54 These findings suggest that IRF-3, but not MyD88 plays a critical role in IR-induced TLR4 activation. Other investigators have also shown that defective TLR4, not TLR2 signalling, increases liver HO1 transcript Y-27632 purchase and protein expression, with cross talk between TLR4 and HO1 proposed as an important mechanism mediating IR injury.57

The term “apoptosis,” meaning the “falling off” of cells, was first coined by Kerr in 1972 to describe a distinct form of cell death that differed morphologically from necrosis.58 Apoptosis is a controlled form of programmed cell death which allows the removal of damaged, senescent or unwanted cells in multicellular organisms without destruction of the cellular environment.

Its activation is regulated by a balance between a multitude of signals. Apoptosis is rarely seen in normal liver, however when it does occur, apoptotic cell death is rapid (2–3 h).59 Morphologically, cell shrinkage occurs as one of the earliest changes.58 It results in loss of contact between adjacent cells associated with disruption of cell surface elements such as microvilli and cell-cell junctions. Nuclear changes occur characterized by condensation of chromatin into crescentic caps at the periphery of the nucleus.58 The chromatin eventually fragments to produce internucleosomal find more DNA fragmentation products of 180–200 base pair chain length.59 This underlies the basis of the “DNA ladder” seen on agarose gel eletrophoresis and the labelling of the 3′-OH ends of DNA strand breaks have been used as markers for apoptosis. Necrosis, in contrast, is associated with non-specific hydrolysis of DNA into smaller fragments and constituents.59 Apoptotic cells ultimately convolute, separate into membrane-bound subcellular fragments of nucleus and intact organelles which aggregate, known as “apoptotic bodies.” Throughout this process, cellular membrane integrity is intact, preventing the release of potentially toxic intracellular contents into the extracellular

space. Apoptotic bodies are rapidly phagocytosed by nearby tissue macrophages. Necrotic cell death occurs as a result selleck kinase inhibitor of acute cellular injury. It is characterized by cellular and organelle swelling resulting from loss of plasma membrane integrity.59 Other morphological changes that accompany subsequent metabolic derangements include: loss of organelle permeability, swelling and dissolution of mitochondria and lysosomes, poorly defined chromatin condensation and formation of plasma blebs. The defects in membrane integrity lead to a release of potentially toxic intracellular contents such as mitochondrial proteins, proteolytic and hydrolytic enzymes into the intercellular space; this incites an inflammatory response. Necrosis typically affects a cluster of cells, unlike apoptosis which occurs in single or scattered cells.