Effects of Cadmium on the Hearing System

Abstract

The functional resemblance between kidney proximal tubular and inner ear epithelial cells which has often been pointed out in the literature led us to hypothesize that nephrotoxic agents that cause renal tubular injury might also impair the function of inner ear cells. As one of the most toxic environmental nephrotoxic agents is cadmium, we aimed to study its effects on hearing experimentally in rats. In this study, increased blood and renal cortical cadmium levels were associated with high cadmium accumulation in ear ossicles and labyrinth in rats exposed to cadmium. The changes in auditory brainstem response (ABR) and otoacoustic emission in 2-month-old male rats exposed to drinking water containing 5 and 15 ppm CdCl2 for 30 days showed that cadmium-induced nephrotoxicity was associated with signs of defective hearing at a concentration of 15 ppm CdCl2 but that 5 ppm CdCl2 caused hearing loss without affecting kidney function. The mean latency of ABR wave 1, which indicates the function of the cochlea, was 1.335 +/- 0.31 ms in the control group and 1.641 +/- 0.052 and 1.74 +/- 0.88 ms in the rats subjected to 5 and 15 ppm CdCl2, respectively (p < 0.001). In the cadmium-treated groups short interpeak wave I-III latencies (p < 0.01) indicated cochlear dysfunction and this was also supported by the distortion product otoacoustic emission results (p < 0.001). Non-significant changes in wave III and V latencies were accepted as evidence of unaltered function of the other parts of the auditory system. These results suggest that hair cells are more sensitive to cadmium than kidney tubule cells and that the cochlear component of hearing is more vulnerable to cadmium toxicity than other parts of the auditory system.

Noise-Induced Hearing Loss in Korean Workers: Co-Exposure to Organic Solvents and Heavy Metals in Nationwide Industries

“…Previous animal experiments show that solvents such as toluene, styrene, xylene, isopropyl alcohol, and ethyl benzene damage the cochlea (predominantly the supporting and outer hair cells) and provoke irreversible sensorineural hearing loss [12]–[16]. Furthermore, heavy metals such as cadmium, lead, mercury, and manganese induce the impairment (i.e., apoptosis and/or degeneration) of inner ear receptor cells, leading to auditory neuronal function disorders [23]–[27]. These findings provide a possible explanation that heavy metals and/or organic solvents condition the cochlea for damage triggered by oxidative stress produced by noise exposure.…”

“…Furthermore, several workplace studies suggest that such solvents are associated with an increased risk of hearing loss [17]–[22]. Heavy metals such as cadmium, lead, mercury, and manganese are reported to impair inner ear cells, leading to auditory function disorders in animal studies [23]–[27]. There is further evidence for their ototoxicity in human studies as well [28]–[30].…”

Lead and Cadmium Levels and Balance and Vestibular Dysfunction among Adult Participants in the National Health and Nutrition Examination Survey (NHANES) 1999–2004

“…There is substantial evidence that implicates associations of impaired balance (Bhattacharya et al 1990, 1995, 2006, 2007; Chia et al 1994, 1996; Després et al 2005; Dick et al 1999; Iwata et al 2005; Kilburn and McKinley 1996; Linz et al 1992; Ratzon et al 2000; Viaene et al 2000; Yokoyama et al 1997, 2002), hearing loss (Agirdir et al 2002; Bertoni and Sprenkle 1988; Bleecker et al 2003; de Abreu and Suzuki 2002; Forst et al 1997; Hwang et al 2009; Lasky et al 2001; Ozcaglar et al 2001; Yokoyama et al 2002), and alterations in auditory evoked potential (Araki et al 1986; Bleecker et al 2003; Murata et al 1993) with exposure to lead and cadmium. However, it is not known whether exposure to lead and cadmium induces vestibular dysfunction specifically.…”

“…Many studies have examined the effects of lead and cadmium exposures on neurobehavioral functions, such as declines in cognitive ability and visuomotor performance (Balbus-Kornfeld et al 1995; Viaene et al 2000), but there is increasing evidence suggesting that exposures are associated with hearing loss and alterations in auditory evoked potentials (Araki et al 1986; Forst et al 1997; Murata et al 1993; Ozcaglar et al 2001). In addition, several studies have reported that workers with occupational exposure to lead have significantly poorer postural balance responses than do unexposed workers (Chia et al 1994, 1996; Dick et al 1999; Iwata et al 2005; Linz et al 1992; Ratzon et al 2000; Yokoyama et al 1997, 2002).…”

The Protective Mechanism of Antioxidants in Cadmium-Induced Ototoxicity in Vitro and in Vivo

“…These observations emphasize the importance of studying the effects of Cd 2+ in other organs. Recently, Ozcaglar et al (2001) reported that hair cells are more sensitive to Cd 2+ than kidney tubule cells, and that the cochlear component of hearing is more vulnerable to Cd 2+ toxicity than other parts of the auditory system. However, the ototoxic mechanism of Cd 2+ on the auditory system is not completely understood.…”