Respiratory bronchiolitis-interstitial lung disease: long-term outcome.

BACKGROUND: The clinical and physiologic features of respiratory bronchiolitis (RB)-interstitial lung disease (ILD) have been previously described; however, the natural history and outcome have not been systematically evaluated. The majority of published reports consider RB-ILD to be a nonprogressive ILD that clinically improves with smoking cessation and antiinflammatory treatment. In this study, we sought to determine the outcome of RB-ILD patients with and without smoking cessation and with and without corticosteroid therapy. METHODS: Thirty-two RB-ILD cases confirmed by surgical lung biopsy were identified from a prospectively enrolled cohort of subjects with ILD. Initial and follow-up data on symptoms, physiology, treatment, and outcome were collected and analyzed. RESULTS: Kaplan-Meier analysis revealed that at least 75% of RB-ILD patients survived > 7 years after diagnosis. Clinical improvement occurred in only 28% of cases, and physiologic improvement occurred in 10.5% of cases. One patient died of progressive ILD, and two patients died of non-small cell lung cancer. While physiologic improvement was limited to those who had ceased smoking, corticosteroids and/or other immunosuppressive therapy had little effect on symptoms or physiology. CONCLUSIONS: This study shows that prolonged survival is common in RB-ILD. However, symptomatic and physiologic improvement occurs in only a minority of patients, and neither smoking cessation nor immunosuppressive therapy is regularly associated with clinically significant benefit.

Alveolar type II cells inhibit fibroblast proliferation: role of IL-1alpha.

Alveolar type II (ATII) cells inhibit fibroblast proliferation in coculture by releasing or secreting a factor(s) that stimulates fibroblast production of prostaglandin E2 (PGE2). In the present study, we sought to determine the factors released from ATII cells that stimulate PGE2 production in fibroblasts. Exogenous addition of rat IL-1alpha to cultured lung fibroblasts induced PGE2 secretion in a dose-response manner. When fibroblasts were cocultured with rat ATII cells, IL-1alpha protein was detectable in ATII cells and in the coculture medium between days 8 and 12 of culture, correlating with the highest levels of PGE2. Furthermore, under coculture conditions, IL-1alpha gene expression increased in ATII cells (but not fibroblasts) compared with either cell cultured alone. In both mixed species (human fibroblasts-rat ATII cells) and same species cocultures (rat fibroblasts and ATII cells), PGE2 secretion was inhibited by the presence of IL-1 receptor antagonist (IL-1Ra) or selective neutralizing antibody directed against rat IL-1alpha (but not IL-1beta). Conditioned media from cocultures inhibited fibroblast proliferation, and this effect was abrogated by the addition of IL-1Ra. Addition of keratinocyte growth factor (KGF) resulted in an earlier increase in PGE2 secretion and fibroblast inhibition (day 8 of coculture). This effect was inhibited by indomethacin but was not altered by IL-1Ra. We conclude that in this coculture system, IL-1alpha secretion by ATII cells is one factor that stimulates PGE2 production by lung fibroblasts, thereby inhibiting fibroblast proliferation. In addition, these studies demonstrate that KGF enhances ATII cell PGE2 production through an IL-1alpha-independent pathway.

Keratinocyte growth factor stimulates alveolar type II cell proliferation through the extracellular signal-regulated kinase and phosphatidylinositol 3-OH kinase pathways.

Keratinocyte growth factor (KGF or FGF-7) stimulates alveolar type II cell proliferation, but little is known about the signaling pathways involved. We investigated the role of the ERK (p42/44 mitogen activated protein [MAP] kinase) and phosphatidylinositol 3-OH kinase (PI3 kinase) pathways on alveolar type II cell proliferation and differentiation. Rat type II cells were cultured on tissue culture plastic and Matrigel in the presence or absence of KGF and specific chemical inhibitors PD98059, LY294002, and rapamycin at various concentrations. Proliferation was measured by thymidine incorporation and DNA quantitation, and differentiation was measured by expression of surfactant protein A and alkaline phosphatase. We demonstrate that KGF activates distal effectors of the PI3 kinase pathway, PKB/Akt, and p70S6 kinase, as well as p42/44 MAP kinase proteins. Inhibition of these pathways with PD98059, LY294002, or rapamycin inhibited type II cell proliferation but had no significant effect on differentiation. KGF did not activate the c-Jun kinase or p38 MAP kinase pathways. We conclude that the p42/44 MAP kinase and PI3 kinase pathways are important in regulating alveolar type II cell proliferation in response to KGF.