Uric acid released from poly(ε-caprolactone) fibers as a treatment platform for spinal cord injury.

Spinal cord injury (SCI) is characterized by a primary mechanical phase of injury, resulting in physical tissue damage, and a secondary pathological phase, characterized by biochemical processes contributing to inflammation, neuronal death, and axonal demyelination. Glutamate-induced excitotoxicity (GIE), in which excess glutamate is released into synapses and overstimulates glutamate receptors, is a major event in secondary SCI. GIE leads to mitochondrial damage and dysfunction, release of reactive oxygen species (ROS), DNA damage, and cell death. There is no clinical treatment that targets GIE after SCI, and there is a need for therapeutic targets for secondary damage in patients. Uric acid (UA) acts as an antioxidant and scavenges free radicals, upregulates glutamate transporters on astrocytes, and preserves neuronal viability in in vitro and in vivo SCI models, making it a promising therapeutic candidate. However, development of a drug release platform that delivers UA locally to the injured region in a controlled manner is crucial, as high systemic UA concentrations can be detrimental. Here, we used the electrospinning technique to synthesize UA-containing poly(ɛ-caprolactone) fiber mats that are biodegradable, biocompatible, and have a tunable degradation rate. We optimized delivery of UA as a burst within 20 min from uncoated fibers and sustained release over 2 h with poly(ethylene glycol) diacrylate coating. We found that both of these fibers protected neurons and decreased ROS generation from GIE in organotypic spinal cord slice culture. Thus, fiber mats represent a promising therapeutic for UA release to treat patients who have suffered a SCI.

Development of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for characterizing caffeine, methylliberine, and theacrine pharmacokinetics in humans.

Coffea liberica possesses stimulant properties without accumulating the methylxanthine caffeine. The basis for this peculiar observation is that methylurates (e.g., theacrine and methylliberine) have replaced caffeine. The stimulant properties of methylurates, alone and in combination with caffeine, have recently been investigated. However, human pharmacokinetics and LC-MS/MS methods for simultaneous measurement of methylxanthines and methylurates are lacking. To address this deficiency, we conducted a pharmacokinetic study in which subjects (n = 12) were orally administered caffeine (150 mg), methylliberine (Dynamine™, 100 mg), and theacrine (TeaCrine®, 50 mg) followed by blood sampling over 24 h. Liquid-liquid extraction of plasma samples containing purine alkaloids and internal standard (13C-Caffeine) were analyzed using a C18 reversed-phase column and gradient elution (acetonitrile and water, both containing 0.1% formic acid). A Waters Xevo TQ-S tandem mass spectrometer (positive mode) was used to detect caffeine, methylliberine, theacrine, and IS transitions of m/z 195.11 â†’ 138.01, 225.12 â†’ 168.02, 225.12 â†’ 167.95, and 198.1 â†’ 140.07, respectively. The method was validated for precision, accuracy, selectivity, and linearity and was successfully applied to characterize the oral pharmacokinetics of caffeine, methylliberine, and theacrine in human plasma. Successful development and application of LC-MS/MS-based methods such as ours for the simultaneous measurement of methylxanthines and methylurates are essential for the characterization of potential pharmacokinetic and pharmacodynamic interactions.

What Is the Biological Function of Uric Acid? An Antioxidant for Neural Protection or a Biomarker for Cell Death.

The main aim of the present study was to investigate the biological function of uric acid. The level of uric acid in different organs in normal male rats was determined with uric acid assay kits, and the expression level of genes in the organs was determined by RNA quantitative sequencing. The correlation analysis between uric acid in the organs and gene expression (measured by FPKM value) was made. Serum uric acid (SUA) in patients with breast cancer or with breast benign tumor was assayed when the diagnosis was made, and SUA in patients with breast cancer was also assayed just after chemotherapy. There were 1937 mRNAs whose expression level significantly correlated with the level of uric acid, and most of which were associated with purine or nucleoside metabolism, cellular metabolism, cell cycles, and cell death pathways. Further analysis showed that the level of uric acid was highly correlated with cell death rather than cell viability. The level of SUA in patients with breast cancer was higher than that in patients with breast benign tumor, and the SUA increased after chemotherapy. All the results suggested that uric acid was mainly synthesized from local nucleosides degraded from dead cells, and uric acid could be an important biomarker for cell death rather than an antioxidant for neural protection.

Recombinant human proteoglycan-4 reduces phagocytosis of urate crystals and downstream nuclear factor kappa B and inflammasome activation and production of cytokines and chemokines in human and murine macrophages.

BACKGROUND: Gout is an inflammatory arthritis caused by monosodium urate monohydrate (MSU) crystals' joint deposition. MSU phagocytosis by resident macrophages is a key step in gout pathogenesis. MSU phagocytosis triggers nuclear factor kappa B (NFκB) activation and production of cytokines and chemokines. Proteoglycan-4 (PRG4) is a glycoprotein produced by synovial fibroblasts and exerts an anti-inflammatory effect in the joint mediated by its interaction with cell surface receptor CD44. PRG4 also binds and antagonizes TLR2 and TLR4. The objective of this study is to evaluate the efficacy of recombinant human PRG4 (rhPRG4) in suppressing MSU-induced inflammation and mechanical allodynia in vitro and in vivo. METHODS: THP-1 macrophages were incubated with MSU crystals ± rhPRG4 or bovine submaxillary mucin (BSM), and crystal phagocytosis, cytokines and chemokines expression and production were determined. NFκB p65 subunit nuclear translocation, NLRP3 induction, caspase-1 activation and conversion of proIL-1ß to mature IL-1ß were studied. MSU phagocytosis by Prg4+/+ and Prg4-/- peritoneal macrophages was determined in the absence or presence of rhPRG4, BSM, anti-CD44, anti-TLR2, anti-TLR4 and isotype control antibodies. Rhodamine-labeled rhPRG4 was incubated with murine macrophages and receptor colocalization studies were performed. Lewis rats underwent intra-articular injection of MSU crystals followed by intra-articular treatment with PBS or rhPRG4. Weight bearing and SF myeloperoxidase activities were determined. RESULTS: rhPRG4 reduced MSU crystal phagocytosis at 4 h (p < 0.01) and IL-1ß, TNF-α, IL-8 and MCP-1 expression and production at 6 h (p < 0.05). BSM did not alter MSU phagocytosis or IL-1ß production in human and murine macrophages. rhPRG4 treatment reduced NFκB nuclear translocation, NLRP3 expression, caspase-1 activation and generation of mature IL-1ß (p < 0.05). MSU-stimulated IL-1ß production was higher in Prg4-/- macrophages compared to Prg4+/+ macrophages (p < 0.001). rhPRG4, anti-CD44, anti-TLR2 and anti-TLR4 antibody treatments reduced MSU phagocytosis and IL-1ß production in murine macrophages (p < 0.05). rhPRG4 preferentially colocalized with CD44 on Prg4-/- peritoneal macrophages compared to TLR2 or TLR4 (p < 0.01). rhPRG4 normalized weight bearing and reduced SF myeloperoxidase activity compared to PBS in vivo. CONCLUSION: rhPRG4 inhibits MSU crystal phagocytosis and exhibits an anti-inflammatory and anti-nociceptive activity in vitro and in vivo. rhPRG4's anti-inflammatory mechanism may be due to targeting CD44 on macrophages.

Phloretin attenuates hyperuricemia-induced endothelial dysfunction through co-inhibiting inflammation and GLUT9-mediated uric acid uptake.

Hyperuricemia is an important risk factor for cardiovascular and renal diseases. Phloretin had shown antioxidant and anti-inflammatory properties, but its role in endothelial injury is rarely reported. In this study, we aimed to investigate the protective effect of phloretin on UA-induced injury in human umbilical vein endothelial cells. The effects of UA and phloretin on cell viability, inflammation, THP-1 monocyte adhesion, endothelial cell tube formation, GLUT9 expression and UA uptake in human umbilical vein endothelial cells were evaluated. The changes of nuclear factor-kappa B/extracellular regulated protein kinases signalling were also analysed. Our results showed that UA reduced cell viability and tube formation, and increased inflammation and monocytes adhesion in human umbilical vein endothelial cells in a dose-dependent manner. In contrast, phloretin significantly attenuated pro-inflammatory factors expression and endothelial injury induced by UA. Phloretin inhibited the activation of extracellular regulated protein kinases/nuclear factor-kappa B pathway, and reduced GLUT9 and it mediated UA uptake in human umbilical vein endothelial cells. These results indicated that phloretin attenuated UA-induced endothelial injury via a synergic mechanism including direct anti-inflammatory effect and lowering cellular UA uptake. Our study suggested that phloretin might be a promising therapy for hyperuricemia-related cardiovascular diseases.

[Determination of theacrine in rat plasma by RP-HPLC].

OBJECTIVE: To establish a method for the determination of theacrine in rat plasma after ig. administration of theacrine. METHOD: Blood sample was taken timely from the eyes canthus of rats. Plasma was isolated and the protein was precipitated by ethyl acetate. Then the plasma concentration of theacrine was determined with RP-HPLC. Caffeine was used as the internal standard. The chromatographic conditions were as follows: Phenomenex Luna C18 (4.6 mm x 250 mm, 5 microm) at 25 degrees C, a mixture of methanol-water (25: 75) as the mobile phase, at the flow rate of 1.0 mL x min(-1) and the detection wavelength of 290 nm. RESULT: The linear range of theacrine was 0.5-100 mg x L(-1) (R2 = 0.998 9). The lower limit of quantification was 0.5 mg x L(-1). The intra-day RSD was 1.49% 4.40% and inter-day RSD was 0.80% -10.27%. The average extraction recoveries of theacrine were 90.3% -95.8% at concentrations of 0.5, 5.0, 50 mg x L(-1). The main pharmacokinetic parameters after ig. administration of theacrine at concentration of 30 mg x kg(-1) were as follow: C(max) (35.45 +/- 30 2.68) mg x L(-1), t(max) (0.51 +/- 0.13) h, t1/2 (3.13 +/- 1.37) h, AUC(0-infinity) (2.65.39 +/- 94.71) mg x L(-1) x h. CONCLUSION: The method has been confirmed to be simple, stable, reproducible and with high specificity, and can be used for the pharmacokinetic study of theacrine in rats.

[Transporter-mediated regulation of pharmacokinetics of lifestyle-related substances].

Recent studies revealed the importance of transporters in the behaviors of small molecules in the body. In mammals, the presence of a lot of transporters has been suggested, such as ATP-binding cassette (ABC) transporters and solute ligand carrier (SLC) transporters, some of which are clarified to be causative genes for various kinds of genetic disorders. In addition, a lot of transporters are known to mediate cellular import or export of drugs, to contribute to the pharmacokinetics of substrate drugs and to be involved in the interindividual differences of drug responses. In this review, I introduce our recent work on the transporter-mediated regulation of pharmacokinetics of lifestyle-related substances, such as cholesterol and urate.

Functional analysis of human sodium-phosphate transporter 4 (NPT4/SLC17A3) polymorphisms.

We analyzed the functional properties of five nonsynonymous single nucleotide polymorphisms (SNPs) in the sodium-phosphate transporter NPT4 gene (SLC17A3) using the Xenopus oocyte expression system. NPT4 variants carrying SNP V257F, G279R, or P378L exhibited reduced transport of [(14)C]para-aminohippurate, [(3)H]bumetanide, [(3)H]estrone sulfate, and [(14)C]urate, when each variant clone was expressed in the plasma membrane of oocytes. This study suggests the possibility that the genetic variation of NPT4 contributes to inter-individual differences in disposition of anionic drugs such as diuretics as well as certain endogenous organic anions such as urate.

Identification and functional characterization of uric acid transporter Urat1 (Slc22a12) in rats.

Uric acid transporter URAT1 contributes significantly to reabsorption of uric acid in humans to maintain a constant serum uric acid (SUA) level. Since alteration of SUA level is associated with various diseases, it is important to clarify the mechanism of change in SUA. However, although expression of mRNA of an ortholog of URAT1 (rUrat1) in rats has been reported, functional analysis and localization have not been done. Therefore, rat rUrat1 was functionally analyzed using gene expression systems and isolated brush-border membrane vesicles (BBMVs) prepared from rat kidney, and its localization in kidney was examined immunohistochemically. Uric acid transport by rUrat1 was chloride (Cl-) susceptible with a Km of 1773µM. It was inhibited by benzbromarone and trans-stimulated by lactate and pyrazinecarboxylic acid (PZA). Cl- gradient-susceptible uric acid transport by BBMVs showed similar characteristics to those of uric acid transport by rUrat1. Moreover, rUrat1 was localized at the apical membrane in proximal tubular epithelial cells in rat kidney. Accordingly, rUrat1 is considered to be involved in uric acid reabsorption in rats in the same manner as URAT1 in humans. Therefore, rUrat1 may be a useful model to study issues related to the role of human URAT1.

Lack of effect of hydrochlorothiazide and low-dose aspirin on the renal clearance of urate and oxypurinol after a single dose of allopurinol in normal volunteers.

AIMS: To determine whether low-dose aspirin and hydrochlorothiazide (HCTZ) affect the renal clearance of oxypurinol and/or urate. METHODS: Healthy volunteers (n = 8) were treated with allopurinol (600 mg, control), and allopurinol (600 mg) co-administered with single doses of aspirin (100 mg) or HCTZ (25 mg) or a combination of the two. RESULTS: Hydrochlorothiazide, low-dose aspirin or a combination of the two, when co-administered with allopurinol, did not significantly alter (P > 0.05) the renal clearance of oxypurinol or urate. In particular, aspirin and HCTZ, when taken together and with allopurinol, did not change (P > 0.05) oxypurinol fractional renal clearance (allopurinol alone: 0.217, 0.173-0.262; combined: 0.202, 0.155-0.250) or urate fractional renal clearance (allopurinol alone: 0.066, 0.032-0.099; combined: 0.058, 0.038-0.078). CONCLUSIONS: A single, low-dose of aspirin or an anti-hypertensive dose of hydrochlorothiazide, when administered alone or together with allopurinol, are unlikely to alter the hypouricaemic effect of allopurinol. The effect of chronic aspirin and HCTZ dosing taken together upon the efficacy of chronic allopurinol therapy in patients with hyperuricaemia needs to be investigated.