Salivary Gland Dysfunction in Stroke Patients Is Associated with Increased Protein Glycoxidation and Nitrosative Stress

Abstract

Stroke is one of the leading causes of disability and death worldwide. Despite intensive medical care, many of the complaints directly threatening the patient's life marginalize their dental needs after the stroke. Recent studies indicate reduced saliva secretion in stroke patients in addition to the increased incidence of caries and periodontal disease. Since oxidative stress plays a vital role in the pathogenesis of salivary gland hypofunction and neurodegenerative disorders (including stroke), this is the first to evaluate the relationship between salivary gland activity and protein glycoxidation and nitrosative damage. The content of glycation and protein oxidation products and nitrosative stress was assessed in nonstimulated (NWS) and stimulated (SWS) whole saliva of stroke patients with normal salivary secretion and hyposalivation (reduced saliva production). The study included 30 patients in the stroke's subacute phase and 30 healthy controls matched by age and sex. We have shown that stroke patients with hyposalivation show increased contents of protein glycation (↑Amadori products and ↑advanced glycation end products), glycoxidation (↑dityrosine), and nitration (↑nitrotyrosine) products compared to stroke cases with normal salivary secretion and control group. Interestingly, higher oxidative/nitrosative stress was found in NWS, which strongly correlates with salivary flow rate, total protein content, and salivary amylase activity. Such relationships were not observed in the control group. Summarizing, oxidative and nitrosative stress may be one of the mechanisms responsible for the impairment of saliva secretion in stroke patients. However, extraglandular sources of salivary oxidative stress in stroke patients cannot be excluded. Further studies to assess salivary gland hypofunction in stroke cases are necessary.