Biomedical subjects

Romeo Ricci

Publications and source records attributed to Romeo Ricci.

13 recordsLinked to original sources

PubMed2006

c-Jun/AP-1 controls liver regeneration by repressing p53/p21 and p38 MAPK activity.

The AP-1 transcription factor c-Jun is a key regulator of hepatocyte proliferation. Mice lacking c-Jun in the liver (c-jun (Deltali*)) display impaired liver regeneration after partial hepatectomy (PH). This phenotype correlates with increased protein levels of the cdk-inhibitor p21 in the liver. We performed PH experiments in several double-knockout mouse models to genetically identify the signaling events regulated by c-Jun. Inactivation of p53 in c-jun (Deltali*) mice abrogated both hepatocyte cell cycle block and increased p21 protein expression. Consistently, liver regeneration was rescued in c-jun (Deltali*) p21 (-/-) double-mutant mice. This indicated that c-Jun controls hepatocyte proliferation by a p53/p21-dependent mechanism. Analyses of p21 mRNA and protein expression in livers of c-jun (Deltali*) mice after PH revealed that the accumulation of p21 protein is due to a post-transcriptional/post-translational mechanism. We have investigated several candidate pathways implicated in the regulation of p21 expression, and observed increased activity of the stress kinase p38 in regenerating livers of c-jun (Deltali*) mice. Importantly, conditional deletion of p38alpha in livers of c-jun (Deltali*) mice fully restored hepatocyte proliferation and attenuated increased p21 protein levels after PH. These data demonstrate that c-Jun/AP-1 regulates liver regeneration through a novel molecular pathway that involves p53, p21, and the stress kinase p38alpha.

Animals↗

PubMed2006

Separase: a universal trigger for sister chromatid disjunction but not chromosome cycle progression.

Separase is a protease whose liberation from its inhibitory chaperone Securin triggers sister chromatid disjunction at anaphase onset in yeast by cleaving cohesin's kleisin subunit. We have created conditional knockout alleles of the mouse Separase and Securin genes. Deletion of both copies of Separase but not Securin causes embryonic lethality. Loss of Securin reduces Separase activity because deletion of just one copy of the Separase gene is lethal to embryos lacking Securin. In embryonic fibroblasts, Separase depletion blocks sister chromatid separation but does not prevent other aspects of mitosis, cytokinesis, or chromosome replication. Thus, fibroblasts lacking Separase become highly polyploid. Hepatocytes stimulated to proliferate in vivo by hepatectomy also become unusually large and polyploid in the absence of Separase but are able to regenerate functional livers. Separase depletion in bone marrow causes aplasia and the presumed death of hematopoietic cells other than erythrocytes. Destruction of sister chromatid cohesion by Separase may be a universal feature of mitosis in eukaryotic cells.

Anaphase↗

PubMed2005

Regression of abdominal aortic aneurysm by inhibition of c-Jun N-terminal kinase.

Abdominal aortic aneurysm (AAA) is a common disease among elderly people that, when surgical treatment is inapplicable, results in progressive expansion and rupture of the aorta with high mortality. Although nonsurgical treatment for AAA is much awaited, few options are available because its molecular pathogenesis remains elusive. Here, we identify JNK as a proximal signaling molecule in the pathogenesis of AAA. Human AAA tissue showed a high level of phosphorylated JNK. We show that JNK programs a gene expression pattern in different cell types that cooperatively enhances the degradation of the extracellular matrix while suppressing biosynthetic enzymes of the extracellular matrix. Selective inhibition of JNK in vivo not only prevented the development of AAA but also caused regression of established AAA in two mouse models. Thus, JNK promotes abnormal extracellular matrix metabolism in the tissue of AAA and may represent a therapeutic target.

Adenoviridae↗

PubMed2005

Distinct functions of junD in cardiac hypertrophy and heart failure.

Cardiac hypertrophic stimuli induce both adaptive and maladaptive growth response pathways in heart. Here we show that mice lacking junD develop less adaptive hypertrophy in heart after mechanical pressure overload, while cardiomyocyte-specific expression of junD in mice results in spontaneous ventricular dilation and decreased contractility. In contrast, fra-1 conditional knock-out mice have a normal hypertrophic response, whereas hearts from fra-1 transgenic mice decompensate prematurely. Moreover, fra-1 transgenic mice simultaneously lacking junD reveal a spontaneous dilated cardiomyopathy associated with increased cardiomyocyte apoptosis and a primary mitochondrial defect. These data suggest that junD promotes both adaptive-protective and maladaptive hypertrophy in heart, depending on its expression levels.

Animals↗

PubMed2004

JNK1 is not essential for TNF-mediated joint disease.

Tumour necrosis factor (TNF) signalling molecules are considered as promising therapeutic targets of antirheumatic therapy. Among them, mitogen-activated protein kinases are thought to be of central importance. Herein, we investigate the role in vivo of TNF-alpha signalling through c-Jun N-terminal kinase (JNK)1 in destructive arthritis. Human TNF transgenic (hTNFtg) mice, which develop inflammatory arthritis, were intercrossed with JNK1-deficient (JNK1-/-) mice. Animals (n = 35) of all four genotypes (wild-type, JNK1-/-, hTNFtg, JNK1-/-hTNFtg) were assessed for clinical and histological signs of arthritis. Clinical features of arthritis (swelling and decreased grip strength) developed equally in hTNFtg and JNK1-/-hTNFtg mice. Histological analyses revealed no differences in the quantity of synovial inflammation and bone erosions or in the cellular composition of the synovial infiltrate. Bone destruction and osteoclast formation were observed to a similar degree in hTNFtg and JNK1-/-hTNFtg animals. Moreover, cartilage damage, as indicated by proteoglycan loss in the articular cartilage, was comparable in the two strains. Intact phosphorylation of JNK and c-Jun as well as expression of JNK2 in the synovial tissue of JNK1-/-hTNFtg mice suggests that signalling through JNK2 may compensate for the deficiency in JNK1. Thus, JNK1 activation does not seem to be essential for TNF-mediated arthritis.

Animals↗

PubMed2004

Requirement of JNK2 for scavenger receptor A-mediated foam cell formation in atherogenesis.

In vitro studies suggest a role for c-Jun N-terminal kinases (JNKs) in proatherogenic cellular processes. We show that atherosclerosis-prone ApoE-/- mice simultaneously lacking JNK2 (ApoE-/- JNK2-/- mice), but not ApoE-/- JNK1-/- mice, developed less atherosclerosis than do ApoE-/- mice. Pharmacological inhibition of JNK activity efficiently reduced plaque formation. Macrophages lacking JNK2 displayed suppressed foam cell formation caused by defective uptake and degradation of modified lipoproteins and showed increased amounts of the modified lipoprotein-binding and -internalizing scavenger receptor A (SR-A), whose phosphorylation was markedly decreased. Macrophage-restricted deletion of JNK2 was sufficient to decrease atherogenesis. Thus, JNK2-dependent phosphorylation of SR-A promotes uptake of lipids in macrophages, thereby regulating foam cell formation, a critical step in atherogenesis.

Animals↗

PubMed2004

Molecular imaging of atherosclerotic plaques using a human antibody against the extra-domain B of fibronectin.

Current imaging modalities of human atherosclerosis, such as angiography, ultrasound, and computed tomography, visualize plaque morphology. However, methods that provide insight into plaque biology using molecular tools are still insufficient. The extra-domain B (ED-B) is inserted into the fibronectin molecule by alternative splicing during angiogenesis and tissue remodeling but is virtually undetectable in normal adult tissues. Angiogenesis and tissue repair are also hallmarks of advanced plaques. For imaging atherosclerotic plaques, the human antibody L19 (specific against ED-B) and a negative control antibody were labeled with radioiodine or infrared fluorophores and injected intravenously into atherosclerotic apolipoprotein E-null (ApoE-/-) or normal wild-type mice. Aortas isolated 4 hours, 24 hours, and 3 days after injection exhibited a selective and stable uptake of L19 when using radiographic or fluorescent imaging. L19 binding was confined to the plaques as assessed by fat staining. Comparisons between fat staining and autoradiographies 24 hours after 125I-labeled L19 revealed a significant correlation (r=0.89; P<0.0001). Minimal antibody uptake was observed in normal vessels from wild-type mice receiving the L19 antibody and in atherosclerotic vessels from ApoE-/- mice receiving the negative control antibody. Immunohistochemical studies revealed increased expression of ED-B not only in murine but also in human plaques, in which it was found predominantly around vasa vasorum and plaque matrix. In summary, we demonstrate selective targeting of atheromas in mice using the human antibody to the ED-B domain of fibronectin. Thus, our findings may set the stage for antibody-based molecular imaging of atherosclerotic plaques in the intact organism.

Adult↗

PubMed2004

Loss of the anaphase-promoting complex in quiescent cells causes unscheduled hepatocyte proliferation.

The anaphase-promoting complex or cyclosome (APC/C) is an ubiquitin protein ligase that together with Cdc20 and Cdh1 targets mitotic proteins for degradation by the proteosome. APC-Cdc20 activity during mitosis triggers anaphase by destroying securin and cyclins. APC-Cdh1 promotes degradation of cyclins and other proteins during G(1). We show that loss of APC/C during embryogenesis is early lethal before embryonic day E6.5 (E6.5). To investigate the role of APC/C in quiescent cells, we conditionally inactivated the subunit Apc2 in mice. Deletion of Apc2 in quiescent hepatocytes caused re-entry into the cell cycle and arrest in metaphase, resulting in liver failure. Re-entry into the cell cycle either occurred without any proliferative stimulus or could be easily induced. We demonstrate that the APC has an additional function to prevent hepatocytes from unscheduled re-entry into the cell cycle.

Anaphase-Promoting Complex-Cyclosome↗

PubMed2003

Dendritic cell-induced autoimmune heart failure requires cooperation between adaptive and innate immunity.

Genetic susceptibility and autoimmunity triggered by microbial infections are factors implicated in the pathogenesis of dilated cardiomyopathy, the most common cause of heart failure in young patients. Here we show that dendritic cells (DCs) loaded with a heart-specific self peptide induce CD4+ T-cell-mediated myocarditis in nontransgenic mice. Toll-like receptor (TLR) stimulation, in concert with CD40 triggering of self peptide-loaded dendritic cells, was shown to be required for disease induction. After resolution of acute myocarditis, DC-immunized mice developed heart failure, and TLR stimulation of these mice resulted in relapse of inflammatory infiltrates. Injection of damaged, syngeneic cardiomyocytes also induced myocarditis in mice if TLRs were activated in vivo. DC-induced myocarditis provides a unifying theory as to how tissue damage and activation of TLRs during infection can induce autoimmunity, relapses and cardiomyopathy.

Adaptation, Physiological↗

PubMed2003

Liver tumor development. c-Jun antagonizes the proapoptotic activity of p53.

The transcription factor c-Jun mediates several cellular processes, including proliferation and survival, and is upregulated in many carcinomas. Liver-specific inactivation of c-Jun at different stages of tumor development was used to study its role in chemically induced hepatocellular carcinomas (HCCs) in mice. The requirement for c-jun was restricted to early stages of tumor development, and the number and size of hepatic tumors was dramatically reduced when c-jun was inactivated after the tumor had initiated. The impaired tumor development correlated with increased levels of p53 and its target gene noxa, resulting in the induction of apoptosis without affecting cell proliferation. Primary hepatocytes lacking c-Jun showed increased sensitivity to TNF-alpha-induced apoptosis, which was abrogated in the absence of p53. These data indicate that c-Jun prevents apoptosis by antagonizing p53 activity, illustrating a mechanism that might contribute to the early stages of human HCC development.

Age Factors↗

PubMed2003

PTEN as a molecular marker to distinguish metastatic from primary synchronous endometrioid carcinomas of the ovary and uterus.

The distinction between two primary carcinomas on the one hand and a metastatic disease on the other hand in patients suffering from synchronous endometrioid carcinomas of the uterus and ovary is difficult. Exclusive histopathologic analysis appears to be insufficient and sometimes misleading. The tumor suppressor PTEN was found to be important in early neoplastic transformation in endometrioid carcinomas of the uterus. In this study, we screened synchronous endometrioid carcinomas of the uterus and ovary of 10 patients for loss of heterozygosity using seven different microsatellite markers at 10q23.3 and for mutations in the entire coding region of PTEN. Point mutations or microdeletions/insertions were found in six patients. Allelic loss at 10q23.3 was detected in eight patients. Based on conventional histology, a metastatic disease was diagnosed in seven patients and a concomitant uterine and ovarian carcinoma in three patients. After molecular analysis, the histopathologic diagnosis of three patients had to be revised. Histopathology represents the standard method to process tumor specimens from these patients. Nevertheless, mutation screen for PTEN and LOH analysis at 10q23.3 provide helpful genetic tools to establish a correct final diagnosis, which is important in view of prognosis and therapeutic implications.

Aged↗

PubMed2002

JunB can substitute for Jun in mouse development and cell proliferation.

The Jun and JunB components of the AP-1 transcription factor are known to have antagonistic functions. Here we show, by a knock-in strategy and a transgenic complementation approach, that Junb can substitute for absence of Jun during mouse development. Junb can rescue both liver and cardiac defects in Jun-null mice in a manner dependent on gene dosage. JunB restores the expression of genes regulated by Jun/Fos, but not those regulated by Jun/ATF, thereby rescuing Jun-dependent defects in vivo as well as in primary fibroblasts and fetal hepatoblasts in vitro. Thus, the transcriptionally less active JunB has the potential to substitute for Jun, indicating that the spatial and temporal regulation of expression of the transcription factor AP-1 may be more important than the coding sequence of its components.

Animals↗

PubMed2002

Osteoclasts are essential for TNF-alpha-mediated joint destruction.

The detailed cellular and molecular mechanisms leading to joint destruction in rheumatoid arthritis, a disease driven by proinflammatory cytokines, are still unknown. To address the question of whether osteoclasts play a pivotal role in this process, transgenic mice that express human TNF (hTNFtg) and that develop a severe and destructive arthritis were crossed with osteopetrotic, c-fos-deficient mice (c-fos(-/-)) completely lacking osteoclasts. The resulting mutant mice (c-fos(-/-)hTNFtg) developed a TNF-dependent arthritis in the absence of osteoclasts. All clinical features of arthritis, such as paw swelling and reduction of grip strength, progressed equally in both groups. Histological evaluation of joint sections revealed no difference in the extent of synovial inflammation, its cellular composition (except for the lack of osteoclasts), and the expression of matrix metalloprotein-ase-3 (MMP-3) and MMP-13. In addition, cartilage damage, proteoglycan loss, and MMP-3, -9, and -13 expression in chondrocytes were similar in hTNFtg and c-fos(-/-)hTNFtg mice. However, despite the presence of severe inflammatory changes, c-fos(-/-)hTNFtg mice were fully protected against bone destruction. These data reveal that TNF-dependent bone erosion is mediated by osteoclasts and that the absence of osteoclasts alters TNF-mediated arthritis from a destructive to a nondestructive arthritis. Therefore, in addition to the use of anti-inflammatory therapies, osteoclast inhibition could be beneficial for the treatment of rheumatoid arthritis.

Animals↗