Multiple roles of cardiac macrophages in heart homeostasis and failure.

Macrophages are essential components of the immune system and play a role in the normal functioning of the cardiovascular system. Depending on their origin and phenotype, cardiac macrophages perform various functions. In a steady-state, these cells play a beneficial role in maintaining cardiac homeostasis by defending the body from pathogens and eliminating apoptotic cells, participating in electrical conduction, vessel patrolling, and arterial tone regulation. However, macrophages also take part in adverse cardiac remodeling that could lead to the development and progression of heart failure (HF) in such HF comorbidities as hypertension, obesity, diabetes, and myocardial infarction. Nevertheless, studies on detailed mechanisms of cardiac macrophage function are still in progress, and could enable potential therapeutic applications of these cells. This review aims to present the latest reports on the origin, heterogeneity, and functions of cardiac macrophages in the healthy heart and in cardiovascular diseases leading to HF. The potential therapeutic use of macrophages is also briefly discussed.

2-O, 3-O desulfated heparin (ODSH) increases bacterial clearance and attenuates lung injury in cystic fibrosis by restoring HMGB1-compromised macrophage function.

BACKGROUND: High mobility group box 1 protein (HMGB1) is an alarmin following its release by immune cells upon cellular activation or stress. High levels of extracellular HMGB1 play a critical role in impairing the clearance of invading pulmonary pathogens and dying neutrophils in the injured lungs of cystic fibrosis (CF) and acute respiratory distress syndrome (ARDS). A heparin derivative, 2-O, 3-O desulfated heparin (ODSH), has been shown to inhibit HMGB1 release from a macrophage cell line and is efficacious in increasing bacterial clearance in a mouse model of pneumonia. Thus, we hypothesized that ODSH can attenuate the bacterial burden and inflammatory lung injury in CF and we conducted experiments to determine the underlying mechanisms. METHODS: We determined the effects of ODSH on lung injury produced by Pseudomonas aeruginosa (PA) infection in CF mice with the transmembrane conductance regulator gene knockout (CFTR-/-). Mice were given ODSH or normal saline intraperitoneally, followed by the determination of the bacterial load and lung injury in the airways and lung tissues. ODSH binding to HMGB1 was determined using surface plasmon resonance and in silico docking analysis of the interaction of the pentasaccharide form of ODSH with HMGB1. RESULTS: CF mice given 25 mg/kg i.p. of ODSH had significantly lower PA-induced lung injury compared to mice given vehicle alone. The CF mice infected with PA had decreased levels of nitric oxide (NO), increased levels of airway HMGB1 and HMGB1-impaired macrophage phagocytic function. ODSH partially attenuated the PA-induced alteration in the levels of NO and airway HMGB1 in CF mice. In addition, ODSH reversed HMGB1-impaired macrophage phagocytic function. These effects of ODSH subsequently decreased the bacterial burden in the CF lungs. In a surface plasmon resonance assay, ODSH interacted with HMGB1 with high affinity (KD = 3.89 × 10-8 M) and induced conformational changes that may decrease HMGB1's binding to its membrane receptors, thus attenuating HMGB1-induced macrophage dysfunction. CONCLUSIONS: The results suggest that ODSH can significantly decrease bacterial infection-induced lung injury in CF mice by decreasing both HMGB1-mediated impairment of macrophage function and the interaction of HMGB1 with membrane receptors. Thus, ODSH could represent a novel approach for treating CF and ARDS patients that have HMGB1-mediated lung injury.

Effect of 1-Carbaldehyde-3,4-dimethoxyxanthone on Prostate and HPV-18 Positive Cervical Cancer Cell Lines and on Human THP-1 Macrophages.

Xanthone derivatives have shown promising antitumor properties, and 1-carbaldehyde-3,4-dimethoxyxanthone (1) has recently emerged as a potent tumor cell growth inhibitor. In this study, its effect was evaluated (MTT viability assay) against a new panel of cancer cells, namely cervical cancer (HeLa), androgen-sensitive (LNCaP) and androgen-independent (PC-3) prostate cancer, and nonsolid tumor derived cancer (Jurkat) cell lines. The effect of xanthone 1 on macrophage functions was also evaluated. The effect of xanthone 1-conditioned THP-1 human macrophage supernatants on the metabolic viability of cervical and prostate cancer cell lines was determined along with its interference with cytokine expression characteristic of M1 profile (IL-1 ≤ ß; TNF-α) or M2 profile (IL-10; TGF-ß) (PCR and ELISA). Nitric oxide (NO) production by murine RAW264.7 macrophages was quantified by Griess reaction. Xanthone 1 (20 µM) strongly inhibited the metabolic activity of the cell lines and was significantly more active against prostate cell lines compared to HeLa (p < 0.05). Jurkat was the cell most sensitive to the effect of xanthone 1. Compound 1-conditioned IL-4-stimulated THP-1 macrophage supernatants significantly (p < 0.05) inhibited the metabolic activity of HeLa, LNCaP, and PC-3. Xanthone 1 did not significantly affect the expression of cytokines by THP-1 macrophages. The inhibiting effect of compound 1 observed on the production of NO by RAW 264.7 macrophages was moderate. In conclusion, 1-carbaldehyde-3,4-dimethoxyxanthone (1) decreases the metabolic activity of cancer cells and seems to be able to modulate macrophage functions.

Origins and diversity of macrophages in health and disease.

Macrophages are the first immune cells in the developing embryo and have a central role in organ development, homeostasis, immunity and repair. Over the last century, our understanding of these cells has evolved from being thought of as simple phagocytic cells to master regulators involved in governing a myriad of cellular processes. A better appreciation of macrophage biology has been matched with a clearer understanding of their diverse origins and the flexibility of their metabolic and transcriptional machinery. The understanding of the classical mononuclear phagocyte system in its original form has now been expanded to include the embryonic origin of tissue-resident macrophages. A better knowledge of the intrinsic similarities and differences between macrophages of embryonic or monocyte origin has highlighted the importance of ontogeny in macrophage dysfunction in disease. In this review, we provide an update on origin and classification of tissue macrophages, the mechanisms of macrophage specialisation and their role in health and disease. The importance of the macrophage niche in providing trophic factors and a specialised environment for macrophage differentiation and specialisation is also discussed.

Chlamydia psittaci Triggers the Invasion of H9N2 Avian Influenza Virus by Impairing the Functions of Chicken Macrophages.

In a pilot study, simultaneous infection with Chlamydia psittaci (C. psittaci) and H9N2 virus induced 20% mortality and severe avian airsacculitis, shedding light on animal models of poultry respiratory diseases. However, the pathogenesis is still unclear. In the current study, we hypothesized that C. psittaci infection execrates macrophage function and facilitates H9N2 infection. To explore the potential mechanism, we studied the effect of C. psittaci and H9N2 on the functions of HD11 cells in vitro by simultaneous infection of C. psittaci and H9N2. At the same time, we used infection with C. psittaci or H9N2 alone as the control groups. The results showed that coinfection with C. psittaci and H9N2 could significantly aggravate the mortality of HD11 cells compared to C. psittaci or H9N2 infection alone. In addition, coinfection with C. psittaci and H9N2 did not induce high C. psittaci loads compared to C. psittaci infection alone at 12- and 24-hours post-inoculation (hpi), but coinfection with C. psittaci and H9N2 could increase the loads of H9N2 compared to H9N2 alone in HD11 cells at 12 hpi. More importantly, inducible nitric oxide synthase (iNOS) expression levels, enzyme activity, nitric oxide (NO) production, and phagocytosis were reduced significantly in the group with C. psittaci and H9N2 coinfection compared to those of H9N2 or C. psittaci alone at 24 hpi. Finally, C. psittaci infection induced robust expressions of type Th2 cytokines interleukin (IL)-4 and IL-10, while interferon gamma (IFN-γ) and tumor necrosis factor-α (TNF-α) displayed a significant decrease compared to H9N2 infection alone at 24 hpi. All the above data indicate that C. psittaci infection can facilitate H9N2 invasion and to aggravate severe avian airsacculitis by impairing macrophage functions.

Characterization and immunologic functions of the macrophage migration inhibitory factor from Japanese sea bass, Lateolabrax japonicus.

Macrophage migration inhibitory factor (MIF) is a cytokine playing critical roles in inflammatory and immune responses. However, its functions have not been well studied in fish. In this study, we identified a MIF molecule from Japanese sea bass (Lateolabrax japonicus; LjMIF). Multiple sequence alignment showed that LjMIF has the typical structural features of MIFs. Phylogenetic tree analysis revealed that LjMIF is most closely related to the yellowfin tuna (Thunnus albacares), large yellow croaker (Larimichthys crocea), and red drum (Sciaenops ocellatus) homologs. Constitutive mRNA expression of LjMIF was detected in all tested tissues, with the highest level in the liver. Upon Vibro harveyi infection, LjMIF transcripts were altered in the tested tissues, including the liver, spleen, and head kidney. Subsequently, we prepared recombinant LjMIF (rLjMIF) and the corresponding antibody (anti-LjMIF). The in vitro study showed that rLjMIF inhibited the trafficking of Japanese sea bass monocytes/macrophages (MO/MΦ) and lymphocytes, but not of neutrophils, while anti-LjMIF had the opposite effect. rLjMIF also enhanced phagocytosis and intracellular killing of V. harveyi by MO/MΦ, while anti-LjMIF only inhibited phagocytosis by MO/MΦ. The in vivo study showed that rLjMIF aggravated the course of V. harveyi infection in Japanese sea bass, but anti-LjMIF increased the survival rate of the fish and decreased the bacterial burden. In conclusion, our observation revealed that LjMIF is closely involved in the immune responses of Japanese sea bass for combating V. harveyi infection.

Polysaccharides extracted from the roots of Bupleurum chinense DC modulates macrophage functions.

The present study aimed to investigate the effects of polysaccharides extracted from Bupleurum chinense DC (BCPs) on macrophage functions. In the in vivo experiment, 1 mL of 5% sodium thioglycollate was injected into the abdomen of the mice on Day 0 and macrophages were harvested on Day 4. The macrophages were cultured in plates and treated with different concentrations of BCPs and stimulus. Effects of BCPs on macrophage functions were assessed by chemotaxis assay, phagocytosis assay and Enzyme-Linked Immunosorbent Assay (ELISA). Our results showed the enhanced chemotaxis, phagocytosis and secretion of nitric oxide (NO) and inflammatory cytokines by macrophages when treated with BCPs. However, when chemotaxis and phagocytosis were up-regulated by complement components or opsonized particles, BCPs inhibited these effects. Also, the NO production induced by lipopolysaccharides (LPS) was suppressed by BCPs mildly. Moreover, BCPs had an inhibitory effect on the [Ca2+]i elevation of macrophages. These results suggested that BCPs exerted modulatory effects on macrophage functions, which may contribute to developing novel approaches to treating inflammatory diseases.

Polysaccharides extracted from the roots of Bupleurum chinense DC modulates macrophage functions / 中国天然药物

The present study aimed to investigate the effects of polysaccharides extracted from Bupleurum chinense DC (BCPs) on macrophage functions. In the in vivo experiment, 1 mL of 5% sodium thioglycollate was injected into the abdomen of the mice on Day 0 and macrophages were harvested on Day 4. The macrophages were cultured in plates and treated with different concentrations of BCPs and stimulus. Effects of BCPs on macrophage functions were assessed by chemotaxis assay, phagocytosis assay and Enzyme-Linked Immunosorbent Assay (ELISA). Our results showed the enhanced chemotaxis, phagocytosis and secretion of nitric oxide (NO) and inflammatory cytokines by macrophages when treated with BCPs. However, when chemotaxis and phagocytosis were up-regulated by complement components or opsonized particles, BCPs inhibited these effects. Also, the NO production induced by lipopolysaccharides (LPS) was suppressed by BCPs mildly. Moreover, BCPs had an inhibitory effect on the [Ca] elevation of macrophages. These results suggested that BCPs exerted modulatory effects on macrophage functions, which may contribute to developing novel approaches to treating inflammatory diseases.

The protection effect of LEAP-2 on the mudskipper (Boleophthalmus pectinirostris) against Edwardsiella tarda infection is associated with its immunomodulatory activity on monocytes/macrophages.

Liver-expressed antimicrobial peptide 2 (LEAP-2) is a cationic peptide that plays an important role in the host's innate immune system. However, the mechanism by which LEAP-2 modulates/regulates the host defense against pathogens remains largely unknown. In this study, we identified a cDNA sequence encoding LEAP-2 homolog (BpLEAP-2) in the mudskipper, Boleophthalmus pectinirostris. Sequence analysis revealed that BpLEAP-2 belonged to the fish LEAP-2A cluster and that it was closely related to ayu LEAP-2. BpLEAP-2 mRNA was detected in a wide range of tissues, with the highest level of transcripts found in the liver. Upon infection with Edwardsiella tarda, BpLEAP-2 mRNA expression was significantly increased in the liver, kidney, spleen, and gill, but decreased in the intestine. Chemically synthesized BpLEAP-2 mature peptide did not exhibit antibacterial activity against E. tarda in vitro. Intraperitoneal injection of BpLEAP-2 (1.0 or 10.0 µg/g) resulted in significantly improved survival rate and reduced tissue bacterial load in E. tarda-infected mudskippers. In E. tarda-infected fish, BpLEAP-2 (0.1, 1.0, or 10.0 µg/g) eliminated E. tarda-induced tissue mRNA expression of BpTNF-α and BpIL-1ß. In monocytes/macrophages (MO/MФ), BpLEAP-2 (1.0 or 10.0 µg/ml) induced chemotaxis, enhanced respiratory burst, and inhibited E. tarda-induced mRNA expression of BpTNF-α and BpIL-1ß. At a concentration of 10.0 µg/ml, BpLEAP-2 also significantly enhanced the bacterial killing efficiency of MO/MФ. No significant effect was seen in the phagocytic activity of MO/MФ upon treatment with BpLEAP-2. Our study provides evidence, for the first time, that LEAP-2 exhibited immunomodulatory effects on immune cells, and protected the host from pathogenic infections independent of direct bacterial killing function.

Activating transcription factor 4 underlies the pathogenesis of arsenic trioxide-mediated impairment of macrophage innate immune functions.

Chronic arsenic exposure to humans is considered immunosuppressive with augmented susceptibility to several infectious diseases. The exact molecular mechanisms, however, remain unknown. Earlier, we showed the involvement of unfolded protein response (UPR) signaling in arsenic-mediated impairment of macrophage functions. Here, we show that activating transcription factor 4 (ATF4), a UPR transcription factor, regulates arsenic trioxide (ATO)-mediated dysregulation of macrophage functions. In ATO-treated ATF4(+/+) wild-type mice, a significant down-regulation of CD11b expression was associated with the reduced phagocytic functions of peritoneal and lung macrophages. This severe immuno-toxicity phenotype was not observed in ATO-treated ATF4(+/-) heterozygous mice. To confirm these observations, we demonstrated in Raw 264.7 cells that ATF4 knock-down rescues ATO-mediated impairment of macrophage functions including cytokine production, bacterial engulfment and clearance of engulfed bacteria. Sustained activation of ATF4 by ATO in macrophages induces apoptosis, while diminution of ATF4 expression protects against ATO-induced apoptotic cell death. Raw 264.7 cells treated with ATO also manifest dysregulated Ca(++) homeostasis. ATO induces Ca(++)-dependent calpain-1 and caspase-12 expression which together regulated macrophage apoptosis. Additionally, apoptosis was also induced by mitochondria-regulated pathway. Restoring ATO-impaired Ca(++) homeostasis in ER/mitochondria by treatments with the inhibitors of inositol 1,4,5-trisphosphate receptor (IP3R) and voltage-dependent anion channel (VDAC) attenuate innate immune functions of macrophages. These studies identify a novel role for ATF4 in underlying pathogenesis of macrophage dysregulation and immuno-toxicity of arsenic.

Molecular characterization and functional analysis of a novel C-type lectin receptor-like gene from a teleost fish, Plecoglossus altivelis.

C-type lectin-like receptors (CLRs) are important pathogen pattern recognition molecules that recognize carbohydrate structures. However, the functions of these receptors in fish keep less known. In this study, we characterized a novel CLR from a teleost fish, Plecoglossus altivelis (ayu), tentatively named PaCD209L. The cDNA of PaCD209L is 1464 nucleotides (nts) in length, encoding a polypeptide of 281 amino acid residues with a calculated molecular weight of 31.5 kDa. Multiple alignment of the deduced amino acid sequences of PaCD209L and other related fish CLRs revealed that the PaCD209L sequence had typical characteristics of fish CLRs, but without Ca(2+)-binding sites. Sequence comparison and phylogenetic tree analysis showed that PaCD209L shared the highest amino acid identity (44%) with rainbow trout (Oncorhynchus mykiss) CD209 aE PaCD209L transcripts were detected in all of the tissues examined, mainly expressed in the brain and heart. Upon Vibrio anguillarum infection, PaCD209L transcripts were upregulated in all tested tissues and in monocytes/macrophages (MO/MΦ). We prepared recombinant PaCD209L (rPaCD209L) by prokaryotic expression and raised antiserum against PaCD209L. Western blot analysis revealed that native PaCD209L was glycosylated, and its protein expression significantly increased in ayu MO/MΦ upon V. anguillarum infection. In addition, rPaCD209L was able to bind Gram-positive and Gram-negative bacteria in the absence of Ca(2+). After PaCD209L was blocked by anti-PaCD209L IgG, the phagocytosis and bacterial killing activity of MO/MΦ significantly decreased. These results suggest that PaCD209L plays an important role in the regulation of MO/MΦ functions in ayu.

In vitro immune toxicity of polybrominated diphenyl ethers on murine peritoneal macrophages: apoptosis and immune cell dysfunction.

Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants and are often detected in the environment, wildlife, and humans, presenting potential threats to ecosystem and human health. PBDEs can cause neurotoxicity, hepatotoxicity, and endocrine disruption. However, data on PBDE immunotoxicity are limited, and the toxicity mechanisms remain largely unknown. Both immune cell death and dysfunction can modulate the responses of the immune system. This study examined the toxic effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and decabromodiphenyl ether (BDE-209) on the immune system by using peritoneal macrophages as the model. The macrophages were exposed to PBDEs, and cell death was determined through flow cytometry and immunochemical blot. The results showed that after 24h of exposure, BDE-47 (>5 µM) and BDE-209 (>20 µM) induced cell apoptosis, increased intracellular reactive oxygen species (ROS) formation and depleted glutathione. BDE-47 was more potent than BDE-209; the cytotoxic concentrations for BDE-47 and BDE-209 were determined to be 5 µM and 20 µM, respectively, during 24h of exposure. However, pretreatment with n-acetyl-l-cysteine (ROS scavenger) partially reversed the cytotoxic effects. Further gene expression analyses on Caspase-3,-8,-9, TNFR1, and Bax revealed that both intrinsic and extrinsic apoptotic pathways were activated. More importantly, non-cytotoxic concentrations BDE-47 (<2 µM) and BDE-209 (<10 µM) could impair macrophage accessory cell function in a concentration-dependent manner, but no effects were observed on phagocytic responses. These revealed effects of PBDEs on macrophages may shed light on the toxicity mechanisms of PBDEs and suggest the necessity of evaluating cellular functionality during the risk assessment of PBDE immunotoxicity.

Peritoneal mast cell degranulation differently affected thioglycollate-induced macrophage phenotype and activity in Dark Agouti and Albino Oxford rats.

AIMS: Macrophages are heterogeneous population of inflammatory cells and, in response to the microenvironment, become differentially activated. The objective of the study was to explore macrophage effector functions during different inflammatory conditions in two rat strains. MAIN METHODS: We have investigated the effects of in vivo treatment with mast cell-degranulating compound 48/80 and/or thioglycollate on peritoneal macrophage phagocytosis and capacity to secrete hydrogen peroxide (H2O2), tumor necrosis factor-α (TNF-α) and nitric oxide (NO) in Dark Agouti (DA) and Albino Oxford (AO) rat strains. Besides, fresh peritoneal cells were examined for the expression of ED1, ED2 and CD86 molecules. KEY FINDINGS: In thioglycollate-elicited macrophages, increased proportion of ED1+ cells was accompanied with elevated phagocytosis of zymosan (DA strain), whereas increased expression level of CD86 molecule on ED2+ macrophages matched elevated secretory capacity for H2O2, TNF-α and NO (AO rats). Although mast cell degranulation induced by compound 48/80 increased the percentages of ED2+ macrophages in both rat strains, the proportion of ED2+ cells expressing CD86 molecule was decreased and increased in DA and AO rats, respectively. Furthermore, in DA strain compound 48/80 diminished macrophage secretion of NO, but stimulated all macrophage functions tested in AO strain. If applied concomitantly, the compound 48/80 additively increased macrophage activity induced by thioglycollate in AO rats. SIGNIFICANCE: Macrophages from DA and AO rat strains show different susceptibility to mediators released from mast cells, suggesting that strain-dependant predisposition(s) toward particular activation pattern is decisive for the macrophage efficacy in response to inflammatory agents.