論文

Although glycerol is a ubiquitous metabolite in mammalian systems, its cellular metabolic pathways and functions have not been fully elucidated. Here, we find that elevated extracellular glycerol modulates intracellular metabolism and pro-inflammatory responses of macrophages. In pro-inflammatory macrophages stimulated with lipopolysaccharide, glycerol is taken up through glycerol channels including Aquaporin 3 (AQP3) and metabolized to glycerol-3-phosphate (G3P), which is then converted to dihydroxyacetone phosphate by glycerol-3-phosphate dehydrogenase 2 (GPD2). This glycerol-driven pathway enhances mitochondrial ATP production, potentially by supplying electrons to the electron transport chain (ETC) via GPD2, and by upregulating the transcription of genes encoding ETC complexes. In addition, glycerol supplementation elevates intracellular acetyl-CoA levels, promotes histone acetylation at the promoters of pro-inflammatory cytokine genes, and consequently increases cytokine gene expression, suggesting enhanced pro-inflammatory response. In vivo experiments, macrophage-specific AQP3 conditional knockout mice exhibit reduced weight gain and adipose tissue inflammation in a high-fat diet-induced obesity model. Our findings provide novel insights into the metabolic regulation and macrophage inflammation by extracellular glycerol.

Environmental humidity is a key determinant of organismal physiology and homeostasis. Although the genetic basis of humidity-driven responses is well established in invertebrates, the molecular and genetic mechanisms by which mammals respond to low humidity remain unclear. Here, using reconstructed 3D epidermal equivalents and a mouse model, we identify transient receptor potential vanilloid 4 (TRPV4) as an important mediator of low-humidity-induced signaling and transcriptional responses in epidermal keratinocytes. In 3D skin models, low-humidity exposure induced rapid water movement, characterized by enhanced apical water loss and concomitant basal-side water uptake within 90 s, followed by TRPV4-dependent Ca2+ influx within 3 min. Pharmacological TRPV4 inhibition suppressed MAPK activation at 30 min and both early (3 h) and late (24 h) low-humidity-induced transcriptional changes. Ca2+ chelation reduced low-humidity-induced ERK and p38 activation, and ERK inhibition attenuated low-humidity-induced gene expression changes at 3 h. In vivo, acute low-humidity exposure in mice elicited epidermal MAPK activation within 15 min and early transcriptional changes at 3 h, with RNA-sequencing analysis showing enrichment of gene sets associated with cell adhesion or inflammatory responses. These signaling and transcriptomic responses were attenuated in the epidermis of keratinocyte-specific Trpv4 conditional knockout mice. Collectively, our findings identify TRPV4 as an important mediator of epidermalresponses to low-humidity stress, providing a molecular basis for low-humidity-driven signaling in the mammalian epidermis.

Water is the most abundant substance in the human body and plays a pivotal role in various bodily functions. While underhydration is associated with the incidence of certain diseases, the specific role of water in gut function remains largely unexplored. Here, we show that water restriction disrupts gut homeostasis, which is accompanied by a bloom of gut microbes and decreased numbers of immune cells, especially Th17 cells, within the colon. These microbial and immunological changes in the gut are associated with an impaired ability to eliminate the enteric pathogen Citrobacter rodentium. Moreover, aquaporin 3, a water channel protein, is required for the maintenance of Th17 cell function and differentiation. Taken together, adequate water intake is critical for maintaining bacterial and immunological homeostasis in the gut, thereby enhancing host defenses against enteric pathogens.

IL-17-producing helper T (Th17) cells are long-lived and serve as central effector cells in chronic autoimmune diseases. The underlying mechanisms of Th17 persistence remain unclear. We demonstrated that abatacept, a CD28 antagonist, effectively prevented the development of skin disease in a Th17-dependent experimental autoimmune dermatitis model. Abatacept selectively inhibited the emergence of IL-7R-negative effector-phenotype T cells while allowing the survival and proliferation of IL-7R+ memory-phenotype cells. The surviving IL-7R+ Th17 cells expressed genes associated with alcohol/aldehyde detoxification and showed potential to transdifferentiate into IL-7R-negative effector cells. Inhibiting aldehyde dehydrogenase reduced IL-7R+ Th17 cells in vivo, independently of CD28, and exhibited additive effects when combined with abatacept. Our findings suggest that CD28 blockade prevents inflammation without eliminating persistent memory cells. These remaining memory cells can be targeted by other drugs, such as aldehyde dehydrogenase inhibitors, to limit their survival, thereby facilitating the treatment of chronic autoimmune diseases.