MMP induced by Gr-1+ cells are crucial for recruitment of Th cells into the airways

MicroRNA-216a inhibits neuronal apoptosis in a cellular Parkinson's disease model by targeting Bax

The study found that microRNAs play an important role in Parkinson's disease (PD). However, the function of MicroRNA-216a (miR-216a) in PD is unclear. Therefore, this experiment aimed to investigate the pathogenesis of miR-216a in PD. Using the toxicity of MPP+ to polyhexamine neurons, apoptosis of SH-SY5Y neuroblastoma cells was induced at different time by MPP+ to construct a stable acute PD cell model. The effects of DNA breakage, mitochondrial membrane potential (A ^ m), caspase-3 activity and nucleosome enrichment on cell apoptosis were detected by flow cytometry, TUNEL. MPP+ increased the toxic effects of dopaminergic neurons in a PD model. The introduction of miR-216a inhibited MPP + -induced neuronal apoptosis. The main manifestations were the decreased levels of positive rate of Tunel cells, caspase 3 activity and nucleosome enrichment factor. Bax was a direct target of miR-216a. In addition, Bax overexpression reversed the effects of miR-216a on neural cells. Bax downstream factors were also involved in miR-216a regulation of MPP + -triggered neuronal apoptosis. miR-216a regulated the progression of PD by regulating Bax, and miR-216a may be a potential target for PD.

Increased expression of CysLT2 receptors in the lung of asthmatic mice and role in allergic responses

Compared with CysLT₁ receptors, the functional role of CysLT₂ receptors in asthma has not been clarified. The purpose of this study was to determine 1) whether CysLT₂ receptors are expressed in the lung of mice and if expression increases in asthmatic mice, and 2) whether CysLT₂ receptors are involved in allergic leukocyte infiltration into the lung and in the development of airway remodeling in asthmatic mice. BALB/c mice were sensitized with ovalbumin (OVA) + Al(OH)₃, and intratracheally challenged with OVA 4 times. Lung tissue was isolated before and after the 4th OVA challenge for detection of CysLT₂ receptors by immunohistochemistry and flow cytometry. The effect of a CysLT₂ receptor antagonist BayCysLT₂RA on multiple antigen challenge-induced leukocyte infiltration into the lung and the development of airway remodeling was evaluated. Even in non-challenged mice, CysLT₂ receptors were expressed in bronchial smooth muscle. After multiple challenges, expression was also observed in leukocytes infiltrating into alveolar spaces. CysLT₂R⁺ leukocytes included alveolar macrophages, conventional dendritic cells, and eosinophils. BayCysLT₂RA significantly inhibited multiple antigen challenge-induced increases in eosinophils and mononuclear cells in the lung. The development of airway remodeling was tended to be suppressed by CysLT₂ receptor antagonist. In conclusion, CysLT₂ receptors were constitutively expressed in the lung, and expression was strengthened in asthmatic mice. Activation of CysLT₂ receptors was functionally involved in allergic leukocyte infiltration into the lung. The CysLT₂ receptor can be a molecular target for the development of new pharmacotherapies for asthma.

Matrix Metalloproteinase-9 Mediates RSV Infection in Vitro and in Vivo

Respiratory Syncytial Virus (RSV) is an important human pathogen associated with substantial morbidity and mortality. The present study tested the hypothesis that RSV infection would increase matrix metalloproteinase (MMP)-9 expression, and that MMP-9 inhibition would decrease RSV replication both in vitro and in vivo. RSV A2 infection of human bronchial epithelial cells increased MMP-9 mRNA and protein release. Cells transfected with siRNA against MMP-9 following RSV infection had lower viral titers. In RSV infected wild-type (WT) mice, MMP-9, airway resistance and viral load peaked at day 2 post infection, and remained elevated on days 4 and 7. RSV infected MMP-9 knockout (KO) mice had decreased lung inflammation. On days 2 and 4 post inoculation, the RSV burden was lower in the MMP-9 KO mice compared to WT controls. In conclusion, our studies demonstrate that RSV infection is a potent stimulus of MMP-9 expression both in vitro and in vivo. Reduction of MMP-9 (via siRNA knockdown, and in MMP-9 KO mice) resulted in decreased viral replication. Our findings suggest MMP-9 is a potential therapeutic target for RSV disease.

The effects of nodakenin on airway inflammation, hyper-responsiveness and remodeling in a murine model of allergic asthma

CONTEXT

Nodakenin is a major coumarin glucoside in the root of Peucedanum decursivum Maxim, a commonly used traditional Chinese medicine for the treatment of asthma and chronic bronchitis for thousands of years.

OBJECTIVE

In this work, the anti-asthma potential of nodakenin was studied by investigation of its effect to suppress airway inflammation, hyper-responsiveness and remodeling in a murine model of chronic asthma.

MATERIALS AND METHODS

BALB/c mice sensitized to ovalbumin (OVA) were challenged with aerosolized OVA for 8 weeks, orally administered with nodakenin at doses of 5, 10 and 20 mg/kg before each OVA challenge.

RESULTS

Compared with the model group, nodakenin treatment markedly inhibited airway inflammation, hyper-responsiveness and remodeling, showing improvement in subepithelial fibrosis, smooth muscle hypertrophy, and goblet cell hyperplasia, and decreased levels of interleukin (IL)-4, IL-5, IL-13 and matrix metalloproteinase-2/-9 in bronchoalveolar lavage fluid, and the level of OVA-specific IgE in serum. In addition, the NF-κB DNA-binding activity in lung tissues was also reduced by nodakenin treatment.

CONCLUSIONS

These data indicated that nodakenin might mitigate the development of chronic experimental allergic asthma.

Presensitizing with a Toll-like receptor 3 ligand impairs CD8 T-cell effector differentiation and IL-33 responsiveness

The synthetic double-stranded RNA poly(I:C) is commonly used as an adjuvant to boost CD8 T-cell function; however, polyinosinic:polycytidylic acid [poly(I:C)] can also suppress autoimmune disease. The mechanism by which a single adjuvant achieves two distinct immunoregulatory roles is unknown. Although it is clear that coadministration of poly(I:C) with antigen elicits strong adjuvant effects in mice, we found that poly(I:C) injection before antigen substantially reduced antigen-dependent CD8 T-cell responses. Notably, CD8 T cells sensitized in poly(I:C)-pretreated mice failed to fully up-regulate IL-33R (ST2), which led to impaired T-cell receptor-independent responses to IL-33. In contrast, nonsensitized effector CD8 T cells responded robustly to IL-33 using a two-signal cytokine mechanism. During an acute lung response to Staphylococcus aureus enterotoxin, peripheral injection of poly(I:C) manifested a suppressive process by inhibiting the differentiation of both antigen- and IL-33-responsive CD8 effectors systemically. These findings highlight that early exposure to double-stranded RNA reverses its role as an adjuvant and, importantly, prevents IL-33R up-regulation on CD8 effector T cells to dampen inflammation.

Revisiting the protective and pathogenic roles of neutrophils: Ly-6G is key!

The physiological and pathophysiological roles of neutrophils in immune homeostasis and disease have been investigated extensively by way of anti-Gr-1 mAb-mediated depletion experiments; however, the ability of the anti-Gr-1 mAb to specifically deplete neutrophils has long been questioned and it is now known that this mAb, which binds Ly6C and Ly6G, is also able to deplete monocytes and subsets of CD8(+) T cells. This, therefore, casts doubt on the previous conclusions regarding the role of neutrophils drawn from studies using this mAb. Another mAb, which targets Ly6G only, has recently been shown to deplete neutrophils specifically and a study by Carr et al. (Eur. J. Immunol. 2011. 41: 2666-2676) in this issue of the European Journal of Immunology utilizes this Ly-6G mAb to reveal the precise role of neutrophils during Listeria monocytogenes (LM) infection. Carr et al. find that monocytes/macrophages, rather than neutrophils, dominate the initial control of LM growth in the spleen, whereas neutrophils in the liver are key for host resistance to LM infection. These data suggest that the previously reported protective or pathogenic roles of neutrophils in disease models need to be reconsidered through anti-Ly6G mAb-mediated depletion experiments.

Compartment-specific remodeling of splenic micro-architecture during experimental visceral leishmaniasis

Progressive splenomegaly is a hallmark of visceral leishmaniasis in humans, canids, and rodents. In experimental murine visceral leishmaniasis, splenomegaly is accompanied by pronounced changes in microarchitecture, including expansion of the red pulp vascular system, neovascularization of the white pulp, and remodeling of the stromal cell populations that define the B-cell and T-cell compartments. Here, we show that Ly6C/G⁺ (Gr-1⁺) cells, including neutrophils and inflammatory monocytes, accumulate in the splenic red pulp during infection. Cell depletion using monoclonal antibody against either Ly6C/G⁺ (Gr-1; RB6) or Ly6G⁺ (1A8) cells increased parasite burden. In contrast, depletion of Ly6C/G⁺ cells, but not Ly6G⁺ cells, halted the progressive remodeling of Meca-32⁺ and CD31⁺ red pulp vasculature. Strikingly, neither treatment affected white pulp neovascularization or the remodeling of the fibroblastic reticular cell and follicular dendritic cell networks. These findings demonstrate a previously unrecognized compartment-dependent selectivity to the process of splenic vascular remodeling during experimental murine visceral leishmaniasis, attributable to Ly6C⁺ inflammatory monocytes.

Critical role of macrophages and their activation via MyD88-NFκB signaling in lung innate immunity to Mycoplasma pneumoniae

Mycoplasma pneumoniae (Mp), a common cause of pneumonia, is associated with asthma; however, the mechanisms underlying this association remain unclear. We investigated the cellular immune response to Mp in mice. Intranasal inoculation with Mp elicited infiltration of the lungs with neutrophils, monocytes and macrophages. Systemic depletion of macrophages, but not neutrophils, resulted in impaired clearance of Mp from the lungs. Accumulation and activation of macrophages were decreased in the lungs of MyD88(-/-) mice and clearance of Mp was impaired, indicating that MyD88 is a key signaling protein in the anti-Mp response. MyD88-dependent signaling was also required for the Mp-induced activation of NFκB, which was essential for macrophages to eliminate the microbe in vitro. Thus, MyD88-NFκB signaling in macrophages is essential for clearance of Mp from the lungs.

Requirement for inducible nitric oxide synthase in chronic allergen exposure-induced pulmonary fibrosis but not inflammation

The role of inducible NO synthase (iNOS) in allergic airway inflammation remains elusive. We tested the hypothesis that iNOS plays different roles during acute versus chronic airway inflammation. Acute and chronic mouse models of OVA-induced airway inflammation were used to conduct the study. We showed that iNOS deletion was associated with a reduction in eosinophilia, mucus hypersecretion, and IL-5 and IL-13 production upon the acute protocol. Such protection was completely abolished upon the chronic protocol. Interestingly, pulmonary fibrosis observed in wild-type mice under the chronic protocol was completely absent in iNOS(-/-) mice despite persistent IL-5 and IL-13 production, suggesting that these cytokines were insufficient for pulmonary fibrosis. Such protection was associated with reduced collagen synthesis and indirect but severe TGF-beta modulation as confirmed using primary lung smooth muscle cells. Although activation of matrix metalloproteinase-2/-9 exhibited little change, the large tissue inhibitor of metalloproteinase-2 (TIMP-2) increase detected in wild-type mice was absent in the iNOS(-/-) counterparts. The regulatory effect of iNOS on TIMP-2 may be mediated by peroxynitrite, as the latter reversed TIMP-2 expression in iNOS(-/-) lung smooth muscle cells and fibroblasts, suggesting that the iNOS-TIMP-2 link may explain the protective effect of iNOS-knockout against pulmonary fibrosis. Analysis of lung sections from chronically OVA-exposed iNOS(-/-) mice revealed evidence of residual but significant protein nitration, prevalent oxidative DNA damage, and poly(ADP-ribose) polymerase-1 activation. Such tissue damage, inflammatory cell recruitment, and mucus hypersecretion may be associated with substantial arginase expression and activity. The results in this study exemplify the complexity of the role of iNOS in asthma and the preservation of its potential as a therapeutic a target.

The metalloprotease-disintegrin ADAM8 is essential for the development of experimental asthma

RATIONALE

Expression of the metalloprotease ADAM8 is increased in patients with asthma, but the functional significance of elevated ADAM8 expression in the context of asthma pathogenesis remains elusive.

OBJECTIVES

To study development of asthma in ADAM8-deficient mice.

METHODS

Ovalbumin-induced asthma was studied in wild-type, ADAM8-deficient, and ADAM8-chimeric mice. Lung inflammation was assessed by histology, analysis of bronchoalveolar lavage, and airway hyperresponsiveness.

MEASUREMENTS AND MAIN RESULTS

ADAM8-deficient mice are highly resistant to the development of ovalbumin-induced airway inflammation and hyperresponsiveness. ADAM8 expression was induced in both hematopoietic cells and the nonhematopoietic microenvironment after induction of asthma, and ADAM8 expression in both cell populations was required for the full manifestation of asthma. Interestingly, loss of ADAM8 on T cells alone was sufficient to significantly decrease the asthma response. The attenuated response was not due to an intrinsic defect in antigen presentation or cytokine production but reflected an impaired migration of T cells, eosinophils, CD11b(+) CD11c(-), and CD11c(+) cells from blood vessels to the lung and alveolar space, suggesting a general hematopoietic cell deficiency in the absence of ADAM8.

CONCLUSIONS

The results show that ADAM8 plays a proinflammatory role in airway inflammation. The milder disease outcome in the absence of ADAM8 suggests that this protein might be an interesting new target in treatment of this, and potentially other, inflammatory diseases in which recruitment of inflammatory cells is an essential part of pathogenesis.