Increased expression level of Hsp70 in the inner ears of mice by exposure to low frequency noise

Vascular endothelium as a target tissue for short-term exposure to low-frequency noise that increases cutaneous blood flow

Harmful health effects of exposure to low-frequency noise (LFN) defined as noise with frequencies at ≤100 Hz on the circulatory system have been a concern. However, there has been no study on the effects of exposure to LFN on the circulatory system with consideration of its frequencies and decibels. In this study, the effects of short-term exposure to broad-band LFNs and their pure-tone components (pure-tone LFNs) on cutaneous blood flow in the extremities including the hands were investigated. In our fieldwork study, we first sampled some kinds of common broad-band LFNs. Our human study then showed that broad-band LFN with a narrower frequency range more strongly increased cutaneous blood flow than did broad-band LFN with a wider frequency range. Pure-tone LFNs of 70-100 Hz at ≤85 dB(Z), but not pure-tone LFNs exceeding 100 Hz, further increased levels of cutaneous blood flow. Our wavelet-transform spectrum analysis of cutaneous blood flow next revealed that the nitric oxide (NO)-dependent and -independent vascular activities of the vascular endothelium were specifically increased by exposure to pure-tone LFN. Our animal study again indicated that exposure to pure-tone LFN increased cutaneous blood flow in mice with impairments of bilateral inner ears as well as cutaneous blood flow in control mice, suggesting a limited effect of inner ear function on the LFN-mediated increase in cutaneous blood flow. The NO-dependent suppressive effect of pure-tone LFN on cutaneous blood flow was confirmed by inhibition of vascular endothelial activity through intravenous injection of an NO inhibitor in wild-type mice. Taken together, the results of this study demonstrated that the vascular endothelium is a target tissue of LFN and that NO is an effector of the LFN-mediated increase in cutaneous blood flow. Since improvement of peripheral circulation could generally promote human health, short-term exposure to LFN may be beneficial for health.

Downregulation of GJB2 and SLC26A4 genes induced by noise exposure is associated with cochlear damage

BACKGROUND

Noise-induced hearing loss (NIHL) is one the major causes of acquired hearing loss in developed countries. Noise can change the pattern of gene expression, inducing sensorineural hearing impairment. There is no investigation on the effects of noise frequency on the expression of GJB2 and SLC26A4 genes involved in congenital hearing impairment in cochlear tissue. Here we investigated the impacts of white and purple noise on gene expression and pathologic changes of cochlear tissue.

METHODS

In this study, 32 adult male Westar rats were randomly divided into experimental groups: WN, animals exposed to white noise with a frequency range of 100-20000 Hz; PN, animals exposed to purple noise with a frequency range of 4-20 kHz, and control group, without noise. The experimental groups were exposed to a 118-120 dB sound pressure level for 8 h per 3 days and 6 days. 1 h and 1 week after termination of noise exposure, cochlear tissue was prepared for pathology and gene expression analysis.

RESULTS

Both white and purple noises caused permanent damage to the cortical, estrosilica systems of hair cells and ganglion of the hearing nerve. GJB2 and SLC26A4 were downregulated in both groups exposed with white and purple noise by increasing the time of noise exposure. However, differences are notably more significant in purple noise, which is more intensified. Also, 1 weak post noise exposure, the downregulation is remarkably higher than 1 h.

CONCLUSIONS

Our findings suggest that downregulation of GJB2 and SLC26A4 genes are associated with pathological injury in response to noise exposure in cochlear tissue. It would be suggested the demand for assessment of RNA and protein expression of genes involved in noise-induced hearing loss and subsequently the practice of hearing protection programs.

Expression, Rapid Purification and Functional Analysis of DnaK from Rhodococcus ruber

BACKGROUND

Heat shock proteins (HSPs) represent a group of important proteins which are produced by all kinds of organisms especially under stressful conditions. DnaK, an Hsp70 homolog in prokaryotes, has indispensable roles when microbes was confronted with stress conditions. However, few data on DnaK from Rhodococcus sp. were available in the literature. In a previous study, we reported that toluene and phenol stress gave rise to a 29.87-fold and 3.93-fold increase for the expression of DnaK from R. ruber SD3, respectively. Thus, we deduced DnaK was in correlation with the organic solvent tolerance of R. ruber SD3.

OBJECTIVE

To elucidate the role of DnaK in the organic solvent tolerance of R. ruber SD3, expression, purification and functional analysis of Dnak from R. ruber SD3 were performed in the present paper.

METHODS

In this article, DnaK from R. ruber SD3 was heterologously expressed in E. coli BL21(DE3) and purified by affinity chromatography. Functional analysis of DnaK was performed using determination of kinetics, docking, assay of chaperone activity and microbial growth.

RESULTS

The recombinant DnaK was rapidly purified by affinity chromatography with the purification fold of 1.9 and the recovery rate of 57.9%. Km, Vmax and Kcat for Dnak from R. ruber SD3 were 80.8 μM, 58.1 nmol/min and 374.3 S-1, respectively. The recombinant protein formed trimer in vitro, with the calculated molecular weight of 214 kDa. According to In-silico analysis, DnaK interacted with other molecular chaperones and some important proteins in the metabolism. The specific activity of catalase in the presence of recombinant DnaK was 1.85 times or 2.00 times that in the presence of BSA or Tris-HCl buffer after exposure to 54 °C for 1h. E. coli transformant with pET28-dnak showed higher growth than E. coli transformant with pET28 at 43°C and in the presence of phenol, respectively.

CONCLUSION

The biochemical properties and the interaction analysis of DnaK from R. ruber SD3 deepened our understanding of DnaK function. DnaK played an important role in microbial growth when R. ruber was subjected to various stress such as heating and organic solvent.

Hsp70/Bmi1-FoxO1-SOD Signaling Pathway Contributes to the Protective Effect of Sound Conditioning against Acute Acoustic Trauma in a Rat Model

Sound conditioning (SC) is defined as “toughening” to lower levels of sound over time, which reduces a subsequent noise-induced threshold shift. Although the protective effect of SC in mammals is generally understood, the exact mechanisms involved have not yet been elucidated. To confirm the protective effect of SC against noise exposure (NE) and the stress-related signaling pathway of its rescue, we observed target molecule changes caused by SC of low frequency prior to NE as well as histology analysis in vivo and verified the suggested mechanisms in SGNs in vitro. Further, we investigated the potential role of Hsp70 and Bmi1 in SC by targeting SOD1 and SOD2 which are regulated by the FoxO1 signaling pathway based on mitochondrial function and reactive oxygen species (ROS) levels. Finally, we sought to identify the possible molecular mechanisms associated with the beneficial effects of SC against noise-induced trauma. Data from the rat model were evaluated by western blot, immunofluorescence, and RT-PCR. The results revealed that SC upregulated Hsp70, Bmi1, FoxO1, SOD1, and SOD2 expression in spiral ganglion neurons (SGNs). Moreover, the auditory brainstem responses (ABRs) and electron microscopy revealed that SC could protect against acute acoustic trauma (AAT) based on a significant reduction of hearing impairment and visible reduction in outer hair cell loss as well as ultrastructural changes in OHCs and SGNs. Collectively, these results suggested that the contribution of Bmi1 toward decreased sensitivity to noise-induced trauma following SC was triggered by Hsp70 induction and associated with enhancement of the antioxidant system and decreased mitochondrial superoxide accumulation. This contribution of Bmi1 was achieved by direct targeting of SOD1 and SOD2, which was regulated by FoxO1. Therefore, the Hsp70/Bmi1-FoxO1-SOD signaling pathway might contribute to the protective effect of SC against AAT in a rat model.

Low-Frequency Noise and Its Main Effects on Human Health—A Review of the Literature between 2016 and 2019

This paper summarizes the presently available knowledge about the association between low-frequency noise and its effects on health. A database was constructed with a total of 142 articles published between 2016 and 2019 regarding low-frequency noise exposure and its effects on health. A total of 39 articles were analysed in depth. The articles were divided into categories according to the effects on human health addressed. Regarding the emitting source, there was a greater number of articles addressing issues related to sources of environmental noise and noise from wind turbines. As for the effects generated on human health, there was a greater number of articles referring to the effects on sleep disorders, discomfort, sensitivity to and irritability from noise, annoyance, hearing loss, and cardiovascular diseases, and these effects are analysed in more detail in the present article.

Application of a human mesoderm tissue elongation system in vitro derived from human induced pluripotent stem cells to risk assessment for teratogenic chemicals

Toxic compounds from the mother's diet and medication in addition to genetic factors and infection during pregnancy remain risks for various congenital disorders and misbirth. To ensure the safety of food and drugs for pregnant women, establishment of an in vitro system that morphologically resembles human tissues has been long desired. In this study, we focused on dorsal mesoderm elongation, one of the critical early development events for trunk formation, and we established in vitro autonomous elongating tissues from human induced pluripotent stem cells (hiPSCs). This artificial tissue elongation is regulated by MYOSIN II and FGF signaling, and is diminished by methylmercury or retinoic acid (RA), similar to in vivo human developmental disabilities. Moreover, our method for differentiation of hiPSCs requires only a short culture period, and the elongation is cell number-independent. Therefore, our in vitro human tissue elongation system is a potential tool for risk assessment assays for identification of teratogenic chemicals via human tissue morphogenesis.

A new method with an explant culture of the utricle for assessing the influence of exposure to low-frequency noise on the vestibule

Health risks attributed to low-frequency noise (LFN) exposure are a serious global issue. Therefore, the development of a method for a prevention based upon risk assessments for LFN is important. Previously in vivo exposure of mice to LFN at 100 Hz, 95 dB for 1 hr produced imbalance with breakage of the otoconial membrane, which covers hair cells as well as impaired activity of hair cells in the vestibule. However, methods for inhibition of LFN-mediated imbalance have not been developed. At present, there are no apparent techniques available with in vitro or ex vivo assessments to evaluate LFN-mediated imbalance by direct administration of preventive chemicals into the vestibule. Our findings demonstrated the usefulness of an explant culture of the utricle with a fluorescent styryl dye, FM1-43FX. In addition, examination of the morphology of the otoconial membrane with explant cultures of utricles was conducted to determine the risk of LFN. Ex vivo exposure of the utricle to LFN at 100 Hz, 95 dB for 1 hr induced breaks in the otoconial membrane as well as decreased uptake of FM1-43FX in hair cells. Taken together, the results of this study provide a novel technique for assessing the risk of LFN exposure using an ex vivo experiment.

Heat shock protein 70 is a key molecule to rescue imbalance caused by low-frequency noise

A previous study showed that people living in urban areas are generally exposed to low-frequency noise (LFN) with frequencies below 100 Hz and sound levels of 60-110 dB in daily and occupational environments. Exposure to LFN has been shown to affect balance in humans and mice. However, there is no information about prevention of LFN-mediated imbalance because of a lack of information about the target region based on health risk assessment of LFN exposure. Here, we show that acute exposure to LFN at 100 Hz, 95 dB, but not at 85 dB or 90 dB, for only 1 h caused imbalance in mice. The exposed mice also had decreased cervical vestibular-evoked myogenic potential (cVEMP) with impaired activity of vestibular hair cells. Since imbalance in the exposed mice was irreversible, morphological damage in the vestibules of the exposed mice was further examined. The exposed mice had breakage of the otoconial membrane in the vestibule. LFN-mediated imbalance and breakage of the otoconial membrane in mice were rescued by overexpression of a stress-reactive molecular chaperone, heat shock protein 70 (Hsp70), which has been shown to be induced by exposure of mice to 12 h per day of LFN at 95 dB for 5 days. Taken together, the results of this study demonstrate that acute exposure to LFN at 100 Hz, 95 dB for only 1 h caused irreversible imbalance in mice with structural damage of the otoconial membrane as the target region for LFN-mediated imbalance, which can be rescued by Hsp70.

Hsp70 (HSP70A1A) downregulation enhances the metastatic ability of cancer cells

Heat shock protein 70 (Hsp70; also known as HSP70A1A) is one of the most induced proteins in cancer cells; however, its role in cancer has not yet been fully elucidated. In the present study, we proposed a hypothetical model in which the silencing of Hsp70 enhanced the metastatic properties of the HeLa, A549 and MCF7 cancer cell lines. We consider that the inability of cells to form cadherin-catenin complexes in the absence of Hsp70 stimulates their detachment from neighboring cells, which is the first step of anoikis and metastasis. Under these conditions, an epithelial-to-mesenchymal transition (EMT) pathway is activated that causes cancer cells to acquire a mesenchymal phenotype, which is known to possess a higher ability for migration. Therefore, we herein provide evidence of the dual role of Hsp70 which, according to international literature, first establishes a cancerous environment and then, as suggested by our team, regulates the steps of the metastatic process, including EMT and migration. Finally, the trigger for the anti-metastatic properties that are acquired by cancer cells in the absence of Hsp70 appears to be the destruction of the Hsp70-dependent heterocomplexes of E-cadherin/catenins, which function like an anchor between neighboring cells.

Improvement of balance in young adults by a sound component at 100 Hz in music

About 80% of young people use personal listening devices (PLDs) including MP3 players to listen to music, which consists of sound components with various frequencies. Previous studies showed that exposure to noise of high intensities affected balance in humans. However, there is no information about a frequency-dependent effect of sound components in music from a PLD on balance in young people. In this study, we determined the associations between sound component levels (dB) at 100, 1000 and 4000 Hz in music from a portable listening device (PLD) and balance objectively determined by posturography in young adults (n = 110). We divided the subjects into two groups (low and high exposure groups) based on cut-off values of sound component levels at each frequency using receiver operating characteristic (ROC) curves. Balance in the high exposure group (≥46.6 dB) at 100 Hz was significantly better than that in low exposure group in logistic regression models adjusted for sex, BMI, smoking status and alcohol intake, while there were no significant associations at 1000 and 4000 Hz. Thus, this study demonstrated for the first time that the sound component at 100 Hz with more than 46.6 dB in music improved balance in young adults.