Noise Trauma-Induced Cortical PV Neuron Dysfunction - PROJECT SUMMARY Noise trauma can lead to loss of parvalbumin-positive inhibitory interneurons in the auditory cortex, which is associated with audiotory processing deficit and tinnitus in rodent models. The mechanisms underlying noise- induced PV neuron loss are unknown. We propose to systematically characterize noise-induced PV neuron deficits and examine the hypothesis that differential activation of TNFR1 and TNFR2 in cortical PV neurons determines the fate of the PV neurons following noise trauma, with TNFR1 biasing for, and TNFR2 biasing against, neuronal loss and dysfunction. Specific Aim 1. Examine cell death as a mechanism of noise-induced PV neuron loss. PV-Cre-tdTomato mice will undergo a procedure to induce noise trauma. Auditory cortical tissue will be collected at four time points (1, 3, 5 and 10 d later) to cover the entire cell death process. Sections of cortical tissue will be double stained for PV and cell death markers (TUNEL staining for apoptosis, and antibody staining of p-RIP3 for necroptosis). Colocalization of tdTomato (driven by a constitutively active promoter to mark all PV neurons even if they stop expressing PV), PV and the cell death markers will be analyzed to quantify PV neuron death vs. lack of PV. Specific Aim 2. Characterize input and output synapses of the surviving cortical PV neurons following noise trauma. PV-Cre-tdTomato and PV-Cre-ChR2-tdTomato mice will undergo the noise trauma procedure. Ten days later, acute auditory cortical slices will be prepared. Patch clamp recording of PV neurons in PV-Cre- tdTomato slices will be made, and excitatory and inhibitory synaptic inputs on PV neurons will be examined. In addition, optogenetically activated PV neuron output onto Layer2/3 pyramidal neurons will be examined. The input-output function, short-term plasticity, and synaptic depletion/recovery dynamics will be characterized. All results will be compared between noise trauma and sham trauma groups. Specific Aim 3. investigate the roles of TNFR1 and TNFR2 in noise-induced PV neuron loss and synaptic dysfunction. We will knock down TNFR1 or TNFR2 in cortical PV neurons of PV-Cre-tdTomato and PV-Cre-ChR2-tdTomato mice using our custom-made viral vectors for Cre-dependent expression of TNFR1 or TNFR2 shRNA. The viral vector expresses GFP to allow comparison between transfected and untransfected PV neurons. We will examine effects of TNFR1 or TNFR2 knockdown on noise-induced PV neuron loss (as in Aim 1), synaptic dysfunction (as in Aim 2) and behavioral deficits (as in Masri et al., 20218).
