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Inflammation is typically associated with the development of fibrosis, cirrhosis and hepatocellular carcinoma. The key role of protein tyrosine phosphatase 1B (PTP1B) in inflammatory responses has focused this study in understanding its implication in liver fibrosis. Here we show that hepatic PTP1B mRNA expression increased after bile duct ligation (BDL), while BDL-induced liver fibrosis was markedly reduced in mice lacking Ptpn1 (PTP1B) as assessed by decreased collagen deposition and α-smooth muscle actin (α-SMA) expression. PTP1B mice also showed a significant increase in mRNA levels of key markers of monocytes recruitment (Cd68, Adgre1 and Ccl2) compared to their wild-type (PTP1B) littermates at early stages of injury after BDL. Interestingly, the lack of PTP1B strongly increased the NADPH oxidase (NOX) subunits Nox1/Nox4 ratio and downregulated Cybb expression after BDL, revealing a pro-survival pattern of NADPH oxidase induction in response to liver injury. Chimeric mice generated by transplantation of PTP1B bone marrow (BM) into irradiated PTP1B mice revealed similar hepatic expression profile of NOX subunits than PTP1B mice while these animals did not show differences in infiltration of myeloid cells at 7 days post-BDL, suggesting that PTP1B deletion in other liver cells is necessary for boosting the early inflammatory response to the BDL. PTP1B BM transplantation into PTP1B mice also led to a blockade of TGF-β and α-SMA induction after BDL. In vitro experiments demonstrated that deficiency of PTP1B in hepatocytes protects against bile acid-induced apoptosis and abrogates hepatic stellate cells (HSC) activation, an effect ameliorated by NOX1 inhibition. In conclusion, our results have revealed that the lack of PTP1B switches NOX expression pattern in response to liver injury after BDL and reduces HSC activation and liver fibrosis.
This article was published in the following journal.
Name: Redox biology
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A subtype of non-receptor protein tyrosine phosphatase that is closely-related to PROTEIN TYROSINE PHOSPHATASE, NON-RECEPTOR TYPE 1. Alternative splicing of the mRNA for this phosphatase results in the production at two gene products, one of which includes a C-terminal nuclear localization domain that may be involved in the transport of the protein to the CELL NUCLEUS. Although initially referred to as T-cell protein tyrosine phosphatase the expression of this subtype occurs widely.
A Src-homology domain-containing protein tyrosine phosphatase found in the CYTOSOL of hematopoietic cells. It plays a role in signal transduction by dephosphorylating signaling proteins that are activated or inactivated by PROTEIN-TYROSINE KINASES.
A subtype of non-receptor protein tyrosine phosphatases that contain two SRC HOMOLOGY DOMAINS. Mutations in the gene for protein tyrosine phosphatase, non-receptor type 11 are associated with NOONAN SYNDROME.
One of four major classes of mammalian serine/threonine specific protein phosphatases. Protein phosphatase 2C is a monomeric enzyme about 42 kDa in size. It shows broad substrate specificity dependent on divalent cations (mainly manganese and magnesium). Three isozymes are known in mammals: PP2C -alpha, -beta and -gamma. In yeast, there are four PP2C homologues: phosphatase PTC1 that have weak tyrosine phosphatase activity, phosphatase PTC2, phosphatase PTC3, and PTC4. Isozymes of PP2C also occur in Arabidopsis thaliana where the kinase-associated protein phosphatase (KAPP) containing a C-terminal PP2C domain, dephosphorylates Ser/Thr receptor-like kinase RLK5.
A subtype of non-receptor protein tyrosine phosphatases that is characterized by the presence of an amino-terminal FERM domain, an intervening region containing one or more PDZ domains, and a carboxyl-terminal phosphatase domain. Expression of this phosphatase subtype has been observed in BONE MARROW; fetal LIVER; LYMPH NODES; and T LYMPHOCYTES.
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