Abstract: TH-PO259

Optogenetic Stimulation of Specific Neural Circuits in the Neuroimmune Reflex Control of Inflammation in AKI

Session Information

Category: Acute Kidney Injury

  • 001 AKI: Basic

Authors

  • Tanaka, Shinji, University of Virginia, Charlottesville, Virginia, United States
  • Inoue, Tsuyoshi, University of Virginia, Charlottesville, Virginia, United States
  • Rosin, Diane L., University of Virginia, Charlottesville, Virginia, United States
  • Guyenet, Patrice G., University of Virginia, Charlottesville, Virginia, United States
  • Okusa, Mark D., University of Virginia, Charlottesville, Virginia, United States
Background

We recently reported that electrical vagus nerve stimulation (VNS) protects mouse kidneys from ischemia-reperfusion injury (IRI) by activating the cholinergic anti-inflammatory pathway (CAP). A limitation of this study is the bidirectional stimulation of both the efferent and afferent vagus nerve fibers. We used optogenetics to begin to distinguish the specific functions of vagus efferent and afferent fibers within the vagus nerve bundle in controlling inflammation by the CAP. Optogenetic stimulation involves the expression of light-reactive ion channels, such as channelrhodopsin-2 (ChR2), in relevant neurons using the Cre/loxP system. When light of a specific wavelength is applied to the target nerve, the ion channels open, resulting in selective activation of the neurons.

Methods

We crossed loxP-STOP-loxP ChR2-eYFP mice with choline acetyltransferase (Chat)-cre and vesicular glutamate transporter 2 (Vglut2)-cre mice to generate Chat-ChR2 and Vglut2-ChR2 mice expressing ChR2 in vagal efferent and afferent fibers, respectively.

Results

ChR2 expression was confirmed by direct observation of the eYFP signal in the cervical vagus nerve. When blue laser (wavelength 473 nm, 50 Hz) was applied to the cervical vagus nerve of Chat-ChR2 mice, heart rate decreased markedly (300→180 bpm) without a change in respiratory rate. Blue laser application to the intact vagus nerve or the central end of the cut vagus nerve of Vglut2-ChR2 mice completely paused breathing by activation of Hering-Breuer inflation reflex, while application to the distal end of the cut vagus nerve did not affect the respiratory rate, which reflects the fact that Hering-Breuer inflation reflex needs afferent vagal input to the brain. In a preliminary experiment, optogenetic VNS (5 Hz to minimize the effect on respiration) in Vglut2-ChR2 mice protected kidneys from IRI.

Conclusion

We have successfully created transgenic mice expressing ChR2 in vagus efferent (Chat-ChR2) and afferent fibers (Vglut2-ChR2) and validated their expression and functional effect following optogenetic stimulation. Our preliminary data showed that selective stimulation of the vagus afferent fibers was protective against kidney IRI. Optogenetics will be useful in identifying selective neural circuits of the CAP that control systemic inflammation and other neural circuits of the kidney.

Funding

  • NIDDK Support