D. L. Morris, A. P. Zampino, A. A. Taraboletti, L. P. Shriver, T. C. Leeper and C. J. Ziegler
Hen egg white lysozyme catalyzes the polymerization of 2-ethynylpyridine in water as the singular protein catalyst. Inhibition and NMR spectroscopy studies support the hypothesis that polymerization takes place in the active site cleft of the protein. This discovery marks the first time a metal-free hydrolase has been observed activating the formation for a conjugated polymer.
Sept 12, 2017
Alexandra Taraboletti , Tia Walker, Robin Avila, He Huang, Joel Caporoso, Erendra Manandhar, Thomas C. Leeper, David A. Modarelli, Satish Medicetty, and Leah P. Shriver
Cuprizone intoxication is a common animal model used to test myelin regenerative therapies to treat diseases such as multiple sclerosis. Mice fed this copper chelator develop reversible, region-specific oligodendrocyte loss and demyelination. While the cellular changes influencing the demyelinating process have been explored in this model, there is no consensus on the biochemical mechanisms of toxicity in oligodendrocytes and if this damage arises from the chelation of copper in vivo. Here we have identified an oligodendroglial cell line that displays sensitivity to cuprizone toxicity and performed global metabolomic profiling to determine biochemical pathways altered by this treatment. We link these changes with alterations in brain metabolism in mice fed cuprizone for two and six weeks. We find that cuprizone induces widespread changes in one carbon and amino acid metabolism as well as alterations in small molecules important for energy generation. We used mass spectrometry to examine chemical interactions important for copper chelation and toxicity. Our results indicate that cuprizone induces global perturbations in cellular metabolism that may be independent of its copper chelating ability and potentially related to its interactions with pyridoxal 5’-phosphate, a co-factor essential for amino acid metabolism.
Feb 10, 2017
Lucas McDonald, Bin Liu, Alexandra Taraboletti, Kyle Whiddon, Leah P. Shriver, Michael Konopka, Qin Liub and Yi Pang
Visualization of subcellular organelles in vivo is critical for basic biomedical research and clinical applications. Two new flavonoids with an amide substituent were synthesized and characterized. The flavonoids were nearly non-fluorescent in aqueous environment, but exhibited two emission peaks (one λem at 495–536 nm and the other at 570–587 nm) in organic solvents, which were assigned to the excited normal (N*) and tautomer (T*) emission. When the dyes were examined on oligodendrocyte cells, they were found to selectively accumulate in the endoplasmic reticulum (ER), a eukaryotic organelle involved in lipid and protein synthesis, giving fluorescence turn-on. The ER-selective flavonoids could be a valuable tool due to its low molecular mass (<500), large Stokes' shift, low toxicity, and biocompatibility.
J. Mater. Chem. B
Kerri L. Shelton, Michael A. DeBord, Patrick O. Wagers, Marie R. Southerland, Alexandra Taraboletti,Nikki K. Robishaw, Daniel P. Jackson, Radisa Tosanovic, William G. Kofron, Claire A. Tessier, Sailaja Paruchuri, Leah P. Shriver, Matthew J. Panzner, and Wiley J. Youngs
The syntheses and characterization of C4 and C5 substituted N,N′-bis(arylmethyl)imidazolium salts with hydrophilic or lipophilic substituents on the imidazole ring are reported. A structure-activity relationship study revealed that the lipophilicity of groups at the C4 and C5 positions plays a crucial role in modulating the efficacy against select non-small cell lung cancer cell lines tested. Compounds 11–17 were determined to be the most active against the panel of cell lines studied. Compounds 11 and 12 were examined by the National Cancer Institute's Developmental Therapeutic Program where they were tested against the NCI-60 human cancer cell line panel in a one-dose and five-dose assay. Compound 11 had high activity against the nine lung cancer lines tested while 12 had cytotoxic effects against 59 of the 60 cell lines. Compound 11 was also studied in a murine model to determine its in vivo toxicity.
Jul 29, 2016
Dimethyl fumarate modulates antioxidant and lipid metabolism in oligodendrocytes
He Huang, Alexandra Taraboletti, and Leah P. Shriver
Oxidative stress contributes to pathology associated with inflammatory brain disorders and therapies that upregulate antioxidant pathways may be neuroprotective in diseases such as multiple sclerosis. Dimethyl fumarate, a small molecule therapeutic for multiple sclerosis, activates cellular antioxidant signaling pathways and may promote myelin preservation. However, it is still unclear what mechanisms may underlie this neuroprotection and whether dimethyl fumarate affects oligodendrocyte responses to oxidative stress. Here, we examine metabolic alterations in oligodendrocytes treated with dimethyl fumarate by using a global metabolomic platform that employs both hydrophilic interaction liquid chromatography-mass spectrometry and shotgun lipidomics. Prolonged treatment of oligodendrocytes with dimethyl fumarate induces changes in citric acid cycle intermediates, glutathione, and lipids, indicating that this compound can directly impact oligodendrocyte metabolism. These metabolic alterations are also associated with protection from oxidant challenge. This study provides insight into the mechanisms by which dimethyl fumarate could preserve myelin integrity in patients with multiple sclerosis.
Apr 11, 2015
Y.J. Chen, S. Hill, H. Huang, A. Taraboletti, K. Cho, R. Gallo, M. Manchester, L.P. Shriver, and G.J. Patti
Neuropathic pain is a chronic, refractory condition that arises after damage to the nervous system. We previously showed that an increased level of the endogenous metabolite N,N-dimethylsphingosine (DMS) in the central nervous system (CNS) is sufficient to induce neuropathic pain-like behavior in rats. However, several important questions remain. First, it has not yet been demonstrated that DMS is produced in humans and its value as a therapeutic target is therefore unknown. Second, the cell types within the CNS that produce DMS are currently unidentified. Here we provide evidence that DMS is present in human CNS tissue. We show that DMS levels increase in demyelinating lesions isolated from patients with multiple sclerosis, an autoimmune disease in which the majority of patients experience chronic pain. On the basis of these results, we hypothesized that oligodendrocytes may be a cellular source of DMS. We show that human oligodendrocytes produce DMS in culture and that the levels of DMS increase when oligodendrocytes are challenged with agents that damage white matter. These results suggest that damage to oligodendrocytes leads to increased DMS production which in turn drives inflammatory astrocyte responses involved in sensory neuron sensitization. Interruption of this pathway in patients may provide analgesia without the debilitating side effects that are commonly observed with other chronic pain therapies.
Aug 21, 2014
Scalability in the Mechanochemical Synthesis of Edge Functionalized Graphene Materials and Biomass-derived Chemicals
Richard G. Blair, Katerina Chagoya, Scott Biltek, Steven Jackson, Ashlyn Sinclair, Alexandra Taraboletti and David T. Restrepo
Mechanochemical approaches to chemical synthesis offer the promise of improved yields, new reaction pathways, and greener syntheses. Scaling these syntheses is a crucial step toward realizing a commercially viable process. Although much work has been performed on laboratory-scale investigations little has been done to move these approaches toward industrially relevant scales. Moving reactions from shaker-type mills and planetary-type mills to scalable solutions can present a challenge. We have investigated scalability through discrete element models, thermal monitoring, and reactor design. We have found that impact forces and macroscopic mixing are important factors in implementing a truly scalable process. These observations have allowed us to scale reactions from a few grams to several hundred grams and we have successfully implemented scalable solutions for the mechanocatalytic conversion of cellulose to value-added compounds and the synthesis of edge-functionalized graphene.