Periodic Reporting for period 1 - Lac-TB (Dissecting the impact of Lactate in Tuberculosis)
Reporting period: 2020-03-23 to 2022-03-22
Tuberculosis (TB) is a pathogen infecting macrophages in the lung where it can persist for decades. It is a global public health challenge; in 2021, 10.6 million people fell ill with TB and 1.6 million died1, despite vaccination and available treatments. The emergence of multidrug resistant TB and new antibiotic resistance strains exacerbate disease burden. Macrophages are capable of bactericidal activity towards Mycobacterium tuberculosis (M.tb) essential for infection control. To design novel host-directed therapies, a better understanding of how M.tb infection impacts host immune responses is crucial.
The overall aim of Lac-TB was to investigate the crosstalk between metabolic and immune responses in the context of M.tb-infection with a particular focus on macrophage responses to lactate, which is an abundant compound in lungs of M.tb-infected individuals. Exploiting this knowledge could be key for the design of new TB therapies, which are an urgent, unmet need.
The overall aim of Lac-TB was to investigate the crosstalk between metabolic and immune responses in the context of M.tb-infection with a particular focus on macrophage responses to lactate, which is an abundant compound in lungs of M.tb-infected individuals. Exploiting this knowledge could be key for the design of new TB therapies, which are an urgent, unmet need.
Lac-TB was structured in three research objectives (ROs), with their respective working packages. The project has achieved most of its objectives and milestones for the period, with relatively minor deviations.
The specific ROs were:
RO1: Identify induced immuno-metabolic responses in latent M.tb infection and active TB disease.
This work resulted in a publication entitled Tuberculosis alters immune-metabolic pathways resulting in perturbed IL-1 responses (Frontiers Immunol. 2022). I also performed a comprehensive review of the literature that resulted in the publication of three review articles: Lactate cross-talk in host-pathogen interactions (Biochem J, 2021), Host Immune-Metabolic Adaptations Upon Mycobacterial Infections and Associated Co-Morbidities (Front Immunol 2021) and Understanding lactate sensing and signalling (Trends Endocrinol Metab 2022).
RO2: Investigate macrophage responses to lactate.
I have shown expression of lactate transporters in both hMDMs and alveolar macrophages (AMs). I have shown that expression of lactate transporters in immune cells differs within the different stages of M.tb infection and TB disease. I characterised the cytokine release profile of AMs when treated with lactate, and shown that IL-8 is one of the key secreted cytokines in response to lactate treatment. Of note, IL-8 plays a key role in neutrophil recruitment and in the outcome of M.tb infection. I defined 3 potential mechanisms by which lactate could be exerting its functions and this is work in progress:
a) Through the formation of lipid droplets
b) Through protein lacytlation
c) Through direct GPCR signalling
The exploration of these 3 mechanisms of lactate-driven responses in macrophages is unprecedented and has the potential to reveal new targets for therapy.
RO3: Investigate the effects of lactate in both an in vitro granuloma system and ex vivo lung tissue M.tb infection model.
I received training and performed MGIA experiments, using a methodology clinically validated for the study and characterisation of TB drugs. I demonstrated that lactate has the capacity to inhibit mycobacterial growth, both of the avirulent strain BCG and of the virulent strain H37Rv. I started to established a human ex vivo lung slice infection model (Figure 8A and 8B). Interestingly, blocking lactate uptake via MCT1 transporter in human lung slices after stimulation with BCG resulted in decreased IL-8 secretion. This confirms the important link between lactate and IL-8 and constitutes an exciting methodological achievement, since TB research in human lung is equally scarce and needed.
Potential users of the results comprise not only TB researchers, but also researchers of a wide variety of disease settings in which lactate is produced in high concentrations and has the capacity to impact immune cell behaviours (e.g. tumour microenvironment, atherosclerosis, hypoxia). Further down the line, if regulating lactate responses achieves therapeutic success, clinicians and patients would also benefit from the generated knowledge.
I successfully delivered a number of local seminars and lab meetings. I also presented two posters, one at the VALIDATE 5th Annual Meeting and another one at the Tuberculosis Keystone Symposia. I was invited to give a talk at the British Thoracic Society Winter meeting (2023) entitled “Novel therapeutics in respiratory infection: targeting immunometabolism”.
Below are the publications that, so far, have been generated through this work:
Llibre A, Smith N, Rouilly V, Musvosvi M, Nemes E, Posseme C, Mabwe S, Charbit B, Kimbung, Mbandi S, Filander E, Africa H, Saint-André V, Bondet V, Bost P, Mulenga H, Bilek N, Albert ML, Scriba TJ, Duffy D. Tuberculosis impacts immune-metabolic pathways resulting in perturbed IL1 responses. Front Immunol. 2022.
Certo M*, Llibre A*, Lee W, Mauro C. Understanding lactate sensing and signalling. Trends Endocrinol Metab 2022. IF: 10.9. Llibre A, Dedicoat M, Burel JG, Demangel C, O’Shea MK, Mauro C. Host immune-metabolic adaptations upon mycobacterial infections and associated co-morbidities. Front Immunol. 2021.
Llibre A*, Grudzinska FS*, O’Shea MK, Duffy D, Thickett DR, Mauro C, Scott A. Lactate cross-talk in host-pathogen interactions. Biochem J. 2021.
Llibre A, Dedicoat M, Burel JG, Demangel C, O’Shea MK, Mauro C. Host immune-metabolic adaptations upon mycobacterial infections and associated co-morbidities. Front Immunol. 2021.
The specific ROs were:
RO1: Identify induced immuno-metabolic responses in latent M.tb infection and active TB disease.
This work resulted in a publication entitled Tuberculosis alters immune-metabolic pathways resulting in perturbed IL-1 responses (Frontiers Immunol. 2022). I also performed a comprehensive review of the literature that resulted in the publication of three review articles: Lactate cross-talk in host-pathogen interactions (Biochem J, 2021), Host Immune-Metabolic Adaptations Upon Mycobacterial Infections and Associated Co-Morbidities (Front Immunol 2021) and Understanding lactate sensing and signalling (Trends Endocrinol Metab 2022).
RO2: Investigate macrophage responses to lactate.
I have shown expression of lactate transporters in both hMDMs and alveolar macrophages (AMs). I have shown that expression of lactate transporters in immune cells differs within the different stages of M.tb infection and TB disease. I characterised the cytokine release profile of AMs when treated with lactate, and shown that IL-8 is one of the key secreted cytokines in response to lactate treatment. Of note, IL-8 plays a key role in neutrophil recruitment and in the outcome of M.tb infection. I defined 3 potential mechanisms by which lactate could be exerting its functions and this is work in progress:
a) Through the formation of lipid droplets
b) Through protein lacytlation
c) Through direct GPCR signalling
The exploration of these 3 mechanisms of lactate-driven responses in macrophages is unprecedented and has the potential to reveal new targets for therapy.
RO3: Investigate the effects of lactate in both an in vitro granuloma system and ex vivo lung tissue M.tb infection model.
I received training and performed MGIA experiments, using a methodology clinically validated for the study and characterisation of TB drugs. I demonstrated that lactate has the capacity to inhibit mycobacterial growth, both of the avirulent strain BCG and of the virulent strain H37Rv. I started to established a human ex vivo lung slice infection model (Figure 8A and 8B). Interestingly, blocking lactate uptake via MCT1 transporter in human lung slices after stimulation with BCG resulted in decreased IL-8 secretion. This confirms the important link between lactate and IL-8 and constitutes an exciting methodological achievement, since TB research in human lung is equally scarce and needed.
Potential users of the results comprise not only TB researchers, but also researchers of a wide variety of disease settings in which lactate is produced in high concentrations and has the capacity to impact immune cell behaviours (e.g. tumour microenvironment, atherosclerosis, hypoxia). Further down the line, if regulating lactate responses achieves therapeutic success, clinicians and patients would also benefit from the generated knowledge.
I successfully delivered a number of local seminars and lab meetings. I also presented two posters, one at the VALIDATE 5th Annual Meeting and another one at the Tuberculosis Keystone Symposia. I was invited to give a talk at the British Thoracic Society Winter meeting (2023) entitled “Novel therapeutics in respiratory infection: targeting immunometabolism”.
Below are the publications that, so far, have been generated through this work:
Llibre A, Smith N, Rouilly V, Musvosvi M, Nemes E, Posseme C, Mabwe S, Charbit B, Kimbung, Mbandi S, Filander E, Africa H, Saint-André V, Bondet V, Bost P, Mulenga H, Bilek N, Albert ML, Scriba TJ, Duffy D. Tuberculosis impacts immune-metabolic pathways resulting in perturbed IL1 responses. Front Immunol. 2022.
Certo M*, Llibre A*, Lee W, Mauro C. Understanding lactate sensing and signalling. Trends Endocrinol Metab 2022. IF: 10.9. Llibre A, Dedicoat M, Burel JG, Demangel C, O’Shea MK, Mauro C. Host immune-metabolic adaptations upon mycobacterial infections and associated co-morbidities. Front Immunol. 2021.
Llibre A*, Grudzinska FS*, O’Shea MK, Duffy D, Thickett DR, Mauro C, Scott A. Lactate cross-talk in host-pathogen interactions. Biochem J. 2021.
Llibre A, Dedicoat M, Burel JG, Demangel C, O’Shea MK, Mauro C. Host immune-metabolic adaptations upon mycobacterial infections and associated co-morbidities. Front Immunol. 2021.
In the work carried out during this fellowship, I identified induced immuno-metabolic responses in latent M.tb infection and active TB disease. In particular, I characterised how different immune-metabolic host responses shape IL1 secretion and downstream affects. Members of the IL1 cytokine family play an essential role in M.tb control. This work has the potential to ease the identification of new therapeutic targets. I also investigated how lactate shapes macrophage responses and I am currently working on 3 different mechanisms behind the lactate-driven effects. These are 1) through the formation of lipid droplets, by lactylated proteins and by signalling through specific GPCR receptors. Finally, I have set up an ex vivo human lung slice model, which will be a unique tool to study local, human responses to mycobacteria.
The data generated so far are exciting and promising, and that it will ease the path to a better understanding of the host response to TB disease, providing new therapeutic opportunities. TB is still today a global health challenge and new therapies are urgently needed. Therefore, the research performed through he MSC-IF has great potential for global impact.
The data generated so far are exciting and promising, and that it will ease the path to a better understanding of the host response to TB disease, providing new therapeutic opportunities. TB is still today a global health challenge and new therapies are urgently needed. Therefore, the research performed through he MSC-IF has great potential for global impact.