Sequential inactivation of Rho GTPases and Lim kinase by Pseudomonas aeruginosa toxins ExoS and ExoT leads to endothelial monolayer breakdown.

Pseudomonas aeruginosa is a major human opportunistic pathogen and one of the most important causal agents of bacteremia. For non-blood-borne infection, bacterial dissemination requires the crossing of the vascular endothelium, the main barrier between blood and the surrounding tissues. Here, we investigated the effects of P. aeruginosa type 3 secretion effectors, namely ExoS, ExoT, and ExoY, on regulators of actin cytoskeleton dynamics in primary endothelial cells. ExoS and ExoT similarly affected the Lim kinase-cofilin pathway, thereby promoting actin filament severing. Cofilin activation was also observed in a mouse model of P. aeruginosa-induced acute pneumonia. Rho, Rac, and Cdc42 GTPases were sequentially inactivated, leading to inhibition of membrane ruffling, filopodia, and stress fiber collapse, and focal adhesion disruption. At the end of the process, ExoS and ExoT produced a dramatic retraction in all primary endothelial cell types tested and thus a rupture of the endothelial monolayer. ExoY alone had no effect in this context. Cell retraction could be counteracted by overexpression of actin cytoskeleton regulators. In addition, our data suggest that moesin is neither a direct exotoxin target nor an important player in this process. We conclude that any action leading to inhibition of actin filament breakdown will improve the barrier function of the endothelium during P. aeruginosa infection.

Protocadherin-12 deficiency leads to modifications in the structure and function of arteries in mice.

We studied the role of protocadherin-12 on arterial function. This protein belongs to the cadherin superfamily and is located at the intercellular junctions of endothelial cells where it promotes homotypic cellular adhesion. We previously showed that mice deficient for PCDH12 exhibited developmental growth retardation owing to placenta defects without altering neither survival nor fertility. Here, we investigated the effects of PCDH12 deficiency on the structural, mechanical properties and functionality of arteries from adult mice. Histological studies of the PCDH12(-/-) mouse arteries have shown age-independent modifications such as ramifications of medial elastic lamellae, accompanied by the appearance of radial fibers linking together two successive concentric elastic lamellae. Mechanical studies also revealed some age-independent modifications in the PCDH12(-/-) mice arteries such as an increase in inner-diameter and circumferential mid-wall stress. Moreover, the PCDH12(-/-) mice exhibited a mild reduction of blood pressure, thus maintaining the inner-diameter close to its normal value and a normal circumferential wall stress for vascular cells. This is likely a compensation mechanism enabling normal blood flow in the arteries. The vascular phenotypic differences observed between PCDH12(-/-) and wild type mice arteries did not seem to be age-dependent, except for some results regarding the carotid artery: the reactivity to acetylcholine and the circumferential mid-wall stress decreased with ageing in the PCDH12(-/-) mice, as opposed to the increase observed in the wild types. In conclusion, deficiency in one specific interendothelial junction component leads to significant changes in the structure and function of the vascular wall. Possible explanations for the observed modifications are discussed.

Tracing the glycogen cells with protocadherin 12 during mouse placenta development.

Among the different trophoblast subtypes of the mouse placenta, the glycogen cells (GC) are one of the trophoblast subtypes that invade the decidua. We previously established that GC specifically expressed protocadherin 12 (PCDH12). In this paper, we investigated the origin of the PCDH12-positive cells and we characterized their fate in the maternal tissues. Our data indicate that they directly originate from the central part of the ectoplacental cone at embryonic day (E) 7.5. PCDH12-positive cells start to accumulate glycogen from E10.5 and the first migrating cells could be observed from this age. Unlike other placental and decidual cells, GC do not express P-cadherin, which may explain their migration properties in this organ. In the decidua, GC settle in the vicinity of the maternal vascular sinuses but do not incorporate in the endothelium. By the end of gestation (E17.5), most GC islets of the decidua enter into a lytic phase and form large lacunae. These lacunae, filled with glycogen, may provide a substantial source of energy at the end of gestation or during delivery. Our data suggest that spongiotrophoblasts and GC are two independent lineages and we bring insights into GC migration and fate.

[Dilated cardiomyopathy and lipid-lowering drug muscle toxicity revealing late-onset Becker's disease]. / Cardiomyopathie dilatée et toxicité musculaire des hypolipémiants: une maladie de Becker de révélation tardive.

INTRODUCTION: The Becker's muscular dystrophy is a genetic myopathy due to mutations of the dystrophin gene, located in the Xp21 region, with a clinical expression usually occurring in young adults. EXEGESIS: We report an atypical case of late onset Becker's muscular dystrophy diagnosed at the age of 57. The patient suffered from mild skeletal muscle involvement revealed by the use of statins and fibrates, associated with severe dilating cardiomyopathy. The DNA analysis showed a deletion of the exons 11-13 in the Xp21 gene. CONCLUSION: The diagnostic of Becker's muscular dystrophy must be considered in all patients with persistently elevated CPK and/or primitive dilated cardiomyopathy, whatever the age of the patient.

[Coexistence of dermatomyositis and macrophagic myofasciitis]. / Coexistence d'une dermatomyosite et d'une myofasciite a macrophages.

INTRODUCTION: An inflammatory myopathy, characterised by joint and muscle pain, chronic asthenia, with infiltration of peri-fascicular epimysium, perimysium and endomysium by cells of the macrophagic line, macrophagic myofasciitis is often associated with other, generally auto-immune, affections. However, the coexistence with another inflammatory myopathy is relatively rare. OBSERVATION: A 29 year-old woman presented with 2 distinct inflammatory myopathies, a macrophagic myofasciitis and a dermatomyositis, which had appeared a few years after. DISCUSSION: In the rare cases in which 2 inflammatory myopathies are combined, the precise relationship between them is unknown, an individual susceptibility to developing muscle diseases is suggested.

Minimal tissue damage after stimulation of the motor thalamus in a case of chorea-acanthocytosis.

Autopsy findings are reported from a patient with chorea-acanthocytosis treated for 2 years by deep brain stimulation (DBS) of the motor thalamus. Postoperative testing showed a progressive improvement in axial truncal spasms. Although relatively high currents were used for 2 years in this patient, postmortem analysis showed minimal tissue damage in the vicinity of the electrode tip. It is concluded that DBS has little impact on the surrounding tissues.

Chorea-acanthocytosis: neuropathology of brain and peripheral nerve.

We report the neuropathological data from a familial case of chorea-acanthocytosis with central and peripheral nervous system involvement. At the age of 34, the patient underwent a peripheral nerve biopsy which was analyzed by light- and electron microscopy. These studies showed a selective reduction in the large diameter myelinated fibre population, with several clusters of regeneration. Remyelinating fibers surrounded by flattened Schwann cell processes were also present. The patient died at the age of 44, and post-mortem macroscopic examination of the brain showed marked atrophy of the caudate. Histological examination of paraffin sections showed almost complete depletion of neurons in the caudate, with severe astrocytic gliosis. The putamen and pallidum were slightly less severely depleted of neurons, but with marked astrocytic gliosis. Diffuse mild gliosis was also evidenced, by immunohistochemistry with anti-GFAP, in the thalamus and subcortical white matter.

Leukemic dissemination within a glioblastoma in a patient with chronic lymphoid leukemia.

Metastasis from an extracranial tumor to a primary central nervous system tumor is a rare event, and most reported cases concern metastases to meningiomas. The authors describe the first case of leukemic cell dissemination within a glioblastoma. The patient likely presented a genetic predisposition to multiple neoplasms, and the unusual localization of leukemic cells might be partly related to the characteristic microvascular proliferation in glioblastoma.

Cholesterol crystal embolization simulating focal myositis.

Cholesterol crystal embolization usually produces characteristic skin lesions. We report a case responsible for myositis of the calf without suggestive skin lesions. The outcome in this 58-year-old patient was spontaneously favorable. Cholesterol crystal embolization can produce a range of clinical symptoms, with the skin, kidneys, and eyes being the most common targets. Generalized forms can result in systemic disease. The diagnosis rests on histological findings, and the treatment is symptomatic. Anticoagulants have been shown to worsen the manifestations, whereas antiplatelet therapy may be useful.

[POEMS syndrome (or Crow-Fukase syndrome)]. / Le syndrome POEMS (ou syndrome de Crow-Fukase).

POEMS is an acronym for polyneuropathy, organomegaly, endocrinopathy, M-protein and skin changes. POEMS syndrome is also called Crow-Fukase syndrome, chiefly in Japan. The 5 above mentioned features are not always present at the first examination. The minimal criteria to establish the diagnosis are the presence of a demyelinating and axonal polyneuropathy associated with an IgA or IgG monoclonal gammopathy, the light chain being almost always lambda, and at least 2 of the 8 other features: sclerosing plasmocytoma, endocrinopathy, skin changes, organomegaly, Castleman's disease, anasarca, papillary edema or thrombocytosis. Among these features, only cutaneous glomeruloid angioma are specific. Ultrastructural identification of uncompacted myelin lamellae on the peripheral nerve biopsy is also a strong argument in favor of the diagnosis. An associated "osteosclerotic" bone lesion must be carefully searched, because its treatment may improve the other features of the syndrome, especially the neuropathy. Cytokines and the vascular growth endothelial factor might play a role in the pathogenesis of this rare multisystemic disorder.

[Inclusion body myositis associated with sacroidosis: a report of 3 cases]. / Association myosite à inclusions et sarcoïdose: à propos de trois cas.

Inclusion body myositis (IBM) is a severe form of idiopathic inflammatory myopathy. A predominantly T CD8+ lymphocytic infiltrate, with focally non-necrotizing muscular fiber invasion, and rimmed-vacuoles are specific histological signs. A few cases of IBM associated with other dysimmune diseases have been reported, but only once with systemic sarcoidosis. We report three cases of muscular sarcoidosis associated with IBM. This very uncommon observation suggests that major complex of histocompatibility, soluble factors, cytokines and adhesion molecules could be involved. Our cases are a novel example of associated dysimmune diseases.

Expression of thymidine kinase driven by an endothelial-specific promoter inhibits tumor growth of Lewis lung carcinoma cells in transgenic mice.

The possibility of inhibiting tumor growth by limiting angiogenesis has raised considerable interest. In this study, we examined the feasibility of inhibiting tumor growth by targeting a suicide gene in the endothelium. Toxicity must be directed solely to angiogenic cells. Therefore, we used the herpes simplex virus-thymidine kinase (TK) gene, in combination with the prodrug ganciclovir (GCV), which affects replicative cells. To test this strategy, we produced transgenic mice carrying the TK gene driven by the vascular endothelial (VE)-cadherin promoter. Lewis lung carcinoma cells were injected subcutaneously to establish tumors and to test the effect of GCV on tumor growth. In two independent transgenic lines, GCV treatment (75 mg/kg/day) resulted in a 66-71% reduction of tumor volume at day 20 postimplantation compared to wild-type mice (650 and 550 versus 1930 mm(3), P<0.02 and 0.01, respectively), whereas no significant difference was observed when vehicle alone was injected. Tumor growth inhibition was accompanied by a marked reduction in tumor vascular density (151 versus 276 vessels/mm(2), P<0.05) and an increase in tumor cell death, suggesting that tumor growth inhibition was caused by a reduction in tumor angiogenesis. Our data support the potential utility of endothelial targeting of suicide genes in cancer therapy.

Peripheral neuropathy associated with mitochondrial disorders: 8 cases and review of the literature.

Forty-three cases of peripheral neuropathy (PN) have been reported in the literature with a proven mitochondria (mt) DNA mutation, and 21 had a peripheral nerve biopsy (PNB). We studied 8 patients, 1 of whom had severe sensory PN, 3 mild PN, and 4 subclinical PN. Nerve biopsy was performed in every case; all patients showed axonal degeneration and 4 showed features of primary myelin damage. In addition, there were 2 crystalline-like inclusions in the Schwann cell cytoplasm of a patient with MERRF, and 1 in a patient with multiple deletions on the mtDNA. There are 11 cases of PNB in the literature with axonal lesions, 5 with demyelination, and 4 with mixed lesions. One PNB was not modified. A few crystalline-like inclusions were seen in 1 case of MERRF. Such inclusions were first reported in the Schwann cell cytoplasm of unmyelinated fibers in a patient with Refsum disease and were considered to be modified mitochondria. However, their mitochondrial origin remains debatable.