Characterization of new chemical compounds acting as cyclic AMP signalling enhancers or disruptors in human peripheral T cells and monocytes

Abstract

Abstract Opportunistic infections due to impaired function of T cells are the main cause of death in HIV infected individuals. It has been shown that T cells from these individuals have elevated levels of cAMP, which inhibits proliferation of T cells through interaction with PKA type I (Skålhegg et al. 1994, Hofmann et al. 1993). Presence of the HIV virus induces cAMP, and cAMP will in turn enhance viral replication (Nokta et al. 1992). By blocking this hyperactivated cAMP/PKA inhibitory pathway, it is possible to normalize proliferation of T cells, and reverse dysfunction caused by the infection. Rp-8-Br-cAMPS, a specific PKA type I antagonist was shown to reverse the inhibition of proliferation of T cells from HIV infected individuals (Aandahl et al. 1998). These findings have given rise to the current drug development project that is trying to find a suitable drug candidate with lowered therapeutic concentration in vivo and higher degree of specificity towards PKA type I than the lead compound Rp-8-Br-cAMPS. Results reported in the first part of this thesis shows that none of analogs tested had a potency higher than Rp-8-Br-cAMPS and that none of them appeared to have toxic properties. O`benzyl ester of Sp-8-Br-cAMPS was toxic at concentrations higher than 125 M, and was not able to inhibit proliferation of T cells to a similar degree as PKA type I agonist Sp-8-Br-cAMPS. Monocytes express Epac1, that is activated by treatment with 8-CPT-2-O`-Me-cAMP and 8-Br-2-O`-Me-cAMP-AM. Epac1 further activates Rap1 leading to a set of biological responses yet to be determined. Sp-8-Br-cAMPS, a specific PKA type I agonist also activates Epac1 but this activation is strongly impaired when compared with Epac1 specific agonists. Involvement of the PKA shown by induction of phosphorylation after treatment with Sp-8-Br-cAMPS and 8-Br-2-O`-Me-cAMP-AM opens for a possibility for interference between PKA and Epac1 pathway in monocytes. In the second part of these master thesis the effects of activation of Rap1 and PKA on production of cytokines in monocytes are studied