Apart from apoptosis and necrosis, there are newer cell deaths that are-
- As the word Suggests, Necroptosis consists of two words NECROSIS and APOPTOSIS.
- We can define Necroptosis as caspase independent programmed cell death.
- By the name we know that necroptosis is both necrosis and apoptosis
- The property of necrosis is inflammation and the property of apoptosis is programmed cell death in necroptosis.
- Necroptosis includes both physiological and pathological cell deaths –
- Physiological – Growth plate formation in human body
- Pathological – Steatohepatitis [fatty liver]
– Reperfusion injury
- In case of CMV [cytomegalovirus], caspase inhibitors are present that doesn’t allow apoptosis to happen but in this case Necroptosis can be a way of cell death.
- Mechanism of Necroptosis –
- 1-2-3 death
- Step 1 :-
In this step, TNF comes and binds to TNF receptor
- Step 2 :-
Due to this binding trio occurs – RIPK1, RIPK3 [receptor interacting protein] and Procaspase8
- Step 3 :-
MLKL phosphorylation occurs in this step and cell death occurs.
- The word Pyroptosis is made up of pyro and ptosis.
- The word pyro means fire that refers to fever here and the word ptosis means falling.
- Pyroptosis is associated with microorganisms.
Examples for Pyroptosis are – Shiegella and Salmonella
- In case of bacteria it binds to NOD receptor, this leads to the formation of inflammosome which is bacteria plus NOD receptor.
- This inflammosome activates several caspase which are –
- Caspase 1 helps in activation of interleukin 1 which is responsible for the fever
- The remaining caspases which are caspase 4, caspase 5 and caspase 11 are responsible for the cell death.
- It is a type of apoptosis occurring in case of lack of natural environment.
- Examples for Anoikis includes –
Hyperglycemia in diabetic microangiopathy
- It appears in anchorage-dependent cells when cells detach from ECM[extracellular matrix]