The Importance Of Apoptosis

INTRODUCTION:

The term Apoptosis was first used by scientists Kerr, Wyllie and Currie in the year 1972. The term “apoptosis” has a Greek origin and means “falling off.” Apoptosis or programmed cell death, can be described as an active process that is seen in multicellular organisms. It is characterized by the activation of biochemical pathways that lead to changes in cell morphology. These morphological changes include: cell shrinkage, DNA fragmentation, chromatin condensation and formation of apoptotic bodies. Changes such as mitochondrial breakdown to release cytochrome c and the translocation of phosphatidylserine from the inner plasma membrane leaflet to the outer leaflet also occur. The changes that occur in the cell, act as signals of

Thus, any dysregulation in apoptosis will act as a contributing factor for various diseases. CD59 death receptor (mediator in the extrinsic pathway of apoptosis) has been implicated in several syndromes such as Multiple Sclerosis (MS), liver failure and stroke. For example, in MS patients, studies have revealed that affected individuals have elevated levels of CD59 in cerebrospinal fluids.

Neuronal apoptosis is seen in post mortem tissues from patients who suffered from neurodegenerative disorders such Alzheimer’s disease, Huntington’s disease and Amyotrophic Lateral Sclerosis. In patients suffering from Alzheimer’s, alterations in expression of genes related to apoptosis (such as Bcl-2 and caspases) were seen along with increased DNA damage. Amyloid-β protein is seen to aggregate in neurons of Alzheimer’s patients, which is a direct inducer of apoptosis. The over expressed genes and additional DNA damage act as triggers of apoptosis which in turn lead to manifestation of the disease

Various assays have been devised to evaluate apoptosis at several points of the cascade. Based on the methodology, the commonly used assays can be classified into the following groups:

1. Changes in cell morphology: morphological changes such as cell shrinkage, membrane blebbing, nuclear condensation, DNA fragmentation and changes in plasma membrane occur. Each of these changes can be quantified using Flow Cytometry. For example, the forward scatter parameter reduces on cell shrinkage while nuclear condensation causes an increase in side scatter.

Apoptotic cells can also be detected using hematoxylin and eosin staining, using light microscopy. Although this is a simple technique, it cannot detect apoptotic cells in early stages and the technique needs to be supplemented with other methods of detection. Transmission Electron Microscopy (TEM) is considered as the gold standard to confirm apoptosis. TEM can detect apoptotic bodies, phagocytosis of apoptotic bodies and nuclear fragmentation among other changes. The main disadvantages of this method include the cost, time required for detection and the low