Clinical studies: Steroid-sparing drugs which suppress inflammatory cytokines that are associated with the formation and maintenance of granulomas would be very useful therapeutics in management of sarcoidosis. In this regard, pentoxifylline (POF) has been reported to inhibit production of IL-2, IL-12, TNF-alpha and, in an open-label clinical study, to improve or stabilize pulmonary sarcoidosis. We therefore conducted a randomized, double-blinded, placebo-controlled trial to assess whether POF treatment would improve or stabilize pulmonary sarcoidosis, and be beneficial as an adjunct to corticosteroid therapy. In our study, POF did not improve primary or secondary endpoints in patients with pulmonary sarcoidosis. Although recurrence of pulmonary sarcoidosis was not considered a formal endpoint, 5/13 POF-treated patients experienced disease recurrence versus 12/14 placebo-treated patients (P < 0.02). There were no spontaneous remissions in the placebo group. After 24 weeks, the mean prednisone dose for POF-treated patients was significantly lower than for placebo-controlled patients (P < 0.006). Adverse effects, primarily gastrointestinal, were reported in 11/13 POF-treated , but in no placebo-treated patients. Thus, although POF may have a corticosteroid-sparing effect in pulmonary sarcoidosis, with concentrations of drug used in this study, gastrointestinal side effects were commonly reported. Basic science studies: Pentoxifylline (POF), a non-specific phosphodiesterase inhibitor, may have beneficial effects in patients with sarcoidosis, via its known inhibition of the production of cytokines such as tumor necrosis factor-alpha (TNF-alpha) and IL-12. Human blood monocyte-derived macrophages from normal volunteers were incubated with and without E. coli 0128:B12 lipopolysaccharide (LPS) (1ug/mL) and 1mM POF for 18 hr, followed by isolation of RNA for hybridization with oligonucleotide-based microarrays. Among mRNAs that were increased at least 2-fold by LPS and significantly inhibited by POF (P < 0.01) were: interferon-stimulated protein, 15kDa (ISG15), epithelial membrane protein 3 (EMP3), 2?-5?-oligoadenylate synthetase 3, 100kDa (OAS3), bone marrow stromal cell antigen 2 (BST2), and IPA proteasome (prosome, macropain) subunit, beta type 9 (PSMB9). In particular, LPS increased expression of ISG15 8.2-fold, which was reduced only to 4.4-fold control values by POF (P< 0.005). Real-time quantitative PCR confirmed the partial reversal by POF of the stimulatory effect of LPS on expression of ISG15. ISG15 may be a relevant target in sarcoidosis since it is known that induction of ISG15 by IFN-alpha results in increased IFN-alpha, a key Th1 cytokine associated with granulomatous responses. Interestingly, LPS failed to induce ISG15 in alveolar macrophages from normal volunteers, which suggests that ISG15 expression may be differently regulated in alveolar macrophages and macrophages derived from blood monocytes. In another study, we found that cAMP-elevating agents, prostaglandin E1 and cholera toxin (which activate adenylyl cyclase via distinct mechanisms), and the cyclic nucleotide phosphodiesterase (PDE) inhibitors, cilostamide (PDE3 inhibitor) and rolipram (PDE4 inhibitor), induced apoptosis in FDCP2 promyeloid cells. The cAMP analogs, 8-bromo-cyclic AMP and Sp-cAMP, also induced apoptosis in these cells. The PKA inhibitor, 8-bromo-Rp-cAMPS, or insulin-like growth factor-1 (which activates both PDE3 and PDE4 in FDCP2 cells), prevented apoptosis induced by cAMP-elevating agents. The pro-apoptotic protein, Bax, was redistributed from cytosol to membranes in apoptotic cells. This redistribution could be prevented by treatment of cells with IGF-1. Removal of serum from culture medium led to dephosphorylation of Erk1/2 and PKB in FDCP2 cells, and cAMP-elevating agents significantly accelerated this process. Activation of phosphatases was found to bbe more important in dephosphorylation of Erk1/2 than inhibition of upstream protein kinases. Our results suggest that in FDCP2 cells, cAMP-elevating agents, acting through PKA and PP2A or PP2A-like protein phosphatases, inhibit Raf-MEK-Erk and PKB signaling and thereby abrogate Erk-and PKB-mediated survival signals, with concurrent translocation of Bax to membranes, perhaps resulting in Bax-mediated apoptosis. On the other hand, in these cells, IGF-1 promotes anti-apoptotic or survival signals, most likely by two mechanisms. IGF-1 activates ERK and PKB via phosphatidyl-inositol-3 kinase (PI3-K) dependent pathways, thus promoting anti-apoptotic signals, which include activation of both PDE3 and PDE4, leading to a reduction in cAMP and consequent inhibition of anti-proliferative and pro-apoptotic effects of cAMP. Taken together, these studies support the hypothesis that, in FDCP2 cells, PDEs function as anti-apoptotic, and protein phosphatases as pro-apoptotic, regulators.
