Nanostring-based multigene assay to predict recurrence for gastric cancer patients after surgery

Despite the benefits from adjuvant chemotherapy or chemoradiotherapy, approximately one-third of stage II gastric cancer (GC) patients developed recurrences. The aim of this study was to develop and validate a prognostic algorithm for gastric cancer (GCPS) that can robustly identify high-risk group for recurrence among stage II patients. A multi-step gene expression profiling study was conducted. First, a microarray gene expression profiling of archived paraffin-embedded tumor blocks was used to identify candidate prognostic genes (N=432). Second, a focused gene expression assay including prognostic genes was used to develop a robust clinical assay (GCPS) in stage II patients from the same cohort (N=186). Third, a predefined cut off for the GCPS was validated using an independent stage II cohort (N=216). The GCPS was validated in another set with stage II GC who underwent surgery without adjuvant treatment (N=300). GCPS was developed by summing the product of Cox regression coefficients and normalized expression levels of 8 genes (LAMP5, CDC25B, CDK1, CLIP4, LTB4R2, MATN3, NOX4, TFDP1). A prospectively defined cut-point for GCPS classified 22.7% of validation cohort treated with chemoradiotherapy (N=216) as high-risk group with 5-year recurrence rate of 58.6% compared to 85.4% in the low risk group (hazard ratio for recurrence=3.16, p=0.00004). GCPS also identified high-risk group among stage II patients treated with surgery only (hazard ratio=1.77, p=0.0053).

[Effect of sequoyitol on expression of NOX4 and eNOS in aortas of type 2 diabetic rats]

The aim of the present study is to investigate the effects of sequoyitol (Seq) on expression of eNOS and NOX4 in aortas of type 2 diabetic rats. Type 2 diabetic rats induced by high fat and high sugar diet and low dose of streptozotocin (STZ, 35 mg x kg(-1)) and were administered Seq (12.5, 25 and 50 mg x kg(-1) x d(-1)) for 6 weeks. The fasting blood glucose (FBG) and body weight were tested. Acetylcholine (Ach) induced endothelium-dependent relaxation and sodium nitroprusside (SNP) induced endothelium-independent relaxation were measured in aortas for estimating endothelial function. Aortic morphological change was observed with HE staining. The level of serum insulin was measured by radioimmunoassay. The total antioxidative capacity (T-AOC), malondialdehyde (MDA) and NO levels in aortas were determined according to the manufacturer's instructions. In addition, the expressions of eNOS and NOX4 in aortas were measured by immunohistochemisty, real-time PCR or Western blotting. The results showed that Seq significantly decreased FBG and insulin resistance, and improved aortic endothelium-dependent vasorelaxation function. The expressions of NOX4 and MDA content were obviously decreased, while the expression of eNOS, the levels of NO and T-AOC increased significantly in aortas of diabetic rats with Seq treatment. In conclusion, Seq protects against aortic endothelial dysfunction of type 2 diabetic rats through down-regulating expression of NOX4 and up-regulating eNOS expression.

[Effect of sequoyitol on expression of NOX4 and eNOS induced with glucose in human umbilical vein endothelial cells]

OBJECTIVE

To investigate the protective effect and mechanism of sequoyitol (Sep) on high glucose-induced human umbilical vein endothelial cells (HUVECs) injury.

METHODS

HUVECs were cultured with high glucose (30 mmol/L) in the presence or absence of sequoyitol (0.1, 1 and 10 micromol/L) for 24 h. Cell proliferation was measured by BrdU marking and cell cycle was detected by flow cytometry. 2', 7'-dichlorofluorescein diacetate was used to evaluate intracellular reactive oxygen species (ROS) levels. The NO, malonydialdehyde (MDA) and H2O2 levels were determined by colorimetric method according to the manufacturer's instructions. The expression of endothelial nitric oxide synthase (eNOS) and NADPH oxidase 4 (NOX4) were measured by real-time PCR and Western blot.

RESULTS

In the present study, we found that sequoyitol pretreatment for 1 h significantly decreased cell injury, promoted cell proliferation. Meanwhile sequoyitol significantly down-regulated NOX4 expression and decreased the level of ROS, MDA and H2O2 and obviously increased NO levels and up-regulated eNOS expression.

CONCLUSION

Sequoyitol alleviates high glucose-induced cell injuries in HUVECs via inhibiting oxidative stress and up-regulating eNOS expression.

Exposure to low- vs iso-osmolar contrast agents reduces NADPH-dependent reactive oxygen species generation in a cellular model of renal injury

Contrast-induced nephropathy represents the third cause of hospital-acquired acute renal failure. This study investigated the effects of low- vs iso-osmolar contrast medium (CM) exposure on NADPH-dependent reactive oxygen species (ROS) generation by tubular cells. X-ray attenuation of iohexol, iopamidol, and iodixanol was assessed at equimolar iodine concentrations and their effects on human renal proximal tubular cells (PTCs) were evaluated with equally attenuating solutions of each CM. Cytotoxicity, apoptosis, and necrosis were investigated by trypan blue exclusion, MTT assay, and annexin V/propidium iodide assay, respectively. ROS production was assessed by DCF assay, NADPH oxidase activity by the lucigenin-enhanced chemiluminescence method, and Nox4 expression by immunoblot. Yielding the same X-ray attenuation, CM cytotoxicity was assessed in PTCs at equimolar iodine concentrations. More necrosis was present after incubation with iohexol and iopamidol than after incubation with equal concentrations of iodixanol. Iohexol and iodixanol at low iodine concentrations induced less cytotoxicity than iopamidol. Moreover, both iohexol and iopamidol induced more apoptosis than iodixanol, with a dose-dependent effect. ROS generation was significantly higher with iopamidol and iohexol compared to iodixanol. NADPH oxidase activity and Nox4 protein expression significantly increased after exposure to iopamidol and iohexol, with a dose-dependent effect, compared with iodixanol. CM-induced Nox4 expression and activity depended upon Src activation. In conclusion, at angiographic concentrations, iodixanol induces fewer cytotoxic effects on cultured tubular cells than iohexol and iopamidol along with a lower induction of Nox4-dependent ROS generation. This enzyme may, thus, represent a potential therapeutic target to prevent iodinated CM-related oxidative stress.

L-carnitine attenuates the development of kidney fibrosis in hypertensive rats by upregulating PPAR-γ

BACKGROUND

The development of renal fibrosis is a consequence of arterial hypertension. L-carnitine plays an essential role in the β-oxidation of fatty acids, and we have previously demonstrated hypotensive, antioxidant, and anti-inflammatory effects of L-carnitine in arterial hypertension. This work aims to analyze the effect of L-carnitine on renal fibrosis and to explore the participation of peroxisome-proliferator activated receptor (PPAR)-γ in this effect.

METHODS

Four groups or rats were used: control, treated with L-carnitine, treated with L-NAME, and treated with L-carnitine + L-NAME. Cultured rat kidney cells were also used to examine the role of PPAR-γ in L-carnitine effect.

RESULTS

An increase in the expression of collagen, transforming growth factor beta 1 (TGF-β1), connective tissue growth factor (CTGF), Nox2, and Nox4 was found in the kidney of L-NAME-treated rats. Hypertensive rats presented with an expansion of renal fibrotic areas, which was also accompanied by overexpression of proinflammatory cytokines, interleukin (IL)-1β, and IL-6. A reduction in the expression of PPAR-γ and in that of anti-inflammatory IL-10 was found in the kidney of these rats. Simultaneous treatment with L-carnitine attenuated the renal fibrosis (which correlated with a reduction of plasma TGF-β1 levels) and the pro-oxidative and proinflammatory status reported in L-NAME groups, with a concomitant increase in the expression of PPAR-γ. Furthermore, the antifibrotic effect of L-carnitine could be blocked by PPAR-γ inhibition.

CONCLUSIONS

This study confirms the efficacy of L-carnitine against hypertension-associated renal fibrosis from in vivo and in vitro studies and suggests that the L-carnitine effect occurs in a PPAR-γ-dependent manner.

Signaling steps in the induction of genomic damage by insulin in colon and kidney cells

Diabetes mellitus (DM), a disease with almost 350 million people affected worldwide, will be the seventh leading cause of death by 2030. Diabetic patients develop various types of complications, among them an increased rate of malignancies. Studies reported the strong correlation between DM and several cancer types, of which colon and kidney cancers are the most common. Hyperinsulinemia, the high insulin blood level characteristic of early diabetes type 2, was identified as a risk factor for cancer development. In previous studies, we showed that an elevated insulin level can induce oxidative stress, resulting in DNA damage in colon cells in vitro and in kidney cells in vitro and in vivo. In the present study, we elucidate the signaling pathway of insulin-mediated genotoxicity, which is effective through oxidative stress induction in colon and kidney. The signaling mechanism is starting by phosphorylation of the insulin and insulin-like growth factor-1 receptors, followed by activation of phosphatidylinositide 3-kinase (PI3K), which in turn activates AKT. Subsequently, mitochondria and nicotinamide adenine dinucleotide phosphate oxidase (NADPH) isoforms (Nox1 and Nox4 in colon and kidney, respectively) are activated for reactive oxygen species (ROS) production, and the resulting excess ROS can attack the DNA, causing DNA oxidation. We conclude that hyperinsulinemia represents an important risk factor for cancer initiation or progression as well as a target for cancer prevention in diabetic patients.

NADPH oxidase 4 limits bone mass by promoting osteoclastogenesis

ROS are implicated in bone diseases. NADPH oxidase 4 (NOX4), a constitutively active enzymatic source of ROS, may contribute to the development of such disorders. Therefore, we studied the role of NOX4 in bone homeostasis. Nox4(-/-) mice displayed higher bone density and reduced numbers and markers of osteoclasts. Ex vivo, differentiation of monocytes into osteoclasts with RANKL and M-CSF induced Nox4 expression. Loss of NOX4 activity attenuated osteoclastogenesis, which was accompanied by impaired activation of RANKL-induced NFATc1 and c-JUN. In an in vivo model of murine ovariectomy–induced osteoporosis, pharmacological inhibition or acute genetic knockdown of Nox4 mitigated loss of trabecular bone. Human bone obtained from patients with increased osteoclast activity exhibited increased NOX4 expression. Moreover, a SNP of NOX4 was associated with elevated circulating markers of bone turnover and reduced bone density in women. Thus, NOX4 is involved in bone loss and represents a potential therapeutic target for the treatment of osteoporosis.

Redox signaling as a therapeutic target to inhibit myofibroblast activation in degenerative fibrotic disease

Degenerative fibrotic diseases encompass numerous systemic and organ-specific disorders. Despite their associated significant morbidity and mortality, there is currently no effective antifibrotic treatment. Fibrosis is characterized by the development and persistence of myofibroblasts, whose unregulated deposition of extracellular matrix components disrupts signaling cascades and normal tissue architecture leading to organ failure and death. The profibrotic cytokine transforming growth factor beta (TGFβ) is considered the foremost inducer of fibrosis, driving myofibroblast differentiation in diverse tissues. This review summarizes recent in vitro and in vivo data demonstrating that TGF β-induced myofibroblast differentiation is driven by a prooxidant shift in redox homeostasis. Elevated NADPH oxidase 4 (NOX4)-derived hydrogen peroxide (H2O2) supported by concomitant decreases in nitric oxide (NO) signaling and reactive oxygen species scavengers are central factors in the molecular pathogenesis of fibrosis in numerous tissues and organs. Moreover, complex interplay between NOX4-derived H2O2 and NO signaling regulates myofibroblast differentiation. Restoring redox homeostasis via antioxidants or NOX4 inactivation as well as by enhancing NO signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases can inhibit and reverse myofibroblast differentiation. Thus, dysregulated redox signaling represents a potential therapeutic target for the treatment of wide variety of different degenerative fibrotic disorders.

Nox4 redox regulation of PTP1B contributes to the proliferation and migration of glioblastoma cells by modulating tyrosine phosphorylation of coronin-1C

Glioblastoma multiforme is a common primary brain tumor in adults and one of the most devastating human cancers. Reactive oxygen species (ROS) generated by NADPH oxidase (Nox) 4 have recently been a focus of attention in the study of glioblastomas, but the molecular mechanisms underlying the actions of Nox4 remain elusive. In this study, we demonstrated that silencing of Nox4 expression by Nox4-targeted siRNA suppressed cell growth and motility of glioblastoma U87 cells, indicating the involvement of Nox4. Furthermore, Nox4-derived ROS oxidized and inactivated protein tyrosine phosphatase (PTP):1B: PTP1B in its active form downregulates cell proliferation and migration. By affinity purification with the substrate-trapping mutant of PTP1B, tyrosine-phosphorylated coronin-1C was identified as a substrate of PTP1B. Its tyrosine phosphorylation level was suppressed by Nox4 inhibition, suggesting that tyrosine phosphorylation of coronin-1C is regulated by the Nox4-PTP1B pathway. Finally, ablation of coronin-1C attenuated the proliferative and migratory activity of the cells. Collectively, these findings reveal that Nox4-mediated redox regulation of PTP1B serves as a modulator, in part through coronin-1C, of the growth and migration of glioblastoma cells, and provide new insight into the mechanistic aspect of glioblastoma malignancy.

NADPH oxidase 4 deficiency reduces aquaporin-2 mRNA expression in cultured renal collecting duct principal cells via increased PDE3 and PDE4 activity

The final control of renal water reabsorption occurs in the collecting duct (CD) and relies on regulated expression of aquaporin-2 (AQP2) in principal CD cells. AQP2 transcription is primarily induced by type 2 vasopressin receptor (V₂R)-cAMP-protein kinase A (PKA) signaling but also by other factors, including TonEBP and NF-κB. NAPDH oxidase 4 (NOX4) represents a major source of reactive oxygen species (ROS) in the kidney. Because NOX-derived ROS may alter PKA, TonEBP and NF-κB activity, we examined the effects of NOX4 depletion on AQP2 expression. Depleted NOX4 expression by siRNA (siNOX4) in mpkCCD_cl4 cells attenuated increased AQP2 mRNA expression by arginine vasopressin (AVP) but not by hypertonicity, which induces both TonEBP and NF-κB activity. AVP-induced AQP2 expression was similarly decreased by the flavoprotein inhibitor diphenyleneiodonium. siNOX4 altered neither TonEBP nor NF-κB activity but attenuated AVP-inducible cellular cAMP concentration, PKA activity and CREB phosphorylation as well as AQP2 mRNA expression induced by forskolin, a potent activator of adenylate cyclase. The repressive effect of siNOX4 on AVP-induced AQP2 mRNA expression was abolished by the non-selective phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine (IBMX) and was significantly decreased by selective PDE antagonists cilostamide and rolipram, but not vinpocetine, which respectively target PDE3, PDE4 and PDE1. Thus, by inhibiting PDE3 and PDE4 activity NOX4-derived ROS may contribute to V₂R-cAMP-PKA signaling and enhance AQP2 transcription.

Nox4 and redox signaling mediate TGF-β-induced endothelial cell apoptosis and phenotypic switch

Transforming growth factor-β (TGF-β) triggers apoptosis in endothelial cells, while the mechanisms underlying this action are not entirely understood. Using genetic and pharmacological tools, we demonstrated that TGF-β induced a moderate apoptotic response in human cultured endothelial cells, which was dependent upon upregulation of the Nox4 NADPH oxidase and production of reactive oxygen species (ROS). In contrast, we showed that ectopic expression of Nox4 via viral vectors (vNox4) produced an antiapoptotic effect. TGF-β caused ROS-dependent p38 activation, whereas inhibition of p38 blunted TGF-β-induced apoptosis. However, vNox4, but not TGF-β, activated Akt, and inhibition of Akt attenuated the antiapoptotic effect of vNox4. Akt activation induced by vNox4 was accompanied by inactivation of the protein tyrosine phosphatase-1B (PTP1B) function and enhanced vascular endothelial growth factor receptor (VEGFR)-2 phosphorylation. Moreover, we showed that TGF-β enhanced Notch signaling and increased expression of the arterial marker EphrinB2 in a redox-dependent manner. In summary, our results suggest that Nox4 and ROS have pivotal roles in mediating TGF-β-induced endothelial apoptosis and phenotype specification. Redox mechanisms may influence endothelial cell functions by modulating p38, PTP1B/VEGFR/Akt and Notch signaling pathways.

Ursolic acid protects monocytes against metabolic stress-induced priming and dysfunction by preventing the induction of Nox4

AIMS

Dietary supplementation with ursolic acid (UA) prevents monocyte dysfunction in diabetic mice and protects mice against atherosclerosis and loss of renal function. The goal of this study was to determine the molecular mechanism by which UA prevents monocyte dysfunction induced by metabolic stress.

METHODS AND RESULTS

Metabolic stress sensitizes or "primes" human THP-1 monocytes and murine peritoneal macrophages to the chemoattractant MCP-1, converting these cells into a hyper-chemotactic phenotype. UA protected THP-1 monocytes and peritoneal macrophages against metabolic priming and prevented their hyper-reactivity to MCP-1. UA blocked the metabolic stress-induced increase in global protein-S-glutathionylation, a measure of cellular thiol oxidative stress, and normalized actin-S-glutathionylation. UA also restored MAPK phosphatase-1 (MKP1) protein expression and phosphatase activity, decreased by metabolic priming, and normalized p38 MAPK activation. Neither metabolic stress nor UA supplementation altered mRNA or protein levels of glutaredoxin-1, the principal enzyme responsible for the reduction of mixed disulfides between glutathione and protein thiols in these cells. However, the induction of Nox4 by metabolic stress, required for metabolic priming, was inhibited by UA in both THP-1 monocytes and peritoneal macrophages.

CONCLUSION

UA protects THP-1 monocytes against dysfunction by suppressing metabolic stress-induced Nox4 expression, thereby preventing the Nox4-dependent dysregulation of redox-sensitive processes, including actin turnover and MAPK-signaling, two key processes that control monocyte migration and adhesion. This study provides a novel mechanism for the anti-inflammatory and athero- and renoprotective properties of UA and suggests that dysfunctional blood monocytes may be primary targets of UA and related compounds.

Inhibition of Notch signaling leads to increased intracellular ROS by up-regulating Nox4 expression in primary HUVECs

The essential roles of Notch pathway in angiogenesis have been reported for years. However, how Notch pathway plays its role in regulating endothelial cells remains largely unknown. In this study we found that blockade of Notch signaling with a γ-secretase inhibitor increased reactive oxygen species (ROS) in primary human umbilical vein endothelial cells (HUVECs) under both normaxic and ischemia/reperfusion (I/R) conditions. Abruption of ROS generation with ROS scavengers or specific inhibitors of ROS production in HUVECs abolished Notch blockade-induced HUVEC proliferation, migration and adhesion, suggesting that the regulation of Notch pathway on endothelial cell behavior is at least partially dependent on its down-regulation of ROS level. We further showed that the enhanced generation of ROS after blocking Notch signal was accompanied by augmented expression of Nox4, which led to increased phosphorylation of VEGFR2 and ERK in HUVECs. In summary, our results have shown that Notch signaling regulates ROS generation by suppressing Nox4, and further modulates endothelial cell proliferation, migration and adhesion.

[The role of NADPH oxidase NOX4 in regulation of proliferation, senescence and differentiation of the cells]

NADPH oxidase NOX4 is a source of reactive oxygen species in many tissue of human body. NOX4 products of activity are connected with various processes that take on the cellular and tissue level. One of them is cellular senescence. The role of this oxidase in the regulation of replicative and oncogene-induced senescence was shown in both normal and cancer cells. On the other hand NOX4 also stimulates to proliferation various types of cancer and primary cells, what promotes pathologies. NOX4 participates in epithelial-mesenchymal transition, important for tumor cells invasion and metastasis. Many research concern the role of NOX4 in the physiology and pathology of the cardiovascular system. It was shown that NOX4 has an impact on vasoconstriction, atherosclerosis development, vascular cells hypertrophy, apoptosis and differentiation. NOX4 plays both positive and negative role in the organism. Better understanding of NOX4 regulation and its involvement in signaling pathways give a hope to control the development of many diseases.

Hsp70 regulation on Nox4/p22phox and cytoskeletal integrity as an effect of losartan in vascular smooth muscle cells

A series of signaling cascades are activated after angiotensin II binds to angiotensin II type I receptor (AT1R), a peptide that is an important mediator of oxidative stress. Hsp70 regulates a diverse set of signaling pathways through interactions with proteins. Here, we tested the hypothesis of angiotensin II AT1R inhibition effect on Hsp70 interaction with Nox4/p22phox complex and Hsp70 leading to actin cytoskeleton modulation in spontaneously hypertensive rats (SHR) vascular smooth muscle cells (VSMCs). SHR and Wistar-Kyotto rats (VSMCs from 8 to 10 weeks) were stimulated with angiotensin II (100 nmol/L) for 15 min (AII), treated with losartan (100 nmol/L) for 90 min (L), and with losartan for 90 min plus angiotensin in the last 15 min (L + AII). Whereas SHR VSMCs exposure to angiotensin II overexpressed AT1R and Nox4 nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase and slightly downregulated caveolin-1 expression, losartan decreased AT1R protein levels and increased caveolin-1 and Hsp70 expression in SHR VSMC membranes. Immunoprecipitation and immunofluorescence confocal microscopy proved interaction and colocalization of membrane translocated Hsp70 and Nox4/p22phox. Increased levels of Hsp70 contrast with the decreased immunoprecipitation of Nox4/p22phox and RhoA in membranes from SHR VSMCs (L) vs SHR VSMCs (AII). Hsp72 depletion resulted in higher Nox4 expression and increased NADPH oxidase activity in VSMCs (L + AII) from SHR when contrasted with nontransfected VSMCs (L + AII). After Hsp72 knockdown in SHR VSMCs, losartan could not impair angiotensin II-enhanced stress fiber formation and focal adhesion assembly. In conclusion, our data showing a negative regulation of Hsp70 on Nox4/p22phox demonstrates a possible mechanism in explaining the antioxidative function joined to cytoskeletal integrity modulation within the effects of losartan in VSMCs from SHR.

Enhancement of doxorubicin cytotoxicity by tanshinone IIA in HepG2 human hepatoma cells

Chlorogenic acid (1), salvianolic acid B (2), and tanshinone IIA (3) are commonly used as chemoprotective agents for chemotherapy in cancer patients. The present study deals with the effect of these three compounds on cytotoxicity of doxorubicin in HepG2 cells. The results showed that 1 and 2 reduced the cytotoxicity of doxorubicin through scavenging ROS generated by doxorubicin in HepG2 cells. The findings suggest that 1 and 2 could enhance the expression of SOD and decrease that of NADPH oxidase, which resulted in the elimination of ROS. On the contrary, 3 enhanced the cytotoxicity of doxorubicin in HepG2 cells. Furthermore, drug interactions between doxorubicin and 3 produce synergistic effects in HepG2 cells.

Polymorphism of rs1836882 in NOX4 gene modifies associations between dietary caloric intake and ROS levels in peripheral blood mononuclear cells

Excessive caloric intake is a contributing risk factor for human metabolic disorders. Caloric restriction may prolong a person's life by lowering the incidence of deadly diseases. Reactive oxygen species (ROS) in peripheral blood mononuclear cells (PBMC) have been associated with the biochemical basis of the relationship between caloric intake and pathophysiologic processes. Polymorphisms associated with ROS generation genes are being increasingly implicated in inter-individual responses to daily caloric intake alterations. In the current study, a single nucleotide polymorphism, rs1836882, in the nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) gene's promoter region was found to modulate associations between dietary caloric intake and ROS levels in PBMC. Based on rs1836882, 656 Chinese Han participants were classified into CC, CT and TT genotypes. ROS levels in PBMC were significantly higher in the CC or CT genotypes compared with the TT genotype with the same increases in daily caloric intake. Using an electrophoretic mobility shift assay, NOX4 promoter region with rs1836882 (T) was observed to have a higher affinity for hepatocyte nuclear factor gamma (HNF3γ) protein than rs1836882 (C). HNF3γ protein over-expression decreased NOX4 gene transcriptional activity in the TT genotype more than in the CC genotype (5.68% vs. 2.12%, P<0.05) in a dual luciferase reporter assay. By silencing the NOX4 gene using small interfering RNA or over-expressing HNF3γ using an expression plasmid, serum from high dietary caloric intake participants decreased ROS levels in PBMC of the TT genotype more than in the CC or CT genotype via HNF3γ down-regulating the NOX4 gene expression signaling pathway. This is the first study to report on the functions of phenotypes of rs1836882 in the NOX4 gene, and it suggests rs1836882 as a candidate gene for interpreting inter-individual ROS levels differences in PBMC induced by alterations in daily caloric intake.

Angiotensin II stimulates cardiac fibroblast migration via the differential regulation of matrixins and RECK

Sustained induction and activation of matrixins (matrix metalloproteinases or MMPs), and the destruction and deposition of extracellular matrix (ECM), are the hallmarks of cardiac fibrosis. The reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) is a unique membrane-anchored endogenous MMP regulator. We hypothesized that elevated angiotensin II (Ang II), which is associated with fibrosis in the heart, differentially regulates MMPs and RECK both in vivo and in vitro. Continuous infusion of Ang II into male C57Bl/6 mice for 2weeks resulted in cardiac fibrosis, with increased expressions of MMPs 2, 7, 9 and 14, and of collagens Ia1 and IIIa1. The expression of RECK, however, was markedly suppressed. These effects were inhibited by co-treatment with the Ang II type 1 receptor (AT1) antagonist losartan. In vitro, Ang II suppressed RECK expression in adult mouse cardiac fibroblasts (CF) via AT1/Nox4-dependent ERK/Sp1 activation, but induced MMPs 2, 14 and 9 via NF-κB, AP-1 and/or Sp1 activation. Further, while forced expression of RECK inhibits, its knockdown potentiates Ang II-induced CF migration. Notably, RECK overexpression reduced Ang II-induced MMPs 2, 9 and 14 activation, but enhanced collagens Ia1 and IIIa1 expression and soluble collagen release. These results demonstrate for the first time that Ang II suppresses RECK, but induces MMPs both in vivo and in vitro, and RECK overexpression blunts Ang II-induced MMP activation and CF migration in vitro. Strategies that upregulate RECK expression in vivo have the potential to attenuate sustained MMP expression, and blunt fibrosis and adverse remodeling in hypertensive heart diseases.

Metabolic syndrome-induced tubulointerstitial injury: role of oxidative stress and preventive effects of acetaminophen

The prevalence of metabolic syndrome persistently increases and affects over 30% of U.S. adults. To study how metabolic syndrome may induce tubulointerstitial injury and whether acetaminophen has renal-protective properties, 4-week-old obese Zucker rats were randomly assigned into three groups, control (OC), vehicle dimethyl sulfoxide (OV), and acetaminophen treatment (30 mg/kg/day for 26 weeks), and lean Zucker rats served as healthy controls. Significant tubulointerstitial injuries were observed in both OC and OV animals, evidenced by increased tubular cell death, tubular atrophy/dilation, inflammatory cell infiltration, and fibrosis. These tubulointerstitial alterations were significantly reduced by treatment with a chronic but low dose of acetaminophen, which acted to diminish NADPH oxidase isoforms Nox2 and Nox4 and decrease tubulointerstitial oxidative stress (reduced tissue superoxide and macromolecular oxidation). Decreased oxidative stress by acetaminophen was paralleled by the reduction of tubular proapoptotic signaling (diminished Bax/Bcl-2 ratio and caspase 3 activation) and the alleviation of tubular epithelial-to-mesenchymal transition (decreased transforming growth factor β, connective tissue growth factor, α-smooth muscle actin, and laminin). These data suggest that increased oxidative stress plays a critical role in mediating metabolic syndrome-induced tubulointerstitial injury and provide the first evidence suggesting that acetaminophen may be of therapeutic benefit for the prevention of tubulointerstitial injury.

NOX4 mediates cytoprotective autophagy induced by the EGFR inhibitor erlotinib in head and neck cancer cells

Most head and neck squamous cell carcinomas (HNSCCs) overexpress epidermal growth factor receptor (EGFR) and EGFR inhibitors are routinely used in the treatment of HNSCC. However, many HNSCC tumors do not respond or become refractory to EGFR inhibitors. Autophagy, which is a stress-induced cellular self-degradation process, has been reported to reduce the efficacy of chemotherapy in various disease models. The purpose of this study is to determine if the efficacy of the EGFR inhibitor erlotinib is reduced by activation of autophagy via NOX4-mediated oxidative stress in HNSCC cells. Erlotinib induced the expression of the autophagy marker LC3B-II and autophagosome formation in FaDu and Cal-27 cells. Inhibition of autophagy by chloroquine and knockdown of autophagy pathway genes Beclin-1 and Atg5 sensitized both cell lines to erlotinib-induced cytotoxicity, suggesting that autophagy may serve as a protective mechanism. Treatment with catalase (CAT) and diphenylene iodonium (DPI) in the presence of erlotinib suppressed the increase in LC3B-II expression in FaDu and Cal-27 cells. Erlotinib increased NOX4 mRNA and protein expression by increasing its promoter activity and mRNA stability in FaDu cells. Knockdown of NOX4 using adenoviral siNOX4 partially suppressed erlotinib-induced LC3B-II expression, while overexpression of NOX4 increased expression of LC3B-II. These studies suggest that erlotinib may activate autophagy in HNSCC cells as a pro-survival mechanism, and NOX4 may play a role in mediating this effect.

Circadian clock control of Nox4 and reactive oxygen species in the vasculature

Recent studies have shown that circadian clock disruption is associated with pathological remodeling in the arterial structure and vascular stiffness. Moreover, chronic circadian disruption is associated with dysfunction in endothelial responses and signaling. Reactive oxygen species have emerged as key regulators in vascular pathology. Previously, we have demonstrated that circadian clock dysfunction exacerbates superoxide production through eNOS uncoupling. To date, the impact of circadian clock mutation on vascular NADPH oxidase expression and function is not known. The goal in the current study was to determine if the circadian clock controls vascular Nox4 expression and hydrogen peroxide formation in arteries, particularly in endothelial and vascular smooth muscle cells. In aorta, there was an increase in hydrogen peroxide and Nox4 expression in mice with a dysfunctional circadian rhythm (Bmal1-KO mice). In addition, the Nox4 gene promoter is activated by the core circadian transcription factors. Lastly, in synchronized cultured human endothelial cells, Nox4 gene expression exhibited rhythmic oscillations. These data reveal that the circadian clock plays an important role in the control of Nox4 and disruption of the clock leads to subsequent production of reaction oxygen species.

Hypoxia downregulates PPARγ via an ERK1/2-NF-κB-Nox4-dependent mechanism in human pulmonary artery smooth muscle cells

The ligand-activated transcription factor peroxisome proliferator-activated receptor γ (PPARγ) regulates metabolism, cell proliferation, and inflammation. Pulmonary hypertension (PH) is associated with reduced PPARγ expression, and hypoxia exposure regimens that cause PH reduce PPARγ expression. This study examines mechanisms of hypoxia-induced PPARγ downregulation in vitro and in vivo. Hypoxia reduced PPARγ mRNA and protein levels, PPARγ activity, and the expression of PPARγ-regulated genes in human pulmonary artery smooth muscle cells (HPASMCs) exposed to 1% oxygen for 72 h. Similarly, exposure of mice to hypoxia (10% O₂) for 3 weeks reduced PPARγ mRNA and protein in mouse lung. Inhibiting ERK1/2 with PD98059 or treatment with siRNA directed against either NF-κB p65 or Nox4 attenuated hypoxic reductions in PPARγ expression and activity. Furthermore, degradation of H₂O₂ using PEG-catalase prevented hypoxia-induced ERK1/2 phosphorylation and Nox4 expression, suggesting sustained ERK1/2-mediated signaling and Nox4 expression in this response. Mammalian two-hybrid assays demonstrated that PPARγ and p65 bind directly to each other in a mutually repressive fashion. We conclude from these results that hypoxic regimens that promote PH pathogenesis and HPASMC proliferation reduce PPARγ expression and activity through ERK1/2-, p65-, and Nox4-dependent pathways. These findings provide novel insights into mechanisms by which pathophysiological stimuli such as hypoxia cause loss of PPARγ activity and pulmonary vascular cell proliferation, pulmonary vascular remodeling, and PH. These results also indicate that restoration of PPARγ activity with pharmacological ligands may provide a novel therapeutic approach in selected forms of PH.

Nox4-derived ROS signaling contributes to TGF-β-induced epithelial-mesenchymal transition in pancreatic cancer cells

Transforming growth factor (TGF)-β induces epithelial-mesenchymal transition (EMT) in pancreatic adenocarcinoma. In this study, we investigated how NADPH oxidase (Nox) 4-generated reactive oxygen species (ROS) regulate TGF-β-induced EMT in pancreatic cancer cells.

MATERIALS AND METHODS

Pancreatic cancer cells were transfected with Nox4 siRNAs or PTP1B mutants and subjected to TGF-β-induced EMT assay. Expression of Nox4, TGF-β, and N-cadherin was immunohistochemically-examined with patient tumor samples.

RESULTS

Treatment of pancreatic cancer cells with TGF-β induced Nox4 expression, indicating that Nox4 represents a major source for ROS production. The Nox4 inhibitor diphenylene iodonium and Nox4 siRNAs blocked TGF-β-induced EMT phenotype including morphological changes, augmented migration, and altered expression of E-cadherin and Snail. Furthermore, PTP1B as a redox-sensor for Nox4-derived ROS participated in TGF-β-promoted EMT. Nox4, TGF-β, and N-cadherin were up-regulated in tumors from pancreatic cancer patients.

CONCLUSIONS

These findings suggest that Nox4-derived ROS, at least in part, transmit TGF-β-triggered EMT signals through PTP1B in pancreatic cancer.

Stress reaction in outer segments of photoreceptors after blue light irradiation

The retina is prone to oxidative stress from many factors which are also involved in the pathogenesis of degenerative diseases. In this study, we used the application of blue light as a physiological stress factor. The aim of this study was to identify the major source of intracellular ROS that mediates blue light-induced detrimental effects on cells which may lead to cytotoxicity. We hypothesized that outer segments are the major source of blue light induced ROS generation. In photoreceptors, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) enzymes and the recently found respiratory chain complexes may represent a major source for reactive oxygen species (ROS), beside mitochondria and chromophores. Therefore, we investigated this hypothesis and analysed the exact localization of the ROS source in photoreceptors in an organotypic culture system for mouse retinas.

Whole eyeball cultures were irradiated with visible blue light (405 nm) with an output power of 1 mW/cm². Blue light impingement lead to an increase of ROS production (detected by H₂DCFDA in live retinal explants), which was particularly strong in the photoreceptor outer segments. Nox-2 and Nox-4 proteins are sources of ROS in blue light irradiated photoreceptors; the Nox inhibitor apocynin decreased ROS stimulated by blue light. Concomitantly, enzyme SOD-1, a member of the antioxidant defense system, indicator molecules of protein oxidation (CML) and lipid oxidation (MDA and 4-HNE) were also increased in the outer segments.

Interestingly, outer segments showed a mitochondrial-like membrane potential which was demonstrated using two dyes (JC-1 and TMRE) normally exclusively associated with mitochondria. As in mitochondria, these dyes indicated a decrease of the membrane potential in hypoxic states or cell stress situations.

The present study demonstrates that ROS generation and oxidative stress occurs directly in the outer segments of photoreceptors after blue light irradiation.

The role of RhoA and cytoskeleton in myofibroblast transformation in hyperoxic lung fibrosis

Myofibroblast transformation is a key process in the pathogenesis of lung fibrosis. We have previously reported that hyperoxia induces RhoA activation in HFL-1 lung fibroblasts and RhoA mediates collagen synthesis in hyperoxic lung fibrosis. In this study, we investigated the role of RhoA and actin cytoskeleton in hyperoxia-induced myofibroblast transformation. Exposure of HFL-1 lung fibroblasts to hyperoxia stimulated actin filament formation, shift of G-actin to F-actin, nuclear colocalization of myocardin-related transcription factor-A (MRTF-A), recruitment of MRTF-A to the α-smooth muscle actin (α-SMA) gene promoter, myofibroblast transformation, and collagen-I synthesis. Inhibition of RhoA by C3 transferase CT-04 or dominant-negative RhoA mutant T19N, and inhibition of ROCK by Y27632, prevented myofibroblast transformation and collagen-I synthesis. Moreover, inhibition of RhoA by CT-04 prevented hyperoxia-induced actin filament formation, shift of G-actin to F-actin, and nuclear colocalization of MRTF-A. In addition, disrupting actin filaments with cytochalasin D or scavenging reactive oxygen species (ROS) with tiron attenuated actin filament formation, nuclear colocalization of MRTF-A, myofibroblast transformation, and collagen-I synthesis. Furthermore, overexpression of constitutively active RhoA mutant Q63L or stabilization of actin filaments recapitulated the effects of hyperoxia on the actin cytoskeleton and nuclear colocalization of MRTF-A, myofibroblast transformation, and collagen-I synthesis. Interestingly, knocking down MRTF-A prevented hyperoxia-induced increase in the recruitment of MRTF-A to the serum response factor transcriptional complex on the α-SMA gene promoter, myofibroblast transformation, and collagen-I synthesis. Finally, Y27632 and tiron attenuated hyperoxia-induced increases in α-SMA and collagen-I in mouse lungs. Together, these results indicate that the actin cytoskeletal reorganization due to the ROS/RhoA-ROCK pathway mediates myofibroblast transformation and collagen synthesis in lung fibrosis of oxygen toxicity. MRTF-A contributes to the regulatory effect of the actin cytoskeleton on myofibroblast transformation during hyperoxia.