Browsing by Subject "Macrophages"

Now showing 1 - 5 of 5

Open Access
Adenosine regulation of danger signaling
(2017-07) Akdemir, İmran
Metabolic and immune related activities converge as main triggers of adenosine accumulation in extracellular space. Adenosine by engaging adenosine A2A and A2B receptors strongly suppresses innate and adaptive immune responses. Although adenosine receptors are being targeted in preclinical and clinical studies, how different danger signals are regulated by adenosine is poorly understood. Here we showed that adenosine receptor stimulation strongly inhibited inflammatory responses while sparing Type-I interferon responses downstream of different danger signals in dendritic cells and macrophages. Mechanistically, danger signals associated with MyD88-dependent inflammatory pathways such as LPS and CpG but not the danger signals associated with IRF3/Type-I interferon pathways such as pA:U and cGAMP increase the expression of adenosine A2A and A2B receptors. Expression of anti-inflammatory NR4A1 was increased after adenosine receptor stimulation in the presence of TLR ligands known to activate MyD88 pathway but not in the presence of cGAMP and pA:U. Overall these results indicate that there is a differential modulation of danger signaling by adenosine rather than overall suppression. Our results have important implications for developing combinatorial approaches to target adenosine and danger signaling pathways to cure immune-related diseases.
Open Access
Jnk1 deficiency in hematopoietic cells suppresses macrophage apoptosis and increases atherosclerosis in low-density lipoprotein receptor null mice
(Lippincott Williams and Wilkins, 2016) Babaev, V. R.; Yeung, M.; Erbay, E.; Ding, L.; Zhang, Y.; May, J. M.; Fazio, S.; Hotamisligil, G. S.; Linton, M. F.
Objective - The c-Jun NH 2 -terminal kinases (JNK) are regulated by a wide variety of cellular stresses and have been implicated in apoptotic signaling. Macrophages express 2 JNK isoforms, JNK1 and JNK2, which may have different effects on cell survival and atherosclerosis. Approach and Results - To dissect the effect of macrophage JNK1 and JNK2 on early atherosclerosis, Ldlr-/- mice were reconstituted with wild-type, Jnk1-/-, and Jnk2-/- hematopoietic cells and fed a high cholesterol diet. Jnk1-/- →Ldlr-/- mice have larger atherosclerotic lesions with more macrophages and fewer apoptotic cells than mice transplanted with wild-type or Jnk2-/- cells. Moreover, genetic ablation of JNK to a single allele (Jnk1+/- /Jnk2-/- or Jnk1-/- /Jnk2+/-) in marrow of Ldlr-/- recipients further increased atherosclerosis compared with Jnk1-/- →Ldlr-/- and wild-type→Ldlr-/- mice. In mouse macrophages, anisomycin-mediated JNK signaling antagonized Akt activity, and loss of Jnk1 gene obliterated this effect. Similarly, pharmacological inhibition of JNK1, but not JNK2, markedly reduced the antagonizing effect of JNK on Akt activity. Prolonged JNK signaling in the setting of endoplasmic reticulum stress gradually extinguished Akt and Bad activity in wild-type cells with markedly less effects in Jnk1-/- macrophages, which were also more resistant to apoptosis. Consequently, anisomycin increased and JNK1 inhibitors suppressed endoplasmic reticulum stress-mediated apoptosis in macrophages. We also found that genetic and pharmacological inhibition of phosphatase and tensin homolog abolished the JNK-mediated effects on Akt activity, indicating that phosphatase and tensin homolog mediates crosstalk between these pathways. Conclusions - Loss of Jnk1, but not Jnk2, in macrophages protects them from apoptosis, increasing cell survival, and this accelerates early atherosclerosis.
Open Access
Macrophage Mal1 deficiency suppresses atherosclerosis in low-density lipoprotein receptor-null mice by activating peroxisome proliferator-activated receptor-g-regulated genes
(Lippincott Williams & Wilkins, 2011) Babaev, V. R.; Runner, R. P.; Fan, D.; Ding, L.; Zhang, Y.; Tao, H.; Erbay, E.; Gorgun, C. Z.; Fazio, S.; Hotamisligil, G. S.; Linton, M. F.
Objective-The adipocyte/macrophage fatty acid-binding proteins aP2 (FABP4) and Mal1 (FABP5) are intracellular lipid chaperones that modulate systemic glucose metabolism, insulin sensitivity, and atherosclerosis. Combined deficiency of aP2 and Mal1 has been shown to reduce the development of atherosclerosis, but the independent role of macrophage Mal1 expression in atherogenesis remains unclear. Methods and Results-We transplanted wild-type (WT), Mal1(-/-), or aP2(-/-) bone marrow into low-density lipoprotein receptor-null (LDLR(-/-)) mice and fed them a Western diet for 8 weeks. Mal1(-/-)-> LDLR(-/-) mice had significantly reduced (36%) atherosclerosis in the proximal aorta compared with control WT -> LDLR(-/-) mice. Interestingly, peritoneal macrophages isolated from Mal1-deficient mice displayed increased peroxisome proliferator-activated receptor-gamma (PPAR gamma) activity and upregulation of a PPAR gamma-related cholesterol trafficking gene, CD36. Mal1(-/-) macrophages showed suppression of inflammatory genes, such as COX2 and interleukin 6. Mal1(-/-)-> LDLR(-/-) mice had significantly decreased macrophage numbers in the aortic atherosclerotic lesions compared with WT -> LDLR(-/-) mice, suggesting that monocyte recruitment may be impaired. Indeed, blood monocytes isolated from Mal1(-/-)-> LDLR(-/-) mice on a high-fat diet had decreased CC chemokine receptor 2 gene and protein expression levels compared with WT monocytes. Conclusion-Taken together, our results demonstrate that Mal1 plays a proatherogenic role by suppressing PPAR gamma activity, which increases expression of CC chemokine receptor 2 by monocytes, promoting their recruitment to atherosclerotic lesions. (Arterioscler Thromb Vasc Biol. 2011;31:1283-1290.)
Open Access
One-Step Fabrication of Biocompatible Multifaceted Nanocomposite Gels and Nanolayers
(American Chemical Society, 2017) Topuz, F.; Bartneck, M.; Pan, Y.; Tacke, F.
Nanocomposite gels are a fascinating class of polymeric materials with an integrative assembly of organic molecules and organic/inorganic nanoparticles, offering a unique hybrid network with synergistic properties. The mechanical properties of such networks are similar to those of natural tissues, which make them ideal biomaterial candidates for tissue engineering applications. Existing nanocomposite gel systems, however, lack many desirable gel properties, and their suitability for surface coatings is often limited. To address this issue, this article aims at generating multifunctional nanocomposite gels that are injectable with an appropriate time window, functional with bicyclononynes (BCN), biocompatible and slowly degradable, and possess high mechanical strength. Further, the in situ network-forming property of the proposed system allows the fabrication of ultrathin nanocomposite coatings in the submicrometer range with tunable wettability and roughness. Multifunctional nanocomposite gels were fabricated under cytocompatible conditions (pH 7.4 and T = 37 °C) using laponite clays, isocyanate (NCO)-terminated sP(EO-stat-PO) macromers, and clickable BCN. Several characterization techniques were employed to elucidate the structure-property relationships of the gels. Even though the NCO-sP(EO-stat-PO) macromers could form a hydrogel network in situ on contact with water, the incorporation of laponite led to significant improvement of the mechanical properties. BCN motifs with carbamate links were used for a metal-free click ligation with azide-functional molecules, and the subsequent gradual release of the tethered molecules through the hydrolysis of carbamate bonds was shown. The biocompatibility of the hydrogels was examined through murine macrophages, showing that the material composition strongly affects cell behavior.
Open Access
Platelet-derived microparticles differentially regulate macrophage polarization
(2016-09) Köksal, Elif Senem
Platelet-derived microparticles (PMPs) shed from platelets upon activation and constitute almost 90% of the circulating microparticles. Due to their versatile cargo, PMPs were associated with the generation of immunosuppressive microenvironment and and thought to promote tumor growth. They are also potential candidates for prevention and treatment of autoimmune diseases. Macrophages are one of the enigmatic cells of the immune system. They are either categorized as ‘M1-type’, mediating an inflammatory environment or ‘M2-type’, mediating an immune suppressive environment. Cardinal signals resulting M1-tropic or M2-tropic macrophage differentiation is not fully understood. However, it is crucial to understand the inducers of macrophage polarization for therapeutic approaches. We aimed to understand the interaction between PMPs with macrophages and wished to understand mechanistic alterations upon macrophages engage with PMPs. In this thesis, we showed that activated human platelets released microparticles and they were internalized by macrophages differentiated from THP1 monocytic cell line. Internalized PMPs co-localized with late endosomes. The phagocytic capacity of M2- polarized THP1 macrophages were greater than M1-polarized macrophages. Strikingly, when THP1 derived macrophages were treated with standalone PMPs our results revealed that these macrophage were unable to mount any detectable cytokine secretion related to M1 or M2 type identity. This prompted us to encapsulate TLR agonists within PMPs and harness them as a carrier system. Different TLR ligands including TLR7 (sensing ssRNA) and TLR9 (sensing ss/ds DNA expressing CpG motifs) ligands were incorporated within PMPs via dehydration-rehydration method that was developed in our laboratory. Upon screening of several TLR agonist candidates on healthy donor PBMCs as well as on purified monocytes, we found that M1-like macrophage differentiation was TLR9 agonist D-type CpG oligodeoxynucleotide loaded PMP dependent whereas M2-like macrophage differentiation was dependent on TLR7 agonist R848 loaded PMPs. In conclusion, this work implicated that PMP treatment of macrophages loaded with suitable ligand combinations might regulate M1/M2 type macrophage differentiation and could be used efficiently either to control tumor development (M1) or to alleviate symptoms of auto-immune/auto-inflammatory diseases (M2).