Macrophages: master regulators of inflammation and fibrosis

Macrophage phenotypes during tissue repair

Mp are crucial for tissue repair and regeneration but can also contribute to tissue damage and fibrosis. Mp can adopt a variety of functional phenotypes in response to different stimuli; two of the best-characterized in vitro phenotypes are a proinflammatory "M1" phenotype, produced by exposure to IFN-γ and TNF-α, and an anti-inflammatory "M2a" phenotype, produced by IL-4 or IL-13. M2a Mp are frequently termed "wound healing" Mp, as they express factors that are important for tissue repair. This review will summarize current knowledge of Mp phenotypes during tissue repair and will argue that these in vivo Mp populations are heterogeneous and temporally regulated and do not conform to existing, in vitro-defined M1 or M2 phenotypes. Mp during the early stages of tissue repair exhibit a more proinflammatory phenotype than their later counterparts, which in turn may exhibit some M2a-associated characteristics. However, phenotypic markers that appear to be coregulated in cultured Mp can be expressed independently of each other in vivo. Additionally, M1- and M2-associated markers may be expressed simultaneously by actual tissue-repair Mp. Improved understanding of Mp phenotypes and their regulation may assist in generation of novel therapies based on manipulating Mp function to improve healing.

Functional complexity of the Leishmania granuloma and the potential of in silico modeling

In human and canine visceral leishmaniasis and in various experimental models of this disease, host resistance is strongly linked to efficient granuloma development. However, it is unknown exactly how the granuloma microenvironment executes an effective antileishmanial response. Recent studies, including using advanced imaging techniques, have improved our understanding of granuloma biology at the cellular level, highlighting heterogeneity in granuloma development and function, and hinting at complex cellular, temporal, and spatial dynamics. In this mini-review, we discuss the factors involved in the formation and function of Leishmania donovani-induced hepatic granulomas, as well as their importance in protecting against inflammation-associated tissue damage and the generation of immunity to rechallenge. Finally, we discuss the role that computational, agent-based models may play in answering outstanding questions within the field.

The importance of the macrophage within the human endometrium

The human endometrium is exposed to cyclical fluctuations of ovarian-derived sex steroids resulting in proliferation, differentiation (decidualization), and menstruation. An influx of leukocytes (up to 15% macrophages) occurs during the latter stages of the menstrual cycle, including menses. We believe the endometrial macrophage is likely to play an important role during the menstrual cycle, especially in the context of tissue degradation (menstruation), which requires regulated repair, regeneration, and phagocytic clearance of endometrial tissue debris to re-establish tissue integrity in preparation for fertility. The phenotype and regulation of the macrophage within the endometrium during the menstrual cycle and interactions with other cell types that constitute the endometrium are currently unknown and are important areas of study. Understanding the many roles of the endometrial macrophage is crucial to our body of knowledge concerning functionality of the endometrium as well as to our understanding of disorders of the menstrual cycle, which have major impacts on the health and well-being of women.

Expanded applications, shifting paradigms and an improved understanding of host-biomaterial interactions

The conventional approach to biomaterial design and development typically focuses upon the mechanical and material properties with long-term objectives that include an inert host immune response and long-lasting mechanical and structural support. The emergence of and interest in tissue engineering and regenerative medicine have driven the development of novel cell-friendly biomaterials, materials with tailored degradation rates, materials with highly specific architectures and surfaces, and vehicles for delivery of bioactive molecules, among numerous other advancements. Each of these biomaterial developments supports specific strategies for tissue repair and reconstruction. These advancements in biomaterial form and function, combined with new knowledge of innate and acquired immune system biology, provide an impetus for re-examination of host-biomaterial interactions, including host-biomaterial interface events, spatial and temporal patterns of in vivo biomaterial remodeling, and related downstream functional outcomes. An examination of such issues is provided herein with a particular focus on macrophage polarization and its implications in tissue engineering and regenerative medicine.

Influence of adalimumab treatment on anastomotic strength, degree of inflammation, and collagen formation: an experimental study on the small intestine of rabbits

BACKGROUND

Adalimumab is a TNF-α inhibitor, which has gained wide use in the treatment of inflammatory bowel diseases. The potential detrimental effect of TNF-α inhibitors on postoperative complications such as anastomotic leakage is unknown. The aim of this study was to investigate the effect of a single therapeutic dose of adalimumab on anastomotic strength inflammation and collagen formation.

METHODS

Twenty-eight female rabbits (1.8-2.2 kg) were allocated to subcutaneous injection with either adalimumab (1.5 mg/kg) (n=14) or placebo (n=14). One week after medication two separate end-to-end anastomoses were performed in the jejunum. The rabbits were killed on the third postoperative day. The anastomosis were subjected to tensile strength analysis and histopathological examination.

RESULTS

No statistically significant differences were found between the two groups regarding maximum tensile strength, inflammation parameters and collagen formation in the anastomosis area. Multiple regression analysis showed no association between maximum tensile strength histological changes, time under anaesthesia, duration of surgery, weight gain, weight loss and number of sutures in either group.

CONCLUSION

We found no statistically significant effect of a single therapeutic dose of adalimumab on anastomotic strength, histological parameters or collagen formation in rabbits.

Macrophage plasticity and the role of inflammation in skeletal muscle repair

Effective repair of damaged tissues and organs requires the coordinated action of several cell types, including infiltrating inflammatory cells and resident cells. Recent findings have uncovered a central role for macrophages in the repair of skeletal muscle after acute damage. If damage persists, as in skeletal muscle pathologies such as Duchenne muscular dystrophy (DMD), macrophage infiltration perpetuates and leads to progressive fibrosis, thus exacerbating disease severity. Here we discuss how dynamic changes in macrophage populations and activation states in the damaged muscle tissue contribute to its efficient regeneration. We describe how ordered changes in macrophage polarization, from M1 to M2 subtypes, can differently affect muscle stem cell (satellite cell) functions. Finally, we also highlight some of the new mechanisms underlying macrophage plasticity and briefly discuss the emerging implications of lymphocytes and other inflammatory cell types in normal versus pathological muscle repair.

p53 Regulates the neuronal intrinsic and extrinsic responses affecting the recovery of motor function following spinal cord injury

Following spinal trauma, the limited physiological axonal sprouting that contributes to partial recovery of function is dependent upon the intrinsic properties of neurons as well as the inhibitory glial environment. The transcription factor p53 is involved in DNA repair, cell cycle, cell survival, and axonal outgrowth, suggesting p53 as key modifier of axonal and glial responses influencing functional recovery following spinal injury. Indeed, in a spinal cord dorsal hemisection injury model, we observed a significant impairment in locomotor recovery in p53(-/-) versus wild-type mice. p53(-/-) spinal cords showed an increased number of activated microglia/macrophages and a larger scar at the lesion site. Loss- and gain-of-function experiments suggested p53 as a direct regulator of microglia/macrophages proliferation. At the axonal level, p53(-/-) mice showed a more pronounced dieback of the corticospinal tract (CST) and a decreased sprouting capacity of both CST and spinal serotoninergic fibers. In vivo expression of p53 in the sensorimotor cortex rescued and enhanced the sprouting potential of the CST in p53(-/-) mice, while, similarly, p53 expression in p53(-/-) cultured cortical neurons rescued a defect in neurite outgrowth, suggesting a direct role for p53 in regulating the intrinsic sprouting ability of CNS neurons. In conclusion, we show that p53 plays an important regulatory role at both extrinsic and intrinsic levels affecting the recovery of motor function following spinal cord injury. Therefore, we propose p53 as a novel potential multilevel therapeutic target for spinal cord injury.

Xiamenmycin attenuates hypertrophic scars by suppressing local inflammation and the effects of mechanical stress

Hypertrophic scarring is a common disease affecting millions of people around the world, but there are currently no satisfactory drugs to treat the disease. Exaggerated inflammation and mechanical stress have been shown to be two main mechanisms of excessive fibrotic diseases. Here we found that a benzopyran natural product, xiamenmycin, could significantly attenuate hypertrophic scar formation in a mechanical stretch-induced mouse model. The compound suppressed local inflammation by reducing CD4+ lymphocyte and monocyte/macrophage retention in fibrotic foci and blocked fibroblast adhesion with monocytes. Both in vivo and in vitro studies found that the compound inhibited the mechanical stress-induced profibrotic effects by suppressing proliferation, activation, fibroblast contraction, and inactivating FAK, p38, and Rho guanosine triphosphatase signaling. Taken together, the compound could simultaneously suppress both the inflammatory and mechanical stress responses, which are the two pivotal pathological processes in hypertrophic scar formation, thus suggesting that xiamenmycin can serve as a potential agent for treating hypertrophic scar formation and other excessive fibrotic diseases.

Monocyte subsets in human liver disease show distinct phenotypic and functional characteristics

Liver fibrosis is a wound healing response to chronic liver injury and inflammation in which macrophages and infiltrating monocytes participate in both the development and resolution phase. In humans, three monocyte subsets have been identified: the classical CD14++CD16-, intermediate CD14++CD16+, and nonclassical CD14+CD16++ monocytes. We studied the phenotype and function of these monocyte subsets in peripheral blood and liver tissue from patients with chronic inflammatory and fibrotic liver diseases. The frequency of intrahepatic monocytes increased in disease compared with control liver tissue, and in both nondiseased and diseased livers there was a higher frequency of CD14++CD16+ cells with blood. Our data suggest two nonexclusive mechanisms of CD14++CD16+ accumulation in the inflamed liver: (1) recruitment from blood, because more than twice as many CD14++CD16+ monocytes underwent transendothelial migration through hepatic endothelial cells compared with CD14++CD16- cells; and (2) local differentiation from CD14++CD16- classical monocytes in response to transforming growth factor β and interleukin (IL)-10. Intrahepatic CD14++CD16+ cells expressed both macrophage and dendritic cell markers but showed high levels of phagocytic activity, antigen presentation, and T cell proliferation and secreted proinflammatory (tumor necrosis factor α, IL-6, IL-8, IL-1β) and profibrogenic cytokines (IL-13), chemokines (CCL1, CCL2, CCL3, CCL5), and growth factors (granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor), consistent with a role in the wound healing response.

CONCLUSION

Intermediate CD14++CD16+ monocytes preferentially accumulate in chronically inflamed human liver as a consequence of enhanced recruitment from blood and local differentiation from classical CD14++CD16- monocytes. Their phagocytic potential and ability to secrete inflammatory and profibrogenic cytokines suggests they play an important role in hepatic fibrogenesis.

Glucocorticoids enhance CD163 expression in placental Hofbauer cells

Periplacental levels of glucocorticoid (GC) peak at parturition, and synthetic GC is administered to women at risk for preterm delivery. However, little is known concerning cell-type-specific effects of GC in placenta. Hofbauer cells (HBCs) are fetal macrophages that are located adjacent to fetal capillaries in placenta. The goal of the current study was to determine whether GC treatment altered HBC gene expression and function. Western blotting and flow cytometry revealed CD163 and folate receptor-β (FR-β), markers of antiinflammatory M2 macrophages, were specifically expressed by primary cultures of HBCs immunopurified from human term placentas. GC receptor mRNA and protein levels were higher in HBCs compared with placental fibroblasts. Treatment of HBCs with cortisol or dexamethasone (DEX) markedly and specifically enhanced CD163 protein and mRNA levels, whereas expression of FR-β and CD68 were largely unresponsive to GC treatment. DEX treatment also increased hemoglobin uptake by HBCs, evidence of enhanced HBC function. The level of CD163 mRNA, but not FR-β or CD68 mRNA, was stimulated in placental explant cultures by DEX treatment, and increased CD163/FR-β and CD163/CD68 mRNA ratios sensitively reflected the response to GC. Maternal GC administration was associated with increased CD163/FR-β and CD163/CD68 mRNA ratios in placentas from women with spontaneous preterm birth. In conclusion, in vitro studies indicated that GC treatment specifically up-regulated CD163 expression in HBCs and enhanced HBC function. In addition, the observed alterations in patterns of expression of macrophage marker genes associated with maternal GC administration suggest that HBCs are in vivo targets of GC action.

FOXM1 (Forkhead box M1) in tumorigenesis: overexpression in human cancer, implication in tumorigenesis, oncogenic functions, tumor-suppressive properties, and target of anticancer therapy

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor and is also intimately involved in tumorigenesis. FOXM1 stimulates cell proliferation and cell cycle progression by promoting the entry into S-phase and M-phase. Additionally, FOXM1 is required for proper execution of mitosis. In accordance with its role in stimulation of cell proliferation, FOXM1 exhibits a proliferation-specific expression pattern and its expression is regulated by proliferation and anti-proliferation signals as well as by proto-oncoproteins and tumor suppressors. Since these factors are often mutated, overexpressed, or lost in human cancer, the normal control of the foxm1 expression by them provides the basis for deregulated FOXM1 expression in tumors. Accordingly, FOXM1 is overexpressed in many types of human cancer. FOXM1 is intimately involved in tumorigenesis, because it contributes to oncogenic transformation and participates in tumor initiation, growth, and progression, including positive effects on angiogenesis, migration, invasion, epithelial-mesenchymal transition, metastasis, recruitment of tumor-associated macrophages, tumor-associated lung inflammation, self-renewal capacity of cancer cells, prevention of premature cellular senescence, and chemotherapeutic drug resistance. However, in the context of urethane-induced lung tumorigenesis, FOXM1 has an unexpected tumor suppressor role in endothelial cells because it limits pulmonary inflammation and canonical Wnt signaling in epithelial lung cells, thereby restricting carcinogenesis. Accordingly, FOXM1 plays a role in homologous recombination repair of DNA double-strand breaks and maintenance of genomic stability, that is, prevention of polyploidy and aneuploidy. The implication of FOXM1 in tumorigenesis makes it an attractive target for anticancer therapy, and several antitumor drugs have been reported to decrease FOXM1 expression.

Fibroblast autophagy in fibrotic disorders

Fibrotic disorders are multistage progressive processes that often arise from different causes and are commonly associated with chronic inflammation. Excessive deposition of extracellular matrix is the hallmark of many fibrotic diseases. This may be due to an excess of fibroblast recruitment and activation, as well as to their differentiation in myofibroblasts. These events may be triggered by cytokines, chemokines and growth factors released by lymphocytes or macrophages. The excessive production of extracellular matrix is apparently due to alterations of metabolic pathways in activated fibroblasts. It has been suggested that a defective autophagy, an important subcellular pathway with multiple homeostatic roles, also recognized as a key component of both innate and acquired immunity, could play a role. In this review we illustrate recent insights in the field, suggesting the possible implication of the immune system in orchestrating the fibrotic response via the modulation of autophagic pathways.

TGF-β-responsive myeloid cells suppress type 2 immunity and emphysematous pathology after hookworm infection

Transforming growth factor β (TGF-β) regulates inflammation, immunosuppression, and wound-healing cascades, but it remains unclear whether any of these functions involve regulation of myeloid cell function. The present study demonstrates that selective deletion of TGF-βRII expression in myeloid phagocytes i) impairs macrophage-mediated suppressor activity, ii) increases baseline mRNA expression of proinflammatory chemokines/cytokines in the lung, and iii) enhances type 2 immunity against the hookworm parasite Nippostrongylus brasiliensis. Strikingly, TGF-β-responsive myeloid cells promote repair of hookworm-damaged lung tissue, because LysM(Cre)TGF-βRII(flox/flox) mice develop emphysema more rapidly than wild-type littermate controls. Emphysematous pathology in LysM(Cre)TGF-βRII(flox/flox) mice is characterized by excessive matrix metalloprotease (MMP) activity, reduced lung elasticity, increased total lung capacity, and dysregulated respiration. Thus, TGF-β effects on myeloid cells suppress helminth immunity as a consequence of restoring lung function after infection.

Molecular analysis of the TGF-beta controlled gene expression program in chicken embryo dermal myofibroblasts

The myofibroblast is a mesenchymal cell characterized by synthesis of the extracellular matrix, plus contractile and secretory activities. Myofibroblasts participate in physiological tissue repair, but can also cause devastating fibrosis. They are present in the tumor stroma of carcinomas and contribute to tumor growth and spreading. As myofibroblasts derive from various cell types and appear in a variety of tissues, there is marked variability in their phenotype. As regulatory mechanisms of wound healing are likely conserved among vertebrates, detailed knowledge of these mechanisms in more distant species will help to distinguish general from specific phenomena. To provide this as yet missing comparison, we analyzed the impact of the chemical inhibition of TGF-beta signaling on gene expression in chicken embryo dermal myofibroblasts. We revealed genes previously reported in mammalian systems (e.g. SPON2, ASPN, COMP, LUM, HAS2, IL6, CXCL12, VEGFA) as well as novel TGF-beta dependent genes, among them PGF, VEGFC, PTN, FAM180A, FIBIN, ZIC1, ADCY2, RET, HHIP and DNER. Inhibition of TGF-beta signaling also induced multiple genes, including NPR3, AGTR2, MTUS1, SOD3 and NOV. We also analyzed the effects of long term inhibition, and found that it is not able to induce myofibroblast dedifferentiation.

Differential Ly-6C expression identifies the recruited macrophage phenotype, which orchestrates the regression of murine liver fibrosis

Although macrophages are widely recognized to have a profibrotic role in inflammation, we have used a highly tractable CCl(4)-induced model of reversible hepatic fibrosis to identify and characterize the macrophage phenotype responsible for tissue remodeling: the hitherto elusive restorative macrophage. This CD11B(hi) F4/80(int) Ly-6C(lo) macrophage subset was most abundant in livers during maximal fibrosis resolution and represented the principle matrix metalloproteinase (MMP) -expressing subset. Depletion of this population in CD11B promoter-diphtheria toxin receptor (CD11B-DTR) transgenic mice caused a failure of scar remodeling. Adoptive transfer and in situ labeling experiments showed that these restorative macrophages derive from recruited Ly-6C(hi) monocytes, a common origin with profibrotic Ly-6C(hi) macrophages, indicative of a phenotypic switch in vivo conferring proresolution properties. Microarray profiling of the Ly-6C(lo) subset, compared with Ly-6C(hi) macrophages, showed a phenotype outside the M1/M2 classification, with increased expression of MMPs, growth factors, and phagocytosis-related genes, including Mmp9, Mmp12, insulin-like growth factor 1 (Igf1), and Glycoprotein (transmembrane) nmb (Gpnmb). Confocal microscopy confirmed the postphagocytic nature of restorative macrophages. Furthermore, the restorative macrophage phenotype was recapitulated in vitro by the phagocytosis of cellular debris with associated activation of the ERK signaling cascade. Critically, induced phagocytic behavior in vivo, through administration of liposomes, increased restorative macrophage number and accelerated fibrosis resolution, offering a therapeutic strategy to this orphan pathological process.

Host responses in tissue repair and fibrosis

Myofibroblasts accumulate in the spaces between organ structures and produce extracellular matrix (ECM) proteins, including collagen I. They are the primary "effector" cells in tissue remodeling and fibrosis. Previously, leukocyte progenitors termed fibrocytes and myofibroblasts generated from epithelial cells through epithelial-to-mesenchymal transition (EMT) were considered the primary sources of ECM-producing myofibroblasts in injured tissues. However, genetic fate mapping experiments suggest that mesenchyme-derived cells, known as resident fibroblasts, and pericytes are the primary precursors of scar-forming myofibroblasts, whereas epithelial cells, endothelial cells, and myeloid leukocytes contribute to fibrogenesis predominantly by producing key fibrogenic cytokines and by promoting cell-to-cell communication. Numerous cytokines derived from T cells, macrophages, and other myeloid cell populations are important drivers of myofibroblast differentiation. Monocyte-derived cell populations are key regulators of the fibrotic process: They act as a brake on the processes driving fibrogenesis, and they dismantle and degrade established fibrosis. We discuss the origins, modes of activation, and fate of myofibroblasts in various important fibrotic diseases and describe how manipulation of macrophage activation could help ameliorate fibrosis.

Inhibition of neddylation represses lipopolysaccharide-induced proinflammatory cytokine production in macrophage cells

Cullin-RING E3 ligases (CRLs) are a class of ubiquitin ligases that control the proteasomal degradation of numerous target proteins, including IκB, and the activity of these CRLs are positively regulated by conjugation of a Nedd8 polypeptide onto Cullin proteins in a process called neddylation. CRL-mediated degradation of IκB, which normally interacts with and retains NF-κB in the cytoplasm, permits nuclear translocation and transactivation of the NF-κB transcription factor. Neddylation occurs through a multistep enzymatic process involving Nedd8 activating enzymes, and recent studies have shown that the pharmacological agent, MLN4924, can potently inhibit Nedd8 activating enzymes, thereby preventing neddylation of Cullin proteins and preventing the degradation of CRL target proteins. In macrophages, regulation of NF-κB signaling functions as a primary pathway by which infectious agents such as lipopolysaccharides (LPSs) cause the up-regulation of proinflammatory cytokines. Here we have analyzed the effects of MLN4924, and compared the effects of MLN4924 with a known anti-inflammatory agent (dexamethasone), on certain proinflammatory cytokines (TNF-α and IL-6) and the NF-κB signaling pathway in LPS-stimulated macrophages. We also used siRNA to block neddylation to assess the role of this molecular process during LPS-induced cytokine responsiveness. Our results demonstrate that blocking neddylation, either pharmacologically or using siRNA, abrogates the increase in certain proinflammatory cytokines secreted from macrophages in response to LPS. In addition, we have shown that MLN4924 and dexamethasone inhibit LPS-induced cytokine up-regulation at the transcriptional level, albeit through different molecular mechanisms. Thus, neddylation represents a novel molecular process in macrophages that can be targeted to prevent and/or treat the LPS-induced up-regulation of proinflammatory cytokines and the disease processes associated with their up-regulation.

Extracellular matrix remodeling: the common denominator in connective tissue diseases. Possibilities for evaluation and current understanding of the matrix as more than a passive architecture, but a key player in tissue failure

Increased attention is paid to the structural components of tissues. These components are mostly collagens and various proteoglycans. Emerging evidence suggests that altered components and noncoded modifications of the matrix may be both initiators and drivers of disease, exemplified by excessive tissue remodeling leading to tissue stiffness, as well as by changes in the signaling potential of both intact matrix and fragments thereof. Although tissue structure until recently was viewed as a simple architecture anchoring cells and proteins, this complex grid may contain essential information enabling the maintenance of the structure and normal functioning of tissue. The aims of this review are to (1) discuss the structural components of the matrix and the relevance of their mutations to the pathology of diseases such as fibrosis and cancer, (2) introduce the possibility that post-translational modifications (PTMs), such as protease cleavage, citrullination, cross-linking, nitrosylation, glycosylation, and isomerization, generated during pathology, may be unique, disease-specific biochemical markers, (3) list and review the range of simple enzyme-linked immunosorbent assays (ELISAs) that have been developed for assessing the extracellular matrix (ECM) and detecting abnormal ECM remodeling, and (4) discuss whether some PTMs are the cause or consequence of disease. New evidence clearly suggests that the ECM at some point in the pathogenesis becomes a driver of disease. These pathological modified ECM proteins may allow insights into complicated pathologies in which the end stage is excessive tissue remodeling, and provide unique and more pathology-specific biochemical markers.

Fibronectin-α4β1 interactions in hepatic cold ischemia and reperfusion injury: regulation of MMP-9 and MT1-MMP via the p38 MAPK pathway

Liver ischemia-reperfusion injury (IRI) remains a challenging problem in clinical settings. The expression of fibronectin (FN) by endothelial cells is a prominent feature of the hepatic response to injury. Here we investigate the effects of the connecting segment-1 (CS-1) peptide therapy, which blocks FN-α4β1 integrin leukocyte interactions, in a well-established model of 24-h cold liver IRI. CS-1 peptides significantly inhibited leukocyte recruitment and local release of proinflammatory mediators (COX-2, iNOS and TNF-α), ameliorating liver IRI and improving recipient survival rate. CS1 therapy inhibited the phosphorylation of p38 MAPK, a kinase linked to inflammatory processes. Moreover, in addition to downregulating the expression of matrix metalloproteinase-9 (MMP-9) in hepatic IRI, CS-1 peptide therapy depressed the expression of membrane type 1-matrix metalloproteinase (MT1-MMP/MMP-14) by macrophages, a membrane-tethered MMP important for focal matrix proteolysis. Inhibition of p38 MAPK activity, with its pharmacological antagonist SB203580, downregulated MMP-9 and MT1-MMP/MMP-14 expressions by FN-stimulated macrophages, suggesting that p38 MAPK kinase pathway controls FN-mediated inductions of MMP-9 and MT1-MMP/MMP-14. Hence, this study provides new insights on the role of FN in liver injury, which can potentially be applied to the development of new pharmacological strategies for the successful protection against hepatic IRI.

The TGF-β co-receptor endoglin regulates macrophage infiltration and cytokine production in the irradiated mouse kidney

BACKGROUND AND PURPOSE

We previously showed that mice with reduced levels of the transforming growth factor-beta (TGF-β) co-receptor endoglin (Eng(+/-) mice) develop less fibrosis and vascular damage after kidney irradiation than their wild type (Eng(+/+) mice) littermates; however, the underlying mechanism was unclear. Results from current studies suggest that this occurs via modulation of the radiation-induced inflammatory response.

MATERIALS AND METHODS

Kidneys of Eng(+/+) and Eng(+/-) mice were irradiated with 16Gy. Mice were sacrificed at 20weeks after irradiation and gene expression and protein levels were analyzed.

RESULTS

Kidney irradiation triggered the infiltration of macrophages in both Eng(+/+) and Eng(+/-) mice, however, levels of macrophage-produced cytokines interleukin 1 beta (Il1b) and interleukin 6 (Il6) were reduced in irradiated Eng(+/-) compared to Eng(+/+) mice. Double immuno-stainings confirmed that IL-6 was produced by macrophages, whereas IL-1β was mainly detected in other cell types. Accordingly, inflammatory cell precursors derived from the bone marrow of Eng(+/-) mice showed impaired ability to express Il1b and Il6 compared to wild type mice.

CONCLUSIONS

Endoglin promotes kidney inflammation after irradiation by regulating macrophage infiltration and interleukin production, thereby promoting pathogenic changes after radiation exposure.

Deacetylation of C/EBPβ is required for IL-4-induced arginase-1 expression in murine macrophages

The amount of arginine available at inflammatory loci is a limiting factor for the growth of several cells of the immune system. IL-4-induced activation of macrophages produced arginase-1, which converts arginine into ornithine, a precursor of polyamines and proline. Trichostatin A (TSA), a pan-inhibitor of histone deacetylases (HDACs), inhibited IL-4-induced arginase-1 expression. TSA showed promoter-specific effects on the IL-4-responsive genes. While TSA inhibited the expression of arginase-1, fizz1, and mrc1, other genes, such as ym,1 mgl1, and mgl2, were not affected. The inhibition of arginase-1 occurred at the transcriptional level with the inhibition of polymerase II binding to the promoter. IL-4 induced STAT6 phosphorylation and binding to DNA. These activities were not affected by TSA treatment. However, TSA inhibited C/EBPβ DNA binding. This inhibitor induced acetylation on lysine residues 215-216, which are critical for DNA binding. Finally, using macrophages from STAT6 KO mice we showed that STAT6 is required for the DNA binding of C/EBPβ. These results demonstrate that the acetylation/deacetylation balance strongly influences the expression of arginase-1, a gene of alternative activation of macrophages. These findings also provide a molecular mechanism to explain the control of gene expression through deacetylase activity.

Myeloid cells in tumor inflammation

Bone marrow derived myeloid cells progressively accumulate in tumors, where they establish an inflammatory microenvironment that is favorable for tumor growth and spread. These cells are comprised primarily of monocytic and granulocytic myeloid derived suppressor cells (MDSCs) or tumor-associated macrophages (TAMs), which are generally associated with a poor clinical outcome. MDSCs and TAMs promote tumor progression by stimulating immunosuppression, neovascularization, metastasis and resistance to anti-cancer therapy. Strategies to target the tumor-promoting functions of myeloid cells could provide substantial therapeutic benefit to cancer patients.

Liver fibrosis: a bidirectional model of fibrogenesis and resolution

Liver fibrosis is the generic response to chronic injury of varying aetiologies. A number of common mechanisms link this response to the pathogenesis of fibrosis in other organs. While long thought to be relentlessly progressive, there is now excellent evidence in both human liver disease and animal models that hepatic fibrosis is potentially reversible. The liver therefore provides an excellent bidirectional model for the study of fibrogenesis and fibrosis resolution. In this article, we will review the evidence for the reversibility of liver fibrosis. We will highlight some of the mechanisms responsible for fibrogenesis and fibrosis regression, focussing on the role of hepatic myofibroblast activation and apoptosis, the importance of matrix metalloproteinases and their tissue inhibitors and the central involvement of hepatic macrophages in orchestrating this process. Finally, we will briefly discuss what renders liver fibrosis irreversible and how this accumulating knowledge base could lead to badly needed anti-fibrotic therapies in the future.

Hepatitis C virus (HCV) protein expression enhances hepatic fibrosis in HCV transgenic mice exposed to a fibrogenic agent

BACKGROUND & AIMS

During chronic HCV infection, activation of fibrogenesis appears to be principally related to local inflammation. However, the direct role of hepatic HCV protein expression in fibrogenesis remains unknown.

METHODS

We used transgenic mice expressing the full length HCV open reading frame exposed to a 'second hit' of the fibrogenic agent carbon tetrachloride (CCl(4)). Both acute and chronic liver injuries were induced in these mice by CCl(4) injections. Liver injury, expression of matrix re-modeling genes, reactive oxygen species (ROS), inflammation, hepatocyte proliferation, ductular reaction and hepatic progenitor cells (HPC) expansion were examined.

RESULTS

After CCl(4) treatment, HCV transgenic mice exhibited enhanced liver fibrosis, significant changes in matrix re-modeling genes and increased ROS production compared to wild type littermates despite no differences in the degree of local inflammation. This increase was accompanied by a decrease in hepatocyte proliferation, which appeared to be due to delayed hepatocyte entry into the S phase. A prominent ductular reaction and hepatic progenitor cell compartment expansion were observed in transgenic animals. These observations closely mirror those previously made in HCV-infected individuals.

CONCLUSIONS

Together, these results demonstrate that expression of the HCV proteins in hepatocytes contributes to the development of hepatic fibrosis in the presence of other fibrogenic agents. In the presence of CCl(4), HCV transgenic mice display an intra-hepatic re-organization of several key cellular actors in the fibrogenic process.

Gene expression profiles associated with depression in patients with chronic hepatitis C (CH-C)

The standard treatment for CH-C, pegylated interferon-α and ribavirin (PEG-IFN + RBV), is associated with depression. Recent studies have proposed a new role for cytokines in the pathogenesis of depression. We aimed to assess differential gene expression related to depression in CH-C patients treated with PEG-IFN + RBV. We included 67 CH-C patients being treated with PEG-IFN+RBV. Of the entire study cohort, 22% had pre-existing depression, while another 37% developed new depression in course of the treatment. Pretreatment blood samples were collected into PAXgene™ RNA tubes, the RNAs extracted from peripheral blood mononuclear cells (PBMCs) were used for one step RT-PCR to profile 160 mRNAs. Differentially expressed genes were separated into up- and down-regulated genes according to presence or absence of depression at baseline (pre-existing depression) or following the initiation of treatment (treatment-related depression). The mRNA expression profile associated with any depression and with treatment-related depression included four and six genes, respectively. Our data demonstrate a significant down-regulation of TGF-β1 and the shift of Th1-Th2 cytokine balance in the depression associated with IFN-based treatment of HCV infection. We propose that TGF-β1 plays an important role in the imbalance of Th1/Th2 in patients with CH-C and depression. With further validation, TGF-β1 and other components of Th1/Th2 regulation pathway may provide a future marker for CH-C patients predisposed to depression.

The evolving story of macrophages in acute liver failure

Acute liver failure (ALF) remains a worldwide problem. The innate immune system acts as an important regulator of ALF. Kupffer cells (KCs), the resident macrophages in liver, play a key role in liver innate immune response. Recent researches have shown that macrophages display a remarkable plasticity and can differentiate into functionally diverse subsets. However, the dynamic polarized phenotypes and functional status of macrophages at different stage of ALF are not clear. In this paper, we present a review of evidence that KCs play a significant role in the pathogenesis of ALF, including the phenotype and functions of macrophages, signaling pathways involved in macrophage functional status and cell-crosstalks of KCs with other immune cells. More information on macrophages will promote a better understanding of the cellular molecular mechanisms of ALF and provide new insights for the development of therapeutic targets for ALF.

The role of urokinase plasminogen activator and plasmin activator inhibitor-1 on vein wall remodeling in experimental deep vein thrombosis

OBJECTIVE

Deep vein thrombosis (DVT) resolution instigates an inflammatory response, resulting in vessel wall damage and scarring. Urokinase-plasminogen activator (uPA) and its inhibitor, plasminogen activator inhibitor-1 (PAI-1), are integral components of the fibrinolytic system, essential for venous thrombosis (VT) resolution. This study determined the vein wall response when exposed to increased and decreased plasmin activity.

METHODS

A mouse inferior vena cava (IVC) ligation model in uPA -/- or PAI-1 -/- and their genetic wild types (B6/SvEv and C57/BL6, respectively) was used to create stasis thrombi, with tissue harvest at either 8 or 21 days. Tissue analysis included gene expression of vascular smooth muscle cells (alpha smooth muscle actin [αSMA], SM22) and endothelial marker (CD31), by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, matrix metalloproteinase (MMP)-2 and -9 activity by zymography, and vein wall collagen by picro-Sirius red histologic analysis. A P < .05 was considered significant.

RESULTS

Thrombi were significantly larger in both 8-day and 21-day uPA -/- as compared with wild type (WT) and were significantly smaller in both 8-day and 21-day PAI-1 -/- as compared with WT. Correspondingly, 8-day plasmin levels were reduced in half in uPA -/- and increased three-fold in PAI-1 -/- when compared with respective WT thrombi (P < .05; n = 5-6). The endothelial marker CD31 was elevated two-fold in PAI-1 -/- mice at 8 days, but reduced 2.5-fold at 21 days in uPA -/- as compared with WT (P = .02; n = 5-6), suggesting less endothelial preservation. Vein wall vascular smooth muscle cell (VSMC) gene expression showed that 8-day and 21-day PAI-1 -/- mice had 2.3- and 3.8-fold more SM22 and 1.8- and 2.3-fold more αSMA expression than respective WT (P < .05; n = 5-7), as well as 1.8-fold increased αSMA (+) cells (P ≤ .05; n = 3-5). No significant difference in MMP-2 or -9 activity was found in the PAI-1 -/- mice compared with WT, while 5.4-fold more MMP-9 was present in 21-day WT than 21-day uPA -/- (P = .03; n = 5). Lastly, collagen was ∼two-fold greater at 8 days in PAI-1 -/- IVC as compared with WT (P = .03; n = 6) with no differences observed in uPA -/- mice.

CONCLUSIONS

In stasis DVT, plasmin activity is critical for thrombus resolution. Divergent vein wall responses occur with gain or loss of plasmin activity, and despite smaller VT, greater vein wall fibrosis was associated with lack of PAI-1.

Mechanisms of fibrosis: therapeutic translation for fibrotic disease

Fibrosis is a pathological feature of most chronic inflammatory diseases. Fibrosis, or scarring, is defined by the accumulation of excess extracellular matrix components. If highly progressive, the fibrotic process eventually leads to organ malfunction and death. Fibrosis affects nearly every tissue in the body. Here we discuss how key components of the innate and adaptive immune response contribute to the pathogenesis of fibrosis. We also describe how cell-intrinsic changes in important structural cells can perpetuate the fibrotic response by regulating the differentiation, recruitment, proliferation and activation of extracellular matrix-producing myofibroblasts. Finally, we highlight some of the key mechanisms and pathways of fibrosis that are being targeted as potential therapies for a variety of important human diseases.

Mechanisms of fibrosis: therapeutic translation for fibrotic disease

Fibrosis is a pathological feature of most chronic inflammatory diseases. Fibrosis, or scarring, is defined by the accumulation of excess extracellular matrix components. If highly progressive, the fibrotic process eventually leads to organ malfunction and death. Fibrosis affects nearly every tissue in the body. Here we discuss how key components of the innate and adaptive immune response contribute to the pathogenesis of fibrosis. We also describe how cell-intrinsic changes in important structural cells can perpetuate the fibrotic response by regulating the differentiation, recruitment, proliferation and activation of extracellular matrix-producing myofibroblasts. Finally, we highlight some of the key mechanisms and pathways of fibrosis that are being targeted as potential therapies for a variety of important human diseases.

In vivo targeting of alveolar macrophages via RAFT-based glycopolymers

Targeting cell populations via endogenous carbohydrate receptors is an appealing approach for drug delivery. However, to be effective, this strategy requires the production of high affinity carbohydrate ligands capable of engaging with specific cell-surface lectins. To develop materials that exhibit high affinity towards these receptors, we synthesized glycopolymers displaying pendent carbohydrate moieties from carbohydrate-functionalized monomer precursors via reversible addition-fragmentation chain transfer (RAFT) polymerization. These glycopolymers were fluorescently labeled and used to determine macrophage-specific targeting both in vitro and in vivo. Mannose- and N-acetylglucosamine-containing glycopolymers were shown to specifically target mouse bone marrow-derived macrophages (BMDMs) in vitro in a dose-dependent manner as compared to a galactose-containing glycopolymer (30- and 19-fold higher uptake, respectively). In addition, upon macrophage differentiation, the mannose glycopolymer exhibited enhanced uptake in M2-polarized macrophages, an anti-inflammatory macrophage phenotype prevalent in injured tissue. This carbohydrate-specific uptake was retained in vivo, as alveolar macrophages demonstrated 6-fold higher internalization of mannose glycopolymer, as compared to galactose, following intratracheal administration in mice. We have shown the successful synthesis of a class of functional RAFT glycopolymers capable of macrophage-type specific uptake both in vitro and in vivo, with significant implications for the design of future targeted drug delivery systems.

Interleukin-12p35 Deletion Promotes CD4 T-Cell–Dependent Macrophage Differentiation and Enhances Angiotensin II–Induced Cardiac Fibrosis

Objective—

Interleukin-12 is essential for the differentiation of naïve T cells into interferon-γ–producing T cells, which regulate inflammatory responses. We investigated this process of regulating hypertension-induced cardiac fibrosis.

Methods and Results—

Mice infused with angiotensin II showed a marked increase in interleukin-12p35 expression in cardiac macrophages. The degree of cardiac fibrosis was significantly enhanced in interleukin-12p35 knockout (p35-KO) mice compared with wild-type (WT) littermates in response to angiotensin II. Fibrotic hearts of p35-KO mice showed increased accumulation of alternatively activated (M2) macrophages and expression of M2 genes such as Arg-1 and Fizz1. Bone marrow–derived macrophages from WT or p35-KO mice did not differ in differentiation in response to angiotensin II treatment; however, in the presence of CD4 + T cells, macrophages from p35-KO mice differentiated into M2 macrophages and showed elevated expression of transforming growth factor-β. Moreover, CD4 + T-cell–treated p35-KO macrophages could stimulate cardiac fibroblasts to differentiate into α-smooth muscle actin–positive and collagen I–positive myofibroblasts in 3-dimensional nanofiber gels. Neutralizing antibodies against transforming growth factor-β inhibited myofibroblast formation induced by M2 macrophages.

Conclusion—

Deficiency in interleukin-12p35 regulates angiotensin II–induced cardiac fibrosis by promoting CD4 + T-cell–dependent differentiation of M2 macrophages and production of transforming growth factor-β.

Human amniotic epithelial cell transplantation induces markers of alternative macrophage activation and reduces established hepatic fibrosis

Chronic hepatic inflammation from multiple etiologies leads to a fibrogenic response that can progress to cirrhosis and liver failure. Transplantation of human amniotic epithelial cells (hAEC) from term delivered placenta has been shown to decrease mild to moderate hepatic fibrosis in a murine model. To model advanced human liver disease and assess the efficacy of hAEC therapy, we transplanted hAEC in mice with advanced hepatic fibrosis. Immunocompetent C57BL/6 mice were administered carbon tetrachloride (CCl₄) twice weekly resulting in bridging fibrosis by 12 weeks. hAEC (2×10⁶) were infused via the tail vein at week 8 or weeks 8 and 10 (single and double dose, respectively). Human cells were detected in mouse liver four weeks after transplantation showing hAEC engraftment. CCl₄ treated mice receiving single or double hAEC doses showed a significant but similar decrease in liver fibrosis area associated with decreased activation of collagen-producing hepatic stellate cells and decreased hepatic protein levels of the pro-fibrogenic cytokine, transforming growth factor-beta1. CCl₄ administration caused hepatic T cell infiltration that decreased significantly following hAEC transplantation. Hepatic macrophages play a crucial role in both fibrogenesis and fibrosis resolution. Mice exposed to CCl₄ demonstrated increased numbers of hepatic macrophages compared to normal mice; the number of macrophages decreased significantly in CCl₄ treated mice given hAEC. These mice had significantly lower hepatic protein levels of the chemokine monocyte chemoattractant protein-1 than mice given CCl₄ alone. Alternatively activated M2 macrophages are associated with fibrosis resolution. CCl₄ treated mice given hAEC showed increased expression of genes associated with M2 macrophages including YM-1, IL-10 and CD206. We provide novel data showing that hAEC transplantation induces a wound healing M2 macrophage phenotype associated with reduction of established hepatic fibrosis that justifies further investigation of this potential cell-based therapy for advanced hepatic fibrosis.

IgG4-Related Fibrotic Diseases from an Immunological Perspective: Regulators out of Control?

Patients with autoimmune pancreatitis have a striking polyclonal elevation of total IgG4 in serum. This observation has been confirmed and extended to other fibrotic conditions (that are therefore called IgG4-related disease) but as yet remains unexplained. The affected tissue contains many IgG4-producing plasma cells embedded in a fibrotic matrix originating from activated mesenchymal (stellate) cells. We propose that the process results from an unusual interaction between two regulatory systems: the regulatory arm of the immune system (including Bregs) and the tissue repair regulatory components orchestrated by the activated stellate cell. This interaction results in ongoing mutual activation, generating TGFbeta, IL10, and vitamin D. This environment suppresses most immune reactions but stimulates the development of IgG4-producing plasma cells.

Tissue-specific differences in inflammatory infiltrate and matrix metalloproteinase expression in adipose tissue and liver of mice with diet-induced obesity

AIM

  While low grade inflammation persists in both visceral fat and hepatic tissue in obesity, these changes often result in progressive disease and fibrosis only in the liver and not in adipose tissue. We hypothesized that a tissue-specific difference in obesity-induced inflammatory cell infiltrate may be responsible for such organ difference in susceptibility to fibrosis.

METHODS

  Mice were fed either standard chow or a high fat diet over 19 weeks. Hepatic steatosis was assessed by histology and quantified via magnetic resonance spectroscopy. Immunohistochemistry staining for macrophage subsets and quantitative reverse transcription-polymerase chain reaction for matrix metalloproteinase (MMP)- and fibrosis-related gene expression was performed in paired livers and visceral (epididymal) fat pads at early (9 weeks) and advanced (19 weeks) stages of progressive diet-induced obesity.

RESULTS

  Up to 19 weeks of high fat feeding led to the development of obesity and hepatic steatosis, as well as increased gene expression of Mmp12, Mmp13 and Timp1 in predominantly adipose tissue, and to a lesser extent of liver tissue. In contrast to visceral fat, cell counts for macrophages as well as profibrogenic gene signaling in liver tissue during development of diet-induced obesity remained largely unchanged.

CONCLUSIONS

  Development of diet-induced obesity in the mouse increased inflammatory macrophages counts in adipose tissue rather than the liver. This was associated with greater increases in MMP expression in adipose tissue compared with liver. We propose that attenuated hepatic MMP expression in livers and adipose tissue of obese mice shifts the balance of fibrogenesis/fibrolysis and predispose the liver to development of fibrosis.

PEGylation of interleukin-10 improves the pharmacokinetic profile and enhances the antifibrotic effectivity in CCl₄-induced fibrogenesis in mice

Liver fibrosis represents a scar formation process as a response to chronic injury and a major cause of death worldwide. To date, no drug is available for this condition. Interleukin-10 (IL-10) has potent anti-inflammatory and antifibrotic properties but its short half-life in the circulation hampers its clinical use. Our aim was therefore to modify IL-10 with polyethylene glycol (PEG) to prolong its circulation time and enhance its effectivity. IL-10 was modified with 5 or 20 kDa PEG. The biological activity was preserved after PEGylation as assessed by inhibition of TNF-α production by macrophages. In vivo, during CCl(4)-induced fibrogenesis in mice, both 5PEG-IL-10 and 20PEG-IL-10 showed a longer circulation time compared to IL-10, which was associated with a significant increased liver accumulation. Immunohistochemical analysis of fibrotic livers of mice receiving treatment with IL-10 or its PEGylated forms, revealed a decrease in markers reflecting HSC and KC activation induced by 5PEG-IL10. Transcription levels of IL-6 were decreased upon treatment with IL-10 and both PEGylated forms, whereas IL-1β levels were only down-regulated by 5PEGIL-10 and 20PEGIL-10. We conclude that PEGylation of IL-10 is a good strategy to attenuate liver fibrosis and that 5PEGIL-10 is the most effective conjugate.

Macrophage polarization: an opportunity for improved outcomes in biomaterials and regenerative medicine

The host response to biomaterials has been studied for decades. Largely, the interaction of host immune cells, macrophages in particular, with implanted materials has been considered to be a precursor to granulation tissue formation, the classic foreign body reaction, and eventual encapsulation with associated negative impacts upon device functionality. However, more recently, it has been shown that macrophages, depending upon context dependent polarization profiles, are capable of affecting both detrimental and beneficial outcomes in a number of disease processes and in tissue remodeling following injury. Herein, the diverse roles played by macrophages in these processes are discussed in addition to the potential manipulation of macrophage effector mechanisms as a strategy for promoting site-appropriate and constructive tissue remodeling as opposed to deleterious persistent inflammation and scar tissue formation.

Perioperative betamethasone treatment reduces signs of bladder dysfunction in a rat model for neurapraxia in female urogenital surgery

BACKGROUND

Information on autonomic neurapraxia in female urogenital surgery is scarce, and a model to study it is not available.

OBJECTIVE

To develop a model to study the impact of autonomic neurapraxia on bladder function in female rats, as well as to assess the effects of corticosteroid therapy on the recovery of bladder function in this model.

DESIGN, SETTING, AND PARTICIPANTS

Female Sprague-Dawley rats were subjected to bilateral pelvic nerve crush (PNC) and perioperatively treated with betamethasone or vehicle. Bladder function and morphology of bladder tissue were evaluated and compared with sham-operated rats.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Western blot, immunohistochemistry, organ bath experiments, and cystometry.

RESULTS AND LIMITATIONS

Sham-operated rats exhibited regular micturitions without nonvoiding contractions (NVCs). Crush of all nerve branches of the pelvic plexus or PNC resulted in overflow incontinence and/or NVCs. Betamethasone treatment improved recovery of regular micturitions (87.5% compared with 27% for vehicle; p<0.05), reduced lowest bladder pressure (8 ± 2 cm H(2)O compared with 21 ± 5 cm H(2)O for vehicle; p<0.05), and reduced the amplitude of NVCs but had no effect on NVC frequency in PNC rats. Compared with vehicle, betamethasone-treated PNC rats had less CD68 (a macrophage marker) in the pelvic plexus and bladder tissue. Isolated bladder from betamethasone-treated PNC rats exhibited better nerve-induced contractions, contained more cholinergic and sensory nerves, and expressed lower amounts of collagen III than bladder tissue from vehicle-treated rats.

CONCLUSIONS

PNC causes autonomic neurapraxia and functional and morphologic changes of isolated bladder tissue that can be recorded as bladder dysfunction during awake cystometry in female rats. Perioperative systemic betamethasone treatment reduced macrophage contents of the pelvic plexus and bladder, partially counteracted changes in the bladder tissue, and had protective effects on micturition function.

Electrical stimulation improves peripheral nerve regeneration in streptozotocin-induced diabetic rats

We discuss if percutaneous electrical stimulation (ES) at 1 mA and 2 Hz after peripheral nerve transection could enhance axonal regeneration and functional recovery in diabetic animals.

METHODS

Four groups of adult rats (group A: normal rats; group B: normal rats with ES; group C: streptozotocin- induced diabetic rats; and group D: streptozotocin-induced diabetic rats with ES) were subjected to sciatic nerve section followed by repair using silicone rubber conduits across a 10-mm gap. Rats in groups B and D received ES for 15 minutes every other day for three weeks. The groups A and C received no ES.

RESULTS

At four weeks after surgery in groups B and D, immunohistochemical staining showed that lamina I and II regions in the dorsal horn ipsilateral to the injury were significantly calcitonin gene-related peptide-immunolabeled, and a significantly higher number of macrophages were recruited in the distal sciatic nerve compared with group C. In groups A, B, and D, electrophysiological results showed higher levels of reinnervation with significantly shorter latencies and faster nerve conductive velocities, and the histologic evaluations showed relatively larger mean values of myelinated axon densities and endoneurial areas compared with group C.

CONCLUSIONS

Thus, the ES may improve the recovery of a severe peripheral nerve injury in diabetic animals, which could be considered as a supplementary treatment in diabetic neurotrauma.

Cellular and molecular mechanisms of chronic inflammation-associated organ fibrosis

Organ fibrosis is a pathological condition associated with chronic inflammatory diseases. In fibrosis, excessive deposition of extracellular matrix (ECM) severely impairs tissue architecture and function, eventually resulting in organ failure. This process is mediated primarily by the induction of myofibroblasts, which produce large amounts of collagen I, the main component of the ECM. Accordingly, the origin, developmental pathways, and mechanisms of myofibroblast regulation are attracting increasing attention as potential therapeutic targets. The fibrotic cascade, from initial epithelial damage to eventual myofibroblast induction, is mediated by complex biological processes such as macrophage infiltration, a shift from Th1 to Th2 phenotype, and by inflammatory mediators such as transforming growth factor-β. Here, we review the current understanding of the cellular and molecular mechanisms underlying organ fibrosis.

Hepatitis B virus particles preferably induce Kupffer cells to produce TGF-β1 over pro-inflammatory cytokines

BACKGROUND

Kupffer cells and related cytokines are thought to play a critical role in liver fibrosis; however, the role played by Kupffer cells in hepatitis B virus-related fibrogenesis is unknown.

METHODS

Primary rat Kupffer cells were cultured with different titres of hepatitis B virus particles and the concentrations of transforming growth factor (TGF)-β1, interleukin (IL)-1, IL-6 and tumour necrosis factor (TNF)-α in the culture supernatant were measured every 24h for 7 days. The mRNA and protein levels of these cytokines in Kupffer cells were also analysed using quantitative real-time polymerase chain reaction and western blotting, respectively.

RESULTS

Kupffer cells maintained normal morphology and function throughout the 7-day exposure to hepatitis B virus. The concentration of TGF-β1 secreted by hepatitis B virus-stimulated Kupffer cells (6 log IU/ml hepatitis B virus) increased 5.38- and 7.75-fold by Days 3 and 7, respectively (p<0.01). Western blotting showed that TGF-β1 expression in Kupffer cells exposed to high titres of hepatitis B virus increased 1.80- and 2.42-fold by Days 3 and 7, respectively (p<0.01). In contrast, Kupffer cell expression and secretion of pro-inflammatory cytokines (IL-6, IL-1 and TNF-α) was unchanged throughout the experiment.

CONCLUSION

Hepatitis B virus preferentially stimulates Kupffer cells to produce the pro-fibrogenic/anti-inflammatory cytokine TGF-β1 rather than the pro-inflammatory cytokines IL-6, IL-1 and TNF-α. This may partly explain why overt liver fibrosis still presents in cases of chronic hepatitis B virus infection with minimal (or no) necro-inflammation.

Identification and characterization of an anti-fibrotic benzopyran compound isolated from mangrove-derived Streptomyces xiamenensis

An anti-fibrotic compound produced by Streptomycesn xiamenensis, found in mangrove sediments, was investigated for possible therapeutic effects against fibrosis. The compound, N-[[3,4-dihydro-3S-hydroxy-2S-methyl-2-(4′R-methyl-3′S-pentenyl)-2H-1-benzopyran-6-yl]carbonyl]-threonine (1), was isolated from crude extracts and its structure, including the absolute configuration was determined by extensive spectroscopic data analyses, Mosher’s method, Marfey’s reagent and quantum mechanical calculations. In terms of biological effects, this compound inhibits the proliferation of human lung fibroblasts (WI26), blocks adhesion of human acute monocytic leukemia cells (THP-1) to a monolayer of WI26 cells, and reduces the contractile capacity of WI26 cells in three-dimensional free-floating collagen gels. Altogether, these data indicate that we have identified a bioactive alkaloid (1) with multiple inhibitory biological effects on lung excessive fibrotic characteristics, that are likely involved in fibrosis, suggesting that this molecule might indeed have therapeutic potential against fibrosis.

LPS counter regulates RNA expression of extracellular proteases and their inhibitors in murine macrophages

Besides their evident importance in host defense, macrophages have been shown to play a detrimental role in different pathological conditions, including chronic inflammation, atherosclerosis, and cancer. Regardless of the exact situation, macrophage activation and migration are intimately connected to extracellular matrix degradation. This process is accomplished by multiple proteolytic enzymes, including serine proteases and members of the matrix metalloproteinase family. In this study, we have utilized qPCR arrays to simultaneously analyze the temporal expression pattern of a range of genes involved in extracellular matrix metabolism in the mouse derived-macrophage cell line RAW 264.7 following stimulation with LPS. Our results revealed that LPS induces the expression of matrix metalloproteinases while at the same time decreased the expression of matrix metalloproteinase inhibitors. The opposite scenario was found for the genes encoding serine proteases, which were downregulated while their inhibitors were upregulated. In addition, intergenic comparison of the expression levels of related proteases revealed large differences in their basal expression level. These data highlight the complexity of the gene expression regulation implicated in macrophage-dependent matrix degradation and furthermore emphasize the value of qPCR array techniques for the investigation of the complex regulation of the matrix degradome.