Salidroside alleviates diabetic neuropathic pain through regulation of the AMPK-NLRP3 inflammasome axis

Advances of traditional Chinese medicine preclinical mechanisms and clinical studies on diabetic peripheral neuropathy

CONTEXT

Diabetic peripheral neuropathy (DPN) results in an enormous burden and reduces the quality of life for patients. Considering there is no specific drug for the management of DPN, traditional Chinese medicine (TCM) has increasingly drawn attention of clinicians and researchers around the world due to its characteristics of multiple targets, active components, and exemplary safety.

OBJECTIVE

To summarize the current status of TCM in the treatment of DPN and provide directions for novel drug development, the clinical effects and potential mechanisms of TCM used in treating DPN were comprehensively reviewed.

METHODS

Existing evidence on TCM interventions for DPN was screened from databases such as PubMed, the Cochrane Neuromuscular Disease Group Specialized Register (CENTRAL), and the Chinese National Knowledge Infrastructure Database (CNKI). The focus was on summarizing and analyzing representative preclinical and clinical TCM studies published before 2023.

RESULTS

This review identified the ameliorative effects of about 22 single herbal extracts, more than 30 herbal compound prescriptions, and four Chinese patent medicines on DPN in preclinical and clinical research. The latest advances in the mechanism highlight that TCM exerts its beneficial effects on DPN by inhibiting inflammation, oxidative stress and apoptosis, endoplasmic reticulum stress and improving mitochondrial function.

CONCLUSIONS

TCM has shown the power latent capacity in treating DPN. It is proposed that more large-scale and multi-center randomized controlled clinical trials and fundamental experiments should be conducted to further verify these findings.

Jinmaitong alleviates diabetic neuropathic pain by inhibiting JAK2/STAT3 signaling in microglia of diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Jinmaitong (JMT) is a prescription of Traditional Chinese Medicine that is composed of 12 crude drugs. It has been used in the treatment of diabetic neuropathic pain (DNP) for more than 30 years.

AIM OF STUDY

Microglia are thought to play an important role in neuropathic pain. This study aimed to evaluate the protective effect of JMT against DNP and to investigate the underlying mechanisms in which the microglia and JAK2/STAT3 signaling pathway were mainly involved.

MATERIALS AND METHODS

The chemical composition of JMT was analyzed using liquid chromatography tandem mass spectrometry. The diabetes model was constructed using 11 to 12-week-old male Zucker diabetic fatty (ZDF) rat (fa/fa). The model rats were divided into 5 groups and were given JMT at three dosages (11.6, 23.2, and 46.4 g/kg, respectively, calculated as the crude drug materials), JAK inhibitor AG490 (positive drug, 10 μg/day), and placebo (deionized water), respectively, for eight weeks (n = 6). Meanwhile, Zucker lean controls (fa/+) were given a placebo (n = 6). Body weight was tested weekly and blood glucose was monitored every 2 weeks. The mechanical allodynia and heat hyperalgesia were assessed using mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) tests. After treatment, the microglia activation marker Iba-1, CD11B, CD68, neuroinflammatory mediators, and mediators of the JAK2/STAT3 signaling pathway were compared between different groups. The mRNA and protein levels of target genes were assessed by quantitative real-time PCR and Western Blot, respectively.

RESULTS

We found that JMT significantly inhibited the overactivation of microglia in spinal cords, and suppressed neuroinflammation of DNP model rats, thereby ameliorating neurological dysfunction and injuries. Furthermore, these effects of JMT could be attributed to the inhibition of the JAK2/STAT3 signaling pathway.

CONCLUSIONS

Our findings suggested that JMT effectively ameliorated DNP by modulating microglia activation via inhibition of the JAK2/STAT3 signaling pathway. The present study provided a basis for further research on the therapeutic strategies of DNP.

Role of microglia in diabetic neuropathic pain

Approximately one-third of the patients with diabetes worldwide suffer from neuropathic pain, mainly categorized by spontaneous and stimulus-induced pain. Microglia are a class of immune effector cells residing in the central nervous system and play a pivotal role in diabetic neuropathic pain (DNP). Microglia specifically respond to hyperglycemia along with inflammatory cytokines and adenosine triphosphate produced during hyperglycemic damage to nerve fibers. Because of the presence of multiple receptors on the microglial surface, microglia are dynamically and highly responsive to their immediate environment. Following peripheral sensitization caused by hyperglycemia, microglia are affected by the cascade of inflammatory factors and other substances and respond accordingly, resulting in a change in their functional state for DNP pathogenesis. Inhibition of receptors such as P2X reporters, reducing cytokine expression levels in the microglial reactivity mechanisms, and inhibiting their intracellular signaling pathways can effectively alleviate DNP. A variety of drugs attenuate DNP by inhibiting the aforementioned processes induced by microglial reactivity. In this review, we summarize the pathological mechanisms by which microglia promote and maintain DNP, the drugs and therapeutic techniques available, and the latest advances in this field.

Pathology of pain and its implications for therapeutic interventions

Pain is estimated to affect more than 20% of the global population, imposing incalculable health and economic burdens. Effective pain management is crucial for individuals suffering from pain. However, the current methods for pain assessment and treatment fall short of clinical needs. Benefiting from advances in neuroscience and biotechnology, the neuronal circuits and molecular mechanisms critically involved in pain modulation have been elucidated. These research achievements have incited progress in identifying new diagnostic and therapeutic targets. In this review, we first introduce fundamental knowledge about pain, setting the stage for the subsequent contents. The review next delves into the molecular mechanisms underlying pain disorders, including gene mutation, epigenetic modification, posttranslational modification, inflammasome, signaling pathways and microbiota. To better present a comprehensive view of pain research, two prominent issues, sexual dimorphism and pain comorbidities, are discussed in detail based on current findings. The status quo of pain evaluation and manipulation is summarized. A series of improved and innovative pain management strategies, such as gene therapy, monoclonal antibody, brain-computer interface and microbial intervention, are making strides towards clinical application. We highlight existing limitations and future directions for enhancing the quality of preclinical and clinical research. Efforts to decipher the complexities of pain pathology will be instrumental in translating scientific discoveries into clinical practice, thereby improving pain management from bench to bedside.

Polyphenols as NLRP3 inflammasome modulators in cardiometabolic diseases: a review of in vivo studies

The nucleotide-binding domain and leucine-rich repeat containing receptors (NLRs) are components of the innate immune system, important in coordinating the inflammatory response. Among them, NLRP3 can form inflammasomes, multiprotein complexes activating the inflammatory caspase-1 and leading, through a cell death-mediated signaling cascade, to the release of several proinflammatory cytokines. Dietary polyphenols, plant secondary metabolites, have been reported to exhibit anti-inflammatory properties, although studies have focused most on their effect on the expression of the final circulating cytokines rather than on the upstream signals activating the NLRP3 inflammasome. The present review explores current knowledge on the potential of dietary polyphenols to regulate the whole NLRP3 inflammasome pathway, in the context of cardiometabolic pathologies (obesity, cardiovascular diseases, type 2 diabetes and non-alcoholic fatty liver disease), based on in vivo studies. A clear tendency towards a decrease in the expression of the whole NLRP3 inflammasome signaling pathway when several animal models were supplemented with polyphenols was observed, commonly showing a dose-response effect; these modifications were concomitant with clinical improvements in the pathologies. Nevertheless, the diversity of doses used, the disparity in polyphenol structures tested and, particularly, the scarce clinical trials and exploration of mechanisms of action show the need to develop further research on the topic.

NLR family pyrin domain containing 3 (NLRP3) inflammasomes and peripheral neuropathic pain - Emphasis on microRNAs (miRNAs) as important regulators

Neuropathic pain is caused by the lesion or disease of the somatosensory system and can be initiated and/or maintained by both central and peripheral mechanisms. Nerve injury leads to neuronal damage and apoptosis associated with the release of an array of pathogen- or damage-associated molecular patterns to activate inflammasomes. The activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome contributes to neuropathic pain and may represent a novel target for pain therapeutic development. In the current review, we provide an up-to-date summary of the recent findings on the involvement of NLRP3 inflammasome in modulating neuropathic pain development and maintenance, focusing on peripheral neuropathic conditions. Here we provide a detailed review of the mechanisms whereby NLRP3 inflammasomes contribute to neuropathic pain via (1) neuroinflammation, (2) apoptosis, (3) pyroptosis, (4) proinflammatory cytokine release, (5) mitochondrial dysfunction, and (6) oxidative stress. We then present the current research literature reporting on the antinociceptive effects of several natural products and pharmacological interventions that target activation, expression, and/or regulation of NLRP3 inflammasome. Furthermore, we emphasize the effects of microRNAs as another regulator of NLRP3 inflammasome. In conclusion, we summarize the possible caveats and future perspectives that might provide successful therapeutic approaches against NLRP3 inflammasome for treating or preventing neuropathic pain conditions.

Ferroptosis-Regulated Cell Death as a Therapeutic Strategy for Neurodegenerative Diseases: Current Status and Future Prospects

Ferroptosis is increasingly being recognized as a key element in the pathogenesis of diverse diseases. Recent studies have highlighted the intricate links between iron metabolism and neurodegenerative disorders. Emerging evidence suggests that iron homeostasis, oxidative stress, and neuroinflammation all contribute to the regulation of both ferroptosis and neuronal health. However, the precise molecular mechanisms underlying the involvement of ferroptosis in the pathological processes of neurodegeneration and its impact on neuronal dysfunction remain incompletely understood. In our Review, we provide a comprehensive analysis and summary of the potential molecular mechanisms underlying ferroptosis in neurodegenerative diseases, aiming to elucidate the disease progression of neurodegeneration. Additionally, we discuss potential therapeutic agents that modulate ferroptosis with the goal of identifying novel drug molecules for the treatment of neurodegenerative disorders.

Salidroside alleviates diet-induced obesity and insulin resistance by activating Nrf2/ARE pathway and enhancing the thermogenesis of adipose tissues

Recent reports suggest that salidroside protects cardiomyocytes from oxidative injury and stimulates glucose uptake by skeletal muscle cells. Despite these findings, the therapeutic potential of salidroside in the treatment of obesity and insulin resistance remains uncertain and requires further investigation. In the present study, the treatment effect of salidroside on the onset and development of the obese phenotype and insulin resistance as well as the underlying mechanisms was investigated using long-term high-fat diet-induced obese mice supplemented with salidroside. We used biochemical kits to determine serum biochemical parameters (including triacylglycerol, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, fasting glucose, and insulin). The results show that salidroside-supplemented animals showed better glucose tolerance and insulin sensitivity, decreased blood lipids, and weight gain (p < .05). Protein expression of p-Nrf2 and Nrf2 was analyzed by western blotting, and the mRNA levels of thermogenic-related genes (Ucp1, Pgc1a, Prdm16, and Cidea) were detected by quantitative RT-PCR. The results show an improvement in lipid peroxidation and Nrf2/ARE signaling, as well as an increased expression of the Ucp1, Pgc1a, Prdm16, and Cidea (p < .05). Our evidence suggests that salidroside alleviates diet-induced obesity and insulin resistance potentially by activating Nrf2/ARE pathway and enhancing the thermogenesis of adipose tissues. This induction represents a potential technique for the management of comorbidities related to obesity and its prevention.

Activation of Protease-Activated Receptor-1 Causes Chronic Pain in Lupus-Prone Mice Via Suppressing Spinal Glial Glutamate Transporter Function and Enhancing Glutamatergic Synaptic Activity

Systemic lupus erythematosus (SLE) is an unpredictable autoimmune disease where the body's immune system mistakenly attacks healthy tissues in many parts of the body. Chronic pain is one of the most frequently reported symptoms among SLE patients. We previously reported that MRL lupus prone (MRL/lpr) mice develop hypersensitivity to mechanical and heat stimulation. In the present study, we found that the spinal protease-activated receptor-1(PAR1) plays an important role in the genesis of chronic pain in MRL/lpr mice. Female MRL/lpr mice with chronic pain had activation of astrocytes, over-expression of thrombin and PAR1, enhanced glutamatergic synaptic activity, as well as suppressed activity of adenosine monophosphate-activated protein kinase (AMPK) and glial glutamate transport function in the spinal cord. Intrathecal injection of either the PAR1 antagonist, or AMPK activator attenuated heat hyperalgesia and mechanical allodynia in MRL/lpr mice. Furthermore, we also identified that the enhanced glutamatergic synaptic activity and suppressed activity of glial glutamate transporters in the spinal dorsal horn of MRL/lpr mice are caused by activation of the PAR1 and suppression of AMPK signaling pathways. These findings suggest that targeting the PAR1 and AMPK signaling pathways in the spinal cord may be a useful approach for treating chronic pain caused by SLE. PERSPECTIVE: Our study provides evidence suggesting activation of PAR1 and suppression of AMPK in the spinal cord induces thermal hyperalgesia and mechanical allodynia in a lupus mouse model. Targeting signaling pathways regulating the PAR1 and AMPK could potentially provide a novel approach to the management of chronic pain caused by SLE.

The emerging role of pyroptosis in neuropathic pain

Neuropathic pain caused by somatosensory system injuries is notoriously difficult to treat. Previous research has shown that neuroinflammation and cell death have been implicated in the pathophysiology of neuropathic pain. Pyroptosis is a form of programmed cell death associated with inflammatory processes, as it can enhance or sustain the inflammatory response by releasing pro-inflammatory cytokines. This review presents the current knowledge on pyroptosis and its underlying mechanisms, including the canonical and noncanonical pathways. Moreover, we discuss recent findings on the role of pyroptosis in neuropathic pain and its potential as a therapeutic target. In conclusion, this review highlights the potential significance of pyroptosis as a promising target for developing innovative therapies to treat neuropathic pain.

Anti-Alzheimer Potential of a New (+)-Pinitol Glycoside Isolated from Tamarindus indica Pulp: In Vivo and In Silico Evaluations

Tamarindus indica Linn (tamarind, F. Leguminosae) is one of the most widely consumed edible fruits in the world. Phytochemical investigation of tamarind pulp n-butanol fraction yielded one new (+)-pinitol glycoside compound 1 (25% w/w), and 1D, 2D NMR, and HRESIMS investigation were used to confirm the new compound's structure. (+)-Pinitol glycoside showed anti-Alzheimer potential that was confirmed in prophylactic and treatment groups by decreasing time for the T-maze test; decreased TAO, brain and serum AChE, MDA, tau protein levels, and β amyloid peptide protein levels; and increasing GPX, SOD levels, and in vivo regression of the neurodegenerative features of Alzheimer's dementia in an aluminum-intoxicated rat model. The reported molecular targets for human Alzheimer's disease were then used in a network pharmacology investigation to examine their complex interactions and identify the key targets in the disease pathogenesis. An in silico-based analysis (molecular docking, binding free energy calculation (ΔG_Binding), and molecular dynamics simulation) was performed to identify the potential targets for compound 1. The findings of this study may lead to the development of dietary supplements for the treatment of Alzheimer's disease.

Role of the inflammasome in insulin resistance and type 2 diabetes mellitus

The inflammasome is a protein complex composed of a variety of proteins in cells and which participates in the innate immune response of the body. It can be activated by upstream signal regulation and plays an important role in pyroptosis, apoptosis, inflammation, tumor regulation, etc. In recent years, the number of metabolic syndrome patients with insulin resistance (IR) has increased year by year, and the inflammasome is closely related to the occurrence and development of metabolic diseases. The inflammasome can directly or indirectly affect conduction of the insulin signaling pathway, involvement the occurrence of IR and type 2 diabetes mellitus (T2DM). Moreover, various therapeutic agents also work through the inflammasome to treat with diabetes. This review focuses on the role of inflammasome on IR and T2DM, pointing out the association and utility value. Briefly, we have discussed the main inflammasomes, including NLRP1, NLRP3, NLRC4, NLRP6 and AIM2, as well as their structure, activation and regulation in IR were described in detail. Finally, we discussed the current therapeutic options-associated with inflammasome for the treatment of T2DM. Specially, the NLRP3-related therapeutic agents and options are widely developed. In summary, this article reviews the role of and research progress on the inflammasome in IR and T2DM.

Effects of NLRP3 on implants placement

Bone stability is precisely controlled by osteoclast-mediated bone resorption and osteoblast-mediated bone formation. When the balance is broken, the integrity of the bone structure will be destroyed. Inflammasomes are important protein complexes in response to pathogen-related molecular models or injury-related molecular models, which can promote the activation and secretion of proinflammatory cytokines and activate a local inflammatory response. NOD-like receptor thermal protein domain associated protein (NLRP) 3 inflammasome can promote bone resorption through the activation of the proinflammatory cytokines interleukin (IL)-1β, IL-18 and the induction of caspase-1-mediated pyroptosis. Inhibiting the production of NLRP3 inflammasome may be beneficial to improve comfort and bone stability. The presence of metal particles and microorganisms around implants can activate NLRP3 and promote bone absorption. NLRP3 inflammasome plays an important role in the maintenance of bone stability around implants, however, most studies focus on orthopedic implants and periodontitis. This article reviews the effects of NLRP3 inflammasome on bone formation, resorption and pain induced by implants, and the possibility of NLRP3 as a target for preventing peri-implantitis is discussed.

Salidroside protects pancreatic β-cells against pyroptosis by regulating the NLRP3/GSDMD pathway in diabetic conditions

The NACHT, LRP, and PYD domains-containing protein 3 (NLRP3) inflammasome-evoked chronic inflammation is involved in the pathogenesis of diabetes mellitus (DM), and the NLRP3/gasdermin D (GSDMD)-mediated canonical pathway of pyroptosis leads to the loss of pancreatic β-cells and failure of pancreatic function in DM. A previous study demonstrated that salidroside (SAL) alleviates the pathological hyperplasia of pancreatic β-cells in db/db mice. However, it is not clear whether the NLRP3/GSDMD pathway-mediated pyroptosis can be regulated by SAL. In addition, the action of SAL on pancreatic β-cells in DM remains poorly understood. Thus, this study aimed to investigate the effects and underlying mechanisms of SAL on pancreatic β-cell pyroptosis. Rat insulinoma (INS-1) cells were cultured in a medium containing either high glucose (HG) or HG plus high insulin (HG-HI), and the effects of SAL on cell viability, AMP-activated protein kinase (AMPK) activity, reactive oxygen species (ROS) generation, NLRP3/GSDMD activation, and pyroptotic body formation were assessed. Streptozocin-induced DM mice were used to further investigate the effects of SAL on pancreatic pyroptosis. The results revealed aberrances on cell viability, AMPK activity, ROS generation, NLRP3/GSDMD activation, and pyroptotic body formation in HG- and HG-HI-exposed INS-1 cells; these abnormal effects were corrected by SAL in both a concentration- and AMPK-dependent manner. Moreover, SAL administration activated AMPK, suppressed NLRP3/GSDMD signaling, and protected pancreatic β-cells against pyroptosis in DM mice. These findings suggest that SAL promotes AMPK activation to suppress NLRP3/GSDMD-related pyroptosis in pancreatic β-cells under DM conditions.

Spinal HDAC6 mediates nociceptive behaviors induced by chronic constriction injury via neuronal activation and neuroinflammation

Neuropathic pain (NP) is often accompanied by psychiatric comorbidities and currently lacks effective treatment. Prior research has shown that HDAC6 plays a crucial role in pain sensitization, but the specific mechanisms remain unclear. HDAC6 inhibitors have been found to alleviate mechanical allodynia caused by inflammation and peripheral nerve damage. In this study, we investigated the cellular mechanisms of HDAC6 in the development and maintenance of neuropathic pain. Our findings indicate that HDAC6 expression in the spinal cord (SC) is upregulated in a time-dependent manner following chronic constriction injury (CCI). HDAC6 is primarily expressed in neurons and microglia in the spinal cord. CCI-induced HDAC6 production was abolished by intrathecal injection of a microglia inhibitor. ACY-1215, a specific HDAC6 inhibitor, significantly reduced CCI-induced mechanical allodynia, but not thermal hyperalgesia. ACY-1215 also inhibited neuron activation and suppressed CCI-induced pyroptosis and neuroinflammatory responses. In summary, our results suggest that HDAC6 contributes to the development and maintenance of NP through neuronal activation and neuroinflammation. HDAC6 may be a promising target for treating NP.

The upregulation of NLRP3 inflammasome in dorsal root ganglion by ten-eleven translocation methylcytosine dioxygenase 2 (TET2) contributed to diabetic neuropathic pain in mice

BACKGROUND

The nucleotide oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) in dorsal root ganglion (DRG) contributes to pain hypersensitivity in multiple neuropathic pain models, but the function of the NLRP3 in diabetic neuropathic pain (DNP) and the regulation mechanism are still largely unknown. Epigenetic regulation plays a vital role in the controlling of gene expression. Ten-eleven translocation methylcytosine dioxygenase 2 (TET2) is a DNA demethylase that contributes to transcriptional activation. TET2 is also involved in high glucose (HG)-induced pathology.

METHODS

DNP was induced in mice via the intraperitoneal injection of streptozotocin (STZ) for five consecutive days and the mechanical threshold was evaluated in STZ-diabetic mice by using von Frey hairs. The expression level of the NLRP3 pathway and TET2 in DRG were determined through molecular biology experiments. The regulation of the NLRP3 pathway by TET2 was examined in in vitro and in vivo conditions.

RESULTS

In the present research, we first established the DNP model and found that NLRP3 pathway was activated in DRG. The treatment of NLRP3 inhibitor MCC950 alleviated the mechanical allodynia of DNP mice. Then we revealed that in STZ-diabetic mice DRG, the genomic DNA was demethylated, and the expression of DNA demethylase TET2 was increased evidently. Using RNA-sequencing analysis, we found that the expression of Txnip, a gene that encodes a thioredoxin-interacting protein (TXNIP) which mediates NLRP3 activation, was elevated in the DRG after STZ treatment. In addition, knocking down of TET2 expression in DRG using TET2-siRNA suppressed the mRNA expression of Txnip and subsequently inhibited the expression/activation of NLRP3 inflammasome in vitro and in vivo as well as relieved the pain sensitivity of DNP animals.

CONCLUSION

The results suggested that the upregulation of the TXNIP/NLRP3 pathway by TET2 in DRG was involved in the pain hypersensitivity of the DNP model.

Perisciatic Nerve Dexmedetomidine Alleviates Spinal Oxidative Stress and Improves Peripheral Mitochondrial Dynamic Equilibrium in a Neuropathic Pain Mouse Model in an AMPK-Dependent Manner

Neuropathic pain (NPP) is a debilitating clinical condition that presently has few effective treatments. NPP is caused by uncontrolled central oxidative stress and inflammation. Preliminary studies indicate that dexmedetomidine (DEX), an agonist of the alpha-2 adrenergic receptor, is beneficial for treating NPP. In this paper, the effects of administering DEX around injured nerves in a chronic constriction injury- (CCI-) induced neuropathic pain mouse model are investigated. According to the results, the perineural DEX significantly reversed the decline in the mechanical threshold and thermal latency in CCI mice ( $p<0.001$ ). In the peripherally affected ischiadic nerve, the perineuronal DEX upregulated the expressions of pAMPK, OPA1, and SNPH but not Drp1 or KIF5B. The aforementioned effects of administering DEX can be partially reversed by compound C, a selective and reversible inhibitor of AMP-activated protein kinase (AMPK). Furthermore, it was found that perineural DEX significantly inhibited the CCI-induced upregulation of the immediate early gene c-Fos, overexpression of the inflammatory factors tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), attenuation of the NADH dehydrogenase complexes I, II, III, and IV, and the repression of ATP, SOD, and GSH in the dorsal horn of the spinal cord (DHSC) ( $p<0.01$ ). These findings indicate that perineuronal DEX protected the injured ischiadic nerves and attenuated neuropathic pain via AMPK activation to improve energy supply in the peripheral injured nerves, alleviate the inflammatory factor release, and inhibit oxidative stress in the DHSC.

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.

Salidroside attenuates high altitude hypobaric hypoxia-induced brain injury in mice via inhibiting NF-κB/NLRP3 pathway

Salidroside (Sal), an active ingredient from Rhodiola crenulate, has been reported to exert neuroprotection in cerebral injury from hypobaric hypoxia (HH) at high altitude. However, it remains to be understood whether its protective effects are related to inflammation suppression. In the present work, we aimed to reveal the mechanism of Sal attenuating HH-induced brain injury in mice caused by an animal hypobaric and hypoxic chamber. Our results provided that Sal could attenuate HH-evoked pathological injury and oxidative stress response by decreasing the content of ROS and MDA, and elevating the activities of SOD and GSH-Px. Sal treatment could partly enhance the energy metabolism, evidenced by increasing the activities of Na⁺-K⁺-ATPase, Ca²⁺-Mg²⁺-ATPase, ATP, SDH, HK and PK, while decreasing the release of LDH and LD. Meanwhile, Sal administration reversed the degradation of tight junction proteins ZO-1, Occludin and Claudin-5. Further, the increased levels of TNF-α, IL-1β and IL-6 were confined with Sal administration under the HH condition. Importantly, Sal could downregulate the proteins expression of p-NF-κB-p65, NLRP3, cleaved-Caspase-1 and ASC. Sal also decreased the protein expression of iNOS and COX2 with the increased CD206 and Arg1 expression. Taken together, these data provided that the inhibited NF-κB/NLRP3 pathway by Sal could attenuate HH-induced cerebral oxidative stress injury, inflammatory responses and the blood brain barrier (BBB) damage, attributing to the improved energy metabolism and the microglial phenotype of anti-inflammatory M2. The findings suggested that Sal was expected to be a promising anti-inflammatory agent for high altitude HH-induced brain injury.

Salidroside inhibits doxorubicin-induced cardiomyopathy by modulating a ferroptosis-dependent pathway

BACKGROUND

Doxorubicin-induced cardiotoxicity (DIC) limits the clinical application of the drug in treatment of cancers and imposes a severe health burden on the patients. Therefore, there is an urgent need to develop alternative therapeutic strategies or drugs to minimize DIC. Salidroside is a phenylpropanoid glycoside extracted from Rhodiola rosea with multiple biological effects such as anti-inflammation and antioxidant properties. However, its mechanism of action in DIC is still poorly understood.

PURPOSE

The present study was aimed to investigate the role of salidroside in DIC and associated mechanism of action for the described effects.

METHODS

Cardiac dysfunction was induced through treatment of mice with doxorubicin in vivo and in vitro. The mechanism of action of salidroside was investigated using western blot assay, qPCR, immunofluorescence, histochemistry, echocardiography, and high-content imaging system.

RESULTS

Results of the current study found that treatment of mice with salidroside significantly improved doxorubicin-induced cardiac dysfunction, ferroptosis-like cell damage, and fibrosis in vivo. Further, it was noted that salidroside inhibited ferroptosis in vivo and in vitro by limiting iron accumulation, restoring GPX4-dependent antioxidant capacity, and preventing lipid peroxidation at the cellular or mitochondrial levels. Mechanistically, salidroside inhibited DOX-induced mitochondrial ROS, Fe2+, and lipid peroxidation as well as restored mitochondrial membrane potential by promoting mitochondrial biogenesis, improving mitochondrial iron-sulfur clusters, and restoring mitochondrial OXPHOS complexes, thereby improving mitochondrial function. In addition, AMPK is a key protein that coordinates mitochondria, metabolism, and ferroptosis. Therefore, it was found that compound C (CC), an AMPK inhibitor, disrupted the regulation of cellular lipid metabolism and mitochondrial function of salidroside as well as led to failure of the protective effect of salidroside against ferroptotic cell death.

CONCLUSIONS

The present study evidently demonstrated the cardioprotective effects of salidroside against doxorubicin-induced cardiomyopathy. Further, salidroside markedly down-regulated ferroptotic cell death by activating AMPK-dependent signaling pathways including regulating abnormal fatty acid metabolism and maintaining mitochondrial function. Therefore, salidroside is can be exploited to develop a novel medication for clinical DIC and salidroside may represent a novel treatment that improves recovery from DIC by targeting ferroptosis.

Salidroside inhibits NLRP3 inflammasome activation and apoptosis in microglia induced by cerebral ischemia/reperfusion injury by inhibiting the TLR4/NF-κB signaling pathway

Background

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is an important mediator of neuroinflammatory responses that regulates inflammatory injury following cerebral ischemia and may be a potential target. Salidroside (Sal) has good anti-inflammatory effects; however, it remains unclear whether Sal can regulate NLRP3 inflammasome activation through the Toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) signaling pathway after cerebral ischemia to alleviate inflammatory injury.

Methods

We established an oxygen-glucose deprivation and reoxygenation (OGD/R) model of BV2 cells and a middle cerebral artery occlusion/reperfusion (MCAO/R) rat model. Cell Counting Kit-8 (CCK-8), flow cytometry and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay were used to detect the viability and apoptosis of BV2 cells. Enzyme-linked immunosorbent assay (ELISA) was used to detect the level of inflammatory factors. 2,3,5-triphenyltetrazolium chloride (TTC) staining and modified Neurological Severity Score (mNSS) were used to detect cerebral infarction volume and neurological deficit in rats. Western blot, immunohistochemistry and immunofluorescence staining were used to detect the protein expression levels.

Results

Our results showed that Sal increased viability, inhibited lactate dehydrogenase (LDH) release, and reduced apoptosis in OGD/R-induced BV2 cells. Sal reduced the levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-8. Following induction by OGD/R, BV2 cells exhibited NLRP3 inflammasome activation and increased protein levels of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), caspase-1, IL-1β, and IL-18. Protein levels of key TLR4 signaling pathway elements, such as TLR4, myeloid differentiation primary response 88 (MyD88), and phosphorylated nuclear factor kappa B p65 (p-NF-κB p65)/NF-κB p65 were upregulated. Interestingly, it was revealed that Sal could reverse these changes. In addition, TAK242, a specific inhibitor of TLR4, had the same effect as Sal treatment on BV2 cells following induction by OGD/R. In the MCAO/R rat model, Sal was also observed to inhibit NLRP3 inflammasome activation in microglia, reduce cerebral infarction volume, and inhibit apoptosis.

Conclusions

In summary, we found that Sal inhibited NLRP3 inflammasome activation and apoptosis in microglia induced by cerebral ischemia/reperfusion injury by inhibiting the TLR4/NF-κB signaling pathway, thus playing a protective role. Therefore, Sal may be a promising drug for the clinical treatment of ischemic stroke.

Salidroside Affects Gut Microbiota Structure in db/db Mice by Affecting Insulin, Blood Glucose and Body Weight

PURPOSE

The purpose of this study was to investigate the regulatory effect of salidroside on the intestinal flora of mice with type 2 diabetes (T2DM) and its protective effect in the body.

PATIENTS AND METHODS

We acclimated 8-week-old mice for 7 days, divided them into 4 groups, and continued dosing for 8 weeks. We recorded weekly blood glucose levels and body weight for each mouse. After the completion of the feeding cycle, the 16S rRNA of the intestinal flora in the mice was sequenced, and the insulin and C-peptide levels in each group of mice were measured. Four samples were taken from each group for liver and kidney section staining.

RESULTS

Our results showed that gut microbiota diversity and function were significantly different between the diabetic mice and healthy mice and that insulin levels, body weight, and blood glucose levels could significantly influence gut microbiota changes at the genus level. The gut microbiota diversity and function of db/db mice were also altered after salidroside administration. Salidroside could attenuate inflammatory damage, lipid accumulation and inflammatory changes in the diabetic liver, as well as diabetic kidney damage. Candidatus arthromitus and Odoribacter are important species of the microbiota during diabetes and may serve as potential therapeutic targets.

CONCLUSION

Our investigation of the associated pathological conditions and fecal microbiota in db/db mice provides new insights into the pathogenesis of T2DM and provides implications for the diagnosis and treatment of T2DM.

Glycosides for Peripheral Neuropathic Pain: A Potential Medicinal Components

Neuropathic pain is a refractory disease that occurs across the world and pharmacotherapy has limited efficacy and/or safety. This disease imposes a significant burden on both the somatic and mental health of patients; indeed, some patients have referred to neuropathic pain as being 'worse than death'. The pharmacological agents that are used to treat neuropathic pain at present can produce mild effects in certain patients, and induce many adverse reactions, such as sedation, dizziness, vomiting, and peripheral oedema. Therefore, there is an urgent need to discover novel drugs that are safer and more effective. Natural compounds from medical plants have become potential sources of analgesics, and evidence has shown that glycosides alleviated neuropathic pain via regulating oxidative stress, transcriptional regulation, ion channels, membrane receptors and so on. In this review, we summarize the epidemiology of neuropathic pain and the existing therapeutic drugs used for disease prevention and treatment. We also demonstrate how glycosides exhibit an antinociceptive effect on neuropathic pain in laboratory research and describe the antinociceptive mechanisms involved to facilitate the discovery of new drugs to improve the quality of life of patients experiencing neuropathic pain.

Probucol attenuates NF-κB/NLRP3 signalling and augments Nrf-2 mediated antioxidant defence in nerve injury induced neuropathic pain

Neuroinflammation is one of the most significant pathological drivers following nerve injury which along with immune cell activation, oxidative stress and other associated molecular mechanisms contribute to development of neuropathic pain characterized by hyperalgesia and allodynia. In the current study we have investigated the pharmacological effect of probucol (prb) using chronic constriction injury (CCI) of sciatic nerve induced neuropathic pain (NP) model in rats. CCI of sciatic nerve resulted in marked decrease in pain threshold along with perturbations in anti-oxidant defence, enhanced inflammatory mediators and abnormal foot posture. Administration of prb at the doses of 8 and 16 mg/kg, p.o. for 14 days significantly attenuated the behavioural, biochemical and functional deficits following CCI of sciatic nerve. To further explore the molecular mechanisms of prb, we assessed the post treatment levels of inflammatory and oxidative stress markers like NLRP3 inflammasome, NF-κB and associated proinflammatory molecules such as IL-1 β, TNF-α & IL-6 along with Nrf-2 and HO-1. Our findings demonstrated that CCI induced changes in levels of these markers were dose dependently reversed by administration of prb. Of note, at molecular level the elevated expression of transcription factors such as NF-κB which is crucial for Nlrp3 activation and diminished levels of Nrf-2 were manifested following CCI induction, these changes were markedly reversed with 14 days treatment of prb at both the doses. Our findings highlighted the dual pharmacological effect of prb, anti-inflammatory and anti-oxidant via modulation of NF-κB/NLRP3 signalling and Nrf-2 pathway in attenuation of CCI of sciatic nerve induced NP.