AMPK and FoxO1 regulate catalase expression in hypoxic pulmonary arterial smooth muscle

Abstract

Background: Hypoxia and reactive oxygen species (ROS) including H 2 O 2 play major roles in triggering and progression of pulmonary vascular remodeling in persistent pulmonary hypertension. Catalase (CAT), the major endogenous enzyme scavenging H 2 O 2 , is regulated in a tissue-and context-specific manner. Objective: To investigate mechanisms by which hypoxia and H 2 O 2 regulate catalase expression, and the role of AMPK-FoxO pathway, in neonatal porcine pulmonary artery smooth muscle (PASMC). Design/Methods: PASMC were grown in hypoxia (10% O 2 ) or normoxia (21% O 2 ) for 72 hr. We measured catalase activity and lipid peroxidation; CAT, FoxO1, and FoxO3a expression by qPCR; protein contents of CAT, FoxOs, p-AMPK, p-AKT, p-JNK, p-ERK1/2 in whole lysates, and FoxOs in nuclear extracts, by immunoblot; and FoxO-1 nuclear localization by immunocytochemistry, quantified by laser scanning cytometry. Results: Hypoxia upregulated CAT transcription, content and activity, by increasing CAT transcription factors FoxO1 and FoxO3a mRNA, and promoting nuclear translocation of FoxO1. However, lipid peroxidation increased in hypoxic PASMC. Among candidate FoxO regulatory kinases, hypoxia activated AMPK, and decreased p-Akt and ERK1/2. AMPK activation increased FoxO1 (total and nuclear) and CAT, while AMPK inhibition inhibited FoxO1 and CAT, but not FoxO3a. Exogenous H 2 O 2 decreased p-AMPK and increased p-AKT in hypoxic PASMC. This decreased active FoxO1, and reduced mRNA and protein content of CAT. Hypoxic induction of CAT, AKT inhibition (LY294002), or addition of PEG-catalase partly ameliorated the H 2 O 2 -mediated loss of nuclear FoxO1. Conclusions: Hypoxia induces catalase expression, though this adaptation is insufficient to protect PASMC from hypoxia-induced lipid peroxidation. This occurs via hypoxic activation of AMPK, which promotes nuclear FoxO1 and thus catalase expression. Exogenous ROS may downregulate cellular antioxidant defenses; H 2 O 2 activates survival factor Akt, decreasing nuclear FoxO1 and thus catalase.

Early glycogen synthase kinase‐3β and protein phosphatase 2A independent tau dephosphorylation during global brain ischaemia and reperfusion following cardiac arrest and the role of the adenosine monophosphate kinase pathway

“…A). AMPK activation in hypoxic situations is known to increase the cellular level of catalase (Sengupta et al ., ; Awad et al ., ). A lower level of catalase after short periods of ischaemia is consistent with the lower levels of AMPK activation that we have observed.…”

“…Further evidence to support the AMPK activity alteration immediately after ischaemia, and during reperfusion comes from the results of testing one of the other main downstream substances of AMPK, which is catalase. There are several schools of thought, showing a direct link between activation of AMPK during hypoxia and increasing the level of cellular catalase (Awad et al, 2014). Sengupta et al (Sengupta et al, 2011) found that hypoxia/reperfusion increased the cardiomyocytes catalase through activation of AMPK.…”

Apelin‐13 administration protects against ischaemia/reperfusion‐mediated apoptosis through the FoxO1 pathway in high‐fat diet‐induced obesity

“…In response to hypoxia, we observed FoxO1 translocation into the nucleus in cardiomyocytes isolated from HFD‐fed mice. Our findings are consistent with results reported by recent studies showing that FoxO1 is mainly localized in the nucleus under hypoxic conditions in a variety of cell lines (Battiprolu et al ., ; Awad et al ., ). Analysis of subcellular localization of FoxO1 revealed that apelin‐13 promotes the retention of FoxO1 in the cytoplasm by preventing its nuclear translocation in response to oxygen deprivation.…”

Transcriptome-wide map of m6A circRNAs identified in hypoxic pulmonary hypertension rat model

“…Furthermore, the FoxO signaling pathway is associated with the apoptosis-resistant and hyperproliferative phenotype of PASMCs (31). Reactive oxygen species (ROS) is increased by hypoxia and activates AMPK-dependent regulation of FoxO1 expression, resulting in increased expression of catalase in PASMCs (43). Our study firstly uncovered that m 6 A influenced the stability of circRNAs, thus affecting the binding of circRNAs and miRNA, resulting in the activation of Wnt and FoxO signaling pathways.…”