Inhibition of cGAS Reduces Brain Injury and Facilitates Neurological Recovery via the STING-Mediated Signaling Pathway After Germinal Matrix Hemorrhage in Neonatal Mice.

BACKGROUND

Germinal matrix hemorrhage (GMH) is a common complication of premature infants with lifelong neurological consequences. Inflammation-mediated blood-brain barrier (BBB) disruption has been implicated as a main mechanism of secondary brain injury after GMH. The cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway plays a crucial role in inflammation, yet its involvement in GMH pathophysiology remains unclear.

METHODS

Collagenase was injected into the right germinal matrix of postnatal day 5 (P5) mouse pups to induce GMH. Either RU.521, or RU.521 combined with a STING agonist SR-717 was administered to the mice after GMH. The number of microglia, proinflammatory cytokines, microglial polarization, BBB permeability, demyelination, and axon degeneration were analyzed by immunofluorescence staining, western blotting, and quantitative real-time PCR. Neurobehavioral functions were evaluated using novel object recognition, Y-maze, and rotarod tests.

RESULTS

After induction of GMH, cGAS and STING were upregulated in the peri-hematomal area with a peak at 24 h, and they were mainly expressed in microglia. RU.521 treatment decreased the number of microglia, proinflammatory cytokines and microglial polarization, preserved BBB integrity, and decreased its permeability after GMH. Moreover, RU.521 decreased GMH-mediated upregulation of STING, phosphorylated TANK-binding kinase 1 (phospho-TBK1), phosphorylated interferon regulatory factor 3 (phospho-IRF3), and interferon-β (IFN-β), diminished demyelination, axon degeneration, and neurological deficits. The STING agonist SR-717 blunted RU.521-induced downregulation of phospho-TBK1, phospho-IRF3 and IFN-β and blocked RU.521-mediated inhibition of inflammation, protected against BBB breakdown, white matter lesions, and neurological dysfunction after GMH.

CONCLUSIONS

Inhibition of cGAS improved white matter lesions and neurological dysfunction by modulating the microglial polarization towards decreased neuroinflammation and maintaining BBB integrity through STING-mediated type I IFN-β production. Thus, cGAS may be a potential therapeutic target for the treatment of GMH.