Oxidative stress is a state of imbalance between oxidation and antioxidant defense system in the body, which may cause multiple organ damage and dysfunction (Garcia-Mesa et al., 2016; Liu et al., 2019). Previous studies indicated that enzymatic and non-enzymatic antioxidant systems could eliminate accumulated reactive oxygen species (ROS) to decrease oxidative stress and ensure host health (Singh and Vinayak, 2017; Li B. et al., 2019). However, multiple factors such as drinking, smoking, weaning, environmental change, heavy metal and endotoxin could result in the massive production and accumulation of ROS and thus causing oxidative stress (Xu J. et al., 2020; Caliri et al., 2021). Studies demonstrated that oxidative stress caused by ROS can cause many chronic diseases in humans and animals such as aging, inflammation, atherosclerosis and even cancer (Wigner et al., 2021; Kalinina et al., 2022). Consequently, reducing oxidative stress is essential to ensure human and animal health. Recently, research about gut microbiota has attracted increasing attention due to its important roles in oxidative stress and oxidative stress-related diseases (Han et al., 2021; Hao et al., 2021).

Gut microbiome interacts with the host and plays a key role in host health (Maslowski et al., 2009; Das et al., 2021). Statistically, the normal intestine harbors over 100 trillion of microorganisms including bacteria (98%), fungi (0.1%), viruses, protists and archaea, approximately ten times the total amount of host cells (Li et al., 2021a). Increasing evidence demonstrated that gut microbiota not only aid in nutritional acquisition of host, such as amino acids/vitamins synthesis and food digestion and absorption, but also make significant contributions in intestinal epithelium differentiation, mucosal immunity and intestinal homeostasis (Chen H. L. et al., 2021; Wozniak et al., 2021). Importantly, gut microbiota also involved in intestinal mucosal barrier maintenance and immune defense system development, indicating its crucial roles in immunity and disease resistance (Lau et al., 2016; Yun et al., 2022). However, gut microbial composition, diversity and abundance continuously shifts under the influence of host- and environmental-related factors including age, diet, weather and oxidative stress (Makki et al., 2018; Li et al., 2022). Earlier studies demonstrated that stabilized gut microbiota could ensure intestinal functions to function properly, whereas significant changes in gut microbial composition and diversity namely gut microbial dysbiosis may result in etiopathology consequences (Qin et al., 2012; Chi et al., 2019). Besides the common gastrointestinal diseases including diarrhea and colitis, disordered gut microbial community and its related metabolites can also affect both near and far organ systems through blood circulation, causing systemic effects (Chassaing et al., 2015; Li Y. et al., 2019). Notably, gut microbial community or microbial signals can also activate intestinal epithelial cell and other cell types to produce physiological ROS that participate in multiple cellular signaling (Wu et al., 2022). However, gut microbial dysbiosis causes over-accumulation of ROS and oxidative stress. Consequently, maintaining gut microbial homeostasis is critical for alleviating oxidative stress and decreasing oxidative stress-related diseases.

Exogenous antioxidants administration has long been considered as an effective way to relieve oxidative stress and prevent oxidant-related diseases (Chen L. et al., 2021). As an important source of functional dietary antioxidant ingredients, polysaccharides derived from plants, animals and microorganisms have been demonstrated to be essential candidates for developing the promising non-toxic antioxidants (Chen et al., 2022). Among plant polysaccharides, radix paeoniae alba polysaccharide (RPAP) has attracted increasing attention because of its multiple health benefits to the host. RPAP is one of the important active components of radix paeoniae alba, which showed multiple important biological activities such as anti-depression, immunological regulation, whitening and alleviating hepatic injury (Zhang et al., 2020). Moreover, recent reports on RPAP also revealed its key roles in the gastrointestinal disease and relieve oxidative stress. For instance, Zhang et al. (2020) demonstrated that RPAP not only possessed DPPH scavenging activity and reducing power but also could alleviate H₂O₂-induced oxidative damage in PC12 cells. Although numerous investigations indicated the positive regulatory effects of RPAP on the host health, it remains unclear whether RPAP could ameliorate intestinal injury and gut microbial dysbiosis caused by LPS. Here, we explored the protective effect of RPAP on LPS induced oxidative damages of intestine.

Oxidative stress has been demonstrated to cause septicemia, acidosis, enteritis, pneumonia and decrease meat quality and fertility (Kuwano et al., 2003; Xu W. et al., 2020). As the organ most susceptible to oxidative stress, oxidative stress in the intestinal system can affect the digestion and absorption of nutrients and cause abnormal glandular secretion, intestinal damage, gastrointestinal dysfunction and intestinal infection, seriously threatening animal production and health (Qiao et al., 2013). Gut microbiota is closely related to gut health, thus the gut microbial homeostasis is inevitably affected by intestinal damage caused by oxidative stress (Zhao et al., 2018). Additionally, gut microbial dysbiosis can further affect intestinal permeability, intestinal mucosal immunity and even other organs such as liver and brain, causing more serious pathological consequences (Boursier et al., 2016). Consequently, maintaining the intestinal health and gut microbial homeostasis is critical for host health. As an effective extract of traditional Chinese medicine, polysaccharides have been demonstrated to exhibit multiple pharmacological effects such as anti-inflammatory, anti-tumor, antioxidant and hypoglycemic, but there are still few studies on RPAP. Here, we systematically explored the protective effects of RPAP administration on intestinal health and microbiota in LPS-induced mice.

Gut microbial diversity has long been regarded as an important indicator for assessing gut microbial homeostasis (Jin et al., 2019). Typically, gut microbial community is in a relatively stable status and this is the prerequisite for intestine to perform various complex physiological functions (Li et al., 2021b). Research indicated that many factors such as gender, age and diet could cause dynamic changes in gut microbiota but this physiological fluctuation cannot destroy intestinal homeostasis and host health (Jiao et al., 2016; Dias et al., 2018). However, strong external stimulus such as antibiotic, oxidative damage, malignant tumor and heavy metal may impair intestinal morphology and environment, which in turn affect microbial growth and survival and force existing microbes to adapt to new environment, causing gut microbial dysbiosis (Lin et al., 2021; Liao et al., 2022). Xu et al. (2019) reported that LPS exposure impaired intestinal morphology and resulted in gut microbial dysbiosis in mice. Moreover, the disruptive effect of LPS on gut microbial homeostasis was also demonstrated in other exploratory experiments (Li et al., 2020; Go et al., 2021). Consistent with previous investigations, we observed that LPS exposure resulted in a significant decrease in the gut microbial alpha-diversity, accompanied by intestinal damage. However, RPAP supplementation increased the gut microbial diversity indices and was positively correlated with its concentration, indicating that RPAP could restore LPS-induced gut microbial dysbiosis. Currently, the decreased gut microbial diversity has been demonstrated to be strongly associated with the progression of multiple chronic diseases such as diabetes, obesity and nonalcoholic fatty liver disease (Musso et al., 2011; Yu et al., 2016). As an important biomarker of gut microbial dysbiosis, decreased gut microbial diversity may impair intestinal barrier function and mucosal immune system, causing severe gastrointestinal infection, diarrhea and colonitis (Koh et al., 2015; Jin et al., 2018). Furthermore, gut microbial dysbiosis also cause pathogenic bacteria and toxic metabolites more easily cross the intestinal barrier and extend its adverse effects beyond the gastrointestinal system, causing systemic effects (Sekirov et al., 2010). Gut microbial beta-diversity is also an important tool for assessing gut microbiota. We observed that the individuals of the C group were clustered together but separated from the LPS group, indicating significant changes in the gut microbial main components. However, the gut microbial main components of the RH group were closer to the C group compared with the LPS group, suggesting the improvement in the gut microbial structure.

Consistent with previous investigations, this study also indicated that LPS exposure caused distinct shifts in gut microbial composition and structure, perturbing gut microbial homeostasis. However, RPAP administration can reverse this phenomenon and result in changes in some functional bacteria, such as Alloprevotella, Lactobacillus, Alistipes, Bacillus and Rikenellaceae_RC9_gut_group, which may play vital roles in intestinal ecosystem and health. Alloprevotella has been reported to produce acetic acid and succinic acid, which contributed to maintaining gut microbial homeostasis and decreasing the risk of lifetime cardiovascular disease (Yuan et al., 2021). Numerous investigations revealed that Lactobacillus possessed important biological properties such as secreting antimicrobial substance, improving the intestinal environment, maintaining intestinal microbial homeostasis (Maroju et al., 2021; Stivala et al., 2021). Besides the above-mentioned characteristics, Lactobacillus also contribute to controlling endotoxin, improving immunity, food digestibility and biological potency, indicating its key roles in host growth and health (Gao et al., 2018; Veisi et al., 2022). Alistipes has been demonstrated to be the potential producer of short-chain fatty acids (SCFAs) (Khan et al., 2020). As the acknowledged intestinal beneficial metabolites, SCFAs have been demonstrated to function against pathogens, decreasing oxidative stress, maintaining gut microbial balance, and regulating the intestinal barrier (Elamin et al., 2013; Pekmez et al., 2019). Furthermore, SCFAs also participated in the positive regulation of the host metabolism, cell proliferation and immunological function (Van Rymenant et al., 2017; Menni and Valdes, 2019). Recently published research also demonstrated their crucial roles in lowering cholesterol, alleviating intestinal inflammation, reducing diabetes and angiocardiopathy (Thandapilly et al., 2018). Several studies involving Rikenellaceae have demonstrated its important roles in degrading plant derived polysaccharide and alleviate inflammation. As a common intestinal probiotic, Bacillus is widely used in industry, agriculture and pharmaceutical production. Research indicated that the antibacterial substances produced by Bacillus have broad-spectrum bactericidal activity and have strong bactericidal effects on many food-related bacteria (Jones and Knight, 2012). Moreover, Bacillus could produce beneficial metabolites such as vitamins, showing great potential in alleviating the gut microbial dysbiosis and treating bacterial infections (Li Y. T. et al., 2019; Wang et al., 2021). In this study, we also found that LPS exposure resulted in a significant increase in some pathogenic bacteria such as Klebsiella, Helicobacter and Enterococcus. Klebsiella, a potential intestinal pathogen, is closely related to multiple diseases such as mastitis, pneumonia, septicemia and hysteritis (Bratu et al., 2005). Early surveys indicated that Helicobacter could result in peptic ulcer, gastritis and even lymphoproliferative gastric lymphoma, seriously threatening the host health (Castano-Rodriguez et al., 2017). Notably, some diseases caused by Helicobacter may eventually progress to gastric cancer that is one of the most common malignancies worldwide and causes approximately 160,000 deaths annually in China (Choi et al., 2018). Enterococcus was previously reported to cause life-threatening cardioperiostitis, sepsis and meningitis (Knoll et al., 2013). Moreover, many antibiotics cannot effectively treat Enterococcus infection due to inherent and acquired resistance (Lebreton et al., 2011). Interestingly, RPAP administration reduces the abundance of these potential pathogenic bacteria, which is beneficial to maintain gut microbial homeostasis and protect host health.

In summary, this study investigated the protective effect of RPAP administration on intestinal health and microbiota in LPS-induced mice. Results indicated that RPAP administration could restore LPS-induced intestinal injury and gut microbial dysbiosis and its effect was positively correlated with concentration. This study filled a gap in the effect of RPAP on the intestinal health and microbial homeostasis caused by LPS and demonstrated that the maintenance of gut microbial balance may be one of the important pathways for RPAP to exert its pharmacological effects. Moreover, these findings also expand the understanding of the health benefits of RPAP and provide a theoretical basis for the development of RPAP products to decrease oxidative stress. However, this study also has some limitations including relatively small sample size and lack of intestinal metabolism experiments.

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found at: https://www.ncbi.nlm.nih.gov/, PRJNA875596.

The animal study was reviewed and approved by the Animal Welfare and Ethics Committee of Nanjing Agricultural University.

KL and AL provided the research idea. TS, KL, YW, and JD contributed reagents, materials, and analysis tools. AL wrote the manuscript. MI, MK, KW, YL, and FW revised the manuscript. All authors contributed to the article and approved the submitted version.

The study was supported by Start-up fund of Nanjing Agricultural University (804131) and Guangxi Science and Technology Project (GuiKeAD22080012, GuiKeAA18242040, and GuiKeZY20198018).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.