Novel In Vitro Assay of the Effects of Kampo Medicines against Intra/Extracellular Advanced Glycation End-Products in Oral, Esophageal, and Gastric Epithelial Cells

Abstract

Kampo medicines are Japanese traditional medicines developed from Chinese traditional medicines. The action mechanisms of the numerous known compounds have been studied for approximately 100 years; however, many remain unclear. While components are normally affected through digestion, absorption, and metabolism, in vitro oral, esophageal, and gastric epithelial cell models avoid these influences and, thus, represent superior assay systems for Kampo medicines. We focused on two areas of the strong performance of this assay system: intracellular and extracellular advanced glycation end-products (AGEs). AGEs are generated from glucose, fructose, and their metabolites, and promote lifestyle-related diseases such as diabetes and cancer. While current technology cannot analyze whole intracellular AGEs in cells in some organs, some AGEs can be generated for 1–2 days, and the turnover time of oral and gastric epithelial cells is 7–14 days. Therefore, we hypothesized that we could detect these rapidly generated intracellular AGEs in such cells. Extracellular AEGs (e.g., dietary or in the saliva) bind to the receptor for AGEs (RAGE) and the toll-like receptor 4 (TLR4) on the surface of the epithelial cells and can induce cytotoxicity such as inflammation. The analysis of Kampo medicine effects against intra/extracellular AGEs in vitro is a novel model.

Analysis of Crude, Diverse, and Multiple Advanced Glycation End-Product Patterns May Be Important and Beneficial

“…Intracellular AGEs are generated in various cells and released or leaked into fluids (e.g., blood, saliva, and urine) as extracellular AGEs [ 10 , 11 , 17 , 18 , 19 , 23 , 24 ]. These AGEs can induce cytotoxicity, thereby including inflammation, because RAGE and TRL4 are expressed on the surfaces of various cells [ 1 , 11 , 26 ]. Furthermore, researchers have attempted to show that AGEs in the fluid correlate with the onset/progression of specific diseases, proving that AGEs could be biomarkers for these diseases [ 11 , 18 , 19 , 23 , 24 , 69 , 70 , 71 ].…”

“…AGEs are produced in beverages and foods because of the presence of saccharides (e.g., glucose and fructose) and proteins, and heating treatment during manufacturing or cooking induces the Maillard reaction [ 1 , 25 , 76 , 77 ]. Because they can combine RAGE and TRL4 [ 78 ], AGEs may induce cytotoxicity via the dietary AGEs-RAGE/TLR4 axis.…”

“…Lifestyle-related diseases (LSRDs), including diabetes mellitus (DM), cardiovascular disease (CVD), and nonalcoholic steatohepatitis (NASH), are a global crisis, mostly in developing countries [ 1 , 2 , 3 , 4 , 5 ]. This is attributed to people consuming excess saccharides (e.g., glucose and fructose), proteins, and lipids.…”

“…Moreover, ancient Chinese medicine considered the concept of DM symptoms [ 7 , 8 ]. Advanced glycation end products (AGEs), which are generated from saccharides/their metabolites or derivatives and proteins, are associated with LSRDs [ 1 , 2 , 3 , 4 , 5 , 9 ]. Although AGEs have been investigated since the early 20th century, when the Maillard reaction was proven [ 9 ], their relationship with human health dates back to ancient times.…”

“…Researchers have investigated LSRDs and AGEs using these technologies. AGEs can be classified as intra- and extracellular AGEs [ 1 , 2 ]. Intracellular AGEs are generated in cells and can induce cell dysfunction and death [ 2 , 9 , 10 , 11 , 12 , 13 , 14 ].…”