Nabumetone: therapeutic use and safety profile in the management of osteoarthritis and rheumatoid arthritis

Renshen Zhuye decoction ameliorates high-fat diet-induced obesity and insulin resistance by modulating gut microbiota and metabolic homeostasis

BACKGROUND

Obesity, characterized by excessive adipose tissue accumulation, has become a global health challenge with rapidly increasing prevalence. It contributes significantly to metabolic disorders including insulin resistance (IR). Renshen-zhuye decoction (RZD), a traditional Chinese medicine formula historically used for diabetes, shows potential for improving metabolic parameters, but its effects and mechanisms in obesity and insulin resistance remain unclear.

PURPOSE

This study aimed to evaluate the therapeutic benefits of RZD on obesity and insulin resistance, and to elucidate the underlying mechanisms through which it improves glucose and lipid metabolism.

METHODS

The role of RZD was evaluated in a high-fat diet (HFD) mouse model. The formula was characterized using UPLC-MS. Comprehensive analyses including histopathological staining, immunofluorescence, biochemical assays, 16S rRNA gene sequencing of gut microbiota, and non-targeted metabolomic analysis were performed. To validate the role of gut microbiota, we employed antibiotic treatment (ABX) to deplete intestinal flora and conducted fecal microbiota transplantation (FMT) experiments.

RESULTS

RZD treatment dose-dependently alleviated HFD-induced dyslipidemia and insulin resistance, improving glucose tolerance, insulin sensitivity, and energy expenditure. Gut microbiota analysis revealed that RZD significantly modulated the composition of intestinal flora and their metabolic profiles. Additionally, RZD reduced intestinal and systemic inflammation by enhancing intestinal barrier integrity, particularly through increased expression of tight junction proteins such as Occludin. Importantly, the beneficial effects of RZD on weight management and glucose homeostasis were antagonized by antibiotic intervention, while FMT experiments confirmed that these improvements were mediated through gut microbiota modulation.

CONCLUSION

This study provides new insights into RZD's modulatory effects on gut microbiota and subsequent improvements in obesity-related metabolic parameters. RZD alleviates HFD-induced obesity and insulin resistance in mice by modulating gut microbiota composition and function, which subsequently improves intestinal barrier integrity, reduces inflammation, and enhances metabolic homeostasis.

Solvent-Controlled and Highly Chemoselective Reduction of α,β-Unsaturated Ketones and Aldehydes

Herein, we establish two highly efficient reductions of α,β-unsaturated ketones and aldehydes via Raney nickel-catalyzed hydrogenation with distinct chemoselectivity, which is controlled by the solvent. This methodology demonstrates a brilliant result when reducing α,β-unsaturated ketones and aldehydes to ketones or alcohols. High isolated yields were obtained for a series of benzalacetone- and cinnamaldehyde-derived substrates without additional column chromatographic purification. The practicability of the methodology was demonstrated by reducing the natural products and synthesizing the approved drug.

Mercapto-NSAIDs generate a non-steroidal anti-inflammatory drug (NSAID) and hydrogen sulfide

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the frontline treatments for inflammation and pain. Hydrogen sulfide (H2S) and related persulfide (RS-SH) are important mediators of antioxidant response and protect cells from oxidative stress. Hybrids of these pharmacological agents have shown promise in clinical trials and are superior to the parent NSAID. Here, we report a new class of NSAID-H2S hybrids, where a strategic placement of a sulfhydryl group adjacent to a carbonyl of a NSAID facilitates the enzymatic generation of H2S. We show that α-mercapto-nabumetone, a derivative of the clinical drug nabumetone, is a substrate for 3-mercaptopyruvate sulfurtransferase (3-MST), an enzyme involved in H2S biosynthesis. The key step of 3-MST catalysis is the cleavage of a C-S bond adjacent to a carbonyl group, which generates an enolate and 3-MST persulfide, which in turn is cleaved under reducing conditions to generate H2S. Guided by a molecular docking study with 3-MST, we prepared two mercapto-nabumetone derivatives, protected as their thioacetates. In the presence of 3-MST, both mercapto-nabumetone derivatives generated H2S and the NSAID in a nearly quantitative yield, produced glutathione persulfide (GS-SH), an important mediator of cellular antioxidant response, and permeated cells to generate H2S. Lastly, to gain insights into the scope of this strategy, we prepared mercapto-NSAID derivatives containing a carboxylic acid. We found that the propensity to generate H2S depended on the nature of the enol that is produced during the transformation of the mercapto-NSAID into the parent NSAID. This offers new insights into 3-MST catalysis and how reaction outcomes can be modulated by the keto-enol equilibrium. Taken together, the atom economical transformation of a clinical NSAID with one strategically placed sulfhydryl group to generate H2S presents new opportunities to enhance the properties of NSAIDs through participation in endogenous H2S biosynthesis.

Natural product extract fractions as potential arthritis treatments: A detailed analysis using in-silico, in-vivo, and in-vitro methods

Two characteristics of the systemic autoimmune disease rheumatoid arthritis (RA) include extra-articular involvement and inflammatory arthritis. It is a long-term inflammatory condition that mostly affects the synovial joints and is often triggered by a confluence of environmental factors, including tobacco use, and genetics. The review investigates natural products' role in arthritis through three key approaches. In-silico analysis identifies molecular mechanisms and targets of these products, revealing their potential for therapeutic use. In-vivo studies evaluate how well these products work and their safety in reducing joint inflammation. In-vitro studies focus on how these compounds interact at the cellular level and their effects on signaling pathways. Together, these approaches offer a comprehensive understanding of how natural products could benefit arthritis management. This review focuses on translational studies and highlights the possible role of natural compounds as adjunctive therapies to conventional arthritis treatments. In conclusion, this study indicates that natural products have potential advantages in treating osteoarthritis and rheumatoid arthritis based on in-silico analysis which shows anti-inflammatory effects, in-vivo studies that reduce joint inflammation, and in-vitro studies that amplify arthritis management. To improve the therapeutic advantages of natural products utilized for treating arthritis, an all-inclusive examination has been done to give direction for the following research efforts.

Biopharmaceutical Characterization and Stability of Nabumetone-Cyclodextrins Complexes Prepared by Grinding

Background: Nabumetone (NAB) is a poorly soluble nonsteroidal anti-inflammatory prodrug (BCS class II drug) whose solubility is significantly improved by complexation with cyclodextrins (CDs). Methods: The solid complexes, in a 1:1 molar ratio, were prepared by mechanochemical activation by grinding, using β-cyclodextrin (β-CD) and its derivatives, hydroxypropyl- and sulfobutylether-β-cyclodextrin (HP-β-CD and SBE-β-CD). The complexation was confirmed by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and attenuated total reflectance Fourier-transformed infrared spectroscopy (ATR-FTIR). Obtained products were further characterized regarding their solubility, in vitro dissolution, permeability and chemical stability. Results: Co-grinding with HP-β-CD and SBE-β-CD yielded products that showed in vitro dissolution profiles in hydrochloric acid medium (pH 1.2) that were substantially different from that of pure NAB, yielding dissolution efficiency enhancements of 34.86 ± 1.64 and 58.30 ± 0.28 times, respectively, for the optimized products. Their in vitro dissolution and gastrointestinal permeability were also studied in a low-volume environment at pH 6.8, corresponding to the intestinal environment. Both β-CD derivatives increased NAB dissolution rate and NAB mass transport across the biomimetic membrane. The effect of β-CD derivatives on NAB chemical stability was studied under the stress conditions by the developed and validated UHPLC-DAD-HRMS method. In acidic conditions, pure and complexed NAB was prone to hydrolytic degradation, yielding one degradation product-pharmacologically inactive NAB metabolite. However, under the oxidative conditions at elevated temperatures, 10 NAB degradation products were identified from co-ground samples. All systems were stable during photo- and long-term stability studies. Conclusions: NAB complexes with HP-β-CD and SBE-β-CD are promising candidates for pharmaceutical product development.

The role of the methoxy group in approved drugs

The methoxy substituent is prevalent in natural products and, consequently, is present in many natural product-derived drugs. It has also been installed in modern drug molecules with no remnant of natural product features because medicinal chemists have been taking advantage of the benefits that this small functional group can bestow on ligand-target binding, physicochemical properties, and ADME parameters. Herein, over 230 methoxy-containing small-molecule drugs, as well as several fluoromethoxy-containing drugs, are presented from the vantage point of the methoxy group. Biochemical mechanisms of action, medicinal chemistry SAR studies, and numerous X-ray cocrystal structures are analyzed to identify the precise role of the methoxy group for many of the drugs and drug classes. Although the methoxy substituent can be considered as the hybridization of a hydroxy and a methyl group, the combination of these functionalities often results in unique effects that can amount to more than the sum of the individual parts.

Nabumetone and flufenamic acid pose a serious risk to aquatic plants: A study with Chlamydomonas reinhardtii as a model organism

The aquatic environment is constantly under threat due to the release of numerous pollutants. Among them, pharmaceuticals constitute a huge and diverse group. Non-steroidal anti-inflammatory drugs (NSAIDs) are increasingly found in water bodies, but knowledge about their potential toxicity is still low. In particular, there is a lack of information about their influences on aquatic plants and algae. We estimated the susceptibility of the microalgae Chlamydomonas reinhardtii to nabumetone (NBT) and flufenamic acid (FFA), focusing on photosynthesis. Due to the differences in the structures of these compounds, it was assumed that these drugs would have different toxicities to the tested green algae. The hypothesis was confirmed by determining the effective concentration values, the intensity of photosynthesis, the intensity of dark respiration, the contents of photosynthetic pigments, the fluorescence of chlorophyll a in vivo (OJIP test), and cell ultrastructure analysis. Assessment of the toxicity of the NSAIDs was extended by the calculation of an integrated biomarker response index (IBR), which is a valuable tool in ecotoxicological studies. The obtained results indicate an over six times higher toxicity of NBT compared to FFA. After analysis of the chlorophyll a fluorescence in vivo, it was found that NBT inhibited electron transport beyond the PS II. FFA, unlike NBT, lowered the intensity of photosynthesis, probably transforming some reaction centers into "silent centers", which dissipate energy as heat. The IBR estimated based on photosynthetic parameters suggests that the toxic effect of FFA results mainly from photosynthesis disruption, whereas NBT significantly affects other cellular processes. No significant alteration in the ultrastructure of treated cells could be seen, except for changes in starch grain number and autophagic vacuoles that appeared in FFA-treated cells. To the best of our knowledge, this is the first work reporting the toxic effects of NBT and FFA on unicellular green algae.

Targeting Pathways and Integrated Approaches to Treat Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic symmetrical systemic disorder that not only affects joints but also other organs such as heart, lungs, kidney, and liver. Approximately there is 0.5%-1% of the total population affected by RA. RA pathogenesis still remains unclear due to which its appropriate treatment is a challenge. Further, multitudes of factors have been reported to affect its progression i.e. genetic factor, environmental factor, immune factor, and oxidative factor. Therapeutic approaches available for the treatment of RA include NSAIDs, DMARDs, enzymatic, hormonal, and gene therapies. But most of them provide the symptomatic relief without treating the core of the disease. This makes it obligatory to explore and reach the molecular targets for cure and long-term relief from RA. Herein, we attempt to provide extensive overlay of the new targets for RA treatment such as signaling pathways, proteins, and receptors affecting the progression of the disease and its severity. Precise modification in these targets such as suppressing the notch signaling pathway, SIRT 3 protein, Sphingosine-1-phosphate receptor and stimulating the neuronal signals particularly efferent vagus nerve and SIRT 1 protein may offer long term relief and potentially diminish the chronicity. To target or alter the novel molecules and signaling pathway a specific delivery system is required such as liposome, nanoparticles and micelles and many more. Present review paper discusses in detail about novel targets and delivery systems for treating RA.

Dissecting CYP1A2 Activation by Arylalkanoic Acid Prodrugs toward the Development of Anti-Inflammatory Agents

Arylalkane-derived prodrugs of arylacetic acids are a small group of substances that have long been known for their anti-inflammatory action. Despite their ease of synthesis and good potential for the development of new potent and safe anti-inflammatory agents, this group of substances has not received much attention from researchers so far. Therefore, representative arylalkane derivatives were investigated through molecular docking techniques to verify the possible hepatic activation mode toward active metabolites by CYP1A2. In this regard, arylalkanoic acid prodrugs were docked with a crystallographic structure of human CYP1A2, in which the enzyme is co-crystallized with the selective competitive inhibitor α-naphthoflavone BHF. Of note, all the examined compounds proved capable of interacting with the enzyme active site in a manner similar to Nabumetone, thus confirming that a productive metabolic transformation is feasible. On the basis of these findings, it is possible to argue that subtle differences in the way CYP1A2 accommodates the ligands depend on the fine details of their molecular structures. Overall, these data suggest that compounds simply formed by an aromatic moiety bearing an appropriate alkane-derived chain could lead to innovative anti-inflammatory agents.

Integrated Transcriptome and Untargeted Metabolomic Analyses Revealed the Role of Methyltransferase Lae1 in the Regulation of Phospholipid Metabolism in Trichoderma atroviride

The putative methyltransferase Lae1 is a global regulator in Trichoderma, which modulates the expression of secondary metabolite gene clusters, possibly via chromatin remodeling. Here we aimed to explore the specific transcription and metabolites profiles regulated by Lae1 in T. atroviride 23. Comparative transcriptomics and metabolome analyses between the lae1 deletion (Mlae1) and over-expressing (Olae1) mutants were performed using RNA sequencing and QTOF-UPLC-MS techniques. In total, 1344 unique differentially expressed genes (DEGs) and 92 metabolites were identified across three strains. The significantly altered metabolic profiles revealed that the lae1 gene modulates central carbon metabolism, amino acid metabolism, secondary metabolism, and phospholipid metabolism. The effects of lae1 on phospholipid metabolism were further explored, and the findings showed that lae1 modulates the composition and function of cell membranes and other metabolic activities, including the phosphotransferase system (PTS) and biosynthesis of secondary metabolites (SM). Phospholipid metabolism is related to energy metabolism, signal transduction, and environmental adaptability of microorganisms. These data showed that Lae1 affects the primary metabolites, phospholipid, as well as the regulation of secondary metabolites in Trichoderma. This study could potentially provoke in-depth investigations of the Lae1-mediated target genes in phospholipid synthesis. The Lae1 may act as a novel target that is associated with disease defense and drug development in the future.

Palladium-Catalyzed β-C(sp3)-H Arylation of Aliphatic Ketones Enabled by a Transient Directing Group

The direct arylation of aliphatic ketones has been developed via Pd-catalyzed β-C(sp³)-H bond functionalization with 2-(aminooxy)-N,N-dimethylacetamide as a novel transient directing group (TDG), which showed remarkable directing ability to generate arylated products in moderate to good yields. Furthermore, the reaction can tolerate abundant substrate of ketones and aryl iodides. This study expands the scope of applications for TDGs.

The eye as the discrete but defensible portal of coronavirus infection

Oculo-centric factors may provide a key to understanding invasion success by SARS-CoV-2, a highly contagious, potentially lethal, virus with ocular tropism. Respiratory infection transmission via the eye and lacrimal-nasal pathway elucidated during the 1918 influenza pandemic, remains to be explored in this crisis. The eye and its adnexae represent a large surface area directly exposed to airborne viral particles and hand contact. The virus may bind to corneal and conjunctival angiotensin converting enzyme 2 (ACE2) receptors and potentially to the lipophilic periocular skin and superficial tear film with downstream carriage into the nasopharynx and subsequent access to the lungs and gut. Adenoviruses and influenza viruses share this ocular tropism and despite differing ocular and systemic manifestations and disease patterns, common lessons, particularly in management, emerge. Slit lamp usage places ophthalmologists at particular risk of exposure to high viral loads (and poor prognosis) and as for adenoviral epidemics, this may be a setting for disease transmission. Local, rather than systemic treatments blocking virus binding in this pathway (advocated for adenovirus) are worth considering. This pathway is accessible with eye drops or aerosols containing drugs which appear efficacious via systemic administration. A combination such as hydroxychloroquine, azithromycin and zinc, all of which have previously been used topically in the eye and which work at least in part by blocking ACE2 receptors, may offer a safe, cost-effective and resource-sparing intervention.

Gel Formulation of Nabumetone and a Newly Synthesized Analog: Microemulsion as a Photoprotective Topical Delivery System

Photostability studies were performed on topical formulations containing the anti-inflammatory drug Nabumetone and an analog newly synthesized in order to achieve better photostability and pharmacokinetic profile. Stability tests, according to the International Conference on Harmonization rules, were applied on ethanol solutions and topical gel formulations of both compounds. The photodegradation profiles were monitored by Multivariate curve resolution applied to the UV spectral data. The inclusion of the compounds in microemulsion was investigated to improve light stability and, at the same time, to ensure a sustained release system for skin delivery. All the formulations in solution, gel, microemulsion, and microemulsion-in-gel were exposed to a forced irradiation of 350 W/m², corresponding to a 21 kJ/m² min, for up to 300 min. Photostability increased significantly for both drugs in the liquid microemulsion and microemulsion-in-gel, compared to the ethanol solution and plain gel, reaching a residual drug of 97% and 98% for Nabumetone and analog in microemulsion-in-gel, respectively. Permeation experiments on the microemulsion-in-gel showed a better performance of the analog formulated at 0.2%, compared to the same formulation of Nabumetone at 0.7%. These results highlight the potential of the designed matrices as delayed drug delivery systems along with the use of lower drug doses leading to reduced side effects.

Gut microbiota in reductive drug metabolism

Gut bacteria are predominant microorganisms in the gut microbiota and have been recognized to mediate a variety of biotransformations of xenobiotic compounds in the gut. This review is focused on one of the gut bacterial xenobiotic metabolisms, reduction. Xenobiotics undergo different types of reductive metabolisms depending on chemically distinct groups: azo (-NN-), nitro (-NO₂), alkene (-CC-), ketone (-CO), N-oxide (-NO), and sulfoxide (-SO). In this review, we have provided select examples of drugs in six chemically distinct groups that are known or suspected to be subjected to the reduction by gut bacteria. For some drugs, responsible enzymes in specific gut bacteria have been identified and characterized, but for many drugs, only circumstantial evidence is available that indicates gut bacteria-mediated reductive metabolism. The physiological roles of even known gut bacterial enzymes have not been well defined.

Aldehydes as Alkylating Agents for Ketones

Common and non-toxic aldehydes are proposed as reagents for alkylation of ketones instead of carcinogenic alkyl halides. The developed reductive alkylation reaction proceeds in the presence of the commercially available ruthenium catalyst [(cymene)RuCl₂ ]₂ (as low as 250 ppm) and carbon monoxide as the reducing agent. The reaction works well for a broad substrate scope, including aromatic and aliphatic aldehydes and ketones. It can be carried out without a solvent and often gives nearly quantitative yields of the products. This straightforward and cost-effective method is promising not only for laboratory application but also for industry, which produces carbon monoxide as a large-scale waste product.

Macular toxicity after short-term hydroxychloroquine therapy

We report an unusual case of hydroxychloroquine (HCQ) toxicity after only 2 months of starting the treatment. A 42-year-old woman presented with visual impairment. Her visual acuity was 20/20 in the right eye and 20/25 in the left eye. Ophthalmologic examination revealed a bull's eye pattern in both eyes which was more prominent in the left eye. She had received HCQ therapy (400 mg/day) for 1 month, and had been taking 200 mg/day for 1 month for the treatment of rheumatoid arthritis. HCQ macular toxicity is rarely seen in short-term use, before 5 years, and to our knowledge, there is only one other case reported in the literature.

Gut microbiota metabolizes nabumetone in vitro: Consequences for its bioavailability in vivo in the rodents with altered gut microbiome

1. The underlying microbial metabolic activity toward xenobiotics is among the least explored factors contributing to the inter-individual variability in drug response. 2. Here, we analyzed the effect of microbiota on a non-steroidal anti-inflammatory drug nabumetone. 3. First, we cultivated the drug with the selected gut commensal and probiotic bacteria under both aerobic and anaerobic conditions and analyzed its metabolites by high-performance liquid chromatography (HPLC) with UV detection. To analyze the effect of microbiota on nabumetone pharmacokinetics in vivo, we administered a single oral dose of nabumetone to rodents with intentionally altered gut microbiome - either rats treated for three days with the antibiotic imipenem or to germ-free mice. Plasma levels of its main active metabolite 6 methoxy-2-naphthylacetic acid (6-MNA) were analyzed at pre-specified time intervals using HPLC with UV/fluorescence detection. 4. We found that nabumetone is metabolized by bacteria to its non-active metabolites and that this effect is stronger under anaerobic conditions. Although in vivo, none of the pharmacokinetic parameters of 6-MNA was significantly altered, there was a clear trend towards an increase of the AUC, Cmax and t_1/2 in rats with reduced microbiota and germ-free mice.

Crystal structure of phospholipase A2 in complex with 1-naphthaleneacetic acid

Phospholipase A₂ (PLA₂ ) is one of the rate limiting enzymes involved in the production of arachidonic acid, a potent inflammatory mediator. PLA₂ is widely distributed all over the animal kingdom. It is also seen in inflammatory exudation and venoms of different organisms. The studies demonstrated that PLA₂ inhibitors have broad spectrum activities that they can either be used against inflammation or envenomation. In this study, the inhibitory activity of 1-napthaleneacetic acid (NAA) against porcine pancreatic PLA₂ has been explained through isothermal titration calorimetry and enzyme kinetics studies. The atomic level of interactions of NAA with PLA₂ was also studied using X-ray crystallography. Apart from these findings, the theoretical binding affinities and mode of interactions of two naphthalene-based NSAIDs such as naproxen (NAP) and nabumetone (NAB) were studied through molecular modeling. The studies proved that the selected ligands are binding at the doorway of the active site cleft and hindering the substrate entry to the active site. The study brings out a potential scaffold for the designing of broad spectrum PLA₂ inhibitors which can be used for inflammation or envenomation. © 2018 IUBMB Life, 70(10):995-1001, 2018.

Palladium-catalyzed site-selective arylation of aliphatic ketones enabled by a transient ligand

A direct arylation of C–H bonds of ketones enabled by a cheap and commercially available transient ligand with high site-selectivity and functional group compatibility is reported.

Human gut microbiota plays a role in the metabolism of drugs

BACKGROUND AND AIMS

The gut microbiome, an aggregate genome of trillions of microorganisms residing in the human gastrointestinal tract, is now known to play a critical role in human health and predisposition to disease. It is also involved in the biotransformation of xenobiotics and several recent studies have shown that the gut microbiota can affect the pharmacokinetics of orally taken drugs with implications for their oral bioavailability.

METHODS

Review of Pubmed, Web of Science and Science Direct databases for the years 1957-2016.

RESULTS AND CONCLUSIONS

Recent studies make it clear that the human gut microbiota can play a major role in the metabolism of xenobiotics and, the stability and oral bioavailability of drugs. Over the past 50 years, more than 30 drugs have been identified as a substrate for intestinal bacteria. Questions concerning the impact of the gut microbiota on drug metabolism, remain unanswered or only partially answered, namely (i) what are the molecular mechanisms and which bacterial species are involved? (ii) What is the impact of host genotype and environmental factors on the composition and function of the gut microbiota, (iii) To what extent is the composition of the intestinal microbiome stable, transmissible, and resilient to perturbation? (iv) Has past exposure to a given drug any impact on future microbial response, and, if so, for how long? Answering such questions should be an integral part of pharmaceutical research and personalised health care.

Carbon-carbon bond cleavage and formation reactions in drug metabolism and the role of metabolic enzymes

Elimination of xenobiotics from the human body is often facilitated by a transformation to highly water soluble and more ionizable molecules. In general, oxidation-reduction, hydrolysis, and conjugation reactions are common biotransformation reactions that are catalyzed by various metabolic enzymes including cytochrome P450s (CYPs), non-CYPs, and conjugative enzymes. Although carbon-carbon (C-C) bond formation and cleavage reactions are known to exist in plant secondary metabolism, these reactions are relatively rare in mammalian metabolism and are considered exceptions. However, various reactions such as demethylation, dealkylation, dearylation, reduction of alkyl chain, ring expansion, ring contraction, oxidative elimination of a nitrile through C-C bond cleavage, and dimerization, and glucuronidation through C-C bond formation have been reported for drug molecules. Carbon-carbon bond cleavage reactions for drug molecules are primarily catalyzed by CYP enzymes, dimerization is mediated by peroxidases, and C-glucuronidation is catalyzed by UGT1A9. This review provides an overview of C-C bond cleavage and formation reactions in drug metabolism and the metabolic enzymes associated with these reactions.

Carbon-carbon bond cleavage in activation of the prodrug nabumetone

Carbon-carbon bond cleavage reactions are catalyzed by, among others, lanosterol 14-demethylase (CYP51), cholesterol side-chain cleavage enzyme (CYP11), sterol 17β-lyase (CYP17), and aromatase (CYP19). Because of the high substrate specificities of these enzymes and the complex nature of their substrates, these reactions have been difficult to characterize. A CYP1A2-catalyzed carbon-carbon bond cleavage reaction is required for conversion of the prodrug nabumetone to its active form, 6-methoxy-2-naphthylacetic acid (6-MNA). Despite worldwide use of nabumetone as an anti-inflammatory agent, the mechanism of its carbon-carbon bond cleavage reaction remains obscure. With the help of authentic synthetic standards, we report here that the reaction involves 3-hydroxylation, carbon-carbon cleavage to the aldehyde, and oxidation of the aldehyde to the acid, all catalyzed by CYP1A2 or, less effectively, by other P450 enzymes. The data indicate that the carbon-carbon bond cleavage is mediated by the ferric peroxo anion rather than the ferryl species in the P450 catalytic cycle. CYP1A2 also catalyzes O-demethylation and alcohol to ketone transformations of nabumetone and its analogs.

Cytochrome P450-activated prodrugs

A prodrug is a compound that has negligible, or lower, activity against a specified pharmacological target than one of its major metabolites. Prodrugs can be used to improve drug delivery or pharmacokinetics, to decrease toxicity, or to target the drug to specific cells or tissues. Ester and phosphate hydrolysis are widely used in prodrug design because of their simplicity, but such approaches are relatively ineffective for targeting drugs to specific sites. The activation of prodrugs by the cytochrome P450 system provides a highly versatile approach to prodrug design that is particularly adaptable for targeting drug activation to the liver, to tumors or to hypoxic tissues.

Progression of macular atrophy after PDT combined with the COX-2 inhibitor Nabumetone in the treatment of neovascular ARMD

AIM

To evaluate photodynamic therapy (PDT) combined with the preferential the cyclooxygenase-2 (COX-2) inhibitor, nabumetone in the treatment of the neovascular age-related macular degeneration (ARMD).

METHODS

A prospective, double-blind, randomized study on 60 patients with subfoveal CNV secondary to ARMD without any previous treatment. Patients were divided into a nabumetone or placebo group. The main endpoints were the change of best-corrected visual acuity (BCVA), central macular thickness (CRT) and number of required PDT treatments.

RESULTS

In the nabumetone group, 27 patients (90%) and 28 (93%) in the placebo group completed the follow-up of 12 months. In the nabumetone group, the mean CRT decreased from 332 μm (SD 68 μm) to 220 μm (SD 46 μm). In the placebo group, CRT decreased from 331 μm (SD 72 μm) to 254 μm (SD 61 μm). The mean BCVA was 0.68 log MAR (SD 0.22 log MAR) in the nabumetone group and 0.62 log MAR (SD 0.23 log MAR) in the placebo group at baseline. This stabilised in the placebo group to 0.66 log MAR (SD 0.33) but deteriorated in the nabumetone group to 0.86 log MAR (SD 0.41 log MAR). There was a significant reduction in the number of required PDTs in the nabumetone group, but significant progression of the RPE atrophy area.

CONCLUSION

Combined PDT with oral intake of the COX-2 inhibitor, nabumetone reduced the number of required PDT retreatments, but worsening BCVA caused by macular atrophy progression. Therefore the combination of the PDT with the nabumetone is not recommended.

Role of carbonyl reducing enzymes in the phase I biotransformation of the non-steroidal anti-inflammatory drug nabumetone in vitro

1. Nabumetone is a clinically used non-steroidal anti-inflammatory drug, its biotransformation includes major active metabolite 6-methoxy-2-naphtylacetic acid and another three phase I as well as corresponding phase II metabolites which are regarded as inactive. One important biotransformation pathway is carbonyl reduction, which leads to the phase I metabolite, reduced nabumetone. 2. The aim of this study is the determination of the role of a particular human liver subcellular fraction in the nabumetone reduction and the identification of participating carbonyl reducing enzymes along with their stereospecificities. 3. Both subcellular fractions take part in the carbonyl reduction of nabumetone and the reduction is at least in vitro the main biotransformation pathway. The activities of eight cytosolic carbonyl reducing enzymes--CBR1, CBR3, AKR1B1, AKR1B10, AKR1C1-4--toward nabumetone were tested. Except for CBR3, all tested reductases transform nabumetone to its reduced metabolite. AKR1C4 and AKR1C3 have the highest intrinsic clearances. 4. The stereospecificity of the majority of the tested enzymes is shifted to the production of an (+)-enantiomer of reduced nabumetone; only AKR1C1 and AKR1C4 produce predominantly an (-)-enantiomer. This project provides for the first time evidence that seven specific carbonyl reducing enzymes participate in nabumetone metabolism.

Discovery of nonsteroidal anti-inflammatory drug and anticancer drug enhancing reprogramming and induced pluripotent stem cell generation

Recent breakthroughs in creating induced pluripotent stem cells (iPSCs) provide alternative means to obtain embryonic stem-like cells without destroying embryos by introducing four reprogramming factors (Oct3/4, Sox2, and Klf4/c-Myc or Nanog/Lin28) into somatic cells. iPSCs are versatile tools for investigating early developmental processes and could become sources of tissues or cells for regenerative therapies. Here, for the first time, we describe a strategy to analyze genomics datasets of mouse embryonic fibroblasts (MEFs) and embryonic stem cells to identify genes constituting barriers to iPSC reprogramming. We further show that computational chemical biology combined with genomics analysis can be used to identify small molecules regulating reprogramming. Specific downregulation by small interfering RNAs (siRNAs) of several key MEF-specific genes encoding proteins with catalytic or regulatory functions, including WISP1, PRRX1, HMGA2, NFIX, PRKG2, COX2, and TGFβ3, greatly increased reprogramming efficiency. Based on this rationale, we screened only 17 small molecules in reprogramming assays and discovered that the nonsteroidal anti-inflammatory drug Nabumetone and the anticancer drug 4-hydroxytamoxifen can generate iPSCs without Sox2. Nabumetone could also produce iPSCs in the absence of c-Myc or Sox2 without compromising self-renewal and pluripotency of derived iPSCs. In summary, we report a new concept of combining genomics and computational chemical biology to identify new drugs useful for iPSC generation. This hypothesis-driven approach provides an alternative to shot-gun screening and accelerates understanding of molecular mechanisms underlying iPSC induction.

Drug discovery for Duchenne muscular dystrophy via utrophin promoter activation screening

BACKGROUND

Duchenne muscular dystrophy (DMD) is a devastating muscle wasting disease caused by mutations in dystrophin, a muscle cytoskeletal protein. Utrophin is a homologue of dystrophin that can functionally compensate for its absence when expressed at increased levels in the myofibre, as shown by studies in dystrophin-deficient mice. Utrophin upregulation is therefore a promising therapeutic approach for DMD. The use of a small, drug-like molecule to achieve utrophin upregulation offers obvious advantages in terms of delivery and bioavailability. Furthermore, much of the time and expense involved in the development of a new drug can be eliminated by screening molecules that are already approved for clinical use.

METHODOLOGY/PRINCIPAL FINDINGS

We developed and validated a cell-based, high-throughput screening assay for utrophin promoter activation, and used it to screen the Prestwick Chemical Library of marketed drugs and natural compounds. Initial screening produced 20 hit molecules, 14 of which exhibited dose-dependent activation of the utrophin promoter and were confirmed as hits. Independent validation demonstrated that one of these compounds, nabumetone, is able to upregulate endogenous utrophin mRNA and protein, in C2C12 muscle cells.

CONCLUSIONS/SIGNIFICANCE

We have developed a cell-based, high-throughput screening utrophin promoter assay. Using this assay, we identified and validated a utrophin promoter-activating drug, nabumetone, for which pharmacokinetics and safety in humans are already well described, and which represents a lead compound for utrophin upregulation as a therapy for DMD.

Pain management for rheumatoid arthritis and cardiovascular or renal comorbidity

BACKGROUND

Pain in rheumatoid arthritis is common, is often multi-factorial and many different pharmacotherapeutic agents are routinely used for pain management. There are concerns that some of the pain pharmacotherapies currently used may increase the risk of adverse events in people with rheumatoid arthritis and concurrent cardiovascular or renal disease.

OBJECTIVES

To systematically assess and collate the scientific evidence on the efficacy and safety of using pain pharmacotherapy in people with rheumatoid arthritis and cardiovascular or renal comorbidities.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library 2010, Issue 4); MEDLINE, from 1950; EMBASE, from 1980; the Cochrane Database of Systematic Reviews (CDSR) and the Database of Abstracts of Reviews of Effects (DARE). We also handsearched the conference proceedings for American College of Rheumatology (ACR) and European League against Rheumatism (EULAR) for 2008-09, and checked the websites of regulatory agencies for reported adverse events, labels and warnings.

SELECTION CRITERIA

We considered randomised controlled trials and non-randomised studies comparing the efficacy and safety of pain pharmacotherapies in patients with rheumatoid arthritis, with and without comorbid cardiovascular or renal conditions.In addition, we also considered controlled before-after studies, interrupted time series, cohort and case control studies and case series (N ≥ 20) to assess safety.For the purpose of our review, pain pharmacotherapy was defined as including simple analgesics (such as paracetamol), non-steroidal anti-inflammatory drugs (NSAIDs), opioids or opioid-like drugs (such as tramadol), and neuromodulators (including anti-depressants, anti-convulsants, and muscle relaxants).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results and planned to extract data and appraise the risk of bias of included studies.

MAIN RESULTS

We did not identify any studies meeting our inclusion criteria. Many of the trials of NSAIDs explicitly excluded patients with cardiovascular or renal comorbidities.We did identify one trial that reported evidence in mixed populations (including both rheumatoid arthritis and osteoarthritis) taking either diclofenac or etoricoxib. In this study, the presence of cardiovascular disease increased the likelihood of a further cardiovascular event three-fold. Patients with two or more cardiovascular comorbidities showed a two-fold increased likelihood of adverse cardiovascular events.

AUTHORS' CONCLUSIONS

There were no trials that specifically compared the efficacy and safety of pain pharmacotherapies for patients with rheumatoid arthritis, with and without comorbid cardiovascular or renal conditions.In the absence of specific evidence in rheumatoid arthritis, current guidelines recommend that NSAIDs be used with caution in the general rheumatoid arthritis population while highlighting the added need for extra vigilance in patients with established cardiovascular disease or risk factors for its development. Current guidelines regarding the use of NSAIDs and opioids in moderate to severe renal impairment should also be applied to the rheumatoid arthritis population.Further research is required to guide clinicians when treating pain in rheumatoid arthritis.

Single dose oral nabumetone for acute postoperative pain in adults

BACKGROUND

Nabumetone is a non-steroidal anti-inflammatory drug (NSAID) used mainly in treating pain associated with arthritis. The usual oral dose for osteoarthritis is 1000 mg daily, and higher doses are not advised in older patients. There are no known systematic reviews of its analgesic efficacy in acute postoperative pain. This review sought to evaluate the efficacy and safety of oral nabumetone in acute postoperative pain, using clinical studies of patients with established pain, and with outcomes measured primarily over 6 hours using standard methods. This type of study has been used for many decades to establish whether drugs have analgesic properties.

OBJECTIVES

To assess the efficacy of single dose oral nabumetone in acute postoperative pain, and any associated adverse events.

SEARCH STRATEGY

We searched The Cochrane Library (Issue 2, 2009), MEDLINE (May 2009); EMBASE via Ovid (May 2009); and the Oxford Pain Relief Database.

SELECTION CRITERIA

Randomised, double-blind, placebo-controlled clinical trials of oral nabumetone for relief of acute postoperative pain in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. The area under the "pain relief versus time" curve was used to derive the proportion of participants with nabumetone and placebo experiencing at least 50% pain relief over 4 to 6 hours, using validated equations. The number needed to treat to benefit (NNT) was calculated using 95% confidence intervals (CI). The proportion of participants using rescue analgesia over a specified time period, and time to use of rescue analgesia, were sought as additional measures of efficacy. Information on adverse events and withdrawals was also collected.

MAIN RESULTS

No studies were identified by the searches that examined oral nabumetone in participants with established postoperative pain.

AUTHORS' CONCLUSIONS

In the absence of evidence of efficacy, at present, for oral nabumetone in acute postoperative pain, its use in this indication is not justified. Because trials clearly demonstrating analgesic efficacy in the most basic of acute pain studies is lacking, use in other indications should be evaluated carefully. Given the large number of available drugs of this and similar classes, there is no urgent research agenda.

A predominate role of CYP1A2 for the metabolism of nabumetone to the active metabolite, 6-methoxy-2-naphthylacetic acid, in human liver microsomes

Nabumetone, a widely used nonsteroidal anti-inflammatory drug, requires biotransformation into 6-methoxy-2-naphthylacetic acid (6-MNA), a close structural analog to naproxen, to achieve its analgesic and anti-inflammatory effects. Despite its wide use, the enzymes involved in metabolism have not been identified. In the present study, several in vitro approaches were used to identify the cytochrome P450 (P450) enzyme(s) responsible for 6-MNA formation. In human liver microsomes (HLMs) 6-MNA formation displayed monophasic Michaelis-Menten kinetics with apparent K(m) and V(max) values (mean +/- S.D.) of 75.1 +/- 15.3 microM and 1304 +/- 226 pmol/min/mg protein, respectively, and formation rate of 6-MNA varied approximately 5.5-fold (179-983 pmol/min/mg protein). 6-MNA activity correlated strongly with both CYP1A2-mediated phenacetin O-deethylation activity and CYP1A2 protein content (r = 0.85 and 0.74, respectively; p < 0.0001 for both). Additional correlations were found with model activities of CYP2C19 and CYP3A4. Of 11 cDNA-expressed recombinant P450s used, recombinant CYP1A2 was the major form catalyzing the 6-MNA formation with an apparent K(m) of 45 microM and V(max) of 8.7 pmol/min/pmol P450. Minor fractions were catalyzed by recombinant P450s CYP1A1, CYP2B6, CYP2C19, CYP2D6, and CYP2E1. Experiments with P450-selective chemical inhibitors and monoclonal anti-P450 antibodies showed that furafylline, a mechanism-based inhibitor CYP1A2, and anti-CYP1A2 antibody markedly inhibited 6-MNA formation, whereas inhibitors for other P450s did not show significant inhibitory effects. Taken together, these studies indicate that the formation of the active metabolite of nabumetone, 6-MNA, is predominantly catalyzed by CYP1A2 in HLMs with only minor contribution of other P450s.