Effects of recombinant human erythropoietin on cerebral blood flow in preterm infants: arterial spin labeling magnetic resonance imaging evaluation / 中国新生儿科杂志

Objective:To study the effects of recombinant human erythropoietin (rhEPO) on cerebral blood flow (CBF) in preterm infants using arterial spin labeling (ASL) magnetic resonance imaging (MRI).Methods:From September 2021 to June 2022, preterm infants (gestational age ≤32 weeks, birth weight ≤1 500 g) admitted to NICU of our hospital within 24 h after birth were randomly assigned into rhEPO group and control group for this prospective study. The rhEPO group was given rhEPO (500 IU/kg iv, once every other day for 2 weeks) within 72 h after birth plus symptomatic supportive treatment. The control group received same amount of normal saline injection. Both groups received brain MRI, diffusion-weighted imaging and ASL at adjusted gestational age of 35~37 weeks and CBF values of interested areas were measured.Results:A total of 85 infants were enrolled, including 40 in the rhEPO group and 45 in the control group. No significant differences existed in the incidences of periventricular-intraventricular hemorrhage, periventricular leukomalacia, focal white matter injury and extensive white matter injury between the two groups ( P>0.05). The CBF values [ml/(100 g·min)] of frontal cortex [left 15.1±3.9 vs. 17.9±3.1, right 15.9 (12.5, 17.8) vs. 18.1(16.1,20.2)], temporal cortex [left 15.8±4.3 vs. 18.6±3.8, right 16.3(13.2,19.4) vs. 18.1(15.7,19.7)], occipital cortex (left 15.8±6.1 vs. 18.8±3.3, right 16.8±5.5 vs. 19.3±4.8), basal ganglia (left 24.7±7.2 vs. 28.7±6.2, right 26.0±7.9 vs. 29.3±6.4) and thalamus (left 32.7±11.8 vs. 37.9±8.6, right 32.1±11.6 vs. 37.6±10.2) in the rhEPO group were significantly lower than the control group ( P<0.05). No significant differences existed of CBF value at the parietal cortex between the two groups ( P>0.05). Conclusions:Early application of rhEPO can reduce CBF in premature infants, which may be related to the neuro-protective effects of EPO.

Antioxidant effect of 4-nerolidylcatechol and -tocopherol in erythrocyte ghost membranes and phospholipid bilayers

4-Nerolidylcatechol (4-NC) is found in Pothomorphe umbellata root extracts and is reported to have a topical protective effect against UVB radiation-induced skin damage, toxicity in melanoma cell lines, and antimalarial activity. We report a comparative study of the antioxidant activity of 4-NC and α-tocopherol against lipid peroxidation initiated by two free radical-generating systems: 2,2′-azobis(2-aminopropane) hydrochloride (AAPH) and FeSO4/H2O2, in red blood cell ghost membranes and in egg phosphatidylcholine (PC) vesicles. Lipid peroxidation was monitored by membrane fluidity changes assessed by electron paramagnetic resonance spectroscopy of a spin-labeled lipid and by the formation of thiobarbituric acid-reactive substances. When lipoperoxidation was initiated by the hydroxyl radical in erythrocyte ghost membranes, both 4-NC and α-tocopherol acted in a very efficient manner. However, lower activities were observed when lipoperoxidation was initiated by the peroxyl radical; and, in this case, the protective effect of α-tocopherol was lower than that of 4-NC. In egg PC vesicles, malondialdehyde formation indicated that 4-NC was effective against lipoperoxidation initiated by both AAPH and FeSO4/H2O2, whereas α-tocopherol was less efficient in protecting against lipoperoxidation by AAPH, and behaved as a pro-oxidant for FeSO4/H2O2. The DPPH (2,2-diphenyl-1-picrylhydrazyl) free-radical assay indicated that two free radicals were scavenged per 4-NC molecule, and one free radical was scavenged per α-tocopherol molecule. These data provide new insights into the antioxidant capacity of 4-NC, which may have therapeutic applications for formulations designed to protect the skin from sunlight irradiation.

Electron paramagnetic resonance study of lipid and protein membrane components of erythrocytes oxidized with hydrogen peroxide

Electron paramagnetic resonance (EPR) spectroscopy of spin labels was used to monitor membrane dynamic changes in erythrocytes subjected to oxidative stress with hydrogen peroxide (H2O2). The lipid spin label, 5-doxyl stearic acid, responded to dramatic reductions in membrane fluidity, which was correlated with increases in the protein content of the membrane. Membrane rigidity, associated with the binding of hemoglobin (Hb) to the erythrocyte membrane, was also indicated by a spin-labeled maleimide, 5-MSL, covalently bound to the sulfhydryl groups of membrane proteins. At 2% hematocrit, these alterations in membrane occurred at very low concentrations of H2O2 (50 µM) after only 5 min of incubation at 37°C in azide phosphate buffer, pH 7.4. Lipid peroxidation, suggested by oxidative hemolysis and malondialdehyde formation, started at 300 µM H2O2 (for incubation of 3 h), which is a concentration about six times higher than those detected with the probes. Ascorbic acid and α-tocopherol protected the membrane against lipoperoxidation, but did not prevent the binding of proteins to the erythrocyte membrane. Moreover, the antioxidant (+)-catechin, which also failed to prevent the cross-linking of cytoskeletal proteins with Hb, was very effective in protecting erythrocyte ghosts from lipid peroxidation induced by the Fenton reaction. This study also showed that EPR spectroscopy can be useful to assess the molecular dynamics of red blood cell membranes in both the lipid and protein domains and examine oxidation processes in a system that is so vulnerable to oxidation.

Structural properties of lipid reconstructs and lipid composition of normotensive and hypertensive rat vascular smooth muscle cell membranes

Multiple cell membrane alterations have been reported to be the cause of various forms of hypertension. The present study focuses on the lipid portion of the membranes, characterizing the microviscosity of membranes reconstituted with lipids extracted from the aorta and mesenteric arteries of spontaneously hypertensive (SHR) and normotensive control rat strains (WKY and NWR). Membrane-incorporated phospholipid spin labels were used to monitor the bilayer structure at different depths. The packing of lipids extracted from both aorta and mesenteric arteries of normotensive and hypertensive rats was similar. Lipid extract analysis showed similar phospholipid composition for all membranes. However, cholesterol content was lower in SHR arteries than in normotensive animal arteries. These findings contrast with the fact that the SHR aorta is hyporeactive while the SHR mesenteric artery is hyperreactive to vasopressor agents when compared to the vessels of normotensive animal strains. Hence, factors other than microviscosity of bulk lipids contribute to the vascular smooth muscle reactivity and hypertension of SHR. The excess cholesterol in the arteries of normotensive animal strains apparently is not dissolved in bulk lipids and is not directly related to vascular reactivity since it is present in both the aorta and mesenteric arteries. The lower cholesterol concentrations in SHR arteries may in fact result from metabolic differences due to the hypertensive state or to genes that co-segregate with those that determine hypertension during the process of strain selection.