Prevalence and characteristics of progressive fibrosing interstitial lung disease in a prospective registry.

BACKGROUND: Progressive fibrosing interstitial lung disease (PF-ILD) is characterised by progressive physiological, symptomatic and/or radiographic worsening. The real-world prevalence and characteristics of PF-ILD remain uncertain. METHODS: Patients were enrolled from the Canadian Registry for Pulmonary Fibrosis between 2015 and 2020. PF-ILD was defined as a relative forced vital capacity (FVC) decline ≥10%, death, lung transplantation or any two of: relative FVC decline ≥5% and <10%, worsening respiratory symptoms or worsening fibrosis on computed tomography of the chest, all within 24 months of diagnosis. Time-to-event analysis compared progression between key diagnostic subgroups. Characteristics associated with progression were determined by multivariable regression. RESULTS: Of 2746 patients with fibrotic ILD (mean±sd age 65±12 years; 51% female), 1376 (50%) met PF-ILD criteria in the first 24 months of follow-up. PF-ILD occurred in 427 (59%) patients with idiopathic pulmonary fibrosis (IPF), 125 (58%) with fibrotic hypersensitivity pneumonitis (HP), 281 (51%) with unclassifiable ILD (U-ILD) and 402 (45%) with connective tissue disease-associated ILD (CTD-ILD). Compared with IPF, time to progression was similar in patients with HP (hazard ratio (HR) 0.96, 95% CI 0.79-1.17), but was delayed in patients with U-ILD (HR 0.82, 95% CI 0.71-0.96) and CTD-ILD (HR 0.65, 95% CI 0.56-0.74). Background treatment varied across diagnostic subtypes, with 66% of IPF patients receiving antifibrotic therapy, while immunomodulatory therapy was utilised in 49%, 61% and 37% of patients with CHP, CTD-ILD and U-ILD, respectively. Increasing age, male sex, gastro-oesophageal reflux disease and lower baseline pulmonary function were independently associated with progression. CONCLUSIONS: Progression is common in patients with fibrotic ILD, and is similarly prevalent in HP and IPF. Routinely collected variables help identify patients at risk for progression and may guide therapeutic strategies.

Effect of continued antifibrotic therapy after forced vital capacity decline in patients with idiopathic pulmonary fibrosis; a real world multicenter cohort study.

RATIONALE: Longitudinal data on the impact of continued, switched or discontinued antifibrotic therapy in patients with idiopathic pulmonary fibrosis (IPF) who have disease progression is needed. OBJECTIVE: We hypothesized that ongoing antifibrotic use (versus discontinuation) in the setting of forced vital capacity (FVC) decline would be associated with less future decline and lower likelihood of a composite outcome of FVC decline, lung transplant, or death. METHODS: We performed a multicenter cohort study using data from the Canadian Registry for Pulmonary Fibrosis in patients with IPF with FVC decline ≥10% over 6 months on antifibrotic therapy. The association of continued, switched or discontinued therapy with (1) further change in FVC and (2) a composite of FVC decline ≥10%, transplant, or death, in the subsequent 6 months, was assessed using adjusted linear and logistic regression modelling, respectively. Generalized estimating equations accounted for repeated observations per patient. RESULTS: 165 patients had a decline in FVC ≥10% over 6 months while receiving antifibrotic therapy. Compared to continued use, antifibrotic discontinuation after FVC decline was associated with greater additional FVC decline (-207 mL 95%CI -353 to -62, p = 0.005) and higher odds of FVC decline ≥10%, transplant, or death (odds ratio 12.2 95%CI 1.2 to 130.5, p = 0.04). There was no difference between continued versus switched antifibrotic therapy. CONCLUSIONS: Ongoing antifibrotic therapy in the setting of FVC decline is associated with less future FVC decline and lower odds of FVC decline ≥10%, transplant, or death in a real-world cohort of IPF.

Treatment Initiation in Patients with Interstitial Lung Disease in Canada.

Rationale: Real-life pharmacological treatment patterns of patients with interstitial lung diseases (ILD) remain elusive. Objectives: To determine how often and with what medications patients with ILD are treated in Canadian tertiary care clinics. Methods: All patients with ILD prospectively enrolled in the Canadian Registry for Pulmonary Fibrosis were included in this observational study. All first instances of medication for each patient were compiled. The time between the diagnosis of ILD and the first initiation of an ILD-related medication was compared across diagnostic categories. Cox proportional hazards models were used to identify variables associated with time-to-treatment initiation, stratified by diagnostic category. Results: Out of 2,652 patients, a total of 1,483 (56%) were treated with an ILD-related medication during the median follow up of 3.0 years (1.4-5.9), including 349/646 (54%) patients with idiopathic pulmonary fibrosis (IPF) who received an antifibrotic. Patients with IPF were treated earlier and in greater proportion than those with non-IPF ILD (P = 0.001). Male sex and lower lung function were associated with shorter time-to-treatment initiation in the full cohort. Conclusions: Overall, 56% of patients with ILD seen across seven Canadian specialized ILD clinics received pharmacological treatment over a median follow up of 3 years. Further studies are needed to assess longitudinal patterns of treatment and their influence on key outcomes.

Binding of filamentous actin to anthrax toxin receptor 1 decreases its association with protective antigen.

ANTXR1 is a type I membrane protein that binds the protective antigen (PA) component of anthrax toxin. The cytosolic domain of ANTXR1 has a novel actin-binding region that influences the interaction of the ectodomain with PA. Here, we have investigated features of the cytosolic domain of ANTXR1 that reduce the association of the receptor with PA. We mutated a stretch of conserved acidic amino acids adjacent to the actin-binding region and found that the mutation increased the affinity for monomeric actin in vitro. ANTXR1 bearing this mutation exhibited increased association with the cytoskeleton and bound less PA compared to the wild-type receptor, confirming the inverse correlation between the two interactions. To determine whether binding of actin is sufficient to regulate the ectodomain, we replaced the actin-binding region of ANTXR1 with that from the yeast protein abp140 and with the WH2 domain of WAVE2. Although both of these domains bound monomeric actin in vitro, only the sequence from abp140 reduced binding of PA to a hybrid receptor. The actin binding regions of ANTXR1 and abp140, but not the WH2 domain, colocalized with actin stress fibers, which suggested that filamentous actin regulates ANTXR1. Consistent with this notion, disruption of actin filaments using latrunculin A increased the amount of PA bound to cells. This work provides evidence that cytoskeletal dynamics regulate ANTXR1 function.

Direct interaction between anthrax toxin receptor 1 and the actin cytoskeleton.

The protective antigen component of anthrax toxin binds the I domain of the anthrax toxin receptors, ANTXR1 and ANTXR2, in a manner akin to how integrins bind their ligands. The I domains of integrins and ANTXR1 both have high- and low-affinity conformations, and the cytosolic tails of these receptors associate with the actin cytoskeleton. The association of ANTXR1 with the cytoskeleton correlates with weakened binding to PA, although a mechanistic explanation for this observation is lacking. Here, we identified a segment in the cytoplasmic tail of ANTXR1 required for its association with the cytoskeleton. We synthesized a 60-mer peptide based on this segment and demonstrated a direct interaction between the peptide and beta-actin, indicating that in contrast to integrins, ANTXR1 does not use an adaptor to bind the cytoskeleton. This peptide orders actin filaments into arrays, demonstrating an actin bundling activity that is novel for a membrane protein.

Cytoskeletal stability and heat shock-mediated thermoprotection of central pattern generation in Locusta migratoria.

Prior exposure to extreme temperatures can induce thermoprotection in migratory locusts, which is important for survival in their natural environment. An important motor activity that needs to be protected is ventilation. The mechanism underlying heat shock is not fully understood, and our goal was to test the idea that cytoskeletal stability is critical for such thermoprotection. Cytoskeletal stabilizers (concanavalin A) and destabilizers (colchicine) were bath-applied in semi-intact locust preparations in both control (C) and pre-treated heat-shocked (3 h, 45 degrees C) animals. We measured parameters of the ventilatory motor pattern during maintained high temperature (43 degrees C) and recorded the times taken for motor pattern generation to fail and then recover on returning to room temperature. We found that concanavalin A mimicked the effects of a prior heat stress in control animals by increasing time to failure and decreasing time to recovery of motor pattern generation. However, colchicine destroyed protection in heat-shocked animals by decreasing time to failure and increasing time to recovery. Our findings confirm that the cytoskeleton has a mechanistic role in preserving neural function at high temperatures, possibly through stabilizing ion channels and other integral membrane proteins (e.g. Na(+)/K(+) ATPase) and their interactions with heat shock proteins.