Abstract
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.
Highlights
The short and long pentraxins constitute an evolutionary conserved superfamily of structurally similar proteins characterized by a pentraxin protein domain [1]
The highest detected salivary PTX3 levels were unrelated to visible blood contamination
No significant difference in mean PTX3 levels was found between the age groups (Fig. 1A), and sex had no obvious influence on Salivary PTX3 morning
Summary
The short and long pentraxins constitute an evolutionary conserved superfamily of structurally similar proteins characterized by a pentraxin protein domain [1]. PTX3 is structurally and functionally related to CRP, its production differs both regarding its non-hepatic cell origin as well as in its inducing stimuli. PTX3 is an acute-phase protein and circulating levels can increase rapidly with the peak concentration typically seen 6–8 h after onset of inflammation [3,5]. It is produced by leukocytes, endothelial cells, and fibroblasts during infection and other inflammatory stimulation (e.g., lipopolysaccharide, interleukin [IL-] 1b, and tumor necrosis factor [TNF]). To CRP, one of the physiologic functions of PTX3 is to activate the classical complement pathway [8]. Immunohistochemical staining of advanced atherosclerotic lesions revealed a strong tissue expression of PTX3 as well as within the atherosclerotic plaque, combined with plasma level increase rapidly after myocardial infarction, indicating that PTX3 might be a marker of early acute myocardial damage [1]
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