Dexamethasone inhibits inflammatory response via down regulation of AP-1 transcription factor in human lung epithelial cells.

The production of inflammatory mediators by epithelial cells in inflammatory lung diseases may represent an important target for the anti-inflammatory effects of glucocorticoids. Activator protein-1 is a major activator of inflammatory genes and has been proposed as a target for inhibition by glucocorticoids. We have used human pulmonary type-II A549 cells to examine the effect of dexamethasone on the phorbol ester (PMA)/Lipopolysaccharide (LPS) induced pro-inflammatory cytokines and AP-1 factors. A549 cells were treated with and without PMA or LPS or dexamethasone and the cell viability and nitric oxide production was measured by MTT assay and Griess reagent respectively. Expression of pro-inflammatory cytokines and AP-1 factors mRNA were measured using semi quantitative RT-PCR. The PMA/LPS treated cells show significant 2-3 fold increase in the mRNA levels of pro-inflammatory cytokines (IL-1ß, IL-2, IL-6, IL-8 and TNF-α), cyclo­oxygenase-2 (COX-2) and specific AP-1 factors (c-Jun, c-Fos and Jun-D). Whereas, pretreatment of cells with dexamethasone significantly inhibited the LPS induced nitric oxide production and PMA/LPS induced mRNAs expression of above pro-inflammatory cytokines, COX-2 and AP-1 factors. Cells treated with dexamethasone alone at both the concentrations inhibit the mRNAs expression of IL-1ß, IL-6 and TNF-α compared to control. Our study reveals that dexamethasone decreased the mRNAs expression of c-Jun and c-Fos available for AP-1 formation suggested that AP-1 is the probable key transcription factor involved in the anti-inflammatory activity of dexamethasone. This may be an important molecular mechanism of steroid action in asthma and other chronic inflammatory lung diseases which may be useful for treatment of lung inflammatory diseases.

Differential expression of AP-1 transcription factors in human prostate LNCaP and PC-3 cells: role of Fra-1 in transition to CRPC status.

Androgen receptor (AR) signaling axis plays a vital role in the development of prostate and critical in the progression of prostate cancer. Androgen withdrawal initially regresses tumors but eventually develops into aggressive castration-resistant prostate cancer (CRPC). Activator Protein-1 (AP-1) transcription factors are most likely to be associated with malignant transformation in prostate cancer. Hence, to determine the implication of AR and AP-1 in promoting the transition of prostate cancer to the androgen-independent state, we used AR-positive LNCaP and AR-negative PC-3 cells as an in vitro model system. The effect of dihydrotestosterone or anti-androgen bicalutamide on the cell proliferation and viability was assessed by MTT assay. Expression studies on AR, marker genes-PSA, TMPRSS2, and different AP-1 factors were analyzed by semi-quantitative RT-PCR and expressions of AR and Fra-1 proteins were analyzed by Western blotting. Dihydrotestosterone induced the cell proliferation in LNCaP with no effect on PC-3 cells. Bicalutamide decreased the viability of both LNCaP and PC-3 cells. Dihydrotestosterone induced the expression of AR, PSA, c-Jun, and Fra-1 in LNCaP cells, and it was c-Jun and c-Fos in case of PC-3 cells, while bicalutamide decreased their expression. In addition, constitutive activation and non-regulation of Fra-1 by bicalutamide in PC-3 cells suggested that Fra-1, probably a key component, involved in transition of aggressive androgen-independent PC-3 cells with poor prognosis.

Apigenin inhibits PMA-induced expression of pro-inflammatory cytokines and AP-1 factors in A549 cells.

Acute and chronic alveolar or bronchial inflammation is thought to be central to the pathogenesis of many respiratory disorders. Cytokines and granulocyte macrophage colony-stimulating factors (GM-CSF) play an important role in chronic inflammation. Activator protein-1 (AP-1) the superfamily of transcription factors is involved in proliferation, differentiation, apoptosis, and transformation including inflammation. Understanding the function and regulation of proinflammatory factors involved in inflammation may provide the novel therapeutic strategies in the treatment of inflammatory diseases. Our aim of the present study is to investigate the pro-inflammatory cytokines and pattern of AP-1 factors expressed during activation of lung adenocarcinoma A549 cells by Phorbol-12-myristate-13-acetate (PMA) and to understand the anti-inflammatory effect of apigenin. A549 cells were treated with and without PMA or apigenin, and the cell viability was assessed by MTT assay. Expressions of inflammatory mediators and different AP-1 factors were analyzed by semi-quantitative RT-PCR. IL-6 protein secreted was analyzed by ELISA, and expressions of IL-1ß, c-Jun, and c-Fos proteins were analyzed by Western blotting. Activation of A549 cells by PMA, induced the expression of pro-inflammatory cytokine (IL-1ß, IL-2, IL-6, IL-8, and TNF-α) mRNAs and secretion of IL-6 and the expression of specific AP-1 factors (c-Jun, c-Fos, and Fra-1). Treatment of cells with apigenin, significantly inhibited PMA-stimulated mRNA expression of above pro-inflammatory cytokines, AP-1 factors, cyclooxygenase-2, and secretion of IL-6 protein. Results suggested that the AP-1 factors may be involved in inflammation and apigenin has anti-inflammatory effect, which may be useful for therapeutic management of lung inflammatory diseases.