Is lactic acid a misunderstood trigger of gout attack for a century?

A gout attack could be viewed as a nucleation event. Many reports have shown that the typical molecular structure of crystallization inhibitors usually contains carboxyl and hydroxyl groups, which could interact with solute molecules through hydrogen bonding, thereby suppressing the nucleation and growth of crystals. Since 1923, l-lactic acid (LA), a molecule with structural features of inhibitors, has been speculated to be a trigger for acute gout because metabolized LA temporarily reduces uric acid excretion and leads to a slow increase in serum uric acid concentration. However, many cases of gout presumably triggered by elevated lactate in a very short period of 4 h are often inexplicable. Here, we present the unexpected result that LA has a significant "opposite effect" on the nucleation and growth of gouty pathological crystals, which is that as the concentration of the additive LA increases, the nucleation and growth of the crystals is suppressed and then facilitated. This approach may help our clarifying the long-standing "misunderstandings" and further understanding the association between metabolized LA and increased risk of gout attacks. Finally, a novel mechanism called "tailed-made occupancy (TMO)" was used to explain the nucleation and crystallization effects of LA on sodium urate monohydrate (MSUM).

Nanocubic cobalt-containing Prussian blue analogue-derived carbon-coated CoFe alloy nanoparticles for noninvasive uric acid sensing.

This work describes an electrochemical sensor for the fast noninvasive detection of uric acid (UA) in saliva. The sensing material was based on a cobalt-containing Prussian blue analogue (Na2-xCo[Fe(CN)6]1-y, PCF). By optimizing the ratio of Co and Fe as 1.5 : 1 in PCF (PCF1.5,0), particles with a regular nanocubic morphology were formed. The calcination of PCF1.5,0 produced a carbon-coated CoFe alloy (CCF1.5), which possessed abundant defects and achieved an excellent electrochemical performance. Subsequently, CCF1.5 was modified on a screen-printed carbon electrode (SPCE) to fabricate the electrochemical sensor, CCF1.5/SPCE, which showed a sensitive and selective response toward salivary UA owing to its good conductivity, sufficient surface active sites and efficient catalytic activity. The determination of UA in artificial saliva achieved the wide linear range of 40 nM-30 µM and the low limit of detection (LOD) of 15.3 nM (3σ/s of 3). The performances of the sensor including its reproducibility, stability and selectivity were estimated to be satisfactory. The content of UA in human saliva was determined and the recovery was in the range of 98-107% and the total RSD was 4.14%. The results confirmed the reliability of CCF1.5/SPCE for application in noninvasive detection.

Colorimetric and fluorometric determination of uric acid by a suspension-based assay using enzyme-immobilized micro-sized particles.

Daily monitoring of serum uric acid levels is very important to provide appropriate treatment according to the constitution and lifestyle of individual hyperuricemic patients. We have developed a suspension-based assay to measure uric acid by adding a sample solution to the suspension containing micro-sized particles immobilized on uricase and horseradish peroxidase (HRP). In the proposed method, the mediator reaction of uricase, HRP, and uric acid produces resorufin from Amplex red. This resorufin is adsorbed onto enzyme-immobilized micro-sized particles simultaneously with its production, resulting in the red color of the micro-sized particles. The concentration of resorufin on the small surface area of the microscopic particles achieves a colorimetric analysis of uric acid with superior visibility. In addition, ethanol-induced desorption of resorufin allowed quantitative measurement of uric acid using a 96-well fluorescent microplate reader. The limit of detection (3σ) and RSD (n = 3) were estimated to be 2.2 × 10-2 µg/mL and ≤ 12.1%, respectively. This approach could also be applied to a portable fluorometer.

Iron-carbon dots embedded in molybdenum single-atom nanoflowers as multifunctional nanozyme for dual-mode detection of hydrogen peroxide and uric acid.

Single-atom catalysts (SACs) have attracted extensive attention in the field of catalysis due to their excellent catalytic ability and enhanced atomic utilization, but the multi-mode single-atom nanozymes for biosensors remain a challenging issue. In this work, iron-doped carbon dots (Fe CDs) were loaded onto the edges and pores of Mo SACs with nanoflower morphology; accordingly, a composite material Fe CDs/Mo SACs was prepared successfully, which improves the catalytic performance and develops a fluorescence mode without changing the original morphology. The steady-state kinetic data indicates that the material prepared have better affinity for substrates and faster reaction rates under optimized conditions. The specific kinetic parameters Km and Vmax were calculated as 0.39 mM and 7.502×10-7 M·s-1 respectively. The excellent peroxidase-like activity of Fe CDs/Mo SACs allows H2O2 to decompose into •OH, which in turn oxidizes colorless o-phenylenediamine (OPD) to yellow 2,3-diaminophenazine (DAP). At the same time, the fluorescence signal of Fe CDs/Mo SACs quenches obviously by DAP at 460 nm through internal filtration effect (IFE), while the characteristic fluorescence response of DAP gradually increases at 590 nm. Based on this sensing mechanism, a sensitive and accurate dual-mode (colorimetric and ratiometric fluorescent) sensor was constructed to detect H2O2 and uric acid, and the rate of recovery and linearity were acceptable for the detection of UA in human serum and urine samples. This method provides a new strategy for rapid and sensitive detection of UA, and also broadens the development of SACs in the field of biosensors.

Non-enzymatic biosensor based on F,S-doped carbon dots/copper nanoarchitecture applied in the simultaneous electrochemical determination of NADH, dopamine, and uric acid in plasma.

This work presents the synthesis and characterization of an innovative F,S-doped carbon dots/CuONPs hybrid nanostructure obtained by a direct mixture between F,S-doped carbon dots obtained electrochemically and copper nitrate alcoholic solution. The hybrid nanostructures synthesized were characterized by absorption spectroscopy in the Ultraviolet region (UV-vis), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and different electrochemical techniques. The fluoride and sulfur-doped carbon dots/CuONPs nanostructures were used to prepare a non-enzymatic biosensor on a printed carbon electrode, exhibiting excellent electrocatalytic activity for the simultaneous determination of NADH, dopamine, and uric acid in the presence of ascorbic acid with a detection limit of 20, 80, and 400 nmol L-1, respectively. The non-enzymatic biosensors were also used to determine NADH, dopamine, and uric acid in plasma, and they did not suffer significant interference from each other.

Interaction-based screening, Monte Carlo Bayesian inference-based de novo design and in vitro verification of adenine-binding peptide.

One of the main reasons for hyperuricemia is high purine intake. The primary strategy for treating hyperuricemia is blocking the purine metabolism enzyme. However, by binding the purine bases directly, we suggested a unique therapeutic strategy that might interfere with purine metabolism. There have been numerous reports of extensive interactions between proteins and purine bases. Adenine, constituting numerous protein co-factors, can interact with the adenine-binding motif. Using Bayesian Inference and Markov chain Monte Carlo sampling, we created a novel adenine-binding peptide Ile-Tyr-Val-Thr based on the structure of the adenine-binding motifs. Ile-Tyr-Val-Thr generates a semi-pocket that can clip the adenine within, as demonstrated by docking. Then, using thermodynamic techniques, the interaction between Ile-Tyr-Val-Thr and adenine was confirmed. The KD value is 1.50e-5 (ΔH = -20.2 kJ/mol and ΔG = -27.6 kJ/mol), indicating the high affinity. In brief, the adenine-binding peptide Ile-Tyr-Val-Thr may help lower uric acid level by blocking the absorption of food-derived adenine.

Crystal structure of the complex of CLEC12A and an antibody that interferes with binding of diverse ligands.

C-type lectin receptors (CLRs) are a family of pattern recognition receptors, which detect a broad spectrum of ligands via small carbohydrate-recognition domains (CRDs). CLEC12A is an inhibitory CLR that recognizes crystalline structures such as monosodium urate crystals. CLEC12A also recognizes mycolic acid, a major component of mycobacterial cell walls, and suppresses host immune responses. Although CLEC12A could be a therapeutic target for mycobacterial infection, structural information on CLEC12A was not available. We report here the crystal structures of human CLEC12A (hCLEC12A) in ligand-free form and in complex with 50C1, its inhibitory antibody. 50C1 recognizes human-specific residues on the top face of hCLEC12A CRD. A comprehensive alanine scan demonstrated that the ligand-binding sites of mycolic acid and monosodium urate crystals may overlap with each other, suggesting that CLEC12A utilizes a common interface to recognize different types of ligands. Our results provide atomic insights into the blocking and ligand-recognition mechanisms of CLEC12A and leads to the design of CLR-specific inhibitors.

Modulation of the dissolution with ASP from a supersaturated solution on a bionic platform for gout pathology crystals.

The core to the treatment of gout is the elimination of pathologic crystal, monosodium urate monohydrate (MSUM). The primary treatment available is to gradually dissolve the "culprit crystals" by lowering the blood uric acid concentration with medications, which often takes a long time and in severe cases must still be treated surgically. Herein, we developed a dynamic bionic platform based on a hydrogel composite membrane (HCM) to screen the direct facilitated solubilization of MSUM crystals by small organic molecules in bionic saturated, or even supersaturated, solutions. The customized and biologically safe (NAGA/PEGDA/NIPAM) HCM, which is consistent with the main amino acid composition of articular cartilage, well mimics the entire process of organic molecules leading to the dissolution of MSUM crystals in the joint system. With the verifications of this platform, it is shown that l-aspartic acid (ASP) significantly promotes the dissolution of MSUM crystals not only in saturated but also in supersaturated solutions. Furthermore, a novel mechanism called "crane effect" was used to explain this "dissolution effect" of ASP on MSUM, which stems from the ability of ASP to lock onto the surface of MSUM crystals through hydrogen bonding by virtue of its two carboxyl groups, and simultaneously its amino group lifts the uric acid molecules from the surface of MSUM crystals by virtue of interactions of hydrogen bonding. The results of bulk crystallization, scanning electron microscopy (SEM), powder X-diffraction (PXRD), and density-functional theory (DFT) studies are quantitatively consistent with this hypothetical "crane effect" mechanism. Hence, this HCM-based functional platform could provide entirely novel ideas and methods for drug design and screening for the treatment of pathological crystal diseases of gout.

Mechanistic insights into the C-type lectin receptor CLEC12A-mediated immune recognition of monosodium urate crystal.

CLEC12A, a member of the C-type lectin receptor family involved in immune homeostasis, recognizes MSU crystals released from dying cells. However, the molecular mechanism underlying the CLEC12A-mediated recognition of MSU crystals remains unclear. Herein, we reported the crystal structure of the human CLEC12A-C-type lectin-like domain (CTLD) and identified a unique "basic patch" site on CLEC12A-CTLD that is necessary for the binding of MSU crystals. Meanwhile, we determined the interaction strength between CLEC12A-CTLD and MSU crystals using single-molecule force spectroscopy. Furthermore, we found that CLEC12A clusters at the cell membrane and seems to serve as an internalizing receptor of MSU crystals. Altogether, these findings provide mechanistic insights for understanding the molecular mechanisms underlying the interplay between CLEC12A and MSU crystals.

Protocol to create a murine subcutaneous air pouch for the study of monosodium urate crystal-induced gout.

Monosodium urate (MSU) crystal deposition in articular joints and bursal tissue causes acute joint inflammation, which is a hallmark of gout. Here, we describe the steps necessary to create a subcutaneous air pouch on the back of mice that resembles this bursa-like space with a synovial lining-like membrane. We then detail the injection of MSU crystals into this pouch, which induces a localized inflammatory response reminiscent of gout and approaches to quantify the inflammatory response. For complete details on the use and execution of this protocol, please refer to Devi et al. (2023),1 de Almeida et al. (2022),2 and Ratsimandresy et al. (2017).3.

Optimization of cardiovascular risk factor management in patients with BCR::ABL1 negative chronic myeloproliferative neoplasms, current knowledge, and perspectives.

The exact prognostic role of cardiovascular (CV) risk factors in patients with BCR::ABL1 negative chronic myeloproliferative neoplasms (MPNs) remains unknown as it is often masked by other MPN-related features that bear strong prognostic impact on thrombotic risk. Therefore, current MPN treatment is not primarily guided by presence of CV risk factors. Treatment of CV risk factors in MPN patients usually mirrors that from the general population, despite the fact that CV risk factors in MPNs have their own specificities. Moreover, the optimal target levels for different metabolic deflections in MPNs (i.e., low-density lipoprotein, serum uric acid, or glycated hemoglobin levels) have not been defined. In the current review, we separately discuss the most important aspects of every individual CV risk factor (arterial hypertension, hyperlipidemia, chronic kidney disease, smoking, diabetes mellitus, hyperuricemia, and obesity and cachexia) in MPNs, summarize recent advances in the field, and propose future directions and research areas which may be needed to appropriately manage CV risk factors in MPNs.

Agents for the Treatment of Gout: Current Advances and Future Perspectives.

Gout is characterized by hyperuricemia and the deposition of monosodium urate (MSU) crystals around joints. Despite the availability of several drugs on the market, its treatment remains challenging owing to the notable side effects, such as hepatorenal toxicity and cardiovascular complications, that are associated with most existing agents. This perspective aims to summarize the current research progress in the development of antigout agents, particularly focusing on xanthine oxidase (XO) and urate anion transporter 1 (URAT1) inhibitors from a medicinal chemistry viewpoint and their preliminary structure-activity relationships (SARs). This perspective provides valuable insights and theoretical guidance to medicinal chemists for the discovery of antigout agents with novel chemical structures, better efficiency, and lower toxicity.

Efficient Synergistic Cooperation of an Arginine-Rich Peptide and Copper Ions in Sodium Urate Crystallization Inhibition.

Although many studies have focused on the role of individual biomolecules or metal ions in the crystallization behavior of sodium urate, the regulatory effects of multiple molecular species still remain mysterious. The synergistic cooperation of biomolecules and metal ions may contribute to unprecedented regulatory effects. Here, the cooperative effect of arginine-rich peptides (APs) and copper ions on the phase behavior, crystallization kinetics, and size/morphology of urate crystals was first investigated. Compared with the individual copper ion and AP, the nucleation induction time of sodium urate is prolonged dramatically (about 48 h), and the nucleation rate of sodium urate is reduced efficiently in a saturated solution due to the synergistic effect of Cu2+ and AP in stabilizing amorphous sodium urate (ASU). The length of sodium urate monohydrate crystals decreases obviously under the synergistic effect of Cu2+ and AP. The comparative experiments of common transition metal cations show that only copper ions can cooperate with AP, which may be due to the strong coordination effect between copper ions with urate and AP. Further studies show that the synergistic effect of copper ions and APs with different chain lengths on the crystallization behavior of sodium urate is significantly different. Both the guanidine functional groups and the length of peptide chains simultaneously determine the synergistic inhibition effect of polypeptides and Cu2+. This work highlights the synergistic inhibition effect of metal ions and cationic peptides on the crystallization of sodium urate, which enriches the understanding of the regulating mechanism of biological mineral crystallization using the synergy of multispecies and offers a new strategy for designing efficient inhibitors for sodium urate crystallization in gout stone diseases.

Efficacy of Theobromine and Its Metabolites in Reducing the Risk of Uric Acid Lithiasis.

Uric acid lithiasis accounts for about 10% of all types of renal lithiasis. The most common causes of uric acid lithiasis are low urinary pH, followed by high concentration of urinary uric acid, and low diuresis. Treatment of patients consists of alkalinization of urine, reducing the consumption of purine-rich foods, and administration of xanthine oxidase inhibitors, because there are no established therapeutic inhibitors of uric acid crystallization. We recently found that theobromine inhibited uric acid crystallization in vitro, and that the increased urinary level of theobromine following its oral consumption was associated with the prevention of uric acid crystallization. In this study, we evaluated the inhibitory effects of theobromine metabolites and other methylxanthine-related compounds on uric acid crystallization. We also measured the urinary concentrations of theobromine and its metabolites in samples from healthy individuals and patients with uric acid stones and compared the extent of uric acid supersaturation and uric acid crystal formation in these different samples. Theobromine and other methylxanthines that lacked a substituent at position 1 inhibited uric acid crystallization, but other methylxanthines did not have this effect. Individuals with clinical parameters that favored uric acid crystallization did not develop uric acid crystals when theobromine and its metabolites were in the urine at high levels. Thus, theobromine and its metabolites reduced the risk of uric acid lithiasis.

Synovial fluid analysis: Relevance for daily clinical practice.

Synovial fluid analysis can provide a prompt and definite diagnosis of crystal-induced arthritis, the most common acute inflammatory arthritis and a cause of chronic arthritis that may mimic rheumatoid, psoriatic, or peripheral spondyloarthritis. In many patients the diagnosis of gout or calcium pyrophosphate arthritis cannot be made with certainty without synovial fluid analysis. Additional information from fluid analysis can assist the clinician in honing the differential diagnosis of non-crystalline arthritis.

Tailored hydrogel composite membrane for the regulated crystallization of monosodium urate monohydrate within coffee's metabolites system.

Herein, a facile bionic research platform with fabricated hydrogel composite membrane (HCM) is constructed to uncover the effects of the main components of coffee's metabolites on MSUM crystallization. Tailored and biosafety polyethylene glycol diacrylate/N-isopropyl acrylamide (PEGDA/NIPAM) HCM allows the proper mass transfer of coffee's metabolites and can well simulate the process of coffee's metabolites acting in the joint system. With the validations of this platform, it is shown that chlorogenic acid (CGA) can hinder the MSUM crystals formation from 45 h (control group) to 122 h (2 mM CGA), which is the most likely reason that reduces the risk of gout after long-term coffee consumption. Molecular dynamics simulation further indicates that the high interaction energy (Eint) between CGA and MSUM crystal surface and the high electronegativity of CGA both contribute to the restraint of MSUM crystal formation. In conclusion, the fabricated HCM, as the core functional materials of the research platform, presents the understanding of the interaction between coffee consumption and gout control.

Ultralight 3D Graphene Oxide Aerogel Decorated with Pd-Fe Nanoparticles for the Simultaneous Detection of Eight Biomolecules.

In this proof-of-concept study, an ultralight graphene oxide aerogel (GOx-Aero) decorated with bimetallic palladium-iron nanoparticles (Pd-Fe) was synthesized and immobilized on a glassy carbon electrode (GCE) for electrochemical sensor applications. The main objective of this work was to develop a sensitive electrochemical sensor capable of simultaneously detecting eight biomolecules, including ascorbic acid (AA), dopamine (DA), uric acid (UA), 8-hydroxyguanine (8HG), guanine (G), adenine (A), thymine (T), and cytosine (C). To the best of our knowledge, this is the first time that an electrochemical sensor has been able to detect eight biomolecules simultaneously. The bimetallic GOx aerogel significantly enhanced the performance of the sensor by increasing the electroactive area, conductivity, and anodic peak current response. The sensor demonstrated sharp, well-defined, and continuous oxidation peaks for all eight analytes of interest and wide linear ranges of 5.0-1750, 0.25-100.0, 0.5-500.0, 0.5-375.0, 0.5-500.0, 0.5-500.0, 5.0-1500.0, and 5.0-1500.0 µM for AA, DA, UA, 8HG, G, A, T, and C, respectively. The prepared sensor also exhibited excellent stability, reproducibility, and sensitivity with a very low limit of detection (LOD) of 553.7, 1.8, 69.6, 43.2, 42.9, 72.3, 57.2, and 318.4 nM for AA, DA, UA, 8HG, G, A, T, and C, respectively. The Pd-Fe-GOx-Aero-GCE was also tested in various real samples such as artificial saliva, artificial cerebrospinal fluid (CSF), salmon sperm DNA, and genomic DNA from calf thymus, where it demonstrated good recovery values. Additionally, the novel developed sensor was used to monitor the interaction between the anticancer drug, cisplatin, which has well-described binding affinity with the G and A bases in DNA. Overall, Pd-Fe-GOx-Aero-GCE displayed an extremely promising platform not only for the simultaneous detection of eight biomolecules in complex biological matrices but also for DNA-drug interaction studies toward the development of electrochemical high-throughput drug screening assays, which is of great importance in the field.

Holey MoS2-based electrochemical sensors for simultaneous dopamine and uric acid detection.

In this study, two-dimensional holey MoS2 (h-MoS2) nanosheets were used to develop electrochemical sensors for simultaneous detection of dopamine (DA) and uric acid (UA). The holes were created on MoS2 layers using hydrogen peroxide (H2O2) in the presence of Bovine Serum Albumin (BSA). h-MoS2 was characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, dynamic light scattering (DLS), and ultraviolet-visible spectroscopy (UV-vis). Electrochemical dopamine and uric acid sensors were prepared by drop-casting h-MoS2 on a glassy carbon electrode (GCE). The electroanalytical performance of the sensors was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) methods. The sensors revealed linear ranges between 50-1200 µM and 200-7000 µM with a limit of detection (LOD) of 4.18 µM and 5.62 µM for DA and UA, respectively. Furthermore, the h-MoS2-based electrochemical sensors showed high stability, sensitivity, and selectivity. The reliability of the sensors was elucidated in human serum. Recoveries ranging between 100.35% and 102.48% were calculated from real sample experiments.

A Novel Polyurethane-Based Polyion Complex Material with Tunable Selectivity against Interferents for Selective Dopamine Determination.

Polyion complex (PIC) materials have been widely used in biosensors due to their molecular selectivity. However, achieving both widely controllable molecular selectivity and long-term solution stability with traditional PIC materials has been challenging due to the different molecular structures of polycations (poly-C) and polyanions (poly-A). To address this issue, we propose a novel polyurethane (PU)-based PIC material in which the main chains of both poly-A and poly-C are composed of PU structures. In this study, we electrochemically detect dopamine (DA) as the analyte and L-ascorbic acid (AA) and uric acid (UA) as the interferents to evaluate the selective property of our material. The results show that AA and UA are significantly eliminated, while DA can be detected with a high sensitivity and selectivity. Moreover, we successfully tune the sensitivity and selectivity by changing the poly-A and poly-C ratios and adding nonionic polyurethane. These excellent results were employed in the development of a highly selective DA biosensor with a detection range from 500 nM to 100 µM and a 3.4 µM detection limit. Overall, our novel PIC-modified electrode has the potential to advance biosensing technologies for molecular detection.

An ultra-sensitive uric acid second generation biosensor based on chemical immobilization of uricase on functionalized multiwall carbon nanotube grafted palm oil fiber in the presence of a ferrocene mediator.

In this work, palm oil fiber (POF) grafted functionalized multiwall carbon nanotube (FMWCNT) decorated ferrocene (Fc) has been drop coated on a platinum electrode (Pt), in which uricase (UOx) has been chemically immobilized for sensitive and selective biosensing of uric acid (UA). Through the use of EDC/NHS, a stable bioelectrode (UOx/Fc/FMWCNT-POF/Pt) was obtained and characterized by FTIR/ATRIR, XRD, Raman, EA/EDX, TGA, SEM, TEM, CV, EIS, CA, and DPV. Results from DPV showed the rapid response of the developed bioelectrode towards UA (0.185 V) with high sensitivity (41.14 µA mM-1) and good limit of detection (19 µM) in the linear range 10-1000 µM. The low value of Michaelis-Menten constant (km = 31.364 µM) shows high affinity of the UA towards the enzyme at the electrode surface. The developed biosensor demonstrates good reproducibility, repeatability, and stability with a deviation of less than 2.5%, and was successfully applied for human blood sample analysis. The CA study revealed a fast response time (2 s) of the sensor. The work has pioneered a new addition to the class of tailorable chemical species for biosensor development and proven to be a promising new tool for point of care testing (POCT) applications.