Biology subjects

Schlezinger, J.

Publications and source records attributed to Schlezinger, J..

6 recordsLinked to original sources

bioRxiv2026

PPARα genotype impacts bone quality and perfluorooctanoic acid-induced effects

Per- and polyfluoroalkyl substances (PFAS) are significant environmental contaminants that cause a number of adverse human health effects. Studies increasingly link exposure to PFAS with disruptions in osteoblast and osteoclast differentiation and function, reduced bone mineral density (BMD), and negative impacts on skeletal structure. In vivo studies on the effects of PFAS on bone health remain limited, with none investigating the impacts in mice expressing human peroxisome proliferator activated receptor (PPAR). Given PFASs ability to interact with the peroxisome proliferator activated receptor family and their importance in bone health, we present work investigating the effects of perfluorooctanoic acid (PFOA) exposure and PPAR genotype (mouse, human or null) on bone quality across two exposure periods (6 and 14 weeks) in mice fed a human relevant diet. In both exposure scenarios, the serum PFOA concentrations were {approx} 50 {micro}g/mL, similar to a highly exposed fluorochemical worker. We began by establishing the liver phenotype across exposures and genotypes. Across genotypes and exposure timing, PFOA increased liver to body weight ratios, but the contribution of increased triglycerides was reduced at 14 weeks. Exposure to PFOA increased hepatic PPAR-dependent gene expression (Acox) in both sexes and exposure periods, but only in mPPAR mice. The effect of PFOA on hepatic CAR- and PXR-dependent gene expression (Cyp2b10 and Cyp3a11, respectively) was more complex; with sex-, genotype-, and exposure timing-dependent differences. Trabecular and cortical bone parameters were not impacted by PFOA treatment, but genotype was a significant factor across sexes and exposure periods. mPPAR mice had higher trabecular tissue mineral density at 9 and 20 weeks of age than hPPAR mice, but the lower trabecular bone volume evident at 9 weeks of age resolved at 20 weeks of age. mPPAR mice had higher cortical tissue mineral density and bone volume than hPPAR and PPAR null mice. Analysis of serum markers of osteoblast and osteoclast activity following 14 weeks of exposure to PFOA revealed a PPAR-dependent decrease in PINP but no effect on CTX. Our results reveal the importance of PPAR genotype for bone quality parameters and emerging evidence of the effect of PFOA on osteoblast activity. Given the unusual mouse bone quality model (sv/129 background), this work underscores the need for future in vivo research shifts to investigate the effects of PFAS on in bone quality.

pharmacology and toxicology↗

bioRxiv2024

PFAS Compounds PFOA and Gen X are Teratogenic to Sea Urchin Embryos

Per-and polyfluorinated substances (PFAS) are synthetic chemicals that are used to make fluoropolymer coatings found in many products, such as non-stick pans, clothing, cosmetics, and food packaging. These highly persistent molecules are known as "forever chemicals" since they neither degrade environmentally nor break down enzymatically within biological systems. PFAS compounds readily contaminate water sources, and as a result, certain PFAS molecules have bioaccumulated in exposed species including humans. The purpose of this study was to define the effect of two PFAS molecules, the ostensibly more toxic perfluorooctanoic acid (PFOA) and the more recent, reportedly safer chemical hexafluoropropylene oxide dimer acid (Gen X), on the development of Lytechinus variegatus sea urchin embryos. We examined the effects of PFOA and Gen X on development and patterning using morphological analysis, immunostaining, HCR-FISH, and Particle Image Velocimetry (PIV). The results show that both PFAS compounds are teratogenic to sea urchin embryos. PFOA and Gen X each function at different intervals during development and provoke distinct phenotypic and gene expression outcomes. Despite beliefs that Gen X would be a safer alternative, our findings indicate that Gen X has earlier and more severe effects on endomesoderm and dorsal-ventral axis specification, neural development and function, and pattern formation compared to PFOA. These results illustrate the dangerous teratogenic potential of environmentally accumulating PFAS like Gen X, underscoring the negative ecological implications that accompany continuing commercial and industrial use of PFAS in the absence of remediation strategies. HIGHLIGHTSO_LIGen X is more teratogenic in sea urchins than PFOA C_LIO_LIGen X acts earlier than PFOA and perturbs axial and germ layer specification C_LIO_LIEach PFAS reduces neural numbers and perturbs ciliary behavior and swimming C_LI

developmental biology↗

bioRxiv2021

Predicting the Effects of Per- and Polyfluoroalkyl Substance Mixtures on Peroxisome Proliferator-Activated Receptor Alpha Activity in Vitro

Human exposure to per- and polyfluoroalkyl substances (PFAS) is ubiquitous, with mixtures of PFAS detected in drinking water, food, household dust, and other exposure sources. Animal toxicity studies and human epidemiology indicate that PFAS may act through shared mechanisms including activation of peroxisome proliferator activated receptor (PPAR). However, the effect of PFAS mixtures on human relevant molecular initiating events remains an important data gap in the PFAS literature. Here, we tested the ability of modeling approaches to predict the effect of diverse PPAR ligands on receptor activity using Cos7 cells transiently transfected with a full length human PPAR (hPPAR) expression construct and a peroxisome proliferator response element-driven luciferase reporter. Cells were treated for 24 hours with two full hPPAR agonists (pemafibrate and GW7647), a full and a partial hPPAR agonist (pemafibrate and mono(2-ethylhexyl) phthalate), or a full hPPAR agonist and a competitive antagonist (pemafibrate and GW6471). Receptor activity was modeled with three additive approaches: effect summation, relative potency factors (RPF), and generalized concentration addition (GCA). While RPF and GCA accurately predicted activity for mixtures of full hPPAR agonists, only GCA predicted activity for full and partial hPPAR agonists and a full agonist and antagonist. We then generated concentration response curves for seven PFAS, which were well-fit with three-parameter Hill functions. The four perfluorinated carboxylic acids (PFCA) tended to act as full hPPAR agonists while the three perfluorinated sulfonic acids (PFSA) tended to act as partial agonists that varied in efficacy between 28-67% of the full agonist, positive control level. GCA and RPF performed equally well at predicting the effects of mixtures with three PFCAs, but only GCA predicted experimental activity with mixtures of PFSAs and a mixture of PFCAs and PFSAs at ratios found in the general population. We conclude that of the three approaches, GCA most accurately models the effect of PFAS mixtures on hPPAR activity in vitro. HighlightsO_LIPerfluorinated carboxylic acids are full human PPAR agonists C_LIO_LIPerfluorinated sulfonic acids are partial human PPAR agonists C_LIO_LIGCA predicts human PPAR activity for mixtures of full and partial agonists C_LIO_LIGCA predicts human PPAR activity for mixtures of agonists and competitive antagonists C_LIO_LIGCA accurately predicts human PPAR activity in response to PFAS mixtures C_LI

pharmacology and toxicology↗

bioRxiv2021

Tributyltin Protects Against Ovariectomy-Induced Trabecular Bone Loss in C57BL/6J Mice with an Attenuated Effect in High Fat Fed Mice

Risk factors for poor bone quality include estrogen loss at menopause, a high fat diet and exposures to drugs/chemicals that activate peroxisome proliferator activated receptor gamma (PPAR{gamma}). We observed that the PPAR{gamma} and retinoid X receptor dual ligand, tributyltin (TBT), repressed periosteal bone formation but enhanced trabecular bone formation in female C57BL6/J mice. Here, we examined the interaction of diet, ovariectomy (OVX) and TBT exposure on bone structure. C57BL/6J mice underwent either sham surgery or OVX at 10 weeks of age. At 12 weeks of age, they were placed on a low (10% kcal) or high (45% kcal) fat, sucrose-matched diet and treated with Vh or TBT (1 or 5 mg/kg) for 14 weeks. OVX increased body weight gain in mice on either diet. TBT enhanced body weight gain in intact mice fed a high fat diet, but decreased weight gain in OVX mice. Elemental tin concentrations increased dose-dependently in bone. TBT had marginal effects on cortical and trabecular bone in intact mice fed a low- or high- fat diet. OVX caused a reduction in cortical and trabecular bone, regardless of diet. In high-fat fed OVX mice, TBT further reduced cortical thickness, bone area and total area. Interestingly, TBT protected against OVX-induced trabecular bone loss in low fat fed mice. The protective effect of TBT was nullified by the high fat diet and accompanied by a significant decrease in serum bone formation markers. Our novel observations will provide new information on basic bone biology, potential therapeutic targets and toxicological pathways.

pharmacology and toxicology↗

bioRxiv2020

Perfluorooctanoic acid activates multiple nuclear receptor pathways and skews expression of genes regulating cholesterol homeostasis in liver of humanized PPARα mice fed an American diet

Humans are exposed to per- and polyfluoroalkyl substances (PFAS) in their drinking water, food, air, dust in their homes, and by direct use of consumer products. Increased concentrations of serum total cholesterol and low density lipoprotein cholesterol are among the endpoints best supported by epidemiology. The objectives of this study were to generate a new model for examining PFAS-induced dyslipidemia and to conduct molecular studies to better define mechanism(s) of action. We tested the hypothesis that PFOA exposure at a human-relevant level dysregulates expression of genes controlling cholesterol homeostasis in livers of mice expressing human PPAR (hPPAR). Female and male hPPAR and PPAR null mice were fed a diet based on the "What we eat in America" analysis and exposed to perfluorooctanoic acid (PFOA) in drinking water (8 {micro}M) for 6 weeks. This resulted in a serum PFOA concentration of 48 g/ml. PFOA increased liver mass, which was associated with histologically-evident lipid accumulation. PFOA induced PPAR and constitutive androstane receptor target gene expression in liver. Expression of genes in four pathways regulating cholesterol homeostasis were also measured. PFOA decreased expression of Hmgcr in a PPAR-dependent manner. PFOA decreased expression of Ldlr and Cyp7a1 in a PPAR-independent manner. Apob expression was not changed. Gene expression in females appeared to be more sensitive to PFOA exposure than in males. This novel study design (hPPAR mice, American diet, long term exposure) generated new insight on the effects of PFOA on cholesterol regulation in the liver and the role of hPPAR.

pharmacology and toxicology↗

bioRxiv2019

A Data-Driven Transcriptional Taxonomy of Adipogenic Chemicals to Identify Emerging Metabolic Health Threats

BackgroundChemicals in disparate structural classes activate specific subsets of PPAR{gamma}s transcriptional programs to generate adipocytes with distinct phenotypes. ObjectivesOur objectives were to 1) establish a novel classification method to predict PPAR{gamma} ligands and modifying chemicals, and 2) create a taxonomy to group chemicals based on their effects on PPAR{gamma}s transcriptome and downstream metabolic functions. We tested the hypothesis that environmental adipogens highly ranked by the taxonomy, but segregated from therapeutic PPAR{gamma} ligands, would induce white but not brite adipogenesis. Methods3T3-L1 cells were differentiated in the presence of 76 chemicals (negative controls, nuclear receptor ligands known to influence adipocyte biology, potential environmental PPAR{gamma} ligands). Differentiation was assessed by measuring lipid accumulation. mRNA expression was determined by RNA-Seq and validated by RT-qPCR. A novel classification model was developed using an amended random forest procedure. A subset of environmental contaminants identified as strong PPAR{gamma} agonists were analyzed by their effects on lipid handling, mitochondrial biogenesis and cellular respiration in 3T3-L1 cells and human preadipocytes. ResultsWe used lipid accumulation and RNA sequencing data to develop a classification system that 1) identified PPAR{gamma} agonists, and 2) sorted chemicals into likely white or brite adipogens. Expression of Cidec was the most efficacious indicator of strong PPAR{gamma} activation. Two known environmental PPAR{gamma} ligands, tetrabromobisphenol A and triphenyl phosphate, which sorted distinctly from therapeutic ligands, induced white adipocyte genes but failed to induce Pgc1a and Ucp1, and induced fatty acid uptake but not mitochondrial biogenesis in 3T3-L1 cells. Moreover, two chemicals identified as highly ranked PPAR{gamma} agonists, tonalide and quinoxyfen, induced white adipogenesis without the concomitant health-promoting characteristics of brite adipocytes in mouse and human preadipocytes. DiscussionA novel classification procedure accurately identified environmental chemicals as PPAR{gamma} ligands distinct from known PPAR{gamma}-activating therapeutics. The computational and experimental framework has general applicability to the classification of as-yet uncharacterized chemicals.

pharmacology and toxicology↗