Analysis of HLA expression in human tumor tissues

Cancer cells can be detected and destroyed by cytotoxic T lymphocytes in many experimental tumor systems, and--as has been well-documented--in some human tumors. In humans however, most diagnosed tumors are not eliminated by T cells but grow steadily, invading and metastasizing until the host is destroyed. Evidence is accumulating that progressive tumor growth occurs not because the immune system is defective or deteriorated, but because the cancer cell is capable of developing a variety of strategies to escape immune recognition. In addition, cancer cells acquire new biological properties to generate invasive capacity in order to migrate and colonize new tissues. Major histocompatibility complex (MHC) antigens are molecules that are specialized in communicating with the T cell receptor and natural killer (NK) cell ligands. With the former, they use the interaction with peptides derived from processed cellular and exogenous proteins to monitor self and non-self status. With the latter, they determine the degree of activation and killing capacity of NK cells by interacting with NK receptors. Any change in the MHC profile of tumor cells (including classical and nonclassical MHC molecules) may therefore have a profound influence on the immune recognition and immune rejection of cancer cells. We have reviewed the data from our laboratory and other groups, and have presented a standardized procedure for analyzing the MHC profile of human tumors with special emphasis on the quality and laboratory use of the material obtained from microdissected tumor samples. Appropriate tissue processing is of particular relevance, since it is not possible to obtain tumor cell lines from most patients. Oncologists require rapid information on the MHC profile of the tumor if gene therapy is envisaged to restore normal MHC class I gene expression.     

Approach to the study of C-glycosyl flavones by ion trap HPLC-PAD-ESI/MS/MS: application to seeds of quince (Cydonia oblonga)

Ion trap HPLC-PAD-ESI/MS/MS has been used to study C-glycosyl flavones in quince seeds. Comparative analysis of the ions [(M-H)-60]-, [(M-H)-90]- and [(M-H)-120]- from 6-C- and 8-C-glycosyl flavone isomers, together with their respective retention times, allowed deductions to be made about the nature of the sugar units and the positions of C-glycosylation. Vicenin-2 (6,8-di-C-glucosyl apigenin), lucenin-2 (6,8-di-C-glucosyl luteolin), stellarin-2 (6,8-di-C-glucosyl chrysoeriol), isoschaftoside (6-C-arabinosyl-8-C-glucosyl apigenin), schaftoside (6-C-glucosyl-8-C-arabinosyl apigenin), 6-C-pentosyl-8-C-glucosyl chrysoeriol and 6-C-glucosyl-8-C-pentosyl chrysoeriol were identified in quince seed.     

Structural mechanism for lipid activation of the Rac-specific GAP, beta2-chimaerin

The lipid second messenger diacylglycerol acts by binding to the C1 domains of target proteins, which translocate to cell membranes and are allosterically activated. Here we report the crystal structure at 3.2 A resolution of one such protein, beta2-chimaerin, a GTPase-activating protein for the small GTPase Rac, in its inactive conformation. The structure shows that in the inactive state, the N terminus of beta2-chimaerin protrudes into the active site of the RacGAP domain, sterically blocking Rac binding. The diacylglycerol and phospholipid membrane binding site on the C1 domain is buried by contacts with the four different regions of beta2-chimaerin: the N terminus, SH2 domain, RacGAP domain, and the linker between the SH2 and C1 domains. Phospholipid binding to the C1 domain triggers the cooperative dissociation of these interactions, allowing the N terminus to move out of the active site and thereby activating the enzyme.     

The [Ru(Hedta)NO](0.1-) system: structure, chemical reactivity and biological assays

The [Ru(II)(Hedta)NO(+)] complex is a diamagnetic species crystallizing in a distorted octahedral geometry, with the Ru-N(O) length 1.756(4) A and the RuNO angle 172.3(4) degrees . The complex contains one protonated carboxylate (pK(a)=2.7+/-0.1). The [Ru(II)(Hedta)NO(+)] complex undergoes a nitrosyl-centered one-electron reduction (chemical or electrochemical), with E(NO+/NO)=-0.31 V vs SCE (I=0.2 M, pH 1), yielding [Ru(II)(Hedta)NO](-), which aquates slowly: k(-NO)=2.1+/-0.4x10(-3) s(-1) (pH 1.0, I=0.2 M, CF(3)COOH/NaCF(3)COO, 25 degrees C). At pHs>12, the predominant species, [Ru(II)(edta)NO](-), reacts according to [Ru(II)(edta)NO](-)+2OH(-)-->[Ru(II)(edta)NO(2)](3-), with K(eq)=1.0+/-0.4 x 10(3) M(-2) (I=1.0 M, NaCl; T=25.0+/-0.1 degrees C). The rate-law is first order in each of the reactants for most reaction conditions, with k(OH(-))=4.35+/-0.02 M(-1)s(-1) (25.0 degrees C), assignable mechanistically to the elementary step comprising the attack of one OH(-) on [Ru(II)(edta)NO](-), with subsequent fast deprotonation of the [Ru(II)(edta)NO(2)H](2-) intermediate. The activation parameters were DeltaH(#)=60+/-1 kJ/mol, DeltaS(#)=-31+/-3 J/Kmol, consistent with a nucleophilic addition process between likely charged ions. In the toxicity up-and-down tests performed with Swiss mice, no death was observed in all the doses administered (3-9.08 x 10(-5) mol/kg). The biodistribution tests performed with Wistar male rats showed metal in the liver, kidney, urine and plasma. Eight hours after the injection no metal was detected in the samples. The vasodilator effect of [Ru(II)(edta)NO](-) was studied in aortic rings without endothelium, and was compared with sodium nitroprusside (SNP). The times of maximal effects of [Ru(II)(edta)NO](-) and SNP were 2 h and 12 min, respectively, suggesting that [Ru(II)(edta)NO](-) releases NO slowly to the medium in comparison with SNP.     

AZT induces oxidative damage to cardiac mitochondria: protective effect of vitamins C and E

AZT (zidovudine) is a potent inhibitor of HIV replication and a major antiretroviral drug used for AIDS treatment. A major limitation in the use of AZT is the occurrence of severe side effects. The aim of this work was to test whether AZT causes oxidative damage to heart mitochondria and whether this can be prevented by supranutritional doses of antioxidant vitamins. An experimental animal model was used in which mice were treated with AZT for 35 days (10 mg/kg/day) in drinking water. Animals treated with antioxidant vitamins were fed the same diet as controls but supplemented with vitamins C (ascorbic acid, 10 g/ kg diet) and E (alpha-dl-tocopherol, 0.6 g/kg diet) for 65 days before sacrifice. This resulted in a daily intake of 1250 mg/kg/day (vitamin C) and 75 mg/kg/day (vitamin E). Cardiac mitochondrial DNA (mtDNA) of mice treated with AZT had over 120% more oxo-dG (8-oxo-7,8-dihydro-2'-deoxyguanosine, which is a biomarker of oxidative damage to DNA) in their mitochondrial DNA than untreated controls. AZT treatment also caused an increase in mitochondrial lipid peroxidation and an oxidation of mitochondrial glutathione. Dietary supplementation with supranutritional doses of the antioxidant vitamins C and E protected against these signs of mitochondrial oxidative stress. The oxidative effects of AZT are probably due to an increase in production of reactive oxygen species by mitochondria of AZT-treated animals, raising the possibility that oxidative stress may play an important role in the cardiotoxicity of AZT.     

The effects of reduced oxygen tension on swine granulosa cell

Follicular growth is characterized by an augmented vascularization, possibly driven by a fall in the oxygen supply. The present study was undertaken to investigate the effects of hypoxia on swine granulosa cells. At first, we quantified oxygen partial pressure (pO₂) in follicular fluid from different size follicles; the granulosa cells collected from large follicles (>5 mm) were subjected for 18 h to normoxia (19% O₂), partial (5% O₂) or total hypoxia (1% O₂). The effects of these conditions were tested on the main parameters of granulosa cell function, steroidogenesis and cell proliferation, and on vascular endothelial growth factor (VEGF), nitric oxide (NO) and superoxide anion (O₂⁻) production. Oxygen tension in follicular fluid was negatively related to follicular size, pointing out a gradual reduction during follicular growth. Severe hypoxic conditions determined a reduction of both 17β estradiol and progesterone production, while partial hypoxia did not seem to affect them. Hypoxia increased VEGF as well as O₂⁻ production in swine granulosa cells without impairing cell growth; in addition, it decreased NO output.

We may conclude that physiological hypoxia could play a pivotal role in the follicular angiogenic process stimulating VEGF synthesis by granulosa cells. ROS are possibly involved in hypoxic signalling.     

Contact sites from human placental mitochondria: characterization and role in progesterone synthesis

To understand the functional compartmentalization of human placental mitochondria, we analyzed the composition and steroidogenic activity of contact sites. Several fractions containing contact sites were isolated using osmotic shock treatment and sucrose gradient centrifugation. These fractions contained various proteins and marker enzymes associated with mitochondrial membranes. The fractions containing the cytochrome P450 side chain cleavage system, cholesterol, nicotinamide adenine dinucleotide phosphate-isocitrate dehydrogenase, porin, and adenosine 5(')-triphosphate-diphosphohydrolase activity showed the capacity to synthesize progesterone. Our observations indicate that all necessary elements and enzymes for steroidogenesis are present and functional in placental mitochondrial contact sites. This organization may facilitate the metabolism of cholesterol delivered to the outer mitochondrial membrane into steroid hormones by the inner mitochondrial membrane cholesterol side chain cleavage system.     

Protective effects of a plant histaminase in myocardial ischaemia and reperfusion injury in vivo

Grass pea seedling histaminase (a copper-diamine oxidase) was found to exert a significant cardioprotection against post-ischaemic reperfusion damage. Electrocardiogram (ECG) recordings from the rats subjected in vivo to ischaemia and reperfusion showed ventricular tachycardia (VT) and ventricular fibrillations (VF) occurring in 9 out of 12 untreated rats whereas no ventricular arrhythmias were found under histaminase (80U/kg body weight) treatment (n=16 rats). Computer-assisted morphometry of the ischaemic reperfused hearts stained with nitroblue tetrazolium showed the extension of damaged myocardium (area at risk and infarct size) significantly reduced in rats treated with histaminase, in comparison with the non-treated rats, whereas no protection was found with the semicarbazide inactivated histaminase. Biochemical markers of ischaemia-reperfusion myocardial tissue damage: malonyldialdehyde (MDA), tissue calcium concentration, myeloperoxidase (MPO), and apoptosis indicator caspase-3 were significantly elevated in untreated post-ischaemic reperfused rats, but significantly reduced under histaminase protection. In conclusion, plant histaminase appears to protect hearts from ischaemia-reperfusion injury by more than one mechanism, essentially involving histamine oxidation, and possibly as reactive oxygen species scavenger, presenting good perspectives for a novel therapeutic approach in treatment of ischaemic heart pathology.