DHI Increases the Proliferation and Migration of Schwann Cells Through the PI3K/AKT Pathway and the Expression of CXCL12 and GDNF to Promote Facial Nerve Function Repair.

The facial nerve is one of the vulnerable nerves in otolaryngology. Repair and recovery of facial nerve injury have a high priority in clinical practice. The proliferation and migration of Schwann cells are considered of great significance in the process of nerve injury repair. Danhong injection (DHI), as a common drug for cardiovascular and cerebrovascular diseases, has been fully certified in neuroprotection research, but its role in facial nerve injury is still not clear. Our study found that DHI can promote the proliferation and migration of RSC96 cells, a Schwann cell line, and this effect is related to the activation of the PI3K/AKT pathway. LY294002, an inhibitor of PI3K, inhibits the proliferation and migration of RSC96 cells. Further studies have found that DHI can also promote the expression of CXCL12 and GDNF at gene and protein levels, and CXCL12 is, while GDNF is not, PI3K/AKT pathway-dependent. Animal experiments also confirmed that DHI could promote CXCL12 and GDNF expression and promote facial nerve function recovery and myelin regeneration. In conclusion, our in vitro and in vivo experiments demonstrated that DHI could promote the proliferation and migration of Schwann cells through the PI3K/AKT pathway and increase the expression of CXCL12 and GDNF to promote facial nerve function repair.

Streptomycin ototoxicity in rat cochlear organotypic cultures.

The purpose of this study is to investigate the ototoxic effect of streptomycin on cochlear hair cells, spiral ganglion cells, and nerve fibers in cochlear organ cultures. The cochlear basilar membrane of three- or four-day-old F344 rats was cultured and treated with various doses of streptomycin for 24 h. Cochlear hair cells and the spiral ganglion neurons were stained with immunofluorescence and were observed under confocal microscope. The increase in hair cell loss was concomitant with the increase in streptomycin sulfate concentrations. Streptomycin impaired both the inner and outer hair cells at a similar degree. The damage to hair cells was more severe at basal turn than apical turn. In contrast, the spiral ganglion neurons and auditory nerve fibers were intact. Streptomycin primarily caused hair cell loss, but not significant impairment in the neural structure in vitro. Streptomycin-induced cochlear hair cell lesion was initiated at the basal turn and extended towards the apical turn. Streptomycin ototoxicity was dose-dependent under in vitro conditions.

[Streptomycin-induced apoptosis of rat cochlear hair cell cultured in vitro].

OBJECTIVE: To evaluate if caspase pathway was involved in streptomycin-induced cell apoptosis in cochlear hair cells. METHODS: F344 rats at postnatal day 3 or 4 were used for the study in cochlear organotypic cultures. The cochlear basilar membrane was micro-dissected out and cultured overnight, and then treated with 1 mmol/L streptomycin for 24 hours. Before the termination, the activity of caspase-8, 9 or 6 were detected with FAM-peptide-FMK labeled caspase-8, 9 or 6, respectively. The stereocilia and cuticular plate of hair cells were stained with TRITC conjugated phalloidin, and the nuclei were stained with Topro-3 DNA probe. The specimens were observed and photographed under confocal fluorescent microscope. RESULTS: Streptomycin with 1 mmol/L causes about 80% cochlear hair cells missing in the basal turn and 10% hair cell loss in the apex. After streptomycin treatment, the nuclear shrinkage and fragmentation were found in most cochlear hair cells, and the caspase-8, caspase-9 and caspase-6 were greatly activated. CONCLUSIONS: Apoptosis is involved in the cochlear hair cells death induced by Streptomycin in vitro. The caspase activities in upstream and downstream are maybe the major apoptotic pathway.