Apoptosis (Programmed Cell Death) -A Review

Journal of Orofacial Sciences, 2012

Cell death is one of the essential processes. Balance between cell division and cell death is of utmost importance for the development and maintenance of multi-cellular organism. Disorders of either process have pathologic consequences and can lead to disturbed embryogenesis, neurodegerative diseases, or the development of cancers. This article reviews the apoptotic as well as anti-apoptotic molecules along with molecular pathways, which may alter in many diseases.

2005

The fact that cell death is not ultimately a bad thing came as a surprise to many researchers. Physiological cell death has been observed in various multicellular organisms. Apoptosis or programmed cell death is the predominant form of physiological cell death by which the organism eliminates unnecessary or damaged single cells. It is a major component of normal development and disease. Apoptosis is characterized by membrane blebbing, shrinkage of the cell, nuclear fragmentation and chromatin condensation. Organelles are preserved almost intact. Cell surface molecules change to assure that apoptotic cells will be immediately recognized and engulfed by neighboring cells or phagocytes leading to little or no inflammation. A wide variety of physiological and pathological stimuli can initiate apoptosis. They act via receptor mechanisms, through biochemical agents, or cause DNA and cell membrane damage. Death receptors that initiate apoptosis include the Fas receptor and the TNF receptor systems. After an appropriate stimulus, the first stage of apoptosis or "decision phase" is the genetic control point of cell death. This is followed by the second stage or "execution phase", which is responsible for the morphological change in apoptosis. The third stage is engulfment of the dying cell followed by degradation of the engulfed cell DNA. There are two overlapping signaling pathways leading to apoptosis, termed the intrinsic and extrinsic pathways. In the intrinsic, various stimuli, such as oxidative stress, lead to mitochondrial dysfunction and the release of pro-apoptotic factors. Ligand binding to cell surface death receptors, such as Fas, activates the extrinsic pathway. During the last decades the molecular mechanisms involved in disordered apoptosis were unraveled, suggesting that cancer, chronic disease, and fetal developmental abnormalities can occur as a result of disordered apoptosis.

Journal of Research and Practice in Dentistry, 2014

Apoptosis is considered as a tightly regulated active process signified by specific morphological and biochemical. On contrary to apoptosis, necrosis is a passive, energy independent pathologic process. The significance of understanding the apoptosis cascade mechanism is imperative as apoptosis being component of both physiological and pathological process. Apoptosis can be stimulated by both physiological and pathological conditions and hence play a role in maintenance of normal homeostasis and in pathogenesis of several diseases. Signaling for apoptosis occurs via caspase dependent and independent pathways that are initiated either from triggering events within the cell or from outside the cell by ligation of death receptors. Present review aims to provide an overview regarding apoptosis, its morphological and biochemical characterstics, its mechanism and its implication in health and diseases.

Proceedings of the National Academy of Sciences, 1996

All multicellular organisms have mechanisms for killing their own cells, and use physiological cell death for defence, development, homeostasis, and aging. Apoptosis is a morphologically recognizable form of cell death that is implemented by a mechanism that has been conserved throughout evolution from nematode to man. Thus homologs of the genes that implement cell death in nematodes also do so in mammals, but in mammals the process is considerably more complex, involving multiple isoforms of the components of the cell death machinery. In some circumstances this allows independent regulation of pathways that converge upon a common end point. A molecular understanding of this mechanism may allow design of therapies that either enhance or block cell death at will.

IOSR Journal of Pharmacy and Biological Sciences, 2014

Apoptosis is the process of programmed cell death (PCD) which usually occurs in multicellular organisms. In this case, biochemical events leads to morphological cell changes and death. Some of these changes are blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation and chromosomal Deoxyribonucleic Acid (DNA) fragmentation. Apoptosis is however distinct from necrosis which is a form of traumatic cell death that results from acute cellular injury. Apoptosis generally confers advantages during an organism's life cycle. One of the advantages can be seen in the differentiation of fingers and toes in a developing human embryo. This occurs because cells between the fingers apoptose and causes the digits to be separate. Unlike necrosis, apoptosis produces cell fragments called apoptotic bodies that phagocytic cells are able to engulf and quickly remove before the contents of the cell can spill out onto surrounding cells and cause damage. Also, between 50 and 70 billion cells die each day due to apoptosis in the average human adult. For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day.. In addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in an extensive variety of diseases whereby excessive apoptosis causes atrophy and an insufficient apoptosis results in uncontrolled cell proliferation leading to cancer or tumour

Hippokratia, 2007

Apoptosis or programmed cell death is a physiological mechanism, characterized by specific morphological and biochemical changes such as cell shrinkage, chromatin condensation, protein cleavage, DNA breakdown and phagocytosis. Apoptosis is a significant contributor to the morphologic and functional development of multicellular organisms. It is also involved in the pathogenesis of several diseases including degenerative diseases of the central nervous system (CNS) like Alzheimer's disease or Parkinson's disease, cancer and immune system dysfunction. There are many factors, mainly proteins, which are involved in the activation, regulation and execution of related events. A fairly detailed outline of apoptotic mechanisms has also started to emerge and to be verified. In this short, focused mini-review, we attempt to outline current evidence regarding the mechanisms and the regulation of apoptosis.

Indian Journal of Clinical Biochemistry, 2007

Apoptosis a physiological mechanism that eliminates excessive, damaged or unwanted cells, is a highly regulated pathway important for maintaining homeostasis in multicellular organisms. It can be initiated through various signals via the extrinsic pathway which involves death receptors, or via the intrinsic pathway which is initiated by intracellular damage and involves the mitochondria and release of cytochrome c from it to further activate caspases. The Bcl-2 family of proteins is situated upstream to the irreversible damage of cellular constituents and is an important checkpoint in the fate of a cell. The pro-apoptotic members, BH3 only members include BID, BAD and BIM. They directly or indirectly activate multidomain BAX/ BAK that constitute the requisite gateway to the intrinsic pathway which operates at the mitochondrial surface and endoplasmic reticulum. In contrast, antiapoptotic members such as Bcl-2, Bcl-XL bind and sequester activation. Downstream of mitochondria, the apoptosome involvement is seen to generate caspase activity. Post mitochondria regulation involves IAPs, and their inhibitors. The pathogenesis of several diseases such as cancer, neurodegenerative disorders, autoimmune disorders, heart disease, infectious diseases including AIDS is closely related to aberrant apoptosis. Consequently interest has emerged in employing various therapeutic approaches such as gene therapy, antisense therapy, recombinant biologicals, organic and combinatorial chemistry, to specifically target apoptosis signaling pathways such as death receptors FAS/TRAIL, p53, IAPs, SMAC and caspases, etc. and are now advancing from preclinical to clinical phase.

2010

Apoptosis, the best known form of programmed cell death, is tightly regulated by a number of sensors, signal transducers and effectors. Apoptosis is mainly active during embryonic development, when deletion of redundant cellular material is required for the correct morphogenesis of tissues and organs; moreover, it is essential for the maintenance of tissue homeostasis during cell life. Cells also activate apoptosis when they suffer from various insults, such as damage to DNA or to other cellular components, or impairment of basic processes, such as DNA replication and DNA repair. Removal of damaged cells is fundamental in maintaining the health of organisms. In addition, apoptosis induction following DNA damage is exploited to kill cancer cells. In this chapter we will review the main features of developmental and induced apoptosis.

European Respiratory Journal, 1996

Three steps can be distinguished in the pathway that leads to cell death.

International Journal of Livestock Research, 2017

Apoptosis, a Programmed Cell Death (PCD), specifically refers to an energy-dependent, genetically controlled process by which unnecessary or damaged single cells self-destruct when the apoptosis genes are activated. The role of apoptosis in physiology is as significant as that of its counterpart, mitosis. It helps in maintaining cellular homeostasis in the animal body. The number of cells increase or decrease when there is alteration in apoptosis during normal development and aging or during disease. Abnormalities in cell death regulation may cause diseases/conditions. Some conditions are caused due to insufficient apoptosis whereas others due to excessive apoptosis. Presently, large numbers of synthetic and natural compounds have been discovered to be effective against certain diseases through the induction of apoptosis in their target cells.

The American Journal of Medicine, 1999

Archives of Surgery, 1998

urrently there is much interest and excitement in the understanding of how cells undergo the process of apoptosis or programmed cell death. Understanding how, why, and when cells are instructed to die may provide insight into the aging process, autoimmune syndromes, degenerative diseases, and malignant transformation. This review focuses on the development of apoptosis and describes the process of programmed cell death, some of the factors that incite or prevent its occurrence, and finally some of the diseases in which it may play a role. The hope is that in the not too distant future we may be able to modify or thwart the apoptotic process for therapeutic benefit.

Pharmacology & Therapeutics, 1996

Unwanted cells are removed by physiological cell death processes that are highly conserved throughout the animal kingdom. Physiological cell death plays an important role in development, tissue homeostasis and defence against viral infection and mutation. This review describes the molecular components that implement this process, the relevance of these to a variety of human diseases, and discusses the potential for novel therapies based on our understanding of them.

2020

Apoptosis process occurs when a cell decides to die by itself. This often happens for the better development and morphological changes of the whole organism, mostly to prevent cell damage and various cancers. Morphological and biochemical changes such as energy dependent mechanism plays a pivotal role in apoptosis or PCD(programmed cell death). It has a significant role in development of embryos, normal and proper cell turnover, homeostasis and its functioning. By this process atrophy of a cell occurs which may be hormone dependent or by chemicals. Due to disturbance in apoptosis or failure of regulation of apoptotic signals may lead to condition like damage of neurons, heart, blood regulation, autoimmune disorders or cancers. Study of apoptosis might play a vast development and acknowledgment of the huge therapeutic and palliative aspects of this. Many researches are going on for to understand thoroughly the mechanism of cell cycle and its pathways that is the key regulator of the ...