Morpho-functional features of in-vitro cell death induced by physical agents.

Based on the study of the recent literature, the aim of this report is to present and discuss in vitro cell death, and, more specifically, apoptosis appearing after exposure to physical conditions such as hyperthermia, hypothermia, UVB radiation and static magnetic fields. Hyperthermia (i.e. variable exposures to 42 degrees C) as well as hypothermia conditions (i.e. variable exposures to 0 degrees C) were considered mild and were both followed by incubation at physiological conditions. Heat exposure can be considered as a powerful apoptotic inducer in a variety of cells, where it induces classical apoptotic changes and well known biochemical pathways. The effect of hyperthermia has been described in adherent human tumour cells that undergo cell rounding and progressively detach from the substrate, due to the concomitant down-regulation of adhesion molecules. Hypothermia instead, as a cold treatment, only occasionally triggers apoptosis, but more frequently induces cell necrosis. UVB radiation induces oxidative stress, leading, in most experimental models, to apoptotic cell death, generally through the intrinsic apoptotic pathway, even if the extrinsic pathway cannot be excluded. Interestingly, UVB radiation appears effective also on cell systems that are normally apoptosis-resistant, such as muscle cells. Most cell alterations induced by static magnetic fields result from alterations at the plasma membrane and microvilli; in this case, apoptotic cell death is rarely detected. Therefore, cell death can be induced with physical agents in dependence on the treatment and cell model employed. In particular, hyperthermia and UVB can be considered a reliable and reproducible apoptotic trigger.