Pentraxin-3 detected in human saliva shows limited correlation with biomarkers associated with systemic inflammation

Pentraxin-3 (PTX3) is a conserved protein of the innate immune system which has been less studied than the pentraxin C-reactive protein (CRP), but it is of relevance in, for example, vascular pathology and pregnancy morbidities. Since the interest in salivary biomarkers in general is increasing, we asked whether PTX3 could be detected in saliva and if any substantial diurnal variation occurs. In addition, we evaluated association with biomarkers of systemic inflammation (interleukin (IL)-1β, IL-6, and IL-8 and CRP), body mass index (BMI), smoking, and age. PTX3 in morning and evening saliva from 106 middle-aged participants of the general population was investigated by ELISA and total protein levels by spectrophotometry. PTX3 was detectable in saliva, and concentrations varied over the day with higher morning concentrations, but the PTX3 relative protein levels (percentage of total protein) were significantly higher in the evening. Sex and age did not impact salivary PTX3, but smoking was associated with lower PTX3 levels. BMI correlated positively with PTX3 in evening saliva. There was no general association with biomarkers of systemic inflammation, except for IL-6. Salivary PTX3 likely reflects the local inflammatory milieu, and adjustments for sampling time, smoking habits, and BMI are needed to adequately interpret PTX3 in saliva.