Treating disease and inflammation could become a far more precise game by hacking the nervous system using bioelectronics rather than drugs. By Gaia Vince.
In ‘Hacking the nervous system’, I wrote about doctors who have successfully treated patients with rheumatoid arthritis by stimulating their vagus nerve with a pacemaker. This restores inflammation’s ‘off switch’ in the spleen, releasing neurotransmitters that reinstate proper regulation of inflammatory immune proteins. The result is less inflammation in the joints, less pain, and reduction of other symptoms of rheumatoid arthritis.
The vagus nerve is involved in many other organs, so neurologists and immunologists are also investigating bioelectronic vagal therapies for inflammatory bowel disease, diabetes, obesity, cancer and asthma.
But the vagus is just one target for electrical therapy, and scientists are beginning to explore other possibilities, too. These include targeting the splenic, splanchnic and hepatic nerve networks that run through the body’s organs, and using deep brain stimulation to treat disorders like Parkinson’s and Alzheimer’s.
Some researchers believe electronic implants that hack the nervous system will one day replace drugs for many conditions. And pharmaceutical companies seem to agree: for example, GlaxoSmithKline is investing billions in bioelectronic innovation, even offering a $1 million prize to the first team to create a device that can “read and write the body’s electrical language” – by which they mean influence an organ’s function using accurate electrical signals. The US government is also investing in the field through the $250 million SPARC initiative and the ElectRx programme.
The challenges remain daunting, though. For a start, we don’t understand the body’s electrical language: the tens of thousands of nerve fibres in the vagus alone are not fully mapped, let alone their signals deciphered. Researchers at Imperial College London are working on that translation task. Stephen Bloom and Chris Toumazou have placed vagus nerve stimulators at the top of rats’ stomachs to record and read the signals sent to the brain to indicate fullness or the presence of different types of food. “The idea is that we should eventually be able to mimic the signals electrically to trick the mind into feeling full or desiring healthier foods,” Bloom explains. “The vagus does detect the type of food you eat, whether it’s protein, fat or high-calorie. And the brain feeds back, making us want certain foods, which can be unhealthy in obese people.” (See also: ‘A nervy way to lose weight’.)
But even if we could record and replicate signals, such as one from the stomach to the brain to report high levels of protein, challenges remain. For example, creating an implant device small enough yet powerful and reliable enough to run the complex microprocessor chip is far beyond our current capabilities.
Nevertheless, the technology is advancing rapidly with smaller pacemakers and implants and new techniques, including laser-firing brain implants that use optogenetics rather than wires to trigger nerve impulses.
The dream is to deliver precise, targeted therapy to groups of cells to promote the release of the body’s natural hormone or immune responses, dial down over-production of cells, or deploy other types of therapy, such as releasing implanted drugs at certain times and doses. The precision is possible because nerves branch in a highly specific and fixed geographical way. So treatment could be aimed at a tumour in a particular location by targeting the peripheral nerve that goes to the left side of the right lung, for example, rather than relying on the systemic approach of chemotherapy and the side-effects that entails.
The field is very young, and it’s certainly not time to throw the medications away, but with early successes in inflammatory disease, obesity and epilepsy, bioelectronic medicine has made an exciting debut.