Effects of AntagomiRs on Different Lung Diseases in Human, Cellular, and Animal Models

Murdaca, Giuseppe; Tonacci, Alessandro; Negrini, Simone; Greco, Monica; Borro, Matteo; Puppo, Francesco; Gangemi, Sebastiano

Overall, a simple explanation of the mechanisms involving antagomiR-21 in lung conditions is provided in Figure 2 . Another miRNA molecule, which is widely expressed in several lung conditions, is miR-155. Several studies demonstrated that this molecule is upregulated in activated immune cells, such as T and B lymphocytes, macrophages, and dendritic cells (DCs). Indeed, miR-155 levels increase in response to inflammatory mediators. Moreover, miRNA-155 can regulate B-cell proliferation, malignancy, antibody production, and the differentiation and function of IL-17-producing helper T cells. Furthermore, miR-155 is induced by LPS, as well as other TLR ligands and proinflammatory Another miRNA molecule, which is widely expressed in several lung conditions, is miR-155. Several studies demonstrated that this molecule is upregulated in activated immune cells, such as T and B lymphocytes, macrophages, and dendritic cells (DCs). Indeed, miR-155 levels increase in response to inflammatory mediators. Moreover, miRNA-155 can regulate B-cell proliferation, malignancy, antibody production, and the differentiation and function of IL-17-producing helper T cells. Furthermore, miR-155 is induced by LPS, as well as other TLR ligands and proinflammatory cytokines [99] [100] [101] . As miR-155 is involved in several processes, it is feasible to understand its role upon many lung disorders. Basing on the hypothesis that miR-155 upregulation could inhibit IL-17 expression and therefore increase susceptibility to secondary bacterial pneumonia, Podsiad et [31] al. conducted a study on wild-type C57BL/6 mice and human lung macrophages in order to investigate the role of miR-155 and the respective antagoMiR upon viral and bacterial pneumonia. They concluded that miR-155 antagomiR ameliorated lung bacterial clearance compared with controls. MiR-155 plays a crucial role also upon ARDS. Triggering receptors expressed on myeloid cells (TREM) proteins are a family of immunoglobulin cell surface receptors expressed on myeloid cells and they are considered as amplifiers of Toll-like receptor (TLR)-induced inflammation. Experiments with antagomiR-155 confirmed that TREM-1-mediated changes were dependent on miR-155. Yuan et al. [32] conducted a study on wild-type C57BL/6J mice and bone marrow-derived macrophages demonstrating that TREM-1 boosted inflammatory response by inducing the expression of miR-155 in macrophages. Therefore, researchers inhibited TREM-1 using a nanomicellar strategy. Neutrophilic inflammation was reduced, thus suggesting that TREM-1 inhibition is a potential therapeutic target for neutrophilic lung inflammation and ARDS. Systemic lupus erythematosus (SLE) is a complex auto-immune disease which can involve several systems, including lungs. Diffuse alveolar hemorrhage (DAH) is a rare but severe complication of SLE and miR-155 showed to have a relevant role. In fact, Zhou et al. [86] found that miR-155 expression was up-regulated during the development of DAH, noticing that this molecule targets several pro-inflammatory mediators. The extent of lung inflammation was markedly reduced in miR-155-knockout (miR-1552/2) mice. Moreover, in vivo silencing of miR-155 using miR-155 antagomiR reduced the incidence of iatrogenic-induced DAH. MiR-155 cooperates with Th2 responses too. In fact, it is extensively expressed in the Th cell, DCs, and macrophages in the lung. MiR-155 was also found to be up-regulated in the nasal mucosa and airway smooth muscle cells of