Determination method for steroid 5alpha-reductase activity using liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry

Advances in steroid research from the pioneering neurosteroid concept to metabolomics: New insights into pregnenolone function

Advances in neuroendocrinology have led to major discoveries since the 19th century, identifying adaptive loops for maintaining homeostasis. One of the most remarkable discoveries was the concept of neurosteroids, according to which the brain is not only a target but also a source of steroid production. The identification of new membrane steroid targets now underpins the neuromodulatory effects of neurosteroids such as pregnenolone, which is involved in functions mediated by the GPCR CB1 receptor. Structural analysis of steroids is a key feature of their interactions with the phospholipid membrane, receptors and resulting activity. Therefore, mass spectrometry-based methods have been developed to elucidate the metabolic pathways of steroids, the ultimate approach being metabolomics, which allows the identification of a large number of metabolites in a single sample. This approach should enable us to make progress in understanding the role of neurosteroids in the functioning of physiological and pathological processes.

New perspectives on the role of the neurosteroid pregnenolone as an endogenous regulator of type-1 cannabinoid receptor (CB1R) activity and function

Pregnenolone is a steroid with specific characteristics, being the first steroid to be synthesised from cholesterol at all sites of steroidogenesis, including the brain. For many years, pregnenolone was defined as an inactive precursor of all steroids because no specific target had been discovered. However, over the last decade, it has become a steroid of interest because it has been recognised as being a biomarker for brain-related disorders through the development of metabolomic approaches and advanced analytical methods. In addition, physiological roles for pregnenolone emerged when specific targets were discovered. In this review, we highlight the discovery of the selective interaction of pregnenolone with the type-1 cannabinoid receptor (CB1R). After describing the specific characteristic of CB1Rs, we discuss the newly discovered mechanisms of their regulation by pregnenolone. In particular, we describe the action of pregnenolone as a negative allosteric modulator and a specific signalling inhibitor of the CB1R. These particular characteristics of pregnenolone provide a great strategic opportunity for therapeutic development in CB1-related disorders. Finally, we outline new perspectives using innovative genetic tools for the discovery of original regulatory mechanisms of pregnenolone on CB1-related functions.

Development of a Liquid Chromatography/Mass Spectrometry-Based Inhibition Assay for the Screening of Steroid 5-α Reductase in Human and Fish Cell Lines

Steroid 5-α reductase (5AR) is responsible for the reduction of steroids to 5-α reduced metabolites, such as the reduction of testosterone to 5-α dihydrotestosterone (DHT). A new adverse outcome pathway (AOP) for 5AR inhibition to reduce female reproduction in fish (AOP 289) is under development to clarify the antiestrogenic effects of 5AR inhibitors in female fish. A sensitive method for the DHT analysis using chemical derivatization and liquid chromatography–tandem mass spectrometry was developed. A cell-based 5AR inhibition assay that utilizes human cell lines, a transient overexpression system, and fish cell lines was developed. The measured IC₅₀ values of two well-known 5AR inhibitors, finasteride and dutasteride, were comparable in the different systems. However, the IC₅₀ of dutasteride in the fish cell lines was lower than that in the human cell lines. Finasteride showed a higher IC₅₀ against the RTG-2 cell line. These results demonstrated that 5ARs inhibition could differ in terms of structural characteristics among species. The assay has high sensitivity and reproducibility and is suitable for the application in 5AR inhibition screening for various endocrine disruption chemicals (EDCs). Future studies will continue to evaluate the quantitative inhibition of 5AR by EDCs to compare the endocrine-disrupting pathway in different species.

Inhibitory activities of some traditional Chinese herbs against testosterone 5α-reductase and effects of Cacumen platycladi on hair re-growth in testosterone-treated mice

ETHNOPHARMACOLOGICAL RELEVANCE

Many traditional Chinese medicines (TCM) have been used for hundreds of years for hair blackening and hair nourishing, and now many of them are commonly used in Chinese herbal shampoo to nourish the hair and promote hair growth.

AIMS OF THE STUDY

The present study was performed to screen 5α-reductase (5αR) inhibitors from traditional Chinese medicines, evaluate its hair growth promoting activity in vivo, and further investigate its effects on androgen metabolism and the expression of 5αR II in hair follicles.

MATERIALS AND METHODS

Nine TCM which were dried, ground and extracted by maceration with 75% ethanol or distilled water were used for screening 5αR inhibitors, and enzymes were extracted from the rat epididymis. The leaves of Platycladus orientalis (L.) Franco was used to evaluate the in vivo anti-androgenic activity. Skin color was observed daily and the hair re-growth was assessed by assigning the hair growth score. The longitudinal sections of hair follicles were used for observing follicle morphology, classifying of distinct stages of hair follicle morphogenesis and calculate the average score. The transverse sections were used for determination of hair follicle counts. Testosterone (T), Dihydrotestosterone (DHT) and Estradiol (E2) levels in serum and skin tissue were detected by ELISA kits. The immunofluorescence assay was used to detect the influence of CP-ext on 5αR expression in dorsal skin.

RESULTS

We found the extract of Ganoderma lucidum (GL-ext), Polygonum multiflori (PM-ext), Cacumen platycladi (CP-ext) and Cynomorium songaricum (CS-ext) showed stronger 5αR inhibitory activity. CP-ext (5mg and 2mg/mouse/day) could significantly shorten the time of the dorsal skin darkening and got longhaired (P<0.01), and showed high hair re-growth promoting activity. Furthermore the histological data of hair follicles in each group showed that CP-ext could promote the growth of hair follicle and slowed down hair follicles enter the telogen. What's more CP-ext significantly reduced DHT levels and down-regulated the expression of 5αRⅡin skin (P<0.01).

CONCLUSIONS

GL-ext, PM-ext, CP-ext and CS-ext showed strong 5αR inhibitory activity. CP-ext possesses high hair growth promoting activity in the in vivo androgen-sensitive mouse model via inhibiting the 5αR activity, decreasing the DHT levels and in turn suppressing the expression of 5αR. Our study may contribute to the development of a new generation of herbal supplements with clearer material basis of pharmacodynamic for treating androgenic alopecia (AGA).

Simultaneous pharmacokinetic and pharmacodynamic analysis of 5α-reductase inhibitors and androgens by liquid chromatography tandem mass spectrometry

Benign prostatic hyperplasia and prostate cancer can be treated with the 5α-reductase inhibitors, finasteride and dutasteride, when pharmacodynamic biomarkers are useful in assessing response. A novel method was developed to measure the substrates and products of 5α-reductases (testosterone, 5α-dihydrotestosterone (DHT), androstenedione) and finasteride and dutasteride simultaneously by liquid chromatography tandem mass spectrometry, using an ABSciex QTRAP(®) 5500, with a Waters Acquity™ UPLC. Analytes were extracted from serum (500 µL) via solid-phase extraction (Oasis(®) HLB), with (13)C3-labelled androgens and d9-finasteride included as internal standards. Analytes were separated on a Kinetex C18 column (150 × 3 mm, 2.6 µm), using a gradient run of 19 min. Temporal resolution of analytes from naturally occurring isomers and mass +2 isotopomers was ensured. Protonated molecular ions were detected in atmospheric pressure chemical ionisation mode and source conditions optimised for DHT, the least abundant analyte. Multiple reaction monitoring was performed as follows: testosterone (m/z 289 → 97), DHT (m/z 291 → 255), androstenedione (m/z 287 → 97), dutasteride (m/z 529 → 461), finasteride (m/z 373 → 317). Validation parameters (intra- and inter-assay precision and accuracy, linearity, limits of quantitation) were within acceptable ranges and biological extracts were stable for 28 days. Finally the method was employed in men treated with finasteride or dutasteride; levels of DHT were lowered by both drugs and furthermore the substrate concentrations increased.

Spectrophotometric method for the assay of steroid 5α-reductase activity of rat liver and prostate microsomes

A simple spectrophotometric method for the assay of steroid 5α-reductase (5α-SR) was developed in which 5α-dihydrotestosterone (5α-DHT) and 5α-androstane-3α,17β-diol (5α-diol), metabolites formed in the NADPH-dependent reduction of testosterone with enzyme sources of 5α-SR, were measured by enzymatic cycling using 3α-hydroxysteroid dehydrogenase in the presence of excess thionicotinamide-adenine dinucleotide (thio-NAD) and NADH. It was found that 5α-SR activity was proportional to the accumulated thio-NADH having an absorption maximum at 400 nm. Because of the high cycling rate (> 600 cycle per min) and no interference from testosterone, enzymatic cycling can determine the sum of 5α-DHT and 5α-diol at the picomole level without separation from excess testosterone. The present method was readily applicable to the assay of 5α-SR activity of rat liver and prostate microsomes as well as to the assay of inhibitory activity of finasteride, a synthetic inhibitor of 5α-SR.

Isolation and pharmacological characterization of fatty acids from saw palmetto extract

Saw palmetto extract (SPE) has been widely used for the treatment of lower urinary-tract symptoms secondary to benign prostatic hyperplasia. The mechanisms of pharmacological effects of SPE include the inhibition of 5alpha-reductase, anti-androgenic effects, anti-proliferative effects, and anti-inflammatory effects. Previously, we showed that SPE bound actively to alpha(1)-adrenergic, muscarinic and 1,4-dihydropyridine calcium channel (1,4-DHP) receptors in the prostate and bladder of rats, whereas its active constituents have not been fully clarified. The present investigation is aimed to identify the main active components contained in hexane and diethyl ether extracts of SPE with the use of column chromatography and preparative HPLC. Based on the binding activity with alpha(1)-adrenergic, muscarinic, and 1,4-DHP receptors, both isolated oleic and lauric acids were deduced to be active components. Authentic samples of oleic and lauric acids also exhibited similar binding activities to these receptors as the fatty acids isolated from SPE, consistent with our findings. In addition, oleic and lauric acids inhibited 5alpha-reductase, possibly leading to therapeutic effects against benign prostatic hyperplasia and related lower urinary-tract symptoms.