Polyamine oxidase activity in peripheral blood of newborn infants with neonatal hyperbilirubinemia: is bilirubin an antioxidant?
BACKGROUND
Neonatal hyperbilirubinemia can be physiological and pathological and most frequently is a consequence of faster erythrocytes (RBC) hemolysis. Free unconjugated bilirubin is a highly toxic compound, especially for the central nervous system. The most abundant polyamines circulating in blood are spermidine (Spd) and spermine (Sp), which are mainly localized in RBC, where they control membrane permeability. Polyamine oxidase (PAO) exerts an important activity in the plasma and erythrocytes of newborn infants with hyperbilirubinemia, catalyzing the oxidative deamination of Sp and Spd, producing potentially toxic agents that induce apoptosis of mammalian cells. The present study investigated polyamine metabolism by measuring PAO activity in the blood of newborn infants with hyperbilirubinemia and explored the possible antioxidant function of bilirubin through monitoring malondialdehyde (MDA) levels.


METHODS
The study included 43 newborns, 10 in the control and 33 in the diseased group. Blood PAO activity and bilirubin and MDA levels were measured using spectrophotometric methods.


CONCLUSIONS
Our results indicate that bilirubin, at physiologic concentrations, protects neonatal erythrocytes against oxidative stress. The positive correlation between PAO activity and MDA levels with high bilirubin concentrations (> 200 micromol/L) in newborn infants indicates that in pathological conditions, bilirubin cannot exert its antioxidant function.


CONCLUSIONS
Investigating the function of polyamines in erythrocytes and the importance of PAO related to hemolysis and bilirubin synthesis is necessary to shed light on the functions of PAO and its metabolites on the permeability of the erythrocyte membrane.
Bjelaković
Gordana
G
Institute of Biochemistry, Medical Faculty, University of Nis, Serbia.
Stojanović
Ivana
I
Jevtović-Stoimenov
Tatjana
T
Kostić
Gordana
G
Sokolović
Dusan
D
Ilić
Mirjana
M
Bjelaković
Ljiljana
L
D000975:Antioxidants / Q000502:physiology*; D001663:Bilirubin / Q000502:physiology*; D004912:Erythrocytes / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D006932:Hyperbilirubinemia / Q000097:blood*; D007231:Infant, Newborn / Q000097:blood*; D016014:Linear Models; D008315:Malondialdehyde / Q000097:blood; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000097:blood*; D000097667:Polyamine Oxidase
D000975:Antioxidants; D001663:Bilirubin; D008315:Malondialdehyde; D000587:Oxidoreductases Acting on CH-NH Group Donors; D000097667:Polyamine Oxidase