Salidroside stimulates DNA repair enzyme Parp-1 activity in mouse HSC maintenance

Salidroside prevents cadmium chloride-induced DNA damage in human fetal lung fibroblasts

BACKGROUND

Cadmium (Cd) is an environmental pollutant and a heavy metal known for its genotoxic effects, which can lead to cancer and other related diseases. Preventing Cd-induced genotoxicity is crucial; however, there is limited research on this topic. Salidroside (SAL), a phenylpropanoid glycoside isolated from Rhodiola rosea L., is a popular medicinal compound with several health benefits. Nevertheless, its therapeutic effect on Cd-induced genotoxicity remains unexplored.

METHODS

Human fetal lung fibroblasts were treated with 20 μM Cd2+ (CdCl2) for 12 h and 5-20 μM SAL was used to test the anti-DNA damage effect. DNA damage was evaluated using γH2AX expression and the alkaline comet assay. Intracellular reactive oxygen species (ROS) levels were measured using flow cytometry.

RESULTS

Exposure to 20 μM Cd2+ for 12 h induced significant DNA damage in human fetal lung fibroblasts, and this effect was notably attenuated by SAL treatment. SAL treatment did not decrease ROS levels in cells treated with Cd2+.

CONCLUSION

SAL effectively prevented Cd2+-induced DNA damage in human fetal lung fibroblasts. However, the underlying mechanism requires further investigation.

Exploring the therapeutic implications of natural compounds modulating apoptosis in vascular dementia

Vascular dementia (VaD) is a prevalent form of dementia stemming from cerebrovascular disease, manifesting in memory impairment and executive dysfunction, thereby imposing a substantial societal burden. Unfortunately, no drugs have been approved for the treatment of VaD due to its intricate pathogenesis, and the development of innovative and efficacious medications is urgently needed. Apoptosis, a programmed cell death process crucial for eliminating damaged or unwanted cells within an organism, assumes pivotal roles in embryonic development and tissue homeostasis maintenance. An increasing body of evidence indicates that apoptosis may significantly influence the onset and progression of VaD, and numerous natural compounds have demonstrated significant therapeutic potential. Here, we discuss the molecular mechanisms underlying apoptosis and its correlation with VaD. We also provide a crucial reference for developing innovative pharmaceuticals by systematically reviewing the latest research progress concerning the neuroprotective effects of natural compounds on VaD by regulating apoptosis. Further high-quality clinical studies are imperative to firmly ascertain these natural compounds' clinical efficacy and safety profiles in the treatment of VaD.

Synthesis and bioactivity evaluation of mirror isomer salidroside derivatives as potent antioxidant and anti-inflammatory agents

A series of derivatives of salidroside with mirror isomer glucose and different phenyl moieties were synthesized by Schmidt glycosylation in satisfactory yields, and their antioxidant and anti-inflammatory activities were evaluated by using LPS-induced RAW264.7 cells. One of the synthesized derivatives ʟ-Sal-4, bearing ʟ-glycosyl and -OMe modification at the phenyl ring, exhibited high activity in inhibiting the production of pro-inflammatory cytokines and oxidative stress biomarker MDA as well as in enhancing the activity of SOD enzyme, compared with the natural product and its corresponding ᴅ-enantiomer. Further proteomic analysis suggested that ʟ-Sal-4 exerted its anti-inflammatory activity through metabolic reprogramming. The in vitro activity showed that ʟ-Sal-4 is a potent antioxidant and anti-inflammatory agent. Our finding indicated that the ʟ-glucose-derived salidroside might be a promising lead compound in the development of salidroside derivatives as therapeutic agents.

Salidroside directly activates HSC70, revealing a new role for HSC70 in BDNF signalling and neurogenesis after cerebral ischemia

Salidroside, a principal bioactive component of Rhodiola crenulata, is neuroprotective across a wide time window in stroke models. We investigated whether salidroside induced neurogenesis after cerebral ischemia and aimed to identify its primary molecular targets. Rats, subjected to transient 2 h of middle cerebral artery occlusion (MCAO), received intraperitoneal vehicle or salidroside ± intracerebroventricular HSC70 inhibitor VER155008 or TrkB inhibitor ANA-12 for up to 7 days. MRI, behavioural tests, immunofluorescent staining and western blotting measured effects of salidroside. Reverse virtual docking and enzymatic assays assessed interaction of salidroside with purified recombinant HSC70. Salidroside dose-dependently decreased cerebral infarct volumes and neurological deficits, with maximal effects by 50 mg/kg/day. This dose also improved performance in beam balance and Morris water maze tests. Salidroside significantly increased BrdU+/nestin+, BrdU+/DCX+, BrdU+/NeuN+, BrdU-/NeuN+ and BDNF+ cells in the peri-infarct cortex, with less effect in striatum and no significant effect in the subventricular zone. Salidroside was predicted to bind with HSC70. Salidroside dose-dependently increased HSC70 ATPase and HSC70-dependent luciferase activities, but it did not activate HSP70. HSC70 immunoreactivity concentrated in the peri-infarct cortex and was unchanged by salidroside. However, VER155008 prevented salidroside-dependent increases of neurogenesis, BrdU-/NeuN+ cells and BDNF+ cells in peri-infarct cortex. Salidroside also increased BDNF protein and p-TrkB/TrkB ratio in ischemic brain, changes prevented by VER155008 and ANA-12, respectively. Additionally, ANA-12 blocked salidroside-dependent neurogenesis and increased BrdU-/NeuN+ cells in the peri-infarct cortex. Salidroside directly activates HSC70, thereby stimulating neurogenesis and neuroprotection via BDNF/TrkB signalling after MCAO. Salidroside and similar activators of HSC70 might provide clinical therapies for ischemic stroke.

Crosstalk between DNA Damage Repair and Metabolic Regulation in Hematopoietic Stem Cells

Self-renewal and differentiation are two characteristics of hematopoietic stem cells (HSCs). Under steady physiological conditions, most primitive HSCs remain quiescent in the bone marrow (BM). They respond to different stimuli to refresh the blood system. The transition from quiescence to activation is accompanied by major changes in metabolism, a fundamental cellular process in living organisms that produces or consumes energy. Cellular metabolism is now considered to be a key regulator of HSC maintenance. Interestingly, HSCs possess a distinct metabolic profile with a preference for glycolysis rather than oxidative phosphorylation (OXPHOS) for energy production. Byproducts from the cellular metabolism can also damage DNA. To counteract such insults, mammalian cells have evolved a complex and efficient DNA damage repair (DDR) system to eliminate various DNA lesions and guard genomic stability. Given the enormous regenerative potential coupled with the lifetime persistence of HSCs, tight control of HSC genome stability is essential. The intersection of DDR and the HSC metabolism has recently emerged as an area of intense research interest, unraveling the profound connections between genomic stability and cellular energetics. In this brief review, we delve into the interplay between DDR deficiency and the metabolic reprogramming of HSCs, shedding light on the dynamic relationship that governs the fate and functionality of these remarkable stem cells. Understanding the crosstalk between DDR and the cellular metabolism will open a new avenue of research designed to target these interacting pathways for improving HSC function and treating hematologic disorders.

Salidroside ameliorates diabetic retinopathy and Müller cell inflammation via the PI3K/Akt/GSK-3β/NF-𝜅B pathway

Purpose

To determine whether salidroside (SAL) modulates inflammatory cytokines in rat retinal Müller cells (rMC-1) in a hyperglycemic environment by investigating the anti-inflammatory mechanisms of SAL in vitro and in vivo.

Methods

A streptozotocin (STZ)-induced diabetic rat model was established to examine the effects of SAL using hematoxylin and eosin (H&E) staining and immunohistochemistry. rMC-1 cells were grown in 50 mM of high-glucose medium. These simulated diabetic conditions were used to evaluate the anti-inflammatory effects of SAL using a Cell Counting Kit-8 (CCK-8) assay, immunofluorescence staining, western blotting, and real-time polymerase chain reaction (qRT‒PCR). H&E staining was used to analyze the number of ganglion cells in the retina. rMC-1 lysates were processed for qRT‒PCR to measure the steady-state mRNA expression levels of inflammatory markers, such as interleukin 6 (IL-6), interleukin 10 (IL-10), and interleukin 1β (IL-1β). Western blot analysis and immunofluorescence staining were performed to determine the levels of these inflammatory markers.

Results

Our study showed that SAL reversed retinal ganglion cell loss and attenuated nuclear factor kappa B (NF-𝜅B) p65 translocation to the nucleus in STZ-induced diabetic rats. Incubating rMC-1 in different concentrations of SAL for 24 to 48 h affected cell viability. Furthermore, SAL treatment significantly decreased the protein levels of IL-6, TNF-α, and IL-1β compared with those in cells cultured in high glucose (HG). The mRNA expression levels of IL-6 and IL-1β were considerably reduced after SAL treatment, whereas the mRNA expression levels of IL-10 were significantly increased. Interestingly, the beneficial effects of SAL on HG-treated rMC-1 cells were abolished by the PI3K inhibitor LY294002.

Conclusions

These results indicate that SAL treatment reduces cytokine activation in cultured rMC-1. Furthermore, SAL prevents diabetic retinopathy (DR), in part, by modulating the PI3K/Akt/GSK-3β/NF-kB pathway to inhibit Müller cell activation. Thus, SAL is expected to be a potential agent for ameliorating the progression of DR.

Design and synthesis of salidroside analogs and their bioactivity against septic myocardial injury

Cardiac tissue suffers much from sepsis, and the incidence of myocardial injury is high in septic patients. The treatment of sepsis myocardial injury (SMI) has been the focus of clinical medicine. Salidroside shows myocardial cell protection, anti-oxidation and anti- inflammation effects, and it is thought as one of the potential compounds to treat sepsis myocardial injury. However, its anti-inflammatory activity is lower and its pharmacokinetic properties are not ideal, which is far from clinical application. Here, a series of salidroside analogs were synthesized, and their bioactivities were evaluated from several aspects, including their anti-oxidant and anti-inflammatory activities in vitro and anti-sepsis myocardial injury activities in vivo. Of all the compounds which synthesized, compounds 2 and 3 exhibited stronger anti-inflammatory activities than the others; after treating LPS-stimulated RAW264.7 or H9c2 cells with each of them, the levels of IL-1β, IL-6 and TNF-α were down-regulated in a dose-dependent manner. In the anti-oxidative stress injury test, compounds 2 and 3 not only markedly increased the survival rate of cells, and but also improved the cellular oxidative stress-related indicators MDA, SOD and cell damage marker LDH in a dose-dependent manner. In the LPS-induced septic rat myocardial injury models (in vivo), the two compounds also showed good bioactivities. They also reduced the expression of IL-1β, IL-6 and TNF-α, and blocked cell damage by suppressing overhauled oxidation in septic rats. In addition, the myocardial injury was significantly improved and the inflammatory infiltration was reduced after treatment with the two compounds. In conclusion, the salidroside analogs (2 and 3) showed promising therapeutical effect on septic myocardial injury in LPS-model rats, and they could be good candidates for clinical trials against inflammation and septic myocardial injury.

Foxm1 haploinsufficiency drives clonal hematopoiesis and promotes a stress-related transition to hematologic malignancy in mice

Clonal hematopoiesis plays a critical role in the initiation and development of hematologic malignancies. In patients with del(5q) myelodysplastic syndrome (MDS), the transcription factor FOXM1 is frequently downregulated in CD34+ cells. In this study, we demonstrated that Foxm1 haploinsufficiency disturbed normal hematopoiesis and conferred a competitive repopulation advantage for a short period. However, it impaired the long-term self-renewal capacity of hematopoietic stem cells, recapitulating the phenotypes of abnormal hematopoietic stem cells observed in patients with MDS. Moreover, heterozygous inactivation of Foxm1 led to an increase in DNA damage in hematopoietic stem/progenitor cells (HSPCs). Foxm1 haploinsufficiency induced hematopoietic dysplasia in a mouse model with LPS-induced chronic inflammation and accelerated AML-ETO9a-mediated leukemogenesis. We have also identified Parp1, an important enzyme that responds to various types of DNA damage, as a target of Foxm1. Foxm1 haploinsufficiency decreased the ability of HSPCs to efficiently repair DNA damage by downregulating Parp1 expression. Our findings suggest that the downregulation of the Foxm1-Parp1 molecular axis may promote clonal hematopoiesis and reduce genome stability, contributing to del(5q) MDS pathogenesis.

Targeting Poly(ADP)ribose polymerase in BCR/ABL1-positive cells

BCR/ABL1 causes dysregulated cell proliferation and is responsible for chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph1-ALL). In addition to the deregulatory effects of its kinase activity on cell proliferation, BCR/ABL1 induces genomic instability by downregulating BRCA1. PARP inhibitors (PARPi) effectively induce cell death in BRCA-defective cells. Therefore, PARPi are expected to inhibit growth of CML and Ph1-ALL cells showing downregulated expression of BRCA1. Here, we show that PARPi effectively induced cell death in BCR/ABL1 positive cells and suppressed colony forming activity. Prevention of BCR/ABL1-mediated leukemogenesis by PARP inhibition was tested in two in vivo models: wild-type mice that had undergone hematopoietic cell transplantation with BCR/ABL1-transduced cells, and a genetic model constructed by crossing Parp1 knockout mice with BCR/ABL1 transgenic mice. The results showed that a PARPi, olaparib, attenuates BCR/ABL1-mediated leukemogenesis. One possible mechanism underlying PARPi-dependent inhibition of leukemogenesis is increased interferon signaling via activation of the cGAS/STING pathway. This is compatible with the use of interferon as a first-line therapy for CML. Because tyrosine kinase inhibitor (TKI) monotherapy does not completely eradicate leukemic cells in all patients, combined use of PARPi and a TKI is an attractive option that may eradicate CML stem cells.

Salidroside protect Chinese hamster V79 cells from genotoxicity and oxidative stress induced by CL-20

Hexanitrohexaazaisowurtzitane (CL-20) is a high-energy elemental explosive widely used in chemical and military fields. CL-20 harms environmental fate, biosafety, and occupational health. However, there is little known about the genotoxicity of CL-20, in particular its molecular mechanisms. Therefore, this study was framed to investigate the genotoxic mechanisms of CL-20 in V79 cells and evaluate whether the genotoxicity could be diminished by pretreating the cells with salidroside. The results showed that CL-20-induced genotoxicity in V79 cells primarily through oxidative damage to DNA and mitochondrial DNA (mtDNA) mutation. Salidroside could significantly reduce the inhibitory effect of CL-20 on the growth of V79 cells and reduce the levels of reactive oxygen species (ROS), 8-hydroxy-2 deoxyguanosine (8-OHdG), and malondialdehyde (MDA). Salidroside also restored CL-20-induced superoxide dismutase (SOD) and glutathione (GSH) in V79 cells. As a result, salidroside attenuated the DNA damage and mutations induced by CL-20. In conclusion, oxidative stress may be involved in CL-20-induced genotoxicity in V79 cells. Salidroside could protect V79 cells from oxidative damage induced by CL-20, mechanism of which may be related to scavenging intracellular ROS and increasing the expression of proteins that can promote the activity of intracellular antioxidant enzymes. The present study for the mechanisms and protection of CL-20-mediated genotoxicity will help further to understand the toxic effects of CL-20 and provide information on the therapeutic effect of salidroside in CL-20-induced genotoxicity.

A distinct subpopulation of leukemia initiating cells in acute precursor B lymphoblastic leukemia: quiescent phenotype and unique transcriptomic profile

In leukemia, a distinct subpopulation of cancer-initiating cells called leukemia stem cells (LSCs) is believed to drive population expansion and tumor growth. Failing to eliminate LSCs may result in disease relapse regardless of the amount of non-LSCs destroyed. The first step in targeting and eliminating LSCs is to identify and characterize them. Acute precursor B lymphoblastic leukemia (B-ALL) cells derived from patients were incubated with fluorescent glucose analog 2-(N-(7-Nitrobenz-2-oxa-1, 3-diazol-4-yl) Amino)-2-Deoxyglucose (NBDG) and sorted based on NBDG uptake. Cell subpopulations defined by glucose uptake were then serially transplanted into mice and evaluated for leukemia initiating capacity. Gene expression profiles of these cells were characterized using RNA-Sequencing (RNA-Seq). A distinct population of NBDG-low cells was identified in patient B-ALL samples. These cells are a small population (1.92% of the entire leukemia population), have lower HLA expression, and are smaller in size (4.0 to 7.0 μm) than the rest of the leukemia population. All mice transplanted with NBDG-low cells developed leukemia between 5 and 14 weeks, while those transplanted with NBDG-high cells did not develop leukemia (p ≤ 0.0001-0.002). Serial transplantation of the NBDG-low mouse model resulted in successful leukemia development. NBDG-medium (NBDG-med) populations also developed leukemia. Interestingly, comprehensive molecular characterization of NBDG-low and NBDG-med cells from patient-derived xenograft (PDX) models using RNA-Seq revealed a distinct profile of 2,162 differentially-expressed transcripts (DETs) (p<0.05) with 70.6% down-regulated in NBDG-low cells. Hierarchical clustering of DETs showed distinct segregation of NBDG-low from NBDG-med and NBDG-high groups with marked transcription expression alterations in the NBDG-low group consistent with cancer survival. In conclusion, A unique subpopulation of cells with low glucose uptake (NBDG-low) in B-ALL was discovered. These cells, despite their quiescence characteristics, once transplanted in mice, showed potent leukemia initiating capacity. Although NBDG-med cells also initiated leukemia, gene expression profiling revealed a distinct signature that clearly distinguishes NBDG-low cells from NBDG-med and the rest of the leukemia populations. These results suggest that NBDG-low cells may represent quiescent LSCs. These cells can be activated in the appropriate environment in vivo, showing leukemia initiating capacity. Our study provides insight into the biologic mechanisms of B-ALL initiation and survival.

Dietary Supplementation of Salidroside Alleviates Liver Lipid Metabolism Disorder and Inflammatory Response to Promote Hepatocyte Regeneration via PI3K/AKT/Gsk3-β Pathway

Fatty liver hemorrhagic syndrome (FLHS) is a chronic hepatic disease which occurs when there is a disorder in lipid metabolism. FLHS is often observed in caged laying hens and characterized by a decrease in egg production and dramatic increase of mortality. Salidroside (SDS) is an herbal drug which has shown numerous pharmacological activities, such as protecting mitochondrial function, attenuating cell apoptosis and inflammation, and promoting antioxidant defense system. We aimed to determine the therapeutic effects of SDS on FLHS in laying hens and investigate the underlying mechanisms through which SDS operates these functions. We constructed oleic acid (OA)-induced fatty liver model in vitro and high-fat diet-induced FLHS of laying hens in vivo. The results indicated that SDS inhibited OA-induced lipid accumulation in chicken primary hepatocytes, increased hepatocyte activity, elevated the mRNA expression of proliferation related genes PCNA, CDK2, and cyclinD1 and increased the protein levels of PCNA and CDK2 (P < 0.05), as well as decreased the cleavage levels of Caspase-9, Caspase-8, and Caspase-3 and apoptosis in hepatocytes (P < 0.05). Moreover, SDS promoted the phosphorylation levels of PDK1, AKT, and Gsk3-β, while inhibited the PI3K inhibitor (P < 0.05). Additionally, we found that high-fat diet-induced FLHS hens had heavier body weight, liver weight, and abdominal fat weight, and severe steatosis in histology, compared with the control group (Con). However, hens fed with SDS maintained lighter body weight, liver weight, and abdominal fat weight, as well as normal liver without hepatic steatosis. In addition, high-fat diet-induced FLHS hens had high levels of serum total cholesterol (TC), triglyceride (TG), alanine transaminase (ALT), and aspartate aminotransferase (AST) compared to the Con group, however, in the Model+SDS group, the levels of TC, TG, ALT, and AST decreased significantly, whereas the level of superoxide dismutase (SOD) increased significantly (P < 0.05). We also found that SDS significantly decreased the mRNA expression abundance of PPARγ, SCD, and FAS in the liver, as well as increased levels of PPARα and MTTP, and decreased the mRNA expression of TNF-α, IL-1β, IL-6, and IL-8 in the Model+SDS group (P < 0.05). In summary, this study showed that 0.3 mg/mL SDS attenuated ROS generation, inhibited lipid accumulation and hepatocyte apoptosis, and promoted hepatocyte proliferation by targeting the PI3K/AKT/Gsk3-β pathway in OA-induced fatty liver model in vitro, and 20 mg/kg SDS alleviated high-fat-diet-induced hepatic steatosis, oxidative stress, and inflammatory response in laying hens in vivo.

Quinacrine-CASIN combination overcomes chemoresistance in human acute lymphoid leukemia

Chemoresistance posts a major hurdle for treatment of acute leukemia. There is increasing evidence that prolonged and intensive chemotherapy often fails to eradicate leukemic stem cells, which are protected by the bone marrow niche and can induce relapse. Thus, new therapeutic approaches to overcome chemoresistance are urgently needed. By conducting an ex vivo small molecule screen, here we have identified Quinacrine (QC) as a sensitizer for Cytarabine (AraC) in treating acute lymphoblastic leukemia (ALL). We show that QC enhances AraC-mediated killing of ALL cells, and subsequently abrogates AraC resistance both in vitro and in an ALL-xenograft model. However, while combo AraC+QC treatment prolongs the survival of primary transplanted recipients, the combination exhibits limited efficacy in secondary transplanted recipients, consistent with the survival of niche-protected leukemia stem cells. Introduction of Cdc42 Activity Specific Inhibitor, CASIN, enhances the eradication of ALL leukemia stem cells by AraC+QC and prolongs the survival of both primary and secondary transplanted recipients without affecting normal long-term human hematopoiesis. Together, our findings identify a small-molecule regimen that sensitizes AraC-mediated leukemia eradication and provide a potential therapeutic approach for better ALL treatment.

Natural Products for Regulating Macrophages M2 Polarization

Macrophages M2 polarization have been taken as an anti-inflammatory progression during inflammation. Natural plant-derived products, with potential therapeutic and preventive activities against inflammatory diseases, have received increasing attention in recent years because of their whole regulative effects and specific pharmacological activities. However, the molecular mechanisms about how different kinds of natural compounds regulate macrophages polarization still unclear. Therefore, in the current review, we summarized the detailed research progress on the active compounds derived from herbal plants with regulating effects on macrophages, especially M2 polarization. These natural occurring compounds including flavonoids, terpenoids, glycosides, lignans, coumarins, alkaloids, polyphenols and quinones. In addition, we extensively discussed the cellular mechanisms underlying the M2 polarization for each compound, which could provide potential therapeutic strategies aiming macrophages M2 polarization.

Synthesis and identification of a novel derivative of salidroside as a selective, competitive inhibitor of monoamine oxidase B with enhanced neuroprotective properties

Salidroside [(2R,3S,4S,5R,6R)-2-(hydroxymethyl)-6-(4-hydroxyphenethoxy)tetrahy-dro-2H-pyran-3,4,5-triol] is an antioxidant, anti-inflammatory and neuroprotective agent, but its drug-like properties are unoptimized and its mechanism of actions is uncertain. We synthesized twenty-six novel derivatives of salidroside and examined them in CoCl₂-treated PC12 cells using MTT assay. pOBz, synthesized by esterifying the phenolic hydroxyl group of salidroside with benzoyl chloride, was one of five derivatives that were more cytoprotective than salidroside, with an EC₅₀ of 0.038 μM versus 0.30 μM for salidroside. pOBz was also more lipophilic, with log P of 1.44 versus -0.89 for salidroside. Reverse virtual docking predicted that pOBz would bind strongly with monoamine oxidase (MAO) B by occupying its entrance and substrate cavities, and by interacting with the inter-cavity gating residue Ile199 and Tyr435 of the substrate cavity. Enzymatic studies confirmed that pOBz competitively inhibited the activity of purified human MAO-B (K_i = 0.041 μM versus K_i = 0.92 μM for salidroside), and pOBz was highly selective for MAO-B over MAO-A. In vivo, pOBz inhibited cerebral MAO activity after middle cerebral artery occlusion with reperfusion in rats, and it reduced cerebral infarct volume, improved neurological function and NeuN expression, and inhibited complement C3 expression and apoptosis. Our results suggest that pOBz is a structurally novel type of competitive and selective MAO-B inhibitor, with potent neuroprotective properties after cerebral ischemia-reperfusion injury in rats.

Contribution of salidroside to the relieve of symptom and sign in the early acute stage of osteoarthritis in rat model

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Rhodiola has been used to treat cough, hemoptysis, fever, pain, bruise and other symptoms which are related to injury and inflammation over a thousand years in traditional Tibetan medicine. Salidroside (p-hydroxyphenethyl-β-D-glucoside) is one of the most potent bioactive ingredients of the genus Rhodiola.

AIM OF STUDY

The present study aimed to explore whether salidroside could alleviate the clinical symptom and sign in the early acute stage of osteoarthritis (OA) in monosodium iodoacetate (MIA) rat model, and its underlying mechanisms.

MATERIALS AND METHODS

Osteoarthritis (OA) was induced in rat knees by intra-articular injection of MIA; simultaneously salidroside was administered by intravenous injection. Pain behaviors were evaluated by knee-bend test, hind limb weight-bearing asymmetry and hind paw mechanical withdrawal threshold. The joint swelling was determined by the difference of knee joint diameter. Inflammatory exudates in synovial fluid were evaluated by leukocyte counting and protein content. Cytokines, chemokines, reactive oxygen species (ROS) and reactive nitrogen species (RNS) markers were determined by Enzyme-linked immunosorbent assay (ELISA) and colorimetric assay in synovial fluid. Pro-inflammatory gene expressions in synovial tissue were detected by quantitative real time RT-PCR (qRT-PCR). Nuclear factor kappa-B (NF-κB) DNA binding assay and western blot were used to determine NF-κB activation and ROS marker protein expression in synovial tissue. Glycosaminoglycan (GAG) content in the cartilage was measured by dimethylmethylene blue method. Hematoxylin and eosin (H&E), Safranin O-fast green and a modified Mankin grading system were used to evaluate the histology of articular cartilage.

RESULTS

Salidroside could alleviate pain and joint swelling in the early acute stage of OA in rat model, reduced the number of leukocytes, total protein content, proinflammatory mediators and ROS/RNS markers in synovial fluid, down regulated the expression of proinflammatory genes in synovium, inhibited the activation of NF- κ B and oxidative stress response in synovium, promoted the synthesis of cartilage GAG, prevented the loss of proteoglycan and chondrocyte degeneration.

CONCLUSIONS

Salidroside effectively alleviates acute symptom and sign of OA in rat model by its anti-inflammatory and antioxidant affects to inhibit synovial inflammation, which provides a new strategy to prevent the onset and progression of OA.

The Role of PARP1 in Monocyte and Macrophage Commitment and Specification: Future Perspectives and Limitations for the Treatment of Monocyte and Macrophage Relevant Diseases with PARP Inhibitors

Modulation of PARP1 expression, changes in its enzymatic activity, post-translational modifications, and inflammasome-dependent cleavage play an important role in the development of monocytes and numerous subtypes of highly specialized macrophages. Transcription of PARP1 is governed by the proliferation status of cells at each step of their development. Higher abundance of PARP1 in embryonic stem cells and in hematopoietic precursors supports their self-renewal and pluri-/multipotency, whereas a low level of the enzyme in monocytes determines the pattern of surface receptors and signal transducers that are functionally linked to the NFκB pathway. In macrophages, the involvement of PARP1 in regulation of transcription, signaling, inflammasome activity, metabolism, and redox balance supports macrophage polarization towards the pro-inflammatory phenotype (M1), which drives host defense against pathogens. On the other hand, it seems to limit the development of a variety of subsets of anti-inflammatory myeloid effectors (M2), which help to remove tissue debris and achieve healing. PARP inhibitors, which prevent protein ADP-ribosylation, and PARP1‒DNA traps, which capture the enzyme on chromatin, may allow us to modulate immune responses and the development of particular cell types. They can be also effective in the treatment of monocytic leukemia and other cancers by reverting the anti- to the proinflammatory phenotype in tumor-associated macrophages.

Persistent DNA damage-induced NLRP12 improves hematopoietic stem cell function

NOD-like receptor 12 (NLRP12) is a member of the nucleotide-binding domain and leucine-rich repeat containing receptor inflammasome family that plays a central role in innate immunity. We previously showed that DNA damage upregulated NLRP12 in hematopoietic stem cells (HSCs) of mice deficient in the DNA repair gene Fanca. However, the role of NLRP12 in HSC maintenance is not known. Here, we show that persistent DNA damage-induced NLRP12 improves HSC function in both mouse and human models of DNA repair deficiency and aging. Specifically, treatment of Fanca-/- mice with the DNA cross-linker mitomycin C or ionizing radiation induces NLRP12 upregulation in phenotypic HSCs. NLRP12 expression is specifically induced by persistent DNA damage. Functionally, knockdown of NLRP12 exacerbates the repopulation defect of Fanca-/- HSCs. Persistent DNA damage-induced NLRP12 was also observed in the HSCs from aged mice, and depletion of NLRP12 in these aged HSCs compromised their self-renewal and hematopoietic recovery. Consistently, overexpression of NLRP12 substantially improved the long-term repopulating function of Fanca-/- and aged HSCs. Finally, persistent DNA damage-induced NLRP12 maintains the function of HSCs from patients with FA or aged donors. These results reveal a potentially novel role of NLRP12 in HSC maintenance and suggest that NLRP12 targeting has therapeutic potential in DNA repair disorders and aging.

M1 and M2 macrophage polarization and potentially therapeutic naturally occurring compounds

Macrophages, as crucial cellular components of innate immunity, are characterized by possessing high plasticity and an abnormal ability to differentiate in response to numerous stimuli. Given this, macrophages show extreme heterogeneity under both physiological and pathological conditions. Typically, macrophages can be polarized into classically activated macrophages (M1) and alternatively activated macrophages (M2) depending on their environment. The relative functions of these two subtypes are almost exactly opposed to one another. Recent studies have suggested that some naturally occurring compounds can exert regulatory effects on the progression of macrophage polarization, which implies that they could be promising therapeutic tools to treat relevant diseases. Therefore, in our current review, we summarize recent studies on several naturally occurring compounds that may possess the ability to regulate macrophage polarization and explore the associated molecular mechanisms.

Salidroside Inhibits Myogenesis by Modulating p-Smad3-Induced Myf5 Transcription

Aim: Salidroside is an active compound extracted from Rhodiola rosea which is used to alleviate fatigue and enhance endurance in high altitude regions. Some studies have demonstrated that salidroside can affect precursor cell differentiation in hematopoietic stem cells, erythrocytes, and osteoblasts. The aim of this study was to investigate the effect of salidroside on myoblast differentiation and to explore the underlying molecular mechanisms of this effect. Methods: C2C12 myoblast cells were treated with different concentrations of salidroside in differentiation media. Real-time PCR, Western blotting, and immunofluorescence assay were employed to evaluate the effects of salidroside on C2C12 differentiation. RNA interference was used to reveal the important role of Myf5 in myogenesis inhibited by salidroside. Chromatin Immunoprecipitation and dual-luciferase reporter assay were utilized to explore the underlying mechanisms of salidroside-induced upregulation of Myf5. Results: We found that salidroside inhibits myogenesis by downregulating MyoD and myogenin, preserves undifferentiated reserve cell pools by upregulating Myf5. Knocking down Myf5 expression significantly rescued the myogenesis inhibited by salidroside. The effect of salidroside on myogenesis was associated with increased phosphorylated Smad3 (p-Smad3). Both SIS3 (Specific inhibitor of p-Smad3) and dominant negative Smad3 plasmid (DN-Smad3) attenuated the inhibitory effect of salidroside on C2C12 differentiation. Moreover, the induction of Myf5 transcription by salidroside was dependent on a Smad-binding site in the promoter region of Myf5 gene. Conclusion and Implications: Our findings identify a novel role and mechanism for salidroside in regulating myogenesis through p-Smad3-induced Myf5 transcription, which may have implications for its further application in combating degenerative muscular diseases caused by depletion of muscle stem cells, such as Duchenne muscular dystrophy or sarcopenia.

Salidroside provides neuroprotection by modulating microglial polarization after cerebral ischemia

BACKGROUND

Following stroke, microglia can be driven to the "classically activated" pro-inflammatory (M1) phenotype and the "alternatively activated" anti-inflammatory (M2) phenotype. Salidroside (SLDS) is known to inhibit inflammation and to possess protective effects in neurological diseases, but to date, the exact mechanisms involved in these processes after stroke have yet to be elucidated. The purpose of this study was to determine the effects of SLDS on neuroprotection and microglial polarization after stroke.

METHODS

Male adult C57/BL6 mice were subjected to focal transient cerebral ischemia followed by intravenous SLDS injection. The optimal dose was determined by evaluation of cerebral infarct volume and neurological functions. RT-PCR and immunostaining were performed to assess microglial polarization. A transwell system and a direct-contact coculture system were used to elucidate the effects of SLDS-induced microglial polarization on oligodendrocyte differentiation and neuronal survival.

RESULTS

SLDS significantly reduced cerebral infarction and improved neurological function after cerebral ischemia. SLDS treatment reduced the expression of M1 microglia/macrophage markers and increased the expression of M2 microglia/macrophage markers after stroke and induced primary microglia from M1 phenotype to M2 phenotype. Furthermore, SLDS treatment enhanced microglial phagocytosis and suppressed microglial-derived inflammatory cytokine release. Cocultures of oligodendrocytes and SLDS-treated M1 microglia resulted in increased oligodendrocyte differentiation. Moreover, SLDS protected neurons against oxygen glucose deprivation by promoting microglial M2 polarization.

CONCLUSIONS

These data demonstrate that SLDS protects against cerebral ischemia by modulating microglial polarization. An understanding of the mechanisms involved in SLDS-mediated microglial polarization may lead to new therapeutic opportunities after stroke.

Rhodiola rosea L.: an herb with anti-stress, anti-aging, and immunostimulating properties for cancer chemoprevention

Purpose of review

Rhodiola rosea extracts have been used as a dietary supplement in healthy populations, including athletes, to non-specifically enhance the natural resistance of the body to both physical and behavior stresses for fighting fatigue and depression. We summarize the information with respect to the new pharmacological activities of Rhodiola rosea extracts and its underlying molecular mechanisms in this review article.

Recent findings

In addition to its multiplex stress-protective activity, Rhodiola rosea extracts have recently demonstrated its anti-aging, anti-inflammation, immunostimulating, DNA repair and anti-cancer effects in different model systems. Molecular mechanisms of Rhodiola rosea extracts's action have been studied mainly along with one of its bioactive compounds, salidroside. Both Rhodiola rosea extracts and salidroside have contrast molecular mechanisms on cancer and normal physiological functions. For cancer, Rhodiola rosea extracts and salidroside inhibit the mTOR pathway and reduce angiogenesis through down-regulation of the expression of HIF-1α/HIF-2α. For normal physiological functions, Rhodiola rosea extracts and salidroside activate the mTOR pathway, stimulate paracrine function and promote neovascularization by inhibiting PHD3 and stabilizing HIF-1α proteins in skeletal muscles. In contrast to many natural compounds, salidroside is water-soluble and highly bioavailable via oral administration and concentrated in urine by kidney excretion.

Summary

Rhodiola rosea extracts and salidroside can impose cellular and systemic benefits similar to the effect of positive lifestyle interventions to normal physiological functions and for anti-cancer. The unique pharmacological properties of Rhodiola rosea extracts or salidroside deserve further investigation for cancer chemoprevention, in particular for human urinary bladder cancer.

Salidroside, a scavenger of ROS, enhances the radioprotective effect of Ex-RAD® via a p53-dependent apoptotic pathway

Salidroside (Sal), the predominant component of a Chinese medicinal herb, Rhodiola rosea L., has become an attractive bioagent due to its significant anti-radiation, antioxidant and immune adjustment effects. We explored the radioprotective effect of Sal to ascertain whether it could enhance the anti-radiation effect of ON 01210.Na (Ex-RAD®) in vivo and in vitro, and elucidate its underlying mechanism. Our data demonstrated that Sal inhibited radiation-induced apoptosis, scavenged reactive oxygen species (ROS), and decreased the DNA damage of human umbilical vein endothelial cells (HUVECs). Sal downregulated the expression of Bax and p53 and increased the ratio of Bcl-2/Bax, which indicated that Sal inhibited the radiation-induced apoptosis through p53-dependent pathways. The radioprotection of the Sal pretreatment was also evidenced by an increasing survival rate of the mice, maintaining antioxidant enzyme levels in the liver, and accelerating hematopoietic recovery. The results suggest that Sal exhibits an excellent radioprotective effect with powerful antioxidant activity in vitro and in vivo. Sal enhanced the radioprotective effect of Ex-RAD by improving the antioxidant effect, the scavenging of ROS, by accelerating hematopoietic recovery and DNA repair as well as by regulating apoptotic and repair signaling pathways. Combined modality treatments were more effective than single-agent treatments, demonstrating the value of multiple-agent radioprotectants.

Neuroprotective Effects of Salidroside in the MPTP Mouse Model of Parkinson's Disease: Involvement of the PI3K/Akt/GSK3β Pathway

The degenerative loss through apoptosis of dopaminergic neurons in the substantia nigra pars compacta plays a primary role in the progression of Parkinson's disease (PD). Our in vitro experiments suggested that salidroside (Sal) could protect against 1-methyl-4-phenylpyridine-induced cell apoptosis in part by regulating the PI3K/Akt/GSK3β pathway. The current study aims to increase our understanding of the protective mechanisms of Sal in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropypridine- (MPTP-) induced PD mouse model. We found that pretreatment with Sal could protect against MPTP-induced increase of the time of turning downwards and climbing down to the floor. Sal also prevented MPTP-induced decrease of locomotion frequency and the increase of the immobile time. Sal provided a protection of in MPTP-induced loss of tyrosine hydroxylase-positive neurons in SNpc and the level of DA, DOPAC, and HVA in the striatum. Furthermore, Sal could increase the phosphorylation level of Akt and GSK3β, upregulate the ratio of Bcl-2/Bax, and inhibit the activation of caspase-3, caspase-6, and caspase-9. These results show that Sal prevents the loss of dopaminergic neurons and the PI3K/Akt/GSK3β pathway signaling pathway may have mediated the protection of Sal against MPTP, suggesting that Sal may be a potential candidate in neuroprotective treatment for PD.

Salidroside exhibits anti-dengue virus activity by upregulating host innate immune factors

Dengue is an arboviral disease with no effective therapy available. Therefore, there is an urgent need to find a potent antiviral agent against dengue virus (DENV). In the present study, salidroside, a main bioactive compound of Rhodiola rosea, was evaluated for its antiviral potential against DENV serotype-2 infection and its effect on host innate immune factors. Antiviral effects of salidroside were examined in DENV-infected cells by western blotting, flow cytometry and real-time PCR. Its underlying mechanism involved in antiviral action was determined by evaluating expression of host innate immune factors including RIG-I, IRF-3, IRF-7, PKR, P-eIF2α and NF-κB. Salidroside potently inhibited DENV infection by decreasing DENV envelope protein expression more than tenfold. Salidroside exerts its antiviral activity by increasing expression of RNA helicases such as RIG-I, thereby initiating a downstream signaling cascade that induces upregulation of IRF-3 and IRF-7. It prevents viral protein synthesis by increasing the expression of PKR and P-eIF2α while decreasing NF-κB expression. It was also found to induce the expression of IFN-α. In addition, the number of NK cells and CD8⁺ T cells were also found to be increased by salidroside treatment in human PBMCs, which are important in limiting DENV replication during early stages of infection. The findings presented here suggest that salidroside exhibits antiviral activity against DENV by inhibiting viral protein synthesis and boosting host immunity by increasing the expression of host innate immune factors and hence could be considered for the development of an effective therapeutic agent against DENV infection.

Hyper-active non-homologous end joining selects for synthetic lethality resistant and pathological Fanconi anemia hematopoietic stem and progenitor cells

The prominent role of Fanconi anemia (FA) proteins involves homologous recombination (HR) repair. Poly[ADP-ribose] polymerase1 (PARP1) functions in multiple cellular processes including DNA repair and PARP inhibition is an emerging targeted therapy for cancer patients deficient in HR. Here we show that PARP1 activation in hematopoietic stem and progenitor cells (HSPCs) in response to genotoxic or oxidative stress attenuates HSPC exhaustion. Mechanistically, PARP1 controls the balance between HR and non-homologous end joining (NHEJ) in double strand break (DSB) repair by preventing excessive NHEJ. Disruption of the FA core complex skews PARP1 function in DSB repair and led to hyper-active NHEJ in Fanca^−/− or Fancc^−/− HSPCs. Re-expression of PARP1 rescues the hyper-active NHEJ phenotype in Brca1^−/−Parp1^−/− but less effective in Fanca^−/−Parp1^−/− cells. Inhibition of NHEJ prevents myeloid/erythroid pathologies associated with synthetic lethality. Our results suggest that hyper-active NHEJ may select for “synthetic lethality” resistant and pathological HSPCs.

Adjunctive Treatment with Rhodiola Crenulata in Patients with Chronic Obstructive Pulmonary Disease--A Randomized Placebo Controlled Double Blind Clinical Trial

Chronic obstructive pulmonary disease (COPD) is a low grade systemic inflammatory disease characterized by dyspnea and exercise intolerance even under standard therapy. Rhodiola crenulata (RC) has been shown to exert anti-inflammatory effects and to enhance exercise endurance, thereby having the potential to treat COPD. In this 12-week, randomized, double-blind, placebo-controlled clinical trial, 57 patients with stable moderate-to-severe COPD aged 70±8.8 years were given RC (250 mg twice/day) (n=38) or a placebo (250 mg twice/day) (n=19) in addition to their standard regimen. There were no significant differences in anthropometrics, quality of life, lung function, six-minute walk and incremental exercise tests between the two groups at enrollment. Over the 12 weeks, RC was well tolerated, significantly reduced triceps skin thickness (Δ=-1 mm, p=.04), change of FEV1 (4.5%, p=.03), and improved workload (Δ=10%, p=.01); although there were no significant differences in these factors between the two groups. However, there were significant between-group differences in tidal volume and ventilation-CO2-output ratio at peak exercise (both p=.05), which were significantly related to peak work rate (both p<.0001). RC tended to protect against acute exacerbation of COPD (p=.1) but not other measurements. RC did not improve the six-minute walk test distance but significantly improved tidal breathing and ventilation efficiency, most likely through improvements in work rate. Further studies with a larger patient population are needed in order to confirm these findings.

TRIAL REGISTRATION

ClinicalTrials.gov number NCT02242461.

Salidroside-Mediated Neuroprotection is Associated with Induction of Early Growth Response Genes (Egrs) Across a Wide Therapeutic Window

Salidroside exhibits anti-inflammatory, anti-oxidative, and anti-apoptotic properties. To identify whether salidroside might be a candidate for treating ischemic stroke, we investigated the effects of salidroside or vehicle, given daily for 6 days, after middle cerebral artery occlusion (MCAO) for 2 h and reperfusion for either 1 or 48 h in rats. Salidroside reduced cerebral infarct volume and significantly improved neurological scores whether started after 1 or 48 h of reperfusion. Microarray analysis showed that 20 % (133/678) of the genes down-regulated by ischemia and 1 h of reperfusion were up-regulated by salidroside, whereas 13 % (105/829) of the genes induced by ischemia-reperfusion were inhibited by salidroside, suggesting that salidroside can reverse effects of ischemia-reperfusion on gene expression. The main enriched functional categories induced by salidroside were genes related to synaptic plasticity, whereas salidroside inhibited genes related to inflammation. Induction of Egr1, Egr2, Egr4, and Arc by salidroside was confirmed by qRT-PCR and western blotting in ischemic brains treated after either 1 or 48 h of reperfusion. The potential protective role of Egr4 in salidroside-mediated neuroprotection was subsequently investigated in CoCl2-treated PC12 cells. Egr4 was dose-dependently induced by salidroside in PC12 cells, and depleting Egr4 with target-specific siRNA increased caspase-3 activity and Bax, but decreased Bcl-xl, which were reversed by salidroside. Finally, we confirmed that salidroside inhibited the Bax/Bcl-xl-related apoptosis after MCAO with reperfusion. In conclusion, salidroside is highly neuroprotective with a wide therapeutic time window after ischemia-reperfusion injury in the rat, and this partially involves induction of Egrs, leading to inhibition of Bax/Bcl-xl-related apoptosis.

Salidroside protects against premature senescence induced by ultraviolet B irradiation in human dermal fibroblasts

OBJECTIVES

Salidroside, the predominant component of a Chinese herbal medicine, Rhodiola rosea L., becomes an attractive bio-agent due to its multifunction. Although it is well proposed that this herbal medicine may have photoprotective effect according to the folk hearsay, the direct supportive experimental evidences linking the drug with skin ageing have rarely been reported so far. The study was conducted to investigate the photoprotective role of salidrosdie and its related mechanisms in vitro.

METHODS

First, a premature senescence model induced by UVB irradiation (250 mJ cm(-2)) in human dermal fibroblasts (HDFs) was established, and senescent phenotypes were evaluated by cell morphology, cell proliferation, senescence-associated beta-galactosidase (SA-β-gal) activity and cell cycle distribution. Then the photoprotective effect of salidroside was investigated. Cells were pre-treated with various doses of salidroside (1, 5 and 10 μM) followed by the sublethal dosage of UVB exposure and then were harvested for various detections, including senescence-associated phenotypes and molecules, alteration of oxidative stress, matrix metalloproteinase-1 (MMP-1) secretion and inflammatory response.

RESULTS

Pre-treatment of salidroside dose dependently reversed the senescent state of HDFs induced by UVB as evidenced by elevated cell viability, decreased SA-β-gal activity and relieving of G1/G0 cell cycle arrest. UVB-induced increased protein expression of cyclin-dependent kinase (CDK) inhibitors p21(WAF) (1) and p16(INK) (4) was also repressed by salidrosdie treatment in a dose-dependent manner. Meanwhile, the increment of malondialdehyde (MDA) level in UVB-irradiated HDFs was inhibited upon salidroside treatment. Additionally, salidroside significantly attenuated UVB-induced synthesis of MMP-1 as well as the production of IL-6 and TNF-α in HDFs.

CONCLUSION

Our data provided the evidences for the protective role of salidroside against UVB-induced premature senescence in HDFs probably via its anti-oxidative property and inhibition on production of MMP-1 and pro-inflammatory cytokines, which indicated its potential utilization as an active ingredient in the preparation of photoprotective formulation.

Oxidative stress-associated protein tyrosine kinases and phosphatases in Fanconi anemia

SIGNIFICANCE

Fanconi anemia (FA) is a genetic disorder featuring chromosomal instability, developmental defects, progressive bone marrow failure, and predisposition to cancer. Besides the predominant role in DNA damage response and/or repair, many studies have linked FA proteins to oxidative stress. Oxidative stress, defined as imbalance in pro-oxidant and antioxidant homeostasis, has been considered to contribute to disease development, including FA.

RECENT ADVANCES

A variety of signaling pathways may be influenced by oxidative stress, particularly the equilibrium between protein kinases and phosphatases, consequently leading to an aberrant phosphorylation state of cellular proteins. Dysfunction of kinases/phosphatases has been implicated in the pathophysiology of human diseases. In FA, evidence is emerging that links abnormal phosphorylation/de-phosphorylation of signaling molecules to clinical complications and malformations.

CRITICAL ISSUES

In this study, we review the recent findings on the oxidative stress-related kinases and phosphatases, particularly tyrosine phosphatases in FA.

FUTURE DIRECTIONS

Understanding the role of oxidative stress-related kinases and phosphatases in FA may provide unique and generic possibilities for the future development of therapeutic strategies by targeting the dysregulated protein kinases and phosphatases in a clinical setting.

Salidroside stimulates mitochondrial biogenesis and protects against H₂O₂-induced endothelial dysfunction

Salidroside (SAL) is an active component of Rhodiola rosea with documented antioxidative properties. The purpose of this study is to explore the mechanism of the protective effect of SAL on hydrogen peroxide- (H₂O₂-) induced endothelial dysfunction. Pretreatment of the human umbilical vein endothelial cells (HUVECs) with SAL significantly reduced the cytotoxicity brought by H₂O₂. Functional studies on the rat aortas found that SAL rescued the endothelium-dependent relaxation and reduced superoxide anion (O2^∙−) production induced by H₂O₂. Meanwhile, SAL pretreatment inhibited H₂O₂-induced nitric oxide (NO) production. The underlying mechanisms involve the inhibition of H₂O₂-induced activation of endothelial nitric oxide synthase (eNOS), adenosine monophosphate-activated protein kinase (AMPK), and Akt, as well as the redox sensitive transcription factor, NF-kappa B (NF-κB). SAL also increased mitochondrial mass and upregulated the mitochondrial biogenesis factors, peroxisome proliferator-activated receptor gamma-coactivator-1alpha (PGC-1α), and mitochondrial transcription factor A (TFAM) in the endothelial cells. H₂O₂-induced mitochondrial dysfunction, as demonstrated by reduced mitochondrial membrane potential (Δψm) and ATP production, was rescued by SAL pretreatment. Taken together, these findings implicate that SAL could protect endothelium against H₂O₂-induced injury via promoting mitochondrial biogenesis and function, thus preventing the overactivation of oxidative stress-related downstream signaling pathways.

Binding to WGR domain by salidroside activates PARP1 and protects hematopoietic stem cells from oxidative stress

AIMS

A component of the base excision repair pathway, poly(ADP-ribose) polymerase-1 (PARP1) functions in multiple cellular processes, including DNA repair and programmed cell death. We previously showed that Salidroside, a phenylpropanoid glycoside isolated from medicinal plants, prevented the loss of hematopoietic stem cells (HSCs) in native mice and rescued HSCs repopulating in transplanted recipients under oxidative stress. The aim of this study was to investigate the mechanism by which PARP1 activation by Salidroside maintains HSCs under oxidative stress.

RESULTS

We found that although there were no spontaneous defects in hematopoiesis in Parp1(-/-) mice, oxidative stress compromised the repopulating capacity of Parp1(-/-) HSCs in transplanted recipient mice. A biochemical study using truncated proteins lacking the defined functional domains of PARP1 showed that the tryptophan-glycine-arginine-rich (WGR) domain of PARP1 was critical for Salidroside binding and subsequent PARP1 activation under oxidative stress. Functionally, complementation of Parp1(-/-) HSCs with full-length PARP1WT, but not the PARP1R591K mutant in WGR domain restored Salidroside-stimulated PARP1 activation in vitro. Mechanistically, activated PARP1 by Salidroside enhanced the repopulating capacity of the stressed HSCs by accelerating oxidative DNA damage repair. INNOVATIONS AND CONCLUSION: Our findings reveal the action of mechanism for Salidroside in PARP1 stimulation and a novel role of PARP1 activation in maintaining HSC function under oxidative stress.

Inflammation-mediated notch signaling skews fanconi anemia hematopoietic stem cell differentiation

Hematopoietic stem cells (HSCs) can either self-renew or differentiate into various types of cells of the blood lineage. Signaling pathways that regulate this choice of self-renewal versus differentiation are currently under extensive investigation. In this study, we report that deregulation of Notch signaling skews HSC differentiation in mouse models of Fanconi anemia (FA), a genetic disorder associated with bone marrow failure and progression to leukemia and other cancers. In mice expressing a transgenic Notch reporter, deletion of the Fanca or Fancc gene enhances Notch signaling in multipotential progenitors (MPPs), which is correlated with decreased phenotypic long-term HSCs and increased formation of MPP1 progenitors. Furthermore, we found an inverse correlation between Notch signaling and self-renewal capacity in FA hematopoietic stem and progenitor cells. Significantly, FA deficiency in MPPs deregulates a complex network of genes in the Notch and canonical NF-κB pathways. Genetic ablation or pharmacologic inhibition of NF-κB reduces Notch signaling in FA MPPs to near wild type level, and blocking either NF-κB or Notch signaling partially restores FA HSC quiescence and self-renewal capacity. These results suggest a functional crosstalk between Notch signaling and NF-κB pathway in regulation of HSC differentiation.