Cell death

{{short description|Biological cell ceasing to carry out its functions}}

Cell death is the event of a biological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, as in programmed cell death, or may result from factors such as diseases, localized injury, or the death of the organism of which the cells are part. Apoptosis or Type I cell-death, and autophagy or Type II cell-death are both forms of programmed cell death, while necrosis is a non-physiological process that occurs as a result of infection or injury.

The term "cell necrobiology" has been used to describe the life processes associated with morphological, biochemical, and molecular changes which predispose, precede, and accompany cell death, as well as the consequences and tissue response to cell death.{{cite journal | vauthors = Nirmala JG, Lopus M | title = Cell death mechanisms in eukaryotes | journal = Cell Biology and Toxicology | volume = 36 | issue = 2 | pages = 145–164 | date = April 2020 | pmid = 31820165 | doi = 10.1007/s10565-019-09496-2 }} The word is derived from the Greek νεκρό meaning "death", βìο meaning "life", and λόγος meaning "the study of". The term was initially coined to broadly define investigations of the changes that accompany cell death, detected and measured by multiparameter flow- and laser scanning- cytometry. It has been used to describe the real-time changes during cell death, detected by flow cytometry.{{cite journal | vauthors = Warnes G, Martins S | title = Real-time flow cytometry for the kinetic analysis of oncosis | journal = Cytometry. Part A | volume = 79 | issue = 3 | pages = 181–191 | date = March 2011 | pmid = 21254392 | doi = 10.1002/cyto.a.21022 | s2cid = 11691981 | doi-access = free }}

Types

= Programmed cell death =

Programmed cell death (PCD) is cell death mediated by an intracellular program.

{{cite journal | vauthors = Engelberg-Kulka H, Amitai S, Kolodkin-Gal I, Hazan R | title = Bacterial programmed cell death and multicellular behavior in bacteria | journal = PLOS Genetics | volume = 2 | issue = 10 | pages = e135 | date = October 2006 | pmid = 17069462 | pmc = 1626106 | doi = 10.1371/journal.pgen.0020135 | doi-access = free }}

{{cite book| vauthors = Green D |title=Means To An End|year=2011|publisher=Cold Spring Harbor Laboratory Press|location=New York|isbn=978-0-87969-887-4|url=http://celldeathbook.wordpress.com/}} PCD is carried out in a regulated process, which usually confers advantage during an organism's life-cycle. For example, the differentiation of fingers and toes in a developing human embryo occurs because cells between the fingers apoptose; the result is that the digits separate. PCD serves fundamental functions during both plant and metazoa (multicellular animals) tissue development.

== Apoptosis ==

File:Apoptotic_cell_disassembly.png

Apoptosis is the processor of programmed cell death (PCD) that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation. It is now thought that – in a developmental context – cells are induced to positively commit suicide whilst in a homeostatic context; the absence of certain survival factors may provide the impetus for suicide. There appears to be some variation in the morphology and indeed the biochemistry of these suicide pathways; some treading the path of "apoptosis", others following a more generalized pathway to deletion, but both usually being genetically and synthetically motivated. There is some evidence that certain symptoms of "apoptosis" such as endonuclease activation can be spuriously induced without engaging a genetic cascade, however, presumably true apoptosis and programmed cell death must be genetically mediated. It is also becoming clear that mitosis and apoptosis are toggled or linked in some way and that the balance achieved depends on signals received from appropriate growth or survival factors.{{cite journal | vauthors = Bowen ID | title = Apoptosis or programmed cell death? | journal = Cell Biology International | volume = 17 | issue = 4 | pages = 365–380 | date = April 1993 | pmid = 8318948 | doi = 10.1006/cbir.1993.1075 | s2cid = 31016389 }}

File:Autophagy.jpg

Certain key proteins primarily employed in the repair of DNA damage can also induce apoptosis when DNA damage exceeds the cell’s repair capability.{{cite journal |vauthors=Bernstein C, Bernstein H, Payne CM, Garewal H |title=DNA repair/pro-apoptotic dual-role proteins in five major DNA repair pathways: fail-safe protection against carcinogenesis |journal=Mutat Res |volume=511 |issue=2 |pages=145–78 |date=June 2002 |pmid=12052432 |doi=10.1016/s1383-5742(02)00009-1 |bibcode=2002MRRMR.511..145B |url=}} These dual role proteins protect against proliferation of unstable damaged cells that might lead to cancer.

== Autophagy ==

Autophagy is cytoplasmic, characterized by the formation of large vacuoles that eat away organelles in a specific sequence prior to the destruction of the nucleus.

{{cite journal | vauthors = Schwartz LM, Smith SW, Jones ME, Osborne BA | title = Do all programmed cell deaths occur via apoptosis? | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 90 | issue = 3 | pages = 980–984 | date = February 1993 | pmid = 8430112 | pmc = 45794 | doi = 10.1073/pnas.90.3.980 | doi-access = free | bibcode = 1993PNAS...90..980S }};and, for a more recent view, see {{cite journal | vauthors = Bursch W, Ellinger A, Gerner C, Fröhwein U, Schulte-Hermann R | title = Programmed cell death (PCD). Apoptosis, autophagic PCD, or others? | journal = Annals of the New York Academy of Sciences | volume = 926 | issue = 1 | pages = 1–12 | year = 2000 | pmid = 11193023 | doi = 10.1111/j.1749-6632.2000.tb05594.x | s2cid = 27315958 | bibcode = 2000NYASA.926....1B }} Macroautophagy, often referred to as autophagy, is a catabolic process that results in the autophagosomic-lysosomal degradation of bulk cytoplasmic contents, abnormal protein aggregates, and excess or damaged organelles. Autophagy is generally activated by conditions of nutrient deprivation but has also been associated with physiological as well as pathological processes such as development, differentiation, neurodegenerative diseases, stress, infection and cancer.

== Other variations of PCD ==

Other pathways of programmed cell death have been discovered.

{{cite journal | vauthors = Kroemer G, Martin SJ | title = Caspase-independent cell death | journal = Nature Medicine | volume = 11 | issue = 7 | pages = 725–730 | date = July 2005 | pmid = 16015365 | doi = 10.1038/nm1263 | s2cid = 8264709 }} Called "non-apoptotic programmed cell-death" (or "caspase-independent programmed cell-death"), these alternative routes to death are as efficient as apoptosis and can function as either backup mechanisms or the main type of PCD.

Some such forms of programmed cell death are anoikis, almost identical to apoptosis except in its induction; cornification, a form of cell death exclusive to the eyes; excitotoxicity; ferroptosis, an iron-dependent form of cell death{{cite journal | vauthors = Dixon SJ, Lemberg KM, Lamprecht MR, Skouta R, Zaitsev EM, Gleason CE, Patel DN, Bauer AJ, Cantley AM, Yang WS, Morrison B, Stockwell BR | title = Ferroptosis: an iron-dependent form of nonapoptotic cell death | journal = Cell | volume = 149 | issue = 5 | pages = 1060–1072 | date = May 2012 | pmid = 22632970 | pmc = 3367386 | doi = 10.1016/j.cell.2012.03.042 }} and Wallerian degeneration.

Plant cells undergo particular processes of PCD similar to autophagic cell death. However, some common features of PCD are highly conserved in both plants and metazoa.

Activation-induced cell death (AICD) is a programmed cell death caused by the interaction of Fas receptor (Fas, CD95)and Fas ligand (FasL, CD95 ligand).{{cite journal | vauthors = Zhang J, Xu X, Liu Y | title = Activation-induced cell death in T cells and autoimmunity | journal = Cellular & Molecular Immunology | volume = 1 | issue = 3 | pages = 186–92 | date = June 2004 | pmid = 16219166 | doi = }} It occurs as a result of repeated stimulation of specific T-cell receptors (TCR) and it helps to maintain the periphery immune tolerance.{{cite journal | vauthors = Kabelitz D, Janssen O | title = Antigen-induced death of T-lymphocytes | journal = Frontiers in Bioscience: A Journal and Virtual Library | volume = 2 | issue = 4| pages = d61–77 | date = February 1997 | pmid = 9159213 | doi = 10.2741/a175 }} Therefore, an alteration of the process may lead to autoimmune diseases. In the other words AICD is the negative regulator of activated T-lymphocytes.

Ischemic cell death, or oncosis, is a form of accidental, or passive cell death that is often considered a lethal injury. The process is characterized by mitochondrial swelling, cytoplasm vacuolization, and swelling of the nucleus and cytoplasm.{{cite encyclopedia|title=Oncosis|url=http://www.copewithcytokines.de/cope.cgi?key=Oncosis|access-date=10 August 2010 | encyclopedia = Cell Communication Online Pathfinder Encyclopaedia (COPE) }}

Mitotic catastrophe is an oncosuppressive mechanism that can lead to cell death that is due to premature or inappropriate entry of cells into mitosis.{{cite journal | vauthors = Vitale I, Galluzzi L, Castedo M, Kroemer G | title = Mitotic catastrophe: a mechanism for avoiding genomic instability | journal = Nature Reviews. Molecular Cell Biology | volume = 12 | issue = 6 | pages = 385–392 | date = June 2011 | pmid = 21527953 | doi = 10.1038/nrm3115 | s2cid = 22483746 }} It is the most common mode of cell death in cancer cells exposed to ionizing radiation and many other anti-cancer treatments.{{cite book| chapter-url=http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-93322008000100021| chapter = Mitotic Catastrophe in Apoptosis, Senescence, and Cancer| vauthors = Ianzini F, Mackey MA | title = Revista Brasileira de Ciências Farmacêuticas | veditors = Gewirtz DA, Holt SE, Grant S |date=2007|volume=44 |publisher=Humana Press|isbn=978-1-58829-527-9|pages=73–91|doi=10.1007/978-1-59745-221-2| url = http://americanae.aecid.es/americanae/es/registros/registro.do?tipoRegistro=MTD&idBib=2696310}}

Immunogenic cell death or immunogenic apoptosis is a form of cell death caused by some cytostatic agents such as anthracyclines, oxaliplatin and bortezomib, or radiotherapy and photodynamic therapy (PDT).{{cite journal | vauthors = Garg AD, Nowis D, Golab J, Vandenabeele P, Krysko DV, Agostinis P | title = Immunogenic cell death, DAMPs and anticancer therapeutics: an emerging amalgamation | journal = Biochimica et Biophysica Acta (BBA) - Reviews on Cancer | volume = 1805 | issue = 1 | pages = 53–71 | date = January 2010 | pmid = 19720113 | doi = 10.1016/j.bbcan.2009.08.003 | url = https://lirias.kuleuven.be/bitstream/123456789/632508/2/BBA-RC%20Review%20-%20Final%20Revised%20MS.doc | url-access = subscription }}

Pyroptosis is a highly inflammatory form of programmed cell death that occurs most frequently upon infection with intracellular pathogens and is likely to form part of the antimicrobial response in myeloid cells.{{cite journal | vauthors = Darzynkiewicz Z, Juan G, Li X, Gorczyca W, Murakami T, Traganos F | title = Cytometry in cell necrobiology: analysis of apoptosis and accidental cell death (necrosis) | journal = Cytometry | volume = 27 | issue = 1 | pages = 1–20 | date = January 1997 | pmid = 9000580 | doi = 10.1002/(sici)1097-0320(19970101)27:1<1::aid-cyto2>3.0.co;2-l | doi-access = free }}

PANoptosis is an innate immune, lytic cell death pathway initiated by innate immune sensors and driven by caspases and RIP kinases through PANoptosome complexes. To date, several PANoptosome complexes have been characterized, including ZBP1-, AIM2-, RIPK1-, NLRC5-/NLRP12-, and NLRP3-PANoptosomes. PANoptosis is critical in innate immune responses for host defense, but it has also been implicated in inflammation and pathology in inflammatory diseases, infections, and cancers. {{Cite web |title=St. Jude finds NLRP12 as a new drug target for infection, inflammation and hemolytic diseases |url=https://www.stjude.org/media-resources/news-releases/2023-medicine-science-news/st-jude-finds-nlrp12-as-a-new-drug-target.html |access-date=2024-03-07 |website=www.stjude.org |language=en}}{{Cite journal |last1=Zheng |first1=Min |last2=Karki |first2=Rajendra |last3=Vogel |first3=Peter |last4=Kanneganti |first4=Thirumala-Devi |date=2020-04-30 |title=Caspase-6 Is a Key Regulator of Innate Immunity, Inflammasome Activation, and Host Defense |journal=Cell |volume=181 |issue=3 |pages=674–687.e13 |doi=10.1016/j.cell.2020.03.040 |issn=1097-4172 |pmc=7425208 |pmid=32298652}}{{Cite journal |last1=Christgen |first1=Shelbi |last2=Zheng |first2=Min |last3=Kesavardhana |first3=Sannula |last4=Karki |first4=Rajendra |last5=Malireddi |first5=R. 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Phagoptosis is cell death resulting from a live cell being phagocytosed (i.e. eaten) by another cell (usually a phagocyte), resulting in death and digestion of the engulfed cell. Phagoptosis can occur to cells that are pathogenic, cancerous, aged, damaged or excess to requirements.{{cite journal | vauthors = Brown GC | title = Cell death by phagocytosis | journal = Nature Reviews. Immunology | volume = 24 | issue = 2 | pages = 91–102 | date = February 2024 | pmid = 37604896 | doi = 10.1038/s41577-023-00921-6 }}

= Necrotic cell death =

Necrosis is cell death where a cell has been badly damaged through external forces such as trauma or infection and occurs in several different forms. It is the sum of what happens to cells after their deaths.{{Cite journal |last1=Fink |first1=Susan L. |last2=Cookson |first2=Brad T. |date=April 2005 |title=Apoptosis, Pyroptosis, and Necrosis: Mechanistic Description of Dead and Dying Eukaryotic Cells |journal=Infection and Immunity |volume=73 |issue=4 |pages=1907–1916 |doi=10.1128/IAI.73.4.1907-1916.2005 |pmid=15784530|pmc=1087413 }} In necrosis, a cell undergoes swelling, followed by uncontrolled rupture of the cell membrane with cell contents being expelled. These cell contents often then go on to cause inflammation in nearby cells.{{cite journal | vauthors = D'Arcy MS | title = Cell death: a review of the major forms of apoptosis, necrosis and autophagy | journal = Cell Biology International | volume = 43 | issue = 6 | pages = 582–592 | date = June 2019 | pmid = 30958602 | doi = 10.1002/cbin.11137 | s2cid = 102347423 }} Necrosis is involved in biological ageing.{{Cite journal |last1=Kern |first1=Carina |last2=Bonventre |first2=Joseph V. |last3=Justin |first3=Alexander W. |last4=Kashani |first4=Kianoush |last5=Reynolds |first5=Elizabeth |last6=Siew |first6=Keith |last7=Davis |first7=Bill |last8=Karakoy |first8=Halime |last9=Grzesiak |first9=Nikodem |last10=Bailey |first10=Damian Miles |date=2025-05-29 |title=Necrosis as a fundamental driver of loss of resilience and biological decline: what if we could intervene? |url=https://www.nature.com/articles/s41388-025-03431-y |journal=Oncogene |language=en |pages=1–12 |doi=10.1038/s41388-025-03431-y |issn=1476-5594}} A form of programmed necrosis, called necroptosis, has been recognized as an alternative form of programmed cell death. It is hypothesized that necroptosis can serve as a cell-death backup to apoptosis when the apoptosis signaling is blocked by endogenous or exogenous factors such as viruses or mutations. Necroptotic pathways are associated with death receptors such as the tumor necrosis factor receptor 1. Identification of cell death was previously classified based on morphology, but in recent years switched to molecular and genetic conditions.

References

Category:Cellular processes

Category:Medical aspects of death