Characterization of novel O-glycans isolated from tear and saliva of ocular rosacea patients.

O-Glycans in saliva and tear isolated from patients suffering from ocular rosacea, a form of inflammatory ocular surface disease, were profiled, and their structures were elucidated using high resolution mass spectrometry. We have previously shown that certain structures, particularly sulfated oligosaccharides, increased in the tear and saliva of rosacea patients. In this study, the structures of these glycans were elucidated using primarily tandem mass spectrometry. There were important similarities in the glycan profiles of tears and saliva with the majority of the structures in common. The structures of the most abundant species common to both tear and saliva, which were also the most abundant species in both, were elucidated. For sulfated species, the positions of the sulfate groups were localized. The majority of the structures were new, with the sulfated glycans comprising mucin core 1- and core 2-type structures. As both saliva and tear are rich in mucins, it is suggested that the O-glycans are mainly components of mucins. The study further illustrates the strong correspondence between the glycans in the tear and saliva of ocular rosacea patients.

Glycomic analysis of tear and saliva in ocular rosacea patients: the search for a biomarker.

The purpose of this study was to study changes in glycosylation in tear and saliva obtained from control and ocular rosacea patients in order to identify potential biomarkers for rosacea. Tear fluid was collected from 51 subjects (28 healthy controls and 23 patients with ocular rosacea). Saliva was collected from 42 of the same subjects (25 controls and 17 patients). Pooled and individual samples were examined to determine overall glycan profiles and individual variations in glycosylation. O-and N- glycans were released from both patients and control subjects. Released glycans were purified and enriched by solid-phase extraction (SPE) with graphitized carbon. Glycans were eluted based on glycan size and polarity. SPE fractions were then analyzed by high-resolution mass spectrometry. Glycan compositions were assigned by accurate masses. Their structures were further elucidated by tandem mass spectrometric using collision-induced dissociation (CID), and specific linkage information was obtained by exoglycosidase digestion. N- and O-glycans were released from 20-µL samples without protein identification, separation, and purification. Approximately 50 N-glycans and 70 O-glycans were globally profiled by mass spectrometry. Most N-glycans were highly fucosylated, while O-glycans were sulfated. Normal tear fluid and saliva contain highly fucosylated glycans. The numbers of sulfated glycans were dramatically increased in tear and saliva of rosacea patients compared to controls. Glycans found in tear and saliva from roseatic patients present highly quantitative similarity. The abundance of highly fucosylated N-glycans in the control samples and sulfated O-glycans in ocular rosacea patient samples may lead to the discovery of an objective diagnostic marker for the disease.