Microglia, the resident immune cell in the brain, contributes to neuroinflammation and neurogenic hypertension by secreting various cytokines and chemokines. ADAM17 shedding of these signaling molecules) in microglia modulates synaptic function but the consequences of this process have not been studied in neurogenic hypertension. Accordingly, we hypothesize that deletion of ADAM17 in microglia opposes microglia activation and cytokine secretion thus preventing the development of neuroinflammation in salt-sensitive hypertension. To test our hypothesis, a new mouse model (ADAM17::CX3CR1-CreERT2; A17-Mic-/-) amenable for selective deletion of ADAM17 in microglia was developed. Following the initiation of deoxycorticosterone acetate plus salt (DOCA-salt) hypertension, tamoxifen was injected intracerebroventricularly to delete ADAM17 in microglia and blood pressure (BP) monitored over 3 weeks. In A17-Mic-/- mice, lacking ADAM17 in microglia, the BP increase induced by DOCA-salt treatment was blunted compared to control mice (127.4±5 vs. 143.4±4 mmHg, P<0.05). However, it was not abated in iRhom2-/- mice (149.5±3 mmHg), lacking the rhomboid protein involved in ADAM17 maturation in microglia, suggesting possible compensation by iRhom1. Interestingly, A17-Mic-/- mice showed a reduced level of proinflammatory cytokines and chemokines in the plasma, including TNF-α (A17-Mic-/-: 5.21±0.97, iRhom2-/-: 3.867±1 vs. control: 20.72±4 pg/mL), IL-6 (A17-Mic-/-: 36.53±11.33, iRhom2-/-: 91.41±14 vs. control: 79.65±15.72 pg/mL) and G-CSF (A17-Mic-/-: 508.4±98.7, iRhom2-/-: 3523±897 vs. 838.2±238.2 pg/mL) and MCP-1 (A17-Mic-/-: 38.41±9, iRhom2-/-: 51.87±7 vs. control: 75.52±12 pg/mL), respectively (P<0.05). Together, our data suggests that conditional deletion of ADAM17 opposes the activation of microglia and reduces pro-inflammatory cytokine and chemokine expression in hypertension. Overall, our data highlights the pivotal role of microglial ADAM17 in regulating salt-sensitive hypertension and the associated inflammation.
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