Os receptores para mineralocorticoides (MR) e glicocorticoides (GR) representam importantes sítios de ligação para os glicocorticoides. Enquanto a ativação crônica e excessiva de GR leva à atrofia do hipocampo, a ativação do MR é neuroprotetora. Considerando as alterações no giro denteado (GD), decorrentes do envelhecimento, e a possível participação do MR e GR neste processo, o objetivo deste trabalho foi correlacionar o desbalanço de tais receptores com a degeneração neuronal nesta região do hipocampo de cães idosos. Para isso, utilizaram-se cortes histológicos do hipocampo de 6 cadáveres caninos jovens/adultos (até 8 anos de idade) e 12 idosos (idade igual ou superior a 10 anos), de ambos os sexos e de qualquer raça, os quais foram submetidos à: coloração de Nissl, para a identificação de células nervosas; imuno-histoquímica, para o estudo da expressão do MR e GR; e marcação fluorescente (fluoro-jade B), para detecção de neurônios em degeneração. A camada polimórfica do GD de cães idosos apresentou redução (em 16%) na contagem de neurônios e maior número de neurônios em degeneração. Em conjunto com estas alterações celulares, a menor marcação/expressão do MR e a menor relação MR:GR foram correlacionadas com a degeneração neuronal na camada polimórfica do GD de cães idosos. Além disso, cadelas idosas apresentaram menor densidade celular na camada granular, quando comparadas aos machos idosos, sugerindo uma ação diferencial dos esteroides sexuais nas alterações do GD. Os resultados indicam que o desbalanço na relação MR:GR pode interferir na sobrevivência neuronal no GD de cães idosos. / The mineralocorticoid (MR) and glucocorticoid (GR) receptors bind the glucocorticoid hormones. The chronic and excessive GR activation leads to hippocampus atrophy. By contrast, MR activation is neuroprotective. Considering the aging changes in the dentate gyrus (DG) and the possible participation of MR and GR in this process, the objective of this study was to correlate the unbalance of these receptors with the neuronal degeneration in this hippocampal region of aged dogs. For that purpose, cadaveric histologic sections of hippocampus of 6 young/adult dogs (until 8 years old) and 12 aged dogs (more than 10 years old), of both sex and any breed, were included. The Nissl staining and imunochemistry were performed to identify nerve cells and to study the MR and GR expression, respectively. Moreover, fluorescent labeling (fluoro- Jade B) was used to detect degenerating neurons. The polimorfic layer of the DG of aged dogs showed reduction (of 16%) on the neurons counting and more degenerating neurons. Together with this cells changes, the less MR expression and MR:GR relation were correlated with the neuronal degeneration in the polimorfic layer of DG of aged dogs. Besides that, aged females presented lower cell density in the granular layer, when compared to aged males, suggesting a differential sex steroid action on changes in the GD. Our results indicate that unbalance on the MR:GR relation may interfere with neuronal survival in the DG of aged dogs.

Submitted by Rosemary Tourinho Pereira (rosemary.pereira@uniceub.br) on 2013-08-01T14:31:40Z No. of bitstreams: 1 Tese_MariliaQueirozDiasJacome_2013.pdf: 2173866 bytes, checksum: 32b85f22d0df7e610695e6c4f0f9ec51 (MD5) / Made available in DSpace on 2013-08-01T14:31:40Z (GMT). No. of bitstreams: 1 Tese_MariliaQueirozDiasJacome_2013.pdf: 2173866 bytes, checksum: 32b85f22d0df7e610695e6c4f0f9ec51 (MD5) Previous issue date: 2013-05 / Made available in DSpace on 2013-10-10T13:09:10Z (GMT). No. of bitstreams: 3 Tese_MariliaQueirozDiasJacome_2013.pdf.txt: 421905 bytes, checksum: 10fed67cea141b2d87e7fdb61dbdd5c3 (MD5) license.txt: 362 bytes, checksum: b9e0d9c10d77debde1a5ea963f0e67b4 (MD5) Tese_MariliaQueirozDiasJacome_2013.pdf: 2173866 bytes, checksum: 32b85f22d0df7e610695e6c4f0f9ec51 (MD5) Previous issue date: 2013-05 / Saber como membros de Comitês de Ética em Pesquisas (CEPs) articulam regulamentação e avaliação pode contribuir para problematizar o processo de revisão ética, vislumbrando diminuir diferenças no trabalho dos comitês. Este estudo tem o objetivo de analisar a organização e funcionamento de CEPs por coordenadores e membros e suas percepções acerca do processo de avaliação ética. Os dados foram coletados com a aplicação de questionários enviados para 645 comitês de ética. Os participantes da pesquisa são coordenadores e demais membros. Os questionários para coordenadores visavam caracterizar o perfil dos comitês e sua operacionalização, enquanto para os membros investigou-se como concebem a avaliação ética. As respostas foram categorizadas por frequência e média das respostas e passaram por teste estatístico. Responderam os questionários aplicados on-line 129 coordenadores e 295 membros. O estudo possibilitou caracterizar os comitês como localizados em instituições de ensino superior, com nove anos ou mais de funcionamento, maioria de membros no primeiro mandato e formação predominante na área de ciências biológicas e da saúde, com mestrado e doutorado, sem especialização nas áreas de bioética e ética em pesquisa. A capacitação dos membros se dá, principalmente, pela leitura das regulamentações e por orientações do coordenador e do secretário do CEP. / JÁCOME, Marília de Queiroz Dias. Análise dos comitês de ética em pesquisa no Brasil: percepção de seus coordenadores e membros. Tese (Doutorado em Bioética). Programa de Pós-Graduação em Bioética, Faculdade de Ciências da Saúde. Bioética: Universidade de Brasília, 2013. Orientação: Tereza Cristina Cavalcanti Ferreira de Araujo.

L’irradiation cérébrale thérapeutique comporte un risque de neurotoxicité tardive irréversible en partie lié à l’effet de l’irradiation sur le compartiment vasculaire cérébrale. Les péricytes et les communications entre les péricytes et les cellules endothéliales jouent un rôle majeur dans la stabilisation des vaisseaux, dans la formation et la régulation de la barrière hématoencéphalique et dans le contrôle du flux sanguin cérébral. Nous montrons, dans un modèle murin d’irradiation cérébrale, que les péricytes sont une cible précoce de l’irradiation cérébrale. Après irradiation, la morphologie des péricytes est modifiée et des marqueurs d’activations du péricytes sont surexprimés. En conséquence, la communication entre péricyte et cellule endothéliale est rompue, ce qui se traduit par une diminution de la capacité du péricyte à induire une constriction vasculaire après stimulation électrique. De façon concomitante, la perméabilité de la barrière hémato-encéphalique est anormalement augmentée après irradiation. Un traitement par thalidomide, administré dans la semaine précédant et suivant l’irradiation, prévient les conséquences de l’irradiation sur les péricytes. Les communications entre péricytes et cellules endothéliales sont maintenues ainsi que les fonctions contractiles des péricytes. L’imperméabilité de la barrière hématoencéphalique est également préservée. La voie de signalisation PDGF-β/PDGFR-β essentielle au recrutement des péricytes par les cellules endothéliales, est, au moins partiellement, impliquée dans l’effet protecteur de la thalidomide. Des études supplémentaires sont nécessaires pour définir les mécanismes sous tendant l’effet de l’irradiation sur les péricytes ainsi que l’effet protecteur de la thalidomide. Nous avons en parallèle mis au point un modèle murin de lymphome cérébral luciférase positif pour vérifier, dans un premier temps, l’innocuité de l’association de la radiothérapie et de la thalidomide et de ses dérivés de la classe des immunomodulateurs (iMids), le lénalidomide et le pomalidomide. Ces trois molécules ne diminuent pas l’effet antitumoral de la radiothérapie, mais l’association de radiothérapie et de pomalidomide est synergique sur la décroissance tumorale mesurée par l’évolution des courbes de bioluminescence. Le concept de normalisation de la vascularisation tumorale fait référence aux molécules capables, non pas de faire régresser les vaisseaux tumoraux anormaux, mais de les « normaliser » pour améliorer, d’une part, la disponibilité des chimiothérapies au sein de la tumeur, et d’autre part, l’oxygénation tumorale pour accroitre l’efficacité de la radiothérapie. Nos résultats sont en faveur d’un tel effet exercé par le pomalidomide dans notre modèle murin de lymphome cérébral, caractérisé par une infiltration tumorale périvasculaire, une fuite capillaire mais sans néo angiogenèse. Nos travaux fournissent un rationnel biologique à de futurs essais cliniques avec les iMids dans le traitement des lymphomes cérébraux primitifs voire des tumeurs malignes cérébrales. / Therapeutic brain irradiation carries a risk of irreversible delayed neurotoxicity partly due to the effect of irradiation on the cerebral vascular compartment. Pericytes and communication between pericytes and endothelial cells play a major role in vessel stabilization in the formation and regulation of the blood-brain barrier and in the control of cerebral blood flow. We show in a murine model of brain irradiation, that pericytes are a target of early brain irradiation. After irradiation, the morphology of pericytes is altered and markers of activation of pericytes are overexpressed. Consequently, communication between the endothelial cell and pericyte is disrupted , which results in a decreased capacity of pericytes for inducing a vascular constriction after electrical stimulation. Concomitantly, the permeability of the blood - brain barrier is abnormally increased after irradiation. Treatment with thalidomide administered in the week before and after irradiation, prevents the effects of irradiation on pericytes . Communication between pericytes and endothelial cells are maintained as well as the contractile properties of pericytes. The impermeability of the blood brain barrier is also preserved. The PDGF-β/PDGFR-β signaling pathway, which is essential for the recruitment of pericytes by endothelial cells, is at least partially involved in the protective effect of thalidomide. Further studies are needed to define the mechanisms underlying the effect of irradiation on the pericytes and the protective effect of thalidomide. We have, in parallel, developed a model of murine luciferase positive CNS lymphoma to verify first, the safety of the combination of radiotherapy and thalidomide and its derivatives of the class of immunomodulators ( IMiDs ), lenalidomide and pomalidomide. These three molecules do not decrease the antitumor effect of radiotherapy, but the antitumoral effect of the association of radiotherapy and pomalidomide is synergistic. The concept of the normalization of the tumor vascularization refers to molecules capable not to induce regression of the abnormal tumor vessels but to "normalize" the tumoral vasculature in order to improve, on one hand , the availability of chemotherapy in the tumor , and on the other hand, the tumor oxygenation to increase the effectiveness of radiotherapy. Our results are in favor of such an effect exerted by pomalidomide in our murine model of cerebral lymphoma, characterized by perivascular tumor infiltration and capillary leak .Our work provide a biological rational for future clinical trials with IMiDs in the treatment of brain lymphomas or malignant brain tumors.

Type-A Î3-amino-butyric acid receptors (GABA_ARs) are pentameric ligand-gated ion channels (pLGICs), which mediate the majority of fast inhibitory neurotransmission in the animal central nervous system. Their dysfunction is related to numerous conditions including epilepsy, insomnia, anxiety, panic disorders, depression and schizophrenia. GABA_ARs are therefore major targets of clinically important drugs, including benzodiazepines and the intravenous general anaesthetics etomidate and propofol, as well as endogenous modulators, for example neurosteroids. Despite recent progress in structural biology of pLGICs, GABA_AR structures remain notoriously elusive. Structural information available at the beginning of this project was limited to the benzamidine-bound homopentameric GABA_AR-Î23, in a desensitised conformation. A large number of fundamental questions, including the molecular architecture of physiological, heteromeric GABA_ARs, their signalling mechanisms, the binding and action modes of their numerous ligands, remained to be answered. During this DPhil project, I employed structural biology techniques (X-ray crystallography and single particle cryo-electron microscopy) to further the molecular understanding of human GABAARs. I used subunit-specific llama nanobodies to aid crystallization of homomeric GABA_A-β3 receptors, which led to a 3.16 Å structure in complex with the general anaesthetic etomidate. This structure elucidates the binding mode of the etomidate, the basis for its subunit selectivity and illustrates conformational changes it triggers. I then used cryo-electron microscopy to determine the first structure of a heteromeric GABA_AR, the human α1b3g2, bound to an activating llama nanobody at a medium (5.2 Å) resolution. The numerous other insights obtained range from unambiguously establishing the subunit arrangement and stoichiometry, to proposing a mechanism for receptor assembly and discovering an unexpected role played by N-linked glycans in this process. The work described here opens multiple avenues for future research. Immediate opportunities include high resolution structural characterization of heteromeric GABA_ARs, via cryo-electron microscopy, further development of nanobodies as novel, high affinity and subunit specific tools to modulate GABA-ergic signalling, and structural characterization of numerous small-molecule modulators, of clinical and physiological relevance, bound to human GABA_ARs.

Made available in DSpace on 2015-04-11T13:38:24Z (GMT). No. of bitstreams: 1 karla.pdf: 1853502 bytes, checksum: 17ad3c01eb4702fcf74f49cac2307780 (MD5) Previous issue date: 2010-11-29 / In Amazonian region, Ampelozizyphus amazonicus Ducke, known as saracura-mirá or cerveja de índio , is used to treat gastrointestinal disorders, as an antidote to snake venoms and to prevent malaria. Chemical studies report the triterpenic saponins as the main constituents, however, chemical standardization of the extracts are not described. The anti-plasmodium effect of the aqueous and ethanolic extracts was not observed neither in vitro in cultured P. falciparum, nor in vivo in mice infected with P. berghei and chickens infected with P. gallinaceum. The isolated compounds were not tried in these experiments. Studies on systemic effects of the extracts and dose-effect correlation are scarce. For these reasons, this work proposes the chemical standardization of the extract and the evaluation of the secondary pharmacology, mainly in the cardiovascular system. The plant was collected in Manacapuru (AM). Due to the high concentration of saponins in stems, the extraction was performed in ethanol 50 % and latter partitioned with n-butanol for the separation of the chemical compounds in preparative HPLC. Six majoritary compounds, identified by the peaks retention time and concentration in sample were used as references. The hydroalcoholic extract and its butanolic fraction have shown a slight CNS depressant effect demonstrated by the potentiation of the sleeping time induced by pentobarbital and ethylic ether. The extracts also produced anxiolytic-like effect in the plus maze test and depression in the tail suspension test in mice. Antinociceptive and anti-inflammatory effects were detected in paw edema induced by formalin and carrageenan in rats. FBut protected the gastric mucosa against cold stress or ethanol induced gastric damage, but not against indomethacin-induced gastric damage. FBut inhibited the gastric secretion in vivo in mice and the H+-K+-ATPase in vitro, suggesting an anti-secretory effect. FBut showed hypotensive effect in rats chronically treated per os and in anesthetized rats after e.v. injection. The atrial automatism was not altered, but negative inotropic effect was observed in rat myocardium in vitro. In rat aorta, FBut relaxed the adrenergic tonus. This effect was partially blocked by L-NAME pre-incubation or mechanical destruction of the endothelium. In rat isolated jejunum, the EC50 of the ACh was increased, however, the maximum contraction was not altered. In rat isolated vas deferens adrenergic contraction, the FBut showed non-competitive antagonistic effect. In depolarized vas deferens, the FBut decreased the contraction induced by CaCl2, suggesting a calcium influx blockade. In rat isolated diaphragm, the directly or indirectly contractions induced by electrical stimulation of the muscle was not altered. In mammalian P-type ATPases, FBut inhibited the gastric H+,K+-ATPase, but did not inhibit the Ca2+-ATPase in vitro. The results indicate that hypotension produced by FBut seems to be related to the relaxation of the adrenergic vascular tonus, possibly due to the activation of the NO synthesis in the endothelial cells. The FBut effects in rat aorta and smooth muscles indicate that other vasodilatory mechanism(s) may be involved, probably calcium channel blockade in vascular smooth muscle. / Na região Amazônica, a Ampelozizyphus amazonicus Ducke, conhecida como saracura-mirá ou cerveja de índio, é utilizada no tratamento de distúrbios gastrintestinais, como anti-inflamatória, antídoto para veneno de cobra e na prevenção da malária. Estudos químicos descrevem o isolamento e identificação de saponinas triterpênicas como as principais substâncias. Não há relatos da padronização de extratos de A. amazonicus. A atividade antiplasmódio dos extratos aquoso e etanólico não foi comprovada in vitro em cultura de P. falciparum e nem in vivo em camundongos e galinhas infectados com P. berghei e P. gallinaceum, respectivamente. A atividade dos compostos isolados não foi testada. Estudos sistêmicos dos extratos correlacionando dose-efeito são raros. Considerando essas informações, este trabalho propõe a padronização química do extrato a ser estudado e a avaliação da farmacodinâmica secundária, principalmente na atividade cardiovascular. Exemplares da planta nativa foram colhidos em Manacapuru, AM. A alta concentração de saponinas dificultou a extração aquosa do pó do caule, optando-se pela extração hidroalcoólica com etanol a 50%, de melhor rendimento, permitindo a partição em n-butanol para a separação dos componentes químicos em cromatografia líquida preparativa. Como referência, foram utilizados os seis componentes majoritários, identificados pelo tempo de retenção e concentração de cada pico. O extrato hidroalcoólico e a fração butanólica, testados com protocolos padronizados para a triagem farmacológica, mostraram efeito depressor leve do SNC comprovado com a potenciação do sono barbitúrico e etéreo. Os extratos produziram também efeitos do tipo ansiolítico no labirinto em cruz elevado e efeito depressor no teste de suspensão pela cauda. Atividades antinociceptiva e anti-inflamatória foram detectadas nos testes da formalina e do edema de pata induzido por carragenina. A fração butanólica (Fbut) protegeu a mucosa gástrica das lesões induzidas por estresse a frio ou por etanol, mas não as induzidas por indometacina, indicando que a atividade anti-úlcera não está relacionada à síntese de prostaglandina. A FBut, inibiu a secreção gástrica in vivo e a H+-K+-ATPase in vitro, sugerindo que esse mecanismo pode ser o responsável pelo efeito antissecretor ácido. A FBut provocou hipotensão quando administrada cronicamente por via oral e quando injetada e.v. em ratos anestesiados. O automatismo atrial não foi alterado, mas em miocárdio de ratos foi observado efeito inotrópico negativo. Em aorta de rato, a FBut relaxou o tônus adrenérgico. Esse efeito foi parcialmente bloqueado pela incubação prévia com L-NAME ou destruição mecânica do endotélio. Na musculatura lisa, a CE50 da ACh foi aumentada sem alteração do efeito máximo em jejuno de rato; em ducto deferente de rato contraído à adição de noradrenalina, a FBut teve efeito antagonista do tipo não- competitivo. Em ducto deferente despolarizado, a FBut diminuiu a contração induzida pela adição de CaCl2, indicando bloqueio do influxo de cálcio. A capacidade contrátil do músculo diafragma de rato estimulado direta ou indiretamente não foi alterada. Em ATPases tipo-P isoladas de mamíferos, a FBut inibiu a atividade da H+,K+-ATPase da mucosa gástrica de porco, mas não a Ca2+-ATPase da coxa de coelho. Os resultados indicam que a FBut produz hipotensão que parece estar relacionada com o relaxamento do tônus vascular adrenérgico, possivelmente decorrente da ativação da via do NO na célula endotelial. A ação da FBut na aorta de rato e na musculatura lisa, indica que outros mecanismos vasodilatadores podem estar envolvidos, como o bloqueio canais de cálcio na musculatura lisa vascular.

<p>Eukaryotic gene transcription plays a regulatory role in mammalian developmental processes. It has been shown that transcriptional control is an important mechanism for specification of neurotransmitter phenotypes. In the mammalian central nervous system, the transcription factor AP-2 family is one of the critical regulatory factors for neural gene expression and neuronal development. It has been shown that several genes in the monoaminergic systems have AP-2 binding sites in regulatory regions, suggesting a regulatory role of AP-2 also in the adult brain. Brainstem monoamines are implicated in the expression of personality traits and imbalances in these systems may give rise to psychiatric disorders. </p><p>The gene encoding AP-2β includes a polymorphic region consisting of a tetranucleotide repeat of [CAAA]_4-5 in intron 2. Studies on AP-2β genotype in relation to personality and platelet MAO activity, a trait-dependant marker for personality, are presented in this thesis. Furthermore, correlations between brainstem levels of AP-2α and AP-2β and monoamine turnover in projection areas in rat forebrain are reported. These results strengthen the notion that the AP-2 family is important regulators of the monoaminergic systems in the adult brain. Furthermore, two studies are presented in this thesis with analyses indicating a role for AP-2 in the molecular mechanism of antidepressant drugs.</p><p>Altogether, this thesis presents data supporting our notion that the transcription factor AP-2 family is involved in the regulation of the monoaminergic systems both pre- and postnatally, and, therefore, might be involved in the pathophysiology of neuropsychiatric disorders.</p>

<p>The CNS monoaminergic systems are considered as the head engine regulating neuropsychiatric functions and personality. Transcription factor AP-2 is known to be essential for the development of the brainstem including the monoaminergic nuclei, and has the ability to regulate many genes in the monoaminergic systems. The ability of transcription factors to regulate specific gene expression, has lately made them hot candidates as drug targets. In this thesis, results indicating a role of AP-2 in the molecular effects of the antidepressant drugs citalopram and phenelzine, are presented. </p><p>A polymorphism in the second intron of the gene encoding AP-2ß has previously been associated with anxiety-related personality traits as estimated by the Karolinska Scales of Personality (KSP). In this thesis, results confirming this association, gained by using a larger material and several different personality scales, are presented. Furthermore, data is presented showing an association between the activity of platelet monoamine oxidase, a trait-dependent marker for personality, and the genotype of the AP-2ß intron 2 polymorphism. </p><p>The functional importance of the AP-2ß intron 2 polymorphism has not yet been elucidated. Included in this thesis are results showing that the AP-2ß intron 2 polymorphism is not in linkage disequilibrium with the only other described polymorphism in the AP-2ß gene, i.e. in the AP-2ß promoter (-67 G/A). Introns have in several studies been shown to include binding sites for regulatory proteins, and thus, to be important in transcriptional regulation. Results are presented demonstrating that one human brain nuclear protein binds only to the long variant of the AP-2ß intron 2 polymorphism. If this protein is involved in the regulation of the AP-2ß gene, it would affect the expression levels of the AP-2ß protein. </p><p>In general, this thesis further establishes the role of transcription factor AP-2 as a regulatory factor of importance for personality and monoaminergic functions.</p>

Several factors contribute to the failure of the central nervous system (CNS) to regenerate after injury. These include inhibition of axonal growth by myelin and glial scar associated molecules, as well as the intrinsic inability of adult CNS neurons to grow long axons in environments that are permissive for younger neurons. Neurons in the peripheral nervous system (PNS) display a much higher capacity to regenerate after injury than CNS neurons, as shown by conditioning lesion experiments and by microtransplantation of dorsal root ganglia neurons into CNS white matter tracts. Our central hypothesis is that neurons of the PNS express specific regeneration associated genes that mediate their enhanced growth response after injury. We have employed a combination of subtractive hybridization, microarray comparison and promoter analysis to probe for genes specific to neurons of the dorsal root ganglia (DRG), using cerebellar granule neurons (CGN) as a reference. We have identified over a thousand different genes, many of whose products form interaction networks and signaling pathways. Moreover, we have identified several dozen transcription factors that may play a role in establishing DRG neuron identity and shape their responses after injury. One of these transcription factors is Signal Transducer and Activator of Transcription 3 (STAT3), previously known to be upregulated in the PNS after a conditioning lesion but not known to be specific to the PNS. Using a real time PCR and immunochemical approaches we have shown that STAT3 is constitutively expressed and selectively active in DRG neurons both in culture and in vivo. We show that the overexpression of wild type STAT3 in cerebellar granule neurons leads to the formation of supernumerary neurites, whereas the overexpression of constitutively active STAT3-C leads to a 20% increase in total neurite outgrowth. It is hoped that the genetic delivery of STAT3-C, potentially combined with co-activators of transcription, will improve functional regeneration of CNS axons in vivo.

Trauma to the central nervous system (CNS) results in an irreversible disruption of axon tracts, often leading to lifelong functional deficits. Despite a large body of research into the mechanisms that underlie the lack of axonal regeneration after CNS injury, there are currently no effective treatments. One major obstacle involves the presence at injury sites of CNS growth-inhibitory molecules, such as myelin proteins and astrocyte-derived chondroitin sulfate proteoglycans (CSPGs), which act as environmental barriers to axonal regeneration. Our lab recently described the identification and characterization of a novel compound, F05, which promotes growth on inhibitory substrates in vitro. I show that F05 improves regeneration in vivo after acute sensory axon transection as well as after optic nerve crush injury. F05 does not target known signaling molecules involved in CSPG or myelin mediated inhibition but does affect growth cone microtubule dynamics, suggesting a potentially novel mechanism of growth promotion. Using a protein microarray, I show that apoptotic signaling pathways may underlie glial-derived inhibition and its relief by F05. In addition, I employed a comparative gene microarray to show that F05 induces similar changes in gene expression as antipsychotics of the piperazine phenothiazine structural class (PhAPs). Indeed, PhAPs share F05’s ability to overcome glial-derived inhibition of cultured CNS neurons and do so through a mechanism dependent on antagonism of calmodulin. These studies have led to the identification of potentially novel clinical treatments for CNS injury as well as a better understanding of environmentally derived growth-inhibitory signaling mechanisms.

Mammalian central nervous system (CNS) neurons lose their ability to regenerate their axons after injury during development. For example, optic nerve injury studies in hamsters have shown that optic nerve axons injured around the time of birth retain the ability to regenerate to their target, but this ability is lost during development (So et al., 1981). The development of an inhibitory CNS environment has been implicated in the inability of the adult CNS to regenerate, however there is also support for this loss being a result of changes in developmental programs intrinsic to the neurons themselves (Goldberg et al., 2002a; Goldberg, 2004). While some molecules have been identified as being involved in intrinsic mechanisms controlling axon growth, there is still much to be discovered. Using genes shown to be regulated in retinal ganglion cells (RGCs) during development (Wang et al., 2007), I performed an overexpression screen in embryonic primary neurons measuring changes in neurite growth. Of these genes, the most significant effect in neurite growth was seen with overexpression of Krüppel-like factor 4 (KLF4), resulting in a greater than 50% decrease in growth. KLF4 is a member of the KLF family of transcription factors which all possess a DNA binding domain containing 3 zinc finger motifs. Outside of the nervous system, KLF4 has been implicated in cancer (Black et al., 2001; Rowland and Peeper, 2006), mitotic growth arrest (Shields et al., 1996) and most recently in the induction of pluripotency (Yamanaka, 2008; Zhao and Daley, 2008). In the CNS, KLF4 has recently been implicated in increasing the sensitivity of cortical neurons to NMDA insult (Zhu et al, 2009), though no effect of KLF4 on neurite growth or regeneration has yet been described. I found that KLF4 overexpression in RGCs results in decreased neurite growth and neurite initiation. KLF4 overexpression also leads to decreases in polarity acquisition in hippocampal neurons, though even when they acquire polarity, they still display decreased neurite growth. Additionally, KLF4 knockout targeted to RGCs leads to an increased neurite growth ability and increased neurite initiation in vitro. In vivo, KLF4 knockout increases RGC axon regeneration after optic nerve injury. Interestingly, KLF4 is one of 17 members of the KLF family, known for their ability to act redundantly and competitively amongst family members for their binding sites. Therefore, we looked to see if other KLFs could affect neurite growth ability. 15 of 17 KLF family members are expressed in RGCs, and their overexpression results in differential effects on neurite growth in both cortical neurons and RGCs. Additionally, many of the family members are developmentally regulated in a manner that typically correlates with their ability to affect neurite growth. For example, KLF6 and -7, whose expression decreases during development, when overexpressed, increase neurite growth, whereas KLF9, whose expression increases developmentally, when overexpressed, decreases neurite growth. Surprisingly, there are multiple KLFs expressed in RGCs that are neurite growth-suppressors, and further study has revealed that the combination of KLF growth enhancers with KLF growth suppressors results in a suppressive or neutral phenotype (Moore et al., 2009), suggesting that to further enhance regeneration after injury in vivo, we will need to additionally remove the growth suppression from other KLF family members. Taken together, these data suggest that KLFs may play an important role in the intrinsic loss of axon growth and regeneration seen during development. Further characterization of downstream targets of KLF4 and other KLF family members may reveal specific neuronal gene targets that could mediate the phenotypic effects of these transcription factors. It is my hope that by determining the developmental programs that underlie the loss of intrinsic axon growth ability of CNS neurons, we may ultimately determine how to revert adult CNS neurons to their embryonic axon growth ability.