Dr. Ron’s Research Review – August 31, 2011

This week’s research review focuses on heavy metals, including the effects of heavy metal music.

A recent review article discussed the adverse effects of low level heavy metal exposure on male reproductive function. The evidence for the effects of low exposure was strongest for cadmium, lead, and mercury and less certain for arsenic. (Wirth and Mijal 2010)

Cadmium may be a metallohormone because it mimics the function of steroid hormones. (Byrne, Divekar et al. 2009)

Cadmium promotes breast cancer cell proliferation by potentiating the interaction between ERalpha and c-Jun. (Siewit, Gengler et al. 2010)

Scientific evidence indicates that long-term exposure to (some) metallic compounds induces different forms of cancer, including breast cancer. (Florea and Busselberg 2011)

Violent lyrics in heavy metal music can increase aggression in males. College students added more hot sauce to to a cup of water they believed another subject would have to drink. (Mast and McAndrew 2011)

Dr. Ron


Articles

Adverse effects of low level heavy metal exposure on male reproductive function

            (Wirth and Mijal 2010) Download

Lead, cadmium, mercury, and arsenic, often referred to as "heavy metals", are toxic for wildlife, experimental animals, and humans. While experimental animal and human occupational studies with high exposure levels generally support an adverse role for these metals in human reproductive outcomes, information on the effects of low, environmentally-realistic exposure levels of these metals on male reproductive outcomes is limited. We review the literature on effects of exposure to low levels of these metals on measures of male fertility (semen quality and reproductive hormone levels) and provide supporting evidence from experimental and occupational studies. Potentially modifying effects of genetic polymorphisms on these associations are discussed. A brief review of the literature on the effects of three trace metals, copper, manganese, and molybdenum, that are required for human health, yet may also cause adverse reproductive effects, follows. Overall, there were few studies examining the effects of exposure to low levels of these metals on male reproductive health. For all metals, there were several well-designed studies with sufficient populations appropriately adjusted for potential confounders and many of these reported harmful effects. However, many studies lacked sufficient numbers of participants to be able to detect differences in outcomes between exposed and non-exposed individuals, did not clearly identify the source and characteristics of the participants, and did not control for other exposures that could alter or contribute to the outcomes. The evidence for the effects of low exposure was strongest for cadmium, lead, and mercury and less certain for arsenic. The potential modifying effects of genetic polymorphisms has not been fully explored. Additional studies on the reproductive effects of these toxic ubiquitous metals on male reproduction are required to expand the knowledge base and to resolve inconsistencies.

Cadmium--a metallohormone?

            (Byrne, Divekar et al. 2009) Download

Cadmium is a heavy metal that is often referred to as the metal of the 20th century. It is widely used in industry principally in galvanizing and electroplating, in batteries, in electrical conductors, in the manufacture of alloys, pigments, and plastics, and in the stabilization of phosphate fertilizers. As a byproduct of smelters, cadmium is a prevalent environmental contaminant. In the general population, exposure to cadmium occurs primarily through dietary sources, cigarette smoking, and, to a lesser degree, drinking water. Although the metal has no known physiological function, there is evidence to suggest that the cadmium is a potent metallohormone. This review summarizes the increasing evidence that cadmium mimics the function of steroid hormones, addresses our current understanding of the mechanism by which cadmium functions as a hormone, and discusses its potential role in development of the hormone dependent cancers.

Cadmium promotes breast cancer cell proliferation by potentiating the interaction between ERalpha and c-Jun

            (Siewit, Gengler et al. 2010) Download

Cadmium is an environmental contaminant that enters the body through diet or cigarette smoke. It affects multiple cellular processes, including cell proliferation, differentiation, and apoptosis. Recently, cadmium has been shown to function as an endocrine disruptor, to stimulate estrogen receptor alpha (ERalpha) activity and promote uterine and mammary gland growth in mice. Although cadmium exposure has been associated with the development of breast cancer, the mechanism of action of cadmium remains unclear. To address this deficit, we examined the effects of cadmium treatment on breast cancer cells. We found that ERalpha is required for both cadmium-induced cell growth and modulation of gene expression. We also determined that ERalpha translocates to the nucleus in response to cadmium exposure. Additionally, we provide evidence that cadmium potentiates the interaction between ERalpha and c-Jun and enhances recruitment of this transcription factor complex to the proximal promoters of cyclin D1 and c-myc, thus increasing their expression. This study provides a mechanistic link between cadmium exposure and ERalpha and demonstrates that cadmium plays an important role in the promotion of breast cancer.

Metals and breast cancer: risk factors or healing agents?

            (Florea and Busselberg 2011) Download

Metals and metal compounds are part of our environment. Several metals are essential for physiological functions (e.g., zinc or magnesium); while the beneficial effects of others are uncertain (e.g., manganese), some metals are proven to be toxic (e.g., mercury, lead). Additionally there are organic metal compounds; some of them are extremely toxic (e.g., trimethyltin, methylmercury), but there is very little knowledge available how they are handled by organisms. Scientific evidence indicates that long-term exposure to (some) metallic compounds induces different forms of cancer, including breast cancer. On the other side, several metal compounds have clinical use in treating life-threatening diseases such as cancer. In this paper we discuss the recent literature that shows a correlation between metal exposure and breast cancer.


Violent Lyrics in Heavy Metal Music Can Increase Aggression in Males

         (Mast and McAndrew 2011) Download

Thirty-five male college students added as much hot sauce as they wanted to a cup of water they believed another subject would have to drink after listening to heavy metal music with violent lyrics, heavy metal music without violent lyrics, or no music at all. Males who were exposed to the music with violent lyrics added more hot sauce to the water than those in the other groups. An equipment failure prevented a definitive analysis of the role played by testosterone in this effect, but the results clearly indicate that it was the lyrics and not other qualities of the music that was responsible for the aggressive behavior.


References

Byrne, C., S. D. Divekar, et al. (2009). "Cadmium--a metallohormone?" Toxicol Appl Pharmacol 238(3): 266-71.

Florea, A. M. and D. Busselberg (2011). "Metals and breast cancer: risk factors or healing agents?" J Toxicol 2011: 159619.

Mast, J. F. and F. T. McAndrew (2011). "Violent Lyrics in Heavy Metal Music Can Increase Aggression in Males." North American Journal of Psychology 13(1): 63-4.

Siewit, C. L., B. Gengler, et al. (2010). "Cadmium promotes breast cancer cell proliferation by potentiating the interaction between ERalpha and c-Jun." Mol Endocrinol 24(5): 981-92.

Wirth, J. J. and R. S. Mijal (2010). "Adverse effects of low level heavy metal exposure on male reproductive function." Syst Biol Reprod Med 56(2): 147-67.