Monocyte Chemoattractant Protein-1 Knockout Mice Research Articles

Mouse model to study pulmonary intravascular macrophage recruitment and lung inflammation in acute necrotizing pancreatitis.

Patients suffering from severe acute pancreatitis (AP) can develop acute lung injury (ALI) with poor outcomes and the mechanisms involved remain incompletely understood. Pulmonary intravascular macrophages (PIMs), which are credited as promoters of ALI, are not constitutively present in humans and rodents; however, there is evidence of PIM recruitment in rodents during some pathological conditions, such as hepatic diseases. Therefore, this study assesses PIM recruitment in the lungs of a mouse model of acute necrotizing pancreatitis (ANP) induced with L-arginine monohydrochloride. Mice were euthanized after 24h, 72h and 120h. Control mice received sham injections of saline. Pancreatic histopathological grading and plasma amylase were used to confirm the development of ANP in L-arginine-treated mice. Histopathological grading of lungs from the ANP mice at 72h showed increased mononuclear phagocytes in alveolar septa, compared to that from the controls. Lungs from the ANP mice also showed increased numbers of CD68-immunopositive alveolar septal macrophages, suggestive of PIM recruitment, compared to those from the controls. Lungs from the ANP mice showed increased expression of IL-6, IL-10, monocyte chemoattractant protein 1 (MCP-1) and von Willebrand factor compared to those from the controls. The recruitment of CD68-positive septal macrophages was not observed in MCP-1 knockout mice with ANP at 72h when compared to C57BL/6 wild-type mice. Taken together, we developed a mouse model of PIM recruitment dependent on MCP-1 that allows us to explore their roles in ANP-associated ALI.

Abstract 582: Vascular Smooth Muscle-derived Macrophage are a Major Source of MCP1 in Atherosclerosis

Smooth muscle cells (SMC) are conventionally thought to promote atherosclerotic plaque stability by investing within the fibrous cap and protecting the blood flow from the harmful inflammatory plaque core. However, lineage tracing studies have shown that SMC in plaque can undergo a Klf4-dependent transition in vivo to a macrophage-like state, characterized by loss of SMC markers and expression of multiple macrophage markers, lipid accumulation, and phagocytic activity. Of major interest, SMC induced to the macrophage state in vitro by cholesterol loading also show increased production of the atheropromoting cytokine MCP1 (Monocyte chemoattractant protein 1). These results are surprising since it has been largely assumed that monocyte derived macrophages are the major source of MCP1 and that this acts to exacerbate lesion pathogenesis by inducing recruitment of additional circulating monocytes. Using MCP1-mCherry reporter mice on an ApoE -/- background, we show that MCP1 is highly expressed by medial and fibrous cap SMC. Further, we show that SMC-specific KLF4 knockout mice, which show marked reductions in the frequency of SMC-derived macrophages, show a 50% decrease in MCP1 immunostaining in late stage atherosclerotic lesions, suggesting that these cells are a major source of MCP-1 and produce it via a Klf4-dependent mechanism. Consistent with this possibility, we demonstrated that SMC-specific tamoxifen conditional MCP1 knockout mice on an ApoE -/- background (Myh11-CreERT2 eYFP ApoE -/- MCP1-mCherry), showed greatly decreased total MCP1 protein level within the aorta. We are currently completing examination of the effects of SMC specific MCP1 KO on late stage lesion pathogenesis in our Myh11-CreERT2 eYFP ApoE -/- MCP1-mCherry mice following 18 weeks of Western diet feeding. Taken together results provide evidence that SMC derived cells are an unexpected major source of MCP1 within lesions.

Pioglitazone Inhibits Periprostatic White Adipose Tissue Inflammation in Obese Mice.

Obesity is associated with an increased incidence of high-grade prostate cancer and poor prognosis for prostate cancer patients. Recently, we showed that obesity-related periprostatic white adipose tissue (WAT) inflammation, characterized by crown-like structures (CLS) consisting of dead or dying adipocytes surrounded by macrophages, was associated with high-grade prostate cancer. It is possible, therefore, that agents that suppress periprostatic WAT inflammation will alter the development or progression of prostate cancer. Pioglitazone, a ligand of PPARγ, is used to treat diabetes and possesses anti-inflammatory properties. Here, our main objectives were to determine whether pioglitazone inhibited obesity-related periprostatic WAT inflammation in mice and then to elucidate the underlying mechanism. Treatment with pioglitazone reduced the density of CLS in periprostatic fat and suppressed levels of TNFα, TGFβ, and the chemokine monocyte chemoattractant protein-1 (MCP-1). Importantly, the ability of pioglitazone to suppress periprostatic WAT inflammation was abrogated in MCP-1 knockout mice. Pioglitazone caused dose-dependent induction of both adiponectin, an anti-inflammatory adipokine, and its receptor AdipoR2 in cultured 3T3-L1 cells and in periprostatic WAT of obese mice. Pioglitazone blocked TNFα-mediated induction of MCP-1 in 3T3-L1 cells, an effect that was attenuated when either adiponectin or AdipoR2 were silenced. Taken together, pioglitazone-mediated induction of adiponectin suppressed the elevation in MCP-1 levels, thereby attenuating obesity-related periprostatic WAT inflammation. These findings strengthen the rationale for future efforts to determine whether targeting the PPARγ-adiponectin-MCP-1 axis will decrease periprostatic adipose inflammation and thereby reduce the risk of high-grade prostate cancer or improve outcomes for men with prostate cancer. Cancer Prev Res; 11(4); 215-26. ©2017 AACR.

Monocyte chemoattractant protein-1 is not required for liver regeneration after partial hepatectomy.

BackgroundLiver regeneration following 70 % partial hepatectomy (PH) requires the coordinated expression of soluble mediators produced by macrophages. Monocyte chemoattractant protein-1 (MCP-1) is a potent stimulus of monocyte recruitment and macrophage activation. The goal of this study was to determine how MCP-1 contributes to liver regeneration.MethodsPH was performed on anesthetized C57Bl/6 (wild type) and MCP-1 knockout mice, and macrophage-produced cytokines and hepatocyte proliferation were measured.ResultsIn wild type mice, hepatic MCP-1 protein levels increased 4–6 h after PH, and elevated plasma MCP-1 levels were detected 12 h after PH. Hepatocyte proliferation was comparable in MCP-1 knockout and wild type mice, as was the expression of macrophage-derived cytokines, TNFα and IL-6, and levels of phosphorylated STAT3. The number of CCR2+ cells in the liver was similar in MCP-1 knockout and wild type mice, which suggests that other chemokines may recruit CCR2+ cells in the absence of MCP-1. Studies with CCR2 knockout mice revealed that hepatocyte proliferation was suppressed ~40 % compared to wild type mice 36 h after PH, but proliferation and liver-body-weight ratios were similar at 48 h.ConclusionThese findings suggest that MCP-1 is not required for PH-induced liver regeneration, yet the role of CCR2 warrants further study.

Ovarian kisspeptin expression is related to age and to monocyte chemoattractant protein-1.

The objective of this study was to test the hypothesis that ovarian kisspeptin (kiss1) and its receptor (kiss1r) expression are affected by age, obesity, and the age- and obesity-related chemokine monocyte chemoattractant protein-1 (MCP-1). Ovaries from reproductive-aged and older C57BL/6J mice fed normal chow (NC) or high-fat (HF) diet, ovaries from age-matched young MCP-1 knockout and young control mice on NC, and finally, cumulus and mural granulosa cells (GCs) from women who underwent in vitro fertilization (IVF) were collected. Kiss1, kiss1r, anti-Mullerian hormone (AMH), and AMH receptor (AMHR-II) messenger RNA (mRNA) expression levels were quantified using real-time polymerase chain reaction (RT-PCR). In mouse ovaries, kiss1 and kiss1r mRNA levels were significantly higher in old compared to reproductive-aged mice, and diet-induced obesity did not alter kiss1 or kiss1r mRNA levels. Compared to young control mice, young MCP-1 knockout mice had significantly lower ovarian kiss1 mRNA but significantly higher AMH and AMHR-II mRNA levels. In human cumulus GCs, kiss1r mRNA levels were positively correlated with age but not with BMI. There was no expression of kiss1 mRNA in either cumulus or mural GCs. These data suggest a possible age-related physiologic role for the kisspeptinergic system in ovarian physiology. Additionally, the inflammatory MCP-1 may be associated with kiss1 and AMH genes, which are important in ovulation and folliculogenesis, respectively.

Monocyte Chemoattractant Protein-1 (MCP-1) Regulates Macrophage Cytotoxicity in Abdominal Aortic Aneurysm

AimsIn abdominal aortic aneurysm (AAA), macrophages are detected in the proximity of aortic smooth muscle cells (SMCs). We have previously demonstrated in a murine model of AAA that apoptotic SMCs attract monocytes and other leukocytes by producing MCP-1. Here we tested whether infiltrating macrophages also directly contribute to SMC apoptosis.Methods and ResultsUsing a SMC/RAW264.7 macrophage co-culture system, we demonstrated that MCP-1-primed RAWs caused a significantly higher level of apoptosis in SMCs as compared to control macrophages. Next, we detected an enhanced Fas ligand (FasL) mRNA level and membrane FasL protein expression in MCP-1-primed RAWs. Neutralizing FasL blocked SMC apoptosis in the co-culture. In situ proximity ligation assay showed that SMCs exposed to primed macrophages contained higher levels of receptor interacting protein-1 (RIP1)/Caspase 8 containing cell death complexes. Silencing RIP1 conferred apoptosis resistance to SMCs. In the mouse elastase injury model of aneurysm, aneurysm induction increased the level of RIP1/Caspase 8 containing complexes in medial SMCs. Moreover, TUNEL-positive SMCs in aneurysmal tissues were frequently surrounded by CD68+/FasL+ macrophages. Conversely, elastase-treated arteries from MCP-1 knockout mice display a reduction of both macrophage infiltration and FasL expression, which was accompanied by diminished apoptosis of SMCs.ConclusionOur data suggest that MCP-1-primed macrophages are more cytotoxic. MCP-1 appears to modulate macrophage cytotoxicity by increasing the level of membrane bound FasL. Thus, we showed that MCP-1-primed macrophages kill SMCs through a FasL/Fas-Caspase8-RIP1 mediated mechanism.

Monocyte chemoattractant protein-1 is a mediator of the anabolic action of parathyroid hormone on bone

Parathyroid hormone (PTH) has a significant role as an anabolic hormone in bone when administered by intermittent injection. Previous microarray studies in our laboratory have shown that the most highly regulated gene, monocyte chemoattractant protein-1 (MCP-1), is rapidly and transiently induced when hPTH(1-34) is injected intermittently in rats. Through further in vivo studies, we found that rats treated with hPTH(1-34) showed a significant increase in serum MCP-1 levels 2 hours after PTH injection compared with basal levels. Using immunohistochemistry, increased MCP-1 expression in osteoblasts and osteocytes is evident after PTH treatment. PTH also increased the number of marrow macrophages. MCP-1 knockout mice injected daily with hPTH(1-34) showed less trabecular bone mineral density and bone volume compared with wild-type mice as measured by peripheral quantitative computed tomography (pQCT) and micro-computed tomography (µCT). Histomorphometric analysis revealed that the increase in osteoclast surface and osteoclast number observed with intermittent PTH treatment in the wild-type mice was completely eliminated in the MCP-1 null mice, as well as much lower numbers of macrophages. Consequently, the lack of osteoclast and macrophage activity in the MCP-1 null mice was paralleled by a reduction in bone formation. We conclude that osteoblast and osteocyte MCP-1 expression is an important mediator for the anabolic effects of PTH on bone.

Neuronal MCP‐1 Mediates Microglia Recruitment and Neurodegeneration Induced by Thiamine Deficiency

Chemokines are implicated in the neuroinflammation of several chronic neurodegenerative disorders. However, the precise role of chemokines in neurodegeneration is unknown. Thiamine deficiency (TD) causes abnormal oxidative metabolism in the brain as well as a well‐defined microglia activation and neurodegeneration in the submedial thalamus nucleus (SmTN). We evaluated the role of chemokines in neurodegeneration and the underlying mechanism in a TD model. TD selectively induced neuronal expression of monocyte chemoattractant protein‐1 (MCP‐1) in the SmTN prior to microglia activation and neurodegeneration. we showed that MCP‐1‐induced neurotoxicity required the presence of microglia. A MCP‐1 neutralizing antibody inhibited MCP‐1‐induced microglia activation and neuronal death in culture and in the thalamus. MCP‐1 knock‐out mice were resistant to TD‐induced neuronal death in SmTN. TD selectively induced the accumulation of reactive oxygen species in neurons, and antioxidants blocked TD‐induced MCP‐1 expression. Together, our results indicated an induction of neuronal MCP‐1 during TD caused microglia recruitment/activation, which exacerbated neurodegeneration.

Neuronal MCP‐1 Mediates Microglia Recruitment and Neurodegeneration Induced by the Mild Impairment of Oxidative Metabolism

Chemokines are implicated in the neuroinflammation of several chronic neurodegenerative disorders. However, the precise role of chemokines in neurodegeneration is unknown. Thiamine deficiency (TD) causes abnormal oxidative metabolism in the brain as well as a well-defined microglia activation and neurodegeneration in the submedial thalamus nucleus (SmTN), which are common features of neurodegenerative diseases. We evaluated the role of chemokines in neurodegeneration and the underlying mechanism in a TD model. Among the chemokines examined, TD selectively induced neuronal expression of monocyte chemoattractant protein-1 (MCP-1) in the SmTN prior to microglia activation and neurodegeneration. The conditioned medium collected from TD-induced neurons caused microglia activation. With a neuron/microglia co-culture system, we showed that MCP-1-induced neurotoxicity required the presence of microglia, and exogenous MCP-1 was able to activate microglia and stimulated microglia to produce cytokines. A MCP-1 neutralizing antibody inhibited MCP-1-induced microglia activation and neuronal death in culture and in the thalamus. MCP-1 knockout mice were resistant to TD-induced neuronal death in SmTN. TD selectively induced the accumulation of reactive oxygen species in neurons, and antioxidants blocked TD-induced MCP-1 expression. Together, our results indicated an induction of neuronal MCP-1 during mild impairment of oxidative metabolism caused by microglia recruitment/activation, which exacerbated neurodegeneration.

Rational design of CCR2 antagonists: a survey of computational studies

Importance of the field: CC-chemokine receptor 2 (CCR2) belongs to the GPCR superfamily and is the primary receptor for monocyte chemoattractant protein-1 (MCP-1), also known as chemokine ligand CCL2. Studies indicate the possible involvement of MCP-1 and CCR2 in various disease conditions, such as rheumatic arthritis, multiple sclerosis, vascular diseases, obesity and diabetes, via the inflammatory pathway. MCP-1 and CCR2 knockout mice under a broad range of stimuli exhibit deficient monocyte recruitment suggesting its potential role in inflammation. Overall, there is evidence that an impairment of monocyte trafficking in inflammation models occurs when there is a loss of MCP-1 effector function. This makes its receptor, CCR2, an attractive target for pharmaceutical research. Several small molecular CCR2 antagonists have been developed, particularly in the industry.Areas covered in this review: In this article, we have summarized the in silico work carried out in the area of CCR2 and reviewed mainly the computer aided drug design (CADD) studies reported on quantitative structure–activity relationship, homology modeling, molecular docking and virtual screening.What the reader will gain: A survey of computational studies for the rational design and development of CCR2 antagonists.Take home message: CADD tools can be used to rationalize the identification of the potential leads and these techniques can be effectively applied in the rapid searching of novel and potent CCR2 antagonists.

Monocyte Chemoattractant Protein-1 (MCP-1), Not MCP-3, Is the Primary Chemokine Required for Monocyte Recruitment in Mouse Peritonitis Induced with Thioglycollate or Zymosan A

MCP-1/CCL2 plays a critical role in monocyte recruitment into sites of immune responses and cancer. However, the role of other MCPs remains unclear. In this study, we generated a novel MCP-1-deficient (designated as MCP-1(Delta/Delta)) mouse model by deleting a 2.3-kb DNA fragment from the mouse genome using the Cre/loxP system. MCP-1 was not produced by LPS-activated MCP-1(Delta/Delta) macrophages; however, the production of MCP-3, coded by the immediate downstream gene, was significantly increased. In contrast, macrophages from another mouse line with a neo-gene cassette in intron 2 produced a significantly lower level of MCP-1 and MCP-3. Decreased MCP-3 production was also detected in previously generated MCP-1-deficient mice in which a neo-gene cassette was inserted in exon 2 (designated as MCP-1 knockout (KO)). Altered MCP-1 and/or MCP-3 production was also observed in vivo in each mouse model in response to i.p. injection of thioglycolate or zymosan. The up- and down-regulation of MCP-3 production in MCP-1(Delta/Delta) and MCP-1 KO mice, respectively, provided us with a unique opportunity to evaluate the role for MCP-3. Despite the increased MCP-3 production in MCP-1(Delta/Delta) mice, thioglycolate- or zymosan-induced monocyte/macrophage accumulation was still reduced by approximately 50% compared with wild-type mice, similar to the reduction detected in MCP-1 KO mice. Thus, up-regulated MCP-3 production did not compensate for the loss of MCP-1, and MCP-3 appears to be a less effective mediator of monocyte recruitment than MCP-1. Our results also indicate the presence of other mediators regulating the recruitment of monocytes in these models.

Recent developments in CCR2 antagonists

Monocyte chemoattractant protein-1 (MCP-1) is a major chemoattractant for monocytes and memory T cells by means of their binding to its specific cell-surface receptor, CC-chemokine receptor-2 (CCR2). CCR2 belongs to the G-protein-coupled seven-transmembrane receptor superfamily. The evidence in favor of CCR2 and MCP-1 having dominant roles in monocyte chemotaxis and chronic inflammation was provided by CCR2 and MCP-1 knockout mice. It has been recognized that CCR2 antagonists are potential therapeutic agents in preventing, treating, or ameliorating a CCR2-mediated inflammatory syndrome or disease such as psoriasis, uveitis, rheumatoid arthritis, multiple sclerosis, asthma, obesity, and chronic obstructive pulmonary disease. This review summarizes recent developments in small-molecule CCR2 antagonists disclosed by patent applications published between 2005 and 2008 and related publications.

Monocyte chemoattractant protein 1 contributes to an adequate immune response in influenza pneumonia

Monocyte chemoattractant protein 1 (MCP-1) and its receptor CCR2 have been shown to play an import role in leukocyte recruitment to sites of infection and inflammation. To investigate the role of MCP-1 during infection with influenza we inoculated wild-type (WT) and MCP-1 knockout (KO) mice with a non-lethal dose of a mouse adapted strain of influenza A. Influenza infection of WT mice resulted in a profound increase in pulmonary MCP-1 levels. MCP-1 KO mice had enhanced weight loss and did not fully regain their body weight during the 14-day observation period. In addition, MCP-1 KO mice demonstrated elevated viral loads 8 days after infection, which was accompanied by reduced leukocyte recruitment into the infected lungs, primarily caused by a diminished influx of macrophages and granulocytes. Moreover, pulmonary levels of IgA were reduced in MCP-1 KO mice. The pulmonary concentrations of tumor necrosis factor-α, interleukin-6, macrophage inflammatory protein 2 and interferon-γ were higher in MCP-1 KO mice. This study shows that MCP-1 contributes to an adequate protective immune response against influenza infection in mice.

Leishmania-Derived Murine Monocyte Chemoattractant Protein 1 Enhances the Recruitment of a Restrictive Population of CC Chemokine Receptor 2-Positive Macrophages

Transgenic Leishmania parasites that encode the murine chemokine monocyte chemoattractant protein 1 (MCP-1) were generated. These parasites transcribed MCP-1 mRNA and secreted MCP-1 protein. Infection of BALB/c, C57BL/6, or MCP-1 knockout (KO) mice with these parasites resulted in minimal lesion development with fewer parasites in the infected foot, lymph node, and spleen compared to wild-type-infected mice. In contrast, transgenic parasites caused substantial lesions with relatively high numbers of parasites in CC chemokine receptor 2 (CCR2) KO mice, indicating that the parasites are viable and healthy and that the lack of lesion development is CCR2 dependent. Prior infection of mice with transgenic parasites offered no protection to subsequent wild-type L. major challenge, suggesting that the transgenic parasites are controlled by an early innate immune response. Consistent with innate immunity, flow cytometry of cells from the ears of mice infected with transgenic parasites revealed an increase in the number of CCR2-positive macrophages by day 7 postinfection. The enumeration of transgenic parasites in ear lesions demonstrated a significant reduction in parasite numbers, which coincided with the increased CCR2-positive macrophage migration. CCR2-positive macrophages isolated from ears of mice infected with transgenic parasites contained virtually no parasites. In vitro studies revealed that optimal parasite killing required the recruitment of CCR2-positive macrophages, followed by stimulation with a combination of both MCP-1 and gamma interferon (IFN-gamma). This work suggests that the parasite-derived MCP-1 can recruit a restrictive population of CCR2-positive macrophages into lesions that can be optimally stimulated by MCP-1 and IFN-gamma to efficiently kill Leishmania parasites.

Monocyte Chemoattractant Protein 1 Does Not Contribute to Protective Immunity against Pneumococcal Pneumonia

To determine the role of monocyte chemoattractant protein 1 (MCP-1) during pneumococcal pneumonia, MCP-1 knockout and wild-type mice were infected with Streptococcus pneumoniae. Pulmonary MCP-1 levels were strongly correlated to bacterial loads in wild-type mice. However, MCP-1 knockout and wild-type mice were indistinguishable with respect to bacterial growth, inflammatory responses, and lethality.

MCP-1 and murine prion disease: Separation of early behavioural dysfunction from overt clinical disease

Prion diseases are chronic, fatal neurodegenerative conditions of the CNS. We have investigated the role of monocyte chemoattractant protein-1 (MCP-1) in the ME7 model of murine prion disease. MCP-1 expression increased in the CNS throughout disease progression and was positively correlated with microglial activation. We subsequently compared the inflammatory response, pathology and behavioural changes in wild-type (wt) mice and MCP-1 knockout mice (MCP-1-/-) inoculated with ME7. Late-stage clinical signs were delayed by 4 weeks in MCP-1-/- mice, and survival time increased by 2-3 weeks. By contrast, early changes in affective behaviours and locomotor activity were not delayed in onset. There was also no difference in microglial activation or neuronal death in the hippocampus and thalamus of wt mice and MCP-1-/- mice. These results highlight an important dissociation between prolonged survival, early behavioural dysfunction and hippocampal/thalamic pathology when considering therapeutic intervention for human prion diseases and other chronic neurodegenerative conditions.

Appearance of monocyte chemoattractant protein 1 (MCP-1) early after thermal injury: role in the subsequent development of burn-associated type 2 T-cell responses.

To determine whether monocyte chemoattractant protein-1 (MCP-1), which initiates subsequent development of burn-associated type 2 T cells, is produced in mice early after thermal injury. A predominance of type 2 T-cell responses is commonly observed in animals and patients with severe thermal injuries. Burn-associated type 2 T cells have been identified as the cells responsible for the increased susceptibility of thermally injured mice to infections with herpes simplex virus type 1 and Candida albicans. Recently, the necessity of MCP-1 for the generation of type 2 T cells was shown in MCP-1 knockout mice. MCP-1 may have an important role in the increased susceptibility of thermally injured mice to various intracellular opportunistic pathogens. The production of MCP-1 in sera or in cultures of various cells prepared from thermally injured mice was measured. Dual-chamber transwell cultures were performed to determine the influence of MCP-1-producing cells on the generation of burn-associated type 2 T cells. Without any stimulation, splenic macrophages from mice (1/2D-M(phi)) produced MCP-1 into their culture fluids 12 hours after thermal injury. Interleukin-4 was detected in culture fluids of splenic T cells from normal mice cultured with 1/2D-M(phi) in a dual-chamber transwell system; however, this cytokine was not produced by normal T cells cultured with normal macrophages in the transwells. Also, normal T cells cultured with 1/2D-M(phi) did not produce interleukin-4 when transwell cultures were performed in the presence of anti-MCP-1 monoclonal antibody. Further, normal T cells directly stimulated with MCP-1 produced interleukin-4 into their culture fluids. Normal T cells, cultured with 1/2D-M(phi) for 24 hours in the transwells and recultured with fresh medium for an additional 7 days, produced interleukin-10 (but not interferon-gamma) and expressed ST2L mRNA (but not interleukin-12 receptor beta2 chain) when they were stimulated with anti-CD3 monoclonal antibody. Results indicate that MCP-1 is produced in mice within 1 day of thermal injury, and the subsequent development of burn-associated type 2 T-cell responses may be triggered by MCP-1 produced early after thermal injury.