Notch Signaling Contributes to the Renoprotective Effects of the Cholinergic Anti-Inflammatory Pathway
- AKI: Mechanisms - III
November 05, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 103 AKI: Mechanisms
- Kuwabara, Shuhei, University of Virginia, Charlottesville, Virginia, United States
- Zheng, Shuqiu, University of Virginia, Charlottesville, Virginia, United States
- Yao, Junlan, University of Virginia, Charlottesville, Virginia, United States
- Okusa, Mark D., University of Virginia, Charlottesville, Virginia, United States
Group or Team Name
- Division of Nephrology and Center for Immunity, Inflammation, and Regenerative Medicine
A novel strategy for the prevention and treatment of AKI is activating the cholinergic anti-inflammatory pathway (CAP), a neuroimmune circuit. The CAP is initiated by vagus nerve stimulation (VNS) and subsequent activation of splenic macrophages (MΦ) to suppress inflammation. Our previous findings suggest the possibility that Notch signaling pathway (Notch), contributes to the renoprotective effects of CAP. However, a direct relationship between the CAP and Notch has not been reported. In the current study, we focused on Notch in MΦ to unravel the molecular mechanism of CAP and to determine the utility of Notch in ameliorating AKI.
To test if VNS activates Notch in MΦ, we performed electrical VNS before ischemia-reperfusion injury (IRI). After IRI, the expression of cytokines and Notch2 receptor in MΦ were assessed by qPCR and flow cytometry. MΦ-specific Notch2 knockout mice were also subjected to VNS to evaluate whether Notch2 mediates anti-inflammatory responses in MΦ. The vagus nerve is heterogeneous and composed of efferent and afferent fibers, and neural circuits related to each fiber bundle are independent though both efferent/afferent VNS attenuate AKI. Thus, to determine if specific neural circuits regulate Notch, we used optogenetics, a tool for controlling the functions of particular neurons by expressing light-responsive proteins such as channelrhodopsin 2 (ChR2).
The mRNA and protein expression of Notch2 was upregulated in splenic MΦ of VNS-treated mice. This was accompanied by a decrease in Tnf-α and an increase in Il-10. In splenic MΦ of Notch2 knockout mice subjected to VNS, Tnf-α was higher and Il-10 was Iower than VNS-treated littermates, indicating that anti-inflammatory effects of the CAP were attenuated by Notch2 deficiency in MΦ. In addition, we performed optogenetic VNS by using transgenic mice expressing ChR2 on vagal efferent fibers. Flow cytometry analysis revealed that efferent VNS did not alter Notch2 protein levels in splenic MΦ.
Our findings suggested that: 1) Notch signaling in splenic MΦ contributes to renoprotection by the CAP, 2) optogenetic stimulation of the vagus nerve showed that efferent VNS does not mediate Notch2 upregulation, suggesting that afferent VNS may be responsible for initiating Notch signaling in splenic MΦ.
- NIDDK Support