A fluorimetric semi-microplate format assay of protein carbonyls in blood plasma.

Oxidative stress, originating from reactive oxygen species (ROS), has been implicated in aging and various human diseases. The ROS generated can oxidize proteins producing protein carbonyl derivatives. The level of protein carbonyls in blood plasma has been used as a measure of overall oxidative stress in the body. Classically, protein carbonyls have been quantitated spectrophotometrically by directly reacting them with 2,4-dinitrophenylhydrazine (DNPH). However, the applicability of this method to biological samples is limited by its low inherent sensitivity. This limitation has been overcome by the development of sensitive enzyme-linked immunosorbent assay (ELISA) methods to measure protein carbonyls. As part of the Healthy Aging in Neighborhoods of Diversity across the Lifespan (HANDL) study, oxidative stress in humans was quantified by measuring blood plasma protein carbonyls using the two commercially available ELISA kits and the spectrophotometric DNPH assay. Surprisingly, two ELISA methods gave very different values for protein carbonyls, both of which were different from the value of the spectrophotometric method. We have developed a fluorescent semi-microplate format assay of protein carbonyls involving direct reaction of protein carbonyls with fluorescein thiosemicarbazide that correlates (R=0.992) with the direct spectrophotometric method. It has a coefficient of variation of 4.99% and is at least 100 times more sensitive than the spectrophotometric method.

Intrathecal delivery of frataxin mRNA encapsulated in lipid nanoparticles to dorsal root ganglia as a potential therapeutic for Friedreich's ataxia.

In Friedreich's ataxia (FRDA) patients, diminished frataxin (FXN) in sensory neurons is thought to yield the predominant pathology associated with disease. In this study, we demonstrate successful usage of RNA transcript therapy (RTT) as an exogenous human FXN supplementation strategy in vitro and in vivo, specifically to dorsal root ganglia (DRG). Initially, 293 T cells were transfected with codon optimized human FXN mRNA, which was translated to yield FXN protein. Importantly, FXN was rapidly processed into the mature functional form of FXN (mFXN). Next, FXN mRNA, in the form of lipid nanoparticles (LNPs), was administered intravenously in adult mice. Examination of liver homogenates demonstrated efficient FXN LNP uptake in hepatocytes and revealed that the mitochondrial maturation machinery had efficiently processed all FXN protein to mFXN in ~24 h in vivo. Remarkably, greater than 50% mFXN protein derived from LNPs was detected seven days after intravenous administration of FXN LNPs, suggesting that the half-life of mFXN in vivo exceeds one week. Moreover, when FXN LNPs were delivered by intrathecal administration, we detected recombinant human FXN protein in DRG. These observations provide the first demonstration that RTT can be used for the delivery of therapeutic mRNA to DRG.

Role of the membrane in the formation of heme degradation products in red blood cells.

AIMS: Red blood cells (RBCs) have an extensive antioxidant system designed to eliminate the formation of reactive oxygen species (ROS). Nevertheless, RBC oxidant stress has been demonstrated by the formation of a fluorescent heme degradation product (excitation (ex) 321 nm, emission (em) 465 nm) both in vitro and in vivo. We investigated the possibility that the observed heme degradation results from ROS generated on the membrane surface that are relatively inaccessible to the cellular antioxidants. MAIN METHODS: Membrane and cytosol were separated by centrifugation and the fluorescence intensity and emission maximum were measured. The effect on the maximum emission of adding oxidized and reduced hemoglobin to the fluorescent product formed when hemin is degraded by hydrogen peroxide (H(2)O(2)) was studied. KEY FINDINGS: 90% of the fluorescent heme degradation products in hemolysates are found on the membrane. Furthermore, these products are not transferred from the cytosol to the membrane and must, therefore, be formed on the membrane. We also showed that the elevated level of heme degradation in HbCC cells that is attributed to increased oxidative stress was found on the membrane. SIGNIFICANCE: These results suggest that, although ROS generated in the cytosol are neutralized by antioxidant enzymes, H(2)O(2) generated by the membrane bound hemoglobin is not accessible to the cytosolic antioxidants and reacts to generate fluorescent heme degradation products. The formation of H(2)O(2) on the membrane surface can explain the release of ROS from the RBC to other tissues and ROS damage to the membrane that can alter red cell function and lead to the removal of RBCs from circulation by macrophages.