br Introduction Increasing investigations show that the eart
Introduction Increasing investigations show that the earthworm extract has various beneficial pharmacological activities, including fibrinolytic  and anticoagulative activity , anti-inflammatory activity , anti-oxidative activity , , peripheral nerve regeneration , bone regeneration  and wound healing , . Earthworms have many advantages, such as beneficial pharmacological activities, abundant resources and low-cost and so on. However, in-depth studies on the active ingredients of earthworms and their pharmacological action are limited. Thus, there is a great potential and prospect for development in this field. In the pre-animal experiments, we observed that the EWAs (earthworm active ingredients) can significantly reduce the levels of ALT (serum alanine aminotransferase) and AST (aspartate aminotransferase) in the acute liver injured mice. Such results suggest that the EWAs may have a protective effect on the liver. The main functions of the endoplasmic reticulum in eukaryotic cells include protein synthesis and protein folding to form the correct three-dimensional conformation . Malfunctions of endoplasmic reticulum induced by various factors, such as ones that regulate protein folding, post-translational modification, lipid and steroid synthesis, gene expression, cellular metabolism and calcium signaling, can lead to UPR (unfolded proteins response), resulting in ERS . As a result, the endoplasmic reticulum launches various coping mechanisms to alleviate the damage, allowing the cell to adapt to the environmental stress. On the other hand, if the recovery of cellular Quercetin is not achieved prolonged ERS triggers apoptosis . ERS-induced apoptosis took part in the pathogenesis and development of disease, such as heart disease , cerebral ischemia , diabetes , atherosclerosis  and cancer . The hepatocyte contains abundant endoplasmic reticulum. ERS in the hepatocyte, especially ERS-mediated hepatocyte injury and apoptosis, might be an important contributor to hepatic diseases , .
Materials and methods
Discussion Tunicamycin is a kind of nucleoside antibiotics, it can inhibit N-acetyl glucosamine transferases, prevent formation of N-linked glycoproteins, perturb ER homeostasis and then cause ERS . In this study, tunicamycin was used as an inducer to establish ERS model in L02 cells. MTT assay indicated that the best condition of establishing ERS model was 60μg/mL tunicamycin treatment for 24h, which was used for the following experiments. GRP78, also known as immunoglobulin heavy chain BIP (binding protein), is an important molecular chaperone in recognizing and binding to unfolded proteins in ERS . Under certain pathological conditions, unfolded proteins accumulate in the ER lumen and necessitate GRP78 dissociation, then induce the UPR. After triggering ERS, expression of GRP78 is dramatically elevated, thus, expression level of GRP78 could be used as an indicator of ERS . CHOP, a member of the CCAAT/enhancer-binding protein family of transcription factors, also known as GADDl53, is a highly inducible gene that is expressed at a very low level in physiological state and up-regulated remarkably in response to various stresses. CHOP is the main upregulated proapoptotic player during excessive ERS . In this research, the expressions of GRP78 and CHOP in L02 cells treated with tunicamycin (60μg/mL) for 24h were investigated by western blotting. We found that the ERS hallmarks, GPR78 and CHOP, were upregulated at the protein level in tunicamycin- induced L02 cells when compared with normal L02 cells. The result showed that the tunicamycin-induced ERS model in L02 cells was successfully established. MTT assay indicated that the EWAs can significantly promote viability of injured L02 cells in a dose dependent manner (0.2–1.6mg/mL). The highest dose EWAs (1.6mg/mL) had no effect on proliferation in normal L02 cells. In follow-up experiments, 0.4mg/mL EWAs was selected for EWAsL and 1.2mg/mL EWAs was selected for EWAsH. TUNEL staining revealed that the EWAs can significantly inhibit the apoptosis in injured L02 cells.