Analgesic Effects of Triterpenoid Saponins From Stauntonia chinensis via Selective Increase in Inhibitory Synaptic Response in Mouse Cortical Neurons

Antinociceptive activity of doliroside B

CONTEXT

Dolichos trilobus Linn (Leguminosae) is often used in Yi ethnic medicine to treat pain, fracture, and rheumatism.

OBJECTIVE

To explore the therapeutic potential of doliroside B (DB) from D. trilobus and its disodium salt (DBDS) and the underlying mechanism in pain.

MATERIALS AND METHODS

In the writhing test, Kunming mice were orally treated with DB and DBDS at doses of 0.31, 0.62, 1.25, 2.5, and 5 mg/kg. Vehicle, morphine, indomethacin, and acetylsalicylic acid were used as negative and positive control on the nociception-induced models, respectively. In the hot plate test, mice were orally treated with DB and DBDS at doses of 2.5, 5, 10, and 20 mg/kg. In the formalin test, mice were orally treated with DB and DBDS at doses of 2.5, 5, 10, and 20 mg/kg. In the meanwhile, lipopolysaccharide-induced inflammatory model in RAW264.7 macrophages was adopted to study the mechanism of pain alleviation for DBDS.

RESULTS

DBDS (5 mg/kg) inhibited the writhing number by 80.2%, which exhibited the highest antinociceptive activity in pain models. DBDS could selectively inhibite the activity of COX-1. Meanwhile, it also reduced the production of NO, iNOS, and IL-6 by 55.8%, 69.0%, and 49.9% inhibition, respectively. It was found that DBDS also positively modulated the function of GABA_A1 receptor.

DISCUSSION AND CONCLUSIONS

DBDS displayed antinociceptive activity by acting on both the peripheral and central nervous systems, which may act on multitargets. Further work is warranted for developing DBDS into a potential drug for the treatment of pain.

Stauntonia chinensis injection relieves neuropathic pain by increasing the expression of PSD-95 and reducing the proliferation of phagocytic microglia

Neuroinflammation induced by engulfment of synapses by phagocytic microglia plays a crucial role in neuropathic pain. Stauntonia chinensis is extracted from Stauntonia chinensis DC, which has been used as a traditional Chinese medicine to control trigeminal neuralgia or sciatica. However, the specific anti-neuralgia mechanism of Stauntonia chinensis is unknown. In this study, the analgesic effect of Stauntonia chinensis injection (SCI) in mice with neuropathic pain and the possible mechanisms are explored. We find that a local injection of 0.1 mL Stauntonia chinensis for 14 days can considerably relieve mechanical hyperalgesia and thermal hyperalgesia in mice with sciatic chronic constriction injury (CCI). Immunofluorescence staining shows that SCI reduces neuroinflammation in the spinal cord of CCI mice. RNA sequencing reveals that the expression of postsynaptic density protein 95 (PSD-95), a postsynaptic scaffold protein, is downregulated in the spinal cord of CCI mice, but upregulated after SCI administration. Immunofluorescence experiments also demonstrate that SCI administration reverses microglia proliferation and PSD-95 downregulation in CCI mice. These data suggest that SCI relieves neuropathic pain by increasing the expression of PSD-95 and reducing the proliferation of phagocytic microglia.

Research progress on drugs for diabetes based on insulin receptor/insulin receptor substrate

The number of people with diabetes worldwide is increasing annually, resulting in a serious economic burden. Insulin resistance is a major pathology in the early onset of diabetes mellitus, and therefore, related drug studies have attracted research attention. The insulin receptor/insulin receptor substrate (INSR/IRS) serves as the primary conduit in the insulin signal transduction cascade, and dysregulation of this pathway can lead to insulin resistance. Currently, there exist a plethora of hypoglycemic drugs in the market; however, drugs that specifically target INSR/IRS are comparatively limited. The literature was collected by direct access to the PubMed database, and was searched using the terms "diabetes mellitus; insulin resistance; insulin receptor; insulin receptor substrate; diabetes drug" as the main keywords for literature over the last decade. This article provides a comprehensive analysis of the structure and function of INSR and IRS proteins, as well as the drugs used for the treatment of diabetes. Additionally, it serves as a valuable reference for the advancement of novel therapeutic agents for diabetes management.

Central and peripheral analgesic active components of triterpenoid saponins from Stauntonia chinensis and their action mechanism

Triterpenoid saponins from Stauntonia chinensis have been proven to be a potential candidate for inflammatory pain relief. Our pharmacological studies confirmed that the analgesic role of triterpenoid saponins from S. chinensis occurred via a particular increase in the inhibitory synaptic response in the cortex at resting state and the modulation of the capsaicin receptor. However, its analgesic active components and whether its analgesic mechanism are limited to this are not clear. In order to further determine its active components and analgesic mechanism, we used the patch clamp technique to screen the chemical components that can increase inhibitory synaptic response and antagonize transient receptor potential vanilloid 1, and then used in vivo animal experiments to evaluate the analgesic effect of the selected chemical components. Finally, we used the patch clamp technique and molecular biology technology to study the analgesic mechanism of the selected chemical components. The results showed that triterpenoid saponins from S. chinensis could enhance the inhibitory synaptic effect and antagonize the transient receptor potential vanilloid 1 through different chemical components, and produce central and peripheral analgesic effects. The above results fully reflect that "traditional Chinese medicine has multi-component, multi-target, and multi-channel synergistic regulation".

Triterpenoid saponins from Psammosilene tunicoides and their antinociceptive activities

Herein, five undescribed oleanane-type triterpenoid saponins, namely, psammosaponins A-E, along with nine known compounds, were isolated from the roots of Psammosilene tunicoides. Moreover, part of the ethanolic extract of P. tunicoides was acid-hydrolyzed and three aglycones were isolated from the resulting hydrolysate. The structures of all compounds were established through extensive analysis involving 1D and 2D NMR experiments, HRESIMS measurements, chemical derivatization, and comparison of spectroscopic data with the values reported in the literature. In all, 10 of the isolated saponins and the three aglycones were evaluated in the acetic acid-induced writhing model for their antinociceptive activity. At a dose of 40 mg/kg, these compounds exhibited significant inhibitory effects on the mouse writhing response, with inhibitions ranging from 31.9% to 79.3%. In addition, the structure-activity relationships of the isolates were discussed. Among the isolates, quillaic acid 3-O-glucuronide and 16α-hydroxygypsogenic acid showed better antinociceptive activity with inhibitions of 79.3% and 73.7%, respectively. Both isolates also exhibited antinociceptive activities in hot plate and formalin tests on mice. Their antinociceptive mechanism was explored in lipopolysaccharide-stimulated RAW 264.7 cells. These isolates could significantly inhibit the production of nitric oxide and interleukin-6 and downregulate the expression levels of inducible NO synthase, COX-1, and COX-2.

LQM10, a guanylhydrazone derivative, reduces nociceptive and inflammatory responses in mice

In the present study, we examined the antinociceptive and anti-inflammatory activities of a guanylhydrazone derivative, (E)-(3,5-di-tert-butyl-4-hydroxybenzylidene)-2-guanylhydrazone hydrochloride (LQM10), in mice. The antinociceptive effect was determined by assessing behavioural responses in different pain models, while anti-inflammatory activity was examined in carrageenan-induced pleurisy. Intraperitoneal LQM10 administration reduced the acetic acid-induced nociceptive behaviour, a phenomenon that was unaltered by pretreatment with yohimbine, atropine, naloxone or glibenclamide. In the formalin assay, LQM10 reduced nociceptive behaviour only in the second phase, indicating an inhibitory effect on inflammatory pain. LQM10 did not alter the pain latency in the hot plate assay and did not impact the locomotor activity of mice in the rotarod assay. In the carrageenan-induced pleurisy assay, LQM10 treatment inhibited critical events involved in inflammatory responses, namely, leucocyte recruitment, plasma leakage and increased inflammatory mediators (tumour necrosis factor Like Properties of Chalchones and Flavonoid Derivatives [TNF]-α and interleukin [IL]-1β) in the pleural exudate. Overall, these results indicate that LQM10 exhibits antinociceptive effects associated with peripheral mechanisms and anti-inflammatory activity mediated via a reduction in leucocyte migration and proinflammatory mediators, rendering this compound a promising candidate for treating pain and inflammatory process.

Diosgenin Exerts Analgesic Effects by Antagonizing the Selective Inhibition of Transient Receptor Potential Vanilloid 1 in a Mouse Model of Neuropathic Pain

Diosgenin is a botanical steroidal saponin with immunomodulatory, anti-inflammatory, anti-oxidative, anti-thrombotic, anti-apoptotic, anti-depressant, and anti-nociceptive effects. However, the effects of diosgenin on anti-nociception are unclear. Transient receptor potential vanilloid 1 (TRPV1) plays an important role in nociception. Therefore, we investigated whether TRPV1 antagonism mediates the anti-nociceptive effects of diosgenin. In vivo mouse experiments were performed to examine nociception-related behavior, while in vitro experiments were performed to examine calcium currents in dorsal root ganglion (DRG) and Chinese hamster ovary (CHO) cells. The duration of capsaicin-induced licking (pain behavior) was significantly reduced following oral and intraplantar administration of diosgenin, approaching levels observed in mice treated with the TRPV1 antagonist N-(4-tertiarybutylphenyl)-4-(3-cholorphyridin-2-yl) tetrahydropyrazine-1(2H)-carbox-amide. Additionally, oral administration of diosgenin blocked capsaicin-induced thermal hyperalgesia. Further, diosgenin reduced capsaicin-induced Ca²⁺ currents in a dose-dependent manner in both DRG and CHO cells. Oral administration of diosgenin also improved thermal and mechanical hyperalgesia in the sciatic nerve constriction injury-induced chronic pain model by reducing the expression of TRPV1 and inflammatory cytokines in DRG cells. Collectively, our results suggest that diosgenin exerts analgesic effects via antagonism of TRPV1 and suppression of inflammation in the DRG in a mouse model of neuropathic pain.

Optimization of the Purifying Process for Columbianetin-β-D-Glucopyranoside from Angelicae Pubescentis Radix and Evaluation of Its Analgesic Activity Using Hot Plate Test

The objective of this work was to provide an economic and practical method for the purification of columbianetin-β-D-glucopyranoside from Angelicae Pubescentis Radix extract. In the static adsorption and desorption, the effects of resin type (D101, HP-20, AB-8, GDX-201, and DA201), contact time (10–360 min), and temperature (298–318 K) were assessed on columbianetin-β-D-glucopyranoside adsorption efficiency in laboratory. GDX-201 resin showed the best adsorption and desorption properties for columbianetin-β-D-glucopyranoside. The kinetic data revealed that the equilibrium time for columbianetin-β-D-glucopyranoside adsorption was achieved within 150 min. Moreover, the adsorption kinetic curve was well in accordance with the pseudo-second-order equation (R² > 0.99). The rate controlling step of the adsorption process was the intraparticle diffusion. The Langmuir isotherm models (R² > 0.99) could describe the whole adsorption process, which was exothermic and spontaneous according to the result of thermodynamics tests. In the dynamic adsorption and desorption process, the optimum loading flow (4, 5, and 6 BV/h), ethanol concentration (0–60%), and elution volume (10–230 mL) were optimized. Under optimal conditions of 4 BV/h loading flow, 6.7 BV loading volume, 25% ethanol, and 14 BV elution volume, the content of columbianetin-β-D-glucopyranoside in the product was increased 29.61-fold from 0.45% to 13.32 ± 0.64% with yield of 88.03 ± 2.76% by an experiment of lab-scale enlargement. Then, columbianetin-β-D-glucopyranoside was further purified by PHPLC and its purity was more than 98%. Additionally, the analgesic activity of the columbianetin-β-D-glucopyranoside was assessed by hot plate test. The experimental results showed that columbianetin-β-D-glucopyranoside significantly increased the latency of pain response in mice. This study demonstrated columbianetin-β-D-glucopyranoside could be as a potentially natural analgesic component. It could be summed up that the established method was successfully applied to purifying columbianetin-β-D-glucopyranoside from Angelicae Pubescentis Radix extract.

The Hydroethanolic Stem Bark Extract of Tieghemella heckelii (A.Chev.) Pierre ex Dubard (Sapotaceae) Produced N-Methyl-D-Aspartate (NMDA) Receptor-Dependent Analgesia and Attenuates Acute Inflammatory Pain via Disruption of Oxidative Stress

BACKGROUND

Tieghemella heckelii stem bark is used in African traditional medicine to treat inflammatory pain conditions. However, these biological actions of the plant have not been proven. This study investigates the phytochemical composition and the mechanisms of analgesic and anti-inflammatory actions of the hydroethanolic stem bark extract of T. heckelii (THBE).

METHODS

Phytochemical composition of THBE was investigated using qualitative and quantitative phytochemical analyses. Anti-inflammatory activity was evaluated using the carrageenan-induced paw oedema assay. Analgesic activity was evaluated using hot plate and acetic acid-induced writhing assays. Mechanism of analgesic action was determined using pharmacological antagonist such as naloxone, atropine, flumazenil, nifedipine, or ketamine. Test agents were administered orally as follows: Tween 80 (5%) (control), diclofenac sodium (DS) 10/tramadol 9 mg/kg (standard), or THBE 10, 100, and 450 mg/kg. Glutathione peroxidase (GPx), superoxide dismutase (SOD), and lipid peroxidation levels were also measured.

RESULTS

THBE which contained 58.45% saponins, 229.04 ± 0.049 GAE mg/g phenolic compounds,and 0.482 ± 0.0028 QE mg/g flavonoids produced (p < 0.5) anti-inflammatory effect of 56.22% and analgesia of 330 ± 72% and 50.4% in the hot plate and writhing assays, respectively, at 10 mg/kg and inhibited oxidative stress by GPx and SOD elevation in rats during inflammation. Ketamine significantly blocked the analgesia of THBE, indicating NMDA receptor-dependent analgesic action. Whereas, naloxone, atropine, nifedipine, and flumazenil could not antagonize the analgesic action of THBE.

CONCLUSION

These results show that THBE produced potent anti-inflammatory effect via disruption of oxidative stress and also generated NMDA receptor-dependent analgesia.

Identification and quantification of oleanane triterpenoid saponins and potential analgesic and anti-inflammatory activities from the roots and rhizomes of Panax stipuleanatus

BACKGROUND

Panax stipuleanatus represents a folk medicine for treatment of inflammation. However, lack of experimental data does not confirm its function. This article aims to investigate the analgesic and anti-inflammatory activities of triterpenoid saponins isolated from P. stipuleanatus.

METHODS

The chemical characterization of P. stipuleanatus allowed the identification and quantitation of two major compounds. Analgesic effects of triterpenoid saponins were evaluated in two models of thermal- and chemical-stimulated acute pain. Anti-inflammatory effects of triterpenoid saponins were also evaluated using four models of acetic acid-induced vascular permeability, xylene-induced ear edema, carrageenan-induced paw edema, and cotton pellet-induced granuloma in mice.

RESULTS

Two triterpenoid saponins of stipuleanosides R1 (SP-R1) and R2 (SP-R2) were isolated and identified from P. stipuleanatus. The results showed that SP-R1 and SP-R2 significantly increased the latency time to thermal pain in the hot plate test and reduced the writhing response in the acetic acid-induced writhing test. SP-R1 and SP-R2 caused a significant decrease in vascular permeability, ear edema, paw edema, and granuloma formation in inflammatory models. Further studies showed that the levels of inflammatory mediators, nitric oxide, malondialdehyde, tumor necrosis factor-α, and interleukin 6 in paw tissues were downregulated by SP-R1 and SP-R2. In addition, the rational harvest of three- to five-year-old P. stipuleanatus was preferable to obtain a higher level of triterpenoid saponins. SP-R2 showed the highest content in P. stipuleanatus, which had potential as a chemical marker for quality control of P. stipuleanatus.

CONCLUSION

This study provides important basic information about utilization of P. stipuleanatus resources for production of active triterpenoid saponins.

Endogenous Opiates and Behavior: 2018

This paper is the forty-first consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2018 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (2), the roles of these opioid peptides and receptors in pain and analgesia in animals (3) and humans (4), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (5), opioid peptide and receptor involvement in tolerance and dependence (6), stress and social status (7), learning and memory (8), eating and drinking (9), drug abuse and alcohol (10), sexual activity and hormones, pregnancy, development and endocrinology (11), mental illness and mood (12), seizures and neurologic disorders (13), electrical-related activity and neurophysiology (14), general activity and locomotion (15), gastrointestinal, renal and hepatic functions (16), cardiovascular responses (17), respiration and thermoregulation (18), and immunological responses (19).

Triterpene Glycosides Isolated from the Edible Sea Cucumber Bohadschia vitiensis and Their Antagonistic Activity against Transient Receptor Potential Ankyrin 1

Transient receptor potential ankyrin 1 (TRPA1) is a cation channel that plays a critical role in the occurrence and transmission of pain. By screening 393 marine invertebrate extracts for their antagonistic activity against TRPA1, it was found that the extract of the edible sea cucumber Bohadschia vitiensis had a remarkable potency. Bioassay-guided separation of the extract resulted in the isolation of six triterpene glycosides, including a novel analog. All six isolated compounds exhibited high inhibitory potency against TRPA1 (IC₅₀ values ranging from 0.60 to 3.26 μM), which is comparable to that of a previously developed synthetic antagonist (A-967079). The discovery of TRPA1 antagonists, originated from this edible sea cucumber, opens the door for the elaboration of the valuable triterpene scaffold for the development of novel safe analgesics.