Effects of Defined Mixtures of Persistent Organic Pollutants (POPs) on Pre-lethal Cytotoxicity in the Human A-498 Kidney Cell Line In Vitro

Mazia Amber,Steven Verhaegen,Lisa Connolly,Karin Elizabeth Zimmer,Hanne Friis Berntsen,Yuling Xie,Erik Ropstad

doi:10.1007/s12403-021-00396-7

Abstract

A total mixture of 29 persistent organic pollutants (POPs) modelled from Scandinavian blood concentrations was used to expose human A-498 kidney cells for 24 h over a concentration range spanning below to above blood level (1/10x, 1x, 50x, 100x, 500x). Its constituent submixtures (PFAA, Br, Cl) and co-mixtures (PFAA + Br, PFAA + Cl, Br + Cl) were also tested. Valinomycin (12 µM) was used as a cytotoxic comparative compound. Cell number (CN), nuclear area (NA), nuclear intensity (NI), mitochondrial membrane potential (MMP), and mitochondrial mass (MM) were assessed using high content analysis (HCA). Only the co-mixtures (PFAA + Cl, PFAA + Br) at 50x and 50x, 500x decreased CN, respectively. NI was increased by the total mixture at 500x and Cl mixture at all concentrations tested. MMP was increased by the total mixture at 100x and 500x, PFAA at 1x, Br + Cl and PFAA + Cl at 100x and 500x, respectively. MM was decreased by the total mixture at 500x. In contrast, valinomycin decreased CN and surviving cells showed a decrease in MMP and an increase in MM. In conclusion, POP exposure altered mitochondrial metabolism and induced cell death via an alternative mechanism to valinomycin. Only specific combinations of individual chemical classes, but not the total mixture, affected cell number.

Highlights

Persistent organic pollutants (POPs) are chemicals that persist in the environment for decades and can bioaccumulate or biomagnify in living organisms
We focused on determining the effects of complex mixtures of persistent organic pollutants (POPs) on the A-498 human epithelial kidney cell line
MitoTracker ® Orange CMTMRos was used as a mitochondrial membrane potential dye evaluate parameters of mitochondrial function: MMP and mitochondrial mass (MM)

Summary

Introduction

Persistent organic pollutants (POPs) are chemicals that persist in the environment for decades and can bioaccumulate or biomagnify in living organisms. POPs tend to accumulate in the metabolic organs including kidneys and liver which may lead to histological alterations in these organs (Tashla et al.2018). We have previously shown that POP mixtures can have detrimental effects on the health of liver cells (Wilson et al 2016). The kidney, another organ, which plays a major role in excretion, may be a target of cytotoxicity for these compounds. Wild arctic foxes exposed to a cocktail of POPs including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) show signs of kidney and liver damage (Pizzorno 2015). PCBs and OCPs have been found to trigger glomerular lesions in Baltic seals and dilation of glomerular capillaries and mesangial deposits in fish (Bergman et al 2001; Koponen et al 2001)

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Conclusion