Disturbed blood flow (d-flow) has been known to induce changes of the cells in the arterial wall, increasing the risk of atherosclerosis. However, the heterogeneity of the vascular cell populations under d-flow remains less understood. To generate d-flow in vivo, partial carotid artery ligation (PCL) was performed. Seven days after ligation, single-cell RNA sequencing of nine left carotid arteries (LCA) from the PCL group (10,262 cells) or control group (14,580 cells) was applied and a single-cell atlas of gene expression was constructed. The integrated analysis identified 15 distinct carotid cell clusters, including 10 d-flow-relevant subpopulations. Among endothelial cells, at least four subpopulations were identified, including Klk8hi ECs, Lrp1hi ECs, Dkk2hi ECs, and Cd36hi ECs. Analysis of GSVA and single-cell trajectories indicated that the previously undescribed Dkk2hi ECs subpopulation was mechanosensitive and potentially transformed from Klk8hi ECs under d-flow. D-flow-induced Spp1hi VSMCs subpopulation that appeared to be endowed with osteoblast differentiation, suggesting a role in arterial stiffness. Among the infiltrating cell subpopulations, Trem2hi Mφ, Birc5hi Mφ, DCs, CD4+ T cells, CXCR6+ T cells, NK cells, and granulocytes were identified under d-flow. Of note, the novel Birc5hi Mφ was identified as a potential contributor to the accumulation of macrophages in atherosclerosis. Finally, Dkk2hi ECs, and Cd36hi ECs were also found in the proatherosclerotic area of the aorta where the d-flow occurs. In conclusion, we presented a comprehensive single-cell atlas of all cells in the carotid artery under d-flow, identified previously unrecognized cell subpopulations and their gene expression signatures, and suggested their specialized functions.

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The neuromodulator hydrogen sulfide (H2S) was shown to exert neuroprotection in different models of Parkinson’s disease (PD) via its anti-inflammatory and anti-apoptotic properties. In this study, we evaluated the effect of an H2S slow-releasing compound GYY4137 (GYY) on a mouse PD model induced by acute injection with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). GYY was intraperitoneally (i.p.) injected once daily into male C57BL/6J mice 3 days before and 2 weeks after MPTP (14 mg/kg, four times at 2-h intervals, i.p.) administration. Saline was given as a control. Behavioral tests (rotarod, balance beam, and grid walking) showed that 50 mg/kg GYY significantly ameliorated MPTP-caused motor impairments. At lower doses (12.5 and 25 mg/kg) GYY exhibited a less obvious effect. Consistent with this, immunohistochemistry and western blot analysis demonstrated that 50 mg/kg GYY attenuated the loss of tyrosine hydroxylase (TH) positive neurons in the substantia nigra and the decrease of TH expression in the striatum of MPTP-treated mice. Moreover, at this regimen GYY relieved the nitrative stress, as indicated by the decreases in nitric oxide (NO) generation and neuronal NO synthase (nNOS) upregulation elicited by MPTP in the striatum. The suppression of GYY on nNOS expression was verified in vitro, and the results further revealed that Akt activation may participate in the inhibition by GYY on nNOS upregulation. More important, GYY reduced the nitrated modification of α-synuclein, a PD-related protein, in MPTP-induced mice. Overall, our findings suggest that GYY attenuated dopaminergic neuron degeneration and reduced α-synuclein nitration in the midbrain, thus exerting neuroprotection in MPTP-induced mouse model of PD.

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