FABP7 expression in normal and stab-injured brain cortex and its role in astrocyte proliferation

Reactive gliosis, in which astrocytes as well as other types of glial cells undergo massive proliferation, is a common hallmark of all brain pathologies. Brain-type fatty acid-binding protein (FABP7) is abundantly expressed in neural stem cells and astrocytes of developing brain, suggesting its role in differentiation and/or proliferation of glial cells through regulation of lipid metabolism and/or signaling. However, the role of FABP7 in proliferation of glial cells during reactive gliosis is unknown. In this study, we examined the expression of FABP7 in mouse cortical stab injury model and also the phenotype of FABP7-KO mice in glial cell proliferation. Western blotting showed that FABP7 expression was increased significantly in the injured cortex compared with the contralateral side. By immunohistochemistry, FABP7 was localized to GFAP(+) astrocytes (21% of FABP7(+) cells) and NG2(+) oligodendrocyte progenitor cells (62%) in the normal cortex. In the injured cortex there was no change in the population of FABP7(+)/NG2(+) cells, while there was a significant increase in FABP7(+)/GFAP(+) cells. In the stab-injured cortex of FABP7-KO mice there was decrease in the total number of reactive astrocytes and in the number of BrdU(+) astrocytes compared with wild-type mice. Primary cultured astrocytes from FABP7-KO mice also showed a significant decrease in proliferation and omega-3 fatty acid incorporation compared with wild-type astrocytes. Overall, these data suggest that FABP7 is involved in the proliferation of astrocytes by controlling cellular fatty acid homeostasis.     

Type-3 ryanodine receptor involved in Ca2+-induced Ca2+ release and transmitter exocytosis at frog motor nerve terminals

Ca(2+)-induced Ca2+ release (CICR) occurs in frog motor nerve terminals after ryanodine receptors (RyRs) are primed for activation by conditioning large Ca2+ entry. We studied which type of RyR exists, whether CICR occurs without conditioning Ca2+ entry and how RyRs are primed. Immunohistochemistry revealed the existence of RyR3 in motor nerve terminals and axons and both RyR1 and RyR3 in muscle fibers. A blocker of RyR, 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8) slightly decreased rises in intracellular Ca2+ ([Ca2+]i) induced by a short tetanus (50 Hz, 1-2s), but not after treatment with ryanodine. Repetitive tetani (50 Hz for 15s every 20s) produced repetitive rises in [Ca2+]i, whose amplitude overall waxed and waned. TMB-8 blocked the waxing and waning components. Ryanodine suppressed a slow increase in end-plate potentials (EPPs) induced by stimuli (33.3 Hz, 15s) in a low Ca2+, high Mg2+ solution. KN-62, a blocker of Ca(2+)/calmoduline-activated protein kinase II (CaMKII), slightly reduced short tetanus-induced rises in [Ca2+]i, but markedly the slow waxing and waning rises produced by repetitive tetani in both normal and low Ca2+, high Mg2+ solutions. Likewise, KN-62, but not KN-04, an inactive analog, suppressed slow increases in EPP amplitude and miniature EPP frequency during long tetanus. Thus, CICR normally occurs weakly via RyR3 activation by single impulse-induced Ca2+ entry in frog motor nerve terminals and greatly after the priming of RyR via CaMKII activation by conditioning Ca2+ entry, thus, facilitating transmitter exocytosis and its plasticity.     

BMP antagonists: their roles in development and involvement in pathophysiology

Bone morphogenetic proteins (BMPs) are phylogenetically conserved signaling molecules that belong to the transforming growth factor (TGF)-beta superfamily, and are involved in the cascades of body patterning and morphogenesis. The activities of BMPs are precisely regulated by certain classes of molecules that are recently recognized as BMP antagonists. BMP antagonists function through direct association with BMPs, thus prohibiting BMPs from binding their cognate receptors. In this review, the classification and functions of BMP antagonists will be discussed, especially focusing on the new family of tissue-specific BMP antagonists composed of uterine sensitization-associated gene 1 (USAG-1) and sclerostin.     

Decrease in the particle size of low-density lipoprotein (LDL) by oxidation

A radical reaction of low-density lipoprotein (LDL) causes fragmentation and cross-link of apolipoprotein B-100 (apoB). LDL (50 microg/ml) was subjected to the well-studied oxidation with Cu(2+) (1.67 microM). The concentration of alpha-tocopherol decreased to 10% of the initial level during the first 30 min. After this lag time, the conjugated diene content, as measured by absorption at 234 nm, started increasing and the residual apoB at 512 kDa determined by immunoblot after SDS-PAGE (sodium dodecylsulfate-polyacrylamide gel electrophoresis) was also decreased. The particle size of LDL determined by nondenaturing gradient gel electrophoresis decreased steadily during the initial 120 min, when residual native apoB was only 30% of the initial level. Plasma was also oxidized with Cu(2+) (400 microM). Under this condition, a clear lag time was not observed and alpha-tocopherol content, apoB, and the LDL particle size were decreased simultaneously. Based on these experiments, we propose that an oxidation reaction is involved in the formation of small dense LDL.     

Visual evoked potentials and event related potentials in congenitally deaf subjects

The purpose was to test parameters of visual evoked potentials (VEPs) and of event-related potentials (ERPs) in deaf subjects to verify visual and cognitive CNS functions in a handicapped group of the population. Three types of visual stimuli (with dominating parvocellular or magnocellular system activation or with cognitive tasks) were used in the study. Six deaf persons (4 women, 2 men, mean age 17 years) and 6 persons with normal hearing (sex- and age-matched) were included in this pilot study. In all types of stimulation, latencies and amplitudes of main VEPs and ERPs components were evaluated. No significant latency differences were found. However, significantly reduced amplitudes were found in the occipital area for responses to motion and cognitive stimuli which might be interpreted as a part of functional reorganization of the extrastriate and cognitive cortical areas of deaf subjects.     

Proinsulin lacking the A7-B7 disulfide bond, Ins2Akita, tends to aggregate due to the exposed hydrophobic surface

A single mutation (C96Y) in the Ins2 gene, which disrupts the A7-B7 disulfide bond, causes the diabetic phenotype in Akita mice. We biochemically analyzed the conformation of wild-type and Akita mutant recombinant proinsulins. Gel filtration chromatography and dynamic light scattering revealed that the apparent size of the mutant proinsulin molecules was significantly larger than that of wild-type proinsulin, even in the absence of intermolecular disulfide bonds. Titration with a hydrophobic probe, 1-anilinonaphthalene-8-sulfonate, demonstrated that the mutant proinsulin was more hydrophobic than the wild type. In addition, circular dichroism studies revealed that the conformation of the mutant proinsulin was less stable than the wild type, which is consistent with the observation that hydrophobic residues are exposed on the surface of the proinsulin molecules. Studies with antiserum against the C-peptide of proinsulin indicated that the mutant proinsulin had an immunoreactivity that was at least one-tenth weaker than wild-type proinsulin, suggesting that the C-peptide of mutant proinsulin is buried inside the aggregate of the proinsulin molecule. These findings indicate that increased hydrophobicity of mutant proinsulin facilitates aggregate formation, providing a clue to the dominant negative effect in the Akita mouse.     

Identification of mono-ubiquitinated LDH-A in skeletal muscle cells exposed to oxidative stress

We previously reported that oxidative stress is associated with unloading-mediated ubiquitination of muscle proteins. To further elucidate the involvement of oxidative stress in ubiquitination, we examined the ubiquitination profile in rat myoblastic L6 cells after treatment with hydrogen peroxide. Hydrogen peroxide induced many ubiquitinated proteins with low molecular masses (less than 60 kDa) as well as high molecular masses (more than 160 kDa). Among them, a 42-kDa-ubiquitinated protein was abundantly accumulated and immediately disappeared after the treatment. Microsequencing revealed that the 42-kDa-protein was identical to the mono-ubiquitinated form of rat lactate dehydrogenase A (LDH-A), and we confirmed that hydrogen peroxide induced the mono-ubiquitination of LDH-A in COS7 cells overexpressing LDH-A and ubiquitin. Under unloading conditions, such as tail-suspension and spaceflight, mono-ubiquitinated LDH was accumulated in gastrocnemius muscle. Interestingly, E-64-d plus pepstatin, lysosomal protease inhibitors, further accumulated mono-ubiquitinated LDH-A in the cells after treatment with hydrogen peroxide, while they did not affect the amount of poly-ubiquitinated LDH. In contrast, epoxomicin, a potent proteasome inhibitor, did not change the amount of mono-ubiquitinated LDH-A in L6 cells treated with hydrogen peroxide, although it significantly increased the amount of poly-ubiquitinated LDH. Our results suggest that oxidative stress induces not only poly-ubiquitination but also mono-ubiquitination of LDH-A, which may be involved in its lysosomal degradation during unloading.     

Immune regulation of protease-activated receptor-1 expression in murine small intestine during Nippostrongylus brasiliensis infection

Infection with gastrointestinal nematodes exerts profound effects on both immune and physiological responses of the host. Helminth infection induces a hypercontractility of intestinal smooth muscle that is dependent on the Th2 cytokines, IL-4 and IL-13, and may contribute to worm expulsion. Protease-activated receptors (PARs) are expressed throughout the gut, and activation of PAR-1 was observed in asthma, a Th2-driven pathology. In the current study we investigated the physiologic and immunologic regulation of PAR-1 in the murine small intestine, specifically 1) the effect of PAR-1 agonists on small intestinal smooth muscle contractility, 2) the effects of Nippostrongylus brasiliensis infection on PAR-1 responses, 3) the roles of IL-13 and IL-4 in N. brasiliensis infection-induced alterations in PAR-1 responses, and 4) the STAT6 dependence of these responses. We demonstrate that PAR-1 activation induces contraction of murine intestinal smooth muscle that is enhanced during helminth infection. This hypercontractility is associated with an elevated expression of PAR-1 mRNA and protein. N. brasiliensis-induced changes in PAR-1 function and expression were seen in IL-4-deficient mice, but not in IL-13- or STAT6-deficient mice, indicating the dependence of IL-13 on the STAT6 signaling pathway independent of IL-4.