INTRODUCTION
Ulcerative colitis (UC) is inflammatory bowel disease (IBD) that differs from Crohn’s disease. UC primarily affects the rectum and extends continuously to the proximal colon (Le Berre et al., 2023). In contrast, Crohn’s disease affects gastrointestinal tract, presenting with discontinuous transmural inflammatory lesions (Dolinger et al., 2024). The course of UC is chronic and relapsing, primarily characterized by symptoms such as diarrhea, mucopurulent and bloody stools, and abdominal pain, which significantly impair patients' quality of life (Kucharzik et al., 2020). Pathogenesis of UC is highly complex, involving genetics, environment, immunity, and microbiota (Petagna et al., 2020). It was revealed that UC is not confined to the intestine as an isolated condition but is closely associated with systemic immune dysregulation, often accompanied by extraintestinal organ damage (Lin et al., 2022). Both the lung and the intestine are mucosal immune organs, interconnected via the circulatory system, lymphatic system, and gut microbial metabolites. Pulmonary barrier function is susceptible to remote regulation by intestinal inflammation, leading to interactive damage along the “gut–lung axis,” which further exacerbates disease complexity and impacts prognosis, posing significant challenges for clinical management (Luo et al., 2023a; Zhang et al., 2024). Clinical treatments for UC often involve glucocorticoids, immunosuppressants, and biologics, yet therapeutic outcomes remain suboptimal (Sands et al., 2023).
In TCM, UC falls under the categories of “abdominal pain”, “hematochezia”. The main cause is considered to be the stagnation of damp-heat in the large intestine, leading to qi stagnation, blood stasis. Modified peony decoction mainly consists of Paeoniae Radix Alba, Scutellariae Radix, Coptidis Rhizoma, Rhei Radix et Rhizoma, Aucklandiae Radix, Arecae Semen, etc., with modifications based on clinical presentation (Jun et al., 2019). In this formulation, Paeoniae Radix Alba serves as the sovereign herb (Jun), characterized by its sweet, bitter, and sour flavor and cold nature. It functions to nourish blood, harmonize blood circulation, soften the liver, alleviate urgency, and relieve pain, effectively addressing core symptoms of UC such as abdominal pain and tenesmus, while also providing a material basis for intestinal mucosal repair. Scutellariae Radix, Coptidis Rhizoma, and Rhei Radix et Rhizoma, with their bitter and cold properties, clear heat, dry dampness, purge fire, and detoxify. Aucklandiae Radix and Arecae Semen regulate qi, promote its movement, relieve stagnation, and alleviate middle-jiao pain. Angelicae Sinensis Radix nourishes and invigorates blood, assisting Paeoniae Radix Alba in harmonizing blood circulation and resolving stasis. A small amount of Cinnamomi Cortex, with its pungent and hot nature, prevents damage to the middle jiao by bitter-cold herbs and facilitates yang movement and qi transformation, collectively acting as assistant herbs. Glycyrrhizae Radix et Rhizoma Praeparata cum Melle harmonizes the various ingredients, tonifies the spleen, and boosts qi, serving as the envoy herb. Zeng and Li found that modified peony decoction could significantly alter the ultrastructure of primary cells from patients with adenomyosis to inhibit cell proliferation and induce apoptosis (Zeng and Li, 2017). Zhou et al. found that modified peony decoction used in the clinical remedy of restless legs syndrome could significantly improve clinical symptom scores and enhance patients’ quality of life, sleep quality, and overall remedy effectiveness (Zhou et al., 2024). Lee et al. found modified peony decoction is applied for premenopausal, perimenopausal, and postmenopausal menopausal-related diseases (Lee et al., 2020). NF-κB activation can trigger immune responses in intestinal mucosal tissues. Wei et al. found peony decoction adopted for UC could significantly reduce inflammatory indices and inflammasome-related proteins, and it could also exert anti-necrotic effects via NF-κB p65 pathway (Wei et al., 2021). Wu et al. noted that potential targets of peony decoction used in the remedy of UC mice included STAT3, IL-1β, IL-6, which could significantly alleviate intestinal mucosal damage and metabolic disorders in mice (Wu et al., 2022a). Wang et al. confirmed that peony decoction alleviates colitis symptoms in UC mice by improving intestinal mucosal permeability and correcting the metabolic changes of M1 macrophages (Wang et al., 2025). These studies have all confirmed the potential therapeutic effects of peony decoction on UC. However, intestinal inflammation is not limited to the intestine itself but may also spread to the lungs through the release of inflammatory mediators and blood circulation, causing pulmonary inflammatory responses. Mechanism of modified peony decoction in treating UC and improving concurrent lung and intestinal barrier injury remains to be verified.
It was hypothesized that the modified peony decoction alleviates pulmonary inflammation and repairs lung-intestinal barrier damage by modulating the Rho/ROCK/NF-κB signaling pathway, thereby inhibiting the release of intestinal inflammatory mediators and reducing the transmission of inflammatory signals to the lungs via systemic circulation. This work established the UC rat model using the immune complex method and analyzed influences of modified peony decoction on pathological changes, tight junction structure, and mucosal barrier function of rat lung-colon tissues. It aims to provide reference materials for understanding the potential mechanisms of concurrent lung and intestinal barrier injury after UC and the therapeutic effects of modified peony decoction.
MATERIALS AND METHODS
Construction of UC model: Thirty-six clean-grade adult male Wistar rats (100-120 g, Beijing Sipeifu Experimental Animal Co., Ltd., China) were used. The UC model was established following the method described by Xie et al. (Xie et al., 2022). After the colonic mucosal epithelial cells from rabbits (Shanghai Enzyme Linked Co., Ltd., China) were cultured, the supernatant was collected and mixed with Freund’s adjuvant (Sigma-Aldrich, USA) to prepare the antigen emulsion. Thirty rats were randomly selected and fed adaptively for 7 days, and were subcutaneously injected with 8 mg of the antigen emulsion in the inguinal region on days 7, 14, and 21. On day 28, after fasting for 48 hours, the rats were anesthetized with 3% pentobarbital sodium (Sigma-Aldrich, USA) at 30 mg/kg via intraperitoneal injection. A gavage needle coated with paraffin oil was used to slowly instill a mixture of 100 mg/kg trinitrobenzene sulfonic acid (Sigma-Aldrich, USA) + 50% ethanol (Nanjing Chemical Reagent Co., Ltd., China) into a 5 cm section of the colon taken from the rat’s anus. The anus was clamped and the rat was hung upside down for 3 minutes. The rat was then placed in a supine position in a breeding cage, allowed to eat and drink freely after full recovery, and regularly observed for mental state, body weight (BW), stool condition, and survival. All animal procedures were approved by the Institutional Animal Care and Use Committee of North China University of Science and Technology, conducted in accordance with guidelines.
Grouping and remedy: Six rats that were not subjected to modeling were used as BC group and received a gavage treatment of 10 mL/kg saline. The 30 successfully modeled rats were randomly grouped, with 6 rats in each:
UC group received a gavage treatment of 10 mL/kg saline after modeling;
MESA group received a gavage treatment of 0.5 g/kg mesalamine (Koohi et al., 2023) after modeling;
LD group received a gavage treatment of 6 g/kg modified peony decoction after modeling;
MD group received a gavage treatment of 12 g/kg modified peony decoction after modeling;
HD group received a gavage treatment of 24 g/kg modified peony decoction after modeling.
All groups were given gavage continuously for 28 days.
General observation: The general condition, stool condition, and hematochezia of the rats were observed. BW changes were recorded on days 0, 1, 7, 14, 21, and 28, and DAI assessed disease activity status of rats. The DAI scoring criteria (Zhuang et al., 2021) were as follows: a weight loss score of 0%, normal stool condition, and negative occult blood in stool (-) was scored as 0; 1-5%, loose, and (+): 1; 6-10%, semi-liquid, and (++): 2; 11-15%, liquid, and significant blood in stool: 3; >15%, liquid, and significant blood in stool: 4. DAI score=(weight loss score + stool condition score + hematochezia score) / 3.
Pathological observation: The day after the last gavage, the rats were anesthetized as described above. Abdomen was opened along the midline, and a 1 cm section of the typical lesion colon tissue from 5-15 cm above the anus was taken; the upper right lobe of the lung was collected after cutting the sternum. The colon contents and lung tissue blood were washed with pre-cooled saline, and tissues were fixed in 10% neutral formalin solution, dehydrated with gradient alcohol, embedded in paraffin, and sectioned into 4 μm thick paraffin slices. According to the instructions of the H&E kit (Beijing Solarbio Co., Ltd., China), the paraffin slices were baked at 65℃ for 2 hours, dewaxed and rehydrated with xylene and gradient alcohol, stained in hematoxylin solution for 5 minutes, rinsed twice; differentiated for 2 seconds, rinsed twice; stained in eosin solution for 2 minutes, rinsed twice; dehydrated with gradient alcohol and xylene. After sealing with neutral gum, the pathological morphological changes were subjected to observation adopting the SZX10 optical microscope (Olympus, Japan). Colonic tissues were primarily evaluated for mucosal integrity, degree of inflammatory cell infiltration, glandular destruction, and crypt abscess formation, with the extent of tissue damage assessed using the modified mucosal damage index (MDI) score. Pulmonary tissues were examined for alveolar structural integrity, thickness of alveolar septa, inflammatory cell infiltration, and damage to the bronchial mucosal epithelium.
1 mm3 of lung tissue was fixed in 2.5% glutaraldehyde and 1% osmium acid (both from Nanjing Chemical Reagent Co., Ltd., China), and ultra-thin sections were prepared. TEM examined the ultrastructure of pulmonary epithelial cells, with a focus on evaluating the continuity and integrity of tight junctions, mitochondrial morphology, ciliary structure, and damage to cytoplasmic organelles, in order to characterize the type and extent of ultrastructural injury in these cells.
Immunofluorescence staining observation: Paraffin sections were taken and processed for dewaxing and rehydration, followed by antigen retrieval. The sections were incubated with 3% hydrogen peroxide in the dark at 25℃ for 20 minutes and then rinsed with PBS. Normal goat serum blocking solution (Sigma-Aldrich, USA) was adopted to block the sections at 25℃ for 30 minutes. Primary antibodies against F-act, VE-cad, and ZO-1 (Abcam, UK) were adopted, incubation overnight at 4℃. Biotinylated goat anti-rat IgG antibody (Abcam, UK) was adopted, incubation at 37℃ for 30 minutes in a humidified chamber. SABC-Cy3 (Beijing Baiao Laibo Technology Co., Ltd., China) was adopted, incubation in the dark at 25℃ for 30 minutes, rinsed and mounted with glycerin. DAPI (Thermo Fisher, USA) was adopted, incubation in the dark for 5 minutes for nuclear counterstaining. After adding an anti-fade agent, they were mounted and subjected to observation adopting a CX33 fluorescence microscope (Olympus, Japan) for immunofluorescence staining.
Western blotting analysis: Lung and intestinal tissues were collected and total protein was subjected to extraction adopting RIPA buffer (Thermo Fisher, USA). The concentration was subjected to determination adopting the bicinchoninic acid assay (Thermo Fisher, USA). An equal amount (50 μg) of total protein was loaded and separated by SDS-PAGE. Proteins were transferred onto a PVDF membrane and blocked at 25°C for 2 hours. The membrane was incubated overnight at 4°C with primary antibodies (1:1000; Abcam, UK) against Rho A, p-Rho A, ROCK1, NF-κB, COX-2, and VEGF. After washing, the membrane was incubated with HRP-conjugated IgG secondary antibody (1:5000; Abcam, UK) at 25°C for 2 hours. The membranes were washed and the protein signals were detected adopting a WD-9423B fully automatic chemiluminescence imager (Beijing Liu Yi Biotechnology Co., Ltd., China). β-actin served as a reference to compute relative expression (RE). Western blot analysis was independently repeated three times to ensure reproducibility of the results.
Statistical processing: Employing SPSS 23.0, datasets underwent normality testing and homogeneity of variance testing. Normally distributed continuous data with homogeneous variance, including colonic tissue damage scores, inflammatory cytokine levels, and protein expression levels, were expressed as x̅±s and were compared using one-way ANOVA. Following ANOVA, Tukey’s honestly significant difference test was applied for pairwise comparisons to correct for multiple testing errors. Distinctions were statistically meaningful when P<0.05.
RESULTS
Contrast of general condition of rats: The BW changes at different time points after modeling were compared (Figure 1A). It was found that the BW of BC group gradually raised, while the BW of UC, MESA, LD, MD, and HD groups decreased on the first day after modeling and then displayed a gradual increasing trend. Body weights were observed different among all groups at all time points except Day 0 (P<0.05). Versus UC group, BC group exhibited higher body weight starting from postoperative Day 1 (P<0.05). The DAI scores at different time points after modeling were then compared (Figure 1B). It was found that the DAI scores of UC, MESA, LD, MD, and HD groups significant raised on the first day after modeling and then displayed a gradual decreasing trend. The DAI scores of HD group were close to those of MESA group. Drastic differences in DAI scores existed among all groups at postoperative days 1, 7, and 14 (P<0.05). The BC group exhibited significantly lower DAI scores from day 1 to day 14 versus UC (P<0.05).
Figure 1. Changes in the general condition of rats. A:BW-time change curve; B: DAI score-time change curve. aP<0.05 vs. UC group;
Contrast of pathological morphology: Lung tissue pathological morphology changes were observed by HE staining and electron microscopy (Figure 2 and Figure 3). It was found that the lung tissue contour in BC group was clear, no edema or fibrosis. In UC group, the lung tissue was significantly congested, with many inflammatory cell infiltrations in the lung interstitium, increased alveolar septa, unclear structure, and a small amount of fibrous tissue proliferation. The degree of lung tissue changes in MESA, LD, MD, and HD groups was improved in contrast to UC group, with MESA group and HD group showing the most significant improvement. A small amount of fibrous tissue proliferation in the lung interstitium, some alveolar tissue structure had recovered.
In Figure 4, the colon mucosa in BC group was intact with neatly arranged glands, and no inflammatory cell infiltration. In UC group, the colon mucosa exhibited varying degrees of defect or necrosis, with inflammatory cell infiltration forming ulcers. The degree of colon tissue lesion in MESA, LD, MD, and HD groups was improved in contrast to UC group, with MESA group and HD group showing the most significant improvement in colon mucosa damage, with slight cell infiltration. The mean colonic pathological injury scores were 0.17 ± 0.28 in the BC group, 2.89 ± 0.505 in the UC group, 1.33 ± 0.47 in the MESA group, 1.83 ± 0.75 in the LD group, 1.72 ± 0.49 in the MD group, and 1.39 ± 0.39 in the HD group. One-way ANOVA revealed a highly statistically significant difference in mean scores among the groups (F=27.79, P<0.001). Post-hoc analysis using Tukey's HSD test showed that compared to the BC group, the other five groups had significantly higher colonic pathological injury scores (P<0.05). Compared to the UC group, the MESA, LD, MD, and HD groups exhibited significantly lower pathological injury scores (P<0.05). The MESA and HD groups showed the lowest scores, with no statistically significant difference between them (P>0.05).
Figure 2. HE staining of lung tissue in rats (200×). A: BC; B: UC; C: MESA; D: LD; E: MD; F: HD.
Figure 3. Electron microscopy observation of lung tissue in rats (200×). A: BC; B: UC; C: MESA; D: LD; E: MD; F: HD.
Figure 4. HE staining observation of colon tissue in rats (200×). A: BC; B: UC; C: MESA; D: LD; E: MD; F: HD.
Note: aP<0.05 vs. BC; bP<0.05 vs. UC; cP<0.05 vs. MESA; dP<0.05 vs. LD; eP<0.05 vs. MD (in all Figures).
Contrast of F-act, VE-cad, and ZO-1: In Figure 5, there was varying degrees of F-act, VE-cad, and ZO-1 in rats. The expression intensity was significantly reduced and was significantly lower in UC group; that in MESA, LD, MD, and HD groups was significantly higher relative to UC group (P<0.05). With increasing dosage, the expression intensity in LD, MD, and HD groups gradually raised.
In Figure 6, there were varying degrees of F-act, VE-cad, and ZO-1 in the colon tissue of rats. Expression intensity was significantly reduced and was significantly lower in UC group; that in MESA, LD, MD, and HD groups was markedly higher relative to UC group (P<0.05). With increasing dosage, the expression intensity in LD, MD, and HD groups also exhibited a gradually increasing trend.
Figure 5. Expression of F-act, VE-cad, and ZO-1 in rat lung tissue (400×). A: immunofluorescence staining for F-act; B: immunofluorescence staining for VE-cad; C: immunofluorescence staining for ZO-1; D: relative F-act; E: relative VE-cad; F: relative ZO-1.
Figure 6. Expression of F-act, VE-cad, and ZO-1 in rat colon tissue (400×). A: immunofluorescence staining for F-act; B: immunofluorescence staining for VE-cad; C: immunofluorescence staining for ZO-1; D: relative F-act; E: relative VE-cad; F: relative ZO-1.
Contrast of key protein expression in Rho/ROCK/NF-κB pathway: In Figure 7, p-Rho A, ROCK1, and NF-κB were markedly raised and were markedly higher in UC group; those in MESA, LD, MD, and HD groups were markedly lower versus UC (P<0.05). With increasing dosage, p-Rho A and ROCK1 in LD group, MD group, and HD group demonstrated a gradually decreasing trend. NF-κB in the lung tissue of MD group was higher relative to LD group and HD group. No significant distinction was noted in the protein expression in colon tissue of LD, MD, and HD groups (P>0.05).
Figure 7. Expression of key proteins in the Rho/ROCK/NF-κB pathway in rat lung and intestinal tissues. A: Western blotting for lung tissue proteins; B: Western blotting for colon tissue proteins; C: relative p-Rho A in lung; D: relative ROCK1 in lung; E: relative NF-κB in lung; F: relative p-Rho in colon; G: relative ROCK1 in colon; H: relative NF-κB in colon.
Contrast of key protein expression in the mucosal barrier: In Figure 8, the levels of COX-2 and VEGF were markedly raised and were markedly higher in UC group; those in MESA, LD, MD, and HD groups were markedly lower versus UC (P<0.05). No significant distinction was noted in COX-2 in the lung and intestinal tissues, and in VEGF in lung tissue of the MESA group, LD group, and MD group (P>0.05); COX-2 and VEGF in lung and intestinal tissues of HD group were markedly lower relative to MD and HD groups (P<0.05).
Figure 8. Expression of key proteins in the mucosal barrier of rat lung and intestinal tissues. A: Western blotting for lung tissue proteins; B: Western blotting for colon tissue proteins; C: relative COX-2 in lung; D: relative VEGF in lung; E: relative COX-2 in colon; F: relative VEGF in colon.
DISCUSSION
Our results revealed that UC rats had decreased BW and raised DAI scores relative to normal rats. Additionally, through HE staining experiment, colonic mucosa of UC rats revealed different degrees of defect or necrosis, accompanied by inflammatory cell infiltration and ulcer formation. The main lesions of UC are in the colonic mucosa and submucosa, characterized by inflammatory cell infiltration and ulcers (Wangchuk et al., 2024). Hence, a reliable UC rat model was successfully established, laying foundation for subsequent experiments. Then, post to modified peony decoction treatment, the BW of UC rats raised, and the DAI scores decreased, with considerable enhancement in colonic mucosal necrosis, inflammatory cell infiltration, and ulcer changes. TCM believes that UC may be related to damp-heat and disharmony of qi and blood (Zheng et al., 2022; Wu et al., 2022b). Modified peony decoction is a commonly used prescription. Modified peony decoction can improve intestinal inflammatory symptoms through mechanisms such as clearing heat, regulating qi and blood (Wu et al., 2023). The above mechanisms are related to suppressing intestinal inflammation, regulating immune function, and improving intestinal microcirculation.
UC shows persistent or recurrent diarrhea and bloody stools as the main clinical manifestations. As reported, patients with inflammatory bowel disease tend to develop pulmonary symptoms, with about 50% of patients showing respiratory symptoms such as dyspnea, cough, or sputum production (Marvisi et al., 2019). From modern embryological studies, structural origin of the lung and intestine is the same, and both the respiratory and gastrointestinal mucosa are part of the common mucosal immune system (Paul et al., 2022). Our results revealed that lung tissue structure of UC rats changed markedly, with inflammatory cell infiltration and pulmonary interstitial fibrosis, and the colon tissue also exhibited inflammatory cell infiltration with raised pathological damage scores. The noted results indicated that UC rats have concurrent damage to the pulmonary and intestinal mucosal barriers. Modern pharmacological studies have confirmed that traditional Chinese medicine can protect intestinal mucosal barrier through mechanisms such as regulating intestinal motility, promoting damaged mucosa repair, improving microcirculation, maintaining intestinal flora balance, and antioxidant stress (Liu et al., 2022; Wang et al., 2024). This study found that modified peony decoction can markedly improve the structural damage of lung and colon tissues in UC rats and reduce inflammatory cell infiltration. The connection structure of colonic epithelial cells and endothelial cells is key to the composition of the intestinal mechanical barrier, with main components including Claudin 5, ZO, and VE-cad (Jiang et al., 2021). Outside the cell, transmembrane proteins interact with transmembrane proteins on adjacent cells to close cell pores; inside the cell, ZO protein families connect and fix; subsequently, they form the fascia structure between adjacent intestinal epithelial cells (Assimakopoulos et al., 2020). This effectively prevents bacteria and antigens from entering intestinal mucosal lamina propria and avoids abnormal immune reactions of the intestinal mucosa. ZO-1 plays an intermediary role in tight junctions, and its combination with the carboxyl terminus of the transmembrane protein Occludin can form the basic structure of tight junctions (Kuo et al., 2022). F-act is the main component of intracellular microfilaments, providing structural support for the cytoskeleton, and it can maintain the tight connection between cells by interacting with cell connection proteins (Chanez-Paredes et al., 2024). VE-cad is an important adhesion connection protein, maintaining the tight connection between cells through calcium ion-dependent interactions (Bandyopadhyay et al., 2021). Expression intensity of F-act, VE-cad, and ZO-1 in lung and colon tissues of UC rats was markedly reduced. It is speculated that the reduction in F-act, VE-cad, and ZO-1 is the pathological basis for the destruction of the intestinal mucosal tight junction structure and may also be key to UC intestinal epithelial barrier function damage and raised permeability. Scutellaria baicalensis and Coptis chinensis are both components of modified peony decoction. Cui et al. found Scutellaria baicalensis extract SP2-1 markedly reduces the BW loss and DAI scores, and repair the damaged colonic mucosal barrier by suppressing the release of pro-inflammatory cytokines and upregulating the expression of ZO-1, Occludin, and Claudin-5 (Cui et al., 2021). Xie et al. found that Coptis chinensis gavage could increase the abundance of Blautia, etc. in the rat intestine, and protect the integrity of the intestinal tight junction structure by suppressing inflammatory reactions, thereby preventing intestinal barrier damage (Xie et al., 2022). Zhou et al. found that Coptis chinensis alkaloids could reverse the intestinal wall swelling and inflammatory cell infiltration in colitis mice, and restore integrity of colonic mucosa by upregulating Claudin 1, etc (Zhou et al., 2023). This indicates that modified peony decoction can regulate the expression of F-act, VE-cad, and ZO-1 in pulmonary and intestinal tissues through various pharmacological actions, thereby protecting the tight junction structure of the pulmonary and intestinal barriers, maintaining the normal function of the pulmonary and intestinal barriers, and repairing damaged tissues.
Mucosal injury-induced increase in intestinal permeability exacerbates bacterial translocation, disrupts intestinal homeostasis, and triggers inflammation (Di Vincenzo et al., 2024). The Rho/ROCK pathway plays a role in regulating cytoskeletal dynamics and maintaining intestinal epithelial cell junctions, with phosphorylation of myosin light chain in this pathway being associated with increased intestinal endothelial permeability (Kimura et al., 2021; Xu and Lin, 2024; Liu et al., 2020). Zhang et al. induced a UC rat model using TNBS and observed significantly elevated expression of p-RhoA and ROCK1 in colonic tissues (Zhang et al., 2021). Similarly, this study found that the expression levels of p-RhoA and ROCK1 in the lung and colonic tissues of UC rats were significantly higher than those in the control group (P<0.05). The Rho/ROCK pathway can activate NF-κB (Yan et al., 2021), and inhibition of the NF-κB pathway promotes colonic mucosal repair (Zhou et al., 2023). This study demonstrated that after administration of modified peony decoction, the levels of p-RhoA, ROCK1, and NF-κB in UC rats were significantly reduced. Activation of NF-κB promotes the release of IL-1, IL-6, and TNF-α, forming an inflammatory cascade (Shostak et al., 2021). Previous studies noted that paconiflorin, peony decoction, and emodin exert anti-inflammatory effects, promote the restoration of intestinal mucosal homeostasis, and inhibit NF-κB in different models (Wang et al., 2022; Chen et al., 2024; Luo et al., 2022). The modified peony decoction demonstrated reparative effects on lung and intestinal tissues, improving the morphological structure of damaged tissues and restoring barrier integrity. This reparative effect is likely mediated through the Rho/ROCK/NF-κB pathway, leading to the suppression of inflammatory responses. The regulation of this pathway by the modified peony decoction represents a key mechanism underlying its anti-inflammatory and protective actions. The regulatory function and reparative effects are interrelated and mutually reinforcing, with the reparative role being indispensable to its overall protective efficacy.
Granulation tissue is required for tissue repair following damage, and the deposition of connective tissue matrix, fibroblasts, and angiogenesis are key to restoring oxygen and nutrient supply to the damaged tissue (Liu et al., 2025). VEGF is a potent angiogenic factor that can promote the proliferation and construction of blood vessels by endothelial cells. In the intestinal barrier, VEGF and COX-2 may maintain intestinal barrier by promoting angiogenesis (Yin et al., 2021). Kim et al. induced a colitis model and found that COX-2 in colon tissue was raised (Kim et al., 2017). Şen et al. indicated that VEGF and COX-2 are markers of UC severity, with their expression upregulated in colonic tissue (Şen et al., 2023). Our work indicated the same, revealing that COX-2 and VEGF act in regulation of concurrent pulmonary and intestinal barrier damage in UC. Subsequently, this study found that after gavage with modified peony decoction, COX-2 and VEGF in lung and colon tissues of UC rats were markedly reduced. There are currently no studies confirming the potential effects of peony decoction on COX-2 and VEGF in inflammatory bowel disease. However, Luo et al. found that peony and licorice decoction could inhibit the expression of COX-2 in a migraine animal model and exert analgesic effects (Luo et al., 2023b). Zhang et al. found peony and licorice decoction could inhibit the expression of VEGF in serum and brain tissue to improve cerebral ischemia-reperfusion injury in rats (Zhang et al., 2016). The above results show that modified peony decoction can improve the pulmonary and intestinal barrier function damage in UC rats by suppressing COX-2 and VEGF. In addition, Luo et al. indicated that Gram-positive bacteria promote UC through the MDP-NOD2 pathway, and paeoniflorin can inhibit the infiltration of Gram-positive bacteria in the intestine, thereby alleviating the disease process (Luo et al., 2021). Hence, effects of modified peony decoction on the intestinal metabolism and microbiota structure in UC rats require to be revealed.
Conclusion: Modified peony decoction promotes repair of pulmonary and intestinal mucosal epithelial structures in UC rats and enhance concurrent damage of pulmonary and intestinal mucosa by suppressing Rho/ROCK/NF-κB pathway and COX-2 and VEGF expression.
Author’s contribution: Conception and study design: Xinyu Zhan and Xin Yan; data acquisition and analysis: Xinyu Zhan, Huiyan Xu, Haimei Zhang, Yongsen Jia, Fanwu Wu, Lingyu Kong and Xin Yan; manuscript draft, editing and revision: Xinyu Zhan and Xin Yan. All authors wrote and approved the final manuscript.
Animal Ethics: All experiments were approved by Ethics Committee of North China University of Science and Technology (Tangshan, China), and in accordance with the Guide for the Care and Use of Laboratory Animals published by the United States National Institutes of Health.
Funding: This work was supported by National Natural Science Foundation Youth Fund Project (81704059) and Hebei Natural Science Foundation (H2022209057).
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