Antimalarial potential of xestoquinone, a protein kinase inhibitor isolated from a Vanuatu marine sponge Xestospongia sp

As part of our search for new antimalarial drugs, we have screened for inhibitors of Pfnek-1, a protein kinase of Plasmodium falciparum, in south Pacific marine sponges. On the basis of a preliminary screening, the ethanolic crude extract of a new species of Xestospongia collected in Vanuatu was selected for its promising activity. A bioassay-guided fractionation led us to isolate xestoquinone which inhibits Pfnek-1 with an IC(50) around 1 microM. Among a small panel of plasmodial protein kinases, xestoquinone showed modest protein kinase inhibitory activity toward PfPK5 and no activity toward PfPK7 and PfGSK-3. Xestoquinone showed in vitro antiplasmodial activity against a FCB1 P. falciparum strain with an IC(50) of 3 microM and a weak selectivity index (SI 7). Xestoquinone exhibited a weak in vivo activity at 5mg/kg in Plasmodium berghei NK65 infected mice and was toxic at higher doses.     

A fraction of neurofibromin interacts with PML bodies in the nucleus of the CCF astrocytoma cell line

Neurofibromatosis type 1 is a common genetic disease that causes nervous system tumors, and cognitive deficits. It is due to mutations within the NF1 gene, which encodes the Nf1 protein. Nf1 has been shown to be involved in the regulation of Ras, cAMP and actin cytoskeleton dynamics. In this study, using immunofluorescence experiments, we have shown a partial nuclear localization of Nf1 in the astrocytoma cell line: CCF and we have demonstrated that Nf1 partially colocalizes with PML (promyelocytic leukemia) nuclear bodies. A direct interaction between Nf1 and the multiprotein complex has further been demonstrated using "in situ" proximity ligation assay (PLA).     

The use of a mirror as a 'social substitute' in laboratory birds

A mirror has been shown to reduce stereotypies in horses housed singly, presumably as it may provide some sort of 'social stimulation'. We investigated here whether a mirror may have such a 'quietening effect' on birds kept in a laboratory, such as European starlings. We observed the reactions to a mirror of starlings of different sexes and with different social experiences. Females and pair-raised males seemed calmer, showing less movement and more comfort behaviour than socially and single-raised birds. The results are discussed in the light of the species' social organization and the effect of social experience. We conclude that a mirror might be a good way to reduce isolation-related stress in laboratory birds, but that sex and social experience of an individual have to be taken into account, as otherwise effects opposite to those wished for may be induced.     

NOV/CCN3 Induces Adhesion of Muscle Skeletal Cells and Cooperates with FGF2 and IGF-1 to Promote Proliferation and Survival

During mammalian development, expression of the Nephroblastoma overexpressed gene (NOV/CCN3) is tightly regulated in skeletal muscles. Ex vivo, ectopic expression of NOV blocks myogenic differentiation. NOV also supports endothelial cell adhesion and angiogenesis through interactions with integrins. Integrins play fundamental roles during myogenesis. In this study, we show that NOV mediates adhesion and spreading of myoblasts. Myoblasts adhesion to NOV does not require proteoglycans and is dependent on integrin β1, whereas spreading involves another RGD-sensitive integrin. The C-Terminal part of NOV as well as full-length is able to support adhesion of myoblasts; in addition, both increase focal-adhesion kinase (FAK) phosphorylation. Furthermore, NOV is an adhesive substrate that, combined with FGF2 or IGF-1, promotes cell specific proliferation and survival, respectively, in a better way than fibronectin. Taken together, these results identify NOV as an adhesion substrate for myoblasts which, in concert with growth factors, could play a role in the physiology of muscle cells.     

Expression of a functional C5a receptor in regenerating hepatocytes and its involvement in a proliferative signaling pathway in rat

Activation of the complement system generates the anaphylatoxin C5a whose activities are mediated through its binding to the widely expressed C5aR. C5aR mRNA and protein expressions are known to be induced in rat hepatocytes under inflammatory conditions. However, little is known about the role of the C5a/C5aR complex in liver and its involvement during a proliferative process. We have evaluated the expression of C5aR in regenerating rat hepatocytes following a partial hepatectomy and in hepatocyte cultures. C5aR induction was observed in hepatocytes from regenerating liver, as well as in normal hepatocytes under a culture-induced stress. The effect of a stimulation by a C5a agonist upon the synthesis of a growth factor/receptor pair (hepatocyte growth factor/c-Met) was also evaluated. Our data demonstrated an up-regulated expression of hepatocyte growth factor and c-Met mRNAs, but we failed to observe a direct mitogenic effect of C5a in culture. However, a significantly increased expression of cyclin E and D1mRNA levels, as well as an increased BrdU incorporation, were observed in rats given an i.v. C5a agonist injection following an 80% partial hepatectomy. These studies demonstrate for the first time that: 1) C5aR is up-regulated during liver regeneration, 2) the binding of C5a to C5aR promotes a growth response, and 3) C5aR is involved in a cell cycle signaling pathway. Taken together, these findings point to a novel role for the hepatic C5aR implicating this complement system in the context of normal or abnormal proliferative pathways.     

Cytokine profiles in peripheral, placental and cord blood in pregnant women from an area endemic for Plasmodium falciparum

During gestation, inflammatory cytokines are sometimes more abundant than growth-promoting cytokines, and via direct or indirect effects, proinflammatory cytokines lead to intrauterine growth retardation. We used an enzyme-linked immunosorbent assay to measure the concentrations of three proinflammatory cytokines, tumor necrosis factor alpha (TNF-alpha), interleukin-12 (IL-12p40), as well as interleukin-15 (IL-15) and monocyte chemotactic protein-1 (MCP-1), in plasma from peripheral, placental and cord blood of thirty pregnant Gabonese women. All of these women lived in Libreville and Lambaréné, two malaria hyperendemic areas. IL-12p40 concentrations were higher in cord blood than in placental or peripheral blood. The MCP-1 concentration was higher in placental blood, than in peripheral or cord blood. IL-15 concentrations were similar at the three sites. MCP-1 concentrations were higher in the placentas of primiparous women than in those of multiparous women. The highest concentrations were found in infected placentas. IL-15 concentrations were significantly higher in peripheral and placental plasma from uninfected women than in plasma from infected women. Strong positive correlations were found between placental and cord IL-12p40 and IL-15 plasma concentrations. Likewise, a strong positive correlation was found between IL-12p40 and MCP-1 concentrations in cord and peripheral plasma. These results suggest that placental, maternal peripheral and cord blood present different cytokine profiles in response to P. falciparum.     

The effect of antibiotic treatment on the supercooling ability of the land snail Helix aspersa (Gastropoda: Pulmonata)

The land snail Helix aspersa is a partially freezing tolerant species whose supercooling ability is limited to ca. -3 to -5 degrees C. One hundred adult snails were subjected to the following two experimental conditions: (i) a starved group, provided with water; (ii) an antibiotic-treated group that was provided with a solution containing a mixture of two antibiotics. The antibiotic group exhibited a T(c) significantly lower than the starved group (-3.94 +/- 1.32 degrees C, n = 40 and -3.07 +/- 0.99, n = 30, t test, p < 0.005). This study showed that bacteria of the gut are likely to elevate animal supercooling points. It is also the first report in which a possible ice-nucleating activity of the gut microflora in a land snail has been suggested by the action of antibiotics on the T(c).     

Activation of C-Jun N-terminal kinase is required for glutathione transferase A4 induction during oxidative stress, not during cell proliferation, in mouse hepatocytes

Expression of the mouse glutathione transferase Alpha 4 (mGSTA4) has been studied during hepatocyte isolation and in cultured hepatocytes. Transient mGSTA4 induction during liver disruption correlated to strong oxidative stress and induction of the Jun N-terminal kinase (JNK) pathway. Similarly, tumor necrosis factor alpha induced both JNK phosphorylation and mGSTA4 expression while specific JNK inhibitor JNKI1 prevented these two events and JNK activator anisomycin strongly induced mGSTA4 expression. We also found that endogenous JNK and mGSTA4 co-immunoprecipitate. A second mGSTA4 induction occurred 2 days after cell seeding concomitantly to DNA replication and was prevented by treatment with mitogen-activated protein kinase (MEK) inhibitor U0126. Our data demonstrate that mGSTA4 is strongly increased during oxidative stress possibly via JNK pathway and during proliferation via MEK/extracellular signal-regulated kinase pathway, and suggest that mGSTA4 might be an endogenous regulator of JNK activity by direct binding.