Oxygen free radical activity in experimental colonic carcinoma

Downregulated miRNA-491-3p accelerates colorectal cancer growth by increasing uMtCK expression

Colorectal carcinoma (CRC) is the second most frequent cancer worldwide. MiR-491-3p, a tumor-suppressive microRNA (miRNA, miR), has been revealed to be abnormally expressed in CRC tissues. Meanwhile, up-regulated ubiquitous mitochondrial creatine kinase (uMtCK) contributes to CRC cell proliferation. Here we aim to explore whether aberrant miR-491-3p expression promotes CRC progression through regulating uMtCK. To this end, miR-491-3p and uMtCK levels were assessed in CRC tissues using quantitative real-time PCR (qRT-PCR). The biological roles of miR-491-3p and uMtCK in regulating CRC growth were evaluated using colony formation assay and mouse Xenograft tumour model. We found that miR-491-3p expression was decreased in CRC tissues compared with matched para-cancerous tissues, whereas uMtCK expression was increased. Functionally, miR-491-3p overexpression repressed SW480 cell growth, whereas miR-491-3p depletion accelerated SW620 cell proliferation and growth. Inversely, uMtCK positively regulated CRC cell proliferation. Mechanistically, miR-491-3p post-transcriptionally downregulated uMtCK expression by binding to 3'-UTR of uMtCK. Consequently, restoring uMtCK expression markedly eliminated the role of miR-491-3p in suppressing CRC growth. Collectively, miR-491-3p functions as a tumour suppressor gene by repressing uMtCK, and may be a potential target for CRC treatment.

Chemoprevention of colon cancer by a synthetic curcumin analog involves amelioration of oxidative stress

The modulating effects of a bisdemethoxycurcumin analog (BDMC-A) on 1,2-dimethylhydrazine (DMH)-induced oxidative stress during colon carcinogenesis was investigated in male Wistar rats. The effects were compared with those of curcumin, a known anticarcinogen. All the animals given a weekly subcutaneous injection of DMH (20 mg/kg body wt.) for 15 weeks developed colon tumors. The colon and intestine administered DMH showed a decrease in lipid peroxidation with a concomitant increase in the activities of GSH-dependent enzymes (glutathione peroxidase, glutathione S-transferase) when compared to untreated control rats. In groups of animals given DMH and BDMC-A no tumors were observed, and the lipid peroxidation as well as the GSH-dependent enzymes showed a pattern similar to that of untreated control rats. We speculate that BDMC-A modulates DMH-induced oxidative stress and offers chemoprevention against colon carcinogenesis, and the modulatory effect is comparable with that of curcumin. Thus, lipid peroxidation and antioxidant status together could be used as markers of colon cancer chemoprevention by BDMC-A.

Role of Rac1 in regulation of NOX5-S function in Barrett's esophageal adenocarcinoma cells

We have shown that a novel NADPH oxidase isoform, NOX5-S, is the major isoform of NADPH oxidases in an esophageal adenocarcinoma (EA) cell line, FLO, and is overexpressed in Barrett's mucosa with high-grade dysplasia. NOX5-S is responsible for acid-induced reactive oxygen species production. In this study, we found that mRNA levels of NOX5-S were significantly higher in FLO EA cells than in the normal human esophageal squamous cell line HET-1A or in a Barrett cell line, BAR-T. The mRNA levels of NOX5-S were also significantly increased in EA tissues. The data suggest that NOX5-S may be important in the development of EA. Mechanisms of functional regulation of NOX5-S are not fully understood. We show that small G protein Rac1 was present in HET-1A cells, BAR-T cells, and EA cell lines FLO and OE33. Rac1 protein levels were significantly higher in FLO and OE33 cells than in HET-1A or BAR-T cells. Knockdown of Rac1 with Rac1 small interfering RNA significantly decreased acid-induced increase in H(2)O(2) production in FLO EA cells. Overexpression of constitutively active Rac1 significantly increased H(2)O(2) production, an increase that was blocked by knockdown of NOX5-S. By immunofluorescence staining and immunoprecipitation, we found that NOX5-S was present in the cytosol of FLO EA cells and colocalized with Rac1 and SERCA1/2 Ca(2+)-ATPase which is located in the endoplasmic reticulum membrane. We conclude that Rac1 may be important in activation of NOX5-S in FLO EA cells.

Long term administration of granulocyte-macrophage colony stimulating factor decreases development of 1-2 dimethylhydrazine-induced colon cancer in rats

BACKGROUND AND OBJECTIVES

The antitumoral activities of granulocyte-macrophage colony stimulating factor (GM-CSF) were shown earlier. In this study, the effects of GM-CSF were investigated on colon cancer induced by 18 weeks of 1-2 dimethylhydrazine (DMH) administration in rats.

METHODS

Four groups received subcutaneous saline (n = 20), 15 mg/kg DMH (n = 30), DMH +6 microg/kg GM-CSF (n = 30), and DMH +12 microg/kg (n = 30) GM-CSF.

RESULTS

The average number of tumors (2.8 vs. 1.5) and mean tumor volume (179 +/- 36 vs. 27 +/- 9 mm(3); means +/- SEM) were reduced in DMH + GM-CSF groups as compared to the DMH group (n = 30, P < 0.01). DMH-induced enhancement of free radicals and lipid peroxidation were decreased in DMH + GM-CSF group (n = 8-12, P < 0.05). The magnitude of DMH-induced alterations in superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities was lowered in the DMH + GM-CSF group (n = 12-16, P < 0.05). DMH-induced increases in the total nitrite/nitrate levels and the nitric oxide synthase (NOS) activity (n = 10-12, P < 0.05) were also reduced in the DMH + GM-CSF group (n = 8-9, P < 0.05).

CONCLUSIONS

The results indicate that GM-CSF inhibits the development of DMH-induced colon cancer in rats and suggest that inhibition of oxidative stress and NO pathway are involved in the observed antitumoral effects.

Oxidative damage in an experimentally induced gastric and gastroduodenal reflux model

The exact pathophysiologic mechanisms of esophageal cell damage and carcinogenesis by gastroesophageal reflux are not clearly understood. The aim of this study was to evaluate the damage to the esophageal epithelium that occurs after acid reflex and mixed acid and bile reflux by assessing histopathology, reactive oxygen species, and DNA damage. Eighty 10-week-old male Sprague-Dawley rats were divided into two groups, an acid reflux group and a mixed (acid/bile) reflux group. Acid reflux was achieved by esophagogastroplasty in which mixed reflux was encouraged via esophagoduodenal anastomosis. Each group contained a control subgroup that underwent sham laparotomy alone. The rats were killed 3, 6, 9, and 12 months after surgery. Malondialdehyde, protein carbonyl content, and DNA damage were determined in lymphocytes. Histopathologic analysis was performed according to the histologic activity index. Inflammation, ulcer, and regeneration in both reflux groups were significantly increased in the esophagus at 3, 6, 9, and 12 months compared with the control group. Mucosal damage was greater in the mixed reflux group compared with the gastric reflux group. Malondialdehyde and carbonyl content in the serum, and DNA damage in lymphocytes, were significantly increased in both reflux groups. At 9 and 12 months, oxidative damage was increased in the mixed reflux group compared with the acid reflux group. Oxygen-derived free radicals seem to be one of the important mediators in the evaluation and generation of reflux esophagitis. The impact of oxygen free radicals, as demonstrated in this study, can be evaluated by assessing the damage that they incur to lipid membranes, serum proteins, and circulating lymphocyte DNA. Serum malondialdehyde and carbonyl content as well as lymphocyte DNA damage were significantly increased in the setting of acid and mixed acid/bile reflux in these rodent models. Further, these serum and lymphocytic changes were associated with esophageal ulceration, inflammation, and regeneration. Evaluation of such markers as serum malondialdehyde and carbonyl content as well as evaluation of lymphocyte DNA might prove to be useful investigations in patients with precancerous and cancerous conditions in addition to conventional methods of diagnosis. Further studies, both animal and human are warranted.

Redox status of dogs with non-hodgkin lymphomas. An ESR study

Free radical and antioxidant parameters in healthy dogs (n=10) and dogs with non-Hodgkin lymphomas (n=11) were measured in blood and lymph node tissue samples before chemotherapy. Enzymatic and other biochemical measurements were performed. We found that (i) free radical concentrations based on ESR spectra of tissues correlated with higher proliferative character; (ii) lymphoma cases showed an impaired antioxidant status; (iii) tumors with low oxidative burst capacity and higher reduced/oxidized glutathione ratio responded better to chemotherapy; and (iv) affected blood and lymph nodes were under strong oxidative stress.

Decreased reactive oxygen generation during H2O2 decomposition in the presence of samples from human rectal cancer

Reactive oxygen species (ROS) have generated a great deal of interest in the clinical field since experimental studies showed the involvement of these species in carcinogenesis. This paper reports the detection of ROS during the decomposition of H2O2 in the presence of samples obtained from tissues of 16 patients with rectal carcinoma (age 64 +/- 9 years) operated on in the Division of Surgical Oncology of Pomeranian Medical University, Szczecin (Poland). The samples were cut from the middle of the resected tumors and from the colonic mucosa (10 cm distant from the tumor and free of disease); they were processed and the supernatants, representing the soluble fraction, were used for measurements. Various methods for measuring free radical activity of the examined samples were used, such as chemiluminescence, fluorescent probe 2',7'-dichlorodihydrofluorescein, spin trap 5,5-dimethyl-pyrroline-1-oxide and EPR, the spectrophotometrically examined formation of diformazan during reduction of the p-nitroblue tetrazolium salt, and bleaching of p-nitrosodimethylalanine. A statistically significant difference (P < 0.001) was noticed in mean chemiluminescence +/- standard error of the mean in the presence of the tumor samples (42.6 +/- 7.3) in comparison to the control samples (234.6 +/- 36.0). Significantly decreased generation of ROS from the decomposition of H2O2 in the presence of the tumor samples in comparison to the control samples was also observed when the above-mentioned methods were used. Tumor samples had significantly lower superoxide dismutase activity (33 +/- 4 U/mg protein) than controls (93 +/- 14 U/mg, P < 0.001), which should contribute to a lower capacity of endogenous H2O2 production and therefore less ROS generation upon H2O2 decomposition. We conclude that the tested samples have different redox properties; this supports a possible role of ROS activity during carcinogenesis. Moreover, we propose a new, simple, and sensitive chemiluminescent method, which might be effective in sample differentiation.

Reduction of bioactive substances in stored donor blood: prestorage versus bedside leucofiltration

Leucocyte filtration has been suggested to improve transfusion products. We studied the effect of prestorage versus bedside leucofiltration on reduction of bioactive substances and leucocyte content in donor blood. Forty-five units of whole blood from healthy blood donors were studied. Of these units, 9 were stored under standard conditions for 35 d, 9 were leucofiltered after donation and then stored for 35 d, and 3x9 units were stored for 7, 21 and 35 d, respectively, before leucofiltration. Samples were collected from blood units immediately after donation, and before and after leucofiltration, and analysed by ELISA and RIA methods for extracellular content of myeloperoxidase (MPO), eosinophil cationic protein (ECP), histamine (HIS) and plasminogen activator inhibitor-1 (PAI-1). Leucocyte content was counted in all samples. In non-filtered blood extracellular MPO, ECP, HIS and PAI-1 were accumulated in a storage time-dependent manner, while prestorage leucofiltration prevented this accumulation. Leucofiltration after storage for 7, 21 or 35 d did not significantly reduce the accumulated bioactive substances, which were similar to levels in non-filtered blood stored for the same period of time. Prestorage and bedside leucofiltration on day 7 reduced the leucocyte content to less than 0.5x10(6)/L, whereas the median content in blood stored for 21 or 35 d was only reduced to 32.0 and 52.2x10(6)/L, respectively. Prestorage leucofiltration may thus be advantageous to bedside leucofiltration.

Superoxide dismutases in relation to the overall survival of colorectal cancer patients

Reactive oxygen metabolites are implicated in the initiation and promotion of cancer. In addition, oxidant scavengers, such as manganese--(Mn-SOD) and copper/zinc--superoxide dismutase (Cu/Zn-SOD), are thought to contribute to colorectal cancer treatment response. In the present study, the prognostic significance of the Mn- and Cu/Zn-SOD antigen content of normal mucosa and carcinomas of 163 patients with colorectal cancer was evaluated in comparison with major clinicopathological parameters, with respect to the 5-year overall survival. The Mn-SOD content of carcinomas was found to be significantly higher than that of normal mucosa, whereas there was no difference in the Cu/Zn-SOD content between the normal mucosa and carcinomas. No association was demonstrable between the Mn-SOD and Cu/Zn-SOD content of the tissues and the assessed clinicopathological parameters (gender, age, localization, differentiation grade, diameter and Dukes' stage), with the exception of the Cu/Zn-SOD and the differentiation grade of the carcinomas. Univariate analysis showed that a high Mn-SOD content of carcinomas was associated with a poor 5-year overall survival of the patients with colorectal cancer. Multivariate analysis including all clinicopathological parameters revealed that this Mn-SOD parameter was prognostically independent. The Mn- and Cu/Zn-SOD content of normal mucosa and the Cu/Zn-SOD content of carcinomas were not associated with the overall survival of the patients. In conclusion, this study demonstrates that for patients with colorectal cancer the Mn-SOD content of colorectal carcinomas has a significant prognostic value that is independent from major clinicopathological parameters, including Dukes' stage.

Chemoprevention of azoxymethane-induced rat colon carcinogenesis by a xanthine oxidase inhibitor, 1'-acetoxychavicol acetate

In our studies to find natural compounds with chemopreventive efficacy in foods, using azoxymethane (AOM)-induced colonic aberrant crypt foci and colonic mucosal cell proliferation as biomarkers, a xanthine oxidase inhibitor, 1'-acetoxychavicol acetate (ACA), present in the edible plant Languas galanga from Thailand was found to be effective. This study was conducted to test the ability of ACA to inhibit AOM-induced colon tumorigenesis when it was fed to rats during the initiation or post-initiation phase. Male F344 rats were given three weekly s.c. injections of AOM (15 mg/kg body weight) to induce colonic neoplasms. They were fed diet containing 100 or 500 ppm ACA for 4 weeks, starting one week before the first dosing of AOM (the initiation feeding). The other groups were fed the ACA diet for 34 weeks, starting one week after the last AOM injection (the post-initiation feeding). At the termination of the study (week 38), AOM had induced 71% incidence of colonic adenocarcinoma (12/17 rats). The initiation feeding with ACA caused significant reduction in the incidence of colon carcinoma (54% inhibition by 100 ppm ACA feeding and 77% inhibition by 500 ppm ACA feeding, P = 0.03 and P = 0.001, respectively). The post-initiation feeding with ACA also suppressed the incidence of colonic carcinoma (45% inhibition by 100 ppm ACA feeding and 93% inhibition by 500 ppm ACA feeding, P = 0.06 and P = 0.00003, respectively). Such inhibition was dose-dependent and was associated with suppression of proliferation biomarkers, such as ornithine decarboxylase activity in the colonic mucosa, and blood and colonic mucosal polyamine contents. ACA also elevated the activities of phase II enzymes, glutathione S-transferase (GST) and quinone reductase (QR), in the liver and colon. These results indicate that ACA could inhibit the development of AOM-induced colon tumorigenesis through its suppression of cell proliferation in the colonic mucosa and its induction of GST and QR. The results confirm our previous finding that ACA feeding effectively suppressed the development of colonic aberrant crypt foci. These findings suggest possible chemopreventive ability of ACA against colon tumorigenesis.

Experimental study on the role of osteoclasts and free radicals in the mandibular invasion of VX2 carcinoma in Japanese white rabbits

Oxygen-derived free radicals are stimulators of bone resorption in vitro and in vivo. We hypothesized that oxygen-derived free radicals or reactive oxygen species (ROS) generated around bone matrix invaded by cancer cells might be associated with the activation or formation of osteoclasts in bone metastasis, and thus the administration of an ROS scavenger or a free-radical scavenger might control osteoclastic bone destruction in tumor metastasis. We examined the ability of VX2 carcinoma cells to generate superoxide anion (O2-) as well as the effects of the O2- scavenger superoxide dismutase (SOD) and the hydrogen peroxide (H2O2) scavenger catalase (CAT) on the activation and formation of osteoclasts in VX2 carcinoma tissue of rabbits. VX2 carcinoma cells generated more O2- than tartrate-resistant acid phosphatase-positive (TRAP+) cells. The TRAP activity from TRAP+ cells in the presence of VX2 carcinoma cells was higher than that from TRAP+ cells in the absence of the carcinoma cells. The addition of SOD but not of CAT into the incubation medium inhibited the TRAP activity from TRAP+ cells in the presence or absence of VX2 carcinoma cells. Similar inhibitory effects were also observed with SOD plus CAT on TRAP+ cells in the presence or absence of carcinoma cells. Intravenous administration of SOD and SOD plus CAT, but not of CAT, caused a decrease in the number of osteoclasts in mandibles implanted with VX2 carcinoma cells, and showed a predominant occupation by osteoclasts with poorly developed ruffled borders in lesions of bone resorption. In contrast, the administration of CAT, but not of SOD and SOD plus CAT, decreased the more mature forms of osteoclasts in implanted mandibles. From the results obtained, it is suggested that O2- may stimulate bone resorption by increasing the activity and number of osteoclasts, and H2O2 may stimulate resorption by enhancing the formation of mature osteoclasts in tumor metastasis. The administration of some ROS or free-radical scavengers to patients with cancer may provide a defense against bone destruction in bone metastatic lesions.

Time-dependent, spontaneous release of white cell- and platelet-derived bioactive substances from stored human blood

BACKGROUND

The mechanisms of the detrimental effects of perioperative allogeneic blood transfusion are still unclear. Previous studies have suggested a higher incidence of adverse effects after the use of blood stored for prolonged time. Therefore, a possible time-dependent release of various white cell- and platelet-derived bioactive substances in stored human red cell suspensions was studied.

STUDY DESIGN AND METHODS

Whole blood (6 units), plasma-reduced whole blood (6 units), and saline-adenine-glucose-mannitol blood (6 units) from 18 unpaid, normal blood donors were stored under standard blood bank conditions at 4 degrees C for 35 days. After refrigeration, samples were collected from all blood bags on Days 0, 2, 5, 9, 14, 21, 28, and 35 of storage. Extracellular concentrations of eosinophil cationic protein, eosinophil protein X, plasminogen activator inhibitor 1, myeloperoxidase, and interleukin 6 were analyzed by enzyme-linked immunosorbent assay and radioimmunoassay. The total intracellular and donor plasma levels of these substances also were analyzed at the time of blood donation.

RESULTS

Eosinophil cationic protein, eosinophil protein X, and myeloperoxidase increased 10- to 25-fold (p < 0.05) in a time-dependent manner in whole blood, plasma-reduced whole blood, and saline-adenine-glucose-mannitol blood during storage for 35 days. Plasminogen activator inhibitor 1 increased threefold to sixfold (p < 0.05) in whole blood and plasma-reduced whole blood, but not in saline-adenine-glucose-mannitol blood. Interleukin 6 was not detected in either plasma or samples obtained from the blood bags.

CONCLUSION

Stored whole blood, plasma-reduced whole blood, and saline-adenine-glucose-mannitol blood may release white cell- and platelet-derived bioactive substances in a time-dependent manner, which may be related to the detrimental effects of perioperative blood transfusions. Therefore, prestorage white cell reduction should be considered for further improvement of red cell suspensions.

Superoxide radical and xanthine oxidoreductase activity in the human heart during cardiac operations

BACKGROUND

The results of clinical trials of xanthine oxidoreductase inhibition in cardiac surgery are encouraging, although studies have failed to localize the enzyme to the human heart and to localize free radical activity to fresh human heart.

METHODS

We adapted a histochemical staining technique based on the reduction of nitro blue tetrazolium to formazan by superoxide radical. In six samples of right atrium graded blindly on a scale of 0 through 4, strong staining (median grade, 3) of the microvasculature was seen. This was blocked by allopurinol in paired sections (median grade, 1; p < 0.01). Chemiluminescence can be used as an index of superoxide radical activity. Atrial samples were taken from 13 patients at five time points during coronary bypass grafting and placed in buffered luminol. Then chemiluminescence was measured.

RESULTS

A 15-fold rise in chemiluminescence (295.93 +/- 39.47 mV) was demonstrated during reperfusion compared with the control value (19.06 +/- 0.47 mV). Chemiluminescence at 1 minute after release of the cross-clamp was significantly higher (p < 0.05) by analysis of variance versus values obtained before bypass and 1 minute before and 30 minutes after reperfusion.

CONCLUSIONS

In this study we have identified superoxide radical activity and a possible generating system (xanthine oxidoreductase) in the human heart.