Elderly-onset hereditary pulmonary alveolar proteinosis and its cytokine profile
© The Author(s). 2017
Received: 20 September 2016
Accepted: 7 February 2017
Published: 17 February 2017
Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by surfactant accumulation, and is caused by disruption of granulocyte/macrophage colony-stimulating factor (GM-CSF) signaling. Abnormalities in CSF2 receptor alpha (CSF2RA) were reported to cause pediatric hereditary PAP. We report here the first case of CSF2RA-mutated, elderly-onset hereditary (h) PAP.
The patient developed dyspnea on exertion, and was diagnosed with PAP at the age of 77 years, based on findings from chest computed tomography scan and bronchoalveolar lavage. She tested negative for GM-CSF autoantibodies, with no underlying disease. Her serum GM-CSF level was elevated (91.3 pg/mL), indicating GM-CSF signaling impairment and genetic defects in the GM-CSF receptor. GM-CSF-stimulated phosphorylation in signal transducer and activator of transcription 5 (STAT5) was not observed, and GM-CSF-Rα expression was defective in her blood cells. Genetic screening revealed a homozygous, single-base C > T mutation at nt 508—a nonsense mutation that yields a stop codon (Q170X)—in exon 7 of CSF2RA. High-resolution analysis of single nucleotide polymorphism array confirmed a 22.8-Mb loss of heterozygosity region in Xp22.33p22.11, encompassing the CSF2RA gene. She was successfully treated with whole lung lavage (WLL), which reduced the serum levels of interleukin (IL)-2, IL-5, and IL-17, although IL-3 and M-CSF levels remained high.
This is the first known report of elderly-onset hPAP associated with a CSF2RA mutation, which caused defective GM-CSF-Rα expression and impaired signaling. The analyses of serum cytokine levels during WLL suggested that GM-CSF signaling might be compensated by other signaling pathways, leading to elderly-onset PAP.
KeywordsHereditary pulmonary alveolar proteinosis GM-CSF GM-CSF receptor Elderly onset Cytokine profile
The lungs reduce alveolar surface tension by producing pulmonary surfactants, which are essential for maintaining smooth breathing. The levels of pulmonary surfactants are balanced between their production by alveolar epithelial cells and clearance by alveolar macrophages. Granulocyte/macrophage colony-stimulating factor (GM-CSF), a 23-kDa monomeric glycoprotein, regulates various functions of the alveolar macrophages, including surfactant catabolism, and plays an important role in pulmonary surfactant homeostasis.
Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by the accumulation of surfactant proteins, which causes progressive respiratory insufficiency [1–3]. Three clinically and etiologically distinct forms of PAP are acknowledged: autoimmune, secondary, and congenital. More than 90% of PAP cases are autoimmune type (aPAP). aPAP is specifically associated with high levels of a neutralizing autoantibody against GM-CSF that impairs GM-CSF-dependent surfactant clearance mediated by alveolar macrophages [4–8].
The GM-CSF signal is conveyed through the GM-CSF receptor on cell surfaces, via signal transducer and activator of transcription 5 (STAT5). The GM-CSF receptor is a dodecameric complex consisting of a ligand-specific alpha (GM-CSF-Rα, CD161) and a beta (GM-CSF-Rβ, CD131) subunit, which is shared with the interleukin (IL)-3 and IL-5 receptors [9, 10].
Recently, it has been reported that abnormalities in the GM-CSF-Rα-encoding alleles (CSF2RA) cause hereditary (h) PAP, presenting as insidious, progressive dyspnea in children; and that increased serum GM-CSF is useful to identify such individuals [11–15]. However, no elderly-onset case with defect in the GM-CSF receptor was reported until date. In the present report, we describe the oldest case of hPAP until date, whose symptoms occurred at the age of 77. The patient suffered severe hypoxemia, underwent a single whole lung lavage (WLL), and showed dramatic improvement.
Measurement of GM-CSF autoantibody levels
The concentration of GM-CSF autoantibodies in the bronchoalveolar lavage fluid (BALF) or serum were measured by sandwich enzyme-linked immunosorbent assay (ELISA), performed as described previously [16, 17], with slight modifications. In brief, 96-well microtiter plates (Maxisorp, Nalge Nunc International, Rochester, NY, U.S.A.) were coated with recombinant human (rh) GM-CSF [1 μg/mL in phosphate-buffered saline (PBS)] at 4 °C overnight, washed with PBS (containing 0.1% Tween 20), and blocked with Stabilcoat (Surmodics, Eden Prairie, MN, U.S.A.) at room temperature for 1 h. The BALF sample was diluted to 1/100 (for patients with PAP) in sample dilution buffer [PBS, 1% (w/v) goat serum, 0.1% (v/v) Tween 20], and 50 μL of the diluted sample was incubated in triplicate wells at room temperature for 40 min. The plates were washed and after addition of ammonium acetate (10 mM, pH 5.0), incubated at room temperature for 15 min to prevent non-specific binding. Next, horseradish peroxidase-conjugated goat anti-human IgG (diluted to 1/3000 with sample dilution buffer) was added, and the plates incubated at room temperature for 30 min. Bound IgG was detected using 3,3,5,5-tetramethylbenzidine substrate solution (50 μL; Bethyl Laboratories, Montgomery, TX, U.S.A.), followed by addition of 1 N H2SO4. The absorbance was read at 450 nm using a microplate reader (Bio-rad, Hercules, CA, U.S.A.).
Peripheral blood mononuclear cells (PBMCs) were cultured on 24-well culture plates at 5 × 105 cells/well. The cells were incubated with GM-CSF (0–1000 ng/mL) for 15 min. Lysed protein extracts were separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis, transferred to a polyvinylidene fluoride membrane, and assessed by standard western blotting procedures, as previously described . Primary antibodies used for detection included anti-human GM-CSF-Rα (Santa Cruz Biotechnology, Santa Cruz, CA, U.S.A.), GM-CSF-Rβc, anti-human STAT5 (Santa Cruz Biotechnology) and phospho (p)-STAT5 (Millipore, Billerica, MA, U.S.A.) antibodies. Peroxidase-labeled anti-rabbit IgG antibody (Sigma-Aldrich, St. Louis, MO, U.S.A.) was used as secondary antibody and the bands were visualized with ECL plus (GE Healthcare, Waukesha, WI, U.S.A.). To enhance the signal, immunoreaction enhancer solution (Can Get Signal, TOYOBO, Osaka, Japan) was used according to the manufacturer’s instructions. Actin was measured as loading control for each sample, using anti-actin antibody (Santa Cruz Biotechnology).
Phosphorylated STAT5 detection by flow cytometry was described previously . Heparinized fresh whole blood was incubated with 50 ng/mL rhGM-CSF and IL-2 for 20 min at 37 °C and fixed. Next, red blood cells were lysed in Fix/Lyse buffer (BD Bioscience, Franklin Lakes, NJ, U.S.A.) for 15 min at 37 °C. White blood cells were collected by centrifugation and fixed in ice-cold methanol at −20 °C for 1 h. After centrifugation, the cells were suspended in 3% fetal bovine serum/0.01% NaN3/PBS solution and incubated with Alexa Fluor 647-labeled anti-pSTAT5 (BD Bioscience). Cells with phosphorylated STAT5 were detected by flow cytometry (Cell Analyzer, Sony, Tokyo, Japan).
Reverse transcription polymerase chain reaction (RT-PCR)
Total RNA was extracted from blood mononuclear cells, using RNA Easy Plus Mini Kit (QIAGEN, Hilden, Germany), and was reverse transcribed with random hexamer primers and the SuperScript III First-Stand Synthesis System for RT-PCR (Invitrogen, Carlsbad, CA, U.S.A.). The cDNAs were subjected to semiquantitative RT-PCR analysis with PrimerSTAR GXL DNA polymerase (Takara Bio, Otsu, Japan) with CSF2RA-specific primers (Additional file 1: Table S1).
The PCR was performed to generate products spanning exons and flanking sequences of the CSF2RA gene, which were purified using the QIAquick DNA extraction kit (QIAGEN) and subjected to nucleotide sequencing using the BigDye Terminator v3.1 cycle sequencing kit (Applied Biosystems, Foster City, CA, U.S.A.) and CSF2RA-specific primers (Supplementary Table). The resulting sequences were compared with published sequences for CSF2RA (GenBank/EMBL/DDBJ under accession number NM_006140).
Array-comparative genomic hybridization (aCGH)
aCGH analysis was performed using the CytoScan HD array kit according to the manufacturer’s protocol (Affymetrix, Santa Clara, CA, U.S.A.). Genetic counseling was performed for the patient before and after genetic analyses.
IL-2, IL-3, IL-4, IL-5, IL-17, and M-CSF were analyzed using ELISA kits (CUSABIO, Wuhan, Hubei Province, P.R. China) according to the manufacturer’s protocol.
A previously healthy, 77-year-old, non-smoking woman, with normal chest radiograph at a medical check-up three years earlier, was referred to our hospital for dyspnea on exertion, which occurred one month earlier. She was a homemaker with no remarkable family history.
The patient was diagnosed with PAP, based on typical findings from chest CT scan and bronchoalveolar lavage. She had no underlying disease. GM-CSF autoantibodies were not detected in either the serum or the BALF. On the other hand, a high level of serum GM-CSF was detected (91.3 pg/mL), indicating disrupted GM-CSF signaling and genetic defects in the GM-CSF receptor. We decided to screen for GM-CSF signaling abnormalities because GM-CSF concentration was extremely high in her BALF.
Further evaluation by aCGH demonstrated a 22.8-Mb region of loss of heterozygosity (LOH) in Xp22.33p22.11, encompassing the CSF2RA gene.
Clinical characteristics of reported cases of hereditary pulmonary alveolar proteinosis
Tanaka et al.
Junne et al.
Juvenile (n = 20)
Age at symptom onset (yr)
GM-CSF antibody (μg/mL)
To investigate the background of the late-onset hPAP in this case, we studied her serum profile for various cytokines. The patient was treated with WLL, which greatly improved oxygenation indices and reduced the serum levels of various cytokines including IL-2, IL-5, and IL-17, indicating relieved inflammatory activation of Th1 and Th17 lymphocytes. In contrast, the serum levels of IL-3 and M-CSF remained high after WLL, indicating that they might be needed even after the treatment procedure. The high activities of IL-3 and M-CSF in the patient might be associated with the clinical course of her late-onset hPAP.
It is notable that GM-CSF, IL-3, IL-4, and IL-5 are coded by neighbor genes located at 5q31.1, and affect the functions of monocytes and macrophages. The serum levels of IL-4, IL-5, and GM-CSF decreased after WLL, while IL-3 levels remained high. Receptors of IL-3 and IL-5 share beta chains with that of GM-CSF. Disruption of the alpha chain of the GM-CSF receptor might affect stoichiometry of the common beta chains, presumably causing substantial alterations in IL-3 and IL-5 signaling. Interestingly, WLL differentially affected the levels of these cytokines in the serum of the patient in this study.
Similar to previous pediatric hPAP cases, the present case also demonstrated a high level of serum GM-CSF and a good response to WLL (Table 1). The increased serum GM-CSF levels might be useful for identifying patients with childhood as well as adult hPAP [19, 20]. The present case showed remarkable response to WLL with regard to oxygenation indices and serum levels of various cytokines that might be associated with compensation of GM-CSF signaling.
This is the first known report of elderly-onset hPAP associated with a genetic defect in CSF2RA, which caused defective GM-CSF-Rα expression and impaired signaling. These results suggest that GM-CSF signaling is compensated by other signaling pathways, leading to elderly-onset or non-symptomatic PAP.
Colony stimulating factor 2 receptor alpha chain
Enzyme-linked immunosorbent assay
Granulocyte/macrophage–colony stimulating factor
Hereditary PAP PAP, pulmonary alveolar proteinosis
The authors thank the investigators and patients who participated in this study; Yuko Ito for measurement of GM-CSF autoantibody levels; and Marie Mori for help with data analysis.
This work was supported in part by grants from the Japanese Ministry of Education, Science and Culture, Ministry of Health, Labor, and Welfare of Japan (H21-Nanchi-Ippan--161, to KN, and H24-Rinkensui-Ippan-003 to RT), Grant-in-Aid for Scientific Research (Category B 15H04829 to KN, Category C 22590852 to RT), and Japan Agency for Medical Research and Development (16ek0109063h0003 to KN, RT).
Availability of data and materials
The nucleotide sequences from the PCR amplicons for each coding exon of CSF2RA from the patient PBMCs, including a homozygous single-base mutation of c.581C > T (p.Q170X), has been registered (GenBank/EMBL/DDBJ accession number LC172167)
Conception and design: MI, KaN, KH, MK, KoN, RT; Analysis and interpretation: MI, KaN, KH, KoN, RT; Drafting and reviewing the manuscript for intellectual content: MI, KaN, MK, KoN, RT; Genetic consideration: KaN, HO, JT, KH, RT; Patient observation and acquisition of data: KN, HO, KA, YU, AH, AS, TT, MN, KH, MK. All authors read and approved the final manuscript.
Authors have no competing interest to declare regarding this study.
Consent for publication
Written informed consent was obtained from the patient’s son for publication of this case report, as the patient recently died of gastric cancer.
Ethics approval and consent to participate
This study was approved by the institutional review boards of Saitama Medical University and Niigata University. Written informed consent to participate in this study was obtained from the patient.
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