Hepatocyte growth factor (HGF) inhibits collagen I and IV synthesis in hepatic stellate cells by miRNA-29 induction

Background

In chronic liver disease, hepatic stellate cells (HSC) transdifferentiate into myofibroblasts, promoting extracellular matrix (ECM) synthesis and deposition. Stimulation of HSC by transforming growth factor-β (TGF-β) is a crucial event in liver fibrogenesis due to its impact on myofibroblastic transition and ECM induction. In contrast, hepatocyte growth factor (HGF), exerts antifibrotic activities. Recently, miR-29 has been reported to be involved in ECM synthesis. We therefore studied the influence of HGF and TGF-β on the miR-29 collagen axis in HSC.

Methodology

HSC, isolated from rats, were characterized for HGF and Met receptor expression by Real-Time PCR and Western blotting during culture induced myofibroblastic transition. Then, the levels of TGF-β, HGF, collagen-I and -IV mRNA, in addition to miR-29a and miR-29b were determined after HGF and TGF-β stimulation of HSC or after experimental fibrosis induced by bile-duct obstruction in rats. The interaction of miR-29 with 3′-untranslated mRNA regions (UTR) was analyzed by reporter assays. The repressive effect of miR-29 on collagen synthesis was studied in HSC treated with miR-29-mimicks by Real-Time PCR and immunoblotting.

Principal Findings

The 3′-UTR of the collagen-1 and −4 subtypes were identified to bind miR-29. Hence, miR-29a/b overexpression in HSC resulted in a marked reduction of collagen-I and -IV synthesis. Conversely, a decrease in miR-29 levels is observed during collagen accumulation upon experimental fibrosis, in vivo, and after TGF-β stimulation of HSC, in vitro. Finally, we show that during myofibroblastic transition and TGF-β exposure the HGF-receptor, Met, is upregulated in HSC. Thus, whereas TGF-β stimulation leads to a reduction in miR-29 expression and de-repression of collagen synthesis, stimulation with HGF was definitely associated with highly elevated miR-29 levels and markedly repressed collagen-I and -IV synthesis.

Conclusions

Upregulation of miRNA-29 by HGF and downregulation by TGF-β take part in the anti- or profibrogenic response of HSC, respectively.     

Phylogenetic grouping, curvature and metabolic scaling in terrestrial invertebrates

For more than a century, the scaling of animal metabolic rates with individual body masses and environmental temperature has predominantly been described by power-law and exponential relationships respectively. Many theories have been proposed to explain these scaling relationships, but were challenged by empirically documented curvatures on double-logarithmic scales. In the present study, we present a novel data set comprising 3661 terrestrial (mainly soil) invertebrate respiration rates from 192 independent sources across a wide range in body masses, environmental temperatures and phylogenetic groups. Although our analyses documented power-law and exponential scaling with body masses and temperature, respectively, polynomial models identified curved deviations. Interestingly, complex scaling models accounting for phylogenetic groups were able to remove curvatures except for a negative curvature at the highest temperatures (>30 °C) indicating metabolic down regulation. This might indicate that the tremendous differences in invertebrate body architectures, ecology and physiology may cause severely different metabolic scaling processes.     

Cheating on ubiquitin with Atg8

Macroautophagy sequesters superflous cytosol and organelles into double-membraned autophagosomes. Over 30 autophagy-related (ATG) genes have been identified without elucidating the molecular details of autophagosome biogenesis. All proposed models for autophagosome formation require membrane fusion events (Fig. 1). Previous studies assumed that the autophagic machinery mediates these membrane fusions in a SNARE-independent manner and identified the ubiquitin-like protein Atg8 as a key component especially for elongation of the forming autophagosome. However, if and how Atg8 mediates membrane fusion and why a ubiquitin-like protein is needed for autophagosome biogenesis remained open questions. Since nuclear envelope growth and fusion of Golgi fragments are topologically similar to autophagosome formation and depend on the AAA (+) ATPase p97/VCP and p47 we analyzed the involvement of their yeast homologues Cdc48 and Shp1 in macroautophagy.     

An enzyme activity capable of endotransglycosylation of heteroxylan polysaccharides is present in plant primary cell walls

Heteroxylans in the plant cell wall have been proposed to have a role analogous to that of xyloglucans or heteromannans, forming growth-restraining networks by interlocking cellulose microfibrils. A xylan endotransglycosylase has been identified that can transglycosylate heteroxylan polysaccharides in the presence of xylan-derived oligosaccharides. High activity was detected in ripe fruit of papaya (Carica papaya), but activity was also found in a range of other fruits, imbibed seeds and rapidly growing seedlings of cereals. Xylan endotransglycosylase from ripe papaya fruit used a range of heteroxylans, such as wheat arabinoxylan, birchwood glucuronoxylan and various heteroxylans from dicotyledonous primary cell walls purified from tomato and papaya fruit, as donor molecules. As acceptor molecules, the enzyme preferentially used xylopentaitol over xylohexaitol or shorter-length acceptors. Xylan endotransglycosylase was active over a broad pH range and could perform transglycosylation reactions up to 55 °C. Xylan endotransglycosylase activity was purified from ripe papaya fruit by ultrafiltration and cation exchange chromatography. Highest endotransglycosylase activity was identified in fractions that also contained high xylan hydrolase activity and correlated with the presence of the endoxylanase CpaEXY1. Recombinant CpaEXY1 protein transiently over-expressed in Nicotiana benthamiana leaves showed both endoxylanase and xylan endotransglycosylase activities in vitro, suggesting that CpaEXY1 is a single enzyme with dual activity in planta. Purified native CpaEXY1 showed two- to fourfold higher endoxylanase than endotransglycosylase activity, suggesting that CpaEXY1 may act primarily as a hydrolase. We propose that xylan endotransglycosylase activity (like xyloglucan and mannan endotransglycosylase activities) could be involved in remodelling or re-arrangement of heteroxylans of the cellulose-non-cellulosic cell wall framework.     

Bioconversion of piceid to resveratrol by selected probiotic cell extracts

Resveratrol exerts several pharmacological activities, including anti-cancer, anti-inflammatory, cardioprotective, or antioxidant effects. However, due to its occurrence in plants more in glycosidic form as piceid, the bioavailability and bioactivity are limited. The enzymatic potential of probiotics for the transformation of piceid to resveratrol was elucidated. Cell extract from Bifidobacteria (B.) infantis, B. bifidum, Lactobacillus (L.) casei, L. plantarum, and L. acidophilus was evaluated for their effect in this bioconversion using high-performance liquid chromatography (HPLC) as analytical tool. Cell extract of B. infantis showed the highest effect on the deglycosylation of piceid to resveratrol, already after 30 min. Cell extracts of all other tested strains showed a significant biotransformation with no further metabolization of resveratrol. The conversion of piceid to resveratrol is of importance to increase bioavailability and bioactivity as shown for anti-inflammation in this study. Cell extracts from probiotics, especially from B. infantis, may be added to piceid containing products, for achieving higher biological effects caused by the bioactivity of resveratrol or by health promoting of the probiotics. These findings open a new perspective of novel combination of cell extracts from probiotics and piceid, in health-promoting pharmaceutical and food products.     

Seasonal variation in the monoterpenes in needles of Picea abies (L.) Karst.

Summary This investigation was conducted to obtain information about the fluctuations in composition and amount of needle monoterpenes during the development of spruce needles. Studies conducted with two Norway spruce clones clearly revealed the existence of fluctuations. In juvenile needles, the amounts of the oxygenated terpenes increase constantly with age during the first 2 months of needle growth. The hydrocarbon terpenes dominate within the first weeks, some of them even showing a very distinct first maximum within the first 3 weeks after bud burst. All terpenes, including the oxygenated ones, have a maximum in June/July, which favours the hypothesis of a substitution of the hydrocarbons later on. There are significant changes even in mature needles of Norway spruce. The terpene level of 1-year-old needles of the clonal trees increased from spring to early summer and then dropped again towards winter. In addition, fluctuations in mature needles were shown for a set of ten wild trees. Needles of the same age class, which emerged in 1986, were sampled 4 times from 1986 to 1988. The needle terpene concentrations of the 1 -year-old needles were considerably lower in spring at the time of bud burst than in autumn. The terpene level of older needles thus seems to be influenced by biosynthetic and catabolic activities.