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Published on: February 9, 2017
Constitutive expression of ICAM-1 in rat microvascular systems analyzed by laser confocal microscopy
Y Iigo1, M Suematsu, T Higashida
1New Product Research Laboratories IV, Daiichi Pharmaceutical Company, Tokyo, Japan.
Insights
Intercellular adhesion molecule-1 (ICAM-1) is constitutively expressed in rat mesenteric postcapillary venules and liver sinusoids. This suggests these microvessels are key sites for leukocyte adhesion during inflammation.
Area of Science:
- Immunology
- Microcirculation Research
- Cell Biology
Background:
- Intercellular adhesion molecule-1 (ICAM-1) plays a crucial role in leukocyte adhesion and trafficking.
- Understanding ICAM-1 expression patterns in microvasculature is vital for comprehending inflammatory responses.
Purpose of the Study:
- To investigate the constitutive expression of ICAM-1 in rat mesenteric and liver microvessels.
- To analyze the interaction between endothelial cells and leukocytes in vivo.
Main Methods:
- Laser confocal fluorescence microscopy was employed to visualize ICAM-1 expression.
- A fluorescein isothiocyanate-labeled monoclonal antibody against rat ICAM-1 (1A29) was used for detection.
- Quantitative analysis of antibody binding was performed for calibration.
Main Results:
- ICAM-1 expression was heterogeneously distributed in mesenteric microvessels, with significantly higher levels in postcapillary venules compared to capillaries and arterioles.
- Liver sinusoids exhibited abundant ICAM-1 expression, comparable to central venules.
- Postcapillary venules showed at least a 10-fold higher density of ICAM-1 compared to other mesenteric microvessels.
Conclusions:
- Postcapillary venules are identified as primary sites for constitutive ICAM-1 expression in the mesentery.
- The findings suggest that postcapillary venules act as active gateways for leukocyte adhesion upon inflammatory stimuli.
- Liver sinusoids also demonstrate significant ICAM-1 expression, indicating their role in inflammatory cell interactions.
Abstract:
The present study aimed to demonstrate constitutive expression of the intercellular adhesion molecule (ICAM)-1 among arterioles, capillaries, and venules in the mesentery and liver and to examine the interaction between cultured endothelial cells and leukocytes in rats. ICAM-1 expression in the microvessels in vivo was visually demonstrated by laser confocal fluorescence microscopy. A monoclonal antibody against rat ICAM-1 (1A29) was labeled with fluorescein isothiocyanate, and the binding ratio between the fluorescence and immunoglobulin was determined for data calibration. Intravascularly administered fluorescein isothiocyanate-labeled 1A29 was distributed heterogeneously among the hierarchy of microvessels in the mesentery: postcapillary venules were the major portion expressing ICAM-1 constitutively, and the density of 1A29 bound to their endothelium was at least 10 times higher than that in true capillaries and arterioles in the same mesentery. On the other hand, the liver expressed ICAM-1 abundantly in sinusoids to the extent similar to that in central venules. These results suggest that postcapillary venules serve as an active gateway with the readiness to help adhere circulating leukocytes exposed to proinflammatory stimuli in acute inflammation.
