Effect of apple phenols on anxiety/depression in a rat model of acute exacerbation of chronic obstructive pulmonary disease

Abstract

BACKGROUND

Chronic obstructive pulmonary disease is a lung disease characterized by airflow limitation and incomplete reversibility. Apple polyphenols (AP) are secondary compounds widely present in apple metabolites. Although AP has a protective effect against acute lung injury, its effects on inflammatory factors, anxiety, and depression in rat models of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) have not been studied.

AIM

To investigate the effects of AP on inflammatory factor levels and anxiety/depression in a rat model of AECOPD.

METHODS

AECOPD rat models were established using cigarette smoke inhalation and airway lipopolysaccharide injection. Seventy-two rats were divided into 6 groups: Control; model; low-dose AP (AP-L); middle-dose AP (AP-M); high-dose AP (AP-H); and AP-H + mcc950 [NOD-like receptor protein 3 (NLRP3) inhibitor]. Body weight, pulmonary function, pathological changes, and serum, lung, and prefrontal lobe levels of interleukin (IL)-6, tumor necrosis factor-α (TNF-α), IL-1β, miR-21, malondialdehyde (MDA), and lactate dehydrogenase (LDH) were assessed. Anxiety/depression were assessed using sucrose-preference and open-field experiments, and NLRP3 expression through western blotting.

RESULTS

Body weight, peak expiratory flow, peak inspiratory flow, forced expiratory volume in 0.3 seconds to forced vital capacity ratio, sucrose preference, total distance traveled, entries into and duration of stay in the central area in model group rats were reduced, while IL-6, TNF-α, IL-1β, miR-21, MDA, and LDH levels, and NLRP3 expression increased. Body weight, peak expiratory flow, peak inspiratory flow, forced expiratory volume in 0.3 seconds to forced vital capacity ratio, sucrose preference, total distance, entries into and duration of stay in the central area in the AP-L, AP-M, AP-H and AP-H + mcc950 groups increased, while NLRP3 IL-6, TNF-α, IL-1β, miR-21, MDA, and LDH levels, and NLRP3 expression were reduced. The efficacy of AP-H was superior to that of AP-M and AP-L, and mcc950 enhanced the protective effect of AP-H.

CONCLUSION

AP effectively improves body weight and lung function, reduces inflammatory cytokine and anxiety/depression levels, and alleviates pathological damage in rats with AECOPD, and is associated with downregulation of NLRP3 expression.

Key Words: Apple polyphenols; Acute exacerbation chronic obstructive pulmonary disease; Inflammatory; Anxiety-depression; NOD-like receptor protein 3

Core Tip: This study investigated the effects of apple polyphenols (AP) in a rat model of acute exacerbation of chronic obstructive pulmonary disease. Results demonstrated that AP treatment, particularly at high doses, effectively improved lung function and body weight and reduced pathological damage. It significantly downregulated the expression of NOD-like receptor protein 3 in lung tissue, leading to decreased levels of pro-inflammatory cytokines and oxidative stress markers in the serum, lung tissue, and prefrontal lobe tissue. Concurrently, AP alleviated anxiety and depression-like behaviors in acute exacerbation of chronic obstructive pulmonary disease model animals. This mechanism is associated with NOD-like receptor protein 3 pathway suppression.

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease characterized by incompletely reversible and progressive airflow limitation[1]. Its clinical manifestations mainly include cough, sputum production, and wheezing, which seriously affect the quality of life of patients[2,3]. The pathogenesis of COPD is complex and affected individuals are susceptible to acute attacks caused by harmful gases or particles in the environment[4]. Patients with acute exacerbation of COPD (AECOPD) have more severe conditions, with inflammatory lesions in the airways and lung parenchyma[5,6]. If not treated in a timely and effective manner, AECOPD may cause a sustained decline in lung function, leading to respiratory failure and, ultimately, death[7]. Presently, the mortality rate of AECOPD in patients ≥ 65 years of age is as high as 30%[8]. Furthermore, treatment with Western medicine can only alleviate symptoms and cannot alter the natural course of the disease[9,10]. Therefore, identifying effective treatment methods for patients with AECOPD is important.

Apple polyphenols (AP) are natural substances extracted from apples that exert strong antioxidant activity[11,12]. Birru et al[13] found that AP phloretin exhibited anti-inflammatory activity in COPD-induced macrophages and human bronchial epithelial cells, and reduced bacterial damage in COPD. Furthermore, Bao et al[14] reported that AP alleviated lung injury caused by cigarette smoke through the p38/mitogen-activated protein kinase signaling pathway. The NOD-like receptor protein 3 (NLRP3) inflammasome is a multi-protein complex that promotes the production of pro-inflammatory cytokines, such as interleukin (IL)-1β, thereby inducing exacerbation of COPD airway inflammation[15,16]. However, virtually no studies have investigated the role of AP in the treatment of AECOPD, and their regulatory mechanisms are poorly understood. Therefore, we hypothesized that AP alleviates the inflammatory response, anxiety, and depression caused by AECOPD by inhibiting NLRP3 expression.

MATERIALS AND METHODS

Materials

Six-week-old, specific pathogen-free grade, male Wistar rats, weighing 200 ± 20 g, with animal license number SCXK (Jing) 2016-0011, were purchased from Beijing Weitonglihua Experimental Animal Co., Ltd (Beijing, China). The animals were housed in dedicated rooms at 24-25 °C, 50% humidity, with 12 hours light and 12 hours dark cycles, access to food and water. AP, lipopolysaccharide (LPS), Tris-Buffered saline with Tween-20, and miR-21 buffer solutions were purchased from Shanghai Yuanye Biotechnology Co., Ltd. (Shanghai, China). mcc950 were purchased from Shanghai Yuanye Biotechnology Co. Ltd. (Shanghai, China). Commercially available assay kits for IL-6, tumor necrosis factor-α (TNF-α), IL-1β, malondialdehyde (MDA), lactate dehydrogenase (LDH), hematoxylin and eosin (HE) staining, as well as the bicinchoninic acid assay were purchased from Beijing Solaibao Technology Co., Ltd (Beijing, China). An enzyme immunoassay reader (PerkinElmer, Waltham, MA, United States), inverted microscope (Olympus, Tokyo, Japan), paraffin slicer (SLEE Medical GmbH, Nieder-Olm, Mainz, Germany), and a self-fabricated smoking box (modified from a fumigation sterilization box; box size: 120 cm × 80 cm × 80 cm) were used. Rabbit monoclonal antibodies against glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and NLRP3 were purchased from Abcam (Cambridge, United Kingdom).

Model establishment and group administration

A rat model of AECOPD was established by exposing the animals to cigarette smoke and injecting LPS into the airways, in combination with nasal administration. Except for the control group, the other groups were anesthetized with 10% chloral hydrate intraperitoneally on days 1 and 14 of modeling. The rats were fixed on an operating table, their throats were exposed, and LPS (1 mg/mL) was administered through a gastric gavage needle. From the 2^nd to 13^th days and from the 15^th to 28^th days of the experiment, the rats were exposed to the smoke from Xiongshi brand cigarettes in a self-fabricated smoking box every day, maintaining a smoke concentration of 5% (equivalent to 30 cigarettes) for 1 hour each time. The modeling period lasted 28 days. Mice in the control group were injected with 1 mg/mL of physiological saline into the tube on day 1 and days 14 of the experiment and were fed normally for the remainder of the time. Except for the control group, on days 29-35, 0.2 mL (2.4 × 10⁹ colony-forming units/mL) of Streptococcus pneumoniae suspension was instilled into the nasal cavity of all other groups, and 0.2 mL of 0.9% sodium chloride was instilled into the nasal cavity of the control group rats each time. On day 4 of the experiment, 1 hour before smoking, rats in the low-dose AP (AP-L), middle-dose AP (AP-M), and high-dose AP (AP-H) groups were intraperitoneally injected with 25 mg/kg (AP-L), 50 mg/kg (AP-M), 100 mg/kg (AP-H), or 100 mg/kg (AP-H) + 10 mg/kg (mcc950), respectively, once daily, until the rats were euthanized 35 days later.

Body weight

Body weight was measured weekly and recorded during the modeling and drug administration periods.

Pulmonary function indicators

The rats were anesthetized intraperitoneally with 10% chloral hydrate, their heads and limbs were fixed, and their necks were disinfected. The subcutaneous tissue of the neck was bluntly separated layer-by-layer until the trachea was exposed. The trachea was inserted and connected to a fully automated lung function tester (FGC-A+). Forced expiratory volume in 0.3 seconds (FEV_0.3) was recorded to calculate the forced vital capacity (FVC) ratio (FEV_0.3/FVC), peak expiratory flow (PEF), and peak inspiratory flow (PIF).

HE staining

Tissue from the left lung lobe tissue was fixed using 4% paraformaldehyde solution, followed by routine dehydration, made transparent using xylene, embedded in paraffin, and cut into sections (5 μm thick). Slices were subjected to routine HE staining to observe pathological changes in lung tissue under a microscope.

Inflammatory factor levels

Blood samples, lung tissue, and prefrontal lobe tissue of the rat brain were collected and centrifuged at 3000 rpm for 10 minutes. The levels of TNF-α, IL-6, IL-1 β, and miR-21 were determined in serum, pulmonary (lung), and frontal lobe tissue homogenate supernatant using enzyme-linked immunosorbent assay. All procedures were performed according to manufacturer’s instructions for the respective kits.

Oxidative stress level

Rat blood, lung tissue, and prefrontal lobe tissue were extracted and centrifuged at 3000 rpm for 10 minutes. MDA and LDH kits were used to determine the serum, pulmonary, and frontal lobe tissue homogenate supernatant levels of MDA and LDH.

Behavioral testing

Evaluation of anxiety and depression levels in rats using sucrose-preference and open-field experiments.

Sucrose-preference experiment: One bottle of 2% sucrose solution and 1 bottle of purified water were placed in each rat cage, and the amount consumed of each was recorded. The sucrose-preference rate (%) was calculated as: Sucrose consumption/total liquid consumption × 100%.

Open-field experiment: Before sampling, the rats were placed in a 100 cm × 10 cm × 50 cm box with black inner walls and bottoms. The bottom of the box consisted of 25 equal-sized 20 cm × 20 cm squares, which were automatically divided using a video-tracking analysis software system (ANY-maze, Wood Dale, IL, United States). Each rat underwent only 1 behavioral test, and the next test was conducted after completion, using a single-blind method. The measurement indicators included the total distance of horizontal movement within 5 minutes, dwell time in the central area, and the number of times the central area was entered.

Western blotting

Total protein was extracted from the lung tissue, quantified, and subjected to sodium dodecyl polyacrylamide gel electrophoresis (i.e., “sodium dodecyl sulfate-polyacrylamide gel electrophoresis”). After wet membrane transfer, the membrane was blocked with skim milk powder. Primary antibodies against NLRP3 (diluted 1:1000) and GAPDH (1:2000), and a secondary antibody (1:1000) were then added for the immune reaction, and a chemiluminescence reagent was added for color development. GAPDH was used as an internal reference, and the relative grayscale values of the target bands were analyzed using ImageJ software.

Statistical analysis

Statistical analyses of the experimental data were performed using SPSS version 27.0 (IBM Corporation, Armonk, NY, United States) and Prism software (GraphPad Inc., San Diego, CA, United States). Measurement data are expressed as mean ± SD. The independent sample t-test was used for intergroup comparisons and one-way analysis of variance was used for multigroup comparisons. Differences with P < 0.05 were considered to be statistically significant.

RESULTS

Comparison of body weight

In the second week after modeling, compared with the control group, the body weights of the model group were decreased (P < 0.01). At three weeks, there was no significant difference in body weight between the AP-L, AP-M, AP-H, and AP-H + mcc950 groups and the model group. At four weeks, compared with the model group, the body weight of the AP-H + mcc950 group increased (P < 0.05) (Figure 1). There were no significant differences in body weights among the AP-L, AP-M, and AP-H groups. At five weeks, compared with the model group, the body weights in the AP-H and AP-H + mcc950 groups increased (P < 0.05). There was no significant difference in body weight between the AP-H and AP-H + mcc950 groups.

Figure 1 Weight changes of rats in each group. Data are presented as mean ± SD (n = 12 per group). ^aP < 0.01 vs control group, ^bP < 0.05 vs model group, ^dP < 0.05 vs low-dose apple polyphenols, ^eP < 0.05 vs middle-dose apple polyphenols. Control: Normal control group; Model: Acute exacerbation of chronic obstructive pulmonary disease model group induced by cigarette smoke and lipopolysaccharide; AP-L: Low-dose apple polyphenols; AP-M: Middle-dose apple polyphenols; AP-H: High-dose apple polyphenols; AP-H + mcc950: High-dose apple polyphenols + NOD-like receptor protein 3 inhibitor.

Comparison of lung function indicators

PEF, PIF, and FEV_0.3/FVC in the model group were lower than those in the control group (P < 0.01). Compared with the model group, AP-L, AP-M, AP-H, and AP-H + mcc950 enhanced PEF, PIF, and FEV_0.3/FVC, and the effect of AP-H was greater than that of AP-L and AP-M (P < 0.05) (Figure 2A-C). The effect of AP-H + mcc950 was superior to that of AP-H alone (P < 0.05).

Figure 2 Compare lung function indicators of different groups of rats. A: Peak expiratory flow; B: Peak inspiratory flow; C: Forced expiratory volume in 0.3 seconds to forced vital capacity ratio. ^aP < 0.01 vs control group, ^bP < 0.05 vs model group, ^cP < 0.01 vs model group, ^dP < 0.05 vs low-dose apple polyphenols (AP), ^eP < 0.05 vs middle-dose AP,^fP < 0.05 vs high-dose AP. PEF: Peak expiratory flow; PIF: Peak inspiratory flow; AP-L: Low-dose apple polyphenols; AP-M: Middle-dose apple polyphenols; AP-H: High-dose apple polyphenols; AP-H + mcc950: High-dose apple polyphenols + NOD-like receptor protein 3 inhibitor.

Pathological examination of lung tissue

As shown in Figure 3, in the control group, the lung tissue structure was normal, the alveolar cavities were clearly visible, the alveolar walls were thin, and no inflammatory cell infiltration was observed. In the model group, the structure of the lung tissue was abnormal, with alveolar hemorrhage and exudation, thickening of the alveolar walls, and obvious infiltration of inflammatory cells. Compared with the model group, the AP-L, AP-M, AP-H, and AP-H + mcc950 groups exhibited reduced pathological damage to lung tissue. Compared with the AP-L and AP-M groups, the AP-H and AP-H + mcc950 groups exhibited better recovery of pathological lung tissue damage in rats, approaching almost normal levels.

Figure 3 Contrast the pathological damage of lung tissue in different groups of rats. Hematoxylin and eosin staining, original magnification (× 200). The red arrow: Alveolar atrophy and alveolar wall thickening; the black arrow: Inflammatory cell infiltration. Control: Normal control group; Model: Acute exacerbation of chronic obstructive pulmonary disease model group induced by cigarette smoke and lipopolysaccharide; AP-L: Low-dose apple polyphenols; AP-M: Middle-dose apple polyphenols; AP-H: High-dose apple polyphenols; AP-H + mcc950: High-dose apple polyphenols + NOD-like receptor protein 3 inhibitor.

Comparison of inflammatory factors

Serum levels of TNF-α, IL-6, IL-1β, and miR-21 in model group rats were increased compared with the control group (P < 0.01). Compared with the model group, the AP-L, AP-M, AP-H and AP-H + mcc950 groups exhibited reduced levels of TNF-α, IL-6, IL-1β, and miR-21 in rat serum, lung tissue and prefrontal lobe tissue of the brain, and the effect of AP-H was better than AP-L and AP-M (P < 0.05) (Figure 4A-L). The effect of AP-H + mcc950 was superior to that of AP-H alone (P < 0.05).

Figure 4 Comparison of the expression of inflammatory factors in serum, lung tissue, and frontal lobe tissue homogenate of rats in different groups. A-D: Inflammatory factors in serum; E-H: Inflammatory factors in lung tissue; I-L: Inflammatory factors in prefrontal lobe tissue of the brain. ^aP < 0.01 vs control group, ^bP < 0.05 vs model group, ^cP < 0.01 vs model group, ^dP < 0.05 vs low-dose apple polyphenols (AP), ^eP < 0.05 vs middle-dose AP,^fP < 0.05 vs high-dose AP. AP-L: Low-dose apple polyphenols; AP-M: Middle-dose apple polyphenols; AP-H: High-dose apple polyphenols; AP-H + mcc950: High-dose apple polyphenols + NOD-like receptor protein 3 inhibitor; TNF: Tumor necrosis factor; IL: Interleukin.

Comparison of oxidative stress levels

Serum levels of MDA and LDH in the model group were higher than those in the control group (P < 0.01). Compared with the model group, AP-L, AP-M, AP-H, and AP-H + mcc950 treatment diminished serum, lung, and prefrontal lobe levels of MDA and LDH (P < 0.05/0.01). AP-H exerted a certain advantage in reducing MDA and LDH levels (P < 0.05) in a dose-dependent manner (Figure 5A-F). The effect of AP-H + mcc950 was better than that of AP-H alone (P < 0.05).

Figure 5 Comparison of the expression of oxidative stress (malondialdehyde and lactate dehydrogenase) levels in serum, lung tissue, and frontal lobe tissue homogenate of rats in different groups. A and B: Oxidative stress in serum; C and D: Oxidative stress in lung tissue; E and F: Oxidative stress in prefrontal lobe tissue of the brain. ^aP < 0.01 vs control group, ^cP < 0.01 vs model group, ^dP < 0.05 vs low-dose apple polyphenols (AP), ^eP < 0.05 vs middle-dose AP,^fP < 0.05 vs high-dose AP. AP-L: Low-dose apple polyphenols; AP-M: Middle-dose apple polyphenols; AP-H: High-dose apple polyphenols; AP-H + mcc950: High-dose apple polyphenols + NOD-like receptor protein 3 inhibitor; MDA: Malondialdehyde; LDH: Lactate dehydrogenase.

Comparison of anxiety and depression in rats

The sucrose-preference rate of the rats in the model group was reduced. The sucrose preference rates of rats in the AP-L, AP-M, AP-H, and AP-H + mcc950 groups were higher than those in the model group (P < 0.01) (Figure 6A). The total distance, number of entries into the central area, and duration of stay in the central area of the model group rats decreased. Compared with the model group, the total distance traveled, number of entries into the central area, and duration of stay in the central area of rats in the AP group with different doses increased, with the AP-H group exhibiting a more significant increase (Figure 6B-D). The effect of AP-H + mcc950 was better than that of AP-H (P < 0.05).

Figure 6 Comparison the levels of depression and anxiety in different groups of rats. A: Sucrose preference rate; B: The total distance; C: Number of entries to the central area; D: Duration of stay in the central area. ^aP < 0.01 vs control group, ^cP < 0.01 vs model group, ^dP < 0.05 vs low-dose apple polyphenols (AP), ^eP < 0.05 vs middle-dose AP,^fP < 0.05 vs high-dose AP. AP-L: Low-dose apple polyphenols; AP-M: Middle-dose apple polyphenols; AP-H: High-dose apple polyphenols; AP-H + mcc950: High-dose apple polyphenols + NOD-like receptor protein 3 inhibitor.

Comparison of NLRP3 protein expression

NLRP3 protein levels were increased in the lung tissue of rats in the model group. NLRP3 protein levels in the lung tissues of rats in the AP-L, AP-M, AP-H, and AP-H + mcc950 groups were lower, and the effect of AP-H was greater than those of AP-M and AP-L (P < 0.05/0.01) (Figure 7). The effect of AP-H + mcc950 was superior to that of AP-H alone (P < 0.05).

Figure 7 Comparison the expression of NOD-like receptor protein 3 protein in lung tissues of rats in different groups. NLPR3: NOD-like receptor protein 3; GAPDH: Glyceraldehyde-3-phosphate dehydrogenase; AP-L: Low-dose apple polyphenols; AP-M: Middle-dose apple polyphenols; AP-H: High-dose apple polyphenols; AP-H + mcc950: High-dose apple polyphenols + NOD-like receptor protein 3 inhibitor.

DISCUSSION

The course of COPD is complex, and its incidence and mortality rates are increasing annually[17]. Currently, COPD ranks fifth among the world’s economic burden and is the primary cause of mortality worldwide[18]. Therefore, there is an urgent need to develop effective treatments to improve disease prognosis. Multiple factors can lead to the progressive exacerbation of airway and lung parenchymal inflammation in patients with COPD, thereby inhibiting lung respiratory function[19]. Smoking and infection are the main factors leading to the onset and aggravation of COPD[20,21].

AP is a general term for polyphenolic compounds founds in apples, which possess anti-inflammatory and antioxidant properties[22,23]. AP inhibited LPS-induced inflammation in mouse monocyte/macrophage RAW264.7 cells[24]. Rudrapal et al[25] found that AP, including catechins and quercetin, prevented acute lung injury caused by cigarette smoke. However, few studies have directly investigated the effects of AP on LPS-induced AECOPD in rats. The establishment of a COPD rat model using smoking combined with intratracheal injection of LPS has been widely recognized[26,27]. In this study, AECOPD was induced in rats by intranasal instillation of Streptococcus pneumoniae based on this method. The results revealed severe pathological damage to the lung tissues of rats in the model group, indicating successful modeling.

PEF, PIF, and FEV_0.3/FVC are key indicators for evaluating lung function in AECOPD, and their decrease reflects the exacerbation of airway obstruction and reduction in lung volume, which severely impairs lung ventilation capacity. Decline in lung function is an important indicator of the deterioration of patients with COPD[28]. Our study demonstrated that after intervention with different concentrations of AP, PEF, PIF, and FEV_0.3/FVC in rats were higher than those in the model group, with the highest concentration observed in the high-dose group, implying that AP can effectively enhance lung function in rat models of AECOPD. A systemic inflammatory response is key to the occurrence and progression of AECOPD[29]. The elevation of inflammatory factors (e.g., IL-6, TNF-α, and IL-1β) leads to lung tissue damage, airway remodeling, and loss of gas exchange function. The inflammatory response is not limited to the lungs but also affects the entire body, further leading to the deterioration of COPD[30]. Our results revealed that intervention with AP could reduce the expression of IL-6, TNF-α, and IL-1β in serum, lung tissue, and frontal lobe tissue homogenate, indicating that AP could inhibit lung inflammation, peripheral inflammation, reduce blood-brain barrier permeability and, thus, inhibit central nervous system inflammation, which may be the main cause of behavioral manifestations of anxiety and depression[31]. MiR-21, an endogenous small single-stranded RNA molecule, is highly expressed in AECOPD[32]. Kim et al[33] discovered that miR-21 is upregulated in CS-induced COPD mice and is expected to become a therapeutic target for this disease. Xie et al[34] found that the expression level of miR-21 is highly sensitive and specific for evaluating the occurrence of COPD. Consistent with previous results, we found that intervention with AP inhibited the expression levels of miR-21 in the serum, lung tissue, and prefrontal lobe tissue of brains of AECOPD rats.

Oxidative stress is the main characteristic of LPS-induced AECOPD. During this period, the levels of MDA and LDH in the serum, lung tissue, and frontal lobe tissue homogenates increased dramatically[35]. Our results also confirmed this finding; after intervention with AP, the levels of MDA and LDH were reduced in a dose-dependent manner. An open-field experiment is a method of evaluating the anxiety level of experimental animals and exploring their behavior and tension independently in a novel environment. The sucrose-preference test is commonly used to evaluate an animal’s response to rewards and is used as an indicator of lack of pleasure[36]. Our results revealed that after administering different doses of AP and AP-H + mcc950, the sucrose-preference rate of rats significantly increased, and the total exercise distance, maximum single exercise distance, and central retention time significantly increased, suggesting that AP and AP-H + mcc950 could alleviate anxiety and depression in AECOPD model rats. This suggests that AP not only inhibits lung inflammation, reduces peripheral inflammation, and decreases the activation of microglia but also reduces nerve conduction and neurotransmitter metabolism, alleviates central nervous system inflammation, and is key to improving anxiety and depression.

NLRP3 is an intracellular receptor that participates in the progression of COPD by inducing the activation and release of pro-inflammatory cytokines IL-1β and IL-6[37]. The NALP3 inflammasome is activated in the lung tissue of AECOPD model rats, and NLRP3 expression is significantly increased[38]. It was speculated that AP treatment of AECOPD rats may be related to the downregulation of the NLRP3 protein. This study found that the relative expression of NLRP3 protein in lung tissue was reduced after intervention with different doses of AP compared with that in the model group, with the AP-H and AP-H + mcc950 groups exhibiting a significant decrease. These results revealed that AP may improve lung function, alleviate anxiety and depression in AECOPD rats via inhibiting NLRP3 protein expression and regulating the levels of TNF-α, IL-6, and IL-1β inflammatory factors. This may be because NLRP3 releases a large amount of inflammatory factors while causing damage to the surrounding neurons, leading to the loss of neuronal function, especially in the prefrontal cortex, thereby exacerbating the symptoms of anxiety and depression.

CONCLUSION

In summary, this study found, for the first time, that AP could effectively increase body weight, improve lung symptoms, reduce pathological damage, lower inflammatory cytokine levels, alleviate anxiety/depression levels in AECOPD model rats, and that its intensity of action is dose-dependent. Its mechanism of action may be related to the downregulation of NLRP3 protein. Future research should focus on exploring whether AP could exert its corresponding regulatory effects through antioxidant (such as nuclear factor erythroid 2-related factor 2) or anti-inflammatory (such as nuclear factor kappa-light-chain-enhancer of activated B cells) pathways to provide more comprehensive and sufficient theoretical support for the clinical application of AP.