Publications by authors named "Rickvinder Besla"

23 Publications

  • Page 1 of 1

Dj1 deficiency protects against atherosclerosis with anti-inflammatory response in macrophages.

Sci Rep 2021 Feb 25;11(1):4723. Epub 2021 Feb 25.

Toronto General Hospital Research Institute, University Health Network, Toronto, ON, M5G 2C4, Canada.

Inflammation is a key contributor to atherosclerosis with macrophages playing a pivotal role through the induction of oxidative stress and cytokine/chemokine secretion. DJ1, an anti-oxidant protein, has shown to paradoxically protect against chronic and acute inflammation. However, the role of DJ1 in atherosclerosis remains elusive. To assess the role of Dj1 in atherogenesis, we generated whole-body Dj1-deficient atherosclerosis-prone Apoe null mice (Dj1Apoe). After 21 weeks of atherogenic diet, Dj1 Apoemice were protected against atherosclerosis with significantly reduced plaque macrophage content. To assess whether haematopoietic or parenchymal Dj1 contributed to atheroprotection in Dj1-deficient mice, we performed bone-marrow (BM) transplantation and show that Dj1-deficient BM contributed to their attenuation in atherosclerosis. To assess cell-autonomous role of macrophage Dj1 in atheroprotection, BM-derived macrophages from Dj1-deficient mice and Dj1-silenced macrophages were assessed in response to oxidized low-density lipoprotein (oxLDL). In both cases, there was an enhanced anti-inflammatory response which may have contributed to atheroprotection in Dj1-deficient mice. There was also an increased trend of plasma DJ-1 levels from individuals with ischemic heart disease compared to those without. Our findings indicate an atheropromoting role of Dj1 and suggests that targeting Dj1 may provide a novel therapeutic avenue for atherosclerosis treatment or prevention.
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http://dx.doi.org/10.1038/s41598-021-84063-6DOI Listing
February 2021

c-Myb Exacerbates Atherosclerosis through Regulation of Protective IgM-Producing Antibody-Secreting Cells.

Cell Rep 2019 05;27(8):2304-2312.e6

Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S1A1, Canada; Department of Immunology, University of Toronto, Toronto, ON M5S1A1, Canada; Toronto General Research Institute, University Health Network, Toronto, ON M5G1L7, Canada; Peter Munk Cardiac Centre, Toronto, ON M5G1L7, Canada. Electronic address:

Mechanisms that govern transcriptional regulation of inflammation in atherosclerosis remain largely unknown. Here, we identify the nuclear transcription factor c-Myb as an important mediator of atherosclerotic disease in mice. Atherosclerosis-prone animals fed a diet high in cholesterol exhibit increased levels of c-Myb in the bone marrow. Use of mice that either harbor a c-Myb hypomorphic allele or where c-Myb has been preferentially deleted in B cell lineages revealed that c-Myb potentiates atherosclerosis directly through its effects on B lymphocytes. Reduced c-Myb activity prevents the expansion of atherogenic B2 cells yet associates with increased numbers of IgM-producing antibody-secreting cells (IgM-ASCs) and elevated levels of atheroprotective oxidized low-density lipoprotein (OxLDL)-specific IgM antibodies. Transcriptional profiling revealed that c-Myb has a limited effect on B cell function but is integral in maintaining B cell progenitor populations in the bone marrow. Thus, targeted disruption of c-Myb beneficially modulates the complex biology of B cells in cardiovascular disease.
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http://dx.doi.org/10.1016/j.celrep.2019.04.090DOI Listing
May 2019

Publisher Correction: Self-renewing resident cardiac macrophages limit adverse remodeling following myocardial infarction.

Nat Immunol 2019 May;20(5):664

Toronto General Hospital Research Institute, University Health Network (UHN), Toronto, Canada.

In the version of this article initially published, the equal contribution of the third author was omitted. The footnote links for that author should be "Sara Nejat" and the correct statement is as follows: "These authors contributed equally: Sarah A. Dick, Jillian A. Macklin, Sara Nejat." The error has been corrected in the HTML and PDF versions of the article.
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http://dx.doi.org/10.1038/s41590-019-0363-8DOI Listing
May 2019

B-Cell Deficiency Lowers Blood Pressure in Mice.

Hypertension 2019 03;73(3):561-570

From the Toronto General Hospital Research Institute, University Health Network, Canada (L.S.D., E.A.S., A.M., T.A., F.B., M.H.).

The proto-oncogene c-myb (and corresponding nuclear transcription factor, c-Myb) regulates the proliferation and differentiation of hematologic and vascular smooth muscle cells; however, the role of c-Myb in blood pressure regulation is unknown. Here, we show that mice homozygous for a hypomorphic c-myb allele ( c-myb ) conferring reduced c-Myb activity manifest reduced peripheral blood and kidney B220 B-cells and have decreased systolic (104±2 versus 120±1 mm Hg; P<0.0001) and diastolic blood pressure (71±2 versus 83±1 mm Hg; P<0.0001) compared with WT (wild type) mice. Additionally, c-myb mice had lower susceptibility to deoxycorticosterone acetate-salt experimental hypertension. Although cardiac (echocardiography) and resistance artery (perfusion myography) functions were normal, metabolic cage studies revealed that c-myb mice had increased 24-hour urine output and sodium excretion versus WT. Reconstitution of WT mice with c-myb bone marrow transplant and chimeric bone marrow transplant using mice lacking B-cells ( J T; h/h>WT and h/h:J T>WT, respectively) decreased blood pressure and increased 24-hour urine output compared with controls ( WT>WT; WT:J T>WT). J T mice also had decreased systolic (103±2 versus 115±1 mm Hg; P<0.0001) and diastolic blood pressure (71±2 versus 79±1; P<0.01) and increased 24-hour urine output versus WT. Real-time quantitative reverse transcription polymerase chain reaction of kidney medulla revealed reduced VR (vasopressin receptor 2) expression in c-myb and J T mice. These data implicate B-cells in the regulation of VR and its associated effects on salt and water handling and blood pressure homeostasis.
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http://dx.doi.org/10.1161/HYPERTENSIONAHA.118.11828DOI Listing
March 2019

Recirculating Intestinal IgA-Producing Cells Regulate Neuroinflammation via IL-10.

Cell 2019 01 3;176(3):610-624.e18. Epub 2019 Jan 3.

Department of Immunology, University of Toronto, Toronto, ON M5S 1A8, Canada. Electronic address:

Plasma cells (PC) are found in the CNS of multiple sclerosis (MS) patients, yet their source and role in MS remains unclear. We find that some PC in the CNS of mice with experimental autoimmune encephalomyelitis (EAE) originate in the gut and produce immunoglobulin A (IgA). Moreover, we show that IgA PC are dramatically reduced in the gut during EAE, and likewise, a reduction in IgA-bound fecal bacteria is seen in MS patients during disease relapse. Removal of plasmablast (PB) plus PC resulted in exacerbated EAE that was normalized by the introduction of gut-derived IgA PC. Furthermore, mice with an over-abundance of IgA PB and/or PC were specifically resistant to the effector stage of EAE, and expression of interleukin (IL)-10 by PB plus PC was necessary and sufficient to confer resistance. Our data show that IgA PB and/or PC mobilized from the gut play an unexpected role in suppressing neuroinflammation.
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http://dx.doi.org/10.1016/j.cell.2018.11.035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6903689PMC
January 2019

Self-renewing resident cardiac macrophages limit adverse remodeling following myocardial infarction.

Nat Immunol 2019 01 11;20(1):29-39. Epub 2018 Dec 11.

Toronto General Hospital Research Institute, University Health Network (UHN), Toronto, Canada.

Macrophages promote both injury and repair after myocardial infarction, but discriminating functions within mixed populations remains challenging. Here we used fate mapping, parabiosis and single-cell transcriptomics to demonstrate that at steady state, TIMD4LYVE1MHC-IICCR2 resident cardiac macrophages self-renew with negligible blood monocyte input. Monocytes partially replaced resident TIMD4LYVE1MHC-IICCR2 macrophages and fully replaced TIMD4LYVE1MHC-IICCR2 macrophages, revealing a hierarchy of monocyte contribution to functionally distinct macrophage subsets. Ischemic injury reduced TIMD4 and TIMD4 resident macrophage abundance, whereas CCR2 monocyte-derived macrophages adopted multiple cell fates within infarcted tissue, including those nearly indistinguishable from resident macrophages. Recruited macrophages did not express TIMD4, highlighting the ability of TIMD4 to track a subset of resident macrophages in the absence of fate mapping. Despite this similarity, inducible depletion of resident macrophages using a Cx3cr1-based system led to impaired cardiac function and promoted adverse remodeling primarily within the peri-infarct zone, revealing a nonredundant, cardioprotective role of resident cardiac macrophages.
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http://dx.doi.org/10.1038/s41590-018-0272-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6565365PMC
January 2019

Aortic Sca-1 Progenitor Cells Arise from the Somitic Mesoderm Lineage in Mice.

Stem Cells Dev 2018 07 31;27(13):888-897. Epub 2018 May 31.

1 Division of Experimental Therapeutics, Toronto General Hospital Research Institute, University Health Network , Toronto, Canada .

Sca-1 progenitor cells in the adult mouse aorta are known to generate vascular smooth muscle cells (VSMCs), but their embryological origins and temporal abundance are not known. Using tamoxifen-inducible Myf5-Cre mice, we demonstrate that Sca-1 adult aortic cells arise from the somitic mesoderm beginning at E8.5 and continue throughout somitogenesis. Myf5 lineage-derived Sca-1 cells greatly expand in situ, starting at 4 weeks of age, and become a major source of aortic Sca-1 cells by 6 weeks of age. Myf5-derived adult aortic cells are capable of forming multicellular sphere-like structures in vitro and express the pluripotency marker Sox2. Exposure to transforming growth factor-β3 induces these spheres to differentiate into calponin-expressing VSMCs. Pulse-chase experiments using tamoxifen-inducible Sox2-Cre mice at 8 weeks of age demonstrate that ∼35% of all adult aortic Sca-1 cells are derived from Sox2 cells. The present study demonstrates that aortic Sca-1 progenitor cells are derived from the somitic mesoderm formed at the earliest stages of somitogenesis and from Sox2-expressing progenitors in adult mice.
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http://dx.doi.org/10.1089/scd.2018.0038DOI Listing
July 2018

BCG Educates Hematopoietic Stem Cells to Generate Protective Innate Immunity against Tuberculosis.

Cell 2018 01;172(1-2):176-190.e19

Meakins-Christie Laboratories, Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill International TB Centre, McGill University Health Centre, Montreal, QC H4A 3J1, Canada. Electronic address:

The dogma that adaptive immunity is the only arm of the immune response with memory capacity has been recently challenged by several studies demonstrating evidence for memory-like innate immune training. However, the underlying mechanisms and location for generating such innate memory responses in vivo remain unknown. Here, we show that access of Bacillus Calmette-Guérin (BCG) to the bone marrow (BM) changes the transcriptional landscape of hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs), leading to local cell expansion and enhanced myelopoiesis at the expense of lymphopoiesis. Importantly, BCG-educated HSCs generate epigenetically modified macrophages that provide significantly better protection against virulent M. tuberculosis infection than naïve macrophages. By using parabiotic and chimeric mice, as well as adoptive transfer approaches, we demonstrate that training of the monocyte/macrophage lineage via BCG-induced HSC reprogramming is sustainable in vivo. Our results indicate that targeting the HSC compartment provides a novel approach for vaccine development.
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http://dx.doi.org/10.1016/j.cell.2017.12.031DOI Listing
January 2018

Effect of removing Kupffer cells on nanoparticle tumor delivery.

Proc Natl Acad Sci U S A 2017 12 5;114(51):E10871-E10880. Epub 2017 Dec 5.

Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON M5S 3G9, Canada;

A recent metaanalysis shows that 0.7% of nanoparticles are delivered to solid tumors. This low delivery efficiency has major implications in the translation of cancer nanomedicines, as most of the nanomedicines are sequestered by nontumor cells. To improve the delivery efficiency, there is a need to investigate the quantitative contribution of each organ in blocking the transport of nanoparticles to solid tumors. Here, we hypothesize that the removal of the liver macrophages, cells that have been reported to take up the largest amount of circulating nanoparticles, would lead to a significant increase in the nanoparticle delivery efficiency to solid tumors. We were surprised to discover that the maximum achievable delivery efficiency was only 2%. In our analysis, there was a clear correlation between particle design, chemical composition, macrophage depletion, tumor pathophysiology, and tumor delivery efficiency. In many cases, we observed an 18-150 times greater delivery efficiency, but we were not able to achieve a delivery efficiency higher than 2%. The results suggest the need to look deeper at other organs such as the spleen, lymph nodes, and tumor in mediating the delivery process. Systematically mapping the contribution of each organ quantitatively will allow us to pinpoint the cause of the low tumor delivery efficiency. This, in effect, enables the generation of a rational strategy to improve the delivery efficiency of nanoparticles to solid tumors either through the engineering of multifunctional nanosystems or through manipulation of biological barriers.
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http://dx.doi.org/10.1073/pnas.1713390114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5754793PMC
December 2017

Macrophage JAK2 deficiency protects against high-fat diet-induced inflammation.

Sci Rep 2017 08 9;7(1):7653. Epub 2017 Aug 9.

Toronto General Hospital Research Institute, University Health Network, Toronto, M5G 1L7, Canada.

During obesity, macrophages can infiltrate metabolic tissues, and contribute to chronic low-grade inflammation, and mediate insulin resistance and diabetes. Recent studies have elucidated the metabolic role of JAK2, a key mediator downstream of various cytokines and growth factors. Our study addresses the essential role of macrophage JAK2 in the pathogenesis to obesity-associated inflammation and insulin resistance. During high-fat diet (HFD) feeding, macrophage-specific JAK2 knockout (M-JAK2) mice gained less body weight compared to wildtype littermate control (M-JAK2) mice and were protected from HFD-induced systemic insulin resistance. Histological analysis revealed smaller adipocytes and qPCR analysis showed upregulated expression of some adipogenesis markers in visceral adipose tissue (VAT) of HFD-fed M-JAK2 mice. There were decreased crown-like structures in VAT along with reduced mRNA expression of some macrophage markers and chemokines in liver and VAT of HFD-fed M-JAK2 mice. Peritoneal macrophages from M-JAK2 mice and Jak2 knockdown in macrophage cell line RAW 264.7 also showed lower levels of chemokine expression and reduced phosphorylated STAT3. However, leptin-dependent effects on augmenting chemokine expression in RAW 264.7 cells did not require JAK2. Collectively, our findings show that macrophage JAK2 deficiency improves systemic insulin sensitivity and reduces inflammation in VAT and liver in response to metabolic stress.
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http://dx.doi.org/10.1038/s41598-017-07923-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5550513PMC
August 2017

Hepatic JAK2 protects against atherosclerosis through circulating IGF-1.

JCI Insight 2017 Jul 20;2(14). Epub 2017 Jul 20.

Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada.

Atherosclerosis is considered both a metabolic and inflammatory disease; however, the specific tissue and signaling molecules that instigate and propagate this disease remain unclear. The liver is a central site of inflammation and lipid metabolism that is critical for atherosclerosis, and JAK2 is a key mediator of inflammation and, more recently, of hepatic lipid metabolism. However, precise effects of hepatic Jak2 on atherosclerosis remain unknown. We show here that hepatic Jak2 deficiency in atherosclerosis-prone mouse models exhibited accelerated atherosclerosis with increased plaque macrophages and decreased plaque smooth muscle cell content. JAK2's essential role in growth hormone signalling in liver that resulted in reduced IGF-1 with hepatic Jak2 deficiency played a causal role in exacerbating atherosclerosis. As such, restoring IGF-1 either pharmacologically or genetically attenuated atherosclerotic burden. Together, our data show hepatic Jak2 to play a protective role in atherogenesis through actions mediated by circulating IGF-1 and, to our knowledge, provide a novel liver-centric mechanism in atheroprotection.
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http://dx.doi.org/10.1172/jci.insight.93735DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5518558PMC
July 2017

-Nitrosoglutathione Reductase Deficiency Confers Improved Survival and Neurological Outcome in Experimental Cerebral Malaria.

Infect Immun 2017 09 18;85(9). Epub 2017 Aug 18.

Sandra Rotman Centre for Global Health, University Health Network, University of Toronto, Toronto, ON, Canada

Artesunate remains the mainstay of treatment for cerebral malaria, but it is less effective in later stages of disease when the host inflammatory response and blood-brain barrier integrity dictate clinical outcomes. Nitric oxide (NO) is an important regulator of inflammation and microvascular integrity, and impaired NO bioactivity is associated with fatal outcomes in malaria. Endogenous NO bioactivity in mammals is largely mediated by -nitrosothiols (SNOs). Based on these observations, we hypothesized that animals deficient in the SNO-metabolizing enzyme, -nitrosoglutathione reductase (GSNOR), which exhibit enhanced -nitrosylation, would have improved outcomes in a preclinical model of cerebral malaria. GSNOR knockout (KO) mice infected with ANKA had significantly delayed mortality compared to WT animals ( < 0.0001), despite higher parasite burdens ( < 0.01), and displayed markedly enhanced survival versus the wild type (WT) when treated with the antimalarial drug artesunate (77% versus 38%; < 0.001). Improved survival was associated with higher levels of protein-bound NO, decreased levels of CD4 and CD8 T cells in the brain, improved blood-brain barrier integrity, and improved coma scores, as well as higher levels of gamma interferon. GSNOR KO animals receiving WT bone marrow had significantly reduced survival following ANKA infection compared to those receiving KO bone barrow ( < 0.001). Reciprocal transplants established that survival benefits of GSNOR deletion were attributable primarily to the T cell compartment. These data indicate a role for GSNOR in the host response to malaria infection and suggest that strategies to disrupt its activity will improve clinical outcomes by enhancing microvascular integrity and modulating T cell tissue tropism.
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http://dx.doi.org/10.1128/IAI.00371-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5563579PMC
September 2017

Paradoxical Suppression of Atherosclerosis in the Absence of microRNA-146a.

Circ Res 2017 Aug 21;121(4):354-367. Epub 2017 Jun 21.

From the Toronto General Hospital Research Institute, University Health Network, Ontario, Canada (H.S.C, R.B., A.L., Z.C., E.A.S., N.K., S.A.M., M.H., M.I.C., C.S.R., J.E.F.); Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada (H.S.C, R.B., A.L., Z.C., E.A.S., N.K., S.A.M., M.H., M.I.C., C.S.R., J.E.F.); Heart and Stroke Richard Lewar Centre of Excellence in Cardiovascular Research, Toronto, Ontario, Canada (H.S.C, R.B., A.L., Z.C., E.A.S., N.K., M.H., M.I.C., C.S.R., J.E.F.); Institute for Cardiovascular Prevention, Ludwig-Maximilians-University Munich, Germany (M.N.-J., A.S.); INSERM, Unit 970, Paris Cardiovascular Research Center-PARCC, France (A.H., C.M.B.); University of Ottawa Heart Institute, Ontario, Canada (M.-A.N., M.G., K.J.R.); and Pharmacology and Nutritional Sciences, University of Kentucky, Lexington (L.C., T.L., R.E.T.).

Rationale: Inflammation is a key contributor to atherosclerosis. MicroRNA-146a (miR-146a) has been identified as a critical brake on proinflammatory nuclear factor κ light chain enhancer of activated B cells signaling in several cell types, including endothelial cells and bone marrow (BM)-derived cells. Importantly, miR-146a expression is elevated in human atherosclerotic plaques, and polymorphisms in the precursor have been associated with risk of coronary artery disease.

Objective: To define the role of endogenous miR-146a during atherogenesis.

Methods And Results: Paradoxically, (low-density lipoprotein receptor null) mice deficient in develop less atherosclerosis, despite having highly elevated levels of circulating proinflammatory cytokines. In contrast, cytokine levels are normalized in mice receiving wild-type BM transplantation, and these mice have enhanced endothelial cell activation and elevated atherosclerotic plaque burden compared with mice receiving wild-type BM, demonstrating the atheroprotective role of miR-146a in the endothelium. We find that deficiency of in BM-derived cells precipitates defects in hematopoietic stem cell function, contributing to extramedullary hematopoiesis, splenomegaly, BM failure, and decreased levels of circulating proatherogenic cells in mice fed an atherogenic diet. These hematopoietic phenotypes seem to be driven by unrestrained inflammatory signaling that leads to the expansion and eventual exhaustion of hematopoietic cells, and this occurs in the face of lower levels of circulating low-density lipoprotein cholesterol in mice lacking in BM-derived cells. Furthermore, we identify sortilin-1(), a known regulator of circulating low-density lipoprotein levels in humans, as a novel target of miR-146a.

Conclusions: Our study reveals that miR-146a regulates cholesterol metabolism and tempers chronic inflammatory responses to atherogenic diet by restraining proinflammatory signaling in endothelial cells and BM-derived cells.
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http://dx.doi.org/10.1161/CIRCRESAHA.116.310529DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5542783PMC
August 2017

Partial Restoration of CFTR Function in cftr-Null Mice following Targeted Cell Replacement Therapy.

Mol Ther 2017 03 8;25(3):654-665. Epub 2017 Feb 8.

Latner Thoracic Surgery Research Laboratories and McEwen Centre for Regenerative Medicine, Toronto General Hospital Research Institute, University of Toronto, Toronto, ON M5G 2C4, Canada. Electronic address:

Cystic fibrosis (CF) is a fatal recessive genetic disorder caused by a mutation in the gene encoding CF transmembrane conductance regulator (CFTR) protein. Alteration in CFTR leads to thick airway mucus and bacterial infection. Cell therapy has been proposed for CFTR restoration, but efficacy has been limited by low engraftment levels. In our previous studies, we have shown that using a pre-conditioning regimen in combination with optimization of cell number and time of delivery, we could obtain greater bone marrow cell (BMC) retention in the lung. Here, we found that optimized delivery of wild-type (WT) BMC contributed to apical CFTR expression in airway epithelium and restoration of select ceramide species and fatty acids in CFTR mice. Importantly, WT BMC delivery delayed Pseudomonas aeruginosa lung infection and increased survival of CFTR recipients. Only WT BMCs had a beneficial effect beyond 6 months, suggesting a dual mechanism of BMC benefit: a non-specific effect early after cell delivery, possibly due to the recruitment of macrophages and neutrophils, and a late beneficial effect dependent on long-term CFTR expression. Taken together, our results suggest that BMC can improve overall lung function and may have potential therapeutic benefit for the treatment of CF.
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http://dx.doi.org/10.1016/j.ymthe.2016.11.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5363215PMC
March 2017

CCL19-CCR7-dependent reverse transendothelial migration of myeloid cells clears Chlamydia muridarum from the arterial intima.

Nat Immunol 2016 Nov 26;17(11):1263-1272. Epub 2016 Sep 26.

Toronto General Research Institute, University Health Network, Toronto, Canada.

Regions of the normal arterial intima predisposed to atherosclerosis are sites of ongoing monocyte trafficking and also contain resident myeloid cells with features of dendritic cells. However, the pathophysiological roles of these cells are poorly understood. Here we found that intimal myeloid cells underwent reverse transendothelial migration (RTM) into the arterial circulation after systemic stimulation of pattern-recognition receptors (PRRs). This process was dependent on expression of the chemokine receptor CCR7 and its ligand CCL19 by intimal myeloid cells. In mice infected with the intracellular pathogen Chlamydia muridarum, blood monocytes disseminated infection to the intima. Subsequent CCL19-CCR7-dependent RTM was critical for the clearance of intimal C. muridarum. This process was inhibited by hypercholesterolemia. Thus, RTM protects the normal arterial intima, and compromised RTM during atherogenesis might contribute to the intracellular retention of pathogens in atherosclerotic lesions.
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http://dx.doi.org/10.1038/ni.3564DOI Listing
November 2016

Primitive Macrophages Drive Coronary Development.

Circ Res 2016 05;118(10):1454-6

From the Peter Munk Cardiac Centre, Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada (C.S.R.); and Departments of Laboratory Medicine and Pathobiology (C.S.R., R.B.) and Immunology (C.S.R.), University of Toronto, Toronto, Ontario, Canada.

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http://dx.doi.org/10.1161/CIRCRESAHA.116.308778DOI Listing
May 2016

c-Myb Regulates Proliferation and Differentiation of Adventitial Sca1+ Vascular Smooth Muscle Cell Progenitors by Transactivation of Myocardin.

Arterioscler Thromb Vasc Biol 2016 07 12;36(7):1367-76. Epub 2016 May 12.

From the Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada (E.A.S., M.C., R.B., A.M., O.E.-M., C.S.R., M.H.); and Heart and Stroke Richard Lewar Centre of Excellence, Ted Rogers Centre for Heart Research, McEwen Centre for Regenerative Medicine, and Peter Munk Cardiac Centre (E.A.S., M.C., R.B., C.S.R., M.H.), Department of Laboratory Medicine and Pathobiology (E.A.S., R.B., C.S.R., M.H.), Department of Immunology (C.C.L., C.S.R.), and Department of Medicine (M.C., M.H.), University of Toronto, Ontario, Canada.

Objective: Vascular smooth muscle cells (VSMCs) are believed to dedifferentiate and proliferate in response to vessel injury. Recently, adventitial progenitor cells were implicated as a source of VSMCs involved in vessel remodeling. c-Myb is a transcription factor known to regulate VSMC proliferation in vivo and differentiation of VSMCs from mouse embryonic stem cell-derived progenitors in vitro. However, the role of c-Myb in regulating specific adult vascular progenitor cell populations was not known. Our objective was to examine the role of c-Myb in the proliferation and differentiation of Sca1(+) adventitial VSMC progenitor cells.

Approach And Results: Using mice with wild-type or hypomorphic c-myb (c-myb(h/h)), BrdU (bromodeoxyuridine) uptake and flow cytometry revealed defective proliferation of Sca1(+) adventitial VSMC progenitor cells at 8, 14, and 28 days post carotid artery denudation injury in c-myb(h/h) arteries. c-myb(h/h) cKit(+)CD34(-)Flk1(-)Sca1(+)CD45(-)Lin(-) cells failed to proliferate, suggesting that c-myb regulates the activation of specific Sca1(+) progenitor cells in vivo and in vitro. Although expression levels of transforming growth factor-β1 did not vary between wild-type and c-myb(h/h) carotid arteries, in vitro differentiation of c-myb(h/h) Sca1(+) cells manifested defective transforming growth factor-β1-induced VSMC differentiation. This is mediated by reduced transcriptional activation of myocardin because chromatin immunoprecipitation revealed c-Myb binding to the myocardin promoter only during differentiation of Sca1(+) cells, myocardin promoter mutagenesis identified 2 specific c-Myb-responsive binding sites, and adenovirus-mediated expression of myocardin rescued the phenotype of c-myb(h/h) progenitors.

Conclusions: These data support a role for c-Myb in the regulation of VSMC progenitor cells and provide novel insight into how c-myb regulates VSMC differentiation through myocardin.
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http://dx.doi.org/10.1161/ATVBAHA.115.307116DOI Listing
July 2016

Circulating Cell Death Biomarkers May Predict Survival in Human Lung Transplantation.

Am J Respir Crit Care Med 2016 07;194(1):97-105

1 Latner Thoracic Surgery Research Laboratories, Division of Thoracic Surgery, University of Toronto, Toronto, Canada; and.

Rationale: Immediate graft performance after lung transplantation is associated with short- and long-term clinical outcomes. However, the biologic mechanism that determines outcomes is not fully understood.

Objectives: To investigate the impact of cell death signals at 24 and 48 hours after lung transplantation on short- and long-term clinical outcomes.

Methods: Plasma samples were collected pretransplantation and at 24 and 48 hours after transplant from 60 bilateral lung transplant recipients. Ten patients had primary graft dysfunction (PGD) grade 3 (PaO2/FiO2 ratio <200 or on extracorporeal membrane oxygenation support) at 72 hours after transplant (PGD group). The remaining 50 patients were defined as the control group. Levels of plasma M30 (signifying epithelial apoptosis), M65 (signifying epithelial apoptosis plus necrosis), and high-mobility group box 1 protein (HMGB-1; signifying necrosis of all cell types) were measured by ELISA and correlated with clinical outcomes. Survival analyses were performed using Kaplan-Meier curves and Cox proportional hazards regression. Prediction accuracy of markers was assessed by calculated area under the curve of receiver operating characteristic graph.

Measurements And Main Results: The PGD group had significantly higher M30 and M65 levels at 24 and 48 hours after transplant compared with the control group. There was no significant difference in HMGB-1. Area under the curve for 1-year survival was 0.86, 0.93, and 0.51 for M30, M65, and HMGB-1 at 48 hours, respectively. Survival analysis showed that higher M30 and M65 levels at 24 and 48 hours were significantly associated with worse survival. M65 at 48 hours remained significant even after adjustment for PGD. HMGB-1 was not significantly associated with survival.

Conclusions: Recipient plasma concentration of epithelial cell death markers (M30, M65) after lung transplantation is negatively correlated with early graft performance and long-term survival.
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http://dx.doi.org/10.1164/rccm.201510-2115OCDOI Listing
July 2016

Self-renewing resident arterial macrophages arise from embryonic CX3CR1(+) precursors and circulating monocytes immediately after birth.

Nat Immunol 2016 Feb 7;17(2):159-68. Epub 2015 Dec 7.

Department of Immunology, University of Toronto, Toronto, Ontario, Canada.

Resident macrophages densely populate the normal arterial wall, yet their origins and the mechanisms that sustain them are poorly understood. Here we use gene-expression profiling to show that arterial macrophages constitute a distinct population among macrophages. Using multiple fate-mapping approaches, we show that arterial macrophages arise embryonically from CX3CR1(+) precursors and postnatally from bone marrow-derived monocytes that colonize the tissue immediately after birth. In adulthood, proliferation (rather than monocyte recruitment) sustains arterial macrophages in the steady state and after severe depletion following sepsis. After infection, arterial macrophages return rapidly to functional homeostasis. Finally, survival of resident arterial macrophages depends on a CX3CR1-CX3CL1 axis within the vascular niche.
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http://dx.doi.org/10.1038/ni.3343DOI Listing
February 2016

Inflammation rapidly reorganizes mouse bone marrow B cells and their environment in conjunction with early IgM responses.

Blood 2015 Sep 13;126(10):1184-92. Epub 2015 Jul 13.

Department of Immunology, University of Toronto, Toronto, ON, Canada; Ontario Cancer Institute, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Department of Medical Biophysics and.

Systemic inflammation perturbs the bone marrow environment by evicting resident B cells and favoring granulopoiesis over lymphopoiesis. Despite these conditions, a subset of marrow B cell remains to become activated and produce potent acute immunoglobulin M (IgM) responses. This discrepancy is currently unresolved and a complete characterization of early perturbations in the B-cell niche has not been undertaken. Here, we show that within a few hours of challenging mice with adjuvant or cecal puncture, B cells accumulate in the bone marrow redistributed away from sinusoid vessels. This response correlates with enhanced sensitivity to CXC chemokine ligand 12 (CXCL12) but not CXCL13 or CC chemokine ligand 21. Concurrently, a number of B-cell survival and differentiation factors are elevated to produce a transiently supportive milieu. Disrupting homing dynamics with a CXC chemokine receptor 4 inhibitor reduced the formation of IgM-secreting cells. These data highlight the rapidity with which peripheral inflammation modifies the marrow compartment, and demonstrate that such modifications regulate acute IgM production within this organ. Furthermore, our study indicates that conversion to a state of emergency granulopoiesis is temporally delayed, allowing B cells opportunity to respond to antigen.
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http://dx.doi.org/10.1182/blood-2015-03-635805DOI Listing
September 2015

Mesenchymal stromal (stem) cell therapy fails to improve outcomes in experimental severe influenza.

PLoS One 2013 15;8(8):e71761. Epub 2013 Aug 15.

Faculty of Medicine, Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.

Rationale: Severe influenza remains a major public health threat and is responsible for thousands of deaths annually. Increasing antiviral resistance and limited effectiveness of current therapies highlight the need for new approaches to influenza treatment. Extensive pre-clinical data have shown that mesenchymal stromal (stem) cell (MSC) therapy can induce anti-inflammatory effects and enhance repair of the injured lung. We hypothesized that MSC therapy would improve survival, dampen lung inflammation and decrease acute lung injury (ALI) in a murine model of severe influenza.

Methods: C57Bl/6 mice were infected with influenza A/PuertoRico/8/34 (mouse-adapted H1N1) or influenza A/Mexico/4108/2009 (swine-origin pandemic H1N1) and administered human or mouse MSCs via the tail vein, either pre- or post- infection. MSC efficacy was evaluated as both an independent and adjunctive treatment strategy in combination with the antiviral agent, oseltamivir. Weight loss and survival were monitored. Inflammatory cells, cytokine/chemokines (IFN-γ, CXCL10, CCL2 and CCL5) and markers of ALI (total protein and IgM), were measured in bronchoalveolar lavage fluid and lung parenchyma.

Results: Administration of murine MSCs or human MSCs in a prophylactic or therapeutic regimen failed to improve survival, decrease pulmonary inflammation/inflammatory cell counts or prevent ALI in influenza virus-infected mice. MSCs administered in combination with oseltamivir also failed to improve outcomes.

Conclusions: Despite similarities in the clinical presentation and pathobiology of ALI and severe influenza, our findings suggest that MSC therapy may not be effective for prevention and/or treatment of acute severe influenza.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0071761PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3744455PMC
September 2014