Brown, J. A. | bioRxiv Science

bioRxiv2019

2'3'-cGAMP is an immunotransmitter produced by cancer cells and regulated by ENPP1

23-cyclic GMP-AMP (cGAMP) is characterized as an intracellular second messenger that is synthesized in response to cytosolic dsDNA and activates the innate immune STING pathway. Our previous discovery of its extracellular hydrolase ENPP1 hinted at the existence of extracellular cGAMP. Here, using mass spectrometry, we detected that cGAMP is continuously exported as a soluble factor by an engineered cell line but then efficiently cleared by ENPP1, explaining why it has escaped detection until now. By developing a potent, specific, and cell impermeable ENPP1 inhibitor, we detected cGAMP export in cancer cell lines commonly used for mouse tumor models. In tumors, depletion of extracellular cGAMP using neutralizing proteins decreased tumor-associated dendritic cells. Boosting extracellular cGAMP by genetic knockout and pharmacological inhibition of ENPP1 increased tumor-associated dendritic cells, shrunk tumors, and synergized with ionizing radiation and anti-CTLA-4 to cure tumors. In conclusion, cGAMP is an anti-cancer immunotransmitter released by tumors and detected by host innate immunity.

biochemistry↗

bioRxiv2018

P2X antagonists inhibit HIV-1 productive infection and inflammatory cytokines IL-10 and IL-1β in a human tonsil explant model

HIV-1 causes a persistent infection of the immune system that is associated with chronic comorbidities. The mechanisms that underlie this inflammation are poorly understood. Emerging literature has implicated pro-inflammatory purinergic receptors and downstream signaling mediators in HIV-1 infection. This study probed whether inhibitors of purinergic receptors would reduce HIV-1 infection and HIV-1 stimulated inflammation. A human ex vivo human tonsil histo-culture infection model was developed to support HIV-1 productive infection and stimulated inflammatory cytokine interleukin-1 beta (IL-1{beta}) and immunosuppressive cytokine, interleukin-10 (IL-10). This study tests whether inhibitors of purinergic receptors would reduce HIV-1 infection and HIV-1 stimulated inflammation. The purinergic P2X1 receptor antagonist, NF449, the purinergic P2X7 receptor antagonists, A438079, and azidothymidine (AZT) were tested in HIV-1 infected human tonsil explants to compare inhibition of HIV-1 infection and HIV-stimulated inflammatory cytokine production. All drugs limited HIV-1 productive infection but P2X-selective antagonists (NF449, and A438079) significantly lowered HIV-stimulated IL-10 and IL-1{beta}. We further observed that P2X1- and P2X7-selective antagonists can act differentially as inhibitors of both HIV-1 infection and HIV-1-stimulated inflammation. Our findings highlight the differential effects of HIV-1 on inflammation in peripheral blood as compared to lymphoid tissue. For the first time, we demonstrate that P2X-selective antagonists act differentially as inhibitors of both HIV-1 infection and HIV-1-stimulated inflammation. Drugs that block these pathways can have independent inhibitory activities against HIV-1 infection and HIV-induced inflammation.\n\nImportancePatients who are chronically infected with HIV-1 experience sequelae related to chronic inflammation. The mechanisms of this inflammation have not been elucidated. Here we describe a class of drugs that target the P2X pro-inflammatory signaling receptors in a human tonsil explant model. This model highlights differences in HIV-1 stimulation of lymphoid tissue inflammation and peripheral blood. These drugs serve to both block HIV-1 infection and production of IL-10 and IL-1{beta} in lymphoid tissue suggesting a novel approach to HIV-1 therapeutics in which both HIV-1 replication and inflammatory signaling are simultaneously targeted.

immunology↗