Recent literature has shown that AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors lacking the GluR2 subunit (thus calcium permeable) are widely expressed in the CNS, especially in interneurons and glia, where they contribute to synaptic transmission and plasticity. Studies have also indicated that calcium permeable AMPARs (CP-AMPARs) are expressed and participate in synaptic regulation in principal neurons, including hippocampal pyramidal neurons. Furthermore, CP-AMPARs and their resultant calcium influx are implicated in various pathophysiological conditions such as ischemia and seizures. However, the synaptic events activated by calcium influx through CP-AMPARs remain unknown. I took advantage of genetically altered mice without (GluR2-/-) or with reduced GluR2 (GluR2+/-), thus allowing the expression and detailed analysis of synaptic CP-AMPARs in hippocampal pyramidal neurons. Utilizing electrophysiological techniques, I demonstrated that these receptors were capable of inducing numerous forms of long-term potentiation (referred to as CP-AMPAR-dependent LTP) through a number of different induction protocols, including high-frequency stimulation (HFS) and theta-burst stimulation (TBS). This included a previously undemonstrated form of protein-synthesis dependent late-LTP (L-LTP) at CA1 synapses that is NMDA-receptor (NMDAR) independent. This form of plasticity was completely blocked by the selective CP-AMPAR inhibitor IEM-1460. Surprisingly, calcium/calmodulin-dependent kinase II (CaMKII), the key protein kinase that is indispensable for NMDAR-dependent LTP at CA1 synapses appeared to be not required for the induction of CP-AMPAR-dependent LTP due to the lack of effect of two separate pharmacological inhibitors (KN-62 and staurosporine) on this form of potentiation. Both KN-62 and staurosporine strongly inhibited NMDAR dependent LTP in control studies. In contrast, inhibitors for the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) cascade (PD98059 and U0126) significantly attenuated this CP-AMPAR-dependent LTP. Additional studies with knockout mice revealed that the ERK/MAPK signalling cascade is likely acting through p-21 activated kinase 1 (or PAK1, a Rho-GTPase associated kinase) dependent mechanisms. These results suggest that distinct synaptic signalling underlies GluR2-lacking CP-AMPAR-dependent LTP, and reinforces the recent notions that CP-AMPARs are important facilitators of synaptic plasticity in the brain.

Recent literature has shown that AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors lacking the GluR2 subunit (thus calcium permeable) are widely expressed in the CNS, especially in interneurons and glia, where they contribute to synaptic transmission and plasticity. Studies have also indicated that calcium permeable AMPARs (CP-AMPARs) are expressed and participate in synaptic regulation in principal neurons, including hippocampal pyramidal neurons. Furthermore, CP-AMPARs and their resultant calcium influx are implicated in various pathophysiological conditions such as ischemia and seizures. However, the synaptic events activated by calcium influx through CP-AMPARs remain unknown. I took advantage of genetically altered mice without (GluR2-/-) or with reduced GluR2 (GluR2+/-), thus allowing the expression and detailed analysis of synaptic CP-AMPARs in hippocampal pyramidal neurons. Utilizing electrophysiological techniques, I demonstrated that these receptors were capable of inducing numerous forms of long-term potentiation (referred to as CP-AMPAR-dependent LTP) through a number of different induction protocols, including high-frequency stimulation (HFS) and theta-burst stimulation (TBS). This included a previously undemonstrated form of protein-synthesis dependent late-LTP (L-LTP) at CA1 synapses that is NMDA-receptor (NMDAR) independent. This form of plasticity was completely blocked by the selective CP-AMPAR inhibitor IEM-1460. Surprisingly, calcium/calmodulin-dependent kinase II (CaMKII), the key protein kinase that is indispensable for NMDAR-dependent LTP at CA1 synapses appeared to be not required for the induction of CP-AMPAR-dependent LTP due to the lack of effect of two separate pharmacological inhibitors (KN-62 and staurosporine) on this form of potentiation. Both KN-62 and staurosporine strongly inhibited NMDAR dependent LTP in control studies. In contrast, inhibitors for the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) cascade (PD98059 and U0126) significantly attenuated this CP-AMPAR-dependent LTP. Additional studies with knockout mice revealed that the ERK/MAPK signalling cascade is likely acting through p-21 activated kinase 1 (or PAK1, a Rho-GTPase associated kinase) dependent mechanisms. These results suggest that distinct synaptic signalling underlies GluR2-lacking CP-AMPAR-dependent LTP, and reinforces the recent notions that CP-AMPARs are important facilitators of synaptic plasticity in the brain.

Dissertation (Ph.D.)--University of South Florida, 2008. / Title from PDF of title page. Document formatted into pages; contains 132 pages. Includes vita. Includes bibliographical references.

Organic nitrates, such as nitroglycerine (NTG), are widely used for their potent vasodilator capacity in the management of coronary artery disease and heart failure. Unfortunately, their beneficial effect is rapidly lost due to the development of nitrate tolerance, which is translated by an impaired vasorelaxation to NTG and an increased oxidative stress production. Although the mechanisms of the development of nitrate tolerance are still not fully elucidated, much interest has been focused in treating nitrate-receiving patients together with other drugs in order to overcome the development of nitrate tolerance. The Nitric Oxide generating enzyme, eNOS, and the superoxide anion generating enzyme, NAD(P)H oxidase, have been suggested to play a role in the development of nitrate tolerance. The aim of this study was to analyse the underlying mechanism by which ramipril, an ACE inhibitor and rosuvastatin, a new molecule of the statin class, are able to protect against the development of nitrate tolerance in the aortas isolated from rats, wild-type (wt) and eNOS-/- mice. <p>These results show that ramipril as well as rosuvastatin are able to protect against the development of nitrate tolerance in the wt and eNOS-/- mice aortas suggesting that eNOS is not necessary for their protective effect. The aortas from nitrate tolerant rats and mice showed a significant increase in the NAD(P)H oxidase activation compared to the aortas from the control and from the co-treated ramipril+NTG or rosuvastatin+NTG animals. In line with these findings were the results obtained by RT-PCR analysis: the mRNA expression of the different subunits of the NAD(P)H oxidase, such as gp91phox, p22phox, were significantly decreased after rosuvastatin or ramipril treatment in wt and eNOS-/- mice aortas. Apocynin, the NAD(P)H oxidase inhibitor was also able to inhibit the development of nitrate tolerance in the rat and mouse aortas. <p>In conclusion, these results suggest that rosuvastatin and ramipril are able to protect against the development of nitrate tolerance by counteracting the nitrate-induced oxidative stress. The mechanism of protection involves a direct interaction with the NAD(P)H oxidase pathway and seems to be completely independent of the eNOS pathway. <p> / Doctorat en sciences pharmaceutiques / info:eu-repo/semantics/nonPublished

Le testicule assure la production des spermatozoïdes et la sécrétion de la testostérone. Chaque fonction est assumée par un compartiment cellulaire distinct: l’épithélium séminifère et le tissu interstitiel. Le cholestérol, présent dans les deux compartiments, est un composé indispensable aux membranes cellulaires et un précurseur essentiel de la testostérone. Dans le compartiment interstitiel, environ 40 % du cholestérol utilisé pour la production hormonale est importé du sang à partir des lipoprotéines HDL et/ou LDL. Dans l’épithélium séminifère, la cellule de Sertoli assure le contrôle et le maintien de la spermatogenèse. Elle a la capacité de synthétiser du cholestérol à partir de l’acétate in vitro, néanmoins, il n’y a pas d’évidence qu’elle le fait in vivo. De plus il existe, au niveau des tubules séminifères, une barrière hémato-testiculaire qui empêche le libre passage de plusieurs composés sanguins, y compris le cholestérol. Nous avons testé l’hypothèse qu’il existe des moyens d’importation du cholestérol sanguin, mais aussi l’exportation du cholestérol intra-tissulaire, qui contourneraient cette barrière et qui contribueraient au maintien du taux intratubulaire du cholestérol compatible avec le bon déroulement de la spermatogenèse. Nous avons comparé les taux de variation de l’expression de l’ARNm et de la protéine des transporteurs sélectifs de cholestérol SR-BI, SR-BII, CD36 et ABCA1 aux taux de variation du cholestérol libre et estérifié au cours de la spermatogenèse chez les souris normales durant le développement postnatal. Afin de mieux apprécier le niveau d’implication de chacun de ces récepteurs, nous avons examiné comment la suppression du gène d’une enzyme comme la lypase hormono-sensible (HSL) ou de celui d’un transporteur de cholestérol comme SR-BI, CD36 ou NPC1 était compensée et comment cette suppression affectait le taux de cholestérol libre et estérifié dans chacun des deux compartiments cellulaires du testicule. Nous avons dans un premier temps mis au point une nouvelle technique d’isolation des testicules en fraction enrichie en tissu interstitiel (ITf) et en tubules séminifères (STf) qui a l’avantage de mieux préserver l’intégrité des formes phosphorylées et glycosylées des protéines comparée aux techniques préexistantes. Les résultats de nos analyses ont montré que l’expression de SR-BI et CD36 étaient maximales dans les ITf au moment où les souris ont complété leur maturité sexuelle et où le niveau de synthèse de la testostérone était maximal. Dans les tubules séminifères, l’expression maximale de SR-BI et le taux le plus élevé de cholestérol estérifié étaient mesurés de façon concomitante à 35 jours après la naissance, au moment où la première vague de l’activité spermatogénétique était complétée. L’expression de l’ABCA1 était maximale au moment où le taux de cholestérol était élevé et minimale au moment où le taux de cholestérol était le plus bas, alors que le niveau d’expression de CD36 était maximal chez l’adulte au moment où le taux de spermiation était le plus élevé. L’expression de SR-BII variait peu dans les deux compartiments cellulaires durant le développement. La suppression génétique de la HSL et de NPC1, qui cause une infertilité chez les souris mâles, était accompagnée d’une accumulation de cholestérol libre et estérifié dans les tubules séminifères. Par contre, la suppression génétique de SR-BI et CD36, qui ne causent pas d’infertilité chez les souris mâles était sans impact significatif sur le taux de cholestérol intratubulaire. Nous avons montré que l’invalidation génétique d’un transporteur sélectif ou d’une enzyme du métabolisme du cholestérol était accompagnée d’un ensemble de mécanismes de compensation visant à maintenir le taux de cholestérol libre aux niveaux semblables à ceux mesurés dans les fractions tissulaires de souris normales. Ensemble, nos résultats ont montré que l’expression des transporteurs sélectifs de cholestérol SR-BI, SR-BII, CD36 et ABCA1 variait en fonction de la spermatogenèse et du taux intratesticulaire du cholestérol suggérant leur contribution au maintien de l’homéostasie du cholestérol intratesticulaire. / The testis is made up of loops of convoluted seminiferous tubules surrounded by interstitial tissue composed of loose connective tissue containing Leydig cells that secrete testosterone into the bloodstream. The seminiferous tubules are lined with a stratified epithelium containing germ cells at various stages of development and the supporting Sertoli cells. Cholesterol is present in both compartments and is crucial for the development of germ cells, the fertility of spermatozoa as well as for testosterone production. In the interstitial compartment, approximately 40 % of the cholesterol used for the hormonal production is imported from blood lipoproteins HDL and LDL. In the seminiferous epithelium, Sertoli cells plays key role in the development and maintenance of spermatogenesis. Sertoli cells have the capacity to synthesize cholesterol from acetate in vitro, however, there is no evidence that they do so in vivo. In addition, there is a blood-testis barrier within the seminiferous tubules that prevents the free passage of several blood compounds including cholesterol. We tested the hypothesis that there are ways of blood cholesterol uptake, but also the intratubular cholesterol efflux that by-pass this barrier and contribute to the cholesterol homeostasis within the tubules. We compared expression patterns of the mRNA and proteins for selective cholesterol transporters SR-BI, SR-BII, CD36 and ABCA1 with those of free and esterified cholesterol during the spermatogenesis in normal mice during the postnatal development. To better appreciate the level of involvement of each receptor, we examined the effect of the deletion of the genes for an enzyme (HSL) or for cholesterol transporters (SR-BI, CD36 or NPC1) on the rate of free and esterified cholesterol in both compartments of the testis. At first, we worked out a new technique to separate the testes into interstitial tissue- (ITf) and seminiferous tubule-enriched fractions (STf) that has the advantage of allowing a more faithful detection of the phosphorylated and glycosylated forms of the proteins compared to existing techniques. Our results showed that the expression of SR-BI and CD36 was maximum in the ITf when mice completed their sexual maturity and reached the peak level of testosterone synthesis. In the seminiferous tubule-enriched fractions, the maximum level of SR-BI expression coincided with the highest level of esterified cholesterol during the development at 35 days, as the first wave of the spermatogenetic activity was completed. ABCA1 reached the highest expression level when cholesterol was high and reached the lowest when cholesterol was at its minimum, while the level of CD36 expression was maximal in the adult tubules as the rate of spermiation was the highest. The knockout of the HSL and NPC1, which renders the male mice infertile, was accompanied by the accumulation of free and esterified cholesterol in the seminiferous tubules. On the other hand, the knockout of SR-BI and CD36, linkes to infertility, did not affect the rate of intratubular cholesterol. Here we showed that genetic withdrawal of a cholesterol transporter or of an enzyme involved in cholesterol metabolism was compensated by other transporters or enzymes in order to maintain the level of free cholesterol similar to those measured in the tissue-enriched fractions of wild-type mice. Together, our results showed that the expression of the selective cholesterol transporters SR-BI, SR-BII, CD36 and ABCA1 varied according to the spermatogenesis and intratesticular cholesterol rate, thus suggesting their contribution to the preservation of the intratesticular cholesterol homeostasis.

Glutamate carboxypeptidase II (GCPII) is a transmembrane glycoprotein, which consists of short intracellular and transmembrane domains, and a large extracellular domain possessing carboxypeptidase activity. In the human body, GCPII fulfils a neuromodulatory function in the brain and facilitates folate absorption in the small intestine. In addition to the brain and small intestine, high level of GCPII is also present in the prostate and kidney. However, GCPII function in these tissues has not been determined yet. To study the role of GCPII in detail, several research groups attempted to inactivate GCPII encoding gene Folh1 in mice. Surprisingly, the experiments led to rather conflicting results ranging from embryonic lethality to generation of viable GCPII-deficient mice without any obvious phenotype. This dissertation project aimed to dissect the discrepancy using alternative strategy for gene modification. For this purpose, we designed TALENs that specifically targeted exon 11 of Folh1 gene and manipulated mouse zygotes of C57BL/6NCrl genetic background. We analysed all genetically modified mice of F0 generation for presence of TALEN-mediated mutations and established 5 different GCPII-mutant mouse colonies from founder mice that altogether carried 2 frame-shift mutations and 3 small in-frame...

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Bacterial infections are a common and deadly threat to vulnerable patients. Alternative strategies to fight infection are needed. β-Glucan, an immunomodulator derived from the fungal cell wall, provokes resistance to infection by inducing trained immunity, a phenomenon that persists for weeks to months. Given the durability of trained immunity, it is unclear which leukocyte populations sustain this effect. Macrophages have a life span that surpasses the duration of trained immunity. Thus, we sought to define the contribution of differentiated macrophages to trained immunity. Our results show that β-glucan protects mice from infection by augmenting recruitment of innate leukocytes to the site of infection and facilitating local clearance of bacteria, an effect that persists for more than 7 d. Adoptive transfer of macrophages, trained using β-glucan, into naive mice conferred a comparable level of protection. Trained mouse bone marrow-derived macrophages assumed an antimicrobial phenotype characterized by enhanced phagocytosis and reactive oxygen species production in parallel with sustained enhancements in glycolytic and oxidative metabolism, increased mitochondrial mass, and membrane potential. β-Glucan induced broad transcriptomic changes in macrophages consistent with early activation of the inflammatory response, followed by sustained alterations in transcripts associated with metabolism, cellular differentiation, and antimicrobial function. Trained macrophages constitutively secreted CCL chemokines and robustly produced proinflammatory cytokines and chemokines in response to LPS challenge. Induction of the trained phenotype was independent of the classic β-glucan receptors Dectin-1 and TLR-2. These findings provide evidence that β-glucan induces enhanced protection from infection by driving trained immunity in macrophages.

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