[Endoplasmic reticulum stress enhances tumor necrosis factor-α expression in rat Kupffer cells to trigger hepatic stellate apoptosis cell through TNFR/caspase-8 pathway]

Endoplasmic Reticulum Stress Contributes to Ventilator-Induced Diaphragm Atrophy and Weakness in Rats

Background: Accumulating evidence indicates that endoplasmic reticulum (ER) stress plays a critical role in the regulation of skeletal muscle mass. In recent years, much attention has been given to ventilator-induced diaphragm dysfunction (VIDD) because it strongly impacts the outcomes of critically ill patients. Current evidence suggests that the enhancement of oxidative stress is essential for the development of VIDD, but there are no data on the effects of ER stress on this pathological process.

Methods: VIDD was induced by volume-controlled mechanical ventilation (MV) for 12 h; Spontaneous breathing (SB, for 12 h) rats were used as controls. The ER stress inhibitor 4-phenylbutyrate (4-PBA), the antioxidant N-acetylcysteine (NAC), and the ER stress inducer tunicamycin (TUN) were given before the onset of MV or SB. Diaphragm function, oxidative stress, and ER stress in the diaphragms were measured at the end of the experiments.

Results: ER stress was markedly increased in diaphragms relative to that in SB after 12 h of MV (all p < 0.001). Inhibition of ER stress by 4-PBA downregulated the expression levels of proteolysis-related genes in skeletal muscle, including Atrogin-1 and MuRF-1, reduced myofiber atrophy, and improved diaphragm force-generating capacity in rats subjected to MV (all p < 0.01). In addition, mitochondrial reactive oxygen species (ROS) production and protein level of 4-HNE (4-hydroxynonenal) were decreased upon 4-PBA treatment in rats during MV (all p < 0.01). Interestingly, the 4-PBA treatment also markedly increased the expression of peroxisome proliferator-activated receptor-gamma co-activator-1alpha (PGC-1α) (p < 0.01), a master regulator for mitochondrial function and a strong antioxidant. However, the antioxidant NAC failed to reduce ER stress in the diaphragm during MV (p > 0.05). Finally, ER stress inducer TUN largely compromised diaphragm dysfunction in the absence of oxidative stress (all p < 0.01).

Conclusion: ER stress is induced by MV and the inhibition of ER stress alleviates oxidative stress in the diaphragm during MV. In addition, ER stress is responsible for diaphragm dysfunction in the absence of oxidative stress. Therefore, the inhibition of ER stress may be another promising therapeutic approach for the treatment of VIDD.

Strategies for Biomaterial-Based Spinal Cord Injury Repair via the TLR4-NF-κB Signaling Pathway

The repair and motor functional recovery after spinal cord injury (SCI) has remained a clinical challenge. Injury-induced gliosis and inflammation lead to a physical barrier and an extremely inhibitory microenvironment, which in turn hinders the recovery of SCI. TLR4-NF-κB is a classic implant-related innate immunomodulation signaling pathway and part of numerous biomaterial-based treatment strategies for SCI. Numerous experimental studies have demonstrated that the regulation of TLR4-NF-κB signaling pathway plays an important role in the alleviation of inflammatory responses, the modulation of autophagy, apoptosis and ferroptosis, and the enhancement of anti-oxidative effect post-SCI. An increasing number of novel biomaterials have been fabricated as scaffolds and carriers, loaded with phytochemicals and drugs, to inhibit the progression of SCI through regulation of TLR4-NF-κB. This review summarizes the empirical strategies for the recovery after SCI through individual or composite biomaterials that mediate the TLR4-NF-κB signaling pathway.

[Baoganning formula alleviates liver fibrosis in mice by inhibiting hepatic IDO1 expression and promoting phenotypic maturation of dendritic cells]

OBJECTIVE

To investigate the protective effect of Bao Gan Ning (BGN), a traditional Chinese medicinal formula, against CCl4-induced liver fibrosis in mice and explore the mechanism.

METHODS

C57BL/6 mice were randomly divided into control group, liver fibrosis model group, positive control group and the low-, middle-, and high-dose BGN groups (n=10). In all but the control group, the mice were subjected to daily intraperitoneal injection of 25% CCl4 (in olive oil) to induce liver fibrosis and intragastric gavage of corresponding drugs. After 8 weeks, serum levels of ALT and AST were detected. Pathological examination of the liver was performed using HE and Sirius Red staining and α-SMA immunohistochemistry. The expression level of indoleamine 2, 3-dioxygenase 1 (IDO1) and phenotypic changes of hepatic DCs in the liver were measured. Another 18 mice were randomly divided into AAV9-NC, AAV9-IDO1 and high-dose BGN + AAV-IDO1 groups (n=6) for corresponding treatment, and 4 weeks later the deposit of hepatic IDO1 and phenotypic changes of the hepatic DCs were analyzed.

RESULTS

Compared with those in the model group, serum AST and ALT levels decreased significantly in BGN group (P < 0.01). Obvious liver fibrosis was observed in the model group, while the mice treated with BGN showed obviously reduced cell necrosis and collagen proliferation in the liver with significantly lowered the expression levels of hepatic α-SMA and IDO1 (P < 0.05). The percentages of CD11C + DCs, CD11C +CD80 + DCs, CD11C +CD86 + DCs, CD11C +CD40 + DCs, CD11C +MHCII + DCs, CD3 + T cells, and CD3 +CD4 + T cells all increased significantly in BGN group as compared with the model group (P < 0.05). In mice with adenovirus-mediated IDO1 overexpression in the liver, BGN treatment significantly lowered the expression level of IDO1 (P=0.000) and increased the percentages of hepatic CD11C +CD40 + DCs, CD11C +MHCII + DCs and CD3 +CD4 + T cells (P < 0.05).

CONCLUSION

BGN can effectively inhibit liver fibrosis in mice possibly by lowering the expression level of IDO1 in the liver, thus improving the function of hepatic DCs and subsequently promoting proliferation of T cells.