Mechanism-based inactivation of cytochrome P450 2B6 by isopsoralen

Mechanistic study of bergamottin-induced inactivation of CYP2C9

Bergamottin (BGM) is a major furanocoumarin constituent of grapefruit and is reported to have inhibitory effects on cytochrome P450 enzymes. This study investigated the chemical interactions between BGM and the enzyme CYP2C9. BGM exhibited time-, concentration-, and NADPH-dependent inhibition of CYP2C9. Co-incubation with diclofenac, a reversible inhibitor of CYP2C9, attenuated the time-dependent enzyme inhibition. Exhaustive dialysis did not restore enzyme activity post-inhibition. Glutathione (GSH) and catalase/superoxide dismutase failed to reverse BGM-induced CYP2C9 inactivation. A GSH trapping study suggested that BGM was metabolized to an epoxide and/or γ-ketoenal that may have been responsible for the enzyme inactivation. In conclusion, BGM can be characterized as a mechanism-based inactivator of CYP2C9 acting via the formation of an epoxide and/or γ-ketoenal.

Mechanism-based inactivation of cytochrome P450 enzymes by natural products based on metabolic activation

Cytochrome P450 enzymes (P450 enzymes) are the most common and important phase I metabolic enzymes and are responsible for the majority of the metabolism of clinical drugs and other xenobiotics. Drug-drug interactions (DDIs) can occur when the activities of P450 enzymes are inhibited. In particular, irreversible inhibition of P450 enzymes may lead to severe adverse interactions, compared to reversible inhibition. Many natural products have been shown to be irreversible inhibitors of P450 enzymes. The risks for intake of naturally occurring irreversible P450 enzyme inhibitors have been rising due to the rapid growth of the global consumption of natural products. Irreversible inhibition is usually called mechanism-based inactivation, which is time-, concentration- and NADPH- dependent. Generally, the formation of electrophilic intermediates is fundamental for the inactivation of P450 enzymes. This review comprehensively classifies natural P450 enzyme inactivators, including terpenoids, phenylpropanoids, flavonoids, alkaloids, and quinones obtained from herbs or foods. Moreover, the structure - activity correlations according to the IC₅₀ (or K_i) values reported in the literature as well as the underlying mechanisms based on metabolic activation are highlighted in depth.

A Review of the Pharmacological Properties of Psoralen

Psoralen is the principal bioactive component in the dried fruits of Cullen corylifolium (L.) Medik (syn. Psoralea corylifolia L), termed "Buguzhi" in traditional Chinese medicine (TCM). Recent studies have demonstrated that psoralen displays multiple bioactive properties, beneficial for the treatment of osteoporosis, tumors, viruses, bacteria, and inflammation. The present review focuses on the research evidence relating to the properties of psoralen gathered over recent years. Firstly, multiple studies have demonstrated that psoralen exerts strong anti-osteoporotic effects via regulation of osteoblast/osteoclast/chondrocyte differentiation or activation due to the participation in multiple molecular mechanisms of the wnt/β-catenin, bone morphogenetic protein (BMP), inositol-requiring enzyme 1 (IRE1)/apoptosis signaling kinase 1 (ASK1)/c-jun N-terminal kinase (JNK) and the Protein Kinase B(AKT)/activator protein-1 (AP-1) axis, and the expression of miR-488, peroxisome proliferators-activated receptor-gamma (PPARγ), and matrix metalloproteinases (MMPs). In addition, the antitumor properties of psoralen are associated with the induction of ER stress-related cell death via enhancement of PERK: Pancreatic Endoplasmic Reticulum Kinase (PERK)/activating transcription factor (ATF), 78kD glucose-regulated protein (GRP78)/C/EBP homologous protein (CHOP), and 94kD glucose-regulated protein (GRP94)/CHOP signaling, and inhibition of P-glycoprotein (P-gp) or ATPase that overcomes multidrug resistance. Furthermore, multiple articles have shown that the antibacterial, anti-inflammatory and neuroprotective effects of psoralen are a result of its interaction with viral polymerase (Pol), destroying the formation of biofilm, and regulating the activation of tumor necrosis factor alpha (TNF-α), transforming growth factor beta (TGF-β), interleukin 4/5/6/8/12/13 (IL-4/5/6/8/12/13), GATA-3, acetylcholinesterase (AChE), and the hypothalamic-pituitary-adrenal (HPA) axis. Finally, the toxic effects and mechanisms of action of psoralen have also been reviewed.

Isopsoralen regulates PPAR‑γ/WNT to inhibit oxidative stress in osteoporosis

The present study aimed to examine the effects of isopsoralen against postmenopausal osteoporosis in an ovariectomized rat model. The ovariectomized rats were treated with three days 10 mg/kg isopsoralen or with three days 20 mg/kg isopsoralen. Alkaline phosphatase, the oxidative stress indicators and caspase‑3/9 were measured using ELISA assay kits. Reverse transcription‑quantitative polymerase chain reaction was used to measure collagen type I (Col I), osteocalcin and osteoprotegerin mRNA levels. Wnt, β‑catenin and peroxisome proliferators‑activated receptor γ (PPAR‑γ) were analyzed using western blot analysis. Isopsoralen suppressed mature adipocyte differentiation of C2C12 cells, inhibited serum calcium and urinary calcium levels, and reduced the structural scores of articular cartilage and cancellous bone in the proximal tibia metaphysis of mice with postmenopausal osteoporosis. Isopsoralen also promoted the activity of alkaline phosphatase and the mRNA expression levels of Col 1, osterix and osteopontin in mice with postmenopausal osteoporosis. Oxidative stress and activities of caspase‑3/9 in the mice with postmenopausal osteoporosis were effectively suppressed by isopsoralen treatment, which upregulated the protein expression of Wnt/β‑catenin and downregulated the protein expression of PPAR‑γ. These findings demonstrated that isopsoralen prevented osteoporosis through the regulation of PPAR‑γ/WNT, inhibiting oxidative stress by targeting the PPAR‑γ/WNT pathway. These results provide evidence of the potential targeted therapy for isopsoralen in the clinical treatment of postmenopausal osteoporosis.