Monocyte activation drives preservation of membrane thiols by promoting release of oxidised membrane moieties via extracellular vesicles
Free Radical Biology and Medicine
Elsevier for Society for Free Radical Biology and Medicine
Reason for embargo
The redox state of cellular exofacial molecules is reflected by the amount of available thiols. Furthermore, surface thiols can be considered as indicators of immune cell activation. One group of thiol containing proteins, peroxiredoxins, in particular, have been associated with inflammation. In this study, we assessed surface thiols of the U937 and Thp1 monocyte cell lines and primary monocytes in vitro upon inflammatory stimulation by irreversibly labelling the cells with a fluorescent derivative of maleimide. We also investigated exofacial thiols on circulating blood mononuclear cells in patients with rheumatoid arthritis and healthy controls. When analysing extracellular vesicles, we combined thiol labelling with the use of antibodies to specific CD markers to exclude extracellular vesicle mimicking signals from thiol containing protein aggregates. Furthermore, differential detergent lysis was applied to confirm the vesicular nature of the detected extracellular events in blood plasma. We found an increase in exofacial thiols on monocytes upon in vitro stimulation by LPS or TNF, both in primary monocytes and monocytic cell lines (p<0.0005). At the same time, newly released extracellular vesicles showed a decrease in their exofacial thiols compared with those from unstimulated cells (p<0.05). We also found a significant elevation of surface thiols on circulating monocytes in rheumatoid arthritis patients (p<0.05) and newly released extracellular vesicles of isolated CD14(+) cells from rheumatoid arthritis patients had decreased thiol levels compared with healthy subjects (p<0.01). Exofacial peroxiredoxin 1 was demonstrated on the surface of primary and cultured monocytes, and the number of peroxiredoxin 1 positive extracellular vesicles was increased in rheumatoid arthritis blood plasma (p<0.05). Furthermore, an overoxidised form of peroxiredoxin was detected in extracellular vesicle-enriched preparations from blood plasma. Our data show that cell surface thiols play a protective role and reflect oxidative stress resistance state in activated immune cells. Furthermore, they support a role of extracellular vesicles in the redox regulation of human monocytes, possibly representing an antioxidant mechanism.
This work was supported by the National Scientific Research Program of Hungary (OTKA) grant no. PD 104369 to KSZT, grant no. PD 112085 to VVK and grant no. 111958 and 120237 to EIB, the MEDINPROT Program (Synergy programs I, III and IV), BMBS COST Action(BM1202), the János Bolyai Research Fellowship of the Hungarian Academy of Sciences (to KVV) and the Kerpel Fronius Program of the Semmelweis University (Astellas Pharma Grant to BSW).
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.
Vol. 108, pp. 56 - 65
Place of publication