Prohibitin is associated with antioxidative protection in hypoxia/reoxygenation-induced renal tubular epithelial cell injury

Self-control study of multi-omics in identification of microenvironment characteristics in urine of uric acid stone

The aim of this study is to perform proteomic and metabolomic analyses in bilateral renal pelvis urine of patients with unilateral uric acid kidney stones to identify the specific urinary environment associated with uric acid stone formation. Using cystoscopy-guided insertion of ureteral catheters, bilateral renal pelvis urine samples are collected. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is employed to identify differentially expressed proteins and metabolites in the urine environment. Differentially expressed proteins and metabolites are further analyzed for their biological functions and potential metabolic pathways through Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. In the urine from the stone-affected side, eight differential proteins were significantly upregulated, and six metabolites were dysregulated. The uric acid stone urinary environment showed an excess of α-ketoisovaleric acid and 3-methyl-2-oxovaleric acid, which may contribute to the acidification of the urine. Functional and pathway analyses indicate that the dysregulated metabolites are mainly associated with insulin resistance and branched chain amino acid metabolism.

Renoprotective potential of myo-inositol on diabetic kidney disease: Focus on the role of the PINK1/Parkin pathway and mitophagy receptors

Recent studies have emphasized the role of mitochondria in renal function as well as in renal injury. Poor mitochondrial quality control mechanisms including mitochondrial fusion, fission and mitophagy are major contributors for progression of diabetic renal injury. The current study is aimed to evaluate the protective role of myo-inositol (MI) against diabetic nephropathy (DN) by utilizing high glucose exposed NRK 52E cell and streptozotocin (STZ) induced DN model. MI supplementation (at doses 37.5 and 75 mg/kg) ameliorated albuminuria and enhanced the renal function as indicated significant improvement in urinary creatinine and urea levels. On the other hand, the western blot analysis of both in vitro and in vivo studies has revealed poor mitophagy in renal cells which was reversed upon myo-inositol treatment. Apart from targeting the canonical PINK1/Parkin pathway, we also focused on the role mitophagy receptors prohibitin (PHB) and NIP3-like protein (NIX). A significant reduction in expression of NIX and PHB2 was observed in renal tissue of diabetic control rats and high glucose exposed NRK 52E cells. Myo-inositol treatment resulted in positive modulation of PINK1/Parkin pathway as well as PHB2 and NIX. Myo-inositol also enhanced the mitochondrial biogenesis in renal tissue of diabetic rat by upregulating Nrf2/SIRT1/PGC-1α axis. The current study thus underlines the renoprotective effect myo-inositol, upregulation of mitophagy proteins and mitochondrial biogenesis upon myo-inositol treatment.

Expression Analysis of 4-Hydroxynonenal Modified Proteins in Schizophrenia Brain; Relevance to Involvement in Redox Dysregulation

Background:

Oxidative damage contributes to the pathophysiology of schizophrenia (SZ). Redox imbalance may lead to increased lipid peroxidation, which produces toxic aldehydes like 4-hydroxynonenal (4-HNE) ultimately leading to oxidative stress. Conversely, implications of oxidative stress points towards an alteration in HNE-protein adducts and activities of enzymatic and antioxidant systems in schizophrenia.

Objectives:

Present study focuses on identification of HNE-protein adducts and its related molecular consequences in schizophrenia pathology due to oxidative stress, particularly lipid peroxidation.

Material and Methods:

Oxyblotting was performed on seven autopsied brain samples each from cortex and hippocampus region of schizophrenia patients and their respective normal healthy controls. Additionally, thiobarbituric acid substances (TBARS), reduced glutathione (GSH) levels and catalase (CAT) activities associated with oxidative stress, were also estimated.

Results:

Obtained results indicates substantially higher levels of oxidative stress in schizophrenia patients than healthy control group represented by elevated expression of HNE-protein adducts. Interestingly, hippocampus region of schizophrenia brain shows increased HNE protein adducts compared to cortex. An increase in catalase activity (4.8876 ± 1.7123) whereas decrease in antioxidant GSH levels (0.213 ± 0.015µmol/ml) have been observed in SZ brain. Elevated TBARS level (0.3801 ± 0.0532ug/ml) were obtained in brain regions SZ patients compared with their controls that reflects an increased lipid peroxidation (LPO).

Conclusion:

Conclusion: We propose the role of HNE modified proteins possibly associated with the pathology of schizophrenia. Our data revealed increase lipid peroxidation as a consequence of increased TBARS production. Furthermore, altered cellular antioxidants pathways related to GSH and CAT also highlight the involvement of oxidative stress in schizophrenia pathology.

Activation of the Integrated Stress Response and ER Stress Protect from Fluorizoline-Induced Apoptosis in HEK293T and U2OS Cell Lines

The prohibitin (PHB)-binding compound fluorizoline as well as PHB-downregulation activate the integrated stress response (ISR) in HEK293T and U2OS human cell lines. This activation is denoted by phosphorylation of eIF2α and increases in ATF4, ATF3, and CHOP protein levels. The blockage of the activation of the ISR by overexpression of GRP78, as well as an increase in IRE1 activity, indicate the presence of ER stress after fluorizoline treatment. The inhibition of the ER stress response in HEK293T and U2OS led to increased sensitivity to fluorizoline-induced apoptosis, indicating a pro-survival role of this pathway after fluorizoline treatment in these cell lines. Fluorizoline induced an increase in calcium concentration in the cytosol and the mitochondria. Finally, two different calcium chelators reduced fluorizoline-induced apoptosis in U2OS cells. Thus, we have found that fluorizoline causes increased ER stress and activation of the integrated stress response, which in HEK293T and U2OS cells are protective against fluorizoline-induced apoptosis.

NOXA upregulation by the prohibitin-binding compound fluorizoline is transcriptionally regulated by integrated stress response-induced ATF3 and ATF4

Fluorizoline is a new synthetic molecule that induces p53-independent apoptosis, in several tumor cell lines and in primary leukemia cells, by selectively targeting prohibitins (PHBs). In this study, we describe how fluorizoline induces BCL-2 homology 3-only protein NOXA, without modulating the protein levels of anti-apoptotic B-cell lymphoma-2 (BCL-2) family members prior to caspase activation, as well as how it synergizes with the BCL-2 and BCL-X_L inhibitor ABT-737 to induce apoptosis. Interestingly, fluorizolinetreatment triggers the activation of the integrated stress response (ISR) in HeLa and HAP1 cells, with increased eukaryotic translation initiation factor 2α phosphorylation, and induction of ATF3, ATF4, and CHOP. Moreover, PHB downregulation induces similar ISR activation and apoptosis as with fluorizoline treatment. In addition, we studied the essential role of the pro-apoptotic protein NOXA in fluorizoline-induced apoptosis and we describe its mechanism of induction in HeLa and HAP1 cells. Moreover, we identified ATF3 and ATF4 as the transcription factors that bind to NOXA promoter upon fluorizoline treatment. Furthermore, using ATF3 and ATF4 CRISPR HeLa and HAP1 cells, we confirmed that both factors mediate the induction of NOXA and apoptosis by fluorizoline. In conclusion, fluorizoline treatment triggers the activation of the ISR that results in the induction of ATF3 and ATF4, important regulators of NOXA transcription in fluorizoline-induced apoptosis.

Involvement of miR-27a-3p in diabetic nephropathy via affecting renal fibrosis, mitochondrial dysfunction, and endoplasmic reticulum stress

Diabetic nephropathy (DN) is acknowledged as a serious chronic complication of diabetes mellitus. Nevertheless, its pathogenesis is complicated and unclear. Thus, in this study, the role of miR-27a-3p-prohibitin/TMBIM6 signaling axis in the progression of DN was elucidated. Type 2 diabetic db/db mice and high glucose (HG)-challenged HK-2 cells were used as in vivo and in vitro models. Our results showed that miR-27a-3p was upregulated and prohibitin or transmembrane BAX inhibitor motif containing 6 (TMBIM6) was downregulated in the kidney tissues of db/db mice and HG-treated HK-2 cells. Silencing miR-27a-3p enhanced the expression of prohibitin and TMBIM6 in the kidney tissues and HK-2 cells. Inhibition of miR-27a-3p improved functional injury, as evidenced by decreased blood glucose, urinary albumin, serum creatinine, and blood urea nitrogen levels. MiR-27a-3p silencing ameliorated renal fibrosis, reflected by reduced profibrogenic genes (e.g., transforming growth factor β1, fibronectin, collagen I and III, and α-smooth muscle actin). Furthermore, inhibition of miR-27a-3p relieved mitochondrial dysfunction in the kidney of db/db mice, including upregulation of mitochondrial membrane potential, complex I and III activities, adenosine triphosphate, and mitochondrial cytochrome C, as well as suppressing reactive oxygen species production. In addition, miR-27a-3p silencing attenuated endoplasmic reticulum (ER) stress, reflected by reduced expression of p-IRE1α, p-eIF2α, XBP1s, and CHOP. Mechanically, we identified prohibitin and TMBIM6 as direct targets of miR-27a-3p. Inhibition of miR-27a-3p protected HG-treated HK-2 cells from apoptosis, extracellular matrix accumulation, mitochondrial dysfunction, and ER stress by regulating prohibitin or TMBIM6. Taken together, we reveal that miR-27a-3p-prohibitin/TMBIM6 signaling axis regulates the progression of DN, which can be a potential therapeutic target.

Mitochondrial Lon protease - depleted HeLa cells exhibit proteome modifications related to protein quality control, stress response and energy metabolism

The ATP-dependent Lon protease is located in the mitochondrial matrix and oxidized proteins are among its primary targets for their degradation. Impairment of mitochondrial morphology and function together with apoptosis were observed in lung fibroblasts depleted for Lon expression while accumulation of carbonylated mitochondrial proteins has been reported for yeast and HeLa Lon deficient cells. In addition, age-related mitochondrial dysfunction has been associated with an impairment of Lon expression. Using a HeLa cell line stably transfected with an inducible shRNA directed against Lon, we have previously observed that Lon depletion results in a mild phenotype characterized by an increase of both production of reactive oxygen species and level of oxidized proteins (Bayot et al., 2014, Biochimie, 100: 38-47). In this study using the same cell line, we now show that Lon knockdown leads to modifications of the expression of a number of specific proteins involved in protein quality control, stress response and energy metabolism, as evidenced using a 2D gel-based proteomic approach, and to alteration of the mitochondrial network morphology. We also show that these effects are associated with decreased proliferation and can be modulated by culture conditions in galactose versus glucose containing medium.

PPARγ and mitophagy are involved in hypoxia/reoxygenation-induced renal tubular epithelial cells injury

Renal tubular epithelial cell (RTEC) injury is the main cause and common pathological process of various renal diseases. Mitochondrial dysfunction (MtD) is a pathological process after renal injury. Mitophagy is vital for mitochondrial function. Hypoxia is a common cause of RTEC injury. Peroxisome proliferator-activated receptor γ (PPARγ) is involved in cell proliferation, apoptosis, and inflammation. Previous studies have shown that the low expression of PPARγ might be involved in hypoxia-induced RTEC injury. The present study aimed to investigate the correlation between PPARγ and mitophagy in damaged RTEC in the hypoxia/reoxygenation (HR) model. The results showed that HR inhibited the expression of PPARγ, but increased the expression of LC3II, Atg5, SQSTM1/P62, and PINK1 in a time-dependent manner. Moreover, mitochondrial DNA (mt DNA) copy number, mitochondria membrane potential (MMP) levels, ATP content, and cell viability were decreased in hypoxic RTECs, the expression of SQSTM1/P62 and PINK1, the release of cytochrome c (cyt C), and production of reactive oxygen species (ROS) were increased. Mitochondrial-containing autophagosomes (APs) were detected using transmission election microscope (TEM) and laser scanning confocal microscope (LSCM). Furthermore, PPARγ protein expression was negatively correlated with that of LC3II, PINK1, and the positive rate of RTEC-containing mitochondrial-containing APs (all p < .05), but positively correlated with cell viability, MMP level, and ATP content (all p < .05). These data suggested that PPARγ and mitophagy are involved in the RTEC injury process. Thus, a close association could be detected between PPARγ and mitophagy in HR-induced RTEC injury, albeit additional investigation is imperative.

Knockdown of NLRC5 attenuates renal I/R injury in vitro through the activation of PI3K/Akt signaling pathway

NLRC5, as the largest member of nucleotide-binding domain and leucine-rich repeat (NLR) family, was involved in various physiological processes, such as inflammation, fibrosis, innate immunity and diabetic nephropathy. However, the role of NLRC5 in acute kidney injury remains unclear. The aim of this study was to investigate the role of NLRC5 in human renal proximal tubular epithelial cells (HK-2) exposed to hypoxia/reoxygenation (H/R). Our results demonstrated that the expression of NLRC5 was significantly up-regulated in HK-2 cells exposed to H/R. Knockdown of NLRC5 significantly improved the viability of HK-2 cells exposed to H/R. In addition, knockdown of NLRC5 efficiently inhibited H/R-induced oxidative stress and apoptosis in HK-2 cells. Mechanistically, knockdown of NLRC5 markedly enhanced the activation of PIK3/Akt signaling pathway in H/R-stimulated HK-2 cells. In summary, our findings indicate that knockdown of NLRC5 attenuates renal I/R injury in vitro through the activation of PI3K/Akt signaling pathway.

Prohibitin: a potential therapeutic target in tyrosine kinase signaling

Prohibitin is a pleiotropic protein that has roles in fundamental cellular processes, such as cellular proliferation and mitochondrial housekeeping, and in cell- or tissue-specific functions, such as adipogenesis and immune cell functions. The different functions of prohibitin are mediated by its cell compartment-specific attributes, which include acting as an adaptor molecule in membrane signaling, a scaffolding protein in mitochondria, and a transcriptional co-regulator in the nucleus. However, the precise relationship between its distinct cellular localization and diverse functions remain largely unknown. Accumulating evidence suggests that the phosphorylation of prohibitin plays a role in a number of cell signaling pathways and in intracellular trafficking. Herein, we discuss the known and potential importance of the site-specific phosphorylation of prohibitin in regulating these features. We will discuss this in the context of new evidence from tissue-specific transgenic mouse models of prohibitin, including a mutant prohibitin lacking a crucial tyrosine phosphorylation site. We conclude with the opinion that prohibitin can be used as a potential target for tyrosine kinase signal transduction-targeting therapy, including in insulin, growth factors, and immune signaling pathways.

Significance of elevated Prohibitin 1 levels in Multiple Sclerosis patients lymphocytes towards the assessment of subclinical disease activity and its role in the central nervous system pathology of disease

Multiple Sclerosis (MS) is an autoimmune-neurodegenerative disorder managed therapeutically by modulating lymphocytes activity which has potential in disease management. Prohibitin 1(PHB) that controls the reactive oxygen species (ROS) and present on the activated lymphocytes have significance in the therapy of MS as esters of fumaric acid that regulates ROS is in phase II/III clinical trials. Thus, we evaluated the expression levels of PHB1 in experimental autoimmune encephalomyelitis (EAE), the animal model of MS and on MS patient's lymphocytes. PHB levels in brain tissue of EAE animals were determined by immunoblotting and on blood lymphocytes from MS relapse, Remission, Optic Neuritis, Neurological controls and Healthy volunteers by FACS using anti-PHB and anti-CD45 antibodies. We observed significant elevation of PHB in EAE brains (91.0 ± 17.59%) vs controls (29.8 ± 12.9%) (p = 0.01) and on lymphocytes of MS patients in acute (73.5 ± 11.20%) or relapsing (69.3 ± 17.33%) phase compared to remission (45.9 ± 8.08%) [p = 0.034 acute vs remission; p = 0.004 relapse vs remission]. Up regulation of PHB in relapsing vs remission MS patients imply the potential use of PHB to clinically evaluate subclinical disease status towards prognosis of an oncoming relapse. Elevated PHB levels in EAE brains signify the role of PHB in regulating ROS and implies PHB's role in oxidative stress.

Retinoic acid receptors α and γ are involved in antioxidative protection in renal tubular epithelial cells injury induced by hypoxia/reoxygenation

Renal interstitial fibrosis (RIF) is a common outcome in various chronic kidney diseases. Injury to renal tubular epithelial cell (RTEC) is major link in RIF. Hypoxia is one of the common factors for RTEC damage. Retinoic acid receptors (RARs), RARα, RARβ and RARγ, are evolutionary conserved and pleiotropic proteins that have been involved in various cellular functions, including proliferation, differentiation, apoptosis, and transcription. Recently, we discovered that aberrant expression of RARs was involved in the development of RIF in rats. Here, we investigated the role of RARs in the hypoxia/reoxygenation (HR) damage model in RTEC with virus-based delivery vectors to knockdown or overexpress RARs. Relevant indicators were detected. Our results showed that HR inhibited RARα and RARγ expressions in a time-dependent manner in RTECs; however, the expression of RARβ was not changed obviously. RARα and RARγ overexpression could protect cells from oxidative stress-induced injury by inhibiting HR-induced intracellular superoxide anion (O2-) generation, cell viability and mitochondria membrane potential (MMP) decrease and transforming growth factor β1 (TGF-β1) expression and promoting endogenous antioxidant defense components, superoxide dismutase (SOD) and glutathione (GSH). Meanwhile, inhibition of RARα and RARγ expressions by small interference RNAs (siRNA) resulted in a less resistance of RTEC to HR as shown in increased O2- production and TGF-β1 expression and decreased cell viability, MMP, SOD and GSH levels. These data indicates that RARα and RARγ act as positive regulators to offset oxidative damage and profibrosis cytokine accumulation and therefore has an antioxidative effect.

MicroRNA-423-5p facilitates hypoxia/reoxygenation-induced apoptosis in renal proximal tubular epithelial cells by targeting GSTM1 via endoplasmic reticulum stress

It has been reported that microRNAs (miRs) can regulate renal response to acute injury and members of them are believed to be important in maintenance of renal function and development of renal injury. We investigated the actions of microRNA-423-5p (miR-423-5p) and glutathione-S-transferase (GST) M1 after acute kidney injury. MiR-423-5p was up-regulated and GSTM1 was down-regulated in human kidney (HK-2) cells subjected to hypoxia/reoxygenation (H/R) and in rat kidneys subjected to ischemia/reperfusion (I/R) injury. Dual luciferase assays revealed miR-423-5p binding to the 3′ untranslated region of GSTM1. Proliferation was lower and apoptosis, ER stress and oxidative stress were all higher in H/R-treated HK-2 cells transfected with or without miR-423-5p mimics and GSTM1 siRNA than in the same cells transfected with miR-423-5p inhibitors and a GSTM1 expression vector. Increased miR-423-5p and decreased GSTM1 mRNA and protein levels were observed in rat kidneys on days 1, 2 and 7 after I/R. Levels had normalized by days 14 and 21. On day 3 after treatment, rats receiving I/R or I/R plus miR-423-5p mimics exhibited higher serum creatinine and urea nitrogen levels than rats receiving I/R plus a miR-423-5p inhibitor. MiR-423-5p and lower GSTM1 mRNA and protein levels were higher in the I/R and I/R plus miR-423-5p mimic groups than in the I/R plus miR-423-5p inhibitors group. These findings demonstrate that after acute kidney injury, miR-423-5p induces ER stress and oxidative stress by inhibiting GSTM1and suppresses repair.

Prohibitin overexpression improves myocardial function in diabetic cardiomyopathy

Prohibitin (PHB) is a highly conserved protein implicated in various cellular functions including proliferation, apoptosis, tumor suppression, transcription, and mitochondrial protein folding. However, its function in diabetic cardiomyopathy (DCM) is still unclear. In vivo, type 2 diabetic rat model was induced by using a high-fat diet and low-dose streptozotocin. Overexpression of the PHB protein in the model rats was achieved by injecting lentivirus carrying PHB cDNA via the jugular vein. Characteristics of type 2 DCM were evaluated by metabolic tests, echocardiography and histopathology. Rats with DCM showed severe insulin resistance, left ventricular dysfunction, fibrosis and apoptosis. PHB overexpression ameliorated the disease. Cardiofibroblasts (CFs) and H9c2 cardiomyoblasts were used in vitro to investigate the mechanism of PHB in altered function. In CFs treated with HG, PHB overexpression decreased expression of collagen, matrix metalloproteinase activity, and proliferation. In H9c2 cardiomyoblasts, PHB overexpression inhibited apoptosis induced by HG. Furthermore, the increased phosphorylation of extracellular signal–regulated kinase (ERK) 1/2 was significantly decreased and the inhibited phosphorylation of Akt was restored in DCM. Therefore, PHB may be a new therapeutic target for human DCM.

Prohibitin 1 Regulates the H19-Igf2 Axis and Proliferation in Hepatocytes

Prohibitin 1 (PHB1) is a mitochondrial chaperone that regulates cell growth. Phb1 knock-out mice exhibit liver injury and hepatocellular carcinoma (HCC). Phb1 knock-out livers show induction of tumor growth-associated genes, H19 and insulin-like growth factor 2 (Igf2). These genes are controlled by the imprinting control region (ICR) containing CCCTC-binding transcription factor (CTCF)-binding sites. Because Phb1 knock-out mice exhibited induction of H19 and Igf2, we hypothesized that PHB1-mediated regulation of the H19-Igf2 axis might control cell proliferation in normal hepatocytes. H19 and Igf2 were induced (8-20-fold) in 3-week-old Phb1 knock-out livers, in Phb1 siRNA-treated AML12 hepatocytes (2-fold), and HCC cell lines when compared with control. Phb1 knockdown lowered CTCF protein in AML12 by ∼30% when compared with control. CTCF overexpression lowered basal H19 and Igf2 expression by 30% and suppressed Phb1 knockdown-mediated induction of these genes. CTCF and PHB1 co-immunoprecipitated and co-localized on the ICR element, and Phb1 knockdown lowered CTCF ICR binding activity. The results suggest that PHB1 and CTCF cooperation may control the H19-Igf2 axis. Human HCC tissues with high levels of H19 and IGF2 exhibited a 40-50% reduction in PHB1 and CTCF expression and their ICR binding activity. Silencing Phb1 or overexpressing H19 in the mouse HCC cell line, SAMe-D, induced cell growth. Blocking H19 induction prevented Phb1 knockdown-mediated growth, whereas H19 overexpression had the reverse effect. Interestingly H19 silencing induced PHB1 expression. Taken together, our results demonstrate that the H19-Igf2 axis is negatively regulated by CTCF-PHB1 cooperation and that H19 is involved in modulating the growth-suppressive effect of PHB1 in the liver.

A novel prohibitin-binding compound induces the mitochondrial apoptotic pathway through NOXA and BIM upregulation

We previously described diaryl trifluorothiazoline compound 1a (hereafter referred to as fluorizoline) as a first-in-class small molecule that induces p53-independent apoptosis in a wide range of tumor cell lines. Fluorizoline directly binds to prohibitin 1 and 2 (PHBs), two proteins involved in the regulation of several cellular processes, including apoptosis. Here we demonstrate that fluorizoline-induced apoptosis is mediated by PHBs, as cells depleted of these proteins are highly resistant to fluorizoline treatment. In addition, BAX and BAK are necessary for fluorizoline-induced cytotoxic effects, thereby proving that apoptosis occurs through the intrinsic pathway. Expression analysis revealed that fluorizoline induced the upregulation of Noxa and Bim mRNA levels, which was not observed in PHB-depleted MEFs. Finally, Noxa^−/−/Bim^−/− MEFs and NOXA-downregulated HeLa cells were resistant to fluorizoline-induced apoptosis. All together, these findings show that fluorizoline requires PHBs to execute the mitochondrial apoptotic pathway.

Reduction of prohibitin expression contributes to left ventricular hypertrophy via enhancement of mitochondrial reactive oxygen species formation in spontaneous hypertensive rats

Left ventricular hypertrophy (LVH) in hypertension is characterized by thickening of myocardium and decrease in heart chamber volume in response to mechanical or pathological stress, but the underlying molecular mechanisms remain to be defined. In this work, we investigate whether mitochondrial prohibitin (PHB) was involved in the progression of LVH in spontaneous hypertensive rats (SHR). First, it was found that mitochondrial dysfunction occurred in left ventricles of SHR. Through analysis using quantitative reverse transcription polymerase chain reaction and Western blotting, it was found that PHB mRNA and mitochondrial PHB levels in left ventricles of SHR were significantly lower than that in Wistar-Kyoto rats. Furthermore, PHB mRNA levels were negatively correlated to left ventricles weight-to-body weight ratio in SHR. Knockdown of PHB led to increased formation of mitochondrial reactive oxygen species (ROS) and reduced activities of complex I, mitochondrial adenosine triphosphate generation and mitochondrial membrane potential in cultured cardiomyocytes. Knockdown of PHB contributed to the cardiomyocyte hypertrophy, which could be attenuated by treatment with the Tempol. Angiotensin II (AngII) was increased in plasma and left ventricles of SHR. Incubation with AngII reduced mitochondrial PHB expression in cardiomyocytes, which was reversed when pretreated with losartan. In conclusion, reduction of PHB expression in left ventricles in SHR contributed to LVH, at least in part, through promoting mitochondrial ROS formation.

HIF-1-mediated metabolic reprogramming reduces ROS levels and facilitates the metastatic colonization of cancers in lungs

Hypoxia-inducible factor 1 (HIF-1) has been associated with distant tumor metastasis; however, its function in multiple metastatic processes has not yet been fully elucidated. In the present study, we demonstrated that cancer cells transiently upregulated HIF-1 activity during their metastatic colonization after extravasation in the lungs in hypoxia-independent and reactive oxygen species (ROS)-dependent manners. Transient activation induced the expression of lactate dehydrogenase A and phosphorylation of the E1α subunit of pyruvate dehydrogenase, which indicated the reprogramming of glucose metabolic pathways from mitochondrial oxidative phosphorylation to anaerobic glycolysis and lactic acid fermentation. The administration of the HIF-1 inhibitor, YC-1, inhibited this reprogramming, increased intratumoral ROS levels, and eventually suppressed the formation of metastatic lung tumors. These results indicate that HIF-1-mediated metabolic reprogramming is responsible for the survival of metastatic cancers during their colonization in lungs by reducing cytotoxic ROS levels; therefore, its blockade by HIF-1-inhibitors is a rational strategy to prevent tumor metastasis.