Priscila O. Carvalho

Lipoprotein (a): Structure, Pathophysiology and Clinical Implications

The chemical structure of lipoprotein (a) is similar to that of LDL, from which it differs due to the presence of apolipoprotein (a) bound to apo B100 via one disulfide bridge. Lipoprotein (a) is synthesized in the liver and its plasma concentration, which can be determined by use of monoclonal antibody-based methods, ranges from < 1 mg to > 1,000 mg/dL. Lipoprotein (a) levels over 20-30 mg/dL are associated with a two-fold risk of developing coronary artery disease. Usually, black subjects have higher lipoprotein (a) levels that, differently from Caucasians and Orientals, are not related to coronary artery disease. However, the risk of black subjects must be considered. Sex and age have little influence on lipoprotein (a) levels. Lipoprotein (a) homology with plasminogen might lead to interference with the fibrinolytic cascade, accounting for an atherogenic mechanism of that lipoprotein. Nevertheless, direct deposition of lipoprotein (a) on arterial wall is also a possible mechanism, lipoprotein (a) being more prone to oxidation than LDL. Most prospective studies have confirmed lipoprotein (a) as a predisposing factor to atherosclerosis. Statin treatment does not lower lipoprotein (a) levels, differently from niacin and ezetimibe, which tend to reduce lipoprotein (a), although confirmation of ezetimibe effects is pending. The reduction in lipoprotein (a) concentrations has not been demonstrated to reduce the risk for coronary artery disease. Whenever higher lipoprotein (a) concentrations are found, and in the absence of more effective and well-tolerated drugs, a more strict and vigorous control of the other coronary artery disease risk factors should be sought.

Activation of EGFR signaling from pilocytic astrocytomas to glioblastomas

Introduction EGFR analyses allow for better correlation between genotype and phenotype in astrocytomas and represent an attractive therapeutic target. Most studies emphasize analyses of EGFR in glioblastomas (GBMs) but do not analyze all grades of astrocytomas (from pilocytic to GBM). The purpose of our study was to evaluate the status of EGFR (expression, deletion, and amplification) and EGFR protein expression in all grades of astrocytomas. Patients and Methods We analyzed a total of 145 surgical tumor specimens that included: 22 pilocytic astrocytomas, 22 grade II astrocytomas, 17 grade III astrocytomas and 84 GBMs. The specimens were compared to 17 non-neoplastic brain tissues obtained from epilepsy surgery. EGFR expression, EGFR amplification and EGFRvIII analyses were performed by quantitative real-time PCR, and protein expression was evaluated by immunohistochemistry. Results EGFR relative overexpression and EGFR amplification were observed, respectively, in 50% and 20% of astrocytomas, while EGFRvIII was only found in GBMs (34.5%, p=0.005). Amongst EGFR-amplified GBM cases, 59% also presented EGFRvIII (p<0.001). Cytoplasmic accumulation of EGFR protein was detected in 75% of astrocytomas, and 21% of the astrocytomas showed nuclear localization (p=0.003). Conclusions EGFR alterations were found in all grades of astrocytomas, from pilocytic to GBMs, while EGFRvIII was exclusively found in GBMs. These findings provide important information on the mechanisms involved in the progression of astrocytomas for determining whether EGFR status can be used for effective and specific therapy.

Association of EGFR c.2073A>T polymorphism with decreased risk of diffusely infiltrating astrocytoma in a Brazilian case-control study

Epidermal growth factor receptor (EGFR) gene overexpression has been implicated in the development of many types of tumors, including glioblastomas, the most frequent diffusely infiltrating astrocytomas. However, little is known about the influence of the polymorphisms of EGFR on EGFR production and/or activity, possibly modulating the susceptibility to astrocytomas. This study aimed to examine the association of two EGFR promoter polymorphisms (c.-191C>A and c.-216G>T) and the c.2073A>T polymorphism located in exon 16 with susceptibility to astrocytomas, EGFR gene expression and survival in a case-control study of 193 astrocytoma patients and 200 cancer-free controls. We found that the variant TT genotype of the EGFR c.2073A>T polymorphism was associated with a significantly decreased risk of astrocytoma when compared with the AA genotype [sex- and age-adjusted odds ratio 0.51, 95% confidence interval 0.26-0.98]. No association of the two promoter EGFR polymorphisms (or combinations of these polymorphisms) and risk of astrocytomas, EGFR expression or survival was found. Our findings suggest that modulation of the EGFR c.2073A>T polymorphism could play a role in future therapeutic approaches to astrocytoma.

A lipid nanoemulsion carrying paclitaxel improves the gene expression of inflammatory factors of heart grafts in rabbits.

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Regression of Atherosclerotic Plaques of Cholesterol-Fed Rabbits by Combined Chemotherapy With Paclitaxel and Methotrexate Carried in Lipid Core Nanoparticles

In previous studies, it was demonstrated that lipid core nanoparticles (LDE) resemble the low-density lipoprotein structure and carrying the antiproliferative agent paclitaxel (PTX) strongly reduced atherosclerosis lesions induced in rabbits by cholesterol feeding. Currently, the aim was to verify whether combining LDE-PTX treatment with methotrexate (MTX) associated with LDE (LDE-MTX) could accelerate the atherosclerosis regression attained with single LDE-PTX treatment, after withdrawing the cholesterol feeding. Thirty-eight rabbits were fed 1% cholesterol chow for 8 weeks. Six of these rabbits were then euthanized for analyses of the aorta (controls). In the remaining rabbits, cholesterol feeding was withdrawn, and those 32 animals were allocated to 3 groups submitted to different 8-week intravenous treatments, all once/week: LDE-PTX (n = 10; 4 mg/kg), LDE-PTX + LDE-MTX (n = 11; 4 mg/kg), and LDE-alone (n = 11). Rabbits were then euthanized and aortas were excised for morphometric, immunohistochemical, and gene expression analyses. After cholesterol feeding withdrawal, in comparison with LDE-alone group, both LDE-PTX and LDE-PTX + LDE-MTX treatments had the ability to increase the regression of plaque areas: −49% in LDE-PTX and −59% for LDE-PTX + LDE-MTX. However, only LDE-PTX + LDE-MTX treatment elicited reduction in the intima area, estimated in −57%. Macrophage presence in aortic lesions was reduced 48% by LDE-PTX and 43% by LDE-PTX + LDE-MTX treatment. Matrix metalloproteinase 9 was reduced by either LDE-PTX (74%) or LDE-PTX + LDE-MTX (78%). Tumor necrosis factor α gene expression was reduced 65% by LDE-PTX and 79% by LDE-PTX + LDE-MTX. In conclusion, treatment with LDE-PTX indeed accelerated plaque reduction after cholesterol feeding; LDE-PTX + LDE-MTX further increased this effect, without any observed toxicity. These results pave the way for the use of combined chemotherapy to achieve stronger effects on aggravated, highly inflamed atherosclerotic lesions.

The Expression of Lipoprotein Receptors Is Increased in the Infarcted Area After Myocardial Infarction Induced in Rats With Cardiac Dysfunction

Left ventricular (LV) remodeling after myocardial infarction constitutes the structural basis for ventricular dysfunction and heart failure. The characterization underlying the expression of lipoprotein receptors in cardiac dysfunction is scarcely explored. The aim of this study was to analyze the status of lipoprotein receptors on the infarcted and noninfarcted areas of LV and to verify whether nanoparticles that mimic the lipid structure of low-density lipoprotein (LDL) and have the ability to bind to LDL receptors (LDE) are taken up more avidly by the noninfarcted LV. 13 male Wistar rats with left coronary artery ligation (myocardial infarction [MI]) and 12 animals with SHAM operation (SHAM) were used in this study. 6 weeks after the procedure, the quantification of low-density lipoprotein receptor (LDLR), LDL receptor-related protein 1 (LRP1), scavenger receptor-class B type I (SR-BI) lipoprotein receptors, and PCNA proliferation marker, and tissue uptake of radioactively labeled LDE were performed. Immunohistochemistry and Western blot analysis showed that LDLR, LRP1, SR-BI, and PCNA, expression in infarcted area of MI was remarkably higher than SHAM and noninfarcted subendocardial (SEN) and interstitial (INT) areas. In addition, in SEN noninfarcted area of MI, the presence of LDLR was about threefold higher than in SHAM SEN and INT noninfarcted areas. The LDE uptake of noninfarcted LV of MI group was about 30% greater than that of SHAM group. In conclusion, these findings regarding the status of lipoprotein receptors after MI induction could help to establish mechanisms on myocardial repairing. In conclusion, infarcted rats with LV dysfunction showed increased expression of lipoprotein receptors mainly in the infarcted area.

Altered Expression in Patients with Heart Failure of Circulating MicroRNAs Related to Lipoprotein Metabolism

Objective: This study aimed to investigate, for the first time, the expression of circulating miRNAs (microRNAs) related to lipoprotein metabolism in patients with HF (heart failure). Methods: Twenty patients with HF and 10 controls without HF were included. BNP (brain natriuretic peptide), a marker of HF severity, plasma lipid parameters and the expression of circulating miRNAs were determined. Key findings: Total, LDL-, non-HDLand HDL-cholesterol, triglycerides, and apo A-I did not differ between both groups, but apo B was lower in the HF group compared to controls (p = 0.007). In respect to miRNAs, miR-33a, miR-144, miR-125, miR-30c, miR-122, miR-26a, miR-185, miR-758 and miR-106b were higher, from tento 25-fold, and miR-10b was lower about 4-fold, in HF group compared to controls. In HF patients a negative correlation between miR-26a and BNP, the marker of disease severity, was found (r = -0.552; p = 0.041). Conclusions: Plasma levels of miRNAs involved in HDL and LDL metabolism regulation were strikingly changed in HF patients. The negative correlation between miR-26a and BNP values may suggest the possibility of the rise of a novel biomarker or therapeutic target in HF.

mRNA levels of low-density lipoprotein receptors are overexpressed in the foci of deep bowel endometriosis.

STUDY QUESTION Is mRNA expression of LDL receptors altered in deep bowel endometriotic foci? SUMMARY ANSWER mRNA expression of LDL receptors is up-regulated in deep bowel endometriotic foci of patients with endometriosis. WHAT IS KNOWN ALREADY Several studies have demonstrated the overexpression of low-density lipoprotein receptors in various tumour cell lines and endometriosis has similar aspects to cancer, mainly concerning the pathogenesis of both diseases. This is the first study we know of to investigate lipoprotein receptors expression in deep endometriosis with bowel involvement. STUDY DESIGN, SIZE, DURATION During 2014–2015, an exploratory case-control study was conducted with 39 patients, including 20 women with a histological diagnosis of deep endometriosis compromising the bowel and 19 women without endometriosis who underwent laparoscopic tubal ligation. PARTICIPANTS/MATERIALS, SETTING, METHODS Peripheral blood samples were collected on the day of surgery for lipid profile analysis, and samples of endometrial tissue and of bowel endometriotic lesions were also collected. The tissue samples were sent for histopathological analysis and for LDL-R and LRP-1 gene expression screening using quantitative real-time PCR. MAIN RESULTS AND THE ROLE OF CHANCE Patients with deep endometriosis had lower LDL-cholesterol than patients without the disease (119 ± 23 versus 156 ± 35; P = 0.001). Gene expression analysis of LDL receptors revealed that LDL-R was more highly expressed in endometriotic lesions when compared to the endometrium of the same patient but not more than in the endometrium of women without endometriosis (0.027 ± 0.022 versus 0.012 ± 0.009 versus 0.019 ± 0.01, respectively; P < 0.001). LRP-1 was more highly expressed in endometriotic lesions, both when compared with the endometrium of the same patient and when compared with the endometrium of patients without the disease (0.307 ± 0.207 versus 0.089 ± 0.076 and versus 0.126 ± 0.072, respectively; P < 0.001). The study also showed that LDL-R gene expression in the endometrium of women with endometriosis was higher during the secretory phase of the menstrual cycle (P = 0.001). LRP-1 gene expression was increased during the secretory phase in the endometrium of women without the disease (P = 0.008). LIMITATIONS, REASONS FOR CAUTION In the endometriotic lesions, the presence of fibrosis is substantial, restricting access to the stromal and glandular components of the lesion. Despite that, we found that LDL receptor mRNA was overexpressed. Future studies may perform laser microdissection to isolate the area of interest in the target tissue, excluding fibrosis contamination. WIDER IMPLICATIONS OF THE FINDINGS This study supports the feasibility of LDL-R targeted therapy in the treatment of deep endometriosis. STUDY FUNDING/COMPETING INTEREST(S) This study was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP #2011/17245-0). The authors have no conflicts of interest to declare.