Noise-induced Hearing Loss Patients Research Articles

Investigating white matter changes in auditory cortex and association fibres related to speech processing in noise-induced hearing loss: a diffusion tensor imaging study

BackgroundThis study explores the impact of noise-induced hearing loss (NIHL) on the microstructural integrity of white matter tracts in the brain, focusing on areas involved in speech processing. While the primary impact of hearing loss occurs in the inner ear, these changes can extend to the central auditory pathways and have broader effects on brain function. Our research aimed to uncover the neural mechanisms underlying hearing loss-related deficits in speech perception and cognition among NIHL patients.MethodsThe study included two groups: nine bilateral NIHL patients and nine individuals with normal hearing. Advanced diffusion tensor imaging techniques were employed to assess changes in the white matter tracts. Regions of interest (ROIs), including the auditory cortex, cingulum, arcuate fasciculus, and longitudinal fasciculus, were examined. Fractional anisotropy (FA) values from these ROIs were extracted for analysis.ResultsOur findings indicated significant reductions in FA values in NIHL patients, particularly in the left cingulum, right cingulum, and left inferior longitudinal fasciculus. Notably, no significant changes were observed in the auditory cortex, arcuate fasciculus, superior longitudinal fasciculus, middle longitudinal fasciculus, and right inferior longitudinal fasciculus, suggesting differential impacts of NIHL on various white matter tracts.ConclusionsThe study's findings highlight the importance of considering association fibres related to speech processing in treating NIHL, as the broader neural network beyond primary auditory structures is significantly impacted. This research contributes to understanding the neurological impact of NIHL and underscores the need for comprehensive approaches in addressing this condition.

Alterations of resting-state functional network connectivity in patients with noise-induced hearing loss: A study based on independent component analysis.

Functional reorganization is a response to auditory deficits or deprivation, and less is known about the overall brain network alterations involving resting-state networks (RSNs) and multiple functional networks in patients with occupational noise-induced hearing loss (NIHL). So this study evaluated resting-state functional network connectivity (FNC) alterations in occupational NIHL using an independent component analysis (ICA). In total, 79 mild NIHL patients (MP), 32 relatively severe NIHL patients (RSP), and 84 age- and education- matched healthy controls (HC) were recruited. All subjects were tested using the Mini-mental State Examination scale, the tinnitus Handicap Inventory scale, the Hamilton Anxiety scale (HAMA) and scanned by T1-3DFSPGR, resting-state functional magnetic resonance imaging sequence in 3.0 T and analysed by the ICA. Seven RSNs were identified, compared with the HC, the MP showed increased FNC within the executive control network (ECN) and enhanced FNC within the default mode network (DMN) and the visual network (VN); compared with the HC, the RSP showed decreased FNC within the ECN and auditory network (AUN), DMN and VN; no significant changes in FNC were found in the MP compared with the RSP. Furthermore, the correlation analysis between the noise exposure time and hearing loss level, HAMA were both negative, and there were no significant correlations between the abnormal RSNs and the hearing level, noise exposure time and HAMA. These findings indicate that different degrees of NIHL involve different alterations in RSNs connectivity and may reveal the neural mechanisms related to emotion-related features and functional abnormalities following long-term NIHL.

Comparative transcriptome profiling reveals RNA splicing alterations and biological function in patients exposed to occupational noise.

Genetic factors play an important role in susceptibility to noise-induced hearing loss (NIHL). Alternative splicing (AS) is an essential mechanism affecting gene expression associated with disease pathogenesis at the post-transcriptional level, but has rarely been studied in NIHL. To explore the role of AS in the development of NIHL, we performed a comprehensive analysis of RNA splicing alterations by comparing the RNA-seq data from blood samples from NIHL patients and subjects with normal hearing who were exposed to the same noise environment. A total of 356 differentially expressed genes, including 23 transcription factors, were identified between the two groups. Of particular note was the identification of 56 aberrant alternative splicing events generated by 41 differentially expressed genes between the two groups, with exon skipping events accounting for 54% of all the differentially alternative splicing (DAS) events. The results of functional enrichment analysis showed that these intersecting DAS genes and differentially expressed genes were significantly enriched in autophagy and mitochondria-related pathways. Together, our findings provide insights into the role of AS events in susceptibility and pathogenesis of NIHL.

Analysis of polymorphic loci of candidate genes in patients with occupational diseases

Introduction. Development and progress features of vibration syndrome (VS) and noise-induced hearing loss (NIHL) are determined by genetic factors to a certain extent. The latter define the relevance of the search for individual approaches to prevention and medical support of patients with these occupational diseases.
 The aim of the study was to investigate the genotypes distribution of polymorphic loci of candidate genes in patients with occupational diseases caused by vibration and noise impact.
 Materials and methods. Polymorphic variants of the HSPA1B (rs1061581), IL17A (rs2275913), IL10 (rs1800872), and TNF-α (rs1800629) genes of three hundred ninety eight males were studied using PCR-RFLP and real-time PCR methods, including 268 patients with VS divided into two groups: VShtv (n = 117) and VScomb (n = 151), in which VS was caused by exposure to hand-transmitted vibration (HTV) or combined exposure to HTV and whole-body vibration (COMB), respectively. The study also involved 96 patients with occupational NIHL diagnosis and 34 individuals of the comparison group without occupational contact with physical factors.
 Results. The increase in GG-HSPA1B (1267A/G) genotype frequency (p=0.058) was found in VScomb patients compared with those from the VShtv group. There was a significant difference in carriers of the C/C genotype of the IL10 (rs1800872) polymorphic locus in the group of NIHL patients relative to the comparison group (p=0.036). The results of regression analysis indicate the carriage of the A allele to reduce the risk of NIHL development.
 Limitations. The limitations include the number of examined cases in all groups, especially in comparison group and the lack of groups of workers with no occupational exposure to a physical factor. 
 Conclusion. The obtained results expand the understanding of the genetic features able to determine sensitivity to the physical factors exposure that define the development of occupational pathology and the issues to be resolved at the next stage of research.

Predictive value of serum proteomic biomarkers for noise-induced hearing loss.

Early detection of noise-induced hearing loss (NIHL) in patients with long-term noise exposure is vital for improving public health and reducing social burden. However, at present, the diagnosis of NIHL mainly depends on audiometric testing, and the primary test is pure-tone audiometry. Moreover, testing requires professional operators and complex equipment; thus, NIHL is often diagnosed at a later disease stage. Using a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomic approach, we identified 9 differentially expressed proteins (DEPs), namely, 6 upregulated serum proteins and 3 downregulated serum proteins, in samples from 50 ground crew personnel working at an air force station. Then, according to the results, we predicted that caldesmon (CALD1), myocilin (MYOC), zyxin (ZYX), creatine kinase M-type (CKM), insulin-like growth factor-binding protein 2 (IGFBP2), complement factor H-related protein 4 (CFHR4), prenylcysteine oxidase 1 (PCYOX1), heat shock cognate 71 kDa protein (HSPA8), and immunoglobulin lambda variable 3-21 (IGLV3-21) were associated with NIHL. We selected these DEPs as variables to perform logistic regression. Finally, a logistic regression model was constructed based on IGFBP2, ZYX, CKM, and CFHR4. The area under the curve was 0.894 (95% CI = 0.812 to 0.977). These findings suggested that IGFBP2, ZYX, CKM, and CFHR4 in serum are differentially expressed in NIHL patients and have the potential to be biomarkers for predicting the risk for NIHL. Further experiments in mice showed that ZYX and IGFBP2 in the cochlear were increased after noise exposure. ZYX and IGFBP2 may be involved in the occurrence and development of NIHL.

Predicting secondary endolymphatic hydrops in patients with noise-induced hearing loss

Background Long-term noise exposure may damage the cochlea and endolymph resorption system, which induces episodic vertigo and/or fluctuating hearing loss in later years. Objective This study adopted clinical symptoms, inner ear test battery, and/or magnetic resonance (MR) imaging to evaluate development of secondary endolymphatic hydrops (EH) in patients with noise-induced hearing loss (NIHL). Methods Forty NIHL patients with secondary EH were assigned to Group A. Another 40 age-and sex-matched NIHL patients without EH were assigned to Group B. All patients underwent an inner ear test battery. MR imaging was performed when diagnosis of EH was equivocal via above testing. Results Group A had significantly higher mean hearing levels (MHLs) than Group B at 1000, 2000, 4000, and 8000 Hz. Both groups displayed a significantly declining sequence of abnormality rates of the inner ear test battery. Under receiver operating characteristic (ROC) curve analysis, the cutoff threshold at 4 kHz for predicting the presence of secondary EH in NIHL patients was 52 dBHL, with a sensitivity of 62% and a specificity of 69%. Conclusions NIHL patients revealing a typical 4 kHz dip-type audiogram with dip threshold >52 dBHL may predict development of secondary EH. A longitudinal follow-up coupled with MR imaging is required for confirmation.

Psychological profile in noise-induced hearing loss patients: a pilot study

Introduction. Noise-induced hearing loss is a rather prevalent condition and can be distressing for a substantial proportion of patients, although researches describing psychological characteristics in noise-induced occupational hearing loss patients are not numerous.The study aims to find the effects of occupational noise on the psychological status among noise-induced hearing loss (NIHL) patients.Methods. Two groups, cross-sectional design. Study sample: 44 occupational noiseinduced male forming NIHL patients group (n = 21) and a control group (n = 23). Both groups were tested using the Russian versions of psychological questionnaires.Results. Almost one third of NIHL patients are the highly anxiety individuals as compared with the healthy participants (p < 0.01). Mixed type of response to the surrounding reality combined a high need for self-actualization with high self-control, tendency to inhibit and restrain behavioral reactions, in this case it is possible to “overlap” both neurotic and behavioral responses, which can affect the general overstrain and manifest by the somatization of the internal conflict. In general, NIHL patients use constructive cognitive, emotional and behavioral coping strategies. Patients use both constructive and tense defense mechanisms. Conclusion. It has been established that in patients with NIHL, in comparison with practically healthy persons, tension accumulates, and a tendency to psychotraumatization appears. However, it is currently difficult to determine whether NIHL is a predisposing factor for these psychological characteristics, so further research is needed to determine how significant this relationship is. Key words: noise-induced hearing loss, occupational noise, psychological profile>˂ 0.01). Mixed type of response to the surrounding reality combined a high need for self-actualization with high self-control, tendency to inhibit and restrain behavioral reactions, in this case it is possible to “overlap” both neurotic and behavioral responses, which can affect the general overstrain and manifest by the somatization of the internal conflict. In general, NIHL patients use constructive cognitive, emotional and behavioral coping strategies. Patients use both constructive and tense defense mechanisms.Conclusion. It has been established that in patients with NIHL, in comparison with practically healthy persons, tension accumulates, and a tendency to psychotraumatization appears. However, it is currently difficult to determine whether NIHL is a predisposing factor for these psychological characteristics, so further research is needed to determine how significant this relationship is.

Plasma metabolomic profiling in workers with noise-induced hearing loss: a pilot study.

Noise-induced hearing loss (NIHL) remains a leading occupational related disease and is a serious public health problem. Hence, the identification of potential biomarkers for NIHL prevention and diagnosis has become an urgent work. To discover potential metabolic biomarkers of NIHL, plasma metabolomics analysis in 62 NIHL patients and 62 normal hearing controls was performed using ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF MS). Orthogonal partial least square-discriminant analysis (OPLS-DA) model was applied to distinguish metabolite profile alterations in plasma samples between the two groups. The metabolites with a variable importance of projection (VIP) value > 1 and P value < 0.05 were considered to be potential metabolic biomarkers. KEGG database was performed to explore the involved pathways of potential biomarkers. Three autophagy-related genes (PI3K, AKT, and ATG5) were selected for further verification, and mRNA levels were detected using RT-qPCR analysis. Twenty plasma metabolites with VIP > 1 and P < 0.05 were significantly altered between the two groups. Totally, seven metabolic pathways involving the glycerophospholipid metabolism, glycosylphosphatidylinositol (GPI)-anchor biosynthesis, autophagy pathway, choline metabolism, the alpha-linolenic acid metabolism and linoleic acid metabolism, and retrograde endocannabinoid pathway were significantly related to NIHL. Furthermore, verification by RT-qPCR suggested that the mRNA expression levels of PI3K and AKT along with ATG5 were significantly lower in the NIHL patients compared with controls. In summary, the present study provides the first evidence that the identified aberrantly altered metabolites may be the potentially valuable biomarkers of NIHL for occupational noise-exposed workers. Autophagy signal pathway may be involved in the occurrence and development of NIHL. Moreover, this present study may be helpful to further better understand the metabolic changes in NIHL and be helpful for the understanding of pathogenic mechanism.

A functional SNP in miR-625-5p binding site of AKT2 3'UTR is associated with noise-induced hearing loss susceptibility in the Chinese population.

The purposes of the current study were to investigate the association of a few of single nucleotide polymorphisms (SNPs) within the AKT2 gene and noise-induced hearing loss (NIHL) susceptibility and explore the potential mechanism underlying NIHL. Three SNPs (rs2304186, rs41275750, and rs76524493) were genotyped in a Chinese population which consists of 690 NIHL patients and 650 normal hearing controls. Bioinformatic analysis was conducted to predict the potential miRNA-binding site of SNPs. Plasmid construction, cell transfection, and dual-luciferase reporter assay were performed to investigate the potential molecular mechanism of SNPs involving in NIHL. The results revealed that rs2304186 GT genotype (OR = 1.41; 95% CI = 1.09-1.83) and TT genotype (OR = 1.51; 95% CI = 1.08-2.10) imparted increased risk of NIHL, and the increased risk could also be found in a dominant model (OR = 1.44; 95% CI = 1.12-1.84). The stratification analysis showed that rs2304186 GT/TT conferred a higher risk for NIHL, especially in subgroups of male, age (35-45 and > 45 years), noise exposure time (> 16 years), and noise exposure level (≤ 85 and ≥ 92 dB), when GG genotype as a reference. Furthermore, the haplotype TCCTACT (rs2304186-rs41275750-rs76524493) was found to be significantly associated with a high risk of NIHL (OR = 1.19; 95% CI = 1.02-1.40). Functional experiments showed that rs2304186 G allele combined with hsa-miR-625-5p mimics could significantly decrease the luciferase activity compared with T allele, indicating that rs2304186 altered the binding affinity of hsa-miR-625-5p to SNP rs2304186 mutation region, thus directly targeting AKT2 gene. In conclusion, our study provides evidence for the first time that SNP rs2304186 of AKT2 3'UTR might affect NIHL susceptibility by altering the binding affinity of has-miR-625-5p to mutation region in an allele-specific manner and it may act as a potential biomarker of NIHL susceptibility.

Histone deacetylase 2 polymorphisms associated with noise-induced hearing loss in Chinese workers.

Noise-induced hearing loss (NIHL) is one of these hazards which has been the second most common sensorineural hearing loss. Single-nucleotide polymorphisms (SNPs) mainly refer to the polymorphism of DNA sequence caused by the variation at the genomic nucleotide level. The influence of histone deacetylase 2 (HDAC2) variants on the risk of NIHL has not been studied. This research explored the association between HDAC2 and the development of NIHL. A total of 1146 industrial workers from one textile factory in east China were recruited to perform a case-control study. Basic clinical data such sex, age, smoking, and drinking was obtained by questionnaires; pure-toneaudiometry (PTA) tests were conducted by specialist physicians. Then, we performed genotyping of five selected SNPs (rs10499080, rs2475631, rs2499618, rs6568819, and rs3757016) in the HDAC2 gene in 600 NIHL patients and 546 controls. Finally, the main influences of the SNPs and their interactions with NIHL were assessed. Under the recessive model, there were statistically significant differences in the genotype frequencies of rs10499080 between two groups, and the results showed that individuals with rs10499080 CC+CT had a lower risk of NIHL (OR = 0.597, 95%CI = 0.357-0.998). Meanwhile, the significant difference in the genotype distributions between cases and controls was found in rs10499080 in the group with noise exposure of ≤ 16 years. But the following haplotype analysis showed that no association between all haplotypes in the HDAC2 gene and NIHL was been found. The genetic polymorphisms rs10499080 and rs6568819 within HDAC2 gene have an association with risk of NIHL. Workers exposed to noise with HDAC2 have a lower risk of NIHL.

Characteristics of auditory brainstom response and auditory steady state evoked responses in noise-induced hearing loss population

Objective: To explore the characteristics of auditory steady state evoked responses (ASSR) and auditory brainstem response (ABR) in noise-induced hearing loss population and the relationship between the response threshold of corresponding frequency and pure tone audiometry (PTA) . Methods: Noise-induced hearing loss patients who completed subjective and objective audiometry in our hospital from October 2014 to October 2018 were collected. The results of PTA, ABR, ASSR and the correlation between subjective and objective audiometry were discussed. Results: A total of 381 ears of 193 patients were enrolled. The difference of 0.5, 1.0, 2.0 and 4.0 kHz between ASSR threshold and PTA was 5.9, 6.9, 11.8 and 1.8 dB, respectively. The correlation coefficients were 0.638, 0.680, 0.657 and 0.608. The difference of 1.0, 2.0, 3.0 and 4.0 kHz between ABR threshold and PTA was 44.2, 35.0, 19.0 and 2.0 dB. With the increase of frequency, the threshold difference between ABRt V wave and PTA decreased gradually. Conclusion: ASSR and ABR response thresholds are valuable in subjective assessment on noise-induced hearing loss. The thresholds of ASSR and ABR at 4 kHz are close to those of PTA.

Research and Discussion on the Relationships between Noise-Induced Hearing Loss and ATP2B2 Gene Polymorphism

Long-term and continuous noise exposure can result in noise-induced hearing loss (NIHL), which is a worldwide problem resulting from the interaction of environmental and genetic factors. The ATP2B2 gene polymorphism can destroy cochlear hair cells and increase the risk of NIHL. A case-control study of 760 Chinese textile workers was conducted to investigate the relationship between ATP2B2 polymorphisms and NIHL susceptibility. Venous blood was collected and questionnaires were conducted by professional physicians. A case group and a control group which were typed by individuals' pure-tone audiometry test results were set. Three polymorphism sites of ATP2B2 were genotyped by using the PCR technique. Analysis results revealed that the C allele of rs3209637 (95%CI = 1.08–2.58, odds ratio (OR) = 1.67, P = 0.027) was a dangerous factor and could add to risks of NIHL in the Chinese employees. The data of stratified analysis revealed that individuals who are exposed to noise > 95 dB with the rs3209637 C genotype have a higher susceptibility to NIHL (OR = 1.34, 95%CI = 1.07–1.68). Multifactor dimensionality reduction analysis revealed that the interaction between rs14154 and rs3209637 is linked to increased NIHL risk, and for the interaction among rs14154, smoking and drinking had the same function (OR = 1.54 and 1.77, 95%CI = 1.15–2.07, 1.33–2.37, and P = 0.0037 and P < 0.0001, respectively). Our results suggest that genetic polymorphism rs3209637 C within ATP2B2 is a risk factor for NIHL among Chinese employees and rs3209637 C could be a potential biomarker for NIHL patients.

Analysis on Risk Factors of Depressive Symptoms in Occupational Noise-induced Hearing Loss Patients: A Cross-sectional Study.

Objective:The aim of this study was to evaluate the risk factors of depressive symptoms in occupational noise-induced hearing loss (NIHL) patients.Methods:A total of 106 patients were divided into depressive symptoms (ONHLPD) and without depressive symptoms (non-ONHLPD) according to the Self-rating Depression Scale. Questionnaires and laboratory data were collected and analyzed. Data were analyzed with independent t-test, Wilcoxon test, Pearson correlation analysis and multiple linear regression models.Results:The prevalence of depressive symptoms was 53.8% in occupational NIHL patients. In ONHLPD, duration of the hearing loss, level of serum cortisol, scores of Pittsburgh Sleep Quality Index and Tinnitus Handicap Inventory were all significantly higher than those of non-ONHLPD.Conclusion:The prevalence of depressive symptoms was relatively high in occupational NIHL patients. Duration of the hearing loss, sleep quality and tinnitus severity were the risk factors for occupational NHIL patients with depressive symptoms.

DNMT1 and DNMT3A haplotypes associated with noise-induced hearing loss in Chinese workers

This study was conducted to explore the effects of DNMT1 and DNMT3A polymorphisms on susceptibility to noise-induced hearing loss (NIHL) in Chinese workers. A total of 2689 industrial workers from a single textile factory were recruited. Venous blood was collected, as were questionnaire and pure-tone audiometry (PTA) data by specialist physicians. Four selected SNPs (rs7578575, rs749131, rs1550117, and rs2228611) in DNMT1 and DNMT3A were genotyped in 527 NIHL patients and 527 controls. Then, main effects of the genotypes and their interactions were evaluated. Results revealed that the GG genotype at rs749131 and the AG/GG genotypes at rs1550117 and rs2228611 [odds ratio (OR) = 1.87, 2.57, and 1.98 respectively], as well as the haplotypes AGGG and TGGA (rs7578578-rs749131-rs1550117-rs2228611) (OR = 1.35 and 1.56, respectively) were associated with an increased risk of NIHL in the Chinese population. Multifactor dimensionality reduction analysis indicated that rs7578575, rs749131, and rs2228611 interact and are related to increased NIHL risk (OR = 1.63). The genetic polymorphisms rs749131 G, rs1550117 G, and rs2228611 G within the DNMT1 and DNMT3A genes are associated with an increased risk of NIHL in the Chinese population and have the potential to act as biomarkers for noise-exposed workers.

Association of genetic variations in FOXO3 gene with susceptibility to noise induced hearing loss in a Chinese population.

Noise induced hearing loss (NIHL), a multifactorial disease involving both genetic and environmental factors, is one of the most important occupational health hazards. Nonetheless, the influence of FOXO3 variants on NIHL risk have not been illuminated. This research was conducted to explore the effects of FOXO3 polymorphisms on individual susceptibility to NIHL. A total of 2689 industrial workers from one textile factory of east China were recruited to participate in the current research. Venous blood was collected, questionnaire and pure-tone audiometry (PTA) was conducted by specialist physicians. Then, we performed genotyping of three selected SNPs (rs2802292, rs10457180, and rs12206094) in FOXO3 gene in 566 NIHL patients and 566 controls. Subsequently, the main effects of genotype and its interactions were evaluated. Our results revealed that individuals with the G allele of rs2802292, G allele of rs10457180, T allele of rs12206094 (OR = 1.43, 1.43, and 1.31 respectively) and the haplotype GAC and others (TGT/GGT/GGC/GAT) (rs2802292-rs10457180-rs12206094) (OR = 1.49 and 2.09 respectively) are associated with an increased risk of NIHL in a Chinese population. Stratified analysis showed that an increased NIHL risk was found in the subjects who exposed to noise >16 years with rs2802292 GG/GT and rs10457180 AG/GG genotype with an OR of 1.62 and 1.66 respectively. Multifactor dimensionality reduction analysis indicated that rs10457180, rs2802292, and rs12206094 have interactions and are related to increased NIHL risk (OR = 1.53). The genetic polymorphism rs2802292, rs10457180, and rs12206094 within FOXO3 gene are associated with an increased risk of NIHL in a Chinese population and have potential to be biomarkers for noise exposed workers.

Assessment the effect of noise on the sacculocolic pathway using vestibular evoked myogenic potential

ObjectiveThe aim of this study was to detect the effect of noise on the sacculocollic pathway using cervical vestibular evoked myogenic potential (c-VEMP) and to check the correlation between the hearing thresholds and the c-VEMP responses in noise-induced hearing loss (NIHL) patients.Patients and methodsThe study included 40 (80 ears) participants. Their ages ranged between 30 and 45 years. They were divided into two groups: 20 (40 ears) participants with NIHL presenting with bilateral notched audiogram at 4kHz, and 20 (40 ears) participants as a control group. All participants in the study were subjected to basic audiological evaluation and VEMP tests.ResultsAs the average pure-tone hearing threshold increased, the c-VEMP latencies prolonged and peak-to-peak amplitude reduced in NIHL patients. Of the 40 ears, c-VEMP was absent in 12 (30%) ears. The latencies prolonged and the peak-to-peak amplitude reduced in 16 (40%) ears. VEMP results were normal in 12 (30%) ears.ConclusionNoise can cause more damage to the vestibular system, especially the sacculocollic pathway.

Analysis of plasma microRNA expression profiles in male textile workers with noise-induced hearing loss

BackgroundCirculating microRNAs (miRNAs) have attracted interests as non-invasive biomarkers of physiological and pathological conditions, which may be applied in noise-induced hearing loss (NIHL). However, no epidemiology studies have yet examined the potential effects of NIHL or noise exposure on miRNA expression profiles. ObjectivesWe sought to identify permanent NIHL-related miRNAs and to predict the biological functions of the putative genes encoding the indicated miRNAs. MethodsIn the discovery stage, we used a microarray assay to detect the miRNA expression profiles between pooled plasma samples from 10 noise-exposed individuals with normal hearing and 10 NIHL patients. In addition, we conducted a preliminary validation of six candidate miRNAs in the same 20 workers. Subsequently, three miRNAs were selected for expanded validation in 23 non-exposed individuals with normal hearing and 46 noise-exposed textile workers which including 23 noise-exposed workers with normal hearing and 23 NIHL patients. Moreover, we predicted the biological functions of the putative target genes using a Gene Ontology (GO) function enrichment analysis. ResultsIn the discovery stage, compared with the noise exposures with normal hearing, 73 miRNAs demonstrated at least a 1.5-fold differential expression in the NIHL patients. In the preliminary validation, compared with the noise exposures, the plasma levels of miR-16-5p, miR-24-3p, miR-185-5p and miR-451a were all upregulated (P < 0.001) in the NIHL patients. In the expanded validation stage, compared with the non-exposures, the plasma levels of miR-24, miR-185-5p and miR-451a were all significantly downregulated (P < 0.001) in the exposures. And compared with the noise exposures, the plasma levels of miR-185-5p and miR-451a were slightly elevated (P < 0.001) in the NIHL patients, which were consistent with the results of preliminary validation and microarray analysis. ConclusionThe two indicated plasma miRNAs may be biomarkers of indicating responses to noise exposure. However, further studies are necessary to prove the causal association between miRNAs changes and noise exposure, and to determine whether these two miRNAs are clear biomarkers to noise exposure.

Association of SOD2 gene polymorphism with noise induced hearing loss in textile industry employees

Noise exposure leads to hearing loss in industrial workers due to release of superoxide anions which damage cochlear epithelium in the ear. These free radicals are regulated by superoxide dismutase 2 (SOD2) and polymorphism in this gene may abet in predisposition to noise induced hearing loss (NIHL). The current study describes prevalence of polymorphism at two different loci of SOD2 gene in NIHL patients and association of smoking habit with NIHL. PCR-SSCP analysis of polymorphic sites revealed mutation in NIHL patients. Results showed thatIVS1+8A/G and IVS3-23T/G SOD2 polymorphisms are associated with NIHL (p 0.01). It is intended that SOD2 polymorphism plays a significant diagnostic role in determining susceptibility of NIHL in Pakistani industry employees. Key words: Superoxide dismutase 2, polymorphism, hearing loss, loci, reactive oxygen species

Sequence of vestibular deficits in patients with noise-induced hearing loss

This study utilized audiometry, and cervical vestibular-evoked myogenic potential (cVEMP), ocular VEMP (oVEMP) and caloric tests to investigate the sequence of vestibular deficits in patients with noise-induced hearing loss (NIHL). Thirty patients with NIHL underwent an inner ear test battery. Another 30 normal controls with age- and sex-matched were included for comparison. The abnormal percentages of the audiometry, and cVEMP, oVEMP and caloric tests were 100, 70, 57 and 33 % in NIHL patients, which showed significant differences from 13, 13, 7 and 3 % in normal controls, respectively. A significantly decreasing trend among the four tests, with the sequence of damage from the cochlea, followed by the saccule, utricle, and semicircular canals was noted in NIHL patients, but not in normal controls. In conclusion, the decreasing order of abnormal percentages in the function of the cochlea, saccule, utricle and semicircular canals after chronic noise exposure further supports that the pars inferior (cochlea and saccule) is more vulnerable to noise exposure than the pars superior (utricle and semicircular canals).

Impaired CD4+CD25+ regulatory T cell activity in the peripheral blood of patients with autoimmune sensorineural hearing loss

CD4+CD25+ regulatory T cells exert an immune regulatory function and thus play an important role in the control of self-reactivity in the pathogenesis of autoimmune inflammatory conditions. The aim of the study presented here is to perform a quantitative and functional analyses of these cells in patients with autoimmune sensorineural hearing loss (ASNHL). T cell subsets (CD4+CD25+, CD4+CD25(high), CD4+, and CD8+) from the peripheral blood of 17 patients with ASNHL, 16 patients with noise induced hearing loss (NHL), and 100 normal controls were analyzed by flow cytometry. The CD4/CD8 ratio was also analyzed. In addition, the suppressive capability of CD4+CD25+ T cells was tested in vitro by measuring their ability to suppress the proliferation and IFN-gamma secretion of CD4+CD25- T cells. No significant difference was found in the T cell subsets of ASNHL patients compared to normal controls or NHL patients, except that the proportion of CD4+ T cells was elevated in ASNHL patients. However, we did observe defective regulatory function of CD4+CD25+ T cells in patients with ASNHL. Our data supported the idea that CD4+CD25+ regulatory T cells played an immunosuppressive function in the periphery. The impaired suppressive activity of these cells may be an important factor in the pathogenesis of ASNHL.