Mitochondrial complex II participates in normoxic and hypoxic regulation of α-keto acids in the murine heart

α-Keto acids (α-KAs) are not just metabolic intermediates but are also powerful modulators of different cellular pathways. Here, we tested the hypothesis that α-KA concentrations are regulated by complex II (succinate dehydrogenase=SDH), which represents an intersection between the mitochondrial respiratory chain for which an important function in cardiopulmonary oxygen sensing has been demonstrated, and the Krebs cycle, a central element of α-KA metabolism. SDH subunit D heterozygous (SDHD(+/-)) and wild-type (WT) mice were housed at normoxia or hypoxia (10% O(2)) for 4 days or 3 weeks, and right ventricular pressure, right ventricle/(left ventricle+septum) ratio, cardiomyocyte ultrastructure, pulmonary vascular remodelling, ventricular complex II subunit expression, SDH activity and α-KA concentrations were analysed. In both strains, hypoxia induced increases in right ventricular pressure and enhanced muscularization of distal pulmonary arteries. Right ventricular hypertrophy was less severe in SDHD(+/-) mice although the cardiomyocyte ultrastructure and mitochondrial morphometric parameters were unchanged. Protein amounts of SDHA, SDHB and SDHC, and SDH activity were distinctly reduced in SDHD(+/-) mice. In normoxic SDHD(+/-) mice, α-ketoisocaproate concentration was lowered to 50% as compared to WT animals. Right/left ventricular concentration differences and the hypoxia-induced decline in individual α-KAs were less pronounced in SDHD(+/-) animals indicating that mitochondrial complex II participates in the adjustment of cardiac α-KA concentrations both under normoxic and hypoxic conditions. These characteristics are not related to the hemodynamic consequences of hypoxia-induced pulmonary vascular remodelling, since its extent and right ventricular pressure were not affected in SDHD(+/-) mice albeit right ventricular hypertrophy was attenuated.     

Spontaneous generation of mammalian prions

Prions are transmissible agents that cause lethal neurodegeneration in humans and other mammals. Prions bind avidly to metal surfaces such as steel wires and, when surface-bound, can initiate infection of brain or cultured cells with remarkable efficiency. While investigating the properties of metal-bound prions by using the scrapie cell assay to measure infectivity, we observed, at low frequency, positive assay results in control groups in which metal wires had been coated with uninfected mouse brain homogenate. This phenomenon proved to be reproducible in rigorous and exhaustive control experiments designed to exclude prion contamination. The infectivity generated in cell culture could be readily transferred to mice and had strain characteristics distinct from the mouse-adapted prion strains used in the laboratory. The apparent ”spontaneous generation” of prions from normal brain tissue could result if the metal surface, possibly with bound cofactors, catalyzed de novo formation of prions from normal cellular prion protein. Alternatively, if prions were naturally present in the brain at levels not detectable by conventional methods, metal surfaces might concentrate them to the extent that they become quantifiable by the scrapie cell assay.     

PATHOGENESIS OF EXPERIMENTAL SHOCK : IV. STUDIES ON LYSOSOMES IN NORMAL AND TOLERANT ANIMALS SUBJECTED TO LETHAL TRAUMA AND ENDOTOXEMIA

Fatal shock was produced in animals by drum trauma, temporary occlusion of the superior mesenteric artery, and bacterial endotoxin. Measurements were made of release of beta glucuronidase and cathepsins from the large granule fractions of livers, and of levels of circulating beta glucuronidase and acid phosphatase in these animals. Experiments were also carried out with animals rendered tolerant by previous exposure to sublethal amounts of trauma or by pretreatment with cortisone. The results show that release of beta glucuronidase and cathepsins from the large granule fraction of liver was increased during traumatic and endotoxin shock in the rat. Similarly, circulating levels of acid phosphatase and beta glucuronidase were increased during traumatic shock in rats and rabbits, and during endotoxin shock in rats. The data also indicate that tolerance to traumatic injury, induced by prior conditioning, prevented the increase in levels of circulating acid phosphatase normally observed after stress, and may have been associated with an increased stability of hepatic lysosomal particles. In addition, cortisone, which appears to "stabilize" hepatic lysosomes in vivo, also reduced the increase in plasma acid phosphatase brought about by endotoxin and trauma. From the foregoing observations, it is suggested that: (a) Disruption of lysosomes and release of their contained enzymes in free, active form may occur in liver and intestine of shocked animals. (b) The activation of lysosomal hydrolases within cells and their release into the circulation may play an important role in exacerbating tissue injury and accelerating the development of irreversibility during shock. (c) The increased stability of lysosomes of tolerant and of cortisone-treated animals may constitute an important component of the resistance of these animals to shock.     

Transgene-driven expression of the Doppel protein in Purkinje cells causes Purkinje cell degeneration and motor impairment

The Doppel (Dpl) and Prion (PrP) proteins show 25% sequence identity and share several structural features with only minor differences. Dpl shows a PrP-like fold of its C-terminal globular domain and lacks the flexible N-terminal tail. The physiological functions of both proteins are unknown. However, ubiquitous Dpl overexpression in the brain of PrP knockout mice correlated with ataxia and Purkinje cell degeneration in the cerebellum. Interestingly, a similar phenotype was reported in transgenic mice expressing an N-terminally truncated PrP (DeltaPrP) in Purkinje cells by the L7 promoter (TgL7-DeltaPrP). Coexpression of full-length PrP rescued both the neurological syndromes caused by either Dpl or DeltaPrP. To evaluate whether the two proteins caused cerebellar neurodegeneration by the same mechanism, we generated transgenic mice selectively expressing Dpl in Purkinje cells by the same L7 promoter. Such mice showed ataxia and Purkinje cell loss that depended on the level of Dpl expression. Interestingly, the effects of high levels of Dpl were not counterbalanced by the presence of two Prnp alleles. By contrast, PrP coexpression was sufficient to abrogate motor impairment and to delay the neurodegenerative process caused by moderate level of Dpl. A similar situation was reported for the corresponding TgL7-DeltaPrP mice supporting the concept that Dpl and DeltaPrP cause cell death, possibly by interfering with a common signaling cascade essential for cell survival.     

Heparanase-neutralizing antibodies attenuate lymphoma tumor growth and metastasis

Heparanase is an endoglycosidase that cleaves heparan sulfate side chains of proteoglycans, resulting in disassembly of the extracellular matrix underlying endothelial and epithelial cells and associating with enhanced cell invasion and metastasis. Heparanase expression is induced in carcinomas and sarcomas, often associating with enhanced tumor metastasis and poor prognosis. In contrast, the function of heparanase in hematological malignancies (except myeloma) was not investigated in depth. Here, we provide evidence that heparanase is expressed by human follicular and diffused non-Hodgkin''s B-lymphomas, and that heparanase inhibitors restrain the growth of tumor xenografts produced by lymphoma cell lines. Furthermore, we describe, for the first time to our knowledge, the development and characterization of heparanase-neutralizing monoclonal antibodies that inhibit cell invasion and tumor metastasis, the hallmark of heparanase activity. Using luciferase-labeled Raji lymphoma cells, we show that the heparanase-neutralizing monoclonal antibodies profoundly inhibit tumor load in the mouse bones, associating with reduced cell proliferation and angiogenesis. Notably, we found that Raji cells lack intrinsic heparanase activity, but tumor xenografts produced by this cell line exhibit typical heparanase activity, likely contributed by host cells composing the tumor microenvironment. Thus, the neutralizing monoclonal antibodies attenuate lymphoma growth by targeting heparanase in the tumor microenvironment.Heparanase is an endo-β-d-glucuronidase capable of cleaving heparan sulfate (HS) side chains at a limited number of sites, releasing saccharide products with appreciable size (4–7 kDa) and biological potency. Enzymatic degradation of HS leads to disassembly of the extracellular matrix (ECM) and correlates with the metastatic potential of tumor-derived cells, attributed to enhanced cell dissemination as a consequence of HS cleavage and remodeling of the ECM and basement membrane underlying epithelial and endothelial cells (1, 2). Heparanase expression is induced in human cancer, most often associating with reduced patients’ survival postoperation, increased tumor metastasis, and higher vessel density (3–5). In addition, heparanase up-regulation is associated with tumors larger in size (3, 5). Likewise, heparanase over-expression enhanced (6, 7), whereas local delivery of anti-heparanase siRNA inhibited (8), the growth of tumor xenografts. These results imply that heparanase function is not limited to tumor metastasis but is engaged in progression of the primary lesion, thus critically supporting the intimate involvement of heparanase in tumor progression and encouraging the development of heparanase inhibitors as anticancer therapeutics (9–12). As a consequence, heparanase inhibitors are currently evaluated in phase 1 clinical trials (13).Heparanase activity is similarly implicated in the progression of multiple myeloma (14–16), but its significance in other hematologic malignancies has not yet been characterized. Lymphomas are a heterogeneous group of cancers that arise from developing lymphocytes and produce tumors predominantly in lymphoid structures (i.e., bone marrow), but also in extranodal tissues. Collectively, lymphomas constitute the fifth most common cancer in North America, with more than 90% of the patients being affected by lymphomas of B-cell origin (17). Despite overall improvements in outcomes of lymphoma, ∼30–40% of patients have disease that is either refractory or relapses after standard therapy (18). Therefore, a better understanding of the molecular pathobiology of lymphomas is needed for the development of new therapeutic approaches. Here, we provide evidence that heparanase is expressed by B-lymphomas and that heparanase inhibitors restrain tumor growth. Furthermore, we describe the development of novel heparanase-neutralizing monoclonal antibodies (mAbs) that attenuate lymphoma growth by targeting heparanase in the tumor microenvironment.     

Antiremodeling effects of iloprost and the dual-selective phosphodiesterase 3/4 inhibitor tolafentrine in chronic experimental pulmonary hypertension

Severe pulmonary hypertension is a disabling disease with high mortality. We investigated acute and chronic effects of iloprost, a long-acting prostacyclin analogue, and the dual-selective phosphodiesterase 3/4 inhibitor tolafentrine in monocrotaline-induced pulmonary hypertension in rats. Twenty-eight and 42 days after administration of the alkaloid, right ventricular systolic pressure increased from 25.8+/-2.0 to 62.9+/-3.4 and 70.5+/-7.4 mm Hg, with concomitant decline in cardiac index, central venous oxygen saturation, and arterial oxygenation. Marked right heart hypertrophy was demonstrated by the strongly elevated ratio of right ventricle/left ventricle plus septum weight, and massive thickening of the precapillary artery smooth muscle layer was shown histologically. Western blot analysis demonstrated increased levels of matrix metalloproteinases (MMPs) -2 and -9 and increased gelatinolytic activities in isolated pulmonary arteries. In these animals, both intravenous iloprost and tolafentrine displayed characteristic features of pulmonary vasodilators. When chronically infused from days 14 to 28, both agents significantly attenuated all monocrotaline-induced hemodynamic and gas exchange abnormalities as well as right heart hypertrophy. Full normalization of all variables including right ventricle size was achieved on combined administration of both agents during this period. This was also true for MMP-2 and MMP-9 expression and activity. Moreover, when iloprost plus tolafentrine was used for late therapeutic intervention, with infusion from days 28 to 42 after full establishment of severe pulmonary hypertension and cor pulmonale, hemodynamic, gas exchange, and cardiac and pulmonary vascular remodeling changes were significantly reversed. We conclude that the combined administration of iloprost and a dual-selective phosphodiesterase 3/4 inhibitor prevents and reverses the development of pulmonary hypertension and cor pulmonale in response to monocrotaline in rats. This regimen may therefore offer a possible antiremodeling therapy in severe pulmonary hypertension.     

B lymphocyte-restricted expression of prion protein does not enable prion replication in prion protein knockout mice

Prion replication in spleen and neuroinvasion after i.p. inoculation of mice is impaired in forms of immunodeficiency where mature B lymphocytes are lacking. In spleens of wild-type mice, infectivity is associated with B and T lymphocytes and stroma but not with circulating lymphocytes. We generated transgenic prion protein knockout mice overexpressing prion protein in B lymphocytes and found that they failed to accumulate prions in spleen after i.p. inoculation. We conclude that splenic B lymphocytes are not prion-replication competent and that they acquire prions from other cells, most likely follicular dendritic cells with which they closely associate and whose maturation depends on them.     

Differential impact of ultrasonically nebulized versus tracheal-instilled surfactant on ventilation-perfusion (VA/Q) mismatch in a model of acute lung injury

In a model of acute lung injury, established by saline lavage of isolated perfused rabbit lungs, the effect of ultrasonic surfactant nebulization on gas exchange was compared with that of tracheal instillation, assessed by the multiple inert gas elimination technique (MIGET). Ultrasonic aerosolization provided particles with a mass median aerodynamic diameter of 4.5 microm (geometric SD, 2.3), the pulmonary deposition of which was monitored on-line by a laserphotometric technique. Under baseline conditions, a narrow unimodal distribution of ventilation and perfusion with shunt-flow ranging below 2% and absence of perfusion of low V A/Q (0.01 < V A/Q < 0.1) areas was noted throughout. This physiological V A/Q matching was not affected by lung deposition of 8.6 mg surfactant/kg body weight (bw), forwarded by 1 h ultrasonic nebulization. In contrast, tracheal bolus injection of 80 mg/ kg bw surfactant in control lungs provoked the appearance of low V A/Q areas (maximum approximately 13% of perfusion) and shunt flow (4 to 6%), in addition to marked ventilation-perfusion mismatch (broadening of perfusion and ventilation distribution) in the midrange V A/Q regions. The saline lavage procedure caused progressive development of shunt flow ( approximately 22%) and perfusion of low V A/Q areas ( approximately 7%), associated with severe V A/Q mismatch. "Rescue" tracheal instillation of 80 mg/kg bw surfactant in lavaged lungs reduced the shunt-flow to approximately 4%, but increased the perfusion of low V A/Q areas to 10 to 14%; V A/Q mismatch in the midrange V A/Q regions was not improved. Ultrasonic deposition of 8.8 mg surfactant/kg bw in the injured lungs reduced the shunt flow to approximately 7% and the perfusion of low V A/Q areas to < 2%, coincident with improvement of V A/Q matching in the midrange V A/Q areas. We conclude that low doses of ultrasonically delivered natural surfactant are similarly effective as "conventional" doses of tracheal-instilled surfactant in reducing shunt flow in an acute lung injury model, but exert more advantageous effects on ventilation perfusion matching.     

Membrane perturbation: studies employing a calcium-sensitive dye, arsenazo III, in liposomes.

A metallochromic dye, arsenazo III [2,7-bis-(2-arsonophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid], has been incorporated into the aquenous interspaces of multilamellar liposomes. multilamellar liposomes. Addition of Ca produced no shift in the absorbance spectrum of dye captured by liposomes, whereas disruption of liposomes by Triton X-100, followed by Ca, produced the spectrum chracteristic of the dye-Ca complex: evidence of latency. Addition of excess ethyleneglycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) reversed the spectal shift. Differences between spectra obtained in this sequence yielded dye efflus. To measure Ca efflux, difference spectra (+/-EGTA) were obtained from cationic liposomes containing Ca after detergent lysis (sensitivity less than 10 mmol/ml). Since liposomes were impermeable either to dye or Ca until perturbed, it was possible to test a variety of membrane-active steroids (diethylstilbesterol, deoxycorticosterone, etiocholanolone) for their capacity to provoke dye efflux from liposomes; preincorporation of cortisol stablized liposomes against dye leak. Immunoglobulin-coated liposomes containing dye were taken up by phagocytes of Mustelus canis, and phagocytic vacuoles stained red-purple after ingestions. Liposomes containing the calcium-sensitive dye constitute a simple, accurate means for determining membrane perturbation and Ca fluxes; their uptake by cells or organelles remains to be exploited further.