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Updated: Jul 14, 2026
10:23
Evaluation of Caspase Activation to Assess Innate Immune Cell Death
Published on: January 20, 2023
Caspase-8-mediated apoptosis in human RPE cells
Ping Yang1, James J Peairs, Ryotaro Tano
1Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Investigative Ophthalmology & Visual Science
|June 27, 2007
Summary
Retinal pigment epithelial cells resist tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis due to low caspase-8 levels. Increasing caspase-8 in these cells could be a strategy for treating proliferative vitreoretinopathy (PVR).
Area of Science:
- Ophthalmology
- Cell Biology
- Molecular Biology
Background:
- Tumor necrosis factor-alpha (TNF-alpha) is implicated in age-related macular degeneration (AMD) and proliferative vitreoretinopathy (PVR).
- Retinal pigment epithelial (RPE) cells exhibit resistance to TNF-alpha-induced apoptosis, even when nuclear transcription factor (NF)-kappaB is blocked.
- The role of caspase-8 in this RPE cell resistance to TNF-alpha-mediated cell death was investigated.
Purpose of the Study:
- To investigate the role of caspase-8 in the resistance of retinal pigment epithelial (RPE) cells to tumor necrosis factor-alpha (TNF-alpha)-mediated apoptosis.
- To compare caspase-8 expression in RPE cells with other ocular and cancer cell types.
- To determine the effect of caspase-8 overexpression and NF-kappaB blockade on RPE cell viability and apoptosis.
Main Methods:
- Measured caspase-8 mRNA and protein levels in various human cell types, including RPE cells, using real-time RT-PCR and Western blot.
- Overexpressed caspase-8 and/or blocked NF-kappaB in RPE and T-98G cells using adenovirus vectors.
- Assessed cell viability, apoptosis (DNA fragmentation, M30 assay), and expression of other caspases and Bid protein.
Main Results:
- Human RPE cells exhibited significantly lower caspase-8 mRNA and protein levels compared to non-neoplastic ocular and cancer cells.
- Overexpression of caspase-8 in RPE cells led to decreased cell viability, activation of caspase-8 and -3, and increased apoptosis.
- NF-kappaB blockade alone did not affect caspase-8-mediated RPE cell death, but enhanced it slightly in the presence of TNF-alpha.
Conclusions:
- Low caspase-8 protein levels in RPE cells, potentially regulated post-transcriptionally, contribute to their resistance to apoptosis.
- This low caspase-8 expression may protect RPE cells in conditions like AMD and promote survival of abnormal cells in PVR.
- Introducing caspase-8 into RPE cells presents a potential therapeutic strategy for treating PVR.
Related Concept Videos
01:24Caspases
Caspase, a family of cysteine proteases, serve as effectors in apoptosis. The ced3 gene in C.elegans was first identified to be involved in apoptosis. This gene encodes the ced-3 caspase that is similar to the interleukin-1-beta converting enzyme or ICE in mammals. In addition to apoptosis, caspases also function in the inflammatory response. Inflammatory caspases are essential in activating pro-inflammatory cytokines that recruit immune cells and block the replication of pathogens inside cells.
01:17The Extrinsic Apoptotic Pathway
The extrinsic apoptotic pathway is initiated when extracellular death-inducing signals, such as specific cytokines, activate the death receptors expressed on the cell surface. The immune cells involved in this pathway are natural killer cells (NK cells) and cytotoxic T-lymphocytes. NK cells are critical in innate immune response, while cytotoxic T-lymphocytes are associated with adaptive immune response. These cells recognize specific receptors expressed on the altered cells and activate...
01:31The Intrinsic Apoptotic Pathway
Internal cellular stress, such as cellular injury or hypoxia, triggers intrinsic apoptosis. The B-cell lymphoma 2 (Bcl-2) family of proteins are the primary regulators of the intrinsic apoptotic pathway. For example, during DNA damage, checkpoint proteins, such as Ataxia Telangiectasia Mutated (ATM protein) and Checkpoints Factor-2 (Chk2) proteins, are activated. These proteins phosphorylate p53 which further activates pro-apoptotic proteins, such as Bax, Bak, PUMA, and Noxa, and inhibits...
01:17Phagocytosis of Apoptotic Cells
Cells undergoing apoptosis form apoptotic bodies that must be removed immediately to prevent inflammation, autoimmune diseases, and necrosis. Phagocytosis is carried out by professional phagocytes such as macrophages or immature dendritic cells. Non-professional phagocytes such as epithelial cells and fibroblasts also take part in this process; however, they are not as effective as professional phagocytes.
Normal cells contain receptors that prevent them from being recognized by phagocytes.
Normal cells contain receptors that prevent them from being recognized by phagocytes.
01:30Apoptosis
Apoptosis is a combination of two Greek words, 'apo' and 'ptosis,' meaning separation and falling off, respectively. Hippocrates used this word to describe gangrene, which was caused due to bandaging of fractured bones. Apoptosis was distinguished from necrosis in 1970 when John Kerr reported observations of morphological changes occurring during apoptosis. During one experiment, he observed that the disruption of blood supply to the liver tissue resulted in a size reduction of the tissue.
01:30Overview of Cell Death
Cell death is an essential process where the body gets rid of old or damaged cells. Cell proliferation and death need to be balanced, as an imbalance between the two may lead to cancer or autoimmune diseases.
Cell death was observed in the early 19th century, but there was no experimental evidence to prove it. In 1842, Carl Vogt first discovered cell death in a metamorphic toad; however, it was not termed ‘cell death.’ Scientists discovered different cell death pathways only in the 20th century...
Cell death was observed in the early 19th century, but there was no experimental evidence to prove it. In 1842, Carl Vogt first discovered cell death in a metamorphic toad; however, it was not termed ‘cell death.’ Scientists discovered different cell death pathways only in the 20th century...