Diminished adenosine A1 receptor expression on macrophages in brain and blood of patients with multiple sclerosis
J B Johnston1, C Silva, G Gonzalez
1Department of Clinical Neurosciences, University of Calgary, Alberta, Canada.
Abstract:
The nucleoside adenosine has been shown to control the production of proinflammatory molecules through its actions on cell surface purine receptors. Previously, we have reported that the adenosine A1 receptor (A1AR) regulates tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) expression and exhibits diminished function in patients with multiple sclerosis (MS; Mayne et al., Ann Neurol 1999;45:633-639). In the present study, A1AR expression in both brain and peripheral blood mononuclear cells (PBMC) from MS and control groups was characterized by fluorescence-activated cell sorting (FACS), reverse transcriptase-polymerase chain reaction (RT-PCR), and immunohistochemical analyses. FACS analyses of PBMC revealed that A1AR expression was chiefly detectable on CD14-positive cells and was reduced by 53.1% (p < 0.01) in MS patients compared to controls. A1AR mRNA levels were reduced by 43.1% (p < 0.001) in the brains of MS patients compared to patients with other neurological diseases and controls. A1AR protein expression in brain was detected primarily in CD45-positive glial cells and was markedly diminished in MS patients. The analysis of A1AR transcripts in the brain revealed that the A1AR-beta transcript was diminished (49.2%) in MS patients compared to controls (p < 0.002). These results indicate that the A1AR, expressed principally on cells of monocyte/macrophage lineage in both brain and blood, is selectively diminished in MS patients. Reduction of the A1AR-beta transcript in MS patients suggests that dysregulated splicing may influence A1AR protein levels, potentially leading to increased macrophage activation and central nervous system inflammation.
Insights
The adenosine A1 receptor (A1AR) is reduced in multiple sclerosis (MS) patients, particularly on immune cells in the brain and blood. This reduction may contribute to central nervous system inflammation in MS.
Area of Science:
- Neuroimmunology
- Molecular Medicine
- Cell Biology
Background:
- Adenosine, via cell surface purine receptors, modulates proinflammatory molecule production.
- The adenosine A1 receptor (A1AR) regulates TNF-alpha and IL-6, with diminished function previously noted in multiple sclerosis (MS).
Purpose of the Study:
- To characterize adenosine A1 receptor (A1AR) expression in the brain and peripheral blood mononuclear cells (PBMC) of MS patients and controls.
- To investigate the potential role of A1AR dysregulation in the pathogenesis of MS.
Main Methods:
- Fluorescence-activated cell sorting (FACS) for cell surface receptor analysis.
- Reverse transcriptase-polymerase chain reaction (RT-PCR) for mRNA expression.
- Immunohistochemical analyses for protein localization and quantification.
Main Results:
- A1AR expression was reduced by 53.1% on CD14-positive cells in MS patient PBMCs compared to controls.
- A1AR mRNA levels were decreased by 43.1% in the brains of MS patients.
- A1AR protein was diminished in CD45-positive glial cells in the MS brain.
- A specific transcript, A1AR-beta, was reduced by 49.2% in MS patient brains.
Conclusions:
- The adenosine A1 receptor (A1AR) is selectively diminished in MS patients, primarily on monocyte/macrophage lineage cells in both the brain and blood.
- Reduced A1AR-beta transcript levels in MS suggest dysregulated splicing may impact A1AR protein levels.
- These molecular changes may contribute to increased macrophage activation and central nervous system inflammation in MS.
