BACKGROUND. Induction of insulin resistance is a key pathway through which obesity increases risk of type 2 diabetes, hypertension, dyslipidemia, and cardiovascular events. Although the detrimental effects of obesity on insulin sensitivity are incompletely understood, accumulation of visceral, subcutaneous, and liver fat and impairment of insulin-induced muscle microvascular recruitment (MVR) may be involved. As these phenotypic changes often coincide in obesity, we aimed to unravel whether they independently contribute to insulin resistance and thus constitute separate targets for intervention. METHODS. We measured visceral (VAT) and subcutaneous adipose tissue (SAT) volumes and intrahepatic lipid (IHL) content by MRI, and whole body glucose disposal (WBGD) and MVR (using contrast-enhanced ultrasound) responses to a euglycemic insulin clamp in lean (n = 25) and abdominally obese men (n = 52). Abdominally obese men were randomized to dietary weight loss intervention or habitual diet. RESULTS. Obesity-associated increases in VAT, SAT, and IHL, along with the decrease in MVR, contributed independently to insulin resistance. Moreover, a dietary weight loss intervention reduced insulin resistance, and mediation analyses showed that decreased IHL and insulin-induced MVR, but not decreased VAT or SAT volumes, independently contributed to improved insulin resistance seen with weight loss. CONCLUSION. Quantifying the mutually independent contributions of visceral and subcutaneous adipose tissue, intrahepatic lipid, and insulin-induced muscle microvascular recruitment reveals distinct targets for treating obesity-associated insulin resistance. TRIAL REGISTRATION. Clinicaltrials.gov NCT01675401. FUNDING. Funding was from the Top Institute Food and Nutrition.
Yvo H.A.M. Kusters, Casper G. Schalkwijk, Alfons J.H.M. Houben, M. Eline Kooi, Lucas Lindeboom, Jos Op ’t Roodt, Peter J. Joris, Jogchum Plat, Ronald P. Mensink, Eugene J. Barrett, Coen D.A. Stehouwer
Genotypic and phenotypic alterations in the bone marrow (BM) microenvironment, in particular in osteoprogenitor cells, have been shown to support leukemogenesis. However, it is unclear how leukemia cells alter the BM microenvironment to create a hospitable niche. Here, we report that acute myeloid leukemia (AML) cells, but not normal CD34+ or CD33+ cells, induce osteogenic differentiation in mesenchymal stromal cells (MSCs). In addition, AML cells inhibited adipogenic differentiation of MSCs. Mechanistic studies identified that AML-derived BMPs activate Smad1/5 signaling to induce osteogenic differentiation in MSCs. Gene expression array analysis revealed that AML cells induce connective tissue growth factor (CTGF) expression in BM-MSCs irrespective of AML type. Overexpression of CTGF in a transgenic mouse model greatly enhanced leukemia engraftment in vivo. Together, our data suggest that AML cells induce a preosteoblast-rich niche in the BM that in turn enhances AML expansion.
V. Lokesh Battula, Phuong M. Le, Jeffrey C. Sun, Khoa Nguyen, Bin Yuan, Ximin Zhou, Sonali Sonnylal, Teresa McQueen, Vivian Ruvolo, Keith A. Michel, Xiaoyang Ling, Rodrigo Jacamo, Elizabeth Shpall, Zhiqiang Wang, Arvind Rao, Gheath Al-Atrash, Marina Konopleva, R. Eric Davis, Melvyn A. Harrington, Catherine W. Cahill, Carlos Bueso-Ramos, Michael Andreeff
Magnesium (Mg2+) plays pleiotropic roles in cellular biology, and it is essentially required for all living organisms. Although previous studies demonstrated intracellular Mg2+ levels were regulated by the complex of phosphatase of regenerating liver 2 (PRL2) and Mg2+ transporter of cyclin M (CNNMs), physiological functions of PRL2 in whole animals remain unclear. Interestingly, Mg2+ was recently identified as a regulator of circadian rhythm–dependent metabolism; however, no mechanism was found to explain the clock-dependent Mg2+ oscillation. Herein, we report PRL2 as a missing link between sex and metabolism, as well as clock genes and daily cycles of Mg2+ fluxes. Our results unveil that PRL2-null animals displayed sex-dependent alterations in body composition, and expression of PRLs and CNNMs were sex- and circadian time–dependently regulated in brown adipose tissues. Consistently, PRL2-KO mice showed sex-dependent alterations in thermogenesis and in circadian energy metabolism. These physiological changes were associated with an increased rate of uncoupled respiration with lower intracellular Mg2+ in PRL2-KO cells. Moreover, PRL2 deficiency causes inhibition of the ATP citrate lyase axis, which is involved in fatty acid synthesis. Overall, our findings support that sex- and circadian-dependent PRL2 expression alter intracellular Mg2+ levels, which accordingly controls energy metabolism status.
Noriko Uetani, Serge Hardy, Simon-Pierre Gravel, Silke Kiessling, Adam Pietrobon, Nau Nau Wong, Valérie Chénard, Nicolas Cermakian, Julie St-Pierre, Michel L. Tremblay
Nonalcoholic fatty liver disease prevalence is soaring with the obesity pandemic, but the pathogenic mechanisms leading to the progression toward active nonalcoholic steatohepatitis (NASH) and fibrosis, major causes of liver-related death, are poorly defined. To identify key components during the progression toward NASH and fibrosis, we investigated the liver transcriptome in a human cohort of NASH patients. The transition from histologically proven fatty liver to NASH and fibrosis was characterized by gene expression patterns that successively reflected altered functions in metabolism, inflammation, and epithelial-mesenchymal transition. A meta-analysis combining our and public human transcriptomic datasets with murine models of NASH and fibrosis defined a molecular signature characterizing NASH and fibrosis and evidencing abnormal inflammation and extracellular matrix (ECM) homeostasis. Dermatopontin expression was found increased in fibrosis, and reversal of fibrosis after gastric bypass correlated with decreased dermatopontin expression. Functional studies in mice identified an active role for dermatopontin in collagen deposition and fibrosis. PPARα activation lowered dermatopontin expression through a transrepressive mechanism affecting the Klf6/TGFβ1 pathway. Liver fibrotic histological damages are thus characterized by the deregulated expression of a restricted set of inflammation- and ECM-related genes. Among them, dermatopontin may be a valuable target to reverse the hepatic fibrotic process.
Philippe Lefebvre, Fanny Lalloyer, Eric Baugé, Michal Pawlak, Céline Gheeraert, Hélène Dehondt, Jonathan Vanhoutte, Eloise Woitrain, Nathalie Hennuyer, Claire Mazuy, Marie Bobowski-Gérard, Francesco Paolo Zummo, Bruno Derudas, Ann Driessen, Guy Hubens, Luisa Vonghia, Wilhelmus J. Kwanten, Peter Michielsen, Thomas Vanwolleghem, Jérôme Eeckhoute, An Verrijken, Luc Van Gaal, Sven Francque, Bart Staels
Pancreatitis is more frequent in type 2 diabetes mellitus (T2DM), although the underlying cause is unknown. We tested the hypothesis that ongoing β cell stress and apoptosis in T2DM induces ductal tree proliferation, particularly the pancreatic duct gland (PDG) compartment, and thus potentially obstructs exocrine outflow, a well-established cause of pancreatitis. PDG replication was increased 2-fold in human pancreas from individuals with T2DM, and was associated with increased pancreatic intraepithelial neoplasia (PanIN), lesions associated with pancreatic inflammation and with the potential to obstruct pancreatic outflow. Increased PDG replication in the prediabetic human-IAPP-transgenic (HIP) rat model of T2DM was concordant with increased β cell stress but preceded metabolic derangement. Moreover, the most abundantly expressed chemokines released by the islets in response to β cell stress in T2DM, CXCL1, -4, and -10, induced proliferation in human pancreatic ductal epithelium. Also, the diabetes medications reported as potential modifiers for the risk of pancreatitis in T2DM modulated PDG proliferation accordingly. We conclude that chronic stimulation and proliferation of the PDG compartment in response to islet inflammation in T2DM is a potentially novel mechanism that serves as a link to the increased risk for pancreatitis in T2DM and may potentially be modified by currently available diabetes therapy.
Belinda Schludi, Abu Saleh Md Moin, Chiara Montemurro, Tatyana Gurlo, Aleksey V. Matveyenko, David Kirakossian, David W. Dawson, Sarah M. Dry, Peter C. Butler, Alexandra E. Butler
Dengue virus (DENV) is the most prevalent mosquito-borne virus causing human disease. Of the 4 DENV serotypes, epidemiological data suggest that DENV-2 secondary infections are associated with more severe disease than DENV-4 infections. Mass cytometry by time-of-flight (CyTOF) was used to dissect immune changes induced by DENV-2 and DENV-4 in human DCs, the initial targets of primary infections that likely affect infection outcomes. Strikingly, DENV-4 replication peaked earlier and promoted stronger innate immune responses, with increased expression of DC activation and migration markers and increased cytokine production, compared with DENV-2. In addition, infected DCs produced higher levels of inflammatory cytokines compared with bystander DCs, which mainly produced IFN-induced cytokines. These high-dimensional analyses during DENV-2 and DENV-4 infections revealed distinct viral signatures marked by different replication strategies and antiviral innate immune induction in DCs, which may result in different viral fitness, transmission, and pathogenesis.
Rebecca E. Hamlin, Adeeb Rahman, Theodore R. Pak, Kevin Maringer, Ignacio Mena, Dabeiba Bernal-Rubio, Uma Potla, Ana M. Maestre, Anthony C. Fredericks, El-ad D. Amir, Andrew Kasarskis, Irene Ramos, Miriam Merad, Ana Fernandez-Sesma
Sepsis can induce an overwhelming systemic inflammatory response, resulting in organ damage and death. Suppressor of cytokine signaling 1 (SOCS1) negatively regulates signaling by cytokine receptors and Toll-like receptors (TLRs). However, the cellular targets and molecular mechanisms for SOCS1 activity during polymicrobial sepsis are unknown. To address this, we utilized a cecal ligation and puncture (CLP) model for sepsis; C57BL/6 mice subjected to CLP were then treated with a peptide (iKIR) that binds the SOCS1 kinase inhibitory region (KIR) and blocks its activity. Treatment with iKIR increased CLP-induced mortality, bacterial burden, and inflammatory cytokine production. Myeloid cell–specific SOCS1 deletion (Socs1Δmyel) mice were also more susceptible to sepsis, demonstrating increased mortality, higher bacterial loads, and elevated inflammatory cytokines, compared with Socs1fl littermate controls. These effects were accompanied by macrophage metabolic reprograming, as evidenced by increased lactic acid production and elevated expression of the glycolytic enzymes hexokinase, lactate dehydrogenase A, and glucose transporter 1 in septic Socs1Δmyel mice. Upregulation was dependent on the STAT3/HIF-1α/glycolysis axis, and blocking glycolysis ameliorated increased susceptibility to sepsis in iKIR-treated CLP mice. These results reveal a role of SOCS1 as a regulator of metabolic reprograming that prevents overwhelming inflammatory response and organ damage during sepsis.
Annie Rocio Piñeros Alvarez, Nicole Glosson-Byers, Stephanie Brandt, Soujuan Wang, Hector Wong, Sarah Sturgeon, Brian Paul McCarthy, Paul R. Territo, Jose Carlos Alves-Filho, C. Henrique Serezani
BACKGROUND. Both seasonal and novel avian influenza viruses can result in severe infections requiring hospitalization. Anti-influenza antibodies (Abs) with Fc-mediated effector functions, such as Ab-dependent cellular cytotoxicity (ADCC), are of growing interest in control of influenza but have not previously been studied during severe human infections. As such, the objective of this study was to examine Fc-mediated Ab functions in humans hospitalized with influenza infection. METHODS. Serum Ab response was studied in subjects hospitalized with either pandemic H7N9 avian influenza virus in China (n = 18) or circulating seasonal influenza viruses in Melbourne, Australia (n = 16). Recombinant soluble Fc receptor dimer ELISAs, natural killer (NK) cell activation assays, and Ab-dependent killing assays with influenza-infected target cells were used to assess the Fc functionality of anti-influenza hemagglutinin (HA) Abs during severe human influenza infection. RESULTS. We found that the peak generation of Fc functional HA Abs preceded that of neutralizing Abs for both severe H7N9 and seasonal influenza infections. Subjects who succumbed to complications of H7N9 infection demonstrated reduced HA-specific Fc receptor–binding Abs (in magnitude and breadth) immediately prior to death compared with those who survived. Subjects who recovered from H7N9 and severe seasonal influenza infections demonstrated increased Fc receptor–binding Abs not only against the homologous infecting strain but against HAs from different influenza A subtypes. CONCLUSION. Collectively, survivors of severe influenza infection rapidly generate a functional Ab response capable of mediating ADCC against divergent influenza viruses. Broadly binding HA Abs with Fc-mediated functions may be a useful component of protective immunity to severe influenza infection. FUNDING. The National Health and Medical Research Council ([NHMRC] grants 1023294, 1041832, and 1071916), the Australian Department of Health, and the joint University of Melbourne/Fudan University International Research and Research Training Fund provided funding for this study.
Hillary A. Vanderven, Lu Liu, Fernanda Ana-Sosa-Batiz, Thi H.O. Nguyen, Yanmin Wan, Bruce Wines, P. Mark Hogarth, Danielle Tilmanis, Arnold Reynaldi, Matthew S. Parsons, Aeron C. Hurt, Miles P. Davenport, Tom Kotsimbos, Allen C. Cheng, Katherine Kedzierska, Xiaoyan Zhang, Jianqing Xu, Stephen J. Kent
We previously showed that angiotensin II (Ang II) increases T cell production of IL-17A, and that mice deficient in IL-17A have blunted hypertension and attenuated renal and vascular dysfunction. It was recently shown that salt enhances IL-17A production from CD4+ T cells via a serum- and glucocorticoid-regulated kinase 1–dependent (SGK1-dependent) pathway. Thus, we tested the hypothesis that SGK1 signaling in T cells promotes hypertension and contributes to end-organ damage. We show that loss of T cell SGK1 results in a blunted hypertensive response to Ang II infusion by 25 mmHg. Importantly, renal and vascular inflammation is abrogated in these mice compared with control mice. Furthermore, mice lacking T cell SGK1 are protected from Ang II–induced endothelial dysfunction and renal injury. Loss of T cell SGK1 also blunts blood pressure and vascular inflammation in response to deoxycorticosterone acetate–salt (DOCA-salt) hypertension. Finally, we demonstrate that the Na+-K+-2Cl– cotransporter 1 (NKCC1) is upregulated in Th17 cells and is necessary for the salt-induced increase in SGK1 and the IL-23 receptor. These studies demonstrate that T cell SGK1 and NKCC1 may be novel therapeutic targets for the treatment of hypertension and identify a potentially new mechanism by which salt contributes to hypertension.
Allison E. Norlander, Mohamed A. Saleh, Arvind K. Pandey, Hana A. Itani, Jing Wu, Liang Xiao, Jooeun Kang, Bethany L. Dale, Slavina B. Goleva, Fanny Laroumanie, Liping Du, David G. Harrison, Meena S. Madhur
A central issue for adoptive cellular immunotherapy is overcoming immunosuppressive signals to achieve tumor clearance. While γδ T cells are known to be potent cytolytic effectors that can kill a variety of cancers, it is not clear whether they are inhibited by suppressive ligands expressed in tumor microenvironments. Here, we have used a powerful preclinical model where EBV infection drives the de novo generation of human B cell lymphomas in vivo, and autologous T lymphocytes are held in check by PD-1/CTLA-4–mediated inhibition. We show that a single dose of adoptively transferred Vδ2+ T cells has potent antitumor effects, even in the absence of checkpoint blockade or activating compounds. Vδ2+ T cell immunotherapy given within the first 5 days of EBV infection almost completely prevented the outgrowth of tumors. Vδ2+ T cell immunotherapy given more than 3 weeks after infection (after neoplastic transformation is evident) resulted in a dramatic reduction in tumor burden. The immunotherapeutic Vδ2+ T cells maintained low cell surface expression of PD-1 in vivo, and their recruitment to tumors was followed by a decrease in B cells expressing PD-L1 and PD-L2 inhibitory ligands. These results suggest that adoptively transferred PD-1lo Vδ2+ T cells circumvent the tumor checkpoint environment in vivo.
Nicholas A. Zumwalde, Akshat Sharma, Xuequn Xu, Shidong Ma, Christine L. Schneider, James C. Romero-Masters, Amy W. Hudson, Annette Gendron-Fitzpatrick, Shannon C. Kenney, Jenny E. Gumperz
Although left ventricular (LV) diastolic dysfunction is often associated with hypertension, little is known regarding its underlying pathophysiological mechanism. Here, we show that the actin cytoskeletal regulator, Rho-associated coiled-coil containing kinase-2 (ROCK2), is a critical mediator of LV diastolic dysfunction. In response to angiotensin II (Ang II), mutant mice with fibroblast-specific deletion of ROCK2 (ROCK2Postn–/–) developed less LV wall thickness and fibrosis, along with improved isovolumetric relaxation. This corresponded with decreased connective tissue growth factor (CTGF) and fibroblast growth factor–2 (FGF2) expression in the hearts of ROCK2Postn–/– mice. Indeed, knockdown of ROCK2 in cardiac fibroblasts leads to decreased expression of CTGF and secretion of FGF2, and cardiomyocytes incubated with conditioned media from ROCK2-knockdown cardiac fibroblasts exhibited less hypertrophic response. In contrast, mutant mice with elevated fibroblast ROCK activity exhibited enhanced Ang II–stimulated cardiac hypertrophy and fibrosis. Clinically, higher leukocyte ROCK2 activity was observed in patients with diastolic dysfunction compared with age- and sex-matched controls, and correlated with higher grades of diastolic dysfunction by echocardiography. These findings indicate that fibroblast ROCK2 is necessary to cause cardiac hypertrophy and fibrosis through the induction CTGF and FGF2, and they suggest that targeting ROCK2 may have therapeutic benefits in patients with LV diastolic dysfunction.
Toru Shimizu, Nikhil Narang, Phetcharat Chen, Brian Yu, Maura Knapp, Jyothi Janardanan, John Blair, James K. Liao
Today, it is known that autoimmune diseases start a long time before clinical symptoms appear. Anti-citrullinated protein antibodies (ACPAs) appear many years before the clinical onset of rheumatoid arthritis (RA). However, it is still unclear if and how ACPAs are arthritogenic. To better understand the molecular basis of pathogenicity of ACPAs, we investigated autoantibodies reactive against the C1 epitope of collagen type II (CII) and its citrullinated variants. We found that these antibodies are commonly occurring in RA. A mAb (ACC1) against citrullinated C1 was found to cross-react with several noncitrullinated epitopes on native CII, causing proteoglycan depletion of cartilage and severe arthritis in mice. Structural studies by X-ray crystallography showed that such recognition is governed by a shared structural motif “RG-TG” within all the epitopes, including electrostatic potential-controlled citrulline specificity. Overall, we have demonstrated a molecular mechanism that explains how ACPAs trigger arthritis.
Changrong Ge, Dongmei Tong, Bibo Liang, Erik Lönnblom, Nadine Schneider, Cecilia Hagert, Johan Viljanen, Burcu Ayoglu, Roma Stawikowska, Peter Nilsson, Gregg B. Fields, Thomas Skogh, Alf Kastbom, Jan Kihlberg, Harald Burkhardt, Doreen Dobritzsch, Rikard Holmdahl
Rejection affects greater than 80% of face transplants, yet no diagnostic criteria for antibody-mediated rejection (AMR) following face transplantation have been established. Given that different treatment strategies are required to address AMR and T cell–mediated rejection (TCMR), there is a critical need to delineate the features that can differentiate these two alloimmune responses. Here, we report the longitudinal immunological examination of what we believe to be the first and only highly sensitized recipient of a crossmatch-positive face transplant up to 4 years following transplantation. We conducted gene expression profiling on allograft biopsies collected during suspected AMR and TCMR episodes as well as during 5 nonrejection time points. Our data suggest that there are distinctive molecular features in AMR, characterized by overexpression of endothelial-associated genes, including ICAM1, VCAM1, and SELE. Although our findings are limited to a single patient, these findings highlight the potential importance of developing and implementing molecular markers to differentiate AMR from TCMR to guide clinical management. Furthermore, our case illustrates that molecular assessment of allograft biopsies offers the potential for new insights into the mechanisms underlying rejection. Finally, our medium-term outcomes demonstrate that face transplantation in a highly sensitized patient with a positive preoperative crossmatch is feasible and manageable.
Thet Su Win, Naoka Murakami, Thiago J. Borges, Anil Chandraker, George Murphy, Christine Lian, Victor Barrera, Shannan Ho Sui, David Schoenfeld, Jessica Teague, Ericka Bueno, Stefan G. Tullius, Bohdan Pomahac, Rachael A. Clark, Leonardo V. Riella
Human cytomegalovirus (HCMV) is the most common congenital infection and a known cause of microcephaly, sensorineural hearing loss, and cognitive impairment among newborns worldwide. Natural maternal HCMV immunity reduces the incidence of congenital infection, but does not prevent the disease altogether. We employed a nonhuman primate model of congenital CMV infection to investigate the ability of preexisting antibodies to protect against placental CMV transmission in the setting of primary maternal infection and subsequent viremia, which is required for placental virus exposure. Pregnant, CD4+ T cell–depleted, rhesus CMV–seronegative (RhCMV-seronegative) rhesus monkeys were treated with either standardly produced hyperimmune globulin (HIG) from RhCMV-seropositive macaques or dose-optimized, potently RhCMV-neutralizing HIG prior to intravenous challenge with an RhCMV mixture. HIG passive infusion provided complete protection against fetal loss in both groups. The dose-optimized, RhCMV-neutralizing HIG additionally inhibited placental transmission of RhCMV and reduced viral replication and diversity. Our findings suggest that the presence of durable and potently neutralizing antibodies at the time of primary infection can prevent transmission of systemically replicating maternal RhCMV to the developing fetus, and therefore should be a primary target of vaccines to eliminate this neonatal infection.
Cody S. Nelson, Diana Vera Cruz, Dollnovan Tran, Kristy M. Bialas, Lisa Stamper, Huali Wu, Margaret Gilbert, Robert Blair, Xavier Alvarez, Hannah Itell, Meng Chen, Ashlesha Deshpande, Flavia Chiuppesi, Felix Wussow, Don J. Diamond, Nathan Vandergrift, Mark R. Walter, Peter A. Barry, Michael Cohen-Wolkowiez, Katia Koelle, Amitinder Kaur, Sallie R. Permar
Airway epithelial cells are prone to the damage caused by lung cancer risk factors, such as cigarette smoking. Little is known about surrogate biomarkers in the bronchial airway epithelium that can be used to assess the effect of potential chemoprevention drugs on lung adenocarcinoma formation/progression. Pioglitazone has been suggested as a chemoprevention drug for lung cancer. To study the mechanisms underlying the role of pioglitazone in lung cancer prevention, we performed transcriptome sequencing (RNA-Seq) and found that Kras signaling was repressed by pioglitazone treatment in the airway epithelial cells of mice with lung adenocarcinoma (FDR q = 9.8E-04). It was also found that glucose metabolic pathways were elevated in the airway epithelium of mice with lung adenocarcinomas and inhibited by pioglitazone treatment (FDR q = 0.01). Downregulation of glucose metabolism genes was also observed in lung tumors of mice treated with pioglitazone. The high-risk expression signature of elevated glucose metabolism was associated with poor survival outcome in multiple lung adenocarcinoma patient populations (P values ranging from 1.0E-9 to 5.5E-5). Our results suggest that the role of pioglitazone in preventing lung adenocarcinoma may depend on inhibiting Kras signaling and glucose metabolism, which may serve as biomarkers of agent action in the airway epithelium.
Donghai Xiong, Jing Pan, Qi Zhang, Eva Szabo, Mark Steven Miller, Ronald A. Lubet, Yian Wang, Ming You
In recent years, the extent of our vulnerability to misinterpretation due to poorly characterized reagents has become an issue of great concern. Antibody reagents have been identified as a major source of error, contributing to the “reproducibility crisis.” In the current report, we define an additional dimension of the crisis; in particular, we define variation of the targets being analyzed. We report that natural variation in the immunoglobulin “constant” region alters the reactivity with commonly used subtype-specific anti-IgG reagents, resulting in cross-reactivity of polyclonal regents with inappropriate targets and blind spots of monoclonal reagents for desired targets. This raises the practical concern that numerous studies characterizing IgG subtypes in human disease may contain errors due to such previously unappreciated defects. These studies also focus attention on the broader concern that genetic variation may affect the performance of any laboratory or research test that uses antibodies for detection.
Heather L. Howie, Meghan Delaney, Xiaohong Wang, Lay See Er, Linda Kapp, Jenna N. Lebedev, James C. Zimring
We previously showed that Th1/type 1 inflammation marked by increased IFN-γ levels in the airways can be appreciated in 50% of patients with severe asthma, despite high dose corticosteroid (CS) treatment. We hypothesized that a downstream target of IFN-γ, CXCL10, which recruits Th1 cells via the cognate receptor CXCR3, is an important contributor to Th1high asthma and CS unresponsiveness. We show high levels of CXCL10 mRNA closely associated with IFNG levels in the BAL cells of 50% of severe asthmatics and also in the airways of mice subjected to a severe asthma model, both in the context of high-dose CS treatment. The inability of CS to dampen IFNG or CXCL10 expression was not because of impaired nuclear translocation of the glucocorticoid receptor (GR) or its transactivational functions. Rather, in the presence of CS and IFN-γ, STAT1 and GR were recruited on critical regulatory elements in the endogenous CXCL10 promoter in monocytes, albeit without any abatement of CXCL10 gene expression. High CXCL10 gene expression was also associated with a mast cell signature in both humans and mice, CXCR3 being also expressed by mast cells. These findings suggest that the IFN-γ–CXCL10 axis plays a central role in persistent type 1 inflammation that may be facilitated by CS therapy through GR-STAT1 cooperation converging on the CXCL10 promoter.
Marc Gauthier, Krishnendu Chakraborty, Timothy B. Oriss, Mahesh Raundhal, Sudipta Das, Jie Chen, Rachael Huff, Ayan Sinha, Merritt Fajt, Prabir Ray, Sally E. Wenzel, Anuradha Ray