Inhibitory effect of Total Flavone of Abelmoschus manihot L. Medic on NMDA receptor-mediated current in cultured rat hippocampal neurons

Total flavone of Abelmoschus manihot regulates autophagy through the AMPK/mTOR signaling pathway to treat intestinal fibrosis in Crohn's disease

BACKGROUND AND AIM

Drug therapy is the treatment of choice for Crohn's disease because it effectively controls or prevents intestinal inflammation. The purpose was to research the molecular mechanism of the total flavones of Abelmoschus manihot (TFA) on intestinal fibrosis in Crohn's disease.

METHODS

A 2,4,6-Trinitrobenzenesulfonic acid (TNBS)-induced colitis model and IGF-1-treated intestinal fibroblasts were established. Then, TFA, 3-MA, and compound C were used treatments. Hematoxylin and eosin, Masson, and Picrosirius red staining were performed to observe the colon tissue. Immunohistochemical staining was used to detect α-SMA expression. Flow cytometry, CCK8, wound healing, and Transwell assays were conducted to determine apoptosis, proliferation, invasion, and migration. Col1a1 and Col3a1 levels were detected using quantitative polymerase chain reaction. Proteins related to autophagy and apoptosis were detected using western blotting.

RESULTS

TFA treated intestinal fibrosis in chronic Crohn's disease. Colon length was the shortest in the ethanol + TNBS group, and TFA treatment significantly improved the situation. Intestinal fibrosis and the percentage of collagen area decreased after TFA treatment. TFA reduced fibrosis by enhancing autophagy stimulation, whereas an autophagy inhibitor reversed the TFA effect. TFA also inhibited migration, proliferation, and collagen synthesis in intestinal fibroblasts. Moreover, it enhanced autophagy and apoptosis of intestinal fibroblasts. TFA upregulated p-AMPK expression and decreases p-mTOR levels. Compound C partially rescued the effect of TFA, indicating that TFA affected intestinal fibroblasts via the AMPK/mTOR pathway in vitro and in vivo. TFA also downregulated Col1a1 and Col3a1 expression.

CONCLUSION

TFA regulates autophagy through AMPK/mTOR signaling pathway to treat intestinal fibrosis, which may provide a new therapy for Crohn's disease treatment.

Neuroprotective Effect of Abelmoschus manihot Flower Extracts against the H2O2-Induced Cytotoxicity, Oxidative Stress and Inflammation in PC12 Cells

The progression of neurodegenerative diseases is associated with oxidative stress and inflammatory responses. Abelmoschus manihot L. flower (AMf) has been shown to possess excellent antioxidant and anti-inflammatory activities. This study investigated the protective effect of ethanolic extract (AME), water extract (AMW) and supercritical extract (AMS) of AMf on PC12 neuronal cells under hydrogen peroxide (H2O2) stimulation. This study also explored the molecular mechanism underlying the protective effect of AME, which was the best among the three extracts. The experimental results showed that even at a concentration of 500 μg/mL, neither AME nor AMW showed toxic effects on PC12 cells, while AMS caused about 10% cell death. AME has the most protective effect on apoptosis of PC12 cells stimulated with 0.5 mM H2O2. This is evident by the finding when PC12 cells were treated with 500 μg/mL AME; the viability was restored from 58.7% to 80.6% in the Treatment mode (p < 0.001) and from 59.1% to 98.1% in the Prevention mode (p < 0.001). Under the stimulation of H2O2, AME significantly up-regulated the expression of antioxidant enzymes, such as catalase, glutathione peroxidase and superoxide dismutase; promoted the production of the intracellular antioxidant; reduced glutathione; and reduced ROS generation in PC12 cells. When the acute inflammation was induced under the H2O2 stimulation, AME significantly down-regulated the pro-inflammatory cytokines and mediators (e.g., TNF-α, IL-1β, IL-6, COX-2 and iNOS). AME pretreatment could also greatly promote the production of nucleotide excision repair (NER)-related proteins, which were down-regulated by H2O2. This finding indicates that AME could repair DNA damage caused by oxidative stress. Results from this study demonstrate that AME has the potential to delay the onset and progression of oxidative stress-induced neurodegenerative diseases.

HPLC and GC-MS based metabolic profiles and in vivo anticonvulsant, sedative, and antinociceptive potentials of truffles Tirmania nivea and Tirmania pinoyi hydromethanolic extracts in mice

GC-MS and HPLC analyses of the hydromethanolic extracts of the truffles Tirmania nivea (TN) and Tirmania pinoyi (TP) revealed the presence of 18 metabolites and 11 polyphenols, respectively. In vivo, TP extract protected against subcutaneous pentylenetetrazole (scPTZ) and maximal electric shock (MES)-induced convulsions faster than TN. TP (100 and 300 mg/kg) showed 100% protection and longer duration than TN in the scPTZ test. Similarly, at 300 mg/kg, TP demonstrated a quicker start (75%) and longer duration of action (100%) than TN in MES test. In scPTZ test, ED₅₀ of TP demonstrated greater anticonvulsant efficacy than TN. In mice given TP and TN treatments, the brain GABA levels were noticeably increased. TP (100 and 300mg/kg) produced a notable sedative effect in open field test, whereas TN (100 or 300 mg/kg) and TP (300 mg/kg) reduced sleep latency by 79, 52, and 45%, respectively. In writhing test, TN (100 or 300mg/kg) significantly enhanced analgesic efficacy by 50 and 87%, respectively. Comparatively, in formalin test, TP and TN at a dosage of 300 mg/kg decreased the length of the licking by 34 and 59%, respectively. For the first time, this study explains the anticonvulsant, sedative, central, and peripheral analgesic activities of truffle extracts.

Comparative Study on Chemical Constituents of Medicinal and Non-Medicinal Parts of Flos Abelmoschus manihot, Based on Metabolite Profiling Coupled with Multivariate Statistical Analysis

According to Chinese Pharmacopoeia (2020 edition), Abelmoschi Corolla (AC) is the dried corolla of Flos Abelmoschus manihot (FAM). Market research has found that AC is often mixed with the non-medicinal parts in FAM, including calyx, stamen, and pistil. However, previous studies have not clarified the relationship between the medicinal and non-medicinal parts of FAM. In this study, in order to investigate whether there is any distinction between the medicinal and non-medicinal parts of FAM, the characterization of the constituents in calyx, corolla, stamen, and pistil was analyzed by UFLC-Triple TOF-MS/MS. Multivariate statistical analysis was used to classify and screen differential constituents between medicinal and non-medicinal parts of FAM, and the relative contents of differential constituents were compared based on the peak intensities. Results showed that 51 constituents in medicinal and non-medicinal parts of FAM were identified, and the fragmentation pathways to different types of constituents were preliminarily deduced by the fragmentation behavior of the identified constituents. Furthermore, multivariate statistical analysis revealed that the medicinal and non-medicinal parts of FAM differed significantly; 20 differential constituents were screened out to reveal the characteristics of metabolic differences. Among them, the relative contents of 19 differential constituents in the medicinal part were significantly higher than those in non-medicinal parts. This study could be helpful in the quality evaluation of AC as well as provide basic information for the improvement of the market standard of AC.

Hydroalcoholic extract from Abelmoschus manihot (Linn.) Medicus flower reverses sleep deprivation-evoked learning and memory deficit

Previous researches have indicated that sleep plays a vital role in cognitive functions. Sleep deprivation (SD) causes learning and memory damage, which is associated with oxidative stress. This study was performed to investigate the neuroprotective effects of an extract of Abelmoschus manihot flower (EAM) against memory deficit induced by SD in mice. The SD model was evoked by multiple platform method for 5 days, successively. The learning and memory-improving effects of EAM were assessed by behavioral trials and the underlying mechanism was investigated by measuring the oxidative stress alteration. Our findings indicated that the SD-induced memory deficit and the EAM treatment improved the cognitive functions of mice in the object location recognition test and passive avoidance task. In addition, EAM effectively improved the activities of the antioxidant enzyme, decreased the content of malondialdehyde (MDA), and restored the protein expression of the brain-derived neurotrophic factor (BDNF), tyrosine kinase B (TrkB) and glutamate receptor 1 (GluR1) in brain tissues. In conclusion, EAM could improve the SD-evoked learning and memory impairments. The possible underlying mechanisms of EAM may be related to its antioxidant capacity and enhanced BDNF/TrkB/GluR1 levels in the hippocampal memory.

Traditional Uses, Chemical Constituents, Biological Properties, Clinical Settings, and Toxicities of Abelmoschus manihot L.: A Comprehensive Review

Abelmoschus manihot, an annual herbal flowering plant, is widely distributed throughout eastern Europe and in temperate and subtropical regions of Asia. Its flowers have been traditionally used for the treatment of chronic kidney disease in China. Currently, more than 128 phytochemical ingredients have been obtained and identified from the flowers, seeds, stems, and leaves of A. manihot. The primary components are flavonoids, amino acids, nucleosides, polysaccharides, organic acids, steroids, and volatile oils. A. manihot and its bioactive constituents possess a plethora of biological properties, including antidiabetic nephropathy, antioxidant, antiadipogenic, anti-inflammatory, analgesic, anticonvulsant, antidepressant, antiviral, antitumor, cardioprotective, antiplatelet, neuroprotective, immunomodulatory, and hepatoprotective activities, and have effects on cerebral infarction, bone loss, etc. However, insufficient utilization and excessive waste have already led to a rapid reduction of resources, meaning that a study on the sustainable use of A. manihot is urgent and necessary. Moreover, the major biologically active constituents and the mechanisms of action of the flowers have yet to be elucidated. The present paper provides an early and comprehensive review of the traditional uses, chemical constituents, pharmacological activities, and pharmaceutical, quality control, toxicological, and clinical settings to emphasize the benefits of this plant and lays a solid foundation for further development of A. manihot.

Quercetin Enhances Inhibitory Synaptic Inputs and Reduces Excitatory Synaptic Inputs to OFF- and ON-Type Retinal Ganglion Cells in a Chronic Glaucoma Rat Model

Background

Glaucoma is a neurodegenerative disease caused by excitotoxic injury of retinal ganglion cells (RGCs). In our previous model of high intraocular pressure, prepared by injecting magnetic beads into the anterior chamber, we demonstrated that an important natural dietary flavonoid compound (quercetin) can improve RGC function. However, it is unclear whether quercetin can improve the synaptic function of RGCs and how quercetin regulates synaptic transmission in rat models of chronic glaucoma.

Methods

A rat model of chronic glaucoma was prepared by electrocoagulation of the superior scleral vein. Electrophysiological electroretinography was used to detect the photopic negative response (PhNR). The whole-cell patch-clamp technique was used to clamp ON- and OFF- type RGCs in sections from normal retinas and from retinas that had been subjected to glaucoma for 4 weeks.

Results

Quercetin can reverse the decrease in PhNR amplitude caused by chronic glaucoma. The baseline frequency of miniature GABAergic inhibitory postsynaptic currents (mIPSCs) in the RGCs of glaucomatous retinal slices was lower than that of the control group. The frequencies of miniature excitatory postsynaptic currents (mEPSCs) were not significantly different between control and glaucomatous RGCs. The baseline frequencies of GABAergic mIPSCs and mEPSCs in OFF-type glaucomatous RGCs were greater than those in ON-type glaucomatous RGCs. Quercetin increased miniature GABAergic inhibitory neurotransmission to RGCs and decreased miniature glutamatergic excitatory neurotransmission, reducing the excitability of the RGCs themselves, thus alleviating the excitability of RGCs in glaucomatous slices.

Conclusion

Quercetin may be a promising therapeutic agent for improving RGC survival and function in glaucomatous neurodegeneration. Quercetin exerted direct protective effects on RGCs by increasing inhibitory neurotransmission and decreasing excitatory neurotransmission to RGCs, thus reducing excitotoxic damage to those cells in glaucoma.

Investigations of the total flavonoids extracted from flowers of Abelmoschus manihot (L.) Medic against α-naphthylisothiocyanate-induced cholestatic liver injury in rats

ETHNOPHARMACOLOGY RELEVANCE

The decoction of the flowers of Abelmoschus manihot (L.) Medic was traditionally used for the treatment of jaundice and various types of chronic and acute hepatitis in Anhui and Jiangsu Provinces of China for hundreds of years. Phytochemical studies have indicated that total flavonoids extracted from flowers of A. manihot (L.) Medic (TFA) were the major constituents of the flowers. Our previous studies have investigated the hepatoprotective effects of the TFA against carbon tetrachloride (CCl4) induced hepatocyte damage in vitro and liver injury in vivo. This study aimed to investigate the protective effects and mechanisms of TFA on α-naphthylisothiocyanate (ANIT)-induced cholestatic liver injury in rats.

MATERIAL AND METHODS

The hepatoprotective activities of TFA (125, 250 and 500mg/kg) were investigated on ANIT-induced cholestatic liver injury in rats. The serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) were used as indices of hepatic cell damage and measured. Meanwhile, the serum levels of alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT), total bilirubin (TBIL), direct bilirubin (DBIL), and total bile acid (TBA) were used as indices of biliary cell damage and cholestasis and evaluated. Hepatic malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), glutathione transferase (GST), tumor necrosis factor-α (TNF-α) and nitric oxide (NO) were measured in the liver homogenates. The bile flow in 4h was estimated and the histopathology of the liver tissue was evaluated. Furthermore, the expression of transporters, bile salt export pump (BSEP), multidrug resistance-associated protein 2 (MRP2), and Na(+)-taurocholate cotransporting polypeptide (NTCP) were studied by western blot and reverse transcription-quantitative real-time polymerase chain reaction (RT-PCR) to elucidate the protective mechanisms of TFA against ANIT-induced cholestasis.

RESULTS

The oral administration of TFA to ANIT-treated rats could reduce the increases in serum levels of ALT, AST, LDH, ALP, GGT, TBIL, DBIL and TBA. Decreased bile flow by ANIT was restored with TFA treatment. Concurrent administration of TFA reduced the severity of polymorphonuclear neutrophil infiltration and other histological damages, which were consistent with the serological tests. Hepatic MDA and GSH contents in liver tissue were reduced, while SOD and GST activities, which had been suppressed by ANIT, were elevated in the groups pretreated with TFA. With TFA intervention, levels of TNF-α and NO in liver were decreased. Additionally, TFA was found to increase the expression of liver BSEP, MRP2, and NTCP in both protein and mRNA levels in ANIT-induced liver injury with cholestasis.

CONCLUSION

TFA exerted protective effects against ANIT-induced liver injury. The possible mechanisms could be related to anti-oxidative damage, anti-inflammation and regulating the expression of hepatic transporters. It layed the foundation for the further research on the mechanisms of cholestasis as well as the therapeutic effects of A. manihot (L.) Medic for the treatment of jaundice.

Pretreatment with the total flavone glycosides of Flos Abelmoschus manihot and hyperoside prevents glomerular podocyte apoptosis in streptozotocin-induced diabetic nephropathy

Diabetic nephropathy (DN) is an important diabetic complication, and podocyte apoptosis plays a critical role in the development of DN. In the present study, we examined the preventive effect of the total flavone glycosides of Flos Abelmoschus manihot (TFA) on urinary microalbumin and glomerular podocyte apoptosis in experimental DN rats. The preliminary oral administration of TFA (200 mg/kg/day) for 24 weeks significantly decreased the urinary microalbumin to creatinine ratio and 24-h urinary total protein in streptozotocin-induced DN rats. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay indicated glomerular cell apoptosis in DN rats was significantly improved by pretreatment with TFA. Furthermore, fluorescence-activated cell sorting and Hoechst 33342 staining suggested preincubation with hyperoside (50 and 200 μg/mL), the major active constituent of TFA, could significantly mitigate cultured podocyte apoptosis induced by the advanced glycation end-products (AGEs). Western blot analysis showed that increased caspase-3 and caspase-8 expressions induced by AGEs were also inhibited by pretreatment with hyperoside at both doses. Our results demonstrate that TFA pretreatment can decrease urinary albumin excretion in early-stage DN, which might be accomplished by preventing renal damage and podocyte apoptosis.

Anticonvulsant, antidepressant-like activity of Abelmoschus manihot ethanol extract and its potential active components in vivo

Depression is the most common psychiatric comorbidity in patients with epilepsy. Searching for antiepileptic (anticonvulsant) and antidepressant-like medicines from natural products is very important for the treatment of this disease. The flower of Abelmoschus manihot (Linn.) Medicus has been reported to have neuroprotective effect against cerebral ischemia injury. In order to further explore the activity of Abelmoschus manihot on the central nervous system, the anticonvulsant and antidepressant-like effects of Abelmoschus manihot ethanol extract (AMEE) as well as its potential active components in vivo was investigated in the present study. It was found that AMEE could protect mice against PTZ-induced clonic convulsions and mortality. AMEE could also decrease immobility time in the FST in mice. Furthermore, the potential active components of AMEE in rat brain were identified by ultra performance liquid chromatography-mass spectrometer (UPLC-MS). Five parent components including isoquercitrin, hyperoside, hibifolin, quercetin-3'-O-glucoside, quercetin and three metabolites were detected in rat brain after administration of AMEE. In conclusion, eight flavonoids were identified in rat brain after administration of AMEE; meanwhile, these flavonoids might represent the potential bioactive components of AMEE and contribute to its anticonvulsant and antidepressant-like activity in vivo.

Antiepileptic potential of flavonoids fraction from the leaves of Anisomeles malabarica

ETHNOPHARMACOLOGICAL RELEVANCE

The plant Chodara (Anisomeles malabarica R.Br. Family: Lamiaceae) has numerous therapeutic utilities in folk medicine.

AIM OF THE STUDY

To isolate and evaluate the anti-epileptic potential of fractions from the ethyl acetate extract (EAE) of Anisomeles malabarica leaves.

MATERIALS AND METHODS

The EA extract (2.12% w/w) of the leaves of Anisomeles malabarica was prepared and fractionated into total flavonoids fraction (AMFF) and tannins fraction (AMTF), which subsequently evaluated for the antiepileptic activity against PTZ- and MES model in wistar rats. Diazepam and phenytoin (2mg/kg and 25mg/kg, i.p., respectively), were used as a reference drugs. Further, the presence of flavonoid was confirmed by chemical test, TLC and HPTLC were done for the identification of the number of flavonoids with reference to standard.

RESULTS

Single dose pretreatment with AMFF (25 and 50mg/kg, i.p.) has found to be effective against both MES and PTZ-convulsions, but associated with a marked decrease in locomotor activity and motor activity performance (i.e., neurotoxic effects), similar to that of diazepam treatment. Interestingly, chronic treatment with AMFF at lower doses (6.25 and 12.5mg/kg, i.p., 1 week) has also produced significant antiepileptic activity, but without causing neurotoxic effects.

CONCLUSION

Thus, it may be concluded that the flavonoids fraction of the EA extract of Anisomeles malabarica leaves has antiepileptic potential against both MES and PTZ convulsion models. Acute treatment (25 and 50mg/kg, i.p.) is associated with neurotoxic activity. Whereas, chronic treatment (6.25 and 12.5mg/kg, i.p., 1 week) also shown significant antiepileptic effect without causing neurotoxic side effects. However, further research is in progress to determine the component(s) of the flavonoids fraction of Anisomeles malabarica involved and their mechanism of action in bringing about the desirable anti-epileptic effect.

Pathologically activated neuroprotection via uncompetitive blockade of N-methyl-D-aspartate receptors with fast off-rate by novel multifunctional dimer bis(propyl)-cognitin

Uncompetitive N-methyl-d-aspartate (NMDA) receptor antagonists with fast off-rate (UFO) may represent promising drug candidates for various neurodegenerative disorders. In this study, we report that bis(propyl)-cognitin, a novel dimeric acetylcholinesterase inhibitor and gamma-aminobutyric acid subtype A receptor antagonist, is such an antagonist of NMDA receptors. In cultured rat hippocampal neurons, we demonstrated that bis(propyl)-cognitin voltage-dependently, selectively, and moderately inhibited NMDA-activated currents. The inhibitory effects of bis(propyl)-cognitin increased with the rise in NMDA and glycine concentrations. Kinetics analysis showed that the inhibition was of fast onset and offset with an off-rate time constant of 1.9 s. Molecular docking simulations showed moderate hydrophobic interaction between bis(propyl)-cognitin and the MK-801 binding region in the ion channel pore of the NMDA receptor. Bis(propyl)-cognitin was further found to compete with [(3)H]MK-801 with a K(i) value of 0.27 mum, and the mutation of NR1(N616R) significantly reduced its inhibitory potency. Under glutamate-mediated pathological conditions, bis(propyl)-cognitin, in contrast to bis(heptyl)-cognitin, prevented excitotoxicity with increasing effectiveness against escalating levels of glutamate and much more effectively protected against middle cerebral artery occlusion-induced brain damage than did memantine. More interestingly, under NMDA receptor-mediated physiological conditions, bis(propyl)-cognitin enhanced long-term potentiation in hippocampal slices, whereas MK-801 reduced and memantine did not alter this process. These results suggest that bis(propyl)-cognitin is a UFO antagonist of NMDA receptors with moderate affinity, which may provide a pathologically activated therapy for various neurodegenerative disorders associated with NMDA receptor dysregulation.

Novel dimeric bis(7)-tacrine proton-dependently inhibits NMDA-activated currents

Bis(7)-tacrine has been shown to prevent glutamate-induced neuronal apoptosis by blocking NMDA receptors. However, the characteristics of the inhibition have not been fully elucidated. In this study, we further characterize the features of bis(7)-tacrine inhibition of NMDA-activated current in cultured rat hippocampal neurons. The results show that with the increase of extracellular pH, the inhibitory effect decreases dramatically. At pH 8.0, the concentration-response curve of bis(7)-tacrine is shifted rightwards with the IC(50) value increased from 0.19+/-0.03 microM to 0.41+/-0.04 microM. In addition, bis(7)-tacrine shifts the proton inhibition curve rightwards. Furthermore, the inhibitory effect of bis(7)-tacrine is not altered by the presence of the NMDA receptor proton sensor shield spermidine. These results indicate that bis(7)-tacrine inhibits NMDA-activated current in a pH-dependent manner by sensitizing NMDA receptors to proton inhibition, rendering it potentially beneficial therapeutic effects under acidic conditions associated with stroke and ischemia.

Quercetin subunit specifically reduces GlyR-mediated current in rat hippocampal neurons

Quercetin is a substance of low molecular weight found in vascular plants with a wide range of biological activities including antioxidative and anti-inflammatory activities. In the present study, the effects of quercetin on native glycine receptors (GlyRs) in cultured rat hippocampal neurons were investigated using a whole-cell patch-clamp technique. Quercetin reversibly and concentration-dependently depressed glycine-induced current (I(Gly)), with an IC50 of 10.7+/-0.24 microM and a Hill coefficient of 1.08+/-0.12. Quercetin depressed maximum I(Gly) and significantly changed the EC50 for glycine and the Hill coefficient. Kinetic analysis indicated that quercetin accelerated the rates of desensitization. Interestingly, after the end of glycine with quercetin coapplication, a transient rebound occurred. The quercetin effects also displayed voltage-dependence, being greater at positive membrane potentials. These effects suggested that quercetin may act as an open channel blocker. Furthermore, in the sequential application protocol, quercetin inhibited the peak amplitude of I(Gly) to a macroscopic degree while slowing GlyR desensitization. These effects implied that quercetin has a depressant effect independent of GlyR channel's opening, which maybe caused by an allosteric mechanism. Strikingly, quercetin inhibited the amplitude of recombinant-induced current mediated by alpha2-, alpha2beta-, alpha3- and alpha3beta-GlyRs but had no effects on alpha1- and alpha1beta-GlyRs that were expressed in HEK293T cells. We also investigated the effects of quercetin on I(Gly) in spinal neurons during development in vitro. The extent of blockade by quercetin on I(Gly) was slighter in spinal neurons than in hippocampal neurons in a development-dependent manner. Taken together, our results suggest that quercetin has possible effects in information processing within a neuronal network by inhibition of I(Gly) and may be useful as a pharmacological probe for identifying the subunit types of GlyRs.