title: Altered expression of nuclear and cytoplasmic histone H1 in pulmonary artery and pulmonary artery smooth muscle cells in patients with IPAH.
abstract: The pathogenesis of idiopathic pulmonary hypertension is poorly understood. This paper utilized histology-based Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI MS) to identify as-yet unknown proteins that may be associated with the structural changes in the pulmonary arterial walls of patients with IPAH. The technology identified significant increases in two fragments of histone H1 in the IPAH cases compared to controls. This finding was further examined using immunofluorescence techniques applied to sections from IPAH and control pulmonary arteries. In addition, cultured pulmonary artery smooth muscle cells (PASMCs) were utilized for Western analysis of histone H1 and importin β and importin 7, immunoprecipitation and assessment of nucleosomal repeat length (NRL). Immunofluorescence techniques revealed that nuclear expression of histone H1 was decreased and the chromatin was less compact in the IPAH cases than in the controls; furthermore, some cases showed a marked increase in cytoplasmic histone H1 expression. Using nuclear and cytoplasmic fractions of cultured PASMCs, we confirmed the reduction in histone H1 in the nucleus and an increase in the cytoplasm in IPAH cells compared to controls. Immunoprecipitation demonstrated a decreased association of histone H1 with importin β while importin 7 was unchanged in the IPAH cells compared to controls. The assessment of NRL revealed that the distance between nucleosomes was increased by ~20 bp in IPAH compared to controls. We conclude that at least two factors contribute to the reduction in nuclear histone H1-fragmentation of the protein and decreased import of histone H1 into the nucleus by importins. We further suggest that the decreased nuclear H1 contributes the less compact nucleosomal pattern in IPAH and this, in turn, contributes to the increase in NRL.
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennesse, USA.
authors.forename: Megha
authors.initials: M
authors.lastname: Talati
authors.forename: Erin
authors.initials: E
authors.lastname: Seeley
authors.forename: Kaori
authors.initials: K
authors.lastname: Ihida-Stansbury
authors.forename: Horace
authors.initials: H
authors.lastname: Delisser
authors.forename: Hayes
authors.initials: H
authors.lastname: McDonald
authors.forename: Fei
authors.initials: F
authors.lastname: Ye
authors.forename: Xueqiong
authors.initials: X
authors.lastname: Zhang
authors.forename: Yu
authors.initials: Y
authors.lastname: Shyr
authors.forename: Richard
authors.initials: R
authors.lastname: Caprioli
authors.forename: Barbara
authors.initials: B
authors.lastname: Meyrick
keywords: idiopathic pulmonary arterial hypertension; importins; linker histones; matrix-assisted laser desorption ionization mass spectrometry; nucleosomal repeat length