Impaired retinoic acid signaling in cerebral cavernous malformations.

The capillary-venous pathology cerebral cavernous malformation (CCM) is caused by loss of CCM1/Krev interaction trapped protein 1 (KRIT1), CCM2/MGC4607, or CCM3/PDCD10 in some endothelial cells. Mutations of CCM genes within the brain vasculature can lead to recurrent cerebral hemorrhages. Pharmacological treatment options are urgently needed when lesions are located in deeply-seated and in-operable regions of the central nervous system.

Novel Chronic Mouse Model of Cerebral Cavernous Malformations.

Background and Purpose- Cerebral cavernous malformations (CCMs) are vascular malformations of the brain that lead to cerebral hemorrhages. A pharmacological treatment is needed especially for patients with nonoperable deep-seated lesions. We and others obtained CCM mouse models that were useful for mechanistic studies and rapid trials testing the preventive effects of candidate drugs.

Systematic pharmacological screens uncover novel pathways involved in cerebral cavernous malformations.

Cerebral cavernous malformations (CCMs) are vascular lesions in the central nervous system causing strokes and seizures which currently can only be treated through neurosurgery. The disease arises through changes in the regulatory networks of endothelial cells that must be comprehensively understood to develop alternative, non-invasive pharmacological therapies. Here, we present the results of several unbiased small-molecule suppression screens in which we applied a total of 5,268 unique substances to mutant worm, zebrafish, mouse, or human endothelial cells.

The CCM1-CCM2 complex controls complementary functions of ROCK1 and ROCK2 that are required for endothelial integrity.

Endothelial integrity relies on a mechanical crosstalk between intercellular and cell-matrix interactions. This crosstalk is compromised in hemorrhagic vascular lesions of patients carrying loss-of-function mutations in cerebral cavernous malformation (CCM) genes. RhoA/ROCK-dependent cytoskeletal remodeling is central to the disease, as it causes unbalanced cell adhesion towards increased cell-extracellular matrix adhesions and destabilized cell-cell junctions.

Network-based analysis of omics data: the LEAN method.

Motivation: Most computational approaches for the analysis of omics data in the context of interaction networks have very long running times, provide single or partial, often heuristic, solutions and/or contain user-tuneable parameters.

Results: We introduce local enrichment analysis (LEAN) for the identification of dysregulated subnetworks from genome-wide omics datasets. By substituting the common subnetwork model with a simpler local subnetwork model, LEAN allows exact, parameter-free, efficient and exhaustive identification of local subnetworks that are statistically dysregulated, and directly implicates single genes for follow-up experiments.

Sulindac metabolites decrease cerebrovascular malformations in CCM3-knockout mice.

Cerebral cavernous malformation (CCM) is a disease of the central nervous system causing hemorrhage-prone multiple lumen vascular malformations and very severe neurological consequences. At present, the only recommended treatment of CCM is surgical. Because surgery is often not applicable, pharmacological treatment would be highly desirable.

Cerebral Cavernous Malformation-1 Protein Controls DLL4-Notch3 Signaling Between the Endothelium and Pericytes.

Background And Purpose: Cerebral cavernous malformation (CCM) is a neurovascular dysplasia characterized by conglomerates of enlarged endothelial channels in the central nervous system, which are almost devoid of pericytes or smooth muscle cells. This disease is caused by loss-of-function mutations in CCM1, CCM2, or CCM3 genes in endothelial cells, making blood vessels highly susceptible to angiogenic stimuli. CCM1- and CCM3-silenced endothelial cells have a reduced expression of the Notch ligand Delta-like 4 (DLL4) resulting in impaired Notch signaling and irregular sprouting angiogenesis.

Regulation of β1 integrin-Klf2-mediated angiogenesis by CCM proteins.

Mechanotransduction pathways are activated in response to biophysical stimuli during the development or homeostasis of organs and tissues. In zebrafish, the blood-flow-sensitive transcription factor Klf2a promotes VEGF-dependent angiogenesis. However, the means by which the Klf2a mechanotransduction pathway is regulated to prevent continuous angiogenesis remain unknown.

Loss of α1β1 soluble guanylate cyclase, the major nitric oxide receptor, leads to moyamoya and achalasia.

Moyamoya is a cerebrovascular condition characterized by a progressive stenosis of the terminal part of the internal carotid arteries (ICAs) and the compensatory development of abnormal "moyamoya" vessels. The pathophysiological mechanisms of this condition, which leads to ischemic and hemorrhagic stroke, remain unknown. It can occur as an isolated cerebral angiopathy (so-called moyamoya disease) or in association with various conditions (moyamoya syndromes).

CCM1-ICAP-1 complex controls β1 integrin-dependent endothelial contractility and fibronectin remodeling.

The endothelial CCM complex regulates blood vessel stability and permeability. Loss-of-function mutations in CCM genes are responsible for human cerebral cavernous malformations (CCMs), which are characterized by clusters of hemorrhagic dilated capillaries composed of endothelium lacking mural cells and altered sub-endothelial extracellular matrix (ECM). Association of the CCM1/2 complex with ICAP-1, an inhibitor of β1 integrin, prompted us to investigate whether the CCM complex interferes with integrin signaling.

EndMT contributes to the onset and progression of cerebral cavernous malformations.

Cerebral cavernous malformation (CCM) is a vascular dysplasia, mainly localized within the brain and affecting up to 0.5% of the human population. CCM lesions are formed by enlarged and irregular blood vessels that often result in cerebral haemorrhages.

Developmental timing of CCM2 loss influences cerebral cavernous malformations in mice.

Cerebral cavernous malformations (CCM) are vascular malformations of the central nervous system (CNS) that lead to cerebral hemorrhages. Familial CCM occurs as an autosomal dominant condition caused by loss-of-function mutations in one of the three CCM genes. Constitutive or tissue-specific ablation of any of the Ccm genes in mice previously established the crucial role of Ccm gene expression in endothelial cells for proper angiogenesis.

CCM1 regulates vascular-lumen organization by inducing endothelial polarity.

Little is known about the molecular mechanisms that regulate the organization of vascular lumen. In this paper we show that lumen formation correlates with endothelial polarization. Adherens junctions (AJs) and VE-cadherin (VEC, encoded by CDH5) are required for endothelial apicobasal polarity in vitro and during embryonic development.

Recent insights into cerebral cavernous malformations: the molecular genetics of CCM.

Cerebral cavernous malformations (CCM) are vascular lesions which can occur as a sporadic (80% of the cases) or familial autosomal dominant form (20%). Three CCM genes have been identified: CCM1/KRIT1, CCM2/MGC4607 and CCM3/PDCD10. Almost 80% of CCM patients affected with a genetic form of the disease harbor a heterozygous germline mutation in one of these three genes.

Tissue-specific conditional CCM2 knockout mice establish the essential role of endothelial CCM2 in angiogenesis: implications for human cerebral cavernous malformations.

Cerebral cavernous malformations (CCM) are vascular malformations of the brain that lead to cerebral hemorrhages. In 20% of CCM patients, this results from an autosomal dominant condition caused by loss-of-function mutations in one of the three CCM genes. High expression levels of the CCM genes in the neuroepithelium indicate that CCM lesions might be caused by a loss of function of these genes in neural cells rather than in vascular cells.

Organ-specific differences in the function of MCP-1 and CXCR3 during cardiac and skin allograft rejection.

Background: Chemokines are well-established to function in the recruitment of leukocytes into allografts in the course of rejection. Moreover, some studies have indicated that there are organ-specific differences in chemokine function, but the mechanism accounting for this difference is not known.

Methods: Fully major histocompatibility complex-mismatched vascularized cardiac transplants or skin transplants were performed using BALB/c (H-2d), C57BL/6 (H-2b), MCP-1-/- (H-2b) and CXCR3-/- (H-2b) mice as donors or recipients.

[The adaptor protein Lnk modulates endothelial cell activation].

Lnk is an adaptator protein involved in B lymphocytes and platelet differentiation and in T lymphocyte activation. We previously reported on Lnk expression and regulation in endothelial cells (ECs) upon activation. In the present study, the involvement of Lnk in the tumor necrosis factor alpha (TNFalpha) pathway was investigated in vitro through Lnk overexpression in primary cultures of human endothelial cells.

The adaptor molecule Lnk negatively regulates tumor necrosis factor-alpha-dependent VCAM-1 expression in endothelial cells through inhibition of the ERK1 and -2 pathways.

Lnk, with APS and SH2-B (Src homology 2-B), belongs to a family of SH2-containing proteins with potential adaptor functions. Lnk regulates growth factor and cytokine receptor-mediated pathways implicated in lymphoid, myeloid, and platelet homeostasis. We have previously shown that Lnk is expressed and up-regulated in vascular endothelial cells (ECs) in response to tumor necrosis factor-alpha (TNFalpha).

Vascular endothelial growth factor-induced signaling pathways in endothelial cells that mediate overexpression of the chemokine IFN-gamma-inducible protein of 10 kDa in vitro and in vivo.

Vascular endothelial growth factor (VEGF), an angiogenesis factor, has recently been found to have potent proinflammatory properties in vivo. However, the mechanism by which it mediates inflammation is poorly understood. In this study, we have evaluated the function of VEGF on the induced expression and function of the T cell chemoattractant chemokine IFN-gamma-inducible protein of 10 kDa (IP-10).

Exogenous tissue inhibitor of metalloproteinase-1 promotes endothelial cell survival through activation of the phosphatidylinositol 3-kinase/Akt pathway.

Control of molecular targets and signaling pathways which improve endothelial cell survival may be an attractive concept for interfering with dysregulated vascular injury and remodeling, a key mechanism for transplant arteriosclerosis and chronic allograft rejection. In addition to inhibiting matrix metalloproteinase activity, it has been suggested by recent studies that the tissue inhibitor of metalloproteinase (TIMP)-1 may inhibit apoptosis in various cell types. The present work examines the possibility that TIMP-1 belongs to a protective pathway via antiapoptotic properties and investigates the signaling pathway mediated by TIMP-1 in human ECs.

RhoA activation mediates phosphatidylinositol 3-kinase-dependent proliferation of human vascular endothelial cells: an alloimmune mechanism of chronic allograft nephropathy.

HLA class I ligation on graft endothelial cells (EC) has been shown to promote graft arteriosclerosis and chronic allograft nephropathy. This study investigated transcriptional and functional changes mediated by anti-HLA antibodies (Ab), developed by transplant recipient, on vascular renal EC. For mimicking interactions that occur between alloantibodies and graft endothelium, HLA-typed primary cultures of human EC were incubated in vitro in the presence of monomorphic or polymorphic anti-HLA class I Ab.

Association of rapamycin and co-stimulation blockade using anti-B7 antibodies in renal allotransplantation in baboons.

Background: Co-stimulation blockade has already been shown to induce transplantation tolerance in rodents, but until now has failed in large animal models. We therefore sought to investigate whether the addition of rapamycin to a co-stimulation blockade regimen could induce tolerance in baboon recipients of a renal allograft and to characterize the immunological characteristics of rejection.

Methods: Two baboons were used for a pharmacological and toxicological analysis and received anti-B7.

The effect of mitoxantrone on anti-pig immunization in baboons.

Besides virological and physiological concerns, the success of xenotransplantation (Xt) is still dependent on the prevention of delayed xenograft rejection (DXR). Although multifactorial, DXR is mainly due to xenonatural antibody (Ab) recognizing their xenogenic antigen (Ag) followed by complement activation. Despite the use of intensive treatments capable of inhibiting the humoral response, DXR can still not be avoided and always occurs within weeks following transplantation.

Rapid selection of differentially expressed genes in TNF[alpha]-activated endothelial cells.

Background: RNA differential display (DD) RT-PCR is a useful method to identify and clone differentially expressed genes. However, the rate of false positives and redundancy associated with this PCR-based method as well as laborious downstream screening steps constitute major limitations. Here we present DD RT-PCR and reverse northern (RN) protocols allowing rapid and acurate identification of genes upregulated in porcine endothelial cells (EC) in response to TNFalpha.

Transcriptional up-regulation of the signaling regulatory protein LNK in activated endothelial cells.

Background: A better understanding of inflammatory processes in endothelial cells (ECs) might reveal new ways of controlling inflammation and graft rejection. This study investigates EC genes regulated in response to human tumor necrosis factor (TNF)-alpha and xenogeneic natural antibodies (XNAs) that contribute to endothelial activation during transplantation.

Methods: Gene expression between resting and activated ECs was investigated by RNA differential display reverse-transcriptase polymerase chain reaction and confirmed by reverse-Northern blot.