Inhibitory effect of oyster hydrolysate on wrinkle formation against UVB irradiation in human dermal fibroblast via MAPK/AP-1 and TGFβ/Smad pathway

Highlights

• Oyster hydrolysate (OH) from Crassostrea gigas increases type I procollagen production.

• OH regulates UVB-induced MAPK/AP-1 signaling cascades and MMPs expression

• OH stimulates type I procollagen synthesis through activating the expression of TGFβ receptor II and Smad3 phosphorylation.

Abstract

The skin keeps the human body healthy from extrinsic stimuli such as ultraviolet (UV) irradiation. However, chronic exposure of these stimuli reduces the number of proteins that constitute the extracellular matrix (ECM) and causes wrinkle formation. The amount of collagen, the main protein that constitutes connective tissue, is reduced in the human skin due to UV radiation. When human dermal fibroblasts were damaged by UVB, UVB increased the MMPs expressions and degraded type I collagen and other ECM proteins. Oyster (Crassostrea gigas) hydrolysate (OH) is known to have anticancer, antioxidant, and anti-apoptotic effects. To scrutinize the anti-wrinkle effect of the OH in the viewpoint of the balance between collagen degradation and synthesis, we conducted the study in UVB damaged human dermal fibroblasts. We determined type I procollagen, MMPs and related proteins using ELISA kit, qRT-PCR and western blot. In our study, we discovered that OH inhibits collagen degradation by regulating MAPKs, AP-1 and MMPs expression. Also, we found that OH promotes collagen production by enhancing TGFβ receptor II expression and Smad3 phosphorylation. These results showed that OH regulates collagen degradation and stimulates collagen synthesis. Through this study, we found that OH is effective in inhibiting wrinkle formation and restore photo-aged human skin. It indicates that OH can be one of the functional materials in the fields of anti-wrinkle research.

Introduction

Skin is the outermost tissue that makes up the human body. It is constituted with several layers containing epidermis, dermis, and hypodermis. The human skin is structurally maintained by extracellular matrix (ECM) in the dermis. The ECM is composed of collagen fibers, elastin fibers and proteoglycans [1]. However, internal and external factors change this structural maintenance. Internal factors including aging, immunological, hormonal, and genetic changes degenerate skin structure and its physiological functions [2]. Also, due to various extrinsic stimuli such as ultraviolet radiation (UV), air pollution and chemical substances, the shape, function, and structure of skin are changed [2].

Among several external factors that cause skin aging, ultraviolet (UV) radiation is the main influential factor [3]. UV is classified with UVA (315-400 nm), UVB (280-315 nm) and UVC (100-280 nm). UV irradiation causes skin damage and continuous damage of UV radiation leads to photoaging [4]. Long term UV irradiation induces direct DNA damage and brought indirect oxidative stress by producing reactive oxygen species (ROS) like hydrogen peroxide, hydroxyl radical, and nitric oxide [[5], [6], [7]]. Elevated DNA damage and ROS increase wrinkle formation, skin thickening and degradation of skin structure [8,9]. Particularly, UVB reaches the upper part of skin dermis and weakens the cells in the dermis. Due to the accumulation of damages, wrinkle, cancer, sagging, hyperpigmentation and other symptoms occurred in photoaged skin [10].

Wrinkle is formed as a result of the collapse of ECM arisen from a reduction of ECM proteins [11]. Collagen is one of the main ECM proteins constituting various fibrous tissues such as tendons, ligament, and skin. Especially type I collagen, which is bountiful (approximately 85%) in the skin dermis, is crucial to managing the structure of connective tissue and the strength of the skin [12]. The precursor of type I collagen is type I procollagen and it is produced in human dermal fibroblasts. Collagen degradation and fragmentation are well-known features in photoaged skin and they are the main characteristics of wrinkle formation [[13], [14], [15]]. ECM proteins, including collagen, are degraded by matrix metalloproteinases (MMPs). MMPs degrade various kinds of extracellular proteins and they're also well-known as carrying out roles such as cell differentiation, proliferation, apoptosis and tissue remodeling [16,17]. Normally, their activity is low, however, MMPs are overexpressed by the chronic UV irradiation [3,18]. Increase of MMPs accelerates the degradation of ECM proteins and leads to malfunction of connective tissue remodeling [19]. It brings imbalance of collagen synthesis and degradation, resulting in collapse structure of ECM. Therefore, managing collagen levels is crucial for maintaining extracellular matrix and human skin.

Bioactive peptides with low molecular weights contain various amino acids and exhibit biological effects [20]. Further, bioactive compounds derived from marine organisms contain numerous amino acids and have the pharmaceutical potential [21]. Oyster (Crassostrea gigias) is a marine food resource abundant in Asia and Europe. Oyster contains several functional substances like vitamin A, B₁, B₂, C, calcium and zinc ion, etc. We prepared oyster hydrolysate (OH) in order to utilize the functional compounds of oyster effectively [22]. OH has been described to have an antioxidant, antiviral and anti-apoptotic effect [[23], [24], [25]]. In our previous study, we have found that the OH, hydrolyzed by commercial enzymes (Protamex and Neutrase) and yeast, an organism, inhibits wrinkle formation in UVB-induced mice [26]. In this research, we proved the wrinkle suppression effect of OH in the viewpoint of the balance of collagen degradation and collagen production and examined the signaling mechanisms focusing on mitogen-activated protein kinases (MAPK) pathway and transforming growth factor β (TGF-β)/Smad pathway in human dermal fibroblasts (HDFs).