Biology subjects

Henderson, C. J.

Publications and source records attributed to Henderson, C. J..

4 recordsLinked to original sources

bioRxiv2022

Defining the in vivo mechanism of air pollutant toxicity using murine stress response biomarkers.

BackgroundAir pollution can cause a wide range of serious human diseases. For the informed instigation of interventions which prevent these outcomes there is an urgent need to develop robust in vivo biomarkers which provide insights into mechanisms of toxicity and relate pollutants to specific adverse outcomes. ObjectiveTo exemplify the application of in vivo stress response reporters in establishing mechanisms of air pollution toxicity and the application of this knowledge in epidemiological studies and potentially in disease prevention. MethodsMurine stress-reporter models (oxidative stress/inflammation, DNA damage and Ah receptor -AhR-activity) and primary mouse and primary human nasal cells were exposed to chemicals present in diesel exhaust emissions, particulate matter (PM) standards (PM2.5-SRM2975, PM10-SRM1648b) or fresh roadside PM10. Stress reporter activity was analysed by luminescence assays and histochemical approaches in a panel of murine tissues. Biochemical, genetic and pharmacological approaches were used to establish the mechanism of the stress responses observed. Pneumococcal adhesion was assessed in exposed primary human nasal epithelial cells (HPNEpC). ResultsNitro-PAHs induced Hmox1 and CYP1a1 reporters in a time- and dose-dependent, cell- and tissue-specific manner. NRF2 pathway mediated this Hmox1-reporter induction. SRM1658b, but not SRM2975, was a potent inducer of NRF2-dependent Hmox1 reporter activity in lung macrophages. Combined use of HPNEpC and in vivo reporters demonstrated that London roadside PM10 particles induced pneumococcal infection in HPNEpC mediated by oxidative stress responses. DiscussionThe combined use of in vivo reporter models with HPNEpC provides a robust approach to define the relationship between air pollutant exposure and health risks. These models can be used to hazard ranking environmental pollutants by considering the complexity of mechanisms of toxicity. These data will facilitate the relationship between toxic potential and the level of pollutant exposure in populations to be established and potentially extremely valuable tools for intervention studies.

pharmacology and toxicology↗

bioRxiv2021

Mathematical modeling quantifies ERK-activity in response to inhibition of the BRAFV600E-MEK-ERK cascade.

BackgroundSimultaneous inhibition of multiple components of the BRAF-MEK-ERK cascade (vertical inhibition) has become a standard of care for treating BRAF-mutant melanoma. However, the molecular mechanism of how vertical inhibition synergistically suppresses intracellular ERK-activity, and consequently cell proliferation, are yet to be fully elucidated. MethodsWe develop a mechanistic mathematical model that describes how the mutant BRAF-inhibitor, dabrafenib, and the MEK-inhibitor, trametinib, affect BRAFV600E-MEK-ERK signalling. The model is based upon a system of chemical reactions that describes cascade signalling dynamics. Using mass action kinetics, the chemical reactions are re-expressed as ordinary differential equations which are parameterised by in vitro data and solved numerically to obtain the temporal evolution of cascade component concentrations. ResultsThe model provides a quantitative method to compute how dabrafenib and trametinib can be used in combination to synergistically inhibit ERK-activity in BRAFV600E-mutant melanoma cells. The model elucidates molecular mechanisms of vertical inhibition of the BRAFV600E-MEK-ERK cascade and delineates how elevated BRAF concentrations generate drug resistance to dabrafenib and trametinib. The computational simulations further suggest that elevated ATP levels could be a factor in drug resistance to dabrafenib. ConclusionsThe model can be used to systematically motivate which dabrafenib-trametinib dose-combinations, for treating BRAFV600E-mutated melanoma, warrant experimental investigation.

cancer biology↗

bioRxiv2020

Application of the in vivo oxidative stress reporter Hmox1 as mechanistic biomarker of arsenic toxicity.

Inorganic arsenic (iAs) is a naturally occurring metalloid present in drinking water and polluted air exposing millions of people globally. Epidemiological studies have linked iAs exposure to the development of numerous diseases including cognitive impairment, cardiovascular failure and cancer. Despite intense research, an effective therapy for chronic arsenicosis has yet to be developed. Laboratory studies have been of great benefit in establishing the pathways involved in iAs toxicity and providing insights into its mechanism of action. However, the in vivo analysis of arsenic toxicity mechanisms has been difficult by the lack of reliable in vivo biomarkers of the effects of iAs. To resolve this issue we have applied the use of our recently developed stress reporter models to study iAs toxicity. The reporter mice Hmox1 (oxidative stress/inflammation; HOTT) and p21 (DNA damage) were exposed to iAs at acute and chronic, environmentally relevant, doses. We observed induction of the oxidative stress reporters in several cell types and tissues, which was largely dependent on the activation of transcription factor NRF2. We propose that our HOTT reporter model can be used as a surrogate biomarker of iAs-induced oxidative stress, and it constitutes a first-inclass platform to develop treatments in arsenicosis. Indeed, in a proof of concept experiment, the HOTT reporter mice were able to predict the therapeutic utility of the antioxidant N-acetyl cysteine in the prevention of iAs associated toxicity.Competing Interest StatementThe authors have declared no competing interest.View Full Text

pharmacology and toxicology↗

bioRxiv2017

Measuring physiological responses to stressors using a novel Hmox1 reporter mouse

Hmox1 protein holds great promise as a biomarker of organismal health as it is highly expressed in stressed or damaged cells. However, documenting Hmox1 expression patterns has thus far only been feasible in simple model organisms with limited relevance to humans. We now report a new Hmox1 reporter line that makes it possible to access this information in mice, the premiere model system for studying human disease and toxicology. Using a state-of-the-art strategy, we express multiple complementary reporter molecules from the murine Hmox1 locus, including firefly luciferase to allow long-term, non-invasive imaging of Hmox1 expression, and {beta}-galactosidase for high-resolution mapping of expression patterns post-mortem. We validate the model by confirming the absence of haplo-insufficiency effects, the fidelity of reporter expression, and its responsiveness to oxidative and inflammatory stimuli. In addition to providing blueprints for Hmox1 expression in mice that provide novel biological insights for follow-up, this work paves the way for the broad application of this model to regulatory toxicology studies and, also, pre-clinical investigations into human degenerative diseases.

physiology↗