Fibroblasts as sentinel cells: role of the CDcd40-CDcd40 ligand system in fibroblast activation and lung inflammation and fibrosis

High-Fat Diet Related Lung Fibrosis-Epigenetic Regulation Matters

Pulmonary fibrosis (PF) is an interstitial lung disease characterized by the destruction of the pulmonary parenchyma caused by excessive extracellular matrix deposition. Despite the well-known etiological factors such as senescence, aberrant epithelial cell and fibroblast activation, and chronic inflammation, PF has recently been recognized as a metabolic disease and abnormal lipid signature was observed both in serum and bronchoalveolar lavage fluid (BALF) of PF patients and mice PF model. Clinically, observational studies suggest a significant link between high-fat diet (HFD) and PF as manifested by high intake of saturated fatty acids (SFAs) and meat increases the risk of PF and mice lung fibrosis. However, the possible mechanisms between HFD and PF remain unclear. In the current review we emphasize the diversity effects of the epigenetic dysregulation induced by HFD on the fibrotic factors such as epithelial cell injury, abnormal fibroblast activation and chronic inflammation. Finally, we discuss the potential ways for patients to improve their conditions and emphasize the prospect of targeted therapy based on epigenetic regulation for scientific researchers or drug developers.

Understanding Inflammation-associated Ophthalmic Pathologies: A Novel 3D Co-culture Model of Monocyte-myofibroblast Immunomodulation

PURPOSE

Inflammation is associated with, and may be causal of, a variety of ophthalmic pathologies. These pathologies are currently difficult to model in vitro because they involve complex interactions between the innate immune system, stromal cells, and other cells that normally maintain ocular tissue homeostasis. Using transscleral drainage channel fibrosis after glaucoma surgery as an example of inflammation-associated ocular fibrosis, we have assessed a simple but novel 3D cell culture system designed to reveal the immunomodulatory impacts of ocular connective tissue cells on monocytes, a major cellular component of the circulating immune system.

METHODS

Primary human Tenon's capsule fibroblasts derived from five unrelated patients were activated into myofibroblasts in 3D collagen matrices under isometric tension, with and without exposure to an inflammatory cytokine-enhanced milieu, and co-cultured with an immortalized human monocyte cell line (THP-1 cells). Quantitative PCR analyses were performed on 8 candidate genes to assess the impacts of inflammatory cytokines on the myofibroblasts and the monocytes in mono-cultures and compared to cells in co-culture to clearly distinguish any co-culture-induced impacts on gene expression.

RESULTS

Our data indicate that both Tenon's capsule myofibroblasts in 3D mono-culture and THP-1 monocytes in suspension mono-culture were responsive to inflammatory cytokine stimuli. Co-culture with Tenon's capsule myofibroblasts significantly modulated the gene expression responses of THP-1 monocytes to inflammatory cytokine stimulation, indicative of an immunomodulatory "feedback" system between these cell types.

CONCLUSION

Our findings provide proof of principle for the use of simple 3D co-culture systems as a means to enhance our understanding of ocular stromal cell interactions with cells of the innate immune system and to provide more informative in vitro models of inflammation-associated ophthalmic pathologies.

Dedicator of Cytokinesis 2 (DOCK2) Deficiency Attenuates Lung Injury Associated with Chronic High-Fat and High-Fructose Diet-Induced Obesity

Obesity is a major risk factor for lung disease development. However, little is known about the impact of chronic high-fat and high-fructose (HFHF) diet-induced obesity on lung inflammation and subsequent pulmonary fibrosis. Herein we hypothesized that dedicator of cytokinesis 2 (DOCK2) promotes a proinflammatory phenotype of lung fibroblasts (LFs) to elicit lung injury and fibrosis in chronic HFHF diet-induced obesity. An HFHF diet for 20 weeks induced lung inflammation and profibrotic changes in wild-type C57BL/6 mice. CD68 and monocyte chemoattractant protein-1 (MCP-1) expression were notably increased in the lungs of wild-type mice fed an HFHF diet. An HFHF diet further increased lung DOCK2 expression that co-localized with fibroblast-specific protein 1, suggesting a role of DOCK2 in regulating proinflammatory phenotype of LFs. Importantly, DOCK2 knockout protected mice from lung inflammation and fibrosis induced by a HFHF diet. In primary human LFs, tumor necrosis factor-α (TNF-α) and IL-1β induced DOCK2 expression concurrent with MCP-1, IL-6, and matrix metallopeptidase 2. DOCK2 knockdown suppressed TNF-α-induced expression of these molecules and activation of phosphatidylinositol 3-kinase/AKT and NF-κB signaling pathways, suggesting a mechanism of DOCK2-mediated proinflammatory and profibrotic changes in human LFs. Taken together, these findings reveal a previously unrecognized role of DOCK2 in regulating proinflammatory phenotype of LFs, potentiation of lung inflammation, and pulmonary fibrosis in chronic HFHF diet-caused obesity.

Inflammatory Immune Responses Trigger Rejection of Allogeneic Fibroblasts Transplanted into Mouse Skin

Fibroblasts, or their homolog stromal cells, are present in most tissues and play an essential role in tissue homeostasis and regeneration. As a result, fibroblast-based strategies have been widely employed in tissue engineering. However, while considered to have immunosuppressive properties, the survival and functionality of allogeneic fibroblasts after transplantation remain controversial. Here, we evaluated innate and adaptive immune responses against allogeneic fibroblasts following intradermal injection into different immune-deficient mouse strains. While allogeneic fibroblasts were rejected 1 week after transplantation in immunocompetent mice, rejection did not occur in immunodeficient γ chain–deficient NOD-SCID (NSG) mice. T-cell- and B-cell-deficient RAG1 knockout mice showed greater loss of fibroblasts by day 5 after transplantation compared with NSG mice (P ≤ 0.05) but prolonged persistence compared with wild-type recipient (P ≤ 0.005). Loss of fibroblasts correlated with the expression of proinflammatory chemokine genes and infiltration of myeloid cells in the transplantation site. Depletion of macrophages and neutrophils delayed rejection, revealing the role of innate immune cells in an early elimination of fibroblasts that is followed by T-cell-mediated rejection in the second week. These findings indicate that the application of allogeneic fibroblasts in tissue engineering products requires further improvements to overcome cell rejection by innate and adaptive immune cells.

Associations of Benzo(ghi)perylene and Heptachlorodibenzo-p-dioxin in Serum of Service Personnel Deployed to Balad, Iraq, and Bagram, Afghanistan Correlates With Perturbed Amino Acid Metabolism in Human Lung Fibroblasts

OBJECTIVE

A study was conducted to identify metabolic-related effects of benzo(ghi)perylene (BghiP) and 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD), on primary human fibroblasts to verify biological associations previously found in occupational health research.

METHODS

Human lung fibroblasts were exposed to BghiP or HpCDD and extracts were analyzed with a metabolome-wide association study to test for pathways and metabolites altered relative to controls. Gene expression was measured by quantitative-real time polymerase chain reaction.

RESULTS

Metabolic perturbations in amino-acid, oxidative stress, and fatty-acid pathways were observed for BghiP and HpCDD. HpCDD but not BghiP exposure increased gene expression of the amino acid transporters SLC7A5 and SLC7A11.

CONCLUSIONS

Exposure to polycyclic aromatic hydrocarbons (PAH) or dioxins perturbs amino acid pathways at physiologically relevant concentrations with different mechanisms. These findings imply an effect on central homeostatic systems by environmental exposures which could have implications on disease susceptibility.

Activated Human Lung Fibroblasts Produce Extracellular Vesicles with Antifibrotic Prostaglandins

The differentiation of interstitial lung fibroblasts into contractile myofibroblasts that proliferate and secrete excessive extracellular matrix is critical for the pathogenesis of pulmonary fibrosis. Certain lipid signaling molecules, such as prostaglandins (PGs), can inhibit myofibroblast differentiation. However, the sources and delivery mechanisms of endogenous PGs are undefined. Activated primary human lung fibroblasts (HLFs) produce PGs such as PGE₂. We report that activation of primary HLFs with IL-1β inhibited transforming growth factor β-induced myofibroblast differentiation in both the IL-1β-treated cells themselves (autocrine signal) and adjacent naive HLFs in cocultures (paracrine signal). Additionally, we demonstrate for the first time that at least some of the antifibrotic effect of activated fibroblasts on nearby naive fibroblasts is carried by exosomes and other extracellular vesicles that contain several PGs, including high levels of the antifibrotic PGE₂. Thus, activated fibroblasts communicate with surrounding cells to limit myofibroblast differentiation and maintain homeostasis. This work opens the way for future research into extracellular vesicle-mediated intercellular signaling in the lung and may inform the development of novel therapies for fibrotic lung diseases.

Trained Immunity Carried by Non-immune Cells

“Trained immunity” is a term proposed by Netea to describe the ability of an organism to develop an exacerbated immunological response to protect against a second infection independent of the adaptative immunity. This immunological memory can last from 1 week to several months and is only described in innate immune cells such as monocytes, macrophages, and natural killer cells. Paradoxically, the lifespan of these cells in the blood is shorter than the duration of trained immunity. This observation suggested that trained immunity could be carried by long lifespan cells such as stem cells and non-immune cells like fibroblasts. It is now evident that in addition to performing their putative function in the development and maintenance of tissue homeostasis, non-immune cells also play an important role in the response to pathogens by producing anti-microbial factors, with long-term inflammation suggesting that non-immune cells can be trained to confer long-lasting immunological memory. This review provides a summary of the current relevant knowledge about the cells which possess immunological memory and discusses the possibility that non-immune cells may carry immunological memory and mechanisms that might be involved.

Human lung fibroblasts produce proresolving peroxisome proliferator-activated receptor-γ ligands in a cyclooxygenase-2-dependent manner

Human lung fibroblasts (HLFs) act as innate immune sentinel cells that amplify the inflammatory response to injurious stimuli. Here, we use targeted lipidomics to explore the hypothesis that HLFs also play an active role in the resolution of inflammation. We detected cyclooxygenase-2 (COX-2)-dependent production of both proinflammatory and proresolving prostaglandins (PGs) in conditioned culture medium from HLFs treated with a proinflammatory stimulus, IL-1β. Among the proresolving PGs in the HLF lipidome were several known ligands for peroxisome proliferator-activated receptor-γ (PPARγ), a transcription factor whose activation in the lung yields potent anti-inflammatory, antifibrotic, and proresolving effects. Next, we used a cell-based luciferase reporter to confirm the ability of HLF supernatants to activate PPARγ, demonstrating, for the first time, that primary HLFs activated with proinflammatory IL-1β or cigarette smoke extract produce functional PPARγ ligands; this phenomenon is temporally regulated, COX-2- and lipocalin-type PGD synthase-dependent, and enhanced by arachidonic acid supplementation. Finally, we used luciferase reporter assays to show that several of the PGs in the lipidome of activated HLFs independently activate PPARγ and/or inhibit NFκB. These results indicate that HLFs, as immune sentinels, regulate both proinflammatory and proresolving responses to injurious stimuli. This novel endogenous resolution pathway represents a new therapeutic target for globally important inflammatory diseases such as chronic obstructive pulmonary disease.

Metabolic reprogramming and inflammation act in concert to control vascular remodeling in hypoxic pulmonary hypertension

Pulmonary hypertension (PH) is a complex, multifactorial syndrome that remains poorly understood despite decades of research. PH is characterized by profound pulmonary artery (PA) remodeling that includes significant fibro-proliferative and inflammatory changes of the PA adventitia. In line with the emerging concept that PH shares key features with cancer, recent work centers on the idea that PH results from a multistep process driven by reprogramming of gene-expression patterns that govern changes in cell metabolism, inflammation, and proliferation. Data demonstrate that in addition to PA endothelial cells and smooth muscle cells, adventitial fibroblasts from animals with experimental hypoxic PH and from humans with PH (hereafter, termed PH-Fibs) exhibit proinflammatory activation, increased proliferation, and apoptosis resistance, all in the context of metabolic reprogramming to aerobic glycolysis. PH-Fibs can also recruit, retain, and activate naïve macrophages (Mϕ) toward a proinflammatory/proremodeling phenotype through secretion of chemokines, cytokines, and glycolytic metabolites, among which IL-6 and lactate play key roles. Furthermore, these fibroblast-activated Mϕ (hereafter, termed FAMϕ) exhibit aerobic glycolysis together with high expression of arginase 1, Vegfa, and I1lb, all of which require hypoxia-inducible factor 1α and STAT3 signaling. Strikingly, in situ, the adventitial Mϕ phenotype in the remodeled PA closely resembles the Mϕ phenotype induced by fibroblasts in vitro (FAMϕ), suggesting that FAMϕ crosstalk involving metabolic and inflammatory signals is a critical, pathogenetic component of vascular remodeling. This review discusses metabolic and inflammatory changes in fibroblasts and Mϕ in PH with the goal of raising ideas about new interventions to abrogate remodeling in hypoxic forms of PH.

Role of hypoxia-inducible factor 1, α subunit and cAMP-response element binding protein 1 in synergistic release of interleukin 8 by prostaglandin E2 and nickel in lung fibroblasts

Numerous epidemiological studies have linked exposure to particulate matter (PM) air pollution with acute respiratory infection and chronic respiratory and cardiovascular diseases. We have previously shown that soluble nickel (Ni), a common component of PM, alters the release of CXC chemokines from cultured human lung fibroblasts (HLF) in response to microbial stimuli via a pathway dependent on disrupted prostaglandin (PG)E2 signaling. The current study sought to identify the molecular events underlying Ni-induced alterations in PGE2 signaling and its effects on IL-8 production. PGE2 synergistically enhances Ni-induced IL-8 release from HLF in a concentration-dependent manner. The effects of PGE2 were mimicked by butaprost and PGE1-alcohol and inhibited with antagonists AH6809 and L-161,982, indicating PGE2 signals via PGE2 receptors 2 and 4. PGE2 and forskolin stimulated cAMP, but it was only in the presence of Ni-induced hypoxia-inducible factor 1, α subunit (HIF1A) that these agents stimulated IL-8 release. The Ni-induced HIF1A DNA binding was enhanced by PGE2 and mediated, in part, by activation of p38 MAPK. Negation of cAMP-response element binding protein 1 or HIF1A using short interfering RNA blocked the synergistic interactions between Ni and PGE2. The results of the current study provide novel information on the ability of atmospheric hypoxia-mimetic metals to disrupt the release of immune-modulating chemokines by HLF in response to PGE2. Moreover, in the presence of HIF1A, cAMP-mediated signaling pathways may be altered to exacerbate inflammatory-like processes in lung tissue, imparting a susceptibility of PM-exposed populations to adverse respiratory health effects.

Molecular and cellular mechanisms of pulmonary fibrosis

Pulmonary fibrosis is a chronic lung disease characterized by excessive accumulation of extracellular matrix (ECM) and remodeling of the lung architecture. Idiopathic pulmonary fibrosis is considered the most common and severe form of the disease, with a median survival of approximately three years and no proven effective therapy. Despite the fact that effective treatments are absent and the precise mechanisms that drive fibrosis in most patients remain incompletely understood, an extensive body of scientific literature regarding pulmonary fibrosis has accumulated over the past 35 years. In this review, we discuss three broad areas which have been explored that may be responsible for the combination of altered lung fibroblasts, loss of alveolar epithelial cells, and excessive accumulation of ECM: inflammation and immune mechanisms, oxidative stress and oxidative signaling, and procoagulant mechanisms. We discuss each of these processes separately to facilitate clarity, but certainly significant interplay will occur amongst these pathways in patients with this disease.

Enteral n-3 fatty acids and micronutrients enhance percentage of positive neutrophil and lymphocyte adhesion molecules: a potential mediator of pressure ulcer healing in critically ill patients

n-3 Fatty acids are recognised as influencing both wound healing and immunity. We assessed the impact of a fish oil- and micronutrient-enriched formula (study formula) on the healing of pressure ulcers and on immune function in critically ill patients in an intensive care unit. A total of forty patients with pressure ulcers and receiving nutritional support were enrolled (intervention group, n 20, received study formula; and a control group, n 20, received an isoenergetic formula). Total and differential leucocyte count and percentage of adhesion molecule positive granulocyte and lymphocyte cells (CD11a, CD11b, CD18 and CD49b) were measured on days 0, 7 and 14. Percentage of positive lymphocytes for CD54, CD49b, CD49d and CD8 were also measured on days 0, 7 and 14. The state of pressure ulcers was assessed by using the pressure ulcer scale for healing tool score on days 7, 14 and 28 of treatment. No between-group differences in patient demographics, anthropometry or diagnostic class were observed. Patients who received the study formula showed significant increases in the percentage of positive CD18 and CD11a lymphocytes and of CD49b granulocytes as compared to controls (P < 0·05). While the severity of pressure ulcers was not significantly different between the two groups on admission, severity increased significantly over time for the control group (P < 0·05), but not for the study group. The present study suggests that a fish oil- and micronutrient-enriched formula may prevent worsening of pressure ulcers and that this effect may be mediated by an effect on adhesion molecule expression.

Electrophilic PPARγ Ligands Attenuate IL-1β and Silica-Induced Inflammatory Mediator Production in Human Lung Fibroblasts via a PPARγ-Independent Mechanism

Acute and chronic lung inflammation is associated with numerous important disease pathologies including asthma, chronic obstructive pulmonary disease and silicosis. Lung fibroblasts are a novel and important target of anti-inflammatory therapy, as they orchestrate, respond to, and amplify inflammatory cascades and are the key cell in the pathogenesis of lung fibrosis. Peroxisome proliferator-activated receptor gamma (PPARγ) ligands are small molecules that induce anti-inflammatory responses in a variety of tissues. Here, we report for the first time that PPARγ ligands have potent anti-inflammatory effects on human lung fibroblasts. 2-cyano-3, 12-dioxoolean-1, 9-dien-28-oic acid (CDDO) and 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) inhibit production of the inflammatory mediators interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), COX-2, and prostaglandin (PG)E₂ in primary human lung fibroblasts stimulated with either IL-1β or silica. The anti-inflammatory properties of these molecules are not blocked by the PPARγ antagonist GW9662 and thus are largely PPARγ independent. However, they are dependent on the presence of an electrophilic carbon. CDDO and 15d-PGJ₂, but not rosiglitazone, inhibited NF-κB activity. These results demonstrate that CDDO and 15d-PGJ₂ are potent attenuators of proinflammatory responses in lung fibroblasts and suggest that these molecules should be explored as the basis for novel, targeted anti-inflammatory therapies in the lung and other organs.

Radiation-induced mast cell mediators differentially modulate chemokine release from dermal fibroblasts

BACKGROUND

Ionizing radiation has been demonstrated to result in degranulation of dermal mast cells. Chemokines are thought to play a crucial role in the early phase of the cutaneous radiation reaction. In human skin, mast cells are located in close proximity to dermal fibroblasts, which thus are a potential target for the action of mast cell mediators.

OBJECTIVE

In this study, we evaluated the effects of mast cell-derived histamine, serotonin, tumour necrosis factor (TNF)-α and tryptase on chemokine release from dermal fibroblasts.

METHODS

Human mast cells (HMC-1) were investigated for histamine release and cytokine production after ionizing radiation using enzyme-linked immunosorbent assay (ELISA) and flow cytometry. Receptor expression on human fetal foreskin fibroblasts (HFFF2) and human adult skin fibroblasts (HDFa) was examined by flow cytometry. Chemokine mRNA and protein expression were analyzed by gene array and ELISA, respectively.

RESULTS

Ionizing radiation significantly increased histamine release and cytokine expression by HMC-1 cells. Receptors for histamine, serotonin, TNF-α and tryptase were detected both in HFFF2 and in HDFa cells. Dermal fibroblasts constitutively expressed distinct sets of chemokine mRNA. Mast cell mediators differentially affected the release of chemokines CCL8, CCL13, CXCL4 and CXCL6 by fibroblasts.

CONCLUSIONS

Our data suggest that radiation-induced mast cell mediators have a tremendous impact on inflammatory cell recruitment into irradiated skin. We postulate the activation of mast cells to be an initial key event in the cutaneous radiation reaction, which might offer promising targets for treatment of both normal tissue side effects in radiation therapy and radiation injuries.

Temporal alterations in cardiac fibroblast function following induction of pressure overload

Increases in cardiovascular load (pressure overload) are known to elicit ventricular remodeling including cardiomyocyte hypertrophy and interstitial fibrosis. While numerous studies have focused on the mechanisms of myocyte hypertrophy, comparatively little is known regarding the response of the interstitial fibroblasts to increased cardiovascular load. Fibroblasts are the most numerous cell type in the mammalian myocardium and have long been recognized as producing the majority of the myocardial extracellular matrix. It is only now becoming appreciated that other aspects of fibroblast behavior are important to overall cardiac function. The present studies were performed to examine the temporal alterations in fibroblast activity in response to increased cardiovascular load. Rat myocardial fibroblasts were isolated at specific time-points (3, 7, 14, and 28 days) after induction of pressure overload by abdominal aortic constriction. Bioassays were performed to measure specific parameters of fibroblast function including remodeling and contraction of 3-dimensional collagen gels, migration, and proliferation. In addition, the expression of extracellular matrix receptors of the integrin family was examined. Myocardial hypertrophy and fibrosis were evident within 7 days after constriction of the abdominal aorta. Collagen gel contraction, migration, and proliferation were enhanced in fibroblasts from pressure-overloaded animals compared to fibroblasts from sham animals. Differences in fibroblast function and protein expression were evident within 7 days of aortic constriction, concurrent with the onset of hypertrophy and fibrosis of the intact myocardium. These data provide further support for the idea that rapid and dynamic changes in fibroblast phenotype accompany and contribute to the progression of cardiovascular disease.

MAST CELLS INDUCE ACTIVATION OF HUMAN LUNG FIBROBLASTS IN VITRO

Mast cells are able to induce proliferation of skin fibroblasts; however, their effect on lung fibroblasts has not been clearly established. Using in vitro cocultures of rat or human mast cells with lung fibroblasts, the authors determined whether mast cells alter proliferation, collagen synthesis, and metalloproteinase production from lung fibroblasts. Mast cells enhanced the proliferation of human fibroblasts (mean +/- SEM: 90% +/- 4.7% increase, P < .001) while inhibiting fibroblast collagen synthesis (48.1% +/- 4.2% decrease, P < .001). Histamine, but not tryptase, significantly enhanced fibroblast proliferation: 92% +/- 5.8% (P < .001) and 39.2% +/- 4.3% (P > 0.05), respectively. Rat mast cell sonicate added to lung fibroblasts induced the activation of metalloproteinase-9 while inhibiting that of metaloproteinase-2. The addition of lipopolysaccharide (LPS)-stimulated lung macrophage supernatant further enhanced the poliferative effect of mast cells on fibroblasts (by 60% +/- 7.8%, P < .001) and induced synthesis of collagen from these cells (190% +/- 28% increase versus control, P < .05). This study demonstrates that mast cells influence several aspects of lung fibroblast function in vitro.

Interrelation of immunity and tissue repair or regeneration

Although tremendous progress has been achieved in understanding the molecular basis of tissue repair and regeneration in diverse model organisms, the tendency of mammals for imperfect healing and scarring rather than regeneration remains unexplained. Moreover, conditions of impaired wound healing, e.g. non-healing skin ulcers associated with diabetes mellitus or vascular disease, as well as excessive scarring, represent major clinical and socio-economical problems. The development of innovative strategies to improve tissue repair and regeneration is therefore an important task that requires a more thorough understanding of the underlying molecular and cellular mechanisms. There is substantial evidence in different model organisms that the immune system is of primary importance in determining the quality of the repair response, including the extent of scarring, and the restoration of organ structure and function. Findings in diverse species support a correlation between the loss of regeneration capacity and maturation of immune competence. However, in recent years, there is increasing evidence on conditions where the immune response promotes repair and ensures local tissue protection. Hence, the relationship between repair and the immune response is complex and there is evidence for both negative and positive roles. We present an overview on recent evidence that highlights the immune system to be key to efficient repair or its failure. First, we summarize studies in different model systems that reveal both promoting and impeding roles of the immune system on the regeneration and repair capacity. This part is followed by a delineation of diverse inflammatory cell types, selected peptide growth factors and their receptors as well as signaling pathways controlling inflammation during tissue repair. Finally, we report on new mechanistic insights on how these inflammatory pathways impair healing under pathological conditions and discuss therapeutic implications.

ISSLS prize winner: repeated disc injury causes persistent inflammation

STUDY DESIGN

An in vivo rat model of disc degeneration with emphasis on characterizing acute and chronic cytokine production.

OBJECTIVE

To compare the morphologic and proinflammatory response between a single and triple-stab injury in attempts to establish mechanisms of chronic disc inflammation.

SUMMARY OF BACKGROUND DATA

The features that distinguish physiologic (asymptomatic) from pathologic (symptomatic) degeneration are unclear. Epidemiologic evidence suggests that cumulative damage and elevated disc cytokine levels may be linked to increased low back pain rates. Although acute injury stimulates a healing response that includes transient cytokine production, repetitive damage may be necessary to trigger the persistent inflammation suspected to underlie chronic pain.

METHODS

Tail discs were exposed surgically and stabbed with a number 11 blade. During the subsequent acute healing phase, triple-stab discs were percutaneously injured with a 23-gauge needle at day 3 and then again at day 6 after the initial blade incision. Cytokine (IL-1 beta, IL-6, IL-8, and TNF-alpha) production was quantified using enzyme linked immunosorbent assay, and, in addition to MAPK signaling pathways (phosphorylated forms of ERK, JNK, and p38), was localized by immunohistochemistry. Disc architecture was evaluated using histology.

RESULTS

Both single-stab and triple-stab discs degenerated with time, yet degeneration was more severe with repeated injury where nuclear proteoglycan was replaced by disorganized collagen. Four days after single-stab, there was a transient peak in IL-1 beta and IL-8 production that was localized to the wound track and associated granulation tissue. By contrast, triple-stab induced an activated annular fibroblast phenotype (p38 positive) that caused a prolonged, diffuse inflammatory response with elevated levels of TNF-alpha, IL-1 beta, and IL-8 up to 28 days after injury. Disc inflammation was accompanied by reactive changes in the adjacent vertebral marrow spaces that was initially lytic at day 4, becoming sclerotic by day 56.

CONCLUSION

Our results demonstrate that repeated injury during active healing leads to persistent inflammation and enhanced disc degeneration. These data support the premise that damage accumulation and its associated inflammation may distinguish pathologic from physiologic disc degeneration. In the future, this triple-stab model may be useful to evaluate the efficacy of anti-inflammatory low back pain treatments.

Connective tissue growth factor expression is regulated by histamine in lung fibroblasts: potential role of histamine in airway remodeling

BACKGROUND

In the inflamed lung of allergic asthma, an aberrant injury-repair response is accompanied by structural changes in the airway, known as airway remodeling. TGF-beta and its downstream mediator connective tissue growth factor (CTGF) are playing a key role in these processes, resulting in irreversible airway remodelling.

OBJECTIVE

As histamine is a key mediator of allergic reactions, we investigated whether histamine is involved in airway remodeling.

METHODS

The effect of histamine and TGF-beta1 on proliferation of lung fibroblast cells IMR-90 was studied by [(3)H]-thymidine proliferation assay. The regulation of CTGF by histamine and TGF-beta1 in lung fibroblasts was analyzed by RT-PCR, real-time PCR, Western blot analysis, and promoter analysis and characterized by specific histamine-receptor antagonists.

RESULTS

Histamine and TGF-beta1 enhanced proliferation of lung fibroblast cells IMR-90. Both induced CTGF mRNA and protein expression with different time kinetics. Whereas TGF-beta1 induced maximal CTGF expression after 12 hours (347% +/- 23%), histamine-induced maximal CTGF expression was lower and delayed (maximum expression of 204% +/- 11% after 48 hours). Histamine and TGF-beta1 stimulated the CTGF promoter and the TGF-beta-response element in the CTGF promoter. The histamine-induced CTGF expression was mediated through the histamine receptor (HR1) and could be completely abolished by TNF-alpha.

CONCLUSIONS

These findings demonstrate that histamine plays a potential role in the induction of airway remodeling mediated by the induction of lung fibroblasts proliferation and CTGF expression.

CLINICAL IMPLICATIONS

This mechanism could be important for prophylactic strategies aiming at airway remodeling and could be a new indication for antihistamine treatment.

Inflammation in wound repair: molecular and cellular mechanisms

In post-natal life the inflammatory response is an inevitable consequence of tissue injury. Experimental studies established the dogma that inflammation is essential to the establishment of cutaneous homeostasis following injury, and in recent years information about specific subsets of inflammatory cell lineages and the cytokine network orchestrating inflammation associated with tissue repair has increased. Recently, this dogma has been challenged, and reports have raised questions on the validity of the essential prerequisite of inflammation for efficient tissue repair. Indeed, in experimental models of repair, inflammation has been shown to delay healing and to result in increased scarring. Furthermore, chronic inflammation, a hallmark of the non-healing wound, predisposes tissue to cancer development. Thus, a more detailed understanding in mechanisms controlling the inflammatory response during repair and how inflammation directs the outcome of the healing process will serve as a significant milestone in the therapy of pathological tissue repair. In this paper, we review cellular and molecular mechanisms controlling inflammation in cutaneous tissue repair and provide a rationale for targeting the inflammatory phase in order to modulate the outcome of the healing response.

Thy-1 expression by cardiac fibroblasts: lack of association with myofibroblast contractile markers

The objective of this study was to investigate the presence of Thy-1 in the myocardium and on cardiac fibroblasts and to determine whether or not cardiac fibroblasts form a heterogeneous population in term of Thy-1 expression. Thy-1 expression was examined by immunohistology of ventricular sections from normal and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Thy-1 immunostaining was detected in connective tissue on alpha8 integrin-positive and discoidin domain receptor 2 (DDR2)-positive fibroblasts. Enhanced Thy-1 staining was observed in the hearts of DOCA-salt rats particularly in areas of interstitial fibrosis. Cardiac mRNA analysis confirmed the increased Thy-1 expression. On cultured cardiac fibroblasts, flow cytofluorometry showed that cells, from primary culture to passage 4, were double positive for Thy-1 and for both alpha8 integrin and DDR2. Analysis of isolated lipid rafts by detergent-free sucrose gradient indicated that Thy-1 protein was probably located in these structures, but it may be located on a membrane microdomain slightly different from those of caveolin-1, as revealed by immunocytochemistry. Differentiation of fibroblasts into myofibroblasts being a characteristic of cardiac fibrosis and scarring, cardiac fibroblasts were stimulated in the presence of transforming growth factor-beta (TGF-beta) or connective tissue growth factor. While the expression of smooth muscle alpha-actin and alpha8 integrin doubled, Thy-1 level, measured by Western blotting and flow cytofluorometry, was not influenced by TGF-beta. These results demonstrate that cardiac fibroblasts express Thy-1 and form a homogeneous population. Thy-1 expression also appears to be independent of fibroblast differentiation. The dichotomy between the increased Tthy-1 expression in the fibrotic area and the lack of association with fibroblast differentiation suggests that Thy-1 may represent a marker of fibroblast proliferation in the myocardium.

Ultrafine particles and platelet activation in patients with coronary heart disease--results from a prospective panel study

Background

Epidemiological studies on health effects of air pollution have consistently shown adverse cardiovascular effects. Toxicological studies have provided evidence for thrombogenic effects of particles.

A prospective panel study in a susceptible population was conducted in Erfurt, Germany, to study the effects of daily changes in ambient particles on various blood cells and soluble CD40ligand (sCD40L, also known as CD154), a marker for platelet activation that can cause increased coagulation and inflammation.

Blood cells and plasma sCD40L levels were repeatedly measured in 57 male patients with coronary heart disease (CHD) during winter 2000/2001. Fixed effects linear regression models were applied, adjusting for trend, weekday and meteorological parameters.

Hourly data on ultrafine particles (UFP, number concentration of particles from 0.01 to 0.1 μm), mass concentration of particles less than 10 and 2.5 μm in diameter (PM₁₀, PM_2.5), accumulation mode particle counts (AP, 0.1–1.0 μm), elemental and organic carbon, gaseous pollutants and meteorological data were collected at central monitoring sites.

Results

An immediate increase in plasma sCD40L was found in association with UFP and AP (% change from geometric mean: 7.1; CI: [0.1, 14.5] and 6.9; CI: [0.5, 13.8], respectively). Platelet counts decreased in association with UFP showing an immediate, a three days delayed (lag 3) and a 5-day average response (% change from the mean: -1.8; CI: [-3.4,-0.2]; -2.4; CI: [-4.5,-0.3] and -2.2; CI: [-4.0,-0.3] respectively).

Conclusion

The increased plasma sCD40L levels support the hypothesis that higher levels of ambient air pollution lead to an inflammatory response in patients with CHD thus providing a possible explanation for the observed association between air pollution and cardiovascular morbidity and mortality in susceptible parts of the population.

Neural-endocrine-immune complex in the central modulation of tumorigenesis: facts, assumptions, and hypotheses

For the precise coordination of systemic functions, the nervous system uses a variety of peripherally and centrally localized receptors, which transmit information from internal and external environments to the central nervous system. Tight interconnections between the immune, nervous, and endocrine systems provide a base for monitoring and consequent modulation of immune system functions by the brain and vice versa. The immune system plays an important role in tumorigenesis. On the basis of rich interconnections between the immune, nervous and endocrine systems, the possibility that the brain may be informed about tumorigenesis is discussed in this review article. Moreover, the eventual modulation of tumorigenesis by central nervous system is also considered. Prospective consequences of the interactions between tumor and brain for diagnosis and therapy of cancer are emphasized.

Scleroderma fibroblasts demonstrate enhanced activation of Akt (protein kinase B) in situ

Recent studies suggest that, in addition to activation and hypersecretion of matrix components, fibroblasts from patients with systemic sclerosis (SSc) are relatively resistant to apoptosis. Transforming growth factor-beta (TGF)-beta is strongly implicated in the pathogenesis of SSc and we and others have shown that TGF-beta can activate Akt, a kinase with potent anti-apoptotic effects. To determine whether Akt was activated in SSc, we quantified phospho-Akt expression in skin fibroblasts in vitro by western blot analysis and a functional kinase assay. In addition, the relative proportion of fibroblasts containing activated Akt in was quantified by immunohistochemistry on skin sections insitu. Analysis of Akt phosphorylation of skin fibroblasts in vitro suggested increased phosphorylation of Akt, and evaluation of skin sections by immunohistochemistry revealed significantly higher percentages of fibroblasts that stained for phospho-Akt compared with controls (78% +/- 14.0% vs 13% +/- 9%, p < 0.001). In addition, co-incident staining of phospho-Akt and alpha-smooth muscle actin was observed in some fibroblasts. These findings indicate that Akt is activated insitu in skin fibroblasts from patients with SSc. Akt activation may contribute to resistance to apoptosis, selection of disease-inducing fibroblasts, and, possibly, myofibroblasts.

Active NF-kappaB signalling is a prerequisite for influenza virus infection

Influenza virus still poses a major threat to human health. Despite widespread vaccination programmes and the development of drugs targeting essential viral proteins, the extremely high mutation rate of influenza virus still leads to the emergence of new pathogenic virus strains. Therefore, it has been suggested that cellular cofactors that are essential for influenza virus infection might be better targets for antiviral therapy. It has previously been reported that influenza virus efficiently infects Epstein-Barr virus-immortalized B cells, whereas Burkitt's lymphoma cells are virtually resistant to infection. Using this cellular system, it has been shown here that an active NF-kappaB signalling pathway is a general prerequisite for influenza virus infection of human cells. Cells with low NF-kappaB activity were resistant to influenza virus infection, but became susceptible upon activation of NF-kappaB. In addition, blocking of NF-kappaB activation severely impaired influenza virus infection of otherwise highly susceptible cells, including the human lung carcinoma cell lines A549 and U1752 and primary human cells. On the other hand, infection with vaccinia virus was not dependent on an active NF-kappaB signalling pathway, demonstrating the specificity of this pathway for influenza virus infection. These results might be of major importance for both the development of new antiviral therapies and the understanding of influenza virus biology.

Mechanisms of pulmonary fibrosis

Tissue injury evokes highly conserved, tightly regulated inflammatory responses and less well-understood host repair responses. Both inflammation and repair involve the recruitment, activation, apoptosis, and eventual clearance of key effector cells. In this review, we propose the concept of pulmonary fibrosis as a dysregulated repair process that is perpetually "turned on" even though classical inflammatory pathways may be dampened or "switched off." Significant regional heterogeneity, with varied histopathological patterns of inflammation and fibrosis, has been observed in individual patients with idiopathic pulmonary fibrosis. We discuss environmental factors and host response factors, such as genetic susceptibility and age, that may influence these varied manifestations. Better understanding of the mechanisms of lung repair, which include alveolar reepithelialization, myofibroblast differentiation/activation, and apoptosis, should offer more effective therapeutic options for progressive pulmonary fibrosis.

Expression of CD154 (CD40 ligand) by human lung fibroblasts: differential regulation by IFN-gamma and IL-13, and implications for fibrosis

The CD40-CD40 ligand (CD40L) system (CD154) is a central means of immune cell communication crucial for Ig class switching and enhanced Ag presentation. CD40 is also a key signaling conduit to activate nonhematopoietic cells, such as fibroblasts and endothelial cells, to produce proinflammatory mediators. Disruption of the CD40-CD40L pathway reduces lung inflammation and fibrosis, autoimmune disease and atherosclerosis. Non-bone marrow-derived structural cells are not known to express CD40L. In this study, we reveal the intriguing finding that primary strains of human lung fibroblasts derived from normal and scarred lung express both CD40L mRNA and protein. Interestingly, CD40L expression is down-regulated by IFN-gamma, a type 1 cytokine with antiscarring properties, and is up-regulated by the profibrogenic type 2 cytokine IL-13. Flow cytometry and laser confocal microscopy revealed that the majority of CD40L was located intracellularly. Importantly, fibroblast strains from human idiopathic pulmonary fibrosis tissue expressed increased levels of CD40L compared with fibroblasts from nonscarred lung. Fibroblasts in the scarred areas of human lung tissue expressed high levels of CD40L. Finally, the blood and lung lavage levels of CD40L are significantly elevated in fibrosis patients compared with normals. These new findings demonstrate that fibroblasts are a new source of CD40L and that those involved in scarring may have undergone a selected expansion for high CD40L expression. Moreover, the antifibrotic activity of IFN-gamma may involve the down-regulation of fibroblast CD40L levels. We speculate that fibroblast-derived CD40L plays a role in promoting fibroblast activation and possibly in interaction with CD40 bearing cells.

Localization of Mast Cells in Endometrial Cysts

PROBLEM

Although the presence of mast cells in endometriosis lesions has been reported, there have been no reports of their pathological localization in ovarian endometrial cysts.

METHODS OF STUDY

The localization of mast cells in ovarian endometrial cysts were investigated using hematoxyline and eosin and toluidine blue staining with light microscopy, immunohistochemical c-kits, and electron microscopy.

RESULTS

Mast cells were identified in endometrial cyst tissues. Few mast cells were localized in the endometrial stroma, which is characteristic of endometrial gland-like regions. Many mast cells were noted around blood vessels and the interstitium with fibrosis, that is, the fibrotic interstitium of endometrial cysts.

CONCLUSIONS

Mast cells may be involved in the development and progression of endometriosis. Localization of mast cells suggests a particularly close relationship with fibrosis and adhesion.

Pathogenetic mechanisms in usual interstitial pneumonia/idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, usually fatal, form of interstitial lung disease characterized by failure of alveolar re-epithelialization, persistence of fibroblasts/myofibroblasts, deposition of extracellular matrix, and distortion of lung architecture which ultimately results in respiratory failure. Clinical IPF is associated with a histopathological pattern of usual interstitial pneumonia (UIP) on surgical lung biopsy. Therapy for this disease with glucocorticoids and other immunomodulatory agents is largely ineffective and recent trials of newer anti-fibrotic agents have been disappointing. While the inciting event(s) leading to the initiation of scar formation in UIP remain unknown, recent advances in our understanding of the mechanisms underlying both normal and aberrant wound healing have shed some light on pathogenetic mechanisms that may play significant roles in this disease. Unlike other fibrotic diseases of the lung, such as those associated with collagen vascular disease, occupational exposure, or chemotherapeutic agents, UIP is not associated with a significant inflammatory response; rather, dysregulated epithelial-mesenchymal interactions predominate. Identification of pathways crucial to fibrogenesis might offer potentially novel therapeutic targets to slow or halt the progression of IPF. This review focuses on evolving concepts of cellular and molecular mechanisms in the pathogenesis of UIP/IPF.

Role of immunoreactions and mast cells in pathogenesis of human endometriosis -morphologic study and gene expression analysis-

STUDY OBJECTIVES

To investigate the pathophysiology of human endometriosis, we examined by morphological and molecular biological methods.

METHODS

Samples of ovarian endometriosis and normal ovarian tissues were obtained laparoscopically after informed consent. A morphological study by toluidine blue staining, immunohistochemistry of c-kit and electron microscopy demonstrated the localization of mast cells in the stromal lesions of endometriosis. Oligonucleotide microarrays were used for gene expression analysis.

RESULTS

Infiltration of numerous mast cells and development of fibrosis was observed throughout the stromal lesions. Gene expression analysis by oligonucleotide microarrays indicated inflammatory immunoreactions in the lesions. Expressions of the FCER1G and PGDS, which are considered to be mast cell-specific genes, were upregulated in the ovarian endometriotic lesions as compared to the normal ovarian tissues. Furthermore, expressions of genes associated with immunological inflammation, such as IL-8, GRO1, GRO2, CXCR4, MCP1, and those related to tissue remodeling (MMP, COL4A2, and COL5A2) were also higher in endometriotic lesions than in the normal ovarian tissue.

CONCLUSIONS

Thus it is likely that mast cells and their related inflammatory immunoreactions via chemokines play important roles in producing fibrosis and adhesions in endometriotic lesions.

Low concentrations of cytokines produced by allergen-stimulated peripheral blood mononuclear cells have potent effects on nasal polyp-derived fibroblasts

Accumulating data show that fibroblasts are important regulators in the development and maintenance of allergic airway inflammation. However, most studies so far have used individual recombinant cytokines in high concentrations, unlikely to be found in vivo. We aimed to investigate how cytokines produced by peripheral blood mononuclear cells (PBMC) affect fibroblast functions. Primary airway fibroblasts where incubated with allergen-stimulated or non-stimulated PBMC supernatants from allergic patients. The levels of cytokines in PBMC supernatants were measured and the expression of CD54, CD40 and CD106 as well as the production of eotaxin, interleukin (IL)-6 and IL-8 were assessed in fibroblasts. Although the levels of single cytokines measured in PBMC supernatants were low, a significant up-regulation of the surface molecules as well as of IL-6 and IL-8 production was found in fibroblasts cultured with allergen-stimulated PBMC supernatants as compared to non-stimulated, while the increase in eotaxin production was not significant. The evaluation of correlations between cytokines produced by PBMC and effects seen on fibroblasts did not indicate a crucial role for any single cytokine. Furthermore, the addition of comparably low concentrations of recombinant interferon (rIFN)-gamma or recombinant tumour necrosis factor (rTNF)-alpha did not induce the same effects as PBMC supernatants, the only exception being TNF-alpha as a direct inducer of CD54 expression. Our results show that synergistic mechanisms has a more important role than single mediators, highlighting important differences between in vitro experiments, where effects of individual mediators are studied, versus the actual situation in vivo.

Cutting edge: proliferating fibroblasts respond to collagenous C1q with phosphorylation of p38 mitogen-activated protein kinase and apoptotic features

Interactions of C1q collagen tails with human fibroblasts induce G(1) mitotic arrest. The hypothesis tested in this study is that the antiproliferative effect of C1q tails is mediated through activation of stress responsive pathway(s). Upon C1q treatment, proliferating fibroblasts were examined by immunoblotting with a panel of Abs to the mitogen-activated protein kinase (MAPK) superfamily. The cells selectively increased phosphorylation of p38 MAPK, upstream dual activator MAPK kinase 3/6, and downstream transcription factors activating transcription factor 2, ETS domain transcription factor 1, and C/EBP homologous protein in a time-dependent manner. Phosphorylations were mediated, in part, by ligation of surface C1q tail-binding calreticulin. These events correlated with the appearance of apoptotic nuclei and DNA fragmentation in the cultures, which increased with a time response curve. The apoptotic features were linked to p38 activities because the selective inhibitor SB203580 prevented both phosphorylation of the pathway and DNA fragmentation. Hence, p38 activation might provide a molecular basis for linking mitotic arrest and apoptosis of fibroblasts by C1q tails.