Uremic toxins and their classification: mechanisms of oral mucosal damage in chronic kidney disease

Аннотация

Uremic toxins, which accumulate due to impaired renal function, have significant systemic effects, including detrimental impacts on the oral mucosa. These toxins are classified into small water-soluble molecules, protein-bound toxins, and middle molecules, each exerting unique pathological effects. This review explores the mechanisms through which these toxins contribute to epithelial dysfunction, oxidative stress, and inflammatory responses in patients with chronic kidney disease (CKD). Understanding these interactions is essential for developing targeted therapeutic strategies to mitigate their impact on oral health. Modern research highlights the importance of a comprehensive approach that considers both morphological changes and immune responses, ultimately allowing physicians to diagnose infertility more accurately and select effective treatment strategies. Therefore, the use of hysteroscopy and immunological markers in reproductive medicine is becoming an integral part of comprehensive examinations for women experiencing infertility issues. Keywords: Uremic toxins, chronic kidney disease, hemodialysis, oral mucosa, inflammation, oxidative stress, cytokines, periodontal disease. immune cell function, reducing the ability of the oral Introduction: Uremic toxins are metabolites that mucosa to combat infections (Oberg et al., 2015). accumulate in the blood due to impaired renal clearance, contributing to systemic complications, Protein-Bound Toxins including oral mucosal dysfunction (Vanholder et al., Protein-bound uremic toxins, such as indoxyl sulfate 2011). These toxins are broadly classified into three (IS), p-cresyl sulfate (PCS), and advanced glycation end categories: small water-soluble molecules, protein- products (AGEs), exhibit significant proinflammatory bound toxins, and middle molecules, each differing in and oxidative effects, particularly in epithelial and size, solubility, and biological impact (Duranton et al., endothelial tissues (Dou et al., 2018). These toxins bind 2012). to serum albumin, limiting their clearance through Small Water-Soluble Molecules dialysis and prolonging their biological impact (Vanholder et al., 2011). Small uremic toxins, typically less than 500 Da, include compounds such as urea, creatinine, and guanidines • Indoxyl sulfate (IS): Derived from tryptophan (Vanholder et al., 2003). Although urea itself is not metabolism, IS has been shown to increase oxidative highly toxic, its hydrolysis in the oral cavity by bacterial stress and inflammatory cytokine production (IL-6, ureases leads to ammonia production, which increases TNF-α) in epithelial cells, contributing to mucosal oral pH and predisposes patients to mucosal irritation atrophy and delayed wound healing (Lekawanvijit & and ulceration (Santos et al., 2016). Furthermore, Krum, 2015). guanidino compounds have been shown to impair • p-Cresyl sulfate (PCS): This toxin, a byproduct International Journal of Medical Sciences And Clinical Research 47 https://theusajournals.com/index.php/ijmscr International Journal of Medical Sciences And Clinical Research (ISSN: 2771-2265) of phenylalanine and tyrosine metabolism, enhances Additionally, the retention of proinflammatory endothelial dysfunction and oxidative stress, leading to cytokines such as IL-1β, IL-6, and TNF-α in the systemic increased susceptibility to periodontitis and mucosal circulation directly influences the inflammatory status inflammation (Brito et al., 2016). of the oral mucosa, leading to increased vascular permeability, fibroblast dysfunction, and delayed tissue • Advanced glycation end products (AGEs): repair (Carrero et al., 2008). These compounds accumulate in the oral mucosa, impairing collagen turnover and reducing epithelial Impact of Uremic Toxins on the Oral Mucosa integrity, which exacerbates tissue fragility and The persistent exposure of oral tissues to uremic toxins inflammation (Witko-Sarsat et al., 2004). results in epithelial dysfunction, microbial imbalance, Middle Molecules and exaggerated inflammatory responses, predisposing CKD patients to a range of oral Middle molecules (500–12,000 Da) include β2- pathologies, including gingivitis, periodontitis, microglobulin, complement factors, and inflammatory xerostomia, and uremic stomatitis (Proctor et al., cytokines, which accumulate in CKD patients and 2005). Understanding the classification and contribute to chronic low-grade inflammation mechanisms of these toxins provides critical insights (Vanholder et al., 2011). Studies indicate that elevated into the development of targeted therapeutic levels of β2-microglobulin in saliva correlate with oral strategies to mitigate their detrimental effects on oral mucosal damage, increased bacterial colonization, and health. a higher risk of oral infections (Stenvinkel et al., 2013). Table 1. Uremic Toxins and Their Effects on the Oral Mucosa Toxin Type Examples Source/Metabolism Main Effects on the Oral Mucosa Small Water- Urea, Creatinine, Prote