|M.Sc Student||Lerner-Indig Liron|
|Subject||Cigarette Smoke effect on Human Monocyte Inflammatory|
Response and Differentiation
|Department||Department of Medicine||Supervisors||Professor Shimon Pollack|
|Professor Abraham Reznick|
|Full Thesis text|
Cigarette smoke (CS) is associated with a variety of human pathologies. Its putative effect on human monocytes may play a role in some of these pathologies. CS contact with various human tissues, in particular human alveolar cells, is associated with nitric oxide (NO·) and other Reactive Oxygen Species exposure. The resulting oxidative stress may affect the regulation of Nuclear Factor-κB activation and the consequent development of different human pathologies.
The goal of our study was to analyze a possible regulatory effect of CS on inflammatory activity of human monocytes and a putative association with NFκB activation. As alveolar mature monocytes (macrophages) are implicated as important mediators of the inflammatory response in bronchial airways, we aimed to investigate also the effect of CS on differentiated monocytes and on the differentiation process.
To study the effect of CS on human monocytes we used a smoking exposure apparatus, developed in Prof. Reznick's lab. Human monocytic cell lines (U937 and THP1), both differentiated (THP1-MΦ) and naïve, and peripheral blood monocytes differentiated to Human Monocyte Derived Macrophages (HMDM) were exposed in different conditions to CS in our system. Secretion of cytokines to the culture medium was screened by cytokine array and quantitatively measured by ELISA. Signal transduction pathways in monocytic cells were analyzed by Western blotting.
Our main findings are that on the one hand, CS has a proinflammatory effect on human monocytes, whereas on the other hand it may impair their differentiation into mature macrophages. Exposure to CS was associated with rapid phosphorylation of Inhibitor-κB (IκBα) and increased secretion of some inflammatory chemokines, particularly Interleukin-8 (IL-8). Inhibition of NFκB activation in cultured monocytic cells resulted in a decrease in IL-8 secretion. These findings suggest that CS exposure of human monocytes is associated with NFκB activation. Exposure to CS was also associated with impairment of monocyte differentiation process, as judged by cellular morphology and CD14 expression. CS affected IL-8 secretion from immature monocytic cells but not from THP1-MΦ. CS exposure was also associated with tyrosine phosphorylation of p38 and Extracellular signal Regulated Kinase (ERK) in differentiated THP1-MΦ and HMDM.
In conclusion, we found that exposure to CS stimulates pro-inflammatory activity of human monocytes through the activation of NFκB pathway. It also interferes with monocyte differentiation. The interference with cellular differentiation together with the increase in pro-inflammatory activity may play a role in the carcinogenic effects of cigarette smoking.