Joint destruction is the major clinic burden in patients with rheumatoid arthritis (RA). It is unclear, though, how this autoimmune disease progresses to the point of deterioration of the joint. Here, we report that in a mouse model of RA the upregulation of TLR2 expression and its a(2,3) sialylation in RANK+ myeloid monocytes mediate the transition from autoimmunity to osteoclast fusion and bone resorption, resulting in joint destruction. The expression of a(2,3) sialyltransferases were significantly increased in RANK+TLR2+ myeloid monocytes, and their inhibition or treatment with a TLR2 inhibitor blocked osteoclast fusion. Notably, analysis of our single-cell RNA-sequencing (scRNA-seq) libraries generated from RA mice revealed a novel RANK+TLR2- subset that negatively regulated osteoclast fusion. Importantly, the RANK+TLR2+ subset was significantly diminished with the treatments, whereas the RANK+TLR2- subset was expanded. Moreover, the RANK+TLR2- subset could differentiate into a TRAP+ osteoclast lineage, but the resulting cells did not fuse to form osteoclasts. Our scRNA-seq data showed that Maf is highly expressed in the RANK+TLR2- subset, and the a(2,3) sialyltransferase inhibitor induced Maf expression in the RANK+TLR2+ subset. The identification of a RANK+TLR2- subset provides a potential explanation for TRAP+ mononuclear cells in bone and their anabolic activity. Further, TLR2 expression and its a(2,3) sialylation in the RANK+ myeloid monocytes could be effective targets to prevent autoimmune-mediated joint destruction.
Sequencing data have been deposited in GEO under accession codes GSE221704
RANK+TLR2+ Myeloid Subpopulation Converts Autoimmune to Joint Destruction in Rheumatoid ArthritisNCBI Gene Expression Omnibus, GSE221704.
- Xu Cao
- Xu Cao
- Xu Cao
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: All animals were kept in the Animal Facility of the Johns Hopkins University School of Medicine. The animal protocol was approved by the Institutional Animal Care and Use Committee of Johns Hopkins University, Baltimore, MD, USA (MO21M276).
- Di Chen, Chinese Academy of Sciences, China
© 2023, Zhang et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Low-protein (LP) diets extend the lifespan of diverse species and are associated with improved metabolic health in both rodents and humans. Paradoxically, many athletes and bodybuilders consume high-protein (HP) diets and protein supplements, yet are both fit and metabolically healthy. Here, we examine this paradox using weight pulling, a validated progressive resistance exercise training regimen, in mice fed either an LP diet or an isocaloric HP diet. We find that despite having lower food consumption than the LP group, HP-fed mice gain significantly more fat mass than LP-fed mice when not exercising, while weight pulling protected HP-fed mice from this excess fat accretion. The HP diet augmented exercise-induced hypertrophy of the forearm flexor complex, and weight pulling ability increased more rapidly in the exercised HP-fed mice. Surprisingly, exercise did not protect from HP-induced changes in glycemic control. Our results confirm that HP diets can augment muscle hypertrophy and accelerate strength gain induced by resistance exercise without negative effects on fat mass, and also demonstrate that LP diets may be advantageous in the sedentary. Our results highlight the need to consider both dietary composition and activity, not simply calories, when taking a precision nutrition approach to health.
Background: Compelling evidence has accumulated on the role of oxidative stress on the endothelial cell (EC) dysfunction underlying acute coronary syndrome. However, unveiling the underlying metabolic determinants has been hampered by the scarcity of appropriate cell models to address cell-autonomous mechanisms of ED dysfunction.
Methods: We have generated endothelial cells derived from thrombectomy specimens from patients affected with acute myocardial infarction (AMI) and conducted phenotypical and metabolic characterization, focused on central carbon metabolism.
Results: AMI-derived endothelial cells (AMIECs), but not control healthy coronary endothelial cells, display impaired growth, migration and tubulogenesis. Metabolically, AMIECs displayed augmented reactive oxygen species (ROS) and glutathione intracellular content, along with a diminished glucose consumption coupled to high lactate production. Consistent with diminished glycolysis in AMIECs, the protein levels of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase type 3, PFKFB3, were downregulated. In contrast, PFKFB4 levels were upregulated, suggesting a shunting of glycolysis towards the pentose phosphate pathway (PPP), supported by upregulation in AMIECs of G6PD, the key enzyme in the oxidative branch of the PPP. Further, the glutaminolytic enzyme GLS was upregulated in AMIECs, providing a mechanistic explanation for the observed increase in glutathione content. Finally, AMIECs displayed a significantly higher mitochondrial membrane potential than control ECs, which, together with high ROS levels, suggest a highly coupled mitochondrial activity in patient ECs.
Conclusions: We suggest high mitochondrial proton coupling underlies the abnormally high production of ROS, balanced by PPP- and glutaminolysis-driven synthesis of glutathione, as a primary, cell-autonomous abnormality driving EC dysfunction in AMI.
Funding: European Commission Horizon 2020; CIBER- Carlos III National Institute of Health, Spain; Ministerio de Economia y Competitividad (MINECO) and Ministerio de Ciencia e Innovación, Spain; Generalitat de Catalunya-AGAUR, Catalonia; Plataforma Temática Interdisciplinar Salud Global (PTI-SG), Spain; British Heart Foundation, UK.