SP221
BPA CONTENTIN HEMODIALYSIS MEMBRANES IMPACT ON REDOX STATUS AND INFLAMMATION

Introduction and Aims: Exposure to bisphenol A (BPA) from plastics and resins is associated with kidney and cardiovascular injury in human and animals studies suggesting a causative link. Health authorities allow BPA use because its rapid renal excretion in healthy humans, but dialysis patients have negligible renal excretion and therefore may accumulate BPA. In a cross-over clinical trial using dialysis membranes containing BPA (polysulfone) or not (polynephron) ,we have recently shown that BPA-containing membranes are associated with higher BPA plasma concentrations and inflammatory biomarkers (JASN 2016). The present work further extends the relationship between BPA and inflammation as well as the potential molecular targets and mechanisms of BPA-associated toxicity in the hemodialysis patient.

Methods:Population studied: . Plasma measurement of inflammation and redox state-related biomarkers by immunoassays. Additionally gene expression by qPCR. were evaluated in peripheral blood mononuclear cells (PBMCs) In vitro analysis : PBMCs obtained from healthy donors stimulated with BPA or dialyzer membranes fibers.Parameters associated with inflammation, oxidative stress and mitochondrial function were examined.Apoptosis and mitochondrial function was also assessed in proximal tubular epithelial call (PTEC) in response to BPA.

Results: A close correlation between pro-inflammatory biomarkers such as C-reactive protein, and interleukin-6 (but not Tweak) and bisphenol A plasma levels was found. We also noted an increase on Nrf2 (key factor on antioxidant response), HO-1 and Prx1 in blood cells of patients with polysulfone (higher BPA levels). In the experiments incubating PBMCs with small polysulfone fiber pieces, there was an increase in BPA release into the supernatant in a dose-dependent manner (e.g. 10 mg polysulfone released 15 ng/ml BPA at 24h.). In addition, a dose-dependent increase in pro-inflammatory cytokines release was also noted. As an example, 10 mg polysulfone fibers per 10E6 cells (but not polynephron fibers) caused a 3.5 fold TNF-α increase and 4.5 fold IL6 increase at 24 h. Similarly, mRNA expression for those cytokines increased up to 22-fold TNF-α and 16-fold IL-6 with 10 mg of polysulfone. Overexpression of oxidative stress response- related genes such as Nrf2, HO-1, NQO-1, SOD-1 and catalase was also noted in response to an increase of fiber amount in cultures. Additional experiments were carried out incubating increasing doses of BPA (in the range found in HD) with PBMCs, examining the cytokine released into the culture mediun. A dose dependent cytokine release was also noted. As a example, 137 ng/ml BPA elicited a 20 fold mRNA TNFα. Some experiments were also performed incubating tubular epithelial cells (HK2 cell line) with BPA. In brief , BPA elicited intra-mitochondrial ROS production and mitochondrial depolarization.

Conclusions: Our results indicate that in patients on hemodialysis, polysulfone membranes release BPA to the medium leading to a higher plasma concentration. This augmentation was associated to the release of proinflammatory cytokines and a pro oxidant state, both in vivo and in vitro .The mechanisms involved seem to be related with mitochondrial depolarization and oxidative stress.