Laurence Lempereur

Nerve growth factor–endothelial cell interaction leads to angiogenesis in vitro and in vivo

Nerve growth factor (NGF) has important functions during embryonic development and on various tissues and organs under normal and pathological conditions during the extrauterine life. RT‐PCR analysis and immunological methods demonstrate that human umbilical vein endothelial cells (HUVECs) express the NGF receptors trkANGFR and p75NTR. NGF treatment caused a rapid phosphorylation of trkANGFR in HUVECs, determining a parallel increase of phosphorylated ERK1/2. Accordingly, NGF induced a significant increase in HUVEC proliferation that was abolished by the trkANGFR inhibitor K252a. Also, HUVECs express significant levels of NGF under standard culture conditions that were up‐regulated during serum starvation. Endogenous NGF was responsible for the basal levels of trkANGFR and ERK1/2 phosphorylation observed in untreated HUVEC cultures. Finally, NGF exerted a potent, direct, angiogenic activity in vivo when delivered onto the chorioallantoic membrane of the chicken embryo. The data indicate that NGF may play an important role in blood vessel formation in the nervous system and in several pathological processes, including tumors and inflammatory diseases. Unraveling mechanisms of NGF‐dependent angiogenesis could provide valuable tools for novel therapeutic approaches in antiangiogenic therapy.

The role of antioxidant supplement in immune system, neoplastic, and neurodegenerative disorders: a point of view for an assessment of the risk/benefit profile

This review will discuss some issues related to the risk/benefit profile of the use of dietary antioxidants. Thus, recent progress regarding the potential benefit of dietary antioxidants in the treatment of chronic diseases with a special focus on immune system and neurodegenerative disorders will be discussed here. It is well established that reactive oxygen species (ROS) play an important role in the etiology of numerous diseases, such as atherosclerosis, diabetes and cancer. Among the physiological defense system of the cell, the relevance of antioxidant molecules, such as glutathione and vitamins is quite well established. Recently, the interest of researchers has, for example, been conveyed on antioxidant enzyme systems, such as the heme oxygenase/biliverdin reductase system, which appears modulated by dietary antioxidant molecules, including polyphenols and beta-carotene. These systems possibly counteract oxidative damage very efficiently and finally modulate the activity of oxidative phenomena occurring, for instance, during pathophysiological processes. Although evidence shows that antioxidant treatment results in cytoprotection, the potential clinical benefit deriving from both nutritional and supplemental antioxidants is still under wide debate. In this line, the inappropriate assumption of some lipophylic vitamins has been associated with increased incidence of cancer rather than with beneficial effects.

Red wine micronutrients as protective agents in Alzheimer-like induced insult.

Plant extract micronutrients are commonly added to diets for health and prevention of degenerative disease. However, there are barriers to the introduction of these products as antioxidant therapies in counteracting chronic human diseases, probably because the molecular bases of their therapeutic potential are poorly clarified. The present study was designed to evaluate the possible protective effect of combined micronutrients present in black grape skin on toxicity induced by 25-35 beta-amyloid peptid or by serum of Alzheimers disease patients, in human umbilical vein endothelial cells (HUVECs). The hypothesis was tested by examining the results of lactic dehydrogenase (LDH) release to estimate cytoplasmic membrane breakdown; activity of mitochondrial complexes, reactive oxygen species (ROS) production and malonyl dialdehyde (MDA) levels as markers of oxidative stress induction and COMET assay to evaluate DNA fragmentation. The results demonstrate that black grape skin extract reduces the ROS production, protects the cellular membrane from oxidative damage, and consequently prevents DNA fragmentation. The experimental results suggest that this natural compound may be used to ameliorate the progression of pathology in AD disease therapy.

Endocannabinoids inhibit release of nerve growth factor by inflammation-activated mast cells.

Nerve growth factor (NGF) is a pleiotropic member of the neurotrophin family. Beside its neuronal effects, NGF plays a role in various processes, including angiogenesis. Mast cells release NGF and are among elements contributing to angiogenesis, a process regulated by arrays of factors, including the inhibitory cannabinoids. The possible inhibitory role of cannabinoids on mast cell-related NGF mitogenic effect on endothelial cells was then investigated. Human mastocytic cells HMC-1, challenged with PMA to yield release of NGF, were preincubated with the endocannabinoid PEA. Then, conditioned media were added to HUVEC cultures. PMA-activated HMC-1 cells released substantial amounts of NGF, whereas PEA inhibited PMA-induced NGF release. HUVEC proliferation increased after treatment with media from activated HMC-1 cells, while was reduced with media from HMC-1 cells treated with PEA. To characterize receptors mediating such effects of PEA, RT-PCR and western blot analysis were performed on HMC-1 cells. None of the two cannabinoid CB1 and CB2 receptors was expressed by HMC-1 cells, which on the other hand expressed the orphan receptor GPR55. PEA was ineffective in inhibiting NGF release from HMC-1 cells treated with PMA and transfected with positive GPR55 RNAi, whereas it induced significant reduction of NGF in cells transfected with the corresponding negative control RNAi. Results indicate that NGF released from inflammatory mast cells induces angiogenesis. Cannabinoids attenuate such pro-angiogenic effects of NGF. Finally, cannabinoids could be considered for antiangiogenic treatment in disorders characterized by prominent inflammation.

Divergent effects of corticotropin releasing hormone on endothelial cell nitric oxide synthase are associated with different expression of CRH type 1 and 2 receptors

Endothelium is a target for an array of factors involved in inflammation. Endothelial cells express receptors for CRH, a neuropeptide produced during inflammation. We report both the concentration‐dependent inhibitory effect of CRH upon cytokine‐stimulated nitrite release by H5V murine endothelioma cells, and its stimulatory one in HUVEC cells. Western blot analysis showed that CRH inhibits cytokine‐stimulated iNOS protein in H5V cells, and, instead, potentiated it in HUVEC cells. H5V cells expressed both CRH receptors (CRH‐R1 and R2) mRNAs, whereas HUVEC cells expressed the CRH‐R2 mRNA solely. CRH increased medium nitrites and iNOS protein expression in H5V cells pretreated with the selective CRH‐R1 antagonist CP 154,526. However, the selective CRH‐R2 antagonist anti‐Svg‐30 failed to produce similar effects. In fact, anti‐Svg‐30 inhibited CRH‐induced increase of nitrite release and iNOS expression in HUVEC cells. Our results confirm the activating role of CRH on endothelial cells, although it suggests its possible inhibitory role in the late phase of the inflammatory response. NO‐mediated effects of CRH on endothelial cells could be exploited in therapeutic strategies related to inflammatory and/or degenerative diseases.

Gastroprotective effect of adrenomedullin administered subcutaneously in the rat

Subcutaneous injections of adrenomedullin prevented reserpine-induced gastric mucosal damage in a dose-dependent manner (1-1000 ng/kg), but did not interfere with the lesions produced by ethanol administration. In pylorus-ligated rats adrenomedullin significantly reduced gastric volume, total and free acid output as well as ulcer formation. The gastroprotective activity of adrenomedullin was not present in rats pretreated with cysteamine. These results suggest that adrenomedullin exerts its antiulcer effect, when it is administered subcutaneously (s.c.), probably by a mechanism which involves somatostatin related transmission.

Protective effects of the sigma agonist pre-084 in the rat retina

Aim: With the rationale that amyloid beta (AB) is toxic to the retina, we here assessed the role of TRAIL, a mediator of AB toxicity and related signal transduction, in a rat model. We also attempted to demonstrate possible protective effects of &sgr;1 receptor agonists in these processes. Methods: AB and the &sgr;1 receptor agonist Pre-084 were injected intravitreally in the anaesthetised rat. In additional experiments, the &sgr;1 receptor antagonist BD1047 was administered to assess specificity of the effects of Pre-084. Western blot analysis was performed on retinas to evaluate the expression of TRAIL and TRAIL receptors in the retina, as well as of Bax and phosphorylated JNK following the different treatments. Lactic dehydrogenase (LDH) levels were measured as a cytotoxicity marker. Results: All TRAIL receptors were expressed in rat retinas. Intravitreal injection of AB in rat eyes induced overexpression of TRAIL and the proapoptotic protein Bax, as well as phosphorylation of JNK. All these effects of AB were abrogated by pretreatment with the &sgr;1 receptor agonist Pre-084. Conclusions: It is likely that TRAIL is a mediator of AB effects on the retina. In light of their specific inhibitory effects upon TRAIL expression, it is plausible to hypothesise that &sgr;1 receptor agonists could represent potential pharmacological tools for restraining AB related retinal damage.

Growth hormone protects human lymphocytes from irradiation-induced cell death.

Undesired effects of cancer radiotherapy mainly affect the hematopoietic system. Growth hormone (GH) participates in both hematopoiesis and modulation of the immune response. We report both r‐hGH cell death prevention and restoration of secretory capacities of irradiated human peripheral blood lymphocytes (PBL) in vitro. r‐hGH induced cell survival and increased proliferation of irradiated cells. Western blot analysis indicated that these effects of GH were paralleled by increased expression of the antiapoptotic protein Bcl‐2. r‐hGH restored mitogen‐stimulated release of IL‐2 by PBL. Preincubation of irradiated lymphocytes with the growth hormone receptor (GHR) antagonists B2036 and G120 K abrogated r‐hGH‐dependent IL‐2 release. These results demonstrate that r‐hGH protects irradiated PBL from death in a specific, receptor‐mediated manner. Such effect of r‐hGH on PBL involves activation of the antiapoptotic gene bcl‐2 and prevention of cell death, associated with preserved functional cell capacity. Finally, potential use of GH as an immunopotentiating agent could be envisioned during radiation therapy of cancer.

Trail interacts redundantly with nitric oxide in rat astrocytes: Potential contribution to neurodegenerative processes

The proapoptotic cytokine TRAIL has been shown to enhance amyloid-beta-dependent neurotoxicity. Here are reported interactions between TRAIL and nitric oxide (NO) in cultured rat astrocytes in vitro. Rat astrocytes expressed all TRAIL receptor mRNAs and proteins. However, TRAIL failed in inducing apoptosis of astrocytes, whereas these cells released substantial amounts of nitrites. A TRAIL-neutralizing antibody was able to prevent LPS-induced iNOS expression in astrocytes. Interestingly, TRAIL induced its own expression in astrocytes. These data suggest that redundancy between TRAIL and NO in astrocytes could be fueling neuronal damage/death processes, potentially uncovering novel molecular targets for the treatment of neurodegenerative disorders.

Behavioral and neurochemical effects of dopaminergic drugs in models of brain injury.

The dopaminergic drugs, ropinirole and dihydroergocryptine (DHECP) were injected subcutaneously (s.c.) at doses of 0.5 and 1 mg/kg/day for 7 days into male rats of the Sprague-Dawley strain. The drug pretreatment reverted amnesia induced in rats by hypobaric hypopxia and tested in active and passive avoidance tasks. Furthermore, a partial restoration of memory retention was found in animals with a 2-month brain occlusive ischemia induced by manipulation of the four major arteries of the brain. No major changes were found in spontaneous motor activity, but drug treatment increased ambulation of animals subjected to acute or chronic experimental manipulation. In a model of kainate-induced epilepsy, ropinirole or DHECP did not affect seizure parameters, but reduced mortality rate. At the end of behavioral procedures, in all animals subjected to hypobaric hypoxia or to brain occlusive ischemia glutathione redox index (glutathione reduced/glutathione oxidized ratio) was measured in the frontal cortex, striatum and hippocampus. It was found that experimental models of brain injury were followed by a decrease of reduced glutathione content in all brain areas. The glutathione redox index was augmented by ropinirole or DHECP treatment in all brain areas. These behavioral and neurochemical findings suggest that ropinirole and DHECP may exert either protective activity (as found in animals pretreated with these drugs and exposed to hypobaric hypoxia) or reversal of brain injury (as found in animals treated after two-month occlusive brain ischemia). Thus, both drugs may be studied as therapeutic agents in brain injuries of various origin.