- Volume 73, Issue 10, 2024

Background. The interplay among human gut microbiota (GM) composition, osteoarthritis (OA) and OA-related medication use has been extensively discussed. However, to date, there has been no exploration of the genetic correlation among these three factors.

Hypothesis/Gap. The potential causal link between GM and OA), and whether medications influence this relationship, remains unclear.

Methods. We utilized bidirectional Mendelian randomization (MR) to explore the genetic associations between GM and OA. We leveraged genome-wide association study (GWAS) summary statistics from the MiBioGen and GO consortia, which provided data on GM taxa and OA cases, respectively. We identified outlier single-nucleotide polymorphisms using radial-MR and assessed causal associations using inverse variance weighting (IVW), weighted median and MR-Egger methods. Robust outcomes, consistent across these methods, were reported. We addressed potential biases through tests for horizontal pleiotropy and heterogeneity, supplemented by the Mendelian randomization pleiotropy residual sum and outlier method. Multivariable MR techniques were applied to adjust for OA medication use using UK Biobank data.

Results. IVW estimates revealed a significant increase in hip OA risk for Gordonibacter and Eubacterium (brachy group) [odds ratio (OR): 1.09, 95% confidence interval (CI): 1.04–1.15, P=7.82E-04; OR: 1.09, 95% CI: 1.03–1.16, P=4.67E-03, respectively]. Conversely, Senegalimassilia, Slackia and Streptococcus exhibited protective effects (OR: 0.88, P=2.14E-02; OR: 0.88, P=3.33E-02; 0.91, P=4.29E-02). Sutterella increased the risk of knee OA (OR=1.15, 95% CI: 1.07–1.25, P=4.06E-04), while Haemophilus decreased it (OR=0.94, 95% CI: 0.88–1.00, P=4.26E-02). No significant heterogeneity or horizontal pleiotropy was observed in the results. Even after accounting for the potential confounding effect of medication, the results remained consistent. No reverse causation was detected.

Conclusions. Our MR study reveals gut microbiome links to OA risk. Associations hold after adjusting for medication, indicating a potential causal connection between GM and OA.

Introduction. Adherence is a major virulence trait in Candida glabrata that, in many strains, depends on the EPA (epithelial adhesin) genes, which confer the ability to adhere to epithelial and endothelial cells of the host. The EPA genes are generally found at subtelomeric regions, which makes them subject to subtelomeric silencing. In C. glabrata, subtelomeric silencing depends on different protein complexes, such as silent information regulator and yKu complexes, and other proteins, such as Repressor/activator protein 1 (Rap1) and Abf1. At the EPA1 locus, which encodes the main adhesin Epa1, we previously found at least two cis-acting elements, the protosilencer Sil2126 and the negative element, that contribute to the propagation of silencing from the telomere to the subtelomeric region.

Hypothesis. Abf1 binds to the regulatory regions of EPA1 and other regions at the telomere E-R, thereby negatively regulating EPA1 transcription.

Aim. To determine whether Abf1 and Rap1 silencing proteins bind to previously identified cis-acting elements on the right telomere of chromosome E (E-R subtelomeric region), resulting in negative regulation of EPA1 transcription and infer Abf1 and Rap1 recognition sites in C. glabrata.

Methodology. We used chromatin immunoprecipitation (ChIP) followed by quantitative PCR to determine the binding sites for Abf1 and Rap1 in the intergenic regions between EPA1 and EPA2 and HYR1 and EPA1, and mutants were used to determine the silencing level of the EPA1 promoter region.

Results. We found that Abf1 predominantly binds to the EPA1 promoter region, leading to negative regulation of EPA1 expression. Furthermore, the mutant abf1-43, which lacks the last 43 amino acids at its C-terminal end and is defective for subtelomeric silencing, exhibits hyperadherence to epithelial cells in vitro compared to the parental strain, suggesting that EPA1 is derepressed. We also determined the motif-binding sequences for Abf1 and Rap1 in C. glabrata using data from the ChIP assays.

Conclusion. Together these data indicate that Abf1 negatively regulates EPA1 expression, leading to decreased adhesion of C. glabrata to epithelial cells.

Introduction. Tissue conditioners modified with antifungals are a potential alternative to denture stomatitis (DS) treatment.

Gap Statement. Information on tissue response to this treatment before its clinical application is lacking.

Aim. This study aimed to evaluate the tissue response of a tissue conditioner modified with antifungals in a rat model of DS.

Methodology. After DS induction for 4 days under antibiotic therapy, Wistar rats had their intraoral devices (IODs) relined with the tissue conditioner Softone without (Soft) or with the MICs against Candida albicans of nystatin (Nys) or chlorhexidine (Chx) complexed or not with β-cyclodextrin (Nys:βCD and Chx:βCD). Three controls were included: healthy rats [negative control (Nc)], rats using a sterile IOD [sterile device (Sd)] and rats with DS that did not receive treatment (DS). After 4 days of treatment, the palatal mucosa under the IODs underwent histological processing for morphohistopathological and histometric analyses, morphology of collagen fibres (birefringence), immunohistochemistry for the expression of cell proliferation (proliferating cell nuclear antigen) and cytokine (IL-1β).

Results. The Nc and Sd groups were similar (P>0.05), displaying epithelial and connective tissues without any discernible changes in the parameters assessed. The DS and Soft groups exhibited pronounced epithelial alterations, cell proliferation and expression of the cytokine IL-1β. In groups treated with drug incorporation (Nys, Chx, Nys:βCD and Chx:βCD), all samples demonstrated a reduction in tissue inflammation or complete tissue recovery, with an epithelium compatible with health. For the immunohistochemical parameters, the Chx, Nys:βCD and Chx:βCD groups were comparable with Nc (P>0.05).

Conclusion. The proposed treatment could be promising for DS, as it led to the tissue recovery of the palatal mucosa. Nevertheless, much lower concentrations of complexed antifungals were required to achieve a similar or higher degree of tissue response compared with uncomplexed drugs in a modified tissue conditioner formulation.