Lactobacillus plantarum capable of producing indole derivative and activating AHR signal transduction and application of lactobacillus plantarum

Abstract

The invention belongs to the technical field of microorganisms, and particularly relates to lactobacillus plantarum capable of producing indole derivatives and activating AHR signal transduction and application of the lactobacillus plantarum. Experiments prove that the lactobacillus plantarum SFFI23 provided by the invention not only can be used for fermenting tryptophan to produce indole derivatives (indoleacetic acid IAA, 3-indole-lactic acid ILA and indole-3-formaldehyde ICA), but also can be used for activating AHR signal transduction and IL-22 / STAT3 pathways, repairing the intestinal barrier function and relieving the colitis symptoms, so that the lactobacillus plantarum SFFI23 has a good practical application value.

Description

Technical Field

[0001] The invention belongs to the technical field of microorganisms, and specifically relates to a plant lactobacillus that produces indole derivatives and has the function of activating AHR signal transduction and its application. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Colitis is a common intestinal disease, among which ulcerative colitis (UC) is of particular concern. The occurrence of UC leads to chronic inflammation of the gastrointestinal tract and significantly increases the risk of colorectal cancer. Histological remission has always been the ultimate goal of UC treatment; however, the current treatment goal is to achieve and maintain clinical and endoscopic remission. Therefore, proper control of dietary nutrition and maintenance of homeostasis in the intestinal microenvironment are essential for the treatment of UC.

[0004] Lactobacillus plantarum is a probiotic widely found in fermented foods. Compared with other probiotics, Lactobacillus plantarum has advantages such as high acid resistance and ability to withstand gastrointestinal pressure. At the same time, previous studies have shown that the regulation of tryptophan metabolism by probiotics can significantly reduce intestinal inflammation in mice, and this effect is closely related to aryl hydrocarbon receptor (AHR) signaling.

[0005] Tryptophan is an aromatic essential amino acid that can only be ingested through diet. It is the only natural amino acid with an indole structure and the amino acid with the lowest content in proteins and cells. At the same time, it is a precursor for the biosynthesis of multiple metabolites. In the distal colon, the intestinal microbiota metabolizes tryptophan to produce a series of indole derivatives. Some indole derivatives are maintained at high concentrations in the intestine and play physiological roles as AHR signaling agonists. AHR is a cytoplasmic receptor that is highly expressed in various cells in the intestinal microenvironment, including lymphocytes, Th17 cells, regulatory T cells, epithelial cells, endothelial cells, and neurons. The activity of AHR signaling significantly affects antigen presentation, T cell differentiation, and innate lymphocyte activation in the intestine, and ultimately affects the regulation of intestinal microenvironment homeostasis and target gene expression. In particular, intestinal AHR signaling plays a crucial role in defense against inflammation. During inflammatory invasion, AHR signaling can increase the transcription efficiency of intestinal interleukin (IL)-22, activate STAT3 expression, and promote the release of immune molecules such as antimicrobial peptides and defense factors, thereby maintaining intestinal barrier function. It has been shown that disordered tryptophan metabolism and reduced AHR signaling can lead to a disordered intestinal environment and the development of intestinal diseases. Therefore, the state of tryptophan metabolism in the body affects intestinal homeostasis through AHR signaling. However, the application of Lactobacillus plantarum in the prevention and treatment of colitis needs to be further explored, and its mechanism of action needs to be further explored to better exert its potential in the prevention and treatment of colitis. Summary of the invention

[0006] In view of the above-mentioned prior art, the present invention aims to provide a plant lactobacillus that produces indole derivatives and has the effect of activating AHR signal transduction and its application. Experiments have shown that the plant lactobacillus can not only ferment tryptophan to produce indole derivatives (including indoleacetic acid IAA, 3-indole-lactic acid ILA and indole-3-carboxaldehyde ICA), but also can activate AHR signal transduction, restore colon cytokine expression and intestinal barrier function, thereby effectively alleviating colitis. Based on the above research results, the present invention is completed.

[0007] In order to achieve the above technical objectives, the technical solution provided by the present invention is as follows:

[0008] The first aspect of the present invention provides a strain of Lactobacillus plantarum SFFI23, which has been deposited in the General Microbiology Center of China National Microbiological Culture Collection Committee (address: No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, China) on April 26, 2024, with a deposit number of CGMCC No. 30453.

[0009] The second aspect of the present invention provides a microbial agent, wherein the microbial agent contains the Lactobacillus plantarum SFFI23 or a culture thereof.

[0010] In the present invention, the Lactobacillus plantarum SFFI23 culture is a substance obtained by culturing Lactobacillus plantarum SFFI23 in a culture medium (all substances in a culture container).

[0011] The third aspect of the present invention provides the use of the above-mentioned Lactobacillus plantarum SFFI23 or the above-mentioned microbial agent in any one or more of the following:

[0012] (a1) Fermentation to produce indole derivatives;

[0013] (a2) preparing a product for preventing and / or treating colitis.

[0014] In the above (a1), the indole derivatives include but are not limited to indoleacetic acid IAA, 3-indole-lactic acid ILA and indole-3-carboxaldehyde ICA.

[0015] In (a2) above, the prevention and / or treatment of colitis is specifically manifested as:

[0016] (a2-1) recovery of colitis-mediated weight loss;

[0017] (a2-2) restoration of colitis-mediated shortening of colon length;

[0018] (a2-3) Alleviate colitis-mediated mucosal structural damage and inflammatory cell infiltration;

[0019] (a2-4) Activate AHR signaling and restore colonic cytokine expression and intestinal barrier function.

[0020] Among them, in (a2-4), the colon cytokines include proinflammatory cytokines and anti-inflammatory cytokines, wherein the proinflammatory cytokines include IL-1β, IL-6 and TNF-α, and the anti-inflammatory cytokines include IL-10.

[0021] The present invention has found through research that Lactobacillus plantarum SFFI23 can reduce the expression of the above-mentioned pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α), increase the expression of anti-inflammatory cytokines (IL-10), and effectively reduce the expression of myeloperoxidase, thereby alleviating the immune imbalance of colitis.

[0022] A fourth aspect of the present invention provides a product, wherein the product comprises the above-mentioned Lactobacillus plantarum SFFI23 or the above-mentioned microbial agent.

[0023] The product has the efficacy of preventing and / or treating colitis.

[0024] The above-mentioned product can be a food or a medicine, preferably a medicine.

[0025] A fifth aspect of the present invention provides a method for preventing and / or treating colitis, comprising administering the above-mentioned Lactobacillus plantarum SFFI23, microbial agent or product to a subject.

[0026] Beneficial technical effects of one or more of the above technical solutions:

[0027] The above technical scheme reports a strain of Lactobacillus plantarum for the first time. Experiments have confirmed that the Lactobacillus plantarum SFFI23 can not only ferment tryptophan to produce indole derivatives (indoleacetic acid IAA, 3-indole-lactic acid ILA and indole-3-carboxaldehyde ICA), but also can activate AHR signal transduction and IL-22 / STAT3 pathway, repair intestinal barrier function, and alleviate colitis symptoms, so it has good practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings required for use in the description of the embodiment will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0029] Figure 1 The metabolite levels of tryptophan fermented by Lactobacillus plantarum of the present invention; (A) Heat map of quantification of ILA, ICA and IAA levels using UPLC-MS / MS; (B) The 10 Lactobacillus plantarum strains with the highest and lowest ILA production; (C) The 10 Lactobacillus plantarum strains with the highest and lowest ICA production; (D) The 10 Lactobacillus plantarum strains with the highest and lowest IAA production. ILA, indole-3-lactic acid; ICA, indole-3-carboxaldehyde; IAA, indole-3-acetic acid.

[0030] Figure 2The effect of Lactobacillus plantarum of the present invention on the disease signs of DSS-induced colitis; (A) Schematic diagram of the experimental design; (B) Representative images of colon length; (C) Weight change; (D) DAI; (E) Colon length; (F) Histological score; (G) Representative micrographs of H&E-stained colon tissue (scale bar 20 μm; magnification 100 times). Trp, tryptophan; DAI, disease activity index. *, compared with the DSS group, p<0.05; **, compared with the DSS group, p<0.01; ***, compared with the DSS group, p<0.001; ****, compared with the DSS group, p<0.0001.

[0031] Figure 3 The effects of Lactobacillus plantarum on DSS-induced colitis cytokine expression, intestinal barrier function and AHR signal; (AF) IL-1β, IL-6, IL-10, IL-22, TNF-α and myeloperoxidase levels were determined using corresponding ELISA kits; (G) Western blot analysis of occludin, STAT3 and p-STAT3; (H) Relative gray value of occludin / GAPDH; (I) Relative gray value of p-STAT3 / STAT3; (J) Western blot analysis of CYP1A1, (K) Relative gray value of CYP1A1 and GAPDH; (L) Correlation analysis between AHR and colitis relief effect. Trp, tryptophan. Compared with the DSS group, p<0.05; **, compared with the DSS group, p<0.01; ***, compared with the DSS group, p<0.001; ****, compared with the DSS group, p<0.0001. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] The present invention is further described below in conjunction with examples. The present invention is further described below by way of examples, but the present invention is not limited to the scope of the embodiments described. Based on the embodiments in the present invention, any variation of the present invention by those skilled in the art without making a creative premise all belongs to the protection scope of the present invention. Meanwhile, in the embodiments of the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0035] In a typical embodiment of the present invention, a strain of Lactobacillus plantarum SFFI23 is provided, which has been deposited in the General Microbiology Center of China National Committee for the Preservation of Microorganisms (address: No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, China) on April 26, 2024, with a deposit number of CGMCC No. 30453.

[0036] In another specific embodiment of the present invention, a microbial agent is provided, wherein the microbial agent contains the Lactobacillus plantarum SFFI23 or a culture thereof.

[0037] In the present invention, the Lactobacillus plantarum SFFI23 culture is a substance obtained by culturing Lactobacillus plantarum SFFI23 in a culture medium (all substances in a culture container).

[0038] In the above culture, the substances include Lactobacillus plantarum SFFI23 (the bacteria itself) and metabolites of Lactobacillus plantarum SFFI23.

[0039] In the present invention, the term "culture" refers to a general term for a liquid or solid culture medium with a microbial population after artificial inoculation and culture. That is, the product obtained by growing and / or amplifying microorganisms, which can be a biologically pure culture of microorganisms, or can contain a certain amount of culture medium, metabolites or other components produced during the culture process. The term "culture" also includes a subculture obtained by subculturing microorganisms, which can be a culture of a certain generation or a mixture of several generations.

[0040] In the present invention, the term "metabolite" refers to the primary metabolites and / or secondary metabolites produced during the metabolism of microorganisms. Primary metabolism refers to the process in which microorganisms absorb various nutrients from the outside world and generate substances and energy to maintain life activities through catabolism and anabolism. The products of primary metabolism are primary metabolites, such as monomers such as monosaccharides or monosaccharide derivatives, nucleotides, vitamins, amino acids, fatty acids, and various macromolecular polymers composed of them, such as proteins, nucleic acids, polysaccharides, lipids, etc. Secondary metabolism refers to the process in which microorganisms use primary metabolites as precursors to synthesize some substances that have no clear function on the life activities of microorganisms during a certain growth period. The products of secondary metabolism are secondary metabolites, which are mostly compounds with relatively complex molecular structures. According to their effects, they can be divided into types such as antibiotics, hormones, alkaloids, toxins, etc.

[0041] In the present invention, the metabolite can be obtained from the culture of the Lactobacillus plantarum SFFI23. The metabolite can be a sterile metabolite of the Lactobacillus plantarum SFFI23 or a bacteria-containing metabolite of the Lactobacillus plantarum SFFI23. The sterile metabolite of the Lactobacillus plantarum SFFI23 can be prepared according to the following method: the Lactobacillus plantarum SFFI23 is cultured in a liquid culture medium, and the Lactobacillus plantarum SFFI23 in the liquid culture (fermentation broth) is filtered out to obtain the sterile metabolite of the Lactobacillus plantarum SFFI23. The bacteria-containing metabolite of the Lactobacillus plantarum SFFI23 can be specifically prepared according to the following method: the Lactobacillus plantarum SFFI23 is cultured in a liquid fermentation medium, and the fermentation broth is collected, and the fermentation broth is the bacteria-containing metabolite of the Lactobacillus plantarum SFFI23.

[0042] In another specific embodiment of the present invention, the bacterial agent may further include excipients acceptable to the bacterial agent, which are not specifically limited herein.

[0043] In another specific embodiment of the present invention, the use of the above-mentioned Lactobacillus plantarum SFFI23 or the above-mentioned microbial agent in any one or more of the following is provided:

[0044] (a1) Fermentation to produce indole derivatives;

[0045] (a2) preparing a product for preventing and / or treating colitis.

[0046] In the above (a1), the indole derivatives include but are not limited to indoleacetic acid IAA, 3-indole-lactic acid ILA and indole-3-carboxaldehyde ICA.

[0047] In (a2) above, the prevention and / or treatment of colitis is specifically manifested as:

[0048] (a2-1) recovery of colitis-mediated weight loss;

[0049] (a2-2) restoration of colitis-mediated shortening of colon length;

[0050] (a2-3) Alleviate colitis-mediated mucosal structural damage and inflammatory cell infiltration;

[0051] (a2-4) Activate AHR signaling and restore colonic cytokine expression and intestinal barrier function.

[0052] Among them, in (a2-4), the colon cytokines include proinflammatory cytokines and anti-inflammatory cytokines, wherein the proinflammatory cytokines include IL-1β, IL-6 and TNF-α, and the anti-inflammatory cytokines include IL-10.

[0053] The present invention has found through research that Lactobacillus plantarum SFFI23 can reduce the expression of the above-mentioned pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α), increase the expression of anti-inflammatory cytokines (IL-10), and effectively reduce the expression of myeloperoxidase, thereby alleviating the immune imbalance of colitis.

[0054] In another specific embodiment of the present invention, a product is provided, wherein the product comprises the above-mentioned Lactobacillus plantarum SFFI23 or the above-mentioned microbial agent.

[0055] The product has the efficacy of preventing and / or treating colitis.

[0056] The above-mentioned product can be a food or a medicine, preferably a medicine.

[0057] When the product is a medicine, specifically, the medicine also includes pharmaceutically acceptable excipients.

[0058] More specifically, the pharmaceutically acceptable excipient is selected from any one or more of a buffer, an excipient, a diluent, a preservative, a wetting agent, an emulsifier, a lubricant, a thickener, a stabilizer, a solubilizer, a suspending agent and a suspending aid.

[0059] Preferably, the pharmaceutically acceptable excipients can be selected from glucose, water, sucrose, glycerol, ethanol, propylene glycol, mannitol, corn starch, gelatin, alginic acid, kaolin, dicalcium phosphate, sodium chloride, cross-linked sodium carboxymethyl cellulose and sodium starch glycolate.

[0060] In another specific embodiment of the present invention, a method for preventing and / or treating colitis is provided, the method comprising administering the above-mentioned Lactobacillus plantarum SFFI23, microbial agent or product to a subject.

[0061] Example

[0062] 1. Materials and Methods

[0063] 1.1.L. plantarum culture

[0064] The 58 Lactobacillus plantarum strains used in this study were provided by Shandong Food Fermentation Industry Research and Design Institute, Qilu University of Technology (Shandong Academy of Sciences). The strains were cultured in MRS medium at 37°C for 18 hours.

[0065] 1.2. Determination of tryptophan metabolites

[0066] The method for measuring tryptophan metabolites of Lactobacillus plantarum is as follows: MRS medium supplemented with 2 g / L tryptophan is inoculated with activated Lactobacillus plantarum. After culturing at 37°C for 24 hours, the culture is centrifuged at 4000 × g for 5 minutes, and then the supernatant is collected and filtered through a 0.22 μm membrane. Tryptophan metabolites are analyzed using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS / MS) (WatersXevo TQ-XS, Waters Co., Milford, USA). The chromatographic conditions are as follows: ACQUITY UPLCBEH C18 column (1.7 μm, 2.0 × 100 mm, Waters Co.), 40°C, 10 μL injection volume, mobile phase A (0.1% formic acid in water), mobile phase B (methanol). The elution gradient of the mobile phase was as follows: 0.00-0.20 min, 90% A; 0.20-3.00 min, from 90% A to 10% A; 3.00-4.00 min, 10% A; 4.00-4.10 min, from 10% A to 90% A; 4.10-5.00 min, 90% A.

[0067] The conditions of the triple quadrupole mass spectrometer were as follows: IonDrive Turbo V electrospray ionization (ESI) interface, curtain gas = 40 psi, IonSpray voltage = ±3000 V, temperature = 450°C, ion source gas 1 = 30 psi, ion source gas 2 = 30 psi.

[0068] Animal experiments

[0069] The experiments were approved by the Ethics Committee of Shandong Normal University (AEECSDNU2024001) and were performed in accordance with the guidelines set by the European Union (Directive 2010 / 63 / EU). The experimental animals used in this study were adult male specific pathogen-free grade C57BL / 6J mice (weight 21-24 g) obtained from Beijing Weitong Lihua Laboratory Animal Technology Co., Ltd. All mice were housed in a temperature (22-24 °C) and humidity-controlled (40-70%) environment with a 12-h light / dark cycle.

[0070] Seventy mice were randomly divided into seven groups (10 mice in each group): control group, DSS group, tryptophan group, and four Lactobacillus plantarum groups (SFFI23, SFFI118, SFFI175, and SFFI50). During the 7-day adaptation period, mice had free access to the commercial AIN93G diet and distilled water. After the adaptation period, the diets of all groups except the control and DSS groups were changed to tryptophan diets (AIN93G diet supplemented with 0.5% tryptophan, adjusted to match the dietary energy content of AIN93G). For all groups except the control group, 2% DSS was added to the drinking water for seven consecutive days after four days to induce colitis symptoms in mice. During these seven days, the four Lactobacillus groups were gavaged with the corresponding Lactobacillus (3×10 9 CFU / 0.3mL / mouse / day), and the control group, DSS group and tryptophan group were gavaged with sterile saline (0.3mL / mouse / day) as a control.

[0071] Body weight and disease activity index (DAI) were measured. At the end of the experiment, mice were sacrificed under isoflurane anesthesia.

[0072] 1.4. Colonic biochemical analysis

[0073] 0.05 g of colon tissue samples were accurately weighed and homogenized in precooled sterile saline. The samples were centrifuged at 4000 × g and 4°C for 15 minutes, and the supernatant was collected. The levels of IL-1β, IL-6, IL-10, IL-22, and TNF-α in the colon were measured using their corresponding kits (Multisciences (LIANKE) Biotech Co., Ltd.).

[0074] 1.5. Histological evaluation

[0075] Colon samples were dehydrated in ethanol, sectioned (5 μm), embedded in paraffin, and stained with hematoxylin and eosin. Histopathological lesions were observed using a microscope (B-510FL microscope, OPTIKA Srl, Ponteranica, Italy) and histopathological scores were performed.

[0076] Western blot analysis

[0077] Western blot analysis was performed using antibodies against CYP1A1 (ab126887, 1:1000; Abcam, USA), occludin (ab216327, 1:2000; Abcam), p-STAT3 (ab76315, 1:1000; Abcam), and STAT3 (ab68153, 1:1000; Abcam).

[0078] 1.7. Correlation analysis

[0079] The correlation between AHR activation and colitis remission was analyzed.

[0080] 2. Results

[0081] 2.1. Tryptophan metabolism in Lactobacillus plantarum is strain-specific

[0082] Metabolism is a basic physiological function of microorganisms. However, tryptophan metabolic pathways vary among microbial species. Based on previous studies, we identified three indole derivatives produced by Lactobacillus plantarum through tryptophan metabolism: ILA, ICA, and IAA. Figure 1As shown, the levels of ILA, ICA, and IAA produced by Lactobacillus plantarum metabolism were quantified. Lactobacillus plantarum showed significant strain specificity in its ability to produce ILA, ICA, and IAA from tryptophan. ILA production ranged from 11.48 to 110.24 μg / mL, ICA production ranged from 0 to 0.31 μg / mL, and IAA production ranged from 0 to 0.35 μg / mL. Among the 58 Lactobacillus plantarum strains evaluated, 3 strains produced less than 0.01 μg / mL of ICA, while 4 strains produced less than 0.01 μg / mL of IAA. In terms of absolute quantity, the production of ILA was significantly higher than that of ICA and IAA. The strain with the highest ILA production of Lactobacillus plantarum was SFFI23, which was 110.24 μg / mL. However, the levels of ICA and IAA produced in SFFI23 were relatively low (ICA was the third lowest and IAA was the second lowest). Lactobacillus plantarum SFFI175 had the highest ICA production of 0.31 μg / mL; its IAA production was also the highest at 0.35 μg / mL. However, this strain had the lowest ILA production of 11.48 μg / mL. In addition, among the tested Lactobacillus plantarum strains, SFFI118 showed excellent production in all three metabolites, with an ILA production level of 77.57 μg / mL (the fourth highest ILA), 0.11 μg / mL ICA (the second highest ICA), and 0.13 μg / mL IAA. SFFI50 showed the fourth lowest ILA production, the lowest ICA production, and the lowest IAA production, and the worst tryptophan metabolism ability among the tested strains. The corresponding product yields of Lactobacillus plantarum SFFI23 and SFFI175 were significantly higher than those of other strains. However, since ICA and IAA are located on the same metabolic shunt, while ILA belongs to a different metabolic shunt, strains with higher ICA metabolic production usually also have higher IAA production, but relatively lower ILA production.

[0083] 2.2. L. plantarum SFFI23 restored body weight and colon length and alleviated histopathological damage

[0084] UC is a chronic inflammation of the colonic mucosa involving relapses and remissions. We established a mouse colitis model by administering DSS in drinking water. In this model, body weight, DAI, colon length, and histopathological scores are intuitive indicators of colitis severity. At the end of the experiment, mice in the DSS group had lost approximately 20% of their body weight ( Figure 2 C, p<0.0001, colon length was significantly shortened ( Figure 2 B, 2E, p<0.00001). Histopathological analysis showed that the colon of mice in the DSS group had obvious mucosal structural damage and inflammatory cell infiltration ( Figure 2G). Compared with the control group mice, the DAI and histopathological scores in the DSS group were significantly increased ( Figure 2 D and 2F, p<0.0001). These results indicate that the colitis model was successfully established.

[0085] Supplementation with Lactobacillus plantarum SFFI175 or SFFI50 had no significant effect on the symptoms of colitis in mice, whereas Lactobacillus plantarum SFPI23 had an alleviating effect on each indicator ( Figure 2 CF, p<0.01). SFFI118 had no significant effect on colon length compared with SFFI23, and no significant reduction in histopathological scores was observed in the SFFI118 group. In addition, mice fed tryptophan alone did not show a significant recovery of pathological indicators ( Figure 2 CF, p>0.05). This suggests that the alleviating effect of SFFI23 and SFFI118 on colitis was not caused by tryptophan.

[0086] Lactobacillus plantarum SFFI23 activates AHR signaling and restores colonic cytokine expression and intestinal barrier function

[0087] To investigate the contribution and potential mechanisms of ILA, ICA, and IAA produced by Lactobacillus plantarum in activating AHR signaling and alleviating colitis, we measured the levels of relevant immune indices. Cytokines are mainly produced by lymphocytes, monocytes, macrophages, and epithelial cells, and have pro-inflammatory or anti-inflammatory effects. In healthy individuals, a dynamic balance exists within the cytokine network, which plays a vital role in intestinal barrier function, host immune regulation, tissue repair, and maintenance of intestinal homeostasis. Several studies have reported significant changes in the expression of pro-inflammatory and anti-inflammatory cytokines in animal models of DSS-induced colitis. Typical changes include upregulation of IL-1β, IL-6, and TNF-α, and downregulation of IL-10.

[0088] In our study, the cytokine profile of the DSS group showed a similar trend ( Figure 3 AC and 3E, p < 0.05). However, the expression of cytokines in mice fed with Lactobacillus plantarum changed to varying degrees. L. plantarum SFFI23 significantly reduced the expression of IL-6 ( Figure 3 B, p<0.01), increased the expression of IL-10 (see Figure 3 C, p<0.0001). L. plantarum SFFI118 and SFFI175 significantly increased the expression of IL-10 ( Figure 3 C, p<0.01). SFFI23 and SFFI118 reduced the expression of IL-1β, but the extent was not significant. In addition, all Lactobacillus plantarum strains significantly reduced the expression of TNF-α ( Figure 3 E, p<0.05). Except for the Lactobacillus plantarum SFFI50 group, myeloperoxidase levels in all other groups showed a decreasing trend. Both IL-6 and TNF-α are proinflammatory cytokines associated with intestinal inflammation and have been extensively studied. They promote TH1 and TH2 cell survival, induce intestinal epithelial cell apoptosis, and impair intestinal barrier function. IL-1β is thought to stimulate T cell proliferation and trigger mucosal immune responses, thereby promoting the upregulation of IL-6 and TNF-α expression. In contrast, as an anti-inflammatory cytokine, IL-10 blocks macrophage metabolism and promotes impaired mitochondrial autophagy, thereby alleviating inflammation. Based on the analysis of cytokine expression, we can preliminarily conclude that Lactobacillus plantarum SFFI23 and SFFI118 partially alleviated the immune imbalance of colitis, among which SFFI23 showed better efficacy.

[0089] In addition to conventional cytokine expression, we also evaluated the intestinal barrier function of mice. The results showed that the expression of tight junction protein occludin was significantly decreased in the DSS group, but a significant recovery was observed in the Lactobacillus plantarum SFFI23 and tryptophan treatment groups ( Figure 3 G and H, p < 0.001). In particular, in the SFFI23 group, the expression of IL-22 was restored to a level comparable to that of healthy mice ( Figure 3 D, p<0.001). In addition, we found that Lactobacillus plantarum SFFI23 and SFFI118 significantly activated intestinal STAT3 signaling, but the effect of SFFI23 was more significant ( Figure 3 I, p<0.0001). IL-22 is secreted by innate and adaptive immune cells. It plays a vital role in maintaining intestinal barrier function and repairing intestinal damage by activating downstream STAT3 signaling. AHR is an important receptor for initiating IL-22 expression in lymphocytes. Under colitis conditions, AHR expression is significantly reduced, leading to abnormal IL-22 signaling. Impaired IL-22 signaling impairs intestinal barrier function and further aggravates colitis. After determining the expression of the AHR ligand CYP1A1 in the colon, it was observed that the combination of Lactobacillus plantarum SFFI23 and tryptophan significantly activated AHR signaling ( Figure 3 J and K, p < 0.0001). By activating AHR signaling, IL-22 and its downstream target STAT3 are activated, which can restore occludin expression in the intestine. This is essential for restoring the integrity of the intestinal epithelium. In summary, Lactobacillus plantarum SFFI23 showed the most effective AHR activation and colitis alleviation effects among the experimental strains, followed by SFFI118, while SFFI175 and SFFI50 did not show any significant effects. This is a typical manifestation of strain specificity.

[0090] Finally, to confirm the correlation between AHR signaling and colitis remission, we performed correlation analysis and quantified it using Pearson’s correlation coefficient. Figure 3 As shown in Figure 1, AHR signaling was strongly positively correlated with colon length (r = 0.86, p < 0.05), IL-22 expression (r = 0.88, p < 0.05), and STAT3 signaling (r = 0.99, p < 0.001). It was also strongly negatively correlated with weight change (r = -0.96, p < 0.01), DAI (r = -0.95, p < 0.01), histological score (r = -0.90, p < 0.05), and IL-6 expression (r = -0.84, p < 0.05). Therefore, it is reasonable to speculate that Lactobacillus plantarum SFFI23 produces high ILA in tryptophan metabolism, activates AHR signaling and IL-22 / STAT3 pathways, repairs intestinal barrier function, and alleviates colitis in mice.

[0091] It should be noted that the above examples are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention is described in detail with reference to the given examples, those skilled in the art may modify or replace the technical solution of the present invention as needed without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A strain of Lactobacillus plantarum SFFI23, which was deposited in the General Microbiology Center of China Microorganism Culture Collection Administration on April 26, 2024, with the deposit number CGMCC No.30453.

2. A microbial agent, characterized in that: The microbial agent contains the Lactobacillus plantarum SFFI23 or its fermentation product or culture thereof.

3. The microbial agent according to claim 2, characterized in that The microbial agent also includes auxiliary materials acceptable to the agent.

4. Use of the plant lactobacillus (Lactobacillus plantarum) SFFI23 according to claim 1 or the microbial agent according to any one of claims 2 to 3 in any one or more of the following: (a1) Fermentation to produce indole derivatives; (a2) preparing a product for preventing and / or treating colitis.

5. The use according to claim 4, characterized in that: In the above (a1), the indole derivatives include indoleacetic acid, 3-indole-lactic acid and indole-3-carboxaldehyde.

6. The use according to claim 4, characterized in that: In (a2), the prevention and / or treatment of colitis is specifically manifested as: (a2-1) recovery of colitis-mediated weight loss; (a2-2) restoration of colitis-mediated shortening of colon length; (a2-3) Alleviate colitis-mediated mucosal structural damage and inflammatory cell infiltration; (a2-4) Activate AHR signaling and restore colonic cytokine expression and intestinal barrier function.

7. The use according to claim 6, characterized in that In (a2-4), the colon cytokines include proinflammatory cytokines and anti-inflammatory cytokines, wherein the proinflammatory cytokines include IL-1β, IL-6 and TNF-α, and the anti-inflammatory cytokines include IL-10.

8. The use according to claim 7, characterized in that The expression of pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) is reduced, the expression of anti-inflammatory cytokines (IL-10) is increased, and the expression of myeloperoxidase is effectively reduced, thereby alleviating the immune imbalance of colitis.

9. A product, characterized in that The product comprises the Lactobacillus plantarum SFFI23 described in claim 1 or the microbial agent described in any one of claims 2-3; the product has the efficacy of preventing and / or treating colitis.

10. The product according to claim 9, characterized in that The product is a food or a medicine.

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