Probiotic Streptococcus salivarius K12 Alleviates Radiation-Induced Oral Mucositis in Mice

Preventive effect of probiotics on oral mucositis induced by anticancer therapy: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Oral mucositis (OM) is a prevalent and painful complication in patients undergoing anticancer treatment, which significantly impacts patients' quality of life (QoL) and adherence to therapy. The use of oral probiotics as a preventive strategy for OM has shown promise, but the clinical evidence remains inconclusive. This meta-analysis of randomized controlled trials (RCTs) aims to evaluate the efficacy of probiotics in preventing OM caused by radiotherapy and/or chemotherapy.

METHODS

A comprehensive search of PubMed, EMBASE, Web of Science, Cochrane Library, and ClinicalTrials.gov was conducted up to January 31, 2024, to identify eligible RCTs. The primary outcomes were the incidences of severe OM and all-grade OM. Secondary outcomes included rates of anticancer treatment completion, clinical response, requirement for enteral nutrition, time course of OM, body weight loss, QoL, and adverse events (AEs). Risk ratios (RRs) with 95% confidence intervals (CIs) were calculated.

RESULTS

A total of 12 RCTs involving 1,376 patients were included in the quantitative analysis. Probiotics administration significantly reduced the risk of severe OM (RR = 0.61, 95%CI: 0.53-0.72, P < 0.001) and all-grade OM (RR = 0.90, 95%CI: 0.82-0.98, P = 0.016) compared to the control group. Multi-strain probiotics formulations were more effective than single-strain probiotics in preventing severe OM (P = 0.011). There were no significant differences between the probiotics and control groups regarding anticancer treatment completion (RR = 1.03, 95%CI: 0.98-1.08, P = 0.198), clinical response to therapy (RR = 1.05, 95%CI: 0.94-1.17, P = 0.406), or the need for enteral nutrition (RR = 1.28, 95%CI: 0.49-3.35, P = 0.680). AEs related to probiotics were rare, with no serious AEs attributable to probiotics use.

CONCLUSIONS

Oral probiotics are both safe and effective in preventing and reducing the severity of OM in patients undergoing anticancer therapy. Multi-strain probiotics demonstrate superior efficacy compared to single-strain probiotics. Further research is warranted to confirm these findings and optimize probiotic treatment strategies for cancer patients.

The Role of Biotics as a Therapeutic Strategy for Oral Mucositis - A Systematic Review

OBJECTIVES

Oral mucositis (OM) is an acute and highly prevalent side effect of cancer treatments. Currently, there is no effective strategy for its prevention or treatment. This systematic review aimed to assess the effectiveness of biotics used as a therapeutic strategy for the management of OM.

MATERIALS AND METHODS

The PRISMA checklist was followed and PubMed, Web of Science, and Scopus were screened for clinical and pre-clinical studies assessing the potential effects of biotics in OM. Inclusion criteria included in vivo studies related to oral mucositis evaluating the effect of biotics, and written in Portuguese, English, French, Spanish, or Dutch. The following exclusion criteria were used: systematic reviews and meta-analyses, reviews, case reports, opinion papers or comments, conference papers, letters without results, articles not related to oral therapy-induced mucositis or biotics, or in vitro articles that do not simulate oral mucositis.

RESULTS

From a total of 1250 articles retrieved, 9 were included in this systematic review. Four clinical studies reported a reduction in oral mucositis occurrence with Lactobacillus species (Lactobacillus casei and Lactobacillus brevis CD2) and Bacillus clausii UBBC07. In pre-clinical studies, Lactococcus lactis genetically modified and Lactobacillus reuteri reduced the severity of OM and Streptococcus salivarius K12 also decreased the size of the ulcers.

CONCLUSION

The findings of this systematic review suggest that probiotic supplementation may potentially reduce the incidence of therapy-induced OM and decrease its severity in patients undergoing cancer treatment. However, the available evidence is marred by significant heterogeneity across studies.

Updated perspectives on the contribution of the microbiome to the pathogenesis of mucositis using the MASCC/ISOO framework

Advances in the treatment of cancer have significantly improved mortality rates; however, this has come at a cost, with many treatments still limited by their toxic side effects. Mucositis in both the mouth and gastrointestinal tract is common following many anti-cancer agents, manifesting as ulcerative lesions and associated symptoms throughout the alimentary tract. The pathogenesis of mucositis was first defined in 2004 by Sonis, and almost 20 years on, the model continues to be updated reflecting ongoing research initiatives and more sophisticated analytical techniques. The most recent update, published by the Multinational Association for Supportive Care in Cancer and the International Society for Oral Oncology (MASCC/ISOO), highlights the numerous co-occurring events that underpin mucositis development. Most notably, a role for the ecosystem of microorganisms that reside throughout the alimentary tract (the oral and gut microbiota) was explored, building on initial concepts proposed by Sonis. However, many questions remain regarding the true causal contribution of the microbiota and associated metabolome. This review aims to provide an overview of this rapidly evolving area, synthesizing current evidence on the microbiota's contribution to mucositis development and progression, highlighting (i) components of the 5-phase model where the microbiome may be involved, (ii) methodological challenges that have hindered advances in this area, and (iii) opportunities for intervention.

Metagenomic analysis demonstrates distinct changes in the gut microbiome of Kawasaki diseases children

Background

Kawasaki disease (KD) has been considered as the most common required pediatric cardiovascular diseases among the world. However, the molecular mechanisms of KD were not fully underlined, leading to a confused situation in disease management and providing precious prognosis prediction. The disorders of gut microbiome had been identified among several cardiovascular diseases and inflammation conditions. Therefore, it is urgent to elucidate the characteristics of gut microbiome in KD and demonstrate its potential role in regulating intravenous immunoglobulin (IVIG) resistance and coronary artery injuries.

Methods

A total of 96 KD children and 62 controls were enrolled in the study. One hundred forty fecal samples had been harvested from KD patients, including individuals before or after IVIG treatment, with or without early coronary artery lesions and IVIG resistance. Fecal samples had been collected before and after IVIG administration and stored at -80°C. Then, metagenomic analysis had been done using Illumina NovaSeq 6000 platform. After that, the different strains and functional differences among comparisons were identified.

Results

First, significant changes had been observed between KD and their controls. We found that the decrease of Akkermansia muciniphila, Faecalibacterium prausnitzii, Bacteroides uniformis, and Bacteroides ovatus and the increase of pathogenic bacteria Finegoldia magna, Abiotrophia defectiva, and Anaerococcus prevotii perhaps closely related to the incidence of KD. Then, metagenomic and responding functional analysis demonstrated that short-chain fatty acid pathways and related strains were associated with different outcomes of therapeutic efficacies. Among them, the reduction of Bacteroides thetaiotaomicron, the enrichment of Enterococcus faecalis and antibiotic resistance genes had been found to be involved in IVIG resistance of KD. Moreover, our data also revealed several potential pathogenetic microbiome of that KD patients with coronary artery lesions.

Conclusion

These results strongly proved that distinct changes in the gut microbiome of KD and the dysfunction of gut microbiomes should be responsible for the pathogenesis of KD and significantly impact the prognosis of KD.

Streptococcus salivarius K12 Alleviates Oral Mucositis in Patients Undergoing Radiotherapy for Malignant Head and Neck Tumors: A Randomized Controlled Trial

PURPOSE

Oral mucositis (OM) is a common debilitating toxicity associated with radiotherapy (RT) for malignant head and neck tumors. This prospective, randomized, double-blind, placebo-controlled trial aimed to evaluate the efficacy and safety of Streptococcus salivarius K12 (SsK12) in reducing the incidence, duration, and severity of severe OM (SOM).

METHODS

A total of 160 patients with malignant head and neck tumors undergoing definitive or postoperative adjuvant RT were randomly assigned (1:1) to receive SsK12 probiotic (n = 80) or placebo (n = 80) at West China Hospital, Sichuan University, Chengdu, China. Patients were instructed to suck SsK12 or placebo lozenges thrice daily from the initiation to the end of RT. OM was evaluated twice a week during RT and once a week thereafter for up to 8 weeks. The primary end point was the incidence of SOM. Adverse events were assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.0.

RESULTS

Baseline patient characteristics were similar in the SsK12 and placebo groups. The incidence of SOM was significantly lower in the SsK12 group as compared with the placebo group (36.6% v 54.2%; P = .0351). The duration (median, 0.0 days v 7.0 days; mean, 8.9 days v 18.3 days; P = .0084) and time to develop SOM (median, not estimable v 42.0 days; hazard ratio, 0.55 [95% CI, 0.34 to 0.89]; log-rank test: P = .0123) were also improved in the case of the SsK12 group. Adverse events were similar between the groups, and mild or moderate gastrointestinal reactions (flatulence or dyspepsia) associated with the lozenges were observed in two patients in the SsK12 group. High-throughput sequencing results indicated that SsK12 inhibited opportunistic pathogens and enriched oral commensals during RT.

CONCLUSION

In this prospective, randomized clinical trial, SsK12 probiotic significantly reduced the incidence, onset, and duration of SOM with a good safety profile.

Association between oral microbial dysbiosis and poor functional outcomes in stroke-associated pneumonia patients

BACKGROUND

Despite advances in our understanding of the critical role of the microbiota in stroke patients, the oral microbiome has rarely been reported to be associated with stroke-associated pneumonia (SAP). We sought to profile the oral microbial composition of SAP patients and to determine whether microbiome temporal instability and special taxa are associated with pneumonia progression and functional outcomes.

METHODS

This is a prospective, observational, single-center cohort study that examined patients with acute ischemic stroke (AIS) who were admitted within 24 h of experiencing a stroke event. The patients were divided into three groups based on the occurrence of pneumonia and the use of mechanical ventilation: nonpneumonia group, SAP group, and ventilator-associated pneumonia (VAP) group. We collected oral swabs at different time points post-admission and analyzed the microbiota using 16 S rRNA high-throughput sequencing. The microbiota was then compared among the three groups.

RESULTS

In total, 104 nonpneumonia, 50 SAP and 10 VAP patients were included in the analysis. We found that SAP and VAP patients exhibited significant dynamic differences in the diversity and composition of the oral microbiota and that the magnitude of this dysbiosis and instability increased during hospitalization. Then, by controlling the potential effect of all latent confounding variables, we assessed the changes associated with pneumonia after stroke and explored patients with a lower abundance of Streptococcus were more likely to suffer from SAP. The logistic regression analysis revealed that an increase in specific taxa in the phylum Actinobacteriota was linked to a higher risk of poor outcomes. A model for SAP patients based on oral microbiota could accurately predict 30-day clinical outcomes after stroke onset.

CONCLUSIONS

We concluded that specific oral microbiota signatures could be used to predict illness development and clinical outcomes in SAP patients. We proposed the potential of the oral microbiota as a non-invasive diagnostic biomarker in the clinical management of SAP patients.

CLINICAL TRIAL REGISTRATION

NCT04688138. Registered 29/12/2020, https://clinicaltrials.gov/ct2/show/NCT04688138 .

Mechanisms underlying the effects, and clinical applications, of oral microbiota in lung cancer: current challenges and prospects

The oral cavity contains a site-specific microbiota that interacts with host cells to regulate many physiological processes in the human body. Emerging evidence has suggested that changes in the oral microbiota can increase the risk of lung cancer (LC), and the oral microbiota is also altered in patients with LC. Human and animal studies have shown that oral microecological disorders and/or specific oral bacteria may play an active role in the occurrence and development of LC through direct and/or indirect mechanisms. These studies support the potential of oral microbiota in the clinical treatment of LC. Oral microbiota may therefore be used in the prevention and treatment of LC and to improve the side effects of anticancer therapy by regulating the balance of the oral microbiome. Specific oral microbiota in LC may also be used as screening or predictive biomarkers. This review summarizes the main findings in research on oral microbiome-related LC and discusses current challenges and future research directions.

From Pathogenesis to Intervention: The Importance of the Microbiome in Oral Mucositis

Oral mucositis (OM) is a common and impactful toxicity of standard cancer therapy, affecting up to 80% of patients. Its aetiology centres on the initial destruction of epithelial cells and the increase in inflammatory signals. These changes in the oral mucosa create a hostile environment for resident microbes, with oral infections co-occurring with OM, especially at sites of ulceration. Increasing evidence suggests that oral microbiome changes occur beyond opportunistic infection, with a growing appreciation for the potential role of the microbiome in OM development and severity. This review collects the latest articles indexed in the PubMed electronic database which analyse the bacterial shift through 16S rRNA gene sequencing methodology in cancer patients under treatment with oral mucositis. The aims are to assess whether changes in the oral and gut microbiome causally contribute to oral mucositis or if they are simply a consequence of the mucosal injury. Further, we explore the emerging role of a patient's microbial fingerprint in OM development and prediction. The maintenance of resident bacteria via microbial target therapy is under constant improvement and should be considered in the OM treatment.

Oral microbiota dysbiosis accelerates the development and onset of mucositis and oral ulcers

With the rapid development of metagenomic high-throughput sequencing technology, more and more oral mucosal diseases have been proven to be associated with oral microbiota shifts or dysbiosis. The commensal oral microbiota can greatly influence the colonization and resistance of pathogenic microorganisms and induce primary immunity. Once dysbiosis occurs, it can lead to damage to oral mucosal epithelial defense, thus accelerating the pathological process. As common oral mucosal diseases, oral mucositis and ulcers seriously affect patients' prognosis and quality of life. However, from the microbiota perspective, the etiologies, specific alterations of oral flora, pathogenic changes, and therapy for microbiota are still lacking in a comprehensive overview. This review makes a retrospective summary of the above problems, dialectically based on oral microecology, to provide a new perspective on oral mucosal lesions management and aims at improving patients' quality of life.

On the Oral Microbiome of Oral Potentially Malignant and Malignant Disorders: Dysbiosis, Loss of Diversity, and Pathogens Enrichment

The role of dysbiosis in the development and progression of oral potentially malignant disorders (OPMDs) remains largely unknown. Here, we aim to characterize and compare the oral microbiome of homogeneous leucoplakia (HL), proliferative verrucous leukoplakia (PVL), oral squamous cell carcinoma (OSCC), and OSCC preceded by PVL (PVL-OSCC). Fifty oral biopsies from HL (n = 9), PVL (n = 12), OSCC (n = 10), PVL-OSCC (n = 8), and healthy (n = 11) donors were obtained. The sequence of the V3-V4 region of the 16S rRNA gene was used to analyze the composition and diversity of bacterial populations. In the cancer patients, the number of observed amplicon sequence variants (ASVs) was lower and Fusobacteriota constituted more than 30% of the microbiome. PVL and PVL-OSCC patients had a higher abundance of Campilobacterota and lower Proteobacteria than any other group analyzed. A penalized regression was performed to determine which species were able to distinguish groups. HL is enriched in Streptococcus parasanguinis, Streptococcus salivarius, Fusobacterium periodonticum, Prevotella histicola, Porphyromonas pasteri, and Megasphaera micronuciformis; PVL is enriched in Prevotella salivae, Campylobacter concisus, Dialister pneumosintes, and Schaalia odontolytica; OSCC is enriched in Capnocytophaga leadbetteri, Capnocytophaga sputigena, Capnocytophaga gingivalis, Campylobacter showae, Metamycoplasma salivarium, and Prevotella nanceiensis; and PVL-OSCC is enriched in Lachnospiraceae bacterium, Selenomonas sputigena, and Prevotella shahii. There is differential dysbiosis in patients suffering from OPMDs and cancer. To the best of our knowledge, this is the first study comparing the oral microbiome alterations in these groups; thus, additional studies are needed.

Current Infections of the Orofacial Region: Treatment, Diagnosis, and Epidemiology

Undoubtedly, diagnosing and managing infections is one of the most challenging issues for orofacial clinicians. As a result of the diversity of symptoms, complicated behavior, and sometimes confusing nature of these conditions, it has become increasingly difficult to diagnose and treat them. It also highlights the need to gain a deeper insight into the orofacial microbiome as we try to improve our understanding of it. In addition to changes in patients' lifestyles, such as changes in diet, smoking habits, sexual practices, immunosuppressive conditions, and occupational exposures, there have been changes in patients' lifestyles that complicate the issue. Recent years have seen the development of new infection treatments due to the increased knowledge about the biology and physiology of infections. This review aimed to provide a comprehensive overview of the types of infections in the mouth, including the types that viruses, fungi, or bacteria may cause. It is important to note that we searched the published literature in the Scopus, Medline, Google Scholar, and Cochran databases from 2010 to 2021 using the following keywords: "Orofacial/Oral Infections," "Viral/Fungal/Bacterial Infections", "Oral Microbiota" And "Oral Microflora" without limiting our search to languages and study designs. According to the evidence, the most common infections in the clinic include herpes simplex virus, human papillomavirus, Candida albicans, Aspergillus, Actinomycosis, and Streptococcus mutans. The purpose of this study is to review the new findings on characteristics, epidemiology, risk factors, clinical manifestations, diagnosis, and new treatment for these types of infectious diseases.

Oral Commensal Streptococci: Gatekeepers of the Oral Cavity

Oral commensal streptococci are primary colonizers of the oral cavity. These streptococci produce many adhesins, metabolites, and antimicrobials that modulate microbial succession and diversity within the oral cavity. Often, oral commensal streptococci antagonize cariogenic and periodontal pathogens such as Streptococcus mutans and Porphyromonas gingivalis, respectively. Mechanisms of antagonism are varied and range from the generation of hydrogen peroxide, competitive metabolite scavenging, the generation of reactive nitrogen intermediates, and bacteriocin production. Furthermore, several oral commensal streptococci have been shown to alter the host immune response at steady state and in response to oral pathogens. Collectively, these features highlight the remarkable ability of oral commensal streptococci to regulate the structure and function of the oral microbiome. In this review, we discuss mechanisms used by oral commensal streptococci to interact with diverse oral pathogens, both physically and through the production of antimicrobials. Finally, we conclude by exploring the critical roles of oral commensal streptococci in modulating the host immune response and maintaining health and homeostasis.

Exploring the alterations and function of skin microbiome mediated by ionizing radiation injury

Background

Radiation-induced skin injury (RISI) is still the most common and severe side effect of radiotherapy. The role of the skin’s microbial barrier in the pathogenesis and progression of RISI needs to be fully investigated.

Methods

This study aimed to explore the alterations in and functions of the skin microbiota in RISI. We applied the unculturable approach to characterize the cutaneous microbiomes of a radiation-induced animal model by sequencing the V1–V3 regions of the 16S ribosomal RNA (rRNA) gene. Combined with the downloaded clinical data of patients, a comprehensive analysis was performed to identify potential radioprotective species and metabolic pathways.

Results

There were no significant differences in the alpha diversity indices (Sobs, Shannon, Simpson, Ace, and Chao) between the acute radiation injury and control groups. Phylum-level analysis of the RISI microbiomes exhibited significant predominance of Firmicutes (mean abundance = 67%, corrected p = 0.0035). The high abundance of Firmicutes was significantly associated with rapid healing of RISI (average relative abundance = 52%; Kruskal–Wallis: p = 5.7E−4). Among its members, Streptococcus, Staphylococcus, Acetivibrio ethanolgignens group, Peptostreptococcus, Anaerofilum, and UCG-002 [linear discriminant analysis (LDA) &gt; 3, p &lt; 0.05] were identified as the core genera of Firmicutes. In addition, Lachnosiraceae and Lactobacillus occupied an important position in the interaction network (r &gt; 0.6, p &lt; 0.05). The differential metabolic pathways of RISI were mainly associated with carbohydrate metabolism (butanoate and propanoate metabolism), amino acid metabolism (tryptophan and histidine metabolism), energy metabolism, and lipid metabolism (fatty acid degradation and biosynthesis).

Conclusion

This study provides new insights into the potential mechanism and skin microbial changes in the progression of RISI. The overwhelming predominance of members of Firmicutes, including Streptococcaceae, Staphylococcaceae, Lachnospiraceae, and Lactobacillus, is potentially related to rapid healing of RISI. The microbiota–metabolite axis plays a critical role in RISI and provides promising therapeutic targets for the treatment of adverse side effects.

Preventive Effect of Probiotics on Oral Mucositis Induced by Cancer Treatment: A Systematic Review and Meta-Analysis

Oral mucositis is a common adverse effect of cancer therapy. Probiotics have been shown to exert anti-inflammatory and immunomodulatory effects. We performed a meta-analysis of randomized controlled trials (RCTs) to investigate whether probiotics can prevent cancer therapy−induced oral mucositis. We searched PubMed, Embase, Cochrane Library, and ClinicalTrials.gov databases for trials related to probiotics and oral mucositis published before September 2022; no language restrictions were applied. The primary outcome was the incidence of oral mucositis and severe oral mucositis. Secondary outcomes were the requirement for enteral nutrition during treatment, body weight loss, and decreased quality of life. The study has been registered in PROSPERO (number: CRD 42022302339). Eight RCTs, including 708 patients, were reviewed; however, a meta-analysis of only seven trials could be performed. Three trials using Lactobacilli-based probiotics reported that the incidence of oral mucositis in the probiotic group was significantly low (risk ratio [RR] = 0.84, 95% confidence interval [CI] = 0.77−0.93, p = 0.0004). Seven trials reported a significantly low incidence of severe oral mucositis in the probiotic group (RR = 0.65, 95% CI = 0.53−0.81, p < 0.0001). The requirement of enteral nutrition was significantly low in the probiotic group (odds ratio = 0.34, 95% CI: 0.13−0.92, p < 0.05). This study demonstrated the effectiveness of probiotics in the prevention and mitigation of cancer therapy−induced oral mucositis. We recommend the use of probiotics to prevent and treat oral mucositis during cancer therapy.

Chemotherapy-associated oral microbiome changes in breast cancer patients

Cytotoxic chemotherapy with or without a combination of humanized monoclonal antibodies is regarded as the gold standard of personalized medicine for the treatment of breast cancer patients. Significant medication-related side effects are common accompanying phenomena for these patients, such as oral discomfort, mucositis, or even osteonecrosis of the jaw. In this study, we analyze the saliva samples of 20 breast cancer patients at three time points throughout their chemotherapy: at the baseline prior to treatment initiation (T1), after four-to-six cycles of chemotherapy (T2), and 1 year after the start of the treatment (T3) to investigate and characterize the long-term effects of chemotherapy on the oral microbiome. We aimed to characterize changes in the oral bacterial microbiome based on 16S rRNA gene amplicon analysis during chemotherapeutic treatment, as a potential target to treat common oral side effects occurring during therapy. The chemotherapeutic drugs used in our study for patient treatment were trastuzumab, docetaxel, pertuzumab, epirubicin, and cyclophosphamide. We find a significant increase in the relative abundance of potentially pathogenic taxa like Escherichia/Shigella and non-significant trends in the relative abundance of, for example, Actinomyces ssp. In conclusion, the role of microbiota in the oral side effects of chemotherapeutic treatment needs to be considered and should be analyzed in more detail using larger patient cohorts. Oral side effects in breast cancer patients undergoing chemotherapy are a common burden and should be treated for a better tolerability of the therapy.

Roles of Toll-Like Receptors in Radiotherapy- and Chemotherapy-Induced Oral Mucositis: A Concise Review

Radiotherapy and/or chemotherapy-induced oral mucositis (RIOM/CIOM) is a common complication in cancer patients, leading to negative clinical manifestations, reduced quality of life, and impacting compliance with anticancer treatment. The composition and metabolic function of the oral microbiome, as well as the innate immune response of the oral mucosa are severely altered during chemotherapy or radiotherapy, promoting the expression of inflammatory mediators by direct and indirect mechanisms. Commensal oral bacteria-mediated innate immune signaling via Toll-like receptors (TLRs) ambiguously shapes radiotherapy- and/or chemotherapy-induced oral damage. To date, there has been no comprehensive overview of the role of TLRs in RIOM/CIOM. This review aims to provide a narrative of the involvement of TLRs, including TLR2, TLR4, TLR5, and TLR9, in RIOM/CIOM, mainly by mediating the interaction between the host and microorganisms. As such, we suggest that these TLR signaling pathways are a novel mechanism of RIOM/CIOM with considerable potential for use in therapeutic interventions. More studies are needed in the future to investigate the role of different TLRs in RIOM/CIOM to provide a reference for the precise control of RIOM/CIOM.

Protective Effects of Cannabidiol on Chemotherapy-Induced Oral Mucositis via the Nrf2/Keap1/ARE Signaling Pathways

Oral mucositis (OM) is a common complication during chemotherapy characterized by ulceration, mucosa atrophy, and necrosis, which seriously interferes with nutritional intake and oncotherapy procedures among patients. However, the efficacy of current treatments for OM remains limited. Cannabidiol (CBD) is a natural cannabinoid with multiple biological activities, including antioxidant and anti-inflammatory potential. In this study, we aimed to investigate the chemopreventive effects and mechanisms of CBD in protecting C57BL/6N mice and human oral keratinocytes (HOK) from 5-fluorouracil- (5-FU-) induced OM. Here, we found that CBD alleviated the severity of 5-FU-induced OM in mice, including improved survival, decreased body weight loss, reduced ulcer sizes, and improved clinical scores. Histologically, CBD restored epithelial thickness and normal structure in tongue tissues. Meanwhile, CBD attenuated reactive oxygen species (ROS) overproduction and improved the antioxidant response, suppressed the inflammatory response, promoted the proliferation of epithelial cells, and inhibited 5-FU-induced apoptosis. In vitro, consistent outcomes showed that CBD suppressed cellular ROS levels, enhanced antioxidant ability, reduced inflammatory response, promoted proliferation, and inhibited apoptosis in 5-FU-treated HOK cells. In particular, CBD upregulated the expression levels of antioxidant enzymes, heme oxygenase-1 (HO-1) and NAD(P)H quinine oxidoreductase 1 (NQO1), by increasing the expression and nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and decreasing Kelch-like ECH-associated protein 1 (Keap1). Notably, the Nrf2 inhibitor ML385 reversed the protective effect of CBD. Nrf2-siRNA transfection also significantly blunted the antioxidant effect of CBD in in vitro OM model. Collectively, our findings suggested that CBD protected against 5-FU-induced OM injury at least partially via the Nrf2/Keap1/ARE signaling pathways, highlighting the therapeutic prospects of CBD as a novel strategy for chemotherapy-induced OM.