Regulation of mitochondrial oxidative phosphorylation through tight control of cytochrome c oxidase in health and disease - Implications for ischemia/reperfusion injury, inflammatory diseases, diabetes, and cancer

Mitochondria are essential to cellular function as they generate the majority of cellular ATP, mediated through oxidative phosphorylation, which couples proton pumping of the electron transport chain (ETC) to ATP production. The ETC generates an electrochemical gradient, known as the proton motive force, consisting of the mitochondrial membrane potential (ΔΨm, the major component in mammals) and ΔpH across the inner mitochondrial membrane. Both ATP production and reactive oxygen species (ROS) are linked to ΔΨm, and it has been shown that an imbalance in ΔΨm beyond the physiological optimal intermediate range results in excessive ROS production. The reaction of cytochrome c oxidase (COX) of the ETC with its small electron donor cytochrome c (Cytc) is the proposed rate-limiting step in mammals under physiological conditions. The rate at which this redox reaction occurs controls ΔΨm and thus ATP and ROS production. Multiple mechanisms are in place that regulate this reaction to meet the cell's energy demand and respond to acute stress. COX and Cytc have been shown to be regulated by all three main mechanisms, which we discuss in detail: allosteric regulation, tissue-specific isoforms, and post-translational modifications for which we provide a comprehensive catalog and discussion of their functional role with 55 and 50 identified phosphorylation and acetylation sites on COX, respectively. Disruption of these regulatory mechanisms has been found in several common human diseases, including stroke and myocardial infarction, inflammation including sepsis, and diabetes, where changes in COX or Cytc phosphorylation lead to mitochondrial dysfunction contributing to disease pathophysiology. Identification and subsequent targeting of the underlying signaling pathways holds clear promise for future interventions to improve human health. An example intervention is the recently discovered noninvasive COX-inhibitory infrared light therapy that holds promise to transform the current standard of clinical care in disease conditions where COX regulation has gone awry.

High sucrose low copper diet in pregnant diabetic rats induces transient oxidative stress, hypoxia, and apoptosis in the offspring's liver

BACKGROUND

Hyperglycemia-related oxidative stress and hypoxia are important mechanisms responsible for diabetes-induced embryopathy and other complications. High sucrose low copper diet (HSD), but not regular diet (RD), induces type 2 diabetes in the inbred Cohen diabetic sensitive (CDs) rats but not in the Sabra control rats. We recently demonstrated long-term changes of DNA methylation and gene expression in various groups of genes, including genes involved in oxidant-antioxidant activity in the liver of 2-4-week-old CDs offspring of diabetic dams. We now studied the postnatal effects of diabetes and/or HSD on several liver metabolic parameters in these offspring.

METHODS

we studied lipid peroxidation, activity of the antioxidants enzymes superoxide dismutase (SOD) and Catalase (CAT). By immunohistochemistry: protein oxidation by nitrotyrosine staining, hypoxia inducing factor1α (HIF1α), apoptosis [caspase 3, bcl-2-like protein (BAX)], proliferation [proliferating cell nuclear antigen (PCNA)] and NF-κB.

RESULTS

In the Sabra rats fed HSD only few, early and transitional changes were observed in lipid peroxidation, SOD and CAT activity. In the CDs fed HSD more significant changes in lipid and protein oxidation, HIF1α, apoptosis and proliferation were observed, persisting for longer.

CONCLUSIONS

The changes in the Sabra rats HSD were attributed to the pro-oxidant effects of the diet and those in the diabetic CDs to the HSD and maternal diabetes. In light of the DNA methylation changes in the liver of the CDs HSD, we presume that changes in gene expression are responsible for our findings, and that similar changes may lead to the metabolic syndrome at adulthood.

Gestational Hypoxia and Developmental Plasticity

Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.