In the inner ear, cyclic guanosine monophosphate (cGMP) signaling has been described as facilitating otoprotection, which was previously observed through elevated cGMP levels achieved by phosphodiesterase 5 inhibition. However, to date, the upstream guanylyl cyclase (GC) subtype eliciting cGMP production is unknown. Here, we show that mice with a genetic disruption of the gene encoding the cGMP generator GC-A, the receptor for atrial and B-type natriuretic peptides, display a greater vulnerability of hair cells to hidden hearing loss and noise- and age-dependent hearing loss. This vulnerability was associated with GC-A expression in spiral ganglia and outer hair cells (OHCs) but not in inner hair cells (IHCs). GC-A knockout mice exhibited elevated hearing thresholds, most pronounced for the detection of high-frequency tones. Deficits in OHC input–output functions in high-frequency regions were already present in young GC-A-deficient mice, with no signs of an accelerated progression of age-related hearing loss or higher vulnerability to acoustic trauma. OHCs in these frequency regions in young GC-A knockout mice exhibited diminished levels of KCNQ4 expression, which is the dominant K+ channel in OHCs, and decreased activation of poly (ADP-ribose) polymerase-1, an enzyme involved in DNA repair. Further, GC-A knockout mice had IHC synapse impairments and reduced amplitudes of auditory brainstem responses that progressed with age and with acoustic trauma, in contrast to OHCs, when compared to GC-A wild-type littermates. We conclude that GC-A/cGMP-dependent signaling pathways have otoprotective functions and GC-A gene disruption differentially contributes to hair-cell damage in a healthy, aged, or injured system. Thus, augmentation of natriuretic peptide GC-A signaling likely has potential to overcome hidden and noise-induced hearing loss, as well as presbycusis.
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Dr. David Lowemann, M.Sc, Ph.D., is a co-founder of the Institute for the Future of Human Potential, where he leads the charge in pioneering Self-Enhancement Science for the Success of Society. With a keen interest in exploring the untapped potential of the human mind, Dr. Lowemann has dedicated his career to pushing the boundaries of human capabilities and understanding.
Armed with a Master of Science degree and a Ph.D. in his field, Dr. Lowemann has consistently been at the forefront of research and innovation, delving into ways to optimize human performance, cognition, and overall well-being. His work at the Institute revolves around a profound commitment to harnessing cutting-edge science and technology to help individuals lead more fulfilling and intelligent lives.
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