Inflammatory cells in lung disease associated with rheumatoid arthritis

Does a window of opportunity for rheumatoid arthritis-associated interstitial lung disease exist?

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammatory synovitis, eventually leading to joint destruction. Remarkable advancements in the emergence of molecular targeted therapies and the treatment strategy based on treat-to-target have made it possible for patients to lead their daily lives without disabilities. Specifically, early diagnosis and appropriate treatment without missing a 'window of opportunity' are crucial for improving joint outcomes. On the other hand, interstitial lung disease (ILD) is an extra-articular complication of RA and has an impact on life prognosis. Importantly, it has become evident that achieving remission of arthritis is critical not only for joint outcomes but also to prevent the irreversible progression of pulmonary fibrosis in RA-ILD. Therefore, a 'window of opportunity' may exist not only for joints but also for RA-ILD. However, within RA-ILD, there are cases that progress from an NSIP pattern or airway involvement to a UIP pattern, while there are cases without progression, suggesting that their disease behavior may be diverse. Thus, accumulating evidence is necessary to accurately determine the disease behavior of RA-ILD. This review provides an overview of clinical and radiological features and treatment strategies for RA-ILD, incorporating the latest findings.

The Role of Bronchoalveolar Lavage in Systemic Sclerosis Interstitial Lung Disease: A Systematic Literature Review

The role of Bronchoalveolar Lavage (BAL) in the evaluation of systemic sclerosis (SSc) interstitial lung disease (ILD) is still controversial. The aim of this systematic literature review was to investigate the use of BAL in SSc-ILD, and to focus on the pros and cons of its real-life application. Methods: PubMed, Cochrane, and Embase were questioned from inception until 31 December 2021. Results: Eighteen papers were finally analyzed. A positive correlation was observed between lung function and BAL cytology; in particular, BAL neutrophilia/granulocytosis was related to lower diffusing capacity for carbon monoxide (DLCO) values and lower forced vital capacity (FVC). Moreover, a positive correlation between BAL cellularity and high-resolution computed tomography (HRCT) findings has been reported by several authors. Cytokines, chemokines, growth factors, coagulation factors, and eicosanoids have all been shown to be present, more often and in higher quantities in SSc-ILD patients than in the health control and, in some cases, they were related to more severe pulmonary disease. There was no consensus regarding the role of BAL cellularity as a predictor of mortality.

Acetylated Diacylglycerol 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol in Autoimmune Arthritis and Interstitial Lung Disease in SKG Mice

Acetylated diacylglycerol 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) is a lipid molecule from the antlers of sika deer that might reduce inflammation by effectively controlling neutrophil infiltration, endothelial permeability and inflammatory chemokine production. Therefore, we evaluated the modulatory effect of PLAG on arthritis and interstitial lung disease (ILD) in an autoimmune arthritis model. We injected curdlan into SKG mice and PLAG was orally administered every day from 3 weeks to 20 weeks after the curdlan injection. The arthritis score was measured every week after the curdlan injection. At 20 weeks post-injection, the lung specimens were evaluated with H&E, Masson's trichrome and multiplexed immunofluorescent staining. Serum cytokines were also analyzed using a Luminex multiple cytokine assay. PLAG administration decreased the arthritis score until 8 weeks after the curdlan injection. However, the effect was not sustained thereafter. A lung histology revealed severe inflammation and fibrosis in the curdlan-induced SKG mice, which was attenuated in the PLAG-treated mice. Furthermore, immunofluorescent staining of the lung tissue showed a GM-CSF+ neutrophil accumulation and a decreased citrullinated histone 3 expression after PLAG treatment. PLAG also downregulated the levels of IL-6 and TNF-α and upregulated the level of sIL-7Rα, an anti-fibrotic molecule. Our results indicate that PLAG might have a preventative effect on ILD development through the resolution of NETosis in the lung.

Possible association of idiopathic pulmonary hemosiderosis with rheumatoid arthritis: A case report

Idiopathic pulmonary hemosiderosis (IPH) is a rare interstitial lung disease, usually occurring in children or young adults. Although several studies reported on the coexistence of IPH and immune system diseases, the association between these conditions has not been well described. The present study reports on the case of a 21-year-old female patient who presented with bilateral lung abnormalities. The patient was admitted due to a 2-year history of progressive exertional dyspnea, as well as arthralgia and joint swelling in the recent 2 months. During the past 15 years, the patient had been diagnosed with anemia and received repeated blood transfusions. Serial chest CT scans indicated an interstitial pattern. On physical examination, the patient had pale skin with a hemoglobin level of 65 g/l and exhibited finger-clubbing. Arterial blood gas analysis revealed hypoxia. Anticyclic-citrullinated protein antibody and rheumatoid factor were highly positive. Pulmonary function tests revealed restrictive ventilation dysfunction and decreased diffusion capacity. Bronchoscopy and biopsy confirmed diffuse alveolar hemorrhage. Following assessment of the etiology, the diagnosis of IPH was made by exclusion. The patient's symptoms and laboratory findings combined also confirmed the diagnosis of rheumatoid arthritis (RA). After receiving corticosteroid treatment, the patient's condition improved, and she was discharged and followed up. Based on this patient and a review of the literature, the present study demonstrated for the first time that IPH may mediate the development of an RA pathology. Therefore, early diagnosis is important for the timely management of IPH, which may also delay or even prevent the development of immune system diseases, e.g. RA, in patients with IPH. Further attention should be paid to determine the association between IPH and immune system diseases in the clinical setting.

Association between nonspecific interstitial pneumonia and presence of CD20+ B lymphocytes within pulmonary lymphoid follicles

Nonspecific interstitial pneumonia (NSIP) is characterised by interstitial infiltration of lymphocytes and varying amounts of interstitial fibrosis. B cells have been suggested to contribute to the pathogenesis of NSIP. However, the relationship between B-lymphocyte and the clinical outcomes of NSIP was unclear. In this study, 50 patients with histopathologically confirmed NSIP from Peking Union Medical College Hospital between April 2003 to December 2012 were retrospectively analyzed. Using immunohistochemical analyses, CD20+ B cells were counted in the lymphoid follicles, perivascular, interstitial, and peribronchiolar regions of lung tissure. The CD20+ lymphocytes were mainly present in the lymphoid follicles. The number of follicular CD20+ lymphocytes was higher in the fibrosing than cellular NSIP pattern [255.08 (132.92-449.71) vs. 121.33 (63.54-282.88)/0.1 mm², p = 0.017]. After 1 year of therapy, the follicular CD20+ lymphocytes were significantly higher in patients whose forced vital capacity (FVC) worsened as compared to those who improved (p = 0.014). Additionally, follicular CD20+ lymphocytes were negatively correlated with the post-treatment percentage change in FVC (rho = -0.397, p = 0.004). However, follicular CD20+ lymphocytes were not correlated with survival. These results suggested that pulmonary follicular CD20+ lymphocytes were correlated with the fibrosing pattern of NSIP and predicted less clinical improvement after treatment.

GM-CSF but not IL-17 is critical for the development of severe interstitial lung disease in SKG mice

Interstitial lung disease (ILD) is a common complication and sometimes a prognostic factor of connective tissue diseases (CTDs) in humans. However, suitable animal model of severe CTD-associated ILD (CTD-ILD) has been limited. In this study, we showed that zymosan-treated SKG mice developed not only arthritis but also chronic-progressive ILD with high mortality over several months. The pathological and clinical features of ILD in zymosan-treated SKG mice were similar to that of human severe CTD-ILD. ILD in this mouse was characterized by massive infiltration of Th17 cells, GM-CSF-producing CD4(+) T cells, and CD11b(+) Gr1(+) neutrophils with fibrosis. Naive SKG T cells were skewed to differentiate into GM-CSF-producing cells, and GM-CSF secreted by T cells enhanced IL-6 and IL-1β production by macrophages, which in turn enhanced differentiation of IL-17A- and/or GM-CSF-producing T cells and infiltration of neutrophils into lung. Neutralization of GM-CSF completely blocked the development of this ILD, and the blocking of IL-6 signaling resulted in partial prevention of it, whereas neutralization of IL-17A did not. In contrast, the progression of arthritis was inhibited by the neutralization of GM-CSF and slightly by the neutralization of IL-17A, but not by the blocking of IL-6 signaling. These data suggested zymosan-treated SKG mice could be a useful mouse model of severe CTD-ILD, and GM-CSF, rather than IL-17A or IL-6, contributed to the development of ILD in zymosan-treated SKG mice, indicating that neutralization of GM-CSF would be a useful therapeutic strategy for severe CTD-ILD.

The multifaceted aspects of interstitial lung disease in rheumatoid arthritis

Interstitial lung disease (ILD) is a relevant extra-articular manifestation of rheumatoid arthritis (RA) that may occur either in early stages or as a complication of long-standing disease. RA related ILD (RA-ILD) significantly influences the quoad vitam prognosis of these patients. Several histopathological patterns of RA-ILD have been described: usual interstitial pneumonia (UIP) is the most frequent one, followed by nonspecific interstitial pneumonia (NSIP); other patterns are less commonly observed. Several factors have been associated with an increased risk of developing RA-ILD. The genetic background plays a fundamental but not sufficient role; smoking is an independent predictor of ILD, and a correlation with the presence of rheumatoid factor and anti-cyclic citrullinated peptide antibodies has also been reported. Moreover, both exnovo occurrence and progression of ILD have been related to drug therapies that are commonly prescribed in RA, such as methotrexate, leflunomide, anti-TNF alpha agents, and rituximab. A greater understanding of the disease process is necessary in order to improve the therapeutic approach to ILD and RA itself and to reduce the burden of this severe extra-articular manifestation.

Interstitial lung disease in the connective tissue diseases

The connective tissue diseases (CTDs) are inflammatory, immune-mediated disorders in which interstitial lung disease (ILD) is common and clinically important. Interstitial lung disease may be the first manifestation of a CTD in a previously healthy patient. CTD-associated ILD frequently presents with the gradual onset of cough and dyspnea, although rarely may present with fulminant respiratory failure. Infection and drug reaction should always be ruled out. A diagnosis of idiopathic ILD should never be made without a careful search for subtle evidence of underlying CTD. Treatment of CTD-ILD typically includes corticosteroids and immunosuppressive agents.

A novel model of rheumatoid arthritis-associated interstitial lung disease in SKG mice

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is associated with increased mortality in up to 10% of patients with rheumatoid arthritis. Lung exposure to cigarette smoke has been implicated in disease development. Little is known about the mechanisms underlying the development of RA-ILD, in part due to the lack of an appropriate mouse model. The objectives of this study were (i) to test the suitability of SKG mice as a model of cellular and fibrotic interstitial pneumonia in the setting of autoimmune arthritis, and (ii) to determine the role of lung injury in the development of arthritis in SKG mice. Lung tissues were evaluated in arthritic SKG mice by quantifying cell accumulation in bronchoalveolar lavage, static compliance, collagen levels, and infiltrating cell phenotypes by flow cytometry and histology. Lung injury was induced by exposure to cigarette smoke or bleomycin. Arthritic SKG mice developed a patchy cellular and fibrotic interstitial pneumonia associated with reduced static compliance, increased collagen levels, and accumulation of inflammatory cells. Infiltrating cells comprised CD4+ T cells, B cells, macrophages, and neutrophils. Chronic exposure to cigarette smoke or initiation of lung injury with bleomycin did not cause arthritis. The pattern of lung disease suggests that arthritic SKG mice represent an authentic model of nonspecific interstitial pneumonia in RA-ILD patients. The lack of arthritis development after cigarette smoke or lung injury suggests that a model where breaches in immunologic tolerance are induced by lung inflammation and injury alone may be overly simplistic.

Pulmonary manifestations of rheumatoid arthritis

Pulmonary disease is a major source of morbidity and mortality in rheumatoid arthritis, manifesting most commonly as interstitial lung disease, airways disease, rheumatoid nodules, and pleural effusions. The diagnostic assessment of respiratory abnormalities is complicated by underlying risk for infection, the use of drugs with known pulmonary toxicity, and the frequency of lung disease related to rheumatoid arthritis itself. Evaluation and management of rheumatoid arthritis-associated pulmonary disease frequently necessitates a multidisciplinary approach.