ABSTRACT
Gastrointestinal reflux disease and eosinophilic esophagitis are characterized by basal cell hyperplasia. The extracellular calcium-sensing receptor (CaSR), a G protein-coupled receptor, which may be activated by divalent agonists, is expressed throughout the gastrointestinal system. The CaSR may regulate proliferation or differentiation, depending on cell type and tissue. The current experiments demonstrate the expression of the CaSR on a human esophageal epithelial cell line (HET-1A) and the location and expression of the CaSR in the human esophagus. CaSR immunoreactivity was seen in the basal layer of normal human esophagus. CaSR expression was confirmed in HET-1A cells by RT-PCR, immunocytochemistry, and Western blot analysis. CaSR stimulation by extracellular calcium or agonists, such as spermine or Mg(2+), caused ERK1 and 2 activation, intracellular calcium concentration ([Ca(2+)](i)) mobilization (as assessed by microspecfluorometry using Fluo-4), and secretion of the multifunctional cytokine IL-8 (CX-CL8). HET-1A cells transiently transfected with small interfering (si)RNA duplex against the CaSR manifested attenuated responses to Ca(2+) stimulation of phospho- (p)ERK1 and 2, [Ca(2+)](i) mobilization, and IL-8 secretion, whereas responses to acetylcholine (ACh) remained sustained. An inhibitor of phosphatidylinositol-specific phospholipase C (PI-PLC) (U73122) blocked CaSR-stimulated [Ca(2+)](i) release. We conclude that the CaSR is present on basal cells of the human esophagus and is present in a functional manner on the esophageal epithelial cell line, HET-1A.
Subject(s)
Calcium Signaling , Epithelial Cells/metabolism , Esophagus/metabolism , Receptors, Calcium-Sensing/metabolism , Acetylcholine/pharmacology , Blotting, Western , Calcium/metabolism , Calcium Signaling/drug effects , Cell Line , Enzyme Activation , Epithelial Cells/drug effects , Esophagus/cytology , Esophagus/drug effects , Estrenes/pharmacology , Humans , Immunohistochemistry , Interleukin-8/metabolism , Magnesium/metabolism , Microspectrophotometry , Mitogen-Activated Protein Kinase 1/metabolism , Mitogen-Activated Protein Kinase 3/metabolism , Phosphodiesterase Inhibitors/pharmacology , Phosphorylation , Polymerase Chain Reaction , Pyrrolidinones/pharmacology , RNA Interference , RNA, Messenger/metabolism , RNA, Small Interfering/metabolism , Receptors, Calcium-Sensing/genetics , Spermine/metabolism , Transfection , Type C Phospholipases/antagonists & inhibitors , Type C Phospholipases/metabolismABSTRACT
The objective was to assess the trend in HIV-1 seroprevalence in an adult population in Uganda. An observational cohort study with four year follow up was done within a cluster of 15 villages in rural Uganda. All residents of 15 villages about 10;000 people were studied. Main outcome measure was to show the prevalence of HIV-1 infection as assessed by enzyme immunoassay.The results showed that during the five year period the overall standardised seroprevalence of HIV-1 showed little change; 8.2in 1990; 7.6in 1994. Among males aged 13-24 years the prevlaence decreased from 3.4to 1.0(P for trend 0.001); among females of the same age the corresponding values were 9.9and 7.3. The decrease was greatest in males aged 20-24 years and females aged 13 - 19 years. This is the first report of a decline in HIV-1 prevlaence among young adults in a general population in sub-saharan Africa with high overall HIV-1 prevlaence. It is too early to conclude that the epidemic in this popualtion is in decline; but the results of this study should be reason for some cautious optimism and encourage the vigorous pursuit of AIDS control measures
