Identification and Quantification of Thymosin β4 in Human Saliva and Tears

Abstract

Thymosin beta(4) (Tbeta(4)) is a ubiquitous, naturally occurring, 43-amino acid peptide that takes part in several biological activities including angiogenesis, inhibition of inflammation, wound healing, chemotaxis, and endothelial cell migration. Recent studies also indicate that Tbeta(4) accelerates corneal wound healing and downregulates several proinflamatory chemokines and cytokines. In this study, we sought to determine whether Tbeta(4) is naturally occurring in human tears and other human bodily fluids, such as saliva. Tear and saliva samples were analyzed by EIA to identify and quantify the amount of Tbeta(4) present. Around 10-20 samples were collected from each of three different age groups: 15-20, 25-35, and >50 years old with n = 30 and n = 60 for tears and saliva, respectively. Exclusion criteria included the use of any topical ophthalmic or topical oral medication and/or history of ocular or oral surgery within the past 6 months. Tears were collected from both eyes using Schirmer's strips. Saliva samples were collected in sterile tubes and were then centrifuged to remove solid particles. Tbeta(4) was found in tear and saliva samples in all age groups. The concentrations ranged from 0.5-7 mug/mL in tears and 0.2-3.6 mug/mL in saliva. In both fluids, Tbeta(4) concentration varied with age and appeared to peak at ages 25-35 years. Studies are in progress to determine if Tbeta(4) levels in saliva and tears demonstrate a circadian rhythm during a 24-h period, as well as to confirm that they vary with age and to explore if they vary with diseased states. This is the first study to report the presence of Tbeta(4) in human tears and saliva. This finding raises the possibility that Tbeta(4) acts as an endogenous agent contributing to the rapid healing of corneal and oral wounds. Considering that Tbeta(4) facilitates reepithelialization and modulates anti-inflammatory mediators, Tbeta(4) could potentially be used therapeutically in the treatment of (a) ocular surface disease and injury of eye and (b) various oral disorders, such as periodontal disease.