Hepatic Postnatal Developmental Expression of Trace Mineral Associated Antioxidant Enzymes

Abstract

Abstract Objectives Oxidative stress is central to the etiology of many diseases of prematurity. Lower antioxidant defenses render premature infants vulnerable to oxidative damage secondary to infection and oxygen therapy. Antioxidant enzymes (AOE) increase perinatally in the blood and lungs. Many AOE require a micronutrient such as selenium (Se) or zinc (Zn) to function at maximum efficacy. These trace elements are low in neonates compared to adults. The liver is an important immune surveillance organ where antioxidant defense is critical for host response. It also plays a major role in micronutrient processing. However, the developmental regulation and expression of AOE in the liver is incompletely described. We hypothesized the neonatal liver would have decreased trace mineral associated AOE. Methods C57BL/6mice were sacrificed at P0, P7, P21 and 8–12 weeks. mRNA and protein expression of key AOE (SOD1, SOD2, SOD3, Gpx1, Gpx4, Msrb1, TrxR1) and factors for Se processing (Sephs2/Sps2, Scly, Pstk) were measured by qPCR and Western blot. Results Hepatic mRNA for selenoenzymes Gpx1 and Msrb1 were developmentally regulated, low at P0 and increased by adult (P < 0.05, n = 5–6). Gpx1 protein increased 7–8-fold and Msrb1 protein increased 6-fold from P0 to adult (P < 0.0001, n = 4). Gene expression of Zn related SOD1 and Mn SOD2 increased postnatally, low at P0 and increased in adult (P < 0.01 n = 5–6). Protein expression for each increased 1.5 and 3-fold from P0 to adult respectively (P < 0.001, n = 4) The mRNA and protein expression for Gpx4, TrxR1 and SOD3 remained constant postnatally. As the greatest increase was observed in selenoenzymes, factors for Se processing were evaluated. Sephs2, Scly and Pstk mRNA increased from P0 compared to P21 and adult mice (P < 0.05, n = 4–6). Protein expression for Pstk and Scly was highest at P21 and protein for Sps2 increased postnatally (P < 0.01, n = 4). Conclusions The liver experiences a postnatal increase in essential trace mineral associated AOE. Additionally, the hepatic machinery for Se processing is low in neonatal mice. We speculate that the neonatal liver is vulnerable to oxidative stress secondary to low AOE defense. We also speculate states that decreased neonatal micronutrient status may further impair the hepatic redox state. Funding Sources CCTSI Child Maternal Health Mentored Grant (L.S).