Taurine enhances mouse cochlear neural stem cells proliferation and differentiation to sprial gangli through activating sonic hedgehog signaling pathway

Taurine promotes axonal sprouting via Shh-mediated mitochondrial improvement in stroke

PURPOSE

Motor function is restored by axonal sprouting in ischemic stroke. Mitochondria play a crucial role in axonal sprouting. Taurine (TAU) is known to protect the brain against experimental stroke, but its role in axonal sprouting and the underlying mechanism are unclear.

METHODS

We evaluated the motor function of stroke mice using the rotarod test on days 7, 14, and 28. Immunocytochemistry with biotinylated dextran amine was used to detect axonal sprouting. We observed neurite outgrowth and cell apoptosis in cortical neurons under oxygen and glucose deprivation (OGD), respectively. Furthermore, we evaluated the mitochondrial function, adenosine triphosphate (ATP), mitochondrial DNA (mtDNA), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PCG-1α), transcription factor A of mitochondria (TFAM), protein patched homolog 1 (PTCH1), and cellular myelocytomatosis oncogene (c-Myc).

RESULTS

TAU recovered the motor function and promoted axonal sprouting in ischemic mice. TAU restored the neuritogenesis ability of cortical neurons and reduced OGD-induced cell apoptosis. TAU also reduced reactive oxygen species, stabilized mitochondrial membrane potential, enhanced ATP and mtDNA content, increased the levels of PGC-1α, and TFAM, and restored the impaired levels of PTCH1, and c-Myc. Furthermore, these TAU-related effects could be blocked using an Shh inhibitor (cyclopamine).

CONCLUSION

Taurine promoted axonal sprouting via Shh-mediated mitochondrial improvement in ischemic stroke.

G protein-coupled receptors in cochlea: Potential therapeutic targets for hearing loss

The prevalence of hearing loss-related diseases caused by different factors is increasing worldwide year by year. Currently, however, the patient’s hearing loss has not been effectively improved. Therefore, there is an urgent need to adopt new treatment measures and treatment techniques to help improve the therapeutic effect of hearing loss. G protein-coupled receptors (GPCRs), as crucial cell surface receptors, can widely participate in different physiological and pathological processes, particularly play an essential role in many disease occurrences and be served as promising therapeutic targets. However, no specific drugs on the market have been found to target the GPCRs of the cochlea. Interestingly, many recent studies have demonstrated that GPCRs can participate in various pathogenic process related to hearing loss in the cochlea including heredity, noise, ototoxic drugs, cochlear structure, and so on. In this review, we comprehensively summarize the functions of 53 GPCRs known in the cochlea and their relationships with hearing loss, and highlight the recent advances of new techniques used in cochlear study including cryo-EM, AI, GPCR drug screening, gene therapy vectors, and CRISPR editing technology, as well as discuss in depth the future direction of novel GPCR-based drug development and gene therapy for cochlear hearing loss. Collectively, this review is to facilitate basic and (pre-) clinical research in this area, and provide beneficial help for emerging GPCR-based cochlear therapies.

Shikonin Attenuates Cochlear Spiral Ganglion Neuron Degeneration by Activating Nrf2-ARE Signaling Pathway

The molecular mechanisms that regulate the proliferation and differentiation of inner ear spiral ganglion cells (SGCs) remain largely unknown. Shikonin (a naphthoquinone pigment isolated from the traditional Chinese herbal medicine comfrey root) has anti-oxidation, anti-apoptosis and promoting proliferation and differentiation effects on neural progenitor cells. To study the protective effect of shikonin on auditory nerve damage, we isolated spiral ganglion neuron cells (SGNs) and spiral ganglion Schwann cells (SGSs) that provide nutrients in vitro and pretreated them with shikonin. We found that shikonin can reduce ouabain, a drug that can selectively destroy SGNs and induce auditory nerve damage, caused SGNs proliferation decreased, neurite outgrowth inhibition, cells apoptosis and mitochondrial depolarization. In addition, we found that shikonin can increase the expression of Nrf2 and its downstream molecules HO-1 and NQO1, thereby enhancing the antioxidant capacity of SGNs and SGSs, promoting cells proliferation, and inhibiting cells apoptosis by activating the Nrf2/antioxidant response elements (ARE) signal pathway. However, knockdown of Nrf2 rescued the protective effect of shikonin on SGNs and SGSs damage. In addition, we injected shikonin pretreatment into mouse that ouabain-induced hearing loss and found that shikonin pretreatment has a defensive effect on auditory nerve damage. In summary, the results of this study indicate that shikonin could attenuate the level of oxidative stress in SGNs and SGSs through the Nrf2-ARE signaling pathway activated, induce the proliferation and differentiation of SGNs, and thereby improve the neurological hearing damage in mice. Therefore, shikonin may be a candidate therapeutic drug for endogenous antioxidants that can be used to treat neurological deafness.