Erythromycin derivatives inhibit HIV-1 replication in macrophages through modulation of MAPK activity to induce small isoforms of C/EBPbeta.

Macrophages (MPhis) are a major source of HIV-1 especially in patients with tuberculosis. There are MPhis that are permissive and those that restrict HIV-1. Regulation of hematopoietic cell kinase (Hck) activity and selective expression of CCAAT enhancer binding protein beta (C/EBPbeta) isoforms greatly contribute to determine distinct susceptibility of MPhis to HIV-1. Resistance is attributable to reduced expression of Hck and augmented expression of an inhibitory small isoform of C/EBPbeta. Derivatives of erythromycin A (EMA) EM201 and EM703 inhibit the replication of HIV-1 in tissue MPhis, at posttranscriptional and translational levels. We demonstrate that EM201 and EM703 convert tissue MPhis from HIV-1 susceptible to HIV-1 resistant through down-regulation of Hck and induction of small isoforms of C/EBPbeta. These drugs inhibit p38MAPK activation which is expressed only in susceptible tissue MPhis. Activated CD4(+)T cells stimulate the viral replication in HIV-1 resistant MPhis through down-regulation of small isoforms of C/EBPbeta via activation of ERK1/2. EM201 and EM703 can inhibit the MAPK activation and inhibit the burst of viral replication produced when CD4(+)T cells and MPhis interact. These EM derivatives may be highly beneficial for repression of residual HIV-1 in the lymphoreticular system of HIV-1-infected patients and offer great promise for the creation of new anti-HIV drugs for the future treatment of AIDS patients.

Lyn, one of the Src-family tyrosine kinases expressed in phagocytes, plays an important role in beta2 integrin-signalling pathways in opsonized zymosan-activated macrophage-like U937 cells.

We have investigated the contribution of Hck, Lyn and Fgr, highly expressed Src family tyrosine kinases (SFKs) in signalling pathways in opsonized zymosan (OZ)-activated phagocytes by using short interfering RNAs (siRNAs). Treatment of macrophage-like U937 cells with the siRNAs targeted to these transcripts decreased the protein content of each kinase to less than half that of untreated cells. Among these siRNAs, siRNA targeted to Lyn was the most effective in diminishing two kinds of phagocyte functions, that is oxidative burst and phagocytosis. Phosphorylation of c-Cbl, a multidomain adaptor protein in the beta2 integrin-signalling pathway, was also largely inhibited by treatment with siRNA to Lyn. Thus, the results with siRNAs highly specific for Hck, Lyn and Fgr suggested that, among these three SFKs, Lyn plays the most important role in signalling pathways downstream of beta2 integrins in OZ-stimulated phagocytes.