Synthesis and characterization of a fluorescent probe for α-tocopherol suitable for fluorescence microscopy

Antioxidant-independent activities of alpha-tocopherol

Alpha-tocopherol (vitamin E) is a plant-derived dietary lipid that is essential for the health of most animals, including humans. Originally discovered as a fertility factor in rodents, the primary health-promoting properties of the vitamin in humans was shown to be protection of neuromuscular functions. Heritable vitamin E deficiency manifests in spinocerebellar ataxia that can be stabilized by timely supplementation with high-dose α-tocopherol. The molecular basis for α-tocopherol's biological activities has been attributed primarily to the vitamin's efficacy in preventing lipid peroxidation in membranes and lipoproteins, but the possibility that the vitamin possesses additional biological activities has been postulated and debated in the literature without conclusive resolution. We designed and synthesized a novel analog of α-tocopherol, 6-hydroxymethyl α-tocopherol (6-HMTC), which retains most of the vitamin's structural, physical and biochemical properties, yet lacks measurable radical-trapping antioxidant activity. 6-HMTC bound to the tocopherol transfer protein with high (nM) affinity, like that of the natural vitamin, attesting to the analog's preservation of structural integrity. Yet, 6-HMTC did not inhibit lipid peroxidation or associated ferroptotic cell death. Notably, 6-HMTC modulated the expression of some genes in a manner essentially identical to that exhibited by α-tocopherol. These findings support the notion that α-tocopherol modulates gene expression via an antioxidant-independent mechanism.

Versatile Metal-Free Arylation of BODIPY and Bis(BF2) Chromophores by Using Arylazosulfones in a Sunflow System

BODIPYs have a well-established role in biological sciences as chemosensors and versatile biological markers due to their chemical reactivity, which allows for fine-tuning of their photophysical characteristics. In this work, we combined the unique reactivity of arylazo sulfones with the advantages of a "sunflow" reactor to develop a fast, efficient, and versatile method for the photochemical arylation of BODIPYs and other chromophores. This approach resulted in red-shifted emitting fluorophores due to extended electronic delocalization at the 3- and 5-positions of the BODIPY core. This method represents an advantageous approach for BODIPY functionalization compared to existing strategies.

Vitamin E sequestration by liver fat in humans

BACKGROUNDWe hypothesized that obesity-associated hepatosteatosis is a pathophysiological chemical depot for fat-soluble vitamins and altered normal physiology. Using α-tocopherol (vitamin E) as a model vitamin, pharmacokinetics and kinetics principles were used to determine whether excess liver fat sequestered α-tocopherol in women with obesity-associated hepatosteatosis versus healthy controls.METHODSCustom-synthesized deuterated α-tocopherols (d3- and d6-α-tocopherols) were administered to hospitalized healthy women and women with hepatosteatosis under investigational new drug guidelines. Fluorescently labeled α-tocopherol was custom-synthesized for cell studies.RESULTSIn healthy subjects, 85% of intravenous d6-α-tocopherol disappeared from the circulation within 20 minutes but reappeared within minutes and peaked at 3-4 hours; d3- and d6-α-tocopherols localized to lipoproteins. Lipoprotein redistribution occurred only in vivo within 1 hour, indicating a key role of the liver in uptake and re-release. Compared with healthy subjects who received 2 mg, subjects with hepatosteatosis had similar d6-α-tocopherol entry rates into liver but reduced initial release rates (P < 0.001). Similarly, pharmacokinetics parameters were reduced in hepatosteatosis subjects, indicating reduced hepatic d6-α-tocopherol output. Reductions in kinetics and pharmacokinetics parameters in hepatosteatosis subjects who received 2 mg were echoed by similar reductions in healthy subjects when comparing 5- and 2-mg doses. In vitro, fluorescent-labeled α-tocopherol localized to lipid in fat-loaded hepatocytes, indicating sequestration.CONCLUSIONSThe unique role of the liver in vitamin E physiology is dysregulated by excess liver fat. Obesity-associated hepatosteatosis may produce unrecognized hepatic vitamin E sequestration, which might subsequently drive liver disease. Our findings raise the possibility that hepatosteatosis may similarly alter hepatic physiology of other fat-soluble vitamins.TRIAL REGISTRATIONClinicalTrials.gov, NCT00862433.FUNDINGNational Institute of Diabetes and Digestive and Kidney Diseases and NIH grants DK053213-13, DK067494, and DK081761.

Vitamin E-inspired multi-scale imaging agent

The production and use of multi-modal imaging agents is on the rise. The vast majority of these imaging agents are limited to a single length scale for the agent (e.g. tissues only), which is typically at the organ or tissue scale. This work explores the synthesis of such an imaging agent and discusses the applications of our vitamin E-inspired multi-modal and multi-length scale imaging agents TB-Toc ((S,E)-5,5-difluoro-7-(2-(5-((6-hydroxy-2,5,7,8-tetramethylchroman-2-yl) methyl) thiophen-2-yl) vinyl)-9-methyl-5H-dipyrrolo-[1,2-c:2',1'-f][1,3,2]diazaborinin-4-ium-5-uide). We investigate the toxicity of TB-Toc along with the starting materials and lipid based delivery vehicle in mouse myoblasts and fibroblasts. Further we investigate the uptake of TB-Toc delivered to cultured cells in both solvent and liposomes. TB-Toc has low toxicity, and no change in cell viability was observed up to concentrations of 10 mM. TB-Toc shows time-dependent cellular uptake that is complete in about 30 min. This work is the first step in demonstrating our vitamin E derivatives are viable multi-modal and length scale diagnostic tools.