Hyperglycemia-triggered ATF6-CHOP pathway aggravates acute inflammatory liver injury by β-catenin signaling

Abstract

Although hyperglycemia has been documented as an unfavorable element that can further induce liver ischemia–reperfusion injury (IRI), the related molecular mechanisms remain to be clearly elaborated. This study investigated the effective manner of endoplasmic reticulum (ER) stress signaling in hyperglycemia-exacerbated liver IRI. Here we demonstrated that in the liver tissues and Kupffer cells (KCs) of DM patients and STZ-induced hyperglycemic mice, the ER stress-ATF6-CHOP signaling pathway is activated. TLR4-mediated pro-inflammatory activation was greatly attenuated by the addition of 4-phenylbutyrate (PBA), one common ER stress inhibitor. The liver IRI in hyperglycemic mice was also significantly reduced after PBA treatment. In addition, deficiency of CHOP (CHOP−/−) obviously alleviates the hepatic IRI, and pro-inflammatory effects deteriorated by hyperglycemia. In hyperglycemic mice, β-catenin expression was suppressed while the ATF6-CHOP signal was activated. In the liver tissues of PBA-treated or CHOP−/− hyperglycemic mice, the expression of β-catenin was restored. Furthermore, CHOP deficiency can induce protection against hyperglycemia-related liver IRI, which was disrupted by the knockdown of β-catenin will cause this protection to disappear. High glucose (HG) treatment stimulated ATF6-CHOP signaling, reduced cellular β-catenin accumulation, and promoted the TLR4-related inflammation of BMDMs. But the above effects were partially rescued in BMDMs with CHOP deficiency or by PBA treatment. In BMDMs cultured in HG conditions, the anti-inflammatory functions of CHOP−/− were destroyed by the knockdown of β-catenin. Finally, chimeric mice carrying WT or CHOP−/− BMDMs by bone marrow transplantation were adopted to verify the above conclusion. The current study suggested that hyperglycemia could trigger ER stress-ATF6-CHOP axis, inhibit β-catenin activation, accelerate inflammation, and deteriorate liver IRI, thus providing the treatment potential for management of sterile liver inflammation in DM patients.

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“…Among these, it is well accepted that excessive inflammatory responses and oxidative stress are the most important factor in the occurrence and process of ALI. Patients with ALI exhibited higher levels of proinflammatory cytokines (TNF-α, IL-1β, and IL-6), lower levels of anti-inflammatory cytokines (IL-10), and lower activities of antioxidative enzymes (total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT)) [ 4 ]. Therefore, inhibition of inflammatory responses and oxidative stress is considered an effective approach for the treatment of ALI.…”