Study on the effect of resveratrol on immune liver injury in mice based on JNK pathway
Immune liver injury is mediated by immune response, often accompanied by inflammatory cell infiltration and disruption of liver cell cord structure. Moreover, this injury is a necessary path for the occurrence and development of end-stage lesions such as liver fibrosis, cirrhosis, and even liver tumors, which determines the outcome and deterioration of the disease. Recently, the incidence rate of immune liver injury in China is increasing year by year. Immunosuppressants are mostly used clinically, but the treatment effect is not obvious, and it is easy to relapse after drug withdrawal. Therefore, it is urgent to seek effective drugs for the prevention and treatment of immune liver injury. Geranium is a member of the Geraniaceae family and the genus Geranium. It is mainly produced in several regions of Northeast and North China, as well as some Asian countries. Geranin is mainly isolated from Geranium wilfordii and has various effects such as antioxidant and anti-inflammatory. Studies have shown that resveratrol reduces the expression of pro apoptotic protein Bax induced by H2O2 and promotes the expression of anti apoptotic protein Bcl-2, but the relevant apoptotic pathways have not been thoroughly studied. In addition, Wu et al.’s study showed that the combination of resveratrol and colchicine can significantly reduce lipopolysaccharide (LPS) – stimulated RAW 264.7 macrophages and acetaminophen (APAP) – induced immune liver injury in mice. At present, we have not found any relevant literature reporting the effect of resveratrol on immune liver injury based on the JNK pathway. Therefore, based on the confirmation by Wu et al. and our research group that resveratrol has a protective effect on D-galactosamine and carbon tetrachloride induced liver injury, this experiment further investigates the effect of resveratrol on LPS induced immune liver injury mice through the JNK pathway and explores its mechanism of action.

The liver is rich in various enzymes, with ALT and AST being the two most common. Generally, the content of transaminases in liver tissue is 100 times higher than that in blood. If 1% of liver cells are damaged, the level of transaminases in serum will double, which is one of the earliest and most sensitive indicators of liver damage feedback. ALP and TBIL are considered important indicators for clinical assessment of liver injury. SOD is an important enzyme antioxidant in the body’s antioxidant system, which reacts to generate oxygen and hydrogen peroxide to eliminate oxygen free radicals in the body, thereby inhibiting subsequent lipid peroxidation reactions. MDA is the end product of peroxidation, which seriously threatens the integrity of cell membrane structure, causing cell swelling and necrosis. The content of MDA in tissues can indirectly reflect the degree of damage to the liver when attacked by free radicals. GSH is not only an important substance for metabolism in the body and the most important reducing substance, but also a substrate for GSH Px, which can eliminate toxic substances such as oxygen free radicals and superoxide anions, and prevent peroxides from invading cell membranes. From the experimental results, it can be seen that the levels of serum ALT, AST, ALP, TBIL, and MDA in LPS induced immune liver injury mice significantly increased, while the activities of SOD and GSH Px significantly decreased, which is consistent with the report by Chou et al. After treatment with resveratrol, the levels of liver function factors ALT, AST, ALP, TBIL, and oxidative stress index MDA in the serum of mice decreased, while the activities of SOD and GSH Px increased significantly. Based on the above experimental results, we speculate that the prevention and treatment of immune liver injury by resveratrol is related to the inhibition of transaminase elevation and antioxidant effects.

IL-1 β is a key target in the inflammatory response. Although it cannot directly damage the liver, high concentrations of IL-1 β can induce inflammatory and immune cells to produce a series of cytokines, leading to inflammatory reactions and erroneous immune responses. The specific mechanism of TNF – α production is that after liver injury occurs, the permeability of the cell membrane increases, promoting Ca2+influx and activating Kupffer cells, leading to a large secretion of TNF – α and exacerbating the degree of liver damage. At the same time, local tissue undergoes inflammatory cell infiltration, and TNF – α can induce IL-6 production. IL-6 can act as a second mediator of TNF – α, leading to extensive cellular degeneration and necrosis in the liver, resulting in severe hepatitis. In this study, after LPS modeling, the levels of IL-1 β, TNF – α, and IL-6 in mouse liver tissue were significantly increased. The upward trend of these indicator data is consistent with Dong et al., and there are significant differences compared to the normal group. It is interesting that treatment with resveratrol can significantly reverse these changes induced by LPS, mainly by reducing the levels of IL-1 β, TNF – α, and IL-6 in tissues and alleviating inflammatory reactions. These results indicate that resveratrol can also prevent and treat immune liver injury through anti-inflammatory effects.

JNK is one of the main members in the MAPKs pathway, involved in signal transduction, inflammatory response, cell apoptosis, and other processes. In the quiescent state of cells, JNK is mainly located in the cytoplasm. After activation through a cascade reaction of upstream signal series amino acid residue phosphorylation modification, JNK in the cytoplasm migrates to the nucleus, fully activating JNK and exhibiting enzymatic activity, participating in cellular regulation. Further research has shown that activation of the JNK pathway leads to cell damage and ultimately triggers apoptosis. It is worth noting that after JNK inhibition, cell damage and apoptosis are also inhibited. ASK1 is located upstream of the JNK pathway and forms complexes with corresponding proteins under normal physiological conditions. However, in pathological conditions, ASK1 can be activated through dual phosphorylation of threonine 183 and tyrosine 185 by MAP2K (such as MKK4 and MKK7). There is still experimental evidence that overexpression of ASK1 can induce hepatocyte apoptosis, while silencing ASK1 can inhibit cell apoptosis. C-Jun is located downstream of the JNK signaling pathway, and activated JNK can further phosphorylate c-Jun, playing an important role in cellular signaling, proliferation, apoptosis, and other life processes. In addition, c-Jun has been regarded as a research target for various diseases such as inflammation and cancer in clinical practice. In this experiment, compared with the normal group, the ratios of p-ASK1/ASK1, p-MKK4/MKK4, p-JNK/JNK, and p-c-Jun/c-Jun in the model group showed an increasing trend, indicating the activation of the JNK pathway; The ratios of p-ASK1/ASK1, p-MKK4/MKK4, p-JNK/JNK, and p-c-Jun/c-Jun in the tissues of each dose group of resveratrol were downregulated to varying degrees compared to the model group, indicating that resveratrol inhibited the activation of JNK and the expression of key proteins in the JNK signaling pathway, thereby weakening liver cell apoptosis activity.

In summary, resveratrol can inhibit elevated transaminase levels, oxidative stress levels, and inflammatory responses, and regulate the JNK signaling pathway to reduce apoptotic activity, indicating that it can significantly improve immune liver injury.