Local Macrophage Research Articles

Infiltration Pattern of Blood Monocytes into the Central Nervous System during Experimental Herpes Simplex Virus Encephalitis.

The kinetics and distribution of infiltrating blood monocytes into the central nervous system and their involvement in the cerebral immune response together with resident macrophages, namely microglia, were evaluated in experimental herpes simplex virus 1 (HSV-1) encephalitis (HSE). To distinguish microglia from blood monocyte-derived macrophages, chimeras were generated by conditioning C57BL/6 recipient mice with chemotherapy regimen followed by transplantation of bone morrow-derived cells that expressed the green fluorescent protein. Mice were infected intranasally with a sub-lethal dose of HSV-1 (1.2x106 plaque forming units). Brains were harvested prior to and on days 4, 6, 8 and 10 post-infection for flow cytometry and immunohistochemistry analysis. The amounts of neutrophils (P<0.05) and «Ly6Chi» inflammatory monocytes (P<0.001) significantly increased in the CNS compared to non-infected controls on day 6 post-infection, which corresponded to more severe clinical signs of HSE. Levels decreased on day 8 for both leukocytes subpopulations (P<0.05 for inflammatory monocytes compared to non-infected controls) to reach baseline levels on day 10 following infection. The percentage of «Ly6Clow» patrolling monocytes significantly increased (P<0.01) at a later time point (day 8), which correlated with the resolution phase of HSE. Histological analysis demonstrated that blood leukocytes colonized mostly the olfactory bulb and the brainstem, which corresponded to regions where HSV-1 particles were detected. Furthermore, infiltrating cells from the monocytic lineage could differentiate into activated local tissue macrophages that express the microglia marker, ionized calcium-binding adaptor molecule 1. The lack of albumin detection in the brain parenchyma of infected mice showed that the infiltration of blood leukocytes was not necessarily related to a breakdown of the blood-brain barrier but could be the result of a functional recruitment. Thus, our findings suggest that blood monocyte-derived macrophages infiltrate the central nervous system and may contribute, with resident microglia, to the innate immune response seen during experimental HSE.

Abstract 14829: Semi-quantitative Assessment of OCT-macrophage Predicts Future Development of Thin-cap Fibroatheroma in Non-culprit Lipid Plaques: A Serial Optical Coherence Tomography Study

Introduction: Previous pathological studies have demonstrated that macrophages play an important role for the deterioration of fibrous cap and the onset of acute coronary syndrome. However, the significance of macrophage on the development of thin-cap fibroatheroma (TCFA) had not been fully evaluated in vivo. Aim: To explore the impact of OCT detected macrophage on the development of TCFA in patients with coronary artery disease using serial OCT images. Methods: A total of 152 non-culprit plaques from 90 patients who had serial OCT imaging at baseline and follow-up (median 6.38 [6.07-12.5] months) were included. TCFA was defined as the plaque with the fibrous cap thickness &lt;65μm.OCT detected macrophage was semi-quantitatively assessed in every 1mm along the entire target plaque using a previously introduced grading system; Grade 0: no macrophage, Grade 1: localized macrophage accumulation, Grade 2: clustered accumulation&lt;1 quadrant, Grade 3: clustered accumulation≥1 quadrant but &lt;3 quadrants, Grade 4: clustered accumulation≥3 quadrants. The summation of 0 to 4 grades was evaluated. Results: Among 45 TCFA at baseline, 19 remain as TCFA [persistent TCFA] and 26 changed to non-TCFA [resolved TCFA] at follow-up (Figure). The macrophage grade in persistent TCFA was significantly greater than that in resolved TCFA (13.0 [8.00-17.0] vs. 4.00 [2.00-8.25] (P&lt;0.001)) at baseline. On the other hand, 11 among 107 non-TCFA at baseline changed to TCFA [acquired TCFA] at follow-up. The macrophage grade in acquired TCFA was significantly greater than that in non-TCFA (14.0 [11.0-19.0] vs. 2.0 [0.00-6.75] (P&lt;0.001)) at baseline. The macrophage grade&gt;7.5 at baseline had good performance in discriminating TCFA from non-TCFA at follow-up (area under the curve [AUC] = 0.884, P&lt;0.001) (Figure). Conclusions: The semi-quantitative evaluation of OCT detected macrophage at baseline had the potential to predict the future development of TCFA in patients with coronary artery disease.

Imaging Macrophage and Hematopoietic Progenitor Proliferation in Atherosclerosis.

Local plaque macrophage proliferation and monocyte production in hematopoietic organs promote progression of atherosclerosis. Therefore, noninvasive imaging of proliferation could serve as a biomarker and monitor therapeutic intervention. To explore (18)F-FLT positron emission tomography-computed tomography imaging of cell proliferation in atherosclerosis. (18)F-FLT positron emission tomography-computed tomography was performed in mice, rabbits, and humans with atherosclerosis. In apolipoprotein E knock out mice, increased (18)F-FLT signal was observed in atherosclerotic lesions, spleen, and bone marrow (standardized uptake values wild-type versus apolipoprotein E knock out mice, 0.05 ± 0.01 versus 0.17 ± 0.01, P<0.05 in aorta; 0.13 ± 0.01 versus 0.28 ± 0.02, P<0.05 in bone marrow; 0.06 ± 0.01 versus 0.22 ± 0.01, P<0.05 in spleen), corroborated by ex vivo scintillation counting and autoradiography. Flow cytometry confirmed significantly higher proliferation of macrophages in aortic lesions and hematopoietic stem and progenitor cells in the spleen and bone marrow in these mice. In addition, (18)F-FLT plaque signal correlated with the duration of high cholesterol diet (r(2)=0.33, P<0.05). Aortic (18)F-FLT uptake was reduced when cell proliferation was suppressed with fluorouracil in apolipoprotein E knock out mice (P<0.05). In rabbits, inflamed atherosclerotic vasculature with the highest (18)F-fluorodeoxyglucose uptake enriched (18)F-FLT. In patients with atherosclerosis, (18)F-FLT signal significantly increased in the inflamed carotid artery and in the aorta. (18)F-FLT positron emission tomography imaging may serve as an imaging biomarker for cell proliferation in plaque and hematopoietic activity in individuals with atherosclerosis.

A Metabolomics-Based Understanding of Pro-Tumorigenic Hypoxia Inducible Factor-1α Activity in Pancreatic Cancer and Local Macrophages

A Metabolomics-Based Understanding of Pro-Tumorigenic Hypoxia Inducible Factor-1α Activity in Pancreatic Cancer and Local Macrophages

TLR3 agonist and Sorafenib combinatorial therapy promotes immune activation and controls hepatocellular carcinoma progression.

Hepatocellular carcinoma (HCC) is associated with high mortality and the current therapy for advanced HCC, Sorafenib, offers limited survival benefits. Here we assessed whether combining the TLR3 agonist: lysine-stabilized polyinosinic-polycytidylic-acid (poly-ICLC) with Sorafenib could enhance tumor control in HCC. Combinatorial therapy with poly-ICLC and Sorafenib increased apoptosis and reduced proliferation of HCC cell lines in vitro, in association with impaired phosphorylation of AKT, MEK and ERK. In vivo, the combinatorial treatment enhanced control of tumor growth in two mouse models: one transplanted with Hepa 1-6 cells, and the other with liver tumors induced using the Sleeping beauty transposon. Tumor cell apoptosis and host immune responses in the tumor microenvironment were enhanced. Particularly, the activation of local NK cells, T cells, macrophages and dendritic cells was enhanced. Decreased expression of the inhibitory signaling molecules PD-1 and PD-L1 was observed in tumor-infiltrating CD8+ T cells and tumor cells, respectively. Tumor infiltration by monocytic-myeloid derived suppressor cells (Mo-MDSC) was also reduced indicating the reversion of the immunosuppressive tumor microenvironment. Our data demonstrated that the combinatorial therapy with poly-ICLC and Sorafenib enhances tumor control and local immune response hence providing a rationale for future clinical studies.

Langerhans Cells Maintain Local Tissue Tolerance in a Model of Systemic Autoimmune Disease.

Systemic autoimmune diseases such as lupus affect multiple organs, usually in a diverse fashion where only certain organs are affected in individual patients. It is unclear whether the "local" immune cells play a role in regulating tissue specificity in relation to disease heterogeneity in systemic autoimmune diseases. In this study, we used skin as a model to determine the role of tissue-resident dendritic cells (DCs) in local and systemic involvement within a systemic lupus disease model. Skin-resident DCs, namely, Langerhans cells (LCs), have been implicated in regulating tolerance or autoimmunity using elegant transgenic models, however, their role in local versus systemic immune regulation is unknown. We demonstrate that although lymphocytes from skin-draining lymph nodes of autoimmune-prone MRL/MpJ-Fas(lpr/lp) (r) (MRL-lpr) mice react spontaneously to a physiological skin self-Ag desmoglein-3, epicutaneous applications of desmoglein-3 induced tolerance that is dependent on LCs. Inducible ablation of LCs in adult preclinical MRL-lpr and MRL/MpJ-Fas(+/+) mice resulted in increased autoantibodies against skin Ags and markedly accelerated lupus dermatitis with increased local macrophage infiltration, but had no effect on systemic autoantibodies such as anti-dsDNA Abs or disease in other organs such as kidneys, lung, and liver. Furthermore, skin-draining lymph nodes of LC-ablated MRL-lpr mice had significantly fewer CD4(+) T cells producing anti-inflammatory cytokine IL-10 than LC-intact controls. These results indicate that a skin-resident DC population regulates local tolerance in systemic lupus and emphasize the importance of the local immune milieu in preventing tissue-specific autoimmunity, yet have no effect on systemic autoimmunity.

Abstract 147: Characterization of the Immune Response to Aortic Aneurysm in a Murine Model

Our understanding of vascular pathology relies on inducible animal models of disease that remain poorly described, and concern exists regarding indirect effects of the inducing agents. We sought to perform a detailed characterization of the immune response to a commonly used murine aneurysm model. Aneurysms were generated in 10 adult C57/Bl6 mice using 2 weeks of oral beta-amino propriono-nitrile (BAPN) administration and 4 weeks of angiotensin-2 (AT2) delivered via osmotic pump. FACS analysis was used to characterize progenitor and hematopoietic cell lines in bone marrow, blood and aorta. 3 mice died of aortic rupture between days 8 and 9. The remaining 7 were compared to age-matched controls. BAPN/AT2 treatment caused aortic dilatation at all aortic regions from the root to the descending thoracic aorta (P&lt;0.01). The suprarenal aorta was aneurysmal in all BAPN/AT2 mice with a maximum diameter of 1.86±0.1mm compared to controls 0.98±0.03mm (P&lt;0.001). In the blood, total cells counts at day 2, 16 and 28 were increased (P&lt;0.001). CD45-2 and B-cell counts were significantly increased in the BAPN/AT2 mice compared to controls (P&lt;0.001). The aorta of BAPN/AT2 mice had significantly increased macrophage counts (P&lt;0.001) with no difference in monocytes, neutrophils, T or B cell counts. Aortic tissue macrophages were predominantly G0 G1 (97±1%) phase. The bone marrow CD45-2 compartment was similar in aneurysmal BAPN/AT2 and control mice but Ly6C lo-inter monocytes were increased in BAPN/AT2 mice. Marrow CD117+/lin- hematopoietic progenitor and stem cells (P=0.4), and differential counts of CD117+/Sca1+ hematopoietic stem cells and CD117+/Sca1- progenitor cells were similar in control and BAPN/AT2 treated mice. BAPN/AT2 induces aortic disease with aneurysmal degeneration of the suprarenal aorta. We observed a significant decrease in aortic macrophage proliferation suggestive of a mechanism of expansion independent of local macrophage proliferation. We did not observe a significant change in the bone marrow stem or progenitor cell compartment suggesting aortic injury is driving inflammation rather than direct stimulus of the marrow compartment by BAPN/AT2.

Abstract O.26: Angiotensin Receptor Blocker, Losartan suppresses coronary arteritis in a Murine Model of Kawasaki Disease. -Effectiveness of IVIG versus Losartan-

Background: Although intravenous immunoglobulin (IVIG) is an established treatment for Kawasaki disease (KD), 5 % of KD patients treated with IVIG still have coronary involvement. Angiotensin receptor blockers (ARBs), beside their antihypertensive effects, also suppress cell infiltration in atherosclerosis. However, the efficacy of ARB for KD has not been established. Objective: We aimed to elucidate if ARB ameliorates coronary arteritis (CA) in a murine model of KD, introduced by Lactobacillus casei wall extract (LCWE). We also aimed to verify whether ARB’s effects are different from those of IVIG. Method: 4-week-old male mice were intraperitoneally injected with LCWE (L, n=15) or PBS (P, n=15). 5 days later, those mice were given IVIG (1g/kg, L+IVIG, n=8), or ARB (losartan 100mg/L in drinking water for 2 wks, L+ARB, n=18). 2 weeks after LCWE injection, histological assessment of the heart and measurement of plasma cytokine levels were performed. IL-6 and mannose receptor (MR) mRNA expressions in the aortic root were studied (n=5 each group) in an additional experiment. Results: CA score was significantly increased by LCWE (L: 8.3±0.5 vs. P: 2.9±0.5, p&lt;0.0001). ARB significantly ameliorated CA (L+ARB: 5.1±0.7 vs. L, p=0.008). The effect of IVIG on CA was milder and not significant (L+IVIG: 6.0±0.9 vs. L). Of note, macrophage infiltration was dramatically decreased by ARB but not by IVIG. IVIG treatment ameliorated serum levels of IL-1β, IL-10 and TNF-α in a milder fashion than ARB. Interestingly, serum IL-6 level was suppressed by ARB, but not by IVIG. Locally up-regulated mRNAs of IL-6 and MR were significantly ameliorated by ARB, with milder effects by IVIG. Conclusions: ARB, rather than IVIG, exerts powerful anti-CA effects with suppressing local macrophage infiltration and systemic/local inflammatory cytokines. Thus, ARB potentially exerts additive anti-CA effects in KD under IVIG treatment.

Monocyte and M1 Macrophage-induced Barrier Defect Contributes to Chronic Intestinal Inflammation in IBD.

Macrophages are key players in inflammatory bowel diseases (IBD). This study aimed to determine site-specific effects of defined macrophage subtypes on the integrity of the intestinal epithelial barrier. Macrophage subtypes in situ in intestinal specimens of patients with IBD were visualized by immunohistochemistry. In vitro polarization of human peripheral CD14 cells yielded M1 or M2 macrophages. The influence of primary monocytes or macrophage subtypes on epithelial barrier integrity was analyzed by transepithelial resistance measurements, Western blot analysis, confocal laser scanning microscopy, and cytometric bead array in a coculture model of primary human macrophages and layers of intestinal epithelial cell lines. The lamina propria of the inflamed intestine in patients with IBD, predominantly in Crohn's disease, is massively infiltrated by CD68 cells also positive for inducible nitric oxide synthase and tumor necrosis factor (TNF) α. The presence of M1 macrophage shifted the balance in the local macrophage compartment towards a proinflammatory state. In the coculture model, monocytes and M1 macrophages reduced transepithelial resistance as a marker for epithelial barrier integrity. The mechanisms for paracellular leakage included intracellular relocalization of tight junction proteins like claudin-2 and epithelial cell apoptosis. Determined by specific cytokine blockade, M1 macrophages exerted their deleterious effect mainly through TNF-α, whereas monocyte-mediated damage was driven by the inflammasome effector cytokines, interleukin-1β and interleukin-18. Lamina propria monocytes and M1 macrophages invading intestinal tissues directly contribute to disrupting the epithelial barrier through deregulation of tight junction proteins and induction of epithelial cell apoptosis, thus driving intestinal inflammation in IBD.

Activated Kupffer cells inhibit insulin sensitivity in obese mice.

Obesity promotes insulin resistance associated with liver inflammation, elevated glucose production, and type 2 diabetes. Although insulin resistance is attenuated in genetic mouse models that suppress systemic inflammation, it is not clear whether local resident macrophages in liver, denoted Kupffer cells (KCs), directly contribute to this syndrome. We addressed this question by selectively silencing the expression of the master regulator of inflammation, NF-κB, in KCs in obese mice. We used glucan-encapsulated small interfering RNA particles (GeRPs) that selectively silence gene expression in macrophages in vivo. Following intravenous injections, GeRPs containing siRNA against p65 of the NF-κB complex caused loss of NF-κB p65 expression in KCs without disrupting NF-κB in hepatocytes or macrophages in other tissues. Silencing of NF-κB expression in KCs in obese mice decreased cytokine secretion and improved insulin sensitivity and glucose tolerance without affecting hepatic lipid accumulation. Importantly, GeRPs had no detectable toxic effect. Thus, KCs are key contributors to hepatic insulin resistance in obesity and a potential therapeutic target for metabolic disease.

Macrophage dynamics are regulated by local macrophage proliferation and monocyte recruitment in injured pancreas.

Pancreas injury by partial duct ligation (PDL) activates a healing response, encompassing β-cell neogenesis and proliferation. Macrophages (MΦs) were recently shown to promote β-cell proliferation after PDL, but they remain poorly characterized. We assessed myeloid cell diversity and the factors driving myeloid cell dynamics following acute pancreas injury by PDL. In naive and sham-operated pancreas, the myeloid cell compartment consisted mainly of two distinct tissue-resident MΦ types, designated MHC-II(lo) and MHC-II(hi) MΦs, the latter being predominant. MHC-II(lo) and MHC-II(hi) pancreas MΦs differed at the molecular level, with MHC-II(lo) MΦs being more M2-activated. After PDL, there was an early surge of Ly6C(hi) monocyte infiltration in the pancreas, followed by a transient MHC-II(lo) MΦ peak and ultimately a restoration of the MHC-II(hi) MΦ-dominated steady-state equilibrium. These intricate MΦ dynamics in PDL pancreas depended on monocyte recruitment by C-C chemokine receptor 2 and macrophage-colony stimulating factor receptor as well as on macrophage-colony stimulating factor receptor-dependent local MΦ proliferation. Functionally, MHC-II(lo) MΦs were more angiogenic. We further demonstrated that, at least in C-C chemokine receptor 2-KO mice, tissue MΦs, rather than Ly6C(hi) monocyte-derived MΦs, contributed to β-cell proliferation. Together, our study fully characterizes the MΦ subsets in the pancreas and clarifies the complex dynamics of MΦs after PDL injury.

Understanding Local Macrophage Phenotypes In Disease: Shape-shifting macrophages

Macrophages are responsive to local tissue signals and alter their phenotypes accordingly. In disease tissues this means that macrophage phenotypes may change with disease progression, exacerbating or facilitating the resolution of the pathology.

Understanding local macrophage phenotypes in disease: modulating macrophage function to treat cancer.

Recent studies have suggested that manipulating the tumor-associated macrophage phenotype is a valid therapeutic approach in cancer. In turn, these studies have given some insight into the factors that polarize macrophages, thereby suggesting alternative therapeutic avenues.

Erythrocyte: Bacteria Killer and Bacteria Pray

Erythrocyte is human blood main bactericidal cell. During movement in blood stream erythrocytes are triboelectrically charged by rubbing to each other and vessel walls and this charge automatically attracts and keeps bacteria on erythrocyte surface. Bacteria fixation on erythrocyte membrane activates the receptors of the membrane and stimulates trans membrane releasing of oxygen from oxyhemoglobin that causes bacteria oxidation and killing. If bacteria survive oxidation and enter erythrocyte they are exposed to higher concentration of oxygen (oxygen reactive species). Very few bacteria survive inside erythrocytes, but some can survive because of lack of oxygen inside erythrocyte and/or bacteria resistance to oxygen reactive species. Killed inside erythrocyte bacteria are released back to plasma and are digested in liver and spleen by local macrophages. Erythrocytes that are injured by bacteria and/or contain killed or living bacteria are destroyed in spleen. Erythrocytes out of bloodstream (in case of hemorrhage, extravasation in lobar pneumonia, etc.) after bacteria engulfment can’t kill bacteria because of lack of oxyhemoglobin and become bacteria container providing both nutrients (protein, iron, carbohydrates, etc.) for bacteria growth and some defense against phagocytes and antibodies. In bloodstream erythrocyte is bacteria killer, out of bloodstream it is bacteria pray.

The Tissue Macrophage Lineage

Despite accumulating evidence suggesting local self-maintenance of tissue macrophages in the steady state, the dogma remains that tissue macrophages derive from monocytes. In this presentation, I will discuss parabiosis, fate mapping, and adoptive transfer approaches that we developed in the laboratory to assess the contribution of monocytes to tissue resident macrophages in the steady state and after cell turnover. Using these approaches we found that monocytes contribute minimally to tissue resident macrophages in the steady state. Similarly, we found that after depletion of lung macrophages, the majority of repopulation occurs by local proliferation in a Csf-1 and Csf-2 dependent manner. This repopulation from a non-circulating population was stochastic and observed in both infection- and inflammatory-induced cytotoxicity of local macrophages. We also found that after bone marrow transplantation, host tissue macrophages retain the capacity to expand when the development of donor tissue macrophages is compromised. These results are consistent with recent results obtained in humans showing that macrophages can form in the absence of circulating monocytes. Collectively, these results indicate that tissue resident macrophages and circulating monocytes should be classified as independent mononuclear phagocyte lineages. Disclosures No relevant conflicts of interest to declare.

Adoptive transfer of M2 macrophages promotes locomotor recovery in adult rats after spinal cord injury.

Classically activated pro-inflammatory (M1) and alternatively activated anti-inflammatory (M2) macrophages populate the local microenvironment after spinal cord injury (SCI). The former type is neurotoxic while the latter has positive effects on neuroregeneration and is less toxic. In addition, while the M1 macrophage response is rapidly induced and sustained, M2 induction is transient. A promising strategy for the repair of SCI is to increase the fraction of M2 cells and prolong their residence time. This study investigated the effect of M2 macrophages induced from bone marrow-derived macrophages on the local microenvironment and their possible role in neuroprotection after SCI. M2 macrophages produced anti-inflammatory cytokines such as interleukin (IL)-10 and transforming growth factor β and infiltrated into the injured spinal cord, stimulated M2 and helper T (Th)2 cells, and produced high levels of IL-10 and -13 at the site of injury. M2 cell transfer decreased spinal cord lesion volume and resulted in increased myelination of axons and preservation of neurons. This was accompanied by significant locomotor improvement as revealed by Basso, Beattie and Bresnahan locomotor rating scale, grid walk and footprint analyses. These results indicate that M2 adoptive transfer has beneficial effects for the injured spinal cord, in which the increased number of M2 macrophages causes a shift in the immunological response from Th1- to Th2-dominated through the production of anti-inflammatory cytokines, which in turn induces the polarization of local microglia and/or macrophages to the M2 subtype, and creates a local microenvironment that is conducive to the rescue of residual myelin and neurons and preservation of neuronal function.

Zoledronate but not denosumab suppresses macrophagic differentiation of THP-1 cells. An aetiologic model of bisphosphonate-related osteonecrosis of the jaw (BRONJ).

Bisphosphonates and denosumab are antiresorptive drugs used for the treatment of osteoporosis and oncological tumors. A severe side effect is osteonecrosis of the jaw. Monocyte/macrophage dysfunction is considered to play a distinct role in osteonecrosis. THP-1 monocytic cells were used in this study to elucidate the influence of zoledronate and denosumab on phorbol-12-myrisate-13-acetate (PMA)-induced macrophage differentiation and function in real-time. Macrophagic differentiation of the THP-1 suspension cells was measured by cell adherence in the presence or absence of different concentrations of zoledronate (0.5, 5, 50μM) and denosumab (1, 10, 20, 40μg/mL) using the real-time xCELLigence system. Additionally, a live/dead staining was performed by fluorescence microscopy. THP-1 cells demonstrated a regular initial PMA-induced differentiation to macrophages by live measurements of cell adherence and by an increase in CD68 surface expression as detected by flow cytometry. The addition of zoledronate led to cell detachment of the THP-1-derived macrophages in a dose-dependent manner in contrast to denosumab. Cell detachment was based on cell death as confirmed by live/dead staining, revealing elevated numbers of dead cells following addition of high zoledronate concentrations. However, denosumab did not deteriorate THP-1 cell viability. Our results demonstrate that zoledronate but not denosumab suppresses monocytic THP-1 cell viability after macrophagic differentiation dose-dependently. This is the first real-time study providing evidence for a dose-dependent immunosuppressive effect of zoledronate in contrast to denosumab on local macrophages.

A new inflammatory role for p53 in human macrophages

A new inflammatory role for p53 in human macrophages

P. gingivalis lipopolysaccharide intensifies inflammation post-myocardial infarction through matrix metalloproteinase-9

Periodontal disease (PD) strongly correlates with increased mortality post-myocardial infarction (MI); however, the underlying mechanisms are unknown. Matrix metalloproteinase (MMP)-9 levels directly correlate with dysfunction and remodeling of the left ventricle (LV) post-MI. Post-MI, MMP-9 is produced by leukocytes and modulates inflammation. We have shown that exposure to Porphyromonas gingivalis lipopolysaccharide (PgLPS), an immunomodulatory molecule identified in PD patients, increases LV MMP-9 levels in mice and leads to cardiac inflammation and dysfunction. The aim of the study was to determine if circulating PgLPS exacerbates the LV inflammatory response post-MI through MMP-9 dependent mechanisms. We exposed wild type C57BL/6J and MMP-9−/− mice to PgLPS (ATCC 33277) for a period of 28days before performing MI, and continued to deliver PgLPS for up to 7days post-MI. We found systemic levels of PgLPS 1) increased MMP-9 levels in both plasma and infarcted LV resulting in reduced wall thickness and increased incidence of LV rupture post-MI and 2) increased systemic and local macrophage chemotaxis leading to accelerated M1 macrophage infiltration post-MI and decreased LV function. MMP-9 deletion played a protective role by attenuating the inflammation induced by systemic delivery of PgLPS. In conclusion, MMP-9 deletion has a cardioprotective role against PgLPS exposure, by attenuating macrophage mediated inflammation.

T cell memory. A local macrophage chemokine network sustains protective tissue-resident memory CD4 T cells.

CD8 tissue-resident memory T (T(RM)) cells provide efficient local control of viral infection, but the role of CD4 T(RM) is less clear. Here, by using parabiotic mice, we show that a preexisting pool of CD4 T(RM) cells in the genital mucosa was required for full protection from a lethal herpes simplex virus 2 (HSV-2) infection. Chemokines secreted by a local network of macrophages maintained vaginal CD4 T(RM) in memory lymphocyte clusters (MLCs), independently of circulating memory T cells. CD4 T(RM) cells within the MLCs were enriched in clones that expanded in response to HSV-2. Our results highlight the need for vaccine strategies that enable establishment of T(RM) cells for protection from a sexually transmitted virus and provide insights as to how such a pool might be established.