Study of tree shrew biology and models: A booming and prosperous field for biomedical research.

The tree shrew ( Tupaia belangeri) has long been proposed as a suitable alternative to non-human primates (NHPs) in biomedical and laboratory research due to its close evolutionary relationship with primates. In recent years, significant advances have facilitated tree shrew studies, including the determination of the tree shrew genome, genetic manipulation using spermatogonial stem cells, viral vector-mediated gene delivery, and mapping of the tree shrew brain atlas. However, the limited availability of tree shrews globally remains a substantial challenge in the field. Additionally, determining the key questions best answered using tree shrews constitutes another difficulty. Tree shrew models have historically been used to study hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, myopia, and psychosocial stress-induced depression, with more recent studies focusing on developing animal models for infectious and neurodegenerative diseases. Despite these efforts, the impact of tree shrew models has not yet matched that of rodent or NHP models in biomedical research. This review summarizes the prominent advancements in tree shrew research and reflects on the key biological questions addressed using this model. We emphasize that intensive dedication and robust international collaboration are essential for achieving breakthroughs in tree shrew studies. The use of tree shrews as a unique resource is expected to gain considerable attention with the application of advanced techniques and the development of viable animal models, meeting the increasing demands of life science and biomedical research.

Mycobacterium vaccae attenuates airway inflammation by inhibiting autophagy and activating PI3K/Akt signaling pathway in OVA-induced allergic airway inflammation mouse model.

PURPOSE: The etiology of asthma remains elusive, with no known cure. Based on accumulating evidence, autophagy, a self-degradation process that maintains cellular metabolism and homeostasis, participates in the development of asthma. Mycobacterium vaccae vaccine (M. vaccae), an immunomodulatory agent, has previously been shown to effectively alleviate airway inflammation and airway remodeling. However, its therapeutic effect on asthma via the regulation of autophagy remains unknown. Therefore, this study aimed to investigate the impact of M. vaccae in attenuating asthma airway inflammation via autophagy-mediated pathways. METHODS: Balb/c mice were used to generate an ovalbumin (OVA)-immunized allergic airway model and were subsequently administered either M. vaccae or M. vaccae + rapamycin (an autophagy activator) prior to each challenge. Next, airway inflammation, mucus secretion, and airway remodeling in mouse lung tissue were assessed via histological analyses. Lastly, the expression level of autophagy proteins LC3B, Beclin1, p62, and autolysosome was determined both in vivo and in vitro, along with the expression level of p-PI3K, PI3K, p-Akt, and Akt in mouse lung tissue. RESULTS: The findings indicated that aerosol inhalation of M. vaccae in an asthma mouse model has the potential to decrease eosinophil counts, alleviate airway inflammation, mucus secretion, and airway remodeling through the inhibition of autophagy. Likewise, M. vaccae could reduce the levels of OVA-specific lgE, IL-5, IL-13, and TNF-α in asthma mouse models by inhibiting autophagy. Furthermore, this study revealed that M. vaccae also suppressed autophagy in IL-13-stimulated BEAS-2B cells. Moreover, M. vaccae may activate the PI3K/Akt signaling pathway in the lung tissue of asthmatic mice. CONCLUSION: In summary, the present study suggests that M. vaccae may contribute to alleviating airway inflammation and remodeling in allergic asthma by potentially modulating autophagy and the PI3K/Akt signaling pathway. These discoveries offer a promising avenue for the development of therapeutic interventions targeting allergic airway inflammation.

Mycobacterium vaccae alleviates allergic airway inflammation and airway hyper-responsiveness in asthmatic mice by altering intestinal microbiota.

Host immunity can influence the composition of the gut microbiota and consequently affect disease progression. Previously, we reported that a Mycobacterium vaccae vaccine could ameliorate allergic inflammation in asthmatic mice by regulating inflammatory immune processes. Here, we investigated the anti-inflammatory effects of M. vaccae on allergic asthma via gut microbiota modulation. An ovalbumin (OVA)-induced asthmatic murine model was established and treated with M. vaccae. Gut microbiota profiles were determined in 18 BALB/c mice using 16S rDNA gene sequencing and metabolomic profiling was performed using liquid chromatography quadrupole time-of-flight mass spectrometry. Mycobacterium vaccae alleviated airway hyper-reactivity and inflammatory infiltration in mice with OVA-induced allergic asthma. The microbiota of asthmatic mice is disrupted and that this can be reversed with M. vaccae. Additionally, a total of 24 differential metabolites were screened, and the abundance of PI(14:1(9Z)/18:0), a glycerophospholipid, was found to be correlated with macrophage numbers (r = 0.52, p = 0.039). These metabolites may affect chemokine (such as macrophage chemoattractant protein-1) concentrations in the serum, and ultimately affect pulmonary macrophage recruitment. Our data demonstrated that M. vaccae might alleviate airway inflammation and hyper-responsiveness in asthmatic mice by reversing imbalances in gut microbiota. These novel mechanistic insights are expected to pave the way for novel asthma therapeutic strategies.

Dosage selection and effect evaluation of sodium pentobarbital in tree shrew anesthesia.

To achieve surgical anesthesia in animal experimentation, it is important to select the appropriate anesthetic dose. However, few studies have investigated the reasonable anesthetic dose in tree shrew (Tupaia belangeri). The aim of the study was to review the literature to determine the most commonly used anesthetic dose in tree shrew and to calculate the reasonable equivalent dose between tree shrew and rat based on the body surface area conversion. Two groups of 10 adult tree shrews each were anesthetized with 1% sodium pentobarbital through intraperitoneal injection separately at doses of 62 mg/kg (equivalent dose) and 40 mg/kg (reported dose). Anesthetic depth and times were assessed in addition to vital signs. The results showed that the dosage was quite different across studies, ranging from 15 mg/kg to 80 mg/kg, with 40 mg/kg being the most frequently reported dose. However, the group of tree shrews anesthetized with the commonly reported dose were unable to meet the requirements of surgery. In contrast, the equivalent dose (62 mg/kg, intraperitoneal injection with sodium pentobarbital) calculated by body surface area conversion could achieve an anesthetic time of 44.28 ± 3.95 min with no serious or fatal effects. During anesthetic monitoring, we found that sodium pentobarbital had an inhibitory effect on the blood pressure, pulse rate, respiratory rate and rectal temperature in tree shrews, especially on the respiratory rate. Thus, our study indicated that the use of the equivalent dose of sodium pentobarbital was effective in anesthetizing tree shrews.

Body surface area-based equivalent dose calculation in tree shrew.

Tree shrew (Tupaia belangeri) is a promising experimental animal in biomedical research, but the equivalent doses of drugs between tree shrew and human and other animals has not been explored, which hinders its further application in a wider scope. The main objective of this article is to provide a method of equivalent dose conversion between tree shrews and other species based on body surface area (BSA). BSA of tree shrews were measured by Image J software, and then the average Km value of tree shrews was figured out based on the body weights and BSA, then the conversion coefficients of equivalent dose among tree shrew and other species of experimental animals were calculated based known data. The Km value of tree shrews was 0.105 ± 0.001. Through BSA conversion, the equivalent dose for tree shrews (D-ts) relative to rats was obtained by formula: D-ts = 1.36 × D-a (rats weighing 200g as example), and the error was less than 10% when the BW of the tree shrew was 0.09 kg-0.15 kg. The coefficients of equivalent dose transferring from tree shrews to human and other species were calculated in article. These parameters could be used to determine a suitable dosing strategy for tree shrew studies.

Plasma volume, cell volume, total blood volume and F factor in the tree shrew.

In this study, the physiological values of volumes of plasma, cells, total blood and the F blood factors were identified in 24 adult tree shrews (Tupaia belangeri; 12 male and 12 female; average BW of 123.9±19.19 g). The two-compartment model method of Evans Blue dye was used to obtain the plasma volume and the venous hematocrit was measured by microhematocrit method. To establish the relationship between body weight (BW) and blood volume of tree shrews, We performed linear fitting for these two datasets. Results were analyzed according to gender and weight (<120g vs.>120g). Statistical significance was assessed using the unpaired student t test and one-way ANOVA. The average volumes per 100g body weight of plasma, red blood cell (RBC) and total blood were 5.42±0.543, 3.24±0.445, and 8.66±0.680ml respectively. The mean body hematocrit, cardiac hematocrit, jugular vein hematocrit, femoral vein hematocrit, and tail vein hematocrit was 37.43±4.096, 39.72±3.219, 43.04±4.717, 40.84±3.041, and 38.71±3.442% respectively. The F cardiac was 0.94±0.072, F jugular vein 0.88±0.118, F femoral vein 0.92±0.111, and the F tail vein 0.97±0.117. Blood volume (ml) was 85.89103×BW (kg). This is the first study to provide the parameters of plasma volume, cell volume, total blood volume and F factor and a baseline for future research on blood physiology of tree shrews.

Preoperative evaluation of cochlear implantation through the round window membrane in the facial recess using high-resolution computed tomography.

PURPOSE: We evaluated the risk of cochlear implantation through the round window membrane in the facial recess through a preoperative analysis of the angle between the facial nerve-round window and the cranial midline using high-resolution temporal bone CT. METHODS: Temporal bone CT films of 176 patients with profound sensorineural hearing loss at our hospital from 2013 to 2015 were reviewed. The preoperative temporal bone CT scans of the patients were retrospectively analysed. The vertical distance (d value) from the leading edge of the facial nerve to the posterior wall of the external auditory canal and the angle (α value) between the line from the leading edge of the facial nerve to the midpoint of the round window membrane and the median sagittal line on the round window membrane plane were measured. Based on intraoperative observation, the round window membrane was divided into complete round window membrane exposure (group A), partial exposure (group B), and unexposed (group C) groups, and statistical analysis was performed. RESULTS: The α value could be effectively measured for all 176 patients (62.60 ± 7.12), and the d value could be effectively measured for 95 cases (5.53 ± 1.00). An analysis of the correlation between the α and d values of these 95 cases found a negative correlation. Of the 176 cases, one-way analysis of variance (ANOVA) showed that the differences among the groups were significant [P = 0.000 (< 0.05)]. CONCLUSION: The angle (α value) between the line connecting the leading edge of the facial nerve to the midpoint of the round window and the median sagittal line measured in preoperative CT scans was associated with the difficulty of intraoperatively exposing the round window membrane. When the α value was larger than a certain degree, the difficulty of exposing the round window membrane was increased. In such cases, the surgeon should fully expose the round window membrane during surgery, which could result decrease the likelihood of complications.

Effect of Y6, an epigallocatechin gallate derivative, on reversing doxorubicin drug resistance in human hepatocellular carcinoma cells.

Cancer cells can acquire resistance to a wide variety of diverse and unrelated drugs, this phenomenon is termed multidrug resistance (MDR). Multidrug resistance has been an obstacle to the success of cancer chemotherapy. The present study investigated the reversal effect of Y6, a new compound obtained by chemically modifying the structure of epigallocatechin-3-gallate (EGCG) extracted from green tea. Y6 was proven to be effective in inhibiting cell proliferation and reversing drug resistance in doxorubicin (DOX) resistant human hepatocellular carcinoma cells (BEL-7404/DOX). BEL-7404/DOX cells were treated with either doxorubicin combination regimen (doxorubicin plus Y6 or epigallocatechin-3-gallate or verapamil separately) or doxorubicin alone. The results showed that cell proliferation was inhibited and late cell apoptosis increased in the combination treatment group, especially in the group treated with doxorubicin plus Y6. Further analysis revealed that the expressions of hypoxia-inducible factor-1α and multidrug resistance 1/P-glycoprotein decreased at both messenger RNA and protein levels by treatments with combined drugs compared to doxorubicin alone. Our results indicated that Y6, as a drug resistance reversal agent, increased the sensitivity of drug resistant cells to doxorubicin. The mechanisms of actions of Y6 in reversal effect were associated with the decreased expression of hypoxia-inducible factor-1α and multidrug resistance 1/P-glycoprotein.

The diagnostic value of measurement of cochlear length and height in temporal bone CT multiplanar reconstruction of inner ear malformation.

CONCLUSION: The cochlear length (CL) and cochlear height (CH) measured through MPR will provide for more accurate quantitative diagnosis of inner ear malformation, and are subsequently convenient for calculating cochlear duct length (CDL) before cochear implant. OBJECTIVES: Qualitative and quantitative diagnosis of inner ear malformation in deaf patients through multiplanar reconstruction (MPR) was performed to provide a reference for cochlear implants. METHODS: One hundred and two cases without sensorineural deafness and 560 patients with sensorineural deafness had MPR of temporal bone computed tomography performed to obtain the standardized cochlear-view and oblique coronal-view images. The inner ear radial lines were measured to formulate normal values for inner ear malformation diagnosing, and the CDL was estimated based on CL. RESULTS: The normal range values of inner ear radial lines were measured and formulated, of which CL was 8.1-9.59 mm and CH was 3.28-3.90 mm. According to inner ear morphology and the normal values measured above, 61 cases of incomplete partition-type II (IP-II) and a high percentage (27/110, 24.5%) of hypoplasia of cochlea (HC) were diagnosed. The HC group was further divided into 1-turn, 1.5-turn, and 2-turn sub-groups, which had CDL of 15.98 ± 1.48 mm, 21.36 ± 0.96 mm, and 26.56 ± 0.60 mm, respectively.

Electrophysiological change in the tensor veli palatini muscle after radiotherapy.

CONCLUSION: Electromyography of the tensor veli palatine (TVP) was abnormal and showed mainly myogenic impairment in patients with nasopharyngeal carcinoma (NPC) with secretory otitis media (SOM) after radiotherapy. The diseased ears showed impairment in opening functions of the eustachian tubes (ETs). OBJECTIVES: To characterize electrophysiology of the TVP muscle using electromyography (EMG) in patients with SOM after radiotherapy of NPC. METHODS: Twenty healthy volunteers and 20 patients with NPC and SOM after radiotherapy were chosen for assessment of EMG of the TVP during swallowing. RESULTS: The measurements of average duration and amplitude of action potential, swallowing contraction duration, and peak voltage in NPC patients with both SOM (n = 25) and healthy ears (n = 6) were significantly lower than those of ears (n = 38) in healthy controls (p < 0.01). In patients with NPC, the average action potential duration and swallowing contraction duration in ears with SOM were lower than those of subjects with healthy ears (p < 0.05), whereas no significant difference was found in average amplitude of action potential and peak voltage between them.

Role of microRNA-21 in regulating 3T3-L1 adipocyte differentiation and adiponectin expression.

MicroRNAs are endogenous small RNAs with a high degree of conservation, participating in a variety of vital activities. In present study, to explore the effect of microRNAs on 3T3-L1 adipocyte differentiation and adiponectin expression, the adipo-related microRNAs were screened and identified by micorRNA microarray. The highly expression plasmid of microRNA-21 with obvious expression up-regulation (miR-21) and its anti-sense (miR-21 inhibitor) were constructed and transfected into 3T3-L1 preadipocytes. The effect of miR-21 on 3T3-L1 adipocyte differentiation was observed, and the protein and mRNA expression level of adiponectin and AP-1 were analyzed. Results showed that, the expression profiles of microRNAs significantly changed during 3T3-L1 adipocyte differentiation. The expression of miR-21 was obviously up-regulated. miR-21 could significantly promote adipocyte differentiation, increase adiponectin mRNA and protein expression, while decrease AP-1 protein level. Meanwhil, miR-21 inhibitor blocked the effects of miR-21 mentioned above. The overexpression of AP-1 could absolutely reverse the stimulatory effect of miR-21 on adiponectin. miR-21 plays an important role in regulating adipocyte differentiation and adiponectin expression by inhibiting AP-1 expression.

[Research on the effect of biyan qingdu granula drug-containing serum on inhibition of nasopharyngeal carcinoma cells growth in vitro].

OBJECTIVE: To investigate the effect of Biyan Qingdu Granula drug-containing serum (BQG-DS) on cell growth and apoptosis in nasopharyngeal carcinoma cell lines CNE1, CNE2, TWO3, C666-1, and explore the antineoplastic mechanism of Biyan Qingdu Granula. METHODS: SD rats were randomly divided into three groups: experimental (Biyan Qingdu Granula) group, positive control (cytoxan) group and negative control group. After administration of drug, the serum was collected from the treated animals. MTT assay was used to examine the effect of BQG-DS on the proliferation of CNE1, CNE2, TWO3, C666-1 cell, and flow cytometry was used to observe the cell cycle distribution. Apoptosis of CNE1, CNE2, TWO3, C666-1 cell was further investigated by inverted microscope. RESULTS: BQG-DS inhibited the proliferation of CNE1, CNE2, TWO3, C666-1 cell and the effects were in a time-and concentration-dependent manner. BQG-DS could also induce apoptosis while the G1 phase was arrested. CONCLUSION: BQG-DS inhibits proliferation of nasopharyngeal carcinoma cells via induction of apoptosis and arrest of cell cycle.

[Inner ear morphological study of guinea pigs with acoustically evoked short latency negative response].

OBJECTIVE: To establish a model of ototoxicity in guinea pigs with acoustically evoked short latency negative response (ASNR) and verify the responsible organ of ASNR based on microscopic characteristics of basal membranes, saccules, utricles and ampulla canalis semicircularis of the inner ear. METHODS: Total of 45 guinea pigs were employed in the experiment, which were randomly divided into the control group (15 subjects, 30 ears) and the deafened group (30 subjects, 60 ears). Each animal experienced auditory brainstem response (ABR). A quick treatment was employed for deafened group consisting of a subcutaneous injection of kanamycin at a dose of 400 mg/kg followed by jugular vein injection of ethacrynic acid at a dose of 40 mg/kg one hour later. The animals were performed ABR test from 7 to 10 days after the drug administration. The deafened group was further divided into ASNR group and non-ASNR group based on the presence of ASNR. All the guinea pigs were sacrificed after ABR tests. The Corti organ, macula sacculi, macula utriculi and crista ampullaris were observed by light microscope. RESULTS: In the deafened group (60 ears), 3 subjects died postoperatively, 27 subjects (54 ears) provided full data. ASNR was elicited in 19 ears (35.2%, 19/54), the thresholds of ASNR were from 110 to 125 dBSPL with average of (121.7 ± 4.5) dBSPL. ASNR latency ranges were 1.80 - 2.08 ms, the average latency of thresholds were (1.93 ± 0.07) ms. The stretched preparation results: overall hair-cell density of macula saccule, macula utriculi and crista ampullaris decreased in order of normal control group, ASNR group and non-ASNR group. There was no difference between the normal group and ASNR group for cell density of macula saccule. Apart from this, statistical differences were found among other groups. CONCLUSIONS: The present study evoked ASNR in an ototoxicity guinea pig model which was profound hearing loss with normal saccular function and normal saccular hair cell density. It suggested that ASNR originates from the saccule and have no relation with cochlear, utricle and semicircular canal according to morphological study.

[Protective effects of N-acetylcysteine on cochlear damage occur in guinea pigs exposed to irradiation].

OBJECTIVE: To explore the protective effects of N-acetylcysteine (NAC) on cochlear damage occurring in irradiated guinea pigs. METHODS: Seventy-two guinea pigs were randomly divided into 4 groups (n = 18 each). Control group received neither NAC nor irradiation, irradiation group received total cranium irradiation of 70 Gy, irradiation & saline group cranium irradiation of 70 Gy and saline solution through a round window and NAC group cranium irradiation of 70 Gy and NAC through a round window. The right ear received radiation. The animals were sacrificed at Day 14 post-irradiation. The specimens were dehydrated, embeded in paraffin and serially cut into 5-µm slices. Sections were stained with immunohistochemistry and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL). The cochlear basal membranes were observed for malondialdehyde (MDA) and superoxide dismutase (SOD) with scanning electron microscope. RESULTS: The cilium of hair cells had no clear loss and apoptotic number of spiral ganglion cells decreased in NAC group. The average optical density value of Caspase 3 in spiral ganglion in NAC group significantly decreased versus the irradiation group (0.08 ± 0.02 vs 0.10 ± 0.01, P < 0.01). The level of MDA of NAC group also decreased versus the irradiation group (0.33 ± 0.05 vs 0.84 ± 0.13, P < 0.05). The level of SOD in the NAC group increased versus the irradiation group (10.7 ± 3.0 vs 8.7 ± 1.3, P < 0.05). The ratio of apoptotic cell in SGC in the NAC group at Day 14 (7.8% ± 1.8%) decreased versus the irradiation group (32.0% ± 8.7%) at Day 14. CONCLUSION: MDA and SOD may be involved in the pathogenesis of cochlear cell damage. And NAC protects the irradiated cochlear cell.

[Analysis of sniffing test in otitis media with effusion].

OBJECTIVE: To explore the roles of the closure disorder of Eustachian tube in occurrence and development of otitis media with effusion (OME). METHODS: Fifty-six adults with OME, 16 children with OME, 66 health adults and 20 health children were selected according to diagnosis criteria. Sniffing test was measured by Tubo-tymanoaerodynamic graphy and the self-designed questionnaires were surveyed in all cases. RESULTS: The positive levels in sniffing test were regarded as external auditory canal press 10dapa lower than baseline of the pressure. The positive rate was 64.86% in adults with OME, which was higher than health adults (P < 0.01). The positive rate was 70.83% in children with OME which was higher than health children (P < 0.05). CONCLUSIONS: The higher positive rate of sniff test in OME patients suggests that closure disorder in Eustachian tube playing an important role in the occurrence and development of OME.

[Reversal effect of matrine on drug resistance of human nasopharyngeal carcinoma cell line].

OBJECTIVE: To study the reversal effect of matrine and its derivatives on drug resistance of human nasopharyngeal carcinoma cell line HONE1/DDP. METHODS: The drug-resistant cell line was established by the human nasopharyngeal carcinoma cells HONE1 with gradually increasing concentration of cisplatin. The matrine and its derivatives were added into the HONE1/DDP according to different concentrations to measure their cytotoxicity. MTT assay was used to measure the reversal effect on the drug resistance of the non-toxic doses of matrine and its derivatives. Cell cycle was measured by flow cytomety. The expression level of MRP1, BAX, BCL-2 was assayed by Western blot. RESULTS: HONE1/DDP indicated drug resistantance. When the non-toxic doses of matrine and its derivatives were used to HONE1/DDP with 24h, the resistance of HONE1/DDP was down-regulated, the reversal fold was 1.45 and 1.77. The cell number of G0/G1-phase increased in matrine group while S phase decreased in matrine derivatives group compared with HONE1/DDP. Compared with HONE1/DDP group, the MRP1 expression levels in HONE1 cells were reduced (P < 0.05), and Matrine group and matrine derivatives group were enhanced (P < 0.05). The expression of BAX was lower while the expression of BCL-2 was higher. CONCLUSION: The resistance of HONE1 cells to DDP is able to increase the expression of MRP1; Matrine and its derivatives can reverse the drug resistance of HONE1/DDP to DDP, its activity may be related to change cell cycle distribution, the inhibition of MRP1 expression and down-regulation of BAX/BCL-2.

[Clinical analyses of sudden sensorineural hearing loss in 14 nasopharyngeal carcinomas following radiotherapy].

OBJECTIVE: To investigate the clinical characteristics and effects of sudden sensorineural hearing loss in nasopharyngeal carcinoma (NPC) following radiotherapy. METHODS: The clinical characteristics and effects in 14 NPC patients (15 ears) with sudden sensorineural hearing loss following radiotherapy were retrospectively analyzed. RESULTS: The sudden sensorineural hearing loss happened more in male subjects than female subjects and more in the left ear than the right ear. Its occurrence time was averaged 6.6 years following radiotherapy. Most of the patients suffered hearing loss prior to the sudden sensorineural hearing loss. The 250, 500, 1000, 2000, 4000 Hz average hearing thresholds: sudden hearing loss ears (78.5 ± 24.7) dBHL, none-sudden hearing loss ears (57.0 ± 32.4) dBHL, among which, 73.33% (11/15) for sensorineural hearing loss, 26.67% (4/15) for mixed hearing loss. 12 cases had complications following radiotherapy. At least one case had posterior circulation barrier. The total effective rate was 26.67% (4/15) and four cases had relapsed and in vain thereafter. CONCLUSIONS: In NPC patients who received radiotherapy, it caused more serious sudden sensorineural hearing loss and the treatment effects were poor and hearing loss was susceptible to relapse. The pathogenesis may be related to the radiation caused posterior circulation disorders.

[Origin of acoustically evoked short latency negative response in guinea pigs].

OBJECTIVE: To establish a model of acoustically evoked short latency negative response (ASNR) in guinea pigs, a model of profound hearing loss with normal saccular functions, and verify the correlation between ASNR and vestibular evoked myogenic potential (VEMP). METHODS: Thirty-two healthy guinea pigs were employed in the experiment, which were randomly divided into control group (16 subjects) and deafened group (16 subjects). Each animal experienced auditory and vestibular tests including auditory brainstem response (ABR), VEMP and caloric test. A quick treatment was employed for deafened group consisting of a subcutaneous injection of kanamycin at a dose of 400 mg/kg followed by a jugular vein injection of ethacrynic acid at a dose of 40 mg/kg one hour later. The animals were received ABR, VEMP and caloric test 7 - 10 days following the drug administration. The deafened group was further divided into ASNR group and non-ASNR group, based on the presence of ASNR. RESULTS: In deafened group, five subjects died postoperatively, 11 subjects (22 ears) provided full data, ASNR was elicited in eight ears (36.4%), the threshold was 120 - 130 dB SPL with mean of (124.4 ± 4.96) dB SPL. Its latency range was 1.75 - 2.60 ms with mean of (2.15 ± 0.27) ms. The mean latency of threshold was (2.34 ± 0.18) ms. All eight ASNR ears presented with VEMP. The VEMP threshold, positive and negative potential latencies proved no statistical difference (P > 0.05) between ASNR group and control group. Significant difference was detected between the VEMP presence of ASNR group and non-ASNR group (P = 0.002). There was no statistically significant correlation between VEMP and caloric test neither between ASNR and caloric test in deafened group. CONCLUSIONS: This study evoked ASNR in an ototoxicity guinea pig model which has profound hearing loss with normal saccular functions. The presence of ASNR correlated with VEMP, however, not correlated with caloric test, suggesting that ASNR and VEMP are both originated from the saccule.

Salicylate initiates apoptosis in the spiral ganglion neuron of guinea pig cochlea by activating caspase-3.

Salicylate-induced ototoxicity leading to sensorineural hearing loss (SNHL) and tinnitus is well documented. However, the exact mechanisms are poorly defined. Caspase-3 is a member of the class of effector caspases and has been activated in nearly every model of apoptosis. To examine its role in salicylate-induced injury, we subjected guinea pigs to treatment with a specific inhibitor zDEVD-FMK via the round window niche (RWN) followed by a systemic injection of salicylate at a dose of 200 mg · kg(-1) · d(-1) i.p. for 10 consecutive days. For those animals administered with salicylate, immunohistochemical studies revealed that caspase-3 was activated in the spiral ganglion neurons (SGNs) and method of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) to identify neuronal apoptosis showed that fragmented nuclei were distributed in Rosenthal's canal. Topical administration of the zDEVD-FMK at a concentration of 500 mM blocked caspase-3 activation and had an effect in reducing the number of TUNEL-positive auditory neurons. In contrast, the inhibitor at a concentration of 125 or 250 mM caused no variation in the expression of activated caspase-3, or in the ratio of TUNEL-positive neurons. These results indicate that caspase-3 is a crucial mediator of apoptosis induced by salicylate in the primary auditory neuron in vivo, and suggest that the specific inhibitor at a relatively high concentration may be therapeutically beneficial in salicylate-induced apoptosis.

Blocking caspase-3-dependent pathway preserves hair cells from salicylate-induced apoptosis in the guinea pig cochlea.

In the present study, we aim to explore whether the caspase-3-dependent pathway is involved in the apoptotic cell death that occurs in the hair cells (HCs) of guinea pig cochlea following a salicylate treatment. Guinea pigs received sodium salicylate (Na-SA), at a dose of 200 mg·kg(-1)·d(-1) i.p., as a vehicle for 5 consecutive days. In some experiments, N-benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethylketone (zDEVD-FMK), a specific apoptosis inhibitor, was directly applied into the cochlea via the round window niche (RWN) prior to salicylate treatment for determination of caspase-3 activation. Alterations in auditory function were evaluated with auditory brainstem responses (ABR) thresholds. Caspase-3 activity was determined by measuring the proteolytic cleavage product of caspase-3 (N-terminated peptide substrate). DNA fragmentation within the nuclei was examined with a terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) method. Ultrastructure variation in the target cell was assessed by electron microscopy (EM). Salicylate treatment initiated an obvious elevation in ABR thresholds with a maximum average shift of 60 dB sound pressure level (SPL), and caused significant apoptosis in both inner (IHCs) and outer (OHCs) hair cells resulted from an evident increasing in immunoreactivity to caspase-3 protease. Transmission electron microscopy (TEM) displayed chromatin condensation and nucleus margination accompanied by cell body shrinkage in the OHCs, but not in the IHCs. Scanning electron microscopy (SEM) showed breakdown, fusion, and loss in the stereociliary bundles at the apex of OHCs rather than IHCs. zDEVD-FMK pretreatment prior to salicylate injection substantially attenuated an expression of the apoptotic protease and protected HCs against apoptotic death, followed by a moderate relief in the thresholds of ABR, an alleviation in the submicroscopic structure was also identified. In particular, disorientation and insertion in the hair bundles at the apex of OHCs was exhibited though no classic apoptotic change found. The above changes were either prevented or significantly attenuated by zDEVD-FMK. These findings indicate that salicylate could damage cochlear hair cells via inducing apoptosis associated with caspase-3 activation.