Related Experiment Video
Updated: Aug 9, 2026
09:31
A Novel Light Damage Paradigm for Use in Retinal Regeneration Studies in Adult Zebrafish
Published on: October 24, 2013
Multiple, parallel cellular suicide mechanisms participate in photoreceptor cell death
Heather R Lohr1, Kannan Kuntchithapautham, Ashish K Sharma
1Department of Neurosciences, Division of Research, Medical University of South Carolina, 173 Ashley Avenue, BSB403, Charleston, SC 29425, USA.
Experimental Eye Research
|April 22, 2006
Summary
Photoreceptor degeneration involves multiple cell death pathways beyond caspase-mediated apoptosis, including autophagy and complement lysis, regardless of the initial trigger. Targeting these diverse mechanisms is crucial for developing effective rescue strategies for retinal dystrophies.
Area of Science:
- Ophthalmology
- Cell Biology
- Genetics
Background:
- Photoreceptor degeneration in human retinal dystrophies was traditionally attributed to caspase-mediated apoptosis.
- Recent findings suggest a more complex interplay of cell death mechanisms, including caspase-independent pathways.
Purpose of the Study:
- To investigate the temporal relationship of various cell death mechanisms during photoreceptor degeneration.
- To determine if different models of photoreceptor dystrophies share common cell death pathways.
Main Methods:
- Utilized three distinct models of photoreceptor degeneration: rd/rd mouse (calcium overload), rds/rds mouse (structural defect), and light-damage (oxidative stress).
- Employed quantitative RT-PCR on laser capture microdissection samples to analyze gene expression of marker genes for apoptosis, autophagy, and complement lysis.
- Correlated gene expression patterns with cell loss (photoreceptor nuclei counts) and apoptosis (TUNEL labeling), alongside enzymatic assays for caspase and lysosomal activity.
Main Results:
- Apoptosis and TUNEL labeling showed consistent temporal correlation across all three models.
- Complement-activated lysis paralleled or preceded apoptosis, while autophagy showed variable temporal patterns relative to apoptosis.
- Increased glucose metabolism preceded cell death, subsequently declining with photoreceptor loss in all models.
Conclusions:
- Photoreceptor degeneration, irrespective of the initiating cause (genetic defect or environmental stress), activates multiple pro-apoptotic and non-caspase-dependent cell death mechanisms.
- Non-caspase-dependent pathways appear to actively contribute to photoreceptor demise, not merely as a passive response.
- Effective therapeutic strategies for photoreceptor dystrophies necessitate targeting these diverse, concurrently activated pathways.
Related Concept Videos
01:22Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
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...
01:22Cellular Injury V: Apoptosis and Autophagy
Cells respond to damage and stress through highly coordinated processes that decide whether they survive or undergo controlled self-destruction. Two major pathways involved in this regulation are apoptosis, a type of programmed cell death, and autophagy, a survival mechanism that helps cells adapt to adverse conditions.ApoptosisApoptosis removes aged or injured cells to maintain tissue balance. During this process, the cell shrinks, chromatin condenses and fragments, and membrane-bound...
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...
01:00Cellular Injury I: Introduction
Cellular injury occurs when a cell cannot maintain homeostasis or adapt to stressors such as hypoxia, toxins, or trauma. Depending on severity and duration, injury may be reversible, allowing recovery, or irreversible, leading to cell death.General Mechanisms of Cell InjuryAlthough causes vary, most cellular injuries arise from a few key mechanisms that disrupt essential functions and often amplify one another. Cell survival depends on the extent and balance of these disturbances.ATP depletion...