O câncer é a principal causa de morte nos paises economicamente desenvolvidos e a segunda em paises em desenvolvimento, resultado, em parte, da grande falta de especificidade dos tratamentos atualmente disponíveis. Por outro lado, uma aplicação clínica muito específica, denominada letalidade sintética, foi recentemente proposta. Nesta abordagem terapêutica os inibidores de poli(ADP-ribose) polimerases (PARP), também conhecidos como PARPis, mostraram-se capazes de induzir a morte celular seletiva em células tumorais com defeitos em BRCA1 e BRCA2 (ambas envolvidas no reparo de quebras duplas - DSBR). Assim, a excitante possibilidade de eliminar as células cancerígenas de maneira seletiva fez com que os PARPis passassem de interessantes ferramentas moleculares às mais promissoras drogas anticâncer da atualidade. Contudo, os mecanismos básicos envolvidos na citotoxicidade dos PARPis continuam pouco conhecidos e suas aplicações restritas a um pequeno grupo de cânceres. Por este motivo, neste trabalho, a citotoxicidade do Olaparib (um inibidor de PARP) foi investigada em um painel de linhagens de câncer colorretal (CRC). Os resultados demonstraram que o Olaparib é uma droga de ação lenta, cuja citotoxicidade pode ser modulada por defeitos genéticos em MLH1 (envolvido no reparo de bases mal-emparelhadas) e no supressor tumoral PTEN. Por outro lado, observou-se que o fenótipo MSI (Instabilidade de microssatélites) e os defeitos genéticos em p53 não influenciaram a citotoxicidade do Olaparib. Além disso, linhagens com resistência adquirida a Oxaliplatina (Oxp) e a 5-Fluorouracil (5- Fu) não apresentaram efeito refratário ao Olaparib, enquanto que linhagens com resistência adquirida a SN-38 (metabólito ativo do Irinotecano) apresentaram um forte efeito refratário. Finalmente, as associações de Oxp ou 5-Fu com Olaparib foram capazes de sensibilizar células com resistência relativa e adquirida. Juntos, estes resultados sugerem uma série de novas possibilidades para o emprego de inibidores de PARP no tratamento de CRC. / Cancer is the main cause of death in developed countries and the second in lessdeveloped countries, that results in part from the low specific treatments available. However, a very specific therapeutic approach, called synthetic lethality, was recently proposed. The best documented synthetic lethal interaction was reported between poly(ADP-ribose) polymerases inhibitors (PARPis) and defects in BRCA1 and BRCA2 (both involved in double-strand break repair - DSBR), which may induce selective cancer cells death. Therefore, the exciting possibility to selectively kill cancer cells has been moving PARPis from interesting molecular tools to the forefront of cancer therapy research. However, the basic mechanisms involved in PARPis cytotoxicity are still poorly studied and its clinical applications are restricted to a small number of malignances. Herein, the Olaparib (PARPi) cytotoxicity was investigated in a colorectal cancer (CRC) cell line panel. The results demonstrated that Olaparib is a slow action drug, which may have its effects increased in cells with MLH1 (involved in mismatch repair) and PTEN (tumor supressor) defects. On the other hand, neither the MSI (microsatellite instability) phenotype nor the p53 defects were observed to influence on Olaparib cytotoxicity. Further, neither Oxp nor 5-Fu resistant cell lines presented cross-resistance to Olaparib, whereas a pronounced cross-resistance was observed for SN-38 (Irinotecan metabolite) resistant cell line. Finally, Olaparib associations with Oxaliplatin or 5-Fluorouracil were shown to sensitize cells with both relative and acquired resistances. Together, these results suggest a series of new possible uses for PARP inhibitors in CRC treatment.

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Major depressive disorder (MDD) is a prevalent and enervating mental illness affecting millions globally. Unfortunately, a significant proportion of patients do not receive clinical benefit from existing antidepressant medications. The limited effectiveness of currently available antidepressant drugs emphasizes the need to identify more effective medications for individuals who are treatment-resistant. We have previously reported abnormally elevated poly (ADP-ribose) polymerase-1 (PARP1) gene expression levels in the postmortem brain from MDD brain donors. PARP1 is a DNA damage repair enzyme that is also linked to neuroinflammation through multiple biochemical pathways. PARP1 upregulation in MDD could indicate a role for this enzyme in the etiopathology of MDD, particularly as it relates to neuroinflammation. In fact, we have shown that drugs that inhibit PARP1 produce antidepressant-like properties in two different rodent behavioral models that mimic depressed mood in humans. In the present study, we utilized a unique rodent behavioral model that produces depressive-like behavior by combining psychological stress with stimulation of inflammation. Depressive behavior produced by this experimental paradigm is not reversed by the prototypical antidepressant fluoxetine. This treatment-resistant depression was elicited by treating rats with injections of lipopolysaccharide (LPS; 0.1 ug/kg/day) and daily exposure to chronic unpredictable stress (CUS) for 28 days. Depressive behaviors were measured with sucrose preference and forced swim tests in 5 treatment groups (n=6-8 rats per group) including unstressed rats, CUS rats, CUS+LPS rats, and CUS+LPS rats treated with either the PARP1 inhibitor 3-aminobenzamide (3AB) or the antidepressant fluoxetine. We evaluated the role of neuroinflammation in this model by measuring the amount of microglial activation in several brain regions in rats from all treatment groups. Microglia activation was measured by quantifying the relative amount of expression of the microglia marker protein, IBA1, using an anti-IBA1 antibody. 3AB demonstrated robust and unique antidepressant activity superior to fluoxetine in the treatment-resistant rat model. IBA1-immunoreactivity levels were elevated in brains from CUS and CUS+LPS rats, although there was no evidence that LPS increased IBA1-immunoreactivity above levels found in CUS rats that did not receive LPS. Levels of IBA1-immunoreactivity in the brains from rats treated with either fluoxetine or 3AB trended lower as compared to the CUS and CUS+LPS groups, although this effect did not reach statistical significance. The lack of significant differences is likely related to small sample sizes; experiments are underway to increase the sample sizes of each group. The findings provide further support for the potential of PARP1 inhibitors in treating MDD and suggest that these drugs may be more effective, or more broadly effective than standard antidepressants.

Apoptosis is a process of the programmed cell death in response to severe mutations in DNA or cell stress. Apoptosis plays a key role in tissue maintenance by eliminating senescent and damaged cells. Various molecules take part in apoptosis, main participants are Bcl-2 protein family and caspases. The latter one are responsible for apoptosis execution, while Bcl-2 protein family regulates apoptotic pathway. Failure of this regulation may cause several pathologies, including development of neoplastic tissue. Human endometrium is a speci c tissue, in which apoptosis is present in cycling pattern. Present study shows expression level of Bcl-2, Bax, Bad, Bid, pro-caspase-3, caspase-3 and PARP in normal, atrophic, hyperplastic and cancerous (Grade I and II) human endometrium. Bad and Bid proteins can be possible breakpoints in neoplastic transfer due to opposit expression in cancerous and hyperplastic endometrium.

Background: Cancer patients are disproportionately affected by generalized anxiety and major depression. For many, current treatments for these conditions are ineffective. In this case report, we present a serendipitous case of anxiety and depression improvement following administration of the poly (ADP-ribose) polymerase (PARP) inhibitor niraparib. Case presentation: A 61-year old woman with a 20-year history of mild depression developed recurrent ovarian carcinoma and was placed on niraparib for maintenance chemotherapy. With the original onset of ovarian cancer, she experienced an episode of major depression that was resolved with sertraline. After recurrence of ovarian cancer, she experienced a recurrence of major depression and a new onset of generalized anxiety that failed to completely respond to multiple medications. After beginning niraparib therapy the patient noticed a rapid resolution of the symptoms of her anxiety and depression, an effect that was limited to 10-14 days. Due to bone marrow suppression, the patient was taken off and restarted on niraparib several times. Each discontinuation of niraparib resulted in return of her depression and anxiety, while each recontinuation of niraparib resulted in an improvement in her mood and anxiety. Conclusions: This case demonstrates rapid and temporary improvement of anxiety and depression following niraparib administration. There is ample preclinical data that PARP signaling may play a role in psychiatric illness. A small amount of indirect data from clinical trials also shows that niraparib may have psychiatric benefits. Further research on PARP inhibition and its potential psychoactive effects is sorely needed.

Oxidative cell death contributes to neuronal cell death in many neurological diseases such as stroke, brain trauma, and Alzheimer's disease. In this study, we explored the involvement of poly(ADP-ribose)-polymerase (PARP) in oxidative stress-induced necroptosis. We showed that PJ34, a potent and specific inhibitor of PARP, can completely inhibit glutamate-induced necroptosis in HT-22 cells. This protective effect was still observed 8 h after glutamate exposure followed by PJ34 treatment. These results suggest that PARP activation plays a critical role in glutamate-induced necroptosis. We also examined the interaction between PARP and a necroptosis inhibitor called necrostatin-1 (Nec-1). Previously, we showed that Nec-1 protects against glutamate-induced oxytosis by inhibiting the translocation of cellular apoptosis-inducing factor (AIF), a downstream target of PARP-1 activation. In this study, Nec-1 reduced PARP activity but had no effect on the expression of PARP-1 in cells treated with glutamate. Nec-1 also did not protect against cell death mediated by the PARP activator N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), although PJ34 did protect against MNNG-mediated cell death. These findings suggest that Nec-1 is not a direct PARP inhibitor and that its signaling target is located upstream of PARP.

How do organisms attain the capacity to regenerate a structure, entire body, or not to regenerate? These are fundamental questions in biology for understanding how replicative systems are evolved to renew, age, and/or die. One outstanding question in regenerative biology that attracts attention is how and why the human central nervous system fails to regenerate after injury. Nervous system injuries are characterized by axonal damage and loss of synaptic function that contribute to debilitating neuronal dysfunctions. Although the molecular underpinnings of axon regeneration are well characterized, very little is known about how and what molecular pathways modulate reformation of synapses within regenerating axons to restore function. Thus, understanding the fundamental molecular and genetic mechanisms of functional axon regeneration (FAR), restoration of both axon and synapse, for the functional recovery of the nervous system remains elusive. In Chapter I, I outline the biology of regeneration and provide evolutionary perspectives of this phenomenon. Then, I provide clinical perspectives of central nervous system regeneration and therapeutic innovations. I next introduce the regulators of axon regeneration and how C. elegans as a genetic system allows detailed characterization of axon regeneration. In Chapter II, using C. elegans as a platform, I show how axon regeneration and synaptic reformation are controlled by distinct genetic pathways. I show how Poly-ADP ribose polymerase (PARP) pathway modulates functional restoration by regulating divergent genetic pathways leading to axon regeneration and synapse restoration. Finally, in Chapter III, I summarize the model of axon regeneration, evolutionary perspectives, and epistemic limitations of C. elegans axon regeneration.

Major depressive disorder (MDD) is a leading cause of disability worldwide, with a lifetime prevalence rate of approximately 20%. Inadequate pharmacological treatment methods for MDD are a significant debilitating factor. Patient estimates suggest that the treatment resistance rate for pharmacological interventions is over 30%. Postmortem analyses of human tissue of individuals diagnosed with MDD have shown an increase in Poly (ADP-ribose) polymerase 1 (PARP-1) mRNA gene expression in prefrontal cortical white matter when compared to psychiatrically normal brain tissue. In order to further investigate this issue, the present study used the social defeat stress/chronic unpredictable stress (SDS + CUS) rodent model of depression to induce a state of chronic psychological distress. Rats were treated with either the PARP-inhibitor, 3-aminobenzamide (3-AB); a common selective serotonin reuptake inhibitor (SSRI) fluoxetine (FLX), or saline. During the stress manipulation we conducted the sucrose preference test, results revealed that saline-treated rats which had undergone SDS + CUS showed significant reductions in sucrose preference compared to all other groups. In addition, a social interaction test was conducted one day after the stress manipulation, and saline-treated stressed animals demonstrated less social interaction compared to all other groups, indicating the stress manipulation was effective. Neurobiological assays were conducted to examine PARP expression, microglial morphology, and proinflammatory cytokine expression. Though we expected to find a decrease, results from immunofluorescence studies of tissue sections revealed an elevation of PARP-1 protein expression in prefrontal cortical gray matter in the FLX/Stress group compared with SAL/Stress group. Microglial morphological changes indicated that the SAL/Stress group had significantly more prolate microglia when compared to all other treatment groups, suggesting early activation of microglia, an indicator of neuroinflammation. Increases in IL-1β and TNF-⍺ expression was observed in the hippocampus of the SAL/Stress group when compared to all other treatment groups. Interestingly, IL-6 expression was significantly elevated in the SAL/Stress group when compared to the FLX/Stress group and the CTRL/No stress group but did not significantly differ from the 3-AB/Stress group. This study revealed therapeutic potential of 3-AB for the treatment of stress-related disorders, as well as the neuroinflammatory mechanisms associated with chronic stress.

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