Metabolism of Non-steroidal Anti-inflammatory Drugs by Peroxidase: Implication for Gastrointestinal Mucosal Lesions

Chinese Medicine Huzhen Tongfeng Formula Effectively Attenuates Gouty Arthritis by Inhibiting Arachidonic Acid Metabolism and Inflammatory Mediators

The Chinese herbal medicine, Huzhen Tongfeng Formula (HZTF), derived from traditional Chinese medicine (TCM) practice, has recognized therapeutic benefits for gouty arthritis (GA). HZTF is currently in the late stage of approval process as a new anti-GA drug application. However, the underlying mechanism of HZTF as an antigout medication is unclear. In this study, we combined network pharmacology and experimental validation approaches to elucidate the mechanism of action of HZTF. First, the relative drug-disease target networks were constructed and analyzed for pathway enrichment. Potential pathways were then validated by in vitro and in vivo experiments. We found that 34 compounds from HZTF matched 181 potential drug targets. Topology analysis revealed 77 core targets of HZTF, which were highly related to gout, following screening of KEGG pathway enrichment. Further analysis demonstrated that the arachidonic acid metabolic pathway was the most relevant pathway involved in the mechanism of HZTF. Validation experiments showed that HZTF significantly inhibited the inflammatory cell infiltration into gouty joints, improved the swelling of affected joints, and increased the pain threshold. HZTF significantly reduced the transcription and production of various cytokines and inflammatory mediators in vitro. In particular, cyclooxygenase (COX)-1, COX-2, and 5-lipoxygenase were simultaneously downregulated. In conclusion, our study suggests that the antigout mechanism of HZTF is associated with the inhibition of the arachidonic acid pathway, resulting in the suppression of inflammatory cytokines and mediators. These findings extend our understanding of the pharmacological action of HZTF, rationalizing the application HZTF as an effective herbal therapy for GA.

Direct detection of diclofenac radical produced by ultraviolet irradiation using electron spin resonance method

Diclofenac, a nonsteroidal anti-inflammatory drug, is commonly used as an antipyretic analgesic owing to its strong anti-inflammatory action in clinical treatment. However, diclofenac can cause injury, with gastrointestinal mucosal lesions and skin photosensitivity as the main side effects. In general, photosensitive drugs contain photosensitive chemical sites, and form free radicals under ultraviolet irradiation, leading to phototoxic reactions. Therefore, this study focuses on free radical production in photosensitive reactions of diclofenac. The free radical production mechanism of diclofenac under ultraviolet irradiation, which might result in photo-toxicity, was clarified using a direct electron spin resonance method. When diclofenac was irradiated with ultraviolet light (254 nm), diclofenac radicals were generated depending on the ultraviolet irradiation time and stably present for 30 min at room temperature. Diclofenac radicals were produced by the ultraviolet irradiation system depending on the dose of diclofenac until 2 mM. Therefore, diclofenac radicals might directly or indirectly react with various biomolecules to cause phototoxicity, other side effects, and new diclofenac pharmacology owing to its stability of diclofenac radicals.

[Direction of strategic use: a new classification of non-steroidal anti-inflammatory drugs based on reactivity with peroxidase]

  The pharmaceutical effects of non-steroidal anti-inflammatory drugs (NSAIDs) occur through the inhibition of prostaglandin H synthase (PGHS). Prostaglandin H2 is produced from arachidonic acid via peroxidase and cyclooxygenase cycles in PGHS. NSAIDs exhibit different levels of reactivity in these reaction cycles. To prevent the development of side effect while maintaining the beneficial effects of drugs, a therapeutic strategy should be used. A new classification of NSAIDs has been proposed based on reactivity to peroxidase. Class 1 includes the majority of NSAIDs, which react with horseradish peroxidase (HRP) compounds I and II. Also, their drugs exhibit spectral changes induced by PGHS peroxidase and diminished ESR signals of the tyrosyl radical of metmyoglobin. They reduce compounds I and II of HRP and scavenge tyrosyl radicals. The branched chain mechanism by which the porphyrin radical is transferred to the tyrosine residue of the protein might be blocked by these NSAIDs. Class 2 includes salicylic acid derivatives that react only with the porphyrin radical and do not react with HRP compound II (oxoferryl species). Class 3 includes aspirin, nimesulide, tolmetin, and arylpropionic acid derivatives, including ibuprofen and the coxibs such as celecoxib and rofecoxib, which are not substrates for HRP or PGHS peroxidase. It seems that the selectivity of NSAIDs to PGHS1 and PGHS2 depends on their reactivity with cyclooxygenase rather than with the peroxidase of PGHS. The best drug for each inflammatory disease should therefore be selected for therapy.

Reactivity of nonsteroidal anti-inflammatory drugs with peroxidase: a classification of nonsteroidal anti-inflammatory drugs

OBJECTIVES

To improve understanding of the essential effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on prostaglandin H synthase (PGHS), the reactivity of NSAIDs with peroxidases and the tyrosyl radical derived from myoglobin was examined.

METHODS

Horseradish peroxidase and myoglobin were used as models of peroxidase and cyclooxygenase of PGHS, respectively.

KEY FINDINGS

From the results, a new classification of NSAIDs has been proposed. Class 1 includes the majority of NSAIDs, which reacted with horseradish peroxidase compound I, thus causing a spectral change by PGHS peroxidase and also including diminished electron spin resonance signals of the tyrosyl radical of myoglobin. They reduced compound I of horseradish peroxidase and scavenged the tyrosyl radical. The branched-chain mechanism by which the porphyrin radical is transferred to the tyrosine residue of the protein might be blocked by these NSAIDs. Class 2 includes salicylic acid derivatives that reacted only with the porphyrin radical and not with horseradish peroxidase compound II (oxoferryl species). Class 3 includes aspirin, nimesulide, tolmetin, and arylpropionic acid derivatives, including ibuprofen and the coxibs of celecoxib and rofecoxib, which are not substrates for horseradish peroxidase or PGHS peroxidase.

CONCLUSIONS

Understanding the essential mode of action of NSAIDs is particularly important for designing an effective therapeutic strategy against inflammatory diseases.

Inactivation of cholinesterase induced by non-steroidal anti-inflammatory drugs with horseradish peroxidase: implication for Alzheimer's disease

AIMS

To clarify the mechanism of the protective effect of non-steroidal anti-inflammatory drugs (NSAIDs) on Alzheimer's disease, inactivation of cholinesterase (ChE) induced by NSAIDs was examined.

MAIN METHODS

Equine ChE and rat brain homogenate were incubated with NSAIDs and horseradish peroxidase (HRP) and H(2)O(2) (HRP-H(2)O(2)). ChE activity was measured by using 5,5'-dithiobis(nitrobenzoic acid). By using electron spin resonance, NSAID radicals induced by reaction with HRP-H(2)O(2) were detected in the presence of spin trap agents.

KEY FINDINGS

Equine ChE was inactivated by mefenamic acid with HRP-H(2)O(2). ChE activity in rat brain homogenate decreased dependent on the concentration of mefenamic acid in the presence of HRP-H(2)O(2). NSAIDs diclofenac, indomethacin, phenylbutazone, piroxicam and salicylic acid inactivated ChE. Oxygen radical scavengers did not prevent inactivation of ChE induced by mefenamic acid with HRP-H(2)O(2). However, spin trap agents 5,5-dimethyl-1-pyrroline-l-oxide and N-methyl-nitrosopropane, reduced glutathione and ascorbic acid strongly inhibited inactivation of ChE, indicating participation of mefenamic acid radicals. Fluorescent emission of ChE peaked at 400 nm, and the Vmax value of ChE changed during interaction of mefenamic acid with HRP-H(2)O(2), indicating that ChE may be inactivated through modification of tyrosine residues by mefenamic radicals.

SIGNIFICANCE

The protective effect of NSAIDs on Alzheimer's disease seems to occur through inactivation of ChE induced by NSAIDs radicals.