A Conversation with Luis de Lecea Roger Bingham: We are in Seattle at Sleep 2009 with Luis de Lecea who is in the department of psychiatry and bio- behavioral sciences at Stanford University. What’s happened since we last spoke? Just to fill you in, I’ve been talking to a lot of the colleagues that we had from the previous meeting and I would like to get some sense of your part of the picture, now, which was largely involving hypocretin. In fact, let’s start with an important paper that you’ve done in the interim. Let me read the title for you from Nature, Neural Substrates of Awakening, I understand that, the brain underpinning awakening, Probed with optogenetic control of hypocretin in neurons. That part needs to be unpacked for a general audience, I think, could you do that for me? Luis de Lecea: Sure. Well, we’ve been fortunate at Stanford to team up with Karl Deisseroth to develop this new technology called optogenetics and what optogenetics means is a new method that allows you to put a new channel, a light activated channel in specific groups of neurons and you can activate the channel and the neurons using light. So we’ve been able to do that using channelrhodopsin, that’s that channel that is light sensitive. We’ve been putting channelrhodopsin neurons, specifically, in mice, and then we can activate those neurons en vivo using an optical fiber that is inserted into the brain. Bingham: Now explain, just remind us why hypocretin neurons are important. De Lecea: Hypocretins were discovered about a decade ago by our group and another group and they’ve been shown to be responsible for stability of wakefulness. For instance, narcoleptics, they fall asleep all the time and they have this cataplexy, which is sudden loss of muscle tone. They have disrupted sleep architecture. Narcolepsy has been used for many years to study sleep because it is one of these diseases that tell you exactly what is about the coordination of sleep states. It turns out that hypocretin is deficient. Narcoleptic patients have dysfunction of the hypocretin system, specifically. Narcoleptics have selective neural degeneration of these neurons that produce hypocretin. Bingham: So this is a genetic component related to having an efficient hypocretin system? De Lecea: Well, narcolepsy is supposed to caused by an autoimmune attack to hypocretin neurons. There might be a genetic susceptibility but it’s an essence an autoimmune disorder. But you can make any animal narcoleptic if you remove hypocretin so there’s a causal relationship between hypocretin activity and narcolepsy. So that’s why there was this hypothesis that hypocretins were actually essential to maintain wakefulness. What we’ve done with the optogenetic technology has been to manipulate hypocretin neurons remotely and determine what is exactly the role of these neurons in the transitions between sleep states and that was something that couldn’t be done using pharmacology or other methods. Bingham: This was a point that came up in a previous conversation with Chiara Cirelli, which was, I said to her, what’s the problem here? It’s something we do, everybody does it everyday. Goes to sleep. Why don’t we understand it? And she was making the point that, yes, it’s slightly embarrassing but the lack of technology up to this point, so it’s sort of a new era in sleep medicine. De Lecea: Absolutely. This new technology that we are talking about such as optogenetics allows us to deconstruct neural circuits and unprecedented cellular specificity and temporal resolution, millisecond temporal resolution. That technology has become available only in the last couple of years. We’ve been fortunate enough to be at the right place at the right time to use these technologies to uncover the underpinnings of sleep and wakefulness. Bingham: Hard to separate sleep and wakefulness from diet, nutrition, metabolism, aging, these are all so intimately bound together. How does your piece fit into that larger picture? De Lecea: Absolutely. The hypocretins, neurons that make hypocretin, this neurotransmitter that is essential for sleep and arousal stability, these neurons happen to be very, very sensitive to metabolism and we believe that these neurons are the sensors that dictate the metabolic status of the organism. So those are the integrators of physiological functions of how alert you are, how hungry you are, how stressed you are and the output of this small group of neurons is responsible for triggering a cascade of events that results in wakefulness. So there are many different mechanisms involving in the regulation of hyper neuron activity and we’re now at a position of manipulating the activity of these neurons as we wish and therefore we can determine exactly when, for instance, we diet, what kind of effect that will have on hyper neuron activity and the activity of all other neural circuits that have to do with sleep and wakefulness. And stress, it’s pretty much the same thing, we know can manipulate brain circuits that are activated by stress and monitor the role of stress on sleep and wakefulness. Bingham: So how does this system, hypocretin system, fit into issues like exercise, learning, I’m thinking like practical applications. De Lecea: Sure. Of course not everything is related to hypocretin but we’re trying to connect those thoughts by manipulating the transitions between sleep states. And of course hypocretin is one way that we can manipulate transitions between sleep and wakefulness and REM sleep. Indeed the exercise has a prominent effect on transmitters that have to do with monoamines, serotonin and dopamine and so on and so forth. And these transmitters have a very, very important role in regulating hypocretin function and sleep and wakefulness by other mechanisms. So we are indeed at the point that we can selectively manipulate dopamine activity or neuralgic activity, exercise and monitor what is the interaction between these transmitter systems and other physical functions, exercise, appetite, and so on and so forth. So we are really at a very exciting moment because we can now do that in living, freely moving animals en vivo and that allows us to generate hypothesis about the, again, the relationship between exercise, diet, stress, and transitions between sleep states. Bingham: That will lead to some practical suggestions. De Lecea: Absolutely. Bingham: So, optogenetics. Again, what kind of equipment are you talking about? De Lecea: In essence, we are introducing this light activated channel using molecular biology methods, using either viruses or transgenic animals to introduce these light activated channels in the neurons that we want and with a specific promoter and that is the [unintelligible] gene promoter but we are doing this in other cell types as well and that is, like I said, with molecular biology methods. Then, once we know that the channel has been introduced in the right cells, we assess the activity of the channel using electrophysiology methods and then we use optical methods, like I said, laser, with a laser source, we deliver that light into the brain then we monitor brain activity on an electro sonogram. The opto of the optogenetic comes from the light activated channel and genetic is genetically encoded light activity channels. That’s sort of a newly coined term in the Deisseroth lab. Bingham: I’m not sure people will know what channel meant in this particular example. De Lecea: A protein that is inserted into the membrane that allows the flow of ions into the neuron and that is basically a normal signaling. The way neurons communicate with each other and transmit electrical signal. In essence, we are bypassing the natural communication between neurons by entering light when we want, where we want. Bingham: Does this kind of technology, would it help resolve some of these issues that are covered in articles like Why Sleep? What are we sleeping for? Is it restorative? Is it pruning? What’s going on? De Lecea: there’s still a very interesting debate going on as to what’s the function of sleep and we hope to be able to answer those questions in the midterm by addressing specifically what’s the posticity, how the specific circuits of neurons react to sleep deprivation and insults to sleep physiology. And by doing that we are hoping to address, specifically, what’s sleep for? What is the function of sleep? We, particularly right now, we are using this optogenetic technology to manipulate sleep so that we can introduce a normal sleep, we can introduce what we call noise or micro arousals. Those are one second awakenings that don’t interfere with a normal amount of sleep but they interfere with sleep architecture. So we can address the issue what is the role of intact sleep architecture on memory function, cognition, performance in general. Bingham: To you, sleep architecture means what? The transitions from different stages of sleep? De Lecea: That’s right. Natural sleep occurs in different cycles and there’s, in human sleep there’re ninety minute sleep cycles, from slow wave to REM sleep, back to non REM sleep and in rodents that’s not consolidated so the cycles are not as defined but the debate is still there as to whether we need sleep for memory consolidation or brain plasticity or we need the exact sequence of events that occur during sleep. In other words, do we need stage one, stage two, stage three or can we mess it all up, maintaining the amount of sleep and basically assessing cognitive functions after these disruptions. Bingham: So you actually put a sort of a very quick kink in the system and see what happens. De Lecea: That’s right. Bingham: And the results so far? De Lecea: Well, the results are still unpolished but we can pretty much conclude that the sequence of events during sleep is essential to consolidate memory and that’s an important aspect of sleep. We need an intact sleep architecture in order to function well. Bingham: How does that work with things like napping or micro naps? De Lecea: That’s a great question, of course, we don’t know yet and that is something we would like to explore. Of course, in rodents, there’s not an available model of napping in rodents because they nap all the time but we are hoping to assess those particular questions in different animal models and obviously humans are not yet available to optogenetic methods but we are hoping to address that in the near future. Bingham: Do you have any children? De Lecea: Yes. Bingham: So you have to be concerned about their sleep hygiene. Do you take anything from the lab that gives you suggestions on what you should do? Information, I mean, not products. De Lecea: No, the quick answer is no. Of course, there is a lot of common sense to maintain their sleep hygiene, of course regular exercise activity and sensible diet. That’s what’s known to be the best and my children have not had any sleep problems so far. So I think, set aside the genetic component, people who have a propensity for insomnia and of course narcolepsy. Other people within the normal phenotype in sleep will need an architecture and will need to use common sense to maintain those sleeping routine. Bingham: What led you into this field in the first place? De Lecea: Coincidence and serendipity. I was initially interested in looking for molecules that were specifically expressed in different, various, restricted brain nuclei and the first gene we isolated was a neuropeptide that was expressed in the cortex in rodents and in order to identify the function of this gene we asked the collaborator to inject the peptide into the brain and look at cortical activity which is where the gene was expressed. Our collaborators recorded an EEG and that’s how I became equated with the technology and the sleep field. The second gene that we pulled out was hypocretin, which was also, of course, involved with sleep as we later learned. Since then, I’ve been mostly involved. Bingham: Have you always wanted to go into science? De Lecea: Yes. Pretty much, yeah, from, I would say, elementary school. I had an uncle who was a mathematician and I was fascinated by his passion for science and I wanted to follow that pathway. Bingham: The point I was making early, though, about the practical applications, I wasn’t sort of forcing connections, I think it was just our perspective, here, that the intersection between experimental science, bench science and social policy is one that has to be acknowledged especially if you are talking about issues such as sleep and learning, education. This kind of work has a bearing on it. De Lecea: Of course, this is basic science. We just want to learn about the basic mechanisms underlying sleep and by learning more about how sleep works, we hope to, not only, of course, learn about the intellectual challenge, but we hope to generate drugs that may help people sleep better, more and better and also treat sleep disorders, which are disabling in some cases. For example, narcolepsy, we can theoretically, now, cure narcolepsy. We have a good orexin receptor selective agonist that’s possibly going to come out in the next ten years or so and that, of course is very rewarding to our field. Bingham: The relationship between narcolepsy and hypocretin neurons is, if you don’t have hypocretin neurons you’re a narcoleptic. So, what would the remedy be in that situation? De Lecea: A molecule would bind in the T Cell receptors and that would essentially wipe out narcolepsy. Cure narcolepsy for good. Bingham: Do you know how prevalent that is? De Lecea: It’s about one in two thousand people. Those are the estimates and another estimate is about one in five thousand. That’s the ballpark. Bingham: You would obviously know the work of Emmanuel Mignot and the notion of, as you said, the idea that narcolepsy is an autoimmune response. Could you just elaborate that a bit? De Lecea: Well, it’s probably too early to tell. There’s very recent data from the Mignot lab suggesting there’s some genetic susceptibility in a segment of the population that have a variant of the T Cell receptor and that suggests that indeed narcolepsy might be autoimmune since a particular combination of that T Cell receptor and MHE complex which is the molecule that binds to the T Cell receptor would probably generate this, sort of, autoimmune attack specific to hypocretin cells but the mechanisms are still unknown and it is still unknown whether it’s autoimmunity or molecule mimicry, bio infection. Bingham: Specifically, specially, affected populations? De Lecea: Right, so the critical population that is affected in narcolepsy is the set of neurons that produce hypocretin. Bingham: Is there an evolutionary story here? No geographical distribution. De Lecea: Within the brain? Oh, you mean, no, no, no. And I think in terms of ethnicity there’s some variance between Asians and Caucasians and African Americans but that has not been resolved yet, actually. Bingham: Do you sometimes feel it’s hard sometimes to get this balance feeling how, explaining to the general public explaining what you do, sounding reductionistic, mechanistic, and where there’s experience of being an integrated, functioning individual. Do you see the disconnect sometimes there? De Lecea: Absolutely. I think during this conversation it also became quite clear that, of course we are doing basic science to understand the basic circuitry, the mechanisms of how those transitions between sleep states might work, how does this translate into a drug, or how does this translate into someone sleeping better? Well, the answer is, of course, we can’t make these connections yet, but, we are making very good progress towards identifying the actual culprits of sleep disorders and that’s extremely challenging and I think during the next few years we are going to see more of that and obviously, that’s exciting. Bingham: I was thinking back to Francis Crick’s remark in his book The Astonishing Hypothesis, which is science in the search for the soul, you’re nothing but a pack of neurons. That’s a very hard. . . De Lecea: Thing to swallow? Well, as Terry Sejnowski would tell us, the bandwidth of our brain is equivalent to ten Internets, which is just a pack of neurons, very well connected. And the connectivity is what makes us who we are. I think those, I would say, simplistic views of sleep as you need sleep to recover, you need sleep to make the neurons better. Those are, again, very simplistic, very reductionistic views of how a very, very complex, interconnected machine works and to me, it’s all about circuitry and the more circuits we can tease apart, the more we learn about how, actually, the brain works and sleep is only one of the many functions of the brain and these regulated connectivities. Bingham: I’m not trying to romanticize this here, but, you know in talking to people that sleep is intimately connected with dreams, the whole consciousness thing, what’s conscious, what’s not conscious, what’s awake, what’s not awake, what’s sleep, what’s not. All those things are, sort of, such an ill defined state of exploration at some point. We still have this old folk psychological sense of what’s going on. This is why I asked the question about here you are getting right down into specific neurons that are implicated in a specific disease, narcolepsy. And I was just making the point that at some point do you think it’s all going to go that way? We will know the function of pretty much all the circuits you are talking about. De Lecea: Well, maybe not but it’s a first step and it’s an essential first step to understand what the circuitry is all about. And I think there’s going to be another level of analysis, which will be the whole connector or how the circuits are connected between each other, which will tell us more about the functions, the higher cognitive functions, but those are the next steps in the next decade or so we will start to learn about those functions that we cannot understand yet. Bingham: Yeah, but if you were at a cocktail party and you say what you do for a living and you said sleep, don’t people start asking you about dreams and stuff like that all that all the time? De Lecea: Sure, but I disconnect that all the time and say, well, I’m only studying the very basics of sleep and things are far ahead from us so time will connect dreams with circuitry that we talked about. Bingham: So that’s in your dreams? De Lecea: That’s in my dreams. Correct. Bingham: Luis de Lecea, thank you very much. De Lecea: Thank you.
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