The mechanisms of inflammation in gout and pseudogout (CPP-induced arthritis).

Recent advances have stimulated new interest in the area of crystal arthritis, as microcrystals can be considered to be endogenous "danger signals" and are potent stimulators of immune as well as non-immune cells. The best known microcrystals include urate (MSU), and calcium pyrophosphate (CPP) crystals, associated with gout and pseudogout, respectively. Acute inflammation is the hallmark of the acute tissue reaction to crystals in both gout and pseudogout. The mechanisms leading to joint inflammation in these diseases involve first crystal formation and subsequent coating with serum proteins. Crystals can then interact with plasma cell membrane, either directly or via membrane receptors, leading to NLRP3 activation, proteolytic cleavage and maturation of pro-interleukin-1β (pro-IL1β) and secretion of mature IL1β. Once released, this cytokine orchestrates a series of events leading to endothelial cell activation and neutrophil recruitment. Ultimately, gout resolution involves several mechanisms including monocyte differentiation into macrophage, clearance of apoptotic neutrophils by macrophages, production of Transforming Growth Factor (TGF-β) and modification of protein coating on the crystal surface. This review will examine these different steps.

Mechanisms of B cell survival induced by BAFF, APRIL and their receptors

RESUME : BAFF est un membre de 1a famille du TNF qui contrôle l'homéostasie des lymphocytes B. BAFF lie les récepteurs TACI, BCMA et BAFF-R sur les cellules B, tandis qu'APRIL, son proche homologue, lie seulement TACI et BCMA. BAFF et APRIL sont des protéines transmembranaires pouvant -être relâchées sous forme de cytokines trimériques solubles suite à un clivage protéolytique. Le BAFF soluble peut s'assembler en 60-mère. Les rôles physiologiques des BAFF membranaires et solubles sont inconnnus. Nous avons étudié la capacité de diverses formes de BAFF et APRIL à activer différents récepteurs. BAFF-R répond à toutes les formes dé BAFF, tandis que TACI nécessite du BAFF ou de l'APRIL membranaire ou oligomérisé pour être activé et pour transmettre des signaux de survie dans les lymphocytes B primaires. TACI ne répond pas aux ligands trimériques bien qu'il puisse les lier. TACI est essentiel pour la réponse humorale aux antigènes présentant des épitoges répétitifs, une réponse qui est indépendante des lymphocytes T (réponse TI-2). Des souris exprimant moins de BAFF ont un pourcentage modérément réduit de lymphocytes B et leur réponse TI-2 est atténuée. Par contre, des souris qui n'expriment que du BAFF membranaire ont encore moins de cellules B mais répondent efficacement aux antigènes TI-2. Ces résultats suggèrent que le BAFF soluble est impliqué dans le maintien de la population des lymphocytes B, alors que le BAFF membranaire peut activer TACI lors d'are réponse TI-2. Le BAFF 60-mère est un autre activateur potentiel de TACI in vivo. Le BAFF 60-mère existe dans des surnageants de cellules productrices de BAFF mais n'est pas détecté dans le plasma de souris saines, même lorsqu'elles présentent des niveaux élevés de BAFF. BAFF 60-mère est néanmoins présent dans le plasma de souris transgéniques pour BAFF et de souris déficientes en TACI. Comme ces deux lignées présentent des signes d'autoimmunité, ces résultats suggèrent que la présence de BAFF 60-mère pourrait être liée à des conditions pathologiques. Summary : The TNF family ligand BAFF is essential for B cell homeostasis. BAFF binds to the receptors TACI, BCMA and BAFF-R on B cells, whereas its close homolog APRIL binds to TACI and BCMA only. BAFF and APRIL are transmembrane proteins, which can be proteolytically processed to release trimeric soluble cytokines. Soluble BAFF 3-mer can further assemble in a 60-mer. The physiological roles of membrane-bound and soluble BAFF are unknown. We studied the ability of various forms of BAFF and APRIL to signal through different receptors. BAFF-R responded to all forms of BAFF, but TACI required membrane-bound, cross-licked or oligomeric BAFF or APRIL in order to transmit productive signals in primary B cells. TACI was unresponsive to trimeric ligands, although it could bind them. TACI is essential for T-cell independent antibody responses to antigens with repetitive epitopes (TI-2 responses). Mice expressing lower than normal levels of BAFF displayed a moderate B cell reduction and impaired TI-2 responses, whereas mice expressing membrane-bound BAFF displayed severe B cell reduction, but unimpaired TI-2 responses. These results suggest that processed BAFF is involved in the maintenance of the B cell pool and that membrane-bound BAFF can activate TACI during T-cell independent humoral responses. BAFF 60-mer is another potential activator of TACI in vivo. BAFF 60-mer was detected in the supernatant of BAFF-producing cells, but not in the plasma of healthy mice with either norma1 or elevated BAFF levels. It was however present in sera of BAFF transgenic mice and TACI-/- mice, both of which suffer from autoimmunity, suggesting that GAFF 60-mer may be linked to pathogenic conditions.

Programmed cell death in Trypanosoma cruzi induced by Bothrops jararaca venom

Cells die through a programmed process or accidental death, know as apoptosis or necrosis, respectively. Bothrops jararaca is a snake whose venom inhibits the growth of Trypanosoma cruzi epimastigote forms causing mitochondrion swelling and cell death. The aim of the present work was to determine the type of death induced in epimastigotes of T. cruzi by this venom. Parasite growth was inhibited after venom treatment, and 50% growth inhibition was obtained with 10 µg/ml. Ultrastructural observations confirmed mitochondrion swelling and kinetoplast disorganization. Furthermore, cytoplasmic condensation, loss of mitochondrion membrane potential, time-dependent increase in phosphatidylserine exposure at the outer leaflet plasma membrane followed by permeabilization, activation of caspase like protein and DNA fragmentation were observed in epimastigotes throughout a 24 h period of venom treatment. Taken together, these results indicate that the stress induced in epimastigote by this venom, triggers a programmed cell death process, similar to metazoan apoptosis, which leads to parasite death.

Neuroendocrine characterization and anorexigenic effects of telmisartan in diet- and glitazone-induced weight gain.

Telmisartan is an angiotensin II receptor blocker with peroxisome proliferator-activated receptor-gamma agonistic properties. Telmisartan prevents weight gain and decreases food intake in models of obesity and in glitazone-treated rodents. This study further investigates the influence of telmisartan and pioglitazone and their association on weight gain and body composition by examining their influence on neuroendocrine mediators involved in food intake. Male C57/Black 6 mice were fed a high-fat diet, weight matched, and randomized in 4 treatment groups: vehicle, pioglitazone, telmisartan, and pioglitazone-telmisartan. Weight gain, food and water intake, body composition, plasma leptin levels, and the hypothalamic expression of neuroendocrine mediators were analyzed. Additional studies were performed with irbesartan and in angiotensin II 1(A) receptor-knockout mice. Telmisartan abolished weight and fat gain in vehicle- and pioglitazone-treated mice while decreasing food intake, the hypothalamic expression of the agouti-related protein, and plasma leptin levels. Modifications in neuropeptide Y and proopiomelanocortin were not consistent with changes in food intake. The effects on weight gain and expression of the agouti-related protein were intermediate with irbesartan. The effects of telmisartan on weight gain were even more pronounced in angiotensin II 1(A) receptor-knockout mice. This study confirms the anorexigenic effects of telmisartan in mice fed a high-fat diet and suggests for the first time a functional role of telmisartan on hypothalamic orexigenic agouti-related protein regulation. These anorexigenic properties abolish both weight gain and body composition modifications in fat-fed and glitazone-treated mice. The anorexigenic properties are independent from the angiotensin II 1(A) receptor.

Moderate exercise blunts oxidative stress induced by normobaric hypoxic confinement

PURPOSE: Both acute hypoxia and physical exercise are known to increase oxidative stress. This randomized prospective trial investigated whether the addition of moderate exercise can alter oxidative stress induced by continuous hypoxic exposure. METHODS: Fourteen male participants were confined to 10-d continuous normobaric hypoxia (FIO2 = 0.139 +/- 0.003, PIO2 = 88.2 +/- 0.6 mm Hg, approximately 4000-m simulated altitude) either with (HCE, n = 8, two training sessions per day at 50% of hypoxic maximal aerobic power) or without exercise (HCS, n = 6). Plasma levels of oxidative stress markers (advanced oxidation protein products [AOPP], nitrotyrosine, and malondialdehyde), antioxidant markers (ferric-reducing antioxidant power, superoxide dismutase, glutathione peroxidase, and catalase), nitric oxide end-products, and erythropoietin were measured before the exposure (Pre), after the first 24 h of exposure (D1), after the exposure (Post) and after the 24-h reoxygenation (Post + 1). In addition, graded exercise test in hypoxia was performed before and after the protocol. RESULTS: Maximal aerobic power increased after the protocol in HCE only (+6.8%, P < 0.05). Compared with baseline, AOPP was higher at Post + 1 (+28%, P < 0.05) and nitrotyrosine at Post (+81%, P < 0.05) in HCS only. Superoxide dismutase (+30%, P < 0.05) and catalase (+53%, P < 0.05) increased at Post in HCE only. Higher levels of ferric-reducing antioxidant power (+41%, P < 0.05) at Post and lower levels of AOPP (-47%, P < 0.01) at Post + 1 were measured in HCE versus HCS. Glutathione peroxidase (+31%, P < 0.01) increased in both groups at Post + 1. Similar erythropoietin kinetics was noted in both groups with an increase at D1 (+143%, P < 0.01), a return to baseline at Post, and a decrease at Post + 1 (-56%, P < 0.05). CONCLUSIONS: These data provide evidence that 2 h of moderate daily exercise training can attenuate the oxidative stress induced by continuous hypoxic exposure.

Volemic status influences the response of plasma atrial natriuretic factor to positive airway pressure.

STUDY OBJECTIVE; To evaluate interactive effects of volemic status and positive end-expiratory pressure (PEEP) on the plasma levels of atrial natriuretic factor (ANF) in assist-controlled mechanical ventilation (MV). DESIGN: Three successive protocols applied in randomized order to each participant. SETTING: Clinical investigation laboratory. PARTICIPANTS: Twenty-one young, healthy adults. INTERVENTIONS: The three protocols were as follows: (1) MV+PEEP, normovolemia; (2) MV+PEEP, hypervolemia; and (3) spontaneous breathing (SB), hypervolemia. In protocols 1 and 2, a preliminary period of SB lasting 2 h was followed by MV alone (0.5 h), MV+20 cm H2O PEEP (1 h), and a recovery period of SB (1.5 h). Hypervolemia was induced by the continuous i.v. infusion of 3 L of 0.9% NaCl in 5 h (protocols 2 and 3). MEASUREMENTS AND RESULTS: Heart rate, BP, and the plasma levels of immunoreactive ANF and catecholamines were measured serially. During hypervolemia, ANF significantly decreased when PEEP was added to MV (protocol 2: from 31.1 +/- 2.7 to 20.7 +/- 1.5 fmol/mL; p < 0.01). This did not occur in normovolemia (protocol 1: from 20.0 +/- to 16.7 +/- 1.2 fmol/mL; p = NS). The different effects of MV+PEEP in normovolemia and hypervolemia were not related to differences in circulating catecholamine levels. CONCLUSIONS: These results demonstrate for the first time (to our knowledge) that volemic status modulates the response of plasma ANF to PEEP in humans. The role of ANF in the water and salt retention induced by MV with PEEP might be limited to hypervolemic conditions.

Plasma angiotensin-(1-8) octapeptide measurement to assess acute angiotensin-converting enzyme inhibition with captopril administered parenterally to normal subjects.

The blood pressure (BP), heart rate (HR), and humoral effects of single intravenous (i.v.) doses of the angiotensin-converting enzyme (ACE) inhibitor captopril was investigated in five normotensive healthy volunteers. Each subject received at 1-week intervals a bolus dose of either captopril (1, 5, and 25 mg) or its vehicle. The study was conducted in a single-blind fashion, and the order of treatment phases was randomized. The different doses of captopril had no acute effect on BP and HR. They induced a dose-dependent decrease in plasma ACE activity and plasma angiotensin II levels. The angiotensin-(1-8) octapeptide was isolated by solid-phase extraction and high-performance liquid chromatography (HPLC) prior to radioimmunoassay (RIA). All three doses of captopril reduced circulating angiotensin II levels within 15 min of drug administration. Only with the 25-mg dose was the angiotensin II concentration below the detection limit at 15 min and still significantly reduced 90 min after drug administration. Simultaneous and progressive decreases in plasma aldosterone levels were observed both with ACE inhibition and during vehicle injection, but the relative fall was more pronounced after captopril administration. No adverse reaction was noticed. These results demonstrate that captopril given parenterally blocks the renin-angiotensin system in a dose-dependent manner. Only with the dose of 25 mg was the inhibition of plasma-converting enzyme activity and the reduction of plasma angiotensin II sustained for at least 1 1/2 h.

Genetic variations in drug-induced liver injury (DILI): resolving the puzzle.

Despite stringent requirements for drug development imposed by regulatory agencies, drug-induced liver injury (DILI) is an increasing health problem and a significant cause for failure to approve drugs, market withdrawal of commercialized medications, and adoption of regulatory measures. The pathogenesis is yet undefined, though the rare occurrence of idiosyncratic DILI (1/100,000–1/10,000) and the fact that hepatotoxicity often recurs after re-exposure to the culprit drug under different environmental conditions strongly points toward a major role for genetic variations in the underlying mechanism and susceptibility. Pharmacogenetic studies in DILI have to a large extent focused on genes involved in drug metabolism, as polymorphisms in these genes may generate increased plasma drug concentrations as well as lower clearance rates when treated with standard medication doses. A range of studies have identified a number of genetic variants in drug metabolism Phase I, II, and III genes, including cytochrome P450 (CYP) 2E1, N-acetyltransferase 2, UDP-glucuronosyltransferase 2B7, glutathione S-transferase M1/T1, ABCB11, and ABCC2, that enhance DILI susceptibility (Andrade et al., 2009; Agundez et al., 2011). Several metabolic gene variants, such as CYP2E1c1 and NAT2 slow, have been associated with DILI induced by specific drugs based on individual drug metabolism information. Others, such as GSTM1 and T1 null alleles have been associated with enhanced risk of DILI development induced by a large range of drugs. Hence, these variants appear to have a more general role in DILI susceptibility due to their role in reducing the cell's antioxidative capacity (Lucena et al., 2008). Mitochondrial superoxide dismutase (SOD2) and glutathione peroxidase 1 (GPX1) are two additional enzymes involved in combating oxidative stress, with specific genetic variants shown to enhance the risk of developing DILI

Light-induced phosphorylation of a membrane protein plays an early role in signal transduction for phototropism in Arabidopsis thaliana.

Blue light is known to cause rapid phosphorylation of a membrane protein in etiolated seedlings of several plant species, a protein that, at least in etiolated pea seedlings and maize coleoptiles, has been shown to be associated with the plasma membrane. The light-driven phosphorylation has been proposed on the basis of correlative evidence to be an early step in the signal transduction chain for phototropism. In the Arabidopsis thaliana mutant JK224, the sensitivity to blue light for induction of first positive phototropism is known to be 20- to 30-fold lower than in wild type, whereas second positive curvature appears to be normal. While light-induced phosphorylation can be demonstrated in crude membrane preparations from shoots of the mutant, the level of phosphorylation is dramatically lower than in wild type, as is the sensitivity to blue light. Another A. thaliana mutant, JK218, that completely lacks any phototropic responses to up to 2 h of irradiation, shows a normal level of light-induced phosphorylation at saturation. Since its gravitropic sensitivity is normal, it is presumably blocked in some step between photoreception and the confluence of the signal transduction pathways for phototropism and gravitropism. We conclude from mutant JK224 that light-induced phosphorylation plays an early role in the signal transduction chain for phototropism in higher plants.

Preconditioning with Triiodothyronine Improves the Clinical Signs and Acute Tubular Necrosis Induced by Ischemia/Reperfusion in Rats.

BACKGROUND Renal ischemia/reperfusion (I/R) injury is manifested by acute renal failure (ARF) and acute tubular necrosis (ATN). The aim of this study was to evaluate the effectiveness of preconditioning with 3, 3, 5 triiodothyronine (T3) to prevent I/R renal injury. METHODOLOGY/PRINCIPAL FINDINGS THE RATS WERE DIVIDED INTO FOUR GROUPS: sham-operated, placebo-treated (SO-P), sham-operated T3- treated (SO- T3), I/R-injured placebo-treated (IR-P), and I/R-injured T3-treated (IR- T3) groups. At 24 h before ischemia, the animals received a single dose of T3 (100 μg/kg). Renal function and plasma, urinary, and tissue variables were studied at 4, 24, and 48 h of reperfusion, including biochemical, oxidative stress, and inflammation variables, PARP-1 immunohistochemical expression, and ATN morphology. In comparison to the SO groups, the IR-P groups had higher plasma urea and creatinine levels and greater proteinuria (at all reperfusion times) and also showed: increased oxidative stress-related plasma, urinary, and tissue variables; higher plasma levels of IL6 (proinflammatory cytokine); increased glomerular and tubular nuclear PARP-1 expression; and a greater degree of ATN. The IR-T3 group showed a marked reduction in all of these variables, especially at 48 h of reperfusion. No significant differences were observed between SO-P and SO-T3 groups. CONCLUSIONS This study demonstrates that preconditioning rats with a single dose of T3 improves the clinical signs and ATN of renal I/R injury. These beneficial effects are accompanied by reductions in oxidative stress, inflammation, and renal PARP-1 expression, indicating that this sequence of factors plays an important role in the ATN induced by I/R injury.

Correlation between plasma concentration of cilazapril and haemodynamic and hormonal effects in healthy man.

1. The haemodynamic and humoral effects of cilazapril, a new angiotensin converting enzyme (ACE) inhibitor, were evaluated in normotensive healthy volunteers. 2. Single oral doses of 1.25, 2.5, 5 and 10 mg of cilazapril inhibited ACE by greater than or equal to 90% and induced the expected pattern of changes of the renin-angiotensin-aldosterone-system. 3. Cilazapril had a long duration of action, since some ACE inhibition was still present 72 h after drug intake. 4. Cilazapril administered intravenously at doses of 5 and 20 micrograms kg-1 for 24 h did not produce any significant effects. 5. During repeated administration of cilazapril for 8 days, no accumulation of cilazaprilat was observed and the clinical tolerance was excellent. 6. In normal volunteers, cilazapril administered orally acts as a potent inhibitor of converting enzyme.

Pharmacological administration of the isoflavone daidzein enhances cell proliferation and reduces high fat diet-induced apoptosis and gliosis in the rat hippocampus.

Soy extracts have been claimed to be neuroprotective against brain insults, an effect related to the estrogenic properties of isoflavones. However, the effects of individual isoflavones on obesity-induced disruption of adult neurogenesis have not yet been analyzed. In the present study we explore the effects of pharmacological administration of daidzein, a main soy isoflavone, in cell proliferation, cell apoptosis and gliosis in the adult hippocampus of animals exposed to a very high-fat diet. Rats made obese after 12-week exposure to a standard or high-fat (HFD, 60%) diets were treated with daidzein (50 mg kg(-1)) for 13 days. Then, plasma levels of metabolites and metabolic hormones, cell proliferation in the subgranular zone of the dentate gyrus (SGZ), and immunohistochemical markers of hippocampal cell apoptosis (caspase-3), gliosis (GFAP and Iba-1), food reward factor FosB and estrogen receptor alpha (ERα) were analyzed. Treatment with daidzein reduced food/caloric intake and body weight gain in obese rats. This was associated with glucose tolerance, low levels of HDL-cholesterol, insulin, adiponectin and testosterone, and high levels of leptin and 17β-estradiol. Daidzein increased the number of phospho-histone H3 and 5-bromo-2-deoxyuridine (BrdU)-ir cells detected in the SGZ of standard diet and HFD-fed rats. Daidzein reversed the HFD-associated enhanced immunohistochemical expression of caspase-3, FosB, GFAP, Iba-1 and ERα in the hippocampus, being more prominent in the dentate gyrus. These results suggest that pharmacological treatment with isoflavones regulates metabolic alterations associated with enhancement of cell proliferation and reduction of apoptosis and gliosis in response to high-fat diet.

The use of liver biopsy evaluation in discrimination of idiopathic autoimmune hepatitis versus drug-induced liver injury.

Distinguishing drug-induced liver injury (DILI) from idiopathic autoimmune hepatitis (AIH) can be challenging. We performed a standardized histologic evaluation to explore potential hallmarks to differentiate AIH versus DILI. Biopsies from patients with clinically well-characterized DILI [n = 35, including 19 hepatocellular injury (HC) and 16 cholestatic/mixed injury (CS)] and AIH (n = 28) were evaluated for Ishak scores, prominent inflammatory cell types in portal and intra-acinar areas, the presence or absence of emperipolesis, rosette formation, and cholestasis in a blinded fashion by four experienced hepatopathologists. Histologic diagnosis was concordant with clinical diagnosis in 65% of cases; but agreement on final diagnosis among the four pathologists was complete in only 46% of cases. Interface hepatitis, focal necrosis, and portal inflammation were present in all evaluated cases, but were more severe in AIH (P < 0.05) than DILI (HC). Portal and intra-acinar plasma cells, rosette formation, and emperiopolesis were features that favored AIH (P < 0.02). A model combining portal inflammation, portal plasma cells, intra-acinar lymphocytes and eosinophils, rosette formation, and canalicular cholestasis yielded an area under the receiver operating characteristic curve (AUROC) of 0.90 in predicting DILI (HC) versus AIH. All Ishak inflammation scores were more severe in AIH than DILI (CS) (P ≤ 0.05). The four AIH-favoring features listed above were consistently more prevalent in AIH, whereas portal neutrophils and intracellular (hepatocellular) cholestasis were more prevalent in DILI (CS) (P < 0.02). The combination of portal inflammation, fibrosis, portal neutrophils and plasma cells, and intracellular (hepatocellular) cholestasis yielded an AUC of 0.91 in predicting DILI (CS) versus AIH. Conclusion: Although an overlap of histologic findings exists for AIH and DILI, sufficient differences exist so that pathologists can use the pattern of injury to suggest the correct diagnosis.

Prediction of sustained antihypertensive efficacy of chronic captopril therapy: relationships to immediate blood pressure response and control plasma renin activity

The blood pressure (BP) lowering effect of the orally active angiotensin converting enzyme inhibitor, captopril (SQ14225), was studied in 59 hypertensive patients maintained on a constant sodium intake. Within 2 hours of the first dose of captopril BP fell from 171/107 to a maximum low of 142/92 mm Hg (p less than 0.001), and after 4 to 8 days to treatment BP averaged 145/94 mm Hg (p less than 0.001). The magnitude of BP drop induced by captopril was significantly correlated to baseline plasma renin activity (PRA) both during the acute phase (r = -0.38, p less than 0.01) and after the 4 to 8-day interval (r = -0.33, p less than 0.01). Because of considerable scatter in individual data, renin profiling was not precisely predictive of the immediate or delayed BP response of separate patients. However, the BP levels achieved following the initial dose of captopril were closely correlated to BP measured after 4 to 8 days of therapy, and appeared to have greater predictive value than control PRA of the long-term efficacy of chronic captopril therapy despite marked BP changes occurring in some patients during the intermediate period. Because of these intermediate BP changes, addition of a diuretic to enhance antihypertensive effectiveness of angiotensin blockade should be restrained for several days after initiation of captopril therapy.

From diabetes to heart disease : studies on dyslipidemia-induced B-cell dysfunction, immunomodulation in heart transplantation, and cardiac stem cell therapy

Diabetes is a growing epidemic with devastating human, social and economic impact. It is associated with significant changes in plasma concentrations of lipoproteins. We tested the hypothesis that lipoproteins modulate the function and survival of insulin-secreting cells. We first detected the presence of several receptors that participate in the binding and processing of plasma lipoproteins and confirmed the internalization of fluorescent LDL and HDL particles in insulin-secreting β-cells. Purified human VLDL and LDL particles reduced insulin mRNA levels and β-cell proliferation, and induced a dose-dependent increase in the rate of apoptosis. In mice lacking the LDL receptor, islets showed a dramatic decrease in LDL uptake and were partially resistant to apoptosis caused by LDL. VLDL-induced apoptosis of β-cells involved caspase-3 cleavage and reduction in levels of the c-Jun N-terminal (JNK) Interacting Protein-1 (IB1/JIP-1). In contrast, the pro-apoptotic signaling of lipoproteins was antagonized by HDL particles or by a small peptide inhibitor of JNK. The protective effects of HDL were mediated, in part, by inhibition of caspase-3 cleavage and activation of the protein kinase Akt/PKB. Heart disease is a major cause of morbidity and mortality among patients with diabetes. When heart failure is refractory to medical therapy and cannot be improved by electrical resynchronization, percutaneous angioplasty or coronary graft bypass surgery, heart transplantation remains a "last resort" therapy. Nevertheless, it is limited by the side effects of immunosuppressive drugs and chronic rejection. Localized expression of immunomodulatory genes in the donor organ can create a state of immune privilege within the graft, and was performed in rodent hearts by infecting cells with an adenovirus encoding indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme in the catabolism of tryptophane. Other strategies are based on genetic manipulation of dendritic cells (DCs) with immunosuppressive genes and in vitro exposure of DCs to agents that prevent their maturation by inflammatory cytokines. Finally, we used 5-bromo-2'-deoxyuridine, which is incorporated into DNA and diluted with cell division, to identify long-term label retaining cells in the adult rodent heart. The majority of these cells were positive for the stem cell antigen-1 (Sca-1) and negative for the endothelial precursor marker CD31. They formed cardiospheres in vitro and showed differentiation potential into mesenchymal cell lineages. When cultured in cardiomyogenic differentiation medium, they expressed cardiac-specific genes. Taken together, these data provide evidence of slow-cycling stem cells in the rodent heart. Chronic shortage of donor organs opens the way to cardiac stem cell therapy in humans, although the long way from animal experimentation to routine therapy in patients may still take several years. - Du diabète de type 2 à la maladie coronarienne : trois études sur les dysfonctions de la cellule sécrétrice d'insuline induites par les dyslipidémies, l'immunomodulation dans la transplantation cardiaque, et la thérapie par des cellules souches myocardiques. Le diabète de type 2 a pris les dimensions d'une épidémie, avec des conséquences sociales et économiques dont nous n'avons pas encore pris toute la mesure. La maladie s'accompagne souvent d'une dyslipidémie caractérisée par une hypertriglycéridémie, des taux abaissés de cholestérol HDL, et des concentrations de cholestérol LDL à la limite supérieure de ce qui est considéré comme acceptable. L'hypothèse à la base de cette étude est qu'une modification des taux plasmatiques de lipoprotéines pourrait avoir une influence directe sur la cellule β sécrétrice d'insuline en modifiant sa fonction, sa durée de vie et son taux de régénération. Dans un premier temps, nous avons mis en évidence, sur la cellule β, la présence de plusieurs récepteurs impliqués dans la captation des lipoprotéines. Nous avons confirmé la fonctionnalité de ces récepteurs en suivant l'internalisation de LDL et de HDL marqués. En présence de VLDL ou de LDL humains, nous avons observé une diminution de la transcription du gène de l'insuline, une prolifération cellulaire réduite, et une augmentation de l'apoptose, toutes fonctions de la dose et du temps d'exposition. L'apoptose induite par les VLDL passe par une activation de la caspase-3 et une réduction du taux de la protéine IB1/JIP-1 (Islet Brain1/JNK Interacting Protein 1), dont une mutation est associée à une forme monogénique de diabète de type 2. Par opposition, les HDL, ainsi que des peptides inhibiteurs de JNK, sont capables de contrer la cascade pro-apoptotique déclenchée, respectivement, par les LDL et les VLDL. Ces effets protecteurs comprennent l'inhibition du clivage de la caspase-3 et l'activation de la protéine kinase Akt/PKB. En conclusion, les lipoprotéines sont des éléments clés de la survie de la cellule β, et pourraient contribuer au dysfonctionnement observé dans le pancréas endocrine au cours du développement du diabète. La maladie cardiaque, et plus particulièrement la maladie coronarienne, est une cause majeure de morbidité et de mortalité chez les patients atteints de diabète. Plusieurs stratégies sont utilisées quotidiennement pour pallier les atteintes cardiaques: traitements médicamenteux, électromécaniques par resynchronisation électrique, ou communément appelés « interventionnels » lorsqu'ils font appel à l'angioplastie percutanée. La revascularisation du myocarde par des pontages coronariens donne également de très bons résultats dans certaines situations. Il existe toutefois des cas où plus aucune de ces approches n'est suffisante. La transplantation cardiaque est alors la thérapie de choix pour un nombre restreint de patients. La thérapie génique, en permettant l'expression locale de gènes immunomodulateurs dans l'organe greffé, permet de diminuer les réactions de rejet inhérentes à toute transplantation (à l'exception de celles réalisées entre deux jumeaux homozygotes). Nous avons appliqué chez des rongeurs cette stratégie en infectant le coeur greffé avec un adénovirus codant pour l'enzyme indoleamine 2,3-dioxygénase (IDO), une enzyme clé dans le catabolisme du tryptophane. Nous avons procédé de manière identique in vitro en surexprimant IDO dans les cellules dendritiques, dont le rôle est de présenter les antigènes aux lymphocytes Τ du receveur. Des expériences similaires ont été réalisées en traitant les cellules dendritiques avec des substances capables de prévenir, en partie du moins, leur maturation par des agents pro-inflammatoires. Finalement, nous avons exploré une stratégie utilisée couramment en hématologie, mais qui n'en est encore qu'à ses débuts au niveau cardiaque : la thérapie par des cellules souches. En traitant des rongeurs avec un marqueur qui s'incorpore dans l'ADN nucléaire, le 5-bromo- 2'-deoxyuridine, nous avons identifié une population cellulaire se divisant rarement, positive en grande partie pour l'antigène embryonnaire Sca-1 et négative pour le marqueur endothélial CD31. En culture, ces cellules forment des cardiosphères et sont capables de se différencier dans les principaux types tissulaires mésenchymateux. Dans un milieu de differentiation adéquat, ces cellules expriment des gènes cardiomyocytaires. En résumé, ces données confirment la présence chez le rongeur d'une population résidente de précurseurs myocardiques. En addenda, on trouvera deux publications relatives à la cellule β productrice d'insuline. Le premier article démontre le rôle essentiel joué par la complexine dans l'insulino-sécrétion, tandis que le second souligne l'importance de la protéine IB1/JIP-1 dans la protection contre l'apoptose de la cellule β induite par certaines cytokines.