Mature peritoneal macrophages take an avascular route into the injured liver and promote tissue repair

Gemcitabine induces polarization of mouse peritoneal macrophages towards M1-like and confers antitumor property by inducing ROS production

In patients with pancreatic cancer (PC), the peritoneal cavity is the second-most common site of metastasis after the liver. Peritoneal macrophages (PMs) have been demonstrated to play a significant role in the peritoneal metastases of different cancers. Gemcitabine (GEM) is known to affect PC-associated immune cells, including macrophages. However, its effect on PMs and its possible clinical implication is yet to be investigated. In this study, mouse-derived PMs were treated with GEM ex vivo to analyze the polarization status. Production of GEM-induced reactive oxygen species (ROS) and reactive nitrogen species was evaluated using DCFH-DA, DAF-FM, and Griess assay. Antitumor effects of PMs on UN-KC-6141and UN-KPC-961 murine PC cells were evaluated in presence and absence of GEM in vitro. Similarly, effect of GEM on human THP-1 macrophage polarization and its tumoricidal effect was studied in vitro. Furthermore, the effect of GEM-treated PMs on peritoneal metastasis of UN-KC-6141 cells was evaluated in a syngeneic mouse model of PC. GEM upregulated M1 phenotype-associated molecular markers (Tnf-α and Inos) in vitro in PMs obtained from naïve mouse. Moreover, IL-4-induced M2-like PMs reverted to M1-like after GEM treatment. Co-culture of UN-KC-6141 and UN-KPC-961 cancer cells with PMs in the presence of GEM increased apoptosis of these cells, whereas cell death was markedly reduced after N-acetyl-L-cysteine treatment. Corroborating these findings co-culture of GEM-treated human THP-1 macrophages also induced cell death in MIAPaCa-2 cancer cells. GEM-treated PMs injected intraperitoneally along with UN-KC-6141 cells into mice extended survival period, but did not stop disease progression and mortality. Together, GEM induced M1-like polarization of PMs from naive and/or M2-polarized PMs in a ROS-dependent manner. GEM-induced M1-like PMs prompted cytotoxicity in PC cells and delayed disease progression in vivo.

M2c Macrophages enhance phalange regeneration of amputated mice digits in an organ co-culture system

Objectives

Delayed anti-inflammatory responses and scar-formation are the main causes for inability of injured body parts such as phalanges to regrow in mammals. Salamanders can regenerate fully scar-free body structures, followed by the appearance of anti-inflammatory responses at the injured site immediately after amputation. This study aimed to evaluate the local regenerative effects of direct amplified anti-inflammatory signals on regeneration of amputated mice digit tips using M2c-macrophages in a co-cultured organ system for the first time.

Materials and Methods

We used the amputated digits from the paws of 18.5E day old C57BL/6J mice. Monocytes were obtained from peripheral blood and co-cultured with amputated digits, which subsequently enhanced the M2c macrophage phenotype induced by IL-10. We also examined the regenerative effects of IL-10 and transcription growth factor-beta 1 (TGF-β1).

Results

The regrowth of new tissue occurred 10 days post-amputation in all groups. This regrowth was related to enhanced Msh homeobox-1 (Msx1), Msh homeobox-2 (Msx2), and bone morphogenic protein-4 (Bmp4) genes. Increased expression of fibroblast growth factor-8 (Fgf-8) also increased the proliferation rate. Histological analyses indicated that epidermal-closure occurred at 3-dpa in all groups. We observed full digit tip regeneration in the co-cultured group. Particularly, there was new tissue regrowth observed with 40 µg/ml of IL-10 and 120 µg/ml of TGF-β. In contrast, the control group had no remarkable digit elongation.

Conclusion

We propose that a direct amplified anti-inflammatory response at the digit injury site can regenerate epithelial and mesenchymal tissues, and might be useful for limb regeneration without scar formation in adult mammals.

Visceral adipose tissue imparts peripheral macrophage influx into the hypothalamus

BACKGROUND

Obesity is characterized by a systemic inflammation and hypothalamic neuroinflammation. Systemic inflammation is caused by macrophages that infiltrate obese adipose tissues. We previously demonstrated that high-fat diet (HFD)-fed male mice exhibited peripheral macrophage infiltration into the hypothalamus, in addition to activation of resident microglia. Since this infiltration contributes to neuroinflammation and neuronal impairment, herein we characterize the phenotype and origin of these hypothalamic macrophages in HFD mice.

METHODS

C57BL/6J mice were fed HFD (60% kcal from fat) or control diet with matching sucrose levels, for 12-16 weeks. Males and females were analyzed separately to determine sex-specific responses to HFD. Differences in hypothalamic gene expression in HFD-fed male and female mice, compared to their lean controls, in two different areas of the hypothalamus, were determined using the NanoString neuroinflammation panel. Phenotypic changes in macrophages that infiltrated the hypothalamus in HFD-fed mice were determined by analyzing cell surface markers using flow cytometry and compared to changes in macrophages from the adipose tissue and peritoneal cavity. Adipose tissue transplantation was performed to determine the source of hypothalamic macrophages.

RESULTS

We determined that hypothalamic gene expression profiles demonstrate sex-specific and region-specific diet-induced changes. Sex-specific changes included larger changes in males, while region-specific changes included larger changes in the area surrounding the median eminence. Several genes were identified that may provide partial protection to female mice. We also identified diet-induced changes in macrophage migration into the hypothalamus, adipose tissue, and peritoneal cavity, specifically in males. Further, we determined that hypothalamus-infiltrating macrophages express pro-inflammatory markers and markers of metabolically activated macrophages that were identical to markers of adipose tissue macrophages in HFD-fed mice. Employing adipose tissue transplant, we demonstrate that hypothalamic macrophages can originate from the visceral adipose tissue.

CONCLUSION

HFD-fed males experience higher neuroinflammation than females, likely because they accumulate more visceral fat, which provides a source of pro-inflammatory macrophages that migrate to other tissues, including the hypothalamus. Our findings may explain the male bias for neuroinflammation and the metabolic syndrome. Together, our results demonstrate a new connection between the adipose tissue and the hypothalamus in obesity that contributes to neuroinflammation and hypothalamic pathologies.

Tissue-Specific Role of Macrophages in Noninfectious Inflammatory Disorders

Chronic inflammation may not begin with local tissue disorders, such as hypoxia, but with the accumulation of critically activated macrophages in one site. The purpose of this review is to analyze the data reported in the scientific literature on the features of the functions of macrophages and their contributions to the development of pathology in various tissues during aseptic inflammation in obese subjects. In individuals with obesity, increased migration of monocytes from the peripheral blood to various tissues, the proliferation of resident macrophages and a change in the balance between alternatively activated anti-inflammatory macrophages (M2) and pro-inflammatory classically activated macrophages (M1) towards the latter have been observed. The primary cause of some metabolic pathologies has been precisely identified as the recruitment of macrophages with an altered phenotype, which is probably typical for many other pathologies. Recent studies have identified phenotypes, such as metabolically activated M (MMe), oxidized (Mox), hemoglobin-related macrophages (Mhem and MHb), M4 and neuroimmunological macrophages (NAM, SAM), which directly and indirectly affect energy metabolism. The high heterogeneity of macrophages in tissues contributes to the involvement of these cells in the development of a wide range of immune responses, including pathological ones. The replenishment of tissue-specific macrophages occurs at the expense of infiltrating monocyte-derived macrophages (MoMFs) in the pathological process. The origin of MoMFs from a general precursor retains their common regulatory mechanisms and similar sensitivity to regulatory stimuli. This makes it possible to find universal approaches to the effect on these cells and, as a consequence, universal approaches for the treatment of various pathological conditions.

Towards understanding the cell surface phenotype, metabolic properties and immune functions of resident macrophages of the peritoneal cavity and splenic red pulp using high resolution quantitative proteomics

Background:Resident macrophages (Mϕs) are distributed throughout the body and are important for maintaining tissue homeostasis and for defence against infections. Tissue Mϕs are highly adapted to their microenvironment and thought to mediate tissue-specific functions involving metabolism and immune defence that are not fully elucidated. Methods:We have used high resolution quantitative proteomics to gain insights into the functions of two types of resident tissue Mϕs: peritoneal cavity Mϕs and splenic red pulp Mϕs.  The cellular expression levels of many proteins were validated by flow cytometry and were consistently in agreement with the proteomics data.Results:Peritoneal and splenic red pulp macrophages displayed major differences in cell surface phenotype reflecting their adaptation to different tissue microenvironments and tissue-specific functions. Peritoneal Mϕs were shown to be enriched in a number of key enzymes and metabolic pathways normally associated with the liver, such as metabolism of fructose, detoxification, nitrogen homeostasis and the urea cycle. Supporting these observations, we show that peritoneal Mϕs are able to utilise glutamine and glutamate which are rich in peritoneum for urea generation.  In comparison, splenic red pulp Mϕs were enriched in proteins important for adaptive immunity such as antigen presenting MHC molecules, in addition to proteins required for erythrocyte homeostasis and iron turnover. We also show that these tissue Mϕs may utilise carbon and nitrogen substrates for different metabolic fates to support distinct tissue-specific roles.Conclusions:This study provides new insights into the functions of tissue Mϕs in immunity and homeostasis.  The comprehensive proteomics data sets are a valuable resource for biologists and immunologists.

Tissue-resident macrophages actively suppress IL-1beta release via a reactive prostanoid/IL-10 pathway

The alarm cytokine interleukin‐1β (IL‐1β) is a potent activator of the inflammatory cascade following pathogen recognition. IL‐1β production typically requires two signals: first, priming by recognition of pathogen‐associated molecular patterns leads to the production of immature pro‐IL‐1β; subsequently, inflammasome activation by a secondary signal allows cleavage and maturation of IL‐1β from its pro‐form. However, despite the important role of IL‐1β in controlling local and systemic inflammation, its overall regulation is still not fully understood. Here we demonstrate that peritoneal tissue‐resident macrophages use an active inhibitory pathway, to suppress IL‐1β processing, which can otherwise occur in the absence of a second signal. Programming by the transcription factor Gata6 controls the expression of prostacyclin synthase, which is required for prostacyclin production after lipopolysaccharide stimulation and optimal induction of IL‐10. In the absence of secondary signal, IL‐10 potently inhibits IL‐1β processing, providing a previously unrecognized control of IL‐1β in tissue‐resident macrophages.

Accelerated liver recovery after acute CCl4 poisoning in rats treated with sodium phthalhydrazide

Pharmacotherapy of hepatobiliary disorders is an important issue due to the high prevalence of liver failure, toxic and viral hepatitis and cirrhosis. The number of stimuli that can potentially induce or accelerate liver recovery is limited; in our study we selected sodium phthalhydrazide, which has been found to promote liver regeneration after partial hepatectomy. We examined the effects of phthalhydrazide on liver morphometric, histological and biochemical parameters in rats intoxicated with CCl₄. Accelerated liver recovery after CCl₄ intoxication in phthalhydrazide-treated animals was evidenced by increased number of liver sinusoidal cells, reduced focal necrosis of hepatocytes and reduced perifocal leukocyte infiltration. Decreased plasma levels of pro-inflammatory cytokines TNF-α and IL-18 and decreased concentrations of IL-6 and IFN-γ in liver homogenates were associated with reduced severity of cholestasis and normalized hepatic protein synthesis in CCl₄-intoxicated rats exposed to phthalhydrazide. Anti-inflammatory and immunomodulating properties of phthahlhydrazide can be an important factor contributing to accelerated liver recovery at early stages of acute CCl₄-toxic liver impairment.

Therapeutic Targeting of Hepatic Macrophages for the Treatment of Liver Diseases

Hepatic macrophages play a central role in maintaining homeostasis in the liver, as well as in the initiation and progression of liver diseases. Hepatic macrophages are mainly derived from resident hepatic macrophages called Kupffer cells or circulating bone marrow-derived monocytes. Kupffer cells are self-renewing and typically non-migrating macrophages in the liver and are stationed in the liver sinusoids in contrast to macrophages originating from circulating monocytes. Kupffer cells regulate liver homeostasis by mediating immunity against non-pathogenic blood-borne molecules, while participating in coordinated immune responses leading to pathogen clearance, leukocyte recruitment and antigen presentation to lymphocytes present in the vasculature. Monocyte-derived macrophages infiltrate into the liver tissue when metabolic or toxic damage instigates and are likely dispensable for replenishing the macrophage population in homeostasis. In recent years, different populations of hepatic macrophages have been identified with distinct phenotypes with discrete functions, far beyond the central dogma of M1 and M2 macrophages. Hepatic macrophages play a central role in the pathogenesis of acute and chronic liver failure, liver fibrosis, non-alcoholic fatty liver disease, alcoholic liver disease, viral hepatitis, and hepatocellular carcinoma, as well as in disease resolution. The understanding of the role of hepatic macrophages in liver diseases provides opportunities for the development of targeted therapeutics for respective malignancies. This review will summarize the current knowledge of the hepatic macrophages, their origin, functions, their critical role in maintaining homeostasis and in the progression or resolution of liver diseases. Furthermore, we will provide a comprehensive overview of the therapeutic targeting strategies against hepatic macrophages developed for the treatment of liver diseases.

Repolarization of Tumor-Associated Macrophages in a Genetically Engineered Nonsmall Cell Lung Cancer Model by Intraperitoneal Administration of Hyaluronic Acid-Based Nanoparticles Encapsulating MicroRNA-125b

Tumor-associated macrophages (TAMs) acquire a pro-tumor (M2) phenotype, which promotes tumor growth, angiogenesis, and metastasis. Certain microRNAs (miRs), such as miR-125b, can reprogram TAMs into an antitumor/pro-inflammatory (M1) phenotype. Using CD44 targeting hyaluronic acid-poly(ethylenimine) (HA-PEI)-based nanoparticles encapsulating miR-125b, we have herein shown macrophage-specific delivery and transfection upon intraperitoneal (i.p.) administration. We have exploited the inherent ability of peritoneal macrophages to migrate toward the inflammation/injury and demonstrated that following intraperitoneal administration of HA-PEI nanoparticles, there is an accumulation of HA-PEI nanoparticles in the macrophage-ablated lung tissues of both naïve and KRAS/p53 double mutant genetically engineered (KP-GEM) nonsmall cell lung cancer (NSCLC) mouse model. Additionally, upon transfection with miR-125b, we observed a >6-fold increase in the M1 to M2 macrophage ratio and 300-fold increase in the iNOS (M1 marker)/Arg-1 (M2 marker) ratio in TAMs as compared to the untreated control group. The results of these studies show that i.p. administered macrophage-specific HA-PEI nanoparticles can successfully transfect TAMs in lung tissues of both naïve mice and a KP-GEM NSCLC mouse model. Successful TAM repolarization toward the M1 phenotype has significant implication in anticancer immunotherapy.

Systemic histone release disrupts plasmalemma and contributes to necrosis in acute pancreatitis

BACKGROUND

Clinical and experimental acute pancreatitis feature histone release within the pancreas from innate immune cells and acinar cell necrosis. In this study, we aimed to detail the source of circulating histones and assess their role in the pathogenesis of acute pancreatitis.

METHODS

Circulating nucleosomes were measured in patient plasma, taken within 24 and 48 h of onset of acute pancreatitis and correlated with clinical outcomes. Using caerulein hyperstimulation, circulating histones were measured in portal, systemic venous and systemic arterial circulation in mice, and the effects of systemic administration of histones in this model were assessed. The sites of actions of circulating histones were assessed by administration of FITC-labelled histones. The effects of histones on isolated pancreatic acinar cells were further assessed by measuring acinar cell death and calcium permeability in vitro.

RESULTS

Cell-free histones were confirmed to be abundant in human acute pancreatitis and found to derive from pancreatitis-associated liver injury in a rodent model of the disease. Fluorescein isothianate-labelled histones administered systemically targeted the pancreas and exacerbated injury in experimental acute pancreatitis. Histones induce charge- and concentration-dependent plasmalemma leakage and necrosis in isolated pancreatic acinar cells, independent of extracellular calcium.

CONCLUSION

We conclude that histones released systemically in acute pancreatitis concentrate within the inflamed pancreas and exacerbate injury. Circulating histones may provide meaningful biomarkers and targets for therapy in clinical acute pancreatitis.

Interleukin-13 reduces cardiac injury and prevents heart dysfunction in viral myocarditis via enhanced M2 macrophage polarization

Viral myocarditis is one of the major causes of congestive heart failure and dilated cardiomyopathy. Recent reports have demonstrated an essential role of cytokines, like interleukin-13 (IL-13), in the pathogenesis of viral myocarditis, while the underlying mechanisms remain poorly defined. Here, using a coxsackie virus B3 (CVB3)-infection model in BALB/C mice, we showed that IL-13 protected mouse heart function in viral myocarditis, seemingly through reduction in T lymphocyte immunity and induction of M2 macrophage polarization. Adoptive transfer to M2 macrophages mimicked the effects of IL-13 on protection from myocarditis, suggesting that the effects of IL-13 may be primarily through regulation of macrophage polarization. Together, our data suggest that application of IL-13 treatment may reduce cardiac Injury and protect heart function in viral myocarditis via enhanced M2 macrophage polarization.