Near Infrared (NIr) Light Increases Expression of a Marker of Mitochondrial Function in the Mouse Vestibular Sensory Epithelium

Summary

Mitochondrial dysfunction is a hallmark of cellular senescence. This paper uses non-invasive near-infrared (NIr) treatment to improve mitochondrial function in the aging mouse vestibular sensory epithelium.

Abstract

Strategies for attenuating decline in balance function with increasing age are predominantly focused on physical therapies including balance tasks and exercise. However, these approaches do not address the underlying causes of balance decline. Using mice, the impact of near infrared light (NIr) on the metabolism of cells in the vestibular sensory epithelium was assessed. Data collected shows that this simple and safe intervention may protect these vulnerable cells from the deleterious effects of natural aging. mRNA was extracted from the isolated peripheral vestibular sensory epithelium (crista ampullaris and utricular macula) and subsequently transcribed into a cDNA library. This library was then probed for the expression of ubiquitous antioxidant (SOD-1). Antioxidant gene expression was then used to quantify cellular metabolism. Using transcranial delivery of NIr in young (4 weeks) and older (8 - 9 months) mice, and a brief treatment regime (90 sec/day for 5 days), this work suggests NIr alone may be sufficient to improve mitochondrial function in the vestibular sensory epithelium. Since there are currently no available, affordable, non-invasive methods of therapy to improve vestibular hair cell function, the application of external NIr radiation provides a potential strategy to counteract the impact of aging on cellular metabolism inthe vestibular sensory epithelium.

Introduction

Declining balance performance and subsequent falls are common, and unfortunately often defining features of natural aging¹. The impact of this decline can be both physical and social, and significantly reduces quality of life for older people. In response, physical therapies and rehabilitation have been the focus of research into falls but have not been associated with consistent reduction in the prevalence of repeated falls. At the same time, work investigating changes in the peripheral or central vestibular system (the system responsible for maintain balance) is scarce, and potential therapeutic strategies targeting these systems and the underlying causes....

Protocol

Ethics Statement: All procedures outlined below were approved by the University of Sydney Animal Ethics Committee.

1. Animals

NOTE: 1 and 8 - 9 month old mice (C57/BL6) were obtained from the Animal Resources Centre (Perth, Australia). Mice were housed in the Bosch Rodent Facility at the University of Sydney.

1. House mice in standard mouse cages on a 12/12 hr light/dark cycle with access to food and water ad libitum.
2. Divide mice in each age group into near infrared (NIr) treated, or sham treated (control) groups for comparison.

2. Near Infrared (NIr) I....

Results

To compare the impact of NIr treatment in young (4 weeks) and older (8 - 9 months) mice we measured the expression of antioxidant superoxide dismutase 1 (SOD-1) in young (n = 16) and older (n = 20) mice that were NIr-treated, sham-treated, or NIr-blocked. Figure 2 shows a significant increase in β-actin normalized SOD-1 expression of more than 2-fold in young NIr-treated animals compared to young sham-treated animals (p < 0.01) and young NIr-blocked animals (p < 0.01). Older NIr-treated animals als.......

Discussion

The representative results described here show that brief transcranial delivery of NIr light (90 sec/day for 5 days) is sufficient to raise the levels of antioxidant expression in older mice when compared with sham-treated mice. While emitted heat could represent a source of mitochondrial and/or neuronal activation, as reported for rat vestibular afferents²⁴ – our measurement of heat emitted by the NIr LED device was <0.2°C over 90 sec, and as such is unlikely to cause the changes described here.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Quantum WARP 10	Quantum Devices	2070N030-A
Screw top microtubules	Quality Scientific Plastics	520-GRD-Q
Ketamine	Parnell, Alexandria Australia
Standard pattern scissors	FST	14001-12
Carbon steel surgical blades #22	Livingstone	SBLDCL 22
Friedman-Pearson rongeurs	FST	16221-14
Stereo microscope	Leica Microsystems	A60S
Dumont #5 SF forceps	FST	11252-00
Isolate II RNA Micro Kit	Bioline	BIO-52075