What is remarkable about the studies is the fact they have used existing medications. The drugs, which are approved for use in humans, were used to eliminate an Escherichia coli infection in frogs. The action of the drugs triggered a reversal of the electrical charge in the cells of the frigs, wiping out the pathogen.
For the study drugs that either depolarize (positively charge) or hyperpolarize (negatively charge) cells were tested. It was found that the negative charge effect is of significance. The drug that achieved this in an optimal way was one called ivermectin. Ivermectin is a medication effective against many types of parasites, such as head lice, scabies, river blindness, strongyloidiasis, and lymphatic filariasis.
Wiping out bacteria
Analyzing what’s happening, Tufts University biologists discovered that administering specific drugs leads to the interior of cells becoming more negatively charged. In tadpoles (of the frog Xenopus laevis), this strengthened the innate immune response to E. coli infection and injury. Hence the researchers have found a hitherto unknown and novel aspect of the immune system. This has been termed “regulation by non-neural bioelectricity.” The finding could be significant, possibly opening up a new approach for clinical applications of the technique in human medicine.
As the lead researcher, Dr. Michael Levin explains: “All cells, not just nerve cells, naturally generate and receive electrical signals.” He adds that by “being able to regulate such non-neural bioelectricity with the many ion channel and neurotransmitter drugs that are already human-approved gives us an amazing new toolkit to augment the immune system’s ability to resist infections.”
Bioelectricity
Bioelectricity refers to electric potentials and currents produced by or occurring within living organisms. These potential vary between one to a few hundred millivolts. Perhaps the best known example is with the electric eel.
Such electric fish produce their electrical fields from a specialized structure called an electric organ. This is made up of modified muscle or nerve cells, which became specialized for producing bioelectric fields stronger than those that normal nerves or muscles produce.
The pathogen killing effect also rests with the immune system. All vertebrates possess two kinds of immunity: the adaptive immune system, which relies on the memory of previous exposure to a specific pathogen; and the innate immune system, which is the first line of defense against pathogens. It is the innate immune system that is being studied in relation to bioelectricity.
Immune system in action
The reason why this is important relates to the role this facet of the immune system plays with tissue repair and regeneration. Also important to the process is the neurotransmitter serotonin, which acts as an intermediary between voltage and immune response. Serotonin is found in all bilateral animals, where it mediates gut movements and the animal’s perceptions of resource availability (primarily to food).
The combination of ivermectin and bioelectricity led to the proportion of embryos the bacterial increasing average 32 percent. This was compared tadpoles not given the drug. Here, with the untreated tadpoles, the mortality in untreated rate was 50 to 70 percent.
It is hoped the developed will lead to a new understanding of innate immunity can lead to new developments for fighting pathogens, especially new ones from which there is no adaptive immune system memory. The longer-term aim is to develop a treatment for people by manipulating the bioelectric microenvironment through new combinations of depolarizing drugs. Before doing so a greater understanding is required of how and why bacteria respond to the changes to cell environment and why they find these changes inhospitable and potentially destructive.
At present it is though the electrical variations alter the membrane potentials of the bacterial cell wall. Death could result from one of the following mechanisms:
Toxic substances produced as a result of electrolysis (such as oxidizing radicals),
Oxidation of enzymes and coenzymes,
Membrane damage leading to leakage of essential cytoplasmic constituents
Decreased bacterial respiratory rate.
The research has been published in the journal npj Regenerative Medicine, under the title “Bioelectric regulation of innate immune system function in regenerating and intact Xenopus laevis.”
In related news, researchers are looking at bioelectric effects further, such as evaluating the antibacterial efficacy of a bioelectric dressing containing silver and zinc against various wound pathogens. With this, the microbial killing is possibly enhanced first by bioelectric field attracted microbes carrying a negative charge to the positive pole containing silver and zinc.
Essential Science
This article is part of Digital Journal’s regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue. Last week we looked at how nanotechnology can be used to rapidly and non-invasively treat broken bones. The week before we reviewed research into Parkinson’s disease that suggested the progression of the disease can be controlled through the use of antibiotics.
