Effect of eicosapentaenoic acid,an omega-3 polyunsaturated fatty acid,on UVR-related cancer risk in humans. An assessment of early genotoxic markers

Dietary omega-3 polyunsaturated fatty acids (omega-3 PUFAs) protect against photocarcinogenesis in animals, but prospective human studies are scarce. The mechanism(s) underlying the photoprotection are uncertain, although omega-3 PUFAs may influence oxidative stress. We examined the effect of supplementation on a range of indicators of ultraviolet radiation (UVR)-induced DNA damage in humans, and assessed effect on basal and post-UVR oxidative status. In a double-blind randomized study, 42 healthy subjects took 4 g daily of purified omega-3 PUFA, eicosapentaenoic acid (EPA), or monounsaturated, oleic acid (OA), for 3 months. EPA was bioavailable; the skin content at 3 months showing an 8-fold rise from baseline, P < 0.01. No consistent pattern of alteration in basal and UVR-exposed skin content of the antioxidants glutathione, vitamins E and C or lipid peroxidation, was seen on supplementation. Sunburn sensitivity was reduced on EPA, the UVR-induced erythemal threshold rising from a mean of 36 (SD 10) mJ/cm(2) at baseline to 49 (16) mJ/cm(2) after supplementation, P < 0.01. Moreover, UVR-induced skin p53 expression, assessed immunohistochemically at 24 h post-UVR exposure, fell from a mean of 16 (SD 5) positive cells/100 epidermal cells at baseline to 8 (4) after EPA supplementation, P < 0.01. Peripheral blood lymphocytes (PBL) sampled on 3 successive days both pre- and post-supplementation, showed no change with respect to basal DNA single-strand breaks or oxidative base modification (8-oxo-dG). However, when susceptibility of PBL to ex vivo UVR was examined using the comet assay, this revealed a reduction in tail moment from 84.4 (SD 3.4) at baseline to 69.4 (3.1) after EPA, P = 0.03. No significant changes were seen in any of the above parameters following OA supplementation. Reduction in this range of early markers, i.e. sunburn, UVR-induced p53 in skin and strand breaks in PBL, indicate protection by dietary EPA against acute UVR-induced genotoxicity; longer-term supplementation might reduce skin cancer in humans.     

Esmolol versus diltiazem in atrial fibrillation following coronary artery bypass graft surgery

PURPOSE: Atrial fibrillation (AF) is the most common arrhythmic complication following coronary artery bypass graft surgery (CABG). The efficacy and safety of esmolol and diltiazem were compared in patients with post-CABG AF. METHODS: This study was a retrospective medical record review of consecutive patients with post-CABG AF > or =15 min in duration with a ventricular rate > or =110 b.p.m. who received either i.v. esmolol (n = 59) or i.v. diltiazem (n = 48) with or without concomitant digoxin therapy at a single university-affiliated teaching hospital. Treatment success was defined as either cardioversion to sinus rhythm or a reduction in the ventricular rate to < or =90 b.p.m. at 24 h after the start of therapy. Time to treatment success and the occurrence of adverse effects were considered secondary outcomes. RESULTS: A total of 107 patients with post-CABG AF were treated with i.v. esmolol (n = 59) or i.v. diltiazem (n = 48). The mean maximum dose of esmolol and diltiazem were 115 +/- 38 microg/kg/min and 11.2 +/- 3.5 mg/h, respectively. The average duration of the esmolol and diltiazem infusions were 19.3 +/- 8.5 h and 20.1 +/- 11.3 h, respectively. Based on the combined efficacy endpoint of cardioversion or ventricular rate control, esmolol was significantly more effective than diltiazem (90% vs 77%; p = 0.038). Time to treatment success was significantly better for esmolol than diltiazem at all time points (1, 2, 4, 6, 12, and 24 h post-treatment). The overall incidence of adverse effects was 44% with esmolol and 60% with diltiazem (p = 0.04). Rates of drug discontinuance for adverse effects were significantly less for esmolol (20%) compared with diltiazem (38%) (p = 0.04). CONCLUSIONS: Esmolol is significantly more effective than diltiazem in the management of post-CABG AF. More patients converted to sinus rhythm with esmolol as compared to diltiazem. Esmolol was associated with fewer adverse effects than diltiazem, including adverse effects leading to drug discontinuance. Due to study design limitations (retrospective data collection), an adequately powered randomised, controlled trial is needed to confirm these preliminary findings.     

Association between an agouti-related protein gene polymorphism and anorexia nervosa

Anorexia nervosa (AN) is a life threatening disorder affecting mostly adolescent women. It is a dramatic psychiatric syndrome accompanied by severe weight loss, hyperactivity and neuroendocrine changes (reviewed in Refs 1 and 2). Several studies have shown a strong genetic component in AN (reviewed in Ref 3). Recent advances in unraveling the mechanisms of weight control point to a crucial role of the melanocortin-4 receptor (MC4-r) system in regulating body weight. The orexigenic neuropeptide agouti-related protein (AGRP), a MC4-r antagonist, plays a crucial role in maintaining body weight, by inducing food intake. The sequence of the coding region of the human AGRP gene (AGRP) was determined and the AGRP of 100 patients with AN was screened for variations. Three single nucleotide polymorphisms (SNPs) were identified and screened in a further 45 patients and 244 controls. Two alleles were in complete linkage disequilibrium and were significantly enriched in anorectic patients (11%; P = 0.015) compared to controls (4.5%). These data indicate that variations of AGRP are associated with susceptibility for AN. This is possibly caused by defective suppression of the MC4-r by the variant AGRP, leading to a decreased feeding signal, increasing the risk of developing AN. These results implicate that antagonism of the MC4-r might be considered as pharmacotherapy for patients with AN.     

Platelet thrombus formation on collagen at high shear rates is mediated by von Willebrand factor-glycoprotein Ib interaction and inhibited by von Willebrand factor-glycoprotein IIb/IIIa interaction

We studied the role of von Willebrand Factor (vWF) in platelet thrombus formation in flowing blood by using a perfusion system and mutant forms of vWF lacking either interaction with glycoprotein Ib (GpIb) or with glycoprotein IIb/IIIa (alphaIIb-beta3). These mutants were added to the blood of patients with severe von Willebrand's disease (vWD) or to normal blood reconstituted with a human albumin solution instead of plasma. This blood was then perfused over collagen type III spray-coated on a glass surface and preincubated for 2 hours with 20 microg/mL plasma vWF. In this way, the adhesion step was mediated by the preincubated plasma vWF bound to collagen type III, whereas thrombus formation was mediated by mutant vWF added to the perfusate. Thrombus formation was absent at all 3 shear rates studied (300, 800, and 2600 s(-1)) when DeltaA1-vWF, lacking interaction with GpIb, was added to the perfusate, indicating the importance of GpIb-vWF interaction for thrombus formation. The interaction of vWF and GpIb is currently thought to be possible under physiological conditions in which the conformation of vWF has been changed by adsorption to a surface. Our results regarding the role of GpIb-vWF interaction in thrombus formation suggest that a second mechanism may operate by which a change may occur in GpIb on the surface of adhered platelets either by activation of the molecule or as a consequence of shear stress. Increased thrombus formation was observed when the Arg-Gly-Gly-Ser-vWF, which does not interact with alphaIIb-beta3, was added to vWD blood and perfused at 2600 s(-1). This increase was not observed in vWD blood at lower shear rates or after addition of Arg-Gly-Gly-Ser-vWF to reconstituted normal blood. Thrombus formation at a high shear rate was largest when either vWF or fibrinogen was present as a single ligand for alphaIIb-beta3 at a high shear rate. When both were present, thrombus formation was decreased. We postulate that thrombus formation is less efficient because of incomplete bridge formation when vWF and fibrinogen are both present as ligands for alphaIIb-beta3.     

Inhibition of intercellular adhesio nmolecule-1 (ICAM-1) expression in ultraviolet B-irradiated human antigen-presenting cells is restored after repair of cyclobutane pyrimidine dimers

The present study assessed the molecular mechanism underlying ultraviolet (UV) B radiation-induced inhibition of the expression of the adhesion molecule ICAM-1 in human antigen-presenting cells (APC). UVB radiation-induced inhibition of ICAM-I expression in human peripheral blood monocytes was associated with the generation of cyclobutane pyrimidine dimers (CPD). CPD were reduced by 60% after treatment with liposomal packed photolyase, an enzyme which removes CPD after absorption of photoreactivating light. Although incomplete, reduction of CPD was associated with complete restoration of ICAM-1 expression at the mRNA and protein level. Neither reduction of CPD level nor restoration of ICAM-1 expression were observed, if monocytes were treated with empty liposomes, or if they were irradiated with photoreactivating light prior to application of photolyase. DNA damage might also induce soluble mediators capable of autocrine inhibition of ICAM-1 expression. UVB irradiation of monocytes did not induce IL-10 production, but resulted in release of prostaglandin (PG) E2. Treatment of unirradiated monocytes with PGE2 completely inhibited ICAM-1 expression, thus mimicking the UVB effect. Inhibition of monocytic PGE2 production by indomethacin, however, did not restore ICAM-1 expression. These results suggest that formation of CPD is necessary and sufficient for UVB radiation-induced inhibition of ICAM-1 expression. In contrast, PGE2 might serve a paracrine role in UVB radiation-induced immunosuppression.     

Damage to the intestinal epithelial barrier by antibiotic pretreatment of salmonella-infected rats is lessened by dietary calcium or tannic acid

Perturbation of the intestinal microbiota by antibiotics predisposes the host to food-borne pathogens like Salmonella. The effects of antibiotic treatment on intestinal permeability during infection and the efficacy of dietary components to improve resistance to infection have not been studied. Therefore, we investigated the effect of clindamycin on intestinal barrier function in Salmonella-infected rats. We also studied the ability of dietary calcium and tannic acid to protect against infection and concomitant diarrhea and we assessed intestinal barrier function. Rats were fed a purified control diet including the permeability marker chromium EDTA (CrEDTA) (2 g/kg) or the same diet supplemented with calcium (4.8 g/kg) or tannic acid (3.75 g/kg). After adaptation, rats were orally treated with clindamycin for 4 d followed by oral infection with Salmonella enteritidis. Two additional control groups were not treated with antibiotics and received either saline or Salmonella. Urine and feces were collected to quantify intestinal permeability, diarrhea, cytotoxicity of fecal water, and Salmonella excretion. In addition, Salmonella translocation was determined. Diarrhea, CrEDTA excretion, and cytotoxicity of fecal water were higher in the clindamycin-treated infected rats than in the non-clindamycin-treated infected control group. Intestinal barrier function was less in the Salmonella-infected rats pretreated with antibiotics compared with the non-clindamycin- treated rats. Both calcium and tannic acid reduced infection-associated diarrhea and inhibited the adverse intestinal permeability changes but did not decrease Salmonella colonization and translocation. Our results indicate that calcium protects against intestinal changes due to Salmonella infection by reducing luminal cytotoxicity, whereas tannic acid offers protection by improving the mucosal resistance.     

A new Ig-superfamily member,molluscan defence molecule (MDM) from Lymnaea stagnalis,is down-regulated during parasitosis

To survive the attacks of the internal defence system (IDS) of their host, parasites have developed various strategies to manipulate the IDS. We present evidence that the avian schistosome parasite Trichobilharzia ocellata affects gene expression in the granular cells, a cell type of the IDS of the intermediate host, the mollusc Lymnaea stagnalis. From a differential screening, a clone was isolated encoding a protein named molluscan defence molecule (MDM), which encompasses five C2-like immunoglobulin (Ig) domains. The protein shares a domain organization and high amino acid sequence identity with hemolin, an Ig-family member of the insect IDS. Interestingly, both MDM and hemolin have highest sequence identity with neural cell adhesion molecules, but lack the typical fibronectin repeats and motifs for membrane anchors. We find that the expression of the MDM gene is gradually down-regulated during the course of parasitosis to ～21% compared to the non-parasitized level, 8 weeks post-infection. Based on our findings, we suggest that MDM is involved in the proper functioning of the Lymnaea IDS, and that down-regulation of MDM is part of the parasite-induced disabling of non-self recognition.