Alveolar type II cell responses to chronic inhalation of chrysotile asbestos in rats

The effects of chronic exposure to chrysotile asbestos on alveolar type II cells were examined in the lungs of Fischer 344 rats. Morphometric and three-dimensional analyses were used to characterize the alveolar type II cell and to determine the relationship of asbestos fiber localization to ultrastructural change in these cells. During the 2-yr period of study, type II cell number and volume increased to values more than 4 times those seen in controls. Ultrastructurally, cisternal dilations of the rough endoplasmic reticulum (RER) composed 12% of the total cell volume after 12 mo of exposure to asbestos and was still 15% of the total cell volume 1 yr after fiber exposure had ended compared to less than 1% in control cells. Asbestos fiber density surrounding these cells was directly proportional to the degree of cisternal dilatation in the cell; however, lamellar body volume and number in these cells were not different from that found in control type II cells. The incidence of a subset of type II cells with large lamellated inclusions was 10-fold greater in regions near bronchiolar-alveolar duct junctions, compared to more distal gas exchange regions of the lungs. Normal-sized lamellar bodies were fused to these large lamellated inclusions. These cells also contained significantly greater numbers of lamellar bodies and multivesicular bodies than those type II cells in more distal lung regions. These ultrastructural changes observed in type II cells may be a simple dose response to inhaled asbestos or the manifestation of two distinct populations of cells in the lungs that respond to asbestos in different ways. Asbestos fiber dose, cellular microenvironment, and aberrations of the cell plasma membrane and/or cell cytoskeleton (i.e., microtubules and filaments) are discussed as potential factors in the changes noted in type II cells.     

Alveolar type II cell response in rats exposed to aerosols of alpha-cristobalite.

Alpha-cristobalite causes pulmonary interstitial disease in humans and experimental animals. Aerosol exposure of rats to cristobalite for 8 days results in early and sustained alveolar type II cell hyperplasia in areas of inflammation characterized by the presence of macrophages and polymorphonuclear leukocytes. Irregular interstitial fibrosis and coalescence of alveoli are apparent by day 120. The inflammatory response is characterized by increased lavage cell recoveries, principally macrophages and neutrophils. Lavage recoveries of protein, nonpolar lipid, phospholipid, and saturated phosphatidylcholine also are increased. The recovery ratio for two important surfactant phospholipids, phosphatidylcholine and phosphatidylglycerol, is decreased at all points following exposure. Our morphologic analyses, together with results correlating lavage cell and lipid recoveries, point to the potential importance of macrophages and neutrophils in the epithelial cell response to cristobalite exposure.     

Alveolar cell hyperplasia in the lungs of smoking dogs

Hyperplasia of bronchiolar epithelium was observed in the lung parenchyma of 14 smoking dogs. Besides the increased number of cell layers in the bronchiolar epithelium, there was a virtual absence of glycogen in the cell cytoplasm. Sheetlike arrangements of squamous cells containing an abundance of tonofilament bundles were found lining alveoli. Type II cells were found adjacent to, and sometimes extending over the squamous cells. In all cases, a proliferation of type II cells was found in the alveolar epithelium, almost completely lining some alveoli. Acinarlike structures also lined by many type II cells were sometimes found near the pleura. Microinvasions of cytoplasmic processes into the underlying connective tissue often occurred through defects in the basal lamina. In some type II cells an unusual content of RER was observed. It possessed electron dense banding ≈ 180 Å wide with a repeat at intervals of ≈ 540 Å and was found in narrow cisternae and in bulbous dilatations of the cisternae of the RER. Fibrogranular material of the same appearance and periodicity was also found in the perinuclear space in some cells. Type II cells are further implicated as a reserve cell or stem cell in metaplastic alterations.     

Silica-induced hypertrophy of type II cells in the lungs of rats

Several investigators have reported the appearance of hypertrophic type II cells in the lungs of silica-treated rats. The purpose of this study was to isolate and characterize these hypertrophic type II cells. Lungs were digested with trypsin and the released cells were separated by using a flow gradient during centrifugal elutriation. Type II cells from control lungs were distributed in the flow gradient as a single population, whereas type II cells from the lungs of silica-treated rats had a bimodal distribution suggesting the presence of two distinct populations of type II cells; one of these populations appeared hypertrophic (type IIB) and the other appeared normal (type II cells; one of these populations appeared hypertrophic (type IIB) and the other appeared normal (type IIA). These two populations of type II cells from silica-treated rats differed significantly in cell size and their lamellar body content. The mean volume of type IIA and type IIB cells was 350 +/- 38 micron 3 and 523 +/- 29 micron 3, respectively. The mean number of lamellar bodies in type IIA and type IIB cells was 77 +/- 53 and 131 +/- 84 per cell, respectively. The mean volume of lamellar bodies was 0.39 +/- 0.09 micron 3 in type IIA cells and 0.66 +/- 0.10 micron 3 in type IIB cells. Type IIA cells were not significantly different from type II cells from the lungs of untreated rats. The distribution of type II cells from silica-treated lungs was such that 2 weeks after a single intratracheal injection of silica (10 mg/rat) type IIB cells accounted for 39.2 +/- 6.4% of the total type II cells recovered after centrifugal elutriation. The general morphological appearance of the isolated type IIA and type IIB cells was similar to that observed in type II cells isolated from untreated rats. These data indicate that hypertrophic type II cells may be isolated from the lungs of silica-treated rats and separated from normal type II cells thus allowing the role of these unusual type II cells in lung injury and repair to be investigated.     

Isolation and characterization of hypertrophic type II cells from the lungs of silica-treated rats

Type II cells isolated from the lungs of rats exposed to silica can be separated into two populations by using centrifugal elutriation. One population, designated type IIA, appears similar to type II cells isolated from control lungs. The second population, designated type IIB, consists of type II cells that are larger than type IIA cells or control type II cells. In addition, the type IIB (or hypertrophic) cells contain lamellar bodies which are larger and more numerous than lamellar bodies in type IIA or control type II cells. After centrifugal elutriation, the type II cell populations were purified by differential adherence on rat IgG-coated culture dishes for biochemical and metabolic studies. Type IIB cells contained elevated amounts of protein and total RNA in comparison to type IIA and control type II cells. Type IIB cells contained approximately 2.5-fold more phospholipid than control type II cells (51.5 +/- 3.0 micrograms/10(6) cells versus 20.5 +/- 4.1 micrograms/10(6) cells). Incorporation of the phospholipid precursors [14C]choline and [3H]palmitate into cellular phosphatidylcholines was also increased in type IIB cells. After 120 minutes of incubation, incorporation of [14C]choline into total phosphatidylcholine by type IIB cells was 250% greater than in controls; at this same time point, incorporation of [3H]palmitate was approximately 150% greater than in controls. Incorporation of [14C]choline into disaturated phosphatidylcholine by type IIB cells was 200% greater than in controls. However, no increased incorporation of [3H]-palmitate into disaturated phosphatidylcholine by type IIB cells was seen. These results suggest that the hypertrophic type II cell is responsible for the increases in surfactant-associated phospholipids in the lungs of rats exposed to silica.     

HIV-1 transgenic rats develop T cell abnormalities

HIV-1 infection leads to impaired antigen-specific T cell proliferation, increased susceptibility of T cells to apoptosis, progressive impairment of T-helper 1 (Th1) responses, and altered maturation of HIV-1-specific memory cells. We have identified similar impairments in HIV-1 transgenic (Tg) rats. Tg rats developed an absolute reduction in CD4+ and CD8+ T cells able to produce IFN-gamma following activation and an increased susceptibility of T cells to activation-induced apoptosis. CD4+ and CD8+ effector/memory (CD45RC- CD62L-) pools were significantly smaller in Tg rats compared to non-Tg controls, although the converse was true for the na?ve (CD45RC+ CD62L+) T cell pool. Our interpretation is that the HIV transgene causes defects in the development of T cell effector function and generation of specific effector/memory T cell subsets, and that activation-induced apoptosis may be an essential factor in this process.     

Characterization of type II intracellular IL-1 receptor antagonist (IL-1ra3): a depot IL-1ra

Three molecular forms of the IL-1 receptor antagonist (IL-1ra) have been identified and cloned. Secreted IL-1ra (sIL-1ra or IL-1ra1) contains a classical leader peptide giving a released mature protein. Two intracellular isoforms, icIL-1ra type I (IL-1ra2) and icIL-1ra type II (IL-1ra3), have no leader sequence, thus predicting that these proteins remain intracellular. In an effort to define its biological role, we structurally and functionally characterized IL-1ra3. Endogenous immunoreactive IL-1ra3 was detected in a variety of inflammatory cells and tissues. We used a gene transfer strategy to explore the possible intracellular functions of IL-1ra3 (and IL-1ra2) and the cell-associated agonist IL-1alpha. The intracellular IL-1ra3 isoform, as well as IL-1ra2, does not block the action of exogenous and endogenous IL-1 under these conditions. Intact IL-1ra3 was released from the cells killed by NK effectors. The intracellular isoforms may represent a reservoir of IL-1ra, released upon cell death, whose function is to limit the pro-inflammatory action of cell debris.     

Donor-derived type II pneumocytes are rare in the lungs of allogeneic hematopoietic cell transplant recipients

Lung injury is a common cause of death and disability. Stem cell-related therapies are widely viewed as offering promise for people suffering from various types of pulmonary diseases, and gender-mismatched bone marrow transplant recipients serve as natural populations in which to study the role of bone marrow-derived stem cells in recovery from pulmonary injury. We evaluated the extent of lung repopulation by type II pneumocyte descendents of adult bone marrow-derived stem cells in allogeneic hematopoietic cell transplant recipients. Recut sections were obtained from five lung biopsy specimens and autopsy lung tissues from four female recipients of transplanted mobilized peripheral blood stem cells or bone marrow from male donors. Sequential immunohistochemistry and fluorescence in situ hybridization was performed on each section to evaluate for Y-chromosome-containing type II pneumocytes. A single Y-chromosome-containing type II pneumocyte was found in one lung biopsy from one hematopoietic cell transplant recipient. After adjustment for the effects of incomplete nuclear sampling, this pneumocyte represented 1.75% of all type II pneumocytes in the biopsy sample. There was no evidence of polyploidy to suggest cell-to-cell fusion. No donor-derived type II pneumocytes were found in samples from the other three patients. In conclusion, repopulation by bone marrow-derived stem cells or their progeny occurs at a low frequency in the lungs of hematopoietic cell transplant recipients. Conversely, proliferation by local stem cell populations appears to be more important for recovery from alveolar injury.     

The IL-1 system in HIV infection: peripheral concentrations of IL-1β, IL-1 receptor antagonist and soluble IL-1 receptor type II

The proinflammatory cytokine IL-1β is thought to be involved in ongoing HIV disease. Furthermore, its naturally occurring inhibitors soluble IL-1 receptor type II (sIL-1RII) and IL-1 receptor antagonist (IL-1Ra) may play a pivotal role in regulating its biological action. To investigate the involvement of the IL-1 system we determined serum levels of IL-1β, IL-1Ra and sIL-1RII in 90 HIV⁺ patients. The obtained values were compared with markers of disease progression such as CD⁺ count, 5′-neopterin, β₂-microglobulin and soluble tumour necrosis factor receptors (sTNF-R) p55 and p75 and then compared with C-reactive protein (CRP), granulocyte count, lL-6 and TNF-α. While IL-1Ra concentrations increased significantly with progressive CDC disease stages, sIL-1RII and IL-1β were not altered in our cohort. IL-1Ra showed statistical relation to decreasing CD4⁺ lymphocytes and increasing 5′-neopterin, β₂-microglobulin, sTNF-R p55, sTNF-R p75. Furthermore, IL-1Ra correlated positively with serum IL-6, TNF-α, CRP and granulocytes. In contrast, sIL-1RII and IL-1β tended to show an inverse correlation or showed no significant relationship to all these parameters. Il-1β was measurable only in a limited number of samples. IL-1Ra showed a clear relationship to acute inflammatory events as well as to the different disease stages. Our data suggest a dissociation between IL-1Ra and sIL-1RII serum levels which may indicate that the two IL-1 binding proteins have different pathophysiological roles in HIV infection.     

The type II decoy receptor of IL-1 inhibits murine collagen-induced arthritis

IL-1 is a key cytokine involved in the inflammatory response. The type II receptor of IL-1 (IL-1RII) acts as a decoy receptor, binding and inhibiting the effect of IL-1. This study was undertaken to establish whether IL-1RII can ameliorate collagen-induced arthritis, a model of inflammatory arthritis in mice. We used human keratinocytes transfected with the human (h)IL-1 RII gene as a source of hIL-1 RII protein. We showed that these cells expressed both the membrane and soluble form of receptor. In vitro, IL-1-stimulated murine macrophage cells showed a decreased expression of TNF-alpha in the presence of hIL-1 RII. We engrafted the hIL-1RII-transfected cells in the back of mice developing collagen-induced arthritis. We found that clinical and histological parameters of arthritis were significantly decreased in mice treated with cells producing hIL-1RII. In addition, hIL-1RII administration was able to reduce the expression of mRNA for IL-6 and myeloperoxidase in the joints of treated animals. These data show that hIL-1 RII anti-inflammatory properties in the model of collagen-induced arthritis in mice and could have a regulatory role in rheumatoid arthritis.     

Quantitation of biologically active IL-1 by a sensitive assay based on immobilized human IL-1 receptor type II (IL-1RII).

A rapid and sensitive solid-phase radioassay is described for the quantitative detection of human interleukin-1 (IL-1) based on its capability to bind the nitrocellulose-immobilized IL-1 receptor solubilized from plasma membranes of a subclone of the human B cell lymphoma Raji. The assay can detect human IL-1 beta levels as low as 1 X 10(-11) M, both in physiological buffers and in human plasma. Much lower sensitivity was observed for human IL-1 alpha (3.7 X 10(-9) M) and murine IL-1 beta (2 X 10(-9) M). This assay has the advantage to specifically detect only the correctly folded biologically active IL-1. Simple pretreatment procedure that selectively removes IL-1 beta from samples has been devised so that the ratio of the two IL-1s isoforms in the sample can be precisely determined. This assay represents a fast method for the simultaneous-testing of large numbers of biological samples.     

Chromosome abnormalities in bovine papillomavirus type 1-transformed Syrian hamster cells before and after tumor formation

Syrian hamster embryonic fibroblasts transformed by infection with bovine papillmavirus type 1 cause tumors when inoculated into hamsters. Chromosome examinations revealed several abnormal clones in the transformed fibroblasts and a variety of additional markers in three tumors. Only one aberration, trisomy 11, was present in each cell. The extra chromosome #11, thus, is considered to be essential for tumor formation in this model system.     

Experimental silicosis. II. Long-term effects of intratracheally instilled quartz on collagen metabolism and morphologic characteristics of rat lungs.

Rats received intratracheal instillations of 50 mg of silica (quartz, 0.5 mu particles). One, 2, 4, 5, 6, 9, and 12 months later, the lungs were evaluated histologically and by various biochemical measurements. The lung content of protein, proline, and hydroxyproline (collagen) were quantitated, as were the synthesis rates of lung collagen and the total lung protein (evaluated with lung minces in vitro. The ratio of newly synthesized and of total lung Type I to Type III collagen was also determined. These experiments were performed in parallel on rats free of chronic respiratory disease and a strain of conventional animals. The authors conclude that 1) the excess collagen deposited in granulomas and/or silicotic nodules as part of the fibrotic response of the lung is similar to normal lung collagen with respect to relative ratios of Types I and III present, in contrast to the response of the lung to oxidant pneumotoxins; 2) the response of the lung to silica continues for at least 1 year; 3) there are essentially no differences in the response of chronic respiratory disease-free Sprague-Dawley and conventional Wistar rats to intratracheally instilled silica. Both strains of rats develop silica-containing granulomas, mature silicotic nodules, and areas of alveolar lipoproteinosis associated with interstitial pneumonitis. Even 1 year after instillation of silica areas of granulomas, silicotic nodules and alveolar lipoproteinosis may be observed in most of the lungs studied; ie, these responses are not mutually exclusive.     

Aspirin-induced increases in soluble IL-1 receptor type II concentrations in vitro and in vivo.

This study examined the influence of low-dose aspirin on interleukin (IL)-1alpha , IL-1 receptor antagonist (IL-1ra), and soluble receptor type II (sIL-1RII) secretion in vivo and in vitro. Blood mononuclear cells were isolated from healthy young men who ingested 81 mg of aspirin on alternate days for 2 weeks and from unmedicated controls. Aspirin had minor effects on ex vivo secretion of IL-1beta and no influence on IL-1ra. In contrast, unstimulated ex vivo secretion of sIL-1RII was over twice as high by cells from aspirin-treated subjects (1115+/-123 vs. 460+/-77 pg/mL, P = 0.02). Lipopolysaccharide-stimulated sIL-1RII secretion was influenced similarly. Plasma sIL-1RII concentrations were 23% higher in aspirin-treated subjects (10.2+/-0.6 vs. 8.4+/-0.3 ng/mL, P = 0.03). In addition, cells from unmedicated subjects cultured in vitro with aspirin (10 microg/mL) secreted significantly greater amounts of sIL-1RII. Thus, low-dose aspirin therapy may prevent inflammation by increasing soluble receptor secretion, thereby preventing IL-1 from binding target cells.