Background: While tumour necrosis factor a (TNF-a) appears to be associated with the development of non-alcoholic steatohepatitis (NASH), its precise role in the pathogenesis of NASH is not well understood. Methods: Male mice deficient in both TNF receptors 1 (TNFR1) and 2 (TNFR2) (TNFRDKO mice) and wildtype mice were fed a methionine and choline deficient (MCD) diet or a control diet for eight weeks, maintaining isoenergetic intake. Results: MCD dietary feeding of TNFRDKO mice for eight weeks resulted in attenuated liver steatosis and fibrosis compared with control wild-type mice. In the liver, the number of activated hepatic Kupffer cells recruited was significantly decreased in TNFRDKO mice after MCD dietary feeding. In addition, hepatic induction of TNF-a, vascular cell adhesion molecule 1, and intracellular adhesion molecule 1 was significantly suppressed in TNFRDKO mice. While in control animals MCD dietary feeding dramatically increased mRNA expression of tissue inhibitor of metalloproteinase 1 (TIMP-1) in both whole liver and hepatic stellate cells, concomitant with enhanced activation of hepatic stellate cells, both factors were significantly lower in TNFRDKO mice. In primary cultures, TNF-a administration enhanced TIMP-1 mRNA expression in activated hepatic stellate cells and suppressed apoptotic induction in activated hepatic stellate cells. Inhibition of TNF induced TIMP-1 upregulation by TIMP-1 specific siRNA reversed the apoptotic suppression seen in hepatic stellate cells. Conclusions: Enhancement of the TNF-a/TNFR mediated signalling pathway via activation of Kupffer cells in an autocrine or paracrine manner may be critically involved in the pathogenesis of liver fibrosis in this NASH animal model.
Mouse transgenesis has proven invaluable for analysis of gene function and generation of human disease models. We describe here the development of a pronuclear injection-based targeted transgenesis (PITT) system, involving site-specific integration in fertilized eggs. The system was applied to two different genomic target loci to generate a series of transgenic lines including fluorescent mice, which reproducibly displayed strong, ubiquitous and stable transgene expression. We also demonstrated that knockdown mice could be readily generated by PITT by taking advantage of the reproducible and highly efficient expression system. The PITT system, which circumvents the problem of unpredictable and unstable transgene expression of conventional random-integration transgenic mice, reduces the time, cost and effort needed to generate transgenic mice, and is potentially applicable to both in vivo ‘gain-of-function’ and ‘loss-of-function’ studies.
It is unclear how hepatic adiponectin resistance and sensitivity mediated by the adiponectin receptor, AdipoR2, contributes to the progression of nonalcoholic steatohepatitis (NASH). The aim of this study was to examine the roles of hepatic AdipoR2 in NASH, using an animal model. We fed C57BL/6 mice a methionine-deficient and choline-deficient (
Differentiation of proplastids into functionally active chloroplasts is one of the most significant changes in cellular organization associated with leaf development in higher plants. This process involves activation of a large number of nuclear and chloroplast genes. A central question, therefore, concerns the nature and origin of the signals that initiate and control this process. The rice nuclear mutant, virescent‐1 (v1), is temperature‐conditional and develops chlorotic leaves when grown at restrictive temperatures. We report here the effects of v1 mutation on the expressions of plastid and nuclear genes during leaf development. In the wild‐type rice seedlings, the transcripts of the plastid RNA polymerase gene (rpoB) and ribosomal protein genes (rps7, rps15) accumulated during a strictly limited period of early leaf development, prior to the accumulation of the transcripts of photosynthetic genes (rbcL, RbcS, psbA, Lhc). This period coincides very closely with the leaf developmental stage (late P4) at which the V1 gene gives the signal that determines the virescent phenotype. On the contrary, in the v1 seedlings grown at a restrictive temperature (20°C), this stage‐specific accumulation of the rpo and rps transcripts was missing. Instead, the accumulation of these transcripts occurred during a later stage of leaf maturation. In such mutant seedlings, the expression of other plastid genes (psbA, rbcL, 16S rDNA) was strongly suppressed and the normal chloroplast development was disturbed. These data indicate that the V1 gene controls the timing of expression of the key plastid genes for the transcription/ translation apparatus that are essential for the subsequent activation of other plastid genes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.