The effects and mechanisms of modified Xiaoyaosan on chronic unpredictable mild stress (CUMS)-induced depressive mice based on network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Clinical research and basic scientific experiments have shown that modified Xiaoyaosan (MXYS) has antidepressant effects, whose system mechanism however has not been thoroughly characterized.

AIM OF THE STUDY

This research was aimed at evaluating the treatment effects of MXYS on chronic unpredictable mild stress (CUMS)-induced depressive mice and exploring underlying mechanisms.

MATERIALS AND METHODS

Whether MXYS has effects on depression was investigated via the depressive behaviors of mice, electron microscopy, real-time quantitative polymerase chain reaction (RT-qPCR), Western blot analysis, immunofluorescence (IF) staining and the stereotaxic injection of adeno-associated viruses (AAVs). In addition, network pharmacology was applied to predict relevant molecular targets and possible mechanisms and perform further in vivo validation.

RESULTS

MXYS is effective in ameliorating the depression-like symptoms of CUMS mice. It can stimulate autophagosome formation, activate the expression of microtubule-associated protein 1 light chain 3 (LC3B), autophagy-related gene 5 (Atg5), Atg7 and neuron-specific nuclear protein (NeuN), and decrease the protein expression sequestosome 1 (SQSTM1/p62). The autophagy-upregulating effect of MXYS was weakened by silencing. The network pharmacology analysis revealed that mitogen-activated protein kinase 1 (MAPK1), MAPK3, serine/threonine-protein kinase (AKT1), proto-oncogene tyrosine-protein kinase (SRC), PI 3 kinase p85 alpha (PIK3R1), catenin (cadherin-associated protein) beta 1 (CTNNB1) and human thrombin activator 1 (HRAS) may be of importance to treat depression by MXYS. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that metabolic and autophagy pathways, pathways in cancer and MAPK, phosphoinositide 3-kinase (PI3K)-Akt and rhoptry-associated protein 1 (Rap1) signaling pathways are involved in the antidepressant effects of MXYS. As suggested by Western blot, the anti-depression mechanism of MXYS is possibly associated with the extracellular signal-regulated protein kinase (ERK)/P38 MAPK signaling pathway.

CONCLUSION

The findings indicate the possible antidepressant effects of MXYS on CUMS mice via triggering autophagy to alleviate neuronal apoptosis and prompting autophagy, which may involve the ERK/P38 MAPK signaling pathway.

The relationship between shifts in the rhizosphere microbial community and root rot disease in a continuous cropping American ginseng system

The root rot disease causes a great economic loss, and the disease severity usually increases as ginseng ages. However, it is still unclear whether the disease severity is related to changes in microorganisms during the entire growing stage of American ginseng. The present study examined the microbial community in the rhizosphere and the chemical properties of the soil in 1-4-year-old ginseng plants grown in different seasons at two different sites. Additionally, the study investigated ginseng plants' root rot disease index (DI). The results showed that the DI of ginseng increased 2.2 times in one sampling site and 4.7 times in another during the 4 years. With respect to the microbial community, the bacterial diversity increased with the seasons in the first, third, and fourth years but remained steady in the second year. The seasonal changing of relative abundances of bacteria and fungi showed the same trend in the first, third, and fourth years but not in the second year. Linear models revealed that the relative abundances of Blastococcus, Symbiobacterium, Goffeauzyma, Entoloma, Staphylotrichum, Gymnomyces, Hirsutella, Penicillium and Suillus spp. were negatively correlated with DI, while the relative abundance of Pandoraea, Rhizomicrobium, Hebeloma, Elaphomyces, Pseudeurotium, Fusarium, Geomyces, Polyscytalum, Remersonia, Rhizopus, Acremonium, Paraphaeosphaeria, Mortierella, and Metarhizium spp. were positively correlated with DI (P < 0.05). The Mantel test showed that soil chemical properties, including available nitrogen, phosphorus, potassium, calcium, magnesium, organic matter, and pH, were significantly correlated to microbial composition. The contents of available potassium and nitrogen were positively correlated with DI, while pH and organic matter were negatively correlated with DI. In summary, we can deduce that the second year is the key period for the shift of the American ginseng rhizosphere microbial community. Disease aggravation after the third year is related to the deterioration of the rhizosphere microecosystem.

Application of vermicompost and biochar suppresses Fusarium root rot of replanted American ginseng

Soil sterilization integrated with agronomic measures is an effective method to reduce soilborne replant diseases. However, the effect of vermicompost or biochar application after soil sterilization on soilborne diseases is poorly understood. A pot experiment was conducted in American ginseng to investigate the effects of vermicompost (VF), biochar (BF), and a combination of vermicompost and biochar (VBF) applied after soil sterilization on the incidence of Fusarium root rot using natural recovery (F) as control. After one growing season, the disease index of root rot, the phenolic acids, and the microbial communities of American ginseng rhizosphere soil were analyzed. The disease index of VF, BF, and VBF decreased by 33.32%, 19.03%, and 80.96%, respectively, compared with F. The highest bacterial richness and diversity were observed in the rhizosphere soil of VBF. Besides, VF and VBF significantly increased the relative abundance of beneficial bacteria (Pseudomonas, Lysobacter, and Chryseolinea) in the rhizosphere soil. Higher concentrations of vanillin, one of the phenolic acids in the roots exudates, were recorded in the rhizosphere soils of BF and VBF. The vanillin concentration showed a significant negative correlation with the disease index. To conclude, vermicompost improved the beneficial bacteria of the rhizosphere soil, while biochar regulated the allelopathic effect of the phenolic acids. The study proposes a combined application of biochar and vermicompost to the rhizosphere soil to control Fusarium root rot of replanted American ginseng effectively. KEY POINTS: Vermicompost improves the relative abundance of rhizosphere beneficial bacteria. Biochar inhibits the degradation of phenolic acids by adsorption. The combination of vermicompost and biochar enhances the disease control effect.

Ethyl Acetate Fraction of Dicliptera chinensis (L.) Juss. Ameliorates Liver Fibrosis by Inducing Autophagy via PI3K/AKT/mTOR/p70S6K Signaling Pathway

OBJECTIVE

To investigate the molecular mechanism underlying the anti-hepatic fibrosis activity of ethyl acetate fraction Dicliptera chinensis (L.) Juss. (EDC) in human hepatic stellate cells (HSCs) in vitro and in a carbon tetrachloride (CCl₄)-induced hepatic fibrosis mouse model in vivo.

METHODS

For in vitro study, HSCs were pre-treated with platelet-derived growth factor (10 ng/mL) for 2 h to ensure activation and treated with EDC for 24 h and 48 h, respectively. The effect of EDC on HSCs was assessed using cell counting kit-8 assay, EdU staining, transmission electron microscopy, immunofluorescence staining, and Western blot, respectively. For in vivo experiments, mice were intraperitoneally injected with CCl₄ (2 ° L/g, adjusted to a 25% concentration in olive oil), 3 times per week for 6 weeks, to develop a hepatic fibrosis model. Forty 8-week-old male C57BL/6 mice were divided into 4 groups using a random number table (n=10), including control, model, positive control and EDC treatment groups. Mice in the EDC and colchicine groups were intragastrically administered EDC (0.5 g/kg) or colchicine (0.2 mg/kg) once per day for 6 weeks. Mice in the control and model groups received an equal volume of saline. Biochemical assays and histological examinations were used to assess liver damage. Protein expression levels of α -smooth muscle actin (α -SMA) and microtubule-associated protein light chain 3B (LC3B) were measured by Western blot.

RESULTS

EDC reduced pathological damage associated with liver fibrosis, downregulated the expression of α -SMA and upregulated the expression of LC3B (P<0.05), both in HSCs and the CCl₄-induced liver fibrosis mouse model. The intervention of bafilomycin A1 and rapamycin in HSCs strongly supported the notion that inhibition of autophagy enhanced α -SMA protein expression levels (P<0.01). The results also found that the levels of phosphoinositide (PI3K), p-PI3K, AKT, p-AKT, mammalian target of rapamycin (mTOR), p-mTOR, and p-p70S6K all decreased after EDC treatment (P<0.05).

CONCLUSIONS

EDC has anti-hepatic fibrosis activity by inducing autophagy and might be a potential drug to be further developed for human liver fibrosis therapy.

[Effects of nutrients deficiency on growth and saponin accumulation of American ginseng]

Mineral nutrient elements are the key factors to maintain the growth and quality of American ginseng. In order to understand the comprehensive effect of different nutrient elements deficiency on American ginseng, 2-year-old American ginsengs were cultivated by Hoagland solution(CK) or 10 different nutrients deficiency solution in sand culture. During the cultivation, the deficient symptom was observed. The plant height, leaf area, biomass, photosynthetic index, root activity, ginsenoside content were measured. The results showed that N, K or Fe deficiency could lead to leaves of American ginseng yellowing. Deficiency N, K, Ca, Mg and B were the main factors that decrease plant height and leaf area. The biomass of plant decreased significantly in all the nutrient deficient treatments(P<0.05)compared with control group, and N, K, Ca or Fe deficiency groups descended over 50%. In the absence of N, K and Fe elements, the P_n, G_s, C_i, T_r and chlorophyll of leaves were decreased mostly. The first three factors decreasing root activity were N, K and Ca deficiency. The effects of nutrient deficiency on saponins of American ginseng were different.Generally, N, P, B, Zn and Cu deficiency resulted the synthesis of saponins decreased significantly(P<0.05). This study contributed to clarify the demand characteristics of American ginseng for different nutrient elements,which is of great significance for the diagnose of nutrient deficiency, the rational fertilizer and the improvement of yield and quality of American ginseng.

Effects of maize rotation on the physicochemical properties and microbial communities of American ginseng cultivated soil

The production of American ginseng (Panax quinquefolius L.) is severely limited by the replant disorders in China. Crop rotation with maize might reduce the replant problems, but little information is available on the effect of maize rotation on soil cultivated with ginseng. In this study, we analyzed nutrients, phenolic acids, and microbial communities in soils from the fields with continuous maize, mono-culture ginseng, and 1-, 3-, and 5-year maize rotation after ginseng. Pot experiments were also conducted to evaluate the performance of replanting ginseng in these soils. The results showed that Mn, Cu, and 5 phenolic acids in ginseng-cultivated soil were significantly decreased by maize rotation. A 5-year maize rotation significantly increased the relative abundance of beneficial soil bacteria, such as Arthrobacter, rather than decreasing the abundances of potential pathogenic genera. Clustering analysis revealed that the physicochemical properties and microbial communities of 3- and 5-year maize rotation soil were more similar to CM than to G soil. The biomass of replanted ginseng root was improved, and root disease was reduced over 3 years of maize rotation. Overall, the results showed that at least a 3-year maize rotation is needed to overcome the replant failure of American ginseng.

A novel strategy for regulated expression of a cytotoxic gene

The tetracycline (Tet) transactivator system is a powerful promoter system to control gene expression. However, expression of a cytotoxic gene in this system has been limited due to the lethal effect caused by low levels of basal expression of the toxic gene. In this report, we describe a novel strategy to express a toxic gene using the Tet system. The barstar gene is placed downstream of a minimal promoter and the barnase gene downstream of the tetracycline responsive element minimal promoter. When barnase is expressed at a basal level, its toxicity in human cell culture is offset by the similar basal level expression of barstar. However, when the barnase expression is induced with the transactivator protein, its overproduction leads to cell death. Therefore, this strategy allows cytotoxicity to be effectively regulated by tetracycline.

A loss of resistance to avirulent bacterial pathogens in tobacco is associated with the attenuation of a salicylic acid-potentiated oxidative burst

The role of salicylic acid (SA) in events occurring before cell death during the hypersensitive reaction (HR) was investigated in leaves of wild-type tobacco Samsun NN and in transgenic lines expressing salicylate hydroxylase (35S-SH-L). Challenge of 35S-SH-L tobacco with avirulent strains of Pseudomonas syringae gave rise to symptoms resembling those normally associated with a compatible response to virulent strains in terms of visible phenotype, kinetics of bacterial multiplication, and escape from the infection site. Compared with responses in wild-type tobacco, both the onset of plant cell death and the induction of an active oxygen species-responsive promoter (AoPR1-GUS) were delayed following challenge of 35S-SH-L plants with avirulent bacteria. The oxidative burst occurring after challenge with avirulent bacteria was visualized histochemically and quantified in situ. H2O2 accumulation at reaction sites was evident within 1 h after inoculation in wild-type tobacco, whereas in 35S-SH-L plants the onset of H2O2 accumulation was delayed by 2-3 h. The delay in H2O2 generation was correlated with a reduction in the transient rise in SA that usually occurred within 1-2 h following inoculation in wild-type plants. Our data indicate that an early transient rise in SA potentiates the oxidative burst, with resultant effects on accumulation of H2O2, plant cell death and also defence-gene induction, factors that together may determine the outcome of plant-pathogen interactions.

Transformation of Arabidopsis with a Brassica SLG/SRK region and ARC1 gene is not sufficient to transfer the self-incompatibility phenotype

Self-incompatibility (SI) promotes outbreeding in flowering plants, and in Brassica SI is genetically controlled by the S locus. Self-incompatible Brassica and self-fertile Arabidopsis belong to the same crucifer family. In addition, a comparative analysis reveals a high degree of microsynteny between the B. campestris S locus and its homologous region in Arabidopsis--with the notable exception that the Brassica SI genes, SLG and SRK, are missing. Brassica ARC1 encodes a component of the SRK signal transduction pathway leading to self-pollen rejection, and no closely related ARC1 homolog has been identified in Arabidopsis. The purpose of the research reported here was to introduce Brassica SI components into Arabidopsis in an attempt to compensate for the missing genes and to investigate whether the SI phenotype can be transferred. Inserts of approximately 40 kb from the fosmid clones F20 and F22, which span the B. napus W1 SLG-SRK region, were cloned into the plant transformation vector pBIBAC2. Transgenic plants were generated that expressed the Brassica SI genes in the flower buds. In addition, the endogenous, SLG-like, gene AtS1 was not co-suppressed by the Brassica SLG transgene. No SI phenotype was observed among the T1 BIBAC2-F20 and BIBAC2-F22 transgenic plants. When the ARC1 gene was transformed into BIBAC2-F20 or BIBAC2-F22 plants, the resulting BIBAC2-F20-ARC1 and BIBAC2-F22-ARC1 plants still set seeds normally, and no rejection response was observed when self-incompatible B. napus W1 pollen was placed on BIBAC2-F20-ARC1 or BIBAC2-F22-ARC1 Arabidopsis stigmas. Taken together, our results suggest that complementing Arabidopsis genome with Brassica SLG, SRK and ARC1 genes is unlikely to be sufficient to transfer the SI phenotype.

The S locus glycoprotein and the S receptor kinase are sufficient for self-pollen rejection in Brassica

Self-incompatibility (SI) is one of several mechanisms that have evolved to prevent inbreeding in plants. SI in Brassica is controlled by the polymorphic S locus complex. Two S locus-encoded proteins are coordinately expressed in the stigma epidermis: the cell wall-localized S locus glycoprotein (SLG) and the plasma membrane-anchored S receptor kinase (SRK). These proteins are thought to recognize a pollen factor that leads to the rejection of self-pollen. Evidence has accumulated that indicates that both proteins are necessary for the ability of the stigma to inhibit self-pollen. However, it has not been possible to prove this necessity definitively or to demonstrate that these genes are sufficient for this phenotype, because previous attempts to transfer this phenotype via transformation have not been successful. In this study, two overlapping S locus genomic clones, which cover approximately 55 kilobases of DNA and contain the SLG, SRK, and an anther-expressed gene in the region common to the two, were introduced into a self-compatible Brassica napus line. The resulting transgenic plants were shown to carry the female part of the SI phenotype, rejecting pollen in a haplotype-specific manner. However, the pollen SI phenotype was not found in any of the transgenic plants. These data show that the SLG and SRK are sufficient for the female side but not the male side of the SI phenotype in Brassica and that there must be an independent pollen S factor encoded outside the cloned region.

Cell-specific expression of salicylate hydroxylase in an attempt to separate localized HR and systemic signalling establishing SAR in tobacco

Abstract There is conflicting evidence concerning the nature of the long-distance signal responsible for establishing the systemic acquired resistance (SAR) state following a local response to an incompatible plant/pathogen interaction. We outline standard inoculation procedures and terminology for experiments used to characterize SAR in Nicotiana tabacum and show that leaf development (age) has dramatic affects on TMV lesion size which needs to be taken into account in experimental design. TMV infection was more efficient at inducing SAR than primary infection with avirulent bacteria. We have examined the effect on SAR induction of altering the accumulation of salicylic acid (SA), through the expression of a salicylate hydroxylase gene (SH-L), in different phases of lesion development using the hydrogen peroxide-responsive AoPR1 promoter and the salicylate-responsive PR1a promoter. Suppression of SA accumulation during the early phases of lesion development in AoPR1-SH-L transgenic tobacco resulted in an attenuated form of SAR compared to wild-type plants, whereas SAR was not exhibited in PR1a-SH-L plants. However, interpretation of data from these experiments was complicated by virus escape from inoculated leaves. Using a GUS reporter it was discovered that the CaMV35S promoter was not expressed constitutively in all cell types of petioles and stems, particularly phloem tissue, whereas the PR1a promoter demonstrated induced expression in the phloem following TMV infection. We suggest two hypotheses for why PR1a-SH-L transgenics do not display SAR: either the systemic expression of PR1a-SH-L is sufficient to suppress SAR, or SA synthesis or translocation in the phloem is essential for SAR.

Structural and transcriptional comparative analysis of the S locus regions in two self-incompatible Brassica napus lines

Self-incompatibility (SI) in Brassica is controlled by a single locus, termed the S locus. There is evidence that two of the S locus genes, SLG, which encodes a secreted glycoprotein, and SRK, which encodes a putative receptor kinase, are required for SI on the stigma side. The current model postulates that a pollen ligand recognizing the SLG/SRK receptors is encoded in the genomic region defined by the SLG and SRK genes. A fosmid contig of approximately 65 kb spanning the SLG-910 and SRK-910 genes was isolated from the Brassica napus W1 line. A new gene, SLL3, was identified using a novel approach combining cDNA subtraction and direct selection. This gene encodes a putative secreted small peptide and exists as multiple copies in the Brassica genome. Sequencing analysis of the 65-kb contig revealed seven additional genes and a transposon. None of these seven genes exhibited features expected of S genes on the pollen side. An approximately 88-kb contig of the A14 S region also was isolated from the B. napus T2 line and sequenced. Comparison of the two S regions revealed that (1) the gene organization downstream of SLG in both S haplotypes is highly colinear; (2) the distance between SLG-A14 and SRK-A14 genes is much larger than that between SLG-910 and SRK-910, with the intervening region filled with retroelements and haplotype-specific genes; and (3) the gene organization downstream of SRK in the two haplotypes is divergent. These observations lead us to propose that the SLG downstream region might be one border of the S locus and that the accumulation of heteromorphic sequences, such as retroelements as well as haplotype-unique genes, may act as a mechanism to suppress recombination between SLG and SRK.

Compromising early salicylic acid accumulation delays the hypersensitive response and increases viral dispersal during lesion establishment in TMV-infected tobacco

To investigate the role of salicylic acid (SA) in the hypersensitive response (HR) its accumulation was compromised during different phases of lesion development by differential expression of a salicylate hydroxylase gene (SH-L). Constitutive suppression of SA accumulation was achieved by expression of a gene fusion between the CaMV35S promoter (35S) and SH-L. Using the H2O2-responsive AoPR1 promoter to drive SH-L SA accumulation could be compromised at an early stage, on lesion formation and possibly prior to visible necrosis, whilst use of the salicylate-responsive PR1a promoter reduced SA accumulation at a later stage as lesions expand. TMV infection of 35S-SH-L and AoPR1-SH-L, but not PR1a-SH-L, tobacco resulted in significantly greater rates of lesion growth than in wild-type tobacco. TMV was detected in asymptomatic tissue surrounding lesions only in 35S-SH-L and AoPR1-SH-L lines; subsequently these transgenic lines exhibited a 'spreading-necrosis' originating from the lesion which entered the stem and eventually other leaves, a phenotype which could be correlated with the presence of TMV particles. Analysis of TMV-infected and 'temperature-shifted' tobacco indicated that both 35S-SH-L and AoPR1-SH-L, but not PR1a-SH-L, transgenics exhibited delayed cell-death compared to wild-type infections. We propose that the SH-L phenotypes indicate that early SA accumulation is a major factor in preventing viral escape, via mechanism(s) which may include influencing the rate of host-cell death and, possibly, an effect on viral function.

Hydrogen peroxide does not function downstream of salicylic acid in the induction of PR protein expression

The roles of salicylic acid (SA) and H2O2 in the induction of PR proteins in tobacco have been examined. Studies were conducted on wild-type tobacco and plants engineered to express a bacterial salicylate hydroxylase capable of metabolizing SA to catechol (SH-L plants). Wild-type and PR-1a-GUS-transformed plants express PR-1a following challenge with Pseudomonas syringae pathovar syringae, SA or 2,6-dichloro-isonicotinic acid (INA). In contrast, SH-L plants failed to respond to SA but did express PR-1a following INA treatment. H2O2 and the irreversible catalase inhibitor 3-amino-1,2,4-triazole (3-AT) were found to be weak inducers of PR-1a expression (relative to SA) in wild-type tobacco but were unable to induce PR-1a in SH-L plants, suggesting that the action of these compounds depends upon the accumulation of SA. A model has been proposed suggesting that SA binds to and inhibits a catalase inducing an increase in H2O2 leading to PR protein expression. Catalase activity has been measured in tobacco and no significant changes in activity following infection with P. syringae pv. syringae were detected. Furthermore, inhibition of catalase activity in vitro in plant extracts requires pre-incubation and only occurs at SA concentrations above 250 microM. Leaf disks preincubated with 1 mM SA do accumulate SA to these levels and PR-1a is efficiently induced but there is no apparent inhibition of catalase activity. It is also shown that a SA-responsive gene, PR-1a, and a H2O2-sensitive gene, AoPR-1, are both relatively insensitive to 3-AT suggesting that induction of these genes is unlikely to be due entirely to inhibition of an endogenous catalase.