Shigeo Shinohara

Effects of adenosine 5′-monophosphate on epidermal turnover

The structure and function of the epidermis is maintained by cell renewal based on epidermal turnover. Epidermal turnover is delayed by aging, and it is thought that the delay of the epidermal turnover is a cause of aging alternation of skin. The epidermal turnover is related to the energy metabolism of epidermal basal cells. Adenosine 5′-triphosphate (ATP) is needed for cell renewal: cell division, and adenosine 5′-monophosphate (AMP) increases the amount of intracellular ATP. These findings suggest that AMP accelerates the epidermal turnover delayed by aging. This study investigated whether AMP and adenosine 5′-monophosphate disodium salt (AMP2Na) accelerates the epidermal turnover. An effect of AMP2Na on cell proliferation was examined by our counting of keratinocytes. An effect of AMP2Na on cell cycle was examined by our counting of basal cells in DNA synthetic period of hairless rats. The effects of AMP2Na (or AMP) on the epidermal turnover were examined by our measuring stratum corneum transit time by use of guinea pigs, and by our measuring stratum corneum surface area by use of hairless rats and in a clinical pharmacological study. The AMP2Na showed two different profiles on the proliferation of primary cultured keratinocytes. At a low concentration it induced cell growth, whereas at a high concentration it inhibited cell growth. The number of basal cells in the DNA synthetic period of AMP2Na was significantly higher than that of the vehicle in hairless rats. The stratum corneum transit time of AMP2Na was significantly shorter than that of the vehicle in guinea pigs. The corneocyte surface area of emulsion containing AMP2Na was significantly smaller than that of the vehicle in volunteers. We conclude that AMP promotes the cell proliferation and the cell cycle progression of epidermal basal cells and accelerates epidermal turnover safely. In addition, AMP is useful for skin rejuvenation in dermatology and aesthetic dermatology.

Chewing Gum Containing Citric Acid Reduces the Burden of Periodontal Pathogens

Objective: In a preliminary study, we noted that citric acid has the potency to induce human beta defensins (hBD-2) in salivary secretions. As hBDs are thought to ameliorate periodontal disease by suppressing key periodontal pathogens we developed a citric acid-containing chewing gum (CA-gum) to test this hypothesis. Here we report, the effect of CA-gum on three major periodontal pathogens Prevotella intermedia (Pi), Tannerella forsythia (Tf), Treponema denti- cola (Td) and Fusobacterium species (Fb). Methods: A randomized, double-blind, placebo-controlled trial with 61 individuals, was conducted over 14 days. Each subject was allowed to chew CA-gum (31 subjects) or placebo gum (30 subjects) at irregular intervals, but was instructed to eat at least three pieces of gum a day. None had active caries, symptoms of gingivitis or periodontal disease, smoking history, or concurrent medication. To determine the levels of oral carriage of the putative pathogens, saliva was collected from each subject by paraffin chewing in a standard manner and, the number of total cultivative microorganisms (CFUs) determined. Five key periodontal pathogens, Pg, Pi, Tf, Td and Fb present in saliva were determined quantitatively using real-time polymerase chain reaction (PCR) (BML Inc., Saitama, JAPAN). Results: Compared with the placebo chewing gum group the CA-gum group had significantly lower levels of Prevotella intermedia, Tannerella forsythia, and Fusobacterium spp. in their saliva. (Wilcoxon t-test; p 0.05).