Biomedical subjects

Marie-Claire Michoud

Publications and source records attributed to Marie-Claire Michoud.

5 recordsLinked to original sources

PubMed2006

Interleukin-8: novel roles in human airway smooth muscle cell contraction and migration.

In patients with cystic fibrosis (CF) and asthma, elevated levels of interleukin-8 (IL-8) are found in the airways. IL-8 is a CXC chemokine that is a chemoattractant for neutrophils through CXCR1 and CXCR2 G protein-coupled receptors. We hypothesized that IL-8 acts directly on airway smooth muscle cells (ASMC) in a way that may contribute to the enhanced airway responsiveness and airway remodeling observed in CF and asthma. The aim of this study was to determine whether human ASMC (HASMC) express functional IL-8 receptors (CXCR1 and CXCR2) linked to cell contraction and migration. Experiments were conducted on cells harvested from human lung specimens. Real-time PCR and fluorescence-activated cell sorting analysis showed that HASMC expressed mRNA and protein for both CXCR1 and CXCR2. Intracellular Ca(2+) concentration ([Ca(2+)](i)) increased from 115 to 170 nM in response to IL-8 (100 nM) and decreased after inhibition of phospholipase C (PLC) with U-73122. On blocking the receptors with specific neutralizing antibodies, changes in [Ca(2+)](i) were abrogated. IL-8 also contracted the HASMC, decreasing the length of cells by 15%, and induced a 2.5-fold increase in migration. These results indicate that HASMC constitutively express functional CXCR1 and CXCR2 that mediate IL-8-triggered Ca(2+) release, contraction, and migration. These data suggest a potential role for IL-8 in causing abnormal airway structure and function in asthma and CF.

Antibodies↗

PubMed2006

Immunotherapy as a disease modifier.

Immunotherapy was formerly the treatment of allergic disease by repeated exposure to allergen. Other approaches to immune modulation have emerged using new knowledge of T cell function. The so-called hygiene hypothesis argues that alterations in our environment have resulted in a failure of the immune system to develop normally, such that excessive Th2 type responses to antigen exposures occur. These observations have prompted therapies designed to promote a shift from Th-2 to Th-1 responses. These therapies include bacterial vaccines and stimulation of the immune system with Toll like receptor ligands or bacterial nucleotide immunostimulatory sequences (CpG motifs). Traditional desensitization immunotherapy is being re-examined and anti-IgE therapy is also enjoying a measure of success.

Asthma↗

PubMed2005

The effects of extracellular purines and pyrimidines on human airway smooth muscle cells.

Extracellular ATP and UTP modulate the function of many cell types through the stimulation of specific P2 receptors, and the inhalation of UTP has been proposed as a therapeutic means of increasing mucociliary clearance in cystic fibrosis patients. The aim of this study was to determine whether P2 receptors are present and functional in human airway smooth muscle (HASM) cells. Experiments were conducted on primary cultures of HASM cells. Reverse transcription-polymerase chain reaction and Western blot analysis showed that P2Y(1), P2Y(2), P2Y(4), and P2Y(6) receptor subtypes are expressed. Exposure to extracellular ATP, UTP, ADP, and UDP at concentrations ranging from 10(-6) to 10(-4) M, produced significant increases in intracellular Ca(2+) that peaked to 491 +/- 51 nM (p < 0.001) with ATP 10(-5) M and to 321 +/- 30 nM with UTP 10(-4) M. ATP and UTP also induced HASM cell contraction, decreasing cell length by 9.9 +/- 4.3 and 5.6 +/- 2.0%, respectively. Pretreatment of the cells with UTP for short periods of time (10 and 30 min) enhanced the peak Ca(2+) release to UTP, whereas repeated and prolonged pretreatment with UTP decreased it. These results indicate that several subtypes of P2Y receptors are present and functional in HASM cells. They also show that the response of the receptors is increased after short periods of exposure to UTP and decreased after prolonged and repeated exposure. Considering that ATP and UTP are endogenous mediators and that analogs of UTP could be used as a therapeutic modality, the role of extracellular triphosphate nucleotides in physiological and pathophysiological processes in the airways warrants further investigation.

Adenosine Triphosphate↗

PubMed2003

Airway smooth muscle cells express functional neurokinin-1 receptors and the nerve-derived preprotachykinin-a gene: regulation by passive sensitization.

Preprotachykinin-A (PPT-A) gene-derived neuropeptides, namely substance P (SP) and neurokinin (NK)A, and their receptors participate in allergen-induced airway responses. Whether airway smooth muscle cells (ASMC) may react directly to SP through expression of the NK-1 receptor or express the gene for the synthesis of SP, the PPT-A gene, is unknown. We demonstrated using reverse transcription-polymerase chain reaction that tracheal SMC (TSMC) from atopic Brown Norway rats contained mRNA transcripts for the full-length isoform of the NK-1 receptor. Flow cytometric analysis indicated that the NK-1 receptor was expressed on the surface of TSMC. This receptor was functional as demonstrated by calcium mobilization in response to SP stimulation. The expression of the NK-1 receptor was not altered in passively sensitized TSMC in response to antigenic stimulation, although this stimulation increased the expression of the chemokine RANTES (regulated on activation, normal T cells expressed and secreted). Using different sets of PCR primers, we showed that TSMC also express the beta, alpha, and its alternative splicing product delta, and possibly the gamma mRNA transcript isoforms of the PPT-A gene. Gene sequencing of the PCR-amplified beta isoform confirmed that it is a transcript product of the rat PPT-A gene, and the production of SP by TSMC was confirmed by enzyme immunoassay. We also showed the beta isoform increased after cell stimulation with rat sera, whether sensitized or not. In conclusion, both the PPT-A gene and NK-1 receptors are expressed by TSMC, which suggests the possibility of autocrine neuropeptidergic mechanisms in these cells. However, these mechanisms are not upregulated by passive sensitization.

Animals↗

PubMed2002

Effects of extracellular triphosphate nucleotides and nucleosides on airway smooth muscle cell proliferation.

Extracellular ATP and uridine triphosphate (UTP) have a range of effects on a wide variety of cells through the activation of P(2) receptors. The aim of this work was to establish if stimulation with ATP and UTP enhances airway smooth muscle (ASM) cell proliferation and to determine the type of receptor mediating this effect. Proliferation of rat ASM cells was assessed through bromodeoxyuridine (BrdU) uptake and by cell counting. At concentrations of 10(-6) and 10(-5) M, ATP and UTP induced significant increases in BrdU incorporation. ATP analogs specific for the P(2X) and P(2Y1) receptor subtypes had no effect. UDP (a P(2Y6) receptor agonist) produced significant decreases in BrdU incorporation and cell counts. Adenosine, the metabolite of ATP, produced an increase in cell proliferation through stimulation of the A(1) receptor. A(2) and A(3) receptor stimulation had no effect. Reverse transcription and polymerase chain reaction analysis showed that mRNA transcripts for the P(2Y2), P(2Y4), P(2Y6), A(1), A(2), and A(3) receptor subtypes were present in cultured ASM cells. These data show that extracellular UTP, ATP, and their metabolites may affect airway remodeling by increasing or by reducing (P(2Y6) receptor) ASM cell proliferation.

Adenosine Triphosphate↗