Elevation of proinflammatory cytokines in patients with Aicardi-Goutières syndrome

Abstract

Objective: This study explores a large panel of cytokines in plasma and CSF of patients with Aicardi-Goutières syndrome (AGS) at different ages, in order to establish signatures of cytokines most predictive of AGS.Methods: Plasma from 22 subjects with known mutations were assayed for cytokines using the Milliplex MAP Immunobead system, and compared to results from 8 age-matched normal controls. CSF of 11 additional patients with mutation-proven AGS was tested in an identical manner and compared to results from age-matched controls. Samples were banked and analysis was carried out retrospectively.Results: Significant elevations were seen in FMS-related tyrosine kinase 3 ligand, IP-10, interleukin (IL)-12p40, IL-15, tumor necrosis factor a, and soluble IL 2 receptor a in both AGS patient plasma and CSF relative to controls. Additionally, this cytokine signature was able to correctly cluster 9 of 11 AGS cases based on CSF values. While most cytokines decreased exponentially with age, a subgroup including IP-10 demonstrated persistent elevation beyond early childhood. Conclusion: Patients with AGS exhibit plasma and CSF elevations of proinflammatory cytokines.Selected cytokines remain persistently elevated beyond the initial disease phase. This panel of proinflammatory cytokines may be considered for use as diagnostic and therapeutic markers of disease, and may permit improved understanding of disease pathogenesis. Neurology Aicardi-Goutières syndrome (AGS) is a heritable disorder, characterized by basal ganglia and white matter calcifications, leukoencephalopathy, and elevated CSF interferon-a (IFN-a).1,2 AGS has long been understood as a neuroimmune disorder with characteristic presentations ranging from a syndrome that mimics in utero viral infections to lupus-like sterile pyrexias, skin, and joint manifestations.2 The disease is caused by mutations in any one of several genes encoding nucleases or other proteins involved in innate cellular immunity: TREX1, 3 RNASEH2A, RNASEH2B, RNASEH2C, 4 and SAMHD1. 5 It is thought that failure of these enzymes in AGS results in accumulation of intracellular nucleic acid species, with subsequent activation of an innate immune response, and neurodegeneration. The exact mechanisms underlying activation of the innate cellular immune response and subsequent disease remains unclear; however, these observations indicate that the disease might be treatable by interrupting the accumulation of endogenous nucleic acids.6 Thus, identifying biomarkers, both to monitor disease progression and to better understand disease pathophysiology, is essential to the ongoing study of AGS.

Phenotypic Variation in Aicardi–Goutières Syndrome Explained by Cell-Specific IFN-Stimulated Gene Response and Cytokine Release

“…Even though IFN-a is considered to be a key biomarker for AGS, the chemokine CXCL10 has also been persistently demonstrated to have an elevated expression in AGS patients (12,13). Consistent with this, our study shows that silencing AGS genes results in an increased expression and release of CXCL10 mainly in astrocytes.…”

“…AGS patients also present elevated CSF levels of FMS-related tyrosine kinase 3 ligand, IL-12p40, IL-15, TNF-a, and soluble IL-2 receptor (13). Interestingly, whereas most cytokines decrease exponentially with age in the CSF of patients, CXCL10 levels are persistently elevated beyond early childhood (13). Similar observations have been described for IFN-stimulated genes (ISGs).…”

“…These are also responsible for the increase in chemokines, such as CXCL10, in the brain of AGS patients (12). AGS patients also present elevated CSF levels of FMS-related tyrosine kinase 3 ligand, IL-12p40, IL-15, TNF-a, and soluble IL-2 receptor (13). Interestingly, whereas most cytokines decrease exponentially with age in the CSF of patients, CXCL10 levels are persistently elevated beyond early childhood (13).…”

Characterization of samhd1 Morphant Zebrafish Recapitulates Features of the Human Type I Interferonopathy Aicardi-Goutières Syndrome

“…Functional knowledge of the zebrafish specific chemokine cxc46 is relatively poor. However, other CXC chemokine family members are upregulated in response to viral infection in zebrafish larvae (18), and increased expression of chemokines has been reported in AGS (42,43). Increased expression of genes encoding the transcription factors irf1b, irf7, stat1b, and cebpb, as observed in our morphants, has also been recorded following exposure to two viruses in zebrafish infection models (18), and significant upregulation of the human orthologs, STAT1 and IRF7 is seen in AGS (7).…”

Ribonuclease H2 mutations induce a cGAS/STING‐dependent innate immune response

“…Upregulation of both transcripts was confirmed by RT–qPCR, and ELISA of culture supernatants from all six Rnaseh2b −/− lines demonstrated significantly increased CCL5 and CXCL10 secretion (Fig 3D and E, and Appendix Fig S2B). Notably, these cytokines have previously been implicated in AGS neuroinflammation in humans (van Heteren et al , 2008; Takanohashi et al , 2013; Cuadrado et al , 2015). We therefore concluded that impaired RNase H2 activity in vitro and in vivo results in a similar inflammatory response to that observed in patients with AGS, and like for Trex1 deficiency (Gall et al , 2012) is present in non‐immune cells.…”