Focusing on the mitochondrial expression of TSPO as a marker and promoter of neuroinflammation
Lead Research Organisation:
Royal Veterinary College
Department Name: Comparative Biomedical Sciences CBS
Abstract
Accumulation of damaged mitochondria is a hallmark of ageing cells and it is particularly debilitating in post-mitotic cells, making the brain particularly vulnerable. Senescent mitochondria undergo structural and functional alterations that reduce their capacity to generate ATP by oxidative phosphorylation, but increase their production of damaging reactive oxygen species (ROS). Such damaged and dangerous mitochondria are normally removed by mitophagy, but ROS inhibits this defence mechanism (1). The opportunity therefore exists for a positive feedback in which damaged mitochondria accumulate and perpetuate their existence. This deleterious outcome may be especially problematic in microglia, because ROS accumulation promotes their activation, and such activation is widely held to underscore neurodegenerative mechanisms (2). Interestingly, microglial activation involves markedly increased expression of the mitochondrial translocator protein (TSPO) receptor (3-5), and changes in this expression can be monitored in animals and patients using radio-labelled ligands detectable by positron emission tomography (PET), such as ligand [18F]GE-180 developed by our collaborators (6).
Consistent with this background, our most recent data highlight that TSPO overexpression increases cellular oxidative stress and an impairment of the Parkin-mediated selection of mitophagy (7). However, it remains unclear whether the TSPO-mediated inhibition of mitophagy contributes to the activation of the microglia and hence if the impaired clearance of defective mitochondria has a role in sustaining their immune response.
Another uncertainty is whether the redox state of the cell influences the affinity of the radio-ligand to the TSPO. If it does, the interpretation of PET images becomes problematic, not least because the redox state can change with age.
We will explore these problems by adopting in vitro and in vivo protocols to modulate TSPO expression and monitor its contribution to cell mitophagy in microglia, correlating the findings with ROS and anti-ROS signalling mechanisms to examine the binding affinity of TSPO ligands and how this may change with age.
This work will outline a fundamental and regulatory pathway, TSPO-dependent, for the activation of the brain's immune cells by impacting the ontology of mitophagy in microglial adaptation via selection of mitochondria during stress conditions. Proof of concept to improve TSPO targeting for advanced PET imaging of neuroinflammation will be also obtained.
Consistent with this background, our most recent data highlight that TSPO overexpression increases cellular oxidative stress and an impairment of the Parkin-mediated selection of mitophagy (7). However, it remains unclear whether the TSPO-mediated inhibition of mitophagy contributes to the activation of the microglia and hence if the impaired clearance of defective mitochondria has a role in sustaining their immune response.
Another uncertainty is whether the redox state of the cell influences the affinity of the radio-ligand to the TSPO. If it does, the interpretation of PET images becomes problematic, not least because the redox state can change with age.
We will explore these problems by adopting in vitro and in vivo protocols to modulate TSPO expression and monitor its contribution to cell mitophagy in microglia, correlating the findings with ROS and anti-ROS signalling mechanisms to examine the binding affinity of TSPO ligands and how this may change with age.
This work will outline a fundamental and regulatory pathway, TSPO-dependent, for the activation of the brain's immune cells by impacting the ontology of mitophagy in microglial adaptation via selection of mitochondria during stress conditions. Proof of concept to improve TSPO targeting for advanced PET imaging of neuroinflammation will be also obtained.
Organisations
People |
ORCID iD |
Michelangelo Campanella (Primary Supervisor) | |
Aarti Singh (Student) |
Publications
Singh A
(2022)
Pyroptosis targeting via mitochondria: An educated guess to innovate COVID-19 therapies.
in British journal of pharmacology
Singh A
(2021)
Pharmacological advances in mitochondrial therapy.
in EBioMedicine
Singh A
(2018)
Common Traits Spark the Mitophagy/Xenophagy Interplay.
in Frontiers in physiology
Gatliff J
(2017)
A role for TSPO in mitochondrial Ca2+ homeostasis and redox stress signaling.
in Cell death & disease
Desai R
(2020)
Mitochondria form contact sites with the nucleus to couple prosurvival retrograde response.
in Science advances
Studentship Projects
Project Reference | Relationship | Related To | Start | End | Student Name |
---|---|---|---|---|---|
BB/M017192/1 | 30/09/2015 | 29/09/2019 | |||
1655762 | Studentship | BB/M017192/1 | 30/09/2015 | 29/09/2019 | Aarti Singh |
Description | The breadth of results we have produced indicate that TSPO possesses an inherently pro-inflammatory role in microglial cells in response to toxins. The accumulation of TSPO, which is an acknowledged factor in neuroinflammation, takes part in the inflammasome assembly by interacting with NLRP3, a multisubunit complex which allows the release of IL-IB, a key pro-inflammatory cytokine. We did find that in TSPO null microglial cells the inflammasome is indeed unable to assemble likely due to the high degree of mitochondrial quality control by targeted autophagy. Our work hints at the mechanistic role played by TSPO in the adaptation of mitochondrial function to an inflammatory phenotype. This can pave the way to novel chemical strategies to mark and alleviate innate inflammatory response in the Central Nervous System by targeting TSPO which is found overexpressed in neurodegenerative conditions such as Parkinson's disease, Alzheimer's diseases and Multiple Sclerosis. |
Exploitation Route | Treating inflammation. |
Sectors | Healthcare Pharmaceuticals and Medical Biotechnology |
Title | Generation of TSPO KO microglial cells |
Description | CRISPR/Cas9 genome editing was undertaken to induce a short deletion in the TSPO gene, resulting a deleterious frameshift. |
Type Of Material | Cell line |
Year Produced | 2016 |
Provided To Others? | No |
Impact | The cell line potentiates identifying the role of TSPO in neuroinflammation |
Description | Biophysical Society Meeting |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | 6000 scientists from a variety of disciplines came together for a 5 day event allowing students to share their research and for senior scientists to share the latest significant scientific findings. |
Year(s) Of Engagement Activity | 2018 |
Description | Early Career Mitochondrial Meeting Poster |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Postgraduate students |
Results and Impact | 50 early career mitochondrial scientists attended this meeting where students and post doctoral scientists gave talks, looked at posters and discussed research activities. |
Year(s) Of Engagement Activity | 2017 |
Description | Invited Talk at the Redox Society of Medicine and Biology Annual Meeting |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Update on our work on the interpay between stress response mecchanims and redox stress |
Year(s) Of Engagement Activity | 2019 |
Description | Invited Talk in conference |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Industry/Business |
Results and Impact | Invited presentation on mitochondrial regulation of inflammation and new regulatory mechanisms we have unveiled. |
Year(s) Of Engagement Activity | 2018 |
Description | Poster Presentation |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other audiences |
Results and Impact | More than 60 scientists attended this meeting discussing about the latest discoveries in the field of autophagy. |
Year(s) Of Engagement Activity | 2019 |
URL | https://autophagy-uk.com/2019/01/25/2019-meeting-glasgow/ |
Description | Poster Presentation for visiting Students |
Form Of Engagement Activity | Participation in an open day or visit at my research institution |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Postgraduate students |
Results and Impact | 20-30 prospective postgraduate students visited the campus to see what projects are on offer as well has have been undertaken by other students. At least 4 students have since expressed interest in joining our group. |
Year(s) Of Engagement Activity | 2018 |
Description | Presentation at TSPO meeting |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Professional Practitioners |
Results and Impact | A small scale TSPO meeting for scientists that work on or in areas related to the protein. Both PIs, Post-docs and PhD students shared their latest findings allowing for much discussion into work that has been done and is currently being done to increase our knowledge of the role of TSPO. |
Year(s) Of Engagement Activity | 2018 |