Gyarmati et al. report on mechanisms underlying the glomeruloprotective and tissue remodeling activity of sparsentan, a dual endothelin-1 and angiotensin II receptor antagonist. The cover shows an immunofluorescence image of p57+ podocytes (red) in glomeruli of a TRPC6-transgenic mouse kidney with focal segmental glomerulosclerosis, indicating the preservation of podocyte number by renoprotective therapies. Image credit: Georgina Gyarmati.
Excessive fructose intake is a risk factor for the development of obesity and its complications. Targeting ketohexokinase (KHK), the first enzyme of fructose metabolism, has been investigated for the management of MASLD. We compared the effects of systemic, small molecule inhibitor of KHK enzymatic activity to hepatocyte-specific, GalNAc-siRNA mediated knockdown of KHK in mice on a HFD. We measured KHK enzymatic activity, extensively quantified glycogen accumulation, performed RNAseq analysis, and enumerated hepatic metabolites using mass spectrometry. Both KHK siRNA and KHK inhibitor led to an improvement in liver steatosis, however, via substantially different mechanisms. KHK knockdown decreased the de novo lipogenesis pathway, whereas the inhibitor increased the fatty acid oxidation pathway. Moreover, KHK knockdown completely prevented hepatic fructolysis and improved glucose tolerance. Conversely, the KHK inhibitor only partially reduced fructolysis, but it also targeted triokinase, mediating the third step of fructolysis. This leads to the accumulation of fructose-1 phosphate, resulting in glycogen accumulation, hepatomegaly, and impaired glucose tolerance. Overexpression of wild-type, but not kinase-dead KHK in cultured hepatocytes increased hepatocyte injury and glycogen accumulation when treated with fructose. The differences between KHK inhibition and knockdown are, in part, explained by the kinase-dependent and independent effects of KHK on hepatic metabolism.
Se-Hyung Park, Taghreed Fadhul, Lindsey R. Conroy, Harrison A. Clarke, Ramon C. Sun, Kristina Wallenius, Jeremie Boucher, Gavin O'Mahony, Alessandro Boianelli, Marie Persson, Sunhee Jung, Cholsoon Jang, Analia S. Loria, Genesee J. Martinez, Zachary A. Kipp, Evelyn A. Bates, Terry D. Hinds, Jr., Senad Divanovic, Samir Softic
Systemic sclerosis (SSc) is characterized by immune system failure, vascular insult, autoimmunity, and tissue fibrosis. Transforming growth factor-beta (TGF-β) is a crucial mediator of persistent myofibroblast activation and aberrant extracellular matrix production in SSc. The factors responsible for this are unknown. By amplifying pattern recognition receptor signaling, Triggering Receptor Expressed on Myeloid Cells 1 (TREM-1) is implicated in multiple inflammatory conditions. In this study, we used novel ligand-independent TREM-1 inhibitors in order to investigate the pathogenic role of TREM-1 in SSc, using preclinical models of fibrosis, and explanted SSc skin fibroblasts. Selective pharmacological TREM-1 blockade prevented and reversed skin fibrosis induced by bleomycin in mice and mitigated constitutive collagen synthesis and myofibroblast features in SSc fibroblasts in vitro. Our results implicate aberrantly activated TREM-1 signaling in SSc pathogenesis, identify a unique approach to TREM-1 blockade, and suggest a potential therapeutic benefit for TREM-1 inhibition.
Swarna Bale, Priyanka Verma, Bharath Yalavarthi, Matija Bajželj, Syed A.M. Hasan, Jenna N. Silverman, Katherine Broderick, Kris A. Shah, Timothy Hamill, Dinesh Khanna, Alexander B. Sigalov, Swati Bhattacharyya, John Varga
Despite proven therapy options for estrogen receptor (ER)-positive breast tumors, a substantial number of ER+ cancer patients exhibit relapse with associated metastasis. Loss of expression of RasGAPs leads to poor outcomes in several cancers, including breast cancer. Mining the TCGA breast cancer RNA-sequencing dataset revealed that low expression of the RasGAP DAB2IP was associated with a significant decrease in relapse-free survival in Luminal A breast cancer patients. Immunostaining demonstrated that DAB2IP loss occurred in grade 2 tumors and higher. Consistent with this, genes upregulated in DAB2IP-low Luminal A tumors were shared with more aggressive tumor subtypes and were associated with proliferation, metastasis, and altered ER signaling. Low DAB2IP expression in ER+ breast cancer cells was associated with increased proliferation, enhanced stemness phenotypes, and activation of IKK, the upstream regulator of the transcription factor NF-kB. Integrating cell-based ChIP-sequencing with motif analysis and TCGA RNA-seq data, we identified a set of candidate NF-kB target genes upregulated with loss of DAB2IP linked with several oncogenic phenotypes, including altered RNA processing. This study provides insight into mechanisms associated with aggressiveness and recurrence within a subset of the typically less aggressive Luminal A breast cancer intrinsic subtype.
Angana Mukherjee, Rasha T. Kakati, Sarah C. Van Alsten, Tyler Laws, Aaron L. Ebbs, Daniel P. Hollern, Philip M. Spanheimer, Katherine A. Hoadley, Melissa A. Troester, Jeremy M. Simon, Albert S. Baldwin
Rheumatoid Arthritis (RA) is an immune-mediated, chronic inflammatory condition. With modern therapeutics and evidence-based management strategies, achieving sustained remission is increasingly common. To prevent complications associated with prolonged use of immunosuppressants, drug tapering or withdrawal is recommended. However, due to the lack of tools that define immunological remission, disease flares are frequent, highlighting the need for a more precision medicine-based approach. Utilising high dimensional phenotyping platforms, we set out to define peripheral blood immunological signatures of sustained remission in RA. We identified that CD8+CD57+KIR2DL1+ NK cells are associated with sustained remission. Functional studies uncovered an NK cell subset characterized by normal degranulation responses and reduced pro-inflammatory cytokine expression, which was elevated in sustained remission. Furthermore, flow cytometric analysis of NK cells from synovial fluid combined with interrogation of a publicly available single cell RNA-seq dataset of synovial tissue from active RA identified a deficiency of the phenotypic characteristics associated with this NK cell remission signature. In summary, we have uncovered a novel RA remission signature associated with compositional changes in NK cell phenotype and function that has implications for understanding the impact of sustained remission on host immunity and distinct features which may define operational tolerance in RA.
Carl Coyle, Margaret Ma, Yann Abraham, Christopher B. Mahony, Kathryn Steel, Catherine Simpson, Nadia Guerra, Adam P. Croft, Stephen Rapecki, Andrew Cope, Rowann Bowcutt, Esperanza Perucha
Human periosteal skeletal stem cells (P-SSCs) are critical for cortical bone maintenance and repair. However, their in vivo identity, molecular characteristics, and specific markers remain unknown. Here, single-cell sequencing revealed human periosteum contains SSC clusters expressing known SSC markers, PDPN and PDGFRA. Notably, human P-SSCs, but not bone marrow SSCs (BM-SSCs), selectively expressed newly identified markers, LRP1 and CD13. These LRP1+CD13+ human P-SSCs were perivascular cells with high osteochondrogenic but minimal adipogenic potential. Upon transplantation into bone injuries in mice, they preserved self-renewal capability in vivo. Single-cell analysis of mouse periosteum further supported the preferential expression of LRP1 and CD13 in Prx1+ P-SSCs. When Lrp1 was conditionally deleted in Prx1-lineage cells, it led to severe bone deformity, short statue, and periosteal defects. By contrast, local treatment with a LRP1 agonist at the injury sites induced early P-SSC proliferation and bone healing. Thus, human and mouse periosteum contains unique osteochondrogenic stem cell subsets, and these P-SSCs express specific markers, LRP1 and CD13, with regulatory mechanism through LRP1 that enhances P-SSC function and bone repair.
Youngjae Jeong, Lorenzo R. Deveza, Laura Ortinau, Kevin Lei, John R. Dawson, Dongsu Park