Neuromuscular effects of acute 2,4-dichlorophenoxyacetic acid (2,4-D) exposure in dogs

2,4-Dichlorophenoxyacetic acid (2,4-D) was administered once orally to adult female mongrel dogs at 0, 25, 50, 75, 100 or 125 mg/kg of body weight (n = 4 per group). Clinical neurological examinations, electromyography (EMG) and motor nerve conduction velocity measurements were carried out before exposure, and on days 1, 3, 7, 14, 21 and 28 post-exposure. On day 7, two dogs per group were killed. Samples of the medial and lateral plantar nerves were removed for teased fiber and semi-thin section analysis; samples of appendicular muscles were removed for histology and histochemistry. Necropsy included histopathological examination of the brain and spinal cord at multiple levels. Remaining dogs were killed on day 28 and their tissues were processed similarly. Transient generalized myotonic discharges were found in skeletal muscles of dogs receiving 50 mg/kg or more of 2,4-D. A few dogs in the higher dosage groups also had mild muscle stiffness, myotonic dimpling and/or lethargy, lasting up to 3 days post-exposure. Other parameters remained within normal limits.     

Effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on the contractile properties of reinnervated rat skeletal muscle

2,4-Dichlorophenoxyacetic acid (2,4-D), a common herbicide, was administered to rats (100 mg/kg, i.p.) during 24 days to determine whether or not it is toxic to regenerating peripheral nerve and reinnervating muscle. The peroneal nerve was crushed 1 cm proximal to the extensor digitorum longus muscle and recordings made in vivo after 1 to 24 days. Functional reinnervation was observed by day 10 and recovery was similar in rats receiving 2,4-D or vehicle. Distal motor latencies and muscle action potentials returned toward normal during the 24 days in a similar manner in 2,4-D and controls. Isometric twitch tensions per muscle weight on indirect stimulation returned to intact values by 17 days, but in the 2,4-D animals they became larger (P less than 0.01) than controls by day 24. The twitch:tetanus ratios were increased at day 10 and returned toward normal values in the controls but remained increased (P less than 0.01) in the 2,4-D animals at 24 days. Similar results were obtained on direct muscle stimulation. The data suggest that 2,4-D is not toxic to nerve during regeneration or muscle reinnervation in the rat, but that it does affect both twitch and tetanus tensions suggesting proliferation as well as disruption of myofibrils.     

2,4-Dichlorophenoxyacetic acid (2,4-D) reduces acetylcholinesterase activity in rat muscle

A single dose (200 mg/kg body weight, i.p.) of 2,4-dichlorophenoxyacetic acid (2,4-D), commonly used as a herbicide, caused significant decreases in acetylcholinesterase (AChE) activity in diaphragm and other muscles of the rat. The 4S, 10S, and 16S forms of AChE were affected. The effect was maximal 15 to 24 h after injection. Choline acetyltransferase (CAT) activity was not affected. Neither AChE nor CAT activities changed in sciatic nerve from 2,4-D-treated animals. Spontaneous locomotor activity decreased dramatically 4 h after 2,4-D treatment. Myotonia that was present 1.5 h after 2,4-D injection became maximal at 2 to 6 h. Twenty-four hours after drug injection, when animals were recovering from myotonia, spontaneous locomotor activity was still depressed to 50% of control values. Prolonged distal motor latencies were observed 15 to 24 h after drug administration. AChE activity and spontaneous locomotor activity returned to control values at 48 h. Thus, 2,4-D causes a decrement of end-plate AChE, as well as behavioral and electrophysiologic changes. Decreased activity of AChE may be an early step in development of the myopathy that occurs after large dose 2,4-D.     

2,4-Dichlorophenoxyacetic acid (2,4-D) does not cause polyneuropathy in the rat

2,4-Dichlorophenoxyacetic acid (2,4-D), a component of Agent Orange, was injected intraperitoneally into adult male Fisher rats for 3–12 weeks. During the period of study gait and toe-spreading reflexes remained normal and distal motor latencies, motor and mixed nerve conduction velocities and amplitudes remained similar (P > 0.05) in animals receiving 2,4-D or vehicle. This study suggests that 2,4-D is not toxic to peripheral nerves in the rat.     

Changes in serotonin-immunoreactivity in the dorsal and median raphe nuclei of rats exposed to 2,4-dichlorophenoxyacetic acid through lactation

Comparison of serotonin-immunoreactive (SER-IR) neurons in nucleus raphe dorsalis (NRD) and median raphe nucleus (MRN) of 25-d-old rat pups exposed to 70 mg/kg/d 2,4-dichloro-phenoxyacetic acid through mothers milk and control pups was made using an immunohistochemical analysis. Significant 2,4-D-treatment-related increase in size and density of SER-IR neuronal somata as well as in fiber length were observed. We postulate that exposure to 2,4-dichlorophe-noxyacetic acid on the first day of life would modify the synthesis of 5-HT or the maturation of the brain serotonergic system.     

2,4-dichlorophenoxyacetic acid through lactation induces astrogliosis in rat brain

Comparison of astroglial immunoreactivity in mesencephalon, cerebellum, and hippocampus of 25-d-old rat pups exposed to 2,4-dichlorophenoxyacetic acid (2,4-D) through the mother's milk was made using a quantitative immunohistochemical analysis. A glial reaction was detected at the level of serotonergic nuclei and extreme astrogliosis in the hippocampus and cerebellum. A quantitative analysis of reactive astrocytes was performed by using GFAP and S-100 protein as specific markers. The study showed a significant increase in their number, size, number of processes, and density of immunostaining in 2,4-D-exposed animals. Exposure to 2,4-dichlorophenoxyacetic acid on the first days of life modifies the astroglial cytoarchitecture in parallel to previously described neuronal changes.     

Asymmetrical development of the monoamine systems in 2,4-dichlorophenoxyacetic acid treated rats

The purpose of this study was to determine whether the regional brain biogenic amine levels in adult rats were altered by pre- and post-natal exposure to 2,4-dichlorophenoxyacetic acid (2,4-D). Pregnant rats were daily orally exposed to 70 mg/kg per day of 2,4-D from gestation day (GD) 16 to post-partum day (PPD) 23. After weaning, the pups were assigned to one of two subgroups: T1 fed with untreated diet up to post-natal day (PND) 90 and T2 (maintained with 2,4-D diet up to PND 90). In addition, we wanted to know the effect of 2,4-D on lateralization in the monoamine systems of the basal ganglia of these adult rats and whether there was any correlation with the behavioral developmental pattern previously reported by us. In this study the content of noradrenaline (NA) was significantly increased in substantia nigra (SN) while it decreased in cerebellum in male and female rats of T2 group. The decreased dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovallinic acid (HVA) contents in cerebellum, midbrain, ventral tegmental area (VTA) and prefrontal cortex (PFc) showed an alteration in the mesocorticolimbic system. However, an increase of DA in SN and of DOPAC and HVA in nucleus accumbens (NAc) in both sexes and of DA and DOPAC (only in females) in striatum was detected. The contents of serotonin (5-hydroxytryptamine, 5-HT) were significantly increased in both sexes in PFc, striatum (St), midbrain, SN and cerebellum. Variations of any monoamine levels in NAc and VTA were determined. T1 rats were irreversibly altered: a diminution in DA and/or DOPAC levels in PFc, midbrain, VTA and cerebellum was determined. Indolamines of these rats were increased in both sexes in PFc and St. There was also a large increase in 5-HT levels in midbrain of male rats. Although no changes in the dopaminergic system with respect to their control values in any side of these brain structures were observed, DA and DOPAC levels were found to be decreased in the right side with respect to the left side in striata and accumbens nuclei in T2 female rats supporting the behavioral rotation previously registered by us in these rats. In addition, the increased 5-HT content detected in both the right and left striata observed in this study could be the answer to the behaviors observed and to the early alterations in dopamine in basal ganglia by 2,4-D in neonatal exposed rats, mediated by a serotonergic modulation on the dopaminergic system.     

Study of tyrosine hydroxylase immunoreactive neurons in neonate rats lactationally exposed to 2,4-dichlorophenoxyacetic Acid

Dopaminergic neurons from the midbrain nuclei substantia nigra (SN; A9) and ventral tegmental area (VTA; A10) were investigated by tyrosine hydroxylase (TH) immunostaining in neonate rat brains exposed to 2,4-dichlorophenoxyacetic acid (2,4-D) through lactation. Dorsal raphe serotonin (5-HT) projections to SN and VTA were also studied by 5-HT transporter (5-HTT) immunostaining and results were quantified by image analysis. Twenty-five-day-old pups exposed to 2,4-D through mothers milk were used. Dams were intraperitoneally administered 70 or 100mg/kg/day of 2,4-D from the 9th to the 25th postpartum day. After 100mg/kg of 2,4-D exposure, a 25% diminution in the SN and a 33% diminution in the VTA neurons' TH immunostaining along with a significantly 5-HT fiber density diminution were observed. The present work supports previous reports which suggest that exposure to 2,4-D during development has multiple effects on CNS.     

Melatonin decreases the oxidative stress produced by 2,4-dichlorophenoxyacetic acid in rat cerebellar granule cells

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most widely used herbicides due to its relatively moderate toxicity and to its biodegradability in the soil. In toxic concentrations, 2,4-D displays strong neurotoxicity, partly due to generation of free radicals. Since melatonin has remarkable antioxidant properties, the objective of this study was to assess to what extent it was effective in preventing the 2,4-D effect on redox balance of rat cerebellar granule cells (CGC) in vitro. Cellular viability, generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), reduced glutathione (GSH) levels, and the activities of the antioxidant enzymes Cu/Zn-superoxide dismutase (Cu/Zn-SOD), Mn-SOD, selenium-glutathione peroxidase (Se-GPx) and catalase (CAT) were measured in CGC exposed to 2,4-D and/or melatonin for 48 h. In CGC cultures exposed to 2,4-D, cell viability, GSH levels and CAT activity decreased significantly whereas ROS generation and Se-GPx activities were augmented. Except for Se-GPx activity, all these changes were counteracted by the concomitant addition of 0.1 or 0.5 mM melatonin. In addition, incubation of CGC with melatonin alone resulted in augmentation of cell viability, GSH levels and Se-GPx activity. RNS generation and SOD activity remained unaffected by either treatment. Since melatonin was able to counteract most of redox changes produced by 2,4-D in CGC in culture, the experimental evidence reported further support the efficacy of melatonin to act as a neuroprotector.     

The action of the herbicide 2,4-dichlorophenoxyacetic acid on the isolated sciatic nerve of the frog (Rana ridibunda)

The isolated sciatic nerve of the frog was used to assess the effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on the peripheral nervous system. For each experiment, both sciatic nerves were used. The evoked compound action potentials of the nerves were monitored for over 48 h as an indication of their viability. The viability of nerve incubated in control saline was compared to the viability of the nerve incubated in saline where 2,4-D was diluted. The minimum effective concentration (minEC) of 2,4-D was estimated to be between 2 and 4 mM.     

Morphological study of 5-HT neurons and astroglial cells on brain of adult rats perinatal or chronically exposed to 2,4-dichlorophenoxyacetic acid

2,4-D is a chlorophenoxyherbicide used worldwide. We have studied the morphological alterations of 5-HT neurons and glial cells in the mesencephalic nuclei of adult rats exposed to 2,4-D both perinatally (during pregnancy and lactation) and chronically (during pregnancy, lactation and after weaning) with quantitative methods. Pregnant rats were daily exposed to 70 mg/kg of 2,4-D from gestation day (GD) 16 to post-natal day (PND) 23 through diet. After weaning, pups were assigned to one of two sub-groups: T1 (fed with untreated diet until PND 90) and T2 (maintained with 2,4-D diet until PND 90). Brain sections were immunocytochemically stained using polyclonal anti-5-HT, anti-GFAP and anti-S-100 protein antibodies as cells markers. 2,4-D exposure during pregnancy and lactancy (T1 group) produced an increase in 5-HT neuronal area and immunoreactivity (IR) in the mesencephalic nuclei studied. However, with the chronical 2,4-D exposure (T2 group) only the 5-HT neuronal area from the dorsal raphe nucleus (DRN) was increased, suggesting an adaptable response of 5-HT neurons in median raphe nucleus (MRN). The presence of reactive astrocytes in mesencephalic nuclei and in hippocampus were also different for the two 2,4-D exposure designs, showing the existence of a correspondence between neuronal changes and astrogliosis. Results support evidences that 2,4-D alters the serotoninergic system and that 5-HT neurons of each mesencephalic nuclei show different responses to the 2,4-D exposure designs which are parallel to astrogliosis.     

Changes in fatty acid composition in myelin lipids after 2,4-dichlorophenoxyacetic butyl ester treatment

Previous studies have shown that 2,4-Dichlorophenoxyacetic butyl ester (2,4-D b.e.) causes hypomyelination in chicks born from eggs externally treated and alters the myelin chemical composition. In this paper the effect of 2,4-D b.e. on myelin phospholipid and fatty acid composition has been examined. The results of our investigations show significant variations in the phospholipid composition, with the phosphatidyl inositol content increased and sphingomyelin and phosphatidyl ethanolamine contents diminished. The fatty acid pattern of the individual myelin lipids is also significantly altered, with an important reduction of long chain fatty acids and an increase of saturated fatty acids. The observed changes in the chemical composition implicate alterations in the intrinsic properties of this membrane.     

Elektronenmikroskopische Befunde bei experimenteller Myopathie durch 2,4-Dichlorphenoxyacetat (2,4-D) beim Warmblüter

Zusammenfassung Die myopathischen Frühveränderungen im Anschluß an die intraperitoneale Injektion von 300 mg/kg 2,4-Dichlorphenoxyacetat (2,4-D) werden am kontrahiert- und am relaxiert-fixierten Skeletmuskel der Ratte elektronenmikroskopisch untersucht. Dabei zeigen rote und weiße Muskelfasern unterschiedliche Strukturveränderungen. In den roten Fasern beobachtet man innerhalb von 2 Std p. i. eine Schwellung der Mitochondrien und eine Zunahme des Glykogengehalts. Diese Veränderungen remittieren entweder innerhalb von 6 Std p. i., oder sie leiten zu degenerativen Mitochondrienveränderungen mit Bildung sog. Myelinfiguren über. Myofibrillenläsionen werden während dieser Stadien in den roten Fasern nicht beobachtet. Dagegen zeigen weiße Fasern im kontrahierten Zustand innerhalb von 2 Std p. i. herdförmige Läsionen einzelner Sarkomere. Im Herdbereich kommen Erweiterungen des sarkoplasmatischen Reticulums vor, sind jedoch nicht obligat vorhanden. Der Glykogengehalt der weißen Fasern ist erniedrigt. Ausgedehntere Myofibrillenläsionen treten innerhalb von 12–24 Std p. i. auf. Auch hiervon scheinen bevorzugt weiße Fasern betroffen zu sein. Ein Vergleich der 2,4-D- mit der Corticosteroidmyopathie (Triamcinolon) ergibt Hinweise, daß bei Myopathieformen mit initial gestörtem Glykogenstoffwechsel die Mitochondrienproliferation die primäre morphologische Reaktionsform der Muskelzelle darstellt. Dieser Vorgang leitet entweder die Remission ein oder er führt zur irreversiblen Mitochondriendegeneration, an welche sich die Läsion der Myofibrillen anschließt. Aus diesen Befunden wird gefolgert, daß eine sekundäre Störung des oxydativen Stoffwechsels der Myofibrillenläsion unmittelbar vorausgeht. — Die Befunde zeigen ferner, daß Muskelkontraktion die Entstehung der Myofibrillenläsionen fördert. Veränderungen an Zellkernen und an den transversalen Tubuli sind kontraktionsbedingt und daher nicht als pathologische Zeichen zu betrachten. Die Beziehungen der 2,4-D-Myopathie zu anderen primären Myopathieformen des Menschen und der Tiere werden erörtert.

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Electron microscopic findings in 2,4-dichlorophenoxyacetate (2,4-D) induced myopathy in mammalsOn the development of early myopathic changes

Summary An electron microscopic study of myopathic changes in relaxed and contracted skeletal muscle was undertaken in rats given intraperitoneal injections of 2,4-dichlorophenoxyacetate (2,4-D; 300 mg/kg). In red fibers mitochondrial swelling and an increase in glycogen content can be seen within 2 hours of the injection. Within 6 hours these changes either return to normal or lead to mitochondrial degeneration with formation of so-called myelin bodies. Myofibrillar lesions were not found in red fibers during these stages. In contracted white fibers, within 2 hours of the injection, lesions of single sarcomeres are observed with and without dilatations of the sarcoplasmic reticulum. This indicates that the alterations of the sarcoplasmic reticulum probably are secondary to the myofibrillar lesions. The glycogen content of white fibers is decreased. More extensive lesions of myofibrils are observed within 12 to 24 hours of the injection. The findings suggest that in this type of disorder of glycogen metabolism mitochondrial proliferation represents the primary reaction of the muscle cell to the noxious agent. Similar conclusions can be reached for corticosteroid-induced myopathies (Triamcinolone) which, by their histochemical characteristics, are closely related to the myopathy resulting from the treatment with 2,4-D. Mitochondrial proliferation may either return to normal or proceed to irreversible degeneration of mitochondria with a consecutive loss of myofibrils. It is concluded from these findings that myofibrillar lesions are due to a secondary disorder of the oxidative metabolism in the muscle cell. — Muscle contraction enhances the development of myofibrillar lesions. Changes in the shape of cell nuclei and in the width of the transverse tubuli are shown to be dependent on contraction; they cannot be regarded as pathological signs. The relations of the myopathy induced by 2,4-D to other primary myopathies in man and animals are discussed.

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft. — Ein Teil der Ergebnisse wurde während der 13. Jahrestagung der Vereinigung Deutscher Neuropathologen und Neuroanatomen am 12.–14. Oktober 1967 in Düsseldorf vorgetragen.     

Effects of 2,4-dichlorophenoxyacetic acid on central nervous system of developmental rats. Associated changes in ganglioside pattern

Neonate rats were treated with 2,4-dichlorophenoxyacetic acid (2,4-D) from the 7th or 12th until the 17th or 25th postnatal day. Two drug dosages were used: 70 and 100 mg/kg body weight of 2,4-D. At the 17th day of age, no changes were observed in body weight, protein and DNA content. However, 25-day-old treated pups showed diminutions in body and brain weight, protein and DNA levels, depending on doses and period of treatment. With respect to ganglioside levels, few changes were observed in treated animals until the 17th day of age. However, at the 25th day, with higher dose and longer treatment a diminution in all parameters analyzed was observed. These results suggest a delay in CNS development when pups were exposed to a very severe chemical injury with 2,4-D. On the other hand, when the chemical injury was not too severe, the brain would be capable to trigger biochemical mechanisms producing a plasticity response which is expressed as changes in ganglioside content and composition.     

Histochemische und morphologische Befunde bei experimenteller Myopathie durch 2,4-Dichlorphenoxyacetat (2,4-D) beim Warmblüter

Zusammenfassung Durch Injektion von 2,4-Dichlorphenoxyacetat (2,4-D) läßt sich an Ratten eine Myopathie erzeugen. Im akuten Stadium-charakterisiert durch die myotone Reaktion-zeigt der Skeletmuskel histochemisch eine selektive Hemmung der Phosphorylase in den dicken (Typ 2-) Muskelfasern, während die Transglucosidase-Aktivität der dünnen (Typ 1-) Fasern erhalten bleibt. Die Hemmung der Phosphorylase in den dicken Fasern entspricht ihrem niedrigeren Gehalt an mitochondrial gebundenen oxydativen Enzymen.-Nach mehrtägiger Behandlung wird sowohl die Phosphorylase in den dicken als auch die Transglucosidase in den dünnen Fasern gehemmt. Außerdem zeigen sich jetzt lichtmikroskcpisch-morphologisch Faserschädigungen wie gestörte Mitochondrienverteilung, Faserschwellung und Fasernekrose mit unspezifischen Gewebsreaktionen. Erst mit diesem Strukturzerfall ändern sich auch Verteilung und Aktivität der oxydativen Enzyme und der ATPase. Pathogenetisch dürfte die selektive Phosphorylasehemmung in den dicken Fasern die Primärschädigung darstellen. Damit ergeben sich Beziehungen dieser Myopathie zur McArdleschen Erkrankung und zu den Myopathien nach Behandlung mit fluorierten Corticosteroiden.

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Histochemical and morphological findings in experimental 2,4-Dichlorophenoxyacetate (2,4-D) myopathy in warmblooded animals

Summary Injection of 2,4-Dichlorophenoxyacetate (2,4-D) gives rise to a myopathy in rats. In the acute state-characterized by a myotonic response-skeletal muscle histochemically shows a selective inhibition of phosphorylase activity in white (type 2-) muscle fibers; transglucidase activity in red (type 1-) fibers remains unchanged. It can be shown, that this selective effect on phosphorylase in white fibers is related to their lower content in mitochondrial oxidative enzymes.-Prolonged treatment results in the inhibition of phosphorylase and transglucosidase as well, and in morphologic fiber damage viz. disturbed distribution of mitochondria, cloudy swelling of fibers and fiber necrosis with unspecific histologic reactions. It is at this point that changes in the distribution and activities of oxidative enzymes and of ATPase occur.-Pathogenetically the selective inhibition of phosphorylase by 2,4-D in white muscle fibers may be regarded to be the primary cause of this myopathy. Its relations to McArdle disease and to myopathy following fluorocorticosteroid treatment in man are discussed.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Experimental myotonia induced in denervated muscles by 2,4-D.

Rats were denervated in one hind limb and injected with 2,4-dichlorophenoxyacetic acid (2,4-D). Isotonic tetanic contractions of the muscles treated with 2,4-D after more than 10 days of denervation revealed prolonged relaxation times similar to those of the intact side and characteristic of clinical myotonia. No myotonic discharges were observed in the muscles denervated for more than 10 days and treated with 2,4-D. The increase in threshold for action potential generation secondary to denervation is suggested as the factor limiting the initiation of the repetitive discharges.     

Detection of small inhibitory effects of acetylsalicylic acid (ASA) by platelet impedance aggregometry in whole blood

Our investigations have demonstrated on 10 volunteers receiving either 500 mg or 100 mg acetylsalicylic acid (ASA) that a low collagen concentration (1 microgram/ml) can best detect the aggregation defect caused by ASA. With the impedance aggregometry the mean inhibition reaches 82% and 52% with 500 mg and 100 mg ASA, respectively. Collagen at higher concentration (3 micrograms/ml) as well as ADP 10 and 25 mumol/l are less sensitive, less than 25% inhibition was recorded. These results suggest that a 1 microgram/ml concentration of collagen is adequate for the control of the ASA effect up to 6 days after intake of 100 mg. Furthermore, the von Willebrand factor (vWF) dependent platelet aggregation induced by 0.6 and 1.0 mg/ml ristocetin was clearly diminished after ASA. Therefore, a ristocetin screening test in whole blood for vWF disorder is possibly distorted when the test is performed within 6 days from ASA administration.     

Altered behaviour in adult mice exposed to a single low dose of DDT and its fatty acid conjugate as neonates

DDT, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane is one of the best-known insecticides which produces neurotoxic syndrome in mammals. DDT is also a world-wide environmental contaminant which is still used in several countries. We have previously reported on pronounced retention of DDT in the neonatal mouse brain. We have also observed that DDT and a DDT metabolite, DDOH, conjugated to palmitic acid (DDOH-PA), which have been found in DDT-treated female rats, affect the muscarinic cholinergic receptors in the brain of the neonatal mouse. We now report that neonatal exposure to a single low oral dose of DDT and DDOH-PA (1.4 mumol/kg b.wt.) also can lead to a permanent hyperactive condition in the mice as adults.     

Metabolic profiling in human SH-SY5Y neuronal cells exposed to perfluorooctanoic acid (PFOA)

Perfluorooctanoic acid (PFOA) is an abundant per- and polyfluoroalkyl substance (PFAS) detected in both indoor and outdoor environments. While studies suggest exposure concerns for humans, studies investigating PFOA-induced neurotoxicity are lacking. To address this gap, we exposed differentiated human SH-SY5Y cells to PFOA (0.1 μM up to 500 μM) at different time points (4, 24, 48, and 72 h) and measured cell viability, Casp3/7 activity, ATP levels, ATP synthase enzyme activity, mitochondrial membrane potential, reactive oxygen species (ROS), oxygen consumption rates for mitochondrial stress test (XFe24 Flux analyzer), glucose utilization, and global metabolome profiles to assess the potential for PFOA-induced neurotoxicity. Treatment with 10 or 100 μM PFOA did not compromise cell viability nor induce cytotoxicity to SH-SY5Y cells over a 48-hour exposure period. However, >250 μM PFOA compromised cell viability, induced cytotoxicity, and induced caspase 3/7 activity at 48 h. ATP levels were reduced in cells treated with 400 μM PFOA for 24 and 48 h, and with 100 μM PFOA and higher at 72 h. ATP synthase activity was inhibited by 250 μM PFOA but was unchanged by PFOA treatment at 200 μM or less. Conversely, mitochondrial membrane potential was reduced by >10 μM PFOA after 24 h. Total ROS was increased with 100 μM PFOA and higher after 4 h of exposure. Several mitochondria-related endpoints (basal respiration, ATP production, maximum respiration) were negatively affected at 250 μM PFOA at both 24- and 48-hour exposure, but were unaltered at concentrations of 100 μM PFOA or less. One exception was mitochondrial spare capacity, which was reduced by 100 μM PFOA after 24-hour exposure. Similarly, glycolysis, glycolytic capacity, and glycolytic reserve of SH-SY5Y cells were not altered by 10 nor 100 μM PFOA. Nontargeted metabolomics was conducted in cells treated with either 10 or 100 μM PFOA for 48 h, as these two concentrations were not cytotoxic and 28 metabolites differed among treatments. Notable was that 10 μM PFOA had little effect on the SH-SY5Y metabolome, and the metabolic profile was not statistically different from media nor solvent controls. On the other hand, 100 μM PFOA shifted the metabolic signature of the neuronal cells, leading to reduced abundance of ATP-related metabolites (adenine, nicotinamide), neurotransmitter precursors (DL-tryptophan, l-tyrosine), and metabolites that protect mitochondria during oxidative stress (betaine, orotic acid, and l-acetyl carnitine). We hypothesize that this metabolic signature may be associated with the reduced mitochondrial membrane potential observed at lower PFOA concentrations. Metabolic shifts appear to precede compromised cell viability, cytotoxicity, and apoptosis. This study generates mechanistic knowledge regarding PFOA-induced neurotoxicity, focusing on mitochondrial oxidative respiration and the neuronal metabolome.