Activation of cGAS-dependent antiviral responses by DNA intercalating agents

Abstract

Acridine dyes, including proflavine and acriflavine, were commonly used as antiseptics before the advent of penicillins in the mid-1940s. While their mode of action on pathogens was originally attributed to their DNA intercalating activity, work in the early 1970s suggested involvement of the host immune responses, characterized by induction of interferon (IFN)-like activities through an unknown mechanism. We demonstrate here that sub-toxic concentrations of a mixture of acriflavine and proflavine instigate a cyclic-GMP-AMP (cGAMP) synthase (cGAS)-dependent type-I IFN antiviral response. This pertains to the capacity of these compounds to induce low level DNA damage and cytoplasmic DNA leakage, resulting in cGAS-dependent cGAMP-like activity. Critically, acriflavine:proflavine pre-treatment of human primary bronchial epithelial cells significantly reduced rhinovirus infection. Collectively, our findings constitute the first evidence that non-toxic DNA binding agents have the capacity to act as indirect agonists of cGAS, to exert potent antiviral effects in mammalian cells.

Mitochondrial DNA drives noncanonical inflammation activation via cGAS–STING signaling pathway in retinal microvascular endothelial cells

“…It was first identified as a conserved enzyme that synthesizes cyclic dinucleotides. Previous studies have shown that cGAS is mainly located in the cytoplasm, and its expression is induced by cytoplasmic dsDNA molecules (27). In this study, we found that cGAS protein tended to decline from 0 to 6 h after treatment with mtDNA.…”

Phosphoinositide Interactions Position cGAS at the Plasma Membrane to Ensure Efficient Distinction between Self- and Viral DNA

“…Notably, cGAS also regulates immune responses in the absence of infection through the detection of endogenous (self) DNA. For instance, cGAS promotes IFN responses to genotoxic stress induced by DNA damaging agents, micronuclei formation, and cellular senescence (Dou et al, 2017;Glü ck et al, 2017;Harding et al, 2017;Hä rtlova et al, 2017;Mackenzie et al, 2017;Pé pin et al, 2017;Yang et al, 2017). cGAS is therefore not only a sensor of pathogens but also a sensor of cellular stress and genomic integrity.…”

Comparative Study Regarding the Properties of Methylene Blue and Proflavine and Their Optimal Concentrations for In Vitro and In Vivo Applications

“…PRO seems to alter the microenvironment of tryptophan residues compared with tyrosine residues [60]. Another effect of PRO observed at the nuclear level is represented by its antitumoral effect [31] with only minimal damage to DNA, which is then potentiated by immune recruitment and, as a non-covalent binder to DNA, it can act as an indirect cyclic GMP-AMP Synthase cGAS agonist [62].…”

“…The response obtained when sub-toxic doses of PRO were used, was directly dependent on cell type, since cytoplasmatic DNA leakage was absent in L929 murine cell, which express functional levels of cGAS and STING. However, the DNA damage was still present [62].…”