Geneviève Mailhot - Academia.edu (original) (raw)

Papers by Geneviève Mailhot

Nutrients, 2020

The last couple of decades have seen an explosion in our interest and understanding of the role o... more The last couple of decades have seen an explosion in our interest and understanding of the role of vitamin D in the regulation of immunity. At the molecular level, the hormonal form of vitamin D signals through the nuclear vitamin D receptor (VDR), a ligand-regulated transcription factor. The VDR and vitamin D metabolic enzymes are expressed throughout the innate and adaptive arms of the immune system. The advent of genome-wide approaches to gene expression profiling have led to the identification of numerous VDR-regulated genes implicated in the regulation of innate and adaptive immunity. The molecular data infer that vitamin D signaling should boost innate immunity against pathogens of bacterial or viral origin. Vitamin D signaling also suppresses inflammatory immune responses that underlie autoimmunity and regulate allergic responses. These findings have been bolstered by clinical studies linking vitamin D deficiency to increased rates of infections, autoimmunity, and allergies. ...

The Clinical biochemist. Reviews / Australian Association of Clinical Biochemists, 2009

Cystic fibrosis (CF) represents the most common lethal autosomal recessive disorder in the Caucas... more Cystic fibrosis (CF) represents the most common lethal autosomal recessive disorder in the Caucasian population. It is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, resulting in abnormal Na(+) and Cl(-) transport in several tissues. Its main clinical manifestations include bronchopulmonary infections along with gastrointestinal and nutritional disorders. Intense and recurrent inflammation ultimately leads to an overabundance of activated neutrophils and macrophages that contribute to free radical generation. Furthermore, CFTR defects directly affect glutathione transport and homeostasis, while intestinal fat malabsorption limits uptake of endogenous antioxidant vitamins. Collectively, these abnormal events disturb the balance between pro- and anti-oxidants and promote oxidative stress, which may play a significant role in CF-related diabetes (CFRD), a severe complication associated with a drastic increase of morbidity and mortality. This review will ...

Connective Tissue Research, 2006

... Mailhot 1 and Mark J. Birnbaum 1 1 Department of Cell Biology, University of Massachusetts Me... more ... Mailhot 1 and Mark J. Birnbaum 1 1 Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts, USA. Department of Cell Biology, S7-242, U. Mass. Medical School, 55 Lake Ave., N., Worcester, MA, 01655, USA. ABSTRACT, Section: ...

Endocrinology, 2000

Little attention has been given to the consequences of the in vivo calcium status on intracellula... more Little attention has been given to the consequences of the in vivo calcium status on intracellular calcium homeostasis despite several pathological states induced by perturbations of the in vivo calcium balance. The aim of these studies was to probe the influence of an in vivo calcium deficiency on the resting cytoplasmic Ca21 concentration and the inositol-1,4,5-trisphosphate-sensitive Ca21 pools. Studies were

American journal of physiology. Gastrointestinal and liver physiology, 2009

Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel highly expressed... more Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel highly expressed in epithelial cells of the gastrointestinal tract. Mutations in the CFTR gene cause cystic fibrosis (CF), a disease characterized by pancreatic insufficiency, fat malabsorption, and steatorrhea. Despite the administration of pancreatic enzymes to normalize malabsorption, CF patients still experienced lipid fecal loss, nutritional deficiencies, and abnormalities in serum lipid profile, suggesting the presence of intrinsic defects in the intestinal handling of nutrients. The objective of the present study was to assess the impact of CFTR gene knockdown on intracellular lipid metabolism of the intestinal Caco-2/15 cell line. Partial CFTR gene inactivation led to cellular lipid accretion of phospholipids, triglycerides, and cholesteryl esters. Likewise, secretion of these lipid fractions was significantly increased following CFTR gene manipulation. As expected from these findings, the outpu...

PloS one, 2010

Abnormal fatty acid composition (FA) in plasma and tissue lipids frequently occurs in homozygous ... more Abnormal fatty acid composition (FA) in plasma and tissue lipids frequently occurs in homozygous and even in heterozygous carriers of cystic fibrosis transmembrane conductance regulator (CFTR) mutations. The mechanism(s) underlying these abnormalities remained, however, poorly understood despite the potentially CFTR contributing role. The aim of the present study was to investigate the impact of CFTR depletion on FA uptake, composition and metabolism using the intestinal Caco-2/15 cell line. shRNA-mediated cftr gene silencing induced qualitative and quantitative modifications in FA composition in differentiated enterocytes as determined by gas-liquid chromatography. With the cftr gene disruption, there was a 1,5 fold increase in the total FA amount, largely attributable to monounsaturated and saturated FA compared to controls. The activity of delta-7 desaturase, estimated by the 16:1(n-7)/16:0, was significantly higher in knockdown cells and consistent with the striking elevation of...

PLoS ONE, 2010

Background: Although mitochondrial dysfunction and oxidative stress are central mechanisms in var... more Background: Although mitochondrial dysfunction and oxidative stress are central mechanisms in various pathological conditions, they have not been extensively studied in the gastrointestinal tract, which is known to be constantly exposed to luminal oxidants from ingested foods. Key among these is the simultaneous consumption of iron salts and ascorbic acid, which can cause oxidative damage to biomolecules.

The Journal of Lipid Research, 2008

The role of intestinal fatty acid binding protein (I-FABP) in lipid metabolism remains elusive. T... more The role of intestinal fatty acid binding protein (I-FABP) in lipid metabolism remains elusive. To address this issue, normal human intestinal epithelial cells (HIEC-6) were transfected with cDNA to overexpress I-FABP and compared with cells treated with empty pQCXIP vector. I-FABP overexpression stimulated mitochondrial [U-14 C]oleate oxidation to CO 2 and acid-soluble metabolites via mechanisms including the upregulation of protein expression and the activity of carnitine palmitoyltransferase 1, a critical enzyme controlling the entry of fatty acid (FA) into mitochondria, and increased activity of 3-hydroxyacyl-CoA dehydrogenase, a mitochondrial b-oxidation enzyme. On the other hand, the gene and protein expression of the key enzymes FA synthase and acetylcoenzyme A carboxylase 2 was decreased, suggesting diminished lipogenesis. Furthermore, I-FABP overexpression caused a decline in [ 14 C]free cholesterol (CHOL) incorporation. Accordingly, a significant lessening was observed in the gene expression of Niemann Pick C1-Like 1, a mediator of CHOL uptake, along with an increase in the transcripts and protein content of ABCA1 and ABCG5/ABCG8, acting as CHOL efflux pumps. Furthermore, I-FABP overexpression resulted in increased levels of mRNA, protein mass, and activity of HMG-CoA reductase, the rate-limiting step in CHOL synthesis. Scrutiny of the nuclear receptors revealed augmented peroxisome proliferator-activated receptor a,g and reduced liver X receptor-a in HIEC-6 overexpressing I-FABP. Finally, I-FABP overexpression did not influence acylcoenzyme A oxidase 1, which catalyzes the first rate-limiting step in peroxisomal FA b-oxidation. Overall, our data suggest that I-FABP may influence mitochondrial FA oxidation and CHOL transport by regulating gene expression and interaction with nuclear receptors

Journal of Cellular Physiology, 2008

Bone morphogenetic proteins (BMPs) play pivotal roles in bone and cartilage growth and repair. Th... more Bone morphogenetic proteins (BMPs) play pivotal roles in bone and cartilage growth and repair. Through phenotypes of short ear mice, which have BMP-5 mutations, a role for BMP-5 in some specific aspects of skeletogenesis and cartilage growth is known. This report examines BMP-5 expression in the growth plate and in differentiating cultures of primary chondrocytes, and the effects of addition of BMP-5 or its inhibition by anti-BMP-5 antibody in chondrocyte cultures. By laser capture microdissection and immunohistochemistry, we found that BMP-5 is expressed in proliferating zone chondrocytes and that the expression increases sharply with hypertrophic differentiation. A similar pattern was observed in differentiating cultures of primary chondrocytes, with BMP-5 expression increasing as cells differentiated, in contrast to other BMPs. BMP-5 added to cultures increased cell proliferation early in the culture period and also stimulated cartilage matrix synthesis. Also, BMP-5 addition to the cultures activated phosphorylation of Smad 1/5/8 and p38 MAP kinase and caused increased nuclear accumulation of phospho-Smads. Anti-BMP-5 antibody inhibited the endogenous BMP-5, reducing cell proliferation and phospho-Smad nuclear accumulation. Together, the results demonstrate that BMP-5 is normally an important regulator of chondrocyte proliferation and differentiation. Whether other BMPs may compensate in BMP-5 lossof-function mutations is discussed. and −8b, is a member of BMP subfamily 60A, characterized by their high degree of amino acid sequence homology .

Histochemistry and Cell Biology, 2009

Although intestinal (I) and liver (L) fatty acid binding proteins (FABP) have been widely studied... more Although intestinal (I) and liver (L) fatty acid binding proteins (FABP) have been widely studied, the physiological significance of the presence of the two FABP forms (I- and L-FABP) in absorptive cells remains unknown as do the differences related to their distribution along the crypt-villus axis, regional expression, ontogeny and regulation in the human intestine. Our morphological experiments supported the expression of I- and L-FABP as early as 13 weeks of gestation. Whereas cytoplasmic immunofluorescence staining of L-FABP was barely detectable in the lower half of the villus and in the crypt epithelial cells, I-FABP was visualized in epithelial cells of the crypt-villus axis in all intestinal segments until the adult period in which the staining was maximized in the upper part of the villus. Immunoelectron microscopy revealed more intense labeling of L-FABP compared with I-FABP, accompanied with a heterogeneous distribution in the cytoplasm, microvilli and basolateral membranes. By western blot analysis, I- and L-FABP at 15 weeks of gestation appeared predominant in jejunum compared with duodenum, ileum, proximal and distal colon. Exploration of the maturation aspect documented a rise in L-FABP in adult tissues. Permanent transfections of Caco-2 cells with I-FABP cDNA resulted in decreased lipid export, apolipoprotein (apo) biogenesis and chylomicron secretion. Additionally, supplementation of Caco-2 with insulin, hydrocortisone and epidermal growth factor differentially modulated the expression of I- and L-FABP, apo B-48 and microsomal triglyceride transfer protein (MTP), emphasizing that these key proteins do not exhibit a parallel modulation. Overall, our findings indicate that the two FABPs display differences in localization, regulation and developmental pattern.

Bone, 2005

Introduction: Isolating and culturing primary chondrocytes such that they retain their cell type ... more Introduction: Isolating and culturing primary chondrocytes such that they retain their cell type and differentiate to a hypertrophic state is central to many investigations of skeletal growth and its regulation. The ability to store frozen chondrocytes has additional scientific and tissue engineering interest. Previous work has produced approaches of varying yield and complexity but does not permit frozen storage of cells for subsequent differentiation in culture. Investigations of growth plate dysplasias secondary to defective osteoclastogenesis in rodent models of osteopetrosis led us to adapt and modify a culture method and to cryopreserve neonatal rat costochondral chondrocytes. Methods: Chondrocytes were isolated from dissected ribs of 3-day-old rat pups by collagenase, hyaluronidase, and trypsin serial digestions. This was done either immediately or after the isolation was interrupted following an initial protease treatment to allow the chondrocytes, still in partially digested rib rudiments, to be frozen and later thawed for culture. Cells were plated in flat-bottom wells and allowed to adhere and grow under different conditions. Choice of media permitted cells to be maintained or induced to differentiate. Cell growth was monitored, as was expression of several relevant genes: collagen types II and X; osteocalcin, Sox9, adipocyte FABP, MyoD, aggrecan, and others. Mineralization was measured by alizarin red binding, and cultures were examined by light, fluorescence, and electron microscopy. Results: Cells retained their chondrocyte phenotype and ability to differentiate and mineralize the collagen-rich extracellular matrix even after freezing-thawing. RT-PCR showed retention of chondrocyte-specific gene expression, including aggrecan and collagen II. The cells had a flattened, ''proliferating zone'' appearance initially, and by 2 weeks post-confluence, exhibited swelling and other salient features of hypertrophic cells seen in vivo. Collagen fibrils were abundant in the extracellular matrix, along with matrix vesicles. The switch to collagen type X as marker for hypertrophy was not rigidly temporally regulated as happens in vivo, but its expression increased during hypertrophic differentiation. Conclusions: This method should prove valuable as a means of studying chondrocyte regulation and has the advantages of simpler initial dissection, yields of a purer chondrocyte population, and the ability to stockpile frozen raw material for subsequent studies. D

Bone, 2007

Hypocalcemia secondary to vitamin D3 (D3) depletion (D−Ca−) perturbs extra- and intracellular cal... more Hypocalcemia secondary to vitamin D3 (D3) depletion (D−Ca−) perturbs extra- and intracellular calcium (Ca). To study the effect of cyclic nutritional changes in the D3 and calcium (Ca) repletion state, we investigated the lasting effects of calcium or D3 repletion on calcium and bone metabolism using a novel depletion–repletion–redepletion protocol. D−Ca− rats presenting osteomalacia without rickets and a significant impairment

Blood, 2006

Osteoclasts differentiate from hematopoietic precursors under systemic and local controls. Chemok... more Osteoclasts differentiate from hematopoietic precursors under systemic and local controls. Chemokines and receptors direct leukocyte traffic throughout the body and may help regulate site-specific bone resorption. We investigated bone gene expression in vivo during rapid osteoclast differentiation induced by colony-stimulating factor 1 (CSF-1) in Csf1-null toothless (tl/tl) rats. Long-bone RNA from CSF-1-treated tl/tl rats was analyzed by high-density microarray over a time course. TRAP (tartrate-resistant acid phosphatase)-positive osteoclasts appeared on day 2, peaked on day 4, and decreased slightly on day 6, as marrow space was expanding. TRAP and cathepsin K mRNA paralleled the cell counts. We examined all chemokine and receptor mRNAs on the arrays. CCL9 was strongly induced and peaked on day 2, as did its receptor, CCR1, and regulatory receptors c-Fms (CSF-1 receptor) and RANK (receptor activator of nuclear factor kappaB). Other chemokines and receptors showed little or no significant changes. In situ hybridization and immunohistochemistry revealed CCL9 in small, immature osteoclasts on day 2 and in mature cells at later times. Anti-CCL9 antibody inhibited osteoclast differentiation in culture and significantly suppressed the osteoclast response in CSF-1-treated tl/tl rats. While various chemokines have been implicated in osteoclastogenesis in vitro, this first systematic analysis of chemokines and receptors during osteoclast differentiation in vivo highlights the key role of CCL9 in this process.

AJP: Gastrointestinal and Liver Physiology, 2008

Journal of Trace Elements in Medicine and Biology, 2014

Background: Zinc status has been previously documented in cystic fibrosis (CF) infants, children ... more Background: Zinc status has been previously documented in cystic fibrosis (CF) infants, children and adolescents. However, despite the increasing life expectancy observed in CF populations, data regarding zinc status of CF adults are surprisingly lacking. The objectives of this study were to (1) characterize zinc status and (2) explore associations between zinc status and clinical outcomes of CF adult patients. Methods: A retrospective chart review was performed for patients who had their plasma zinc measured between 2009 and 2012. Data included demographics, clinical characteristics, biochemical parameters and co-morbid conditions. Results: A total of 304 CF patients were included in the study. These patients displayed a good nutritional status (mean BMI ± SD: 22.7 ± 3.5) and moderate lung disease (mean FEV 1 ± SD: 66.3 ± 22.2). Low plasma zinc concentration (<9.2 mol/L) was found in 68 out of 304 CF patients (22.4%). Compared to patients with normal zinc, those with low zinc had significantly lower forced vital capacity and forced expiratory volume in one second. 72% of CF adults with low zinc suffered from bone disease (vs 49% with normal zinc, p = 0.037) and 79% had impaired glycemic status (vs 58%, p = 0.016). Accordingly, negative correlations were found between plasma zinc and glucose (r = −0.139, p = 0.0001), HbA1c (r = −0.237, p = 0.0001) and fructosamine (r = −0.134, p = 0.034). In multiple linear regression, albumin and glycemic status were significant predictors of plasma zinc. Conclusion: Our data indicated that nearly one quarter of CF adults with good nutritional status and moderate lung disease had low plasma zinc concentration and that low zinc status was associated with worse clinical outcomes.