Violeta Arsenescu

Polychlorinated Biphenyl-77 Induces Adipocyte Differentiation and Proinflammatory Adipokines and Promotes Obesity and Atherosclerosis

Background Obesity, an inflammatory condition linked to cardiovascular disease, is associated with expansion of adipose tissue. Highly prevalent coplanar polychlorinated biphenyls (PCBs) such as 3,3′,4,4′-tetrachlorobiphenyl (PCB-77) accumulate in adipose tissue because of their lipophilicity and increase with obesity. However, the effects of PCBs on adipocytes, obesity, and obesity-associated cardiovascular disease are unknown. Objectives In this study we examined in vitro and in vivo effects of PCB-77 on adipocyte differentiation, proinflammatory adipokines, adipocyte morphology, body weight, serum lipids, and atherosclerosis. Methods PCB-77 or 2,2′,4,4,5,5′-hexachlorobiphenyl (PCB-153) was incubated with 3T3-L1 adipocytes either during differentiation or in mature adipocytes. Concentration-dependent effects of PCB-77 were contrasted with those of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). For in vivo studies, we treated C57BL/6 wild-type (WT) or aryl hydrocarbon receptor (AhR)−/− mice with vehicle or PCB-77 (49 mg/kg, by intraperitoneal injection) and examined body weight gain. In separate studies, we injected ApoE−/− mice with vehicle or PCB-77 over a 6-week period and examined body weight, adipocyte size, serum lipids, and atherosclerosis. Results Low concentrations of PCB-77 or TCDD increased adipocyte differentiation, glycerol–3-phosphate dehydrogenase activity, and expression of peroxisome proliferator–activated receptor γ, whereas higher concentrations inhibited adipocyte differentiation. Effects of PCB-77 were abolished by the AhR antagonist α-naphthoflavone. PCB-77 promoted the expression and release of various proinflammatory cytokines from 3T3-L1 adipocytes. Administration of PCB-77 increased body weight gain in WT but not AhR−/− mice. ApoE−/− mice injected with PCB-77 exhibited greater body weight, adipocyte hypertrophy, serum dyslipidemia, and augmented atherosclerosis. Conclusions Our findings suggest that PCB-77 may contribute to the development of obesity and obesity-associated atherosclerosis.

Role of the xenobiotic receptor in inflammatory bowel disease

Background: Gene‐environment interplay modulates inflammatory bowel diseases (IBD). Dioxin‐like compounds can activate the aryl hydrocarbon receptor (AhR) and alter macrophage function as well as T‐cell polarization. We hypothesized that attenuation of the AhR signaling pathway will ameliorate colitis in a murine model of IBD. Methods: Dextran sulfate sodium (DSS) colitis was induced in C57BL/6 AhR null mice (AhR−/−), heterozygous mice (AhR−/+), and their wildtype (WT) littermates. Clinical and morphopathological parameters were used to compare the groups. Patients: AhR pathway activation was analyzed in biopsy specimens from 25 IBD patients and 15 healthy controls. Results: AhR−/− mice died before the end of the treatment. However, AhR−/+ mice exhibited decreased disease activity compared to WT mice. The AhR−/+ mice expressed less proinflammatory cytokines such as tumor necrosis factor alpha (TNF‐&agr;) (6.1‐ versus 15.7‐fold increase) and IL17 (23.7‐ versus 67.9‐fold increase) and increased antiinflammatory IL‐10 (2.3‐fold increase) compared with the AhR+/+ mice in the colon. Colonic macrophage infiltration was attenuated in the AhR−/+ group. AhR and its downstream targets were significantly upregulated in IBD patients versus control (CYP1A1 −19.9, and IL8‐ 10‐fold increase). Conclusions: Attenuation of the AhR receptor expression resulted in a protective effect during DSS‐induced colitis, while the absence of AhR exacerbated the disease. Abnormal AhR pathway activation in the intestinal mucosa of IBD patients may promote chronic inflammation. Modulation of AhR signaling pathway via the diet, cessation of smoking, or administration of AhR antagonists could be viable strategies for the treatment of IBD. (Inflamm Bowel Dis 2010;)

Intestinal Epithelial Serum Amyloid A Modulates Bacterial Growth In Vitro and Pro-Inflammatory Responses in Mouse Experimental Colitis

BackgroundSerum Amyloid A (SAA) is a major acute phase protein of unknown function. SAA is mostly expressed in the liver, but also in other tissues including the intestinal epithelium. SAA reportedly has anti-bacterial effects, and because inflammatory bowel diseases (IBD) result from a breakdown in homeostatic interactions between intestinal epithelia and bacteria, we hypothesized that SAA is protective during experimental colitis.MethodsIntestinal SAA expression was measured in mouse and human samples. Dextran sodium sulfate (DSS) colitis was induced in SAA 1/2 double knockout (DKO) mice and in wildtype controls. Anti-bacterial effects of SAA1/2 were tested in intestinal epithelial cell lines transduced with adenoviral vectors encoding the CE/J SAA isoform or control vectors prior to exposure to live Escherichia coli.ResultsSignificant levels of SAA1/SAA2 RNA and SAA protein were detected by in situ hybridization and immunohistochemistry in mouse colonic epithelium. SAA3 expression was weaker, but similarly distributed. SAA1/2 RNA was present in the ileum and colon of conventional mice and in the colon of germfree mice. Expression of SAA3 was strongly regulated by bacterial lipopolysaccharides in cultured epithelial cell lines, whereas SAA1/2 expression was constitutive and not LPS inducible. Overexpression of SAA1/2 in cultured epithelial cell lines reduced the viability of co-cultured E. coli. This might partially explain the observed increase in susceptibility of DKO mice to DSS colitis. SAA1/2 expression was increased in colon samples obtained from Crohns Disease patients compared to controls.ConclusionsIntestinal epithelial SAA displays bactericidal properties in vitro and could play a protective role in experimental mouse colitis. Altered expression of SAA in intestinal biopsies from Crohns Disease patients suggests that SAA is involved in the disease process..

TNF-α and the Development of the Neonatal Immune System: Implications for Inhibitor Use in Pregnancy

Inflammatory bowel diseases, Crohn’s disease, and ulcerative colitis have an unpredictable course during and after pregnancy (1). There is a great deal of interest in treating moderate to severe active inflammatory bowel disease with anti-tumor necrosis factor (anti-TNF) biologics in pregnant women (2). We lack definitive information about the effects of these agents on the development of the immune system of the human fetus and the newborn baby. Anti-TNF agents fall within US Food and Drug Administration’s (FDA) category B regarding fetal risk, indicating that no adequate and well-controlled studies have been conducted in pregnant or nursing women. Here, we review animal studies (of both mice and nonhuman primates) that examine the role of TNF and its inhibitors in the normal development of the immune system.

Induction of gene pattern changes associated with dysfunctional lipid metabolism induced by dietary fat and exposure to a persistent organic pollutant

Environmental modulators of chronic diseases can include nutrition, lifestyle, as well as exposure to environmental toxicants such as persistent organic pollutants. A study was designed to explore gene expression changes as affected by both dietary fat and exposure to the polychlorinated biphenyl PCB77. Mice were fed for 4 months diets enriched with high-linoleic acid oils (20% and 40% as calories), and during the last 2 months half of each group was exposed to PCB77. Ribonucleic acids (RNA) were extracted from liver tissue to determine gene expression changes using DNA microarray analysis. Our microarray data demonstrated a significant interaction between dietary fat and PCB exposure. Deregulated genes were organized into patterns describing the interaction of diet and PCB exposure. Annotation of the deregulated genes matching these probe sets revealed a significant high-fat mediated induction of genes associated with fatty acid metabolism, triacylglycerol synthesis and cholesterol catabolism, which was down-regulated in animals exposed to PCB77. Many of these genes are regulated by the peroxisome proliferator activated receptor-alpha (PPARalpha), and changes in PPARalpha gene expression followed the same gene pattern as described above. These results provide insight into molecular mechanisms of how dietary fat can interact with environmental pollutants to compromise lipid metabolism.

Adiponectin and Plant-Derived Mammalian Adiponectin Homolog Exert a Protective Effect in Murine Colitis

BackgroundHypoadiponectinemia has been associated with states of chronic inflammation in humans. Mesenteric fat hypertrophy and low adiponectin have been described in patients with Crohn’s disease. We investigated whether adiponectin and the plant-derived homolog, osmotin, are beneficial in a murine model of colitis.MethodsC57BL/6 mice were injected (i.v.) with an adenoviral construct encoding the full-length murine adiponectin gene (AN+DSS) or a reporter—LacZ (Ctr and V+DSS groups) prior to DSS colitis protocol. In another experiment, mice with DSS colitis received either osmotin (Osm+DSS) or saline (DSS) via osmotic pumps. Disease progression and severity were evaluated using body weight, stool consistency, rectal bleeding, colon lengths, and histology. In vitro experiments were carried out in bone marrow-derived dendritic cells.ResultsMice overexpressing adiponectin had lower expression of proinflammatory cytokines (TNF, IL-1β), adipokines (angiotensin, osteopontin), and cellular stress and apoptosis markers. These mice had higher levels of IL-10, alternative macrophage marker, arginase 1, and leukoprotease inhibitor. The plant adiponectin homolog osmotin similarly improved colitis outcome and induced robust IL-10 secretion. LPS induced a state of adiponectin resistance in dendritic cells that was reversed by treatment with PPARγ agonist and retinoic acid.ConclusionAdiponectin exerted protective effects during murine DSS colitis. It had a broad activity that encompassed cytokines, chemotactic factors as well as processes that assure cell viability during stressful conditions. Reducing adiponectin resistance or using plant-derived adiponectin homologs may become therapeutic options in inflammatory bowel disease.

Polychlorinated biphenyl 77 augments angiotensin II-induced atherosclerosis and abdominal aortic aneurysms in male apolipoprotein E deficient mice

Infusion of angiotensin II (AngII) to hyperlipidemic mice augments atherosclerosis and causes formation of abdominal aortic aneurysms (AAAs). Each of these AngII-induced vascular pathologies exhibit pronounced inflammation. Previous studies demonstrated that coplanar polychlorinated biphenyls (PCBs) promote inflammation in endothelial cells and adipocytes, two cell types implicated in AngII-induced vascular pathologies. The purpose of this study was to test the hypothesis that administration of PCB77 to male apolipoprotein E (ApoE) -/- mice promotes AngII-induced atherosclerosis and AAA formation. Male ApoE-/- mice were administered vehicle or PCB77 (49 mg/kg, i.p.) during week 1 and 4 (2 divided doses/week) of AngII infusion. Body weights and total serum cholesterol concentrations were not influenced by administration of PCB77. Systolic blood pressure was increased in AngII-infused mice administered PCB77 compared to vehicle (156±6 vs 137±5 mmHg, respectively). The percentage of aortic arch covered by atherosclerotic lesions was increased in AngII-infused mice administered PCB77 compared to vehicle (2.0±0.4 vs 0.9±0.1%, respectively). Lumen diameters of abdominal aortas determined by in vivo ultrasound and external diameters of excised suprarenal aortas were increased in AngII-infused mice administered PCB77 compared to vehicle. In addition, AAA incidence increased from 47 to 85% in AngII-infused mice administered PCB77. Adipose tissue in close proximity to AAAs from mice administered PCB77 exhibited increased mRNA abundance of proinflammatory cytokines and elevated expression of components of the renin-angiotensin system (angiotensinogen, angiotensin type 1a receptor (AT1aR)). These results demonstrate that PCB77 augments AngII-induced atherosclerosis and AAA formation.

Autoimmune enteropathy with a CD8 + CD7 - T-cell small bowel intraepithelial lymphocytosis: case report and literature review

BackgroundAdult onset autoimmune enteropathy (AIE) is a rare condition characterized by diarrhea refractory to dietary therapy diagnosed in patients with evidence of autoimmune conditions. Auto-antibodies to gut epithelial cells and other tissues are commonly demonstrated. Despite increasing awareness, the pathogenesis, histologic, immunologic and clinical features of AIE remain uncertain. There remains controversy regarding the diagnostic criteria, the frequency and types of auto-antibodies and associated autoimmune conditions, and the extent and types of histologic and immunologic abnormalities. CD4+ T-cells are thought to at least responsible for this condition; whether other cell types, including B- and other T-cell subsets are involved, are uncertain. We present a unique case of AIE associated with a CD8+CD7- lymphocytosis and review the literature to characterize the histologic and immunologic abnormalities, and the autoantibodies and autoimmune conditions associated with AIE.Case PresentationWe present a case of immune mediated enteropathy distinguished by the CD8+CD7- intra-epithelial and lamina propria lymphocytosis. Twenty-nine cases of AIE have been reported. The majority of patients had auto-antibodies (typically anti-enterocyte), preferential small bowel involvement, and predominately CD3+ CD4+ infiltrates. Common therapies included steroids or immuno-suppressive agents and clinical response with associated with histologic improvement.ConclusionsAIE is most often characterized (1) IgG subclass anti-epithelial cell antibodies, (2) preferential small bowel involvement, and (3) CD3+ alphabeta TCR+ infiltrates; there is insufficient evidence to conclude CD4+ T-cells are solely responsible in all cases of AIE.

Inflammatory Bowel Disease: How Effective Is TNF-α Suppression?

Crohn’s Disease (CD) results from inappropriate response toward commensal flora. Earlier studies described CD as a Th1 mediated disease. Current models view both phenotypes as a continuum of various permutations between Th1, Th2 and Th17 pathways compounded by a range of Treg disfunctions. In the present paper, we develop a mathematical model, by a system of differential equations, which describe the dynamic relations among these T cells and their cytokines. The model identities four groups of CD patients according to up/down regulation of Th1 and Th2. The model simulations show that immunosuppression by TNF-α blockage benefits the group with Th1High/Th2Low while, by contrast, the group with Th1Low/Th2High will benefit from immune activation.

Impact of Obesity on Ulcerative Colitis Phenotype

induced intestinal lesions were examined in rats. The role of intestinal motility, capsaicinsensitive sensory neurons (CSSNs) and nitric oxide (NO) in the effects of the drugs was also examined. METHODS: Male Wistar rats were treated with IND (10 mg/kg, p.o.) after a 16 h-fast (for gastric ulcers) or without fasting (for intestinal ulcers). The animals were autopsied 24 h after IND administration, and the stomach and small intestine were examined for lesions. Intestinal motility was measured using a balloon method in anesthetized rats. RESULTS: 1. Gastric lesions: IND produced many linear lesions in the corpus mucosa, and the lesion index (LI, total length) in the vehicle-treated group was 25.6±5.3 mm (n=7). The LI was significantly (P<0.05) decreased by pretreatment with oral doses (mg/kg) of CIM (100), RAN (30), FAM (10), OPZ (30), LPZ (30) and RPZ (30). 2. Small intestinal lesions: IND produced many lesions in the middle and lower parts of the small intestine. The LI in the vehicle-treated group was 57.0±10.0 mm (n=10). (a) Effects of H2-RAs: CIM, RAN and FAM increased the LI by 94% (P<0.01), 82% (P<0.01), and 68% (P<0.05), respectively. H2-RAs (3-30, i.v.) did not directly affect intestinal motility, but they did increase the motility induced by IND (10, s.c.). (b) Effects of PPIs: OPZ (100) and RPZ (100) significantly (P<0.05) increased the LI by 48% and 33%, respectively, whereas LPZ (30) significantly (P<0.01) decreased the LI by 61%. The inhibitory effect of LPZ was abolished by functional ablation of CSSNs (20, 30 and 50 mg/kg of capsaicin was administered s.c. for 3 consecutive days 2 weeks before the experiment) or pretreatment with L-NAME (a NO synthase inhibitor). CONCLUSIONS: Though H2-RAs and PPIs markedly inhibited the formation of gastric lesions induced by IND, they (except for LPZ) increased the formation of small intestinal lesions. The results suggest that antisecretory drugs aggravate intestinal lesions induced by NSAIDs, probably by increasing the amount of indigestive foods in the intestine and by increasing intestinal motility. LPZ, though having a potent antisecretory action, inhibited the formation of intestinal lesions, and this action can be explained by its protective action on the mucosa via CSSNs and NO.