Salivary proteome profile of women during fertile phase of menstrual cycle as characterized by mass spectrometry

Abstract Background Human saliva contains several biomolecules, especially proteins, some of which have been found to serve as biomarkers of different physiological statuses and/or pathological conditions. Saliva is a much superior biological material for investigation over the other body fluids. Several salivary proteins are present in minute quantities whereupon there is possibility to express the hormone receptors, stress proteins or antimicrobial peptides at subtle to major variations which can reveal the physiological and/or pathological statuses. Ovulation is such a critical physiological process that its non-invasive prediction has several advantages. It has been postulated that saliva, with one or more of biomolecules in it such as proteins, amino acids, antioxidants, antimicrobial peptides, and such others would effectively serve as non-invasive predictor(s)/detector(s) of ovulation.Methods Samples were collected from women volunteers and the procedure adopted was approved by the Institutional Ethical Committee (DM/2014/101/38), Bharathidasan University. The saliva samples were collected between 8.00 to 9.00 AM from 30 healthy female volunteers (age, mean = 24, range = 19 - 30), with prior written consent. The protein expression pattern during different phases of menstrual cycle was analyzed using HR-LC-MS/MS and MALD TOF/TOF.Results The functional annotation of salivary proteins identified therein revealed that the proteins get assigned to the class of “extracellular proteins” which are concerned with regulatory functions. As many as 530 proteins showed up in the saliva during ovulation phase whereas there were only 251 proteins during post-ovulation phase. The protein expression was also analyzed using 2D gel electrophoresis and it was found that the salivary proteins focused at pH range 4-7 and molecular weight around 97-14 kDa. The unique/differentially expressed protein spots appeared during ovulation phase was identified by MALDI-TOF analysis.Conclusions According to spot analysis, Cystatin-S, Prolactin-inducible protein, Cystatin-A, Cystatin-SN, BPI fold-containing family A member 2, Alpha-tubulin N-acetyltransferase 1, and Carbonic anhydrase 6 were highly expressed during ovulation phase. These proteins could serve as an indicator(s) for ovulation after extensive validation studies.