Heightened endoplasmic reticulum stress in the lungs of patients with chronic obstructive pulmonary disease: the role of Nrf2-regulated proteasomal activity.

TitleHeightened endoplasmic reticulum stress in the lungs of patients with chronic obstructive pulmonary disease: the role of Nrf2-regulated proteasomal activity.
Publication TypeJournal Article
Year of Publication2009
AuthorsMalhotra D, Thimmulappa R, Vij N, Navas-Acien A, Sussan T, Merali S, Zhang L, Kelsen SG, Myers A, Wise R, Tuder R, Biswal S
JournalAm J Respir Crit Care Med
Volume180
Issue12
Pagination1196-207
Date Published2009 Dec 15
ISSN1535-4970
KeywordsAged, Animals, Apoptosis, Biomarkers, Blotting, Western, Disease Models, Animal, Endoplasmic Reticulum, Female, Fluorescent Antibody Technique, Humans, Lung, Male, Mice, Mice, Inbred C57BL, Middle Aged, NF-E2-Related Factor 2, Oxidative Stress, Proteasome Endopeptidase Complex, Pulmonary Disease, Chronic Obstructive, Reverse Transcriptase Polymerase Chain Reaction, Smoking
Abstract

RATIONALE: Nuclear factor erythroid 2-related factor 2 (Nrf2), an important regulator of lung antioxidant defenses, declines in chronic obstructive pulmonary disease (COPD). However, Nrf2 also regulates the proteasome system that degrades damaged and misfolded proteins. Because accumulation of misfolded proteins in the endoplasmic reticulum (ER) causes ER stress and ER stress-induced apoptosis, Nrf2 may potentially prevent ER stress-mediated apoptosis in COPD.

OBJECTIVES: To determine whether Nrf2-regulated proteasome function affects ER stress-mediated apoptosis in COPD.

METHODS: We assessed the expression of Nrf2, Nrf2-dependent proteasomal subunits, proteasomal activity, markers of ER stress, and apoptosis in emphysematous lungs of mice exposed to cigarette smoke (CS) as well as peripheral lung tissues from normal control subjects and patients with COPD.

MEASUREMENTS AND MAIN RESULTS: Compared with wild-type mice, emphysematous lungs of CS-exposed Nrf2-deficient mice exhibited markedly lower proteasomal activity and elevated markers of ER stress and apoptosis. Furthermore, compared with normal control subjects, lungs of patients with mild and advanced COPD showed a marked decrease in the expression of Nrf2-regulated proteasomal subunits and total proteasomal activity. However, they were associated with greater levels of ER stress and apoptosis markers. In vitro studies have demonstrated that enhancing proteasomal activity in Beas2B cells either by sulforaphane, an activator of Nrf2, or overexpression of Nrf2-regulated proteasomal subunit PSMB6, significantly inhibited cigarette smoke condensate (CSC)-induced ER stress and cell death.

CONCLUSIONS: Impaired Nrf2 signaling causes significant decline in proteasomal activity and heightens ER stress response in lungs of patients with COPD and CS-exposed mice. Accordingly, pharmacological approaches that augment Nrf2 activity may protect against COPD progression by both up-regulating antioxidant defenses and relieving ER stress.

DOI10.1164/rccm.200903-0324OC
Alternate JournalAm. J. Respir. Crit. Care Med.
PubMed ID19797762
PubMed Central IDPMC2796732
Grant ListCTSA UL RR 025005 / RR / NCRR NIH HHS / United States
P30ES003819 / ES / NIEHS NIH HHS / United States
P50ES015903 / ES / NIEHS NIH HHS / United States
P50HL084945 / HL / NHLBI NIH HHS / United States
R01HL081205 / HL / NHLBI NIH HHS / United States
R03 HL096931 / HL / NHLBI NIH HHS / United States
R03 HL096931-01 / HL / NHLBI NIH HHS / United States
R03 HL096931-02 / HL / NHLBI NIH HHS / United States
RHL096931 / / PHS HHS / United States