.

PURPOSE

The objective of this work was to investigate the potential roles of salidroside against diabetic nephropathy and the underlying molecular mechanisms.

METHODS

Streptozocin was given to obese mice to generate diabetic nephropathy animal model. Salidroside was administered to these mice and proteinuria, podocyte integrity, renal morphology and fibrosis, mitochondrial biogenesis were examined.

RESULTS

Our results showed that salidroside treatment greatly attenuates diabetic nephropathy as evidenced by decreased urinary albumin, blood urea nitrogen and serum creatinine. Morphological analysis indicated that salidroside improves renal structures in diabetic nephropathy. The decreases in nephrin and podocin expression were markedly reversed by salidroside. Moreover, kidney fibrosis in diabetic nephropathy mice was largely prevented by salidroside. Mechanistically, in salidroside-treated mice, the mitochondrial DNA copy and electron transport chain proteins were significantly enhanced. Meanwhile, the reduced Sirt1 and PGC-1α expression in diabetic nephropathy was almost completely counteracted in the presence of salidroside.

CONCLUSIONS

Our data showed that salidroside plays a beneficial role against diabetic nephropathy in mice, which probably via Sirt1/PGC-1α mediated mitochondrial biogenesis.

Salidroside mitigates hypoxia/reoxygenation injury by alleviating endoplasmic reticulum stress‑induced apoptosis in H9c2 cardiomyocytes

Endoplasmic reticulum (ER) stress‑induced apoptosis serves a crucial role in the development of myocardial ischemia/reperfusion (I/R) injury. Salidroside is a phenylpropanoid glycoside isolated from Rhodiola rosea L., which is a plant often used in traditional Chinese medicine. It possesses multiple pharmacological actions and protects against myocardial I/R injury in vitro and in vivo. However, it is not yet clear whether ER stress or ER stress‑induced apoptosis contributes to the cardioprotective effects of salidroside against myocardial I/R injury. Hence, hypoxia/reoxygenation (H/R)‑treated H9c2 cardiomyocytes were used in the current study to mimic myocardium I/R injury in vivo. It was hypothesized that salidroside alleviates ER stress and ER stress‑induced apoptosis, thereby reducing H/R injury in H9c2 cells. The results demonstrated that salidroside attenuated H/R‑induced H9c2 cardiomyocyte injury, as cell viability was increased, lactate dehydrogenase release was decreased, morphological changes in apoptotic cells were ameliorated and the apoptosis ratio was reduced compared with the H/R group. ER stress was reversed, indicated by the downregulation of glucose regulated protein 78 and C/EBP homologous protein following pretreatment with salidroside. In addition, salidroside attenuated ER stress‑induced apoptosis, as the expression of cleaved caspase‑12 and pro‑apoptotic protein Bcl‑2 associated X protein and activity of caspase‑3 was decreased, while the expression of anti‑apoptotic protein Bcl‑2 was increased following pretreatment with salidroside. Furthermore, the results indicated that salidroside decreases the activation of the ER stress‑associated signaling pathway, as the expression of phosphorylated protein kinase RNA (PKR)‑like ER kinase (p‑PERK) and phosphorylated inositol‑requiring enzyme‑1α (p‑IRE1α) proteins were decreased following pretreatment with salidroside. These results demonstrate that salidroside protects against H/R injury via regulation of the PERK and IRE1α pathways, resulting in alleviation of ER stress or ER stress‑induced apoptosis in H9c2 cardiomyocytes.

Long-term social isolation inhibits autophagy activation, induces postsynaptic dysfunctions and impairs spatial memory

. Moreover, we found that L-PWSI increased the protein expression of p-AKT/AKT, p-mTOR/mTOR and p62, whereas the protein levels of LC3B and Beclin1 were decreased indicating an inhibition in autophagy activity. Intraperitoneal injection of rapamycin significantly potentiated fEPSP slope and cognition-related proteins expression in the L-PWSI mice. These results therefore suggest that L-PWSI induces postsynaptic dysfunction by disrupting the interaction between AMPAR, NMDAR and PSD-95, and inhibit the autophagy activity which led to impaired spatial memory and cognitive function.

Loss of VAPB Regulates Autophagy in a Beclin 1-Dependent Manner

Autophagy is an evolutionarily-conserved self-degradative process that maintains cellular homeostasis by eliminating protein aggregates and damaged organelles. Recently, vesicle-associated membrane protein-associated protein B (VAPB), which is associated with the familial form of amyotrophic lateral sclerosis, has been shown to regulate autophagy. In the present study, we demonstrated that knockdown of VAPB induced the up-regulation of beclin 1 expression, which promoted LC3 (microtubule-associated protein light chain 3) conversion and the formation of LC3 puncta, whereas overexpression of VAPB inhibited these processes. The regulation of beclin 1 by VAPB was at the transcriptional level. Moreover, knockdown of VAPB increased autophagic flux, which promoted the degradation of the autophagy substrate p62 and neurodegenerative disease proteins. Our study provides evidence that the regulation of autophagy by VAPB is associated with the autophagy-initiating factor beclin 1.

Dopaminergic neurons show increased low-molecular-mass protein 7 activity induced by 6-hydroxydopamine in vitro and in vivo

Background

Abnormal expression of major histocompatibility complex class I (MHC-I) is increased in dopaminergic (DA) neurons in the substantia nigra (SN) in Parkinson’s disease (PD). Low-molecular-mass protein 7 (β5i) is a proteolytic subunit of the immunoproteasome that regulates protein degradation and the MHC pathway in immune cells.

Methods

In this study, we investigated the role of β5i in DA neurons using a 6-hydroxydopamine (6-OHDA) model in vitro and vivo.

Results

We showed that 6-OHDA upregulated β5i expression in DA neurons in a concentration- and time-dependent manner. Inhibition and downregulation of β5i induced the expression of glucose-regulated protein (Bip) and exacerbated 6-OHDA neurotoxicity in DA neurons. The inhibition of β5i further promoted the activation of Caspase 3-related pathways induced by 6-OHDA. β5i also activated transporter associated with antigen processing 1 (TAP1) and promoted MHC-I expression on DA neurons.

Conclusion

Taken together, our data suggest that β5i is activated in DA neurons under 6-OHDA treatment and may play a neuroprotective role in PD.

Electronic supplementary material

The online version of this article (10.1186/s40035-018-0125-9) contains supplementary material, which is available to authorized users.

Salidroside protects renal tubular epithelial cells from hypoxia/reoxygenation injury in vitro

Oxidative stress, inflammation and cell apoptosis are important mechanisms of renal ischemia/reperfusion (I/R) injury. Salidroside, a natural phenylpropanoid glycoside, possesses anti-inflammatory, anti-oxidative, and anti-apoptotic effects. However, the effect of salidroside on renal I/R injury has not been fully elucidated. The present study aimed to investigate the effect of salidroside on renal I/R injury in vitro. Our results showed that salidroside improved the viability of human renal tubular epithelial cells (HK-2) in response to hypoxia/reoxygenation (H/R). Salidroside caused apparent decrease in the levels of reactive oxygen species (ROS) and malondiaidehyde (MDA), and significant increase in superoxide dismutase (SOD) activity in HK-2 cells. Pretreatment with salidroside markedly inhibited the production levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 in a dose-dependent manner. Salidroside treatment exhibited significant increase in Bcl-2 expressions, and decrease in Bax expressions and caspase-3 activity when compared with the H/R group. Salidroside decreased the levels of toll-like receptor 4 (TLR4) and p-p65 in HK-2 cells. Overexpression of TLR4 significantly attenuated the effects of salidroside on cell viability, oxidative stress, cytokine production and cell apoptosis in HK-2 cells. These findings indicated that salidroside protected HK-2 cells from H/R stimulation, which was mediated by the TLR4/NF-κB pathway.

Pharmacological activities, mechanisms of action, and safety of salidroside in the central nervous system

The primary objective of this review article was to summarize comprehensive information related to the neuropharmacological activity, mechanisms of action, toxicity, and safety of salidroside in medicine. A number of studies have revealed that salidroside exhibits neuroprotective activities, including anti-Alzheimer's disease, anti-Parkinson's disease, anti-Huntington's disease, anti-stroke, anti-depressive effects, and anti-traumatic brain injury; it is also useful for improving cognitive function, treating addiction, and preventing epilepsy. The mechanisms underlying the potential protective effects of salidroside involvement are the regulation of oxidative stress response, inflammation, apoptosis, hypothalamus-pituitary-adrenal axis, neurotransmission, neural regeneration, and the cholinergic system. Being free of side effects makes salidroside potentially attractive as a candidate drug for the treatment of neurological disorders. It is evident from the available published literature that salidroside has potential use as a beneficial therapeutic medicine with high efficacy and low toxicity to the central nervous system. However, the definite target protein molecules remain unclear, and clinical trials regarding this are currently insufficient; thus, guidance for further research on the molecular mechanisms and clinical applications of salidroside is urgent.

Salidroside Promotes the Pathological α-Synuclein Clearance Through Ubiquitin-Proteasome System in SH-SY5Y Cells

Parkinson's disease (PD) is characterized by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc) and the presence of Lewy bodies (LBs) in the surviving SNc neurons. LBs formation is caused by the accumulation of α-synuclein (α-syn) or phosphorylated α-syn at serine-129 (pSer129-α-syn), which is implicated in the pathological progression of PD. Salidroside (Sal), the main active ingredient of the root of Rhodiola rosea L., has been reported to have potent neuroprotective properties in our previous investigations. Here, we investigated the effects of Sal on 6-OHDA and overexpresssion of WT/A30P-α-syn-induced pathological α-syn increase and the mechanism behind it in SH-SY5Y cells. We found Sal displays neuroprotective effects against 6-hydroxydopamine (6-OHDA)-induced cytotoxicity. Sal decreased the pSer129-α-syn level mainly by maintaining the normal function of ubiquitin-proteasome system (UPS). Furthermore, Sal promoted the clearance of α-syn and protected the cell viability mainly through recovered the 20S proteasome activity in WT/A30P-α-syn-transfected cells. These data provide new mechanistic insights into the neuroprotective effects of Sal and Sal may be a promising therapy to slow neurodegeneration in PD. Highlights: Sal protects cells and decreases the pSer129-α-syn protein level in 6-OHDA-induced impairmental and dysfunctional SH-SY5Y cells. Sal promotes the clearance of α-syn and protects the cell viability mainly through recovering the 20S proteasome activity in WT/A30P-α-syn plasmids transfected cells. Maintaining the normal function of the UPS may be one of the important mechanisms of Sal in neuroprotective effects.

Influence of salidroside, a neuroactive compound of Rhodiola rosea L., on alcohol tolerance development in rats

Introduction: In recent years, the search for potential neuroprotective properties of salidroside and its ability to influence the activity of nervous system become the subject of intense studies of many research groups. None of these studies, however, include an attempt to determine the effect of salidroside on the course of alcohol tolerance in vivo.

Objective: The aim of this study was to investigate the ability of salidroside to inhibit the development of alcohol tolerance in rats, determining whether the effect of its action may occur in a dose-dependent manner, reducing both metabolic and central tolerance without affecting body temperature in control rats.

Methods: Male Wistar rats were injected daily with ethanol at a dose of 3 g/kg for 9 consecutive days to produce ethanol tolerance. Salidroside in two doses (4.5 mg/kg and 45 mg/kg b.w.) or vehiculum was administered orally. On the 1st, 3rd, 5th and 8th day a hypothermic effect of ethanol was measured, while the loss of righting reflex procedure was performed on the 2nd, 4th, 6th and 7th day. On the 9th day rats were treated with salidroside, sacrificed 1 h after ethanol injections and blood was collected for blood-ethanol concentration measurement.

Results: Salidroside at a dose of 45 mg/kg inhibited the development of tolerance to hypothermic and sedative effects of ethanol, whereas insignificant elevation of blood-ethanol concentration was observed. The dose of 4.5 mg/kg b.w. had minimal effect, only small inhibition of tolerance to hypothermic action was observed. Salidroside affected neither body mass growth nor body temperature in non-alcoholic (control) rats.

Conclusions: Results of the study indicate that salidroside at a dose of 45 mg/kg inhibited the development of tolerance to the hypothermic effect of ethanol. Observed inhibition of tolerance to the sedative effect of ethanol seems to be associated with salidroside influence on the central nervous system. A comprehensive explanation of the abovementioned observations requires further pharmacological and pharmacodynamic studies.

Electroacupuncture Alleviates Motor Symptoms and Up-Regulates Vesicular Glutamatergic Transporter 1 Expression in the Subthalamic Nucleus in a Unilateral 6-Hydroxydopamine-Lesioned Hemi-Parkinsonian Rat Model

Previous studies have shown that electroacupuncture (EA) promotes recovery of motor function in Parkinson's disease (PD). However the mechanisms are not completely understood. Clinically, the subthalamic nucleus (STN) is a critical target for deep brain stimulation treatment of PD, and vesicular glutamate transporter 1 (VGluT1) plays an important role in the modulation of glutamate in the STN derived from the cortex. In this study, a 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD was treated with 100 Hz EA for 4 weeks. Immunohistochemical analysis of tyrosine hydroxylase (TH) showed that EA treatment had no effect on TH expression in the ipsilateral striatum or substantia nigra pars compacta, though it alleviated several of the parkinsonian motor symptoms. Compared with the hemi-parkinsonian rats without EA treatment, the 100 Hz EA treatment significantly decreased apomorphine-induced rotation and increased the latency in the Rotarod test. Notably, the EA treatment reversed the 6-OHDA-induced down-regulation of VGluT1 in the STN. The results demonstrated that EA alleviated motor symptoms and up-regulated VGluT1 in the ipsilateral STN of hemi-parkinsonian rats, suggesting that up-regulation of VGluT1 in the STN may be related to the effects of EA on parkinsonian motor symptoms via restoration of function in the cortico-STN pathway.

Familial Parkinson's Disease-Associated L166P Mutant DJ-1 is Cleaved by Mitochondrial Serine Protease Omi/HtrA2

Parkinson's disease (PD) is the most common neurodegenerative movement disorder. Mutations in the DJ-1, including L166P, are responsible for recessive early-onset PD. Many lines of evidence have shown that L166P is not only a loss-of-function mutant, but also a pro-apoptotic-like protein that results in mitochondrial dysfunction. L166P has been reported to be unstable and to mislocalize to mitochondria. However, the mechanisms underlying the instability of L166P compared to wild-type DJ-1 remain largely unknown. Here, we showed that Omi/HtrA2, a mitochondrial serine protease that has also been linked to the pathogenesis of PD, contributed to L166P instability. Omi directly interacted with and cleaved L166P in mitochondria to decrease the L166P level. However, Omi did not bind and cleave wild-type DJ-1. Moreover, Omi cleaved L166P at both serine residues 3 and 121, while L166P-induced cell death under H₂O₂ treatment was alleviated by over-expression of Omi. Our data reveal a bridge between DJ-1 and Omi, two PD-associated genetic factors, which contributes to our understanding of the pathogenesis of PD.

SIRT1 mediates salidroside-elicited protective effects against MPP+ -induced apoptosis and oxidative stress in SH-SY5Y cells: involvement in suppressing MAPK pathways

Parkinson's disease (PD) is a progressive neurodegenerative disease, leading to tremor, rigidity, bradykinesia, and gait impairment. Salidroside has been reported to exhibit antioxidative and neuroprotective properties in PD. However, the underlying neuroprotective mechanisms effects of salidroside are poorly understood. Recently, a growing body of evidences suggest that silent information regulator 1 (SIRT1) plays important roles in the pathophysiology of PD. Hence, the present study investigated the roles of SIRT1 in neuroprotective effect of salidroside against N-methyl-4-phenylpyridinium (MPP⁺ )-induced SH-SY5Y cell injury. Our findings revealed that salidroside attenuates MPP⁺ -induced neurotoxicity as evidenced by the increase in cell viability, and the decreases in the caspase-3 activity and apoptosis ratio. Simultaneously, salidroside pretreatment remarkably increased SIRT1 activity, SIRT1 mRNA and protein levels in MPP⁺ -treated SH-SY5Y cell. However, sirtinol, a SIRT1 activation inhibitor, significantly blocked the inhibitory effects of salidroside on MPP⁺ -induced cytotoxicity and apoptosis. In addition, salidroside abolished MPP⁺ -induced the production of reactive oxygen species (ROS), the up-regulation of NADPH oxidase 2 (NOX2) expression, the down-regulations of superoxide dismutase (SOD) activity and glutathione (GSH) level in SH-SY5Y cells, while these effects were also blocked by sirtinol. Finally, we found that the inhibition of salidroside on MPP⁺ -induced phosphorylation of p38, extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) were also reversed by sirtinol in SH-SY5Y cells. Taken together, these results indicated that SIRT1 contributes to the neuroprotection of salidroside against MPP⁺ -induced apoptosis and oxidative stress, in part through suppressing of mitogen-activated protein kinase (MAPK) pathways.

Transcription Factors: Potential Cell Death Markers in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disease with a long preclinical phase. The continuous loss of dopaminergic (DA) neurons is one of the pathogenic hallmarks of PD. Diagnosis largely depends on clinical observation, but motor dysfunctions do not emerge until 70%-80% of the nigrostriatal nerve terminals have been destroyed. Therefore, a biomarker that indicates the degeneration of DA neurons is urgently needed. Transcription factors are sequence-specific DNA-binding proteins that regulate RNA synthesis from a DNA template. The precise control of gene expression plays a critical role in the development, maintenance, and survival of cells, including DA neurons. Deficiency of certain transcription factors has been associated with DA neuron loss and PD. In this review, we focus on some transcription factors and discuss their structure, function, mechanisms of neuroprotection, and their potential for use as biomarkers indicating the degeneration of DA neurons.