Biology subjects

De Miranda, B. R.

Publications and source records attributed to De Miranda, B. R..

8 recordsLinked to original sources

bioRxiv2026

Metabolism of trichloroethylene following inhalation exposure in mice

Trichloroethylene (TCE) is a pervasive environmental pollutant associated with elevated risk of developing Parkinson's disease (PD). Studies characterizing TCE metabolism in humans indicate that 40 - 75% of the absorbed dose is metabolized, suggesting that TCE toxicity may be attributable to its metabolites. However, there is limited knowledge of TCE metabolite neurotoxicity. We conducted a TCE inhalation study in mice followed by high-resolution mass spectrometry (HRMS) on brain, liver, and blood to identify which TCE metabolites were present following human-relevant TCE exposure. Mice were exposed to 100 ppm TCE for 4 hours. Plasma, brain, and liver were collected from each animal up to 24 hours after exposure. We developed a method capable of detecting TCE metabolites trichloroacetic acid (TCA), dichloroacetic acid (DCA), monochloroacetic acid (MCA), trichloroethanol (TCEOH), trichloroethanol glucuronide (TCEOH-gluc), S-(1,2-dichlorovinyl)glutathione (DCVG), S-(1,2-dichlorovinyl)-L-cysteine (DCVC), N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (NAcDCVC), and untargeted metabolites using a single extraction protocol on a liquid chromatography-based mass spectrometry system (LC-MS/MS). Targeted analysis of TCE-exposed biological samples identified DCA, TCA, and TCEOH-gluc. Untargeted analysis of TCE-exposed mouse brain revealed previously established and novel pathway perturbations associated with TCE exposure. Together, these findings indicate that DCA, TCA, and TCEOH-gluc are the most prevalent TCE metabolites in mice. The novel pathways perturbed by TCE exposure warrant further exploration to better understand the mechanisms underlying the toxicity of TCE and its metabolites

pharmacology and toxicology↗

bioRxiv2024

LRRK2 kinase inhibition protects against Parkinson's disease-associated environmental toxicants

Idiopathic Parkinsons disease (PD) is epidemiologically linked with exposure to toxicants such as pesticides and solvents, which comprise a wide array of chemicals that pollute our environment. While most are structurally distinct, a common cellular target for their toxicity is mitochondrial dysfunction, a key pathological trigger involved in the selective vulnerability of dopaminergic neurons. We and others have shown that environmental mitochondrial toxicants such as the pesticides rotenone and paraquat, and the organic solvent trichloroethylene (TCE) appear to be influenced by the protein LRRK2, a genetic risk factor for PD. As LRRK2 mediates vesicular trafficking and influences endolysosomal function, we postulated that LRRK2 kinase activity may inhibit the autophagic removal of toxicant damaged mitochondria, resulting in elevated oxidative stress. Conversely, we suspected that inhibition of LRRK2, which has been shown to be protective against dopaminergic neurodegeneration caused by mitochondrial toxicants, would reduce the intracellular production of reactive oxygen species (ROS) and prevent mitochondrial toxicity from inducing cell death. To do this, we tested in vitro if genetic or pharmacologic inhibition of LRRK2 (MLi2) protected against ROS caused by four toxicants associated with PD risk - rotenone, paraquat, TCE, and tetrachloroethylene (PERC). In parallel, we assessed if LRRK2 inhibition with MLi2 could protect against TCE-induced toxicity in vivo, in a follow up study from our observation that TCE elevated LRRK2 kinase activity in the nigrostriatal tract of rats prior to dopaminergic neurodegeneration. We found that LRRK2 inhibition blocked toxicant-induced ROS and promoted mitophagy in vitro, and protected against dopaminergic neurodegeneration, neuroinflammation, and mitochondrial damage caused by TCE in vivo. We also found that cells with the LRRK2 G2019S mutation displayed exacerbated levels of toxicant induced ROS, but this was ameliorated by LRRK2 inhibition with MLi2. Collectively, these data support a role for LRRK2 in toxicant-induced mitochondrial dysfunction linked to PD risk through oxidative stress and the autophagic removal of damaged mitochondria.

neuroscience↗

bioRxiv2023

Sexually dimorphic mechanisms of VGLUT-mediated protection from dopaminergic neurodegeneration

Parkinsons disease (PD) targets some dopamine (DA) neurons more than others. Sex differences offer insights, with females more protected from DA neurodegeneration. The mammalian vesicular glutamate transporter VGLUT2 and Drosophila ortholog dVGLUT have been implicated as modulators of DA neuron resilience. However, the mechanisms by which VGLUT2/dVGLUT protects DA neurons remain unknown. We discovered DA neuron dVGLUT knockdown increased mitochondrial reactive oxygen species in a sexually dimorphic manner in response to depolarization or paraquat-induced stress, males being especially affected. DA neuron dVGLUT also reduced ATP biosynthetic burden during depolarization. RNA sequencing of VGLUT+ DA neurons in mice and flies identified candidate genes that we functionally screened to further dissect VGLUT-mediated DA neuron resilience across PD models. We discovered transcription factors modulating dVGLUT-dependent DA neuroprotection and identified dj-1{beta} as a regulator of sex-specific DA neuron dVGLUT expression. Overall, VGLUT protects DA neurons from PD-associated degeneration by maintaining mitochondrial health.

neuroscience↗

bioRxiv2023

Low-dose inhalation exposure to trichloroethylene induces dopaminergic neurodegeneration in rodents

Trichloroethylene (TCE) is one of the most pervasive environmental contaminants in the world and is associated with Parkinson disease (PD) risk. Experimental models in rodents show that TCE is selectively toxic to dopaminergic neurons at high doses of ingestion, however, TCE is a highly volatile toxicant, and the primary pathway of human exposure is inhalation. As TCE is a highly lipophilic, volatile organic contaminant (VOC), inhalation exposure results in rapid diffusion throughout the brain, avoiding first-pass hepatic metabolism that necessitated high doses to recapitulate exposure conditions observed in human populations. We hypothesized that inhalation of TCE would induce significantly more potent neurodegeneration than ingestion and better recapitulate environmental conditions of vapor intrusion or off gassing from liquid TCE. To this end, we developed a novel, whole-body passive exposure inhalation chamber in which we exposed 10-month-old male and female Lewis rats to 50 ppm TCE (time weighted average, TWA) or filtered room air (control) over 8 weeks. In addition, we exposed 12-month-old male and female C57Bl/6 mice to 100 ppm TCE (TWA) or control over 12 weeks. Both rats and mice exposed to chronic TCE inhalation showed significant degeneration of nigrostriatal dopaminergic neurons as well as motor and gait impairments. TCE exposure also induced accumulation of pSer129-Syn in dopaminergic neurons as well as microglial activation within the substantia nigra of rats. Collectively, these data indicate that TCE inhalation causes highly potent dopaminergic neurodegeneration and recapitulates some of the observed neuropathology associated with PD, providing a future platform for insight into the mechanisms and environmental conditions that influence PD risk from TCE exposure.

neuroscience↗

bioRxiv2022

Oral ingestion of the environmental toxicant trichlorethylene in rats induces alterations in the gut microbiome: relevance to idiopathic Parkinson's disease

Microbial alterations within the gut microbiome appear to be a common feature of individuals with Parkinsons disease (PD), providing further evidence for the role of the gut-brain axis in PD development. As a major site of contact with the environment, questions have emerged surrounding the cause and effect of alterations to the gut microbiome by environmental contaminants associated with PD risk, such as pesticides, metals, and organic solvents. Recent data from our lab shows that ingestion of the industrial byproduct and environmental pollutant trichloroethylene (TCE) induces key Parkinsonian pathology within aged rats, including the degeneration of dopaminergic neurons, -synuclein accumulation, neuroinflammation, and endolysosomal deficits. As TCE is the most common organic contaminant within drinking water, we postulated that ingestion of TCE associated with PD-related neurodegeneration may alter the gut microbiome to a similar extent as observed in persons with PD. To assess this, we collected fecal samples from adult rats treated with 200 mg/kg TCE over 6 weeks via oral gavage - the dose that produced nigrostriatal neurodegeneration - and analyzed the gut microbiome via whole genome shotgun sequencing. Our results showed changes in gut microorganisms reflective of the microbial signatures observed in individuals with idiopathic PD, such as decreased abundance of short-chain fatty acid producing Blautia and elevated lactic-acid producing Bifidobacteria, as well as genera who contain species previously reported as opportunistic pathogens such as Clostridium. From these experimental data, we postulate that TCE exposure within contaminated drinking water could induce alterations of the gut microbiome that contributes to chronic disease risk, including idiopathic PD.

pharmacology and toxicology↗

bioRxiv2020

VGLUT modulates sex differences in dopamine neuron vulnerability to age-related neurodegeneration

Age is the greatest risk factor for Parkinsons disease (PD) which causes progressive loss of dopamine (DA) neurons, with males at greater risk than females. We found that vesicular glutamate transporter (VGLUT) expression mediates vulnerability to age-related DA neurodegeneration in a sex-dependent manner, providing a new mechanism for sex differences in selective DA neuron vulnerability. These findings lay the groundwork for novel therapeutic strategies to boost neuronal resilience throughout aging.

neuroscience↗

bioRxiv2020

The industrial solvent trichloroethylene induces LRRK2 kinase activity and dopaminergic neurodegeneration in a rat model of Parkinson's disease

Gene-environment interaction is implicated in the majority of idiopathic Parkinsons disease (PD) risk, and some of the most widespread environmental contaminants are selectively toxic to dopaminergic neurons. Pesticides have long been connected to PD incidence, however, it has become increasingly apparent that other industrial byproducts likely influence neurodegeneration. For example, organic solvents, which are used in chemical, machining, and dry-cleaning industries, are of growing concern, as decades of solvent use and their effluence into the environment has contaminated much of the worlds groundwater and soil. Like some pesticides, certain organic solvents, such as the chlorinated halocarbon trichloroethylene (TCE), are mitochondrial toxicants, which are collectively implicated in the pathogenesis of dopaminergic neurodegeneration. Recently, we hypothesized a possible gene-environment interaction may occur between environmental mitochondrial toxicants and the protein kinase LRRK2, mutations of which are the most common genetic cause of familial and sporadic PD. In addition, emerging data suggests that elevated wildtype LRRK2 kinase activity also contributes to the pathogenesis of idiopathic PD. To this end, we investigated whether chronic, systemic TCE exposure (200 mg/kg) in aged rats produced wildtype LRRK2 activation and influenced predegenerative dopaminergic dysfunction. Interestingly, we found that TCE not only induced LRRK2 kinase activity in the brain, but produced a significant dopaminergic lesion in the nigrostriatal tract, elevated oxidative stress, and caused endolysosomal dysfunction and protein accumulation (-synuclein). Together, these data suggest that TCE-induced LRRK2 kinase activity contributed to the selective toxicity of dopaminergic neurons. We conclude that gene-environment interactions between certain industrial contaminants and LRRK2 likely influence PD risk.

pharmacology and toxicology↗

bioRxiv2020

Protection from α-synuclein-induced dopaminergic neurodegeneration by overexpression of the mitochondrial import receptor TOM20 in the rat midbrain

Dopaminergic neurons of the substantia nigra are selectively vulnerable to mitochondrial dysfunction, which is hypothesized to be an early and fundamental pathogenic mechanism in Parkinsons disease (PD). Mitochondrial function depends on the successful import of nuclear-encoded proteins, many of which are transported through the TOM20-TOM22 outer mitochondrial membrane import receptor machinery. Recent data suggests that post-translational modifications of -synuclein promote its interaction with TOM20 at the outer mitochondrial membrane and thereby inhibit normal protein import, which leads to dysfunction and death of dopaminergic neurons. As such, preservation of mitochondrial import in the face of -synuclein accumulation might be a strategy to prevent dopaminergic neurodegeneration, however, this is difficult to assess using current in vivo models of PD. To this end, we established an exogenous co-expression system, utilizing AAV2 vectors to overexpress human -synuclein and TOM20, individually or together, in the adult Lewis rat substantia nigra in order to assess whether TOM20 overexpression attenuates -synuclein-induced dopaminergic neurodegeneration. Twelve weeks after viral injection, we observed that AAV2-TOM20 expression was sufficient to prevent loss of nigral dopaminergic neurons caused by AAV2-Syn overexpression. The observed TOM20-mediated dopaminergic neuron preservation appeared to be due, in part, to the rescued import of nuclear-encoded mitochondrial electron transport chain proteins that were inhibited by -synuclein overexpression. In addition, TOM20 overexpression rescued the import of the chaperone protein GRP75/mtHSP70/mortalin, a stress-response protein involved in -synuclein-induced injury. Collectively, these data indicate that TOM20 expression prevents -synuclein-induced mitochondrial dysfunction, which is sufficient to rescue dopaminergic neurons in the adult rat brain.

neuroscience↗