Nitrated Fatty Acids Reverse Cigarette Smoke-Induced Alveolar Macrophage Activation and Inhibit Protease Activity via Electrophilic S-Alkylation
Authors: Raju C Reddy
Sowmya P Lakshmi
Ramamohan R Muchumarri
Aravind T Reddy
Journal: PLoS ONE (2016)
Discipline: Multidisciplinary
Keywords: Nitrated fatty acids; NFAs; anti-inflammatory activities; electrophiles; peroxisome proliferator-activated receptor Œ≥
Affiliations: 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.

Abstract:  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 Œ≥ (PPARŒ≥) 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-Œ∫B while upregulating those of PPARŒ≥. 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 PPARŒ≥ knockout mice, pointing to a PPARŒ≥-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 PPARŒ≥ agonists, underlies their protective effects in chronic obstructive pulmonary disease (COPD) and support their therapeutic potential in this disease. 

Retracted: No

PubPeer comments:
 I am questioning the MS data presented in Figure 6D (Table) for two reasons: The values presented in the table have the same last digit repeated (0 and 6), please see black blue and green rectangles. Many series of values are identical with respect to the last two digits, when comparing different treatment groups, please see blue, red and orange rectangles. I find this challenging from a statistical point of view.  , 
 #1 There might also be a problem with one of the figures, as mentioned by Schneider Leonid on his twitter https: twitter.com schneiderleonid status 1202582276095315968 , 
 #2 Apparently I am not clever enough to understand the meaning of that twitter post. (I.e., * You sure will agree this Fig 5 is not same gel, but presented as one, even with overlay. *) Can someone translate it into plain english and explain what exactly is the concern with that gel (in Fig 5)?? , 
 #2 Thanks. Figure 5 clearly is supposed to be same blot, probed twice, hence the overlay. But the bands do not overlay, those are two different blots.  ,