Increased expression of uncoupling protein 2 in HepG2 cells attenuates oxidative damage and apoptosis

The Impact of Niclosamide Exposure on the Activity of Antioxidant Enzymes and the Expression of Glucose and Lipid Metabolism Genes in Black Carp (Mylopharyngodon piceus)

Niclosamide (NIC, 2',5-dichloro-4'-nitrosalicylanilide) is a salicylanilide molluscicide, and the extensive utilization and environmental pollution associated with NIC engender a potential hazard to both human health and the wellbeing of aquatic organisms. However, the mechanism of the chronic toxicity of NIC at environmentally relevant concentrations in terms of oxidative stress, metabolic disorder, and barrier functions in black carp (Mylopharyngodon piceus) is unknown. Therefore, healthy juvenile black carp (M. piceus) (average weight: 38.2 ± 2.5 g) were exposed to NIC at an environmentally realistic concentration (0, 10, and 50 μg/L) for 28 days. The findings of this study indicate that exposure to NIC resulted in reductions in weight gain, decreased activity of antioxidant enzymes, and increased expression of the Nrf2 gene. Furthermore, the liver demonstrated a greater accumulation of NIC than that in the gut and gills, as determined with a chemical analysis. Additionally, NIC exposure led to a significant reduction in ATP content and the activity of Na+/K+-ATPase and Ca2+/Mg2+-ATPase in the gut. Meanwhile, exposure to NIC resulted in a decrease in the liver glucose (Glu) level, gut cholesterol (CHO), and glycogen (Gln) and triglyceride (TG) content in all examined tissues. Conversely, it led to an increase in tissue lactic acid (LA) and acetyl-CoA levels, as well as LDH activity. Furthermore, NIC exposure at environmentally relevant concentrations demonstrated an upregulation in the expression of genes associated with glycolysis, such as PK and GK, while concurrently downregulating the gluconeogenesis gene G6Pase. Additionally, NIC exhibited an upregulation in the expression of genes related to β-oxidation, such as CPT1 and ACOX, while downregulating genes involved in triglyceride synthesis, including SREBP1, GPAT, FAS, and ACC1. Moreover, NIC facilitated fatty acid transportation through the overexpression of FATP and Fat/cd36. These results suggest that chronic exposure to NIC is associated with oxidative stress, compromised barrier function, and metabolic disorder. Moreover, these results underscore the significance of assessing the potential consequences of NIC for black carp and aquatic environments for aquaculture.

Mechanisms Underlying the Protective Effect of Maternal Zinc (ZnSO4 or Zn-Gly) against Heat Stress-Induced Oxidative Stress in Chicken Embryo

Environmental factors such as high temperature can cause oxidative stress and negatively affect the physiological status and meat quality of broiler chickens. The study was conducted to evaluate the effects of dietary maternal Zn-Gly or ZnSO4 supplementation on embryo mortality, hepatocellular mitochondrial morphology, liver antioxidant capacity and the expression of related genes involved in liver oxidative mechanisms in heat-stressed broilers. A total of 300 36-week-old Lingnan Yellow broiler breeders were randomly divided into three treatments: (1) control (basal diet, 24 mg zinc/kg); (2) inorganic ZnSO4 group (basal diet +80 mg ZnSO4/kg); (3) organic Zn-Gly group (basal diet +80 mg Zn-Gly/kg). The results show that maternal zinc alleviated heat stress-induced chicken embryo hepatocytes’ oxidative stress by decreasing the content of ROS, MDA, PC, 8-OHdG, and levels of HSP70, while enhancing T-SOD, T-AOC, CuZn-SOD, GSH-Px, CTA activities and the content of MT. Maternal zinc alleviated oxidative stress-induced mitochondrial damage in chick embryo hepatocytes by increasing mitochondrial membrane potential and UCP gene expression; and Caspase-3-mediated apoptosis was alleviated by increasing CuZn-SOD and MT gene expression and decreasing Bax gene expression and reducing the activity of caspase 3. Furthermore, maternal zinc treatment significantly increased Nrf2 gene expression. The results above suggest that maternal zinc can activate the Nrf2 signaling pathway in developing chick embryos, enhance its antioxidant function and reduce the apoptosis-effecting enzyme caspase-3 activities, thereby slowing oxidative stress injury and tissue cell apoptosis.

Breast cancer growth and proliferation is suppressed by the mitochondrial targeted furazano[3,4-b]pyrazine BAM15

BACKGROUND

Enhanced metabolic plasticity and diversification of energy production is a hallmark of highly proliferative breast cancers. This contributes to poor pharmacotherapy efficacy, recurrence, and metastases. We have previously identified a mitochondrial-targeted furazano[3,4-b]pyrazine named BAM15 that selectively reduces bioenergetic coupling efficiency and is orally available. Here, we evaluated the antineoplastic properties of uncoupling oxidative phosphorylation from ATP production in breast cancer using BAM15.

METHODS

The anticancer effects of BAM15 were evaluated in human triple-negative MDA-MB-231 and murine luminal B, ERα-negative EO771 cells as well as in an orthotopic allograft model of highly proliferative mammary cancer in mice fed a standard or high fat diet (HFD). Untargeted transcriptomic profiling of MDA-MB-231 cells was conducted after 16-h exposure to BAM15. Additionally, oxidative phosphorylation and electron transfer capacity was determined in permeabilized cells and excised tumor homogenates after treatment with BAM15.

RESULTS

BAM15 increased proton leak and over time, diminished cell proliferation, migration, and ATP production in both MDA-MB-231 and EO771 cells. Additionally, BAM15 decreased mitochondrial membrane potential, while inducing apoptosis and reactive oxygen species accumulation in MDA-MB-231 and EO771 cells. Untargeted transcriptomic profiling of MDA-MB-231 cells further revealed inhibition of signatures associated with cell survival and energy production by BAM15. In lean mice, BAM15 lowered body weight independent of food intake and slowed tumor progression compared to vehicle-treated controls. In HFD mice, BAM15 reduced tumor growth relative to vehicle and calorie-restricted weight-matched controls mediated in part by impaired cell proliferation, mitochondrial respiratory function, and ATP production. LC-MS/MS profiling of plasma and tissues from BAM15-treated animals revealed distribution of BAM15 in adipose, liver, and tumor tissue with low abundance in skeletal muscle.

CONCLUSIONS

Collectively, these data indicate that mitochondrial uncoupling may be an effective strategy to limit proliferation of aggressive forms of breast cancer. More broadly, these findings highlight the metabolic vulnerabilities of highly proliferative breast cancers which may be leveraged in overcoming poor responsiveness to existing therapies.

Oxidative Stress-A Key Player in the Course of Alcohol-Related Liver Disease

Oxidative stress is known to be an inseparable factor involved in the presentation of liver disorders. Free radicals interfere with DNA, proteins, and lipids, which are crucial in liver metabolism, changing their expression and biological functions. Additionally, oxidative stress modifies the function of micro-RNAs, impairing the metabolism of hepatocytes. Free radicals have also been proven to influence the function of certain transcriptional factors and to alter the cell cycle. The pathological appearance of alcohol-related liver disease (ALD) constitutes an ideal example of harmful effects due to the redox state. Finally, ethanol-induced toxicity and overproduction of free radicals provoke irreversible changes within liver parenchyma. Understanding the underlying mechanisms associated with the redox state in the course of ALD creates new possibilities of treatment for patients. The future of hepatology may become directly dependent on the effective action against reactive oxygen species. This review summarizes current data on the redox state in the natural history of ALD, highlighting the newest reports on this topic.

Genipin enhances the antitumor effect of elesclomol in A549 lung cancer cells by blocking uncoupling protein-2 and stimulating reactive oxygen species production

The uncoupling protein-2 (UCP2) serves a role in tumor aggressiveness and anticancer resistance, which is considered to be associated with its ability to attenuate reactive oxygen species (ROS) production. We hypothesized that UCP2 may protect cancer cells from elesclomol-induced cytotoxicity, and that this may be overcome by blocking UCP2 function with genipin. In A549 lung cancer cells that exhibited high UCP2 expression, treatment with elesclomol alone induced limited changes in glucose uptake, ROS production and cell survival. By contrast, both UCP2 knockdown and genipin treatment mildly reduced glucose uptake, increased ROS production and decreased cell survival. Combining genipin and elesclomol further reduced glucose uptake and increased cellular and mitochondrial ROS production. Moreover, co-treatment with genipin and elesclomol reduced the colony forming capacity to 50.6±7.4% and the cell survival to 42.0±3.4% of that in the control cells (both P<0.001). Suppression of cell survival by treatment with elesclomol and genipin was enhanced in the presence of an exogenous ROS inducer and attenuated by a ROS scavenger. The cytotoxic effects of combining genipin and elesclomol were accompanied by reduced mitochondrial membrane potential and occurred through apoptosis as demonstrated by Annexin V assay and increased protein cleavage of PARP and caspase-3. Finally, in an A549 ×enograft mouse model, tumor growth was only modestly retarded by treatment with elesclomol or genipin alone, but was markedly suppressed by combining the two drugs compared with that in the control group (P=0.008). Therefore, high UCP2 expression may limit the antitumor effect of elesclomol by attenuating ROS responses, and this may be overcome by co-treatment with genipin; combining elesclomol and genipin may be an effective strategy for treating cancers with high UCP2.

Efficacy and mechanism of combination of oxaliplatin with PKM2 knockdown in colorectal cancer

M2 isomer of pyruvate kinase (PKM2), a key enzyme in aerobic glycolysis, is closely related to cancer development and progression. Suppression of PKM2 exhibits synergistic effects with docetaxel in lung cancer, but the therapeutic potential in colorectal cancer (CRC) is unclear. The aim of the present study was to explore the synergic effects and mechanism of knocking down PKM2 combined with oxaliplatin (a chemosensitizer) treatment in two CRC cell lines (HCT116 and DLD1). The PKM2 gene was initially knocked down using small interfering (si)RNAs (si155 and si156). Subsequently, the effects of PKM2-siRNAs and oxaliplatin, on CRC cells were determined using MTS, cell cycle analysis and apoptosis assays. The mechanism of targeting PKM2 was explored by detecting glucose uptake, lactate secretion fluxes, and the levels of glucose-6-phosphate dehydrogenase (G6PD) mRNA, glutathione (GSH) and reactive oxygen species (ROS). Cell viability in the experimental groups (PKM2-siRNAs, oxaliplatin, PKM2-siRNAs + oxaliplatin) was significantly reduced compared with the control group, and combination treatments (PKM2-siRNAs + oxaliplatin) were more effective than single treatments (PKM2-siRNAs and oxaliplatin only groups). Similar results were observed with the apoptosis assay. The combination groups showed synergistic effects compared with both single treatment groups. Furthermore, glucose uptake and lactate secretion and mRNA levels of G6PD and PKM2 were decreased after PKM2 knockdown in the PKM2-siRNAs and PKM2-siRNAs + oxaliplatin groups. The GSH levels in the PKM2-siRNAs group was significantly lower compared with the negative control group. The ROS levels in the PKM2-siRNAs groups were also significantly increased. The combination of PKM2-siRNAs and oxaliplatin had synergistic effects on CRC cells (HCT116 and DLD1). PKM2 silencing may alter energy metabolism in cancer cells and initiate ROS-induced apoptosis after downregulation of the pentose phosphate pathway by PKM2-siRNAs.

Oxidative stress in alcohol-related liver disease

Alcohol consumption is one of the leading causes of the global burden of disease and results in high healthcare and economic costs. Heavy alcohol misuse leads to alcohol-related liver disease, which is responsible for a significant proportion of alcohol-attributable deaths globally. Other than reducing alcohol consumption, there are currently no effective treatments for alcohol-related liver disease. Oxidative stress refers to an imbalance in the production and elimination of reactive oxygen species and antioxidants. It plays important roles in several aspects of alcohol-related liver disease pathogenesis. Here, we review how chronic alcohol use results in oxidative stress through increased metabolism via the cytochrome P450 2E1 system producing reactive oxygen species, acetaldehyde and protein and DNA adducts. These trigger inflammatory signaling pathways within the liver leading to expression of pro-inflammatory mediators causing hepatocyte apoptosis and necrosis. Reactive oxygen species exposure also results in mitochondrial stress within hepatocytes causing structural and functional dysregulation of mitochondria and upregulating apoptotic signaling. There is also evidence that oxidative stress as well as the direct effect of alcohol influences epigenetic regulation. Increased global histone methylation and acetylation and specific histone acetylation inhibits antioxidant responses and promotes expression of key pro-inflammatory genes. This review highlights aspects of the role of oxidative stress in disease pathogenesis that warrant further study including mitochondrial stress and epigenetic regulation. Improved understanding of these processes may identify novel targets for therapy.

Uncoupling protein-2 regulates M1 macrophage infiltration of gingiva with periodontitis

Periodontitis is an inflammatory disease accompanied by alveolar bone loss. Moreover, M1 macrophages play a critical role in the development of periodontal disease. Uncoupling protein-2 (UCP2) is a mitochondrial transporter protein that controls M1 macrophage activation by modulating reactive oxygen species (ROS) production. We investigated the role of UCP2 in M1 macrophage infiltration in gingival tissues with periodontitis. We found that the expression of UCP2 was upregulated in M1 macrophages infiltrating human periodontal tissues with periodontitis. Macrophage-specific knockout of UCP2 could increase the infiltration of macrophage and exacerbate inflammatory response in a mouse gingiva affected with periodontitis, induced by Porphyromonas gingivalis-LPS (Pg-LPS) injection. The loss of UCP2 may contribute to the enhanced abilities of proliferation, migration, pro-inflammatory cytokine secretion, and ROS production in Pg-LPS-treated macrophages. Our results indicate that UCP2 has an important role in M1 macrophage polarization in the periodontal tissue with periodontitis. It might be helpful to provide theoretical basis for design of new therapeutic strategies for periodontitis.

Synergistic activation of mitochondrial metabolism and the glutathione redox couple protects HepG2 hepatocarcinoma cells from palmitoylcarnitine-induced stress

Fatty acid stress can have divergent effects in various cancers. We explored how metabolic and redox flexibility in HepG2 hepatocarcinoma cells mediates protection from palmitoylcarnitine. HepG2 cells, along with HCT 116 and HT29 colorectal cancer cells were incubated with 100 μM palmitoylcarnitine for up to 48 h. Mitochondrial H₂O₂ emission, glutathione, and cell survival were assessed in HT29 and HepG2 cells. 100 μM palmitoylcarnitine promoted early growth in HepG2 cells by ~8% after 48 h versus decreased cell survival observed in HT29 and HCT 116 cells. Palmitoylcarnitine increased mitochondrial respiration at physiological and maximal concentrations of ADP, while lowering cellular lactate content in HepG2 cells, suggesting a switch to mitochondrial metabolism. HepG2 cell growth was associated with an early increase in H₂O₂ emission by 10 min, followed by a decrease in H₂O₂ at 24 h that corresponded with increased glutathione content, suggesting a redox-based compensatory mechanism. In contrast, abrogation of HT29 cell proliferation was related to decreased mitochondrial respiration (likely due to cell death) and decreased glutathione. Concurrent glutathione depletion with BSO prevented palmitoylcarnitine-induced growth in HepG2 cells, indicating that glutathione was critical for promoting growth following palmitoylcarnitine. Inhibiting UCP2 with genipin sensitized HepG2 cells to palmitoylcarnitine, suggesting that activation of UCP2 may be a 2nd redox-based mechanism conferring protection. These findings suggest that HepG2 cells possess inherent metabolic and redox flexibility relative to HT29 cells that confers protection from palmitoylcarnitine-induced stress via adaptive increases in mitochondrial respiratory control, glutathione buffering, and induction of UCP2.

Mitochondrial determinants of chemoresistance

Chemoresistance constitute nowadays the major contributor to therapy failure in most cancers. There are main factors that mitigate cell response to therapy, such as target organ, inherent sensitivity to the administered compound, its metabolism, drug efflux and influx or alterations on specific cellular targets, among others. We now know that intrinsic properties of cancer cells, including metabolic features, substantially contribute to chemoresistance. In fact, during the last years, numerous reports indicate that cancer cells resistant to chemotherapy demonstrate significant alterations in mitochondrial metabolism, membrane polarization and mass. Metabolic activity and expression of several mitochondrial proteins are modulated under treatment to cope with stress, making these organelles central players in the development of resistance to therapies. Here, we review the role of mitochondria in chemoresistant cells in terms of metabolic rewiring and function of key mitochondria-related proteins.

Oxidative stress and mitochondrial uncoupling protein 2 expression in hepatic steatosis induced by exposure to xenobiotic DDE and high fat diet in male Wistar rats

Oxidative stress plays a key role in steatohepatitis induced by both xenobiotic agents and high fat diet (HFD). The present study aimed to evaluate hepatic oxidative stress and anti-oxidant systems response in rats exposed to HFD and/or non-toxic dose of dichlorodiphenyldichloroethylene (DDE), the first metabolite of dichlorodiphenyltrichloroethane. Groups of 8 rats were so treated for 4 weeks: 1- standard diet (N group); 2- standard diet plus DDE (10 mg/kg b.w.) (N+DDE group); 3- HFD (D group); 4- HFD plus DDE (D+DDE group). Oxidative stress was analyzed by determining malondialdehyde as lipid peroxidation product, while the anti-oxidant systems were evaluating by measuring the levels of the principal cytosolic and mitochondrial antioxidant proteins and enzymes, namely superoxide dismutase 1 and 2 (SOD1, SOD2), glutathione peroxidase 1 (GPx1) and uncoupling protein 2 (UCP2) involved in the control of hepatic reactive oxygens species (ROS) accumulation. The results showed malondialdehyde accumulation in livers of all groups, confirming the pro-oxidant effects of both HFD and DDE, but with a greater effect of DDE in absence of HFD. In addition, we found different levels of the analyzed anti-oxidant systems in the different groups. DDE mainly induced UCP2 and SOD2, while HFD mainly induced GPx1. Noteworthy, in the condition of simultaneous exposure to DDE and HFD, the anti-oxidant response was more similar to the one induced by HFD than to the response induced by DDE. Present findings confirmed that both HFD and xenobiotic exposure induced hepatic oxidative stress and showed that the anti-oxidant defense response was not the same in the diverse groups, suggesting that UCP2 induction could be an adaptive response to limit excessive ROS damage, mainly in condition of xenobiotic exposure.

Metabolic aspects in NAFLD, NASH and hepatocellular carcinoma: the role of PGC1 coactivators

Alterations of hepatic metabolism are critical to the development of liver disease. The peroxisome proliferator-activated receptor-γ coactivators (PGC1s) are able to orchestrate, on a transcriptional level, different aspects of liver metabolism, such as mitochondrial oxidative phosphorylation, gluconeogenesis and fatty acid synthesis. As modifications affecting both mitochondrial and lipid metabolism contribute to the initiation and/or progression of liver steatosis, nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC), a link between disrupted PGC1 pathways and onset of these pathological conditions has been postulated. However, despite the large quantity of studies, the scenario is still not completely understood, and some issues remain controversial. Here, we discuss the roles of PGC1s in healthy liver and explore their contribution to the pathogenesis and future therapy of NASH and HCC.

Increased fucoxanthin in Chaetoceros calcitrans extract exacerbates apoptosis in liver cancer cells via multiple targeted cellular pathways

•

Both treatments inhibited cancer proliferation in a time and dose dependent manner.

•

FxRF treatment were effective in inducing apoptosis in HepG2 cells than crude extract.

•

Treatments stimulated regulation in cell signalling, apoptotic and antioxidant genes.

In this study, anti-proliferative effects of C. calcitrans extract and its fucoxanthin rich fraction (FxRF) were assessed on human liver HepG2 cancer cell line. Efficacy from each extract was determined by cytotoxicity assay, morphological observation, and cell cycle analysis. Mechanisms of action observed were evaluated using multiplex gene expression analysis. Results showed that CME and FxRF induced cytotoxicity to HepG2 cells in a dose and time-dependent manner. FxRF (IC₅₀: 18.89 μg.mL⁻¹) was found to be significantly more potent than CME (IC₅₀: 87.5 μg.mL⁻¹) (p < 0.05). Gene expression studies revealed that anti-proliferative effects in treated cells by C. calcitrans extracts were mediated partly through the modulation of numerous genes involved in cell signaling (AKT1, ERK1/2, JNK), apoptosis (BAX, BID, Bcl-2, APAF, CYCS) and oxidative stress (SOD1, SOD2, CAT). Overall, C. calcitrans extracts demonstrated effective intervention against HepG2 cancer cells where enhanced apoptotic activities were observed with increased fucoxanthin content.

Expression of UCP2 is associated with sensitivity to platinum-based chemotherapy for ovarian serous carcinoma

The standard treatment for ovarian serous carcinoma is maximum debulking surgery and platinum-based chemotherapy. Despite the high response rate for chemotherapy, the majority of patients will be resistant to first-line agents and the prognosis for these patients is particularly poor. Currently there are no reliable methods to determine or predict platinum resistance. Uncoupling protein 2 (UCP2) is widely expressed in cancer cells and regulates the production of mitochondrial reactive oxygen species (ROS). A reduction in ROS is associated with carcinogenesis and chemoresistance. Downregulation of UCP2 significantly causes increased cell death following chemotherapy. The present study investigated the association between UCP2 expression and platinum sensitivity. The study included 54 patients with ovarian serous carcinoma (FIGO stages III and IV) who were treated at Osaka City University Hospital between January 2005 and December 2012. Patients were divided into a platinum-sensitive group (n=27) and platinum-resistant group (n=27) based on the platinum-free interval, which was calculated from the time of last platinum administration to the time of recurrence. UCP2 expression in human ovarian serous carcinoma cells was inhibited by genipin, and changes in carboplatin sensitivity were examined. The UCP2 weighted score was lower in the platinum-sensitive group than in the platinum resistant-group (P=0.005). In addition, patients in the low UCP2 expression group were more sensitive to platinum-based chemotherapy than those in the high UCP2 expression group (P=0.001). Sensitivity to carboplatin was significantly increased when UCP2 was inhibited in human ovarian serous carcinoma cells in vitro. UCP2 expression may be a predictive marker of the efficacy of platinum-based chemotherapy for patients with ovarian serous carcinoma.

Plant-Derived Anticancer Agents: Lessons from the Pharmacology of Geniposide and Its Aglycone, Genipin

For centuries, plants have been exploited by mankind as sources of numerous cancer chemotherapeutic agents. Good examples of anticancer compounds of clinical significance today include the taxanes (e.g., taxol), vincristine, vinblastine, and the podophyllotoxin analogues that all trace their origin to higher plants. While all these drugs, along with the various other available therapeutic options, brought some relief in cancer management, a real breakthrough or cure has not yet been achieved. This critical review is a reflection on the lessons learnt from decades of research on the iridoid glycoside geniposide and its aglycone, genipin, which are currently used as gold standard reference compounds in cancer studies. Their effects on tumour development (carcinogenesis), cancer cell survival, and death, with particular emphasis on their mechanisms of actions, are discussed. Particular attention is also given to mechanisms related to the dual pro-oxidant and antioxidant effects of these compounds, the mitochondrial mechanism of cancer cell killing through reactive oxygen species (ROS), including that generated through the uncoupling protein-2 (UCP-2), the inflammatory mechanism, and cell cycle regulation. The implications of various studies for the evaluation of glycosidic and aglycone forms of natural products in vitro and in vivo through pharmacokinetic scrutiny are also addressed.

UCP2 expression may represent a predictive marker of neoadjuvant chemotherapy effectiveness for locally advanced uterine cervical cancer

Concurrent chemoradiotherapy is the standard treatment for locally advanced uterine cervical cancer. However, effective neoadjuvant chemotherapy (NAC) can reduce tumor size and facilitate hysterectomy for locally advanced uterine cervical cancer. NAC treatment could improve the prognosis of patients with locally advanced cervical cancer. However, if NAC is ineffective, radiotherapy must be pursued. This causes a delay in initiating the core treatment and results in a worse prognosis. Therefore, the identification of predictive markers of whether NAC is likely to be effective for the treatment of locally advanced uterine cervical cancer could improve patient prognosis. Uncoupling protein 2 (UCP2) is broadly expressed in cancer cells, and suppresses mitochondrial reactive oxygen species (ROS) production. UCP2 contributes to both carcinogenesis and chemoresistance by reducing ROS. Downregulation of UCP2 results in significantly increased cell death following chemotherapy. The present study investigated the association between UCP2 expression and NAC effectiveness. A total of 58 patients with locally advanced uterine cervical cancer (stage IIIA or IIIB) treated at Osaka City University Hospital between April 1995 and March 2010 were examined. Tumor tissue samples were obtained by punch biopsy prior to NAC. UCP2 expression was examined immunohistochemically and scored using a weighted scoring system. Patients were divided into NAC effective (n=34) and ineffective (n=24) groups. Furthermore, UCP2 expression in human uterine cervical cancer cells was inhibited by genipin, and changes in cisplatin sensitivity were examined. UCP2 weighted score was higher in the NAC ineffective group than in the NAC effective group (P=0.038). Additionally, the low UCP2 expression group was more sensitive to NAC than the high UCP2 expression group (P=0.041). Sensitivity to cisplatin was significantly increased when UCP2 was inhibited in human uterine cervical cancer cells in vitro. UCP2 expression may become a predictive marker of whether NAC is effective for patients with locally advanced uterine cervical cancer, which could improve patient prognosis.

Effect of HSP27 and Cofilin in the injury of hypoxia/reoxygenation on hepatocyte membrane F-actin microfilaments

Hypoxia-reoxygenation (H/R) injury hepatocyte models were established to simulate the ischemia/reperfusion injury of transplanted organ. Through the study of the molecular mechanism of H/R on the F-actin damage of the liver cytomembrane, the mechanism of F-actin damage induced by ischemia and reperfusion was studied from the level of cell and molecule.The hypoxic environment of cells in vitro was simulated by chemical hypoxia agent CoCl2. Liver cells were detected by MTT, H/R group was subdivided into 3 subgroups: H/R 2, 4, and 6 h. Changes of cell shape and the growth state, apoptosis, ultrastructural changes, and the changes in F-actin microfilament content were observed. Heat shock protein 27 (HSP27), Cofilin, and F-actin gene and protein levels were determined by real-time polymerase chain reaction and western blot assay, respectively.Cells showed circular adherence growth under normal circumstances, while the spindle cells and shedding cells were significantly increased in H/R groups. Apoptosis cells in H/R group were increased significantly with the extension of hypoxia time. The number of endoplasmic reticulum was decreased significantly in the H/R group, the mitochondrion hydropic was degenerated and the glycogen was disappeared. The F-actin fibers in the H/R group were disordered, the morphology of the fibers was obviously decreased, and the fluorescence staining decreased obviously (P < .05). The transcription and expression levels of HSP27, Cofilin, and F-actin were significantly lower than those in the control group (P < .05).These results demonstrate that H/R can affect the correct assembly of F-actin microfilaments and weakens the normal cycle of F-actin microfilaments through inhibiting the protein expression and gene transcription of HSP27 and Cofilin in hepatocytes, thereby changing the skeleton of F-actin microfilaments.

Mitochondrial Uncoupling Protein 2 in human cumulus cells is associated with regulating autophagy and apoptosis, maintaining gap junction integrity and progesterone synthesis

To explore the roles of mitochondrial Uncoupling Protein 2 (UCP2) in cumulus cells (CCs), human CCs were cultured in vitro, and the UCP2 was inhibited by treatment with Genipin, a special UCP inhibitor, or by RNA interference targeting UCP2. No significant differences in adenosine triphosphate levels and the ratio of ADP/ATP were observed after UCP2 inhibition. UCP2 inhibition caused a significant increase in cellular oxidative damage, which was reflected in alterations to several key parameters, including reactive oxygen species (ROS) and lipid peroxidation levels and the ratio of reduced GSH to GSSG. UCP2 blocking resulted in an obvious increase in active Caspase-3, accompanied by the decline of proactive Caspase-3 and a significant increase in the LC3-II/LC3-I ratio, suggesting that UCP2 inhibition triggered cellular apoptosis and autophagy. The mRNA and protein expression of connexin 43 (Cx43), a gap junction channel protein, were significantly reduced after treatment with Genipin or siRNA. The progesterone level in the culture medium was also significantly decreased after UCP2 inhibition. Our data indicated that UCP2 plays highly important roles in mediating ROS production and regulating apoptosis and autophagy, as well as maintaining gap junction integrity and progesterone synthesis, which suggests that UCP2 is involved in the regulation of follicle development and early embryo implantation and implies that it might serve as a potential biomarker for oocyte quality and competency.

Thermogenic protein UCP1 and UCP3 expression in non-small cell lung cancer: relation with glycolysis and anaerobic metabolism

Uncoupling protein 1 (UCP1) is a proton transporter/channel residing on the inner mitochondrial membrane and is involved in cellular heat production. Using immunohistochemistry, we investigated the expression of UCP1 and UCP3 in a series of 98 patients with non-small cell lung cancer (NSCLC) treated with surgery. Expression patterns were correlated with histopathological variables, prognosis, and the expression of enzymes/proteins related to cell metabolism. Bronchial epithelium did not express UCP1 or UCP3, while alveolar cells strongly expressed UCP1. In tumors, strong expression of UCP1 and UCP3 was recorded in 43/98 (43.8%) and 27/98 (27.6%) cases, respectively. UCP1 was significantly associated with squamous cell histology (P = 0.05), whilst UCP3 was more frequently overexpressed in large cell carcinomas (P = 0.08), and was inversely related to necrosis (P = 0.009). In linear regression analysis, UCP1 was directly related to markers of glycolysis [hexokinase (HXKII) and phosphofructokinase (PFK1)] and anaerobic glucose metabolism [pyruvate dehydrogenase kinase (PDK1) and lactate dehydrogenase (LDH5)]. UCP3 was directly linked with a glucose transporter (GLUT2), monocarboxylate transporter (MCT2), glycolysis markers (PFK1 and aldolase), and with the phosphorylation of pyruvate dehydrogenase (pPDH). Kaplan-Meier survival analysis showed that UCP3 was significantly related to poor prognosis in squamous cell carcinomas (P = 0.04). UCP1 and UCP3 are overexpressed in a large subgroup of non-small cell lung tumors and their expression coincides with increased glucose absorption, intensified glycolysis, and anaerobic glucose usage. Whether UCPs are targets for therapeutic interventions in lung cancer is a hypothesis that demands further investigation.

Omega-9 Oleic Acid Induces Fatty Acid Oxidation and Decreases Organ Dysfunction and Mortality in Experimental Sepsis

Sepsis is characterized by inflammatory and metabolic alterations, which lead to massive cytokine production, oxidative stress and organ dysfunction. In severe systemic inflammatory response syndrome, plasma non-esterified fatty acids (NEFA) are increased. Several NEFA are deleterious to cells, activate Toll-like receptors and inhibit Na⁺/K⁺-ATPase, causing lung injury. A Mediterranean diet rich in olive oil is beneficial. The main component of olive oil is omega-9 oleic acid (OA), a monounsaturated fatty acid (MUFA). We analyzed the effect of OA supplementation on sepsis. OA ameliorated clinical symptoms, increased the survival rate, prevented liver and kidney injury and decreased NEFA plasma levels in mice subjected to cecal ligation and puncture (CLP). OA did not alter food intake and weight gain but diminished reactive oxygen species (ROS) production and NEFA plasma levels. Carnitine palmitoyltransferase IA (CPT1A) mRNA levels were increased, while uncoupling protein 2 (UCP2) liver expression was enhanced in mice treated with OA. OA also inhibited the decrease in 5' AMP-activated protein kinase (AMPK) expression and increased the enzyme expression in the liver of OA-treated mice compared to septic animals. We showed that OA pretreatment decreased NEFA concentration and increased CPT1A and UCP2 and AMPK levels, decreasing ROS production. We suggest that OA has a beneficial role in sepsis by decreasing metabolic dysfunction, supporting the benefits of diets high in monounsaturated fatty acids (MUFA).

MiR-214 increases the sensitivity of breast cancer cells to tamoxifen and fulvestrant through inhibition of autophagy

BACKGROUND

Tamoxifen (TAM) and fulvestrant (FUL) are the major drugs for patients with estrogen receptor-positive (ER(+)) breast cancers. However, the development of endocrine resistance is the impediment for successful treatment. We aimed to explore the mechanisms of endocrine resistance and therapeutic strategy for overcoming resistance against TAM and FUL.

METHODS

Experiments were performed in ER(+) and estrogen/TAM-sensitive MCF7 cells and antiestrogen-resistant MCF7/LCC9 cells. The expression of miR-214 and uncoupling protein 2 (UCP2) was determined by RT-qPCR and Western blot in breast cancer cells and human breast cancer tissue specimens. Cell autophagy was examined by fluorescent probe monodansyl cadaverine (MDC) and GFP-LC3-II-positive punctate identified by confocal microscopy. Apoptotic cells were determined by Annexin V-FITC/PI staining. The potential regulatory target of miR-214 was determined by prediction tool, target protein expression and luciferase reporter assay.

RESULTS

4-OHT/FUL treatment resulted in induction of apoptosis as well as autophagy in breast cancer cells. Autophagy might be the major cause of endocrine resistance to 4-OHT or FUL. MiR-214 increased the sensitivity of breast cancer cells to the 4-OHT/FUL-induced apoptosis through inhibition of autophagy. Importantly, a negative correlation was established between miR-214 and UCP2 in human breast cancer tissue specimens assayed by RT-qPCR. UCP2 was identified to be a direct target of miR-214. Further study in MCF7/LCC9 cells indicated that endocrine resistance might arise from activation of the PI3K-Akt-mTOR pathway, thereby inducing autophagy by overexpression of UCP2.

CONCLUSION

MiR-214 increased the sensitivity of breast cancer cells to TAM and FUL through inhibition of autophagy by targeting UCP2. MiR-214 shows potential as a novel therapeutic strategy for overcoming endocrine resistance in ER(+) breast cancers.

UCP2 inhibition sensitizes breast cancer cells to therapeutic agents by increasing oxidative stress

Modulation of oxidative stress in cancer cells plays an important role in the study of the resistance to anticancer therapies. Uncoupling protein 2 (UCP2) may play a dual role in cancer, acting as a protective mechanism in normal cells, while its overexpression in cancer cells could confer resistance to chemotherapy and a higher survival through downregulation of ROS production. Thus, our aim was to check whether the inhibition of UCP2 expression and function increases oxidative stress and could render breast cancer cells more sensitive to cisplatin (CDDP) or tamoxifen (TAM). For this purpose, we studied clonogenicity, mitochondrial membrane potential (ΔΨm), cell viability, ROS production, apoptosis, and autophagy in MCF-7 and T47D (only the last four determinations) breast cancer cells treated with CDDP or TAM, in combination or without a UCP2 knockdown (siRNA or genipin). Furthermore, survival curves were performed in order to check the impact of UCP2 expression in breast cancer patients. UCP2 inhibition and cytotoxic treatments produced a decrease in cell viability and clonogenicity, in addition to an increase in ΔΨm, ROS production, apoptosis, and autophagy. It is important to note that CDDP decreased UCP2 protein levels, so that the greatest effects produced by the UCP2 inhibition in combination with a cytotoxic treatment, with regard to treatment alone, were observed in TAM+UCP2siRNA-treated cells. Moreover, this UCP2 inhibition caused autophagic cell death, since apoptosis parameters barely increased after UCP2 knockdown. Finally, survival curves revealed that higher UCP2 expression corresponded with a poorer prognosis. In conclusion, UCP2 could be a therapeutic target in breast cancer, especially in those patients treated with tamoxifen.

Metabolic phenotype-microRNA data fusion analysis of the systemic consequences of Roux-en-Y gastric bypass surgery

Background/Objectives:

Bariatric surgery offers sustained marked weight loss and often remission of type 2 diabetes, yet the mechanisms of establishment of these health benefits are not clear.

Subjects/Methods:

We mapped the coordinated systemic responses of gut hormones, the circulating miRNAome and the metabolome in a rat model of Roux-en-Y gastric bypass (RYGB) surgery.

Results:

The response of circulating microRNAs (miRNAs) to RYGB was striking and selective. Analysis of 14 significantly altered circulating miRNAs within a pathway context was suggestive of modulation of signaling pathways including G protein signaling, neurodegeneration, inflammation, and growth and apoptosis responses. Concomitant alterations in the metabolome indicated increased glucose transport, accelerated glycolysis and inhibited gluconeogenesis in the liver. Of particular significance, we show significantly decreased circulating miRNA-122 levels and a more modest decline in hepatic levels, following surgery. In mechanistic studies, manipulation of miRNA-122 levels in a cell model induced changes in the activity of key enzymes involved in hepatic energy metabolism, glucose transport, glycolysis, tricarboxylic acid cycle, pentose phosphate shunt, fatty-acid oxidation and gluconeogenesis, consistent with the findings of the in vivo surgery-mediated responses, indicating the powerful homeostatic activity of the miRNAs.

Conclusions:

The close association between energy metabolism, neuronal signaling and gut microbial metabolites derived from the circulating miRNA, plasma, urine and liver metabolite and gut hormone correlations further supports an enhanced gut-brain signaling, which we suggest is hormonally mediated by both traditional gut hormones and miRNAs. This transomic approach to map the crosstalk between the circulating miRNAome and metabolome offers opportunities to understand complex systems biology within a disease and interventional treatment setting.

Uncoupling protein 2 regulates palmitic acid-induced hepatoma cell autophagy

Mitochondrial uncoupling protein 2 (UCP2) is suggested to have a role in the development of nonalcoholic steatohepatitis (NASH). However, the mechanism remains unclear. Autophagy is an important mediator of many pathological responses. This study aims to investigate the relationship between UCP2 and hepatoma cells autophagy in palmitic acid- (PA-) induced lipotoxicity. H4IIE cells were treated with palmitic acid (PA), and cell autophagy and apoptosis were examined. UCP2 expression, in association with LC3-II and caspase-3, which are indicators of cell autophagy and apoptosis, respectively,was measured. Results demonstrated that UCP2 was associated with autophagy during PA-induced hepatic carcinoma cells injury. Tests on reactive oxygen species (ROS) showed that UCP2 overexpression strongly decreases PA-induced ROS production and apoptosis. Conversely, UCP2 inhibition by genipin or UCP2 mRNA silencing enhances PA-induced ROS production and apoptosis. Autophagy partially participates in this progress. Moreover, UCP2 was associated with ATP synthesis during PA-induced autophagy. In conclusion, increasing UCP2 expression in hepatoma cells may contribute to cell autophagy and antiapoptotic as result of fatty acid injury. Our results may bring new insights for potential NASH therapies.

Diets enriched in trans-11 vaccenic acid alleviate ectopic lipid accumulation in a rat model of NAFLD and metabolic syndrome

Trans11-18:1 (vaccenic acid, VA) is one of the most predominant naturally occurring trans fats in our food chain and has recently been shown to exert hypolipidemic effects in animal models. In this study, we reveal new mechanism(s) by which VA can alter body fat distribution, energy utilization and dysfunctional lipid metabolism in an animal model of obesity displaying features of the metabolic syndrome (MetS). Obese JCR:LA-cp rats were assigned to a control diet that included dairy-derived fat or the control diet supplemented with 1% VA. VA reduced total body fat (-6%), stimulated adipose tissue redistribution [reduced mesenteric fat (-17%) while increasing inguinal fat mass (29%)] and decreased adipocyte size (-44%) versus control rats. VA supplementation also increased metabolic rate (7%) concomitantly with an increased preference for whole-body glucose utilization for oxidation and increased insulin sensitivity [lower HOMA-IR (-59%)]. Further, VA decreased nonalcoholic fatty liver disease activity scores (-34%) and reduced hepatic (-27%) and intestinal (-39%) triglyceride secretion relative to control diet, while exerting differential transcriptional regulation of SREBP1 and FAS amongst other key genes in the liver and the intestine. Adding VA to dairy fat alleviates features of MetS potentially by remodeling adipose tissue and attenuating ectopic lipid accumulation in a rat model of obesity and MetS. Increasing VA content in the diet (naturally or by fortification) may be a useful approach to maximize the health value of dairy-derived fats.

The combination of TRPM8 and TRPA1 expression causes an invasive phenotype in lung cancer

Our recent studies have shown that hypothermic microenvironment promotes tumor progression and that the molecular sensors for cold are the transient receptor potential (TRP) channels TRPM8 and TRPA1. To evaluate the contribution of TRPM8 and TRPA1 to cancer malignancy, we screened cell subpopulations from Lewis lung cancer (LLC) using limiting dilutions and Western blotting. We identified that LLC-1 cells express 3-fold more TRPM8 than TRPA1, LLC-2 cells express TRPM8 at levels similar to TRPA1, and LLC-3 cells express TRPM8 at one-third the level of TRPA1. LLC-2 cells showed greater adhesion, migration, invasiveness and resistance to hypothermia than LLC-1 and LLC-3 cells, although LLC-2 cells had a longer doubling time. TRPM8 or TRPA1 knockdown using siRNA promoted cell proliferation and decreased adhesion and invasiveness in LLC-2 cells. When assessed for UCP2 staining, LLC-1 cells showed increased staining compared to LLC-2 cells, both of which had more UCP2-positive cells than the LLC-3 subpopulation. In an autophagy assay, hypothermia induced substantially less autophagy in LLC-1 cells than in LLC-2 cells, which displayed decreased autophagy compared to LLC-3 cells. Moreover, mice injected with LLC-2 cells had significantly more spontaneous and experimental lung metastases and a shorter overall survival time than mice injected with LLC-1 or LLC-3 cells. Importantly, LLC-2 cells were also more resistant to activated spleen CTL and the chemotherapeutic drug doxorubicin than LLC-1 and LLC-3 cells in vitro. Collectively, our data suggest that TRPM8 induces UCP2 to trigger metabolic transformation, whereas TRPA1 induces autophagy during adverse conditions, and the combination of both genes contributes directly to an invasive phenotype in lung cancer.

Mitochondrial uncoupling protein 2 regulates the effects of paclitaxel on Stat3 activation and cellular survival in lung cancer cells

Growing evidence suggests that Stat3 contributes to chemoresistance. However, the impact of chemotherapy on Stat3 activity is unclear. We found that paclitaxel activated Stat3 in the human lung cancer cell lines PC14PE6AS2 (AS2) and H157, whereas it reduced Stat3 activation in A549 and H460 cells. Pretreatment of AS2 and H157 cells with rotenone, an inhibitor of mitochondrially produced reactive oxygen species (ROS), or carbonyl cyanide p-(trifluoromethoxy)-phenylhydrazone (FCCP), a mitochondrial uncoupler, suppressed the paclitaxel-induced activation of Stat3. Uncoupling protein 2 (UCP-2), located in the inner membrane of the mitochondria, can reduce ROS production in conditions of oxidative stress. UCP-2 protein expression in the four cancer cell lines was higher than that in normal lung epithelial cells (NL-20), but its expression was lower in AS2 and H157 cells relative to A549 and H460 cells. Silencing high UCP-2 expression with small interfering RNA (siRNA) in A549 and H460 cells restored paclitaxel-induced Stat3 activation. In addition, paclitaxel-induced Stat3 activation led to the upregulation of survivin and Mcl-1, which in turn facilitated cell survival. Moreover, the CL1-5 subline had lower UCP-2 expression relative to the parental CL1-0 cells. Treatment with paclitaxel activated Stat3 in CL1-5 but not in CL1-0 cells, whereas in CL1-5 cells, the overexpression of UCP-2 with complementary DNA (cDNA) blocked Stat3 activation. In lung cancer patients, low UCP-2 expression in cancer cells was a predictor of a poor response to chemotherapy. Therefore, UCP-2 modulates the ROS/Stat3 signaling pathway and response to chemotherapy treatment in lung cancer cells. Targeting UCP-2, ROS and Stat3 pathways may improve anticancer therapies.

Effects of the antioxidant drug tempol on renal oxygenation in mice with reduced renal mass

We tested the hypothesis that reactive oxygen species (ROS) contributed to renal hypoxia in C57BL/6 mice with &frac56; surgical reduction of renal mass (RRM). ROS can activate the mitochondrial uncoupling protein 2 (UCP-2) and increase O(2) usage. However, UCP-2 can be inactivated by glutathionylation. Mice were fed normal (NS)- or high-salt (HS) diets, and HS mice received the antioxidant drug tempol or vehicle for 3 mo. Since salt intake did not affect the tubular Na(+) transport per O(2) consumed (T(Na/)Q(O2)), further studies were confined to HS mice. RRM mice had increased excretion of 8-isoprostane F(2α) and H(2)O(2), renal expression of UCP-2 and renal O(2) extraction, and reduced T(Na/)Q(O2) (sham: 20 ± 2 vs. RRM: 10 ± 1 μmol/μmol; P < 0.05) and cortical Po(2) (sham: 43 ± 2, RRM: 29 ± 2 mmHg; P < 0.02). Tempol normalized all these parameters while further increasing compensatory renal growth and glomerular volume. RRM mice had preserved blood pressure, glomeruli, and patchy tubulointerstitial fibrosis. The patterns of protein expression in the renal cortex suggested that RRM kidneys had increased ROS from upregulated p22(phox), NOX-2, and -4 and that ROS-dependent increases in UCP-2 led to hypoxia that activated transforming growth factor-β whereas erythroid-related factor 2 (Nrf-2), glutathione peroxidase-1, and glutathione-S-transferase mu-1 were upregulated independently of ROS. We conclude that RRM activated distinct processes: a ROS-dependent activation of UCP-2 leading to inefficient renal O(2) usage and cortical hypoxia that was offset by Nrf-2-dependent glutathionylation. Thus hypoxia in RRM may be the outcome of NADPH oxidase-initiated ROS generation, leading to mitochondrial uncoupling counteracted by defense pathways coordinated by Nrf-2.

Mitochondrial uncoupling protein-2 deficiency protects steatotic mouse hepatocytes from hypoxia/reoxygenation

Steatotic livers are sensitive to ischemic events and associated ATP depletion. Hepatocellular necrosis following these events may result from mitochondrial uncoupling protein-2 (UCP2) expression. To test this hypothesis, we developed a model of in vitro steatosis using primary hepatocytes from wild-type (WT) and UCP2 knockout (KO) mice and subjected them to hypoxia/reoxygenation (H/R). Using cultured hepatocytes treated with emulsified fatty acids for 24 h, generating a steatotic phenotype (i.e., microvesicular and broad-spectrum fatty acid accumulation), we found that the phenotype of the WT and UCP2 KO were the same; however, cellular viability was increased in the steatotic KO hepatocytes following 4 h of hypoxia and 24 h of reoxygenation; Hepatocellular ATP levels decreased during hypoxia and recovered after reoxygenation in the control and UCP2 KO steatotic hepatocytes but not in the WT steatotic hepatocytes; mitochondrial membrane potential in WT and UCP2 KO steatotic groups was less than control groups but higher than UCP2 KO hepatocytes. Following reoxygenation, lipid peroxidation, as measured by thiobarbituric acid reactive substances, increased in all groups but to a greater extent in the steatotic hepatocytes, regardless of UCP2 expression. These results demonstrate that UCP2 sensitizes steatotic hepatocytes to H/R through mitochondrial depolarization and ATP depletion but not lipid peroxidation.

UCP2 inhibits ROS-mediated apoptosis in A549 under hypoxic conditions

The Crosstalk between a tumor and its hypoxic microenvironment has become increasingly important. However, the exact role of UCP2 function in cancer cells under hypoxia remains unknown. In this study, UCP2 showed anti-apoptotic properties in A549 cells under hypoxic conditions. Over-expression of UCP2 in A549 cells inhibited reactive oxygen species (ROS) accumulation (P<0.001) and apoptosis (P<0.001) compared to the controls when the cells were exposed to hypoxia. Moreover, over-expression of UCP2 inhibited the release of cytochrome C and reduced the activation of caspase-9. Conversely, suppression of UCP2 resulted in the ROS generation (P = 0.006), the induction of apoptosis (P<0.001), and the release of cytochrome C from mitochondria to the cytosolic fraction, thus activating caspase-9. These data suggest that over-expression of UCP2 has anti-apoptotic properties by inhibiting ROS-mediated apoptosis in A549 cells under hypoxic conditions.

Mitochondrial recoupling: a novel therapeutic strategy for cancer?

Recent findings link metabolic transformation of cancer cells to aberrant functions of mitochondrial uncoupling proteins (UCPs). By inducing proton leak, UCPs interfere with mitochondrial synthesis of adenosine 5'-triphosphate, which is also a key determinant of glycolytic pathways. In addition, UCP suppress the generation of superoxide, a byproduct of mitochondrial electron transport and a major source of oxidative stress. The near ubiquitous UCP2 becomes highly abundant in some cancers and may advance metabolic reprogramming, further disrupt tumour suppression, and promote chemoresistance. Here we review current evidence to suggest that inhibition of mitochondrial uncoupling may eliminate these responses and reveal novel anti-cancer strategies.

Mitochondrial uncoupling protein 2 expression in colon cancer and its clinical significance

AIM: To detect the expression of mitochondrial uncoupling protein 2 (UCP2) in colon cancer and analyze the relation between UCP2 expression and clinical pathological features of colon cancer.

METHODS: Fifteen colon tissue samples and 15 its adjacent tissue samples were obtained from colon cancer patients during surgical interventions. UCP2 expression was detected with immunohistochemical method in 10 normal controls, 10 hyperplastic polyp patients, 20 tubular adenoma patients and 78 colon cancer patients. Patients with rectal cancer were excluded. Quantitative reverse transcription polymerase chain reaction and Western blotting were used to detect UCP2 expressions in colon cancer tissue samples and its adjacent tissue samples. Relation between UCP2 expression and clinical pathological features of colon cancer was also analyzed.

RESULTS: The UCP2 mRNA expression level was four-fold higher in colon cancer tissue samples than in its adjacent tissue samples. The UCP2 protein expression level was three-fold higher in colon cancer tissue samples than in its adjacent normal tissue samples. The UCP2 was mainly expressed in cytoplasm. The UCP2 was not expressed in normal colon mucosa. Strong positive staining for UCP2 with a diffuse distribution pattern was identified throughout the mucosa in colon cancer tissue samples with a positive expression rate of 85.9%. The UCP2 expression level was higher in colon cancer tissue samples at clinical stages III and IV than in those at stage I + II. Univariate analysis showed that the high UCP2 expression level was significantly correlated to colon cancer metastasis (hazard ratio = 4.321, confidence interval = 0.035-0.682, P = 0.046).

CONCLUSION: UCP2 is highly expressed in human colon cancer tissue and may be involved in colon cancer metastasis.

Mitochondrial uncoupling inhibits p53 mitochondrial translocation in TPA-challenged skin epidermal JB6 cells

The tumor suppressor p53 is known to be able to trigger apoptosis in response to DNA damage, oncogene activation, and certain chemotherapeutic drugs. In addition to its transcriptional activation, a fraction of p53 translocates to mitochondria at the very early stage of apoptosis, which eventually contributes to the loss of mitochondrial membrane potential, generation of reactive oxygen species (ROS), cytochrome c release, and caspase activation. However, the mitochondrial events that affect p53 translocation are still unclear. Since mitochondrial uncoupling has been suggested to contribute to cancer development, herein, we studied whether p53 mitochondrial translocation and subsequent apoptosis were affected by mitochondrial uncoupling using chemical protonophores, and further verified the results using a siRNA approach in murine skin epidermal JB6 cells. Our results showed that mitochondrial uncoupling blocked p53 mitochondrial translocation induced by 12-O-tetradecanoylphorbol 13-acetate (TPA), a known tumor promoter to induce p53-mediated apoptosis in skin carcinogenesis. This blocking effect, in turn, led to preservation of mitochondrial functions, and eventually suppression of caspase activity and apoptosis. Moreover, uncoupling protein 2 (UCP2), a potential suppressor of ROS in mitochondria, is important for TPA-induced cell transformation in JB6 cells. UCP2 knock down cells showed enhanced p53 mitochondrial translocation, and were less prone to form colonies in soft agar after TPA treatment. Altogether, our data suggest that mitochondrial uncoupling may serve as an important regulator of p53 mitochondrial translocation and p53-mediated apoptosis during early tumor promotion. Therefore, targeting mitochondrial uncoupling may be considered as a novel treatment strategy for cancer.

Genipin-induced inhibition of uncoupling protein-2 sensitizes drug-resistant cancer cells to cytotoxic agents

Uncoupling protein-2 (UCP2) is known to suppress mitochondrial reactive oxygen species (ROS) production and is employed by drug-resistant cancer cells to mitigate oxidative stress. Using the drug-sensitive HL-60 cells and the drug-resistant MX2 subline as model systems, we show that genipin, a UCP2 inhibitor, sensitizes drug-resistant cells to cytotoxic agents. Increased MX2 cell death was observed upon co-treatment with genipin and different doses of menadione, doxorubicin, and epirubicin. DCFH-DA fluorimetry revealed that the increase in MX2 cell death was accompanied by enhanced cellular ROS levels. The drug-induced increase in ROS was linked to genipin-mediated inhibition of mitochondrial proton leak. State 4 and resting cellular respiratory rates were higher in the MX2 cells in comparison to the HL-60 cells, and the increased respiration was readily suppressed by genipin in the MX2 cells. UCP2 accounted for a remarkable 37% of the resting cellular oxygen consumption indicating that the MX2 cells are functionally reliant on this protein. Higher amounts of UCP2 protein were detected in the MX2 versus the HL-60 mitochondria. The observed effects of genipin were absent in the HL-60 cells pointing to the selectivity of this natural product for drug-resistant cells. The specificity of genipin for UCP2 was confirmed using CHO cells stably expressing UCP2 in which genipin induced an ∼22% decrease in state 4 respiration. These effects were absent in empty vector CHO cells expressing no UCP2. Thus, the chemical inhibition of UCP2 with genipin sensitizes multidrug-resistant cancer cells to cytotoxic agents.

Clinical significance of mitochondrial uncoupling protein 2 expression in colon cancer

AIM: To detect the distribution and expression of uncoupling protein 2 (UCP2) and to analyze its relationship with clinicopathological parameters in colon cancer.

METHODS: The distribution of UCP2 in colon cancer, colon adenoma, colon hyperplastic polyps and normal colon tissue was detected by immunohistochemistry. The expression of UCP2 mRNA and protein in colon cancer and tumor-adjacent normal tissue was detected by quantitative RT-PCR and Western blot, respectively. The relationship between UCP2 expression and clinicopathological parameters in colon cancer was then analyzed.

RESULTS: Quantitative RT-PCR and Western blot analyses showed that the expression levels of UCP2 mRNA and protein in cancer tissue were about 4- and 3-fold higher than those in tumor-adjacent normal colon tissue, respectively. UCP2 was mainly localized in the cytoplasm compartment in cancer tissue, but was almost undetectable in normal colon mucosa. The positive rates of UCP2 expression in colon adenocarcinoma, colon adenoma and hyperplastic colonic polyps were 85.9%, 55% and 20%, respectively. The expression level of UCP2 in patients with stage III/IV colon cancer was significantly higher than that in patients with stage I/ II disease. The positive rate of UCP2 expression was higher in colon cancer patients with metastasis than in those without metastasis.

CONCLUSION: The expression level of UCP2 is higher in colon cancer than in normal colon tissue. UCP2 may be involved in tumor progression and metastasis in colon cancer.

Role of uncoupling proteins in cancer

Uncoupling proteins (UCPs) are a family of inner mitochondrial membrane proteins whose function is to allow the re-entry of protons to the mitochondrial matrix, by dissipating the proton gradient and, subsequently, decreasing membrane potential and production of reactive oxygen species (ROS). Due to their pivotal role in the intersection between energy efficiency and oxidative stress, UCPs are being investigated for a potential role in cancer. In this review we compile the latest evidence showing a link between uncoupling and the carcinogenic process, paying special attention to their involvement in cancer initiation, progression and drug chemoresistance.

Uncoupling protein-2 and cancer

Cancer cells respond to unfavorable microenvironments such as nutrient limitation, hypoxia, oxidative stress, and host defense by comprehensive metabolic reprogramming. Mitochondria are linked to this complex adaptive response and emerging evidence indicates that uncoupling protein-2 (UCP2), a mitochondrial inner membrane anion carrier, may contribute to this process. Effects of UCP2 on mitochondrial bioenergetics, redox homeostasis, and oxidant production in cancer cells may modulate molecular pathways of macromolecular biosynthesis, antioxidant defense, apoptosis, cell growth and proliferation, enhancing robustness and promoting chemoresistance. Elucidation of these interactions may identify novel anti-cancer strategies.

Detection of uncoupling protein-2 (UCP2) as a mitochondrial modulator of apoptosis

There is an increasing evidence that uncoupling protein-2 (UCP2), a recently identified molecular sensor and suppressor of mitochondrial reactive oxygen species (ROS), plays an important role in -regulating apoptosis in different cell systems. A great technical difficulty that many groups have encountered is the reliable detection of endogenously or exogenously expressed UCP2 protein. The goal of this -chapter is to introduce the reader to techniques that we have successfully used over the years to detect UCP2 protein in various mouse and human specimens. These techniques include mitochondrial isolation and submitochondrial fractionation followed by Western blotting and UCP2 immunohistochemistry. We find that sample preparation is a key to success and it allows one to produce relevant and important data using commercially available antibodies.

Protection of regenerating liver after partial hepatectomy from carbon tetrachloride hepatotoxicity in rats: roles of mitochondrial uncoupling protein 2 and ATP stores

Uncoupling protein 2 (UCP(2)), an inner mitochondrial membrane protein, can limit the generation of reactive oxygen species (ROS) and protect cells from injuries mediated by oxidative stress. We investigated the effect of upregulation of UCP(2) in the regenerating liver 96 h after 68% partial hepatectomy (PH) on the self-protection of regenerating liver against carbon tetrachloride (CCl(4)) poisoning. Hepatotoxicity was induced in vivo by administering CCl(4) to rats that had undergone PH. After CCl(4) poisoning, the regenerating liver appeared to have less histological damage and lower serum alanine aminotransferase (ALT) levels. Lower malondialdehyde production and higher glutathione contents were also observed in the regenerating liver compared with the sham-operated liver after CCl(4) poisoning. UCP(2) expression was markedly elevated in the regenerating liver, and further increased after CCl(4) intoxication. Mitochondrial membrane potential and adenosine triphosphate stores maintained higher levels in the regenerating liver than in sham-operated liver after CCl(4) intoxication. The results showed that the regenerating liver exhibited a potent ability to resist CCl(4) intoxication, and the autoprotection of regenerating liver might result from reduction of ROS by UCP(2) and maintenance of higher ATP stores.

Mitochondria and energetic depression in cell pathophysiology

Mitochondrial dysfunction is a hallmark of almost all diseases. Acquired or inherited mutations of the mitochondrial genome DNA may give rise to mitochondrial diseases. Another class of disorders, in which mitochondrial impairments are initiated by extramitochondrial factors, includes neurodegenerative diseases and syndromes resulting from typical pathological processes, such as hypoxia/ischemia, inflammation, intoxications, and carcinogenesis. Both classes of diseases lead to cellular energetic depression (CED), which is characterized by decreased cytosolic phosphorylation potential that suppresses the cell's ability to do work and control the intracellular Ca(2+) homeostasis and its redox state. If progressing, CED leads to cell death, whose type is linked to the functional status of the mitochondria. In the case of limited deterioration, when some amounts of ATP can still be generated due to oxidative phosphorylation (OXPHOS), mitochondria launch the apoptotic cell death program by release of cytochrome c. Following pronounced CED, cytoplasmic ATP levels fall below the thresholds required for processing the ATP-dependent apoptotic cascade and the cell dies from necrosis. Both types of death can be grouped together as a mitochondrial cell death (MCD). However, there exist multiple adaptive reactions aimed at protecting cells against CED. In this context, a metabolic shift characterized by suppression of OXPHOS combined with activation of aerobic glycolysis as the main pathway for ATP synthesis (Warburg effect) is of central importance. Whereas this type of adaptation is sufficiently effective to avoid CED and to control the cellular redox state, thereby ensuring the cell survival, it also favors the avoidance of apoptotic cell death. This scenario may underlie uncontrolled cellular proliferation and growth, eventually resulting in carcinogenesis.

Hypoxia, HIF1 and glucose metabolism in the solid tumour

It has been known for many years that cellular metabolism within the solid tumour is markedly different from that of the corresponding normal tissue. The transcription factor hypoxia-inducible factor 1 (HIF1) has been implicated in regulating many of the genes that are responsible for the metabolic difference. However, it remains unclear how this 'aerobic glycolysis', originally described by Otto Warburg, offers tumour cells a growth advantage. As discussed in this Perspective, new data suggests that this metabolic switch may provide a benefit to the tumour not by increasing glycolysis but by decreasing mitochondrial activity.