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Pharmacologic Inhibition (pharmacologic + inhibition)

Distribution by Scientific Domains

Medical Sciences	83%

Selected Abstracts

Signalling and regulation of collagen I synthesis by ET-1 and TGF-,1

FEBS JOURNAL, Issue 24 2005
Angelika Horstmeyer
Endothelin-1 (ET-1) plays an important role in tissue remodelling and fibrogenesis by inducing synthesis of collagen I via protein kinase C (PKC). ET-1 signals are transduced by two receptor subtypes, the ETA- and ETB-receptors which activate different G, proteins. Here, we investigated the expression of both ET-receptor subtypes in human primary dermal fibroblasts and demonstrated that the ETA-receptor is the major ET-receptor subtype expressed. To determine further signalling intermediates, we inhibited G,i and three phospholipases. Pharmacologic inhibition of G,i, phosphatidylcholine-phospholipase C (PC-PLC) and phospholipase D (PLD), but not of phospholipase C,, abolished the increase in collagen I by ET-1. Inhibition of all phospholipases revealed similar effects on TGF-,1 induced collagen I synthesis, demonstrating involvement of PC-PLC and PLD in the signalling pathways elicited by ET-1 and TGF-,1. ET-1 and TGF-,1 each stimulated collagen I production and in an additive manner. ET-1 further induced connective tissue growth factor (CTGF), as did TGF-,1, however, to lower levels. While rapid and sustained CTGF induction was seen following TGF-,1 treatment, ET-1 increased CTGF in a biphasic manner with lower induction at 3 h and a delayed and higher induction after 5 days of permanent ET-1 treatment. Coincidentally at 5 days of permanent ET-1 stimulation, a switch in ET-receptor subtype expression to the ETB-receptor was observed. We conclude that the signalling pathways induced by ET-1 and TGF-,1 leading to augmented collagen I production by fibroblasts converge on a similar signalling pathway. Thereby, long-time stimulation by ET-1 resulted in a changed ET-receptor subtype ratio and in a biphasic CTGF induction. [source]

Specific role for acyl CoA:Diacylglycerol acyltransferase 1 (Dgat1) in hepatic steatosis due to exogenous fatty acids,

HEPATOLOGY, Issue 2 2009
Claudio J. Villanueva
Nonalcoholic fatty liver disease, characterized by the accumulation of triacylglycerols (TGs) and other lipids in the liver, often accompanies obesity and is a risk factor for nonalcoholic steatohepatitis and fibrosis. To treat or prevent fatty liver, a thorough understanding of hepatic fatty acid and TG metabolism is crucial. To investigate the role of acyl CoA:diacylglycerol acyltransferase 1 (DGAT1), a key enzyme of TG synthesis, in fatty liver development, we studied mice with global and liver-specific knockout of Dgat1. DGAT1 was required for hepatic steatosis induced by a high-fat diet and prolonged fasting, which are both characterized by delivery of exogenous fatty acids to the liver. Studies in primary hepatocytes showed that DGAT1 deficiency protected against hepatic steatosis by reducing synthesis and increasing the oxidation of fatty acids. In contrast, lipodystrophy (aP2-SREBP-1c436) and liver X receptor activation (T0901317), which increase de novo fatty acid synthesis in liver, caused steatosis independently of DGAT1. Pharmacologic inhibition of Dgat1 with antisense oligonucleotides protected against fatty liver induced by a high-fat diet. Conclusion: Our findings identify a specific role for hepatic DGAT1 in esterification of exogenous fatty acids and indicate that DGAT1 contributes to hepatic steatosis induced by this mechanism. (HEPATOLOGY 2009.) [source]

COX-2 inhibits Fas-mediated apoptosis in cholangiocarcinoma cells

HEPATOLOGY, Issue 3 2002
Ugochukwu C. Nzeako
Fas expression has been shown to negatively regulate the progression of cholangiocarcinoma cells in xenografts. However, many human cholangiocarcinomas express Fas, suggesting these cancers have developed mechanisms to inhibit Fas-mediated apoptosis. Cyclooxygenase-2 (COX-2), which generates prostanoids, is expressed by many cholangiocarcinomas. Therefore, our aim was to determine whether COX-2 expression inhibits death receptor,mediated apoptosis in KMBC cells, a cholangiocarcinoma cell line. These cells express messenger RNA for the death receptors Fas, tumor necrosis factor receptor 1 (TNF-R1), death receptor 4 (DR4), and DR5. Agonists for these death receptors, CH-11, TNF-,, and TRAIL all induced apoptosis. However, COX-2, whether induced by proinflammatory cytokines or transient transfection, only significantly inhibited Fas-mediated apoptosis. The COX-2 inhibitor NS-398 restored Fas-mediated apoptosis in COX-2 transfected cells. Prostaglandin E2 reduced apoptosis and mitochondrial depolarization after treatment with the Fas agonist CH-11. Of a variety of antiapoptotic proteins examined, COX-2/prostaglandin E2 only increased expression of Mcl-1, an antiapoptotic member of the Bcl-2 family. In conclusion, these data suggest that prostanoid generation by COX-2 specifically inhibits Fas-mediated apoptosis, likely by up-regulating Mcl-1 expression. Pharmacologic inhibition of COX-2 may be useful in augmenting Fas-mediated apoptosis of cholangiocarcinoma cells. [source]

Protease-activated receptor-induced Akt activation , regulation and possible function

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2007
J. C. RESÉNDIZ
Summary.,Background:,Thrombin induces the activation of the platelet serine/threonine kinase Akt. Akt activation is dependent on its phosphorylation at Thr308 and Ser473. The mechanism by which thrombin induces Akt phosphorylation is controversial, as is the role of Akt in platelet function. Objectives:,To investigate how protease-activated receptors (PARs) stimulate Akt and the role that Akt plays in human platelet function. Methods:,Platelets were stimulated through PAR1 or PAR4. Specific inhibitors were used to evaluate, by Western blotting, signaling pathways regulating Akt phosphorylation, and the role of activated Akt was evaluated by aggregometry and flow cytometry. Results:,Phospholipase C (PLC) controls Akt phosphorylation elicited by PARs. Stimulation of PAR1 or PAR4 resulted in rapid Akt phosphorylation, independently of secreted ADP and phosphatidylinositol-3-kinase (PI3K) activation. Akt phosphorylation ,60 s after PAR1 stimulation became entirely dependent on the purinergic receptor P2Y12 and the activation of PI3K. In contrast, PAR4 partially sustained Akt phosphorylation independently of P2Y12 and PI3K for up to 300 s. Pharmacologic inhibition of Akt reduced P-selectin expression and fibrinogen binding in platelets stimulated through PAR1, and delayed platelet aggregation in response to submaximal PAR1 or PAR4 stimulation, although aggregation at 300 s was unaffected. Conclusions:,Platelet PAR stimulation causes rapid Akt phosphorylation downstream of PLC, whereas with continuous stimulation, ADP and PI3K are required for maintaining Akt phosphorylation. Activated Akt regulates platelet function by modulating secretion and ,IIb,3 activation. [source]

Medical therapy for Crohn's disease strictures

INFLAMMATORY BOWEL DISEASES, Issue 1 2004
Gert Van Assche MD
Abstract Intestinal fibrostenosis is a frequent and debilitating complication of Crohn's disease (CD), not only resulting in small bowel obstruction, but eventually in repeated bowel resection and short bowel syndrome. Over one third of patients with CD have a clear stenosing disease phenotype, often in the absence of luminal inflammatory symptoms. Intestinal fibrosis is a consequence of chronic transmural inflammation in CD. As in other organs and tissues, phenotypic transformation and activation of resident mesenchymal cells, such as fibroblasts and smooth muscle cells, underlie fibrogenesis in the gut. The molecular mechanisms and growth factors involved in this process have not been identified. However, it is clear that inflammatory mediators may have effects on mesenchymal cells in the submucosa and the muscle layers that are profoundly different from their action on leukocytes or epithelial cells. Transforming growth factor-beta (TGF-,), for instance, has profound anti-inflammatory activity in the mucosa and probably serves to keep physiologic inflammation at bay, but at the same time it appears to be driving the process of fibrosis in the deeper layers of the gut. Tumor necrosis factor, on the other hand, has antifibrotic bioactivity and pharmacologic inhibition of this cytokine carries a theoretical risk of enhanced stricture formation. Endoscopic management of intestinal strictures with balloon dilation is an accepted strategy to prevent or postpone repeated surgery, but careful patient selection is of paramount importance to ensure favorable long-term outcomes. Specific medical therapy aimed at preventing or reversing intestinal fibrosis is not yet available, but candidate molecules are emerging from research in the liver and in other organs. [source]

Anti-CD28 Antibody-Induced Kidney Allograft Tolerance Related to Tryptophan Degradation and TCR, Class II, B7+ Regulatory Cells

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 10 2005
Fabienne Haspot
B7/CTLA-4 interactions negatively regulate T-cell responses and are necessary for transplant tolerance induction. Tolerance induction may therefore be facilitated by selectively inhibiting the B7/CD28 pathway without blocking that of B7/CTLA-4. In this study, we selectively inhibited CD28/B7 interactions using a monoclonal antibody modulating CD28 in a rat model of acute kidney graft rejection. A short-term treatment abrogated both acute and chronic rejection. Tolerant recipients presented few alloantibodies against donor MHC class II molecules, whereas untreated rejecting controls developed anti-MHC class I and II alloantibodies. PBMC from tolerant animals were unable to proliferate against donor cells but could proliferate against third-party cells. The depletion of B7+, non-T cells fully restored this reactivity whereas purified T cells were fully reactive. Also, NK cells depletion restored PBMC reactivity in 60% of tolerant recipients. Conversely, NK cells from tolerant recipients dose-dependently inhibited alloreactivity. PBMC anti-donor reactivity could be partially restored in vitro by blocking indoleamine-2,3-dioxygenase (IDO) and iNOS. In vivo, pharmacologic inhibition of these enzymes led to the rejection of the otherwise tolerated transplants. This study demonstrates that an initial selective blockade of CD28 generates B7+ non-T regulatory cells and a kidney transplant tolerance sustained by the activity of IDO and iNOS. [source]