Evaluation of cellular purine transport and metabolism in the Caco-2 cell using comprehensive high-performance liquid chromatography method for analysis of purines

Single-cell calcium monitoring of Caco-2 cell co-cultured with intestinal microbiome through carbon fiber based potentiometric microelectrode

The Caco-2 cells were used as intestinal epithelial cell model to illustrate the hyperuricemia (HUA) mechanism under the co-culture of the imbalanced intestinal microbiome in this work. The uric acid (UA) concentration in the HUA process was monitored, and could be up to 425 μmol/L at 8 h co-cultured with the imbalanced intestinal microbiome. Single-cell potentiometry based on ion-selective microelectrode was used to study extracellular calcium change, which is hypothesized to play an important role in the UA excretion. The potential signal of the calcium in the extremely limited microenvironment around single Caco-2 cell was recorded through the single-cell analysis platform. The potential signal of sharp decrease and slow increase followed within a few seconds indicates the sudden uptake and gradually excretion process of calcium through the cell membrane. Moreover, the value of the potential decrease increases with the increase of the time co-cultured with the imbalanced intestinal microbiome ranging from 0 to 8 h. The Ca2+ concentration around the cell membrane could decrease from 1.3 mM to 0.4 mM according to the potential decrease of 27.0 mV at the co-culture time of 8 h. The apoptosis ratio of the Caco-2 cells also exhibits time dependent with the co-culture of the imbalanced intestinal microbiome, and was 39.1 ± 3.6 % at the co-culture time of 8 h, which is much higher than the Caco-2 cells without any treatment (3.9 ± 2.9 %). These results firstly provide the links between the UA excretion with the apoptosis of the intestinal epithelial cell under the interaction of the imbalanced intestinal microbiome. Moreover, the apoptosis could be triggered by the calcium signaling.

Continuous flow biocatalysis: synthesis of purine nucleoside esters catalyzed by lipase TL IM from Thermomyces lanuginosus

Purine nucleoside ester is one of the derivatives of purine nucleoside, which has antiviral and anticancer activities. In this work, a continuous flow synthesis of purine nucleoside esters catalyzed by lipase TL IM from Thermomyces lanuginosus was successfully achieved. Various parameters including solvent, reaction temperature, reaction time/flow rate and substrate ratio were investigated. The best yields were obtained with a continuous flow microreactor for 35 min at 50 °C with the substrate ratio of 1 : 5 (nucleosides to vinyl esters) in the solvent of tert-amyl alcohol. 12 products were efficiently synthesized with yields of 78-93%. Here we reported for the first time the use of lipase TL IM from Thermomyces lanuginosus in the synthesis of purine nucleoside esters. The significant advantages of this methodology are a green solvent and mild conditions, a simple work-up procedure and the highly reusable biocatalyst. This research provides a new technique for rapid synthesis of anticancer and antiviral nucleoside drugs and is helpful for further screening of drug activity.

The ecto-enzymes CD73 and adenosine deaminase modulate 5'-AMP-derived adenosine in myofibroblasts of the rat small intestine

Adenosine is a versatile signaling molecule recognized to physiologically influence gut motor functions. Both the duration and magnitude of adenosine signaling in enteric neuromuscular function depend on its availability, which is regulated by the ecto-enzymes ecto-5'-nucleotidase (CD73), alkaline phosphatase (AP), and ecto-adenosine deaminase (ADA) and by dipyridamole-sensitive equilibrative transporters (ENTs). Our purpose was to assess the involvement of CD73, APs, ecto-ADA in the formation of AMP-derived adenosine in primary cultures of ileal myofibroblasts (IMFs). IMFs were isolated from rat ileum longitudinal muscle segments by means of primary explant technique and identified by immunofluorescence staining for vimentin and α-smooth muscle actin. IMFs confluent monolayers were exposed to exogenous 5'-AMP in the presence or absence of CD73, APs, ecto-ADA, or ENTs inhibitors. The formation of adenosine and its metabolites in the IMFs medium was monitored by high-performance liquid chromatography. The distribution of CD73 and ADA in IMFs was detected by confocal immunocytochemistry and qRT-PCR. Exogenous 5'-AMP was rapidly cleared being almost undetectable after 60-min incubation, while adenosine levels significantly increased. Treatment of IMFs with CD73 inhibitors markedly reduced 5'-AMP clearance whereas ADA blockade or inhibition of both ADA and ENTs prevented adenosine catabolism. By contrast, inhibition of APs did not affect 5'-AMP metabolism. Immunofluorescence staining and qRT-PCR analysis confirmed the expression of CD73 and ADA in IMFs. Overall, our data show that in IMFs an extracellular AMP-adenosine pathway is functionally active and among the different enzymatic pathways regulating extracellular adenosine levels, CD73 and ecto-ADA represent the critical catabolic pathway.

Simultaneous quantification by HPLC of purines in umami soup stock and evaluation of their effects on extracellular and intracellular purine metabolism

Ribonucleotide flavor enhancers such as inosine monophosphate (IMP) and guanosine monophosphate (GMP) provide umami taste, similarly to glutamine. Japanese cuisine frequently uses soup stocks containing these nucleotides to enhance umami. We quantified 18 types of purines (nucleotides, nucleosides, and purine bases) in three soup stocks (chicken, consommé, and dried bonito soup). IMP was the most abundant purine in all umami soup stocks, followed by hypoxanthine, inosine, and GMP. The IMP content of dried bonito soup was the highest of the three soup stocks. We also evaluated the effects of these purines on extracellular and intracellular purine metabolism in HepG2 cells after adding each umami soup stock to the cells. An increase in inosine and hypoxanthine was evident 1 h and 4 h after soup stock addition, and a low amount of xanthine and guanosine was observed in the extracellular medium. The addition of chicken soup stock resulted in increased intracellular and extracellular levels of uric acid and guanosine. Purine metabolism may be affected by ingredients present in soups.