Analysis of cytokine-induced NO-dependent apoptosis using RNA interference or inhibition by 1400W

Erhöhte NF-κB- und iNOS-Expression in Keratozyten von Keratokonuspatienten – Hinweise auf eine entzündliche Komponente?

Hintergrund In den letzten Jahren mehren sich Hinweise auf eine entzündliche Komponente beim Keratokonus (KC). Ein Schlüsselgen bei entzündlichen Prozessen ist der Nuclear Factor Kappa B (NF-κB). NF-κB ist ein Transkriptionsfaktor, der unter anderem das Enzym Nitric Oxide Synthase (NOS), das mit dem konkurrierenden Enzym Arginase (Arg) bei entzündlichen Prozessen involviert ist, aktiviert. Ziel dieser Studie war es, die Isotypen von NOS und Arginase zu analysieren, die Expression NF-κB, NOS und Arginase sowie den regulativen Mechanismus von NOS und Arginase in Keratozyten von Keratokonuspatienten mithilfe des Inhibitors 1400W in vitro zu untersuchen.

Methoden Primäre humane Keratozyten wurden durch enzymatische Behandlung mit Kollagenase A aus humanen Korneoskleralscheiben (n = 8) und von Explantaten von geplanten perforierenden Keratoplastiken (KC-Patienten) isoliert (n = 8) und in DMEM/F12-Kulturmedium, versetzt mit 5% fetalem Kälberserum, kultiviert. Die Expression von NF-κB, NOS und Arginase wurden mit quantitativer PCR (qPCR) und Westernblot-Analyse (WB) untersucht. Nitrit- und Ureakonzentrationen im Zellkulturüberstand wurden nach Zugabe des NOS-Inhibitors 1400W (0 – 40 µM) analysiert.

Ergebnisse In den Keratozyten wurden ausschließlich die Isotypen iNOS (induzierbare NO-Synthase) und Arg-II nachgewiesen. Die mRNA-Expression von NF-κB und iNOS waren in KC-Keratozyten höher als in normalen Zellen (p = 0,0135 und p = 0,0001), während in der Arg-II-Expression keine Unterschiede messbar waren. Im WB war bei NF-κB eine höhere Bandenintensität messbar (p = 0,0012), bei iNOS konnten keine Unterschiede in der Bandenintensität nachgewiesen werden. Im Überstand der KC-Keratozyten wurden geringere Konzentrationen von Nitrit und Urea nach Zugabe des Inhibitors 1400W gemessen (p = ≤ 0,014), nicht jedoch bei normalen Zellen (p ≥ 0,178).

Schlussfolgerung Aufgrund der erhöhten Expression von NF-κB und iNOS muss von einer inflammatorischen Komponente beim Keratokonus ausgegangen werden. Die unterschiedliche Regulation der KC-Keratozyten durch den iNOS-Inhibitor 1400W legt eine veränderte metabolische Aktivität nahe, die durch entzündliche Prozesse hervorgerufen werden kann.

β cell protection by inhibition of iNOS through lentiviral vector-based strategies

Cytoprotective gene transfer to pancreatic islet β cell s may prove useful in preventing their destruction and prolonging islet graft survival after transplantation in patients with type 1 diabetes mellitus. A host of therapeutically relevant transgenes may potentially be incorporated into an appropriate gene delivery vehicle and used for islet modification. To examine this, we utilised a robust model of cytokine-induced β cell pathophysiology. Using this model, it is clear that antioxidant gene transfer confers no cytoprotective benefit. In contrast, we demonstrated that gene-based approaches to inhibit the activation of NF-κBNF-κB following cytokine exposure harbours therapeutic utility in preserving islet β cell viability in the face of cytokine toxicity. We identified that NF-κB-dependent induction of iNOSiNOS is a critical determinant of β cell fate following cytokine exposure. Having identified the pivotal role of iNOS activation in cytokine-induced β cell pathophysiology, lentiviral vectors may be used to efficiently deliver small interfering RNARNA molecules to confer efficient iNOS gene silencing. We have shown that lentiviral vector-based shRNA delivery holds significant promise in preserving β cell viability following cytotoxic cytokine exposure.

NO to breast: when, why and why not?

Nitric oxide is a pleiotropic ancestral molecule, which elicits beneficial effect in many physiological settings but is also tenaciously expressed in numerous pathological conditions, particularly breast tumors. Nitric oxide is particularly harmful in adipogenic milieu of the breast, where it initiates and promotes tumorigenesis. Epidemiological studies have associated populations at a greater risk for developing breast cancer, predominantly estrogen receptor positive tumors, to express specific polymorphic forms of endothelial nitric oxide synthase, that produce sustained low levels of nitric oxide. Low sustained nitric oxide generates oxidative stress and inflammatory conditions at susceptible sites in the heterogeneous microenvironment of the breast, where it promotes cancer related events in specific cell types. Inflammatory conditions also stimulate inducible nitric oxide synthase expression, which dependent on the microenvironment, could promote or inhibit mammary tumors. In this review we re-examine the mechanisms by which nitric oxide promotes initiation and progression of breast cancer and address some of the controversies in the field.

Native mRNA antisense-accessible sites library for the selection of antisense oligonucleotides, PNAs, and siRNAs

A procedure for rapidly generating a library of antisense-accessible sites on native mRNAs (mRNA antisense-accessible sites library [MASL]) is described that involves reverse transcription of whole cell mRNA extracts with a random oligodeoxynucleotide primer followed by mRNA-specific polymerase chain reaction (PCR). Antisense phosphorothioate oligodeoxynucleotides (ODNs), peptide nucleic acids (PNAs), and small interfering RNAs (siRNAs) can then be identified by screening against the antisense-accessible sites. The utility of this methodology is demonstrated for the identification of more effective inhibitors of inducible nitric oxide synthase (iNOS) induction than have previously been reported. This method may also be useful for constraining folding calculations of native mRNAs and for designing mRNA imaging probes.

Effect of iNOS and NF-kappaB gene silencing on beta-cell survival and function

PURPOSE

Type I diabetes results from beta-cell death and dysfunction, induced by infiltration of immune cells and local production of inflammatory cytokines. Therefore, we investigated the effect of iNOS and NF-kappaB gene silencing on beta-cell survival and function.

METHODS

Rat insulinoma INS-1E cells were transfected with chemically synthesized siRNA after complex formation with Lipofectamine 2000. Cells were then treated with a cocktail of inflammatory cytokines (IL-1beta+ TNF-alpha+ IFN-alpha), and glucose stimulated-insulin response and viability were determined. iNOS and NF-kappaB gene expression was assessed at mRNA level by real time RT-PCR. The effect of gene silencing was also correlated with cytokine-induced NO production and apoptosis.

RESULTS

Transfection of INS-1E cells with siRNAs silenced iNOS and NF-kappaB gene expression and reduced NO production in a sequence-specific manner without causing significant loss of cell viability and function. However, the abrogation of NO production did not prevent INS-1E cells from cytokine-induced apoptosis, suggesting that this event may not be totally dependent on NO production.

CONCLUSION

The gene silencing approach presented here is capable of attenuating the effects of inflammatory cytokines, such as iNOS expression and NO production and it will help to identify new target genes to improve islet transplantation.

The Rational Design of β Cell Cytoprotective Gene Transfer Strategies: Targeting Deleterious iNOS Expression

Islet transplantation represents a promising therapeutic strategy for the treatment of type 1 diabetes mellitus (T1DM) [Hakim and Papalois (Ann Ital Chir 75:1-7, 2004); Jaeckel et al. (Internist (Berl) 45:1268-1280, 2004); Sutherland et al. (Transplant Proc 36:1697-1699, 2004)]. The insulin-secreting pancreatic beta cells of the islet allograft are, however, subject to recurrent immune-mediated damage. Principal among the molecular culprits involved in this destructive process is the proinflammatory cytokine IL-1beta. IL-1beta-induced beta cell destruction may be mediated by the generation of NO and/or ROS, although the relative importance of NO and ROS in this process remains unclear. This study broadly encompassed three arms of investigation: the first of these was geared toward the establishment of a robust in vitro cell system for the study of IL-1beta-induced pathophysiology; the second arm aimed to provide a comparative analysis of the gene transfer profiles of the three most commonly used gene transfer vehicles, namely plasmid vectors, adenoviral vectors, and lentiviral vectors, in the aforementioned cell system; the final arm aimed to screen an array of potentially cytoprotective gene transfer strategies incorporating the optimal gene transfer vectors. Briefly, we established an in vitro beta cell system that accurately reflected primary beta cell cytokine-induced pathophysiology. That is, IL-1beta exposure (100 U/ml) induced a time-dependent decrease in rat insulinoma (RIN) cell viability, which coincided with an induction in iNOS expression and nitrite accumulation. Gene transfer studies using plasmid, adenoviral, or lentiviral vectors underscored the superiority of viral vector-based gene transfer strategies for the manipulation of this beta cell line. Using these vectors, we provide evidence that NF-kappaB-based iNOS inhibition confers significant protection against IL-1beta-induced damage whereas antioxidant overexpression fails to provide protection. Conferred cytoprotection was associated with a suppression of iNOS expression and nitrite accumulation. From a therapeutic standpoint, gene transfer strategies employing efficient viral vectors to target iNOS activation may harbour therapeutic potential in preserving beta cell survival against proinflammatory cytokine exposure.

Beta cell cytoprotection using lentiviral vector-based iNOS-specific shRNA delivery

Cytokine-induced beta cell pathophysiology is characterised by the induction of iNOS expression. Inhibition of iNOS expression protects beta cells from cytokine-mediated destruction. The development of vector-based shRNA strategies capable of stably suppressing iNOS expression may provide a novel platform to protect beta cells from cytokine toxicity. In this report the utility of lentiviral shRNA vectors to silence iNOS expression was evaluated with respect to insulinoma cell viability, the induction of iNOS expression and the accumulation of nitrite in a cytokine-induced beta cell toxicity model. Here, we report for the first time on the use of lentiviral vector-based shRNA delivery to efficiently suppress the IL-1beta-mediated induction of iNOS expression, the accumulation of nitrite and provide significant protection against the cytotoxic effects of IL-1beta exposure. Moreover, non-specific knockdown of endogenous beta cell nNOS did not occur.

Nitric oxide, a double edged sword in cancer biology: Searching for therapeutic opportunities

Nitric oxide (NO) is a pleiotropic molecule critical to a number of physiological and pathological processes. The last decade has witnessed major advances in dissecting NO biology and its role in cancer pathogenesis. However, the complexity of the interactions between different levels of NO and several aspects of tumor development/progression has led to apparently conflicting findings. Furthermore, both anti-NO and NO-based anticancer strategies appear effective in several preclinical models. This paradoxical dichotomy is leaving investigators with a double challenge: to determine the net impact of NO on cancer behavior and to define the therapeutic role of NO-centered anticancer strategies. Only a comprehensive and dynamic view of the cascade of molecular and cellular events underlying tumor biology and affected by NO will allow investigators to exploit the potential antitumor properties of drugs interfering with NO metabolism. Available data suggest that NO should be considered neither a universal target nor a magic bullet, but rather a signal transducer to be modulated according to the molecular makeup of each individual cancer and the interplay with conventional antineoplastic agents.