Scientific American - March 2015

1 PLANETARY SCIENCEO ceans from the SkiesTECHNOLOGYA Wo r l d without SecretsPUBLIC HEALTHThe War on CuresBioelectronic medicine could create an off switch for arthritis, diabetes, even cancerMARCH 2015 2015 Scientific AmericanMarch 2015 Volume 312 Number 3ON THE COVERM arch 2015 , 1An overactive immune system can produce an inflamma-tory reaction that affects organs throughout the body. When the nervous system senses excessive inflammation, it tries to activate an immunological off switch, sometimes with limited effectiveness. Medical implants that enhance the anti-inflammatory process may help fight rheumatoid arthritis and other diseases.

2 Image by Bryan ELECTRONICS 28 Shock MedicineDoctors may soon treat inflammatory and autoimmune disorders with electricity. By Kevin J. TraceyPLANETARY SCIENCE 36 Oceans from the SkiesDid Earth s water come from comets, asteroids or something else entirely? New evidence is rekindling the debate. By David Jewitt and Edward D. YoungTECHNOLOGY 44 Sound BytesEars are such terrific pattern finders that scientists are using them to find cancer cells and particles from space. By Ron CowenPUBLIC HEALTH 48 Ebola War Africa s crisis has jump-started efforts to develop critically needed vaccines and treatments.

3 By Helen BranswellCLIMATE CHANGE 56 Fantasy IslandThe rush to save coral atolls from rising seas may be doing more harm than good. By Simon D. DonnerSCIENCE AND SOCIETY 64 Our Transparent FutureNow that no secret is safe, what will become of our society and its institutions? By Daniel C. Dennett and Deb RoySPECIAL REPORTINNOVATIONS IN THE MICROBIOME S3 The Peacekeepers Among the trillions of microbes in the human intestinal tract, a few play an outsize role in keeping us healthy. By Moises Velasquez-ManoffS5 Why Microbiome Treatments Could Pay Off Soon By Rob Knight S7 The Gene-Microbe Link By Ruth E.

4 Ley S9 INFOGRAPHIC Your Microbes at Work: Fiber Fermenters Keep Us HealthyS10 Microbiome Engineering By Justin L. Sonnenburg S13 Thinking from the Gut A new class of drugs aimed at the microbiome may make effective treatments for anxiety, depression and other mood disorders. By Charles Schmidt S14 The Diverse Microbiome of the Hunter-Gatherer By Stephanie L. SchnorrJUSTIN McMANUS Getty Images (broken seawall on Tarawa atoll, Republic of Kiribati) 2015 Scientific AmericanStimulation of the nervous system could replace drugs for inflammatory and autoimmune conditions By Kevin J.

5 TraceyMEDICINESHOCKIN BRIEFE xposure to heat, pressure, light or chemicals sets in motion a process to ensure that bodily organs do not overreact to these stresses. Nerve signals that link the brain and the rest of the body inhibit the mak ing of immune molecules that cause stimulation of neural pathways with an implanted medical device may assist the body in sup pressing inflammation. Bioelectronic medicine is the name of the new discipline that uses elec trical stimulation to treat inflamma tion and other disorders.

6 28 Scientific American , March 2015 MEDICAL ELECTRONICS 2015 Scientific American 2015 Scientific AmericanMarch 2015 , 29 Illustration by Bryan ChristieMEDICINESHOCK 2015 Scientific American 2015 Scientific American30 Scientific American , March 2015I am a brain surgeon who is fascinated by inflam-mation. Along with my laboratory colleagues, I examine molecules that cause in flam mation so that we can discover methods for alleviating the pain, swelling and tissue damage that is a conse-quence of many diseases. Some of this work has already benefited patients.

7 In 1987 I published the results of an experiment that targeted an inflam-matory molecule called tumor necrosis factor, or TNF, to rescue lab baboons from the consequences of lethal infection a study that contributed to the discovery of a new class of drugs for inflammatory, autoimmune and other diseases that disrupt the normal functioning of the body s immunological defenses. As a neurosurgeon, I am also intensely interested in the workings of the brain. A surprising discovery we made in the late 1990s, again involving TNF, merged insights from neurosci-ence and immunology.

8 We inadvertently discovered that neuro-logical reflexes predictable responses to certain sensory stimu-li block the production of TNF. This insight culminated in an invention I devised to treat inflammation using small, electrical nerve stimulators implanted in patients. The use of nerve-stimulating electronic devices to treat inflammation and reverse disability is laying the foundation for a new discipline called bioelectronic medicine. It is being tested in clinical studies of patients with rheumatoid arthritis and other diseases. It is based on a deceptively simple concept of harness-ing the body s natural reflexes to develop an array of effective, safe and economical alternatives to many pills and injectable drugs.

9 By precisely targeting the biological processes underlying disease, this nerve-stimulating technology should help avoid the troublesome side effects of many drugs. THE REFLEX CIRCUITHeat, toucH, pressure, ligHt and the presence of specific mole-cules generate an electrical signal in nerve cells called sensory neurons. This electrical information is transmitted to interneu-rons, another type of nerve cell in the central nervous system that passes the incoming impulse along to motor neurons, which complete the third and final stage in the simple reflex circuit.

10 The subsequent firing of the motor neuron sends electrical sig-nals back to the body s muscles and organs, triggering behaviors ranging from the withdrawal of a finger from a hot plate to the dilation of an airway during a three-mile run. Simple reflex circuits harmonize the activity of individual organs, so that you do not have to consciously plan the minute actions that keep your body functioning efficiently. When you leap from a chair and run up the stairs to answer the ring of a telephone, you do not have to think about coordinating your respiration, heart rate and blood pressure.