Monocyte chemotactic protein-1 regulates leukocyte recruitment during gastric ulcer recurrence induced by tumor necrosis factor-alpha

TNF-alpha has numerous biological activities, including the induction of chemokine expression, and is involved in many gastric injuries. C-C chemokines [monocyte chemotactic protein (MCP)-1 and macrophage inflammatory protein (MIP)-1alpha] and C-X-C chemokines [MIP-2 and cytokine-induced neutrophil chemoattractant (CINC)-2alpha] mediate chemotaxis of monocytes and neutrophils, respectively. We examined the roles of TNF-alpha and dynamics of chemokine expression in gastric ulceration including ulcer recurrence and indomethacin-induced injury. Rats with healed chronic gastric ulcers received intraperitoneal TNF-alpha to induce ulcer recurrence. Some rats were given neutralizing antibodies against neutrophils or MCP-1 together with TNF-alpha. In a separate experiment, rats were orally administered 20 mg/kg indomethacin with or without pretreatment with pentoxifylline (an inhibitor of TNF-alpha synthesis) or anti-MCP-1 antibody. TNF-alpha (1 microg/kg) induced gastric ulcer recurrence after 48 h, which was completely prevented by anti-neutrophil antibody. TNF-alpha increased the number of macrophages and MCP-1 mRNA expression in scarred mucosa from 4 h, whereas it increased MPO activities (marker of neutrophil infiltration) and mRNA expression of MIP-2 and CINC-2alpha from 24 h. Anti-MCP-1 antibody inhibited leukocyte infiltration with reduction of the levels of C-X-C chemokines and prevented ulcer recurrence. Indomethacin treatment increased TNF-alpha/chemokine mRNA expression from 30 min and induced macroscopic erosions after 4 h. Pentoxifylline inhibited the indomethacin-induced gastric injury with reduction of neutrophil infiltration and expression of chemokine (MCP-1, MIP-2, and CINC-2alpha). Anti-MCP-1 antibody also inhibited the injury and these inflammatory responses but did not affect TNF-alpha mRNA expression. In conclusion, increased MCP-1 triggered by TNF-alpha may play a key role in gastric ulceration by regulating leukocyte recruitment and chemokine expression.     

SLC5A9/SGLT4, a new Na+-dependent glucose transporter, is an essential transporter for mannose, 1,5-anhydro-D-glucitol, and fructose

We isolated a cDNA clone of SLC5A9/SGLT4 from human small intestinal full-length cDNA libraries, and functionally characterized it in vitro. The messenger RNA encoding SGLT4 was mainly expressed in the small intestine and kidney, among the human tissues tested. COS-7 cells transiently expressing SGLT4 exhibited Na(+)-dependent alpha-methyl-D-glucopyranoside (AMG) transport activity with an apparent K(m) of 2.6 mM, suggesting that SGLT4 is a low affinity-type transporter. The rank order of naturally occurring sugar analogs for the inhibition of AMG transport was: D-mannose (Man) > D-glucose (Glc) > D-fructose (Fru) = 1,5-anhydro-D-glucitol (1,5AG) > D-galactose (Gal). Recognition of Man as a substrate was confirmed by direct uptake of Man into the cell. COS-7 cells expressing a putative murine SGLT4 ortholog showed similar Na(+)-dependent AMG transport activity and a similar deduced substrate specificity. These results suggest that SGLT4 would have unique physiological functions (i.e., absorption and/or reabsorption of Man, 1,5AG, and Fru, in addition to Glc).     

Investigation of phosphorylation status of OdhI protein during penicillin- and Tween 40-triggered glutamate overproduction by <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

Glutamate overproduction by Corynebacterium glutamicum is triggered by treatment with penicillin or Tween 40 and is accompanied by a decrease in 2-oxoglutarate dehydrogenase complex (ODHC) activity. We have reported that de novo synthesis of OdhI, which inhibits ODHC activity by interacting specifically with the E1o subunit of ODHC (OdhA), is induced by penicillin, and that odhI overexpression induces glutamate overproduction in the absence of any triggers for glutamate overproduction. In this study, to determine the function of OdhI in glutamate overproduction by C. glutamicum, changes in OdhI levels and phosphorylation status during penicillin- and Tween 40-induced glutamate overproduction were examined by western blot. The synthesis of both unphosphorylated and phosphorylated OdhI was increased by addition of Tween 40 or penicillin and the levels of unphosphorylated OdhI, which can inhibit ODHC activity, was significantly higher than those of phosphorylated OdhI, which is unable to inhibit ODHC activity. Meanwhile, the OdhA levels were maintained throughout the culture. These results indicate that OdhI synthesis is induced by additions of penicillin and Tween 40 and most synthesized OdhI is unphosphorylated, resulting in the decrease in ODHC activity and glutamate overproduction. Similarly, in the odhI-overexpressing strain, both unphosphorylated and phosphorylated OdhI were synthesized, while the levels of OdhA were nearly constant throughout culture. Our results suggest that high level of unphosphorylated OdhI regulates glutamate overproduction by C. glutamicum.     

Molecular basis of guanine nucleotide dissociation inhibitor activity of human neuroglobin by chemical cross-linking and mass spectrometry

Oxidized human neuroglobin (Ngb), a heme protein expressed in the brain, has been proposed to act as a guanine nucleotide dissociation inhibitor (GDI) for the GDP-bound form of the heterotrimeric G protein alpha-subunit (Galpha(i)). Here, to elucidate the molecular mechanism underlying the GDI activity of Ngb, we used an glutathione-S-transferase pull-down assay to confirm that Ngb competes with G-protein betagamma-subunits (Gbetagamma) for binding to Galpha(i), and identified the Galpha(i)-binding site in Ngb by chemical cross-linking with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and sulfo-N-hydroxysuccinimide, coupled with mass spectrometry (MS). Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS analysis for tryptic peptides derived from the cross-linked Ngb-Galpha(i) complex revealed several binding regions in Ngb. Furthermore, MALDI-TOF/TOF MS analysis of the cross-linked Ngb and Galpha(i) peptides, together with the MS/MS scoring method, predicted cross-linking between Glu60 (Ngb) and Ser206 (Galpha(i)), and between Glu53 (Ngb) and Ser44 (Galpha(i)). Because Ser206 of Galpha(i) is located in the region that contacts Gbetagamma, binding of Ngb could facilitate the release of Gbetagamma from Galpha(i). Binding of Ngb to Galpha(i) would also inhibit the exchange of GDP for GTP, because Ser44 (Galpha(i)) is adjacent to the GDP-binding site and Glu53 (Ngb), which is cross-linked to Ser44 (Galpha(i)), could be located close to GDP. Thus, we have identified, for the first time, the sites of interaction between Ngb and Galpha(i), enabling us to discuss the functional significance of this binding on the GDI activity of Ngb.     

Interaction with IQGAP1 links APC to Rac1, Cdc42, and actin filaments during cell polarization and migration

Rho family GTPases, particularly Rac1 and Cdc42, are key regulators of cell polarization and directional migration. Adenomatous polyposis coli (APC) is also thought to play a pivotal role in polarized cell migration. We have found that IQGAP1, an effector of Rac1 and Cdc42, interacts directly with APC. IQGAP1 and APC localize interdependently to the leading edge in migrating Vero cells, and activated Rac1/Cdc42 form a ternary complex with IQGAP1 and APC. Depletion of either IQGAP1 or APC inhibits actin meshwork formation and polarized migration. Depletion of IQGAP1 or APC also disrupts localization of CLIP-170, a microtubule-stabilizing protein that interacts with IQGAP1. Taken together, these results suggest a model in which activation of Rac1 and Cdc42 in response to migration signals leads to recruitment of IQGAP1 and APC which, together with CLIP-170, form a complex that links the actin cytoskeleton and microtubule dynamics during cell polarization and directional migration.     

Ranging behavior of Mahale chimpanzees: a 16 year study

We have analyzed the ranging patterns of the Mimikire group (M group) of chimpanzees in the Mahale Mountains National Park, Tanzania. During 16 years, the chimpanzees moved over a total area of 25.2 or 27.4 km², as estimated by the grid-cell or minimum convex polygon (MCP) methods, respectively. Annually, the M group used an average of 18.4 km², or approximately 70 %, of the total home-range area. The chimpanzees had used 80 % of their total home range after 5 years and 95 % after 11 years. M group chimpanzees were observed more than half of the time in areas that composed only 15 % of their total home range. Thus, they typically moved over limited areas, visiting other parts of their range only occasionally. On average, the chimpanzees used 7.6 km² (in MCP) per month. Mean monthly range size was smallest at the end of the rainy season and largest at the end of the dry season, but there was much variability from year to year. The chimpanzees used many of the same areas every year when Saba comorensis fruits were abundant between August and January. In contrast, the chimpanzees used several different areas of their range in June. Here range overlap between years was relatively small. Over the 16 years of the study we found that the M group reduced their use of the northern part of their range and increased their frequency of visits to the eastern mountainous side of their home range. Changes in home-range size correlated positively with the number of adult females but not with the number of adult males. This finding does not support a prediction of the male-defended territory model proposed for some East African chimpanzee unit-groups.     

Factors associated with severity of daytime sleepiness and indications for initiating treatment in patients with periodic limb movements during sleep

Obstructive sleep apnea syndrome (OSAS) is closely associated with hypertension. Activity of angiotensin II (Ang II) and non-dipping nocturnal blood pressure (BP) variability are implicated in hypertension-related target organ damage. We examined the correlation between OSAS with serum Ang II levels and evaluated the risk of non-dipping BP variability in 180 patients with essential hypertension (EHT). Eligible patients were divided into three subgroups based on their apnea-hypopnea index (AHI) evaluated by polysomnography. EHT alone, EHT with mild OSAS, and EHT with moderate/severe OSAS. Ambulatory BP monitoring was used to calculate mean BP over 24 h, as well as diurnal and nocturnal BP variability. Serum Ang II was determined with enzyme-linked immun-osorbent assay. EHT patients with OSAS had significantly higher systolic BP calculated either over 24 h, or by diurnal or nocturnal monitoring (P < 0.05). More EHT patients with OSAS showed non-dipping BP profiles than did EHT patients alone (P < 0.05). The number of patients with non-dipping BP increased with increasing OSAS severity. Surgical treatment alleviated OSAS and reduced AHI (P < 0.05). Preoperative serum Ang II in EHT patients with OSAS was significantly higher than that in those without OSAS (P < 0.05), and showed a rising trend with OSAS severity (P < 0.05). Postoperative serum Ang II, BP and the incidence of non-dipping BP were reduced by surgery to levels lower than preoperative values in patients with OSAS. We therefore conclude that OSAS leads to increased serum Ang II and increased risk of non-dipping BP in patients with EHT.

     

Requirements of basic amino acid residues within the lectin-like domain of LOX-1 for the binding of oxidized low-density lipoprotein.

Lectin-like OxLDL receptor-1 (LOX-1) was identified as the major receptor for oxidized low-density lipoprotein (OxLDL) in aortic endothelial cells. LOX-1 is a type II membrane protein that structurally belongs to the C-type lectin family. Here, we found that the lectin-like domain of LOX-1 is essential for ligand binding, but the neck domain is not. In particular, the large loop between the third and fourth cysteine of the lectin-like domain plays a critical role for OxLDL binding as well as C-terminal end residues. Alanine-directed mutagenesis of the basic amino acid residues around this region revealed that all of the basic residues are involved in OxLDL binding. Simultaneous mutations of these basic residues almost abolished the OxLDL-binding activity of LOX-1. Electrostatic interaction between basic residues in the lectin-like domain of LOX-1 and negatively charged OxLDL is critical for the binding activity of LOX-1.