Therapeutic perspectives on uricases for gout

Immunogenicity-masking delivery of uricase against hyperuricemia and gout

Improving the activity of uricase and lowering its immunogenicity remain significant challenges in the enzyme replacement management of hyperuricemia and related inflammatory diseases. Herein, an immunogenicity-masking strategy based on engineered red blood cells (RBCs) was developed for effective uricase delivery against both hyperuricemia and gout. The dynamic membrane of RBCs enabled high resistance to protease inactivation and hydrogen peroxide accumulation. Benefiting from these advantages, a single infusion of RBC-loaded uricase (Uri@RBC) performed prolonged blood circulation and sustained hyperuricemia management. Importantly, RBCs masked the immunogenicity of uricase, leading to the maintenance of UA-lowering performance after repeated infusion through reduced antibody-mediated macrophage clearance. In an acute gout model, Uri@RBC profoundly alleviated joint edema and inflammation with minimal systemic toxicity. This study supports the employment of immunogenicity-masking tools for efficient and safe enzyme delivery, and this strategy may be leveraged to improve the usefulness of enzyme replacement therapies for managing a wide range of inflammatory diseases.

Maximization of uricase production in a column bioreactor through response surface methodology-based optimization

Uricase (EC 1.7.3.3) is an oxidoreductase enzyme that is widely exploited for diagnostic and treatment purposes in medicine. This study focuses on producing recombinant uricase fromE. coliBL21 in a bubble column bioreactor (BCB) and finding the optimal conditions for maximum uricase activity. The three most effective variables on uricase activity were selected through the Plackett-Burman design from eight different variables and were further optimized by the central composite design of the response surface methodology (RSM). The selected variables included the inoculum size (%v/v), isopropylβ-d-1-thiogalactopyranoside (IPTG) concentration (mM) and the initial pH of the culture medium. The activity of uricase, the final optical density at 600 nm wavelength (OD600) and the final pH were considered as the responses of this optimization and were modeled. As a result, activity of 5.84 U·ml-1and a final OD600of 3.42 were obtained at optimum conditions of 3% v/v inoculum size, an IPTG concentration of 0.54 mM and a pH of 6.0. By purifying the obtained enzyme using a Ni-NTA agarose affinity chromatography column, 165 ± 1.5 mg uricase was obtained from a 600 ml cell culture. The results of this study show that BCBs can be a highly effective option for large-scale uricase production.

In vivo study of newly developed albumin-conjugated urate oxidase for gout treatment

BACKGROUND

Exogenously providing engineered Uox with enhanced half-life is one of the important urate-lowering treatments for gout. The potential of PAT101, a recombinant human albumin (rHA)-conjugated variant, was evaluated and compared as a novel gout treatment through various in vivo studies with PAT101 and competing drugs.

METHODS

PAT101 was produced by site-specific conjugation of rHA and Aspergillus flavus Uox (AfUox-rHA) through clickable non-natural amino acid (frTet) and Inverse electron demand Diels-Alder (IEDDA) reaction. In vivo pharmacokinetics, efficacy tests and in vitro immunogenetic assay were performed after single or multiple doses of PAT101 and its competitors in BALB/c mice, transgenic (TG) mice, Sprague-Dawley (SD) rats, and non-human primate (NHP).

RESULTS

The half-life of PAT101 in single-dose treated TG mice was more than doubled compared to pegloticase. In SD rats with 4 weeks of repeated administration of rasburicase, only 24% of Uox activity remained, whereas in PAT101, it was maintained by 86%. In the Uox KO model, the survival rate of PAT101 was comparable to that of pegloticase. In addition, human PBMC-based CD4+/CD8+ T-cell activation analysis demonstrated that PAT101 has a lower immune response compared to the original drug, rasburicase.

CONCLUSION

All results suggest that this rHA-conjugated AfUox, PAT101, can be provided as a reliable source of Uox for gout treatment.

Mechanisms and rationale for uricase use in patients with gout

Xanthine oxidase inhibitors such as allopurinol and febuxostat have been the mainstay urate-lowering therapy (ULT) for treating hyperuricaemia in patients with gout. However, not all patients receiving oral ULT achieve the target serum urate level, in part because some patients cannot tolerate, or have actual or misconceived contraindications to, their use, mainly due to comorbidities. ULT dosage is also limited by formularies and clinical inertia. This failure to sufficiently lower serum urate levels can lead to difficult-to-treat or uncontrolled gout, usually due to poorly managed and/or under-treated gout. In species other than humans, uricase (urate oxidase) converts urate to allantoin, which is more soluble in urine than uric acid. Exogenic uricases are an exciting therapeutic option for patients with gout. They can be viewed as enzyme replacement therapy. Uricases are being used to treat uncontrolled gout, and can achieve rapid reduction of hyperuricaemia, dramatic resolution of tophi, decreased chronic joint pain and improved quality of life. Availability, cost and uricase immunogenicity have limited their use. Uricases could become a leading choice in severe and difficult-to-treat gout as induction and/or debulking therapy (that is, for lowering of the urate pool) to be followed by chronic oral ULT. This Review summarizes the evidence regarding available uricases and those in the pipeline, their debulking effect and their outcomes related to gout and beyond.

The landscape of pathophysiology guided therapeutic strategies for gout treatment

INTRODUCTION

Gout is a common autoinflammatory disease caused by hyperuricemia with acute and/or chronic inflammation as well as tissue damage. Currently, urate-lowering therapy (ULT) and anti-inflammatory therapy are used as first-line strategies for gout treatment. However, traditional drugs for gout treatment exhibit some unexpected side effects and are not suitable for certain patients due to their comorbidity with other chronic disease.

AREAS COVERED

In this review, we described the pathophysiology of hyperuricemia and monosodium urate (MSU) crystal induced inflammatory response during gout development in depth and comprehensively summarized the advances in the investigation of promising ULT drugs as well as anti-inflammatory drugs that might be safer and more effective for gout treatment.

EXPERT OPINION

New drugs that are developed based on these molecular mechanisms exhibited great efficacy on reduction of disease burden both in vitro and in vivo, implying their potential for clinical application. Moreover, hyperthermia also showed regulation effect on MSU crystals formation and the signaling pathways involved in inflammation.

Pegloticase efficacy and safety in kidney transplant recipients; results of the phase IV, open-label PROTECT clinical trial

INTRODUCTION

Kidney transplant (KT) recipients have a high prevalence and severity of gout. Pegloticase (pegylated recombinant uricase) rapidly metabolizes serum uric acid (sUA), and its efficacy is not impacted by kidney function.

METHODS

This open-label, Phase 4 trial (PROTECT NCT04087720) examined safety and efficacy of pegloticase in 20 participants with KT > 1 year prior to enrollment and with uncontrolled gout (sUA ≥7 mg/dL, intolerance/inefficacy to urate lowering therapy, and ≥1 of the following: tophi, chronic gouty arthritis, ≥2 flares in past year) and functioning KT (estimated glomerular filtration rate [eGFR] ≥15 mL/min/1.73 m2 ) on stable immunosuppression therapy.

RESULTS

The primary endpoint was sUA response during month 6 (sUA < 6 mg/dL for ≥80% of time). The study enrolled 20 participants (mean ± SD); age: 53.9 ± 10.9 years, time since KT: 14.7 ± 6.9 years, sUA: 9.4 ± 1.5 mg/dL, gout duration: 8.4 ± 11.6 years; all on ≥2 stable doses of immunosuppression agents. Pegloticase (8 mg intravenous every 2 weeks) in KT recipients with uncontrolled gout showed a high response rate of 89% (16/18 responders). Two participants discontinued treatment solely due to COVID-19 concerns prior to month 6 were not included in the primary analysis. Pegloticase exposures were higher than those historically observed with pegloticase monotherapy, and no anaphylaxis or infusion reaction events occurred during the study.

CONCLUSIONS

This improved response rate to pegloticase in the KT population reflects observations from other trials and reports on immunomodulation with pegloticase. As the KT population has a high prevalence of gout and limitations with oral urate lowering medication options, these findings suggest a potential option for uncontrolled gout therapy in KT participants.

A Randomized, Placebo-Controlled Study of Methotrexate to Increase Response Rates in Patients with Uncontrolled Gout Receiving Pegloticase: Primary Efficacy and Safety Findings

OBJECTIVE

To assess efficacy, safety, pharmacokinetics, and immunogenicity of pegloticase plus methotrexate (MTX) versus pegloticase plus placebo cotreatment for uncontrolled gout in a randomized, placebo-controlled, double-blind trial.

METHODS

This study included adults with uncontrolled gout, defined as serum urate ≥7 mg/dl, oral urate-lowering therapy failure or intolerance, and presence of ongoing gout symptoms including ≥1 tophus, ≥2 flares in the past 12 months, or gouty arthritis. Key exclusion criteria included MTX contraindication, current immunosuppressant use, G6PDH deficiency, and estimated glomerular filtration rate <40 ml/minute/1.73 m² . Patients were randomized 2:1 to 52 weeks of pegloticase (8 mg biweekly) with either oral MTX (15 mg/week) or placebo. The primary end point was the proportion of treatment responders during month 6 (defined as serum urate <6 mg/dl for ≥80% of visits during weeks 20-24). Efficacy was evaluated in all randomized patients (intent-to-treat population), and safety was evaluated in all patients receiving ≥1 blinded MTX or placebo dose.

RESULTS

A total of 152 patients were randomized, 100 to receive pegloticase plus MTX, 52 to receive pegloticase plus placebo. Significantly higher treatment response occurred during month 6 in the MTX group versus the placebo group (71.0% [71 of 100 patients] versus 38.5% [20 of 52 patients], respectively; between-group difference 32.3% [95% confidence interval 16.3%, 48.3%]) (P < 0.0001 for between-group difference). During the first 6 months of pegloticase plus MTX or pegloticase plus placebo treatment, 78 (81.3%) of 96 MTX patients versus 47 (95.9%) of 49 placebo patients experienced ≥1 adverse event (AE), most commonly gout flare (64 [66.7%] of 96 MTX patients and 34 [69.4%] of 49 placebo patients). Reports of AEs and serious AEs were comparable between groups, but the infusion reaction rate was considerably lower with MTX cotherapy (4.2% [4 of 96 MTX patients, including 1 patient who had anaphylaxis]) than with placebo cotherapy (30.6% [15 of 49 placebo patients, 0 who had anaphylaxis]) (P < 0.001). Antidrug antibody positivity was also lower in the MTX group.

CONCLUSION

MTX cotherapy markedly increased pegloticase response rate over placebo (71.0% versus 38.5%) during month 6 with no new safety signals. These findings verify higher treatment response rate, lower infusion reaction incidence, and lower immunogenicity when pegloticase is coadministered with MTX.

Mega-Dose Vitamin C Ameliorates Nonalcoholic Fatty Liver Disease in a Mouse Fast-Food Diet Model

In previous studies, the increasing clinical importance of nonalcoholic fatty liver disease (NAFLD) has been recognized. However, the specific therapeutic strategies or drugs have not been discovered. Vitamin C is a water-soluble antioxidant and is a cofactor in many important biosynthesis pathways. Recently, many researchers have reported that the mega-dose vitamin C treatment had positive effects on various diseases. However, the precise relationship between mega-dose vitamin C and NAFLD has not been completely elucidated. This study has been designed to discover the effects of mega-dose vitamin C on the progression of NAFLD. Twelve-week-old wild-type C57BL6 mice were fed chow diets and high-fat and high-fructose diet (fast-food diet) ad libitum for 11 weeks with or without of vitamin C treatment. Vitamin C was administered in the drinking water (1.5 g/L). In this study, 11 weeks of the mega-dose vitamin C treatment significantly suppressed the development of nonalcoholic steatohepatitis (NASH) independently of the catabolic process. Vitamin C supplements in fast-food diet fed mice significantly decreased diet ingestion and increased water intake. Histopathological analysis revealed that the mice fed a fast-food diet with vitamin C water had a mild renal injury suggesting osmotic nephrosis due to fructose-mediated purine derivatives. These data suggest that the mega-dose vitamin C treatment suppresses high-fructose-diet-mediated NAFLD progression by decreasing diet ingestion and increasing water intake.

Enhancing the Response Rate to Recombinant Uricases in Patients with Gout

Refractory, or uncontrolled, gout is a chronic, progressive, inflammatory arthropathy resulting from continued urate deposition after failed attempts to lower serum uric acid below the therapeutic threshold with oral urate-lowering therapies such as allopurinol and febuxostat. Recombinant uricase is increasingly being used to treat refractory gout; however, the immunogenicity of uricase-based therapies has limited the use of these biologic therapies. Antidrug antibodies against biologic therapies, including uricase and PEGylated uricase, can lead to loss of urate-lowering response, increased risk of infusion reactions, and subsequent treatment failure. However, co-therapy with an immunomodulator can attenuate antidrug antibody development, potentially increasing the likelihood of sustained urate lowering, therapy course completion, and successful treatment outcomes. This review summarizes evidence surrounding the use of immunomodulation as co-therapy with recombinant uricases.

Uricase-deficient rats with similarly stable serum uric acid to human’s are sensitive model animals for studying hyperuricemia

The aim of this study was to provide a sensitive model animal for studying hyperuricemia. Male uricase-deficient rats, named Kunming-DY rats, were raised for 130 days, or orally administered with purines and other chemicals. Serum uric acid (SUA) in the animals was assayed, and the UA level in their organs and their 24-h excretion was determined. Genes in the jejunum, ileum, kidney and liver related to UA synthesis and transportation were detected by quantitative RNA sequencing. Uricase-deficient rats have a high level of SUA and are sensitive to xanthine, adenosine, inosine, allopurinol, and alcohol. Besides, the high level of SUA in male uricase-deficient rats was stable, much higher than that in wild-type rats but similar to that in men. The distribution pattern of UA in uricase-deficient rats’ organs was different from that in wild-type rats. The kidney, liver, and small intestine were the top three organs where UA distributed, but the UA in the small intestine, colon, lung, thymus, and brain was less affected by uricase deficiency, indicating that these organs are constitutive distribution organs in UA. The 24-h UA excreted by a uricase-deficient rat was about five times higher than that excreted by a wild-type rat. However, the 24-h UA excreted through feces was not significantly changed. Both the urine volume and UA in uricase-deficient rats significantly increased, and more than 90% of UA was excreted via urine. The expression of xanthine dehydrogenase was not upregulated. Some genes of transporter associated with uric acid excretion in the kidney were significantly regulated, though not sufficient to explain the increase in SUA. In conclusion, male uricase-deficient rats’ UA metabolism is similar to that of men. The elevation of SUA in uricase-deficient rats is caused by uricase deficiency, and uricase-deficient rats are a sensitive model for studying hyperuricemia.

Design of Bacillus fastidious Uricase Mutants Bearing Long Lagging Phases Before Exponential Decreases of Activities Under Physiological Conditions

Under physiological conditions, Bacillus fastidious uricase (BFU) activity shows negligible lagging phase before the exponential decrease; mutants are thus designed for long lagging phases before exponential activity decreases. On homodimer surface of BFU (4R8X.pdb), the last fragment ANSEYVAL at the C-terminus forms a loop whose Y319 is H-bonded by the buried D257 in the same monomer. Within 1.5 nm from the α-carboxyl group of the last leucine (L322), E30, K26, D257, R258, E311, K312 and E318 from the same monomer plus D126 and K127 from a monomer of the other homodimer generate an electrostatic interaction network. Within 1.5 nm from Y319, D307 and R310 in the same monomer interact with ionized residues around the inter-chain β-sheet in the same homodimer. Mutagenesis of Y319R is designed to strengthen the original interactions and concomitantly generate new electrostatic attractions between homodimers. Under physiological conditions, the mutant V144A/Y319R showed an approximately 4 week lagging phase before the exponential activity decrease, an apparent half-life of activity nearly three folds of mutant V144A, but comparable activity. The introduction of ionizable residues into the C-terminus contacting the other homodimer for additional and/or stronger electrostatic attractions between homodimers may be a universal approach to thermostable mutants of uricases.

The Effective Control of Hyperuricemia in Cancer Patients: A New Recombinant Conjugated Variant of Urate Oxidase

Objective:

Management of hyperuricemia is crucial to controlling tumor lysis syndrome (TLS) during cancer therapy. Urate oxidase (UOX) that catalyzes the enzymatic oxidation of uric acid into allantoin, is effective in lowering plasma uric acid levels and controlling hyperuricemia. Recently, we developed a new recombinant conjugate variant of UOX therapeutic drug using PASylation technology. This study was designed to evaluate the stability, plasma half-life and immunogencity of PASylated UOX.

Methods:

A recombinant variant of PASylated UOX from the Aspergillus flavus was manufactured using bioinformatics and experimental techniques. Ex vivo evaluation of stability of PASylated UOX was done in 50% human serum. For half-life test, recombinant PASylated UOX and rasburicase were administered at 1.5 mg/kg to 10 rats in two different groups and samples were collected after injection Production of antibodies against PASylated drug was also assayed.

Results:

Residual activity of PASylated UOX in 50% human serum was higher than rasburicase and native UOX. Stability of PASylated UOX at 25°C and 37°C was also higher than rasburicase and native UOX. The PASylated half-life was ~32.1 hours, whereas half-life for rasburicase and native UOX was ~25.1 and ~22.8 hours, respectively. In immunogenicity examination, there is 33% and 36% decrease in the absorbance of native UOX and rasburicase, respectively when compared with that of PASylated UOX.

Conclusion:

Our data confirmed the efficacy and stability of PASylated UOX in comparison to the rasburicase. In summary, the results indicated that PASylated UOX drug is effective at lowering plasma uric acid levels with prolonged plasma half-life and decreased cost.

Determination of PEGylation homogeneity of polyethylene glycol-modified canine uricase

Polyethylene glycol-modified canine uricase (PEG-UHC) was prepared by modifying the ε-amino group of lysine residues on the canine uricase (UHC) protein to near-saturation with 5 kDa monomethoxyl-polyethylene glycol succinimide (mPEG-SPA-5k). In order to accurately determine the PEGylation uniformity of PEG-UHC, CZE, 3-8% gradient gel SDS-PAGE, and imaging CIEF (iCIEF) analyses were compared. CZE could not effectively separate PEG-UHC proteins with different degrees of modification, 3-8% gradient gel SDS-PAGE could separate PEG-UHC into seven gel bands; however, most of the gel bands were smeared or blurred, and the separation of PEG-UHC samples by iCIEF was significantly better than that by 3-8% gradient gel SDS-PAGE. Under denatured conditions, iCIEF separated 12 pI peaks, and could also accurately quantify the relative monomer PEG-UHC content. More than 85% of the total monomeric PEG-UHC was conjugated with 7-12 PEG molecules; of this 85%, approximately 40% was conjugated with 9-10 PEG molecules. These results demonstrated that iCIEF exhibits good potential for determining the PEGylation homogeneity of PEGylated protein drugs.

Antihyperuricemic efficacy of Scopoletin-loaded Soluplus micelles in yeast extract/potassium oxonate-induced hyperuricemic mice

Scopoletin (Sco) has great potential for hyperuricemia therapy. However, the relatively low oral bioavailability of Sco limits its further applications. Soluplus-based Sco micelles (Sco-Ms) were successfully prepared in our previous work. The oral bioavailability of Sco-Ms was increased by 438% compared with free Sco. In this study, we aimed to compare the biodistribution and antihyperuricemic efficacy of Sco and Sco-Ms, and explore their therapeutic mechanisms as well. We studied the tissue biodistribution of Sco and Sco-Ms after they were orally administered to mice. The antihyperuricemic effect and the therapeutic mechanisms of Sco and Sco-Ms were evaluated using yeast extract/potassium oxonate-induced hyperuricemia model in mice. The Sco concentration in each tissue was significantly higher than that of Sco suspension after orally administrating Sco-Ms to mice. Oral delivery of Sco-Ms exhibited significantly stronger hypouricemic efficacy in hyperuricemic mice than Sco. Meanwhile, Sco-Ms showed a better protective effect on mice kidney injury. The hypouricemic efficacy of Sco was due to promoting the excretion of uric acid via modulating the alteration of gene expression levels of renal uric acid transporter (URAT1), glucose transporter (GLUT9), and organic anion transporter 1 (OAT1). Sco-Ms could not only restore the dysregulation of URAT1, GLUT9, and OAT1 more effectively, but also down-regulate the activity of hepatic xanthine oxidase (XOD) to inhibit the production of uric acid. In conclusion, taken together, Sco-Ms represents a potential oral strategy for the treatment of hyperuricemia.

High-Dose IV Administration of Rasburicase Suppresses Anti-rasburicase Antibodies, Depletes Rasburicase-Specific Lymphocytes, and Upregulates Treg Cells

Therapeutic proteins can be potent agents for treating serious diseases, but in many patients these proteins provoke antibody responses that blunt therapeutic efficacy. Intravenous administration of high doses of some proteins induces immune tolerance, but the mechanisms underlying this effect are poorly understood. As a model to study tolerance induction in mice, we used rasburicase, a commercial recombinant uricase used for the treatment of hyperuricemia. Intraperitoneal (i.p.) injection of rasburicase without or with alum adjuvants induced a clear anti-rasburicase antibody response, but intravenous (i.v.) injection did not. The lack of response to i.v. rasburicase was apparently due to active immune suppression since i.v.-treated mice showed blunted antibody and reduced T cell responses to subsequent i.p. injections of rasburicase. This blunted response was associated with a decrease in rasburicase-specific B cell and T cell responses and an increase in proportion of CD4⁺ FoxP3⁺ regulatory T cells (Treg) in the spleen. We examined the number of lymphocytes in peripheral blood after rasburicase i.v. injection. Rasburicase caused a transient reduction in B and T cells, but a robust and sustained depletion of rasburicase-specific B cells. Further experiments showed that rasburicase i.v. injection decreased the number of lymphocytes and was associated with apoptosis of both B cells and activated T cells and that the enhanced percentage of Treg cells was likely mediated by a macrophage-dependent pathway. Thus, our data suggest that apoptosis and depletion of antigen-specific B lymphocytes and upregulation of Treg cells may play important roles in the immune suppression induced by intravenous administration of a therapeutic protein.

Pharmacokinetics of Polyethylene Glycol-Modified Canine Uricase Following Single and Multiple Intravenous Injections in Cynomolgus Monkeys

BACKGROUND AND OBJECTIVE

Polyethylene glycol-modified canine uricase (PEG-UHC) prepared with a lower-molecular-weight (5 kDa) PEG is used to treat gout. This study investigated the comparative pharmacokinetics of single and multiple doses of PEG-UHC administered intravenously and a single dose of uricase (UHC) administered intravenously in cynomolgus monkeys.

METHODS

A noncompartmental model was used to fit the plasma drug concentration-time curve and calculate the pharmacokinetic parameters of PEG-UHC, which were compared with those obtained for UHC at the equivalent dose (2 mg/kg). To study the pharmacokinetics after multiple dose administration, cynomolgus monkeys were administered five intravenous injections of PEG-UHC (0.5 mg/kg), with one injection performed every 15 days.

RESULTS

The area under the curve (AUC) and the maximum plasma concentration (C_max) of PEG-UHC were positively correlated with dose, whereas plasma half-life (t_1/2) and clearance (CL) did not change significantly with increasing dose, suggesting that these pharmacokinetic characteristics are linear. Intravenous PEG-UHC exhibited an average t_1/2 that was 125.79 times longer and an AUC_0-t that was 64.45 times larger than the corresponding values for UHC at the same dose (2 mg/kg), while the CL of PEG-UHC was 1/72.73 times the CL of intravenous UHC. The plasma drug concentration reached a steady state after five injections, and the t_1/2 values following the first and last drug administration did not differ significantly.

CONCLUSION

Our data show that PEG-UHC is markedly superior to UHC in terms of duration of action, and that the pharmacokinetics of PEG-UHC in cynomolgus monkeys are linear. Sequential administration of PEG-UHC did not accelerate drug clearance. Our findings provide the basis for future clinical studies of PEG-UHC.

Computational Analysis of Therapeutic Enzyme Uricase from Different Source Organisms

Background:

Hyperuricemia and gout are the conditions, which is a response of accumulation of uric acid in the blood and urine. Uric acid is the product of purine metabolic pathway in humans. Uricase is a therapeutic enzyme that can enzymatically reduces the concentration of uric acid in serum and urine into more a soluble allantoin. Uricases are widely available in several sources like bacteria, fungi, yeast, plants and animals.

Objective:

The present study is aimed at elucidating the structure and physiochemical properties of uricase by insilico analysis.

Methods:

A total number of sixty amino acid sequences of uricase belongs to different sources were obtained from NCBI and different analysis like Multiple Sequence Alignment (MSA), homology search, phylogenetic relation, motif search, domain architecture and physiochemical properties including pI, EC, Ai, Ii, and were performed.

Results:

Multiple sequence alignment of all the selected protein sequences has exhibited distinct difference between bacterial, fungal, plant and animal sources based on the position-specific existence of conserved amino acid residues. The maximum homology of all the selected protein sequences is between 51-388. In singular category, homology is between 16-337 for bacterial uricase, 14-339 for fungal uricase, 12-317 for plants uricase, and 37-361 for animals uricase. The phylogenetic tree constructed based on the amino acid sequences disclosed clusters indicating that uricase is from different source. The physiochemical features revealed that the uricase amino acid residues are in between 300- 338 with a molecular weight as 33-39kDa and theoretical pI ranging from 4.95-8.88. The amino acid composition results showed that valine amino acid has a high average frequency of 8.79 percentage compared to different amino acids in all analyzed species.

Conclusion:

In the area of bioinformatics field, this work might be informative and a stepping-stone to other researchers to get an idea about the physicochemical features, evolutionary history and structural motifs of uricase that can be widely used in biotechnological and pharmaceutical industries. Therefore, the proposed in silico analysis can be considered for protein engineering work, as well as for gout therapy.

Metal-Assisted and Microwave-Accelerated Decrystallization of Pseudo-Tophus in Synthetic Human Joint Models

In this paper, we tested a hypothesis that the metal-assisted and microwave-accelerated decrystallization (MAMAD) technique, based on the combined use of low-power medical microwave heating (MWH) and gold nanoparticles (Au NPs), can be used to decrystallize laboratory-prepared monosodium urate monohydrate crystal aggregate (pseudo-tophus) placed in three-dimensional (3D) synthetic human joint models. To simulate a potential treatment of chronic tophaceous gout using the MAMAD technique, we used three different 3D synthetic human joint models and assessed the percent mass reduction (PMR, i.e., decrystallization) of pseudo-tophus and microwave-induced synthetic skin patch damage after MAMAD sessions (a MAMAD session = 120 s of MWH in the presence of Au NPs). Our three synthetic joint models are: Model 1: Application of seven MAMAD sessions in a closed synthetic joint with a pseudo-bursa containing a pseudo-tophus submerged in a solution of 20 nm Au NPs followed by dehydration of pseudo-tophus after each MAMAD session to assess PMR. Model 2: Application of seven MAMAD sessions in a closed or open synthetic joint with a pseudo-bursa containing a pseudo-tophus submerged in a solution of Au NPs followed by intermittent dehydration of pseudo-tophus after seven MAMAD sessions to assess PMR. Model 3: Application of 18 MAMAD sessions in a rotated closed synthetic joint (three sides are heated separately) with a pseudo-bursa containing a pseudo-tophus submerged in a solution of Au NPs followed by dehydration after every three MAMAD sessions to assess PMR. After a single MAMAD session, pseudo-tophus exposed to MWH and Au NPs had an average PMR of 8.30% (up to an overall PMR of 15%), and microwave-induced damage to the synthetic skin can be controlled by the use of a sacrificial skin sample and by adjusting the duration and the number of the MAMAD sessions. Computational electromagnetic simulations predict a 10% absorption of electric field by the pseudo-tophus placed in the synthetic joint models, which led us to conclude that a medical microwave source with higher power than 20 W can potentially be used with the MAMAD technique.

Designing a mutant Candida uricase with improved polymerization state and enzymatic activity

As human uricase has been silenced during evolution, counterparts from other species become an alternative for the treatment of hyperuricemia. Candida uricase is a promising option among them, but its aggregation propensity remains a major obstacle to clinical use. In this study, we designed two mutations according to homology-modeled 3D structure of Candida uricase: Cys249Ser substitution and C-terminal Leu deletion. The wild-type uricase and three mutants containing either or both of the mutations were expressed in Escherichia coli BL21 and validated by mass spectrometry. Size-exclusion chromatography and electrophoresis analysis demonstrated that aggregation was induced by interchain disulfide bonds and could be significantly avoided by Cys249Ser substitution. In combination with Cys249Ser substitution, deletion of Leu increased the enzymatic activity by 8%. Taken together, mutant containing both mutations is chosen as our target protein which is comparatively more suitable for therapeutic use. In addition, homology-modeled 3D structure was proved to be an efficient approach for protein engineering.

Oral uricase eliminates blood uric acid in the hyperuricemic pig model

An elevated level of serum uric acid-hyperuricemia, is strongly associated with the development of gout and chronic kidney disease (CKD) which is often accompanied by a significantly reduced glomerular filtration rate (GFR). In the present study, we investigated the extra-renal elimination of uric acid via the intestine in a healthy pig model and the effect of oral uricase therapy on plasma uric acid concentrations in pigs with induced hyperuricemia and CKD. The experiment was conducted on eleven, ten-week-old pigs (n = 11). The porcine model of CKD was developed by performing 9/10 nephrectomy surgery on eight pigs. A stable model of hyperuricemia was established in only five of the eight nephrectomized pigs by frequent injections of uric acid (UA) into the jugular vein. All pigs (three healthy pigs and five CKD pigs) were operated for implantation of jugular vein catheters and the three healthy pigs also had portal vein catheters inserted. Blood uric acid concentrations were measured spectrophotometrically, using the Uric Acid Assay Kit (BioAssay Systems, Hayward, USA). The piglets with CKD received orally administered uricase (treatment) and served as their own controls (without uricase supplementation). Oral uricase therapy significantly decreased plasma uric acid concentrations in pigs with CKD, whereas hyperuricemia was observed in the pigs whilst not being treated with uricase. Urinary uric acid excretion was similar during both the treatment and control periods during the first 8 h and 24 h after UA infusions in the CKD pigs. To demonstrate the elimination of UA via the intestine, the healthy pigs were infused with UA into the jugular vein. The blood collected from the jugular vein represents circulating UA concentrations and the blood collected from the portal vein represents the concentration of UA leaving the intestine. The final (after 2 h) concentration of UA was significantly lower in blood collected from the portal vein compared to that collected from the jugular vein (3.34 vs. 2.43 mg/dL, respectively, p = 0.024). The latter allows us to suggest that UA is eliminated from the blood via the gut tissue.

Converting Red Blood Cells to Efficient Microreactors for Blood Detoxification

A simple method to convert red blood cells (RBCs) into efficient microreactors is reported. Triton X-100 is employed at finely tuned concentrations to render RBCs highly permeable to substrates, while low concentrations of glutaraldehyde are used to stabilize cells. The ability for blood detoxification of these microreactors is demonstrated.

Biodistribution, hypouricemic efficacy and therapeutic mechanism of morin phospholipid complex loaded self-nanoemulsifying drug delivery systems in an experimental hyperuricemic model in rats

OBJECTIVES

This study aimed to compare the biodistribution and hypouricemic efficacy of morin and morin-phospholipid complex loaded self-nanoemulsifying drug delivery systems (MPC-SNEDDS), as well as to explore their therapeutic mechanisms.

METHODS

We studied the biodistribution of morin and MPC-SNEDDS after they were orally administered to rats. The hypouricemic efficacy and the therapeutic mechanisms of morin and MPC-SNEDDS were evaluated using potassium oxonate-induced hyperuricemic model in rats.

KEY FINDINGS

With enhanced morin concentration in liver and kidney, oral delivery of MPC-SNEDDS exhibited significantly stronger urate-lowering effect in hyperuricemic rats than morin. The hypouricemic efficacy of morin was due to reduced production of uric acid via inhibiting the mRNA expression of hepatic xanthine dehydrogenase/xanthine oxidase (XDH/XO), as well as decreased urate reabsorption via modulating the alteration of mRNA levels of glucose transporter (mGLUT9), renal organic anion transporter 1 (mOAT1) and uric acid transporter (mURAT1). MPC-SNEDDS dually inhibited mRNA expression and activity of hepatic XDH/XO and restored the dysregulation of renal mGLUT9, mOAT1 and mURAT1, contributing to its superior urate-lowering efficacy.

CONCLUSION

The results demonstrated the great potential of MPC-SNEDDS as an alternative oral strategy for active agents in treating hyperuricemia.

Inflammasome activation in the liver: Focus on alcoholic and non-alcoholic steatohepatitis

Upregulation of the inflammatory cascade is a major element both in the progression of steatohepatitis to severe alcoholic hepatitis as well as in the progression of NASH to advanced NASH with fibrosis. The mechanisms underpinning these changes are only partially understood. Activation of the inflammatory cascade requires multiple stimuli and in this report, we discuss the role of inflammasomes that activate IL-1β as well as the sterile and pathogen-derived danger signals that results in inflammasome activation and inflammation in alcoholic and non-alcoholic steatohepatitis. The dynamics of inflammasome activation, the cell types involved and the trigger signals appear to be somewhat different between ASH and NASH. Further studies are needed to dissect the pathology-related differences between these two major forms of steatohepatitis. Clinical and therapeutic implications of inflammasome activation in steatohepatitis are also discussed.

Cloning and expression of Aspergillus flavus urate oxidase in Pichia pastoris

Urate oxidase is an important enzyme with therapeutic and diagnostic applications. Rasburicase is a recombinant urate oxidase enzyme approved by FDA to use in the treatment of hyperuricemia conditions. Various hosts such as Saccharomyces cerevisiae, Hansenula polymorpha and Escherichia coli have been used to express the enzyme. Today, Pichia pastoris is considered as an important host for heterologous protein expression since it has beneficial characteristics such as strong promoters, simple scale up, post translational modifications, high cell density cultivation and simple genetic manipulation. In this study, Aspergillus flavus urate oxidase gene was cloned in pPICZαA expression vector and expressed in P. pastoris. The recombinant urate oxidase was expressed in secretory form and was confirmed through RT-PCR, SDS-PAGE analysis and western blotting. The enzyme activity was determined using a colorimetric assay. A production yield of 0.43 U/ml of culture supernatant was obtained.

Pharmacokinetics considerations for gout treatments

INTRODUCTION

Patients with gout often have comorbid conditions such as renal failure, cardiovascular disease and metabolic syndrome. The presence and required treatment of these conditions can make the treatment of gout challenging. Knowledge of the pharmacokinetics of the available drugs for the management of gout is mandatory.

AREAS COVERED

A MEDLINE PubMed search for articles published in English from January 1990 to January 2014 was completed using the terms: pharmacokinetics, colchicine, canakinumab, allopurinol, febuxostat, pegloticase, gout, toxicity, drug interaction.

EXPERT OPINION

Colchicine is a drug with a narrow therapeutic-toxicity window. Co-prescription with strong CYP3A4 or P-glycoprotein inhibitors can greatly modify its pharmacokinetics and is to be avoided. Elimination of canakinumab mainly occurs via intracellular catabolism, following receptor mediator endocytosis. Canakinumab appears to be a good alternative for patients with contraindications to colchicine, NSAIDs and corticosteroids. For patients with renal impairment, some authors recommend that the allopurinol maximum dosage should be adjusted to creatinine clearance. If the urate target cannot be achieved, the therapy should be switched to febuxostat, which is appropriate with mild-to-moderate renal failure. Anti-pegloticase antibodies affect the pharmacokinetics of the drug because they increase its clearance, with loss of pegloticase activity.

[Diagnosis and management of gout in Austria. Survey of current practice considering the EULAR recommendations]

BACKGROUND AND OBJECTIVES

Gout shows an increasing incidence and has become a major health problem in the Western world. Despite effective treatment options, neither diagnosis nor therapeutic efforts can be regarded sufficient to date. It was of interest to investigate current handling of gout among Austrian rheumatologists.

MATERIAL AND METHODS

In 2012, a survey of Austrian rheumatologists concerning diagnosis and management of hyperuricemia and gout was performed. With the consent of the Austrian Society of Rheumatology, 574 society members (343 via electronic mail, 23 via mail) were sent a questionnaire consisting of 17 questions. This is the first survey assessing the management of gout among Austrian rheumatologists.

RESULTS

The overall response rate was 22.1 %. Of all the contacted members (email and mail), 19.9 % answered the questionnaire electronically and only 5.6 % by mail. The adherence to the EULAR recommendations for gout ranged between 69 and 95 % (median 84 %).

CONCLUSION

Among Austrian rheumatologists, the knowledge about gout, its diagnostic and imaging procedures, management and therapeutic goals is good and mainly in line with current international recommendations. To improve the management of patients with gout and hyperuricemia, a more frequent referral to rheumatologists could be beneficial.

The emerging role of biotechnological drugs in the treatment of gout

One of the most important therapeutic advances obtained in the field of rheumatology is the availability of the so-called bio(techno)logical drugs, which have deeply changed treatment perspectives in diseases such as rheumatoid arthritis and ankylosing spondylitis. According to the steadily increasing attention on gout, due to well-established prognostic and epidemiology implications, in the last 5 years, the same change of perspective has been observed also for this disease. In fact, several bio(techno)logical agents have been investigated both for the management of the articular gout symptoms, targeting mainly interleukin-1β, as well as urate-lowering therapies such as recombinant uricases. Among the IL-1β inhibitors, the majority of studies involve drugs such as anakinra, canakinumab, and rilonacept, but other compounds are under development. Moreover, other potential targets have been suggested, as, for example, the TNF alpha and IL-6, even if data obtained are less robust than those of IL-1β inhibitors. Regarding urate-lowering therapies, the recombinant uricases pegloticase and rasburicase clearly showed their effectiveness in gout patients. Also in this case, new compounds are under development. The aim of this review is to focus on the various aspects of different bio(techno)logical drugs in gouty patients.

The human peroxisome in health and disease: the story of an oddity becoming a vital organelle

Since the first report by Rhodin in 1954, our knowledge on mammalian microbodies/peroxisomes has known several periods. An initial two decades period (1954-1973) has contributed to the biochemical individualisation of peroxisomes as a new class of subcellular organelles (de Duve, 1965). The corresponding research period failed to define a clear role of mammalian peroxisomes in vital functions and intermediary metabolism, explaining why feeling that peroxisomes might be in the human cell oddities has prevailed during several decades. The period standing from 1973 to nowadays has progressively removed this cell oddity view of peroxisomes by highlighting vital function and metabolic role of peroxisomes in health and disease along with genetic and metabolic regulation of peroxisomal protein content, organelle envelope formation and protein signal targeting mechanisms. Research on peroxisomes and their response to various drugs and metabolites, dietary and physiological conditions has also played a key role in the discovery of peroxisome proliferator activated receptors (PPARs) belonging to the nuclear hormone receptor superfamily and for which impact in science and medicine goes now by far beyond that of the peroxisomes.