Effects of GRP78 on Endoplasmic Reticulum Stress and Inflammatory Response in Macrophages of Large Yellow Croaker (Larimichthys crocea)

Endoplasmic reticulum (ER) homeostasis plays a vital role in cell physiological functions. Various factors can destroy the homeostasis of the ER and cause ER stress. Moreover, ER stress is often related to inflammation. Glucose-regulated protein 78 (GRP78) is an ER chaperone, which plays a vital role in maintaining cellular homeostasis. Nevertheless, the potential effects of GRP78 on ER stress and inflammation is still not fully elucidated in fish. In the present study, ER stress and inflammation was induced by tunicamycin (TM) or palmitic acid (PA) in the macrophages of large yellow croakers. GRP78 was treated with an agonist/inhibitor before or after the TM/PA treatment. The results showed that the TM/PA treatment could significantly induce ER stress and an inflammatory response in the macrophages of large yellow croakers whereas the incubation of the GRP78 agonist could reduce TM/PA-induced ER stress and an inflammatory response. Moreover, the incubation of the GRP78 inhibitor could further induce TM/PA-induced ER stress and an inflammatory response. These results provide an innovative idea to explain the relationship between GRP78 and TM/PA-induced ER stress or inflammation in large yellow croakers.

Automated summary

Endoplasmic reticulum (ER) homeostasis is important for cell physiological functions and disruption of ER homeostasis can lead to ER stress and inflammation. Glucose-regulated protein 78 (GRP78), an ER chaperone, is crucial for maintaining cellular homeostasis, but its effects on ER stress and inflammation in fish are not fully understood. In this study, ER stress and inflammation were induced in macrophages of large yellow croakers by tunicamycin (TM) or palmitic acid (PA), and the effects of GRP78 agonist/inhibitor were examined. The results showed that the TM/PA treatment induced ER stress and inflammation, which were reduced by GRP78 agonist treatment, while GRP78 inhibitor treatment further induced ER stress and inflammation. These findings provide novel insights into the relationship between GRP78 and TM/PA-induced ER stress or inflammation in large yellow croakers.