Nitrated Fatty Acids Reverse Cigarette Smoke-Induced Alveolar Macrophage Activation and Inhibit Protease Activity via Electrophilic S-Alkylation.
Nitrated fatty acids (NFAs), endogenous products of nonenzymatic reactions of NO-derived reactive nitrogen species with unsaturated fatty acids, exhibit substantial anti-inflammatory activities. They are both reversible electrophiles and peroxisome proliferator-activated receptor γ (PPARγ) agonists, but the physiological implications of their electrophilic activity are poorly understood. We tested their effects on inflammatory and emphysema-related biomarkers in alveolar macrophages (AMs) of smoke-exposed mice. NFA (10-nitro-oleic acid or 12-nitrolinoleic acid) treatment downregulated expression and activity of the inflammatory transcription factor NF-κB while upregulating those of PPARγ. It also downregulated production of inflammatory cytokines and chemokines and of the protease cathepsin S (Cat S), a key mediator of emphysematous septal destruction. Cat S downregulation was accompanied by decreased AM elastolytic activity, a major mechanism of septal destruction. NFAs downregulated both Cat S expression and activity in AMs of wild-type mice, but only inhibited its activity in AMs of PPARγ knockout mice, pointing to a PPARγ-independent mechanism of enzyme inhibition. We hypothesized that this mechanism was electrophilic S-alkylation of target Cat S cysteines, and found that NFAs bind directly to Cat S following treatment of intact AMs and, as suggested by in silico modeling and calculation of relevant parameters, elicit S-alkylation of Cys25 when incubated with purified Cat S. These results demonstrate that NFAs' electrophilic activity, in addition to their role as PPARγ agonists, underlies their protective effects in chronic obstructive pulmonary disease (COPD) and support their therapeutic potential in this disease.
Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, United States of America.|Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, 15240, United States of America.
Aravind T
AT
Reddy
Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, United States of America.|Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, 15240, United States of America.
Sowmya P
SP
Lakshmi
Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, United States of America.|Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, 15240, United States of America.
Ramamohan R
RR
Muchumarri
Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, United States of America.|Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, 15240, United States of America.
Raju C
RC
Reddy
D000478:Alkylation / Q000187:drug effects*; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D015415:Biomarkers / Q000378:metabolism; D002403:Cathepsins / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D005227:Fatty Acids / Q000502:physiology*; D007249:Inflammation / Q000378:metabolism; D008262:Macrophage Activation / Q000187:drug effects*; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism; D009566:Nitrates / Q000502:physiology; D009829:Oleic Acids / Q000494:pharmacology; D047495:PPAR gamma / Q000378:metabolism; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy / Q000378:metabolism; D011656:Pulmonary Emphysema / Q000188:drug therapy / Q000378:metabolism; D012906:Smoke / Q000009:adverse effects; D012907:Smoking / Q000009:adverse effects*; D014026:Nicotiana / Q000009:adverse effects; D015854:Up-Regulation / Q000187:drug effects
C521487:10-nitro-oleic acid; D000893:Anti-Inflammatory Agents; D015415:Biomarkers; D005227:Fatty Acids; D016328:NF-kappa B; D009566:Nitrates; D009829:Oleic Acids; D047495:PPAR gamma; D012906:Smoke; D002403:Cathepsins; C028217:cathepsin S