Bouchra Gharib

Imaging Experimental Cerebral Malaria In Vivo: Significant Role of Ischemic Brain Edema

The first in vivo magnetic resonance study of experimental cerebral malaria is presented. Cerebral involvement is a lethal complication of malaria. To explore the brain of susceptible mice infected with Plasmodium berghei ANKA, multimodal magnetic resonance techniques were applied (imaging, diffusion, perfusion, angiography, spectroscopy). They reveal vascular damage including blood-brain barrier disruption and hemorrhages attributable to inflammatory processes. We provide the first in vivo demonstration for blood-brain barrier breakdown in cerebral malaria. Major edema formation as well as reduced brain perfusion was detected and is accompanied by an ischemic metabolic profile with reduction of high-energy phosphates and elevated brain lactate. In addition, angiography supplies compelling evidence for major hemodynamics dysfunction. Actually, edema further worsens ischemia by compressing cerebral arteries, which subsequently leads to a collapse of the blood flow that ultimately represents the cause of death. These findings demonstrate the coexistence of inflammatory and ischemic lesions and prove the preponderant role of edema in the fatal outcome of experimental cerebral malaria. They improve our understanding of the pathogenesis of cerebral malaria and may provide the necessary noninvasive surrogate markers for quantitative monitoring of treatment.

Protection against cerebral malaria by the low-molecular-weight thiol pantethine

We report that administration of the low-molecular-weight thiol pantethine prevented the cerebral syndrome in Plasmodium berghei ANKA-infected mice. The protection was associated with an impairment of the host response to the infection, with in particular a decrease of circulating microparticles and preservation of the blood–brain barrier integrity. Parasite development was unaffected. Pantethine modulated one of the early steps of the inflammation–coagulation cascade, i.e., the transbilayer translocation of phosphatidylserine at the cell surface that we demonstrated on red blood cells and platelets. In this, pantethine mimicked the inactivation of the ATP-binding-cassette transporter A1 (ABCA1), which also prevents the cerebral syndrome in this malaria model. However, pantethine acts through a different pathway, because ABCA1 activity was unaffected by the treatment. The mechanisms of pantethine action were investigated, using the intact molecule and its constituents. The disulfide group (oxidized form) is necessary to lower the platelet response to activation by thrombin and collagen. Thio-sensitive mechanisms are also involved in the impairment of microparticle release by TNF-activated endothelial cells. In isolated cells, the effects were obtained by cystamine that lacks the pantothenic moiety of the molecule; however, the complete molecule is necessary to protect against cerebral malaria. Pantethine is well tolerated, and it has already been administered in other contexts to man with limited side effects. Therefore, trials of pantethine treatment in adjunctive therapy for severe malaria are warranted.

Infection and disease in human schistosomiasis mansoni are under distinct major gene control

INSERM U399, Immunology and Genetic of Parasitic Diseases/Laboratory of Parasitology-Mycology, Faculty of Medicine, Universite de la Mediterranee, Marseille, France Institute of Nuclear Medicine and Molecular Biology, University of Gezira, Gezira, Sudan Laboratorio De Imunologia, Faculdade de Medicina do Triangulo Mineiro, Mineiro, Brazil Alzaiem Alazihri University, Omdurman, Sudan Faculty of Medicine, University of Gezira, Gezira, Sudan INSERM U436 Paris, France

Experimental schistosomiasis, protective aspects of granulomatous reaction in the mouse liver

We show two mechanisms of liver protection by the granulomatous reaction against Schistosoma mansoni eggs entrapped in the organ. First, eosinophil peroxidase and its substrate H2O2 are released by inflammatory cells in the immediate vicinity of the parasite eggs. The efficiency of this process was demonstrated by administration of antioxidants to infected mice. The treatment, which reduces H2O2 production, significantly improved the ability of parasite eggs to hatch after collection from the liver. Secondly, we labeled the released egg antigens in liver histological sections and we found that the lattice of collagen fibers which is built around eggs appears to create a barrier preventing released compounds from diffusing freely in surrounding tissues. Together, oxidative processes and antigen containment allow the parasitized liver to cope with the dual threat posed by parasite eggs, i.e. a highly resistant chitinous eggshell and the release of toxic substances.

Ecdysteroid and juvenile hormone changes in Bombyx mori eggs, related to the initiation of diapause

We describe a method for the routine determination of changes in juvenile hormone levels in insect eggs. The hormones are first converted into their diol derivatives, then they are purified from other lipids and separated by high‐performance liquid chromatography (HPLC). The radioimmunoassay of the fractions was then determined. The method permits the simultaneous assay of ecdysteroids, and it was used for determining the hormonal changes in Bombyx eggs during the pre‐diapause development. Our major finding is that the hormonal content of eggs dramatically increased prior to the initiation of diapause. This hormonal rise included ecdysone, 20‐OH‐ecdysone and 3 juvenile hormones. The HPLC retention time of the latter corresponded to JH1 JH2 and JH3. Subsequently, the embryos entered diapause and the hormonal content of eggs was reduced to traces of ecdysteroids. These dramatic changes in juvenile hormone levels during early embryogenesis raise a number of issues which are developed in the discussion.

Pantethine Alters Lipid Composition and Cholesterol Content of Membrane Rafts, With Down-Regulation of CXCL12-Induced T Cell Migration

Pantethine, a natural low‐molecular‐weight thiol, shows a broad activity in a large range of essential cellular pathways. It has been long known as a hypolipidemic and hypocholesterolemic agent. We have recently shown that it exerts a neuroprotective action in mouse models of cerebral malaria and Parkinsons disease through multiple mechanisms. In the present study, we looked at its effects on membrane lipid rafts that serve as platforms for molecules engaged in cell activity, therefore providing a target against inappropriate cell response leading to a chronic inflammation. We found that pantethine‐treated cells showed a significant change in raft fatty acid composition and cholesterol content, with ultimate downregulation of cell adhesion, CXCL12‐driven chemotaxis, and transendothelial migration of various T cell types, including human Jurkat cell line and circulating effector T cells. The mechanisms involved include the alteration of the following: (i) CXCL12 binding to its target cells; (ii) membrane dynamics of CXCR4 and CXCR7, the two CXCL12 receptors; and (iii) cell redox status, a crucial determinant in the regulation of the chemokine system. In addition, we considered the linker for activation of T cells molecule to show that pantethine effects were associated with the displacement from the rafts of the acylated signaling molecules which had their palmitoylation level reduced.. In conclusion, the results presented here, together with previously published findings, indicate that due to its pleiotropic action, pantethine can downregulate the multifaceted process leading to pathogenic T cell activation and migration. J. Cell. Physiol. 230: 2415–2425, 2015.

Metabolic changes and inflammation in cultured astrocytes from the 5xFAD mouse model of Alzheimer's disease: Alleviation by pantethine.

Astrocytes play critical roles in central nervous system homeostasis and support of neuronal function. A better knowledge of their response may both help understand the pathophysiology of Alzheimer’s disease (AD) and implement new therapeutic strategies. We used the 5xFAD transgenic mouse model of AD (Tg thereafter) to generate astrocyte cultures and investigate the impact of the genotype on metabolic changes and astrocytes activation. Metabolomic analysis showed that Tg astrocytes exhibited changes in the glycolytic pathway and tricarboxylic acid (TCA) cycle, compared to wild type (WT) cells. Tg astrocytes displayed also a prominent basal inflammatory status, with accentuated reactivity and increased expression of the inflammatory cytokine interleukin-1 beta (IL-1β). Compensatory mechanisms were activated in Tg astrocytes, including: i) the hexose monophosphate shunt with the consequent production of reducing species; ii) the induction of hypoxia inducible factor-1 alpha (HIF-1α), known to protect against amyloid-β (Aβ) toxicity. Such events were associated with the expression by Tg astrocytes of human isoforms of both amyloid precursor protein (APP) and presenilin-1 (PS1). Similar metabolic and inflammatory changes were induced in WT astrocytes by exogenous Aβ peptide. Pantethine, the vitamin B5 precursor, known to be neuroprotective and anti-inflammatory, alleviated the pathological pattern in Tg astrocytes as well as WT astrocytes treated with Aß. In conclusion, our data enlighten the dual pathogenic/protective role of astrocytes in AD pathology and the potential protective role of pantethine.

Effect of Pantethine on Ovarian Tumor Progression and Choline Metabolism

Epithelial ovarian cancer remains the leading cause of death from gynecologic malignancy among women in developed countries. New therapeutic strategies evaluated with relevant preclinical models are urgently needed to improve survival rates. Here, we have assessed the effect of pantethine on tumor growth and metabolism using magnetic resonance imaging and high-resolution proton magnetic resonance spectroscopy (MRS) in a model of ovarian cancer. To evaluate treatment strategies, it is important to use models that closely mimic tumor growth in humans. Therefore, we used an orthotopic model of ovarian cancer where a piece of tumor tissue, derived from an ovarian tumor xenograft, is engrafted directly onto the ovary of female mice, to maintain the tumor physiological environment. Treatment with pantethine, the precursor of vitamin B5 and active moiety of coenzyme A, was started when tumors were ~100 mm3 and consisted of a daily i.p. injection of 750 mg/kg in saline. Under these conditions, no side effects were observed. High-resolution 1H MRS was performed on treated and control tumor extracts. A dual-phase extraction method based on methanol/chloroform/water was used to obtain lipid and water-soluble fractions from the tumors. We also investigated effects on metastases and ascites formation. Pantethine treatment resulted in slower tumor progression, decreased levels of phosphocholine and phosphatidylcholine, and reduced metastases and ascites occurrence. In conclusion, pantethine represents a novel potential, well-tolerated, therapeutic tool in patients with ovarian cancer. Further in vivo preclinical studies are needed to confirm the beneficial role of pantethine and to better understand its mechanism of action.

The Energy Crisis in Parkinson’s Disease: A Therapeutic Target

The energy demand of the brain is very large: it accounts for 20% of the body’s energy consumption, even though its weight is less than 2% of the total body mass. In the adult, brain energy comes primarily from glucose through oxidative glycolysis. The end product is acetyl-coenzyme A (acetyl-CoA), which enters the mitochondria and feeds into the tricarboxylic acid (TCA) cycle to produce energy in the form of reductants, such as NADH. The chemical energy of NADH is then used by the respiratory chain, or electron transport chain, to synthesize ATP (Fig. 1). Energy depletion is a major factor in the cascade of events culminating in dopaminergic neuronal death in Parkinson’s disease (PD). There are two reasons for that. First, a frequent feature of the disease, as well as of other neurodegenerative diseases, is an alteration of glucose metabolism. Second, there is a decrease of mitochondrial respiratory chain activity due to, in particular, inhibition of the electron transport system complex I (NADH-ubiquinone oxidoreductase). Complex I activity is redox-dependent and thiol-regulated; therefore its inhibition is associated with oxidative stress. Depletion of GSH, a major antioxidant and redox modulator, is observed in the substantia nigra of parkinsonian patients, as well as in the mouse MPTP model of the disease. Conversely, the restoration of GSH levels preserves complex I activity. Accordingly, the maintenance of cellular redox homeostasis by thiol agents protects against nigrostriatal toxicity. In the case of the alteration of glucose metabolism, the brain has the ability to adapt its metabolism and to increase its reliance on lipids for energy production, through fatty acid βoxidation. The process involves a mitochondrial oxido-reductase superfamily with broad substrate specificity. The penultimate step of the process is catalyzed by L-3-hydroxyacylCoA dehydrogenase (HADH II) (EC 1.1.1.35). HADH II overexpression protects against acute brain injury and chronic neurodegeneration. By-products of fatty acid β−oxidation are the ketone bodies β-hydroxybutyrate and acetoacetate. When injected into mice or rats, or administered in the form of a ketogenic diet, ketone bodies have a protective role in a broad spectrum of cerebral injuries and diseases. In the present report, we examine the brain energy metabolism, its alterations associated with PD and how fatty acid β-oxidation can compensate such impairment. Energy store boosting agents have potential therapeutic properties. Pantethine, the precursor of vitamin

Pantethine Down-Regulates Leukocyte Recruitment and Inflammatory Parameters in a Mouse Model of Allergic Airway Inflammation

Background Migration of leukocytes into airways is the hallmark of allergic asthma. The aim of this study was to target the pathological process using pantethine, a pleiotropic natural compound which has been recently shown to down-regulate chemokine-driven T cell migration. Material/Methods Mice were sensitized to the Leishmania LACK antigen, then treated or not treated with pantethine and exposed to LACK or saline aerosol. After sacrifice of the animals, cells in the bronchoalveolar lavage were analyzed and inflammatory parameters were determined to evaluate inflammation seriousness. Results As compared to untreated animals, pantethine-treated animals displayed a moderated response to the allergen, as documented by decreased infiltration of inflammatory cells (all types), in addition to reduced levels of lung Th2 cytokines and circulating LACK-specific IgE. Conclusions These data reveal the potential therapeutic importance of pantethine to moderate allergic asthma pathology. The compound has been previously shown to exert a broad range of protective activity in animals and in humans, with few or no adverse effects.