Adenovirus expressing Fas ligand gene decreases airway hyper-responsiveness and eosinophilia in a murine model of asthma

Gene Therapy for Immunoglobulin E, Complement-Mediated, and Eosinophilic Disorders

Immunoglobulin E, complement, and eosinophils play an important role in host defense, but dysfunction of each of these components can lead to a variety of human disorders. In this review, we summarize how investigators have adapted gene therapy and antisense technology to modulate immunoglobulin E, complement, and/or eosinophil levels to treat these disorders.

Inhibition of the kinase ITK in a mouse model of asthma reduces cell death and fails to inhibit the inflammatory response

Interleukin-2 (IL-2)-inducible T cell kinase (ITK) mediates T cell receptor (TCR) signaling primarily to stimulate the production of cytokines, such as IL-4, IL-5, and IL-13, from T helper 2 (TH2) cells. Compared to wild-type mice, ITK knockout mice are resistant to asthma and exhibit reduced lung inflammation and decreased amounts of TH2-type cytokines in the bronchoalveolar lavage fluid. We found that a small-molecule selective inhibitor of ITK blocked TCR-mediated signaling in cultured TH2 cells, including the tyrosine phosphorylation of phospholipase C-γ1 (PLC-γ1) and the secretion of IL-2 and TH2-type cytokines. Unexpectedly, inhibition of the kinase activity of ITK during or after antigen rechallenge in an ovalbumin-induced mouse model of asthma failed to reduce airway hyperresponsiveness and inflammation. Rather, in mice, pharmacological inhibition of ITK resulted in T cell hyperplasia and the increased production of TH2-type cytokines. Thus, our studies predict that inhibition of the kinase activity of ITK may not be therapeutic in patients with asthma.

Characterization and functional studies of forkhead box protein 3(-) lymphocyte activation gene 3(+) CD4(+) regulatory T cells induced by mucosal B cells

The induction of mucosal tolerance has been demonstrated to be an effective therapeutic approach for the treatment of allergic diseases. Our previous study demonstrated that Peyer's patch B cells could convert naive T cells into regulatory T cells (so-called Treg -of-B(P) cells); however, it is important to characterize this particular subset of Treg -of-B cells for future applications. This study aimed to investigate the role of lymphocyte activating gene 3 (LAG3) in mediating the regulatory function of Treg -of-B(P) cells induced by mucosal follicular B (FOB) cells. Microarray analysis and real-time polymerase chain reaction (PCR) were used to assess the gene expression pattern of Treg -of-B(P) cells. To evaluate the role of LAG3, the in-vitro suppressive function and the alleviation of airway inflammation in a murine model of asthma was assessed. Our data indicated that FOB cells isolated from Peyer's patches had the ability to generate more suppressive Treg -of-B cells with LAG3 expression, compared with CD23(lo) CD21(lo) B cells. LAG3 is not only a marker for Treg -of-B(P) cells, but also participate in the suppressive ability. Moreover, CCR4 and CCR6 could be detected on the LAG3(+) , not LAG3(-) , Treg -of-B(P) cells and would help cells homing to allergic lung. In the murine model of asthma, the adoptive transfer of LAG3(+) Treg -of-B(P) cells was able to sufficiently suppress T helper type 2 (Th2) cytokine production, eosinophil infiltration and alleviate asthmatic symptoms. LAG3 was expressed in Treg -of-B(P) cells and was also involved in the function of Treg -of-B(P) cells. In the future, this particular subset of Treg -of-B cells might be used to alleviate allergic symptoms.

Small interfering RNA targeting T-cell Ig mucin-3 decreases allergic airway inflammation and hyperresponsiveness

Since CD4+ T cells play a pivotal role in the development of airway inflammation and hyperresponsiveness, targeting activated CD4+ T cell subsets and increasing the cells with regulatory function would be a logical therapeutic approach. We showed that this outcome can be achieved by local therapy with Tim-3, which is a negative regulator of CD4+ T cells. Tim-3 expression was up-regulated by ovalbumin (OVA) induction. Attenuating Tim-3 expression by RNA interference suppressed allergen-induced immune responses. Intranasal application of Tim-3 shRNA diminished airway inflammation and hyperresponsiveness. Multiple mechanisms were involved in the inhibitory effects, including regulation the imbalance of Th1/Th17 and increasing Treg cell expression. Our results indicate that the Tim-3 pathway is highly involved in the regulation of asthma. Targeting Tim-3 by siRNA may hold therapeutic potential in preventing the development of allergic asthma.

Systemic FasL neutralization increases eosinophilic inflammation in a mouse model of asthma

BACKGROUND

Eosinophils and lymphocytes are pathogenically important in allergic inflammation and sensitive to Fas-mediated apoptosis. Fas ligand (FasL) activity therefore should play a role in regulating the allergic immune response. We aimed to characterize the role of FasL expression in airway eosinophilia in Aspergillus fumigatus (Af)-induced sensitization and to determine whether FasL neutralization alters the inflammatory response.

METHODS

Sensitized Balb/c mice were killed before (day 0) and 1, 7 and 10 days after a single intranasal challenge with Af. Animals received either neutralizing antibody to FasL (clone MFL4) or irrelevant hamster IgG via intraperitoneal injection on days -1 and 5. FasL expression, BAL and tissue inflammatory cell and cytokine profile, and apoptosis were assessed.

RESULTS

Postchallenge FasL gene expression in BAL cells and TUNEL positivity in the airways coincided with the height of inflammatory cell influx on day 1, while soluble FasL protein was released on day 7, preceding resolution of the inflammatory changes. Although eosinophil numbers showed a negative correlation with soluble FasL levels in the airways, MBP(+) eosinophils remained TUNEL negative in the submucosal tissue, throughout the 10-day period after Af challenge. Systemic FasL neutralization significantly enhanced BAL and tissue eosinophil counts. This effect was associated with increased activation of T cells and release of IL-5, IL-9, and GM-CSF in the BAL fluid of mice, indicating an involvement of pro-eosinophilic survival pathways.

CONCLUSIONS

FasL activity may play an active role in resolving eosinophilic inflammation through regulating T cells and pro-eosinophilic cytokine release during the allergic airway response.

α-Galactosylceramide-induced airway eosinophilia is mediated through the activation of NKT cells

Invariant NKT (iNKT) cells bridge innate and adaptive immune responses, resulting in the expansion of Ag-specific B and T cell responses. α-Galactosylceramide (α-GalCer), the most studied glycolipid that activates iNKT cells, has been proposed to be an effective adjuvant against infections and tumors. We found that the activation of iNKT cells by intranasal injection of α-GalCer induced airway eosinophilia in naive mice. Eosinophils, which mediate tissue damage and dysfunction by secreting mediators, play important roles in the pathogenesis of allergic diseases. In this study, we investigated the mechanism of how eosinophils are recruited to the lung by α-GalCer. Our results demonstrated that α-GalCer-induced eosinophil inflammation was mediated through iNKT cells. These cells secreted IL-5 to recruit eosinophils directly to the lung and/or secreted IL-4 and IL-13 to recruit eosinophils indirectly by inducing lung epithelial cells, endothelial cells, and fibroblast to secrete the eosinophil chemoattractant eotaxin. In addition, in the OVA-alum murine model of allergic asthma, α-GalCer administration in OVA-immunized mice also increased airway eosinophilia after challenge. Given our findings, intranasal administration of α-GalCer induced airway eosinophilic inflammation in both naive and allergic mice. Hence, it remains to be determined whether the activation of iNKT cells would be applicable in therapeutics for human diseases.

Arsenic trioxide alleviates airway hyperresponsiveness and eosinophilia in a murine model of asthma

Asthma is one of the most common chronic airway inflammatory diseases. The clinical hallmarks of asthma include elevated serum levels of immunoglobulin E (IgE), eosinophilic inflammation and airway hyper-responsiveness (AHR). Arsenic trioxide (As2O3) is considered a carcinogen; however, it has also been used to treat diseases, such as syphilis, in traditional Chinese and Western medicine. Today, As2O3 is used as one of the standard therapies for acute promyelocytic leukemia (APL). Previous studies have indicated that As2O3 can induce apoptosis in eosinophils. However, the effect of As2O3 on asthma has not been investigated. We used ovalbumin (OVA)-immunized mice as a model for asthma and treated mice with As2O3 at doses of 2.5 and 5 mg/kg. The mice were then monitored for OVA-specific IgE production, airway inflammatory cell infiltration and AHR. We found that administration of As2O3 in OVA-immunized mice abrogated airway eosinophil recruitment by downregulating eotaxin expression but did not alter serum IgE or IL-5 levels in bronchoalveolar lavage fluid (BALF). Furthermore, the development of AHR and cellular infiltration into the airway were reduced by treating mice with As2O3. In vitro data suggested that low concentrations of As2O3 could induce only a small degree of apoptosis in primary pulmonary cells but could significantly inhibit the secretion of eotaxin by these cells. These results indicate that the administration of As2O3 to OVA-immunized mice can suppress lung allergic inflammatory responses. As2O3 might therefore have therapeutic potential in treating allergic airway inflammatory diseases.

A role for Bid in eosinophil apoptosis and in allergic airway reaction

Bid, a proapoptotic member of Bcl-2 family, is involved in Fas receptor signaling. Fas activation promotes human eosinophil cell death and is believed to accelerate the resolution of pulmonary Th2-driven allergic reaction in mice. We hypothesized that Bid would regulate eosinophil apoptosis and Ag-induced airway inflammation, particularly eosinophilia. C57BL/6 Bid(-/-) and wild-type mice were immunized and repeatedly challenged with OVA, and bronchoalveolar lavage (BAL) fluid, lung, and spleen were collected 4-240 h after the final challenge. Cultured BAL eosinophils from Bid-deficient mice showed resistance to Fas-mediated apoptotic DNA fragmentation, phosphatidylserine exposure, mitochondria depolarization, and caspase-3 activity. In addition, OVA-challenged Bid(-/-) mice had higher BAL eosinophilia and a lower proportion of BAL apoptotic eosinophils than Bid(+/+) mice. This was accompanied by augmented BAL levels of the eosinophilotactic cytokine, IL-5, and of the eosinophil-associated mediators, TGF-beta1 and fibronectin. Finally, cultured OVA-stimulated lung mononuclear cells and splenocytes from Bid-deficient mice showed increased release of the Th2-type cytokines, IL-4 and IL-5, but no change in cell number. We conclude that Bid modulates BAL eosinophilia by regulating both eosinophil apoptosis and Th2-type cytokine production.

Role of breast regression protein 39 (BRP-39)/chitinase 3-like-1 in Th2 and IL-13-induced tissue responses and apoptosis

Mouse breast regression protein 39 (BRP-39; Chi3l1) and its human homologue YKL-40 are chitinase-like proteins that lack chitinase activity. Although YKL-40 is expressed in exaggerated quantities and correlates with disease activity in asthma and many other disorders, the biological properties of BRP-39/YKL-40 have only been rudimentarily defined. We describe the generation and characterization of BRP-39(-/-) mice, YKL-40 transgenic mice, and mice that lack BRP-39 and produce YKL-40 only in their pulmonary epithelium. Studies of these mice demonstrated that BRP-39(-/-) animals have markedly diminished antigen-induced Th2 responses and that epithelial YKL-40 rescues the Th2 responses in these animals. The ability of interleukin13 to induce tissue inflammation and fibrosis was also markedly diminished in the absence of BRP-39. Mechanistic investigations demonstrated that BRP-39 and YKL-40 play an essential role in antigen sensitization and immunoglobulin E induction, stimulate dendritic cell accumulation and activation, and induce alternative macrophage activation. These proteins also inhibit inflammatory cell apoptosis/cell death while inhibiting Fas expression, activating protein kinase B/AKT, and inducing Faim 3. These studies establish novel regulatory roles for BRP-39/YKL-40 in the initiation and effector phases of Th2 inflammation and remodeling and suggest that these proteins are therapeutic targets in Th2- and macrophage-mediated disorders.

Ozone inhalation induces exacerbation of eosinophilic airway inflammation and hyperresponsiveness in allergen-sensitized mice

BACKGROUND

Ozone (O(3)) exposure evokes asthma exacerbations by mechanisms that are poorly understood. We used a murine model to characterize the effects of O(3) on allergic airway inflammation and hyperresponsiveness and to identify factors that might contribute to the O(3)-induced exacerbation of asthma.

METHODS

BALB/c mice were sensitized and challenged with Aspergillus fumigatus (Af). A group of sensitized and challenged mice was exposed to 3.0 ppm of O(3) for 2 h and studied 12 h later (96 h after Af challenge). Naive mice and mice exposed to O(3) alone were used as controls. Bronchoalveolar lavage (BAL) cellular and cytokine content, lung function [enhanced pause (P(enh))], isometric force generation by tracheal rings and gene and protein expression of Fas and FasL were assessed. Apoptosis of eosinophils was quantified by FACS.

RESULTS

In sensitized mice allergen challenge induced a significant increase of P(enh) and contractile force in tracheal rings that peaked 24 h after challenge and resolved by 96 h. O(3) inhalation induced an exacerbation of airway hyperresponsiveness accompanied by recurrence of neutrophils and enhancement of eosinophils 96 h after allergen challenge. The combination of allergen and O(3) exposure inhibited Fas and FasL gene and protein expression and eosinophil apoptosis and increased interleukin-5 (IL-5), granulocyte-macrophage-colony stimulating factor (GM-CSF) and G-CSF protein levels.

CONCLUSIONS

O(3) affects airway responsiveness of allergen-primed airways indirectly by increasing viability of eosinophils and eosinophil-mediated pathological changes.

Small interfering RNA against interleukin-5 decreases airway eosinophilia and hyper-responsiveness

Interleukin-5 (IL-5) has been suggested to be involved in the development of airway hyper-responsiveness (AHR). Both clinical and experimental investigations have shown strong correlation between the presence of eosinophils and AHR. In this study, we used small interfering RNA (siRNA) as an approach to inhibiting the expression of IL-5 and reducing AHR. siRNAs targeting IL-5 were characterized in vitro, and siRNA-expressing lentiviruses were administered intratracheally to OVA-sensitized BALB/c mice. AHR, cytokine levels, serum levels of OVA-specific antibodies and infiltration of inflammatory cells were analyzed to investigate the effects of siRNA in an OVA-induced murine model of asthma. Lentivirus-delivered siRNA targeting IL-5 efficiently moderated the characteristics of asthma, including AHR, cellular infiltration of lung tissues, eotaxin levels in the bronchoalveolar lavage fluid and IL-5 mRNA levels in lungs in the mouse model of asthma. However, there was no effect on OVA-specific IgE level. These data demonstrate that siRNA delivered by the lentiviral system is an efficacious therapeutic strategy for asthma.

Effects of adenovirus-expressing IL-10 in alleviating airway inflammation in asthma

BACKGROUND

Allergic asthma strongly correlates with airway inflammation caused by cytokines secreted by allergen-specific type-2 T helper (Th2) cells, but the immunologic regulation of cell function is yet to be acquired. Further, IL-10 has been found to exert both antiinflammatory and immunoregulatory activities. This study aimed to elucidate the therapeutic effects of IL-10 administration via adenovirus-mediated gene delivery on airway inflammation in the ovalbumin (OVA)-induced murine model of asthma.

METHODS

BALB/c mice were sensitized by intraperitoneal injections with OVA and challenged by nebulized OVA. The sensitized mice were given an intratracheal delivery of adenoviral vector expressing the murine IL-10 gene (AdIL-10), or mock adenoviral vector 4 days before the inhalation challenge of the OVA. Inflammatory parameters, such as the development of airway hyper-responsiveness (AHR), bronchial lavage fluid eosinophils, and chemokines were assayed.

RESULTS

Intratracheal administration of AdIL-10 could efficiently inhibit antigen-induced AHR and significantly decrease the number of eosinophils and neutrophils in the bronchoalveolar lavage fluid of OVA-sensitized and challenged mice during the effector phase.

CONCLUSIONS

Our data showed that the intratracheal transfer of the IL-10 gene could affect the recruitment of inflammatory cells during the challenge phase in a way that would result in the inhibition of airway inflammation. These findings suggest that the development of an immunoregulatory strategy based on IL-10 might shed light on more effective treatment.

Caffeic acid phenethyl ester modifies the Th1/Th2 balance in ileal mucosa after γ-irradiation in the rat by modulating the cytokine pattern

AIM: To pharmacologically modulate Th polarization in the ileum exposed to ionizing radiation by using the immuno-modulatory/apoptotic properties of Caffeic Acid Phenethyl Ester (CAPE).

METHODS: Rats received CAPE (30 mg/kg) treatment ip 15 min prior to intestinal 10 Gy γ-irradiation and once a day for a 6 d period after irradiation. Expression of genes implicated in Th differentiation in ileal mucosa (IL-23/IL-12Rβ2), Th cytokine responses (IFN-γ, IL-2, IL-4, IL-13), Th migratory behaviour (CXCR3, CCR5, CCR4), Th signalling suppressors (SOCS1, SOCS3), transcription factor (T-Bet, GATA-3) and apoptosis (FasL/Fas, TNF/TNFR, XIAP, Bax, caspase-3) was analyzed by RT-PCR 6 h and 7 d post-irradiation. CD4⁺ and TUNEL positive cells were visualized by immunostaining.

RESULTS: The expression of Th1-related cytokine/chemokine receptors (IFN-γ, IL-2, CXCR3, CCR5) was repressed at 7 d post-irradiation while Th2 cell cytokine/chemokines (IL-4, IL-13, CCR4) were not repressed or even upregulated. The irradiation-induced Th2 profile was confirmed by the upregulation of both Th2-specific transcription factor GATA-3 and SOCS3. Although an apoptosis event occurred 6 h after 10 Gy of intestinal γ-irradiation, apoptotic mediator analysis showed a tendency to apoptotic resistance 7 d post-irradiation. CAPE amplified apoptotic events at 6h and normalized Bax/ FasL expressions at 7 d.

CONCLUSION: CAPE prevented the ileal Th2 immune response by modulating the irradiation-influenced cytokine environment and apoptosis.

Resolution of airway disease: removal of inflammatory cells through apoptosis, egression or both?

Pathogenic granulocytes (eosinophils and neutrophils) infiltrate airway tissues in asthma and chronic obstructive pulmonary disease. Granulocytes release tissue-toxic and inflammatory mediators, making their removal an important pharmacological goal. Removal is thought to be accomplished through apoptosis followed by engulfment by macrophages. Thus, the molecular mechanisms of granulocyte apoptosis have been unravelled and pro-apoptotic actions that target granulocytes have been proposed as desirable features of future airway drugs. However, observations in vitro and in airway lumen that support this role of granulocyte apoptosis translate poorly to airway tissues in vivo. Either apoptosis cannot be demonstrated, even at the resolution of airway inflammation, or, when significant granulocyte apoptosis is induced in airway tissues in vivo, there is insufficient engulfment of apoptotic granulocytes. Therefore, apoptotic eosinophils and neutrophils in airway tissues undergo secondary necrosis, causing inflammation. As an alternative or complement to the apoptosis hypothesis, in vivo work indicates that egression to the airway lumen can produce swift non-injurious removal of tissue granulocytes. Once in the airway lumen, granulocytes can undergo apoptosis and engulfment, be trapped by secretions and plasma exudates and be removed by mucociliary escalator mechanisms. In this article, we propose that egression into the airway lumen is an effective mode of inflammatory cell disposal that connotes novel drug opportunities.

Fas-ligand-expressing adenovirus-transfected dendritic cells decrease allergen-specific T cells and airway inflammation in a murine model of asthma

T cells expressing a type-2 T helper profile of cytokines (Th2 cells) have been demonstrated to play an important role in the initiation and progression of allergic asthma, and it is well known that Fas ligand (FasL) induces apoptosis when bound to its receptor, Fas. In the present study, we examined the possibility of modulating asthma manifestations by dendritic cells (DCs) genetically engineered to express FasL (DC-FasL), which could deliver a death signal to T cells in an antigen-specific manner. The delivery of DC-FasL into ovalbumin (OVA)-immunized allergic mice decreased the airway hyper-responsiveness (AHR). Moreover, we established a mouse model of airway inflammation by using an adoptive transfer of Th2 cells derived from ovalbumin T cell receptor transgenic mice to study the effect of DC-FasL on airway reactivity. The administration of DC-FasL in Th2-cell-induced allergic mice had significantly decreased AHR, airway inflammation, and IL-4, IL-5 and IL-13 production. Furthermore, the numbers of OVA-specific T cells were decreased in the lung of mice receiving DC-FasL. These results demonstrate that FasL-expressing dendritic cells might be applied for the modulation of allergic responses.

Modification of dendritic cell function as a tool to prevent and treat allergic asthma

Atopic asthma is a chronic inflammatory disease of the airways, characterized by airway hyperreactivity and mucus hypersecretion that result in intermittent airway obstruction. This chronic inflammation is the result of an aberrant Th2-mediated response to innocuous environmental proteins. The prevalence of this disease has increased dramatically in the industrialized world in the last decades. Current treatment is mainly based on pharmacological interventions, which control the disease but are not curative. Although the etiology is not completely understood, it becomes increasingly clear that dendritic cells play an important role in both the sensitization phase and maintenance of the disease. In this review, we explore the different possibilities to exploit dendritic cell vaccines in order to prevent the development of (or inhibit established) atopic asthma.

Anti-Fas mAb-induced apoptosis and cytolysis of airway tissue eosinophils aggravates rather than resolves established inflammation

Background

Fas receptor-mediated eosinophil apoptosis is currently forwarded as a mechanism resolving asthma-like inflammation. This view is based on observations in vitro and in airway lumen with unknown translatability to airway tissues in vivo. In fact, apoptotic eosinophils have not been detected in human diseased airway tissues whereas cytolytic eosinophils abound and constitute a major mode of degranulation of these cells. Also, Fas receptor stimulation may bypass the apoptotic pathway and directly evoke cytolysis of non-apoptotic cells. We thus hypothesized that effects of anti-Fas mAb in vivo may include both apoptosis and cytolysis of eosinophils and, hence, that established eosinophilic inflammation may not resolve by this treatment.

Methods

Weeklong daily allergen challenges of sensitized mice were followed by airway administration of anti-Fas mAb. BAL was performed and airway-pulmonary tissues were examined using light and electron microscopy. Lung tissue analysis for CC-chemokines, apoptosis, mucus production and plasma exudation (fibrinogen) were performed.

Results

Anti-Fas mAb evoked apoptosis of 28% and cytolysis of 4% of eosinophils present in allergen-challenged airway tissues. Furthermore, a majority of the apoptotic eosinophils remained unengulfed and eventually exhibited secondary necrosis. A striking histopathology far beyond the allergic inflammation developed and included degranulated eosinophils, neutrophilia, epithelial derangement, plasma exudation, mucus-plasma plugs, and inducement of 6 CC-chemokines. In animals without eosinophilia anti-Fas evoked no inflammatory response.

Conclusion

An efficient inducer of eosinophil apoptosis in airway tissues in vivo, anti-Fas mAb evoked unprecedented asthma-like inflammation in mouse allergic airways. This outcome may partly reflect the ability of anti-Fas to evoke direct cytolysis of non-apoptotic eosinophils in airway tissues. Additionally, since most apoptotic tissue eosinophils progressed into the pro-inflammatory cellular fate of secondary necrosis this may also explain the aggravated inflammation. Our data indicate that Fas receptor mediated eosinophil apoptosis in airway tissues in vivo may cause severe disease exacerbation due to direct cytolysis and secondary necrosis of eosinophils.

Targeting memory Th2 cells for the treatment of allergic asthma

Th2 memory cells play an important role in the pathogenesis of allergic asthma. Evidence from patients and experimental models indicates that memory Th2 cells reside in the lungs during disease remission and, upon allergen exposure, become activated effectors involved in disease exacerbation. The inhibition of memory Th2 cells or their effector functions in allergic asthma influence disease progression, suggesting their importance as therapeutic targets. They are allergen specific and can potentially be suppressed or eliminated using this specificity. They have distinct activation, differentiation, cell surface phenotype, migration capacity, and effector functions that can be targeted singularly or in combination. Furthermore, memory Th2 cells residing in the lungs can be treated locally. Capitalizing on these unique attributes is important for drug development for allergic asthma. The aim of this review is to present an overview of therapeutic strategies targeting Th2 memory cells in allergic asthma, emphasizing Th2 generation, differentiation, activation, migration, effector function, and survival.

Considering Fas ligand as a target for therapy

About a decade ago, the death factor Fas ligand (FasL) was identified as the natural trigger of Fas/CD95-dependent apoptosis and as an inducer of Fas-dependent activation-induced cell death. Meanwhile, it is known that this molecule not only contributes to target cell lysis in the immune system but also to the establishment of immune privilege and tumour survival. Because delivering a specific antiproliferative signal to T lymphocytes is of major biomedical interest, the FasL/Fas system has gained much attention over the last few years. However, only recently it became evident that the biology of FasL is more complex than initially anticipated. FasL displays a complex pattern of inducible and constitutive expression associated with a number of different functions as a death factor or a co-stimulatory/accessory molecule in lymphocyte activation. Thus, side effects are likely to occur following systemic administration of, for example, anti-FasL medication, not only because of the constitutive FasL expression on cells within immune privileged tissues and vascular endothelium. In addition, FasL comes in different forms: as a surface molecule, as a protease-shed soluble variant or secreted in vesicles. Because increased levels of soluble FasL (sFasL) have been determined in various immunological and non-immunological diseases, it has been suggested that sFasL might serve as a prognostic or diagnostic marker even though the pathophysiological cause for its enhanced production is hardly known in most cases. This review summarises the current facts and ideas about the clinical and pharmacological potential of FasL and sFasL as targets for therapeutic interventions.

In vivo gene silencing (with siRNA) of pulmonary expression of MIP-2 versus KC results in divergent effects on hemorrhage-induced, neutrophil-mediated septic acute lung injury

Lung injury in trauma patients exposed to a secondary infectious/septic challenge contributes to the high morbidity/mortality observed in this population. Associated pathology involves a dys-regulation of immune function, specifically, sequestration of activated polymorphonuclear neutrophils (PMN) in the lungs. The targeting of PMN is thought to involve the release of chemokines from cells within the local environment, creating a concentration gradient along which PMN migrate to the focus of inflammation. Keratinocyte-derived chemokine (KC) and macrophage-inflammatory protein-2 (MIP-2) are murine neutrophil chemokines identified as playing significant but potentially divergent roles in the pathogenesis of acute lung injury (ALI). In the current study, we examined the contribution of local pulmonary cells to the production of KC and MIP-2 and the pathogenesis of ALI. We hypothesized that local silencing of KC or MIP-2, via the local administration of small interference RNA (siRNA) against KC or MIP-2, following traumatic shock/hemorrhage (Hem), would suppress signaling for PMN influx to the lung, thereby reducing ALI associated with a secondary septic challenge (cecal ligation and puncture). Assessment of siRNA local gene silencing was done in green fluorescent protein (GFP)-transgenic, overexpressing mice. A marked suppression of GFP expression was observed in the lung 24 h following intratracheal (i.t.) instillation of GFP siRNA, which was not observed in the liver. To test our hypothesis, siRNA against KC or MIP-2 (75 ug/C3H/Hen mouse) was instilled (i.t.) 2 h post-Hem (35 mm Hg for 90 min, 4x LRS Rx.). Twenty-four hours after, mice were subjected to septic challenge and then killed 24 h later. i.t. MIP-2 siRNA significantly (P < 0.05, ANOVA-Tukey's test, n = 5-6/group) reduced tissue and plasma interleukin (IL)-6, tissue MIP-2 (enzyme-linked immunosorbent assay), as well as neutrophil influx [myeloperoxidase (MPO) activity]. In contrast, KC siRNA treatment reduced plasma KC, tissue KC, and IL-6 but produced no significant reduction in plasma IL-6 or MPO. Neither treatment reduced tissue or plasma levels of tumor necrosis factor alpha compared with vehicle. These data support not only our hypothesis that local pulmonary chemokine production of MIP-2, to a greater extent than KC, contributes to the pathogenesis of PMN-associated ALI following Hem but also the use of siRNA as a potential therapeutic.