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Changes in Expression of Receptor-Interacting Protein Kinase 1 in Secondary Neural Tissue Damage Following Spinal
Haruo Kanno1, Hiroshi Ozawa2, Kyoichi Handa1
1Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
Introduction:
Necroptosis is a form of programmed cell death that is different from apoptotic cell death. Receptor-interacting protein kinase 1 (RIPK1) plays a particularly important function in necroptosis execution. This study investigated changes in expression of RIPK1 in secondary neural tissue damage following spinal cord injury in mice. The time course of the RIPK1 expression was also compared with that of apoptotic cell death in the lesion site.
Methods And Materials:
Immunostaining for RIPK1 was performed at different time points after spinal cord injury. The protein expressions of RIPK1 were determined by western blot. The RIPK1 expressions in various neural cells were investigated using immunohistochemistry. To investigate the time course of apoptotic cell death, TUNEL-positive cells were counted at the different time points. To compare the incidence of necroptosis and apoptosis, the RIPK1-labeled sections were co-stained with TUNEL.
Results:
The RIPK1 expression was significantly upregulated in the injured spinal cord. The upregulation of RIPK1 expression was observed in neurons, astrocytes, and oligodendrocytes. The increase in RIPK1 expression started at 4 hours and peaked at 3 days after injury. Time course of the RIPK1 expression was similar to that of apoptosis detected by TUNEL. Interestingly, the increased expression of RIPK1 was rarely observed in the TUNEL-positive cells. Furthermore, the number of RIPK1-positive cells was significantly higher than that of TUNEL-positive cells.
Conclusions:
This study demonstrated that the expression of RIPK1 increased in various neural cells and peaked at 3 days following spinal cord injury. The temporal change of the RIPK1 expression was analogous to that of apoptosis at the lesion site. However, the increase in RIPK1 expression was barely seen in the apoptotic cells. These findings suggested that the RIPK1 might contribute to the pathological mechanism of the secondary neural tissue damage after spinal cord injury.
Insights
Receptor-interacting protein kinase 1 (RIPK1) expression increases in neural cells after spinal cord injury, suggesting a role in secondary damage. RIPK1 upregulation occurs alongside apoptosis but is not found in apoptotic cells.
Area of Science:
- Neuroscience
- Cell Biology
- Pathology
Background:
- Necroptosis is a programmed cell death pathway distinct from apoptosis.
- Receptor-interacting protein kinase 1 (RIPK1) is crucial for necroptosis execution.
- Spinal cord injury (SCI) triggers secondary neural tissue damage.
Purpose of the Study:
- Investigate RIPK1 expression changes in secondary neural tissue damage after SCI in mice.
- Compare the temporal profile of RIPK1 expression with apoptotic cell death.
- Determine RIPK1's cellular localization in the injured spinal cord.
Main Methods:
- Immunostaining and Western blot to assess RIPK1 protein levels.
- Immunohistochemistry to identify RIPK1 in specific neural cell types (neurons, astrocytes, oligodendrocytes).
- TUNEL assay to quantify apoptotic cells and co-staining with RIPK1 to compare cell death pathways.
Main Results:
- RIPK1 expression was significantly upregulated in neurons, astrocytes, and oligodendrocytes post-SCI.
- RIPK1 levels increased starting at 4 hours and peaked at 3 days after injury.
- RIPK1 expression kinetics mirrored apoptosis, but RIPK1 was rarely found in TUNEL-positive (apoptotic) cells.
Conclusions:
- RIPK1 expression increases in various neural cells following SCI, peaking at 3 days.
- While RIPK1 temporal changes parallel apoptosis, it is not significantly expressed in apoptotic cells.
- RIPK1 may play a role in the pathological mechanisms underlying secondary neural tissue damage after SCI.
