Disorder-to-Order Markers of a Cyclic Hexapeptide Inspired from the Binding Site of Fertilin β Involved in Fertilization Process

Synthetic peptides mimicking the binding site of fertilin β to its receptor, integrin α6β1, were shown to inhibit sperm-egg fusion when added to in vitro media. In contrast, the synthetic cyclic hexapeptide, cyclo(Cys¹-Ser²-Phe³-Glu⁴-Glu⁵-Cys⁶), named as cFEE, proved to stimulate gamete fusion. Owing to its biological specificity, this hexapeptide could help improve the in vitro fertilization pregnancy rate in human. In an attempt to establish the structure-activity relationship of cFEE, its structural dynamics was herein analyzed by means of ultraviolet circular dichroism (UV-CD) and Raman scattering. The low concentration CD profile in water, containing mainly a deep minimum at ∼202 nm, is consistent with a rather unordered chain. However, an ordering trend of the peptide loop has been observed in a less polar solvent such as methanol, where the UV-CD signal shape is formed by a double negative marker at ∼202/215 nm, indicating the presence of a type-II' β-turn. Raman spectra recorded in aqueous samples upon a 100-fold concentration increase, still showed an important population (∼30%) of the disordered structure. The structural flexibility of the disulfide bridge was confirmed by the Raman markers arising from the Cys¹-Cys⁶ disulfide bond-stretch motions. Density functional theory calculations highlighted the formation of the type-II' β-turn on the four central residues of cFEE (i.e., -Ser²-Phe³-Glu⁴-Glu⁵-) either with a left- or with a right-handed disulfide. The structure with a left-handed S-S bond, however, appears to be more stable.

Effects of short-term DHEA intake on hormonal responses in young recreationally trained athletes: modulation by gender

BACKGROUND

Dehydroepiandrosterone (DHEA) figures on the World Anti-Doping Agency list of prohibited substances in sport because it is assumed that athletes expect a significant increase in testosterone through DHEA administration. The literature on the hormonal effects of DHEA intake nevertheless appears to be very scant in healthy young subjects, especially women.

PURPOSE

We examined the effects of DHEA on adrenal and gonadal hormones, IGF1 and free T3 in healthy young male and female recreationally trained volunteers.

METHODS

The study followed a double-blind, randomized-order crossover design. Lean healthy young men (n = 10) and women (n = 11), with all women using oral contraceptives, were treated daily with 100 mg of DHEA and placebo for 4 weeks. DHEA, DHEA-sulfate (DHEA-S), androstenedione, total testosterone (Tes), dihydrotestosterone (DHT), SHBG, estrone, cortisol, IGF1, and free T3 were measured before, in the middle and at the end of each treatment, as were blood glucose, liver transaminases and lipid status.

RESULTS

We observed a significant increase in DHEA, DHEA-S, androstenedione, Tes, DHT, and estrone in both men and women in the middle and at the end of DHEA treatment, but the increase in Tes was more marked in women (p < 0.001) than men (p < 0.05). No changes were found in the other parameters, irrespective of gender.

CONCLUSION

In young athletes, DHEA administration induces significant blood hormonal changes, some modulated by gender, which can be used as biomarkers of doping.

Herbal tea extracts inhibit Cytochrome P450 3A4 in vitro

OBJECTIVES

Ciclosporin and sirolimus, two immunosuppressive agents with narrow therapeutic windows, are mainly metabolized by Cytochrome 3A4 (CYP3A4). A clinical case of toxic blood levels of these drugs after the consumption of a '24-flavours' tea was reported. This study aims to identify the causative ingredients of the 24-flavour herbal tea in the inhibition of CYP3A4 metabolism.

METHODS

Two commercially available 24-flavour tea products purchased in Hong Kong and the six plant constituents were tested for their CYP3A4 inhibitory effects utilizing an in-vitro fluorometric assay.

KEY FINDINGS

Of the commercially available teas available in Hong Kong, the most potent inhibitory effect was observed with the tea consumed in the initial clinical case. Of the six universal constituents, chrysanthemum exhibited the greatest inhibitory effect, with an IC50 of 95.7 μg/ml. Dandelion, liquorice and bishop's weed have IC50 of 140.6, 148.4 and 185.5 μg/ml, respectively. Field mint and Japanese honeysuckle have weaker inhibitory effect on CYP3A4 with IC50 of 1153.3 and 1466.3 μg/ml.

CONCLUSIONS

This study confirms the possible implication of herbal tea constituents in the inhibition of ciclosporin and sirolimus' CYP3A4 metabolism. Combined usage of herbal teas with drug should be closely monitored.