Protein tyrosine phosphatase α mediates profibrotic signaling in lung fibroblasts through TGF-β responsiveness

Fibrotic lung diseases represent a diverse group of progressive and often fatal disorders with limited treatment options. Although the pathogenesis of these conditions remains incompletely understood, receptor type protein tyrosine phosphatase α (PTP-α encoded by PTPRA) has emerged as a key regulator of fibroblast signaling. We previously reported that PTP-α regulates cellular responses to cytokines and growth factors through integrin-mediated signaling and that PTP-α promotes fibroblast expression of matrix metalloproteinase 3, a matrix-degrading proteinase linked to pulmonary fibrosis. Here, we sought to determine more directly the role of PTP-α in pulmonary fibrosis. Mice genetically deficient in PTP-α (Ptpra(-/-)) were protected from pulmonary fibrosis induced by intratracheal bleomycin, with minimal alterations in the early inflammatory response or production of TGF-β. Ptpra(-/-) mice were also protected from pulmonary fibrosis induced by adenoviral-mediated expression of active TGF-β1. In reciprocal bone marrow chimera experiments, the protective phenotype tracked with lung parenchymal cells but not bone marrow-derived cells. Because fibroblasts are key contributors to tissue fibrosis, we compared profibrotic responses in wild-type and Ptpra(-/-) mouse embryonic and lung fibroblasts. Ptpra(-/-) fibroblasts exhibited hyporesponsiveness to TGF-β, manifested by diminished expression of αSMA, EDA-fibronectin, collagen 1A, and CTGF. Ptpra(-/-) fibroblasts exhibited markedly attenuated TGF-β-induced Smad2/3 transcriptional activity. We conclude that PTP-α promotes profibrotic signaling pathways in fibroblasts through control of cellular responsiveness to TGF-β.

Increased rainfall is associated with increased risk for legionellosis

Legionnaires' disease (LD) is caused by Legionella species, most of which live in water. The Mid-Atlantic region experienced a sharp rise in LD in 2003 coinciding with a period of record-breaking rainfall. To investigate a possible relationship, we analysed the association between monthly legionellosis incidence and monthly rainfall totals from January 1990 to December 2003 in five Mid-Atlantic states. Using negative binomial model a 1-cm increase in rainfall was associated with a 2.6% (RR 1.026, 95% CI 1.012-1.040) increase in legionellosis incidence. The average monthly rainfall from May to September 1990-2002 was 10.4 cm compared to 15.7 cm from May to September 2003. This change in rainfall corresponds to an increased risk for legionellosis of approximately 14.6% (RR 1.146, 95% CI 1.067-1.231). Legionellosis incidence increased during periods of increased rainfall; identification of mechanisms that increase exposure and transmission of Legionella during rainfall might lead to opportunities for prevention.

IL-12 p80 is an innate epithelial cell effector that mediates chronic allograft dysfunction

RATIONALE

Bronchiolitis obliterans syndrome is the leading cause of chronic lung allograft dysfunction. We have demonstrated that respiratory viral infection is a bronchiolitis obliterans syndrome risk factor and virus-dependent injury induces expression of innate airway epithelial genes belonging to the interleukin (IL)-12 family. Thus, we hypothesized that epithelial cell IL-12 family members could mediate lung allograft dysfunction.

OBJECTIVES

We used mouse and human allograft specimens to evaluate the role of epithelial cell IL-12 family members in allograft dysfunction associated with and without viral infection.

METHODS

Murine and human IL-12 family members were characterized and manipulated in allografts and then correlated with epithelial cell injury, immune cell accumulation, and collagen deposition.

RESULTS

In a mouse model of lung transplantation, concurrent viral infection and allogeneic transplantation increased epithelial injury and this was followed by exaggerated accumulation of macrophages and collagen deposition. This virus-driven allograft dysfunction was associated with an epithelial innate response manifested by a synergistic increase in the production of the macrophage chemoattractant IL-12 p80 (p80), but not IL-12 or IL-23. Blockade or overexpression of donor epithelial p80 resulted in a corresponding abrogation or enhancement of macrophage accumulation and allograft dysfunction. We extended these findings to human recipients with viral infection and transplant bronchitis and again observed excessive epithelial p80 expression that correlated with increased macrophage accumulation.

CONCLUSIONS

These experiments support a role for an enhanced epithelial innate response as a central process in allograft dysfunction and identify the macrophage chemoattractant p80 as an innate epithelial effector of disease progression.

The significance of a single episode of minimal acute rejection after lung transplantation

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) remains the leading obstacle to better long-term outcomes after lung transplantation. Acute rejection has been identified as the primary risk factor for BOS, but the impact of minimal acute rejection, especially a solitary episode, has usually been discounted as clinically insignificant.

METHODS

We performed a retrospective cohort study of 259 adult lung transplant recipients to determine the risk of BOS associated with a single episode of A1 rejection, without recurrence or subsequent progression to a higher grade. The cohort was divided into 3 groups based on the severity of acute rejection (none, single episode of A1, and single episode of A2). We determined the risks of BOS stages 1, 2, 3, and death for each group using univariate and multivariate Cox regression analyses.

RESULTS

A solitary episode of A1 rejection was a significant risk factor for BOS stages 1 and 2, but not stage 3 or death, in the univariate analysis. Multivariate Cox regression models confirmed that the risk of BOS attributable to a single episode of A1 rejection was independent of other potential risk factors, such as community acquired respiratory viral infections, number of HLA mismatches, and cytomegalovirus pneumonitis. Likewise, univariate and multivariate analyses demonstrated that a single episode of A2 rejection was a significant risk factor for all stages of BOS but not death.

CONCLUSIONS

A single episode of minimal acute rejection without recurrence or subsequent progression to a higher grade is a significant predictor of BOS independent of other risk factors.

Measles outbreak in the Republic of the Marshall Islands, 2003

BACKGROUND

Measles is a highly contagious viral infection. Measles transmission can be prevented through high population immunity (>or=95%) achieved by measles vaccination. In the Republic of the Marshall Islands (RMI), no measles cases were reported during 1989-2002; however, a large measles outbreak occurred in 2003. Reported 1-dose measles vaccine coverage among children aged 12-23 months varied widely (52-94%) between 1990 and 2000.

METHODS

RMI is a Pacific island nation (1999 population: 50,840). A measles case was defined as fever, rash, and cough, or coryza, or conjunctivitis, in an RMI resident between July 13 and November 7, 2003. A vaccination campaign was used for outbreak control.

RESULTS

Of the 826 reported measles cases, 766 (92%) occurred in the capital (Majuro). There were 186 (23%) cases in infants aged <1 year and 309 (37%) of cases in persons aged >or=15 years. The attack rate was highest among infants (Majuro atoll: 213 cases/1,000 infants). Among cases aged 1-14 years, 281 (59%) reported no measles vaccination before July 2003. There were 100 hospitalizations and 3 deaths. The measles H1 genotype was identified. The vaccination campaign resulted in 93% coverage among persons aged 6 months to 40 years. Interpretation Populations without endemic measles transmission can accumulate substantial susceptibility and be at risk for large outbreaks when measles virus is imported. 'Islands' of measles susceptibility may develop in infants, adults, and any groups with low vaccine coverage. To prevent outbreaks, high population immunity must be sustained by maintaining and documenting high vaccine coverage.

Minimal acute rejection after lung transplantation: a risk for bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) is a major cause of lung allograft dysfunction. Although previous studies have identified mild to severe rejection (grade>or=A2) as a risk factor for BOS, the role of minimal rejection (grade A1) remains unclear. To determine if A1 rejection by itself is a risk factor for BOS, we performed a retrospective cohort study on 228 adult lung transplant recipients over a 7-year period. Cohorts were defined by their most severe rejection episode (none, A1 only, and >or=A2) and analyzed for the subsequent development and progression of BOS using univariate and multivariate time-dependent Cox regression analysis. In the univariate model, the occurrence of isolated minimal rejection was a risk factor for all stages of BOS. Similarly, multivariate models that included HLA mismatch, cytomegalovirus pneumonitis, community acquired viral infection, underlying disease and type of transplant demonstrated that A1 rejection was a distinct risk factor for BOS. Furthermore, the associated risk with A1 rejection was slightly greater than the risk from >or=A2 and treatment of A1 rejection decreased the risk for subsequent BOS stage 1. We conclude that minimal rejection is associated with an increased risk for BOS development and progression that is comparable to A2 rejection.

Respiratory viral infections are a distinct risk for bronchiolitis obliterans syndrome and death

Bronchiolitis obliterans syndrome (BOS) is the major obstacle to long-term survival after lung transplantation, in part because its pathogenesis is poorly understood and treatment options are limited. To identify unique risk factors for BOS and death, we performed a retrospective cohort study on 259 consecutive adult lung transplant recipients over a 5-year period. The demographic and clinical characteristics of this population were analyzed for an association between BOS or death and potential risk factors, including community-acquired respiratory viral (CARV) infections, acute rejection, and cytomegalovirus pneumonitis. Respiratory syncytial virus, parainfluenza, influenza, and adenovirus accounted for 21 CARV infections. Univariate and multivariate time-dependent Cox regression analyses demonstrated that this CARV group was more likely to develop BOS, death, and death from BOS. Furthermore, these trends were more pronounced in patients with evidence of lower respiratory tract-CARV (lower-CARV) infections. Notably, the CARV and lower-CARV infections were risk factors for BOS, death, and death from BOS distinct from the risk attributable to acute rejection. Identification of CARV and lower-CARV infections as BOS and mortality risk factors has important clinical implications and may provide insight into disease pathogenesis and accelerate the development of novel treatment strategies to modify post-CARV BOS.

IL-12 p40 homodimer-dependent macrophage chemotaxis and respiratory viral inflammation are mediated through IL-12 receptor beta 1

Leukocyte recruitment to the airway lumen is a central feature of inflammatory conditions such as asthma and respiratory viral infection. Characterization of mediators that regulate leukocyte recruitment in these conditions revealed increased IL-12 p40 homodimer (p80) levels were associated with enhanced airway macrophage accumulation. To examine this association, we used in vivo and in vitro assays to demonstrate p80, but not IL-12 or p40, provided a macrophage chemoattractant signal. Macrophages from genetically deficient mice indicated p80-dependent chemotaxis was independent of IL-12 and required IL-12Rbeta1 (Rbeta1) expression. Furthermore, analysis of murine cell lines and primary culture macrophages revealed Rbeta1 expression, with an intact cytoplasmic tail, was necessary and sufficient to mediate p80-dependent chemotaxis. To examine the role for Rbeta1 in mediating macrophage accumulation in vivo, we contrasted Sendai virus-driven airway inflammation in wild-type and Rbeta1-deficient mice. Despite similar viral burden and production of the macrophage chemoattractant p80, the Rbeta1-deficient mice displayed a selective decrease in airway macrophage accumulation and resistance to viral-dependent mortality. Thus, Rbeta1 mediates p80-dependent macrophage chemotaxis and inhibition of the p80-Rbeta1 interaction may provide a novel anti-inflammatory strategy to manipulate the inflammation associated with asthma and respiratory viral infection.