Hypertension Increases Susceptibility to Lead-Induced Microglial Polarization via ANT1-Mediated Mitochondrial DNA/cGAS/STING Signaling.

Hypertensive individuals are concurrently at risk of heavy metal exposure, particularly lead (Pb). However, it remains unclear whether individuals with hypertension are more sensitive to the neurotoxicity induced by Pb exposure. Here, we established a hypertension model of mice with Pb exposure for 2, 4, 8, 12, and 24 weeks to detect the temporal and spatial changes in microglial polarization. Pb-exposed and hypertensive mice exhibited a notably higher proportion of M1 as early as 4 and 8 weeks, but a lower proportion of M2 as early as 4 and 12 weeks. Notably, hypertension exacerbated Pb-induced microglial polarization, which reached a plateau at 12 weeks. Elevated inducible nitric oxide synthase and reduced arginase-1 protein expressions were observed in the prefrontal cortex, hippocampus, and hypothalamus of the Pb, hypertension (HTN), and Pb+HTN groups, with the most pronounced alterations occurring in the prefrontal cortex. Furthermore, treatment with minocycline (microglial polarization inhibitor) markedly alleviated the depression-like behavior of mice in the Pb+HTN group. Bioinformatics analysis revealed that the differentially expressed genes of microglia following Pb and angiotensin II combined exposure were mainly enriched in the cyclic GMP-AMP synthase/stimulator of interferon genes (cGAS/STING) pathway. In addition, the protein expression of the cGAS/STING pathway was significantly upregulated both in vitro and in vivo, especially in the Pb+HTN group. Inhibition of cGAS significantly alleviated the increase in M1-type microglia and the decrease in M2-type microglia in hypertensive mice with Pb exposure. Meanwhile, mitochondrial DNA (mtDNA) leakage of microglia was observed under Pb and angiotensin II exposure, and the activation of the cGAS/STING pathway by mtDNA was proven to play an important role in microglial polarization. Adenine nucleotide translocase 1 (ANT1) was identified as the pivotal protein regulating mtDNA leakage via bioinformatics analyses and was proven by in vitro and in vivo studies. Collectively, hypertensive mice are more sensitive to Pb-induced neurotoxicity, which is mediated by the ANT1-regulated mtDNA/cGAS/STING signaling pathway, which then subsequently induces microglial polarization.