Angiotensin II (Ang II) is a peptide hormone that, like many cytokines, acts as a proinflammatory agent and growth factor. After injury to the liver, the hormone assists in tissue repair by stimulating hepatocytes and hepatic stellate cells to synthesize extracellular matrix proteins and secrete secondary cytokines and by stimulating myofibroblasts to proliferate. However, under conditions of chronic liver injury, all of these effects conspire to promote pathologic liver fibrosis. Much of this effect of Ang II results from activation of the proinflammatory NF-B transcription factor in response to stimulation of the type 1 Ang II receptor, a G protein-coupled receptor. Here, we characterize a previously undescribed signaling pathway mediating Ang II-dependent activation of NF-B, which is composed of three principal proteins, CARMA3, Bcl10, and MALT1. Blocking the function of any of these proteins, through the use of either dominant-negative mutants, RNAi, or gene targeting, effectively abolishes Ang II-dependent NF-B activation in hepatocytes. In addition, Bcl10 ؊/؊ mice show defective hepatic cytokine production after Ang II treatment. Evidence also is presented that this pathway activates NF-B through ubiquitination of IKK␥, the regulatory subunit of the I B kinase complex. These results elucidate a concrete series of molecular events that link ligand activation of the type 1 Ang II receptor to stimulation of the NF-B transcription factor. These findings also uncover a function of the CARMA, Bcl10, and MALT1 proteins in cells outside the immune system. G protein-coupled receptor ͉ hepatocyte ͉ IkB kinase ͉ inflammation ͉ ubiquitination

Proper regulation of nuclear factor-κB (NF-κB) transcriptional activity is required for normal lymphocyte function, and deregulated NF-κB signaling can facilitate lymphomagenesis. We demonstrate that the API2-MALT1 fusion oncoprotein created by the recurrent t(11;18)(q21;q21) in mucosa-associated lymphoid tissue (MALT) lymphoma induces proteolytic cleavage of NF-κB inducing kinase (NIK) at Arg325. NIK cleavage requires the concerted actions of both fusion partners and generates a C-terminal NIK fragment that retains kinase activity and is resistant to proteasomal degradation. The resulting deregulated NIK activity is associated with constitutive noncanonical NF-κB signaling, enhanced B-cell adhesion, and apoptosis resistance. Our study reveals the gain-of-function proteolytic activity of a fusion oncoprotein and highlights the importance of the noncanonical NF-κB pathway in B-lymphoproliferative disease.

Objective-The direct role of leptin in vascular disease remains controversial. The objective of this study was to examine the effects of leptin treatment on atherosclerosis and thrombosis in atherosclerotic-prone mice. Methods and Results-Sixteen-week-old, male apolipoprotein E-deficient mice were treated with injections of recombinant leptin (125 g per day IP; nϭ10) or vehicle (nϭ10) 4 and platelets. 5 Plasma leptin levels have also been correlated with cardiovascular complications in humans, an effect independent of body mass index and traditional risk factors. 6 -8 Nevertheless, the direct role of leptin in vascular disease remains controversial. Atherosclerotic mouse models with complete deficiency of leptin suggest that the absence of leptin might promote atherosclerosis. 9,10 However, these studies have been confounded by the extreme obesity and dyslipidemia that result from the loss of leptin-mediated central effects. 9,10 As a result, the direct effect of leptin on atherosclerosis has not yet been addressed. Therefore, to examine the direct role of leptin in atherosclerosis, we analyzed the effect of exogenous recombinant murine leptin on atherosclerosis using apolipoprotein E (apoE)-deficient mice.In addition, we tested the effects of chronic leptin therapy on thrombosis in these atherosclerotic-prone mice to determine whether potential metabolic improvements achieved with leptin therapy would outweigh the acute prothrombotic effect of leptin described previously. 11,12 Methods MiceMale apoE-deficient mice were purchased from the Jackson Laboratory (stock No. 002052; Bar Harbor, Maine) and provided Western chow (TD88137; Harlan Teklad) from 14 to 20 weeks of age. All procedures complied with the principles of laboratory and animal care established by the National Society for Medical Research and were approved by the University of Michigan committee on use and care of animals. Leptin TreatmentBeginning at 16 weeks of age, mice received 200 L intraperitoneal injections daily of either 125 g of recombinant murine leptin (R & D Systems) or vehicle control (nϭ10 per group). The dose of leptin chosen was based on a protocol used to achieve weight loss and fertility in leptin-deficient mice. 13 We determined that a 4-week duration of injections at this dose would be adequate to test the hypothesis that leptin promotes atherosclerosis in this particular model of hyperlipidemia. 14 http://atvb.ahajournals.org/ Downloaded from esthesia (100 mg/kg). Mice were perfused with saline and fixed using formalin with a 25-gauge needle inserted into the left ventricle at a rate of 1 mL/min. After formalin fixation, the arterial tree was meticulously dissected from the carcass and placed in 70% ethanol for Ն72 hours. The surface area occupied by atherosclerosis was then quantitated at the thoracic aorta and major branches, including the brachiocephalic, carotid, and subclavian arteries, via Oil Red O staining and quantitative morphometry, as described previously. 15 The lesion area was calculated for the control and treat...