PPARß/δ activation protects against hepatic ischaemia-reperfusion injury.

BACKGROUND AND AIMS: Hepatic ischaemia/reperfusion injury (HIRI) is a pathophysiological process that occurs during the liver resection and transplantation. Reportedly, peroxisome proliferator-activated receptor ß/δ (PPARß/δ) can ameliorate kidney and myocardial ischaemia/reperfusion injury. However, the effect of PPARß/δ in HIRI remains unclear. METHODS: Mouse hepatic ischaemia/reperfusion (I/R) models were constructed for in vivo study. Primary hepatocytes and Kupffer cells (KCs) isolated from mice and cell anoxia/reoxygenation (A/R) injury model were constructed for in vitro study. Liver injury and inflammation were investigated. Small molecular compounds (GW0742 and GSK0660) and adenoviruses were used to interfere with PPARß/δ. RESULTS: We found that PPARß/δ expression was increased in the I/R and A/R models. Overexpression of PPARß/δ in hepatocytes alleviated A/R-induced cell apoptosis, while knockdown of PPARß/δ in hepatocytes aggravated A/R injury. Activation of PPARß/δ by GW0742 protected against I/R-induced liver damage, inflammation and cell death, whereas inhibition of PPARß/δ by GSK0660 had the opposite effects. Consistent results were obtained in mouse I/R models through the tail vein injection of adenovirus-mediated PPARß/δ overexpression or knockdown vectors. Furthermore, knockdown and overexpression of PPARß/δ in KCs aggravated and ameliorated A/R-induced hepatocyte injury, respectively. Gene ontology and gene set enrichment analysis showed that PPARß/δ deletion was significantly enriched in the NF-κB pathway. PPARß/δ inhibited the expression of p-IKBα and p-P65 and decreased NF-κB activity. CONCLUSIONS: PPARß/δ exerts anti-inflammatory and anti-apoptotic effects on HIRI by inhibiting the NF-κB pathway, and hepatocytes and KCs may play a synergistic role in this phenomenon. Thus, PPARß/δ is a potential therapeutic target for HIRI.

The PGC1α/NRF1-MPC1 axis suppresses tumor progression and enhances the sensitivity to sorafenib/doxorubicin treatment in hepatocellular carcinoma.

Targeting energy metabolism holds the potential to effectively treat a variety of malignant diseases, and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α) is a key regulator of energy metabolism. However, PGC1α's role in cancer, especially in hepatocellular carcinoma (HCC) remains largely unknown. In the present study, we reported that PGC1α was significantly downregulated in HCC cell lines and specimens. Moreover, reduced expression of PGC1α in tumor cells was correlated with poor prognosis. PGC1α overexpression substantially inhibited cell proliferation and induced apoptosis in vitro and in vivo. On the contrary, the knockdown of PGC1α produced the opposite effect. The mechanism was at least partially due to the upregulation of mitochondrial pyruvate carrier 1 (MPC1) caused by PGC1α, which promoted mitochondrial biogenesis by binding to nuclear respiratory factor 1 (NRF1). Consequently, the production of cellular reactive oxygen species (ROS) caused by mitochondrial oxidation was elevated above a critical threshold for survival. Furthermore, we found that PGC1α could enhance the antitumor activity of sorafenib and doxorubicin in HCC through ROS accumulation-mediated cell death. These results indicate that PGC1α/NRF1-MPC1 axis is involved in HCC progression and could be a promising target for HCC treatment.

PGC1α promotes cholangiocarcinoma metastasis by upregulating PDHA1 and MPC1 expression to reverse the Warburg effect.

PGC1α acts as a central regulator of mitochondrial metabolism, whose role in cancer progression has been highlighted but remains largely undefined. Especially, it is completely unknown about the effect of PGC1α on cholangiocarcinoma (CCA). Here we showed that PGC1α overexpression had no impact on CCA growth despite the decreased expression of PGC1α in CCA compared with adjacent normal tissue. Instead, PGC1α overexpression-promoted CCA metastasis both in vitro and in vivo. Mechanistically, for the first time, we illuminated that PGC1α reversed the Warburg effect by upregulating the expression of pyruvate dehydrogenase E1 alpha 1 subunit and mitochondrial pyruvate carrier 1 to increase pyruvate flux into the mitochondria for oxidation, whereas simultaneously promoting mitochondrial biogenesis and fusion to mediate the metabolic switch to oxidative phosphorylation. On the one hand, enhanced mitochondrial oxidation metabolism correlated with elevated reactive oxygen species (ROS) production; on the other hand, increased PGC1α expression upregulated the expression levels of mRNA for several ROS-detoxifying enzymes. To this end, the ROS levels, which were elevated but below a critical threshold, did not inhibit CCA cells proliferation. And the moderately increased ROS facilitated metastatic dissemination of CCA cells, which can be abrogated by antioxidants. Our study suggests the potential utility of developing the PGC1α-targeted therapies or blocking PGC1α signaling axis for inhibiting CCA metastasis.