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Abstract

Heme oxygenase-1 (HO-1) is an inducible, detoxifying enzyme that is critical for limiting oxidative stress, inflammation, and cellular injury within the CNS and other tissues. Here, we demonstrate a deficiency of HO-1 expression in the brains of HIV-infected individuals. This HO-1 deficiency correlated with cognitive dysfunction, HIV replication in the CNS, and neuroimmune activation. In vitro analysis of HO-1 expression in HIV-infected macrophages, a primary CNS HIV reservoir along with microglia, demonstrated a decrease in HO-1 as HIV replication increased. HO-1 deficiency correlated with increased culture supernatant glutamate and neurotoxicity, suggesting a link among HIV infection, macrophage HO-1 deficiency, and neurodegeneration. HO-1 siRNA knockdown and HO enzymatic inhibition in HIV-infected macrophages increased supernatant glutamate and neurotoxicity. In contrast, increasing HO-1 expression through siRNA derepression or with nonselective pharmacologic inducers, including the CNS-penetrating drug dimethyl fumarate (DMF), decreased supernatant glutamate and neurotoxicity. Furthermore, IFN-γ, which is increased in CNS HIV infection, reduced HO-1 expression in cultured human astrocytes and macrophages. These findings indicate that HO-1 is a protective host factor against HIV-mediated neurodegeneration and suggest that HO-1 deficiency contributes to this degeneration. Furthermore, these results suggest that HO-1 induction in the CNS of HIV-infected patients on antiretroviral therapy could potentially protect against neurodegeneration and associated cognitive dysfunction.

Authors

Alexander J. Gill ... Benjamin B. Gelman, Dennis L. Kolson

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Abstract

Regulatory T cells (Tregs), which express CD4 and FOXP3, are critical for modulating the immune response and promoting immune tolerance. Consequently, methods to expand Tregs for therapeutic use are of great interest. While transfer of Tregs after massive ex vivo expansion can be achieved, in vivo expansion of Tregs would be more practical. Here, we demonstrate that targeting the CD45 tyrosine phosphatase with a tolerogenic anti-CD45RB mAb acutely increases Treg numbers in WT mice, even in absence of exogenous antigen. Treg expansion occurred through substantial augmentation of homeostatic proliferation in the preexisting Treg population. Moreover, anti-CD45RB specifically increased Treg proliferation in response to cognate antigen. Compared with conventional T cells, Tregs differentially regulate their conjugation with DCs. Therefore, we determined whether CD45 ligation could alter interactions between Tregs and DCs. Live imaging showed that CD45 ligation specifically reduced Treg motility in an integrin-dependent manner, resulting in enhanced interactions between Tregs and DCs in vivo. Increased conjugate formation, in turn, augmented nuclear translocation of nuclear factor of activated T cells (NFAT) and Treg proliferation. Together, these results demonstrate that Treg peripheral homeostasis can be specifically modulated in vivo to promote Treg expansion and tolerance by increasing conjugation between Tregs and DCs.

Authors

Geoffrey Camirand ... Christopher E. Rudd, David M. Rothstein

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Abstract

Ovarian cancer (OvCa) metastasizes to organs in the abdominal cavity, such as the omentum, which are covered by a single layer of mesothelial cells. Mesothelial cells are generally thought to be “bystanders” to the metastatic process and simply displaced by OvCa cells to access the submesothelial extracellular matrix. Here, using organotypic 3D cultures, we found that primary human mesothelial cells secrete fibronectin in the presence of OvCa cells. Moreover, we evaluated the tumor stroma of 108 human omental metastases and determined that fibronectin was consistently overexpressed in these patients. Blocking fibronectin production in primary mesothelial cells in vitro or in murine models, either genetically (fibronectin 1 floxed mouse model) or via siRNA, decreased adhesion, invasion, proliferation, and metastasis of OvCa cells. Using a coculture model, we determined that OvCa cells secrete TGF-β1, which in turn activates a TGF-β receptor/RAC1/SMAD-dependent signaling pathway in the mesothelial cells that promotes a mesenchymal phenotype and transcriptional upregulation of fibronectin. Additionally, blocking α5 or β1 integrin function with antibodies reduced metastasis in an orthotopic preclinical model of OvCa metastasis. These findings indicate that cancer-associated mesothelial cells promote colonization during the initial steps of OvCa metastasis and suggest that mesothelial cells actively contribute to metastasis.

Authors

Hilary A. Kenny ... David Bowtell, Ernst Lengyel

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Abstract

Liraglutide is a glucagon-like peptide-1 (GLP-1) analog marketed for the treatment of type 2 diabetes. Besides lowering blood glucose, liraglutide also reduces body weight. It is not fully understood how liraglutide induces weight loss or to what degree liraglutide acts directly in the brain. Here, we determined that liraglutide does not activate GLP-1–producing neurons in the hindbrain, and liraglutide-dependent body weight reduction in rats was independent of GLP-1 receptors (GLP-1Rs) in the vagus nerve, area postrema, and paraventricular nucleus. Peripheral injection of fluorescently labeled liraglutide in mice revealed the presence of the drug in the circumventricular organs. Moreover, labeled liraglutide bound neurons within the arcuate nucleus (ARC) and other discrete sites in the hypothalamus. GLP-1R was necessary for liraglutide uptake in the brain, as liraglutide binding was not seen in Glp1r–/– mice. In the ARC, liraglutide was internalized in neurons expressing proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Electrophysiological measurements of murine brain slices revealed that GLP-1 directly stimulates POMC/CART neurons and indirectly inhibits neurotransmission in neurons expressing neuropeptide Y (NPY) and agouti-related peptide (AgRP) via GABA-dependent signaling. Collectively, our findings indicate that the GLP-1R on POMC/CART-expressing ARC neurons likely mediates liraglutide-induced weight loss.

Authors

Anna Secher ... Niels Vrang, Lotte Bjerre Knudsen

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Abstract

Glioblastoma (GBM) is the most common and lethal brain tumor in adults. Glioma-initiating cells (GICs) are stem-like cells that have been implicated in glioblastoma progression and recurrence; however, the distinct properties of GICs and non-GICs within GBM tumors are largely uncharacterized. Here, we evaluated stem cell–associated microRNA (miR) expression in GICs from GBM patients and GICs derived from xenografted human glioma cell lines and determined that miR-33a promotes GIC growth and self-renewal. Moreover, evaluation of a GBM tissue array revealed that higher miR-33a expression was associated with poor prognosis of GBM patients. Antagonizing miR-33a function in GICs reduced self-renewal and tumor progression in immune-compromised mice, whereas overexpression of miR-33a in non-GICs promoted the display of features associated with GICs. We identified the mRNAs encoding phosphodiesterase 8A (PDE8A) and UV radiation resistance–associated gene (UVRAG) as direct miR-33a targets. PDE8A and UVRAG negatively regulated the cAMP/PKA and NOTCH pathways, respectively; therefore, miR-33a–dependent reduction of these proteins promoted growth and self-renewal of GICs by enhancing PKA and NOTCH activity. Furthermore, in GBM specimens, there was an inverse correlation between the expression levels of miR-33a and PDE8A and UVRAG expression. These findings reveal a miR-33a–centered signaling network that promotes GIC maintenance and has potential as a therapeutic target for GBM treatment.

Authors

Hui Wang ... Huibo Wang, Xiao-Fan Wang

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Abstract

Parkinson’s disease (PD) is the most prevalent hypokinetic movement disorder, and symptomatic PD pathogenesis has been ascribed to imbalances between the direct and indirect pathways in the basal ganglia circuitry. Here, we applied glutamate receptor blockers to the subthalamic nucleus (STN) of parkinsonian rats and evaluated locomotor behaviors via single-unit and local-field recordings. Using this model, we found that inhibition of NMDAergic cortico-subthalamic transmission ameliorates parkinsonian motor deficits without eliciting any vivid turning behavior and abolishes electrophysiological abnormalities, including excessive subthalamic bursts, cortico-subthalamic synchronization, and in situ beta synchronization in both the motor cortex and STN. Premotor cortex stimulation revealed that cortico-subthalamic transmission is deranged in PD and directly responsible for the excessive stimulation-dependent bursts and time-locked spikes in the STN, explaining the genesis of PD-associated pathological bursts and synchronization, respectively. Moreover, application of a dopaminergic agent via a microinfusion cannula localized the therapeutic effect to the STN, without correcting striatal dopamine deficiency. Finally, optogenetic overactivation and synchronization of cortico-subthalamic transmission alone sufficiently and instantaneously induced parkinsonian-associated locomotor dysfunction in normal mice. In addition to the classic theory emphasizing the direct-indirect pathways, our data suggest that deranged cortico-subthalamic transmission via the NMDA receptor also plays a central role in the pathophysiology of parkinsonian motor deficits.

Authors

Ming-Kai Pan, Chun-Hwei Tai, Wen-Chuan Liu, Ju-Chun Pei, Wen-Sung Lai, Chung-Chin Kuo

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Abstract

Millions of patients worldwide are affected by craniofacial deformations caused by congenital defects or trauma. Current surgical interventions have limited therapeutic outcomes; therefore, methods that would allow cartilage restoration are of great interest. A number of studies on embryonic limb development have shown that chondrogenesis is initiated by cellular condensation, during which mesenchymal progenitors aggregate and form 3D structures. Here, we demonstrated efficient regeneration of avascular elastic cartilage from in vitro–grown mesenchymal condensation, which recapitulated the early stages of chondrogenesis, including transient vascularization. After transplantation of vascularized condensed progenitors into immunodeficient mice, we used an intravital imaging approach to follow cartilage maturation. We determined that endothelial cells are present inside rudimentary cartilage (mesenchymal condensation) prior to cartilage maturation. Recreation of endothelial interactions in culture enabled a recently identified population of adult elastic cartilage progenitors to generate mesenchymal condensation in a self-driven manner, without requiring the support of exogenous inductive factors or scaffold materials. Moreover, the culture-grown 3D condensed adult–derived progenitors were amenable to storage via simple freezing methods and efficiently reconstructed 3D elastic cartilage upon transplantation. Together, our results indicate that transplantation of endothelialized and condensed progenitors represents a promising approach to realizing a regenerative medicine treatment for craniofacial deformations.

Authors

Takanori Takebe ... Jiro Maegawa, Hideki Taniguchi

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Abstract

Glaucoma is a leading cause of blindness, afflicting more than 60 million people worldwide. Increased intraocular pressure (IOP) due to impaired aqueous humor drainage is a major risk factor for the development of glaucoma. Here, we demonstrated that genetic disruption of the angiopoietin/TIE2 (ANGPT/TIE2) signaling pathway results in high IOP, buphthalmos, and classic features of glaucoma, including retinal ganglion degeneration and vision loss. Eyes from mice with induced deletion of Angpt1 and Angpt2 (A1A2FloxWB mice) lacked drainage pathways in the corneal limbus, including Schlemm’s canal and lymphatic capillaries, which share expression of the PROX1, VEGFR3, and FOXC family of transcription factors. VEGFR3 and FOXCs have been linked to lymphatic disorders in patients, and FOXC1 has been linked to glaucoma. In contrast to blood endothelium, in which ANGPT2 is an antagonist of ANGPT1, we have shown that both ligands cooperate to regulate TIE2 in the lymphatic network of the eye. While A1A2FloxWB mice developed high IOP and glaucoma, expression of ANGPT1 or ANGPT2 alone was sufficient for ocular drainage. Furthermore, we demonstrated that loss of FOXC2 from lymphatics results in TIE2 downregulation, suggesting a mechanism for ocular defects in patients with FOXC mutations. These data reveal a pathogenetic and molecular basis for glaucoma and demonstrate the importance of angiopoietin ligand cooperation in the lymphatic endothelium.

Authors

Benjamin R. Thomson ... Tsutomu Kume, Susan E. Quaggin

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Abstract

The peptide hormone glucagon-like peptide-1 (GLP-1) enhances glucose-induced insulin secretion and inhibits both gastric emptying and glucagon secretion. GLP-1 receptor (GLP-1R) agonists control glycemia via glucose-dependent mechanisms of action and promote weight loss in obese and diabetic individuals. Nevertheless, the mechanisms and cellular targets transducing the weight loss effects remain unclear. Two recent studies in the JCI provide insight into the neurons responsible for this effect. Sisley et al. reveal that GLP-1R agonist–induced weight loss requires GLP-1Rs in the CNS, while Secher et al. reveal that a small peptide GLP-1R agonist penetrates the brain and activates a subset of GLP-1R–expressing neurons in the arcuate nucleus to produce weight loss. Together, these two studies elucidate pathways that inform strategies coupling GLP-1R signaling to control of body weight in patients with diabetes or obesity.

Authors

Laurie L. Baggio, Daniel J. Drucker

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September 2014


124-9-cover

September 2014 Issue

On the cover:
Protecting against interepithelial adhesion

This cover image shows a false-colored murine embryo on day 11.5 of development with GFP labeling of the periderm, an epidermal layer that exists transiently during embryogenesis. On page 3891, Rebecca Richardson, Nigel Hammond, and colleagues uncover a vital role for the periderm in preventing abnormal epithelial adhesion during murine development and in a case of a rare human congenital condition known as cocoon syndrome.

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Jci_impact_2014_09

September 2014 Impact

JCI Impact is a digest of the research, reviews, and other features published in each month's issue of the Journal of Clinical Investigation.

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Review Series - More

Review_series_86
Nephrology
Series edited by John R. Sedor

Nephrology encompasses the study of normal kidney function, kidney disease, and kidney replacement therapy, including kidney transplantation and dialysis. Kidney diseases are a serious public health problem, with nearly 12% of American adults suffering from chronic kidney disease (CKD). Importantly, kidney dysfunction is associated with the increasingly common conditions of obesity, diabetes, and hypertension. Recent technological advances, including genetic and epigenetic screens, metabolic profiling, new model systems, and the use of kidney biopsies for diagnosis and treatment, have created new avenues for the study of kidney pathology. Reviews in this series provide a survey of kidney pathogenesis, including hypertension, diabetic kidney disease, IgA nephropathy, idiopathic membranous nephropathy, acute kidney injury, fibrosis, and mechanisms mediating graft failure after transplantation.

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