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Abstract

TGF-β is considered a master switch in the pathogenesis of organ fibrosis. The primary mediators of this activity are the SMAD proteins, particularly SMAD3. In the current study, we have developed a cell-penetrating peptide (CPP) conjugate of the HIV TAT protein that is fused to an aminoterminal sequence of sorting nexin 9 (SNX9), which was previously shown to bind phosphorylated SMAD3 (pSMAD3). We determined that specifically preventing the nuclear import of pSMAD3 using the TAT-SNX9 peptide inhibited profibrotic TGF-β activity in murine cells and human lung fibroblasts as well as in vivo with no demonstrable toxicity. TGF-β signaling mediated by pSMAD2, bone morphogenetic protein 4 (BMP4), EGF, or PDGF was unaffected by the TAT-SNX9 peptide. Furthermore, while the TAT-SNX9 peptide prevented TGF-β’s profibrotic activity in vitro as well as in 2 murine treatment models of pulmonary fibrosis, a 3–amino acid point mutant that was unable to bind pSMAD3 proved ineffective. These findings indicate that specifically targeting pSMAD3 can ameliorate both the direct and indirect fibroproliferative actions of TGF-β.

Authors

Jeong-Han Kang, Mi-Yeon Jung, Xueqian Yin, Mahefatiana Andrianifahanana, Danielle M. Hernandez, Edward B. Leof

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Abstract

Capillary malformation–arteriovenous malformation (CM-AVM) is a blood and lymphatic vessel (LV) disorder that is caused by inherited inactivating mutations of the RASA1 gene, which encodes p120 RasGAP (RASA1), a negative regulator of the Ras small GTP-binding protein. How RASA1 mutations lead to the LV leakage defects that occur in CM-AVM is not understood. Here, we report that disruption of the Rasa1 gene in adult mice resulted in loss of LV endothelial cells (LECs) specifically from the leaflets of intraluminal valves in collecting LVs. As a result, valves were unable to prevent fluid backflow and the vessels were ineffective pumps. Furthermore, disruption of Rasa1 in midgestation resulted in LEC apoptosis in developing LV valves and consequently failed LV valvulogenesis. Similar phenotypes were observed in induced RASA1-deficient adult mice and embryos expressing a catalytically inactive RASA1R780Q mutation. Thus, RASA1 catalytic activity is essential for the function and development of LV valves. These data provide a partial explanation for LV leakage defects and potentially other LV abnormalities observed in CM-AVM.

Authors

Philip E. Lapinski, Beth A. Lubeck, Di Chen, Abbas Doosti, Scott D. Zawieja, Michael J. Davis, Philip D. King

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Abstract

Osteoporosis is a metabolic bone disorder associated with compromised bone strength and an increased risk of fracture. Inhibition of the differentiation of bone-resorbing osteoclasts is an effective strategy for the treatment of osteoporosis. Prior work by our laboratory and others has shown that MYC promotes osteoclastogenesis in vitro, but the underlying mechanisms are not well understood. In addition, the in vivo importance of osteoclast-expressed MYC in physiological and pathological bone loss is not known. Here, we have demonstrated that deletion of Myc in osteoclasts increases bone mass and protects mice from ovariectomy-induced (OVX-induced) osteoporosis. Transcriptomic analysis revealed that MYC drives metabolic reprogramming during osteoclast differentiation and functions as a metabolic switch to an oxidative state. We identified a role for MYC action in the transcriptional induction of estrogen receptor–related receptor α (ERRα), a nuclear receptor that cooperates with the transcription factor nuclear factor of activated T cells, c1 (NFATc1) to drive osteoclastogenesis. Accordingly, pharmacological inhibition of ERRα attenuated OVX-induced bone loss in mice. Our findings highlight a MYC/ERRα pathway that contributes to physiological and pathological bone loss by integrating the MYC/ERRα axis to drive metabolic reprogramming during osteoclast differentiation.

Authors

Seyeon Bae, Min Joon Lee, Se Hwan Mun, Eugenia G. Giannopoulou, Vladimir Yong-Gonzalez, Justin R. Cross, Koichi Murata, Vincent Giguère, Marjolein van der Meulen, Kyung-Hyun Park-Min

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Abstract

Chronic liver disease with cirrhosis is the 12th leading cause of death in the United States, and alcoholic liver disease accounts for approximately half of all cirrhosis deaths. Chronic alcohol consumption is associated with intestinal bacterial dysbiosis, yet we understand little about the contribution of intestinal fungi, or mycobiota, to alcoholic liver disease. Here we have demonstrated that chronic alcohol administration increases mycobiota populations and translocation of fungal β-glucan into systemic circulation in mice. Treating mice with antifungal agents reduced intestinal fungal overgrowth, decreased β-glucan translocation, and ameliorated ethanol-induced liver disease. Using bone marrow chimeric mice, we found that β-glucan induces liver inflammation via the C-type lectin–like receptor CLEC7A on Kupffer cells and possibly other bone marrow–derived cells. Subsequent increases in IL-1β expression and secretion contributed to hepatocyte damage and promoted development of ethanol-induced liver disease. We observed that alcohol-dependent patients displayed reduced intestinal fungal diversity and Candida overgrowth. Compared with healthy individuals and patients with non–alcohol-related cirrhosis, alcoholic cirrhosis patients had increased systemic exposure and immune response to mycobiota. Moreover, the levels of extraintestinal exposure and immune response correlated with mortality. Thus, chronic alcohol consumption is associated with an altered mycobiota and translocation of fungal products. Manipulating the intestinal mycobiome might be an effective strategy for attenuating alcohol-related liver disease.

Authors

An-Ming Yang, Tatsuo Inamine, Katrin Hochrath, Peng Chen, Lirui Wang, Cristina Llorente, Sena Bluemel, Phillipp Hartmann, Jun Xu, Yukinori Koyama, Tatiana Kisseleva, Manolito G. Torralba, Kelvin Moncera, Karen Beeri, Chien-Sheng Chen, Kim Freese, Claus Hellerbrand, Serene M.L. Lee, Hal M. Hoffman, Wajahat Z. Mehal, Guadalupe Garcia-Tsao, Ece A. Mutlu, Ali Keshavarzian, Gordon D. Brown, Samuel B. Ho, Ramon Bataller, Peter Stärkel, Derrick E. Fouts, Bernd Schnabl

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Abstract

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with a prevalence of 1 million persons worldwide. The fibrosis spreads from affected alveoli into contiguous alveoli and leads to death by asphyxiation. We previously discovered that the IPF lung harbors fibrogenic mesenchymal progenitor cells (MPCs) that serve as a cell of origin for disease-mediating myofibroblasts. In a prior genomewide transcriptional analysis, we found that IPF MPCs displayed increased expression of S100 calcium-binding A4 (S100A4), a protein linked to cancer cell proliferation and invasiveness. Here, we have examined whether S100A4 mediates MPC fibrogenicity. Ex vivo analysis revealed that IPF MPCs had increased levels of nuclear S100A4, which interacts with L-isoaspartyl methyltransferase to promote p53 degradation and MPC self-renewal. In vivo, injection of human IPF MPCs converted a self-limited bleomycin-induced mouse model of lung fibrosis to a model of persistent fibrosis in an S100A4-dependent manner. S100A4 gain of function was sufficient to confer fibrotic properties to non-IPF MPCs. In IPF tissue, fibroblastic foci contained cells expressing Ki67 and the MPC markers SSEA4 and S100A4. The expression colocalized in an interface region between myofibroblasts in the focus core and normal alveolar structures, defining this region as an active fibrotic front. Our findings indicate that IPF MPCs are intrinsically fibrogenic and that S100A4 confers MPCs with fibrogenicity.

Authors

Hong Xia, Adam Gilbertsen, Jeremy Herrera, Emilian Racila, Karen Smith, Mark Peterson, Timothy Griffin, Alexey Benyumov, Libang Yang, Peter B. Bitterman, Craig A. Henke

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Abstract

Runt-related transcription factor 1 (RUNX1) is generally considered to function as a tumor suppressor in the development of leukemia, but a growing body of evidence suggests that it has pro-oncogenic properties in acute myeloid leukemia (AML). Here we have demonstrated that the antileukemic effect mediated by RUNX1 depletion is highly dependent on a functional p53-mediated cell death pathway. Increased expression of other RUNX family members, including RUNX2 and RUNX3, compensated for the antitumor effect elicited by RUNX1 silencing, and simultaneous attenuation of all RUNX family members as a cluster led to a much stronger antitumor effect relative to suppression of individual RUNX members. Switching off the RUNX cluster using alkylating agent–conjugated pyrrole-imidazole (PI) polyamides, which were designed to specifically bind to consensus RUNX-binding sequences, was highly effective against AML cells and against several poor-prognosis solid tumors in a xenograft mouse model of AML without notable adverse events. Taken together, these results identify a crucial role for the RUNX cluster in the maintenance and progression of cancer cells and suggest that modulation of the RUNX cluster using the PI polyamide gene-switch technology is a potential strategy to control malignancies.

Authors

Ken Morita, Kensho Suzuki, Shintaro Maeda, Akihiko Matsuo, Yoshihide Mitsuda, Chieko Tokushige, Gengo Kashiwazaki, Junichi Taniguchi, Rina Maeda, Mina Noura, Masahiro Hirata, Tatsuki Kataoka, Ayaka Yano, Yoshimi Yamada, Hiroki Kiyose, Mayu Tokumasu, Hidemasa Matsuo, Sunao Tanaka, Yasushi Okuno, Manabu Muto, Kazuhito Naka, Kosei Ito, Toshio Kitamura, Yasufumi Kaneda, Paul P. Liu, Toshikazu Bando, Souichi Adachi, Hiroshi Sugiyama, Yasuhiko Kamikubo

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Abstract

Voltage-gated sodium channel (NaV) mutations cause genetic pain disorders that range from severe paroxysmal pain to a congenital inability to sense pain. Previous studies on NaV1.7 and NaV1.8 established clear relationships between perturbations in channel function and divergent clinical phenotypes. By contrast, studies of NaV1.9 mutations have not revealed a clear relationship of channel dysfunction with the associated and contrasting clinical phenotypes. Here, we have elucidated the functional consequences of a NaV1.9 mutation (L1302F) that is associated with insensitivity to pain. We investigated the effects of L1302F and a previously reported mutation (L811P) on neuronal excitability. In transfected heterologous cells, the L1302F mutation caused a large hyperpolarizing shift in the voltage-dependence of activation, leading to substantially enhanced overlap between activation and steady-state inactivation relationships. In transfected small rat dorsal root ganglion neurons, expression of L1302F and L811P evoked large depolarizations of the resting membrane potential and impaired action potential generation. Therefore, our findings implicate a cellular loss of function as the basis for impaired pain sensation. We further demonstrated that a U-shaped relationship between the resting potential and the neuronal action potential threshold explains why NaV1.9 mutations that evoke small degrees of membrane depolarization cause hyperexcitability and familial episodic pain disorder or painful neuropathy, while mutations evoking larger membrane depolarizations cause hypoexcitability and insensitivity to pain.

Authors

Jianying Huang, Carlos G. Vanoye, Alison Cutts, Y. Paul Goldberg, Sulayman D. Dib-Hajj, Charles J. Cohen, Stephen G. Waxman, Alfred L. George Jr.

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Abstract

Osteoclasts are the cells responsible for bone resorption, a process that is essential for the maintenance of healthy bones. Bone diseases, such as osteoporosis, which are characterized by high rates of bone resorption and loss of bone mass, may benefit from treatments that inhibit osteoclast formation and/or function. The RANKL/RANK pathway is critical for both osteoclast formation and function, and these effects are thought to be mediated by the transcription factor nuclear factor of activated T cells, cytoplasmic 1 (NFATc1). In this issue of the JCI, Bae et al. challenge the convention that NFATc1 is the sole critical regulator of RANKL/RANK-dependent osteoclast activation. Specifically, the authors show that MYC drives metabolic reprogramming in osteoclasts and that MYC induces estrogen receptor–related receptor α (ERRα) to regulate osteoclastogenesis. Importantly, both loss of MYC and pharmacological inhibition of ERRα attenuated bone loss in a mouse model of osteoporosis. Together, the results of this study suggest that the MYC/ERRα pathway should be further explored as a drug target for bone diseases.

Authors

Joseph Lorenzo

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May 2017

127 5 cover

May 2017 Issue

On the cover:
Revisiting salt and water balance

Rakova et al. and Kitada et al. report that glucocorticoid-driven responses to changes in salt alter sodium and water handling and metabolism in mice and in cosmonauts participating in long-term space-flight simulations. The cover shows an image of autophagy in murine skeletal muscle overlaid on an outer space–inspired background. Image credit: Dominic Doyle.

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Jci tm 2017 05

May 2017 JCI This Month

JCI This Month is a digest of the research, reviews, and other features published each month.

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Review Series - More

Nuclear Receptors

Series edited by Mitchell A. Lazar

Nuclear receptors are a class of intracellular proteins that sense and respond to a variety of endogenous hormones, vitamins, and xenobiotic endocrine disruptors by modulating gene expression. These proteins have well-established roles in the regulation of energy balance and the skeletal system, and they are emerging as important players in other areas of human physiology and disease. Humans have 48 nuclear receptors that all possess an N-terminal transactivation domain, a highly conserved central region DNA-binding domain, and a C-terminal ligand-binding domain. Ligand binding results in the transactivation of specific genes within a given tissue. Notably, a number of nuclear receptors do not have a known endogenous ligand and structural studies indicate that they may not bind ligands at all, but instead recruit other nuclear receptors or chromatin modifiers to control gene expression. Nuclear receptor activity can be modulated through interactions with other nuclear receptors or transcriptional coactivator or corepressor proteins, as well as through modulation by numerous growth factor and cytokine signaling cascades that induce various posttranslational modifications. Reviews in this series examine the role of nuclear receptors in metabolic syndrome, cardiovascular disease, liver function, hormone-dependent cancers, responses to common therapeutic agents, genetic disorders, the effects of vitamin D, and parasitic disease.

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