Biology subjects

Kikuchi, K.

Publications and source records attributed to Kikuchi, K..

3 recordsLinked to original sources

bioRxiv2020

Mitochondrial dysfunction underlying sporadic inclusion body myositis is ameliorated by the mitochondrial homing drug MA-5

Sporadic inclusion body myositis (sIBM) is the most common idiopathic inflammatory myopathy, and several reports have suggested that mitochondrial abnormalities are involved in its etiology. We recruited 9 sIBM patients and found significant histological changes and an elevation of growth differential factor 15 (GDF15), a marker of mitochondrial disease, strongly suggesting the involvement of mitochondrial dysfunction. Bioenergetic analysis of sIBM patient myoblasts revealed impaired mitochondrial function. Decreased ATP production, reduced mitochondrial size and reduced mitochondrial dynamics were also observed in sIBM myoblasts. Cell vulnerability to oxidative stress also suggested the existence of mitochondrial dysfunction. Mitochonic acid-5 (MA-5) increased the cellular ATP level, reduced mitochondrial ROS, and provided protection against sIBM myoblast death. MA-5 also improved the survival of sIBM skin fibroblasts as well as mitochondrial morphology and dynamics in these cells. The reduction in the gene expression levels of Opa1 and Drp1 was also reversed by MA-5, suggesting the modification of the fusion/fission process. These data suggest that MA-5 may provide an alternative therapeutic strategy for treating not only mitochondrial diseases but also sIBM.

neuroscience↗

bioRxiv2020

A zebrafish functional genomics model to investigate the role of human A20 variants in vivo

Germline loss-of-function variation in TNFAIP3, encoding A20, has been implicated in a wide variety of autoinflammatory and autoimmune conditions, with acquired somatic missense mutations linked to cancer progression. Furthermore, human sequence data reveals that the A20 locus contains ~400 non-synonymous coding variants which are largely uncharacterised. The growing number of A20 coding variants with unknown function, but potential clinical impact, poses a challenge to traditional mouse-based approaches. Here we report the development of a novel functional genomics approach that utilises the new A20-deficient zebrafish (Danio rerio) model to investigate the impact of TNFAIP3 genetic variants in vivo. Similar to A20-deficient mice, A20-deficient zebrafish are hyper-responsive to inflammatory triggers and exhibit spontaneous early lethality. While ectopic addition of human A20 rescued A20-null zebrafish from lethality, missense mutations at two conserved A20 residues, S381A and C243Y reversed this protective effect. Ser381 represents a phosphorylation site important for enhancing A20 activity that is abrogated by its mutation to alanine, or by a C243Y mutation that associates with human autoimmune disease. These data reveal an evolutionarily conserved role for A20, but also demonstrate how a zebrafish functional genomics pipeline can be utilized to investigate the in vivo significance of medically relevant TNFAIP3 gene variants. This approach could be utilised to investigate genetic variation for other conserved genes.

genetics↗

bioRxiv2019

Chronic infection of adult zebrafish with rough or smooth variant Mycobacterium abscessus causes necrotising inflammation and differential activation of host immunity

Infections caused by Mycobacterium abscessus are increasing in prevalence within patient groups with respiratory comorbidities. Initial colonisation by the smooth colony M. abscessus (S) can be followed by an irreversible genetic switch into a highly inflammatory rough colony M. abscessus (R), often associated with a decline in pulmonary function. Our understanding of the role of adaptive immunity in M. abscessus pathogenesis is largely unknown. Here, we have used intraperitoneal infection of adult zebrafish to model M. abscessus pathogenesis in the context of fully functioning host immunity. We find infection with the R variant penetrates host organs causing an inflammatory immune response leading to necrotic granuloma formation within 2 weeks. The R bacilli are targeted by T cell-mediated immunity and burden is constrained. Strikingly, the S variant colonises host internal surfaces at high loads and is met with a robust innate immune response but little T cell-mediated immunity. Invasive granuloma formation is delayed in S variant infection compared to R variant infection upon which T cell-mediated immunity is required to control infection. In mixed infections, the S variant outcompetes the R variant. We also find the R variant activates host immunity to the detriment of S variant M. abscessus in mixed infections. These findings demonstrate the applicability of the adult zebrafish to model persistent M. abscessus infection and provide insight into the immunopathogenesis of chronic M. abscessus infection.

microbiology↗