ACTIVITY OF HUMAN PLACENTAL PARAOXONASE (PON) THROUGH THE USE OF DIFFERENT SUBSTRATES

DI MARTINO, DEBORAH; RODRIGUEZ, PIUQUE M.; LOSILLA, VANESA; GUIÑAZU ALANIZ, NATALIA LORENA; VERA, BERTA

Mar del Plata

Congreso; Reunión anual de sociedades de biociencias; 2023

Sociedad Argentina de Investigación Clínica

It has been reported that women living close to agricultural areas at the Alto Valle of Río Negro and Neuquén region are at risk of organophosphate pesticides (OP) exposure. Paraoxonases (PONs) are enzymes linked to OP detoxification and oxidative stress defense. Three isoforms are known: PON1, PON2 and PON3 with dissimilar activities towards bioactivated OP, which also exhibit arylesterase and thiolactonase activity. The objective was to evaluate the PON expression and activity in human placenta. Expression was evaluated by qPCR and western blot. The hydrolase activity of PON was evaluated using different substrates, by 4-nitrophenyl acetate, and phenyl acetate the arylesterase activity and with dihydrocumarin the lactonase activity evaluate. Substrate-activity curves were performed, and concentrations selected were 2.5 mM (4-nitrophenyl acetate), 1 mM (phenyl acetate) and 4 mM (dihydrocumarin). Since PON activity is calcium dependent different concentrations of EDTA were used to evaluate the inhibition of the enzymatic activity. Six (6) placentas were analysed. The placenta showed the expression of PON2 and PON3 transcripts. PON2 protein expression was confirmed by Western blot. The placenta demonstrated arylesterase and lactonase activities. For arylesterase the results obtained indicate a mean activity (mean ± SD, umoles/min/ug prot) of 31.93 ± 12.48 for 4-nitrophenyl acetate and 33.93 ± 16.02 for phenyl acetate. The mean lactonase activity was 45.34 ± 17.61 umoles/min/ug prot for dihydrocumarin. The results obtained clearly indicate the presence of active PON isoforms in the placenta, with both arylesterase and lactonase activities. Since the PON family participates in the protection against oxidative damage and lipid peroxidation, the modulation of stress, the detoxification of reactive molecules, the implication of PON regulation by chemical contaminants in the placenta is worthy to be studied.