Cholesterol transport between red blood cells and lipoproteins contributes to cholesterol metabolism in blood

Lipoproteins play a key role in transport of cholesterol to and from tissues. Recent studies have also demonstrated that red blood cells (RBCs), which carry large quantities of free cholesterol in their membrane, play an important role in reverse cholesterol transport. However, the exact role of RBCs in systemic cholesterol metabolism is poorly understood. RBCs were incubated with autologous plasma or isolated lipoproteins resulting in a significant net amount of cholesterol moved from RBCs to HDL, while cholesterol from LDL moved in the opposite direction. Furthermore, the bi-directional cholesterol transport between RBCs and plasma lipoproteins was saturable and temperature-, energy-, and time-dependent, consistent with an active process. We did not find LDLR, ABCG1, or scavenger receptor class B type 1 in RBCs but found a substantial amount of ABCA1 mRNA and protein. However, specific cholesterol efflux from RBCs to isolated apoA-I was negligible, and ABCA1 silencing with siRNA or inhibition with vanadate and Probucol did not inhibit the efflux to apoA-I, HDL, or plasma. Cholesterol efflux from and cholesterol uptake by RBCs from Abca1^+/+ and Abca1^−/− mice were similar, arguing against the role of ABCA1 in cholesterol flux between RBCs and lipoproteins. Bioinformatics analysis identified ABCA7, ABCG5, lipoprotein lipase, and mitochondrial translocator protein as possible candidates that may mediate the cholesterol flux. Together, these results suggest that RBCs actively participate in cholesterol transport in the blood, but the role of cholesterol transporters in RBCs remains uncertain.     

Evaluation of downward movements of Japanese eel Anguilla japonica inhabiting brackish water areas

This study evaluated the size and age distributions and otolith microchemistry of the Japanese eel Anguilla japonica in freshwater and brackish water areas in the Aki and Tsuchikawa rivers for 1 year, and in brackish water areas in the Asahi River for 3 years to understand the movements of Japanese eels between continental habitats of different salinity after recruitment (n = 759). For all three rivers, the total length (L_T) and age distributions were consistent; yellow eels captured in the upper brackish water (Aki River: 353.5 ± 77.4 mm and 3.0 ± 0.8 years; Tsuchikawa River: 287.7 ± 87.3 mm and 3.7 ± 1.3 years; Asahi River: 418.2 ± 112.1 mm and 4.2 ± 1.7 years) were smaller and younger than not only those in the fresh water of the two rivers but also those in the lowest brackish water sampling areas (Aki River: 436.0 ± 71.6 mm and 3.8 ± 1.1 years; Tsuchikawa River: 370.9 ± 121.7 mm and 4.9 ± 2.3 years; Asahi River: 558.5 ± 85.9 mm and 5.7 ± 1.7 years). In the Asahi River, these tendencies were found throughout the 3 years. Otolith analysis indicated that the majority of the eels captured in the lowest brackish water areas had moved down from upstream. These results suggest that Japanese eels inhabiting saline water generally move from the upper estuary as they grow. The upper estuary can be an important area for the management of this species because these eels spend their early continental growth life there.     

α-Amylase expressed in human small intestinal epithelial cells is essential for cell proliferation and differentiation

α-Amylase, which plays an essential role in starch degradation, is expressed mainly in the pancreas and salivary glands. Human α-amylase is also detected in other tissues, but it is unclear whether the α-amylase is endogenously expressed in each tissue or mixed exogenously with one expressed by the pancreas or salivary glands. Furthermore, the biological significance of these α-amylases detected in tissues other than the pancreas and salivary glands has not been elucidated. We discovered that human α-amylase is expressed in intestinal epithelial cells and analyzed the effects of suppressing α-amylase expression. α-Amylase was found to be expressed at the second-highest messenger RNA level in the duodenum in human normal tissues after the pancreas. α-Amylase was detected in the cell extract of Caco-2 intestinal epithelial cells but not secreted into the culture medium. The amount of α-amylase expressed increased depending on the length of the culture of Caco-2 cells, suggesting that α-amylase is expressed in small intestine epithelial cells rather than the colon because the cells differentiate spontaneously upon reaching confluence in culture to exhibit the characteristics of small intestinal epithelial cells rather than colon cells. The α-amylase expressed in Caco-2 cells had enzymatic activity and was identified as AMY2B, one of the two isoforms of pancreatic α-amylase. The suppression of α-amylase expression by small interfering RNA inhibited cell differentiation and proliferation. These results demonstrate for the first time that α-amylase is expressed in human intestinal epithelial cells and affects cell proliferation and differentiation. This α-amylase may induce the proliferation and differentiation of small intestine epithelial cells, supporting a rapid turnover of cells to maintain a healthy intestinal lumen.     

Reduced Serum Selenium Concentration in Miscarriage Incidence of Indonesian Subjects

Selenium is an essential nutrient for human health, and maternal selenium concentration has been reported to be associated with pregnancy outcome. To further investigate the possible role of selenium (Se) in miscarriage, we conducted a case–control study to evaluate the correlations among selenium status, glutathione peroxidase activity, and spontaneous abortion. A total of 46 subjects with normal pregnancies and 25 subjects with spontaneous abortion were recruited, and their serum selenium concentrations and serum glutathione peroxidase activities were analyzed. The total serum selenium concentrations in subjects with normal pregnancies were significantly higher than those of subjects with spontaneous abortion; however, the glutathione peroxidase activities were similar in both groups. We further separated the subjects into smoking and nonsmoking groups, and the logistic regression analysis suggested that total serum selenium concentration, but not serum glutathione peroxidase activity or smoking, was significantly correlated with the incidence of miscarriage. The present study thus reaffirms that low serum selenium levels are associated with miscarriage and that selenium plays an important role in pregnancy maintenance.     

Facilitated Hyperpolarization Signaling in Vascular Smooth Muscle-overexpressing TRIC-A Channels

The TRIC channel subtypes, namely TRIC-A and TRIC-B, are intracellular monovalent cation-specific channels and likely mediate counterion movements to support efficient Ca²⁺ release from the sarco/endoplasmic reticulum. Vascular smooth muscle cells (VSMCs) contain both TRIC subtypes and two Ca²⁺ release mechanisms; incidental opening of ryanodine receptors (RyRs) generates local Ca²⁺ sparks to induce hyperpolarization and relaxation, whereas agonist-induced activation of inositol trisphosphate receptors produces global Ca²⁺ transients causing contraction. Tric-a knock-out mice develop hypertension due to insufficient RyR-mediated Ca²⁺ sparks in VSMCs. Here we describe transgenic mice overexpressing TRIC-A channels under the control of a smooth muscle cell-specific promoter. The transgenic mice developed congenital hypotension. In Tric-a-overexpressing VSMCs from the transgenic mice, the resting membrane potential decreased because RyR-mediated Ca²⁺ sparks were facilitated and cell surface Ca²⁺-dependent K⁺ channels were hyperactivated. Under such hyperpolarized conditions, L-type Ca²⁺ channels were inactivated, and thus, the resting intracellular Ca²⁺ levels were reduced in Tric-a-overexpressing VSMCs. Moreover, Tric-a overexpression impaired inositol trisphosphate-sensitive stores to diminish agonist-induced Ca²⁺ signaling in VSMCs. These altered features likely reduced vascular tonus leading to the hypotensive phenotype. Our Tric-a-transgenic mice together with Tric-a knock-out mice indicate that TRIC-A channel density in VSMCs is responsible for controlling basal blood pressure at the whole-animal level.     

A hydrophobic amino acid cluster inserted into the C-terminus of a recycling cell surface receptor functions as an endosomal sorting signal

Cell surface receptors ubiquitylated after ligand stimulation are internalized and delivered to the lysosomal pathway for degradation. Ubiquitylated receptors are captured by ESCRT protein complexes that sort them to the lysosomal pathway. Hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) is a component of endosomal sorting complexes required for transport (ESCRT)-0 that recognizes ubiquitin attached to receptors, indicating that it functions as a key molecule for ubiquitin-dependent endosomal sorting. In a previous study on interleukin (IL)-2 receptor β (IL-2Rβ) and IL-4 receptor α (IL-4Rα), which are constitutively internalized without ligand stimulation, we revealed that Hrs bound to IL-2Rβ and IL-4Rα in a ubiquitin-independent manner, and identified a hydrophobic amino acid cluster in the cytoplasmic region of IL-2Rβ and IL-4Rα as the Hrs-interacting domain. However, a chimeric receptor containing the hydrophobic amino acid cluster inserted into the C-terminal of IL-2Rα was not delivered to late endosomes, but recycled back to the plasma membrane. In the present study, we explored the functional domain related to endosomal sorting in IL-2Rβ together with the hydrophobic amino acid cluster, and discovered the importance of an approximately 30-amino acid stretch following the C-terminus of the hydrophobic amino acid cluster in IL-2Rβ. Even though the amino acid stretch following the hydrophobic amino acid cluster was composed of arbitrary amino acids, such a stretch was also permissive for the sorting ability, suggesting that the hydrophobic amino acid cluster functions as an endosomal sorting signal. These findings clarify part of the molecular mechanism underlying the ubiquitin-independent endosomal sorting of cytokine receptors that are constitutively internalized without ligand stimulation.     

A CD4 mimic as an HIV entry inhibitor: Pharmacokinetics

To date, several small molecules of CD4 mimics, which can suppress competitively the interaction between an HIV-1 envelope glycoprotein gp120 and a cellular surface protein CD4, have been reported as viral entry inhibitors. A lead compound 2 (YYA-021) with relatively high potency and low cytotoxicity has been identified previously by SAR studies. In the present study, the pharmacokinetics of the intravenous administration of compound 2 in rats and rhesus macaques is reported. The half-lives of compound 2 in blood in rats and rhesus macaques suggest that compound 2 shows wide tissue distribution and relatively high distribution volumes. A few hours after the injection, both plasma concentrations of compound 2 maintained micromolar levels, indicating it might have promise for intravenous administration when used combinatorially with anti-gp120 monoclonal antibodies.     

Fish oil supplementation for two generations increases insulin sensitivity in rats

We investigated the effect of fish oil supplementation for two consecutive generations on insulin sensitivity in rats. After the nursing period (21 days), female rats from the same prole were divided into two groups: (a) control group and (b) fish oil group. Female rats were supplemented with water (control) or fish oil at 1 g/kg body weight as a single bolus for 3 months. After this period, female rats were mated with male Wistar rats fed on a balanced chow diet (not supplemented). Female rats continued to receive supplementation throughout gestation and lactation periods. The same treatment was performed for the next two generations (G1 and G2). At 75 days of age, male offspring from G1 and G2 generations from both groups were used in the experiments. G1 rats did not present any difference with control rats. However, G2 rats presented reduction in glycemia and lipidemia and improvement in in vivo insulin sensitivity (model assessment of insulin resistance, insulin tolerance test) as well as in vitro insulin sensitivity in soleus muscle (glucose uptake and metabolism). This effect was associated with increased insulin-stimulated p38 MAP kinase phosphorylation and lower n-6/n-3 fatty acid ratio, but not with activation of proteins from insulin signaling (IR, IRS-1 and Akt). Global DNA methylation was decreased in liver but not in soleus muscle. These results suggest that long-term fish oil supplementation improves insulin sensitivity in association with increased insulin-stimulated p38 activation and decreased n-6:n-3 ratio in skeletal muscle and decreased global DNA methylation in liver.     

Rapid PaperMicrobial Oxygenation of Organo-metallic Bissulfides Leading to Formation of Planar Chirality and C2 Symmetry

1,2-Bis(methylthiomethyl)ferrocene (3) was oxidized by Corynebacterium equi IFO 3730 to give monosulfoxide 4 in two diastereomeric forms with (1S,2R,S_S) and (1S,2R,R_S) configurations in a ratio of 4:1, while 1,1′-bis(methylthiomethyl)ferrocene (5) was oxidized by Penicillium frequentans IFO 5692 to (R)-monosulfoxide 6 and then preferentially to (R,R)-bissulfoxide 7. Thus, the bacterial monooxygenase generated specific planar chirality in the metallocenic monosulfoxide, and the fungal enzyme formed C₂ symmetry in the bissulfoxide.