Autosomal dominant polycystic kidney disease (ADPKD), the most common monogenic nephropathy, is characterized by phenotypic variability exceeding genic effects. Dysregulated metabolism and immune cell function are key disease modifiers. The tryptophan metabolites, kynurenines, produced through IDO1, are known immunomodulators. Here, we study the role of tryptophan metabolism in PKD using an orthologous disease model (C57Bl/6J Pkd1RC/RC). We found elevated kynurenine and IDO1 levels in Pkd1RC/RC kidneys versus wildtype. Further, IDO1 levels were increased in ADPKD cell lines. Genetic Ido1 loss in Pkd1RC/RC animals resulted in reduced PKD severity as measured by %kidney weight/body weight and cystic index. Consistent with an immunomodulatory role of kynurenines, Pkd1RC/RC;Ido1-/- mice presented with significant changes in the cystic immune microenvironment (CME) versus controls. Kidney macrophage numbers decreased and CD8+ T cell numbers increased, both known PKD modulators. Also, pharmacological IDO1 inhibition in Pkd1RC/RC mice and kidney specific Pkd2 knockout mice with rapidly progressive PKD resulted in less severe PKD versus controls with similar changes in the CME as in the genetic model. Our data suggest that tryptophan metabolism is dysregulated in ADPKD and that its inhibition results in changes to the CME and slows disease progression, making IDO1 a novel therapeutic target for ADPKD.
Dustin T. Nguyen, Emily K. Kleczko, Nidhi Dwivedi, Marie-Louise T. Monaghan, Berenice Y. Gitomer, Michel B. Chonchol, Eric T. Clambey, Raphael A. Nemenoff, Jelena Klawitter, Katharina Hopp
Mitochondria are dynamic organelles responsible for energy production and many processes central to cellular function. Alterations in mitochondrial function is associated with human fibrotic lung diseases, including idiopathic pulmonary fibrosis (IPF). Pulmonary fibrosis is characterized by stiffening of the extracellular matrix (ECM). Fibroblasts migrate in the direction of greater stiffness, a phenomenon termed durotaxis. The mechanically guided fibroblast migration could be a crucial step in the progression of lung fibrosis. In this study, we identified mitochondria as an important mechanotransducer at the intersection between extracellular mechanical signals and durotactic lung fibroblast migration. Primary human lung fibroblasts sense increasing matrix stiffness with a change of mitochondrial dynamics in favor of mitochondrial fission and increased production of ATP. Mitochondria polarize in the direction of a physiologically relevant stiffness gradient, with conspicuous localization to the leading edge, primarily lamellipodia and filopodia, of migrating lung fibroblasts. Matrix stiffness-regulated mitochondrial fission and durotactic lung fibroblast migration are mediated by a DRP1/MFF-dependent pathway. Importantly, we found that the DRP1/MFF pathway is activated in fibrotic lung myofibroblasts in both human IPF and bleomycin-induced mouse lung fibrosis. Our findings suggest that energy-producing mitochondria need to be sectioned via fission and repositioned in durotactic lung fibroblasts to meet the higher energy demand. This represents a new mechanism through which mitochondria may contribute to the progression of fibrotic lung diseases. Inhibition of durotactic migration of lung fibroblasts may play an important role in preventing the progression of IPF.
Ting Guo, Chun-sun Jiang, Shan-Zhong Yang, Yi Zhu, Chao He, A. Brent Carter, Veena B. Antony, Hong Peng, Yong Zhou
Although glycogen synthase kinase β (Gsk3β) has been shown to regulate tissue inflammation, whether and how it regulates inflammation resolution vs. inflammation activation is unclear. In a murine liver partial warm ischemia/reperfusion injury (IRI) model, we found that Gsk3β inhibitory phosphorylation increased at both the early activation and late resolution stages of the disease. Myeloid Gsk3β deficiency not only alleviated liver injuries, but also facilitated the restoration of liver homeostasis. Depletion of Kupffer cells (KCs) prior to the onset of liver ischemia diminished the differences between the WT and Gsk3β KO mice in the activation of liver IRI. However, the resolution of liver IRI remained accelerated in the Gsk3β KO mice. In CD11b-DTR mice, Gsk3β deficient bone marrow-derived macrophages (BMMs) facilitated the resolution of liver IRI as compared with WT cells. Furthermore, Gsk3β deficiency promoted the reparative phenotype differentiation in vivo in liver infiltrating macrophages and in vitro in BMMs. Gsk3 pharmacological inhibition promoted the resolution of liver IRI in WT, but not myeloid MerTK deficient, mice. Thus, Gsk3β regulates liver IRI at both activation and resolution stages of the disease. Gsk3 inactivation enhances the pro-resolving function of liver infiltrating macrophages in MerTK–dependent manner.
Hanwen Zhang, Ming Ni, Han Wang, Jing Zhang, Dan Jin, Ronald W. Busuttil, Jerzy W. Kupiec-Weglinski, Wei Li, Xuehao Wang, Yuan Zhai
Antibiotic-induced shifts in the indigenous gut microbiota influence normal skeletal maturation. Current theory implies that gut microbiota actions on bone occur through a direct gut-bone signaling axis. However, our prior work supports that a gut-liver signaling axis contributes to gut microbiota effects on bone. Purpose was to investigate the effects of minocycline, a systemic antibiotic treatment for adolescent acne, on pubertal/post-pubertal skeletal maturation. Sex-matched specific-pathogen-free(SPF) and germ-free(GF) C57BL/6T mice were administered a clinically relevant minocycline dose from age 6-12 weeks. Minocycline caused dysbiotic shifts in the gut bacteriome and impaired skeletal maturation in SPF mice, but did not alter the skeletal phenotype in GF mice. Minocycline administration in SPF mice disrupted the intestinal farnesoid X receptor(FXR)-fibroblast growth factor 15(FGF15) axis, a gut-liver endocrine axis supporting systemic bile acid homeostasis. Minocycline-treated SPF mice had increased serum conjugated bile acids that are FXR antagonists, suppressed osteoblast function, decreased bone mass, impaired bone microarchitecture and fracture resistance. Stimulating osteoblasts with the serum bile acid profile from minocycline-treated SPF mice recapitulated the suppressed osteogenic phenotype found in vivo, which was mediated through attenuated FXR-signaling. This work introduces bile acids as a novel mediator of gut-liver signaling actions contributing to gut microbiota effects on bone.
Matthew D. Carson, Amy J. Warner, Jessica D. Hathaway-Schrader, Vincenza L. Geiser, Joseph D. Kim, Joy E. Gerasco, William D. Hill, John J. Lemasters, Alexander V. Alekseyenko, Yongren Wu, Hai Yao, Jose I. Aguirre, Caroline Westwater, Chad M. Novince
Metastatic clear cell renal cell carcinomas (ccRCC) are resistant to DNA damaging chemotherapies, limiting therapeutic options for patients whose tumours are resistant to tyrosine kinase inhibitors and/or immune checkpoint therapies. Here we show that mouse and human ccRCC are frequently characterised by high levels of endogenous DNA damage and that cultured ccRCC cells exhibit intact cellular responses to chemotherapy-induced DNA damage. We identify that pharmacological inhibition of the DNA damage sensing kinase ATR with the orally administered, potent and selective drug M4344 (also called gartisertib) induces anti-proliferative effects in ccRCC cells due to replication stress and the accumulation of DNA damage in S phase. In some cells, DNA damage persists into subsequent G2/M and G1 phases, leading to the frequent accumulation of micronuclei. Daily single agent treatment with M4344 inhibited the growth of ccRCC xenograft tumours. M4344 synergises with chemotherapeutic drugs including cisplatin and carboplatin and the PARP inhibitor olaparib in mouse and human ccRCC cells. Weekly M4344 plus cisplatin treatment showed in vivo therapeutic synergy in ccRCC xenografts and was efficacious in an autochthonous mouse ccRCC model. These studies identify ATR inhibition as a potential novel therapeutic option for ccRCC.
Philipp Seidel, Anne Rubarth, Kyra Zodel, Asin Peighambari, Felix Neumann, Yannick Federkiel, Hsin Huang, Rouven Hoefflin, Mojca Adlesic, Christian Witt, David J. Hoffmann, Patrick Metzger, Ralph K. Lindemann, Frank T. Zenke, Christoph Schell, Melanie Boerries, Dominik von Elverfeldt, Wilfried Reichardt, Marie Follo, Joachim Albers, Ian J. Frew
JCI This Month is a digest of the research, reviews, and other features published each month.