IU Indianapolis ScholarWorks :: Browsing by Author "Nass, Richard"

Browsing by Author "Nass, Richard"

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Air Pollution Exposure and the Lung-Brain Axis: Implications for Alzheimer's Disease
(2022-03) Greve, Hendrik Jacob; Oblak, Adrian; Block, Michelle; Nass, Richard; Landreth, Gary
Alzheimer’s disease (AD) is a devastating neurodegenerative disease that is expected to affect approximately 6.2 million Americans. Despite its high prevalence, the mechanisms underlying AD remain poorly understood. In recent years, increasing reports indicate that exposure to urban air pollution is a risk factor for the development of AD. However, the mechanistic underpinnings of this association are not well studied. Rats exposed to diesel exhaust (DE) showed neuroinflammation and impaired expression of TREM2 and disease-associated microglia (DAM), a cell subtype hypothesized to play beneficial roles during neurodegeneration, markers. Microglia in the cortex of rats exposed to DE, also showed decreased association with the vasculature, providing a novel link between the microglia and the brain vasculature. Examining the functional role of TREM2 during DE exposures, Trem2-/- mice showed an altered pro-inflammatory profile in both the brain and lungs in response to DE particles as well as altered phagocytic oxidase related gene expression. Examining another prominent component of air pollution, ozone (O3), in a mouse model of AD, it was discovered that subchronic O3 exposure exacerbates amyloid pathology through impaired microglial-plaque association in 5xFAD mice. 5xFAD mice exposed to O3 also showed increased expression of pro-inflammatory cytokines, increased markers of dystrophic neurites, and decreased expression of key acetylcholinergic pathway components. Examining the peri-plaque microenvironment, it was discovered that O3 dysregulates key DAM proteins and amyloid processing proteins. In the lung, it was found that O3 exacerbated immune cell infiltration in 5xFAD mice compared to WT controls, suggesting that ongoing amyloid pathology regulates pulmonary immune response to air pollution. To examine how O3-induced pulmonary immune responses may be signaling to the CNS, we examined the serum of 5xFAD mice, where HMGB1, VEGF, and IL-9 were upregulated. Injection of rHMGB1 into mice showed similar gene changes to 5xFAD mice exposed to O3, along with impaired Trem2 expression. Using a peripheral myeloid specific knock-out model of HMGB1, we also show that HMGB1 regulates O3-induced Trem2 expression impairment. Taken together, these data support that air pollution exposure impairs TREM2, DAM cells, and the microglial plaque response through a bidirectional lung-brain axis to exacerbate AD-like pathology.
G protein-coupled receptor kinase-2 (GRK-2) regulates serotonin metabolism through the monoamine oxidase AMX-2 in Caenorhabditis elegans
(American Society for Biochemistry and Molecular Biology, 2017-04-07) Wang, Jianjun; Luo, Jiansong; Aryal, Dipendra K.; Wetsel, William C.; Nass, Richard; Benovic, Jeffrey L.; Pharmacology and Toxicology, School of Medicine
G protein-coupled receptors (GPCRs) regulate many animal behaviors. GPCR signaling is mediated by agonist-promoted interactions of GPCRs with heterotrimeric G proteins, GPCR kinases (GRKs), and arrestins. To further elucidate the role of GRKs in regulating GPCR-mediated behaviors, we utilized the genetic model system Caenorhabditis elegans Our studies demonstrate that grk-2 loss-of-function strains are egg laying-defective and contain low levels of serotonin (5-HT) and high levels of the 5-HT metabolite 5-hydroxyindole acetic acid (5-HIAA). The egg laying defect could be rescued by the expression of wild type but not by catalytically inactive grk-2 or by the selective expression of grk-2 in hermaphrodite-specific neurons. The addition of 5-HT or inhibition of 5-HT metabolism also rescued the egg laying defect. Furthermore, we demonstrate that AMX-2 is the primary monoamine oxidase that metabolizes 5-HT in C. elegans, and we also found that grk-2 loss-of-function strains have abnormally high levels of AMX-2 compared with wild-type nematodes. Interestingly, GRK-2 was also found to interact with and promote the phosphorylation of AMX-2. Additional studies reveal that 5-HIAA functions to inhibit egg laying in a manner dependent on the 5-HT receptor SER-1 and the G protein GOA-1. These results demonstrate that GRK-2 modulates 5-HT metabolism by regulating AMX-2 function and that 5-HIAA may function in the SER-1 signaling pathway.
Human Nav1.5 F1486 deletion associated with long-QT syndrome leads to deficiency in inactivation and reduces lidocaine sensitivity
(2012-03-19) Song, Weihua; Shou, Weinian; Cummins, Theodore R.; Chen, Peng-Sheng; Hudmon, Andrew; Nass, Richard; Khanna, Rajesh
The cardiac voltage-gated sodium channel α subunit Nav1.5 generates the cardiac sodium current, which is essential for the initiation and propagation of the cardiac action potentials. Mutations of SCN5A, the gene that encodes Nav1.5, have been well documented to cause long-QT syndrome (LQTs) by disrupting channel inactivation and increasing late sodium current. Previous studies have revealed the importance of the intracellular loop region between transmembrane domain III and IV of sodium channel α subunit in regulating the fast inactivation. A recent clinical case study reported an infant patient with LQTs carrying a phenylalanine (F) deletion at amino acid 1486 of the Nav1.5 channel. This study reported that the patient showed severe cardiac arrhythmia reflected as LQTs and subsequent ventricular tachycardia, which was refractory to antiarrhythmic drug lidocaine treatment. Therefore, it was hypothesized that the deletion of F1486 on Nav1.5 would substantially alter electrophysiological properties of the channel and reduce the potency of lidocaine on sodium channel. Using HEK293 cells and neonatal rat cardiomyocytes, the F1486del channel was functionally characterized by whole-cell patch clamp techniques. Studies revealed that the deletion of F1486 causes a combination of changes including a loss-of-function alteration reflected as a substantial reduction of peak current density and a number of gain-of-function alterations including reduced channel inactivation, substantial augmentation of late sodium current, and an increase in ramp current. In addition, lidocaine sensitivity was dramatically reduced. By contrast, the voltage for half maximal activation (V1/2) and the time constant for channel deactivation for the F1486del channel were identical to the wild type channels. Using neonatal rat cardiomyocytes, we were able to study the functional consequence of F1484del on action potential duration (APD). Cardiomyocytes expressing F1486del channel have substantial APD prolongation and prominent spontaneous early afterdepolarizations, which likely underlie the subsequent LQTs in the patient. Taken together, despite the reduction in peak current density, the substantial gain-of-function changes are sufficient to cause the APD prolongation, which is a prominent characteristic of LQTs. These findings provide knowledge for understanding the relationships between sodium channel structure, pharmacology and the physiological consequence of sodium channel mutations that underlie LQT3.
Methylmercury exposure increases lipocalin related (lpr) and decreases activated in blocked unfolded protein response (abu) genes and specific miRNAs in Caenorhabditis elegans
(Elsevier, 2013-10-24) Rudgalvyte, Martina; VanDuyn, Natalia; Aarnio, Vuokko; Heikkinen, Liisa; Peltonen, Juhani; Lakso, Merja; Nass, Richard; Wong, Garry; Department of Pharmacology and Toxicology, School of Medicine
Methylmercury (MeHg) is a persistent environmental and dietary contaminant that causes serious adverse developmental and physiologic effects at multiple cellular levels. In order to understand more fully the consequences of MeHg exposure at the molecular level, we profiled gene and miRNA transcripts from the model organism Caenorhabditis elegans. Animals were exposed to MeHg (10µM) from embryo to larval 4 (L4) stage and RNAs were isolated. RNA-seq analysis on the Illumina platform revealed 541 genes up- and 261 genes down-regulated at a cutoff of 2-fold change and false discovery rate-corrected significance q < 0.05. Among the up-regulated genes were those previously shown to increase under oxidative stress conditions including hsp-16.11 (2.5-fold), gst-35 (10.1-fold), and fmo-2(58.5-fold). In addition, we observed up-regulation of 6 out of 7 lipocalin related (lpr) family genes and down regulation of 7 out of 15 activated in blocked unfolded protein response (abu) genes. Gene Ontology enrichment analysis highlighted the effect of genes related to development and organism growth. miRNA-seq analysis revealed 6–8 fold down regulation of mir-37-3p, mir-41-5p, mir-70-3p, and mir-75-3p. Our results demonstrate the effects of MeHg on specific transcripts encoding proteins in oxidative stress responses and in ER stress pathways. Pending confirmation of these transcript changes at protein levels, their association and dissocation characteristics with interaction partners, and integration of these signals, these findings indicate broad and dynamic mechanisms by which MeHg exerts its harmful effects.
Micro-RNA regulation of hepatic drug metabolism : age-related changes in micro-RNA expression and genetic variants in micro-RNA target sites
(2017-08-31) Burgess, Kimberly Sherrelle; Skaar, Todd C.; Arrizabalaga, Gustavo; Cummins, Theodore; Desta, Zeruesenay; Nass, Richard; Zhang, Jian-Tian
Developmental changes in the liver significantly impact drug disposition. Due to the emergence of microRNAs as important regulators of drug disposition, we hypothesize that age-dependent change in microRNA expression and genetic variants in microRNA target sites contribute to variability in drug disposition. In human liver tissues, expression of 533 microRNAs and over 14,000 genes were measured. In all, 114 microRNAs were upregulated and 72 downregulated from fetal to pediatric, and 2 and 3, respectively, from pediatric to adult. Among these microRNAs, 99 microRNA-mRNA interactions were predicted or have previously been validated to target drug disposition genes and over 1,000 significant negative correlations were observed between miRNA-mRNA pairs. We validated these interactions using various cell culture models. Genetic variants in the promoter and coding regions of drug disposition genes have also been shown to alter enzyme expression and/or activity. However, these variants do not account for all variability in enzyme activity. Emerging evidence has shown that variants in the 3’UTR may explain variable drug response by altering microRNA regulation. Five 3’UTR variants were associated with significantly altered CYP2B6 activity in healthy human volunteers. The rs70950385 (AG>CA) variant was associated with decreased CYP2B6 activity among normal metabolizers. In vitro luciferase assays confirmed that the CA allele altered miR 1275 targeting of CYP2B6 mRNA. Due to the large number of 3’UTR variants predicted to alter microRNA regulation, a high-throughput method, PASSPORT-seq, was developed to test over 100 3’UTR variants simultaneously in different cell lines. Thirty-eight variants resulted in FDR-significant altered expression between wild-type and variant sequences. Our data suggest a mechanism for the marked changes in hepatic gene expression between the fetal and pediatric developmental periods, support a role for these age dependent microRNAs in regulating drug disposition, and provide strong evidence that 3’UTR variants are also an important source of variability in drug disposition.
The putative multidrug resistance protein MRP-7 inhibits methylmercury-associated animal toxicity and dopaminergic neurodegeneration in Caenorhabditis elegans
(Wiley, 2014-03) VanDuyn, Natalia; Nass, Richard; Department of Pharmacology and Toxicology, IU School of Medicine
Parkinson’s disease (PD) is the most prevalent neurodegenerative motor disorder worldwide, and results in the progressive loss of dopamine (DA) neurons in the substantia nigra pars compacta. Gene-environment interactions are believed to play a significant role in the vast majority of PD cases, yet the toxicants and the associated genes involved in the neuropathology are largely ill-defined. Recent epidemiological and biochemical evidence suggests that methylmercury (MeHg) may be an environmental toxicant that contributes to the development of PD. Here we report that a gene coding for the putative multidrug resistance protein MRP-7 in Caenorhabditis elegans (C. elegans) modulates whole animal and DA neuron sensitivity to MeHg. In this study we demonstrate that genetic knockdown of MRP-7 results in a 2-fold increase in Hg levels and a dramatic increase in stress response proteins associated with the endoplasmic reticulum, golgi apparatus, and mitochondria, as well as an increase in MeHg-associated animal death. Chronic exposure to low concentrations of MeHg induces MRP-7 gene expression, while exposures in MRP-7 genetic knockdown animals results in a loss of DA neuron integrity without affecting whole animal viability. Furthermore, transgenic animals expressing a fluorescent reporter behind the endogenous MRP-7 promoter indicate that the transporter is expressed in DA neurons. These studies show for the first time that a multidrug resistance protein is expressed in DA neurons, and its expression inhibits MeHg-associated DA neuron pathology.
RNA-Seq Reveals Acute Manganese Exposure Increases Endoplasmic Reticulum Related and Lipocalin mRNAs in Caenorhabditis elegans
(Wiley, 2016-02) Rudgalvyte, Martina; Peltonen, Juhani; Lakso, Merja; Nass, Richard; Wong, Garry; Department of Pharmacology and Toxicology, IU School of Medicine
Manganese (Mn) is an essential nutrient; nonetheless, excessive amounts can accumulate in brain tissues causing manganism, a severe neurological condition. Previous studies have suggested oxidative stress, mitochondria dysfunction, and impaired metabolism pathways as routes for Mn toxicity. Here, we used the nematode Caenorhabditis elegans to analyze gene expression changes after acute Mn exposure using RNA-Seq. L1 stage animals were exposed to 50 mM MnCl2 for 30 min and analyzed at L4. We identified 746 up- and 1828 downregulated genes (FDR corrected p < 0.05; two-fold change) that included endoplasmic reticulum related abu and fkb family genes, as well as six of seven lipocalin-related (lpr) family members. These were also verified by qRT-PCR. RNA interference of lpr-5 showed a dramatic increase in whole body vulnerability to Mn exposure. Our studies demonstrate that Mn exposure alters gene transcriptional levels in different cell stress pathways that may ultimately contribute to its toxic effects.
The role of charge in the toxicity of polymer-coated cerium oxide nanomaterials to Caenorhabditis elegans
(Elsevier, 2017-10) Arndt, Devrah A.; Oostveen, Emily K.; Triplett, Judy; Butterfield, D. Allan; Tsyusko, Olga V.; Collin, Blanche E.; Starnes, Daniel L.; Cai, Jian; Klein, Jon B.; Nass, Richard; Unrine, Jason M.; Department of Pharmacology and Toxicology, School of Medicine
This study examined the impact of surface functionalization and charge on ceria nanomaterial toxicity to Caenorhabditis elegans. The examined endpoints included mortality, reproduction, protein expression, and protein oxidation profiles. Caenorhabditis elegans were exposed to identical 2–5 nm ceria nanomaterial cores which were coated with cationic (diethylaminoethyl dextran; DEAE), anionic (carboxymethyl dextran; CM), and non-ionic (dextran; DEX) polymers. Mortality and reproductive toxicity of DEAE-CeO2 was approximately two orders of magnitude higher than for CM-CeO2 or DEX-CeO2. Two-dimensional gel electrophoresis with orbitrap mass spectrometry identification revealed changes in the expression profiles of several mitochondrial-related proteins and proteins that are expressed in the C. elegans intestine. However, each type of CeO2 material exhibited a distinct protein expression profile. Increases in protein carbonyls and protein-bound 3-nitrotyrosine were also observed for some proteins, indicating oxidative and nitrosative damage. Taken together the results indicate that the magnitude of toxicity and toxicity pathways vary greatly due to surface functionalization of CeO2 nanomaterials.
Systemic and cerebral iron homeostasis in ferritin knock-out mice
(PLoS, 2015-01-28) Li, Wei; Garringer, Holly J.; Goodwin, Charles B.; Richine, Briana; Acton, Anthony; VanDuyn, Natalia; Muhoberac, Barry B.; Irimia-Dominguez, Jose; Chan, Rebecca J.; Peacock, Munro; Nass, Richard; Ghetti, Bernardino; Vidal, Ruben; Department of Pathology and Laboratory Medicine, IU School of Medicine
Ferritin, a 24-mer heteropolymer of heavy (H) and light (L) subunits, is the main cellular iron storage protein and plays a pivotal role in iron homeostasis by modulating free iron levels thus reducing radical-mediated damage. The H subunit has ferroxidase activity (converting Fe(II) to Fe(III)), while the L subunit promotes iron nucleation and increases ferritin stability. Previous studies on the H gene (Fth) in mice have shown that complete inactivation of Fth is lethal during embryonic development, without ability to compensate by the L subunit. In humans, homozygous loss of the L gene (FTL) is associated with generalized seizure and atypical restless leg syndrome, while mutations in FTL cause a form of neurodegeneration with brain iron accumulation. Here we generated mice with genetic ablation of the Fth and Ftl genes. As previously reported, homozygous loss of the Fth allele on a wild-type Ftl background was embryonic lethal, whereas knock-out of the Ftl allele (Ftl-/-) led to a significant decrease in the percentage of Ftl-/- newborn mice. Analysis of Ftl-/- mice revealed systemic and brain iron dyshomeostasis, without any noticeable signs of neurodegeneration. Our findings indicate that expression of the H subunit can rescue the loss of the L subunit and that H ferritin homopolymers have the capacity to sequester iron in vivo. We also observed that a single allele expressing the H subunit is not sufficient for survival when both alleles encoding the L subunit are absent, suggesting the need of some degree of complementation between the subunits as well as a dosage effect.

Browsing by Author "Nass, Richard"

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