RESUMO
Intracerebral hemorrhage is often accompanied by oxidative stress induced by reactive oxygen species, which causes abnormal mitochondrial function and secondary reactive oxygen species generation. This creates a vicious cycle leading to reactive oxygen species accumulation, resulting in progression of the pathological process. Therefore, breaking the cycle to inhibit reactive oxygen species accumulation is critical for reducing neuronal death after intracerebral hemorrhage. Our previous study found that increased expression of nicotinamide adenine dinucleotide phosphate oxidase 4 (NADPH oxidase 4, NOX4) led to neuronal apoptosis and damage to the blood-brain barrier after intracerebral hemorrhage. The purpose of this study was to investigate the role of NOX4 in the circle involving the neuronal tolerance to oxidative stress, mitochondrial reactive oxygen species and modes of neuronal death other than apoptosis after intracerebral hemorrhage. We found that NOX4 knockdown by adeno-associated virus (AAV-NOX4) in rats enhanced neuronal tolerance to oxidative stress, enabling them to better resist the oxidative stress caused by intracerebral hemorrhage. Knockdown of NOX4 also reduced the production of reactive oxygen species in the mitochondria, relieved mitochondrial damage, prevented secondary reactive oxygen species accumulation, reduced neuronal pyroptosis and contributed to relieving secondary brain injury after intracerebral hemorrhage in rats. Finally, we used a mitochondria-targeted superoxide dismutase mimetic to explore the relationship between reactive oxygen species and NOX4. The mitochondria-targeted superoxide dismutase mimetic inhibited the expression of NOX4 and neuronal pyroptosis, which is similar to the effect of AAV-NOX4. This indicates that NOX4 is likely to be an important target for inhibiting mitochondrial reactive oxygen species production, and NOX4 inhibitors can be used to alleviate oxidative stress response induced by intracerebral hemorrhage.
RESUMO
Phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP) is a new-found tumor suppressor in a variety of tumors. While, it is still unknown about its role in glioma. In this study, we found that LHPP is abnormally decreasing or absent in glioblastoma, and the low expression of LHPP is associated with poor median survival in glioma patients. Functional assay revealed that LHPP-overexpression significantly inhibited U87MG and U118MG growth in vitro and in vivo. As to the mechanism, mass-spectrometric analysis indicated that the LHPP interacting proteins were mainly enriched in regulation of energy metabolism, including Carbon metabolism, Oxidative phosphorylation, and Glycolysis. Seahorse assay and metabolites detection confirmed that LHPP-overexpression obviously impeded glycolysis and respiration in U87MG and U118MG cells. For the further study, western blot assay showed that the protein level of PKM2 at dimeric, tetrameric, and total protein, were all decreased significantly, and its enzymatic activity was decreased as well. ChIP and RNAseq integrated analysis indicated that the decreased protein level of PKM2 was independent of PKM2 transcription, and LHPP did not reprogram transcription level of metabolic genome. Co-IP and immunofluorescence assay manifested that LHPP interacted with PKM2, and this interaction interfered the protein stability, then induced ubiquitin-mediated degradation of PKM2. Rescue assay confirmed that restoring the expression of PKM2 effectively reversed the restrained energy metabolism and the inhibited cancer cell growth caused by LHPP-overexpression in U87MG and U118MG cells. Taking together, we demonstrated that LHPP impedes the glycolysis and respiration during energy metabolic process via inducing ubiquitin-mediated degradation of PKM2, thus inhibits the growth of glioblastoma.