Per- and polyfluoroalkyl substances (PFAS), manmade chemicals that accumulate in the body over time, have been linked to liver disease and cancer, but it is not yet clear how they cause damage. Researchers from the Keck School of Medicine of USC used a lab model of the human liver to analyze changes at the cellular level, finding that some PFAS triggered fat accumulation and others caused cell damage linked to cancer. The study was just published in the journal Environment International .
The liver removes toxins from the blood, making it particularly vulnerable to PFAS, which enter the body through contaminated drinking water, food packaging and consumer products. While previous research has linked PFAS to liver problems in people and animal models, pinpointing the underlying biology has been more difficult.
In the present study, the researchers used spheroids, sophisticated 3D models that recreate the structure of the liver using cells from human donors. This approach gives a detailed view of cellular interactions and allows insights to move faster toward clinical applications.
"We developed a new framework to analyze how PFAS affect the liver on a cellular and molecular level, where we exposed human liver cells to four types of PFAS in the lab, then measured changes in gene expression and fat buildup," said Ana Maretti-Mira, PhD , assistant professor of research medicine at the Keck School of Medicine and the study's senior author.
Each substance had a different effect on liver cells, but all four interfered with immune processes and disrupted communication between cells. Researchers also observed differences in how liver cells from male and female donors responded to PFAS exposure. The findings can help inform clinical trials aimed at reducing the harms of PFAS, but they also highlight the urgent need to limit individual exposure.
The study is part of the Southern California Superfund Research and Training Program for PFAS Assessment, Remediation and Prevention, or ShARP Center , a National Institutes of Health-funded effort that unites USC researchers to advance research and solutions for PFAS contamination.
Understanding the mechanism
To explore the link between PFAS and liver health at the cellular level, the researchers used liver spheroids, miniature models of the liver made from cells of 10 human donors (five male and five female). In the lab, they exposed the spheroids to four types of PFAS commonly found at high levels in the blood: perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS), perfluorooctanesulfonic acid (PFOS) and perfluorononanoic acid (PFNA). Each chemical was tested separately to determine its specific effects on liver cells.
After seven days of exposure, the researchers separated the spheroids into individual cells for analysis. They used single-cell RNA sequencing to analyze gene expression and a dye-based method to measure fat buildup in the spheroids under a microscope.
All four PFAS interrupted cell signaling and immune functions, but exact changes varied from one chemical to the next. Both PFOA and PFHxs increased fat accumulation—PFOA by causing cells to produce more fat and PFHxS by causing cells to retain fat.
"These are different cellular processes with the same result," Maretti-Mira said. "Understanding the exact mechanism is what may ultimately allow us to design targeted interventions."
Both PFOS and PFNA triggered cancer-related changes in cells, but PFNA had a stronger effect, increasing activity in cellular pathways related to inflammation, oxidative stress and DNA repair. Of the cells exposed to PFNA, 61.3% showed gene changes linked to cancer.
The researchers also found that liver cells from male and female donors responded differently to PFAS exposure. PFOA has stronger effects on female liver cells, while PFOS had stronger effects on cells from male donors. These findings suggest that the biological mechanisms of liver damage may vary by sex, which could point to different strategies for treatment.
Reducing harm from PFAS
A better understanding of how PFAS harm the liver is an important step toward developing targeted treatments. Some drugs, including those that regulate how the liver processes fat, are already approved by the U.S. Food and Drug Administration and could soon be tested for treating PFAS-related liver damage.
The findings also underscore the need to limit PFAS exposure, both through stronger regulations and individual actions, Maretti-Mira said.
"These chemicals change our bodies and we cannot wait for government regulations to take effect. Be aware of how you can be exposed and try to limit that exposure," she said, including drinking only filtered water and avoiding nonstick cookware.
Maretti-Mira and her colleagues are now analyzing data from a follow-up study that tested the combined effects of PFOA, PFHxS, PFOS and PFNA on human liver cells.
About this research
In addition to Maretti-Mira, the study's other authors are Lucy Golden-Mason, Chikako Matsuba and Yufen Wang from the Department of Medicine, Keck School of Medicine of USC, University of Southern California; Matthew P. Salomon from the Department of Cancer Biology, Keck School of Medicine of USC, University of Southern California; and Veronica Wendy Setiawan and Lida Chatzi from the Department of Population and Public Health Sciences, Keck School of Medicine of USC, University of Southern California.
This research was supported by the National Institute of Environmental Health Sciences Superfund Research Program [P42ES036506]; the National Institutes of Health [P30ES007048, R01DK117004, R01ES030691, R01ES029944, R01ES030364 and U01HG013288]; and the Advancing Tools for Human Early Life-course Exposome Research and Translation Project [874583].
