Module 11: Cell Stress, Inflammatory Responses and Cell Death

Abstract

Cells have intrinsic signalling mechanisms that are capable of sensing various deleterious conditions, both normal and pathological, and respond by mounting a variety of stress responses. Examples of normal signals are the cytokines that induce inflammatory responses in cells. Pathological signals include UV and X-ray irradiation, hydrogen peroxide (H2O2), abrupt anoxia and physicochemical injury through heat or noxious chemicals. A process of wound healing can function to repair the damage caused by such injuries. In many cases, especially if the stress signal is not too severe, the cell can survive and can even become tolerant to further insults. If cells are growing, such sub-lethal insults can either cause the cell to stop growing temporarily to allow adequate time to repair the damage, or the process of cell proliferation can be stopped more permanently and the cell will enter a state of senescence . Another example of an evolutionarily conserved survival mechanism is autophagy , which enables cells to cope with periods of starvation. If such stresses become too severe, however, the cell dies, either through a process of necrosis, which is rapid and catastrophic, or through a slower and more controlled process that is carried out by a highly regulated process of programmed cell death known as apoptosis .