Oxidation of Naringenin, Apigenin, and Genistein by Human Family 1 Cytochrome P450 Enzymes and Comparison of Interaction of Apigenin with Human P450 1B1.1 and Scutellaria P450 82D.1

Heme-thiolate monooxygenase cytochrome P450 1B1, an old dog with many new tricks

Cytochrome P450 CYP1B1 is a heme-thiolate monooxygenase traditionally recognized for its xenobiotic functions and extrahepatic expressions. Recent studies have suggested that CYP1B1 is also expressed in hepatic stellate cells, immune cells, endothelial cells, and fibroblasts within the tumor microenvironment, as well as tumor cells themselves. CYP1B1 is responsible for the metabolism of a wide range of substrates, including xenobiotics such as drugs, environmental chemicals, and endobiotics such as steroids, retinol, and fatty acids. Consequently, CYP1B1 and its associated exogenous and endogenous metabolites have been critically implicated in the pathogenesis of many diseases. Understanding the mode of action of CYP1B1 in different pathophysiological conditions and developing pharmacological inhibitors that allow for systemic or cell type-specific modulation of CYP1B1 may pave the way for novel therapeutic opportunities. This review highlights the significant role of CYP1B1 in maintaining physiological homeostasis and provides a comprehensive discussion of recent advancements in our understanding of CYP1B1's involvement in the pathogenesis of diseases such as fibrosis, cancer, glaucoma, and metabolic disorders. Finally, the review emphasizes the therapeutic potential of targeting CYP1B1 for drug development, particularly in the treatment and prevention of cancers and liver fibrosis. SIGNIFICANCE STATEMENT: CYP1B1 plays a critical role in various physiological processes. Dysregulation or genetic mutations of the gene encoding this enzyme can lead to health complications and may increase the risk of diseases such as cancer and liver fibrosis. In this review, we summarize recent preclinical and clinical evidence that underscores the potential of CYP1B1 as a therapeutic target.

Saponins in soy reduce NNK-induced lung cancer by increasing plasma isoflavone levels

Recently, we found, using a cigarette carcinogen-induced lung cancer model, that soy protein isolate (SPI) was superior to casein in preventing lung cancer. In this study, we have attempted to identify the component(s) within SPI responsible for this chemopreventive effect. We fractionated the SPI using ethanol to separate the ethanol-soluble fraction (ESF) and the washed SPI and compared their efficacy to diets made with amino acids that comprise soy protein or casein, in preventing lung tumor formation in A/J mice. Only the ethanol-soluble fraction was as effective as SPI in preventing lung tumor formation. Since isoflavones and saponins are known ethanol-soluble bioactives from soy, we added isoflavones, or saponins or both to casein and found that isoflavones or saponins alone did not reduce lung nodule formation. However, when we combined soy saponins and isoflavones, we saw a significant (P < 0.05) reduction in NNK-induced lung nodules, and an increase in plasma isoflavone levels, suggesting that the saponins may enhance the bioavailability of the isoflavones in these mice. Taken together, we suggest that the superior efficacy of SPI over casein could be attributed, at least in part, to the synergistic effect of the soy saponins and isoflavones.

Apigenin improves testosterone synthesis by regulating endoplasmic reticulum stress

Obesity is a growing epidemic among reproductive-age men, which can cause and exacerbate male infertility by means of associated comorbidities, endocrine abnormalities, and direct effects on the fidelity and throughput of spermatogenesis. A prominent consequence of male obesity is a reduction in testosterone levels. Natural products have shown tremendous potential anti-obesity effects in metabolic diseases. This study aimed to investigate the potential of apigenin (AP) to alleviate testicular dysfunction induced by a high-fat diet (HFD) and to investigate the underlying mechanisms, focusing on endoplasmic reticulum stress (ERS) and testosterone synthesis. A murine model of obesity was established using HFD-fed mice. The effects of AP on obesity, lipid metabolism, testicular dysfunction, and ERS were assessed through various physiological, histological, and molecular techniques. Administration of AP (10 mg/kg) ameliorated HFD-induced obesity and testicular dysfunction in a mouse model, as evidenced by decreased body weight, improved lipid profiles and testicular pathology, and restored protein levels related to testosterone. Furthermore, in vitro studies demonstrated that AP relieved ERS and recovered testosterone synthesis in murine Leydig cells (TM3) treated with free fatty acids (FFAs). It was also observed that AP rescued testosterone synthesis enzymes in TM3 cells, similar to that observed with the inhibitor of the PERK pathway (GSK2606414). In addition, ChIP, qPCR, and gene silencing showed that the C/EBP homologous protein (CHOP) bound directly to the promoter region of steroidogenic STAR and negatively modulated its expression. Collectively, AP has remarkable potential to alleviate HFD-induced obesity and testicular dysfunction. Its protective effects are attributable partly to mitigating ERS and restoring testosterone synthesis in Leydig cells.

Review of the pharmacokinetics of French maritime pine bark extract (Pycnogenol®) in humans

The French maritime pine bark extract Pycnogenol® is a proprietary product from Pinus pinaster Aiton. It complies with the quality specifications in the United States Pharmacopeia monograph "Pine extract" in the section of dietary supplements. Pycnogenol® is standardized to contain 65-75% procyanidins which are a variety of biopolymers consisting of catechin and epicatechin monomeric units. The effects of Pycnogenol® have been researched in a multitude of human studies. The basis for any in vivo activity is the bioavailability of constituents and metabolites of the extract. General principles of compound absorption, distribution, metabolism and elimination as well as specific data from studies with Pycnogenol® are summarized and discussed in this review. Based on plasma concentration profiles it can be concluded that low molecular weight constituents of the extract, such as catechin, caffeic and ferulic acid, taxifolin are readily absorbed from the small intestine into systemic circulation. Procyanidin oligomers and polymers are subjected to gut microbial degradation in the large intestine yielding small bioavailable metabolites such as 5-(3',4'-dihydroxyphenyl)-γ-valerolactone. After intake of Pycnogenol®, constituents and metabolites have been also detected in blood cells, synovial fluid and saliva indicating a substantial distribution in compartments other than serum. In studies simultaneously investigating concentrations in different specimen, a preferential distribution of individual compounds has been observed, e.g., of ferulic acid and 5-(3',4'-dihydroxyphenyl)-γ-valerolactone into synovial fluid compared to serum. The main route of elimination of constituents and metabolites of the French pine bark extract is the renal excretion. The broad knowledge accumulated regarding the pharmacokinetics of compounds and metabolites of Pycnogenol® constitute a rational basis for effects characterized on a cellular level and observed in human clinical studies.