Molecule mystery
A Winnipeg researcher and her team are working to crack the case of a rare condition that robs some newborns of the oxygen they need to survive
By Mike Daly
Winnipeg Regional Health Authority
Published Friday, May 31, 2019
She doesn’t own a deerstalker hat. She doesn’t smoke a pipe. And her research is anything but elementary-level, my dear Watson.
But for nearly two decades, Dr. Shyamala Dakshinamurti, a neonatologist and researcher at Children’s Hospital and the Children’s Hospital Research Institute of Manitoba, has been a persistent and dogged Sherlock Holmes of the medical world, trying to figure out why some babies are robbed of the oxygen they need to survive their first days out of the womb.
Now, she may be on the verge of an important turning point in her quest to unravel the mystery.
Five years ago, Dakshinamurti and her research team became the first in the world to discover that the problem may be caused by the shutdown of a “gatekeeper” molecule in an infant’s lung.
Today, the Winnipeg researcher and her team are preparing to test several variations of a compound that may be able to get the molecule working properly.
If successful, the treatment would go a long way to enhancing outcomes for babies born with Persistent Pulmonary Hypertension of the Newborn (PPHN), which affects an average of 30 to 40 infants every year in Manitoba.
This potentially fatal condition occurs when a baby’s lungs fail to make a smooth transition from life in the womb – where mom supplies the oxygen the baby requires – to life outside the womb, where the baby has to supply oxygen on its own.
Ordinarily, the transition takes place without a hitch. As the baby takes its first breaths, oxygen causes blood vessels in its lungs to expand, allowing blood to rush in, gather oxygen, and transport it to the brain, organs, and other parts of the body. In just a matter of minutes, the baby turns from blue to a healthy shade of pink, signalling a successful transition from mom’s life support system to circulatory independence.
“All of that has to happen quickly, and there are many triggers that help ensure it happens,” Dakshinamurti says. “But if you’re short of oxygen before or during birth, or there are complications of the birth such as infection, those triggers can shut off. The blood vessels in the lungs remain tightly constricted and no blood goes in. And that’s the only way you can get this handoff of oxygen going to the body.”
Without that successful handoff, an uneventful birth an go from almost mundane to a full-blown crisis in minutes. Worse still, it’s something that no one sees coming.
“These aren’t babies who develop this condition due to some congenital problem. They are perfectly healthy babies until labour. A woman would be going to her doctor’s appointments thinking everything is normal, only to have this happen during labour. It’s devastating.”
That was the case for Dakshinamurti’s aunt, who lost a child to PPHN many years ago.
“I didn’t know until just a few years ago that I had a cousin who died from PPHN. He was born about the same time I was. My aunt had a difficult labour and lost her baby to PPHN three days later. She didn’t speak about it for years. For her and every mother with a baby with PPHN, it’s devastating, and they are traumatized.”
It’s also difficult for those providing care in the baby’s first hours.
“To care for a baby with PPHN is frankly terrifying. They are the sickest babies in the neonatal intensive care unit,” Dakshinamurti says. “Of all the forms of hypertension, this is the one that will kill you the quickest. As a doctor, you’ve only got days to turn this around.”
Dakshinamurti’s interest in PPHN began when she was still a student in neonatology, the study of the development and disorders of newborn children.
“When I was in training, pursuing my fellowship in neonatology, these were the kids who would keep me up at night,” she says. “I’d be sitting at the bedside realizing very quickly that we were out of tools and that there was nothing more I could do. I would come off shift and realize how little help I had been. The answer, ‘I don’t know’ was an answer that, as a trainee, I got tired of hearing and, as a doctor, I got tired of giving. That’s the reason I wanted to conduct research into PPHN. And I’ve been studying it for almost 20 years now.”
There have been a number of breakthroughs in that time, resulting in a significant drop in mortality rates. “When I started in 2001, the mortality rate for PPHN babies was around 30 per cent, as opposed to 10 per cent now.”
Dakshinamurti attributes the drop to advances in ventilator technology, which have helped physicians mechanically supply oxygen to the lungs, particularly in newborns. In the 1990s, the advent of nitric oxide, an inhaled medication used to relax the blood vessels of the lungs, also made an impact, becoming a “first-line” medication used in the treatment of PPHN.
“Prior to nitric oxide, your likelihood of getting out of this was pretty slim,” Dakshinamurti says.
Other treatments followed, including Sildenafil, a drug more commonly known as Viagra, which has become nearly synonymous with the treatment of erectile dysfunction in adult men.
“For whatever other uses Viagra has, it has one interesting use in babies: it dilates very specific areas of the circulation, including the lung’s blood vessels. Because it’s cheaper than nitric oxide, a lot of developing countries are using that as their first-line treatment. And yes, it works on some of the kids, and yet we still don’t have a lot of other drugs in our tool kit. And so, when I’m working in the neonatal intensive care unit at night and I’m looking after a baby with PPHN, I’ve got the oxygen going, I’ve got the nitric oxide going, we have the Sildenafil ready to go – then what? If those didn’t work, and the baby’s still blue, the clock is ticking.”
And that’s where the detective work comes in.
“If you want to understand the nuts and bolts of why something goes wrong, you really can’t study it from the outside. You have to look at the blood vessels; you have to look at the cells of those blood vessels; you have to look at the molecules in the cells of those blood vessels to figure out why they are not working. Why one baby responds to treatment while another doesn’t isn’t obvious from the outside,” she says.
Dakshinamurti and her extended research team – which includes molecular biologist Dr. Prashen Chelikani and chemistry expert Dr. John Sorensen – have been trying to answer that question, among others, since 2001.
As she explains, when babies do not get enough oxygen, their lungs go into spasm.
“They just kind of slam shut. When that happens, muscles in those blood vessels thicken, and the flow of blood is reduced. Over time, that becomes irreversible. Once the pipe walls get too thick to push blood through, the baby’s heart will start to fail. Studies have shown that you’ve got about a week before the walls of those blood vessels become so thick that the heart is going to start to struggle. By two weeks, those pipes are solid, and you can’t push blood through at all. Babies have valiant little hearts, but they do fail under these conditions.”
In the lab, Dakshinamurti’s team is trying to determine why blood vessels go into spasm and what makes them relax. They’ve learned that the drugs used to relax blood vessels knock on different receptors – different doors – of the cell. But most of them converge on a single “gatekeeper” molecule, an enzyme called adenylyl cyclase that ordinarily signals the blood vessels to relax.
“It turns out that when they are short of oxygen, adenylyl cyclase molecules stop working. So we can have all these drugs to try to get the blood vessels to relax, and they will come up against a dead end because the gatekeeper molecule doesn’t work. That’s something our lab was the first to report, and we’ve been studying it for the last five years.”
Dakshinamurti likens the study to undercover surveillance.
“It’s like a spy game where one molecule will leave a message for another molecule to take forward. It’s how messages get communicated inside a cell. So the job of the scientist is to be the guy with the binoculars inside the bushes trying to figure out who is talking to who after the drug arrives at the doorway. If adenylyl cyclase isn’t doing its job, the messages stop right there.”
The team is currently studying Forskolin, a compound that is known to “turn on” adenylyl cyclase. Derived from the coleus plant well-known to gardeners, and commonly available at health supplement stores, Forskolin represents a promising lead in the fight against PPHN.
Unfortunately, the knowledge that it turns on adenylyl cyclase is far from being a clinically-ready breakthrough. That’s because there is not just one kind of adenylyl cyclase molecule, but 10. Some regulate blood pressure in the lungs, while others are responsible for helping your heart to pump. Still others are responsible for getting your guts to move and for absorbing fluid from your bowels. All 10 are activated by Forskolin, which is problematic, to say the least.
“Forskolin will turn on every adenylyl cyclase molecule in your body, but you’ll die of diarrhea before it does anything to your lungs,” Dakshinamurti explains. “So it’s a little more complicated than saying that because we’ve identified adenylyl cyclase as the gatekeeper, we’ve found the right suspect. Rather, it’s like having 10 suspects who look exactly alike.”
For Forskolin to be of use, a means will have to be found to target its effects on the one adenylyl cyclase molecule in the lung’s blood vessels that is shut off by a lack of oxygen.
“It’s only in the last couple of years that we’ve begun to tell the difference between the 10 different adenylyl cyclase molecules,” Dakshinamurti says. “Can we get at which one is found in the lung? And can we target that one type without triggering the rest of them?”
Those are difficult questions, but Dakshinamurti is optimistic.
“By looking at the structure of the adenylyl cyclase molecule, we realized that of the 10 types, there are about four of them that we can find in the lung blood vessels. And there’s one of them in particular – the main one in blood vessels and particularly important in newborns – that lack of oxygen shuts off. So we’re trying to target it by adapting Forskolin to fit only the one adenylyl cyclase molecule and not the others. That’s the quest. We have made eight versions of that Forskolin molecule so far, and we’re in the process of testing whether we can make it specific to the adenylyl cyclase in the lung blood vessels. The long-term goal is to be able to develop one more drug that will work when our existing drugs won’t.”
If or, hopefully, when that quest proves successful, it will still be a minimum of 10 years before the resulting drug could be clinically tested and available for use. For Dakshinamurti, that would mean 30 years or more of her professional life dedicated to PPHN research.
It’s been a long road, one that started with a gift her father, Dr. Krishnamurti Dakshinamurti – now a professor emeritus at the University of Manitoba’s College of Medicine and a senior advisor at the St. Boniface Hospital Research Centre – gave to his inquisitive young daughter.
“When I was a child, my dad got me one of those plastic human body models, where you could remove the transparent outside to get down to what the insides of the body look like,” Dakshinamurti says. “I think it was called The Visible Human, and if only the body were made like that. When you’re seeing a human from the outside and something’s not working, you wish they were like the Visible Human and you could see right through to the molecules. That’s not possible, but by using a scientific approach, we can come to understand what must be busted on the inside.”
It’s a question of time and painstaking effort, Dakshinamurti says.
“It takes persistence and not getting thrown off when the results don’t align with what you were thinking, or when you were barking up the wrong tree altogether,” she says. “The people who go into medical research are the type of people who will plant a seed and dig it up to see if it’s sprouted yet. That kind of curiosity makes you a terrible gardener, but a good scientist.”
And though much research on PPHN remains to be done, Dakshinamurti says she’s in it for the long haul.
“Cutting the mortality rate for PPHN would be brilliant, and having another drug in the toolkit is always useful. But having an understanding of how some of these fundamental building blocks in our body connect with each other – how the body talks to itself, and how a lack of oxygen derails that for babies affected by PPHN – that’s the biggie.”
Mike Daly is a communications specialist with the Winnipeg Regional Health Authority.