Significance of rosiglitazone inhibiting TLR4 expression in partial hepatic ischemia/reperfusion of mice

Metformin Attenuates Ischemia-reperfusion Injury of Fatty Liver in Rats Through Inhibition of the TLR4/NF-κB Axis

Background

Donor organs for liver transplantation may often have fatty liver disease, which confers a higher sensitivity to ischemia/reperfusion injury. At present, there is no effective treatment for the condition. Evidence has suggested that metformin, the first-line medication for diabetes, has protective effects against many disorders. However, the potential role of metformin in ischemia/reperfusion injury in fatty liver disease remains unclear.

Aims

To examine the effect of metformin treatment during ischemia/reperfusion injury in fatty liver and determine the possible mechanisms.

Study Design

Animal experimentation.

Methods

Sprague-Dawley male rats were fed a high-fat diet (520 kcal/100 g) for 14 weeks and then were subjected to the orthotopic autologous liver transplantation model. Sections of liver tissue were stained with hematoxylin and eosin to visualize the damage. Blood and liver samples were used to analyze the related proteins and components involved in the inflammatory signaling pathway.

Results

We found that metformin significantly ameliorated the ischemia/reperfusion injury of the fatty liver through a reduction in alanine aminotransferase/aspartate aminotransferase concentrations in the serum and a decrease in dead cells, as shown by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay (p<0.05). In addition, metformin significantly attenuated interleukin (IL)-6, IL-1β, and tumor necrosis factor-α production and increased the expression of active caspase-3 and Bax in the liver (p<0.05). Mechanistically, metformin suppressed the activation of toll-like receptor 4 (TLR4)/NF-κB signaling (p<0.05), resulting in a decreased inflammatory response and apoptosis.

Conclusion

Our findings demonstrated that metformin attenuated ischemia/reperfusion injury in fatty liver disease via the TLR4/NF-κB axis, suggesting that metformin could have potential therapeutic applications in ischemia/reperfusion injury associated with liver transplantation.

Novel Targets for Treating Ischemia-Reperfusion Injury in the Liver

Liver ischemia-reperfusion injury (IRI) is a major complication of hemorrhagic shock, liver transplantation, and other liver surgeries. It is one of the leading causes for post-surgery hepatic dysfunction, always leading to morbidity and mortality. Several strategies, such as low-temperature reperfusion and ischemic preconditioning, are useful for ameliorating liver IRI in animal models. However, these methods are difficult to perform in clinical surgeries. It has been reported that the activation of peroxisome proliferator activated receptor gamma (PPARγ) protects the liver against IRI, but with unidentified direct target gene(s) and unclear mechanism(s). Recently, FAM3A, a direct target gene of PPARγ, had been shown to mediate PPARγ’s protective effects in liver IRI. Moreover, noncoding RNAs, including LncRNAs and miRNAs, had also been reported to play important roles in the process of hepatic IRI. This review briefly discussed the roles and mechanisms of several classes of important molecules, including PPARγ, FAM3A, miRNAs, and LncRNAs, in liver IRI. In particular, oral administration of PPARγ agonists before liver surgery or liver transplantation to activate hepatic FAM3A pathways holds great promise for attenuating human liver IRI.

Rosiglitazone Regulates TLR4 and Rescues HO-1 and NRF2 Expression in Myometrial and Decidual Macrophages in Inflammation-Induced Preterm Birth

INTRODUCTION

Elevated inflammation accounts for approximately 30% of preterm birth (PTB) cases. We previously reported that targeting the peroxisome proliferator-activated receptor gamma (PPARγ) pathway reduced the incidence of PTB in the mouse model of endotoxin-induced PTB. The PPARγ has proven anti-inflammatory functions and its activation via rosiglitazone significantly downregulated the systemic inflammatory response and reduced PTB and stillbirth rate by 30% and 41%, respectively, in our model. Oxidative stress is inseparable from inflammation, and rosiglitazone has a reported antioxidative activity. In the current study, we therefore aimed to evaluate whether rosiglitazone treatment had effects outside of inflammatory pathway, specifically on the antioxidation pathway in our model.

METHODS

Pregnant C57BL/6J mice (E16.5) were treated with phosphate-buffered saline (PBS), rosiglitazone (Rosi), lipopolysaccharide (LPS; 10µg in 200µL 1XPBS), or LPS + Rosi (6 hours after the LPS injection). The myometrial and decidual tissues were collected and processed for macrophage isolation using magnetic cell sorting and F4/80+ antibody. Expression levels of antioxidative factors- Nrf2 and Ho-1-along with the LPS receptor Tlr4 were quantified by quantitative polymerase chain reaction. The protein levels were assessed by immunofluorescence staining.

RESULTS

Both the decidual and myometrial macrophages from the LPS-treated animals showed significantly lowered expression of Ho-1 and Nrf2 and higher expression of Tlr4 when compared to the PBS control group. The macrophages from the animals in the LPS + Rosi group had significantly elevated expression of Ho-1 and Nrf2 and downregulated expression of Tlr4 when compared to the LPS group.

CONCLUSION

Rosiglitazone administration prevents PTB by downregulating inflammation and upregulating antioxidative response.

Tauroursodeoxycholic acid affects PPARγ and TLR4 in Steatotic liver transplantation

Numerous steatotic livers are discarded for transplantation because of their poor tolerance to ischemia-reperfusion (I/R). We examined whether tauroursodeoxycholic acid (TUDCA), a known inhibitor of endoplasmic reticulum (ER) stress, protects steatotic and nonsteatotic liver grafts preserved during 6 h in University of Wisconsin (UW) solution and transplanted. The protective mechanisms of TUDCA were also examined. Neither unfolded protein response (UPR) induction nor ER stress was evidenced in steatotic and nonsteatotic liver grafts after 6 h in UW preservation solution. TUDCA only protected steatotic livers grafts and did so through a mechanism independent of ER stress. It reduced proliferator-activated receptor-γ (PPARγ) and damage. When PPARγ was activated, TUDCA did not reduce damage. TUDCA, which inhibited PPARγ, and the PPARγ antagonist treatment up-regulated toll-like receptor 4 (TLR4), specifically the TIR domain-containing adaptor inducing IFNβ (TRIF) pathway. TLR4 agonist treatment reduced damage in steatotic liver grafts. When TLR4 action was inhibited, PPARγ antagonists did not protect steatotic liver grafts. In conclusion, TUDCA reduced PPARγ and this in turn up-regulated the TLR4 pathway, thus protecting steatotic liver grafts. TLR4 activating-based strategies could reduce the inherent risk of steatotic liver failure after transplantation.

Rosiglitazone negatively regulates c-Jun N-terminal kinase and toll-like receptor 4 proinflammatory signalling during initiation of experimental aortic aneurysms

OBJECTIVE

Development and rupture of aortic aneurysms (AA) is a complex process involving inflammation, cell death, tissue and matrix remodelling. The thiazolidinediones (TZDs) including Rosiglitazone (RGZ) are a family of drugs which act as agonists of the nuclear peroxisome proliferator-activated receptors and have a broad spectrum of effects on a number of biological processes in the cardiovascular system. In our previous study we have demonstrated that RGZ has a marked effect on both aneurysm rupture and development, however, the precise mechanism of this is unknown.

METHODS AND RESULTS

In the present study, we examined possible targets of RGZ action in the early stages of Angiotensin II-induced AA in apolipoprotein E-deficient mice. For this purpose we employed immunoblotting, ELISA and antibody array approaches. We found that RGZ significantly inhibited c-Jun N-terminal kinase (JNK) phosphorylation and down-regulated toll-like receptor 4 (TLR4) expression at the site of lesion formation in response to Angiotensin II infusion in the initiation stage (6-72 h) of experimental AA development. Importantly, this effect was also associated with a decrease of CD4 antigen and reduction in production of TLR4/JNK-dependant proinflammatory chemokines MCP-1 and MIP-1α.

CONCLUSION

These data suggest that RGZ can modulate inflammatory processes by blocking TLR4/JNK signalling in initiation stages of AA development.