Thymosin β4 and β10 Levels in Pre-Term Newborn Oral Cavity and Foetal Salivary Glands Evidence a Switch of Secretion during Foetal Development

Sonia Nemolato,Barbara Manconi,Chiara Fanali,Costantino Romagnoli,Gavino Faa,Massimo Castagnola,Eliana Di Felice,Alessandro Riva,Irene Messana,Giovanni Vento,Chiara Tirone,Daniela Fanni,Tiziana Cabras,Rosanna Inzitari

doi:10.1371/journal.pone.0005109

Sonia Nemolato, Barbara Manconi + Show 12 more

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https://doi.org/10.1371/journal.pone.0005109

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Abstract

BackgroundThymosin β4, its sulfoxide, and thymosin β10 were detected in whole saliva of human pre-term newborns by reversed-phase high performance chromatography coupled to electrospray ion-trap mass spectrometry.Methodology/Principal FindingsDespite high inter-individual variability, concentration of β-thymosins increases with an inversely proportional trend to postmenstrual age (PMA: gestational age plus chronological age after birth) reaching a value more than twenty times higher than in adult whole saliva at 190 days (27 weeks) of PMA (thymosin β4 concentration: more than 2.0 µmol/L versus 0.1 µmol/L). On the other hand, the ratio between thymosin β4 and thymosin β10 exhibits a constant value of about 4 along all the range of PMA (190–550 days of PMA) examined. In order to investigate thymosin β4 origin and to better establish the trend of its production as a function of gestational age (GA), immunohistochemical analysis of major and minor salivary glands of different pre-term fetuses were carried out, starting from 84 days (12 weeks) of gestational age. Reactive granules were seen in all glands with a maximum of expression around 140–150 days of GA, even though with high inter- and intra-individual variability. In infants and adults reactive granules in acinar cells were not observed, but just a diffuse cytoplasmatic staining in ductal cells.SignificanceThis study outlines for the first time that salivary glands during foetal life express and secrete peptides such as β-thymosins probably involved in the development of the oral cavity and its annexes. The secretion increases from about 12 weeks till to about 21 weeks of GA, subsequently it decreases, almost disappearing in the period of expected date of delivery, when the gland switches towards the secretion of adult specific salivary peptides. The switch observed may be an example of further secretion switches involving other exocrine and endocrine glands during foetal development.

Highlights

Beta thymosins are ubiquitous peptides having interesting intraand extra-cellular functions, whose name derives from their first characterization from thymus extracts [1,2]
Thymosin b4 (Tb4) has been detected in human whole saliva and tears by immunological techniques [12] and recent studies of our group evidenced that in the oral cavity a main contribution derives from crevicular fluid [13], where, as demonstrated by Reti and co-workers [14], Tb4 plays an important role in suppressing the production of interleukin-8 following stimulation by tumour-necrosis factor a and it acts on the whole as antimicrobial, anti-inflammatory and anti-apoptotic peptide on gingival fibroblasts
In the majority of subjects the concentration of Tb4 measured in the range 27–31 weeks (190– 210 days) of postmenstrual age (PMA) was 1–2 mmol/L, but one subject showed a spike to about 6 mmol/L

Summary

Introduction

Beta thymosins are ubiquitous peptides having interesting intraand extra-cellular functions, whose name derives from their first characterization from thymus extracts [1,2]. Thymosin b4 (Tb4) is usually the most abundant b-thymosin in the cytoplasm of most cell types and it plays pivotal roles in the cell cytoskeletal system as G-actin sequestring peptide [3]. The secretion pathway is not fully understood, recent studies highlighted various extra-cellular roles for these peptides [1]. Tb4 has been detected in human whole saliva and tears by immunological techniques [12] and recent studies of our group evidenced that in the oral cavity a main contribution derives from crevicular fluid [13], where, as demonstrated by Reti and co-workers [14], Tb4 plays an important role in suppressing the production of interleukin-8 following stimulation by tumour-necrosis factor a and it acts on the whole as antimicrobial, anti-inflammatory and anti-apoptotic peptide on gingival fibroblasts. Thymosin b4, its sulfoxide, and thymosin b10 were detected in whole saliva of human pre-term newborns by reversed-phase high performance chromatography coupled to electrospray ion-trap mass spectrometry

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