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Early expression of intercellular adhesion molecule-1 in the corneal endothelium stimulated by endotoxin: an
K Yamaguchi1, S Takahashi, K Sasaki
1Department of Ophthalmology, Yamagata University School of Medicine, Japan.
Insights
Salmonella typhimurium endotoxin significantly increases intercellular adhesion molecule-1 (ICAM-1) in rat corneal endothelium. This heightened ICAM-1 expression, particularly along cytoplasmic processes, is crucial for neutrophil binding.
Area of Science:
- Ophthalmology
- Immunology
- Cell Biology
Background:
- Intercellular adhesion molecule-1 (ICAM-1) plays a role in inflammatory responses.
- Endotoxins can trigger inflammatory cascades in ocular tissues.
- Understanding ICAM-1's role in the corneal endothelium is vital for managing ocular inflammation.
Purpose of the Study:
- To investigate the three-dimensional localization of ICAM-1 in the corneal endothelium.
- To determine the effect of Salmonella typhimurium endotoxin on ICAM-1 expression.
- To explore the relationship between ICAM-1 and neutrophil binding mechanisms.
Main Methods:
- Immuno-scanning electron microscopy (immuno-SEM) was employed for high-resolution imaging.
- Lewis rats were injected with Salmonella typhimurium endotoxin.
- Corneal tissues were collected at various time points and labeled with anti-ICAM-1 antibodies conjugated to gold particles.
Main Results:
- ICAM-1 antigen significantly increased on the corneal endothelium by 3 hours post-endotoxin injection.
- Quantitatively, ICAM-1 particle density rose from baseline levels to over 14.4/microns2 at 3 hours, peaking at 25.4/microns2 at 12 hours.
- ICAM-1 was localized along cytoplasmic processes, particularly at their summits.
Conclusions:
- Salmonella typhimurium endotoxin effectively augments ICAM-1 expression in the corneal endothelium.
- The observed increase in ICAM-1 is time-dependent, with significant elevation occurring within hours of endotoxin exposure.
- The association of ICAM-1 with cytoplasmic processes suggests a key role in mediating neutrophil adhesion to the corneal endothelium during inflammation.
Abstract:
Three-dimensional localization of the intercellular adhesion molecule-1 (ICAM-1) in the corneal endothelium stimulated by Salmonella typhimurium endotoxin was investigated using immuno-scanning electron microscopy (SEM). Samonella typhimurium endotoxin, 100 micrograms, was injected in Lewis rats weighing 200 grams. The animals, including the controls, were sacrificed and both eyes enucleated at 0, 3, 12 and 24 hours after injection (n = 3 each time). After resection, the corneas were immersed in hypothermic University of Wisconsin solution with monoclonal mouse-anti-rat ICAM-1 IgG and then goat-anti-mouse IgG coupled to 15 nm gold particles. Then the corneas were prepared conventionally for scanning electron microscopy. Histotopographical examination with immuno-SEM revealed that ICAM-1 antigen increased on the corneal endothelium by 3 hours postinjection. The particles were arranged along the cytoplasmic processes, especially at the summits. The number of particles was 3.3 +/- 0.8/microns2 in the control, 3.6 +/- 0.8/microns2 at 0 hour, 14.4 +/- 0.9/microns2 at 3 hours, 25.4 +/- 1.4/microns2 at 12 hours, and 22.7 +/- 2.6/microns2 at 24 hours postinjection. ANOVA indicated that the time-course was an important factor (P < 0.01). Our results showed that ICAM-1 could be augmented in the corneal endothelium by endotoxin. The interrelationship between ICAM-1 expression and cytoplasmic processes seems to be important for the neutrophil-binding mechanism.