Cellular Stress Responses

Abstract

Cells encounter many internal and external stimuli, some of which may induce stresses, when they are a part of a normal tissue or when they grow in a culture. These stresses trigger responses which may change cellular responses to subsequent environmental signals or even cause cell death. Exposure to stress over time may cause the accumulation of damage to DNA, proteins and lipids. If not repaired, this will enhance susceptibility to aging associated illnesses, like neurodegenerative diseases, diabetes, heart diseases, etc., and to cancer. The cellular stress responses must be taken into account when the cells are used in cell therapies and in regenerative medicine. The cellular stress response is a reaction to changes or fluctuations of extracellular conditions, which damage the structure and function of macromolecules (Kultz, 2003). Depending on the severity and duration of stress encountered, cells either re-establish cellular homeostasis to the former state or adopt an altered state in the new environment. Therefore, different stressors and different intensities of stresses trigger different cellular responses: (1) induce cell repair mechanisms; these use considerable amounts of available resources and often result in recovery of normal cells, (2) induce cell responses that result in temporary adaptation to some stressors, (3) induce autophagy or (4) trigger cell death. Some important mechanisms of cell adaptation to stress and their inducers will be described in this chapter.