Mast cells and biogenic amines in radiation-induced pulmonary fibrosis

The controversial role of mast cells in fibrosis

Fibrosis is a medical condition characterized by an excessive deposition of extracellular matrix compounds such as collagen in tissues. Fibrotic lesions are present in many diseases and can affect all organs. The excessive extracellular matrix accumulation in these conditions can often have serious consequences and in many cases be life-threatening. A typical event seen in many fibrotic conditions is a profound accumulation of mast cells (MCs), suggesting that these cells can contribute to the pathology. Indeed, there is now substantialv evidence pointing to an important role of MCs in fibrotic disease. However, investigations from various clinical settings and different animal models have arrived at partly contradictory conclusions as to how MCs affect fibrosis, with many studies suggesting a detrimental role of MCs whereas others suggest that MCs can be protective. Here, we review the current knowledge of how MCs can affect fibrosis.

The diversity of myeloid immune cells shaping wound repair and fibrosis in the lung

In healthy circumstances the immune system coordinates tissue repair responses in a tight balance that entails efficient inflammation for removal of potential threats, proper wound closure, and regeneration to regain tissue function. Pathological conditions, continuous exposure to noxious agents, and even ageing can dysregulate immune responses after injury. This dysregulation can lead to a chronic repair mechanism known as fibrosis. Alterations in wound healing can occur in many organs, but our focus lies with the lung as it requires highly regulated immune and repair responses with its continuous exposure to airborne threats. Dysregulated repair responses can lead to pulmonary fibrosis but the exact reason for its development is often not known. Here, we review the diversity of innate immune cells of myeloid origin that are involved in tissue repair and we illustrate how these cell types can contribute to the development of pulmonary fibrosis. Moreover, we briefly discuss the effect of age on innate immune responses and therefore on wound healing and we conclude with the implications of current knowledge on the avenues for future research.

Celastrol enhances Nrf2 mediated antioxidant enzymes and exhibits anti-fibrotic effect through regulation of collagen production against bleomycin-induced pulmonary fibrosis

Pulmonary fibrosis (PF) is characterized by excessive accumulation of extracellular matrix components in the alveolar region which distorts the normal lung architecture and impairs the respiratory function. The aim of this study is to evaluate the anti-fibrotic effect of celastrol, a quinine-methide tri-terpenoid mainly found in Thunder God Vine root extracts against bleomycin (BLM)-induced PF through the enhancement of antioxidant defense system. A single intratracheal instillation of BLM (3 U/kg.bw) was administered in rats to induce PF. Celastrol (5 mg/kg) was given intraperitoneally, twice a week for a period of 28 days. BLM-induced rats exhibits declined activities of enzymatic and non-enzymatic antioxidants which were restored upon treatment with celastrol. BLM-induced rats show increased total and differential cell counts as compared to control and celastrol treated rats. Histopathological analysis shows increased inflammation and alveolar damage; while assay of hydroxyproline and Masson's trichrome staining shows an increased collagen deposition in BLM-challenged rats that were decreased upon celastrol treatment. Celastrol also reduces inflammation in BLM-induced rats as evidenced by decrease in the expressions of mast cells, Tumor necrosis factor-alpha (TNF- α) and matrix metalloproteinases (MMPs) 2 and 9. Further, Western blot analysis shows that celastrol is a potent inducer of NF-E2-related factor 2 (Nrf2) and it restores the activities of Phase II enzymes such as hemoxygenase-1 (HO-1), glutathione-S-transferase (GSTs) and NADP(H): quinine oxidoreductase (NQO1) which were declined upon BLM administration. The results of this study show evidence on the protective effect of celastrol against BLM-induced PF through its antioxidant and anti-fibrotic effects.

Role of the KATP channel in the protective effect of nicorandil on cyclophosphamide-induced lung and testicular toxicity in rats

This study is the first to investigate the role of the KATP channel in the possible protection mediated by nicorandil against cyclophosphamide-induced lung and testicular toxicity in rats. Animals received cyclophosphamide (150 mg/kg/day, i.p.) for 2 consecutive days and then were untreated for the following 5 days. Nicorandil (3 mg/kg/day, p.o.) was administered starting from the day of cyclophosphamide injection with or without glibenclamide (5 mg/kg/day, p.o.). Nicorandil administration significantly reduced the cyclophosphamide-induced deterioration of testicular function, as demonstrated by increases in the level of serum testosterone and the activities of the testicular 3β- hydroxysteroid, 17β-hydroxysteroid and sorbitol dehydrogenases. Furthermore, nicorandil significantly alleviated oxidative stress (as determined by lipid peroxides and reduced glutathione levels and total antioxidant capacity), as well as inflammatory markers (tumour necrosis factor-α and interleukin-1β), in bronchoalveolar lavage fluid and testicular tissue. Finally, the therapy decreased the levels of fibrogenic markers (transforming growth factor-β and hydroxyproline) and ameliorated the histological alterations (as assessed by lung fibrosis grading and testicular Johnsen scores). The co-administration of glibenclamide (a KATP channel blocker) blocked the protective effects of nicorandil. In conclusion, KATP channel activation plays an important role in the protective effect of nicorandil against cyclophosphamide-induced lung and testicular toxicity.

Daidzein exhibits anti-fibrotic effect by reducing the expressions of Proteinase activated receptor 2 and TGFβ1/smad mediated inflammation and apoptosis in Bleomycin-induced experimental pulmonary fibrosis

Pulmonary fibrosis (PF) is a progressive lethal disorder. In this study, the effect of daidzein, a soyisoflavone against Bleomycin (BLM) induced PF in rats was elucidated. A single intratracheal instillation of BLM (3 U/kg.bw) was administered in rats to induce PF. Daidzein (0.2 mg/kg) was administered subcutaneously, twice a week for a period of 28 days. Daidzein restored the histological alteration and aberrant collagen deposition, suppressed the mast cells, and reduced the expressions of Cyclooxygenase 2 (COX2) and Nuclear factor kappa B (Nf-kB) in lung tissue of BLM-induced rats. Treatment with daidzein reduced the expression of Matrix metalloproteinase 2 (MMP-2) and increased the expression of Tissue inhibitor of matrixmetalloproteinases 1 (TIMP 1). Recently, Proteinase activated receptor 2 (PAR2) has been reported to play a major role in the progression of PF. Confocal microscopic and immunoblot analysis revealed that BLM injured rat lungs exhibited increased expression of PAR2 that was reduced upon treatment with daidzein. During BLM induction, Transforming growth factor beta (TGFβ1) was found to be up-regulated along with p-smad2/3, a mediator of TGFβ signaling. Further, daidzein regulated the apoptosis by modulating the expressions of Bcl-2, Bax and caspase 3. This study provides evidence on the anti-fibrotic role of daidzein in BLM-induced experimental fibrosis.

Do variations in mast cell hyperplasia account for differences in radiation-induced lung injury among different mouse strains, rats and nonhuman primates?

The role of mast cell infiltrates in the pathology of radiation damage to the lung has been a subject of continuing investigation over the past four decades. This has been accompanied by a number of proposals as to how mast cells and the secretory products thereof participate in the generation of acute inflammation (pneumonitis) and the chronic process of collagen deposition (fibrosis). An additional pathophysiology examines the possible connection between mast cell hyperplasia and pulmonary hypertension through the release of vasoactive mediators. The timing and magnitude of pneumonitis and fibrosis are known to vary tremendously among different genetic mouse strains and animal species. Therefore, we have systematically compared mast cell numbers in lung sections from nine mouse strains, two rat strains and nonhuman primates (NHP) after whole thorax irradiation (WTI) at doses ranging from 10-15 Gy and at the time of entering respiratory distress. Mice of the BALB/c strain had a dramatic increase in interstitial mast cell numbers, similar to WAG/Rij and August rats, while relatively low levels of mast cell infiltrate were observed in other mouse strains (CBA, C3H, B6, C57L, WHT and TO mice). Enumeration of mast cell number in five NHPs (rhesus macaque), exhibiting severe pneumonitis at 17 weeks after 10 Gy WTI, also indicated a low response shared by the majority of mouse strains. There appeared to be no relationship between the mast cell response and the strain-dependent susceptibility towards pneumonitis or fibrosis. Further investigations are required to explore the possible participation of mast cells in mediating specific vascular responses and whether a genetically diverse mast cell response occurs in humans.

Effects of lipopolysaccharide on the response of C57BL/6J mice to whole thorax irradiation

BACKGROUND AND PURPOSE

Inflammatory and fibrogenic processes play a crucial role in the radiation-induced injury in the lung. The aim of the present study was to examine whether additive LPS exposure in the lung (to simulate respiratory infection) would affect pneumonitis or fibrosis associated with lung irradiation.

MATERIAL AND METHODS

Wildtype C57Bl/6J (WT-C57) and TNFα, TNFR1 and TNFR2 knockout ((-/-)) mice, in C57Bl/6J background, were given whole thorax irradiation (10 Gy) with or without post-irradiation intratracheal administration of LPS (50μg/mice). Functional deficit was examined by measuring breathing rate at various times after treatment. Real-time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and immunohistochemistry were used to analyze the protein expression and m-RNA of Interleukin-1 alpha (IL-1α), Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), Tumour Necrosis Factor alpha (TNFα) and Transforming Growth Factor beta (TGFβ) in the lung at various times after treatment. Inflammatory cells were detected by Mac-3 (macrophages) and Toluidine Blue (mast cells) staining. Collagen content was estimated by hydroxyproline (total collagen) and Sircol assay (soluble collagen). Levels of oxidative damage were assessed by 8-hydroxy-2-deoxyguanosine (8-OHdG) staining.

RESULTS

LPS exposure significantly attenuated the breathing rate increases following irradiation of WT-C57, TNFR1(-/-) and TNFR2(-/-)mice and to a lesser extent in TNFα(-/-) mice. Collagen content was significantly reduced after LPS treatment in WT-C57, TNFR1(-/-) and TNFα(-/-) mice and there was a trend in TNFR2(-/-) mice. Similarly there were lower levels of inflammatory cells and cytokines in the LPS treated mice.

CONCLUSIONS

This study reveals a mitigating effect of early exposure to LPS on injury caused by irradiation on lungs of C57Bl mice. The results suggest that immediate infection post irradiation may not impact lung response negatively in radiation-accident victims, however, further studies are required in different animal models, and with specific infectious agents, to confirm and extend our findings.

Serotonin and ionizing radiation synergistically affect proliferation and adhesion molecule expression of malignant melanoma cells

BACKGROUND

Mast cells are key effectors of the immune system and are involved in a variety of physiological and pathophysiological processes. Dermal mast cells have been demonstrated to degranulate as a consequence of ionizing radiation exposure. Mast cells accumulate at the periphery of skin tumours including malignant melanoma. Melanoma cells thus represent a potential target for the action of mediators released from irradiated mast cells.

OBJECTIVE

In this study, we evaluated the effects of serotonin and ionizing radiation on the proliferation and the adhesion molecule expression of malignant melanoma cells.

METHODS

Human mast cells (HMC-1) were examined for serotonin release after irradiation using an enzyme-linked immunosorbent assay (ELISA). Protein expression of serotonin receptors and adhesion molecules on human melanoma cells (IPC-298) was investigated by flow cytometry. Cell attachment to fibronectin was determined by an adhesion assay. Proliferation and cell cycle kinetics were analysed by proliferation assay and 5-bromodeoxyuridine (BrdU)/DNA dual parameter flow cytometry, respectively.

RESULTS

Ionizing radiation exposure resulted in serotonin release by HMC-1 cells. Expression of serotonin receptors was detected on IPC-298 cells. Serotonin enhanced the radiation-induced reduction in melanoma cell proliferation. Serotonin and ionizing radiation synergistically increased the expression of adhesion molecules on melanoma cells and improved cell adhesion to fibronectin. The up-regulation of cellular adhesion molecule expression was attenuated by inhibitors to phosphatidylinositol 3-kinase, mitogen-activated protein (MAP) ERK kinase and protein kinase C.

CONCLUSIONS

Our data suggest that serotonin released from irradiated dermal mast cells modulates the radiation response of human melanoma cells. We postulate that radiation-induced mast cell degranulation and mediator release have a great impact on malignant melanoma cell development.

Cellular inflammatory infiltrate in pneumonitis induced by a single moderate dose of thoracic x radiation in rats

The goal of these studies was to characterize the infiltrating inflammatory cells during pneumonitis caused by moderate doses of radiation. Two groups of male rats (WAG/RijCmcr, 8 weeks old) were treated with single 10- or 15-Gy doses of thoracic X radiation; a third group of age-matched animals served as controls. Only 25% rats survived the 15-Gy dose. Bronchoalveolar lavage fluid and whole lung mounts were subjected to cytological and histological evaluation after 8 weeks for distribution of resident macrophages, neutrophils, lymphocytes and mast cells. There was a modest increase in airway and airspace-associated neutrophils in lungs from rats receiving 15 Gy. Mast cells (detected by immunohistochemistry for tryptase) increased over 70% with 10 Gy and over 13-fold after 15 Gy, with considerable leakage of tryptase into blood vessels and airways. Circulating levels of eight inflammatory cytokines were not altered after 10 Gy but appeared to decrease after 15 Gy. In summary, there were only modest increases in cellular inflammatory infiltrate during pneumonitis after a non-lethal dose of 10 Gy, but there was a dramatic rise in mast cell infiltration after 15 Gy, suggesting that circulating levels of mast cell products may be useful markers of severe pneumonitis.

Ionizing radiation induces degranulation of human mast cells and release of tryptase

PURPOSE

Skin fibrosis is a hallmark of ionizing radiation-induced tissue injury and we hypothesized that mast cells via their products (especially tryptase) are involved in this event. We therefore investigated whether: (i) irradiation with 5 Gray (Gy) is able to induce the release of the typical mast cell mediator tryptase from human mast cells (HMC-1) in vitro, (ii) this effect can be influenced by application of clinically relevant mast cell blockers, and (iii) irradiation leads to mast cell degranulation in ex vivo skin culture models.

MATERIALS AND METHODS

The human mast cell line (HMC)-1, as well as ex vivo skin tissue served as experimental models. Fluorescence activated cell sorting (FACS), Enzyme linked immunosorbent assays (ELISA), mast cell degranulation assays and immunohistochemistry were applied.

RESULTS

Ionizing radiation induces a time-dependent, statistically significant increase in the release of tryptase by HMC-1 cultured in vitro. Mast cell degranulation and secretion of tryptase was partially, but not significantly, inhibited by pre-incubation with the histamine-1 receptor (H1) blocker cetirizine. Mast cell degranulation was also clearly evident after irradiation using an ex vivo skin culture model of mastocytoma tissue.

CONCLUSIONS

We propose that ionizing radiation leads to a degranulation of dermal mast cells, an event which is accompanied by the release of tryptase.

Epigallocatechin-3-gallate augments antioxidant activities and inhibits inflammation during bleomycin-induced experimental pulmonary fibrosis through Nrf2-Keap1 signaling

The mechanism involved in the enhancement of antioxidant activities and resolved inflammation after epigallocatechin-3-gallate (EGCG) treatment during bleomycin-induced pulmonary fibrosis is investigated in this study. The levels of reactive-oxygen species (ROS), lipid peroxidation (LPO), hydroxyproline and the activity of myeloperoxidase (MPO) were increased due to bleomycin challenge and were brought back to near normal status on EGCG supplementation. The decreased antioxidant status due to bleomycin challenge was also restored upon EGCG treatment. Bleomycin-induced rats showed increased cell counts as compared to control and EGCG-treated rats. Histopathological analysis showed increased inflammation and alveolar damage, while picrosirius red staining showed an increased collagen deposition in bleomycin-challenged rats that were decreased upon EGCG treatment. Immunohistochemical, immunofluorescent and immunoblot studies revealed that EGCG supplementation decreased the levels of nuclear factor-kappaB (NF-kappaB), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta), which were increased upon bleomycin induction. The declined activities of Phase II enzymes such as glutathione-S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1) in bleomycin-injured rats were restored upon EGCG treatment. Confocal microscopy, immunoblot and RT-PCR studies confirm that EGCG is a potent inducer of NF-E2-related factor 2 (Nrf2). Expression of Kelch like ECH-associated protein (Keap)-1, a vital factor in Nrf2 signaling cascade was analyzed by immunoblotting. However, there was no significant change in the expression of Keap1 in control and experimental groups. This study demonstrates the involvement of Nrf2-Keap1 signaling through which EGCG enhances antioxidant activities and Phase II enzymes with subsequent restraint inflammation during bleomycin-induced pulmonary fibrosis.

Involvement of intracellular expression of FGF12 in radiation-induced apoptosis in mast cells

Several fibroblast growth factors (FGFs) are able to reduce and improve radiation-induced tissue damage through the activation of surface fibroblast growth factor receptors (FGFRs). In contrast, some FGFs lack classical signal sequences, which play roles in the release of FGFs, and the intracellular function of these FGFs is not well clarified. In this study, we evaluated the transcript levels of 22 FGFs in a human mast cell line, HMC-1, using quantitative RT-PCR and found that FGF2 and FGF12 were expressed in HMC-1 cells. FGF12 not only lacks classical signal sequences but also fails to activate FGFRs. HMC-1 cells were transfected with an expression vector of FGF12 to clarify the intracellular function of FGF12 after irradiation. The overexpression of FGF12 in HMC-1 cells decreased ionizing radiation-induced apoptosis, and siRNA-mediated repression of FGF12 expression augmented apoptosis in HMC-1 cells. The overexpression of FGF12 strongly suppressed the marked augmentation of apoptosis induced by inhibition of the MEK/ERK pathway with PD98059. In contrast, the mitogen-activated protein kinase (MAPK) scaffold protein islet brain 2 (IB2), which was reported to bind to FGF12, did not interfere with the anti-apoptotic effect of FGF12. The expression of FGF12 transcripts was also detected in murine cultured mast cells derived from bone marrow or fetal skin. These findings suggest that FGF12 intracellularly suppresses radiation-induced apoptosis in mast cells independently of IB2.

Release of neuroendocrine products in the pulmonary circulation during intermittent hypoxia in isolated rat lung

The aim of this study was to evaluate the release of neuroendocrine (NE) products into the pulmonary circulation during intermittent hypoxia (IH) in isolated buffer-perfused and ventilated rat lungs. Isolated single-pass perfused rat lungs were repeatedly ventilated with hypoxic (2% O(2)) and normoxic (21% O(2)) gases for 5-min intervals. Perfusate collected during the study was analysed for bombesin-like-peptides (BLPs) and serotonin. In addition, immunohistochemical evaluation of the neuropeptides calcitonin gene-related peptide (CGRP) and chromogranin A (CgA) in the lung was performed. During IH, perfusate levels of BLPs decreased compared to lungs ventilated with normoxic gas only. After 15 min of IH, perfusate levels of BLPs were significantly lower than at corresponding time in normoxic lungs (2.6+/-0.7 pg ml(-1) versus 9.2+/-1.9 pg ml(-1), p=0.036). No significant difference between the study groups was observed in perfusate levels of serotonin. Immunohistochemical evaluation of the lungs revealed significantly increased number of pulmonary NE cells immunoreactive for CGRP in IH ventilated lungs compared to controls (10.1+/-1.5 neuroepithelial bodies (NEBs) (cm(2))(-1) versus 5.0+/-1.5 NEBs (cm(2))(-1), p=0.032). No change in the immunoreactivity for CgA was observed. The present study suggests that intermittent periods of hypoxia are associated with a rapid physiological modulation of the release of NE products into the pulmonary circulation in an isolated rat lung model.

Novel and extensive aspects of paraquat-induced pulmonary fibrogenesis: comparative and time-course microarray analyses in fibrogenic and non-fibrogenic rats

Although paraquat (PQ) is widely known to induce pulmonary fibrosis, the molecular mechanisms are poorly understood. Therefore, to bring a new dimension to the elucidation of the mechanisms, we conducted microarray experiments to investigate the expression profiles of 1,090 genes in the lungs during the progressive phase of PQ-induced pulmonary fibrosis in rats. After several s.c. injections of PQ, rats were divided into a fibrogenic group and a non-fibrogenic group. Time-course gene expression analysis of the fibrogenic group showed altered gene regulation throughout the experimental period. The expression levels of many cell membrane channel, transporter, and receptor genes were substantially altered. These genes were classified into two categories: polyamine transporter- and electrolyte/fluid balance-related genes. Moreover, comparative analysis of the fibrogenic and the non-fibrogenic group revealed 36 genes with significantly different patterns of expression, including the pro-apoptotic gene Bad. This indicates that Bad is a key factor in apoptosis and that apoptosis provides a major turning point in PQ-induced pulmonary fibrosis. Notably, subtypes of transforming growth factor (TGF)-beta genes that are considered to play a pivotal role in fibrogenesis showed no differences in expression between the two groups, though TGF-beta3 was markedly induced in both groups. These results provide novel and extensive insights into the molecular mechanisms that lead to pulmonary fibrosis after exposure to PQ.

Factors effecting the Th2-like immune response after gamma-irradiation: low production of IL-12 heterodimer in antigen-presenting cells and small expression of the IL-12 receptor in T cells

Ionizing radiation is known to reduce the helper T (Th) 1-like function, but not the Th2-like function, resulting in a Th1/Th2 imbalance. While this has been known for some time, the mechanism behind the preferential suppression of the Th1 cell activation has not yet been explained. The aim is to elucidate the mechanism in the Th cell imbalance after ionizing irradiation. C57BL/6 mice, 7 weeks old, received whole-body gamma-irradiation (WBI) of 5 Gy. In all instances, the spleen and peritoneal cells were obtained from mice 7 weeks after irradiation. To distinguish Th1 and Th2 cell function, interferon (IFN)-gamma and interleukin (IL)-4 produced by these cells were analysed by an enzyme-linked immunosorbent assay (ELISA). To isolate the primary T cells, the anti-CD90.2 microbead-conjugated antibody was used and the labelled cells were separated by magnetic cell sorting (MACS). To investigate the influence of the IL-12p70 secreted by the antigen-presenting cells, ovalbumin (OVA)-primed peritoneal adherent cells (PAC) were fixed by 1% paraformaldehyde and co-cultured with OVA-specific Th cells in the presence of supernatant of PAC culture with OVA for 16 h. IL-12 receptor, signal transducers and activators of transcription 4 (STAT4) and IFN-gamma expression in the T cells of the WBI mice were detected by reverse transcriptase-polymerase chain reaction (RT-PCR). The spleen lymphocytes of WBI mice showed a depression of IFN-gamma production against OVA, although the total IL-12 was highly secreted. However, the heterodimer IL-12, biologically active protein, was induced less in WBI mice. Although the OVA-specific Th cells were co-cultured with fixed OVA-primed PAC obtained from normal mice, the OVA-specific Th cells showed a decreased IFN-gamma secretion in the presence of the culture supernatant of the activated PAC from the WBI mice. In addition, recombinant IL-12p70 restored the cytokine balance of the OVA-specific Th cells. However the cytokine balance of primary T cells from WBI mice was not completely restored by the normal antigen-presenting cells that abundantly secrete IL-12p70. It was assumed that after WBI, the regenerated T cells also have some problems. It was then observed that the IL-12 receptor expression and intracellular levels of the STAT4 were much lower in the T cells of the WBI mice. The results suggest that the shifted response of the helper T cells after WBI exposure is due not only due to a significant suppression of the secretion of the IL-12p70 in the antigen-presenting cells, but also to the lower expression of the IL-12 receptor on T cells.

The production of collagen and the activity of mast-cell chymase increase in human skin after irradiation therapy

Fibrosis is a common complication of radiotherapy. The pathogenesis of radiation-induced fibrosis is not known in detail. There is increasing evidence to suggest that mast cells contribute to various fibrotic conditions. Several mast-cell mediators have been proposed to have a role in fibrogenesis. Tryptase and chymase, the predominant proteins in mast cells, have been shown to induce fibroblast proliferation and collagen synthesis in vitro. In order to explore the role of mast cells in irradiation-induced fibrosis, we analyzed skin biopsies and suction blister fluid (SBF) samples from the lesional and healthy-looking skin of 10 patients who had been treated for breast cancer with surgery and radiotherapy. The biopsies were analyzed histochemically for mast-cell tryptase, chymase, kit receptor, and tumor necrosis factor-alpha. Skin collagen synthesis was assessed by determining the levels of type I and III procollagen amino-terminal propeptides (PINP and PIIINP) in SBF and using immunohistochemical staining for PINP. Immunohistochemical stainings for prolyl-4-hydroxylase reflecting collagen synthesis and chymase immunoreactivity in irradiated and control skin were also performed. The mean level of procollagen propeptides in SBF, which reflects actual skin collagen synthesis in vivo, was markedly increased in irradiated skin compared to corresponding healthy control skin areas. The mean number of PINP-positive fibroblasts was also significantly increased in the upper dermis of radiotherapy-treated skin. The number of cells positive for tryptase, chymase and kit receptor was markedly increased in irradiated skin. In addition, using double-staining techniques, it was possible to demonstrate that in some areas of the dermis, tryptase-positive mast cells and fibroblasts are closely associated. These findings suggest a possible role of mast cells in enhanced skin collagen synthesis and fibrosis induced by radiotherapy.

Mast cell basic fibroblast growth factor in silicosis

To investigate the role of mast cells (MC) and their fibrogenic growth factors in silicosis, we performed quantitative immunohistochemistry for MC tryptase and for basic fibroblast growth factor (bFGF) in lung tissue from silicotic and control subjects. Anti-bFGF antibody was bound to lung MC, basement membrane, endothelial cells, and smooth-muscle cells. Morphometric analysis revealed that the volume density (V(v)) of MC was increased in silicotic lung and that the V(v) of bFGF-positive (bFGF(+)) cells was significantly higher than normal in silicotic lung. Most MC contained bFGF (rho = 0.88, p < 0.001). The V(v) of collagen/reticulin fibers was increased in silicosis and correlated with the V(v) of bFGF(+) cells (rho = 0.81, p < 0.001). Immature silicotic nodules contained bFGF(+) MC throughout the loose array of collagen/reticulin fibers. In large, mature nodules, the density of collagen/reticulin fibers was higher, and bFGF(+) MC were found only in the nodule periphery. Because of this circumferential MC alignment in silicotic nodules, we observed a negative correlation between the V(v) of bFGF(+) MC and the density of collagen/reticulin fibers in silicotic nodules (rho = -0.80, p < 0.001) and between the V(v) of all other nodule-associated cells and the density of collagen/reticulin fibers in the hypocellular nodule centers (rho = -0.84, p < 0.001). We conclude that MC that produce bFGF may play an important role in the development of silicosis.

Bronchoalveolar lavage in bronchiolitis obliterans organizing pneumonia primed by radiation therapy to the breast

BACKGROUND

Growing evidence indicates that unilateral lung irradiation for breast cancer may "prime" the development of migratory lung infiltrates with histologic features of bronchiolitis obliterans organizing pneumonia.

OBJECTIVE

Our purpose was to evaluate the cytologic and immunocytologic features of bronchoalveolar lavage in this condition.

METHODS

We analyzed the profile bronchoalveolar lavage cell differentials and lymphocyte subpopulations of 11 women with bronchiolitis obliterans organizing pneumonia syndrome after radiation therapy for breast cancer in comparison to 9 healthy women.

RESULTS

The bronchoalveolar lavage analysis demonstrated a significant increase in the percentage of lymphocytes (36.7% +/- 5.4% vs 8.6% +/- 1.1%, P =.0002), neutrophils (3.8% +/- 1.2% vs 0.6% +/- 0.2%, P =.005), eosinophils (2.4% +/- 1% vs 0.3% +/- 0.1%, P =.01), and mast cells (1.4% +/- 0.6% vs 0.1% +/- 0.02%, P =.05) with a significant decrease in the percentage of macrophages (56.1% +/- 6% vs 90.3% +/- 1.4%, P =.0002) in patients with bronchiolitis obliterans organizing pneumonia compared with the control subjects. The percentage of CD3(+) cells was significantly increased in patients with bronchiolitis obliterans organizing pneumonia (93.7% +/- 1.3% vs 70.9% +/- 4%, P =.0004), with a significant decrease in CD4(+) cells (32.7% +/- 4.7% vs 55.4% +/- 2. 6%, P =.002) and a significant increase in CD8(+) cells (61.2% +/- 4. 8% vs 37.5% +/- 2.9%, P =.003) in comparison to control subjects. The CD4/CD8 ratio was significantly reduced in patients with bronchiolitis obliterans organizing pneumonia compared with control subjects (0.6% +/- 0.1% vs 1.5% +/- 0.1%, P =.001).

CONCLUSION

These data add to the view that unilateral lung irradiation for breast cancer may "prime" the development of a syndrome quite similar to idiopathic bronchiolitis obliterans organizing pneumonia.

[Suberosis: involvement of bronchoalveolar +mastocytes in the genesis of interstitial involvement]

Suberosis--the lung disease suffered by cork industry workers--may present in the form of either hypersensitivity pneumonitis (HP) or obstructive pulmonary disease (OPD) with asthma-like symptoms or chronic bronchitis. Mast cells play an important role in pulmonary inflammation and are particularly implicated in the rapid release of mediators in bronchoconstriction and the production of cytokines and mediators of fibroblast activity. Increased numbers of mast cells are present in bronchoalveolar lavage (BAL) fluid in interstitial lung diseases, suggesting that these cells also participate in chronic inflammatory processes and in pulmonary fibrosis.

OBJECTIVES

To assess the participation of mas cells in interstitial pulmonary inflammation in cork industry workers by histochemically analyzing their presence in BAL fluid. Foreseeing the possible implication of bronchoalveolar mast cells in the pathogenesis of suberosis, we also studied their relation to various signs and symptoms of the disease, to respiratory function parameters and to degree of alveolitis.

PATIENTS AND METHODS

Thirty-one cork industry workers with respiratory symptoms related to occupational exposure were enrolled. Occupational and case histories were taken. Physical examinations were complemented by chest X-rays, plethysmography/spirometry, fiberoptic bronchoscopy with BAL, and determination of carbon monoxide diffusing capacity (DLCO) and arterial blood gases at rest. Patient classification (20 with HP and 11 with OPD) was based on clinical and functional criteria and analysis of BAL fluid. Mast cells in cytospinned samples treated with two different stains [May-Grunwald-Giemsa (MGG) and Toluidine Blue (Tol.Bl.)] were counted by two observers and the results were compared.

MAIN RESULTS

Good correlation between the two staining methods was confirmed (rs = 0.86, p < 0.0001). Correlation between the two observers was also good (MGG rs = 0.86, Yol.Bl. rs = 0.87, p < 0.0001). The number of mast cells in BAL fluid was significantly higher in patients with HP [13.4 +/- 4.5 (x +/- SEM)] than in those with OPD (0.9 +/- 0.3; p < 0.002, Mann Whitney test). The subgroup of eight patients with poorer respiratory function (CV and/or DLCO < 80% of reference value) also had higher mast cell counts in BAL (19.9 +/- 7.7 versus 3.5 +/- 1.7; p = 0.002). We also saw a negative relation between mast cell counts in BAL fluid and lung function parameters: total lung capacity (rs = -0.68, p = 0.005) and DLCO (rs = -0.54, p = 0.008). Mast cell recovery from BAL fluid was positively related to severity of alveolitis in terms of total cell counts (rs = 0.62, p = 0.002), absolute lymphocyte counts (rs = 0.56, p = 0.006) and albumin levels (rs = 0.68, p = 0.003).

CONCLUSIONS

Our findings suggest that mast cells participate in interstitial lung cell response to the inhalation of organic cork dust, particularly when HP is the form of presentation. Moreover, mas cell recruitment on the alveolar surface seems to be related to the intersity of lymphocytosis and interstitial pulmonary inflammation and to lung function deterioration in affected patients.

Blockade of CD40-CD40 ligand interactions protects against radiation-induced pulmonary inflammation and fibrosis

This study investigated whether CD40-CD40 ligand (L) interactions are important in mediating ionizing radiation-induced lung toxicity. Radiotherapy is a key component in the management of malignant diseases and is a conditioning regimen for bone marrow transplantation. Unfortunately, radiation therapy is particularly toxic to the lung, potentially inducing a fatal pneumonitis and fibrosis, thus limiting its effectiveness. There are no therapies that protect against the development of radiation-induced lung toxicity. Using a mouse model of radiation-induced lung toxicity, a monoclonal anti-CD40L antibody (MR1) that disrupts CD40-CD40L interactions was tested for the ability to reduce lung injury. C57BL/6 mice were pretreated with either nothing, MR1, or hamster IgG 24 h prior to a single dose of 15 Gray ionizing radiation to the thorax. During the following 26 weeks, mice continued to receive MR1 or hamster IgG twice per week. MR1 protected against death from radiation pneumonitis and fibrosis and dramatically reduced lung pathology as evidenced by a limited influx of inflammatory cells, minimal collagen deposition, and septal thickening. MR1 also prevented radiation-induced pulmonary mastocytosis and blunted expression of cyclooxygenase-2, a proinflammatory enzyme responsible for prostaglandin synthesis. Disruption of CD40-CD40L interactions may offer a new mode of intervention to protect against radiation-induced pulmonary toxicity.

Biochemical and connective tissue changes in cyclophosphamide-induced lung fibrosis in rats

The present investigation was designed to characterize the biochemical and connective tissue components and to correlate the significance of morphological and biochemical perturbations in cyclophosphamide (CP)-induced lung fibrosis in rats. Lung fibrosis was induced in male Wistar rats by intraperitoneal injection of 20 mg/100 g body weight of CP, and their pneumotoxic derangements were characterized during an early destructive phase followed by a proliferative and synthetic phase. Serum angiotensin-converting enzyme (ACE) activity was higher in CP-treated rats at days 2, 3, 5, 7, and 11, but there was a significant decrease in lung ACE activity during the same time period. Elevated levels of beta-glucuronidase activity were observed in the lung lavage fluid of CP-administered rats days 2, 3, 5, and 7. Lung myeloperoxidase activity was higher in CP rats. Of significance was the presence of collagenase and collagenolytic cathepsin in the lavage fluid of CP rats, when compared with the barely detectable levels in controls. A similar increase in these enzyme activities was also noticed in the lung tissue of CP rats during the same experimental period. Lavage fluid hydroxyproline content was higher in CP rats when compared with controls. Similarly, lung protein and DNA levels were elevated significantly after treatment with CP. The pulmonary histamine and serotonin contents were significantly higher in CP rats. The incorporation of [3H]thymidine into lung total DNA, [3H]proline into lung hydroxyproline, and [35S]sulphate into lung glycosaminoglycan, measured as indicators of lung DNA, collagen, and glycosaminoglycan synthesis, respectively, was also higher in CP groups. Increased levels of hydroxyproline, elastin, hexosamine, total hexose, fucose, sialic acid, and uronic acid in the lungs of rats 14, 28, and 42 days after CP insult were characterized as biomarkers of CP-induced interstitial changes. These findings indicate that CP-induced lung fibrosis results in alterations not only in collagen synthesis and accumulation, but also in glycosaminoglycan and glycoprotein content.

Is radiation-induced degranulation of mast cells in salivary glands induced by substance P?

Although DNA is the critical target for the lethal effects of irradiation, the precise mechanisms by which irradiation causes damage in tissues and biological systems is not fully understood. In the present study, the number of mast cells and the expression of the neuropeptide substance P (SP) in salivary glands were examined 10 days after a regimen of irradiation. The irradiation was given as a single dose or 5 consecutive days with daily doses of 7 Gy up to a total dose of 35 Gy. In addition, the number of mast cells and the expression of SP were examined 2 and 24 h after a single dose of 7 Gy. Immunohistochemical staining for 5-hydroxytryptamine (5-HT) and staining with avidin peroxidase and toluidine blue were used to detect mast cells. At examination 2 and 24 h after irradiation treatment, no change in the number of mast cells and the pattern of SP expression was observed. Ten days after irradiation there was a remarkable reduction in the number of mast cells in all the three glands, but there was a marked increase in the number of nerve fibers showing SP-like immunoreactivity in the parenchyme. The results show that early time-dependent alterations in the density of mast cells occur in response to irradiation, and that these changes occur concomitantly with changes in the expression of SP. Since the peripheral nervous system is a main regulator of salivary gland function, it is tempting to speculate that the nervous system interacts with mast cells via SP in modulating irradiation provoked tissue responses in salivary glands.

Metaplastic transformation of urinary bladder epithelium: effect on mast cell recruitment, distribution, and phenotype expression

Mucosal mast cells (MCs) are normally found in the connective tissue stroma but are redistributed into the epithelium in conditions associated with immunoglobulin E responses, such as allergic inflammation and nematode infections, as well as in interstitial cystitis, a condition of unknown etiology. The potential role of epithelium-derived factors in this response prompted this inquiry into growth and differentiation signaling in normal tissue as well as in tissues from five different metaplastic conditions of the urothelium (cystitic cystica, cystitis glandularis, colonic metaplasia, squamous cell metaplasia, and nephrogenic metaplasia). Expression of the two major human MC growth factors, stem cell factor (or kit ligand) and interleukin 6, was detected using immunohistochemistry. In the case of interleukin 6, its mRNA expression was also detected using in situ reverse transcription-polymerase chain reaction. Among the different metaplastic lesions, nephrogenic metaplasia was the only one associated with an abundance of MCs, which were distributed within or in close relationship to the epithelium. Unlike in the other types of metaplasia, the epithelium strongly co-expressed interleukin 6 and stem cell factor. The MCs expressed the stem cell factor receptor CD117 and exhibited a variable tryptase immunoreactivity, but lacked chymase. They also displayed a relative deficiency of granular glycosaminoglycan, as indicated by a lack of metachromasia, and were sensitive to strong aldehyde fixation. The findings suggest that the MC response in nephrogenic metaplasia may be the result of local epithelial stem cell factor/interleukin 6 expression.

Inhaled corticosteroid reduced lamina reticularis of the basement membrane by modulation of insulin-like growth factor (IGF)-I expression in bronchial asthma

BACKGROUND

Pathological studies of bronchial biopsy specimens have confirmed the apparent thickening of lamina reticularis of the epithelial basement membrane. Corticosteroids have proven to be most effective in modifying airway inflammation. However, there is not much data on the effects of corticosteroid-treatment on the basement membrane.

OBJECTIVE

To investigate the effects of inhaled beclomethasone dipropionate (BDP) on the thickness of basement membrane and cellular infiltration into the bronchial mucosa, and the expression of growth factors in patients with asthma.

METHODS

We studied bronchial biopsies from 24 asthmatic patients before and after treatment with inhaled BDP, 400 microg twice a day or placebo, for 6 months in a double-blind manner. Each subject recorded daily asthma symptoms and peak expiratory flow (PEF). Lung function and bronchial responsiveness to methacholine were measured before and after treatment. The thickness of the basement membrane was determined by electron microscopy. Inflammatory cells and the expression of growth factors were examined by immunohistochemistry in endobronchial biopsy specimens.

RESULTS

After 6 months of treatment, we observed a significant improvement of asthma symptoms (P<0.01), PEF (P<0.01), diurnal variation of PEF (P<0.05), and airway responsiveness (P< 0.05) in the BDP group compared with the placebo group. This was accompanied by a significant decrease in the thickness of the lamina reticularis (P < 0.001), and in the number of activated eosinophils (P<0.01), T-lymphocytes (P<0.01), and fibroblasts (P < 0.05) in BDP-treated patients. There was also a reduction in the expression of insulin-like growth factor (IGF)-I (P < 0.01). Significant correlation was found between the IGF-I expression and collagen thickening (rs = 0.34, P<0.01), and the number of fibroblasts (rs = 0.45, P < 0.01).

CONCLUSION

These results suggest that corticosteroid treatment in asthma can reduce the lamina reticular thickness by modulation of IGF-I expression with consequent inhibition of the airway infiltration by inflammatory cells, and therefore may help to prevent remodelling of the airways.

Increased transforming growth factor beta (TGF-beta) immunoreactivity is independently associated with chronic injury in both consequential and primary radiation enteropathy

PURPOSE

Radiation enteropathy is characterized by sustained increase in transforming growth factor beta (TGF-beta) immunoreactivity and connective tissue mast cell (CTMC) hyperplasia that may be responsible for progressive fibrosis and lead to clinical complications. We examined to what extent these chronic molecular and cellular phenomena are associated with acute mucosal breakdown (consequential injury) and/or direct (primary) radiation injury in late-responding compartments.

METHODS AND MATERIALS

Rat small intestine was exposed to 50.4 Gy x-irradiation given either over 18 days (2.8 Gy daily or 5.6 Gy every other day) or 9 days (2.8 Gy twice daily or 5.6 Gy daily). Intestinal complications were recorded and groups of animals were euthanized at 2 and 26 weeks to assess subacute and chronic injury. Histopathologic changes were assessed with a radiation injury scoring system (RIS), total TGF-beta immunoreactivity was quantified with computerized image analysis, and CTMC hyperplasia was assessed in toluidine blue-stained sections.

RESULTS

TGF-beta immunoreactivity and CTMC hyperplasia colocalized in areas of injury and were highly significantly correlated. Increased fraction size and decreased overall treatment time were associated with increased RIS (p < 0.01 and p < 0.00001), increased TGF-beta immunoreactivity (p = 0.01 andp < 0.001), and degree of CTMC hyperplasia (p = 0.01 and p < 0.001). Postradiation CTMC numbers increased across treatment groups from 2 to 26 weeks (p < 0.01). TGF-beta immunoreactivity was independently associated with chronic intestinal wall fibrosis (p = 0.003).

CONCLUSION

This in vivo study supports in vitro evidence linking increased TGF-beta immunoreactivity and mast cell hyperplasia and strongly suggests their involvement in the molecular pathogenesis of both primary and consequential radiation enteropathy.

The potential role of mast cells in lung allograft rejection

To perform a retrospective pilot study of the potential role of mast cells in acute and chronic rejection of the lung allograft, transbronchial biopsies of 29 patients with acute rejection and six patients with bronchiolitis obliterans were stained with antibodies to mast cell tryptase. The number of mast cells per unit area were counted, and compared with a control group of normal lung biopsies stained in a similar fashion. Increasing grades of acute rejection were associated with progressively more mast cells per high-power microscopic field. The presence of bronchiolitis obliterans was accompanied by the greatest numbers of mast cells. Mast cells may play a role in the acute rejection response to the lung allograft and in the development of bronchiolitis obliterans.

Altered immunohistochemical localization of basic fibroblast growth factor after bleomycin-induced lung injury

Basic fibroblast growth factor (bFGF) is a potent inducer of growth and proliferation for many cell types involved in wound healing. Although bFGF has previously been identified in lung tissue, its role in the pathogenesis of pulmonary fibrosis is unknown. We investigated the distribution of bFGF after bleomycin-induced lung injury in the rat in hope of learning how bFGF might participate in the process of lung injury, repair and fibrosis. Increased immunoreactive bFGF was found in the extracellular matrix after bleomycin and co-localized to a marker of active cell proliferation. This suggests that bFGF may participate in directing cell proliferation following lung injury. In addition, a marked increase in the number of mast cells with strong reactivity for bFGF was found at days 14 and 21 after bleomycin. These cells may represent a source of bFGF during the fibroproliferative stage after lung injury.

Relationship between cells obtained by bronchoalveolar lavage and survival in idiopathic pulmonary fibrosis

BACKGROUND

The relationship between cell types in bronchoalveolar lavage (BAL) fluid and the clinical course of patients with idiopathic pulmonary fibrosis (IPF) has been the subject of several studies. However, the results of these studies are not conclusive. The aim of this study was to investigate the relationship between the absolute and relative cell numbers in BAL fluid from patients with IPF and their survival.

METHODS

Results obtained from the initial BAL fluid analyses of all histologically proven cases of IPF (n = 49) were selected retrospectively. Cox's proportional hazards survival analysis was used for estimating the relationship between absolute and relative cell numbers and survival.

RESULTS

A negative relationship was found between both the absolute numbers and percentages of eosinophils in BAL fluid samples and survival. No such relationship was demonstrated for the absolute numbers or the percentages of any other cell type.

CONCLUSIONS

Although this study has restrictions, these findings suggest a negative relationship between the absolute numbers and percentages of eosinophils in BAL fluid samples and survival in patients with IPF.

Role of histamine in a rat model of colitis

We examined the possible involvement of mast cells in a rat model of colitis, by monitoring levels of histamine at various times after inducing inflammation with intrarectal trinitrobenzene sulfonic acid in 50% ethanol. The ability of a histamine H1 antagonist, diphenhydramine, to modify colitis was also assessed. As expected, trinitrobenzene sulfonic acid in 50% ethanol induced a sustained colitis. Myeloperoxidase levels in macroscopically damaged tissue peaked at one week, and declined thereafter. In contrast, tissue histamine levels were normal at one week, then increased in damaged tissue to approximately four times normal levels at four weeks. Indices of inflammation were markedly suppressed at one week by diphenhydramine, while tissue histamine levels were unaffected. Chronic colitis in rats is thus apparently accompanied by a local mast cell hyperplasia or influx. Moreover, antagonism of a major mast cell mediator, histamine, significantly reduces the severity of inflammation in this model.

Tryptase immunoreactive mast cell hyperplasia in bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD), the most common cause of chronic lung disease in prematurely born infants, is histologically characterized by various degrees of airway and alveolar septal fibrosis. Tryptase, a serine protease specific to mast cells, has been shown to have potent fibroblast mitogenic properties and in addition has been shown to be increased in adult fibrotic lung disorders. Based on this analogy, the distribution of pulmonary mast cells exhibiting tryptase immunoreactivity was investigated by immunoperoxidase staining in autopsy specimens of infants dying with BPD. Morphologically normal lung specimens from similarly aged infants dying of sudden infant death syndrome (SIDS) served as controls. Tryptase-positive mast cell counts were performed at 250x from at least 10 random fields in bronchial, peribronchiolar, and alveolar regions. Compared to controls, in lung sections exhibiting typical histologic features of long-standing BPD, tryptase positive cells were significantly increased in bronchial (23.9 +/- 3.6 vs 14.4 +/- 2.3) and peribronchiolar (15.3 +/- 3.2 vs 4.63 +/- 0.6) regions compared to controls (P < 0.05, Student's t test). In particular, alveolar regions exhibiting moderate to severe degrees of septal fibrosis exhibited a dramatic increase in the number of tryptase-positive cells (9.83 +/- 1.89 vs 0.34 +/- 0.18, P = 0.003). These findings of a tryptase-positive mast cell hyperplasia in BPD suggest potential roles of mast cells as well as tryptase in the pathogenesis of this disease.

Messages and handshakes: cellular interactions in pulmonary fibrosis

A better understanding of early cellular events following pulmonary injury may permit the identification of those patterns of response which are destined to progress to fibrosis. Interactions between inflammatory, fibroblastic and epithelial cells appear to play crucial roles in fibrogenesis. Intercellular communication may be via "messages" delivered by soluble mediators or "handshakes" at sites of cell-to-cell contact. In this review, we question the validity of some prevailing concepts about the importance of growth factor secretion by alveolar macrophages; examine the possible role of activated T-lymphocytes in regulating macrophage production of mediators; and hypothesise that whereas fibroblast proliferation may primarily be stimulated by macrophage-derived cytokines, accumulation of collagen may be regulated by growth factors expressed by injured alveolar epithelial cells.

A role for mast cells in the progression of Duchenne muscular dystrophy? Correlations in dystrophin-deficient humans, dogs, and mice

Dystrophin deficiency has been shown to be the underlying cause of Duchenne muscular dystrophy. Although dystrophin-deficient homologous animal models have been identified (dog, mouse, and cat), the clinical expression of the biochemical defect is species-specific. Thus, while the genetics and biochemistry of Duchenne dystrophy is understood, the pathophysiological cascade leading to muscle weakness in only humans and dogs remains obscure. To begin to dissect the pathophysiology at the histological level, we undertook a systematic study of mast cells in normal and dystrophin-deficient muscle. Mast cells have been implicated in the development of fibrosis in other disorders, and progressive fibrosis has been hypothesized to mediate the failure of muscle regeneration in human and dog dystrophin deficiency. Our results show a strong correlation between mast cell content and localization, and the clinico-histopathological progression in humans, dogs and mice. The mast cell increases were disease specific: other dystrophic myopathies with normal dystrophin generally did not show substantial increases in mast cell content or degranulation. Our data suggest that mast cell accumulation and degranulation may cause the grouped necrosis characteristic of dystrophin deficiency in all species.