Xiaohui Bai

Curcumin attenuates peroxynitrite-induced neurotoxicity in spiral ganglion neurons.

The present study was designed to investigate the effect of curcumin on peroxynitrite (ONOO(-))-induced damage in rat spiral ganglion neurons (SGNs). The primary cultured rat SGNs were exposed to ONOO(-) with or without curcumin pretreatment. Cell viability was measured by MTT assay. Apoptosis was determined by Ho.33342 and propidium iodide (PI) double staining and flow cytometry. The cellular glutathione (GSH) content, superoxide dismutase (SOD) activity and malonaldehyde (MDA) levels were evaluated by spectrophotometer. The mRNA expressions of Apaf-1, Caspase-9, Caspase-3, Bcl-2, and Bax were examined by RT-PCR, while, the protein expressions of mitochondrial and cytosolic cytochrome c, Caspase-9, Caspase-3, Bcl-2 and Bax proteins were determined by Western blot respectively. The cell viability was markedly reduced, while, the apoptotic rate increased significantly after exposure of ONOO(-) (100μM) to SGNs. The activity of SOD and level of GSH were notably reduced, whereas, the MDA level was significantly increased. Pretreatment with curcumin protected SGNs against ONOO(-)-induced cell damage, declined the apoptotic rate, and improved the levels of SOD and GSH, decreased the elevation of MDA. ONOO(-) induced cytochrome c release from the mitochondria of SGNs and subsequently activated Caspase-9, Caspase-3 and cell apoptosis. Meanwhile, pretreatment with curcumin abrogated cytochrome c release, blocked activation of Caspase-3, and altered the expression of Bcl-2 family triggered by ONOO(-). Our data indicate that curcumin can attenuate ONOO(-)-induced damage in SGNs by the anti-oxidative activity as well as protect mitochondria from oxidative stress.

Regulation of chondrocyte differentiation by ADAMTS-12 metalloproteinase depends on its enzymatic activity

Abstract.ADAMTS-12, a metalloproteinase that belongs to ADAMTS family, is strongly upregulated during chondrogenesis and demonstrates prominent expression in the growth plate chondrocytes. ADAMTS-12 potently inhibits chondrocyte differentiation, as revealed by altered expression of both early and later genes critical for chondrogenesis. In addition, ADAMTS-12-mediated inhibition of chondrogenesis depends on its enzymatic activity, since its point mutant lacking enzymatic activity completely loses this activity. Furthermore, the C-terminal four thrombospondin motifs known to bind COMP substrate is necessary for its full proteolytic activity and inhibition of chondrocyte differentiation. Mechanism studies demonstrate that ADAMTS-12 induces PTHrP, whereas it inhibits IHH during chondrogenesis. Furthermore, PTHrP induces ADAMTS-12 and ADAMTS-12 is hardly detectable in PTHrP-/-growth plate chondrocytes. Importantly, knocking down ADAMTS-12 mRNA levels or blocking ADAMTS-12 activity almost abolishes the PTHrP-mediated inhibition of type X collagen expression. Collectively, these findings demonstrate that ADAMTS-12, a downstream molecule of PTHrP signaling, is a novel regulator of chondrogenesis.

Identification of a novel missense mutation in the WFS1 gene as a cause of autosomal dominant nonsyndromic sensorineural hearing loss in all‐frequencies

Hearing loss is the most common sensory disorder affecting 278 million people in the world, and more than 60% of hearing loss patients can be attributed to genetic causes. Although many loci have been linked to hereditary hearing impairment, most of the causative genes have not been identified as yet. The goal of this study was to investigate the cause of dominantly inherited sensorineural all‐frequency hearing loss in a six‐generation Chinese family. We performed exome sequencing to screen responsible candidate genes in three family members with all‐frequency hearing loss and one member with normal hearing. Sanger sequencing was employed to examine the variant mutations in the members of this family and 200 healthy persons. PCR‐RFLP was performed to further confirm the nucleotide mutation. A novel missense mutation c.2389G > A (GAC → AAC) in WFS1 gene was identified, which was co‐segregated with the hearing loss phenotype. No mutation was found in 200 controls and the family members with normal hearing in this site. The present study identifies, for the first time, a novel mutation in WFS1 gene that causes non‐syndromic hearing loss in all, rather than in low or high, frequencies.

The Three-Dimensional Culture System with Matrigel and Neurotrophic Factors Preserves the Structure and Function of Spiral Ganglion Neuron In Vitro

Whole organ culture of the spiral ganglion region is a resourceful model system facilitating manipulation and analysis of live sprial ganglion neurons (SGNs). Three-dimensional (3D) cultures have been demonstrated to have many biomedical applications, but the effect of 3D culture in maintaining the SGNs structure and function in explant culture remains uninvestigated. In this study, we used the matrigel to encapsulate the spiral ganglion region isolated from neonatal mice. First, we optimized the matrigel concentration for the 3D culture system and found the 3D culture system protected the SGNs against apoptosis, preserved the structure of spiral ganglion region, and promoted the sprouting and outgrowth of SGNs neurites. Next, we found the 3D culture system promoted growth cone growth as evidenced by a higher average number and a longer average length of filopodia and a larger growth cone area. 3D culture system also significantly elevated the synapse density of SGNs. Last, we found that the 3D culture system combined with neurotrophic factors had accumulated effects in promoting the neurites outgrowth compared with 3D culture or NFs treatment only groups. Together, we conclude that the 3D culture system preserves the structure and function of SGN in explant culture.

Otitis media in sperm-associated antigen 6 (Spag6)-deficient mice.

Mammalian SPAG6 protein is localized to the axoneme central apparatus, and it is required for normal flagella and cilia motility. Recent studies demonstrated that the protein also regulates ciliogenesis and cilia polarity in the epithelial cells of brain ventricles and trachea. Motile cilia are also present in the epithelial cells of the middle ear and Eustachian tubes, where the ciliary system participates in the movement of serous fluid and mucus in the middle ear. Cilia defects are associated with otitis media (OM), presumably due to an inability to efficiently transport fluid, mucus and particles including microorganisms. We investigated the potential role of SPAG6 in the middle ear and Eustachian tubes by studying mice with a targeted mutation in the Spag6 gene. SPAG6 is expressed in the ciliated cells of middle ear epithelial cells. The orientation of the ciliary basal feet was random in the middle ear epithelial cells of Spag6-deficient mice, and there was an associated disrupted localization of the planar cell polarity (PCP) protein, FZD6. These features are associated with disordered cilia orientation, confirmed by scanning electron microscopy, which leads to uncoordinated cilia beating. The Spag6 mutant mice were also prone to develop OM. However, there were no significant differences in bacterial populations, epithelial goblet cell density, mucin expression and Eustachian tube angle between the mutant and wild-type mice, suggesting that OM was due to accumulation of fluid and mucus secondary to the ciliary dysfunction. Our studies demonstrate a role for Spag6 in the pathogenesis of OM in mice, possibly through its role in the regulation of cilia/basal body polarity through the PCP-dependent mechanisms in the middle ear and Eustachian tubes.

The probable role of tumor stem cells for lymph node metastasis in supraglottic carcinoma.

Tumor stem cells (TSC), which are considered as likely candidates for the origin of cancer, are deduced to be responsible for tumor metastasis theoretically. We therefore investigated whether TSC were associated with lymph node metastasis in supraglottic carcinoma. Immunohistochemistry was performed for CD44, CD133, and LYVE-1 to detect TSC and lymphatic vessel density (LVD) in 66 primary supraglottic carcinoma tissue samples from 30 patients with lymph node metastasis (N+) and 36 patients without (N0). Reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot were used to detect the expression of CD44 and CD133 at mRNA and protein levels in N+ and N0 primary tumors. The LVD was 22.4 ± 10.26 in 30N+ and 6.8 ± 4.09 in 36N0 samples subjected to immunohistochemistry, which was associated with their clinical nodal stages. There were 43.33% CD44-positive and 93.33% CD133-positive samples in 30N+, and 13.89% CD44-positive and 44.44% CD133-positive samples in 36N0 (P < 0.05). However, in each positive slide, there were only 5∼10% CD44-positive cells, but 70∼85% CD133-possitive cells. The expressions of CD44 and CD133 of N+ obtained through RT-PCR and Western blot were significantly higher than those of N0. These results suggest that TSC identified through CD44-positive cells in N+ were significantly higher than those in N0, indicating that TSC may be responsible for lymph node metastasis. CD133, whose expression is not restricted to TSC, may be unspecific for TSC identification in hypostatic supraglottic carcinoma.

Novel compound heterozygous mutations in MYO7A gene associated with autosomal recessive sensorineural hearing loss in a Chinese family

OBJECTIVES Mutations in MYO7A gene have been reported to be associated with Usher Syndrome type 1B (USH1B) and nonsyndromic hearing loss (DFNB2, DFNA11). Most mutations in MYO7A gene caused USH1B, whereas only a few reported mutations led to DFNB2 and DFNA11. The current study was designed to investigate the mutations among a Chinese family with autosomal recessive hearing loss. METHODS In this study, we present the clinical, genetic and molecular characteristics of a Chinese family. Targeted capture of 127 known deafness genes and next-generation sequencing were employed to study the genetic causes of two siblings in the Chinese family. Sanger sequencing was employed to examine those variant mutations in the members of this family and other ethnicity-matched controls. RESULTS We identified the novel compound heterozygous mutant alleles of MYO7A gene: a novel missense mutation c.3671C>A (p.A1224D) and a reported insert mutation c.390_391insC (p.P131PfsX9). Variants were further confirmed by Sanger sequencing. These two compound heterozygous variants were co-segregated with autosomal recessive hearing loss phenotype. The gene mutation analysis and protein sequence alignment further supported that the novel compound heterozygous mutations were pathogenic. CONCLUSION The novel compound heterozygous mutations (c.3671C>A and c.390_391insC) in MYO7A gene identified in this study were responsible for the autosomal recessive sensorineural hearing loss of this Chinese family.

Apoptosis-Inducing Factor Is Involved in Gentamicin-Induced Vestibular Hair Cell Death

Aim: Vestibular hair cell loss in response to different stimuli may be attributable to the occurrence of apoptosis, in which apoptosis-inducing factor (AIF) is an important regulator mediating apoptotic process independent of caspases. This study was designed to investigate the possible involvement of AIF in gentamicin (GM)-induced vestibular hair cell death. Methods: Vestibular organs from postnatal day 3 or 4 rats were maintained in tissue culture and were exposed to 2 mg/ml GM for up to 72 h. Vestibular hair cell viability was quantified by MTT assay. Apoptosis was determined by flow cytometry. AIF activation was examined by RT-PCR. The expressions of the mitochondrial protein and cytoplasm protein of AIF were detected by Western blot. Results: GM could significantly inhibit the cell viability of vestibular hair cells in a dose- and time-dependent manner. The number of apoptotic cells treated with GM was higher than that of cells not treated with GM. RT-PCR showed upregulation of AIF mRNA under GM. Western blot showed that AIF from mitochondria was decreased, whereas AIF from cytoplasm was increased after GM exposure. Conclusions: AIF participates in GM-induced apoptosis of vestibular hair cells.

GJB2, SLC26A4, and mitochondrial DNA12S rRNA hot-spots in 156 subjects with non-syndromic hearing loss in Tengzhou, China

Abstract Conclusion: In this cohort of 156 non-syndromic hearing-impaired subjects of Tengzhou area, the most common deafness-associated genes GJB2, SLC26A4 and mtDNA 12S rRNA were investigated by SNPscan efficiently. GJB2 c.235delC and SLC26A4 c.IVS7-2A > G were the most common mutation sites. Objectives: Until now, there is no systematic gentic analysis in patients with non-syndromic hearing loss for Tengzhou area, so we evaluated the molecular etiology to investigate the hot-sports. Methods: Peripheral blood samples were obtained from 156 patients with severe-to-profound non-syndromic deafness in Tengzhou. The SNP scan assay technique was performed for a rapid multiplex genetic screening to detect the 115 mutations of the most common three genes. All results were statistically analyzed with SPSS software. Results: Among the 156 analyzed patients, 60 patients were demonstrated with deafness genes, accounting for 38.46% (60/156), including GJB2 (22.44%, 35/156), SLC26A4 (13.66%, 22/156), and mtDNA 12S rRNA (2.56%, 4/156). In this study, we confirmed 23 deafness-causing mutations and 27 different allelic combinations including GJB2 (eight variants, 11 allelic combinations), SLC26A4 (13 variants, 16 allelic combinations) and mtDNA 12S rRNA (two variants). The occurrence rates of these deafness-causing mutations GJB2 c.235delC and SLC26A4 c.IVS7-2A > G were significantly higher than other mutation sites (p < 0.01).

Mutation Analysis of the Common Deafness Genes in Patients with Nonsyndromic Hearing Loss in Linyi by SNPscan Assay

Hearing loss is a common sensory disorder, and at least 50% of cases are due to a genetic etiology. Although hundreds of genes have been reported to be associated with nonsyndromic hearing loss, GJB2, SLC26A4, and mtDNA12SrRNA are the major contributors. However, the mutation spectrum of these common deafness genes varies among different ethnic groups. The present work summarized mutations in these three genes and their prevalence in 339 patients with nonsyndromic hearing loss at three different special education schools and one childrens hospital in Linyi, China. A new multiplex genetic screening system “SNPscan assay” was employed to detect a total of 115 mutations of the above three genes. Finally, 48.67% of the patients were identified with hereditary hearing loss caused by mutations in GJB2, SLC26A4, and mtDNA12SrRNA. The carrying rate of mutations in the three genes was 37.76%, 19.75%, and 4.72%, respectively. This mutation profile in our study is distinct from other parts of China, with high mutation rate of GJB2 suggesting a unique mutation spectrum in this area.