Ortho-phenylphenol exposure impairs porcine sperm motility through AMPK/AKT signaling pathway

Ortho-phenylphenol (OPP), as an active ingredient of disinfectants, has been worldwide utilized as fungicides and antibacterial agents in hospital, agriculture, wood preservation, and veterinary products. However, little is known about the toxic effects of OPP on male reproduction, especially sperm motility, and the underlying mechanisms. In this study, we chose porcine sperms as in vitro model to investigate the effects and mechanisms of OPP exposure on sperm motility. Our results indicated that porcine sperm motility decreases significantly in a dose-dependent manner after exposed to OPP. Additionally, ATP synthesis deficiency was revealed by downregulation of ATP synthase subunit beta and adenosine 5'-monophosphate-activated protein kinase expression. Furthermore, OPP disturbed the expression of TP53 and PTEN, which contributed to AKT pathway deactivation. OPP exposure also disrupted platelet-derived growth factor receptor A expression, which further inhibited 3-phosphoinositide-dependent protein kinase 1 activation, resulting in protein kinase B and pyruvate dehydrogenase phosphatase catalytic subunit 1 deactivation. In conclusion, these observations suggest that OPP exposure decreases porcine sperm motility by disturbing the AMPK/AKT signaling pathway. Environ. Mol. Mutagen. 2019. © 2019 Wiley Periodicals, Inc.

Paper-Based Resazurin Assay of Inhibitor-Treated Porcine Sperm

Porcine sperm motility was assessed via resazurin reduction color change in sperm cells using a novel paper-based assay of our own design. We applied mixtures of resazurin solution and porcine semen onto hydrophilic test circles on our paper-based device and investigated the resulting reduction reaction expressed as red and blue color intensity (RBCI). We quantified this reaction using a blue/pink color ratio from our 8 × 3 = 24 bit RGB color image. To examine enzymatic reactivity in sperm cells, we used two inhibitors: 3-Nitropropanoic acid (3-NPA) and 3-Bromopyruvic acid (3-BP). 3-NPA inhibits the citric acid cycle and electron transfer reaction in mitochondria, but did not strongly reduce sperm motility in our tests. 3-BP decreases reactivity of both mitochondrial electron transfer and glycolytic enzymes in cytosol, which significantly lowers porcine sperm motility. RBCIs of 3-NPA- and 3-BP-treated samples were significantly lower compared to our untreated control (p < 0.025). Based on these results, we feel that resazurin can be used to estimate the amount of reductants with and without inhibitor treatment. For continued research assessing the molecular mechanisms of resazurin reduction in porcine sperm, a combination assay using two or more redox indicators (e.g., resazurin and Thiazolyl Blue Tetrazolium Bromide (MTT)) embedded into our paper-based device could further our understanding of sperm cell bioenergetics.