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Several collagen types are important for maintaining skin structure and function. Previous reports show that L-hydroxyproline (Hyp), N-acetyl-L-hydroxyproline (AHyp), and L-alanyl-L-glutamine (Aln-Gln) are biological active substances with collagen synthesis-promoting effects. In this study, we combined the promotive effects of pulsed electrical stimulation (PES) with three amino acid derivatives (AADs) in human dermal fibroblasts. Fibroblasts were exposed to PES with a 4,800 Hz pulse frequency and a voltage at 1 V or 5 V for 15 minutes. The gene expression of type I and Ⅲ collagen (fibrillar collagen), type Ⅳ and Ⅶ collagen (basement membrane collagen and anchoring fibril collagen) were measured by RT-PCR 48 hours after PES. PES alone promoted the expression of COL1A1 and COL3A1 at 5 V but did not alter that of COL4A1 and COL7A1. Each AAD and the AAD mixture promoted the expression of COL4A1 and COL7A1 but either repressed, or did not alter, that of COL1A1 and COL3A1. Compared to treatment with each AAD, PES at 5 V with Hyp promoted the expression of COL1A1 and COL3A1, enhanced COL3A1 expression with AHyp, and stimulated COL3A1 expression with Aln-Gln, while COL4A1 and COL7A1 expressions were not affected. PES and the AAD mixture significantly promoted COL4A1 expression in a voltage-dependent manner, and COL1A1 and COL3A1 demonstrated a similar but nonsignificant trend, whereas COL7A1 expression was not affected. The combination of PES with each AAD or the AAD mixture may improve skin structure and function by increasing the expression of basement membrane collagen and dermal fibrillar collagen.

ε-Poly-L-lysine (PLL) is a cationic polymer consisting of 25 to 35 L-lysine residues that adheres to the surface of skin as well as hair. However, the properties of PLL regarding its adhesion to the skin remain to be elucidated. In this study, we examined the staining of stratum corneum (SC) with fluorescence-labeled PLL and explored its relationship with skin condition.Alexa Fluor 488-labeled PLL (AF-PLL) was reacted with tape-stripped stratum corneum (SC), and the staining properties were monitored by fluorescence microscopy. Clinical study was performed by measuring the water content of the cheek SC and transepidermal water loss (TEWL), and the tape-stripped SC was subjected to staining with AF-PLL.AF-PLL staining of the SC was inhibited at acidic pH or by the addition of high concentration of salt solution, suggesting the involvement of ionic interaction between PLL and the SC, at least in part. The AF-PLL staining was inhibited by unlabeled PLL or various alkyl amines, but not by L-lysine monomer. AF-PLL staining was observed inside the corneocytes as well as surrounding cornified envelope. Clinical study revealed that AF-PLL staining intensity of the SC was negatively correlated with its water content and positively correlated with its TEWL.PLL can efficiently adhere to SC and AF-PLL staining of SC can be applied to evaluate skin conditions.

Belt electrode skeletal muscle electrical stimulation (B-SES) is a stimulation method that can simultaneously contract multiple muscle groups. Although the beneficial effects of B-SES in clinical situations have been elucidated, its molecular mechanism remains unknown. Here, we developed a novel rodent B-SES ankle stimulation system to test whether low-frequency stimulation prevents denervation-induced muscle atrophy.Electrical stimulations (7‒8 Hz, 30 min) with ankle belt electrodes were applied to Sprague–Dawley rats, daily for one week. All animals were assigned to control (CONT), denervation-induced atrophy (DEN), and DEN + electrical stimulation (ES) groups. The tibial anterior (TA) and gastrocnemius (GAS) muscles were used to examine the effects of ES treatment.Seven days of continuous stimulation induced significantly higher muscle wet weights and muscle fiber cross-sectional areas(CSA) in both TA and GAS muscles compared to those in the DEN group. B-SES suppressed the decrease in mitochondrial biosynthesis, quantity, and enzyme activity in TA and GAS muscles. mRNAs levels of muscle proteolytic molecules Atrogin-1 and Murf1 were largely increased by denervation, but B-SES repressed their expression.In conclusion, low-frequency electrical stimulation of bilateral ankles by belt electrodes is effective for preventing denervation-induced atrophy in multiple muscles by maintaining mitochondrial quantity, enzyme activity, and suppressing muscle protein degradation.