The Curtis Clock laboratory has a real interest in metabolism, which is a really broad term and means different things to different people. We are interested in how different fuels (sugars , fats, proteins) are metabolised (broken down) within immune cells, and if this has an impact on how that immune cell functions. The key metabolic organelle within a cell is the mitochondria, that is where the breakdown parts of these fuels end up and are converted to energy (ATP). We are a Clock lab, so our raison d’etre (so to speak) is to unravel how different fuels are metabolised within immune cells at different times of day and how the mitochondria work at different times of day, and how that impacts the response of the immune cell at that time of day. This is what we now term “Circadian Immunometabolism”. This leads me on nicely to our title, before the age of electricity, our forefathers never ate in the middle of the night, we believe that our immune system becomes dysfunctional when it has to deal with food during a time when we now believe our immune system is undergoing repair and restoration. So to begin to get at these big questions, Mariana and George have two exciting projects ongoing. Mariana, who is a postdoc in the laboratory, will show how our mitochondria are changing over the course of the day in dendritic cells (these are cells of the innate immune system and are the ones that feed information to our adaptive immune system) (see Fig. 1). The title of her talk is
“Those mitochondria have got rhythms! Mitochondrial activity and antigen processing in dendritic cells is dependent on the molecular clock protein BMAL1”.
George, a PhD student in the lab, is dissecting down into the cells to figure out how the electron transport chain (the side of action for ATP synthesis) is controlled by the clock. The title of his talk is
“Metabolic pathways in a macrophage lacking a molecular clock”
More details of what we do can be found here: www.Curtisclocklab.com
Last week was another superb week for circadian research in the Molecular and Cellular Therapeutics Department. The Curtis Laboratory published our first big paper on the immune body clock in Nature Communications. This study originated back in 2013. I was still a postdoc in Prof. Luke O’Neills laboratory at Trinity College and was intrigued by some of the studies that showed that multiple sclerosis (MS) was affected by the circadian disruption. A key study showed that teenagers who work shift work before the age of 18 are more susceptible to multiple sclerosis in later life. I wondered if we would see any differences in multiple sclerosis if we disturbed the immune body clock. I approached Prof. Kingston Mills also at Trinity College, who is one of the world leaders of multiple sclerosis and has a key mouse model that recapitulates certain features of MS, called experimental autoimmune encephalomyelitis (EAE). The first experiment we conducted was to see if a mouse which does not have the molecular clock in macrophages was more susceptible to disease, and low and behold it was! This project was driven by one of the most talented researchers that I have ever had the pleasure of working with, Dr. Caroline Sutton, who is a senior postdoctoral fellow in Prof. Mills lab. This project is a great example of collaboration between multiple labs, Mills, O’Neill and my own new group here at RCSI.
And if that wasn’t enough! We also hosted the circadian expert Prof. Qing-jun Meng for our second institutional seminar series on Thursday. Prof. Meng is a world expert on clocks in the musculoskeletal system at University of Manchester. I met Qing-jun in 2013, and have followed his research intensely. He has made seminal discoveries on the impact of the clock on cartilage and invertebral disk function and how this leads to diseases of ageing, such as osteoarthritis and lower back pain. He had the audience enthralled for an hour with his rhythmic images of cells glowing with 24-hour rhythms, and his use of Google searches. It was an absolute pleasure to have Qing-jun with us for the day, and I hope that we can have him back again in the near future.
Some news features on the article can be found here:
Last Monday while in Amsterdam with my Mam and two sisters, a friend of mine sent a text to let me know that the 2017 Nobel Laureates in Physiology and Medicine were Hall, Rosbash and Young. They were awarded the Nobel for their work in identifying the key genes that create circadian or body clock rhythms in the fruit fly. My feet literally were stuck to the ground, it was thrilling to know that these gentlemen would get the recognition that they so deserve, but also what this will mean for the field of science that I am so passionate about. The body clock is the molecular timekeeping system that exists in practically every organism on the earth and in every cell in our body. Simply put, it allows the cell to tell what time of day it is. Why is that important? We live on a spinning planet and because of the earth’s rotation to the sun, all life on earth has been subjected to daily periods of light and heat, dark and cold. The body clock allows us to anticipate and respond to these 24-hour predictable environmental changes and synchronises our physiology to it. For example, the body clock increases cortisol levels in the body ahead of awakening, this helps us to become active once we wake. The body clock also increases expression of digestive enzymes in the intestinal tract during daylight hours (this is why curry chips at 3am is never a great idea!).
Back in the 80’s Hall, Rosbash and Young independently isolated a gene called Period, they showed how the gene encodes a protein PER that builds up in cells at night and degrades during the day. This daily rise and fall of PER essentially allow the cell to track time of day. How thrilling it must have been for them to observe this daily change in the mRNA levels of Period gene (Figure 1- black line), all that is changing along the x-axis is the time of day.
So what does this mean three decades later? We have made great strides in understanding how the molecular clock works. We now know that the clock keeps time by a series of transcriptional-translational feedback loops. We also know that the clock controls 40% of all coding genes within the body. The body clock controls all aspects of our physiology from metabolism to immunity.
Many diseases, such as osteoarthritis and cardiovascular disease, are highly time of day dependent. Moreover, it appears that disruption of our body clocks, caused by our non-stop 24/7 lifestyle and exposure to artificial light at all times of day, is partly responsible for the increase in chronic inflammatory diseases. Unfortunately, most cell culture systems are not synchronized with the time of day, and this, in my opinion, is one of the main reasons that many researchers unknowingly neglect this field. Finally, we are making great strides in attempting to time specific treatments to the right time of day, an area called chronotherapy. Therefore, it is my hope that this increased awareness of the body clock will bring more researchers into this fascinating field. If we don’t fully understand how our body clock controls physiology and disease we will certainly be left in the dark.
Annie Curtis is a Research Lecturer and runs the Immune Clock laboratory at MCT and is fascinated by all things body clock related.
Asthma is of particular relevance to the area of circadian control of immunity, since it is a disease with very strong clinical evidence demonstrating regulation by circadian variation. Airway hypersensitivity and asthma attacks are more common at night in humans. The molecular basis for this is unknown and no model of asthma in animals with genetic distortion of the molecular clock exists.
In this study, we showed that mice lacking the main clock transcription factor BMAL1 in myeloid cells have increased lung inflammation demonstrated by higher numbers of eosinophils and increased IL-5 (key pathogenic cytokine in asthma that recruits eosinophils).This suggests that Bmal1 is a potent negative regulator, in myeloid cells in the context of allergic asthma. Our findings might explain the increase in asthma incidents during the night in humans when BMAL1 expression is low.
Last week’s departmental talks encompassed a Deep Dive into Clock biology in Macrophages affecting the Inflammatory Response. This area is the focus of the Immune-Clock laboratory of Dr. Annie Curtis, a recent recruit to RCSI.
Jamie Early (PhD student of the Curtis Lab) currently residing in the Luke O’Neill Laboratory presented his findings on the role of the circadian clock in suppressing inflammation in macrophages and if the anti-oxidant transcription factor and redox sensor NRF2 plays a role. His talk was titled ‘The macrophage clock is a key controller of the anti-oxidant and inflammatory response via the transcription factor Nrf2’.
Second up, we had Mariana Cervantes (PhD student and visiting scientist from the Instituto Politecnico Nacional (IPN) in Mexico) present her talk titled ‘The macrophage clock is having a profound impact on mitochondrial dynamics- what are the implications for inflammation?’
Mariana is interested in how mitochondria alter their morphology, either fusing together to form networks or fragmenting into smaller units termed fission. She is trying to uncover if the clock is regulating this process and if so what are the implications for the inflammatory response.
Our Immune-clock laboratory has a real interest in metabolism and how alterations in metabolic pathways termed “metabolic reprogramming” can shape the type of immune response. This area called “Immunometabolism” has exploded in the last 5 years, and the implications are massive. It appears that macrophages use one metabolic pathway to become highly proinflammatory and another metabolic pathway to resolve inflammation and promote wound healing. So why is our laboratory so interested in this? Well, if you think about daily changes in our environment, the two biggest are the sleep/wake cycle and the other is feeding/fasting. It is now clear that clocks in metabolic tissues like the liver/pancreas/adipose tissue prepare the body to deal with this daily rhythm in feeding/fasting. Based on this, our interest is to figure out if the clock within macrophages is somehow altering its metabolism over the course of the day and is that leading to changes in macrophage function, particularly the inflammatory response.
Body clocks tend to garner quite a bit of attention from the media. Folks are obsessed with sleep, either they cant get enough or they are getting too much, and all of us can relate to the symptoms of jet lag and morning versus evening types. Therefore it’s a great topic to discuss with wider audiences. I really enjoy chatting with people about the implications of our internal timing system and that research now shows that living in synchrony with your body clock can improve overall health. For the SFI Science week I was asked to provide an interview to the Daily Star called “The Science of Sleep Explained”. I was also asked to go on the “Alive and Kicking” show on Newstalk Radio with Ciara Kelly, you can listen to the interview: What type of sleeper are you? Are you an owl or a lark?