Study on the Prevention and Mechanism of Moringa Leaf Polysaccharides in Treating Ulcerative Colitis in Mice
Ulcerative colitis (UC) is a highly complex non-specific, recurrent colitis disease that often leads to colonic mucosal ulceration and ulceration, frequent abdominal pain, diarrhea, rectal bleeding, and other clinical symptoms. Due to its recurrent and difficult to cure nature, it seriously affects the patient’s normal life and increases the risk of secondary infection and colon cancer. Eric et al. found that the pathogenesis of UC is closely related to the impairment of intestinal barrier function and changes in the intestinal microenvironment. When the intestinal mucosal barrier is damaged, immune cells in the intestinal lamina propria are exposed to external antigens and pathogens, and activated immune cells produce an inflammatory cascade reaction in the body, causing T cell subsets to mediate non-specific Th2 immune responses. At the same time, TLR4 signals to the adaptor protein MyD88, leading to the activation of NF – κ B and promoting the expression of pro-inflammatory factors such as interleukin-1 β (IL-1 β) and tumor necrosis factor – α (TNF – α), disrupting the intestinal immune homeostasis and further damaging intestinal epithelial cells. At the same time, the composition of gut microbiota has a significant impact on the development and function of the immune system. When the ratio of beneficial and pathogenic bacteria in the gut is imbalanced, toxins, intestinal bacteria, and antigens enter the body, exacerbating intestinal mucosal inflammation and excessive oxidative stress response in UC patients. This suggests that interventions targeting inflammatory factors and gut microbiota are effective targets for preventing and treating UC.

Moringa oleifera, originally from India, is widely planted in tropical and subtropical regions of Africa and Asia. In recent years, it has been extensively cultivated in Yunnan and Guangxi regions of China. In 2012, it was approved by the Chinese Ministry of Health as a new resource food and an important food resource for both medicine and food in China. The nutritional value of Moringa leaves is extremely high. Long term consumption of Moringa leaf foods can enhance the human immune system and also have a certain disease prevention effect. Its main bioactive components are polyphenols, flavonoids, and polysaccharides, which exert significant anti-inflammatory, antioxidant, and anti-tumor effects. At present, there are relatively few reports on Moringa oleifera leaf polysaccharide (MOLP) both domestically and internationally, and it is still limited to the optimization of traditional extraction processes and chemical composition analysis. The preventive and therapeutic effects of MOLP on enteritis are not yet clear. Therefore, this experiment used DSS induction to establish a UC mouse model and observed the improvement effect of MOLP on inflammatory response and intestinal microbiota in acute colitis mice. The aim is to clarify the mechanism of MOLP’s preventive and therapeutic effects on UC, in order to provide ideas for pharmacological research and clinical disease treatment of MOLP.

 

In recent years, the incidence rate of UC in the world has increased year by year. Compared with European countries, the incidence rate of UC in China has increased faster. Modern medicine often uses glucocorticoids, salicylic acid preparations, and immunosuppressants to intervene in the treatment of UC in clinical practice, but the easy recurrence and serious drug side effects after discontinuation make it a thorny issue in the medical community. With the continuous deepening of clinical applications, plant polysaccharides from pure natural sources have attracted attention for their safety, accessibility, anti-inflammatory activity, and efficient immune enhancement effects. As one of the effective active ingredients in Moringa leaves, polysaccharides from Moringa leaves have been studied for their functional activities, mainly focusing on lowering blood lipids, blood sugar, anti-tumor and antioxidant effects. In order to explore the preventive and therapeutic effects of MOLP on enteritis, DSS was used to establish a UC model and treat it. The results showed that after modeling, mice exhibited symptoms such as diarrhea, bloody stools, weight loss, increased DAI scores, and shortened colon length, indicating successful modeling and significant effects. After treatment with MOLP, the weight loss of UC mice can be significantly improved, the DAI score can be reduced, colon mucosal damage and inflammatory infiltration can be alleviated, the levels of pro-inflammatory factors IL-1 β, TNF – α, HMGB1 in mouse serum and colon can be down regulated, the level of anti-inflammatory factor IL-10 can be up-regulated, and the phosphorylation of P65 and I κ B α can be inhibited to prevent excessive activation of TLR4/NF – κ B signaling pathway, maintain intestinal microbiota homeostasis, and exert a preventive and therapeutic effect on UC by inhibiting the body’s inflammatory response and regulating the structure of mouse intestinal microbiota.
Inflammatory cytokines are an indispensable part of the occurrence and development of UC. They are produced by immune cells and stimulate the proliferation of antigen-specific effector cells and mediate local and systemic inflammation through the interaction between immune cells. Under normal circumstances, macrophages have a weak response to inflammatory signals and are less likely to promote their production in immunocompromised cells. However, during the onset of UC, activated macrophages and dendritic cells secrete various cytokines such as TNF – α, INF – γ, IL-1 β, IL-10, etc. to regulate the inflammatory response. Upregulation or overactivation of these cytokines can lead to T cell imbalance and Treg/Th1, Th2, Th17 imbalance, promoting the accumulation of neutrophils in inflammatory sites, reducing electrolyte secretion in epithelial cells, increasing membrane permeability, and further exacerbating the inflammatory response. The drugs and natural products used to treat UC can effectively alleviate the imbalance of inflammatory factor concentration and expression levels. Xiao et al. found that total alkaloids of Sophora alopecuroides can alleviate inflammation by regulating the levels of pro-inflammatory factors IL-1 β, IL-23, and IL-17 in UC mice and increasing the level of anti-inflammatory factor IL-10. This study found through the detection of IL-1 β, TNF – α, HMGB1, and IL-10 in the serum of UC mice that MOLP can significantly inhibit the expression of pro-inflammatory factors and upregulate the level of anti-inflammatory factors. At the same time, real-time fluorescence quantitative PCR technology was used to detect tissue inflammatory factors, and the results showed that MOLP can effectively alleviate the expression of IL-1 β, TNF – α, HMGB1 mRNA in the colon tissue of UC mice and increase the expression of IL-10 mRNA. In addition, MPO is a characteristic enzyme of neutrophils, a hemoglobinase secreted by neutrophils or macrophages in certain tissues, and is a member of the heme peroxidase family. We can evaluate the degree of neutrophil infiltration in tissues by detecting the activity of MPO in mouse colon tissues. The results showed that MOLP could significantly inhibit the activity of MPO in UC mice and reduce the number of neutrophils in colon tissue. The generation of inflammatory factors and the increase in MPO activity mentioned above are closely related to the core position of the TLR4/NF – κ B signaling pathway. TLR4 plays an important role in recognizing pathogenic microorganisms and controlling acquired immune responses in innate immunity. When TLR4 is activated, it is signal transduced by the adaptor protein MyD88, inducing phosphorylation, ubiquitination, and degradation of I κ B, releasing NF κ B p50/p65 dimers. The activated dimers enter the nucleus and immediately initiate the transcription of various cytokines, leading to an increase in the number of IL-1 β, TNF – α, etc., causing inflammation to persist and continue to expand. Zhang et al. found that the NF – κ B signaling pathway in the colon of UC mice was overactivated, and targeted inhibition of NF – κ B signaling pathway activation was effective in alleviating UC. This study found that compared to the Con group, the activity of MPO in the colon tissue of DSS group mice was significantly increased, and the expression of TLR4 and MyD88 proteins was significantly increased. The p-P65 and p-I κ B α proteins were upregulated, and the ratio of p-P65/P65 and p-I κ B α/I κ B α also increased. After treatment with MOLP, the above abnormal expression was effectively inhibited, indicating that MOLP can exert its preventive and therapeutic effects on UC by inhibiting the excessive activation of TLR4/NF – κ B signaling pathway and suppressing the abnormal expression of inflammatory factors.
Under normal circumstances, the intestine has a complete barrier function. The gut microbiota, along with the intestinal epithelial layer, mucous layer, and intestinal lymphatic system, form the mechanical, chemical, and biological barriers of the intestinal mucosa, which can prevent pathogenic antigens from invading the body and maintain normal functioning. When inflammation occurs in the intestine, the gut microbiota is disrupted, the intestinal barrier is destroyed, and intestinal permeability increases. Harmful bacteria and their metabolites such as endotoxins are absorbed into the bloodstream, further exacerbating the damage to mucosal epithelial cells and the mucosal barrier, thus forming a vicious cycle that leads to recurrent UC. This study investigated the effect of MOLP on the gut microbiota of UC mice through 16S rRNA gene sequencing. It was found that MOLP can increase the diversity of gut microbiota in UC mice, restore the ratio of Campylobacter and Bacteroidetes, regulate the relative abundance of different microbiota, and promote the recovery of gut microbiota structure to normal levels. The two most common phyla in the digestive system are Firmicutes and Bacteroidetes. Studies have found that Firmicutes and Bacteroidetes in colitis mice are significantly reduced, while MOLP treatment significantly alleviates the imbalance of the two dominant bacterial groups. This is similar to the results reported by Sun et al. that purple sweet potato polysaccharides can alleviate the decrease in Firmicutes and Bacteroidetes ratio in UC mice caused by DSS modeling, suggesting that increasing the proportion of these two dominant bacterial groups may have a protective effect on colitis mice. Further research analysis shows that butyrate can provide an acidic environment in the intestine to inhibit the growth of harmful bacteria, maintain electrolyte balance, and promote the repair of mucosal inflammation. Butyrate is mainly produced by Firmicutes bacteria in the intestine in the body. Increasing the number of Firmicutes has a protective effect on intestinal inflammation. This study found that MOLP can promote the increase of Firmicutes in UC mice, stimulate the microbial activity of beneficial bacteria, and inhibit the growth of pathogenic bacteria.
The results of this experiment indicate that in the DSS induced UC mouse model, MOLP can significantly alleviate colon shortening, weight loss, and elevated DAI scores in UC mice, reduce the levels of pro-inflammatory cytokines IL-1 β, TNF – α, and HMGB1 in the serum and colon tissues of UC mice, regulate the overactivation of TLR4/NF – κ B, and regulate the diversity, composition, and relative abundance of intestinal microbiota in UC mice, thereby exerting a preventive and protective effect on UC. The next step in the future will be to explore the role of MOLP in UC from multiple perspectives such as chemical barriers and immune barriers. This study aims to provide new ideas for the development and utilization of Moringa leaves and the anti-inflammatory effects of MOLP.