ABSTRACT: The loss of functional caspase-10 promotes inflammatory cell death in macrophages and a fibrotic response of hepatic stellate cells, which may affect the pathogenesis of PBC.
Project description:Formation of the Death-Inducing Signalling Complex (DISC) initiates the extrinsic apoptotic signalling cascade. Caspase-8 and its regulator cFLIP control death signalling by binding to the receptor via DISC-bound FADD. By elucidating the function of Caspase-10, a close homologue of caspase-8, we unexpectedly found that caspase-10 negatively regulates caspase-8-mediated cell death signalling in the DISC. We demonstrate that caspase-10 inhibits the activation of caspase-8 independent of cFLIP. Furthermore, we show that caspase-8 does not compete with other tandem DED proteins such as cFLIP or caspase-10 in binding via FADD to the receptor as current models suggest. By utilizing caspase-8 knockout cells, we demonstrate that caspase-8 has to be placed upstream of both cFLIP and caspase-10 in the DISC. We further show that DISC formation and/or stability depends on caspase-8 but is independent from its enzymatic activity. Surprisingly, we identified caspase-10 to rewire DISC-signalling to NF-kB activation and cell survival. Our data are consistent with a model in which caspase-10 and cFLIP co-ordinately regulate caspase-8-mediated cell death signalling.
Project description:Comparison of longitudinal transcriptomic profiles of activated human primary hepatic stellate cells to activated human primary hepatic stellate cells that are treated with anti-fibrotic inhibitor reveals inflammatory signaling as a key pathway that is modulated during pro-fibrotic activation and repressed during attenuation of fibrotic response.
Project description:Primary biliary cholangitis (PBC), formally known as primary biliary cirrhosis, is an autoimmune liver disease of unknown pathogenesis. Consequently, therapeutic targets for PBC have yet to be identified. As CD4+ T cells play a pivotal role in immunological dysfunction observed in PBC, we analyzed microRNA(miRNA) and mRNA expression in CD4+ T cells to investigate PBC pathogenesis and identify novel therapeutic targets.
Project description:Primary biliary cholangitis (PBC), formally known as primary biliary cirrhosis, is an autoimmune liver disease of unknown pathogenesis. Consequently, therapeutic targets for PBC have yet to be identified. As CD4+ T cells play a pivotal role in immunological dysfunction observed in PBC, we analyzed microRNA(miRNA) and mRNA expression in CD4+ T cells to investigate PBC pathogenesis and identify novel therapeutic targets.
Project description:Background and Aims: Inflammasome-mediated caspase-1 activity regulates the maturation and release of the pro-inflammatory cytokines interleukin (IL)-1M-CM-^_ and IL-18. Recently, we showed that caspase-1 deficiency strongly reduces high fat diet-induced adiposity although the mechanism is still unclear. We now aimed to elucidate the mechanism by which caspase-1 deficiency reduces modulates resistance to high fat diet-feeding fat accumulation in adipose tissue by focusing on the role of caspase-1 in the regulation of triglyceride (TG)-rich lipoprotein metabolism. Methods: Caspase-1 deficient and wild-type mice (both C57Bl/6 background) were used to determine postprandial TG kinetics, intestinal TG absorption, VLDL-TG production as well as TG clearance, all of which strongly contribute to the supply of TG for storage in adipose tissue. Micro-array and qPCR analysis were used to unravel intestinal and hepatic metabolic pathways involved. Results: Caspase-1 deficiency reduced the postprandial response to an oral lipid load, while tissue specific clearance of TG-rich lipoproteins was not changed. Indeed, an oral olive oil gavage containing [3H]TG revealed that caspase-1 deficiency significantly decreased intestinal chylomicron-TG production and reduced the uptake of [3H]TG-derived FA by liver, muscle, and adipose tissue. Similarly, caspase-1 deficiency reduced the hepatic VLDL-TG production without reducing VLDL-apoB production, despite an elevated hepatic TG content. Pathway analysis revealed that caspase-1 deficiency reduces intestinal and hepatic expression of genes involved in lipogenesis. Conclusions: Absence of caspase-1 reduces assembly and secretion of TG-rich lipoproteins, thereby reducing the availability of TG-derived FA for uptake by peripheral organs including adipose tissue. We anticipate that caspase-1 represents a novel link between innate immunity and lipid metabolism. Keywords: Expression profiling by array Wild-type (WT) and Casp1-null mice were maintained at lab chow. Animals, aged between 14 and 16 weeks (n=3 per genotype), were killed and liver and intestinal segments were removed. Livers were isolated from mice that were fasted over night, whereas intesines were removed from mice 2 hrs after they received an oral lipid load.Total RNA was isolated and subjected to gene expression profiling.
Project description:Background and Aims: Inflammasome-mediated caspase-1 activity regulates the maturation and release of the pro-inflammatory cytokines interleukin (IL)-1ß and IL-18. Recently, we showed that caspase-1 deficiency strongly reduces high fat diet-induced adiposity although the mechanism is still unclear. We now aimed to elucidate the mechanism by which caspase-1 deficiency reduces modulates resistance to high fat diet-feeding fat accumulation in adipose tissue by focusing on the role of caspase-1 in the regulation of triglyceride (TG)-rich lipoprotein metabolism. Methods: Caspase-1 deficient and wild-type mice (both C57Bl/6 background) were used to determine postprandial TG kinetics, intestinal TG absorption, VLDL-TG production as well as TG clearance, all of which strongly contribute to the supply of TG for storage in adipose tissue. Micro-array and qPCR analysis were used to unravel intestinal and hepatic metabolic pathways involved. Results: Caspase-1 deficiency reduced the postprandial response to an oral lipid load, while tissue specific clearance of TG-rich lipoproteins was not changed. Indeed, an oral olive oil gavage containing [3H]TG revealed that caspase-1 deficiency significantly decreased intestinal chylomicron-TG production and reduced the uptake of [3H]TG-derived FA by liver, muscle, and adipose tissue. Similarly, caspase-1 deficiency reduced the hepatic VLDL-TG production without reducing VLDL-apoB production, despite an elevated hepatic TG content. Pathway analysis revealed that caspase-1 deficiency reduces intestinal and hepatic expression of genes involved in lipogenesis. Conclusions: Absence of caspase-1 reduces assembly and secretion of TG-rich lipoproteins, thereby reducing the availability of TG-derived FA for uptake by peripheral organs including adipose tissue. We anticipate that caspase-1 represents a novel link between innate immunity and lipid metabolism. Keywords: Expression profiling by array
Project description:Liver fibrosis is a reversible wound-healing response to liver injury and hepatic stellate cells (HSCs) are central cellular players that mediate hepatic fibrogenesis. However, the molecular mechanisms that govern this process remain unclear. Here, we reveal a novel cistromic circuit in HSCs comprising the vitamin D receptor (VDR) and SMAD transcription factors that restrains the intensity of hepatic fibrogenesis. Ligand-activated VDR suppresses TGFβ1-induced pro-fibrotic gene expression in HSCs. Administration of a vitamin D analogue, calcipotriol, diminishes the fibrotic response in a mouse model of liver fibrosis, while VDR knockout mice spontaneous develop extensive hepatic fibrosis by age 6 months. Using ChIP-Seq, we find that the anti-fibrotic properties of VDR are due to crosstalk with SMAD, mediated by their co-occupancy of DNA-binding sites on pro-fibrotic genes. Specifically, SMAD binding potentiates local chromatin accessibility to enhance VDR recruitment at the same cis-regulatory elements, which reciprocally antagonizes the interaction between SMAD3 and chromatin and limits the assembly of transcriptional activation complexes at fibrotic genes, a process that is enhanced by the presence of VDR agonists. These results not only establish this coordinated VDR/SMAD cistromic circuit as a master regulator of hepatic fibrogenesis, but also support VDR as a potential drug target to ameliorate liver fibrosis. Identification of VDR, SMAD3 and H3 binding sites in human stellate LX2 cells that were pre-treated with calcipotriol (100nM) for 16 hrs (where calcipotriol treatment is indicated) followed by incubation of calcipotriol (100nM) or TGFβ1 (1ng/ml) for another 4 hours (where indicated).