3-nitrotyrosine and 2-phenyl-4-4-5-5-tetramethylimidazoline-1-oxyl-3-oxide

The purposes of these studies were to quantify the concentrations of total nitrate and nitrite (NO(x)(-)) cyclic guanosine monophosphate (cGMP), and nitrotyrosine over skin surface in normal weight healthy volunteers (n = 64) compared to overweight/obese subjects (n = 54). A semi-circular plastic tube was taped to the skin along acupuncture points (acupoints), meridian line without acupoint (MWOP), and nonmeridian control and filled with a 2-Phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl solution for 20 min. The concentrations of NO(x)(-), cGMP, and nitrotyrosine in the samples were quantified in a blinded fashion using chemiluminescence and enzyme-linked immunosorbent assay, respectively. In normal weight healthy volunteers, NO(x)(-) and cGMP concentrations were consistently increased over the pericardium meridian (PC) 4-7 compared with nonmeridian areas. NO(x)(-) concentration is enhanced over the bladder meridian (BL) 56-57, but cGMP level is similar between the regions. In overweight/obese subjects, NO(x)(-) contents were increased or tended to be elevated over PC and BL regions. cGMP is paradoxically decreased over PC acupoints and nonmeridian control on the forearm but the decreases were blunted along BL regions on the leg. Nitrotyrosine concentrations are markedly elevated (five- to sixfold) over both PC and BL in all areas of overweight/obese subjects. This is the first evidence showing that nitrotyrosine level is tremendously elevated over skin accompanied by paradoxical changes in nitric oxide (NO)-cGMP concentrations over PC skin region in overweight/obese subject. The results suggest that NO-related oxidant inflammation is systemically enhanced while cGMP generation is impaired over PC skin region but not over BL region in obesity.

Topics: Acupuncture Points; Adult; Cyclic GMP; Cyclic N-Oxides; Female; Humans; Imidazoles; Male; Nitrates; Nitric Oxide; Nitrites; Obesity; Skin; Tyrosine

Different lines of evidence suggest that nitric oxide (NO) plays a key role in the pathogenesis of inflammatory neuropathies; however, it is still unclear which structures in the peripheral nerve are the primary targets of NO-mediated nerve injury. To address this issue, we determined the expression of NO metabolites in sural nerve biopsies and in cerebrospinal fluid from patients with inflammatory neuropathies and studied the pathologic effects of NO in an in vitro model of myelinated Schwann cell-neuron cocultures. In cerebrospinal fluid samples, nitrite levels remained unaltered; however, nitrotyrosine, a marker for peroxynitrite formation, could be identified in nerve biopsies from patients with inflammatory neuropathies. In an in vitro model of Schwann cell neuron cocultures, high concentrations of NO induced robust demyelination, which was the result of NO-mediated axonal injury, whereas Schwann cell viability remained unaffected. These findings suggest that in contrast to Schwann cells, sensory neurons are the primary target of NO-mediated cytotoxicity and the loss of myelin is the result of selective damage to axons rather than a direct harmful effect to Schwann cells. Our findings imply that NO contributes to the pathologic changes seen in the inflamed peripheral nervous system, which is characterized by the features of axonal injury and subsequent myelin degradation, previously described as Wallerian-like degeneration.

Topics: Animals; Cell Survival; Cells, Cultured; Coculture Techniques; Culture Media, Conditioned; Cyclic N-Oxides; Dose-Response Relationship, Drug; Drug Interactions; Embryo, Mammalian; Free Radical Scavengers; Ganglia, Spinal; Humans; Imidazoles; Neurites; Neurons; Nitric Oxide; Nitric Oxide Donors; Nitroso Compounds; Polyradiculoneuropathy; Rats; Schwann Cells; Sural Nerve; Tyrosine