Hyperpolarized 13C magnetic resonance spectroscopy (MRS) provides unprecedented opportunities to obtain clinical diagnostic information through in vivo monitoring of metabolic pathways. The continuing advancement of this field relies on the identification of molecular probes that can effectively interrogate pathways critical to disease. In this report, we describe the synthesis, development, and in vivo application of sodium [1-13C]-glycerate ([13C]-Glyc) as a novel probe for evaluating glycolysis using hyperpolarized 13C MRS. This agent was prepared by a concise synthetic route and formulated for dynamic nuclear polarization. [13C]-Glyc displayed a high level of polarization and long spin–lattice relaxation time—both of which are necessary for future clinical investigations. In vivo spectroscopic studies with hyperpolarized [13C]-Glyc in rat liver furnished metabolic products, [13C]-labeled pyruvate and lactate, originating from glycolysis. The levels of production and relative intensities of these metabolites were directly correlated with the induced glycolytic state (fasted versus fed groups). This work establishes hyperpolarized [13C]-Glyc as a novel agent for clinically relevant 13C MRS studies of energy metabolism and further provides opportunities for evaluating intracellular redox states in biochemical investigations.

Purpose The intracellular lactate to pyruvate concentration ratio is a commonly used tissue assay biomarker of redox, being proportional to free cytosolic [NADH]/[NAD+]. In this work, we assess the utility of hyperpolarized [1-13C]alanine, and the subsequent detection of the intracellular products of [1-13C]pyruvate and [1-13C]lactate, as an useful substrate for assessing in vivo redox levels in the liver. Methods Animal experiments were conducted to measure in vivo metabolism at baseline and following ethanol infusion. A solution of 80-mM hyperpolarized [1-13C]alanine was injected intravenously at baseline (n=8) and 45-min post-ethanol infusion (n=4), immediately followed by the dynamic acquisition of 13C MRS spectra. Results In vivo rat liver spectra showed peaks from [1-13C]alanine and the products of [1-13C]lactate, [1-13C]pyruvate, and 13C-bicarbonate. A significantly increased 13C-lactate/13C-pyruvate ratio was observed following ethanol infusion (8.46±0.58 at baseline versus 13.58±0.69 post-ethanol, p<0.001) consistent with the increased NADH produced by liver metabolism of ethanol to acetaldehyde and then acetate. A decrease in 13C-bicarbonate production was also noted, potentially reflecting ethanol-induced mitochondrial redox changes. Conclusion A method to measure in vivo tissue redox using hyperpolarized [1-13C]alanine is presented, with the validity of the proposed 13C-pyruvate/13C-lactate metric tested using an ethanol challenge to alter liver redox state.

Reactive oxygen species (ROS) are essential cellular metabolites widely implicated in many diseases including cancer, inflammation, and cardiovascular and neurodegenerative disorders. Yet, ROS signaling remains poorly understood, and their measurements are a challenge due to high reactivity and instability. Here, we report the development of 13C-thiourea as a probe to detect and measure H2O2 dynamics with high sensitivity and spatiotemporal resolution using hyperpolarized 13C magnetic resonance spectroscopic imaging. In particular, we show 13C-thiourea to be highly polarizable and to possess a long spin–lattice relaxation time (T1), which enables real-time monitoring of ROS-mediated transformation. We also demonstrate that 13C-thiourea reacts readily with H2O2 to give chemically distinguishable products in vitro and validate their detection in vivo in a mouse liver. This study suggests that 13C-thiourea is a promising agent for noninvasive detection of H2O2 in vivo. More broadly, our findings outline a viable clinical application for H2O2 detection in patients with a range of diseases.

The clinically approved cytoprotector amifostine, designated WR-2721, [S-2-(3-aminopropylamino)ethylphosphorothioic acid], protects against both radiation and drug-induced mutagenesis in animal systems. These effects extend over a wide concentration range making amifostine a strong candidate for evaluation as a possible cancer chemopreventive agent. To better identify and develop potential intermediate biomarkers for chemoprevention at the molecular level we applied the technique of differential display RT-PCR to assess the effects of both the thiol (SH), i.e. WR1065 and the disulfide (SS), i.e. WR-33278, metabolites of amifostine on gene expression in CHO-AA8 cells. Cells were exposed to either 40 microM or 4 mM of each agent for 30 min, and subsequent changes in gene expression were identified and contrasted to that found in corresponding untreated control cells. One band that showed a differential response was sequenced and was found to have 78% homology with a segment of the human pHL-1 cDNA clone contained in GenBank. This clone contains a COX III mitochondrial DNA insert and two exons of human c-myc. Northern blot analyses were performed by using the cloned human c-myc exon 1 probe to confirm whether c-myc gene expression was affected. Repression of c-myc expression was observed under all of the conditions evaluated. An exposure of cells to 40 microM of the disulfide form of amifostine was the most effective in repressing c-myc, i.e. 27% of control level. A concentration of 4 mM of the disulfide form reduced gene expression to 45% of the control level, while the thiol form was less effective, with 4 mM and 40 microM concentrations reducing c-myc gene expression to 65% and 46% of control levels, respectively.