PGE2 induces apoptosis of hepatic stellate cells and attenuates liver fibrosis in mice by downregulating miR-23a-5p and miR-28a-5p

MicroRNAs (miRNAs), small noncoding RNAs modulating messenger RNA (mRNA) and protein expression, have emerged as key regulatory molecules in chronic liver diseases, whose end stage is hepatic fibrosis, a major global health burden. Pharmacological strategies for prevention or treatment of hepatic fibrosis are still limited, what makes it necessary to establish a better understanding of the molecular mechanisms underlying its pathogenesis. In this context, we have recently shown that cyclooxygenase-2 (COX-2) expression in hepatocytes restricts activation of hepatic stellate cells (HSCs), a pivotal event in the initiation and progression of hepatic fibrosis. Here, we evaluated the role of COX-2 in the regulation of a specific set of miRNAs on a mouse model of CCl₄ and bile duct ligation (BDL)-induced liver fibrosis. Our results provide evidence that COX-2 represses miR-23a-5p and miR-28-5p expression in HSC. The decrease of miR-23a-5p and miR-28-5p expression promotes protection against fibrosis by decreasing the levels of pro-fibrogenic markers α-SMA and COL1A1 and increasing apoptosis of HSC. Moreover, we demonstrate that serum levels of miR-28-5p are decreased in patients with chronic liver disease. These results suggest a protective effect exerted by COX-2-derived prostanoids in the process of hepatofibrogenesis.     

Successional changes in the morphology and ecological responses of a grazed pasture ecosystem in Central Spain

Morphological characteristics related to spatial occupation, reproduction and adaptations to grazing were used to characterize the most frequent species in a therophytic pastureland of Central Spain.Periodic ploughing is a traditional practice in these pastures and allows observation of successional change. In the present study, four neighbouring slopes of differing time since last ploughing were chosen. Species biomass was measured at different times during the annual growing season for two different slope positions.Grazing pressure is an important environmental factor affecting ecosystem organization, the most palatable plants tending to show increasing biomass with succession. In the most mature stages, there is a predominance of species characterized by horizontal occupation of space and sprouting after mowing or grazing.During succession segregation of the different morphological characteristics occurs in slope sectors related to geomorphological dynamics. Similarly, phenological development tends to be later in pastures in the lowest slope zones, due probably to their greater summer soil moisture content.Nomenclature follows: Tutin et al., 1964–1980. Flora Europaea.     

Temporal changes in therophytic communities across the boundary of disturbed-intact ecosystems

External control processes cause continual compositional and structural readjustments of Mediterranean pasture ecosystems. Such control processes include herbivore grazing, meteorological fluctuations and traditional management activities, which determine the stable environment where the succession occurs. Traditional management in this ecosystem frequently involves periodic ploughing or controlled fires.Experimental disturbances were applied to pastures of different maturity. Recovery was studied by relating information gathered for each disturbed system to successional age. The boundary between original systems of differing ages and the newly created systems was studied to compare the space-time evolution of therophytic communities. Permanent transects perpendicular to the disturbance boundaries and containing many small plots were sampled during consecutive years.Sampling plots located on both sides of the boundaries were classified into communities, in order to detect the space-time pasture evolution in successive years. Annual conditional probabilities were calculated for transitions between the recognised communities. During succession different strategies were detected in response to meteorological variations. In pioneer successional stages, substitutions of one community by another in the same space seem to be random. However, greater determinism was detected in more mature pastures, where, in addition, communities' abundance does not respond to meteorological change.Nomenclature follows T. G. Tutin et al. 1964–1980. Flora Europaea. Cambridge University Press, Cambridge.     

In vitro effects of levamisole and ivermectin against Echinococcus granulosus protoscoleces

The in vitro effects of levamisole and ivermectin against Echinococcus granulosus protoscoleces were studied by means of light and electron microscopy. Both drugs had a protoscolicidal activity that increased proportionally with increasing concentrations of the drugs. Ivermectin showed the more rapid effects and caused contraction and paralysis of protoscoleces. A paralyzing effect was also observed with levamisole, followed by irreversible tissue vacuolation leading to death.     

Structural determinants for rCNT2 sorting to the plasma membrane of polarized and non-polarized cells

rCNT2 (rat concentrative nucleoside transporter 2) (Slc28a2) is a purine-preferring concentrative nucleoside transporter. It is expressed in both non-polarized and polarized cells, where it is localized in the brush border membrane. Since no information about the domains implicated in the plasma membrane sorting of rCNT2 is available, the present study aimed to identify structural and functional requirements for rCNT2 trafficking. The comprehensive topological mapping of the intracellular N-terminal tail revealed two main features: (i) a glutamate-enriched region (NPGLELME) between residues 21 and 28 that seems to be implicated in the stabilization of rCNT2 in the cell surface, since mutagenesis of these conserved glutamates resulted in enhanced endocytosis; and (ii) mutation of a potential protein kinase CK2 domain that led to a loss of brush border-specific sorting. Although the shortest proteins assayed (rCNT2-74AA, -48AA and -37AA) accumulated intracellularly and lost their brush border membrane preference, they were still functional. A deeper analysis of CK2 implication in CNT2 trafficking, using a CK2-specific inhibitor [DMAT (2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole)] and other complementary mutations mimicking the negative charge provided by phosphorylation (S46D and S46E), demonstrated an effect of this kinase on rCNT2 activity. In summary, the N-terminal tail of rCNT2 contains dual sorting signals. An acidic region is responsible for its proper stabilization at the plasma membrane, whereas the putative CK2 domain (Ser(46)) is implicated in the apical sorting of the transporter.