Michela Terlizzi

Inflammasome: cancer's friend or foe?

High serum concentrations of IL-1β and IL-18 are correlated to malignancies with low-rate survival from the time of diagnosis. The multimeric complex of the inflammasome is responsible for IL-1β/IL-18 synthesis/release. A number of endogenous (damage-associated molecular patterns) and exogenous (pathogen-associated molecular patterns) stimuli can provide signals for inflammasome activation in cancer. These stimuli can behave as tumor promoters via inducing chronic inflammation that, rather than providing a protective response to loss of tissue homeostasis, aberrantly facilitates tumor development. This view is contrasted in animal models of colon cancer in which the activation of some inflammasome complexes is associated with tumor protection. More studies are needed to understand the biology of the inflammasome in cancer and explore its therapeutic potential.

Hydrogen sulfide inhalation ameliorates allergen induced airway hypereactivity by modulating mast cell activation.

Compelling evidence suggests that hydrogen sulfide represents an important gaseous transmitter in the mammalian respiratory system. In the present study, we have evaluated the role of mast cells in hydrogen sulfide-induced effects on airways in a mouse model of asthma. Mice were sensitized to ovalbumin and received aerosol of a hydrogen sulfide donor (NaHS; 100 ppm) starting at day 7 after ovalbumin challenge. Exposure to hydrogen sulfide abrogated ovalbumin-induced bronchial hypereactivity as well as the increase in lung resistance. Concomitantly, hydrogen sulfide prevented mast cell activity as well as FGF-2 and IL-13 upregulation. Conversely, pulmonary inflammation and the increase in plasmatic IgE levels were not affected by hydrogen sulfide. A lack of hydrogen sulfide effects in mast cell deficient mice occurred. Primary fibroblasts harvested from ovalbumin-sensitized mice showed an increased proliferation rate that was inhibited by hydrogen sulfide aerosol. Furthermore, ovalbumin-induced transdifferentiation of pulmonary fibroblasts into myofibroblasts was reversed. Finally, hydrogen sulfide did abrogate in vitro the degranulation of the mast cell-like RBL-2H3 cell line. Similarly to the in vivo experiments the inhibitory effect was present only when the cells were activated by antigen exposure. In conclusion, inhaled hydrogen sulfide improves lung function and inhibits bronchial hyper-reactivity by modulating mast cells and in turn fibroblast activation.

S1P‐induced airway smooth muscle hyperresponsiveness and lung inflammation in vivo: molecular and cellular mechanisms

Sphingosine‐1‐phosphate (S1P) has been shown to be involved in the asthmatic disease as well in preclinical mouse experimental models of this disease. The aim of this study was to understand the mechanism(s) underlying S1P effects on the lung.

Human Lung Cancer–Derived Immunosuppressive Plasmacytoid Dendritic Cells Release IL-1α in an AIM2 Inflammasome-Dependent Manner

Plasmacytoid dendritic cells (pDCs) highly populate lung tumor masses and are strictly correlated to bad prognosis, yet their role in lung cancer is controversial. To understand their role in lung cancer, we isolated pDCs from human samples of lung obtained from non-small cell lung cancer patients undergoing thoracic surgery. Tumor masses presented a higher percentage of pDCs than healthy tissues; pDCs were in the immunosuppressive phenotype, as determined by higher levels of CD33 and PD-L1. Despite higher HLA-A and HLA-D expression, cancerous pDCs did not exert cytotoxic activity against tumor cells but instead promoted their proliferation. In this scenario, cancerous pDCs were able to produce high levels of IL-1α. This effect was observed on the specific activation of the inflammasome absent in melanoma 2 (AIM2), which led to higher cytoplasmic calcium release responsible for calpain activation underlying IL-1α release. The blockade of type I interferon receptor and of AIM2 via the addition of LL-37 significantly reduced the release of IL-1α, which was still high after Nod-like receptor P3 inhibition via glibenclamide. More important, mitochondrial-derived reactive oxygen species sequester diminished AIM2-dependent IL-1α release. Our data demonstrate that lung tumor-associated pDCs are responsive to the activation of AIM2 that promotes calcium efflux and reactive oxygen species from mitochondria, leading to calpain activation and high levels of IL-1α, which facilitate tumor cell proliferation in the lung.

B Cell Depletion Increases Sphingosine-1-Phosphate–Dependent Airway Inflammation in Mice

Sphingosine-1-phosphate (S1P) has been widely associated with inflammation-based lung pathologies. Because B cells play a critical role as antigen-presenting and/or Ig-producing cells during asthmatic conditions, we wanted to dissect the role of these cells in S1P-dependent airway hyperreactivity and inflammation. Mice were sensitized to ovalbumin or exposed to S1P. Ovalbumin sensitization caused airway hyperreactivity coupled to an increased lung infiltration of B cells, which was significantly reduced after the inhibition of sphingosine kinases I/II. Similarly, the sole administration of S1P increased bronchial reactivity compared with vehicle and was accompanied by a higher influx of B cells in a time-dependent manner. This effect was associated with higher levels of IL-13, transforming growth factor-β, IL-10, and T regulatory cells. In addition, isolated S1P-derived lung B cells increased CD4(+) and CD8(+) T cell proliferation in vitro, and their suppressive nature at Day 14 was associated with the higher release of transforming growth factor-β and IL-10 when they were cocultured. Therefore, to prove the role of B cells in S1P-mediated airway inflammation, and because CD20 expression, contrary to major hystocompatibility complex I and major hystocompatibility complex II, was up-regulated at Day 14, CD20(+) B cells were depleted by means of a specific monoclonal antibody. The absence of CD20(+) B cells increased airway reactivity and inflammation in S1P-treated mice compared with control mice. These data imply that sphingosine kinase/S1P-mediated airway inflammation is countered by B cells via the induction of an immune-suppressive environment to reduce asthma-like outcomes in mice.

Plasmacytoid Dendritic Cells Play a Key Role in Tumor Progression in Lipopolysaccharide-Stimulated Lung Tumor–Bearing Mice

The antitumor activity of LPS was first described by Dr. William Coley. However, its role in lung cancer remains unclear. The aim of our study was to elucidate the dose-dependent effects of LPS (0.1–10 μg/mouse) in a mouse model of B16-F10–induced metastatic lung cancer. Lung tumor growth increased at 3 and 7 d after the administration of low-dose LPS (0.1 μg/mouse) compared with control mice. This was associated with an influx of plasmacytoid dendritic cells (pDCs), regulatory T cells, myeloid-derived suppressor cells, and CD8+ regulatory T cells. In contrast, high-dose LPS (10 μg/mouse) reduced lung tumor burden and was associated with a greater influx of pDCs, as well as a stronger Th1 and Th17 polarization. Depletion of pDCs during low-dose LPS administration resulted in a decreased lung tumor burden. Depletion of pDCs during high-dose LPS treatment resulted in an increased tumor burden. The dichotomy in LPS effects was due to the phenotype of pDCs, which were immunosuppressive after the low-dose LPS, and Th1- and T cytotoxic–polarizing cells after the high-dose LPS. Adoptive transfer of T cells into nude mice demonstrated that CD8+ T cells were responsible for pDC recruitment following low-dose LPS administration, whereas CD4+ T cells were required for pDC influx after the high-dose LPS. In conclusion, our data suggest differential effects of low-dose versus high-dose LPS on pDC phenotype and tumor progression or regression in the lungs of mice.

IL-1α and IL-1β-producing macrophages populate lung tumor lesions in mice

Macrophages highly populate tumour microenvironment and are referred to as tumor-associated macrophages (TAMs). The inflammasome is a multiprotein complex responsible of IL-1 like cytokines release, which biology has been widely studied by using bone-marrow-derived macrophages to mimic a physiological and/or host defense condition. To understand the role of this complex in lung tumor-associated macrophages (TAMs), we isolated and cultured broncho-alveolar lavage (BAL)-derived cells of lung tumor-bearing mice. The stimulation of lung TAMs with LPS+ATP increased the release of IL-1β. The inhibition of NLRP3 by means of glybenclamide significantly reduced IL-1β release. Similarly, C3H-derived, caspase-1 ko and caspase-11 ko TAMs released significantly reduced levels of IL-1β. Moreover, the stimulation of lung TAMs with the sole LPS induced a significant release of IL-1α, which was significantly reduced after caspase-1 pharmacological inhibition, and in TAMs genetically lacking caspase-1 and caspase-11. The inhibition of calpain I/II by means of MDL28170 did not alter IL-1α release after LPS treatment of lung TAMs. To note, the inoculation of LPS-treated bone marrow-derived macrophages into carcinogen-exposed mice increased lung tumor formation. In contrast, the depletion of TAMs by means of clodronate liposomes reduced lung tumorigenesis, associated to lower in vivo release of IL-1α and IL-1β. In conclusion, our data imply lung tumor lesions are populated by macrophages which pro-tumor activity is regulated by the activation of the NLRP3 inflammasome that leads to the release of IL-1α and IL-1β in a caspase-11/caspase-1-dependent manner.

Role of the inflammasome in chronic obstructive pulmonary disease (COPD)

Inflammation is central to the development of chronic obstructive pulmonary disease (COPD), a pulmonary disorder characterized by chronic bronchitis, chronic airway obstruction, emphysema, associated to progressive and irreversible decline of lung function. Emerging genetic and pharmacological evidence suggests that IL-1-like cytokines are highly detected in the sputum and broncho-alveolar lavage (BAL) of COPD patients, implying the involvement of the multiprotein complex inflammasome. So far, scientific evidence has focused on nucleotide-binding oligomerization domain-like receptors protein 3 (NLRP3) inflammasome, a specialized inflammatory signaling platform that governs the maturation and secretion of IL-1-like cytokines through the regulation of caspase-1-dependent proteolytic processing. Some studies revealed that it is involved during airway inflammation typical of COPD. Based on the influence of cigarette smoke in various respiratory diseases, including COPD, in this view we report its effects in inflammatory and immune responses in COPD mouse models and in human subjects affected by COPD. In sharp contrast to what reported on experimental and clinical studies, randomized clinical trials show that indirect inflammasome inhibitors did not have any beneficial effect in moderate to severe COPD patients.Inflammation is central to the development of chronic obstructive pulmonary disease (COPD), a pulmonary disorder characterized by chronic bronchitis, chronic airway obstruction, emphysema, associated to progressive and irreversible decline of lung function. Emerging genetic and pharmacological evidence suggests that IL-1-like cytokines are highly detected in the sputum and broncho-alveolar lavage (BAL) of COPD patients, implying the involvement of the multiprotein complex inflammasome. So far, scientific evidence has focused on nucleotide-binding oligomerization domain-like receptors protein 3 (NLRP3) inflammasome, a specialized inflammatory signaling platform that governs the maturation and secretion of IL-1-like cytokines through the regulation of caspase-1-dependent proteolytic processing. Some studies revealed that it is involved during airway inflammation typical of COPD. Based on the influence of cigarette smoke in various respiratory diseases, including COPD, in this view we report its effects in inflammatory and immune responses in COPD mouse models and in human subjects affected by COPD. In sharp contrast to what reported on experimental and clinical studies, randomized clinical trials show that indirect inflammasome inhibitors did not have any beneficial effect in moderate to severe COPD patients.

Human peripheral blood mononuclear cells (PBMCs) from smokers release higher levels of IL-1-like cytokines after exposure to combustion-generated ultrafine particles

Ultrafine particles (UFP) generated by combustion processes are often associated with adverse health effects. However, little is known about the inflammatory processes generated by UFP that may underlie their toxicological activity. Murine macrophages (J774.1 cells) and human peripheral blood mononuclear cells (PBMCs) were used to evaluate the molecular mechanism underlying the pro-inflammatory activity of UFP. The addition of soot particles to J774.1 cells induced a concentration-dependent release of IL-1α, IL-1β and IL-33 This effect was not associated with cell death and, in contrast to literature, was pronounced at very low concentrations (5–100 pg/ml). Similarly, UFP induced the release of IL-1α, IL-18 and IL-33 by PBMCs. However, this effect was solely observed in PBMCs obtained from smokers, as the PBMCs from non-smokers instead released higher levels of IL-10. The release of these cytokines after UFP exposure was caspase-1- and NLRP3 inflammasome-dependent in PBMCs from healthy smokers, whereas IL-1α release was calpain-dependent. These results show that UFP at very low concentrations are able to give rise to an inflammatory process that is responsible for IL-1α, IL-18 and IL-33 release, which is pronounced in PBMCs from smokers, confirming that these individuals are especially susceptible to inflammatory-based airway diseases once exposed to air pollution.

Disodium cromoglycate inhibits asthma-like features induced by sphingosine-1-phosphate

Compelling evidence suggests the involvement of sphingosine-1-phosphate (S1P) in the pathogenesis of asthma. The systemic administration of S1P causes asthma like features in the mouse involving mast cells. In this study we investigated whether disodium cromoglycate (DSCG), administered as a preventative treatment as in human therapy, could affect S1P effects on airways. BALB/c mice, treated with DSCG, received subcutaneous administration of S1P. Bronchi and pulmonary tissues were collected and functional, molecular and cellular studies were performed. DSCG inhibited S1P-induced airway hyper-reactivity as well as pulmonary inflammation. DSCG decreased the recruitment of solely mast cells and B cells in the lung. IgE serum levels, prostaglandin D2, mucus production and IL-13 were also reduced when mice were pretreated with DSCG. S1P induced pulmonary expression of CD23 on T and B cells, that was reversed by DSCG. Conversely, S1P failed to upregulate CD23 in mast cell-deficient Kit W-sh/W-sh mice. In conclusion we have shown that DSCG inhibits S1P-induced asthma like features in the mouse. This beneficial effect is due to a regulatory action on mast cell activity, and in turn to an inhibition of IgE-dependent T and B cells responses.