Liquid chromatography method for simultaneous quantification of ATP and its degradation products compatible with both UV-Vis and mass spectrometry

PEGylated AIEgens for dual sensing of ATP and H2S and cancer cells photodynamic therapy

Fluorescent sensors have been widely applied for biosensing, but probes for both multiple analytes sensing and photodynamic therapy (PDT) effect are less reported. In this article, we reported three AIE-based probes anchored with different mass-weight polyethylene glycol (PEG) tails, i.e., TPE-PEG160, TPE-PEG350, and TPE-PEG750, for both adenosine-5'-triphosphate (ATP) and hydrogen sulfide (H2S) detection and also cancer cells photodynamic therapy. TPE-PEGns (n = 160, 350 and 750) contain the tetraphenylethylene-based fluorophore core, the pyridinium and amide anion binding sites, the H2S cleavable disulfide bond, and the hydrophilic PEG chain. They exhibit a good amphiphilic property and can self-assemble nona-aggregation with a moderated red emission in an aqueous solution. Importantly, the size of aggregation, photophysical property, sensing ability and photosensitivity of these amphiphilic probes can be controlled by tuning the PEG chain length. Moreover, the selected probe TPE-PEG160 has been successfully used to detect environmental H2S and image ATP levels in living cells, and TPE-PEG750 has been used for photodynamic therapy of tumor cells under light irradiation.

Evaluation of purine-nucleoside degrading ability and in vivo uric acid lowering of Streptococcus thermophilus IDCC 2201, a novel antiuricemia strain

This study evaluated 15 lactic acid bacteria with a focus on their ability to degrade inosine and hypo-xanthine-which are the intermediates in purine metabolism-for the management of hyperuricemia and gout. After a preliminary screening based on HPLC, Lactiplantibacillus plantarum CR1 and Lactiplantibacillus pentosus GZ1 were found to have the highest nucleoside degrading rates, and they were therefore selected for further characterization. S. thermophilus IDCC 2201, which possessed the hpt gene encoding hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and exhibited purine degradation, was also selected for further characterization. These three selected strains were examined in terms of their probiotic effect on lowering serum uric acid in a Sprague-Dawley (SD) rat model of potassium oxonate (PO)-induced hyperuricemia. Among these three strains, the level of serum uric acid was most reduced by S. thermophilus IDCC 2201 (p < 0.05). Further, analysis of the microbiome showed that administration of S. thermophlilus IDCC 2201 led to a significant difference in gut microbiota composition compared to that in the group administered with PO-induced hyperuricemia. Moreover, intestinal short-chain fatty acids (SCFAs) were found to be significantly increased. Altogether, the results of this work indicate that S. thermophilus IDCC 2201 lowers uric acid levels by degrading purine-nucleosides and also restores intestinal flora and SCFAs, ultimately suggesting that S. thermophilus IDCC 2201 is a promising candidate for use as an adjuvant treatment in patients with hyperuricemia.

Uric acid formation is driven by crosstalk between skeletal muscle and other cell types

Hyperuricemia is implicated in numerous pathologies, but the mechanisms underlying uric acid production are poorly understood. Using a combination of mouse studies, cell culture studies, and human serum samples, we sought to determine the cellular source of uric acid. In mice, fasting and glucocorticoid treatment increased serum uric acid and uric acid release from ex vivo-incubated skeletal muscle. In vitro, glucocorticoids and the transcription factor FoxO3 increased purine nucleotide degradation and purine release from differentiated muscle cells, which coincided with the transcriptional upregulation of AMP deaminase 3, a rate-limiting enzyme in adenine nucleotide degradation. Heavy isotope tracing during coculture experiments revealed that oxidation of muscle purines to uric acid required their transfer from muscle cells to a cell type that expresses xanthine oxidoreductase, such as endothelial cells. Last, in healthy women, matched for age and body composition, serum uric acid was greater in individuals scoring below average on standard physical function assessments. Together, these studies reveal skeletal muscle purine degradation is an underlying driver of uric acid production, with the final step of uric acid production occurring primarily in a nonmuscle cell type. This suggests that skeletal muscle fiber purine degradation may represent a therapeutic target to reduce serum uric acid and treat numerous pathologies.

Mitochondrial-Targeted AIE-Active Fluorescent Probe Based on Tetraphenylethylene Fluorophore with Dual Positive Charge Recognition Sites for Monitoring ATP in Cells

Adenosine triphosphate (ATP), as an important intracellular energy currency produced in mitochondria, is closely related to various diseases in living organisms. Currently, the biological application of AIE fluorophore as a fluorescent probe for ATP detection in mitochondria is rarely reported. Herein, D-π-A and D-A structure-based tetraphenylethylene (TPE) fluorophores were employed to synthesize six different ATP probes (P1-P6), and the phenylboronic acid groups and dual positive charge sites of probes could interact with the vicinal diol of ribose and negatively charged triphosphate structure of ATP, respectively. However, P1 and P4 with a boronic acid group and a positive charge site had poor selectivity for ATP detection. In contrast, P2, P3, P5, and P6 with dual positive charge sites exhibited better selectivity than P1 and P4. In particular, P2 had more advantages of high sensitivity, selectivity, and good time stability for ATP detection than P3, P5, and P6, which was ascribed to its D-π-A structure, linker 1 (1,4-bis(bromomethyl)benzene), and dual positive charge recognition sites. Then, P2 was employed to detect ATP, and it exhibited a low detection limit of 3.62 μM. Moreover, P2 showed utility in the monitoring of mitochondrial ATP level fluctuations.

Intrinsic adaptations in OXPHOS power output and reduced tumorigenicity characterize doxorubicin resistant ovarian cancer cells

Although the development of chemoresistance is multifactorial, active chemotherapeutic efflux driven by upregulations in ATP binding cassette (ABC) transporters are commonplace. Chemotherapeutic efflux pumps, like ABCB1, couple drug efflux to ATP hydrolysis and thus potentially elevate cellular demand for ATP resynthesis. Elevations in both mitochondrial content and cellular respiration are common phenotypes accompanying many models of cancer cell chemoresistance, including those dependent on ABCB1. The present study set out to characterize potential mitochondrial remodeling commensurate with ABCB1-dependent chemoresistance, as well as investigate the impact of ABCB1 activity on mitochondrial respiratory kinetics. To do this, comprehensive bioenergetic phenotyping was performed across ABCB1-dependent chemoresistant cell models and compared to chemosensitive controls. In doxorubicin (DOX) resistant ovarian cancer cells, the combination of both increased mitochondrial content and enhanced respiratory complex I (CI) boosted intrinsic oxidative phosphorylation (OXPHOS) power output. With respect to ABCB1, acute ABCB1 inhibition partially normalized intact basal mitochondrial respiration between chemosensitive and chemoresistant cells, suggesting that active ABCB1 contributes to mitochondrial remodeling in favor of enhanced OXPHOS. Interestingly, while enhanced OXPHOS power output supported ABCB1 drug efflux when DOX was present, in the absence of chemotherapeutic stress, enhanced OXPHOS power output was associated with reduced tumorigenicity.

Skeletal muscle contraction kinetics and AMPK responses are modulated by the adenine nucleotide degrading enzyme AMPD1

AMP deaminase 1 (AMPD1; AMP → IMP + NH3) deficiency in skeletal muscle results in an inordinate accumulation of AMP during strenuous exercise, with some but not all studies reporting premature fatigue and reduced work capacity. To further explore these inconsistencies, we investigated the extent to which AMPD1 deficiency impacts skeletal muscle contractile function of different muscles and the [AMP]/AMPK responses to different intensities of fatiguing contractions. To reduce AMPD1 protein, we electroporated either an inhibitory AMPD1-specific miRNA encoding plasmid or a control plasmid, into contralateral EDL and SOL muscles of C57BL/6J mice (n = 48 males, 24 females). After 10 days, isolated muscles were assessed for isometric twitch, tetanic, and repeated fatiguing contraction characteristics using one of four (None, LOW, MOD, and HIGH) duty cycles. AMPD1 knockdown (∼35%) had no effect on twitch force or twitch contraction/relaxation kinetics. However, during maximal tetanic contractions, AMPD1 knockdown impaired both time-to-peak tension (TPT) and half-relaxation time (½ RT) in EDL, but not SOL muscle. In addition, AMPD1 knockdown in EDL exaggerated the AMP response to contractions at LOW (+100%) and MOD (+54%) duty cycles, but not at HIGH duty cycle. This accumulation of AMP was accompanied by increased AMPK phosphorylation (Thr-172; LOW +25%, MOD +34%) and downstream substrate phosphorylation (LOW +15%, MOD +17%). These responses to AMPD1 knockdown were not different between males and females. Our findings demonstrate that AMPD1 plays a role in maintaining skeletal muscle contractile function and regulating the energetic responses associated with repeated contractions in a muscle- but not sex-specific manner.NEW & NOTEWORTHY AMP deaminase 1 (AMPD1) deficiency has been associated with premature muscle fatigue and reduced work capacity, but this finding has been inconsistent. Herein, we report that although AMPD1 knockdown in mouse skeletal muscle does not change maximal isometric force, it negatively impacts muscle function by slowing contraction and relaxation kinetics in EDL muscle but not SOL muscle. Furthermore, AMPD1 knockdown differentially affects the [AMP]/AMPK responses to fatiguing contractions in an intensity-dependent manner in EDL muscle.