Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

A doença periodontal é a doença crônica mais prevalente nas doenças orais. Dentre os mediadores desse processo contam-se a Resolvina E1 (RvE1), um mediador pró-resolução da inflamação capaz de diminuir a perda óssea secundária á doença periodontal em coelhos, e o oxido nítrico (NO), o qual pode ser produzido em grandes quantidades pela ação de citocinas e estimular a diferenciação e atividade osteoclástica. O objetivo deste estudo foi investigar os efeitos da RvE1 em osteoclastos (OCs) em cultura e os mecanismos envolvidos, bem como o papel do NO na progressão da periodontite experimental em ratos e as alterações sistémicas resultantes de danos oxidativos. A diferenciação de OCs foi induzida em células de medula óssea de camundongos C57BL/6 em cultura (7 dias) e tratadas com diferentes doses de RvE1. NFkB e Akt fosforilada foram analisadas por Western blotting e a expressão gênica de NO sintase (NOS) induzível (iNOS) por \"real-time\" PCR. A participação dos receptores ChemR23 e BLT-1 na resposta à RvE1 foi estudada em membranas isoladas de OCs empregando radioligantes. A perda óssea alveolar e danos em órgãos periféricos foram analisados em ratos com periodontite induzida por ligadura (P) e sob tratamento de longo prazo com o inibidor não-seletivo de NOS, L-NAME. Os animais receberam L-NAME durante as 2 semanas prévias à indução da periodontite e até o momento do sacrifício (3, 7 ou 14 após a ligadura). A perda óssea alveolar foi avaliada radiograficamente, e análises do conteúdo de proteínas contendo nitrotirosina (NT), espécies reativas do ácido tiobarbitúrico (TBARs) e atividade da mieloperoxidase (MPO) foram realisadas em amostras de coração, baço, rim, fígado e pulmão. RvE1 (3 ng/mL) através da ativação do receptor para BLT-1 (mas não ChemR23) inibiu a diferenciação e atividade de OCs (p<0,05) após 5 ou 7 dias de cultura, assim como a fosforilação dos dois sítios da Akt e a traslocação do NF-<font face=\"symbol\">kB para o núcleo, um evento chave tanto na diferenciação de OCs (p<0,05) como na diminuição da expressão de iNOS. In vivo, ratos P (dia 7) mostraram um aumento na expressão de NT cardíaca e MPO renal em comparação ao grupo Sham (S; p<0,05). L-NAME resultou em aumento de NT hepática no grupo P no dia 3 (p<0,05), mas diminuição da NT cardíaca no dia 7 (p<0,01). Em comparação ao grupo P, ratos P+LN mostraram um aumento significativo na MPO hepática, cardíaca e renal no dia 3 (p<0,05), mas diminuição de MPO (dia 7) e TBARs esplênico (dia 3, p<0,05). Em resumo, mostramos que a RvE1 ligando-se ao receptor para BLT-1 inibe a diferenciação e atividade de OCs interferindo com a sinalização de Akt e NF-<font face=\"symbol\">kB, e consequentemente inibindo a expressão da iNOS, e que o NO tem um papel central na periodontite, não só relacionado a consequências locais na perda óssea alveolar, como também em órgãos periféricos distantes. / The periodontal disease is the most prevalent chronic disease in oral diseases. Among the mediators of this process, is the Resolvin E1 (RvE1), a novel mediator pro-resolving of inflammation that is capable to decrease alveolar bone loss secondary to periodontal disease in rabbits; and the nitric oxide (NO), that can be produced in large amount, induced by cytokines and it can stimulate the osteoclast differentiation and activity. The aim of this study is to investigate the effects of RvE1 on osteoclasts (OCs) culture and the pathway involved, also the role of NO in the progression of experimental periodontitis in rats and systemic alterations due to oxidative damage. The OCs differentiation was induced in bone marrow cell culture from C57BL/6 mice (7 days) and treated with various doses of RvE1. NF<font face=\"symbol\">kB and Akt phosphorylation were analyzed with Western blotting and the genic expression of NO synthase (NOS) inducible (iNOS) with \"Real Time\" PCR. The role of receptors ChemR23 and BLT-1 was accessed in OCs isolated membranes performing radioligants. The alveolar bone loss and peripheral organ damage was assessed in rats with ligature-induced periodontitis (P) under a long-term treatment of a NOS inhibitor, L-NAME. The animals received L-NAME from two weeks prior to periodontitis induction and until their sacrifice (3, 7 and 14 days after ligature). The alveolar bone loss was evaluated radiographically, and the protein nitrotyrosine (NT) content, reactive species of thiobarbituric acid (TBARs) and myeloperoxidase activity (MPO) were analyzed in samples of heart, spleen, kidney, lungs and kidneys. RvE1 (3 ng/mL) trough BLT-1 receptor activation (but not ChemR23) inhibits the OCs differentiation and activity (p<0.05) after 5 or 7 days of the culture, as well as the Akt phosphorylation and NF-<font face=\"symbol\">kB translocation to the nucleus, a key event both in OCs differentiation (p<0.05) and iNOS expression decreases. In vivo, P rats (day 7) show an increase of heart NT and renal MPO, but lower lung MPO activity in comparison to the Sham group (S; p<0.05). L-NAME leads to an increase the liver NT expression in P rats on day 3 (p<0.05), but decreases the cardiac NT on day 7 (p<0.01). In comparison with the P group, P+LN rats showed significantly increased liver, heart and kidney MPO content on day 3 (p<0.05), but lower lung MPO (day 7) and spleen TBARs (day 3) content (p<0.05). In summary we have shown that RvE1 binding on BLT-1 receptor inhibits OCs differentiation and activity by interfering with Akt and NF-<font face=\"symbol\">kB signaling and consequently iNOS inhibition, and NO has a central role on periodontitis, not only related to the local consequences on alveolar bone resorption, but also on distant peripheral organs.

The skeleton is a dynamic organ that undergoes a continual process known as bone remodeling. Bone remodeling is necessary to maintain structural integrity, heal micro-fractures caused by from daily wear and tear, and to store and release essential ions and minerals. Remodeling is a highly regulated process, with bone resorption precisely balanced by bone formation under homeostatic conditions. In the setting of rheumatoid arthritis (RA), an inflammatory condition affecting joints, this balance is lost and bone around inflamed joints is eroded. These so-called "bone erosions" compromise joint function, causing disability. Osteoclasts, multinucleated cells of hematopoietic origin, are the only cells known to resorb bone. Osteoclasts are found at erosion sites in human joints, and data from mouse models of inflammatory arthritis suggest that osteoclasts are required for erosions to form in bone. The canonical pathway of osteoclast differentiation requires stimulation of myeloid precursors by the cytokine Receptor Activator of NF-Kappa B ligand (RANKL) through its receptor, RANK. In the inflamed joint, RANKL expression can be induced on mesenchymal lineage cells by inflammatory cytokines such as tumor necrosis factor alpha (TNF alpha). Surprisingly, our lab observed bone erosions and osteoclast formation in a mouse model of RA in the absence of RANK. Thus we hypothesized that in addition to RANKL expression, the cytokine milieu in RA may directly stimulate osteoclast formation. It was recently reported that the inflammatory cytokines TNF alpha and interleukin-6 (IL-6) in combination stimulate osteoclast differentiation, independent of exogenous RANKL. We have reproduced these results and shown that these osteoclast-like cells form entirely independently of RANK signaling. However, TNF alpha/IL-6 induced osteoclast formation still requires the transcription factor Nuclear Factor of Activated T cells (NFATc1), a master regulator of RANK-mediated osteoclast differentiation, as well as co-stimulatory signaling provided by the immunoreceptor tyrosine based activation motif (ITAM)-containing DNAX-activating protein (DAP12) molecules. We also showed that TNF alpha/IL-6 induced osteoclast formation requires activity of IL-6 receptor (IL-6R), as osteoclast formation can be inhibited through co-culture with an IL-6R blocking antibody (MR16-1). Finally, using an in vivo mouse model of RA in RANK-deficient mice, we tested whether blocking IL-6R with MR16-1 antibody protects against the formation of periarticular bone erosions. Our results suggest that a RANK-independent pathway of osteoclast formation contributes to inflammatory bone erosions. Targeting this pathway may improve outcomes for RA patients.

Multiple Myeloma (MM) is an incurable plasma cell malignancy and, although novel treatment regimes in the past decade have improved patient outcome, long-term treatment leads to relapse and refractory disease. The centrosomal kinase NEK2 is found overexpressed in MM and promotes chromosomal instability, drug resistance and increased proliferation. Although much research shows NEK2 having a detrimental effect in cancer, much of its mechanisms of overexpression and drug resistance has not been studied in detail. In this work we expand our understanding of NEK2 in MM. Using Tandem Affinity Purification coupled with Mass Spectrometry, we show that NEK2 directly interacts with the de-ubiquitinase USP7. We confirm this interaction in cell lines of MM and lung cancer. Since USP7 has been shown to have important cancer-promoting roles we tested if USP7 was necessary for NEK2-driven bortezomib resistance. We found that USP7 shRNA was sufficient to sensitize the bortezomib resistant NEK2 overexpressing cells to bortezomib. Surprisingly, we found that USP7 inhibition with shRNA or by treatment with the small molecule USP7 inhibitor P5091 led to depletion of NEK2 protein in every cell line tested. Previous research shows USP7’s main function is a de-ubiquitinase and, since NEK2 is a target of the ubiquitin-proteasome system, we hypothesized USP7 may be de-ubiquitinating NEK2. Through western blots and immunoprecipitations, we show the NEK2-USP7 interaction promotes the de-ubiquitination and subsequent stabilization of NEK2, presenting USP7 as the first discovered de-ubiquitinating enzyme of NEK2. To understand how NEK2 promotes drug resistance in cancer we studied a previously published list of NEK2-regulated genes and, using the UCSC genome browser (Track Name:GM12878+TNFa RELA) ChIP-seq data, we found approximately half of these genes have the NF-κB transcription factor p65 bound throughout the gene sequence. We also produced a signaling score using an average of 11 known targets of NF-κB and patients with high NEK2 showed a significantly increased score of NF-κB signaling. Additionally, through western blots and immunofluorescence, we found that patients with high NEK2 protein levels consisitently had activation higher signal of p65 protein and phosphorylated p65 at Serine 536, indicative of increased activity. We then causally show NEK2 activates canonical NF-κB by performing western blots and a dual-luciferase reporter assay on control and NEK2 overexpressing cells. Using AKT and PP1α inhibitors, we found that NEK2 drives NF-κB by phosphorylating and inactivating PP1α, leading to hyperactive AKT. Using this model of NEK2-NF-κB activation, we aimed at targeting NEK2 directly with the small molecule drugs INH1 (depletes NEK2 protein) and P5091 (inhibits USP7 activity) in empty vector control cells, NEK2 overexpressing cells or cells with an acquired drug resistance phenotype. Our results show that both INH1 and P5091 can overcome bortezomib resistance in cell lines and in vivo. Another aspect of MM disease we targeted in this work was bone disease. Bone disease in MM is common and causes bone pain and fractures but a much is still regarding what drives these lesions. We found that NEK2 expression in patients correlates with a presence of bone lesions, based on FDG-PET scan and MRI. Using our previously published list of NEK2 regulated genes, we found Heparanase (HPSE) is directly correlated to NEK2 expression. HPSE is an extracellular protein shown to promote differentiation of the bone destroying cell, osteoclast. Using western blots, RT-qPCR and ELISA, we found NEK2 increases HPSE expression and extracellular release. HPSE was also on the list of genes upregulated by NEK2 found to have p65 bound to the gene, thus we tested if NEK2 was driving HPSE through the NF-κB. Accordingly, we found NEK2 drives HPSE through the NF-κB pathway and, consistent with our previous results, in a USP7-dependent manner. Using bone marrow macrophages and conditioned media from empty vector control or NEK2 overexpressing cells, we found NEK2 promtoes increased differentiation of osteoclasts and inhibition of HPSE blocked this effect, strongly suggesting HPSE is the mediator of this effects. Importantly these findings were recapitulated in vivo. Empty vector or NEK2 overexpressing cells were injected through the tail vein to allow dissemination to the bone marrow. microCT and Xray revealed mice injected with NEK2 overexpressing cells showed reduced bone density, compared to empty vector cells. Additionally, H&E and TRAP staining confirmed our in vitro results by showing higher osteoclast levels in bone sections of mice injected with NEK2 overexpressing cells. Lastly, we show a novel role for the ATPase TRIP13 as a cofactor for USP7 de-ubiquitinating activity. TRIP13 is overexpressed in cancer, has been shown to be an oncogene and promotes drug resistance. By systematically targeting TRIP13 overexpressing cells with drugs that inhibit different pathways we found TRIP13 drug resistance is diminished by inhibiting USP7. We found that TRIP13 binds with USP7 and by western blots and immunoprecipitations we show it is necessary for the de-ubiquitination of NEK2. Furthermore, we also found TRIP13 shows a hyperactive USP7 phenotype, shuttling PTEN out of the nucleus and stabilizing MDM2, in a USP7 dependent manner. In summary, this work shows the de-ubiquitinase USP7, coupled with the ATPase TRIP13 stabilizes NEK2 by de-ubiquitination, this leads to accumulation of NEK2 and activation of the canonical NF-κB pathway through PP1α/AKT, which promotes drug resistance and activates HPSE, increasing osteoclast differentiation and bone destruction.

Includes bibliographical references (leaves 355-403)

Diss. (sammanfattning) Umeå : Umeå universitet, 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Thesis (Ph.D.)--University of Adelaide, Dental School, 2002. / Includes bibliographical references (leaves 355-403).

Thesis (M.Med.Sc.)--University of Western Australia, 2003.