Neurotrophic and migratory properties of an olfactory ensheathing cell line.

Olfactory ensheathing cells (OECs) are a unique type of macroglia required for normal olfactory axonal regeneration throughout the lifetime of an individual. Recent evidence in the literature suggests that OECs transplanted into injured spinal cords may facilitate axonal regeneration. In this study, we evaluated the neurotrophic properties of OECs using a homogeneous clonal cell line (nOEC), which does not contain contaminating cell types found in all primary OEC cultures. The results indicate that nOECs express mRNA for NGF, BDNF, NT-4/5, and neuregulins, but not for NT-3 or CNTF. In addition, nOECs secrete NGF, BDNF, and neuregulin, but retain NT-4/5 intracellularly. Finally, prelabeled nOECs derived from rat survived transplantation into a dorsal hemisected region of the hamster spinal cord and migrated only in the injured, dorsal portion of the spinal cord. This migratory pattern suggests that the nOECs are viable in vivo and respond to signals originating from the injured neuronal cells and their processes.

Neuregulins and erbB receptor expression in adult human oligodendrocytes.

We have previously reported that neonatal rat oligodendrocytes (OLGs) express and secrete neuregulins (NRGs) (Raabe et al., 1997). This laboratory has also shown that NRGs stimulate the differentiation of neonatal rat OLGs and that these cells express the erbB receptors for NRGs (Raabe et al., 1997). In this study, we have characterized NRG expression in adult human OLG cultures isolated from the temporal lobe resection of intractable epilepsy patients. Using immunocytochemistry and Western blotting, we find that adult human OLGs contain both the alpha and beta isoforms of NRGs. In addition, Western blots show that the adult human OLGs secrete both isoforms as N-glycosylated molecules. These cells also express all four erbB receptor subtypes, and possibly an activated erbB receptor. The observation that these cells synthesize and secrete their own NRGs, and possibly express a tyrosine-phosphorylated erbB receptor, is consistent with autocrine and/or paracrine signaling. Amplification of this signaling may provide a useful mechanism to stimulate differentiation of adult human OLGs in demyelinating disease.

Singlet oxygen-mediated inactivation of acetylcholinesterase: a comparison of purified enzyme in solution and enzyme bound to K562 leukemia cells.

We have compared the singlet oxygen-mediated inactivation of acetylcholinesterase (ACE) in solution with the inactivation of ACE on the surface of K562 leukemia cells. In solution, the actions of the singlet-oxygen quenchers, methionine, azide, disodium [N,N'-ethylenebis (5-sulfosalicylideneimminato)]nickelate(II) (Ni-chelate 1) and disodium [(N,N'-2,3-propionic acid)bis(5-sulfosal-icylideneimminato)] nickelate(II) (Ni-chelate 2) could be explained quantitatively by assuming their only mechanism of action was to quench singlet oxygen. The singlet oxygen quenchers, azide, Ni-chelate 1 and Ni-chelate 2, caused smaller inhibitions in the rate of singlet oxygen-mediated inactivation of ACE on K562 cells than ACE in solution. The effects of these quenchers and of deuterium oxide were interpreted using a mathematical model of singlet-oxygen quenching and diffusion to estimate the lifetime of singlet oxygen near the cell surface. The azide quenching data and the deuterium-oxide data gave lifetimes of 0.9 +/- 0.2 microsecond and 0.45 +/- 0.15 microsecond, respectively. The increases in ACE inactivation lifetime caused by the nickel chelates were anomalously large. The unexpectedly large quenching due to the nickel chelates may have been due to a nonuniform distribution of the chelates in the cytoplasm with a large concentration of the chelate near the cell membrane.