NADPH oxidase-mediated redox signaling: roles in cellular stress response, stress tolerance, and tissue repair

Persistent reduced oxygen requirement following blood transfusion during recovery from hemorrhagic shock

Our study intended to determine the effects on oxygen uptake (VO2) of restoring a normal rate of O2 delivery following blood transfusion (BT) after a severe hemorrhage (H). Spontaneously breathing urethane anesthetized rats were bled by removing 20 ml/kg of blood over 30 min. Rats were then infused with their own shed blood 15 min after the end of H. At mid-perfusion, half of the rats received a unique infusion of the decoupling agent 2,4-dinitrophenol (DNP, 6 mg/kg). VO2 and arterial blood pressure (ABP) were continuously measured throughout the study, along with serial determination of blood lactate concentration [La]. Animals were euthanized 45 min after the end of reperfusion; liver and lungs were further analyzed for early expression of oxidative stress gene using RT-PCR. Our bleeding protocol induced a significant decrease in ABP and increase in [La], while VO2 dropped by half. The O2 deficit progressively accumulated during the period of bleeding reached -114 ± 53 ml/kg, just before blood transfusion. Despite the transfusion of blood, a significant O2 deficit persisted (-82 ± 59 ml/kg) 45 min after reperfusion. This slow recovery of VO2 was sped up by DNP injection, leading to a fast recovery of O2 deficit after reperfusion, becoming positive (+460 ± 132 ml/kg) by the end of the protocol, supporting the view that O2 supply is not the main controller of VO2 dynamics after BT. Of note is that DNP also enhanced oxidative stress gene expression (up-regulation of NADPH oxidase 4 in the lung for instance). The mechanism of slow recovery of O2 requirement/demand following BT and the resulting effects on tissues exposed to relatively high O2 partial pressure are discussed.

The hepatic cannabinoid 1 receptor as a modulator of hepatic energy state and food intake

The cannabinoid 1 receptor (CB1R) has a well-established role in appetite regulation. Central CB1R antagonists, notably rimonabant, induced weight loss and improved the metabolic profile in obese individuals, but were discontinued due to psychiatric side-effects. The CB1R is also expressed peripherally, where its effects include promotion of liver fat accumulation, which consumes ATP. Type 2 diabetes in obese subjects is linked to excess liver fat, whilst there is a negative correlation between hepatic ATP content and insulin resistance. A decreased hepatic ATP/AMP ratio increases food intake by signals via the vagus nerve to the brain. The hepatic cannabinoid system is highly upregulated in obesity, and the effects of hepatic CB1R activation include increased activity of lipogenic and gluconeogenic transcription factors. Thus, blockade of hepatic CB1Rs could contribute significantly to the weight-reducing and insulin-sensitizing effects of CB1R antagonists. Additionally, upregulation of the hepatic CB1R may contribute to chronic liver inflammation, fibrosis and cirrhosis from causes including obesity, alcoholism and viral hepatitis. Peripheral CB1R antagonists induce weight loss and metabolic improvements in obese rodents; however, as there is evidence that hepatic CB1Rs are predominately intracellular, due to high intrinsic clearance, many drugs may not effectively block these receptors and therefore have limited efficacy. Hepatoselective CB1R antagonists may be effective at reducing hepatic steatosis, insulin resistance and bodyweight in obese, diabetic patients, with far fewer side-effects than first-generation CB1R antagonists. Additionally, such compounds may be effective in treating inflammatory liver disease, such as non-alcoholic steatohepatitis, reducing the likelihood of disease progression to cirrhosis or cancer.

Cytotoxin-induced NADPH oxides activation: roles in regulation of cell death

Numerous studies have shown that a variety of cytotoxic agents can activate the NADPH oxidase system and induce redox-dependent regulation of cellular functions. Cytotoxin-induced NADPH oxidase activation may either exert cytoprotective actions (e.g., survival, proliferation, and stress tolerance) or cause cell death. Here we summarize the experimental evidence showing the context-dependent dichotomous effects of NADPH oxidase on cell fate under cytotoxic stress conditions and the potential redox signaling mechanisms underlying this phenomenon. Clearly, it is difficult to create a unified paradigm on the toxicological implications of NADPH oxidase activation in response to cytotoxic stimuli. We suggest that interventional strategies targeting the NADPH oxidase system to prevent the adverse impacts of cytotoxins need to be contemplated in a stimuli- and cell type-specific manner.

Effects of n-3 polyunsaturated fatty acids (ω-3) supplementation on some cardiovascular risk factors with a ketogenic Mediterranean diet

Background: the ketogenic diet (KD) has become a widely used nutritional approach for weight loss. Some of the KD’s positive effects on metabolism and cardiovascular risk factors are similar to those seen after n-3 polyunsaturated fatty acids (ω-3) supplementation. We hypothesized that a ketogenic Mediterranean diet with phytoextracts combined with ω-3 supplementation may have increased positive effects on cardiovascular risk factors and inflammation. Methods: We analyzed 34 male overweight subjects; aged between 25 and 65 years who were overall healthy apart from overweight. The subjects followed a ketogenic diet protocol for four weeks; with (KDO3) or without (KD) ω-3 supplementation. Results: All subjects experienced a significant loss of body weight and body fat and there was no significant differences between treatment (body weight: KD—4.7 kg, KDO3—4.03 kg, body fat KD—5.41 kg, KDO3—5.86 kg). There were also significant decreases in total cholesterol, LDL-c, and glucose levels. Triglycerides and insulin levels decreased more in KDO3 vs. KD subjects, with a significant difference. All the investigated inflammatory cytokines (IL-1β, IL-6, TNF-α) decreased significantly in KDO3 subjects whilst only TNF-α showed a significant decrease in KD subjects over the 12 month study period. No significant changes were observed in anti-inflammatory cytokines (IL-10 and IL-1Ra), creatinine, urea and uric acid. Adiponectin increased significantly only in the KDO3 group. Conclusions: ω-3 supplementation improved the positive effects of a ketogenic Mediterranean diet with phytoextracts on some cardiovascular/metabolic risk factors and inflammatory state.

Organochlorine insecticides induce NADPH oxidase-dependent reactive oxygen species in human monocytic cells via phospholipase A2/arachidonic acid

Bioaccumulative organohalogen chemicals, such as organochlorine (OC) insecticides, have been increasingly associated with disease etiology; however, the mechanistic link between chemical exposure and diseases, such as atherosclerosis, cancer, and diabetes, is complex and poorly defined. Systemic oxidative stress stemming from OC exposure might play a vital role in the development of these pathologies. Monocytes are important surveillance cells of the innate immune system that respond to extracellular signals possessing danger-associated molecular patterns by synthesizing oxyradicals, such as superoxide, for the purpose of combating infectious pathogens. We hypothesized that OC chemicals can be toxic to monocytes because of an inappropriate elevation in superoxide-derived reactive oxygen species (ROS) capable of causing cellular oxidative damage. Reactive oxyradicals are generated in monocytes in large part by NADPH oxidase (Nox). The present study was conducted to examine the ability of two chlorinated cyclodiene compounds, trans-nonachlor and dieldrin, as well as p,p'-DDE, a chlorinated alicyclic metabolite of DDT, to stimulate Nox activity in a human monocytic cell line and to elucidate the mechanisms for this activation. Human THP-1 monocytes treated with either trans-nonachlor or dieldrin (0.1-10 μM in the culture medium) exhibited elevated levels of intracellular ROS, as evidenced by complementary methods, including flow cytometry analysis using the probe DCFH-DA and hydroethidine-based fluorometric and UPLC-MS assays. In addition, the induced reactive oxygen flux caused by trans-nonachlor was also observed in two other cell lines, murine J774 macrophages and human HL-60 cells. The central role of Nox in OC-mediated oxidative stress was demonstrated by the attenuated superoxide production in OC-exposed monocytes treated with the Nox inhibitors diphenyleneiodonium and VAS-2870. Moreover, monocytes challenged with OCs exhibited increased phospho-p47(phox) levels and enhanced p47(phox) membrane localization compared to that in vehicle-treated cells. p47(phox) is a cytosolic regulatory subunit of Nox, and its phosphorylation and translocation to the NOX2 catalytic subunit in membranes is a requisite step for Nox assembly and activation. Dieldrin and trans-nonachlor treatments of monocytes also resulted in marked increases in arachidonic acid (AA) and eicosanoid production, which could be abrogated by the phospholipase A2 (PLA2) inhibitor arachidonoyltrifluoromethyl ketone (ATK) but not by calcium-independent PLA2 inhibitor bromoenol lactone. This suggested that cytosolic PLA2 plays a crucial role in the induction of Nox activity by increasing the intracellular pool of AA that activates protein kinase C, which phosphorylates p47(phox). In addition, ATK also blocked OC-induced p47(phox) serine phosphorylation and attenuated ROS levels, which further supports the notion that the AA pool liberated by cytosolic PLA2 is responsible for Nox activation. Together, the results suggest that trans-nonachlor and dieldrin are capable of increasing intracellular superoxide levels via a Nox-dependent mechanism that relies on elevated intracellular AA levels. These findings are significant because chronic activation of monocytes by environmental toxicants might contribute to pathogenic oxidative stress and inflammation.

Identification of NADPH oxidase as a key mediator in the post-ischemia-induced sequestration and degradation of the GluA2 AMPA receptor subunit

A hallmark of ischemic/reperfusion injury is a change in subunit composition of synaptic 2-amino-3-(3-hydroxy-5-methylisoazol-4-yl)propionic acid receptors (AMPARs). This change in AMPAR subunit composition leads to an increase in surface expression of GluA2-lacking Ca(2+) /Zn(2+) permeable AMPARs. These GluA2-lacking AMPARs play a key role in promoting delayed neuronal death following ischemic injury. At present, the mechanism(s) responsible for the ischemia/reperfusion-induced subunit composition switch and degradation of the GluA2 subunit remain unclear. In this study, we investigated the role of NADPH oxidase, and its importance in mediating endocytosis and subsequent degradation of the GluA2 AMPAR subunit in adult rat hippocampal slices subjected to oxygen-glucose deprivation/reperfusion (OGD/R) injury. In hippocampal slices pre-treated with the NADPH oxidase inhibitor apocynin attenuated OGD/R-mediated sequestration of GluA2 and GluA1 as well as prevent the degradation of GluA2. We provide compelling evidence that NADPH oxidase mediated sequestration of GluA1- and GluA2- involved activation of p38 MAPK. Furthermore, we demonstrate that inhibition of NADPH oxidase blunts the OGD/R-induced association of GluA2 with protein interacting with C kinase-1. In summary, this study identifies a novel mechanism that may underlie the ischemia/reperfusion-induced AMPAR subunit composition switch and a potential therapeutic target.

Endoplasmic reticulum stress, genome damage, and cancer

Endoplasmic reticulum (ER) stress has been linked to many diseases, including cancer. A large body of work has focused on the activation of the ER stress response in cancer cells to facilitate their survival and tumor growth; however, there are some studies suggesting that the ER stress response can also mitigate cancer progression. Despite these contradictions, it is clear that the ER stress response is closely associated with cancer biology. The ER stress response classically encompasses activation of three separate pathways, which are collectively categorized the unfolded protein response (UPR). The UPR has been extensively studied in various cancers and appears to confer a selective advantage to tumor cells to facilitate their enhanced growth and resistance to anti-cancer agents. It has also been shown that ER stress induces chromatin changes, which can also facilitate cell survival. Chromatin remodeling has been linked with many cancers through repression of tumor suppressor and apoptosis genes. Interplay between the classic UPR and genome damage repair mechanisms may have important implications in the transformation process of normal cells into cancer cells.

Regulator of G protein signaling 6 is a critical mediator of both reward-related behavioral and pathological responses to alcohol

Alcohol is the most commonly abused drug worldwide, and chronic alcohol consumption is a major etiological factor in the development of multiple pathological sequelae, including alcoholic cardiomyopathy and hepatic cirrhosis. Here, we identify regulator of G protein signaling 6 (RGS6) as a critical regulator of both alcohol-seeking behaviors and the associated cardiac and hepatic morbidities through two mechanistically divergent signaling actions. RGS6(-/-) mice consume less alcohol when given free access and are less susceptible to alcohol-induced reward and withdrawal. Antagonism of GABA(B) receptors or dopamine D2 receptors partially reversed the reduction in alcohol consumption in RGS6(-/-) animals. Strikingly, dopamine transporter inhibition completely restored alcohol seeking in mice lacking RGS6. RGS6 deficiency was associated with alterations in the expression of genes controlling dopamine (DA) homeostasis and a reduction in DA levels in the striatum. Taken together, these data implicate RGS6 as an essential regulator of DA bioavailability. RGS6 deficiency also provided dramatic protection against cardiac hypertrophy and fibrosis, hepatic steatosis, and gastrointestinal barrier dysfunction and endotoxemia when mice were forced to consume alcohol. Although RGS proteins canonically function as G-protein regulators, RGS6-dependent, alcohol-mediated toxicity in the heart, liver, and gastrointestinal tract involves the ability of RGS6 to promote reactive oxygen species-dependent apoptosis, an action independent of its G-protein regulatory capacity. We propose that inhibition of RGS6 might represent a viable means to reduce alcohol cravings and withdrawal in human patients, while simultaneously protecting the heart and liver from further damage upon relapse.

New paradigms in the repair of oxidative damage in human genome: mechanisms ensuring repair of mutagenic base lesions during replication and involvement of accessory proteins

Oxidized bases in the mammalian genome, which are invariably mutagenic due to their mispairing property, are continuously induced by endogenous reactive oxygen species and more abundantly after oxidative stress. Unlike bulky base adducts induced by UV and other environmental mutagens in the genome that block replicative DNA polymerases, oxidatively damaged bases such as 5-hydroxyuracil, produced by oxidative deamination of cytosine in the template strand, do not block replicative polymerases and thus need to be repaired prior to replication to prevent mutation. Following up our earlier studies, which showed that the Nei endonuclease VIII like 1 (NEIL1) DNA glycosylase, one of the five base excision repair (BER)-initiating enzymes in mammalian cells, has enhanced expression during the S-phase and higher affinity for replication fork-mimicking single-stranded (ss) DNA substrates, we recently provided direct experimental evidence for NEIL1's role in replicating template strand repair. The key requirement for this event, which we named as the 'cow-catcher' mechanism of pre-replicative BER, is NEIL1's non-productive binding (substrate binding without product formation) to the lesion base in ss DNA template to stall DNA synthesis, causing fork regression. Repair of the lesion in reannealed duplex is then carried out by NEIL1 in association with the DNA replication proteins. NEIL1 (and other BER-initiating enzymes) also interact with several accessory and non-canonical proteins including the heterogeneous nuclear ribonucleoprotein U and Y-box-binding protein 1 as well as high mobility group box 1 protein, whose precise roles in BER are still obscure. In this review, we have discussed the recent advances in our understanding of oxidative genome damage repair pathways with particular focus on the pre-replicative template strand repair and the role of scaffold factors like X-ray repairs cross-complementing protein 1 and poly (ADP-ribose) polymerase 1 and other accessory proteins guiding distinct BER sub-pathways.

Damage response involves mechanisms conserved across plants, animals and fungi

All organisms are constantly exposed to adverse environmental conditions including mechanical damage, which may alter various physiological aspects of growth, development and reproduction. In plant and animal systems, the damage response mechanism has been widely studied. Both systems posses a conserved and sophisticated mechanism that in general is aimed at repairing and preventing future damage, and causes dramatic changes in their transcriptomes, proteomes, and metabolomes. These damage-induced changes are mediated by elaborate signaling networks, which include receptors/sensors, calcium (Ca(2+)) influx, ATP release, kinase cascades, reactive oxygen species (ROS), and oxylipin signaling pathways. In contrast, our current knowledge of how fungi respond to injury is limited, even though various reports indicate that mechanical damage triggers reproductive processes. In fungi, the damage response mechanism has been studied more in depth in Trichoderma atroviride. Interestingly, these studies indicate that the mechanical damage response involves ROS, Ca(2+), kinase cascades, and lipid signaling pathways. Here we compare the response to mechanical damage in plants, animals and fungi and provide evidence that they appear to share signaling molecules and pathways, suggesting evolutionary conservation across the three kingdoms.

Rhizoma Dioscoreae Nipponicae polysaccharides protect HUVECs from H2O2-induced injury by regulating PPARγ factor and the NADPH oxidase/ROS-NF-κB signal pathway

AIM

Polysaccharides were extracted from Rhizoma Dioscoreae Nipponicae to investigate whether Rhizoma Dioscoreae Nipponicae polysaccharides (RDNP) can act as an antioxidant and PPARγ agonist to protect HUVECs from H2O2-induced injury.

METHODS

HUVECs (human umbilical vein endothelial cells) were treated with RDNP in the presence/absence of H2O2. Kits and Fenton reaction were used to produce free radicals. Reagent kits of LDH, MDA, SOD, T-AOC and GSH-Px were used to evaluate the cell injuries and the antioxidant activity of RDNP. Intracellular reactive oxygen species (ROS) generation was detected by 2', 7'-dichlorofluorescein diacetate (DCFH-DA). Western blot was used to evaluate the protein expression of Nox4, p22phox, NF-κB/p65, phospho-NF-κB/p65, IκB as well as PPARγ, ICAM-1 and VCAM-1. Real time quantitative reverse transcriptive polymerase chain reaction (qRT-PCR) was used to confirm the expressions of Nox4, p22phox, ICAM-1 and VCAM-1 mRNA.

RESULTS

RDNP inhibited the production of superoxide anion radical, hydroxyl radical and the lipid peroxidation both in hepatic cells and red blood cells (RBC). It also reduced LDH and MDA levels and enhanced intracellular SOD, T-AOC as well as GSH-Px activities in H2O2-treated HUVECs. Furthermore, RDNP could inhibit ROS generation, Nox4, p22phox, NF-κB/p65, phospho-NF-κB/p65, ICAM-1 and VCAM-1 expression, and it could also inhibit IκB degradation and activate PPARγ expression in HUVECs.

CONCLUSIONS

RDNP could protect HUVECs from H2O2-induced injury through interfering PPARγ-NADPH oxidase/ROS-NF-κB pathway. This study will provide new pharmacological evidence that RDNP has positive significance for prevention and treatment of atherosclerosis (AS).

Sestrin2, a Regulator of Thermogenesis and Mitohormesis in Brown Adipose Tissue

Sestrin2 is a stress-inducible protein that functions as an antioxidant and inhibitor of mTOR complex 1. In a recent study, we found that Sestrin2 overexpression in brown adipocytes interfered with normal metabolism by reducing mitochondrial respiration through the suppression of uncoupling protein 1 (UCP1) expression. The metabolic effects of Sestrin2 in brown adipocytes were dependent on its antioxidant activity, and chemical antioxidants produced similar effects in inhibiting UCP1-dependent thermogenesis. These observations suggest that low levels of reactive oxygen species (ROS) in brown adipocytes can actually be beneficial and necessary for proper metabolic homeostasis. In addition, considering that Sestrins are ROS inducible and perform ROS detoxifying as well as other metabolism-controlling functions, they are potential regulators of mitohormesis. This is a concept in which overall beneficial effects result from low-level oxidative stress stimuli, such as the ones induced by caloric restriction or physical exercise. In this perspective, we incorporate our recent insight obtained from the Sestrin2 study toward a better understanding of the relationship between ROS, Sestrin2, and mitochondrial metabolism in the context of brown adipocyte physiology.

Role of sestrin2 in the regulation of proinflammatory signaling in macrophages

Sestrins (Sesns) are conserved antioxidant proteins that accumulate in cells in response to various stresses. However, the regulatory roles of Sesn2 in the immune system and in inflammatory responses remain obscure. In the present study, we investigated whether Sesn2 regulates Toll like receptor (TLR)-mediated inflammatory signaling and sought to identify the molecular mechanism responsible. In cells expressing Sesn2, it was found that Sesn2 almost completely inhibited lipopolysaccharide (LPS)-induced NO release and iNOS expression. A gene knockdown experiment confirmed the role of Sesn2 in LPS-activated RAW264.7 cells. Consistently, proinflammatory cytokine (e.g., TNF-α, IL-6, and IL-1β) release and expression were inhibited in Sesn2-expressing cells. Furthermore, Sesn2 prevented LPS-elicited cell death and ROS production via inhibition of NADPH oxidase. NF-κB and AP-1 are redox-sensitive transcription factors that regulate the expressions of diverse inflammatory genes. Surprisingly, Sesn2 specifically inhibited AP-1 luciferase activity and its DNA binding, but not those of NF-κB. AP-1 inhibition by Sesn2 was found to be due to a lack of JNK, p38, and c-Jun phosphorylation. Next, we investigated whether Sesn2 protects galactosamine (Gal)/LPS-induced liver injury in mice infected with a recombinant adenovirus Sesn2 (Ad-Sesn2). Ad-Sesn2 present less severe hepatic injury as supported by decreases in the ALT, AST, and hepatocyte degeneration. Moreover, Ad-Sesn2 attenuated Gal/LPS-induced proinflammatory gene expression in mice. The study shows that Sesn2 inhibits TLR-induced proinflammatory signaling and protects cells by inhibiting JNK- or p38-mediated c-Jun phosphorylation.

An alternative to nerve repair using an antioxidant compound: a histological study in rats

The fascicular composition and organisation of the inferior alveolar nerve (IAN) were determined to confirm the microarchitecture of the IAN bundles into each of the mandibular teeth, including the composition of the mental nerve. The aim of this study was to evaluate peripheral nerve repair after the application of an antioxidant compound to the damaged nerve tissue to elevate the concentration and bioavailability of elements capable of favouring tissue repair. Twenty-five Wistar rats were divided into groups: The Control 1 (Ctl 1) (n = 5) animals had the ischiatic nerve exposed with no suture injury and were sacrificed at 30 days post-operatively. The Control 2 (Ctl 2) (n = 10) animals had the ischiatic nerve exposed, and the nerve was injured using suture in three distinct regions. In the experimental (Exp) animals (n = 10), an antioxidant organic compound was applied to the nerve injury site. The animals with nerve injury (Ctl2 and Exp group) were sacrificed at 15 and 30 days post-operatively. The histological analysis showed less degeneration in the Exp group at 15 and 30 days post-operatively. Nerve neoformation forming a connection between the distal and proximal suture sites was observed in the experimental group. This study presented an alternative to nerve repair using an antioxidant compound.

Prion Protein Signaling in the Nervous System—A Review and Perspective

Prion protein (PrPC) was originally known as the causative agent of transmissible spongiform encephalopathy (TSE) but with recent research, its true function in cells is becoming clearer. It is known to act as a scaffolding protein, binding multiple ligands at the cell membrane and to be involved in signal transduction, passing information from the extracellular matrix (ECM) to the cytoplasm. Its role in the coordination of transmitters at the synapse, glyapse, and gap junction and in short- and long-range neurotrophic signaling gives PrPC a major part in neural transmission and nervous system signaling. It acts to regulate cellular function in multiple targets through its role as a controller of redox status and calcium ion flux. Given the importance of PrPC in cell physiology, this review considers its potential role in disease apart from TSE. The putative functions of PrPC point to involvement in neurodegenerative disease, neuropathic pain, chronic headache, and inflammatory disease including neuroinflammatory disease of the nervous system. Potential targets for the treatment of disease influenced by PrPC are discussed.

Postoperative Hyperoxia (60%) Worsens Hepatic Injury in Mice

Background:

Liver damage by ischemia and reperfusion injury is a risk factor for morbidity and mortality after liver surgery. Postoperative oxygen treatment is routinely applied in the postanesthesia and intensive care unit after liver surgery. The risks of aggravating the injury by increasing inspiratory oxygen from 21 to 60% in the postoperative period were investigated in mice.

Methods:

Parameters of liver injury were compared after induction of hepatic ischemia–reperfusion injury, by clamping the left liver lobe for 45 min, and reperfusion for 24 h either under normoxic (21% oxygen) or hyperoxic (60% oxygen) conditions (n = 22 per group). The extent of tissue injury and oxidative responses was analyzed in the presence or absence of polymorphonuclear leukocytes, functional Kupffer cells, and the p47phox unit of the nicotinamide adenine dinucleotide phosphate oxidase (n = 6 to 11 per group).

Results:

Compared with postoperative normoxic conditions, hyperoxia increased cell damage (glutamate-pyruvate transaminase: 1,870 [±968 SD] vs. 60% 2,981 [±1,038 SD], 21 vs. 60% oxygen, in U/l as mean ± SD; P < 0.01), liver weights (341 ± 52 vs. 383 ± 44, 21 vs. 60% oxygen, in mg as mean ± SD; P = 0.02), damage scores (1.9 ± 0.8 vs. 3.1 ± 1.0, 21 vs. 60% oxygen, score as mean ± SD; P = 0.02), and reactive oxygen species (15.0 ± 12.0 vs. 30.4 ± 19.2, 21 vs. 60% oxygen, in μmol/l as mean ± SD; P < 0.05). The aggravation of the tissue damaging effects as a result of hyperoxia was not seen in mice with depletions of polymorphonuclear leukocytes or Kupffer cells, or with nonfunctioning nicotinamide adenine dinucleotide phosphate oxidase.

Conclusion:

Liver injury after ischemia was significantly aggravated by hyperoxia as a consequence of immune cell-mediated oxidative burst. Further studies are needed to elucidate whether routine delivery of high inspirational oxygen concentrations postoperatively should be limited.

Mitochondrial reactive oxygen species and cancer

Mitochondria produce reactive oxygen species (mROS) as a natural by-product of electron transport chain activity. While initial studies focused on the damaging effects of reactive oxygen species, a recent paradigm shift has shown that mROS can act as signaling molecules to activate pro-growth responses. Cancer cells have long been observed to have increased production of ROS relative to normal cells, although the implications of this increase were not always clear. This is especially interesting considering cancer cells often also induce expression of antioxidant proteins. Here, we discuss how cancer-associated mutations and microenvironments can increase production of mROS, which can lead to activation of tumorigenic signaling and metabolic reprogramming. This tumorigenic signaling also increases expression of antioxidant proteins to balance the high production of ROS to maintain redox homeostasis. We also discuss how cancer-specific modifications to ROS and antioxidants may be targeted for therapy.

Oxidative stress contributes to orthopedic trauma-induced acute kidney injury in obese rats

After trauma, obese patients have an increased risk of developing acute kidney injury (AKI). We have demonstrated that obese Zucker (OZ) rats, but not lean Zucker (LZ) rats, develop AKI 24 h after orthopedic trauma. ROS have been implicated in the pathophysiology of AKI in models of critical illness. However, the contribution of ROS to trauma-induced AKI in the setting of obesity has not been determined. We hypothesized that AKI in OZ rats after trauma is mediated by increased oxidative stress. Male LZ and OZ rats were divided into control and trauma groups, with a subset receiving treatment after trauma with the antioxidant apocynin (50 mg/kg ip, 2 mM in drinking water). The day after trauma, glomerular filtration rate, plasma creatinine, urine kidney injury molecule-1, and albumin excretion as well as renal oxidant and antioxidant activity were measured. After trauma, compared with LZ rats, OZ rats exhibited a significant decrease in glomerular filtration rate along with significant increases in plasma creatinine and urine kidney injury molecule-1 and albumin excretion. Additionally, oxidative stress was significantly increased in OZ rats, as evidenced by increased renal NADPH oxidase activity and urine lipid peroxidation products (thiobarbituric acid-reactive substances), and OZ rats also had suppressed renal superoxide dismutase activity. Apocynin treatment significantly decreased oxidative stress and AKI in OZ rats but had minimal effects in LZ rats. These results suggest that ROS play an important role in AKI in OZ rats after traumatic injury and that ROS may be a potential future therapeutic target in the obese after trauma.

Oxidized LDL-induced angiogenesis involves sphingosine 1-phosphate: prevention by anti-S1P antibody

BACKGROUND AND PURPOSE

Neovascularization occurring in atherosclerotic lesions may promote plaque expansion, intraplaque haemorrhage and rupture. Oxidized LDL (oxLDL) are atherogenic, but their angiogenic effect is controversial; both angiogenic and anti-angiogenic effects have been reported. The angiogenic mechanism of oxLDL is partly understood, but the role of the angiogenic sphingolipid, sphingosine 1-phosphate (S1P), in this process is not known. Thus, we investigated whether S1P is involved in the oxLDL-induced angiogenesis and whether an anti-S1P monoclonal antibody can prevent this effect.

EXPERIMENTAL APPROACH

Angiogenesis was assessed by capillary tube formation by human microvascular endothelial cells (HMEC-1) cultured on Matrigel and in vivo by the Matrigel plug assay in C57BL/6 mice.

KEY RESULTS

Human oxLDL exhibited a biphasic angiogenic effect on HMEC-1; low concentrations were angiogenic, higher concentrations were cytotoxic. The angiogenic response to oxLDL was blocked by the sphingosine kinase (SPHK) inhibitor, dimethylsphingosine, by SPHK1-siRNA and by an anti-S1P monoclonal antibody. Moreover, inhibition of oxLDL uptake and subsequent redox signalling by anti-CD36 and anti-LOX-1 receptor antibodies and by N-acetylcysteine, respectively, blocked SPHK1 activation and tube formation. In vivo, in the Matrigel plug assay, low concentrations of human oxLDL or murine oxVLDL also triggered angiogenesis, which was prevented by i.p. injection of the anti-S1P antibody.

CONCLUSION AND IMPLICATIONS

These data highlight the role of S1P in angiogenesis induced by oxLDL both in HMEC-1 cultured on Matrigel and in vivo in the Matrigel plug model in mice, and demonstrate that the anti-S1P antibody effectively blocks the angiogenic effect of oxLDL.

Proline metabolism increases katG expression and oxidative stress resistance in Escherichia coli

The oxidation of l-proline to glutamate in Gram-negative bacteria is catalyzed by the proline utilization A (PutA) flavoenzyme, which contains proline dehydrogenase (PRODH) and Δ(1)-pyrroline-5-carboxylate (P5C) dehydrogenase domains in a single polypeptide. Previous studies have suggested that aside from providing energy, proline metabolism influences oxidative stress resistance in different organisms. To explore this potential role and the mechanism, we characterized the oxidative stress resistance of wild-type and putA mutant strains of Escherichia coli. Initial stress assays revealed that the putA mutant strain was significantly more sensitive to oxidative stress than the parental wild-type strain. Expression of PutA in the putA mutant strain restored oxidative stress resistance, confirming that depletion of PutA was responsible for the oxidative stress phenotype. Treatment of wild-type cells with proline significantly increased hydroperoxidase I (encoded by katG) expression and activity. Furthermore, the ΔkatG strain failed to respond to proline, indicating a critical role for hydroperoxidase I in the mechanism of proline protection. The global regulator OxyR activates the expression of katG along with several other genes involved in oxidative stress defense. In addition to katG, proline increased the expression of grxA (glutaredoxin 1) and trxC (thioredoxin 2) of the OxyR regulon, implicating OxyR in proline protection. Proline oxidative metabolism was shown to generate hydrogen peroxide, indicating that proline increases oxidative stress tolerance in E. coli via a preadaptive effect involving endogenous hydrogen peroxide production and enhanced catalase-peroxidase activity.

Arsenic, cadmium, mercury and nickel stimulate cell growth via NADPH oxidase activation

Exposure to metals and metalloids including arsenic, cadmium, mercury, and nickel has been a worldwide health problem for several decades. The aim of this study was to learn how metal-induced oxidative stress triggers cell proliferation, a process of great significance for cancer. NADPH oxidase (NOX) activity and cell proliferation were measured as endpoints in both NOX-deficient and NOX-proficient cells. The X chromosome linked CGD (X-CGD) human promyelocytic leukemia PLB-985 cells lacking gp91phox and the X-CGD cells re-transfected with gp91phox (X-CGD-gp91(phox)) were used together with immortalized human keratinocyte cells (HaCaT). The cells were exposed to different concentrations of the metals alone or together with the NOX inhibitor, diphenyleneiodonium (DPI). We found that the studied metals increased NOX activity. They stimulated cell proliferation in HaCaT and X-CGD-gp91(phox) cells at concentrations below 1μM but not in the X-CGD cells that lack functional NOX. Addition of DPI attenuated the metal-induced cell proliferation. At concentrations above 1μM these metals inhibited cell proliferation. Based on these findings, we propose that many environmental pollutants, including metals and also endogenous NOX-activators such as oxidants and growth factors, interfere with cell growth kinetics by increasing the levels of the diffusible molecule H2O2. Here, we provide evidence that NOXs is central to the mechanism of metal-mediated reactive oxygen species production and stimulation of cell proliferation.

Nox2 knockout delays infarct progression and increases vascular recovery through angiogenesis in mice following ischaemic stroke with reperfusion

Evidence suggests the NADPH oxidases contribute to ischaemic stroke injury and Nox2 is the most widely studied subtype in the context of stroke. There is still conjecture however regarding the benefits of inhibiting Nox2 to improve stroke outcome. The current study aimed to examine the temporal effects of genetic Nox2 deletion on neuronal loss after ischaemic stroke using knockout (KO) mice with 6, 24 and 72 hour recovery. Transient cerebral ischaemia was induced via intraluminal filament occlusion and resulted in reduced infarct volumes in Nox2 KO mice at 24 h post-stroke compared to wild-type controls. No protection was evident at either 6 h or 72 h post-stroke, with both genotypes exhibiting similar volumes of damage. Reactive oxygen species were detected using dihydroethidium and were co-localised with neurons and microglia in both genotypes using immunofluorescent double-labelling. The effect of Nox2 deletion on vascular damage and recovery was also examined 24 h and 72 h post-stroke using an antibody against laminin. Blood vessel density was decreased in the ischaemic core of both genotypes 24 h post-stroke and returned to pre-stroke levels only in Nox2 KO mice by 72 h. Overall, these results are the first to show that genetic Nox2 deletion merely delays the progression of neuronal loss after stroke but does not prevent it. Additionally, we show for the first time that Nox2 deletion increases re-vascularisation of the damaged brain by 72 h, which may be important in promoting endogenous brain repair mechanisms that rely on re-vascularisation.

Simvastatin attenuates angiotensin II‑induced inflammation and oxidative stress in human mesangial cells

Chronic kidney disease (CKD) is an intractable disease in which inflammation and oxidative stress are important. In the present study, the effect of simvastatin on inflammation and oxidative stress induced by angiotensin II (Ang II) in human mesangial cells (HMCs) and its corresponding mechanism was examined. In the in vitro experiment, HMCs were pretreated either without additives (control group) or with simvastatin at different concentrations (0, 0.1, 1 or 10 µM) for 1 h and were then stimulated by Ang II (1 µM) for 24 h. Following stimulation, the cells were collected for analysis using quantitative polymerase chain reaction, western blotting and dihydroethidium staining. The supernatant of the cells was collected and analyzed using an enzyme‑linked immunosorbent assay. The results demonstrated that simvastatin suppressed the increased mRNA expression of monocyte chemoattractant protein‑1, tumor necrosis factor‑α, interleukin (IL)‑1β and IL‑6 and the content of reactive oxygen species induced by Ang II in a dose‑dependent manner. In addition, simvastatin decreased the protein expression of cyclooxygenase‑2 (COX‑2), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and protein kinase C (PKC) as well as the content of prostaglandin E2 and the phosphorylation level of nuclear factor‑κB (NF‑κB) p65 in a dose‑dependent manner. Furthermore, simvastatin significantly increased the protein expression of peroxisome proliferator‑activated receptor γ (PPARγ). Therefore, simvastatin suppressed inflammation and oxidative stress in Ang II‑stimulated HMCs via COX‑2, PPARγ, NF‑κB, NADPH oxidase and PKCs, thereby exerting a protective effect on CKD.

Photo-protective effect of americanin B against ultraviolet B-induced damage in cultured human keratinocytes

Excessive ultraviolet (UV) radiation, a constituent of sunlight, can induce multiple types of skin damage. We recently demonstrated that americanin B, a lignin compound, protected cells against hydrogen peroxide (H2O2)-induced damage by exerting antioxidant effects and inhibiting apoptosis. In this study, we investigated the ability of americanin B to protect against cell injury induced by UVB (280-320nm), the most harmful UV wavelengths, in human HaCaT keratinocytes. Americanin B absorbed UVB, eliminated UVB-induced intracellular reactive oxygen species (ROS), and decreased the extent of UVB-induced oxidative modification of lipids, proteins, and DNA. In addition, americanin B inhibited UVB-induced apoptosis, as indicated by reductions in apoptotic body formation and DNA fragmentation. Furthermore, americanin B reversed the depolarization of the mitochondrial membrane induced by UVB exposure. These protective activities were associated with down-regulation of apoptosis-promoting proteins, Bax, caspase-9, and caspase-3 and up-regulation of an apoptosis inhibitor, Bcl-2. These results suggest that americanin B can protect human keratinocytes against UVB-induced cell damage.

NADPH oxidase and the cardiovascular toxicity associated with smoking

Smoking is one of the most serious but preventable causes of cardiovascular disease (CVD). Key aspects of pathological process associated with smoking include endothelial dysfunction, a prothrombotic state, inflammation, altered lipid metabolism, and hypoxia. Multiple molecular events are involved in smokinginduced CVD. However, the dysregulations of reactive oxygen species (ROS) generation and metabolism mainly contribute to the development of diverse CVDs, and NADPH oxidase (NOX) has been established as a source of ROS responsible for the pathogenesis of CVD. NOX activation and resultant ROS production by cigarette smoke (CS) treatment have been widely observed in isolated blood vessels and cultured vascular cells, including endothelial and smooth muscle cells. NOX-mediated oxidative stress has also been demonstrated in animal studies. Of the various NOX isoforms, NOX2 has been reported to mediate ROS generation by CS, but other isoforms were not tested thoroughly. Of the many CS constituents, nicotine, methyl vinyl ketone, and α,β-unsaturated aldehydes, such as, acrolein and crotonaldehyde, appear to be primarily responsible for NOX-mediated cytotoxicity, but additional validation will be needed. Human epidemiological studies have reported relationships between polymorphisms in the CYBA gene encoding p22phox, a catalytic subunit of NOX and susceptibility to smoking-related CVDs. In particular, G allele carriers of A640G and -930^A/G polymorphisms were found to be vulnerable to smoking-induced cardiovascular toxicity, but results for C242T studies are conflicting. On the whole, evidence implicates the etiological role of NOX in smoking-induced CVD, but the clinical relevance of NOX activation by smoking and its contribution to CVD require further validation in human studies. A detailed understanding of the role of NOX would be helpful to assess the risk of smoking to human health, to define high-risk subgroups, and to develop strategies to prevent or treat smoking-induced CVD.

Thymoquinone attenuates Doxorubicin-induced nephrotoxicity in rats: Role of Nrf2 and NOX4

Doxorubicin (DOX) is a chemotherapeutic drug widely used for the treatment of various neoplastic conditions. However, its application is limited because of its toxic effects in many organs. Nephrotoxicity is a serious effect of DOX. The aim of this study was to determine the protective effect of thymoquinone (TQ), a predominant bioactive constituent of Nigella sativa oil, with well documented potent anti-oxidative and anti-inflammatory effects. Male Sprague Dawley rats received DOX (3.5mg/kg twice weekly) with or without TQ (50mg/kg/day, oral supplementation) for 3weeks. Elevated levels of serum urea, creatinine and urinary albumin excretion were observed in DOX-treated animals, indicating DOX-induced nephrotoxicity. Moreover, enhanced lipid peroxidation (LPO), as equivalents of malondialdehyde (MDA), in the renal tissue was accompanied by a significant decrease in the activities of superoxide dismutase (SOD) and glutathione-S-transferase (GST) in DOX-treated group. In addition, DOX treatment induced significant increase in renal levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and NADPH oxidase 4 (NOX-4), and marked decrease in interleukin-10 (IL-10) levels, nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA levels and nuclear binding activity. Histopathological analysis showed severe damage in the renal tissue of DOX treated animals. Animals treated with TQ were found to have markedly reduced renal damage with restoration of all mentioned markers toward normal values. In conclusion, DOX-induced renal damage involved a redox imbalance in renal tissue, which could be reversed by TQ, suggesting a possible potential role for TQ in DOX-induced nephrotoxicity.

Endosulfan induces COX-2 expression via NADPH oxidase and the ROS, MAPK, and Akt pathways

Endosulfan (1,4,5,6,7,7-hexachloro-8,9,10-trinorborn-5-en-2,3-ylenebismet-hylene) is correlated with endocrine disruption, reproductive, and immune dysfunctions. Recently, endosulfan was shown to have an effect on inflammatory pathways, but its influence on cyclooxygenase-2(COX-2) expression is unclear. This study investigated the effects of COX-2 and molecular mechanisms by endosulfan in murine macrophage RAW 264.7 cells. Endosulfan significantly induced COX-2 protein and mRNA levels, as well as COX-2 promoter-driven luciferase activity and the production of prostaglandin E2, a major COX-2 metabolite. Transfection experiments with several human COX-2 promoter constructs revealed that endosulfan activated NF-κB, C/EBP, AP-1, and CREB. Moreover, Akt and mitogen-activated protein kinases (MAPK) were significantly activated by endosulfan. Moreover, endosulfan increased production of the ROS and the ROS-producing NAPDH-oxidase (NOX) family oxidases, NOX2, and NOX3. Endosulfan-induced Akt/MAPK pathways and COX-2 expression were attenuated by DPI, a specific NOX inhibitor, and the ROS scavenger N-acetylcysteine. These results demonstrate that endosulfan induces COX-2 expression via NADPH oxidase, ROS, and Akt/MAPK pathways. These findings provide further insight into the signal transduction pathways involved in the inflammatory effects of endosulfan.

Respiratory risks from household air pollution in low and middle income countries

A third of the world's population uses solid fuel derived from plant material (biomass) or coal for cooking, heating, or lighting. These fuels are smoky, often used in an open fire or simple stove with incomplete combustion, and result in a large amount of household air pollution when smoke is poorly vented. Air pollution is the biggest environmental cause of death worldwide, with household air pollution accounting for about 3·5-4 million deaths every year. Women and children living in severe poverty have the greatest exposures to household air pollution. In this Commission, we review evidence for the association between household air pollution and respiratory infections, respiratory tract cancers, and chronic lung diseases. Respiratory infections (comprising both upper and lower respiratory tract infections with viruses, bacteria, and mycobacteria) have all been associated with exposure to household air pollution. Respiratory tract cancers, including both nasopharyngeal cancer and lung cancer, are strongly associated with pollution from coal burning and further data are needed about other solid fuels. Chronic lung diseases, including chronic obstructive pulmonary disease and bronchiectasis in women, are associated with solid fuel use for cooking, and the damaging effects of exposure to household air pollution in early life on lung development are yet to be fully described. We also review appropriate ways to measure exposure to household air pollution, as well as study design issues and potential effective interventions to prevent these disease burdens. Measurement of household air pollution needs individual, rather than fixed in place, monitoring because exposure varies by age, gender, location, and household role. Women and children are particularly susceptible to the toxic effects of pollution and are exposed to the highest concentrations. Interventions should target these high-risk groups and be of sufficient quality to make the air clean. To make clean energy available to all people is the long-term goal, with an intermediate solution being to make available energy that is clean enough to have a health impact.

Over-inhibition of NADPH oxidase reduce the wound healing in liver of finfish

Wound healing is a complex process involving soluble mediators, blood cells, extracellular matrix, and parenchymal cells in a response that occurs after surgical procedure or traumatic injury. The present study aims to investigate the ROS producing from the injury that involved in the wound healing using the ZFL (zebrafish liver cell) and tilapia partial hepatectomy model. In the ZFL, we observed that while over-inhibition of NADPH activity leading to reduce the wound healing moreover, experiment of the oxidative stress by the extracellular hydrogen peroxide exactly presented to increase the PCNA, BrdU and Ki-67 histopathological repair response of tilapia liver follow partial hepatectomy. We conclude that over inhibition of the NADPH oxidase by DPI may reduce the cell even the tissue in the progress of healing after the injury.

Iron and thiols as two major players in carcinogenesis: friends or foes?

Iron is the most abundant metal in the human body and mainly works as a cofactor for proteins such as hemoglobin and various enzymes. No independent life forms on earth can survive without iron. However, excess iron is intimately associated with carcinogenesis by increasing oxidative stress via its catalytic activity to generate hydroxyl radicals. Biomolecules with redox-active sulfhydryl function(s) (thiol compounds) are necessary for the maintenance of mildly reductive cellular environments to counteract oxidative stress, and for the execution of redox reactions for metabolism and detoxification. Involvement of glutathione S-transferase and thioredoxin has long attracted the attention of cancer researchers. Here, I update recent findings on the involvement of iron and thiol compounds during carcinogenesis and in cancer cells. It is now recognized that the cystine/glutamate transporter (antiporter) is intimately associated with ferroptosis, an iron-dependent, non-apoptotic form of cell death, observed in cancer cells, and also with cancer stem cells; the former with transporter blockage but the latter with its stabilization. Excess iron in the presence of oxygen appears the most common known mutagen. Ironically, the persistent activation of antioxidant systems via genetic alterations in Nrf2 and Keap1 also contributes to carcinogenesis. Therefore, it is difficult to conclude the role of iron and thiol compounds as friends or foes, which depends on the quantity/distribution and induction/flexibility, respectively. Avoiding further mutation would be the most helpful strategy for cancer prevention, and myriad of efforts are being made to sort out the weaknesses of cancer cells.

Testosterone stimulates Duox1 activity through GPRC6A in skin keratinocytes

Testosterone is an endocrine hormone with functions in reproductive organs, anabolic events, and skin homeostasis. We report here that GPRC6A serves as a sensor and mediator of the rapid action of testosterone in epidermal keratinocytes. The silencing of GPRC6A inhibited testosterone-induced intracellular calcium ([Ca(2+)]i) mobilization and H2O2 generation. These results indicated that a testosterone-GPRC6A complex is required for activation of Gq protein, IP3 generation, and [Ca(2+)]i mobilization, leading to Duox1 activation. H2O2 generation by testosterone stimulated the apoptosis of keratinocytes through the activation of caspase-3. The application of testosterone into three-dimensional skin equivalents increased the apoptosis of keratinocytes between the granular and stratified corneum layers. These results support an understanding of the molecular mechanism of testosterone-dependent apoptosis in which testosterone stimulates H2O2 generation through the activation of Duox1.

Upregulation of intermediate-conductance Ca2+-activated K+ channels (KCNN4) in porcine coronary smooth muscle requires NADPH oxidase 5 (NOX5)

Aims

NADPH oxidase (NOX) is the primary source of reactive oxygen species (ROS) in vascular smooth muscle cells (SMC) and is proposed to play a key role in redox signaling involved in the pathogenesis of cardiovascular disease. Growth factors and cytokines stimulate coronary SMC (CSMC) phenotypic modulation, proliferation, and migration during atherosclerotic plaque development and restenosis. We previously demonstrated that increased expression and activity of intermediate-conductance Ca²⁺-activated K⁺ channels (KCNN4) is necessary for CSMC phenotypic modulation and progression of stenotic lesions. Therefore, the purpose of this study was to determine whether NOX is required for KCNN4 upregulation induced by mitogenic growth factors.

Methods and Results

Dihydroethidium micro-fluorography in porcine CSMCs demonstrated that basic fibroblast growth factor (bFGF) increased superoxide production, which was blocked by the NOX inhibitor apocynin (Apo). Apo also blocked bFGF-induced increases in KCNN4 mRNA levels in both right coronary artery sections and CSMCs. Similarly, immunohistochemistry and whole cell voltage clamp showed bFGF-induced increases in CSMC KCNN4 protein expression and channel activity were abolished by Apo. Treatment with Apo also inhibited bFGF-induced increases in activator protein-1 promoter activity, as measured by luciferase activity assay. qRT-PCR demonstrated porcine coronary smooth muscle expression of NOX1, NOX2, NOX4, and NOX5 isoforms. Knockdown of NOX5 alone prevented both bFGF-induced upregulation of KCNN4 mRNA and CSMC migration.

Conclusions

Our findings provide novel evidence that NOX5-derived ROS increase functional expression of KCNN4 through activator protein-1, providing another potential link between NOX, CSMC phenotypic modulation, and atherosclerosis.

M1 and M2 macrophages: the chicken and the egg of immunity

The purpose of this perspective is to describe a critical advance in understanding how immune responses work. Macrophages are required for all animal life: 'Inhibit' type macrophages in all animals (called M1) can rapidly kill pathogens, and are thus the primary host defense, and 'Heal' type macrophages (M2) routinely repair and maintain tissue integrity. Macrophages perform these activities in all animals without T cells, and also in T cell-deficient vertebrates. Although adaptive immunity can amplify macrophage polarization, the long-held notion that macrophages need to be 'activated' or 'alternatively activated' by T cells is incorrect; indeed, immunology has had it backward. M1/M2-type macrophages necessarily direct T cells toward Th1- or Th2-like activities, respectively. That such macrophage-innate activities are the central directing element in immune responses is a dramatic change in understanding how immune systems operate. Most important, this revelation is opening up whole new approaches to immunotherapy. For example, many modern diseases, such as cancer and atherosclerosis, may not display 'foreign' antigens. However, there are clear imbalances in M1/M2-type responses. Correcting such innate imbalances can result in better health. Macrophages are the chicken and the egg of immunity.

A key role of the mitochondrial citrate carrier (SLC25A1) in TNFα- and IFNγ-triggered inflammation

The chronic induction of inflammation underlies multiple pathological conditions, including metabolic, autoimmune disorders and cancer. The mitochondrial citrate carrier (CIC), encoded by the SLC25A1 gene, promotes the export of citrate from the mitochondria to the cytoplasm, a process that profoundly influences energy balance in the cells. We have previously shown that SLC25A1 is a target gene for lipopolysaccharide signaling and promotes the production of inflammatory mediators. We now demonstrate that SLC25A1 is induced at the transcriptional level by two key pro-inflammatory cytokines, tumor necrosis factor-α (TNFα) and interferon-γ (IFNγ), and such induction involves the activity of the nuclear factor kappa B and STAT1 transcription factors. By studying the down-stream events following SLC25A1 activation during signals that mimic inflammation, we demonstrate that CIC is required for regulating the levels of nitric oxide and of prostaglandins by TNFα or IFNγ. Importantly, we show that the citrate exported from mitochondria via CIC and its downstream metabolic intermediate, acetyl-coenzyme A, are necessary for TNFα or IFNγ to induce nitric oxide and prostaglandin production. These findings provide the first line of evidence that the citrate export pathway, via CIC, is central for cytokine-induced inflammatory signals and shed new light on the relationship between energy metabolism and inflammation.

Effects of the novel compound DK223 ([1E,2E-1,2-Bis(6-methoxy-2H-chromen-3-yl)methylene]hydrazine) on migration and proliferation of human keratinocytes and primary dermal fibroblasts

Wound healing plays an important role in protecting the human body from external infection. Cell migration and proliferation of keratinocytes and dermal fibroblasts are essential for proper wound healing. Recently, several studies have demonstrated that secondary compounds produced in plants could affect skin cells migration and proliferation. In this study, we identified a novel compound DK223 ([1E,2E-1,2-bis(6-methoxy-2H-chromen-3-yl)methylene]hydrazine) that concomitantly induced human keratinocyte migration and dermal fibroblast proliferation. We evaluated the regulation of epithelial and mesenchymal protein markers, such as E-cadherin and Vimentin, in human keratinocytes, as well as extracellular matrix (ECM) secretion and metalloproteinase families in dermal fibroblasts. DK223 upregulated keratinocyte migration and significantly increased the epithelial marker E-cadherin in a time-dependent manner. We also found that reactive oxygen species (ROS) increased significantly in keratinocytes after 2 h of DK223 exposure, returning to normal levels after 24 h, which indicated that DK223 had an early shock effect on ROS production. DK223 also stimulated fibroblast proliferation, and induced significant secretion of ECM proteins, such as collagen I, III, and fibronectin. In dermal fibroblasts, DK223 treatment induced TGF-β1, which is involved in a signaling pathway that mediates proliferation. In conclusion, DK223 simultaneously induced both keratinocyte migration via ROS production and fibroblast proliferation via TGF-β1 induction.

In vivo imaging of inflammatory phagocytes

Inflammation contributes to the pathophysiology of many diseases. In this report, we present noninvasive bioluminescence imaging methods that distinguish acute and chronic inflammation in mouse models. Systemic delivery of luminol (5-amino-2,3-dihydro-1,4-phthalazinedione) enables detection of acute inflammation largely mediated by tissue-infiltrating neutrophils, whose myeloperoxidase (MPO) activity is required for luminol bioluminescence. In contrast, bioluminescence from injection of lucigenin (bis-N-methylacridinium nitrate) closely correlates with late phase and chronic inflammation. Lucigenin bioluminescence is independent of MPO and, instead, requires phagocyte NADPH oxidase (Phox) activity in macrophages. We are able to visualize tissue inflammation resulting from wound healing, bacterial infection, foreign substance implantation, and antitumor immune responses. Given the central role of inflammation in a variety of disorders, we believe these noninvasive imaging methods can help dissect the differential roles of neutrophils and macrophages in a variety of pathological conditions.

Human placenta-derived mesenchymal stem cells promote hepatic regeneration in CCl4 -injured rat liver model via increased autophagic mechanism

Mesenchymal stem cells (MSCs) have great potential for cell therapy in regenerative medicine, including liver disease. Even though ongoing research is dedicated to the goal of bringing MSCs to clinical applications, further understanding of the complex underlying mechanisms is required. Autophagy, a type II programmed cell death, controls cellular recycling through the lysosomal system in damaged cells or tissues. However, it is still unknown whether MSCs can trigger autophagy to enhance regeneration and/or to provide a therapeutic effect as cellular survival promoters. We therefore investigated autophagy's activation in carbon tetrachloride (CCl4 )-injured rat liver following transplantation with chorionic plate-derived MSCs (CP-MSCs) isolated from placenta. The expression markers for apoptosis, autophagy, cell survival, and liver regeneration were analyzed. Whereas caspase 3/7 activities were reduced (p < .05), the expression levels of hypoxia-inducible factor-1α (HIF-1α) and factors for autophagy, survival, and regeneration were significantly increased by CP-MSCs transplantation. Decreased necrotic cells (p < .05) and increased autophagic signals (p < .005) were observed in CCl4 -treated primary rat hepatocytes during in vitro coculture with CP-MSCs. Furthermore, the upregulation of HIF-1α promotes the regeneration of damaged hepatic cells through an autophagic mechanism marked by increased levels of light chain 3 II (LC 3II). These results suggest that the administration of CP-MSCs promotes repair by systemically concomitant mechanisms involving HIF-1α and autophagy. These findings provide further understanding of the mechanisms involved in these processes and will help develop new cell-based therapeutic strategies for regenerative medicine in liver disease.

Oxidative exposure impairs TGF-β pathway via reduction of type II receptor and SMAD3 in human skin fibroblasts

Exposure to oxidants results in cellular alterations that are implicated in aging and age-associated diseases. Here, we report that brief, low-level oxidative exposure leads to long-term elevation of cellular reactive oxygen species (ROS) levels and oxidative damage in human skin fibroblasts. Elevated ROS impairs the transforming growth factor-β (TGF-β) pathway, through reduction of type II TGF-β receptor (TβRII) and SMAD3 protein levels. This impairment results in reduced expression of connective tissue growth factor (CTGF/CCN2) and type I collagen, which are regulated by TGF-β. Restoration of TβRII and SMAD3 together, but not separately, reinstates TGF-β signaling and increases CTGF/CCN2 and type I collagen levels. Treatment with the anti-oxidant N-acetylcysteine reduces ROS elevation and normalizes TGF-β signaling and target gene expression. These data reveal a novel linkage between limited oxidant exposure and altered cellular redox homeostasis that results in impairment of TGF-β signaling. This linkage provides new insights regarding the mechanism by which aberrant redox homeostasis is coupled to decline of collagen production, a hallmark of human skin aging.

Aging-associated oxidative stress leads to decrease in IAS tone via RhoA/ROCK downregulation

Internal anal sphincter (IAS) tone plays an important role in rectoanal incontinence (RI). IAS tone may be compromised during aging, leading to RI in certain patients. We examined the influence of oxidative stress in the aging-associated decrease in IAS tone (AADI). Using adult (4-6 mo old) and aging (24-30 mo old) rats, we determined the effect of oxidative stress on IAS tone and the regulatory RhoA/ROCK signal transduction cascade. We determined the effect of the oxidative stress inducer LY83583, which produces superoxide anions (O2 (·-)), on basal and stimulated IAS tone before and after treatment of intact smooth muscle strips and smooth muscle cells with the O2 (·-) scavenger SOD. Our data showed that AADI was associated with a decrease in RhoA/ROCK expression at the transcriptional and translational levels. Oxidative stress with a LY83583-mediated decrease in IAS tone and relaxation of IAS smooth muscle cells was associated with a decrease in RhoA/ROCK signal transduction, which was reversible by SOD. In addition, LY83583 caused a significant decrease in IAS contraction produced by the RhoA activator and a known RhoA/ROCK agonist, U46619, that was also reversible by SOD. The inhibitory effects of LY83583 and the ROCK inhibitor Y27632 on the U46619-induced increase in IAS tone were similar. We conclude that an increase in oxidative stress plays an important role in AADI in the elderly and may be one of the underlying mechanisms of RI in certain aging patients.

Targeting the Renin-angiotensin system combined with an antioxidant is highly effective in mitigating radiation-induced lung damage

PURPOSE

To investigate the outcome of suppression of the renin angiotensin system using captopril combined with an antioxidant (Eukarion [EUK]-207) for mitigation of radiation-induced lung damage in rats.

METHODS AND MATERIALS

The thoracic cavity of female Sprague-Dawley rats was irradiated with a single dose of 11 Gy. Treatment with captopril at a dose of 40 mg/kg/d in drinking water and EUK-207 given by subcutaneous injection (8 mg/kg daily) was started 1 week after irradiation (PI) and continuing until 14 weeks PI. Breathing rate was monitored until the rats were killed at 32 weeks PI, when lung fibrosis was assessed by lung hydroxyproline content. Lung levels of the cytokine transforming growth factor-β1 and macrophage activation were analyzed by immunohistochemistry. Oxidative DNA damage was assessed by 8-hydroxy-2-deoxyguanosine levels, and lipid peroxidation was measured by a T-BARS assay.

RESULTS

The increase in breathing rate in the irradiated rats was significantly reduced by the drug treatments. The drug treatment also significantly decreased the hydroxyproline content, 8-hydroxy-2-deoxyguanosine and malondialdehyde levels, and levels of activated macrophages and the cytokine transforming growth factor-β1 at 32 weeks. Almost complete mitigation of these radiation effects was observed by combining captopril and EUK-207.

CONCLUSION

Captopril and EUK-207 can provide mitigation of radiation-induced lung damage out to at least 32 weeks PI after treatment given 1-14 weeks PI. Overall the combination of captopril and EUK-207 was more effective than the individual drugs used alone.

Bisphenol A induces oxidative stress-associated DNA damage in INS-1 cells

Bisphenol A (BPA), an endocrine disruptor, is widely used to manufacture polycarbonate plastic and epoxy resins. Many studies have demonstrated that BPA can play a role in reproductive toxicity and affect the normal metabolic function. Recent research has shown that BPA can influence the function of pancreatic islets. In this study, our aim is to assess the DNA damage induced by BPA and to clarify the mechanism, by use of rat insulinoma INS-1 cells. INS-1 cells were exposed to different doses of BPA (0, 25, 50, 100 μM). We conducted the single-cell gel electrophoresis (SCGE) assay to measure DNA damage, and studied proteins such as p53 and p-Chk2 (T68) by Western blotting, in order to verify the (geno)toxicity of BPA. Moreover, we examined intracellular reactive oxygen species (ROS) and glutathione (GSH) to discuss the possible mechanism of DNA damage. The results show that BPA caused an increased in DNA strand-breaks along with greater DNA migration from the nucleus into the comet tail. The expression of DNA damage-associated proteins (p53 and p-Chk2 (T68)) was significantly increased. The exposure to various doses of BPA caused a significant increase in intracellular ROS and a significant reduction in the level of GSH. N-Acetyl cysteine, an inhibitor of intracellular ROS formation, can significantly reduce the generation of intracellular reactive oxygen.