g., production of nitric oxide and reactive oxygen species), and immunological disease were most severely affected by dexamethasone (Fig. 3).
Dexamethasone and Pneumocystis infection were found to have opposite effects on certain genes. Of the 32 genes that were up-regulated by dexamethasone but down-regulated by Pneumocystis infection (Table 3), cadherin 17 (Cdh17) and glutathione-S-transferase alpha type2 (Gsta2) genes were most profoundly affected. Dexamethasone treatment increased Cdh17 expression by 7.15 fold, but Pneumocystis infection not only reversed this effect but also decreased its expression by 1.61 fold. Similarly, dexamethasone up-regulated Gsta2 by 4.77 fold, but Pneumocystis infection decreased it by 2.63 fold. Cadherin (calcium dependent adhesion molecule) plays a very important role in cell adhesion and assembly click here of the actin cytoskeleton [28]. Actin filaments are Selleckchem Androgen Receptor Antagonist linked to α-catenin and to the cell membrane through vinculin which is linked to E-cadherin [29]. The decrease in cadherin
expression during PCP may be a reason why AMs are defective in phagocytosis, as this function requires the actin cytoskeleton. Glutathione S-transferases (GSTs) link reduced glutathione via a sulfhydryl group to electrophilic centers on a variety Tubastatin A order of substrates [30]. This activity detoxifies compounds such as peroxidized lipids [31] that are generated during oxidative stress. The reduction in GST expression during PCP may explain the reduction in AM number as a decrease in GST expression would increase the concentration of toxic molecules such as reactive oxygen species [32] which can trigger
apoptosis of AMs [33]. Equally important are genes that were down-regulated by dexamethasone but up-regulated by Pneumocystis infection. Among these genes (Spp1, Irf1, Cxcr4, Crp, Il1rn, Irf8, RT1-Aw2, Ier3, and Ccnl1) (Table 5), the secreted phosphoprotein 1 (Spp1) gene has the most dramatic reversal by Pneumocystic Orotidine 5′-phosphate decarboxylase infection followed by interferon regulatory factor 1 (Irf1). The SPP1 protein is also known as bone sialoprotein, early T-lymphocyte activation (ETA-1), and most commonly osteopontin (Opn). Opn is one of the most abundantly expressed proteins in various lung diseases; it mediates diverse cellular functions such as adhesion, migration, and survival of several cell types including macrophages, T cells and dentritic cells [34, 35]. OPN also functions as a Th1 cytokine, promotes cell-mediated immune responses, and plays a role in chronic inflammatory and autoimmune diseases and activation of immune cells [34]. Opn can be cleaved by thrombin to expose the sequence SVVYGLR which is a ligand of integrin receptors α4β1, α9β1, and α9β4 that are present on monocytes, macrophages, neutrophils, T cells, and mast cells [36, 37].