Cholesterol diet and effect of long-term withdrawal on plaque development and composition in the thoracic aorta of New Zealand White rabbits

Aims

Experimental study on plaque progression, regression and composition in atherosclerotic thoracic aorta of hypercholesterolemic rabbits after long-term withdrawal of cholesterol-enriched diet (CED).

Methods

Rabbits were fed 2% cholesterol for 6 weeks followed by withdrawal periods for 15, 23, 34, 68, or 78 weeks. Cholesterol, triglyceride, and phospholipids levels in blood and cholesterol concentrations in aorta were quantified. Plaque size and cellularity, phenotype of macrophages and smooth muscle cells were (immuno)histomorphometrically analyzed in segments of the thoracic aorta.

Results

After 6 weeks of CED, blood cholesterol levels were about 80-fold higher, whereas atherosclerosis and cholesterol content in the thoracic aorta were only minimally increased. However, the latter significantly increased within 15 weeks after cholesterol withdrawal, while serum cholesterol level was still 10-fold increased. Thereafter plaque area and cholesterol content remained almost unchanged until the end of the study despite a long-term normalization of serum cholesterol level after withdrawal of CED. Directly after 6 weeks of CED the densities of macrophages and apoptotic cells within plaques were highest, decreasing after cholesterol withdrawal, whereas, vice versa the density of smooth muscle cells (SMCs) significantly increased.

Conclusion

We suggest that atherosclerotic plaques respond to long-term withdrawal of CED by decrease in number and phenotype of macrophages and increase of SMCs without regression of the lesion size. The cellular changes are suggested to considerably contribute to higher plaque stability.     

Identification of a novel biomarker for oxidative stress induced by hydrogen peroxide in primary human hepatocytes using the 2‐nitrobenzenesulfenyl chloride isotope labeling method

Aim: Oxidative stress is involved in the progression of non‐alcoholic steatohepatitis (NASH). However, there are few biomarkers that are easily measured and accurately reflect the disease states. The aim of this study was to identify novel oxidative stress markers using the 2‐nitrobenzenesulfenyl (NBS) stable isotope labeling method and to examine the clinical utility of these diagnostic markers for NASH. Methods: Proteins extracted from phosphate buffered saline‐ and hydrogen peroxide‐loaded human primary hepatocyte were labeled with the [¹²C]‐ and [¹³C]‐NBS reagents, respectively. Pairs of peaks with 6‐Da differences in which the [¹³C]‐NBS labeling was more intense than the [¹²C]‐NBS labeling were detected by MALDI‐TOF/MS and identified by MS/MS ion searching. Results: Four pairs of peaks, m/z 1705–1711, m/z 1783–1789, m/z 1902–1908 and m/z 2790–2796, were identified as cytochrome c oxidase VIb (COX6B), liver carboxylesterase 1 (CES1), carbamoyl‐phosphate synthase 1 (CPS1) and superoxide dismutase (MnSOD), respectively. Furthermore, serum MnSOD protein levels were significantly higher in NASH patients than in simple steatosis (SS) patients. The serum MnSOD levels tended to increase in parallel with the stage of fibrosis. Conclusion: The NBS labeling technique was useful to identify biomarkers. Serum MnSOD may be a useful biomarker that can distinguish between SS and NASH.     

Manganese superoxide dismutase polymorphism and risk of skin cancer (United States)

Objective

We assessed whether the functional V16A polymorphism in the MnSOD gene is associated with skin cancer risk.

Methods

We conducted a nested case–control study (219 melanoma, 286 squamous cell carcinoma (SCC), and 300 basal cell carcinoma (BCC) cases, and 873 matched controls) within the Nurses’ Health Study. Genotyping was performed by the 5′ nuclease assay (TaqMan^®). We used logistic regression to model the association between the genotype and skin cancer risk.

Results and conclusions

Overall, there was no significant association between this polymorphism and the risk of each type of skin cancer. No significant interaction was observed between this polymorphism and sunburn history and constitutional susceptibility on skin cancer risk. For interactions between intakes of α-carotene and β-carotene and the MnSOD polymorphism on SCC, the inverse association of intake of either carotene with SCC risk was limited to the Val carriers, whereas no association was observed among women with the AA genotype. We observed an interaction between total vitamin C intake and the MnSOD polymorphism on melanoma risk. No interaction was observed for the intakes of other carotenoids, vitamin E, and vitamin A. Further research is needed to confirm these possible associations.

     

Tumor suppressive activity of a variant isoform of manganese superoxide dismutase released by a human liposarcoma cell line

A cell line derived from a pleiomorphic liposarcoma, named LSA, was previously reported to secrete (a) factor(s) exhibiting oncotoxic properties. The present article describes the isolation, purification and sequence analysis of a protein released by LSA cells into conditioned culture medium. This protein proved to be a variant isoform of manganese superoxide dismutase (MnSOD), hence its designation as LSA-type-MnSOD. This LSA-type-SOD differed from conventional SODs in its secretion by producer cells, contrasting with the normal localization of SODs in the mitochondrial matrix. Interestingly, during the protein purification process, LSA-type-SOD cosegregated with a cytotoxic activity directed against a number of tumor cell lines, as determined under in vitro conditions. This cytopathic effect was most likely due to LSA-type-SOD, since it could be fully reproduced using recombinant SOD that was expressed from cDNA clones isolated from LSA cells mRNA preparations and henceforth designated L-rSOD. In addition to its manifestation in cell lines kept in tissue culture, the oncotoxicity of LSA-type-SOD was further reflected in a remarkable capacity of this protein for suppression of mammary tumors in Balb-C-FR(III) mice. Animals subcutaneously injected with L-rSOD in the tumor area showed a complete disruption of established mammary carcinomas, as monitored by nuclear magnetic resonance (NMR) scanning. Moreover, metastatic spreading, which was readily detected in the control group, was suppressed in the treated animals. Altogether these data suggest that LSA-type-SOD interferes with survival and spreading of neoplastically transformed cells and deserves to be future validated as a therapeutic agent against cancer, either alone or in combination with conventional treatments.     

特异启动子调控的MDR1和MnSOD基因对骨髓的选择性保护作用

目的探讨特异保护骨髓细胞免受抗癌药物及射线损害的新途径。方法 构建了由APN骨髓特异性启动子调控的耐药、耐辐射基因的逆转录病毒载体,导入骨髓母细胞及癌细胞中,用细胞存活实验对耐药耐辐射性能进行观察。分离小鼠骨髓细胞,经转染基因后,再输回到预先用射线处理以破坏骨髓系统的同种受体小鼠体内。经化疗药物或射线处理后,不同时间采血,计算白细胞数,观察在药物或射线照射后导入耐药或耐辐射基因对造血细胞的保护作用。结果 导入MDR1基因的KGla细胞对秋水仙素、足叶乙甙、长春新碱、阿霉素及紫杉醇与对照组相比,各提高了10.6,10.4,11.2,4.2和14.2倍。导入由APN启动子驱动的MnSOD基因,使KGla细胞比对照组对射线(10 Gy)的耐受性提高3.7倍。相反,导入以上两个基因后,肝癌细胞BEL7402的化、放疗耐受性未见明显变化。体内实验表明,转染了MDR1和MnSOD基因的小鼠血液中,白细胞数量明显高于对照组(P<0.01)。结论体外由APN骨髓启动子调控的MDR1和MnSOD基因能特异性地保护骨髓细胞,而对肿瘤细胞无明显影响。体内,在用药物或射线处理动物时能重建造血功能。此研究为肿瘤患者在接受化、放疗时特异性保护骨髓系统,提供了新的思路和依据。     

Nitration of manganese superoxide dismutase during ocular inflammation

Reactive nitrogen species, in particular, peroxynitrite (ONOO(-)) have been proposed to play an important role in the pathogenesis of endotoxin-induced uveitis (EIU). Tyrosine nitration by ONOO(-) has been shown in other model systems to inhibit the activity of the superoxide anion quenching enyzme, manganese superoxide dismutase (MnSOD), perhaps contributing to progression of disease. In this study, it is confirmed through immunoanalysis that nitrated proteins are produced during EIU, and furthermore, that MnSOD is a target of nitration during the inflammatory response. In addition, through microsequencing analyses, nitrated albumin--apparent in both control and EIU eyes--was identified. Positive immunostaining of nitrated proteins was seen in the ciliary epithelium, inflammatory cells, and protein exudate of eyes from rats injected with endotoxin. Incubation of nitrotyrosine immunoprecipitates from the iris and ciliary body (ICB) with a polyclonal antibody against MnSOD revealed that nitrated MnSOD was present only in the ICB of EIU rats. When the total activity of the enzyme was examined, it was observed that despite the presence of nitrated MnSOD, activity was increased relative to control. Analysis of MnSOD mRNA and protein from the ICB of both groups demonstrated an increase in mRNA expression and consequently a three- to five-fold increase in MnSOD protein in EIU rats as compared to control rats. Further examination of MnSOD protein expression through immunohistochemistry noted enhanced immunostaining in the ciliary epithelium of eyes of EIU rats. Additional investigation of a 70 kDa band apparent in nitrotyrosine immunoprecipitates from the ICB of control and EIU rats revealed that the plasma protein albumin is nitrated as well. This protein is present as a result of the breakdown of the blood-aqueous barrier during inflammation. In summary, two endogenous nitration targets, albumin and MnSOD, were identified. Nitrated MnSOD appears to be specifically targeted to the ICB during inflammation, underscoring the importance of the interface in EIU. Furthermore, the expression and activity of the enzyme is increased in the ICB during EIU, perhaps regulating reactive nitrogen species produced within the cells. This study implicates ONOO(-) in the pathogenesis of EIU and imparts the putative role MnSOD plays in disease resolution.     

MnSOD expression is less frequent in tumour cells of invasive breast carcinomas than in in situ carcinomas or non-neoplastic breast epithelial cells

Manganese superoxide dismutase (MnSOD) is an antioxidant enzyme capable of neutralizing superoxide anion molecules. In previous studies it has been suggested to suppress both tumour proliferation and apoptosis. This study investigated 65 invasive, 50 in situ and 19 benign hyperplastic breast lesions for its immunohistochemical expression. MnSOD expression was also tested with in situ hybridization. To study cell proliferation, apoptosis and their association with MnSOD expression the neoplastic breast lesions were immunostained with a monoclonal antibody to Ki-67 and the extent of apoptosis in them was determined by the TUNEL method. 32/65 (49%) of the invasive ductal carcinomas, 41/50 (82%) of the in situ and 15/19 (79%) of the benign hyperplasias expressed the MnSOD protein. There were significantly more MnSOD positive cases in in situ carcinoma and in benign hyperplasia than in invasive carcinoma (p=0.00016 and p=0.022, respectively). Positivity was also more frequently found in non-neoplastic ductal and acinar epithelial cells than in invasive carcinoma. On the other hand, neoplastic epithelial cells of invasive and in situ carcinoma showed strong positivity more often than the epithelial cells of benign hyperplasia or non-neoplastic epithelium. In breast lesions, MnSOD positivity did not associate with proliferation or apoptosis. The lower frequency of MnSOD positive cases in invasive breast carcinoma suggests that the lack of its expression might contribute to the development of an invasive breast carcinoma phenotype and that it could in this way operate as a tumour suppressor gene, as previously suggested.