Michel Kermici

Bifidobacterium longum lysate, a new ingredient for reactive skin

Please cite this paper as: Bifidobacterium longum lysate, a new ingredient for reactive skin. Experimental Dermatology 2010; 19: e1–e8.

Electrochemical determination of femtomole amounts of free reduced and oxidized glutathione: Application to human hair follicles

A simple and sensitive high-performance liquid chromatographic technique has been developed for the quantification of free reduced and free oxidized glutathione in biological samples. After acidic extraction and isocratic separation of the compounds of interest on a reversed-phase column, both forms of glutathione are quantified with a coulometric detector working in the oxidative mode. The limit of detection is 125 fmol for reduced glutathione and 400 fmol for the oxidized form (signal-to-noise ratio of 3). This sensitivity allows the measurement of the small amount of glutathione present in a single hair follicle. The technique is well adapted to microsamples, i.e. for non-invasive sampling technique (hair, skin, tears, etc.) and can be adapted to various cells or tissues.

Evidence for an age-correlated change in glutathione metabolism enzyme activities in human hair follicle

In this investigation, glutathione peroxidase (GSH-PX), glutathione reductase (GSSG-RD), glutathione-S-transferase (GSH-S-T), gamma-glutamyl transpeptidase (gamma-GT) and glucose-6-phosphate dehydrogenase (G6PDH) were measured in human hair follicle obtained by plucking as source of keratinized cells. This non-invasive method was used on 27 men and women volunteers ranging from 19 to 102 years. Our results show that GSSG-RD, GSH-S-T, gamma-GT and G6PDH activities decrease as a function of age, whereas GSH-PX activity does not vary. We discriminated 2 groups: a first one from 19 to 60 years with a large dispersion of the enzymatic activities and a second one corresponding to elderly people (up to 70) with a smaller dispersion of the values. This study suggests the keratinocytes possess an age-correlated enzymatic detoxification response potential.

Direct quantitative digital autoradiography—thin-layer chromatography of 3α,3β- and 5α-reduced and 17β-dehydrogenated androgens derived from testosterone metabolism

Abstract A digital autoradiographic—thin-layer chromatographic method involving simple steps is described for thorough separation of eight major androgens (testosterone, androstenedione, dihydrotestosterone, androsterone, epiandrosterone, androstanedione, 3α-androstanediol and 3β-androstanediol) derived from testosterone metabolism. Their direct quantification is performed by radioscanning, which avoids tedious plate-scraping and liquid scintillation counting. Satisfactory accuracy is obtained by both external standardization of plates by calibrated amounts of radiolabelled standard steroids and internal standardization of bioassays by radiolabelled squalane. Coefficients of variation are below 8.5% in the range 100–500 dpm. Some analytical criteria related to chromatographic conditions and quantification parameters depending on position-sensitive proportional counter are discussed.

Changes in glutathione content in human hair follicle keratinocytes as a function of age of donor: relation with glutathione dependent enzymes

Glutathione (GSH) plays an important role in cellular protection during ageing. The hair plucking technique is a non‐invasive method for the direct biochemical study of keratinocytes. Hair was taken from the suboccipital area of 63 volunteers (men and women whose ages ranged from 13 to 103 years). The results show a diminution in the glutathione content as a function of age. We compare two groups of population: group A (less than 80) and group B (more than 80). A remarkable fact is observed: group B displays a weak dispersion of the values as compared to A. The glutathione content (nmol 10−3 mg DNA) is 5.42 ± 0.60 for A and 1.86 ± 0.35 for B. A reduction of 88% was observed in glutathione reductase activity and of 78% in the activity of glutathione‐S‐transferase from group A to group B. The glutathione peroxidase activity remains relatively constant. The decrease in the GSH concentration and the constancy of the glutathione peroxidase suggest that the capacity of the cell to protect itself from peroxides remains unchanged but that the GSH concentration may become the limiting factor.

Direct quantitative digital autoradiography of testosterone metabolites in the pilosebaceous unit: an environmentally advantageous trace radioactive technology

Androgen metabolism is one of the major keys for a better understanding of conditions such as androchronogenetic alopecia, acne, and other androgen-related skin disorders. This paper addresses the process by which testosterone metabolism leads to the following major androgens: androstenedione, dihydrotestosterone, 3 alpha- and 3 beta-androstanediol, androsterone, epiandrosterone, and androstanedione. Our report describes a methodology developed for the direct quantitative measurement from the silica gel plate of these metabolites. After detailing the chromatographic procedures to achieve the complete separation of the seven testosterone metabolites on a single plate, specifications are given for obtaining accurate measurements by 1) calibration of the radiodetectors and 2) internal and external standardization of samples and plates. Analytical criteria are discussed in terms of comparison of the level of sensitivity, reproducibility, and practicability obtained by both the linear analyzer and the direct digital autoradiograph. Signals as weak as 25 dpm were easily detected and calibration curves were obtained for the range of 50-500 dpm. For biological measurements the coefficients of variation do not exceed 10%. Given the difficulty of obtaining large amounts of microdissected subfractions of the pilosebaceous unit and the necessity of evaluating the complete pattern of testosterone transformed into its 3 alpha,3 beta-, 5 alpha-reduced and 17 beta-dehydrogenated secondary derivatives, digital autoradiography appears to be a powerful yet simple tool for studying androgen metabolism. In addition, this methodology offers an important environmental advantage: the high sensitivity of the detectors makes it possible to minimize the quantities of radioactive materials that must be handled or discarded.