No abstract

Gas6/TAM receptor activity contributes to the activation of pulmonary fibroblasts in IPF, suggesting that targeting this RTK pathway might be an effective antifibrotic strategy in this disease.

Idiopathic pulmonary fibrosis (IPF) is a fibrotic lung disease of unknown etiopathogenesis with limited therapeutic options. IPF is characterized by an abundance of fibroblasts and loss of epithelial progenitors, which cumulates in unrelenting fibrotic lung remodeling and loss of normal oxygenation. IPF has been challenging to model in rodents; nonetheless, mouse models of lung fibrosis provide clues as to the natural progression of lung injury and remodeling, but many have not been useful in predicting efficacy of therapeutics in clinical IPF. We provide a detailed methodologic description of various iterations of humanized mouse models, initiated by the i.v. injection of cells from IPF lung biopsy or explants specimens into severe combined immunodeficiency (SCID)/beige or nonobese diabetic SCID g mice. Unlike cells from normal lung samples, IPF cells promote persistent, nonresolving lung remodeling in SCID mice. Finally, we provide examples and discuss potential advantages and pitfalls of humanspecific targeting approaches in a humanized SCID model of pulmonary fibrosis.

BackgroundPhospholipases C (PLCs) are virulence factors found in several bacteria. In Mycobacterium tuberculosis (Mtb) they exhibit cytotoxic effects on macrophages, but the mechanisms involved in PLC-induced cell death are not fully understood. It has been reported that induction of cell necrosis by virulent Mtb is coordinated by subversion of PGE2, an essential factor in cell membrane protection.ResultsUsing two Mtb clinical isolates carrying genetic variations in PLC genes, we show that the isolate 97-1505, which bears plcA and plcB genes, is more resistant to alveolar macrophage microbicidal activity than the isolate 97-1200, which has all PLC genes deleted. The isolate 97-1505 also induced higher rates of alveolar macrophage necrosis, and likewise inhibited COX-2 expression and PGE2 production. To address the direct effect of mycobacterial PLC on cell necrosis and PGE2 inhibition, both isolates were treated with PLC inhibitors prior to macrophage infection. Interestingly, inhibition of PLCs affected the ability of the isolate 97-1505 to induce necrosis, leading to cell death rates similar to those induced by the isolate 97-1200. Finally, PGE2 production by Mtb 97-1505-infected macrophages was restored to levels similar to those produced by 97-1200-infected cells.ConclusionsMycobacterium tuberculosis bearing PLCs genes induces alveolar macrophage necrosis, which is associated to subversion of PGE2 production.

Lung fibrosis is an unabated wound healing response characterized by the loss and aberrant function of lung epithelial cells. Herein, we report that extracellular Clusterin promoted epithelial cell apoptosis whereas intracellular Clusterin maintained epithelium viability during lung repair. Unlike normal and COPD lungs, IPF lungs were characterized by significantly increased extracellular Clusterin whereas the inverse was evident for intracellular Clusterin. In vitro and in vivo studies demonstrated that extracellular Clusterin promoted epithelial cell apoptosis while intercellular Clusterin modulated the expression of the DNA repair proteins, MSH2, MSH6, OGG1 and BRCA1. The fibrotic response in Clusterin deficient (CLU−/−) mice persisted after bleomycin and it was associated with increased DNA damage, reduced DNA repair responses, and elevated cellular senescence. Remarkably, this pattern mirrored that observed in IPF lung tissues. Together, our results show that cellular localization of Clusterin leads to divergent effects on epithelial cell regeneration and lung repair during fibrosis.

Innate immune cells play a critical role during the onset of HIV infection and remain active until the final events that characterize AIDS. The viral impact on innate immune cell response may be a result of direct infection or indirect modulation, and each cell type responds in a specific manner to HIV. During HIV infection, the immune system works in a dynamic way, where innate and adaptive cells contribute with each other stimulating their function and modulating phenotypes and consequently infection resolution. Understanding the alterations in the cell populations induced by the virus is pivotal and can help to combat HIV at the time of infection and above all, to prevent the establishment of viral reservoirs. In this review, we will describe the frequency and the subtypes of infected cells such as of monocytes, DCs, neutrophils, eosinophils, mast cells/basophils, NK cells, NKT cells and γδ T cells, and we discuss the possibility of cell-targeting strategies. Our aim is to consolidate the existing knowledge of the interaction between HIV and cells that constitute the innate immune response.

Idiopathic pulmonary fibrosis (IPF) is a fibrotic lung disease, with unknown etiopathogenesis and suboptimal therapeutic options. Previous reports have shown that increased T cell numbers and CD28 null phenotype is predictive of prognosis in IPF, suggesting that these cells might have a role in this disease. Flow cytometric analysis of explanted lung cellular suspensions showed a significant increase in CD8 + CD28 null T cells in IPF relative to normal lung explants. Transcriptomic analysis of CD3 + T cells isolated from IPF lungs explants revealed a loss of CD28 transcript expression and elevation of proinflammatory cytokine expression in IPF relative to normal T cells. IPF lung explant derived T cells (enriched with CD28 null T cells), but not normal donor lung CD28 + T cells induced dexamethasone resistant lung remodeling in humanized NSG mice. Finally, CD28 null T cells expressed similar CTLA4 and significantly higher levels of PD-1 proteins relative to CD28 + T cells and blockade of either proteins in humanized NSG mice, using anti-CTLA4, or anti-PD1, mAb treatment accelerated lung fibrosis. Together, these results demonstrate that IPF CD28 null T cells may promote lung fibrosis but the immune checkpoint proteins, CTLA-4 and PD-1, appears to limit this effect.

Monocytes are key cells in the immune dysregulation observed during human immunodeficiency virus (HIV) infection. The events that take place specifically in monocytes may contribute to the systemic immune dysfunction characterized by excessive immune activation in infected individuals, which directly correlates with pathogenesis and progression of the disease. Here, we investigated the immune dysfunction in monocytes from untreated and treated HIV + patients and associated these findings with epigenetic changes. Monocytes from HIV patients showed dysfunctional ability of phagocytosis and killing, and exhibited dysregulated cytokines and reactive oxygen species production after M. tuberculosis challenge in vitro. In addition, we showed that the expression of enzymes responsible for epigenetic changes was altered during HIV infection and was more prominent in patients that had high levels of soluble CD163 (sCD163), a newly identified plasmatic HIV progression biomarker. Among the enzymes, histone acetyltransferase 1 (HAT1) was the best epigenetic biomarker correlated with HIV - sCD163 high patients. In conclusion, we confirmed that HIV impairs effector functions of monocytes and these alterations are associated with epigenetic changes that once identified could be used as targets in therapies aiming the reduction of the systemic activation state found in HIV patients.