Proto-Oncogenes and Cell Cycle Gene Expression in Normal and Neoplastic Oral Epithelial Cells Stimulated With Soluble Factors From Single and Dual Biofilms of Candida albicans and Staphylococcus aureus

A customizable and defined medium supporting culturing of Candida albicans, Staphylococcus aureus, and human oral epithelial cells

Candida albicans, an opportunistic oral pathogen, synergizes with Staphylococcus aureus, allowing bacteria to co-invade and systemically disseminate within the host. Studying human-microbe interactions creates the need for a universal culture medium that supports fungal, bacterial, and human cell culturing, while allowing sensitive analytical approaches such as OMICs and chromatography techniques. In this study, we established a fully defined, customizable adaptation of Dulbecco's modified Eagle medium (DMEM), allowing multi-kingdom culturing of S. aureus, C. albicans, and human oral cell lines, whereas minimal version of DMEM (mDMEM) did not support growth of S. aureus, and neither did supplementation with dextrose, MEM non-essential amino acids, pyruvate, and Glutamax. This new medium composition, designated as "mDMEM-DMP," promoted growth of all tested S. aureus strains. Addition of 25 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) further improved growth, while higher concentrations did not improve growth any further. Higher concentrations of HEPES did result in prolonged stabilization of medium pH. mDMEM-DMP promoted (hyphal) C. albicans monoculturing and co-culturing on both solid and semi-solid surfaces. In contrast to S. aureus, addition of HEPES reduced C. albicans maximum culture optical density (OD). Finally, only buffered mDMEM-DMP (100 mM HEPES) was successful in maintaining the metabolic activity of human oral Ca9-22 and HO1N1 cell lines for 24 hours. Altogether, our findings show that mDMEM-DMP is a versatile and potent culture medium for both microbial and human cell culturing, providing a customizable platform to study human as well as microbial molecular physiology and putative interactions.

IMPORTANCE

Interaction between microbes and the host are in the center of interest both in disease and in health. In order to study the interactions between microbes of different kingdoms and the host, alternative media are required. Synthetic media are useful as they allow addition of specific components. In addition, well-defined media are required if high-resolution analyses such as metabolomics and proteomics are desired. We describe the development of a synthetic medium to study the interactions between C. albicans, S. aureus, and human oral epithelial cells. Our findings show that mDMEM-DMP is a versatile and potent culture medium for both microbial and human cell culturing, providing a customizable platform to study human as well as microbial molecular physiology and putative interactions.

The potential of EGCG in modulating the oral-gut axis microbiota for treating inflammatory bowel disease

Inflammatory bowel disease (IBD) is a recurrent chronic intestinal disorder that includes ulcerative colitis (UC) and Crohn's disease (CD). Its pathogenesis involves intricate interactions between pathogenic microorganisms, native intestinal microorganisms, and the intestinal immune system via the oral-gut axis. The strong correlation observed between oral diseases and IBD indicates the potential involvement of oral pathogenic microorganisms in IBD development. Consequently, therapeutic strategies targeting the proliferation, translocation, intestinal colonization and exacerbated intestinal inflammation of oral microorganisms within the oral-gut axis may partially alleviate IBD. Tea consumption has been identified as a contributing factor in reducing IBD, with epigallocatechin gallate (EGCG) being the primary bioactive compound used for IBD treatment. However, the precise mechanism by which EGCG mediates microbial crosstalk within the oral-gut axis remains unclear. In this review, we provide a comprehensive overview of the diverse oral microorganisms implicated in the pathogenesis of IBD and elucidate their colonization pathways and mechanisms. Subsequently, we investigated the antibacterial properties of EGCG and its potential to attenuate microbial translocation and colonization in the gut, emphasizing its role in attenuating exacerbations of IBD. We also elucidated the toxic and side effects of EGCG. Finally, we discuss current strategies for enhancing EGCG bioavailability and propose novel multi-targeted nano-delivery systems for the more efficacious management of IBD. This review elucidates the role and feasibility of EGCG-mediated modulation of the oral-gut axis microbiota in the management of IBD, contributing to a better understanding of the mechanism of action of EGCG in the treatment of IBD and the development of prospective treatment strategies.

Worldwide trend in research on Candida albicans and cancer correlations: a comprehensive bibliometric analysis

Objective

Candida albicans (C. albicans), an opportunistic pathogen, is implicated in the carcinogenesis of various cancers, thereby significantly impacting human health. This study conducts an in-depth analysis of the prevailing research dynamics concerning the relationship between C. albicans and cancer over the past decade, offering a comprehensive overview of the knowledge structure and emerging focal points in this field through bibliometric scrutiny.

Methods

A methodical quantitative and visual scrutiny of pertinent literature from the Web of Science Core Collection (WoSCC) spanning the previous decade was carried out employing VOS Viewer and CiteSpace software.

Results

From January 1, 2014, to January 1, 2024, a comprehensive corpus of 1,259 articles was delineated. Prominent research institutions included the Egyptian Knowledge Bank, Cairo University, and King Saud University. The top three prolific countries were the United States, China, and India. Among the authors, Mohamed, Gehad G., Mahmoud, Walaa H., and Netea, Mihai G., emerged as the most prolific, with Pfaller, Ma being distinguished as the most frequently cited author. The journal Molecules published the highest number of articles, while PLoS One had the highest citation count. Nature had the highest impact factor. The research focal points in this field encompassed the interactions between C. albicans and cancer, the correlation with oral cancer, the underlying mechanisms of C. albicans carcinogenic potential, as well as antifungal and anticancer therapies.

Conclusion

This investigation constitutes a pioneering bibliometric analysis elucidating the trends and advancements in research regarding the correlation between C. albicans and cancer. Said analyses uncover the prevailing research focal points and trends, offering insightful guidance for subsequent inquiry in this domain.

Systematic review registration

https://www.webofscience.com/wos/woscc/summary/df33afba-f843-41e8-b932-cb3678eb8243-e92e7316/relevance/1.

Oral Microbiota: A New Insight into Cancer Progression, Diagnosis and Treatment

The polymorphic microbiome has been defined as one of the "Hallmarks of Cancer". Extensive studies have now uncovered the role of oral microbiota in cancer development and progression. Bacteria, fungi, archaea, and viruses in the oral cavity interact dynamically with the oral microenvironment to maintain the oral micro-ecological homeostasis. This complex interaction is influenced by many factors, such as maternal transmission, personal factors and environmental factors. Dysbiosis of oral microbiota can disturbed this host-microbiota interaction, leading to systemic diseases. Numerous studies have shown the potential associations between oral microbiota and a variety of cancers. However, the underlying mechanisms and therapeutic insights are still poorly understood. In this review, we mainly focus on the following aspects: (1) the factors affect oral microbiota composition and function; (2) the interaction between microenvironment and oral microbiota; (3) the role of multi-kingdom oral microbiota in human health; (4) the potential underlying mechanisms and therapeutic benefits of oral microbiota against cancer. Finally, we aim to describe the impact of oral microbiota on cancer progression and provide novel therapeutic insights into cancer prevention and treatment by targeting oral microbiota.

Candida species as potential risk factors for oral squamous cell carcinoma: Systematic review and meta-analysis

Oral squamous cell carcinoma (OSCC) is considered a multifactorial disease and has been associated with microbial infections, although the association with Candida spp. is still controversial. This systematic review focused on clinical trials which evaluated the relation between oral Candida spp colonization and OSCC. PubMed; Scopus; Embase; Web of Science and Scientific Direct were assessed. Independent reviewers conducted the diagram steps. For data extraction the PRISMA protocol was followed. The quality analysis of case-control studies was performed based on the Newcastle-Ottawa scale. Meta-analysis was performed to evaluate the frequency of Candida spp and the levels of microbial acetaldehyde production (MAP) being odds ratio (OR) the effect-measure applied. Eight and six studies were included in the qualitative analysis and meta-analysis, respectively. It was noted that there was a significantly higher frequency of Candida species (p = 0.0003/OR = 9.50) in patients diagnosed with OSCC than healthy patients, especially Candida krusei (p = 0.0167/OR=4.62). Candida spp., from oral cancer patients demonstrated significantly greater biofilm, biofilm metabolic activity, phospholipase, proteinase activity and a higher production of MAP (p = 0.0111/OR = 2.67). Candida species may have a potential role in OSCC development. Further studies should be conducted to elucidate the mechanism of action of Candida spp and others risk factors in the development of OSCC.

Cross-kingdom Microbial Interactions Within the Oral Cavity and Their Implications for Oral Disease

Purpose of Review

This review serves to highlight the cross-kingdom interactions that can occur within the human oral cavity between fungus Candida albicans and oral bacteria, and their impact on the delicate balance between oral health and disease.

Recent Findings

A growing number of physical, chemical, and metabolic networks have been identified that underpin these cross-kingdom interactions. Moreover, these partnerships are often synergistic and can modulate microbial burden or virulence. This, in turn, can drive the onset or progression of oral diseases such as dental caries, periodontitis, denture-associated stomatitis, and oral cancer.

Summary

The impact of cross-kingdom interactions on the cellular, biochemical, and communal composition of oral microbial biofilms is increasingly clear. With growing insight into these processes at the molecular level, so this knowledge can be used to better inform the development of novel strategies to manipulate the oral microbiota to promote oral health and combat oral disease.

Extracellular lipids of Candida albicans biofilm induce lipid droplet formation and decreased response to a topoisomerase I inhibitor in dysplastic and neoplastic oral cells

OBJECTIVE

Some microorganisms, i.e., Candida albicans, have been associated with cancer onset and development, although whether the fungus promotes cancer or whether cancer facilitates the growth of C. albicans is unclear. In this context, microbial-derived molecules can modulate the growth and resistance of cancer cells. This study isolated extracellular lipids (ECL) from a 36-h Candida albicans biofilm incubated with oral dysplastic (DOK) and neoplastic (SCC 25) cells, which were further challenged with the topoisomerase I inhibitor camptothecin (CPT), a lipophilic anti-tumoral molecule.

METHODOLOGY

ECL were extracted from a 36-h Candida albicans biofilm with the methanol/chloroform precipitation method and identified with Nuclear Magnetic Resonance (1H-NMR). The MTT tetrazolium assay measured ECL cytotoxicity in DOK and SCC 25 cells, alamarBlue™ assessed cell metabolism, flow cytometry measured cell cycle, and confocal microscopy determined intracellular features.

RESULTS

Three major classes of ECL of C. albicans biofilm were found: phosphatidylinositol (PI), phosphatidylcholine (PC), and phosphatidylglycerol (PG). The ECL of C. albicans biofilm had no cytotoxic effect on neither cell after 24 hours, with a tendency to disturb the SCC 25 cell cycle profile (without statistical significance). The ECL-induced intracellular lipid droplet (LD) formation on both cell lines after 72 hours. In this context, ECL enhanced cell metabolism, decreased the response to CPT, and modified intracellular drug distribution.

CONCLUSION

The ECL (PI, PC, and PG) of 36-h Candida albicans biofilm directly interacts with dysplastic and neoplastic oral cells, highlighting the relevance of better understanding C. albicans biofilm signaling in the microenvironment of tumor cells.

Cross-kingdom interaction between Candida albicans and oral bacteria

Candida albicans is a symbiotic fungus that commonly colonizes on oral mucosal surfaces and mainly affects immuno-compromised individuals. Polymicrobial interactions between C. albicans and oral microbes influence the cellular and biochemical composition of the biofilm, contributing to change clinically relevant outcomes of biofilm-related oral diseases, such as pathogenesis, virulence, and drug-resistance. Notably, the symbiotic relationships between C. albicans and oral bacteria have been well-documented in dental caries, oral mucositis, endodontic and periodontal diseases, implant-related infections, and oral cancer. C. albicans interacts with co-existing oral bacteria through physical attachment, extracellular signals, and metabolic cross-feeding. This review discusses the bacterial-fungal interactions between C. albicans and different oral bacteria, with a particular focus on the underlying mechanism and its relevance to the development and clinical management of oral diseases.

The Relationship between Mutations in Gene-Specific Domains of Salivary Fibronectin (cFn) and Dynamin-2 (Dynm-2) and the Development of Porphyromonas gingivalis-Initiated Periodontitis

Periodontitis is a chronic inflammatory disease characterized by the destruction of the supporting structures of the teeth. Its high prevalence and negative effects on quality of life make it one of the current problems in dentistry. Porphyromonas gingivalis (P. gingivalis) is the predominant periodontal pathogen that expresses a number of virulence factors involved in the pathogenesis of periodontitis. P. gingivalis fimbriae are a critical factor in the interaction between the organism and the host tissue. They promote both bacterial adhesion and invasion into the target sites. Fimbriae are capable of binding to human saliva components, extracellular matrix proteins, and commensal bacteria, as well as firmly binding to the cellular integrin α5β1. After attachment to α5β1-integrin, P. gingivalis is captured by cellular pseudopodia, which makes invagination through an actin-mediated pathway possible. It has been proven that the invagination event also requires the participation of the host cell dynamin, actin fibers, microtubules and lipid rafts. Work has emerged investigating mutations in the proline-rich terminal domain (PRD) and their impact on disease development. Salivary antimicrobial peptides are early protective factors against microbial attack. Of great interest is fibronectin (FN) as the main competitor of P. gingivalis fimbriae. The FN can interact with cells in three different regions: the central cell-binding domain (CCBD), the COOH terminal heparin-binding domain (Hep2), and the type III connecting segment (IIICS), including the CS1 region (Yamada, 1991). CCBD is the major cell-adhesion domain of FN and contains an Arg–Gly–Asp (RGD) motif that is recognized by members of the cell adhesion receptor integrin family, including a5b1, which is the primary FN receptor in many cell types. The work focuses on identifying the relationship between the development of periodontitis and the presence of mutations in the adhesion domains of salivary proteins such as cellular fibronectin (cFN) and dynamin-2 (DYNM2).

Candida albicans induces upregulation of programmed death ligand 1 in oral squamous cell carcinoma

BACKGROUND

The potential association between Candida albicans (C. albicans) infection and oral squamous cell carcinoma (OSCC) has been noticed for a long time. Programmed death ligand-1 (PD-L1) is a key molecule of tumor immune escape and tumor progression. This study aimed to explore whether C. albicans could influence PD-L1 expression in OSCC in vitro and in mouse model.

METHODS

OSCC cell lines (Cal27 and HN6) were infected with C. albicans for 2 and 24 h, then PD-L1 expression was detected by quantitative real-time polymerase chain reaction (RT-qPCR), western blot (WB), and flow cytometry (FCM). To identify the underlying mechanisms, PD-L1 expression in OSCC cells treated with heat-inactivated C. albicans or with biofilm metabolites derived from C. albicans were explored respectively. Meanwhile, signaling pathways involved in PD-L1 regulation were explored by RT-qPCR, and the candidate genes were verified by WB. Moreover, an OSCC mouse model induced by 4-nitroquinoline-1 oxide was used to further explore the role of C. albicans infection in PD-L1 expression in vivo.

RESULTS

C. albicans and heat-inactivated C. albicans upregulated the PD-L1 expression in Cal27 and HN6 cells. Various signaling pathways involved in PD-L1 regulation were influenced by C. albicans infection. Among them, TLR2/MyD88 and TLR2/NF-κB pathways might participate in this process. Furthermore, PD-L1 expression in oral mucosa epithelium was upregulated by C. albicans infection in both normal and OSCC mice.

CONCLUSIONS

This study suggests that C. albicans could induce upregulation of PD-L1 in OSCC in vitro and in mouse model, which might due to the activation of TLR2/MyD88 and TLR2/NF-κB pathways.

In it together: Candida-bacterial oral biofilms and therapeutic strategies

Under natural environmental settings or in the human body, the majority of microorganisms exist in complex polymicrobial biofilms adhered to abiotic and biotic surfaces. These microorganisms exhibit symbiotic, mutualistic, synergistic, or antagonistic relationships with other species during biofilm colonization and development. These polymicrobial interactions are heterogeneous, complex and hard to control, thereby often yielding worse outcomes than monospecies infections. Concerning fungi, Candida spp., in particular, Candida albicans is often detected with various bacterial species in oral biofilms. These Candida-bacterial interactions may induce the transition of C. albicans from commensal to pathobiont or dysbiotic organism. Consequently, Candida-bacterial interactions are largely associated with various oral diseases, including dental caries, denture stomatitis, periodontitis, peri-implantitis, and oral cancer. Given the severity of oral diseases caused by cross-kingdom consortia that develop hard-to-remove and highly drug-resistant biofilms, fundamental research is warranted to strategically develop cost-effective and safe therapies to prevent and treat cross-kingdom interactions and subsequent biofilm development. While studies have shed some light, targeting fungal-involved polymicrobial biofilms has been limited. This mini-review outlines the key features of Candida-bacterial interactions and their impact on various oral diseases. In addition, current knowledge on therapeutic strategies to target Candida-bacterial polymicrobial biofilms is discussed.

Insights into the activation of oral keratinocyte cell death by Candida albicans and Staphylococcus aureus biofilms

Polymicrobial biofilms comprising Candida albicans and Staphylococcus aureus can increase the frequency and severity of oral diseases. This study assessed oral keratinocyte cell death, apoptosis and/or necrosis, promoted by soluble factors from single and dual biofilms of S. aureus and C. albicans. The soluble factors were obtained from the 16-h biofilm growth media. Cell viability was assessed by MTT and cell membrane damage by LDH. SEM was used for morphology changes. Assessment of apoptosis and necrosis was performed using annexin V and propidium iodide and caspases -2, -3, -6, -8 and -9. Statistical analysis was conducted with ANOVA and Tukey tests (α = 5%). Dual biofilms promoted the greatest harmful effect on oral cells, with a viability rate of 31.76%, damage to cell membranes and LDH released. Dual biofilms also induced higher percentages of necrotic cells (24.95%). Apoptosis was associated with caspases -2, -3, -6 and -8 activation.