Over expression of the inflammatory cytokines MMPs and

Over expression of the inflammatory cytokines, MMPs and COX-2 act as an important inducer of chronic inflammation. COX-2 catalyzes the biosynthesis of prostaglandins (PGs), and induced expression was observed in S63845 stimulated with pro-inflammatory cytokines or bacterial lipopolysaccharide (Khanapure et al., 2007, Suleyman et al., 2007). COX-2 is overexpressed in various cancer tissues and this has been linked to inflammation, inflammatory disorders and tumorigenesis (Gilroy et al., 2001, Mantovani et al., 2008). The present study also showed the COX-2 mRNA was expressed at low levels in control A549 cells, but transiently induced by PMA treatment. Whereas, the cells treated with 1μM concentration of dexamethasone significantly decreased the PMA induced expression of COX-2 mRNA level. Similar observation was made with RAW 264.7 cells and bone marrow-derived macrophages (BMMs) where dexamethasone inhibit the LPS induced mRNA expression of COX-2 gene (Joanny et al., 2012). In cancer cells like A549, HeLa, etc., there is always the presence of basal COX-2 expression. As dexamethasone is anti-inflammatory in nature, the addition of dexamethasone alone is marginally reducing the basal COX-2 expression observed in control cells. Many of the inflammatory genes are commonly over-expressed during chronic non-resolving inflammation. Intriguingly, recent data have shown that glucocorticoid administration for 1h following endotoxin (LPS) challenge is immunosuppressive, administration of the same glucocorticoid dose prior to LPS challenge augments immune responses (Frank et al., 2010). Glucocorticoids repress transcription of many genes encoding pro-inflammatory cytokines, chemokines, cell adhesion molecules and key enzymes involved in the initiation and/or maintenance of the host inflammatory response (Perretti and Ahluwalia, 2000, Smoak and Cidlowski, 2004). Glucocorticoids inhibit the expression of inflammatory mediators in macrophages and other cells and have used in the treatment of many immune-mediated inflammatory diseases (Newton, 2000). Our study show that the pretreatment of A549 cells with dexamethasone (0.1 or 1μM) significantly decreased the PMA or LPS induced mRNAs expression of pro-inflammatory cytokines ((IL-1β, IL-2, IL-6, IL-8 and TNF-α) in a dose dependent manner suggested the protective effects of synthetic glucocorticoid dexamethasone on LPS-induced inflammation. Our results correlate with the findings of Yamazaki et al. who reported that the glucocorticoids inhibit the synthesis of interleukin (IL)-1, TNF-α, IL-1β, IL-6, MMP-I, and COX-2 mRNAs expression in SW982 cells (Yamazaki et al., 2003). Human hosts activate multiple TFs such as AP-1 and NF-κB that mediate inflammation (Miller et al., 2000, Huang et al., 2008). Glucocorticoids play a key role in the suppression of inflammation by inhibiting the transcription of the cytokines through binding to the GR and the activated GR interacts with transcription factors, such as AP-1, NF-κB and CCAAT/enhancer-binding protein-β (De Bosscher et al., 2003). AP-1 complexes normally function as positive factors in regulating inflammation and the cell cycle. Yet, different combinations of AP-1 members express differential biological effects (Shaulian and Karin, 2002). AP-1 mediates the release of inflammatory mediators such as IL-8 (Yeo et al., 2004) and regulates angiogenesis caused by pathogen infection (Ye et al., 2007). AP-1 also interacts with other TFs to cope up with the pathogen development (Ravichandran et al., 2006) and modulates the expression of inflammatory mediators during infection with Group B Streptococcus (Vallejo et al., 2000) suggested that the biological functions of AP-1 are complex and depends on cell type (Adcock et al., 1994). The ability of GR to repress the activity of NF-κB and AP-1 as well as other key immune modulatory transcription factors has been a major focus of research into the mechanisms underlying the (Al-Harbi et al., 2016) anti-inflammatory effects of glucocorticoids. Studies reported that dexamethasone inhibits TNF-α induced MCP-1 production via suppression of AP-1 binding activity in human glomerular endothelial cells (Park et al., 2004). A number of mechanisms have been proposed for the anti-inflammatory actions of dexamethasone, including repression of inflammatory cytokine genes by inhibition of transcriptions factors, as well as induction of anti-inflammatory cytokines such as IL-10 (Goulding, 2004). Dexamethasone inhibits LPS-induced Acute Lung Injury through Inhibition of NF-κB, COX-2, and Pro-inflammatory Mediators in a mouse model (Al-Harbi et al., 2016). Previous studies showed the effect of dexamethasone on the expression of c-Jun and c-Fos in different regions of the neonatal brain. Dexamethasone-induced shift of the ratio of c-Jun to c-Fos transcript levels in the brainstem of neonatal rats towards a predominance of c-Jun may induce the expression of genes that contain AP-1 response elements in the promoters, since the glucocorticoid receptor can be involved in protein–protein interactions with the Jun/Jun homodimer of the AP-1 complex (Sukhareva et al., 2016). Hence in the present study, we reported the expression pattern of whole set of AP-1 factors (c-Jun, Jun-B, Jun-D and c-Fos, Fra-1 and, Fra-2) except Fos-B in PMA/LPS induced inflammation and also the effect of dexamethasone on it. A549 cells treated with PMA induced the expression of c-Jun, Jun-D, Jun-B, Fra-1, Fra-2 and c-Fos at different levels, whereas pretreatment of cells with dexamethasone significantly decreased the PMA induced mRNA levels of c-Jun and c-Fos in a dose dependent manner while, Jun-D, Jun-B and Fra-1 were marginally decreased. While in LPS induced inflammation dexamethasone significantly decreases the c-Jun and c-Fos AP-1 factor suggested that the anti-inflammatory activity of dexamethasone is through inhibition of AP-1 subunits c-Jun and c-Fos. Our result consistent with the findings of (Adcock et al., 1994) who reported that cytokines induced both c-Jun and c-Fos are reduced by dexamethasone in human lung tissue. Our findings suggest that c-Jun and c-Fos are the major AP-1 factors involved in inflammation and thus AP-1 may be the major transcription factor for the target of classic GR-mediated trans-repression. This may be an important molecular mechanism of steroid action in asthma and other chronic inflammatory diseases that need further investigation.