Oxygen free radicals and redox biology of organelles

Abstract

The presence and supposed roles of reactive oxygen species (ROS) were reported in literature in a myriad of instances. However, the breadth and depth of their involvement in cellular physiology and pathology, as well as their relationship to the redox environment can only be guessed from specialized reports. Whatever their circumstances of formation or consequences, ROS seem to be conspicuous components of intracellular milieu. We sought to verify this assertion, by collecting the available evidence derived from the most recent publications in the biomedical field. Unlike other reviews with similar objectives, we centered our analysis on the subcellular compartments, namely on organelles, grouped according to their major functions. Thus, plasma membrane is a major source of ROS through NAD(P)H oxidases located on either side. Enzymes of the same class displaying low activity, as well as their components, are also present free in cytoplasm, regulating the actin cytoskeleton and cell motility. Mitochondria can be a major source of ROS, mainly in processes leading to apoptosis. The protein synthetic pathway (endoplasmic reticulum and Golgi apparatus), including the nucleus, as well as protein turnover, are all exquisitely sensitive to ROS-related redox conditions. The same applies to the degradation pathways represented by lysosomes and peroxisomes. Therefore, ROS cannot be perceived anymore as a mere harmful consequence of external factors, or byproducts of altered cellular metabolism. This may explain why the indiscriminate use of anti-oxidants did not produce the expected "beneficial" results in many medical applications attempted so far, underlying the need for a deeper apprehension of the biological roles of ROS, particularly in the context of the higher cellular order of organelles.

Peptide-receptive Major Histocompatibility Complex Class I Molecules Cycle between Endoplasmic Reticulum and cis-Golgi in Wild-type Lymphocytes

“…It has been suggested that binding of high affinity peptide is accompanied by opening and closing of disulfide bonds either within class I (6,(77)(78)(79) or between ERp57 and tapasin in the loading complex (12). Because Ero1, the source of disulfide oxidizing equivalents, is restricted to the ER, conditions in the Golgi may be more reducing (80,81), and this could induce class I molecules to release their low affinity peptides prior to their return to the ER. Further work is needed to test these hypotheses.…”

Adipose Tissue Hypoxia, A Conceptual Alometric View

“…Mitochondrial operation may be hampered not only by lack of oxygen as fi nal acceptor of electrons, but also for excessive proton pumping, which in the end may damage the mitochondrial membranes, alter the cytoplasmic redox equilibrium [36] and interfere with calcium and other ion signalling [37]. The action of uncoupling proteins may help protect the integrity of the system [38].…”

Effect of TiO2 Nanoparticles on Antioxidant Enzymes Activity and Biochemical Biomarkers in Pinto Bean (Phaseolus vulgaris L.)

“…It has long been recognized that high levels of free radicals or reactive oxygen species (ROS) can inflict direct damage to lipids. The primary sources of endogenous ROS production are the mitochondria, plasma membrane, endoplasmic reticulum, and peroxisomes (Moldovan and Moldovan, 2004). Lipid peroxidation or reaction of oxygen with unsaturated lipids produces a wide variety of oxidation products.…”