Slade, Luke et al. (2021) International Worm Meeting "The Mitochondria-targeted hydrogen sulfide delivery improves health and mitochondrial function in a C. elegans primary mitochondrial disease model"

Whiteman, Matthew, Etheridge, Timothy, Slade, Luke, Torregrossa, Roberta

[International Worm Meeting, 2021]

Introduction: Primary mitochondrial diseases (PMD) are genetically inherited disorders culminating in poor health and premature death. C. elegans possess vast orthologous genes associated with PMD, allowing high throughput analysis of the functional consequences of mutant genes. The endogenous gaseous mediator hydrogen sulfide (H2S) is an evolutionary conserved mitochondrial electron source and post-translational regulator across species. Since H2S augments cellular bioenergetics in conditions where mitochondrial dysfunction is a consequence of disease, we investigated whether mitochondria-targeted H2S using novel compounds we have developed (mtH2S) could restore cellular bioenergetics where mitochondrial dysfunction is a direct cause of the disease state (e.g. PMD). Methods: We characterised life/healthspan of 40 C. elegans homologues of human PMD mutations to identify PMD genes associated with poor health using a high-throughput microfluidic device. PMD strains displaying reduced life and/or health were assessed for improved health/longevity in the presence of our novel mtH2S molecules. Strains showing mtH2S -induced improvements were further assessed for ATP production, mitochondrial deltaΨm, oxygen consumption and total sulfide. Results: Seven PMD mutants were characterised with 5 showing reduced survival/locomotion. Of these, 2 strains displayed significant improvement with mtH2SD (100nM). Animals with widespread electron transport chain deficiency (gfm-1 and mrsp-16) were not responsive to mtH2S. abtm-1 mutants showed no improvement in life/healthspan despite significant preservation of mitochondrial deltaΨm on day 2 of adulthood. However, in a complex I mutant (nuo-4; a Leigh syndrome orthologue), mtH2SD significantly reversed the decline in ATP levels, preserved mitochondrial deltaΨm and increased survival/movement. Furthermore, mtH2S compounds significantly increased global sulfide levels in a complex IV mutant (sco-1), preserving mitochondrial deltaΨm and delaying severe movement decline (untreated sco-1: 32% of population active vs 68% in mtH2S sco-1 at day 6). Conclusion: Our data shows for the first time that mtH2S are potent molecules in PMD, effective in the nM range, and present a novel approach to at least delay mitochondrial perturbations in a variety of PMD disorders. Complete characterisation of all known PMD orthologues will significantly contribute to the precise disease mechanisms of PMD and potential therapeutics.

Ma, Amy T. et al. (2011) International Worm Meeting "Innate immune response to microsporidian infection."

Troemel, Emily R., Ma, Amy T.

[International Worm Meeting, 2011]

Nematocida parisii is a natural intracellular pathogen of C. elegans and was originally isolated from a wild-caught worm near Paris. N. parisii is an obligate intracellular parasite in the Microsporidia phylum, which is made up of over 1200 species of fungal-related pathogens that infect a wide range of hosts (Troemel, 2011). Microsporidia infect their hosts by injecting infectious sporoplasm directly into host cells via a specialized infection apparatus contained within spores, called a polar tube. After infection, N. parisii reproduces within the intestinal cell as a replicative meront and is in direct contact with the host cell cytostol. Subsequently, spore formation occurs and spores exit host cells to establish new infections. During later stages of infection, intestinal cells are loaded with N. parisii spores and eventually C. elegans die prematurely. We are interested in identifying novel components of the C. elegans innate immune that are elicited in response to N. parisii infection. First, to see if previously identified pathogen defense pathways are involved in host response to N. parisii infection, we are knocking down select pathways and evaluating changes in N. parisii infection. Previously, we have shown that pmk-1 and daf-2 have little effect on pathogen development (Troemel, et al., 2008), indicating that response to this natural intracellular pathogen may be distinct from response to predominantly extracellular pathogens. To identify novel components of innate immune response, we are undertaking an unbiased RNAi screen to identify host genes that affect the rate of N. parisii development and C. elegans survival. This work will contribute to the overall understanding of C. elegans defense against pathogen infection and could identify novel mechanisms for C. elegans to contain intracellular pathogens. References. Troemel, E. (2011). New Models of Microsporidiosis: Infections in Zebrafish, C. elegans, and Honey Bee. PLoS Pathogens, 7 (2), e1001243. Troemel, E., Felix, M.-A., Whiteman, N., Barriere, A., & Ausubel, F. (2008). Microsporidia are natural intracellular parasites of the nematode Caenorhabditis elegans. PLoS biology, 6 (12), 2736-52.